Polyurethane and method for its preparation and use

Abstract

The application discloses polyurethane and a preparation method and application thereof, and the preparation method comprises the following steps: mixing a first reactant and polytetrahydrofuran from which water is removed, stirring for 0.5-3 hours, adding dibutyl tin dilaurate and stirring for 2-4 hours to obtain a first reaction system; taking adipic acid dihydrazide and butanedione oxime as chain extenders; uniformly dispersing a second reactant and the chain extenders in N,N-dimethylformamide to obtain a mixed solution; and under stirring, dropping the mixed solution into the first reaction system to perform polymerization to obtain a viscous liquid containing polyurethane. The preparation method of the polyurethane is based on a prepolymer chain extension method, the polyurethane is designed in terms of specific sequence length and dynamic bond sequence distribution, the mechanical properties and recyclability of the polyurethane are significantly improved, and in combination with the stability of aramid fibers in aramid fabric, the polyurethane fabric anti-puncture composite material can be recycled for multiple times.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a polyurethane, its preparation method, and its application. Background Technology

[0002] High-performance fiber-reinforced stab-resistant composites are made by combining high-molecular polymers as a coating with high-performance fiber fabrics (aramid, polyimide, etc.). Due to their balance of protective performance and wearing comfort, they are widely used in stab-resistant clothing. However, in traditionally designed stab-resistant composites, the interfacial compatibility between the high-performance fibers and the conventional matrix is ​​poor, making them prone to damage. Furthermore, most current stab-resistant composites use non-reprocessable resins and gels as the matrix, making material recycling impossible. Protective equipment is often discarded entirely after use, resulting in resource waste and failing to meet the needs of sustainable development and recycling.

[0003] For example, patent CN116005465A (publication date: April 25, 2023) discloses a modified polyurethane-aramid anti-stab composite material, which improves the interfacial properties between the matrix and the fiber, but has limited anti-stab performance (anti-stab force value is less than 120N) and does not have the ability to be recycled; patent CN116695456A (publication date: September 5, 2023) discloses a dual nanocomposite gel coating anti-stab composite material containing hydrogen bonds and photothermal conversion agents, which has certain self-healing properties, but the self-healing efficiency of puncture damage is only 52%, and the repair conditions are harsh (requiring a high temperature of 120℃), making it difficult to achieve the goal of green recycling.

[0004] Against this backdrop, the recyclability and recycling of materials are not only an environmental requirement but also a direction for the future development of protective materials. If a recyclable matrix system with reversible chemical bonds can be constructed, material recycling can be achieved while maintaining protective performance, significantly reducing manufacturing costs and carbon emissions, and providing a sustainable solution for green protective equipment. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a polyurethane.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned polyurethane. This method is based on the prepolymer-chain extension method, in which a low molecular weight prepolymer (present in the first reaction system described below) is first synthesized, and then a chain extender is added to gradually extend the molecular chain. By controlling the molecular weight distribution of the prepolymer and the chain extender step by step, the design of specific sequence lengths and block sequence distributions of the multiple dynamic bond network of polyurethane can be achieved.

[0007] Another object of the present invention is to provide the application of the above-mentioned polyurethane in improving the puncture resistance of materials.

[0008] Another objective of this invention is to provide a method for preparing a polyurethane fabric stab-resistant composite material, which combines a viscous liquid containing polyurethane with an aramid fabric, significantly improving interfacial adhesion and recyclability while optimizing stab-resistant performance.

[0009] Another objective of this invention is to provide a method for recycling the above-mentioned polyurethane fabric stab-resistant composite material, thereby enabling multiple recycling and reprocessing of polyurethane.

[0010] The objective of this invention is achieved through the following technical solutions.

[0011] A polyurethane, with the following structural formula:

[0012] ,in,

[0013] for ,

[0014] for ,

[0015] for ,

[0016] for , n1∶m1∶n2∶m2=(1~10)∶(1~12)∶(1~10)∶(1~12)。

[0017] The above-mentioned method for preparing polyurethane includes the following steps:

[0018] Step 1), mix the first reactant and the dehydrated polytetrahydrofuran, stir for 0.5-3 h, then add dibutyltin dilaurate and stir for 2-4 h to obtain the first reaction system. The ratio of the molar amount of polytetrahydrofuran, the molar amount of the first reactant and the volume amount of dibutyltin dilaurate is (10-50):(5-30):0.4. The molar amount is in mmol and the volume amount is in mL. The first reactant is isophorone diisocyanate.

