A polycarboxylate dispersant and its preparation method and application

Abstract

The present invention provides a polycarboxylate dispersant. By introducing a macromolecular lignin sulfonate group containing a large number of sulfonic acid groups, alcoholic hydroxyl groups, phenolic hydroxyl groups, and benzene rings, and a polyether structure into the polycarboxylate structure, the polycarboxylate dispersant, described herein, is used in pesticide dry suspension concentrates and exhibits advantages such as a higher suspension rate, longer-lasting thermal storage stability, and improved salt resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of pesticide adjuvants, and in particular to a polylignin sulfonate modified polycarboxylate dispersant and a preparation method thereof. Background Art

[0002] Polycarboxylate dispersants have long carbon chains, numerous active adsorption sites, and side chains that act as steric repulsion. Due to their unique structure, they possess excellent dispersing properties in suspended systems. They are high-performance hyperdispersants widely used in industries such as high-performance concrete, coatings, inks, and pesticides. Early polycarboxylates were primarily copolymerized with carboxylic acid monomers and other unsaturated monomers, which presented numerous challenges in their application across various industries. Consequently, lignin sulfonates, the most commercially important derivative of lignin, are inexpensive and readily available. Combined with their inherent ability to act as dispersants and possessing multiple active functional groups, polycarboxylates can be easily modified through chemical reactions. Consequently, they are commonly used as raw materials to improve the performance of polycarboxylates.

[0003] At present, polycarboxylates chemically modified by lignin sulfonates are mainly used in cement water reducers, coal water slurry additives, water treatment agents and other fields. There are almost no reports on their application in pesticides. The main approaches are summarized as follows:

[0004] Pathway 1: Free radical polymerization of lignin sulfonate double bonds with unsaturated carboxylic acid monomers. For example, in patent application No. 202010308414.6, the carbon-carbon double bonds of sodium lignosulfate are polymerized with the carbon-carbon double bonds of polyoxyethylene allyl ester. The resulting composition reacts with styrene-maleic anhydride copolymer to form a composite water reducer. However, lignin itself is a copolymer macromolecule with a very low content of carbon-carbon double bonds. Therefore, using its unsaturated double bonds for main chain copolymerization is not only hindered by steric hindrance, but also difficult or inefficient due to the low content of double bonds. Consequently, the proportion of double bonds actually participating in the copolymerization is very small, thus failing to significantly improve performance.

[0005] Pathway 2: The hydroxyl group of lignin sulfonate is esterified with a small monomer, an unsaturated carboxylic acid, and then used as an unsaturated monomer in a free radical polymerization to synthesize a polycarboxylate with a side-chain lignin sulfonate graft copolymer. For example, Patent ZL201410673611.2 first produces a modified calcium lignin sulfonate by an esterification condensation reaction between calcium lignin sulfonate and acrylic acid. Then, using the monomer methyl allyl polyoxyethylene ether, modified calcium lignin sulfonate, and acrylic acid, a modified polycarboxylate superplasticizer is produced through free radical copolymerization in the presence of a chain transfer agent, sodium methacrylate sulfonate, and an initiator, ammonium persulfate. These esterification condensations of lignin sulfonate with acrylic acid are all carried out in deionized water. As is well known, esterification reactions are reversible, and the presence of large amounts of water in the system can result in very low reaction yields or even no reaction. Therefore, the esterification grafting modification strategy described in the above patent is not very feasible.

[0006] Route 3: Synthesize lignin as a halogenated initiator for ATRP polymerization or a chain transfer agent for RAFT polymerization. This introduces terminal polycarboxylates, which not only achieves controllable polymerization but also allows for modification of the polycarboxylates via the lignin base. For example, US9914870B2 esterifies the phenolic hydroxyl groups on lignin with 2-bromoisobutyryl bromide, followed by atom transfer radical polymerization (ATRP) with methyl methacrylate. The Xu group (Green Chemistry, DOI: 10.1039 / C6GC00859C) reacted the alcoholic hydroxyl groups in the lignin structure with 4-cyano-4-(phenylcarbonylthio)pentanoic acid to form a lignin macromolecular chain transfer agent. This was then RAFT-polymerized with C=C unsaturated monomers in dry toluene. Since the lignin used is insoluble in water, each of the above reactions needs to be carried out in an organic solvent, such as pyridine, tetrahydrofuran, dichloromethane, toluene, etc., and expensive bromoisobutyryl bromide and 4-cyano-4-(phenylcarbonylsulfonylthio) valeric acid reagents are also required. These will increase the difficulty and cost of operation in actual large-scale industrial production. Wang Guangbin's master's thesis (Chinese Academy of Forestry, 2019.) uses lignin sulfonate phenolic hydroxyl groups to react with carbon disulfide in an alkaline solution, further reacts with methyl bromoacetate to form a sulfonated lignin-based chain transfer agent, and then further reacts with acrylamide for RAFT polymerization. Although all of them are carried out in the aqueous phase, the carbon disulfide used belongs to the top ten malodorous raw materials, and it is volatile, toxic, and has the risk of polluting the production environment.

[0007] In the pesticide industry, companies are gradually emerging that are engaged in the research and production of polycarboxylate dispersants. However, they are all copolymerized carboxylic acid monomers and other unsaturated monomers in organic solvents. On the one hand, the process operation is cumbersome, and the raw materials used are expensive and the high cost leads to high product prices. On the other hand, due to the late start of domestic research on this topic, the basic theoretical research on carboxylate copolymer dispersants is weak. Therefore, the types of pesticide polycarboxylate dispersants developed and their application performance, including grinding viscosity, salt resistance, and dispersion effect, are not ideal. Summary of the Invention

[0008] 1. Problem to be solved

[0009] In view of the problem that the existing polycarboxylate dispersant products used in the pesticide field have unsatisfactory performance, one of the purposes of the present invention is to provide a polycarboxylate dispersant;

[0010] In view of the problems of poor operability and industrial applicability of the existing preparation methods of polycarboxylate dispersant products used in the pesticide field, the second object of the present invention is to provide a preparation method of a polycarboxylate dispersant.

