Preparation method and application of high-toughness water-based environment-friendly emulsion

Abstract

This invention relates to the field of coatings and adhesives, specifically disclosing a method for preparing and applying a high-toughness, water-based, environmentally friendly emulsion. The emulsion is composed of butyl acrylate, methyl methacrylate, modified rosin acrylate monomers, and maleimide-modified CNC, among other components. A cross-linked network is constructed by utilizing the Diels-Alder reaction between the furan rings in the modified rosin acrylate monomers and the maleimide groups on the surface of the maleimide-modified CNC. This emulsion exhibits both high toughness and high hardness, is storage stable, and demonstrates excellent impact resistance, low-temperature flexibility, and adhesion after film formation. Furthermore, it has low VOC content, no free formaldehyde, and is environmentally compliant, making it widely applicable in coatings and adhesives used in medium- and low-temperature applications such as automotive interiors, flexible packaging, and leather finishing.

Description

Technical Field

[0001] This invention relates to the field of coatings and adhesives, and in particular to a method for preparing and applying a high-toughness water-based environmentally friendly emulsion. Background Technology

[0002] Global environmental awareness has increased and regulations have become more stringent, limiting the application of solvent-based emulsions in coatings, adhesives, and other fields. Water-based emulsions, due to their low VOC and environmentally friendly advantages, have become the industry mainstream. Among them, acrylic water-based emulsions are widely used in architectural coatings, industrial coatings, wood adhesives, and other fields due to their excellent film-forming properties, weather resistance, corrosion resistance, and cost advantages.

[0003] However, existing acrylic waterborne emulsions suffer from "hot-sticky and cold-brittle" defects due to insufficient toughness, especially in medium and low temperature environments. They are prone to cracking at low temperatures and easily become brittle and fall off after deformation at room temperature, making it difficult to meet the long-term use requirements of high-end fields such as automotive interiors, flexible packaging, and leather coatings that operate at medium and low temperatures. Researchers have developed three main toughening technologies: First, core-shell structure modification, which constructs "hard inside and soft outside" particles by controlling the composition of core-shell monomers (such as organosilicon modification and organic-inorganic hybrid core-shell emulsions) to improve mechanical properties through synergistic effects; second, nanoparticle composite modification, which introduces carbon nanotubes, nano-ZnO, etc. to achieve toughening while taking into account heat resistance and wear resistance; and third, elastic component blending / copolymerization modification, which improves flexibility by adding elastic curing agents or introducing flexible monomers to lower the glass transition temperature.

[0004] While these technologies have yielded some results, they also have significant shortcomings: core-shell modification presents a challenge in balancing performance; while organosilicon modification improves "hot adhesion and cold brittleness," it reduces bond strength, makes interfacial compatibility difficult to control, and results in insufficient emulsion stability; nanoparticles are prone to aggregation, requiring complex modifications, increasing costs, and potentially introducing harmful additives, with excessive additions leading to a resurgence of brittleness; elastic component modification significantly reduces coating hardness, and some components have poor compatibility and are prone to phase separation, limiting the toughening effect; furthermore, some technologies use toxic monomers or generate byproducts, which does not align with the green and low-carbon concept. Existing toughening technologies, while partially improving toughness, are not optimized for low- and medium-temperature service scenarios: core-shell modified emulsions exhibit decreased interfacial compatibility and significant toughness degradation at low temperatures; nanoparticle aggregation exacerbates stress concentration at low temperatures, leading to cracking; elastic component modification tends to over-soften in the room to medium-temperature range, affecting hardness and stability, and none of these technologies can achieve a long-term balance between "high toughness and high hardness" at low and medium temperatures.

[0005] Therefore, the development of acrylate waterborne emulsions that combine high toughness, excellent comprehensive performance, and environmental friendliness has become a research focus and urgent need in this field. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for preparing and applying a high-toughness, water-based, environmentally friendly emulsion.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A high-toughness, water-based, environmentally friendly emulsion comprises the following components in parts by weight: 45-55 parts butyl acrylate, 35-45 parts methyl methacrylate, 1-2 parts acrylic acid, 5-10 parts modified rosin acrylate monomer, 0.5-2.0 parts maleimide-modified cellulose nanocrystals (maleimide-modified CNC), 80-100 parts deionized water, 0.3-0.5 parts initiator, and 0.1-0.2 parts pH adjuster; wherein the initiator is ammonium persulfate, and the pH adjuster is sodium bicarbonate.

