JP4661215B2 - Metallic coating method and laminated coating film - Google Patents

Description

  The present invention relates to a metallic coating method and a laminated coating film that can be applied to the coating of automobile bodies, parts, etc., and in particular, metallic coating that can provide a design rich in metallic feeling with good orientation of glitter materials such as vapor-deposited metal pieces. The present invention relates to a method and a laminated coating film.

  In metallic coatings for automobile bodies and parts, coating using vapor-deposited aluminum flakes with good light reflectivity is used as a glittering material in order to provide a metallic appearance-rich (metallic) appearance design. However, in such a conventional metallic coating, even if it is intended to realize a metal-like design with a metallic paint using a bright material such as vapor-deposited aluminum flakes, it is possible to use only small objects such as small products and parts. It cannot be realized, and it is practically impossible to realize a coating process with a short production tact such as an automatic coating line for an object having a large coating area such as an automobile body.

  In addition, a conventional metallic coating method in an automobile body painting line is to coat a film thickness of about 15 μm in two stages using a metallic bell-type coating machine. In this case, the paint NV value (Non Volatile value; non-volatile) The solid content) is about 20%. Even if a highly reflective vapor deposited aluminum flake or the like is used for such a conventional metallic paint, it cannot be said that the orientation in the resulting metallic coating structure is sufficient, and a metallic design is not obtained.

  Therefore, the present inventors have developed a technique for controlling the orientation of the glittering material in the coating process of an automobile body or the like, and have proposed a metallic metallic coating method using vapor-deposited aluminum or the like (Patent Document 1).

However, in the metallic metallic coating method described above, the metallic base paint is applied in two stages so that the base film thickness is about 8 μm, so the amount of glittering material such as vapor deposited aluminum is increased, and the conventional silver metallic There was a problem that the cost was remarkably high compared to painting.
JP 2003-313500 A

An object of this invention is to provide the metallic coating method and laminated coating film from which the design rich in metal feeling is obtained, reducing the usage-amount of a luster material.
In order to achieve the above object, according to the present invention, an intermediate coating step for forming an intermediate coating layer directly or indirectly on the surface of an object to be coated using an intermediate coating, and a metallic base coating are used. A metallic base coating step for forming a metallic base coating layer on the surface of the intermediate coating layer, and a clear coating step for forming a clear coating layer on the surface of the metallic coating layer using a clear coating. In the coating method, the intermediate coating step includes a first intermediate coating step of forming a first intermediate coating layer using a pigment-containing intermediate coating, and a pigment-free intermediate coating or clear coating. have a second intermediate coating process for forming a second intermediate coating film layer on the surface of the first intermediate coating film layer using, as the metallic base coating, and luster pigment 10 to 30 wt%, the molecular weight 25000-50000 A paint solid content substrate containing 10-50% by weight of a rosacetate butyrate resin and an acrylic-melamine resin as a remaining amount, and a paint solid content of 1-10% using an ester solvent and / or a ketone solvent %, The dry thickness of the metallic base coating film layer is 2.5 to 3.5 μm, and between the second intermediate coating process and the metallic base coating process. the coating method characterized by have a coating baking step in baking the first intermediate coating film layer and the second intermediate coating film layer simultaneously is provided.

  In the present invention, since the second intermediate coating film layer as the base of the metallic base coating film layer is formed using an intermediate coating or clear coating that does not contain a pigment, the surface of the second intermediate coating film layer Becomes extremely smooth. And, when the metallic base paint is applied to the smooth surface of the second intermediate coating film layer, the glittering material is well oriented even if it is applied with a thin film thickness. For example, the thickness can be reduced to 5 μm or less. As a result, it is possible to provide a metallic coating design rich in metallic feeling while reducing the amount of use of the glitter material.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a process diagram showing an embodiment of the coating method of the present invention, FIG. 2 is a sectional view showing a laminated coating film obtained by the embodiment of the coating method of the present invention, and FIG. 3 is a metallic base according to the coating method of the present invention. FIG. 4 is a cross-sectional view showing a coating film forming mechanism when forming a paint film using the metallic base paint according to the coating method of the present invention, FIG. FIG. 6 is a graph showing an example of the change over time of the viscosity of the metallic base paint according to the coating method of the present invention, and FIG. 6 is a side view showing an outline of the rolling test.

