Polyurethane hot melt adhesive for filter element and preparation method thereof

Abstract

The present application discloses a polyurethane hot melt adhesive for a filter element and a preparation method thereof, and relates to the field of hot melt adhesives. The polyurethane hot melt adhesive comprises a polymeric diol, a diisocyanate, a chain extender, a catalyst and an antioxidant in a weight ratio of (80-90): (25-30): (1.5-1.8): (0.1-0.2): (0.05-0.07), wherein the polymeric diol comprises 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol, polytetrahydrofuran ether diol and polycarbonate diol in a weight ratio of (4-6): (2-3): (2-3). The polyurethane hot melt adhesive of the present application has the characteristics of good solvent resistance, good acid and alkali resistance and good resistance to cyclic high and low temperature changes, and at the same time has high bonding strength to the substrate, so that the polyurethane hot melt adhesive can be used in complex and changeable environments.

Description

Technical Field

[0001] The present application relates to the field of hot melt adhesives, and in particular to a polyurethane hot melt adhesive and a preparation method thereof. The polyurethane hot melt adhesive can be used for a filter element. Background Art

[0002] Polyurethane hot melt adhesive is widely used in many fields due to its excellent flexibility and good bonding strength. Filter elements may be exposed to various solvents during use and need to maintain stable performance over a wide temperature range. However, traditional polyurethane hot melt adhesives have limitations in solvent resistance, acid and alkali resistance, and resistance to cyclic high and low temperature changes, which restricts its application in certain special environments. Therefore, it is of great significance to improve the solvent resistance, acid and alkali resistance, and resistance to cyclic high and low temperature changes of polyurethane hot melt adhesives to broaden the application areas of polyurethane hot melt adhesives. Summary of the invention

[0003] In order to improve the problems of poor solvent resistance, acid and alkali resistance, and resistance to cyclic high and low temperature changes of polyurethane hot melt adhesives in the related art, the present application provides a polyurethane hot melt adhesive and a preparation method thereof.

[0004] In the first aspect, the polyurethane hot melt adhesive provided in the present application adopts the following technical solution:

[0005] A polyurethane hot melt adhesive comprises a polymeric diol, a diisocyanate, a chain extender, a catalyst and an antioxidant, wherein the weight ratio of the polymeric diol, the diisocyanate, the chain extender, the catalyst and the antioxidant is (80-90):(25-30):(1.5-1.8):(0.1-0.2):(0.05-0.07), wherein the polymeric diol comprises 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol, polytetramethylene ether glycol and polycarbonate diol, and the weight ratio of the 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol, polytetramethylene ether glycol and polycarbonate diol is (4-6):(2-3):(2-3).

[0006] The present application adopts (3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol, polytetramethylene glycol and polycarbonate diol in combination with diisocyanate to prepare a polyurethane hot melt adhesive, wherein, on the basis of polytetramethylene glycol and polycarbonate diol, an appropriate amount of 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol is introduced, which can effectively improve the solvent resistance, acid and alkali resistance and cyclic high and low temperature change resistance of the polyurethane hot melt adhesive, and at the same time, it can also improve the bonding strength of the polyurethane hot melt adhesive to the substrate, so that the polyurethane hot melt adhesive can be used in complex and changeable environments.

[0007] In some specific embodiments, the raw materials for preparing the 3-(4-fluorophenyl)ethyl acrylate grafted polyether diol include 3-(4-fluorophenyl)ethyl acrylate, polypropylene glycol, a chain transfer agent and an initiator, and the weight ratio of the 3-(4-fluorophenyl)ethyl acrylate, polypropylene glycol, the chain transfer agent and the initiator is (0.02-0.04):10:(0.01-0.02):(0.01-0.02).

[0008] In the present application, 3-(4-fluorophenyl)ethyl acrylate grafted polyether diol is prepared by reacting 3-(4-fluorophenyl)ethyl acrylate, polypropylene glycol, a chain transfer agent and an initiator in a weight ratio of (0.02-0.04):10:(0.01-0.02):(0.01-0.02). By controlling the appropriate 3-(4-fluorophenyl)ethyl acrylate grafting rate, the polyurethane hot melt adhesive maintains good uniform coating properties after melting, which is beneficial to further improve the bonding strength, solvent resistance, acid and alkali resistance and other properties of the polyurethane hot melt adhesive to the substrate.

