A biomass-based surfactant-type thickener and its preparation method

Abstract

This invention discloses a biomass-based surfactant-type thickener and its preparation method, belonging to the field of thickener technology. The thickener is prepared by emulsion polymerization using biomass-based surfactants such as dodecyl glucoside or sodium lauryl laurate, along with various monomers, including hydrophobic and hydrophilic monomers. The preparation process includes steps such as forming an initial emulsion aqueous phase, preparing a hydrophobic monomer emulsion, mixing functional monomers to form a composite emulsion, and temperature-controlled dropwise addition reaction. Compared with existing technologies, the thickener of this invention exhibits excellent high-temperature shear viscosity retention and structural recovery performance. Furthermore, being derived from biomass, it is environmentally friendly, readily degradable, and suitable for water-based systems such as latex paints and adhesives.

Description

Technical Field

[0001] This invention relates to the field of thickener technology, and in particular to a biomass-based surfactant-type thickener and its preparation method. Background Technology

[0002] With the widespread application of waterborne coatings, adhesives, and related waterborne systems, the performance requirements for thickeners, as crucial additives for regulating the rheological properties of these systems, are constantly increasing. Compared to traditional inorganic and cellulose-based thickeners, associative polymeric thickeners can form dynamic network structures in the aqueous phase through hydrophobic association and hydrogen bonding between molecules, offering significant advantages in improving application performance and storage stability. Meanwhile, biomass-based thickeners, based on renewable resources, are gradually becoming an important development direction in this field due to their environmental friendliness and biodegradability.

[0003] In the prior art, patent CN117586135 A achieves good thickening effect by synergistically constructing a thickening system with biomass-based surfactants and inorganic salts. However, this system is highly dependent on inorganic salts, and its structural stability is limited under complex usage conditions. Patent CN119775482 A prepares an associative emulsion thickener through copolymerization of multiple monomers, which improves the stability of latex paint under different temperature conditions to a certain extent. However, it mainly relies on petrochemical-based monomers, lacks a reversible associative structure, and there is still room for improvement in the synergistic effect between functional monomers.

[0004] In summary, on the one hand, existing thickener technologies for biomass-based thickening systems are sensitive to added salts or the operating environment, exhibiting limited high-temperature and shear stability. On the other hand, existing associative emulsion thickeners, while improving performance, often fail to simultaneously consider biomass source, structural recovery ability, and long-term stability. Therefore, there is an urgent need to develop a biomass-based surfactant-type thickener that achieves high stability and adaptability through the synergistic design of functional monomers and process optimization, based on a biomass-based surfactant system. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to provide a biomass-based surfactant-type thickener and its preparation method.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A method for preparing a biomass-based surfactant-type thickener is as follows: Step 1: Add biomass-based surfactants to water and form an initial emulsion aqueous phase under stirring conditions; Step 2: Mix dodecyl methacrylate, diethyl itaconic acid, and cyclohexyl methacrylate, then add water, biomass-based surfactant, and initiator, and disperse to obtain a hydrophobic monomer emulsion. Step 3: Add functional monomers, methyl acrylate, acrylic acid, 2-hydroxyethyl acrylate, diacetone acrylamide, N-ethylacrylamide, N-octylacrylamide, ethylene glycol dimethacrylate, water and biomass-based surfactants to the hydrophobic monomer emulsion, and form a composite monomer emulsion under stirring conditions. Step 4: The composite monomer emulsion is added dropwise to the initial emulsified aqueous phase under heating conditions. After the addition is complete, an initiator is added and the mixture is kept warm. After the reaction is complete, the mixture is cooled and filtered to obtain a biomass-based surfactant-type thickener.

