Oil-resistant thermoplastic polyurethane elastomer and preparation method and application thereof

Abstract

This invention discloses an oil-resistant thermoplastic polyurethane elastomer, its preparation method, and its applications. The polyurethane elastomer, based on 100% of the total raw material mass, is made from the following raw materials in the following mass percentages: polyester polyol 40-75%; diisocyanate 20-55%; chain extender 5-15%. The polyester polyol includes polyester polyol A1 containing polar groups and polyester polyol A2 without polar groups. The thermoplastic polyurethane elastomer of this invention can be used for extended periods in oily environments at 140°C while maintaining high strength, meeting the requirements of relevant fields. It exhibits excellent oil resistance and superior mechanical properties, including high strength, aging resistance, low abrasion, and low compression set.

Description

Technical Field

[0001] This invention relates to a polyurethane elastomer, and more particularly to a thermoplastic polyurethane elastomer, its preparation method, and its application. Background Technology

[0002] Currently, most oil-resistant materials on the market are nitrile rubber, silicone rubber, chloroprene rubber, acrylate rubber, and polysulfide rubber, which use their own polar nitrile groups or polar groups introduced into the main chain or side chain to prevent the invasion of oily molecules. For example, patent CN104558727B improves the vulcanization performance of graphene oxide-epoxidized styrene-butadiene rubber composites by forming chemical bonds between epoxidized styrene-butadiene rubber and graphene oxide; patent CN111621017A uses trifluoropropylmethylcyclotrisiloxane, methylvinylcyclosiloxane and dimethylcyclosiloxane as raw materials to prepare ternary copolymer fluorosilicone rubber with good oil resistance; patent CN107531852B prepares nitrile-containing high-saturation copolymer rubber through α,β-ene unsaturated nitrile monomer units, α,β-ene unsaturated monocarboxylic acid ester monomer units and conjugated diene monomer units; patent CN111647114A prepares chlorinated acrylate rubber with excellent processing performance through alkyl acrylate, chloroprene rubber latex, hydroxy acrylate and olefinic unsaturated monomers containing carboxyl groups.

[0003] However, although these modified rubbers have certain advantages in oil resistance, they still have defects such as low temperature resistance, low physical properties and poor processing performance. In addition, they require vulcanization crosslinking, which is a complicated process and cannot meet actual needs.

[0004] Thermoplastic polyurethane elastomer (TPU) is a block polymer composed of hard segments formed by the reaction of chain extenders and diisocyanates, and soft segments formed by polyols. Due to its molecular structure, it exhibits rubber elasticity at low temperatures and can be plasticized and molded upon heating. It is a material that can be reprocessed and molded, possessing advantages such as high mechanical strength, wear resistance, good toughness, good processability, and wide range of applications. Therefore, the development of TPU with good oil resistance can replace traditional rubber in applications requiring oil resistance, solving the problems that traditional oil-resistant rubber cannot address. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a thermoplastic polyurethane elastomer with excellent oil resistance. This invention designs the molecular structure of the polyester polyol component, increasing the polarity of the TPU molecules by introducing polar groups. Furthermore, it increases the ester group density in the polyester polyol component by selecting diols and diacids with shorter chain segments, and simultaneously introduces amide groups into the polyol branches. These factors all actively enhance the polarity of the TPU molecules, significantly improving their oil resistance. In addition, this invention introduces small-molecule chain extenders containing double bonds through process control, providing crosslinking reaction sites for this oil-resistant TPU. Controlling crosslinking during hard segment chain extension results in a more compact TPU molecular structure, preventing the penetration of oily molecules and effectively improving the oil resistance of the prepared thermoplastic polyurethane.

[0006] Another objective of this invention is to provide a method for preparing thermoplastic polyurethane elastomers. This method, from the perspective of molecular structure design, first synthesizes polyester polyol raw materials containing polar groups, and then prepares the polyurethane elastomer through conventional processes. This avoids complex processes such as vulcanization and crosslinking, and has good process applicability.

[0007] Another object of the present invention is to provide an application of thermoplastic polyurethane elastomer in injection molded and extruded products, preferably in products such as cutting wheels, rubber rollers, sliding wheels, and seals.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] An oil-resistant thermoplastic polyurethane elastomer, based on 100% of the total mass of raw materials, is made from the following raw materials comprising the following mass percentages:

[0010] Polyester polyol 40-75%, preferably 45-65%;

[0011] 20-55% diisocyanate, preferably 30-50%;

[0012] Chain extender 5-15%, preferably 5-10%.

