Hyperbranched epoxy resin as well as preparation method and application thereof in coating

Abstract

The invention belongs to the technical field of coatings, and discloses hyperbranched epoxy resin and a preparation method and application thereof in coatings, the resin has a highly branched topological structure, the viscosity of the resin at 25 DEG C is 200-2000 mPa.s, and the epoxy value of the resin is 0.25-0.50 eq / 100g. The novel hyperbranched epoxy resin with low viscosity and high reaction activity is provided, and the hyperbranched epoxy resin can be used for preparing a high-temperature-resistant coating. A coating system scheme of'functional layered design 'and'interlayer reaction window construction' is innovatively provided, and inherent contradictions between high performance and environmental protection property, high adhesive force and high flexibility, and deep reinforcement and surface super wear resistance of a traditional epoxy coating are systematically solved; specifically, the resin can realize high solid content and even solvent-free coating, and accords with the environmental protection trend; according to the multi-layer composite coating constructed based on the adjustable characteristic, the comprehensive protection performance far better than that of a single coating is achieved through interlayer molecular-level interpenetrating cross-linking, and the multi-layer composite coating particularly shows excellent adhesive force, impact resistance and durability on porous base materials such as concrete.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a hyperbranched epoxy resin, its preparation method, and its application in coatings. Background Technology

[0002] Epoxy resins are widely used as key film-forming substances in protective coatings, floor coatings, and composite matrix due to their excellent adhesion, chemical stability, and mechanical properties. Traditional bisphenol A type epoxy resins have a linear molecular structure. In coating applications, they are usually mixed with a curing agent and then coated and cured to form a continuous protective coating on the substrate surface.

[0003] However, the structural characteristics of linear epoxy resins also bring some inherent limitations: (1) Linear epoxy resin melt has high viscosity. In order to achieve an applicable coating viscosity, a large amount of volatile organic solvents or reactive diluents are often required, which is contrary to increasingly stringent environmental regulations. (2) The regular network structure of the cured coating results in high internal stress and high brittleness, making it prone to cracking or peeling when subjected to substrate deformation or impact. (3) For porous or easily cracked substrates such as concrete and wood, ordinary epoxy coatings are difficult to balance between deep penetration and reinforcement and high surface strength and wear resistance. A single coating often cannot meet the comprehensive performance requirements under complex working conditions.

[0004] To balance the low viscosity, high toughness, and multifunctionality of coatings, the industry has explored various approaches, such as modifying epoxy resins with flexible segments or blending them with other resins. However, these methods often come at the cost of sacrificing the coating's hardness, heat resistance, or adhesion, and are complex to produce limited performance improvements. Therefore, developing a novel epoxy resin material and designing innovative coating application solutions based on its properties to systematically address the aforementioned technical contradictions in the field of high-performance, environmentally friendly coatings has become a critical issue that urgently needs to be addressed. Summary of the Invention

[0005] This invention aims to provide a hyperbranched epoxy resin, its preparation method, and its application in coatings to solve the problems mentioned in the background art. This invention provides a novel hyperbranched epoxy resin with low viscosity and high reactivity, and innovatively proposes a coating system scheme of "functional layered design" and "interlayer reaction window construction," systematically solving the inherent contradictions between high performance and environmental friendliness, high adhesion and high flexibility, and deep reinforcement and ultra-wear resistance of traditional epoxy coatings. Specifically, the resin itself can achieve high solids content and even solvent-free coating, conforming to environmental protection trends; the multi-layer composite coating constructed based on its adjustable characteristics achieves comprehensive protective performance far exceeding that of a single coating through inter-molecular-level interpenetrating cross-linking, exhibiting particularly excellent adhesion, impact resistance, and durability on porous substrates such as concrete.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A hyperbranched epoxy resin having a highly branched topological structure, a viscosity of 200-2000 mPa·s at 25°C, and an epoxy value of 0.25-0.50 eq / 100g.

[0007] Preferably, the branching nucleus of the resin is trimethylolpropane, pentaerythritol, or dipentaerythritol.

[0008] A method for preparing a hyperbranched epoxy resin includes the following steps: S1, the branched nucleus molecules and the catalyst are heated to 60-80℃ under an inert atmosphere; S2, add epichlorohydrin dropwise to the system of S1 at a uniform rate, control the dropping time to be 1-3 hours, and maintain the reaction temperature; After S3 is added, the temperature is raised to 90-120℃ and the reaction continues for 2-5 hours. S4. After the reaction is complete, the hyperbranched epoxy resin is obtained through post-treatment.

