Thermoplastic polyurethane elastomer, polyurethane foam material as well as preparation method and application of thermoplastic polyurethane elastomer and polyurethane foam material

Abstract

The invention belongs to the technical field of polymer materials, and provides a thermoplastic polyurethane elastomer, a polyurethane foam material and a preparation method and application of the thermoplastic polyurethane elastomer and the polyurethane foam material, the HDI residual quantity in the thermoplastic polyurethane elastomer is 0.01 wt%-0.3 wt%, and the NCO residual quantity of a foamed product is smaller than 100 ppm. By controlling the residual amount of isocyanate, the polyurethane foam material prepared by foaming is high in foaming ratio, high in percentage of close area and free of hollowing, melting scars and air holes; the high-resilience foam material has high resilience and excellent mechanical properties, and fully meets the performance requirements on high-performance foam materials in the industry.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane materials, specifically relating to a thermoplastic polyurethane elastomer, a polyurethane foam material, its preparation method, and its application. Background Technology

[0002] Supercritical foam materials made from TPU are widely used in packaging, footwear and other fields due to their advantages such as light weight, breathability, environmental friendliness and good resilience.

[0003] The foaming processes for thermoplastic polyurethane foam materials mainly include bead foaming, sheet foaming, preform foaming, mucell injection molding, and continuous extrusion foaming.

[0004] Patent CN 117209779 A discloses a thermoplastic polyurethane elastomer material, a thermoplastic polyurethane foam material, its preparation method, and its applications. This invention introduces an intermediate product containing a prepolymer capped with a single NCO group. The NCO group in the prepolymer capped with the single NCO group undergoes an addition reaction with the amide bond of the thermoplastic polyurethane elastomer in a twin-screw extruder. This allows the molecular chain segments of the prepolymer capped with the single NCO group to be grafted onto the molecular chain segments of the thermoplastic polyurethane elastomer, forming a branched molecular chain structure in the thermoplastic polyurethane. This improves the melt strength of the low molecular weight thermoplastic polyurethane elastomer, thereby improving its foaming properties. However, this method increases the difficulty of preparation, is cumbersome, and results in a high material density.

[0005] CN 115141351 A discloses a low-exudation, low-odor, and yellowing-resistant thermoplastic polyurethane elastomer. It uses a low-free-content polyurethane prepolymer with HDI-terminated ends (less than 0.1 wt%) as the main raw material, BDO as a chain extender, and specific additives, combined with a twin-screw extrusion method to prepare a TPU with low exudation, low odor, yellowing resistance, fast molding, and excellent heat resistance and mechanical properties. However, the patent uses a prepolymer method, which requires a two-step process, resulting in high operating time and costs. Furthermore, it only controls the NCO content in the prepolymer, not the NCO content in the finished product. Failure to control the NCO content in the finished product can lead to inconsistent YI (Yeast Intake) during TPU application, large batch-to-batch variations in heat resistance, and batch-to-batch instability, requiring frequent parameter adjustments during product preparation.

[0006] Supercritical fluid foaming technology fully utilizes the rapid diffusion rate and high solubility of supercritical fluids (N2, CO2) in polymers. During foaming, the polymer is in a semi-solid state; the molten zone allows for cell growth, while the unmelted zone provides melt strength, maintaining the cell structure. Subsequent rapid depressurization induces extremely high nucleation rates, resulting in a cell structure with micro / nano-sized cells and high pore density. Compared to chemical foaming, supercritical foaming exhibits a finer cell structure and more stable properties. TPU foaming involves the plastic deformation of molecular chains. To control the deformation (foaming) capability of the elastomer matrix, it is necessary to further understand the plastic and elastic deformation during cell growth and cell structure shaping from the perspective of molecular chain / network motion. Different TPU structures correspond to different foaming properties, including the influence of chemical structure, condensed matter structure, and cell structure on the elastic properties, compression set, and tensile / tear strength of elastomer foam materials. Currently, thermoplastic elastomer physically foamed materials are mostly used in footwear and sports protection. In footwear applications, there are still problems such as uneven cell structure, severe shrinkage, thick skin, and surface hollowness, accompanied by small air bubbles. Secondary granulation and the addition of nucleating agents are required to control shrinkage and surface bubbles.

[0007] Therefore, developing a thermoplastic polyurethane foam material with uniform cell size, high closed-cell rate, high expansion ratio, low shrinkage, good resilience, smooth surface, no bubbles, and no hollow areas is an urgent problem to be solved in this field. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a thermoplastic polyurethane elastomer, a polyurethane foam material, its preparation method, and its application. By controlling the NCO content in TPU, the stability and expandability of TPU are increased, the foaming process is controllable, the cell size is uniform, the closed-cell rate is high, the resilience is good, the surface is smooth and wrinkle-free, there are no bubbles, and the skin thickness is controllable.