[0007] The preparation method of the biomass-based surfactant-type thickener is as follows, in parts by weight: Step 1: Add 2.5-7 parts of biomass-based surfactant to 70-100 parts of water, and stir at 100-300 r / min for 10-40 min at 20-40℃ to form an initial emulsion aqueous phase; Step 2: Mix 20-35 parts of dodecyl methacrylate, 5-15 parts of diethyl itaconic acid, and 40-55 parts of cyclohexyl methacrylate evenly, then add 40-50 parts of water, 1-2 parts of biomass-based surfactant, and 0.04-0.08 parts of initiator. Disperse the mixture at 600-1200 r / min for 5-15 min to obtain a hydrophobic monomer emulsion. Step 3: In the hydrophobic monomer emulsion obtained in Step 2, add 0.5-2 parts of functional monomer, 5-10 parts of methyl acrylate, 20-30 parts of acrylic acid, 5-10 parts of 2-hydroxyethyl acrylate, 3-8 parts of diacetone acrylamide, 1-5 parts of N-ethylacrylamide, 1-5 parts of N-octylacrylamide, 0.4-0.8 parts of ethylene glycol dimethacrylate, 70-100 parts of water and 1.5-4 parts of biomass-based surfactant, and stir at 400-800 r / min for 10-20 min to form a stable composite monomer emulsion; Step 4: Add the composite monomer emulsion obtained in Step 3 to the initial emulsion aqueous phase in Step 1 at a uniform rate over 1-3 hours at 50-70℃. After the addition is complete, add 0.04-0.08 parts of initiator and keep the temperature constant at 50-70℃ for 2-6 hours. After the reaction is complete, stop heating, allow the system to cool naturally to room temperature, filter to remove a small amount of gel, and you will get a biomass-based surfactant thickener.

[0008] The biomass-based surfactant is at least one of dodecyl glucoside and sodium lauryl oleate.

[0009] The initiator is ammonium persulfate.

[0010] The functional monomer is at least one of 2-methyl-2-acrylate-2-(2-oxo-1-imidazolinyl)ethyl ester, 1,3-divinyl-2-imidazolinone, N-vinylimidazolium, 4-acryloylmorpholine, vinylpyrrolidone, N-vinylcaprolactam, betaine, and 2-acrylamido-2-methylpropanesulfonic acid.

[0011] Preferably, the functional monomer is composed of 1,3-divinyl-2-imidazolinone and N-vinylcaprolactam in a mass ratio of 0.5-2:0.5-2.

[0012] More preferably, the functional monomer is composed of 1,3-divinyl-2-imidazolinone, N-vinylcaprolactam and 2-acrylamido-2-methylpropanesulfonic acid in a mass ratio of 2-4:2-4:1-3.

[0013] Step 3 can also be performed using the following method: In the hydrophobic monomer emulsion obtained in step 2, 5-10 parts of methyl acrylate, 20-30 parts of acrylic acid, 5-10 parts of 2-hydroxyethyl acrylate, 3-8 parts of diacetone acrylamide, 1-5 parts of N-ethylacrylamide, 1-5 parts of N-octylacrylamide, 0.4-0.8 parts of ethylene glycol dimethacrylate, 70-100 parts of water and 1.5-4 parts of biomass-based surfactant are added simultaneously. The mixture is stirred at 400-800 r / min for 1-10 min, and then 0.5-2 parts of functional monomer are added. The mixture is stirred at 400-800 r / min for 5-15 min to form a stable composite monomer emulsion.

[0014] This invention introduces functional monomers into the preparation method of biomass-based surfactant-type thickeners to construct reversible associative structures. Existing biomass-based surfactant-type thickeners mainly rely on the physical association between hydrophobic monomers to achieve thickening. Their structures are prone to deassociation under high temperature or strong shear conditions, resulting in insufficient viscosity retention and structural recovery. Therefore, this invention first introduces functional monomers with polarity or capable of forming multiple interactions into the existing emulsion polymerization system. These monomers participate in polymerization and are distributed within the polymer chain segments. Through hydrogen bonding, electrostatic interactions, or polar interactions, new reversible interaction sites are introduced on the basis of the original hydrophobic association, thereby initially improving the structural stability and high-temperature and shear resistance of the thickener.

[0015] Building upon the ability of single functional monomers to improve system performance, this invention further recognizes that different functional monomers exhibit significant complementarity in their mechanisms of action. Therefore, by compounding functional monomers with multifunctional crosslinking characteristics with functional monomers possessing flexible association or strong hydrogen bonding capabilities, they are synergistically integrated within the same polymer system. One type of functional monomer is used to construct a stable network framework, while the other type enhances reversible association capabilities under high temperature and shear conditions, thereby forming a composite associative network that combines strength and toughness, achieving a synergistic improvement in thickening performance and stability.

