Commonly used additives in improving the properties of powder coatings include anti caking agents (loosening agents or loosening agents), boosting agents, and accelerators. Anti caking agent (loosening agent or loosening agent) is an additive added to improve the dry powder fluidity of powder coatings, prevent powder coatings from caking, and improve the storage stability of powder coatings. Some powder coatings, especially due to the low glass transition temperature of resins and curing agents, have a low glass transition temperature when prepared. When the ambient temperature is high, the dry powder fluidity of the powder coating is poor, and it is even easy to agglomerate. In order to prevent agglomeration of powder coatings, when selecting resins, curing agents, and additives, high glass transition temperature varieties should be selected. In the process of manufacturing powder coatings, anti agglomeration agents (loosening agents or loosening agents) should be added internally or externally to solve the problem. These additives are special functional additives that only exist in powder coatings. The commonly used internally added loosening agent in powder coatings is TL102 loosening agent from Guangzhou Tianlong Trading, with a dosage of 1% of the formula amount; Hubei Hongtu Chemical's Hot445 loosening agent is used at a dosage of 0.5% to 0.6% of the formula amount. In solvent based coatings, fumed silica is used as a matting agent and as an anti caking and loosening agent in powder coatings. It is added to powder coatings by an additional dry mixing method, with an addition amount of 0.1% to 0.5% of the total powder coating amount. Booster is an additive added to improve the electrostatic performance of powder coatings during electrostatic powder coating. Due to changes in the composition of powder coatings, their electrostatic properties also change. Therefore, in order to improve the powder loading rate of powder coatings, it is necessary to add an electric booster. In addition, the charging method of electrostatic powder coatings using electrostatic spray guns is different, and the electrostatic effect of powder coatings is different. For friction charged powder coatings using polyester resin, an electric booster must be added to achieve better charging effect in the friction spray gun system. Promoters for powder coatings are additives added to reduce the curing reaction temperature or accelerate the curing reaction speed of powder coatings, and are also commonly used in various powder coatings.
In addition to the aforementioned additives, other additives need to be added as needed to improve the appearance and performance of powder coating films. The additives added to improve the appearance of the coating include defoamers, edge coverage modifiers (anti flow and sagging agents), dispersants, etc; The additives added to improve certain properties of the coating include anti scratch agents (anti scratch agents), anti yellowing agents, slippery agents (slippery agents), ultraviolet light absorbers, anti-static agents, hardeners, plasticizers, tougheners, antibacterial agents, flame retardants, etc. Defoamers are additives that must be added when electrostatic powder coating is applied to materials such as cast iron, cast aluminum, and hot-dip galvanized steel, in order to prevent the gas in the pinholes and sand holes of the workpiece from escaping in a timely manner, and to prevent the formation of particles (particles) or volcanic pits during the solidification of powder coatings into films. The defoaming principle of this defoamer is significantly different from that of solvent based and water-based coatings. The working principle of other additives is basically the same as that of solvent based and water-based coatings, and will not be introduced here.
Powder coating, as a decorative material, is widely used on the surface of workpieces. The main products that achieve this special texture effect are texture additives, such as floating agents, sanding agents, wrinkle agents, etc. However, in actual production applications, there are more or less deficiencies in the auxiliary products of different manufacturers.
1. Sanding agent
Sanding agents mostly belong to substances such as fluorinated resins or waxes, mainly in the form of cotton wool or powder, and are hygroscopic and easy to agglomerate. The texture performance obtained by different manufacturers and varieties varies, and the gloss, texture, etc. can also be adjusted by adding or adding bentonite.
Due to the uneven dispersion of the sanding agent in the powder coating due to its cotton like clusters, customers may misunderstand the excessive dosage and even suspect the purity of the sanding agent. At the same time, uneven dispersion can also lead to inconsistent gloss in various parts of the coating film or between batches. Most customers mix and stir with fillers before adding them to the powder.
The addition of bentonite can adjust the texture and luster of the coating film, but excessive dosage can lead to rough coating film. At the same time, there is a problem of difficult extrusion in the extrusion process, and the resulting sheet material is also too hard to crush. Bentonite is obtained through special treatment, and its own odor and other defects cause smoke and odor when added to powder coatings.
2. Floating agent
Floating agents themselves are a type of surface active agent, commonly used are acrylic compounds with similar composition to leveling agents. They are dispersed in different resins and are affected by the glass transition temperature of the resin. In summer, when the temperature is too high, floating agents have the disadvantage of agglomeration. At the same time, when added to powder coatings, there will be no appearance of wrinkles when left for a long time.