[0008] Preferably, the method for preparing the modified rosin acrylate monomer includes the following steps: A1: Add disproportionated rosin and industrial ethanol to the reactor, stir and heat to 60-70℃ to completely dissolve the disproportionated rosin; then slowly add a 10-20% sodium hydroxide solution while stirring, adjust the pH of the system to 10-11, and stir at a constant temperature for 1.5-2 hours. After the reaction is complete, allow it to stand and separate into layers, separate the lower aqueous phase, slowly add a 10-15% hydrochloric acid solution to the aqueous phase, adjust the pH to 2-3, continue stirring for 20-30 minutes, filter and collect the precipitate, wash with deionized water until the washing solution is neutral, place the precipitate in a vacuum drying oven at 60-70℃ and dry for 4-6 hours to obtain a white powder of dehydroabsic acid concentrate for later use. A2: Add dehydroabsic acid and glycidyl furfural ether to the reactor and stir until homogeneous. Then add tetrabutylammonium bromide and hydroquinone as a polymerization inhibitor. Next, purge the system with nitrogen 3-4 times and maintain the nitrogen atmosphere. Then raise the temperature to 110-120℃ and stir the reaction at a constant temperature for 2.0-2.5h. After the reaction is completed, a reaction system containing intermediate 1 is obtained. A3: Cool the above reaction system to 80-85℃, control the stirring rate at 300-400 r / min, slowly add methacrylic anhydride, and simultaneously add 4-dimethylaminopyridine. Control the addition time to 30-60 min. After the addition is complete, maintain a constant temperature of 80-85℃ and stir for 2-3 h. After the reaction is complete, add deionized water at 50-60℃ to the reaction system, stir and wash 3-4 times, let it stand to separate into layers and remove the aqueous phase. Finally, dry the organic phase under vacuum conditions of 70-80℃ and -0.09 MPa to -0.07 MPa to obtain the modified rosin acrylate monomer.

[0009] Preferably, in step A2, the molar ratio of dehydroabietic acid to glycidyl furfuryl ether is 1:(1.02-1.10).

[0010] Preferably, in step A2, the mass of tetrabutylammonium bromide and hydroquinone are 0.3-0.4% and 0.05-0.08% of the total mass of dehydroabietic acid and glycidyl furfural ether, respectively.

[0011] Preferably, in step A3, the molar ratio of intermediate 1 to 4-dimethylaminopyridine is 1:(0.2-0.3).

[0012] Using the above technical solution, disproportionated rosin is used as raw material. First, dehydroabietic acid is obtained through alkali dissolution and acid precipitation. Then, dehydroabietic acid reacts with glycidyl furfuryl ether in an epoxy ring-opening reaction under the protection of tetrabutylammonium bromide catalyst and nitrogen gas to generate intermediate 1 containing a furan ring. Finally, intermediate 1 reacts with methacrylic anhydride in the presence of 4-dimethylaminopyridine catalyst to introduce acrylate double bonds. After washing and vacuum drying, the modified rosin acrylate monomer is obtained. The reaction route is as follows:

[0013] Preferably, the preparation method of the maleimide-modified CNC includes the following steps: S1: Add 3-aminopropyltriethoxysilane (APTES) and anhydrous DMF to the reactor, stir until completely dissolved, then place the reactor in an ice-water bath to cool to 0-5℃. Slowly add maleic anhydride dropwise through a constant pressure dropping funnel over a period of 30-60 minutes while stirring. After the addition is complete, maintain a constant temperature of 0-5℃ and stir for 1.5-2.5 hours to generate intermediate A. Subsequently, add triethylamine and acetic anhydride to the system, heat to 50-60℃ and stir, set the reaction time, and complete the dehydration and cyclization. After the reaction is complete, remove the solvent and low-boiling-point byproducts to obtain intermediate B for later use. S2: Add cellulose nanocrystals (CNC) and sulfuric acid with a mass fraction of 60-64% to the reaction vessel, stir at 45-50℃ for 2-3 hours; add deionized water to terminate the reaction, centrifuge, wash repeatedly with deionized water until neutral, dialyze for 70-72 hours to obtain a CNC suspension; then centrifuge the CNC, wash with anhydrous ethanol and anhydrous toluene in sequence to obtain a toluene-dispersed CNC slurry; add intermediate B, reflux and stir at 100-110℃ for 12-24 hours, then centrifuge the precipitate, wash with anhydrous toluene and anhydrous ethanol 3-4 times each, freeze-dry to obtain maleimide-modified CNC.

[0014] Preferably, in step S1, the reaction time is 4-6 hours.

[0015] Preferably, in step S2, the mass ratio of intermediate B to CNC is 1:(4-5).

[0016] Using the above technical solution, APTES undergoes an amidation reaction with maleic anhydride at low temperature to generate intermediate A, which is then dehydrated and cyclized with acetic anhydride at elevated temperature to form maleimide functional groups, generating intermediate B. Subsequently, CNC is purified by sulfuric acid hydrolysis, washing, and dialysis, and then undergoes a silanization grafting reaction with intermediate B under high-temperature reflux. The ethoxy groups of APTES are hydrolyzed and combined with the hydroxyl groups on the CNC surface, grafting maleimide groups onto the CNC surface, thus obtaining maleimide-modified CNC. The reaction route is as follows:

