Composite nylon powder as well as preparation method and application thereof

Abstract

The invention relates to composite nylon powder as well as a preparation method and application thereof. The composite nylon powder is prepared through a solvent precipitation method, at least one of the copper powder, the modified silicon dioxide and the modified montmorillonite serves as a modifier, operation is easy and convenient, the prepared composite nylon powder has the particle size and the melting point suitable for the SLS technology, and the mechanical property of a sintered material is outstanding.

Description

Technical Field

[0001] The present invention relates to the field of nylon powder, and in particular to a composite nylon powder and a preparation method and application thereof. Background Art

[0002] PA (nylon) is a typical crystalline polymer material with advantages such as high thermal stability, excellent comprehensive mechanical properties, low melt viscosity, good toughness and good wear resistance. PA powder material can be sintered through the selective laser sintering (SLS) process to obtain sintered parts with high strength and dense structure. PA12, as the PA material with the lowest amide group content, has the lowest water absorption rate of all grades and a low melting point. The engineering parts prepared with PA12 have the lowest molding shrinkage rate, making it very suitable for use as a molding raw material in the SLS process.

[0003] With the recent development of 3D printing technology, SLS has demonstrated numerous advantages over other manufacturing techniques. PA powder materials excel in 3D printing. According to research, PA12 accounts for 90% of the market share for commercial polymer powder materials used in SLS processes. The exceptional properties of PA12 under SLS processing remain unmatched by other polymers.

[0004] With the gradual development and popularization of SLS technology, the functionality provided by single polymer materials is limited, failing to meet the demand for multifunctional devices in practical applications. Polymer materials are more easily modified to enhance the performance of individual materials. While PA materials offer good overall performance, mechanical properties and thermal deformation resistance still need to be improved when preparing certain functional components with demanding performance requirements. Furthermore, SLS places very stringent demands on PA powders, typically requiring a particle size distribution within the range of 30-150μm (some literature reports a particle size distribution of 20-80μm as optimal), a smooth surface, and a nearly spherical geometry. Industrially produced PA resins are generally pelletized. To obtain a spherical PA12 powder with an appropriate particle size distribution and a regular shape, the pellets must be processed. Different preparation methods produce different results, so choosing the right powder preparation method plays a crucial role.

[0005] Therefore, the performance of the material can be further improved by modifying the PA material, that is, preparing composite nylon powder to meet the performance requirements of sintered parts in processing and production. Summary of the Invention

[0006] In response to the problems existing in the prior art, the present invention provides a composite nylon powder and a preparation method and application thereof. The composite nylon powder has a particle size and melting point suitable for the SLS process, and the sintered material has outstanding mechanical properties.

[0007] In the present invention, the composite nylon powder comprises: 80-99% of nylon and 1-20% of a modifier, wherein the modifier is at least one of copper powder, modified silicon dioxide and modified montmorillonite.

[0008] Preferably, the nylon is selected from at least one of nylon 6, nylon 66, nylon 11 and nylon 12, more preferably nylon 12.

[0009] Preferably, the composite nylon powder is spherical or quasi-spherical, and has a particle size distribution of D10 = 0.5-25 μm, D50 = 25-80 μm, and D90 = 85-120 μm; more preferably, D10 is 0.5 μm, 1 μm, 2 μm, 5 μm, 10 μm, 15 μm, 20 μm, and 25 μm, D50 is 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, and 80 μm, and D90 is 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, and 120 μm. Still preferably, the particle size distribution is D10=3-15 μm, D50=40-65 μm, and D90=95-110 μm.

[0010] Preferably, the composite nylon powder has a core-shell structure, wherein the core is the modifier and the shell is nylon.

[0011] Preferably, the modifier is copper powder, or modified silicon dioxide, or modified montmorillonite, or a mixture of copper powder and modified silicon dioxide in a mass ratio of 1-2:2-1.

[0012] Most preferably, the modifier is a mixture of copper powder and modified silicon dioxide in a mass ratio of 1:1.

[0013] Preferably, the content of the modifier is 1-10%, preferably 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%.

[0014] When the modifier is copper powder, modified silicon dioxide, or a mixture of copper powder and modified silicon dioxide in a mass ratio of 1-2:2-1, the content of the modifier is 5-10%. When the modifier is modified montmorillonite, the content of the modifier is 1-5%, preferably 1-3%.

