On the construction method of the hottest Waterbor

Brief discussion on the construction methods of Waterborne Wood Coatings

brief discussion on the construction methods of Waterborne Wood Coatings

December 14, 2018

0 preface we often say that coatings are semi-finished products. Only when they are coated on the surface of different substrates and form a complete film can their use value be realized. The coating changes from a liquid fluid (except powder coating) to a solidified film, which is attached to the surface of the substrate to decorate and protect the coated object. We usually take the excellent performance of solid film as our goal. Excellent formulation development and good production technology are the guarantee for us to obtain high-quality coatings. Coating construction plays a vital role in this process. As the saying goes, "three coatings, seven construction", although not all in this proportion, but also stressed the importance of construction

the requirements for smoothness and fineness of inner and outer wall emulsion paint film are not high, and the texture paint even requires rough texture; Some coatings, such as 3C plastic paint, have extremely high requirements for surface effect and cannot accept any defects. There are wood coatings with various effects, such as mirror smooth wood floor coatings, outdoor wood coatings requiring rough texture, modern furniture coatings as bright as new, American painting effect coatings that return to nature, open painting that shows the original style of beautiful wood grain, and fully closed solid color painting that completely disappears wood. In addition to the performance of the coating itself, the construction technology also plays a very important role in achieving this coating effect

with the gradual transition of wood coatings to water-based, the construction technology of water-based wood coatings has also undergone new changes. Some waterborne wood coatings can adopt simpler construction methods, some become more complex in order to achieve the effect of solvent based coatings, some waterborne wood coatings can adopt more efficient construction methods, and some have to adjust the formula to meet the new construction requirements. According to different wood materials, different coating requirements, different construction environments, different workpiece shapes and sizes, users of water-based Wood Coatings apply different construction methods and processes to present perfect water-based wood coating coatings for consumers. The following briefly introduces various construction methods of waterborne wood coatings

1 construction method of water-based Wood Coatings 1.1 the most traditional construction method - brushing

when lifting wood coatings, the most traditional construction method we can think of is brushing. From the exquisite lacquerware in the ancient tombs of Mawangdui in Changsha, to the on-site painting of anti-corrosion wood hydrophilic platforms in modern residential areas, as well as the painting of some family door covers, window covers and furniture, you can see the figure of the worker master. The solvent based coating film-forming resin is dissolved in organic solvents, and the resin is in a fully stretched form, so the coating gloss and leveling of the solvent based coating are high. Most of the resins of waterborne wood coatings are dispersed in water in the form of lotion. The resins are spherical and have different particle sizes. Therefore, the gloss and leveling of waterborne wood coatings are worse than solvent based coatings. Compared with water-based wood coatings, solvent based coatings, especially nitrocellulose coatings, are more suitable for brushing. We used to see all kinds of hand swept paints in building materials supermarkets

water based wood coatings are still applied in some places, especially in outdoor anti-corrosion wood projects requiring on-site construction, as well as some refurbished wood buildings. In many European and American countries, especially in Canada, many families are keen to live in wooden houses. Most of these wooden houses are produced in Jiangsu and Zhejiang regions of China. When they leave the factory, they have been painted with wood coatings. Generally, water-based pure acrylic wood coatings are used, which has better weather resistance than solvent based coatings

painting is pure human labor, without the help of any modern equipment, so the performance requirements of waterborne wood coatings are very high, and the craftsmanship requirements of construction workers are also very high. Painting requires a faster drying speed of the paint, and requires that the paint hanging performance of the facade construction paint is good and cannot flow. The painting of water-based Wood Coatings requires good leveling of the film, otherwise obvious brush marks will be left on the surface of the film. For the coating film with high surface requirements, it needs to be polished with sandpaper after drying each time the coating is brushed. If the leveling property of the coating is not good, most of the coating film will be polished off, so it needs to be painted many times. "Twice the effort" is to describe this state. The biggest advantage of water-based wood paint brushing is that no matter the on-site construction master or the owner who moved in afterwards, they don't have to endure the pungent smell of solvent, and they can operate as non dangerous goods in the production, transportation and sales stages of paint

1.2 the most conventional construction method - spraying

the so-called spraying is that the coating is sprayed rapidly from a small hole with the help of a certain pressure. Because the pressure disappears instantly after the coating leaves the nozzle, the liquid coating is atomized into several fog points and flies to the surface of the substrate. According to whether the air source is used as the power, it can be divided into airless spraying and airy spraying. The former is often used for the construction of internal and external wall emulsion paint, while the most typical application of the latter is the construction of wood paint. Air spraying can realize better atomization of the coating, spray the coating onto the surface of the substrate, and prevent sagging to a certain extent

in addition, the spraying construction can be aimed at any surface shape. By adjusting the air pressure, the amount of paint flow, the moving speed of the spray gun, the distance between the spray gun and the substrate and the opening angle of the spraying sector, the thickness, efficiency and flatness of the coating film can be controlled. Solvent based wood coatings and water-based wood coatings are also suitable for spraying construction, but after atomization, solvent based coatings are more volatile, smell heavier, and have worse safety, while water-based Wood Coatings do not have such problems. In addition, the viscosity of coating for spraying is generally required to be lower than that of coating for brushing, which is often 20 ~ 25s (4 cups)