[0019] In step 1), polytetrahydrofuran is heated at 100-140°C for 1-3 hours under a nitrogen atmosphere to remove moisture, thereby obtaining polytetrahydrofuran after moisture removal.

[0020] In step 1), the stirring speed is 100~400 rpm and the stirring temperature is 70~90℃.

[0021] Step 2), adipate dihydrazide and dimethylglyoxime are used as chain extenders. The second reactant and the chain extender are uniformly dispersed in N,N-dimethylformamide to obtain a mixed solution. The ratio of the second reactant, adipate dihydrazide and dimethylglyoxime is (10~60):(10~30):(10~30) by molar amount. Under stirring, the mixed solution is added dropwise to the first reaction system to carry out the polymerization reaction and obtain a viscous liquid containing polyurethane. The ratio of polytetrahydrofuran in the first reaction system to dimethylglyoxime in the mixed solution is (5~20):(6~24) by molar amount. The second reactant is isophorone diisocyanate.

[0022] In step 2), the ratio of the molar amount of dimethylglyoxime to the volume amount of N,N-dimethylformamide is (2~12):(5~50), where the molar amount is in mmol and the volume amount is in mL.

[0023] In step 2), the stirring speed is 100~400 rpm.

[0024] In step 2), the polymerization temperature is 50~70℃ and the polymerization time is 10~18h.

[0025] The above-mentioned application of polyurethane in improving the puncture resistance of materials.

[0026] A method for preparing a polyurethane fabric stab-resistant composite material includes: immersing an aramid fabric that has been alkali-washed in the viscous liquid for 1-10 minutes, removing it, uniformly coating it with the viscous liquid, and hot-pressing it to obtain the polyurethane fabric stab-resistant composite material.

[0027] In the above technical solution, the steps to obtain the aramid fabric after alkali washing include: immersing the aramid fabric in an aqueous sodium hydroxide solution (the concentration of sodium hydroxide in the aqueous sodium hydroxide solution is 1~3wt%) for 2~10 hours, and then drying it to obtain the aramid fabric after alkali washing.

[0028] In the above technical solution, the polyurethane fabric stab-resistant composite material is prepared by using 250~600mL of viscous liquid per square meter.

[0029] In the above technical solution, the temperature of hot pressing is 55~85℃, the pressure of hot pressing is 1~10Mpa, and the time of hot pressing is 1~15min.

[0030] The polyurethane fabric stab-resistant composite material obtained by the above preparation method.

[0031] The recycling method for the above-mentioned polyurethane fabric stab-resistant composite material includes the following steps:

[0032] Step 1: Immerse the polyurethane fabric stab-resistant composite material in the first solvent until the polyurethane on the polyurethane fabric stab-resistant composite material is completely dissolved to obtain liquid and solid fabric materials. Use the second solvent to ultrasonically clean the solid fabric material and then dry it to constant weight to obtain the recycled aramid fabric. The first solvent is one or a mixture of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, acetone, tetrahydrofuran, chloroform and dichloromethane. The second solvent is anhydrous ethanol or an aqueous ethanol solution with an ethanol concentration ≥80% by volume.

[0033] In step 1, the water is stirred once every 30 to 60 minutes during the soaking process, and each stirring time is 10 to 60 seconds.

[0034] In step 1, the soaking temperature is 30~60℃ and the soaking time is 2~12h.

[0035] In step 1, the drying temperature is 25~85℃.

[0036] In step 1, the ultrasonic cleaning is performed 2 to 5 times.

[0037] Step 2: Heat the liquid at 40~60℃ to concentrate it until the first solvent in the liquid evaporates, and obtain the recovered polyurethane.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] (1) The polyurethane preparation method of the present invention is based on the prepolymer-chain extension method, which designs the specific sequence length and dynamic bond sequence distribution of polyurethane to achieve significant improvement in the mechanical properties and recyclability of polyurethane. Combined with the stability of aramid fibers in aramid fabric, the polyurethane fabric anti-stab composite material can be reprocessed multiple times.

[0040] (2) The present invention adopts a technical method of combining high-performance polyurethane with high-strength fabric (aramid fabric), and fully coats the prepared high-toughness polyurethane onto the aramid fabric. The excellent interfacial interaction between polyurethane and aramid fabric produces a synergistic toughening effect, so that the prepared polyurethane fabric anti-stab composite material has excellent anti-stab effect.

