Development of environmentally friendly high-performance two-component waterborne epoxy paint!

introduction

Two-component waterborne epoxy coatings are widely used in various industries, such as rail transit, steel structures and construction machinery

In the process of changing oil to water, on the one hand, the transformation of the production line must adapt to the new process requirements, and on the other hand, higher requirements are put forward for water-based coatings

In view of the above problems, it is urgent to design a two-component epoxy coating with excellent comprehensive performance

1 experiment

Water-based color paste and coating preparation

Add deionized water, dispersant, defoamer, and anti-flash rust agent into the grinding bucket in sequence, stir evenly, add carbon black, titanium dioxide, talc, and precipitated barium sulfate in sequence, disperse evenly by high-speed disperser, then grind and grind To fineness ≤30µm

Preparation of paint film

The cold-rolled steel plate (145 mm×60mm) is degreasing, polished with 300-mesh sandpaper and wiped clean with industrial alcohol

2 Results and discussion

2.

The emulsions used in this research are all bisphenol A epoxy resin emulsions, and their epoxy equivalents are all 900~1100 according to the emulsion supply form.

This is because the waterborne epoxy emulsion is made by adding an emulsifier to the epoxy resin and then dispersing it at high speed.

Table 1 Different emulsions with Aradur 38-1 curing agent performance

2.
2 Selection of water-based epoxy curing agent

After selecting the emulsion, the curing agent is compared
.
The results of chemical resistance are shown in Figure 1.
The ordinate axis is the number of days.
It can be seen that water-based amine curing agents have good alkali resistance, but there is a large gap in acid resistance
.
3986 has excellent acid and alkali resistance
.
The water resistance performance is shown in Figure 2, which compares the water resistance under the conditions of 40°C warm water and 100°C boiling water
.
It is found that the water resistance of 3986 and 3EC150 Y is better, and the performance of resistance to warm water is consistent with the performance trend of resistance to boiling water
.

The neutral salt spray resistance performance is shown in Figure 3.
The salt spray performance is better than 6062 and 3986
.
The results of the pot life test are shown in Figure 4.
After simulating high-temperature storage, the gloss retention rate of 3986 can reach 40%
.
From the above experimental analysis, it can be seen that the water-based amine curing agent of different manufacturers has a greater impact on the water-based epoxy paint film.
This is due to the large difference in the formulation and process of different manufacturers, and the different emphasis on the performance of the curing agent
.

38-1 curing agent focuses on low active hydrogen equivalent to reduce the amount of curing agent and achieve cost saving; TOD 3EC-150Y focuses on water resistance, which can withstand 40℃ hot water up to 9d; CTW-6062 curing agent focuses on paint film The corrosion resistance
.
Each curing agent has its own advantages, but the performance is not comprehensive enough
.
When Aradur 3986 curing agent is used, its water resistance, salt spray resistance, chemical resistance and pot life are good, and the paint film performance is balanced without shortcomings
.
Choose Aradur 3986 as the curing agent
.

Figure 1 Comparison of chemical resistance of different water-based amines

Figure 2 Comparison of water resistance of different water-based amine curing agents

Figure 3 Salt spray resistance of different curing agents

Figure 4 Comparison of the pot life of different curing agents

2.
3 Selection of anti-rust pigments

Chromium-containing anti-rust pigments are more toxic and harmful to the environment
.
It is the mainstream trend to use zinc phosphate, modified phosphate, and modified silicate to replace chromium-containing anti-rust pigments and fillers
.
The use of zinc phosphate pigments and fillers can achieve better anti-corrosion effects, and the effect of chromium-containing pigments and fillers can be reached or even exceeded when the addition amount is fixed
.
The salt spray performance results of different types of anti-rust pigments are shown in Table 2
.

However, in the experiment, it was found that the anti-corrosion performance of the pigment paste decreased after being stored for a period of time, especially when the curing agent resin was used to grind the color paste, as the heat storage time increased, the anti-corrosion performance decreased significantly
.
This is because zinc phosphate pigments and fillers can react with the active amine and ammonium salt in the curing agent
.
The use of modified phosphate instead of ordinary zinc phosphate improves the stability of the pigment paste, but it still fails to meet the requirements
.
The modified phosphate compound calcium aluminum polyphosphate hydrated silicate can obtain better salt spray resistance and storage stability
.

Table 2 Salt spray performance of different types of anti-rust pigments

The above-mentioned optimal modified orthophosphate/aluminum polyphosphate hydrated silicate antirust pigment was used to prepare coatings, and the influence of different addition amounts on salt spray performance was verified
.
As the amount of anti-rust pigment increases, its anti-corrosion performance increases
.
When the usage amount reaches 6%/2% of modified orthophosphate/aluminum polyphosphate hydrated silicate, the salt spray resistance of the coating is the best
.
The salt spray resistance change is not obvious when the anti-rust pigment is further added
.
It is better to use the addition amount of 5%/1% or 6%/2%
.

2.
4 Analysis of paint film performance

According to the previous experimental results, the combination of CTW-6062 emulsion and Aradur 3986 has determined the type and amount of anti-rust pigment
.
Verify the performance of the water-based epoxy coating again
.
The results showed that salt spray resistance, 40℃ hot water resistance, pot life, chemical resistance and thermal storage performance all met the expectations of the experiment.
A two-component waterborne epoxy coating with excellent comprehensive performance was prepared
.

Concluding remarks

Water-based bisphenol A epoxy emulsion has little effect on water-based two-component epoxy coatings, while water-based amine curing agents have a greater impact on water-based two-component coatings
.
By comparing the water resistance, chemical resistance, salt spray resistance and pot life of paint films with different water-based amine curing agents, CTW-6062 emulsion and Aradur 3986 curing agent were selected to prepare water-based two-component epoxy coatings
.
By comparing different zinc phosphate and modified zinc phosphate anti-rust pigments and fillers, modified phosphate/calcium aluminum polyphosphate hydrated silicate is preferred as the anti-rust pigment and filler
.
The water-based two-component epoxy coating has excellent performance and no shortcomings, and has a wide range of applications
.