Washable modified rosin resin, preparation method thereof and washable mark pen ink

Abstract

The invention discloses washable modified rosin resin, a preparation method thereof and washable mark pen ink. Wherein the washable modified rosin resin is prepared from the following components in parts by weight: 40 to 60 parts of natural rosin and 15 to 30 parts of maleic anhydride; 5 to 15 parts of polyol; 15 to 38 parts of an acrylic ester monomer; 3 to 10 parts of a pH responsive monomer; wherein the pH (Potential of Hydrogen) responsive monomer is dimethylaminoethyl methacrylate. Natural rosin is modified by adopting maleic anhydride and polyhydric alcohol, so that a molecular structure contains a large number of polar groups such as carboxyl, hydroxyl, ester groups and ether bonds, good stability is achieved, sedimentation and layering of pigments in ink can be effectively prevented when the rosin is prepared into the ink, and uniformity and consistency of writing colors are guaranteed. By adding the pH responsive monomer, in a cleaning state, tertiary amine groups are protonized, molecular chains are curled, the hydrophilicity is remarkably enhanced, the adhesive force is greatly reduced, and super-easy cleaning is realized.

Description

Technical Field

[0001] This invention relates to the field of pen manufacturing technology, and in particular to a washable modified rosin resin and its preparation method, as well as a washable marker ink. Background Technology

[0002] Existing acrylic-modified rosin resins, after drying and forming a film, often exhibit strong water resistance and even alkali resistance. This makes it difficult to clean the ink from clothing or skin with alkaline solutions such as soapy water when it is accidentally applied. Furthermore, existing systems have insufficient moisture retention; after a short period of time with the cap open, the pen tip is prone to forming a skin and becoming clogged, severely impacting the user experience.

[0003] Therefore, the existing technology still needs further improvement and enhancement. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a water-washable modified rosin resin and its preparation method, as well as a water-washable marker ink. The aim is to solve the problems in the prior art where rosin resin has high viscosity, poor writing smoothness, and difficulty in balancing washability and adhesion at high solid content.

[0005] In a first aspect, embodiments of the present invention provide a water-washable modified rosin resin, which, by weight, comprises: 40-60 parts of natural rosin, 15-30 parts of maleic anhydride, 5-15 parts of polyol, and 15-38 parts of acrylate monomers; 3-10 parts of pH-responsive monomer; wherein the pH-responsive monomer is dimethylaminoethyl methacrylate.

[0006] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0007] As a preferred technical solution, the water-washable modified rosin resin contains 10-20 parts of hydroxyethyl acrylate and 5-18 parts of acryloylmorpholine as the acrylate monomers.

[0008] As a preferred technical solution, the water-washable modified rosin resin further includes 0.5-3 parts of acid catalyst, 1-3 parts of initiator, 2-6 parts of organic neutralizer, 3-8 parts of inorganic neutralizer, and deionized water.

[0009] As a preferred technical solution, the water-washable modified rosin resin, wherein the organic neutralizing agent is AMP-95, the inorganic neutralizing agent is KOH, and the pH value of the water-washable modified rosin resin aqueous solution is 8.0-8.5.

[0010] Secondly, a method for preparing a water-washable modified rosin resin as described above, comprising the following steps: Natural rosin resin is mixed and melted with a solvent, and then maleic anhydride and a catalyst are added to carry out an addition reaction to obtain a reaction mixture. The reaction mixture was cooled, and a polyol was added to carry out an esterification reaction. The acid value was controlled to 130-140 mgKOH / g to obtain the esterified product. Grafting is performed by first adding a portion of acrylate monomers and initiators to the esterified compound, and then adding the pH-responsive monomers and the remaining initiators. The reaction is kept at a constant temperature until the acid value decreases to 70-80 mgKOH / g. After cooling, water is added for dilution, and a neutralizing agent is added to adjust the pH value to obtain the water-washable modified rosin resin.

[0011] As a preferred technical solution, the preparation method, wherein a portion of the acrylate monomer and initiator are first added dropwise to the ester for grafting, and then the pH-responsive monomer and the remaining initiator are added dropwise, specifically including: A mixture of hydroxyethyl acrylate, acrylmorpholine, and benzoyl peroxide was added dropwise at a temperature of 180-185℃. Continue adding the mixture of dimethylaminoethyl methacrylate and benzoyl peroxide dropwise.

[0012] As a preferred technical solution, in the preparation method, the solid content of the water-washable modified rosin resin is 45-50%.

[0013] Thirdly, a washable marker ink, wherein, by weight percentage, its components include: Pigment paste 25-35%; Moisturizer 5-8%; 15-20% of the water-washable modified rosin resin according to any one of claims 1-4; Additives: 0.5-2%; The remainder is deionized water.

[0014] As a preferred technical solution, the washable marker ink contains a humectant that is a mixture of propylene glycol and sorbitol; the pH value of the washable marker ink is 8.0-8.5.

[0015] As a preferred technical solution, the washable marker ink includes, in which the additives include: preservatives and brighteners.

