Preparation method of hot melt adhesive for express bag

Abstract

The invention relates to the technical field of hot melt adhesives, and discloses a preparation method of a hot melt adhesive for an express bag. The hot melt adhesive for the express bag is prepared from the following raw materials in parts by weight: 60 to 80 parts of low-density polyethylene, 10 to 20 parts of modified polyurethane, 15 to 25 parts of styrene-butadiene-styrene thermoplastic elastomer, 5 to 9 parts of polyethylene wax, 8 to 15 parts of reinforcing filler and 0.2 to 0.6 part of antioxidant, low-density polyethylene is used as a main raw material, and modified polyurethane, styrene-butadiene-styrene thermoplastic elastomer, reinforcing filler and other functional aids are added, so that the adhesive property, high temperature resistance, mechanical property and water resistance of a matrix are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of hot melt adhesives, and in particular to a method for preparing hot melt adhesives for express bags. Background Art

[0002] The rapid development of the express delivery industry has driven the development of related industries, among which hot melt adhesives used for express bag packaging have also developed rapidly. Commonly used hot melt adhesives include polyethylene hot melt adhesive, polyester hot melt adhesive and polyurethane hot melt adhesive, etc. Polyethylene hot melt adhesive is currently the most widely used sealing adhesive. It seals by spraying a layer of polyethylene hot melt adhesive on the seal of the express bag. It has the advantages of fast curing, low cost, non-toxic and odorless, good bonding strength and good sealing.

[0003] However, the high temperature resistance of polyethylene hot melt adhesive is generally between 50-80℃, and it is easily affected by high temperature environment. It is easy to soften, become sticky or even stick in high temperature environment, which affects the use effect. In addition, polyethylene hot melt adhesive has poor water resistance, and it is easy to fall off when it comes into contact with water, and the bonding force will be significantly reduced, which seriously affects the use effect. Therefore, researchers need to modify the shortcomings of polyethylene hot melt adhesive to improve the high temperature resistance, water resistance, bonding performance and other comprehensive properties of hot melt adhesive. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for preparing hot melt adhesive for express bags.