[0017] A method for preparing a high-toughness, water-based, environmentally friendly emulsion includes the following steps: Step 1: Add 50% of the total amount of deionized water in the formula to a pre-emulsification tank equipped with a high-speed disperser, turn on the stirrer at 300-500 r / min, slowly add maleimide-modified CNC, intermittently sonicate the dispersion with an ultrasonic cell disruptor for 10-15 min, add sodium bicarbonate and stir to dissolve, and obtain the dispersion. Step 2: In a separate container, mix butyl acrylate, methyl methacrylate, acrylic acid and modified rosin acrylate monomers, and stir until homogeneous to obtain a mixed oil phase; under high-speed dispersion at 1000-1500 r / min, slowly add the mixed oil phase dropwise to the dispersion, and after the addition is complete, continue high-speed stirring and emulsification for 20-30 min to obtain a uniform white pre-emulsion. Step 3: Add 20% of the remaining formula amount of deionized water and 10% of the amount of pre-emulsion to another reactor, turn on the stirring and heat to 75-80℃, add 1 / 3 of the amount of pre-dissolved ammonium persulfate aqueous solution with a mass fraction of 3-5% to initiate the reaction, and after a faint blue light appears and the liquid surface is slightly boiling, maintain for 15-20 minutes to obtain the seed emulsion. Step 4: Place the remaining 90% of the pre-emulsion in a constant pressure funnel and add it dropwise to a four-necked flask containing the seed emulsion, while simultaneously adding the remaining 2 / 3 of the ammonium persulfate aqueous solution; control the dropping rate to stabilize the temperature at 80-82℃, and the dropping time is 2.5-3.5 hours; after the dropping is complete, raise the temperature to 85-87℃ and keep it at this temperature for 1-2 hours to promote the Diels-Alder cyclization reaction between the maleimide groups on the surface of the maleimide-modified CNC and the furan ring in the modified rosin acrylate monomer; cool down to 25-35℃, adjust the pH value to 7-8, filter and discharge to obtain the finished product.

[0018] Preferably, the high-toughness water-based environmentally friendly emulsion is used in coatings or adhesives.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention utilizes a seed emulsion copolymerization method to prepare a high-toughness, water-based, environmentally friendly emulsion using maleimide-modified CNC and modified rosin acrylate monomers, combined with butyl acrylate, methyl methacrylate, and other components. Maleimide-modified CNC is introduced and dispersed in situ within polymer particles. During the heat preservation stage of the preparation process, the maleimide groups grafted onto the CNC surface undergo a Diels-Alder reaction with the furan rings on the copolymerized modified rosin acrylate monomers, forming an "intra-particle crosslinking" structure within each latex particle, with CNC as the crosslinking node. This crosslinking structure not only prevents CNC aggregation but also endows the emulsion with excellent storage stability. After film formation, these crosslinked particles fuse together, constructing a stable nano-reinforced network within the coating film, thereby achieving a balance between high hardness and high toughness. The main application scenarios are room temperature or medium temperature environments, such as automotive interiors, flexible packaging, and leather finishing.

[0020] 2. This invention uses an all-water-based system, with widely available and environmentally friendly raw materials. The reaction conditions are strictly controlled during the preparation process to avoid byproduct residues. The resulting product has low volatile organic compound (VOC) content and no free formaldehyde was detected, meeting the stringent environmental performance requirements of the modern coatings and adhesives industry. Attached Figure Description

[0021] Figure 1 The ¹H NMR spectrum of the modified rosin acrylate monomer prepared in Example 1 of this invention; Figure 2 The ¹H NMR spectrum of product B prepared in Example 1 of this invention; Figure 3 The infrared spectra of intermediate 1, dehydroabsic acid, and modified rosin acrylate monomer prepared in Example 1 of this invention are shown below. Figure 4 The infrared spectra of the CNC, intermediate B, and maleimide-modified CNC prepared in Example 1 of this invention are shown below. Figure 5 The infrared spectra of the modified rosin acrylate monomer, maleimide-modified CNC, and high-toughness waterborne environmentally friendly emulsion prepared in Example 1 of this invention are shown. Detailed Implementation

[0022] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0023] Example 1: I. Preparation of modified rosin acrylate monomer: A1: Add disproportionated rosin and industrial ethanol to the reactor, stir and heat to 65℃ to completely dissolve the disproportionated rosin; then slowly add 15% sodium hydroxide solution while stirring, adjust the pH of the system to 10.5, and stir at a constant temperature for 1.6 h. After the reaction is complete, allow it to stand and separate into layers, separate the lower aqueous phase, slowly add 12% hydrochloric acid solution to the aqueous phase, adjust the pH to 2.5, continue stirring for 25 min, filter and collect the precipitate, wash with deionized water until the washing solution is neutral, place the precipitate in a vacuum drying oven at 65℃ and dry for 5 h to obtain a white powder of dehydroabsic acid concentrate for later use. A2: Add 4.6g of dehydroabsic acid and 2.48g of glycidyl furfuryl ether to the reactor and stir until homogeneous. Then add 0.025g of tetrabutylammonium bromide and 0.00425g of hydroquinone. Next, purge the system with nitrogen three times and maintain the nitrogen atmosphere. Then raise the temperature to 115℃ and stir the reaction at a constant temperature for 2.2h. After the reaction is completed, a reaction system containing intermediate 1 is obtained. A3: Cool the above reaction system to 82℃, control the stirring rate at 350 r / min, and slowly add 2.37 g of methacrylic anhydride, while simultaneously adding 0.464 g of 4-dimethylaminopyridine. The addition time is controlled at 40 min. After the addition is complete, maintain a constant temperature of 82℃ and stir for 2.5 h. After the reaction is complete, add 55℃ deionized water to the reaction system, stir and wash three times, allow to stand for layering, remove the aqueous phase, and finally dry the organic phase under vacuum conditions of 75℃ and -0.08 MPa to obtain the modified rosin acrylate monomer. Dissolve a small amount of the modified rosin acrylate monomer in dimethyl sulfoxide and perform 1H NMR spectroscopy detection. Figure 1 As shown, the analysis is as follows: δ 7.42-6.85: The signal peak in this region belongs to the proton hydrogen of the aromatic ring on the rosin skeleton, corresponding to chemical shifts of 7.42 ppm (1H), 7.13 ppm (1H), 7.00 ppm (1H) and 6.85 ppm (1H), respectively; δ 6.43-6.36: The signal peak in this region belongs to the proton hydrogen of the double bond on the furan ring, corresponding to chemical shifts of 6.43 ppm (1H) and 6.36 ppm (1H), confirming the introduction of the furan ring structure; δ 5.90-5.79: The signal peak in this region belongs to the vinyl hydrogen (=CH2) at the end of the methacrylate group, corresponding to chemical shifts of 5.90 ppm (1H) and 5.79 ppm (1H), confirming the successful introduction of the acrylate double bond; the ¹H The peak positions, peak shapes, and integrals of the NMR spectrum correspond one-to-one with the hydrogen atom environments of the target compound, verifying the correctness of the compound structure. Figure 3 Infrared spectra of intermediate 1, dehydroabietic acid, and modified rosin acrylate monomer: Dehydroabietic acid at ~3398 cm⁻¹-1 The broad, diffuse peak of the carboxylic acid dimer at ~1695 cm⁻¹ -1 The C=O peak of the conjugated carboxylic acid and ~1285 cm⁻¹ -1 The CO coupling peak completely disappeared after the formation of intermediate 1, and was replaced by a peak at ~1730 cm⁻¹. -1 The strong peak of the ester carbonyl group, ~3450 cm⁻¹ -1 The peak of the secondary hydroxyl group of the epoxy ring-opening structure is of medium width, and the peak of the newly introduced furan ring is at ~3115 cm⁻¹. -1 ~1600 cm -1 ~1020cm -1 A set of characteristic absorptions; after further esterification to obtain modified rosin acrylate monomers, ~3450 cm⁻¹ -1 The hydroxyl peak almost disappeared, and the ester carbonyl peak (~1730cm) -1 ) and COC peak (~1160 cm) -1 The strength is enhanced. The above confirms the stepwise structural evolution from dehydroabsic acid through epoxy ring opening, furan ring introduction, and esterification grafting of acrylate double bonds.

