Shape memory type high-temperature-resistant flame-retardant polyether TPU and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, and particularly discloses a shape memory type high-temperature-resistant flame-retardant polyether TPU and a preparation method thereof.According to the TPU, through molecular chain design, a terephthalic acid structure and an amide structure are introduced into a polyether type thermoplastic polyurethane elastomer to serve as hard segment constituent parts, so that the temperature resistance is remarkably improved; meanwhile, intrinsic flame retardance is achieved through the copolymerized phosphorus flame retardant unit, and the migration and degradation problems of a traditional additive flame retardant are avoided; in addition, a micro-phase separation structure of the soft segment and the hard segment is utilized, so that the material is endowed with a shape memory function. According to the invention, quaternary ammonium salt micromolecules are introduced as an antibacterial part and copolymerized to a TPU molecular chain, the antibacterial property is enhanced without causing discoloration or degradation caused by silver ions, the preparation method adopts a prepolymer method, and efficient synthesis is realized by controlling the raw material ratio, the reaction temperature and the catalyst; the TPU has excellent comprehensive performance and is suitable for the fields of electronic device coating, automobile parts, medical equipment and the like.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a shape memory type high temperature resistant flame retardant polyether TPU and its preparation method. Background Technology

[0002] Thermoplastic polyurethane elastomer (TPU) is a block copolymer formed by microphase separation of soft segments (usually polyether or polyester glycol) and hard segments (diisocyanate and chain extender). It has excellent elasticity, abrasion resistance and processing properties. However, traditional TPU has limitations in terms of temperature resistance, flame retardancy and functionalization. For example, the heat distortion temperature of ordinary TPU is low (usually below 80°C), and it is easy to soften and deform in high-temperature environments, which limits its application in automotive engine compartments or high-temperature components of electronic devices. In addition, TPU has poor flame retardancy, which usually needs to be improved by adding halogen or phosphorus flame retardants. However, added flame retardants are prone to migration and precipitation, which leads to performance degradation, discoloration or environmental pollution after long-term use.

[0003] In the field of shape memory TPU, existing technologies mostly use polyester soft segments such as polycaprolactone (PCL) to achieve deformation recovery through thermally induced shape memory effect. However, polyester TPU is prone to hydrolysis, has poor weather resistance, and a narrow shape memory temperature range. In recent years, some studies have introduced aromatic diisocyanates (such as MDI) or nanofillers to improve temperature resistance and flame retardancy, but this often sacrifices the flexibility and shape memory performance of the material.

[0004] In the field of antibacterial TPU, a common technique is to add silver or zinc ions as antibacterial agents. However, silver ions can easily cause material oxidation, discoloration, and biotoxicity, and high addition levels may lead to TPU degradation. Quaternary ammonium salt antibacterial agents can avoid these problems through chemical bonding, but existing technologies mostly use surface coatings or physical blending, which have poor durability.

[0005] To address the above problems, this invention proposes a molecular chain modification scheme: terephthalic acid and amide structures are copolymerized into the TPU hard segment, significantly improving temperature resistance and rigidity; simultaneously, phosphorus-based flame retardant units and quaternary ammonium salt antibacterial agents are covalently introduced into the TPU molecular chain, achieving inherent flame retardancy and long-lasting antibacterial properties; furthermore, through the microphase separation design of polyether soft and hard segments, the material is endowed with excellent shape memory function. This design differs significantly from existing technologies: firstly, through the synergistic effect of terephthalic acid and amide structures, the heat distortion temperature of TPU can be increased to over 120°C while maintaining good processability; secondly, the copolymerization of flame retardant and antibacterial units avoids the defects of additives; finally, the shape memory performance is achieved through molecular chain design, with a recovery rate of over 95%. Summary of the Invention

[0006] The purpose of this invention is to provide a shape memory type high temperature resistance and flame retardant polyether TPU and its preparation method, so as to solve the problems of poor temperature resistance, insufficient flame retardancy, weak shape memory function and easy degradation of existing TPU.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A shape memory type high temperature resistance and flame retardant polyether TPU comprises a polymer chain formed by copolymerization of the following components: polyether glycol, diisocyanate, chain extender, terephthalic acid derivative, amide-containing chain extender, phosphorus-containing flame retardant unit, and quaternary ammonium salt small molecule; wherein, the terephthalic acid derivative and the amide-containing chain extender serve as hard segments; the phosphorus-containing flame retardant unit is covalently linked to the TPU molecular chain; the quaternary ammonium salt small molecule is introduced into the TPU molecular chain through copolymerization; and the polyether glycol serves as a soft segment, forming a microphase-separated structure with the hard segment.

