Hydroxyl acrylic acid aqueous dispersion with high solid content and low viscosity and preparation method thereof

Abstract

The invention discloses a high-solid-content low-viscosity hydroxy acrylic acid aqueous dispersion and a preparation method thereof, and relates to the technical field of aqueous dispersions. The hydroxyl acrylic acid water-based dispersion is a dispersion system of a polymer in a water phase, and reaction monomers of the polymer comprise 70-90 parts of (methyl) acrylate monomers, 5-20 parts of hydroxyl acrylate monomers and 5-30 parts of hydroxyl macromonomers; the hydroxyl macromonomer is a (methyl) acrylated polyol oligomer, and the molecular weight Mn of the hydroxyl macromonomer is 250-600. The hydroxy acrylic acid water-based dispersion can increase the solid content and reduce the emulsion viscosity, and can be directly used for preparing environment-friendly high-performance water-based paint or adhesive; meanwhile, use of organic solvents is reduced in the production process, and VOC emission is reduced.

Description

Technical Field

[0001] This invention relates to the field of aqueous dispersion technology, and more specifically, to an aqueous dispersion of hydroxyacrylic acid with high solids content and low viscosity, and a method for preparing the same. Background Technology

[0002] Hydroxyacrylate polymers are versatile functional polymers. Their molecular side chains have active hydroxyl functional groups, which can chemically react with isocyanate groups to form cross-linked structures, making them widely used in the coatings industry.

[0003] Traditional hydroxyl acrylate polymers are typically obtained through solution polymerization or emulsion polymerization. Solution polymerization can produce high molecular weight polymers, but the resulting products have extremely high viscosity, requiring large amounts of organic solvents for dilution, leading to significant VOC emissions and affecting processing performance. Emulsion polymerization is more environmentally friendly, but the high water content in the dispersion system limits the solids content, generally making it difficult to exceed 40%. As the solids content increases, the viscosity of traditional acrylic emulsions rises sharply, affecting coatability and application performance, thus restricting their application scenarios.

[0004] In the synthesis of hydroxyl acrylate polymers, hydroxyl-containing functional monomers are typically used as core monomers to provide crosslinking reaction sites. However, commonly used hydroxyl monomers (such as 2-hydroxyethyl acrylate, HEMA) systems have higher viscosity at high molecular weights, making it difficult to prepare hydroxyl acrylate resins that simultaneously meet the requirements of high solids content and low viscosity. Studies have shown that using macromonomers can significantly reduce the viscosity of polymer systems, providing a theoretical basis for the preparation of low-viscosity polymer systems. However, there is currently a lack of technical solutions that combine this strategy with controlled radical polymerization for the preparation of aqueous dispersions.

[0005] Furthermore, the current classic process for producing water-dispersible hydroxyl acrylic resin involves free radical polymerization in an organic solvent (such as propylene glycol methyl ether, butanol, or isopropanol), followed by distillation to remove all or part of the solvent, neutralization, and dilution with water to convert to an aqueous phase. This process, which converts the organic phase to an aqueous phase, not only easily leads to poor emulsion dispersion stability, but also results in VOC emissions due to the use of organic solvents, placing a significant burden on the environment. Patent CN107540785A provides a water-dispersible hydroxyl acrylic resin and its preparation method. Under pressure, a mixture of monomers and initiator is dropwise added to an organic solvent, and hydroxyl acrylic resin is obtained through free radical solution polymerization. After neutralization, dilution with water, and dispersion, the hydroxyl acrylic resin is obtained. While this method can reduce VOCs to some extent, it relies on high pressure (0.5–1.5 MPa), which not only increases the stringent requirements for production equipment but also increases the risk of leakage under high pressure. Therefore, it is necessary to develop a method for preparing aqueous dispersions of hydroxyacrylic acid that can achieve both high solids content and low viscosity, while also solving the technical problems of poor dispersion stability and organic solvent contamination. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a hydroxy acrylic acid aqueous dispersion that has the characteristics of high solids content and low viscosity.