[0024] II. Preparation of maleimide-modified CNC: S1: Add 10g of APTES and 100mL of anhydrous DMF to the reactor, stir until completely dissolved, then place the reactor in an ice-water bath to cool to 2℃. Slowly add 4.4g of maleic anhydride dropwise through a constant-pressure dropping funnel over a period of 40min, stirring continuously. After the addition is complete, maintain the temperature at 2℃ and stir for 2h to generate intermediate A. Subsequently, add 1g of triethylamine and 5.83g of acetic anhydride to the system, raise the temperature to 55℃ and stir for 5h to complete dehydration and cyclization. After the reaction is complete, remove the solvent and low-boiling-point byproducts to obtain intermediate B, which is then set aside. Dissolve a small amount of intermediate B in dimethyl sulfoxide and perform 1H NMR spectroscopy. Figure 2 As shown, the analysis is as follows: δ 6.70 (s, 2H): attributed to the olefin proton (=CH) on the maleimide ring; δ 3.82 (q, 6H): attributed to the methylene proton (-O-CH2-CH3) bonded to oxygen in the triethoxysilane group; δ 0.71 (t, 2H): attributed to the methylene proton (-Si-CH) directly bonded to the silicon atom. 2- The peak positions, peak shapes, and integrals of the ¹H NMR spectrum correspond one-to-one with the hydrogen atom environments of the target compound, verifying the correctness of the compound structure.

[0025] S2: Add 61g of CNC and 123mL of 62% sulfuric acid to the reaction vessel and stir at 48℃ for 2.5h. Add deionized water to terminate the reaction. After centrifugation and repeated washing with deionized water until neutral, dialyze for 71h to obtain a CNC suspension. Then centrifuge the CNC and wash it with anhydrous ethanol and anhydrous toluene to obtain a toluene-dispersed CNC slurry. Add 13.6g of intermediate B and reflux at 105℃ for 20h. Then centrifuge the precipitate and wash it with anhydrous toluene and anhydrous ethanol three times each. Freeze-dry to obtain maleimide-modified CNC. Figure 4 Infrared spectra of the prepared CNC, intermediate B, and maleimide-modified CNC: The changes in infrared spectra from CNC to intermediate B and then to maleimide-modified CNC clearly demonstrate the chemical reaction process at each step. The infrared spectrum of the CNC raw material is broad and strong at ~3400 cm⁻¹. -1 With the hydroxyl stretching peak as the core, bound to ~2902 cm⁻¹ -1 The methyl / methylene stretching peak at ~1175 cm⁻¹ -1 With ~1100cm -1 The characteristic peak of C–O–C glycosidic bond, ~1030 cm⁻¹ -1 The strong C–O absorption bands of the hydroxyl groups in cellulose within the range constitute a typical infrared fingerprint spectrum of cellulose nanocrystals. After synthesizing intermediate B, a new set of characteristic peaks appeared in the spectrum: ~1775 cm⁻¹. -1 and ~1710 cm -1 The locations are respectively attributed to the C=O asymmetric and symmetric stretching vibrations (imide I band) of the maleimide ring, ~1385 cm⁻¹ -1 It is a C–N–C stretching vibration (imide II band), ~830 cm -1 This corresponds to the out-of-plane bending vibration of the C–H bond in a cis double bond, and at ~950 cm. -1 The characteristic absorption of ethoxySi–O–C2H5 was observed at ~3400 cm⁻¹, confirming the successful introduction of the silane coupling agent structure. When intermediate B was grafted onto the CNC surface via silanization, the spectrum of the maleimide-modified CNC showed the most direct evidence of successful grafting: ~3400 cm⁻¹ -1 The intensity of the hydroxyl absorption peak at this location is significantly weaker than that of the CNC raw material, indicating that some hydroxyl groups on the CNC surface have undergone a condensation reaction with the silane coupling agent; ~1775 cm⁻¹ -1 With ~1710 cm -1 maleimide carbonyl doublet and ~830 cm⁻¹ -1 The cis-C–H out-of-plane bending peak was retained, directly confirming the successful grafting of the maleimide functional group; more importantly, ~950 cm⁻¹ -1The ethoxy characteristic peak at ~1030 cm⁻¹ almost completely disappeared, indicating that the Si–OEt group of intermediate B had been completely hydrolyzed and condensed, forming a stable Si–O–Si and Si–O–CNC bonded network. Furthermore, at ~1030 cm⁻¹... -1 In the region, due to the superposition of cellulose C–O absorption and Si–O–Si and Si–O–C absorption, the bands show obvious broadening, which further confirms the successful occurrence of silanization condensation grafting reaction, thus fully demonstrating the gradual structural evolution process from cellulose nanocrystals through silane coupling agent intermediates to maleimide-functionalized CNC.

