A thermoplastic polyurethane elastomer with low internal heat generation, and a preparation method and application thereof

Abstract

The application discloses a kind of low endogenous heat thermoplastic polyurethane elastomer and its preparation method and application, and the TPU has extremely low endogenous heat, excellent air tightness, extrusion stability and thermal stability.The thermoplastic polyurethane elastomer includes the following components according to weight fraction:40-70 parts of polyol, 20-50 parts of diisocyanate, 3-25 parts of small molecule diol chain extender and 0.1-5 parts of 1-benzylpiperidine derivative diol chain extender.The thermoplastic polyurethane elastomer prepared by the application is suitable for air tube, conveyor belt, pipe and other application fields.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane technology, and particularly relates to a thermoplastic polyurethane elastomer with low internal heat generation, its preparation method, and its application. Background Technology

[0002] Thermoplastic polyurethane elastomer (TPU) is a comprehensive material composed of thermodynamically incompatible soft and hard segments, possessing excellent properties such as high strength, high toughness, and high elasticity. TPU can be processed into a variety of products, such as pipes, films, and complex molded bodies, through various melt processing methods, such as injection molding and extrusion, and can be widely used in various industries.

[0003] The demand for materials to resist internal heat is gradually increasing in various high-speed applications and long-term fatigue applications. For example, the inner tube of a high-speed bicycle needs to maintain low internal heat, sufficient strength and air tightness at different and constantly changing frequencies.

[0004] Patent CN113583432A discloses a technique for preparing low-internal-heat polyurethane. It involves reacting hydroxyl-terminated polybutadiene with polyester polyols and diisocyanates to adjust the molecular structure and reduce internal heat, and introducing silane coupling agent-modified Al2O3 to improve wear resistance. However, the alkenyl monomers used in this method exhibit thermal aging and crosslinking in this application scenario, leading to thermal stress concentration during subsequent use, significantly reducing service life and safety. Patent CN111961186A, by selecting diisocyanates and polyols with high molecular rigidity, regularity, and symmetry, and introducing inorganic fillers to improve the heat resistance of the elastomer and reduce internal heat, falls under the modification field and cannot effectively improve the low-internal-heat level of the bulk structure.

[0005] Patent CN110951034B proposes a technology for preparing polyurethane elastomers with high load-bearing capacity and low internal heat generation. This involves using polymethylene polyphenyl isocyanate and 1,2,6-hexanetriol to reduce the regularity of the elastomer structure, thereby decreasing internal heat generation, while simultaneously increasing the degree of crosslinking to improve the material's load-bearing strength. However, the polyurethane prepared by this method suffers from high processing temperatures, unstable extrusion, and localized defects, making it difficult to adapt to the processing and application of extruded products.

[0006] Therefore, a new solution is needed to address the above problems. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a thermoplastic polyurethane elastomer with excellent low internal heat generation, which can be used for extrusion processing while maintaining a long-term low internal heat generation effect.

[0008] In a first aspect, the present invention provides a low-endothermic thermoplastic polyurethane elastomer, prepared using raw materials comprising the following parts by weight:

[0009] 40-70 parts polyols;

[0010] 20-50 parts diisocyanate;

[0011] 3-25 parts small molecule diol chain extender;

[0012] 0.1-5 parts of 1-benzylpiperidine-derived diol chain extender, for example, 0.1, 0.5, 1, 2, 3, 4, or 5 parts, preferably 0.4-4 parts.

[0013] In the thermoplastic polyurethane elastomer of the present invention, the polyol is selected from at least one of polyester polyol, polyether polyol, polycaprolactone polyol and polycarbonate polyol, preferably with a number average molecular weight of 600-4000 g / mol, more preferably 1000-2500 g / mol.

[0014] The polyester polyol is a linear polymeric polyol prepared using a commonly used synthetic method in the industry, obtained from a diacid and a diol; wherein the diacid is one or more of succinic acid, adipic acid, and sebacic acid, and the diol is one or more of ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, and diethylene glycol; preferably, the polyester polyol is one or more of polybutylene adipate and polyhexane adipate.

