Research on anti-yellowing powder coating of HAA type air conditioner external unit

Abstract:The gradual replacement of TGIC cured powder coatings is the future trend, but due to the yellowing problem caused by structural defects in the HAA system, it can be well suppressed

In this paper, through the effect of antioxidant addition in resin and HAA curing agent systems of different manufacturers on the anti-yellowing properties, the experimental results show that for different systems, the effect is close, the effect is l% is the best, and the effect is insufficient

preface

As a kind of coating with the advantages of solvent-free, pollution-free, recyclable and energy-saving, powder coatings have gradually occupied a certain share of the coating market, especially in the online coatingol.

At present, China is a big country in home appliances and is gradually moving towards a strong country in

Among the many alternative products of TGIC, the largest amount of current use is haa-type curing agent

The purpose of this paper is to improve the experimental study of HAA type powder on the problem of anti-yellowing by adding corresponding additives

1.

Due to the chemical structure of HAA, aliphatic amines are easily oxidized, including light, heat, oxidants, etc.

At present, the antioxidant with better effect on the market is a chain termination antioxidant, which can interrupt the growth of the chain by reacting with free radicals, thereby reducing the occurrence
of oxidation.

Select a certain blocked phenol high molecular weight type antioxidant produced in China, and the hindered phenol antioxidant has the advantages of high efficiency and non-toxicity, non-coloring, non-pollution, small volatility, etc.
, and is one
of the most excellent antioxidant varieties recognized internationally.

These antioxidants can be used in
polyethylene, polypropylene, ABS resins, nylon, polyurethanes, polystyrene, rubber, adhesives, coatings and petroleum products.

It is a very effective processing stabilizer that can well inhibit the high-temperature discoloration phenomenon produced by polymers
.

The chemical structure is as follows: tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] pentaerythritol ester

The main performance indicators are shown in Table 1:

2.
Test equipment

SLJ-32 twin screw extruder, mixing equipment, ACM milling system, small electrostatic spraying equipment, electrothermal drying box, SP60 colorimeter
.

3.
Test process

Since the color of the air conditioner is mainly gray, this test takes ordinary HAA type gray powder coating as the main formula, baking 15min@180 °C and 30min@230 °C, respectively, contrasting color difference, △L, △a, △b, △E, comparing the anti-yellowing effect
of antioxidants on this powder coating.

In order to reflect the effect of antioxidants on anti-yellowing, a set of powder coatings of the same color of ordinary TGIC curing type 93:7 was added at the same time in the experiment, and the difference
between HAA curing type and TGIC curing type was compared.

Formulation results are shown in Table 2
.

From the test results, it can be seen that:

1.
Adding a certain amount of this antioxidant can indeed play a significant anti-yellowing effect;

2, the amount of addition is different, the effect is not the same, the optimal amount is 1%, add 1% of the amount, you can reduce the yellow variable value by half;

3.
The addition of l% antioxidant can make the anti-yellow effect of HAA type close to
the effect of ordinary HAA type resin.

This shows that antioxidants effectively inhibit the oxidation process of HAA, but too much may cause the opposite effect and increase the possibility
of yellowing.

Due to the different manufacturers of HAA resin, there may be differences in raw materials and processes, considering the differences that may be caused by different manufacturers of resins, the test replaces two other HAA-type curing resins of different manufacturers, one is the same acid value resin (acid value: 28-32mg KOH/g) and the other is a resin with a lower acid value (acid number: 19-24mg KOH/g).

At the same time, we selected a haa curing agent from another manufacturer and conducted the same test to verify the effect of antioxidants in different types of HAA resins and different HAA curing agents, comparing the yellowing results
.
Also baked 180 ° C@15min and 230 ° C@3omin respectively, contrasting color difference, △L, △a, △b, △E, the results are as follows: Table 3, Table 4, Table 5:

The resin 2 formulation results are as follows:

The test results of HAA resin 2 and HAA curing agent 2 are as follows:

The resin 3 formulation results are as follows:

The results of the above tests can be seen:

(1) The addition of different resins and different HAA, antioxidants can play an anti-yellowing effect;

(2) Different manufacturers, resins of different acid numbers, HAA curing agents of different manufacturers, antioxidants can all work;

(3) In the HAA resin of different acid numbers, different manufacturers, and the HAA curing agent of different manufacturers, the effect of adding antioxidants is close, and the effect of 1% is the best, and the effect of a small amount or excess is insufficient
.

This antioxidant can play the same effect
for different manufacturers and HAA types with different acid values.
The yellowing cause of HAA is mainly the structural cause of HAA curing agent, different resins may have different yellowing results, but the effect is consistent, and the structure of HAA curing agent of different manufacturers is the same
.

The experimental results can be seen that for the HAA curing agent, the addition of about 1% of this antioxidant can improve the yellowing performance
of haa curing powder coatings.

4.
Conclusion

TGIC curing powder coatings are gradually replaced by the future trend, from the experiment can be seen, HAA curing agent itself structural defects caused by the yellowing problem, by adding a suitable amount of antioxidants, can be well suppressed
.

In terms of temperature resistance and yellowing resistance, HAA type can already meet the requirements of air conditioning external powder, with the improvement of other performance, the future will gradually replace the use of TGIC powder coating in the field of air conditioning external unit, play a more environmentally friendly and energy-saving role
.