A core-shell type aqueous hydroxy acrylate microsphere emulsion, its preparation method and application

Abstract

The present application relates to a kind of core-shell type water-based hydroxyl acrylate microspheres emulsion and its preparation method and application. Core-shell water-based monodisperse acrylate emulsion is prepared by in-situ multi-stage variable speed drop method, including the following steps: core layer polymerization: after heating kettle bottom liquid, initiator solution is added, then multi-stage variable speed drop is added to core layer pre-emulsion containing core layer monomer, after adjusting pH using neutralizing agent, polyacrylate core layer emulsion is obtained;Shell polymerization: multi-stage variable speed drop is added to polyacrylate core layer emulsion containing shell pre-emulsion containing shell monomer and initiator solution, heat preservation, cooling, after reaction is completed, terminating agent is added, after adjusting pH using neutralizing agent, core-shell type water-based hydroxyl acrylate microspheres emulsion is obtained. The emulsion is used in exterior wall coating, wood coating or antirust coating field. Compared with prior art, the microspheres emulsion synthesized by the present application has the advantages of high solid content, high hydroxyl value, uniform particle size, etc.

Description

Technical Field

[0001] This invention relates to the field of waterborne coatings technology, specifically to a core-shell type waterborne hydroxy acrylate microsphere emulsion, its preparation method, and its application. Background Technology

[0002] With increasingly stringent controls on volatile organic compound (VOC) emissions in the coatings industry and a growing awareness of green development, the use of solvent-based coatings is facing unprecedented restrictions, leading to increased attention on VOC-free or low-VOC environmentally friendly coatings. Water-based coatings, high-solids coatings, powder coatings, and radiation-cured coatings are among the rapidly developing green coatings, with water-based coatings becoming the preferred choice for environmentally friendly coatings.

[0003] Acrylic emulsions are widely used in the preparation of waterborne coatings. Compared with solvent-based coatings, waterborne coatings have certain shortcomings in terms of film gloss, fullness, hardness, scratch resistance, and abrasion resistance. The main reasons severely restricting the development of waterborne coatings are poor compatibility between the dispersion and the curing agent, lower film gloss and hardness, and higher price. Therefore, chemical modification of the emulsion structure and optimization of the synthesis process are necessary.

[0004] Hydroxyacrylate emulsions are prepared via emulsion polymerization. Chinese patent CN 105199049 B relates to a core-shell structured hydroxyacrylate emulsion and its preparation method; however, the pre-emulsion preparation method is very complex, increasing process time. Chinese patent CN 101787098 A relates to a method for preparing a hybrid acrylate emulsion. During the preparation process, the monomers are not pre-emulsified, resulting in a wide particle size distribution in the prepared hybrid acrylate emulsion latex particles, affecting the final performance of the coating film. US patent USP 7402632 (July 22, 2008) reports a functional polyacrylate emulsion with a certain group end-capped structure, formulated with an isocyanate curing agent to create a water-based two-component polyurethane coating. This coating can cure at room temperature and exhibits good weather resistance, adhesion, and stain resistance. However, it suffers from drawbacks such as low hydroxyl content, low solids content, weak dispersion of polyurethane curing agents, and poor appearance of the two-component coating.

[0005] Various methods have been attempted to modify acrylic emulsions in the prior art. Zhang Yalian et al. (China Coatings, 2016, 31(7):19-22.) prepared a self-crosslinking acrylic emulsion with a core-shell structure using a semi-continuous emulsion polymerization method. They determined the optimal dosage of crosslinking monomers methacrylic acid (MAA), diacetone acrylamide (DAAM), and organosilicon monomers to improve the performance of wood primers and topcoats prepared from this emulsion. Most of the functional monomers mentioned in the prior art are relatively expensive. This patent mainly prepares a dispersion with both excellent coating gloss and hardness by controlling the ratio of core-shell monomers, while reducing costs. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of poor compatibility between waterborne acrylate resins and curing agents, low gloss and hardness of coatings, and high prices in the prior art. By developing a rapid pre-emulsification, segmented variable-speed polymerization method and core-shell monomer design, a core-shell type waterborne hydroxyl acrylate microsphere emulsion with high solid content, high hydroxyl value, and uniform particle size is synthesized, along with its preparation method and application.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] This invention utilizes a high-speed homogenizer for pre-emulsification, which improves emulsification efficiency and shortens pre-emulsification time. High-speed pre-emulsification also ensures finer and more stable pre-emulsified particles. By segmenting the dropping rate of the pre-emulsified monomers, the reaction at different polymerization stages can be adjusted. In the first stage, a slower dropping rate is controlled to ensure slower microsphere growth in the initial initiation phase, resulting in more uniform and stable synthesized microspheres. In the second stage, the dropping rate can be appropriately increased to improve reaction efficiency.

[0009] The microspheres exhibit a specific proportional relationship in terms of core and shell thickness, hydroxyl content, and glass transition temperature. This ensures good compatibility between the emulsion and the isocyanate curing agent. While maintaining a certain level of hardness in the microsphere core layer, the flexibility of the microsphere shell is enhanced, allowing the isocyanate to be fully adsorbed onto the microsphere surface and rapidly swell and diffuse. This results in a more complete reaction between the curing agent and the hydroxyl groups, leading to more uniform and dense cross-linking. The resulting paint film possesses high gloss and good hardness. The specific scheme is as follows:

[0010] A method for preparing a core-shell type aqueous hydroxy acrylate microsphere emulsion, comprising the following steps, wherein the core-shell aqueous monodisperse acrylate core-shell emulsion is prepared by an in-situ multi-stage variable-rate dropwise addition method:

[0011] Core layer polymerization: After heating the bottom liquid, an initiator solution is added, and then a core layer pre-emulsion containing core layer monomers is added dropwise in multiple stages at varying speeds. After adjusting the pH with a neutralizing agent, a polyacrylate core layer emulsion is obtained.

[0012] Shell polymerization: A shell pre-emulsion containing shell monomers and an initiator solution are added dropwise to a polyacrylate core emulsion at varying speeds in multiple stages. The mixture is kept warm and cooled. After the reaction is complete, a terminator is added, and the pH is adjusted with a neutralizing agent to obtain a core-shell type aqueous hydroxy acrylate microsphere emulsion.

[0013] Furthermore, the multi-stage variable-rate dropping of the core layer pre-emulsion includes at least three stages: the first stage has a dropping rate of 0.1-1 ml / min and a time of 0.1-10 min; the second stage has a dropping rate of 0.2-5 ml / min and a time of 0.2 min-3 h; and the third stage has a dropping rate of 0.4-10 ml / min and a time of 1-8 h, with a total dropping time of less than 240 min.

[0014] Furthermore, the multi-stage variable-speed drop addition of the shell pre-emulsion and the initiator solution includes at least two stages: the first stage involves dropping the shell pre-emulsion at a rate of 1-2 ml / min for 20-60 min; the second stage involves dropping the initiator solution at a rate of 0.1-1 ml / min, with a total drop addition time of less than 150 min.

[0015] Furthermore, the core pre-emulsion is a pre-emulsion mixture of water, a mixed emulsifier, a core monomer, and a chain transfer agent; the shell pre-emulsion is a pre-emulsion mixture of water, a mixed emulsifier, and a shell monomer; the bottom liquid includes water and a mixed emulsifier; and the initiator solution includes water and an initiator.

[0016] Furthermore, the core layer monomer comprises the following components in parts by mass:

[0017]

[0018] The shell monomer comprises the following components in parts by weight:

[0019]

[0020] Further, the chain transfer agent is optionally at least one compound having a thiol group, including tert-butylthiol, alkyl thioacetate, mercaptoethanol, mercaptopropionic acid, 2-ethylhexyl mercaptoacetate, mercaptopropyltrimethoxysilane, n-dodecylthiol or tert-dodecylthiol, preferably alkyl thioacetate or alkyl ester of mercaptopropionic acid, specifically preferably 2-ethylhexyl mercaptoacetate or isooctyl mercaptopropionic acid;

[0021] The α,β-monoene unsaturated monocarboxylic acids include acrylic acid, methacrylic acid, ethylacrylic acid, acryloxypropionic acid, methacryloyloxypropionic acid, acryloxyacetic acid, methacryloyloxyacetic acid, and their salts, anhydrides, and mixtures, preferably acrylic acid or methacrylic acid;

[0022] The esters of the α,β-monoene unsaturated monocarboxylic acids include esters of α,β-monoene unsaturated monocarboxylic acids and C1-C10 alkanols, specifically including esters of (meth)acrylic acid and C1-C10 alkanols, optionally at least one compound selected from methyl methacrylate, ethyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, tert-butyl ethyl methacrylate, n-hexyl methacrylate, n-heptyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, ethylhexyl methacrylate, n-nonyl methacrylate, n-decyl methacrylate, and isooctyl methacrylate; preferably methyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, and isooctyl methacrylate.

