CN111873427B - Preparation method of multi-component copolymerized nylon powder for selective laser sintering - Google Patents
Preparation method of multi-component copolymerized nylon powder for selective laser sintering Download PDFInfo
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Abstract
A preparation method of multi-component copolymerized nylon powder for selective laser sintering comprises the following steps: adding the poly-copolymerized nylon granules into a cryogenic grinder, and carrying out primary grinding in liquid nitrogen at a temperature of between 90 ℃ below zero and 130 ℃ below zero at a grinding rotor frequency of between 15Hz and 30Hz to obtain poly-copolymerized nylon powder coarse material with D50 of between 200 and 500 mu m; mixing the crude poly-copolymerized nylon powder with a grinding aid to obtain a mixed crude material, adding the mixed crude material into a cryogenic grinder, and carrying out secondary grinding in liquid nitrogen at the temperature of-100 to-160 ℃ at the grinding rotor frequency of 25 to 50Hz to obtain fine poly-copolymerized nylon powder with the D50=30 to 70 mu m; adding a flow assistant, an antioxidant and a reinforcing agent, and mixing at a low speed for 20-60 min to obtain the multi-component copolymerized nylon powder for selective laser sintering. According to the invention, the multielement copolymerized nylon granules are treated by a cryogenic grinding method to obtain powder coarse materials, and then the powder coarse materials are subjected to cryogenic grinding after the grinding aid is added, so that the multielement copolymerized nylon powder for selective laser sintering, which has low sintering temperature, high toughness and good surface quality, can be obtained.
Description
Technical Field
The invention belongs to the technical field of additive manufacturing, and particularly relates to a preparation method of multi-component copolymerized nylon powder for selective laser sintering.
Background
Additive manufacturing is a technology for manufacturing objects by using three-dimensional model data in a layer-by-layer stacking mode, and has the unique advantages of short production period in small batch, no redundant tailings in production, high production flexibility and the like, so the additive manufacturing has more and more attention in the manufacturing industry in recent years. The Selective Laser Sintering (SLS) technology has the unique advantages of simple manufacturing process, no need of a supporting structure, extremely high material utilization rate and the like, and becomes one of additive manufacturing technologies which are developed fastest and have industrial production capacity.
As is well known, there are three commonly used SLS sintered materials: high polymer powders, metal powders and ceramic powders. Wherein the high polymer material has lower melting point and higher viscosity, so that the forming is easier, and the high polymer material is widely applied to the industries of hand boards, spaceflight, medical treatment and the like. Among all high polymer materials, nylon materials have the highest absorption efficiency of laser, and nylon itself is used as one of five engineering plastics and has mature application in various industries. Therefore, among the polymer materials for SLS, nylon occupies 90% or more of the market.
At present, the commercially successful nylon materials in the market mainly comprise high-temperature materials with better mechanical properties such as PA11 and PA12, and PA6 with extremely high modulus, and composites thereof. The multi-component copolymerized nylon (COPA) with many advantages such as low sintering main temperature, low crystallinity and good toughness is rarely reported. The fundamental reason is that the COPA material is prepared by polycondensation of monomers such as PA6, P66, PA12 and PA610, and the complexity of the self-repeating monomers determines that the preparation route is complex and the requirements on equipment and process are precise when the COPA adopts a solvent method commonly used by other SLS nylon materials, such as CN201811252408 and CN 201910865021. Obviously, the preparation of the COPA by using a solvent method not only significantly increases the manufacturing cost, but also more importantly, the monomer of the COPA has greater risks of unstable structural damage such as fracture, grafting and recombination in a solvent synthesis route, and finally, the materials of different batches have obvious performance fluctuation. Therefore, the most popular method for processing COPA powder in the conventional field is cryogenic pulverization. In recent years, there are numerous documents and patents that optimize cryogenic grinding schemes, such as CN106111289A, CN 210617323U. However, the above schemes mainly develop optimization around low production efficiency and production cost, but inherent defects of the copious cooling pulverized COPA powder, such as wide particle size distribution, low apparent density, irregular powder particle shape and the like, cannot be remarkably improved under the condition of not changing a hardware structure, so that the powder has relatively poor flowability, the mechanical property of a finished workpiece is insufficient, and the use of the COPA powder in the SLS technical field is greatly limited.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides a preparation method of a multi-component copolymerized nylon powder for selective laser sintering, which aims to solve the technical problems of wide particle size distribution, low apparent density, irregular powder particle shape and the like of the multi-component copolymerized nylon powder prepared by the prior art.
