A green and environment-friendly high methyl etherified resin adhesive and a preparation method thereof

Abstract

The present application belongs to the technical field of environmental protection chemical materials, and particularly relates to a green and environment-friendly high-methyl-etherified resin adhesive and a preparation method thereof. The adhesive comprises a high-methyl-etherified melamine formaldehyde resin matrix and temperature-sensitive slow-release capsules dispersed therein. The capsules are composed of a temperature-sensitive liposome encapsulating a formaldehyde adsorbent and a VOC adsorbent. The preparation method comprises the following steps: synthesizing the resin matrix through a two-step method; preparing the temperature-sensitive liposome by using an ether injection method to encapsulate the adsorbents, and then obtaining capsule powder through freeze-drying; and finally, compounding the two. Through the intelligent response release characteristics of the temperature-sensitive capsules, the present application can accurately release the adsorbents in the curing temperature range of the adhesive, realize in-situ efficient capture of free formaldehyde and volatile organic compounds generated in the curing process, thereby significantly reducing the pollutant emissions in the coating process, and not affecting the original mechanical properties and workability of the adhesive.

Description

Technical Field

[0001] This invention relates to the field of environmentally friendly chemical materials technology, specifically to a green and environmentally friendly high-methyl etherified resin adhesive and its preparation method. Background Technology

[0002] Highly methylated melamine-formaldehyde resin (HMMM), as a type of high-performance amino resin, is widely used as a key crosslinking agent in solvent-based or high-solids coatings due to its excellent crosslinking efficiency, outstanding chemical resistance, high gloss, and good thermal stability. It is widely applied in industrial coating fields such as automobiles, coil coatings, and furniture. However, during its curing and crosslinking process, residual free formaldehyde in the resin itself, as well as formaldehyde, methanol, and other byproducts generated by the cleavage of ether bonds at high temperatures, are released as volatile organic compounds (VOCs) and harmful air pollutants, posing potential risks to the production environment and human health, and are increasingly subject to stringent environmental regulations.

[0003] To reduce formaldehyde release from amino resins, existing technologies mainly focus on two approaches: one is modification during the resin synthesis stage, such as optimizing the process to increase the degree of etherification to stabilize the molecular structure, or adding scavenging agents like urea or caprolactam for post-treatment; the other is adding powdered or liquid formaldehyde scavengers to the coating formulation. However, the first method has limited effectiveness against newly generated formaldehyde during curing, while the second method suffers from a mismatch between the timing of addition and the peak formaldehyde release. Traditional adsorbents may be prematurely consumed or have their stability affected during the coating's storage period, while failing to fully release when they are needed in the early stages of curing, resulting in low scavenging efficiency.

[0004] In recent years, microencapsulation technology has provided new insights into the intelligent development of functional additives. Temperature-sensitive materials, especially liposomes with phase transition behavior, can undergo structural transformation when the external temperature reaches their specific phase transition point, thereby achieving controlled release of their contents. If a temperature-sensitive capsule could be designed with a release trigger temperature precisely matching the curing initiation temperature of amino resin, and encapsulating a highly efficient adsorbent within it, it would be possible to achieve "precise treatment at the time and place of pollutant generation," a problem that current technologies have not yet effectively solved. Therefore, developing a highly methylated resin adhesive that integrates an intelligent responsive pollution control unit is of urgent need and significant value in promoting the green upgrading of the coatings industry. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a green and environmentally friendly high-methyl etherified resin adhesive, which is formulated from the following components in parts by weight: resin matrix: 1000-2000 parts, thermosensitive sustained-release capsule powder: 15-60 parts, polyoxyethylene sorbitan monooleate: 2-6 parts, and polyether-modified polysiloxane: 1-3 parts.

