A kind of odorless coating film-forming aid and preparation method thereof

Abstract

The present invention belongs to the technical field of film-forming agents, and in particular relates to a film-forming agent for odorless coatings and a preparation method thereof. The active polymer in the film-forming agent uses renewable polyphenol ellagic acid as a starting material, utilizes the multiple phenolic hydroxyl groups in its structure to react with propylene oxide through ring-opening polymerization to form a polyether segment, and then introduces disulfide through acylation and nucleophilic substitution reactions to prepare the film-forming agent. The film-forming agent has a boiling point of over 290°C and is an odorless film-forming agent. When used in civilian water-based coatings, it will not cause the coating to produce an unpleasant odor, can effectively increase the film-forming speed of the coating, and can also improve the gloss, impact resistance and wear resistance of the coating.

Description

Technical Field

[0001] The present invention relates to the technical field of film-forming aids, in particular to a film-forming aid for odorless coatings and a preparation method thereof. Background Art

[0002] Coalescents are a key component of coatings. They aid in film formation. Good film-forming properties enhance the overall performance of the coating, reduce porosity, and further improve film properties such as scrub resistance, water washability, and gloss. Therefore, the selection of coalescents is crucial to producing excellent coatings.

[0003] Solvent-based coatings typically use a relatively high molecular weight resin as a base, creating a homogeneous system that forms a continuous film as the solvent evaporates. However, water-based coatings, which use water as a medium, are heterogeneous polymers, relying on water evaporation to deform and fuse polymer particles to form a film. The softer the polymer, the better the fusion and the denser the film. However, coatings often require a certain degree of flexibility and hardness, so the polymer's glass transition temperature is designed to be high, and the minimum film-forming temperature is usually above room temperature. If the coating is left to cure at room temperature, the film formation rate will be too slow, resulting in poor anti-blocking and abrasion resistance.

[0004] Chinese patent application publication number CN107974115A discloses a coating film-forming agent. Using styrene resin, isooctyl acrylate, C9 petroleum resin, and urea-formaldehyde resin as base materials, and adding methylcellulose, triethyl borate, ethylene glycol dimethacrylate, and alginate, the resulting film-forming agent exhibits excellent spreadability, smoothness, and adhesion, effectively enhancing the protective effect and service life of the coating. Resin-based film-forming agents are typically used in solvent-based coatings. In water-based coatings, coating defects often occur due to an imbalance between the water evaporation rate and resin coagulation, as well as differences in surface tension.

[0005] The main component of a commonly used coalescing agent in water-based paints is dodecyl alcohol ester, which is prepared from isobutyraldehyde. Dodecyl alcohol ester has a pungent odor, and its volatile gases can irritate the respiratory tract. When used in residential paints, it produces an unpleasant odor, which can be detrimental to the health of both applicators and users. Its boiling point is between 250°C and 255°C, making it a low-VOC paint. However, its eventual release into the atmosphere can cause ecological pollution. Summary of the Invention

[0006] The present invention aims to provide a film-forming aid for odorless coatings and a method for preparing the same. This technical solution utilizes the phenolic hydroxyl groups of ellagic acid and propylene oxide to produce polyether segments through ring-opening polymerization. Disulfide bonds are introduced into the segments to produce a polymer. Using isooctyl adipate as a solvent, dioctyl terephthalate (a high-boiling, low-volatility plasticizer) and polyoxypropylene oleate as a surfactant, the resulting film-forming aid has a boiling point exceeding 290°C and is odorless. Its use in civilian water-based coatings does not produce an unpleasant odor, poses no health risks to construction workers or users, and improves the gloss, friction resistance, and impact resistance of water-based coatings.

[0007] The present invention provides a film-forming aid for a odorless coating, comprising a polymer, a first solvent, a stabilizer, a surfactant, and a plasticizer; the mass ratio of the polymer, the first solvent, the stabilizer, the surfactant, and the plasticizer is 1:(2-3):(0.012-0.025):(0.011-0.025):(0.2-0.3); the polymer is prepared by ring-opening polymerization of ellagic acid and propylene oxide to form a polyether segment, and then introducing a disulfide bond to prepare the polymer; the structural formula of the polymer is as follows:

[0008] ,

[0009] Here, n is an integer between 4 and 8.

[0010] Preferably, the first solvent is isooctyl adipate.

[0011] Preferably, the stabilizer is any one or more of glycerol, sodium salt of acrylic acid copolymer, hydroxyethyl cellulose, and ammonium dihydrogen phosphate.

