Urea-formaldehyde resin / polyurethane composite modified material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of microcapsule materials, and mainly relates to a urea-formaldehyde resin / polyurethane composite modified material as well as a preparation method and application thereof. The urea resin / polyurethane composite modified material is prepared from the following raw materials in parts by mass: 25-35 parts of melamine; 35 to 40 parts of formaldehyde; 15 to 25 parts of urea; 3 to 8 parts of polyvinyl alcohol; 0.1 to 2 parts of a surfactant; 90 to 120 parts of water; 55 to 65 parts of a core material; 0.1 to 1 part of a cross-linking agent; 1-5 parts of a silane coupling agent; 0.1 to 3 parts of silicon dioxide; 1 to 3 parts of isocyanate; 0.1 to 2 parts of polyethylene glycol; 0.001 to 0.01 part of a catalyst; 0.01 to 0.05 part of triethylamine; and 5 to 10 parts of cyclohexane. The strength of the microcapsule can be improved, and the water resistance of the microcapsule is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of microcapsule materials, and particularly relates to a urea-formaldehyde resin / polyurethane composite modified material and a preparation method and application thereof. BACKGROUND

[0002] Microcapsule technology is widely used in the field of adhesives as an important coating technology. It can protect the core material from the external environment and achieve controlled release of the core material by wrapping the liquid or solid core material in the wall material to form a small capsule.

[0003] Urea-formaldehyde resin is often used as the wall material of microcapsules due to its low cost and easy film formation. However, the traditional urea-formaldehyde resin wall material has many defects. For example, the strength of urea-formaldehyde resin itself is not high and it is easy to break, which leads to the easy breakage of microcapsules during production, storage and use, resulting in the leakage of core material and the reduction of the performance and service life of the adhesive. In addition, the water resistance of urea-formaldehyde resin is poor and it is easy to hydrolyze in a humid environment, which further reduces the stability of microcapsules.

[0004] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0005] In view of the above shortcomings of the prior art, the present application aims to provide a urea-formaldehyde resin / polyurethane composite modified material and a preparation method and application thereof, which can improve the strength of microcapsules and improve the water resistance of microcapsules.

[0006] The technical scheme of the present application is as follows: A urea-formaldehyde resin / polyurethane composite modified material, according to mass parts, comprises the following raw materials: Melamine: 25-35 parts; Formaldehyde: 35-40 parts; Urea: 15-25 parts; Polyvinyl alcohol: 3-8 parts; Surfactant: 0.1-2 parts; Water: 90-120 parts; Core material: 55-65 parts; Crosslinking agent: 0.1-1 parts; Silane coupling agent: 1-5 parts; Silicon dioxide: 0.1-3 parts; Isocyanate: 1-3 parts; Polyethylene glycol: 0.1-2 parts; Catalyst: 0.001-0.01 parts; Triethylamine: 0.01-0.05 parts; Cyclohexane: 5-10 parts.

[0007] Melamine, urea, and formaldehyde undergo copolymerization to form a triazine ring-reinforced urea-formaldehyde resin wall material, providing a core heat-resistant skeleton. Polyvinyl alcohol chemically crosslinks with the hydroxymethyl groups of urea-formaldehyde resin, embedding flexible segments into the rigid structure to balance strength and toughness. Surfactants reduce the emulsification resistance of the core material, forming a uniform coating layer to ensure stable encapsulation of the core material. A crosslinking agent (glutaraldehyde) strengthens the wall material network through multi-point crosslinking of aldehyde groups with amino / hydroxyl groups, improving water resistance. Isocyanate and polyethylene glycol form a polyurethane prepolymer under the action of a catalyst. Triethylamine stabilizes the isocyanate groups, and cyclohexane serves as a solvent to achieve uniform dispersion of the prepolymer. Ultimately, a gradient structure of "core material - urea-formaldehyde resin wall material - polyurethane outer layer" is formed, achieving a synergistic effect of core material protection, wall material reinforcement, and interfacial compatibility.

