Polyamide particles, method for producing the same, and method for using the same

Abstract

To provide polyamide particles having a narrow particle diameter distribution and little variation in shapes, and a production method of the particles.SOLUTION: A production method of polyamide particles may include: mixing a mixture comprising a polyamide, a carrier fluid that is immiscible with the polyamide, and nanoparticles at a temperature greater than a melting point or softening temperature of the polyamide and at a shear rate sufficiently high to disperse the polyamide in the carrier fluid; cooling the mixture to below the melting point or softening temperature of the polyamide to form solidified particles of polyamide particles having a circularity of 0.90 or greater and comprising the polyamide and the nanoparticles associated with an outer surface of the polyamide particles; and separating the solidified particles from the carrier fluid.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to polyamide particles and methods for manufacturing such particles. Such particles, particularly highly spherical polyamide particles, can be useful, inter alia, as starting materials for additive manufacturing.

Background Art

[0002] Three-dimensional (3D) printing, also known as additive manufacturing, is a rapidly growing field of technology. 3D printing has traditionally been used for rapid prototyping work, but this technology is increasingly being adopted for the manufacture of commercial and industrial objects, which can have structural and mechanical tolerances that are quite different from rapid prototyping.

[0003] 3D printing operates by depositing (a) small droplets or streams of a meltable or solidifiable material, or (b) powder microparticles, at a deposition location and then consolidating them into a larger object, which can have any number of complex shapes. Such deposition and consolidation processes are typically carried out under computer control to build up the larger object layer by layer. In certain examples, the consolidation of powder particles may be carried out within a 3D printing system using a laser to promote selective laser sintering (SLS). Incomplete interlayer fusion can lead to structural weaknesses and can be a problem for printing objects with strict structural and mechanical tolerances.

[0004] Powdery fine particles that can be used in 3D printing include thermoplastic polymers including thermoplastic elastomers, metals, and other curable substances. A wide array of thermoplastic polymers is known, but particularly when using powder bed fusion (PBF), relatively few have properties suitable for use in 3D printing. Additive manufacturing methods using powder materials include PBF, selective laser sintering (SLS), selective heat sintering (SHM), selective laser melting (SLM), electron beam melting (EBM), binder jetting, and multi jet fusion (MJF). In the SLS printing method, the particles are fused by energy from a high-power laser. Typical thermoplastic polymers suitable for use in 3D printing include those having a sharp melting point and a recrystallization point about 20°C to 50°C lower than the melting point. This difference may enable more effective coalescence to occur between adjacent polymer layers, thereby promoting improvement in structural and mechanical integrity.

[0005] In order to achieve good printing performance using powdery fine particles, particularly polymer powdery fine particles, the powdery fine particles need to maintain good flow characteristics in the solid state. The flow characteristics can be evaluated, for example, by measuring the proportion of powdery fine particles that can pass through a standard sieve of a specific size from a sample and / or by measuring the angle of repose. A high proportion of sieveable powdery fine particles may indicate that the fine particles are not aggregated and are present substantially as individual fine particles, which can be characteristic of easy powder flow. Further, the lower the value of the angle of repose, the more characteristic it can be of easy powder flow. A relatively narrow particle size distribution and regularity of particle shape in the sample can also help promote good powder flow performance.

[0006] Commercially available powder microparticles are often obtained by cryogenic grinding or precipitation processes, which can result in irregular particle shapes and a wide particle size distribution. Irregular particle shapes may reduce the powder flow performance during the 3D printing process. In addition, powder microparticles with irregular shapes, especially those obtained from current commercial processes, have insufficient efficiency during filling following deposition and consolidation, such that extensive void formation can occur within the printed object because the powder microparticles are not densely packed during deposition. A wide particle size distribution can also be a problem in this regard. Insufficient powder flow performance can be addressed to some extent by dry blending with fillers and flow aids, but these techniques can have limited effectiveness when using softer polymeric materials such as elastomers due to particle agglomeration. SUMMARY OF THE INVENTION

[0007] The present disclosure relates to polyamide particles and methods for manufacturing such particles. Such particles, particularly highly spherical polyamide particles, can be useful, inter alia, as starting materials for additive manufacturing.

[0008] Described herein is a method comprising mixing a mixture comprising a polyamide, a carrier fluid immiscible with the polyamide, and nanoparticles at a temperature higher than the melting point or softening temperature of the polyamide and at a shear rate high enough to disperse the polyamide in the carrier fluid, cooling the mixture to below the melting point or softening temperature of the polyamide to form solidified particles comprising polyamide particles having a circularity of 0.90 or greater and comprising polyamide and nanoparticles associated with the outer surface of the polyamide particles, and separating the solidified particles from the carrier fluid.

[0009] Described herein is a composition comprising particles comprising polyamide particles having a circularity of 0.90 or greater and comprising polyamide and nanoparticles associated with the outer surface of the polyamide particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The following figures are included to illustrate certain aspects of the embodiments and should not be regarded as exclusive embodiments. Those skilled in the art can contemplate significant modifications, changes, combinations, and equivalents in the form and function of the disclosed subject matter that fall within the scope of the present disclosure.

[0011]

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Mode for Carrying Out the Invention

[0012] The present disclosure relates to polyamide particles and a method for manufacturing such particles. Such particles, particularly highly spherical polyamide particles, can be useful, inter alia, as starting materials for additive manufacturing.

[0013] More specifically, the polyamide particles described herein are produced by a melt emulsification method, in which the polyamide is dispersed as a melt in a carrier fluid that is immiscible with the polyamide. A sufficient amount of shear force is used to form droplets of the polyamide melt in the carrier fluid. An emulsifying stabilizer (e.g., nanoparticles and / or surfactants) provides surface tension at the phase interface between the carrier fluid and the polyamide melt. When the melt emulsification process is complete, the dispersion is cooled and the polymer is solidified into polyamide particles.

[0014] Without being bound by theory, during the melt emulsification process, the emulsifying stabilizer is mainly present at the interface between the polymer melt and the carrier fluid. As a result, when the mixture is cooled, the emulsifying stabilizer will remain at the above interface. Advantageously, the emulsifying stabilizer on the surface of the resulting particles can assist the flow characteristics of the resulting particles.

[0015] As described above, conventional methods for forming polyamide particles with good fluidity involve at least two steps, which are a first step of forming the particles (e.g., by cryogenic grinding or precipitation process) and purifying them, and a second step of coating the particles to some extent with a flow promoter such as nanoparticle silica, carbon black, or PTFE particles. The method described herein advantageously produces polyamide particles having a coating that improves the fluidity of the particles in one process.

[0016] Furthermore, without being bound by theory, the method of the present disclosure is considered to be capable of producing particles with a more homogeneous coverage rate of the emulsifying stabilizer and further improving the fluidity. The improved fluidity is particularly advantageous in additive manufacturing applications such as 3D printing.

[0017] Definitions and Test Methods As used herein, the term "immiscibility" refers to a mixture of two or more components that, when combined, form two or more phases having a solubility in each other of less than 5% by weight at room temperature at ambient pressure or, if solid at room temperature, at the melting point of the components. For example, polyethylene oxide having a molecular weight of 10,000 g / mol is solid at room temperature and has a melting point of 65°C. Thus, if a certain material is liquid at room temperature and this material and the above polyethylene oxide have a solubility in each other of less than 5% by weight at 65°C, the above polyethylene oxide is said to be immiscible with this material.

[0018] As used herein, the term "oxide" refers to both metal oxides and non-metal oxides. For the purposes of the present disclosure, silicon is considered to be a metal.

[0019] As used herein, the relationship expressed by the terms "associated", "association", and their grammatical variations between an emulsifier stabilizer and a surface refers to chemical bonding and / or physical adhesion of the emulsifier stabilizer to the surface. Without being bound by theory, although this specification describes the association between a polymer and an emulsifier stabilizer, it is considered that the association is mainly a physical adhesion state via hydrogen bonding and / or other mechanisms. However, there may be a certain degree of chemical bonding occurring.

[0020] When the term "embed" is used herein with respect to the surface of nanoparticles and polymer particles, it refers to the nanoparticles extending at least partially into the surface such that the polymer contacts the nanoparticles to a greater extent than when the nanoparticles are simply placed on the surface of the polymer particles.

[0021] In this specification, D10, D50, D90, and diameter span are mainly used to describe particle size. When the term "D10" is used herein, it refers to the diameter value in the case where the particles constituting 10% of the sample (by volume unless otherwise specified) have a diameter less than a certain value. When the term "D50" is used herein, it refers to the diameter value in the case where the particles constituting 50% of the sample (by volume unless otherwise specified) have a diameter less than a certain value. When the term "D90" is used herein, it refers to the diameter value in the case where the particles constituting 90% of the sample (by volume unless otherwise specified) have a diameter less than a certain value.

[0022] When the terms "diameter span", "span", and "span size" are used herein to refer to diameter, they provide an indication of the spread of the particle size distribution and are calculated as (D90 - D10) / D50 (again, each D value is volume-based unless otherwise stated).

[0023] The particle size can be determined by light scattering techniques using a Malvern MASTERSIZER™ 3000 or analysis of optical digital micrographs. Unless otherwise stated, light scattering techniques are used to analyze the particle size.

[0024] For light scattering techniques, the control sample was glass beads having a diameter in the range of 15 μm to 150 μm of the trademarked "Quality Assurance Standard QAS4002™" obtained from Malvern Analytical Ltd. Unless otherwise stated, the sample was analyzed as a dry powder. The particles to be analyzed were dispersed in air and analyzed using an AERO S dry powder dispersion module together with the MASTERSIZER™ 3000. The particle size was derived using the instrument software from a plot of volume density as a function of particle size.

[0025] When the terms "circularity" and "sphericity" are used herein with respect to particles, they refer to how close the particles are to a perfect sphere. To determine circularity, an optical microscope image of the particle is taken. The perimeter length (P) and area (A) of the particle within the plane of the microscope image are calculated (e.g., using a SYSMEX FPIA 3000 particle shape and size analyzer available from Malvern Instruments). The circularity of the particle is C EA / P, where C EA is the circumference of a circle having an area corresponding to the area (A) of the actual particle.

[0026] When the term "sintering period" is used herein, it refers to the difference between the melting temperature (Tm) start point and the crystallization temperature (Tc) start point, i.e., (Tm - Tc) start point. Tm, Tm (start point), Tc, and Tc (start point) are measured by differential scanning calorimetry according to ASTM E794-06(2018) using a heating rate of 10 °C / min and a cooling rate of 10 °C / min.

[0027] When the term "shearing force" is used herein, it refers to agitation or a similar process that induces mechanical stirring in a fluid.

[0028] When the term "aspect ratio" is used in this specification, it refers to the ratio of the length divided by the width. Here, the length is assumed to be greater than the width.

[0029] Unless otherwise specified, the melting point of the polymer is determined using ASTM E794-06(2018) with a heating rate and a cooling rate of 10 °C / min.

