Environment-friendly acrylic resin system with low monomer residue and preparation method thereof

Abstract

The invention belongs to the technical field of polymer chemistry and environment-friendly coatings, and particularly relates to a low-monomer-residue environment-friendly acrylic resin system and a preparation method thereof. The system comprises acrylate copolymer resin modified by ionic liquid-in-situ free radical induction-block copolymerization and small organic molecule 2-hydroxy-4-methoxyphenylacetamide, and is matched with a coalescing agent, a cross-linking agent, a flatting agent, a foam inhibitor and a light stabilizer. By introducing the 1-ethyl-3-methylimidazolium hexafluorophosphate ionic liquid, accurate regulation and control of free radical migration rate and chain growth in the polymerization process are realized, and monomer residues are effectively reduced; meanwhile, the phenolic hydroxyl group and the acylamino group of the 2-hydroxy-4-methoxyphenylacetamide are utilized to act, so that the bonding of hydrogen bonds and polarity among resin chains is enhanced, and the formed film is more compact and stable. The obtained resin system has high transparency, low VOC (volatile organic compound) emission and excellent yellowing resistance and adhesion performance, and is applicable to the fields of environment-friendly coatings, light-cured ink and functional polymer materials.

Description

Technical Field

[0001] This invention relates to the fields of polymer chemistry and environmentally friendly coatings, specifically to an environmentally friendly acrylic resin system with low monomer residue and its preparation method. Background Technology

[0002] Acrylic resins are widely used in coatings, inks, adhesives, and UV-curable materials due to their excellent film-forming properties, good weather resistance, high transparency, and stable mechanical properties. However, traditional acrylic resin systems often suffer from low monomer conversion rates and high residual monomer content during polymerization. This results in the volatile release of residual acrylate monomers into the resin, causing VOC pollution, which not only affects the safety and environmental performance of the product but also reduces film quality and long-term stability. To reduce monomer residue, existing technologies often employ methods such as increasing reaction temperature, extending reaction time, or increasing initiator dosage. However, these methods often lead to increased side reactions, darker resin color, uneven molecular weight distribution, and unstable crosslinking density, making it difficult to simultaneously achieve low residual monomer content and excellent performance.

[0003] Traditional acrylic acid systems typically lack effective control over polymerization radicals, resulting in uneven reaction rates, random chain growth, and a tendency to form defective segments and residual unreacted double bonds, affecting resin density and film strength. Existing modification methods, such as RAFT, ATRP, or reversible addition-fragmentation polymerization, can partially improve structural controllability, but these methods are complex, costly, and have poor industrial feasibility.

[0004] Therefore, there is an urgent need to develop an acrylic resin system with controllable structure, balanced reaction rate, and the ability to effectively reduce monomer residue while maintaining good mechanical and environmental performance. If an ionic liquid-induced free radical migration and block synergistic regulation mechanism can be introduced during polymerization, combined with an organic small molecule auxiliary structure possessing hydrogen bonding and polar interactions, high conversion rate and low monomer residue can be achieved at conventional temperatures, providing a new solution for environmentally friendly, high-performance acrylic resins. Summary of the Invention

[0005] To overcome the problems of high monomer residue, poor reaction controllability, and severe environmental pollution in the aforementioned background technologies of acrylic resins, the present invention aims to provide a low-monomer-residue environmentally friendly acrylic resin system and its preparation method. This invention employs ionic liquid-in-situ free radical induced-block copolymerization technology to structurally modify acrylate copolymer resins and introduces 2-hydroxy-4-methoxyphenylacetamide, a small organic molecule with phenolic hydroxyl and amide groups. Through hydrogen bonding and polar synergistic effects, the interchain forces of the resin are regulated, thereby achieving high-conversion polymerization and low-residue control under conventional conditions. This invention significantly reduces monomer residue and achieves high-conversion polymerization; the resulting resin exhibits excellent film-forming properties, high transparency, and strong adhesion; the system is stable, non-toxic, halogen-free, and has low VOCs and good environmental friendliness.

