Modified melamine functional adjuvant from lignin depolymerization products and method of making

Abstract

The present application belongs to the technical field of lignin processing, and more particularly relates to a modified melamine functional additive of lignin depolymerization product and a preparation method thereof. A lignin depolymerization product with rich active functional groups such as phenolic hydroxyl groups, methoxyl groups and ester groups is obtained by depolymerizing lignin. The modified melamine functional additive of lignin depolymerization product is prepared by hydroxymethylation, sulfonation, acid polymerization, alkaline reforming and spray drying, and has good dispersing performance, compatibility and high water reducing rate. Therefore, the modified melamine functional additive of lignin depolymerization product has multiple functions such as water reducing, grinding aid, dispersing and reinforcing, and can be used as ceramic additives, soil conditioners, dye dispersants, concrete water reducing agents and coal water slurry dispersants, etc., showing strong market potential and environmental protection value. The present application uses lignin, a byproduct of pulp industry, as raw material, which is not only rich in resources and low in cost, but also promotes waste resource utilization and helps to achieve the goal of carbon peak and carbon neutralization.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of lignin processing, and more particularly relates to a lignin depolymerization product modified melamine functional aid and a preparation method thereof. BACKGROUND

[0002] Sulfonated melamine resin, as an anionic surfactant, is formally named sulfonated melamine formaldehyde resin, which is carefully constructed through complex chemical reactions. This process begins with the delicate combination of melamine and aldehyde compounds to form a hydroxymethyl melamine intermediate, which is then converted into melamine sulfonate under the catalysis of a sulfonating agent, and finally condensed into a high molecular form through polycondensation. The dense sulfonic acid groups in the molecular structure of sulfonated melamine resin, like an invisible pair of hands, exhibit excellent dispersion ability for solid particles in solution, thus playing an indispensable role in various industrial fields such as ceramic additives, coal water slurry stabilization, dye dispersion, and concrete modification.

[0003] In particular, the sulfonic acid groups in sulfonated melamine resin can intelligently recognize and tightly adhere to the surfaces of various powder particles due to their strong anchoring properties, and adjust the anchoring strategy according to the polarity differences of the particles. Once adsorption is complete, the extended chain structure builds a solid spatial barrier around the particles, effectively preventing particle aggregation. At the same time, the ionization of sulfonic acid groups further optimizes the charge distribution on the particle surface, enhancing the electrostatic repulsion between particles, thereby ensuring the long-term stability of the dispersion system.

[0004] However, despite the excellent performance of sulfonated melamine resin, it still faces many challenges in practical applications. Traditional melamine-based dispersants have the problems of single functionality, high viscosity affecting construction, sensitivity to raw material clay content, difficulty in dosage control, and rising production costs, which limit their wider application. Therefore, developing a new type of melamine-based dispersant with low cost and stable performance has become an urgent problem in the industry.

[0005] To address these challenges, researchers have turned their attention to lignin, a natural high molecular organic compound. As the main component of plant skeletons, lignin not only has abundant reserves, low price, environmental friendliness and renewability, but also has the unique ability to provide aryl compounds, showing great economic and environmental potential. By combining lignin with melamine polymers and using chemical modification methods, a dispersant product with better performance and more comprehensive functions can be created.

[0006] Although there have been studies attempting to modify lignin through different paths to prepare lignin and melamine-based composite dispersants, these methods often have harsh reaction conditions, complex processes, many by-products, and unstable product performance. Therefore, exploring a new method that is more efficient, environmentally friendly, and can overcome the steric hindrance problem between lignin and melamine has become the focus of current research. This innovation not only hopes to significantly improve the performance of the dispersant and broaden its application range, but also will inject new vitality into the sustainable development of related industries. SUMMARY

[0007] In view of the above technical problems, the present application provides a lignin depolymerization product modified melamine functional additive and a preparation method thereof, in order to prepare a lignin depolymerization product modified melamine functional additive with small steric hindrance, multiple functions and complete modification through simple operation steps, mild reaction conditions, conventional production equipment, low production cost and clean production process, and to expand new technical paths for the utilization of lignin resources.

[0008] To achieve the above-mentioned purpose, in a first aspect, the present application provides a preparation method of a lignin depolymerization product modified melamine functional additive, comprising the following steps:

[0009] S1, uniformly stirring lignin, activator and water, adding catalyst for hydrothermal reaction, cooling the reaction liquid, removing solid residues to obtain liquid lignin depolymerization product;

[0010] S2, adding melamine, aldehyde compound and water to the lignin depolymerization product, uniformly stirring, then heating to a first temperature for a first time period, then adding a sulfonating agent, heating to a second temperature for a second time period;

[0011] S3, cooling to a third temperature, adding an acid adjusting agent to adjust the reaction system to a first pH value, performing acid polycondensation reaction for a third time period, adding an alkaline adjusting agent to adjust the reaction system to a second pH value, heating to a fourth temperature for a fourth time period, cooling and discharging, spray drying to obtain the lignin depolymerization product modified melamine functional additive.

[0012] The lignin used in the present application is selected from one or more lignins obtained from Masson pine, bamboo cane, giant reed grass, wheat straw, birch, bagasse, curved willow, royal bamboo, eucalyptus, reed, poplar, anemarrhena asphodeloides, and rice straw.