[0023] The vinyl aromatic compounds include styrene, 2-methylstyrene, 4-methylstyrene, 2-butylstyrene, 4-butylstyrene or 4-decylstyrene, preferably styrene.

[0024] The hydroxyalkyl methacrylates mentioned include hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, or 6-hydroxyhexyl acrylate.

[0025] Furthermore, the amount of chain transfer agent added is 0.05-5% of the sum of the weights of the shell monomer and the core monomer, preferably 0.5-2%; during mixing, a high-speed homogenizer is used with a rotation speed of 5000-20000 rpm, preferably 7500-15000 rpm, and most preferably 9000-13000 rpm, for a time of 0.5-5 min; the ratio of the core and shell monomers in the microspheres is 1 / 4-4 / 1, more preferably 1 / 2-2 / 1; the amount of initiator added accounts for 0.1-1.0% of the total mass of the core monomer, preferably 0.3-0.7%, and most preferably 0.4-0.6%; when adjusting the pH, a neutralizing agent is used to adjust the pH to 7.0-8.0.

[0026] Furthermore, the hybrid emulsifier is composed of anionic emulsifier and nonionic emulsifier, and the mass ratio of anionic emulsifier to nonionic emulsifier is 1:(1-5).

[0027] The anionic emulsifier is an organic acid sodium, including sodium dodecyl sulfonate (SLS), sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS), sodium dodecyl diphenyl ether disulfonate (SLDED), sodium styrene sulfonate (SSS), or sodium stearate (SAS), preferably sodium dodecylbenzene sulfonate or sodium dodecyl sulfate.

[0028] The nonionic emulsifier is an isomeric alcohol polyoxyethylene ether with the structural formula RO-(CH2CH2O). n -H, where R is a subset of C m H 2m+1 The general formula is an alkyl group, where m is 8, 10, 11, or 13, preferably 10 and 13; and n is 3, 5, 6, 7, 8, 10, or 12, preferably 6, 7, or 8; for example, when m is 13 and n is 7, C 13 H 27 -O-(CH2CH2O)7-H, abbreviated as 1307, the abbreviation rules are the same for other structures;

[0029] The initiator includes sodium persulfate, potassium persulfate, or ammonium persulfate, preferably ammonium persulfate; the neutralizing agent includes ammonia, sodium hydroxide, N,N-dimethylethanolamine, or triethylamine; the terminating agent includes tert-butyl hydroperoxide and / or sodium bisulfite; it can be tert-butyl hydroperoxide and sodium bisulfite in a mass ratio of 1:1.

[0030] A core-shell aqueous hydroxy acrylate microsphere emulsion prepared by the method described above. The emulsion has an adjustable particle size of 50-120 nm, a solid content of 40-50%, a hydroxyl content of 10-130 mg KOH / g, and the microspheres are uniform in size, monodisperse, and have a distribution index (PDI) < 0.05. After monomer design and polymerization control, the ratio of the glass transition temperatures of the core and shell layers in the microspheres is -3 / 1 to 3 / 1, with the core layer glass transition temperature being 30-90℃ and the shell layer glass transition temperature being -30 to 30℃. The hydroxyl content of the microspheres in the emulsion accounts for 1-5% of the total monomer mass, preferably 2-3%; the core-shell hydroxyl content ratio is 1 / 4-4 / 1. The glass transition temperature (Tg) of polymer copolymers is usually affected by the copolymer composition and directly determines the polymer's performance and application range; therefore, obtaining an accurate glass transition temperature is crucial. The Fox equation is often used theoretically and empirically to calculate the relationship between the glass transition temperature of polymers and their polymer composition. The common form of Fox's formula in most textbooks and reference books is:

[0031]

[0032] Where Tg is the glass transition temperature of the copolymer, Tg1 and Tg2 are the glass transition temperatures of component 1 and component 2 in the copolymer, respectively, and w1 and w2 are the mass fractions of component 1 and component 2, respectively. This invention calculates the theoretical Tg of the copolymer using the Fox formula, and experimental verification results are close to the theoretical calculation value.

[0033] An application of the core-shell type aqueous hydroxy acrylate microsphere emulsion as described above, the emulsion being used in the fields of exterior wall coatings, wood coatings, or rust-preventive coatings.

[0034] Compared with the prior art, the acrylate core-shell microsphere emulsion of the present invention is prepared by an in-situ multi-stage variable-speed dropwise addition method, which has high solid content, low viscosity and good storage stability. The microsphere particle size is controllable, the particle size distribution coefficient is low and it has monodispersity. Through monomer design and polymerization control, the microspheres have a certain proportional relationship in terms of core and shell thickness, hydroxyl content and glass transition temperature, so that the emulsion has good compatibility with isocyanate curing agent. The isocyanate can be fully adsorbed on the surface of microspheres and rapidly swell and diffuse, so that it reacts more fully with hydroxyl groups. The resulting paint film has high gloss and good hardness and wear resistance. Detailed Implementation

[0035] The embodiments of the present invention are described in detail below. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0036] A method for preparing a core-shell type aqueous hydroxy acrylate microsphere emulsion specifically includes the following steps:

[0037] (a) Preparation of core layer pre-emulsion: After mixing water, emulsifier, and core layer monomers, pre-emulsify for 0.5-5 min using a high-speed homogenizer at a speed of 5000-20000 rpm. The weight proportions of the main core layer monomers are as follows:

[0038]

[0039] (b) Preparation of shell pre-emulsion: After mixing water, emulsifier, shell monomers and chain transfer agent, pre-emulsify for 0.5-5 min using a high-speed homogenizer at a speed of 5000-20000 rpm. The weight parts of the main shell monomers are as follows:

[0040]

[0041] (c) Core layer polymerization: Add emulsifier and water to the reaction flask, purge with nitrogen, turn on the stirring and temperature control device, and control the temperature at 70-90℃. After adding the initiator, add the pre-emulsion dropwise between 1-10 min, and the dropwise addition time is between 1-5 h. After the dropwise addition is completed, adjust the pH to 7.0-8.0 with a neutralizing agent and keep warm for 10-60 min to obtain polyacrylate core layer emulsion;

[0042] (d) Shell polymerization: Based on the core emulsion, the shell pre-emulsion and initiator are added dropwise for 1-5 hours. After the addition is completed, the mixture is kept warm for 0.5-5 hours. After the reaction is completed, a terminator is added and a neutralizer is used to adjust the pH to 7.0-8.0 to obtain a core-shell type aqueous monodisperse hydroxy acrylate microsphere emulsion.

[0043] Example 1

[0044] A method for preparing a core-shell type aqueous hydroxy acrylate microsphere emulsion specifically includes the following steps:

[0045] Preparation of bottom liquid Z0: Under a nitrogen atmosphere, 43 parts of deionized water and 1.4 parts of mixed emulsifier (composed of 1 part of tridecyl alcohol polyoxyethylene ether and 0.4 parts of sodium dodecyl diphenyl ether disulfonate) are added to a 1L polymerization reactor equipped with a stirrer, condenser and peristaltic pump feeding device, and the temperature inside the reactor is raised to 80°C.

[0046] Preparation of initiator solution I1: Add 2.5 parts of deionized water and 0.3 parts of ammonium persulfate as initiator to an initiator tank equipped with a stirrer and a constant flow metering device at room temperature and pressure, and stir until completely dissolved for later use.