[0011] 2. Technical solution

[0012] One of the objects of the present invention is to provide a method for preparing a polycarboxylate dispersant, which comprises the following steps:

[0013] At least the following steps are included:

[0014] S1. First, lignin sulfonate is treated with hydrochloric acid; then, it is reacted with sodium trithiocarbonate to obtain a poly-lignin sulfonate chain transfer agent; wherein the poly-lignin sulfonate chain transfer agent unit structure is shown in the following general formula 1:

[0015]

[0016] S2. In the presence of an initiator, a polylignin sulfonate-based chain transfer agent reacts with an unsaturated acid, an unsaturated acid polyether ester, and an unsaturated macromonomer. After the reaction is completed, the pH value is adjusted (using an alkali) to a range of 7 to 9 to obtain the polycarboxylate dispersant.

[0017] By preparing a poly-lignin sulfonate-based star-shaped chain transfer agent as a RAFT agent, poly-lignin sulfonate groups can be efficiently and directly introduced into the polycarboxylate end groups and chains, forming a divergent poly-lignin sulfonate-based star-shaped modified polycarboxylate structure. Furthermore, a large number of active groups from the lignin sulfonate are introduced. This significantly increases the steric hindrance of the poly-lignin sulfonate-modified polycarboxylate dispersant, helping to improve the suspension efficiency, thermal storage stability, and salt resistance of the application formulation.

[0018] Furthermore, the general structural formula of the unsaturated acid is shown in the following general formula 2:

[0019]

[0020] R1 is any one of -H or -CH3;

[0021] R2 is z is an integer satisfying 0≤z≤3, when When present, it can form anhydrides with COOH;

[0022] The general structural formula of the unsaturated acid polyether ester is shown in the following general formula 3:

[0023]

[0024] R3 is any one of -H or -CH3;

[0025] m is any integer from 1 to 50;

[0026] n is any integer from 1 to 20;

[0027] The general structural formula of the unsaturated macromonomer is shown in the following general formula 4:

[0028]

[0029] o is any integer from 2 to 40;

[0030] k is any integer from 2 to 40;

[0031] p is any integer between 0 and 1.

[0032] Furthermore, the unsaturated acid is preferably any one or more of itaconic acid, maleic anhydride, acrylic acid, fumaric acid, methacrylic acid, and itaconic anhydride;

[0033] The unsaturated acid polyether ester is preferably any one or more of C1-C18 alkyl alcohol polyoxyethylene ether (EO=1-50) acrylate and C1-C18 alkyl alcohol polyoxyethylene ether (EO=1-50) methacrylate;

[0034] The unsaturated macromonomer is preferably any one or more of allyl polyoxyethylene ether (EO=2-40) and allyl polyoxyethylene polyoxypropylene methyl ether (EO=2-40 / PO=2-40 mixed).

[0035] Furthermore, the unsaturated acid polyether ester can be synthesized in a variety of ways according to existing technologies: 1) direct catalytic esterification of polyether and unsaturated acid (Yang Xiaoling. Synthesis of fatty alcohol polyoxyethylene ether methacrylate [J]. Applied Chemical Industry, 2013, 42 (8): 1445-1447; Liu Yunlong. Preparation and characterization of acrylic acid polyethylene glycol-400 monoester [J]. Plastics Industry, 2009, 37 (10): 9-12; US6362364; CN10111738A); 2) catalytic transesterification of polyether and unsaturated acid ester (CN101092478A; CN1316398A; Liu Jixian. Preparation and characterization of fatty alcohol polyoxyethylene ether methacrylate [J]. Petrochemical Industry, 2008, 37 (2): 174-177).

[0036] In the present invention, the unsaturated acid polyether ester can be prepared by the following method: unsaturated carboxylic acid or carboxylic acid ester and polyether alcohol are reacted in the presence of a catalyst and a polymerization inhibitor, with water as the water-carrying agent, at a reaction temperature of 70-150° C. for 5-20 hours.

[0037] Furthermore, the initiator is preferably a water-soluble azo compound initiator, further one or more of azobisisobutylamidine hydrochloride, 4,4'azobis(4-cyanovaleric acid), cumene hydroperoxide, and tert-butyl peroxide.

[0038] The alkali is one of sodium hydroxide, potassium hydroxide, ethanolamine, triethanolamine or ammonia water.

[0039] Furthermore, in S1, the molar ratio of the lignin sulfonate, hydrochloric acid, and sodium trithiocarbonate is 1:(1-3):(0.5-1.5).

[0040] Furthermore, in S1, the lignin sulfonate is treated with a hydrochloric acid solution and then reacted with a solution containing sodium trithiocarbonate; wherein,

[0041] The concentration of the hydrochloric acid solution is 35wt%;

[0042] The concentration of sodium trithiocarbonate in the solution is 40 wt %.

[0043] Furthermore, in S2, the molar ratio of the monomer unsaturated acid, the monomer unsaturated acid polyether ester, and the unsaturated macromonomer is 1:(0.5-5):(0.5-5); the monomer unsaturated acid polyether ester and the unsaturated macromonomer both have long polyether chains, large molecular weights, and large steric hindrances, which will lead to decreased polymerization activity. Therefore, the preferred molar ratio should not be higher than that of the unsaturated acid;

[0044] The amount of the polylignin sulfonate chain transfer agent is 0.5% to 5% of the total molar amount of the unsaturated acid, the monomeric unsaturated acid polyether ester and the unsaturated macromonomer;

[0045] The dosage of the initiator is 0.5% to 5% of the total molar amount of the unsaturated acid, the monomeric unsaturated acid polyether ester and the unsaturated macromonomer.

