Special polyurethane adhesive as well as preparation method and application thereof

Abstract

The invention relates to the technical field of polyurethane adhesives, and particularly discloses a special polyurethane adhesive as well as a preparation method and application thereof. The invention discloses a special polyurethane adhesive. Comprising the following raw materials in parts by weight: 40 to 45 parts of castor oil, 25 to 30 parts of polycaprolactone glycol, 30 to 35 parts of isophorone diisocyanate, 0.05 to 0.1 part of dibutyltin dilaurate, 5 to 8 parts of dimethylolpropionic acid, 3 to 5 parts of a sulfur-containing chain extender, 4 to 6 parts of a functional filler, 3 to 5 parts of hexadecyl trimethoxy silane, 8 to 12 parts of hydroxyethyl methylacrylate, 0.8 to 1.2 parts of a photoinitiator and 60 to 70 parts of deionized water. The special polyurethane adhesive prepared by the invention adopts a unique raw material formula and process, has the characteristics of light curing and water dispersion, forms a compact cross-linked network after being cured, shows excellent heat and humidity resistance, interface bonding strength and mechanical stability, and can be applied to the field of adhesive materials. The adhesive is suitable for material surfaces with high-performance bonding requirements in the fields of automobiles, electronics, buildings and aerospace.

Description

Technical Field

[0001] The invention relates to the technical field of polyurethane adhesives, and particularly discloses a special polyurethane adhesive and a preparation method and application thereof. Background Art

[0002] Polyurethane adhesives, due to their excellent flexibility, low-temperature resistance, and good bonding properties, are widely used in fields such as automotive, electronics, construction, and aerospace, which have stringent requirements for high-performance bonding. With the continuous improvement of material performance requirements across various industries, especially in the context of service in hot and humid environments, high-reliability connections, and increasingly stringent environmental regulations, the development of new polyurethane adhesives that combine efficient curing characteristics, excellent moisture and heat resistance, high-strength interfacial adhesion, and environmental friendliness has become a technical challenge that the industry urgently needs to solve.

[0003] Although traditional solvent-based polyurethane adhesives have good comprehensive performance, the environmental pollution and health risks caused by solvent volatilization are significant, making it difficult to meet the current development trend of green manufacturing. Water-based polyurethane adhesives use water as a dispersion medium and have the advantage of low VOC emissions. However, their curing process relies on water evaporation, and they are prone to problems such as low curing efficiency and insufficient resistance to moisture and heat aging of the adhesive film in a humid environment. Moreover, a single water dispersion system is difficult to form a highly dense cross-linked network, resulting in a significant attenuation of the interfacial bonding strength under long-term moisture and heat cycling conditions. In addition, although conventional photocurable polyurethane systems can achieve rapid curing through ultraviolet light irradiation, single photocuring reactions are often limited by the reaction activity of functional groups and insufficient cross-linking density, resulting in the mechanical stability and chemical resistance of the cured adhesive layer being difficult to meet the application requirements of high-demand fields such as aerospace.

[0004] In terms of functional filler modification, one-dimensional nanomaterials such as halloysite nanotubes have become an ideal choice for improving the mechanical properties of adhesives due to their unique tubular structure and large specific surface area. However, the compatibility problem between their surface polar groups and the polyurethane matrix leads to poor filler dispersion and insufficient interfacial bonding force, making it difficult to fully exert the strengthening and toughening effect. The introduction of sulfur-containing chain extenders can improve the cross-linked network structure through the special bonding effect of the sulfur element, but the traditional chain extender synthesis process has problems such as low reaction efficiency and imprecise functional group regulation, which makes it difficult to effectively control the balance between the cross-linking density and toughness of the adhesive layer. Therefore, in response to the problems of insufficient moisture and heat resistance, limited interfacial bonding strength, single curing method and poor compatibility of functional fillers in the prior art, the present invention provides a special polyurethane adhesive and its preparation method and application to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a special polyurethane adhesive and its preparation method and application. The prepared polyurethane adhesive adopts a unique raw material formula and process, has both light curing and water dispersion properties, forms a dense cross-linked network after curing, and exhibits excellent moisture and heat resistance, interfacial bonding strength and mechanical stability. It is suitable for material surfaces with high-performance bonding requirements in the automotive, electronics, construction and aerospace fields.