[0005] The purpose of the present invention can be achieved through the following technical solutions: A hot melt adhesive for express bags, comprising the following raw materials in parts by weight: 60-80 parts of low-density polyethylene, 10-20 parts of modified polyurethane, 15-25 parts of styrene-butadiene-styrene thermoplastic elastomer, 5-9 parts of polyethylene wax, 8-15 parts of reinforcing filler, and 0.2-0.6 parts of antioxidant; The antioxidant is one of antioxidant 1010 or antioxidant 168; The modified polyurethane is prepared by the following steps: Step A1, under nitrogen conditions, stir 2,3-diazinone in methanol, then slowly add allylamine, then heat to 30-40°C, react for 3-5h, and rotary evaporate to obtain a nitrogen heterocyclic derivative; Step A2, dispersing maleic anhydride uniformly in N,N-dimethylformamide, recorded as maleic anhydride solution; under nitrogen conditions, dispersing ethylenediamine in N,N-dimethylformamide, slowly adding the maleic anhydride solution, and stirring at room temperature for 24 hours, then pouring the above solution into distilled water and letting it stand for 1 hour, filtering and drying to obtain a maleic anhydride derivative; Step A3, uniformly dispersing a nitrogen heterocyclic derivative, a maleic anhydride derivative and 2,4,5,6-tetrafluoro-1,3-phenylenediamine in a mixture of acetonitrile and sodium hydroxide, respectively, and recording them as a nitrogen heterocyclic derivative solution, a maleic anhydride derivative solution and a 2,4,5,6-tetrafluoro-1,3-phenylenediamine solution; then dispersing cyanuric chloride in acetonitrile, transferring to an ice water bath, slowly adding the nitrogen heterocyclic derivative solution, stirring to react for 3-4 hours, then heating to 40-50° C., slowly adding the maleic anhydride derivative to react for 4-5 hours, finally heating to 90° C., adding the 2,4,5,6-tetrafluoro-1,3-phenylenediamine solution to react for 5-7 hours, filtering with suction, and drying to obtain a modified end-capped product; Step A4, under nitrogen conditions, the polyurethane prepolymer, the modified end-capping product and dibutyltin dilaurate are uniformly mixed, and the temperature is raised to 90-110° C., and stirred for reaction for 1-2 hours to obtain a modified polyurethane; Further, in step A1, the usage ratio of 2,3-phthalazinone, methanol and allylamine is 0.01-0.03 mol: 200 mL: 0.01-0.03 mol; Further, in step A2, the dosage ratio of ethylenediamine, N,N-dimethylformamide, maleic anhydride solution and distilled water is 0.01-0.03 mol: 100 mL: 50 mL: 200 mL, and the dosage ratio of maleic anhydride and N,N-dimethylformamide in the maleic anhydride solution is 0.01-0.03 mol: 50 mL; Further, in step A3, the usage ratio of cyanuric chloride, acetonitrile, nitrogen heterocyclic derivative solution, maleic anhydride derivative solution and 2,4,5,6-tetrafluoro-1,3-phenylenediamine solution is 0.01-0.02 mol: 200 mL: 50 mL: 50 mL: 50 mL; Further, in step A3, the amount ratio of the nitrogen heterocyclic derivative, acetonitrile and sodium hydroxide in the nitrogen heterocyclic derivative solution is 0.01-0.02 mol: 50 mL: 0.4-0.8 g, the amount ratio of the maleic anhydride derivative, acetonitrile and sodium hydroxide in the maleic anhydride derivative solution is 0.01-0.02 mol: 50 mL: 0.4-0.8 g, and the amount ratio of 2,4,5,6-tetrafluoro-1,3-phenylenediamine, acetonitrile and sodium hydroxide in the 2,4,5,6-tetrafluoro-1,3-phenylenediamine solution is 0.01-0.02 mol: 50 mL: 0.4-0.8 g; Further, in step A4, the usage ratio of the polyurethane prepolymer, the modified end-capped product and dibutyltin dilaurate is 10-20 g: 2-5 g: 0.0001-0.0005 g; Furthermore, the polyurethane prepolymer in step A4 is a polyether PTMG-TDI type polyurethane prepolymer. The reinforcing filler is prepared by the following steps: Step B1, under nitrogen conditions, toluene diisocyanate is dispersed in N,N-dimethylformamide, and heated to 60-80°C and stirred for 10-20 minutes, halloysite nanotubes are added and stirred for 2-4 hours, KH-550 (silane coupling agent) is added at room temperature and stirred for 4-6 hours, centrifuged, washed, and vacuum dried to obtain organosilicon-halloysite nanomaterials; Step B2, dispersing the organosilicon-halloysite nanotubes evenly in a mixture of ethanol and deionized water (the volume ratio of ethanol to deionized water is 4:1), adding dimethyldiethoxysilane and hexadecyltrimethoxysilane and stirring evenly, transferring to a 30-50° C. water bath and stirring for reaction for 2-3 hours, filtering, washing, and drying to obtain a reinforcing filler; Further, in step B1, the usage ratio of toluene diisocyanate, N,N-dimethylformamide, halloysite nanotubes and KH-550 is 1.7-5.1 g: 100 mL: 2-6 g: 1.1-3.3 g; Furthermore, in step B2, the usage ratio of the organosilicon-halloysite nanotubes, the mixed solution, dimethyldiethoxysilane and hexadecyltrimethoxysilane is 5-10 g: 200 mL: 1-2 g: 0.5-1.5 g.

[0006] A method for preparing hot melt adhesive for express bags comprises the following steps: Weigh the raw materials by weight, mix and stir the low-density polyethylene, modified polyurethane, styrene-butadiene-styrene thermoplastic elastomer, polyethylene wax, reinforcing filler and antioxidant evenly, put them into an internal mixer, mix them at 170-200°C for 5-15 minutes, cool, discharge and pelletize to obtain the hot melt adhesive for express bags.

