Modified waterborne polyurethane adhesive and preparation method thereof

Abstract

The application discloses a modified water-based polyurethane adhesive and a preparation method thereof, and relates to the technical field of adhesives.The application comprises the following raw materials in parts by mass: carbon dioxide-based polycarbonate polyol 70-84 parts, hexamethylene diisocyanate 8-9.6 parts, isophorone diisocyanate 3-3.6 parts, dibutyltin dilaurate 0.01-0.012 parts, N-methyl pyrrolidone 10-12 parts, dimethylol propionic acid 3.5-4.2 parts, 1,4-butanediol 1-1.2 parts, modified polyurethane dispersion 21-25.2 parts, silane-terminated dynamic crosslinking agent 2-2.5 parts, triethylamine 2.8-3.4 parts, acetone 40-60 parts, deionized water 200-220 parts, and ethylenediamine aqueous solution 10-12 parts.The introduction of the modified polyurethane dispersion and the silane-terminated dynamic crosslinking agent effectively improves the substrate universality, water resistance and temperature resistance of the adhesive.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, specifically to a modified waterborne polyurethane adhesive and its preparation method. Background Technology

[0002] Waterborne polyurethane adhesives use water as the dispersion medium and have core advantages such as being environmentally friendly and low in VOCs, easy to apply, flexible, and compatible with a variety of substrates. They overcome the environmental hazards and safety risks of solvent-based polyurethane adhesives and have therefore been widely used in many fields such as wood processing, leather finishing, flexible packaging lamination, automotive interior bonding, and building decoration.

[0003] However, modified waterborne polyurethane adhesives still have the following performance shortcomings in practical applications: First, their substrate versatility is limited, and they have poor compatibility with composite systems with large polarity differences (such as metal and plastic), easily leading to uneven adhesion and reduced peel strength. Second, their water resistance is poor; the hydrophilic groups remaining in the cured film easily absorb moisture, causing the adhesive interface to gradually peel off and performance to decline significantly in humid environments or under water immersion conditions. Third, their temperature stability is insufficient; at high temperatures (above 80℃), the movement of molecular chain segments intensifies, easily causing softening and deformation, while at low temperatures (below -10℃), they exhibit brittleness, limiting their application in extreme temperature environments. Therefore, the substrate versatility, water resistance, and temperature resistance of existing modified waterborne polyurethane adhesives still need to be improved. Summary of the Invention

[0004] The purpose of this invention is to provide a modified waterborne polyurethane adhesive and its preparation method, thereby solving the following technical problems:

[0005] Existing modified waterborne polyurethane adhesives still suffer from poor substrate compatibility, water resistance, and temperature resistance.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A modified waterborne polyurethane adhesive comprises the following raw materials in parts by weight: 70-84 parts of carbon dioxide-based polycarbonate polyol, 8-9.6 parts of hexamethylene diisocyanate, 3-3.6 parts of isophorone diisocyanate, 0.01-0.012 parts of dibutyltin dilaurate, 10-12 parts of N-methylpyrrolidone, 3.5-4.2 parts of dimethylolpropionic acid, 1-1.2 parts of 1,4-butanediol, 21-25.2 parts of modified polyurethane dispersion, 2-2.5 parts of silane-terminated dynamic crosslinking agent, 2.8-3.4 parts of triethylamine, 40-60 parts of acetone, 200-220 parts of deionized water, and 10-12 parts of ethylenediamine aqueous solution;

[0008] The modified polyurethane dispersion is prepared from graphene oxide powder, silane coupling agent KH550, polypropylene glycol 400, polypropylene glycol 1000, isophorone diisocyanate, and dibutyltin dilaurate.

[0009] The silane-terminated dynamic crosslinking agent is prepared from pinacol phenylboronic acid, 1,3-propanediol, p-toluenesulfonic acid, isophorone diisocyanate, dibutyltin dilaurate, and silane coupling agent KH550.

[0010] Preferably, the modified polyurethane dispersion is prepared as follows:

[0011] A1: Add deionized water to anhydrous ethanol and stir for 10-20 min. Then add graphene oxide powder and sonicate for 2-3 h. Then add silane coupling agent KH550 dropwise while stirring and reflux at 50 °C for 24-25 h. After cooling to room temperature, filter and wash, then redisperse in N-methylpyrrolidone. Finally, add polypropylene glycol 400 and sonicate at 30 °C for 1 h to obtain an aminated graphene oxide dispersion.