[0006] The present invention provides a special polyurethane adhesive, which adopts the following technical solution:

[0007] A special polyurethane adhesive is composed of the following raw materials in parts by weight: 40-45 parts of castor oil, 25-30 parts of polycaprolactone diol, 30-35 parts of isophorone diisocyanate, 0.05-0.1 parts of dibutyltin dilaurate, 5-8 parts of dimethylolpropionic acid, 3-5 parts of a sulfur-containing chain extender, 4-6 parts of a functional filler, 3-5 parts of hexadecyltrimethoxysilane, 8-12 parts of hydroxyethyl methacrylate, 0.8-1.2 parts of a photoinitiator, and 60-70 parts of deionized water.

[0008] The second object of the present invention is to provide a method for preparing the special polyurethane adhesive, comprising the following steps:

[0009] S1. Dehydrate castor oil and polycaprolactone diol under vacuum at 110-120° C. for 1-2 hours, cool to 78-82° C., add isophorone diisocyanate and dibutyltin dilaurate, and react in a nitrogen atmosphere for 2-4 hours to obtain a polyurethane prepolymer;

[0010] S2. Cool the polyurethane prepolymer to 65-70°C, add dimethylol propionic acid and sulfur-containing chain extender in sequence, react at 75-80°C for 1-2 hours, add functional filler and hexadecyltrimethoxysilane, and react at 60-65°C for 2-4 hours to obtain a modified prepolymer;

[0011] S3. Add hydroxyethyl methacrylate and photoinitiator to the modified prepolymer, react at 60-65°C until the -NCO content is ≤2%, add triethylamine dropwise to adjust the pH to neutral, add deionized water at a high-speed emulsification speed of 10000-15000 rpm for 20-30 minutes, and finally vacuum degas to obtain a special polyurethane adhesive.

[0012] Preferably, the preparation step of the sulfur-containing chain extender in step S2 is: dissolving 2,2-dihydroxymethylbutyric acid and thioglycolic acid in acetone, adding triethylamine, and reflux reacting at 75-80° C. for 4-6 hours under nitrogen protection, and then distilling under reduced pressure to obtain the sulfur-containing chain extender.

[0013] Preferably, the preparation steps of the sulfur-containing chain extender include 10-15 parts of 2,2-dihydroxymethylbutyric acid, 5-8 parts of thioglycolic acid, 40-45 parts of acetone and 0.5-0.8 parts of triethylamine in parts by weight.

[0014] Preferably, the preparation steps of the functional filler in step S2 are:

[0015] A1. Dispersing halloysite nanotubes in toluene, ultrasonically treating for 30-35 minutes, adding hexadecyltrimethoxysilane and concentrated hydrochloric acid, and refluxing at 78-84°C under nitrogen for 20-24 hours, followed by centrifugation, washing, and drying to obtain modified halloysite nanotubes;

[0016] A2. Dissolve vanillin and bis(4-hydroxyphenyl) disulfide in toluene, add p-toluenesulfonic acid, and reflux at 105-110° C. for 6-8 hours, then distill under reduced pressure, recrystallize, and dry to obtain vanillin-grafted disulfide.

[0017] A3. Modified halloysite nanotubes and vanillin-grafted disulfide are mixed in a mass ratio of (5-8):(1-3), stirred at 68-75°C for 1-2 hours, and then filtered and dried to obtain a functional filler.

[0018] Preferably, in step A1, the ingredients are 8-12 parts by weight of halloysite nanotubes, 30-35 parts of toluene, 3-5 parts of hexadecyltrimethoxysilane and 0.5-1 part of concentrated hydrochloric acid.

[0019] Preferably, in step A2, the ingredients are 5-8 parts by weight of vanillin, 3-6 parts by weight of bis(4-hydroxyphenyl)disulfide, 30-35 parts by weight of toluene, and 0.2-0.5 parts by weight of p-toluenesulfonic acid.

[0020] Preferably, the photoinitiator in step S3 is 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0021] The special polyurethane adhesive designed by the present invention is used in the fields of automobiles, electronics, construction or aerospace, and is used for bonding the surfaces of materials that require moisture and heat resistance and high-strength bonding.

[0022] In summary, the present invention has the following beneficial effects:

[0023] 1. The present invention combines raw materials such as sulfur-containing chain extenders, functional fillers, and modified prepolymers with deionized water to construct a special polyurethane adhesive system with both light-curing and water-dispersible properties. The sulfur-containing chain extender, through its special bonding ability, forms stable chemical bonds between polyurethane molecular chains, optimizing the cross-linked network structure; the functional filler undergoes special modification treatment to effectively improve its compatibility with the polyurethane matrix and enhance the stability of the system; the modified prepolymer, through the synergistic effect of multiple raw materials, imparts excellent mechanical properties and environmental adaptability to the adhesive. The photoinitiator and hydroxyethyl methacrylate work synergistically to enable the adhesive to quickly initiate a free radical polymerization reaction under light, achieving rapid curing and significantly improving production efficiency; in addition, the polyurethane prepolymer is prepared using castor oil, polycaprolactone diol, and other raw materials, reducing dependence on traditional petrochemical resources, lowering production costs and environmental impact.