[0046] Furthermore, in S1, a hydrochloric acid solution is added dropwise to the lignin sulfonate solution at a temperature of 30-40° C., and the reaction is carried out until the pH value reaches 7-8;

[0047] Then, a solution containing sodium trithiocarbonate is added dropwise, and after the addition is completed, a heat preservation treatment is performed, and after the temperature is lowered, an aqueous solution containing a poly-lignin sulfonate-based star-shaped structure chain transfer agent is obtained.

[0048] Furthermore, in S2, the polylignin sulfonate-based chain transfer agent is contacted and mixed with the unsaturated acid, unsaturated acid polyether ester and unsaturated macromonomer, and then reacted under N2 atmosphere at 50-120°C for 5-12 hours, then reduced to 40°C and spray-dried to obtain a powder solid, which is the polycarboxylate dispersant.

[0049] A polycarboxylate dispersant, wherein the polycarboxylate dispersant is a polylignin sulfonate modified polycarboxylate star-shaped structure dispersant having a weight average molecular weight in the range of 20,000 to 30,000;

[0050] The polycarboxylate dispersant is prepared by any of the above methods.

[0051] Any of the above-mentioned polycarboxylate dispersants is used as a pesticide dispersant.

[0052] Beneficial effects

[0053] The polycarboxylate dispersant provided by the present invention starts from the structure of the polycarboxylate and uses a homemade lignin sulfonate star-shaped chain transfer agent to participate in RAFT polymerization to modify it:

[0054] 1. More efficiently and directly introduce lignin sulfonate groups to form a special star-shaped polycarboxylate structure with multiple lignin sulfonate groups at the end and in the chain, which greatly increases the steric hindrance, effectively prevents the aggregation of pesticide molecules, and improves the thermal storage temperature and suspension rate of the application preparation.

[0055] 2. Active groups such as macromolecular lignin sulfonate groups and polyether segments containing a large number of sulfonic acid groups, alcoholic hydroxyl groups, phenolic hydroxyl groups, and benzene rings are introduced into the terminal position of the polycarboxylate dispersant structure to act on the pesticide particles, so that it can be used in pesticide dry suspension concentrates. It has the advantages of low grinding viscosity, higher suspension rate, more lasting thermal storage stability, and better salt resistance.

[0056] 3. The raw materials used in preparing the lignin sulfonate chain transfer agent are inexpensive and readily available, resulting in low production costs. No foul-smelling, toxic, or volatile organic reagents are used, and water is used throughout the process, making it environmentally friendly. Furthermore, the synthesized chain transfer agent does not need to be separated from the reaction solution; the aqueous solution can be directly used in the next reaction, simplifying the process. Therefore, the process of the present invention is a pollution-free, clean production process with excellent industrial value. DETAILED DESCRIPTION

[0057] The present disclosure may be more readily understood by reference to the following description in conjunction with the examples, all of which constitute a part of this disclosure. It should be understood that the present disclosure is not limited to the specific products, methods, conditions, or parameters described and / or illustrated herein. Further, the terms used herein are for the purpose of describing specific embodiments by way of example only and are not intended to be limiting unless otherwise indicated.

[0058] It should also be understood that, for the sake of clarity, certain features of the present disclosure may be described herein in the context of separate embodiments, but may also be provided in combination with each other in a single embodiment. That is, unless clearly incompatible or specifically not included, each separate embodiment is considered to be combinable with any other embodiment, and the combination is considered to represent another different embodiment. Conversely, for the sake of simplicity, various features of the present disclosure described in the context of a single embodiment may also be provided individually or in any sub-combination. Finally, although a particular embodiment may be described as part of a series of steps or part of a more general structure, each step or sub-structure itself may also be considered to be an independent embodiment.

[0059] Unless otherwise indicated, it should be understood that each individual element in a list and each combination of individual elements in that list will be interpreted as a different embodiment. For example, a list of embodiments expressed as "A, B, or C" should be interpreted to include embodiments "A," "B," "C," "A or B," "A or C," "B or C," or "A, B, or C."

[0060] In this disclosure, the singular forms of the articles "a," "an," and "the" also include the corresponding plural reference, and a reference to a specific value includes at least that specific value unless the context clearly dictates otherwise. Thus, for example, a reference to "a substance" is a reference to at least one of that substance and equivalents thereof.

[0061] Terms including ordinal numbers such as "first" and "second" may be used to explain various components or fluids, but these components and fluids are not limited by these terms. Therefore, without departing from the teachings of the present disclosure, these terms are only used to distinguish the component / fluid from another component / fluid.

[0062] When items are described by using the conjunction terms "... and / or..." etc., the description should be understood to include any one and all combinations of one or more of the associated listed items.

[0063] In general, the use of the term "about" indicates an approximate value that can vary depending on the desired properties obtained by the disclosed subject matter and will be interpreted in a context-dependent manner based on function. Therefore, one of ordinary skill in the art will be able to interpret a certain degree of difference on a case-by-case basis. In some cases, the number of important figures used when expressing a particular value can be a representative technique for determining the difference allowed by the term "about". In other cases, a gradient in a range of values can be used to determine the range of differences allowed by the term "about". Further, all ranges in this disclosure are inclusive and combinable, and reference to a value stated in a range includes every value within that range.

[0064] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs; and the terms used herein include any and all combinations of one or more of the associated listed items.

[0065] The present invention is further described below with reference to specific examples, which, however, are not intended to limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0066] The essential features and significant effects of the present invention can be reflected in the following embodiments. The described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Therefore, they do not limit the present invention in any way. Those skilled in the art may make some non-essential improvements and adjustments based on the contents of the present invention, which all fall within the scope of protection of the present invention.

[0067] Example 1

[0068] Add 40g of water to 10g of sodium lignin sulfonate and stir to dissolve until clear. Raise the temperature to 30-40°C and dropwise add 1g of 35% concentrated hydrochloric acid. After addition, stir and react until the pH reaches 7-8. Maintain the temperature at 30-40°C and dropwise add 2g of a 40% aqueous sodium trithiocarbonate solution. After addition, maintain the temperature for 12 hours and cool to obtain a clear, brownish-yellow liquid, which is the aqueous solution of the poly-lignin sulfonate chain transfer agent.