[0006] As another aspect of the present invention, a method for preparing the above-mentioned highly methylated resin adhesive is also provided, the details of which are as follows: S1, hydroxymethylation reaction: First, melamine and formaldehyde aqueous solution are added to a reaction vessel and stirred evenly. Then, 5% sodium hydroxide aqueous solution is added to adjust the pH of the system to 8.5-9.0. The hydroxymethylation reaction is carried out at a stirring rate of 200-400 rpm, the reaction temperature is controlled at 75-85℃, and the reaction time is 80-100 min until the solution is clear. After the reaction is completed, the system is cooled to 55-60℃ to obtain the hydroxymethylation reaction solution. Let n be the multiplier and n∈ The amount of melamine added is [126n, 132n] g, and the concentration of the formaldehyde aqueous solution is 37 wt%, and its added amount is [243n, 324n] mL. Note: This step is a hydroxymethylation reaction. Under weakly alkaline conditions, the amino groups on the melamine molecule undergo an addition reaction with formaldehyde to generate a polyhydroxymethyl melamine intermediate. Controlling the pH at 8.5~9.0 and the temperature at 75~85℃ aims to optimize the reaction rate and selectivity, ensuring the generation of an intermediate with a high hydroxymethyl content, laying the foundation for achieving a high degree of etherification in the subsequent process, while avoiding excessive polycondensation. S2, Etherification reaction: First, methanol is added to the hydroxymethylation reaction solution obtained in S1, and then a 10% formic acid aqueous solution is added to adjust the pH of the system to 4.0-5.0 for etherification reaction. The reaction temperature is controlled at 58-65℃ and the reaction time is 100-130 min. After the reaction is completed, a 5% sodium hydroxide aqueous solution is added to adjust the pH of the system to 8.5-9.0 to obtain the etherified resin solution. Let n be the multiplier and n∈ Therefore, the amount of methanol added is [320n, 380n] mL; Note: This step is an etherification reaction. Under acidic catalysis, hydroxymethyl groups react with excess methanol to form methoxy groups. Maintaining a weakly acidic pH range of 4.0-5.0 and a reaction temperature of 58-65°C can effectively promote the forward etherification reaction and inhibit side reactions, thereby obtaining a resin with high methoxylation degree and low free formaldehyde content. After the reaction is completed, neutralizing to a weakly alkaline state can terminate the reaction and ensure product storage stability. S3, Post-processing: Excess methanol, water and small molecule byproducts are removed from the etherified resin solution obtained by vacuum distillation in S2. The distillation temperature is controlled at 60~65℃ and the system vacuum degree is -0.085 ~ -0.095 MPa until the resin solid content in the resin system is 65~70%, and the resin matrix is ​​obtained. Note: This step removes low-boiling-point components through vacuum distillation, which can purify the resin, increase the solid content, and directly reduce the volatile organic compound content in the product; S4. Preparation and compounding of thermosensitive sustained-release capsules: Thermosensitive sustained-release capsules targeting formaldehyde-VOC adsorption were prepared using thermosensitive liposome encapsulation technology and then compounded with the resin matrix prepared in S3 to obtain a highly methylated resin adhesive.

[0007] Note: This step outlines the core strategy of functional modification; by introducing self-prepared temperature-sensitive sustained-release capsules, the adhesive is given the function of intelligently responding to release adsorbents, thereby actively capturing pollutants during the curing process and improving the environmental performance of the product.

[0008] Furthermore, the specific steps for preparing and compounding the thermosensitive sustained-release capsules in S4 are as follows: S4-1. Preparation of core material: Mix formaldehyde adsorbent and VOC adsorbent and add to deionized water. Stir evenly and then ultrasonically disperse for 30-40 minutes at a power of 250-300 W and a frequency of 40-50 kHz to obtain a uniform core material suspension. Let n be the multiplier and n∈ The amount of formaldehyde adsorbent added is [10n, 20n] g, the amount of VOC adsorbent added is [5n, 10n] g, and the amount of deionized water added is [1000n, 1200n] mL. Explanation: In this step, two complementary adsorbents are evenly dispersed to form the core material of the capsule; the formaldehyde adsorbent mainly relies on the chemical capture of formaldehyde by surface-active amino groups, while the VOC adsorbent utilizes its porous structure to physically adsorb various small organic molecules. The combination of the two can achieve synergistic treatment of the main pollutants in solidified waste gas. S4-2. Preparation of membrane material solution: Dissolve hydrogenated soybean phospholipids and cholesterol in anhydrous ethanol and stir until homogeneous to obtain membrane material solution; Let n be the multiplier and n∈ The amount of hydrogenated soybean lecithin added is [10n, 15n] g, the amount of cholesterol added is [1.2n, 2.3n] g, and the amount of anhydrous ethanol added is [350n, 500n] mL. Note: This step involves preparing the membrane material solution to form a lipid bilayer; hydrogenated soybean phospholipids are the main film-forming material, with a relatively high phase transition temperature; cholesterol is used to regulate the arrangement density of phospholipid molecules and membrane stability, and the ratio of the two is key to accurately controlling the final capsule phase transition temperature; S4-3, Preparation of capsule suspension: Under stirring at 500 rpm, the membrane material solution in S4-2 is added dropwise at a rate of 1~1.2 mL / min to the core material suspension in S4-1, which is preheated to 55~60℃; after the addition is complete, the mixture is kept warm and stirred for 2.5~3 h; then the system is naturally cooled to room temperature and granulated by passing it through 0.45 μm and 0.22 μm microporous membranes in sequence to obtain the capsule suspension; The volume ratio of the membrane solution to the core suspension is 1:10; Note: This step assembles thermosensitive liposome capsules using the ethanol injection method; under conditions higher than the phospholipid phase transition temperature, the membrane material ethanol solution is injected into the aqueous core material suspension, and the phospholipid molecules are oriented to coat the adsorbent particles, forming vesicles; by controlling the dropping rate and stirring conditions, capsules with uniform particle size distribution can be obtained. S4-4, freeze-drying: Add trehalose to the capsule suspension obtained in S4-3, pre-freeze at -40℃ for 4~5 h, and freeze-dry at -50℃ and 10 Pa for 24~30 h to obtain solid thermosensitive sustained-release capsule powder; Let n be the multiplier and n∈ The amount of capsule suspension added is [100n, 200n] mL, and the amount of trehalose added is [0.6n, 1.7n] g; Note: This step transforms the liquid suspension of capsules into a solid powder through freeze-drying, which greatly improves the product's storage stability and transportation convenience; trehalose, as a freeze-drying protectant, can maintain the integrity of the liposome structure during dehydration, preventing the capsules from rupturing during freeze-drying and rehydration. S4-5, Compounding: Mix the resin matrix obtained in S3 with the thermosensitive sustained-release capsule powder obtained in S4-4 evenly, then add polyoxyethylene sorbitan monooleate and polyether modified polysiloxane, and disperse at 1200~1300 rpm for 30~40 min to obtain highly methylated resin adhesive. Let n be the multiplier and n∈ The amount of resin matrix added is [1000n, 2000n] g, the amount of thermosensitive sustained-release capsule powder added is [15n, 60n] g, the amount of oxyethylene sorbitan monooleate added is [2n, 6n] g, and the amount of polyether modified polysiloxane added is [1n, 3n] g.

