Polycarboxylic acid dispersing agent and preparation method thereof

Abstract

The invention relates to a polycarboxylic acid dispersing agent and a preparation method thereof, and the polycarboxylic acid dispersing agent is prepared from the following raw materials in parts by weight: 28-32 parts of sodium methylallyl sulfonate; 170 to 190 parts of polyether monomer; 8-12 parts of a modified amide monomer; 16 to 18 parts of unsaturated acid monomer; 1.8 to 2.2 parts of an oxidizing agent; 1.8 to 2.2 parts of a reducing agent; 2.2 to 2.8 parts of a chain transfer agent; and water; the polyether monomer is prepared from the following raw materials: phosphate ester, ethylene oxide and epoxypropane; the modified amide monomer is obtained by modifying N-hydroxymethyl acrylamide with a sulfating agent. According to the invention, the modified amide monomer containing a strong polar sulfate group and the polyether monomer with a specific EO / PO chain segment ratio are copolymerized, so that the synergistic effect of'reinforced anchoring 'and'steric hindrance' is realized, the defects of unfirm anchoring and insufficient steric hindrance of a traditional dispersant are overcome, the adsorption stability of the dispersant on the surface of a pigment is obviously enhanced, and the dispersion is more stable. Therefore, the viscosity of the coating is obviously reduced, and the fluidity of the coating is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete admixtures, in particular to a polycarboxylic dispersant and a preparation method thereof. BACKGROUND

[0002] In the industrial field of coatings, inks and the like, dispersants are key additives to ensure the stable and uniform dispersion of solid particles such as pigments in liquid media. The currently widely used coating dispersants in China mainly focus on high molecular electrolytes (such as polyacrylic acid sodium salt) and polycarboxylic acid and its derivatives. Such traditional dispersants usually adsorb on the surface of pigment particles through the hydrophobic groups in their molecular structure, while the hydrophilic groups extend into the aqueous medium, achieving the initial dispersion of particles through electrostatic repulsion.

[0003] However, in actual application, the above-mentioned conventional dispersants still have obvious limitations.

[0004] Firstly, the anchoring firmness of the molecular structure to pigment particles, especially to inorganic pigments with high surface energy (such as titanium dioxide, calcium carbonate, etc.) and cement particles, is insufficient, resulting in poor adsorption stability, easy desorption under the action of storage or construction shear force, and further causing the re-agglomeration and flocculation of pigment particles.

[0005] Secondly, the steric hindrance effect provided by traditional dispersants is weak, and the molecular chain segment design is single, making it difficult to build a persistent and effective three-dimensional barrier to counteract the van der Waals attraction between particles.

[0006] The above two defects together lead to poor stability of the dispersion system, which is manifested as increased viscosity and decreased flowability of the coating, and may produce flocculated particles, affecting the appearance and performance of the final coating film.

[0007] Therefore, there is an urgent need in the art to develop a new type of high-efficiency dispersant which can not only strongly anchor on the surface of pigment particles, but also provide stronger and more stable steric hindrance, thereby achieving significant reduction in the viscosity of the coating system, improvement in flowability and guarantee of long-term dispersion stability. SUMMARY

[0008] Therefore, it is necessary to provide a polycarboxylic dispersant and a preparation method thereof, aiming to solve the problems existing in the prior art.

[0009] To achieve the above-mentioned purpose, the present application provides a technical solution:

[0010] A polycarboxylic dispersant, the preparation raw materials of the polycarboxylic dispersant include, in terms of parts by weight:

[0011]

[0012] The raw material for preparing the polyether monomer comprises phosphate, ethylene oxide and propylene oxide.

[0013] The modified amide monomer is modified from N-hydroxymethyl acrylamide by a sulfuric acid agent.

[0014] More specifically, the unsaturated acid monomer is at least one of acrylic acid and methacrylic acid.

[0015] The oxidizing agent is at least one of hydrogen peroxide and ammonium persulfate.

[0016] The reducing agent is at least one of sodium hypophosphite, sodium phosphate, ascorbic acid and sodium bisulfite.

[0017] The chain transfer agent is mercaptoacetic acid and mercaptoethanol.

