3D printing polypropylene powder with thermal conductivity and preparation method thereof

Abstract

The application provides a kind of 3D printing polypropylene powder product with heat conduction performance and its preparation method, the particle size of the polypropylene powder D10=10~40 μm, D50=50~90 μm, D98=100~150 μm, melting point is 150~170 ℃, thermal conductivity is 0.4~0.9 W / m·K.By adding nano boron nitride and metal fiber in polypropylene matrix, the thermal conductivity of the material is significantly improved, and the compatibility between nano boron nitride, metal fiber and polypropylene is further improved by using coupling agent and compatibilizer.A special mixing preparation process ensures that the nano filler and polypropylene are closely combined after laser sintering, so that the printed part has good thermal conductivity, and the mechanical properties, especially toughness and heat resistance, are greatly improved.The polypropylene powder of the application is suitable for SLS printing technology, and has important application prospect in the field of high-performance mechanical parts and heat-conducting materials.

Description

Technical Field

[0001] This invention relates to the field of polymer materials science, and more specifically, to a 3D printing polypropylene powder with thermal conductivity and a method for preparing the same. Background Technology

[0002] 3D printing technology, also known as additive manufacturing, is one of the most promising and competitive processes in modern manufacturing. It encompasses multiple fields such as materials science, information technology, and precision mechanical engineering, and can directly transform digital models into solid parts without relying on molds and fixtures. This technology greatly improves the production flexibility of manufacturing, and is particularly suitable for manufacturing complex structures and customized products.

[0003] Depending on the processing method, 3D printing technology can be divided into several processes, including Fused Deposition Modeling (FDM), Stereolithography (SLA), and Selective Laser Sintering (SLS). SLS technology uses a laser to sinter powder material layer by layer to create three-dimensional solid parts. It is a supportless process with high material utilization and is suitable for forming complex structures. Compared with other 3D printing processes, SLS can directly generate parts with high mechanical strength and precision without the need for support structures, and therefore is widely used in industrial manufacturing. Patent US 6136948 describes in detail an SLS method for preparing three-dimensional solids using polymer powder.

[0004] The materials that can be selected for SLS forming technology are very diverse, including various powder materials such as metals, ceramics, and polymers. Polymer powders have certain advantages due to their lower forming temperature, lower laser power requirements, and lower energy consumption. However, the types of polymer powders that can currently be successfully applied in the SLS process to produce high-quality products are still relatively limited, mainly focusing on polyamides (such as PA12). Other polymer powders are rarely used, and there is an urgent need to develop more types of polymer powders to expand the application scope of SLS technology.

[0005] In recent years, SLS technology has gradually incorporated polypropylene (PP) materials. Due to its excellent chemical resistance, good fatigue resistance, and high impact strength, polypropylene is particularly suitable for manufacturing parts in the automotive, consumer goods, and medical industries. However, because PP itself has poor thermal conductivity, significant heat accumulation occurs during SLS printing, affecting the dimensional stability and surface quality of the printed parts. Furthermore, PP exhibits significant volume shrinkage during melt crystallization, and its high crystallinity makes it prone to warping and shrinkage during SLS printing. Patent CN101602871 addresses this issue. In addition, currently widely used polypropylene powders fail to meet the requirements of high-end industrial applications in terms of mechanical strength and elasticity, particularly in terms of high toughness and impact resistance. Summary of the Invention

[0006] To address the shortcomings and deficiencies of existing technologies, this invention provides a 3D printing polypropylene powder product with thermal conductivity and its preparation method. This polypropylene powder possesses a suitable particle size distribution, excellent sphericity, good thermal conductivity, and powder flowability. During SLS printing, it can effectively reduce warpage and deformation, and improve the molding accuracy, heat resistance, and mechanical properties of the parts. The PP powder of this invention is particularly suitable for selective laser sintering (SLS) to prepare various molded products.