[0047] Preparation of pre-emulsion Z1: 22 parts of deionized water and 1.26 parts of mixed emulsifier (composed of 1 part of tridecyl alcohol polyoxyethylene ether and 0.26 parts of sodium dodecyl diphenyl ether disulfonate), 0.5 parts of 2-ethylhexyl mercaptoacetate, 24 parts of styrene, 10 parts of methyl methacrylate, 3 parts of hydroxyethyl methacrylate, 4 parts of methacrylic acid, and 3 parts of isooctyl acrylate were added to the pre-emulsion tank and sheared at 10,000 rpm for 2 min using a high-speed homogenizer.

[0048] Preparation of pre-emulsion Z2: 28 parts of deionized water and 0.74 parts of mixed emulsifier (composed of 0.4 parts of tridecyl alcohol polyoxyethylene ether and 0.34 parts of sodium dodecyl diphenyl ether disulfonate), 0.5 parts of chain transfer agent, 10 parts of styrene, 12 parts of methyl methacrylate, 12 parts of hydroxyethyl methacrylate, 2 parts of butyl methacrylate, 13 parts of butyl acrylate, 4 parts of methacrylic acid, and 3 parts of isooctyl acrylate were added to a pre-emulsion tank and sheared at 10,000 rpm for 2 min.

[0049] Preparation of initiator solution C2: Add 5 parts of deionized water and 0.1 parts of sodium persulfate as initiator, stir until completely dissolved and set aside.

[0050] When the temperature inside the polymerization reactor reaches 80℃, initiator solution I1 is added to the reactor all at once. After 2 minutes, pre-emulsion Z1 is added at a dropping rate of 0.5 ml / min. After 1 minute of dropping, the rate is adjusted to 1 ml / min. The total dropping time of Z1 is controlled within 240 minutes. After the dropping is complete, 1 part ammonia water is added to adjust the pH to 7.0, and the mixture is kept at this temperature for 10 minutes.

[0051] After 10 minutes, pre-emulsion Z2 was added to the polymerization reactor at a dropping rate of 1.6 ml / min. After 40 minutes, initiator solution I2 was added dropwise at a dropping rate of 0.1 ml / min. The dropping time of Z2 and I2 was controlled within 150 minutes. After the dropping was completed, the reactor was kept at this temperature for 60 minutes. The polymerization reactor was then naturally cooled to 70°C, and 0.5 parts of tert-butyl hydroperoxide and 0.5 parts of sodium bisulfite were added dropwise. The polymerization reactor was then naturally cooled to below 60°C, and the pH was adjusted to 7.2 with 1.5 parts of ammonia. The mixture was stirred for 10 minutes, and the discharge and filtration performance were tested to obtain the preparation method of the core-shell type aqueous hydroxy acrylate microsphere emulsion.

[0052] The solid content is 48.1%, the particle size is 100 nm, the total hydroxyl content is 2%, the hydroxyl content core-shell ratio is 1:4, the core-shell mass ratio is 1:1, the core Tg is 83℃, and the shell Tg is 30℃.

[0053] Example 2

[0054] A method for preparing a core-shell type aqueous hydroxy acrylate microsphere emulsion specifically includes the following steps:

[0055] Preparation of bottom liquid Z0: Under a nitrogen atmosphere, add 40 parts of deionized water and 1.4 parts of mixed emulsifier (composed of 1 part of tridecyl alcohol polyoxyethylene ether and 0.4 parts of sodium dodecyl diphenyl ether disulfonate) to a 1L polymerization reactor equipped with a stirrer, condenser and peristaltic pump feeding device, and heat the reactor to 70°C.

[0056] Preparation of initiator solution I1: At room temperature and pressure, add 2.5 parts of deionized water and 0.28 parts of ammonium persulfate as initiator to an initiator tank equipped with a stirrer and a constant flow metering device, and stir until completely dissolved for later use.

[0057] Preparation of pre-emulsion Z1: 23 parts of deionized water and 1.4 parts of mixed emulsifier (composed of 1.1 parts of tridecyl alcohol polyoxyethylene ether and 0.3 parts of sodium dodecyl diphenyl ether disulfonate), 1 part of 2-ethylhexyl mercaptoacetate, 10 parts of styrene, 10 parts of methyl methacrylate, 11 parts of hydroxyethyl methacrylate, 5 parts of butyl methacrylate, 7 parts of butyl acrylate, 2 parts of methacrylic acid, and 5 parts of isooctyl acrylate were added to a pre-emulsion tank and sheared at 5000 rpm for 5 min.

[0058] Preparation of pre-emulsion Z2: 21 parts of deionized water and 0.6 parts of mixed emulsifier (composed of 0.3 parts of tridecyl alcohol polyoxyethylene ether and 0.3 parts of sodium dodecyl diphenyl ether disulfonate), 5 parts of styrene, 4 parts of hydroxyethyl methacrylate, 27 parts of butyl acrylate, 4 parts of methacrylic acid, and 10 parts of isooctyl acrylate were added to the pre-emulsion tank and sheared at 5000 rpm for 5 min using a high-speed homogenizer.

[0059] Preparation of initiator solution C2: Add 5 parts of deionized water and 0.12 parts of sodium persulfate as initiator, stir until completely dissolved and set aside.

[0060] When the temperature inside the polymerization reactor reaches 70℃, initiator solution I1 is added to the reactor all at once. One minute later, pre-emulsion Z1 is added at a dropping rate of 1 ml / min for 10 minutes, then the rate is adjusted to 5 ml / min. After the addition is complete, 1 part ammonia is added to adjust the pH to 7.0, and the reactor is kept at this temperature for 20 minutes. After 20 minutes, pre-emulsion Z2 is added to the reactor at a dropping rate of 10 ml / min. After 40 minutes, initiator solution I2 is added to the reactor at a dropping rate of 0.5 ml / min. The dropping time for both Z2 and I2 is controlled within 150 minutes. After the addition is complete, the reactor is kept at this temperature for 30 minutes. The polymerization reactor was naturally cooled to 70°C, and 0.5 parts of tert-butyl hydroperoxide and 0.5 parts of sodium bisulfite were added dropwise. The polymerization reactor was then naturally cooled to below 60°C, and the pH was adjusted to 7.2 with 1.5 parts of ammonia. The mixture was stirred for 10 minutes, and the discharge and filtration performance were tested to obtain the preparation method of the core-shell type aqueous hydroxy acrylate microsphere emulsion.

[0061] The solid content is 50.2%, the particle size is 150nm, the total hydroxyl content is 2%, the hydroxyl content core-shell ratio is 3:1, the core-shell mass ratio is 1:1, the core Tg is 30℃, and the shell Tg is -30℃.

[0062] Example 3

[0063] A method for preparing a core-shell type aqueous hydroxy acrylate microsphere emulsion specifically includes the following steps:

[0064] Preparation of bottom liquid Z0: Under a nitrogen atmosphere, 48 parts of deionized water and 1.4 parts of mixed emulsifier (composed of 1 part of tridecyl alcohol polyoxyethylene ether and 0.4 parts of sodium dodecyl diphenyl ether disulfonate) are added to a 1L polymerization reactor equipped with a stirrer, condenser and peristaltic pump feeding device, and the temperature inside the reactor is raised to 80°C.

[0065] Preparation of initiator solution I1: At room temperature and pressure, add 2.5 parts of deionized water and 0.28 parts of ammonium persulfate as initiator to an initiator tank equipped with a stirrer and a constant flow metering device, and stir until completely dissolved for later use.

[0066] Preparation of pre-emulsion Z1: 26 parts of deionized water and 1.4 parts of mixed emulsifier (composed of 1.1 parts of tridecyl alcohol polyoxyethylene ether and 0.3 parts of sodium dodecyl diphenyl ether disulfonate), 2 parts of 2-ethylhexyl mercaptoacetate, 27 parts of styrene, 4 parts of methyl methacrylate, 7.7 parts of hydroxyethyl methacrylate, 6.3 parts of butyl acrylate, 2 parts of acrylic acid, and 3 parts of isooctyl acrylate were added to a pre-emulsion tank and sheared at 9000 rpm for 3 min.