[0007] One of the objectives of this invention is to provide a method for preparing an aqueous dispersion of hydroxyacrylic acid, which produces a product with stable dispersibility. Furthermore, the use of an aqueous system reduces the use of organic solvents and VOC emissions, thus promoting green production.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A hydroxyacrylic acid aqueous dispersion is provided, wherein the dispersion is a polymer dispersion system in an aqueous phase, and the reactive monomers of the polymer comprise the following components in parts by weight: 70-90 parts of (meth)acrylate monomers, 5-20 parts of hydroxyacrylate monomers, 5-30 parts of hydroxyl macromonomer; The hydroxyl macromonomer is a (meth)acrylated polyol oligomer with a molecular weight Mn of 250-600.

[0009] Preferably, the molecular weight Mn of the hydroxyl macromonomer is 300-500; more preferably, the molecular weight Mn is 350-450.

[0010] The (meth)acrylates of this invention refer to the collective term for methacrylates and / or acrylates.

[0011] In some embodiments, the polydispersity index (Mw / Mn) of the polymer is ≤1.3. Preferably, the Mw / Mn is 1.2-1.3.

[0012] Preferably, the (meth)acrylate monomer is selected from one or more of butyl acrylate, methyl methacrylate, ethyl acrylate, isooctyl acrylate, isobornyl methacrylate, and hydroxyethyl methacrylate.

[0013] In some embodiments, the hydroxyacrylate monomer is selected from one or more of 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 4-hydroxybutyl acrylate.

[0014] In some embodiments, the hydroxyl macromonomer is selected from one or more of hydroxyl polyether glycol acrylate, castor oil modified acrylate, polycaprolactone modified hydroxyethyl acrylate, polyethylene glycol monoacrylate, and polyester acrylate oligomers.

[0015] Preferably, the hydroxyl macromonomer accounts for 5 to 20 wt% of the total amount of the reactants.

[0016] In some embodiments, the dispersion has a solids content of ≥30% and a dynamic viscosity of ≤2000 mPa·s at 25°C.

[0017] In some embodiments, the polymer is formed by free radical polymerization of the reactive monomers, and the reaction system further includes: 0.1-2 wt% chain transfer agent and 0.1-0.5 wt% initiator, based on the total amount of the reactive monomers.

[0018] In some embodiments, the sulfur-containing chain transfer agent is a sulfur-containing chain transfer agent; preferably, the chain transfer agent is a xanthate compound and / or a dithiocarbamate compound; more preferably, the xanthate compound is selected from one or more of O-ethyl-S-(1-methoxycarbonylethyl) xanthate, sodium ethyl xanthate, dimethyl xanthate, phenyl xanthate, and glycerol trixanthate. The sulfur-containing free radical regulating group of the sulfur-containing chain transfer agent of the present invention can effectively control the growth of the polymer chain, achieving precise adjustment of molecular weight and dispersion.

[0019] In some embodiments, the initiator is selected from one or more of persulfates, azo initiators, or organic peroxides.

[0020] Optionally, the persulfate includes, but is not limited to, potassium persulfate and ammonium persulfate; the azo initiator includes, but is not limited to, azobisisobutyramidine hydrochloride and azobisisobutyramidine imidazoline; and the organic peroxide includes, but is not limited to, benzoyl peroxide and tert-butyl peroxide.

[0021] Preferably, the initiator is selected from potassium persulfate, the initiation temperature is 70~80℃, and the reaction time is 3~6 hours.

[0022] A method for preparing an aqueous dispersion of hydroxyacrylic acid is provided, comprising the following steps: The raw material components are uniformly dispersed in an aqueous solvent and subjected to free radical polymerization under an inert gas atmosphere at 50-80°C to obtain the aqueous dispersion of hydroxyacrylic acid.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: In the aqueous dispersion of hydroxyl acrylic acid of the present invention, a hydroxyl macromonomer with a high molecular weight and hydroxyl functional group is introduced into the polymerization system as a reactive stabilizer or flexible segment. After polymerization, the macromonomer forms a long segment or cross-linked structure containing hydroxyl groups, which can increase the solid content and reduce the viscosity of the emulsion. It can be directly used to formulate environmentally friendly high-performance waterborne coatings or adhesives.

