A polyurethane elastomer and a method for producing the same

Abstract

The application discloses a polyurethane elastomer and a preparation method thereof. Raw materials of the polyurethane elastomer include polymer polyol, diisocyanate and chain extender, etc., wherein the polymer polyol is prepared by condensation reaction or ester exchange reaction of aromatic diacid, ester or anhydride thereof and raw materials such as polyether glycol, the polyurethane elastomer of the application has a molecular structure containing hard segments obtained by reaction of isocyanate and small-molecule polyol chain extender, and soft segments containing ester bond connected aromatic group-polyether glycol block copolymer structure, and can realize the following performances: keeping high mechanical properties (specifically represented by high elastic recovery rate, tensile modulus and breaking strength), and endowing the polyurethane elastomer with excellent hydrolysis resistance, oil resistance, wear resistance and low-temperature flexibility.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane elastomer preparation technology, specifically relating to a polyurethane elastomer and its preparation method. Background Technology

[0002] Polyurethane elastomers are heat- and plasticizable elastomers that can be activated by secondary heating for use as hot melt adhesives. With their excellent properties and wide range of applications, they have become one of the most important elastomer materials. Polyurethane elastomers (TPU) are block polymers composed of hard segments formed by the reaction of chain extenders and diisocyanates, and soft segments formed by polymeric polyols and isocyanates. Due to the characteristics of its molecular structure, it exhibits rubber-like elasticity at low temperatures and can be plasticized and molded upon heating. It is a material that can be secondary processed and molded, possessing advantages such as high mechanical strength, wear resistance, good toughness, good processability, and wide applicability. These properties make polyurethane widely used in many fields such as footwear, cables, clothing, automobiles, pharmaceuticals, pipes, films, and sheets. Compared to rubber, polyurethane elastomer final products generally do not require vulcanization crosslinking, which can shorten the reaction cycle, reduce energy consumption, and reduce pollution during the production process. Because polyurethane is essentially a linear polymer, it can be processed using the same technologies and equipment as plastics, such as injection molding, extrusion, blow molding, calendering, and casting, making it particularly suitable for mass production of small and medium-sized parts. Waste materials can be recycled and reused, and different additives or fillers can be used in the production or processing process to improve certain physical properties and reduce costs.

[0003] Generally, polyurethane elastomers are classified into two types: polyester and polyether. Polyester-type polyurethane elastomers are oil-resistant but not hydrolyzable, while polyether-type polyurethane elastomers are hydrolyzable but not oil-resistant. Long-term use in humid and hot environments can cause hydrolysis or swelling of TPU molecular chains, reducing their mechanical properties and greatly limiting their applications. In order to adapt to different external environments, it is very important to develop a polyurethane elastomer that is both hydrolyzable and oil-resistant while maintaining good mechanical properties. Summary of the Invention

[0004] This invention provides a polyurethane elastomer and its preparation method. The polyurethane elastomer prepared by this invention maintains good mechanical properties while also exhibiting hydrolysis resistance and oil resistance.

[0005] This invention provides a polyurethane elastomer, the raw materials of which include a polymeric polyol, a diisocyanate and a chain extender. The polymeric polyol is obtained from raw materials including substances of type A and type B through a condensation reaction or an ester exchange reaction. The substances of type A include aromatic dicarboxylic acids, their esters or anhydrides, and the substances of type B include polyether glycols.

[0006] Furthermore, the polymer polyol of the present invention comprises a repeating unit shown in formula (1) and a capped alcohol hydroxyl group:

[0007]

[0008] R1 is at least one of aromatic rings or heterocyclic aromatic rings, and the mass content of R1 in the repeating unit of formula (1) is 4.5% to 44%, preferably 20% to 44%, more preferably 35% to 44%; R2 is at least one of saturated alkane groups with 2 to 5 carbon atoms; x is 2 to 20; the mass percentage of the repeating unit shown in formula (1) in the polymer polyol is greater than 75%. When the content of aromatic group R1 in the polymer polyol is too high, it will lead to excessive rigidity of the final polymer polyol, resulting in excessive viscosity, which is not conducive to the production process of polyurethane elastomer; when the content of aromatic group R1 in the polymer polyol is too low, it will have an adverse effect on the recovery modulus of polyurethane elastomer.