[0030] Unless otherwise specified, the softening temperature or softening point of the polymer is determined according to ASTM D6090-17. The softening temperature can be measured using a cup-and-ball apparatus available from Mettler-Toledo with a heating rate of 1 °C / min and a 0.50-gram sample.

[0031] The angle of repose is a measure of the flowability of the powder. The measured value of the angle of repose was determined using a Hosokawa Micron Powder Characteristics Tester PT-R using ASTM D6393-14, "Standard Test Method for Bulk Solids Characterized by Carr Indices".

[0032] The Hausner ratio (H r ) is a measure of the flowability of the powder, and H r = ρ tap / ρ bulk is calculated by, where ρ bulk is the bulk density according to ASTM D6393-14, and ρ tap is the tapped density according to ASTM D6393-14.

[0033] As used herein, the term "embed" with respect to the surface of nanoparticles and polymer particles means that the nanoparticles extend at least partially inside the surface of the polymer particles, such that the polymer comes into contact with the nanoparticles to a greater extent than when the nanoparticles are simply placed on the surface of the polymer particles.

[0034] As used herein, unless otherwise specified, the viscosity of the carrier fluid is the kinematic viscosity at 25 °C measured according to ASTM D445-19. For commercially obtained carrier fluids (e.g., PDMS oil), the kinematic viscosity data cited herein are provided by the manufacturer, whether measured according to the aforementioned ASTM or according to another standard measurement technique.

[0035] Polyamide Particles and Method of Manufacture Figure 1 is a flowchart of a non-limiting exemplary method 100 of the present disclosure. A mixture 110 is produced by combining polyamide 102, carrier fluid 104, and emulsifying stabilizer 106 (reference numeral 108). Components 102, 104, and 106 can be added in any order and can include mixing and / or heating during the process 108 of combining components 102, 104, and 106.

[0036] Next, the mixture 110 is processed (reference numeral 112) by applying a shear force to the mixture 110 that is sufficiently high at a temperature higher than the melting point or softening temperature of the polyamide 102, and a molten emulsion 114 is formed. Since the above temperature is higher than the melting point or softening temperature of the polyamide 102, the polyamide 102 becomes a polymer melt. The shear rate should be sufficient to disperse the polymer melt in the carrier fluid 104 as droplets (i.e., the polymer emulsion 114). Without being bound by theory, it is believed that when all other factors are the same, increasing the shear force should decrease the size of the droplets of the polymer melt in the carrier fluid 104. However, at some point, there may be diminishing returns from increasing the shear force and decreasing the droplet diameter, or there may be fragmentation into the droplet contents that degrades the quality of the particles produced.

[0037] Examples of mixing devices used to produce the molten emulsion 114 include, but are not limited to, extruders (e.g., continuous extruders, batch extruders, etc.), stirred reactors, blenders, reactors equipped with in-line homogenizer systems, and devices derived therefrom.

[0038] Next, the molten emulsion 114 inside and / or outside the mixing vessel is cooled (116) to solidify the polymer droplets and obtain polyamide polymer particles (also referred to as solidified polyamide polymer particles). The cooled mixture 118 is then processed (reference numeral 120) to separate the polyamide polymer particles 122 from other components 124 (e.g., the carrier fluid 104, the excess emulsifying stabilizer 106, etc.), and the polyamide polymer particles 122 can be washed or otherwise purified. The polyamide polymer particles 122 include the polyamide polymer 102 and at least a portion of the emulsifying stabilizer 106 that coats the outer surface of the polyamide polymer particles 122. The emulsifying stabilizer 106 or a portion thereof can be deposited as a uniform coating on the polyamide polymer particles 122. In some cases, i.e., cases that may depend on non-limiting factors such as temperature (including the cooling rate), the type of polyamide polymer 102, and non-limiting factors such as the type and particle size of the emulsifying stabilizer 106, the nanoparticles of the emulsifying stabilizer 106 can be at least partially embedded within the outer surface of the polyamide polymer particles 122 during the process of associating with the polyamide polymer particles 122. Even if such embedding does not occur, at least the nanoparticles within the emulsifying stabilizer 106 remain strongly associated with the polyamide polymer particles 122, thereby facilitating their further use. Symmetrically, blending pre-formed polyamide fine particles (e.g., those formed by cryogenic grinding or precipitation processes) with a flow aid such as silica nanoparticles in a dry state cannot firmly and uniformly coat the polyamide fine particles with the flow aid.

[0039] Advantageously, the carrier fluid and the washing solvent of the systems and methods described herein (e.g., method 101) can be regenerated and reused. One skilled in the art will recognize any necessary washing of the used carrier fluid and solvent required for the regeneration process.

[0040] When selecting the polyamide 102 and the carrier fluid 104, it should be considered that the polyamide 102 and the carrier fluid 104 are immiscible at various processing temperatures (for example, in the range from room temperature to the processing temperature). An additional factor that can be considered is the viscosity difference (for example, the viscosity difference itself or the viscosity ratio) between the molten polyamide 102 and the carrier fluid 104 at the processing temperature. The viscosity difference can affect droplet breakup and particle size distribution.

[0041] Examples of polyamide 102 include polycaproamide (nylon 6, polyamide 6, or PA6), poly(hexamethylene succinamide) (nylon 4,6, polyamide 4,6, or PA4,6), polyhexamethylene adipamide (nylon 6,6, polyamide 6,6, or PA6,6), polypentamethylene adipamide (nylon 5,6, polyamide 5,6, or PA5,6), polyhexamethylene sebacamide (nylon 6,10, polyamide 6,10, or PA6,10), polidecaamide (nylon 11, polyamide 11, or PA11), polidodecaamide (nylon 12, polyamide 12, or PA12), polyhexamethylene terephthalamide (nylon 6T, polyamide 6T, or PA6T), nylon 10,10 (polyamide 10,10, or PA10,10), nylon 10,12 (polyamide 10,12, or PA10,12), nylon 10,14 (polyamide 10,14, or PA10,14), nylon 10,18 (polyamide 10,18, or PA10,18), nylon 6,18 (polyamide 6,18, or PA6,18), nylon 6,12 (polyamide 6,12, or PA6,12), nylon 6,14 (polyamide 6,14 or PA6,14), nylon 12,12 (polyamide 12,12, or PA12,12), etc., and any combination thereof, but not limited thereto. Copolymers can also be used. Examples of copolymers include, but are not limited to, PA11 / 10,10, PA6 / 11, PA6,6 / 6, PA11 / 12, PA10,10 / 10,12, PA10,10 / 10,14, PA11 / 10,36, PA11 / 6,36, PA10,10 / 10,36, PA6T / 6,6, etc., and any combination thereof. When a number (separated by a comma) follows polyamide (PA), the polyamide has the first number of main chain carbons between the nitrogens of the part without pendant =O and the second number of main chain carbons between the two nitrogens of the part with pendant =O. As a non-limiting example, nylon 6,10 is [NH-(CH2)6-NH-CO-(CH2)8-CO] nIt is as follows. When a number (plural possible) and a number (plural possible) follow, separated by a backslash, after a polyamide (PA), the polyamide is a copolymer of the polyamide indicated by the numbers before and after the backslash. Examples of polyamide elastomers include, but are not limited to, polyesteramide, polyetheresteramide, polycarbonate-esteramide, and polyether-block-amide elastomer.

[0042] Polyamide 102 can have a melting point or softening temperature of about 50 °C to about 450 °C (or about 50 °C to about 125 °C, about 100 °C to about 175 °C, about 150 °C to about 280 °C, about 200 °C to about 350 °C, or about 300 °C to about 450 °C).

[0043] Polyamide 102 can have a glass transition temperature (ASTM E1356-08(2014), provided that the heating and cooling rates are 10 °C / min) of about -50 °C to about 400 °C (or about -50 °C to about 0 °C, or about -25 °C to about 50 °C, or about 0 °C to about 150 °C, or about 100 °C to about 250 °C, or about 150 °C to about 300 °C, or about 200 °C to about 400 °C).

[0044] Polyamide 102 may optionally contain additives. Typically, the additives are present before adding polyamide 102 to mixture 110. Thus, in the polyamide melt droplets and the resulting polyamide particles, the additives are dispersed throughout the polyamide. Thus, for clarity, this additive is referred to herein as an "internal additive". The internal additive may be blended with the polyamide immediately before or well in advance of making mixture 110.

[0045] When describing the amounts of components in the compositions described herein (e.g., mixture 110 and polyamide particles 122), weight percentages based on polyamide 102 without internal additives are used. For example, if polyamide 102 contains 10 wt% internal additives and 90 wt% polyamide, a composition containing 1 wt% emulsifier stabilizer relative to the weight of 100 g of that polyamide 102 is a composition containing 0.9 g of emulsifier stabilizer, 90 g of polyamide, and 10 g of internal additives.

[0046] The internal additives may be present in polyamide 102 at about 0.1 wt% to about 60 wt% (or about 0.1 wt% to about 5 wt%, about 1 wt% to about 10 wt%, about 5 wt% to about 20 wt%, about 10 wt% to about 30 wt%, about 25 wt% to about 50 wt%, or about 40 wt% to about 60 wt%). For example, polyamide 102 may contain about 70 wt% to about 85 wt% polyamide and about 15 wt% to about 30 wt% internal additives such as glass fibers or carbon fibers.

[0047] Examples of internal additives include, but are not limited to, fillers, reinforcing agents, pigments, pH adjusters, and combinations thereof. Examples of fillers include, but are not limited to, glass fibers, glass particles, mineral fibers, carbon fibers, oxide particles (e.g., titanium dioxide and zirconium dioxide), metal particles (e.g., aluminum powder), and any combination thereof. Examples of pigments include, but are not limited to, organic pigments, inorganic pigments, carbon black, and any combination thereof.

[0048] Optionally, another thermoplastic polymer may be used in combination with the polyamide. Examples of thermoplastic polymers that may be used with one or more polyamides include polyurethanes, polyethylenes, polypropylenes, polyacetals, polycarbonates, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polytrimethylene terephthalate (PTT), polyhexamethylene terephthalate, polystyrenes, polyvinyl chlorides, polytetrafluoroethylene, polyesters (e.g., polylactic acid), polyethers, polyethersulfones, polyetheretherketones, polyacrylates, polymethacrylates, polyimides, acrylonitrile butadiene styrene (ABS), polyphenylene sulfides, vinyl polymers, polyarylene ethers, polyarylene sulfides, polysulfones, polyetherketones, polyamideimides, polyetherimides, polyetheresters, polyether blocks and polyamide blocks (PEBA or polyether block amide) containing copolymers, graft or non-graft thermoplastic polyolefins, functionalized or non-functionalized ethylene / vinyl monomer polymers, functionalized or non-functionalized ethylene / alkyl (meth)acrylate, functionalized or non-functionalized (meth)acrylic acid polymers, functionalized or non-functionalized ethylene / vinyl monomer / alkyl (meth)acrylate terpolymers, ethylene / vinyl monomer / carbonyl terpolymers, ethylene / alkyl (meth)acrylate / carbonyl terpolymers, methyl methacrylate-butadiene-styrene (MBS) type core-shell polymers, polystyrene-block-polybutadiene-block-poly(methyl methacrylate) (SBM) block terpolymers, chlorinated or chlorosulfonated polyethylene, polyvinylidene fluoride (PVDF), phenolic resins, poly(ethylene / vinyl acetate), polybutadiene, polyisoprene, styrenic block copolymers, polyacrylonitrile, silicones, etc., and any combination thereof, but not limited thereto. Copolymers containing one or more of the foregoing may also be used in the methods and systems described herein.