[0013] The polyester polyol includes polyester polyol A1 containing polar groups and polyester polyol A2 without polar groups; preferably, polyester polyol A2 accounts for 20-100% of the total mass of polyester polyol, more preferably 50-100%, and most preferably 80-100%.

[0014] In a preferred embodiment of the present invention, the polyester polyol A1 has a functionality of 2 and a molecular weight of 400-3000 g / mol;

[0015] The polyester polyol A2 has a functionality of 2 and a molecular weight of 400–3000 g / mol.

[0016] In a preferred embodiment of the present invention, the polyester polyol A1 is prepared by reacting a dicarboxylic acid containing a polar group with a diol; the polyester polyol A2 is prepared by reacting an aliphatic dicarboxylic acid with a diol.

[0017] In a preferred embodiment of the present invention, the dicarboxylic acid containing a polar group is a compound expressed by the following structural formula: Wherein, n is a natural number from 0 to 6, preferably n = 1 to 4; m is 1 or 2; R is a polar group -F, -Cl, -Br, -CN or -NO2; preferably, the dicarboxylic acid containing a polar group is selected from at least one of 4-chlorophthalic acid, 4-fluorophthalic acid, 4-bromophthalic acid, 4-nitroxyphthalic acid, and 4-chlorophthaloylaminomalonic acid, 4-fluorophthaloylaminomalonic acid, 4-bromophthaloylaminomalonic acid, and 4-nitroxyphthaloylaminomalonic acid.

[0018] For the above dicarboxylic acids containing polar groups, the preparation process of 4-chlorophthalic acid is as follows:

[0019] 4-chloro-o-xylene and potassium permanganate are mixed in an aqueous solution at 50-80°C (e.g., at a molar ratio of 1:1.05) and subjected to an oxidation reaction for 3-6 hours. After the reaction is complete, the oxidation product is acidified with concentrated hydrochloric acid (36-38%) for 0.5-1 hours, followed by extraction with an organic solvent (e.g., ethyl acetate) and purification of the organic phase to obtain the product 4-chlorophthalic acid. The preparation processes for other 4-halophthalic acids or 4-nitrified phthalic acids can be simplified by referring to similar methods. The only difference is that 4-chloro-o-xylene is replaced with a raw material containing the corresponding polar functional group. For example, to prepare 4-fluorophthalic acid, 4-chloro-o-xylene is replaced with 4-fluoro-o-xylene; to prepare 4-bromophthalic acid, 4-chloro-o-xylene is replaced with 4-bromo-o-xylene; and to prepare 4-nitrified phthalic acid, 4-chloro-o-xylene is replaced with 4-nitro-o-xylene.

[0020] In addition, the preparation process of 4-chlorophthalamide malonic acid is as follows:

[0021] Aminomalonic acid is mixed with 4-chlorophthalic anhydride (e.g., at a molar ratio of 1:1.2), heated in an oil bath to 110-160°C, reacted at this temperature for 20-50 minutes, and then poured into hot water while still hot. After cooling and crystallization, the resulting crystals are recrystallized with 20-30% ethanol to obtain the product 4-chlorophthalamide-aminomalonic acid. The preparation processes for other 4-halophthalamide malonic acids or 4-nitrophthalamide malonic acids can be simplified by referring to similar methods. The only difference is that the 4-chlorophthalic anhydride is replaced with a raw material containing the corresponding polar functional group. For example, to prepare 4-fluorophthalamide malonic acid, the 4-chlorophthalic anhydride is replaced with 4-fluorophthalic anhydride; to prepare 4-bromophthalamide malonic acid, the 4-chlorophthalic anhydride is replaced with 4-bromophthalic anhydride; and to prepare 4-nitrophthalamide malonic acid, the 4-chlorophthalic anhydride is replaced with 4-nitrophthalic anhydride.

[0022] The aliphatic dicarboxylic acid is a compound expressed by the following structural formula: HOOC-C x H 2x -COOH, wherein x is a natural number from 2 to 10, preferably x = 2, 4, 6 or 8; preferably, the aliphatic dicarboxylic acid is one or more of adipic acid, succinic acid, and sebacic acid;

[0023] The diol is a dicarboxylic acid with 1 to 10 carbon atoms, preferably one or more of ethylene glycol, propylene glycol, butanediol, diethylene glycol, dipropylene glycol, and hexanediol.

