Waterborne acrylate emulsion based on structured hydrophobic particle modification as well as preparation method and application of waterborne acrylate emulsion

Abstract

The invention relates to the technical field of hydrophobic materials, in particular to a water-based acrylate emulsion based on structured hydrophobic particle modification as well as a preparation method and application of the water-based acrylate emulsion. The industrial problems that hydrophobic particles are prone to agglomeration and the hydrophobic effect is not lasting are solved. According to the emulsion, long-chain alkyl silane modified silicon dioxide serves as a structured hydrophobic phase, in-situ hybridization is carried out on the structured hydrophobic phase, a hydrophobic silane coupling agent, an acrylate monomer and the like through a semi-continuous emulsion polymerization method, and a stable micro-nano rough structure and a low-surface-energy surface are successfully constructed in a coating. According to the preparation method, a physical hydrophobic structure and chemical hydrophobic components are ingeniously combined, the prepared emulsion is good in stability, the water contact angle after film forming can reach 110 degrees or above, and the emulsion has excellent static hydrophobic and dynamic moisture-resistant performance and has wide application prospects in the fields of buildings, textiles, leather and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrophobic materials, in particular to a water-based acrylate emulsion modified by structured hydrophobic particles and a preparation method and application thereof. BACKGROUND

[0002] Hydrophobic materials have wide applications in self-cleaning surfaces, anti-icing, waterproof fabrics, anti-corrosion coatings and other fields. Currently, there are two main technical paths to construct hydrophobic coatings: one is to use low surface energy substances (such as organic fluorine and organic silicon), and the other is to construct micro-nano rough structures on the surface.

[0003] Water-based acrylate emulsion is environmentally friendly and has good film-forming properties, but it is inherently hydrophilic. The existing technology often gives it hydrophobicity in the following ways:

[0004] 1. Adding small molecule hydrophobic agents: such as paraffin and silicone oil, but they are easy to migrate and precipitate, and the effect is not long-lasting.

[0005] 2. Copolymerization of fluorine / silicon monomers: the effect is good, but fluorine-containing monomers are high in cost and have environmental controversy, and organic silicon monomers may affect film formation and adhesion.

[0006] 3. Physical incorporation of hydrophobic particles: such as silicon dioxide, but the particles are easy to agglomerate, affecting the stability of the emulsion and the transparency, mechanical properties of the coating.

[0007] Publication No. CN115386279A discloses a fluorine-containing acrylate hydrophobic anticorrosive coating and a preparation method thereof. The coating is composed of 100 parts by mass of epoxy resin, 5-20 parts by mass of fluorine-containing acrylate, and 5 parts by mass of epoxy curing agent. The fluorine-containing acrylate is a diblock polymer polymerized from methyl hexafluorobutyl acrylate and glycidyl methacrylate as main raw materials, with the addition of initiators, catalysts and complexing agents. The fluorine-containing acrylate hydrophobic anticorrosive coating is prepared by adjusting the feeding ratio of raw materials and using the interaction between groups. Its hydrophobic performance is poor and its stability is low.

[0008] Therefore, it is necessary to develop a hydrophobic emulsion with long-lasting hydrophobic performance, good stability and no influence on the basic physical and chemical properties of the emulsion. SUMMARY

[0009] Therefore, the present application provides a water-based acrylate emulsion modified by structured hydrophobic particles and a preparation method and application thereof. The structured hydrophobic particles and the polymer monomers are uniformly hybridized in situ by one-step pre-emulsification and two-step feeding method.

[0010] To solve the problems in the prior art, the technical scheme adopted by the present application is as follows: a water-based acrylate emulsion modified by structured hydrophobic particles, comprising the following raw materials by weight:

[0011] 8-20 parts of (meth)acrylate monomers, 1-5 parts of functional crosslinking monomers, 1-5 parts of hydrophobic silane coupling agent, 3-10 parts of long-chain alkylsilane modified silica, 1-2 parts of reactive emulsifier, 0.3-0.8 parts of initiator, 0.1-0.6 parts of buffer, and 100-150 parts of deionized water.

