CN117736468A - Polypropylene powder for selective laser sintering and preparation method thereof - Google Patents
Polypropylene powder for selective laser sintering and preparation method thereof Download PDFInfo
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- CN117736468A CN117736468A CN202311764548.9A CN202311764548A CN117736468A CN 117736468 A CN117736468 A CN 117736468A CN 202311764548 A CN202311764548 A CN 202311764548A CN 117736468 A CN117736468 A CN 117736468A
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- -1 Polypropylene Polymers 0.000 title claims abstract description 129
- 239000004743 Polypropylene Substances 0.000 title claims abstract description 129
- 229920001155 polypropylene Polymers 0.000 title claims abstract description 129
- 239000000843 powder Substances 0.000 title claims abstract description 82
- 238000002360 preparation method Methods 0.000 title claims abstract description 20
- 238000000110 selective laser sintering Methods 0.000 title claims abstract description 18
- 239000003085 diluting agent Substances 0.000 claims abstract description 85
- 238000000034 method Methods 0.000 claims abstract description 49
- 239000002245 particle Substances 0.000 claims abstract description 29
- 230000008569 process Effects 0.000 claims abstract description 22
- 239000012456 homogeneous solution Substances 0.000 claims abstract description 18
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 94
- 238000001816 cooling Methods 0.000 claims description 37
- 239000007788 liquid Substances 0.000 claims description 36
- 239000000203 mixture Substances 0.000 claims description 26
- 238000003756 stirring Methods 0.000 claims description 26
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 claims description 19
- KCXZNSGUUQJJTR-UHFFFAOYSA-N Di-n-hexyl phthalate Chemical compound CCCCCCOC(=O)C1=CC=CC=C1C(=O)OCCCCCC KCXZNSGUUQJJTR-UHFFFAOYSA-N 0.000 claims description 18
- 238000010438 heat treatment Methods 0.000 claims description 13
- 239000002244 precipitate Substances 0.000 claims description 12
- 238000001291 vacuum drying Methods 0.000 claims description 12
- 239000000155 melt Substances 0.000 claims description 11
- 238000006243 chemical reaction Methods 0.000 claims description 10
- 238000002425 crystallisation Methods 0.000 claims description 10
- 230000008025 crystallization Effects 0.000 claims description 10
- 235000011187 glycerol Nutrition 0.000 claims description 9
- 238000003828 vacuum filtration Methods 0.000 claims description 9
- 238000009835 boiling Methods 0.000 claims description 7
- 230000003993 interaction Effects 0.000 claims description 6
- 238000002844 melting Methods 0.000 claims description 5
- 230000008018 melting Effects 0.000 claims description 5
- RZRNAYUHWVFMIP-KTKRTIGZSA-N 1-oleoylglycerol Chemical compound CCCCCCCC\C=C/CCCCCCCC(=O)OCC(O)CO RZRNAYUHWVFMIP-KTKRTIGZSA-N 0.000 claims description 4
- PYGXAGIECVVIOZ-UHFFFAOYSA-N Dibutyl decanedioate Chemical compound CCCCOC(=O)CCCCCCCCC(=O)OCCCC PYGXAGIECVVIOZ-UHFFFAOYSA-N 0.000 claims description 4
- 238000004140 cleaning Methods 0.000 claims description 4
- 238000004090 dissolution Methods 0.000 claims description 4
- RZRNAYUHWVFMIP-HXUWFJFHSA-N glycerol monolinoleate Natural products CCCCCCCCC=CCCCCCCCC(=O)OC[C@H](O)CO RZRNAYUHWVFMIP-HXUWFJFHSA-N 0.000 claims description 4
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 claims description 3
- 239000012046 mixed solvent Substances 0.000 claims description 2
- HORIEOQXBKUKGQ-UHFFFAOYSA-N bis(7-methyloctyl) cyclohexane-1,2-dicarboxylate Chemical compound CC(C)CCCCCCOC(=O)C1CCCCC1C(=O)OCCCCCCC(C)C HORIEOQXBKUKGQ-UHFFFAOYSA-N 0.000 claims 1
- 239000011368 organic material Substances 0.000 claims 1
- 239000002904 solvent Substances 0.000 abstract description 20
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- 238000004519 manufacturing process Methods 0.000 abstract description 4
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- 239000002861 polymer material Substances 0.000 abstract description 3
- 238000002145 thermally induced phase separation Methods 0.000 abstract description 3