  The coating method according to the present invention is, for example, a coating method using a metallic base paint exhibiting a high metallic feeling close to the metal itself, having an FI value of 21 or more, which is a metallic feeling index of X-Rite, Any coating method may be used as long as the surface of the underlying layer immediately below the coating layer is extremely smooth. For example, the required smoothness of the underlying layer is 9.0 or less for the long wave (LW) and 25 or less for the short wave (SW) in terms of the measured value of the wave scan manufactured by BKY Gardner.

  As a specific example of a coating method for obtaining such a smooth underlayer, an example in which an automobile body is applied to an object to be coated will be described below. However, the coating method according to the present invention is limited only to these embodiments. Therefore, each element disclosed in these embodiments is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  In this specification, the material applied to the object to be coated is called a paint, and is a layer formed on the surface of the object to be coated by applying this paint, uncured before curing and cured after curing. The coating layer, these uncured coating layer and the cured coating layer are collectively referred to as a coating layer.

  As shown in FIG. 2, the laminated coating film according to the present embodiment is formed on the surface of the electrodeposition coating layer 102 formed on the surface of the automobile body that is the article 101 and the surface of the electrodeposition coating layer 102. The first intermediate coating layer 103a, the second intermediate coating layer 103b formed on the surface of the first intermediate coating layer 103a, and the surface of the second intermediate coating layer 103b. The metallic base coating layer 104 and a clear coating layer 105 formed on the surface of the base coating layer 104.

  As materials constituting the automobile body 101 that is the object to be coated, plastics can be applied in addition to various metal materials such as a steel plate and an aluminum plate. . In the coating method according to the present invention, an automobile part other than an automobile body or various objects to be coated other than an automobile can be used as an object to be painted.

  Prior to the electrodeposition coating process A, the automobile body 101 is carried into a pretreatment process, where the oil adhering to the automobile body 101 is degreased and cleaned using an alkaline cleaning solution or the like, and then the surface of the automobile body 101 is phosphoric acid. Form a chemical conversion film of zinc.

  Next, the automobile body 101 on which the chemical conversion film is formed is carried into the electrodeposition coating step A, where the automobile body 101 is immersed in an electrodeposition tank filled with a cationic electrodeposition coating material or an anionic electrodeposition coating material. By applying a predetermined voltage between the body 101 and the electrodeposition paint, an uncured electrodeposition coating layer 102 is formed on the surface of the automobile body 101 by an electrophoretic action. In the subsequent electrodeposition rinsing process, excess electrodeposition paint adhering to the surface of the automobile body 101 is washed away by spraying or dipping using industrial water or pure water, and the washed electrodeposition paint is recovered and reused. Use.

  Subsequently, the automobile body 101 which has completed the electrodeposition washing process is carried into an electrodeposition drying furnace which is an electrodeposition baking process B, and is cured by baking, for example, at 160 ° C. to 180 ° C. for 15 to 30 minutes. 102 is obtained. The film thickness of the electrodeposition coating layer 101 is, for example, 10 to 40 μm, although it varies depending on the specifications and parts of the automobile body 101.

  The coating material constituting the first intermediate coating layer 103a includes polyester resins such as polyester-melamine resin and polyester-epoxy resin, acrylic resins such as acrylic-melamine resin, acrylic-urethane resin, acrylic-epoxy resin, and vinyl chloride. A thermosetting paint, a room temperature curable paint or a two-component curable paint comprising a vinyl acetate copolymer resin, a urethane resin, a cellulose resin, etc. as a main component, and a colorant or additive added thereto, It is a water-based paint using a solvent or an organic solvent-based paint using an organic solvent as a solvent. That is, it is an intermediate coating containing a pigment such as a colorant. Then, the paint diluted with a solvent is applied to the surface of the electrodeposition coating layer 102 by using a coating machine such as a spray coating gun or a rotary atomizing coating gun in the first intermediate coating process C shown in FIG. Paint.

  When the first intermediate coating film layer 103a is formed, the second intermediate coating film layer 103b is formed in the second intermediate coating process D by wet-on-wet.

  Examples of the coating material constituting the second intermediate coating layer 103b include polyester resins such as polyester-melamine resin and polyester-epoxy resin, acrylic resins such as acrylic-melamine resin, acrylic-urethane resin, and acrylic-epoxy resin. Is a thermosetting paint, a room temperature curable paint or a two-component curable paint obtained by adding an additive as necessary, and a water-based paint or an organic solvent containing water as a solvent. It is an organic solvent-based paint. That is, it is a paint obtained by removing a pigment such as a colorant from the paint constituting the first intermediate coating film layer 103a. Therefore, the second intermediate coating film layer 103b can also be formed by using a clear paint constituting the clear coating film layer 105 described later.