[0049] When combining polyamide with other thermoplastic polymers as necessary, a compatibilizer may be used. The compatibilizer can improve the blending efficiency and / or effectiveness of the polymers. Examples of polymer compatibilizers include PROPOLDER™ MPP2020 20 (polypropylene, available from Polygroup Inc.), PROPOLDER™ MPP2040 40 (polypropylene, available from Polygroup Inc.), NOVACOM™ HFS2100 (maleic anhydride-functionalized high-density polyethylene polymer, available from Polygroup Inc.), KEN-REACT™ CAPS™ L™ 12 / L (organometallic coupling agent, available from Kenrich Petrochemicals), KEN-REACT™ CAPOW™ L™ 12 / H (organometallic coupling agent, available from Kenrich Petrochemicals), KEN-REACT™ LICA™ 12 (organometallic coupling agent, available from Kenrich Petrochemicals), KEN-REACT™ CAPS™ KPR™ 12 / LV (organometallic coupling agent, available from Kenrich Petrochemicals), KEN-REACT™ CAPOW™ KPR™ 12 / H (organometallic coupling agent, available from Kenrich Petrochemicals), KEN-REACT™ titanates & zirconates (organometallic coupling agent, available from Kenrich Petrochemicals), VISTAMAXX™ (ethylene-propylene copolymer, available from ExxonMobil), SANTOPRENE™ (thermoplastic vulcanizate of ethylene-propylene-diene rubber and polypropylene, available from ExxonMobil), VISTALON™ (ethylene-propylene-diene rubber, available from ExxonMobil), EXACT™ (plastomer, available from ExxonMobil), EXXELOR™ (polymer resin, available from ExxonMobil), FUSABOND™ M603 (random ethylene copolymer, available from Dow),FUSABOND (trademark) E226 (anhydrous modified polyethylene, available from Dow), BYNEL (trademark) 41E710 (coextrudable adhesive resin, available from Dow), SURLYN (trademark) 1650 (ionomer resin, available from Dow), FUSABOND (trademark) P353 (chemically modified polypropylene copolymer, available from Dow), ELVALOY (trademark) PTW (ethylene terpolymer, available from Dow), ELVALOY (trademark) 3427AC (copolymer of ethylene and butyl acrylate, available from Dow), LOTADER (trademark) AX8840 (ethylene acrylate terpolymer, available from Arkema), LOTADER (trademark) 3210 (ethylene acrylate terpolymer, available from Arkema), LOTADER (trademark) 3410 (ethylene acrylate terpolymer, available from Arkema), LOTADER (trademark) 3430 (ethylene acrylate terpolymer, available from Arkema), LOTADER (trademark) 4700 (ethylene acrylate terpolymer, available from Arkema), LOTADER (trademark) AX8900 (ethylene acrylate terpolymer, available from Arkema), LOTADER (trademark) 4720 (ethylene acrylate terpolymer, available from Arkema), BAXXODUR (trademark) EC301 (amine for epoxy, available from BASF), BAXXODUR (trademark) EC311 (amine for epoxy, available from BASF), BAXXODUR (trademark) EC303 (amine for epoxy, available from BASF), BAXXODUR (trademark) EC280 (amine for epoxy, available from BASF), BAXXODUR (trademark) EC201 (amine for epoxy, available from BASF), BAXXODUR (trademark) EC130 (amine for epoxy, available from BASF), BAXXODUR (trademark) EC110 (amine for epoxy, available from BASF), styrene, polypropylene, polyamide, polycarbonate, EASTMAN (trademark) G-3003 (maleic anhydride grafted polypropylene, available from Eastman), RETAIN (trademark) (polymer modifier, available from Dow), AMPLIFY TY (trademark) (maleic anhydride graft polymer,available from Dow), INTUNE™ (olefin block copolymer, available from Dow), and any combination thereof, including but not limited to these.,

[0050] Polyamide 102 and other thermoplastic polymers (if included) can be present cumulatively in mixture 110 in an amount of about 5 wt% to about 60 wt% (or about 5 wt% to about 25 wt%, about 10 wt% to about 30 wt%, about 20 wt% to about 45 wt%, about 25 wt% to about 50 wt%, or about 40 wt% to about 60 wt%) of the combined amount of polyamide 102, other thermoplastic polymers (if included), and carrier fluid 104. Other thermoplastic polymers (if included) can be present in an amount of about 0.1 wt% to about 40 wt% (or about 0.1 wt% to about 10 wt%, about 1 wt% to about 25 wt%, or about 10 wt% to about 40 wt%) of the combined amount of polyamide 102 and other thermoplastic polymers.

[0051] Suitable carrier fluid 104 has a viscosity of about 1,000 cSt to about 150,000 cSt (or about 1,000 cSt to about 60,000 cSt, about 40,000 cSt to about 100,000 cSt, or about 75,000 cSt to about 150,000 cSt) at 25°C.

[0052] Examples of the carrier fluid 104 include, but are not limited to, silicone oil, fluorinated silicone oil, perfluorinated silicone oil, polyethylene glycol, alkyl-terminated polyethylene glycol (e.g., C1-C4 terminal alkyl groups such as tetraethylene glycol dimethyl ether (TDG)), paraffin, liquid petrolatum, mink oil, turtle oil, soybean oil, perhydrosqualene, sweet almond oil, carophyllum oil, palm oil, pearl rim oil, grapeseed oil, sesame oil, corn oil, rapeseed oil, sunflower oil, cottonseed oil, apricot oil, castor oil, avocado oil, jojoba oil, olive oil, cereal germ oil, esters of lanolinic acid, esters of oleic acid, esters of lauric acid, esters of stearic acid, aliphatic esters, higher fatty acids, aliphatic alcohols, polysiloxanes modified with fatty acids, polysiloxanes modified with aliphatic alcohols, polysiloxanes modified with polyoxyalkylene, and any combination thereof. Examples of silicone oil include, but are not limited to, polydimethylsiloxane, methylphenylpolysiloxane, alkyl-modified polydimethylsiloxane, alkyl-modified methylphenylpolysiloxane, amino-modified polydimethylsiloxane, amino-modified methylphenylpolysiloxane, fluorine-modified polydimethylsiloxane, fluorine-modified methylphenylpolysiloxane, polyether-modified polydimethylsiloxane, polyether-modified methylphenylpolysiloxane, and any combination thereof. The carrier fluid 104 may have one or more phases. For example, polysiloxanes modified with fatty acids and polysiloxanes modified with aliphatic alcohols (preferably having a similar chain length to the fatty acids and aliphatic alcohols) may form a single-phase carrier fluid 104. In another example, a carrier fluid 104 containing silicone oil and alkyl-terminated polyethylene glycol may form a two-phase carrier fluid 104.

[0053] The carrier fluid 104 may be present in the mixture 110 in an amount of about 40 wt% to about 95 wt% (or about 75 wt% to about 95 wt%, about 70 wt% to about 90 wt%, about 55 wt% to about 80 wt%, about 50 wt% to about 75 wt%, or about 40 wt% to about 60 wt%) of the combined amount of the polyamide 102 and the carrier fluid 104.

[0054] Optionally, the carrier fluid 104 may have a density of about 0.6 g / cm 3 to about 1.5 g / cm 3 and the polyamide 102 may have a density of about 0.7 g / cm 3 to about 1.7 g / cm 3 However, the polyamide has a higher density than the density of the carrier fluid.

[0055] The emulsifying stabilizers used in the methods and compositions of the present disclosure may include nanoparticles (e.g., oxide nanoparticles, carbon black, polymer nanoparticles, and combinations thereof), surfactants, etc., and any combination thereof.

[0056] The oxide nanoparticles may be metal oxide nanoparticles, non-metal oxide nanoparticles, or mixtures thereof. Examples of oxide nanoparticles include, but are not limited to, silica, titania, zirconia, alumina, iron oxide, copper oxide, tin oxide, boron oxide, cerium oxide, thallium oxide, tungsten oxide, etc., and any combination thereof. Mixed metal oxides and / or non-metal oxides such as aluminosilicates, borosilicates, and aluminoborosilicates are also included in the term metal oxides. The oxide nanoparticles may be hydrophilic or hydrophobic, and may be natural particles or the result of surface treatment of the particles. For example, silica nanoparticles having a hydrophobic surface treatment such as dimethylsilyl, trimethylsilyl, etc. may be used in the methods and compositions of the present disclosure. In addition, silica having a functional surface treatment such as a methacrylate functional group may be used in the methods and compositions of the present disclosure. Non-functionalized oxide nanoparticles may also be suitable for use.

[0057] Examples of commercially available silica nanoparticles include AEROSIL® (e.g., AEROSIL® R812S (hydrophobically modified surface and silica nanoparticles with an average diameter of about 7 nm and a BET surface area of 260 ± 30 m 2 / g), AEROSIL® RX50 (hydrophobically modified surface and silica nanoparticles with an average diameter of about 40 nm and a BET surface area of 35 ± 10 m 2 / g), AEROSIL® 380 (hydrophobically modified surface and silica nanoparticles with a BET surface area of 380 ± 30 m 2 / g)), etc., and any combination thereof, but not limited thereto.

[0058] Carbon black is another type of nanoparticle that can be present as an emulsifier stabilizer in the compositions and methods disclosed herein. Various grades of carbon black are familiar to those skilled in the art, and any of them can be used herein. Other nanoparticles that can absorb infrared rays may similarly be used.

[0059] Polymer nanoparticles are another type of nanoparticle that can be present as an emulsifier stabilizer in the disclosure herein. Suitable polymer nanoparticles may include one or more polymers that are thermosetting and / or cross-linked so as not to melt when processed by melt emulsification according to the disclosure within this specification. High molecular weight thermoplastic polymers having a high melting point or decomposition point may similarly include suitable polymer nanoparticle emulsifier stabilizers.

[0060] The nanoparticles can have an average diameter (D50 based on volume) of about 1 nm to about 500 nm (or about 10 nm to about 150 nm, about 25 nm to about 100 nm, about 100 nm to about 250 nm, or about 250 nm to about 500 nm).

[0061] The nanoparticles are about 10 m 2 / g to about 500 m 2 / g (or about 10 m 2 / g to about 150 m 2 / g, about 25 m2 / g to about 100 m 2 / g, about 100 m 2 / g to about 250 m 2 / g, or 250 m 2 / g to about 500 m 2 may have a BET surface area of ( / g).