[0026] III. Preparation of High-Toughness Waterborne Environmentally Friendly Emulsions: Formula: 45g butyl acrylate, 35g methyl methacrylate, 1g acrylic acid, 5g modified rosin acrylate monomer, 0.5g maleimide-modified CNC, 80g deionized water, 0.3g initiator, 0.1g pH adjuster; the initiator is ammonium persulfate; the pH adjuster is sodium bicarbonate.

[0027] Step 1: Add 50% of the total amount of deionized water in the formula to a pre-emulsification tank equipped with a high-speed disperser, start stirring at 300 r / min, slowly add maleimide-modified CNC, intermittently sonicate the dispersion with an ultrasonic cell disruptor for 10 min, add sodium bicarbonate and stir to dissolve, and obtain the dispersion. Step 2: In a separate container, mix butyl acrylate, methyl methacrylate, acrylic acid and modified rosin acrylate monomers, and stir until homogeneous to obtain a mixed oil phase; under high-speed dispersion at 1000 r / min, slowly add the mixed oil phase dropwise to the dispersion, and after the addition is complete, continue high-speed stirring and emulsification for 20 min to obtain a uniform white pre-emulsion. Step 3: Add 20% of the remaining formula amount of deionized water and 10% of the amount of pre-emulsion to another reactor, turn on the stirring and heat to 75°C, add 1 / 3 of the amount of pre-dissolved 3% ammonium persulfate aqueous solution to initiate the reaction, and after a faint blue light appears and the liquid surface is slightly boiling, maintain for 15 minutes to obtain the seed emulsion. Step 4: Place the remaining 90% of the pre-emulsion in a constant pressure funnel and add it dropwise to a four-necked flask containing the seed emulsion, while simultaneously adding the remaining 2 / 3 of the ammonium persulfate aqueous solution; control the dropping rate to stabilize the temperature at 80℃, and the dropping time is 2.5 hours; after the dropping is complete, raise the temperature to 85℃ and keep it at this temperature for 1 hour to promote the Diels-Alder cyclization reaction between the maleimide groups on the surface of the maleimide-modified CNC and the furan ring in the modified rosin acrylate monomer; cool to 25℃, adjust the pH to 7, filter and discharge to obtain the finished product; Figure 5Infrared spectra of the prepared modified rosin acrylate monomer, maleimide-modified CNC, and high-toughness waterborne environmentally friendly emulsion: The infrared spectrum of the high-toughness waterborne environmentally friendly emulsion showed significant changes compared to the modified rosin acrylate monomer and maleimide-modified CNC: the monomer's ~1637 cm⁻¹... -1 The complete disappearance of the polymerizable bimodal peaks indicates that the free radical polymerization reaction has proceeded completely; the ester carbonyl peak (~1730 cm⁻¹) -1 The peak became the strongest in the entire spectrum, and the COC region (~1235 and ~1160 cm⁻¹) was the strongest. -1 The acrylate copolymer exhibits a typical bimodal pattern, while the maleimide ring shows a characteristic bimodal pattern (1710 cm⁻¹). -1 The strength is significantly reduced but still remains, while the furan ring has a length of ~1015 cm. -1 The effect was also significantly reduced, indicating that the Diels-Alder crosslinking reaction consumed some of the furan and maleimide groups; ~1030cm -1 The region exhibits band broadening due to the contribution of CO and Si-O-Si from CNC. This confirms that the emulsion has been successfully constructed as a cross-linked network structure with acrylate copolymer as the main component, and rosin rigidity introduced through reversible cross-linking of DA and CNC nano-reinforcement.

[0028] Example 2: Preparation of a high-toughness waterborne environmentally friendly emulsion: Formula: 50g butyl acrylate, 38g methyl methacrylate, 1.5g acrylic acid, 8g modified rosin acrylate monomer, 1.8g maleimide-modified CNC, 90g deionized water, 0.4g initiator, 0.15g pH adjuster; the initiator is ammonium persulfate; the pH adjuster is sodium bicarbonate.