[0009] In some specific embodiments, the viscosity of the polypropylene glycol is 500-600 mPa.s.

[0010] In the present application, the viscosity of the polypropylene glycol used in the 3-(4-fluorophenyl)ethyl acrylate grafted polyether diol is controlled within the range of 500-600mPa.s, which can enable the polyurethane hot melt adhesive to maintain good uniform coating properties after melting, and is beneficial to further improve the bonding strength, solvent resistance, acid and alkali resistance and other properties of the polyurethane hot melt adhesive to the substrate.

[0011] In some specific embodiments, the chain transfer agent is at least one of n-octyl mercaptan, n-dodecyl mercaptan, tert-dodecyl mercaptan, and thioglycolic acid, and the initiator is an azo initiator.

[0012] In some specific embodiments, the molecular weight of the polytetramethylene ether diol is 1000-2000, and the molecular weight of the polycarbonate diol is 1000-1500.

[0013] In the present application, the molecular weight of polytetramethylene ether diol and polycarbonate diol is preferably controlled within the above range, which is beneficial to improving the resistance of the polyurethane hot melt adhesive to cyclic high and low temperature changes.

[0014] In some specific embodiments, the diisocyanate is at least one of isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, and diphenylmethane diisocyanate.

[0015] In some specific embodiments, the chain extender includes a linear glycol and a branched glycol, and the weight ratio of the linear glycol to the branched glycol is 1:(1-1.5).

[0016] In the present application, the chain extender is preferably a composition in which the weight ratio of straight-chain glycol to branched glycol is 1: (1-1.5), which is beneficial to improve the wettability of the polyurethane hot melt adhesive to the substrate, further enhance the bonding strength between the polyurethane hot melt adhesive and the substrate, while taking into account good resistance to cyclic high and low temperature changes.

[0017] In some specific embodiments, the straight-chain diol is at least one of ethylene glycol, 1,3-propylene glycol, and 1,4-butanediol, and the branched diol is at least one of 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,4-dimethyl-1,5-pentanediol, and neopentyl glycol.

[0018] In some specific embodiments, the antioxidant is at least one of antioxidant 1010 and antioxidant 1076, and the catalyst is at least one of dibutyltin dilaurate, 2,2-dimorpholinyl diethyl ether, and stannous octoate.

[0019] In a second aspect, the present application provides a method for preparing a polyurethane hot melt adhesive using the following technical solution:

[0020] A method for preparing a polyurethane hot melt adhesive comprises the following steps:

[0021] 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol, polytetramethylene glycol, polycarbonate diol and antioxidant are dehydrated and mixed, and then diisocyanate is added, and the temperature is raised to 75-90°C, and the vacuum degree is maintained at -0.04MPa to -0.08MPa. After reacting for 3-4h, a chain extender and a catalyst are added, and the reaction is continued at 75-90°C for 1-1.5h before discharging to obtain a polyurethane hot melt adhesive.

[0022] In the present application, the above method is used to prepare polyurethane hot melt adhesive, which is conducive to obtaining a polyurethane hot melt adhesive with good solvent resistance, good acid and alkali resistance, and good resistance to cyclic high and low temperature changes. At the same time, it can also improve the bonding strength of the polyurethane hot melt adhesive to the substrate, so that the polyurethane hot melt adhesive can be used in complex and changeable environments.

[0023] In summary, this application at least includes the following beneficial technical effects:

[0024] (1) The present application adopts (3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol, polytetramethylene glycol and polycarbonate diol in combination with diisocyanate to prepare a polyurethane hot melt adhesive. In particular, on the basis of polytetramethylene glycol and polycarbonate diol, an appropriate amount of 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol is introduced, which can effectively improve the solvent resistance, acid and alkali resistance and cyclic high and low temperature resistance of the polyurethane hot melt adhesive, and at the same time, it can also improve the bonding strength of the polyurethane hot melt adhesive to the substrate, so that the polyurethane hot melt adhesive can be used in complex and changeable environments.

