A kind of heat-sensitive epoxy curing agent and preparation method thereof and epoxy resin composition

Abstract

The invention discloses a heat-sensitive epoxy curing agent, a preparation method and an epoxy resin composition. The epoxy resin composition contains a heat-sensitive epoxy curing agent, and the viscosity increases slowly after being mixed with the resin, has a long storage period, and has a low post-curing temperature. The curing agent is a low-viscosity liquid at room temperature, and has good construction. Convenience, the molecular structure contains epoxy groups, and has good compatibility with epoxy resins. The phenolic hydroxyl groups can be dissociated after increasing the temperature to form a phenalkamine-like structure, which can quickly catalyze the polymerization of tertiary amines and epoxy resins, especially It is suitable for composite material infusion molding process that requires long operation time.

Description

technical field [0001] The invention belongs to the field of epoxy resins, relates to epoxy resin curing agents, and more particularly relates to heat-sensitive epoxy curing agents and epoxy resin compositions. Background technique [0002] Epoxy resin is widely used in composite material manufacturing and other fields due to its good heat resistance, mechanical properties, adhesion, electrical insulation and chemical corrosion resistance. Epoxy resin is generally liquid or solid at room temperature. Molecules or oligomers, which form a three-dimensional cross-linked network structure after reacting with the curing agent. imidazoles, etc. [0003] When epoxy resin is used in large-scale composite material systems, the resin needs to be able to flow fully in the mold before curing. At this time, the mixed system needs to have a long pot life, and even does not react at room temperature. When the mold temperature is raised , curing agent and epoxy resin for cross-linking cur...

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Problems solved by technology

[0004] The heat-sensitive curing agents commonly used in large-scale composite materials mainly include four types of ketimine, dicyandiamide, organic acid anhydride and microcapsules. Ketimine is easy to absorb moisture in the air and decomposes, which has high requirements for the construction environment; dicyandiamide It is solid at room temperature and has poor compatibility with epoxy resins; organic acid anhydrides are easily hydrolyzed, resulting in poor moisture resistance, and are not easy to chemically modify, and the post-curing temperature is high; the preparation process of microcapsules is strict, and the capsule film The thickness will have varying degrees of impact on storage, transportation and use, making industrial application difficult

[0005] US4335228A proposes to use acyl group to replace modified imidazole. Because the strong electron-withdrawing effect of acyl group weakens the electron-donating ability of imine, the energy barrier for its reaction with epoxy resin is increased, and it loses curing activity at room temperature, thus having better heat sensitivity. , and when the temperature rises enough to overcome the energy barrier of the reaction between imine and epoxy resin, the acyl-substituted imidazole curing agent can restore the curing activity, but the modified imidazole is generally solid and compatible with the epoxy resin Poor sex

[0006] EP543675A proposes to use microcapsules to coat modified imidazole, and to release the curing agent by breaking the microcapsules into a film under heating and pressure conditions. Capsule wall material remains in the curing system, affecting material properties

[0007] CN105837798A proposes to adopt monothiocarboxylic acid and epoxy resin to carry out ring-opening addition, and thiol is sealed, and this curing agent can automatically convert thiol group under the condition of catalyst or no catalyst, and epoxy resin reaction, but the dissociation temperature of the acetylation reaction of thiol group dissociation is relatively high, which does not meet the requirements of the large-scale composite material infusion process;

[0008] CN101885832A proposes to use polyamines and carbonyl compounds to react to prepare imine compounds of secondary amines to block them, and the imine structure in the curing agent is hydrolyzed to produce hydrophilic amine groups in the water environment. The carbonyl compound exists in the system as a toughening agent, reducing the mechanical properties of the material

[0009] US4092293A is initiator with pentaerythritol, initiates propylene oxide polymerization, with allyl capping, and H 2 S reaction to obtain polythiol The disadvantage of this preparation method is that the reaction steps are complicated, the conditions are harsh, the price of raw materials is relatively expensive, and the cost is high.

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