[0009] Optionally, R2 in formula (1) is at least one of saturated alkane groups having 2-5 carbon atoms, preferably at least two of saturated alkane groups having 2-5 carbon atoms;

[0010] In the molecular structure of the polymer polyol of the present invention, R2 is preferably a saturated alkane group with 2-5 carbon atoms. Theoretically, the fewer carbon atoms in R2, the higher the density of its ether oxygen bond, which enhances the interaction between the soft and hard segments in the prepared polyurethane elastomer molecule, thereby increasing the tensile modulus and recovery modulus. However, it is detrimental to elongation. Conversely, the more carbon atoms in R2, the lower the density of the ether oxygen bond, which weakens the interaction between the soft and hard segments of the polyurethane elastomer, resulting in an increased plastic deformation rate. In the polymer polyol of the present invention, the polyether segment is usually derived from polyethylene glycol and polypropylene glycol. The polyurethane elastomer obtained in this way has good tensile modulus and recovery modulus while ensuring that the plastic deformation rate does not increase significantly. Moreover, compared with polytetrahydrofuran with 4 carbon atoms, the polyether segment with 2-3 carbon atoms is less expensive.

[0011] In actual production, polymer polyols synthesized by copolymerization of monomers with different carbon atom numbers are preferred. Specifically, the polyether segments of the polymer polyol can be structures in which saturated alkane groups with 2, 3, or 4 carbon atoms are arranged alternately by ether oxygen bonds. The polyether segments can be mixtures of at least two of polytetrahydrofuran, polypropylene glycol, and polyethylene glycol, or segments of copolymer diols obtained by reacting tetrahydrofuran, ethylene oxide, propylene oxide, 2-methyltetrahydrofuran, or 3-methyltetrahydrofuran. Preferably, the polyether segments are segments of copolymer diols obtained by reacting tetrahydrofuran with at least one of ethylene oxide, propylene oxide, 2-methyltetrahydrofuran, or 3-methyltetrahydrofuran. This can reduce costs and adjust performance.

[0012] Optionally, the average functionality of the terminal hydroxyl groups of the linear polymer polyol is 1.95-2.00, and the number average molecular weight of the polymer polyol is 800-5000.

[0013] According to the present invention, the average functionality of the terminal hydroxyl groups of the polymer polyol can be 1.95-2.00, preferably 1.96-2.00, and more preferably 1.98-2.00. This ensures that the polymer polyol can be smoothly terminalized with isocyanate and subsequently extended by a chain extender. If the average functionality is greater than 2.00, when the polymer polyol is used as a raw material for preparing polyurethane, the resulting polyurethane may have a cross-linked structure, thus failing to form a chain-like polyurethane. Such polyurethane has excessively high melt viscosity during production, hindering continuous production. If the average functionality is low, the molecular weight of the resulting polyurethane will also be low, thus affecting the performance of the polyurethane elastomer. In actual reactions, the polyether diol may undergo dehydration of the terminal hydroxyl groups to form double bonds during condensation polymerization / ring-opening polymerization. Furthermore, due to limitations in actual reaction performance, the condensation reaction or transesterification reaction of the polyether diol to the polymer polyol cannot be 100% completed. Therefore, the final average functionality of the polymer polyol generally cannot reach 2.00.

[0014] Here, "average functionality" refers to the average number of moles of alcohol hydroxyl groups that can participate in the reaction per mole of polymer polyol. In this invention, considering the dehydration of terminal hydroxyl groups in polyether diols to form double bonds and the presence of unreacted carboxyl groups, the average functionality of alcohol hydroxyl groups can be calculated using the following formula:

[0015] Functionality = 2 * number of moles of hydroxyl groups / (number of moles of hydroxyl groups + number of moles of carboxyl groups + number of moles of double bonds)

[0016] The number-average molecular weight of the polymer polyol of the present invention can be 800-5000, preferably 800-2000, more preferably 800-1500, and most preferably 800-1450. A higher number-average molecular weight of the polymer polyol results in higher viscosity, which is detrimental to metering and transportation, making continuous industrial-scale operation difficult. However, if the molecular weight of the polymer polyol is too low, the required uniform molecular weight of the polyurethane prepolymer during the polyurethane elastomer polymerization reaction necessitates the participation of more diisocyanates in the synthesis, leading to a higher content of urethane groups in the prepolymer. This enhances the interaction between prepolymer molecules, increasing viscosity. Moreover, the resulting polyurethane has a shorter soft segment length. Since the entropy elasticity of polyurethane mainly comes from the soft segment, a shorter soft segment leads to a decrease in the elastic recovery performance of the polyurethane elastomer, but also increases the modulus. Experiments have shown that a number-average molecular weight of 800-5000 for the polymer polyol can ensure sufficient elastic modulus in the polyurethane elastomer while achieving continuous industrial production.