[0062] The nanoparticles can be included in the mixture 110 at a concentration of about 0.01 wt% to about 10 wt% (or about 0.01 wt% to about 1 wt%, about 0.1 wt% to about 3 wt%, about 1 wt% to about 5 wt%, or about 5 wt% to about 10 wt%) based on the weight of the polyamide polymer 102.

[0063] The surfactant can be anionic, chaotropic, nonionic, or zwitterionic. Examples of surfactants include, but are not limited to, sodium dodecyl sulfate, sorbitan oleate, poly[dimethylsiloxane-co-[3-(2-(2-hydroxyethoxy)ethoxy)propylmethylsiloxane], sodium docusate (sodium 1,4-bis(2-ethylhexoxy)-1,4-dioxobutane-2-sulfonate), and any combination thereof. Commercially available examples of surfactants include CALFAX® DB-45 (sodium dodecyldiphenyloxide disulfonate, available from Pilot Chemicals), SPAN® 80 (sorbitan maleate nonionic surfactant), MERPOL® surfactant (available from Stepan Company), TERGITOL™ TMN-6 (water-soluble nonionic surfactant, available from DOW), TRITON® X-100 (octylphenol ethoxylate, available from SigmaAldrich), IGEPAL® CA-520 (polyoxyethylene(5) isooctylphenyl ether, available from SigmaAldrich), BRIJ® S10 (polyethylene glycol octadecyl ether, available from SigmaAldrich), and any combination thereof, but are not limited to these.

[0064] The surfactant may be included in the mixture 110 at a concentration of about 0.01 wt% to about 10 wt% (or about 0.01 wt% to about 1 wt%, about 0.5 wt% to about 2 wt%, about 1 wt% to about 3 wt%, about 2 wt% to about 5 wt%, or about 5 wt% to about 10 wt%) based on the weight of the polyamide 102. Alternatively, the mixture 110 may not contain (or be absent of) the surfactant.

[0065] The weight ratio of the nanoparticles to the surfactant may be about 1:10 to about 10:1 (or about 1:10 to about 1:1, about 1:5 to about 5:1, or about 1:1 to about 10:1).

[0066] As described above, the components 102, 104, and 106 may be added in any order and may include mixing and / or heating in the process 108 that includes the components 102, 104, and 106. For example, the emulsifying stabilizer 106 may first be dispersed in the carrier fluid 104, optionally with heating of the dispersion, before adding the polyamide polymer 102. In another non-limiting example, the polyamide polymer 102 may be heated to produce a polymer melt, to which the carrier fluid 104 and the emulsifying stabilizer 106 are added together or in either order. In yet another non-limiting example, the polyamide polymer 102 and the carrier fluid 104 may be mixed at a temperature above the melting point or softening temperature of the polyamide polymer 102 and at a shear rate sufficient to disperse the polyamide polymer melt in the carrier fluid 104. Then, the emulsifying stabilizer 106 is added to form the mixture 110 and may be maintained under suitable process conditions for a set period of time.

[0067] The process of combining components 102, 104, and 106 in any combination (reference numeral 108) can be carried out in a mixing device used in process 112 and / or in another suitable container. As a non-limiting example, polyamide polymer 102 may be heated to a temperature higher than the melting point or softening temperature of polyamide polymer 102 in the mixing device used in process 112, and emulsifying stabilizer 106 may be dispersed in carrier fluid 104 in another container. This dispersion may then be added to the melt of polyamide polymer 102 in the mixing device used in process 112.

[0068] The mixing device used in process 112 for producing molten emulsion 114 should be able to maintain molten emulsion 114 at a temperature higher than the melting point or softening temperature of polyamide polymer 102 and apply a shear rate sufficient to disperse the polymer melt as droplets in carrier fluid 104.

[0069] Examples of mixing devices used in process 112 for producing molten emulsion 114 include, but are not limited to, stirred reactors, blenders, reactors having in-line homogenizer systems, and devices derived therefrom.

[0070] Process 112 and the formation of molten emulsion 114 are carried out over a set period under suitable process conditions (e.g., temperature, shear rate, etc.).

[0071] The temperature of process 112 and the temperature at which molten emulsion 114 is formed should be higher than the melting point or softening temperature of polyamide polymer 102 and lower than the decomposition temperature of any of the components 102, 104, and 106 in mixture 110. For example, the temperature of process 112 and the formation of molten emulsion 114 may be only about 1 °C to about 50 °C (or about 1 °C to about 25 °C, about 5 °C to about 30 °C, or about 20 °C to about 50 °C) higher than the melting point or softening temperature of polyamide polymer 102, provided that the temperature of process 112 and the formation of molten emulsion 114 is lower than the decomposition temperature of any of the components 102, 104, and 106 in mixture 110.

[0072] The shear rate for the formation of Process 112 and the molten emulsion 114 should be high enough to disperse the polymer melt as droplets into the carrier fluid 104. The droplets should include droplets having a diameter of about 1000 μm or less (or about 1 μm to about 1000 μm, about 1 μm to about 50 μm, about 10 μm to about 100 μm, about 10 μm to about 250 μm, about 50 μm to about 500 μm, about 250 μm to about 750 μm, or about 500 μm to about 1000 μm).

[0073] The time for maintaining the temperature and shear rate for the formation of Process 112 and the molten emulsion 114 may be from 10 seconds to 18 hours or more (or 10 seconds to 30 minutes, 5 minutes to 1 hour, 15 minutes to 2 hours, 1 to 6 hours, or 3 to 18 hours). Without being bound by theory, it is considered that Process 112 can be stopped when a steady state of the droplet diameter is reached. That time may depend, inter alia, on the temperature, the shear rate, the composition of the polyamide polymer 102, the composition of the carrier fluid 104, and the composition of the emulsifying stabilizer 106.

[0074] The molten emulsion 114 may then be cooled (116). The cooling 116 can be from low speed (e.g., enabling the cooling of the molten emulsion under ambient conditions) to high speed (e.g., quenching). For example, the cooling rate may range from about 10 °C / hour to about 100 °C / second to almost instantaneous by quenching (e.g., dry ice) (or about 10 °C / hour to about 60 °C / hour, or about 0.5 °C / minute to about 20 °C / minute, or about 1 °C / minute to about 5 °C / minute, or about 10 °C / minute to about 60 °C / minute, or about 0.5 °C / second to about 10 °C / second, or about 10 °C / second to about 100 °C / second).

[0075] During cooling, little or no shear force may be applied to the molten emulsion 114. In some cases, the shear force applied during heating may be applied during cooling.

[0076] The cooled mixture 118 resulting from the cooling treatment 116 of the molten emulsion 114 includes solidified polyamide polymer particles 122 (or simply polyamide polymer particles) and other components 124 (e.g., the carrier fluid 104, excess emulsifying stabilizer 106, etc.). The polyamide polymer particles may be dispersed in the carrier fluid or may have settled in the carrier fluid.

[0077] Next, the cooled mixture 118 may be processed (reference numeral 120) to separate the polyamide polymer particles 122 (or simply the polyamide polymer particles 122) from the other components 124. Suitable processes include, but are not limited to, washing, filtration, centrifugation, decantation, etc., and any combination thereof.

[0078] The solvent used to wash the polyamide polymer particles 122 should generally (a) be miscible with the carrier fluid 104 and (b) be non-reactive (e.g., non-swelling and non-dissolving) with the polyamide polymer 102. The choice of solvent depends, inter alia, on the composition of the carrier fluid and the composition of the polyamide polymer 102.

[0079] Examples of solvents include hydrocarbon solvents (e.g., pentane, hexane, heptane, octane, cyclohexane, cyclopentane, decane, dodecane, tridecane, and tetradecane), aromatic hydrocarbon solvents (e.g., benzene, toluene, xylene, 2-methylnaphthalene, and cresol), ether solvents (e.g., diethyl ether, tetrahydrofuran, diisopropyl ether, and dioxane), ketone solvents (e.g., acetone and methyl ethyl ketone), alcohol solvents (e.g., methanol, ethanol, isopropanol, and n-propanol), ester solvents (e.g., ethyl acetate, methyl acetate, butyl acetate, butyl propionate, and butyl butyrate), halogenated solvents (e.g., chloroform, bromoform, 1,2-dichloromethane, 1,2-dichloroethane, carbon tetrachloride, chlorobenzene, and hexafluoroisopropanol), water, etc., and any combination thereof, but are not limited thereto.

[0080] The solvent can be removed from the polyamide polymer particles 122 by drying using a suitable method such as air drying, heat drying, vacuum drying, freeze drying, or a hybrid thereof. The heating can preferably be carried out at a temperature lower than the glass transition temperature of the polyamide polymer (e.g., about 50 °C to about 150 °C).

[0081] The polyamide polymer particles 122 after separation from the other components 124 may optionally be further classified to produce purified polyamide polymer particles 128. For example, to narrow the particle size distribution (or reduce the diameter span), the polyamide polymer particles 122 can be passed through a sieve having a pore size of about 10 μm to about 250 μm (or about 10 μm to about 100 μm, about 50 μm to about 200 μm, or about 150 μm to about 250 μm).

[0082] In another exemplary purification technique, the polyamide polymer particles 122 can be washed with water to remove the surfactant while maintaining substantially all of the nanoparticles associated with the surface of the polyamide polymer particles 122. In yet another exemplary purification technique, the polyamide polymer particles 122 can be blended with additives to obtain the desired final product. For clarity, such additives are blended with the polyamide particles 122 or other particles obtained from the methods described herein after the particles have solidified, and thus such additives are referred to herein as "external additives". Examples of external additives include flow aids, other polymer particles, fillers, etc., and any combination thereof.

[0083] In some cases, the surfactant used in the production of the polyamide polymer particles 122 may be undesirable in downstream applications. Thus, yet another exemplary purification technique may include at least substantially removing the surfactant from the polyamide polymer particles 122 (e.g., by washing and / or thermal decomposition).

[0084] The polyamide polymer particles 122 and / or the purified polyamide polymer particles 128 (referred to as particles 122 / 128) can be characterized by their composition, physical structure, etc.

[0085] As described above, the emulsifying stabilizer is at the interface between the polymer melt and the carrier fluid. As a result, when the mixture is cooled, the emulsifying stabilizer remains at or near the interface. Thus, the structure of the particles 122 / 128 generally includes (a) an emulsifying stabilizer dispersed on the outer surface of the particles 122 / 128, and / or (b) an emulsifying stabilizer embedded in the outer portion (e.g., the outer 1% by volume) of the particles 122 / 128.

[0086] Furthermore, when voids are formed inside the polymer melt droplets, the emulsifying stabilizer 106 should generally be present (and / or embedded) at the interface between the inside of the voids and the polyamide polymer. The voids generally do not contain polyamide polymer. Rather, the voids can contain, for example, a carrier fluid, air, or be empty. The particles 122 / 128 can contain up to about 5% by weight (or about 0.001% to about 5% by weight, about 0.001% to about 0.1% by weight, about 0.01% to about 0.5% by weight, about 0.1% to about 2% by weight, or about 1% to about 5% by weight) of the carrier fluid.

