A core-shell type silica-polyamide composite toughening agent and a method of applying the same

Abstract

The application provides a core-shell type silica-polyamide composite toughening agent and an application method thereof. The preparation of the composite toughening agent comprises the following steps: first, surface modification of nano-silica is carried out by using a silane coupling agent; then, the modified nano-silica is used as a core, and a polyamide monomer is in-situ polymerized on the surface of the core to form a shell layer, so that the composite toughening agent with a core-shell structure is obtained. Through the structural design of the "rigid silica core" and the "tough polyamide shell", the composite toughening agent can greatly improve the flexibility and impact resistance of the coating when it is applied to the powder coating, and meanwhile, the composite toughening agent has high hardness, effectively solves the technical problem that the hardness and toughness of the powder coating are difficult to be considered at the same time, has good compatibility, a simple preparation process, and is suitable for industrial popularization.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite materials technology, and particularly relates to a core-shell type silica-polyamide composite toughening agent and its application method. Background Technology

[0002] Powder coatings, especially polyester resin-based powder coatings, are widely used for metal surface protection and decoration due to their environmental friendliness, high efficiency, and excellent coating performance. With the expansion of downstream application areas (such as new energy vehicle components, outdoor building materials, and high-end home appliances), more stringent requirements are being placed on the comprehensive mechanical properties of coatings: not only is high hardness required to ensure wear resistance and scratch resistance, but also excellent flexibility and impact resistance are needed to withstand deformation and impact during installation, transportation, or use.

[0003] Currently, common methods to improve the toughness of powder coatings include adding elastomers, plasticizers, or flexible resins. However, these methods often come at the cost of sacrificing coating hardness, heat resistance, or adhesion. On the other hand, while directly adding rigid nanoparticles (such as silica) can improve hardness and modulus, it is prone to agglomeration due to poor interfacial compatibility, which in turn causes stress concentration, making the coating brittle and reducing its impact resistance.

[0004] Therefore, how to provide a highly efficient toughening agent that can synergistically improve the hardness and toughness of the coating and has good compatibility with the resin matrix is ​​a problem that this invention urgently needs to solve. Summary of the Invention

[0005] The purpose of this invention is to provide a core-shell type silica-polyamide composite toughening agent and its preparation method, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides a core-shell type silica-polyamide composite toughening agent, characterized in that the preparation of the composite toughening agent includes the following steps: (1) Add nano-silica to anhydrous ethanol and ultrasonically disperse for 30-60 min. Then slowly add a mixed solution of silane coupling agent and ethanol. Stir the reaction at room temperature for 2-4 h. After the reaction is completed, perform post-treatment to obtain modified nano-silica. (2) Add the modified nano silica obtained in step (1) into anhydrous ethanol and ultrasonically disperse for 10-30 min. Then add organic solvent, surfactant, polyamide monomer and initiator. Under nitrogen atmosphere, heat to 60-80℃ and stir for 4-8 h. After the reaction is completed, post-treatment is performed to obtain core-shell type silica-polyamide composite toughening agent.

[0007] As a further improvement, the silane coupling agent in step (1) is at least one of γ-methacryloxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane.

[0008] As a further improvement, the mass ratio of polyamide monomer to modified nano-silica in step (2) is 1.5-2.5:1.

[0009] As a further improvement, the polyamide monomer in step (2) is at least one of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, caprolactam, and dodecanoic acid.

[0010] As a further improvement, the polyamide monomer is acrylamide and 2-acrylamido-2-methylpropanesulfonic acid; the molar ratio of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid is 1:1.2-3.

[0011] As a further improvement, the surfactant in step (2) is polyvinylpyrrolidone.

[0012] As a further improvement, the initiator is any one of ammonium persulfate and azobisisobutyronitrile.

[0013] As a further improvement, the particle size of the nano-silica in step (1) is 20-60 nm.

[0014] The present invention also provides a method for applying a core-shell type silica-polyamide composite toughening agent, characterized in that it is applied to the toughening modification of powder coatings to obtain toughened modified coatings.