[0007] On one hand, the present invention provides a 3D printing polypropylene powder with thermal conductivity, wherein the polypropylene powder has a particle size of D10 = 10-40 μm, D50 = 50-90 μm, D98 = 100-150 μm, a melting point of 150-170℃, and a thermal conductivity of 0.4-0.9 W / m·K; the powder is prepared from raw materials comprising the following parts by weight:

[0008] (a) 100 parts by weight of polypropylene;

[0009] (b) 5-45 parts by weight of elastomer, preferably 10-30 parts by weight, preferably 13-28 parts by weight;

[0010] (c) 3-15 parts by weight of nano boron nitride, preferably 5-10 parts by weight, more preferably 5.5-9 parts by weight, and even more preferably 6-8 parts by weight;

[0011] (d) 5-20 parts by weight of metal fiber, preferably 5-15 parts by weight, more preferably 7.5-12 parts by weight, and even more preferably 8-10 parts by weight;

[0012] (e) Antioxidant 0.3-3.5 parts by weight, preferably 0.5-2 parts by weight;

[0013] (f) 0.5-10 parts by weight of coupling agent, preferably 2-8 parts by weight, more preferably 3-6 parts by weight;

[0014] (g) 0.5-10 parts by weight of compatibilizer, preferably 2-8 parts by weight, more preferably 3-6 parts by weight;

[0015] (h) 0.5-10 parts by weight of flow aid, preferably 2-8 parts by weight, more preferably 3-6 parts by weight;

[0016] (i) 0.5-10 parts by weight of antistatic agent and / or lubricant, preferably 2-8 parts by weight, more preferably 2.5-7 parts by weight, and most preferably 2.5-5 parts by weight.

[0017] In this invention, the polypropylene is a copolymerized metallocene catalytic polypropylene (mPP), wherein the ethylene content is 0-30%, the isotacticity is 80%-90%, the melt flow index is 5-50 g / 10 min at 230℃ and 2.16 kg, and the elongation at break is >300%.

[0018] In this invention, the elastomer is selected from one or more combinations of styrene-butadiene-styrene block copolymer, styrene-ethylene-butene-styrene block copolymer, and styrene-isobutylene-styrene block copolymer, with a styrene content of 10-35%, and the styrene content is further optimized to 18-30%.

[0019] In this invention, the particle size of the boron nitride is 80-150 nm, and is further optimized to 100-120 nm.

[0020] In this invention, the metal fiber is selected from alumina fiber and stainless steel fiber, with a preferred length of 50-200 μm, further optimized to 80-120 μm, and a preferred diameter of 1-25 μm, further optimized to 5-15 μm.

[0021] In this invention, the antioxidant is one or a combination of two of hindered phenolic antioxidants and phosphite antioxidants, and is further optimized to be a combination of antioxidant 1010, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and antioxidant 168, tris[2,4-di-tert-butylphenyl]phosphite.

[0022] In this invention, the coupling agent is one or a combination of two or more of silane coupling agents, titanate coupling agents, and phosphate coupling agents.

[0023] In this invention, the compatibilizer is one or a combination of two or more of glycidyl methacrylate, glycidyl acrylate, and ethylene-acrylic acid copolymer.

[0024] In this invention, the flow aid is one or more of dimethylchlorosilane-treated silica and polydimethylsiloxane-treated silica. Preferably, the flow aid BET has a specific surface area of ​​150-250 m². 2 / g, with a carbon content of 2.0 to 7.0 wt%, more preferably 3.5 to 5.5 wt%.

[0025] In this invention, the antistatic agent is one or a combination of two of trialkylmethylammonium chloride and sodium alkyl sulfonate.

[0026] In this invention, the lubricant is one or a combination of calcium stearate, zinc stearate and low molecular weight polyethylene wax.

[0027] On the other hand, the present invention also provides a method for preparing 3D printing polypropylene powder with thermal conductivity, the method comprising the following steps:

[0028] 1) Disperse (d) metal fibers / (c) nano boron nitride in an ethanol solution containing 0.5-3% coupling agent and treat at 40-60℃ for 2-8 hours. Then filter out the product, wash with water and dry it.