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- 229920000642 polymer Polymers 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 8
- 239000007791 liquid phase Substances 0.000 description 8
- 230000006911 nucleation Effects 0.000 description 7
- 238000010899 nucleation Methods 0.000 description 7
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 6
- 239000012071 phase Substances 0.000 description 6
- 238000002156 mixing Methods 0.000 description 5
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- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
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- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 3
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- 238000010146 3D printing Methods 0.000 description 2
- HRELNAWNYHNHHO-UHFFFAOYSA-N bis(7-methyloctyl) benzene-1,2-dicarboxylate cyclohexane Chemical compound C1CCCCC1.C(CCCCCC(C)C)OC(C=1C(C(=O)OCCCCCCC(C)C)=CC=CC1)=O HRELNAWNYHNHHO-UHFFFAOYSA-N 0.000 description 2
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- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 description 2
- NHTMVDHEPJAVLT-UHFFFAOYSA-N Isooctane Chemical compound CC(C)CC(C)(C)C NHTMVDHEPJAVLT-UHFFFAOYSA-N 0.000 description 1
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 1
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- JVSWJIKNEAIKJW-UHFFFAOYSA-N dimethyl-hexane Natural products CCCCCC(C)C JVSWJIKNEAIKJW-UHFFFAOYSA-N 0.000 description 1
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Abstract
The application provides polypropylene powder for selective laser sintering and a preparation method thereof, and belongs to the technical field of polymer materials. According to the method, a thermally induced phase separation technology is utilized, high-melting-point polypropylene particles, low-melting-point polypropylene particles, a diluent and a non-diluent are heated under normal pressure to form a homogeneous solution, and then the temperature is reduced to separate out polypropylene from the homogeneous solution, so that polypropylene composite powder with narrow particle size distribution and high sphericity is obtained, and the problems of uneven particle size distribution of the powder prepared by adopting a low-temperature mechanical crushing method in the prior art are effectively solved; the preparation process is carried out at normal pressure and lower temperature, the polypropylene is separated from the solvent completely after precipitation, the solvent can be recycled, the diluents and the non-diluents in the solvent are both green and environment-friendly, the post-treatment process of the product is not needed, and the industrial mass production is easy to realize.
Description
Technical Field
The application belongs to the technical field of polymer materials, and particularly relates to polypropylene powder for selective laser sintering and a preparation method thereof.
Background
Polypropylene is a semi-crystalline polymer, and is widely applied to the field of 3D printing base materials due to excellent performance, so that a higher sintering rate can be obtained, and the density of a sintered part can reach more than 95%.
In the related art, the preparation method of the polypropylene powder for selective laser sintering mainly comprises a low-temperature mechanical crushing method and a solution precipitation method.
The low-temperature mechanical pulverization method is to pulverize polymer pellets by a mechanical pulverization method by utilizing the characteristics that polymers become brittle and are easy to pulverize mechanically under a low-temperature environment. Although the low-temperature crushing method has simple process, the implementation of the method is not separated from cryogenic equipment, so that the cost and the energy consumption are high, and most importantly, the prepared powder has uneven particle size distribution, irregular morphology and poor fluidity, can directly influence the powder spreading effect and the quality of a formed part, and cannot completely meet the requirement of selective laser sintering on polymer powder materials.