[0016] Building upon the synergistic effect of bifunctional monomers, this invention further introduces a functional monomer with strong hydration capabilities or ionic properties as a third component, enabling the system to simultaneously possess multiple mechanisms of action, including cross-linking, hydrogen bonding, hydration, and electrostatic stabilization. This third functional monomer can form a stable hydration layer around the polymer chain, inhibit network collapse under shear or high-temperature conditions, and promote rapid reconstruction after structural damage, thereby significantly improving the long-term stability and structural recovery capability of the thickener under extreme usage conditions.

[0017] Building upon the synergistic effects of multiple functional monomers, this invention further optimizes the process design by controlling the timing of functional monomer addition to the composite monomer emulsion. This allows ordinary monomers to preferentially form the basic polymerization structure before guiding the functional monomers to participate in subsequent polymerization processes. This process improvement effectively avoids the random consumption of functional monomers in the early stages of polymerization, ensuring their distribution within the effective functional regions of the polymer chains. This improves the utilization efficiency of functional groups, thereby amplifying the synergistic effect without altering the formulation composition and optimizing the overall performance of the thickener.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects: 1) This invention introduces functional monomers into a biomass-based surfactant-type thickening system, enabling the thickener to form multiple reversible interactions on the basis of the original hydrophobic association, which significantly improves the structural stability of the system under high temperature and shear conditions.

[0019] 2) This invention, through the synergistic compounding of different functional monomers, enables the polymer chain segments to simultaneously possess crosslinking, hydrogen bonding, and polar interaction sites, thereby constructing a more stable network structure with self-healing capabilities, thus improving the overall performance of the thickener.

[0020] 3) Based on the functional monomer compounding, this invention further introduces monomers with strong hydration ability, which effectively enhances the interaction between polymer chains and the aqueous phase, inhibits network collapse under high temperature conditions, and improves the long-term stability of the system.

[0021] 4) By optimizing the way functional monomers are added to the composite monomer emulsion, this invention makes the distribution of functional groups in the polymer more reasonable, improves their efficiency in association and synergistic effect, and further amplifies the synergistic effect.

[0022] 5) This invention uses biomass-based surfactants in the emulsion polymerization process, which not only improves the stability of the emulsion system, but also reduces the dependence on traditional petrochemical resources, and has good environmental protection and application adaptability. Detailed Implementation

[0023] In the embodiments and comparative examples of this invention, all raw materials are commercially available products.

[0024] Example 1 A method for preparing a biomass-based surfactant-type thickener is as follows: Step 1: Add 3.5 parts of dodecyl glucoside and 1 part of sodium laurylate to 90 parts of water, and stir at 200 r / min for 25 min at 30℃ to form an initial emulsion aqueous phase; Step 2: Mix 28 parts of dodecyl methacrylate, 10 parts of diethyl itaconic acid, and 48 parts of cyclohexyl methacrylate evenly, then add 45 parts of water, 1.5 parts of dodecyl glucoside, and 0.06 parts of ammonium persulfate. Disperse the mixture at 900 r / min for 10 min to obtain a hydrophobic monomer emulsion. Step 3: In the hydrophobic monomer emulsion obtained in Step 2, add 1.2 parts of functional monomer, 8 parts of methyl acrylate, 25 parts of acrylic acid, 7 parts of 2-hydroxyethyl acrylate, 5 parts of diacetone acrylamide, 3 parts of N-ethylacrylamide, 2.5 parts of N-octylacrylamide, 0.6 parts of ethylene glycol dimethacrylate, 85 parts of water, 2 parts of dodecyl glucoside, and 0.7 parts of sodium lauryl acrylate in sequence. Stir at 600 r / min for 15 min to form a stable composite monomer emulsion. Step 4: The composite monomer emulsion obtained in Step 3 is added dropwise at a uniform rate to the initial emulsion aqueous phase in Step 1 over 2 hours at 60°C. After the addition is complete, 0.06 parts of ammonium persulfate are added, and the mixture is kept at 60°C for 4 hours. After the reaction is complete, heating is stopped, the system is allowed to cool naturally to room temperature, and a small amount of gel is removed by filtration to obtain the biomass-based surfactant thickener.