[0009] To achieve the objectives of this invention, the following technical solution is adopted:

[0010] A thermoplastic polyurethane elastomer has an NCO residue of 0.01wt%-0.3wt%, preferably 0.01wt%-0.21wt%, more preferably 0.03wt%-0.15wt%, such as 0.03wt%, 0.04wt%, 0.05wt%, 0.06wt%, 0.07wt%, 0.08wt%, 0.09wt%, and 0.1wt%. Preferably, the thermoplastic polyurethane elastomer is placed at ≤35°C for ≤60 days, preferably ≤15 days, before proceeding to the next step.

[0011] Preferably, the residual NCO content of the polyurethane foam product is <100ppm.

[0012] The residual NCO content of the thermoplastic polyurethane elastomer described in this invention is between 0.01wt% and 0.3wt%. If the residual NCO content of the thermoplastic polyurethane elastomer is less than 0.01wt%, the polyurethane foam product prepared will have a low closed-cell ratio and a high open-cell structure. If the residual NCO content of the thermoplastic polyurethane elastomer is greater than 0.3wt%, its foaming ratio will be small, the pores will increase, and the surface bubbles will increase, making it difficult to obtain polyurethane foam products with a high foaming ratio.

[0013] The raw materials for preparing the thermoplastic polyurethane elastomer include a combination of diisocyanate, polymeric polyol and chain extender;

[0014] Preferably, the diisocyanate includes any one or a combination of at least two of hexamethylene diisocyanate, isophorone diisocyanate, phenyl diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated phenyl diisocyanate.

[0015] Preferably, the polymeric polyol comprises polyether polyol and / or polyester polyol.

[0016] Preferably, the polyester polyol includes any one or a combination of at least two of alkyd polyester polyols, polycaprolactone polyols, or polycarbonate polyols.

[0017] Preferably, the polyether polyol includes any one or a combination of at least two of polyoxypropylene polyol, polytetrahydrofuran polyol, or copolyether polyol;

[0018] Preferably, the chain extender comprises a diamine and / or a diol;

[0019] Preferably, the diamine comprises any one or a combination of at least two of 3,3'-dichloro-4,4'-diaminodiphenylmethane, 3,5-diamino-p-chlorobenzoate isobutyl ester, diethyltoluenediamine, or 3,5-dimethylthiotoluenediamine.

[0020] Preferably, the diol includes any one or a combination of at least two of the following: diol, hexanediol, ethylene glycol, propylene glycol, methyl propylene glycol, diethylene glycol, 1,4-cyclohexanediol, or neopentyl glycol.

[0021] In this invention, unless otherwise specified, propylene glycol includes various isomers of propylene glycol such as 1,3-propanediol and 1,2-propanediol. Similarly, butanediol, hexanediol, etc. are general terms that include their different isomers.

[0022] Preferably, the Shore hardness of the thermoplastic polyurethane elastomer is 80A-70D, for example, it can be 80A, 82A, 85A, 88A, 90A, 92A, 95A, 98A, 62D, 65D or 68D, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range. Further preferred values ​​are 80A-55D, and more preferably 85A-97A.

[0023] For example, the Shore hardness of the thermoplastic polyurethane elastomer is obtained by the method in ASTM D2240-05.

[0024] Preferably, the tear strength of the thermoplastic polyurethane elastomer is ≥120 N / mm, for example, it can be 120 N / mm, 130 N / mm, 140 N / mm, 150 N / mm, 160 N / mm, 170 N / mm, 180 N / mm, 190 N / mm, 200 N / mm, 210 N / mm, 220 N / mm or 230 N / mm, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, and 130-170 N / mm is further preferred.

[0025] The method for preparing the thermoplastic polyurethane elastomer includes: polymerizing isocyanate, polyol and chain extender to obtain thermoplastic polyurethane elastomer.

[0026] Preferably, isocyanate, polyol and chain extender are polymerized, extruded and granulated, and then passed through a microwave heating system with a power of 0.5-5w / g; the heating zone length is 0.5-5m, the heating time is 1-90s, the material is heated more uniformly, and the residual NCO is more consistent.

[0027] To reduce the NCO content in thermoplastic polyurethane elastomers, the requirements of this invention can be met by strictly controlling the amount of isocyanate component added, increasing the curing time, controlling the addition rate of isocyanate component, and extending the reaction time. Specific operating methods are not limited.