[0007] Beneficial effects of the present invention: The hot melt adhesive for express bags prepared by the present invention uses low-density polyethylene as the main raw material, and is added with functional additives such as modified polyurethane, styrene-butadiene-styrene thermoplastic elastomer, reinforcing filler, etc., so as to improve the bonding performance, high temperature resistance, mechanical properties and water resistance of the base.

[0008] In the modified polyurethane, the double bond in allylamine is first reacted with the secondary amine in 2,3-diazinone to obtain a nitrogen heterocyclic derivative; then maleic anhydride and ethylenediamine are reacted to obtain a maleic anhydride derivative containing an imide structure; then cyanuric chloride is used as an intermediate to react with a nitrogen heterocyclic derivative, a maleic anhydride derivative and 2,4,5,6-tetrafluoro-1,3-phenylenediamine to obtain a modified end-capped product; finally, the amino group in the modified end-capped product is reacted with the isocyanate group in the polyurethane prepolymer to obtain the modified polyurethane. The modified polyurethane in the matrix not only improves the mechanical properties of the matrix, but also improves the high temperature resistance and bonding performance of the matrix; the modified polyurethane introduces imide structure, triazine structure, nitrogen heterocycle and fluorine element with excellent heat resistance, which can synergistically improve the high temperature resistance of the matrix; in addition, the modified polyurethane contains a large number of polar groups (such as urea bonds, carbamates, ether bonds, etc.), which have stronger adsorption and can better penetrate into the surface of the bonded object to form a stronger bonding effect, thereby improving the bonding strength of the matrix.

[0009] In the reinforcing filler, the isocyanate group in toluene diisocyanate is first reacted with the hydroxyl group on the surface of the halloysite nanotube, and then the remaining isocyanate group is reacted with the amino group in KH-550 to obtain the silicone-halloysite containing urea group; then the siloxane on the surface of the silicone-halloysite is hydrolyzed and condensed with dimethyldiethoxysilane and hexadecyltrimethoxysilane to obtain the reinforcing filler. The reinforcing filler in the matrix can not only fill the gaps in the hot melt adhesive, improve the density of the matrix, reduce the curing shrinkage, but also improve the water resistance of the matrix; among them, the halloysite nanotubes can use their own unique tubular structure to form a physical barrier in the matrix, reduce the erosion of water on the surface and inside of the hot melt adhesive, improve the water resistance of the matrix, and increase the service life of the hot melt adhesive. At the same time, the nanotubes still have structural stability at high temperatures and can improve the high temperature resistance of the matrix; the silicone and long-chain alkane structure coated on the surface of the halloysite nanotubes can form a waterproof layer on the surface of the matrix, have good hydrophobicity, and can effectively prevent moisture from penetrating into the interior of the matrix, thereby improving the water resistance of the matrix; in addition, the urea group formed in the reinforcing filler also has a certain water resistance. DETAILED DESCRIPTION