[0006] The objective of this invention can be achieved through the following technical solutions: A low-monomer residue environmentally friendly acrylic resin system, the resin system comprising the following raw materials in parts by weight: 60-90 parts of acrylate copolymer resin modified by ionic liquid-in-situ free radical induction-block copolymerization; 5-20 parts of 2-hydroxy-4-methoxyphenylacetamide; 3-8 parts of film-forming aid; 1-5 parts of crosslinking agent; 0.3-1 part of leveling agent; 0.2-0.5 parts of antifoaming agent; and 0.2-1 part of light stabilizer; wherein the 2-hydroxy-4-methoxyphenylacetamide is a simple organic small molecule containing phenolic hydroxyl and amide groups.

[0007] Optionally, the acrylate copolymer resin modified by ionic liquid-in-situ free radical induced-block copolymerization comprises the following raw materials in parts by weight: 20-40 parts of methyl methacrylate; 30-50 parts of butyl acrylate; 10-25 parts of hydroxyethyl acrylate; 5-15 parts of acrylic acid; 1-5 parts of 1-ethyl-3-methylimidazolium hexafluorophosphate; 0.3-1 part of azobisisobutyronitrile; and 0.2-0.6 parts of butyl p-hydroxybenzoate.

[0008] Optionally, the preparation method of acrylate copolymer resin modified by ionic liquid-in-situ free radical induced-block copolymerization includes the following steps: (1) Methyl methacrylate, butyl acrylate, hydroxyethyl acrylate, acrylic acid and 1-ethyl-3-methylimidazolium hexafluorophosphate are mixed, stirred evenly and then subjected to deoxygenation treatment to obtain a mixture; (2) Add azobisisobutyronitrile to the mixture to carry out the polymerization reaction; (3) Add a mixture of hydroxyethyl acrylate and acrylic acid dropwise and add an initiator to continue the reaction to form a block copolymer structure; (4) After the reaction is complete, the temperature is lowered and butyl p-hydroxybenzoate is added for stabilization treatment to obtain the resin; (5) The resin was subjected to degassing under reduced pressure, filtration and vacuum residue removal to obtain acrylate copolymer resin modified by ionic liquid-in-situ free radical induced-block copolymerization.

[0009] Optionally, the reaction conditions in step (1) are stirring and bubbling to remove oxygen for 15 to 30 minutes under nitrogen protection.

[0010] Optionally, the reaction conditions for step (2) are: reaction temperature 70-78℃, reaction time 1.5-2.5 hours; and the reaction conditions for step (3) are: maintaining temperature 70-78℃, dropping time 1-1.5 hours, and continuing reaction for 1.5-2.5 hours.

[0011] Optionally, the reaction conditions in step (4) are cooling to 50–60°C and stirring for 20–40 minutes; the reaction conditions in step (5) are reduced pressure. 0.06~ Degas at 0.09 MPa for 10–20 minutes, then remove residues by vacuum rotation for 30–60 minutes.

[0012] Optionally, the film-forming aid is a mixture of dipropylene glycol butyl ether and triethylene glycol monobutyl ether in a mass ratio of 1:1; the crosslinking agent is a mixture of hexamethylene diisocyanate trimer and glycidyl acrylate in a mass ratio of 2:1; the leveling agent is a mixture of polydimethylsiloxane and hydroxypropyl acrylate in a mass ratio of 1:3; the antifoaming agent is a mixture of polyether-modified polysiloxane and isobutanol in a mass ratio of 1:2; and the light stabilizer is a mixture of hindered amine light stabilizer HALS770 and ultraviolet absorber UV-327 in a mass ratio of 1:1.

[0013] Optionally, a method for preparing a low-monomer-residue environmentally friendly acrylic resin system includes the following steps: S1, the acrylate copolymer resin modified by ionic liquid-in-situ free radical-induced-block copolymerization is mixed with 2-hydroxy-4-methoxyphenylacetamide to form a homogeneous system; S2, add film-forming aid, crosslinking agent, leveling agent, antifoaming agent and light stabilizer to the homogeneous system in sequence, stir evenly to obtain a mixed system; S3, the mixed system is subjected to degassing treatment under reduced pressure to obtain a finished product of environmentally friendly acrylic resin system with low monomer residue.

