[Literature Interpretation] How to prepare high-performance epoxy emulsion with narrow particle size distribution and good storage stability, this article tells you!

Keywords: epoxy resin emulsifier, waterborne epoxy coating, epoxy emulsion

Author's Guide

1.

2.

The above is the author’s family statement, for reference only.

Background introduction

Water-based paint has the characteristics of low toxicity, low odor, little or almost no harm to human health and the environment

Through the chemical modification method, it is not difficult to prepare a water-based epoxy emulsion with stable storage and small particle size

However, the disadvantage of the reverse rotation method is that the particle size of the emulsion is difficult to control, the particle size distribution is wide, and the dispersion stability is poor

research content

1.

Using ethanolamine (ETA), epoxy resin, and polyethylene glycol diglycidyl ether (PEGDGE) as raw materials, an epoxy resin emulsifier is synthesized through a ring-opening reaction.

2.

Add 50g of self-made emulsifier and 100g of E51 into the container
.
The temperature of the water bath of the system is maintained at 60 ~ 70℃
.
Under high-speed stirring at 3000-4000 rpm, slowly add water to the container at a speed of 4 ml/min
.
The viscosity of the system drops first and then rises slowly
.
When the viscosity reaches its peak, the drip rate is increased to 5ml/min
.
As the amount of water added increases, the viscosity of the system begins to drop again
.
When the viscosity drops suddenly, it indicates that the system has completed the reversal process from W/O to O/W
.
At this time, quickly add water to adjust the theoretical solid content of the water-based epoxy emulsion to 55%
.
Similarly, the emulsification process of NPPN631 and E20 is the same
.
Add 50g of self-made emulsifier and 100g of E51 into the container
.
The temperature of the water bath of the system is maintained at 60 ~ 70℃
.
Under high-speed stirring at 3000-4000 rpm, slowly add water to the container at a speed of 4 ml/min
.
The viscosity of the system drops first and then rises slowly
.
When the viscosity reaches its peak, the drip rate is increased to 5ml/min
.
As the amount of water added increases, the viscosity of the system begins to drop again
.
When the viscosity drops suddenly, it indicates that the system has completed the reversal process from W/O to O/W
.
At this time, quickly add water to adjust the theoretical solid content of the water-based epoxy emulsion to 55%
.
Similarly, the emulsification process of NPPN631 and E20 is the same
.

3.
Preparation of waterborne epoxy coatings

Mix water-based epoxy dispersions WEP631, WEP51, WEP20 and water-based epoxy curing agent Banco901 according to the molar ratio of epoxy groups to active hydrogen at 1:1 (mass ratios of 1.
7:1, 1.
9:1, and 4:1), and add 10% water adjusts the viscosity
.
Paint 23±3μm thick water-based epoxy paint on tinplate (120mm*50mm) and glass plate (100mm*100mm)
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The coating film was dried at room temperature for 7 days to ensure that the emulsion and curing agent reacted completely
.

Results discussion

1.
The influence of emulsifier structure on emulsification performance

2.
Infrared analysis

3.
The influence of the amount of emulsifier on the particle size of the emulsion

4.
Performance of waterborne epoxy coating

5.
Glass transition temperature

6.
Thermogravimetric analysis

7.
Comparison of curing mechanism of two waterborne epoxy coating systems

in conclusion

Using self-made emulsifiers, three kinds of waterborne epoxy emulsions with small particle size and good storage stability were successfully prepared by the reverse rotation method
.
The emulsifier prepared with the molar ratio of PGEDGE to E20 epoxy resin at 2:1 has good emulsifying ability for E20, E51 and NPPN631 epoxy resins, with a Kraff characteristic of 56°C and an HLB value of 16
.
Use this emulsifier to emulsify epoxy resin.
When preparing water-based epoxy emulsion, the best emulsifier dosage is 33%
.
For the three emulsions of WEP631, WEP51 and WEP20, the coating prepared by WEP631 emulsion is superior to WEP51 and WEP20 in terms of thermal stability and hardness
.
The film performance of the water-based epoxy emulsion mixed with the water-based epoxy curing agent is better than the performance of the mixed epoxy resin and the water-based epoxy curing agent, which is mainly related to the different curing mechanism
.

Reference materials: 

AiD, Mo R, Wang H, et al.
Preparation of waterborne epoxy dispersion and its application in 2K waterborne epoxy coatings[J].
Progress in Organic Coatings, 2019,136:105258.