Due to differences in the melting level and fluidity of the powder coating base powder made from different manufacturers' resins, the three-dimensional texture of the floating agent after external mixing is inconsistent or does not produce patterns. Customers need to choose a suitable floating agent based on the resin of their respective manufacturers.
In terms of formula design for texture powder, consideration should be given to the generation of shrinkage defects in the coating film. Even after mixing with floating agents, shrinkage defects in the coating film cannot be avoided, and other manufacturers of floating agents are also the same. Customers should adjust the addition of formula components based on actual situations. It is still worth noting that there are still white spots in the addition of floating agents to dark powder coatings.
3. Sponge agent
Sponge agent is a special texture additive of metal complexes, which has a harmful effect on the eyes. When using it, attention should be paid to occupational health protection.
Adding this type of additive to powder coatings may result in difficulty or lack of grain formation. The key factor is that the resin powder of powder coatings is higher, generally over 60%. Secondly, high-temperature baking and thick coating are required. Usually, this type of powder coating is used for decorative effects, and the coating film is not weather resistant and has defects such as exposing the bottom.
4. Moire agent and dot dispersant
There are few varieties of artistic powder coatings, which are difficult to process, have poor product repeatability, and have a beautiful coating appearance. Most of these auxiliary products are mailed by customers as samples, but many cannot produce corresponding results. To achieve the desired effect, mature and stable processing techniques are required.
5. Wrinkling agent
Wrinkle agent is an auxiliary agent that achieves wrinkle effect through the principle of uneven surface tension of the coating film, and its dosage and composition have a direct impact on the size of wrinkles in the coating film. Similar to sanding agents, this type of product should consider its dispersion in powder coatings to adjust its dosage reasonably.
During use, customers should consider the disadvantage of exposing the bottom after addition, as well as the impact of the melting and flowability of the resin. There may be inconsistencies in the grain of different resins after addition. Customers should choose the appropriate variety based on the different resins they use.
Additives are also an important component in powder coating formulations. Although their dosage is relatively small compared to resins, curing agents, pigments, and fillers, accounting for only a few thousandths to a few percent of the total formula, their effect on the performance of coatings and film cannot be ignored. In some cases, additives play a decisive role. For example, in the formulation of thermosetting powder coatings that require a flat and smooth appearance of the coating film, without additives such as leveling agents, it is impossible to obtain a coating film without shrinkage holes, etc. There are differences in the types of additives required for different powder coating varieties, but in terms of basic requirements, the following conditions should be met:
1. The amount of additives used in the formula is very small. In order to achieve uniform dispersion of additives, it is required to be easily dispersed during the manufacturing of powder coatings.
2. From the perspective of color matching for powder coatings, it is best for additives to be colorless or light colored to avoid coloring the powder coating.
3. The chemical stability of additives is good. In the manufacturing, storage, and use of powder coatings, except for special needs (such as the chemical reaction of accelerators during the baking and curing process), they generally do not react with resins, curing agents, pigments, and fillers, and are not affected by air, moisture, temperature, and environmental conditions.
4. From the perspective of human health and environmental protection, it is best for additives to be non-toxic or low toxic.
5. Considering the storage stability of powder coatings and the convenience of adding additives during the manufacturing process, it is best to use additives in the form of solid powders and have good compatibility with resins and curing agents.
6. The commonly used additives in powder coatings include leveling agents, brighteners, degassing agents, defoamers, dispersants, antistatic agents, friction charged additives, accelerators, anti caking agents (loosening or loosening agents), powder loading rate modifiers, hardness modifiers, anti scratch agents, anti sagging agents, plasticizers, antioxidants, ultraviolet light absorbers, photosensitizers, antibacterial agents, wrinkle agents, orange grain agents, moire agents, hammer grain agents, sand grain agents The most commonly used additives include leveling agents, brighteners, degassing agents, defoamers, etc.
1. Antioxidants (or heat stabilizers) are used to prevent yellowing of coatings during over baking. In general, they are a mixture of steric hindrance inhibitory antioxidants and hydrolysis resistant organic phosphates. Powder coatings can undergo aging, yellowing, and other phenomena after being baked at high temperatures or exposed to sunlight, which seriously affect the appearance and performance of products. To prevent or reduce this trend, adding antioxidants or heat stabilizers is usually used to achieve this. Although there are many factors that affect film aging, such as the quality and type of resins, pigments, additives, coating formulation design, production process, temperature, atmosphere, humidity, and other natural factors, the application of appropriate additives has indeed reduced the occurrence of this trend. Antioxidants are substances that inhibit or delay the oxidative degradation of polymers. There are many varieties of antioxidants with varying effects, which can be divided into two categories based on their mechanisms: one is called chain breaking antioxidants, which react with free radicals produced in polymers to interrupt chain growth, also known as main antioxidants; Another type is called preventive antioxidants, which can inhibit or slow down the generation of free radicals during the initiation process, also known as auxiliary antioxidants. The main antioxidants include hindered phenols, secondary aromatic amines, and auxiliary antioxidants include phosphite esters, dithiocarbamate metal salts, etc.
