Application and research of fluorocarbon surfactants in water-based wood coatings

, Shenzhen Changhui New Materials Technology Co., Ltd. Chen YaozuAbstract: In the wave of environmental protection, the paint industry is also looking for its own direction, water-based is an important way. However, "know easy to do", because of the water-based paint luster, adhesion, water resistance and smooth wetting and solvent-based coatings compared to a certain gap, so in industrial paint and other special coatings, solvent-based coatings still occupy the vast majority of the market.but the pressure to protect the environment and make efficient use of petroleum resources make hydration an irreversible trend in the coatings industry. To solve the technical problem is the key to the water-based coating industry. This paper focuses on the application of fluorocarbon surfactants in water-based coatings, especially water-based wood coatings, in the hope that the promotion of water-based wood coatings can be helpful.fluorocarbon surfactant introduction first introduce the concept of surface stress. Inside the substance, each molecule is symmetrically and in equilibrium by the forces of the molecules around it. On the other hand, molecules on the surface are subjected to a symmetrical force, on the one hand by the inner molecule, on the other hand, by other material molecules in contact with the surface of the substance. The two forces are unbalanced, and the result of interaction is a surface stress at the interface between the two substances, the direction of which is related to the surface of the substance. To make an image metaphor, like a balloon, filled with water, that layer of cortical film is equivalent to surface stress, it has the tendency to reduce the surface area of water, into a spherical. If the effects of Earth's gravity are ignored, all water droplets should be spherical.and fluorocarbon surfactants are such a class of substances, its molecules have both polar groups (hydrophobic structure) and non-polar groups (hydrophobic structure), so that it is active in the interface of two-phase matter, can reduce surface stress, thereby changing the interface properties of the substance, just like needles on the surface of the membrane, so that the skin shrinkage capacity is reduced. Depending on the hydrophobic structure of surfactants, they can be divided into hydrocarbon, silicone and fluorocarbon surfactants.fluorocarbon surfactant refers to a class of surfactants in which hydrogen in the hydrocarbon chain of a common surfactant is replaced in whole or in part by fluorine atoms. C-F chain chemical stability and thermal stability are very high, in addition, the radius of fluorine atoms than hydrogen atoms, can completely cover the carbon atoms, Van der Worrest is small, that is, the intermodal force is small, so fluorocarbon surfactants have many ordinary hydrocarbon surfactants do not have characteristics:first: very strong surf activity. As long as the low concentration in water can strongly reduce the surface pressure of water, improve the moisture and permeability of the water-like system. Because fluorine atoms are very difficult to polarize, the fluorocarbon chain polarity is smaller than the hydrocarbon chain. It is precisely because of this low polarity that the fluorocarbon chain is water-repulsive and oil-repulsive, and therefore has high surf activity in organic solvents.second: excellent stability. Because the key of fluorocarbon bonds can be very large, not easy to be destroyed, so it has excellent chemical stability and thermal stability, can be used in hydrocarbon active agents can not be stable in the presence of the occasion, such as high temperature, strong acid, strong alkali solution.third: high production costs. Fluorine is the most electro-negative element, so the equipment requirements are very high, coupled with the synthesis of fluorocarbon surfactant process is also relatively complex, resulting in the current world's fluorocarbon surfactant production capacity is not large, high cost, market price is not cheap.like ordinary surfactants, the classification of fluorocarbon surfactants can be divided into two categories of non-ion and ion types according to their polar group structure. Non-ionized hydrophobic base is generally polyoxyethylene ether products, soluble in water, organic solvents (including acid, alkali media), and other types of active agents are better compatible. Because it is not ionized in water, the pH is stable, but it should be avoided in strong oxidizing medium, so as not to cause the ether key to break. Non-ionized fluorocarbon surfactants are also the most widely used in water-based coatings. Ion-type fluorocarbon surfactants can be divided into anion-type, cation-type and two-sex ion-type fluorocarbon surfactants according to the differences of hydro-hydro-based.effect of fluorocarbon surfactants What are the magical effects of fluorocarbon surfactants in water-based coatings?wetting due to the water-like system's own surface pressure is large, 72 Dan or so. For some low surface energy surface or surface oil, ordinary paint is difficult to wet and spread, often caused by the consequences of shrinking edges, shrink holes, craters. At this time, fluorocarbon surfactants can be added to improve the wetting of the coating to the substrate.。 