[0010] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0011] Example 1: Modified polyurethane is prepared by the following steps: Step A1, under nitrogen conditions, 0.01 mol of 2,3-diazinone was stirred evenly in 200 mL of methanol, and then 0.01 mol of allylamine was slowly added, and then the temperature was raised to 30° C., reacted for 3 h, and rotary evaporated to obtain a nitrogen heterocyclic derivative; Step A2, 0.01 mol of maleic anhydride was evenly dispersed in 50 mL of N, N-dimethylformamide, recorded as maleic anhydride solution; under nitrogen conditions, 0.01 mol of ethylenediamine was dispersed in 100 mL of N, N-dimethylformamide, 50 mL of maleic anhydride solution was slowly added, and stirred at room temperature for 24 h, and then the above solution was poured into 200 mL of distilled water and allowed to stand for 1 h, filtered and dried to obtain a maleic anhydride derivative; Step A3, uniformly dispersing the nitrogen heterocyclic derivative, maleic anhydride derivative and 2,4,5,6-tetrafluoro-1,3-phenylenediamine in a mixture of acetonitrile and sodium hydroxide, respectively, recorded as nitrogen heterocyclic derivative solution, maleic anhydride derivative solution and 2,4,5,6-tetrafluoro-1,3-phenylenediamine solution; then dispersing 0.01 mol of cyanuric chloride in 200 mL of acetonitrile, transferring to an ice water bath, slowly adding 50 mL of the nitrogen heterocyclic derivative solution, stirring for reaction for 3 h, then heating to 40° C., slowly adding 50 mL of maleic anhydride derivative for reaction for 4 h, finally heating to 90° C., adding 50 mL The 2,4,5,6-tetrafluoro-1,3-phenylenediamine solution was reacted for 5 hours, filtered and dried to obtain a modified end-capped product. The amount ratio of the nitrogen heterocyclic derivative, acetonitrile and sodium hydroxide in the nitrogen heterocyclic derivative solution was 0.01 mol: 50 mL: 0.4 g, the amount ratio of the maleic anhydride derivative, acetonitrile and sodium hydroxide in the maleic anhydride derivative solution was 0.01 mol: 50 mL: 0.4 g, and the amount ratio of 2,4,5,6-tetrafluoro-1,3-phenylenediamine, acetonitrile and sodium hydroxide in the 2,4,5,6-tetrafluoro-1,3-phenylenediamine solution was 0.01 mol: 50 mL: 0.4 g; Step A4: Under nitrogen conditions, 10 g of polyurethane prepolymer, 2 g of modified end-capping product and 0.0001 g of dibutyltin dilaurate are mixed evenly, and the temperature is raised to 90° C. and stirred for reaction for 1 hour to obtain modified polyurethane. The polyurethane prepolymer is a polyether PTMG-TDI type polyurethane prepolymer.

[0012] The reinforcing filler is prepared by the following steps: Step B1, under nitrogen conditions, 1.7 g of toluene diisocyanate was dispersed in 100 mL of N,N-dimethylformamide, and heated to 60° C. and stirred for 10 min, 2 g of halloysite nanotubes were added and stirred for 2 h, 1.1 g of KH-550 was added at room temperature and stirred for 4 h, centrifuged, washed, and vacuum dried to obtain organosilicon-halloysite nanomaterials; Step B2, disperse 5 g of organosilicon-halloysite nanotubes evenly in a mixture of 200 mL of ethanol and deionized water (the volume ratio of ethanol to deionized water is 4:1), add 1 g of dimethyldiethoxysilane and 0.5 g of hexadecyltrimethoxysilane and stir evenly, transfer to a 30°C water bath and stir to react for 2 h, filter, wash and dry to obtain a reinforced filler.

[0013] Example 2: Modified polyurethane is prepared by the following steps: Step A1, under nitrogen conditions, 0.02 mol of 2,3-diazinone was stirred evenly in 200 mL of methanol, and then 0.02 mol of allylamine was slowly added, and then the temperature was raised to 35° C., reacted for 4 h, and rotary evaporated to obtain a nitrogen heterocyclic derivative; Step A2, 0.02 mol of maleic anhydride was evenly dispersed in 50 mL of N, N-dimethylformamide, recorded as maleic anhydride solution; under nitrogen conditions, 0.02 mol of ethylenediamine was dispersed in 100 mL of N, N-dimethylformamide, 50 mL of maleic anhydride solution was slowly added, and stirred at room temperature for 24 h, and then the above solution was poured into 200 mL of distilled water and allowed to stand for 1 h, filtered and dried to obtain a maleic anhydride derivative; Step A3, uniformly dispersing the nitrogen heterocyclic derivative, maleic anhydride derivative and 2,4,5,6-tetrafluoro-1,3-phenylenediamine in a mixture of acetonitrile and sodium hydroxide, respectively, recorded as nitrogen heterocyclic derivative solution, maleic anhydride derivative solution and 2,4,5,6-tetrafluoro-1,3-phenylenediamine solution; then dispersing 0.015 mol of cyanuric chloride in 200 mL of acetonitrile, transferring to an ice water bath, slowly adding 50 mL of the nitrogen heterocyclic derivative solution, stirring to react for 3.5 h, then heating to 45 ° C, slowly adding 50 mL of maleic anhydride derivative to react for 4.5 h, finally heating to 90 ° C, adding 50 mL The 2,4,5,6-tetrafluoro-1,3-phenylenediamine solution was reacted for 6 hours, filtered and dried to obtain a modified end-capped product. The amount ratio of the nitrogen heterocyclic derivative, acetonitrile and sodium hydroxide in the nitrogen heterocyclic derivative solution was 0.015 mol: 50 mL: 0.6 g, the amount ratio of the maleic anhydride derivative, acetonitrile and sodium hydroxide in the maleic anhydride derivative solution was 0.015 mol: 50 mL: 0.6 g, and the amount ratio of 2,4,5,6-tetrafluoro-1,3-phenylenediamine, acetonitrile and sodium hydroxide in the 2,4,5,6-tetrafluoro-1,3-phenylenediamine solution was 0.015 mol: 50 mL: 0.6 g; Step A4: Under nitrogen conditions, 15 g of polyurethane prepolymer, 3.5 g of modified end-capped product and 0.0003 g of dibutyltin dilaurate are mixed evenly, and the mixture is heated to 100° C. and stirred for reaction for 1.5 h to obtain a modified polyurethane. The polyurethane prepolymer is a polyether PTMG-TDI type polyurethane prepolymer.