  A coating material that does not contain a pigment such as a colorant is smoother than a general intermediate coating material that contains a pigment because the coating film surface is not uneven due to the pigment. However, if the first intermediate coating layer 103a is also composed of an intermediate coating without pigment, it is difficult to conceal the electrodeposition coating layer 102 with only the metallic base coating 104. Therefore, the first intermediate coating layer 103a is formed using a paint containing a pigment such as a colorant.

  Next, the automobile body 101 that has completed the second intermediate coating process is carried into an intermediate coating drying furnace that is an intermediate coating baking process E, and the undried first body is, for example, 120 to 160 ° C. for 10 to 30 minutes. The intermediate coating layer 103a and the second intermediate coating layer 103b are baked simultaneously. As a result, a cured first intermediate coating layer 103a and second intermediate coating layer 103b are obtained. The thickness of each of the first intermediate coating film layer 103a and the second intermediate coating film layer 103b is, for example, 10 to 40 μm, although it varies depending on the specification and part of the automobile body 101. In particular, the second intermediate coating layer 103b is desirably 10 μm or more in order to ensure desired smoothness.

  In addition, although the 1st intermediate coating process C and the 2nd intermediate coating process D which were shown in FIG. 1 comprised wet-on-wet, in order to improve the solvent evaporative property of the 1st intermediate coating film layer 103a, the 1st A preheating step for evaporating the solvent contained in the first intermediate coating layer 103a may be provided between the coating step C and the second intermediate coating step D. In this preheating step, the uncured first intermediate coating layer 103a is heated at a temperature lower than the curing temperature of the intermediate coating using a lamp or a hot air blower.

  After the first intermediate coating film layer 103a and the second intermediate coating film layer 103b cured in the intermediate coating baking process E are formed, the surface of the second intermediate coating film layer 103b in the next metallic base coating process F Apply metallic base paint.

  Here, the metallic base paint used in this example is a paint obtained by diluting a paint base with an ester solvent and / or a ketone solvent so that the solid content becomes 1 to 10% by weight. In the solid content, it contains 10 to 30% by weight of a glittering material, 10 to 50% by weight of cellulose acetate butyrate resin (molecular weight 25,000 to 50000), and an acrylic-melamine resin as the remaining amount. In addition to the above components, additives such as pigments, plasticizers, curing agents, surface conditioners, anti-settling agents, adhesion-imparting agents, and anti-sagging agents may be included as coating film forming elements.

  In this paint substrate, the glittering material, cellulose acetate butyrate resin (hereinafter also referred to as CAB resin) and acrylic-melamine resin are non-volatile solids and function as coating film forming elements, and the CAB resin is so-called. Functions as a viscous resin.

  FIG. 4 shows the coating formation mechanism of the metallic base paint according to this example. As shown on the left side of FIG. 4, the second intermediate coating film layer 103b in which the flying paint particles 10 including the glittering material 1 are the objects to be coated. The coating particles 10 are deformed and flattened according to the flight speed, the particle diameter, the dilution rate of the coating substrate, and the like, and the scaly glittering material 1 is applied. Tries to orient so that the plane portion is parallel to the second intermediate coating layer 103b. After coating, the paint 10 further spreads to the surroundings depending on the particle deformation energy and viscosity due to the flight speed and the like, and tries to form an uncured film. (B) in FIG.

  Next, when the diffusion of the paint 10 is completed and an uncured film of the paint is formed, the setting of the paint 10 to the second intermediate coating film layer 103b is completed ((c) to (d) in the figure) Thereafter, the uncured coating film shrinks in volume as the solvent evaporates. Accordingly, the glittering material 1 is further oriented in parallel ((d) in the figure), and the metallic base coating layer 104 is completed.

  In this example, in the process of forming the metallic base coating film layer described above, the glittering material 1 is not allowed to flow but wet at the initial stage (FIG. (C)) when setting the coating material to the second intermediate coating film layer 103b. One of the main objectives is to guide the paint to a certain state and further promote parallel orientation of the glittering material 1 by the subsequent volume shrinkage, and propose a paint composition and paint properties that can realize this.

