Innovation and Application of Outdoor Wrinkle Powder Coatings

Abstract: Although hydroxypolyester/tetramethoxymethylglycuril (TMMGU) type wrinkle powder coating is not a new product, its high-priced raw materials limit its wide application, and the research and development work of this system powder coating is also very small
.

Based on a large amount of experimental research and practical application experience, the author detailed the performance and application of this system powder coating.

Wrinkle powder coatings have various names in the industry, such as cotton paint, water grain powder coatings, etc.
The surface of the coating has a special texture effect and excellent decorative properties .
Online coatingol.
com
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Therefore, wrinkle powder coatings are widely used in the coating of indoor and outdoor products such as hardware, furniture, electrical appliances, and anti-theft doors
.

Wrinkle powder coatings are divided into epoxy/dicyandiamide type and hydroxy polyester/tetramethoxymethyl glycoluril type, which are respectively used in the coating of indoor decorative products and outdoor durable decorative products
.

The raw materials for preparing epoxy/dicyandiamide-type wrinkle powder coatings are abundant in the domestic market, and the raw materials are easy to purchase and low in price.
Therefore, such powder coatings have been widely used and promoted in the domestic market once they are launched
.

However, hydroxypolyester/tetramethoxymethylglycuril (TMMGU) type wrinkle powder coatings need to be imported due to key raw materials, and there are only a handful of domestic suppliers

With the development of domestic powder coating raw material technology, this passive deadlock has been broken, the price of key raw materials will be reduced by more than 50%, and the purchase of raw materials will become simple, easy and relaxed! It will inevitably bring a storm to the promotion and application of outdoor wrinkle powder coatings in the domestic market!

2.

Durable wrinkle powder coating has excellent outdoor weather resistance and anti-aging degradation, and can be used for coating indoor and outdoor products
.

The current method of formulating outdoor durable wrinkle powder coatings is to use low hydroxyl value polyester resin and TMMGU resin to form a coating with wrinkle effect under the catalysis of WL series amine blocked sulfonic acid

(1) All adopt a main resin design formula

It needs to be pointed out that the hydroxyl polyester resin suitable for P/TMMGU type wrinkle powder coating has the best hydroxyl value of 30±5mgKOH/g
.

The increase in the hydroxyl value of the resin is not conducive to the formation of wrinkles on the coating surface
.
Hydroxy polyester resin with a hydroxyl value of 40±5mgKOH/g can be used, but try not to use it
.

Polyester resin with a hydroxyl value of 50±5mgKOH/g is mainly used for polyurethane powder coatings, not for P/TMMGU powder coatings
.

(2) Both adopt a main crosslinking agent that has a slower crosslinking reaction speed with the main resin
.
The curing agent of indoor wrinkle powder coatings is ordinary dicyandiamide, and it cannot be used to replace dicyandiamide or accelerate dicyandiamide, otherwise the surface effect of wrinkles cannot be formed
.

The curing agent of outdoor wrinkle powder coatings is TMMGU resin, which is the only type of amino resin used in powder coatings
.
TMMGU resin was pioneered by Cytec Corporation in the United States, and its domestic price has always been relatively high
.

Now Shanxi Taiyuan Keyuanda Company has made TMMGU resin domestically, and after multiple batches of stability tests, it can fully meet the use of P/TMMGU type wrinkle powder coatings.
The price of the resin is much lower than that of imported similar products
.

(3) Reaction catalysts are used in the formulations to promote the formation of wrinkles on the coating surface
.
The catalyst used in indoor wrinkle powder coatings is aluminum acetylacetonate, which has a strong catalytic effect on the ring-opening and curing of epoxy groups
.

Nanhai Chemical’s XG605-1A, Wuhan Yanhuang and Dongguan Zhongtian’s MCD, and Jietongda’s SA208 are all such products
.

