Preparation method and application of a styrene acrylate polymer emulsion

Abstract

The present application relates to the technical field of polymer preparation, and in particular to a preparation method and application of a styrene acrylate polymer emulsion, the preparation method comprising the following steps: S1, adding a reactive cationic emulsifier into deionized water to obtain an emulsifier solution; S2, mixing styrene, acrylate, a co-stabilizer and an initiator, then adding the mixture into the emulsifier solution, ultrasonic treatment, and reacting at 60-70 DEG C for 5-7 h under the protection of inert gas to obtain the styrene acrylate polymer emulsion. The monomer conversion rate of the preparation method is high, the particle size distribution of the obtained styrene acrylate polymer emulsion is uniform, and the application range is wide.

Description

Technical Field

[0001] This invention relates to the field of polymer preparation technology, specifically to a method for preparing and applying a styrene-acrylate polymer emulsion. Background Technology

[0002] Styrene-acrylate polymers, as an important class of polymer materials, possess irreplaceable application value in various fields such as coatings, adhesives, plastics modification, and textile auxiliaries, thanks to the excellent rigidity, weather resistance, and chemical stability imparted by styrene units, and the good flexibility, adhesion, and film-forming properties provided by acrylate units. In the coatings industry, these polymers can be used as film-forming resins, giving coatings excellent scrub resistance and gloss. In the adhesives field, by adjusting the monomer ratio of styrene and acrylate, a balance between adhesive strength and aging resistance can be achieved to meet the bonding requirements of different substrates. Therefore, optimizing their preparation process and improving the overall performance of the products has always been a research focus in the field of polymer materials.

[0003] Currently, the mainstream preparation method for styrene-acrylate polymers is mainly free radical polymerization, specifically including emulsion polymerization, solution polymerization, and bulk polymerization. For example, patent CN110540615B discloses a styrene-acrylate, its preparation method, and its application. This styrene-acrylate consists of a hard monomer phase mainly composed of styrene and a soft monomer phase mainly composed of soft monomer polymers such as butyl acrylate and methyl methacrylate. It can be used as a binder in water-based inks, giving the ink layer hardness, strength, anti-tack properties, water resistance, and film-forming properties, making it suitable for coating plastic films. However, existing emulsion polymerization processes still have many technical problems that need to be solved in practical applications: Firstly, to ensure emulsion stability, traditional processes require the addition of a large amount of emulsifiers (such as sodium dodecyl sulfate, nonylphenol polyoxyethylene ether, etc.). These emulsifiers remaining in the polymer film will significantly reduce the water resistance and adhesion of the coating, causing the coating to easily blister and peel off in humid environments. Patent CN114901709B discloses an aqueous polymer dispersion and its preparation. This dispersion contains a styrene acrylate polymer emulsion, which can be polymerized by free radical polymerization at 1 wt%. 90 wt% of a monomer comprising at least one optionally substituted styrene (a); 10 wt% 99 wt% of monomers comprising at least one (meth)acrylate alkyl ester (b); and 0 The monomer (c) is obtained by comprising 9 wt% of a monomer (c) containing at least one ethylene-type unsaturated monomer different from monomer (b). The polymerization is carried out in a polymerization medium containing a cationic prepolymer capable of at least 10 wt% free radical polymerization. 55 wt% of monomers comprising at least one ethylene-type unsaturated quaternary amine and / or tertiary amine (i), 35 wt% 90 wt% of a monomer containing at least one optionally substituted styrene (ii), and 0 The polymer dispersion was obtained by comprising 55 wt% of a monomer (iii) containing at least one alkyl (meth)acrylate. The oligomer content in the polymer dispersion was ≤1.4 wt%, calculated from the dry polymer content. While solution polymerization avoids the water resistance problems caused by emulsifiers and produces a uniform reaction system with easily controllable product molecular weight distribution, it requires the use of large amounts of organic solvents. These organic solvents are not only volatile and toxic, posing hazards to operator health and the environment, but also require recycling and purification in subsequent processes, increasing equipment investment and production energy consumption, which is inconsistent with the current development trend of green chemistry and energy conservation and emission reduction.