[0025] (2) In the present application, the chain extender is preferably a composition in which the weight ratio of straight-chain diol to branched diol is 1: (1-1.5), which is beneficial to improve the wettability of the polyurethane hot melt adhesive to the substrate, further enhance the bonding strength between the polyurethane hot melt adhesive and the substrate, while taking into account good resistance to cyclic high and low temperature changes. DETAILED DESCRIPTION

[0026] The present application is further described below through specific examples and comparative examples. However, it should be noted that the specific material ratios, process conditions and results described in the embodiments of the present invention are only used to illustrate the present invention and cannot be used to limit the scope of protection of the present invention.

[0027] Preparation Example

[0028] [Preparation Example 1]

[0029] A 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol comprises 0.02 kg of 3-(4-fluorophenyl)ethyl acrylate, 10 kg of polypropylene glycol with a viscosity of 520 mPa.s, 0.01 kg of n-dodecyl mercaptan, 0.01 kg of azobisisobutyronitrile and 10 kg of tetrahydrofuran.

[0030] 1. The preparation method of (4-fluorophenyl) ethyl acrylate grafted polypropylene glycol comprises the following steps:

[0031] Ethyl 3-(4-fluorophenyl)acrylate was dissolved in tetrahydrofuran, and then polypropylene glycol, n-dodecyl mercaptan and azobisisobutyronitrile were added, stirred evenly, and heated to 125°C under nitrogen protection. After reacting for 2.5 hours, the residual monomer and tetrahydrofuran were removed by reduced pressure distillation to obtain ethyl 3-(4-fluorophenyl)acrylate.

[0032] [Preparation Example 2]

[0033] A 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol comprises 0.04 kg of 3-(4-fluorophenyl)ethyl acrylate, 10 kg of polypropylene glycol with a viscosity of 600 mPa.s, 0.02 kg of n-dodecyl mercaptan, 0.02 kg of azobisisobutyronitrile and 10 kg of tetrahydrofuran.

[0034] The preparation method of 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol comprises the following steps:

[0035] Ethyl 3-(4-fluorophenyl)acrylate was dissolved in tetrahydrofuran, and then polypropylene glycol, n-dodecyl mercaptan and azobisisobutyronitrile were added, stirred evenly, and heated to 130°C under nitrogen protection. After reacting for 2.0 hours, the residual monomers and tetrahydrofuran were removed by reduced pressure distillation to obtain ethyl 3-(4-fluorophenyl)acrylate.

[0036] [Preparation Example 3]

[0037] A 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol, which is different from [Preparation Example 2] in that the amount of 3-(4-fluorophenyl)ethyl acrylate used is 0.08 kg.

[0038] [Preparation Example 4]

[0039] A 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol, which is different from [Preparation Example 2] in that the viscosity of the polypropylene glycol is 800 mPa.s.

[0040] [Preparation Example 5]

[0041] A styrene-grafted polypropylene glycol, which differs from [Preparation Example 1] in that 3-(4-fluorophenyl)ethyl acrylate is replaced by an equal amount of styrene.

[0042] Example

[0043] [Example 1]

[0044] A polyurethane hot melt adhesive comprises 80 kg of polymerized diol, 25 kg of isophorone diisocyanate, 1.5 kg of 1,4-butanediol, 0.1 kg of dibutyltin dilaurate and 0.05 kg of antioxidant 1010, wherein the polymerized diol comprises 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol, polytetramethylene ether glycol and polycarbonate diol, and the weight ratio of 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol, polytetramethylene ether glycol and polycarbonate diol is 4:3:3.

[0045] In this embodiment, 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol is 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol prepared in [Preparation Example 1], polytetramethylene ether diol is polytetramethylene ether diol with a molecular weight of 2000 produced by BASF Mitsubishi, and polycarbonate diol is polycarbonate diol with a molecular weight of 1000 produced by Asahi Chemical Industry of Japan.