[0024] The preparation processes for the polyester polyols A1 and A2 can be carried out conventionally based on the raw materials described above, referring to existing polyester polyol processes, for example:

[0025] A dicarboxylic acid and a diol (molar ratio 1:1.05–1.5) are reacted at 120–150°C and atmospheric pressure. Water produced during the reaction is collected by distillation. After 2–4 hours of reaction, the temperature is raised to 180–240°C within 15–30 minutes to promote the reaction and the collection of the water byproduct. The reaction continues for 1–3 hours, after which the pressure of the reaction system is reduced to below 10 kPa, preferably below 5 kPa, and 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 high temperature and under vacuum for another 2–6 hours. Products with different molecular weights are obtained by detecting the hydroxyl value and acid value of the polyester polyol.

[0026] The catalyst is one of isopropyl titanate, tetrabutyl titanate, dibutyltin dilaurate, stannous octoate, and bismuth laurate. Preferably, the amount of catalyst added is 0.01-0.1% of the total mass of the reaction system (diacid + diol).

[0027] In a preferred embodiment of the present invention, the diisocyanate is selected from one or more of aromatic diisocyanates and aliphatic diisocyanates, preferably one or more of toluene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, and isophorone diisocyanate.

[0028] In a preferred embodiment of the present invention, the chain extender comprises a diol containing a double bond and a diol not containing a double bond, wherein the molar ratio of the diol containing a double bond in the chain extender is 10-100%, preferably 30-80%.

[0029] Preferably, the diol containing a double bond is one or more of butenyl glycol, hexenyl glycol, pentenyl glycol, and heptenyl glycol; the diol without a double bond is a diol with 1 to 10 carbon atoms, preferably 2 to 4, preferably one or more of ethylene glycol, 1,4-butanediol, 1,3-propanediol, and dipropylene glycol.

[0030] A method for preparing an oil-resistant thermoplastic polyurethane elastomer as described above, using a one-step method of manual casting or machine casting, includes the following steps:

[0031] Polyester polyol, chain extender, and polyurethane catalyst are stirred and mixed evenly at 55-140°C. Diisocyanate is added and the mixture is stirred rapidly at 500-1500 rpm to carry out the reaction. After reacting for 20-60 seconds, the mixture is quickly poured into a mold, placed in an oven for curing, crushed, and then injection molded to obtain the polyurethane elastomer.

[0032] In a preferred embodiment of the present invention, the polyester polyol and chain extender are first dried in an oven at 80-120°C for 4-6 hours to remove moisture.

[0033] In a preferred embodiment of the present invention, the curing conditions are 10-12 hours of hot air treatment at 80-110°C.

[0034] In a preferred embodiment of the present invention, the polyurethane catalyst is one or more of stannous octoate, dibutyltin dilaurate, and dibutyltin dioctanoate;

[0035] Preferably, the amount of polyurethane catalyst added is 0 to 0.03% of the total mass of polyester polyol, diisocyanate, and chain extender, preferably 0.003 to 0.02%.

[0036] An application of the oil-resistant thermoplastic polyurethane elastomer described above is as follows: the polyurethane elastomer is used as a raw material for preparing injection-molded or extruded products with high oil resistance requirements, and is preferably used as a raw material for cutting wheels, rubber rollers, sliding wheels, and seals.

[0037] The thermoplastic polyurethane elastomer of this invention can be used for a long time in an oily environment at 140°C while still maintaining high strength, meeting the requirements of related fields. It has excellent oil resistance and excellent mechanical properties, including high strength, aging resistance, low wear, and low compression set. Detailed Implementation

[0038] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0039] In the examples, the abrasion test was performed according to ISO 4649, the Shore hardness test according to ASTM D2240, the tensile test according to ASTM D412, the tear strength according to ASTM D624, the compression set according to ASTM D395, and the Vicat softening point according to ASTM D1525.

[0040] Key raw material information in the examples:

[0041] PEA2500: Polyethylene glycol adipate, molecular weight 2500 g / mol, Wanhua Chemical Co., Ltd.

[0042] Butenediol: Purchased from Sinopharm Co., Ltd.

[0043] 1,2-Butanediol: Purchased from Sinopharm Co., Ltd.