In order to solve the technical problems, the invention provides a preparation method of a multi-component copolymerized nylon powder for selective laser sintering, which comprises the following steps:
step one, adding the multi-component copolymerized nylon granules into a cryogenic grinder, and carrying out primary grinding at a grinding rotor frequency of 15-30 Hz in a liquid nitrogen environment atmosphere at the temperature of-90 to-130 ℃ to obtain multi-component copolymerized nylon powder coarse material with D50 of 200-500 mu m;
step two, mixing the multicomponent copolymer nylon powder coarse material and a grinding aid to obtain a mixed coarse material, adding the mixed coarse material into a cryogenic grinder, and carrying out secondary grinding in a liquid nitrogen environment atmosphere at-100 to-160 ℃ at a grinding rotor frequency of 25 to 50Hz to obtain the multicomponent copolymer nylon fine powder with D50=30 to 70 mu m;
adding a flow assistant, an antioxidant and a reinforcing agent into the multi-component copolymerized nylon fine powder, and mixing at a low speed of 100-300 r/min for 20-60 min to obtain multi-component copolymerized nylon powder for selective laser sintering; wherein the content of the first and second substances,
the weight ratio of the multielement copolymerized nylon fine powder to the flow additive to the antioxidant to the reinforcing agent is as follows: 100: 0.2-3: 0.1-2: 0-50.
As a further preferable embodiment of the present invention, the mixing of the multicomponent copolymerized nylon powder coarse material and the grinding aid to obtain a mixed coarse material specifically includes:
and stirring the multi-component copolymerized nylon powder coarse material and the grinding aid in a high-speed stirrer at a rotating speed of 600-1500 r/min for 2-10 min to prepare a mixed coarse material.
As a further preferable scheme of the invention, the calculation formula of the grinding aid in the weight percentage M of the mixed coarse material is as follows:
wherein D is the average particle size of the grinding aid, D is D50 of the multi-component copolymerized nylon powder coarse material, ρ D is the density of the grinding aid, ρ D is the density of the multi-component copolymerized nylon powder coarse material, K is the coverage coefficient, and K is 20-200%.
As a further preferred embodiment of the present invention, K = 100%.
In a further preferred embodiment of the present invention, the multicomponent copolymerized nylon pellet has a repeating monomer structure composed of three or more nylon monomers.
In a further preferred embodiment of the present invention, the poly-copolymerized nylon pellets have a repeating monomer structure consisting of monomers PA6 and PA66, and any one of monomers PA46, PA610, PA10, PA12 and PA 1212.
In a further preferred embodiment of the present invention, the temperature of the liquid nitrogen environment in the second step is 10 to 30 ℃ below the embrittlement point of the multicomponent copolymerized nylon pellet.
In a further preferred embodiment of the present invention, the grinding aid is one or a mixture of two or more of a flow aid, an antioxidant and a reinforcing agent, and the grinding aid has an average particle diameter of 0.01 to 10 μm.
As a further preferable scheme of the present invention, the flow assistant is one or more of fumed silica, nano silicon carbide, nano calcium oxide, nano alumina, titanium dioxide and calcium carbonate.
As a further preferable scheme of the invention, the reinforcing agent is one or more of glass beads, glass fibers, carbon fibers, micaceous stone, calcium chloride, titanium dioxide and talcum powder.
The preparation method of the multicomponent copolymerized nylon powder for selective laser sintering comprises the steps of carrying out primary treatment on multicomponent copolymerized nylon granules by a cryogenic pulverization method to obtain powder coarse materials, then adding a grinding aid, and carrying out secondary cryogenic pulverization, so that the multicomponent copolymerized nylon powder for selective laser sintering, which is low in sintering temperature, high in toughness and good in surface quality, can be obtained. And the grinding aid is quantitatively added into the copolymerized nylon coarse powder, so that the covering degree of the aid on the surface of the copolymerized nylon powder reaches an ideal range, and the aid can generate a uniform collision effect on the copolymerized nylon powder in the cryogenic grinding process. The efficiency of cryogenic processing is improved, and meanwhile, the toughness of the material is not reduced. The multi-component copolymerized nylon finished powder has the advantages of optimal particle size distribution, apparent density and more regular powder particle shape, and the comprehensive performance of the material is improved; the phenomena of cracking, powder throwing, dust raising and the like of the powder in the selective laser sintering process are avoided, the mechanical performance and the sintering stability of the selective laser sintering workpiece are improved finally, and the application field of selective laser sintering is widened.