[0012] A2: Polypropylene glycol 1000 was dehydrated under vacuum at 100℃ for 1.5-2h, then cooled to 70℃ and added isophorone diisocyanate and dibutyltin dilaurate under a nitrogen atmosphere and stirred for 2-3h. Then, aminated graphene oxide dispersion was added and stirred at 60℃ under a nitrogen atmosphere for 6-7h. Then, N-methylpyrrolidone was removed by rotary evaporation at 60℃ and -0.09MPa. Finally, it was redispersed with acetone to obtain the modified polyurethane dispersion.

[0013] Preferably, the ratio of anhydrous ethanol, deionized water, graphene oxide powder, silane coupling agent KH550, N-methylpyrrolidone, and polypropylene glycol 400 in A1 is 190-200mL:20mL:0.5g:2g:150mL:10g.

[0014] Preferably, the ratio of polypropylene glycol 1000, isophorone diisocyanate, dibutyltin dilaurate, aminated graphene oxide dispersion, and acetone in A2 is 30g:8.7-9g:0.001g:200g:50mL.

[0015] Preferably, the preparation method of the silane-terminated dynamic crosslinking agent is as follows:

[0016] B1: Add pinacol phenylboronic acid, 1,3-propanediol, and p-toluenesulfonic acid to anhydrous toluene and reflux at 110°C under a nitrogen atmosphere for 6-8 hours. After cooling, wash and dry the organic phase with anhydrous magnesium sulfate for 12-15 hours. After filtration, remove toluene by rotary evaporation to obtain a dihydroxy-terminated borate ester chain extender.

[0017] B2: Mix the dihydroxy-terminated borate ester chain extender and 1,4-butanediol evenly to obtain a chain extender mixture;

[0018] B3: Isophorone diisocyanate and dibutyltin dilaurate are added to anhydrous tetrahydrofuran, and a chain extender mixture is added dropwise while stirring at 0-5℃. The mixture is then reacted at 70℃ for 2-2.5h, followed by the addition of silane coupling agent KH550 at 60℃ and the reaction for 4-5h. Finally, tetrahydrofuran is removed by rotary evaporation to obtain a silane-terminated dynamic crosslinking agent.

[0019] Preferably, the ratio of anhydrous toluene, pinacol phenylboronic acid, 1,3-propanediol, and p-toluenesulfonic acid in B1 is 50 mL: 13.3 g: 9.8-10 g: 0.05 g.

[0020] Preferably, the mass ratio of the dihydroxy-terminated borate ester chain extender and 1,4-butanediol in B2 is 5.1-5.2:1.3-1.4.

[0021] Preferably, the ratio of anhydrous tetrahydrofuran, isophorone diisocyanate, dibutyltin dilaurate, chain extender mixture, and silane coupling agent KH550 in B3 is 50-55 mL: 13.3 g: 0.0003 g: 6.4-6.6 g: 6.6 g.

[0022] A method for preparing a modified waterborne polyurethane adhesive includes the following steps:

[0023] S1: Add dimethylolpropionic acid and 1,4-butanediol to N-methylpyrrolidone and stir at 60°C for 30-50 min to obtain a mixed solution;

[0024] S2: Dehydrate the carbon dioxide-based polycarbonate polyol, add hexamethylene diisocyanate, isophorone diisocyanate, and dibutyltin dilaurate at 85°C under nitrogen atmosphere and react for 2-2.5 h. Then, add the mixed solution dropwise and react for 1.5-2 h. Next, add the modified polyurethane dispersion and stir at 80°C for 1-1.2 h. After cooling to 60°C, add the silane-terminated dynamic crosslinking agent and stir for 4-6 h. After cooling to 35°C, add triethylamine and stir for 5-6 h. Then, add acetone at 25°C. Finally, pour the mixture into deionized water at 5-10°C while stirring and stir for 15-20 min. Then, add the ethylenediamine aqueous solution dropwise while stirring and stir at 35°C for 40-60 min. After removing the acetone, filter to obtain the modified waterborne polyurethane adhesive.

[0025] Preferably, the mass fraction of the ethylenediamine aqueous solution in S2 is 10%.

[0026] The beneficial effects of this invention are:

[0027] This invention provides a modified waterborne polyurethane adhesive and its preparation method. The invention improves the substrate versatility, water resistance and temperature resistance of the waterborne polyurethane adhesive through the following method.

