Resin for paper coating and preparation method thereof, water-based coating agent and application

Abstract

The invention belongs to the field of coating agents, and provides a resin for paper coating, a preparation method of the resin, a water-based coating agent and application of the water-based coating agent. The resin is prepared from the following raw materials in parts by weight: 40 to 60 parts of vegetable oil, 40 to 60 parts of alcohol, 90 to 110 parts of rosin, 15 to 35 parts of acidic substances, 10 to 20 parts of hydroxymethyl resin, 60 to 80 parts of alkali and 300 to 500 parts of distilled water. The preparation method of the resin comprises the following steps: (1) reacting vegetable oil with alcohol to obtain an alcoholysis substance; (2) mixing rosin, an acidic substance and hydroxymethyl resin for reaction to obtain an adduct; then adding the alcoholysis substance into the adduct for reaction to obtain alkyd resin; and (3) adding alkali and distilled water into the alkyd resin for neutralization to obtain the coating agent resin. Compared with the prior art, the prepared coating agent resin is good in stability and has excellent waterproof and oil-proof performance, and the whole resin preparation process is easy to operate, green, environmentally friendly, non-toxic and harmless.

Description

Technical Field

[0001] This invention belongs to the field of coating resins, specifically relating to a resin for paper coating, its preparation method, an aqueous coating agent, and its application. Background Technology

[0002] With increasing environmental awareness, water-based coatings are gradually becoming an ideal alternative to traditional solvent-based coatings due to their low volatile organic compound (VOC) content, non-toxicity, and ease of use. However, existing water-based coatings still have some problems in practical applications, such as unstable coating performance, poor water resistance, insufficient oil resistance, and inadequate adhesion. These problems limit their widespread application in certain fields. Therefore, developing a high-performance and environmentally friendly water-based coating is of great significance.

[0003] Rosin is an abundant renewable resource and an important chemical raw material, widely used in coating, ink, and paint industries. Rosin contains carboxyl groups and double bonds, allowing for modification reactions such as esterification and addition. Furthermore, the two active centers in rosin can introduce the rosin skeleton into other materials, imparting physical and chemical properties such as waterproofing. The rigid phenanthrene ring structure in rosin significantly affects the tackifying and film-forming properties of resins. Hydroxymethyl resin, due to its numerous hydroxyl groups and good tackifying and compatibility, synergizes with carboxyl-containing rosin on the paper surface, forming a good interaction with the voids in the paper fibers, thus creating a good oil film and providing excellent waterproofing. Simultaneously, due to its highly reactive hydroxymethyl structure, it can react with various chemical substances to form extended and complex spatial configurations. These complex structures possess extremely strong intramolecular forces and high stability, significantly increasing the resin's oil resistance. However, since both rosin and carboxyl groups are relatively brittle, flexible substances, such as vegetable oils, need to be added. Vegetable oils are a renewable resource, widely available, environmentally friendly, and inexpensive. Their low functionality not only reduces the average functionality of a system and the likelihood of gelation, but also increases the flexibility of resin molecules, thus balancing resin performance. Furthermore, the addition of alkyd resins increases molecular linear density and cohesive force, also contributing to good oil-resistant properties.

[0004] Chinese invention patent application CN 1956851A discloses a coating agent for protecting recording layers, comprising carboxyl-modified polyvinyl alcohol (A), polyamide polyamine epihalool (B), and polyethylene imide (C). The degree of saponification of the carboxyl-modified polyvinyl alcohol (A) is 90–99.5% (molar fraction). Applying this composition to a recording medium using a specific method imparts excellent water resistance to the recording medium. The inventors speculate that this effect may be due to the ionic interactions and covalent bonds formed between the carboxyl-modified polyvinyl alcohol (A), polyamide polyamine epihalool (B), and polyethylene imide (C).

[0005] Another Chinese invention patent application, CN 101638540A, discloses a polyvinyl alcohol (PVA) coating liquid and its production process. The mass percentages of the components in the PVA coating liquid described in this invention are as follows: PVA 6%-20%, tackifier 0.5%-5%, crosslinking agent 0.5%-10%, synthetic inorganic material 0.01%-1%, catalyst 0.1%-3%, plasticizer 1%-15%, and water 56%-91.39%. The production process of the PVA coating liquid described in this invention is as follows: the synthetic inorganic material, catalyst, plasticizer, and water are mixed evenly in a predetermined ratio. Then, PVA is added and mixed evenly. After swelling, the mixture is heated to 90-95°C and stirred for at least 2 hours until the PVA is completely dissolved. Then, the crosslinking agent and tackifier are added and mixed evenly, stirred for at least half an hour, and then the solution is filtered through a 100-200 mesh sieve to obtain the PVA coating liquid. This invention describes the above-mentioned polyvinyl alcohol coating liquid and its production process, which can effectively solve the problems of poor barrier properties, low adhesion strength to the substrate, and relatively complex production process of existing polyvinyl alcohol coating liquids.