[0014] Optionally, the reaction conditions for step S1 are stirring at 60°C for 1–2 hours; the reaction conditions for step S2 are adding each auxiliary agent sequentially at room temperature and stirring for 15–30 minutes; and the reaction conditions for step S3 are under reduced pressure. 0.06~ Degas at 0.09 MPa for 10–20 minutes.

[0015] The beneficial effects of this invention are: The beneficial effects of this invention are that by introducing 1-ethyl-3-methylimidazolium hexafluorophosphate ionic liquid to construct an in-situ free radical induction system, dynamic regulation of free radical migration rate and self-equilibrium growth of block segments are achieved, resulting in a monomer conversion rate of over 99% and a residual amount of less than 0.2%. At the same time, the phenolic hydroxyl and amide groups of 2-hydroxy-4-methoxyphenylacetamide form multi-point hydrogen bonds and polar interactions, significantly improving the close packing of resin molecular chains and interfacial bonding strength, thereby obtaining an environmentally friendly acrylic resin system with low residual monomer, high density, resistance to yellowing, and stable structure. Attached Figure Description

[0016] The invention will now be further described with reference to the accompanying drawings.

[0017] Figure 1 The infrared spectra of the acrylate copolymer resin and the acrylate copolymer resin modified by ionic liquid-in-situ free radical-induced-block copolymerization are compared. Figure 2 A bar chart comparing the monomer conversion rate test results of samples with different ratios; Figure 3 A bar chart comparing the transmittance test results of samples with different ratios; Figure 4 A bar chart comparing the haze test results of samples with different ratios; Figure 5 A bar chart comparing the test results of ΔE* color difference changes for samples with different ratios. Detailed Implementation

[0018] The present invention will be further described below with reference to specific embodiments. However, the present invention is not limited to the following embodiments. Equivalent adjustments made without departing from the spirit and essence of the present invention should also be considered to fall within the protection scope of the present invention.

[0019] Example 1 The purpose of this embodiment is to verify whether an ionic liquid-induced polymerization system can achieve low monomer residue and stable film-forming properties of the resin at a lower component ratio.

[0020] S1. Take 20 parts of methyl methacrylate, 30 parts of butyl acrylate, 10 parts of hydroxyethyl acrylate, 5 parts of acrylic acid, and 1 part of 1-ethyl-3-methylimidazolium hexafluorophosphate and mix them evenly. Under nitrogen protection, bubble and remove oxygen for 20 minutes. Add 0.3 parts of azobisisobutyronitrile to the system and react at 72°C for 2 hours. Slowly add the remaining hydroxyethyl acrylate and acrylic acid mixture, and at the same time add 0.1 parts of azobisisobutyronitrile. Maintain 72°C and continue to react for 2 hours to form a block copolymer structure. After the reaction is completed, cool down to 55°C, add 0.2 parts of p-hydroxybenzoate and stir for 30 minutes. After degassing under reduced pressure and filtering with a 100-mesh filter, remove residues under vacuum at 45°C for 40 minutes to obtain acrylate copolymer resin modified by ionic liquid-in-situ free radical induced-block copolymerization. S2, take 60 parts of acrylate copolymer resin modified by ionic liquid-in-situ free radical induced-block copolymerization, add 5 parts of 2-hydroxy-4-methoxyphenylacetamide, stir at 60℃ for 1 hour to form a homogeneous system, then add 3 parts of film-forming aid, 1 part of crosslinking agent, 0.3 parts of leveling agent, 0.2 parts of defoaming agent, and 0.2 parts of light stabilizer in sequence, and stir at room temperature for 20 minutes; S3, for the mixed system in Degassing at 0.08 MPa for 15 minutes yields a finished product of an environmentally friendly acrylic resin system with low monomer residue.