[0024] 2. The functional filler of the present invention is prepared by modifying halloysite nanotubes through silane coupling and compounding them with vanillin-grafted disulfide. The unique tubular structure of the modified halloysite nanotubes forms physical crosslinking points in the polyurethane matrix, while the active groups in the vanillin-grafted disulfide chemically react with the polyurethane molecular chains, and the two synergistically form a stable interfacial bond. This structure allows the functional filler to be evenly dispersed in the matrix, giving the adhesive excellent cohesion and toughness, enabling it to adapt to the bonding requirements of surfaces of different materials. At the same time, the functional filler effectively inhibits degradation reactions in hot and humid environments, maintaining the stability of the adhesive's physical and chemical properties and significantly improving its resistance to hot and humid conditions.

[0025] 3. The sulfur-containing chain extender designed in the present invention introduces thioether bonds and carboxyl active groups into the molecular structure through the esterification reaction of thioglycolic acid and 2,2-dihydroxymethylbutyric acid. The special electronic structure of the sulfur element can significantly enhance the polar interactions between polyurethane molecular chains, forming a denser network structure during the crosslinking process. This chain extender can not only accurately control the chain segment length and crosslinking point distribution of the polyurethane prepolymer, giving the adhesive excellent flexibility and impact resistance, but also effectively inhibits molecular chain breakage and hydrolysis reactions in wet and hot environments through the chemical stability of the thioether bond, thereby significantly improving the wet and hot aging resistance and long-term service reliability of the adhesive layer. In addition, the synergistic effect of the sulfur-containing groups and the surface active sites of the functional filler further enhances the interfacial bonding between the filler and the matrix, enabling the adhesive to form a high-strength bonding interface on surfaces of different materials. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used are purchased from conventional biochemical reagent stores unless otherwise specified. The quantitative experiments in the following examples were all repeated three times, and the data are the average or mean ± standard deviation of the three repeated experiments.

[0028] Example 1

[0029] A method for preparing a special polyurethane adhesive comprises the following steps:

[0030] Preparation of a sulfur-containing chain extender: 10 g of 2,2-dihydroxymethylbutyric acid, 5 g of thioglycolic acid, 40 g of acetone, and 0.5 g of triethylamine were added to a three-necked flask. Under nitrogen protection, the mixture was refluxed at 75°C with a stirring rate of 300 rpm for 6 h. The acetone and excess triethylamine were then removed by reduced pressure distillation to obtain a sulfur-containing chain extender.

[0031] Preparation of functional filler: A1. Disperse 8 g of halloysite nanotubes in 30 g of toluene, treat under ultrasonic conditions of 200 W and 40 kHz for 30 min, then add 3 g of hexadecyltrimethoxysilane and 0.5 g of concentrated hydrochloric acid, reflux at 78 ° C and nitrogen protection at a stirring rate of 250 rpm for 24 h, centrifuge, wash and dry to obtain modified halloysite nanotubes; A2: Mix 5 g of vanillin, 3 g of bis(4-hydroxyphenyl) disulfide, 30 g of toluene and 0.2 g of p-toluenesulfonic acid, reflux at 105 ° C at a stirring rate of 200 rpm for 8 h, then distill under reduced pressure, recrystallize and dry to obtain vanillin grafted disulfide; A3. Mix 5 g of modified halloysite nanotubes with 1 g of vanillin grafted disulfide, stir at 68 ° C at a stirring rate of 300 rpm for 2 h, filter and dry to obtain functional filler.

[0032] Preparation of adhesive: S1. Add 40g of castor oil and 25g of polycaprolactone diol into a reactor, dehydrate at 110°C and a vacuum degree of -0.1MPa for 2h, cool to 78°C, add 30g of isophorone diisocyanate and 0.05g of dibutyltin dilaurate, and react for 4h at a stirring rate of 200rpm in a nitrogen atmosphere to obtain a polyurethane prepolymer; S2: Cool the polyurethane prepolymer to 65°C, add 5g of dihydroxymethylpropionic acid and 3g of sulfur-containing chain extender in sequence, react for 2h at a stirring condition of 75°C and 200rpm, then add 4g of functional filler and 3g of hexadecyltrimethoxysilane, and react for 4h at a stirring rate of 60°C and 200rpm to obtain a modified prepolymer. S3: Add 8 g of hydroxyethyl methacrylate and 0.8 g of 2-hydroxy-2-methyl-1-phenyl-1-propanone to the modified prepolymer, react at 60°C and a stirring rate of 200 rpm until the -NCO content is ≤2%, add triethylamine dropwise to adjust the pH to neutral, then add 60 g of deionized water at a high-speed emulsification of 10,000 rpm, emulsify for 30 minutes, and finally degas under vacuum conditions of -0.1 MPa and 60°C for 1 hour to obtain a special polyurethane adhesive.