The relationship between the addition of BNK-4021 fluorocarbon surfactants and the surface stress of water. First the surface strength of the water is: 72 dan/cm, while the coating system added BNK-4021 fluorocarbon surfactant to reduce the surface stress to 17. Of course, fluorocarbon surfactants are suitable for all water-based coatings and water-based ink systems.second, leveling is also due to surface stress reasons, water-like paint, especially water-like baking paint, especially easy to produce orange skin fish eyes, can be improved by adding fluorocarbon surfactants. For some water-like paints with low viscosity requirements, fluorocarbon surfactants can also be added to increase leveling without increasing viscosity.third, water resistance compared to solvent-based coatings, water-based coatings water resistance is always not ideal. If fluorocarbon surfactants are added, so that the surface of the water-based coating film is covered with a layer of hydrophobic fluorocarbon molecules, water molecules can not penetrate, thus improving water resistance.fourth, solvent resistance Due to the characteristics of fluorocarbon-based hydrophobic oil, fluorocarbon-based molecular film formed on the surface of the coating, but also solvent-resistant oil-resistant effect.the fifth, improve the resistance to stains General stains can be divided into hydro-water-based stains and oil-resistant stains. Generally oil-free paint film is not waterproof stains, and hydrophobic paint film has non-oil-resistant stains, only added fluorocarbon surfactant paint film can be waterproof oily various stains., high temperature activity Some water-like baking paint baking temperature reached 150 degrees to 200 degrees, and fluorocarbon surfactants remain stable at such temperatures and play a role.Seventh, improve the anti-adhesion water system, especially the phenylpropyl emulsion system is generally less anti-adhesive, if the addition of fluorocarbon surfactants, the formation of fluorocarbon film on the surface of the paint film, to improve the anti-adhesion help.8th, adhesion Because the wet film of water-based coating can wet the substrate surface very well, so increase the adhesion of the coating, and does not affect the re-painting, of course, the effect of this on adhesion is not decisive. Mainly depends on the performance of the resin.the ninth, gloss coating leveling improved, gloss also has a certain rise.considerations for the use of fluorocarbon surfactantsSince fluorocarbon surfactants have so many advantages, what are the things to be aware of in their application? Or take BNK-4021 fluorocarbon surfactants as an example:first, the price of added fluorocarbon surfactants is higher, if the market price of 100% effective content of perfluorocarbon surfactants is more than one thousand. However, the amount of fluorocarbon surfactants added is also very small, compared with one percent of hydrocarbons and four to six thousandths of silicones, the amount of fluorocarbon surfactants added is only five to one thousandth. In this way, the formula will increase the cost by seven cents to a piece of about four cents, slightly higher than the use of hydrocarbon surfactants or silicone surfactants. But it has improved the product grade. Of course, if the use of the United States Milliken: BNK-4021 fluorocarbon surface agent, not only will not rise, but more reasonable costs than silicon products.Second, the use of method BNK-4021 fluorocarbon surfactants, do not need any processing, in the coating, directly added to the coating system by drip-added way, compared to silicone products, fluorocarbon surfactants will not stabilize the bubble.third, environmental issues when it comes to fluorine-related products, one might think of a statement made by the U.S. Environmental Protection Agency (EPA) about perfluoroic acid (PFOA) some time ago. Perfluoroxinate (PFOA) may be potentially toxic to the human body and the natural environment. Some manufacturers have developed alternative products. Currently, Milliken's products are fluorocarbon surfactants containing only four atom-based perfluorocarbons, manufactured and sold in accordance with U.S. Environmental Protection Agency (EPA) testing guidelines.that engineers who have used silicone surfactants for the fourth and most important recoil problems tend to worry about recoated issues. BNK-4021 in any formulation system, regardless of any film-forming conditions, will not occur between the second or repeated coating of the bottom bite and poor adhesion and other phenomena. Of course, if you apply different coatings, the problem is not certain.fifth, compatible problem Due to the stability of the fluorocarbon surfactant itself, especially the non-ion type of fluorocarbon surfactant, almost does not react with any strong acids and alkalis. It works well in a variety of resin systems, including acrylic, polyurethane, ammonia and epoxy