Chain extender containing hydrazide structure as well as preparation method and application of chain extender

Abstract

The invention discloses a chain extender containing a hydrazide structure, a preparation method of the chain extender and application of the chain extender in preparation of polyurethane. The chain extender containing the hydrazide structure is prepared by carrying out Michael addition reaction on raw materials including a hydrazide compound and unsaturated carboxylic ester; the Michael addition reaction comprises a reaction process of carrying out addition on amino in the hydrazide compound and a carbon-carbon unsaturated bond in the unsaturated carboxylic ester to generate secondary amine. According to the invention, the problem that a solvent is needed and / or high-temperature melting is needed when a hydrazide compound is used as a polyurethane chain extender can be solved, and a thermoplastic polyurethane elastomer material with relatively high mechanical strength and toughness and excellent mechanical recovery performance can be prepared.

Description

Technical Field

[0001] The invention relates to the field of new materials, and in particular to a chain extender containing a hydrazide structure and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Polyurethane is one of the most promising polymer materials and is known as the "fifth plastic". Polyurethane materials have the advantages of strong impact resistance, high elongation at break and good tear resistance, and are widely used in foams, coatings, adhesives and elastomers. Chain extenders are additives that can further react with the functional groups at the ends of linear polymer chains to further increase the molecular weight of the polymer. They are also necessary to improve the mechanical properties of polyurethane materials. At present, although polyurethane materials prepared by commonly used aliphatic alcohol chain extenders such as butanediol (BDO) have good weather resistance, some systems have low strength; aromatic chain extenders contain a large number of benzene rings, and the material strength is high but it is easy to yellow. Most amine chain extenders can introduce urea groups into the polymer chain after reacting with -NCO. The hydrogen bonding effect makes the prepared polyurethane materials have higher strength, but there is also a disadvantage of too fast reaction speed, so their application is limited in practice. 3,3'-Dichloro-4,4'-diaminodiphenylmethane (MOCA), the most widely used amine chain extender with steric effect, has a relatively controllable reaction rate, but it has a high benzene ring content, is prone to yellowing, and is highly toxic and carcinogenic to humans, making it an undesirable polyurethane chain extender.

[0004] Hydrazide compounds are a class of multifunctional compounds. Their diversity and reactivity make them important chemicals in many industrial and scientific fields. They have many applications such as crosslinking agents, adhesives, corrosion inhibitors, curing agents, and medicine. Hydrazide compounds are mainly used in the field of epoxy curing agents, and there are also related studies in polyurethane products, but their high melting point, easy thermal decomposition, poor solubility and other problems affect their application in the polyurethane field. In the prior art, the combination of hydrazide compounds and polyurethane products is mainly in the field of waterborne polyurethane, and the water solubility thereof is utilized to disperse in waterborne polyurethane emulsion to achieve the purpose of crosslinking. For example, patents CN101759861A and CN102863939B both add adipic acid dihydrazide aqueous solution to the emulsion during the preparation process of waterborne polyurethane to utilize its reactivity for crosslinking, thereby achieving the improvement of curing and mechanical properties of waterborne polyurethane. However, the preparation process of conventional thermoplastic polyurethane elastomer is different from that of waterborne polyurethane, and the moisture content of raw materials must be strictly controlled, otherwise the active isocyanate component will react with the moisture to affect the overall performance. For the use of hydrazide compounds, it is necessary to consider the method of adding them by melting into liquid. However, we found during use that hydrazide compounds generally have a high melting point, generally higher than 150°C, and require a high temperature to melt, and are easily decomposed at high temperatures. At the same time, even if the high-temperature melted hydrazide compound is added to a prepolymer or polyol component at a temperature of about 100°C, it will quickly precipitate and solidify, and cannot react normally as a chain extender component. In order to solve the problem of using hydrazide compounds in thermoplastic polyurethane products, some studies have used solvent methods to react. For example, patents CN114933723A and CN117624538A both use high boiling point solvent N,N-dimethylacetamide (DMAC) to dissolve and disperse adipic acid dihydrazide and the like. Solvents are also used in literature, such as "Healable, degradable polyurethane elastomers with excellent mechanical properties based on multiple hydrogen bonds". However, we found in our research that the solubility of hydrazide compounds such as adipic acid dihydrazide in solvents such as N,N-dimethylformamide (DMF) or N,N-dimethylacetamide described in the above literature is limited, and dimethyl sulfoxide is slightly better. A large amount of solvent is required, and the higher the boiling point of the solvent, the more difficult it is to completely remove it from the reaction system later. The product performance will be affected by the solvent residue, and the use of a large amount of high boiling point solvents not only increases the production cost and pollutes the environment, but is also not suitable for large-scale production.