[0044] MDI: 4,4'-Diphenylmethane diisocyanate, Wanhua Chemical

[0045] HMDI: 4,4'-Dicyclohexylmethane diisocyanate, Wanhua Chemical

[0046] [Preparation Example 1] Preparation of Polyester A: Polyethylene Phthalate 2500

[0047] 1 mol of phthalic acid and 1.05 mol of ethylene glycol were added to a glass reactor. Under nitrogen protection, the reaction was carried out at 138°C for 2 hours. The temperature was then raised to 200°C within 15 minutes and the reaction was continued at 200°C for another 2 hours. The system pressure was then reduced to below 1 kPa using an oil pump, and the reaction continued for another 2 hours. Isopropyl titanate catalyst was added at a concentration of 0.06% of the total mass of the reaction system, and the reaction was continued at 200°C for another 6 hours. The product was sampled and measured to have an acid value of 0.067 mg KOH / g and a hydroxyl value of 46.12 mg KOH / g. The product temperature was adjusted to approximately 100°C before discharge. Polyethylene phthalate with a molecular weight of 2429.25 g / mol was obtained and denoted as polyester A.

[0048] [Preparation Example 2] Preparation of Polyester B: Polyethylene 4-chlorophthalate 2500

[0049] Preparation of 4-chlorophthalic acid: 1 mol of 4-chloroo-xylene and 1.05 mol of potassium permanganate were dissolved in 1.5 L of aqueous solution and reacted at 50 °C for 6 h to obtain the oxidation product. The oxidation product was acidified with 36% concentrated hydrochloric acid for 40 min, extracted with ethyl acetate, and purified by organic phase to obtain the product 4-chlorophthalic acid.

[0050] 13 CNMR (101MHz DMSO-d6), δ: 139.4, 133.9, 128.9, 126.8, 134.3, 131.0, 167.6.

[0051] 1 mol of 4-chlorophthalic acid and 1.05 mol of ethylene glycol were added to a glass reactor. Under nitrogen protection, the reaction was carried out at 138°C for 2 hours. The temperature was then raised to 200°C within 15 minutes and the reaction was continued at 200°C for another 2 hours. The system pressure was then reduced to below 1 kPa using an oil pump, and the reaction continued for another 2 hours. Isopropyl titanate catalyst was added at a concentration of 0.06% of the total mass of the reaction system, and the reaction was continued at 200°C for another 6 hours. The product was sampled and measured to have an acid value of 0.049 mg KOH / g and a hydroxyl value of 46.9 mg KOH / g. The product temperature was adjusted to approximately 100°C before discharge. Polyethylene chlorophthalate with a molecular weight of 2389.83 g / mol was obtained and denoted as polyester B.

[0052] [Preparation Example 3] Preparation of Polyester C: Poly(ethylene phthalamide malonate) 2500

[0053] Preparation of phthalamide malonic acid: 0.1 mol aminomalonic acid and 0.12 mol phthalic anhydride were mixed and heated in an oil bath to 140°C. After reacting at this temperature for 30 min, the mixture was poured into hot water while still hot and cooled to crystallize. The resulting crystals were recrystallized with 30% ethanol to obtain the product phthalamide malonic acid.

[0054] 13 CNMR (101MHz DMSO-d6), δ: 132.2, 132.0, 123.7, 168.2, 174.1, 71.4.

[0055] 1 mol of phthalamide malonic acid and 1.05 mol of ethylene glycol were added to a glass reactor. Under nitrogen protection, the reaction was carried out at 145℃ for 2 hours. The temperature was then raised to 220℃ within 30 minutes, and the reaction was continued at 220℃ for 3 hours. The system pressure was then reduced to below 1 kPa using an oil pump, and the reaction was continued for another 2 hours. Isopropyl titanate catalyst was added at a concentration of 0.08% of the total mass of the reaction system, and the reaction was continued at 200℃ for 6 hours. The product was sampled and measured to have an acid value of 0.049 mg KOH / g and a hydroxyl value of 45.8 mg KOH / g. The product temperature was adjusted to approximately 100℃ before discharge. Polyethylene phthalamide malonate was prepared with a molecular weight of 2447.16 g / mol, denoted as polyester C.

[0056] [Preparation Example 4] Preparation of Polyester D: Polyethylene 4-chlorophthalamide malonate 2500

[0057] Preparation of 4-chlorophthalamide malonic acid: 0.1 mol aminomalonic acid and 0.12 mol 4-chlorophthalic anhydride were mixed and heated in an oil bath to 140°C. After reacting at this temperature for 30 min, the mixture was poured into hot water while hot and cooled to crystallize. The resulting crystals were recrystallized with 30% ethanol to obtain 4-chlorophthalamide malonic acid.

