Reversible piezochromic thermoplastic polyurethane elastomers and methods of making the same

Abstract

The present application relates to a kind of reversible pressure-induced color change thermoplastic polyurethane elastomer and its preparation method.The reversible pressure-induced color change thermoplastic polyurethane elastomer includes, by weight parts, dihydric alcohol of tetraphenyl ethene group 50-80, diisocyanate 10-30, catalyst 0.005-0.02 and chain extender 1-10;The dihydric alcohol containing tetraphenyl ethene group is synthesized by polymerization reaction from aliphatic diacid and dihydric alcohol raw materials.The present application uses special macromolecular dihydric alcohol containing tetraphenyl ethene group as raw material to prepare pressure-induced color change thermoplastic polyurethane elastomer, after material processing and shaping, molecule free activity is limited, when material is extruded and deformed by external force, the rotation of benzene ring in tetraphenyl ethene molecule which can freely rotate is limited, the non-radiative transition mainly by rotation is reduced, molecule luminescence is enhanced, so that the material has the performance of pressure-induced color change.

Description

Technical Field

[0001] This invention relates to a reversible pressure-sensitive color-changing thermoplastic polyurethane elastomer and its preparation method, belonging to the technical field of thermoplastic polyurethane elastomers. Background Technology

[0002] Tetraphenylene oxide (TPE) has four rotatable benzene rings connected to its double bonds. In dilute solutions, these four benzene rings can rotate freely, releasing most of the energy through rotation, resulting in very weak fluorescence. However, increasing the solution concentration or in the solid state causes TPE molecules to aggregate, and the intermolecular forces become stronger. This restricts the rotation of the benzene rings, reducing rotational non-radiative transitions, thus greatly enhancing molecular luminescence. This phenomenon, where TPE does not emit light in dilute solutions but emits strong fluorescence when aggregated at high concentrations, is called aggregation-induced emission (AIE). When TPE molecules are introduced into thermoplastic polyurethane elastomers, the molecules' free movement is restricted after processing and molding. When the material is subjected to external force and deformation, the rotation of the benzene rings, which were originally free to rotate, is restricted, reducing rotational non-radiative transitions and enhancing molecular luminescence.

[0003] Chinese invention patent CN109400836A discloses a polyurethane derivative containing a triarylamine structure and tetraphenylethylene groups. A prepolymer is generated by copolymerizing 1,2-bis(4-hydroxyphenyl)-1,2-diphenylethylene, 4,4′-diphenylmethane diisocyanate, and N,N′-bis(4-aminophenyl)-N,N′-di-2-naphthyl-1,4-phenylenediamine (or N,N′-bis(4-aminophenyl)-N,N′-di-2-naphthyl-1,4-biphenyldiamine) to produce an electrochromic prepolymer. However, the synthesis and application of this prepolymer are relatively cumbersome. Furthermore, it requires dissolving the prepolymer in an organic solvent before application, and the color-changing coating is only formed after the solvent evaporates. This process introduces some pollution.

[0004] Chinese invention patent with publication number CN116855163A discloses a flexible pressure-sensitive color-changing polyurethane anti-corrosion primer, which physically mixes a solid pressure-sensitive color-changing indicator with polyurethane resin. However, it has a large stress concentration inside, weak physical properties, and cannot withstand high-intensity use environments. Moreover, this material is only suitable for spraying operations, and its application in other processing fields is limited.

[0005] Chinese invention patent CN116836583A discloses an anti-counterfeiting color-changing ink. The hyposensitive color-changing material requires a cumbersome pretreatment process including dissolution, filtration, and pH adjustment. Other modifiers require further processes such as stirring and ultrasonic dispersion. The preparation process is complex and relatively long.

[0006] Therefore, the urgent need is to find a pressure-sensitive thermoplastic polyurethane elastomer that is stable in performance, simple in production process, highly efficient in production, and widely applicable. Summary of the Invention

[0007] To address the above-mentioned problems, this invention provides a reversible compressive color-changing thermoplastic polyurethane elastomer and its preparation method.

[0008] In a first aspect, the present invention provides a reversible pressure-sensitive thermoplastic polyurethane elastomer, wherein the raw materials for preparation, by weight, include: 50-80 parts of a diol containing tetraphenylethylene groups, 10-30 parts of diisocyanate, 0.005-0.02 parts of catalyst, and 1-10 parts of chain extender; wherein the diol containing tetraphenylethylene groups is synthesized by polymerization reaction of aliphatic diacids and diol raw materials.

[0009] Among them, the specific point values ​​for 50-80 portions can be 50, 53, 58, 62, 65, 70, 74, 78, 80, etc.; the specific point values ​​for 10-30 portions can be 10, 13, 16, 20, 24, 27, 30, etc.; and the specific point values ​​for 1-10 portions can be 1, 2, 4, 5, 7, 8, 10, etc. The specific point values ​​for each portion range can be selected.

[0010] The specific point values ​​for 0.005-0.02 units can be 0.005, 0.008, 0.012, 0.015, 0.018, 0.02, etc., and any specific point value within the above range can be selected.

[0011] This invention achieves the preparation of reversible pressure-sensitive thermoplastic polyurethane elastomers through specific raw material combinations and synthesis methods, solving the problems of cumbersome synthesis, weak performance, and limited applications in existing technologies. Specifically, the reversible pressure-sensitive thermoplastic polyurethane elastomer, as a thermoplastic material, is easy to process and mold. Using a polyol containing tetraphenylethylene groups as a raw material, this group is introduced into the soft segments of the thermoplastic polyurethane elastomer. When the material is subjected to external force, the aggregation-induced luminescence properties of the tetraphenylethylene groups achieve the pressure-sensitive color-changing effect, and the modified performance does not decrease with repeated use. Diisocyanate forms the polyurethane backbone structure and, together with the chain extender, forms the hard segments of the thermoplastic polyurethane elastomer, providing rigidity and enhancing the material's mechanical strength and durability.