[0017] In this invention, the polymeric polyol is obtained from raw materials including substances of type A and type B through a condensation reaction or transesterification reaction. Substance of type A is an aromatic diacid containing an aromatic group, its esterified form, or an anhydride. The aromatic group is a group containing an aromatic ring or a heterocyclic aromatic ring. Optionally, the aromatic diacid in this invention can be selected from one or more of terephthalic acid, isophthalic acid, phthalic acid, biphenyl dicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,5-furandicarboxylic acid, terephthalic acid, isophthalic acid, and phthalic acid. Preferably, its esterified form is obtained by reacting the aromatic diacid with a monohydric alcohol with a boiling point below 150°C.

[0018] Optionally, in the B-type substances, the number average molecular weight of the polyether glycol is 100-1000, preferably the degree of polymerization of the polyether glycol is 2-20, and more preferably the degree of polymerization of the polyether glycol is 3-10. The polyether glycol may be selected from one or more of polyethylene glycol, polypropylene glycol, polytrimethylene ether glycol, and polytetrahydrofuran ether glycol.

[0019] Optionally, in addition to the substances mentioned above, other substances such as aliphatic dicarboxylic acids and small molecule diols may be added to the A and B substances as modifiers to adjust the properties of polyurethane.

[0020] Further, the diisocyanate is one or more of diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and their isomers.

[0021] A method for preparing the polyurethane elastomer described above includes the following steps:

[0022] (1) The diisocyanate, polymer polyol and chain extender are injected into the extruder using a metering and conveying system respectively;

[0023] (2) The mixture from step (1) is reacted, extruded, granulated and cured at 120-220°C to obtain the polyurethane elastomer.

[0024] An application of the polyurethane elastomer described above is characterized in that the polyurethane elastomer is used as a raw material for preparing injection-molded or extruded products, preferably as a raw material for cutting wheels, rubber rollers, sliding wheels, and seals.

[0025] Beneficial effects:

[0026] The thermoplastic polyurethane elastomer of the present invention comprises polymeric polyols, diisocyanates, and chain extenders. The polymeric polyols are obtained by condensation or transesterification reactions of aromatic diacids, their esters, or their anhydrides with polyether diols. Using these polymeric polyols as raw materials, compared to conventional methods using polyester or polyether polyols, results in the inclusion of ester-linked aromatic group-polyether block structures in the soft segments of the polyurethane molecules. This reduces the density of ester groups or ether oxygen bonds in the polyurethane molecules, resulting in polyurethanes with both good hydrolysis and oil resistance. Furthermore, the use of these polymeric polyols as raw materials allows the polyurethane molecules to contain ester-linked aromatic group-polyether block structures in the soft segments. Compared to conventional polymeric polyol raw materials, polyurethanes with this structure exhibit better mechanical properties (specifically, higher elastic recovery rate, tensile modulus, and tensile strength). Additionally, the aromatic diacid ester structure also exhibits better hydrolysis resistance compared to conventional fatty acid esters. Detailed Implementation

[0027] The thermoplastic polyurethane elastomer of the present invention is obtained by reacting a specific polymeric polyol with a diisocyanate and a chain extender. The specific polymeric polyol is obtained by condensation or transesterification of a type A substance, including an aromatic diacid, its esterification, or anhydride, and a type B substance, including a polyether glycol, as raw materials. The specific preparation method can employ industry-known synthesis processes. For example, the aromatic diacid and polyether glycol are reacted at 120–150°C and atmospheric pressure, while the water produced in the reaction is collected by distillation. After reacting for 2–4 hours, the temperature is raised to 180–240°C within 15–30 minutes to promote the reaction and collect the byproduct water. After continuing the reaction for 1–3 hours, the pressure of the reaction system is reduced to below 10 kPa, preferably below 5 kPa, more preferably below 0.2 kPa, and the reaction continues for another 1–3 hours to reduce the water content of the system. A catalyst is added, and the reaction is maintained at a high temperature and vacuum environment for another 2–6 hours. By controlling the hydroxyl value and acid value of the polymeric polyol, products with different molecular weight requirements can be obtained.

[0028] Furthermore, by weight percentage, the raw materials of the polyurethane elastomer include 10-45 parts of diisocyanate, 35-90 parts of polymeric polyol, and 4-17 parts of chain extender.