[0009] Note: This step finalizes the compounding of the smart capsules with the resin matrix; the wetting agent (polyoxyethylene sorbitan monooleate) helps the capsules disperse in the resin; the defoamer (polyether-modified polysiloxane) prevents high-speed dispersion from introducing air bubbles that could affect product performance; this process ensures that the functional capsules are evenly distributed in the adhesive without compromising the original application and curing properties of the resin.

[0010] Furthermore, the preparation method of the formaldehyde adsorbent in S4-1 is as follows: S4-1-A1. Mix alkali lignin and urea evenly, add deionized water and stir. React hydrothermally at 180~220℃ for 8~12 h. After cooling, filter, wash and dry to obtain nitrogen-doped lignin precursor. Let n be the multiplier and n∈ Then the amount of alkali lignin added is [10n, 20n] g, the amount of urea added is [5n, 20n] g, and the amount of deionized water added is [200n, 400n] mL; Explanation: This step uses a hydrothermal method to combine biomass alkali lignin with urea; under high temperature and high pressure hydrothermal environment, urea decomposes and reacts with lignin, doping nitrogen elements into the lignin backbone in the form of amino groups, forming a precursor rich in active nitrogen sites. S4-1-A2. Nitrogen-doped lignin precursor is heated to 600~800℃ at a rate of 5℃ / min under nitrogen protection, calcined for 2~3 h, and then ground after natural cooling to obtain amino-modified lignin-based porous carbon microspheres, i.e. formaldehyde adsorbent.

[0011] Explanation: This step transforms the precursor into a porous carbon material through high-temperature oxygen-limited calcination (carbonization). This process not only forms a rich microporous structure to provide a huge specific surface area, but also retains some nitrogen-containing functional groups (such as amino groups). These amino groups can form irreversible chemical bonds with formaldehyde, thereby achieving efficient and long-lasting formaldehyde capture capabilities.

[0012] Furthermore, the preparation method of the VOC adsorbent in S4-1 is as follows: S4-1-B1. First, dissolve β-cyclodextrin in deionized water, add 5% sodium hydroxide aqueous solution to adjust the pH of the system to 10.0~11.0, then add epichlorohydrin and react at 50~60℃ for 4~6 h to obtain cross-linked cyclodextrin polymer solution. Let n be the multiplier and n∈ Then the amount of β-cyclodextrin added is [20n, 30n] g, the amount of deionized water added is [200n, 300n] mL, and the amount of epichlorohydrin added is [20n, 30n] mL; Note: In this step, under alkaline conditions, epichlorohydrin is used as a crosslinking agent to link β-cyclodextrin molecules into a three-dimensional network polymer. This crosslinked structure enhances the stability of the material and retains the unique hydrophobic cavity structure of the cyclodextrin molecules. This cavity can effectively adsorb various VOC molecules such as benzene series compounds, alcohols, and esters through host-guest inclusion interactions.

[0013] S4-1-B2: Mix the graphene oxide dispersion with the cross-linked cyclodextrin polymer solution, and after ultrasonic dispersion, freeze at -18℃ for 12~24 h to completely solidify it; then place the frozen sample in a freeze dryer and dry it under vacuum conditions below -50℃ and 10Pa for 24~48 h to obtain cyclodextrin-graphene oxide hybrid aerogel, which is then ground and used to obtain a VOC adsorbent. Let n be the multiplier and n∈ The concentration of the graphene oxide dispersion is 2 mg / mL, and its addition amount is [50n, 100n] mL, while the addition amount of the cross-linked cyclodextrin polymer solution is [100n, 150n] mL.