[0012] Furthermore, the hydrophobic silane coupling agent is at least one of hexadecyltrimethoxysilane and dodecyltrimethoxysilane.

[0013] Furthermore, the reactive emulsifier is DNS-250.

[0014] Furthermore, the initiator is ammonium sulfate.

[0015] Furthermore, the buffer is such as sodium bicarbonate.

[0016] Furthermore, long-chain alkylsilane-modified silica is obtained by dispersing hydrophilic silica nanoparticles in toluene, adding long-chain alkylsilane, reacting under reflux for 6-12 hours, and then washing and drying.

[0017] Furthermore, the long-chain alkylsilane is hexadecyltrimethoxysilane or octadecyltrichlorosilane.

[0018] A method for preparing an aqueous acrylic emulsion based on structured hydrophobic particle modification includes the following steps:

[0019] 1) Pre-emulsification: Reactive emulsifier, (meth)acrylate monomer, functional crosslinking monomer, hydrophobic silane coupling agent, long-chain alkylsilane modified silica and 60-70% deionized water are subjected to high-speed shear emulsification to obtain a pre-emulsion.

[0020] 2) Seed emulsion preparation: Add the remaining deionized water, buffer and 10-15% of the pre-emulsion obtained in step 1) to the reactor, heat to 75-80℃ under nitrogen protection, add 30-50% of the initiator aqueous solution, react for 20-40 minutes to obtain the seed emulsion.

[0021] 3) Droplet polymerization: The remaining pre-emulsion and the remaining initiator aqueous solution are simultaneously added dropwise to the seed emulsion obtained in step 2), and the addition is completed within 2-3 hours, while controlling the reaction temperature at 78-82℃;

[0022] 4) Post-processing: After the addition is complete, heat to 85℃ and keep warm for 1 hour, then cool down and filter to obtain the final product.

[0023] The above-mentioned method is used to prepare waterborne acrylic emulsion structured hydrophobic emulsions in the preparation of self-cleaning coatings, waterproof fabrics, waterproof leather or anti-adhesive coatings.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. Precise and controllable process: The present invention ensures the initial uniformity of hydrophobic particles in the polymerization system through the pre-emulsification step; the growth process of latex particles is precisely controlled by the drop-addition polymerization method, which is conducive to the formation of a regular coating structure.

[0026] 2. High hybridization efficiency: The in-situ polymerization of this invention effectively encapsulates hydrophobic particles inside polymer latex particles, achieving true molecular / nanoscale hybridization and avoiding the defects of physical blending.

[0027] 3. Stable product performance: The gradient heating and sufficient heat preservation and curing process of this invention ensures high conversion rate and excellent emulsion stability, and the water contact angle after film formation can reach more than 110°.

[0028] 4. Good reproducibility: The method of this invention can be mass-produced and has high reproducibility. Attached Figure Description

[0029] Figure 1 Average particle size distribution for preparing waterborne acrylate emulsions modified with structured hydrophobic particles;

[0030] Figure 2 Line graphs showing the water contact angles of various embodiments and comparative examples;

[0031] Figure 3 Bar charts showing the water absorption rates of various embodiments and comparative examples. Detailed Implementation

[0032] The present invention will be described in further detail below with reference to specific embodiments, but the implementation of the present invention includes, but is not limited to, the scope represented by the following embodiments.

[0033] Example 1:

[0034] An aqueous acrylic emulsion based on structured hydrophobic particle modification comprises the following raw materials in parts by weight:

[0035] Methyl methacrylate (MMA): 18 parts, butyl acrylate (BA): 67 parts, hydroxyethyl acrylate (HEA): 3 parts, hexadecyltrimethoxysilane: 4 parts, octadecyltrichlorosilane modified silica (particle size 20nm): 6 parts, reactive emulsifier (DNS-250): 1.5 parts, ammonium persulfate (APS): 0.7 parts, sodium bicarbonate: 0.3 parts, deionized water: 120 parts.