[0004] Therefore, there is an urgent need in the market to develop a method for preparing styrene acrylate polymer emulsions that is stable and environmentally friendly. Summary of the Invention

[0005] In view of the problems existing in the prior art, the purpose of this invention is to obtain a method for preparing a styrene acrylate polymer emulsion with high stability, environmental friendliness, high monomer conversion rate and uniform particle size distribution.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides a method for preparing a styrene-acrylate polymer emulsion, comprising the following steps: S1. Add the reactive cationic emulsifier to deionized water and stir for 30-40 minutes to obtain an emulsifier solution; S2. Styrene, acrylate, stabilizer, and initiator are mixed and stirred for 20-30 minutes. Then, an emulsifier solution is added and sheared at 1000-2000 rpm for 15-25 minutes under a pressure of 75-85 psi. The mixture is then subjected to low-temperature ultrasonic treatment and nitrogen gas is continuously introduced and allowed to stand for 20-30 minutes. After that, the temperature is raised to 60-70℃ and the reaction is carried out under nitrogen protection for 5-7 hours. The pH of the reaction system is controlled at 1-5 throughout the reaction process to obtain a styrene-acrylate polymer emulsion.

[0007] In some embodiments, the stabilizer is n-hexadecane.

[0008] In some embodiments, the ultrasonic treatment has a power of 300-400W and a duration of 5-7 minutes.

[0009] In some embodiments, the reactive cationic emulsifier has the following structural formula: n is an integer between 8 and 13.

[0010] In some embodiments, the method for preparing the reactive cationic emulsifier includes the following steps: (1) Add 3-buten-1-ol and KOH to the reactor, replace the air in the reactor with an inert gas, add a catalyst, and when the reaction temperature rises to 130-140℃, control the pressure to 0.2-0.5MPa, add ethylene oxide, react for 1-2 hours, cool, depressurize, and obtain product A; (2) Add product A obtained in step (1) and 6-chlorohexanoic acid to dichloromethane, then add a catalyst, extract and rotary evaporate to obtain product B; (3) Add the product B obtained in step (2) and sodium N-methyltaurate to DMF, react at 75-85℃ for 6-7h, and then rotary evaporate to obtain product C; (4) Add the product C obtained in step (3) to n-hexane along with p-chloromethylstyrene and pyridine, and react at 5-10℃ for 4-6 h. The reactive cationic emulsifier is obtained by rotary evaporation.

[0011] In some embodiments, the co-catalyst is Ca(OEt)2 / H3PO4.

[0012] In some embodiments, the amount of the co-catalyst added is 3%-8% of the molar amount of 3-buten-1-ol.

[0013] In some embodiments, the catalyst is concentrated sulfuric acid.

[0014] In some embodiments, the amount of catalyst added is 4%-10% of the molar amount of product A.

[0015] This invention first synthesizes allyl polyoxyethylene ether from 3-buten-1-ol and ethylene oxide, then esterifies it with 6-chlorohexanoic acid to introduce ester groups and chlorine atoms. Further, the chlorine atoms undergo a substitution reaction with sodium N-methyltaurate to introduce hydrophilic sulfonate groups and tertiary amine nitrogen atoms. Finally, the quaternization reaction between p-chloromethylstyrene and tertiary amine nitrogen atoms generates a cationic emulsifier containing two polymerizable groups. At the start of polymerization, the emulsifier molecules are regularly arranged on the surface of monomer droplets. After polymerization, it can actively participate in the copolymerization reaction of monomers (such as styrene, acrylates, etc.) and become part of the polymer chain. This "double insurance" mechanism greatly improves the copolymerization fixation efficiency of emulsifiers on polymer particles, solving the industry problem of traditional small molecule emulsifiers easily migrating after polymerization and affecting product performance. In addition, the cationic hydrophilic head can effectively adsorb on the surface of monomer droplets, reduce interfacial tension, and prevent droplets from undergoing Ostwald ripening or coalescence before polymerization through electrostatic repulsion, ensuring the stability of the fine emulsion polymerization reaction system. Furthermore, the covalent bond anchoring mechanism of this invention provides an effective solution for the preparation of high-performance polymers in the field of fine emulsion polymerization with extremely high requirements for water resistance, purity, and stability.