  When such principal points are observed from changes in the viscosity of the paint (coating film), the relationship shown in FIG. 5 is obtained.

  In FIG. 5, a curve A shows a change in viscosity with time in an example of a metallic base paint according to the present example, and a curve B shows a change in posting of viscosity in an example of a conventional metallic base paint.

  As shown in FIG. 6, the time required for rolling the ball on the vertical axis is as follows: 10 μm of the test paint was applied to a tin plate coated with an A4 size intermediate coating at room temperature and normal pressure, and this tin plate was 5 °. After tilting to the following predetermined angle θ, an iron ball of 5.5 g with 11 mmφ was gently rolled from the top of the tin plate, and the required time was measured in time series at regular intervals.

  As shown in FIG. 5, in the metallic base paint (curve A) of this example, typically, the time required for rolling is less than 10 seconds from application to coating formation, A viscosity rise time range of 2 seconds and a touch dry time range of less than 3 seconds exist in this order, and the dry time range is within 2 minutes from the time of application, and the viscosity rise time range is within 3 minutes thereafter. After this, it can be seen that it becomes the finger touch drying time region. It should be noted that the initial stage when setting the paint of interest in this example to the second intermediate coating film layer 103b corresponds to the initial stage of the viscosity increase time region in curve A.

  On the other hand, in the conventional metallic base paint (curve B), the required rolling ball time does not increase after coating, and the viscosity does not increase, and the viscosity decreases very slowly after 1 minute after coating. It is. Accordingly, the parallel alignment of the glittering material after the paint setting as described above does not occur.

  In the metallic base paint of this example, the maximum value of the required rolling time is in the viscosity increase time region, and is preferably 15 to 30 seconds, more preferably 20 to 30 seconds, More preferably, it is 25 to 30 seconds. If the maximum time required for rolling is less than 15 seconds, the surface of the metallic base coating layer 104 is already dry and the glittering material is difficult to orient when the coating contracts, and if it exceeds 30 seconds, the viscosity of the coating itself is high. In this case, the glittering material is difficult to be oriented.

  In addition, the metallic base paint of this example typically contains 1 to 10% by weight of the total amount of non-volatile solids in the initial state before application (that is, the NV value is 1 to 10% by weight). The NV value in the drying time region is 20 to 30% by weight, preferably 25 to 30% by weight, and the NV value in the viscosity increase time region is 40 to 60% by weight, preferably 50 to 55% by weight. When the NV value in the undried time region is less than 20% by weight, the coating film viscosity is low and the orientation may be disturbed. May not happen. Further, when the NV value in the viscosity increase time region is less than 40% by weight, the viscosity of the coating film does not increase and the required rolling ball time may be 15 seconds or less. When the NV value exceeds 60% by weight, the coating film is dried. The required rolling time may be shorter than 15 seconds.

  Examples of the glittering material contained in the paint base material of the metallic base paint according to this example include pearl pigments and metal flakes, and metal flakes obtained by vapor deposition are typical, but good reflectivity. It is preferable to use evaporated aluminum flakes.

  Such a glittering material typically has a scaly shape, but the size is preferably 10 to 100 μm at the maximum length and 0.01 to 0.2 μm in thickness. If the maximum length portion is less than 10 μm, sufficient reflection may not be obtained, and if it exceeds 100 μm, a problem may occur in the sedimentation property of the glittering material in the paint circulation device. On the other hand, when the thickness is less than 0.01 μm, the shape stability in the circulation of the paint may be inferior. Sometimes.

  In addition, the compounding quantity of a luster material is 10 to 30 weight% of a coating material base material. If the amount is less than 10% by weight, the surface area of the glittering material is small and sufficient light reflection may not be obtained. If the amount exceeds 30% by weight, the amount of the glittering material is so large that problems such as sedimentation of the glittering material occur during coating circulation. Sometimes.

  The CAB resin functions as a so-called viscous resin, and strongly develops viscosity as the ester solvent or ketone solvent evaporates after coating. In this way, the viscosity of the viscous resin develops as the solvent component of the applied paint evaporates, so that the flow of the glittering material arranged in parallel as described above is suppressed, and thereby the paint has an appearance close to metal. Is easily obtained.