[0036] The long-chain alkylsilane-modified silica is obtained by dispersing hydrophilic silica nanoparticles in toluene, adding long-chain alkylsilane, reacting under reflux for 6-12 hours, and then washing and drying.

[0037] The long-chain alkylsilane is hexadecyltrimethoxysilane or octadecyltrichlorosilane.

[0038] A method for preparing an aqueous acrylic emulsion based on structured hydrophobic particle modification, comprising the following steps:

[0039] 1) Pre-emulsification: Add reactive emulsifier (DNS-250), methyl methacrylate (MMA), butyl acrylate (BA), hydroxyethyl acrylate (HEA), hexadecyltrimethoxysilane, octadecyltrichlorosilane modified silica and 60% deionized water to an emulsification tank and perform high-speed shear emulsification to obtain pre-emulsion A.

[0040] High-speed shear emulsification: Turn on the high-speed disperser and continuously shear at 5000 rpm for 30 minutes until the mixture becomes a uniform milky white fluid with no obvious particle agglomerates, forming a stable "monomer-particle" pre-emulsion (denoted as pre-emulsion A). This step is crucial to ensuring uniform particle dispersion and stability of the subsequent polymerization reaction;

[0041] 2) Seed emulsion preparation:

[0042] Add the remaining deionized water, buffer (sodium bicarbonate), and 15% of the total amount of preemulsion A to a four-necked flask equipped with a stirrer, condenser, thermometer, and two constant-pressure dropping funnels. Start stirring (200 rpm) and purge with nitrogen for atmosphere replacement for approximately 20-30 minutes. Raise the system temperature to 75-80°C, then quickly add 40% of the total amount of initiator (ammonium persulfate) aqueous solution (initiator dissolved in an appropriate amount of water). Maintain this temperature for 30 minutes. A significant Tyndall effect can be observed in the system, and the emulsion will exhibit a stable blue glow, indicating that the seed emulsion has been successfully formed and the latex particles are of uniform size.

[0043] 3) Droplet polymerization:

[0044] Step 1 Drop Addition (Main Polymerization): The remaining pre-emulsion A and the remaining initiator aqueous solution are simultaneously and uniformly added to the seed emulsion obtained in Step 2 through two independent dropping funnels over 2-3 hours; the dropping rate is strictly controlled and the reaction temperature is maintained at 78-82℃. This stage is the key period for the growth of polymer latex particles and the encapsulation of hydrophobic particles to form a "core-shell" structure.

[0045] The second step, dropwise addition (surface modification): After all pre-emulsion A has been added, a separate aqueous solution containing a small amount of functional monomer (such as 1-2 parts acrylic acid) and a small amount of emulsifier can be prepared as a replenishing solution and slowly added to the system over 0.5 hours. This step aims to further optimize the charge density and stability of the latex particle surface.

[0046] High-temperature curing and elimination of residual monomers

[0047] Incubation and maturation: After all materials have been added, raise the temperature of the reaction system to 85±2℃ and maintain this temperature for 1-1.5 hours. This is to promote the full reaction of the remaining monomers, increase the monomer conversion rate (>99%), and enhance the structural stability of the latex particles.

[0048] To completely eliminate residual monomers, a small amount of redox initiator (such as a combination of tert-butyl hydroperoxide and sodium formaldehyde sulfoxylate) can be added during the heat preservation stage to carry out a post-elimination reaction and further reduce the VOC content.

[0049] 4) Post-treatment: After the addition is complete, heat to 85℃ and maintain for 1 hour. Cool the reaction system to below 40℃ using circulating water. Slowly add an appropriate amount of pH adjuster (such as ammonia) to adjust the pH of the emulsion to a weakly alkaline range of 7.5-8.5 to improve the storage stability of the emulsion. Finally, filter the emulsion using a 200-300 mesh filter cloth to remove the very small amount of gel particles that may be generated during the polymerization process, and obtain the final product—a structurally stable and high-performance structured hydrophobic emulsion.