[0016] In some embodiments, the molar ratio of 3-buten-1-ol to ethylene oxide is 1:(8-13).

[0017] In some embodiments, the molar ratio of product A to 6-chlorohexanoic acid in step (2) is 1:(1-1.5). In some embodiments, the molar ratio of product B to sodium N-methyltaurate in step (3) is 1:(1-1.5).

[0018] In some embodiments, the molar ratio of product C to p-chloromethylstyrene in step (4) is 1:(1-1.5).

[0019] In some embodiments, the acrylate is acrylic acid, methacrylic acid and its derivatives, hexanediol diacrylate, ethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate and pentaerythritol tetraacrylate.

[0020] In some embodiments, the derivatives include esters, nitriles, amides, and silanes.

[0021] Preferably, the acrylate is a mixture of methacrylate, hexanediol diacrylate and pentaerythritol tetraacrylate, wherein the mass ratio of the three is 1:(0.2-0.5):(0.1-0.3).

[0022] In some embodiments, the mass ratio of styrene to acrylate is 1:(2-10).

[0023] In some embodiments, the particle size of the styrene acrylate polymer emulsion is 100-400 nm.

[0024] Preferably, the particle size of the styrene acrylate polymer emulsion is 200-300 nm.

[0025] The second aspect of the present invention provides the application of a styrene acrylate polymer emulsion in metal protective liquids, electronic-grade coating agents, and pulp barrier coatings.

[0026] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention copolymerizes styrene, acrylate, stabilizer and reactive cationic emulsifier by fine emulsion polymerization to prepare a styrene acrylate polymer emulsion, which has the advantages of uniform particle size, high monomer conversion rate and stable emulsion system.

[0027] (2) The present invention prepares a reactive cationic emulsifier that can participate in the copolymerization reaction of monomers, improves the copolymerization fixation efficiency of emulsifier on polymer particles, solves the industry problem that traditional small molecule emulsifiers are easy to migrate after polymerization and affect product performance. In addition, the monomer droplets are very small and stable. There are almost no condensates in the entire polymerization process. The reaction is stable and controllable, and the batch reproducibility is very good, which is conducive to industrial production. Detailed Implementation

[0028] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0029] The compounds and related reagents used in the following examples and comparative examples are all commercially available.

[0030] Unless otherwise specified, the post-processing steps such as "rotary evaporation", "drying", "extraction", and "reduced pressure distillation" used below are routine operations for those skilled in the art, and can be selected according to actual operation.

[0031] Preparation Example 1 The preparation method of reactive cationic emulsifier-1 includes the following steps: (1) Add 1 mol of 3-buten-1-ol and 1 mol of KOH to the reactor, replace the air in the reactor with nitrogen, add 0.05 mol of Ca(OEt)2 / H3PO4, raise the temperature to 135℃, control the pressure at 0.4 MPa, add 10.2 mol of ethylene oxide, react for 1.5 hours, cool, depressurize, and distill under reduced pressure to obtain product A, with the following structural formula: n=10; (2) Add 1 mol of product A obtained in step (1) and 1.1 mol of 6-chlorohexanoic acid to 5000 mL of dichloromethane, then add 0.08 mol of 95 wt% concentrated sulfuric acid, extract with deionized water, collect the organic phase, and rotary evaporate to obtain product B, with the following structural formula: n=10; (3) Add 1 mol of product B obtained in step (2) and 1.1 mol of sodium N-methyltaurate to 3000 mL of DMF, react at 80 °C for 6.5 h, and rotary evaporate to obtain product C, with the following structural formula: n=10; (4) Add 1 mol of product C obtained in step (3), 1.1 mol of p-chloromethylstyrene, and 1 mol of pyridine to 3000 mL of n-hexane, react at 7 °C for 5 h, and rotary evaporate to obtain reactive cationic emulsifier-1.