[0012] Preferably, the surfactant is polyoxypropylene oleate.

[0013] Preferably, the plasticizer is dioctyl terephthalate.

[0014] The present invention also provides a method for preparing a film-forming aid for odorless coatings, comprising:

[0015] Step S1, dissolving ellagic acid in a second solvent, adding a catalyst, and carrying out a first reaction under nitrogen protection and light protection to obtain an intermediate, and then adding propylene oxide to the intermediate system to carry out a second reaction to obtain an ellagic acid derivative;

[0016] Step S2, dissolving the ellagic acid derivative in a third solvent, adding triethylamine, and then adding p-toluenesulfonyl chloride under ice bath conditions to react to obtain a sulfonylated ellagic acid derivative;

[0017] Step S3, adding 2-hydroxyethyl disulfide dropwise to a sodium hydroxide alcohol solution to react to obtain a sodium salt of 2-hydroxyethyl disulfide;

[0018] Step S4: dissolving the sulfonylated ellagic acid derivative in a second solvent, adding sodium salt of 2-hydroxyethyl disulfide under stirring, reacting, adding dilute hydrochloric acid to terminate the reaction, collecting the solid by centrifugation, and washing to obtain a polymer.

[0019] Step S5: dissolving the polymer in the first solvent, adding a stabilizer, a surfactant and a plasticizer, and stirring to obtain a film-forming aid.

[0020] Preferably, in step S1, the second solvent is any one or more of N,N-dimethylformamide and dimethyl sulfoxide.

[0021] Preferably, in step S1, the catalyst is any one or more of sodium carbonate, potassium carbonate, and triethylamine.

[0022] Preferably, in step S1, the temperature of the first reaction is 40-55° C., and the time of the first reaction is 1-3 h.

[0023] Preferably, in step S1, the temperature of the second reaction is 60-100° C., and the time of the second reaction is 5-10 h.

[0024] Preferably, in step S1, the mass ratio of the ellagic acid, the second solvent, the catalyst, and propylene oxide is 1:(2-3):(0.05-0.15):(0.15-0.45).

[0025] Preferably, in step S2, the third solvent is any one or more of dichloromethane and tetrahydrofuran.

[0026] Preferably, in step S2, the reaction temperature is 25-50° C., and the reaction time is 6-12 h.

[0027] Preferably, in step S2, the mass ratio of the ellagic acid derivative, the third solvent, triethylamine, and p-toluenesulfonyl chloride is 1:(2-3):(1.5-3):(1.1-1.5).

[0028] Preferably, in step S3, the mass ratio of sodium hydroxide to anhydrous ethanol in the sodium hydroxide alcohol solution is 1:(5-9).

[0029] Preferably, in step S3, the reaction temperature is 50-80° C., and the reaction time is 0.5-2 h.

[0030] Preferably, in step S3, the mass ratio of the 2-hydroxyethyl disulfide to the sodium hydroxide alcohol solution is 1:(1.5-2).

[0031] Preferably, in step S4, the stirring temperature is 20-30°C.

[0032] Preferably, in step S4, the reaction temperature is 50-80° C., and the reaction time is 6-12 h.

[0033] Preferably, in step S4, the washing solvent is diethyl ether.

[0034] Preferably, in step S4, the mass ratio of the sulfonylated ellagic acid derivative, the second solvent, and the sodium salt of 2-hydroxyethyl disulfide is 1:(2-3):(1.1-1.5).

[0035] Preferably, in step S5, the stirring temperature is 30-45° C., and the stirring time is 0.5-1 h.

[0036] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0037] (1) This application uses ellagic acid as the core, and uses the hydroxyl groups in the ellagic acid structure to react with propylene oxide through ring-opening polymerization to introduce polyether segments into the ellagic acid. The polyether segments are introduced into segments containing disulfide bonds through acylation and nucleophilic substitution reactions to prepare a new polymer. The ellagic acid molecule contains multiple phenolic hydroxyl groups, which provide multiple reaction sites. Therefore, the prepared polymer has a high degree of branching. Under the condition of the same branched chain molecular weight, the degree of entanglement between molecular chains of polymers with a high degree of branching is significantly lower than that of linear or less branched polymers. The movement of the main chain is hindered to a certain extent by the branches, which reduces the close contact and entanglement opportunities between the main chains. It is more likely to cause relative slip and diffusion in the solution or during the film formation process, thus significantly accelerating the film formation speed of the coating. Secondly, the branched segments of polymers with a high degree of branching can hinder the close arrangement of the segments, reduce the formation of hydrogen bonds and van der Waals forces between the chains, and reduce the glass transition temperature. Therefore, it can significantly reduce the curing temperature of the coating. In addition, polymers with a high degree of branching will form nano-scale concave-convex structures on the surface of the coating, further reducing the interfacial contact area and reducing the tendency to adhesion.