[0009] Preferably, the catalyst is tetrabutylammonium bromide, tetraethylammonium bromide, or triphenylphosphine, and its amount is 0.5%-2.0% of the molecular weight of the branched nucleus.

[0010] An application of hyperbranched epoxy resin in coatings involves using hyperbranched epoxy resins of different viscosities and functionalities to formulate different coatings in a multilayer coating with complementary properties.

[0011] Preferably, hyperbranched epoxy resins of different viscosities and functionalities are applied using specific interlayer application sequences.

[0012] Preferably, the multilayer coating comprises at least: A primer coating for penetrating a substrate, formulated with a low-viscosity type of the hyperbranched epoxy resin; An intermediate layer for stress buffering, formulated with the hyperbranched epoxy resin of a flexible modified type. A surface coating for surface protection, formulated from the aforementioned hyperbranched epoxy resin of high functionality and high hardness type.

[0013] Preferably, the specific interlayer construction sequence is as follows: when applying two adjacent layers, the next layer should be applied within a specific time window after the previous layer has surface dried but before it has fully dried.

[0014] Preferably, After the base coat is applied, the coating time window for the intermediate layer is 30 minutes to 4 hours; After the intermediate layer is coated, the coating time window for the topcoat layer is 1 to 6 hours.

[0015] Preferably, the application specifically involves forming a composite protective coating on a concrete, metal, or wood substrate that combines high adhesion, high flexibility, and high abrasion resistance.

[0016] The beneficial effects of this technical solution compared to existing technologies are as follows: (1) By using epoxy resin with a highly branched topology, the resin provided by the present invention has a viscosity that is significantly lower than that of traditional linear resin at the same molecular weight. This characteristic makes it possible to formulate high solids or solvent-free coatings, greatly reducing the emission of volatile organic compounds. At the same time, the lower viscosity also improves the leveling and penetration performance of the coating, making construction more convenient. (2) Breaking through the limitations of single coating performance, a multi-layer composite coating system was creatively proposed and constructed. By accurately applying different types of hyperbranched epoxy resin to the corresponding functional layers, the coating simultaneously possesses excellent substrate adhesion, flexible crack resistance and high surface hardness and wear resistance on a macroscopic level, achieving synergistic optimization and overall multiplication of performance indicators. (3) By using the core process of “interlayer construction during the time window after surface drying and before actual drying”, the adjacent coatings are encouraged to undergo sufficient molecular diffusion and co-reaction at the interface, forming a gradient transition layer of chemical bonding and physical interpenetration, thereby eliminating the weak interface between layers and integrating the multilayer coatings into a dense and solid whole. This not only greatly improves the peel strength and durability of the coating, but also serves as the fundamental guarantee for achieving long-term composite protection, especially suitable for the protection needs under harsh working conditions such as concrete and metal. Attached Figure Description

[0017] Figure 1 The preparation process flow diagram provided by the present invention; Figure 2 This is a cross-sectional schematic diagram of the multilayer composite coating system provided by the present invention. Detailed Implementation

[0018] This invention aims to provide a novel epoxy resin material and its systematic application solution, to solve the prominent problems faced by traditional linear epoxy resins in the field of high-performance coatings, such as high viscosity, high brittleness, and the difficulty of a single coating meeting multiple performance requirements. The overall technical solution consists of three parts: 1. To provide a novel hyperbranched epoxy resin with a specific parameter range; 2. Provide an efficient preparation method for this resin; 3. To provide an innovative coating application system and construction method based on the unique physicochemical properties of the resin, thereby fundamentally achieving a comprehensive improvement in coating performance.

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments: I. On Hyperbranched Epoxy Resins and Their Preparation This invention provides a hyperbranched epoxy resin, the core feature of which is a highly branched three-dimensional spherical topology. Compared with traditional linear bisphenol A type epoxy resins, this structure makes the molecular chains less prone to tight entanglement, thus resulting in a lower melt viscosity at the same molecular weight. The hyperbranched epoxy resin of this invention has a typical viscosity range of 200 to 2000 mPa·s at 25°C and an epoxy value range of 0.25 to 0.50 eq / 100g. This specific parameter range ensures that the resin itself possesses both good flowability and sufficient reactivity, laying the foundation for the subsequent formulation of different types of coatings.

[0020] To achieve the above performance, in a preferred embodiment, the hyperbranched epoxy resin uses polyol molecules as the core for constructing the branched structure, i.e., the "branching core". Suitable branching cores include, but are not limited to, trimethylolpropane, pentaerythritol and dipentaerythritol. These molecules have three or more hydroxyl groups and can serve as multifunctional starting points. Through reaction with epoxy end-capping agents, branched chains are extended outward to grow and finally form the target product.