[0033] Example 2

[0034] A method for preparing a special polyurethane adhesive comprises the following steps:

[0035] Preparation of sulfur-containing chain extender: 12 g of 2,2-dihydroxymethylbutyric acid, 6 g of thioglycolic acid, 42 g of acetone and 0.6 g of triethylamine were refluxed at 78°C for 5 h at a stirring rate of 350 rpm under nitrogen protection, and then distilled under reduced pressure to obtain the sulfur-containing chain extender.

[0036] Preparation of functional filler: A1. Disperse 10 g of halloysite nanotubes in 32 g of toluene, treat under ultrasonic conditions of 250 W and 40 kHz for 33 min, add 4 g of hexadecyltrimethoxysilane and 0.7 g of concentrated hydrochloric acid, reflux at 80 ° C and nitrogen protection at a stirring rate of 280 rpm for 22 h, centrifuge, wash and dry to obtain modified halloysite nanotubes; A2. Mix 6 g of vanillin, 4 g of bis(4-hydroxyphenyl) disulfide, 32 g of toluene and 0.3 g of p-toluenesulfonic acid, reflux at 108 ° C at a stirring rate of 220 rpm for 7 h, distill under reduced pressure, recrystallize and dry to obtain vanillin grafted disulfide; A3. Mix 6 g of modified halloysite nanotubes with 2 g of vanillin grafted disulfide, stir at 70 ° C at a stirring rate of 320 rpm for 1.5 h, filter and dry to obtain functional filler.

[0037] Preparation of adhesive: S1. Dehydrate 42g of castor oil and 27g of polycaprolactone diol at 115°C and a vacuum degree of -0.1MPa for 1.5h, cool to 80°C, add 32g of isophorone diisocyanate and 0.07g of dibutyltin dilaurate, and react for 3h at a stirring rate of 220rpm in a nitrogen atmosphere to obtain a polyurethane prepolymer; S2. Cool the polyurethane prepolymer to 67°C, add 6g of dimethylolpropionic acid and 4g of sulfur-containing chain extender in sequence, react at 78°C and 220rpm for 1.5h, then add 5g of functional filler and 4g of hexadecene. Alkyltrimethoxysilane is reacted at 62°C and a stirring rate of 220 rpm for 3 hours to obtain a modified prepolymer; S3, 10g of hydroxyethyl methacrylate and 1g of 2-hydroxy-2-methyl-1-phenyl-1-propanone are added to the modified prepolymer, and the mixture is reacted at 62°C and a stirring rate of 220 rpm until the -NCO content is ≤2%, triethylamine is added dropwise to adjust the pH value to a neutral value, and then 65g of deionized water is added at a high-speed emulsification of 12000 rpm, emulsified for 25 minutes, and finally degassed at a vacuum degree of -0.1 MPa and 60°C for 0.8h to obtain a special polyurethane adhesive.

[0038] Example 3

[0039] A method for preparing a special polyurethane adhesive comprises the following steps:

[0040] Preparation of sulfur-containing chain extender: 15 g of 2,2-dihydroxymethylbutyric acid, 8 g of thioglycolic acid, 45 g of acetone and 0.8 g of triethylamine were refluxed at 80° C. for 4 h at a stirring rate of 400 rpm under nitrogen protection, and the sulfur-containing chain extender was obtained by vacuum distillation.

[0041] Preparation of functional fillers: A1. Disperse 12 g of halloysite nanotubes in 35 g of toluene, treat with ultrasound at 300 W and 40 kHz for 35 min, add 5 g of hexadecyltrimethoxysilane and 1 g of concentrated hydrochloric acid, reflux at 84 ° C under nitrogen protection at a stirring rate of 300 rpm for 20 h, centrifuge, wash and dry to obtain modified halloysite nanotubes; A2. Mix 8 g of vanillin, 6 g of bis(4-hydroxyphenyl) disulfide, 35 g of toluene and 0.5 g of p-toluenesulfonic acid, reflux at 110 ° C at a stirring rate of 250 rpm for 6 h, distill under reduced pressure, recrystallize and dry to obtain vanillin grafted disulfide; A3. Mix the modified halloysite nanotubes (8 g) with the vanillin grafted disulfide (3 g), stir and react at 75 ° C at a stirring rate of 350 rpm for 1 h, filter and dry to obtain the functional filler.