[0012] The diol containing tetraphenylethylene groups has a hydroxyl value of 20-200 mg KOH / g, an acid value of 0.15-0.35 mg KOH / g, and a molecular weight of 1000-4000 g / mol.

[0013] The hydroxyl value of the diol containing the tetraphenylethylene group can be 20, 30, 45, 57, 60, 78, 80, 100, 110, 140, 180, 200, etc.; the specific point values ​​of 0.15-0.35 can be 0.15, 0.2, 0.25, 0.28, 0.3, 0.33, 0.35, etc.; the 1000-4000 can be 1000, 1500, 1800, 2000, 2400, 2800, 3000, 3500, 4000, etc. Specific point values ​​within the above range can be selected.

[0014] Preferably, the aliphatic dicarboxylic acid is selected from aliphatic dicarboxylic acid A containing a tetraphenylethylene group; the aliphatic dicarboxylic acid also includes aliphatic dicarboxylic acid B; the molar ratio of aliphatic dicarboxylic acid A containing a tetraphenylethylene group to aliphatic dicarboxylic acid B is 0.5-1:1-1.5.

[0015] The specific point value of 0.5-1 can be 0.5, 0.68, 0.7, 0.89, 0.92, etc., and any specific point value within the above range can be selected.

[0016] The specific point value of 1-1.5 can be 1.0, 1.1, 1.25, 1.3, 1.46, 1.5, etc., and any specific point value within the above range can be selected.

[0017] The aliphatic dicarboxylic acid A containing the tetraphenylethylene group is selected from any one or a combination of at least two of 1,2-diphenyl-1,2-di(4-carboxyphenyl)ethylene, (E)-4,4'-(1,2-diphenyl-1,2-diyl)dibenzoic acid, and tetraphenyl-3,5-dicarboxylic acid.

[0018] The aliphatic dicarboxylic acid B is selected from any one or a combination of at least two of the following: malonic acid, 1,4-succinic acid, 1,5-glutaric acid, 2-methyl-1,4-succinic acid, 2,2-dimethyl-1,3-malonic acid, 1,6-hexanoic acid, α-methylglutaric acid, β-methylglutaric acid, α-ethylsuccinic acid, α-(dimethyl)succinic acid, n-propylmalonic acid, 1,7-heptanediol, octanoic acid, azelaic acid, sebacic acid, dodecanoic acid, dimer acid, terephthalic acid, isophthalic acid, and phthalic acid.

[0019] Preferably, the diol raw material is selected from any one or a combination of at least two of the following: ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, 2,5-dimethyl-2,5-hexanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, dipropylene glycol, and diethylene glycol.

[0020] Preferably, the diisocyanate is selected from aromatic diisocyanates and / or aliphatic diisocyanates; the aromatic diisocyanate is selected from any one of diphenylmethane diisocyanate, toluene diisocyanate, or phenylmethylene diisocyanate; the aliphatic diisocyanate is selected from any one or a combination of at least two of hexamethylene diisocyanate, isophorone diisocyanate, or dicyclohexylmethane diisocyanate.

[0021] Preferably, the chain extender is selected from any one or a combination of at least two of the following: ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanediol, neopentyl glycol, hydroquinone bis(β-hydroxyethyl) ether, hydrogenated bisphenol A, dihydroxyethyl terephthalate, resorcinol dihydroxyethyl ether, glycerol α-allyl ether, TMP monoallyl ether, 3,3-dichloro-4,4-diaminodiphenylmethane, isobutyl 3,5-diamino-p-chlorobenzoate, diethyltoluenediamine, 3,5-dimethylthiotoluenediamine, 4,4-methylenebis(3-chloro-2,6-diethylaniline), and 1,3-propanediol-bis(4-aminobenzoate).

[0022] The catalyst is selected from any one or a combination of at least two of the following: amine catalysts, organobismuth catalysts, organotin catalysts, organozinc catalysts, organolead catalysts, organocobalt catalysts, and organomercury catalysts.

[0023] Preferably, the raw materials for preparation further include 0.5-3.5 parts by weight of auxiliary agents; the auxiliary agents include antioxidants and / or hydrolytic stabilizers.

[0024] The specific point values ​​for 0.5-3.5 units can be 0.5, 0.8, 1.2, 1.5, 1.8, 2, 2.4, 2.8, 3, 3.5, etc. Any specific point value within the above range can be selected.

[0025] In a second aspect, the present invention provides a method for preparing the reversible pressure-sensitive thermoplastic polyurethane elastomer described in the first aspect, comprising the following steps: (1) mixing aliphatic dicarboxylic acid A and aliphatic dicarboxylic acid B containing tetraphenylethylene groups with diol raw materials, and obtaining a diol containing tetraphenylethylene groups through a polymerization reaction; (2) mixing the diol containing tetraphenylethylene groups obtained in step (1) with diisocyanate and chain extender, and molding it after melt polymerization to obtain the reversible pressure-sensitive thermoplastic polyurethane elastomer.

[0026] This preparation method simplifies the production process through specific steps, avoids the use of solvents, and improves the uniformity and applicability of materials, thereby solving the problems of cumbersome, polluting, and inefficient processes in existing technologies. Specifically, in step (1), aliphatic diacids A and B containing tetraphenylethylene groups are mixed with diol raw materials and polymerized to generate diols containing tetraphenylethylene groups. This ensures that the tetraphenylethylene groups are directly integrated into the diol molecular structure, providing a basic unit for the pressure-sensitive color-changing function, and avoiding the performance instability and complexity of additional additives caused by physical mixing. In step (2), the generated diol containing tetraphenylethylene groups is mixed with diisocyanate and chain extender and then melt-polymerized to form a mold. Material synthesis and molding are directly achieved through melt polymerization, eliminating the solvent dissolution and volatilization links, reducing environmental pollution, simplifying the process and improving efficiency. At the same time, the melting process promotes the uniform bonding of molecular chains, enhancing the stability and application breadth of materials.