[0021] like Figure 1 As shown, a specific method for preparing hyperbranched epoxy resin is provided, using trimethylolpropane as an example. However, it should be understood that a similar process can be used when using other polyols such as pentaerythritol or dipentaerythritol as branching cores. First, accurately weighed trimethylolpropane and the catalyst are added together to a four-necked flask equipped with a stirrer, thermometer, dropping funnel and nitrogen inlet tube. Nitrogen is introduced to replace the air while stirring to form an inert atmosphere. Then the system is slowly heated to a preset temperature of 60°C to 80°C. The catalyst can be one of tetrabutylammonium bromide, tetraethylammonium bromide or triphenylphosphine, and its amount is usually 0.5% to 2.0% of the mass of trimethylolpropane to effectively promote the reaction. After the temperature stabilizes, epichlorohydrin is added dropwise to the reaction system at a uniform rate through a dropping funnel. The dropping process needs to be precisely controlled, and the dropping time should be controlled within 1 to 3 hours. During this period, the reaction temperature needs to be maintained within the initially set range of 60°C to 80°C by adjusting the heating rate or cooling to prevent local overheating and side reactions. The molar amount of epichlorohydrin needs to be precisely calculated based on the theoretical functionality of the target product, and it is usually much more than the molar amount of hydroxyl groups. After the epichlorohydrin is added dropwise, the temperature of the reaction system is gradually increased to 90°C to 120°C, and the reaction is continued to be stirred at this temperature for 2 to 5 hours to ensure that the ring-opening and ring-closing reactions are fully carried out, ensuring that the branched structure is fully formed and that the epoxy end-capping is achieved. After the reaction is completed, unreacted epichlorohydrin and any low-boiling-point byproducts that may be generated in the system are removed by conventional post-treatment methods such as vacuum distillation, thus obtaining a clear, viscous target hyperbranched epoxy resin. By adjusting the type of branching nuclei, the amount of catalyst, and the reaction temperature and time, a series of resin products with adjustable viscosity and epoxy value within the above target range can be obtained, such as low-viscosity and high-functionality types.

[0022] II. Innovative Applications of Hyperbranched Epoxy Resins in Coatings like Figure 2 As shown, the most critical contribution of this invention lies in proposing a groundbreaking coating system design concept and construction method to fully leverage the unique advantages of the aforementioned hyperbranched epoxy resins. The core application idea is that instead of using a single type of resin for a single coating, a series of hyperbranched epoxy resins with different viscosities, functionalities, or specific modifications are systematically used to construct a multi-layer composite coating system with complementary functions and synergistic effects on the same substrate, supplemented by key interlayer construction control technologies.

[0023] Specifically, this application solution involves building an architecture that includes at least three functional layers: 1. The first layer is the base coat, whose core function is to deeply penetrate and reinforce the substrate (especially porous substrates such as concrete). To achieve this, a low-viscosity hyperbranched epoxy resin prepared by the method of this invention should be used for formulation. The viscosity of this resin at 25°C is preferably 200 to 500 mPa·s. The extremely low viscosity ensures that the coating formulation still has excellent flowability and permeability even under high solids content or solvent-free conditions, effectively wetting and penetrating into the micropores of the substrate to form a strong "anchoring" effect.

[0024] 2. The second layer is the intermediate layer, whose core function is to absorb and buffer stress, preventing the coating from cracking or peeling due to substrate deformation or external impact. For this purpose, a flexible modified hyperbranched epoxy resin is required. This resin can be obtained by introducing flexible segments (such as polyetheramine, long-chain aliphatic diacid, etc.) to modify the aforementioned hyperbranched structure during the synthesis process, or by compounding it with flexible curing agents and toughening agents during paint formulation. This layer gives the coating system good flexibility and resistance to deformation.

[0025] 3. The third layer is the topcoat, whose core function is to provide excellent surface hardness, wear resistance, chemical corrosion resistance, and other ultimate protective properties. Therefore, it is necessary to select a high-functionality, high-hardness hyperbranched epoxy resin for formulation. The epoxy functionality of this resin is usually higher than 6. At the same time, sufficient wear-resistant fillers, such as nano-alumina, silicon carbide, or corundum powder with a particle size in the range of 0.1 to 10 micrometers, need to be added to the coating formulation. The amount added can be adjusted between 10% and 40% of the total mass of the coating according to the wear resistance requirements. The high-functionality resin ensures the crosslinking density, while the inherent low viscosity of the hyperbranched structure allows the coating to maintain good workability and leveling properties even with a high filler content, which is difficult to achieve with traditional linear resins.