[0029] Optionally, the chain extender may be one or more of ethylene glycol, 1,4-butanediol, diethylene glycol, 1,6-hexanediol, 1,3-propanediol, and 1,4-dihydroxymethylcyclohexane.

[0030] Optionally, the chain extender of the present invention may also contain some trimethylolpropane, pentaerythritol, sucrose, etc., to partially crosslink the polyurethane molecules and increase the modulus of the polyurethane elastomer.

[0031] Optionally, a portion of 4,4'-methylenebis(2-chloroaniline) may be added to the chain extender, and a portion of multifunctional isocyanates may be selected from the isocyanate raw materials to partially crosslink the polyurethane molecules, thereby increasing the modulus and wear resistance of the prepared polyurethane elastomer.

[0032] In addition, based on the polyurethane elastomer prepared by this invention, some common additives, such as antioxidants, flame retardants, and leveling agents, can be added as needed.

[0033] The present invention also provides a method for preparing polyurethane elastomer, which employs a one-step method or a prepolymerization method.

[0034] The one-step method includes mixing a polymeric polyol, a diisocyanate, and a chain extender, and then extruding the mixture through a twin-screw extruder to obtain the polyurethane elastomer. When the raw materials for the polyurethane elastomer also include other components, these other components are mixed with the polymeric polyol and diisocyanate, and then extruded through the twin-screw extruder to prepare the polyurethane elastomer.

[0035] The prepolymerization method includes prepolymerizing a polymeric polyol with a diisocyanate, and then adding a chain extender to react and prepare the polyurethane elastomer.

[0036] A method for preparing a polyurethane elastomer as described above, using a one-step method, includes the following steps: mixing a polymeric polyol, a chain extender, and a catalyst at 55–140°C until homogeneous; adding diisocyanate and rapidly stirring at 150–300 rpm to carry out the reaction; reacting at a temperature of 140–250°C and a pressure of 4–7 MPa for 10–20 min; degassing under vacuum; injecting the mixture into a mold; curing the mixture in an oven / drying tunnel; then crushing and injection molding to obtain the polyurethane elastomer.

[0037] Another method for preparing polyurethane elastomers, as described above, employs a prepolymerization method, comprising the following steps: (1) reacting a polymeric polyol with a diisocyanate to form a prepolymer; and (2) polymerizing the prepolymer with a chain extender. The prepolymer is then injected into a twin-screw extruder, reacted at 200°C and 5 MPa for 10–20 min, extruded, continuously granulated underwater, and subsequently cured to obtain a thermoplastic polyurethane elastomer.

[0038] An application of a polyurethane elastomer, wherein the polyurethane elastomer is the polyurethane elastomer described above, or the polyurethane elastomer prepared by the above method, can be used as a raw material for preparing injection molded or extruded products, and is preferably used as a raw material for cutting wheels, rubber rollers, sliding wheels, and seals.

[0039] Example

[0040] The present invention will be described in more detail below through embodiments, wherein the specific testing methods for the parameters involved are as follows:

[0041] 1. Average functionality:

[0042] Functionality = 2 * number of moles of hydroxyl groups / (number of moles of hydroxyl groups + number of moles of carboxyl groups + number of moles of double bonds).

[0043] The acid value was determined using the method described in HG / T 2708-1995; the hydroxyl value was determined using the method described in HG / T 2709 / 1995; and the degree of unsaturation was determined using the method described in GB / T 12008.6-2010. The corresponding acid value, hydroxyl value, and degree of unsaturation were then converted into the molar number of the corresponding end groups in the polymer diol.

[0044] 2. According to standard GBT 1040.2-2006, thermoplastic polyurethane elastomer granules were hot-pressed into a film with a thickness of 500 micrometers using a flat vulcanizing machine, and then cut into standard dumbbell-shaped strips. Tensile and five-cycle tests were performed (according to the method described in ASTM D412) to measure their tensile modulus.

[0045] 3. Hydrolysis resistance test

[0046] The sample was immersed in a 70°C, 17% NaOH solution for 1 hour, rinsed off the residual alkali with clean water, dried, and then subjected to tensile and five-cycle tests.

[0047] 4. Oil resistance test

[0048] Immerse the sample in oil (straight-chain alkanes, cycloalkanes, aromatics) at 70℃ for 24 hours, ensuring the sample is at least 10 cm below the liquid surface and bottom of the container during immersion. Immediately after immersion, wipe off any residual liquid and perform mechanical property tests.

[0049] The present invention will be further described below with reference to the embodiments. The following examples are only for illustration and are not intended to limit the scope of the present invention.