[0042] Preparation of adhesive: S1. Place 45g of castor oil and 30g of polycaprolactone diol in a reactor, dehydrate at 120°C and vacuum degree -0.1MPa for 1h, cool to 82°C, add 35g of isophorone diisocyanate and 0.1g of dibutyltin dilaurate, and react at a stirring rate of 250rpm in a nitrogen atmosphere for 2h to obtain a polyurethane prepolymer; S2. Cool the polyurethane prepolymer to 70°C, add 8g of dimethylolpropionic acid and 5g of sulfur-containing chain extender in sequence, react at 80°C and 250rpm for 1h, and then add 6g of functional filler and 5g of hexadecane. S3, adding 12g of hydroxyethyl methacrylate and 1.2g of 2-hydroxy-2-methyl-1-phenyl-1-propanone to the modified prepolymer, reacting at 65°C and a stirring rate of 250rpm until the -NCO content is ≤2%, adding triethylamine dropwise to adjust the pH to neutral, then adding 70g of deionized water at a high-speed emulsification of 15000rpm, emulsifying for 20min, and finally degassing for 0.5h at a vacuum degree of -0.1MPa and 60°C to obtain a special polyurethane adhesive.

[0043] Example 4

[0044] A method for preparing a special polyurethane adhesive comprises the following steps:

[0045] Preparation of sulfur-containing chain extender: 13 g of 2,2-dihydroxymethylbutyric acid, 6.5 g of thioglycolic acid, 43 g of acetone and 0.65 g of triethylamine were refluxed at 77°C for 5 h at a stirring rate of 330 rpm under nitrogen protection, and the sulfur-containing chain extender was obtained by vacuum distillation.

[0046] Preparation of functional filler: A1. Disperse 10 g of halloysite nanotubes in 33 g of toluene, treat under ultrasonic conditions of 250 W and 40 kHz for 33 min, add 4 g of hexadecyltrimethoxysilane and 0.7 g of concentrated hydrochloric acid, reflux at 81 ° C. under nitrogen protection at a stirring rate of 270 rpm for 23 h, centrifuge, wash and dry to obtain modified halloysite nanotubes; A2. Mix 6.5 g of vanillin, 4.5 g of bis(4-hydroxyphenyl) disulfide, 33 g of toluene and 0.35 g of p-toluenesulfonic acid, reflux at 107 ° C. at a stirring rate of 230 rpm for 7 h, distill under reduced pressure, recrystallize and dry to obtain vanillin grafted disulfide; A3. Mix 6.5 g of modified halloysite nanotubes with 2.5 g of vanillin grafted disulfide, stir at 72 ° C. at a stirring rate of 330 rpm for 1.5 h, filter and dry to obtain functional filler.

[0047] Preparation of adhesive: S1. Dehydrate 43g of castor oil and 28g of polycaprolactone diol at 118°C and vacuum degree -0.1MPa for 1.2h, cool to 81°C, add 33g of isophorone diisocyanate and 0.08g of dibutyltin dilaurate, and react for 2.5h at a stirring rate of 230rpm in a nitrogen atmosphere to obtain a polyurethane prepolymer; S2. Cool the polyurethane prepolymer to 68°C, add 6.5g of dihydroxymethylpropionic acid and 4g of sulfur-containing chain extender in sequence, react for 1.5h at 77°C and 230rpm, and then add 5g of functional filler and 4g of Hexadecyltrimethoxysilane is reacted at 63°C and a stirring rate of 230 rpm for 3 hours to obtain a modified prepolymer; S3, 10 g of hydroxyethyl methacrylate and 1 g of 2-hydroxy-2-methyl-1-phenyl-1-propanone are added to the modified prepolymer, and the mixture is reacted at 63°C and a stirring rate of 230 rpm until the -NCO content is ≤2%, triethylamine is added dropwise to adjust the pH value to a neutral value, and then 68 g of deionized water is added at a high-speed emulsification of 13000 rpm, emulsified for 25 minutes, and finally degassed at a vacuum degree of -0.1 MPa and 60°C for 0.7 hour to obtain a special polyurethane adhesive.

