A 3D printed foamed product and its preparation process

Abstract

The present invention discloses a preparation process of a 3D foamed product, comprising the following steps: S1: Mix a first high molecular resin with a second high molecular resin powder to obtain a powder to be foamed; S2: Subject the powder to be foamed to supercritical foaming in a supercritical fluid to obtain a foamed powder; S3: Perform selective laser sintering on the foamed powder to obtain a foamed product. The present invention also discloses a foamed product prepared by the above preparation process. In the preparation process disclosed by the present invention, the foaming and laser sintering temperatures are lower than the melting point of the high molecular resin powder, and there will be no problem that the internal foaming structure is damaged due to melting. At the same time, during the laser sintering process, the second high molecular resin on the surface causes the foamed powder to be welded together, preventing the bubbles in the first high molecular resin from escaping with the laser irradiation due to too high a sintering temperature, thereby obtaining a high magnification foamed product. The preparation process of the present invention is simple, the product repeatability is high, and it is suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the field of polymer material processing, and particularly relates to a 3D printed foamed product and a preparation process thereof. Background Art

[0002] 3D printing technology, also known as additive technology, is a preparation process that uses three-dimensional data as a basis and manufactures parts or physical objects by means of material stacking. Compared with the traditional "subtractive manufacturing method", it has high material utilization rate, low cost, does not require traditional tools, jigs, machine tools or any molds, and can quickly and accurately convert a three-dimensional model into a solid, and is widely used in the fields of tissue engineering, aerospace, energy storage, electronics and devices, vehicle manufacturing, engineering composite materials, etc. 3D printing technology is mainly divided into fused deposition modeling technology (FDM method), stereolithography (SLA method), solvent casting molding (SC-3DP method) and selective laser sintering technology (SLS method) according to the different cores of the manufacturing plastic preparation process.

[0003] More than 80% of the polymer materials applied to 3D printing in the market are hard materials, which limits their application in industries such as wearable devices, medical sensors, and shoe soles. Combining foamed materials with 3D printing can prepare flexible and lightweight materials. At present, the common method is to first use 3D printing for shaping and then perform foaming. For example, Chinese Patent Document CN106493968A discloses a method and device for producing foamed products in combination with 3D printing. This method is to first print a three-dimensional model according to the product requirements, then infiltrate this three-dimensional model in a supercritical infiltration unit, and then perform steam foaming in a foaming box to obtain a foamed product. However, the foamed product obtained in this way has a rough appearance and cannot fully utilize the advantages of 3D printing. Chinese Patent Document CN110193931A discloses a method for 3D printing a high-performance foam shoe midsole. This method is to first impregnate shoe thermoplastic elastomer resin particles in a supercritical gas and then slowly release the pressure, and then print and foam the material using the fused deposition molding method to obtain a 3D printed foam shoe midsole. The foamed product prepared by this method has a small foaming ratio, the extrusion parameters are not easy to control, the material foams after melting and extruding, the cell structure is uncontrollable, and the dimensional accuracy of the foamed product is low. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the disadvantages of low accuracy and small foaming ratio of the foamed product when using 3D printing technology to prepare foamed products from existing thermoplastic elastomers, and to provide a 3D printed foamed product and a preparation process thereof.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] The present invention provides a preparation process for a 3D printed foamed product, including the following steps:

[0007] S1: Mix the first polymer resin and the second polymer resin powder to obtain the powder to be foamed.

[0008] S2: Subject the powder to be foamed to supercritical foaming in a supercritical fluid to obtain a foamed powder with the first polymer resin wrapped by the second polymer resin.

[0009] S3: Perform selective laser sintering on the foamed powder to produce a foamed product.

[0010] Furthermore, the molecular weight of the first polymer resin is 100,000 - 500,000, the hardness is 50 - 95A, the melting point is 110 - 200 °C, and the particle size is 20 - 70 μm.

[0011] The molecular weight of the second polymer resin is 30,000 - 400,000, the hardness is 40 - 90A, the melting point is 90 - 180 °C, and the particle size is 10 - 20 μm.