[0008] Polyurethane, with its excellent elasticity and toughness, is blended with urea-formaldehyde resin in the form of a polyurethane prepolymer solution to form an interpenetrating network structure. This composite structure not only retains the low cost and easy film-forming advantages of urea-formaldehyde resin, but more importantly, it significantly compensates for the shortcomings of urea-formaldehyde resin, such as insufficient strength and poor water resistance. The introduction of polyurethane endows the composite wall material with higher elasticity and impact resistance, making it less prone to breakage under external forces. At the same time, the hydrophobicity of polyurethane effectively improves the hydrolysis resistance of the composite material, ensuring the long-term stability of the microcapsules in humid environments.

[0009] Furthermore, the surfactant includes sodium dodecylbenzenesulfonate; Silane coupling agents include KH-550; Isocyanates include isophorone diisocyanates; The catalyst includes dibutyltin dilaurate.

[0010] This application also provides a method for preparing a urea-formaldehyde resin / polyurethane composite modified material, comprising the following steps: preparing melamine-modified urea-formaldehyde resin / polyurethane composite microcapsules using melamine, urea, formaldehyde, water, polyvinyl alcohol, surfactant, core material, and crosslinking agent; The silane coupling agent was mixed with melamine-modified urea-formaldehyde resin / polyvinyl alcohol composite microcapsules to obtain the first mixture; Silica is mixed with the first mixture to obtain the second mixture; Isocyanate, polyethylene glycol, catalyst, triethylamine, and cyclohexane are mixed at 65-75°C under inert gas protection to obtain a polyurethane prepolymer solution. The second mixture is added to the polyurethane prepolymer solution and reacted for 4.5-5.5 hours to obtain the third mixture; The third mixture is dried, washed, and dried again to obtain a urea-formaldehyde resin / polyurethane composite modified material.

[0011] Polyurethane prepolymer solutions retain highly active -NCO end groups, which can chemically bond with hydroxyl and amino groups on the surface of the second mixture, forming a strong interfacial bond. In contrast, commercially available polyurethanes are mostly end products, and their active groups may be blocked or insufficient, leading to weakened interfacial bonding. Furthermore, polyurethane prepolymer solutions can have their mechanical properties, thermal stability, and hydrophilicity / hydrophobicity precisely controlled by adjusting the ratio of hard and soft segments, the degree of crosslinking, and the molecular weight distribution, thus meeting the requirements of composite modified materials.

[0012] The polyurethane prepolymer solution forms a homogeneous solution in cyclohexane. When mixed with a second mixture, the volatility of cyclohexane allows for an integrated "reaction-drying" process. If the commercially available polyurethane is an aqueous system, switching the solvent system is necessary, which may trigger phase separation; if it is a solvent-based system, solvent residue may affect performance.

[0013] Furthermore, the preparation method of melamine-modified urea-formaldehyde resin / polyvinyl alcohol composite microcapsules includes the following steps: Melamine, urea, formaldehyde and water are mixed, the pH is adjusted to 8.0-8.5, and the mixture is reacted at 70-75℃ for 1-2 hours to obtain a prepolymer. Polyvinyl alcohol, surfactant and prepolymer are mixed, and then the core material is added and mixed at high speed to obtain an emulsion.

[0014] Adjust the pH of the emulsion to 3.0-3.8, and stir the reaction at 75-80℃ for 2.5-3.5 hours; After the reaction is complete, add the crosslinking agent and stir for 30-60 minutes. Cooling, filtering, washing, and drying yielded melamine-modified urea-formaldehyde resin / polyvinyl alcohol composite microcapsules.

[0015] Furthermore, after adding the core material, stir and emulsify at 750-850 rpm for 20-40 minutes.

[0016] Furthermore, the silane coupling agent and melamine-modified urea-formaldehyde resin / polyvinyl alcohol composite microcapsules were stirred and reacted for 2.5-3.5 hours; during stirring, the reaction system was ultrasonically treated at a frequency of 35-45 kHz for 20-40 minutes to obtain the first mixture.

[0017] High-speed stirring at 750-850 rpm and ultrasonic treatment for 20-40 min form a dual mixing mechanism of "macro-shearing-micro-cavitation". High-speed shearing achieves micron-level fragmentation of core material droplets, while the ultrasonic cavitation effect enhances the adsorption and reaction of silane coupling agent on the microcapsule surface through microjets. The two work synergistically to improve emulsification efficiency and surface modification uniformity, thereby optimizing the performance of composite microcapsules.