[0015] Preferably, the copper powder is ultrafine copper powder with a particle size of 300 to 500 mesh, preferably 400 mesh.

[0016] Preferably, the particle size of the modified silica and the modified montmorillonite is less than 100 μm.

[0017] In a preferred embodiment, the modified silica is a product of silica modified with a silane coupling agent.

[0018] Preferably, the preparation method of the modified silicon dioxide comprises:

[0019] Silicon dioxide is reacted with a silane coupling agent in an organic solvent to obtain modified silicon dioxide.

[0020] Preferably, the method comprises: ultrasonically dispersing silicon dioxide in anhydrous ethanol to obtain a silicon dioxide dispersion solution; dropwise adding glacial acetic acid into a 40-60% ethanol aqueous solution to adjust the solution pH to 3-4, adding a certain amount of silane coupling agent, mixing and stirring to pre-decompose the silane coupling agent, and then adding the silane coupling agent to the silicon dioxide dispersion solution, heating and refluxing the solution, centrifuging, washing, drying, grinding, and sieving to obtain modified silicon dioxide.

[0021] Preferably, the silane coupling agent is selected from at least one of KH550, KH560, KH570, and KH792.

[0022] In a preferred embodiment, the modified montmorillonite is a product obtained by modifying montmorillonite with a long-chain cationic surfactant.

[0023] Preferably, the long-chain cationic surfactant is at least one of dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, didodecyldimethylammonium chloride, ditetradecyldimethylammonium chloride, dihexadecyldimethylammonium chloride, dioctadecyldimethylammonium chloride, didodecyldimethylammonium bromide, ditetradecyldimethylammonium bromide, dihexadecyldimethylammonium bromide, disoctadecyldimethylammonium bromide, dodecylamine, tetradecylamine, hexadecylamine and octadecylamine.

[0024] Preferably, the preparation method of the modified montmorillonite comprises:

[0025] The modified montmorillonite is obtained by reacting the montmorillonite with a long-chain cationic surfactant in water.

[0026] Preferably, the method comprises: stirring and mixing montmorillonite with water at 50-80° C. to form a montmorillonite solution; dissolving a long-chain cationic surfactant in water and adjusting the pH to 2.5-3.5 with concentrated hydrochloric acid, then adding the surfactant dropwise to the montmorillonite solution, stirring for reaction, washing, drying, grinding, and sieving to obtain modified montmorillonite.

[0027] In one embodiment, the method for preparing the composite nylon powder comprises:

[0028] Add nylon and methanol or ethanol into the autoclave, then add the modifier, seal and heat to 160-175°C, keep constant temperature and pressure for 1-5 hours, then cool to precipitate the composite nylon powder, and obtain the composite nylon powder through discharge, separation, washing, drying, grinding and sieving.

[0029] Preferably, the methanol is more than 90% methanol, and the ethanol is more than 90% ethanol; more preferably, the methanol is 95% methanol, and the ethanol is 95% ethanol.

[0030] Preferably, the mass ratio of nylon to methanol or ethanol is 1:6-20, preferably 1:8-10.

[0031] Preferably, heat to 170-175° C. and keep warm for 2-3 hours.

[0032] Preferably, the temperature is cooled to below 60°C.

[0033] Preferably, it is sieved through a 150 mesh sieve.

[0034] In another embodiment, the present invention also provides a method for preparing the composite nylon powder, the preparation method comprising:

[0035] Add nylon and methanol or ethanol into an autoclave, seal and heat to 160-175°C, maintain constant temperature and pressure for 1-5 hours, then cool to allow composite nylon powder to precipitate, and obtain composite nylon powder through discharge, separation, washing, drying, grinding and sieving.

[0036] Preferably, the methanol is more than 90% methanol, and the ethanol is more than 90% ethanol; more preferably, the methanol is 95% methanol, and the ethanol is 95% ethanol.

[0037] Preferably, the mass ratio of nylon to methanol or ethanol is 1:6-20, preferably 1:8-10.

[0038] Preferably, heat to 170-175° C. and keep warm for 2-3 hours.

[0039] Preferably, the temperature is cooled to below 60°C.

[0040] Preferably, it is sieved through a 150 mesh sieve.