[0014] The reinforcing filler is prepared by the following steps: Step B1, under nitrogen conditions, 3.4 g of toluene diisocyanate was dispersed in 100 mL of N,N-dimethylformamide, and heated to 70° C. and stirred for 15 min, 4 g of halloysite nanotubes were added and stirred for 3 h, 2.2 g of KH-550 was added and stirred at room temperature for 5 h, centrifuged, washed, and vacuum dried to obtain organosilicon-halloysite nanomaterials; Step B2, disperse 7.5 g of organosilicon-halloysite nanotubes evenly in a mixture of 200 mL of ethanol and deionized water (the volume ratio of ethanol to deionized water is 4:1), add 1.5 g of dimethyldiethoxysilane and 1 g of hexadecyltrimethoxysilane and stir evenly, transfer to a 40°C water bath and stir to react for 2.5 h, filter, wash and dry to obtain a reinforced filler.

[0015] Example 3: Modified polyurethane is prepared by the following steps: Step A1, under nitrogen conditions, 0.03 mol of 2,3-diazinone was stirred evenly in 200 mL of methanol, and then 0.03 mol of allylamine was slowly added, and then the temperature was raised to 40° C., reacted for 5 h, and rotary evaporated to obtain a nitrogen heterocyclic derivative; Step A2, 0.03 mol of maleic anhydride was uniformly dispersed in 50 mL of N, N-dimethylformamide, recorded as maleic anhydride solution; under nitrogen conditions, 0.03 mol of ethylenediamine was dispersed in 100 mL of N, N-dimethylformamide, 50 mL of maleic anhydride solution was slowly added, and stirred at room temperature for 24 h, and then the above solution was poured into 200 mL of distilled water and allowed to stand for 1 h, filtered and dried to obtain a maleic anhydride derivative; Step A3, uniformly dispersing the nitrogen heterocyclic derivative, maleic anhydride derivative and 2,4,5,6-tetrafluoro-1,3-phenylenediamine in a mixture of acetonitrile and sodium hydroxide, respectively, recorded as nitrogen heterocyclic derivative solution, maleic anhydride derivative solution and 2,4,5,6-tetrafluoro-1,3-phenylenediamine solution; then dispersing 0.02 mol of cyanuric chloride in 200 mL of acetonitrile, transferring to an ice water bath, slowly adding 50 mL of the nitrogen heterocyclic derivative solution, stirring to react for 4 h, then heating to 50° C., slowly adding 50 mL of maleic anhydride derivative to react for 5 h, finally heating to 90° C., adding 50 mL The 2,4,5,6-tetrafluoro-1,3-phenylenediamine solution was reacted for 7 hours, filtered and dried to obtain a modified end-capped product. The amount ratio of the nitrogen heterocyclic derivative, acetonitrile and sodium hydroxide in the nitrogen heterocyclic derivative solution was 0.02 mol: 50 mL: 0.8 g, the amount ratio of the maleic anhydride derivative, acetonitrile and sodium hydroxide in the maleic anhydride derivative solution was 0.02 mol: 50 mL: 0.8 g, and the amount ratio of 2,4,5,6-tetrafluoro-1,3-phenylenediamine, acetonitrile and sodium hydroxide in the 2,4,5,6-tetrafluoro-1,3-phenylenediamine solution was 0.02 mol: 50 mL: 0.8 g; Step A4: Under nitrogen conditions, 20 g of polyurethane prepolymer, 5 g of modified end-capping product and 0.0005 g of dibutyltin dilaurate are mixed evenly, and the mixture is heated to 110° C. and stirred for reaction for 2 h to obtain a modified polyurethane. The polyurethane prepolymer is a polyether PTMG-TDI type polyurethane prepolymer.