[0006] Another Chinese invention patent application, CN 119866366 A, discloses a dispersant and an aqueous coating composition. The dispersant comprises a styrene-maleic acid organoammonium salt copolymer (A) and an epoxide alkane adduct (B) selected from alcohols, carboxylic acids, amines, and amides, consisting of at least one active hydrogen compound (carbon number 4-18) and comprising an epoxide alkane (carbon number 2-4, molar addition number 3-50). The active hydrogen compound has a branched alkyl chain with carbon numbers 4-18. The molar ratio (s:m) of the styrene unit (s) to the maleic acid ammonium salt unit (m) constituting the styrene-maleic acid ammonium salt copolymer is preferably 80:20-40:60, and the weight ratio (A:B) of the styrene-maleic acid ammonium salt copolymer (A) to the polyoxyethylene compound (B) is preferably 10:90-90:10. According to the description of the invention, the dispersant provided can exhibit excellent dispersibility, and even when added to a water-based coating agent, the water resistance of the resulting coating film will not be reduced.

[0007] With the advent of the low-carbon era, many sectors are practicing low-carbon and environmentally friendly practices, including the packaging materials industry. Green packaging materials have become a clear future development trend in the packaging industry, with the development trend of paper materials being the most eye-catching. Currently, China's packaging industry, especially the flexible packaging industry, is entering a period of rapid development, and the packaging of products such as food, pharmaceuticals, and cigarettes is also developing towards convenience, safety, environmental protection, and low cost. However, plain paper packaging materials have shortcomings in terms of oil and water resistance, which to some extent limits their application. Therefore, it is necessary to develop a resin for paper coating that can meet the requirements for paper's water and oil resistance, which is of positive significance for promoting the green and sustainable development of the packaging industry, especially the paper packaging industry. Summary of the Invention

[0008] This invention addresses the problems existing in the prior art by providing a resin for paper coating, its preparation method, and its application. Compared with the prior art, the coating resin prepared by this invention has good stability, excellent waterproof and oil-proof properties, is easy to operate, and the entire resin preparation process is green, environmentally friendly, non-toxic, and harmless.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A resin for paper coating, wherein the raw materials of the resin, by weight, include 40-60 parts vegetable oil, 40-60 parts alcohol, 90-110 parts rosin, 15-35 parts acidic substances, 10-20 parts hydroxymethyl resin, 60-80 parts alkali, and 300-500 parts distilled water.

[0010] Preferably, the vegetable oil is at least one of non-drying vegetable oil, semi-drying vegetable oil, and drying vegetable oil; Preferably, the non-drying vegetable oil is at least one of castor oil, coconut oil, and peanut oil; Preferably, the semi-drying vegetable oil is at least one of soybean oil, cottonseed oil, and sunflower seed oil; Preferably, the drying vegetable oil is at least one of tung oil, linseed oil, and hemp oil.

[0011] More preferably, the non-drying vegetable oil is at least one of castor oil and peanut oil; the semi-drying vegetable oil is at least one of soybean oil and sunflower seed oil; and the drying vegetable oil is at least one of tung oil and linseed oil.

[0012] Preferably, the alcohol is at least one selected from diols, triols, and tetraols; the diol is at least one selected from ethylene glycol, diethylene glycol, and triethylene glycol; the triol is at least one selected from glycerol and trimethylolpropane; and the tetraol is pentaerythritol.

[0013] More preferably, the diol is at least one of diethylene glycol and triethylene glycol; the triol is at least one of glycerol and trimethylolpropane; and the tetraol is pentaerythritol.

[0014] Preferably, the rosin is at least one of resin rosin, wood rosin, and oil rosin; the resin rosin is at least one of Masson rosin, wetland rosin, and Simao rosin.

[0015] More preferably, the rosin is at least one of resin rosin and oil rosin.

[0016] More preferably, the rosin is at least one of Masson rosin and Simao rosin.

[0017] Preferably, the acidic substance is at least one of a saturated acid and an unsaturated acid; the acidic substance is at least one of a monobasic acid and a dibasic acid.

[0018] Preferably, the saturated acid is at least one selected from benzoic acid, terephthalic acid, phthalic acid, phthalic anhydride, isophthalic acid, hexahydrophthalic anhydride, succinic acid, adipic acid, octanoic acid, and sebacic acid; and the unsaturated acid is at least one selected from fumaric acid, maleic acid, maleic anhydride, acrylic acid, itaconic acid, citraconic acid, tetrahydrophthalic acid, and nadic anhydride.