[0024] The method for preparing the aqueous dispersion of hydroxyacrylic acid of the present invention involves free radical polymerization in an aqueous system, resulting in a stable dispersion system of polymer particles in water. This method reduces the use of organic solvents during production, meets national requirements for VOC emissions, and is conducive to green production. Attached Figure Description

[0025] Figure 1 This is a DSC measurement result diagram of an aqueous dispersion of hydroxyacrylic acid according to Example 1 of the present invention.

[0026] Figure 2 This is a graph showing the results of dynamic light scattering measurement of an aqueous dispersion of hydroxyacrylic acid in Example 2 of the present invention.

[0027] Figure 3 These are before-and-after comparison images of an aqueous dispersion of hydroxyacrylic acid before and after one month of storage, as shown in Example 2 of the present invention. The left image shows a freshly prepared aqueous dispersion of hydroxyacrylic acid, and the right image shows a sample of the aqueous dispersion of hydroxyacrylic acid after one month of storage. Detailed Implementation

[0028] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0029] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0030] The hydroxyl macromonomers in the following examples include: PEGDA: Hydroxy-hydroxy polyether glycol acrylate, molecular weight Mn is 400; SR604, Sartamomer.

[0031] PCL-FA2D: Polycaprolactone-modified hydroxyethyl acrylate, molecular weight Mn is 400; Placcel FA-2D, Daicel Corporation, Japan. Example

[0032] A hydroxyacrylic acid aqueous dispersion, the raw material comprising the following components in parts by weight: 40 parts of butyl acrylate (BA) 40 parts of methyl methacrylate (MMA) 10 parts of 2-hydroxyethyl acrylate (HEMA) 10 parts of hydroxyl polyether glycol acrylate (PEGDA) 0.2 parts initiator, Chain transfer agent 1.0 part, 500 portions of deionized water.

[0033] The initiator is potassium persulfate (KPS); the chain transfer agent is O-ethyl-S-(1-methoxycarbonylethyl) xanthate.

[0034] A method for preparing an aqueous dispersion of hydroxyacrylic acid includes the following steps: S1. Add 500 g of deionized water and 0.2 g of potassium persulfate initiator to the reactor and stir slowly. S2, add 40g of BA, 40g of MMA, 10g of HEMA and 10g of PEGDA to the aqueous phase respectively; then add 1.0g of O-ethyl-S-(1-methoxycarbonylethyl) xanthate, a controllable free radical polymerization chain transfer agent, and stir at room temperature until the monomers are completely dispersed.

[0035] S3, adjust the pH of the system to 7, heat to 75℃, then purge with nitrogen for 5 min, and maintain at 75℃ with stirring for 4 h to carry out the polymerization reaction. After the reaction is completed, cool to room temperature to obtain a milky white aqueous dispersion.

[0036] A series of aqueous dispersions of hydroxyacrylic acid are provided, which differ from Example 1 in that the mass fractions of the components in each example and comparative example are shown in Table 1, and their physicochemical properties are as follows: Table 1. Components and physicochemical properties of Examples 1-4 and Comparative Example 1.

[0037]

[0038] Solid content: determined according to the method of standard GB / T 1725-2007, and weighed after baking in an oven at 120℃ for 60 minutes.

[0039] Hydroxyl content: determined according to the method of standard GB / T 12008.3-2009.

[0040] Viscosity: The viscosity was measured using a Brookfield viscometer according to the method of standard GB / T 2794-2022. The test conditions were: temperature 25℃, rotor model LV3, and rotation speed 30 rpm.