[0008] Preferably, the polymer chain comprises the following components formed by copolymerization reaction: 60-150 parts of polyether glycol, 30-60 parts of diisocyanate, 5-20 parts of chain extender, 2-10 parts of terephthalic acid derivative, 1.5-8.5 parts of chain extender containing amide structure, 2-6 parts of phosphorus-containing flame retardant unit, and 1-5 parts of quaternary ammonium salt small molecule.

[0009] Preferably, the polyether glycol is one or more of polytetrahydrofuran ether glycol, polypropylene glycol, or polyethylene glycol, with a number average molecular weight of 500-3000 g / mol.

[0010] Preferably, the diisocyanate is one or more of 4,4'-diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, or isophorone diisocyanate; and the chain extender is one or more of 1,4-butanediol, ethylene glycol, or 1,6-hexanediol.

[0011] Preferably, the terephthalic acid derivative is one or more of dimethyl terephthalate, diethyl terephthalate, or terephthalic acid, and its molar percentage in the TPU hard segment is 5%-20%.

[0012] Preferably, the chain extender containing the amide structure is one or more of hexamethylenediamine, ethylenediamine, or p-phenylenediamine, and its molar percentage in the TPU hard segment is 5%-15%.

[0013] Preferably, the phosphorus-containing flame retardant unit is a reactive phosphorus compound, including one or more of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, bis(2-hydroxyethyl)methyl phosphate, or phosphoryl dichloride, and its mass percentage of phosphorus in the TPU molecular chain is 0.5%-3%.

[0014] Preferably, the quaternary ammonium salt small molecule is one or more of methacryloyloxyethyltrimethylammonium chloride, dimethyl diallyl ammonium chloride, or alkyl quaternary ammonium salt, and its molar percentage in the TPU molecular chain is 1%-10%.

[0015] A method for preparing shape memory type high temperature resistance and flame retardant polyether TPU as described above includes the following steps: Preparation of prepolymer: Polyether glycol, diisocyanate, terephthalic acid derivative and phosphorus-containing flame retardant unit are reacted at 60-80℃ for 1-3 hours under inert gas protection to form isocyanate-terminated prepolymer; Chain extension reaction: The prepolymer obtained in step one is mixed with chain extender, chain extender containing amide structure and quaternary ammonium salt small molecules at 70-90℃ and reacted for 0.5-2 hours to obtain TPU polymer; Post-processing: The TPU polymer is granulated and dried to obtain the final product.

[0016] Preferably, the reaction catalyst in step one is an organotin catalyst, including dibutyltin dilaurate or stannous octoate, and its amount is 0.01%-0.1% of the total raw material mass; the reaction in step two is carried out in a solvent, wherein the solvent is N,N-dimethylformamide or dimethyl sulfoxide, and its amount is 10%-30% of the total raw material mass.

[0017] The beneficial effects of this invention are: This invention enhances the rigidity of TPU hard segments and significantly improves the heat distortion temperature by introducing terephthalic acid and amide structures, making it suitable for high-temperature environments. Phosphorus-based flame-retardant units are copolymerized onto the chain to prevent migration, resulting in durable and environmentally friendly flame-retardant performance. The microphase separation structure allows for programmable deformation of the material after heating, with a high recovery rate, making it suitable for smart devices. Quaternary ammonium salt copolymerization avoids silver ion issues, providing durable and safe antibacterial properties. The material simultaneously maintains high mechanical strength, elasticity, and processability, and exhibits good compatibility with materials such as PA6 / PA66, making it suitable for use as a coating support material.

[0018] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing embodiments of this application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart of the method for producing shape memory high-temperature resistant and flame-retardant polyether TPU according to the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0022] Example 1 A shape memory type high temperature resistant flame retardant polyether TPU was prepared, with the following raw material ratio (by mass): Polyether glycol (polytetrahydrofuran ether glycol, Mn=1000 g / mol): 100 parts Diisocyanate (4,4'-diphenylmethane diisocyanate): 50 parts Chain extender (1,4-butanediol): 10 parts Terephthalic acid derivative (dimethyl terephthalate): 8 parts Contains amide chain extender (hexamethylenediamine): 5 parts Phosphorus-containing flame retardant unit (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide): 5 parts Quaternary ammonium salt small molecule (methacryloyloxyethyltrimethylammonium chloride): 3 parts Catalyst (dibutyltin dilaurate): 0.05 parts Solvent (N,N-dimethylformamide): 30 parts The preparation method is as follows: Prepolymer preparation: Under nitrogen protection, polytetrahydrofuran ether diol, 4,4'-diphenylmethane diisocyanate, dimethyl terephthalate and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide are added to a reactor, heated to 70°C, and stirred for 2 hours to obtain a terminal isocyanate-based prepolymer; Chain extension reaction: The prepolymer is cooled to 60°C, and 1,4-butanediol, hexamethylenediamine and methacryloyloxyethyltrimethylammonium chloride are added, along with N,N-dimethylformamide solvent. The temperature is raised to 80°C, and the reaction is carried out for 1 hour to obtain a viscous polymer; Post-treatment: The polymer is extruded and granulated, and then vacuum dried at 80°C for 12 hours to obtain TPU particles.