[0048] Comparative Example 1

[0049] A method for preparing a specialty polyurethane adhesive differs from Example 4 in that thioglycolic acid is not introduced into the sulfur-containing chain extender. Specifically, the sulfur-containing chain extender is prepared by adding 13g of 2,2-dimethylolbutyric acid, 6.5g of glycolic acid, 43g of acetone, and 0.65g of triethylamine to a three-necked flask. Under nitrogen, the mixture is refluxed at 77°C for 5 hours at a stirring rate of 330 rpm. The acetone and excess triethylamine are then removed by reduced pressure distillation to obtain a sulfur-free chain extender. The remaining raw material composition and preparation method are the same as those in Example 4.

[0050] Comparative Example 2

[0051] A method for preparing a special polyurethane adhesive, which differs from Example 4 in that modified halloysite nanotubes are not used. Specifically, the preparation steps of the functional filler are as follows: A1. 10g of halloysite nanotubes are not modified with hexadecyltrimethoxysilane, and the subsequent steps are directly carried out. A2. 6.5g of vanillin, 4.5g of bis(4-hydroxyphenyl) disulfide, 33g of toluene and 0.35g of p-toluenesulfonic acid are mixed, and refluxed at 107°C with a stirring rate of 230rpm for 7h, followed by reduced pressure distillation, recrystallization and drying to obtain vanillin grafted disulfide. A3. 10g of unmodified halloysite nanotubes are mixed with 2.5g of vanillin grafted disulfide, and the mixture is stirred at 72°C with a stirring rate of 330rpm for 1.5h, and filtered and dried to obtain the functional filler. The remaining raw material compositions and preparation methods are the same as those in Example 4.

[0052] Comparative Example 3

[0053] A method for preparing a specialty polyurethane adhesive differs from Example 4 in that the functional filler is not modified by vanillin grafting. Specifically, the functional filler preparation steps are as follows: A1. Disperse 10g of halloysite nanotubes in 33g of toluene and treat with ultrasound at 250W and 40kHz for 33 minutes. Then, add 4g of hexadecyltrimethoxysilane and 0.7g of concentrated hydrochloric acid. Reflux at 81°C under nitrogen at a stirring rate of 270 rpm for 23 hours. Centrifuge, wash, and dry to obtain the modified halloysite nanotubes, which are then used directly as the functional filler. The remaining raw material composition and preparation method are the same as in Example 4.

[0054] Comparative Example 4

[0055] A method for preparing a special polyurethane adhesive differs from Example 4 in that the photoinitiator is physically mixed. Specifically, the adhesive preparation steps are as follows: S1. Dehydrate 43g of castor oil and 28g of polycaprolactone diol at 118°C and a vacuum of -0.1MPa for 1.2 hours, cool to 81°C, add 33g of isophorone diisocyanate and 0.08g of dibutyltin dilaurate, and react for 2.5 hours in a nitrogen atmosphere at a stirring rate of 230 rpm to obtain a polyurethane prepolymer. S2. Cool the polyurethane prepolymer to 68°C, sequentially add 6.5g of dimethylolpropionic acid and 4g of a sulfur-containing chain extender, and react at 77°C and 230 rpm for 1.5 hours. Then, add 5g of a functional filler and 4g of hexadecyltrimethoxysilane, and react at 63°C and 230 rpm for 3 hours to obtain a modified prepolymer. S3: 1 g of 2-hydroxy-2-methyl-1-phenyl-1-propanone was mechanically blended with the modified prepolymer. The mixture was stirred at 63°C and 230 rpm for 30 minutes. Triethylamine was then added dropwise to adjust the pH to neutral. 68 g of deionized water was then added at 13,000 rpm for emulsification. The mixture was emulsified for 25 minutes and degassed at -0.1 MPa and 60°C for 0.7 hours to obtain a special polyurethane adhesive. The remaining raw material composition and preparation method were the same as those in Example 4.

[0056] Comparative Example 5

[0057] A method for preparing a special polyurethane adhesive, which differs from Example 4 in that no sulfur-containing chain extender is added. Specifically, the adhesive preparation steps are as follows: S1, dehydrate 43g of castor oil and 28g of polycaprolactone diol at 118°C and a vacuum degree of -0.1MPa for 1.2h, cool to 81°C, add 33g of isophorone diisocyanate and 0.08g of dibutyltin dilaurate, and react for 2.5h at a stirring rate of 230rpm in a nitrogen atmosphere to obtain a polyurethane prepolymer; S2, cool the polyurethane prepolymer to 68°C, add 6.5g of dihydroxymethylpropionic acid in sequence, react at 77°C and 230rpm for 1.5h, and then add 5g of functional filler and 4g of hexadecyl tris(III) to the mixture. Methoxysilane was reacted at 63°C and a stirring rate of 230 rpm for 3 hours to obtain a modified prepolymer; S3, 10g of hydroxyethyl methacrylate and 1g of 2-hydroxy-2-methyl-1-phenyl-1-propanone were added to the modified prepolymer and reacted at 63°C and a stirring rate of 230 rpm until the -NCO content was ≤2%. Triethylamine was then added dropwise to adjust the pH to neutral. Subsequently, 68g of deionized water was added at a high-speed emulsification rate of 13,000 rpm and emulsified for 25 minutes. Finally, degassing was performed at a vacuum degree of -0.1 MPa and 60°C for 0.7 hours to obtain a special polyurethane adhesive without the addition of a sulfur-containing chain extender. The remaining raw material composition and preparation method were the same as in Example 4.