[0041] (3) The polyurethane preparation method of the present invention does not use traditional catalysts such as metal catalysts or photoinitiators, effectively avoiding toxic residues. The preparation process is simple and easy to carry out, and the raw materials are all conventional and readily available materials, which meet the needs of environmental protection and sustainable development and can be adapted to existing polyurethane production processes. Attached Figure Description

[0042] Figure 1The structural formulas of the polyurethanes in Examples 1-5 of this invention are shown below;

[0043] Figure 2 The tensile stress-strain diagrams are for the polyurethane elastomers of Examples 1-5 and Comparative Example 1 of this invention.

[0044] Figure 3 The diagram shows the anti-puncture performance of the polyurethane fabric anti-puncture composite material of Examples 1-5 of the present invention, the polyurethane coated anti-puncture composite fabric of Comparative Example 1, and the aramid material of Comparative Example 2.

[0045] Figure 4 The figures show the stab resistance performance of the polyurethane fabric stab-resistant composite material of Examples 1-5 of the present invention, the polyurethane coated stab-resistant composite fabric of Comparative Example 1, and the aramid material of Comparative Example 2.

[0046] Figure 5 Fourier transform infrared (FT-IR) spectra of the recycled aramid fabric obtained from cyclic testing (n=5) of the aramid material of Comparative Example 2 and the polyurethane fabric stab-resistant composite material of Example 2.

[0047] Figure 6 Fourier transform infrared (FT-IR) spectra of the recovered polyurethane fabric stab-resistant composite material obtained from cyclic testing (n=5) of the polyurethane fabric stab-resistant composite material of Example 2 and Example 2.

[0048] Figure 7 The diagram shows the results of the anti-piercing performance of the polyurethane fabric stab-resistant composite material of Example 2 without cyclic testing. "1st" shows the results of the anti-piercing performance of the recovered polyurethane fabric stab-resistant composite material obtained after cyclic testing (i=1) of the polyurethane fabric stab-resistant composite material of Example 2. "2nd" shows the results of the anti-piercing performance of the recovered polyurethane fabric stab-resistant composite material obtained after cyclic testing (i=2) of the polyurethane fabric stab-resistant composite material of Example 2. "3rd" shows the results of the anti-piercing performance of the recovered polyurethane fabric stab-resistant composite material obtained after cyclic testing (i=3) of the polyurethane fabric stab-resistant composite material of Example 2. "4th" shows the results of the anti-piercing performance of the recovered polyurethane fabric stab-resistant composite material obtained after cyclic testing (i=4) of the polyurethane fabric stab-resistant composite material of Example 2. "5th" shows the results of the anti-piercing performance of the recovered polyurethane fabric stab-resistant composite material obtained after cyclic testing (i=5) of the polyurethane fabric stab-resistant composite material of Example 2.

[0049] Figure 8 This is a schematic diagram of the puncture head. Figure 8 The cone tip is on the left side of the center, and the blade tip is on the right side. Detailed Implementation

[0050] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0051] The aramid fabric used in the following examples (weight: 200 g / m², thickness: 0.32 mm, warp and weft density: 60 yarns / 10 cm, yarn fineness: 1500 denier) was purchased from Yixing Zhongtan Technology Co., Ltd.

[0052] The reagents used in the following examples have the following sources and purities:

[0053] Polytetrahydrofuran (PTMEG, Mn≈1000), isophorone diisocyanate (IPDI, 99%), dibutyltin dilaurate (DBTDL, 98%), adipic acid dihydrazide (AD, 98%) and dimethylglyoxime (DMG, 98%) were all purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0054] Sodium hydroxide (96%), N,N-dimethylformamide (DMF, AR) and anhydrous ethanol (99%) were purchased from Tianjin Jiangtian Chemical Technology Co., Ltd.

[0055] In the following examples, the concentration of sodium hydroxide in the sodium hydroxide aqueous solution is 1 wt%.

[0056] Example 1 (for comparison)

[0057] A method for preparing a polyurethane fabric stab-resistant composite material includes: immersing an aramid fabric that has been alkali-washed in a viscous liquid containing polyurethane for 1 minute, then removing it, uniformly coating it with the viscous liquid containing polyurethane, hot-pressing it at 60°C and 3 MPa for 10 minutes, and air-drying it to obtain the polyurethane fabric stab-resistant composite material. The polyurethane fabric stab-resistant composite material is prepared by using 300 mL of viscous liquid per square meter.