[0038] (2) In the polymer prepared in this application, a disulfide bond-containing segment is introduced into the polyether segment through acylation and nucleophilic substitution reaction. The impact resistance and wear resistance of the coating containing the polymer film-forming agent are significantly improved. This is because the disulfide bond has a low bond energy and will preferentially break under the action of external force, converting mechanical energy into chemical energy. When the stress is released, the sulfur radicals can recombine to form disulfide bonds, allowing the material to restore its original structure and avoid permanent damage. The same is true for wear resistance. During the friction process, the friction stress causes the disulfide bonds to break preferentially, reducing the energy transferred to the matrix. The sulfur radicals generated after the breakage quickly recombine to restore the cross-linked structure of the molecular chain and avoid material wear caused by permanent breakage.

[0039] (3) The boiling point of the film-forming aid prepared in this application exceeds 290°C. This is due to the enhanced van der Waals forces between the molecular chains of the high molecular weight polymer, the disulfide bonds introduced into the molecular chains, and the enhanced dipole forces between the molecules. Higher energy is required to overcome these intermolecular forces to achieve vaporization, resulting in an increase in the boiling point. Using isooctyl adipate as a solvent and compounding it with dioctyl terephthalate can increase the boiling point of the system. Adding high-boiling-point oleic acid polyoxypropylene ether as a surfactant prevents the particles in the system from agglomerating through steric hindrance and electrostatic repulsion, forming a stable dispersion. This dispersed state increases the contact points between molecules, so that the system as a whole requires higher energy to break the intermolecular forces and achieve boiling, further increasing the boiling point of the system.

[0040] (4) In the technical solution of this application, renewable phenols are used to replace ordinary petroleum-based phenols to reduce carbon footprint. The film-forming agent prepared from the obtained polymer can reduce the VOC content. This is because the polymer with a high degree of branching has a low intrinsic viscosity. Even at a high solid content, the melt viscosity is still significantly lower than that of a linear polymer. The presence of branches makes the molecular chains stack more densely, thereby reducing the free volume between molecules. Linear molecules have no branches, and the molecular chains are not as dense as branched molecular chains. Therefore, the free volume is relatively larger, but the molecular chains of linear molecules are more entangled, which will lead to uneven free volume distribution and thus hinder the movement of molecular chains. Although the free volume of branched molecular chains is reduced, the degree of entanglement between molecular chains is low, and the molecular chains are arranged more evenly. Therefore, the free volume distribution is uniform and more regular, which is conducive to more efficient sliding of molecular chains in a limited space, so that the polymer can maintain the fluidity required for construction at a low solvent content. Chemical bonds such as disulfide bonds in polymer molecules can quickly cross-link and fix the solvent, inhibiting the generation and release of VOCs. Low-branched polymers, especially linear polymers, have highly entangled molecular chains and require organic solvents such as toluene and xylene to reduce viscosity. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a flow chart for the preparation of a film-forming aid for odorless coatings.

[0042] Figure 2 Schematic diagram of the polymer synthesis route. DETAILED DESCRIPTION

[0043] The following examples are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0044] The model of the sodium salt of acrylic acid copolymer used in the examples and comparative examples is Disperbx 8070N (Siperson New Materials (Shanghai) Co., Ltd.).

[0045] Unless otherwise specified, the reagents and equipment involved in the following examples were purchased from commercial channels.

[0046] Example 1

[0047] like Figure 1 As shown, a film-forming aid for a odorless coating, the preparation method of which comprises:

[0048] Step S1: dissolving 10 g of ellagic acid in 20 g of N, N-dimethylformamide, adding 0.5 g of sodium carbonate, and reacting at 40° C. for 3 h under nitrogen protection and in the dark to obtain an intermediate. 1.5 g of propylene oxide was further added to the intermediate system, and the reaction was carried out at 60° C. for 10 h to obtain an ellagic acid derivative.

[0049] Step S2: dissolve 10 g of ellagic acid derivative in 20 g of dichloromethane, add 15 g of triethylamine, add 11 g of p-toluenesulfonyl chloride under ice bath conditions, and react at 25° C. for 12 h to obtain a sulfonylated ellagic acid derivative.