[0029] 2) Add (a) polypropylene, (b) elastomer and (g) compatibilizer to a high-speed mixer, then add (e) antioxidant and (i) antistatic agent and / or lubricant, and mix at 1500 rpm for 15 minutes. Then add nano boron nitride and metal fiber treated in step 1) to the high-speed mixer, continue mixing for 25 minutes and then discharge the material. Then feed it into a twin-screw feed hopper and use twin-screw extrusion to melt and mix evenly. The melt extrusion temperature is 200℃. Then granulate and dry it under the drying conditions of 80℃×2h.

[0030] 3) The plastic particles obtained in step 2) are cooled with liquid nitrogen and then cryogenically pulverized to obtain plastic powder raw material;

[0031] 4) Mix the plastic powder raw material obtained in step 3) and (h) flow aid evenly to finally obtain a 3D printing polypropylene powder product with thermal conductivity.

[0032] The beneficial effects of this invention are as follows:

[0033] 1. Polypropylene has relatively low thermal conductivity, which leads to uneven heat distribution in the SLS process. This invention significantly improves the thermal conductivity of polypropylene powder by adding nano boron nitride and metal fibers, making the heat distribution more uniform during SLS 3D printing, reducing the heat accumulation effect, thereby effectively reducing the warping and deformation of printed parts, and improving the dimensional accuracy and surface quality of the molded parts.

[0034] 2. The significant polarity difference between nano-boron nitride and metal fibers and polypropylene leads to poor compatibility.

[0035] The powder preparation method provided by the invention cleverly separates the addition of the compatibilizer from the use of the coupling agent, which not only avoids...

[0036] This will increase the complexity of existing processes, but it can also effectively improve the compatibility of nano-boron nitride, metal fibers, and polypropylene.

[0037] This enhances the overall performance of the material while maintaining the characteristics of simple processing and controllable cost, avoiding complex processing steps.

[0038] 3. This invention prepares polypropylene powder using a low-temperature pulverization method. Polypropylene powder obtained by traditional methods has a different texture.

[0039] It is brittle and hard, and after being crushed, it forms irregular shapes, usually in the form of thin, irregular strips, resulting in poor powder flowability.

[0040] Poor. This invention found that adding an elastomer significantly improved the pulverization effect, resulting in a powder with a near-spherical morphology.

[0041] High sphericity. Detailed Implementation

[0042] The present invention will be further described below through specific embodiments, but it should be understood that the scope of the present invention is not limited thereto.

[0043] The features, beneficial effects, and advantages of this invention will become apparent to those skilled in the art upon reading the disclosure of this specification.

[0044] Unless otherwise specified, all preparations and tests described herein took place at 25°C.

[0045] The terms “comprising,” “including,” “containing,” “having,” “comprising,” or other variations thereof are intended to cover non-closed inclusion, and no distinction is made between these terms. The term “comprising” means that other steps and components may be added without affecting the final result. The term “comprising” also includes the terms “consisting of” and “substantially consisting of”. The compositions and methods / processes of the present invention may comprise, consist of, and substantially consist of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein.

[0046] Preparation and usage instructions

[0047] Without further detailed explanation, it is believed that those skilled in the art can fully utilize the present invention based on the above description. The following embodiments are intended to further illustrate and demonstrate specific implementations within the scope of the present invention. Therefore, the embodiments should be understood as being used only to illustrate the present invention in more detail, and not to limit the scope of the present invention in any way.

[0048] The following examples further illustrate preferred embodiments within the scope of the present invention. These examples are merely illustrative and not intended to limit the scope of the invention, as many variations can be made to the invention without departing from its essence and scope.

[0049] A method for preparing 3D-printed polypropylene powder products with thermal conductivity includes the following steps:

[0050] (a) Disperse metal fibers / nano boron nitride in an ethanol solution containing 0.5-3% coupling agent and treat at 40-60°C for 2-8 hours. Then filter out the product, wash with water and dry it.

[0051] (b) Add polypropylene, elastomer, and compatibilizer to a high-speed mixer, then add antioxidants and other additives, and mix at 1500 rpm for 15 minutes. Then add the nano-boron nitride and metal fibers treated in step (a) to a high-speed mixer, continue mixing for 25 minutes, and discharge the mixture. Then feed the mixture into a twin-screw extruder and melt-mix it evenly. The melt extrusion temperature is 200°C, and the rotation speed is [missing information].