[0041] In another embodiment, the present invention also provides a composite nylon powder prepared by the method for preparing the composite nylon powder.

[0042] In another embodiment, the present invention also provides an application of the composite nylon powder, wherein the composite nylon powder is used for 3D printing.

[0043] Beneficial effects

[0044] The present invention provides a composite nylon powder, a preparation method, and an application thereof. The composite nylon powder of the present invention is prepared by a solvent precipitation method, which is simple to operate. The obtained composite nylon powder has a particle size and melting point suitable for the SLS process, and the sintered material has outstanding mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 : Flow chart of conditions for modifying nano-SiO2;

[0046] Figure 2 : Infrared spectrum test results of silica samples before and after modification;

[0047] Figure 3 :Flow chart of conditions for modifying montmorillonite;

[0048] Figure 4 : Infrared spectrum test results of montmorillonite samples before and after modification;

[0049] Figure 5 : Experimental flow chart for preparing nylon 12 powder;

[0050] Figure 6 : 150x scanning electron microscope image of PA12 powder;

[0051] Figure 7 : 150x scanning electron microscopy image of 10% SiO2 / PA12 powder;

[0052] Figure 8 : 150x scanning electron microscopy image of 10% Cu / PA12 powder;

[0053] Figure 9 : 150x scanning electron microscopy image of 10% Cu+SiO2 / PA12 powder;

[0054] Figure 10 : 150x scanning electron microscopy image of 10% CMNT / PA12 powder. DETAILED DESCRIPTION

[0055] The present invention is described in more detail below to facilitate understanding of the present invention.

[0056] The experimental methods in the following examples are all conventional methods unless otherwise specified. If no specific techniques or conditions are specified in the examples, they were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0057] Instruments and equipment

[0058] Laboratory reactor; beaker; glass rod; round-bottom flask; condenser; analytical balance; desiccator; pH meter; centrifuge; constant temperature water bath; ultrasonic cleaning machine; filtration device (circulating water multi-purpose filtration pump), filter flask; drying oven; mortar; rock crusher; MS2000 laser particle size distribution analyzer (wet dispersion system, multiple narrow peak mode (spherical)); Fourier transform infrared spectrometer.

[0059] Preparation Example 1: Modification of Nanosilica

[0060] The modification scheme of nano-SiO2 is as follows: Figure 1 As shown, 10g of nano-silica was poured into 250mL of anhydrous ethanol and ultrasonically dispersed for 30min to obtain a dispersed solution of nano-SiO2; 15mL of water and 15mL of anhydrous ethanol were mixed, glacial acetic acid was added dropwise to adjust the pH of the solution to about 3.5, a certain amount of KH550 was added so that the silane coupling agent KH550 content was 7% of the ethanol diluted solution, mixed and stirred to pre-decompose KH550, and the above mixed liquid was slowly added to the dispersed solution of nano-SiO2; the obtained mixed solution was stirred and refluxed at 70°C for 4h (stirring speed was 420r / min), and after the reaction was completed, it was centrifuged and the solid was repeatedly washed with anhydrous ethanol and deionized water to remove residual coupling agent molecules on the solid surface. The obtained solid was placed in a drying oven and dried at 80°C, and then ground for 20min. Finally, a modified SiO2 powder with a particle size of less than 100μm was screened through a 150-mesh standard test sieve.

[0061] Preparation Example 2: Modification of Nanosilica

[0062] The same as Example 1, wherein the content of silane coupling agent KH550 is set to 14% of the ethanol diluted solution to obtain modified nano-SiO2.

[0063] After silica is modified with silane coupling agent, it should be at 1650cm -1 There is a characteristic absorption peak of the NH in-plane deformation vibration of the -NH2 functional group at 3500 cm -1 The NH stretching vibration peak of the -NH2 functional group appears near 2950cm -1 The methyl and methylene stretching vibration peaks of the coupling agent appear on the left and right. Figure 2 As shown, new characteristic peaks -NH2 and -CH2 are generated on the surface of the modified nano-silica, indicating that the silane coupling agent KH550 is combined with the surface of the nano-silica and the modification is completed.