[0025] The functional monomer is 2-methyl-2-acrylate-2-(2-oxo-1-imidazolinyl)ethyl ester.

[0026] Example 2 The preparation method of a biomass-based surfactant-type thickener is basically the same as that in Example 1, except that the functional monomer is 1,3-divinyl-2-imidazolinone.

[0027] Example 3 The preparation method of a biomass-based surfactant-type thickener is basically the same as that in Example 1, except that the functional monomer is N-vinylimidazole.

[0028] Example 4 The preparation method of a biomass-based surfactant-type thickener is basically the same as that in Example 1, except that the functional monomer is 4-acryloylmorpholine.

[0029] Example 5 The preparation method of a biomass-based surfactant-type thickener is basically the same as that in Example 1, except that the functional monomer is vinylpyrrolidone.

[0030] Example 6 The preparation method of a biomass-based surfactant-type thickener is basically the same as that in Example 1, except that the functional monomer is N-vinylcaprolactam.

[0031] Example 7 The preparation method of a biomass-based surfactant-type thickener is basically the same as that in Example 1, except that the functional monomer is betaine.

[0032] Example 8 The preparation method of a biomass-based surfactant-type thickener is basically the same as that in Example 1, except that the functional monomer is composed of 1,3-divinyl-2-imidazolinone and N-vinylcaprolactam in a mass ratio of 1:1.

[0033] Example 9 The preparation method of a biomass-based surfactant-type thickener is basically the same as that in Example 1, except that the functional monomer is composed of vinylpyrrolidone and betaine in a mass ratio of 1:1.

[0034] Example 10 The preparation method of a biomass-based surfactant-type thickener is basically the same as that in Example 1, except that the functional monomers are composed of 1,3-divinyl-2-imidazolinone, N-vinylcaprolactam and 2-acrylamido-2-methylpropanesulfonic acid in a mass ratio of 3:3:2.

[0035] Example 11 The preparation method of a biomass-based surfactant-type thickener is basically the same as that in Example 10, except that step 3 can also be performed using the following method: In the hydrophobic monomer emulsion obtained in step 2, 8 parts of methyl acrylate, 25 parts of acrylic acid, 7 parts of 2-hydroxyethyl acrylate, 5 parts of diacetone acrylamide, 3 parts of N-ethylacrylamide, 2.5 parts of N-octylacrylamide, 0.6 parts of ethylene glycol dimethacrylate, 85 parts of water, 2 parts of dodecyl glucoside, and 0.7 parts of sodium lauryl acrylate were added sequentially. The mixture was stirred at 600 r / min for 5 min, and then 1.2 parts of functional monomer were added. The mixture was stirred at 600 r / min for 10 min to form a stable composite monomer emulsion.

[0036] The functional monomers are composed of 1,3-divinyl-2-imidazolinone, N-vinylcaprolactam, and 2-acrylamido-2-methylpropanesulfonic acid in a mass ratio of 3:3:2.

[0037] Comparative Example 1 The preparation method of a biomass-based surfactant-type thickener is basically the same as that in Example 11, except that the functional monomer is not added.

[0038] Test Example 1 high temperature Shear viscosity retention test: The thickeners prepared in the examples and comparative examples were added to a standard acrylic emulsion system (solid content 50%) at an addition amount of 0.8 wt%, and stirred thoroughly. The initial apparent viscosity (shear rate 10 s) was measured using a rotational rheometer at 25°C. -1 ), denoted as η0; the sample was kept in a constant temperature environment of 60℃ for 24 hours; then, under the condition of 60℃, it was subjected to a 1000s... -1 Shearing rate was applied for 5 min; after shearing, the mixture was allowed to stand at 25℃ for 30 min, and the apparent viscosity was measured again and recorded as η1. Calculate viscosity retention using the following formula: Viscosity retention rate (%) = η1 / η0 × 100% Each group of samples was measured in parallel three times, and the average value was taken. The test results are shown in Table 1.