[0016] Compared with the prior art, the embodiments of the present invention have the following advantages: This invention modifies natural rosin using maleic anhydride and polyols, resulting in a molecular structure rich in polar groups such as carboxyl, hydroxyl, ester, and ether bonds. This modification provides excellent stability, superior wetting and dispersion of pigments, and compatibility with other components. When used to prepare ink, it effectively prevents pigment sedimentation and stratification, ensuring stable performance during storage and use, and guaranteeing uniform and consistent writing color. Furthermore, the washable modified rosin resin prepared using maleic anhydride possesses excellent gloss. The numerous polar groups endow the resin with excellent wetting and leveling properties on writing surfaces. Therefore, water-based washable marker ink prepared using this water-washable modified rosin resin flows smoothly and forms a smooth thin layer on both rough and smooth surfaces of various media such as glass, wood, canvas, and plastic, and dries quickly. The resulting ink film exhibits uniform pigment distribution, high color saturation, gloss, opacity, and fastness, resulting in excellent writing performance. This invention incorporates a pH-responsive monomer, which maintains a hydrophobic state in a neutral environment (writing state), allowing the resin molecular chains to extend and form a strong interaction with the substrate, thus providing excellent adhesion. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a method for preparing a water-washable modified rosin resin according to an embodiment of the present invention. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with specific examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. Simultaneously, the steps or actions in the method description can be rearranged or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various orders in the specification are merely for the clear description of a particular embodiment and do not imply a mandatory order, unless otherwise stated that a particular order must be followed. The numbering itself in this document, such as "first," "second," etc., is only used to distinguish the described objects and has no sequential or technical meaning. All instruments and materials used are commercially available products.

[0020] This invention provides a washable modified rosin resin, comprising, by weight: 40-60 parts natural rosin, 15-30 parts maleic anhydride, 5-15 parts polyol, 15-38 parts acrylate monomer, and 3-10 parts pH-responsive monomer; wherein the pH-responsive monomer is dimethylaminoethyl methacrylate. By modifying the natural rosin, its molecular structure contains a large number of polar groups such as carboxyl, hydroxyl, ester, and ether bonds. These polar groups enable the modified resin to have excellent stability and good wetting and dispersibility for pigments. Simultaneously, due to the presence of the pH-responsive monomer, the modified resin maintains a hydrophobic state in a neutral environment (writing state), with the resin molecular chains extended, forming a strong interaction with the substrate and providing excellent adhesion. In an alkaline environment (washing state), the tertiary amine groups are protonated, the molecular chains coil, hydrophilicity is significantly enhanced, adhesion is greatly reduced, and ultra-easy cleaning is achieved.

[0021] In some embodiments of the present invention, the water-washable modified rosin resin further includes: an acid catalyst, an initiator, an organic neutralizer, and an inorganic neutralizer. The acid catalyst includes, but is not limited to, fumaric acid, maleic acid, and maleic acid. The initiator can be di-tert-butyl peroxide or benzoyl peroxide. The organic neutralizer is AMP-95, and the inorganic neutralizer is KOH. Neutralizing the resin by combining AMP-95 and KOH (organic and inorganic neutralizers) can greatly improve the resin's weather resistance stability.

[0022] Based on the same inventive concept, such as Figure 1 As shown in the figure, this invention also provides a method for preparing a water-washable modified rosin resin, comprising the following steps: S101. Natural rosin resin is mixed and melted with a solvent, and maleic anhydride and a catalyst are added to carry out an addition reaction to obtain a reaction mixture. S102. Cool the reaction mixture, add a polyol to carry out an esterification reaction, control the acid value to 130-140 mgKOH / g, and obtain the esterified product. S103. Grafting is performed by first adding a portion of acrylate monomers and initiators to the esterified compound, and then adding the pH-responsive monomers and the remaining initiators. The reaction is kept at a constant temperature until the acid value decreases to 70-80 mgKOH / g. S104. After cooling, dilute with water and add a neutralizing agent to adjust the pH value to obtain the water-washable modified rosin resin.

[0023] The preparation method described in this embodiment uses readily available raw materials and has clear process steps. The resulting water-washable modified rosin resin exhibits excellent stability and pH responsiveness.

[0024] Based on the same inventive concept, embodiments of the present invention also provide a washable marker ink, comprising, by weight percentage: 25-35% pigment paste; 5-8% humectant; 15-20% washable modified rosin resin; 0.5-2% additives; and the balance being deionized water. The pigment paste includes at least one of pigment red, pigment blue, pigment white, pigment black, pigment yellow, pigment green, and pigment orange; the humectant is a mixture of propylene glycol and sorbitol; and the additives include, but are not limited to, preservatives and extenders.

[0025] The above technical solution will be further explained and illustrated through specific preparation examples below.

[0026] Example 1 Weigh the following raw materials by weight: 40 parts natural rosin (Yunnan Grade 1 rosin), 15 parts maleic anhydride (analytical grade), 8 parts pentaerythritol (industrial grade), 13 parts hydroxyethyl acrylate, 10 parts acrylmorpholine, 3 parts dimethylaminoethyl methacrylate (DMAEMA), 1.5 parts fumaric acid (acid catalyst), 2 parts benzoyl peroxide (initiator), 4 parts AMP-95 (2-amino-2-methyl-1-propanol), 5 parts potassium hydroxide, 80 parts deionized water, and 30 parts xylene (solvent). Add 40 parts of natural rosin resin to a reactor and heat to 150°C under nitrogen protection, stirring until the rosin resin is completely melted and dissolved. After the system becomes clear, add 20 parts maleic anhydride and 1.5 parts fumaric acid in batches. The first 10 parts of maleic anhydride are added over 30 minutes, and the remaining 10 parts are added over the next 20 minutes to avoid localized overheating due to a single addition. The temperature was raised to 180℃ and maintained for 2.5 hours. The double bonds in maleic anhydride react with the conjugated double bonds in rosin resin to form an adduct containing a carboxyl group. The reaction progress was monitored by measuring the acid value. When the acid value rose to 210-220 mgKOH / g, it indicated that the addition reaction was basically complete.