[0064] Preparation Example 3: Modification of sodium montmorillonite (Na-MMT)

[0065] The modification process of sodium montmorillonite is as follows: Figure 3As shown. Weigh 20g MMT and 500mL deionized water, mix them and add them to a two-necked flask, place it in a 60℃ water bath, and stir for 30min to obtain MMT solution; weigh an appropriate amount of octadecyltrimethylammonium bromide (CTAB) and dissolve it in 50mL deionized water, and add concentrated hydrochloric acid dropwise to adjust the solution pH to 3 to form a protonated solution. Add the above protonated solution dropwise to the MMT solution, react for 3h under constant temperature and high-speed stirring in a water bath to obtain CMMT solution; centrifuge, and repeatedly wash the solid with anhydrous ethanol and deionized water until Br can no longer be detected with silver nitrate solution. - The cleaned CMMT was placed in a vacuum drying oven at 80°C and dried for 12 hours, ground for 20 minutes, and finally sieved through a 150-mesh standard test sieve to obtain CMMT powder with a particle size of less than 100 μm.

[0066] like Figure 4 As shown in the figure, after montmorillonite is modified with CTAB, the -1 、2852cm -1 , and 1468cm -1 A new absorption peak appeared at 2924 cm -1 and 2852cm -1 The stretching vibration peaks of -CH3- and -CH2- are 1468 cm -1 The peaks at -CH3- and -CH2- are characteristic absorption peaks of CTAB, indicating that CTAB has successfully intercalated between the MMT interlayers, demonstrating successful surface modification. Based on the intensity of the peaks, it can be seen that a CTAB content of 30% is optimal for preparing modified montmorillonite.

[0067] Example 1: Preparation of nylon 12 powder by solvent precipitation

[0068] The experimental process is as follows Figure 5 As shown, nylon 12 (melting temperature approximately 183°C) and 95% ethanol were added to an autoclave at a solute / solvent ratio of 1:8 (g / g). The autoclave was replaced with nitrogen three times, sealed, and heated to 170°C with stirring at 400 rpm. After maintaining constant temperature and pressure for 3 hours, a saturated nylon resin ethanol solution was obtained. The solution was then cooled to below 60°C to precipitate nylon 12 powder. The nylon 12 powder was then discharged, separated, cleaned, dried, ground, and passed through a 150-mesh sieve.

[0069] Example 2: Preparation of nylon 12 composite powder by precipitation method

[0070] Nylon 12 and 95% ethanol were added to an autoclave at a solute / solvent ratio of 1:8 (g / g). A certain amount of modifier was then added, and the autoclave was replaced with nitrogen three times. The autoclave was sealed and heated to 170°C with stirring at 400 rpm. After maintaining constant temperature and pressure for 3 hours, the autoclave was cooled to below 60°C to precipitate the nylon 12 composite powder. The nylon 12 composite powder was obtained through discharge, separation, washing, drying, grinding, and filtration through a 150-mesh sieve.

[0071] Among them, the modifiers are 5% and 10% of ultrafine copper powder (400 mesh), 5% and 10% of modified SiO2 of Preparation Example 1, 5% and 10% of a mixture of ultrafine copper powder (400 mesh) and modified SiO2 of Preparation Example 1 in a mass ratio of 1:1, and 1%, 3%, 5% and 10% of 30% CTAB modified montmorillonite of Preparation Example 3.

[0072] Performance and Results:

[0073] 1. Powder morphology analysis

[0074] The PA12 powders were analyzed by scanning electron microscope to observe the microstructure of the composite powders and the size of the nuclei. Figure 6-10 shown.

[0075] 2. Particle size distribution analysis

[0076] The particle size distribution of each powder was measured using an MS2000 laser particle size analyzer. The distribution table is shown in Table 1 below:

[0077] Table 1: Particle size distribution of PA12 and composite powder

[0078]

[0079] 3. Thermal performance analysis

[0080] 6.00 mg to 7.00 mg of sample was placed in an Al2O3 crucible and placed in a differential scanning calorimeter. Under an Ar atmosphere, the temperature was first raised from room temperature to 300°C at a rate of 10°C / min, maintained for 3 minutes, and then cooled to room temperature at a rate of 10°C / min. Based on the TG-DSC thermal analysis data, the melting points of the PA12 powder and the composite powder can be obtained, as shown in Table 2 below:

[0081] Table 2: Melting points of PA12 and composite powders

[0082]

[0083]

[0084] 3. Mechanical properties analysis

[0085] Parts made of different types of nylon powder are prepared by melt molding: according to the melting points of different powders, the temperature of the muffle furnace is raised to 200℃~230℃, the powder is spread evenly on the part mold, the mold is placed in the muffle furnace and heated until the powder temperature reaches above its melting point. After observing the powder until it melts and forms, it is taken out of the furnace, the mold is cooled to room temperature by condensed water, and the part is taken out.

