A method for preparing high solids content latex

Abstract

This invention provides a method for preparing high-solids-content latex, comprising the following steps: adding a nonionic emulsifier and an alkylphenol polyoxyethylene ether emulsifier to anionic latex, adjusting the pH to acidic using hydrochloric acid, and then heating to obtain a high-solids-content latex. The method for preparing high-solids-content latex provided in this application utilizes pH adjustment to disrupt the original emulsification system, introducing a new emulsification system. This separates the polymerization emulsification system from the agglomeration emulsification system, allowing the agglomeration process to be decoupled from the polymerization reaction, resulting in better agglomeration effect and ultimately increasing the particle size of the latex.

Description

Technical Field

[0001] This invention relates to the field of latex technology, and more particularly to a method for preparing high-solids-content latex. Background Technology

[0002] Agglomeration is an effective method to increase the particle size of emulsions. Utilizing physicochemical methods to agglomerate small-diameter latex particles (typically below 100 nm) into larger particles is a crucial step in determining whether high-solids styrene-butadiene latex can be obtained. Essentially, this process involves changes in the adsorption mode of emulsifiers on the particle surface of latex particles under external stimuli (such as changes in pH, pressure, and ionic strength). This leads to an increase in the interfacial energy between the latex particles and the continuous phase, thermodynamically reducing the stability of the latex particles. Consequently, the particles aggregate to reduce the interfacial area, enhance their stability, and ultimately become larger-diameter latex particles.

[0003] The commonly used acid agglomeration method reduces the electrostatic repulsion between latex particles through charge neutralization. While the process principle and method are simple, its reproducibility is low due to factors such as solution pH and the type of emulsifier. Furthermore, the acid and salt residues remaining in the latex particles after agglomeration can degrade the product's aging resistance, heat resistance, and color. Therefore, although this type of agglomeration method has existed for a long time, its industrial application is limited.

[0004] Therefore, providing a method with good agglomeration effect and minimal influence from the polymerization reaction system to increase the particle size of the emulsion is crucial for the production of high solids content latex. Summary of the Invention

[0005] The technical problem solved by this invention is to provide a method for preparing high solids content latex, and the preparation method provided in this application can increase the latex particle size.

[0006] In view of this, this application provides a method for preparing high-solids-content latex, comprising the following steps:

[0007] Nonionic emulsifiers and alkylphenol polyoxyethylene ether emulsifiers are added to anionic latex, and the pH is adjusted to acidic using hydrochloric acid. After heating, a high solids content latex is obtained.

[0008] Preferably, the nonionic emulsifier is selected from one or more of polyoxyethylene derivatives, alkylolamides, fatty acid esters, alkylamine oxides, and N-alkylpyrrolidones.

[0009] Preferably, the alkylphenol polyoxyethylene ether emulsifier is selected from one or more of dodecylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, and dinonylphenol polyoxyethylene ether.

[0010] Preferably, the anionic latex is used as the base, the amount of nonionic emulsifier added is 2-10 phr, and the amount of alkylphenol polyoxyethylene ether emulsifier added is 2-10 phr.

[0011] Preferably, the anionic latex is used as the base, the amount of nonionic emulsifier added is 2-6 phr, and the amount of alkylphenol polyoxyethylene ether emulsifier added is 2-6 phr.

[0012] Preferably, the pH value is 2 to 3.

[0013] Preferably, the temperature for heating is 80–100°C.

[0014] Preferably, the high-solids-content latex has an average particle size of 180–320 nm and a solids content of 60–70%.

[0015] This application provides a method for preparing high-solids-content latex, primarily targeting anionic emulsion systems. Specifically, it involves adding a nonionic emulsifier and an alkylphenol polyoxyethylene ether emulsifier to anionic latex, adjusting the pH to acidic using hydrochloric acid, and then heating to obtain a high-solids-content latex. The method provided in this application significantly increases the surface energy of the latex by adding a nonionic emulsifier and adjusting the pH, thereby promoting latex aggregation and increasing the latex particle size. Simultaneously, the alkylphenol polyoxyethylene ether emulsifier, acting as a co-emulsifier, itself contributes to aggregation. After pH adjustment, it exists as an emulsifier in the system, and temperature changes can alter its emulsifying ability to promote aggregation, ultimately increasing the latex particle size. Detailed Implementation

[0016] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0017] To address the issue of increasing the particle size of anionic latex, this application provides a method for preparing high-solids-content latex, which combines acid agglomeration with a polymeric agglomerant to prepare stable, large-particle-size, high-solids-content latex. Specifically, this invention discloses a method for preparing high-solids-content latex, comprising the following steps:

[0018] Nonionic emulsifiers and alkylphenol polyoxyethylene ether emulsifiers are added to anionic latex, and the pH is adjusted to acidic using hydrochloric acid. After heating, a high solids content latex is obtained.