Detailed Description
In order to solve the technical problems in the prior art, the invention provides a multi-component copolymerized nylon powder for selective laser sintering, which comprises the following steps:
step one, adding the multicomponent copolymer nylon granules into a cryogenic grinder, and carrying out primary grinding at a grinding rotor frequency of 15-30 Hz in a liquid nitrogen environment atmosphere at the temperature of-90 to-130 ℃ to obtain crude multicomponent copolymer nylon powder with D50 of 200-500 mu m;
and step two, mixing the multicomponent copolymer nylon powder coarse material with a grinding aid to obtain a mixed coarse material, adding the mixed coarse material into a cryogenic grinder, and carrying out secondary grinding at a grinding rotor frequency of 25-50 Hz in a liquid nitrogen environment atmosphere with the temperature of-100 to-160 ℃ (preferably 10-30 ℃ below the embrittlement point of the multicomponent copolymer nylon granules) to obtain the multicomponent copolymer nylon fine powder with the D50= 30-70 mu m.
Adding a flow assistant, an antioxidant and a reinforcing agent into the multi-component copolymerized nylon fine powder, and mixing at a low speed of 100-300 r/min for 20-60 min to obtain multi-component copolymerized nylon powder for selective laser sintering; wherein the content of the first and second substances,
the weight ratio of the multielement copolymerized nylon fine powder to the flow additive to the antioxidant to the reinforcing agent is as follows: 100: 0.2-3: 0.1-2: 0-50. In this step, it should be noted that, in the third step, a reinforcing agent may be added to the fine powder of the copolymerized nylon, or the reinforcing agent may not be added, that is, the content of the reinforcing agent is 0. Preferably, the content of the reinforcing agent is 10-30, so that the size stability and the mechanical property of the multi-component copolymerized nylon material workpiece can be ensured, and the toughness of the multi-component copolymerized nylon material workpiece can also be ensured, namely the performance of the multi-component copolymerized nylon material workpiece is better ensured.
In order to further improve the particle size distribution and the flowability of the powder, preferably, the mixing of the multipolymer nylon powder coarse material and the grinding aid to obtain the mixed coarse material specifically comprises:
and stirring the multi-component copolymerized nylon powder coarse material and the grinding aid in a high-speed stirrer at a rotating speed of 600-1500 r/min for 2-10 min to prepare a mixed coarse material.
In order to achieve the best grinding effect of the grinding aid on the semi-finished powder without reducing the toughness of the material, it is further preferable that the calculation formula of the grinding aid in the weight percentage M of the mixed coarse material is as follows:
wherein D is the average particle size of the grinding aid, D is D50 of the multi-component copolymerized nylon powder coarse material, ρ D is the density of the grinding aid, ρ D is the density of the multi-component copolymerized nylon powder coarse material, K is the coverage coefficient, and K is 20-200%. Further preferably, K = 100%.
Specifically, the multi-component copolymerized nylon granules are of a repeating monomer structure consisting of three or more nylon monomers, wherein the nylon monomers are PA6, PA66, PA610, PA10, PA12 and the like, and preferably, the multi-component copolymerized nylon granules are of a repeating monomer structure consisting of monomer PA6, PA66 and any one of monomer PA46, PA610, PA10, PA12 and PA1212, so that the multi-component copolymerized nylon powder sintered by selective laser has the beneficial effects of low melting point and higher toughness.
Specifically, the grinding aid is one or a mixture of more than two of a flow aid, an antioxidant and a reinforcing agent, and the average particle size of the grinding aid is 0.01-10 μm. A single agent is preferred as a grinding aid (e.g., only a flow aid, only an antioxidant, or only a reinforcing agent) to provide better dispersion of the grinding aid on the surface of the nylon powder.
In specific implementation, the flow assistant is one or more of fumed silica, nano silicon carbide, nano calcium oxide, nano aluminum oxide, titanium dioxide and calcium carbonate; the reinforcing agent is one or more of glass beads, glass fibers, carbon fibers, mica stones, calcium chloride, titanium dioxide and talcum powder; the antioxidant is 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene, 2, 6-di-tert-butyl-4-methyl-phenol; n, N ' -di (3, 5-di-tert-butyl-4-hydroxyphenyl propionamide), 2,2' -ethylene bis ((4, 6-di-tert-butylphenyl) fluorophosphite, and tetrakis ((2, 4-di-tert-butylphenyl) -4,4' -biphenylbisphosphite, or a mixture of two or more thereof.