The solvent precipitation method is to dissolve the polymer in a proper solvent under the high temperature and high pressure environment, and then to adopt the method of changing the temperature or adding other solvents to precipitate the polymer in powder form. Because polypropylene belongs to nonpolar crystalline polymer materials, the polypropylene is insoluble in common solvents at normal temperature, and can be dissolved in nonpolar solvents such as toluene, benzene and the like at high temperature. The publication CN 105802012a and CN 106589418A et al prepare polypropylene powder by solvent precipitation that can be used for selective laser sintering. Although the method can prepare the polypropylene powder with proper particle size and high sphericity and completely meets the requirement of selective laser sintering, the method needs to be carried out under high-temperature and high-pressure environment, and the energy consumption is high, and the organic solvents adopted by the method, such as benzene, carbon tetrachloride, hexane, isooctane, xylene and the like, remain in the powder and have huge influence on the environment due to large-scale use, and the method is difficult to be produced on a large scale because of the need of strict and complex post-treatment process treatment.
Therefore, there is a need to provide a polypropylene powder for selective laser sintering and a method for preparing the same, which solve the above-mentioned problems in the prior art.
Disclosure of Invention
The application provides polypropylene powder for selective laser sintering and a preparation method thereof, which aim at the problems that the thermodynamic property of the polypropylene powder for selective laser sintering is unstable and the polymer powder for selective laser sintering is prepared at lower temperature and normal pressure in the prior art, and the sensitivity of the system viscosity to the temperature is reduced in the phase separation process so as to solve the problems of poor sphericity and uneven size of the polypropylene powder prepared by a low-temperature mechanical crushing method; the diluent and the non-diluent in the solvent are both green and environment-friendly, and can be recycled after phase separation at normal temperature, and the solvent post-treatment process is economical, simple and convenient, and is easy to realize industrialized mass production, so that the problem that the solvent precipitation method needs complex post-treatment to remove toxic solvents is solved.
In order to solve the technical problems, the technical scheme of the application is as follows:
a method for preparing polypropylene powder for selective laser sintering, comprising the steps of:
s1: adding 3-10 parts by weight of high-melt-index polypropylene particles, 1-5 parts by weight of low-melt-index polypropylene particles, 45-70 parts by weight of diluent and 15-51 parts by weight of non-diluent into a reaction container, and raising the temperature to be above the melting point of polypropylene to enable the two polypropylene particles to be completely dissolved in a mixed solvent consisting of the diluent and the non-diluent to obtain a homogeneous solution;
s2: maintaining the homogeneous solution for a certain period of time, cooling to crystallization temperature, and continuing constant-temperature stirring until insoluble precipitate is formed in the solution to obtain a solid-liquid mixture;
s3: and cooling the solid-liquid mixture to room temperature, performing vacuum filtration to obtain powder, cleaning the powder with ethanol, and then removing ethanol attached to the surface of the powder by vacuum drying to obtain the polypropylene powder.
Preferably, the melt mass flow index of the high melt index polypropylene particles is 100-200g/10min; the melt mass flow index of the low melt index polypropylene particles is 3-10g/10min.
Preferably, the diluent is a high boiling point organic substance with strong interaction with polypropylene; the non-diluent is a high boiling point organic that has weak interactions with the polypropylene.
Preferably, the diluent is selected from one of cyclohexane 1, 2-diisononyl phthalate, dihexyl phthalate or glycerol monooleate; the non-diluent is selected from one of glycerin, propylene carbonate or dibutyl sebacate.
Preferably, the step S1 of "raising the temperature above the dissolution temperature of polypropylene" specifically includes the following steps:
raising the temperature to 170-190 ℃ according to the heating rate of 3-4 ℃/min, and continuously stirring according to the stirring rate of 100-500rpm during the heating process.
Preferably, the step S2 specifically includes the following steps:
and (3) preserving the homogeneous solution for 30-180min, then cooling to 120-130 ℃ at a cooling rate of 0.5-5 ℃/min, and continuously stirring at constant temperature for 60-180min until insoluble precipitate is formed in the solution, thus obtaining a solid-liquid mixture.
Preferably, in step S3, the number of times of washing the powder with ethanol is three, each washing time is 10min, and the washing temperature condition is 40 ℃.
Preferably, the mass percentage of the ethanol is not less than 99%.
Preferably, in step S3, the temperature of the vacuum drying is 60 ℃.
The application also provides polypropylene powder for selective laser sintering, which is prepared by the preparation method.