[0087] The polyamide polymer 102 can be present in the particles 122 / 128 in an amount of about 90% to about 99.5% by weight (or about 90% to about 95% by weight, about 92% to about 97% by weight, or about 95% to about 99.5% by weight) of the particles 122 / 128.

[0088] The emulsifying stabilizer 106 may be present in the particles 122 / 128 in an amount of about 10 wt% or less (or about 0.01 wt% to about 10 wt%, about 0.01 wt% to about 1 wt%, about 0.5 wt% to about 5 wt%, about 3 wt% to about 7 wt%, or about 5 wt% to about 10 wt%) of the particles 122 / 128. When purified to at least substantially remove surfactants or another emulsifying stabilizer, the emulsifying stabilizer 106 may be present in the particles 128 in an amount of less than 0.01 wt% (or 0 wt% to about 0.01 wt%, or 0 wt% to 0.001 wt%).

[0089] When forming polyamide microparticles in accordance with the disclosure of this specification, at least a portion of the nanoparticles, such as silica nanoparticles, can be disposed as a coating on the outer surface of the polyamide microparticles. At least a portion of the surfactant, if it is used, can likewise associate with the outer surface. The coating can be disposed substantially uniformly on the outer surface. As used herein with respect to the coating, the term "substantially uniform" refers to a uniform coating thickness over the surface positions coated by the coating composition (e.g., nanoparticles and / or surfactant), particularly over the entire outer surface. The emulsifier stabilizer 106 can form a coating that covers at least 5% (or about 5% to about 100%, about 5% to about 25%, about 20% to about 50%, about 40% to about 70%, about 50% to about 80%, about 60% to about 90%, or about 70% to about 100%) of the surface area of the particles 122 / 128. When purified to at least substantially remove the surfactant or another emulsifier stabilizer, the emulsifier stabilizer 106 can be present in the particles 128 in an amount less than 25% (or 0% to about 25%, about 0.1% to about 5%, about 0.1% to about 1%, about 1% to about 5%, about 1% to about 10%, about 5% to about 15%, or about 10% to about 25%) of the surface area of the particles 128. The coverage rate of the emulsifier stabilizer 106 on the outer surface of the particles 122 / 128 can be determined using image analysis of SEM micrographs. The emulsifier stabilizer 106 can form a coating that covers at least 5% (or about 5% to about 100%, about 5% to about 25%, about 20% to about 50%, about 40% to about 70%, about 50% to about 80%, about 60% to about 90%, or about 70% to about 100%) of the surface area of the particles 122 / 128. When purified to at least substantially remove the surfactant or another emulsifier stabilizer, the emulsifier stabilizer 106 can be present in the particles 128 in an amount less than 25% (or 0% to about 25%, about 0.1% to about 5%, about 0.1% to about 1%, about 1% to about 5%, about 1% to about 10%, about 5% to about 15%, or about 10% to about 25%) of the surface area of the particles 128. The coverage rate of the emulsifier stabilizer 106 on the outer surface of the particles 122 / 128 can be determined using image analysis of SEM micrographs.

[0090] The particles 122 / 128 may have a D10 of about 0.1 μm to about 125 μm (or about 0.1 μm to about 5 μm, about 1 μm to about 10 μm, about 5 μm to about 30 μm, about 1 μm to about 25 μm, about 25 μm to about 75 μm, about 50 μm to about 85 μm, or about 75 μm to about 125 μm), a D50 of about 0.5 μm to about 200 μm (or about 0.5 μm to about 10 μm, about 5 μm to about 50 μm, about 30 μm to about 100 μm, about 30 μm to about 70 μm, about 25 μm to about 50 μm, about 50 μm to about 100 μm, about 75 μm to about 150 μm, or about 100 μm to about 200 μm), and a D90 of about 3 μm to about 300 μm (or about 3 μm to about 15 μm, about 10 μm to about 50 μm, about 25 μm to about 75 μm, about 70 μm to about 200 μm, about 60 μm to about 150 μm, or about 150 μm to about 300 μm), with D10 < D50 < D90. The particles 122 / 128 may also have a diameter span of about 0.2 to about 10 (or about 0.2 to about 0.5, about 0.4 to about 0.8, about 0.5 to about 1.0, about 1 to about 3, about 2 to about 5, or about 5 to about 10). Without limitation, a diameter span value of 1.0 or more is considered wide, and a diameter span value of 0.75 or less is considered narrow. Without limitation, a diameter span value of 1.0 or more is considered wide, and a diameter span value of 0.75 or less is considered narrow.

[0091] In a first non-limiting example, the particles 122 / 128 may have a D10 of about 0.1 μm to about 10 μm, a D50 of about 0.5 μm to about 25 μm, and a D90 of about 3 μm to about 50 μm, with D10 < D50 < D90. The particles 122 / 128 may have a diameter span of about 0.2 to about 2.

[0092] In a second non-limiting example, the particles 122 / 128 may have a D10 of about 5 μm to about 30 μm, a D50 of about 30 μm to about 70 μm, and a D90 of about 70 μm to about 120 μm, with D10 < D50 < D90. The particles 122 / 128 may have a diameter span of about 1.0 to about 2.5.

[0093] In a third non-limiting example, the particles 122 / 128 can have a D10 of about 25 μm to about 60 μm, a D50 of about 60 μm to about 110 μm, and a D90 of about 110 μm to about 175 μm. Note that D10 < D50 < D90. The particles 122 / 128 can have a diameter span of about 0.6 to about 1.5.

[0094] In a fourth non-limiting example, the particles 122 / 128 can have a D10 of about 75 μm to about 125 μm, a D50 of about 100 μm to about 200 μm, and a D90 of about 125 μm to about 300 μm. Note that D10 < D50 < D90. The particles 122 / 128 can have a diameter span of about 0.2 to about 1.2.

[0095] In a fifth non-limiting example, the particles 122 / 128 can have a D10 of about 1 μm to about 50 μm (or about 5 μm to about 30 μm, about 1 μm to about 25 μm, or about 25 μm to about 50 μm), a D50 of about 25 μm to about 100 μm (or about 30 μm to about 100 μm, about 30 μm to about 70 μm, about 25 μm to about 50 μm, or about 50 μm to about 100 μm), and a D90 of about 60 μm to about 300 μm (or about 70 μm to about 200 μm, about 60 μm to about 150 μm, or about 150 μm to about 300 μm). Note that D10 < D50 < D90. The particles 122 / 128 can also have a diameter span of about 0.4 to about 3 (or about 0.6 to about 2, about 0.4 to about 1.5, or about 1 to about 3).

[0096] The particles 122 / 128 can have a circularity of about 0.9 or more (or about 0.90 to about 1.0, about 0.93 to about 0.99, about 0.95 to about 0.99, about 0.97 to about 0.99, or about 0.98 to 1.0).

[0097] The particles 122 / 128 can have an angle of repose of about 20° to about 45° (or about 25° to about 35°, about 30° to about 40°, or about 35° to about 45°).

[0098] Particle 122 / 128 may have a Hausner ratio of about 1.0 to about 1.5 (or about 1.0 to about 1.2, about 1.1 to about 1.3, about 1.2 to about 1.35, or about 1.3 to about 1.5).

[0099] Particle 122 / 128 has a bulk density of about 0.3 g / cm 3 ~ about 0.8 g / cm 3 (or about 0.3 g / cm 3 ~ about 0.6 g / cm 3 , about 0.4 g / cm 3 ~ about 0.7 g / cm 3 , about 0.5 g / cm 3 ~ about 0.6 g / cm 3 , or about 0.5 g / cm 3 ~ about 0.8 g / cm 3 ) and may have a bulk density of.

[0100] Depending on the temperature and shear rate of process 112, and the composition and relative concentrations of components 102, 104, and 106, different shapes of the structure constituting particle 122 / 128 have been observed. Typically, particle 122 / 128 includes substantially spherical particles (having a circularity of about 0.97 or more). However, other structures including disk structures and elongated structures have been observed in particle 122 / 128. Therefore, particle 122 / 128 may include one or more of (a) substantially spherical particles having a circularity of 0.97 or more, (b) disk structures having an aspect ratio of about 2 to about 10, and (c) elongated structures having an aspect ratio of 10 or more. Each of the (a), (b), and (c) structures has an emulsifying stabilizer dispersed on the outer surface of the (a), (b), and (c) structures and / or an emulsifying stabilizer embedded in the outer portion of the (a), (b), and (c) structures. At least some of the (a), (b), and (c) structures may aggregate. For example, the elongated structure of (c) may be located on the surface of the substantially spherical particles of (a).

[0101] Particle 122 / 128 may have a sintering window within 10 °C, preferably within 5 °C, of the sintering window of the thermoplastic polymer 102 (including one or more polyamides and optionally one or more other thermoplastic polymers).

[0102] Use of Polyamide Particles The polyamide particles described herein can be used in 3D printing processes, particularly those using selective laser sintering to promote particle consolidation. The polyamide particles of the present disclosure can exhibit advantageous properties over polymer particles having irregular shapes or a broader particle distribution, such as commercially available ones. In non-limiting examples, the polyamide particles of the present disclosure can be consolidated at a lower laser power and reduce the degree of void formation in objects produced by 3D printing.

[0103] The 3D printing process of the present disclosure includes depositing the polyamide particles of the present disclosure on the surface of a specific shape and, after deposition, heating at least a portion of the deposited polyamide particles to promote their consolidation and form a consolidated body (object), and the consolidated body has a porosity of about 1% or less after consolidation. For example, the heating and consolidation of the polyamide particles can be carried out in a 3D printing apparatus using a laser so that heating and consolidation are carried out by selective laser sintering.

[0104] Any of the polyamide particles disclosed herein can be incorporated into a composition suitable for 3D printing. The selection of the composition and type of polyamide microparticles can be made based on various factors, including but not limited to the laser output used for selective laser sintering, the type of object to be produced, and the intended use conditions of the object.

[0105] Examples of objects that can be 3D printed using the polyamide particles of the present disclosure include containers (e.g., containers for food, beverages, cosmetics, personal care compositions, pharmaceuticals, etc.), shoe soles, toys, furniture parts and decorative household goods, plastic gears, screws, nuts, bolts, cable ties, automotive parts, medical items, prostheses, orthopedic implants, aerospace / aircraft-related parts, generation of artifacts to assist in education, 3D anatomical models to assist in surgery, robotics supplies, biomedical devices (orthoses), household appliances, dental supplies, electronic devices, sports supplies, etc., but are not limited thereto.

[0106] Other uses of the polyamide microparticles of the present disclosure may include, but are not limited to, use as fillers for paints and powder coatings, inkjet materials, and electrophotographic toners.