[0014] Note: This step involves preparing a hybrid aerogel using freeze-drying technology. The addition of graphene oxide provides a continuous framework and a large specific surface area, which, together with the cross-linked cyclodextrin polymer, forms a lightweight, high-porosity three-dimensional network structure. This structure significantly increases the contact and adsorption sites for VOC molecules and exhibits good structural strength.

[0015] Furthermore, the relationship between the mass ratio of hydrogenated soybean phospholipids to cholesterol in S4-2 and the phase transition temperature of the thermosensitive sustained-release capsule powder in S4-4 is as follows: When the mass ratio of hydrogenated soybean phospholipids to cholesterol is 10:1.5, the phase transition temperature of the thermosensitive sustained-release capsule powder is 105~115℃. When the mass ratio of hydrogenated soybean phospholipids to cholesterol is 10:1.7, the phase transition temperature of the thermosensitive sustained-release capsule powder is 115~125℃. When the mass ratio of hydrogenated soybean phospholipids to cholesterol is 10:2.0, the phase transition temperature of the thermosensitive sustained-release capsule powder is 125~135℃.

[0016] Note: Cholesterol acts as a membrane regulator; increasing its proportion increases the molecular packing density of the lipid bilayer, thereby shifting the phase transition temperature of the capsule to a higher temperature. By precisely controlling the mass ratio of hydrogenated soybean phospholipids to cholesterol, the trigger release temperature of the capsule can be precisely controlled within the resin curing temperature range of 110~150℃, achieving "on-demand" release of the adsorbent.

[0017] As another aspect of the present invention, the application of the above-mentioned green and environmentally friendly high methyl ether resin adhesive is also provided. The high methyl ether resin adhesive designed in this invention is used in the crosslinking curing component of metal coil coatings or industrial baking topcoats. During the crosslinking curing process of the above-mentioned industrial baking topcoat, at 110~150°C, the temperature-sensitive slow-release capsules contained in the adhesive can release adsorbents in response to the curing temperature, thereby capturing and reducing free formaldehyde and VOCs generated in the system in situ.

[0018] Compared with existing highly methylated resin adhesives, the advantages of this invention are: (1) This invention creatively combines thermosensitive sustained-release capsule technology with resin adhesive. The capsule uses hydrogenated soybean lecithin and cholesterol as wall materials. By precisely controlling the ratio, its phase change temperature can be precisely matched with the resin curing temperature (e.g., 115~125℃). Before the coating cures, the adsorbent is completely encapsulated without affecting the stability of the system. Once the baking and curing stage is entered, the temperature triggers the phase change of the capsule wall material, and the adsorbent is released rapidly and in a concentrated manner. It can efficiently capture the large amount of free formaldehyde and VOC generated at this time, realizing the source treatment of "immediate production and immediate elimination", and significantly reducing the exhaust gas emissions of the coating process.

[0019] (2) The main resin of this invention is synthesized using an optimized two-step process. By controlling the conditions of the hydroxymethylation and etherification reactions, a resin matrix with high methyl etherification degree, low free formaldehyde, and high stability is obtained. The functional capsules, as independent units, are added in powder form during the compounding stage. Through the selection of optimal wetting agents and dispersion processes, they can be uniformly dispersed in the resin without affecting its core application properties such as leveling, curing, and crosslinking. Finally, the adhesive retains the traditional advantages of high hardness, high adhesion, and chemical resistance, while also possessing environmental protection functions.

[0020] (3) In the preparation of the adsorbent, alkali lignin (a by-product of papermaking) and β-cyclodextrin (a biological source) are selected as raw materials, which reflects the high-value utilization of biomass resources and is an environmentally friendly process. Attached Figure Description

[0021] Figure 1 This is a flowchart of the preparation process of the present invention; Figure 2 This is a data graph of the temperature-sensitive capsule characteristic test in the experimental example, where the midpoint of the temperature = (high end value of the phase change temperature range - low end value of the phase change temperature range) / 2; Figure 3 This is a data graph showing the environmental performance test results of the curing process in the experimental example; Figure 4 This is a data graph of the adhesive storage stability test in the experimental example. Detailed Implementation

[0022] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.

[0023] Example 1: This example describes a method for preparing a green and environmentally friendly highly methylated resin adhesive under certain parameters.