The invention also provides the multielement copolymerized nylon powder for selective laser sintering, which is prepared by the preparation method of the multielement copolymerized nylon powder for selective laser sintering in any embodiment.
In order to make the technical solutions of the present invention better understood and realized by those skilled in the art, the technical solutions of the present invention are described in detail below by way of examples.
Comparative example 1
COPA pellets consisting of PA6, PA66 and PA10 were charged into a cryogenic pulverizer and pulverized at a pulverizing rotor frequency of 50Hz in a liquid nitrogen atmosphere at-160 ℃ to obtain a COPA fine powder of D50=50 μm. Adding 0.5 part of fumed silica, 0.8 part of 1,3, 5-trimethyl-2, 4, 6-tri (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene and 30 parts of glass beads with the average particle size of 10 mu m into the COPA fine powder, and mixing at a low speed of 200r/min for 30min to obtain the multi-component copolymerized nylon powder for selective laser sintering. And sintering the powder in an SLS device at a sintering main temperature of 112 ℃ to obtain a finished workpiece.
Example 1
The COPA granules consisting of PA6, PA66 and PA10 are added into a cryogenic pulverizer, primary pulverization is carried out in a liquid nitrogen environment atmosphere at-100 ℃ at a pulverization rotor frequency of 20Hz to obtain a crude poly-copolymerized nylon powder material with D50=400 μm, 30 parts of glass beads with the average particle size of 10 μm are added into 100 parts of the crude poly-copolymerized nylon powder material, the mixture is stirred in a high-speed stirrer at a rotating speed of 800r/min for 8min, the mixed crude material is added into the cryogenic pulverizer again, secondary pulverization is carried out in a liquid nitrogen environment atmosphere at-140 ℃ at a pulverization rotor frequency of 45Hz to obtain the COPA fine powder with D50=50 μm. Adding 0.5 part of fumed silica and 0.8 part of 1,3, 5-trimethyl-2, 4, 6-tri (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene into the COPA fine powder, and mixing at a low speed of 200r/min for 30min to obtain the multi-copolymerized nylon powder for selective laser sintering. And sintering the powder in an SLS device at the sintering main temperature of 113 ℃ to obtain a finished workpiece.
Example 2
Adding COPA granules consisting of PA6, PA66 and PA10 into a cryogenic pulverizer, performing primary pulverization in a liquid nitrogen environment atmosphere at-100 ℃ at a pulverizing rotor frequency of 20Hz to obtain a nylon powder coarse material with D50=400 μm, adding 14.7 parts of glass beads with an average primary particle size of 10 μm into 100 parts of the nylon powder coarse material according to the formula calculation amount, stirring in a high-speed stirrer at a rotating speed of 800r/min for 8min, adding the mixed coarse material into the cryogenic pulverizer again, and performing secondary pulverization in a liquid nitrogen environment atmosphere at-140 ℃ at a pulverizing rotor frequency of 45Hz to obtain COPA fine powder with D50=50 μm. 0.5 part of fumed silica, 0.8 part of 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene and 35.3 parts of glass beads with the average particle size of 10 mu m are added into the COPA fine powder and mixed at a low speed of 200r/min for 30min to obtain the multi-component copolymerized nylon powder for selective laser sintering. And sintering the powder in an SLS device at a sintering main temperature of 114 ℃ to obtain a finished workpiece.
Example 3
The COPA granules consisting of PA6, PA66 and PA10 are added into a cryogenic pulverizer, and are subjected to primary pulverization in a liquid nitrogen environment atmosphere at-100 ℃ at a pulverizing rotor frequency of 20Hz to obtain a multi-component copolymerized nylon powder coarse material with D50=400 μm, 14.7 parts of glass beads with an average primary particle size of 10 μm are added into 100 parts of the multi-component copolymerized nylon powder coarse material according to the formula calculation amount, the mixture is stirred in a high-speed stirrer at a rotating speed of 800r/min for 8min, the mixed coarse material is added into the cryogenic pulverizer again, and is subjected to secondary pulverization in a liquid nitrogen environment atmosphere at-140 ℃ at a pulverizing rotor frequency of 45Hz to obtain a COPA fine powder with D50=50 μm. Adding 0.5 part of fumed silica, 0.8 part of 1,3, 5-trimethyl-2, 4, 6-tri (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene and 15.3 parts of glass beads with the average particle size of 10 mu m into the COPA fine powder, and mixing at a low speed of 200r/min for 30min to obtain the multi-component copolymerized nylon powder for selective laser sintering. And sintering the powder in an SLS device at a sintering main temperature of 112 ℃ to obtain a finished workpiece.
