Preparation method of high-temperature-resistant high-strength polyurethane-imide elastomer

Abstract

The invention discloses a preparation method of a high-temperature-resistant high-strength polyurethane-imide elastomer, and belongs to the field of high-performance thermoplastic polyurethane elastomers, and the preparation method comprises the following steps: adding diisocyanate and polyol into a flask, and carrying out a heat preservation reaction in an inert atmosphere to obtain a first polyurethane prepolymer; adding a dihydric alcohol chain extender into the first polyurethane prepolymer, and continuously reacting at normal temperature to obtain a second polyurethane prepolymer; slowly dropwise adding an aromatic dianhydride solution into the second polyurethane prepolymer, and continuously reacting to obtain a polymer solution; and pouring the polymer solution into a tetrafluoroethylene mold, and annealing to obtain the high-temperature-resistant high-strength polyurethane-imide elastomer. Aromatic dianhydride or a mixture of dihydric alcohol and aromatic dianhydride is independently selected as a chain extender, an imide structure is introduced into a polyurethane chain segment after reaction, the tensile strength of the obtained elastomer is 30 MPa or above, and the heat-resistant temperature is 180 DEG C or above.

Description

Technical Field

[0001] This invention relates to the field of high-performance thermoplastic polyurethane elastomer technology, and in particular to a method for preparing a high-temperature resistant, high-strength polyurethane-imide elastomer. Background Technology

[0002] Polyurethane elastomers are a class of multifunctional polymers composed of soft and hard segments separated by a microphase structure. This unique microstructure gives them the high elasticity of rubber, the high strength of plastics, and excellent wear resistance, oil resistance, and processability. Therefore, polyurethane elastomers are widely used in automotive parts, industrial seals, footwear materials, and electronic packaging. However, their mechanical properties, especially modulus and strength, decrease rapidly at temperatures exceeding 120°C. Prolonged exposure to high temperatures causes thermal aging and oxidative degradation in polyurethane elastomers, resulting in significant permanent deformation (creep) or irreversible plastic flow, leading to loss of functionality. This inherent heat resistance deficiency severely restricts the application of polyurethane elastomers in more demanding fields such as aerospace, high-end equipment manufacturing, and military applications.

[0003] Currently, to address the issue of insufficient heat resistance in polyurethane elastomers, the industry mainly employs two technical approaches for optimization: physical blending and chemical modification. (1) Chemical modification method: For example, Chinese invention patent with publication number CN118955865A discloses a method for preparing high temperature resistant polyurethane elastomer. The core of this technical solution is to introduce a polyarylether ketone polymer containing urethane groups as a modifier, and combine it into the polyurethane system through chemical means, and use the excellent thermal stability of polyarylether ketone itself to improve the heat resistance of the entire material system.

[0004] (2) Physical blending method: For example, Chinese invention patent with publication number CN118027342A discloses a high heat-resistant thermoplastic polyurethane elastomer composite material and its preparation method. The method adopts a physical blending process, in which specific nanoparticle fillers (such as inorganic nano oxides, montmorillonite, etc.) are used as reinforcing phases and dispersed into the polyurethane elastomer matrix. The method utilizes the restrictive effect of nanoparticles on molecular chain movement and their own thermal stability to improve the heat distortion temperature and long-term heat resistance of the composite material.

[0005] Although the aforementioned existing technologies have improved the heat resistance of polyurethane elastomers to some extent, they all have obvious limitations and it is difficult to achieve an ideal balance between performance and cost in industrial applications.

[0006] First, the main drawback of the chemical modification method represented by CN118955865A is that the synthesis route of the polyarylether ketone modifiers used is usually quite complex, involving multiple steps and harsh process conditions, resulting in high production costs. At the same time, the purity of the modifier is difficult to control precisely, and impurities may have a negative impact on the final performance of polyurethane. More importantly, while improving heat resistance, this method often makes limited contributions to the intrinsic mechanical properties of the material (such as tensile strength, elongation at break, and elastic recovery), resulting in a "one-sided" problem.

[0007] Secondly, the core challenge of the physical blending method represented by CN118027342A lies in the fact that nanoparticles, due to their extremely high specific surface area and surface energy, are prone to agglomeration in polymer melts, forming secondary aggregates that are difficult to disperse. This uneven dispersion not only fails to fully utilize the reinforcing and heat-resistant effects of nanofillers, but may also create stress concentration points in the matrix, becoming the starting point for material failure, thereby impairing the mechanical properties and reliability of the material.