[0024] S1, hydroxymethylation reaction: Take 126 g of melamine and 243 g of 37 wt% formaldehyde aqueous solution, add them to the reaction vessel and stir; add 5% sodium hydroxide aqueous solution to adjust the pH to 8.8; react at 300 rpm and 80℃ for 90 min; cool to 58℃ to obtain hydroxymethylation reaction solution; S2, Etherification reaction: Add 320 mL of methanol to the entire reaction solution of S1, and then add 10% formic acid aqueous solution to adjust the pH to 4.5; react at 62℃ for 120 min; after the reaction is complete, add 5% sodium hydroxide aqueous solution to adjust the pH to 8.8 to obtain etherified resin solution; S3, Post-processing: The S2 resin solution was distilled under reduced pressure at 62℃ and -0.09 MPa until the solid content was 68%, to obtain the resin matrix; S4. Preparation and compounding of thermosensitive sustained-release capsules: S4-1. Preparation of core material: Take 15 g of formaldehyde adsorbent (amino-modified lignin-based porous carbon microspheres), 7.5 g of VOC adsorbent (cyclodextrin-graphene oxide hybrid aerogel), add 1100 mL of deionized water, and ultrasonically disperse at 300W for 35 min to obtain a core material suspension. S4-2. Preparation of membrane material solution: Take 12 g of hydrogenated soybean lecithin and 2.04 g of cholesterol (mass ratio 10:1.7) and dissolve them in 400 mL of anhydrous ethanol; S4-3. Preparation of capsule suspension: At 55℃, the membrane material solution is added dropwise to the core material suspension (volume ratio 1:10) at a rate of 1 mL / min, and stirred for 2.8 h; after cooling, it is filtered through 0.45 μm and 0.22 μm filter membranes. S4-4, Freeze-drying: Take 150 mL of capsule suspension, add 1.26 g of trehalose (9% of the dry weight of lipids), pre-freeze at -40℃ for 4.5 h, freeze-dry at -50℃ and 10 Pa for 28 h to obtain capsule powder; S4-5, Compounding: Take 1000 g of resin matrix, 15 g of capsule powder, 2 g of polyoxyethylene sorbitan monooleate, and 1 g of polyether-modified polysiloxane, disperse at 1250 rpm for 35 min to obtain adhesive 1.

[0025] Example 2: Unlike Example 1, the amount of 37 wt% formaldehyde aqueous solution added in S1 is 324 g.

[0026] Example 3: Unlike Example 1, the amount of 37 wt% formaldehyde aqueous solution added in S1 is 202.5 g.

[0027] Example 4: Unlike Example 1, the amount of 37 wt% formaldehyde aqueous solution added in S1 is 364.5 g.

[0028] Example 5: Unlike Example 1, the amount of methanol added in S2 is 256 mL.

[0029] Example 6: Unlike Example 1, the amount of methanol added in S2 is 380 mL.

[0030] Example 7: Unlike Example 1, formic acid was used to adjust the reaction pH to 4.0 in S2.

[0031] Example 8: Unlike Example 1, formic acid was used to adjust the reaction pH to 5.0 in S2.

[0032] Example 9: Unlike Example 1, in S4-2, 12 g of hydrogenated soybean lecithin and 1.8 g of cholesterol were used (mass ratio 10:1.5).

[0033] Example 10: Same as Example 1 (i.e., mass ratio 10:1.7).

[0034] Example 11: Unlike Example 1, in S4-2, 12 g of hydrogenated soybean lecithin and 2.4 g of cholesterol were used (mass ratio 10:2.0).

[0035] Example 12: Unlike Example 1, in S4-1, 20 g of formaldehyde adsorbent and 5 g of VOC adsorbent were used (mass ratio 4:1).

[0036] Example 13: Unlike Example 1, in S4-1, 10 g of formaldehyde adsorbent and 10 g of VOC adsorbent were used (mass ratio 1:1).

[0037] Example 14: Unlike Example 1, the amount of thermosensitive sustained-release capsule powder added in S4-5 is 7.5 g (accounting for 0.75% of the resin matrix).

[0038] Example 15: Unlike Example 1, the amount of thermosensitive sustained-release capsule powder added in S4-5 is 30 g (accounting for 3.0% of the resin matrix).

[0039] Example 16: Unlike Example 1, the dispersion rate in S4-5 is 1000 rpm.

[0040] Example 17: Unlike Example 1, the dispersion time in S4-5 is 20 min.

[0041] Example 18: Unlike Example 1, polyoxyethylene sorbitan monooleate was not added in S4-5.

[0042] Example 19: Control adhesive for thermosensitive capsules.

[0043] The preparation method is the same as in Example 1, but the entire S4 step is omitted. During compounding, only the resin matrix is ​​mixed evenly with polyoxyethylene sorbitan monooleate and polyether-modified polysiloxane. This mixture is designated as adhesive 19.

[0044] Example 20: Adhesive containing blank capsules (without adsorbent).

[0045] The preparation method is the same as in Example 1, but in S4-1, no formaldehyde adsorbent or VOC adsorbent is added; only an equal volume of deionized water is used to prepare a blank core material suspension, and the subsequent steps are the same. An adhesive containing the blank temperature-sensitive capsule is obtained, denoted as Adhesive 20.