[0028] (1) The amino groups on the surface of the aminated graphene oxide of the present invention can form hydrogen bonds or strong physical adsorption with the hydroxyl groups on the metal surface and the hydroxyl groups of wood cellulose, thereby enhancing the chemical bonding force; the silane group of the silane coupling agent KH550 will first undergo a condensation reaction with the hydroxyl groups on the surface of the graphene oxide to form Si-O-graphene covalent bonds, and the remaining unreacted silane group will further condense after hydrolysis to form a siloxane crosslinking network. Its low surface energy characteristics can also improve the wetting performance of the adhesive layer on non-polar plastics. At the same time, the high specific surface area of ​​the aminated graphene oxide can enhance the physical adsorption effect; the uniform dispersion of the aminated graphene oxide sheets in the adhesive layer can also fill the micropores on the surface of the substrate, increase the interfacial contact area, and enable the adhesive to form a stable bond to different types of substrates such as polar, non-polar, porous, and dense substrates, thereby improving the bonding strength of the adhesive to different substrates and thus improving the universality of the substrate. Aminated graphene oxide sheets are hydrophobic, and their sheet structure forms a physical barrier, extending the penetration path of water molecules and effectively inhibiting water diffusion. Aminated graphene oxide and the polyurethane matrix can form chemical bonds through the reaction of amino groups with isocyanates, reducing the exposure of hydrophilic groups and decreasing water absorption and swelling. The siloxane crosslinking structure introduced by the silane coupling agent KH550, after hydrolysis and reduction, forms a dense siloxane network, further enhancing the water resistance of the adhesive layer, improving the strength retention rate after immersion in water, and significantly improving the water resistance of the adhesive. The high-modulus sheets of graphene oxide can hinder microcrack propagation, absorb impact energy, and prevent low-temperature brittle fracture. The strong interfacial bonding between aminated graphene oxide and polyurethane can inhibit the rigid shrinkage of molecular chains at low temperatures, improving the flexibility and crack resistance of the adhesive layer. Amination modification improves the dispersion stability of aminated graphene oxide in the adhesive layer, effectively avoiding adhesive layer defects caused by agglomeration at low temperatures and improving the retention rate of bond strength at low temperatures. The sheet-like structure of aminated graphene oxide can block heat transfer and slow down the thermal motion and degradation of polyurethane molecular chains. The cross-linked network formed by aminated graphene oxide and polyurethane can improve the thermal stability of the adhesive layer and inhibit softening and flow at high temperatures. The high specific surface area of ​​aminated graphene oxide can also adsorb small molecules generated by the thermal degradation of polyurethane, reduce the damage of thermal aging to the bonding interface, improve the strength retention rate at high temperatures, and broaden the applicable temperature range of the adhesive.

[0029] (2) The methoxysilane at the end of the silane-terminated dynamic crosslinking agent of the present invention will hydrolyze to generate silanol groups under the action of moisture or hydroxyl groups on the substrate surface, and then form a strong Si-O-substrate covalent bond with -OH, -COOH and other groups on the substrate surface, effectively improving the bonding strength to polar substrates such as wood, metal and glass; In addition to the hydrogen bonding effect of polyurethane, the amino and urea groups in the crosslinking agent can also form multiple hydrogen bonds with the hydroxyl groups of wood cellulose. At the same time, the siloxane segments can also improve the penetration of the adhesive layer into the porous structure of wood, further improving the bonding strength; The siloxane group introduced by the silane coupling agent KH550 has low surface energy characteristics, which can improve the wetting performance of the adhesive layer on non-polar plastics, solve the problem of weak adhesion of 1,4-butanediol system to non-polar plastics, improve interfacial compatibility, and comprehensively broaden the substrate universality of the adhesive. The Si-O-substrate bonds formed between the silane-terminated dynamic crosslinking agent and the substrate are hydrolysis-resistant, protecting the bonding interface and preventing interfacial failure caused by water molecule intrusion. While the borate ester bonds are not hydrolysis-resistant, they possess dynamic reversibility; when water molecule intrusion causes some borate ester bonds to break, they can recombine upon drying, restoring some or all of the cohesive strength. The strong hydrophobicity of the siloxane segments further prevents water penetration. The siloxane segments in the silane-terminated dynamic crosslinking agent exhibit excellent flexibility, lowering the overall glass transition temperature of the adhesive. Simultaneously, the dynamic reversibility of the borate ester bonds allows for reversible breakage and recombination at low temperatures to relieve stress, better preserving molecular chain flexibility and improving low-temperature flexibility and bond strength retention. The crosslinking network formed by the silane-terminated dynamic crosslinking agent has higher stability and is less prone to breakage at high temperatures. When the adhesive layer is heated, the crosslinking network can also undergo topological rearrangement through bond exchange, releasing internal stress, preventing adhesive layer cracking, improving high-temperature strength retention, and broadening the adhesive's applicable temperature range.