  The molecular weight of the CAB resin is 25,000 to 50,000, preferably 25,000 to 35,000, more preferably 26,000 to 34,000, and 28,000 to 32,000. Is more preferable. When the molecular weight of the CAB resin is less than 25,000, the coating film viscosity is low and the orientation of the glittering material is disturbed. If it exceeds 50,000, the viscosity is too high and the glittering material cannot be sufficiently oriented.

  In addition, the compounding quantity of CAB resin is 10 to 50 weight% of a coating material base material. If it is less than 10% by weight, sufficient viscosity cannot be exhibited, and if it exceeds 50% by weight, the acrylic-melamine resin for curing the coating film is relatively reduced and sufficient performance such as coating film adhesion cannot be exhibited.

  The acrylic-melamine resin mainly functions as a material for curing the coating film. The blending amount of the acryl-melamine resin is set so that the remaining amount of the coating substrate, that is, the total of the above-described glittering material and CAB resin is 100% by weight.

  In this example, in addition to the components described above, the paint base material includes pigments, plasticizers, curing agents, surface conditioners, anti-settling agents, adhesion-imparting agents, and anti-sagging agents as coating film forming elements. It is also possible to add additives, but in this case too, the blending amount of the acrylic-melamine resin is such that the total of all other components and this acrylic-melamine resin is 100% by weight. Good.

  The ester solvent and the ketone solvent function as a diluent for the above-mentioned paint base material. Specifically, 3-acetic acid-methoxy-butyl, 2-ethanol acetate, alkylbenzene, ethyl acetate, toluene and the like are the main components. You can list thinners.

  As described above, the metallic base paint of this example is obtained by diluting the paint base with the ester solvent, the ketone solvent, or a mixed solvent thereof, and the dilution ratio is 1 to 10 in terms of the solid content in the paint. % By weight.

  In this example, by adopting such a dilution ratio, the viscosity of the coating particles (flying particles) to be applied is reduced, and the deformation of the coating particles on the surface of the object to be coated (second intermediate coating layer 103b) is deformed. Compared with the case of the conventional metallic base paint, it is strongly caused, and vapor deposited metal flakes such as aluminum flakes in the paint can be arranged almost parallel to the surface of the object to be coated (FIG. 4A). If the dilution ratio exceeds 10% by weight, the coating particles are not sufficiently deformed at the time of coating, and if it is less than 1% by weight, the discharge amount of the coating machine increases, which is substantially difficult to apply in the coating line. Become.

  Particularly in this example, the above-described metallic base paint is applied to the surface of the above-described second intermediate coating film layer 103b rich in smoothness, so that the glittering material can be sufficiently satisfactorily obtained even in the case of a thin film as shown in FIG. 1 parallel orientation can be realized. That is, if the smoothness of the surface of the object to be coated is poor, a certain thickness is required for the glittering material to fill the unevenness and align it in parallel with the coating surface, as shown in FIG. When the surface of the article 103b is smoothed in advance, the glitter material 1 does not need to fill the unevenness, and the film thickness can be reduced accordingly.

  The metallic base coating layer 104 of this example is formed by using the metallic base coating described above, and 10 to 30% by weight of a glittering material, 10 to 50% by weight of CAB resin, and an acrylic-melamine resin as the remaining amount. And the FI value is 21 or more.

  Here, the FI value is a metallic feeling index of X-Rite, and is specifically defined by the following formula (1).

(Equation 1)
FI = 2.69 {(L _{15 °} -L _{110 °} ) ^1.11 / (L _{45 °} ) ^0.86 (1)
In the formula (1), L _{15 °} , L _{110 °} , and L _{45 °} are angles of 15 °, 45 °, and 110 ° on the surface of the flat coating film using the standard light source D ₆₅ defined in JIS as the light source. The intensity of the reflected light when it is incident on is shown.

  The metallic base coating layer 104 of this example has an FI value of 21 or more, and more preferably 23 or more. When the FI value is less than 21, the reflection of “exact metal” cannot be obtained.

  In particular, the metallic base coating layer 104 of this example preferably has a dry film thickness of 2.5 to 5 μm, and more preferably 2.5 to 3.5 μm. As described above, since the underlying layer immediately below the metallic base coating layer 104 is the second intermediate coating layer 103b having excellent smoothness, the metallic base coating layer 104 is formed of a thin film as described above. However, the orientation of the glittering material 1 is sufficiently good. Therefore, the amount of the expensive glittering material used can be reduced by thinning the metallic base coating film layer 104 to 5 μm or less. If the thickness of the metallic base coating layer 104 is less than 2.5 μm, a sufficient metal feeling cannot be obtained, and if it exceeds 5 μm, the amount of glittering material increases, which is disadvantageous in terms of cost. .