[0015] The polyether polyol is obtained by ring-opening polymerization of an epoxy compound using an active hydrogen compound as an initiator; wherein the active hydrogen compound is selected from one or more of ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, and dipropylene glycol, and the epoxy compound is selected from one or more of propylene oxide, tetrahydrofuran, and ethylene oxide; preferably, the polyether polyol is polytetramethylene ether glycol;

[0016] The polycaprolactone polyol is formed by ring-opening polymerization of monomer ε-caprolactone and an initiator, wherein the initiator is one or more of 1,4-butanediol, 1,6-hexanediol, diethylene glycol, and ethylene glycol; preferably, the initiator is 1,4-butanediol.

[0017] The polycarbonate polyol is prepared by transesterification of a small molecule diol and a small molecule carbonate; wherein the small molecule diol is one or more selected from 1,6-hexanediol, 1,4-butanediol, 1,4-cyclohexanediol, 1,5-pentanediol, and 3-methylpentanediol; and the small molecule carbonate is one or more selected from dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diphenyl carbonate, ethylene carbonate, or propylene carbonate; more preferably, the small molecule carbonate is dimethyl carbonate.

[0018] The diisocyanate is one or more of aromatic diisocyanate, aliphatic diisocyanate and alicyclic diisocyanate, preferably aromatic diisocyanate, more preferably one or more of diphenylmethane diisocyanate, phenylmethylene diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate and 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate;

[0019] In the thermoplastic polyurethane elastomer of the present invention, the small molecule diol chain extender is an aliphatic diol or an aromatic diol, preferably selected from one or more of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, methylpropanediol, 1,4-cyclohexanediol, and terephthalic acid.

[0020] In the thermoplastic polyurethane elastomer of the present invention, the 1-benzylpiperidine-derived diol chain extender has the following structure:

[0021] or its enantiomer

[0022] In a specific embodiment, the thermoplastic polyurethane elastomer may be supplemented with additives such as antioxidants, light stabilizers, ultraviolet absorbers, lubricants, and hydrolysis resistant agents as needed.

[0023] In another specific embodiment, during the preparation of the thermoplastic polyurethane elastomer, any one or a combination of organotin, organobismuth, organopotassium, and organozinc may be selectively added as a polymerization catalyst.

[0024] In a second aspect, the present invention provides a method for preparing the above-mentioned thermoplastic polyurethane elastomer, characterized in that it includes the following preparation steps:

[0025] 1) Mix the polyol, the flexible auxiliaries, and the 1-benzylpiperidine-derived diol chain extender, stir until uniform, and the mixing temperature is 50-120℃, preferably 80-110℃;

[0026] 2) The mixture obtained in 1) is fed into a kneader with diisocyanate, small molecule diol chain extender and optional catalyst in proportion, and then fed into a twin-screw extruder for uniform mixing. After reactive extrusion, underwater pelletizing and drying, thermoplastic polyurethane elastomer is obtained.

[0027] The extrusion temperature is 120-280℃. Since the extruder temperature range cannot be infinite, the specific temperature setting can be a single or repeated point value of 120℃, 150℃, 180℃, 200℃ or 220℃. The preferred temperature range is 160℃-200℃.

[0028] The present invention provides three aspects of the application of the above-mentioned thermoplastic polyurethane elastomer in the fields of pneumatic inner tubes, conveyor belts, and pipes.

[0029] The beneficial effects of this invention are as follows:

[0030] This invention uses linear polyols to construct soft segments, ensuring the molding performance and heat resistance of the elastomer. The chain extender introduces 1-benzylpiperidine-derived diol chain extender containing large-volume side groups. Its steric hindrance effect improves the rigidity of the hard segments, enhances the heat resistance of the material, and to a certain extent disrupts the overall regularity of hardness, thereby improving the thermodynamic compatibility of the soft and hard segments and reducing the endogenous heat generated by the soft and hard phases under high-frequency friction. Detailed Implementation

[0031] The present invention will be further described below with reference to examples. The test conditions of the present invention can be adjusted as needed, and are not limited to the test conditions of this embodiment.

[0032] Unless otherwise specified, all raw materials used in this invention are commercially available conventional products.