[0008] In summary, existing technologies cannot effectively improve the heat resistance of polyurethane elastomers while perfectly balancing their processing convenience, cost control, and core mechanical properties. Therefore, developing a new modification strategy that can significantly and stably improve the heat resistance of polyurethane elastomers while ensuring or even optimizing their excellent mechanical properties has become a key technical problem urgently needing to be solved in this field, and has significant practical implications and broad application prospects. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a method for preparing a high-temperature resistant and high-strength polyurethane-imide elastomer. The prepared high-temperature resistant and high-strength polyurethane-imide elastomer not only has excellent high-temperature resistance, but also has good mechanical properties, which can meet the requirements for use under high-temperature conditions.

[0010] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for preparing a high-temperature resistant, high-strength polyurethane-imide elastomer includes the following steps: Step 1: Add diisocyanate and polyol in a molar ratio of 2.2 to 2:1 into a flask and react under an inert atmosphere. After the reaction is complete, the first polyurethane prepolymer is obtained. Step 2: Add a diol chain extender to the first polyurethane prepolymer and continue the reaction at 50°C. After the reaction is complete, the second polyurethane prepolymer is obtained. Step 3: Slowly add an aromatic dianhydride solution that has been dissolved in a solvent to the second polyurethane prepolymer, and continue the reaction. After the reaction is complete, a polymer solution is obtained. Step 4: Pour the polymer solution into a tetrafluoroethylene mold and anneal it to obtain a high-temperature resistant, high-strength polyurethane-imide elastomer.

[0011] A further improvement of the technical solution of the present invention is that, in step 1, the diisocyanate is one or two of diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, 1,4-cyclohexane diisocyanate and 1,4-phenyl diisocyanate.

[0012] A further improvement of the technical solution of the present invention is that, in step 1, the polypolyol is one of a polyether-type diol with a molecular weight in the range of 1000 g / mol to 2000 g / mol or a polyester-type diol with a molecular weight in the range of 1000 g / mol to 2000 g / mol.

[0013] A further improvement of the technical solution of the present invention is that: in step 1, the heat preservation reaction temperature is 70~85℃ and the reaction time is 2~3h.

[0014] A further improvement of the technical solution of the present invention is that, in step 2, the diol chain extender is any one or more of ethylene glycol, 1,3-propylene glycol, and 1,4-butanediol.

[0015] A further improvement of the technical solution of the present invention is that: in step 2, the molar ratio of the diol chain extender to the first polyurethane prepolymer is 0.15~0.2:1; and the reaction time is 1~1.5h.

[0016] A further improvement of the technical solution of the present invention is that: in step 3, the aromatic dianhydride is pyromellitic dianhydride or biphenyl dianhydride; and the solvent is N,N-dimethylformamide or N-methylpyrrolidone.

[0017] A further improvement of the technical solution of the present invention is that: in step 3, the molar ratio of the aromatic dianhydride to the second polyurethane prepolymer is 0.8~0.85:1; the reaction temperature is 90~95℃; and the reaction time is 2.5~3h.

[0018] A further improvement of the technical solution of the present invention is that: in step 4, the annealing temperature is 80~90℃; the annealing time is 10~12h.

[0019] A further improvement of the technical solution of the present invention is that: in step 4, the tensile strength of the high-temperature resistant and high-strength polyurethane-imide elastomer prepared is above 30 MPa, and the heat resistance temperature is above 180℃.

[0020] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows: 1. This invention selects inexpensive and readily available aromatic dianhydrides as a chain extender. Through the reaction of aromatic dianhydrides with isocyanates, imide groups are introduced into the polyurethane chain segments. The excellent mechanical rigidity and thermal stability of the imide structure enhance the mechanical properties and heat resistance of the polyurethane elastomer.

[0021] 2. This invention involves adding a mixed chain extender of diols and aromatic dianhydrides or an aromatic dianhydride chain extender to a polyurethane prepolymer to prepare a thermoplastic polyurethane-imide elastomer. The aryl imide ring structure is introduced into the thermoplastic polyurethane-imide elastomer through a reaction. As the hard segment of the thermoplastic polyurethane-imide elastomer, the rigid structure of the imide improves the stability of the hard phase region, further enhancing the microphase separation degree of the thermoplastic polyurethane-imide elastomer.

[0022] 3. The high-temperature resistant, high-strength thermoplastic polyurethane-imide elastomer prepared by this invention achieves 900% elongation at break, 50 MPa tensile strength, and a viscous flow temperature of 180°C with only 20% hard segment content. While ensuring the mechanical properties of the polyurethane elastomer, it significantly improves its thermal stability, better addressing the shortcomings of polyurethane elastomers in high-temperature applications.