[0027] The reaction temperature was lowered to 165℃, and 8 parts of pentaerythritol were added under stirring. Pentaerythritol is a tetraol, and its four hydroxyl groups can undergo esterification with the carboxyl groups on the adduct to form a cross-linked network structure. The reaction temperature was controlled at 165-170℃ and maintained for 3 hours. Water is generated during the esterification reaction, and it is separated and discharged through a water separator on the reflux condenser to ensure the forward reaction. The acid value was measured periodically. When the acid value dropped to 135 mgKOH / g, it indicated that the esterification reaction had reached the expected level. At this point, the resin molecular weight was appropriate, ensuring a certain degree of polymerization while reserving sufficient active sites for subsequent grafting reactions.

[0028] The reaction temperature was raised to 182℃. A monomer-initiator mixture was prepared by pre-mixing 13 parts hydroxyethyl acrylate, 10 parts acrylomorpholine, and 1.2 parts benzoyl peroxide. This mixture was added dropwise to the reaction system at a uniform rate over 1.5 hours, maintaining the temperature at 180-185℃ and the stirring speed at 200 rpm. Hydroxyethyl acrylate and acrylomorpholine underwent a free radical grafting reaction with the resin molecular chain under the initiation of benzoyl peroxide. The hydroxyl groups of hydroxyethyl acrylate could further esterify with the residual carboxyl groups on the resin, forming a grafted crosslinked structure; the morpholine ring of acrylomorpholine has weak basicity and good hydrophilicity, which can improve the stability of the resin in the aqueous phase.

[0029] After the first stage of addition, the reaction was maintained at this temperature for 30 minutes to ensure the grafting reaction proceeded fully. Five parts of dimethylaminoethyl methacrylate (DMAEMA) were mixed thoroughly with 0.8 parts of benzoyl peroxide and added dropwise to the reaction system at a uniform rate over one hour. DMAEMA molecules contain tertiary amine groups with a pKa value of approximately 7.5-8.0, and can undergo protonation / deprotonation transitions under different pH conditions. By using a segmented dropwise addition method, DMAEMA was grafted a second time onto the resin chain that had already formed the initial grafted structure, ensuring that the pH-responsive groups were evenly distributed within the resin molecules. If all monomers were added simultaneously in a one-step method, due to the differences in reactivity among the monomers, DMAEMA might preferentially participate in the reaction or be unevenly distributed, affecting the pH-responsive performance of the final product.

[0030] After the second stage of dropwise addition is completed, the reaction is continued at 182℃ for 2 hours, and samples are taken periodically to determine the acid value. At this point, it indicates that the grafting reaction is basically complete. The resin now has both a hydrophobic rosin backbone and grafted side chains, as well as a hydrophilic morpholine ring and a pH-responsive tertiary amine group, forming an amphiphilic structure.

[0031] Lower the reaction temperature to below 90℃ and begin dilution with water. First, add 20 parts deionized water and stir slowly for 30 minutes to initially disperse the resin. Then, dissolve 4 parts AMP-95 and 5 parts potassium hydroxide in 20 parts deionized water to prepare a compound neutralizing agent aqueous solution. Under vigorous stirring, slowly add the neutralizing agent aqueous solution to the resin system over 30 minutes. During neutralization, proton transfer occurs between the carboxyl and tertiary amine groups on the resin molecules, forming carboxyl and ammonium salt structures, significantly improving the water solubility of the resin. AMP-95 is an organic amino alcohol with low volatility and good film-forming aid properties; potassium hydroxide is an inorganic strong base. The combination of the two can rapidly neutralize carboxyl groups and moderately adjust the protonation degree of tertiary amine groups.

[0032] The neutralization reaction was carried out at 80-85℃ with stirring for at least 40 minutes to ensure thorough and uniform neutralization. The pH of the system was monitored using a pH meter, and the final pH was controlled at 8.2 by adjusting the amount of potassium hydroxide. At this point, the solid content of the resin aqueous solution was measured to be 48%, and the liquid was a pale yellow, semi-transparent liquid with good fluidity. Xylene solvent was recovered by distillation to obtain a pH-responsive, washable modified rosin resin aqueous solution for later use.

[0033] The pH response performance of the obtained resin was tested: buffer solutions with pH values ​​of 7.0, 8.0, 9.0, 10.0, and 11.0 were prepared, and the resin aqueous solution was diluted to a solid content of 5%. Solubility was observed in buffer solutions with different pH values. The results showed that in the pH range of 7.0-8.5, the resin exhibited a microemulsion state with slight turbidity; at pH values ​​of 9.0-10.0, transparency increased but colloidal stability was maintained; at pH ≥ 10.5, the resin completely dissolved to form a clear and transparent solution. This pH response characteristic is attributed to the protonation equilibrium of the tertiary amine group of DMAEMA; in neutral or weakly alkaline environments, the tertiary amine is partially protonated, and the resin exhibits amphiphilicity while maintaining moderate hydrophobicity; in strongly alkaline environments, the degree of deprotonation of the tertiary amine increases, hydrophilicity is enhanced, and the resin solubility is significantly improved.

[0034] Example 2 Three groups of samples were prepared, with other raw materials and processes the same as in Example 1, only the ratio of hydroxyethyl acrylate and acrylmorpholine was changed: Sample 2-1: 10 parts hydroxyethyl acrylate, 5 parts acrylmorpholine; Sample 2-2: 15 parts hydroxyethyl acrylate, 12 parts acrylmorpholine; Sample 2-3: 20 parts hydroxyethyl acrylate, 18 parts acrylmorpholine.