[0021] Example 2 The purpose of this embodiment is to verify the limiting control effect of the synergistic effect of ionic liquids and the compactness of the resin structure under high component ratio conditions.

[0022] S1. Mix 40 parts of methyl methacrylate, 50 parts of butyl acrylate, 25 parts of hydroxyethyl acrylate, 15 parts of acrylic acid, and 5 parts of 1-ethyl-3-methylimidazolium hexafluorophosphate. Deoxygenate by bubbling under nitrogen protection for 30 minutes. Add 1 part of azobisisobutyronitrile and react at 78°C for 2 hours. Slowly add the remaining hydroxyethyl acrylate and acrylic acid mixture and add 0.2 parts of azobisisobutyronitrile. Maintain the temperature at 78°C and continue the reaction for 2 hours to form a block copolymer structure. After the reaction is completed, cool down to 50°C and add 0.6 parts of butyl paraben. Stir for 40 minutes. After degassing under reduced pressure and filtration through a 200-mesh filter, remove residues under vacuum at 55°C for 60 minutes to obtain a high-density acrylate copolymer resin modified by ionic liquid-in-situ free radical induced-block copolymerization.

[0023] S2, take 90 parts of acrylate copolymer resin modified by ionic liquid-in-situ free radical induced-block copolymerization, add 20 parts of 2-hydroxy-4-methoxyphenylacetamide, stir at 60℃ for 2 hours to form a homogeneous system, then add 8 parts of film-forming aid, 5 parts of crosslinking agent, 1 part of leveling agent, 0.5 parts of defoaming agent, and 1 part of light stabilizer in sequence, and stir at room temperature for 30 minutes; S3, for the mixed system in Degassing at 0.09 MPa for 20 minutes yielded an environmentally friendly acrylic resin system with low monomer residue.

[0024] Example 3 The purpose of this embodiment is to verify the overall performance balance of the resin system under a medium ratio, including low residual monomer, high transparency and film uniformity.

[0025] S1, mix 30 parts of methyl methacrylate, 40 parts of butyl acrylate, 20 parts of hydroxyethyl acrylate, 10 parts of acrylic acid, and 3 parts of 1-ethyl-3-methylimidazolium hexafluorophosphate. Stir until homogeneous, bubble under nitrogen protection to remove oxygen for 25 minutes, add 0.5 parts of azobisisobutyronitrile, react at 75°C for 2 hours, add the remaining hydroxyethyl acrylate and acrylic acid mixture dropwise and add 0.2 parts of azobisisobutyronitrile, continue the reaction for 2 hours to form a block copolymer structure; after the reaction is completed, cool to 55°C, add 0.4 parts of p-hydroxybenzoate and stir for 30 minutes; after degassing under reduced pressure, filter through 150 mesh, and remove residues under vacuum at 50°C for 45 minutes to obtain an acrylate copolymer resin modified by ionic liquid-in-situ free radical induced-block copolymerization; Figure 1 Infrared spectral comparison results show that the acrylate copolymer resin modified by ionic liquid-in-situ free radical-induced-block copolymerization exhibits significant changes at multiple characteristic peaks, with the peak at 3450 cm⁻¹ being particularly prominent. -1 The intensity of the –OH stretching vibration peak at 1730 cm⁻¹ is significantly enhanced and slightly red-shifted, indicating that hydrogen bonding occurs between the hydroxyl group and the ionic liquid cation in the system; -1 A slight red shift in the carbonyl peak indicates a change in the chemical environment of the ester group after copolymerization. The modified sample shows a peak at 1565 cm⁻¹. -1 1050 cm -1 870 cm -1 and 620 cm -1 New absorption peaks appeared at 1245 cm⁻¹, corresponding to C=N, P–F / C–F, imidazole ring C–H, and P–F bending vibrations, respectively, proving that the ionic liquid component had been successfully introduced into the polymer structure. Meanwhile, at 1245 cm⁻¹... -1 and 1110 cm -1 The enhanced intensity of the C–O–C and C–O stretching peaks indicates the formation of the block copolymer structure and the promotion of molecular chain polarity. Overall, the infrared changes verify the success of the ionic liquid-in-situ free radical induced block copolymer modification, which improves the chemical homogeneity and structural stability of the resin. S2, take 75 parts of acrylate copolymer resin modified by ionic liquid-in-situ free radical induced-block copolymerization, add 10 parts of 2-hydroxy-4-methoxyphenylacetamide, stir at 60℃ for 1.5 hours to form a homogeneous system; add 5 parts of film-forming aid, 3 parts of crosslinking agent, 0.5 parts of leveling agent, 0.3 parts of defoaming agent, and 0.5 parts of light stabilizer in sequence, and stir at room temperature for 25 minutes; S3, placing the mixed system in Degassing at 0.08 MPa for 15 minutes yielded an environmentally friendly acrylic resin system with low monomer residue.