[0107] Non-limiting exemplary embodiments A first non-limiting embodiment of the present disclosure includes a mixture comprising a polyamide, a carrier fluid that is immiscible with the polyamide, and nanoparticles (including, for example, oxide nanoparticles, carbon black, and / or polymer nanoparticles). The method includes mixing the mixture at a temperature above the melting point or softening temperature of the polyamide and at a shear rate high enough to disperse the polyamide in the carrier fluid, cooling the mixture to a temperature below the melting point or softening temperature of the polyamide to form solidified particles comprising polyamide particles having a circularity of 0.90 or greater and comprising polyamide and nanoparticles associated with the outer surface of the polyamide particles, and separating the solidified particles from the carrier fluid. The first non-limiting embodiment may further include one or more of the following elements: Element 1: At least a portion of the nanoparticles are embedded in the outer surface of the polyamide particles; Element 2: At least a portion of the polyamide particles have voids, and the voids contain nanoparticles at the void / polyamide interface; Element 3: Element 2, and the nanoparticles are embedded in the surface of the void / polyamide interface; Element 4: Element 2, and the voids contain the carrier fluid; Element 5: The solidified particles further include an elongated structure, and the elongated structure contains polyamide with nanoparticles associated with the outer surface thereof; Element 6: The nanoparticles form a coating that covers less than 5% of the surface of the polyamide particles; Element 7: The nanoparticles form a coating that covers at least 5% of the surface of the polyamide particles; Element 8: The nanoparticles form a coating that covers at least 25% of the surface of the polyamide particles; Element 9: The nanoparticles form a coating that covers at least 50% of the surface of the polyamide particles; Element 10: The polyamide is present in the mixture at 5 wt% to 60 wt% of the mixture; Element 11: The nanoparticles are present in the mixture at 0.01 wt% to 10 wt% of the polyamide; Element 12: The nanoparticles have an average diameter of 1 nm to 500 nm; Element 13: The polyamide is selected from the group consisting of aliphatic polyamides, polyphthalamides, aramids, and any combination thereof;Element 14: The polyamide is selected from the group consisting of polycaproamide, poly(hexamethylene succinamide), polyhexamethylene adipamide, polypentamethylene adipamide, polyhexamethylene sebacamide, polyundecamide, polydodecamide, polyhexamethylene terephthalamide, nylon 10,10, nylon 10,12, nylon 10,14, nylon 10,18, nylon 6,18, nylon 6,12, nylon 6,14, nylon 12,12, semi-aromatic polyamide, aromatic polyamide, polyesteramide, polyetheresteramide, polycarbonate-esteramide, polyether-block-amide elastomer, any copolymer thereof, and any combination thereof; Element 15: The melting point or softening temperature of the polyamide is 50°C to 450°C; Element 16: The carrier fluid is selected from the group consisting of silicone oil, fluorinated silicone oil, perfluorinated silicone oil, polyethylene glycol, alkyl-terminated polyethylene glycol, paraffin, liquid petrolatum, mink oil, turtle oil, soybean oil, perhydrosqualene, sweet almond oil, carophyllum oil, palm oil, pearl rim oil, grape seed oil, sesame oil, corn oil, rapeseed oil, sunflower oil, cottonseed oil, apricot oil, castor oil, avocado oil, jojoba oil, olive oil, cereal germ oil, esters of lanolinic acid, esters of oleic acid, esters of lauric acid, esters of stearic acid, aliphatic esters, higher fatty acids, aliphatic alcohols, polysiloxanes modified with fatty acids, polysiloxanes modified with aliphatic alcohols, polysiloxanes modified with polyoxyalkylene, and any combination thereof; Element 17: Element 16, and the silicone oil is selected from the group consisting of polydimethylsiloxane, methylphenylpolysiloxane, alkyl-modified polydimethylsiloxane, alkyl-modified methylphenylpolysiloxane, amino-modified polydimethylsiloxane, amino-modified methylphenylpolysiloxane, fluorine-modified polydimethylsiloxane, fluorine-modified methylphenylpolysiloxane, polyether-modified polydimethylsiloxane, polyether-modified methylphenylpolysiloxane, and any combination thereof;Element 18: The carrier fluid has a viscosity of 1,000 cSt to 150,000 cSt at 25°C; Element 19: The carrier fluid has a density of 0.6 g / cm; 3 ~1.5 g / cm 3 and the polyamide has a density of 0.7 g / cm 3 ~1.7 g / cm 3 ; Element 20: The mixing is carried out in a stirred reactor; Element 21: The mixture further contains a surfactant; Element 22: The solidified particles have a D10 of about 0.5 μm to about 125 μm, a D50 of about 1 μm to about 200 μm, and a D90 of about 70 μm to about 300 μm, and D10 < D50 < D90; Element 23: The solidified particles have a diameter span of about 0.2 to about 10; Element 24: The solidified particles have a D10 of about 5 μm to about 30 μm, a D50 of about 30 μm to about 70 μm, and a D90 of about 70 μm to about 120 μm, and D10 < D50 < D90; Element 25: It is Element 24, and the solidified particles have a diameter span of about 1.0 to about 2.5; Element 26: The solidified particles have a D10 of about 25 μm to about 60 μm, a D50 of about 60 μm to about 110 μm, and a D90 of about 110 μm to about 175 μm, and D10 < D50 < D90; Element 27: It is Element 26, and the solidified particles have a diameter span of about 0.6 to about 1.5; Element 28: The solidified particles have a D10 of about 75 μm to about 125 μm, a D50 of about 100 μm to about 200 μm, and a D90 of about 125 μm to about 300 μm, and D10 < D50 < D90; Element 29: It is Element 28, and the solidified particles have a diameter span of about 0.2 to about 1.2. Element 30: The solidified particles have a circularity of about 0.97 to about 1.0; and Element 31: The solidified particles have a Hausner ratio of about 1.0 to about 1.35. Examples of combinations include, but are not limited to: a combination of Element 1 and one or more of Elements 2 to 31; a combination of Element 2 and one or more of Elements 3 to 31; a combination of Element 10 and one or more of Elements 3 to 9 and 11 to 31; and a combination of one or more of Elements 1 to 12 and one or more of Elements 13 to 31.

[0108] A second non-limiting example of the present disclosure is a composition comprising polyamide particles having a circularity of 0.90 or greater, and particles comprising polyamide particles and nanoparticles associated with the outer surface of the polyamide particles. The second non-limiting embodiment may further include one or more of the following elements: Element 1; Element 2; Element 3; Element 4; Element 5; Element 6; Element 7; Element 8; Element 9; Element 10; Element 11; Element 12; Element 13; Element 14; Element 15; Element 22; Element 23; Element 24; Element 25; Element 26; Element 27; Element 28; Element 29; Element 30; Element 31; and Element 32: The polyamide is present in 90 wt% to 99.5 wt% of the particles. Element 2 may also be combined with one or more of Elements 16-19. Any combination of elements from the first non-limiting embodiment and Element 32, and any of the foregoing elements, may be included in the second non-limiting embodiment.

[0109] Item Claim 1. A method comprising: mixing a mixture comprising a polyamide, a carrier fluid immiscible with the polyamide, and nanoparticles at a temperature higher than the melting point or softening temperature of the polyamide and at a shear rate high enough to disperse the polyamide in the carrier fluid; cooling the mixture to below the melting point or softening temperature of the polyamide to form solidified particles comprising polyamide particles having a circularity of 0.90 or greater and comprising polyamide and nanoparticles associated with the outer surface of the polyamide particles; and separating the solidified particles from the carrier fluid.

[0110] Claim 2. The method of Claim 1, wherein at least a portion of the nanoparticles are embedded in the outer surface of the polyamide particles.

[0111] Claim 3. The method of Claim 1, wherein at least a portion of the polyamide particles have voids, and the voids contain nanoparticles at the void / polyamide interface.

[0112] Claim 4. The method of Claim 3, wherein the nanoparticles are embedded in the surface of the void / polyamide interface.

[0113] Claim 5. The method according to claim 3, wherein the void contains a carrier fluid.

[0114] Claim 6. The composition according to claim 1, wherein the solidified particles further comprise an elongated structure, and the elongated structure comprises polyamide with nanoparticles associated on the outer surface thereof.

[0115] Claim 7. The composition according to claim 1, wherein the nanoparticles form a coating covering less than 5% of the surface of the polyamide particles.

[0116] Claim 8. The composition according to claim 1, wherein the nanoparticles form a coating covering at least 5% of the surface of the polyamide particles.

[0117] Claim 9. The composition according to claim 1, wherein the nanoparticles form a coating covering at least 25% of the surface of the polyamide particles.

[0118] Claim 10. The composition according to claim 1, wherein the nanoparticles form a coating covering at least 50% of the surface of the polyamide particles.

[0119] Claim 11. The method according to claim 1, wherein the polyamide is present in the mixture at 5 wt% to 60 wt% of the mixture.

[0120] Claim 12. The method according to claim 1, wherein the nanoparticles are present in the mixture at 0.01 wt% to 10 wt% of the polyamide.

[0121] Claim 13. The method according to claim 1, wherein the nanoparticles have an average diameter of 1 nm to 500 nm.

[0122] Claim 14. The method according to claim 1, wherein the polyamide is selected from the group consisting of aliphatic polyamides, polyphthalamides, aramids, and any combination thereof.

[0123] Item 15. The method according to Item 1, wherein the polyamide is selected from the group consisting of polycaproamide, poly(hexamethylene succinamide), polyhexamethylene adipamide, polypentamethylene adipamide, polyhexamethylene sebacamide, polyundecamide, polydodecamide, polyhexamethylene terephthalamide, nylon 10,10, nylon 10,12, nylon 10,14, nylon 10,18, nylon 6,18, nylon 6,12, nylon 6,14, nylon 12,12, semi-aromatic polyamide, aromatic polyamide, polyesteramide, polyetheresteramide, polycarbonate-esteramide, polyether-block-amide elastomer, any copolymer thereof, and any combination thereof.

[0124] Item 16. The method according to Item 1, wherein the melting point or softening temperature of the polyamide is 50°C to 450°C.

[0125] Item 17. The method according to Item 1, wherein the carrier fluid is selected from the group consisting of silicone oil, fluorinated silicone oil, perfluorinated silicone oil, polyethylene glycol, alkyl-terminated polyethylene glycol, paraffin, liquid petrolatum, mink oil, turtle oil, soybean oil, perhydrosqualene, sweet almond oil, carophyllum oil, palm oil, palm kernel oil, grape seed oil, sesame oil, corn oil, rapeseed oil, sunflower oil, cottonseed oil, apricot oil, castor oil, avocado oil, jojoba oil, olive oil, cereal germ oil, esters of lanolinic acid, esters of oleic acid, esters of lauric acid, esters of stearic acid, aliphatic esters, higher fatty acids, aliphatic alcohols, polysiloxanes modified with fatty acids, polysiloxanes modified with aliphatic alcohols, polysiloxanes modified with polyoxyalkylene, and any combination thereof.

[0126] Item 18. The method according to item 17, wherein the silicone oil is selected from the group consisting of polydimethylsiloxane, methylphenylpolysiloxane, alkyl-modified polydimethylsiloxane, alkyl-modified methylphenylpolysiloxane, amino-modified polydimethylsiloxane, amino-modified methylphenylpolysiloxane, fluorine-modified polydimethylsiloxane, fluorine-modified methylphenylpolysiloxane, polyether-modified polydimethylsiloxane, polyether-modified methylphenylpolysiloxane, and any combination thereof.