[0050] The following Examples 1a to 4a and Comparative Example 1a were prepared under the same heating program and vacuum conditions. Specifically, the reaction steps were as follows: the raw materials were put into the reactor, nitrogen gas was introduced to replace the air in the reactor; the stirring in the reactor was turned on at a speed of 150 rpm; the system was heated to 150°C and held for 5 hours; the temperature was further increased to 230°C and held until the water content of the system reached more than 90% of the theoretical value and the solution became homogeneous; tetraisopropyl titanate catalyst was added, and the vacuum was gradually reduced to 2000 Pa; when the acid value was lower than 0.5 mg KOH / g, the polymer polyol was obtained.

[0051] Example 1a, Preparation of polymer polyols

[0052] 17 parts by weight of polyethylene glycol PEG600 (number average molecular weight 600) and 2.7 parts by weight of terephthalic acid were added to a reactor equipped with a fractionation column and a distillation receiver. Nitrogen gas was introduced to replace the air in the reactor. The temperature was programmed and a vacuum was applied to prepare a polymer polyol P1 with an average functionality of 1.98 and a corresponding number average molecular weight of 1500 g / mol.

[0053] Example 2a, Preparation of polymer polyols

[0054] 8.5 parts by weight of polytetrahydrofuran PTG650 (number average molecular weight 650), 8.5 parts by weight of polyethylene glycol PEG600 (number average molecular weight 600), and 3.52 parts by weight of terephthalic acid were added to a reactor equipped with a fractionation column and a distillation receiver. Nitrogen gas was purged to displace the air in the reactor. The temperature was programmed and a vacuum was applied to prepare a polymeric polyol P2 with an average functionality of 1.98 and a corresponding number average molecular weight of 1800 g / mol.

[0055] Example 3a, Preparation of polymer polyols

[0056] 17 parts by weight of polyethylene glycol PEG600 (number average molecular weight 600) and 3.8 parts by weight of naphthalenecarboxylic acid were added to a reactor equipped with a fractionation column and a distillation receiver. Nitrogen gas was introduced to replace the air in the reactor. The temperature was programmed and a vacuum was applied to prepare a polymer polyol P3 with an average functionality of 1.98 and a corresponding number average molecular weight of 1900 g / mol.

[0057] Example 4a, Preparation of Polymer Polyols

[0058] 17 parts by weight of poly(1,3-propanediol) PPG950 (number average molecular weight 950) and 2.65 parts by weight of terephthalic acid were added to a reactor equipped with a fractionation column and a distillation receiver. Nitrogen gas was introduced to displace the air in the reactor. The temperature was programmed and a vacuum was applied to prepare a polymeric polyol P4 with an average functionality of 1.98 and a corresponding number average molecular weight of 3450 g / mol.

[0059] Using the polymer polyols prepared in Examples 1a-4a above, different polyurethane elastomers were prepared according to the raw material composition and dosage shown in Table 1. The specific methods are as follows:

[0060] The polymer polyol, chain extender, and diisocyanate were injected into a twin-screw extruder at a speed of 200 r / min using a metering and conveying system. The reaction, extrusion, and continuous underwater granulation were carried out at 200℃ and 5MPa, followed by post-curing to obtain thermoplastic polyurethane elastomer.

[0061] Table 1. Raw material composition and dosage for each embodiment and comparative example.

[0062]

[0063]

[0064] The polyurethane elastomers prepared in the above embodiments were hot-pressed into films with a thickness of 500 micrometers using a flat vulcanizing machine. These films were then removed and placed in a standard constant temperature and humidity laboratory (23°C, 50% humidity) for 24 hours. Afterward, they were cut into standard dumbbell-shaped specimens. The specimens prepared in Examples 1-4 and Comparative Examples 1-2 correspond to TPU-F1, TPU-F2, TPU-F3, TPU-F4, TPU-FC1, and TPU-FC2, respectively. The tensile modulus, hydrolysis resistance, and oil resistance were tested and evaluated according to the methods described above. The performance of the polyurethane elastomers prepared in each embodiment and comparative example is shown in Table 2.