[0050] Step S3: dissolving 10 g of sodium hydroxide in 40 g of anhydrous ethanol to prepare a sodium hydroxide alcohol solution with a concentration of about 20%, adding 10 g of 2-hydroxyethyl disulfide dropwise to 15 g of the 20% sodium hydroxide alcohol solution, and reacting at 50° C. for 2 h to obtain the sodium salt of 2-hydroxyethyl disulfide.

[0051] Step S4: 10 g of the sulfonylated ellagic acid derivative was dissolved in 20 g of N, N-dimethylformamide, and 11 g of sodium salt of 2-hydroxyethyl disulfide was added under stirring at 20° C. The mixture was reacted at 50° C. for 12 h, and dilute hydrochloric acid was added to terminate the reaction. The solid was collected by centrifugation and washed with ether to obtain a polymer, such as Figure 2 shown.

[0052] Step S5: dissolving 10 g of the polymer in 20 g of isooctyl adipate, adding 0.12 g of sodium salt of acrylic acid copolymer, 0.11 g of polyoxypropylene oleate, and 2 g of dioctyl terephthalate, and stirring at 30° C. for 1 h to obtain a film-forming aid.

[0053] Example 2

[0054] like Figure 1 As shown, a film-forming aid for a odorless coating, the preparation method of which comprises:

[0055] Step S1: dissolve 10 g of ellagic acid in 25 g of dimethyl sulfoxide, add 1 g of potassium carbonate, and react at 45°C for 2 h under nitrogen protection and in the dark to obtain an intermediate. 2.5 g of propylene oxide is further added to the intermediate system, and the reaction is carried out at 75°C for 7 h to obtain an ellagic acid derivative.

[0056] Step S2: dissolve 10 g of ellagic acid derivative in 25 g of tetrahydrofuran, add 20 g of triethylamine, add 12 g of p-toluenesulfonyl chloride under ice bath conditions, and react at 35° C. for 9 h to obtain a sulfonylated ellagic acid derivative.

[0057] Step S3: dissolving 10 g of sodium hydroxide in 60 g of anhydrous ethanol to prepare a sodium hydroxide alcohol solution with a concentration of about 15%, adding 10 g of 2-hydroxyethyl disulfide dropwise to 20 g of the 15% sodium hydroxide alcohol solution, and reacting at 65° C. for 1.5 h to obtain the sodium salt of 2-hydroxyethyl disulfide.

[0058] Step S4: dissolve 10 g of the sulfonylated ellagic acid derivative in 25 g of dimethyl sulfoxide, add 12 g of sodium salt of 2-hydroxyethyl disulfide under stirring at 25° C., react at 65° C. for 10 h, add dilute hydrochloric acid to terminate the reaction, collect the solid by centrifugation, and wash the solid with ether to obtain a polymer, such as Figure 2 shown.

[0059] Step S5: dissolving 10 g of the polymer in 25 g of isooctyl adipate, adding 0.16 g of propylene glycol, 0.18 g of polyoxypropylene oleate, and 2.5 g of dioctyl terephthalate, and stirring at 35° C. for 1 h to obtain a film-forming aid.

[0060] Example 3

[0061] like Figure 1 As shown, a film-forming aid for a odorless coating, the preparation method of which comprises:

[0062] Step S1: dissolve 10 g of ellagic acid in 20 g of dimethyl sulfoxide, add 1.5 g of triethylamine, and react at 50° C. for 1 h under nitrogen protection and in the dark to obtain an intermediate. 3.5 g of propylene oxide is further added to the intermediate system, and the reaction is carried out at 90° C. for 6 h to obtain an ellagic acid derivative.

[0063] Step S2: dissolve 10 g of ellagic acid derivative in 20 g of tetrahydrofuran, add 25 g of triethylamine, add 13 g of p-toluenesulfonyl chloride under ice bath conditions, and react at 40° C. for 7 h to obtain a sulfonylated ellagic acid derivative.

[0064] Step S3: dissolving 10 g of sodium hydroxide in 80 g of anhydrous ethanol to prepare a sodium hydroxide alcohol solution with a concentration of about 12%, adding 10 g of 2-hydroxyethyl disulfide dropwise to 15 g of the 12% sodium hydroxide alcohol solution, and reacting at 70° C. for 1 h to obtain the sodium salt of 2-hydroxyethyl disulfide.