[0069] 7.2 g of acrylic acid, 24.5 g of isotridecyl acrylate polyether ester (Mn=490 g / mol), 30 g of propylene glycol polyoxyethylene ether (Mn=600 g / mol) and water were added sequentially to the aqueous solution of the polylignin sulfonate chain transfer agent prepared in step (1) and mixed thoroughly. The temperature was raised to 80° C. under N2 protection, 3 g of cumene hydroperoxide was added, and a RAFT polymerization reaction was carried out in an aqueous medium for 12 hours. The temperature was then lowered to 40° C., the pH was adjusted to 7-9 with a sodium hydroxide aqueous solution, and the powder solid was obtained by spray drying to obtain the polylignin sulfonate modified polycarboxylate dispersant.

[0070] The weight average molecular weight of the prepared polylignin sulfonate modified polycarboxylate dispersant was determined to be 26,600 by gel chromatography coupled with laser light scattering, using a mixture of 50 mM NaH2PO4 solution and methanol (70:30% (v / v)) as the mobile phase and polyethylene glycol 10,000 as the standard.

[0071] Example 2

[0072] Add 40g of water to 10g of sodium lignin sulfonate and stir to dissolve until clear. Raise the temperature to 30-40°C and dropwise add 0.5g of 35% concentrated hydrochloric acid. After addition, stir and react until the pH reaches 7-8. Maintain the temperature at 30-40°C and dropwise add 1g of a 40% aqueous sodium trithiocarbonate solution. After addition, maintain the temperature for 12 hours and cool to obtain a clear, brownish-yellow liquid, which is the aqueous solution of the poly-lignin sulfonate chain transfer agent.

[0073] 7.2 g of acrylic acid, 37 g of isotridecyl acrylate polyether ester (Mn=490 g / mol), 45 g of propylene glycol polyoxyethylene ether (Mn=600 g / mol) and water were added to the aqueous solution of the polylignin sulfonate chain transfer agent prepared in step (1) in sequence and mixed thoroughly. The mixture was heated to 100° C. under N2 protection, 2.0 g of cumene hydroperoxide was added and RAFT polymerization was carried out in an aqueous medium for 8 hours. The mixture was cooled to 40° C., the pH was adjusted to 7-9 with an aqueous sodium hydroxide solution, and the mixture was spray-dried to obtain a powder solid, thereby obtaining a polylignin sulfonate-modified polycarboxylate dispersion.

[0074] The weight average molecular weight of the prepared polylignin sulfonate modified polycarboxylate dispersion was determined to be 27,300 by gel chromatography coupled with laser light scattering, using a 50 mM NaH2PO4 solution and a methanol mixture (70:30% (v / v)) as the mobile phase and polyethylene glycol 10,000 as the standard.

[0075] Example 3

[0076] Add 40g of water to 10g of sodium lignin sulfonate and stir to dissolve until clear. Raise the temperature to 30-40°C and dropwise add 0.35g of 35% concentrated hydrochloric acid. After addition, stir and react until the pH reaches 7-8. Maintain the temperature at 30-40°C and dropwise add 0.7g of a 40% aqueous sodium trithiocarbonate solution. After addition, maintain the temperature for 12 hours and cool to obtain a clear, brownish-yellow liquid, which is the aqueous solution of the poly-lignin sulfonate chain transfer agent.

[0077] 7.2 g of acrylic acid, 49 g of isotridecyl acrylate polyether ester (Mn=490 g / mol), 60 g of propylene glycol polyoxyethylene ether (Mn=600 g / mol) and water were added sequentially to the aqueous solution of the polylignin sulfonate-based RAFT chain transfer agent prepared in step (1), and the mixture was thoroughly mixed. The mixture was heated to 100° C. under N2 protection, and 1.2 g of cumene hydroperoxide was added to carry out RAFT polymerization in an aqueous medium for 8 hours. The temperature was then lowered to 40° C., and the pH was adjusted to 7-9 with an aqueous sodium hydroxide solution. The mixture was spray-dried to obtain a powder solid, thereby obtaining a polylignin sulfonate-modified polycarboxylate dispersion.

[0078] The weight average molecular weight of the prepared polylignin sulfonate modified polycarboxylate dispersion was determined to be 29800 by gel chromatography coupled with laser light scattering, using a 50 mM NaH2PO4 solution and a methanol mixture (70:30% (v / v)) as the mobile phase and polyethylene glycol 10000 as the standard.

[0079] Example 4

[0080] Add 40g of water to 10g of sodium lignin sulfonate and stir to dissolve until clear. Raise the temperature to 30-40°C and dropwise add 0.35g of 35% concentrated hydrochloric acid. After addition, stir and react until the pH reaches 7-8. Maintain the temperature at 30-40°C and dropwise add 0.7g of a 40% aqueous sodium trithiocarbonate solution. After addition, maintain the temperature for 12 hours and cool to obtain a clear, brownish-yellow liquid, which is the aqueous solution of the poly-lignin sulfonate chain transfer agent.

[0081] 8.6 g of methacrylic acid, 24.5 g of isotridecyl acrylate polyether ester (Mn=490 g / mol), 30 g of propylene glycol polyoxyethylene ether (Mn=600 g / mol) and water were added sequentially to the aqueous solution of the polylignin sulfonate-based RAFT chain transfer agent prepared in step (1) and mixed thoroughly. The mixture was heated to 100° C. under N2 protection, and 0.5 g of azobisisobutylamidine hydrochloride was added to carry out RAFT polymerization in an aqueous medium for 8 hours. The mixture was then cooled to 40° C. and the pH was adjusted to 7-9 with a sodium hydroxide aqueous solution. The mixture was spray-dried to obtain a powder solid, thereby obtaining a polylignin sulfonate-modified polycarboxylate dispersion.