Example 4
Adding COPA granules consisting of PA6, PA66 and PA12 into a cryogenic pulverizer, performing primary pulverization in a liquid nitrogen environment atmosphere at-110 ℃ at a pulverization rotor frequency of 15Hz to obtain a multi-component copolymerized nylon powder coarse material with D50=400 μm, adding 0.10 part of fumed silica with 70nm average primary particle size into 100 parts of the multi-component copolymerized nylon powder coarse material according to a formula calculation amount, stirring for 6min in a high-speed stirrer at a rotating speed of 1000r/min, adding the mixed coarse material into the cryogenic pulverizer again, and performing secondary pulverization in a liquid nitrogen environment atmosphere at-150 ℃ at a pulverization rotor frequency of 43Hz to obtain COPA fine powder with D50=45 μm. Adding 0.4 part of fumed silica, 0.3 part of 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene and 10 parts of glass beads into the COPA fine powder, and mixing at a low speed of 300r/min for 40min to obtain the multi-component copolymerized nylon powder for selective laser sintering. And sintering the powder in an SLS device at a sintering main temperature of 122 ℃ to obtain a finished workpiece.
Example 5
COPA pellets comprising PA6, PA66 and PA12 were fed into a cryogenic pulverizer, and subjected to primary pulverization at a pulverization rotor frequency of 25Hz in a liquid nitrogen atmosphere at-120 ℃ to obtain a multicomponent copolymerized nylon powder crude material D50=400 μm, 0.16 parts of fumed silica having an average primary particle size of 100nm was added to 100 parts of the multicomponent copolymerized nylon powder crude material in an amount calculated according to the formula, and stirred in a high-speed stirrer at a rotation speed of 1000r/min for 6min, and the mixed crude material was fed into the cryogenic pulverizer again, and subjected to secondary pulverization at a pulverization rotor frequency of 40Hz in a liquid nitrogen atmosphere at-160 ℃ to obtain a COPA fine powder D50=46 μm. Adding 0.34 part of fumed silica, 0.2 part of 2, 6-di-tert-butyl-4-methyl-phenol and 20 parts of glass beads into the COPA fine powder, and mixing at a low speed of 200r/min for 45min to obtain the multi-component copolymerized nylon powder for selective laser sintering. And sintering the powder in an SLS device at a sintering main temperature of 112 ℃ to obtain a finished workpiece.
Example 6
Adding COPA granules consisting of PA6, PA66 and PA1212 into a cryogenic pulverizer, performing primary pulverization in a liquid nitrogen environment atmosphere at-120 ℃ at a pulverizing rotor frequency of 30Hz to obtain a crude product of the multi-component copolymerized nylon powder with D50=450 μm, adding 0.05 part of nano silicon carbide with an average primary particle size of 40nm to 100 parts of the crude product of the multi-component copolymerized nylon powder according to a formula calculation amount, stirring in a high-speed stirrer at a rotating speed of 1000r/min for 6min, adding the mixed crude product into the cryogenic pulverizer again, and performing secondary pulverization in a liquid nitrogen environment atmosphere at-150 ℃ at a pulverizing rotor frequency of 43Hz to obtain a fine COPA powder with D50=55 μm. Adding 0.95 part of nano silicon carbide, 0.8 part of N, N' -bis (3, 5-di-tert-butyl-4-hydroxyphenyl propionamide) and 20 parts of glass fiber into the COPA fine powder, and mixing at a low speed of 250r/min for 45min to obtain the multi-component copolymerized nylon powder for selective laser sintering. And sintering the powder in an SLS device at a sintering main temperature of 126 ℃ to obtain a finished workpiece.
TABLE 1 data of various performance tests of sintered workpiece of multicomponent copolymerized nylon powder for selective laser sintering
As can be seen from table 1, by comparing examples 1 and 2 with comparative example 1, the flowability of the final powder can be improved by adding a proper amount of grinding aid to the primarily pulverized polynary copolymerized nylon powder as the grinding aid, so that the powder has better powder spreading surface and sintering bath at the selective laser sintering stage, the sintering of the final powder is more compact, and the mechanical properties of the workpiece are improved.
