Exploration of influencing factors of polyester-TGIC type wrinkle pattern powder coating

Abstract: In this paper, the effects of
polyester resin, filler, additives, spraying and baking processes in polyester-TGIC wrinkle pattern powder coating when using cellulose acetate butyrate as a wrinkle agent were explored through comparative experiments.

introduction

Wrinkle pattern powder coating is a kind of fine art powder coating with a line pattern on the surface by adding pigment to wrinkle powder, which has strong decorative properties, can cover up the defects of the substrate itself, and is not easy to appear shrinkage;

Its surface leveling does not have too high requirements, and is widely used in doors and windows, steel and wood furniture, sewing machines, instruments, small electromechanical shells and other fields
.

Most of the wrinkle pattern powder coating is made of polyester-epoxy system, anti-corrosion performance is better, aging performance is poor, the use of QUVB accelerated aging box for aging test, 50 hours of loss of light, pulverization phenomenon, can only be used for indoor paint online coatingol.
com
.

The use of polyester-TGIC type wrinkle pattern powder for 250-300 hours will appear more serious loss of light and chalking phenomenon, can be used outdoors
.

This paper mainly discusses the effects
of polyester resin type, type of filler, ratio of polyester resin to pigment filler, amount of curing accelerator, amount of wrinkle agent and other factors on the powder and coating film in polyester-TGIC system.

1.
Experimental part

1.
1 Test raw materials and basic formulas

The raw materials and basic formulations used are shown in Table 1 below:

1.
2 Test equipment

Test equipment: electronic balance, extruder, mill, electrostatic spray gun, oven, QUVB accelerated aging box, coating film thickness meter
.

1.
3 Reaction principle

The reaction principle of wrinkle pattern powder coating is that when the powder coating is grilled and cured, the surface tension of the melt leveling coating is large, while the surface tension of the wrinkle agent is small
.

Due to the poor compatibility between two substances with different surface tension, the side with small surface tension cannot completely reduce the surface tension of the party with large surface tension, and the tension of the two different substances coexists with each other, so that a bumpy coating appearance
is formed.

1.
4 Test Methods

Weigh the raw materials according to the formula components, mix evenly and be evenly extruded by melting and mixing by the twin screw extruder, press the tablet to cool, crush the mill after crushing, pass through the 180 mesh standard sieve, obtain a powder coating with uniform particle size, and dry mix
the prepared powder coating with the pigment.

Using electrostatic spraying, voltage control 70-90kV, air pressure control at 0.
5×105-1.
5×105Pa, curing conditions of 200°C/1Omin
.
The coating and powder are then
tested for performance.

2.
Results and discussion

2.
1 Effect of different polyester resin varieties on wrinkle pattern powder coating

Resin is an important component of powder coating film-forming substances, and some of its technical indicators directly affect the performance of
the final coating.
In this test, five different polyester resins in Table 2 were selected for comparison, and their powder coating formulations and powder and coating properties were shown in Table 3
.

It can be seen from the results of Table 3 that in Formula 1, although the viscosity of polyester resin A is large, its acid value is low, the gelatinization time is long, the coating cannot be completely cured under the baking condition of 200 °C/10min, the coating texture is large and flat, and the lines are relatively blurred
.

In Formula 4, the viscosity of polyester resin D is low, but its reactivity is much higher than that of A, so its coating can also form a texture, and the texture formed by polyester resin A is more three-dimensional
.

In the polyester-TGIC type wrinkle pattern powder system, the acid value and viscosity of the polyester resin have a great influence
on the coating texture.

Under normal circumstances, when the viscosity of polyester resin is similar, the higher its acid value, the higher the reactivity, the shorter the gelatinization time, the smaller the texture formed, and the stronger
the three-dimensional sense.

The lower the acid number, the lower the reactivity, the longer the gelling time, the larger the texture formed, and the weaker
the three-dimensional sense.

2.
2 Effect of different filler varieties on wrinkle pattern powder coating

In wrinkle pattern powder coating, different fillers also have a greater impact
on the pattern texture due to their different oil absorption.

In this test, four different fillers were selected for comparison: barite powder, precipitated barium sulfate, light calcium carbonate and mica powder, and the filler varieties and technical indicators are shown in Table 4, and the powder coating formula and powder and coating properties are shown in Table 5
.

From the results of Table 5, it can be seen that the melt viscosity of fillers with large oil absorption is also large, and the leveling is not easy to unfold during baking, and the texture formed is also small
.
Fillers with small oil absorption also have smaller melt viscosity, easy leveling when baking, and larger
textures.

The oil absorption of barite powder, precipitated barium sulfate, light calcium carbonate and mica powder gradually increased, and the surface texture gradually became smaller, but it could still form a better texture, so the influence of filler varieties on wrinkle pattern powder coating was less
than that of several other factors.

2.
3 Effect of different resin and pigment filler ratio on wrinkle pattern powder coating

In wrinkle pattern powder coating, the ratio of resin to pigment filler has a greater influence
on the pattern.
The three ratios of resin and pigment filler were compared, and the powder coating formula and powder and coating properties were shown in Table 6
.

Through the change of the amount of pigment filler in Table 6 (increase or decrease of 10% dosage), it can be seen that when the amount of pigment filler increases, its texture is relatively small, because the amount of pigment filler increases, its melt viscosity increases, and leveling during baking is not easy to unfold, so the texture obtained is relatively small
.

When the amount of pigment filler is reduced, the texture is relatively large, because the amount of pigment filler is reduced, the melt viscosity is reduced, and the surface of the coating is easier to level during the baking process, and the texture formed is relatively large
.

