The sealing water polyurethane coating crosslinking agent

The sealing water polyurethane coating crosslinking agent

Two-component waterborne polyurethane is a polyol component and crosslinking agent component mix, mix without an exhausted, cannot continue to use again, cause waste of raw materials, components and crosslinking agent of NCO group activity is higher, room temperature can react with the water in the atmosphere so that it is bad.

If the NCO groups react with some sort of blocking agent, was prepared under normal temperature and stable material, when used by heating again to restore its original structure and isocyanate react with compounds containing hydroxyl, can get the original pu and can solve the above problems.

Enclosed crosslinking agent has good stability in water, is widely used in water in the system, but the NCO group activity is very high, prone to adverse reactions, the deblocking temperature is high, the NCO group will happen dimer, melamine, affections generated formate or biuret, so it is very important to develop low deblocking temperature sealants.

Closed - unsealing mechanism. The reaction of sealants and isocyanates is a typical nucleophilic reaction. Mechanism of the reaction process can be used two explanations: one is to eliminate - bonus mechanism, namely, under a certain temperature, enclosed isocyanate is decomposed into sealants and free isocyanate, including free isocyanate continue to react with the hydroxyl component to generate two-component polyurethane.

In addition, the addition of the hydroxyl group to the closed NCO group is formed by the addition of the hydroxyl group and the closed NCO group.

Type of sealant. Commonly used in closed waterborne polyurethane crosslinker sealants with isopropyl alcohol, phenol, caprolactam, methyl ethyl ketone oxime, imidazole, sodium bisulfite, diethyl malonate, etc. According to the sealing temperature and water solubility, the sealing agent is selected. In a closed reaction, when the NCO group is attached to the electron instead of the base, it can facilitate the closing of the reaction. And even if you have an electron substitution, you can promote the solution.




Chinese name: Diethyl toluene diamine(DETDA)

Diethyltoluenediamine packing： net weight 200KG/ galvanized iron drum (a small cabinet pallet loaded 16 tons), 1000KG/IB barrels (a small cabinet loaded 18 tons or 23 tons of ISOTANK).


Alcohol and phenol sealants. An alcohol-type sealant has a high solution temperature and low reactivity, so it can be stable in water. The storage stability of the electrodeposition primer is very strong, so it is a sealant with 2-ethyl hexanol.

Phenolic compounds and reaction mechanism of isocyanate with alcohol and isocyanate reaction mechanism, are all NCO group with active hydrogen reaction, respectively to generate carbamic acid ester and phenyl carbamate, phenolic compounds with benzene ring in the conjugate effect, lead to the reaction of phenolic hydroxyl activity than alcohol hydroxyl is weak, so the phenolic sealants compared with alcohols deblocking temperature is low, but closed reaction is slow, need to heat or add catalyst under the condition of the reaction speed.

It is very suitable for the seal of the fatty family isocyanate, which is lower than the alcohol and phenols. Wang Li etc with TDI and TMP as raw material to synthesize polyurethane pre polymers, with methyl ethyl ketone oxime for sealants synthetic water-based polyurethane crosslinker, the results showed that the crosslinking agent closed low temperature storage stability and good solution.

Zhong Yan etc with isocyanate trimer and MPEG as reaction raw materials, with different sealants closed residual NCO groups, preparation of water dispersible polyurethane crosslinker, closed, the results show that when the MPEG molecular weight is less than 2000, with methyl ethyl ketone oxime as a blocking agent, preparation of enclosed waterborne polyurethane crosslinking agent with proper viscosity and good stability.

Imidazole and amidine, pyrazole and triazole. Because of the presence of hydrogen bonds, imidazole and amidine, pyrazole and triazole sealing agents are relatively low. Zhou jing jing, etc with IPDI and TMP as raw material via addition reaction, DMPA as chain extender, again with triethylamine (TEA) and salt, 2 - methyl imidazole (2 - MI) for sealants seal end, get a can unlock the waterborne polyurethane crosslinking agent at room temperature. The results show that the crosslinking agent can significantly reduce the reaction rate of isocyanate and water and increase the gel time.

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