[0023] 4. The high-temperature resistant and high-strength thermoplastic polyurethane-imide elastomer prepared by this invention has convenient raw material selection, simple preparation method and process control, and is easy to industrialize. It has certain application value in the fields of high-temperature sealing and tires. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 The storage modulus-temperature curves of the samples prepared in the embodiments and comparative examples of this invention were obtained by DMA testing. Figure 2 This is a mass percentage-temperature curve obtained by TG testing of the samples prepared in the embodiments and comparative examples of this invention. Detailed Implementation

[0025] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products or devices.

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments: In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The processes and methods used in the comparative examples are, unless otherwise specified, conventional methods in the art.

[0027] A method for preparing a high-temperature resistant, high-strength polyurethane-imide elastomer includes the following steps: Step 1: Add diisocyanate and polyol in a molar ratio of 2.2 to 2:1 to a flask and react for 2 to 3 hours under an inert atmosphere and at a temperature of 70 to 85°C. After the reaction is complete, the first polyurethane prepolymer is obtained. The diisocyanate is one or two of the following: diphenylmethane diisocyanate (MDI), 1,5-naphthalene diisocyanate (NDI), 1,4-cyclohexane diisocyanate (CHDI), and 1,4-phenyl diisocyanate (PPDI).

[0028] Preferably, the diisocyanate is 1,4-phenyl diisocyanate (PPDI) or 1,5-naphthalene diisocyanate (NDI).

[0029] The polyol is one of a polyether-type diol with a molecular weight ranging from 1000 g / mol to 2000 g / mol or a polyester-type diol with a molecular weight ranging from 1000 g / mol to 2000 g / mol. Specifically, polytetrahydrofuran diol or polycaprolactone diol with a molecular weight of 2000 g / mol may be selected; polytetrahydrofuran diol is preferred.

[0030] Step 2: Add a diol chain extender to the first polyurethane prepolymer and continue the reaction at 50°C. After the reaction is complete, the second polyurethane prepolymer is obtained. Diol chain extenders are any one or more of ethylene glycol, 1,3-propylene glycol, and 1,4-butanediol.

[0031] The molar ratio of the diol chain extender to the first polyurethane prepolymer is 0.15~0.2:1; the reaction time is 1~1.5h.

[0032] Step 3: Slowly add an aromatic dianhydride solution that has been dissolved in a solvent to the second polyurethane prepolymer, and continue the reaction at a temperature of 90-95°C for 2.5-3 hours. After the reaction is complete, a polymer solution is obtained. The solvent is N,N-dimethylformamide or N-methylpyrrolidone.

[0033] Aromatic dianhydrides (which are also chain extenders) are pyromellitic dianhydrides or biphenyl dianhydrides.

[0034] Preferably, the aromatic dianhydride is pyromellitic dianhydride.

[0035] The molar ratio of aromatic dianhydride (chain extender) to the second polyurethane prepolymer is 0.8~0.85:1.

[0036] Step 4: Pour the polymer solution into a tetrafluoroethylene mold and anneal it to obtain a high-temperature resistant, high-strength polyurethane-imide elastomer.

[0037] The annealing temperature is 80~90℃; the annealing time is 10~12h.

[0038] The following are some of the raw materials used in the examples and comparative examples: The following are products manufactured by a certain biochemical technology company in Shanghai: terephthalic diisocyanate, polytetrahydrofuran diol (molecular weight 2000 g / mol), ethylene glycol, 1,3-propylene glycol, and 1,4-butanediol. The products manufactured by a certain technology company in Beijing are: methylpyrrolidone and pyromellitic dianhydride.

[0039] Example 1 A method for preparing a high-temperature resistant, high-strength polyurethane-imide elastomer includes the following steps: Step 1: Add 3.52g of terephthalic diisocyanate and 20g of polytetrahydrofuran diol (molecular weight 2000g / mol) to a four-necked flask under nitrogen protection, heat to 85℃, and keep the reaction at this temperature for 2 hours to obtain the first polyurethane prepolymer. Step 2: Add 0.09g of ethylene glycol to the first polyurethane prepolymer and react at 50℃ for 1h to obtain the second polyurethane prepolymer; Step 3: Slowly add a solution of 1.85g of pyromellitic dianhydride dissolved in N-methylpyrrolidone to the second polyurethane prepolymer, react at room temperature for 0.5h, then heat to 95℃ and keep the temperature for 2.5h. After the reaction is complete, a polymer solution is obtained. Step 4: Pour the polymer solution obtained in Step 3 into a tetrafluoroethylene mold and anneal it in an 80℃ oven for 12 hours. After annealing, a high-temperature resistant and high-strength polyurethane-imide elastomer is obtained.