[0005] Therefore, it is necessary to develop a method that can improve the problem of hydrazide compounds being difficult to dissolve and melt, so that the hydrazide structure can be widely used in polyurethane material systems. Summary of the invention

[0006] In view of the above technical problems and the deficiencies in the art, the present invention provides a class of chain extenders containing hydrazide structures and preparation methods and applications thereof, which can solve the problems that hydrazide compounds require solvents and / or high-temperature melting when used as polyurethane chain extenders, and can prepare thermoplastic polyurethane elastomer materials with high mechanical strength and toughness and excellent mechanical recovery properties.

[0007] In a first aspect, the present invention provides a chain extender containing a hydrazide structure, which can be prepared by a Michael addition reaction of raw materials including a hydrazide compound and an unsaturated carboxylic acid ester; the Michael addition reaction includes a reaction process in which an amino group in the hydrazide compound and a carbon-carbon unsaturated bond in the unsaturated carboxylic acid ester are added to form a secondary amine;

[0008] The hydrazide compound includes at least one of oxalic acid dihydrazide, maleic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide and azelaic acid dihydrazide;

[0009] The unsaturated carboxylic acid ester includes at least one of unsaturated dicarboxylic acid ester and unsaturated monocarboxylic acid ester; the unsaturated dicarboxylic acid ester includes at least one of dimethyl maleate, diethyl maleate, dibutyl maleate, dimethyl itaconate, dibutyl itaconate and dimethyl citrate; the unsaturated monocarboxylic acid ester includes at least one of methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate and butyl methacrylate.

[0010] The chain extender containing hydrazide structure described in the present invention is a kind of secondary amine chain extender.

[0011] Furthermore, the molar ratio of the hydrazide compound to the unsaturated carboxylic acid ester may be 1:2-4.

[0012] In a second aspect, the present invention provides a method for preparing the chain extender containing a hydrazide structure according to the first aspect, comprising:

[0013] In the presence or absence of a catalyst, the hydrazide compound and the unsaturated carboxylic acid ester are subjected to a Michael addition reaction to obtain the chain extender containing a hydrazide structure.

[0014] For example, the preparation method of the chain extender containing a hydrazide structure may specifically include:

[0015] The hydrazide compound and the catalyst are dissolved in an ethanol aqueous solution, heated to the reaction temperature of the Michael addition reaction under inert atmosphere protection for reflux dispersion, the unsaturated carboxylic acid ester is added dropwise and / or in batches for constant temperature reaction, and vacuum devolatilization is performed after the reaction is completed, and low-boiling substances are removed and then washed and dried to obtain the chain extender containing the hydrazide structure. Operations such as vacuum devolatilization, washing, and drying can remove unreacted monomers, catalysts, and ethanol aqueous solvents in the system to obtain a pure secondary amine chain extender containing a hydrazide structure, which satisfies the requirement of stable and controllable reactivity.

[0016] The main function of the ethanol aqueous solution is to dissolve and disperse the hydrazide compound and the unsaturated carboxylic acid ester, form a reaction interface to improve the degree of reaction, and ethanol has a low boiling point and can be completely removed in post-treatment. In some embodiments, the amount of the ethanol aqueous solution added is only 20%-40% of the total weight of the hydrazide compound and the unsaturated carboxylic acid ester.

[0017] Optionally, the volume fraction of ethanol in the ethanol aqueous solution is 50%-80%.

[0018] The inert atmosphere of the present invention refers to an atmosphere that does not participate in the reaction. Optionally, the inert atmosphere is a nitrogen atmosphere and / or a rare gas atmosphere.

[0019] The main purpose of adding the unsaturated carboxylic acid ester dropwise and / or in batches is to control the temperature stability of the system and avoid a significant temperature surge in the reaction temperature that affects the color of the product. Optionally, the unsaturated carboxylic acid ester is added at a rate of 1-10 g / min.

[0020] Optionally, the vacuum degree of the vacuum devolatilization is ≤10 kPa.

[0021] Optionally, the vacuum devolatilization time is 4-8 hours.

[0022] The detergent used in the washing can be water, and the washing process can be carried out under normal pressure.

[0023] The catalyst may include at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.

[0024] In some embodiments, the catalyst may be used in an amount of 0.1% to 0.5% of the total weight of the hydrazide compound and the unsaturated carboxylic acid ester.

[0025] In the present invention, the reaction temperature of the Michael addition reaction can be 60-80° C., and the reaction time can be 8-24 h.

[0026] In a third aspect, the present invention provides the use of the chain extender containing a hydrazide structure in the first aspect in the preparation of polyurethane, wherein the polyurethane comprises a thermoplastic polyurethane elastomer and the like.

[0027] Furthermore, in the application, no solvent is used in the preparation process of the polyurethane.

[0028] In the application, the chain extender containing a hydrazide structure can be reacted with components such as polyisocyanate and polyol through a prepolymer method or a one-step method to prepare a thermoplastic polyurethane elastomer.