[0046] Example 21: A binder for directly mixing adsorbents.

[0047] The preparation method is the same as in Example 1, but steps S4-2 to S4-4 are omitted. In step S4-5, during compounding, the formaldehyde adsorbent and VOC adsorbent powder (total 22.5 g) are directly mixed with the resin matrix and other additives. This mixture is designated as binder 21.

[0048] Examples 22-24: Adhesives for capsules with different phase change temperatures (corresponding to products in Examples 9-11).

[0049] The thermosensitive sustained-release capsule powders prepared in Examples 9, 10, and 11 were compounded according to the S4-5 ratio of Example 1 to obtain binder 22 (low temperature phase change), binder 23 (medium temperature phase change / same as binder 1), and binder 24 (high temperature phase change).

[0050] Example 25: Adhesive using common formaldehyde scavengers.

[0051] The preparation method is the same as in Example 19 (without capsules). After obtaining the resin matrix in S3, 4% by weight of a urea-borax mixture (mass ratio 8:1) is added, stirred for 30 minutes, and then compounded. This is designated as binder 25.

[0052] Experimental example: Performance testing and data analysis.

[0053] 1. Temperature-sensitive capsule characteristic test The capsule powders prepared in Examples 9, 10, 11 and Example 1 (S4-4) were tested.

[0054] Methods: Phase transition temperature was determined by differential scanning calorimetry; encapsulation efficiency after 7 days of storage at low temperature (40℃) was determined by centrifugation; core material release rate was determined after 15 minutes in phosphate buffer at 120℃. Results are shown in the table below: Table 1. Temperature-sensitive capsule characteristic test

[0055] As can be seen from the data in Table 1, when the ratio of phospholipids to cholesterol is 10:1.7, the phase transition temperature (117-123℃) best matches the typical curing temperature, resulting in a high release rate. At a ratio of 10:2.0, the phase transition temperature is too high, leading to a low triggered release rate.

[0056] 2. Environmental performance test of the curing process.

[0057] Adhesives 1, 19, 20, 21, 22, 24, and 25 were tested.

[0058] Methods: The adhesive and hydroxyl acrylic resin were mixed in a specific ratio to form a paint, which was then sprayed onto a tinplate sheet and cured at 140℃ for 20 minutes. The formaldehyde release from the cured film in a sealed chamber was determined according to GB / T 23993-2009; the total VOCs were determined by gas chromatography. The results are shown in the table below: Table 2 Environmental performance test of the curing process

[0059] It can be seen that adhesive 1 (containing a phase change-matched temperature-sensitive capsule) has the lowest formaldehyde and VOC release, and its environmental performance is significantly better than other control samples. Compared with adhesive 19, which has no adsorption function, and adhesive 20, which contains only blank capsules, this demonstrates the core role of the temperature-sensitive capsule and its internal adsorbent. Compared with adhesive 21, which directly mixes the adsorbent, this demonstrates the importance of encapsulation technology in protecting the adsorbent's activity and preventing its premature deactivation. Compared with adhesives 22 (too low) and 24 (too high), which do not match the capsule's phase change temperature, this demonstrates the criticality of precisely matching the release timing with the curing window. Compared with adhesive 25, which uses a traditional formaldehyde scavenger, this highlights the synergistic VOC removal capability of the composite adsorbent of this invention.

[0060] 3. Adhesive base application performance test.

[0061] Adhesives 1, 19, 21, 25 and the products of Examples 14-15 were tested.

[0062] Methods: Prepare the test plate according to Test 2. Pencil hardness was measured according to GB / T 6739-2006; adhesion (grade 0 being the best) was measured according to GB / T 9286-2021; impact resistance (positive / negative impact, 50 kg·cm) was measured according to GB / T 1732-2020; and flexibility (shaft diameter 2 mm) was measured according to GB / T 6742-2007. The results are shown in the table below: Table 3 Adhesive Base Application Performance Tests

[0063] It can be seen that the adhesive 1 prepared at the preferred addition amount (1.5%) exhibits pencil hardness, adhesion, impact resistance, and flexibility of a coating film that are at an equally excellent level as the base resin (adhesive 19) and the sample using a conventional trapping agent (adhesive 25). This indicates that the present invention, while providing excellent environmental protection functions, completely maintains the original mechanical properties of the resin. However, the adhesive 21, which directly mixes the adsorbent, suffers a decline in various properties due to the adsorbent disrupting the density of the paint film; when the amount of temperature-sensitive capsules added is too high (Example 15, 3.0%), it also has a significant negative impact on the hardness, adhesion, and toughness of the paint film.

[0064] 4. Adhesive storage stability test.

[0065] Adhesives 1, 21 and the products of Examples 16-18 were tested.

