Aqueous dispersant based on acrylic block copolymer and preparation method thereof

Abstract

The invention relates to the technical field of auxiliary chemicals, in particular to a waterborne dispersing agent based on an acrylic block copolymer and a preparation method of the waterborne dispersing agent. The prepared aqueous dispersant is prepared by polymerizing an acrylic acid hard monomer, a soft monomer, a functional monomer containing double bonds, a phosphate monomer and a reactive emulsifier at a mild temperature through a pre-emulsification-synchronous dropwise adding process. A phosphate group and an epoxy group are introduced to achieve a synergistic effect, so that efficient anchoring and wetting of pigment particles are realized; when being applied to pigment color paste, the viscosity reducer shows excellent viscosity reduction capacity and storage stability, and the coloring strength and glossiness are remarkably improved; the preparation process is simplified and efficient, the energy consumption is greatly reduced, and the method is suitable for high-performance environment-friendly color paste production in the fields of printing ink, coating and the like.

Description

Technical Field

[0001] This invention relates to the field of chemical additives technology, and more specifically, to an aqueous dispersant based on an acrylic block copolymer and its preparation method. Background Technology

[0002] As a core additive for pigment dispersion, water-based dispersants directly affect the viscosity, stability, and color strength of pigment pastes. Current mainstream technologies include polyurethane-based and acrylic-modified polyurethane dispersants, which, while achieving basic dispersion functions, have significant limitations in environmental friendliness, process efficiency, and application performance.

[0003] However, existing polyurethane dispersions rely on organic solvents to reduce viscosity, leading to excessive VOC emissions, and the viscosity of the pigment paste increases significantly after high-temperature storage. While acrylic-modified systems reduce solvent use, residual monomers affect environmental friendliness, and the physical anchoring mechanism of silanes has limited effect on difficult-to-disperse pigments, restricting the improvement of tinting strength. Both technologies require multiple high-temperature reactions, resulting in high energy consumption and imprecise molecular weight control.

[0004] To address the bottlenecks in solvent residue, insufficient storage stability, and improvement of coloring power, there is an urgent need to develop a solvent-free, low-energy dispersant synthesis process. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an aqueous dispersant based on acrylic block copolymers and its preparation method, thereby solving the core problems in existing technologies, such as environmental defects caused by residual organic solvents, application bottlenecks due to excessive viscosity of pigment pastes at high pigment concentrations, insufficient thermal storage stability, and limited improvement of pigment tinting strength.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing an aqueous dispersant based on an acrylic block copolymer includes the following steps:

[0008] S1. Pre-emulsification: Mix 15-25 wt% hard acrylic monomer, 10-20 wt% soft acrylic monomer, 5-10 wt% functional monomer, 2-5 wt% phosphate ester monomer, 1-3 wt% reactive emulsifier with 50% deionized water, and emulsify by high-speed shearing for 30 min to obtain a pre-emulsion.

[0009] S2. Block copolymerization: Add the remaining deionized water, 10% of the preemulsion obtained in step S1, and 50% of the initiator solution to the reactor. Under nitrogen protection, raise the temperature to 75-80℃ to initiate polymerization. Simultaneously add the remaining preemulsion and the remaining initiator solution dropwise, controlling the dropwise addition time to 2.5-3.5h.

[0010] S3. Post-treatment: After the addition is complete, keep the temperature at 75-80℃ for 1 hour, cool down to 45-50℃, add 1-2wt% neutralizing agent to adjust the pH to 7-8, and filter out the material.

[0011] Preferably, the acrylic hard monomer is a combination of methyl methacrylate and styrene in a mass ratio of (3-4):1; the phosphate monomer is Sipomer PAM-200.

[0012] Preferably, the functional monomer comprises acrylic acid and glycidyl methacrylate in a mass ratio of (3-5):(5-7); and the mass ratio of phosphate monomer to glycidyl methacrylate is 1:(1.2-1.8).

[0013] Preferably, the reactive emulsifier is allyl polyoxyethylene ether ammonium sulfate.

[0014] Preferably, the initiator in step S2 is an azobisisobutyramidine hydrochloride solution, and its amount is 0.2-0.5% of the total weight of all monomers.

[0015] Preferably, the acrylic block copolymer comprises hydrophobic blocks and hydrophilic blocks; the hydrophobic blocks are composed of methyl methacrylate, styrene and phosphate monomers; the hydrophilic blocks are composed of acrylic acid, glycidyl methacrylate and reactive emulsifiers.

[0016] Preferably, 0.1-0.3 wt% of chain transfer agent 3-mercaptopropionic acid is added simultaneously with the addition of the remaining preemulsion.