[0029] As a general inventive concept, in a fourth aspect, the present invention provides a polyurethane, wherein the raw material composition of the polyurethane includes polyol, polyisocyanate and the chain extender containing hydrazide structure described in the first aspect. The polyurethane includes thermoplastic polyurethane elastomer and the like.

[0030] The present invention does not impose any particular limitation on the polyol and the polyisocyanate (eg, diisocyanate, etc.), and materials commonly used in the art may be used.

[0031] For example, the polyisocyanate may include at least one of diphenylmethane diisocyanate, hydrogenated phenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

[0032] For example, the polyol may include at least one of polyethylene adipate, polyethylene adipate-1,4-butylene adipate, polyethylene adipate-1,6-hexanediol, polyethylene adipate-1,4-butylene adipate, polyethylene adipate-1,6-hexanediol, polyethylene adipate-1,4-butylene adipate-1,6-hexanediol, polyethylene adipate-propylene glycol, polyethylene adipate monoacetal, polycaprolactone, polycarbonate-1,6-hexanediol, polytetrahydrofuran, and polypropylene glycol.

[0033] The polyurethane is prepared by using the chain extender containing hydrazide structure of the present invention. The obtained polyurethane material contains acylurea structure and can form hard phase region with multiple dynamic hydrogen bonds. It not only has high mechanical strength and toughness, but also has excellent mechanical recovery performance.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1) The present invention obtains a secondary amine compound containing a hydrazide structure by reacting a hydrazide compound with an unsaturated carboxylic acid ester, and the secondary amine compound can be used as a chain extender in the synthesis of polyurethane materials. The chain extender prepared by the present invention has a melting point lower than 100° C. and can be prepared and used in the same manner as a conventional chain extender, without the problem of high-temperature melting or high-temperature deterioration. The use process also does not require the addition of high-boiling point solvents such as DMF, DMAC, and N-methylpyrrolidone (NMP). At the same time, the problem that the primary amino group reacts too quickly and is easy to gel can be solved. The preparation and use process is environmentally friendly and suitable for large-scale production.

[0036] 2) The chain extender prepared based on the present invention is applied to thermoplastic polyurethane elastomer, and the reaction is normal, and a product with excellent performance can be prepared. The hard segment structure thereof has an acyl urea structure, which can form multiple hydrogen bonds, has good strength and resilience, and has excellent mechanical recovery properties, and can be used as a self-healing elastomer material. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a graph showing the test results of the differential scanning calorimetry (DSC) of the chain extender containing a hydrazide structure of the product of Example 1.

[0038] Figure 2 This is the infrared spectrum of the chain extender containing hydrazide structure of the product in Example 1. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0040] The melting point of a chain extender can be determined accurately or in a range by any of the following methods:

[0041] Method 1: Use DSC to test the melting temperature and determine the melting point of the chain extender, with a heating and cooling rate of 10℃ / min;

[0042] Method 2: Whether the material melts into a uniform liquid during the preparation process in a 100°C oven is used to determine whether the melting point of the chain extender is lower than 100°C, and then determine whether the polyurethane can be prepared in the conventional manner.

[0043] Preparation of chain extender:

[0044] Example 1

[0045] Dissolve 200g of adipic acid dihydrazide and 0.92g of tetramethylammonium hydroxide in 150mL of 50vol% ethanol aqueous solution, start stirring under nitrogen protection, heat to 70℃ and reflux for dispersion; weigh 413.69g of dimethyl maleate and add it to the constant pressure dropping funnel, drop it into the system, and complete the addition within 1 hour. Control the system temperature to 70℃ and continue the reaction for 20 hours; after the reaction is completed, vacuum devolatilization is carried out with a vacuum degree of 4kPa for 6 hours to remove low-boiling substances in the system, and then restore the pressure to normal and add pure water for washing. Repeat the washing 3 times and filter the product. Dry the filter cake in a vacuum oven at 100℃ for 12 hours. Cool it to obtain a chain extender containing a hydrazide structure. This product is a uniform liquid after being dried in an oven at 100℃ for 5 hours. The product of this example was tested by infrared and DSC. Figure 1 The DSC spectrum shows that the high temperature melting point of the product drops to 96°C, which is lower than 100°C. Figure 2 The infrared spectrum shows that the characteristic peak of the carbon-carbon double bond of dimethyl maleate disappears, proving that the addition reaction is completed.

[0046] Example 2

[0047] 300g of adipic acid dihydrazide and 2.14g of tetraethylammonium hydroxide were dissolved in 250mL of 60vol% ethanol aqueous solution, stirred under nitrogen protection, and heated to 80℃ for reflux dispersion; 770.95g of diethyl maleate was weighed and added into a constant pressure dropping funnel, and added dropwise to the system, and the addition was completed within 1.5h, and the system temperature was controlled to 80℃ for continued reaction for 18h; after the reaction was completed, vacuum devolatilization was carried out, and the vacuum degree was 3kPa for 6h to remove low-boiling substances in the system, and then pure water was added after returning to normal pressure for washing, and the washing was repeated 3 times, and the product was filtered, and the filter cake was dried in a vacuum oven at 100℃ for 12h, and the chain extender containing hydrazide structure was obtained by cooling. This product was a uniform liquid after being dried in an oven at 100℃ for 5h, and the infrared results showed that the addition reaction of the carbon-carbon double bond had been completed.