[0019] Preferably, the saturated acid is at least one of benzoic acid, phthalic anhydride, succinic acid, and adipic acid; and the unsaturated acid is at least one of fumaric acid and maleic anhydride.

[0020] Preferably, the hydroxymethyl resin is at least one commercially available resin; Preferably, the commercially available hydroxymethyl resin is at least one of HY-2045 and HY-2055; A second objective of this invention is to provide a method for preparing the resin for paper coating, comprising the following steps: (1) Reaction of vegetable oil with alcohol yields alcoholysis products; (2) The rosin, acidic substance, and hydroxymethyl resin are mixed and reacted to obtain an adduct; (3) Add the alcoholysis product to the adduct to react and obtain alkyd resin; (4) Add alkali and distilled water to alkyd resin to carry out neutralization reaction, and the coating agent resin is obtained.

[0021] Preferably, the reaction in step (1) requires the addition of a catalyst, the amount of which is 5-10‰ of the mass of the vegetable oil; the catalyst is at least one of an inorganic base or an inorganic salt.

[0022] Preferably, the inorganic base or inorganic salt is at least one of LiOH, KOH, Ca(OH)2, Mg(OH)2, and LiAc.

[0023] More preferably, the inorganic base or inorganic salt catalyst is at least one of LiOH, KOH, and LiAc.

[0024] More preferably, the inorganic base or inorganic salt catalyst is at least one of LiOH and LiAc.

[0025] Preferably, the reaction in step (1) requires heating, and the heating temperature is 240-260°C.

[0026] More preferably, the heating temperature is 245–255°C.

[0027] Preferably, the reaction in step (1) requires heating and heat preservation for 2 to 5 hours.

[0028] More preferably, the heat preservation time is 3 to 4 hours.

[0029] Preferably, the amount of hydroxymethyl resin used in step (2) is 13.8% to 18.5% of the rosin mass.

[0030] Preferably, the reaction in step (2) requires heating, and the heating temperature is 220-230°C.

[0031] Preferably, the reaction in step (2) requires heat preservation for 2 to 3 hours.

[0032] Preferably, the reaction in step (3) requires the addition of a catalyst, and the amount of the catalyst is 3 to 10‰ of the rosin mass.

[0033] Preferably, the catalyst for the reaction in step (3) is a phosphorus-containing esterification catalyst.

[0034] Preferably, the phosphorus-containing catalyst in step (3) is at least one of hypophosphite, calcium hypophosphite, potassium di-tert-butyl phosphate (DBPP), sodium ibandronate (SDID), and IRGANOX™ 1425.

[0035] More preferably, the catalyst in step (3) is hypophosphorous acid, potassium di-tert-butyl phosphate (DBPP), or IRGANOX. TM At least one of 1425, wherein the amount of the catalyst is 3-5‰ of the rosin mass.

[0036] Preferably, the reaction in step (3) requires heating and heat preservation. The heating temperature is 250-270°C, and the heat preservation time is 5-10 hours.

[0037] More preferably, the heating temperature is 255–265°C; and the heat preservation time after heating is 6–8 hours.

[0038] Preferably, the alkali mentioned in step (4) is at least one of triethylamine, ethanolamine, diethanolamine, triethanolamine, diphenylamine, triphenylamine, ammonia, sodium hydroxide, and potassium hydroxide; Preferably, the alkali in step (4) is at least one of triethylamine, ethanolamine, and ammonia.

[0039] Preferably, the reaction in step (4) requires heating and heat preservation. The heating temperature is 55-75°C, and the heat preservation time is 2-5 hours.

[0040] More preferably, the heating temperature is 65-70°C; and the heat preservation time after heating is 3-4 hours.

[0041] A third objective of this invention is to provide an aqueous coating agent whose raw materials include the aforementioned resin for paper coating.

[0042] Another object of the present invention is to provide the application of the resin described herein or the resin prepared by the described preparation method in the preparation of paper coating.

[0043] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention provides a resin for paper coating, wherein the raw material rosin used in the resin has a rigid phenanthrene ring structure in its molecule, which can increase the tackification and film-forming properties of the resin on the paper surface.

[0044] (2) The resin used for paper coating also contains hydroxymethyl resin. Because hydroxymethyl resin contains more hydroxyl groups and has good tackification and compatibility, it works synergistically with carboxyl-containing rosin on the paper surface and can form a good interaction with the voids on the paper fiber surface, thereby forming a good oil film on the paper surface and achieving a good waterproof effect. At the same time, due to its highly active hydroxymethyl groups, it can react with the raw materials to form an extended spatial configuration with a complex structure. This complex structure has a strong intramolecular force and a strong stability, which greatly increases the oil-resistant performance of the resin.