[0018] Furthermore, the silane coupling agent is ultrasonically mixed with an organic solvent to obtain a silane coupling agent solution; the silane coupling agent solution is then mixed with melamine-modified urea-formaldehyde resin / polyvinyl alcohol composite microcapsules to obtain a first mixture. Silica is ultrasonically mixed with an organic solvent to obtain a silica dispersion; the silica dispersion is then mixed with the first mixture to obtain a second mixture. The organic solutions used for silane coupling agent solutions and silica dispersions may be the same or different.

[0019] Furthermore, the silane coupling agent and the organic solvent are ultrasonically mixed at a weight ratio of 1:4-6 to obtain a silane coupling agent solution.

[0020] Furthermore, silica and organic solvent are ultrasonically mixed at a weight ratio of 1:8-12 to obtain a silica dispersion.

[0021] This application also provides an application of a urea-formaldehyde resin / polyurethane composite modified material in industrial adhesives.

[0022] The urea-formaldehyde resin / polyurethane composite modified material of this application adopts a gradient structure, achieving a performance leap through the synergistic function of each layer. The core material is located in the inner layer, serving as a functional carrier and providing core functions; the urea-formaldehyde resin forms a triazine ring skeleton through copolymerization of melamine and urea, imparting rigidity and heat resistance, while the hydroxyl groups of polyvinyl alcohol chemically crosslink with the hydroxymethyl groups of urea-formaldehyde resin, balancing strength and toughness; the outermost polyurethane layer forms a flexible protective layer through the polymerization reaction of isocyanate and polyethylene glycol, and its polar groups can form hydrogen bonds / secondary valence bonds with downstream industrial adhesives, improving interfacial compatibility.

[0023] This structure achieves uniform stress distribution through a "rigid-flexible" gradient transition: the rigid network of urea-formaldehyde resin resists external impacts, while the flexible layer of polyurethane absorbs residual stress, reducing the risk of microcapsule rupture. The ethoxy groups of the silane coupling agent (KH-550) are covalently bonded to the hydroxyl groups on the urea-formaldehyde resin surface, while the amino groups bridge the polyurethane and adhesives, forming a chemical anchor. Silica particles are embedded in the polyurethane layer, reducing agglomeration through steric hindrance. In industrial adhesives, this results in high strength, high water resistance, and easy dispersibility, extending the adhesive layer's service life and expanding its application scenarios.

[0024] Compared with the prior art, this application has the following beneficial effects: 1. This application achieves a significant strength boost in modified materials through a gradient structure of "rigid skeleton + flexible compensation." The triazine ring skeleton formed by copolymerizing melamine and urea imparts high modulus and heat resistance; polyvinyl alcohol chemically crosslinks with the hydroxymethyl group of urea-formaldehyde resin through hydroxyl groups, embedding flexible segments within the rigid network to balance brittleness. An outer layer also polymerizes to form a flexible buffer layer, absorbing external stress and reducing microcapsule rupture. Crosslinking agents such as glutaraldehyde further strengthen the wall material network structure through multi-point crosslinking of aldehyde groups with amino / hydroxyl groups, effectively solving the problems of fragility and low strength of traditional urea-formaldehyde resins.

[0025] 2. The hydroxyl groups of polyvinyl alcohol undergo esterification and cross-linking with urea-formaldehyde resin, forming a dense three-dimensional network that reduces the penetration pathway of water molecules. The aldehyde groups of the cross-linking agent undergo bifunctional cross-linking with the amino / hydroxyl groups of the wall material molecular chains, improving the water resistance. The hydrophobicity of the outer polyurethane layer complements that of the urea-formaldehyde resin, preventing moisture intrusion. The silanol generated by the ethoxy hydrolysis of the silane coupling agent KH-550 covalently bonds with the hydroxyl groups on the surface of the urea-formaldehyde resin, forming a Si-OC protective layer. Silica particles reduce agglomeration through steric hindrance, synergistically improving overall water resistance.