[0029] Step 1: Add 50% of the total amount of deionized water in the formula to a pre-emulsification tank equipped with a high-speed disperser, start stirring at 400 r / min, slowly add maleimide-modified CNC, intermittently sonicate the dispersion with an ultrasonic cell disruptor for 12 min, add sodium bicarbonate and stir to dissolve, and obtain the dispersion. Step 2: In a separate container, mix butyl acrylate, methyl methacrylate, acrylic acid and modified rosin acrylate monomers, and stir until homogeneous to obtain a mixed oil phase; under high-speed dispersion at 1200 r / min, slowly add the mixed oil phase dropwise to the dispersion, and after the addition is complete, continue high-speed stirring and emulsification for 25 min to obtain a uniform white pre-emulsion. Step 3: Add 20% of the remaining formula amount of deionized water and 10% of the amount of pre-emulsion to another reactor, turn on the stirring and heat to 78°C, add 1 / 3 of the amount of pre-dissolved 4% ammonium persulfate aqueous solution to initiate the reaction, and after a faint blue light appears and the liquid surface is slightly boiling, maintain for 18 minutes to obtain the seed emulsion. Step 4: Place the remaining 90% of the pre-emulsion in a constant pressure funnel and add it dropwise to a four-necked flask containing the seed emulsion, while simultaneously adding the remaining 2 / 3 of the ammonium persulfate aqueous solution; control the dropping rate to stabilize the temperature at 81℃, and the dropping time is 3.0h; after the dropping is completed, raise the temperature to 86℃ and keep it at this temperature for 1.5h to promote the Diels-Alder cyclization reaction between the maleimide groups on the surface of the maleimide-modified CNC and the furan ring in the modified rosin acrylate monomer; cool down to 30℃, adjust the pH value to 7.5, filter and discharge to obtain the finished product.

[0030] The preparation methods of the modified rosin acrylate monomer and maleimide modified CNC are the same as in Example 1.

[0031] Example 3: Preparation of a high-toughness waterborne environmentally friendly emulsion: Formula: 55g butyl acrylate, 45g methyl methacrylate, 2g acrylic acid, 10g modified rosin acrylate monomer, 2.0g maleimide-modified CNC, 100g deionized water, 0.5g initiator, 0.2g pH adjuster; the initiator is ammonium persulfate; the pH adjuster is sodium bicarbonate.

[0032] Step 1: Add 50% of the total amount of deionized water in the formula to a pre-emulsification tank equipped with a high-speed disperser, start stirring at 500 r / min, slowly add maleimide-modified CNC, intermittently sonicate the dispersion with an ultrasonic cell disruptor for 15 min, add sodium bicarbonate and stir to dissolve, and obtain the dispersion. Step 2: In a separate container, mix butyl acrylate, methyl methacrylate, acrylic acid and modified rosin acrylate monomers, and stir until homogeneous to obtain a mixed oil phase; under high-speed dispersion at 1500 r / min, slowly add the mixed oil phase dropwise to the dispersion, and after the addition is complete, continue high-speed stirring and emulsification for 30 min to obtain a uniform white pre-emulsion. Step 3: Add 20% of the remaining formula amount of deionized water and 10% of the amount of pre-emulsion to another reactor, turn on the stirring and heat to 80°C, add 1 / 3 of the amount of pre-dissolved 5% ammonium persulfate aqueous solution to initiate the reaction, and after a faint blue light appears and the liquid surface is slightly boiling, maintain for 20 minutes to obtain seed emulsion. Step 4: Place the remaining 90% of the pre-emulsion in a constant pressure funnel and add it dropwise to a four-necked flask containing the seed emulsion, while simultaneously adding the remaining 2 / 3 of the ammonium persulfate aqueous solution; control the dropping rate to stabilize the temperature at 82℃, and the dropping time is 3.5h; after the dropping is completed, raise the temperature to 87℃ and keep it at this temperature for 2h to promote the Diels-Alder cyclization reaction between the maleimide groups on the surface of the maleimide-modified CNC and the furan ring in the modified rosin acrylate monomer; cool down to 35℃, adjust the pH value to 8, filter and discharge to obtain the finished product.

[0033] The preparation methods of the modified rosin acrylate monomer and maleimide modified CNC are the same as in Example 1.

[0034] Comparative Example 1: Based on Example 2, the difference is that the maleimide-modified CNC in the formulation is replaced with a regular CNC, and the rest is the same as in Example 2.

[0035] Comparative Example 2: Based on Example 2, the difference is that the modified rosin acrylate monomer in the formulation is replaced with unmodified disproportionated rosin, and the rest is the same as in Example 2.

[0036] Comparative Example 3: Based on Example 2, the difference is that the modified rosin acrylate monomer was removed from the formulation, while the rest is the same as in Example 2.

[0037] Comparative Example 4: Based on Example 2, the difference is that maleimide-modified CNC is removed from the formulation, and the rest is the same as Example 2.

[0038] Comparative Example 5: Based on Example 2, the difference is that the modified rosin acrylate monomer and maleimide modified CNC are removed from the formulation, and the rest is the same as Example 2.

[0039] Test example: The following tests were conducted on the emulsion products prepared in Examples 1-3 and Comparative Examples 1-5 above.