[0019] Commonly used anionic emulsifiers exhibit reduced emulsifying ability at lower pH levels, leading to increased surface energy of emulsion particles and decreased compatibility between the emulsion particle phase and the aqueous phase. Changes in pH typically result in demulsification due to this decreased compatibility. However, this application incorporates alkylphenol polyoxyethylene ether nonionic surfactants as stabilizers before pH adjustment, ensuring the emulsion remains stable after pH adjustment. By altering the pH, the emulsion system is modified, and the unique physicochemical properties of the modified emulsion system facilitate agglomeration, thereby increasing the latex particle size.

[0020] In the preparation of high-solids-content latex, this application focuses on anionic emulsion systems to increase latex particle size. The anionic latex is a type of anionic latex well-known to those skilled in the art.

[0021] The nonionic emulsifier acts as a stabilizer, protecting the latex and maintaining its stability during pH adjustment. The nonionic emulsifier is selected from one or more of polyoxyethylene derivatives, alkylolamides, fatty acid esters, alkylamine oxides, and N-alkylpyrrolidones. More specifically, the nonionic emulsifier is selected from laurate or stearate.

[0022] The alkylphenol polyoxyethylene ether emulsifier, acting as a secondary emulsifier, can itself contribute to agglomeration. After pH adjustment, it exists as an emulsifier in the system, and temperature changes further enhance its emulsifying ability, promoting agglomeration. The alkylphenol polyoxyethylene ether emulsifier is selected from one or more of dodecylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, and dinonylphenol polyoxyethylene ether.

[0023] In this application, the anionic latex is used as the base, the amount of nonionic emulsifier added is 2 to 10 phr, and the amount of alkylphenol polyoxyethylene ether emulsifier added is 2 to 10 phr. Specifically, the amount of nonionic emulsifier added is 2 to 6 phr, and the amount of alkylphenol polyoxyethylene ether emulsifier added is 2 to 6 phr.

[0024] According to this invention, after adding a nonionic emulsifier and an alkylphenol polyoxyethylene ether emulsifier to the anionic latex, the pH is adjusted to acidic, specifically to pH 2-3. This application utilizes pH to disrupt the original emulsification system and introduce a new emulsification system, separating the polymerization emulsification system from the agglomeration emulsification system, thus detaching the agglomeration process from the influence of the polymerization reaction and achieving better agglomeration results. Finally, this application raises the temperature to 80-100°C to ensure the emulsifying ability of the alkylphenol polyoxyethylene ether emulsifier.

[0025] The method for preparing high-solids-content latex provided in this application is applicable to most anionic emulsion systems; the agglomeration is less affected by the emulsion system in the polymerization reaction, which can improve the polymerization efficiency; and it is easier to implement with good agglomeration effect. Experimental results show that the average particle size of the high-solids-content latex prepared in this application is 180–320 nm, and the solid content is 60–70%.

[0026] To further understand the present invention, the preparation method of high solids content latex provided by the present invention will be described in detail below with reference to the embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0027] The base latex used in the following embodiments is a base latex produced by the device and provided by Jingbo Zhongju New Materials Co., Ltd. The physical properties of the base latex are shown in Table 1.

[0028] Table 1. Physical property data of the base latex used in the embodiments.

[0029]

[0030] Preparation of alkylphenol polyoxyethylene ethers:

[0031] 1 mol of phenol was added to a reaction vessel, along with 0.75 kg of catalyst resin. Then, 2 mol of C8-C9 olefins were added under stirring. The mixture was heated to 140°C and refluxed for 8 hours. After cooling, the mixture was transferred to a distillation vessel, and a vacuum was applied. The alkylphenol fraction was removed at 220 Pa. The alkylphenol was then added to a condensation vessel, along with 2.6 kg of sodium hydroxide as a catalyst. The mixture was heated to melt, and the air in the vessel was replaced with nitrogen. After the air was removed, ethylene oxide was introduced, controlling the reaction temperature at 150-160°C and the reaction pressure at 0.2-0.3 MPa. When the amount of ethylene oxide introduced reached 9 mol, a sample was taken to measure the hydroxyl value. The condensation reaction was complete when the hydroxyl value reached 70-80 mg KOH / g. The pH of the solution was adjusted to 5.0-7.0 with acetic acid to obtain alkylphenol polyoxyethylene ether.