[0067] Preparation of pre-emulsion Z2: 25 parts of deionized water and 0.6 parts of mixed emulsifier (composed of 0.3 parts of tridecyl alcohol polyoxyethylene ether and 0.3 parts of sodium dodecyl diphenyl ether disulfonate), 10 parts of styrene, 3 parts of methyl methacrylate, 15.3 parts of hydroxyethyl methacrylate, 16.7 parts of butyl acrylate, 2 parts of acrylic acid, and 3 parts of isooctyl acrylate were added to the pre-emulsion tank and sheared at 9000 rpm for 3 min using a high-speed homogenizer.

[0068] Preparation of initiator solution C2: Add 8 parts of deionized water and 0.12 parts of sodium persulfate as initiator, stir until completely dissolved and set aside.

[0069] When the temperature inside the polymerization reactor reaches 80℃, initiator solution I1 is added to the reactor all at once. After 5 minutes, pre-emulsion Z1 is added at a dropping rate of 0.4 ml / min. After another 5 minutes, the dropping rate is adjusted to 1 ml / min, and the total dropping time of Z1 is controlled within 240 minutes. After the addition is complete, 1 part ammonia water is added to adjust the pH to 7.0, and the reactor is kept at this temperature for 30 minutes. After 30 minutes, pre-emulsion Z2 is added to the reactor at a dropping rate of 5 ml / min. After another 40 minutes, initiator solution I2 is added to the reactor at a dropping rate of 0.1 ml / min, and the dropping time of Z2 and I2 is controlled within 150 minutes. After the addition is complete, the reactor is kept at this temperature for 60 minutes. The polymerization reactor was naturally cooled to 70°C, and 0.3 parts of tert-butyl hydroperoxide and 0.3 parts of sodium bisulfite were added dropwise. The polymerization reactor was then naturally cooled to below 60°C, and the pH was adjusted to 7.2 with 1.5 parts of ammonia. The mixture was stirred for 10 minutes, and the discharge and filtration performance were tested to obtain the preparation method of the core-shell type aqueous hydroxy acrylate microsphere emulsion.

[0070] The solid content is 43.2%, the particle size is 120 nm, the total hydroxyl content is 3%, the hydroxyl content core-shell ratio is 1:2, the core-shell mass ratio is 1:1, the core Tg is 51℃, and the shell Tg is 9.8℃.

[0071] Example 4

[0072] A method for preparing a core-shell type aqueous hydroxy acrylate microsphere emulsion specifically includes the following steps:

[0073] Preparation of bottom liquid Z0: Under a nitrogen atmosphere, 48 parts of deionized water and 1.4 parts of mixed emulsifier (composed of 1 part of tridecyl alcohol polyoxyethylene ether and 0.4 parts of sodium dodecyl diphenyl ether disulfonate) are added to a 1L polymerization reactor equipped with a stirrer, condenser and peristaltic pump feeding device, and the temperature inside the reactor is raised to 80°C.

[0074] Preparation of initiator solution I1: At room temperature and pressure, add 2.5 parts of deionized water and 0.28 parts of ammonium persulfate as initiator to an initiator tank equipped with a stirrer and a constant flow metering device, and stir until completely dissolved for later use.

[0075] Preparation of pre-emulsion Z1: 27 parts of deionized water and 1.4 parts of mixed emulsifier (composed of 1.1 parts of tridecyl alcohol polyoxyethylene ether and 0.3 parts of sodium dodecyl diphenyl ether disulfonate), 0.5 parts of isooctyl mercaptopropionate, 31.5 parts of styrene, 5 parts of methyl methacrylate, 11.5 parts of hydroxyethyl methacrylate, and 2 parts of acrylic acid were added to the pre-emulsion tank and sheared at 20,000 rpm for 0.5 min using a high-speed homogenizer.

[0076] Preparation of pre-emulsion Z2: 25 parts of deionized water and 0.6 parts of mixed emulsifier (composed of 0.3 parts of tridecyl alcohol polyoxyethylene ether and 0.3 parts of sodium dodecyl diphenyl ether disulfonate), 3 parts of styrene, 11.5 parts of hydroxyethyl methacrylate, 25.5 parts of butyl acrylate, 2 parts of acrylic acid, and 8 parts of isooctyl acrylate were added to the pre-emulsion tank and sheared at 20,000 rpm for 0.5 min using a high-speed homogenizer.

[0077] Preparation of initiator solution C2: Add 8 parts of deionized water and 0.12 parts of sodium persulfate as initiator, stir until completely dissolved and set aside.

[0078] When the temperature inside the polymerization reactor reaches 90℃, initiator solution I1 is added to the reactor all at once. Two minutes later, pre-emulsion Z1 is added at a dropping rate of 0.5 ml / min for another 2 minutes. The dropping rate is then adjusted to 1 ml / min, with the total dropping time of Z1 controlled within 240 minutes. After the addition is complete, 1 part ammonia is added to adjust the pH to 7.0, and the reactor is kept at this temperature for 10 minutes. Ten minutes later, pre-emulsion Z2 is added to the reactor at a dropping rate of 1.6 ml / min. Forty minutes later, initiator solution I2 is added to the reactor at a dropping rate of 0.1 ml / min, with the dropping time of Z2 and I2 controlled within 150 minutes. After the addition is complete, the reactor is kept at this temperature for 60 minutes. The polymerization reactor was naturally cooled to 70°C, and 0.5 parts of tert-butyl hydroperoxide and 0.5 parts of sodium bisulfite were added dropwise. The polymerization reactor was then naturally cooled to below 60°C, and the pH was adjusted to 7.2 with 1.5 parts of ammonia. The mixture was stirred for 10 minutes, and the discharge and filtration performance were tested to obtain the preparation method of the core-shell type aqueous hydroxy acrylate microsphere emulsion.

[0079] The solid content is 42.3%, the particle size is 110 nm, the total hydroxyl content is 3%, the hydroxyl content core-shell ratio is 1:1, the core-shell mass ratio is 1:1, the core Tg is 91.7℃, and the shell Tg is -27℃.

[0080] Example 5

[0081] A method for preparing a core-shell type aqueous hydroxy acrylate microsphere emulsion specifically includes the following steps:

[0082] Preparation of bottom liquid Z0: Under a nitrogen atmosphere, 48 parts of deionized water and 1.4 parts of mixed emulsifier (composed of 1 part of tridecyl alcohol polyoxyethylene ether and 0.4 parts of sodium dodecyl diphenyl ether disulfonate) are added to a 1L polymerization reactor equipped with a stirrer, condenser and peristaltic pump feeding device, and the temperature inside the reactor is raised to 80°C.

[0083] Preparation of initiator solution I1: At room temperature and pressure, add 2.5 parts of deionized water and 0.28 parts of ammonium persulfate as initiator to an initiator tank equipped with a stirrer and a constant flow metering device, and stir until completely dissolved for later use.

[0084] Preparation of pre-emulsion Z1: 25 parts of deionized water and 1.4 parts of mixed emulsifier (composed of 1.1 parts of tridecyl alcohol polyoxyethylene ether and 0.3 parts of sodium dodecyl diphenyl ether disulfonate), 1 part of isooctyl mercaptopropionate, 15 parts of styrene, 10 parts of methyl methacrylate, 15 parts of hydroxyethyl methacrylate, 2 parts of acrylic acid, and 3 parts of isooctyl acrylate were added to the pre-emulsion tank and sheared at 9000 rpm for 2 min using a high-speed homogenizer.

[0085] Preparation of pre-emulsion Z2: 25 parts of deionized water and 0.6 parts of mixed emulsifier (composed of 0.3 parts of tridecyl alcohol polyoxyethylene ether and 0.3 parts of sodium dodecyl diphenyl ether disulfonate), 10 parts of styrene, 5 parts of methyl methacrylate, 15 parts of hydroxyethyl methacrylate, 1 part of butyl methacrylate, 14 parts of butyl acrylate, 2 parts of acrylic acid, and 3 parts of isooctyl acrylate were added to a pre-emulsion tank and sheared at 9000 rpm for 2 min.

[0086] Preparation of initiator solution C2: Add 6 parts of deionized water and 0.12 parts of sodium persulfate as initiator, and stir until completely dissolved for later use.

