Effect of promoter on polyester epoxy powder coating properties.

Pan, Gaoxintian, Jinshunyu
Jiangsu Lanling Chemical Group Co., Ltd.
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studied the effects of different promoter varieties on polyester epoxy powder coating and coating properties, the same promoter varieties on different polyester resin varieties of polyester epoxy powder coating and coating properties, as well as the effect of different catalyst dosage on the same polyester epoxy powder coating and coating properties.
introduction
polyester epoxy powder coatings are composed of polyester resins, epoxy resins, pigments and additives.
In the composition of additives, in addition to the commonly used leveling agents, dispersants, degassing agents, loose agents, etc., in order to meet the reaction activity of powder coatings, that is, to meet the conditions for baking curing and the need to add curing promoter, so that the coating performance to meet the user's requirements .
with the rapid development of China's powder coating and coating industry, in order to meet the needs of various uses, the development of polyester resin and epoxy resin varieties, basically to meet the general needs.
not fully meet the needs of special purposes. In the development of polyester resin varieties for powder coatings, different amounts of curing promoters are added.
However, due to the raw material production units, product prices, resin compatible and other reasons did not find the ideal resin varieties, should consider the activity of familiar resin varieties after adjustment, one of the specific measures is to add promoters to the formula.
In powder coating formulations, the main role of the promoter is to improve the reaction activity of the resin with the curing agent (or resin), to increase the curing reaction rate of the film or shorten the curing reaction time, or to adjust the gel time of the powder coating and the fluidity of the melting level.
There are many kinds of promoters used in polyester epoxy powder coating system, commonly used in metal oxides (zinc oxide), shamamine (mide), tymamine (diazine chloride), gymonium salt ( salt) and so on.
to understand the effects of different promoter varieties on the properties of polyester epoxy powder coatings and coatings made from the same polyester resin;
The effect of the promoter of the same variety on the polyester epoxy powder coating and coating properties of different manufacturers or different models of polyester resin preparation, and the effect of different dosages of
promoter on the performance of powder coating and coating of the same polyester resin, etc., are of great significance for the design of polyester powder coating, the selection of the variety and dosage of the promoter, and the selection of polyester resin. This paper studies this.
Test Part
2.1 Test equipment and instruments
test equipment has laboratory twin screw extruder, shredder, electrostation powder spray equipment;
2.2 Test raw materials
raw materials are: polyester resin-1, polyester resin-2, polyester resin-3, polyester resin-4, epoxy E-12, promoter-12 1 (mide), promoter-2 (mide), promoter-3 ( salt), titanium white powder R940, precipitated sulphate, leveling agent, dispersant, degassing agent and other additives.
2.3 Test Method
Weighed according to the formula of the powder coating, the powder coating is made by →melting extrusion→ through →sieve (180 mesh)" by the formulation method of the general powder coating.
then determines the gel time and melting level flow of the powder coating, and after electrostectrotective spraying on a cold-rolled steel plate of 0.5 mm, the coating performance is detected by curing 15 min at 180 degrees C, 190 degrees C, and 200 degrees C, respectively.
results and discussion
3.1 Effects of different promoters on the performance of the same polyester epoxy powder coating
selection promoter-1, promoter-2, promoter-3, polyester resin-1 and epoxy E-12 preparation polyester epoxy powder coating, respectively. The effects of different promoters on polyester epoxy powder coating and coating properties are found in Table 1.Table
1 test results show that different promoter varieties have different effects on the gel time, melting flatness, gloss and impact strength of the same polyester epoxy powder coating, especially on the impact intensity of the coating film after freezing.
because the structure of different promoters is different, the catalytic structure is also different, so the promotion effect is also different. Therefore, it is necessary to choose the appropriate promoter variety according to the requirements of powder coating and coating performance.
3 powder coatings made with different promoters and powder coatings without promoters (blank) are cured to 15min at 180 degrees C, 190 degrees C and 200 degrees C respectively, comparing the changes in the color difference of the coating film (E), the test results are seen in Table 2.
Table 2 test results show that the color difference between the promoter-3 is minimal, whether it is based on a model of baking curing at 180 degrees C of the booster or a model of baking curing at 180 degrees C without the promoter.
therefore from the film color and heat resistance considerations, the choice of promoter-3 is better.
3.2 Effects of the same promoter on different polyester resin epoxy powder coatings
Select promoter-3, with polyester resin-1, polyester resin-2, polyester resin-3, polyester resin-4 produced by different manufacturers, respectively, the effect of polyester epoxy powder coating on the performance of powder coating and coating film is compared, the test results can be seen in Table 3.
