0 Preface
In addition to the protective function of general paints, the art paints also have a strong decorative effect, which is full of three-dimensional and flickering, and is widely used in the surface coating of interiors and handicrafts. Art paint not only protects and decorates the surface of the object, but also increases the added value of the product. It has been favored by the majority of users and has gradually become a high-grade decoration material in the decoration industry.
With the rapid development of science and technology, the competition in the market has intensified, and the decorative requirements for the appearance of engineering machinery have been increasing. In order to meet the individual needs of users, high decoration, high environmental protection and low consumption have become the art of painting technology in large engineering machinery industry. development trend. The types and scope of art paints are constantly developing and changing. New art paints and painting techniques are constantly emerging. Hammer paint, orange paint, sprinkle paint and other ugly paints, crack paint, pearl paint, chameleon paint and other high decoration. The emergence and application of sexual paint not only makes the appearance of the product more colorful, but also brings people a strong mental infection and visual enjoyment. This paper reviews the characteristics, principles and on-site construction performance of several art paints that are currently used in the construction machinery industry.
Research and application of art paint in construction machinery industry
1 crack paint
1.1 Introduction to crack paint
Crack lacquer, also known as lacquer lacquer, is a kind of art lacquer. It is a cracked topcoat that is obviously different from the color of the primer. It is sprayed on the surface of the coated object to form a crack with uniform texture, changeable, patchy and three-dimensional beauty. Named for the effect.
1.2 crack paint formation principle
During the process of crack topcoat film formation, due to the rapid evaporation of the solvent, cracks are generated inside the paint film due to uneven force, and irregular crack gaps are exhibited, thereby making the base paint different in color from the crack top coat. Appeared in the crack gap to form a good, uniform crack pattern. Generally, the greater the contrast between the color of the crack primer and the topcoat, the stronger the stereoscopic effect and the better the effect.
Studies have shown that crack formation depends on the interaction force between the coating and the coating. When the paint is in an isolated state, it shrinks uniformly in all directions; when the paint is on the substrate, the paint film is affected by the fluidity of the primer in addition to its own tensile force and tensile force, resulting in uneven shrinkage of the topcoat. Stress concentration, when this stress is greater than the tensile strength of the coating film, it cracks and forms cracks. Conversely, when the primer is not flexible, the top coat will not cause stress concentration and will not crack; and when the top coat stress is less than the large tensile strength of the paint film, it will not crack. The formation of the crack effect is largely related to the composition of the coating. When the weak chain of the coating molecular chain is small and the bonding strength is small, the crack will be relatively flat when cracked (Fig. 1a-1c); otherwise, when the molecular chain is The bonding strength is large, and the cracking point is more, forming a curved and uneven skin texture effect (Fig. 1d). For example, the size and uniformity of crack spraying are guaranteed. In production, crack paint is generally applied to the spraying of small workpieces, such as decorative planes such as hoardings and box covers.
1.3 crack paint construction performance
1. Substrate selection: The substrate for spraying cracked paint can be widely selected, such as steel, wood, fiberglass and plastic products.
2. Coating selection: In order to ensure better corrosion resistance, appearance decoration and environmental protection of engineering machinery products, two-component epoxy type skin primer, water-based resin topcoat and flexible curing agent with a slightly longer curing time are generally selected. , coating coating system. Because if the curing time is too short, it will be difficult to control the coating process of the topcoat. The cracking of the paint film is difficult and the effect is poor. Considering environmental protection and safety, the water-based topcoat has become an increasingly popular choice.
3. Painting process: The spraying process of cracked paint is the same as the ordinary paint spraying process, generally: substrate pretreatment - spray crack primer - dry - spray crack topcoat - dry - spray varnish - dry. Since the cracked paint itself is loose and lacks the proper adhesion to the primer, a varnish must also be applied to the surface of the cracked paint to increase the bond strength to the cracked paint and the adhesion to the primer.