[0023] Example 2 Raw material ratio (by mass): Polyether glycol (polypropylene oxide glycol, Mn=1500 g / mol): 100 parts Diisocyanate (toluene diisocyanate): 45 parts Chain extender (ethylene glycol): 8 parts 10 parts of terephthalic acid derivative (terephthalic acid): Contains amide chain extender (ethylenediamine): 4 parts Phosphorus-containing flame retardant unit (bis(2-hydroxyethyl)methyl phosphate): 6 parts Quaternary ammonium salt small molecule (dimethyl diallyl ammonium chloride): 4 parts Catalyst (stannous octoate): 0.03 parts Solvent (dimethyl sulfoxide): 25 parts The preparation steps are the same as in Example 1.

[0024] Example 3 Raw material ratio (by mass): Polyether glycol (polyethylene oxide glycol, Mn=2000 g / mol): 100 parts Diisocyanate (hexamethylene diisocyanate): 55 parts Chain extender (1,6-hexanediol): 12 parts Terephthalic acid derivative (diethyl terephthalate): 7 parts Contains amide chain extender (p-phenylenediamine): 6 parts Phosphorus-containing flame retardant unit (phosphoryl dichloride): 4 parts Small molecule quaternary ammonium salt (alkyl quaternary ammonium salt): 2 parts Catalyst (dibutyltin dilaurate): 0.08 parts Solvent (N,N-dimethylformamide): 35 parts The preparation steps are the same as in Example 1.

[0025] Comparative Example 1 Using a standard formula: Polytetrahydrofuran ether diol (Mn=1000, 100 parts) 4,4'-Diphenylmethane diisocyanate (40 parts) 1,4-Butanediol (12 parts) 0.05 parts catalyst.

[0026] The preparation method is the same as in Example 1.

[0027] Comparative Example 2 Based on the formulation of Comparative Example 1, 5 parts of an additive phosphorus-based flame retardant (tris(2-chloropropyl) phosphate) and 2 parts of silver ion antibacterial masterbatch were added by physical blending and melt blending granulation in a twin-screw extruder.

[0028] Comparative Example 3 High hard segment content formula: Polytetrahydrofuran ether diol (Mn=1000, 80 parts) 4,4'-Diphenylmethane diisocyanate (60 parts) 1,4-Butanediol (20 parts) The preparation method is the same as in Example 1.

[0029] Test methods and standards Heat distortion temperature (HDT): ASTM D648, load 1.82 MPa, to evaluate the short-term heat resistance of the material.

[0030] Thermal stability (Td5%): TGA analysis was performed at the temperature at which the material lost 5% of its weight under a nitrogen atmosphere to assess its long-term thermal stability.

[0031] Flame retardant performance: UL-94 vertical burning test, recording flammability rating and afterflame time.

[0032] Limiting Oxygen Index (LOI): ASTM D2863, measures the minimum oxygen concentration required for a material to ignite.

[0033] Shape memory performance: Cyclic testing was conducted using a thermomechanical analyzer. The sample was stretched to 100% strain at a high temperature (deformation temperature Td, set as HDT+10℃), cooled and fixed, unloaded, and then heated to Td. The shape retention rate (Rf) and shape recovery rate (Rr) were recorded.

[0034] Antibacterial properties: GB / T 31402, against *E. coli* (ATCC 25922), testing the inhibition rate after 24 hours. The samples were then subjected to accelerated aging (immersion in a 70℃ water bath for 7 days) and tested again to evaluate durability.

[0035] Mechanical properties: ASTM D412, tested for tensile strength and elongation at break.

[0036] Color stability (ΔE): The color change (ΔE value) of a sample after 100 hours of accelerated aging in a UV aging chamber is measured using a colorimeter. ΔE > 2 is perceptible to the naked eye.

[0037] Migration resistance: Place the film sample between two pure white ABS sheets and maintain it at 70℃ and 0.5MPa pressure for 24 hours, then observe whether there is any additive precipitation or contamination on the ABS sheets.