[0048] Example 3

[0049] 300g of adipic acid dihydrazide and 1.5g of tetrapropylammonium hydroxide were dissolved in 200mL of 60vol% ethanol aqueous solution, stirred under nitrogen protection, and heated to 75℃ for reflux dispersion; 444.78g of methyl acrylate was weighed and added into a constant pressure dropping funnel, and the addition was completed within 1h, and the system temperature was controlled at 75℃ to continue the reaction for 19h; after the reaction was completed, vacuum devolatilization was carried out, and the vacuum degree was 3kPa for 6h to remove low-boiling substances in the system, and then pure water was added after returning to normal pressure for washing, and the washing was repeated 3 times, and the product was filtered, and the filter cake was dried in a vacuum oven at 100℃ for 12h, and the chain extender containing hydrazide structure was obtained by cooling. This product was a uniform liquid after being dried in an oven at 100℃ for 5h, and the infrared results showed that the addition reaction of the carbon-carbon double bond had been completed.

[0050] Example 4

[0051] 500g of adipic acid dihydrazide and 3.39g of tetrabutylammonium hydroxide were dissolved in 300mL of 50vol% ethanol aqueous solution, stirred under nitrogen protection, and heated to 80℃ for reflux dispersion; 632.15g of methyl methacrylate was weighed and added into a constant pressure dropping funnel, and added dropwise to the system, and the addition was completed within 1.5h, and the system temperature was controlled at 80℃ to continue the reaction for 20h; after the reaction was completed, vacuum devolatilization was carried out, and the vacuum degree was 2kPa for 4h to remove low-boiling substances in the system, and then pure water was added after returning to normal pressure for washing, and the washing was repeated 3 times, and the product was filtered, and the filter cake was dried in a vacuum oven at 100℃ for 12h, and the chain extender containing hydrazide structure was obtained by cooling. This product was a uniform liquid after being dried in an oven at 100℃ for 5h, and the infrared results showed that the addition reaction of the carbon-carbon double bond had been completed.

[0052] Example 5

[0053] 400g of succinic acid dihydrazide and 3.70g of tetrabutylammonium hydroxide were dissolved in 400mL of 70vol% ethanol aqueous solution, stirred under nitrogen protection, and heated to 75℃ for reflux dispersion; 1082.11g of dimethyl itaconate was weighed and added into a constant pressure dropping funnel, and added dropwise to the system within 2h, and the system temperature was controlled to 75℃ for continued reaction for 20h; after the reaction, vacuum devolatilization was carried out, and the vacuum degree was 2kPa for 4h to remove low-boiling substances in the system, and then pure water was added for washing after returning to normal pressure, and the washing was repeated 3 times, and the product was filtered, and the filter cake was dried in a vacuum oven at 100℃ for 12h, and the chain extender containing hydrazide structure was obtained by cooling. This product was a uniform liquid after being dried in an oven at 100℃ for 5h, and the infrared results showed that the addition reaction of the carbon-carbon double bond had been completed.

[0054] Example 6

[0055] 300g of succinic acid dihydrazide and 2.75g of tetrabutylammonium hydroxide were dissolved in 300mL of 80vol% ethanol aqueous solution, stirred under nitrogen protection, and heated to 70℃ for reflux dispersion; 616.48g of ethyl acrylate was weighed and added into a constant pressure dropping funnel, and added dropwise to the system within 2h, and the system temperature was controlled to 70℃ for continued reaction for 20h; after the reaction, vacuum devolatilization was carried out, and the vacuum degree was 2kPa for 4h to remove low-boiling substances in the system, and then pure water was added after returning to normal pressure for washing, and the washing was repeated 3 times, and the product was filtered, and the filter cake was dried in a vacuum oven at 100℃ for 12h, and the chain extender containing hydrazide structure was obtained by cooling. This product was a uniform liquid after being dried in an oven at 100℃ for 5h, and the infrared results showed that the addition reaction of carbon-carbon double bonds had been completed.