[0027] Preferably, the polymerization reaction conditions in step (1) are to react at 140-180℃ first, and then raise the temperature to 190-220℃ for vacuum devolatilization treatment.

[0028] The specific point values ​​for 140-180℃ can be 140, 145, 152, 158, 165, 172, 178, 180, etc., and the specific point values ​​for 190-220℃ can be 190, 195, 203, 208, 215, 220, etc., and any specific point value within the above temperature range can be selected.

[0029] Specifically, the steps of step (1) are as follows: Under nitrogen protection, small molecule aliphatic dicarboxylic acid A containing tetraphenylethylene groups, small molecule aliphatic dicarboxylic acid B, small molecule diol raw materials and polyester synthesis catalyst are mixed, heated to 140-180℃, and reacted at a constant temperature for 1-5 hours; then, the temperature is further increased to 190-220℃ within 0.5-2 hours, and when the acid value is lower than 5mgKOH / g, the vacuum is turned on to remove water and small molecule diols from the system, and the reaction continues until the hydroxyl value is 20-200mg KOH / g and the acid value is 0.15-0.35mg KOH / g.

[0030] Specifically, the steps of step (2) are as follows:

[0031] S1: Heat and melt the diol containing tetraphenylethylene groups, remove water under vacuum for 1-3 hours, add the additives, stir evenly, and stir for more than or equal to 3 hours to obtain component A;

[0032] S2: Heat the diisocyanate to melt, then add component A and catalyst, stir for 5-10 minutes, and wait for the viscosity to rise to 10000-20000 mPa·s to obtain polyurethane prepolymer;

[0033] S3: Add a chain extender to the polyurethane prepolymer obtained in S2 to further extend the chain reaction. Stir for 1-2 minutes. The melt viscosity will increase further. Pour into a tray to solidify and cure at 90-95℃ for 3-5 hours. After curing, crush the sample into particles.

[0034] S4: Place the crushed particles from S3 into a 90℃ oven and dry for 4 hours, then use an injection molding machine to form test pieces with dimensions of 2mm×200mm×150mm.

[0035] The beneficial effects of this invention are as follows:

[0036] This invention uses diols containing tetraphenylethylene groups as raw materials to prepare thermoplastic polyurethane elastomers that can change color under pressure. After the material is processed and molded, the free movement of molecules is restricted. When the material is deformed by external force, the rotation of the benzene ring in the tetraphenylethylene molecule, which was originally able to rotate freely, is restricted, reducing non-radiative transitions that are mainly rotational. This enhances molecular luminescence, thereby giving the material the property of changing color under pressure. Detailed Implementation

[0037] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0038] The macromolecular diol described in the following examples is a polyester diol with a special structure, which is formed by the dehydration condensation of a diacid monomer and a diol monomer. The resulting macromolecular structure is capped with hydroxyl groups at both ends and contains multiple repeating ester groups. It is a polyester compound containing two terminal hydroxyl groups.

[0039] The specific reagent sources in the following examples are as follows:

[0040] Adipic acid is from Shanghai Aladdin Biochemical Technology Co., Ltd., product number A421037.

[0041] 1,2-Diphenyl-1,2-di(4-carboxyphenyl)ethylene (TPE26) is from Shanghai Haohong Biomedical Technology Co., Ltd., product code 1181284.

[0042] Butylene glycol (BDO) is from Shanghai Aladdin Biochemical Technology Co., Ltd., product number B150845.

[0043] Tetrabutyl titanate is from Shanghai Aladdin Biochemical Technology Co., Ltd., product number T104105.

[0044] (E)-4,4'-(1,2-stilbene-1,2-diyl)dibenzoic acid (TPE-CA) is from Sigma-Aldrich (Shanghai) Trading Co., Ltd., product code 797359.

[0045] Tetraphenyl-3,5-dicarboxylic acid is from Zhengzhou Yande Biotechnology Co., Ltd.

[0046] Diphenylmethane diisocyanate (MDI) is sourced from Wanhua Chemical Group Co., Ltd.

[0047] Antioxidant 1010 is from Tianjin Lianlong New Materials Co., Ltd.

[0048] Antioxidant 1076 is from Tianjin Lianlong New Materials Co., Ltd.

[0049] The hydrolysis stabilizer carbodiimide comes from Hubei Yunmei Technology Co., Ltd.

[0050] Hexamethylene diisocyanate (HDI) is from Wanhua Chemical Group Co., Ltd.

[0051] Ethylene glycol (EG) is from Jiangsu Runfeng Synthetic Technology Co., Ltd.

[0052] Succinic acid comes from Shandong Feiyang Chemical Co., Ltd.

[0053] Propylene glycol (PG) is from Jiangsu Runfeng Synthetic Technology Co., Ltd.

[0054] Dibutyltin dilaurate is from Shanghai Aladdin Biochemical Technology Co., Ltd., product number D100274.

[0055] The polybutylene adipate polyester polyol (Mw=2000) is from Huada Chemical Group Co., Ltd., model number T-44.

[0056] Example 1

[0057] Preparation of diols containing tetraphenylethylene groups:

[0058] Under nitrogen protection, 1000g of adipic acid, 959g of 1,2-diphenyl-1,2-di(4-carboxyphenyl)ethylene, 822g of butanediol and 1g of tetrabutyl titanate were mixed and heated to 150℃ and reacted at a constant temperature for 4 hours. Then, the temperature was further increased to 200℃ within 1 hour, and the reaction was continued until the acid value was lower than 5mg KOH / g. At this point, a vacuum was opened to remove water and butanediol from the system. The reaction was continued until the hydroxyl value was 56.0mg KOH / g and the acid value was 0.20mg KOH / g, yielding a diol containing tetraphenylethylene groups.