[0058] The steps for obtaining the alkaline-washed aramid fabric include: immersing the aramid fabric in a sodium hydroxide aqueous solution for 3 hours and then drying it to obtain the alkaline-washed aramid fabric.

[0059] The method for preparing a viscous liquid containing polyurethane includes the following steps:

[0060] Step 1): Under a nitrogen atmosphere, 10 mmol of polytetrahydrofuran was injected into a four-necked flask equipped with a mechanical stirrer. The stirring speed was set to 150 rpm, and the mixture was heated at 120°C for 1 hour to remove moisture, resulting in dehydrated polytetrahydrofuran. The dehydrated polytetrahydrofuran was then cooled to 80°C and stirred for 1 hour. Under continuous stirring, dibutyltin dilaurate was added as a catalyst and stirred for 2 hours to obtain the first reaction system. The molar ratio of polytetrahydrofuran to dibutyltin dilaurate was 25:1. The molar ratio is expressed in mmol, and the volume ratio is expressed in mL.

[0061] Step 2): Adipate dihydrazide and dimethylglyoxime were used as chain extenders. Isophorone diisocyanate and the chain extenders were uniformly dispersed in N,N-dimethylformamide to obtain a mixed solution. The ratio of isophorone diisocyanate, adipate dihydrazide, and dimethylglyoxime was 4:1:1 by molar amount. The stirring speed was adjusted to 200 rpm, and the mixed solution was added dropwise to the first reaction system. The polymerization reaction was carried out at 60°C for 12 h to obtain a viscous liquid containing polyurethane. The ratio of polytetrahydrofuran in the first reaction system to dimethylglyoxime in the mixed solution was 2:1 by molar amount. The molar amount of dimethylglyoxime and the volume amount of N,N-dimethylformamide were 4:11. The units of molar amount are mmol and the units of volume amount are mL. The structural formula of the obtained polyurethane is as follows: Figure 1 As shown, n1∶m1∶n2∶m2=1∶1∶1∶1.

[0062] Examples 2-5

[0063] A method for preparing a polyurethane fabric stab-resistant composite material includes: immersing an aramid fabric that has been alkali-washed in a viscous liquid containing polyurethane for 1 minute, then removing it, uniformly coating it with the viscous liquid containing polyurethane, hot-pressing it at 70°C and 3 MPa for 6 minutes, and then air-drying it to obtain the polyurethane fabric stab-resistant composite material. The polyurethane fabric stab-resistant composite material is prepared by using 400 mL of viscous liquid per square meter.

[0064] The steps for obtaining the alkaline-washed aramid fabric include: immersing the aramid fabric in a sodium hydroxide aqueous solution for 3 hours and then drying it to obtain the alkaline-washed aramid fabric.

[0065] The method for preparing a viscous liquid containing polyurethane includes the following steps:

[0066] Step 1): Under a nitrogen atmosphere, polytetrahydrofuran was injected into a four-necked flask equipped with a mechanical stirrer. The stirring speed was set to 150 rpm, and the mixture was heated at 120°C for 1 hour to remove moisture, resulting in dehydrated polytetrahydrofuran. The first reactant and the dehydrated polytetrahydrofuran were mixed and stirred at 80°C for 1 hour. Then, dibutyltin dilaurate was added as a catalyst and stirred for 2 hours to obtain a viscous solution as the first reaction system. The ratio of the molar amount of polytetrahydrofuran, the molar amount of the first reactant, and the volume amount of dibutyltin dilaurate is X, where the molar amount is in mmol and the volume amount is in mL. The first reactant is isophorone diisocyanate, and the amount of dibutyltin dilaurate added is 0.4 mL.

[0067] Step 2): Adipate dihydrazide and dimethylglyoxime are used as chain extenders. The second reactant and the chain extender are uniformly dispersed in N,N-dimethylformamide to obtain a mixed solution. The ratio of the second reactant, adipate dihydrazide, and dimethylglyoxime is Y, by molar amount. The stirring speed is adjusted to 200 rpm, and the mixed solution is added dropwise to the first reaction system. The polymerization reaction is carried out at 60°C for 15 h to obtain a viscous liquid containing polyurethane. The second reactant is isophorone diisocyanate. The ratio of polytetrahydrofuran in the first reaction system to dimethylglyoxime in the mixed solution is Z, by molar amount. The ratio of the molar amount of dimethylglyoxime to the volume amount of N,N-dimethylformamide is T. The molar amount is expressed in mmol, and the volume amount is expressed in mL. The structural formula of the obtained polyurethane is as follows: Figure 1 As shown, n1∶m1∶n2∶m2=K.

