Recycling methods for thermoplastic materials

Abstract

A method for reusing thermoplastic recycled materials includes a step (a) of mixing the thermoplastic recycled materials and a formulation, and a step (b) of granulating to obtain organic polymer granules. The thermoplastic recycled materials are used in an amount of 50-90 parts by weight and have a weight-average molecular weight of 40,000-90,000 g / mol. The formulation includes thermoplastic polyurethane granules and a chain extender. The thermoplastic polyurethane granules are used in an amount of 10-50 parts by weight and have a weight-average molecular weight of 80,000-200,000 g / mol. The chain extender is used in an amount of 0.5-2 parts by weight and is selected from at least one of styrene-maleic anhydride copolymers, polyfunctional epoxy copolymers with a functionality of 3 or more and less than 8, and polyfunctional polyisocyanates with a functionality of 3 or more and less than 8. This invention provides a method for improving the material properties of thermoplastic recycled materials to produce reusable organic polymer granules.

Description

[Technical Field]

[0001] This invention relates to the recycling or processing of waste materials, and in particular to a method for the reuse of thermoplastic recycled materials. [Previous Technology]

[0002] Thermoplastic polymers such as thermoplastic polyurethane, polypropylene, and polyethylene terephthalate are widely used in the manufacture of components in industries such as automobiles, footwear, and textiles due to their good chemical stability and durability. However, the process of manufacturing components from thermoplastic polymers often involves high-temperature treatment. Although this does not affect the specifications of the resulting components, the high temperature causes thermal degradation of the thermoplastic polymers, leading to a decline in the material properties of the components. Furthermore, the processed products produced after recycling and subsequent processing of discarded components often fail to meet the specifications required for reuse.

[0003] Therefore, how to develop a method to convert recycled waste parts into materials that meet reuse specifications is one of the current research directions of industry players. [Summary of the Invention]

[0004] Therefore, the object of the present invention is to provide a method for reusing thermoplastic recycled materials.

[0005] Therefore, the method for reusing thermoplastic recycled materials of the present invention includes a step (a) and a step (b).

[0006] Step (a) is to mix a thermoplastic recycled material and a formulation, wherein the amount of the thermoplastic recycled material is from 50 parts by weight to 90 parts by weight and the weight average molecular weight is from 40,000 g / mol to 90,000 g / mol, the formulation includes a plurality of thermoplastic polyurethane particles and a chain extender, the amount of the thermoplastic polyurethane particles is from 10 parts by weight to 50 parts by weight and the weight average molecular weight is from 80,000 g / mol to 200,000 g / mol, the amount of the chain extender is from 0.5 parts by weight to 2 parts by weight and is selected from at least one of styrene-maleic anhydride copolymer, polyfunctional epoxy copolymer with a functionality of 3 or more and less than 8, and polyfunctional polyisocyanate with a functionality of 3 or more and less than 8.

[0007] Step (b) involves granulation to obtain multiple organic polymer particles.

[0008] The advantage of the present invention is that it provides a method for designing and adding a formulation including thermoplastic polyurethane particles and a chain extender to improve the material properties of thermoplastic recycled materials, thereby obtaining organic polymer granules that can be recycled into various parts.

Implementation Method

[0009] Referring to Figure 1, an embodiment of the method for reusing thermoplastic recycled material of the present invention includes a step (a), a step (b), and a step (c) to make the thermoplastic recycled material reusable for manufacturing various parts.

[0010] Step (a) involves mixing a thermoplastic recycled material and a formulation comprising a plurality of thermoplastic polyurethane granules and a chain extender. Preferably, the amounts of the thermoplastic recycled material, the thermoplastic polyurethane granules, and the chain extender are as follows: the amount of the thermoplastic recycled material is 50 to 90 parts by weight, the amount of the thermoplastic polyurethane granules is 10 to 50 parts by weight, and the amount of the chain extender is 0.5 to 2 parts by weight.

[0011] In detail, the thermoplastic recycled material is obtained from 3D printed parts that include thermoplastic polyurethane. Because thermoplastic polyurethane undergoes thermal degradation during high-temperature molding, the weight-average molecular weight of the recycled thermoplastic material decreases. For example, during the selective laser sintering of thermoplastic polyurethane to produce shoe midsoles, the thermoplastic polyurethane degrades to a weight-average molecular weight as low as 40,000 g / mol to 90,000 g / mol. When such thermoplastic recycled material undergoes another high-temperature molding process, insufficient viscosity in the molten state occurs, resulting in substandard recycled products and failing to achieve the purpose of reusing the thermoplastic recycled material.