[0013] The acid adjusting agent used in the present application is one or more of sulfamic acid, oxalic acid, tartaric acid, sulfuric acid, phosphoric acid, citric acid, salicylic acid, maleic acid, succinic acid, and benzoic acid.

[0014] The alkaline regulator adopted by the present application is one or several of sodium hydroxide, sodium pyrophosphate, potassium hydroxide, sodium diphosphate, sodium tripolyphosphate, sodium polyphosphate, and sodium tetraborate.

[0015] The present application uses an activator and a catalyst to perform a hydrothermal depolymerization reaction on lignin, and the number of main active functional groups such as phenolic hydroxyl groups of the depolymerized lignin is significantly increased, which is beneficial to further modification and improves the application value in various fields. The lignin depolymerization product is directly reacted with melamine and aldehyde compounds under specific conditions to prepare a lignin depolymerization product modified melamine dispersant, the preparation process is simple, the reaction conditions are mild, the obtained product has rich phenolic hydroxyl groups and sulfonic acid groups, has strong reactivity, and can produce effective electrostatic repulsion and steric hindrance effect on slurry particles.

[0016] According to some preferred embodiments, the amount of each raw material is 5.0% to 20.0% by mass.

[0017] Lignin 5.0% to 20.0%;

[0018] Activator 5% to 10%;

[0019] Catalyst 0.3% to 1.0%;

[0020] Melamine 6.5% to 15.5%;

[0021] Aldehyde compound 19.0% to 34.0%;

[0022] Sulfonating agent 10.0% to 18.0%;

[0023] Acid regulator 0.1% to 1.5%;

[0024] Alkaline regulator 0.2% to 0.8%;

[0025] Water 25.0% to 50.0%.

[0026] According to some preferred embodiments, the activator is an alkali activator, preferably the alkali activator is one or several of KOH, NaOH, Ca(OH)2, Mg(OH)2, LiOH, and MgO.

[0027] According to some preferred embodiments, the catalyst is a metal catalyst, preferably the metal catalyst is one or several of Ni-Fe, Ni-Co, Ni-Mg, Ni-Zn, Ni-Al, and Ni-Zn-Co.

[0028] According to some preferred embodiments, the aldehyde compound is one or several of formaldehyde, acetaldehyde, glyoxal, butyl aldehyde, isobutyl aldehyde, or glutaraldehyde.

[0029] According to some preferred embodiments, the sulfonating agent is one or more of sodium sulfite, sodium bisulfite, sodium metabisulfite, potassium sulfite, ammonium sulfite, sulfamic acid, and sodium sulfanilate.

[0030] According to some preferred embodiments, the first temperature is 50-80℃, and the first time period is 0.5-2.5h; preferably, the second temperature is 75-105℃, and the second time period is 1-3h.

[0031] According to some preferred embodiments, the third temperature is 55-85℃, the first pH value is 4-6, and the third time period is 0.5-2.5h; preferably, the fourth temperature is 60-90℃, the second pH value is 8-10, and the fourth time period is 2-4h.

[0032] According to some preferred embodiments, in S1, the temperature of the hydrothermal reaction is 180-250℃, and the reaction time is 1-5h, and the reaction solution is cooled to 35-50℃.

[0033] In a second aspect, the inventors provide a lignin depolymerization product modified melamine functional aid, which is prepared by the preparation method of the first aspect of the present application. Preferably, the relative molecular mass Mn of the lignin depolymerization product modified melamine functional aid is 4300-40000.

[0034] Differing from the prior art, the above technical solution obtains a lignin depolymerization product with rich active functional groups such as phenolic hydroxyl groups, methoxyl groups, and ester groups by depolymerizing lignin, and thus is more easily chemically modified. The lignin depolymerization product modified melamine functional aid is prepared by hydroxymethylation, sulfonation, acidic polymerization, alkaline reforming, and spray drying, and has strong dispersing performance, good compatibility, and high water-reducing rate. The lignin depolymerization product modified melamine functional aid of the present application has multiple functions such as water-reducing, grinding-aiding, dispersing, and reinforcing, and can be used as a ceramic additive, a soil conditioner, a dye dispersant, a concrete water-reducing agent, and a coal water slurry dispersant, etc., and thus exhibits strong market potential and environmental protection value. The present application uses lignin, a byproduct of the pulp industry, as a raw material, and thus not only has abundant resources and low cost, but also has a simple preparation process and mild reaction conditions, and promotes the resource utilization of waste and helps achieve the goal of carbon peak and carbon neutrality.

[0035] The above summary of the invention is only a summary of the technical solutions of the present application. In order for those skilled in the art to more clearly understand the technical solutions of the present application, and to implement the content of the written description of the specification, and in order for the above and other purposes, characteristics and advantages of the present application to be more easily understood, the following describes the specific embodiments of the present application. DETAILED DESCRIPTION

[0036] To explain possible application scenarios, technical principles, specific implementation schemes, and the purposes and effects of the present application in detail, the following embodiments are described in detail. The embodiments described herein are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0037] In this paper, the term "embodiment" means that the specific features, structures or characteristics described in conjunction with the embodiment can be included in at least one embodiment of the present application. The term "embodiment" appearing at various places in the specification does not necessarily refer to the same embodiment, and does not particularly limit its independence or association with other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the technical features mentioned in each embodiment can be combined in any way to form a corresponding implementable technical solution.