[0066] Method: The sample was placed in a 40℃ oven, periodically removed and allowed to return to 25℃ before viscosity was measured. The viscosity change rate after 14 days was calculated. The results are shown in the table below: Table 4 Adhesive Storage Stability Test

[0067] As shown in Table 4, adhesive 1, prepared using the complete process, exhibits good storage stability, with a viscosity increase of only 11.5% after 14 days of accelerated aging. Adhesive 21, which directly mixes the adsorbent, shows the worst stability, with a viscosity surge of 66.7%, due to uncontrolled interactions between the unencapsulated adsorbent and the resin components. Imperfect compounding processes also affect stability: insufficient dispersion rate (Example 16) and excessively short dispersion time (Example 17) lead to uneven capsule dispersion, causing slight sedimentation and increased viscosity; while the absence of a wetting agent (Example 18) results in severe capsule aggregation and sedimentation, increasing the viscosity change rate to 37.1%. This fully demonstrates the necessity of an optimized compounding process for ensuring product uniformity and storage stability.

Claims

1. A green and environmentally friendly highly methylated resin adhesive, characterized in that, It is formulated from the following components in parts by weight: Resin matrix: 1000~2000 parts, thermosensitive sustained-release capsule powder: 15~60 parts, polyoxyethylene sorbitan monooleate: 2~6 parts, polyether modified polysiloxane: 1~3 parts.

2. The preparation method of the green and environmentally friendly high-methyl etherified resin adhesive as described in claim 1, characterized in that, Includes the following steps: S1, hydroxymethylation reaction: First, melamine and formaldehyde aqueous solution are added to a reaction vessel and stirred evenly. Then, 5% sodium hydroxide aqueous solution is added to adjust the pH of the system to 8.5-9.

0. The hydroxymethylation reaction is carried out at a stirring rate of 200-400 rpm, the reaction temperature is controlled at 75-85℃, and the reaction time is 80-100 min until the solution is clear. After the reaction is completed, the system is cooled to 55-60℃ to obtain the hydroxymethylation reaction solution. Let n be the multiplier and n∈ The amount of melamine added is [126n, 132n] g, and the concentration of the formaldehyde aqueous solution is 37 wt%, and the amount added is [243n, 324n] mL. S2, Etherification reaction: First, methanol is added to the hydroxymethylation reaction solution obtained in S1, and then a 10% formic acid aqueous solution is added to adjust the pH of the system to 4.0-5.0 for etherification reaction. The reaction temperature is controlled at 58-65℃ and the reaction time is 100-130 min. After the reaction is completed, a 5% sodium hydroxide aqueous solution is added to adjust the pH of the system to 8.5-9.0 to obtain the etherified resin solution. Let n be the multiplier and n∈ The amount of methanol added is [320n, 380n] mL; S3, Post-processing: Excess methanol, water and small molecule byproducts are removed from the etherified resin solution obtained by vacuum distillation in S2. The distillation temperature is controlled at 60~65℃ and the system vacuum degree is -0.085 ~ -0.095 MPa until the resin solid content in the resin system is 65~70%, and the resin matrix is ​​obtained. S4. Preparation and compounding of thermosensitive sustained-release capsules: Thermosensitive sustained-release capsules targeting formaldehyde-VOC adsorption were prepared using thermosensitive liposome encapsulation technology and then compounded with the resin matrix prepared in S3 to obtain a highly methylated resin adhesive.

3. The preparation method of the green and environmentally friendly high-methyl etherified resin adhesive as described in claim 2, characterized in that, The specific steps for preparing and compounding the thermosensitive sustained-release capsules in S4 are as follows: S4-1. Preparation of core material: Mix formaldehyde adsorbent and VOC adsorbent and add to deionized water. Stir evenly and then ultrasonically disperse for 30-40 minutes at a power of 250-300 W and a frequency of 40-50 kHz to obtain a uniform core material suspension. Let n be the multiplier and n∈ The amount of formaldehyde adsorbent added is [10n, 20n] g, the amount of VOC adsorbent added is [5n, 10n] g, and the amount of deionized water added is [1000n, 1200n] mL. S4-2. Preparation of membrane material solution: Dissolve hydrogenated soybean phospholipids and cholesterol in anhydrous ethanol and stir until homogeneous to obtain membrane material solution; Let n be the multiplier and n∈ The amount of hydrogenated soybean lecithin added is [10n, 15n] g, the amount of cholesterol added is [1.2n, 2.3n] g, and the amount of anhydrous ethanol added is [350n, 500n] mL. S4-3, Preparation of capsule suspension: Under stirring at 500 rpm, the membrane material solution in S4-2 is added dropwise at a rate of 1~1.2 mL / min to the core material suspension in S4-1, which is preheated to 55~60℃; after the addition is complete, the mixture is kept warm and stirred for 2.5~3 h; then the system is naturally cooled to room temperature and granulated by passing it through 0.45 μm and 0.22 μm microporous membranes in sequence to obtain the capsule suspension; The volume ratio of the membrane solution to the core suspension is 1:10; S4-4, freeze-drying: Add trehalose to the capsule suspension obtained in S4-3, pre-freeze at -40℃ for 4~5 h, and freeze-dry at -50℃ and 10 Pa for 24~30 h to obtain solid thermosensitive sustained-release capsule powder; Let n be the multiplier and n∈ The amount of the capsule suspension added is [100n, 200n] mL, and the amount of trehalose added is [0.6n, 1.7n] g; S4-5, Compounding: Mix the resin matrix obtained in S3 with the thermosensitive sustained-release capsule powder obtained in S4-4 evenly, then add polyoxyethylene sorbitan monooleate and polyether modified polysiloxane, and disperse at 1200~1300 rpm for 30~40 min to obtain highly methylated resin adhesive. Let n be the multiplier and n∈ The amount of resin matrix added is [1000n, 2000n] g, the amount of thermosensitive sustained-release capsule powder added is [15n, 60n] g, the amount of oxyethylene sorbitan monooleate added is [2n, 6n] g, and the amount of polyether modified polysiloxane added is [1n, 3n] g.