[0038] Experimental Results and Discussion 1. Temperature resistance and thermal stability Table 1: Results of Temperature Resistance and Thermal Stability Tests The test results above show that the HDT and Td5% of the three embodiments of the present invention are significantly higher than those of conventional TPU (Comparative Example 1) and additive TPU (Comparative Example 2). This directly proves that copolymerizing terephthalic acid and amide structures into hard segments can effectively enhance the rigidity and thermal stability of molecular chains.

[0039] Example 3 exhibits the highest temperature resistance, thanks to the regular hard segment structure formed by the HDI and p-phenylenediamine it uses.

[0040] Comparative Example 3 improved temperature resistance by increasing the hard segment content, but its HDT and Td5% were still lower than those of the embodiments of the present invention.

[0041] 2. Flame retardant properties Table 2: Flame retardant performance test results The test results above show that all embodiments of the present invention achieve the optimal UL-94 V-0 rating and have an LOI value of over 30%, demonstrating excellent and stable inherent flame retardant properties.

[0042] Although Comparative Example 2 also achieved a V-0 rating by adding tris(2-chloropropyl)phosphate, its average afterflame time and LOI value were inferior to those of the present invention, indicating that the gas-phase condensation mechanism of the copolymer flame retardant is more efficient.

[0043] The poor flame retardancy of Comparative Example 3 proves that simply increasing the hard segment content cannot effectively improve flame retardancy.

[0044] 3. Shape memory performance Table 3: Shape memory performance test results (average of 5 cycles) The test results above show that the embodiments of the present invention exhibit excellent shape memory performance (Rf and Rr both > 95%), which is attributed to its designed microphase separation structure: the polyether soft segment provides the reversible phase, and the modified hard segment serves as the stationary phase.

[0045] Comparative Examples 1 and 2 have limited shape memory performance due to the lack of a clear microphase separation structure.

[0046] The results of Comparative Example 3 are very convincing: although its high rigidity hard segment brings a high shape fixation rate (92%), the poor chain segment movement ability results in an extremely low shape recovery rate (65%), and the shape memory function is basically lost; this, in turn, proves the technical breakthrough of the present invention in achieving a balance between high temperature resistance and excellent shape memory.

[0047] 4. Antibacterial properties and durability Table 4: Antibacterial performance test results (inhibition rate against E. coli) %) The above test results show that, due to the chemical bonding of quaternary ammonium salt to the molecular chain, the embodiments of the present invention exhibit durable and stable antibacterial properties, with almost no decrease in antibacterial rate after accelerated aging, and no migration or discoloration.

[0048] The results of Comparative Example 2 clearly exposed the fatal flaw of the additive silver ion antibacterial agent: although the initial antibacterial rate was high, the antibacterial rate dropped significantly after aging due to the dissolution and oxidation of silver ions, resulting in severe yellowing of the material (high ΔE value). At the same time, the antibacterial agent migrated and contaminated the contacting material. This perfectly confirms the advantage of "reducing the subsequent degradation and discoloration of the material caused by silver ions" mentioned in the background art of this invention.

[0049] 5. Mechanical properties Table 5: Mechanical Performance Test Results The test results above show that the embodiments of the present invention, while achieving high temperature resistance and flame retardancy, maintain good mechanical strength and elasticity (high elongation at break).

[0050] Comparative Example 2, due to the addition of small molecule additives, damaged the TPU structure to some extent, resulting in a decrease in strength.

[0051] Although Comparative Example 3 has the highest strength, it has an extremely low elongation at break, and the material is brittle, which limits its processing and application range. This again demonstrates the advantage of the present invention in terms of overall performance balance.

[0052] Through a systematic comparative experiment of the above three embodiments and three comparative examples, the present invention can draw the following clear conclusions: 1. The shape memory high temperature resistance and flame retardant polyether TPU provided by the present invention comprehensively surpasses the comparative examples representing the prior art in four core performance indicators: temperature resistance, inherent flame retardancy, shape memory and long-lasting antibacterial properties.

[0053] 2. Its superior performance is directly derived from the synergistic effect achieved through molecular design by introducing terephthalic acid / amide structure, phosphorus flame retardant unit and quaternary ammonium salt antibacterial unit into the TPU molecular chain through copolymerization.

[0054] 3. Experimental data directly prove that the present invention solves industry problems such as easy migration, short lifespan, and discoloration and degradation of materials caused by additives (as shown in Comparative Example 2), as well as the difficulty in achieving both high temperature resistance and shape memory function (as shown in Comparative Example 3).