On the other hand, as is clear from comparison between example 1 and example 2, the sintering temperatures are almost the same because the mass ratios of the raw material components are the same. However, in the example 1, a high content of grinding aid is added in the primary cryogenic cooling process, the excessive grinding aid not only completely covers the nylon powder, but also early collides with the grinding aid to agglomerate, and although the finally sintered workpiece also plays a role in enhancing, the agglomerated reinforcing agent is equivalent to an insufficient point in the workpiece, so that the elongation at break is remarkably reduced.
Comparing example 2 and example 3, the content of the reinforcing agent in the preferred range not only can perform a reinforcing function to the material, but also the toughness of the material is not poor.
From examples 3 and 4, it can be seen that the multicomponent copolymerized nylon powder having good fluidity and excellent mechanical properties can be obtained by quantitatively adding various single additives as a grinding aid.
As can be seen from examples 2, 3, 4, 5, and 6, the method is generally applicable to multi-copolymerized nylons with different repeat monomers, the sintering temperatures of the materials with different repeat monomers are all maintained at a low temperature level, and the obtained finished powder has good powder flowability, sintering stability and mechanical properties.
The above-mentioned embodiments only express various embodiments of the present invention, and the description thereof is more specific and detailed, but not meant to limit the scope of the invention. It will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended that the scope of the invention be limited only by the claims appended hereto.
Claims (7)
1. A preparation method of multi-component copolymerized nylon powder for selective laser sintering is characterized by comprising the following steps:
step one, adding the multicomponent copolymer nylon granules into a cryogenic grinder, and carrying out primary grinding at a grinding rotor frequency of 15-30 Hz in a liquid nitrogen environment atmosphere at the temperature of-90 to-130 ℃ to obtain crude multicomponent copolymer nylon powder with D50 of 200-500 mu m;
step two, mixing the multicomponent copolymer nylon powder coarse material and a grinding aid to obtain a mixed coarse material, adding the mixed coarse material into a cryogenic grinder, and carrying out secondary grinding at a grinding rotor frequency of 25-50 Hz in a liquid nitrogen environment atmosphere at-100 to-160 ℃ to obtain the multicomponent copolymer nylon fine powder with D50= 30-70 mu m;
adding a flow assistant, an antioxidant and a reinforcing agent into the multi-component copolymerized nylon fine powder, and mixing at a low speed of 100-300 r/min for 20-60 min to obtain multi-component copolymerized nylon powder for selective laser sintering; wherein the content of the first and second substances,
the weight ratio of the multielement copolymerized nylon fine powder to the flow additive to the antioxidant to the reinforcing agent is as follows: 100: 0.2-3: 0.1-2: 0 to 50; wherein, the first and the second end of the pipe are connected with each other,
the method for preparing the mixed coarse material by mixing the multicomponent copolymerized nylon powder coarse material and the grinding aid specifically comprises the following steps:
stirring the multicomponent copolymer nylon powder coarse material and a grinding aid in a high-speed stirrer at a rotating speed of 600-1500 r/min for 2-10 min to prepare a mixed coarse material;
the grinding aid is one or a mixture of more than two of a flow aid, an antioxidant and a reinforcing agent, and the average particle size of the grinding aid is 0.01-10 mu m;
the calculation formula of the grinding aid in the weight percentage M of the mixed coarse material is as follows:
wherein D is the average particle size of the grinding aid, D is D50 of the multi-component copolymerized nylon powder coarse material, ρ D is the density of the grinding aid, ρ D is the density of the multi-component copolymerized nylon powder coarse material, K is the coverage coefficient, and K is 20-200%.
2. The method of claim 1, wherein K = 100%.
3. The method of claim 1, wherein the multipolymer nylon pellets have a repeating monomer structure consisting of three or more nylon monomers.
4. The method of claim 3, wherein the poly-copolymerized nylon pellets have a repeating monomer structure consisting of the monomers PA6 and PA66, and any one of the monomers PA46, PA610, PA10, PA12 and PA 1212.
5. The preparation method according to claim 1, wherein the liquid nitrogen environment temperature in the second step is 10-30 ℃ below the brittle point of the multicomponent copolymerized nylon pellets.
6. The preparation method of claim 5, wherein the flow aid is one or more of fumed silica, nano silicon carbide, nano calcium oxide, nano alumina, titanium dioxide and calcium carbonate.
7. The preparation method according to claim 6, wherein the reinforcing agent is one or more of glass beads, glass fibers, carbon fibers, micaceous stone, calcium chloride, titanium dioxide and talcum powder.
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