[0032] Preparation Example 2 The preparation method of reactive cationic emulsifier-2 is the same as that of preparation example 1, except that the amount of ethylene oxide added is 14.2 mol.

[0033] Preparation Example 3 The preparation method of reactive cationic emulsifier-3 is the same as that of preparation example 1, except that the amount of ethylene oxide added is 7.2 mol.

[0034] Preparation Example 4 The preparation method of reactive cationic emulsifier-4 is the same as that of preparation example 1, except that 3-buten-1-ol is replaced by an equal amount of 3-methyl-3-buten-1-ol.

[0035] Preparation Example 5 The preparation method of reactive cationic emulsifier-5 is the same as that of preparation example 1, except that 6-chlorohexanoic acid is replaced with 8-chlorooctanoic acid in equal amounts.

[0036] Preparation Example 6 The preparation method of reactive cationic emulsifier-6 is the same as that of preparation example 1, except that chloromethylstyrene is replaced by 4-chloro-1-butene in equal amounts.

[0037] Example 1 A method for preparing a styrene-acrylate polymer emulsion includes the following steps: S1. Add 0.4g of reactive cationic emulsifier-1 to 50ml of deionized water and stir for 35min to obtain an emulsifier solution; S2. 1g of styrene, 4g of acrylate (the mass ratio of methacrylate, hexanediol diacrylate and pentaerythritol tetraacrylate is 1:0.4:0.2), and 0.15g of styrene were sheared at 1500rpm for 20min under a pressure of +80psi. The mixture was then sonicated at 0℃ with a power of 350W for 6min. Nitrogen gas was continuously introduced and the mixture was allowed to stand for 25min. After that, the temperature was raised to 65℃ and the reaction was carried out under nitrogen protection for 6h. The pH of the reaction system was controlled to be 3 by 0.1M HCl throughout the reaction process to obtain a styrene-acrylate polymer emulsion.

[0038] Example 2 A method for preparing a styrene-acrylate polymer emulsion includes the following steps: S1. Add 0.4g of reactive cationic emulsifier-1 to 50ml of deionized water and stir for 35min to obtain an emulsifier solution; S2. Mix 1g styrene, 2g acrylate (methacrylate, hexanediol diacrylate and pentaerythritol tetraacrylate in a mass ratio of 1:0.2:0.1), 0.15g n-hexadecane and 0.25g azobisisobutyronitrile and stir for 25min. Then add all the emulsifier solution and shear at 2000rpm under 75psi pressure for 15min. Ultrasonic treatment at 0℃ with a power of 300W for 7min. Continuously purge with nitrogen and let stand for 20min. Then raise the temperature to 60℃ under nitrogen protection and react for 5h. The pH of the reaction system is controlled to 1 by 0.1M HCl throughout the reaction process to obtain a styrene-acrylate polymer emulsion.

[0039] Example 3 A method for preparing a styrene-acrylate polymer emulsion includes the following steps: S1. Add 0.4g of reactive cationic emulsifier-1 to 50ml of deionized water and stir for 35min to obtain an emulsifier solution; S2. Mix 1g styrene, 10g acrylate (methacrylate, hexanediol diacrylate and pentaerythritol tetraacrylate in a mass ratio of 1:0.5:0.3), 0.15g n-hexadecane and 0.25g azobisisobutyronitrile and stir for 25min. Then add all the emulsifier solution and shear at 1000rpm under 85psi pressure for 25min. Ultrasonic treatment at 0℃ with a power of 400W for 5min. Continuously purge with nitrogen and let stand for 30min. Then raise the temperature to 70℃ and react under nitrogen protection for 7h. The pH of the reaction system is controlled to be 5 by 0.1M HCl throughout the reaction process to obtain a styrene-acrylate polymer emulsion.