[0045] (3) The resin used for paper coating also contains a flexible vegetable oil. As a renewable resource, vegetable oil is widely available, environmentally friendly, and inexpensive. Vegetable oil has low functionality, which can not only reduce the average functionality of the system and reduce the possibility of gelation, but also increase the flexibility of the resin molecules by adding vegetable oil. This balances the brittleness and rigidity of rosin and its adducts obtained by reacting with acidic substances and hydroxymethyl resin, effectively improving the performance of the resin.

[0046] (4) The resin used for paper coating also contains alkyd resin. The addition of alkyd resin not only effectively increases the cohesive force of the resin, but also increases the linear density of the molecules, thus achieving a good oil-resistant effect.

[0047] (5) Compared with the prior art, the present invention has expanded the scope of application of rosin and vegetable oil in the field of paper coating resin. The prepared coating resin has good stability, excellent waterproof and oil-proof properties, and the entire resin preparation process is easy to operate, green and environmentally friendly, non-toxic and harmless. Detailed Implementation

[0048] It is worth noting that the raw materials used in this invention are all commercially available products, and their sources are not specifically limited.

[0049] Examples and Comparative Examples The examples and comparative examples are formed by taking different values ​​of each parameter based on the preparation method. The parameters A, B, C, D, E, F, G, H, I, T1, T2, T3, T4, t1, t2, t3, and t4 are shown in Table 1. Table 2 shows the specific types, amounts, and process parameters of the raw materials used to prepare the resin for paper coating.

[0050] Examples 1-7 provide resins for paper coating, the preparation methods of which are as follows: (1) A vegetable oil of mass A, an alcohol of mass B, and catalyst 1 of mass C were heated to react at a heating temperature of T1 and a reaction time of t1 to obtain the alcoholysis product. (2) Take D rosin, E acidic substance, and F hydroxymethyl resin, heat them to react at T2 for t2 to obtain an adduct, then add the alcoholysis product from step (1) and catalyst 2 with G mass, heat them to react at T3 for t3 to obtain an alkyd resin. (3) Add alkali of mass H and distilled water of mass I to the alkyd resin obtained in step (2) for neutralization reaction. The reaction temperature is T4 and the reaction time is t4 to obtain the resin for paper coating.

[0051] Comparative Example 1 The difference between this comparative example and Example 1 is that the amount of vegetable oil used in step (1) is reduced by 1 / 3.

[0052] Comparative Example 2 The difference between this comparative example and Example 1 is that the amount of alcohol used in step (1) is reduced by 1 / 3.

[0053] Comparative Example 3 The difference between this comparative example and Example 1 is that the amount of rosin used in step (2) is reduced by 1 / 3.

[0054] Comparative Example 4 The difference between this comparative example and Example 1 is that the amount of acidic substance used in step (2) is reduced by 1 / 3.

[0055] Comparative Example 5 The difference between this comparative example and Example 1 is that the amount of hydroxymethyl resin used in step (2) is reduced by 1 / 3.

[0056] Comparative Example 6 The difference between this comparative example and Example 1 is that the amount of hydroxymethyl resin used in step (2) is reduced by 1 / 2.

[0057] Comparative Example 7 The difference between this comparative example and Example 1 is that the amount of hydroxymethyl resin used in step (2) is reduced by 2 / 3.

[0058] Comparative Example 8 The difference between this comparative example and Example 1 is that the hydroxymethyl resin described in step (2) is completely removed.