[0012] Preferably, the first polymer resin and the second polymer resin are of the same type of polymer resin material, and the melting point of the first polymer resin is higher than that of the second polymer resin.

[0013] The polymer resin material is one of polylactic acid, polypropylene, polyethylene, polyvinylidene fluoride, polyolefin elastomer, polyamide, thermoplastic polyurethane, polyamide elastomer, and polyester elastomer.

[0014] Preferably, the mass ratio of the first polymer resin powder to the second polymer powder is (4 - 49):1;

[0015] The rotation speed of the mixing is 400 - 1000 r / min, and the mixing time is 90 - 180 min.

[0016] Furthermore, the supercritical foaming is to place the powder to be foamed in an autoclave, introduce a supercritical fluid to impregnate the powder to be foamed therein, and then relieve the pressure for foaming.

[0017] Preferably, the impregnation time is 10 - 30 min, the impregnation pressure is 5 - 40 MPa, and the pressure relief rate is 10 - 300 MPa / s;

[0018] A mesh is provided at the pressure relief port to prevent the powder from flowing out of the pressure relief port with the gas or blocking the pressure relief port;

[0019] The impregnation temperature is lower than the melting point of any component in the powder to be foamed;

[0020] The supercritical fluid is nitrogen and / or carbon dioxide.

[0021] Further, the selective laser sintering uses a CO2 laser, the scanning speed of the CO2 laser is 5 - 10 m / s, the scanning spacing is 0.02 - 3 mm, and the power is 2 - 30 W; and / or,

[0022] The selective laser sintering is to transfer the foaming powder to a powder bed to form a powder layer, the temperature of the powder bed is 50 - 90 °C, and the thickness of the powder layer is 60 - 200 μm.

[0023] The present invention also provides a foamed product prepared by the above preparation process.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The preparation process of the 3D printed foamed product provided by the present invention uses the selective laser sintering technology to prepare the foamed product. Its main material is a high molecular resin with a relatively wide molecular weight distribution and a relatively wide melting range, which is suitable for the selective laser sintering preparation process. At the same time, during the foaming and 3D printing processes, the temperature is lower than the melting point of the first high molecular resin, and there will be no problem that the internal foaming structure is damaged due to melting, so that the obtained foamed product has high precision, and the foaming ratio will not be affected during the 3D printing process.

[0026] 2. The present invention mixes the first high molecular resin and the second high molecular resin. During foaming, the second high molecular resin is too small in particle size to wrap the bubbles and attaches to the surface of the first high molecular resin after foaming. When laser sintering, the second high molecular resin powder dispersed on the surface of the first high molecular resin powder first fuses, making the foaming powder fuse together, and also ensuring that the bubbles in the foaming powder do not run out with the laser irradiation, thereby obtaining a high-ratio foamed product.

[0027] 3. The present invention uses a supercritical fluid as a physical foaming agent, which is environmentally friendly, colorless and odorless. The supercritical fluid can also be recycled, and at the same time, it avoids the problem of reducing the molecular weight of the foaming material when using a chemical foaming agent, thereby increasing the foaming ratio.

[0028] 4. The preparation process of the present invention is simple, the product repeatability is high, and it is suitable for industrial production. Detailed Embodiments

[0029] The following embodiments are provided to better understand the present invention further. It is not limited to the best embodiment, and does not limit the content and protection scope of the present invention. Any product that is the same as or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior art features falls within the protection scope of the present invention.

[0030] For those where specific experimental procedures or conditions are not specified in the examples, the operations or conditions of the conventional experimental procedures described in the literature in this field can be followed. For reagents or instruments whose manufacturers are not specified, they are all conventional reagent products that can be obtained through commercial purchases.