[0039] Table 1

[0040] Test Example 2 Cut Resume loop test: The thickener obtained in Examples 1 and 2013 was added at 0.8 wt% to a standard acrylic emulsion system (solid content 50%) and stirred thoroughly. The following test procedure was performed using a rotational rheometer at 25°C: Low shear phase: 10s -1 Record the stable viscosity η for 300 seconds.a ; High shear phase: 1000s -1 This lasts for 120 seconds and damages the structure. Recovery phase: Switch back to 10 seconds -1 The recovery viscosity η was recorded after 600 seconds. r ; Calculate the structural recovery rate using the following formula: Structural restoration rate (%) = η r / η a ×100% Each group was measured in parallel three times, and the average value was taken. The relevant test data are summarized in Table 2.

[0041] Table 2

[0042] Comparative Example 1 uses a non-functional monomer, relying solely on hydrophobic monomer association. Under high-temperature shear, the network is easily destroyed, resulting in low viscosity retention and structural recovery. Examples 1-7 introduce single-functional monomers, enhancing intermolecular interactions through hydrogen bonding and electrostatic interactions. However, the single-functional group has a limited effect, leading to limited performance improvement. The N-vinylcaprolactam in Example 6, containing a hexa-lactam structure, maintains strong hydrogen bonding at high temperatures, and its flexible chain buffers shear forces. Compared to other single-functional monomers, it maintains a more stable thickening network, thus exhibiting superior performance.

[0043] Example 8 combines 1,3-divinyl-2-imidazolinone (multi-point crosslinking nodes) with N-vinylcaprolactam (high-temperature stable hydrogen bonding sites) to form a rigid crosslinking and flexible associative synergistic network: imidazolinone provides a multi-point interconnected framework, and caprolactam is dispersed between the framework to enhance reversible association at high temperatures. This avoids the defects of a single rigid node being easily brittle and a single flexible site being easily dissociated. The viscosity retention rate and structural recovery rate after high-temperature shear are improved simultaneously.

[0044] Example 10 introduces 2-acrylamido-2-methylpropanesulfonic acid, whose highly polar sulfonic acid groups form a stable hydration layer on the molecular chain, forming a triple synergy with the crosslinking nodes of imidazolinone and the hydrogen bonding sites of caprolactam: the electrostatic repulsion of the sulfonic acid groups can inhibit excessive network shrinkage at high temperatures, and at the same time, as a supplementary stabilizer, it assists in the rapid reconstruction of hydrogen bonds and crosslinking nodes after shearing failure, further enhancing the stability of the network under extreme conditions. Therefore, the performance is further improved compared to Example 8.

[0045] Example 11 employs a process of first mixing ordinary monomers and then adding functional monomers, which avoids random copolymerization of functional monomers with hydrophobic monomers in the initial stage, allowing functional groups to be more concentrated in the outer region of the polymer chain. The crosslinking nodes of imidazolinone, the hydrogen bonding sites of caprolactam, and the hydration layer of 2-acrylamido-2-methylpropanesulfonic acid can all be exposed and participate in the action more efficiently, reducing internal ineffective crosslinking and maximizing the utilization rate of each functional group. Therefore, under the same formulation, the high-temperature shear stability and structural recovery ability are optimal.

Claims

1. A method for preparing a biomass-based surfactant-type thickener, characterized in that, The process is as follows: Step 1: Add biomass-based surfactants to water to form an initial emulsified aqueous phase under stirring conditions; Step 2: Mix dodecyl methacrylate, diethyl itaconic acid, and cyclohexyl methacrylate, then add water, biomass-based surfactant, and initiator, and disperse to obtain a hydrophobic monomer emulsion. Step 3: Add functional monomers, methyl acrylate, acrylic acid, 2-hydroxyethyl acrylate, diacetone acrylamide, N-ethylacrylamide, N-octylacrylamide, ethylene glycol dimethacrylate, water and biomass-based surfactants to the hydrophobic monomer emulsion, and form a composite monomer emulsion under stirring conditions. Step 4: The composite monomer emulsion is added dropwise to the initial emulsified aqueous phase under heating conditions. After the addition is complete, an initiator is added and the mixture is kept warm. After the reaction is complete, the mixture is cooled and filtered to obtain a biomass-based surfactant-type thickener.