[0038] Unless otherwise defined, the meanings of the technical terms used herein are the same as those commonly understood by those skilled in the art to which the present application belongs; the use of related terms herein is only for the purpose of describing specific embodiments, and is not intended to limit the present application.

[0039] In the description of the present application, the phrase "and / or" is a description of the logical relationship between the objects, which means that there can be three relationships, for example, A and / or B, which means that there are three cases: A exists, B exists, and A and B exist at the same time. In addition, the character " / " in this paper generally represents that the associated objects before and after are a "or" logical relationship.

[0040] In the present application, terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual quantity, primary and secondary or order relationship between the entities or operations.

[0041] Without more limitations, in the present application, the "includes", "contains", "has" or other similar expressions used in the sentence are intended to cover non-exclusive inclusion, and these expressions do not exclude the presence of other elements in the process, method or product including the described elements, so that the process, method or product including a series of elements can not only include those limited elements, but also include other elements not explicitly listed, or also include elements inherent to such process, method or product.

[0042] As the same understanding in the <Examination Guidelines>, in the present application, the expressions such as "greater than", "less than", "exceed" are understood as not including the number; the expressions such as "above", "below", "within" are understood as including the number. In addition, in the description of the embodiments of the present application, the meaning of "multiple" is two or more (including two), and similar expressions related to "multiple" are also understood in this way, for example, "multiple groups", "multiple times", etc., unless otherwise explicitly specified.

[0043] Unless otherwise expressly specified or limited, in the description of the embodiments of the present application, the terms "mount", "connect", "connect", "fix", "set" and the like should be understood in a broad sense. For example, the "connection" can be fixed connection, or detachable connection, or integrated setting; it can be mechanical connection, or electrical connection, or communication connection; it can be direct connection, or indirect connection through intermediate medium; it can be the communication inside two elements or the interaction relationship between two elements. For those skilled in the art to which the present application belongs, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0044] The existing melamine dispersant technology has multiple defects: functional products are scarce, it is difficult to meet the diversified needs of the market; the high viscosity characteristics limit the application in high blending and low water-binder ratio materials, and are sensitive to the clay content of sand and gravel aggregate, with poor construction adaptability; the rising price of raw material melamine increases the production cost, further aggravating the application challenge. In addition, the existing research method of lignin modified melamine polymer is complex, the reaction condition is harsh, the product performance is single, and there are problems of incomplete modification and great difficulty in synthesis, which limits its wide application.

[0045] Therefore, the present application aims to develop a low-cost, stable performance lignin depolymerization product modified melamine functional additive, which efficiently depolymerizes lignin by innovatively using alkali activator and metal catalyst, and precisely controls the directional polymerization process of depolymerization products, successfully overcomes the steric hindrance problem between lignin and melamine polymer, realizes effective reaction and functionalization improvement. The dispersant of the present application not only has low dosage and excellent dispersion performance, but also has wide application range, which can cover ceramic additives, soil improver, dye dispersant, concrete water reducing agent and coal water slurry dispersant, etc. multiple fields, effectively broadening the utilization way of lignin, promoting the development of renewable resources and the development of circular economy, providing strong technical support for environmental protection and energy saving, low-carbon economy and the realization of carbon peak and carbon neutralization target.

[0046] In the present application, unless otherwise specified, the reagents used are commercially available in the art.

[0047] In the present application, unless otherwise specified, the test methods and equipment are the test methods and equipment commonly used in the art.

[0048] Example 1

[0049] The present example provides a method for preparing a lignin depolymerization product modified melamine functional additive, which comprises the following steps:

[0050] In a reactor, 87.8 kg of bamboo lignin, 58.9 kg of potassium hydroxide, and 155.1 kg of water were stirred uniformly, 6.1 kg of Ni-Fe was added, and the reaction was carried out at 250°C for 3.4 h. After cooling to 48°C, the solid residue was removed to obtain a lignin depolymerization product. To the depolymerization product, 164.9 kg of water, 100.4 kg of melamine, and 294.6 kg of formaldehyde were added and stirred uniformly, and then the temperature was raised to 75°C and the reaction was carried out for 2.0 h. 122.2 kg of sodium sulfite was added, the temperature was raised to 100°C, and the reaction was continued for 2.0 h. After reducing the temperature of the system to 60°C, 6.8 kg of salicylic acid was added, the pH value of the system was adjusted to about 5, and the reaction was carried out for 2 h. Then 3.2 kg of sodium hydroxide was added to adjust the pH value of the system to about 10, and the reaction was carried out at a reaction temperature of 100°C for 2.0 h. After cooling, the product was discharged as a brownish liquid. The obtained liquid was dried by a spray dryer, the inlet temperature of the spray tower was 230°C, and the outlet temperature was 80°C. The obtained solid product was a lignin depolymerization product modified melamine functional additive. Gel permeation chromatography was used to test the molecular weight of the product, and the relative molecular mass Mn was 14850.