[0068] The values ​​of X, Y, Z, T, and K are shown in Table 1.

[0069] Table 1

[0070] Comparative Example 1

[0071] A method for preparing a polyurethane-coated stab-resistant composite fabric includes: immersing an aramid fabric after alkali washing in a viscous liquid containing polyurethane for 1 minute, then removing it, uniformly coating it with the viscous liquid containing polyurethane, hot-pressing it at 60°C and 3 MPa for 10 minutes, and air-drying it naturally to obtain a polyurethane-coated stab-resistant composite material. The polyurethane-coated stab-resistant composite fabric is prepared by using 300 mL of viscous liquid per square meter.

[0072] The steps for obtaining the alkaline-washed aramid fabric include: immersing the aramid fabric in a sodium hydroxide aqueous solution for 3 hours and then drying it to obtain the alkaline-washed aramid fabric.

[0073] The method for preparing a viscous liquid containing polyurethane includes the following steps:

[0074] Step 1): Under a nitrogen atmosphere, 10 mmol of polytetrahydrofuran was injected into a four-necked flask equipped with a mechanical stirrer. The stirring speed was set to 200 rpm, and the mixture was heated at 120°C for 1 h to remove moisture, resulting in dehydrated polytetrahydrofuran. Isophorone diisocyanate and dehydrated polytetrahydrofuran were mixed and stirred at 80°C for 1 h. Then, dibutyltin dilaurate was added as a catalyst and stirred for 2 h to obtain a viscous solution as the first reaction system. The molar ratio of polytetrahydrofuran, the molar ratio of isophorone diisocyanate, and the volume ratio of dibutyltin dilaurate was 10:25:0.4. The molar ratio is in mmol, and the volume ratio is in mL.

[0075] Step 2): Adipate dihydrazide and dimethylglyoxime are used as chain extenders. The chain extenders are uniformly dispersed in N,N-dimethylformamide to obtain a mixed solution. The ratio of adipate dihydrazide to dimethylglyoxime is 5:10 by molar amount. The mixed solution is added dropwise to the first reaction system, and the polymerization reaction is carried out at 60°C for 12 hours to obtain a viscous liquid containing polyurethane. The ratio of polytetrahydrofuran in the first reaction system to dimethylglyoxime in the mixed solution is 10:10 by molar amount. The ratio of the molar amount of dimethylglyoxime to the volume amount of N,N-dimethylformamide is 3:7. The molar amount is expressed in mmol, and the volume amount is expressed in mL.

[0076] Comparative Example 2

[0077] Aramid fabric (10cm*10cm) purchased from Yixing Zhongtan Technology Co., Ltd. was immersed in sodium hydroxide aqueous solution for 3 hours, hot-pressed at 60℃ and 3Mpa for 10 minutes, and then naturally dried to obtain aramid material as comparative example 2.

[0078] The viscous liquids containing polyurethane from Examples 1-5 and Comparative Example 1 were vacuum dried at 60°C for 12 hours to obtain polyurethane elastomers. The tensile stress-strain properties of the polyurethane elastomers were tested according to the method in GB / T 528-2009. The polyurethane elastomers were elongated strips (approximately 30mm × 10mm × 7mm in size). Tensile tests were conducted at a constant rate of 50mm / min at room temperature. The experimental results are as follows: Figure 2 As shown. By Figure 2It is evident that, through the design of specific block sequence lengths, the mechanical properties of the polyurethane elastomers in Examples 2-4 are significantly superior to those in Examples 1 and Comparative Example 1. In particular, the polyurethane elastomer in Example 2 exhibits an elongation at break exceeding 1300% and a tensile strength exceeding 30 MPa. This demonstrates that the present invention effectively enhances the strength and toughness of polyurethane through a specific block sequence distribution design, providing support for improving the puncture resistance of the prepared polyurethane fabric puncture-resistant composite material.