[0026] To achieve a perfect superposition of the above three-layer structural performance rather than a simple stacking, this invention reveals a crucial construction control point: a specific inter-layer construction sequence.

[0027] Specifically, when applying two adjacent layers, the application must be carried out within a specific physicochemical time window between the surface dryness and the complete dryness of the previous layer. For the base coat and intermediate layer, this time window is typically 30 minutes to 4 hours after the base coat is applied; for the intermediate layer and top coat, it is 1 hour to 6 hours after the intermediate layer is applied. During this period, the previous coating has initially formed a gel network and lost its fluidity (surface dryness), but the interior has not yet fully cross-linked and cured (not completely dry), and still has high reactivity. When the next layer is applied at this time, the active components (resin and curing agent) in the two coatings can undergo sufficient intermolecular diffusion, interweaving, and co-reaction at the interface, thereby forming a strong, gradient-transition chemical bond and interpenetrating network structure at the physical interface of the two layers, rather than a clear, easily peelable weak interface layer. This is the key to the integrated performance of "high adhesion, high flexibility, and high abrasion resistance" of this multi-layer coating system.

[0028] Based on the above-mentioned resin, coating design, and construction methods, the hyperbranched epoxy resin and its application solutions provided by this invention are particularly suitable for preparing composite protective coatings with extremely high comprehensive performance requirements on various substrates such as concrete, metal, or wood. For example, it can be used in fields such as high-standard industrial flooring, heavy machinery protective coatings, bridge anti-corrosion coatings, and high-grade wood coatings. It systematically solves the common industry problems in the background technology, such as the difficulty in balancing high environmental protection requirements and high performance, high coating brittleness, and the inability of a single coating to meet complex protection needs.

[0029] The above descriptions are merely embodiments of the present invention. Commonly known technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention. These modifications and improvements should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims. The specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A hyperbranched epoxy resin, characterized in that: The resin has a highly branched topological structure, a viscosity of 200-2000 mPa·s at 25°C, and an epoxy value of 0.25-0.50 eq / 100g.

2. The hyperbranched epoxy resin according to claim 1, characterized in that: The branching nuclei of the resin are trimethylolpropane, pentaerythritol, or dipentaerythritol.

3. A method for preparing a hyperbranched epoxy resin according to any one of claims 1-2, characterized in that, Includes the following steps: S1, the branched nucleus molecules and the catalyst are heated to 60-80℃ under an inert atmosphere; S2, add epichlorohydrin dropwise to the system of S1 at a uniform rate, control the dropping time to be 1-3 hours, and maintain the reaction temperature; After S3 is added, the temperature is raised to 90-120℃ and the reaction continues for 2-5 hours. S4. After the reaction is complete, the hyperbranched epoxy resin is obtained through post-treatment.

4. The method according to claim 3, characterized in that: The catalyst is tetrabutylammonium bromide, tetraethylammonium bromide, or triphenylphosphine, and its amount is 0.5%-2.0% of the molecular weight of the branched nucleus.

5. The application of a hyperbranched epoxy resin according to any one of claims 1-4 in coatings, characterized in that: The hyperbranched epoxy resins of different viscosities and functionalities were used to formulate different coatings in a multilayer coating with complementary properties.

6. The application according to claim 5, characterized in that: The hyperbranched epoxy resins of different viscosities and functionalities were coated using specific interlayer application sequences.

7. The application according to claim 5, characterized in that, The multilayer coating includes at least: A primer coating for penetrating a substrate, formulated with a low-viscosity type of the hyperbranched epoxy resin; An intermediate layer for stress buffering, formulated with a flexible modified version of the hyperbranched epoxy resin. A surface coating for surface protection, formulated from the aforementioned hyperbranched epoxy resin of high functionality and high hardness type.

8. The application according to claim 6, characterized in that, The specific interlayer construction sequence is as follows: when applying two adjacent layers, the next layer must be applied within a specific time window after the previous layer has surface dried but before it has fully dried.

9. The application according to claim 7, characterized in that: After the base coat is applied, the coating time window for the intermediate layer is 30 minutes to 4 hours; After the intermediate layer is coated, the coating time window for the topcoat layer is 1 to 6 hours.

10. The application according to claim 8, characterized in that: The specific application involves forming a composite protective coating on concrete, metal, or wood substrates that combines high adhesion, high flexibility, and high abrasion resistance.

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