The beneficial effects of this application lie in:
(1) By using a thermally induced phase separation technology, high-melt-index polypropylene particles, low-melt-index polypropylene particles, a diluent and a non-diluent are heated to form a homogeneous solution under normal pressure, polypropylene powder is separated out after cooling, high pressure is not required in the preparation process, the adopted temperature is slightly higher than the melting point of polypropylene, high-temperature conditions are not required, and the production energy consumption in the preparation process can be reduced;
(2) The diluent and the non-diluent are green and environment-friendly, and are completely split-phase at room temperature and can be recycled;
(3) The preparation method has the advantages that the mixed material of the high-melt-index polypropylene particles and a small amount of low-melt-index polypropylene particles is adopted for preparation, the small amount of low-melt-index polypropylene can serve as nucleation sites for high-melt-index polypropylene liquid drops and crystal nuclei, the liquid drops of the low-melt-index polypropylene are coated for nucleation, more importantly, the problem that the high-melt-index polypropylene is easy to be affected by temperature due to too fast molecular chain movement and too fast crystallization rate in the cooling process to cause poor forming can be effectively solved, the stability in the balling process is improved, and the polypropylene composite powder with narrow particle size distribution, high sphericity and excellent structural stability is obtained.
Drawings
FIG. 1 shows a microscopic view of the polypropylene powder prepared in comparative example 1;
FIG. 2 shows a microscopic view of the polypropylene powder prepared in comparative example 2;
FIG. 3 shows a microscopic view of the polypropylene powder prepared in comparative example 3;
FIG. 4 shows a microscopic view of the polypropylene powder prepared in example 1;
FIG. 5 shows a microscopic view of the polypropylene powder prepared in example 2;
FIG. 6 shows a microscopic view of the polypropylene powder prepared in example 3;
FIG. 7 shows a microscopic view of the polypropylene powder prepared in example 4.
Detailed Description
The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, are intended to be within the scope of the present application.
Referring to fig. 1-7 in combination, the present application provides a method for preparing polypropylene powder for selective laser sintering, comprising the steps of:
s1: according to the weight fraction, 3-10 parts of high-melt-index polypropylene particles, 1-5 parts of low-melt-index polypropylene particles, 45-70 parts of diluent and 15-51 parts of non-diluent are added into a reaction vessel, the temperature is increased to be higher than the dissolution temperature of polypropylene, and the two polypropylene particles are completely dissolved in a solvent to obtain a homogeneous solution.
The melt mass flow index (MFR) of the high melt index polypropylene particles is 100-200g/10min; the melt mass flow index (MFR) of the low melt index polypropylene particles is 3-10g/10min. Wherein the melt mass flow index (MFR) of the polypropylene is measured according to ISO 1133 at 230℃under a load of 2.16 kg.
The diluent is a high boiling point organic matter with strong interaction with polypropylene; the non-diluent is a high boiling point organic that has weak interactions with the polypropylene. Preferably, the diluent is selected from one of cyclohexane 1, 2-diisononyl phthalate, dihexyl phthalate or glycerol monooleate; the non-diluent is selected from one of glycerin, propylene carbonate or dibutyl sebacate.
The diluent and the non-diluent are green and environment-friendly, can keep phase separation at normal temperature, are favorable for recycling after preparation is completed, can not cause pollution emission, and can be well suitable for industrial mass production.
The step S1 of raising the temperature to above the dissolution temperature of the polypropylene specifically comprises the following steps:
raising the temperature to 170-190 ℃ according to the heating rate of 3-4 ℃/min, and continuously stirring according to the stirring rate of 100-500rpm during the heating process.
The melting point of the polypropylene is 164-170 ℃, the temperature is slowly increased to a temperature slightly higher than the melting point of the polypropylene, and the oxidation phenomenon is not easy to occur while the polypropylene is ensured to be melted. The stirring process can fully contact the melted polypropylene with the solvent, so that the polypropylene can be well dissolved in the solvent.