[0051] Example 2

[0052] The present example provides a method for preparing a lignin depolymerization product modified melamine functional additive, which comprises the following steps:

[0053] In a reactor, 148.3 kg of reed lignin, 51.7 kg of potassium hydroxide, and 162.1 kg of water were stirred uniformly, 7.2 kg of Ni-Co was added, and the reaction was carried out at 250°C for 3.4 h. After being cooled to 48°C, the solid residue was removed to obtain a lignin depolymerization product. 177.9 kg of water, 81.1 kg of melamine, and 228.4 kg of acetaldehyde were added to the depolymerization product and stirred uniformly, and then the temperature was increased to 60°C, and the reaction was carried out for 2.5 h. 132.8 kg of sodium metabisulfite was added, the temperature was increased to 70°C, and the reaction was continued for 3.5 h. After the temperature of the system was reduced to 65°C, 6.5 kg of benzoic acid was added, the pH value of the system was adjusted to about 5, and the reaction was carried out for 2.5 h. Then 4.0 kg of potassium hydroxide was added to adjust the pH value of the system to about 9, and the reaction was carried out at a reaction temperature of 70°C for 3.5 h. After being cooled, the product was discharged, and a brownish liquid product was obtained. The obtained liquid was dried by a spray dryer, the inlet temperature of the spray tower was 230°C, and the outlet temperature was 80°C. The obtained solid product was a lignin depolymerization product modified melamine functional additive, and the molecular weight was tested by a gel permeation chromatograph, and the relative molecular mass Mn was 25650.

[0054] Example 3

[0055] The present example provides a preparation method of a lignin depolymerization product modified melamine functional additive, which comprises the following steps:

[0056] In a reactor, 55.3 kg of achnatherum lessingianum lignin, 55.8 kg of potassium hydroxide, and 150.2 kg of water were stirred uniformly, 4.2 kg of Ni-Zn was added, and the reaction was carried out at 250°C for 3.4 h. After being cooled to 48°C, the solid residue was removed to obtain a lignin depolymerization product. 154.8 kg of water, 119.2 kg of melamine, and 310.9 kg of formaldehyde were added to the depolymerization product and stirred uniformly, the temperature was increased to 95°C, and the reaction was carried out for 1.5 h. 139.1 kg of sodium bisulfite was added, the temperature was increased to 100°C, and the reaction was continued for 3.0 h. After the temperature of the system was reduced to 55°C, 5.7 kg of sulfamic acid was added, the pH value of the system was adjusted to about 6, and the reaction was carried out for 2.0 h. Then 4.8 kg of sodium diphosphate was added to adjust the pH value of the system to about 8, and the reaction was carried out at a reaction temperature of 100°C for 2.5 h. After being cooled, the product was discharged, and a brownish liquid product was obtained. The obtained liquid was dried by a spray dryer, the inlet temperature of the spray tower was 230°C, and the outlet temperature was 80°C. The obtained solid product was a lignin depolymerization product modified melamine functional additive, and the molecular weight was tested by a gel permeation chromatograph, and the relative molecular mass Mn was 15760.

[0057] Example 4

[0058] The present example provides a preparation method of a lignin depolymerization product modified melamine functional additive, which comprises the following steps:

[0059] In a reactor, 114.6 kg of poplar lignin, 60.4 kg of potassium hydroxide, and 160.5 kg of water were stirred uniformly, 7.8 kg of Ni-Fe was added, and the reaction was carried out at 250°C for 3.4 h. After the system was cooled to 48°C, the solid residue was removed to obtain a lignin depolymerization product. To the depolymerization product, 174.5 kg of water, 87.2 kg of melamine, and 235.9 kg of formaldehyde were stirred uniformly, and the temperature was increased to 80°C. The reaction was carried out for 2.0 h. Then, 152.4 kg of potassium sulfite was added, the temperature was increased to 95°C, and the reaction was continued for 4.0 h. After the temperature of the system was reduced to 50°C, 2.9 kg of tartaric acid was added, the pH value of the system was adjusted to about 6, and the reaction was carried out for 2.0 h. Then, 3.8 kg of sodium pyrophosphate was added to adjust the pH value of the system to about 10, and the reaction was carried out at a reaction temperature of 95°C for 3.0 h. After cooling, the product was discharged, and the obtained liquid was dried by using a spray dryer. The inlet temperature of the spray tower was 230°C, and the outlet temperature was 80°C. The obtained solid product was a lignin depolymerization product modified melamine functional additive. The molecular weight of the product was tested by using a gel permeation chromatograph, and the relative molecular mass Mn was 19280.