[0050] To improve the dispersibility and reactivity of long-chain alkylsilane-modified silica in the monomer phase, it can be pre-mixed with a portion of hydrophobic silane coupling agent (accounting for 1 / 3-1 / 2 of the total amount) under high-speed stirring before pre-emulsification, and activated at 50-60℃ for 0.5-1 hours.

[0051] The aqueous acrylic emulsion prepared in Example 1 has high hydrophobicity.

[0052] Example 2:

[0053] An aqueous acrylic emulsion based on structured hydrophobic particle modification comprises the following raw materials in parts by weight:

[0054] Methyl methacrylate (MMA): 10 parts, butyl acrylate (BA): 76 parts, hydroxyethyl acrylate (HEA): 2 parts, dodecyltrimethoxysilane: 2 parts, hexadecyltrimethoxysilane-modified silica (particle size 30nm): 4 parts, reactive emulsifier (DNS-250): 1.2 parts, ammonium persulfate (APS): 0.6 parts, sodium bicarbonate: 0.3 parts, deionized water: 110 parts.

[0055] Preparation method: Same as in Example 1.

[0056] The aqueous acrylic emulsion prepared in Example 2 has high elasticity and hydrophobicity, making it suitable for flexible substrates (such as fabrics and leather). It is an emulsion that maintains good hydrophobicity while having high elasticity.

[0057] Example 3: A waterborne acrylic emulsion based on structured hydrophobic particle modification, comprising the following raw materials in parts by weight:

[0058] Methyl methacrylate (MMA): 8 parts, butyl acrylate (BA): 72 parts, hydroxyethyl acrylate (HEA): 2 parts, hexadecyltrimethoxysilane: 2 parts, paraffin emulsion (solid content 40%): 5 parts (equivalent to 2 parts paraffin, as an auxiliary hydrophobic agent), octadecyltrichlorosilane modified silica: 3 parts, reactive emulsifier (DNS-250): 1.2 parts, ammonium persulfate (APS): 0.5 parts, sodium bicarbonate: 0.3 parts, deionized water: 115 parts.

[0059] Preparation method: Same as in Example 1, but during pre-emulsification, the paraffin emulsion needs to be added together with other monomers for co-emulsification, and the dripping time is shortened to 2.5 hours.

[0060] The aqueous acrylic emulsion prepared in Example 3 is a low-cost, high-stability type.

[0061] Comparative Example 1 (unstructured hydrophobic particles)

[0062] The formulation is exactly the same as in Example 1, but without the addition of octadecyltrichlorosilane-modified silica.

[0063] Results: The water contact angle was only 85°, and the water absorption rate was as high as 25.1%. This proves that high hydrophobicity cannot be achieved by chemical hydrophobicity alone, and micro-nano rough structures are crucial.

[0064] Comparative Example 2 (Physical Blending Comparison)

[0065] First, an acrylate emulsion without hydrophobic components was prepared using conventional methods. Then, an equal amount of modified silica from Example 1 was directly mixed into the finished emulsion under low-speed stirring.

[0066] Results: The emulsion showed significant sedimentation after one week of storage, but could be redispersed after stirring. The water contact angle after film formation was 98°, but after water rinsing or slight abrasion, the hydrophobicity dropped sharply to below 85°. This demonstrates that the physical blending effect is not durable and is unstable.

[0067] Performance Summary Table

[0068]

[0069] *Note: The hydrophobic properties of Comparative Example 2 are not durable.

[0070] like Figure 1 The figure shows the average particle size of the aqueous acrylate emulsion prepared based on structured hydrophobic particle modification.