S2: and (3) after the homogeneous phase solution is kept for a certain time, cooling to 120-130 ℃, and continuing constant-temperature stirring until insoluble precipitate is formed in the solution, so as to obtain a solid-liquid mixture.
The temperature of the homogeneous solution is kept for 30-180min to obtain a relatively stable solution temperature, and then the solution is cooled to 120-130 ℃ at a cooling rate of 0.5-5 ℃/min, and is stirred at constant temperature for 60-180min.
Based on the principle of thermally induced phase separation, polypropylene polymers form homogeneous solutions with high boiling point, low molecular weight diluents and non-diluents at high temperatures, and the proportions of the components in the system are generally adjusted to provide moderate interactions between the polymer and the solvent and non-solvent. With the decrease of temperature, the balance of the phase state in the system is broken, a certain phase is in a metastable state, and the solution is subjected to solid-liquid or liquid-liquid phase separation, so that the free energy of the system is reduced.
The system is internally provided with two polymers, namely low-melt polypropylene and high-melt polypropylene, and because the low-melt polypropylene and the solvent have higher liquid-liquid phase separation temperature in the cooling process, the low-melt polypropylene and the solvent are separated out in the form of liquid drops, so that the low-melt polypropylene is coated with liquid drops nucleation sites of the liquid drops and crystal nuclei of the high-melt polypropylene when the high-melt polypropylene is subjected to liquid-liquid phase separation and crystallization solidification. The process can improve the crystallinity and sphericity of the powder, and obtain the polypropylene composite powder with narrow particle size distribution and high sphericity. And the sensitivity of the viscosity to temperature in the nucleation process can be effectively reduced by adding the low-melt-index polypropylene with good heat stability, so that the stable and high-temperature-resistant polypropylene composite powder is obtained.
In the thermal phase separation technology, liquid-liquid phase separation and solidification crystallization are in a competitive relationship, when a uniform solution is cooled, the high melt index polypropylene has low viscosity, the molecular chains move too fast, the crystallization rate is fast, the temperature is greatly influenced in the cooling process, and the polymer is rich in phase and does not respond to form liquid drops in the liquid-liquid phase separation process, so that the solidification crystallization is dominant. If the powder is prepared by a thermal phase separation method using only high melt index polypropylene particles, the stability of the pelletization process is poor and the obtained powder has poor sphericity and uneven size. And the low melt index polypropylene is singly used, so that the melt strength of the low melt index polypropylene is too high, the processing is difficult, and the polypropylene is easily changed into a continuous phase due to the excessively high polymer solid content, so that the powder state is irregular floccules.
In order to solve the problem, in the technical scheme of the application, a small amount of low-melt-index polypropylene is added into the high-melt-index polypropylene, and the low-melt-index polypropylene has larger molecular weight, poorer flexibility and slow molecular chain movement, so that on one hand, the viscosity in a solution can be increased, and the heat transfer rate in the cooling process is slowed down, thereby reducing the sensitivity of the system viscosity to the temperature, and further obtaining a more stable powder structure; on the other hand, because the high melt-index polypropylene and the low melt-index polypropylene belong to the same substance, the compatibility of the two substances is good, and chain segments are entangled in the cooling process, the chain segment movement speed of the high melt-index polypropylene in the liquid-liquid phase separation and solidification crystallization process can be obviously reduced, and the phase separation temperature of the low melt-index polypropylene in the solution is higher than that of the melt-index polypropylene, so that the crystallization rate is reduced in the liquid-liquid phase separation process, the nucleation energy barrier of a system can be reduced in the form of liquid drops, nucleation sites are provided for the liquid-liquid phase separation and solidification crystallization process of the high melt-index polypropylene, and the nucleation process of the high melt-index polypropylene is promoted, so that the polypropylene powder with uniform powder size, good stability and excellent performance is obtained.
S3: and cooling the solid-liquid mixture to room temperature, performing vacuum filtration to obtain powder, cleaning the powder with ethanol, and then removing ethanol attached to the surface of the powder by vacuum drying to obtain the polypropylene powder.