[0060] Example 5

[0061] The present example provides a preparation method of a lignin depolymerization product modified melamine functional additive. The method comprises the following steps:

[0062] In a reactor, 100.3 kg of curly willow lignin, 64.7 kg of potassium hydroxide, and 259.6 kg of water were stirred uniformly, 3.6 kg of Ni-Al was added, and the reaction was carried out at 250°C for 3.4 h. After the system was cooled to 48°C, the solid residue was removed to obtain a lignin depolymerization product. To the depolymerization product, 192.4 kg of water, 70.1 kg of melamine, and 190.6 kg of glyoxal were stirred uniformly, and the temperature was increased to 85°C. The reaction was carried out for 2.5 h. Then, 109.4 kg of sodium bisulfite / ammonium sulfite (mass ratio of 2:1) was added, the temperature was increased to 95°C, and the reaction was continued for 2.5 h. After the temperature of the system was reduced to 50°C, 1.9 kg of sulfuric acid was added, the pH value of the system was adjusted to about 3, and the reaction was carried out for 2.0 h. Then, 7.4 kg of sodium phosphate was added to adjust the pH value of the system to about 10, and the reaction was carried out at a reaction temperature of 95°C for 2.0 h. After cooling, the product was discharged, and the obtained liquid was dried by using a spray dryer. The inlet temperature of the spray tower was 230°C, and the outlet temperature was 80°C. The obtained solid product was a lignin depolymerization product modified melamine functional additive. The molecular weight of the product was tested by using a gel permeation chromatograph, and the relative molecular mass Mn was 17720.

[0063] Example 6

[0064] The present example provides a preparation method of a lignin depolymerization product modified melamine functional additive, which comprises the following steps:

[0065] In a reactor, 70.3 kg of Huangzhu lignin and birch lignin (lignin obtained by preparing Huangzhu and birch in a mass ratio of 3:1), 75.1 kg of potassium hydroxide, and 189.6 kg of water were stirred uniformly, 5 kg of Ni-Fe was added, and the reaction was carried out at 250℃ for 3.4 h. After cooling to 48℃, the solid residue was removed to obtain a lignin depolymerization product. To the depolymerization product, 155.4 kg of water, 129.7 kg of melamine, and 229.9 kg of butyl aldehyde were added and stirred uniformly, and the temperature was increased to 70℃ and reacted for 1.5 h. 129.2 kg of sodium sulfite / amino benzenesulfonic acid sodium (mass ratio of 2:1) was added, and after the temperature was increased to 90℃, the reaction was continued for 3.5 h. After the temperature of the system was reduced to 50℃, 11.5 kg of succinic acid was added, the pH value of the system was adjusted to about 4, and the reaction was carried out for 3.0 h. Then 4.3 kg of sodium hydroxide / potassium hydroxide (mass ratio of 1:1) was added to adjust the pH value of the system to about 8, and the reaction was carried out at a reaction temperature of 90℃ for 2.5 h. After cooling, the product was discharged, and the obtained liquid was dried by a spray dryer, the inlet temperature of the spray tower was 230℃, and the outlet temperature was 80℃. The obtained solid product was a lignin depolymerization product modified melamine functional additive, and the molecular weight was tested by a gel permeation chromatograph, and the relative molecular mass Mn was 32720.

[0066] Example 7

[0067] The present example provides a preparation method of a lignin depolymerization product modified melamine functional additive, which comprises the following steps:

[0068] In a reactor, 144.6 kg of pine and bagasse lignin (lignin prepared with a mass ratio of pine to bagasse of 4:1), 53.1 kg of potassium hydroxide, and 214.7 kg of water were stirred uniformly, 9.4 kg of Ni-Mg was added, and the reaction was carried out at 250°C for 3.4 h. After the system was cooled to 48°C, the solid residue was removed to obtain a lignin depolymerization product. To the depolymerization product, 144.3 kg of water, 90.3 kg of melamine, and 232.9 kg of glutaraldehyde were stirred uniformly, and the temperature was increased to 65°C. The reaction was carried out for 2.5 h. 100.2 kg of sodium pyrosulfite / sodium p-aminobenzenesulfonate (mass ratio of 2:1) was added, the temperature was increased to 80°C, and the reaction was continued for 3.5 h. After the temperature of the system was reduced to 60°C, 6.2 kg of phosphoric acid was added, the pH value of the system was adjusted to about 5.5, and the reaction was carried out for 3.0 h. Then, 4.3 kg of sodium tetraborate was added to adjust the pH value of the system to about 9, and the reaction was carried out at a reaction temperature of 80°C for 3.0 h. After cooling, the product was discharged, and the obtained liquid was dried by using a spray dryer. The inlet temperature of the spray tower was 230°C, and the outlet temperature was 80°C. The obtained solid product was a lignin depolymerization product modified melamine functional additive. The molecular weight of the product was tested by using a gel permeation chromatograph, and the relative molecular mass Mn was 28270.

[0069] Example 8

[0070] The present example provides a method for preparing a lignin depolymerization product modified melamine functional additive. The method comprises the following steps:

[0071] In a reactor, 98.6 kg of eucalyptus and poplar lignin (lignin prepared with a mass ratio of eucalyptus to poplar of 2:1), 64.5 kg of potassium hydroxide, and 157.9 kg of water were stirred uniformly, 6.4 kg of Ni-Zn was added, and the reaction was carried out at 250°C for 3.4 h. After the system was cooled to 48°C, the solid residue was removed to obtain a lignin depolymerization product. To the depolymerization product, 132.1 kg of water, 135.5 kg of melamine, and 280.2 kg of formaldehyde were stirred uniformly, and the temperature was increased to 75°C. The reaction was carried out for 2.5 h. 114.8 kg of sodium pyrosulfite was added, the temperature was increased to 100°C, and the reaction was continued for 2.5 h. After the temperature of the system was reduced to 65°C, 7.8 kg of salicylic acid / maleic acid (mass ratio of 3:1) was added, the pH value of the system was adjusted to about 6, and the reaction was carried out for 1.5 h. Then, 2.2 kg of sodium hydroxide was added to adjust the pH value of the system to about 9, and the reaction was carried out at a reaction temperature of 100°C for 1.5 h. After cooling, the product was discharged, and the obtained liquid was dried by using a spray dryer. The inlet temperature of the spray tower was 230°C, and the outlet temperature was 80°C. The obtained solid product was a lignin depolymerization product modified melamine functional additive. The molecular weight of the product was tested by using a gel permeation chromatograph, and the relative molecular mass Mn was 27230.