[0012] These thermoplastic polyurethane particles are particles composed of thermoplastic polyurethane with a weight average molecular weight of 80,000 g / mol to 200,000 g / mol.

[0013] The chain extender is selected from at least one of styrene-maleic anhydride copolymer, polyfunctional epoxy copolymer with a functionality of 3 or more and less than 8, and polyfunctional polyisocyanate with a functionality of 3 or more and less than 8. In particular, the chain extender with a functionality of 3 or more can promote the formation of branched structures, so that the viscosity of the thermoplastic recycled material is significantly increased after being mixed with the chain extender. At the same time, the chain extender with a functionality of less than 8 can reduce the gelation problem caused by crosslinking reaction during mixing and subsequent processing.

[0014] In this embodiment, step (a) is to mix at 160°C to 210°C. However, it should be noted that the mixing temperature, time, speed, etc., must be optimized according to different production machines and actual needs.

[0015] Step (b) involves granulating the material obtained in step (a) using, for example, a twin-screw extruder to obtain multiple organic polymer granules with improved viscosity properties. Testing revealed that these organic polymer granules exhibit a shear viscosity of 270 cP to 1000 cP at 190°C and a shear rate of 50 s⁻¹, a shear viscosity of 200 cP to 600 cP at 190°C and a shear rate of 500 s⁻¹, and a shear viscosity of 150 cP to 350 cP at 190°C and a shear rate of 2000 s⁻¹.

[0016] Step (c) involves melting the organic polymer granules at 200°C to 220°C to form a melt, mixing it with a supercritical fluid, and then injection molding it to obtain a finished product, such as a shoe midsole. In this embodiment, based on a total melt volume of 100 wt%, 25 wt% to 26 wt% of supercritical carbon dioxide is mixed with the melt to form a homogeneous phase, and then injection molded under working conditions of 180°C to 220°C and a pressure of 20 kg / cm² to 100 kg / cm².

[0017] Refer to Table 1. Examples 1-12 respectively use recycled shoe midsoles containing thermoplastic polyurethane (r-LUV92A, with a weight-average molecular weight of 46,000 g / mol and a Shore A hardness of 92 degrees) in different amounts as thermoplastic recycled material (r-LUV92A, with a weight-average molecular weight of 46,000 g / mol and a Shore A hardness of 92 degrees), combined with different types and amounts of thermoplastic polyurethane granules (SP9552 TW is a product of BASF Elastollan® series, a polyether-type thermoplastic polyurethane granule with a weight-average molecular weight of 85,000 g / mol and a Shore A hardness of 95 degrees; U.90A10 is a product of Covestro Utechllan® series, a polyester-type thermoplastic polyurethane granule with a weight-average molecular weight of 180,000 g / mol and a Shore A hardness of 90 degrees), and different types and amounts of chain extenders (SMA3000 is Cray Valley manufactured styrene-maleic anhydride copolymer products; ADR4370 is a BASF manufactured polyfunctional epoxy copolymer product with a functionality of 3 to 6; C HK is a Tosoh manufactured polyfunctional polyisocyanate product with a functionality of 3), and the shear viscosity of the obtained organic polymer particles was tested (190°C, shear rates of 50 s⁻¹, 500 s⁻¹ and 2000 s⁻¹, according to the ASTM D3835-24 (2024) standard test method), and the test results are recorded in Table 2.

[0018] The difference between Comparative Examples 1-3 and Experimental Examples 1-12 is that: Comparative Example 1 used 100 parts by weight of thermoplastic recycled material and did not use thermoplastic polyurethane granules and chain extender; Comparative Example 2 did not use chain extender; and Comparative Example 3 used 100 parts by weight of thermoplastic recycled material and did not use thermoplastic polyurethane granules.