[0052] 300 rpm, then granulate and dry at 80℃ for 2 hours;

[0053] (c) The plastic particles obtained in step (b) are cooled with liquid nitrogen and then pulverized at low temperature to obtain plastic powder raw material with particle size D10 = 10-40 μm, D50 = 50-90 μm, and D98 = 100-150 μm;

[0054] (d) Mix the plastic powder raw material and flow aid obtained in step 1 again and stir until homogeneous. The stirring conditions are as follows: speed 90 rpm

[0055] The thermally conductive 3D printing polypropylene powder described in this invention was finally obtained after running at 5000 rpm for 10 minutes.

[0056] product.

[0057] In the following examples, the particle size and particle size distribution of the obtained polypropylene powder were characterized using a laser particle size analyzer (Mastersizer 2000, Malvern, UK).

[0058] Examples 1-6 of 3D Printing Polypropylene Powder with Thermal Conductivity

[0059] Based on the component compositions of Examples 1-6, polypropylene powder products were prepared according to the above preparation method. The polypropylene powders obtained in Examples 1-6 have a narrow particle size distribution, good flowability, and good thermal conductivity, enabling them to perform SLS printing well without warping or deformation of the parts. They also exhibit high tensile strength and good toughness, making them suitable for various applications.

[0060]

[0061]

[0062]

[0063]

[0064] Comparative Examples 1-5 of Polypropylene Powder for Selective Laser Sintering

[0065]

[0066]

[0067] Compared with Example 1, Comparative Example 1, which did not add nano-boron nitride and metal fibers, showed a significant decrease in the thermal conductivity of the part. Comparative Examples 2 and 3, also lacking nano-boron nitride and metal fibers, showed a slight decrease in thermal conductivity due to the absence of their synergistic effect. This indicates that nano-boron nitride and metal fiber filling plays a crucial role in the thermal conductivity of the material. Furthermore, the absence of nano-boron nitride and metal fibers led to a decrease in the performance of the part, particularly its tensile properties. Comparative Examples 4 and 5, which did not add compatibilizers and coupling agents, showed poor bonding between the nano-boron nitride and metal fibers and the polypropylene resin, affecting the performance of the part and significantly reducing its tensile properties.

[0068] Although the present invention has been described in detail, modifications within the spirit and scope of the invention will be readily apparent to those skilled in the art. Furthermore, it should be understood that the aspects described in the invention, the parts of different embodiments, and the various features listed can be combined or interchanged in whole or in part. In the various embodiments described above, those embodiments referencing another embodiment can be appropriately combined with other embodiments, as will be understood by those skilled in the art. Moreover, those skilled in the art will understand that the foregoing description is merely illustrative and not intended to limit the invention.

Claims

1. A 3D printing polypropylene powder with thermal conductivity, said powder being prepared from raw materials comprising the following parts by weight: (a) 100 parts by weight of polypropylene; (b) 5-45 parts by weight of elastomer, preferably 10-30 parts by weight, preferably 13-28 parts by weight; (c) 3-15 parts by weight of nano boron nitride, preferably 5-10 parts by weight, more preferably 5.5-9 parts by weight, and even more preferably 6-8 parts by weight; (d) 5-20 parts by weight of metal fiber, preferably 5-15 parts by weight, more preferably 7.5-12 parts by weight, and even more preferably 8-10 parts by weight; (e) Antioxidant 0.3-3.5 parts by weight, preferably 0.5-2 parts by weight; (f) 0.5-10 parts by weight of coupling agent, preferably 2-8 parts by weight, more preferably 3-6 parts by weight; (g) 0.5-10 parts by weight of compatibilizer, preferably 2-8 parts by weight, more preferably 3-6 parts by weight; (h) 0.5-10 parts by weight of flow aid, preferably 2-8 parts by weight, more preferably 3-6 parts by weight; (i) 0.5-10 parts by weight of antistatic agent and / or lubricant, preferably 2-8 parts by weight, more preferably 2.5-7 parts by weight, and most preferably 2.5-5 parts by weight.