[0059] Preparation of compressible color-changing thermoplastic polyurethane elastomers:

[0060] (1) Heat 1000g of diol containing tetraphenylethylene group to 75°C, dehydrate under vacuum of less than 20kPa for 2h, raise the temperature to 85°C, add the following additives: 3g antioxidant 1010, 3g antioxidant 1076, 2g hydrolysis stabilizer carbodiimide, stir under nitrogen protection for 3h to obtain component A;

[0061] (2) Heat 719g of diphenylmethane diisocyanate (MDI) to 65°C, add component A and 0.5g of dibutyltin dilaurate while stirring, stir for 8 minutes, and wait until the viscosity of the system rises to 18000mPa·s to obtain polyurethane prepolymer;

[0062] (3) Add 215g of 1,4-butanediol (pre-melted at 45℃), stir for 2 minutes, the viscosity of the system will increase further, quickly pour the melt into a tray to cool and solidify, put the solidified material into a 90℃ oven to mature for 4 hours, and crush the matured material into granules.

[0063] (4) The crushed particles from step (3) are placed in a 90°C oven and dried for 4 hours, and then molded into test pieces with dimensions of 2mm×200mm×150mm by injection molding.

[0064] Example 2

[0065] Preparation of diols containing tetraphenylethylene groups:

[0066] Under nitrogen protection, 1000g of adipic acid, 959g of 1,2-diphenyl-1,2-di(4-carboxyphenyl)ethylene, 822g of butanediol and 1g of tetrabutyl titanate were mixed and heated to 150℃ and reacted at a constant temperature for 4 hours. Then, the temperature was further increased to 200℃ within 1 hour, and the reaction was continued until the acid value was lower than 5mg KOH / g. At this point, a vacuum was opened to remove water and butanediol from the system. The reaction was continued until the hydroxyl value was 56.0mg KOH / g and the acid value was 0.20mg KOH / g, yielding a diol containing tetraphenylethylene groups.

[0067] Preparation of compressible color-changing thermoplastic polyurethane elastomers:

[0068] (1) Heat 1000g of diol containing tetraphenylethylene group to 75°C, dehydrate under vacuum of less than 20kPa for 2h, raise the temperature to 85°C, add the following additives: 3g antioxidant 1010, 3g antioxidant 1076, 2g hydrolysis stabilizer carbodiimide, stir under nitrogen protection for 3h to obtain component A;

[0069] (2) Heat 451g of diphenylmethane diisocyanate (MDI) to 65°C, add component A and 0.5g of dibutyltin dilaurate while stirring, stir for 8 minutes, and wait until the viscosity of the system rises to 18000mPa·s to obtain polyurethane prepolymer;

[0070] (3) Add 118g of 1,4-butanediol (pre-heated to 45℃ for melting), stir for 2 minutes, the viscosity of the system will increase further, quickly pour the melt into a tray to cool and solidify, put the solidified material into a 90℃ oven to mature for 4 hours, and crush the matured material into granules.

[0071] (4) The crushed particles from step (3) are placed in a 90°C oven and dried for 4 hours, and then molded into test pieces with dimensions of 2mm×200mm×150mm by injection molding.

[0072] Example 3

[0073] Preparation of diols containing tetraphenylethylene groups:

[0074] Under nitrogen protection, 1000g of adipic acid, 959g of 1,2-diphenyl-1,2-di(4-carboxyphenyl)ethylene, 822g of butanediol and 1g of tetrabutyl titanate were mixed and heated to 150℃ and reacted at a constant temperature for 4 hours. Then, the temperature was further increased to 200℃ within 1 hour, and the reaction was continued until the acid value was lower than 5mg KOH / g. At this point, a vacuum was opened to remove water and butanediol from the system. The reaction was continued until the hydroxyl value was 56.0mg KOH / g and the acid value was 0.20mg KOH / g, yielding a diol containing tetraphenylethylene groups.

[0075] Preparation of compressible color-changing thermoplastic polyurethane elastomers:

[0076] (1) Heat 1000g of diol containing tetraphenylethylene group to 75°C, dehydrate under vacuum of less than 20kPa for 2h, raise the temperature to 85°C, add the following additives: 3g antioxidant 1010, 3g antioxidant 1076, 2g hydrolysis stabilizer carbodiimide, stir under nitrogen protection for 3h to obtain component A;

[0077] (2) Heat 322g of diphenylmethane diisocyanate (MDI) to 65°C, add component A and 0.5g of dibutyltin dilaurate while stirring, stir for 8 minutes, and wait until the viscosity of the system rises to 18000mPa·s to obtain polyurethane prepolymer;

[0078] (3) Add 71g of 1,4-butanediol (pre-heated to 45℃ for melting), stir for 2 minutes, the viscosity of the system will increase further, quickly pour the melt into a tray to cool and solidify, put the solidified material into a 90℃ oven to mature for 4 hours, and crush the matured material into granules.

[0079] (4) The crushed particles from step (3) are placed in a 90°C oven and dried for 4 hours, and then molded into test pieces with dimensions of 2mm×200mm×150mm by injection molding.

[0080] Example 4

[0081] Preparation of diols containing tetraphenylethylene groups:

[0082] Under nitrogen protection, 1000g of adipic acid, 959g of (E)-4,4'-(1,2-stilbene-1,2-diyl)benzoic acid (TPE-CA), 822g of butanediol and 1g of tetrabutyl titanate were mixed and heated to 150℃ and reacted at a constant temperature for 4h. Then, the temperature was further increased to 200℃ within 1h, and the reaction was continued until the acid value was lower than 5mg KOH / g. At this point, a vacuum was opened to remove water and butanediol from the system. The reaction was continued until the hydroxyl value was 56.0mg KOH / g and the acid value was 0.20mg KOH / g, yielding a diol containing tetraphenylethylene groups.

