JP2006183128A - Coating pretreatment method and coating pretreatment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating pretreatment method by which the throwing power of an electrodeposition coating film in an automobile body is made satisfactory. <P>SOLUTION: An automobile body 4 is subjected to degreasing treatment and washing treatment, and is subjected to chemical conversion treatment with a chemical conversion treatment liquid, and, thereafter, the automobile body is warmed to a temperature equal to that of an electrodeposition liquid at the electrodeposition coating in a pure water washing stage. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pretreatment method and a paint pretreatment apparatus which are performed before electrodeposition coating is applied to the surfaces of automobile bodies and parts.

  Electrodeposition coating is generally used as an undercoat for automobile bodies, but before this electrodeposition coating is applied, so-called pretreatment is performed in which the automobile body is washed or a chemical conversion film is formed.

  Conventional electrodeposition coating pretreatment includes degreasing and cleaning processes to remove oil, iron powder, dust, etc. adhering to the car body, and surface adjustment to form a zinc phosphate conversion coating on the cleaned body surface.・ It consists of a chemical conversion treatment process. Of these, the surface conditioning process increases the number of reaction starting points in the next zinc phosphate-based chemical conversion treatment process by adsorbing the surface conditioning agent component on the surface of the object to be treated. It plays the role of accelerating the film-forming reaction, becoming the nucleus of the zinc phosphate film crystal.

  However, in the zinc phosphate chemical conversion treatment method, the surface adjustment step is necessary as described above in order to accelerate the formation reaction of the chemical conversion film. In addition, since the zinc phosphate chemical conversion treatment method forms a chemical conversion film by a chemical reaction, chemical conversion sludge is inevitably generated, and for this reason, a wastewater treatment device containing chemical conversion sludge, a cleaning device for cleaning the body, and Equipment such as a draining and drying furnace is required.

  By the way, the electrodeposition coating is performed by heating the electrodeposition paint to a temperature of 25 ° C. to 35 ° C., and maintaining the temperature in such a temperature range improves the throwing power of the electrodeposition coating film. However, in the pretreatment method based on the above-described zinc phosphate chemical conversion treatment method, the body is immersed in a chemical conversion treatment solution at 35 ° C. to 40 ° C., so the automobile body is once heated, but the cleaning step after the chemical conversion treatment step And the body is cooled by the storage process. In addition, when an automobile body treated with a zinc phosphate-based chemical conversion treatment liquid is heated to this temperature range and electrodeposition coating is performed, there is a problem that appearance defects such as contamination skin (decrease in smoothness) occur.

It is an object of the present invention to provide a pre-painting method and a pre-painting treatment apparatus that can improve the throwing power of an electrodeposition coating film on an automobile body.
In order to achieve the above object, the pre-painting treatment method of the present invention is a pre-painting treatment method in which a chemical conversion film is formed on the surface of an automobile body that is an object to be treated before electrodeposition coating. After performing a cleaning process and performing a chemical conversion treatment with a chemical conversion treatment liquid, the automobile body is heated to a temperature equivalent to the electrodeposition liquid at the time of electrodeposition coating.

  Further, the coating pretreatment apparatus of the present invention is a coating pretreatment apparatus installed in a pre-process of an electrodeposition coating apparatus, and a degreasing and cleaning apparatus that performs a degreasing process and a cleaning process on an automobile body that is an object to be processed, A chemical conversion treatment tank provided after the degreasing and cleaning apparatus and filled with the chemical conversion treatment liquid to immerse the automobile body, and provided after the chemical conversion treatment liquid tank, the automobile body is electrically connected to the electrodeposition coating. And heating means for heating to a temperature equivalent to the landing temperature.

  In the present invention, there is no drainage drying step after surface adjustment or chemical conversion treatment, storage step, etc., and a degreasing cleaning step followed by a chemical conversion treatment step, a cleaning step with a heated cleaning liquid following the chemical conversion treatment step, the cleaning step Following the direct electrodeposition coating process, the car body is heated to the electrodeposition liquid temperature in the cleaning process, so the pretreatment process can be shortened and the throwing power of the electrodeposition coating is improved. .

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 plan layout view showing an example of a coating process to which a pre-painting treatment method and a pre-treatment device of the present invention are applied, and FIG. 2 shows an embodiment of the pre-painting method and pre-painting device of the present invention. FIG. 3 is a side view, and FIG. 3 is an apparatus configuration diagram showing an embodiment of a chemical conversion treatment apparatus according to the pre-painting treatment method and the pre-painting treatment apparatus of the present invention.