[0028] Preferably, the molar amount of NCO groups in the isocyanate is denoted as n1, and the total molar amount of active hydrogen groups in the polyol and chain extender is denoted as n2, where n1:n2 is 1:(0.9-1.2), for example, 1:0.91, 1:0.92, 1:0.93, 1:0.94, 1:0.95, 1:0.96, 1:0.97, 1:0.98, 1:0.99, 1:0.992, 1:0.995, 1:0.998, 1:1, or 1:1.01. 2. 1:1.015, 1:1.018, 1:1.02, 1:1.03, 1:1.04, 1:1.05, 1:1.06, 1:1.07, 1:1.08, 1:1.09, 1:1.1, 1:1.11, 1:1.12, 1:1.13, 1:1.14, 1:1.15, 1:1.16, 1:1.17, 1:1.18, 1:1.19, 1:1.20, etc., with 1:(0.95-1.05) being further preferred.

[0029] Wherein, the total molar amount of active hydrogen groups in the polyol and chain extender represents the total molar amount of hydroxyl and amino (if any); when the chain extender is a small molecule diol, the total molar amount of active hydrogen groups in the polyol and chain extender is the total molar amount of hydroxyl; when the chain extender includes a small molecule diamine, the total molar amount of active hydrogen groups in the polyol and chain extender is the total molar amount of hydroxyl and amino.

[0030] Preferably, based on the total mass of the isocyanate, polyol, and chain extender as 100%, the amount of isocyanate added is 12%-35%, for example, it can be 13%, 14%, 15%, 16%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, or 34%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, but 15%-30% is further preferred.

[0031] Preferably, based on the total mass of the isocyanate, polyol, and chain extender as 100%, the amount of chain extender added is 0.7%-25%, for example, it can be 0.7%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, or 14.5%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0032] Preferably, the polymerization reaction is carried out in the presence of a catalyst.

[0033] In this invention, the type of catalyst is not specifically limited, and any catalyst known in the art that can catalyze the reaction of active hydrogen with NCO groups to generate carbamate groups is applicable to this invention.

[0034] Preferably, the catalyst comprises any one or a combination of at least two of organotin catalysts, amine catalysts, and organobismuth catalysts, and more preferably any one or a combination of at least two of organobismuth catalysts, stannous octoate, and triethylamine.

[0035] Preferably, the mass of the catalyst is 0.001%-0.5% based on 100% of the polyol, for example, it can be 0.002%, 0.005%, 0.008%, 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4% or 0.45%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0036] In this invention, other additives such as antioxidants, UV auxiliaries, hydrolysis-resistant agents, and tackifiers may also be added. Preferably, the polymerization reaction is carried out in an extruder.

[0037] Preferably, the extruder includes a screw extruder, and more preferably a twin-screw extruder.

[0038] Preferably, the method for preparing the thermoplastic polyurethane elastomer includes: mixing isocyanate, polyol, chain extender and optionally antioxidant evenly to obtain a mixture; injecting the mixture into a screw extruder for polymerization reaction, and then extruding and granulating to obtain the thermoplastic polyurethane elastomer (granules).

[0039] Preferably, the granules obtained from granulation are packaged and stored after cooling.

[0040] The present invention also provides a polyurethane foam material, which is obtained by foaming the thermoplastic polyurethane elastomer described in the present invention.

[0041] Preferably, the foaming method includes supercritical fluid foaming.

[0042] This invention provides a method for preparing a polyurethane foam material as described in the second aspect, the method comprising the following steps:

[0043] The thermoplastic polyurethane elastomer of the present invention is foamed under pressure using a physical foaming agent; after foaming, the pressure is released and the material is cured to obtain the polyurethane foam material.

[0044] Preferably, the physical foaming agent includes any one or a combination of at least two of nitrogen, carbon dioxide, methane, propane, butane, and pentane.

[0045] Preferably, the foaming method includes supercritical fluid foaming.

[0046] Preferably, the physical foaming agent includes nitrogen and / or carbon dioxide, more preferably supercritical nitrogen and / or supercritical carbon dioxide, and even more preferably a combination of critical carbon dioxide or supercritical carbon dioxide and supercritical nitrogen.

[0047] It should be noted that the material form of the thermoplastic polyurethane elastomer is not limited, for example, it can be beads, sheets or plates; the foaming form can be bead foaming, plate foaming, preform foaming, injection foaming, etc.

[0048] In a preferred embodiment, the thermoplastic polyurethane elastomer is in the form of beads, and the preparation method includes: mixing the beads, a physical foaming agent, and a solvent to obtain a suspension; foaming the suspension under pressure; and depressurizing and curing the foam after foaming to obtain the polyurethane foam material (beads).

[0049] Preferably, the solvent includes water.