The number of times of ethanol washing the powder is three, the washing time is 10min each time, and the washing temperature is 40 ℃. The mass percentage of the ethanol is not less than 99 percent. The temperature of the vacuum drying was 60 ℃.
The cleaning process is used for removing the solvent attached to the solid surface, so that the purity of the product is maintained.
The application also provides 3D printing selective laser sintering polypropylene powder, which is prepared by the preparation method.
In order to verify the relevant properties of the polypropylene powder obtained by the preparation method of the present application, the following comparative tests were set up:
comparative example 1
(1) Adding polypropylene with a melt index of 191g/10min, dihexyl phthalate (diluent) and glycerol (non-diluent) into a reaction container according to a mass fraction of 5:85:10, mixing to form a homogeneous solution in a stirring and heating mode, wherein the stirring speed is 260rpm, and preserving heat for 1h when the temperature is increased to 180 ℃ to fully and uniformly mix the solution;
(2) Then cooling to 120 ℃ at a cooling rate of 3 ℃/min, and preserving heat for 1h, wherein insoluble precipitate is formed in the solution, so as to obtain a solid-liquid mixture;
(3) Cooling the solid-liquid mixture obtained in the step (2) to room temperature, removing liquid (diluent and non-diluent) by means of vacuum filtration to obtain powder, washing the powder with ethanol at 40 ℃ for three times, wherein the washing time is 10min, and the mass percent of the ethanol used for washing is not less than 99%, so as to obtain a mixed system of the ethanol and the diluent; and separating the washed ethanol from the mixed system of the diluent and the non-diluent, and removing the ethanol by vacuum drying at 60 ℃ to obtain polypropylene powder.
Comparative example 2
(1) Polypropylene with the melt index of 69g/10min, dihexyl phthalate (diluent) and glycerin (non-diluent) are added into a reaction vessel according to the mass fraction of 5:85:10, and are mixed to form a homogeneous solution by stirring and heating, wherein the stirring speed is 300rpm, and the temperature is kept for 1h when the temperature is increased to 180 ℃, so that the solution is fully and uniformly mixed.
(2) Then cooling to 120 ℃ at a cooling rate of 3 ℃/min, and preserving heat for 1h, wherein insoluble precipitate is formed in the solution, so as to obtain a solid-liquid mixture;
(3) Cooling the solid-liquid mixture obtained in the step (2) to room temperature, removing liquid (diluent and non-diluent) by means of vacuum filtration to obtain solid, washing the solid with ethanol at 40 ℃ for three times, wherein the washing time is 10min, and the mass percent of the ethanol used for washing is not less than 99%, so as to obtain a mixed system of the ethanol and the diluent; and separating the washed ethanol from the mixed system of the diluent and the non-diluent, and separating the ethanol by reduced pressure distillation at 60 ℃ to obtain polypropylene powder.
Comparative example 3
(1) Polypropylene with the melt index of 3.8g/10min, dihexyl phthalate (diluent) and glycerin (non-diluent) are added into a reaction vessel according to the mass part ratio of 5:85:10, and are mixed to form a homogeneous solution by stirring and heating, wherein the stirring speed is 300rpm, and the temperature is kept for 1h when the temperature is increased to 180 ℃ so that the solution is fully and uniformly mixed.
(2) Then cooling to 120 ℃ at a cooling rate of 3 ℃/min, and preserving heat for 1h, wherein insoluble precipitate is formed in the solution, so as to obtain a solid-liquid mixture;
(3) Cooling the solid-liquid mixture obtained in the step (2) to room temperature, removing liquid (diluent and non-diluent) by means of vacuum filtration to obtain powder, washing the powder with ethanol at 40 ℃ for three times, wherein the washing time is 10min, and the mass percent of the ethanol used for washing is not less than 99%, so as to obtain a mixed system of the ethanol and the diluent; and separating the washed ethanol from the mixed system of the diluent and the non-diluent, and removing the ethanol by vacuum drying at 60 ℃ to obtain polypropylene powder.