[0082] The weight average molecular weight of the prepared polylignin sulfonate modified polycarboxylate dispersion was determined to be 28400 by gel chromatography coupled with laser light scattering, using a 50 mM NaH2PO4 solution and a methanol mixture (70:30% (v / v)) as the mobile phase and polyethylene glycol 10000 as the standard.

[0083] Example 5

[0084] Add 40g of water to 10g of sodium lignin sulfonate and stir to dissolve until clear. Raise the temperature to 30-40°C and dropwise add 0.35g of 35% concentrated hydrochloric acid. After addition, stir and react until the pH reaches 7-8. Maintain the temperature at 30-40°C and dropwise add 0.7g of a 40% aqueous sodium trithiocarbonate solution. After addition, maintain the temperature for 12 hours and cool to obtain a clear, brownish-yellow liquid, which is an aqueous solution of a poly-lignin sulfonate-based RAFT chain transfer agent.

[0085] 9.8 g of maleic anhydride, 24.5 g of isotridecyl acrylate polyether ester (Mn=490 g / mol), 30 g of propylene glycol polyoxyethylene ether (Mn=600 g / mol) and water were added to the aqueous solution of the polylignin sulfonate chain transfer agent prepared in step (1) in sequence and mixed thoroughly. The mixture was heated to 100° C. under N2 protection, and 0.5 g of tert-butyl peroxide was added to carry out RAFT polymerization in an aqueous medium for 8 hours. The mixture was cooled to 40° C. and the pH was adjusted to 7-9 with an aqueous sodium hydroxide solution. The mixture was spray-dried to obtain a powder solid, which is a polylignin sulfonate modified polycarboxylate dispersion.

[0086] The weight average molecular weight of the prepared polylignin sulfonate modified polycarboxylate dispersion was determined to be 27,800 by gel chromatography coupled with laser light scattering, using a 50 mM NaH2PO4 solution and a methanol mixture (70:30% (v / v)) as the mobile phase and polyethylene glycol 10,000 as the standard.

[0087] Example 6

[0088] Add 40g of water to 10g of sodium lignin sulfonate and stir to dissolve until clear. Raise the temperature to 30-40°C and dropwise add 0.35g of 35% concentrated hydrochloric acid. After addition, stir and react until the pH reaches 7-8. Maintain the temperature at 30-40°C and dropwise add 0.7g of a 40% aqueous sodium trithiocarbonate solution. After addition, maintain the temperature for 12 hours and cool to obtain a clear, brownish-yellow liquid, which is the aqueous solution of the poly-lignin sulfonate chain transfer agent.

[0089] 7.2 g of acrylic acid, 22.4 g of acrylic acid isomeric decanol polyether ester (Mn=448 g / mol), 50 g of propenyl polyoxyethylene ether (Mn=1000 g / mol) and water were added sequentially to the aqueous solution of the polylignin sulfonate-based chain transfer agent prepared in step (1) and mixed thoroughly. The mixture was heated to 100° C. under N2 protection, and 0.5 g of tert-butyl peroxide was added to carry out RAFT polymerization in an aqueous medium for 8 hours. The mixture was then cooled to 40° C. and the pH was adjusted to 7-9 with a potassium hydroxide aqueous solution. The mixture was spray-dried to obtain a powder solid, thus obtaining a polylignin sulfonate-modified polycarboxylate dispersion.

[0090] The weight average molecular weight of the prepared polylignin sulfonate modified polycarboxylate dispersion was determined to be 30,000 by gel chromatography coupled with laser light scattering, using a 50 mM NaH2PO4 solution and a methanol mixture (70:30% (v / v)) as the mobile phase and polyethylene glycol 10,000 as the standard.

[0091] Example 7

[0092] Add 40g of water to 10g of sodium lignin sulfonate and stir to dissolve until clear. Raise the temperature to 30-40°C and dropwise add 0.35g of 35% concentrated hydrochloric acid. After addition, stir and react until the pH reaches 7-8. Maintain the temperature at 30-40°C and dropwise add 0.7g of a 40% aqueous sodium trithiocarbonate solution. After addition, maintain the temperature for 12 hours and cool to obtain a clear, brownish-yellow liquid, which is the aqueous solution of the poly-lignin sulfonate chain transfer agent.

[0093] 11.6 g of fumaric acid, 52.7 g of methyl acrylate polyether ester (Mn=1054 g / mol), 50 g of propylene polyoxyethylene ether (Mn=1000 g / mol) and water were added to the aqueous solution of the polylignin sulfonate chain transfer agent prepared in step (1) in sequence and mixed thoroughly. The mixture was heated to 100° C. under N2 protection, and 0.5 g of dibenzoyl peroxide was added to carry out RAFT polymerization in an aqueous medium for 8 hours. The temperature was then lowered to 40° C., and the pH was adjusted to 7-9 with an ethanolamine aqueous solution. The mixture was spray-dried to obtain a powder solid, thereby obtaining a polylignin sulfonate-modified polycarboxylate dispersion.

[0094] The weight average molecular weight of the prepared polylignin sulfonate modified polycarboxylate dispersion was determined to be 20,000 by gel chromatography coupled with laser light scattering, using a 50 mM NaH2PO4 solution and a methanol mixture (70:30% (v / v)) as the mobile phase and polyethylene glycol 10,000 as the standard.

[0095] Example 8

[0096] Add 40g of water to 10g of sodium lignin sulfonate and stir to dissolve until clear. Raise the temperature to 30-40°C and dropwise add 0.35g of 35% concentrated hydrochloric acid. After addition, stir and react until the pH reaches 7-8. Maintain the temperature at 30-40°C and dropwise add 0.7g of a 40% aqueous sodium trithiocarbonate solution. After addition, maintain the temperature for 12 hours and cool to obtain a clear, brownish-yellow liquid, which is the aqueous solution of the poly-lignin sulfonate chain transfer agent.