[0026] Comparative Example 1 The purpose of this comparative example is to verify the effect of ionic liquid-in-situ free radical induced-block copolymerization modification on reducing monomer residue and improving film-forming properties.

[0027] S1, mix 30 parts of methyl methacrylate, 40 parts of butyl acrylate, 20 parts of hydroxyethyl acrylate, and 10 parts of acrylic acid evenly without adding 1-ethyl-3-methylimidazolium hexafluorophosphate. Deoxygenate by bubbling under nitrogen protection for 25 minutes, then add 0.5 parts of azobisisobutyronitrile (AIBN). React at 75°C for 2 hours, then add the remaining hydroxyethyl acrylate and acrylic acid mixture dropwise and add 0.2 parts of AIBN. Continue the reaction for 2 hours to form a common acrylate copolymer resin. After the reaction is complete, cool to 55°C, add 0.4 parts of butyl paraben, and stir for 30 minutes. After degassing under reduced pressure, filter through a 150-mesh filter and remove residues under vacuum at 50°C for 45 minutes to obtain an acrylate copolymer resin that has not been modified by ionic liquid-in-situ free radical induced-block copolymerization. S2, take 75 parts of acrylate copolymer resin that has not been modified by ionic liquid-in-situ free radical-induced-block copolymerization, add 10 parts of 2-hydroxy-4-methoxyphenylacetamide, stir at 60℃ for 1.5 hours to form a homogeneous system; add 5 parts of film-forming aid, 3 parts of crosslinking agent, 0.5 parts of leveling agent, 0.3 parts of defoaming agent, and 0.5 parts of light stabilizer in sequence, and stir at room temperature for 25 minutes; S3, placing the mixed system in Degassing was performed at 0.08 MPa for 15 minutes to obtain an unmodified acrylic resin system with low monomer residue.

[0028] Comparative Example 2 The purpose of this comparative example is to verify the role of 2-hydroxy-4-methoxyphenylacetamide in improving intermolecular binding forces and structural compactness.

[0029] S1, mix 30 parts of methyl methacrylate, 40 parts of butyl acrylate, 20 parts of hydroxyethyl acrylate, 10 parts of acrylic acid, and 3 parts of 1-ethyl-3-methylimidazolium hexafluorophosphate. Stir until homogeneous, bubble under nitrogen protection to remove oxygen for 25 minutes, add 0.5 parts of azobisisobutyronitrile, react at 75°C for 2 hours, add the remaining hydroxyethyl acrylate and acrylic acid mixture dropwise and add 0.2 parts of azobisisobutyronitrile, continue reaction for 2 hours to form a block copolymer structure; after the reaction is completed, cool to 55°C, add 0.4 parts of p-hydroxybenzoate and stir for 30 minutes; after degassing under reduced pressure, filter through 150 mesh, and remove residues under vacuum at 50°C for 45 minutes to obtain acrylate copolymer resin modified by ionic liquid-in-situ free radical induced-block copolymerization; S2, take 75 parts of acrylate copolymer resin modified by ionic liquid-in-situ free radical induced-block copolymerization, without adding 2-hydroxy-4-methoxyphenylacetamide, directly add 5 parts of film-forming aid, 3 parts of crosslinking agent, 0.5 parts of leveling agent, 0.3 parts of defoaming agent and 0.5 parts of light stabilizer in sequence, stir at room temperature for 25 minutes to form a mixed system; S3, placing the mixed system in Degassing was performed at 0.08 MPa for 15 minutes to obtain an organic-free small molecule acrylic resin system.