[0019] Table 1 Thermoplastic recycled materials formula thermoplastic polyurethane particles Chain extender source Dosage (parts by weight) type Dosage (parts by weight) type Dosage (parts by weight) Experimental Example 1 r-LUV92A 90 SP9552 TW 10 SMA3000 1.5 2 r-LUV92A 90 SP9552 TW 10 ADR4370 1.5 3 r-LUV92A 80 SP9552 TW 20 ADR4370 1.5 4 r-LUV92A 70 SP9552 TW 30 ADR4370 1.5 5 r-LUV92A 60 SP9552 TW 40 ADR4370 1.5 6 r-LUV92A 50 SP9552 TW 50 ADR4370 1.5 7 r-LUV92A 80 U.90A10 20 ADR4370 1.5 8 r-LUV92A 80 U.90A10 20 ADR4370 1.0 9 r-LUV92A 80 U.90A10 20 ADR4370 0.5 10 r-LUV92A 80 U.90A10 20 SMA3000 1.8 11 r-LUV92A 80 U.90A10 20 C‑HK 1.5 -12 r-LUV92A 80 U.90A10 20 C‑HK 1.0 Comparative Example 1 r-LUV92A 100 -- -- -- -- 2 r-LUV92A 80 U.90A10 20 -- -- 3 r-LUV92A 100 -- -- ADR4370 1.5 annotation: 1. "r-LUV92A" is a shoe midsole made from recycled selective laser sintered thermoplastic polyurethane, with a weight-average molecular weight of 46,000 g / mol and a Shore A hardness of 92. 2. "SP9552 TW" is BASF Elastollan ® The products in this series are polyether-type thermoplastic polyurethane granules with a weight-average molecular weight of 85,000 g / mol and a Shore A hardness of 95 degrees. 3. "U.90A10" is Covestro Utechllan ® The products in this series are polyester-type thermoplastic polyurethane granules with a weight-average molecular weight of 180,000 g / mol and a Shore A hardness of 90 degrees. 4. "SMA3000" is a styrene-maleic anhydride copolymer product manufactured by Cray Valley. 5. "ADR4370" is a multifunctional epoxy copolymer product manufactured by BASF, with a functionality of 3 to 6. 6. "C-HK" is short for CORONATE HK, a multifunctional polyisocyanate product manufactured by Tosoh with a functionality of 3. 7. "--" indicates that it is not used.

[0020] Table 2 Detection results of organic polymer particles Shear viscosity (cP) at 190℃ The shear rate is 50 s. -1 The shear rate is 500 s. -1 The shear rate is 2000 s. -1 Experimental Example 1 592 330 159 2 580 313 165 3 635 355 170 4 672 336 179 5 884 456 284 6 975 573 322 7 685 402 208 8 457 356 186 9 294 203 152 10 645 335 168 11 633 364 185 12 438 330 171 Comparative example 1 106 95 77 2 258 196 144 3 238 170 136 Note: Shear viscosity is tested in accordance with the ASTM D3835-24 (2024) standard test method.

[0021] Comparison shows that, regarding the shear viscosity at 190°C and a shear rate of 50 s⁻¹, the lowest among Experimental Examples 1-12 is 294 cP in Experimental Example 9, but it is still much higher than the highest among Comparative Examples 1-3, namely 258 cP in Comparative Example 2. Furthermore, considering the shear viscosity at shear rates of 500 s⁻¹ and 2000 s⁻¹, Experimental Examples 1-12 are also much higher than Comparative Examples 1-3, confirming that the organic polymer granules produced by steps (a) and (b) of this invention do indeed exhibit better material properties.

[0022] The organic polymer granules of Experimental Examples 3 to 5, 7 to 9 and Comparative Example 2 were subjected to the same step (c), and the hardness (ASTM D2240-15(2021) standard test method), specific gravity (ASTM D297(2022) standard test method), tensile strength (ASTM D412-16(2021) standard test method), elongation (ASTM D412-16(2021) standard test method), tear strength (ASTM D624-00(2020) standard test method), rebound rate (ASTM D2632-15(2019) standard test method), and compression set (ASTM D395-18(2025) standard test method) of the resulting products were tested. The test results are recorded in Table 3.

[0023] Table 3 Experimental Example Comparative example 3 4 5 7 8 9 2 Finished product Test results Hardness (Asker C) 50~53 50~55 50~55 50~55 48~52 45~50 58~65 Specific gravity (g / cm³) 0.26 0.23 0.22 0.21 0.20 0.19 0.32 Tensile strength (kg / cm²) 28.9 27.1 25.0 24.8 24.5 22.9 35.8 Elongation (%) 328 312 325 307 317 286 425 Tear strength (kg / cm) 16.5 15.4 14.8 14.5 14.2 13.7 19.5 Rebound rate (%) 26 twenty four 28 30 32 33 twenty three Compression distortion (%) 59.5 61.3 59.6 59.4 60.0 65.9 48.5 annotation: 1. Hardness testing is performed in accordance with the ASTM D2240-15 (2021) standard testing method. 2. The specific gravity is tested in accordance with the ASTM D297 (2022) standard test method. 3. Tensile strength testing shall be conducted in accordance with the ASTM D412-16 (2021) standard test method. 4. The elongation is tested in accordance with the ASTM D412-16 (2021) standard test method. 5. Tear strength testing is conducted in accordance with the ASTM D624-00 (2020) standard testing method. 6. The rebound rate was tested in accordance with the ASTM D2632-15 (2019) standard test method. 7. Compression distortion is tested in accordance with the ASTM D395-18 (2025) standard test method.