[0056] Example 7

[0057] 200g of maleic acid dihydrazide and 0.95g of tetramethylammonium hydroxide were dissolved in 150mL of 50vol% ethanol aqueous solution, stirred under nitrogen protection, and heated to 70℃ for reflux dispersion; 325.80g of methyl acrylate was weighed and added into a constant pressure dropping funnel, and added dropwise to the system within 1h, and the system temperature was controlled at 70℃ to continue the reaction for 20h; after the reaction, vacuum devolatilization was carried out, and the vacuum degree was 4kPa for 6h to remove low-boiling substances in the system, and then pure water was added after returning to normal pressure for washing, and the washing was repeated 3 times, and the product was filtered, and the filter cake was dried in a vacuum oven at 100℃ for 12h, and the chain extender containing hydrazide structure was obtained by cooling. This product was a uniform liquid after being dried in an oven at 100℃ for 5h, and the infrared results showed that the addition reaction of the carbon-carbon double bond had been completed.

[0058] Example 8

[0059] Dissolve 300g of azelaic acid dihydrazide and 2.05g of tetraethylammonium hydroxide in 250mL of 60vol% ethanol aqueous solution, start stirring under nitrogen protection, heat to 80℃ and reflux for dispersion; weigh 361.05g of ethyl acrylate and add it into a constant pressure dropping funnel, drop it into the system, and complete the addition within 1.5h, control the system temperature to 80℃ and continue the reaction for 18h; after the reaction is completed, vacuum devolatilization is carried out with a vacuum degree of 3kPa for 6h to remove low-boiling substances in the system, and then restore the pressure to normal and add pure water for washing. Repeat the washing 3 times and filter the product, dry the filter cake in a vacuum oven at 100℃ for 12h, and cool it to obtain a chain extender containing a hydrazide structure. This product is a uniform liquid after being dried in an oven at 100℃ for 5h, and infrared results show that the addition reaction of the carbon-carbon double bond has been completed.

[0060] Thermoplastic polyurethane elastomer is prepared by using the chain extender of the present invention:

[0061] Example 9

[0062] The product prepared in Example 1 was used as a chain extender, a polycaprolactone diol with a molecular weight of 2000 g / mol was selected as the polyol, and diphenylmethane diisocyanate was selected as the diisocyanate. 350 g of the polycaprolactone polyol and 67.29 g of the product of Example 1 were weighed, and the prepared chain extender and polyol were melted into liquids at 100 ° C and stirred to mix evenly. 82.71 g of diphenylmethane diisocyanate was added and stirred at high speed for 40 seconds. After the viscosity of the material increased, it was poured into a polytetrafluoroethylene tray, aged in an oven at 100 ° C for 24 hours, and then cooled to room temperature to obtain a thermoplastic polyurethane elastomer (TPU) product. The material was crushed and prepared into standard specimens by injection molding for evaluation.

[0063] Example 10

[0064] The product prepared in Example 1 was used as a chain extender, a polycaprolactone diol with a molecular weight of 1500 g / mol was selected as the polyol, and diphenylmethane diisocyanate was selected as the diisocyanate. 390 g of polycaprolactone polyol and 91.85 g of the product of Example 1 were weighed, and the prepared chain extender and polyol were melted into liquid at 100 ° C and stirred to mix evenly. 118.15 g of diphenylmethane diisocyanate was added and stirred at high speed for 40 seconds. After the viscosity of the material increased, it was poured into a polytetrafluoroethylene tray, aged in an oven at 100 ° C for 24 hours, and then cooled to room temperature to obtain a thermoplastic polyurethane elastomer (TPU) product. The material was crushed and prepared into standard specimens by injection molding for evaluation.

[0065] Embodiment 11

[0066] The product prepared in Example 1 was used as a chain extender, polytetramethylene diisocyanate with a molecular weight of 1800 g / mol was selected as the polyol, and hexamethylene diisocyanate was selected as the diisocyanate. 335 g of polytetramethylene diisocyanate and 96.60 g of the product of Example 1 were weighed, and the prepared chain extender and polyol were melted into liquids and stirred to mix evenly at 100 ° C. 68.40 g of hexamethylene diisocyanate was added and stirred at high speed for 80 seconds. After the viscosity of the material increased, it was poured into a polytetrafluoroethylene tray, aged in an oven at 100 ° C for 24 hours, and then cooled to room temperature to obtain a thermoplastic polyurethane elastomer (TPU) product. The material was crushed and prepared into standard specimens by injection molding for evaluation.

[0067] Example 12

[0068] The product prepared in Example 3 was used as a chain extender, a polycaprolactone diol with a molecular weight of 2000 g / mol was selected as the polyol, and diphenylmethane diisocyanate was selected as the diisocyanate. 420 g of polycaprolactone polyol and 72.09 g of the product of Example 3 were weighed, and the prepared chain extender and polyol were melted into liquid at 100° C. and stirred to mix evenly. 107.91 g of diphenylmethane diisocyanate was added and stirred at high speed for 60 seconds. After the viscosity of the material increased, it was poured into a polytetrafluoroethylene tray, aged in an oven at 100° C. for 24 hours, and then cooled to room temperature to obtain a TPU product. The material was crushed and prepared into standard specimens by injection molding for evaluation.