[0035] The preparation process of all three groups of samples was carried out according to the steps of Example 1. In the segmented copolymerization stage, the first stage involved adding the appropriate ratio of hydroxyethyl acrylate and acrylamide morpholine mixture, and the second stage involved adding 5 parts of DMAEMA, while keeping other conditions unchanged.

[0036] The performance comparison test results are as follows: Sample 2-1: Final acid value 73 mgKOH / g, resin aqueous solution solid content 47%, pH=8.3. The resin film after film formation has high hardness, reaching grade H in pencil hardness, but slightly poor flexibility, exhibiting minor cracking in a 180-degree bending test. The aqueous solution viscosity is 250 mPa·s (25℃, NDJ-5S rotational viscometer), indicating good flowability. Immersing in an alkaline solution at pH=10.5 for 5 minutes causes the resin film to begin swelling and softening, and it essentially dissolves after 10 minutes.

[0037] Sample 2-2: Final acid value 75 mgKOH / g, resin aqueous solution solid content 48%, pH=8.2. The resin film after film formation showed a good balance between hardness and flexibility, with a pencil hardness of HB grade, and no cracking after 180-degree bending. The viscosity of the aqueous solution was 420 mPa·s, which was moderate. It began to dissolve after 3 minutes in an alkaline solution with pH=10.5 and completely dissolved after 8 minutes, showing a fast response speed.

[0038] Samples 2-3: Final acid value 78 mgKOH / g, resin aqueous solution solid content 49%, pH=8.1. The resin film after film formation exhibits excellent flexibility, with a pencil hardness of 2B, but is relatively soft. The aqueous solution viscosity is 680 mPa·s, which is relatively high. It begins to dissolve rapidly after immersion in an alkaline solution at pH=10.5 for 2 minutes and completely dissolves within 5 minutes, exhibiting the fastest response.

[0039] Therefore, increasing the hydroxyethyl acrylate content improves the crosslinking density and hardness of the resin, but excessive amounts can lead to decreased flexibility. Similarly, increasing the acrylomorpholine content improves hydrophilicity and pH response speed, but too much can reduce resin hardness and water resistance. A good balance between hardness, flexibility, and response speed is achieved when the hydroxyethyl acrylate content is 10-20 parts and the acrylomorpholine content is 5-18 parts, making it suitable for marker ink applications.

[0040] Example 3 Three groups of samples were prepared. Except for the amount of DMAEMA used, the raw materials and processes were the same as in Example 1. Sample 3-1: 3 DMAEMA samples; Sample 3-2: 6.5 DMAEMA samples; Sample 3-3: 10 DMAEMA samples.

[0041] pH response performance comparison test: The three groups of resins were prepared into aqueous solutions with a solid content of 5%, and the changes in transmittance were observed in different pH buffer solutions. The transmittance was measured at a wavelength of 600 nm using a UV-Vis spectrophotometer. The higher the transmittance, the better the solubility.

[0042] Sample 3-1: The transmittance was 65% at pH=8.0, 82% at pH=10.0, and 94% at pH=11.0. It has a wide pH response range, but its hydrophobicity is insufficient near the application pH (8.0-8.5), which may result in weak ink adhesion.

[0043] Sample 3-2: Transmittance was 58% at pH=8.0, 76% at pH=10.0, and 96% at pH=11.0. It maintains moderate hydrophobicity within the application pH range, and its solubility is significantly improved at washing pH (≥10.5). The response curve is steep, making it suitable for water-washable ink applications.

[0044] Sample 3-3: The transmittance was 48% at pH=8.0, 68% at pH=10.0, and 95% at pH=11.0. It exhibits strong hydrophobicity and good adhesion within the application pH range, but the improvement in solubility at pH=10.0 is not significant, requiring a higher pH (≥11.0) for rapid dissolution, thus demanding higher cleaning conditions.

[0045] In summary, DMAEMA can achieve pH responsiveness in the range of 3-10 parts, but the addition amount should be controlled at 6-8 parts to ensure both adequate adhesion at the application pH and rapid dissolution under the action of conventional alkaline cleaning agents (pH=10.5-11.0).

[0046] Example 4 Control sample 4-1: 13 parts of hydroxyethyl acrylate, 10 parts of acrylamide, 5 parts of DMAEMA and 2 parts of benzoyl peroxide were mixed and added dropwise to the reaction system after the esterification reaction was completed. Other conditions were the same as in Example 1.

[0047] Example Sample 4-2: Following the steps of Example 1, hydroxyethyl acrylate and acrylamide were added dropwise first, followed by DMAEMA.

[0048] Performance comparison of the two groups of samples: pH response consistency: Five batches of samples were prepared, and their dissolution time in a solution at pH=10.5 was tested. The dissolution time of control sample 4-1 was 6-12 minutes, with large differences between batches; the dissolution time of example sample 4-2 was 7-9 minutes, showing good reproducibility.

[0049] The segmented copolymerization process ensures that acrylate monomers form the basic graft layer first, and then pH-responsive monomers are introduced for functional modification by controlling the order and timing of the addition of different monomers. This avoids the compositional deviation and uneven distribution problems caused by monomer competition in the one-step process, and significantly improves the stability and controllability of product performance.