[0058] 13 CNMR (101MHz DMSO-d6), δ: 132.3, 137.8, 129.0, 127.6, 133.4, 130.1, 168.2, 174.1, 71.4.

[0059] 1 mol of 4-chlorophthalamide malonic acid and 1.05 mol of ethylene glycol were added to a glass reactor. Under nitrogen protection, the reaction was carried out at 145℃ for 2 hours. The temperature was then raised to 220℃ within 30 minutes, and the reaction was continued at 220℃ for 3 hours. The system pressure was then reduced to below 1 kPa using an oil pump, and the reaction was continued for another 2 hours. Isopropyl titanate catalyst was added at a concentration of 0.08% of the total mass of the reaction system, and the reaction was continued at 200℃ for 6 hours. The product was sampled and measured to have an acid value of 0.066 mg KOH / g and a hydroxyl value of 45.1 mg KOH / g. The product temperature was adjusted to approximately 100℃ before discharge. Polyethylene 4-chlorophthalamide malonate was prepared with a molecular weight of 2484.17 g / mol, denoted as polyester D.

[0060] [Preparation Example 5] Preparation of Polyester E: Poly(hexanediol phthalamide malonate) 2500

[0061] 1 mol of phthalamide malonic acid and 1.05 mol of hexanediol were added to a glass reactor. Under nitrogen protection, the reaction was carried out at 145℃ for 2 hours. The temperature was then raised to 220℃ within 15 minutes, and the reaction was continued at 220℃ for 3 hours. The system pressure was reduced to below 1 kPa using an oil pump, and the reaction was continued for another 3 hours. Isopropyl titanate catalyst was added at a concentration of 0.06% of the total mass of the reaction system, and the reaction was continued at 200℃ for 6 hours. The product was sampled and measured to have an acid value of 0.061 mg KOH / g and a hydroxyl value of 43.5 mg KOH / g. The product temperature was adjusted to approximately 100℃ before discharge. Hexanediol phthalamide malonic acid ester was prepared with a molecular weight of 2477.31 g / mol, denoted as polyester E.

[0062] [Preparation Example 6] Preparation of Polyester F: Poly(4-chlorophthalamide hexanediol) 2500

[0063] 1 mol of 4-chlorophthalamide malonic acid and 1.05 mol of hexanediol were added to a glass reactor. Under nitrogen protection, the reaction was carried out at 145℃ for 2 hours. The temperature was then raised to 220℃ within 15 minutes, and the reaction was continued at 220℃ for 3 hours. The system pressure was reduced to below 1 kPa using an oil pump, and the reaction was continued for another 3 hours. Isopropyl titanate catalyst was added at a concentration of 0.06% of the total mass of the reaction system, and the reaction was continued at 200℃ for 6 hours. The product was sampled and measured to have an acid value of 0.066 mg KOH / g and a hydroxyl value of 45.5 mg KOH / g. The product temperature was adjusted to approximately 100℃ before discharge. Poly(4-chlorophthalamide malonic acid) hexanediol ester with a molecular weight of 2462.36 g / mol was prepared and denoted as polyester F.

[0064] [Preparation Example 7] Preparation of Polyester G: Polyethylene 4-chlorophthalamide malonate 1000

[0065] 1 mol of 4-chlorophthalamide malonic acid and 1.05 mol of ethylene glycol were added to a glass reactor. Under nitrogen protection, the reaction was carried out at 145℃ for 1 hour. The temperature was then raised to 220℃ within 30 minutes, and the reaction was continued at 220℃ for 1.5 hours. The system pressure was then reduced to below 1 kPa using an oil pump, and the reaction was continued for another hour. Isopropyl titanate catalyst was added at a concentration of 0.02% of the total mass of the reaction system, and the reaction was continued at 200℃ for 4 hours. The product was sampled and measured to have an acid value of 0.081 mg KOH / g and a hydroxyl value of 106.19 mg KOH / g. The product temperature was adjusted to approximately 100℃ before discharge. Polyethylene 4-chlorophthalamide malonate was prepared with a molecular weight of 1055.79 g / mol, denoted as Polyester G.