[0069] Embodiment 13

[0070] The product prepared in Example 3 was used as a chain extender, a polycaprolactone diol with a molecular weight of 2000 g / mol was selected as the polyol, and diphenylmethane diisocyanate was selected as the diisocyanate. 390 g of polycaprolactone polyol and 91.62 g of the product of Example 3 were weighed, and the prepared chain extender and polyol were melted into liquid at 100° C. and stirred to mix evenly. 118.38 g of diphenylmethane diisocyanate was added and stirred at high speed for 60 seconds. After the viscosity of the material increased, it was poured into a polytetrafluoroethylene tray, aged in an oven at 100° C. for 24 hours, and then cooled to room temperature to obtain a TPU product. The material was crushed and prepared into standard specimens by injection molding for evaluation.

[0071] Embodiment 14

[0072] The product prepared in Example 5 was used as a chain extender, polybutylene adipate diol with a molecular weight of 1800 g / mol was selected as the polyol, and diphenylmethane diisocyanate was selected as the diisocyanate. 390 g of polybutylene adipate diol and 98.97 g of the product of Example 5 were weighed, and the prepared chain extender and polyol were melted into liquid at 100° C. and stirred to mix evenly. 111.03 g of diphenylmethane diisocyanate was added and stirred at high speed for 60 seconds. After the viscosity of the material increased, it was poured into a polytetrafluoroethylene tray, aged in an oven at 100° C. for 24 hours, and then cooled to room temperature to obtain a TPU product. The material was crushed and prepared into standard specimens by injection molding for evaluation.

[0073] Embodiment 15

[0074] The product prepared in Example 5 was used as a chain extender, polybutylene adipate diol with a molecular weight of 1800 g / mol was selected as the polyol, and hexamethylene diisocyanate was selected as the diisocyanate. 325 g of polybutylene adipate diol and 104.6 g of the product of Example 5 were weighed, and the prepared chain extender and polyol were melted into liquid at 100° C. and stirred to mix evenly. 70.4 g of hexamethylene diisocyanate was added and stirred at high speed for 100 seconds. After the viscosity of the material increased, it was poured into a polytetrafluoroethylene tray, aged in an oven at 100° C. for 24 hours, and then cooled to room temperature to obtain a TPU product. The material was crushed and prepared into standard specimens by injection molding for evaluation.

[0075] Example 16

[0076] The product prepared in Example 6 was used as a chain extender, polytetramethylene ether diol with a molecular weight of 1000 g / mol was selected as the polyol, and diphenylmethane diisocyanate was selected as the diisocyanate. 300 g of polytetramethylene ether diol and 79.58 g of the product of Example 6 were weighed, and the prepared chain extender and polyol were melted into liquid at 100 ° C and stirred to mix evenly. 129.42 g of diphenylmethane diisocyanate was added and stirred at high speed for 50 seconds. After the viscosity of the material increased, it was poured into a polytetrafluoroethylene tray, aged in an oven at 100 ° C for 24 hours, and then cooled to room temperature to obtain a TPU product. The material was crushed and prepared into standard specimens by injection molding for evaluation.

[0077] Embodiment 17

[0078] The product prepared in Example 7 was used as a chain extender, polytetramethylene glycol with a molecular weight of 1000 g / mol was selected as the polyol, and diphenylmethane diisocyanate was selected as the diisocyanate. 325 g of polytetramethylene glycol and 49.56 g of the product of Example 7 were weighed, and the prepared chain extender and polyol were melted into liquid at 100° C. and stirred to mix evenly. 125.44 g of diphenylmethane diisocyanate was added and stirred at high speed for 50 seconds. After the viscosity of the material increased, it was poured into a polytetrafluoroethylene tray, aged in an oven at 100° C. for 24 hours, and then cooled to room temperature to obtain a TPU product. The material was crushed and prepared into standard specimens by injection molding for evaluation.

[0079] Embodiment 18

[0080] The product prepared in Example 8 was used as a chain extender, polybutylene adipate diol with a molecular weight of 2000 g / mol was selected as the polyol, and diphenylmethane diisocyanate was selected as the diisocyanate. 300 g of polybutylene adipate diol and 99.74 g of the product of Example 8 were weighed, and the prepared chain extender and polyol were melted into liquid at 100° C. and stirred to mix evenly. 100.26 g of diphenylmethane diisocyanate was added and stirred at high speed for 70 seconds. After the viscosity of the material increased, it was poured into a polytetrafluoroethylene tray, aged in an oven at 100° C. for 24 hours, and then cooled to room temperature to obtain a TPU product. The material was crushed and prepared into standard specimens by injection molding for evaluation.