[0050] Preferably, the mass ratio of the solvent to the beads is (0.5-2):1.

[0051] In another preferred embodiment, the thermoplastic polyurethane elastomer is in the form of sheets or plates, or preforms. The preparation method includes: placing the sheets or plates in a foaming device, filling them with a physical foaming agent, performing two-stage foaming under pressure, and then depressurizing and curing them after foaming to obtain the polyurethane foam material (sheets or plates).

[0052] Preferably, during the first stage of foaming:

[0053] Preferably, the foaming pressure is 10-50 MPa.

[0054] Preferably, the foaming temperature is 100-180℃.

[0055] Preferably, the foaming time is 0.1-10 hours.

[0056] Preferably, during the second stage of foaming:

[0057] Preferably, the foaming pressure is 0-10 MPa.

[0058] Preferably, the foaming temperature is 120-180℃.

[0059] Preferably, the foaming time is 0.1-10 hours.

[0060] In another preferred embodiment, the thermoplastic polyurethane elastomer is made of injection-molded foam. TPU particles are injected into the molten section through an injection-molded foaming system, where nitrogen and carbon dioxide are introduced. The nitrogen flow rate is set to 0.1-2 kg / hr, and the carbon dioxide flow rate is also set to 0.1-2 kg / hr. The injection molding machine temperature is set to 170-280°C. The screw's intermediate check valve can maintain a melt pressure of 1-25 MPa for an extended period (10-2000 s) after the screw stops rotating. The back pressure in front of the screw head is 5-30 MPa, corresponding to a pressure of 10-30 MPa at the gas injection point. The injection speed is 10-250 milliseconds / s, the mold temperature is 10-90°C, and the cooling time is 10-500 s, ensuring sufficient cooling of the part.

[0061] In this invention, "pressure relief" means releasing pressure.

[0062] As a preferred embodiment of the present invention, the preparation method includes the following steps:

[0063] Thermoplastic polyurethane elastomer beads, a physical foaming agent, and a solvent are mixed to obtain a suspension; the suspension is then foamed sequentially under a pressure of 10-50 MPa; the foaming temperature is 100-160℃ and the time is 0.1-24 h; after foaming is completed, the pressure is released to obtain the polyurethane foam material (foamed beads).

[0064] Optionally, the polyurethane foam material (foamed beads) is placed in a mold and molded under heat treatment conditions to obtain a molded article (e.g., a sheet).

[0065] Preferably, the heat treatment is performed by heat treatment with steam.

[0066] Preferably, the pressure of the water vapor is 0.8-2.5 bar.

[0067] As another preferred embodiment of the present invention, the preparation method includes the following steps:

[0068] Thermoplastic polyurethane elastomer in sheet, plate, or preform form is placed in a foaming device, filled with a physical foaming agent, and foamed under a pressure of 10-50 MPa. The foaming is divided into two stages: the first foaming temperature is 100-180℃ and the time is 0.1-24h; the second foaming temperature is 120-180℃ and the time is 0.1-10h to obtain the polyurethane foam material (foamed sheet or foamed board).

[0069] Preferably, the density of the polyurethane foam material is 0.03-0.18 g / cm³. 3 ,

[0070] Preferably, the closed-cell ratio of the polyurethane foam material is >90%;

[0071] Preferably, the surface of the polyurethane foam material is free of bubbles and voids.

[0072] Preferably, the polyurethane foam material is used in shoe soles, yoga mats, insoles, packaging materials, etc.

[0073] Compared with the prior art, the present invention has the following beneficial effects:

[0074] The thermoplastic polyurethane elastomer provided by this invention, by controlling the NCO content, produces foamed products with a closed-cell rate of >90%, and no bubbles, voids, or wrinkles on the surface, fully meeting the industry's performance requirements for high-performance foam materials. Attached Figure Description

[0075] Figure 1 This is a surface effect diagram of the polyurethane foam board of Embodiment 2 of the present invention;

[0076] Figure 2 This is a surface effect diagram of the polyurethane foam board of Comparative Example 1 of the present invention. Detailed Implementation

[0077] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0078] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not limited to those elements and may also include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0079] "Optionally," "optionally," or "any one" means that the matter or event described thereafter may or may not occur, and the description includes both the possibility that the event occurs and the possibility that the event does not occur.

[0080] In the following specific embodiments of the present invention, the materials for which no preparation method is provided are all commercially available chemicals, and the specific information of the materials is as follows:

[0081]

[0082] In the following specific embodiments of the present invention, the main testing methods for thermoplastic polyurethane elastomers and polyurethane foam materials are as follows:

[0083] (1) NCO residue

[0084] GB / T 12009.4-2016, HG / T 2409-2023

[0085] (2) Hardness

[0086] The specimens were injection molded to a 2mm diameter and tested according to the method in standard ASTM D2240-05 to obtain the Shore A hardness.