[0026] 3. The amino groups of the silane coupling agent KH-550 bridge the polar groups of polyurethane, improving the compatibility between the composite modified material and the adhesive; silica particles are embedded in the polyurethane layer, reducing agglomeration through steric hindrance. High-speed stirring and ultrasonic treatment form a dual mixing mechanism of "macroscopic shearing-microscopic cavitation," ensuring micron-level fragmentation of the core material droplets and uniform adsorption of the silane coupling agent. Ultimately, the uniformity of dispersion of the microcapsules (composite modified material) in the adhesive is effectively improved, stress concentration is reduced, the service life of the adhesive layer is extended, and the application scenarios of industrial adhesives are expanded. Detailed Implementation

[0027] To facilitate understanding of this application, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of this application.

[0028] This application provides a urea-formaldehyde resin / polyurethane composite modified material, comprising the following raw materials by weight: Melamine: 25-35 parts; Formaldehyde (37% aqueous solution): 35-40 parts; Urea: 15-25 parts; Polyvinyl alcohol (PVA): 3-8 parts; Surfactant: 0.1-2 parts; Water: 90-120 parts; Core material (epoxy resin): 55-65 parts (E-44); Crosslinking agent: 0.1-1 part; Silane coupling agent: 1-5 parts; Silica: 0.1-3 parts; Isocyanate: Isophorone diisocyanate (IPDI): 1-3 parts; Polyethylene glycol (PEG): 0.1-2 parts; Catalyst: 0.001-0.01 parts; Triethylamine: 0.01-0.05 parts; Cyclohexane: 5-10 parts.

[0029] The surfactant is preferably sodium dodecylbenzenesulfonate (SDBS), the silane coupling agent is preferably KH-550, the isocyanate is preferably isophorone diisocyanate (IPDI), and the catalyst is preferably dibutyltin dilaurate (DBTDL). The silica is preferably fumed silica.

[0030] This application also provides a method for preparing a urea-formaldehyde resin / polyurethane composite modified material, comprising the following steps: Step 1: Preparation of melamine-modified urea-formaldehyde resin / polyvinyl alcohol composite microcapsules: Step 1-1: Add melamine, urea, formaldehyde, and water to a 250mL three-necked flask. Start stirring and control the stirring speed at 150-250rpm. Adjust the pH value to 8.0-8.5 by adding sodium hydroxide solution (5-15wt%) dropwise. Heat the reaction vessel to 70-75℃ and maintain the reaction for 1-2 hours. The prepolymer is obtained.

[0031] Steps 1-2: Add PVA and surfactant to the prepolymer and continue stirring for 5-20 minutes. Then, slowly add E-44 epoxy resin to the mixture. Increase the stirring speed to 750-850 rpm and emulsify at high speed for 20-40 minutes to obtain the emulsion.

[0032] Steps 1-3: Adjust the pH of the above emulsion to 3.0-3.8 by adding hydrochloric acid solution (5-15wt%) dropwise. Continue stirring and maintain the reaction temperature at 75-80℃ for 2.5-3.5 hours.

[0033] Steps 1-4: After the reaction is complete, add 25% glutaraldehyde aqueous solution as a crosslinking agent and continue stirring for 30-60 minutes.

[0034] Steps 1-5: Cool to room temperature, filter using a Buchner funnel, and wash the filter cake three times with deionized water. Dry the washed filter cake in a vacuum drying oven at 60℃ for 12 hours to obtain melamine-modified urea-formaldehyde resin / polyvinyl alcohol composite microcapsules.

[0035] Step 2: Dissolve the silane coupling agent (KH-550) in ethanol and stir until homogeneous to obtain a silane coupling agent solution. The weight ratio of silane coupling agent to ethanol is 1:4-6.

[0036] Melamine-modified urea-formaldehyde resin / polyvinyl alcohol composite microcapsules were added to a silane coupling agent solution and stirred until homogeneous. The reaction mixture was stirred continuously at room temperature for 2.5-3.5 hours, while simultaneously sonicating the reaction system at a frequency of 35-45 kHz for 20-40 minutes. This yielded the first mixture.