[0040] 1. Basic performance (1) Solid content: determined according to standard GB / T 1725-2007.

[0041] (2) Particle size and dispersibility: The average particle size (D50) and polydispersity index (PDI) of the emulsion particles were measured by laser particle size analyzer to characterize the particle size distribution and stability of the emulsion.

[0042] (3) Room temperature storage stability: The emulsion was sealed and placed in a room temperature environment. Observe for any stratification, precipitation, flocculation or demulsification within 6 months.

[0043] 2. Core Performance (1) Tensile strength and elongation at break: The tensile strength and elongation at break of the emulsion after film formation at room temperature (23±2℃) were tested in accordance with the standard GBT16777-2008.

[0044] (2) Pencil hardness: The hardness of the emulsion film was tested according to standard GB / T 6739-2022. (3) Impact resistance: The impact resistance performance is tested in accordance with the standard GB / T 1732-2020.

[0045] (4) Low temperature flexibility: Refer to standard GB / T 1731-2020: After the emulsion film is treated at low temperature, the coating is bent 180° around a shaft of different diameter under low temperature (-20℃) conditions, and the coating is observed to see if cracks, peeling and other phenomena occur.

[0046] (5) Adhesion: Adhesion is tested according to GB / T 9286-2021.

[0047] 3. Environmental performance (1) VOC content: determined according to standard GB / T 23986.2-2023.

[0048] (2) Free formaldehyde content: determined according to standard GB 18583-2008.

[0049] Table 1. Basic performance test results of the examples and comparative examples.

[0050] Table 2. Test results of core performance and environmental performance of the examples and comparative examples.

[0051] Data Analysis: Analysis of the data in Tables 1 and 2 shows that the emulsions prepared in Examples 1-3 possess excellent storage stability, good comprehensive mechanical properties, and environmental friendliness. Among them, Example 2 achieves the best balance between high hardness and high toughness, while Examples 1 and 3 have similar performance. This confirms that the crosslinking network constructed by the modified rosin acrylate monomer and maleimide-modified CNC through the Diels-Alder reaction is the key to achieving synergistic toughening and enhancement. Especially in medium and low temperature environments, this crosslinking network exhibits excellent structural stability and impact resistance, which is very suitable for applications such as automotive interiors and leather finishing that have stringent toughness requirements and low operating temperatures, effectively overcoming the defect of traditional materials being prone to cracking at low temperatures.

[0052] Compared to Example 2, the emulsion in Comparative Example 1 exhibited larger particle size and precipitation, resulting in significantly reduced mechanical properties. This was due to severe agglomeration caused by the lack of hydrophobic modification of ordinary CNC, and the absence of maleimide groups on the surface, preventing chemical bonding with furan rings. Comparative Example 2 showed stratification and had the worst performance because the unmodified rosin was only used as a physical additive, resulting in poor compatibility and easy migration, and the lack of furan ring structures prevented it from participating in network construction. Although Comparative Examples 3, 4, and 5 were stable during storage due to the good compatibility of each individual component or the base system, their performance was inferior to that of Example 2. Comparative Example 3 lacked the rigid support of rosin monomers and furan sites, leading to incomplete network construction; Comparative Example 4 lacked CNC nano-reinforcing nodes, resulting in insufficient energy dissipation; Comparative Example 5, due to the simultaneous absence of modified rosin acrylate monomers, maleimide-modified CNC, and crosslinking structures, exhibited the typical defects of insufficient toughness found in base emulsions.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A high-toughness, water-based, environmentally friendly emulsion, characterized in that, The product comprises the following components in parts by weight: 45-55 parts butyl acrylate, 35-45 parts methyl methacrylate, 1-2 parts acrylic acid, 5-10 parts modified rosin acrylate monomer, 0.5-2.0 parts maleimide-modified CNC, 80-100 parts deionized water, 0.3-0.5 parts initiator, and 0.1-0.2 parts pH adjuster; wherein the initiator is ammonium persulfate and the pH adjuster is sodium bicarbonate.

2. The high-toughness water-based environmentally friendly emulsion according to claim 1, characterized in that, The method for preparing the modified rosin acrylate monomer includes the following steps: A1: Add disproportionated rosin and industrial ethanol to the reactor, stir and heat to 60-70℃ to completely dissolve the disproportionated rosin; then slowly add a 10-20% sodium hydroxide solution while stirring, adjust the pH of the system to 10-11, and stir at a constant temperature for 1.5-2 hours. After the reaction is complete, allow it to stand and separate into layers, separate the lower aqueous phase, slowly add a 10-15% hydrochloric acid solution to the aqueous phase, adjust the pH to 2-3, continue stirring for 20-30 minutes, filter and collect the precipitate, wash with deionized water until the washing solution is neutral, place the precipitate in a vacuum drying oven at 60-70℃ and dry for 4-6 hours to obtain a white powder of dehydroabsic acid concentrate for later use. A2: Add dehydroabsic acid and glycidyl furfuryl ether to the reactor and stir until homogeneous. Then add tetrabutylammonium bromide and the polymerization inhibitor hydroquinone. Next, purge the system with nitrogen 3-4 times and maintain the nitrogen atmosphere. Then raise the temperature to 110-120℃ and stir the reaction at a constant temperature for 2.0-2.5h. After the reaction is completed, a reaction system containing intermediate 1 is obtained. A3: Cool the above reaction system to 80-85℃, control the stirring rate at 300-400 r / min, slowly add methacrylic anhydride, and simultaneously add 4-dimethylaminopyridine. Control the addition time to 30-60 min. After the addition is complete, maintain a constant temperature of 80-85℃ and stir for 2-3 h. After the reaction is complete, add deionized water at 50-60℃ to the reaction system, stir and wash 3-4 times, let it stand to separate into layers and remove the aqueous phase. Finally, dry the organic phase under vacuum conditions of 70-80℃ and -0.09 MPa to -0.07 MPa to obtain the modified rosin acrylate monomer.