[0087] (3) Tear strength

[0088] 2mm specimens were injection molded and tested according to the method in standard ASTM D624-00(2020).

[0089] (4) Density

[0090] The test shall be performed in accordance with the method in standard ASTM D792.

[0091] (5) Closed-pore ratio

[0092] SEM was used to test the closed-cell ratio and calculate the closed-cell rate by measuring the ratio of closed-cell to open-cell.

[0093] (6) Number of bubbles

[0094] Bubbles were located visually within 100cm. 2 Number of bubbles inside

[0095] The following will use several embodiments as examples to describe in detail the thermoplastic polyurethane elastomer, polyurethane foam material and its preparation method of the present invention, but the thermoplastic polyurethane elastomer, polyurethane foam material and its preparation method of the present invention are not limited to these embodiments.

[0096] Example 1

[0097] A thermoplastic polyurethane elastomer and its preparation method are disclosed. The preparation method is as follows: 0.64 parts by weight of PBA-800, 0.281 parts by weight of HDI, 0.079 parts by weight of 1,4-butanediol, 0.001 parts by weight of bismuth catalyst, 0.01 parts by weight of antioxidant 1010, and 0.01 parts by weight of light stabilizer 622 are pumped into a casting system and mixed evenly to obtain a mixture. The mixture is then cast into a twin-screw extruder for continuous reaction synthesis to obtain the thermoplastic polyurethane elastomer. The extrusion temperature is 220℃ and the screw speed is 210 rpm. After pelletizing, the thermoplastic polyurethane elastomer is heated in a microwave heater at 2 W / g for a heating length of 2 m for 60 s to obtain thermoplastic polyurethane elastomer (TPU) beads. The beads are then cooled to 25℃ and stored. The NCO content is tested, and the test results are shown in Table 1.

[0098] A polyurethane foam material and its preparation method are disclosed. The preparation method is as follows: Using TPU beads provided in this embodiment (stored at 35°C for 7 days), 0.5 kg of the TPU beads and 4 kg of water are added to a 20 L high-pressure reactor. Carbon dioxide at 12 MPa is introduced to form a suspension. The temperature is then raised to 140°C, and the pressure is maintained at 12 MPa for 2 hours of constant temperature foaming. The gas in the pressure vessel is then discharged into the atmosphere, and the TPU foam beads are dried to obtain TPU foam beads. The obtained TPU foam beads are filled into a mold with a length of 300 mm × width of 200 mm × thickness of 40 mm. Water vapor at a pressure of 1.3 bar is used to compress the particles by 13% along the thickness direction of the mold to bond and form a molded foam product. The residual NCO content is tested, and the product is then placed at room temperature for 48 hours for performance evaluation. The data are shown in Table 1.

[0099] Example 2

[0100] A thermoplastic polyurethane elastomer and its preparation method are disclosed. The preparation method is as follows: 0.7 parts by weight of PTMEG-1000, 0.237 parts by weight of HDI, 0.064 parts by weight of 1,4-butanediol, 0.001 parts by weight of stannous octoate, and 0.02 parts by weight of antioxidant 1024 are pumped to a casting system and mixed evenly to obtain a mixture. The mixture is then cast onto a twin-screw extruder for continuous reaction synthesis to obtain a thermoplastic polyurethane elastomer. The extrusion temperature is 220℃, the screw speed is 195 rpm, and the elastomer is heated by a microwave heater at 2 W / g for a length of 2 m and a heating time of 60 s to obtain a thermoplastic polyurethane elastomer (NCO content is tested). The elastomer is then cooled to below 30℃ and stored to obtain TPU particles. These particles are then injection molded into 2 mm test pieces. The test results are shown in Table 1.

[0101] A polyurethane foam material and its preparation method are disclosed. The preparation method is as follows: TPU beads provided in this embodiment (stored at 28°C for 3 days) are extruded into a 15mm thick sheet using a screw extruder. The sheet is placed in a foaming reactor, filled with 3MPa carbon dioxide and 17MPa nitrogen, heated to 130°C, and maintained at a pressure of 20MPa for 3 hours of constant temperature and pressure foaming. Then, the carbon dioxide and nitrogen in the pressure vessel are released into the atmosphere. The sheet is placed at room temperature for 4 hours, then placed back into the foaming reactor, filled with 3MPa carbon dioxide, heated to 150°C, and maintained at a constant temperature for 30 minutes. Then, the carbon dioxide and nitrogen in the pressure vessel are released into the atmosphere. The TPU foam sheet is obtained, and the performance evaluation data of the NCO residue are shown in Table 1.