[0066] [Preparation Example 8] Preparation of Polyester H: Polyethylene phthalamide malonate 1000

[0067] 1 mol of 4-chlorophthalamide malonic acid and 1.05 mol of ethylene glycol were added to a glass reactor. Under nitrogen protection, the reaction was carried out at 145°C for 1 hour. The temperature was then raised to 220°C within 30 minutes, and the reaction was continued at 220°C for 1.5 hours. The system pressure was then reduced to below 1 kPa using an oil pump, and the reaction was continued for another hour. Isopropyl titanate catalyst was added at a concentration of 0.02% of the total mass of the reaction system, and the reaction was continued at 200°C for 4 hours. The product was sampled and measured to have an acid value of 0.077 mg KOH / g and a hydroxyl value of 105.1 mg KOH / g. The product temperature was adjusted to approximately 100°C before discharge. Polyethylene phthalamide malonate was prepared with a molecular weight of 1066.77 g / mol, denoted as polyester H.

[0068] [Preparation Example 9] Preparation of Polyester I: Polyethylene 4-chlorophthalamide malonate 3000

[0069] 1 mol of 4-chlorophthalamide malonic acid and 1.05 mol of ethylene glycol were added to a glass reactor. Under nitrogen protection, the reaction was carried out at 145℃ for 2 hours. The temperature was then raised to 220℃ within 30 minutes, and the reaction was continued at 220℃ for 3 hours. The system pressure was reduced to below 1 kPa using an oil pump, and the reaction was continued for 1 hour. Isopropyl titanate catalyst was added at a concentration of 0.08% of the total mass of the reaction system, and the reaction was continued at 200℃ for 7 hours. The product was sampled and measured to have an acid value of 0.066 mg KOH / g and a hydroxyl value of 37.2 mg KOH / g. The product temperature was adjusted to approximately 100℃ before discharge. Polyethylene 4-chlorophthalamide malonate with a molecular weight of 3010.79 g / mol was prepared and designated as Polyester I.

[0070] [Preparation Example 10] Preparation of Polyester J: Poly(ethylene phthalamide malonate) 3000

[0071] 1 mol of 4-chlorophthalamide malonic acid and 1.05 mol of ethylene glycol were added to a glass reactor. Under nitrogen protection, the reaction was carried out at 145℃ for 2 hours. The temperature was then raised to 220℃ within 30 minutes, and the reaction was continued at 220℃ for 3 hours. The system pressure was then reduced to below 1 kPa using an oil pump, and the reaction was continued for another hour. Isopropyl titanate catalyst was added at a concentration of 0.08% of the total mass of the reaction system, and the reaction was continued at 200℃ for 7 hours. The product was sampled and measured to have an acid value of 0.077 mg KOH / g and a hydroxyl value of 36.9 mg KOH / g. The product temperature was adjusted to approximately 100℃ before discharge. Polyethylene phthalamide malonate was prepared with a molecular weight of 3034.32 g / mol, denoted as Polyester J.

[0072] [Preparation Example 11] Preparation of Polyester K: Polybutylene phthalamide malonate 2500

[0073] 1 mol of phthalamide malonic acid and 1.05 mol of butanediol were added to a glass reactor. Under nitrogen protection, the reaction was carried out at 145℃ for 2 hours. The temperature was then raised to 220℃ within 15 minutes, and the reaction was continued at 220℃ for 3 hours. The system pressure was then reduced to below 1 kPa using an oil pump, and the reaction was continued for another 3 hours. Isopropyl titanate catalyst was added at a concentration of 0.06% of the total mass of the reaction system, and the reaction was continued at 200℃ for 6 hours. The product was sampled and measured to have an acid value of 0.063 mg KOH / g and a hydroxyl value of 41.5 mg KOH / g. The product temperature was adjusted to approximately 100℃ before discharge. Butanediol phthalamide malonate was prepared with a molecular weight of 2487.21 g / mol, denoted as polyester K.

[0074] [Preparation Example 12] Preparation of Polyester L: Polybutylene 4-chlorophthalamide malonate 2500

[0075] 1 mol of 4-chlorophthalamide malonic acid and 1.05 mol of butanediol were added to a glass reactor. Under nitrogen protection, the reaction was carried out at 145℃ for 2 hours. The temperature was then raised to 220℃ within 15 minutes, and the reaction was continued at 220℃ for 3 hours. The system pressure was reduced to below 1 kPa using an oil pump, and the reaction was continued for another 3 hours. Isopropyl titanate catalyst was added at a concentration of 0.06% of the total mass of the reaction system, and the reaction was continued at 200℃ for 6 hours. The product was sampled and measured to have an acid value of 0.066 mg KOH / g and a hydroxyl value of 41.3 mg KOH / g. The product temperature was adjusted to approximately 100℃ before discharge. Polybutylene 4-chlorophthalamide malonate was prepared with a molecular weight of 2491.25 g / mol, denoted as polyester L.

