A spherical polymer powder material for selective laser sintering and a method of making the same

Abstract

The application discloses a kind of spherical polymer powder materials for selective laser sintering, including polymer 3-13 parts, diluent 45-65 parts, dispersing agent 32-52 parts by mass fraction, wherein the polymer is polypropylene homo- or copolymer, and the dispersing agent is selected from 1,3-propanediol, 1,3-butanediol, 1,4-butanediol.The application also discloses a kind of spherical polymer powder materials for selective laser sintering preparation method.The application is prepared under normal pressure Polymer powder, high sphericity, narrow particle size distribution, simple preparation process, solvent can be recycled, with good industrialization prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer materials, and particularly relates to a spherical polymer powder material for selective laser sintering and a preparation method thereof. BACKGROUND

[0002] The selective laser sintering technology (SLS) is one of additive manufacturing technologies, and powder can be sintered into a shape layer by layer through layer-by-layer manufacturing and layer-by-layer stacking. The powder in the sintering area is heated to make the particle boundaries intersect and bond together, and the powder in the unsintered area is still in a loose state, which supports the next layer of sintering, so that no support material and mold are needed, and the forming part is not limited by the complexity of the shape, and the SLS technology has become one of the most widely used additive manufacturing technologies.

[0003] The selection of forming materials is an important part of the SLS technology, which directly affects the forming speed, precision and performance of the sintering process. The materials applied to the SLS technology include metal powder materials, polymer powder materials and ceramic powder materials. The polymer powder material has a lower melting temperature, and its sintering power and forming temperature are much lower than those of metal and ceramic powder materials. In addition, the surface tension of the polymer powder material is small, and it will not appear “spheroidization” phenomenon like metal powder in the sintering process, and the internal pores of the sintered part will not cause the density of the sintered part to decrease, which can ensure good mechanical properties. At present, the polymer powder has become the most widely used SLS forming material. Among them, polypropylene, as one of the five general-purpose plastics, has excellent heat resistance, chemical stability and processing fluidity, and is low in price, so it is necessary to prepare polypropylene powder that can be used in the SLS technology.

[0004] The current methods for preparing polypropylene powder for SLS mainly include solvent precipitation method and cryogenic crushing method. The solvent precipitation method needs to be dissolved under high pressure and high temperature conditions, and has high requirements for equipment. In patent CN107383593B, xylene, toluene, diphenyl ether and other solvents are selected to prepare polypropylene powder, but the selected solvents are harmful to the environment. The cryogenic crushing method is also a common method for preparing polypropylene powder for SLS. Patent CN104031319A describes that polypropylene is prepared into powder by the cryogenic crushing method. Although this method is simple in preparation process, the prepared powder has a wide particle size distribution and irregular shape, which seriously affects the forming precision of the SLS sintered part. Therefore, it is necessary to develop a method for preparing polypropylene powder with simple preparation process, environmental friendliness, narrow particle size distribution and high sphericity. SUMMARY

[0005] The purpose of the embodiments of the application is to provide a spherical polymer powder material for selective laser sintering with narrow particle size distribution and high sphericity, and a preparation method thereof, which can obtain polymer powder with good powder laying effect at a lower temperature, thereby solving the technical problems involved in the background art.

[0006] To solve the above technical problems, the application is implemented as follows:

[0007] A spherical polymer powder material for selective laser sintering, comprising, in mass fraction, 3-13 parts of a polymer, 45-65 parts of a diluent, and 32-52 parts of a dispersant, wherein the polymer is a homopolymer or copolymer of polypropylene, and the dispersant is selected from 1,3-propanediol, 1,3-butanediol, and 1,4-butanediol.

[0008] In some embodiments, the diluent is dioctyl terephthalate, diisononyl phthalate, or glycerol monooleate.

[0009] The application also discloses a preparation method of the spherical polymer powder material for selective laser sintering.

[0010] The polymer, the diluent, and the dispersant are added into a reaction kettle in a certain proportion, heated and stirred under normal pressure to fully mix and obtain a uniform solution.

[0011] After the uniform solution is kept for a certain time, the polymer is separated from the uniform solution by programmed cooling.

[0012] The separated polymer is washed with ethanol, and dried to obtain a polymer powder.

[0013] In some embodiments, the heating and stirring under normal pressure to fully mix comprises:

[0014] The heating temperature is 130-160°C.

[0015] In some embodiments, the heating and stirring under normal pressure to fully mix comprises:

[0016] The stirring rate is 20-500 rpm.

[0017] In some embodiments, the keeping of the mixed solution for a certain time comprises:

[0018] The keeping time is 1-3 h.

[0019] In some embodiments, the separation of the polymer from the mixed solution by programmed cooling comprises:

[0020] The cooling rate is 1-5°C / min.