[0030] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. The embodiments described below are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] Unless otherwise specified, the following information pertains to some of the raw materials used in the following embodiments and comparative examples of this invention:

[0033] The carbon dioxide-based polycarbonate polyol (Mw=3000) was purchased from Guangdong Dazhi Environmental Protection Technology Co., Ltd.

[0034] Example 1: A method for preparing a modified waterborne polyurethane adhesive is as follows:

[0035] S1: Add 20 mL of deionized water to 190 mL of anhydrous ethanol and stir for 10 min. Then add 0.5 g of graphene oxide powder and sonicate for 2 h. Then add 2 g of silane coupling agent KH550 dropwise while stirring and reflux at 50 °C for 24 h. After cooling to room temperature, filter with a polyethersulfone filter membrane with a pore size of 0.22 μm and wash repeatedly with anhydrous ethanol 5 times. Then redisperse in 150 mL of N-methylpyrrolidone. Finally, add 10 g of polypropylene glycol 400 and sonicate at 30 °C for 1 h to obtain an aminated graphene oxide dispersion.

[0036] S2: 30g of polypropylene glycol 1000 was dehydrated under vacuum at 100℃ for 1.5h, then cooled to 70℃ and 8.7g of isophorone diisocyanate and 0.001g of dibutyltin dilaurate were added under a nitrogen atmosphere and stirred for 2h. Then 200g of aminated graphene oxide dispersion was added and stirred for 6h under a nitrogen atmosphere at 60℃. N-methylpyrrolidone was then removed by rotary evaporation at 60℃ and -0.09MPa. Finally, the mixture was redispersed with 50mL of acetone to obtain the modified polyurethane dispersion.

[0037] S3: Add 13.3g of pinacol phenylboronic acid, 9.8g of 1,3-propanediol, and 0.05g of p-toluenesulfonic acid to 50mL of anhydrous toluene and reflux at 110℃ under a nitrogen atmosphere for 6h. After cooling to room temperature, wash twice with saturated sodium bicarbonate solution, then wash once with deionized water. The organic phase is then dried with anhydrous magnesium sulfate for 12h. After filtration, toluene is removed by rotary evaporation to obtain a dihydroxy-terminated borate ester chain extender.

[0038] S4: Mix 5.1g of dihydroxy-terminated borate ester chain extender and 1.3g of 1,4-butanediol evenly to obtain a chain extender mixture;

[0039] S5: Add 13.3g of isophorone diisocyanate and 0.0003g of dibutyltin dilaurate to 50mL of anhydrous tetrahydrofuran, and add 6.4g of chain extender mixture dropwise at 0.1g / min while stirring at 0℃. After naturally heating to room temperature, react at 70℃ for 2h, then cool to 60℃ and add 6.6g of silane coupling agent KH550 dropwise at 0.2g / min. After reacting at 60℃ for 4h, remove tetrahydrofuran by rotary evaporation to obtain silane-terminated dynamic crosslinking agent;

[0040] S6: Add 3.5g of dimethylolpropionic acid and 1g of 1,4-butanediol to 10g of N-methylpyrrolidone and stir at 60℃ for 30min to obtain a mixed solution;

[0041] S7: 70g of carbon dioxide-based polycarbonate polyol was dehydrated at 100℃ and -0.095MPa vacuum for 1.5h. After cooling to 85℃, 8g of hexamethylene diisocyanate, 3g of isophorone diisocyanate, and 0.01g of dibutyltin dilaurate were added under nitrogen atmosphere and reacted for 2h. Then, 14.5g of the mixed solution was added dropwise at 0.5g / min and reacted at 85℃ for 1.5h. Next, 21g of modified polyurethane dispersion was added and stirred at 800r / min at 80℃ for 1h. After cooling to 60℃, 2g of silane-terminated dynamic crosslinking agent was added and stirred at 400r / min at 60℃. After stirring at 1200 rpm for 4 hours and cooling to 35°C, 2.8 g of triethylamine was added and stirred at 1200 rpm for 5 hours. Then, 40 g of acetone was added in three portions at 25°C. Finally, 200 g of deionized water at 5°C was poured in while stirring at 1200 rpm and stirred for 15 minutes. Then, 10 g of 10% ethylenediamine aqueous solution was added dropwise at 0.6 g / min while stirring at 600 rpm and stirred at 35°C for 40 minutes. The acetone was removed in a 40°C water bath under a vacuum of -0.09 MPa. The mixture was then filtered through a 300-mesh filter cloth to obtain the modified waterborne polyurethane adhesive.