[0050] Example 5 Four groups of samples were prepared with the same grafting reaction products, only the type and ratio of neutralizing agent were changed: Sample 5-1: neutralized with only AMP-95, 8 parts, without adding KOH; Sample 5-2: neutralized with only KOH, 6 parts, without adding AMP-95; Sample 5-3: 2 parts AMP-95 + 3 parts KOH; Sample 5-4: 6 parts AMP-95 + 8 parts KOH; Sample 5-5 (Example 1): 4 parts AMP-95 + 5 parts KOH.

[0051] After neutralization, the pH of each sample was adjusted to the range of 8.0-8.5, and the stability and film-forming properties of the resin aqueous solution were tested. Sample 5-1: The resin aqueous solution was clear in appearance, but slight stratification occurred after standing at 25℃ for 7 days, indicating moderate stability. The film exhibited good flexibility after formation, but the drying speed was slow, requiring 35 minutes for surface drying at 25℃.

[0052] Sample 5-2: The resin aqueous solution appeared slightly turbid with a small amount of insoluble particles. After filtration, its stability was acceptable; no significant changes were observed after standing at 25℃ for 14 days. The film formed had high hardness but poor flexibility and was prone to cracking during drying. The drying speed was fast, with a surface drying time of 12 minutes.

[0053] Sample 5-3: The resin aqueous solution was clear and transparent, and remained stable after standing at 25°C for 30 days without stratification or precipitation. It exhibited good film-forming properties, with a balance between hardness and flexibility, and a surface drying time of 20 minutes.

[0054] Sample 5-4: The resin aqueous solution is clear and transparent with excellent stability, but the solid content is low (43%), requiring increased water dilution, which is not conducive to transportation and storage. It has excellent film-forming properties, but excessive neutralizing agent will increase costs.

[0055] Sample 5-5: The resin aqueous solution was clear and transparent, stable after standing at 25℃ for more than 30 days, with a solid content of 48%, exhibiting the best overall performance. After film formation, it achieved a hardness of HB grade, showed no cracking after 180-degree bending, and had a surface drying time of 18 minutes.

[0056] Therefore, while the organic neutralizing agent AMP-95 alone provides good film-forming aid properties, its neutralization speed is slow, requiring a long stirring time, and its neutralization effect on tertiary amine groups is limited. While the inorganic neutralizing agent KOH alone offers rapid neutralization, it can easily lead to localized over-neutralization, causing resin aggregation and the formation of insoluble particles, thus affecting stability. Using a combination of AMP-95 and KOH for neutralization, leveraging the rapid neutralization effect of KOH and the buffering and stabilizing effect of AMP-95, achieves uniform and thorough neutralization. Simultaneously, the pH value is precisely adjusted to 8.0-8.5, ensuring the stability of the resin aqueous solution and keeping the pH-responsive groups in an optimal state, thus guaranteeing the ink's performance during application.

[0057] Example 6 Weigh the following components by weight percentage: 30% red pigment paste, 4% propylene glycol, 2.5% sorbitol, 18% (by solids) of pH-responsive washable modified rosin resin prepared in Example 1, 0.2% defoamer, 0.3% leveling agent, and deionized water to 100%.

[0058] In a container equipped with a high-speed disperser, first add 60% deionized water and start stirring at 800 rpm. While stirring, add propylene glycol and sorbitol sequentially, stirring for 10 minutes to fully dissolve the humectant. The humectant prevents the ink from drying and forming a skin during storage and use. Propylene glycol has strong hygroscopic properties and good solubility, while sorbitol is a polyol with long-lasting moisturizing effects and is gentle on the skin. The combination of these two ingredients keeps the ink moist while preventing excessive moisture absorption and smudging.

[0059] A pH-responsive, washable modified rosin resin aqueous solution (48% solids content) was slowly added to the above mixture, and the stirring speed was gradually increased to 1200 rpm. The mixture was dispersed for 30 minutes to ensure that the resin was uniformly dispersed in the aqueous phase. At this pH (approximately 8.2), the resin exhibited a microemulsion state, forming a stable continuous phase with the humectant and water.

[0060] Add the pigment paste while stirring at high speed, increasing the stirring speed to 1500 rpm and dispersing for 40 minutes. The pigment particles in the pigment paste are fully dispersed under mechanical shear force, and resin molecules adsorb onto the surface of the pigment particles, forming a steric hindrance protective layer to prevent pigment aggregation and sedimentation. Reduce the stirring speed to 600 rpm, and add the defoamer and leveling agent sequentially, stirring for 10 minutes. The defoamer (silicone-based) eliminates air bubbles generated during dispersion, preventing ink foaming from affecting writing smoothness; the leveling agent (polyether-modified silicone) reduces the surface tension of the ink, improving its spreadability on paper or whiteboard surfaces, resulting in uniform and continuous writing lines.

[0061] Finally, adjust the ink to the target weight using the remaining deionized water and stir for 15 minutes to mix thoroughly. The pH value of the ink was measured to be 8.3 using a pH meter, within the target range of 8.0-8.5. The ink was then filtered through a 200-mesh filter to remove any undispersed particles and impurities, resulting in a uniform and fine marker ink.

[0062] The resulting ink underwent performance testing: The viscosity was measured at 25℃ using an NDJ-5S rotational viscometer and was 28.6 mPa·s, which is suitable for marker writing. It will not cause ink bleeding due to too low a viscosity, nor will it cause ink flow problems due to too high a viscosity.

[0063] The ink was left to stand at 25°C for 30 days, and no layering, sedimentation, or color difference was observed, demonstrating excellent stability. Ink was filled into the marker and written on regular printer paper and a whiteboard for testing. Writing was smooth, with even lines and rich color. On paper, the ink dried within 5 seconds without rubbing against the hand; on the whiteboard, the ink adhered firmly and was not easily removed by wiping with fingers.