[0072] The performance of the modified melamine functional auxiliary prepared from the lignin depolymerization product of the above-mentioned embodiments 1-8 was tested. The testing method is as follows:

[0073] The specific steps for testing the molecular weight thereof by using a gel permeation chromatograph are as follows:

[0074] After the auxiliary sample was freeze-dried by a vacuum freeze dryer for 3 days, the characterization test of the molecular structure was performed. The number average molecular weight (Mn), the weight average molecular weight (Mw) and the polydispersity index (PDI) of the product were determined by using a Waters 1515 gel permeation chromatograph (GPC) and a Waters 2414 refractive index detector. n w Before calibration, the series of standard substances were configured into an aqueous solution with a concentration of 0.3%, and a standard working curve was determined; a sample solution with a concentration of about 0.3% was configured by using 0.1 mol / L sodium nitrate, and then the molecular weight distribution was determined.

[0075] Comparative Example 1

[0076] The present comparative example provides a preparation method of a dispersant, which comprises the following steps:

[0077] In a reactor, 154.8 kg of water, 119.2 kg of melamine and 310.9 kg of formaldehyde were uniformly stirred, and the temperature was increased to 95℃, and reacted for 1.5 h. 139.1 kg of sodium bisulfite was added, and after the temperature was increased to 100℃, the reaction was continued for 3.0 h. After the temperature of the system solution was reduced to 55℃, 5.7 kg of sulfamic acid was added, the pH value of the system was adjusted to about 6, and the reaction was continued for 2.0 h. Then 4.8 kg of sodium diphosphate was added to adjust the pH value of the system to about 8, and the reaction was continued for 2.5 h at a reaction temperature of 100℃. After cooling, the product was discharged, and the obtained liquid was dried by using a spray dryer, the inlet temperature of the spray tower was 230℃, and the outlet temperature was 80℃. The obtained solid product was a melamine functional auxiliary, and the molecular weight thereof was tested by using a gel permeation chromatograph, and the relative molecular mass Mn was 11450.

[0078] Comparative Example 2

[0079] The present comparative example provides a preparation method of a dispersant, which comprises the following steps:

[0080] ​Stir 55.3 kg of meadow grass lignin, 154.8 kg of water, 119.2 kg of melamine, and 310.9 kg of formaldehyde uniformly, and heat to 95°C, and react for 1.5 h. Add 139.1 kg of sodium bisulfite, heat to 100°C, and continue to react for 3.0 h. After reducing the temperature of the system solution to 55°C, add 5.7 kg of sulfamic acid, adjust the pH value of the system to about 6, and react for 2.0 h. Then add 4.8 kg of sodium diphosphate to adjust the pH value of the system to about 8, and react for 2.5 h at a reaction temperature of 100°C. After cooling, discharge the product, which is a brownish liquid. Dry the obtained liquid by using a spray dryer, with an inlet temperature of 230°C and an outlet temperature of 80°C. The obtained solid product is a modified melamine functional additive of lignin depolymerization product. The molecular weight of the product is tested by using a gel permeation chromatograph, and the relative molecular mass Mn is 13650.

[0081] The performance of the functional additive prepared in the above is tested.

[0082] Application Example 1

[0083] Application of the modified melamine functional additive of lignin depolymerization product in ceramic additives

[0084] The composition of the ceramic slurry used in the present application example is shown in Table 1. The products obtained in Examples 1-8 and Comparative Examples 1-2 are added to the ceramic slurry as ceramic additives, and the fluidity, viscosity, and green strength of the obtained mixture are compared. The results are shown in Table 2. The fluidity is tested according to the national standard GB / T 1723-93; the viscosity is tested according to the national standard GB / T 2794-2013; and the green strength is tested according to the international standard GB / T 3810.4-2006 Part 4: Determination of modulus of rupture and breaking strength.

[0085] Table 1 Composition of the ceramic slurry (wt%)

[0086]

[0087] Table 2 Fluidity, viscosity, and green strength of the product after adding ceramic additives

[0088]

[0089] Note: Unlike Example 3, Comparative Example 1 is a melamine functional additive product prepared by directly using melamine, formaldehyde, and sodium bisulfite without adding lignin, and Comparative Example 2 is a modified melamine functional additive of lignin depolymerization product prepared by using melamine, formaldehyde, and sodium bisulfite under the condition of adding the same lignin as in Example 3.