[0037] Ultrasonic treatment was performed 30 minutes after stirring.

[0038] The ultrasonic treatment (20-40 minutes) is entirely contained within the time window of the stirred reaction (2.5-3.5 hours). Ultrasonic treatment is initiated 30 minutes after the reaction begins and continues until approximately one hour of reaction time, covering the critical stages of the reaction. This enhances micro-mixing and mass transfer through cavitation effects (microjets, localized high temperature and pressure) and mechanical vibration, accelerating the hydrolysis and condensation reactions of the silane coupling agent and promoting its chemical bonding with the microcapsule surface (e.g., the reaction of Si-OH with -OH on the microcapsule surface to form Si-OC bonds).

[0039] Step 3: Disperse fumed silica in ethanol and sonicate for 20-40 minutes to obtain a fumed silica dispersion. The weight ratio of fumed silica to ethanol is 1:8-12.

[0040] The first mixture was added to the fumed silica dispersion and stirred until homogeneous to obtain the second mixture.

[0041] Step 4: Add IPDI, PEG, DBTDL and triethylamine to cyclohexane, and stir until homogeneous at 65-75℃ under inert gas protection to obtain a polyurethane prepolymer solution.

[0042] The second mixture is added to the polyurethane prepolymer solution and stirred until homogeneous. The reaction is allowed to proceed for 4.5-5.5 hours, allowing the polyurethane prepolymer to polymerize on the surface of the microcapsules, forming a polyurethane-modified layer. This yields the third mixture.

[0043] Step 5: Place the flask containing the third mixture into a vacuum drying oven, evacuate to -0.06 MPa, maintain for 20-40 minutes, and then slowly release the vacuum.

[0044] Step 6: Filtration. Wash the filter cake three times alternately with ethanol and deionized water. Dry the washed filter cake in a vacuum drying oven at 35-45℃ for 12-36 hours to obtain the urea-formaldehyde resin / polyurethane composite modified material.

[0045] The urea-formaldehyde resin / polyurethane composite modified material of this application is preferably used in the field of industrial adhesives.

[0046] The present application will be further described below through specific embodiments.

[0047] Example 1 A urea-formaldehyde resin / polyurethane composite modified material, comprising the following raw materials: Melamine: 30g; Formaldehyde (37% aqueous solution): 38g; Urea: 20g; Polyvinyl alcohol (PVA-124): 5g; Sodium dodecylbenzenesulfonate (SDBS): 1g; Water: 100g; Core material (E-44 epoxy resin): 60g; Crosslinking agent (25% glutaraldehyde aqueous solution): 0.3g; Silane coupling agent (KH-550): 3g; Ethanol (90%) Fumed silica: 0.8g (AEROSIL 200, Evonik Degussa); Isophorone diisocyanate (IPDI): 2g; Polyethylene glycol (PEG400): 1g; Dibutyltin dilaurate (DBTDL): 0.003g; Triethylamine: 0.02g; Cyclohexane: 7g.

[0048] A method for preparing a urea-formaldehyde resin / polyurethane composite modified material includes the following steps: Step 1: Preparation of melamine-modified urea-formaldehyde resin / polyvinyl alcohol composite microcapsules: Step 1-1: Add melamine, urea, formaldehyde, and water to a 250mL three-necked flask. Start stirring and control the stirring speed at 200rpm. Adjust the pH to 8.5 by adding sodium hydroxide solution (10wt%) dropwise. Heat the reaction vessel to 72℃ and maintain the reaction for 1.5 hours. Obtain the prepolymer.

[0049] Steps 1-2: Add PVA and SDBS to the prepolymer above and continue stirring for 10 minutes. Then, slowly add E-44 epoxy resin to the mixture. Increase the stirring speed to 800 rpm and emulsify at high speed for 30 minutes. The emulsion is then obtained.

[0050] Steps 1-3: Adjust the pH of the above emulsion to 3.5 by adding hydrochloric acid solution (10wt%) dropwise. Continue stirring and maintain the reaction temperature at 78℃ for 3 hours.

[0051] Steps 1-4: After the reaction is complete, add 25% glutaraldehyde aqueous solution as a crosslinking agent and continue stirring for 45 minutes.