[0064] Write on cotton cloth and let it air dry for 10 minutes to simulate a child's ink staining their clothes. Prepare an alkaline cleaning solution (pH=10.5, 0.5% NaOH aqueous solution), immerse the ink-stained cotton cloth in the solution, and gently rub. The ink stain begins to dissolve and fade within 15 seconds, and is mostly removed after 30 seconds. After rinsing, the cotton cloth is clean and has no obvious residue.

[0065] Example 7 Three groups of inks were prepared, with the same components and processes as in Example 6, except for the amount of resin used: Ink 7-1: Resin content 15%; Ink 7-2: Resin content 17.5%; Ink 7-3: Resin content 20%.

[0066] Performance comparison test results: After writing on the whiteboard, wipe it 10 times with a dry cloth and observe the ink residue. Ink 7-1 faded significantly after 5 wipes, indicating slightly weak adhesion; Ink 7-2 remained clear after 10 wipes, indicating moderate adhesion; Ink 7-3 showed almost no change after 10 wipes, indicating strong adhesion.

[0067] After writing on the cotton cloth and allowing it to dry, treat it with a pH=10.5 cleaning solution. Ink 7-1 was completely removed within 20 seconds, making it the easiest to clean; Ink 7-2 was mostly removed within 30 seconds, showing good cleaning results; Ink 7-3 required 45 seconds and vigorous rubbing to remove, increasing the difficulty of cleaning.

[0068] When the resin content is 15%, the ink has good fluidity and excellent washability, but its writing adhesion and wiping resistance are slightly weaker, making it suitable for occasions such as temporary doodles where durability is not a major concern. When the resin content is 20%, the writing adhesion is strong and the durability is good, but the washability is somewhat reduced, requiring a slightly longer or stronger alkaline cleaning process. When the resin content is 17-18%, an ideal balance can be achieved between writing performance and washability.

[0069] Ink 7-1 has a viscosity of 23.2 mPa·s, good fluidity but may flow too quickly; Ink 7-2 has a viscosity of 28.6 mPa·s, moderate viscosity; Ink 7-3 has a viscosity of 42 mPa·s, high viscosity, may flow slightly slower in fine-tipped markers.

[0070] The surface drying time was measured after writing on the printing paper. Ink 7-1 had a surface drying time of 13 seconds, which was fast but the film was relatively thin; Ink 7-2 had a surface drying time of 18 seconds, which balanced the drying speed and film quality; Ink 7-3 had a surface drying time of 25 seconds, which was slightly slower but the film was dense.

[0071] The three ink groups were placed in a 40℃ oven for 14 days, and the changes in color and performance were observed. Inks 7-1 and 7-2 showed no significant changes and excellent stability; ink 7-3 showed a slight increase in viscosity (from 42 to 45 mPa·s), which may be due to slow cross-linking caused by excessive resin content.

[0072] Example 8 Three groups of inks were prepared. Except for the different ratios of humectants, the other components and processes were the same as in Example 6: Ink 8-1: only 6.5% propylene glycol was used, without the addition of sorbitol; Ink 8-2: 3% propylene glycol and 2% sorbitol were mixed; Ink 8-3: 5% propylene glycol and 3% sorbitol were mixed; Ink 8-4 (Example 6): 4% propylene glycol and 2.5% sorbitol were mixed.

[0073] Each group of inks was coated onto a glass plate to form an ink film approximately 50 μm thick. The films were then placed in an environment of 25°C and 50% relative humidity, and the drying and skinning time was observed. Ink 8-1 began to show edge skinning after 3 hours and was completely dry after 6 hours; Ink 8-2 began to form a skin after 5 hours and was dry after 9 hours; Ink 8-3 remained moist after 12 hours and was completely dry after 24 hours; Ink 8-4 began to form a skin after 7 hours and was dry after 12 hours, exhibiting moderate moisture retention.

[0074] Write on regular printer paper and observe the ink penetration and smudging. Ink 8-1 penetrates less, the lines are clear, but the ink is relatively dry and the color saturation is slightly low; Ink 8-2 penetrates moderately, the lines are clear, and the color is full; Ink 8-3 penetrates significantly, the lines have slight smudging, and the ink is visible on the back of the paper; Ink 8-4 penetrates slightly, the lines are clear, and the color is full.

[0075] Ink was filled into marker pens, the caps were opened to expose the nibs, and the pens were placed in a 25°C environment for different periods of time. The caps were then replaced, and the pens were tested for normal writing performance. Ink 8-1 showed that after 2 hours of exposure, the nib dried out and ink flow was difficult; Ink 8-2 showed normal writing performance after 6 hours of exposure, but ink flow became less smooth after 8 hours; Ink 8-3 showed normal writing performance after 24 hours of exposure, but excessive moisture may cause ink to slowly seep from the nib during storage; Ink 8-4 showed normal writing performance after 8 hours of exposure, but ink flow became less smooth after 12 hours, which meets actual usage requirements.

[0076] While propylene glycol alone is inexpensive, its moisturizing effect is limited and it evaporates quickly. Sorbitol, as a polyol, offers long-lasting moisturizing effects, but excessive use can make the ink too wet, increasing smudging and bleeding problems. A combination of propylene glycol and sorbitol, with a total amount controlled at 5-8%, provides sufficient moisturizing to prevent the pen tip from drying out and the ink from forming a skin, without causing smudging and bleeding due to excessive moisturizing. This combination is suitable for the characteristics of marker inks. Example 9 The red marker ink prepared in Example 6 was used for application tests on a variety of common substrates: Regular printing paper, children's drawing book paper, and watercolor paper.