From table 3 test results, it can be known that promoter-3 with different manufacturers of polyester resin preparation polyester epoxy powder coating, the powder coating gel time has an impact, but the impact is not too large, the melting level of the powder coating flow has a greater impact.
this is because polyester resin manufacturers design the activity of polyester resins, taking into account the baking curing conditions of powder coatings set at 180 degrees C, 15 min.
So the activity and gel time of polyester resin between the plants will not be very different, but the raw materials used by the manufacturers are different, the resin structure is different, the melting viscosity is different, so that the melting level of powder coating flow is also larger differences.
With this promoter powder coating, when baking and curing 15 min at different temperatures of 180 degrees C, 190 degrees C and 200 degrees C, the gloss of the coating film varies greatly, but there is no obvious effect on the impact strength of the coating film at room temperature, however, the impact strength under freezing has a certain impact.
The results of this test show that the same promoter has a very different effect on the performance of powder coatings and coatings made from different manufacturers of polyester resins, so it is necessary to go through a comparative test between different polyester resins and promoters to select the best match between polyester resins and promoters.
addition, the same promoter for different manufacturers of polyester resin preparation polyester epoxy powder coating film color difference, to catalyst-free powder coating 180 degrees C, curing 15 min coating as the standard;
different polyester resin powder coatings with promoters-3 are compared with the color difference (E) of the coating film cured at 180 degrees C, 190 degrees C and 200 degrees C respectively, the color difference of polyester resin-4 is the smallest and the best heat resistance of the coating film.
and polyester resin-2 color difference is the largest, coating film heat resistance is the worst, its coating heat resistance is as follows:
polyester resin -4> polyester resin -1> polyester resin-3> polyester resin-2
according to the requirements of the coating heat resistance and color difference, the choice of polyester resin varieties or promoter varieties is also an important problem in the design of powder coatings.
3.3 Effects of different promoter dosages on polyester epoxy powder coatings
Table
4 test results show that with the increase in the amount of promoters in the formulation, the gel time of powder coating is significantly shortened, the melting level fluidity is also smaller tendency, and the frozen impact performance of the coating film also has a certain impact, the dosage at 0.40 g is the best performance.
addition, in a certain amount of range, the promoter on the impact strength of the coating film has no obvious effect on the film gloss effect is not obvious law.
Table 5 test results show that with the increase of the amount of promoters in the formulation, the gel time of powder coating is significantly shortened, and the melting flow is significantly smaller, but there is no obvious difference in the effect of gloss, impact strength and freezing impact strength of the coating film. Table
6 test results show that with the increase in the amount of promoters in the formulation, the gel time of powder coating is significantly shortened, the melting level fluidity is also significantly smaller, and the frozen impact performance of the coating film also has a certain impact, the dosage at 0.40 g is the best performance.
also in a certain amount range, there is no obvious effect on coating film gloss and impact strength.
results of Tables 4 to 6 show that in general in polyester epoxy powder coating system, with the increase of the amount of promoters, the gel time of powder coating is shortened, and the fluidity of melting level is also reduced.
, adding and adjusting the amount of promoter can adjust the baking time and temperature of the powder coating, and is very effective in preventing problems such as film hanging.
the above test, the effect on the gloss and impact strength of the coating film is not obvious, but the effect on the frozen impact strength of the coating film is more obvious.
therefore, according to the user's requirements for powder coating and coating performance, the selection of the best promoter variety and dosage is one of the important contents of powder coating formulation design.
Conclusion
(1) In a polyester epoxy powder coating system made with the same polyester resin and different varieties of promoters, different promoter varieties have an effect on the gel time and melting level fluidity of powder coatings.
the impact strength of the coating film, especially the freezing impact intensity is greater, and the effect on the color difference of the coating film is also significantly different when baking and curing at different temperatures. Therefore, the appropriate promoter variety must be selected.
(2) In the polyester epoxy powder coating system made with the same promoter and polyester resin from different manufacturers, polyester resin varieties have a certain effect on the gel time of powder coating, which has a greater effect on melting level fluidity
Therefore, a suitable resin variety must be selected to match.
(3) In the system of making polyester epoxy powder coating system with the same polyester resin and the same promoter of different dosages, the gel time of powder coating is significantly shortened with the increase of the amount of promoter, and the fluidity of melting level is also reduced.
, although there is no obvious effect on the gloss and impact strength of the coating film, it has a significant effect on the freezing impact strength of the coating film. Therefore, consideration must be given to selecting the appropriate amount of promoter.
In short, in order to obtain a suitable reaction activity, excellent coating mechanical properties (especially under freezing shock strength) and good heat resistance (small color difference) polyester epoxy powder coating, must choose a good promoter variety and dosage, but also choose a good polyester resin varieties (manufacturers) to match.
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