[0046] In addition, the preparation method of the polyurethane hot melt adhesive comprises the following steps:

[0047] 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol, polytetramethylene glycol, polycarbonate diol and antioxidant 1010 are dehydrated and mixed, and then isophorone diisocyanate is added, the temperature is raised to 75°C, and the vacuum degree is maintained at -0.04 MPa. After reacting for 4 hours, the vacuuming is stopped, 1,4-butanediol and dibutyltin dilaurate are added, and the reaction is continued at 75°C for 1.5 hours before discharging the material to obtain a polyurethane hot melt adhesive.

[0048] [Example 2]

[0049] A polyurethane hot melt adhesive comprises 90kg of polymerized diol, 30kg of diphenylmethane diisocyanate, 1.8kg of 1,3-propylene glycol, 0.2kg of dibutyltin dilaurate and 0.07kg of antioxidant 1076, wherein the polymerized diol comprises 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol, polytetramethylene ether glycol and polycarbonate diol, and the weight ratio of 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol, polytetramethylene ether glycol and polycarbonate diol is 6:2:2.

[0050] In this embodiment, 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol is 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol prepared in [Preparation Example 2], polytetramethylene ether diol is polytetramethylene ether diol with a molecular weight of 1000 produced by BASF Mitsubishi, and polycarbonate diol is polycarbonate diol with a molecular weight of 2000 produced by Asahi Chemical Industry of Japan.

[0051] In addition, the preparation method of the polyurethane hot melt adhesive comprises the following steps:

[0052] 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol, polytetramethylene glycol, polycarbonate diol and antioxidant 1076 are dehydrated and mixed, and then diphenylmethane diisocyanate is added, the temperature is raised to 90°C, and the vacuum degree is maintained at -0.08MPa. After reacting for 3 hours, the vacuuming is stopped, 1,3-propylene glycol and dibutyltin dilaurate are added, and the reaction is continued at 90°C for 1 hour before discharging the material to obtain a polyurethane hot melt adhesive.

[0053] [Example 3]

[0054] A polyurethane hot melt adhesive, which is different from [Example 1] in that: 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol adopts 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol prepared in [Preparation Example 3].

[0055] [Example 4]

[0056] A polyurethane hot melt adhesive, which is different from [Example 1] in that: 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol adopts 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol prepared in [Preparation Example 4].

[0057] [Example 5]

[0058] A polyurethane hot melt adhesive, which differs from [Example 1] in that 1,4-butanediol is replaced by an equal amount of 2-methyl-1,3-propanediol.

[0059] [Example 6]

[0060] A polyurethane hot melt adhesive, which differs from [Example 1] in that: 1,4-butanediol is replaced by a combination of equal amounts of 1,4-butanediol and 2-methyl-1,3-propanediol, with 0.75 kg of 1,4-butanediol and 0.75 kg of 2-methyl-1,3-propanediol.

[0061] Comparative Example

[0062] [Comparative Example 1]

[0063] A polyurethane hot melt adhesive, which differs from [Example 1] in that:

[0064] In this comparative example, 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol was replaced by an equal amount of styrene grafted polypropylene glycol in [Preparation Example 5].

[0065] [Comparative Example 2]

[0066] A polyurethane hot melt adhesive, which differs from [Example 1] in that:

[0067] In this comparative example, polytetramethylene glycol and polycarbonate glycol were replaced by equal amounts of 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol obtained in [Preparation Example 1].

[0068] [Comparative Example 3]

[0069] A polyurethane hot melt adhesive, which differs from [Example 1] in that:

[0070] In this comparative example, polycarbonate diol was replaced by an equal amount of polytetramethylene glycol.

[0071] [Comparative Example 4]

[0072] A polyurethane hot melt adhesive, which differs from [Example 1] in that:

[0073] In this comparative example, polytetramethylene ether diol is replaced by an equal amount of 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol obtained in [Preparation Example 1].

[0074] [Comparative Example 5]

[0075] A polyurethane hot melt adhesive, which differs from [Example 1] in that:

[0076] In this comparative example, the weight ratio of 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol, polytetramethylene ether glycol and polycarbonate diol is 2:5:3.