[0065] Step S4: 10 g of the sulfonylated ellagic acid derivative was dissolved in 20 g of dimethyl sulfoxide, and 13 g of sodium salt of 2-hydroxyethyl disulfide was added under stirring at 30° C. The mixture was reacted at 70° C. for 8 h, and dilute hydrochloric acid was added to terminate the reaction. The solid was collected by centrifugation and washed with ether to obtain a polymer, such as Figure 2 shown.

[0066] Step S5: dissolving 10 g of the polymer in 25 g of isooctyl adipate, adding 0.2 g of hydroxyethyl cellulose, 0.22 g of polyoxypropylene oleate, and 3 g of dioctyl terephthalate, and stirring at 40° C. for 0.5 h to obtain a film-forming aid.

[0067] Example 4

[0068] like Figure 1 As shown, a film-forming aid for a odorless coating, the preparation method of which comprises:

[0069] Step S1: dissolve 10 g of ellagic acid in 30 g of dimethyl sulfoxide, add 1.5 g of triethylamine, and react at 55° C. for 1 h under nitrogen protection and in the dark to obtain an intermediate. 4.5 g of propylene oxide is then added to the intermediate system, and the reaction is carried out at 100° C. for 5 h to obtain an ellagic acid derivative.

[0070] Step S2: dissolving 10 g of ellagic acid derivative in 30 g of tetrahydrofuran, adding 30 g of triethylamine, adding 15 g of p-toluenesulfonyl chloride under ice bath conditions, and reacting at 50° C. for 6 h to obtain a sulfonylated ellagic acid derivative.

[0071] Step S3: dissolving 10 g of sodium hydroxide in 90 g of anhydrous ethanol to prepare a sodium hydroxide alcohol solution with a concentration of about 10%, adding 10 g of 2-hydroxyethyl disulfide dropwise to 20 g of the 10% sodium hydroxide alcohol solution, and reacting at 80° C. for 0.5 h to obtain the sodium salt of 2-hydroxyethyl disulfide.

[0072] Step S4: dissolving 10 g of the sulfonylated ellagic acid derivative in 30 g of dimethyl sulfoxide, adding 15 g of the sodium salt of 2-hydroxyethyl disulfide under stirring at 30° C., reacting at 80° C. for 6 h, and adding dilute hydrochloric acid to terminate the reaction. The solid was collected by centrifugation and washed with ether to obtain a polymer.

[0073] Step S5: dissolving 10 g of the polymer in 30 g of isooctyl adipate, adding 0.25 g of ammonium dihydrogen phosphate and 0.25 g of polyoxypropylene oleate, and 3 g of dioctyl terephthalate, and stirring at 45° C. for 0.5 h to obtain a film-forming aid.

[0074] Comparative Example 1

[0075] A film-forming aid for a odorless coating, the preparation method of which is different from that of Example 3 in that phenol is used instead of ellagic acid in step S1.

[0076] Comparative Example 2

[0077] A film-forming aid for a odorless coating, the preparation method of which is different from that of Example 3 in that p-hydroxyphenol is used instead of ellagic acid in step S1.

[0078] Comparative Example 3

[0079] A film-forming aid for a odorless coating, the preparation method of which is different from that of Example 3 in that the sodium salt of 2-hydroxyethyl disulfide is not added in step S4.

[0080] Performance testing:

[0081] The waterborne acrylic paint, waterborne polyurethane paint and waterborne epoxy resin paint to which the film-forming aids prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were added were subjected to the following performance tests, specifically:

[0082] (1) The film-forming time of the film-forming aids prepared in Examples 1 to 4 and Comparative Examples 1 to 3 in water-based acrylic paint, water-based polyurethane paint, and water-based epoxy resin paint was tested, respectively. The prepared film layer was touched with a finger, and the time when fingerprints no longer appeared on the film layer was recorded, i.e., the film-forming time.

[0083] (2) Anti-adhesion performance: Apply the coating to the substrate and dry it to form a film. Place the two substrates with the coated surfaces facing each other and apply a certain amount of pressure. Then place them in a drying oven at 50-60°C for 24 hours. Observe the difficulty of separating the substrates and check the degree of damage to the coating surface. The evaluation grades are divided into A, B, and C, with A being the best and C being the worst.

[0084] (3) Glossiness: Apply the coating on a matte black substrate and let it dry to form a film. Use a gloss meter to measure the glossiness of the coating.