4. Spraying process requirements and precautions for each process: Whether the cracked paint can present a uniform and beautiful pattern on the surface of the workpiece is not only related to the performance of the cracked paint itself, but also closely related to the corresponding coating technology and environment. In the production process, the following influencing factors must be paid attention to ensure the normal and efficient implementation of the crack lacquer process. (1) Before the construction, the pattern must be sprayed on the small sample plate of the sprayed primer. According to the effect of crack size, select the construction viscosity of the crack top coat, the thickness of the paint film, adjust the shape of the spray gun, the air pressure, and the amount of paint ( Stereotype), control spray gun speed, distance, spraying method, atomization status, paint color ratio. (2) After the primer is sprayed, it is leveled and dried. After the paint film reaches the surface dry state, it can wet the wet spray crack top coat. The difference from conventional products is that the crack primer cannot be dried to a dry state, otherwise the adhesion between the primer and the topcoat will be affected, and the crack effect will not be obtained. (3) The thickness of the top coat should be completely covered by the color of the primer, and the thickness of the paint film can be controlled according to the size of the crack to be obtained. When the crack is cracked, it generally expands from the edge to the middle. The grain in the early stage of the crack is shallow and thin. As the time increases, the crack grows and becomes thicker and thicker. Generally, the paint film has large cracks, small cracks in the paint film, fast cracking speed, and uniform film thickness, and the crack size is uniform and uniform. If a large crack effect is required, the thickness of the primer film should be thicker, and the crack paint should be sprayed more than 2-3 times, and the gas volume does not need to be too large; if a small crack is required, the opposite is true. (4) After spraying the varnish, in order to obtain a good hardness of the paint film, it is generally dried. Drying at 150°C, the hardness of the paint film is the highest, the hardness of the paint film at the medium temperature of 80°C is second, and the hardness of the paint film at room temperature is the worst. (5) Choice of temperature and humidity: Since the crack paint is sensitive to temperature and humidity, the ambient humidity is too high, the temperature is too high, and the temperature is too low. It is not suitable for construction. In order to avoid adverse effects, the temperature is generally 25 degrees Celsius and the relative humidity is 75%. It is better. When the temperature is high, the solvent evaporates quickly. It is necessary to spray the top coat as soon as possible, otherwise the primer is too dry and the crack is not easy to appear. Cracking of water-based cracked paints usually begins within 20min-40min of the spray finish, depending on ambient temperature, humidity and coating thickness. Generally, the spraying environment has a high temperature and cracks faster. Even in an environment where closed air does not flow, cracks can be formed completely. (6) Spray guns with additional oil paint and water-based paint should also be used separately, otherwise it will easily cause secondary pollution to the paint film.
2 pearl paint
With the increasing demand for highly decorative (high-fidelity, high-brightness, high-flash colorization) of mechanical topcoats, metallic glitter paints and pearlescent surfaces with pearlescent, glittering and flop effects The application of paint is gradually increasing.
2.1 flop effect
The arrangement state of the metallic pigment and the pearlescent pigment in the coating film has a great influence on the flop effect. That is, at the same incident angle, the brightness of the coating film changes strongly as the angle of view of the observer changes. If the flake pigments are randomly arranged in the coating film, the light irradiation exhibits diffuse reflection on these pigments, and the flop effect is small; if the arrangement of the flake pigments in the coating film has a regular orientation, the incident The light exhibits a directional reflection on its surface. As a result, the reflected light intensity is large at a certain angle, and the light intensity is weak at other angles, resulting in a strong flop effect [1].
2.2 principle of pearlescent paint formation
Metallic paint, also known as metal flash paint, is named after the coating is doped with fine metallic pigments (such as aluminum, copper powder, etc.), and a layer of varnish is added to the outside of the metallic paint to protect it. After the coating film is formed, the metallic pigments are aligned in different layers, and after the light is incident on the metal particles, the particles are reflected by the paint film, so that the metal looks like a sparkle. By changing the shape and size of the metal powder particles, it is possible to control the glittering degree of the metallic flash paint film.