[0083] Preparation of compressible color-changing thermoplastic polyurethane elastomers:

[0084] (1) Heat 1000g of diol containing tetraphenylethylene group to 75°C, dehydrate under vacuum of less than 20kPa for 2h, raise the temperature to 85°C, add the following additives: 3g antioxidant 1010, 3g antioxidant 1076, 2g hydrolysis stabilizer carbodiimide, stir under nitrogen protection for 3h to obtain component A;

[0085] (2) Heat 719g of diphenylmethane diisocyanate (MDI) to 65°C, add component A and 0.5g of dibutyltin dilaurate while stirring, stir for 8 minutes, and wait until the viscosity of the system rises to 18000mPa·s to obtain polyurethane prepolymer;

[0086] (3) Add 215g of 1,4-butanediol (pre-melted at 45℃), stir for 2 minutes, the viscosity of the system will increase further, quickly pour the melt into a tray to cool and solidify, put the solidified material into a 90℃ oven to mature for 4 hours, and crush the matured material into granules.

[0087] (4) The crushed particles from step (3) are placed in a 90°C oven and dried for 4 hours, and then molded into test pieces with dimensions of 2mm×200mm×150mm by injection molding.

[0088] Example 5

[0089] Preparation of diols containing tetraphenylethylene groups:

[0090] Under nitrogen protection, 1000g of adipic acid, 959g of tetraphenyl-3,5-dicarboxylic acid, 822g of butanediol and 1g of tetrabutyl titanate were mixed and heated to 150℃ and reacted at a constant temperature for 4 hours. Then, the temperature was further increased to 200℃ within 1 hour, and the reaction was continued until the acid value was lower than 5mg KOH / g. At this point, a vacuum was opened to remove water and butanediol from the system. The reaction was continued until the hydroxyl value was 56.0mg KOH / g and the acid value was 0.2mg KOH / g, yielding a diol containing tetraphenylethylene groups.

[0091] Preparation of compressible color-changing thermoplastic polyurethane elastomers:

[0092] (1) Heat 1000g of diol containing tetraphenylethylene group to 75°C, dehydrate under vacuum of less than 20kPa for 2h, raise the temperature to 85°C, add the following additives: 3g antioxidant 1010, 3g antioxidant 1076, 2g hydrolysis stabilizer carbodiimide, stir under nitrogen protection for 3h to obtain component A;

[0093] (2) Heat 719g of diphenylmethane diisocyanate (MDI) to 65°C, add component A and 0.5g of dibutyltin dilaurate while stirring, stir for 8 minutes, and wait until the viscosity of the system rises to 18000mPa·s to obtain polyurethane prepolymer;

[0094] (3) Add 215g of 1,4-butanediol (pre-melted at 45℃), stir for 2 minutes, the viscosity of the system will increase further, quickly pour the melt into a tray to cool and solidify, put the solidified material into a 90℃ oven to mature for 4 hours, and crush the matured material into granules.

[0095] (4) The crushed particles from step (3) are placed in a 90°C oven and dried for 4 hours, and then molded into test pieces with dimensions of 2mm×200mm×150mm by injection molding.

[0096] Example 6

[0097] Preparation of diols containing tetraphenylethylene groups:

[0098] Under nitrogen protection, 1000g of adipic acid, 1438g of 1,2-diphenyl-1,2-di(4-carboxyphenyl)ethylene, 924g of butanediol and 1g of tetrabutyl titanate were mixed and heated to 150℃ and reacted at a constant temperature for 4 h. Then, the temperature was further increased to 200℃ within 1 h, and the reaction was continued until the acid value was lower than 5mg KOH / g. At this point, a vacuum was opened to remove water and butanediol from the system. The reaction was continued until the hydroxyl value was 56.0mg KOH / g and the acid value was 0.2 mg KOH / g, yielding a diol containing tetraphenylethylene groups.

[0099] Preparation of compressible color-changing thermoplastic polyurethane elastomers:

[0100] (1) Heat 1000g of diol containing tetraphenylethylene group to 75°C, dehydrate under vacuum of less than 20kPa for 2h, raise the temperature to 85°C, add the following additives: 3g antioxidant 1010, 3g antioxidant 1076, 2g hydrolysis stabilizer carbodiimide, stir under nitrogen protection for 3h to obtain component A;

[0101] (2) Heat 719g of diphenylmethane diisocyanate (MDI) to 65°C, add component A and 0.5g of dibutyltin dilaurate while stirring, stir for 8 minutes, and wait until the viscosity of the system rises to 18000mPa·s to obtain polyurethane prepolymer;

[0102] (3) Add 215g of 1,4-butanediol (pre-melted at 45℃), stir for 2 minutes, the viscosity of the system will increase further, quickly pour the melt into a tray to cool and solidify, put the solidified material into a 90℃ oven to mature for 4 hours, and crush the matured material into granules.

[0103] (4) The crushed particles from step (3) are placed in a 90°C oven and dried for 4 hours, and then molded into test pieces with dimensions of 2mm×200mm×150mm by injection molding.

[0104] Example 7

[0105] Preparation of diols containing tetraphenylethylene groups:

[0106] Under nitrogen protection, 1000g of adipic acid, 959g of 1,2-diphenyl-1,2-di(4-carboxyphenyl)ethylene, 822g of butanediol and 1g of tetrabutyl titanate were mixed and heated to 150℃ and reacted at a constant temperature for 4h. Then, the temperature was further increased to 200℃ within 1h, and the reaction was continued until the acid value was lower than 5mg KOH / g. At this point, a vacuum was opened to remove water and butanediol from the system. The reaction was continued until the hydroxyl value was 56.0mg KOH / g and the acid value was 0.2mg KOH / g, yielding a diol containing tetraphenylethylene groups.