[0017] An aqueous dispersant based on an acrylic block copolymer, which is prepared by the aforementioned method.

[0018] This application has the following beneficial effects: By introducing a synergistic anchoring mechanism between phosphate monomers and glycidyl methacrylate (GMA), a bifunctional group structure is constructed in the acrylic block copolymer: the phosphate groups significantly enhance the wetting and adsorption capacity of the pigment surface, while the epoxy groups form chemical crosslinks with the active sites of the pigment during high-temperature film formation, thereby completely eliminating the use of solvents and achieving a super strong anchoring effect; combined with the intramolecular bonding design of reactive emulsifiers and the low-temperature polymerization process of pre-emulsification-synchronous drop addition, the environmental defects caused by solvent residues in traditional dispersants, the application bottleneck of high viscosity of high-concentration pigment pastes, and the industry problem of insufficient thermal storage stability are successfully solved, ultimately achieving comprehensive performance advantages of zero VOC emissions, extremely low viscosity, excellent storage stability, and significantly improved coloring power. Detailed Implementation

[0019] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited to the scope described in the embodiments.

[0020] Example 1 (Basic Formula)

[0021] A method for preparing an aqueous dispersant based on an acrylic block copolymer includes the following steps:

[0022] S1. Pre-emulsification: Add 18g of methyl methacrylate, 5g of styrene, 10g of butyl acrylate, 5g of isooctyl acrylate, 3g of acrylic acid, 4g of glycidyl methacrylate, 3g of Sipomer PAM-200, 2g of allyl polyoxyethylene ether ammonium sulfate, and 24g of deionized water (50% of the total water volume of 48g) to the reactor. Shear emulsify at 8000rpm for 30min to obtain a pre-emulsion.

[0023] S2. Block copolymerization: In a separate reactor, add the remaining 24g of water, heat to 80℃, add 10% (approximately 7.4g) of the pre-emulsion and 50% of the azobisisobutyramidine hydrochloride solution (0.3g of azobisisobutyramidine hydrochloride dissolved in 10g of water), and react under N2 protection for 15min until it turns bluish; at a constant temperature of 80℃, add the remaining pre-emulsion (approximately 66.6g) dropwise at 0.5ml / min, and simultaneously add the remaining azobisisobutyramidine hydrochloride solution (approximately 5.15g) and 0.2g of 3-mercaptopropionic acid dropwise at 0.1ml / min, with the total dropwise addition time controlled to approximately 3h.

[0024] S3. Post-treatment: After the addition is complete, keep it at 80℃ for 1 hour, cool it down to 50℃, add 1.5g of triethanolamine to neutralize to pH=7-8, and discharge it through a 400-mesh filter to obtain an aqueous dispersant based on acrylic block copolymer.

[0025] Example 2 (High glycidyl methacrylate + Low phosphate ester)

[0026] A method for preparing an aqueous dispersant based on an acrylic block copolymer includes the following steps:

[0027] S1. Pre-emulsification: Add 18g of methyl methacrylate, 5g of styrene, 10g of butyl acrylate, 5g of isooctyl acrylate, 3g of acrylic acid, 5.6g of glycidyl methacrylate, 2g of Sipomer PAM-200, 2g of allyl polyoxyethylene ether ammonium sulfate, and 24g of deionized water (50% of the total water volume of 48g) to the reactor. Shear emulsify at 8000rpm for 30min to obtain a pre-emulsion.

[0028] S2. Block copolymerization: In a separate reactor, add the remaining 24g of water, heat to 80℃, add 10% (approximately 7.46g) of the pre-emulsion and 50% of the azobisisobutyramidine hydrochloride solution (0.3g of azobisisobutyramidine hydrochloride dissolved in 10g of water), react under N2 protection for 15min until it turns bluish; at a constant temperature of 80℃, add the remaining pre-emulsion (approximately 67.14g) dropwise at 0.4ml / min, and simultaneously add the remaining azobisisobutyramidine hydrochloride solution (approximately 5.15g) and 0.2g of 3-mercaptopropionic acid dropwise at 0.1ml / min, with the total dropwise addition time controlled to approximately 3.5h.

[0029] S3. Post-treatment: After the addition is complete, keep it at 80℃ for 1 hour, cool it down to 50℃, add 1.5g of triethanolamine to neutralize to pH=7-8, and discharge it through a 400-mesh filter to obtain an aqueous dispersant based on acrylic block copolymer.