The catalyst used in outdoor wrinkle powder coatings is an amine-blocked sulfonic acid catalyst.
This type of catalyst is very expensive, such as ACTIRON®32-18A from France's SYNTHRON company (effective active ingredients about 50%), and Cytec's ADDITOL®920 with resin as a carrier.
(5% of effective active ingredients)
.

The WL series catalysts (effective active ingredients 65%±2%) pioneered by the author in China are in the process of applying for national patents
.
The performance of the WL series catalyst is equivalent to that of imported similar catalysts, with a high content of effective active ingredients and a small amount.
The price is basically half of the imported products, which is beneficial to reduce the cost of the formulation
.

(4) Reaction rate regulators are used in the formulations
.
The use of reaction rate modifiers in wrinkle powder coatings can improve the fluctuations in the physical and mechanical properties of the coating caused by the increase or decrease in the amount of catalyst, and help improve the gloss of the coating
.

The indoor wrinkle powder coating uses a 6/4 type polyester resin with a medium acid value (52~58mgKOH/g) and a medium-speed reaction.
The polyester was originally designed for epoxy/polyester hybrid powder coatings
.

Outdoor wrinkle powder coatings use closed or internally closed isocyanate resin as the reaction rate regulator
.
This type of isocyanate resin is dominated by products from Degussa and Bayer, and has a higher price
.

Domestic Hangzhou Jintian Chemical Co.
, Ltd.
has developed a sealed isocyanate resin—TS280, which has been introduced to the market
.
The product has a relatively low price and is suitable for the development of outdoor wrinkle powder coating products for domestic enterprises
.

(5) Wrinkle powder coatings are selective to fillers
.
In the formulation design of wrinkle powder coatings, different types or levels of fillers will more or less affect the gloss and texture of the coating
.

When designing indoor and outdoor wrinkle powder coatings, product designers must recognize the influence of fillers on the gloss and texture of the coating.
The author believes that ultra-fine barium sulfate is the best choice.
Too coarse) and slightly alkaline calcium carbonate (including heavy and light types) are used as fillers for this type of powder coating
.

(6) The curing conditions are similar
.
The curing conditions of thermosetting powder coatings depend on slow-reacting components.
Both epoxy-based and hydroxy-polyester-based wrinkle powder coatings have slow-reacting cross-linking components, so the curing conditions are 15min@200℃ or higher
.

3.
Extended development and innovation of outdoor wrinkle powder coatings

Outdoor wrinkle powder coatings (P/TMMGU type) are widely used in foreign-funded enterprises.
Due to the monopoly of technology, raw materials and prices, domestic companies have not been able to widely and effectively develop the development, application and innovation of P/TMMGU type wrinkle powder coatings
.

At present, the domestic raw materials used in the development of outdoor wrinkle powder coatings have been basically solved, the supply of goods is sufficient, and the price is low, which is conducive to the development of such products
.
As P/TMMGU type wrinkle products are no longer new products, this article will not discuss the product design of P/TMMGU type wrinkle powder coatings too much
.

3.
1 Reticulated powder coating

Reticulated powder coating is a type of powder coating with reticulated texture appearance developed on the basis of wrinkle powder coating.
The reticulated texture is very clear (Figure 1 and Figure 2).
The outdoor reticulated powder coating formula is shown in Table 2
.

Formula 2 shows that the anilox powder coating is obtained by adding an anilox agent (usually using an anilox agent as an anilox agent) on the basis of the formula of the wrinkle powder coating
.

Under normal circumstances, the film-forming substance content in the anilox powder coating formulation is higher than that in the wrinkle powder coating formulation, and with the increase of the film-forming substance content, the coating texture has a higher definition and a larger pattern
.