[0052] Steps 1-5: Cool to room temperature, filter using a Buchner funnel, and wash the filter cake three times with deionized water. Dry the washed filter cake in a vacuum drying oven at 60℃ for 12 hours to obtain melamine-modified urea-formaldehyde resin / polyvinyl alcohol composite microcapsules.

[0053] Step 2: Dissolve the silane coupling agent (KH-550) in ethanol and stir until homogeneous to obtain a silane coupling agent solution. The weight ratio of silane coupling agent to ethanol is 1:5.

[0054] Melamine-modified urea-formaldehyde resin / polyvinyl alcohol composite microcapsules were added to a silane coupling agent solution and stirred until homogeneous. The reaction mixture was stirred continuously at room temperature for 3 hours, while simultaneously ultrasonically treating the reaction system at a frequency of 40 kHz for 30 minutes. The resulting mixture was the first mixture.

[0055] Step 3: Disperse fumed silica in ethanol and sonicate for 30 minutes. This yields a fumed silica dispersion. The weight ratio of fumed silica to ethanol is 1:10.

[0056] The first mixture was added to the fumed silica dispersion and stirred until homogeneous to obtain the second mixture.

[0057] Step 4: Add IPDI, PEG, DBTDL and triethylamine to cyclohexane, and stir until homogeneous under inert gas (nitrogen) protection at 70°C to obtain a polyurethane prepolymer solution.

[0058] The second mixture was added to the polyurethane prepolymer solution and stirred until homogeneous. The reaction was allowed to proceed for 5 hours, allowing the polyurethane prepolymer to polymerize on the surface of the microcapsules, forming a polyurethane-modified layer. This yielded the third mixture.

[0059] Step 5: Place the flask containing the third mixture into a vacuum drying oven, evacuate to -0.06 MPa, maintain for 30 minutes, and then slowly release the vacuum.

[0060] Step 6: Filtration. Wash the filter cake three times alternately with ethanol and deionized water. Dry the washed filter cake in a vacuum drying oven at 40℃ for 24 hours to obtain the urea-formaldehyde resin / polyurethane composite modified material.

[0061] Performance testing: 1. Dispersibility: The urea-formaldehyde resin / polyurethane composite modified material was added to the epoxy resin adhesive. The particle size distribution of the microcapsules was measured using a laser particle size analyzer, and the dispersion of the urea-formaldehyde resin / polyurethane composite modified material in the adhesive was observed using an optical microscope. This is the initial dispersion state.

[0062] Then, the particles were stored at 50°C and 85% humidity for 3 months, and the particle size distribution was measured and observed again. This is the dispersion state after storage.

[0063] Testing showed that, under initial dispersion conditions, the urea-formaldehyde resin / polyurethane composite modified material was uniformly dispersed in the adhesive without significant agglomeration.

[0064] In the dispersed state after storage, the urea-formaldehyde resin / polyurethane composite modified material is uniformly dispersed in the adhesive with little change in particle size distribution and no obvious agglomeration.

[0065] 2. Mechanical strength: The urea-formaldehyde resin / polyurethane composite modified material is added to the epoxy resin adhesive, and the tensile shear strength of the adhesive is tested according to GB / T 7124-2008 standard. This is the initial strength.

[0066] Then, after storing at 50℃ and 85% humidity for 3 months, the tensile shear strength was measured again; this is the strength after treatment.

[0067] The initial strength was tested to be 30 MPa, and the strength after treatment was 29 MPa.

[0068] Comparative Example 1 A microcapsule, the preparation method of which includes the following steps: Step 1: Add melamine, urea, formaldehyde, and water to a 250mL three-necked flask. Start stirring and control the stirring speed at 150-250rpm. Adjust the pH value to 8.0-8.5 by adding sodium hydroxide solution (5-15wt%) dropwise. Heat the reaction vessel to 70-75℃ and maintain the reaction for 1-2 hours. Obtain the prepolymer.

[0069] Step 2: Add PVA and surfactant to the prepolymer and continue stirring for 5-20 minutes. Then, slowly add E-44 epoxy resin to the mixture. Increase the stirring speed to 750-850 rpm and emulsify at high speed for 20-40 minutes to obtain the emulsion.