[0077] Five-year-old children were allowed to draw freely on various types of paper for 30 minutes using markers filled with ink from Example 6. The writing smoothness, color reproduction, and the children's experience were observed. During the drawing process, a real-life scenario was simulated, allowing ink to stain the children's white cotton T-shirts.

[0078] On regular printer paper, the ink writes smoothly, producing even lines and vibrant, rich colors, with a smooth feel when drawing. Due to the thinness of the paper, there is slight bleed-through in some areas, but this does not affect usability. Writing is best done on children's drawing paper, with clear lines, strong color expression, and no bleed-through, allowing children to freely color and outline. On watercolor paper, due to the coarse paper fibers, the ink absorbs slightly, resulting in slightly duller colors, but it is still usable.

[0079] During the drawing process, children accidentally got ink on their hands and clothes. Immediately wiping their hands with a damp paper towel easily removed the ink stains without residue. After allowing the ink on the clothes to air dry for 15 minutes, a washing solution was prepared using household laundry detergent. The T-shirt was soaked for 5 minutes, and the stained area was gently rubbed. The ink dissolved quickly, the aqueous solution turning a pale pink, and the stain was almost completely gone after 30 seconds. After rinsing, the T-shirt returned to its white color, with only a very slight stain (almost invisible to the naked eye) remaining at the original stained area, which is perfectly acceptable. Compared to stains caused by traditional oil-based markers, which are difficult to completely remove even with professional stain removers, the washability of this invention's ink is a significant advantage.

[0080] Standard teaching whiteboard (painted steel plate surface).

[0081] Teachers used markers filled with ink from Example 6 to write teaching content on a whiteboard, including text, formulas, and simple diagrams. After writing, the markers were left in place for 30 minutes, followed by a cleaning test.

[0082] The ink writes smoothly and evenly on the whiteboard surface, producing vibrant and eye-catching colors that are clearly visible even from the back of the classroom. The ink dries quickly, surface-drying in approximately 15 seconds, preventing teachers from smudged their writing. After 30 minutes, the ink adheres firmly and will not be accidentally wiped away when students erase the edges of the whiteboard, meeting the durability requirements for use in teaching.

[0083] Using a regular whiteboard cleaner spray, spray the ink onto the surface, let it sit for 10 seconds, and then wipe it with a whiteboard eraser. Most ink stains will be removed in one wipe, while a few darker areas may require a second spray and wiping. In contrast, wiping with pure water requires 5-8 repeated wipings to remove most of the ink and often leaves light-colored marks. Using a dilute NaOH solution (pH=11.0, 0.1%), the ink begins to dissolve instantly upon contact with the solution, and a single wipe is sufficient to completely remove it, leaving the whiteboard surface clean and like new.

[0084] Home walls (latex paint coating), tile surfaces, glass doors and windows.

[0085] Marker writing was performed on various substrate surfaces, including lines and large areas of color. After 24 hours of natural drying, a simulated long-term adhesion scenario was implemented, followed by a cleaning test.

[0086] On a latex-painted wall, ink writes smoothly and the color is vibrant. Due to the wall's microporous structure, the ink slightly seeps in. After 24 hours of drying, spraying with an alkaline cleaner (pH=10.5) and gently brushing with a soft brush for 2 minutes removes most of the ink stains, leaving very faint traces that do not affect the overall appearance. If a strong alkaline cleaner (pH=11.5) is used, brushing for 1 minute will completely remove the ink, restoring the wall to its original condition.

[0087] On tile surfaces, the ink adheres firmly and does not rub off with a finger after drying. It can be completely removed with a single spray of alkaline cleaner and a wipe with a damp cloth, providing excellent cleaning results. The cleaning effect on glass surfaces is similar to that on tiles; the ink dissolves quickly under alkaline conditions and is easily removed.

[0088] Comparative Test: Using traditional alcohol-based markers to draw on the same substrate requires repeated scrubbing with a special cleaning solvent (containing organic solvents) after drying to remove the ink. This cleaning process also produces an irritating odor and is unfriendly to humans and the environment. The ink of this invention can be removed with just ordinary alkaline detergent and water, making it safe and environmentally friendly, especially suitable for temporary doodles in homes with children.

[0089] Example 10 The ink prepared in Example 6 was dispensed into sealed bottles and stored under the following conditions: Store at 25℃ (simulating normal storage environment); store at 40℃ (simulating high-temperature transportation or summer storage); store at -5℃ (simulating winter storage).

[0090] Sampling and testing of viscosity, pH value, color, particle size distribution, and other indicators are conducted regularly (0 days, 7 days, 30 days, 90 days, 180 days).

[0091] Test results: After 180 days of storage at 25℃, the ink showed no change in appearance, maintaining a uniform and fine red liquid state. The viscosity increased slightly from the initial 28.6 mPa·s to 30.2 mPa·s, a change of <10%, which is within the normal fluctuation range. The pH value remained stable between 8.2 and 8.4, with no significant drift. Color measurement (using a colorimeter) showed ΔE <1.5, indicating extremely small color difference, imperceptible to the naked eye. The particle size distribution D90 increased from 4.2 μm to 4.8 μm, while maintaining good dispersion with no significant aggregation or sedimentation.