[0040] Example 2 A method for preparing a high-temperature resistant, high-strength polyurethane-imide elastomer includes the following steps: Step 1: Add 3.36g of terephthalic diisocyanate and 20g of polytetrahydrofuran diol (molecular weight 2000g / mol) to a four-necked flask under nitrogen protection, heat to 80℃, and maintain the temperature for 2.5h to obtain the first polyurethane prepolymer. Step 2: Add 0.14g of 1,3-propylene glycol to the first polyurethane prepolymer and react at 50°C for 1.3h to obtain the second polyurethane prepolymer; Step 3: Slowly add a solution of 1.81g of pyromellitic dianhydride dissolved in N-methylpyrrolidone to the second polyurethane prepolymer, react at room temperature for 0.5h, then raise the temperature to 93℃ and keep it at that temperature for 2.8h. After the reaction is complete, a polymer solution is obtained. Step 4: Pour the polymer solution obtained in Step 3 into a tetrafluoroethylene mold and anneal it in an oven at 85°C for 11 hours. After annealing, a high-temperature resistant and high-strength polyurethane-imide elastomer is obtained.

[0041] Example 3 A method for preparing a high-temperature resistant, high-strength polyurethane-imide elastomer includes the following steps: Step 1: Add 3.20g of terephthalic diisocyanate and 20g of polytetrahydrofuran diol (molecular weight 2000g / mol) to a four-necked flask under nitrogen protection, heat to 70℃, and keep the reaction at this temperature for 3h to obtain the first polyurethane prepolymer. Step 2: Add 0.18g of 1,4-butanediol to the first polyurethane prepolymer and react at 50°C for 1.5h to obtain the second polyurethane prepolymer; Step 3: Slowly add a solution of 1.74 g of pyromellitic dianhydride dissolved in N-methylpyrrolidone to the second polyurethane prepolymer, react at room temperature for 0.5 h, then raise the temperature to 90 °C and keep it at that temperature for 3 h. After the reaction is complete, a polymer solution is obtained. Step 4: Pour the polymer solution obtained in Step 3 into a tetrafluoroethylene mold and anneal it in a 90℃ oven for 10 hours. After annealing, a high-temperature resistant and high-strength polyurethane-imide elastomer is obtained.

[0042] Comparative Example 1 The preparation method of the polyurethane-imide elastomer in this comparative example includes the following steps: Step 1: Add 3.21g of terephthalic diisocyanate and 20g of polytetrahydrofuran diol (molecular weight 2000g / mol) to a four-necked flask under nitrogen protection, heat to 75℃, and keep the reaction at this temperature for 2 hours to obtain polyurethane prepolymer. Step 2: Slowly add a solution of 2.18g of pyromellitic dianhydride dissolved in N-methylpyrrolidone to the polyurethane prepolymer, react at room temperature for 0.5h, then raise the temperature to 90℃ and keep it at that temperature for 2.5h. After the reaction and bonding, a polymer solution is obtained. Step 3: Pour the polymer solution into a tetrafluoroethylene mold and anneal it in an 80℃ oven for 12 hours. After annealing, polyurethane-imide elastomer is obtained.

[0043] Comparative Example 2 The preparation method of the polyurethane-imide elastomer in this comparative example includes the following steps: (1) Add 3.21g of terephthalic diisocyanate and 20g of polytetramethylene ether glycol to a four-necked flask under nitrogen protection, heat to 75°C, and keep the reaction at this temperature for 2 hours to obtain polyurethane prepolymer; (2) Add 0.90 g butanediol to the polyurethane prepolymer, react at room temperature for 0.5 h, then heat to 60 °C and react for 1.5 h. After the reaction is complete, a polymer solution is obtained. (3) The polymer solution is poured into a tetrafluoroethylene mold and annealed in an oven at 80°C for 12 hours. After annealing, polyurethane-imide elastomer is obtained.

[0044] Mechanical properties of the samples from the examples and comparative examples were tested according to GB / T 528-2009, and the test results are shown in Table 1.