[0087] When the temperature inside the polymerization reactor reaches 80℃, initiator solution I1 is added to the reactor all at once. Two minutes later, pre-emulsion Z1 is added at a dropping rate of 0.4 ml / min. After 1 minute of dropping, the rate is adjusted to 0.8 ml / min, with the total dropping time of Z1 controlled within 240 minutes. After the addition is complete, 1 part ammonia is added to adjust the pH to 7.0, and the reactor is kept at this temperature for 10 minutes. Ten minutes later, pre-emulsion Z2 is added to the reactor at a dropping rate of 1.6 ml / min. After 40 minutes, initiator solution I2 is added to the reactor at a dropping rate of 0.1 ml / min, with the dropping time of Z2 and I2 controlled within 150 minutes. After the addition is complete, the reactor is kept at this temperature for 60 minutes. The polymerization reactor was naturally cooled to 70°C, and 0.5 parts of tert-butyl hydroperoxide and 0.5 parts of sodium bisulfite were added dropwise. The polymerization reactor was then naturally cooled to below 60°C, and the pH was adjusted to 7.2 with 1.5 parts of ammonia. The mixture was stirred for 10 minutes, and the discharge and filtration performance were tested to obtain the preparation method of the core-shell type aqueous hydroxy acrylate microsphere emulsion.

[0088] The solid content is 45.4%, the particle size is 100 nm, the total hydroxyl content is 4%, the core-shell ratio of hydroxyl content is 1:1, the core-shell mass ratio is 1:1, the core Tg is 53℃, and the shell Tg is 17.2℃.

[0089] Example 6

[0090] A method for preparing a core-shell type aqueous hydroxy acrylate microsphere emulsion, specifically including the following steps:

[0091] Preparation of bottom liquid Z0: Under a nitrogen atmosphere, 48 parts of deionized water and 1.4 parts of mixed emulsifier (composed of 1 part of tridecyl alcohol polyoxyethylene ether and 0.4 parts of sodium dodecyl diphenyl ether disulfonate) are added to a 1L polymerization reactor equipped with a stirrer, condenser and peristaltic pump feeding device, and the temperature inside the reactor is raised to 80°C.

[0092] Preparation of initiator solution I1: Add 2.5 parts of deionized water and 0.25 parts of ammonium persulfate as initiator to an initiator tank equipped with a stirrer and a constant flow metering device at room temperature and pressure, and stir until completely dissolved for later use.

[0093] Preparation of pre-emulsion Z1: 10 parts of deionized water, 1.04 parts of mixed emulsifier (composed of 0.92 parts of tridecyl alcohol polyoxyethylene ether and 0.12 parts of sodium dodecyl diphenyl ether disulfonate), 1 part of mercaptoethanol, 7.4 parts of styrene, 2 parts of methyl methacrylate, 4.6 parts of hydroxyethyl methacrylate, 5 parts of butyl acrylate, and 1 part of methacrylic acid were added to the pre-emulsion tank and sheared at 10,000 rpm for 2 min using a high-speed homogenizer.

[0094] Preparation of pre-emulsion Z2: 42 parts of deionized water and 0.96 parts of mixed emulsifier (composed of 0.48 parts of tridecyl alcohol polyoxyethylene ether and 0.48 parts of sodium dodecyl diphenyl ether disulfonate), 16.1 parts of styrene, 10 parts of methyl methacrylate, 18.4 parts of hydroxyethyl methacrylate, 30.5 parts of butyl acrylate, 2 parts of methacrylic acid, and 3 parts of isooctyl acrylate were added to a pre-emulsion tank and sheared at 10,000 rpm for 2 min.

[0095] Preparation of initiator solution C2: Add 6 parts of deionized water and 0.16 parts of sodium persulfate as initiator, stir until completely dissolved and set aside.

[0096] When the temperature inside the polymerization reactor reaches 70℃, initiator solution I1 is added to the reactor all at once. Two minutes later, pre-emulsion Z1 is added at a dropping rate of 0.5 ml / min for 30 minutes. The dropping rate is then adjusted to 1 ml / min, with the total dropping time of Z1 controlled within 240 minutes. After the addition is complete, 1 part ammonia is added to adjust the pH to 7.0, and the reactor is kept at this temperature for 15 minutes. Ten minutes later, pre-emulsion Z2 is added to the reactor at a dropping rate of 1.6 ml / min. Forty minutes later, initiator solution I2 is added to the reactor at a dropping rate of 0.1 ml / min, with the dropping time of Z2 and I2 controlled within 150 minutes. After the addition is complete, the reactor is kept at this temperature for 30 minutes. Add 0.3 parts of tert-butyl hydroperoxide and 0.3 parts of sodium bisulfite, naturally cool the polymerization reactor to below 60°C, adjust the pH to 7.2 with 1.5 parts of ammonia, stir for 10 minutes, and test the discharge and filtration performance to obtain the preparation method of core-shell type aqueous hydroxy acrylate microsphere emulsion.

[0097] The solid content is 45.4%, the particle size is 110 nm, the total hydroxyl content is 3%, the hydroxyl content core-shell ratio is 1:4, the core-shell mass ratio is 1:4, the core Tg is 38.6℃, and the shell Tg is 8.6℃.

[0098] Example 7

[0099] A method for preparing a core-shell type aqueous hydroxy acrylate microsphere emulsion, specifically including the following steps:

[0100] Preparation of bottom liquid Z0: Under a nitrogen atmosphere, 48 parts of deionized water and 1.4 parts of mixed emulsifier (composed of 1 part of tridecyl alcohol polyoxyethylene ether and 0.4 parts of sodium dodecyl diphenyl ether disulfonate) are added to a 1L polymerization reactor equipped with a stirrer, condenser and peristaltic pump feeding device, and the temperature inside the reactor is raised to 90°C.

[0101] Preparation of initiator solution I1: Add 2.5 parts of deionized water and 0.27 parts of ammonium persulfate as initiator to an initiator tank equipped with a stirrer and a constant flow metering device at room temperature and pressure, and stir until completely dissolved for later use.

[0102] Preparation of pre-emulsion Z1: 16 parts of deionized water and 1.2 parts of mixed emulsifier (composed of 1 part of tridecyl alcohol polyoxyethylene ether and 0.2 parts of sodium dodecyl diphenyl ether disulfonate), 1 part of 2-ethylhexyl mercaptoacetate, 10 parts of styrene, 10 parts of methyl methacrylate, 7.7 parts of hydroxyethyl methacrylate, 1.6 parts of butyl acrylate, 1 part of acrylic acid, and 3 parts of isooctyl acrylate were added to a pre-emulsion tank and sheared at 10,000 rpm for 1 min.

[0103] Preparation of pre-emulsion Z2: 34 parts of deionized water and 0.8 parts of mixed emulsifier (composed of 0.4 parts of tridecyl alcohol polyoxyethylene ether and 0.4 parts of sodium dodecyl diphenyl ether disulfonate), 13.4 parts of styrene, 10 parts of methyl methacrylate, 15.3 parts of hydroxyethyl methacrylate, 23 parts of butyl acrylate, 2 parts of acrylic acid, and 3 parts of isooctyl acrylate were added to the pre-emulsion tank and sheared at 10,000 rpm for 1 min using a high-speed homogenizer.

[0104] Preparation of initiator solution C2: Add 8 parts of deionized water and 0.13 parts of sodium persulfate as initiator, stir until completely dissolved and set aside.

[0105] When the temperature inside the polymerization reactor reaches 80℃, initiator solution I1 is added to the reactor all at once. Two minutes later, pre-emulsion Z1 is added at a dropping rate of 0.5 ml / min. After 1 minute of dropping, the rate is adjusted to 2 ml / min, with the total dropping time of Z1 controlled within 240 minutes. After the addition is complete, 1 part ammonia water is added to adjust the pH to 7.0, and the reactor is kept at this temperature for 10 minutes. Ten minutes later, pre-emulsion Z2 is added to the reactor at a dropping rate of 4 ml / min. After 40 minutes, initiator solution I2 is added to the reactor at a dropping rate of 0.2 ml / min, with the dropping time of Z2 and I2 controlled within 150 minutes. After the dropping is complete, the reactor is kept at this temperature for 180 minutes. The polymerization reactor was naturally cooled to 70°C, and 0.5 parts of tert-butyl hydroperoxide and 0.5 parts of sodium bisulfite were added dropwise. The polymerization reactor was then naturally cooled to below 60°C, and the pH was adjusted to 7.2 with 1.5 parts of ammonia. The mixture was stirred for 10 minutes, and the discharge and filtration performance were tested.