[0040] Example 4 A method for preparing a styrene acrylate polymer emulsion, the specific implementation method is the same as in Example 1, except that reactive cationic emulsifier-1 is replaced by reactive cationic emulsifier-2 in equal amounts.

[0041] Example 5 A method for preparing a styrene acrylate polymer emulsion, the specific implementation method is the same as in Example 1, except that reactive cationic emulsifier-1 is replaced by reactive cationic emulsifier-3 in equal amounts.

[0042] Example 6 A method for preparing a styrene acrylate polymer emulsion, the specific implementation method is the same as in Example 1, except that reactive cationic emulsifier-1 is replaced by reactive cationic emulsifier-4 in equal amounts.

[0043] Example 7 A method for preparing a styrene acrylate polymer emulsion, the specific implementation method is the same as in Example 1, except that reactive cationic emulsifier-1 is replaced by an equal amount of reactive cationic emulsifier-5.

[0044] Example 8 A method for preparing a styrene acrylate polymer emulsion, the specific implementation method is the same as in Example 1, except that reactive cationic emulsifier-1 is replaced by an equal amount of reactive cationic emulsifier-6.

[0045] Example 9 A method for preparing a styrene acrylate polymer emulsion, the specific implementation method is the same as in Example 1, except that the amount of acrylate added is 6g.

[0046] Comparative Example 1 A method for preparing a styrene acrylate polymer emulsion, the specific implementation method is the same as in Example 1, except that the reactive cationic emulsifier-1 is replaced by an equal amount of emulsifier NP-10.

[0047] Performance testing The styrene acrylate polymer emulsions obtained in each embodiment and comparative example were subjected to the following tests.

[0048] 1. Monomer conversion rate: The specific method is as follows: Weigh the reaction vessel and record it as m0. After the reaction is completed, cool the emulsion to room temperature, add 0.1% hydroquinone by mass of styrene to terminate the reaction, and then place it in a forced-air oven at 70℃ to dry to constant weight. Weigh and record the weight as m1. Monomer conversion rate = (m1-m0) / total mass of added styrene, acrylate and emulsifier × 100%.

[0049] 2. Particle size and polydispersity index The Z-average particle size and polydispersity index (PDI) of the emulsion were determined using a nanoparticle size analyzer at 25°C and a scattering angle of 90°. The values ​​were taken as averages from three parallel measurements.

[0050] The test results are shown in Table 1: Table 1 As shown in Table 1, the styrene-acrylate polymer emulsions of Examples 1-3 exhibited high monomer conversion rates and uniform particle size. A comparison of Examples 4 and 5 with Example 1 reveals that altering the ratio of 3-buten-1-ol to ethylene oxide decreased the emulsifying ability of the emulsifier, leading to a decrease in monomer conversion rate and uneven particle size distribution. A comparison of Examples 6 and 1 shows that replacing 3-buten-1-ol with an equal amount of 3-methyl-3-buten-1-ol may have affected its reaction with ethylene oxide due to steric hindrance, resulting in decreased emulsifying properties of the emulsifier, decreased monomer conversion rate, and uneven particle size distribution. Examples 7 and... The comparison of Example 1 shows that replacing 6-chlorohexanoic acid with an equal amount of 8-chlorooctanoic acid may lead to droplet aggregation, increased particle size, and uneven distribution. The comparison between Example 8 and Example 1 shows that replacing p-chloromethylstyrene with an equal amount of 4-chloro-1-butene may reduce the interaction forces between benzene rings, affecting the emulsification effect and resulting in uneven particle size distribution of the emulsion. The comparison between Example 9 and Example 1 shows that changing the ratio of styrene to acrylate may lead to higher emulsion viscosity, resulting in uneven particle size distribution of the emulsion. The comparison between Example 1 and Comparative Example 1 shows that directly using commercially available emulsifiers deteriorates the various properties of the emulsion.