[0058] Comparative Example 6

[0059] A method for preparing a special polyurethane adhesive differs from Example 4 in that the polyurethane prepolymer is not modified with a functional filler. Specifically, the adhesive preparation steps are as follows: S1: Dehydrate 43g of castor oil and 28g of polycaprolactone diol at 118°C and a vacuum of -0.1MPa for 1.2 hours, cool to 81°C, add 33g of isophorone diisocyanate and 0.08g of dibutyltin dilaurate, and react for 2.5 hours in a nitrogen atmosphere at a stirring rate of 230 rpm to obtain a polyurethane prepolymer. S2: Cool the polyurethane prepolymer to 68°C, sequentially add 6.5g of dimethylolpropionic acid and 4g of a sulfur-containing chain extender, and react at 77°C and 230 rpm for 1.5 hours. Then, add 4g of hexadecyltrimethoxysilane and react at 63°C and 230 rpm for 3 hours to obtain a prepolymer without the addition of a functional filler. S3: 10 g of hydroxyethyl methacrylate and 1 g of 2-hydroxy-2-methyl-1-phenyl-1-propanone were added to the prepolymer and reacted at 63°C and a stirring rate of 230 rpm until the -NCO content was ≤2%. Triethylamine was then added dropwise to adjust the pH to neutral. 68 g of deionized water was then added at a high-speed emulsification rate of 13,000 rpm. The mixture was emulsified for 25 minutes, and finally degassed at a vacuum of -0.1 MPa and 60°C for 0.7 hours to obtain a specialty polyurethane adhesive not modified with a functional filler. The remaining raw material composition and preparation method were the same as in Example 4.

[0060] Performance Testing

[0061] The performance tests were performed on the special polyurethane adhesives prepared in Examples 1-4 and Comparative Examples 1-6:

[0062] 1. Moisture and heat resistance: The tensile strength retention after moisture and heat aging (85°C / 95% RH, 500h) of the special polyurethane adhesives prepared in Examples 1-4 and Comparative Examples 1-6 was tested with reference to GB / T1740-2007. The test results are shown in Table 1.

[0063] 2. Mechanical properties: The tensile strength and elongation at break of the special polyurethane adhesives prepared in Examples 1-4 and Comparative Examples 1-6 were tested with reference to GB / T6329-1996. The test results are shown in Table 1.

[0064] 3. Interface bonding strength test: The interface bonding strength test of the special polyurethane adhesives prepared in Examples 1-4 and Comparative Examples 1-6 was performed with reference to GB / T7124-2008 standard. The test results are shown in Table 1.

[0065] Table 1

[0066] Test items Moisture and heat resistance% Tensile strength MPa Elongation at break % Curing time Bonding strength Mpa Example 1 88 35.2 480 35 15.6 Example 2 91 37.8 510 34 16.8 Example 3 89 36.5 495 36 16.2 Example 4 93 39.0 525 35 17.3 Comparative Example 1 71 28.1 380 62 11.2 Comparative Example 2 68 30.5 350 60 9.80 Comparative Example 3 75 32.0 410 61 12.5 Comparative Example 4 82 34.5 430 58 13.4 Comparative Example 5 65 25.0 310 70 9.10 Comparative Example 6 73 27.5 365 72 10.7

[0067] The special polyurethane adhesives prepared in Examples 1-4 of the present invention are significantly superior to Comparative Examples 1-6 in terms of performance such as moisture and heat resistance, tensile strength, elongation at break, curing time, and bonding strength. The moisture and heat resistance of the embodiment is as high as 93%, the tensile strength is as high as 39.0 MPa, the elongation at break is as high as 525%, the curing time is as short as 34 seconds, and the bonding strength is as high as 17.3 MPa; while the moisture and heat resistance of the comparative example is only as high as 82%, the tensile strength is as high as 34.5 MPa, the elongation at break is as high as 430%, the curing time is as short as 58 seconds, and the bonding strength is as high as 13.4 MPa. Through collaborative optimization, the present invention achieves a balance between high moisture and heat resistance, high-strength bonding, and rapid curing, meeting the requirements of engineering applications in harsh environments.