[0065] Table 2-1 Performance Tests:

[0066] TPU-F1 8.35 528 33.6 27.5 TPU-F2 8.27 573 33.2 26.8 TPU-F3 8.98 496 35.2 28.1 TPU-F4 6.56 690 35.8 24.2 TPU-FC1 8.06 653 31.5 31.2 TPU-FC2 7.85 589 30.8 32.3

[0067] Table 2-2 Hydrolysis Resistance Test:

[0068]

[0069]

[0070] After being soaked in NaOH solution for a certain period of time, the tensile modulus, breaking strength, elongation at break, and permanent deformation rate of the samples prepared in Examples 1-4 did not change significantly. Their mechanical properties remained close to or even surpassed those of the polyether-type polyurethane elastomer in Comparative Example 1, maintaining good mechanical properties. In contrast, the conventional polyester-type polyurethane elastomer in Comparative Example 2 crumbled after soaking for one hour and could not be tested. This indicates that the polyurethane elastomer prepared using the polymer polyol of this invention possesses excellent hydrolysis resistance.

[0071] Table 2-3 Oil resistance test:

[0072] TPU-F1 8.16 498 28.6 30.1 TPU-F2 8.04 513 29.4 29.6 TPU-F3 8.47 485 32.1 31.2 TPU-F4 5.82 630 28.4 35.3 TPU-FC1 5.03 480 15.8 65.3 TPU-FC2 7.29 592 29.8 34.3

[0073] The test results of the samples prepared in Examples 1-4 and Comparative Examples 1-2 in the table above show that, for example, the polyurethane elastomers prepared using the polymer polyol of the present invention have excellent tensile modulus, tensile strength, and lower elongation at break and compressive set. After immersion in high-temperature oil, the tensile modulus, tensile strength, and compressive set of Examples 1-4 did not change significantly, remaining close to or exceeding those of Comparative Example 2, and far superior to the polyether-type Comparative Example 1. This indicates that the polyurethane elastomers prepared using the polymer polyol of the present invention as raw material possess good oil resistance.

Claims

1. A polyurethane elastomer, comprising polymeric polyol, diisocyanate, and chain extender as raw materials, characterized in that, The polymer polyol is obtained from raw materials including substances of type A and type B through condensation reaction or transesterification reaction, wherein substances of type A include aromatic dicarboxylic acids, their esters or anhydrides, and substances of type B include polyether glycols; the polymer polyol is composed of repeating units and capped alcohol hydroxyl groups as shown in formula (1): Equation (1), Wherein R1 is at least one of an aromatic ring or a heterocyclic aromatic ring, and the mass content of R1 in the repeating unit of formula (1) is 4.5%-44%; R2 is at least one of the saturated alkane groups having 2-3 carbon atoms; x is 2-20; The average functionality of the capped hydroxyl groups of the polymer polyol is 1.95-2.00, and the number average molecular weight is 800-5000.

2. The polyurethane elastomer according to claim 1, characterized in that, The number average molecular weight of the polymer polyol is 800-2000.

3. The polyurethane elastomer according to claim 1, characterized in that, The number average molecular weight of the polymer polyol is 800-1500.

4. The polyurethane elastomer according to claim 1, characterized in that, The mass content of R1 in the repeating unit of formula (1) is 4.5%-40%.

5. The polyurethane elastomer according to claim 1, characterized in that, The mass content of R1 in the repeating unit of formula (1) is 10%-35%.

6. The polyurethane elastomer according to claim 1, characterized in that, R2 is at least two of saturated alkane groups having 2-3 carbon atoms.

7. The polyurethane elastomer according to claim 1, characterized in that: The diisocyanate is selected from one or more of diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and their isomers.

8. The polyurethane elastomer according to claim 1, characterized in that: The chain extender is selected from one or more of ethylene glycol, 1,4-butanediol, diethylene glycol, 1,6-hexanediol, 1,3-propanediol, and 1,4-dihydroxymethylcyclohexane.

9. The polyurethane elastomer according to claim 1, characterized in that: Based on the total weight of the polyurethane elastomer, the raw materials of the polyurethane elastomer include 10-45 parts of diisocyanate, 35-90 parts of polymeric polyol, and 4-17 parts of chain extender.

10. The method for preparing the polyurethane elastomer according to any one of claims 1-9, characterized in that, Includes the following steps: (1) The diisocyanate, polymer polyol and chain extender are injected into the twin-screw extruder by a metering and conveying system respectively; (2) The mixture from step (1) is reacted, extruded, granulated and cured at 120-220°C to obtain the polyurethane elastomer.

11. An application of the polyurethane elastomer as described in any one of claims 1-9, characterized in that, The polyurethane elastomer is used as a raw material for preparing injection-molded or extruded products.

12. An application of the polyurethane elastomer as described in claim 11, characterized in that, The polyurethane elastomer is used as a raw material for cutting wheels, rubber rollers, sliding wheels, and seals.

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