[0042] Example 2: A method for preparing a modified waterborne polyurethane adhesive is as follows:

[0043] S1: Add 20 mL of deionized water to 195 mL of anhydrous ethanol and stir for 15 min. Then add 0.5 g of graphene oxide powder and sonicate for 2.5 h. Then add 2 g of silane coupling agent KH550 dropwise while stirring and reflux at 50 °C for 24.5 h. After cooling to room temperature, filter with a polyethersulfone membrane with a pore size of 0.22 μm and wash repeatedly with anhydrous ethanol 6 times. Then redisperse in 150 mL of N-methylpyrrolidone. Finally, add 10 g of polypropylene glycol 400 and sonicate at 30 °C for 1 h to obtain an aminated graphene oxide dispersion.

[0044] S2: 30g of polypropylene glycol 1000 was vacuum dehydrated at 100℃ for 1.8h, then cooled to 70℃ and 8.9g of isophorone diisocyanate and 0.001g of dibutyltin dilaurate were added under a nitrogen atmosphere and stirred for 2.5h. Then 200g of aminated graphene oxide dispersion was added and stirred at 60℃ under a nitrogen atmosphere for 6.5h. N-methylpyrrolidone was then removed by rotary evaporation at 60℃ and -0.09MPa. Finally, the mixture was redispersed with 50mL of acetone to obtain the modified polyurethane dispersion.

[0045] S3: Add 13.3 g of pinacol phenylboronic acid, 9.9 g of 1,3-propanediol, and 0.05 g of p-toluenesulfonic acid to 50 mL of anhydrous toluene and reflux at 110 °C under a nitrogen atmosphere for 7 h. After cooling to room temperature, wash twice with saturated sodium bicarbonate solution and once with deionized water. Then dry the organic phase with anhydrous magnesium sulfate for 13.5 h, filter, and remove toluene by rotary evaporation to obtain a dihydroxy-terminated borate ester chain extender.

[0046] S4: Mix 5.15g of dihydroxy-terminated borate ester chain extender and 1.35g of 1,4-butanediol evenly to obtain a chain extender mixture;

[0047] S5: Add 13.3g of isophorone diisocyanate and 0.0003g of dibutyltin dilaurate to 53mL of anhydrous tetrahydrofuran, and add 6.5g of chain extender mixture dropwise at 0.1g / min while stirring at 3℃. After naturally heating to room temperature, react at 70℃ for 2.3h, then cool to 60℃ and add 6.6g of silane coupling agent KH550 dropwise at 0.2g / min. After reacting at 60℃ for 4.5h, remove tetrahydrofuran by rotary evaporation to obtain silane-terminated dynamic crosslinking agent;

[0048] S6: Add 3.8g of dimethylolpropionic acid and 1.1g of 1,4-butanediol to 11g of N-methylpyrrolidone and stir at 60℃ for 40min to obtain a mixed solution;

[0049] S7: 77g of carbon dioxide-based polycarbonate polyol was dehydrated at 100℃ and -0.095MPa vacuum for 1.8h. After cooling to 85℃, 8.8g of hexamethylene diisocyanate, 3.3g of isophorone diisocyanate, and 0.011g of dibutyltin dilaurate were added under nitrogen atmosphere and reacted for 2.3h. Then, 15.9g of the mixed solution was added dropwise at 0.5g / min and reacted at 85℃ for 1.8h. Next, 23.1g of modified polyurethane dispersion was added and stirred at 800r / min for 1.1h at 80℃. The temperature was then lowered to 60℃, and 2.3g of silane-terminated dynamic crosslinking agent was added and stirred at 60℃. The mixture was stirred at 400 r / min for 5 h at ℃, cooled to 35℃, and then 3.1 g of triethylamine was added and stirred at 1200 r / min for 5.5 h. Subsequently, 50 g of acetone was added in four portions at 25℃. Finally, 210 g of deionized water at 8℃ was poured in while stirring at 1200 r / min and stirred for 18 min. Then, 11 g of 10% ethylenediamine aqueous solution was added dropwise at 0.6 g / min while stirring at 600 r / min and stirred at 35℃ for 50 min. The acetone was removed in a 40℃ water bath under a vacuum of -0.09 MPa. The mixture was then filtered through a 300-mesh filter cloth to obtain the modified waterborne polyurethane adhesive.