[0090] From the results of the above table, when the molecular weight of the product is too large, the flow performance will be affected; when the molecular weight is too small, the green body bending strength will be affected. Compared with other products, the product obtained in Example 3 (the obtained auxiliary has a molecular weight of 15760) and Example 5 (the obtained auxiliary has a molecular weight of 17720) has a suitable molecular weight, and not only the ceramic slurry has a fast flow-out time, but also the green body bending strength is high, so the product is suitable for being used as a ceramic additive. The ceramic slurry added with the auxiliary of Comparative Example 1 and 2 has a long flow-out time, low green body bending strength and high viscosity, which reduces the construction efficiency of the process such as slurry injection, impregnation or coating and increases the difficulty of process control of the ceramic product with fast forming or high precision requirement, has a negative impact on the overall performance of the ceramic product, increases the waste rate and cost, and reduces the forming precision and surface quality. Therefore, the lignin depolymerization product modified melamine functional auxiliary provided by the application is more suitable for being used as a ceramic dispersant than the auxiliary provided by Comparative Example 1-2, and especially when the molecular weight of the lignin depolymerization product modified melamine functional auxiliary is 5000-20000, the auxiliary has excellent effects of short ceramic slurry flow-out time and high green body bending strength.

[0091] Application Example 2

[0092] Application of the lignin depolymerization product modified melamine functional auxiliary as a dye dispersant

[0093] In order to investigate the possibility of the product as a dye dispersant, the products obtained in Examples 1-8 and Comparative Example 1-2 are added into olive T dye in an equal amount, and the addition amount is 150% of the dye. The heat-resistant stability of various auxiliaries to the vat dye is detected and rated according to HG / T 3507-2008 “Sodium lignosulfonate dispersant” and HG / T 3399 2001 “Determination of dye diffusion performance”, and the test results are shown in Table 3.

[0094] Table 3 Comparison of heat-resistant stability of products

[0095]

[0096] From the results of Table 3, when the molecular weight of the obtained product is too large, the dispersion performance will be affected, which leads to the re-agglomeration of the dye; when the molecular weight is too small, the high-temperature stability will be affected. Compared with other products, the product obtained in Example 2 (the obtained auxiliary has a molecular weight of 25650) and Example 8 (the obtained auxiliary has a molecular weight of 27230) has a suitable molecular weight, and the heat-resistant stability is more, so the product is suitable for being used as a dye dispersant. Therefore, the lignin depolymerization product modified melamine functional auxiliary obtained by the application has a molecular weight of 15000-30000, so the auxiliary is suitable for being used as a dye dispersant.

[0097] Application Example 3

[0098] Application of lignin depolymerization product modified melamine functional adjuvant as concrete water reducing agent

[0099] To investigate the possibility of the product as a concrete admixture, the performance of the products obtained in Examples 1-8 and Comparative Examples 1-2 was tested, and the method was referred to JG / T223-2007, with evergreen cement as the research object, and the test results are shown in Table 4.

[0100] Table 4: Strength and fluidity comparison of the products

[0101]

[0102] As can be seen from the results in Table 4, when the molecular weight of the obtained product is too large, it will affect its flow performance, and when the molecular weight is too small, it will affect its compressive strength. Compared with other products, the products obtained in Example 4 (the molecular weight of the obtained adjuvant is 19280) and Example 5 (the molecular weight of the obtained adjuvant is 17720) have appropriate molecular weight, large net paste fluidity, large compressive strength and small change value after storage, and are suitable for concrete water reducing agent. Therefore, in summary, the lignin depolymerization product modified melamine functional adjuvant obtained by the present application has a molecular weight of 10000-25000, which is suitable for concrete water reducing agent.

[0103] Application Example 4

[0104] Application of lignin depolymerization product modified melamine functional adjuvant as coal water slurry dispersant

[0105] To investigate the possibility of the product as a coal water slurry additive, the dispersibility and stability of the coal water slurry of the products obtained in Examples 1-8 and Comparative Examples 1-2 were tested. Black mountain coal was selected as the research object, after crushing, ore grinding, screening and grading, a certain amount of water and the product as dispersant (addition amount was 0.3wt%) were added, stirred uniformly, and different concentrations of coal water slurry were obtained, and the test results are shown in Table 5.

[0106] Table 5: Comparison of dispersibility and stability of the products

[0107]

[0108] As can be seen from the results of Table 5, when the molecular weight of the obtained product is too large, the additive can cause a significant increase in the viscosity of the coal water slurry, thereby reducing the flowability of the coal water slurry; when the molecular weight is too small, the additive can perform poorly in maintaining the suspended state of coal particles, failing to provide sufficient protection against settling and aggregation, and thus reducing the stability of the coal water slurry. Compared with other products, the products obtained in Example 7 (with a molecular weight of 28270) and Example 8 (with a molecular weight of 27230) have a suitable molecular weight, a high slurry concentration, and a large viscosity, and are suitable as coal water slurry dispersants. Therefore, in summary, the lignin depolymerization product modified melamine functional additive obtained in the present application has a molecular weight of 20,000-35,000, and is suitable as a coal water slurry dispersant.

[0109] Application Example 5

[0110] Application of the lignin depolymerization product modified melamine functional additive as a soil improver

[0111] To investigate the possibility of the product as a soil improver, the properties of the products obtained in Examples 1-8 and Comparative Examples 1-2 were tested according to GB / T 42817-2023, with yellow-red soil as the soil matrix. The test results are shown in Table 6.