[0106] The solid content is 45.3%, the particle size is 90 nm, the total hydroxyl content is 3%, the core-shell ratio of hydroxyl content is 1:2, the core-shell mass ratio is 1:2, the core Tg is 56.7℃, and the shell Tg is 13℃.

[0107] Example 8

[0108] A method for preparing a core-shell type aqueous hydroxy acrylate microsphere emulsion, specifically including the following steps:

[0109] Preparation of bottom liquid Z0: Under a nitrogen atmosphere, 48 parts of deionized water and 1.4 parts of mixed emulsifier (composed of 1 part of tridecyl alcohol polyoxyethylene ether and 0.4 parts of sodium dodecyl diphenyl ether disulfonate) are added to a 1L polymerization reactor equipped with a stirrer, condenser and peristaltic pump feeding device, and the temperature inside the reactor is raised to 90°C.

[0110] Preparation of initiator solution I1: Add 2.5 parts of deionized water and 0.33 parts of ammonium persulfate as initiator to an initiator tank equipped with a stirrer and a constant flow metering device at room temperature and pressure, and stir until completely dissolved for later use.

[0111] Preparation of pre-emulsion Z1: 34 parts of deionized water and 1.6 parts of mixed emulsifier (composed of 1.2 parts of tridecyl alcohol polyoxyethylene ether and 0.4 parts of sodium dodecyl diphenyl ether disulfonate), 1 part of 2-ethylhexyl mercaptoacetate, 23.4 parts of styrene, 11.05 parts of methyl methacrylate, 17.25 parts of hydroxyethyl methacrylate, 10 parts of butyl acrylate, 2 parts of acrylic acid, and 3 parts of isooctyl acrylate were added to a pre-emulsion tank and sheared at 10,000 rpm for 2 min.

[0112] Preparation of pre-emulsion Z2: 16 parts of deionized water and 0.4 parts of mixed emulsifier (composed of 0.2 parts of tridecyl alcohol polyoxyethylene ether and 0.2 parts of sodium dodecyl diphenyl ether disulfonate), 5 parts of styrene, 5 parts of methyl methacrylate, 5.75 parts of hydroxyethyl methacrylate, 12.55 parts of butyl acrylate, 2 parts of acrylic acid, and 3 parts of isooctyl acrylate were added to a pre-emulsion tank and sheared at 10,000 rpm for 2 min.

[0113] Preparation of initiator solution C2: Add 6 parts of deionized water and 0.07 parts of sodium persulfate as initiator, and stir until completely dissolved for later use.

[0114] When the temperature inside the polymerization reactor reaches 80℃, initiator solution I1 is added to the reactor all at once. Two minutes later, pre-emulsion Z1 is added at a dropping rate of 0.1 ml / min. After 5 minutes of dropping, the rate is adjusted to 0.2 ml / min. After the addition is complete, 1 part ammonia is added to adjust the pH to 7.0, and the reactor is kept at this temperature for 30 minutes. Ten minutes later, pre-emulsion Z2 is added to the reactor at a dropping rate of 0.4 ml / min. After 40 minutes, initiator solution I2 is added to the reactor at a dropping rate of 0.1 ml / min. The dropping time for both Z2 and I2 is controlled within 150 minutes. After the addition is complete, the reactor is kept at this temperature for 300 minutes. The polymerization reactor was naturally cooled to 70°C, and 0.5 parts of tert-butyl hydroperoxide and 0.5 parts of sodium bisulfite were added dropwise. The polymerization reactor was then naturally cooled to below 60°C, and the pH was adjusted to 7.2 with 1.5 parts of ammonia. The mixture was stirred for 10 minutes, and the discharge and filtration performance were tested to obtain the preparation method of the core-shell type aqueous hydroxy acrylate microsphere emulsion.

[0115] The solid content is 45.4%, the particle size is 80 nm, the total hydroxyl content is 3%, the core-shell ratio of hydroxyl content is 3:1, the core-shell mass ratio is 2:1, the core Tg is 66.7℃, and the shell Tg is 3.1℃.

[0116] Example 9

[0117] A method for preparing a core-shell type aqueous hydroxy acrylate microsphere emulsion, specifically including the following steps:

[0118] Preparation of bottom liquid Z0: Under a nitrogen atmosphere, 40 parts of deionized water and 1.4 parts of mixed emulsifier (composed of 1 part of tridecyl alcohol polyoxyethylene ether and 0.4 parts of sodium dodecyl diphenyl ether disulfonate) are added to a 1L polymerization reactor equipped with a stirrer, condenser and peristaltic pump feeding device, and the temperature inside the reactor is raised to 80°C.

[0119] Preparation of initiator solution I1: At room temperature and pressure, add 2.5 parts of deionized water and 0.36 parts of ammonium persulfate as initiator to an initiator tank equipped with a stirrer and a constant flow metering device, and stir until completely dissolved for later use.

[0120] Preparation of pre-emulsion Z1: 42 parts of deionized water and 1.76 parts of mixed emulsifier (composed of 1.28 parts of tridecyl alcohol polyoxyethylene ether and 0.48 parts of sodium dodecyl diphenyl ether disulfonate), 1 part of 2-ethylhexyl mercaptoacetate, 23 parts of styrene, 29.3 parts of methyl methacrylate, 18.6 parts of hydroxyethyl methacrylate, 4 parts of butyl acrylate, 2 parts of acrylic acid, and 3 parts of isooctyl acrylate were added to a pre-emulsion tank and sheared at 10,000 rpm for 2 min.

[0121] Preparation of pre-emulsion Z2: 10 parts of deionized water, 0.24 parts of mixed emulsifier (composed of 0.12 parts of tridecyl alcohol polyoxyethylene ether and 0.12 parts of sodium dodecyl diphenyl ether disulfonate), 2 parts of styrene, 2 parts of methyl methacrylate, 4.6 parts of hydroxyethyl methacrylate, 10.4 parts of butyl acrylate, and 1 part of acrylic acid were added to a pre-emulsion tank and sheared at 8000 rpm for 2 min using a high-speed homogenizer.

[0122] Preparation of initiator solution C2: Add 6 parts of deionized water and 0.04 parts of sodium persulfate as initiator, and stir until completely dissolved for later use.

[0123] When the temperature inside the polymerization reactor reaches 80℃, initiator solution I1 is added to the reactor all at once. Two minutes later, pre-emulsion Z1 is added at a dropping rate of 0.5 ml / min. After 1 minute of dropping, the rate is adjusted to 1 ml / min, with the total dropping time of Z1 controlled within 240 minutes. After the addition is complete, 1 part ammonia water is added to adjust the pH to 7.0, and the reactor is kept at this temperature for 10 minutes. Ten minutes later, pre-emulsion Z2 is added to the reactor at a dropping rate of 1.6 ml / min. After 40 minutes, initiator solution I2 is added to the reactor at a dropping rate of 0.1 ml / min, with the dropping time of Z2 and I2 controlled within 150 minutes. After the dropping is complete, the reactor is kept at this temperature for 60 minutes. The polymerization reactor was naturally cooled to 70°C, and 0.5 parts of tert-butyl hydroperoxide and 0.5 parts of sodium bisulfite were added dropwise. The polymerization reactor was then naturally cooled to below 60°C, and the pH was adjusted to 7.2 with 1.5 parts of ammonia. The mixture was stirred for 10 minutes, and the discharge and filtration performance were tested to obtain the preparation method of the core-shell type aqueous hydroxy acrylate microsphere emulsion.

[0124] The solid content is 46.2%, the particle size is 140nm, the total hydroxyl content is 3%, the hydroxyl content core-shell ratio is 4:1, the core-shell mass ratio is 4:1, the core Tg is 70℃, and the shell Tg is -4℃.

[0125] Comparative Example 1

[0126] The ratio of core-shell monomers was adjusted to 1:5, and other conditions were the same as in Example 1, to prepare a core-shell type hydroxy acrylic emulsion and a topcoat.