[0059] Table 1

[0060] Table 2

[0061] Test case Specifically, the structural characterization and determination methods of related indicators of the resins prepared for paper coating in Examples 1-7 and Comparative Examples 1-8 are as follows: Ultraviolet: The UV-2550 double-beam ultraviolet-visible spectrophotometer (Shimadzu, Japan) was used to analyze the samples. The scanning range was 200nm-380nm and the scanning accuracy was 1nm. The samples were dissolved in ethyl acetate or ethanol. Infrared: Measurements were performed using an FTIR-8400S Fourier Transform Infrared Spectrometer (Shimadzu, Japan). Samples were analyzed using the KBr pellet or liquid mold method. The wavenumber range was 4000-500 cm⁻¹. -1 ; Appearance: The appearance of the resin was determined according to GB 1721-79 "Determination of Appearance and Transparency of Varnishes, Oils and Diluents". The physical properties such as the state and transparency of the sample were observed. The test results are shown in Table 3. Color: Refer to GB / T 1722-1992 "Method for Determination of Color of Varnishes, Oils and Thinners". In this invention, unless otherwise specified, all measured colors are solid color codes. The test results are shown in Table 3. Acid value: According to GB 6743-86 "Determination of Acid Value of Paints and Varnishes". Weigh the sample into an Erlenmeyer flask, accurate to 1 mg, and add 25 ml of mixed solvent (95% ethanol and toluene mixed reagent in a volume ratio of 1:2) to completely dissolve the sample. Add 2-4 drops of phenolphthalein indicator solution to the sample solution, and immediately titrate with 0.1 mol / L KOH ethanol standard solution to the endpoint (the solution turns pink and does not fade within 30 seconds). Record the volume of KOH ethanol standard solution consumed at the titration endpoint. Perform a blank test using an equal volume of mixed solvent, and record the volume of KOH ethanol standard solution consumed. Calculate the results according to the relevant formula. The test results are shown in Table 3. Hydroxyl value: According to GB / T 7383-2020 "Determination of hydroxyl value of nonionic surfactants", the test results are shown in Table 3; Viscosity: The test method refers to GB / T 2794-95 "Determination of viscosity of adhesives", and the test results are shown in Table 3. Solid content: The determination method refers to GB / T 1725-79 "Determination of Solid Content in Coatings". Weigh 1-2 grams of resin sample using the subtraction method and place it on a dry, clean, and pre-weighed petri dish. Then, place it in a drying oven at 160℃ for a certain period of time, remove it, cool it to room temperature in a desiccator, weigh it, and then place it back in the oven for 30 minutes. Remove it, cool it to room temperature in a desiccator, and weigh it again. Continue this process until the weight difference between two weighings is no greater than 0.01 grams. Perform parallel determinations on two samples, take the average value, and calculate the results using relevant formulas. The test results are shown in Table 3. pH value: Determination of the acidity and alkalinity of the solution: Place a small piece of test paper on a watch glass or glass slide, use a clean and dry glass rod to dip the test liquid into the middle of the test paper, observe the color after the change stabilizes, compare it with the standard color chart, record the relevant data, and the test results are shown in Table 3.

[0062] Water Absorption: Referring to GB / T 1540-2002 "Determination of Water Absorption of Paper and Paperboard (Cobb Method)", cut the treated sample into 10 circular samples (5 on each side) with a diameter of (125±5) mm. Measure 100 mL of water into the cylinder using a graduated cylinder. Then place the weighed sample on the annular surface of the cylinder with the test surface facing down. Cover the sample with the cap and clamp it to fix it to the cylinder. Set the test time, rotate the cylinder 180°, and start the stopwatch. 10 to 15 seconds before the water absorption ends, turn the cylinder right side up, loosen the cap clamping device, remove the sample, and place it with the absorbent surface facing down on the pre-laid absorbent paper. Place another absorbent paper on top of the sample, and immediately use a metal roller to roll it back and forth once within 4 seconds without applying any other pressure to absorb the remaining water on the sample surface. Quickly remove the sample, fold it in half with the absorbent side facing inwards, then fold it in half again and weigh it, accurate to 0.001g. Calculate the average value of the finite element of 5 samples from each side separately, and use this as the test result for the front and back sides of the sample; if the front and back sides are not distinguished, calculate the average value of the finite element of both sides. The test results are shown in Table 3. Oil resistance: The oil resistance of the surface of the article was evaluated according to the Test Method TAPPIT 559cm-02 of the Pulp and Paper Industry Technical Association (TAPPI). The kit value ranged from 1 to 12, with higher values ​​indicating better oil resistance. The test results are shown in Table 3.

[0063] To confirm the prepared resin, ultraviolet-visible spectroscopy (UV-vis) was used to characterize this type of resin. Due to the structural similarity, the resin product of Example 1, as well as the alcoholysis resin, hydroxymethyl resin and esterified alkyd resin after linseed oil alcoholysis, were selected for testing and analysis. The test results are shown below. 1) UV-vis (A, nm) of alcoholysis resin: 270.83, 281.65.

[0064] 2) Hydroxymethyl resin HY-2045 UV-vis (A, nm): 281.44, 285.45.

[0065] 3) Alkyd resin UV-vis (A, nm): 252.81, 280.42.

[0066] 4) UV-vis (A, nm) of coating agent resin: 203.08, 203.99.