generally, the spraying adopts manual operation, and the painters hold the spray gun for coating, which has high technical requirements for the workers. The coating requires both good fullness and no sagging, and requires careful attention, concentration and good physical strength. Most of the time, the workers' masters operate standing. For solvent based coatings, the workers' masters also have to endure solvent volatilization, so the painting work is often the work with higher wages in furniture factories. Most wood products factories and furniture factories have special painting workshops. In addition to air compressors and spray guns, there are large and small painting platforms and hangers. Exhaust fans are installed on the walls of the workshops to discharge volatile solvents and paint fog spots that cannot fall on the surface of the substrate to the outside. At present, the painting workshops of many wood products factories use spray water curtain cabinets to recycle the paint that has not fallen on the substrate with water curtain instead of being discharged into the air

in order to improve the efficiency of construction, many furniture factories set up spray lines, using reciprocating spray guns, setting the flow, pressure, spray angle and distance of the spray guns, as well as the speed and position of the assembly line. Through the cooperation of several spray guns, high-efficiency and automatic coating can be achieved. For wood furniture with complex shapes, in order to achieve perfect coating effect, industrial robot arms can even be used to keep the distance between the nozzle and the substrate surface consistent, so as to achieve perfect coating effect. In order to improve the drying speed of coatings, there are special drying equipment in modern coating workshops, so that spraying - drying - grinding - re spraying can form an efficient working process. The drying of solvent based coatings is often forced by hot air, which is accompanied by a large amount of volatilization of solvents in a short time. At present, the most advanced equipment for drying waterborne wood coatings is the infrared drying equipment, which uses the infrared of a specific wavelength to cause the resonance of water molecules and leave the film surface, so as to realize the film drying under the condition of minimum energy consumption

1.3 the most painstaking construction method - wiping

the so-called wiping is to wipe back and forth on the surface of wood with cotton cloth or non-woven fabric dipped in paint. Wiping is not used alone. It is often used to color wood. It can also be painted directly by mixing the color essence into the primer or finish paint, but this construction process often gives people the feeling that the color is in the paint, floating on the surface of wood, rather than the natural color of wood, which lacks a sense of hierarchy. Therefore, a separate painting process is necessary. Paint the wood after changing its color. Alcohol soluble colorants or rub color treasures are often obtained by mixing the red, yellow and black colorants into the required color according to the formula, filling them with wood coatings and stirring them evenly. Solvent based paint is not absorbed by wood, so it can be directly rubbed on the white wood. The cloth can stay longer where the color is light, and the cloth can be rubbed repeatedly where the color is dark until it is consistent with the surrounding color

waterborne wood coatings cannot be applied according to such a construction process. Wood is a base material that is easy to absorb water. The absorption speed of different parts is different. The amount of chromatin kept on the wiping cloth and the speed of wiping cloth movement will lead to uneven color and difficult to correct. The usual process is to make a transparent thin primer on the surface of the blank, and then polish the wood surface after drying. On the one hand, it can prevent the "swelling" of wood caused by water-based chromatin. On the other hand, it can ensure that even if some parts are too dark, they can be wiped evenly by repeated wiping. Often the color of a single brush is lighter. The current popular process is to no longer use the colorant without resin system alone, but to add alkali soluble resin to the colorant or directly add water-based Wood Coatings (depending on the stability of the system) to improve the wet adhesion of the colorant

if necessary, a small amount of color essence can be mixed into the subsequent waterborne wood primer and topcoat to deepen the coloring and finish, which is the case with the so-called bottom coloring and surface finishing. Painting requires workers to concentrate on wood. Any uneven color, color difference and floating color are unacceptable. Every inch of wood should be wiped back and forth many times until the color is completely uniform. It is really a laborious work. In addition, the water-based wood coating used for pencil surface coating is also rubbed, but it is different from our traditional understanding of rubbed

the pencil keeps passing from top to bottom from a rubber bowl full of paint. The rubber at the bottom rubs the aqueous wood paint in the rubber bowl onto the blank surface of the pencil during the friction with the pencil. Whether it is a round or hexagonal pencil, you can use this rubbing method. The author saw such a construction scene in a pencil factory in Yiwu

1.4 the simplest construction method - dip coating

coating is a semi-finished product. We hope to use the fastest way to construct and turn the semi-finished product into the final film. There are many ways to achieve this transformation, and dip coating is undoubtedly the most convenient one. We have always lamented that the film performance of waterborne wood coatings can not catch up with solvent based coatings, and there is a gap with solvent based coatings in terms of construction performance. However, in terms of construction methods, water-based coatings have great advantages, especially dip coating construction. Since the cost of water as a diluent is almost zero, and the solvent volatilizes into the atmosphere after the paint tank is opened, it does no harm to the environment and the construction personnel. Therefore, dip coating construction has become the patent of water-based coatings, of which water is the most widely used