[0127] Comparative Example 2

[0128] A method for preparing a core-shell type aqueous hydroxy acrylate microsphere emulsion differs from that in Example 1 in that:

[0129] Preparation of pre-emulsion Z1: 28 parts of deionized water and 0.74 parts of mixed emulsifier (composed of 0.4 parts of tridecyl alcohol polyoxyethylene ether and 0.34 parts of sodium dodecyl diphenyl ether disulfonate), 0.5 parts of 2-ethylhexyl mercaptoacetate, 10 parts of styrene, 12 parts of methyl methacrylate, 12 parts of hydroxyethyl methacrylate, 2 parts of butyl methacrylate, 13 parts of butyl acrylate, 4 parts of methacrylic acid, and 3 parts of isooctyl acrylate were added to a pre-emulsion tank and sheared at 10,000 rpm for 2 min.

[0130] Preparation of pre-emulsion Z2: 22 parts of deionized water, 1.26 parts of mixed emulsifier (composed of 1 part of tridecyl alcohol polyoxyethylene ether and 0.26 parts of sodium dodecyl diphenyl ether disulfonate), 24 parts of styrene, 10 parts of methyl methacrylate, 3 parts of hydroxyethyl methacrylate, 4 parts of methacrylic acid, and 3 parts of isooctyl acrylate were added to the pre-emulsion tank and sheared at 10,000 rpm for 2 min using a high-speed homogenizer.

[0131] The core glass transition temperature was adjusted to 30°C, and the core glass transition temperature was adjusted to 80°C, with specific formulations as shown in Z1 and Z2. Other conditions were the same as in Example 1, and a core-shell type hydroxy acrylic emulsion and topcoat were prepared.

[0132] Comparative Example 3

[0133] A method for preparing a core-shell type aqueous hydroxy acrylate microsphere emulsion differs from that in Example 1 in that:

[0134] Preparation of pre-emulsion Z1: 22 parts of deionized water and 1.26 parts of mixed emulsifier (composed of 1 part of tridecyl alcohol polyoxyethylene ether and 0.26 parts of sodium dodecyl diphenyl ether disulfonate), 0.5 parts of 2-ethylhexyl mercaptoacetate, 24 parts of styrene, 10 parts of methyl methacrylate, 2.5 parts of hydroxyethyl methacrylate, 4 parts of methacrylic acid, and 3 parts of isooctyl acrylate were added to the pre-emulsion tank and sheared at 10,000 rpm for 2 min using a high-speed homogenizer.

[0135] Preparation of pre-emulsion Z2: 28 parts of deionized water and 0.74 parts of mixed emulsifier (composed of 0.4 parts of tridecyl alcohol polyoxyethylene ether and 0.34 parts of sodium dodecyl diphenyl ether disulfonate), 0.5 parts of chain transfer agent, 10 parts of styrene, 12 parts of methyl methacrylate, 12.5 parts of hydroxyethyl methacrylate, 2 parts of butyl methacrylate, 13 parts of butyl acrylate, 4 parts of methacrylic acid, and 3 parts of isooctyl acrylate were added to a pre-emulsion tank and sheared at 10,000 rpm for 2 min.

[0136] The ratio of hydroxyl content in the core and shell layers was adjusted to 1:5, with specific formulations as shown in Z1 and Z2. Other conditions were the same as in Example 1, and a core-shell type hydroxyl acrylic emulsion and topcoat were prepared.

[0137] Comparative Example 4

[0138] The droplet acceleration of the pre-emulsion was uniformly adjusted to a constant rate of 1 ml / min, and other conditions were the same as in Example 1, to prepare a core-shell type hydroxy acrylic emulsion and a topcoat.

[0139] Comparative Example 5

[0140] The droplet acceleration of the pre-emulsion was uniformly adjusted to a constant rate of 2 ml / min, and other conditions were the same as in Example 1, to prepare a core-shell type hydroxy acrylic emulsion and a topcoat.

[0141] Comparative Example 6

[0142] The pre-emulsification method was changed to mechanical stirring at 600 rpm for 30 min, and other conditions were the same as in Example 1, to prepare a core-shell type hydroxy acrylic emulsion and a topcoat.

[0143] The fineness of the film scraping after mixing the core-shell emulsions prepared in Examples 1-9 and Comparative Examples 1-6 with the isocyanate curing agent, and the gloss and hardness of the topcoat prepared by mixing with the isocyanate curing agent and other components at room temperature according to Table 1 were tested. The test results are shown in Table 2.

[0144] Table 1. Formulation of Water-Based Two-Component White Topcoat

[0145]

[0146]

[0147] The titanium dioxide paste in the formulation is composed of three components: 75 wt% R930 titanium dioxide, 17.5 wt% water, and 7.5 wt% BYK190. The film-forming aid is diethylene glycol butyl ether, the wetting agent is BYK345, and the thickener is WT202. In two-component coating formulation, an important parameter is a = -NCO / -OH, i.e., the equivalent ratio of isocyanate groups to hydroxyl groups. If -NCO and -OH react completely, the theoretical value of a = 1. However, in water-based coatings, the large amount of water and other potentially reactive groups inevitably consume some of the -NCO. Therefore, in two-component water-based coatings, a > 1 is usually required. The best method for determining the a value is to conduct a gradient experiment in the application system to ascertain the optimal ratio. The conventional a value is approximately between 1.2 and 1.4; this invention experimentally verifies that the -NCO / -OH ratio is 1.3.

[0148] Table 2. Performance test results of emulsion and topcoat

[0149]

[0150]

[0151] The table shows that the monomer mass ratio of the core-shell microspheres, the glass transition temperature of the core-shell layer, the hydroxyl content ratio of the core and shell layers, the molecular weight of the emulsion, and the monomer feeding rate during the reaction process all have a significant impact on the final properties of the emulsion. An excessively high monomer ratio in the core-shell layer negates the advantages of the core-shell structure. The glass transition temperature of the core-shell layer, the hydroxyl content ratio of the core and shell layers, and the molecular weight of the emulsion all contribute to improving compatibility with the curing agent, allowing the isocyanate to be fully adsorbed on the surface of the microspheres and rapidly swell and diffuse. This results in a more complete reaction between the curing agent and the hydroxyl groups, leading to a paint film with high gloss, good hardness, and wear resistance.

[0152] The dropping rate during the reaction process is a crucial means of controlling the particle size and distribution of the emulsion. Too slow a dropping rate leads to excessively long reaction times and increased energy consumption, while too fast a dropping rate affects the particle size and distribution of the synthesized microspheres, resulting in microspheres with larger sizes, wider particle size distributions, and decreased dispersion stability, leading to more precipitation. Adjusting the dropping rate through a variable-speed method can control the emulsion particle size while reducing energy consumption. Pre-emulsification using a homogenizer can improve the stability of the pre-emulsion and make the particle size of the synthesized microspheres more controllable.