However, when the amount of pigment filler is too small, its melt viscosity is low, if the viscosity of polyester resin is also low, it is easy to appear sagging phenomenon, at this time it is necessary to change the resin variety or add curing accelerator to accelerate the reaction rate, so as to improve its sagging phenomenon
.

As shown in Figure 1, Formula 10, Formula 2, Formula 11, the amount of pigment filler decreases sequentially, and the texture formed by the coating increases
sequentially.

2.
4 Effect of different dosage of additives on wrinkle pattern powder coating

In wrinkle pattern powders, wrinkle agents have a crucial effect on
the texture of their coatings.
If no wrinkle agent is added, the coating is difficult to form a texture, and for the amount of wrinkle agent, we generally control it at 0.
1%-0.
3%.

As the amount increases, the texture of the coating decreases until it becomes flat
.
Curing accelerators can change the reaction rate of powder coatings, thus affecting the coating texture
.

Using different wrinkle agent dosage and different curing accelerator dosage to compare, the powder coating formula and powder and coating performance are shown in Table 7
.

From the results of Table 7, it can be seen that when the amount of wrinkle agent is too small, as shown in Recipe 12 in Figure 2, the three-dimensional texture becomes stronger, but the coating appears to be exposed, and the intermingling of lines is blurred
.

With the increase of the amount of wrinkle agent, as shown in Formula 2 and Formula 13 in Figure 2, its texture tends to be normal, and the coating gradually changes from a larger pattern and a strong three-dimensional sense to a smaller pattern, a weak three-dimensional sense, and the lines are gradually clear
.

The main function of the curing accelerator is to accelerate the reaction rate, the dosage increases, the gelling time of the corresponding powder coating is also shortened, and the viscosity of the system is closely related
to its reaction rate and gelling time.

When heating and baking, the molten viscosity decreases with the extension of heating time, at this time lines begin to form, when the coating begins to crosslink and cure, the melt viscosity begins to rise, the paint flow slows down, the crosslinking curing reaction reaches a certain level, the paint stops flowing, and the texture is fixed
.

As shown in Recipe 14 and Recipe 15 of FIG.
3, as the amount of curing accelerator increases, the surface texture gradually becomes smaller and the lines become blurred until it is shown
in Recipe 16 of FIG.
3.

The amount of curing accelerator is too large, the reaction rate is too fast, the viscosity of the system rises rapidly, the powder coating has been cured before leveling is completed, and its coating cannot form wrinkles and lines
.

2.
5 Effect of spraying and baking process on wrinkle pattern powder coating

2.
5.
1 Effect of spraying process on wrinkle pattern powder coating

The spraying process has a great influence
on the coating film texture formed by the wrinkle pattern powder.
Spraying is too thick, which is easy to produce the disadvantages of sagging, poor mechanical properties and poor adhesion, and at the same time uses more powder, and the cost increases
.

The texture of the coating film will be larger when spraying thickly, so you should try to spray thin points when spraying the wrinkle pattern powder of small patterns, and you can spray thick points
when spraying large patterns.

Generally, the thickness of the wrinkle pattern powder film is 80-120μm, so that the surface of the coating film is not easy to show the bottom: as shown in Figure 4 below, the comparison of the same wrinkle pattern powder in thin spraying and normal spraying, the left is thin spray, and its film thickness is 50-80μm
.

Its coating grain is small, the lines are blurred, the bottom is exposed, the right side is normal spraying, the film thickness is 80-120μm, its surface pattern is normal, the lines are clear
.

2.
5.
2 Effect of baking process on wrinkle pattern powder coating

The baking process is mainly the temperature and heating rate
of the oven.
When the oven temperature is low, the wrinkle pattern powder has a longer time to fully level, and the lines formed are larger and flatter
.

When the oven temperature is high, the curing time of the powder becomes shorter, and the resulting lines become smaller and more three-dimensional
.
Figure 5 shows the comparison of the same wrinkle pattern powder under different baking conditions
.

On the left, the oven temperature is heated from room temperature to 200 °C to end baking, the texture formed is larger and flatter, and the pigment on the grain will also be dispersed, unable to form a clear line like the right one;

The one on the right is the texture formed by direct baking at an oven temperature of 200 °C, which has a strong three-dimensional sense and clear texture lines
.

3.
Conclusion

3.
1 In polyester-TGIC type wrinkle pattern powder coating, the polyester resin type has a greater influence on the texture, and the texture formed by the resin with higher acid value and faster reaction rate is smaller, while the texture formed by the resin with larger viscosity is stronger
.

3.
2 In polyester-TGIC type wrinkle pattern powder coating, the type of filler has no greater impact on the texture than polyester resin, but there is still a certain impact, and the larger the oil absorption of the filler, the texture is generally small and three-dimensional
.

3.
3 In polyester-TGIC type wrinkle pattern powder coating, the amount of wrinkle agent has a crucial impact on the texture, generally with the increase of the amount, its texture becomes smaller and the three-dimensional sense becomes weaker
.
The right amount of curing accelerator can speed up the reaction rate and make the texture more three-dimensional
.

3.
4 In polyester-TGIC type wrinkle pattern powder coating, spraying and baking also have a greater impact on the texture of the coating, generally the thickness of the large pattern film is controlled at 80-120μm, and the small pattern can be
thinner.
When baking, the oven temperature can be raised first, and then the sprayed workpiece can be put in, which can make the coating texture effect change less
.

3.
5 There are many factors affecting the texture size of polyester-TGIC type wrinkle pattern powder, and any change of factors will have a significant impact
on its appearance.
In actual production, it needs to be adjusted according to the situation to achieve the desired texture effect
.