[0016] The reinforcing filler is prepared by the following steps: Step B1, under nitrogen conditions, 5.1 g of toluene diisocyanate was dispersed in 100 mL of N,N-dimethylformamide, and heated to 80° C. and stirred for 20 min, 2-6 g of halloysite nanotubes were added and stirred for 4 h, 3.3 g of KH-550 was added and stirred at room temperature for 6 h, centrifuged, washed, and vacuum dried to obtain organosilicon-halloysite nanomaterials; Step B2, disperse 10g of organosilicon-halloysite nanotubes evenly in a mixture of 200mL of ethanol and deionized water (the volume ratio of ethanol to deionized water is 4:1), add 2g of dimethyldiethoxysilane and 1.5g of hexadecyltrimethoxysilane and stir evenly, transfer to a 50°C water bath and stir to react for 3h, filter, wash and dry to obtain a reinforced filler.

[0017] Example 4: A method for preparing a hot melt adhesive for express bags comprises the following steps: 60 parts of low-density polyethylene, 10 parts of modified polyurethane prepared in Example 1, 15 parts of styrene-butadiene-styrene thermoplastic elastomer, 5 parts of polyethylene wax, 8 parts of reinforcing filler prepared in Example 1, and 0.2 parts of antioxidant 1010; Weigh the raw materials by weight, mix the low-density polyethylene, the modified polyurethane prepared in Example 1, the styrene-butadiene-styrene thermoplastic elastomer, the polyethylene wax, the reinforcing filler prepared in Example 1 and the antioxidant 1010, put them into an internal mixer, mix them at 170°C for 5 minutes, cool, discharge and pelletize to obtain the hot melt adhesive for express bags.

[0018] Example 5: A method for preparing a hot melt adhesive for express bags comprises the following steps: 70 parts of low-density polyethylene, 15 parts of modified polyurethane prepared in Example 2, 20 parts of styrene-butadiene-styrene thermoplastic elastomer, 7 parts of polyethylene wax, 12 parts of reinforcing filler prepared in Example 2, and 0.4 parts of antioxidant 168; The raw materials are weighed by weight, and the low-density polyethylene, the modified polyurethane prepared in Example 2, the styrene-butadiene-styrene thermoplastic elastomer, the polyethylene wax, the reinforcing filler prepared in Example 2 and the antioxidant 168 are mixed and stirred evenly, put into an internal mixer, and mixed at 180° C. for 10 min. The mixture is cooled, discharged, and pelletized to obtain the hot melt adhesive for express bags.

[0019] Example 6: A method for preparing a hot melt adhesive for express bags comprises the following steps: 80 parts of low-density polyethylene, 20 parts of modified polyurethane prepared in Example 3, 25 parts of styrene-butadiene-styrene thermoplastic elastomer, 9 parts of polyethylene wax, 15 parts of reinforcing filler prepared in Example 3, and 0.6 parts of antioxidant 1010; Weigh the raw materials by weight, mix the low-density polyethylene, the modified polyurethane prepared in Example 3, the styrene-butadiene-styrene thermoplastic elastomer, the polyethylene wax, the reinforcing filler prepared in Example 3 and the antioxidant 1010, put them into an internal mixer, mix them at 200°C for 15 minutes, cool, discharge and pelletize to obtain the hot melt adhesive for express bags.