[0030] Example 3 (High phosphate ester + Low glycidyl methacrylate)

[0031] A method for preparing an aqueous dispersant based on an acrylic block copolymer includes the following steps:

[0032] S1. Pre-emulsification: Add 18g of methyl methacrylate, 5g of styrene, 10g of butyl acrylate, 5g of isooctyl acrylate, 5.6g of acrylic acid, 2.4g of glycidyl methacrylate, 5g of Sipomer PAM-200, 2g of allyl polyoxyethylene ether ammonium sulfate, and 24g of deionized water (50% of the total water volume of 48g) to the reactor. Shear emulsify at 8000rpm for 30min to obtain a pre-emulsion.

[0033] S2. Block copolymerization: In a separate reactor, add the remaining 24g of water, heat to 75℃, add 10% (approximately 7.7g) of the pre-emulsion and 50% of the azobisisobutyramidine hydrochloride solution (0.2g of azobisisobutyramidine hydrochloride dissolved in 10g of water), and react for 15min under N2 protection until it turns blue; at a constant temperature of 75℃, add the remaining pre-emulsion (approximately 69.3g) dropwise at 0.6ml / min, and simultaneously add the remaining azobisisobutyramidine hydrochloride solution (approximately 5.1g) and 0.2g of 3-mercaptopropionic acid dropwise at 0.1ml / min, with the total dropwise addition time controlled to approximately 2.5h.

[0034] S3. Post-treatment: After the addition is complete, keep it at 80℃ for 1 hour, cool it down to 50℃, add 1.5g of triethanolamine to neutralize to pH=7-8, and discharge it through a 400-mesh filter to obtain an aqueous dispersant based on acrylic block copolymer.

[0035] Example 4 (Single soft monomer + high emulsifier)

[0036] A method for preparing an aqueous dispersant based on an acrylic block copolymer includes the following steps:

[0037] S1. Pre-emulsification: Add 18g of methyl methacrylate, 5g of styrene, 15g of butyl acrylate, 3g of acrylic acid, 4g of glycidyl methacrylate, 3g of Sipomer PAM-200, 3g of allyl polyoxyethylene ether ammonium sulfate, and 24g of deionized water (50% of the total water volume of 48g) to the reactor, and shear emulsify at 8000rpm for 30min to obtain a pre-emulsion.

[0038] S2. Block copolymerization: In a separate reactor, add the remaining 24g of water, heat to 75℃, add 10% (approximately 7.5g) of the pre-emulsion and 50% of the azobisisobutyramidine hydrochloride solution (0.3g of azobisisobutyramidine hydrochloride dissolved in 10g of water), and react for 15min under N2 protection until it turns bluish; at a constant temperature of 75℃, add the remaining pre-emulsion (approximately 67.5g) dropwise at 0.5ml / min, and simultaneously add the remaining azobisisobutyramidine hydrochloride solution (approximately 5.15g) and 0.2g of 3-mercaptopropionic acid dropwise at 0.1ml / min, with the total dropwise addition time controlled to approximately 3h.

[0039] S3. Post-treatment: After the addition is complete, keep it at 80℃ for 1 hour, cool it down to 50℃, add 1.5g of triethanolamine to neutralize to pH=7-8, and discharge it through a 400-mesh filter to obtain an aqueous dispersant based on acrylic block copolymer.

[0040] Example 5 (Glycidyl methacrylate-free + hydrophilic chain extender)

[0041] A method for preparing an aqueous dispersant based on an acrylic block copolymer includes the following steps:

[0042] S1. Pre-emulsification: Add 18g of methyl methacrylate, 5g of styrene, 10g of butyl acrylate, 5g of isooctyl acrylate, 8g of acrylic acid, 3g of Sipomer PAM-200, 2g of allyl polyoxyethylene ether ammonium sulfate, and 20g of deionized water (50% of the total water volume of 40g) to the reactor. Shear emulsify at 8000rpm for 30min to obtain a pre-emulsion.

[0043] S2. Block copolymerization: In a separate reactor, add the remaining 20g of water, heat to 80℃, add 10% (approximately 7.1g) of the pre-emulsion and 50% of the azobisisobutyramidine hydrochloride solution (0.2g of azobisisobutyramidine hydrochloride dissolved in 10g of water), and react for 15min under N2 protection until it turns bluish; at a constant temperature of 80℃, add the remaining pre-emulsion (approximately 63.9g) dropwise at 0.5ml / min, and simultaneously add the remaining azobisisobutyramidine hydrochloride solution (approximately 5.1g) and 0.2g of 3-mercaptopropionic acid dropwise at 0.1ml / min, with the total dropwise addition time controlled to approximately 3h.