3.
2 Moire powder coating

Moire powder coatings are also based on the principle of incompatibility.
There are many ways to formulate moire powder coatings:

(1) Epoxy type moire powder coating, prepared by adding moire agent on the basis of epoxy type moire powder;

(2) Epoxy/polyester type moire powder coating, made of special 6/4 type polyester resin, with proper amount of aluminum acetylacetonate (wrinkle catalyst) and external moire agent;

(3) Low acid value carboxyl polyester resin and matting type GMA acrylic resin are prepared according to a specific ratio, and external moire agent is added;

④The low hydroxyl value hydroxy polyester resin and TMMGU are catalyzed by WL amine blocked sulfonic acid, and the moire agent is added to form a very stable moire effect coating.
The appearance of the coating is shown in Figures 3 to 4, and the typical formula is shown in Table 3.

.

P/TMMGU type moire powder coating is also obtained by adding moire agent on the basis of wrinkle powder coating.
The difference from the texture formulation is that the external mixed additive used is moire agent instead of texture agent
.

Compared with wrinkle and anilox powder coating formulations, the film-forming substance content of moire powder coating formulations is significantly higher than that of wrinkle and anilox powder formulations.
Generally, the higher the content of the film-forming substance, the larger the particle size of the moire agent and the smaller the amount used, the formation The more obvious the moiré effect, the larger the pattern
.

3.
3 Peacock pattern powder coating

P/TMMGU type wrinkle powder coatings and epoxy/DICY type wrinkle powder coatings are different due to different film-forming materials and different curing mechanisms, resulting in P/TMMGU type wrinkle powders being more distinctive than epoxy/DICY type wrinkle powders and better product decoration
.

If you carefully observe the appearance of the two kinds of wrinkle coatings, you can find the subtle differences in the textures of the two, that is, the textures are different
.
The more intuitive difference is that the P/TMMGU type powder is catalyzed by WL amine blocked sulfonic acid, and externally added dot pollen can form the appearance of peacock pattern (dot flower effect), as shown in Figures 5-6
.

And this special peacock pattern effect cannot be achieved by other types of powder coatings
.
The formula of peacock pattern powder coating is shown in Table 4
.

Peacock pattern powder coating is a variant or extension of dot flower powder coating, which is formed by mixing one type of wrinkle base powder with one, two or more types of dot pollen
.
Epoxy-type wrinkle powder coatings cannot achieve the appearance of peacock lines, and dot pollen cannot exhibit color effects in epoxy-type wrinkle powder coatings
.

In P/TMMGU wrinkle powder coatings, the color of dot pollen is similar to or better than that of hammer powder or other ordinary flat powder coatings, so it can form a peacock pattern appearance
.

Affected by the pattern of the base powder, the effect of P/TMMGU peacock pattern is obviously different from that of ordinary dot flower powder, and it is more like the color effect of peacock feathers
.

4.
Application and research of epoxy polymer in outdoor reticulated and moire powder coatings

Blocked isocyanates are widely used in P/TMMGU type wrinkle, net, moire and peacock powder coatings, which can not only adjust the reaction speed, but also effectively reduce the occurrence of "nodal" defects
.

P/TMMGU powder coating is catalyzed by amine-blocked sulfonic acid, and blocked isocyanate is not the only coating surface regulator
.

Epoxy polymer has dual adjustment effects on pattern and gloss for P/TMMGU type texture and moire powder coatings, such as TGIC, PT910, PT912, GMA acrylic resin, etc.
Bisphenol A epoxy resin is the most typical representative
.

The test formula is shown in Table 5, and the coating film performance test results are shown in Table 6.
The coating film baking condition during the test is 15min@200℃
.

The test results in Table 6 show that the addition of different amounts of epoxy resin to the formulation of the P/TMMGU type wrinkle powder coating will significantly affect the surface luster, texture and mechanical properties of the coating
.

In particular, when the epoxy resin is added at 4%, the coating has a regular "crocodile skin" appearance effect, which is what we usually call the "moire pattern" effect, but at this time, no "moire pattern agent" is added to the formula.
"
.

The results in Table 6 also show that when the amount of epoxy resin added in the formula exceeds 6%, the wrinkle effect of the coating film basically disappears, and the mechanical properties are significantly reduced
.
Therefore, it can be preliminarily confirmed that the amount of epoxy resin added in the P/TMMGU type wrinkle powder coating is below 6%
.