[0077] Performance testing

[0078] Test 1, tensile shear strength: After the polyurethane hot melt adhesive in each embodiment and comparative example is melted, it is coated between two PP substrates, the bonding surface length is 1.25 cm, the adhesive layer thickness is 0.2 mm, and after standing for 48 hours in an environment with a temperature of 25°C and a humidity of 80%, a test sample is obtained. The tensile shear strength test is performed on the test sample with reference to GB / T 7124-2008, wherein the higher the tensile shear strength, the higher the bonding strength of the polyurethane hot melt adhesive to the substrate.

[0079] Test 2, solvent resistance: Prepare the test sample according to Test 1, then put the test sample into isopropanol, soak it in 25℃ environment for 1000h, take it out, wash it with water, dry it naturally, and then conduct tensile shear strength test on the test sample according to GB / T 7124-2008.

[0080] Test 3, acid and alkali resistance: Prepare the test sample according to Test 1, then put the test sample into a 5% hydrochloric acid solution and a 5% sodium hydroxide solution, soak it at 25°C for 1000h, take it out, wash it with water, dry it naturally, and then conduct tensile shear strength test on the test sample according to GB / T 7124-2008.

[0081] Test 4, resistance to cyclic high and low temperature changes: Prepare the test sample according to Test 1, place the prepared test sample at 85°C for 12 hours, transfer it to -20°C environment and place it for 12 hours, repeat the above high and low temperature cycle treatment steps 30 times, and then perform tensile shear strength test on the test sample according to GB / T 7124-2008.

[0082] Table 1

[0083]

[0084]

[0085] According to Example 1 and Comparative Example 1 and in combination with the test results in Table 1, it can be seen that after 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol is replaced by styrene grafted polypropylene glycol, the solvent resistance, acid and alkali resistance, and cyclic high and low temperature resistance of the polyurethane hot melt adhesive are all reduced, indicating that the use of 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol together with polytetramethylene ether diol and polycarbonate diol as polymerized diols is more conducive to improving the various properties of the polyurethane hot melt adhesive.

[0086] According to Example 1 and Comparative Examples 2-4 and in combination with the test results in Table 1, it can be seen that when 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol is used alone as a polymeric diol to react with diisocyanate to prepare a polyurethane hot melt adhesive, the polyurethane hot melt adhesive will have a problem of poor coating dispersibility, which is not conducive to the improvement of the shear strength, solvent resistance, acid and alkali resistance, and cyclic high and low temperature variability of the polyurethane hot melt adhesive. Secondly, after polycarbonate diol is replaced by polytetrahydrofuran ether diol, the shear strength between the polyurethane hot melt adhesive and the substrate decreases, and the solvent resistance, acid and alkali resistance, and cyclic high and low temperature variability of the polyurethane hot melt adhesive are all deteriorated. In addition, after polytetrahydrofuran ether diol is replaced by an equal amount of 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol, on the one hand, it affects the uniform coating of the polyurethane hot melt adhesive, and on the other hand, it affects the low-temperature toughness of the polyurethane hot melt adhesive, thereby also causing a decrease in the cyclic high and low temperature variability of the polyurethane hot melt adhesive. In summary, it is shown that the use of 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol together with polytetramethylene ether diol and polycarbonate diol as polymerized diols is more conducive to improving the various properties of polyurethane hot melt adhesives.

[0087] According to Example 1 and Comparative Example 5 and in combination with the test results in Table 1, it can be seen that in Comparative Example 5, the weight ratio of 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol, polytetramethylene ether diol and polycarbonate diol is not within the range of (4-6): (2-3): (2-3) of the present application, and the shear strength, solvent resistance, acid and alkali resistance and resistance to cyclic high and low temperature changes of the polyurethane hot melt adhesive are all deteriorated, indicating that the ratio of 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol, polytetramethylene ether diol and polycarbonate diol is also the key reason why the polyurethane hot melt adhesive of the present application has high shear strength, good solvent resistance, good acid and alkali resistance and good resistance to cyclic high and low temperature changes.