Pearlescent paint, also known as mica paint, is a kind of metal flash paint, named after the addition of pearlescent pigment to the paint. The pearlescent effect is due to the addition of mica pigment coated with titanium dioxide and iron oxide [2]. (1) After the light is incident on the mica particles, the color of titanium dioxide and iron oxide is first applied. (2) The incident light passes through the pigment flakes with uniform particles and fine particle size, and complex refraction and interference occur. (3) The combination mica itself has a special, transparent color. The visible light is reflected twice on the surface of the titanium dioxide film and the mica, and the two reflected light produces an optical interference effect under certain conditions. In this way, the visible light is re-introduced into the human eye through multiple reflections and refractions. Therefore, the pearl paint gives a colorful and dazzling look, as if the pearl pieces are glittering in depth and layering.
2.3 pearl paint construction performance
Note on the coating process: The luster of the pearl paint comes from the deep layer of the paint film, and the pearl powder is a transparent thin layer. The more transparent the medium, the less light is lost. Therefore, it is necessary to avoid the use of masking pigments and additives which are liable to cause turbidity during the painting process. In the paint film, the pearlescent pigment film coating is arranged as parallel as possible to the surface of the paint film to give a more brilliant pearlescent effect (Fig. 2a-2f). Therefore, during the coating process, the wet film should be allowed to have sufficient fluidity to ensure that the pigment particles can automatically reach the parallel orientation. Such as Sany Heavy Industry's pump truck, crane vehicle metal pearl paint, Terex crane cab pearl paint, Xugong crane, rhinestone paint used on fire trucks, etc., which became the focus of the show due to its flashing metallic pearlescent effect. .
3 chameleon paint
3.1 Introduction to Chameleon Paint
Chameleon paint is a special paint that produces color changes with the help of other substances. Generally divided into: temperature change paint, UV light color paint, natural light color change paint (chameleon) at different angles. The temperature-changing paint contains microcapsules which can cause chemical reaction and discoloration when heated. The ultraviolet color change is a color which is exhibited by the microcapsules containing the photosensitive color change in response to ultraviolet light.
3.2 The principle of chameleon paint formation
The core technology of chameleon paint lies in the new nano-paint. The nano- and titanium dioxide mixed with aluminum powder pigment/nano-titanium dioxide coated mica pearlescent pigment is added to the coating to make the coating produce a mysterious and transformed flop effect [3].
The mechanism of production is as follows: It is generally believed that nano-sized titanium dioxide has a unique surface effect, a volume effect ultraviolet shielding and a flop effect, and thus is widely used in coating additives. Nano-titanium dioxide with rutile structure has a flop effect, that is, from different angles, the coating has different colors [4]. Nano-titanium dioxide can transmit visible light and cover the visible light to a certain extent, which causes the transmitted light to reflect on the surface of aluminum powder and titanium dioxide to produce different viewing angle effects.
When the incident light is incident on the nano-titanium dioxide particles, the blue light will be strongly scattered due to the small particle size, and the green light and the red light will have a strong reflection (in the yellow phase). The film surface is different depending on the viewing angle. Present different hues. Nano-titanium dioxide is added to the metal glitter topcoat, which can greatly enhance the traditional popular topcoats. The color-changing car with a metallic flash topcoat containing nano-titanium dioxide was first manufactured by Ford in the United States in 1989. Chameleon paint is formed by adding special mica powder to the adjusted metal paint. Due to the special shape of the mica (very thin sheet), the reflection of light is directional, so the chameleon paint coating will show different colors as the line of sight changes [5].
3.3 Chameleon paint construction performance
The process of spraying the chameleon paint is the same as that of the normal product. After the topcoat is dried, add appropriate amount of discoloration powder to the varnish. After mixing evenly, spray on the surface of the topcoat to form a test panel with different color-changing effects (Fig. 3a-3d). Before spraying the varnish, the top coat should be dried as much as possible to avoid the infiltration of the color changing powder and affect the color change effect.
The color of the car is not really changing, but from different angles, the body color is different, and its core technology lies in the new car paint. How to reduce the construction cost of color changing paint will be a new topic for people to study.
4 ugly paint
Large construction machinery and equipment due to the rough surface and poor flatness of the sheet, resulting in uneven surface. The use of special coatings such as sprinkle paint, orange paint, hammer paint, etc. to form a three-dimensional paint film on the surface of the workpiece, not only can cover the unevenness of the surface of the product, but also reduce the amount of putty and polishing time, and reduce the labor of employees. The strength simplifies the process flow, shortens the production cycle, saves the raw materials, and eliminates the hidden trouble of the later putty cracking. It is an ideal decorative coating for the large machinery industry.