[0055] This invention enhances the rigidity of TPU hard segments and significantly improves the heat distortion temperature by introducing terephthalic acid and amide structures, making it suitable for high-temperature environments. Phosphorus-based flame-retardant units are copolymerized onto the chain to prevent migration, resulting in durable and environmentally friendly flame-retardant performance. The microphase separation structure allows for programmable deformation of the material after heating, with a high recovery rate, making it suitable for smart devices. Quaternary ammonium salt copolymerization avoids silver ion issues, providing durable and safe antibacterial properties. The material simultaneously maintains high mechanical strength, elasticity, and processability, and exhibits good compatibility with materials such as PA6 / PA66, making it suitable for use as a coating support material.

[0056] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. 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 shape memory type high temperature resistant flame retardant polyether TPU, characterized in that, The polymer chain comprises the following components formed through a copolymerization reaction: polyether glycol, diisocyanate, chain extender, terephthalic acid derivative, amide-containing chain extender, phosphorus-containing flame-retardant unit, and quaternary ammonium salt small molecule; wherein, the terephthalic acid derivative and the amide-containing chain extender serve as hard segments; the phosphorus-containing flame-retardant unit is covalently linked to the TPU molecular chain; the quaternary ammonium salt small molecule is introduced into the TPU molecular chain through copolymerization; and the polyether glycol serves as a soft segment, forming a microphase-separated structure with the hard segments.

2. The shape memory type high temperature resistant flame retardant polyether TPU according to claim 1, characterized in that, The polymer chain is formed by copolymerization of the following components: 60-150 parts of polyether glycol, 30-60 parts of diisocyanate, 5-20 parts of chain extender, 2-10 parts of terephthalic acid derivative, 1.5-8.5 parts of chain extender containing amide structure, 2-6 parts of phosphorus-containing flame retardant unit, and 1-5 parts of quaternary ammonium salt small molecule.

3. The shape memory type high temperature resistant flame retardant polyether TPU according to claim 1, characterized in that, The polyether glycol is one or more of polytetrahydrofuran ether glycol, polypropylene glycol, or polyethylene glycol, with a number average molecular weight of 500-3000 g / mol.

4. The shape memory type high temperature resistant flame retardant polyether TPU according to claim 1, characterized in that, The diisocyanate is one or more of 4,4'-diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, or isophorone diisocyanate; the chain extender is one or more of 1,4-butanediol, ethylene glycol, or 1,6-hexanediol.

5. The shape memory type high temperature resistant flame retardant polyether TPU according to claim 1, characterized in that, The terephthalic acid derivative is one or more of dimethyl terephthalate, diethyl terephthalate, or terephthalic acid, and its molar percentage in the TPU hard segment is 5%-20%.

6. The shape memory type high temperature resistant flame retardant polyether TPU according to claim 1, characterized in that, The chain extender containing the amide structure is one or more of hexamethylenediamine, ethylenediamine, or p-phenylenediamine, and its molar percentage in the TPU hard segment is 5%-15%.

7. The shape memory type high temperature resistant flame retardant polyether TPU according to claim 1, characterized in that, The phosphorus-containing flame retardant unit is a reactive phosphorus compound, including one or more of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, bis(2-hydroxyethyl)methyl phosphate, or phosphoryl dichloride, and its mass percentage of phosphorus in the TPU molecular chain is 0.5%-3%.

8. The shape memory type high temperature resistant flame retardant polyether TPU according to claim 1, characterized in that, The quaternary ammonium salt small molecule is one or more of methacryloyloxyethyltrimethylammonium chloride, dimethyl diallyl ammonium chloride, or alkyl quaternary ammonium salt, and its molar percentage in the TPU molecular chain is 1%-10%.

9. A method for preparing shape memory type high temperature resistant flame retardant polyether TPU as described in any one of claims 1-8, characterized in that, Includes the following steps: Preparation of prepolymer: Polyether glycol, diisocyanate, terephthalic acid derivative and phosphorus-containing flame retardant unit are reacted at 60-80℃ for 1-3 hours under inert gas protection to form isocyanate-terminated prepolymer; Chain extension reaction: The prepolymer obtained in step one is mixed with chain extender, chain extender containing amide structure and quaternary ammonium salt small molecules at 70-90℃ and reacted for 0.5-2 hours to obtain TPU polymer; Post-processing: The TPU polymer is granulated and dried to obtain the final product.

10. The method for preparing shape memory type high temperature resistant flame retardant polyether TPU according to claim 9, characterized in that, In step 1, the reaction catalyst is an organotin catalyst, including dibutyltin dilaurate or stannous octoate, and its amount is 0.01%-0.1% of the total raw material mass; in step 2, the reaction is carried out in a solvent, which is N,N-dimethylformamide or dimethyl sulfoxide, and its amount is 10%-30% of the total raw material mass.

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