[0045] Table 1. Mechanical property test results of the examples and comparative examples As can be seen from the data in Table 1 above, in Examples 1-3, compared with Comparative Examples 1 and 2, the tensile strength of the high-temperature resistant and high-strength polyurethane-imide elastomers prepared using mixed chain extenders (diol chain extenders and aromatic dianhydride chain extenders) is higher than 38 MPa, which significantly improves the tensile strength; and the elongation at break and tear strength are also significantly higher than those of the polyurethane-imide elastomers prepared in Comparative Examples 1 and 2, showing excellent comprehensive mechanical properties.

[0046] DMA tests were performed on the elastomer samples prepared in Examples 1-3 and Comparative Examples 1-2. The storage modulus test results are shown in [Figure 1]. Figure 1 .

[0047] Storage modulus reflects the elastic behavior of the elastomer. As the temperature increases, the storage modulus of the sample decreases, and the inflection point temperature after the plateau is the viscous flow temperature. As shown in Table 2, the thermoplastic polyurethane-imide elastomer prepared using both alcohol and anhydride chain extenders has a viscous flow temperature above 180℃, which is more than 40℃ higher than that of Comparative Example 2.

[0048] TG tests were performed on samples from Examples 1-3 and Comparative Examples 1-2, and the test results are shown in [Figure number missing]. Figure 2 , Figure 2 The relevant information is shown in Table 2.

[0049] Table 2. DMA and TG test results of the examples and comparative examples

[0050] In Table 2, T d5% The temperature representing 5% weight loss of the sample is shown in Table 2. As can be seen from the data, the thermal decomposition temperature of the thermoplastic polyurethane-imide elastomer prepared using glycol chain extenders and anhydride chain extenders is more than 20°C higher than that of the polyurethane elastomer in Comparative Example 2, indicating improved heat resistance. However, the addition of glycol chain extenders weakened the tight arrangement of aromatic structures in the polyurethane-imide elastomer to some extent, resulting in a decrease in thermal decomposition temperature compared to the elastomer in Comparative Example 1.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high-temperature resistant, high-strength polyurethane-imide elastomer, characterized in that, Includes the following steps: Step 1: Add diisocyanate and polyol in a molar ratio of 2.2 to 2:1 into a flask and react under an inert atmosphere. After the reaction is complete, the first polyurethane prepolymer is obtained. Step 2: Add a diol chain extender to the first polyurethane prepolymer and continue the reaction at 50°C. After the reaction is complete, the second polyurethane prepolymer is obtained. Step 3: Slowly add an aromatic dianhydride solution that has been dissolved in a solvent to the second polyurethane prepolymer, and continue the reaction. After the reaction is complete, a polymer solution is obtained. Step 4: Pour the polymer solution into a tetrafluoroethylene mold and anneal it to obtain a high-temperature resistant, high-strength polyurethane-imide elastomer.

2. The preparation method according to claim 1, characterized in that, In step 1, the diisocyanate is one or two of diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, 1,4-cyclohexane diisocyanate, and 1,4-phenyl diisocyanate.

3. The preparation method according to claim 1, characterized in that, In step 1, the polyol is one of a polyether with a molecular weight in the range of 1000 g / mol to 2000 g / mol or a polyester with a molecular weight in the range of 1000 g / mol to 2000 g / mol.

4. The preparation method according to claim 1, characterized in that, In step 1, the heat preservation reaction temperature is 70~85℃, and the reaction time is 2~3h.

5. The preparation method according to claim 1, characterized in that, In step 2, the diol chain extender is any one or more of ethylene glycol, 1,3-propylene glycol, and 1,4-butanediol.

6. The preparation method according to claim 1, characterized in that, In step 2, the molar ratio of the diol chain extender to the first polyurethane prepolymer is 0.15~0.2:1; the reaction time is 1~1.5h.

7. The preparation method according to claim 1, characterized in that, In step 3, the aromatic dianhydride is pyromellitic dianhydride or biphenyl dianhydride; the solvent is N,N-dimethylformamide or N-methylpyrrolidone.

8. The preparation method according to claim 1, characterized in that, In step 3, the molar ratio of the aromatic dianhydride to the second polyurethane prepolymer is 0.8~0.85:1; the reaction temperature is 90~95℃; and the reaction time is 2.5~3h.

9. The preparation method according to claim 1, characterized in that, In step 4, the annealing temperature is 80~90℃; the annealing time is 10~12h.

10. The preparation method according to claim 1, characterized in that, In step 4, the tensile strength of the high-temperature resistant, high-strength polyurethane-imide elastomer prepared is above 30 MPa, and the heat resistance temperature is above 180℃.

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