A processing step and method for coating a tpu

Abstract

The present application relates to the technical field of 3D printing, in particular to a processing step and method of a coating process TPU. The present application uses the post-processing technology of the formed part to process the formed part, which not only improves the FDM printing speed by 3-4 times, can realize the successful printing of complex models that cannot be realized in the FDM printing process of TPU, and breaks through the color printing of flexible materials. Moreover, after the processing of the formed part, the interlayer bonding force is greatly increased, and the surface effect is equivalent to the SLA surface fineness. Such a process not only breaks the limitation of 3D printing that can only print single color with special design shoes, but also greatly reduces the printing equipment cost, the formed part printing cost, improves the efficiency, realizes color printing, and more importantly, the printed object can be directly worn. At the same time, the hardness of the formed part of the present application will be maintained at about 70A, which is suitable for printing various wearable products and is suitable for various industries.

Description

Technical Field

[0001] This invention relates to a coating process for TPU and its processing steps and methods, belonging to the field of 3D printing technology. Background Technology

[0002] With the continuous development of the 3D printing industry, 3D printing is becoming increasingly integrated into people's lives. Currently, 3D-printed shoes using SLA (Single-Component Lamination) technology are experiencing phenomenal popularity and sales. However, SLA-printed shoes are limited by the two-component nature of SLA, restricting them to printing only specially designed shoes and single-color products. While FDM (Fiber Direct Molding) has seen the development of specialized TPU-printed shoes, its widespread adoption has been hampered by slow printing speeds and limitations in shape. In 2023, with the increased printing speed and technological maturity of FDM, it became possible to print colorful TPU shoes. However, market feedback indicates that the main drawbacks of TPU in FDM molding—slow speed, poor interlayer bonding, and insufficient surface smoothness—prevent its widespread application. This invention not only enables multi-color shoe printing but also allows for the direct molding of various wearable products, such as bags, watch straps, toys, and flexible products. Summary of the Invention

[0003] The purpose of this invention is to provide a processing step and method for coated TPU. By using a post-processing technique to treat the molded part, the printing speed of FDM printing of conventional TPU is increased by 3-4 times, and colorful flexible printing is achieved. After treatment, the interlayer bonding force of the molded part is greatly increased, and the surface effect is comparable to that of SLA. This process not only breaks the limitation of 3D printing only of specific designs, but also greatly reduces printing costs and improves efficiency. More importantly, the printed objects can be directly worn.

[0004] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0005] A processing method for coated TPU, comprising the following steps:

[0006] S1. Preparation of printing filament coating material, mainly composed of 80 parts of PVB powder, methanol solution, DMF solution, methyl ethyl ketone solution, and TPU polyurethane particles, wherein the concentration of the methanol solution is above 95%;

[0007] S2. Prepare special TPU raw materials, mainly composed of TPU64D, polybutylene adipate / terephthalate (PBAT), polycaprolactone, polyvinyl alcohol, plasticizer dibutyl phthalate, silane coupling agent, and allyl polyoxyalkyl epoxy ether. After mixing, granulate and shape to obtain TPU polymer for later use.

[0008] S3. Wire drawing is performed using a single-screw wire drawing processing equipment. The processing equipment and process are existing technologies, as shown in patent (CN114752196A2).

[0009] S4. Using the three-dimensional molding technology of FDM 3D printing, the product is printed into a molded part.

[0010] S5. Secondary processing of the molded part to obtain 3D printed products made of TPU additive manufacturing.

[0011] Preferably, the specific steps in S1 are as follows:

[0012] S11. PVB powder is thoroughly dissolved in a certain amount of methanol solvent by stirring to form a methanol solution of PVB, thus preparing solution one;

[0013] S12. Mix 70% DMF solution and 20% butanone solution by percentage to form a mixed solution, and add 10% TPU polyurethane particles to dissolve the TPU polyurethane particles in the mixed solution to prepare solution two.