Amine blocked sulfonic acid is a special catalyst
.
During the baking and curing process of P/TMMGU powder coating, it will be decomposed into two compounds, organic acid and amine.
Amine volatile matter will volatilize with the heating process.
Organic acid will effectively catalyze the reaction between TMMGU resin and hydroxyl
.

In fact, the amine cannot be completely volatilized during the powder baking process, and the remaining amine will block the "acid-catalyzed TMMGU-hydroxyl reaction"
.

Since the amine produced by the catalyst decomposition has a tertiary amine structure, which has a catalytic effect on the opening of the epoxy group, the addition of the epoxy resin consumes the residual amine and also consumes a small amount of carboxyl groups on the hydroxyl polyester
.

With the sharp decrease in the number of amine and polyester carboxyl groups, the catalytic effect of organic acid on the reaction process reaches the limit, which is beneficial to the reduction of the gloss of the coating film
.
However, with the increase of epoxy resin, the excessive epoxy resin is not conducive to the catalytic effect, which will cause the gloss to rise again
.

Because the reaction mechanism of "hydroxypolyester + TMMGU + WL catalyst" is very complicated, the addition of epoxy resin will produce a certain interference effect, which affects the appearance of the final coating to a certain extent, so no tortoise is added to the powder coating formulation.
The texture agent also produces a moiré effect
.

This feature of epoxy polymer makes it easy to design moire powder coatings.
If you use anilox or moire agent again, different coating effects will appear
.

5.
Application and research of outdoor wrinkle powder coating

Compared with epoxy type wrinkle powder coatings, a significant feature of P/TMMGU type wrinkle powder coatings is that it has excellent weather resistance and can be used for the coating of interior and outdoor metal products.
This is the universal application of P/TMMGU type wrinkle powder coatings.
Reason
.

Another use of P/TMMGU type wrinkle powder coating can not be ignored, that is, it can be cured in a direct-fired oven, and the gloss and texture of the coating film change slightly
.

When the direct-fired baking furnace is used for curing, the fuel used in the direct-fired baking furnace is coal, oil, natural gas, gas, etc.
, and inorganic oxides such as C, S, P, and N will be produced during the combustion process.
The cross-linked and cured coating film produces certain catalytic effects and side effects
.

If this kind of inorganic oxide enters the furnace, it will undoubtedly affect the film formation process of the coating melt and solidification, especially the cross-linking reaction process, and change the physical and chemical properties of the coating film and the appearance of the coating
.

Such as adhesion, gloss, color, and the appearance of the texture of the coating film, which will eventually lead to peeling, poor interlayer adhesion, large-area loss of gloss, yellowing and discoloration, and texture changes
.

Whether it is P/TMMGU type wrinkle powder coating for outdoor use or epoxy/DICY type wrinkle powder coating for indoor use, the appearance of wrinkles is formed under the action of a specific catalyst
.

Practical application shows that due to the direct-fired baking furnace in some coating plants, when epoxy/DICY type wrinkle powder is used for coating, the coating film is severely lost and the texture is severely reduced, resulting in serious consequences of product coating failure !

Powder manufacturers and coating companies are at a loss
.
The author discovered in the process of on-site technical service to customers that the use of P/TMMGU type wrinkle powder coating can solve the problems of serious loss of gloss and serious change in texture of epoxy/DICY type wrinkle powder coating during baking
.

Therefore, when the customer cannot change the oven conditions, it is an inevitable choice to use P/TMMGU type wrinkle powder coating for painting!

6.
Summary

P/TMMGU type powder coating is a unique type of powder coating.
Many of its properties and uses have yet to be developed.
I believe that more related products will come out in the industry in the near future
.

For the Chinese people who love colorful and colorful life, the love for P/TMMGU powder coatings is born spontaneously
.
It is believed that with the substantial reduction in the price of related raw materials, this type of powder coating will have a broad development space in China
.