[0030] Performance testing 1. Monomer Conversion Rate Test To evaluate the polymerization conversion efficiency of monomers in the resin system, a solids content determination method was used. Approximately 1.00 g of resin solution from each sample was placed in a pre-weighed aluminum dish, and the initial mass was recorded. The sample was placed in a forced-air drying oven and heated at 105°C for 1 hour. It was then removed and cooled to room temperature in a desiccator, and weighed again. This drying and weighing process was repeated until the difference between two weighings did not exceed 0.001 g. The percentage of solid mass after drying relative to the initial sample mass was calculated as the solids content of the system, reflecting the monomer conversion rate. Each sample group was tested three times, and the average value was used as the result. The trend of polymerization conversion level changes for different systems can be displayed in the form of a bar chart.

[0031] 2. Transmittance and Haze Tests To determine the optical transparency and haze of the resin film, a UV-Vis spectrophotometer was used. The sample was uniformly coated onto an optical-grade glass plate, with the dry film thickness controlled at approximately 50 ± 5 micrometers, and cured for 7 days at 23 ± 2℃ and 50 ± 5% relative humidity. Using an integrating sphere, the UV-Vis spectrophotometer scanned within the wavelength range of 400–800 nm to measure the total transmittance and diffuse transmittance, with a blank substrate used as a reference. Using transmittance at 550 nm as a representative data point, the haze percentage was calculated to evaluate the transparency, uniformity, and optical quality of the resin film.

[0032] 3. Pencil Hardness Test To test the surface scratch resistance of the resin film, the pencil hardness test was used. The sample was uniformly coated onto a degreased aluminum plate, with a dry film thickness controlled at approximately 50 micrometers, and cured for 7 days at 23±2℃ and 50±5% relative humidity. Before testing, a pencil was sharpened and ground into a semi-circular tip, placed at a 45° angle on the film surface, and pushed along the film surface for 6 cm under a 750g load. Pencil grades were changed sequentially from hardest to softest (6H to 6B), and the highest hardness grade that did not produce obvious scratches was taken as the surface hardness level of the sample.

[0033] 4. Adhesion test To evaluate the interfacial bonding performance between the coating and the substrate, a cross-cutting method was used for testing. Samples were coated onto cold-rolled steel sheets to form a dry film approximately 50 micrometers thick, which was then cured in a constant temperature and humidity environment for 7 days. A six-blade cutter was used to cut the film surface into 100 grids, with a grid spacing of 1 mm, and the cut depth reached the substrate. Standard 3M 610 tape was then applied to the cut areas, pressed firmly, left to stand for 20 seconds, and then quickly peeled off at a 90° angle. After peeling off the tape, the peeling was observed using a 10x magnifying glass, and the adhesion grade was assessed according to a 0-5 standard to determine the bonding strength between the coating and the substrate.

[0034] 5. Yellowing resistance test To evaluate the photoaging resistance and color stability of the resin film, an accelerated aging test was conducted. The sample was uniformly coated onto a glass substrate to form a dry film approximately 50 micrometers thick, which was then cured at room temperature for 7 days. The sample was then placed in a UV aging chamber using a UVA-340 lamp at an irradiance of 0.89 W / m² at 340 nm. The test procedure consisted of alternating cycles of 8 hours of UV irradiation at 60°C and 4 hours of condensation at 50°C, for a total aging time of 300 hours. Before and after aging, the Lab* value of the sample surface was measured using a spectrophotometer under D65 light source and a 10° viewing angle. The color difference before and after aging was compared to evaluate the resin system's resistance to yellowing and long-term color stability.