[0153] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A process for the preparation of a core-shell aqueous hydroxyl acrylate microspheres emulsion, characterized in that, The core-shell waterborne monodisperse acrylate emulsion is prepared by in-situ multi-stage variable speed dropping method, comprising the following steps: Core layer polymerization: after heating the kettle bottom liquid, adding initiator solution, then multi-stage variable speed dropping the core layer pre-emulsion containing core layer monomers, adjusting pH with neutralizing agent, obtaining polyacrylate core layer emulsion; Shell layer polymerization: multi-stage variable speed dropping the shell layer pre-emulsion containing shell layer monomers and initiator solution into the polyacrylate core layer emulsion, keeping warm, cooling, adding terminating agent after reaction, then adjusting pH with neutralizing agent, obtaining core-shell waterborne hydroxyl acrylate microsphere emulsion; The core layer pre-emulsion is a pre-emulsion mixture of water, mixed emulsifier, core layer monomers and chain transfer agent; the shell layer pre-emulsion is a pre-emulsion mixture of water, mixed emulsifier and shell layer monomers; the kettle bottom liquid comprises water and mixed emulsifier; the initiator solution comprises water and initiator; the terminating agent comprises tert-butyl hydroperoxide and / or sodium bisulfite; When mixing and configuring the core layer pre-emulsion and the shell layer pre-emulsion, a high-speed homogenizer is used, the rotation speed is 5000-20000 rpm, and the time is 0.5-5 min; The core layer monomers comprise the following components with the following mass fractions: α, β-monoolefinic monobasic acid 2.5-10 Ester of α, β-monoolefinic monobasic acid 10-45 Vinyl aromatic compound 20-60 (meth)acrylic acid hydroxyalkyl ester 5-30; The shell layer monomers comprise the following components with the following mass fractions: α, β-monoolefinic monobasic acid 2.5-8 Ester of α, β-monoolefinic monobasic acid 40-75 Vinyl aromatic compound 5-20 (meth)acrylic acid hydroxyalkyl ester 5-30; The core-shell layer hydroxyl content ratio is 1 / 4-4 / 1; The microsphere core layer and shell layer monomer usage ratio is 1 / 4-4 / 1; The core layer glass transition temperature is 30-90℃, and the shell layer glass transition temperature is -30~30℃; The multi-stage variable speed dropping of the core layer pre-emulsion is divided into two stages, and the total dropping time is controlled within 240 minutes, wherein the dropping speed of the first stage is 0.5 ml / min, the time is 1 minute, the dropping speed of the second stage is 1 ml / min; or the dropping speed of the first stage is 1 ml / min, the dropping time is 10 minutes, the dropping speed of the second stage is 5 ml / min; or the dropping speed of the first stage is 0.4 ml / min, the dropping time is 5 minutes, the dropping speed of the second stage is 1 ml / min; or the dropping speed of the first stage is 0.5 ml / min, the dropping time is 2 minutes, the dropping speed of the second stage is 1 ml / min; or the dropping speed of the first stage is 0.4 ml / min, the dropping time is 1 minute, the dropping speed of the second stage is 0.8 ml / min; or the dropping speed of the first stage is 0.5 ml / min, the dropping time is 30 minutes, the dropping speed of the second stage is 1 ml / min; or the dropping speed of the first stage is 0.5 ml / min, the dropping time is 1 minute, the dropping speed of the second stage is 2 ml / min; or the dropping speed of the first stage is 0.1 ml / min, the dropping time is 5 minutes, the dropping speed of the second stage is 0.2 ml / min; or the dropping speed of the first stage is 0.5 ml / min, the dropping time is 1 minute, the dropping speed of the second stage is 1 ml / min; The multi-stage variable speed dropping of the core layer pre-emulsion is divided into two stages, and the total dropping time is controlled within 240 minutes, wherein the dropping speed of the first stage is 0.5 ml / min, the time is 1 minute, the dropping speed of the second stage is 1 ml / min; or the dropping speed of the first stage is 1 ml / min, the dropping time is 10 minutes, the dropping speed of the second stage is 5 ml / min; or the dropping speed of the first stage is 0.4 ml / min, the dropping time is 5 minutes, the dropping speed of the second stage is 1 ml / min; or the dropping speed of the first stage is 0.5 ml / min, the dropping time is 2 minutes, the dropping speed of the second stage is 1 ml / min; or the dropping speed of the first stage is 0.4 ml / min, the dropping time is 1 minute, the dropping speed of the second stage is 0.8 ml / min; or the dropping speed of the first stage is 0.5 ml / min, the dropping time is 30 minutes, the dropping speed of the second stage is 1 ml / min; or the dropping speed of the first stage is 0.5 ml / min, the dropping time is 1 minute, the dropping speed of the second stage is 2 ml / min; or the dropping speed of the first stage is 0.1 ml / min, the dropping time is 5 minutes, the dropping speed of the second stage is 0.2 ml / min; or the dropping speed of the first stage is 0.5 ml / min, the dropping time is 1 minute, the dropping speed of the second stage is 1 ml / min; 2. The method for preparing a core-shell type aqueous hydroxy acrylate microsphere emulsion according to claim 1, characterized in that, The chain transfer agent includes tert-butyl mercaptan, alkyl mercaptoacetate, mercaptoethanol, mercaptopropionic acid, mercaptopropyltrimethoxysilane, n-dodecyl mercaptan or tert-dodecyl mercaptan; The α, β-mono-olefinically unsaturated monocarboxylic acid includes acrylic acid, methacrylic acid, ethyl acrylic acid, methacryloyloxypropionic acid, acryloyloxyacetic acid, methacryloyloxyacetic acid, and their salts, anhydrides and mixtures; The ester of the α, β-mono-olefinically unsaturated monocarboxylic acid is selected from (meth)acrylic acid methyl ester, ethyl acrylic acid methyl ester, (meth)acrylic acid ethyl ester, ethyl acrylic acid ethyl ester, (meth)acrylic acid n-propyl ester, (meth)acrylic acid isopropyl ester, (meth)acrylic acid n-butyl ester, (meth)acrylic acid isobutyl ester, (meth)acrylic acid tert-butyl ester, ethyl acrylic acid tert-butyl ester, (meth)acrylic acid n-hexyl ester, (meth)acrylic acid n-heptyl ester, (meth)acrylic acid n-octyl ester, (meth)acrylic acid n-nonyl ester, (meth)acrylic acid n-decyl ester, (meth)acrylic acid isooctyl ester; The vinyl aromatic compound includes styrene, 2-methylstyrene, 4-methylstyrene, 2-butylstyrene, 4-butylstyrene or 4-decylstyrene. The (meth)acrylic acid hydroxyalkyl ester includes hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate or 6-hydroxyhexyl acrylate.

3. The method of claim 1, wherein the method is characterized by, The chain transfer agent is added in an amount of 0.5-2% of the total weight of the shell monomer and the core monomer; the initiator is added in an amount of 0.1-1.0% of the total mass of the core monomer; when adjusting the pH, the neutralizing agent is used to adjust the pH to 7.0-8.

0.

4. The method of claim 1, wherein the method is characterized by, The mixed emulsifier is compounded by an anionic emulsifier and a nonionic emulsifier, and the mass ratio of the anionic emulsifier to the nonionic emulsifier is 1: (1-5) ; The anionic emulsifier includes sodium dodecyl sulfonate, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, sodium dodecyl diphenyl ether disulfonate, sodium styrene sulfonate or sodium stearate. The non-ionic emulsifier is isomeric alcohol polyoxyethylene ether, the structural formula is R-O-(CH2CH2O) n H, wherein R is an alkyl group satisfying C m H 2m+1 of the general formula, m is 8, 10, 11, 13; wherein n is 3, 5, 6, 7, 8, 10, 12; The initiator includes sodium persulfate, potassium persulfate or ammonium persulfate; and the neutralizing agent includes ammonia, sodium hydroxide, N, N-dimethyl ethanolamine or triethylamine.

5. A core-shell type aqueous hydroxyl acrylate microsphere emulsion prepared by the method according to any one of claims 1-4.

6. Use of the core-shell type aqueous hydroxyl acrylate microspheres emulsion according to claim 5, characterized in that, The emulsion is used in the field of exterior wall coatings, wood coatings or anti-rust coatings. The vinyl aromatic compound includes styrene, 2-methylstyrene, 4-methylstyrene, 2-butylstyrene, 4-butylstyrene or 4-decylstyrene. The (meth)acrylic acid hydroxyalkyl ester includes hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate or 6-hydroxyhexyl acrylate. The chain transfer agent is added in an amount of 0.5-2% of the total weight of the shell monomer and the core monomer; the initiator is added in an amount of 0.1-1.0% of the total mass of the core monomer; when adjusting the pH, the neutralizing agent is used to adjust the pH to 7.0-8.

0. The mixed emulsifier is compounded by an anionic emulsifier and a nonionic emulsifier, and the mass ratio of the anionic emulsifier to the nonionic emulsifier is 1: (1-5) ; The anionic emulsifier includes sodium dodecyl sulfonate, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, sodium dodecyl diphenyl ether disulfonate, sodium styrene sulfonate or sodium stearate. The initiator includes sodium persulfate, potassium persulfate or ammonium persulfate; and the neutralizing agent includes ammonia, sodium hydroxide, N, N-dimethyl ethanolamine or triethylamine.

5. A core-shell type aqueous hydroxyl acrylate microsphere emulsion prepared by the method according to any one of claims 1-4. The emulsion is used in the field of exterior wall coatings, wood coatings or anti-rust coatings.

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