[0070] Step 3: Adjust the pH of the above emulsion to 3.0-3.8 by adding hydrochloric acid solution (5-15wt%) dropwise. Continue stirring and maintain the reaction temperature at 75-80℃ for 2.5-3.5 hours.

[0071] Step 4: After the reaction is complete, add 25% glutaraldehyde aqueous solution as a crosslinking agent and continue stirring for 30-60 minutes.

[0072] Step 5: Cool to room temperature, filter using a Buchner funnel, and wash the filter cake three times with deionized water. Dry the washed filter cake in a vacuum drying oven at 60°C for 12 hours to obtain microcapsules.

[0073] Performance testing: 1. Dispersibility: Tests showed that the microcapsules were uniformly dispersed in the adhesive under the initial dispersion state, and no obvious agglomeration occurred.

[0074] In the dispersed state after storage, the microcapsules are unevenly dispersed in the adhesive, with an increased average particle size and a wide and uneven particle size distribution, resulting in agglomeration.

[0075] 2. Mechanical strength: The initial strength was tested to be 25 MPa, and the strength after treatment was 20 MPa.

[0076] Comparative Example 1, while maintaining good dispersion in its initial dispersed state, showed a significant decrease in water resistance and mechanical strength after omitting subsequent treatment steps such as silane coupling agent and polyurethane prepolymer solution. After high temperature and high humidity treatment, its dispersibility deteriorated.

[0077] Comparative Example 2 A urea-formaldehyde resin / polyurethane composite modified material, which differs from Example 1 in that melamine is omitted.

[0078] Performance testing: 1. Dispersibility: Tests showed that the urea-formaldehyde resin / polyurethane composite modified material was uniformly dispersed in the adhesive under the initial dispersion state, and no obvious agglomeration occurred.

[0079] In the dispersed state after storage, the urea-formaldehyde resin / polyurethane composite modified material is more uniformly dispersed in the adhesive, with a slightly larger average particle size and a wider particle size distribution than before, and a small amount of local agglomeration occurs.

[0080] 2. Mechanical strength: The initial strength was tested to be 27 MPa, and the strength after treatment was 23.5 MPa.

[0081] Comparative Example 2 omitted melamine compared to Example 1. This prevented some synergistic effects in the system from being achieved, resulting in decreased mechanical strength and poor water resistance. However, it is worth emphasizing that this effect is not due to melamine alone, but rather to the chemical and physical synergies between melamine and other substances.

[0082] Commercially available urea-formaldehyde resin microcapsules were used as comparative example 3.

[0083] Performance testing: 1. Dispersibility: Tests showed that, under initial dispersion conditions, commercially available urea-formaldehyde resin microcapsules were dispersed relatively evenly in adhesives without significant agglomeration.

[0084] In the dispersed state after storage, commercially available urea-formaldehyde resin microcapsules are unevenly dispersed in adhesives, with a wide and uneven particle size distribution, and localized obvious agglomeration and rupture phenomena.

[0085] 2. Mechanical strength: The initial strength was tested to be 21 MPa, and the strength after treatment was 15 MPa.

[0086] Based on the test data, it can be seen that the composite modified material of Example 1 has significantly improved mechanical strength, water resistance and dispersibility compared with commercially available urea-formaldehyde resin microcapsules, and its performance has been effectively improved.

[0087] It should be understood that the application of this application is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of this application.

Claims

1. A urea-formaldehyde resin / polyurethane hybrid modified material, characterized by, By mass, including the following preparation raw materials: Melamine: 25-35 parts; Formaldehyde: 35-40 parts; Urea: 15-25 parts; Polyvinyl alcohol: 3-8 parts; Surfactant: 0.1-2 parts; Water: 90-120 parts; Core material: 55-65 parts; Crosslinking agent: 0.1-1 parts; Silane coupling agent: 1-5 parts; Silicon dioxide: 0.1-3 parts; Isocyanate: 1-3 parts; Polyethylene glycol: 0.1-2 parts; Catalyst: 0.001-0.01 parts; Triethylamine: 0.01-0.05 parts; Cyclohexane: 5-10 parts.