[0102] Example 3

[0103] A thermoplastic polyurethane elastomer and its preparation method are disclosed. The preparation method is as follows: 0.7 parts by weight of PTMEG-1000, 0.27 parts by weight of HMDI, 0.03 parts by weight of 1,4-butanediol, 0.001 parts by weight of triethylamine, and 0.02 parts by weight of antioxidant 1024 are pumped to a casting system and mixed evenly to obtain a mixture. The mixture is then cast onto a twin-screw extruder for continuous reaction synthesis to obtain a thermoplastic polyurethane elastomer. The extrusion temperature is 220℃, the screw speed is 195 rpm, and the elastomer is heated by a microwave heater at 2 W / g for a length of 2 m and a heating time of 60 s to obtain a thermoplastic polyurethane elastomer (NCO content is tested). The elastomer is then cooled to below 30℃ for storage to obtain TPU beads. 2 mm test pieces are then injection molded from these beads. The test results are shown in Table 1.

[0104] A polyurethane foam material and its preparation method are disclosed. The preparation method is as follows: TPU beads provided in this embodiment (stored at 28°C for 3 days) are extruded into a 15mm thick sheet using a screw extruder. The sheet is placed in a foaming reactor, filled with 5MPa carbon dioxide and 15MPa nitrogen, heated to 130°C, and maintained at a pressure of 20MPa for 3 hours of constant temperature and pressure foaming. Then, the carbon dioxide and nitrogen in the pressure vessel are released into the atmosphere. The sheet is placed at room temperature for 4 hours, then placed back into the foaming reactor, filled with 3MPa carbon dioxide, heated to 150°C, and maintained at a constant temperature for 30 minutes. Then, the carbon dioxide and nitrogen in the pressure vessel are released into the atmosphere. The TPU foam sheet is obtained, and the performance evaluation data of the NCO residue are shown in Table 1.

[0105] Example 4

[0106] A thermoplastic polyurethane elastomer and its preparation method are disclosed. The preparation method is as follows: 0.7 parts by weight of PTMEG-1000, 0.225 parts by weight of MDI, 0.075 parts by weight of 1,4-butanediol, 0.001 parts by weight of triethylamine, and 0.02 parts by weight of antioxidant 1024 are pumped to a casting system and mixed evenly to obtain a mixture. The mixture is then cast onto a twin-screw extruder for continuous reaction synthesis to obtain a thermoplastic polyurethane elastomer. The extrusion temperature is 220℃, the screw speed is 195 rpm, and the mixture is heated by a microwave heater at 2 W / g for a length of 2 m and a heating time of 60 s. The obtained thermoplastic polyurethane elastomer is cooled and pelletized (NCO content is tested), and stored at a temperature below 30℃ to obtain TPU beads. These beads are then injection molded into 2 mm test pieces. The test results are shown in Table 1.

[0107] A polyurethane foam material and its preparation method are disclosed. The preparation method is as follows: TPU beads provided in this embodiment (stored at 28°C for 3 days) are extruded into a 15mm thick sheet using a screw extruder. The sheet is placed in a foaming reactor, filled with 3.5MPa carbon dioxide and 16.5MPa nitrogen, heated to 130°C, and maintained at a pressure of 20MPa for 4 hours of constant temperature and pressure foaming. Then, the carbon dioxide and nitrogen in the pressure vessel are released into the atmosphere. The sheet is placed at room temperature for 20 hours, then placed back into the foaming reactor, filled with 3MPa carbon dioxide, heated to 152°C, and maintained at a constant temperature for 20 minutes. Then, the carbon dioxide and nitrogen in the pressure vessel are released into the atmosphere. The TPU foam sheet is obtained, and the performance evaluation data of the NCO residue are shown in Table 1.

[0108] Example 5

[0109] A thermoplastic polyurethane elastomer and its preparation method are disclosed. The preparation method is as follows: 0.7 parts by weight of PCDL-2000, 0.217 parts by weight of HDI, 0.083 parts by weight of 1,4-butanediol, 0.001 parts by weight of bismuth catalyst, and 0.005 parts by weight of UV-P are transported to a casting system by a gear pump and mixed evenly to obtain a mixture. The mixture is then cast onto a twin-screw extruder for continuous reaction synthesis to obtain a thermoplastic polyurethane elastomer. The extrusion temperature is 220℃, the screw speed is 180 rpm, and the mixture is heated by a microwave heater at 2 W / g for a heating length of 2 m and a heating time of 60 s. The obtained thermoplastic polyurethane elastomer is cooled and pelletized, and stored at a temperature below 30℃ to obtain TPU beads. 2 mm test pieces are then injection molded from these beads. The test results are shown in Table 1.