[0044] S3. Post-treatment: After the addition is complete, keep it at 80℃ for 1 hour, cool it down to 40℃, add 1.5g of triethanolamine to neutralize to pH=7-8, and discharge it through a 400-mesh filter to obtain an aqueous dispersant based on acrylic block copolymer.

[0045] The aqueous dispersants prepared in Examples 1-5 above were tested for solid content, pH, viscosity, and particle size. The data are shown in Table 1.

[0046] Table 1 Basic Properties of Water-Based Dispersants

[0047]

[0048] As shown in Table 1, the solid content of the aqueous dispersant prepared by the present invention is between 35-40%, and the viscosity is ≤110mPa·s. Among them, Example 3 has the lowest viscosity due to its high phosphate ester content, which has strong wetting properties.

[0049] The aqueous dispersant prepared in Examples 1-5 above was mixed with carbon black to prepare a black paste using conventional methods and tested. The data are shown in Table 2. The formula of the black paste is: 30 wt% Seiko-1000 Black, 5 wt% aqueous dispersant, 40 wt% butyl acetate, and 25 wt% propylene glycol methyl ether acetate.

[0050] Table 2 Properties of Black Paste

[0051]

[0052] Table 2 shows that the viscosity of the black paste in Examples 1-5 is ≤220 mPa·s, while that in Example 3, due to the strong wettability of 5% phosphate ester, reaches the optimal 188 mPa·s. Example 3 achieves a tinting strength of 120% due to the high phosphate ester anchoring and low glycidyl methacrylate reducing steric hindrance. The viscosity variation of all black paste samples is ≤10%, with Example 3 exhibiting the best stability due to its narrow molecular weight distribution.

[0053] The aqueous dispersants prepared in Examples 1-5 above were subjected to environmental protection testing, and the test data are shown in Table 3:

[0054] Table 3 Environmental friendliness and residue analysis

[0055]

[0056] As shown in Table 3, the reactive emulsifier and phosphate ester monomer work synergistically (Examples 1-4), and the solvent residue can achieve VOCs ≤ 1.5 g / L (compliant with the national standard ≤ 80 g / L); the acrylic acid (AA) residue in Example 5 is slightly higher, but still better than the industry standard (about 0.1%).

[0057] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an aqueous dispersant based on an acrylic block copolymer, characterized in that, Includes the following steps: S1. Pre-emulsification: Mix 15-25 wt% hard acrylic monomer, 10-20 wt% soft acrylic monomer, 5-10 wt% functional monomer, 2-5 wt% phosphate ester monomer, 1-3 wt% reactive emulsifier with 50% deionized water, and emulsify by high-speed shearing for 30 min to obtain a pre-emulsion. S2. Block copolymerization: Add the remaining deionized water, 10% of the preemulsion obtained in step S1, and 50% of the initiator solution to the reactor. Under nitrogen protection, raise the temperature to 75-80℃ to initiate polymerization. Simultaneously add the remaining preemulsion and the remaining initiator solution dropwise, controlling the dropwise addition time to 2.5-3.5h. S3. Post-treatment: After the addition is complete, keep the temperature at 75-80℃ for 1 hour, cool down to 45-50℃, add 1-2wt% neutralizing agent to adjust the pH to 7-8, and filter out the material.

2. The preparation method according to claim 1, characterized in that, The acrylic hard monomer is a combination of methyl methacrylate and styrene, with a mass ratio of (3-4):1; the phosphate monomer is Sipomer PAM-200.

3. The preparation method according to claim 1, characterized in that, The functional monomers comprise acrylic acid and glycidyl methacrylate in a mass ratio of (3-5):(5-7); the mass ratio of phosphate monomer to glycidyl methacrylate is 1:(1.2-1.8).

4. The preparation method according to claim 1, characterized in that, The reactive emulsifier is allyl polyoxyethylene ether ammonium sulfate.

5. The preparation method according to claim 1, characterized in that, In step S2, the initiator is an azobisisobutyramidine hydrochloride solution, and its amount is 0.2-0.8% of the total weight of all monomers.

6. The preparation method according to claim 1, characterized in that, The acrylic block copolymer comprises hydrophobic and hydrophilic blocks; the hydrophobic blocks are composed of methyl methacrylate, styrene and phosphate monomers; the hydrophilic blocks are composed of acrylic acid, glycidyl methacrylate and reactive emulsifiers.

7. The preparation method according to claim 1, characterized in that, Add 0.1-0.3 wt% chain transfer agent 3-mercaptopropionic acid simultaneously while adding the remaining preemulsion.

8. An aqueous dispersant based on an acrylic block copolymer, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

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