[0107] Preparation of compressible color-changing thermoplastic polyurethane elastomers:

[0108] (1) Heat 1000g of diol containing tetraphenylethylene group to 75°C, dehydrate under vacuum of less than 20kPa for 2h, raise the temperature to 85°C, add the following additives: 3g antioxidant 1010, 3g antioxidant 1076, 2g hydrolysis stabilizer carbodiimide, stir under nitrogen protection for 3h to obtain component A;

[0109] (2) Heat 637g of hexamethylene diisocyanate (HDI) to 30°C, add component A and 0.5g of dibutyltin dilaurate while stirring, stir for 8 minutes, and wait until the viscosity of the system rises to 18000mPa·s to obtain polyurethane prepolymer;

[0110] (3) Add 298g of 1,4-butanediol (pre-melted at 45℃), stir for 2 minutes, the viscosity of the system will increase further, quickly pour the melt into a tray to cool and solidify, put the solidified material into a 90℃ oven to mature for 4 hours, and crush the matured material into granules.

[0111] (4) The crushed particles from step (3) are placed in a 90°C oven and dried for 4 hours, and then molded into test pieces with dimensions of 2mm×200mm×150mm by injection molding.

[0112] Example 8

[0113] Preparation of diols containing tetraphenylethylene groups:

[0114] Under nitrogen protection, 1000g of adipic acid, 959g of 1,2-diphenyl-1,2-di(4-carboxyphenyl)ethylene, 822g of butanediol and 1g of tetrabutyl titanate were mixed and heated to 150℃ and reacted at a constant temperature for 4h. Then, the temperature was further increased to 200℃ within 1h, and the reaction was continued until the acid value was lower than 5mg KOH / g. At this point, a vacuum was opened to remove water and butanediol from the system. The reaction was continued until the hydroxyl value was 56.0mg KOH / g and the acid value was 0.2mg KOH / g, yielding a diol containing tetraphenylethylene groups.

[0115] Preparation of compressible color-changing thermoplastic polyurethane elastomers:

[0116] (1) Heat 1000g of diol containing tetraphenylethylene group to 75°C, dehydrate under vacuum of less than 20kPa for 2h, raise the temperature to 85°C, add the following additives: 3g antioxidant 1010, 3g antioxidant 1076, 2g hydrolysis stabilizer carbodiimide, stir under nitrogen protection for 3h to obtain component A;

[0117] (2) Heat 773g of diphenylmethane diisocyanate (MDI) to 65°C, add component A and 0.5g of dibutyltin dilaurate while stirring, stir for 8 minutes, and wait until the viscosity of the system rises to 18000mPa·s to obtain polyurethane prepolymer;

[0118] (3) Add 162g of ethylene glycol (pre-heated to 45℃ to melt), stir for 2 minutes, the viscosity of the system will increase further, quickly pour the melt into a tray to cool and solidify, put the solidified material into a 90℃ oven to mature for 4 hours, and crush the matured material into granules.

[0119] (4) The crushed particles from step (3) are placed in a 90°C oven and dried for 4 hours, and then molded into test pieces with dimensions of 2mm×200mm×150mm by injection molding.

[0120] Example 9

[0121] Preparation of diols containing tetraphenylethylene groups:

[0122] Under nitrogen protection, 808g of succinic acid, 959g of 1,2-diphenyl-1,2-di(4-carboxyphenyl)ethylene, 822g of butanediol and 1g of tetrabutyl titanate were mixed and heated to 150℃ and reacted at a constant temperature for 4h. Then, the temperature was further increased to 200℃ within 1h, and the reaction was continued until the acid value was lower than 5mg KOH / g. At this point, a vacuum was opened to remove water and butanediol from the system. The reaction was continued until the hydroxyl value was 56.0mg KOH / g and the acid value was 0.2mg KOH / g, yielding a diol containing tetraphenylethylene groups.

[0123] Preparation of compressible color-changing thermoplastic polyurethane elastomers:

[0124] (1) Heat 1000g of diol containing tetraphenylethylene group to 75°C, dehydrate under vacuum of less than 20kPa for 2h, raise the temperature to 85°C, add the following additives: 3g antioxidant 1010, 3g antioxidant 1076, 2g hydrolysis stabilizer carbodiimide, stir under nitrogen protection for 3h to obtain component A;

[0125] (2) Heat 719g of diphenylmethane diisocyanate (MDI) to 65°C, add component A and 0.5g of dibutyltin dilaurate while stirring, stir for 8 minutes, and wait until the viscosity of the system rises to 18000mPa·s to obtain polyurethane prepolymer;

[0126] (3) Add 215g of 1,4-butanediol (pre-melted at 45℃), stir for 2 minutes, the viscosity of the system will increase further, quickly pour the melt into a tray to cool and solidify, put the solidified material into a 90℃ oven to mature for 4 hours, and crush the matured material into granules.

[0127] (4) The crushed particles from step (3) are placed in a 90°C oven and dried for 4 hours, and then molded into test pieces with dimensions of 2mm×200mm×150mm by injection molding.

[0128] Example 10

[0129] Preparation of diols containing tetraphenylethylene groups:

[0130] Under nitrogen protection, 1000g of adipic acid, 959g of 1,2-diphenyl-1,2-di(4-carboxyphenyl)ethylene, 695g of butanediol and 1g of tetrabutyl titanate were mixed and heated to 150℃ and reacted at a constant temperature for 4h. Then, the temperature was further increased to 200℃ within 1h, and the reaction was continued until the acid value was lower than 5mg KOH / g. At this point, a vacuum was opened to remove water and butanediol from the system. The reaction was continued until the hydroxyl value was 56.0mg KOH / g and the acid value was 0.2mg KOH / g, yielding a diol containing tetraphenylethylene groups.