Example 1
(2) Adding high-melt polypropylene (MIR=191 g/10 min), low-melt polypropylene (MIR=3.8 g/10 min), dihexyl phthalate (diluent) and glycerin (non-diluent) into a reaction container according to the mass parts of 4:1:80:15, mixing to form a homogeneous solution by stirring and heating, wherein the stirring speed is 260rpm, and preserving heat for 1h when the temperature is increased to 180 ℃ to fully and uniformly mix the solution;
(2) Then cooling to 120 ℃ at a cooling rate of 3 ℃/min, and preserving heat for 2 hours, wherein insoluble precipitate is formed in the solution, so as to obtain a solid-liquid mixture;
(3) Cooling the solid-liquid mixture obtained in the step (2) to room temperature, removing liquid (diluent and non-diluent) by means of vacuum filtration to obtain powder, washing the powder with ethanol at 40 ℃ for three times, wherein the washing time is 10min, and the mass percent of the ethanol used for washing is not less than 99%, so as to obtain a mixed system of the ethanol and the diluent; and separating the washed ethanol from the mixed system of the diluent and the non-diluent, and removing the ethanol by vacuum drying at 60 ℃ to obtain polypropylene powder.
Example 2
(1) Adding high-melt polypropylene (MIR=191 g/10 min), low-melt polypropylene (MIR=3.8 g/10 min), dihexyl phthalate (diluent) and glycerin (non-diluent) into a reaction container according to the mass parts of 3:2:85:10, mixing to form a homogeneous solution by stirring and heating, wherein the stirring speed is 300rpm, and preserving heat for 2 hours when the temperature is increased to 180 ℃ to fully and uniformly mix the solution;
(2) Then cooling to 125 ℃ at a cooling rate of 5 ℃/min, and preserving heat for 2 hours, wherein insoluble precipitate is formed in the solution, so as to obtain a solid-liquid mixture;
(3) Cooling the solid-liquid mixture obtained in the step (2) to room temperature, removing liquid (diluent and non-diluent) by means of vacuum filtration to obtain powder, washing the powder with ethanol at 40 ℃ for three times, wherein the washing time is 10min, and the mass percent of the ethanol used for washing is not less than 99%, so as to obtain a mixed system of the ethanol and the diluent; and separating the washed ethanol from the mixed system of the diluent and the non-diluent, and removing the ethanol by vacuum drying at 60 ℃ to obtain polypropylene powder.
Example 3
(1) Adding high-melt-index polypropylene (MIR=191 g/10 min), medium-melt-index polypropylene (MIR=69 g/10 min), dihexyl phthalate (diluent) and glycerin (non-diluent) into a reaction container according to the mass parts of 4:1:80:15, mixing to form a homogeneous solution by stirring and heating, wherein the stirring speed is 400rpm, and preserving heat for 2 hours when the temperature is increased to 180 ℃ to fully and uniformly mix the solutions;
(2) Then cooling to 125 ℃ at a cooling rate of 3 ℃/min, and preserving heat for 3 hours, wherein insoluble precipitate is formed in the solution, so as to obtain a solid-liquid mixture;
(3) Cooling the solid-liquid mixture obtained in the step (2) to room temperature, removing liquid (diluent and non-diluent) by means of vacuum filtration to obtain powder, washing the powder with ethanol at 40 ℃ for three times, wherein the washing time is 10min, and the mass percent of the ethanol used for washing is not less than 99%, so as to obtain a mixed system of the ethanol and the diluent; and separating the washed ethanol from the mixed system of the diluent and the non-diluent, and vacuum drying at 60 ℃ to remove the ethanol to obtain polypropylene powder.