[0079] The polyurethane fabric puncture-resistant composite materials obtained in Examples 1-5, the polyurethane-coated puncture-resistant composite fabric of Comparative Example 1, and the aramid material of Comparative Example 2 were used as samples. A quasi-static puncture resistance test was performed on each sample using a HT-2402 universal tensile testing machine from Taiwan Hongda Instrument Co., Ltd., according to the method of EN 388:2016. The puncture rate was 100 mm / min, and the sample size was 100 mm × 100 mm. The puncture head was a conical or blade-like tip (e.g., ...). Figure 8 As shown, Figure 8 The cone tip is located to the left of the center, and the blade tip is located to the right. The cone force is obtained from the cone tip, and the blade force is obtained from the blade tip. Each group of samples was tested five times during the experiment, and the average value was taken. The experimental results are as follows: Figures 3-4 As shown in Table 2.

[0080] Table 2

[0081] As shown in Table 2, the aramid material of Comparative Example 2 and the polyurethane-coated anti-stab composite fabric of Comparative Example 1 have poor anti-stab performance, while the polyurethane fabric anti-stab composite materials prepared in Examples 2-5 of this invention have high adhesion between the polyurethane and the aramid fabric after alkali washing, and have good anti-stab effect.

[0082] Example 6

[0083] Perform a cyclic test by repeating the following steps n times to obtain a polyurethane fabric stab-resistant composite material that has undergone n cycles: each time, perform the following "Recycling Method of Polyurethane Fabric Stab-Resistant Composite Material" once, and then perform the following "Preparation Method of Recycled Polyurethane Fabric Stab-Resistant Composite Material" once.

[0084] The recycling method for polyurethane fabric stab-resistant composite materials includes the following steps:

[0085] Step 1: Immerse the polyurethane fabric stab-resistant composite material in a first solvent at 60°C for 3 hours. During the immersion process, stir every 30 minutes, gently stirring with a glass rod for 30 seconds each time, until the polyurethane on the polyurethane fabric stab-resistant composite material is completely dissolved, obtaining liquid and solid fabric materials. Use a second solvent to ultrasonically clean the solid fabric material 3 times, and then dry it at 60°C to constant weight to obtain the recovered aramid fabric. The first solvent is N,N-dimethylformamide, and the second solvent is anhydrous ethanol.

[0086] Step 2: Heat and concentrate the liquid from Step 1 at 50°C for 4 hours until the first solvent (N,N-dimethylformamide) in the liquid evaporates, and the recovered polyurethane is obtained.

[0087] The preparation method of the recycled polyurethane fabric stab-resistant composite material includes: diluting the recycled polyurethane to 4 mL with N,N-dimethylformamide, stirring at 200 rpm for 6 h to obtain a viscous liquid, immersing the recycled aramid fabric in the viscous liquid for 1 min and then taking it out, uniformly scraping the viscous liquid, hot-pressing it at 60℃ and 3 MPa for 10 min, and then air-drying it to obtain the recycled polyurethane fabric stab-resistant composite material.

[0088] When the "Recycling Method of Polyurethane Fabric Puncture-Resistant Composite Material" was executed for the first time in the cyclic test, the polyurethane fabric puncture-resistant composite material used was the polyurethane fabric puncture-resistant composite material of Example 2 that had undergone the above-mentioned "Quasi-Static Puncture Resistance Test".

[0089] The FT-IR spectra of the aramid material in Comparative Example 2 and the recovered aramid fabric from n repeated operations (n=5) were detected using a Fourier transform infrared spectroscopy (FT-IR) instrument. The results are as follows: Figure 5 As shown. By Figure 5 It can be seen that the structure of the recycled aramid fabric did not undergo significant changes.

[0090] The FT-IR spectra of the polyurethane fabric stab-resistant composite material of Example 2 and the recovered polyurethane fabric stab-resistant composite material from n repeated operations (n=5) were detected using Fourier transform infrared spectroscopy. The results are as follows: Figure 6 As shown. By Figure 6 It can be seen that the structure of the recycled polyurethane fabric stab-resistant composite material did not undergo significant changes.

[0091] In the aforementioned cyclic test, after each repetition, a "quasi-static puncture resistance test" was performed on the recovered polyurethane fabric puncture-resistant composite material. The puncture head was a cone. When the cyclic test was repeated 5 times, the stress-strain curves obtained after each repetition were as follows: Figure 7 As shown in Table 3, the cone force values ​​are as follows. The cone force loss rate for each repeated operation is calculated using the following formula:

[0092]

[0093] Among them, F i (N) is the cone puncture force value of the recovered polyurethane fabric puncture-resistant composite material obtained when repeating the operation for the i-th time, i = 1 to 5, and F0(N) is the cone puncture force value of the polyurethane fabric puncture-resistant composite material of Example 2, F0 = 320.7N.