[0085] (4) VOC content: The VOC content of the waterborne acrylic paint, waterborne polyurethane paint, and waterborne epoxy resin paint containing the film-forming aids prepared in Examples 1 to 4 and Comparative Examples 1 to 3 was tested according to the method specified in ISO 11890-2-2013.

[0086] (5) Impact resistance: Apply the coating on the substrate and dry it to form a film. Place the impact tester on a stable platform, and the guide tube should be perpendicular to the horizontal plane. Use the weight controller to adjust the weight of the impact tester to a certain height, and place the test plate flat on the base with the paint film facing up (forward impact) or facing down (backward impact). The distance between the edge of the test plate at the impact point and the edge of the test plate shall not be less than 10 mm, and the distance between the edges of adjacent impact points shall not be less than 10 mm. Press the weight controller button, and the weight will fall freely on the punch. Take out the test plate and observe whether the paint film on the test plate has cracks, wrinkles or peeling under natural sunlight or artificial sunlight, and record the maximum impact force it can withstand.

[0087] (6) Wear resistance: Fix the coated substrate on an abrasion tester and rub the coating with a rubber grinding wheel. Add a weight of a specified weight to the rubber grinding wheel and rub it through the rotation of the rubber grinding wheel to measure the wear resistance of the coating.

[0088] Table 1 Coating film formation time measurement data

[0089]

[0090] As shown in Table 1, the film-forming aids prepared in Examples 1 through 4, when added to water-based acrylic, water-based polyurethane, and water-based epoxy coatings, all promote rapid film formation at room temperature. Example 3 exhibits the best results, with film formation times of less than 15 minutes for all three coatings. The film-forming aids prepared in Comparative Examples 1 through 3, when added to the coatings, all achieve film formation times exceeding 20 minutes. Comparative Example 1 exhibits the worst performance, with film formation times exceeding 30 minutes.

[0091] When the molecular weight of the branches is the same, polymers with a higher degree of branching exhibit significantly lower levels of inter-chain entanglement than linear or less branched polymers. Consequently, the chain segments are more susceptible to relative slippage and diffusion in solution or during film formation. Comparative Example 1 uses phenol as the starting material. Comparative Example 2, compared to Comparative Example 1, has an additional substituent on the benzene ring of the starting material. However, the resulting film-forming aids exhibit lower levels of branching than Examples 1-3. Consequently, the coating film-forming time is significantly prolonged.

[0092] Table 2 Coating anti-adhesion test data

[0093]

[0094] Note: The evaluation grades are divided into A, B and C, with A being the best and C being the worst.

[0095] Materials with good anti-blocking properties typically have excellent film-forming properties, as they can form a continuous and stable film on the substrate, effectively preventing blocking. As shown in Table 2, the three coatings added with the film-forming aids prepared in Examples 1 through 4 all achieved anti-blocking properties above Grade A. However, the coatings prepared with Comparative Examples 1 through 3 exhibited significantly lower anti-blocking properties than the Examples.

[0096] Highly branched hyperbranched polymers can form nanoscale concave-convex structures on the membrane surface. This high surface roughness results in a more dispersed distribution of molecular chains, weakening intermolecular interactions. The branches, in turn, hinder other molecules from approaching the main chain, preventing excessive entanglement, thereby increasing the steric hindrance of each molecular chain. A more pronounced steric hindrance effect further reduces the interfacial contact area and lowers the tendency to adhere. Conversely, a lower surface roughness results in less steric hindrance. Comparative Examples 1 and 2 have lower branching levels than Examples 1 to 4, resulting in significantly lower surface roughness and steric hindrance than the Example groups, leading to lower anti-adhesion performance.

[0097] Table 3 Coating gloss measurement data

[0098]

[0099] As shown in Table 3, by adding the film-forming aids prepared in Examples 1 to 4, the glossiness of the three coatings was above 80%, while by adding the film-forming agents prepared in Comparative Examples 1 to 3, the glossiness of the three coatings was significantly reduced. Among them, the glossiness of the water-based acrylic coating with the film-forming aid prepared in Comparative Example 1 was only 58%, the glossiness of the water-based polyurethane coating was only 64%, and the glossiness of the water-based epoxy resin coating was only 55%.

[0100] Polymers with a high degree of branching typically have functional groups at the end of each branch, and the cross-linking density can reach 3-5 times that of linear polymers, forming a uniform three-dimensional network structure that inhibits volume shrinkage and cracking after film formation. As a result, the surface smoothness and gloss retention of the film are higher than those of linear systems. Low-branched polymers, on the other hand, have sparse cross-linking sites, which can lead to uneven film shrinkage, microcracks on the surface, and a significant reduction in gloss due to increased diffuse reflection.

