Environment-friendly curing agent with ultra low free TDI (toluene diisocyanate) content and preparation method thereof

Abstract

The invention relates to an environment-friendly curing agent with an ultra low free TDI (toluene diisocyanate) content and a preparation method thereof. The environment-friendly curing agent comprises the compositions in percent by weight: 35%-45% of TDI, 9%-12% of TMP (trimethylolpropane), 3%-4% of a modified dihydric alcohol, 0.05%-0.06% of a catalyst, 0.05%-0.06% of a polymerization inhibitor, 0.1%-0.2% of an ultraviolet-ray absorber, 0.2%-0.3% of a dewatering agent, and 38%-52% of a butyl ester. The beneficial effects comprise that the TDI-TMP curing agent is synthesized through a chemical synthetic method by selecting the ratio of NCO (isocyanate group) to OH to be 3.1:1-3.2:1, three composite catalysts such as a tertiary amine, an alkylphosphine and zinc naphthenate are employed for catalysis and for promoting rapid reduction of free TDI content and enabling the product to possess high NCO content and low TDI content, so that performances are guaranteed and also environment protection requirements are reached.

Description

technical field [0001] The invention relates to the technical field of an environment-friendly curing agent, in particular to an environment-friendly curing agent with ultra-low free TDI content and a preparation method thereof. [0002] Background technique [0003] The national mandatory standard "Limit Standards of Hazardous Substances in Solvent-Based Wood Coatings for Interior Decoration Materials" GB18581-2009 stipulates that the content of free toluene diisocyanate TDI after the curing agent is mixed with paint must be less than 0.4%, and the synthetic curing agent free toluene diisocyanate must be less than 0.4%. Isocyanate TDI should be less than 1.2%. The international standard is that the mass fraction of free toluene diisocyanate TDI is not more than 0.5%. [0004] Among them, toluene diisocyanate TDI and trimethylolpropane TMP adducts are a common curing agent for two-component polyurethane coatings at home and abroad. They have the advantages of light color a...

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Problems solved by technology

[0007] 1. Molecular distillation is the most effective method to reduce TDI of free toluene diisocyanate, and it is also the most popular method in the world at present. However, the equipment used in molecular distillation is expensive and complicated, and the process is relatively strict. Its development and application are still in my country. in its infancy

[0008] 2. The direct synthesis method has been widely used by domestic curing agent manufacturers in recent years because it does not require additional equipment, is low in cost, and is easy to promote. However, its free toluene diisocyanate TDI content is generally high, and the free toluene diisocyanate TDI content is above 2%. , while the mandatory national standard "Limited Standards for Hazardous Substances in Solvent-Based Wood Coatings for Interior Decoration Materials" GB18581-2009 stipulates that the content of free toluene diisocyanate TDI after the curing agent is mixed with paint must be less than 0.4%, that is, the free TDI content of the synthetic curing agent is required The TDI content of toluene diisocyanate should be less than or equal to 1.2%, while the free toluene diisocyanate TDI content of the curing agent synthesized by this method in China is more than 2%, which does not meet the requirements of national standards

In addition, in order to reduce the free content of toluene diisocyanate TDI as much as possible in the direct synthesis method, catalysts are usually added to deepen the reaction, which is likely to cause fast reaction speed in the later stage, and improper control can easily lead to abnormal production problems such as high viscosity and even curing.

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