[0033] The raw materials used are as follows:

[0034] (A) Polyols:

[0035] PBA (polybutylene adipate diol), molecular weight 2000 g / mol, Wanhua Chemical Group Co., Ltd.

[0036] PTMG (polytetramethylene ether glycol), molecular weight 1000 g / mol, Wanhua Chemical Group Co., Ltd.

[0037] BG-PCL (butanediol-initiated polycaprolactone diol), molecular weight 2000 g / mol, Wanhua Chemical Group Co., Ltd.

[0038] PCDL (polycarbonate diol, HD200), molecular weight 2000 g / mol, Wanhua Chemical Group Co., Ltd.

[0039] (B) Diisocyanate:

[0040] MDI (diphenylmethane diisocyanate), Wanhua Chemical Group Co., Ltd.

[0041] (C) Small molecule diol chain extenders:

[0042] BDO (1,4-butanediol), Wanhua Chemical Group Co., Ltd.

[0043] (D) The raw materials involved in the synthesis of 1-benzylpiperidine-derived diol chain extender are: (5-ethynyl-2,2-dimethyl-1,3-dioxolane-4-)methanol, Aurora; methanesulfonyl chloride, N-(trimethylsilylmethyl)benzylamine, 1,4-dicyanophthalic acid, dichloromethane, potassium carbonate, tetrabutylammonium iodide, acetonitrile, 1,4-naphthoonitrile, isopropanol, N-methylmorpholine N-oxide, osmium tetroxide, tert-butanol, triethylamine, tetrabutylammonium iodide, ethyl acetate, TCI;

[0044] A typical synthetic method for the 1-benzylpiperidine-derived diol chain extender in this invention can be found in the preparation method described in "Synthesis of polyhydroxy piperidines and their analogues: a novel approach towards selective inhibitors of α-glucosidase" (Organic & Biomolecular Chemistry), which involves the following steps: 1) Under an argon atmosphere at 0°C, methanesulfonyl chloride (3.82 mL, 49.35 mmol) is added dropwise to a solution of (5-ethynyl-2,2-dimethyl-1,3-dioxolane-4-)methanol (7.0 g, 44.87 mmol) and triethylamine (6.87 mL, 49.35 mmol) in 100 mL of dichloromethane. 1) After heating and stirring for 5 h, product a was extracted; 2) Product a and N-(trimethylsilylmethyl)benzylamine were dissolved in acetonitrile solution, and product b was extracted by ethyl acetate under catalytic reflux with anhydrous potassium carbonate and tetrabutylammonium iodide; 3) Product b and 1,4-dicyanophthalic acid were irradiated with infrared light to generate product c; 4) N-methylmorpholine N-oxide (50% aqueous solution) and osmium tetroxide were added to the tert-butanol suspension of product c at a volume ratio of 1.2:1, stirred at room temperature for 24 h, and then distilled under reduced pressure to obtain 1-benzylpiperidine-derived diol chain extender.

[0045] The above-described synthetic route for 1-benzylpiperidine-derived diol chain extenders is only a typical route in the existing technology. With technological breakthroughs, the choice of chain extender is not limited to the products of this synthetic route.

[0046] All raw materials used in this invention are added to the reaction system in parts by weight.

[0047] Example 1

[0048] A low-internal-heat thermoplastic polyurethane elastomer is prepared by means of the following components by weight: 233 parts PBA, 100 parts diphenylmethane diisocyanate, 25 parts 1,4-butanediol, and 1.8 parts 1-benzylpiperidine derivative diol chain extender. The 1-benzylpiperidine derivative diol chain extender and the polyol are mixed uniformly in a storage tank. Then, the components are mixed uniformly in a kneader and fed into a twin-screw extruder. After reactive extrusion, underwater pelletizing, and drying, thermoplastic polyurethane elastomer granules are obtained, wherein the extrusion temperature is set to 185°C.

[0049] Examples 2-6

[0050] The formulations for Examples 2-6 are shown in Table 1, and the preparation methods are the same as those for Example 1.