[0050] Example 3: A method for preparing a modified waterborne polyurethane adhesive is as follows:

[0051] S1: Add 20 mL of deionized water to 200 mL of anhydrous ethanol and stir for 20 min. Then add 0.5 g of graphene oxide powder and sonicate for 3 h. Then add 2 g of silane coupling agent KH550 dropwise while stirring and reflux at 50 °C for 25 h. After cooling to room temperature, filter with a polyethersulfone filter membrane with a pore size of 0.22 μm and wash repeatedly with anhydrous ethanol 7 times. Then redisperse in 150 mL of N-methylpyrrolidone. Finally, add 10 g of polypropylene glycol 400 and sonicate at 30 °C for 1 h to obtain an aminated graphene oxide dispersion.

[0052] S2: 30g of polypropylene glycol 1000 was dehydrated under vacuum at 100℃ for 2h, then cooled to 70℃ and 9g of isophorone diisocyanate and 0.001g of dibutyltin dilaurate were added under a nitrogen atmosphere and stirred for 3h. Then 200g of aminated graphene oxide dispersion was added and stirred at 60℃ under a nitrogen atmosphere for 7h. N-methylpyrrolidone was then removed by rotary evaporation at 60℃ and -0.09MPa. Finally, it was redispersed with 50mL of acetone to obtain the modified polyurethane dispersion.

[0053] S3: Add 13.3g of pinacol phenylboronic acid, 10g of 1,3-propanediol, and 0.05g of p-toluenesulfonic acid to 50mL of anhydrous toluene and reflux at 110℃ under a nitrogen atmosphere for 8h. After cooling to room temperature, wash three times with saturated sodium bicarbonate solution, then wash once with deionized water. The organic phase is then dried with anhydrous magnesium sulfate for 15h. After filtration, toluene is removed by rotary evaporation to obtain a dihydroxy-terminated borate ester chain extender.

[0054] S4: Mix 5.2g of dihydroxy-terminated borate ester chain extender and 1.4g of 1,4-butanediol evenly to obtain a chain extender mixture;

[0055] S5: Add 13.3g of isophorone diisocyanate and 0.0003g of dibutyltin dilaurate to 55mL of anhydrous tetrahydrofuran, and add 6.6g of chain extender mixture dropwise at 0.1g / min while stirring at 5℃. After naturally heating to room temperature, react at 70℃ for 2.5h, then cool to 60℃ and add 6.6g of silane coupling agent KH550 dropwise at 0.2g / min. After reacting at 60℃ for 5h, remove tetrahydrofuran by rotary evaporation to obtain silane-terminated dynamic crosslinking agent;

[0056] S6: Add 4.2g of dimethylolpropionic acid and 1.2g of 1,4-butanediol to 112g of N-methylpyrrolidone and stir at 60℃ for 50min to obtain a mixed solution;

[0057] S7: 84g of carbon dioxide-based polycarbonate polyol was dehydrated at 100℃ and -0.095MPa vacuum for 2h. After cooling to 85℃, 9.6g of hexamethylene diisocyanate, 3.6g of isophorone diisocyanate, and 0.012g of dibutyltin dilaurate were added under nitrogen atmosphere and reacted for 2.5h. Then, 17.4g of the mixed solution was added dropwise at 0.5g / min and reacted at 85℃ for 2h. Next, 25.2g of modified polyurethane dispersion was added and stirred at 800r / min at 80℃ for 1.2h. The mixture was then cooled to 60℃ and 2.5g of silane-terminated dynamic crosslinking agent was added and stirred at 60℃. Stir at 400 rpm for 6 hours, cool to 35°C, add 3.4 g of triethylamine and stir at 1200 rpm for 6 hours. Then, add 60 g of acetone in 5 portions at 25°C. Finally, pour in 220 g of deionized water at 5-10°C while stirring at 1200 rpm and stir for 20 minutes. Then, add 12 g of 10% ethylenediamine aqueous solution dropwise at 0.6 g / min while stirring at 600 rpm and stir at 35°C for 60 minutes. Remove acetone in a 40°C water bath under a vacuum of -0.09 MPa. Filter with a 300-mesh filter cloth to obtain the modified waterborne polyurethane adhesive.