[0092] After 90 days of accelerated aging storage at 40℃, the ink viscosity increased to 33.5 mPa·s, still within an acceptable range. The pH value remained stable, and the color deepened slightly (ΔE=2.3), but remained within the normal range. The particle size distribution D90 increased to 5.5 μm, close to the upper limit but not exceeding it. Writing tests showed no significant decline in performance, and washability remained good.

[0093] After being stored at -5℃ for 7 days, the ink showed slight thickening, but the viscosity returned to normal upon returning to 25℃, with no irreversible changes. After three freeze-thaw cycles, the ink performance remained stable, with no stratification or sedimentation, demonstrating good cold resistance.

[0094] In summary, this invention provides a washable modified rosin resin, its preparation method, and a washable marker ink. The washable modified rosin resin, by weight, comprises: 40-60 parts natural rosin, 15-30 parts maleic anhydride, 5-15 parts polyol, 15-38 parts acrylate monomer, and 3-10 parts pH-responsive monomer; wherein the pH-responsive monomer is dimethylaminoethyl methacrylate. The raw materials for this invention are widely available, and the cost is controllable. Natural rosin resin is abundant and inexpensive; other monomers and additives are conventional chemical raw materials, easily procured. The preparation process is mature and reliable, with low equipment requirements, suitable for large-scale industrial production. By introducing the pH-responsive monomer DMAEMA into the rosin resin modification system, the resin is endowed with environmentally responsive properties. The tertiary amine groups in the resin molecules undergo protonation / deprotonation transitions according to changes in environmental pH. In neutral or weakly alkaline environments (pH 7-9), they maintain moderate hydrophobicity, allowing the ink to adhere firmly to various substrate surfaces during use. In strongly alkaline environments (pH ≥ 10.5), their hydrophilicity significantly increases, causing the ink film to dissolve and disperse rapidly, achieving quick and thorough water washing. This intelligent response mechanism fundamentally solves the contradiction between writing performance and washability in traditional washable marker inks. The resin is neutralized using a compound of organic neutralizer AMP-95 and inorganic neutralizer KOH. The synergistic effect of these two agents achieves uniform and thorough neutralization, while precisely adjusting the pH of the resin aqueous solution to 8.0-8.5. This ensures the storage stability of the resin aqueous solution, preventing excessive protonation and aggregation, while also keeping the tertiary amine groups in an optimal responsive state, ensuring moderate adhesion at the application pH and rapid dissolution at the washing pH, thus optimizing responsiveness.

[0095] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A water-washable modified rosin resin, characterized in that, By weight, it includes: 40-60 parts natural rosin, 15-30 parts maleic anhydride, 5-15 parts polyol, and 15-38 parts acrylate monomers; 3-10 parts of pH-responsive monomer; wherein the pH-responsive monomer is dimethylaminoethyl methacrylate.

2. The water-washable modified rosin resin according to claim 1, characterized in that, The acrylate monomers include 10-20 parts of hydroxyethyl acrylate and 5-18 parts of acryloylmorpholine.

3. The water-washable modified rosin resin according to claim 1, characterized in that, It also includes 0.5-3 parts of acid catalyst, 1-3 parts of initiator, 2-6 parts of organic neutralizer, 3-8 parts of inorganic neutralizer, and deionized water.

4. The water-washable modified rosin resin according to claim 3, characterized in that, The organic neutralizing agent is AMP-95, the inorganic neutralizing agent is KOH, and the pH value of the water-washable modified rosin resin aqueous solution is 8.0-8.

5.

5. A method for preparing a water-washable modified rosin resin as described in any one of claims 1 to 4, characterized in that, Includes the following steps: Natural rosin resin is mixed and melted with a solvent, and then maleic anhydride and a catalyst are added to carry out an addition reaction to obtain a reaction mixture. The reaction mixture was cooled, and a polyol was added to carry out an esterification reaction. The acid value was controlled to 130-140 mg KOH / g to obtain the esterified product. Grafting is performed by first adding a portion of acrylate monomers and an initiator to the esterified compound, followed by adding the pH-responsive monomer and the remaining initiator. To achieve a good film-forming and washable effect, the acid value of the resin generally needs to reach 120 mg kOH / g. Good washability is achieved only after neutralization into a salt. After the resin film is formed, it can be dissolved in water at room temperature without the need for alkaline water washing. After cooling, water is added for dilution, and a neutralizing agent is added to adjust the pH value to obtain the water-washable modified rosin resin.

6. The preparation method according to claim 5, characterized in that, Grafting is performed by first adding a portion of the acrylate monomer and initiator to the esterified compound, followed by adding the pH-responsive monomer and the remaining initiator. Specifically, this includes: A mixture of hydroxyethyl acrylate, acrylmorpholine, and benzoyl peroxide was added dropwise at a temperature of 180-185℃. Continue adding the mixture of dimethylaminoethyl methacrylate and benzoyl peroxide dropwise.

7. The preparation method according to claim 5, characterized in that, The solid content of the water-washable modified rosin resin is 45-50%.

8. A washable marker ink, characterized in that, Its components, by weight percentage, include: Pigment paste 25-35%; Moisturizer 5-8%; 15-20% of the water-washable modified rosin resin according to any one of claims 1-4; Additives: 0.5-2%; The remainder is deionized water.

9. The washable marker ink according to claim 8, characterized in that, The humectant is a mixture of propylene glycol and sorbitol; the water-washable marker ink has a pH of 8.0-8.

5.

10. The washable marker ink according to claim 8, characterized in that, The additives include: preservatives and brighteners.

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