Coating with isocyanate crosslinking agent

Coating with isocyanate crosslinking agent,Is an important component of the polyurethane adhesives and coating, is widely used on the current domestic N 100 type (HDI biuret crosslinking agent), TDI and TDI and small molecules polyols as TMP adduct.

As a new generation of advanced polyurethane adhesives and coating of crosslinking agent, contain different urea acid ester base of HDI trimer more and more be taken seriously.

HDI trimer was HDI of under the effect of catalyst and the isocyanate crosslinking agent, theory of functionality for 3, isocyanate root mass fraction is 25%. But because of the limits of the selectivity of catalyst and reaction conditions, usually get a 3 get together the product is a mixture of multiple components, the actual functionality is more than 3, isocyanate root mass fraction is less than 25%.

In reference to the relevant data, on the basis of the HDI trimer synthesis mechanism, catalyst, introduce the properties and applications.

And the mechanism of the HDI. Isocyanate group, nitrogen and oxygen density of electron cloud is big, strong electronegativity; And carbon electron cloud density is small, positively charged, so the carbon becomes electrophilic center, vulnerable to the attack of the nucleophilic reagent. Under the effect of catalyst, the isocyanate group bonus to each other, cause polymerization reaction. Under type said HDI and the general mechanism of reaction, including A - B on behalf of the catalyst.

As you can see, there are many active intermediates, and the reaction of HDI can form different reaction products, along with the change of external conditions, since the HDI products from the mass fraction of each component in the different, isocyanate root mass fraction also have differences.

Since the products have a trimer of HDI, dimers, carbide imide, linear polymer and annular polymer, etc. End product which mainly depends on the active intermediates.

In the HDI and the product, often there is a certain amount of cyclic polymer, lead to product of isocyanate root mass fraction is lower than the theoretical value. Cyclic polymer formation is due to generate trimer side effects of the active intermediates, there is evidence that reaction generated trimer can further reaction and reactive intermediates.




Chinese name: Diethyl toluene diamine(DETDA)

Physical and chemical properties: light yellow transparent liquid, slightly soluble in water, soluble in alcohols, ethers, ketones and other polar organic solvents, and polyether, polyester polyol compatibility.

Density 1.022

Viscosity (20 ℃) ??mPa·ss290±10

Pour Point ℃-9

Boiling point of310°C

Flash Point°C161.1°C


HDI and the response of the catalyst. Catalyst reported in literatures can be divided into the following categories:

Metal salt catalysts. Alkali metal salts used as isocyanate early base and the reaction catalyst, for HDI, alkali metal salt and the advantage of transition metal salts is in 3 get together the product does not contain dimers, does not decompose to produce HDI monomer during storage.

But under the action of the polymerization is quite heavy, unable to effectively control, easy to cause deep polymerization, polymer mass fraction in the product increased, isocyanate root of the products, low mass fraction, high viscosity, and tile products often have appeared;

Another must be added at the end of the reaction, such as benzoyl chloride, p-toluene sulfonic acid, inorganic acid to terminate the reaction such as phosphoric acid, so that there will be insoluble in the formation of metal salts of product result in product tourne. If you want to remove the metal salt, you have to join a large number of solvent dilution filter, and then steamed in addition to the solvent.

DABI etc with tributyl tin oxide, tetrabutyl chromium oxide, tetrabutyl titanium oxide, naphthalene acid aluminum, cobalt naphthenate as catalyst, such as reaction at high temperature, got close to the ideal structure of melamine products. Analysis data show that in tributyl tin oxide, the first generation trimer, only in the most after the consumption of HDI, polymer formation.

The composite catalyst. The combination of long chain fatty acid metal salt and phenol, HDI and the product can be obtained, at the end of the reaction is to terminate the agent. Piperazine and its derivatives with tertiary amine combinations as HDI and the catalyst have been reported. But piperazine with carcinogenesis, and have hours of the induction period of polymerization, the polymerization reaction after the start of exothermic, cannot undertake bulk polymerization, solvent must be added to control the reaction.

Copyright: Zhang Jia Gang YaRui Chemical co.,Ltd 

Diethyl toluene diamine(DETDA)  http://www.yaruichem.com