  In order to apply the metallic base paint, a conventionally known rotary atomizing bell type coater can be used. In this case, the shaping air flow rate is preferably set to 400 to 800 Nl / min. The speed can be secured, and the coating particle deformation energy at the time of coating can be sufficiently imparted. If the shaping air flow rate is less than 400 Nl / min, the deformation energy of the paint particles may be insufficient, and if it exceeds 800 Nl / min, it is difficult to cope with air supply on the coating machine side.

  Returning to FIG. 1, after applying the metallic base coating to the surface of the second intermediate coating layer 103 b to form the undried metallic base coating layer 104, the flashoff or preheating is performed for about 1 to 2 minutes, and then The clear paint is applied to the inner and outer plates of the body in the clear coating process G in FIG.

  The clear paint is mainly composed of polyester resin, acrylic resin, polyvinyl acetate vinyl chloride copolymer resin, urethane resin, cellulose resin, etc., and various additives are added to this as thermosetting paint or room temperature curable paint or A two-component curable coating, which is diluted with a solvent, is applied to the surface of the metallic base coating layer 104 in a clear coating process G using a coating machine such as a spray coating gun or a rotary atomizing coating gun. Paint. As a result, a transparent clear coating layer 105 is formed. The thickness of the clear coating layer 105 is, for example, 10 to 40 μm, although it varies depending on the specification and part of the automobile body. Note that the clear paint according to this example can use either a water-based paint or an organic solvent-based paint.

  After applying the clear paint, after standing for a few minutes (setting), the body is carried into the overcoat baking step H, and the metallic base coating layer 104 and the clear coating layer 105 formed by applying the body are simultaneously applied. For example, baking is performed at 120 to 160 ° C. for 10 to 30 minutes.

  As described above, the electrodeposition coating layer 102, the first intermediate coating layer 103a, the second intermediate coating layer 103b, the metallic base coating layer 104, and the clear coating layer 105 are cured on the surface of the automobile body 101. A coating film is formed.

  In particular, since the second intermediate coating film layer 103b of this example is formed using an intermediate coating or clear coating that does not contain a pigment, the surface smoothness is extremely high. When a metallic base paint containing a glittering material is applied to the surface of the smooth second intermediate coating film layer 103b, the glittering material is oriented in parallel even if it is a thin film. Therefore, the amount of expensive glittering material used can be reduced.

  As mentioned above, although embodiment of the coating method of this invention was described, a more specific Example is given and this invention is demonstrated further in detail.

  A steel plate 101 was electrodeposited using a conventionally known electrodeposition paint to form a 20 μm electrodeposition coating layer 102. 15 μm of a polyester-melamine resin-based intermediate coating (manufactured by Nippon Paint Co., Ltd.) as the first intermediate coating was applied to the surface of the electrodeposition coating layer 102. For the coating, a rotary atomizing bell type coater (ABB921 type, cup diameter φ = 50 mm) is used, the rotation speed is 25000 rpm, the shaping air flow rate is 250 Nl / min, the discharge amount is 150 ml / min, the applied voltage is -60 kV, and the coating linear velocity. The coating was carried out at 25 m / min and with 4 coatings.

  After the flash-off within 1 minute, 10 μm of an acrylic-melamine resin-based intermediate coating (Nippon Paint Co., Ltd.) containing no pigment as the second intermediate coating was applied. For painting, a rotary atomizing bell type coater (ABB921 type, cup diameter φ = 50 mm) is used. The rotational speed is 25000 rpm, the shaping air flow rate is 250 Nl / min, the discharge rate is 100 ml / min, the applied voltage is -60 kV, and the coating linear velocity. The coating was carried out at 25 m / min and with 4 coatings.

  This was baked at 140 ° C. for 20 minutes. When the smoothness of the obtained intermediate coating film layer was measured by a wave scan manufactured by BYK Gardner, LW = 3.5 and SW = 23.3.