[0031] Example 1

[0032] This example provides a preparation process for 3D printed foamed products, including the following steps:

[0033] (1) Put 85 parts of the first thermoplastic polyurethane elastomer powder and 15 parts of the second thermoplastic polyurethane elastomer powder into a high-speed mixer and mix them at a speed of 500 r / min for 90 min to obtain the powder to be foamed; among them, the molecular weight of the first thermoplastic polyurethane elastomer powder is 100,000, the hardness is 85A, the melting point is 160 °C, and the particle size is 40 μm. The molecular weight of the second thermoplastic polyurethane elastomer powder is 70,000, the hardness is 80A, the melting point is 110 °C, and the particle size is 20 μm;

[0034] (2) Put the powder to be foamed into an autoclave, introduce a supercritical gas with a carbon dioxide to nitrogen ratio of 7:3, the gas pressure is 25 MPa, the impregnation temperature is 105 °C, impregnate for 20 min, relieve pressure and foam, and the pressure relief rate is 25 MPa / s to obtain foamed powder with a particle size of about 80 μm;

[0035] (3) Transfer the foamed powder to a selective laser sintering device, select a CO2 laser, the scanning speed is 5 m / s, the scanning spacing is 0.07 mm, the power is 5 w, weld the mixed foamed powder, the powder bed temperature is 80 °C, and the powder layer thickness is 90 μm to obtain a foamed product, and the foaming ratio of the foamed product is 8 times.

[0036] Example 2

[0037] This example provides a preparation process for 3D printed foamed products, including the following steps:

[0038] (1) Put 90 parts of the first polypropylene powder and 10 parts of the second polypropylene powder into a high-speed mixer and mix them at a speed of 1000 r / min for 120 min to obtain the powder to be foamed; among them, the molecular weight of the first polypropylene powder is 230,000, the hardness is 93A, the melting point is 180 °C, and the particle size is 50 μm. The molecular weight of the second polypropylene powder is 170,000, the hardness is 80A, the melting point is 160 °C, and the particle size is 20 μm;

[0039] (2) Put the powder to be foamed into an autoclave, introduce supercritical carbon dioxide, the gas pressure is 40 MPa, the impregnation temperature is 150 °C, impregnate for 30 min, open the exhaust valve, relieve pressure and foam, and the pressure relief rate is 100 MPa / s to obtain foamed powder with a particle size of about 150 μm;

[0040] (3) Transfer the foaming powder to a selective laser sintering device. Select a CO2 laser with a scanning speed of 8 m / s, a scanning spacing of 0.02 mm, and a power of 4 w to weld the mixed foaming powder. The powder bed temperature is 50 °C and the powder layer thickness is 200 μm to obtain a foamed product with a foaming ratio of 25 times.

[0041] Example 3

[0042] This example provides a preparation process for 3D printed foamed products, including the following steps:

[0043] (1) Put 80 parts of the first thermoplastic polyolefin elastomer powder and 20 parts of the second thermoplastic polyolefin elastomer powder into a high-speed mixer and mix them at a rotation speed of 800 r / min for 180 minutes to obtain the powder to be foamed. The molecular weight of the first thermoplastic polyolefin elastomer powder is 250,000, the hardness is 85A, the melting point is 110 °C, and the particle size is 70 μm. The molecular weight of the second thermoplastic polyolefin elastomer powder is 180,000, the hardness is 75A, the melting point is 90 °C, and the particle size is 20 μm;

[0044] (2) Put the powder to be foamed into an autoclave, introduce supercritical carbon dioxide, with a gas pressure of 40 MPa, an impregnation temperature of 80 °C, impregnate for 10 min, relieve pressure and foam, with a pressure relief rate of 40 MPa / s, to obtain a foaming powder with a particle size of about 160 μm;

[0045] (3) Transfer the foaming powder to a selective laser sintering device. Select a CO2 laser with a scanning speed of 7 m / s, a scanning spacing of 0.06 mm, and a power of 2 w to weld the mixed foaming powder. The powder bed temperature is 60 °C and the powder layer thickness is 170 μm to obtain a foamed product with a foaming ratio of 12 times.