[0018] Preferably, the raw material for preparing the polyether monomer comprises, in parts by weight:

[0019] 95-105 parts of phosphate;

[0020] 240-260 parts of ethylene oxide;

[0021] 240-260 parts of propylene oxide.

[0022] Preferably, the raw material for preparing the phosphate comprises:

[0023]

[0024] Preferably, the raw material for preparing the polyether monomer further comprises, in parts by weight, 0.1-0.3 parts of a catalyst and / or 0.8-1.2 parts of a neutralizing agent.

[0025] Preferably, the catalyst comprises at least one of sodium hydroxide, potassium hydroxide, sodium methoxide and sodium hydride.

[0026] The neutralizing agent comprises glacial acetic acid.

[0027] Preferably, the preparation step of the polyether monomer is as follows:

[0028] The phosphate is added to the reactor, which is heated to 45-55°C and dehydrated under reduced pressure to -0.06-0.08 MPa until the moisture content is less than 0.08%;

[0029] After dehydration, the catalyst is added, the pressure of the reactor is drawn to -0.06-0.08 MPa, and the oxygen in the system is removed.

[0030] After deoxygenation, the ethylene oxide is introduced, and after the pressure stabilizes, the propylene oxide is introduced.

[0031] After the reaction is completed, the temperature is lowered to 80-90℃, a neutralizing agent is added for neutralization, and filtration is performed to obtain the polyether monomer.

[0032] Preferably, the sulfating agent comprises at least one of chlorosulfonic acid and methane sulfonyl chloride.

[0033] Preferably, the raw materials for preparing the modified amide monomer comprise, in parts by weight:

[0034] N-hydroxymethyl acrylamide 55-60 parts;

[0035] Chlorosulfonic acid 60-70 parts.

[0036] Preferably, the raw materials for preparing the N-hydroxymethyl acrylamide comprise, in parts by weight:

[0037]

[0038] Specifically, the polymerization inhibitor is sodium carbonate, and the aqueous formaldehyde solution is a 37wt% aqueous formaldehyde solution.

[0039] The application also provides a preparation method of the polycarboxylic acid dispersant, characterized in that the method comprises the following steps:

[0040] The sodium methyl allyl sulfonate, the polyether monomer, the unsaturated acid monomer, and water are uniformly stirred to obtain a mother liquor;

[0041] The A liquid, the B liquid, and the C liquid are added dropwise into the mother liquor, and after the dropwise addition is completed, the reaction is kept for a certain period of time, and the reaction is completed to obtain the product;

[0042] The A liquid is a mixed solution of an oxidizing agent and water;

[0043] The B liquid is a mixed solution of an unsaturated acid monomer, an amide monomer, and water;

[0044] The C liquid is a mixed solution of a reducing agent, a chain transfer agent, and water.

[0045] The application has the following beneficial effects:

[0046] 1. "anchoring-hindrance" synergy, high efficiency, stability, and significant viscosity reduction: by copolymerizing the modified amide monomer containing a strong polar sulfate group with the polyether monomer with a specific EO / PO segment ratio, the synergy of "strengthening anchoring" and "steric hindrance" is achieved. This design effectively overcomes the defects of poor anchoring and insufficient steric hindrance of traditional dispersants, significantly enhances the adsorption stability of the dispersant on the pigment surface, effectively prevents particle flocculation, thereby significantly reducing the viscosity of the paint and improving its flowability.

[0047] 2. High negative charge gives strong electrostatic repulsion, improves early dispersion and storage stability: To solve the problem of insufficient charge density of traditional dispersants, high negative groups such as phosphate and sulfate are introduced into the molecular chain to greatly enhance the electrostatic repulsion of the dispersant. This property not only assists the space steric effect to further prevent flocculation, but also significantly improves the early dispersion efficiency of the pigment and the viscosity retention of the coating system, ensuring the storage stability.

[0048] 3. Multi-functional group gradient design to achieve wide-spectrum and efficient dispersion: By introducing monomers containing -COOH, -SO3-, phosphate groups, etc. for terpolymerization, a dispersant structure with multi-level space steric hindrance and multi-gradient potential difference is constructed. This design effectively solves the problem of single function and poor adaptability of traditional dispersants, making it efficient and durable for dispersing various building coating powders, and showing excellent universality and comprehensive performance. DETAILED DESCRIPTION

[0049] In order to better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below in conjunction with specific examples.