[0021] In some embodiments, the drying to obtain a polymer powder comprises:

[0022] The drying temperature is 60-80°C.

[0023] Compared with the prior art, the application has the following technical effects:

[0024] (1) High-boiling 1,3-propanediol, 1,3-butanediol, and 1,4-butanediol are selected as dispersants, which can effectively prevent polymer-lean phase particles from agglomeration and can adjust the interaction force between the polymer and the diluent, so that a uniform solution can be phase-separated into liquid-liquid phases when cooled, and the polymer-lean phase can nucleate and grow in a solution state, thereby reducing the requirements of polymer powder on the preparation conditions;

[0025] (2) By adding high-boiling 1,3-propanediol, 1,3-butanediol, and 1,4-butanediol as dispersants, the polymer nucleation barrier is effectively reduced, the polymer-lean phase droplets preferentially nucleate and grow around the dispersants, the nucleation rate of the polymer-lean phase droplets is improved, and the nucleation can start in the early stage of cooling, thereby improving the crystallinity and sphericity of the powder, and obtaining a polymer powder with narrow particle size distribution, high sphericity, and good mechanical properties;

[0026] (3) The polymer, the diluent, and the dispersant can form a uniform solution after heating at normal pressure without high pressure, and the diluent and the dispersant can completely phase-separate at room temperature, and the solvent can be recycled. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a microscope morphology diagram of a spherical polymer powder material for selective laser sintering provided by the embodiment of the application. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the application.

[0029] The terms "first", "second", and the like in the description and claims of the application are used for distinguishing between similar objects and are not necessarily used to describe a particular sequential or chronological order. It is to be understood that the use of such terms is only meant to distinguish between objects for ease of description and not meant to limit the example embodiments of the application that enable a selective laser sintering of a spherical polymer powder material to a specific sequence or order, unless otherwise specifically indicated. Furthermore, these terms "first", "second", and the like are used an interchangeable with "one or more", "one or more of", or "at least one". Also, the term "and / or" includes combinations thereof, i.e. "A and / or B" means "A or B or both".

[0030] The selective laser sintering of a spherical polymer powder material provided by the example embodiments of the application will be described in detail below with reference to specific examples and application scenarios.

[0031] The selective laser sintering of a spherical polymer powder material provided by the example embodiments of the application includes, by mass fraction, 3-13 parts of a polymer, 45-65 parts of a diluent, and 32-52 parts of a dispersant, wherein the polymer is a homopolymer or copolymer of polypropylene, and the dispersant is selected from 1,3-propanediol, 1,3-butanediol, and 1,4-butanediol.

[0032] In some embodiments, the diluent is dioctyl terephthalate, diisononyl phthalate, or glycerol monooleate.

[0033] The application also discloses a preparation method of the selective laser sintering of a spherical polymer powder material, including:

[0034] By mass fraction, 3-13 parts of a polymer, 45-65 parts of a diluent, and 32-52 parts of a dispersant are added to a reaction kettle in a certain proportion, heated and stirred at a normal pressure and a temperature of 130-160°C to fully mix and uniformly, at a stirring rate of 20-500 rpm, to obtain a uniform solution.

[0035] After the uniform solution is kept for 1-3 hours, the polymer is separated from the uniform solution by programmed cooling at a cooling rate of 1-5°C / min.

[0036] The separated polymer is washed with ethanol and dried at a temperature of 60-80°C to obtain a polymer powder.

[0037] Referring again to Figure 1 As shown in the microscope, the polymer powder prepared by the application has a narrow particle size distribution and high sphericity.

[0038] The preparation method of the selective laser sintering of a spherical polymer powder material disclosed by the application will be described in detail below with reference to specific examples and comparative examples.

[0039] Example 1:

[0040] Copolymerized polypropylene / dioctyl terephthalate / 1,3-butanediol was added to the reaction kettle in a mass ratio of 5 / 55 / 40, mixed into a uniform solution at 150°C, 200 rpm stirring rate, and incubated for 3h, then the mixture was removed after cooling to 60°C at a cooling rate of 5°C / min, washed thoroughly with ethanol and dried at 70°C to obtain a polymer powder.

[0041] Example 2:

[0042] Copolymerized polypropylene / diisononyl phthalate / 1,3-butanediol was added to the reaction kettle in a mass ratio of 7 / 65 / 28, mixed into a uniform solution at 140°C, 300 rpm stirring rate, and incubated for 2h, then the mixture was removed after cooling to 60°C at a cooling rate of 5°C / min, washed thoroughly with ethanol and dried at 80°C to obtain a polymer powder.

[0043] Example 3:

[0044] Homopolymerized polypropylene / dioctyl terephthalate / 1,4-butanediol was added to the reaction kettle in a mass ratio of 7 / 60 / 33, mixed uniformly at 150°C, 300 rpm stirring rate, and incubated for 2h, then the mixture was removed after cooling to 60°C at a cooling rate of 3°C / min, washed thoroughly with ethanol and dried at 70°C to obtain a polymer powder.