[0014] S13. Mix the solutions obtained in steps S11 and S12 at a mass ratio of 8:2, and then perform an evaporation process to obtain a solid substance.

[0015] S14. The solid material obtained in step S13 is granulated to form PVB polymer for later use.

[0016] Furthermore, in step S12, the viscosity of solution two is controlled at 0.0006-0.0008 mPa·s.

[0017] Preferably, in step S2, the mass ratio is used as follows:

[0018] TPU64D 60-80%, polybutylene adipate / terephthalate (PBAT) 5-15%, polycaprolactone 6-8%, polyvinyl alcohol 1-10%, plasticizer dibutyl phthalate 2-6%, silane coupling agent 1-3%, allyl polyoxyalkylene epoxy ether 3-10 parts.

[0019] Furthermore, in step S3, the PVB polymer prepared in step S14 is used as the outer layer material, and the TPU polymer prepared in step S2 is used as the inner layer material. They are co-extruded into 3D printing filaments with a diameter of 1.75 mm.

[0020] Preferably, the FDM printing speed in step S4 is 10-12 mm³ / s per unit volume. Since the conventional hardness of TPU is 95A, it is relatively soft, and the printing speed is generally 3.6 mm³ / s per unit volume. However, the hardness of TPU after PVB coating is 82D, which is harder and directly affects the FDM printing speed. After extensive testing, the current per unit volume speed is 10-12 mm³ / s, which is 3-4 times faster than conventional TPU. Moreover, it enables easy printing of complex models and multi-color printing.

[0021] Preferably, the specific steps in step S5 are as follows:

[0022] S51. Immerse the molded part in an alcohol or methanol solution for 10-20 minutes. The prepared polymer will dissolve and form a film under the action of methanol or alcohol, forming a smooth film surface on the surface of the molded part. This eliminates the "layer lines" in the FDM printing process and improves the surface finish. The PVB polymer inside the molded part dissolves and forms a sol after being immersed in alcohol, which can completely fill the gaps in the molded part and greatly improve the interlayer bonding force.

[0023] S52. After removing the molded part from the solvent, use an alcohol fumigation process to remove the solvent from the surface of the molded part, and further utilize the effect of PVB gel to enhance the interlayer bonding force.

[0024] Furthermore, in step S51, ultrasonic equipment is used to simultaneously vibrate during immersion.

[0025] This invention has at least the following beneficial effects:

[0026] 1. This invention utilizes post-processing technology to treat the molded parts, which not only increases the FDM printing speed by 3-4 times, but also greatly increases the interlayer bonding force and the surface finish is comparable to that of SLA. This process not only breaks the limitation that 3D printing can only print special designs, but also greatly reduces printing costs and improves efficiency. More importantly, the printed objects can be printed in multiple colors and worn directly, which greatly promotes the further development of the industry.

[0027] 2. In this invention, the PVB on the surface of the molded part is dissolved to form a film, and the PVB inside is dissolved and softened by alcohol or methanol. Therefore, the hardness of the molded part is greatly reduced, and the final hardness will be maintained at about 75A. This hardness is suitable for printing various wearable products and is applicable to various industries such as shoes, bags, watch straps, and toys. Detailed Implementation

[0028] The following will describe the implementation of this application in detail with reference to the embodiments, so that the implementation process of how this application uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0029] Example 1:

[0030] A processing method for coated TPU, comprising the following steps:

[0031] S1. Preparation of printing filament coating material, mainly composed of 80 parts of PVB powder, methanol solution, DMF solution, methyl ethyl ketone solution, and TPU polyurethane particles, with the concentration of methanol solution being above 95%;

[0032] S2. Prepare special TPU raw materials, mainly composed of TPU64D, polybutylene adipate / terephthalate (PBAT), polycaprolactone, polyvinyl alcohol, plasticizer dibutyl phthalate, silane coupling agent, and allyl polyoxyalkyl epoxy ether. After mixing, granulate and shape to obtain TPU polymer for later use.