  FIG. 1 and FIG. 2 show an example of the pretreatment to the electrodeposition process in the painting process, and the first half of the painting line is outlined with reference to the same drawing. In the following description, the process of removing oil, iron powder, dust, etc. adhering to the white body and the generic name of the apparatus will be referred to as degreasing and cleaning process A or degreasing and cleaning apparatus A, and then forming a chemical conversion coating on the white body. And a generic name of the apparatus is referred to as a chemical conversion treatment step B or a chemical conversion treatment apparatus B, and a process for forming an undried electrodeposition coating film on the body on which the chemical conversion film is formed and a generic name of the apparatus are referred to as an electrodeposition process C or electrodeposition. The coating device C is called the electrodeposition water washing step D or the electrodeposition water washing device D, and the process of washing off the excess electrodeposition paint adhering to the body after that is called the electrodeposition water washing step D or the electrodeposition water washing device D. A general term for the drying process and its apparatus is referred to as an electrodeposition baking process E or an electrodeposition drying furnace 28.

  First, the white body that has finished the assembly of the pressed parts is transferred from the carriage to the painting hanger 3 by the drop lifter 1 of the vehicle body assembly line, and conveyed to the painting line by the overhead conveyor 2.

  Since the white body 4 carried into the painting line is attached with press oil, iron powder by welding, and other dust, these oils, iron powder and dust are removed in the degreasing cleaning process A before chemical conversion treatment. Removed. In the example shown in FIG. 2, the degreasing and cleaning step A mainly includes a pre-degreasing step A1 and a main degreasing step A2 for removing oil, and a degreasing liquid and a body 4 used in the preliminary degreasing step A1 and the main degreasing step A2. It consists of a first water washing step A3 and a second water washing step A4 for removing iron powder and dust adhering to.

  As shown in FIG. 2, the preliminary degreasing step A1 is a so-called shower-type liquid contact method in which the degreasing liquid stored in the tank 5 is pumped up and sprayed from the nozzle 6 toward the body 4. For A2, a so-called full dip type liquid contact method is adopted in which the body 4 is completely immersed in the degreasing liquid stored in the degreasing tank 7. However, the coating pretreatment method and apparatus according to the present invention are not limited to such a liquid contact method and the number of steps (in this example, two steps of preliminary degreasing and main degreasing), and can be changed as appropriate.

  In addition, the first water washing step A3 is a so-called shower type liquid contact method in which the working water stored in the tank 8 is pumped up and sprayed from the nozzle 9 toward the body 4, whereas the second water washing step A4 is A so-called full-dip type liquid contact method is adopted in which the body 4 is completely immersed in the working water accommodated in the washing tank 10 so as to contact the liquid. However, the coating pretreatment method and apparatus according to the present invention are not limited to such a liquid contact method and the number of stages (in this example, two stages of first water washing and second water washing), and can be appropriately changed. The apparatus constituting the degreasing and cleaning step A described above is the degreasing and cleaning apparatus A.

  In order to form a chemical conversion film on the surface of the white body 4 cleaned by the degreasing cleaning process A, a chemical conversion treatment process B is provided. The chemical conversion treatment step B of this example is a chemical conversion film formation step B1, a pure water washing step B2 for preventing rusting by the chemical conversion treatment liquid and heating the body 4 to the electrodeposition liquid temperature of 25 ° C. to 35 ° C. The draining and drying furnace after the surface adjustment step and the chemical conversion treatment step, and the storage line for temporarily retracting the body are not provided.

  In particular, in this example, a chemical conversion treatment liquid containing, for example, zirconium ions and / or titanium ions, and fluorine ions, and containing substantially no phosphate ions is used as the chemical conversion treatment liquid.

  In the chemical conversion treatment containing phosphate ions, a chemical conversion film is formed by a precipitation reaction (chemical reaction) by ion exchange with iron, zinc, and aluminum constituting the body. For example, zirconium ions and / or titanium ions, and In the chemical conversion treatment with the chemical conversion treatment liquid containing fluorine ions, the chemical conversion film is formed not by a film formation mechanism by a chemical reaction but by a physical action such as coding. When this type of chemical conversion treatment liquid is used, it is advantageous in that no chemical conversion sludge (reaction product) is generated and a surface adjustment step is not required, as compared with a zinc phosphate chemical conversion treatment liquid.