[0127] Item 19. The method according to item 1, wherein the carrier fluid has a viscosity of 1,000 cSt to 150,000 cSt at 25°C.

[0128] Item 20. The method according to item 1, wherein the carrier fluid has a density of 0.6 g / cm 3 ~1.5 g / cm 3 and the polyamide has a density of 0.7 g / cm 3 ~1.7 g / cm 3 .

[0129] Item 21. The method according to item 1, wherein the mixing is carried out in a stirred reactor.

[0130] Item 22. The method according to item 1, wherein the mixture further comprises a surfactant.

[0131] Item 23. The method according to item 1, wherein the solidified particles have a D10 of about 0.5 μm to about 125 μm, a D50 of about 1 μm to about 200 μm, and a D90 of about 70 μm to about 300 μm, and D10 < D50 < D90.

[0132] Item 24. The method according to item 1, wherein the solidified particles have a diameter span of about 0.2 to about 10.

[0133] Item 25. The method according to item 1, wherein the solidified particles have a D10 of about 5 μm to about 30 μm, a D50 of about 30 μm to about 70 μm, and a D90 of about 70 μm to about 120 μm, and D10 < D50 < D90.

[0134] Item 26. The method according to Item 25, wherein the solidified particles have a diameter span of about 1.0 to about 2.5.

[0135] Item 27. The method according to Item 1, wherein the solidified particles have a D10 of about 25 μm to about 60 μm, a D50 of about 60 μm to about 110 μm, and a D90 of about 110 μm to about 175 μm, and D10 < D50 < D90.

[0136] Item 28. The method according to Item 27, wherein the solidified particles have a diameter span of about 0.6 to about 1.5.

[0137] Item 29. The method according to Item 1, wherein the solidified particles have a D10 of about 75 μm to about 125 μm, a D50 of about 100 μm to about 200 μm, and a D90 of about 125 μm to about 300 μm, and D10 < D50 < D90.

[0138] Item 30. The method according to Item 29, wherein the solidified particles have a diameter span of about 0.2 to about 1.2.

[0139] Item 31. The method according to Item 1, wherein the solidified particles have a circularity of about 0.97 to about 1.0.

[0140] Item 32. The method according to Item 1, wherein the solidified particles have a Hausner ratio of about 1.0 to about 1.35.

[0141] Item 33. The method according to Item 1, wherein the nanoparticles include oxide nanoparticles.

[0142] Item 34. The method according to Item 1, wherein the nanoparticles include carbon black.

[0143] Item 35. The method according to Item 1, wherein the nanoparticles include polymer nanoparticles.

[0144] Item 36. The method according to Item 1, wherein the mixture further includes a thermoplastic polymer that is not polyamide.

[0145] Item 37. The method according to item 36, wherein the thermoplastic polymer is a thermoplastic elastomer.

[0146] Item 38. A composition comprising particles containing polyamide particles having a circularity of 0.90 or more and nanoparticles associated with the outer surface of the polyamide and the polyamide particles.

[0147] Item 39. The composition according to item 38, wherein at least a part of the nanoparticles is embedded in the outer surface of the particles.

[0148] Item 40. The composition according to item 38, wherein the polyamide is present in an amount of 90% to 99.5% by weight of the particles.

[0149] Item 41. The composition according to item 38, wherein at least a part of the particles has voids, and the voids contain nanoparticles at the void / polyamide interface.

[0150] Item 42. The composition according to item 41, wherein the nanoparticles are embedded at the void / polyamide interface.

[0151] Item 43. The composition according to item 41, wherein the voids contain a carrier fluid having a viscosity of 1,000 cSt to 150,000 cSt at 25°C.

[0152] Item 44. The composition according to item 38, wherein the particles further comprise an elongated structure, and the elongated structure contains polyamide with nanoparticles associated with the outer surface of the elongated structure.

[0153] Item 45. The composition according to item 38, wherein the nanoparticles form a coating covering less than 5% of the surface of the particles.

[0154] Item 46. The composition according to item 38, wherein the nanoparticles form a coating covering at least 5% of the particle surface.

[0155] Item 47. The composition according to item 38, wherein the nanoparticles form a coating covering at least 25% of the particle surface.

[0156] Item 48. The composition according to item 38, wherein the nanoparticles form a coating that covers at least 50% of the particle surface.

[0157] Item 49. The composition according to item 38, wherein the nanoparticles have an average diameter of 1 nm to 500 nm.

[0158] Item 50. The composition according to item 38, wherein the polyamide is selected from the group consisting of aliphatic polyamides, polyphthalamides, aramids, and any combination thereof.

[0159] Item 51. The composition according to item 38, wherein the polyamide is selected from the group consisting of polycaproamide, poly(hexamethylene succinamide), polyhexamethylene adipamide, polypentamethylene adipamide, polyhexamethylene sebacamide, polyundecamide, polydodecamide, polyhexamethylene terephthalamide, nylon 10,10, nylon 10,12, nylon 10,14, nylon 10,18, nylon 6,18, nylon 6,12, nylon 6,14, nylon 12,12, semi-aromatic polyamides, aromatic polyamides, polyester amides, polyether ester amides, polycarbonate-ester amides, polyether-block-amide elastomers, any copolymers thereof, and any combination thereof.

[0160] Item 52. The composition according to item 38, wherein the melting point or softening temperature of the polyamide is 50°C to 450°C.

[0161] Item 53. The composition according to item 38, wherein the particles have a D10 of about 0.5 μm to about 125 μm, a D50 of about 1 μm to about 200 μm, and a D90 of about 70 μm to about 300 μm, and D10 < D50 < D90.

[0162] Item 54. The composition according to item 53, wherein the particles have a diameter span of about 0.2 to about 10.

[0163] Item 55. The composition according to item 38, wherein the particles have a D10 of about 5 μm to about 30 μm, a D50 of about 30 μm to about 70 μm, and a D90 of about 70 μm to about 120 μm, and D10 < D50 < D90.

[0164] Item 56. The composition according to item 55, wherein the particles have a diameter span of about 1.0 to about 2.5.

[0165] Item 57. The composition according to item 38, wherein the particles have a D10 of about 25 μm to about 60 μm, a D50 of about 60 μm to about 110 μm, and a D90 of about 110 μm to about 175 μm, and D10 < D50 < D90.

[0166] Item 58. The composition according to item 57, wherein the particles have a diameter span of about 0.6 to about 1.5.

[0167] Item 59. The composition according to item 38, wherein the particles have a D10 of about 75 μm to about 125 μm, a D50 of about 100 μm to about 200 μm, and a D90 of about 125 μm to about 300 μm, and D10 < D50 < D90.

[0168] Item 60. The composition according to item 59, wherein the solidified particles have a diameter span of about 0.2 to about 1.2.

[0169] Item 61. The composition according to item 38, wherein the particles have a circularity of about 0.90 to about 1.0.

[0170] Item 62. The composition according to item 38, wherein the particles have a Hausner ratio of about 1.0 to about 1.5.

[0171] Item 63. The composition according to item 38, wherein the nanoparticles include oxide nanoparticles.

[0172] Item 64. The composition according to item 38, wherein the nanoparticles include carbon black.

[0173] Item 65. The composition according to item 38, wherein the nanoparticles include polymer nanoparticles.

[0174] Item 66. The composition according to item 38, wherein the polyamide particles further contain a thermoplastic polymer that is not a polyamide.

[0175] Item 67. The composition according to item 66, wherein the thermoplastic polymer is a thermoplastic elastomer.

[0176] Unless otherwise stated, all numbers representing amounts of components, properties such as molecular weight, and process conditions used in this specification and the associated claims should be understood to be modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and the appended claims are approximations that may vary depending upon the desired properties sought to be obtained by embodiments of the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be construed in light of the reported number of significant digits and by applying ordinary rounding techniques.

[0177] One or more exemplary embodiments incorporating the embodiments of the invention disclosed herein are presented herein. For clarity, not all features of a physical implementation are described or shown in this application. In developing a physical implementation incorporating an embodiment of the invention, it will be understood that numerous implementation-specific decisions must be made in order to achieve the developer's goals, such as compliance with system-related, business-related, government-related, and other constraints, which may vary by implementation and sometimes. Although the developer's efforts may be time-consuming, such efforts would be routine work for those skilled in the art and would result in the benefits of this disclosure.

[0178] Compositions and methods are described herein using the term "comprising" various components or steps, but the compositions and methods may also "consist essentially of" or "consist of" various components and steps.

[0179] The following examples of preferred or representative embodiments are given to facilitate a better understanding of the embodiments of the present invention. The following examples should not be construed as limiting or defining the scope of the present invention.

Example

[0180] Example 1. Using a 1 L stirred reactor available from Parr Instruments, polyamide 6 particles were prepared by melt emulsification. The reactor was filled with 20 wt% polyamide 6 and 80 wt% of 10,000 cSt PDMS oil. The mixture was then heated to 225 °C while stirring at 1000 rpm using a double four-blade propeller. After about 60 minutes, the mixture was discharged onto dry ice from the reactor to quench the mixture. The mixture was then filtered and washed to recover the polymer particles. The obtained polymer particles were passed through a 150 μm sieve. About 40 wt% of the polyamide 6 that passed through the 150 μm sieve was charged to the reactor. Figure 2 is an SEM micrograph of the particles after sieving, showing a wide range of particle sizes.

[0181] Example 2. Using a 2 L glass reactor manufactured by Buchi AG, polyamide 12 particles were prepared by melt emulsification. The reactor was filled with 1 wt% AEROSIL® R812S silica nanoparticles in 10,000 cSt PDMS oil (relative to the weight of polyamide 12 in the final mixture). After heating the mixture to 200 °C, polyamide 12 pellets were added in an amount of 23 wt% based on the combined weight of PDMS oil and polyamide 12. The reactor was mixed at 500 rpm for 30 minutes. The obtained mixture was discharged and cooled to ambient temperature at a rate of about 1 °C to about 3 °C per minute. The mixture was then washed with heptane and filtered through a 90 mm WHATMAN® #1 paper filter to recover the polymer particles. The obtained polymer particles were air-dried overnight in a draft. The dried particles had a D50 of about 227 μm, and the dried particles that passed through a 150 μm sieve had a D50 of about 124 μm.