[0020] Comparative Example 1: This comparative example is a hot melt adhesive. The difference from Example 6 is that commercially available polyurethane resin is used instead of the modified polyurethane prepared in Example 3, and the rest are the same.

[0021] Comparative Example 2: This comparative example is a hot melt adhesive. The difference from Example 6 is that the reinforcing filler prepared in Example 3 is replaced by halloysite nanotubes, and the rest is the same.

[0022] The hot melt adhesives prepared in Examples 4-6 and Comparative Examples 1-2 were subjected to performance tests: High temperature resistance test: refer to GB / T1633-2000 standard to test the softening point of the sample; 180° peel strength test: Test according to GB / T2790-81; Tensile strength and elongation at break test: Test according to GB1040-2006; Water resistance test: Through the patch hydrolysis test, the peel strength retention rate after immersion in a water bath at 30°C for 7 days is tested; The performance test results are shown in Table 1: Table 1: Performance test results

[0023] As can be seen from Table 1, after the high temperature resistance, 180° peel strength, mechanical properties and water resistance tests, the hot melt adhesive prepared by the present invention has a softening point in the range of (128-136)°C, a tensile strength in the range of (23.6-24.7) MPa, an elongation at break in the range of (489-525)%, a 180° peel strength in the range of (110-117) N / 25 mm, and a peel strength retention rate in the range of (73-79)%, indicating that the hot melt adhesive has excellent high temperature resistance, mechanical properties, bonding strength and water resistance, and has a good application prospect in express bags.

[0024] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the scope defined by the concept of the invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing hot melt adhesive for express bags, characterized in that: The invention comprises the following raw materials in parts by weight: 60-80 parts of low-density polyethylene, 10-20 parts of modified polyurethane, 15-25 parts of styrene-butadiene-styrene thermoplastic elastomer, 5-9 parts of polyethylene wax, 8-15 parts of reinforcing filler, and 0.2-0.6 parts of antioxidant; The hot melt adhesive for express bags is prepared by the following steps: Weigh the raw materials by weight, mix and stir the low-density polyethylene, modified polyurethane, styrene-butadiene-styrene thermoplastic elastomer, polyethylene wax, reinforcing filler and antioxidant evenly, put them into an internal mixer, mix them at 170-200° C. for 5-15 minutes, cool, discharge and pelletize to obtain the hot melt adhesive for express bags; The modified polyurethane is prepared by the following steps: Step A1, under nitrogen conditions, stir 2,3-diazinone in methanol, then slowly add allylamine, then heat to 30-40°C, react for 3-5h, and rotary evaporate to obtain a nitrogen heterocyclic derivative; Step A2, dispersing maleic anhydride uniformly in N,N-dimethylformamide, recorded as maleic anhydride solution; under nitrogen conditions, dispersing ethylenediamine in N,N-dimethylformamide, slowly adding the maleic anhydride solution, and stirring at room temperature for 24 hours, then pouring the above solution into distilled water and letting it stand for 1 hour, filtering and drying to obtain a maleic anhydride derivative; Step A3, uniformly dispersing a nitrogen heterocyclic derivative, a maleic anhydride derivative and 2,4,5,6-tetrafluoro-1,3-phenylenediamine in a mixture of acetonitrile and sodium hydroxide, respectively, and recording them as a nitrogen heterocyclic derivative solution, a maleic anhydride derivative solution and a 2,4,5,6-tetrafluoro-1,3-phenylenediamine solution; then dispersing cyanuric chloride in acetonitrile, transferring to an ice water bath, slowly adding the nitrogen heterocyclic derivative solution, stirring to react for 3-4 hours, then heating to 40-50° C., slowly adding the maleic anhydride derivative to react for 4-5 hours, finally heating to 90° C., adding the 2,4,5,6-tetrafluoro-1,3-phenylenediamine solution to react for 5-7 hours, filtering with suction, and drying to obtain a modified end-capped product; Step A4, under nitrogen conditions, the polyurethane prepolymer, the modified end-capping product and dibutyltin dilaurate are uniformly mixed, and the temperature is raised to 90-110° C., and stirred for reaction for 1-2 hours to obtain a modified polyurethane; The reinforcing filler is prepared by the following steps: Step B1, under nitrogen conditions, toluene diisocyanate is dispersed in N,N-dimethylformamide, and heated to 60-80°C and stirred for 10-20 minutes, halloysite nanotubes are added and stirred for 2-4 hours, KH-550 is added at room temperature and stirred for 4-6 hours, centrifuged, washed, and vacuum dried to obtain organosilicon-halloysite nanomaterials; Step B2, disperse the organosilicon-halloysite nanotubes evenly in a mixture of ethanol and deionized water, add dimethyldiethoxysilane and hexadecyltrimethoxysilane and stir evenly, transfer to a 30-50°C water bath and stir to react for 2-3h, filter, wash and dry to obtain a reinforced filler.