[0058] Comparative Example 1:

[0059] Compared with Example 1, this comparative example only omits the addition of "aminated graphene oxide dispersion" during the preparation of S2. All other steps and parameters are the same, and will not be repeated here. The final product is a modified waterborne polyurethane adhesive.

[0060] Comparative Example 2:

[0061] Compared with Example 1, this comparative example only replaces the "silane-terminated dynamic crosslinking agent" added during the preparation of S7 with "1,4-butanediol". All other steps and parameters are the same, and will not be repeated here. The modified waterborne polyurethane adhesive is finally obtained.

[0062] Performance testing:

[0063] Determination of bond strength:

[0064] Referring to GB / T 15254-2014 standard, groups 1 (0.5cm thick PVC board and 0.5cm thick wood board), 2 (0.5cm thick wood board and 0.5cm thick steel plate), and 3 (0.5cm thick steel plate and 0.5cm thick PVC board) were used. Adhesive was applied between the two materials in each group, and the mixture was heated in a 60℃ oven for 10 minutes. After bonding, a 10kg weight was applied for 1 hour, and after releasing the pressure and allowing it to stand for 24 hours, the 180° peel strength (N / mm) of each group was measured. The bonding strength (N / mm) of the modified waterborne polyurethane adhesives prepared in Examples 1-3 and Comparative Examples 1-2 of this invention was measured using the above method. The results are shown in Table 1.

[0065] Water resistance test:

[0066] Take a 0.5cm thick polyvinyl chloride (PVC) board and a 0.5cm thick wooden board, apply glue, heat in a 60℃ oven for 10 minutes, bond them together, apply pressure with a 10kg weight for 1 hour, release the pressure and let stand for 24 hours, then measure their 180° peel strength (N / mm). Immerse them in 30℃ deionized water for 12 hours and measure their 180° peel strength (N / mm) again. Then calculate the peel strength retention rate (%) after immersion in water. The water resistance (%) of the modified waterborne polyurethane adhesives prepared in Examples 1-3 and Comparative Examples 1-2 of this invention was determined according to the above method. The test results are shown in Table 1.

[0067] Temperature resistance determination:

[0068] Take a 0.5cm thick polyvinyl chloride (PVC) board and a 0.5cm thick wooden board, apply glue, heat in a 60℃ oven for 10 minutes, and after bonding, press with a 10kg weight at 25℃ for 1 hour. After releasing the pressure and letting it stand for 24 hours, measure its 180° peel strength (N / mm). Then measure the 180° peel strength (N / mm) at -20℃ or 90℃ after being placed at -20℃ or 90℃ for another 12 hours. Then calculate the peel strength retention rate (%) after treatment at -20℃ or 90℃. The temperature resistance (%) of the modified waterborne polyurethane adhesives prepared in Examples 1-3 and Comparative Examples 1-2 of this invention was measured according to the above method. The test results are shown in Table 1.

[0069] Table 1: Performance test results of Examples 1-3 and Comparative Examples 1-2

[0070]

[0071] Data Analysis:

[0072] As can be seen from Table 1, the modified waterborne polyurethane adhesive prepared in the embodiments of the present invention has excellent substrate compatibility, water resistance, and temperature resistance.