[0086] The bending and tensile properties of the parts were tested using a universal testing machine. The results are shown in Tables 3 and 4 below:

[0087] Table 3: Bending properties of PA12 and composite powder parts

[0088]

[0089] Table 4: Tensile properties of PA12 and composite powder parts

[0090]

[0091] The Shore hardness test was performed on the prepared hardness parts using a Shore hardness tester. The results are shown in Table 5 below:

[0092] Table 5: Hardness of PA12 and composite powder parts

[0093]

[0094] The test results show that the PA12 powder prepared by the solvent precipitation method has a narrow particle size distribution, with an average particle size of 28μm, meeting SLS requirements. The addition of the modifier increases the average particle size of the PA12 composite powder, but remains essentially below 60μm. Both the PA12 powder and the composite powder exhibit good sphericity. Compared to PA12 powder, the melting points of all types of composite powders increase somewhat, but decrease with increasing the additive level to 10%.

[0095] Mechanical properties improved across all PA12 composite powder types. While SiO2 / PA12, Cu / PA12, and Cu+SiO2 / PA12 showed minimal differences at modifier addition levels of 5% and 10%, the Cu+SiO2 composite modifier exhibited significant improvements, achieving a synergistic effect compared to Cu / PA12 and SiO2 / PA12 composite powders. For CMMT, mechanical properties initially increased and then decreased as the content increased from 0, reaching optimal mechanical properties at a content of 1-3%. Hardness exhibited similar changes to mechanical properties.

[0096] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A composite nylon powder comprising: 80-99% of nylon and 1-20% of a modifier, wherein the modifier is at least one of copper powder, modified silicon dioxide and modified montmorillonite.

2. The composite nylon powder according to claim 1, characterized in that The nylon is selected from at least one of nylon 6, nylon 66, nylon 11, and nylon 12, and is more preferably nylon 12.

3. The composite nylon powder according to claim 1, characterized in that The composite nylon powder is spherical or quasi-spherical, and has a particle size distribution of D10=0.5-25 μm, D50=25-80 μm, and D90=85-120 μm; preferably, the particle size distribution is D10=3-15 μm, D50=40-65 μm, and D90=95-110 μm.

4. The composite nylon powder according to claim 1, characterized in that The composite nylon powder has a core-shell structure, wherein the core is a modifier and the shell is nylon.

5. The composite nylon powder according to claim 1, characterized in that The modifier is copper powder, or modified silicon dioxide, or modified montmorillonite, or a mixture of copper powder and modified silicon dioxide in a mass ratio of 1-2:2-1.

6. The composite nylon powder according to claim 1, characterized in that The modified silicon dioxide is a product obtained by modifying silicon dioxide with a silane coupling agent; and the modified montmorillonite is a product obtained by modifying montmorillonite with a long-chain cationic surfactant.

7. The composite nylon powder according to claim 1, characterized in that The preparation method of the composite nylon powder comprises: Add nylon and methanol or ethanol into the autoclave, then add the modifier, seal and heat to 160-175°C, keep constant temperature and pressure for 1-5 hours, then cool to precipitate the composite nylon powder, and obtain the composite nylon powder through discharge, separation, washing, drying, grinding and sieving.

8. A method for preparing the composite nylon powder according to any one of claims 1 to 7, comprising: Add nylon and methanol or ethanol into an autoclave, seal and heat to 160-175°C, maintain constant temperature and pressure for 1-5 hours, then cool to allow composite nylon powder to precipitate, and obtain composite nylon powder through discharge, separation, washing, drying, grinding and sieving.

9. A composite nylon powder prepared by the method for preparing the composite nylon powder according to claim 8.

10. Use of the composite nylon powder according to any one of claims 1 to 7 and 9, wherein: The composite nylon powder is used for 3D printing.

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