[0182] Example 3. Particles of polyamide 12 (Samples 3-1 to 3-44) were prepared by melt emulsification in a 1 L glass kettle reactor. 10,000 cSt PDMS oil, 23% polyamide 12 (obtained from RTP, EMX-Grivory, or Arkema) relative to the combined weight of PDMS oil and polyamide 12, and a desired amount of silica nanoparticles (AEROSIL® R812S or AEROSIL® RX50) relative to the weight of polyamide 12 were added to the glass kettle. The order of addition was either (c) mixing the PDMS oil and silica nanoparticles into a good dispersion and then adding the polyamide, or (d) adding the PDMS oil, polyamide, and silica nanoparticles prior to mixing. Next, the nitrogen headspace purge was turned on and the mixture was heated to the desired temperature (e.g., 200 °C, 210 °C, or 220 °C) at 260 rpm for 90 minutes. Once that temperature was reached, the rotor speed was increased to the desired rpm. Samples were taken at various time points. Once sampling was complete, heating and stirring were stopped, the reactor was cooled to room temperature, and the mixture was discharged. The resulting mixture was filtered and washed with heptane. The obtained particles were air dried overnight in a draft. Optionally, the dried particles were screened (scr) through a 150 μm sieve. Table 1 lists the details of the experiment and the characteristics of the obtained particles.

[0183] For Samples 3-45 to 3-47, polyamide 12 particles were prepared by melt emulsification using a 2 L stainless steel reactor manufactured by Buchi AG. The reactor was filled with 0.67 wt% AEROSIL® R812S silica nanoparticles in 60,000 cSt PDMS oil (relative to the weight of polyamide 12 in the final mixture) and sealed without N2 purge. The mixture was heated to 250 °C at a heating rate of 3.68 °C / min, and then pellets of polyamide 12 at 30 wt% relative to the combined weight of PDMS oil and polyamide 12 were added. When the reactor temperature reached 245 °C, the vent valve was slowly opened and the reactor was purged with N2 at a flow rate of 2 - 3 scfh. The reactor was mixed at 650 rpm for 60 minutes. The resulting mixture was cooled to below 60 °C with gentle stirring at 50 rpm and discharged. Then, the treated samples taken at 40 minutes, 60 minutes, and at final room temperature were washed with heptane and filtered through a 90 mm WHATMAN® #1 paper filter to recover the polymer particles. The obtained polymer particles were air dried overnight in a draft. The dried particles had a D50 of about 21.3 μm, and the final dried particles passing through a 150 μm sieve had a D50 of about 21.5 μm.

[0184] For Samples 3-48 to 3-50, polyamide 12 particles were prepared by melt emulsification using a 2 L stainless steel reactor manufactured by Buchi AG. The reactor was filled with 0.67 wt% AEROSIL® R812S silica nanoparticles in 60,000 cSt PDMS oil (relative to the weight of polyamide 12 in the final mixture) and purged with N2 at a flow rate of 2 - 3 scfh. The mixture was heated to 250 °C at a ramp rate of 3.68 °C / min, and then pellets of polyamide 12 at 30 wt% relative to the combined weight of PDMS oil and polyamide 12 were added. The reactor was mixed at 650 rpm for 60 minutes. The resulting mixture was cooled to below 60 °C while gently stirring at 50 rpm and discharged. Process samples taken at the 50-minute and 60-minute time points and at room temperature were then washed with heptane and filtered through a 90 mm WHATMAN® #1 paper filter to recover the polymer particles. The final room temperature samples were aggregated and the particle size was not measured. The polymer particles obtained and taken at 60 minutes were air dried overnight in a draft. The dried particles had a D50 of approximately 25.8 μm, and the dried particles passing through a 150 μm sieve had a D50 of approximately 26.4 μm.

[0185] For Samples 3-51 to 3-53, polyamide 12 particles were prepared by melt emulsification using a 2 L stainless steel reactor manufactured by Buchi AG. The reactor was filled with 0.67 wt% AEROSIL® R812S silica nanoparticles in 60,000 cSt PDMS oil (relative to the weight of polyamide 12 in the final mixture) and purged with N2 at a flow rate of 2 to 3. The mixture was heated to 250 °C at a ramp rate of 5.68 °C / min, and then 30 wt% polyamide 12 pellets were added relative to the combined weight of PDMS oil and polyamide 12. The reactor was mixed at 650 rpm for 60 minutes. The resulting mixture was cooled to below 60 °C while gently stirring at 50 rpm and discharged. Next, the process samples taken at the 60-minute time point and at room temperature were washed with heptane and filtered through a 90 mm WHATMAN® #1 paper filter to recover the polymer particles. The final room temperature samples were aggregated and the particle size was not measured. The obtained polymer particles taken at 60 minutes were air-dried overnight in a draft. The dried particles had a D50 of approximately 33.8 μm, and the dried particles passing through a 150 μm sieve had a D50 of approximately 34.9 μm.

[0186]

Table 1-1

[0187]

Table 1-2

[0188] Figure 3 shows the SEM micrograph of Sample 3-4. Figure 4 shows the SEM micrograph of Sample 3-10. Figure 5 shows the SEM micrograph of Sample 3-15. Figure 6 shows the SEM micrograph of Sample 3-26. Figure 7 shows the SEM micrograph of Sample 3-30. Figures 8 to 11 show the SEM micrographs of Samples 3-31, 3-32, 3-33, and 3-34.

[0189] This example shows that reducing the concentration of silica nanoparticles in the mixture increases the particle size but decreases the diameter span (for example, compare 3-17 to 3-18 and 3-28 to 3-29). Further, increasing the temperature decreases the particle size but increases the diameter span (for example, compare 3-17 to 3-18, 3-20 to 3-21, and 3-24 to 3-25). It is also clear that a mixing time exceeding about 10 minutes has a minimal effect on the particle size and diameter span.

[0190] Example 4. SEM micrographs of commercially available polyamide particle materials used in 3D printing were taken. See Table 2.

[0191]

Table 2

[0192] Comparing the SEM micrographs of the commercially available samples with those of Samples 3-4, 3-10, 3-15, 3-26, 3-30, 3-31, 3-32, 3-33, and 3-34 of Example 3, the particles produced by the method described herein have a higher circularity and a higher silica nanoparticle coverage on the surface of the polyamide particles.

[0193] Example 5. Three sets of samples were prepared using RTP polyamide 12. 10,000 cSt PDMS, 23 wt% polyamide 12 based on the combined weight of PDMS and polyamide, 1 wt% Aerosil® R812S silica nanoparticles based on the weight of the polyamide, and optionally a surfactant (wt% based on the weight of the polyamide) were placed in a glass kettle reactor. The headspace was purged with argon and the reactor was maintained under a positive argon pressure. The components were heated above 220 °C over about 60 minutes with stirring at 300 rpm. At the above temperature, the rotation speed was increased to 1250 rpm. This treatment was stopped after 90 minutes and cooled to room temperature with stirring. The resulting mixture was filtered and washed with heptane. A portion of the obtained particles was screened (scr) through a 150 μm sieve. Table 3 includes additional components of the mixture and properties of the obtained particles.

[0194]

Table 3

[0195] Figures 16 and 17 are the volume density particle size distributions of the screened and unscreened particles, respectively.

[0196] This example shows that the inclusion of a surfactant and the composition of the surfactant can be another tool used to adjust the characteristics of the particles.

[0197] Example 6. Polyamide 12 microparticles were produced using a 25 mm² twin-screw extruder (Werner & Pfleiderer ZSK-25). The carrier fluid was PDMS oil with a viscosity of 60,000 cSt at room temperature. The concentrations of the components in the final mixture in the extruder are shown in Table 4. Polymer pellets were added to the extruder, brought to a predetermined temperature, and then a preheated carrier liquid in which silica nanoparticles were dispersed was added to the molten polymer in the extruder. The other operating parameters are shown in Table 4. The mixture was then discharged into a container and cooled to room temperature over several hours. Light scattering particle size data are also provided in Table 4.

[0198]

Table 4

[0199] Accordingly, the present invention is well adapted to attain the above-described objects and advantages, as well as the inherent advantages therein. The specific embodiments disclosed above are merely exemplary, and the present invention can be modified and implemented in different but equivalent ways that will be apparent to those skilled in the art having the benefit of the teachings herein. Further, it is not intended to be limited to the details of the structures or designs shown herein other than as described in the following claims. Accordingly, the specific exemplary embodiments disclosed above may be varied, combined, or modified, and it is obvious that all such variations are contemplated within the scope and spirit of the present invention. The present invention, as exemplified herein, may be practiced in the absence of any element specifically disclosed herein and / or in the absence of any of the elements disclosed herein. Compositions and methods are described in terms of the terms "comprising," "containing," or "including" various components or steps, but the compositions and methods may also "consist essentially of" or "consist of" the various components and steps. All numbers and ranges disclosed above may vary somewhat. Whenever a numerical range having a lower limit and an upper limit is disclosed, any number and any included range within that range are specifically disclosed as if they were individually disclosed. In particular, all ranges of values (in the form of "from about a to about b," or equivalently "approximately a to b," or equivalently "from approximately a - b" as disclosed herein) are to be understood to describe all numbers and ranges within the broad range of values. Also, the terms in the claims have their plain ordinary meaning unless explicitly and clearly defined by the patent owner. Additionally, when used in the claims, the indefinite articles "a" or "an" are defined herein to mean one or more of the elements that they introduce.

Claims

1. Shearing a mixture comprising a polyamide, a carrier fluid immiscible with the polyamide, and nanoparticles at a temperature higher than the melting point or softening temperature of the polyamide and at a shear rate high enough to disperse the polyamide in the carrier fluid, Cooling the mixture to below the melting point or softening temperature of the polyamide to form solidified particles comprising polyamide particles having a circularity of 0.90 or more, the polyamide particles comprising the polyamide and the nanoparticles physically adhered to the outer surface of the polyamide particles (wherein the polyamide particles have a D10 of 0.5 μm to 125 μm, a D50 of 1 μm to 200 μm, and a D90 of 70 μm to 300 μm, and D10 < D50 < D90), and Separating the solidified particles from the carrier fluid, wherein the carrier fluid is selected from the group consisting of silicone oil, fluorinated silicone oil, perfluorinated silicone oil, polyethylene glycol, alkyl-terminated polyethylene glycol, paraffin, liquid petrolatum, mink oil, turtle oil, soybean oil, perhydrosqualene, sweet almond oil, carophyllum oil, palm oil, palm kernel oil, grape seed oil, sesame oil, corn oil, rapeseed oil, sunflower oil, cottonseed oil, apricot oil, castor oil, avocado oil, jojoba oil, olive oil, cereal germ oil, esters of lanolinic acid, esters of oleic acid, esters of lauric acid, esters of stearic acid, aliphatic esters, higher fatty acids, aliphatic alcohols, polysiloxanes modified with fatty acids, polysiloxanes modified with aliphatic alcohols, polysiloxanes modified with polyoxyalkylene, and any combination thereof.

2. The method according to claim 1, wherein at least a part of the nanoparticles extends inside the outer surface of the polyamide particles.

3. The method according to claim 1, wherein the nanoparticles are present in the mixture at 0.01% to 10% by weight based on the weight of the polyamide.

4. The method according to claim 1, wherein the temperature at the time of shearing exceeds the melting point or softening temperature of the polyamide by 1°C to 50°C. **Claim 5** The method according to claim 1, wherein the cooling is carried out at a rate of 10°C / hour to 100°C / second.

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