[0046] Example 4

[0047] This example provides a preparation process for 3D printed foamed products, including the following steps:

[0048] (1) Put 98 parts of the first polylactic acid powder and 2 parts of the second polylactic acid powder into a high-speed mixer and mix them at a rotation speed of 400 r / min for 180 minutes to obtain the powder to be foamed. The molecular weight of the first polylactic acid powder is 200,000, the hardness is 80A, the melting point is 140 °C, and the particle size is 20 μm. The molecular weight of the second thermoplastic polyolefin elastomer powder is 150,000, the hardness is 60A, the melting point is 120 °C, and the particle size is 10 μm;

[0049] (2) Put the powder to be foamed into an autoclave, introduce supercritical carbon dioxide, with a gas pressure of 15 MPa, an impregnation temperature of 110 °C, impregnate for 20 min, relieve pressure and foam, with a pressure relief rate of 300 MPa / s, to obtain a foaming powder with a particle size of about 50 μm;

[0050] (3) Transfer the foaming powder to a selective laser sintering device. Select a CO2 laser with a scanning speed of 10 m / s, a scanning spacing of 3 mm, and a power of 15 w to weld the mixed foaming powder. The powder bed temperature is 90 °C and the powder layer thickness is 60 μm to obtain a foamed product with a foaming ratio of 13 times.

[0051] Example 5

[0052] This example provides a preparation process for 3D printed foamed products, including the following steps:

[0053] (1) Put 80 parts of the first thermoplastic polyester elastomer powder and 20 parts of the second thermoplastic polyester elastomer powder into a high-speed mixer and mix them at a speed of 800 r / min for 100 min to obtain the powder to be foamed. The molecular weight of the first thermoplastic polyester elastomer powder is 120,000, the hardness is 88A, the melting point is 151 °C, and the particle size is 40 μm. The molecular weight of the second thermoplastic polyester elastomer powder is 80,000, the hardness is 82A, the melting point is 139 °C, and the particle size is 10 μm;

[0054] (2) Put the powder to be foamed into an autoclave, introduce supercritical carbon dioxide with a gas pressure of 5 MPa, an impregnation temperature of 130 °C, impregnate for 30 min, relieve pressure for foaming, and the pressure relief rate is 10 MPa / s to obtain a foaming powder with a particle size of about 80 μm;

[0055] (3) Transfer the foaming powder to a selective laser sintering device. Select a CO2 laser with a scanning speed of 10 m / s, a scanning spacing of 0.05 mm, and a power of 30 w to weld the mixed foaming powder. The powder bed temperature is 90 °C and the powder layer thickness is 90 μm to obtain a foamed product with a foaming ratio of 8 times.

[0056] Comparative Example 1

[0057] The difference between this comparative example and Example 1 is only that the fused deposition modeling printing method is used for molding.

[0058] This comparative example provides a preparation process for 3D printed foamed products, including the following steps:

[0059] (1) Put 85 parts of the first thermoplastic polyurethane elastomer powder and 15 parts of the second thermoplastic polyurethane elastomer powder into a high-speed mixer and mix them at a speed of 500 r / min for 90 minutes to obtain the powder to be foamed. The molecular weight of the first thermoplastic polyurethane elastomer powder is 100,000, the hardness is 85A, the melting point is 160 °C, and the particle size is 40 μm. The molecular weight of the second thermoplastic polyurethane elastomer powder is 70,000, the hardness is 80A, the melting point is 110 °C, and the particle size is 20 μm;

[0060] (2) Transfer the foaming powder to a fused deposition modeling 3D printer for 3D printing. The printer chamber temperature is 200 °C, and the temperature at the nozzle is 150 °C to print the article to be foamed.

[0061] (3) Place the article to be foamed in an autoclave, introduce a supercritical gas with a carbon dioxide to nitrogen ratio of 7:3, a gas pressure of 25 MPa, an impregnation temperature of 105 °C, impregnate for 60 min, relieve pressure for foaming, and the pressure relief rate is 25 MPa / s to obtain a foamed article with a foaming ratio of 6 times.

[0062] The appearance of the article obtained by this printing method is rough and the dimensional deformation is serious; the autoclave impregnation foaming time is long and the industrialization efficiency is low.

[0063] Comparative Example 2

[0064] The difference between this comparative example and Example 1 is only that the second polymer resin is not added.