[0097] 13 g of itaconic acid, 32.5 g of isotridecyl acrylate polyether ester (Mn=650 g / mol), 30 g of propylene glycol polyoxyethylene ether (Mn=600 g / mol) and water were added to the aqueous solution of the polylignin sulfonate chain transfer agent prepared in step (1) in sequence and mixed thoroughly. The mixture was heated to 100° C. under N2 protection, and 0.5 g of dibenzoyl peroxide was added to carry out RAFT polymerization in an aqueous medium for 8 hours. The mixture was then cooled to 40° C. and the pH was adjusted to 7-9 with an aqueous ammonia solution. The mixture was spray-dried to obtain a powder solid, thus obtaining a polylignin sulfonate-modified polycarboxylate dispersion.

[0098] The weight average molecular weight of the prepared polylignin sulfonate modified polycarboxylate dispersion was determined to be 24,800 by gel chromatography coupled with laser light scattering, using a 50 mM NaH2PO4 solution and a methanol mixture (70:30% (v / v)) as the mobile phase and polyethylene glycol 10,000 as the standard.

[0099] Application Example 1

[0100] The polylignin sulfonate modified polycarboxylate prepared in Examples 1-8 of the present invention was used as a dispersant to prepare a 70% pyraclostrobin-propineb dry suspension concentrate, which was compared with similar products such as domestic SD-816 (Shida) and imported Tesperse 2700 (Huntsman).

[0101] The 70% pyraclostrobin-propineb dry suspension concentrate includes the following components in percentage by weight: 5% pyraclostrobin, 65% propineb, 3% TERWET 1004, 6% polylignin sulfonate-modified polycarboxylate, 2% D-425, 5% ammonium sulfate, 2% sucrose, 0.3% organosilicon defoamer, and kaolin to 100%.

[0102] Grinding process:

[0103] Add polylignin sulfonate-modified polycarboxylate, D-425, citric acid, wetting agent 1004, ammonium sulfate, sucrose, silicone defoamer, kaolin, water, pyraclostrobin, and propineb into a stirred tank, controlling the water content to 35% ground solids. Mix thoroughly. Wet sand mill the material at 1800 rpm using 1.6 mm zirconia sand mill media equal in weight to the material. Keep the grinding temperature between 20-40°C until the particle size (D90) is less than 5 μm.

[0104] Spray drying:

[0105] The spray drying parameters were set as an inlet air temperature of 132° C., an outlet air temperature of 60.5° C., and a feed pressure of 3 MP, and spray drying was performed to obtain a 70% pyraclostrobin·propineb dry suspension product.

[0106] The test content and methods are as follows:

[0107] 1. Grinding viscosity

[0108] Under the same conditions, wet sand grinding is performed on a sand mill. The viscosity of the liquid is tested during the grinding process by adding different additives.

[0109] 2. Suspension rate determination

[0110] The suspension rate was determined according to the method of GB / T14825.

[0111] 3. Disintegration in water

[0112] In a 25°C constant temperature bath, take a 100mL stoppered graduated cylinder (inner height 22.5cm, inner diameter 28mm) and add 90mL of distilled water; add 0.5g of water-dispersible granule sample into the graduated cylinder, clamp the middle of the stoppered graduated cylinder, plug the mouth of the graduated cylinder, and rotate around the center at a speed of 8r / min until the sample is completely disintegrated and dispersed in the graduated cylinder. Record the disintegration time. The disintegration time is used to detect the disintegration property, which is generally stipulated to be less than 3min.

[0113] 4. Thermal Storage Stability

[0114] The water-dispersible granules were placed into ampoules, 5.0 g per bottle, sealed, and placed in an oven at 54°C to 52°C. After heat storage for 14 days, the suspension rate of the water-dispersible granules after heat storage was measured according to the method of GB / T19136-2003.

[0115] 5. Dispersibility

[0116] Fill 99 mL of tap water into a 100 mL graduated cylinder, weigh 1 g of dry suspension sample, and

[0117] The particles were poured into water and visually observed for dispersion. Dispersion was classified into three levels: excellent, good, and poor. Excellent dispersion refers to rapid dispersion, with a mist-like distribution. Good dispersion refers to spontaneous dispersion in water, with some particles slowly sinking, but resuming dispersion after a period of gentle shaking. Poor dispersion refers to a lack of dispersion in water, with many particles sinking directly. Sinking particles require vigorous shaking to disperse, and some may not disperse at all. The results are shown in Table 1.

[0118] Table 1 Dispersion effect of 70% pyraclostrobin·propineb dry suspension prepared by various dispersants in triple standard hard water

[0119]

[0120]

[0121] Application Example 2

[0122] The polylignin sulfonate-modified polycarboxylate prepared in Examples 1-8 of the present invention was used as a dispersant to prepare a 10% pyraclostrobin + 30% tebuconazole dry suspension concentrate, which was compared with similar products such as domestic SD-816 (Shida) and imported Tesperse2700 (Huntsman).

[0123] The 10% pyraclostrobin+30% tebuconazole dry suspension concentrate includes the following components in percentage by mass: sp-2836: 5%, polylignin sulfonate end-group polycarboxylate: 15%, wetting agent K12: 1%, and filler precipitated barium sulfate makes up 100%.

[0124] Grinding process: SP-2836, polylignin sulfonate-modified polycarboxylate, wetting agent K12, barium sulfate, water, pyraclostrobin, and tebuconazole are placed in a stirred tank in the order specified, with the water level controlled to achieve a grinding solids content of 45%. Stir thoroughly. Using a 1.6mm zirconia grinding medium equal in weight to the material, wet sand mill at 1800 rpm and a grinding temperature of 20-40°C until the particle size D90 is less than 5μm.