[0110] A polyurethane foam material and its preparation method are disclosed. The preparation method is as follows: TPU beads provided in this embodiment (stored at 15°C for 1 day) are injection molded into shoe blanks. The shoe blanks are placed in a foaming kettle, filled with 4 MPa carbon dioxide and 18 MPa nitrogen, and kept at a constant temperature until the temperature is raised to 135°C. The pressure is maintained at 22 MPa, and foaming is carried out at constant temperature and pressure for 3 hours. Then, the carbon dioxide and nitrogen in the pressure vessel are released into the atmosphere. The board is placed at room temperature for 6 hours, then placed in the foaming kettle again, filled with 3 MPa nitrogen, heated to 150°C, and kept at a constant temperature for 30 minutes. Then, the carbon dioxide and nitrogen in the pressure vessel are released into the atmosphere. The foamed shoe material is obtained, and its performance evaluation data are shown in Table 1.

[0111] Example 6

[0112] A thermoplastic polyurethane elastomer and its preparation method are disclosed. The preparation method is as follows: 0.7 parts by weight of PCL-2000, 0.220 parts of HDI, 0.08 parts of 1,4-butanediol, 0.002 parts of bismuth catalyst, and 0.02 parts of antioxidant 1010 are pumped to a casting system and mixed evenly to obtain a mixture. The mixture is then cast onto a twin-screw extruder for continuous reaction synthesis to obtain the thermoplastic polyurethane elastomer. The extrusion temperature is 220℃, the screw speed is 180 rpm, and the screw rotation speed is 230 rpm. The elastomer is heated by a microwave heater at 2 W / g for 2 m for 60 s. The obtained thermoplastic polyurethane elastomer is cooled and pelletized, then stored at a temperature below 30℃ to obtain TPU beads. 2 mm test pieces are then injection molded from these beads. The test results are shown in Table 1.

[0113] A polyurethane foam material and its preparation method are disclosed. The preparation method is as follows: TPU beads provided in this embodiment (stored at 30°C for 15 days) are passed through an injection molding foaming system. Nitrogen and carbon dioxide are introduced into the melting section. The nitrogen flow rate is set to 0.3 kg / HR, and the carbon dioxide flow rate is set to 0.5 kg / HR. The injection molding machine temperature is set to 190°C. The screw intermediate check valve can maintain a melt pressure of 8.5 MPa for a long time (600 s) after the screw stops rotating. The back pressure in front of the screw head is 10 MPa, and the pressure at the corresponding gas injection point is 23 MPa. The injection speed is 120 milliseconds / s, the mold temperature is 60°C, and the cooling time is 200 s. The part is fully cooled, and its performance evaluation data are shown in Table 1.

[0114] Comparative Example 1

[0115] A thermoplastic polyurethane elastomer and its preparation method are disclosed. The preparation method is as follows: 0.7 parts by weight of PTMEG-1000, 0.237 parts by weight of HDI, 0.064 parts by weight of 1,4-butanediol, 0.001 parts by weight of stannous octoate, and 0.02 parts by weight of antioxidant 1024 are pumped to a casting system and mixed evenly to obtain a mixture. The mixture is then cast onto a twin-screw extruder for continuous reaction synthesis to obtain a thermoplastic polyurethane elastomer. The extrusion temperature is 220°C and the screw speed is 195 rpm. The obtained thermoplastic polyurethane elastomer is cooled and pelletized (NCO content is tested) to obtain a thermoplastic polyurethane elastomer (NCO content is tested). 2 mm test pieces are then injection molded from the pellets, and the test results are shown in Table 1.

[0116] A polyurethane foam material and its preparation method are disclosed. The preparation method is as follows: TPU beads provided in this embodiment (stored at 28°C for 3 days) are extruded into a 15mm thick board using a screw extruder. The board is placed in a foaming reactor, filled with 3MPa carbon dioxide and 17MPa nitrogen, heated to 140°C, and maintained at a pressure of 20MPa for constant temperature and pressure foaming for 3 hours. Then, the carbon dioxide and nitrogen in the pressure vessel are released into the atmosphere. The TPU foam board is obtained, and the NCO residue and its performance evaluation data are shown in Table 1.