systems. It also has synergies with thickeners, dispersants and deboists in formulations.application of fluorocarbon surfactants in a variety of water-based coatings introduction Water-based wood coatings are in addition to the inner and outer wall latex paint, the most market potential of water-based paint products. Water-based wood coatings are used in doors, windows, furniture, floors and other places, usually for its hardness, fullness, water and oil resistance and stain resistance put forward higher requirements. For plumpness, hardness and drying speed these properties are related to the choice of resin and the combination of solvents, and have little to do with the use of surfactants. However, for water resistance, solvent resistance and leveling, the use of fluorocarbon surfactants can improve the performance of water-based wood coating paint to a considerable extent.-based metal coatings is another important application of water-based coatings. At present, many places in foreign countries where mild anti-corrosion requirements have been used water-based metal anti-rust coating. This aspect of the country is just beginning to take off. However, due to the lack of water resistance of the coating film, it is often used indoors. If fluorocarbon surfactants are applied in water-based metal rust-proof coatings, the water resistance of the coating film can be improved to a certain degree. For water-based metal paint, the application of fluorocarbon surfactants can help improve the surface effect of the paint film, because at high temperatures, traditional surfactants do not work very well, while fluorocarbon surfactants can help wet the leveling, prevent the occurrence of shrink edges, shrink holes, craters and orange peels. For some metal surfaces with lower surfaces, such as aluminum alloy surfaces, water-based coatings with fluorocarbon surfactants can help wet the flow level and increase adhesion.and exterior wall latex paint is the most widely used water-based coating. A variety of new features of wall coatings have been developed, such as negative ion wall coatings, fire protection coatings, elastic cracking coatings, and a variety of one-in-one products, basically by adding functional fillers, or using one or more additives, or using resins with certain excellent properties. The application of fluorocarbon surfactants in the inner and outer wall latex paints can also enable the coating to have certain special functions. In the inner wall coating, the addition of fluorocarbon surfactant can play a waterproof and oil-resistant, easy to clean stains. The addition of fluorocarbon surfactants to the exterior paint can improve the water resistance, acid rain resistance and soil resistance of the paint film.water-based automotive coatings are highly technical coatings, the current application is still limited to the automotive coating, that is, the color of the coating, in primers and mask glossy paint has not been applied. Due to the very high requirements of automotive paint on the surface effect, not only requires excellent wetting leveling, but also requires color paste or metal pigments can be arranged and oriented, fluorocarbon surfactants can also play a role in this regard, some large foreign automotive original paint manufacturers in water-oriented automotive paint have added fluorocarbon surfactants.Water-based wood coatings using fluorocarbon surfactant introduction the previous mention of fluorocarbon surfactants in a variety of water-based coatings can play a role, but the current practical application is not many, for two reasons, first, fluorocarbon surfactant The price of agents is higher, some low-grade water-based paint can not use this product, of course, there are some technical personnel do not know much about the reasons for such products; the water-based wood coatings are different. On the one hand, the mainstream wood lacquer products on the market are solvent-based polyurethane system, the price of products is higher, leaving room for the development of water-based coatings. On the other hand, the use of traditional surfactants does not solve the problem due to the very low surface pressure of the wood surface. Therefore, the application of fluorocarbon surfactants in water-based wood coatings is the most obvious and meaningful. from a technical point of view, there are three difficulties in the development of water-based wood coatings. first, wetting the leveling problem. Plastics are made up of non-polar hydrocarbon unsaturated low molecules, with low surface pressure and difficulty wetting plastic surfaces with surfaceactants such as hydrocarbons and silicones. Thus, the phenomenon of shrinking edges or orange peels occurs. This makes it difficult for water-like paint to moisten and spread, thus forming a shrink hole. We have helped a customer with a comparative test, as follows: Table 1 Control table for the application of different surfactant effects in water-based wood coatings: Surfactants Additions Surface Effects Surface Stress (Dain/cm) HC surfactant 1% more shrink holes, crater 30 or so BNK-LK600 leveling agent (silicon) 0.5%