Modified polyurethane elastic curing agent and preparation method thereof

Abstract

The invention discloses a modified polyurethane elastic curing agent. The modified polyurethane elastic curing agent is prepared from the following raw materials in part by weight: 38 to 45 parts of polyester resin, and 12 to 16 parts of toluene diisocynate, wherein the content of hydroxyl groups of the polyester resin is 7.2 to 7.8 percent. In the curing agent, the polyester resin which has highflexibility and contains 7.2 to 7.8 percent of hydroxyl groups is adopted; and long chain aliphatic diacids with high flexibility, aromatic diacids containing benzene ring structures and excessive long-chain diols are introduced into the structure of the polyester resin, so that the polyester resin also has the characteristics of high flexibility, high glass transition temperature, high hydroxyl content and high reaction activity. Therefore, the two-component polyurethane elastic curing agent synthesized by reacting the polyester resin and a toluene diisocynate monomer containing NCO groups has the advantages of high hardness, high flexibility, and high activity when reacting with the hydroxyl groups. The reaction activity and the hardness and flexibility of paint films can be synchronously met when a crosslinking reaction of the polyurethane curing agent and a paint component containing the hydroxyl groups are performed for film formation.

Description

technical field [0001] The invention relates to the technical field of curing agents, in particular to modified polyurethane elastic curing agents and a preparation method thereof. Background technique [0002] The two-component polyurethane curing agent contains active isocyanate groups, which can cross-link with paint components containing active hydroxyl groups to form paint films with various properties. [0003] The general two-component polyurethane curing agent is a kind of curing agent with the largest production volume and the most widely used in my country, which is synthesized by using trimethylolpropane (TMP) and toluene diisocyanate (TDI) through a specific formula and process reaction. Due to the limitation of the characteristics of raw materials, this kind of curing agent has low flexibility. When it reacts with hydroxyl-containing paint components to form a film, it cannot meet the special requirements of some paint films to have certain flexibility. [0004...

AI Technical Summary

Problems solved by technology

Due to the limitation of the characteristics of raw materials, this kind of curing agent has low flexibility. When it reacts with hydroxyl-containing paint components to form a film, it cannot meet the special requirements of some paint films to have a certain degree of flexibility.

[0004] Some polyurethane curing agent manufacturers use general hydroxyl-containing alkyd resins and NCO-containing toluene diisocyanate (TDI) to synthesize modified polyurethane curing agents through specific formulas and processes. The content is less than 5.5%, and relatively speaking, the saturated fatty acid content in the alkyd resin formula is more, while the hard monomeric acid content containing the benzene ring structure is less. The alkyd resin itself has low hardness, small molecular weight, and short molecular chain. And the excess of polyol is less, and the effective hydroxyl content in the molecular structure is low. When this alkyd resin is used to modify the polyurethane curing agent, the obtained polyurethane curing agent has many disadvantages: the effective NCO content is low, the hardness Low

When the polyurethane curing agent cross-links with the hydroxyl-containing paint component to form a film, the cross-linking reaction activity is low, the drying speed is slow, the cross-linking density is poor, the paint film hardness is low, the adhesion is poor, and the flexibility is poor.

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