[0035] Table 1 Performance test results of the low monomer residue environmentally friendly acrylic resin system As shown in Table 1, the samples from different systems exhibit significant differences in polymerization conversion rate, optical properties, mechanical properties, and weather resistance.

[0036] From the perspective of monomer conversion rate Figure 2 Examples 1-3 showed significantly higher conversion rates than the comparative system, all exceeding 97%, with Example 3 reaching the highest at 99.1%. This indicates that ionic liquid-induced and block copolymerization structures can effectively promote complete monomer polymerization and reduce free radical side reactions and the accumulation of unreacted residual monomers. The unmodified system had the lowest conversion rate at only 90.3%, demonstrating that ionic liquid modification plays a crucial role in improving reaction efficiency.

[0037] From the perspective of optical performance indicators Figure 3 In the examples, the light transmittance of the systems was all above 90%. Figure 4 The haze was below 2.5%, indicating high transparency and film uniformity. Example 3 showed the highest transmittance (93.6%) and the lowest haze (1.5%), suggesting that the modified structure had a more compact and uniform molecular arrangement, reducing light scattering. In contrast, the comparative systems showed significantly lower transmittance, especially Comparative Example 1 at only 85.2%, indicating poor compatibility of the unmodified system and a tendency for microphase separation during film formation.

[0038] In terms of mechanical properties, the pencil hardness of Examples 2 and 3 both reached 3H, while that of Example 1 was 2H. The film surface was dense and had good scratch resistance. In contrast, the hardness of the comparative system was lower, especially the unmodified sample, which was only HB. This indicates that the synergistic effect of ionic liquid and organic small molecules improved the crosslinking density between polymer chains and the strength of the film.

[0039] In terms of adhesion performance, the samples in the examples all had an adhesion rating between 0 and 1, showing excellent interfacial bonding. In contrast, Comparative Example 1 had an adhesion rating of 3, with obvious peeling, while Comparative Example 2 had a rating of 2. This indicates that the introduction of small organic molecules helps to improve the interaction force between the resin and the substrate and improve the interfacial energy matching.

[0040] In terms of resistance to yellowing, Figure 5 The color difference ΔE of the systems in the examples was less than 1.6, with Example 3 showing the lowest value at only 1.1, indicating that it exhibited the best resistance to photo-oxidation and long-term color stability. The comparative samples showed significantly higher ΔE values, especially the unmodified system at 2.8, suggesting that the ionic liquid-induced polymerization and the synergistic structure of 2-hydroxy-4-methoxyphenylacetamide effectively inhibited degradation and yellowing reactions under UV irradiation, thus endowing the system with excellent photostability.

[0041] In summary, Example 3 showed the best performance in multiple indicators such as polymerization conversion rate, optical transparency, mechanical strength, adhesion and yellowing resistance, demonstrating the significant effect of the ionic liquid-organic small molecule synergistic modification system in improving the overall performance of the resin.

Claims

1. A low-monomer residue environmentally friendly acrylic resin system, characterized in that, The resin system comprises the following raw materials in parts by weight: 60-90 parts of acrylate copolymer resin modified by ionic liquid-in-situ free radical induction-block copolymerization; 5-20 parts of 2-hydroxy-4-methoxyphenylacetamide; 3-8 parts of film-forming aid; 1-5 parts of crosslinking agent; 0.3-1 part of leveling agent; 0.2-0.5 parts of antifoaming agent; and 0.2-1 part of light stabilizer; wherein the 2-hydroxy-4-methoxyphenylacetamide is a simple organic small molecule containing phenolic hydroxyl and amide groups.

2. The low monomer residue environmentally friendly acrylic resin system according to claim 1, characterized in that, The acrylate copolymer resin modified by ionic liquid-in-situ free radical induced-block copolymerization comprises the following raw materials in parts by weight: methyl methacrylate 20-40 parts; butyl acrylate 30-50 parts; hydroxyethyl acrylate 10-25 parts; acrylic acid 5-15 parts; 1-ethyl-3-methylimidazolium hexafluorophosphate 1-5 parts; azobisisobutyronitrile 0.3-1 part; and butyl p-hydroxybenzoate 0.2-0.6 parts.