[0094] Table 3

[0095] Depend on Figure 7 As shown in Table 3, the polyurethane fabric stab-resistant composite material prepared in Example 2 of the present invention has a certain degree of recyclability.

[0096] Comparative Example 3

[0097] When the polyurethane-coated stab-resistant composite fabric of Comparative Example 1, which has completed the "quasi-static puncture resistance test", is used to perform the "cyclic test" of Example 6, the recovery rate of the recovered polyurethane is less than 50%, that is, the recovery rate is low. When the "preparation method of the recovered polyurethane fabric stab-resistant composite material" in the "cyclic test" is continued, the polyurethane on the recovered polyurethane fabric stab-resistant composite material is relatively thin and cannot achieve the stab-resistant performance of the technical solution of the present invention.

[0098] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing polyurethane, characterized in that, The structural formula of polyurethane is: ， in, for , for , for , for n1∶m1∶n2∶m2=(1~10)∶(1~12)∶(1~10)∶(1~12); The preparation method of polyurethane includes the following steps: Step 1) Mix the first reactant with the dehydrated polytetrahydrofuran (PTMEG) and stir for 0.5-3 hours. Then add dibutyltin dilaurate and stir for 2-4 hours to obtain the first reaction system. The molar ratio of PTMEG, the first reactant and the dibutyltin dilaurate is 10:5:0.

4. The molar ratio is in mmol and the volume ratio is in mL. The first reactant is isophorone diisocyanate. Step 2): Adipate dihydrazide and dimethylglyoxime are used as chain extenders. The second reactant and the chain extender are uniformly dispersed in N,N-dimethylformamide to obtain a mixed solution. The ratio of the second reactant, adipate dihydrazide, and dimethylglyoxime by molar amount is 30:15:

10. Under stirring, the mixed solution is added dropwise to the first reaction system to carry out the polymerization reaction and obtain a viscous liquid containing polyurethane. The ratio of polytetrahydrofuran (PTMEG) in the first reaction system to dimethylglyoxime in the mixed solution by molar amount is 10:

10. The second reactant is isophorone diisocyanate. The Mn of polytetrahydrofuran (PTMEG) is 1000.

2. A method for preparing polyurethane, characterized in that, The structural formula of polyurethane is: ， in, for , for , for , for n1∶m1∶n2∶m2=(1~10)∶(1~12)∶(1~10)∶(1~12); The preparation method of polyurethane includes the following steps: Step 1) Mix the first reactant with the dehydrated polytetrahydrofuran (PTMEG) and stir for 0.5-3 hours. Then add dibutyltin dilaurate and stir for 2-4 hours to obtain the first reaction system. The molar ratio of PTMEG, the first reactant, and the dibutyltin dilaurate is 15:10:0.

4. The molar ratio is in mmol and the volume ratio is in mL. The first reactant is isophorone diisocyanate. Step 2): Adipate dihydrazide and dimethylglyoxime are used as chain extenders. The second reactant and the chain extender are uniformly dispersed in N,N-dimethylformamide to obtain a mixed solution. The ratio of the second reactant, adipate dihydrazide, and dimethylglyoxime by molar amount is 40:15:

10. Under stirring, the mixed solution is added dropwise to the first reaction system to carry out the polymerization reaction and obtain a viscous liquid containing polyurethane. The ratio of polytetrahydrofuran (PTMEG) in the first reaction system to dimethylglyoxime in the mixed solution by molar amount is 15:

10. The second reactant is isophorone diisocyanate. The Mn of polytetrahydrofuran (PTMEG) is 1000.

3. A method for preparing polyurethane, characterized in that, The structural formula of polyurethane is: ， in, for , for , for , for n1∶m1∶n2∶m2=(1~10)∶(1~12)∶(1~10)∶(1~12); The preparation method of polyurethane includes the following steps: Step 1) Mix the first reactant with the dehydrated polytetrahydrofuran (PTMEG) and stir for 0.5-3 hours. Then add dibutyltin dilaurate and stir for 2-4 hours to obtain the first reaction system. The molar ratio of PTMEG, the first reactant, and the dibutyltin dilaurate is 12:8:0.