[0065] This comparative example provides a preparation process for 3D printed foamed articles, including the following steps:

[0066] (1) Use thermoplastic polyurethane elastomer powder as the foaming powder to be used; the molecular weight of the thermoplastic polyurethane elastomer powder is 100,000, the hardness is 85A, the melting point is 160 °C, and the particle size is 40 μm;

[0067] (2) Place the foaming powder to be used in an autoclave, introduce a supercritical gas with a carbon dioxide to nitrogen ratio of 7:3, a gas pressure of 25 MPa, an impregnation temperature of 105 °C, impregnate for 20 min, relieve pressure for foaming, and the pressure relief rate is 25 MPa / s to obtain a foaming powder with a particle size of about 80 μm;

[0068] (3) Transfer the foaming powder to a selective laser sintering device, select a CO2 laser, a scanning speed of 5 m / s, a scanning spacing of 0.07 mm, a power of 5 w, weld the mixed foaming powder, the powder bed temperature is 80 °C, and the powder layer thickness is 90 μm to obtain a foamed article with a foaming ratio of 5 times.

[0069] Without adding the second polymer resin with a lower melting point and particle size, during laser sintering, the melting and welding of the first polymer resin powder will cause the internal gas to leak out. At the same time, due to the relatively high melting point of the first polymer resin, the welding effect is not good, affecting the final foaming ratio and the appearance of the foamed article.

[0070] Obviously, the above examples are only for clear illustration and not limitations on the implementation methods. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A preparation process for a 3D printed foamed product, characterized in that, It includes the following steps: S1: Mix the first polymer resin and the second polymer resin powder to obtain the powder to be foamed; S2: Put the powder to be foamed into an autoclave for impregnation. After the impregnation is completed, depressurize and foam it to make the powder to be foamed perform supercritical foaming in a supercritical fluid, and obtain the foamed powder with the second polymer resin wrapping the first polymer resin; The impregnation time is 10 - 30 min, the impregnation pressure is 5 - 40 MPa, and the depressurization rate is 10 - 300 MPa / s; The impregnation temperature is lower than the melting point of any component in the powder to be foamed; The supercritical fluid is nitrogen and / or carbon dioxide; S3: Perform selective laser sintering on the foamed powder to obtain a foamed product; The molecular weight of the first polymer resin is 100,000 - 500,000, the hardness is 50 - 95A, the melting point is 110 - 200 °C, and the particle size is 20 - 70 μm; The molecular weight of the second polymer resin is 30,000 - 400,000, the hardness is 40 - 90A, the melting point is 90 - 180 °C, and the particle size is 10 - 20 μm; The melting point of the first polymer resin is greater than that of the second polymer resin; The selective laser sintering uses a CO2 laser. The scanning speed of the CO2 laser is 5 - 10 m / s, the scanning spacing is 0.02 - 3 mm, and the power is 2 - 30 w; and / or, the selective laser sintering is to transfer the foamed powder to a powder bed to form a powder layer. The temperature of the powder bed is 50 - 90 °C, and the thickness of the powder layer is 60 - 200 μm.

2. The preparation process according to any one of claims 1, characterized in that, The first polymer resin and the second polymer resin are the same type of polymer resin material, and the melting point of the first polymer resin is greater than that of the second polymer resin.

3. The preparation process according to claim 2, characterized in that, The polymer resin material is one of polylactic acid, polypropylene, polyethylene, polyvinylidene fluoride, polyolefin elastomer, polyamide, thermoplastic polyurethane, polyamide elastomer, and polyester elastomer.

4. The preparation process according to any one of claims 1-3, characterized in that, The mass ratio of the first polymer resin powder to the second polymer powder is (4 - 49):1; The rotation speed of the mixing is 400 - 1000 r / min, and the mixing time is 90 - 180 min.

5. The preparation process according to claim 4, characterized in that, The supercritical foaming is to place the powder to be foamed in an autoclave, introduce a supercritical fluid to impregnate the powder to be foamed therein, and then depressurize and foam it.

6. A foamed product, characterized in that, It is prepared by the preparation process according to any one of claims 1 - 5.