2. The 3D printing polypropylene powder with thermal conductivity as described in claim 1, characterized in that, The polypropylene is a copolymerized metallocene catalytic polypropylene (mPP) with an ethylene content of 0-30%, an isotacticity of 80%-90%, a melt flow index of 5-50 g / 10 min at 230℃ and 2.16 kg, and an elongation at break of >300%.

3. The 3D printing polypropylene powder with thermal conductivity as described in claim 1 or 2, characterized in that, The elastomer is selected from one or more of styrene-butadiene-styrene block copolymers, styrene-ethylene-butene-styrene block copolymers, and styrene-isobutylene-styrene block copolymers, with a styrene content of 10-35%, and the styrene content is further optimized to 18-30%.

4. The 3D printing polypropylene powder with thermal conductivity as described in any one of claims 1-3, characterized in that, The boron nitride particles have a particle size of 80–150 nm, further optimized to 100–120 nm; and / or, the metal fiber is selected from alumina fiber and stainless steel fiber, with a length preferably of 50–200 μm, further optimized to 80–120 μm, and a diameter preferably of 1–25 μm, further optimized to 5–15 μm.

5. The 3D printing polypropylene powder with thermal conductivity as described in any one of claims 1-4, characterized in that, The antioxidant is one or a combination of two of hindered phenolic antioxidants and phosphite antioxidants, and is further optimized to be a combination of antioxidant 1010, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and antioxidant 168, tris[2,4-di-tert-butylphenyl]phosphite.

6. The 3D printing polypropylene powder with thermal conductivity as described in any one of claims 1-5, characterized in that, The coupling agent is one or a combination of two or more of silane coupling agents, titanate coupling agents, and phosphate coupling agents; and / or, the compatibilizer is one or a combination of two or more of glycidyl methacrylate, glycidyl acrylate, and ethylene-acrylic acid copolymer.

7. The 3D printing polypropylene powder with thermal conductivity as described in any one of claims 1-6, characterized in that, The flow aid is one or more of dimethylchlorosilane-treated silica and polydimethylsiloxane-treated silica; preferably, the flow aid BET has a specific surface area of ​​150-250 m². 2 / g, with a carbon content of 2.0 to 7.0 wt%, more preferably 3.5 to 5.5 wt%.

8. The 3D printing polypropylene powder with thermal conductivity as described in any one of claims 1-7, characterized in that, The antistatic agent is one or a combination of two of trialkylmethylammonium chloride and sodium alkyl sulfonate; and / or, the lubricant is one or a combination of calcium stearate, zinc stearate and low molecular weight polyethylene wax.

9. The 3D printing polypropylene powder with thermal conductivity as described in any one of claims 1-8, characterized in that, The polypropylene powder has a particle size of D10 = 10-40 μm, D50 = 50-90 μm, D98 = 100-150 μm, a melting point of 150-170℃, and a thermal conductivity of 0.4-0.9 W / m·K.

10. The method for preparing thermally conductive 3D printing polypropylene powder according to any one of claims 1-8, characterized in that, The method includes the following steps: 1) Disperse (d) metal fibers / (c) nano boron nitride in an ethanol solution containing 0.5-3% coupling agent and treat at 40-60℃ for 2-8h. Then filter out the product, wash with water and dry it. 2) Add (a) polypropylene, (b) elastomer and (g) compatibilizer to a high-speed mixer, then add (e) antioxidant and (i) antistatic agent and / or lubricant, and mix at 1500 rpm for 15 minutes. Then add nano boron nitride and metal fiber treated in step 1) to the high-speed mixer, continue mixing for 25 minutes and discharge the material. Then feed it into a twin-screw feed hopper and use twin-screw extrusion to melt and mix evenly. The melt extrusion temperature is 200℃. Then granulate and dry it under the drying conditions of 80℃×2h. 3) The plastic particles obtained in step 2) are cooled with liquid nitrogen and then cryogenically pulverized to obtain plastic powder raw material; 4) Mix the plastic powder raw material obtained in step 3) and (h) flow aid evenly to finally obtain a 3D printing polypropylene powder product with thermal conductivity.

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