[0015] As a further improvement, the preparation of the toughening modified coating includes the following steps: (1) Take 80-100 parts of polyester resin, 1-10 parts of core-shell silica-polyamide composite toughening agent, and 0-5 parts of additives by weight, place them in a high-speed mixer, and stir and mix at 25-40℃ for 5-15 minutes to obtain a premix. (2) The premixed material is added to a twin-screw extruder, the temperature of each section of the extruder is controlled at 120-180℃, the screw speed is 100-300r / min, melt-blending, extrusion granulation, and post-treatment to obtain toughened modified coating.

[0016] As a further improvement, the additives include a leveling agent, an antioxidant, and a curing agent; the leveling agent is acrylate leveling agent BZ-658, the antioxidant is antioxidant 1010, and the curing agent is isocyanate curing agent IPDI.

[0017] As a further improvement, the amount of core-shell silica-polyamide composite toughening agent added in step (1) is 3-6 parts.

[0018] Compared with the prior art, the beneficial effects of the present invention are: This invention, through a structural design of a "rigid silica core" and a "tough polyamide shell," produces a toughening agent that simultaneously and significantly improves the coating's flexibility (no cracking after 180° bending) and impact resistance (≥70 kg·cm), while maintaining high hardness (≥2H). This solves the technical problem that traditional toughening methods often lead to a decrease in hardness. By surface grafting modification of nano-silica, making it the core for the chemical growth of the polyamide shell, the bottleneck problem of easy agglomeration of nanoparticles in the resin is fundamentally solved, ensuring the uniform dispersion of the toughening agent in the final coating. This composite toughening agent has good compatibility with polyester resins used in powder coatings, processes smoothly under standard extrusion processes, and produces powder coatings with excellent leveling properties, dense coatings, and smooth surfaces, without affecting the original construction process. Detailed Implementation

[0019] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0020] In the following examples, nano-silica was purchased from Shandong Xinbaiyi Metal Materials Co., Ltd., with the grade XBY-SiO2; polyvinylpyrrolidone was purchased from Huzhou Shenhua Polymer Materials Co., Ltd., with the model K90; polyester resin was a commercially available product of our company, with the model P3902; leveling agent was purchased from Guangdong Shunde Shibang Jiaming Chemical Co., Ltd., with the model BZ-658; and curing agent was purchased from Jinan Xinwo Chemical Co., Ltd., with the model IPDI.

[0021] Example 1 The synthesis of core-shell silica-polyamide composite toughening agent 1 includes the following steps: (1) 10g of nano silica was added to 200mL of anhydrous ethanol and ultrasonically dispersed for 40min. Then, a mixed solution consisting of 5g of γ-methacryloxypropyltrimethoxysilane and 50mL of anhydrous ethanol was slowly added dropwise. The mixture was stirred at room temperature for 3h. After the reaction was completed, the mixture was centrifuged, washed 3 times with ethanol, and vacuum dried at 60℃ for 6h to obtain modified nano silica. (2) Take 10g of modified nano silica and add it to 150mL of anhydrous ethanol. Disperse it by ultrasonication for 15min. Then add 30mL of ethyl acetate, 2g of polyvinylpyrrolidone, 2.9g of acrylamide, 16.6g of 2-acrylamido-2-methylpropanesulfonic acid and 0.3g of ammonium persulfate. Heat the mixture to 65℃ under a nitrogen atmosphere and stir for 5h. After the reaction is completed, collect the product by centrifugation, wash it 3 times with ethanol and 3 times with deionized water, and dry it under vacuum at 60℃ for 8h to obtain core-shell silica-polyamide composite toughening agent 1.