2. The urea-formaldehyde resin / polyurethane hybrid modified material according to claim 1, characterized by, The surfactant includes sodium dodecyl benzene sulfonate; The silane coupling agent includes KH-550; The isocyanate includes isophorone diisocyanate; The catalyst includes dibutyl tin dilaurate.

3. A method for producing the urea-formaldehyde resin / polyurethane composite modified material according to any one of claims 1 to 2, characterized by, Including the following steps: Using melamine, urea, formaldehyde, water, polyvinyl alcohol, surfactant, core material, crosslinking agent to prepare melamine modified urea-formaldehyde resin / polyvinyl alcohol composite microcapsule; Mixing the silane coupling agent with the melamine modified urea-formaldehyde resin / polyvinyl alcohol composite microcapsule to obtain a first mixture; Mixing the silicon dioxide with the first mixture to obtain a second mixture; Mixing the isocyanate, polyethylene glycol, catalyst, triethylamine, cyclohexane at 65-75℃ under inert gas protection to obtain a polyurethane prepolymer solution; Adding the second mixture to the polyurethane prepolymer solution and reacting for 4.5-5.5h to obtain a third mixture; Drying, washing, and drying the third mixture to obtain a urea-formaldehyde resin / polyurethane composite modified material.

4. The production method of urea-formaldehyde resin / polyurethane complex modified material according to claim 3, characterized by, The method for preparing the melamine modified urea-formaldehyde resin / polyvinyl alcohol composite microcapsule includes the following steps: Mixing melamine, urea, formaldehyde, and water, adjusting the pH to 8.0-8.5, and reacting at 70-75℃ for 1-2h to obtain a prepolymer; Mixing the polyvinyl alcohol, surfactant, and prepolymer, then adding the core material and stirring at high speed to obtain an emulsion. Adjusting the pH of the emulsion to 3.0-3.8, stirring and reacting at 75-80℃ for 2.5-3.5h; After the reaction is completed, adding the crosslinking agent and stirring for 30-60min; Cooling, filtering, washing, and drying to obtain the melamine modified urea-formaldehyde resin / polyvinyl alcohol composite microcapsule.

5. The preparation method of the urea-formaldehyde resin / polyurethane composite modified material according to claim 3, characterized in that, After adding the core material, stirring and emulsifying at 750-850rpm for 20-40min.

6. The preparation method of the urea-formaldehyde resin / polyurethane composite modified material according to claim 3, characterized in that, Mixing the silane coupling agent with the melamine modified urea-formaldehyde resin / polyvinyl alcohol composite microcapsule and stirring for 2.5-3.5h; during the stirring, ultrasonically treating the reaction system at a frequency of 35-45kHz for 20-40min to obtain a first mixture.

7. The preparation method of the urea-formaldehyde resin / polyurethane composite modified material according to claim 3, characterized in that, Mixing the silane coupling agent with an organic solvent ultrasonically to obtain a silane coupling agent solution; mixing the silane coupling agent solution with the melamine modified urea-formaldehyde resin / polyvinyl alcohol composite microcapsule to obtain a first mixture Mixing the silicon dioxide with an organic solvent ultrasonically to obtain a silicon dioxide dispersion; mixing the silicon dioxide dispersion with the first mixture to obtain a second mixture; The organic solvents used by the silane coupling agent solution and the silicon dioxide dispersion are the same or different.

8. The method for preparing urea-formaldehyde resin / polyurethane complex modified material according to claim 7, characterized in that, Mixing the silane coupling agent with the organic solvent ultrasonically at a weight ratio of 1:4-6 to obtain a silane coupling agent solution.

9. The preparation method of the urea-formaldehyde resin / polyurethane composite modified material according to claim 7, characterized in that, Silica and organic solvent are mixed by weight ratio 1:8-12 ultrasonically to obtain silica dispersion.

10. The use of the obtained urea-formaldehyde resin / polyurethane composite modified material prepared according to the method of preparing the urea-formaldehyde resin / polyurethane composite modified material based on any one of claims 1-2 or 3-9 in industrial glue.