4.1 sprinkle paint
Sprinkling art paint refers to the paint on the surface of the product like dripping water drops. It is a paint that can protect the surface of the object and has a sense of fineness. It is often used for the finishing of instruments, equipment and metal products. The sprinkle paint has a beautiful appearance and is highly decorative, which can cover the mechanical damage and rough uneven surface defects of the surface of the coated object.
The formation of the sprinkling shape is mainly based on the spraying technique, and it is generally sprayed twice during the painting process. Firstly, according to the conventional spraying process, the primer is evenly covered. After it is completely dried, the nozzle with larger diameter is used. At a lower pressure, the thick paint liquid is sprayed into a sparse raindrop paint point on the workpiece. On the surface, the paint liquid is too late to level the solvent and has evaporated to form a droplet of water droplets of uniform size and substantially uniform spacing (see Figures 4a-4b). The full putty craft requires a high-skilled level of putty, and the paint film has the potential to crack. The actual application of the sprinkle paint process is obvious, and the operability is obvious. By selecting the appropriate gun cap, controlling the appropriate spray pressure, and spraying the paint to the proper construction viscosity, the sprinkle effect can be achieved. . At present, the art paint process is applied to the weight structure of the FAYAT road roller, the weight of the BAUERCG26, the weight of the Xugong crane, and the load of the loaders such as the temporary workers, Longgong and Shantui.
4.2 orange paint
Orange paint is prepared from resins, auxiliaries (including orange peel), thinners and pigments. Named for the texture of orange peel or leather on the surface of the workpiece [7]. The sprayed qualified orange paint has clear lines and strong three-dimensional effect, which can well cover the rough and uneven defects of various metal surfaces and play the role of art decoration (Fig. 4c-4d).
The construction process of orange lacquer is the same as that of conventional paint. When spraying, it is necessary to spray the primer anti-rust primer first, and the primer should be evenly covered. After completely drying, use ordinary low-pressure spray gun to spray the top coat. Generally, the orange topcoat needs to be sprayed two times. When the site is constructed, the viscosity of the paint and the speed of the gun can be controlled according to the size of the orange grain required. At present, our company's crane products have taken the lead in using the orange paint process on the hooks, which not only improves the work efficiency of the hook spray, but also improves the appearance and decoration of the products.
4.3 hammer paint
Hammer paint is made of synthetic resin, non-floating aluminum powder, additives and solvents. The formation of the hammer pattern is to use the spray of the spray gun to produce a thick and uneven shallow round spot, the non-floating aluminum powder in the round spot is precipitated, the varnish floats up, and a boundary is formed with the pigment. At the same time, the solvent volatilizes to produce a vortex. Under the synergistic action of the silicone oil additive, the sinking aluminum powder is rotated, and the aluminum powder is squeezed around the paint point to show a shallow pot-shaped hammer flower. The reflected light of the aluminum powder on the shallow basin surface interferes with the hammer pattern [6]. The aluminum powder pigment forms the hammer pattern mainly by means of spraying various coating points on the surface of the object to flow to each other, and the aluminum powder forms a vortex varnish which is formed one after another by the rotating surface, slightly floating on the aluminum powder, so that these vortexes It shows a glittering aluminum metallic luster and a uniform and beautiful hammer pattern.
5 Development prospects
The development of art paints is changing with each passing day. It is not only the research of scientific mechanism and the research of laboratory experiments, but also the development of art paints. At the 2014 International Engineering Machinery Shanghai International BMW Exhibition, more internationally renowned top construction machinery manufacturers used a variety of fine art paints, such as Xugong's shiny rhinestone paint, Sany Heavy Industry Pearlescent Paint, and colorful art paints. In order to provide high-grade decorative effects for the products, and to enhance the added value of the products, and to meet the individual needs of customers, the construction machinery industry has great development prospects.
With the maturity of construction machinery manufacturing technology, customers have stricter requirements on the appearance of mechanical products. Further development of engineering machinery functional art paints with rich appearance and increasingly complete functions will become a research hotspot for painters.
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