[0076] [Examples 1-17 and Comparative Examples 1-4]

[0077] Different types of polyurethane elastomers (TPU) were prepared according to the raw material composition and dosage shown in Table 1. The specific methods are as follows:

[0078] Polyester polyol and chain extender were dried in ovens at 100℃ and 80℃ for 5 hours to remove moisture. Calculated amounts of polyester polyol and chain extender were mixed at 65℃ and stirred evenly with a paddle mixer. Then, calculated amounts of diisocyanate were added, and the mixture was stirred until the temperature rose to approximately 120℃. The gelation time was 2 minutes, at which point stirring was stopped, and the mixture was quickly poured into a steel tray lined with PTFE cloth. The resulting cured material was cured in an oven at 100℃ for 12 hours, then crushed and injection molded into specimens of different shapes at 220℃. The injection-molded specimens were cured in an oven at 80℃ for 12 hours, then removed and placed in a standard constant temperature and humidity laboratory (23℃, 50% humidity) for 24 hours. After acclimatization, different shaped strips were cut for testing and evaluation.

[0079] Table 1. Raw material composition and dosage for each embodiment and comparative example

[0080]

[0081]

[0082] The properties of the polyurethane elastomers prepared in each embodiment and comparative example were tested as shown in Table 2, and the results are recorded in Table 2. From the test results of Examples 2, 9, 15 and Examples 13, 14, 16 in Table 2, it can be seen that, for example, after one month of storage in high-temperature oil, the hardness, tensile strength, and compression set of Example 2 are better than those of Example 15, while Example 15 is better than Example 9. This indicates that increasing the ester group density in the polyester polyol is beneficial to improving the oil resistance of the prepared TPU. A comparison of Comparative Examples 1-3 with Examples 12 and 17 shows that the technical solution of this invention can improve the polarity of TPU molecules and thus improve its oil resistance by introducing Cl-containing polar groups. Further comparison with Comparative Examples 4, Examples 2, and Examples 13 shows that the introduction of amide groups further improves the oil resistance of the TPU. Further comparison of the test results of Examples 2 and 4-5 shows that as the proportion of Cl-containing polar groups in the raw polyester polyol increases, the oil resistance of the prepared TPU gradually increases. A comparison of Examples 1-11, 15, and 17 with Examples 12-14 and 16 shows that, when TPU is prepared using only polyester polyols containing Cl polar groups as raw materials without adding chain extenders containing double bonds, the resulting products exhibit slightly inferior oil resistance, but still show significant performance advantages compared to the products in Comparative Examples 1-4. This indicates that the present invention can achieve an initial improvement in the oil resistance of TPU by introducing polar groups. In addition, the addition of butene glycol containing double bonds in the chain extender can provide crosslinking reaction sites, which greatly improves the oil resistance of TPU. Moreover, the oil resistance effect is best when the proportion of butene glycol reaches about 50%. Comparing Examples 6-7 shows that when the hard segment content increases, the hardness and physical properties of the TPU product increase. With the support of Cl polar groups, amide groups, and chain extenders containing double bonds, the product has very high oil resistance, and its performance remains almost unchanged within one month of high-temperature oil resistance. Comparative examples 1-11 show that the TPUs prepared in the range of 1000-3000 molecular weight of polyester polyols containing polar functional groups all have good oil resistance.

[0083] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

[0084] Table 2. Performance Test Results

[0085]

[0086]

Claims

1. An oil-resistant thermoplastic polyurethane elastomer, characterized in that, Based on the total mass of raw materials (100%), it is made from the following raw materials, comprising the following mass percentages: Polyester polyol 40-75%, Diisocyanate 20-55%, Chain extender 5-15%; The polyester polyols include polyester polyol A1 containing polar groups and polyester polyol A2 without polar groups. The polyester polyol A1 is prepared by reacting a dicarboxylic acid containing a polar group with a diol; the dicarboxylic acid containing a polar group is selected from at least one of 4-chlorophthalic acid, 4-fluorophthalic acid, 4-bromophthalic acid, 4-nitrophthalic acid, and 4-chlorophthaloylaminomalonic acid, 4-fluorophthaloylaminomalonic acid, 4-bromophthaloylaminomalonic acid, and 4-nitrophthaloylaminomalonic acid. The chain extender includes diols containing double bonds and diols without double bonds, with the molar ratio of diols containing double bonds in the chain extender being 10 to 100%.