[0112] Table 6 Comparison of soil bulk density, soil pH value, and soil organic matter of the products

[0113]

[0114] As can be seen from the results of Table 6, the additive with a smaller molecular weight has a smaller effect on the soil bulk density and organic matter content, and the additive with a larger molecular weight has a larger effect on the soil bulk density and organic matter content. The additive with a larger molecular weight can increase the contact area and structural stability between soils, thereby reducing the bulk density. Compared with other products, the products obtained in Example 7 (with a molecular weight of 28270) and Example 8 (with a molecular weight of 27230) have a suitable molecular weight, the best improvement effect on soil bulk density, a large increase in soil pH value, and the most obvious improvement effect on soil organic matter content, and are suitable as soil improvers. Therefore, in summary, the lignin depolymerization product modified melamine functional additive obtained in the present application has a molecular weight of 25,000-40,000, and is suitable as a soil improver.

[0115] As can be known from the above, the lignin depolymerization product with rich active functional groups such as phenolic hydroxyl, methoxyl, ester group and the like is obtained by depolymerizing lignin, the modified melamine functional aid of the lignin depolymerization product is prepared through hydroxymethylation, sulfonation, acid polymerization, alkaline reforming and spray drying, and has good dispersing performance, compatibility and high water reducing rate. Therefore, the modified melamine functional aid of the lignin depolymerization product has water reducing, grinding aid, dispersing and reinforcing effects, can be used as ceramic additives, soil improvers, dye dispersants, concrete water reducing agents and coal water slurry dispersants, and shows strong market potential and environmental protection value.

[0116] Finally, it should be noted that although the above embodiments have been described in the specification of the application, the patent protection scope of the application should not be limited. Any technical solution obtained by replacing or modifying the equivalent structure or equivalent process based on the essential concept of the application, using the content described in the specification of the application, and directly or indirectly implementing the technical solutions of the above embodiments in other related technical fields, is included in the patent protection scope of the application.

Claims

1. A method for preparing a melamine-based functional additive modified from lignin depolymerization products, characterized in that, Includes the following steps: S1. Stir lignin, activator and water evenly, add catalyst to carry out hydrothermal reaction, and after the reaction solution is cooled and solid residue is removed, liquid lignin depolymerization product is obtained. S2. Melamine, aldehyde compound and water are added to the lignin depolymerization product, stirred evenly and heated to the first temperature for the first time period, and then sulfonating agent is added and heated to the second temperature for the second time period. S3. Cool down to the third temperature, add an acidic regulator to adjust the reaction system to the first pH value, carry out the third time period of acidic polycondensation reaction, add an alkaline regulator to adjust the reaction system to the second pH value, heat up to the fourth temperature and react for the fourth time period, cool down and discharge the material, spray dry, and obtain the lignin depolymerization product modified melamine functional additive. The usage of each raw material, expressed as a percentage by mass, is as follows: Lignin 5.0%–20.0%; Activator 5%–10%; Catalyst 0.3%–1.0%; Melamine content: 6.5%–15.5%; Aldehydes accounted for 19.0%–34.0%; Sulfonating agent 10.0%~18.0%; Acidity regulator 0.1%–1.5%; Alkalinity regulator: 0.2%–0.8%; Water content: 25.0%–50.0%; The activator is an alkaline activator, selected from one or more of KOH, NaOH, Ca(OH)2, Mg(OH)2, LiOH, and MgO; The catalyst is a metal catalyst, selected from one or more of Ni-Fe, Ni-Co, Ni-Mg, Ni-Zn, Ni-Al, and Ni-Zn-Co.

2. The preparation method according to claim 1, characterized in that, The aldehyde compounds are one or more of formaldehyde, acetaldehyde, glyoxal, butyraldehyde, isobutyraldehyde, or glutaraldehyde.

3. The preparation method according to claim 1, characterized in that, The sulfonating agent is one or more of sodium sulfite, sodium bisulfite, sodium metabisulfite, potassium sulfite, ammonium sulfite, aminosulfonic acid, and sodium p-aminobenzenesulfonate.

4. The preparation method according to claim 1, characterized in that, The first temperature is 50–80°C, and the first time period is 0.5–2.5 h.

5. The preparation method according to claim 4, characterized in that, The second temperature is 75–105℃, and the second time period is 1–3 hours.

6. The preparation method according to claim 1, characterized in that, The third temperature is 55–85°C, the first pH value is 4–6, and the third time period is 0.5–2.5 h.

7. The preparation method according to claim 6, characterized in that, The fourth temperature is 60–90°C, the second pH value is 8–10, and the fourth time period is 2–4 hours.

8. The preparation method according to claim 1, characterized in that, In step S1, the temperature of the hydrothermal reaction is 180–250°C, the reaction time is 1–5 h, and the reaction solution is cooled to 35–50°C.

9. A melamine-based functional additive modified with lignin depolymerization products, characterized in that, It is prepared by any one of the preparation methods in claims 1-8.

10. A melamine-based functional additive modified with lignin depolymerization products according to claim 9, characterized in that, The relative molecular mass Mn of the lignin depolymerization product modified melamine-based functional additive is 4300-40000.

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