[0101] Table 4 VOC content determination data of coatings

[0102]

[0103] As shown in the data in Table 4, the VOC contents of the coatings to which the film-forming aids prepared in Examples 1 to 4 were added were significantly lower than those of the coatings to which the film-forming aids prepared in Comparative Examples 1 to 3 were added.

[0104] Low-branched polymers, especially linear polymers, have highly entangled molecular chains and need to rely on organic solvents such as toluene and xylene to reduce viscosity. Polymers with a high degree of branching have low intrinsic viscosity, and even at high solid content, the melt viscosity is still significantly lower than that of linear polymers. Linear molecules have no branches, and the molecular chain stacking is not as dense as branched molecular chains, but the molecular chains of linear molecules are more severely entangled, which will lead to uneven free volume distribution and thus hinder the movement of molecular chains. Although the free volume of branched molecular chains is reduced, the degree of entanglement between molecular chains is low, the molecular chains are more evenly arranged, and the free volume distribution is more uniform and regular, which is conducive to more efficient sliding of molecular chains in a limited space. This allows the polymer to maintain the fluidity required for construction at a low solvent content, can quickly cross-link and fix the solvent, and inhibit the generation and release of VOCs.

[0105] Table 5 Test data of coating impact resistance

[0106]

[0107] As shown in the data in Table 5, the coatings of the three coatings to which the film-forming aids prepared in Examples 1 to 4 were added had impact resistance of more than 50 kg / cm, which was significantly higher than the coatings to which the film-forming aids prepared in Comparative Examples 1 to 3 were added. Among them, the performance of Comparative Example 3 was the worst, and the impact strength of the three coatings was all below 40 kg / cm.

[0108] The film-forming aid prepared in Comparative Example 3 does not incorporate disulfide bond segments into the polymer. Disulfide bonds have low bond energies and preferentially break under external forces, converting mechanical energy into chemical energy. Upon stress release, sulfhydryl radicals recombine to form disulfide bonds, restoring the material's original structure and preventing permanent damage. Therefore, the introduction of disulfide bond segments into the polymer can effectively improve the impact resistance of the coating.

[0109] Table 6 Test data of coating wear resistance

[0110]

[0111] According to the data in Table 6, the coatings of the three coatings with the addition of the film-forming aids prepared in Examples 1 to 4 did not show any changes on the coating surface after 5000 frictions, while the coatings of the three coatings with the addition of the film-forming aid prepared in Comparative Example 1 showed slight wear after 5000 frictions, the coating of the water-based epoxy resin coating with the addition of the film-forming aid prepared in Comparative Example 2 showed obvious wear after 5000 frictions, and the coatings of the three coatings with the addition of the film-forming aid prepared in Comparative Example 3 all showed obvious wear after 5000 frictions.

[0112] The coatings of the three coatings with the film-forming aid prepared in Example 1 showed slight wear after 10,000 frictions, the coatings of the water-based polyurethane coating with the film-forming aid prepared in Example 2 showed slight wear after 10,000 frictions, the coatings of the water-based polyurethane coating and the water-based epoxy resin coating with the film-forming aid prepared in Example 3 showed slight wear after 10,000 frictions, and the coating of the water-based acrylic coating with the film-forming aid prepared in Example 4 showed slight wear after 10,000 frictions; the coatings of the water-based polyurethane coating and the water-based epoxy resin coating with the film-forming aid prepared in Comparative Example 1 showed warping after 10,000 frictions, the coating of the water-based epoxy resin coating with the film-forming aid prepared in Comparative Example 2 fell off after 10,000 frictions, and the coatings of the three coatings with the film-forming aid prepared in Comparative Example 3 all fell off after 10,000 frictions.

[0113] Experiments demonstrated that the wear resistance of coatings containing the film-forming aids prepared in Examples 1 through 4 was significantly superior to that of coatings containing the film-forming aids prepared in Comparative Examples 1 through 3. The film-forming aid prepared in Comparative Example 3 lacked disulfide bonds and, therefore, exhibited the worst wear resistance. During friction, stress concentration at the contact interface preferentially breaks disulfide bonds, converting mechanical energy into chemical energy and reducing the energy transferred to the substrate. The resulting sulfur radicals rapidly recombine in stress-free areas, restoring the cross-linked molecular structure and preventing material wear due to permanent fracture.