[0050] In the examples, the test methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are commercially available unless otherwise specified.

[0051] Example 1

[0052] The preparation method comprises the following steps:

[0053] (1) Add 80 g of ethylene glycol monoethyl ether acrylate to a flask, then add 5 g of deionized water, heat to 55℃, then slowly add 120 g of P2O5, react for 3 h, and after the reaction is completed, keep for 1 h to obtain a phosphate ester.

[0054] (2) Add 100 g of the phosphate ester to a high-pressure reaction kettle, heat to 50℃, and reduce the pressure to -0.07 Mpa to dehydrate to a moisture content of <0.08%.

[0055] After dehydration is completed, sodium hydroxide is added. The pressure in the reaction kettle is drawn to -0.07 Mpa, then 0.4 Mpa of nitrogen gas is charged, and the process is repeated three times to remove excess oxygen in the system.

[0056] After degassing is completed, 250 g of ethylene oxide is introduced, and after the reaction is completed, the temperature is lowered to 80℃, 1 g of glacial acetic acid is added for neutralization, and filtration is performed to obtain polyether monomer A.

[0057] (3) Add acrylamide 100 g, deionized water 50 g to a four-necked flask, stir and dissolve, then add hydroquinone 0.1 g, sodium carbonate 2.5 g, and heat to 45±2℃;

[0058] Drop 110 g 37 wt% formaldehyde aqueous solution at a drop rate of 10 mL / h, and keep the reaction for 2.5 h after dropping. Vacuum drying gives N-hydroxymethyl acrylamide.

[0059] (4) Add 58 g N-hydroxymethyl acrylamide and 250 g anhydrous dichloromethane into a four-necked flask, stir to dissolve, and then pass nitrogen for 30 min. Add 78 g triethylamine. Cool to 0-5 ℃ in an ice bath, and drop 76 g chlorosulfonic acid (5 mL / h). After dropping, warm to 25 ℃, and react for 1 h. Pour the reaction solution into ice water, separate the organic phase, wash with ice water twice, dry with anhydrous sodium sulfate, and remove the solvent by distillation under reduced pressure to obtain modified amide monomer A.

[0060] (5) Accurately weigh 30 g of sodium methyl allyl sulfonate, 180 g of polyether monomer A, and 10 g of acrylic acid, and put them into a four-necked reaction flask. Start stirring, add 40 g of deionized water, and stir the mixture solution uniformly to obtain a mother liquor.

[0061] Prepare solution A: 2 g of hydrogen peroxide + 20 g of deionized water;

[0062] Prepare solution B: 8 g of acrylic acid + 10 g of modified amide monomer A + 20 g of deionized water;

[0063] Prepare solution C: 2 g of sodium hypophosphite + 2.5 g of mercaptoacetic acid + 20 g of deionized water.

[0064] At room temperature, add solutions A, B, and C into the mother liquor at the same time, and the drop time is 70 min. After the drop is completed, keep the temperature for 30 min, and add 4 g of 30 wt% sodium hydroxide solution to adjust the pH to obtain the polycarboxylic acid dispersant.

[0065] Example 2

[0066] The preparation method comprises the following steps:

[0067] (1) Add 78 g of ethylene glycol monoethyl ether acrylate and 4.5 g of deionized water into a flask, heat to 53 ℃, and then slowly add 115 g of P2O5. React for 3.2 h, and keep the temperature for 1.2 h after the reaction is completed to obtain a phosphate ester.

[0068] (2) Add 100 g of the phosphate ester into a high-pressure reaction kettle, heat to 48 ℃, and dehydrate to -0.065 Mpa to meet the reaction requirement. After the dehydration is completed, add 0.15 g of sodium hydroxide. Draw the pressure in the reaction kettle to -0.065 Mpa, and then charge 0.35 Mpa of nitrogen, and repeat the process three times to remove excess oxygen in the system. After the degassing is completed, introduce 245 g of ethylene oxide, and then introduce 255 g of propylene oxide after the pressure is constant. After the reaction is completed, cool to 82 ℃, add 0.9 g of glacial acetic acid for neutralization, and filter to obtain the polyether monomer A.