2. The film formation of thermosetting powder coatings with curing agents and curing accelerators is achieved by adding a certain chemical substance and causing it to undergo cross-linking reaction with the base resin under certain conditions to form an insoluble and non melting three-dimensional network structure of polymers. This crosslinking reaction is called curing reaction, where the chemical substance that initiates the curing reaction is called a curing agent, and the chemical substance that can cause the curing reaction temperature to decrease or speed up is called a curing promoter. As a polymer material, the performance of thermosetting powder coating mainly depends on the structure and aggregation state of the base resin used. The curing agent and curing promoter play a decisive role in their aggregation state. Therefore, the variety, dosage, and crosslinking reaction conditions of curing agents and curing accelerators are all key factors affecting the various properties of powder coatings.
3. Antistatic agents and charge control agents can reduce the surface resistivity of powder coatings and coatings by adding them. Although the results obtained are similar, the uses of these two additives are different. Antistatic agents improve the ability of coatings to transmit static electricity to the ground, while charge control agents improve the powder loading rate and the ability of powders to penetrate Faraday cages. By using a corona discharge device, particles can be charged through discharge adsorption. However, this charging efficiency is very low, as only 0.15% of the air ions generated by corona are adsorbed onto the powder particles. The remaining air ions are transferred to the workpiece and accumulate and precipitate on the powder layer. The lower the resistivity of powder particles, the higher their charging efficiency. Therefore, antistatic agents can improve the charging efficiency of powder particles. This can reduce the spraying time and reduce the working voltage.
With the advancement of current coating technology, UV curable coatings are gradually replacing traditional solvent based coatings and becoming a focus of industry attention. Matting powder meets the needs of market development, conforms to the trend of industry development, and adheres to the purpose of focusing on each sub field of coatings. By innovating scientific and technological innovation, improving research and development skills, and improving production processes, we have launched another sub variety - UV curing special matting powder, which is suitable for various types of UV curing coatings. It is particularly ideal for 100% solid UV coating systems and 100% solid UV full matte roller coating systems.
With the advancement of current coating technology, UV curable coatings are gradually replacing traditional solvent based coatings and becoming a focus of industry attention. Matting powder meets the needs of market development, conforms to the trend of industry development, and adheres to the purpose of focusing on each sub field of coatings. By innovating scientific and technological innovation, improving research and development skills, and improving production processes, we have launched another sub variety - UV curing special matting powder, which is suitable for various types of UV curing coatings. It is particularly ideal for 100% solid UV coating systems and 100% solid UV full matte roller coating systems.
After special surface treatment, the extinction powder can scatter incident light in a specific way, causing light to scatter through the extinction powder particles on the surface of the paint film, ultimately achieving the extinction effect. The product has the characteristics of high extinction efficiency, high transparency, low oil absorption, superior feeling, and scratch resistance.
The new extinction powder adopts breakthrough technology to address the problem of difficulty in extinction of 100% UV coatings, and by reducing oil absorption, high addition levels become a reality. In addition, UV ink requires maintaining the smoothness and scratch resistance of the paint film even when the coating is very thin, and achieving the best effect of the paint film through special surface treatment techniques.
1. Low oil absorption: After special treatment, the oil absorption is low and the thixotropy is small. When the addition amount is large, it will not have a serious thickening and thixotropy effect on the system. It is suitable for 100% solid UV coating systems and 100% solid UV full matte roller coating systems. In their systems, the foam is unstable and easier to defoaming.
2. Excellent extinction efficiency: The extinction efficiency is much higher than that of similar products with the same particle size and porosity, and excellent extinction effect can be achieved with only a small amount of addition, thereby reducing costs.
3. Good transparency of the paint film: Special surface treatment is adopted, which can scatter incident light in a specific way, causing light to scatter through the extinction powder particles on the surface of the paint film, ultimately achieving extinction effect. This can achieve excellent transparency of the paint film, greatly superior to other similar products.
4. Excellent scratch resistance and hand feel: it provides a good smoothness and excellent wear resistance and scratch resistance to the paint film, without affecting other mechanical properties of the film.
5. Outstanding physical and chemical stability and anti settling properties: This series of products are extremely easy to disperse and can be evenly and directly dispersed in low viscosity coatings without affecting other application performance of the coatings. Due to the use of organic surface treatment, the anti settling performance is excellent, and there will be no agglomeration or sedimentation.