[0071] like Figure 2 As shown, the water contact angle of Example 1 is 121°, the water contact angle of Example 2 is 112°, the water contact angle of Example 3 is 105°, the water contact angle of Comparative Example 1 is 85°, and the water contact angle of Comparative Example 2 is 98°, indicating that the emulsion prepared by the present invention has excellent hydrophobic properties.

[0072] like Figure 3 As shown, the water absorption rate of Example 1 was 6.8%, that of Example 2 was 9.5%, that of Example 3 was 11.2%, that of Comparative Example 1 was 25.1%, and that of Comparative Example 2 was 18.5%, indicating that the emulsion prepared by the present invention has excellent stability.

[0073] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited thereto. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, 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 content of the present invention, should fall within the scope of protection of the present invention.

Claims

1. A waterborne acrylic emulsion based on structured hydrophobic particle modification, characterized in that, Including the following parts by weight of raw materials: 8-20 parts of (meth)acrylate monomers, 1-5 parts of functional crosslinking monomers, 1-5 parts of hydrophobic silane coupling agent, 3-10 parts of long-chain alkylsilane modified silica, 1-2 parts of reactive emulsifier, 0.3-0.8 parts of initiator, 0.1-0.6 parts of buffer, and 100-150 parts of deionized water.

2. The aqueous acrylic emulsion based on structured hydrophobic particle modification according to claim 1, characterized in that, The hydrophobic silane coupling agent is at least one of hexadecyltrimethoxysilane and dodecyltrimethoxysilane.

3. The aqueous acrylic emulsion based on structured hydrophobic particle modification according to claim 1 or 2, characterized in that, The reactive emulsifier is DNS-250.

4. The aqueous acrylic emulsion based on structured hydrophobic particle modification according to claim 3, characterized in that, The initiator is ammonium sulfate.

5. The aqueous acrylic emulsion based on structured hydrophobic particle modification according to claim 4, characterized in that, The buffer is, for example, sodium bicarbonate.

6. The aqueous acrylic emulsion based on structured hydrophobic particle modification according to claim 5, characterized in that, The long-chain alkylsilane-modified silica is obtained by dispersing hydrophilic silica nanoparticles in toluene, adding long-chain alkylsilane, reacting under reflux for 6-12 hours, and then washing and drying.

7. The aqueous acrylic emulsion based on structured hydrophobic particle modification according to claim 6, characterized in that, The long-chain alkylsilane is hexadecyltrimethoxysilane or octadecyltrichlorosilane.

8. The method for preparing an aqueous acrylic emulsion based on structured hydrophobic particle modification according to claim 1, characterized in that, The steps are as follows: 1) Pre-emulsification: Reactive emulsifier, (meth)acrylate monomer, functional crosslinking monomer, hydrophobic silane coupling agent, long-chain alkylsilane modified silica and 60-70% deionized water are subjected to high-speed shear emulsification to obtain a pre-emulsion. 2) Seed emulsion preparation: Add the remaining deionized water, buffer and 10-15% of the pre-emulsion obtained in step 1) to the reactor, heat to 75-80℃ under nitrogen protection, add 30-50% of the initiator aqueous solution, react for 20-40 minutes to obtain the seed emulsion. 3) Droplet polymerization: The remaining pre-emulsion and the remaining initiator aqueous solution are simultaneously added dropwise to the seed emulsion obtained in step 2), and the addition is completed within 2-3 hours, while controlling the reaction temperature at 78-82℃; the temperature of the reaction system is raised to 85±2℃ and kept at this temperature for 1-1.5 hours; Adding a redox initiator during the heat preservation stage to carry out a post-elimination reaction reduces VOC content; 4) Post-processing: After the addition is complete, heat to 85℃ and keep warm for 1 hour, then cool down and filter to obtain the final product.

9. The application of the waterborne acrylic emulsion structured hydrophobic emulsion prepared by the method of claim 8 in the preparation of self-cleaning coatings, waterproof fabrics, waterproof leather or anti-adhesive coatings.

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