[0067] The data above shows that after the addition resin of the hydroxymethyl resin reaction reacts with the linseed oil alcoholysis resin, the characteristic absorption peaks at 285.45 nm and 281.44 nm attributed to hydroxymethyl resin, and the characteristic absorption peaks at 281.65 nm and 270.83 nm attributed to the alcoholysis resin of linseed oil, exhibit a significant blue shift. The resulting esterified alkyd resin generates new characteristic absorption peaks at 280.42 nm and 252.81 nm, indicating that the strongly electron-withdrawing carboxyl groups of the acid and the phenolic hydroxyl groups on the hydroxymethyl resin have a color-reducing effect. Furthermore, the water-based coating resin product obtained after the esterified alkyd resin is neutralized by alkali shows that due to the generation of anions and cations and the strong interaction between the ions, the characteristic absorption peaks of the above-mentioned esterified product are further blue-shifted to 203.99 nm and 203.08 nm. In summary, after alcoholysis, linseed oil was esterified with adducts of rosin, hydroxymethyl resin, and acidic substances, followed by neutralization with alkalis such as ammonia, thus successfully synthesizing a class of water-based coating resins for paper.

[0068] To further confirm the prepared resins, Fourier transform infrared spectroscopy (FTIR) was used to characterize these resins. The test results for alcoholysis resins, hydroxymethyl resins, esterified alkyd resins, and coating resin products are shown below.

[0069] 1) Alcohololysis resin FTIR (KBr disc, cm) -1 ): 3384.96, 3010.21, 2929.35, 2855.4, 2074.5, 1736.23, 1647.37, 1460.32, 1243.1, 1182.33, 1116.08, 1044.06, 925.75, 863.92; 717.14.

[0070] 2) Hydroxymethyl resin HY-2045 FTIR (KBr disc, cm) -1): 3369.8, 3049.82, 2960.25, 2904.56, 2867.99, 1654.31, 1609.67, 1487.54, 1462.93, 1393.05, 1363.09, 1297.68, 1212.25, 1122.20, 1072.43, 942.16, 922.43, 1044.06, 925.75, 878.7, 820.93, 730.36, 694.04, 665.53, 549.12. 3) Alkyd resin FTIR (KBr disc, cm) -1 ): 3419.09, 2928.88, 2869.44, 1842.6, 1778.71, 1728.09, 1602.87, 1460.5, 1386.76, 1244.5, 1177.65, 1050.14, 947.13, 924.09, 880.49, 853.35, 818.82, 781.81, 714.12, 675.11, 565.23. 4) Coating agent resin FTIR (KBr disc, cm) -1 ): 3436.35, 2070.94, 1636.07, 1548.3, 1444.82, 1398.6, 1110.75, 1042.63, 993.97, 523.32.

[0071] The data above show that after the addition resin reacted with hydroxymethyl resin and then reacted with linseed oil alcoholysis resin, the characteristic peaks changed significantly, some of the characteristic peaks disappeared, and some new characteristic peaks were generated. Among them, the alcoholysis resin is attributed to 1736.23 cm⁻¹. -1 The characteristic blue peak shifted to 1728.09 cm. -1 This peak represents the newly formed ester group from the reaction of rosin carboxyl groups with alcohol, while other reactants retain some characteristic absorption peaks, such as 947.13 and 924.09 cm⁻¹ for hydroxymethyl resin. -1 The characteristic absorption peak for rosin is located at 1460.5 cm⁻¹. -1 and 1386.76cm -1 The characteristic absorption peak of the phenanthrene ring structure is located at 1050.14 cm⁻¹, and adipic acid is located at this peak. -1 The characteristic absorption peak is located at 714.12 cm⁻¹, and benzoic acid is located at 714.12 cm⁻¹. -1 The characteristic absorption peak and the adduct are located at 1778.71 cm⁻¹. -1 The characteristic absorption peak of the alkyd resin was observed at 3419.09 cm⁻¹. Furthermore, the aqueous coating agent resin product obtained after further neutralization of the esterified alkyd resin with alkali showed a peak at 3419.09 cm⁻¹. -1The characteristic absorption peak of the hydroxyl group shifted to 3436.35 cm⁻¹. -1 Furthermore, the characteristic peaks become smoother and broader because the anions and cations generated by neutralization form stronger and more stable molecular hydrogen bonds with the hydroxyl groups in water. Additionally, after neutralization, some characteristic peaks disappear, while new peaks are generated at 2070.94 cm⁻¹. -1 and 1636.07cm -1 The characteristic absorption peaks at the specified locations are observed. In summary, after alcoholysis, linseed oil was esterified with adducts of rosin, hydroxymethyl resin, and acidic substances, followed by neutralization with alkalis such as ammonia, thus successfully synthesizing a class of water-based coating resins for paper.

[0072] Since the structure and characterization of the resins in other embodiments and comparative examples are similar to those in the product of Example 1 above, they will not be described in detail here.