2. The oil-resistant thermoplastic polyurethane elastomer according to claim 1, characterized in that, Based on the total mass of raw materials (100%), it is made from the following raw materials, comprising the following mass percentages: Polyester polyols 45-65%; Diisocyanate 30-50%; Chain extender 5-10%.

3. The oil-resistant thermoplastic polyurethane elastomer according to claim 1, characterized in that, Polyester polyol A2 accounts for 20-100% of the total mass of polyester polyols.

4. The oil-resistant thermoplastic polyurethane elastomer according to claim 3, characterized in that, Polyester polyol A2 accounts for 50-100% of the total mass of polyester polyols.

5. The oil-resistant thermoplastic polyurethane elastomer according to claim 4, characterized in that, Polyester polyol A2 accounts for 80-100% of the total mass of polyester polyols.

6. The oil-resistant thermoplastic polyurethane elastomer according to claim 1, characterized in that, The polyester polyol A1 has a functionality of 2 and a molecular weight of 400–3000 g / mol. The polyester polyol A2 has a functionality of 2 and a molecular weight of 400–3000 g / mol.

7. The oil-resistant thermoplastic polyurethane elastomer according to claim 1, characterized in that, The diol is a diol with 1 to 10 carbon atoms.

8. The oil-resistant thermoplastic polyurethane elastomer according to claim 7, characterized in that, The diol is one or more of ethylene glycol, propylene glycol, butanediol, diethylene glycol, dipropylene glycol, and hexanediol.

9. The oil-resistant thermoplastic polyurethane elastomer according to claim 1, characterized in that, The diisocyanate is selected from one or more of aromatic diisocyanates and aliphatic diisocyanates.

10. The oil-resistant thermoplastic polyurethane elastomer according to claim 9, characterized in that, The diisocyanate is selected from one or more of toluene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, and isophorone diisocyanate.

11. The oil-resistant thermoplastic polyurethane elastomer according to claim 1, characterized in that, The diol containing a double bond is one or more of butenyl glycol, hexenyl glycol, pentenyl glycol, and heptenyl glycol; the diol without a double bond is a diol with 1 to 10 carbon atoms.

12. The oil-resistant thermoplastic polyurethane elastomer according to claim 1, characterized in that, The diol without double bonds is a diol with 2 to 4 carbon atoms.

13. The oil-resistant thermoplastic polyurethane elastomer according to claim 1, characterized in that, The diol without double bonds is one or more of ethylene glycol, 1,4-butanediol, 1,3-propanediol, and dipropylene glycol.

14. A method for preparing an oil-resistant thermoplastic polyurethane elastomer as described in any one of claims 1-13, characterized in that, Includes the following steps: Polyester polyol, chain extender, and polyurethane catalyst are stirred and mixed evenly at 55-140°C. Diisocyanate is added and the mixture is stirred rapidly at 500-1500 rpm to carry out the reaction. After reacting for 20-60 seconds, the mixture is quickly poured into a mold, placed in an oven for curing, crushed, and then injection molded to obtain the polyurethane elastomer.

15. The method for preparing the oil-resistant thermoplastic polyurethane elastomer according to claim 14, characterized in that, The curing conditions are: 80–110°C under hot air for 10–12 hours.

16. The method for preparing the oil-resistant thermoplastic polyurethane elastomer according to claim 14, characterized in that, The polyurethane catalyst is one or more of stannous octoate, dibutyltin dilaurate, and dibutyltin dioctoate.

17. The method for preparing the oil-resistant thermoplastic polyurethane elastomer according to claim 16, characterized in that, The amount of polyurethane catalyst added is 0 to 0.03% of the total mass of polyester polyol, diisocyanate, and chain extender.

18. The method for preparing the oil-resistant thermoplastic polyurethane elastomer according to claim 16, characterized in that, The amount of polyurethane catalyst added is 0.003 to 0.02% of the total mass of polyester polyol, diisocyanate, and chain extender.

19. An application of the oil-resistant thermoplastic polyurethane elastomer as described in any one of claims 1-13, characterized in that, The polyurethane elastomer is used as a raw material for preparing injection-molded or extruded products.

20. An application of the oil-resistant thermoplastic polyurethane elastomer as described in any one of claims 1-13, 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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