Application of fluorocarbon surfactants in waterborne plastic coatings

The lower the surface tension of the substrate, the more valuable the use of fluorocarbon surfactants. Due to the extremely low surface tension of plastics, the selection of fluorocarbon surfactants is almost essential in the system of water-based plastic coatings. In terms of the market, the current domestic production of water-based plastic coatings companies are still less, most of them are still in the formulation of the research and development stage, but the prospects of water-based plastic coatings are very broad.

introduction

In the tide of environmental protection, waterborne coating is an important trend and way. However, due to the gloss, adhesion, water resistance and leveling wettability of water-based coatings compared with solvent-based coatings there is a certain gap, so in industrial coatings and other special coatings, solvent-based coatings still occupy the vast majority of the market.

However, with the continuous improvement of the awareness of environmental protection and effective use of oil resources, water has become an irreversible trend in the paint industry, and solving technical problems is the key to the waterborne paint industry. This paper focuses on the application of fluorocarbon surfactants in water-based coatings, especially water-based plastic coatings, hoping to be helpful to the promotion of water-based plastic coatings.

1. Characteristics of fluorocarbon surfactants

Fluorocarbon surfactants have three characteristics that ordinary hydrocarbon surfactants do not have: ① strong surface activity. As long as the concentration in water is very low, it can effectively reduce the surface tension of water, improve the wettability and permeability of the water-based system, and the fluorocarbon chain has both hydrophobicity and oleophobic. ② Excellent stability. ③ High production cost.

In water-based coatings, fluorocarbon surfactants can improve the wettability, leveling property and water resistance of the coating to the substrate, improve the stain resistance, adhesion resistance, adhesion and gloss, and have high temperature activity stability (150 ~ 200℃).

The use of 2 fluorocarbon surfactants in waterborne plastic coatings

Fluorocarbon surfactants can play a certain role in a variety of water-based coatings, but the current practical application is not many, there are two reasons: first, the price of fluorocarbon surfactants is high, some low-grade water-based coatings do not use this product; Second, because the surface tension difference between the coating and the substrate is not very large when used on the surface of wood or metal, the use of general hydrocarbons or silicone surfactants can solve the problem, and there is no need to use fluorocarbon surfactants with higher prices. However, the situation is different for water-based plastic coatings. On the one hand, the current mainstream plastic coating products on the market are the use of solvent-based acrylic acid system, the price of the product is higher, to the development of water-based plastic coatings to create space. On the other hand, due to the extremely low surface tension of the plastic surface, the use of traditional surfactants cannot solve the problem. Therefore, the application of fluorocarbon surfactants in water-based plastic coatings has the most obvious effect and is also the most significant.

From a technical point of view, the development of water-based plastic coatings has three difficulties, including:

(1) Wetting levelling problem. Plastic is made of non-polar hydrocarbon unsaturated low molecular polymerization, surface tension is very low, the use of general hydrocarbon or silicone surfactants is difficult to wet the plastic surface, resulting in shrinkage or orange peel phenomenon. Moreover, there are often release agents on the plastic surface, which makes it difficult for water-based coatings to wet and spread, resulting in the formation of shrinkage holes.

(2) Adhesion problems. The most conventional plastic substrates, including PE, PP, ABS, PC and so on. From the current technical development of water-based resins, the adhesion of water-based plastic coatings on ABS and PC is no longer a problem. The use of fluorocarbon surfactants further enhances adhesion and scratch resistance. For PP and PE, only by adding fluorocarbon surfactants can not solve the problem. The solution is often to use a special adhesion accelerator for the plastic substrate to treat it first, and then apply water-based plastic paint.

(3) The problem of aluminum silver paste. At present, the largest variety of plastic coatings is silver powder paint. For solvent-based coatings, the technology of silver powder paint is very mature; For water-based coatings, the price of silver paste and its orientation during the coating drying process are really big problems. Domestic water-based aluminum silver paste for building water-based metal coatings can also be used, if the use of plastic surface is not good, aluminum silver paste for plastic surface is basically monopolized by several foreign companies. On the other hand, even good aluminum silver paste can not play a role if the orientation is not good. Due to the special surface tension effect of fluorocarbon surfactants, they can continue to play a role in the drying process of water-based coatings and help the orientation of silver paste.