[0073] In addition, the aqueous coating agent resin prepared in the embodiments and comparative examples of the present invention was coated according to the method of GB / T 10335.6-2023 "Coated Paper and Paperboard Part 6: Aqueous Coated Paper": Take a test paper, fold it on all four sides, and glue the four corners firmly to make a sample box with a bottom length and width of 50 mm and a height of 50 mm on all four sides. Then place it on a dry glass plate or flat plate lined with filter paper, pour the aqueous coating agent into the sample box, add liquid to about 20 mm from the top edge, let it stand for 10 minutes, and ensure that no liquid seeps out, then the coating is successful, and test its performance indicators. The relevant test results are shown in Table 3.

[0074] Table 3

[0075] As shown in Table 3, the water-based coating resin prepared according to the examples exhibits excellent performance, with a water absorption rate of only 1.7~2.5 (g / m³). 2 Its oil resistance reaches level 10-11 (kit value), and when coated on paper, it has excellent waterproof and oil-proof effects, fully meeting the relevant requirements for paper applications.

[0076] The coating resin prepared in Comparative Example 1, due to a reduction of 1 / 3 in the amount of vegetable oil, showed increased water absorption, with its water absorption decreasing from 1.7 (g / m³). 2 The concentration increased to 4.3 (g / m³). 2 The water absorption increased by 153%, but at the same time, its oil resistance deteriorated, dropping from grade 11 (kit value) to grade 8 (kit value), a decrease of 3 grades.

[0077] The coating resin prepared in Comparative Example 2, due to a reduction of 1 / 3 in the amount of reactive alcohol, showed increased water absorption, with its water absorption decreasing from 1.7 (g / m³).2 The concentration of g / m³ increased to 5. 2 The water absorption increased by 194%, but at the same time, its oil resistance deteriorated, dropping from grade 11 (kit value) to grade 7 (kit value), a decrease of 4 grades.

[0078] The coating resin prepared in Comparative Example 3, due to a reduction of 1 / 3 in the amount of rosin, showed increased water absorption, with its water absorption decreasing from 1.7 (g / m³). 2 The concentration increased to 5.8 (g / m³). 2 The water absorption increased by 241%, but at the same time, its oil resistance deteriorated, dropping from grade 11 (kit value) to grade 8 (kit value), a decrease of 3 grades.

[0079] The coating resin prepared in Comparative Example 4, due to a reduction of 1 / 3 in the amount of acidic substance, showed increased water absorption, with its water absorption decreasing from 1.7 (g / m³). 2 The concentration increased to 4.6 (g / m³). 2 The water absorption increased by 171%, but at the same time, its oil resistance deteriorated, dropping from grade 11 (kit value) to grade 7 (kit value), a decrease of 4 grades.

[0080] The coating resin prepared in Comparative Example 5, due to a reduction of 1 / 3 in the amount of hydroxymethyl resin, showed increased water absorption, with its water absorption decreasing from 1.7 (g / m³). 2 The concentration increased to 7.0 (g / m³). 2 The water absorption increased by 312%, but at the same time, its oil resistance deteriorated, dropping from level 11 (kit value) to level 6 (kit value), a decrease of 5 levels.

[0081] The coating resin prepared in Comparative Example 6, due to a reduction of 1 / 2 in the amount of hydroxymethyl resin, showed increased water absorption, with its water absorption decreasing from 1.7 (g / m³). 2 The concentration increased to 9.4 (g / m³). 2 The water absorption increased by 450%, but at the same time, its oil resistance deteriorated, dropping from grade 11 (kit value) to grade 4 (kit value), a decrease of 7 grades.

[0082] The coating resin prepared in Comparative Example 7, due to a reduction of 2 / 3 in the amount of hydroxymethyl resin, showed increased water absorption, with its water absorption decreasing from 1.7 (g / m³). 2 The concentration increased to 11.6 (g / m³). 2 The water absorption increased by 582%, but at the same time, its oil resistance deteriorated, dropping from level 11 (kit value) to level 3 (kit value), a decrease of 8 levels.

[0083] The coating resin prepared in Comparative Example 8, due to the complete removal of hydroxymethyl resin, exhibited increased water absorption, with its water absorption decreasing from 1.7 (g / m³). 2 The concentration increased to 16.3 (g / m³). 2 The water absorption increased by 859%, but at the same time, its oil resistance deteriorated, dropping from level 11 (kit value) to level 2 (kit value), a decrease of 9 levels.