[0114] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A film-forming aid for a clean-taste coating, characterized in that: The film-forming aid comprises a polymer, a first solvent, a stabilizer, a surfactant, and a plasticizer; the mass ratio of the polymer, the first solvent, the stabilizer, the surfactant, and the plasticizer is 1:(2-3):(0.012-0.025):(0.011-0.025):(0.2-0.3); the polymer is prepared by ring-opening polymerization of ellagic acid and propylene oxide to form a polyether segment, and then introducing a disulfide bond to prepare the polymer; the structural formula of the polymer is as follows: ， Here, n is an integer between 4 and 8.

2. The odorless coating film-forming aid according to claim 1, characterized in that: The first solvent is isooctyl adipate; the stabilizer is any one or more of glycerol, sodium salt of acrylic acid copolymer, hydroxyethyl cellulose, and ammonium dihydrogen phosphate; the surfactant is polyoxypropylene oleate; and the plasticizer is dioctyl terephthalate.

3. A method for preparing the odorless coating film-forming aid according to claim 1 or 2, comprising: Step S1, dissolving ellagic acid in a second solvent, adding a catalyst, and carrying out a first reaction under nitrogen protection and light protection to obtain an intermediate, and then adding propylene oxide to the intermediate system to carry out a second reaction to obtain an ellagic acid derivative; Step S2, dissolving the ellagic acid derivative in a third solvent, adding triethylamine, and then adding p-toluenesulfonyl chloride under ice bath conditions to react to obtain a sulfonylated ellagic acid derivative; Step S3, adding 2-hydroxyethyl disulfide dropwise to a sodium hydroxide alcohol solution to react to obtain a sodium salt of 2-hydroxyethyl disulfide; Step S4, dissolving the sulfonylated ellagic acid derivative in a second solvent, adding sodium salt of 2-hydroxyethyl disulfide under stirring, reacting, adding dilute hydrochloric acid to terminate the reaction, collecting the solid by centrifugation, and washing to obtain a polymer; Step S5: dissolving the polymer in the first solvent, adding a stabilizer, a surfactant and a plasticizer, and stirring to obtain a film-forming aid.

4. The method for preparing a film-forming aid for odorless coatings according to claim 3, characterized in that: In step S1, the second solvent is any one or more of N, N-dimethylformamide and dimethyl sulfoxide; and the catalyst is any one or more of sodium carbonate, potassium carbonate and triethylamine.

5. The method for preparing a film-forming aid for odorless coatings according to claim 3, characterized in that: In step S1, the temperature of the first reaction is 40-55° C., and the time of the first reaction is 1-3 hours; the temperature of the second reaction is 60-100° C., and the time of the second reaction is 5-10 hours; the mass ratio of ellagic acid, the second solvent, the catalyst, and propylene oxide is 1:(2-3):(0.05-0.15):(0.15-0.45).

6. The method for preparing a film-forming aid for odorless coatings according to claim 3, characterized in that: In step S2, the third solvent is any one or more of dichloromethane and tetrahydrofuran; the reaction temperature is 25-50° C., and the reaction time is 6-12 h; and the mass ratio of the ellagic acid derivative, the third solvent, triethylamine, and p-toluenesulfonyl chloride is 1:(2-3):(1.5-3):(1.1-1.5).

7. The method for preparing a film-forming aid for odorless coatings according to claim 3, characterized in that: In step S3, the mass ratio of sodium hydroxide to anhydrous ethanol in the sodium hydroxide alcohol solution is 1:(5-9); the reaction temperature is 50-80° C., and the reaction time is 0.5-2 h; and the mass ratio of 2-hydroxyethyl disulfide to the sodium hydroxide alcohol solution is 1:(1.5-2).

8. The method for preparing a film-forming aid for odorless coatings according to claim 3, characterized in that: In the step S4, the stirring temperature is 20-30° C.; the reaction temperature is 50-80° C.; and the reaction time is 6-12 h.

9. The method for preparing a film-forming aid for odorless coatings according to claim 3, characterized in that: In step S4, the washing solvent is diethyl ether; the mass ratio of the sulfonylated ellagic acid derivative, the second solvent, and the sodium salt of 2-hydroxyethyl disulfide is 1:(2-3):(1.1-1.5).

10. The method for preparing a film-forming aid for odorless coatings according to claim 3, characterized in that: In step S5, the stirring temperature is 30-45° C., and the stirring time is 0.5-1 h.

Images