[0041] Polydispersity index (PDI) (Mw / Mn): determined by gel permeation chromatography (GPC) according to standard GB / T 21863-2008.

[0042] 1. DSC characterization: The aqueous dispersion sample of hydroxyacrylic acid from Example 1 was subjected to DSC analysis, and the results are as follows: Figure 1 As shown, the glass transition temperature (Tg) of this polymer is 20°C.

[0043] 2. Characterization of paint film properties The samples from Examples 1-2 were dried at 60°C after film formation, and the following performance tests were conducted. The results are shown in Table 2.

[0044] Table 2

[0045] 3. Dynamic light scattering characterization: The particle size distribution in the aqueous dispersion of hydroxyacrylic acid from Example 2 was characterized using dynamic light scattering; the results are as follows. Figure 2 As shown, the average particle size was measured to be 150 nm.

[0046] 4. Shear stability: The sample obtained in Example 2 was sheared at 2000 rpm for 30 min in a high-speed disperser, and then filtered for observation. The results showed that no demulsification or flocculent material was produced, proving that it was not affected by large shear force agitation.

[0047] 5. Long-term stability: The pH value of the aqueous emulsion obtained in Example 2 was measured to be 7.5. The sample was left to stand for one month, and the results were as follows... Figure 3 As shown, no obvious sedimentation was observed in the dispersion.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A hydroxyacrylic acid aqueous dispersion, characterized in that, The dispersion is a polymer dispersion system in an aqueous phase, and the reactive monomers of the polymer comprise the following components by mass: 70-90 parts of (meth)acrylate monomers, 5-20 parts of hydroxyacrylate monomers, 5-30 parts of hydroxyl macromonomer; The hydroxyl macromonomer is a (meth)acrylated polyol oligomer with a molecular weight Mn of 250-600.

2. The aqueous dispersion of hydroxyacrylic acid according to claim 1, characterized in that, The polydispersity index (Mw / Mn) of the polymer is ≤1.

3.

3. The aqueous dispersion of hydroxyacrylic acid according to claim 1, characterized in that, The (meth)acrylate monomers are selected from any one or more of butyl acrylate, methyl methacrylate, ethyl acrylate, isooctyl acrylate, isobornyl methacrylate, and hydroxyethyl methacrylate.

4. The aqueous dispersion of hydroxyacrylic acid according to claim 1, characterized in that, The hydroxy acrylate monomers are selected from any one or more of 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 4-hydroxybutyl acrylate.

5. The aqueous dispersion of hydroxyacrylic acid according to claim 1, characterized in that, The hydroxyl macromonomer is selected from any one or more of hydroxyl polyether glycol acrylate, castor oil modified acrylate, polycaprolactone modified hydroxyethyl acrylate, polyethylene glycol monoacrylate, and polyester acrylate oligomers.

6. The aqueous dispersion of hydroxyacrylic acid according to any one of claims 1-5, characterized in that, The dispersion has a solid content of ≥30% and a dynamic viscosity of ≤2000 mPa·s at 25℃.

7. The aqueous dispersion of hydroxyacrylic acid according to claim 1, characterized in that, The polymer is formed by free radical polymerization of the reactive monomers, and the reaction system also includes: 0.1-2 wt% chain transfer agent and 0.1-0.5 wt% initiator, based on the total amount of the reactive monomers.

8. The aqueous dispersion of hydroxyacrylic acid according to claim 7, characterized in that, The chain transfer agent is a xanthate ester compound and / or a dithiocarbamate compound.

9. The aqueous dispersion of hydroxyacrylic acid according to claim 7, characterized in that, The initiator is selected from one or more of persulfates, azo initiators, and organic peroxides.

10. A method for preparing the aqueous dispersion of hydroxyacrylic acid according to any one of claims 1-9, characterized in that, Includes the following steps: The raw material components are uniformly dispersed in an aqueous solvent and subjected to free radical polymerization under an inert gas atmosphere at 50-80°C to obtain the aqueous dispersion of hydroxyacrylic acid.

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