[0084] In summary, this application designs and prepares water-based coating agents for paper using vegetable oils, reactive alcohols, acidic substances, rosin, and hydroxymethyl resins. By precisely controlling the amount, type, and ratio of these substances, the resin exhibits excellent waterproof and oil-repellent properties. For example, a rigid structure is prepared by the addition and degree of addition of rosin and acidic substances, and further reacted with hydroxymethyl resin to prepare a more rigid and complex molecular structure. A high-linear-density, high-cohesion alkyd molecular structure is prepared by reacting reactive alcohols with adducts. A specific amount of vegetable oil is introduced into the coating agent molecules through alcoholysis to form a flexible segment molecular structure. Through these methods, especially the introduction of hydroxymethyl resin, the waterproof and oil-repellent properties of the coating agent resin are greatly improved, thereby enabling the widespread use of this type of resin in paper coating.

[0085] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A resin for paper coating, characterized in that, The raw materials for the resin, by weight, include 40-60 parts vegetable oil, 40-60 parts alcohol, 90-110 parts rosin, 15-35 parts acidic substances, 10-20 parts hydroxymethyl resin, 60-80 parts alkali, and 300-500 parts distilled water.

2. The resin according to claim 1, characterized in that, The vegetable oil is at least one of non-drying vegetable oil, semi-drying vegetable oil, and drying vegetable oil; the non-drying vegetable oil is at least one of castor oil, coconut oil, and peanut oil; the semi-drying vegetable oil is at least one of soybean oil, cottonseed oil, and sunflower seed oil; and the drying vegetable oil is at least one of tung oil, linseed oil, and hemp oil.

3. The resin according to claim 1, characterized in that, The alcohol is at least one of diols, triols, and tetraols; the diol is at least one of ethylene glycol, diethylene glycol, and triethylene glycol; the triol is at least one of glycerol and trimethylolpropane; and the tetraol is pentaerythritol.

4. The resin according to claim 1, characterized in that, The rosin is at least one of resin rosin, wood rosin, and oil rosin; the resin rosin is at least one of Masson rosin, wetland rosin, and Simao rosin.

5. The resin according to claim 1, characterized in that, The acidic substance is at least one of saturated acid and unsaturated acid; the acidic substance is at least one of monobasic acid and dibasic acid; the saturated acid is at least one of benzoic acid, terephthalic acid, phthalic acid, phthalic anhydride, isophthalic acid, hexahydrophthalic anhydride, succinic acid, adipic acid, octanoic acid, and sebacic acid; the unsaturated acid is at least one of fumaric acid, maleic acid, maleic anhydride, acrylic acid, itaconic acid, citraconic acid, tetrahydrophthalic acid, and nadic anhydride.

6. The resin according to claim 1, characterized in that, The hydroxymethyl resin is at least one of HY-2045 and HY-2055.

7. A method for preparing a resin for paper coating according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Reaction of vegetable oil with alcohol yields alcoholysis products; (2) The rosin, acidic substance, and hydroxymethyl resin are mixed and reacted to obtain an adduct; (3) Add the alcoholysis product to the adduct to react and obtain alkyd resin; (4) Add alkali and distilled water to alkyd resin to carry out neutralization reaction, and you will get the product.

8. The preparation method according to claim 7, characterized in that: The reaction in step (1) requires the addition of a catalyst, the amount of which is 5-10‰ of the mass of the vegetable oil; the catalyst is at least one of an inorganic base or an inorganic salt. The inorganic base or inorganic salt is at least one of LiOH, KOH, Ca(OH)2, Mg(OH)2, and LiAc; or, the inorganic base or inorganic salt catalyst is at least one of LiOH, KOH, and LiAc; or, the inorganic base or inorganic salt catalyst is at least one of LiOH and LiAc. And / or, the reaction described in step (1) requires heating at a temperature of 240–260°C and the holding time after heating is 2–5 h; And / or, the amount of hydroxymethyl resin used in step (2) is 13.8%-18.5% of the rosin mass, the reaction in step (2) requires the addition of a catalyst, the amount of the catalyst is 3-10‰ of the rosin mass, and the catalyst for the reaction is a phosphorus-containing esterification catalyst; the esterification catalyst is hypophosphoric acid, potassium di-tert-butyl phosphate, or IRGANOX. TM At least one of 1425; And / or, the reaction described in step (3) requires heating, with a heating temperature of 250 to 270°C and a holding time of 5 to 10 hours after heating; And / or, the base in step (4) is at least one of triethylamine, ethanolamine, diethanolamine, triethanolamine, diphenylamine, triphenylamine, ammonia, sodium hydroxide, and potassium hydroxide; or, the base is at least one of triethylamine, ethanolamine, and ammonia. And / or, the reaction described in step (4) requires heating, with a heating temperature of 55 to 75°C and a holding time of 2 to 5 hours after heating.

9. A water-based coating agent, characterized in that, Its raw materials include the resin for paper coating as described in any one of claims 1-6.

10. The use of a resin according to any one of claims 1-6 or a resin prepared by the preparation method according to claims 7-8 in the preparation of paper coating.

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