Coating process: water-based wood coating, full sealing varnish, coloring coating process

Core tip: in the wood painting, the fully closed varnish coloring coating is the most common painting style Because it can not only reveal the wood grain through the bottom coloring, but also reflect the sense of hierarchy through the color difference between the bottom color and the face color At the same time of wood protection, it gives the wood a great sense of beauty and achieves an excellent decorative effect Therefore, in the whole field of wood painting occupies a large proportion With the development of solvent based wood coatings, the coating process has been very mature However, in the development process of waterborne wood coatings, this process is difficult to promote This is due to water-based Wood Coatings Shenyang steel structure fireproof coating construction expert punde Building Fire Engineering Co., Ltd Recommended introduction: since its establishment, Shenyang punde Construction Fire Engineering Co., Ltd has cultivated a group of professional construction teams with excellent equipment, rich experience and serious responsibility with advanced and scientific management methods and strict engineering quality assurance and after-sales service system It has undertaken a number of fire system installation projects, which has been praised by customers Every idea and special requirement of you will be fully considered by us and fully realized in the construction technology, which will become the cornerstone of our successful long-term development We are looking forward to your invitation, to provide you with quality services and high-quality technical support! All construction coatings have passed ISO9001 Paint Home News: in the wood painting, the fully enclosed varnish painting is the most common painting style Because it can not only reveal the wood grain through the bottom coloring, but also reflect the sense of hierarchy through the color difference between the bottom color and the face color At the same time of wood protection, it gives the wood a great sense of beauty and achieves an excellent decorative effect Therefore, in the whole field of wood painting occupies a large proportion With the development of solvent based wood coatings, the coating process has been very mature However, in the development process of waterborne wood coatings, this process is difficult to promote This is because the water-based Wood Coatings take water as the solvent and have high surface tension When the traditional coloring method (adding the colorant to the top coat) is adopted, it is often because the top coat is not well wetted on the base material, resulting in local non coloring or uneven coloring, which is difficult to achieve the ideal decorative effect, Thus, the application of water-based wood coatings is limited to solid color coating (pigment colorant coloring) and some varnish natural color coating, which restricts the rapid development of water-based wood coatings The problem of water-based Wood Coatings sealing varnish coloring is a problem that has to be solved in the development process of water-based wood coatings Based on this problem, according to the performance characteristics of water-based wood coatings, through experiments and production practice, this paper discusses the problem of fully closed (semi closed) varnish coloring coating of water-based wood coatings 1 In the process of bottom coloring and the application of bottom colorant in the closed coating of wood, the coating process of general solvent based wood coatings is generally as follows: base material - bottom coloring - primer - surface finishing - finish In the specific construction process, different coloring methods and colorants will be selected according to the substrate or coating effect For example, in case of dark color effect (such as coffee color), Grice color can be used for bottom color According to different base materials or color effect, choose whether to make head sealing before Grice wiping; in case of light color effect (such as cherry color), the bottom color can be directly modified with color essence and diluent, and then make head primer If there is a big difference in the color of the base material, green water (diluent and color essence) shall be used to repair the color of the base material before repairing, so that the color of the base material is basically the same In the above coating process, the water-based wood coatings are the same as the solvent based wood coatings The difference is that when using the solvent based wood coatings for light color coating, the first degree of sealing shall be done before the color repair, so as to make the color of the colored base material uniform and fresh When using the water-based wood coatings, the first degree of sealing bottom shall be done, The bottom color will be difficult to wet the substrate because of the high tension of water; if the head is not closed, the bottom color will be uneven and less refreshing because of the different absorption degree of capillary to the color agent In the actual production, it is generally not required to seal the head If the requirement for the freshness of the background color is high, the head sealing bottom can be done first, and then some alcohol solvents (such as ethanol) can be used to dilute the water-based color essence for the bottom color When this kind of coloring method is adopted, the first degree primer shall be sprayed after coloring to fix the color The first degree primer shall not be too thick and wet during construction, otherwise the colorant will penetrate into the primer and cause blooming After the first primer is completely dry, the primer can be directly sprayed, generally 2-3 coats of primer are required 2 The commonly used method and agent of surface color modification 2.1 water color modification water color modification refers to the method of adding water-based color essence into water or some alcohol solvents for color modification When diluting with water, because the primer is not easy to be wetted by water, it is easy to get hairy During operation, it must be sprayed very dry Once it is wet, there will be hairy spots, which is difficult to operate When alcohol ether solvent is used for dilution, the coloring is easy, but the color control is difficult because there is no film-forming substance in the water In the open or semi open coloring [1], the author mentioned the method of using special color repair water, but this method is not suitable for the large-area operation of water-based wood coatings This is because in the large-area operation of the full closed coating, in order to ensure the flatness and uniformity of the board surface, the top coat generally needs to be sprayed thicker, which will make the lower colorant dissolve and penetrate into the top coat Due to the different absorption degree of the color agent after sanding the primer and the uneven spraying during construction, when the color agent is dissolved into the top coat, it will be different in depth and light, resulting in blooming In case of small area operation, the thickness and drying speed of top coat can be controlled, so small area operation will not