[0081] Comparative Example 1: Adipic acid dihydrazide is used to directly participate in the reaction

[0082] Adipic acid dihydrazide was used as a chain extender, polycaprolactone diol with a molecular weight of 2000 g / mol was selected as the polyol, and diphenylmethane diisocyanate was selected as the diisocyanate. 350 g of polycaprolactone polyol and 42.33 g of adipic acid dihydrazide were weighed, prepared at 100 °C and stirred, but it was difficult to mix evenly. Adipic acid dihydrazide still existed in the form of powder and agglomerated and precipitated. 107.67 g of diphenylmethane diisocyanate was added and stirred at high speed for 100 s. The viscosity of the material did not change significantly. Adipic acid dihydrazide was always in a powdery state in the system, and subsequent treatment and performance evaluation could not be performed.

[0083] Comparative Example 2: High temperature melting of adipic acid dihydrazide was used for the reaction

[0084] Adipic acid dihydrazide was used as a chain extender, a polycaprolactone diol with a molecular weight of 2000 g / mol was selected as the polyol, and diphenylmethane diisocyanate was selected as the diisocyanate. 350 g of polycaprolactone polyol and 42.33 g of adipic acid dihydrazide were weighed, wherein the polycaprolactone polyol was prepared at 100° C., adipic acid dihydrazide was melted at 200° C. (smoke was emitted during the melting process, which may be due to the decomposition of adipic acid dihydrazide), and then stirred and mixed. Adipic acid dihydrazide was added to the polycaprolactone polyol and quickly precipitated into a solid insoluble solid, which could not be mixed evenly as in Comparative Example 1. 107.67 g of diphenylmethane diisocyanate was added and stirred at high speed for 100 s. The viscosity of the material did not change significantly, and subsequent treatment and performance evaluation could not be performed.

[0085] Comparative Example 3: Chain extension reaction of adipic acid dihydrazide using solvent method

[0086] Adipic acid dihydrazide was used as a chain extender, polycaprolactone diol with a molecular weight of 2000 g / mol was selected as the polyol, and diphenylmethane diisocyanate was selected as the diisocyanate. 350 g of polycaprolactone polyol and 42.33 g of adipic acid dihydrazide were weighed, 1000 mL of DMF solvent was added, the temperature was raised to 100 °C and stirring was continued until the adipic acid dihydrazide was completely dissolved, and then 107.67 g of diphenylmethane diisocyanate was added and stirring was continued to react. Gel appeared in the system after stirring for about 20 seconds, and subsequent treatment and performance evaluation could not be carried out.

[0087] Comparative Example 4: Using the prepolymer method and then using solvent dispersion to extend the chain

[0088] Adipic acid dihydrazide is used as a chain extender, polyol is selected as polycaprolactone diol with a molecular weight of 2000g / mol, and diisocyanate is selected as diphenylmethane diisocyanate. First, 350g of polycaprolactone polyol is added to the reactor for dehydration, and then the temperature is controlled at 80°C, 107.67g of diphenylmethane diisocyanate is added, and the reaction is carried out for 2h to obtain a polyurethane prepolymer. Prepare 42.33g of adipic acid dihydrazide and add it to 1000mL of dimethyl sulfoxide (DMSO) solvent. After it is fully dissolved at 80°C, the prepared prepolymer is added to the solvent system, stirred for reaction for 1h, and then the reaction liquid is transferred to a tray and heated at 80°C for 24h to volatilize part of the solvent. Then, the tray with the sample is placed in a vacuum oven at 100°C and vacuum dried for more than 24h to obtain a polyurethane elastomer product.

[0089] Comparative Example 5: Preparation of polyurethane using conventional 1,4-butanediol as chain extender

[0090] Conventional diol 1,4-butanediol was used as a chain extender, polycaprolactone diol with a molecular weight of 2000g / mol was selected as the polyol, and diphenylmethane diisocyanate was selected as the diisocyanate. 350g of polycaprolactone polyol and 27.23g of chain extender 1,4-butanediol were weighed, prepared at 100°C and stirred to mix evenly, 122.77g of diphenylmethane diisocyanate was added and stirred at high speed for 40s. After the viscosity of the material increased, it was poured into a polytetrafluoroethylene tray, aged in an oven at 100°C for 24h, and then cooled to room temperature to obtain a TPU product. The material was crushed and prepared into standard specimens by injection molding for evaluation.

[0091] Table 1 shows the performance test results of the TPU products prepared in the above examples and comparative examples.