[0117] Table 1

[0118]

[0119]

[0120] As shown in Table 1, the NCO residue of the TPU elastomer provided by this invention is between 0.01 wt% and 0.3 wt%, which gives it excellent foaming properties. The polyurethane foam materials obtained using this elastomer have high expansion ratios, low densities, uniform cell size, and stable cell shape, as well as low shrinkage, high resilience, and excellent mechanical properties. Specifically, the density of the polyurethane foam materials in Examples 1-5 is 0.06-0.18 g / cm³. 3 With a closed-cell rate of >90%, it is a foaming material with excellent comprehensive performance.

[0121] The NCO residue in the TPU elastomer in Comparative Example 1 is not within the scope defined by this invention, resulting in poor foaming performance.

[0122] The applicant declares that this invention illustrates the thermoplastic polyurethane elastomer, polyurethane foam material, its preparation method, and applications through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection and disclosure scope of this invention.

Claims

1. A thermoplastic polyurethane elastomer, characterized in that, The residual NCO content of the thermoplastic polyurethane elastomer is 0.01wt%-0.3wt%, preferably 0.01wt%-0.21wt%, and more preferably 0.03wt%-0.15wt%. Preferably, the thermoplastic polyurethane elastomer is placed at ≤35°C for ≤60 days, more preferably ≤15 days, before proceeding to the next step.

2. The polyurethane elastomer according to claim 1, characterized in that, The residual NCO content of the polyurethane foam product is <100ppm.

3. The polyurethane elastomer according to any one of claims 1-2, characterized in that, The Shore hardness of the thermoplastic polyurethane elastomer is 80A-70D, more preferably 80A-55D, and even more preferably 85A-97A; Preferably, the tear strength of the thermoplastic polyurethane elastomer is ≥120 N / mm, and more preferably 130-170 N / mm.

4. The polyurethane elastomer according to any one of claims 1-3, characterized in that, The raw materials for preparing the thermoplastic polyurethane elastomer include a combination of diisocyanate, polymeric polyol and chain extender; Preferably, the diisocyanate includes any one or a combination of at least two of hexamethylene diisocyanate, isophorone diisocyanate, phenyl diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated phenyl diisocyanate. Preferably, the polymeric polyol comprises polyether polyol and / or polyester polyol; Preferably, the polyester polyol includes any one or a combination of at least two of alkyd polyester polyols, polycaprolactone polyols, or polycarbonate polyols. Preferably, the polyether polyol includes any one or a combination of at least two of polyoxypropylene polyol, polytetrahydrofuran polyol, or copolyether polyol; Preferably, the chain extender comprises a diamine and / or a diol; Preferably, the diamine comprises any one or a combination of at least two of 3,3'-dichloro-4,4'-diaminodiphenylmethane, 3,5-diamino-p-chlorobenzoate isobutyl ester, diethyltoluenediamine, or 3,5-dimethylthiotoluenediamine. Preferably, the diol includes any one or a combination of at least two of the following: diol, hexanediol, ethylene glycol, propylene glycol, methyl propylene glycol, diethylene glycol, 1,4-cyclohexanediol, or neopentyl glycol.

5. The method for preparing the thermoplastic polyurethane elastomer according to any one of claims 1-4 comprises: Isocyanate, polyol and chain extender undergo polymerization reaction to obtain thermoplastic polyurethane elastomer; Preferably, isocyanate, polyol and chain extender are polymerized, extruded and granulated, and then passed through a microwave heating system with a power of 0.5-5w / g; the heating zone length is 0.5-5m, the heating time is 1-90s, the material is heated more uniformly, and the residual NCO is more consistent; Preferably, the molar amount of NCO groups in the isocyanate is denoted as n1, and the total molar amount of active hydrogen groups in the polyol and chain extender is denoted as n2, with n1:n2 being 1:(0.9-1.2), more preferably 1:(0.95-1.05).

6. A polyurethane foam material, wherein the polyurethane foam material is obtained by foaming the thermoplastic polyurethane elastomer according to any one of claims 1-3 or the polyurethane elastomer prepared by the preparation method according to any one of claims 4-6.

7. The polyurethane foam material according to claim 6, characterized in that, The foaming method includes supercritical fluid foaming.

8. The method for preparing polyurethane foam material according to claim 6 or 7, wherein the preparation method comprises the following steps: The thermoplastic polyurethane elastomer of the present invention is foamed under pressure using a physical foaming agent; after foaming, the pressure is released and the material is cured to obtain the polyurethane foam material. Preferably, the density of the polyurethane foam material is 0.03-0.18 g / cm³. 3 , Preferably, the closed-cell ratio of the polyurethane foam material is >90%; Preferably, the surface of the polyurethane foam material is free of bubbles and voids.

9. The polyurethane foam material according to claim 6 or 7 or the polyurethane foam prepared by the preparation method according to claim 8 is used in the fields of shoe soles, yoga mats, insoles, and packaging materials.

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