[0033] S3. Wire drawing is performed using a single-screw wire drawing processing equipment. The processing equipment and process are existing technologies, as shown in patent (CN114752196A2).

[0034] S4. Using the three-dimensional molding technology of FDM 3D printing, the product is printed into a molded part.

[0035] S5. Secondary processing of the molded part to obtain 3D printed products made of TPU additive manufacturing.

[0036] The specific steps in S1 are as follows:

[0037] S11. PVB powder is thoroughly dissolved in a certain amount of methanol solvent by stirring to form a methanol solution of PVB, thus preparing solution one;

[0038] S12. Mix 70% DMF solution and 20% butanone solution by percentage to form a mixed solution, and add 10% TPU polyurethane particles to dissolve the TPU polyurethane particles in the mixed solution to prepare solution two.

[0039] S13. Mix the solutions obtained in steps S11 and S12 at a mass ratio of 8:2, and then perform an evaporation process to obtain a solid substance.

[0040] S14. The solid material obtained in step S13 is granulated to form PVB polymer for later use.

[0041] In step S12, the viscosity of solution two is controlled between 0.0006 and 0.0008 mPa·s.

[0042] In step S2, the mass ratio is used as follows:

[0043] The formula consists of 72% TPU64D, 15% polybutylene adipate / terephthalate (PBAT), 6% polycaprolactone, 6% polyvinyl alcohol, 4% dibutyl phthalate plasticizer, 2% silane coupling agent, and 5 parts allyl polyoxyalkylene epoxy ether.

[0044] In step S3, the PVB polymer prepared in step S14 is used as the outer layer material, and the TPU polymer prepared in step S2 is used as the inner layer material. They are co-extruded into 3D printing filaments with a diameter of 1.75 mm.

[0045] In step S4, the FDM printing speed is 10-12 mm³ / s per unit volume.

[0046] The specific steps in step S5 are as follows:

[0047] S51. Immerse the molded part in an alcohol or methanol solution for 10-20 minutes. The prepared polymer will dissolve and form a film under the action of methanol or alcohol, forming a smooth film surface on the surface of the molded part. This eliminates the "layer lines" in the FDM printing process and improves the surface finish. The PVB polymer inside the molded part dissolves and forms a sol after being immersed in alcohol, which can completely fill the gaps in the molded part and greatly improve the interlayer bonding force.

[0048] S52. After removing the molded part from the solvent, use an alcohol fumigation process to remove the solvent from the surface of the molded product.

[0049] In step S51, ultrasonic equipment is used to vibrate simultaneously during immersion.

[0050] The difference between Example 2 and Example 1 lies in the TPU polymer content, calculated by mass ratio:

[0051] The following ingredients are mixed: 60% TPU64D, 10% polybutylene adipate / terephthalate (PBAT), 8% polycaprolactone, 10% polyvinyl alcohol, 2% dibutyl phthalate plasticizer, 3% silane coupling agent, and 10 parts allyl polyoxyalkylene epoxy ether. The mixture is then granulated to obtain the TPU polymer for later use.

[0052] The difference between Example 3 and Example 2 lies in the TPU polymer content, calculated by mass ratio:

[0053] The following ingredients are mixed: 60% TPU64D, 5% polybutylene adipate / terephthalate (PBAT), 6% polycaprolactone, 1% polyvinyl alcohol, 2% dibutyl phthalate plasticizer, 1% silane coupling agent, and 3 parts allyl polyoxyalkylene epoxy ether. The mixture is then granulated to obtain the TPU polymer for later use.