[0092] Table 1

[0093] Tensile Strength Elongation at break Fixed stretch recovery rate Degree of hydrogen bonding Stress repair rate Strain repair rate standard ASTM D638 ASTM D638 HG / T 3322 - - - unit MPa ％ ％ ％ ％ ％ Example 9 44.53 951.34 92 51.3 84.2 92.4 Example 10 43.87 1000.43 93 50.9 83.7 91.8 Embodiment 11 42.18 934.29 91 50.3 82.5 90.2 Example 12 40.85 905.41 89 49.1 80.4 88.7 Embodiment 13 46.14 1050.57 92 52.2 85.0 93.5 Embodiment 14 45.33 987.58 91 51.6 84.8 94.2 Embodiment 15 40.48 900.82 90 52.4 83.7 90.9 Example 16 47.42 995.50 91 52.0 85.6 92.3 Embodiment 17 41.8 937.1 90 50.4 81.9 90.7 Embodiment 18 37.82 842.8 88 51.6 84.3 91.2 Comparative Example 4 25.21 975.79 87 48.6 77.1 84.8 Comparative Example 5 30.66 625.31 75 40.1 40.3 62.5

[0094] It can be seen that the thermoplastic polyurethane elastomer prepared based on the technical solution of the present invention has excellent strength, recovery and self-healing properties, and its performance is better than that of the product prepared by the adipic acid dihydrazide solvent method. There is no tedious step of removing the solvent, and there is no influence of residual solvent on the performance of the product.

[0095] The chain extender of the present invention is prepared by reacting hydrazide compounds with unsaturated carboxylic acid esters, which can improve the problems of high melting point, difficulty in melting and poor solubility of hydrazide compounds, and can be used normally as a chain extender component of thermoplastic polyurethane elastomer. Compared with the prior art, the technical solution of the present invention can solve the problem that a large amount of high boiling point solvent is required when hydrazide compounds are directly used as chain extenders. The polyurethane elastomer prepared based on the present invention has excellent mechanical strength, resilience and self-healing properties, is suitable for large-scale production, and has good application and promotion prospects.

[0096] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. Chain extenders containing hydrazide structures, It is characterized in that The product is prepared by subjecting raw materials including hydrazide compounds and unsaturated carboxylic acid esters to Michael addition reaction; the Michael addition reaction includes a reaction process in which an amino group in the hydrazide compound and a carbon-carbon unsaturated bond in the unsaturated carboxylic acid ester are added to generate a secondary amine; The hydrazide compound includes at least one of oxalic acid dihydrazide, maleic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide and azelaic acid dihydrazide; The unsaturated carboxylic acid ester includes at least one of unsaturated dicarboxylic acid ester and unsaturated monocarboxylic acid ester; the unsaturated dicarboxylic acid ester includes at least one of dimethyl maleate, diethyl maleate, dibutyl maleate, dimethyl itaconate, dibutyl itaconate and dimethyl citrate; the unsaturated monocarboxylic acid ester includes at least one of methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate and butyl methacrylate.

2. The chain extender containing a hydrazide structure according to claim 1, It is characterized in that The molar ratio of the hydrazide compound to the unsaturated carboxylic acid ester is 1:2-4.

3. The method for preparing a chain extender containing a hydrazide structure according to claim 1 or 2, It is characterized in that include: In the presence or absence of a catalyst, the hydrazide compound and the unsaturated carboxylic acid ester are subjected to a Michael addition reaction to obtain the chain extender containing a hydrazide structure.

4. The method for preparing the chain extender containing hydrazide structure according to claim 3, It is characterized in that The preparation method of the chain extender containing a hydrazide structure specifically comprises: The hydrazide compound and the catalyst are dissolved in an ethanol aqueous solution, and the temperature is raised to the reaction temperature of the Michael addition reaction under the protection of an inert atmosphere for reflux dispersion, and the unsaturated carboxylic acid ester is added dropwise and / or in batches for constant temperature reaction. After the reaction is completed, vacuum devolatilization is performed, and low-boiling substances are removed, followed by washing and drying to obtain the chain extender containing the hydrazide structure.

5. The method for preparing the chain extender containing hydrazide structure according to claim 4, It is characterized in that The amount of the ethanol aqueous solution added is 20%-40% of the total weight of the hydrazide compound and the unsaturated carboxylic acid ester; The volume fraction of ethanol in the ethanol aqueous solution is 50%-80%; The inert atmosphere is a nitrogen atmosphere and / or a rare gas atmosphere; The unsaturated carboxylic acid ester has a dropping speed of 1-10 g / min; The vacuum degree of the vacuum devolatilization is ≤10kPa; The vacuum devolatilization time is 4-8h.

6. The method for preparing the chain extender containing a hydrazide structure according to any one of claims 3 to 5, It is characterized in that The catalyst comprises at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide; The amount of the catalyst used is 0.1%-0.5% of the total weight of the hydrazide compound and the unsaturated carboxylic acid ester.

7. The method for preparing a chain extender containing a hydrazide structure according to any one of claims 3 to 5, It is characterized in that The reaction temperature of the Michael addition reaction is 60-80° C., and the reaction time is 8-24 h.

8. Use of the chain extender containing a hydrazide structure according to claim 1 or 2 in the preparation of polyurethane.

9. The use according to claim 8, It is characterized in that No solvent is used in the preparation process of the polyurethane.

10. A polyurethane, It is characterized in that The raw materials of the polyurethane include polyol, polyisocyanate and the chain extender containing hydrazide structure as claimed in claim 1 or 2.

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