2. A method for preparing hot melt adhesive for express bags according to claim 1, characterized in that: In step A1, the usage ratio of 2,3-phthalazinone, methanol and allylamine is 0.01-0.03 mol:200 mL:0.01-0.03 mol.

3. A method for preparing hot melt adhesive for express bags according to claim 1, characterized in that: In step A2, the dosage ratio of ethylenediamine, N,N-dimethylformamide, maleic anhydride solution and distilled water is 0.01-0.03 mol:100 mL:50 mL:200 mL, and the dosage ratio of maleic anhydride and N,N-dimethylformamide in the maleic anhydride solution is 0.01-0.03 mol:50 mL.

4. A method for preparing hot melt adhesive for express bags according to claim 1, characterized in that: In step A3, the dosage ratio of cyanuric chloride, acetonitrile, nitrogen heterocyclic derivative solution, maleic anhydride derivative solution and 2,4,5,6-tetrafluoro-1,3-phenylenediamine solution is 0.01-0.02 mol: 200 mL: 50 mL: 50 mL: 50 mL.

5. A method for preparing hot melt adhesive for express bags according to claim 4, characterized in that: The amount ratio of the nitrogen heterocyclic derivative, acetonitrile and sodium hydroxide in the nitrogen heterocyclic derivative solution is 0.01-0.02 mol:50 mL:0.4-0.8 g, the amount ratio of the maleic anhydride derivative, acetonitrile and sodium hydroxide in the maleic anhydride derivative solution is 0.01-0.02 mol:50 mL:0.4-0.8 g, and the amount ratio of 2,4,5,6-tetrafluoro-1,3-phenylenediamine, acetonitrile and sodium hydroxide in the 2,4,5,6-tetrafluoro-1,3-phenylenediamine solution is 0.01-0.02 mol:50 mL:0.4-0.8 g.

6. A method for preparing hot melt adhesive for express bags according to claim 1, characterized in that: In step A4, the usage ratio of the polyurethane prepolymer, the modified end-capping product and dibutyltin dilaurate is 10-20g: 2-5g: 0.0001-0.0005g, and the polyurethane prepolymer is a polyether PTMG-TDI type polyurethane prepolymer.

7. A method for preparing hot melt adhesive for express bags according to claim 1, characterized in that: In step B1, the usage ratio of toluene diisocyanate, N,N-dimethylformamide, halloysite nanotubes and KH-550 is 1.7-5.1 g: 100 mL: 2-6 g: 1.1-3.3 g.

8. The method for preparing hot melt adhesive for express bags according to claim 1, characterized in that: In step B2, the usage ratio of the organosilicon-halloysite nanotubes, the mixed solution, dimethyldiethoxysilane and hexadecyltrimethoxysilane is 5-10 g: 200 mL: 1-2 g: 0.5-1.5 g.

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