[0125] Spray drying: The spray drying parameters were set at an inlet air temperature of 110°C, an outlet air temperature of 60°C, and a feed pressure of 3 MPa. Spray drying was performed to obtain a 10% pyraclostrobin + 30% tebuconazole dry suspension product. The results are shown in Table 2 below:

[0126] Table 2 Dispersion effect of 10% pyraclostrobin + 30% tebuconazole dry suspension prepared by each dispersant in triple standard hard water

[0127] dispersants Grinding viscosity / mPa·s Disintegration / s Dispersibility Suspension rate / % Thermal storage stability / % Example 1 388 28 excellent 97％ 96％ Example 2 399 29 excellent 95.5％ 93％ Example 3 393 30 excellent 94％ 93％ Example 4 388 31 excellent 98％ 97.5％ Example 5 392 33 good 96％ 94％ Example 6 390 34 good 94％ 92％ Example 7 396 32 good 95.7％ 95％ Example 8 390 32 excellent 96.4％ 95％ 2700 398 34 excellent 92％ 89％ SD-816 412 33 good 90％ 86％

[0128] As shown in Tables 1 and 2, Tesperse 2700 and most of the polylignin sulfonate-terminated polycarboxylates of Examples 1-8, used as dispersants for preparing 70% pyraclostrobin and propineb and 10% pyraclostrobin + 30% tebuconazole dry suspensions, exhibited superior dispersibility in triple-hard water, while SD-816 exhibited slightly inferior dispersibility. However, neither Tesperse 2700 nor SD-816 exhibited comparable viscosity reduction, disintegration in triple-hard water, suspension efficiency, and thermal storage stability compared to the star-shaped polylignin sulfonate-modified polycarboxylate dispersants of Examples 1-8. This is because the polycarboxylates prepared in Examples 1-8 can be introduced into both ends and chains of macromolecular lignin sulfonate groups and polyether segments containing a large number of sulfonic acid groups, alcoholic hydroxyl groups, phenolic hydroxyl groups, and benzene rings. Active groups, such as lignin sulfonate groups, can have a strong ability to encapsulate and adsorb the original drug, have a good viscosity reduction effect during the grinding process, and make the entire system more uniformly crushed during the grinding process. In addition, it is known from relevant literature that sulfonic acid groups can enhance the salt resistance of the dispersant. As a strong hydrophilic group, it can also enable the preparation to quickly wet, disintegrate, and disperse in water, making the suspension system more stable. On the other hand, the star-shaped macromolecular polylignin sulfonate end groups can increase the steric hindrance of the polycarboxylate molecules, which is also beneficial for stabilizing the water-dispersible granule suspension system. Moreover, there are a large number of active groups on the polylignin sulfonate end groups, and the pesticide molecules contain a large amount of nitrogen and oxygen elements. The large number of active groups introduced are more likely to produce hydrogen bonds with the pesticide molecules, thereby making the dispersant more firmly adsorbed on the pesticide molecules, further increasing the stability of the dispersion system.

[0129] Therefore, the polylignin sulfonate-modified polycarboxylates in Examples 1 to 8 of the present invention are used to prepare 70% pyraclostrobin·propineb and 10% pyraclostrobin+30% tebuconazole dry suspension concentrates, which have better overall performance than similar products such as domestic SD-816 (Shida) and imported Tesperse 2700 (Huntsman).

[0130] Comparative Example 1

[0131] The types and amounts of raw materials involved in this comparative example are the same as those in Example 1, and the steps for preparing a lignin sulfonate-modified polycarboxylate dispersant are as follows:

[0132] a. Preparation of modified lignin sulfonate: 10 g of lignin sulfonate and 0.24 g of acrylic acid were weighed, 17 g of deionized water was added, and 0.26 g of 30% hydrogen peroxide solution was added as an initiator, and the mixture was reacted at 100° C. for 3 hours to obtain the modified lignin sulfonate;

[0133] b. Take 27.5 g of the modified lignin lignin sulfonate aqueous solution, 30 g of propylene glycol polyoxyethylene ether (Mn = 600 g / mol), 24.5 g of isomeric tridecyl alcohol polyether acrylate (Mn = 490 g / mol), and 0.5 g of chain transfer agent sodium methacrylate sulfonate and add them to 55 g of deionized water to prepare a base solution;

[0134] c. Add 6.96 g of acrylic acid to 28 g of deionized water, mix well, and stir to prepare solution A.

[0135] d. Take 3 g of cumene hydroperoxide and add it to 180 g of deionized water, mix them, and stir them evenly to prepare solution B;

[0136] e. When the temperature of the base liquid is 80-90°C, solution A in step c is added dropwise to the base liquid for 1 hour, and solution B in step d is added dropwise to the base liquid for 1.5 hours;

[0137] f. After the addition is completed, the copolymerization reaction is carried out by heat preservation for 30 minutes. After the reaction is completed, 50% sodium hydroxide aqueous solution is added to adjust the pH value to 6-7, the mixture is stirred for 20 minutes, and the powder solid is obtained by spray drying to obtain the modified polycarboxylate water reducer.

[0138] The weight average molecular weight of the prepared poly-lignin sulfonate end-group polycarboxylate dispersant was determined to be 13600 by gel chromatography coupled with laser light scattering, using a mixture of 50 mM NaH2PO4 solution and methanol (70:30% (v / v)) as the mobile phase and polyethylene glycol 10000 as the standard.

[0139] The poly-lignin sulfonate modified polycarboxylate prepared in Comparative Example 1 was used as a dispersant to prepare a 70% pyraclostrobin-propineb dry suspension concentrate for comparison with Example 1. The results are shown in Table 3 below.