Example 4
(1) Adding high-melt polypropylene (MIR=191 g/10 min), low-melt polypropylene (MIR=3.8 g/10 min), glycerol monooleate (diluent) and dibutyl sebacate (non-diluent) into a reaction container according to the mass parts of 3:2:85:10, mixing to form a homogeneous solution by stirring and heating, wherein the stirring speed is 300rpm, and preserving heat for 2 hours when the temperature is increased to 180 ℃ to fully and uniformly mix the solution;
(2) Then cooling to 120 ℃ at a cooling rate of 1 ℃/min, and preserving heat for 2 hours, wherein insoluble precipitate is formed in the solution, so as to obtain a solid-liquid mixture;
removing liquid (diluent and non-diluent) to obtain powder, washing the powder with ethanol at 40deg.C for three times, wherein the washing time is 10min, and the mass percentage of ethanol used for washing is not less than 99%, to obtain a mixed system of ethanol and diluent; and separating the washed ethanol from the mixed system of the diluent and the non-diluent, and removing the ethanol by vacuum drying at 60 ℃ to obtain polypropylene powder.
The polypropylene powder prepared in comparative examples 1-3 and examples 1-4 is observed by SEM, the obtained microscopic images are shown in figures 1-7, and as can be seen from figures 1-3, the prepared polypropylene powder has poor size uniformity and a certain degree of accumulation; from fig. 4 to fig. 7, it can be seen that the polypropylene powder prepared by the preparation method of the present application has moderate size, narrow particle size distribution, and good sphericity, and no agglomeration phenomenon occurs between the powders, which indicates that the polypropylene powder with more excellent performance can be obtained by the preparation method of the present application.
The embodiments of the present application have been described above with reference to the accompanying drawings, but the present application is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and many forms may be made by those of ordinary skill in the art without departing from the spirit of the present application and the scope of the claims, which are also within the protection of the present application.
Claims (10)
1. A method for preparing polypropylene powder for selective laser sintering, comprising the steps of:
s1: adding 3-10 parts by weight of high-melt-index polypropylene particles, 1-5 parts by weight of low-melt-index polypropylene particles, 45-70 parts by weight of diluent and 15-51 parts by weight of non-diluent into a reaction container, and raising the temperature to be above the melting point of polypropylene to enable the two polypropylene particles to be completely dissolved in a mixed solvent consisting of the diluent and the non-diluent to obtain a homogeneous solution;
s2: maintaining the homogeneous solution for a certain period of time, cooling to crystallization temperature, and continuing constant-temperature stirring until insoluble precipitate is formed in the solution to obtain a solid-liquid mixture;
s3: and cooling the solid-liquid mixture to room temperature, performing vacuum filtration to obtain powder, cleaning the powder with ethanol, and then removing ethanol attached to the surface of the powder by vacuum drying to obtain the polypropylene powder.
2. The process according to claim 1, wherein the high melt index polypropylene particles have a melt mass flow index of 100 to 200g/10min; the melt mass flow index of the low melt index polypropylene particles is 3-10g/10min.
3. The method of claim 1, wherein the diluent is a high boiling point organic material that interacts strongly with the polypropylene; the non-diluent is a high boiling point organic that has weak interactions with the polypropylene.
4. A method of preparation according to claim 3, wherein the diluent is selected from one of cyclohexane 1, 2-dicarboxylic acid diisononyl ester, dihexyl phthalate or glycerol monooleate; the non-diluent is selected from one of glycerin, propylene carbonate or dibutyl sebacate.
5. The method according to claim 1, wherein the step S1 of raising the temperature above the dissolution temperature of polypropylene comprises the following steps:
raising the temperature to 170-190 ℃ according to the heating rate of 3-4 ℃/min, and continuously stirring according to the stirring rate of 100-500rpm during the heating process.
6. The preparation method according to claim 1, wherein the step S2 specifically comprises the steps of:
and (3) preserving the homogeneous solution for 30-180min, then cooling to 120-130 ℃ at a cooling rate of 0.5-5 ℃/min, and continuously stirring at constant temperature for 60-180min until insoluble precipitate is formed in the solution, thus obtaining a solid-liquid mixture.
7. The method according to claim 1, wherein in step S3, the ethanol is washed three times for 10min at 40 ℃.
8. The method according to claim 7, wherein the mass percentage of ethanol is not less than 99%.
9. The method according to claim 1, wherein in step S3, the vacuum drying temperature is 60 ℃.
10. A polypropylene powder for selective laser sintering, characterized in that it is prepared by the preparation method according to any one of claims 1 to 9.
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