[0024] Comparison shows that the test results of Experimental Examples 3 to 5 and 7 to 9 are all better than those of Comparative Example 2. For example, the hardness values ​​of Experimental Examples 3 to 5 and 7 to 9 are 45 to 55 Asker C, while the hardness value of Comparative Example 2 is 58 to 65 Asker C, indicating that the experimental examples have better elasticity than the comparative examples. The specific gravity of Experimental Examples 3 to 5 and 7 to 9 is 0.19 to 0.26 g / cm³, which is much better than that of Comparative Example 2 (0.32 g / cm³), indicating lightweight characteristics. The tensile strength of Experimental Examples 3 to 5 and 7 to 9 is 22.9 to 28.9 kg / cm², which is much better than that of Comparative Example 2 (35.8 kg / cm²), indicating better softness, etc. This proves that the material properties of thermoplastic recycled materials can be improved through steps (a) and (b) of the present invention, thereby strengthening the mechanical properties of the finished product, such as hardness, specific gravity, and tensile strength, so that the finished product has industrial application value.

[0025] In summary, the method for reusing thermoplastic recycled materials of the present invention, by first mixing the thermoplastic recycled materials with the formula and then granulating them, enables the resulting organic polymer granules to be used to produce finished products that meet the required specifications, thereby realizing the reuse of thermoplastic recycled materials. Therefore, the purpose of the present invention can indeed be achieved.

[0026] However, the above description is only an embodiment of the present invention and should not be construed as limiting the scope of the present invention. Any simple equivalent changes and modifications made in accordance with the scope of the patent application and the contents of the patent specification shall still fall within the scope of the patent of the present invention. [Simplified Explanation of the Diagram]

[0027] Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, wherein: Figure 1 is a flowchart illustrating an embodiment of the method for reusing thermoplastic recycled materials of the present invention.

Claims

1. A method for reusing thermoplastic recycled materials, comprising: a step (a), mixing a thermoplastic recycled material and a formulation, wherein, The thermoplastic recycled material is used in an amount of 50 to 90 parts by weight and has a weight-average molecular weight of 40,000 g / mol to 90,000 g / mol. The formulation includes multiple thermoplastic polyurethane particles and a chain extender. The thermoplastic polyurethane particles are used in an amount of 10 to 50 parts by weight and have a weight-average molecular weight of 80,000 g / mol to 200,000 g / mol. The chain extender is used in an amount of 0.5 to 2 parts by weight and is selected from at least one of styrene-maleic anhydride copolymer, polyfunctional epoxy copolymer with a functionality of 3 or more and less than 8, and polyfunctional polyisocyanate with a functionality of 3 or more and less than 8. The formulation includes a step (b) of granulation to obtain multiple organic polymer particles.

2. The method for reusing thermoplastic recycled materials as described in claim 1, wherein, The thermoplastic recycled material is recycled from parts that have been 3D printed and include thermoplastic polyurethane.

3. The method for reusing thermoplastic recycled materials as described in claim 2, wherein, This 3D printing is selective laser sintering.

4. The method for reusing thermoplastic recycled materials as described in claim 1, wherein, Step (a) is performed at 160°C to 210°C.

5. The method for reusing thermoplastic recycled materials as described in claim 1 further includes a step (c) of melting the organic polymer particles and mixing them with a supercritical fluid before injection molding a finished product.

6. The method for reusing thermoplastic recycled materials as described in claim 5, wherein, The shear viscosity of these organic polymer particles is 270 cP to 1000 cP at 190°C and a shear rate of 50 s⁻¹, 200 cP to 600 cP at 190°C and a shear rate of 500 s⁻¹, and 150 cP to 350 cP at 190°C and a shear rate of 2000 s⁻¹.

7. The method for reusing thermoplastic recycled materials as described in claim 5, wherein, Step (c) involves melting the organic polymer particles at 200°C to 220°C.

8. The method for reusing thermoplastic recycled materials as described in claim 5, wherein, Step (c) is injection molding under working conditions of 180°C to 220°C and pressure of 20 kg / cm2 to 100 kg / cm2.

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