In addition to the three aspects mentioned above, fluorocarbon surfactants can also help improve the water and solvent resistance of water-based plastic coatings. Due to the reduction of the surface friction coefficient of the film, the scratch resistance of the film can also be increased. For some water-based plastic coatings that need to be baked, they can also play a good role under high temperature conditions. Due to the low surface tension of plastics, fluorocarbon surfactants generally need to be added to one-thousandth of the solid content to be able to play a good role.

3 Precautions for the use of fluorocarbon surfactants

Take 3MFluoradFC-4430 as an example:

(1) Amount of addition. The price of fluorocarbon surfactants is high, if it is 100% effective content of perfluorocarbon surfactants market prices are more than 1000 yuan /kg. However, the addition amount of fluorocarbon surfactant is also very small, compared with the addition amount of hydrocarbons 1% and organosilicon 4‰ ~ 6‰, the addition amount of fluorocarbon surfactant is only 0.5‰ ~ 1‰. In this way, the cost of about 0.7 to 1.4 yuan will be increased in the formula, which is slightly higher than the use of hydrocarbon surfactants or organosilicon surfactants, but it improves the product grade.

(2) Usage method. For fluorocarbon surfactants with 100% solid content, they are generally waxy yellow solids at low temperatures and need to be heated and melted before use. Before use, it is best to use a polar alcohol ether solvent to prepare a 9.1% solution for accurate addition. It is only necessary to stir gently when preparing the diluted solution to avoid bubbles. Additions are best added to the system during the paint blending phase.

(3) Environmental protection issues. Speaking of fluorine-related products, some time ago, the U.S. Environmental Protection Agency (EPA) issued a statement about perfluorooctanoate amines (PFOA). Perfluorooctanoate amine (PFOA) can be potentially toxic to humans and the natural environment, and some manufacturers have developed alternative products. In May 2000, the 3M plant voluntarily stopped production of PFOS. Currently, 3M's products contain only four carbon atoms of fluorocarbon based perfluorinated butyl fluorocarbon surfactants, which are manufactured and marketed in accordance with the United States Environmental Protection Agency (EPA) testing guidelines.

(4) Repainting problem. 3MFluoradFC-4430 does not bite or adhere poorly between second or multiple coatings in any formulation system, regardless of the film forming conditions. Of course, if different coatings are used, the problem is a different matter.

(5) Compatibility issues. Due to the stability of fluorocarbon surfactants themselves, especially non-ionic fluorocarbon surfactants, almost no reaction with any strong acids and bases. In a variety of resin systems, including acrylic, polyurethane, amino and epoxy systems, can play a good role. Moreover, it has synergistic effect on thickener, dispersant and defoamer in the formula.

4 Conclusion

The lower the surface tension of the substrate, the more valuable the use of fluorocarbon surfactants. Due to the extremely low surface tension of plastics, the selection of fluorocarbon surfactants is almost essential in the system of water-based plastic coatings. In terms of the market, the current domestic production of water-based plastic coatings companies are still less, most of them are still in the formulation of the research and development stage, but the prospects of water-based plastic coatings are very broad. South Korea's Samsung has reportedly decided to use water-based plastic paint on all Samsung mobile phones by the end of 2008, and we believe other mobile phone manufacturers will follow suit. For some export products, due to the implementation of more stringent environmental standards in Europe and the United States, more and more export products will use water-based plastic coatings.

Finally, it should be noted that although fluorocarbon surfactants can help solve many problems in the application of water-based plastic coatings, they are not panacea. The performance of film forming substances is the most fundamental factor to determine the performance of water-based plastic coatings, the promotion of water-based plastic coatings first depends on the development of resin technology, the correct formula and production process and construction methods can improve the performance of water-based plastic coatings, and the use of fluorocarbon surfactants can help the promotion of water-based plastic coatings.