[0069] (3) Into a four-necked flask, 98 g of acrylamide and 48 g of deionized water were added and stirred to dissolve, then 0.09 g of hydroquinone and 2.3 g of sodium carbonate were added, and the temperature was raised to 44°C; 105 g of 37 wt% formaldehyde aqueous solution was added dropwise at a rate of 9 mL / h, and after the dropwise addition was completed, the reaction was maintained for 2.3 h, and vacuum drying was performed to obtain N-hydroxymethyl acrylamide.

[0070] (4) Into a four-necked flask, 56 g of N-hydroxymethyl acrylamide and 260 g of anhydrous dichloromethane were added and stirred to dissolve, then 75 g of triethylamine was bubbled with nitrogen for 28 min; the temperature was lowered to 1-4°C in an ice bath, 75 g of chlorosulfonic acid was added dropwise at a rate of 4.5 mL / h, and after the dropwise addition was completed, the temperature was raised to 23°C and the reaction was maintained for 1.2 h; the reaction solution was poured into ice water, the organic phase was separated, washed with ice water twice, dried over anhydrous sodium sulfate, and the solvent was removed by distillation under reduced pressure to obtain modified amide monomer A.

[0071] (5) 29 g of sodium methyl allyl sulfonate, 175 g of polyether monomer A, and 9 g of acrylic acid were accurately weighed and placed in a four-necked reaction flask, deionized water 38 g was added, and the mixture solution was stirred uniformly to obtain a mother liquor.

[0072] Configuration A liquid: hydrogen peroxide 1.9 g + 19 g of deionized water;

[0073] Configuration B liquid: acrylic acid 8 g + modified amide monomer A 9 g + 19 g of deionized water;

[0074] Configuration C liquid: sodium hypophosphite 1.9 g + mercaptoacetic acid 2.3 g + 19 g of deionized water.

[0075] At room temperature, A, B, and C liquids were added dropwise into the mother liquor at the same time, and the dropwise addition time was 65 min. After the dropwise addition was completed, the temperature was maintained for 28 min, 3.8 g of 30 wt% sodium hydroxide solution was added to adjust the pH, and the polycarboxylic acid dispersant was obtained.

[0076] Example 3

[0077] The preparation method comprises the following steps:

[0078] (1) 83 g of ethylene glycol monoethyl ether acrylate was added to a flask, 5.5 g of deionized water was added, heated to 57°C, then 125 g of P2O5 was slowly added, and the reaction was maintained for 2.8 h, and after the reaction was completed, the temperature was maintained for 0.8 h to obtain a phosphate ester.

[0079] (2) 100 g of phosphate ester was added to a high-pressure reaction kettle, heated to 52°C, and dehydrated to -0.075 Mpa under reduced pressure to meet the reaction requirements. After dehydration, 0.25 g of sodium hydroxide was added. The pressure in the reaction kettle was extracted to -0.075 Mpa, and then 0.45 Mpa of nitrogen was charged, and the process was repeated three times to remove excess oxygen in the system. After degassing, 255 g of ethylene oxide was introduced, and after the pressure did not change, 245 g of propylene oxide was introduced, and after the reaction was completed, the temperature was lowered to 78°C, 1.1 g of glacial acetic acid was added for neutralization, and filtration was performed to obtain polyether monomer A.

[0080] (3) Acrylamide 103 g, deionized water 52 g, stirring and dissolving, then adding hydroquinone 0.11 g, sodium carbonate 2.7 g, heating to 46°C; drop 115 g 37wt% formaldehyde solution, drop speed 11 mL / h, after drop, keep warm for 2.7 h, vacuum drying to obtain N-hydroxymethyl acrylamide.

[0081] (4) Add 59 g of N-hydroxymethyl acrylamide, 290 g of anhydrous dichloromethane to a four-necked flask, stir and dissolve, then pass nitrogen for 32 min, add 80 g of triethylamine; ice bath cooling to 0-3°C, drop 82 g of chlorosulfonic acid (drop speed 5.5 mL / h), after drop, heating to 27°C for 0.8 h; pour the reaction solution into ice water, separate the organic phase, wash with ice water twice, dry with anhydrous sodium sulfate, and remove the solvent by reduced pressure distillation to obtain modified amide monomer A.