3. The high-toughness water-based environmentally friendly emulsion according to claim 2, characterized in that, In step A2, the molar ratio of dehydroabietic acid to glycidyl furfural ether is 1:(1.02-1.10).

4. The high-toughness water-based environmentally friendly emulsion according to claim 2, characterized in that, In step A2, the mass of tetrabutylammonium bromide and hydroquinone are 0.3-0.4% and 0.05-0.08% of the total mass of dehydroabietic acid and glycidyl furfural ether, respectively.

5. The high-toughness water-based environmentally friendly emulsion according to claim 2, characterized in that, In step A3, the molar ratio of intermediate 1 to 4-dimethylaminopyridine is 1:(0.2-0.3).

6. The high-toughness water-based environmentally friendly emulsion according to claim 1, characterized in that, The preparation method of the maleimide-modified CNC includes the following steps: S1: Add 3-aminopropyltriethoxysilane and anhydrous DMF to the reactor and stir until completely dissolved. Then, place the reactor in an ice-water bath to cool to 0-5°C. Slowly add maleic anhydride dropwise through a constant-pressure dropping funnel over a period of 30-60 minutes while stirring. After the addition is complete, maintain the temperature at 0-5°C and stir for 1.5-2.5 hours to generate intermediate A. Subsequently, add triethylamine and acetic anhydride to the system, heat to 50-60°C, and stir while maintaining the temperature. Set the reaction time to complete the dehydration and cyclization. After the reaction is complete, remove the solvent and low-boiling-point byproducts to obtain intermediate B for later use. S2: Add cellulose nanocrystals (CNC) and sulfuric acid (60-64% by mass) to the reaction vessel and stir at 45-50℃ for 2-3 hours. Add deionized water to terminate the reaction. After centrifugation and repeated washing with deionized water until neutral, dialyze for 70-72 hours to obtain a CNC suspension. Then centrifuge the CNC and wash it with anhydrous ethanol and anhydrous toluene to obtain a toluene-dispersed CNC slurry. Add intermediate B and reflux at 100-110℃ for 12-24 hours. Then centrifuge the precipitate and wash it with anhydrous toluene and anhydrous ethanol 3-4 times each. Freeze-dry to obtain maleimide-modified CNC.

7. The high-toughness water-based environmentally friendly emulsion according to claim 6, characterized in that, In step S1, the reaction time is 4-6 hours.

8. The high-toughness water-based environmentally friendly emulsion according to claim 6, characterized in that, In step S2, the mass ratio of intermediate B to CNC is 1:(4-5).

9. A method for preparing a high-toughness waterborne environmentally friendly emulsion as described in claim 1, characterized in that, Includes the following steps: Step 1: Add 50% of the total amount of deionized water in the formula to a pre-emulsification tank equipped with a high-speed disperser, turn on the stirrer at 300-500 r / min, slowly add maleimide-modified CNC, intermittently sonicate the dispersion with an ultrasonic cell disruptor for 10-15 min, add sodium bicarbonate and stir to dissolve, and obtain the dispersion. Step 2: In a separate container, mix butyl acrylate, methyl methacrylate, acrylic acid and modified rosin acrylate monomers, and stir until homogeneous to obtain a mixed oil phase; under high-speed dispersion at 1000-1500 r / min, slowly add the mixed oil phase dropwise to the dispersion, and after the addition is complete, continue high-speed stirring and emulsification for 20-30 min to obtain a uniform white pre-emulsion. Step 3: Add 20% of the remaining formula amount of deionized water and 10% of the amount of pre-emulsion to another reactor, turn on the stirring and heat to 75-80℃, add 1 / 3 of the amount of pre-dissolved ammonium persulfate aqueous solution with a mass fraction of 3-5% to initiate the reaction, and after a faint blue light appears and the liquid surface is slightly boiling, maintain for 15-20 minutes to obtain the seed emulsion. Step 4: Place the remaining 90% of the pre-emulsion in a constant pressure funnel and add it dropwise to a four-necked flask containing the seed emulsion, while simultaneously adding the remaining 2 / 3 of the ammonium persulfate aqueous solution; control the dropping rate to stabilize the temperature at 80-82℃, and the dropping time is 2.5-3.5 hours; after the dropping is complete, raise the temperature to 85-87℃ and keep it at this temperature for 1-2 hours to promote the Diels-Alder cyclization reaction between the maleimide groups on the surface of the maleimide-modified CNC and the furan ring in the modified rosin acrylate monomer; cool down to 25-35℃, adjust the pH value to 7-8, filter and discharge to obtain the finished product.

10. The application of the high-toughness waterborne environmentally friendly emulsion as described in any one of claims 1-9 in coatings or adhesives used in medium and low temperature applications.

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