[0022] Example 2 The synthesis of core-shell silica-polyamide composite toughening agent 2 includes the following steps: (1) 10g of nano silica was added to 200mL of anhydrous ethanol and ultrasonically dispersed for 50min. Then, a mixed solution consisting of 5g of γ-aminopropyltriethoxysilane and 50mL of anhydrous ethanol was slowly added dropwise. The mixture was stirred at room temperature for 4h. After the reaction was completed, the mixture was centrifuged, washed three times with ethanol, and vacuum dried at 60℃ for 6h to obtain modified nano silica. (2) 12g of modified nano silica was added to 150mL of anhydrous ethanol and ultrasonically dispersed for 15min. Then, 30mL of N,N-dimethylformamide, 2g of polyvinylpyrrolidone, 2.1g of acrylamide, 18.4g of 2-acrylamido-2-methylpropanesulfonic acid and 0.3g of ammonium persulfate were added. The mixture was heated to 75℃ under a nitrogen atmosphere and stirred for 6h. After the reaction was completed, the product was collected by centrifugation, washed 3 times each with ethanol and deionized water, and dried under vacuum at 60℃ for 8h to obtain core-shell silica-polyamide composite toughening agent 2.

[0023] Example 3 Synthesis of core-shell silica-polyamide composite toughening agent 3: It is basically the same as in Example 1, except that 2.9g acrylamide and 16.3g 2-acrylamido-2-methylpropanesulfonic acid are replaced with 13.6g caprolactam.

[0024] Example 4 Synthesis of core-shell silica-polyamide composite toughening agent 4: It is basically the same as in Example 1, except that 2.9g acrylamide and 16.3g 2-acrylamido-2-methylpropanesulfonic acid are replaced with 4.3g acrylamide and 12.4g 2-acrylamido-2-methylpropanesulfonic acid.

[0025] Comparative Example 1 The synthesis of core-shell silica-polyamide composite toughening agent 5 includes the following steps: 10g of unmodified nano-silica was added to 150mL of anhydrous ethanol and ultrasonically dispersed for 15min. Then, 30mL of ethyl acetate, 2g of polyvinylpyrrolidone, 2.9g of acrylamide, 16.6g of 2-acrylamido-2-methylpropanesulfonic acid and 0.3g of ammonium persulfate were added. The mixture was heated to 65℃ under a nitrogen atmosphere and stirred for 5h. After the reaction was completed, the product was collected by centrifugation, washed three times each with ethanol and deionized water, and dried under vacuum at 60℃ for 8h to obtain core-shell silica-polyamide composite toughening agent 5.

[0026] Application Example 1 Toughening modified coating 1: (1) By weight, take 100 parts of polyester resin for powder coating, 5 parts of core-shell type silica-polyamide composite toughening agent, 1 part of leveling agent, 0.5 parts of antioxidant, and 3 parts of curing agent, stir and mix at 35°C for 8 minutes to obtain a premix. (2) The premixed material is added to a twin-screw extruder at 125°C in the feeding section, 155°C in the melting section, and 165°C in the die head section. The screw speed is 180 r / min. The mixture is mixed for 6 min, extruded and granulated, cooled to room temperature, and pulverized through a 100-mesh sieve to obtain toughened modified coating 1.

[0027] Application Example 2 Toughening modified coating 2: It is basically the same as application example 1, except that 5 parts of core-shell silica-polyamide composite toughening agent 1 are replaced with 5 parts of core-shell silica-polyamide composite toughening agent 2.

[0028] Application Example 3 Toughening modified coating 3: It is basically the same as application example 1, except that 5 parts of core-shell silica-polyamide composite toughening agent 1 are replaced with 5 parts of core-shell silica-polyamide composite toughening agent 3.

[0029] Application Example 4 Toughening modified coating 4: It is basically the same as application example 1, except that 5 parts of core-shell silica-polyamide composite toughening agent 1 are replaced with 5 parts of core-shell silica-polyamide composite toughening agent 4.

[0030] Application Comparative Example 1 Toughening modified coating 5: It is basically the same as application example 1, except that 5 parts of core-shell silica-polyamide composite toughening agent 1 are replaced with 5 parts of core-shell silica-polyamide composite toughening agent 5.

