Development And Application Of MDI-TMP Curing Agent

Polyurethane was synthesized with isocyanate and polyol by a stepwise polymerization,which was widely used in the area of foam, elastomer, paint, adhesive, fiber and biomaterial.Diphenyl methane diisocyanate (MDI) has several advantages in isocyanate family, such aslow toxic, low cost, corrosion resistance and good flexibility. However, hardness of MDI isnot sufficient because of the molecular structure, the drying time is slow and theperformance of the paint film is poor, which result in its less use than that of TDI. Amongthem, MDI-TMP type curing agent is large limited in the promotion of market due to its lowtolerance and high viscosity.In this contribution, we are focus on the preparation technology and modification ofMDI-TMP type curing agent with low viscosity, high tolerance, high hardness and fastdrying. Addition reaction mechanism and dynamic characterization for MDI and TMP arefurther studied. The main contents of the paper include the following aspects:1). Discussion of preparation technology and optimum proposal for MDI-TMP typeprepolymer: MDI-50, TMP and ethyl acetate was selected as the starting material. Theoptimal reaction temperature was at60°C. Butyl acetate batch feeding can not onlyincrease the rate of reaction, but also reduce the free monomer. Three alkyl phosphate andbenzoyl chloride were selected as catalyst and polymerization inhibitor and the ratio was fitat1:0.8. It would be desirable that the total amount of catalyst is0.1%wt. The molar ratioof–NCO to-OH was1.1～1.2:1. An MDI-TMP type curing agent with48-52%solidcontent,6.8-7.3-NCO content, less than1.0F-MDI content, less than15s viscosity andlarger than2.5tolerance value can be obtained.2). FTIR spectroscopy (FT-IR), gas chromatography (GC), gel permeationchromatography (GPC) and mass spectrometry (MS) and other characterization methodswere explored to study the properties of the products. The effect of catalyst, reactiontemperature and controlling reaction end-point on the structure and properties of theMDI-TMP type curing agent was also discussed. Focused research of addition reaction dynamic characterization for MDI and TMP were studied. An example was explored theeffects of reaction temperature on reaction rate. The result showed that the addition reactionof MDI was followed the first order reaction. The kinetic constants is0.00437min-1and theaverage activation energy (Ea) is56.29kJ mol-1.3). Various modified alcohols were added to improve the tolerance of the curing agent.The result shows that Carpoly DB-211Resin with the range of additive amount in10-20%had good modified effect on the performance of the curing agent and the products with lessthan1.0F-MDI content and larger than2.5tolerance value can be obtained. Compared themodified curing agent (GZ43M) with the curing agent is used on the market, the resultsshowed that most of the performance of GZ43M were very close to that of W850B. Thetolerance, adhesive force and the fullness of the paint film were better than those of W850B,but the hardness and drying rate had shortcomings. In order to overcome the drawbacksabove, a mixing use with W950M (TDI-TMP type) curing agent, a product curing agentwith all aspects of good performance can be obtained.