[0045] Example 4:

[0046] Copolymerized polypropylene / diisononyl phthalate / 1,3-butanediol was added to the reaction kettle in a mass ratio of 5 / 65 / 28, mixed uniformly at 145°C, 200 rpm stirring rate, and incubated for 1h, then the mixture was removed after cooling to 60°C at a cooling rate of 5°C / min, washed thoroughly with ethanol and dried at 80°C to obtain a polymer powder.

[0047] Example 5:

[0048] Homopolymerized polypropylene / glycerol monooleate / 1,4-butanediol was added to the reaction kettle in a mass ratio of 7 / 65 / 28, mixed uniformly at 155°C, 300 rpm stirring rate, and incubated for 2h, then the mixture was removed after cooling to 60°C at a cooling rate of 5°C / min, washed thoroughly with ethanol and dried at 80°C to obtain a polymer powder.

[0049] Comparative Example 1:

[0050] The copolymerized polypropylene / dioctyl terephthalate was added into the reaction kettle in a mass ratio of 5 / 95, and after being mixed into a uniform solution at 150℃ and 200rpm stirring rate, it was incubated for 3h, then it was taken out after being cooled to 60℃ at a cooling rate of 5℃ / min, washed thoroughly with ethanol and dried at 70℃ to obtain a polymer powder.

[0051] The polymer powders obtained from Examples 1-5 and the polymer powder obtained from Comparative Example 1 were tested, and the test results are shown in Table 1.

[0052] Table 1 Test data of polymer powders of Comparative Example 1 and Examples 1-4

[0053]

[0054] As can be seen from Table 1, the polymer powders obtained from Examples 1-5 have not only a narrow particle size distribution and high sphericity, but also higher crystallinity and bulk density compared with the polymer powder obtained from Comparative Example 1.

[0055] Compared with the prior art, the present application has the following technical effects:

[0056] (1) High-boiling 1,3-propanediol, 1,3-butanediol, and 1,4-butanediol are selected as dispersants, which can effectively prevent the polymer-lean particles from agglomerating and forming clusters, and on the other hand, they have weak interactions with the diluent, which can adjust the interaction force between the polymer and the diluent, so that the homogeneous solution can undergo liquid-liquid phase separation when cooled, and under this condition, the polymer-lean phase can nucleate and grow in a solution state, reducing the requirements of the polymer powder on the preparation conditions;

[0057] (2) By adding high-boiling 1,3-propanediol, 1,3-butanediol, and 1,4-butanediol as dispersants, the polymer nucleation barrier is effectively reduced, the polymer-lean droplets preferentially nucleate and grow around the dispersants, improving the nucleation rate of the polymer-lean droplets, so that they can start to nucleate in the early stage of cooling, improving the crystallinity and sphericity of the powder, and obtaining a polymer powder with narrow particle size distribution, high sphericity, and good mechanical properties;

[0058] (3) The polymer, diluent, and dispersant can form a homogeneous solution after heating under normal pressure, without the need for high pressure, and the diluent and dispersant completely separate at room temperature, and the solvent can be recycled.

[0059] The embodiments of the present application are described above with reference to the accompanying drawings, but the present application is not limited to the specific embodiments described above, and the specific embodiments described above are merely illustrative, but not restrictive, and a person of ordinary skill in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims.

Claims

1. A spherical polymeric powder material for selective laser sintering, characterized in that, According to mass parts, including polymer 3-13 parts, diluent 45-65 parts, dispersant 32-52 parts, wherein the polymer is a homopolymer or copolymer of polypropylene, the diluent is selected from any one of dioctyl terephthalate, diisononyl phthalate, glycerol monooleate; the dispersant is selected from any one of 1,3-propanediol, 1,3-butanediol, 1,4-butanediol; The spherical polymer powder material for selective laser sintering is prepared by the following method: According to mass parts, 3-13 parts of polymer, 45-65 parts of diluent, 32-52 parts of dispersant are added to the reaction kettle in a certain proportion, heated to 130-160℃ under normal pressure, stirred and fully mixed to obtain a uniform solution; After the uniform solution is kept for a certain time, the polymer is separated out from the uniform solution by programmed cooling, and the cooling rate is 1-5℃ / min; The separated polymer is washed with ethanol, dried at a temperature of 60-80℃ to obtain a polymer powder.

2. The spherical polymeric powder material for selective laser sintering according to claim 1, characterized in that, The heating, stirring and fully mixing under normal pressure include: The stirring rate is 20-500rpm.

3. The spherical polymeric powder material for selective laser sintering according to claim 1, characterized in that, The uniform solution is kept for 1-3h.

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