3. The low monomer residue environmentally friendly acrylic resin system according to any one of claims 1 or 2, characterized in that, The preparation method of the acrylate copolymer resin modified by ionic liquid-in-situ free radical induced-block copolymerization includes the following steps: (1) Methyl methacrylate, butyl acrylate, hydroxyethyl acrylate, acrylic acid and 1-ethyl-3-methylimidazolium hexafluorophosphate are mixed, stirred evenly and then subjected to deoxygenation treatment to obtain a mixture; (2) Add azobisisobutyronitrile to the mixture to carry out the polymerization reaction; (3) Add a mixture of hydroxyethyl acrylate and acrylic acid dropwise and add an initiator to continue the reaction to form a block copolymer structure; (4) After the reaction is complete, the temperature is lowered and butyl p-hydroxybenzoate is added for stabilization treatment to obtain the resin; (5) The resin was subjected to degassing under reduced pressure, filtration and vacuum residue removal to obtain acrylate copolymer resin modified by ionic liquid-in-situ free radical induced-block copolymerization.

4. The low monomer residue environmentally friendly acrylic resin system according to claim 3, characterized in that, The reaction conditions for step (1) are stirring and bubbling to remove oxygen for 15 to 30 minutes under nitrogen protection.

5. The low monomer residue environmentally friendly acrylic resin system according to claim 3, characterized in that, The reaction conditions for step (2) are: reaction temperature 70-78℃, reaction time 1.5-2.5 hours; the reaction conditions for step (3) are: maintaining temperature 70-78℃, dropping time 1-1.5 hours, and continuing reaction for 1.5-2.5 hours.

6. The low monomer residue environmentally friendly acrylic resin system according to claim 3, characterized in that, The reaction conditions for step (4) are: cooling to 50-60°C and stirring for 20-40 minutes; the reaction conditions for step (5) are: reduced pressure. 0.06~ Degas at 0.09 MPa for 10–20 minutes, then remove residues by vacuum rotation for 30–60 minutes.

7. The low monomer residue environmentally friendly acrylic resin system according to claim 1, characterized in that, The film-forming aid is composed of dipropylene glycol butyl ether and triethylene glycol monobutyl ether in a mass ratio of 1:1; the crosslinking agent is composed of hexamethylene diisocyanate trimer and glycidyl acrylate in a mass ratio of 2:1; the leveling agent is composed of polydimethylsiloxane and hydroxypropyl acrylate in a mass ratio of 1:3; the antifoaming agent is composed of polyether-modified polysiloxane and isobutanol in a mass ratio of 1:2; and the light stabilizer is composed of hindered amine light stabilizer HALS770 and ultraviolet absorber UV-327 in a mass ratio of 1:

1.

8. A method for preparing a low-monomer-residue environmentally friendly acrylic resin system, wherein the low-monomer-residue environmentally friendly acrylic resin system is as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1, the acrylate copolymer resin modified by ionic liquid-in-situ free radical-induced-block copolymerization is mixed with 2-hydroxy-4-methoxyphenylacetamide to form a homogeneous system; S2, add film-forming aid, crosslinking agent, leveling agent, antifoaming agent and light stabilizer to the homogeneous system in sequence, stir evenly to obtain a mixed system; S3, the mixed system is subjected to degassing treatment under reduced pressure to obtain a finished product of environmentally friendly acrylic resin system with low monomer residue.

9. The method for preparing a low-monomer-residue environmentally friendly acrylic resin system according to claim 8, characterized in that, The reaction conditions for step S1 are stirring at 60°C for 1-2 hours; the reaction conditions for step S2 are adding each auxiliary agent sequentially at room temperature and stirring for 15-30 minutes; the reaction conditions for step S3 are under reduced pressure. 0.06~ Degas at 0.09 MPa for 10–20 minutes.

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