cause problems generally, and large area operation shall be used with caution 2.2 varnish repair method varnish repair method refers to the method of adding colorant to clear primer or clear finish paint for color repair, generally spraying This method is often used in opaque color or translucent color (coloring with opaque or translucent pigment), but it is very difficult in transparent color (generally using water-based color essence), especially in the painting of office furniture with high color consistency requirements, this method can hardly meet the requirements of mass production The main problems are: (1) shrink edge or black edge This phenomenon occurs when the color is repaired to be wet The phenomenon is that there is no color around the board or the color is too thick The former is due to the high surface tension of water, while the latter is due to the strong fluidity of finish paint, which flows to the edge and forms a black edge under the action of spray gun air flow or gravity In fact, these two problems exist when the water-based varnish is not colored, but when the varnish is not colored, because the film is transparent after drying, it is not obvious (2) Orange peel, pitting or white spots Due to the above problems in varnish color repair, the construction personnel had to spray the top coat dry by adjusting the oil and gas volume of the spray gun during color repair When the colored varnish reaches the surface of the base material, its viscosity is very high or even it has become particles If the film cannot be leveled, orange peel or pockmark will appear, and the surface effect is very poor If the surface of the base material is not smooth enough or the base material of the varnish is not well wetted, the pits will show white spots due to the lack of color (3) Color difference control is still difficult When using varnish for color modification, due to the film-forming substance in the colorant, the color development of the colorant is enhanced and the color control is convenient However, the appearance of the wet film of water-based wood paint is mostly translucent or opaque During the field construction, the construction personnel repair the color according to the color of the color plate If the wet film is opaque, the difficulty of color control is greatly increased In varnish, In order to enhance the burnability, reduce the gloss or improve the film performance, some powder (such as polish agent or extinction powder) or wax slurry will be added, no matter the primer or the finish, which makes the wet film transparency of water-based Wood Coatings worse and increases the difficulty of color control Therefore, this method has many disadvantages 2.3 special repair paint repair method 2.3.1 design principle and characteristics of special repair paint there are some disadvantages in the surface repair construction of all closed coloring coating of water-based wood coatings In order to understand the problem of surface repair, it is necessary to study a product specially used for surface repair Special finishing varnish is specially designed to solve the problem of surface finishing It is a kind of product after adding water-based dye on the basis of common varnish, removing some functional materials (such as polishing agent, extinction powder, etc.) from the primer or finishing coat, and enhancing the operability and convenience during the paint cleaning and finishing construction Through repeated tests and comparison, and through production application, the author thinks that the production problems can be solved better by using special finishing varnish than by using finishing water This is because in the process of color repair control, there are more film-forming substances in the varnish, which can make the color appear well in the process of operation, and fix the color, avoiding the occurrence of color biting in the next process (i.e the color permeates into the top coat unevenly during the construction of the top coat) In addition, compared with repair water and common varnish, this kind of repair paint has the following advantages: (1) good construction operability; (2) convenient color control; (3) VOC emission reduction (alcohol soluble repair water is not used because it contains more alcohol or alcohol ether solvents); (4) production cost reduction (repair paint itself has a certain filling effect, which can reduce the coating thickness of the top paint, VOC in the toner water is volatile 2.3.2 color control factors 2.3.2.1 waterborne resin waterborne wood coatings resin (emulsion or dispersion type) are generally light yellow translucent or opaque opaque The worse the transparency of the resin itself, the more difficult the color contrast is when the color is applied or when it is constructed Therefore, the water-based resin should be as transparent as possible when making the finishing varnish 2.3.2.2 other factors that affect the transparency of varnish when using common varnish for color modification, the reason why color control is difficult is that there are some non transparent materials that affect the transparency of varnish or affect the adhesion between layers, such as polishing agent, opaque wax slurry, extinction powder, etc These materials should be removed as far as possible to make the function of the varnish more specific 2.3.3 influencing factors of construction control 2.3.3.1 the ideal effect of rheological repair is to get a flat and smooth plane with uniform color In order to achieve this effect as much as possible, there must be no shrinking edge, black edge, sagging, orange peel and particles in the construction process In the actual construction process, a small amount of orange peel and particles are unavoidable, which can be filled by appropriate sanding and finishing coat covering, and finally get a better coating effect There are almost no shrink edge, black edge and flow hang problems Therefore, it is necessary to effectively limit the flow of paint liquid during the construction of finishing varnish In order to ensure the flatness of the board surface, the coating after construction should be as flat as possible, which requires that the finishing varnish should have a certain level In general, the problem of leveling can be solved by selecting the appropriate thickener and prolonging the drying time of the film 2.3.3.2 construction viscosity in batch production, the color repair is completed by hand The spray equipment generally adopts the lower pot type ordinary air spray gun, and the diameter of the spray gun is generally 1.3mm or 1.5mm The construction viscosity shall be adjusted properly according to the size of spraying objects When the construction objects are large, the viscosity shall be lower appropriately, generally in 13-15s (2 × salt field cup); when the construction objects are small, the viscosity shall be higher appropriately, which can be in 16-20s (2 × salt field cup) This is because in large area operation, the distance between the spray gun and the surface of the object to be coated will be far, the time for the paint mist to be exposed in the air will be longer, and the viscosity of the paint mist when it reaches the surface of the object to be coated will be higher