[0068] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A special polyurethane adhesive, characterized in that: It is composed of the following raw materials in parts by weight: 40-45 parts of castor oil, 25-30 parts of polycaprolactone diol, 30-35 parts of isophorone diisocyanate, 0.05-0.1 parts of dibutyltin dilaurate, 5-8 parts of dimethylolpropionic acid, 3-5 parts of sulfur-containing chain extender, 4-6 parts of functional filler, 3-5 parts of hexadecyltrimethoxysilane, 8-12 parts of hydroxyethyl methacrylate, 0.8-1.2 parts of photoinitiator and 60-70 parts of deionized water.

2. The method for preparing the special polyurethane adhesive according to claim 1, characterized in that: The following steps are involved: S1. Dehydrate castor oil and polycaprolactone diol under vacuum at 110-120° C. for 1-2 hours, cool to 78-82° C., add isophorone diisocyanate and dibutyltin dilaurate, and react in a nitrogen atmosphere for 2-4 hours to obtain a polyurethane prepolymer; S2. Cool the polyurethane prepolymer to 65-70°C, add dimethylol propionic acid and sulfur-containing chain extender in sequence, react at 75-80°C for 1-2 hours, add functional filler and hexadecyltrimethoxysilane, and react at 60-65°C for 2-4 hours to obtain a modified prepolymer; S3. Add hydroxyethyl methacrylate and photoinitiator to the modified prepolymer, react at 60-65°C until the -NCO content is ≤2%, add triethylamine dropwise to adjust the pH to neutral, add deionized water at a high-speed emulsification speed of 10000-15000 rpm for 20-30 minutes, and finally vacuum degas to obtain a special polyurethane adhesive.

3. The method for preparing the special polyurethane adhesive according to claim 2, characterized in that: The preparation steps of the sulfur-containing chain extender in step S2 are as follows: dissolving 2,2-dihydroxymethylbutyric acid and thioglycolic acid in acetone, adding triethylamine, and reflux reacting at 75-80° C. for 4-6 hours under nitrogen protection, followed by reduced pressure distillation to obtain the sulfur-containing chain extender.

4. The method for preparing the special polyurethane adhesive according to claim 3, characterized in that: The composition comprises, by weight, 10-15 parts of 2,2-dihydroxymethylbutyric acid, 5-8 parts of thioglycolic acid, 40-45 parts of acetone and 0.5-0.8 parts of triethylamine.

5. The method for preparing the special polyurethane adhesive according to claim 2, characterized in that: The preparation steps of the functional filler in step S2 are: A1. Dispersing halloysite nanotubes in toluene, ultrasonically treating for 30-35 minutes, adding hexadecyltrimethoxysilane and concentrated hydrochloric acid, and refluxing at 78-84°C under nitrogen for 20-24 hours, followed by centrifugation, washing, and drying to obtain modified halloysite nanotubes; A2. Dissolve vanillin and bis(4-hydroxyphenyl) disulfide in toluene, add p-toluenesulfonic acid, and reflux at 105-110° C. for 6-8 hours, then distill under reduced pressure, recrystallize, and dry to obtain vanillin-grafted disulfide. A3. Modified halloysite nanotubes and vanillin-grafted disulfide are mixed in a mass ratio of (5-8):(1-3), stirred at 68-75°C for 1-2 hours, and then filtered and dried to obtain a functional filler.

6. The method for preparing the special polyurethane adhesive according to claim 5, characterized in that: In step A1, the components include, by weight, 8-12 parts of halloysite nanotubes, 30-35 parts of toluene, 3-5 parts of hexadecyltrimethoxysilane, and 0.5-1 part of concentrated hydrochloric acid.

7. The method for preparing the special polyurethane adhesive according to claim 5, characterized in that: In step A2, the components include, by weight, 5-8 parts of vanillin, 3-6 parts of bis(4-hydroxyphenyl)disulfide, 30-35 parts of toluene and 0.2-0.5 parts of p-toluenesulfonic acid.

8. The method for preparing the special polyurethane adhesive according to claim 2, characterized in that: In step S3, the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone.

9. Use of the polyurethane adhesive according to claim 1 or the polyurethane adhesive prepared by the method according to any one of claims 2 to 8, characterized in that: The polyurethane adhesive is used in the fields of automobiles, electronics, construction or aerospace, and is used for bonding the surfaces of materials that require moisture and heat resistance and high-strength bonding.