[0131] Preparation of compressible color-changing thermoplastic polyurethane elastomers:

[0132] (1) Heat 1000g of diol containing tetraphenylethylene group to 75°C, dehydrate under vacuum of less than 20kPa for 2h, raise the temperature to 85°C, add the following additives: 3g antioxidant 1010, 3g antioxidant 1076, 2g hydrolysis stabilizer carbodiimide, stir under nitrogen protection for 3h to obtain component A;

[0133] (2) Heat 719g of diphenylmethane diisocyanate (MDI) to 65°C, add component A and 0.5g of dibutyltin dilaurate while stirring, stir for 8 minutes, and wait until the viscosity of the system rises to 18000mPa·s to obtain polyurethane prepolymer;

[0134] (3) Add 215g of 1,4-butanediol (pre-melted at 45℃), stir for 2 minutes, the viscosity of the system will increase further, quickly pour the melt into a tray to cool and solidify, put the solidified material into a 90℃ oven to mature for 4 hours, and crush the matured material into granules.

[0135] (4) The crushed particles from step (3) are placed in a 90°C oven and dried for 4 hours, and then molded into test pieces with dimensions of 2mm×200mm×150mm by injection molding.

[0136] Comparative Example 1

[0137] Preparation of compressible color-changing thermoplastic polyurethane elastomers:

[0138] (1) 1000 g of polybutylene adipate polyester polyol (Mw=2000) was heated to 75°C and dehydrated under vacuum of less than 20 kPa for 2 h. The temperature was then raised to 85°C and the following additives were added: 3 g antioxidant 1010, 3 g antioxidant 1076, and 2 g hydrolytic stabilizer carbodiimide. The mixture was stirred for 3 h under nitrogen protection to obtain component A.

[0139] (2) Heat 719g of diphenylmethane diisocyanate (MDI) to 65°C, add component A and 0.5g of dibutyltin dilaurate while stirring, stir for 8 minutes, and wait until the viscosity of the system rises to 18000mPa·s to obtain polyurethane prepolymer;

[0140] (3) Add 215g of 1,4-butanediol (pre-melted at 45℃), stir for 2 minutes, the viscosity of the system will increase further, quickly pour the melt into a tray to cool and solidify, put the solidified material into a 90℃ oven to mature for 4 hours, and crush the matured material into granules.

[0141] (4) The crushed particles from step (3) are placed in a 90°C oven and dried for 4 hours, and then molded into test pieces with dimensions of 2mm×200mm×150mm by injection molding.

[0142] Test case

[0143] The reversible compressive color-changing thermoplastic polyurethane elastomers prepared in Examples 1-10 and Comparative Example 1

[0144] Test method:

[0145] The hardness of the reversible pressure-sensitive thermoplastic polyurethane elastomer was tested using the ASTM D2240 test method, with an SLX-A Shore hardness tester. Method: A flat sample with a thickness greater than 6 mm was placed on the sample stage. The indenter was lowered and pressed into the sample for 15 seconds before the reading was taken. The value displayed on the table is the hardness value. Five different locations were measured, and the average value was taken.

[0146] Tensile strength and elongation at break were tested using ASTM D412 (Die C) method with an AI-7000S1 tensile testing machine. Method: For tensile strength testing, the specimen was cut into dumbbell-shaped strips with a center width of 6 mm, and the tensile rate was 200 mm / min.

[0147] Fluorescence quantum yield was measured in situ using the fiber optic probe method according to GB / T 44454-2024 standard. Method: A dark chamber environment was created using black material in the upper and lower clamps and sample travel area of ​​the tensile testing machine. The excitation and collection fiber optic probes were fixed on both sides of the sample. The tensile testing machine was set to fixed tensile rates of 0%, 30%, 60%, and 100%.

[0148] The performance of the samples in Examples 1-10 and Comparative Example 1 is shown in Table 1:

[0149] Table 1. Product performance data of Examples 1-10 and Comparative Example 1

[0150]

[0151] In Example 1 and Comparative Example 1 of this invention, the same formulation and process are used, and the molecular weight of the macromolecular diol is the same, but the monomer composition of the macromolecular diol is different. Example 1 adds TPE26 containing tetraphenylethylene groups. In the fluorescence test, Example 1 exhibits obvious fluorescence during stretching. Furthermore, in Example 1, the fluorescence quantum yield increases with increasing stretching ratio. The fluorescence quantum yield is lower when the stretching ratio is ≤30%, and higher when it is >30%. This is because when the external force is small, the orientation degree of the polymer chain segments is small, and the increase in quantum yield is relatively slow. Later, with the continuous increase in elongation, the orientation degree of the polymer chain segments increases, the chain segments are arranged more tightly, and the degree of restriction between molecules increases, resulting in a decrease in the amplitude of molecular rotor rotation. During dynamic rotation, the energy of the non-radiative dissipation of excited states decreases, manifesting as an increase in quantum yield and enhanced fluorescence intensity, with a more significant increase in the magnitude of the increase.

[0152] Examples 1-3 used the same raw materials, macromolecular diols with the same molecular weight, and the same proportion of TPE26 monomer. The hard segment content was different in the three examples, which in turn led to different amounts of macromolecular diols and different absolute contents of TPE26. As can be seen from the fluorescence quantum yield data in Table 1, at the same elongation, the higher the TPE26 content, the higher the fluorescence quantum yield.

[0153] In Examples 1, 4, and 5, different small molecule dicarboxylic acids A containing tetraphenylethylene groups were used, while other formulation parameters were the same. In the fluorescence test, the fluorescence quantum yields of the three samples were similar, indicating that the fluorescence quantum yield of the pressure-sensitive color-changing material is related to the content of tetraphenylethylene groups.

[0154] In Examples 1 and 6, macromolecular diols with the same molecular weight and the same formulation parameters were used, but the proportions of diacid A and diacid B in the macromolecular diols were different. In Example 6, the proportion of diacid A containing tetraphenylethylene groups was higher. In the fluorescence test, Example 6 had a higher fluorescence quantum yield at the same stretching ratio.