[0082] (5) Accurately weigh 31 g of sodium methyl allyl sulfonate, 185 g of polyether monomer A, and 11 g of acrylic acid, and place them in a four-necked reaction flask. Add 42 g of deionized water and stir the mixture solution uniformly to obtain a mother liquor.

[0083] Configuration A liquid: hydrogen peroxide 2.1 g + 21 g deionized water;

[0084] Configuration B liquid: acrylic acid 8 g + modified amide monomer A 11 g + 21 g deionized water;

[0085] Configuration C liquid: sodium hypophosphite 2.1 g + mercaptoacetic acid 2.7 g + 21 g deionized water.

[0086] At room temperature, A, B, and C liquids were added to the mother liquor simultaneously, and the drop time was 75 min. After the drop was completed, it was kept warm for 32 min, 4.2 g of 30wt% sodium hydroxide solution was added to adjust the pH, and the polycarboxylic acid dispersant was obtained.

[0087] Comparative Example 1

[0088] The other steps are the same as Example 1, except that:

[0089] Replace ethylene glycol monoethyl ether acrylate with equal mass of allyl alcohol.

[0090] Comparative Example 2

[0091] The other steps are the same as in Example 1, except that:

[0092] Sodium methyl allyl sulfonate is not added.

[0093] Comparative Example 3

[0094] The other steps are the same as in Example 1, except that:

[0095] In step 4, the amount of N-hydroxymethylacrylamide used in the preparation of the modified amide monomer is 20g.

[0096] The specific testing methods for each performance aspect are as follows:

[0097] Dispersibility test: First, the styrene-acrylic emulsion, water, and dispersant were placed in a disperser and dispersed at 300 rpm for 1 min to prepare a liquid. After adding the powder according to the formula, it was dispersed at 800 rpm for 5 min. The initial viscosity (characterized by KU value) was measured using a Stormer viscometer. Dispersibility was evaluated using two methods:

[0098] 1. For the same dispersant dosage, the lower the KU value, the better the dispersibility;

[0099] 2. When the same initial viscosity (85±5KU) is achieved, the lower the amount of dispersant, the better the dispersibility.

[0100] Dispersion retention test: The mixture after the initial viscosity test is placed into a covered container, and the viscosity is tested again after standing for 120 minutes. The viscosity increase is characterized by the ΔKU value. The smaller the ΔKU value within the same standing time, the better the dispersion retention.

[0101] Powder-opening ability test: Styrene-acrylic emulsion, water, and dispersant were dispersed in a disperser at 300 r / min for 1 min to obtain a liquid material. After adding the powder according to the formula, the mixture was dispersed at 350 r / min for 3 min. The coating was poured onto a glass plate, spread evenly using a wet film preparer, and placed at 22℃ for 1 day. The number of particles on the dry film surface was observed; the fewer the particles, the better the powder-opening ability. The dispersibility, dispersion retention, and powder-opening ability test results of each dispersant are detailed in Table 1.

[0102] Table 1. Results of Dispersant Performance Tests

[0103]

[0104] As shown in Table 1, compared with the comparative examples, the dispersant products of Examples 1-3 of this application can significantly reduce the amount of dispersant added to achieve the same initial viscosity, indicating that the dispersant can improve the early dispersion of pigments.

[0105] Example 1 uses ethylene glycol monoethyl ether acrylate as the starting material, while Comparative Example 1 uses allyl alcohol instead. This results in a significant increase in the amount of dispersant in Comparative Example 1, and a substantial reduction in dispersion efficiency and anchoring ability, indicating that ethylene glycol monoethyl ether acrylate has significant performance as a starting material.

[0106] Example 1 added sodium methyl allyl sulfonate, while Comparative Example 2 did not add this component. The dispersion stability and powder-opening effect of Comparative Example 2 decreased significantly, highlighting the key role of this component in improving performance.