[0140] Table 3 Dispersion effect of 70% pyraclostrobin·propineb dry suspension prepared by various dispersants in triple standard hard water

[0141] dispersants Grinding viscosity / mPa·s Disintegration / s Dispersibility Suspension rate / % Thermal storage stability / % Example 1 300 30 excellent 90％ 90％ Comparative Example 1 608 78 Difference 80.5％ 67.5％

[0142] The polylignin sulfonate modified polycarboxylate prepared in Comparative Example 1 was used as a dispersant to prepare a 10% pyraclostrobin + 30% tebuconazole dry suspension concentrate, and compared with Example 1. The results are shown in Table 4 below.

[0143] Table 4 Dispersion effect of 10% pyraclostrobin + 30% tebuconazole dry suspension prepared by each dispersant in triple standard hard water

[0144] dispersants Grinding viscosity / mPa·s Disintegration / s Dispersibility Suspension rate / % Thermal storage stability / % Example 1 388 28 excellent 97％ 96％ Comparative Example 1 654 80 Difference 75.5％ 65％

[0145] The weight-average molecular weight of Comparative Example 1 is much lower than that of Example 1. Reasons for this: Comparative Example 1 synthesizes a modified lignin sulfonate polycarboxylate via a graft copolymerization process: In the first step, acrylic acid is prepared by esterification and esterified with the alcoholic hydroxyl groups of the lignin sulfonate. As is well known, lignin sulfonate is a high molecular weight with significant steric hindrance. Furthermore, the esterification reaction is reversible, and failure to promptly remove water from the system will result in a very low reaction yield or even no reaction. Insufficient grafting of the modified lignin sulfonate intermediate in the first step results in a very low lignin sulfonate content in the subsequent polycarboxylate product, thus failing to achieve the lignin sulfonate modification effect of Example 1. Therefore, the performance of Comparative Example 1 in both dry suspension concentrate formulations is significantly inferior to that of Example 1. Furthermore, the synthetic process of Comparative Example 1 is also less simple and convenient than that of Example 1.

[0146] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description. The above description of the disclosed embodiments enables professionals and technicians in this field to implement or use the present invention. Various modifications to these embodiments will be apparent to professionals and technicians in this field, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will comply with the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a polycarboxylate dispersant, characterized in that: The polycarboxylate dispersant is a polylignin sulfonate modified polycarboxylate dispersant; At least the following steps are included: S1. First, lignin sulfonate is treated with hydrochloric acid; then reacted with sodium trithiocarbonate to obtain a multi-lignin sulfonate-based star-shaped chain transfer agent; wherein the multi-lignin sulfonate-based star-shaped chain transfer agent unit structure is as follows: ； S2 in the presence of an initiator, the poly lignin sulfonate chain transfer agent and the unsaturated acid, unsaturated acid polyether ester and unsaturated macromonomer reaction, the reaction is completed to adjust the pH value in the range of 7 to 9 to obtain the poly lignin sulfonate modified polycarboxylate dispersant; The unsaturated acid is any one or more of acrylic acid, methacrylic acid, itaconic acid, and fumaric acid; The unsaturated acid polyether ester is an isomeric tridecanol polyether ester of acrylic acid; The unsaturated macromonomer is propylene polyoxyethylene ether.

2. The preparation method of a polycarboxylate dispersant according to claim 1, wherein The initiator is one or more of azobisisobutylamidine hydrochloride, 4,4'-azobis(4-cyanovaleric acid), cumene hydroperoxide, and tert-butyl peroxide.

3. The preparation method of a polycarboxylate dispersant according to claim 1, wherein In S1, the molar ratio of the lignin sulfonate, hydrochloric acid, and sodium trithiocarbonate is 1:(1-3):(0.5-1.5).

4. The preparation method of the polycarboxylate dispersant according to claim 3, wherein In S1, lignin sulfonate is treated with a hydrochloric acid solution and then reacted with a solution containing sodium trithiocarbonate; wherein, The concentration of the hydrochloric acid solution is 35wt%; The concentration of sodium trithiocarbonate in the solution is 40 wt %.

5. The preparation method of the polycarboxylate dispersant according to claim 1, wherein In S2, the molar ratio of the unsaturated acid, the unsaturated acid polyether ester, and the unsaturated macromonomer is 1:(0.5-5):(0.5-5); The amount of the polylignin sulfonate chain transfer agent is 0.5% to 5% of the total molar amount of the unsaturated acid, the unsaturated acid polyether ester and the unsaturated macromonomer; The amount of the initiator used is 0.5% to 5% of the total molar amount of the unsaturated acid, the unsaturated acid polyether ester and the unsaturated macromonomer.

6. The method for preparing a polycarboxylate dispersant according to any one of claims 1 to 5, wherein: In S1, a hydrochloric acid solution is added dropwise to a lignin sulfonate solution at a temperature of 30-40° C., and the reaction is carried out until the pH value reaches 7-8; Then, a solution containing sodium trithiocarbonate is added dropwise, and after the addition is completed, a heat preservation treatment is performed, and after the temperature is lowered, an aqueous solution containing a poly-lignin sulfonate-based star-shaped structure chain transfer agent is obtained.

7. The method for preparing a polycarboxylate dispersant according to any one of claims 1 to 5, wherein: In the S2, the polylignin sulfonate-based chain transfer agent is contacted and mixed with the unsaturated acid, unsaturated acid polyether ester and unsaturated macromonomer, and then reacted at 50-120° C. under initiator conditions and N2 atmosphere for 5-12 hours, then lowered to 40° C., adjusted to a pH value of 7-9, and spray-dried to obtain a powder solid, which is the polylignin sulfonate-modified polycarboxylate dispersant.

8. A polycarboxylate dispersant, characterized in that The polycarboxylate dispersant is a polylignin sulfonate modified polycarboxylate star-shaped structure dispersant having a weight average molecular weight in the range of 20,000 to 30,000; The polycarboxylate dispersant is prepared by the method according to any one of claims 1 to 7.

9. The use of a polycarboxylate dispersant prepared by the method according to any one of claims 1 to 7 or a polycarboxylate dispersant according to claim 8, characterized in that: It is used as a pesticide dispersant.

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