Next, as a metallic base paint, a paint base comprising 73% by weight of acrylic-melamine resin manufactured by Nippon Paint Co., Ltd., 17% by weight of evaporated aluminum paste and 10% by weight of CAB resin (381-0.5, molecular weight of 30,000 manufactured by EASTMAN). A material diluted with 3000 % by weight of ethyl acetate was used. This metallic base coating was applied to the surface of the above-mentioned intermediate coating layer by 2.5 μm. For the coating, a rotary atomizing bell type coater (ABB metallic bell type, cup diameter φ = 70 mm) is used. The rotational speed is 25000 rpm, the shaping air flow rate is 700 Nl / min, the discharge amount is 150 ml / min, the applied voltage is −60 kV, the coating The coating was performed at a linear velocity of 54 m / min and a coating frequency of 4 times.

  After 3 minutes of flash-off at room temperature, an organic solvent-based clear paint (Bellcoat No. 7300 manufactured by Nippon Oil & Fats Co., Ltd.) was rotated at a rotational speed of 25,000 rpm and shaping air of 300 Nl using a rotary atomizing bell type coater. / Min, discharge rate 200 cc / min, applied voltage -80 kV, gun distance 20 cm.

  These metallic base coating layer and clear coating layer were baked at 140 ° C. for 20 minutes.

  When the FI value of the obtained multilayer coating film was measured using a MA68 measuring instrument manufactured by X-Rite, the FI value was 23.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

It is process drawing which shows embodiment of the coating method of this invention. It is sectional drawing which shows the laminated coating film obtained by embodiment of the coating method of this invention. It is a coating film sectional view for demonstrating the orientation effect | action of the metallic base luster material which concerns on the coating method of this invention. It is sectional drawing which shows the coating-film structure mechanism at the time of forming a coating film using the metallic base coating material which concerns on the coating method of this invention. It is a graph which shows an example of the time-dependent change of the viscosity of the metallic base coating material which concerns on the coating method of this invention. It is a side view which shows the outline | summary of a rolling test.

Explanation of symbols

101 ... Coating object (car body)
DESCRIPTION OF SYMBOLS 102 ... Electrodeposition coating layer 103a ... 1st intermediate coating layer 103b ... 2nd intermediate coating layer 104 ... Metallic base coating layer 105 ... Clear coating layer

Claims (5)

An intermediate coating process in which an intermediate coating film layer is formed directly or indirectly on the surface of the object to be coated using the intermediate coating;
A metallic base coating step of forming a metallic base coating layer on the surface of the intermediate coating layer using a metallic base coating;
A clear coating step of forming a clear coating layer on the surface of the metallic coating layer using a clear coating, and a coating method comprising:
The intermediate coating step includes a first intermediate coating step in which a first intermediate coating layer is formed using an intermediate coating containing a pigment;
A second intermediate coating step of forming a second intermediate coating layer on the surface of the first intermediate coating layer using an intermediate coating or clear coating that does not contain a pigment;
As the metallic base paint, a paint solid content base material containing 10-30% by weight of a glittering material, 10-50% by weight of a cellulose acetate butyrate resin having a molecular weight of 25,000-50000, and an acrylic-melamine resin as the remaining amount, Using a metallic base paint diluted with an ester solvent and / or ketone solvent so that the solid content of the paint is 1 to 10% by weight,
The dry thickness of the metallic base coating layer is 2.5 to 3.5 μm,
Coating having an intermediate coating baking step of simultaneously baking the first intermediate coating layer and the second intermediate coating layer between the second intermediate coating step and the metallic base coating step Method. The coating method according to claim 1, further comprising a top baking process in which the metallic base coating layer and the clear coating layer are simultaneously baked after the clear coating step. The metallic base paint has an undried time range in which the rolling time required by the rolling test is less than 10 seconds between the coating and the coating film formation under the conditions of normal temperature and normal pressure, and the rolling time is 10 to 10. There are a 30 second viscosity rise time region and a finger touch drying time region in which the rolling ball required time is less than 3 seconds,
The undried time region is within 2 minutes from the time of coating deposition, the is within the viscosity rise time domain subsequent 3 minutes, according to claim 1 or 2, characterized in that the drying time domain touch the finger after the Painting method. The coating method according to claim 3 , wherein a maximum value of the required rolling time is in the viscosity increase time range and is 15 to 30 seconds. 5. The coating method according to claim 3 , wherein the NV value in the undried time region is 20 to 30% by weight, and the NV value in the viscosity increase time region is 40 to 60% by weight.

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