[0032] Control group 1

[0033] Take 200g of base latex, add 8g of laurate and 8g of alkylphenol polyoxyethylene ether, stir for 5 minutes, then add 3.5g of water, heat to 80℃, stir for 10 minutes, test the particle size of the latex, and dehydrate the prepared latex at 75℃ to a viscosity of about 800cp.

[0034] Control group 2

[0035] Take 200g of base latex, add 16g of water, stir for 5 minutes, then add 3.5g of HCl, heat to 80℃, stir for 10 minutes, test the particle size of the latex, and dehydrate the prepared latex at 75℃ to a viscosity of about 800cp.

[0036] Control group 3

[0037] Take 200g of base latex, add 8g of laurate, stir for 5 minutes, then add 3.5g of HCl, heat to 80℃, stir for 10 minutes, test the particle size of the latex, and dehydrate the prepared latex at 75℃ to a viscosity of about 800cp.

[0038] Control group 4

[0039] Take 200g of base latex, add 8g of alkylphenol polyoxyethylene ether, stir for 5min, then add 3.5g of HCl, heat to 80℃, stir for 10min, test the particle size of the latex, and dehydrate the prepared latex at 75℃ to a viscosity of about 800cp.

[0040] Example 1

[0041] Take 200g of base latex, add 8g of laurate and 8g of alkylphenol polyoxyethylene ether, stir for 5min, then add 3.5g of HCl, heat to 80℃, stir for 10min, test the particle size of the latex, and dehydrate the prepared latex at 75℃ to a viscosity of about 800cp.

[0042] Example 2

[0043] Take 200g of base latex, add 6g of laurate and 8g of alkylphenol polyoxyethylene ether, stir for 5min, then add 3.5g of HCl, heat to 80℃, stir for 10min, test the particle size of the latex, and dehydrate the prepared latex at 75℃ to a viscosity of about 800cp.

[0044] Example 3

[0045] Take 200g of base latex, add 10g of laurate and 8g of alkylphenol polyoxyethylene ether, stir for 5min, then add 3.5g of HCl, heat to 80℃, stir for 10min, test the particle size of the latex, and dehydrate the prepared latex at 75℃ to a viscosity of about 800cp.

[0046] Example 4

[0047] Take 200g of base latex, add 12g of laurate and 8g of alkylphenol polyoxyethylene ether, stir for 5min, then add 3.5g of HCl, heat to 80℃, stir for 10min, test the particle size of the latex, and dehydrate the prepared latex at 75℃ to a viscosity of about 800cp.

[0048] Example 5

[0049] Take 200g of base latex, add 8g of laurate and 6g of alkylphenol polyoxyethylene ether, stir for 5min, then add 3.5g of HCl, heat to 80℃, stir for 10min, test the particle size of the latex, and dehydrate the prepared latex at 75℃ to a viscosity of about 800cp.

[0050] Example 6

[0051] Take 200g of base latex, add 8g of laurate and 10g of alkylphenol polyoxyethylene ether, stir for 5min, then add 3.5g of HCl, heat to 80℃, stir for 10min, test the particle size of the latex, and dehydrate the prepared latex at 75℃ to a viscosity of about 800cp.

[0052] Example 7

[0053] Take 200g of base latex, add 8g of laurate and 12g of alkylphenol polyoxyethylene ether, stir for 5min, then add 3.5g of HCl, heat to 80℃, stir for 10min, test the particle size of the latex, and dehydrate the prepared latex at 75℃ to a viscosity of about 800cp.

[0054] The properties of the latexes prepared in the above examples and the control group were tested, and the test results are shown in Table 2.

[0055] Table 2 Performance data of latex prepared in the examples and control group

[0056]

[0057] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0058] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a high-solids-content latex, comprising the following steps: Nonionic emulsifiers and alkylphenol polyoxyethylene ether emulsifiers are added to anionic latex, stirred for 5 minutes, and then hydrochloric acid is added to adjust the pH to 2-3. The temperature is raised to 80°C and stirred for 10 minutes to obtain a high solids content latex. Based on the anionic latex, the amount of nonionic emulsifier added is 2-6 phr, and the amount of alkylphenol polyoxyethylene ether emulsifier added is 2-6 phr. The nonionic emulsifier is selected from lauryl esters; The alkylphenol polyoxyethylene ether emulsifier is selected from one or more of dodecylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, and dinonylphenol polyoxyethylene ether.

2. The preparation method according to claim 1, characterized in that, The high-solids-content latex has an average particle size of 180-320 nm and a solids content of 60-70%.

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