[0051] Comparative Example 1

[0052] A thermoplastic polyurethane elastomer is prepared by means of the following components by weight: 214 parts PBA, 100 parts diphenylmethane diisocyanate, and 26.4 parts 1,4-butanediol. The components are mixed evenly in a kneader and fed into a twin-screw extruder. After reactive extrusion, underwater pelletizing, and drying, thermoplastic polyurethane elastomer granules are obtained, wherein the extrusion temperature is set to 185°C.

[0053] Comparative Examples 2-4

[0054] The formulations of Comparative Examples 2-4 are shown in Table 1, and the preparation methods are the same as those of Comparative Example 1.

[0055] Table 1 Composition of thermoplastic polyurethane elastomers

[0056]

[0057] The thermoplastic polyurethane elastomers in Examples 1-6 and Comparative Examples 1-4 were subjected to mechanical property tests. The hardness test standard was ASTM D2240-15, the tensile strength test standard was ASTM D412-16, and the tear strength test standard was ASTM D624-00.

[0058] Table 2 Performance Test Results

[0059]

[0060]

[0061] As can be seen from the test data in Table 2, compared with their corresponding comparative examples 1-4, Examples 1-6 showed improved tensile strength and tear strength while maintaining consistent hardness to the maximum extent. At the same time, the elongation at break did not decrease significantly. That is, after introducing the 1-benzylpiperidine-derived diol chain extender, the material has a stronger ability to resist tension during the tensile process and can withstand greater tensile stress under the same deformation.

[0062] Endogenous heat testing methods:

[0063] DMA tests were performed on the 0.2 mm thick film strips of elastomer extruded from Examples 1-6 and Comparative Examples 1-4 to study the endogenous thermal behavior. The test conditions were performed using a Mettler SDTA861e dynamic thermomechanical analyzer, set to 100 Hz, in stretch mode, with temperature scanning from -50°C to 120°C.

[0064] Extrusion performance evaluation methods:

[0065] Based on the product's flow characteristics, appropriate extrusion parameters were set, and film extrusion tests were conducted. After the extruded film stabilized, a section of film approximately 30 cm long and 5 cm wide was randomly selected. The extruded film was then graded according to the film appearance grading standards, which are as follows:

[0066] Level 1: The film is bright and smooth, with uniform width and thickness, and no obvious gel points are observed within the observation range.

[0067] Level 2: The film is flat, with uniform width and thickness, no large or medium gel points, and the observation range is small with fewer than 10 gel points.

[0068] Level 3: The film is extruded smoothly with no large gel points, and the number of medium gel points within the observation range is less than or equal to 10, or the number of small gel points is less than or equal to 2 per square centimeter.

[0069] Large gel points: areas embedded in the extruded film with a diameter greater than 0.01 mm. 2 Crystal points;

[0070] Medium gel point: The area embedded in the extruded film is greater than 0.001 mm². 2 And less than or equal to 0.01mm 2 Crystal points;

[0071] Small gel dots: those embedded in the extruded film with an area of ​​less than 0.001 mm. 2 Crystal points;

[0072] The results of the perfection test of the extruded products are included in Tables 3 and 4.

[0073] Table 3 Performance test results of the embodiments

[0074]

[0075] Table 4 Comparative Performance Test Results

[0076]

[0077]

[0078] As can be seen from the test data in Tables 3 and 4, compared with Comparative Examples 1-4, Examples 1-6 of the present invention have lower loss tangent values ​​(tanδ) and less internal heat generation during use. Furthermore, the extrusion grade of the products after film stretching in each case was determined to be level three, and the extruded film strips from Examples 1-6 had fewer gel point defects on the surface compared to Comparative Examples 1-4. This indicates that the introduction of the 1-benzylpiperidine-derived diol chain extender can improve the strength of the material, adapt to higher tension environments, reduce internal heat generation, improve surface defects in the product, ensure good extrusion results, and achieve reliable stability in use.