4. The preparation method of a green and environmentally friendly highly methylated resin adhesive as described in claim 2, characterized in that, The method for preparing the formaldehyde adsorbent described in S4-1 is as follows: S4-1-A1. Mix alkali lignin and urea evenly, add deionized water and stir. React hydrothermally at 180~220℃ for 8~12 h. After cooling, filter, wash and dry to obtain nitrogen-doped lignin precursor. Let n be the multiplier and n∈ Then the amount of alkali lignin added is [10n, 20n] g, the amount of urea added is [5n, 20n] g, and the amount of deionized water added is [200n, 400n] mL; S4-1-A2. The nitrogen-doped lignin precursor is heated to 600~800℃ at a rate of 5℃ / min under nitrogen protection, calcined for 2~3 h, and then ground after natural cooling to obtain amino-modified lignin-based porous carbon microspheres, i.e., formaldehyde adsorbent.

5. The preparation method of a green and environmentally friendly highly methylated resin adhesive as described in claim 2, characterized in that, The preparation method of the VOC adsorbent described in S4-1 is as follows: S4-1-B1. First, dissolve β-cyclodextrin in deionized water, add 5% sodium hydroxide aqueous solution to adjust the pH of the system to 10.0~11.0, then add epichlorohydrin and react at 50~60℃ for 4~6 h to obtain cross-linked cyclodextrin polymer solution. Let n be the multiplier and n∈ Then the amount of β-cyclodextrin added is [20n, 30n] g, the amount of deionized water added is [200n, 300n] mL, and the amount of epichlorohydrin added is [20n, 30n] mL; S4-1-B2. The graphene oxide dispersion is mixed with the cross-linked cyclodextrin polymer solution, and after being ultrasonically dispersed evenly, it is frozen at -18℃ for 12~24 h to completely solidify it; then the frozen sample is placed in a freeze dryer and dried under vacuum conditions of -50℃ and below 10Pa for 24~48 h to obtain cyclodextrin-graphene oxide hybrid aerogel, which is then ground and used to obtain a VOC adsorbent. Let n be the multiplier and n∈ The concentration of the graphene oxide dispersion is 2 mg / mL, and the amount added is [50n, 100n] mL, while the amount added of the cross-linked cyclodextrin polymer solution is [100n, 150n] mL.

6. The preparation method of a green and environmentally friendly highly methylated resin adhesive as described in claim 2, characterized in that, The relationship between the mass ratio of hydrogenated soybean phospholipids to cholesterol in S4-2 and the phase transition temperature of the thermosensitive sustained-release capsule powder in S4-4 is as follows: When the mass ratio of hydrogenated soybean phospholipids to cholesterol is 10:1.5, the phase transition temperature of the thermosensitive sustained-release capsule powder is 105~115℃. When the mass ratio of hydrogenated soybean phospholipids to cholesterol is 10:1.7, the phase transition temperature of the thermosensitive sustained-release capsule powder is 115~125℃. When the mass ratio of hydrogenated soybean phospholipids to cholesterol is 10:2.0, the phase transition temperature of the thermosensitive sustained-release capsule powder is 125~135℃.

7. The application of the adhesive as described in claim 1 or the adhesive prepared by the method according to any one of claims 2 to 6, characterized in that, The adhesive is used in the cross-linking curing components of metal coil coatings or industrial baking topcoats.

8. The application as described in claim 7, characterized in that, During the crosslinking and curing process of the industrial baking topcoat, the adhesive contains temperature-sensitive slow-release capsules that can release adsorbents in response to the curing temperature at 110~150°C, thereby capturing and reducing free formaldehyde and VOCs generated in the system in situ.

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