6. Excellent compatibility: After repeated laboratory tests, this series of extinction powders have good compatibility with most UV resins, without precipitation or other issues, making them more convenient to use in UV systems and achieving better comprehensive performance.
After customer testing, the same formula has a better extinction effect than imported products.
1. Compatibility between powder coating additives and resins
This is the first thing to pay attention to when selecting additives. Powder coating additives must remain stable in powder coatings for a long time in order to achieve their expected effectiveness. So the commonly used additives should have compatibility with epoxy, polyester, acrylic and other resins. So usually, to compare the compatibility between powder coating additives and resins, the method used is based on their structural similarity. For example, leveling agents are the main additives in the production of powder coatings, which can reduce the surface tension difference of the coating film, play a role in homogenizing the coating film and eliminating shrinkage holes, and achieve a smooth and glossy surface after curing. When using, additives with carriers such as E-12 carriers cannot be used in formulas with pure polyester systems. Additionally, the applicable systems for leveling produced by each company are different, which requires powder manufacturers to find suitable resins to match, and the same applies to brighteners. As usual, the B68 type chemical extinction agent containing cyclic amidines and polybasic acid salts is only suitable for systems with epoxy. If used in other systems, it not only loses its expected effect, but also has a negative impact on the coating film.
2. Adaptability of powder coating additives to production processes
When designing the formula of certain powder coating additives, it should be considered that due to the harsh production process conditions, such as high temperature, low temperature, high-speed shear, etc., which may cause the decomposition, volatilization, and failure of the powder coating additives, resulting in formula failure. For example, some pattern powder coating additives cannot be extruded together with the base material by the extruder, but are later added to the finished powder, only in this way can their desired pattern be displayed. Because during the extrusion melting process, the pattern additives have already been pre reacted, resulting in no patterns or different pattern sizes, tactile differences, and three-dimensional effects during film formation.
In the process of combining two or more additives with the base material, in order to fully utilize the effectiveness of the additives, they must be fully dispersed in the powder coating base material and can be combined with the base material in different feeding orders.
Experienced technical engineers know that the sequence and process conditions of mixing or adding various powder coating additives with substrates into the finished product process are very important, as they directly affect the mixing effect and film performance.
3. The multiplicity of powder coating additives in powder coatings
Some powder coating additives not only play a main role, but also have dual or multiple effects. Therefore, when designing the formula, we must consider comprehensively, such as adjusting the dosage in the formula or simplifying the formula. For example, zinc oxide is a common chemical that can replace a portion of titanium dioxide as a white pigment; At the same time, it has a certain degree of conductivity and is suitable for applications that require anti-static or conductive properties; It also has the function of shielding ultraviolet rays, especially for 240-380/ μ The UV light within the m range has good protective ability; Of course, it also has anti mold, bactericidal effects, and improves the coating performance of resin containing carboxyl groups. It can be seen that choosing an effective additive requires a thorough understanding of its various functions.
4. Fully utilize the mutual effects between powder coating additives
The synergistic effect of powder coating additives refers to the synergistic effect of two or more additives when used in appropriate combination. Of course, the opposite of synergy is adversarial effect. For example, when carbon black is combined with thiophenol antioxidants in pure polyester outdoor powder coatings, it has excellent synergistic antioxidant effect. However, when used together with steric hindered amine or phenolic antioxidants, the original stabilizing effect of the coating is weakened due to the antagonistic effect.
5. The effect of powder coating additives on the performance of powder coatings
We know that some powder coating additives, while exerting their normal functions, sometimes have to have adverse effects on certain properties of powder coatings. This is closely related to the amount of additives used. At present, there is a low-temperature curing agent on the market that can cure powder coatings into films within 120 ℃/30 minutes, which is of course what we need. Because such low curing conditions can bring huge economic benefits and provide application possibilities for materials that cannot be baked at high temperatures, greatly expanding the application field of powder coatings. But according to our experiments, adding this low-temperature curing agent will have a significant impact on the adhesion of the coating. These are all things that we should fully understand when selecting powder coating additives when designing formulas.
6. Restrictions on the Use of Powder Coatings on Powder Coating Additives
The application of powder coating additives is often constrained by the ultimate use of powder coating films. Different types of powder coatings have requirements for the color, odor, pollution resistance, durability, electrical properties, heat resistance, and cold resistance of powder coating additives.
7. Price of powder coating additives
Those familiar with powder coatings know that the proportion of powder coating additives in the powder coating formulation system is generally small, but the price is very expensive. Therefore, sometimes the price is also an important factor in measuring its use. Usually, we can choose several products of the same type from different suppliers for comparative testing, and choose low-priced products with the same effect. Many domestic manufacturers produce powder coating additives that are generally comparable to similar products produced abroad.