2. The preparation method of the biomass-based surfactant-type thickener as described in claim 1, characterized in that, The method is as follows, by weight: Step 1: Add 2.5-7 parts of biomass-based surfactant to 70-100 parts of water, and stir at 100-300 r / min for 10-40 min at 20-40℃ to form an initial emulsion aqueous phase; Step 2: Mix 20-35 parts of dodecyl methacrylate, 5-15 parts of diethyl itaconic acid, and 40-55 parts of cyclohexyl methacrylate evenly, then add 40-50 parts of water, 1-2 parts of biomass-based surfactant, and 0.04-0.08 parts of initiator. Disperse the mixture at 600-1200 r / min for 5-15 min to obtain a hydrophobic monomer emulsion. Step 3: In the hydrophobic monomer emulsion obtained in Step 2, add 0.5-2 parts of functional monomer, 5-10 parts of methyl acrylate, 20-30 parts of acrylic acid, 5-10 parts of 2-hydroxyethyl acrylate, 3-8 parts of diacetone acrylamide, 1-5 parts of N-ethylacrylamide, 1-5 parts of N-octylacrylamide, 0.4-0.8 parts of ethylene glycol dimethacrylate, 70-100 parts of water and 1.5-4 parts of biomass-based surfactant, and stir at 400-800 r / min for 10-20 min to form a stable composite monomer emulsion; Step 4: Add the composite monomer emulsion obtained in Step 3 to the initial emulsion aqueous phase in Step 1 at a uniform rate over 1-3 hours at 50-70℃. After the addition is complete, add 0.04-0.08 parts of initiator and keep the temperature constant at 50-70℃ for 2-6 hours. After the reaction is complete, stop heating, allow the system to cool naturally to room temperature, filter to remove a small amount of gel, and you will get a biomass-based surfactant thickener.

3. The method for preparing the biomass-based surfactant-type thickener as described in claim 1 or 2, characterized in that, The biomass-based surfactant is at least one of dodecyl glucoside and sodium lauryl oleate.

4. The method for preparing the biomass-based surfactant-type thickener as described in claim 1 or 2, characterized in that, The initiator is ammonium persulfate.

5. The method for preparing the biomass-based surfactant-type thickener as described in claim 1 or 2, characterized in that, The functional monomer is at least one of 2-methyl-2-acrylate-2-(2-oxo-1-imidazolinyl)ethyl ester, 1,3-divinyl-2-imidazolinone, N-vinylimidazolium, 4-acryloylmorpholine, vinylpyrrolidone, N-vinylcaprolactam, betaine, and 2-acrylamido-2-methylpropanesulfonic acid.

6. The method for preparing the biomass-based surfactant-type thickener as described in claim 1 or 2, characterized in that, The functional monomers are composed of 1,3-divinyl-2-imidazolinone and N-vinylcaprolactam in a mass ratio of 0.5-2:0.5-2.

7. The method for preparing the biomass-based surfactant-type thickener as described in claim 1 or 2, characterized in that, The functional monomers are composed of 1,3-divinyl-2-imidazolinone, N-vinylcaprolactam and 2-acrylamido-2-methylpropanesulfonic acid in a mass ratio of 2-4:2-4:1-3.

8. The method for preparing the biomass-based surfactant-type thickener as described in claim 1 or 2, characterized in that, Step 3 can also be performed using the following method: In the hydrophobic monomer emulsion obtained in step 2, 5-10 parts of methyl acrylate, 20-30 parts of acrylic acid, 5-10 parts of 2-hydroxyethyl acrylate, 3-8 parts of diacetone acrylamide, 1-5 parts of N-ethylacrylamide, 1-5 parts of N-octylacrylamide, 0.4-0.8 parts of ethylene glycol dimethacrylate, 70-100 parts of water and 1.5-4 parts of biomass-based surfactant are added simultaneously. The mixture is stirred at 400-800 r / min for 1-10 min, and then 0.5-2 parts of functional monomer are added. The mixture is stirred at 400-800 r / min for 5-15 min to form a stable composite monomer emulsion.

9. A biomass-based surfactant-type thickener, characterized in that, It is prepared by the preparation method described in any one of claims 1-8.

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