[0054] The difference between Example 4 and Example 3 lies in the TPU polymer content, calculated by mass ratio:

[0055] The following ingredients are mixed: 80% TPU64D, 8% polybutylene adipate / terephthalate (PBAT), 8% polycaprolactone, 10% polyvinyl alcohol, 6% dibutyl phthalate plasticizer, 3% silane coupling agent, and 10 parts allyl polyoxyalkylene epoxy ether. The mixture is then granulated to obtain the TPU polymer for later use.

[0056] Tests showed that different polymer ratios had little impact on the overall post-processing of the printed product, but the time required for soaking and dissolving varied. This ensured that after processing, the FDM printing speed was increased by 3-4 times, and the interlayer bonding strength was greatly increased. The surface finish was comparable to that of SLA. This process not only breaks the limitation that 3D printing can only print special designs, but also greatly reduces printing costs and improves efficiency. More importantly, the printed objects can be colorful and can be worn directly.

[0057] If certain terms are used in the specification and claims to refer to specific components, those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The term "comprising" as used throughout the specification and claims is an open-ended term and should be interpreted as "comprising but not limited to." "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error.

[0058] It should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or system that includes that element.

[0059] The foregoing description illustrates and describes several preferred embodiments of the present invention. However, as previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A processing method for coated TPU, characterized in that, The processing steps are as follows: S1. Preparation of printing filament coating material, mainly composed of 80 parts of PVB powder, methanol solution, DMF solution, methyl ethyl ketone solution, and TPU polyurethane particles, wherein the concentration of the methanol solution is above 95%; The specific steps in S1 are as follows: S11. PVB powder is thoroughly dissolved in a certain amount of methanol solvent by stirring to form a methanol solution of PVB, thus preparing solution one; S12. Mix 70% DMF solution and 20% butanone solution by percentage to form a mixed solution, and add 10% TPU polyurethane particles to dissolve the TPU polyurethane particles in the mixed solution to prepare solution two. S13. Mix the solutions obtained in steps S11 and S12 at a mass ratio of 8:2, and then perform an evaporation process to obtain a solid substance. S14. The solid material obtained in step S13 is granulated to form PVB polymer for later use. S2. Prepare special TPU raw materials, mainly composed of TPU64D, polybutylene adipate / terephthalate (PBAT), polycaprolactone, polyvinyl alcohol, plasticizer dibutyl phthalate, silane coupling agent, and allyl polyoxyalkyl epoxy ether. After mixing, granulate and mold to obtain TPU polymer for later use. S3. The PVB polymer prepared in step S14 is used as the outer layer material and the TPU polymer prepared in step S2 is used as the inner layer material. The 3D printing filament is extruded by a concentric co-extrusion special processing equipment and the diameter of the 3D printing filament is 1.75 mm. S4. Using the three-dimensional molding technology of FDM 3D printing, the product is printed into a molded part. S5. Secondary processing of the molded part to obtain 3D printed products made of TPU additive manufacturing; The specific steps in step S5 are as follows: S51. Immerse the molded parts in an alcohol or methanol solution for 10-20 minutes; S52. After removing the molded part from the solvent, use an alcohol fumigation process to fumigate for 30-40 minutes to remove the solvent from the surface of the molded part.

2. The processing method for coated TPU according to claim 1, characterized in that: In step S12, the viscosity of solution two is controlled between 0.0006 and 0.0008 mPa·s.

3. The processing method for coated TPU according to claim 1, characterized in that: In step S2, the mass ratio is used as follows: TPU64D 60-80%, polybutylene adipate / terephthalate (PBAT) 5-15%, polycaprolactone 6-8%, polyvinyl alcohol 1-10%, plasticizer dibutyl phthalate 2-6%, silane coupling agent 1-3%, allyl polyoxyalkylene epoxy ether 3-10 parts.

4. The processing method for coated TPU according to claim 1, characterized in that: In step S4, the FDM printing speed is 10-12 mm³ / s per unit volume.

5. The processing method for coated TPU according to claim 1, characterized in that: In step S51, ultrasonic equipment is used to simultaneously vibrate the device during immersion.