[0079] The applicant declares that the above description is merely a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements or modifications made to the principles of the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A thermoplastic polyurethane elastomer with low endogenous heat generation, characterized in that, Prepared using raw materials comprising the following parts by weight: 40-70 parts polyols; 20-50 parts diisocyanate; 3-25 parts small molecule diol chain extender; 0.1-5 parts of 1-benzylpiperidine-derived diol chain extender; The small molecule diol chain extender is one or more of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, methylpropanediol, 1,4-cyclohexanediol, and terephthalic acid. The 1-benzylpiperidine-derived diol chain extender has the following structure: or its enantiomer 2. The thermoplastic polyurethane elastomer according to claim 1, characterized in that, The polyols mentioned above have a number average molecular weight of 600-4000 g / mol.

3. The thermoplastic polyurethane elastomer according to claim 2, characterized in that, The polyols mentioned above have a number average molecular weight of 1000-2500 g / mol.

4. The thermoplastic polyurethane elastomer according to claim 1, characterized in that, The polyol is selected from at least one of polyester polyol, polyether polyol, polycaprolactone polyol, and polycarbonate polyol.

5. The thermoplastic polyurethane elastomer according to claim 4, characterized in that, The polyester polyol is a linear polymerized polyol, prepared from a diacid and a diol; wherein the diacid is selected from one or more of succinic acid, adipic acid, and sebacic acid, and the diol is selected from one or more of ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, and diethylene glycol.

6. The thermoplastic polyurethane elastomer according to claim 5, characterized in that, The polyester polyol is one or more of polybutylene adipate and polyhexyl adipate.

7. The thermoplastic polyurethane elastomer according to claim 4, characterized in that, The polyether polyol is obtained by ring-opening polymerization of an epoxy compound using an active hydrogen compound as an initiator; wherein the active hydrogen compound is selected from one or more of ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, and dipropylene glycol; and the epoxy compound is selected from one or more of propylene oxide, tetrahydrofuran, and ethylene oxide.

8. The thermoplastic polyurethane elastomer according to claim 7, characterized in that, The polyether polyol is polytetramethylene ether diol.

9. The thermoplastic polyurethane elastomer according to claim 4, characterized in that, The polycaprolactone polyol is formed by ring-opening polymerization of monomer ε-caprolactone and an initiator, wherein the initiator is selected from one or more of 1,4-butanediol, 1,6-hexanediol, diethylene glycol, and ethylene glycol.

10. The thermoplastic polyurethane elastomer according to claim 4, characterized in that, The polycarbonate polyol is prepared by transesterification of a small molecule diol and a small molecule carbonate; wherein the small molecule diol is selected from one or more of 1,6-hexanediol, 1,4-butanediol, 1,4-cyclohexanediol, 1,5-pentanediol, and 3-methylpentanediol; and the small molecule carbonate is selected from one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diphenyl carbonate, ethylene carbonate, or propylene carbonate.

11. The thermoplastic polyurethane elastomer according to claim 1, characterized in that, The diisocyanate is one or more of aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates.

12. The thermoplastic polyurethane elastomer according to claim 11, characterized in that, The diisocyanate is one or more of diphenylmethane diisocyanate, phenylmethylene diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, and 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate.

13. The thermoplastic polyurethane elastomer according to any one of claims 1-12, characterized in that, The thermoplastic polyurethane elastomer also includes one or more additives selected from antioxidants, light stabilizers, ultraviolet absorbers, lubricants, and hydrolysis resistant agents.

14. The thermoplastic polyurethane elastomer according to any one of claims 1-12, characterized in that, The thermoplastic polyurethane elastomer also includes a catalyst, which is selected from any one or more of organotin, organobismuth, organopotassium, and organozinc.

15. A method for preparing a thermoplastic polyurethane elastomer according to any one of claims 1-14, characterized in that, Includes the following steps: A polyol, optional auxiliaries, and a 1-benzylpiperidine-derived diol chain extender are mixed; then, the mixture is fed into a kneader, a twin-screw extruder, extruded, underwater pelletized, and dried to obtain a thermoplastic polyurethane elastomer.

16. The preparation method according to claim 15, characterized in that, The extrusion temperature is 120℃-280℃.

17. The application of the thermoplastic polyurethane elastomer according to any one of claims 1-14 or the thermoplastic polyurethane elastomer prepared by the preparation method according to claim 15 or 16 in the fields of pneumatic inner tubes, conveyor belts, and pipes.

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