[0073] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A modified waterborne polyurethane adhesive, characterized in that, The raw materials include the following parts by weight: 70-84 parts of carbon dioxide-based polycarbonate polyol, 8-9.6 parts of hexamethylene diisocyanate, 3-3.6 parts of isophorone diisocyanate, 0.01-0.012 parts of dibutyltin dilaurate, 10-12 parts of N-methylpyrrolidone, 3.5-4.2 parts of dimethylolpropionic acid, 1-1.2 parts of 1,4-butanediol, 21-25.2 parts of modified polyurethane dispersion, 2-2.5 parts of silane-terminated dynamic crosslinking agent, 2.8-3.4 parts of triethylamine, 40-60 parts of acetone, 200-220 parts of deionized water, and 10-12 parts of ethylenediamine aqueous solution; The modified polyurethane dispersion is prepared from graphene oxide powder, silane coupling agent KH550, polypropylene glycol 400, polypropylene glycol 1000, isophorone diisocyanate, and dibutyltin dilaurate. The silane-terminated dynamic crosslinking agent is prepared from pinacol phenylboronic acid, 1,3-propanediol, p-toluenesulfonic acid, isophorone diisocyanate, dibutyltin dilaurate, and silane coupling agent KH550. The preparation method of the modified polyurethane dispersion is as follows: A1: Add deionized water to anhydrous ethanol and stir for 10-20 min. Then add graphene oxide powder and sonicate for 2-3 h. Then add silane coupling agent KH550 dropwise while stirring and reflux at 50 °C for 24-25 h. After cooling to room temperature, filter and wash, then redisperse in N-methylpyrrolidone. Finally, add polypropylene glycol 400 and sonicate at 30 °C for 1 h to obtain an aminated graphene oxide dispersion. A2: Polypropylene glycol 1000 was dehydrated under vacuum at 100℃ for 1.5-2h, then cooled to 70℃ and added isophorone diisocyanate and dibutyltin dilaurate under a nitrogen atmosphere and stirred for 2-3h. Then, aminated graphene oxide dispersion was added and stirred at 60℃ under a nitrogen atmosphere for 6-7h. Then, N-methylpyrrolidone was removed by rotary evaporation at 60℃ and -0.09MPa. Finally, it was redispersed with acetone to obtain the modified polyurethane dispersion. The ratio of anhydrous ethanol, deionized water, graphene oxide powder, silane coupling agent KH550, N-methylpyrrolidone, and polypropylene glycol 400 in A1 is 190-200mL:20mL:0.5g:2g:150mL:10g. The ratio of polypropylene glycol 1000, isophorone diisocyanate, dibutyltin dilaurate, aminated graphene oxide dispersion, and acetone in A2 is 30g:8.7-9g:0.001g:200g:50mL. The preparation method of the silane-terminated dynamic crosslinking agent is as follows: B1: Add pinacol phenylboronic acid, 1,3-propanediol, and p-toluenesulfonic acid to anhydrous toluene and reflux at 110°C under a nitrogen atmosphere for 6-8 hours. After cooling, wash and dry the organic phase with anhydrous magnesium sulfate for 12-15 hours. After filtration, remove toluene by rotary evaporation to obtain a dihydroxy-terminated borate ester chain extender. B2: Mix the dihydroxy-terminated borate ester chain extender and 1,4-butanediol evenly to obtain a chain extender mixture; B3: Add isophorone diisocyanate and dibutyltin dilaurate to anhydrous tetrahydrofuran, and add the chain extender mixture dropwise while stirring at 0-5℃. Then react at 70℃ for 2-2.5h, then add silane coupling agent KH550 dropwise at 60℃ and react for 4-5h. Finally, remove tetrahydrofuran by rotary evaporation to obtain silane-terminated dynamic crosslinking agent. The ratio of anhydrous toluene, pinacol phenylboronic acid, 1,3-propanediol, and p-toluenesulfonic acid in B1 is 50 mL: 13.3 g: 9.8-10 g: 0.05 g; The mass ratio of the dihydroxy-terminated borate ester chain extender and 1,4-butanediol in B2 is 5.1-5.2:1.3-1.

4. The ratio of anhydrous tetrahydrofuran, isophorone diisocyanate, dibutyltin dilaurate, chain extender mixture, and silane coupling agent KH550 described in B3 is 50-55 mL: 13.3 g: 0.0003 g: 6.4-6.6 g: 6.6 g.

2. A method for preparing the modified waterborne polyurethane adhesive according to claim 1, characterized in that, Includes the following steps: S1: Add dimethylolpropionic acid and 1,4-butanediol to N-methylpyrrolidone and stir at 60°C for 30-50 min to obtain a mixed solution; S2: Dehydrate the carbon dioxide-based polycarbonate polyol, add hexamethylene diisocyanate, isophorone diisocyanate, and dibutyltin dilaurate at 85°C under a nitrogen atmosphere and react for 2-2.5 h. Then, add the mixed solution dropwise and react for 1.5-2 h. Next, add the modified polyurethane dispersion and stir at 80°C for 1-1.2 h. After cooling to 60°C, add the silane-terminated dynamic crosslinking agent and stir for 4-6 h. After cooling to 35°C, add triethylamine and stir for 5-6 h. Then, add acetone at 25°C. Finally, pour the mixture into deionized water at 5-10°C while stirring and stir for 15-20 min. Then, add the ethylenediamine aqueous solution dropwise while stirring and stir at 35°C for 40-60 min. After removing the acetone, filter to obtain the modified waterborne polyurethane adhesive.

3. The method for preparing the modified waterborne polyurethane adhesive according to claim 2, characterized in that, The mass fraction of the ethylenediamine aqueous solution in S2 is 10%.

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