[0051] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a styrene-acrylate polymer emulsion, characterized in that, Includes the following steps: S1. Add the reactive cationic emulsifier to deionized water and stir for 30-40 minutes to obtain an emulsifier solution; S2. Styrene, acrylate, stabilizer, and initiator are mixed and stirred for 20-30 minutes. Then, an emulsifier solution is added and sheared at 1000-2000 rpm for 15-25 minutes under a pressure of 75-85 psi. The mixture is then subjected to low-temperature ultrasonic treatment and nitrogen gas is continuously introduced and allowed to stand for 20-30 minutes. After that, the temperature is raised to 60-70℃ and the reaction is carried out under nitrogen protection for 5-7 hours. The pH of the reaction system is controlled at 1-5 throughout the reaction process to obtain a styrene-acrylate polymer emulsion.

2. The method for preparing the styrene-acrylate polymer emulsion according to claim 1, characterized in that, The structural formula of the reactive cationic emulsifier is as follows: n is an integer between 8 and 13. The method for preparing the styrene-acrylate polymer emulsion according to claim 1, characterized in that the method for preparing the reactive cationic emulsifier comprises the following steps: (1) Add 3-buten-1-ol and KOH to the reactor, replace the air in the reactor with an inert gas, add a co-catalyst, heat to 130-140℃, control the pressure at 0.2-0.5MPa, add ethylene oxide, react for 1-2 hours, cool, depressurize, and obtain product A; (2) Add product A obtained in step (1) and 6-chlorohexanoic acid to dichloromethane, then add a catalyst, extract and rotary evaporate to obtain product B; (3) Add the product B obtained in step (2) and sodium N-methyltaurate to DMF, react at 75-85℃ for 6-7h, and then rotary evaporate to obtain product C; (4) Add the product C obtained in step (3) to n-hexane along with p-chloromethylstyrene and pyridine, and react at 5-10℃ for 4-6 h. The reactive cationic emulsifier is obtained by rotary evaporation.

3. The method for preparing the styrene-acrylate polymer emulsion according to claim 2, characterized in that, The molar ratio of 3-buten-1-ol to ethylene oxide is 1:(8-13).

4. The method for preparing the styrene-acrylate polymer emulsion according to claim 2, characterized in that, The molar ratio of product A to 6-chlorohexanoic acid in step (2) is 1:(1-1.5).

5. The method for preparing the styrene-acrylate polymer emulsion according to claim 2, characterized in that, The molar ratio of product B to sodium N-methyltaurate in step (3) is 1:(1-1.5).

6. The method for preparing the styrene-acrylate polymer emulsion according to claim 2, characterized in that, The molar ratio of product C to p-chloromethylstyrene in step (4) is 1:(1-1.5).

7. The method for preparing the styrene-acrylate polymer emulsion according to claim 1, characterized in that, The acrylate is a mixture of acrylic acid, methacrylic acid and its derivatives, hexanediol diacrylate, ethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate and pentaerythritol tetraacrylate.

8. The method for preparing the styrene-acrylate polymer emulsion according to claim 1, characterized in that, The mass ratio of styrene to acrylate is 1:(2-10).

9. The method for preparing the styrene-acrylate polymer emulsion according to claim 1, characterized in that, The particle size of the styrene acrylate polymer emulsion is 100-400 nm.

10. The application of a styrene acrylate polymer emulsion prepared by any one of claims 1-9 in metal protective liquids, electronic-grade coating agents, and pulp barrier coatings.

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