4. The molar ratio is in mmol and the volume ratio is in mL. The first reactant is isophorone diisocyanate. Step 2): Adipate dihydrazide and dimethylglyoxime are used as chain extenders. The second reactant and the chain extender are uniformly dispersed in N,N-dimethylformamide to obtain a mixed solution. The ratio of the second reactant, adipate dihydrazide, and dimethylglyoxime by molar amount is 42:26:

13. Under stirring, the mixed solution is added dropwise to the first reaction system to carry out the polymerization reaction, resulting in a viscous liquid containing polyurethane. The ratio of polytetrahydrofuran (PTMEG) in the first reaction system to dimethylglyoxime in the mixed solution by molar amount is 12:

13. The second reactant is isophorone diisocyanate. The Mn of polytetrahydrofuran (PTMEG) is 1000.

4. A method for preparing polyurethane, characterized in that, The structural formula of polyurethane is: ， in, for , for , for , for n1∶m1∶n2∶m2=(1~10)∶(1~12)∶(1~10)∶(1~12); The preparation method of polyurethane includes the following steps: Step 1) Mix the first reactant with the dehydrated polytetrahydrofuran (PTMEG) and stir for 0.5-3 hours. Then add dibutyltin dilaurate and stir for 2-4 hours to obtain the first reaction system. The molar ratio of PTMEG, the first reactant, and the dibutyltin dilaurate is 10:8:0.

4. The molar ratio is in mmol and the volume ratio is in mL. The first reactant is isophorone diisocyanate. Step 2): Adipate dihydrazide and dimethylglyoxime are used as chain extenders. The second reactant and the chain extender are uniformly dispersed in N,N-dimethylformamide to obtain a mixed solution. The ratio of the second reactant, adipate dihydrazide, and dimethylglyoxime by molar amount is 35:21:

16. Under stirring, the mixed solution is added dropwise to the first reaction system to carry out the polymerization reaction and obtain a viscous liquid containing polyurethane. The ratio of polytetrahydrofuran (PTMEG) in the first reaction system to dimethylglyoxime in the mixed solution by molar amount is 10:

16. The second reactant is isophorone diisocyanate. The Mn of polytetrahydrofuran (PTMEG) is 1000.

5. The preparation method according to any one of claims 1 to 4, characterized in that, In step 1), polytetrahydrofuran (PTMEG) is heated at 100-140°C for 1-3 hours under a nitrogen atmosphere to remove moisture, thereby obtaining polytetrahydrofuran (PTMEG) after moisture removal.

6. The preparation method according to any one of claims 1 to 4, characterized in that, In step 1), the stirring speed is 100~400 rpm and the stirring temperature is 70~90℃.

7. The preparation method according to any one of claims 1 to 4, characterized in that, In step 2), the ratio of the molar amount of dimethylglyoxime to the volume amount of N,N-dimethylformamide is (2~12):(5~50), where the molar amount is in mmol and the volume amount is in mL.

8. The preparation method according to any one of claims 1 to 4, characterized in that, In step 2), the polymerization temperature is 50~70℃ and the polymerization time is 10~18h.

9. A method for preparing a polyurethane fabric stab-resistant composite material, characterized in that, include: After alkali washing, the aramid fabric is immersed in a viscous liquid containing polyurethane obtained by the polyurethane preparation method according to any one of claims 1 to 4 for 1 to 10 minutes, then removed and uniformly coated with the viscous liquid, followed by hot pressing to obtain a polyurethane fabric stab-resistant composite material. The polyurethane fabric stab-resistant composite material is prepared by using 250 to 600 mL of viscous liquid per square meter.

10. The preparation method according to claim 9, characterized in that, The hot pressing temperature is 55~85℃, the hot pressing pressure is 1~10Mpa, and the hot pressing time is 1~15min.

11. A method for recycling a polyurethane fabric stab-resistant composite material, characterized in that, Includes the following steps: Step 1: Immerse the polyurethane fabric stab-resistant composite material obtained by the preparation method of claim 9 in the first solvent until the polyurethane on the polyurethane fabric stab-resistant composite material is completely dissolved to obtain liquid and solid fabric materials. Use the second solvent to ultrasonically clean the solid fabric material and then dry it to constant weight to obtain the recovered aramid fabric. The first solvent is one or a mixture of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, acetone, tetrahydrofuran, chloroform and dichloromethane, and the second solvent is anhydrous ethanol or an aqueous solution of ethanol. Step 2: Heat the liquid at 40~60℃ to concentrate it until the first solvent in the liquid evaporates, and obtain the recovered polyurethane.

12. The application of a viscous liquid containing polyurethane obtained by the polyurethane preparation method according to any one of claims 1 to 4 in improving the puncture resistance of materials.

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