[0088] According to Example 1 and Example 5-6 and the test results in Table 1, it can be seen that the use of a composition of a specific ratio of a straight-chain diol and a branched diol as a chain extender can improve the shear strength of the polyurethane hot melt adhesive while improving the cyclic high and low temperature change resistance of the polyurethane hot melt adhesive. When a branched diol is used alone as a chain extender, although the shear strength of the polyurethane hot melt adhesive is improved, the cyclic high and low temperature change resistance of the polyurethane hot melt adhesive is reduced.

[0089] This specific implementation manner is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the specific implementation manner as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A polyurethane hot melt adhesive, characterized in that: It includes a polymeric diol, a diisocyanate, a chain extender, a catalyst and an antioxidant, wherein the weight ratio of the polymeric diol, the diisocyanate, the chain extender, the catalyst and the antioxidant is (80-90): (25-30): (1.5-1.8): (0.1-0.2): (0.05-0.07), wherein the polymeric diol includes 3-(4-fluorophenyl) ethyl acrylate grafted polypropylene glycol, polytetramethylene glycol and polycarbonate diol, and the weight ratio of the 3-(4-fluorophenyl) ethyl acrylate grafted polypropylene glycol, polytetramethylene glycol and polycarbonate diol is (4-6): (2-3): (2-3); The raw materials for preparing the 3-(4-fluorophenyl)ethyl acrylate grafted polyether diol include 3-(4-fluorophenyl)ethyl acrylate, polypropylene glycol, a chain transfer agent and an initiator. The weight ratio of the 3-(4-fluorophenyl)ethyl acrylate, polypropylene glycol, the chain transfer agent and the initiator is (0.02-0.04):10:(0.01-0.02):(0.01-0.02).

2. The polyurethane hot melt adhesive according to claim 1, characterized in that: The viscosity of the polypropylene glycol is 500-600 mPa.s.

3. The polyurethane hot melt adhesive according to claim 1, characterized in that: The chain transfer agent is at least one of n-octyl mercaptan, n-dodecyl mercaptan, tert-dodecyl mercaptan and thioglycolic acid, and the initiator is an azo initiator.

4. A polyurethane hot melt adhesive according to any one of claims 1 to 3, characterized in that: The molecular weight of the polytetramethylene ether diol is 1000-2000, and the molecular weight of the polycarbonate diol is 1000-1500.

5. A polyurethane hot melt adhesive according to any one of claims 1 to 3, characterized in that: The diisocyanate is at least one of isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate and diphenylmethane diisocyanate.

6. A polyurethane hot melt adhesive according to any one of claims 1 to 3, characterized in that: The chain extender comprises a linear glycol and a branched glycol, and the weight ratio of the linear glycol to the branched glycol is 1:(1-1.5).

7. The polyurethane hot melt adhesive according to claim 6, characterized in that: The linear diol is at least one of ethylene glycol, 1,3-propylene glycol, and 1,4-butylene glycol, and the branched diol is at least one of 2-methyl-1,3-propylene glycol, 3-methyl-1,5-pentanediol, 2,4-dimethyl-1,5-pentanediol, and neopentyl glycol.

8. A polyurethane hot melt adhesive according to any one of claims 1 to 3, characterized in that: The antioxidant is at least one of antioxidant 1010 and antioxidant 1076, and the catalyst is at least one of dibutyltin dilaurate, 2,2-dimorpholinyl diethyl ether, and stannous octoate.

9. The method for preparing a polyurethane hot melt adhesive according to any one of claims 1 to 8, characterized in that: The following steps are involved: 3-(4-fluorophenyl)ethyl acrylate grafted polypropylene glycol, polytetramethylene glycol, polycarbonate diol and antioxidant are dehydrated and mixed, and then diisocyanate is added, the temperature is raised to 75-90°C, and the vacuum degree is maintained at -0.04MPa~-0.08MPa. After reacting for 3-4h, a chain extender and a catalyst are added, and the reaction is continued at 75-90°C for 1-1.5h before discharging to obtain a polyurethane hot melt adhesive.

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