[0031] Application Comparative Example 2 Toughening modified coating 6: It is basically the same as application example 1, except that 5 parts of core-shell type silica-polyamide composite toughening agent 1 are replaced with 5 parts of unmodified nano silica.

[0032] The toughened modified coatings prepared using Examples 1-4 and Comparative Examples 1-2 were subjected to tests for flexibility, hardness, and impact resistance. The test methods are as follows: Flexibility (180° bending test): conducted according to GB / T 6742-2007, with a bending shaft diameter of 2 mm; Hardness: determined according to GB / T 6739-2022; Impact resistance: tested according to GB / T 1732-2020; The test results are shown in Table 1, and are as follows: Table 1 The results of the above comparative experiments show that the core-shell silica-polyamide composite toughening agent prepared by the present invention can enable the powder coating to achieve 180° bending without cracking, impact resistance ≥70kg·cm, and coating hardness above 2H, thus solving the contradiction of traditional powder coatings where "toughening reduces hardness and maintaining hardness results in insufficient toughness".

[0033] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A core-shell type silica-polyamide composite toughening agent, characterized in that, The preparation of the composite toughening agent includes the following steps: (1) Add nano-silica to anhydrous ethanol and ultrasonically disperse for 30-60 min. Then slowly add a mixed solution of silane coupling agent and ethanol. Stir the reaction at room temperature for 2-4 h. After the reaction is completed, perform post-treatment to obtain modified nano-silica. (2) Add the modified nano silica obtained in step (1) into anhydrous ethanol and ultrasonically disperse for 10-30 min. Then add organic solvent, surfactant, polyamide monomer and initiator. Under nitrogen atmosphere, heat to 60-80℃ and stir for 4-8 h. After the reaction is completed, post-treatment is performed to obtain core-shell type silica-polyamide composite toughening agent.

2. The core-shell silica-polyamide composite toughening agent according to claim 1, characterized in that, In step (1), the silane coupling agent is at least one of γ-methacryloxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane.

3. The core-shell silica-polyamide composite toughening agent according to claim 1, characterized in that, In step (2), the mass ratio of polyamide monomer to modified nano-silica is 1.5-2.5:

1.

4. The core-shell silica-polyamide composite toughening agent according to claim 1, characterized in that, In step (2), the polyamide monomer is at least one of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, caprolactam, and dodecanoic acid.

5. The core-shell silica-polyamide composite toughening agent according to claim 1, characterized in that, The polyamide monomers are acrylamide and 2-acrylamido-2-methylpropanesulfonic acid; the molar ratio of acrylamide to 2-acrylamido-2-methylpropanesulfonic acid is 1:1.2-3.

6. The core-shell silica-polyamide composite toughening agent according to claim 1, characterized in that, The surfactant used in step (2) is polyvinylpyrrolidone.

7. The core-shell silica-polyamide composite toughening agent according to claim 1, characterized in that, The particle size of the nano-silica in step (1) is 20-60 nm.

8. The method of applying a core-shell silica-polyamide composite toughening agent according to any one of claims 1-7, characterized in that, It is applied to the toughening modification of powder coatings to obtain toughened modified coatings.

9. The application method of the core-shell silica-polyamide composite toughening agent according to claim 8, characterized in that, The preparation of the toughening modified coating includes the following steps: (1) Take 80-100 parts of polyester resin, 1-10 parts of core-shell silica-polyamide composite toughening agent, and 0-5 parts of additives by weight, place them in a high-speed mixer, and stir and mix at 25-40℃ for 5-15 minutes to obtain a premix. (2) The premixed material is added to a twin-screw extruder, the temperature of each section of the extruder is controlled at 120-180℃, the screw speed is 100-300r / min, melt-blending, extrusion granulation, and post-treatment to obtain toughened modified coating.

10. The application method of the core-shell silica-polyamide composite toughening agent according to claim 9, wherein the amount of core-shell silica-polyamide composite toughening agent added in step (1) is 3-6 parts.

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