[0155] Comparing Example 1 and Example 7, the only difference in the formulation is that the aromatic isocyanate diphenylmethane diisocyanate is replaced with the aliphatic isocyanate hexamethylene diisocyanate. The physical properties and pressure-luminescence performance of the two are almost identical, indicating that the pressure-luminescence performance in this invention is not affected by the type of isocyanate.

[0156] Comparing Example 1 and Example 8, the only difference in the formulation is that the chain extender 1,4-butanediol is replaced with ethylene glycol. The physical properties and pressure luminescence performance of the two are almost identical, indicating that the pressure luminescence performance in this invention is not affected by the type of chain extender.

[0157] Comparing Example 1 and Example 9, the only difference in the formulation is that the small molecule dicarboxylic acid B adipic acid in the preparation of macromolecular diols is replaced with succinic acid. The physical properties and pressure-luminescence properties of the two are almost identical, indicating that the pressure-luminescence properties in this invention are not affected by the type of small molecule dicarboxylic acid B.

[0158] Comparing Example 1 and Example 10, the only difference in the formulation is that the small molecule diol butanediol in the preparation of macromolecular diols is replaced with propylene glycol. The physical properties and pressure-luminescence properties of the two are almost identical, indicating that the pressure-luminescence properties in this invention are not affected by the type of small molecule diol.

[0159] Examples 1-10 all contain tetraphenylethylene groups, and the materials all exhibit fluorescence when stretched. When the stretching rate returns to 0%, the fluorescence is almost undetectable, indicating that the compressive color-changing material only exhibits fluorescence during tensile deformation, and the fluorescence disappears when no external force is applied.

[0160] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A reversible compressive color-changing thermoplastic polyurethane elastomer, characterized in that, The raw materials for preparation, by weight, include: 50-80 parts of a diol containing tetraphenylethylene groups, 10-30 parts of diisocyanate, 0.005-0.02 parts of catalyst, and 1-10 parts of chain extender; the diol containing tetraphenylethylene groups is synthesized by polymerization reaction of diacid A containing tetraphenylethylene groups, aliphatic diacid B, and diol raw materials, wherein the molar ratio of diacid A containing tetraphenylethylene groups to aliphatic diacid B is 0.5-1:1-1.

5.

2. The reversible compressive color-changing thermoplastic polyurethane elastomer according to claim 1, characterized in that, The dicarboxylic acid A containing the tetraphenylethylene group is selected from any one or a combination of at least two of 1,2-diphenyl-1,2-di(4-carboxyphenyl)ethylene, (E)-4,4'-(1,2-diphenyl-1,2-diyl)dibenzoic acid, and tetraphenyl-3,5-dicarboxylic acid.

3. The reversible compressive color-changing thermoplastic polyurethane elastomer according to claim 1, characterized in that, The aliphatic dicarboxylic acid B is selected from any one or a combination of at least two of the following: malonic acid, 1,4-succinic acid, 1,5-glutaric acid, 2-methyl-1,4-succinic acid, 2,2-dimethyl-1,3-malonic acid, 1,6-hexanoic acid, α-methylglutaric acid, β-methylglutaric acid, α-ethylsuccinic acid, α-(dimethyl)succinic acid, n-propylmalonic acid, 1,7-heptanoic acid, octanoic acid, azelaic acid, sebacic acid, dodecanoic acid, and dimer acids.

4. The reversible compressive color-changing thermoplastic polyurethane elastomer according to claim 1, characterized in that, The diol raw materials are selected from any one or a combination of at least two of the following: ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, 2,5-dimethyl-2,5-hexanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, dipropylene glycol, and diethylene glycol.

5. The reversible compressive color-changing thermoplastic polyurethane elastomer according to claim 1, characterized in that, The diisocyanate is selected from aromatic diisocyanates and / or aliphatic diisocyanates; the aromatic diisocyanate is selected from any one of diphenylmethane diisocyanate, toluene diisocyanate or phenyl dimethylene diisocyanate; the aliphatic diisocyanate is selected from any one or a combination of at least two of hexamethylene diisocyanate, isophorone diisocyanate or dicyclohexylmethane diisocyanate.

6. The reversible compressive color-changing thermoplastic polyurethane elastomer according to claim 1, characterized in that, The chain extender is selected from any one or a combination of at least two of the following: ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanediol, neopentyl glycol, hydroquinone bis(β-hydroxyethyl) ether, hydrogenated bisphenol A, dihydroxyethyl terephthalate, resorcinol dihydroxyethyl ether, glycerol α-allyl ether, TMP monoallyl ether, 3,3-dichloro-4,4-diaminodiphenylmethane, isobutyl 3,5-diamino-p-chlorobenzoate, diethyltoluenediamine, 3,5-dimethylthiotoluenediamine, 4,4-methylenebis(3-chloro-2,6-diethylaniline), and 1,3-propanediol-bis(4-aminobenzoate).

7. The reversible compressive color-changing thermoplastic polyurethane elastomer according to claim 1, characterized in that, The catalyst is selected from any one or a combination of at least two of the following: amine catalysts, organobismuth catalysts, organotin catalysts, and organozinc catalysts.

8. The reversible compressive color-changing thermoplastic polyurethane elastomer according to claim 1, characterized in that, The raw materials used in the preparation also include 0.5-3.5 parts by weight of auxiliary agents; the auxiliary agents include antioxidants and / or hydrolytic stabilizers.

9. A method for preparing the reversible compressive color-changing thermoplastic polyurethane elastomer according to any one of claims 1-7, characterized in that, Includes the following steps: (1) A dicarboxylic acid A containing tetraphenylethylene groups and an aliphatic dicarboxylic acid B are mixed with diol raw materials and polymerized to obtain a diol containing tetraphenylethylene groups; (2) The diol containing tetraphenylethylene groups obtained in step (1) is mixed with diisocyanate and chain extender, and then melt-polymerized and molded to obtain reversible compressive color-changing thermoplastic polyurethane elastomer.

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