[0107] In Example 1, N-hydroxymethylacrylamide was used in sufficient proportion to ensure the complete functionality of the modified amide monomer A. In Comparative Example 3, the amount of N-hydroxymethylacrylamide used in the preparation step of this monomer was reduced, which weakened the synergistic effect of the multifunctional groups of the dispersant and deteriorated the overall performance.

[0108] In summary, this application achieves excellent performance of the dispersant at low dosage by accurately selecting starting materials, rationally adding sodium methyl allyl sulfonate, and controlling the dosage of N-hydroxymethyl acrylamide. This effectively improves the viscosity stability and powder dispersion effect of the coating system, and solves the core pain points of traditional dispersants, such as high dosage and unstable performance.

[0109] It should be noted that the specific parameters or reagents in the above embodiments are specific or preferred embodiments under the concept of the present invention, and not limitations thereof; those skilled in the art can make adaptive adjustments within the concept and protection scope of the present invention.

Claims

1. A polycarboxylic acid dispersant, characterized in that, The raw materials for preparing the polycarboxylic acid dispersant, by weight, include: and water; The raw materials for preparing the polyether monomer include phosphate esters, ethylene oxide, and propylene oxide; The modified amide monomer is obtained by modifying N-hydroxymethylacrylamide with a sulfation agent.

2. The polycarboxylic acid dispersant according to claim 1, characterized in that, The raw materials for preparing the polyether monomer, by weight, include: 95-105 parts of phosphate ester; 240-260 parts of ethylene oxide; 240-260 parts of propylene oxide.

3. The polycarboxylic acid dispersant according to claim 2, characterized in that, The raw materials for preparing the phosphate ester, by weight, include: 75-85 parts of ethylene glycol monoethyl ether acrylate; 110-130 parts of phosphorus pentoxide; and 4-6 parts water.

4. The polycarboxylic acid dispersant according to claim 2, characterized in that, The raw materials for preparing the polyether monomer also include 0.1-0.3 parts by weight of catalyst and / or 0.8-1.2 parts by weight of neutralizer.

5. The polycarboxylic acid dispersant according to claim 4, characterized in that, The catalyst includes at least one of sodium hydroxide, potassium hydroxide, sodium methoxide, and sodium hydride; The neutralizing agent includes glacial acetic acid.

6. The polycarboxylic acid dispersant according to claim 5, characterized in that, The preparation steps of the polyether monomer are as follows: Add phosphate ester to the reactor, heat to 45℃~55℃, reduce pressure to -0.06MPa~-0.08MPa to dehydrate until the moisture content is <0.08%; After dehydration is complete, a catalyst is added, the pressure in the reactor is pumped down to -0.06MPa to -0.08MPa, and oxygen in the system is removed. After deoxidation is complete, ethylene oxide is introduced, and after the reaction reaches a stable pressure, propylene oxide is introduced to react. After the reaction is complete, the temperature is lowered to 80-90℃, a neutralizing agent is added for neutralization, and the polyether monomer is obtained by filtration.

7. The polycarboxylic acid dispersant according to claim 1, characterized in that, The sulfating agent includes at least one of chlorosulfonic acid and methanesulfonyl chloride.

8. The polycarboxylic acid dispersant according to claim 1, characterized in that, The raw materials for preparing the modified amide monomer, by weight, include: 55-60 parts of N-hydroxymethylacrylamide; 60-70 parts of chlorosulfonic acid.

9. The polycarboxylic acid dispersant according to claim 1, characterized in that, The raw materials for preparing N-hydroxymethylacrylamide, by weight, include:

10. A method for preparing a polycarboxylic acid dispersant as described in any one of claims 1 to 9, characterized in that, Including the following steps: Sodium methyl allyl sulfonate, polyether monomer, unsaturated acid monomer and water were stirred evenly to obtain the mother liquor; Add solutions A, B, and C dropwise to the mother liquor. After the addition is complete, keep the temperature constant for the reaction. Once the reaction is complete, the polycarboxylic acid dispersant is obtained. Solution A is a mixed solution of oxidant and water; Solution B is a mixed solution of unsaturated acid monomers, amide monomers, and water; Solution C is a mixed solution of reducing agent, chain transfer agent and water.

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