For example, zirconium ions and / or titanium ions and fluorine ions are contained, the content of zirconium ions and / or titanium ions is 20 to 500 ppm on a weight basis, and the content of fluorine ions is zirconium ions. And / or a chemical conversion treatment solution having a molar ratio of 6 times or more with respect to titanium ions, substantially containing no phosphate ions, and having a pH of 2 to 5, or vanadium ions, cerium ions, nickel Chemical conversion solution with addition of rust preventive metal such as ion, manganese ion, cobalt ion, zirconium ion and / or titanium ion, fluorine ion, and soluble epoxy resin, zirconium ion and / or titanium ion content is 20 to 500 ppm on a mass basis, The content of iodine ion, relative zirconium ion and / or titanium ions, not less than 6 times by molar ratio, soluble epoxy resin, the resin 100g per -NH ₂ and / or _-NH ^{3 +} at least 0.1 A chemical conversion treatment solution having a molarity, substantially not containing phosphate ions, and having a pH of 2.5 to 4.5, hexavalent chromium ions of 2 g / liter or more, sulfate ions of 20 to 2000 ppm, fluorine of less than 400 ppm, And a chemical conversion treatment solution containing 20 to 1000 ppm of one or two ions selected from zirconium ions and titanium ions and having a pH of 0.5 to 2.0, or colloidal silica, dry silica, or alkali metal silicate. It is a chemical conversion treatment liquid containing 1 to 5 g / liter of one or more kinds of silica sols at a solid content concentration. However, it is not limited to this chemical conversion treatment liquid, and any chemical conversion treatment liquid may be used as long as a chemical conversion film is formed by a physical action not depending on a chemical reaction.

  The chemical conversion treatment apparatus B shown in FIG. 3 has a treatment tank 11 through which the body 4 mounted on the coating hanger 3 passes, and the body 4 is also raised and lowered as the overhead conveyor 2 is raised and lowered. The body 4 can be immersed in the formed chemical conversion solution. This corresponds to the chemical conversion film forming step B1 shown in FIG. In addition, although the so-called full dip type processing tank 11 is shown in the same figure, only the lower part of the body 4 is immersed and the half dip type in which the upper part of the body 4 is showered, or the entire body 4 is subjected to chemical conversion treatment by the shower method. It is also possible to adopt.

  In the chemical conversion film forming step B1 using the above-described chemical conversion treatment solution containing zirconium ions, so-called chemical conversion sludge does not occur, so that it is not necessary to provide a special sludge removal device in the processing tank 11. In this example, a circulation pipe 15 having a filter 12, a pump 13, and a discharge nozzle 14 is provided for the purpose of removing dust contained in the chemical conversion treatment liquid in the treatment tank 11 and stirring the chemical conversion treatment liquid.

  The chemical conversion treatment liquid consumed in the treatment tank 11 is replenished at a predetermined timing from a tank for storing a chemical conversion treatment liquid for replenishment (not shown).

  Returning to FIG. 2, a pure water washing step B2 is provided following the chemical conversion film forming step B1, and this pure water washing step B2 is performed with pure water (or deionized water) contained in the water washing tank 16 as shown in FIG. This is a so-called full dip type water washing method in which the body 4 is completely immersed in water. As described above, the pure water washing step B2 has an electrodeposition in order to prevent rust from being generated on the body before the electrodeposition step when the pH of the chemical conversion treatment solution is 2 to 5 and acidic. This is for heating the automobile body in order to improve the turning ability.

  In order to achieve the latter purpose, the pure water in the rinsing tank 16 is maintained at a predetermined temperature by the heat exchanger 17. That is, as shown in FIG. 3, the exhaust of the coating drying furnace 28 in the electrodeposition process has reached about 200 ° C., so that the exhaust is guided to the heat exchanger 17 while the pure water contained in the washing tank 16 is used. Is guided to the heat exchanger 17 by the pump 18. Thereby, the pure water of the washing tank 16 is heated. Here, in this example, in order to warm the temperature of the automobile body 4 to a desired temperature, the flow rate of pure water led to the heat exchanger 17 and / or the exhaust from the paint drying furnace 28 led to the heat exchanger 17. This flow rate can also be controlled in accordance with the actual temperature of the rinsing tank 16. Specifically, a flow rate adjustment valve is provided in the pipe 19 between the washing tank 16 and the heat exchanger 17, or a flow rate adjustment valve is provided in the pipe 20 between the exhaust port of the coating drying furnace 28 and the heat exchanger 17. In addition, a temperature sensor is provided in the rinsing tank 16, and this is feedback-controlled.

  FIG. 4 is a result of an experiment confirming the reversibility of the electrodeposition film thickness with respect to the temperature of the water rinsing tank 16, and is an example in which the body is heated after the chemical conversion treatment using the above-described chemical conversion treatment solution containing zirconium ions. According to this result, when pure water at room temperature of 16 ° C. was accommodated in the rinsing tank 16, an applied voltage of 105 V was required to obtain a standardized electrodeposition film thickness of 15 μm. When pure water of 26 ° C. to 27 ° C. is accommodated in the rinsing tank 16, an applied voltage of 100V is sufficient to obtain the same electrodeposition film thickness of 15 μm, and pure water of 30 ° C. to 33 ° C. is used in the rinsing tank 20 It was confirmed that an applied voltage of 90 V is sufficient when the battery is accommodated in the container. At this time, even if the temperature of pure water was increased from 26 ° C. to 33 ° C., there was no problem in the appearance quality of the electrodeposition coating film.

  On the other hand, FIG. 5 is an example in which the body is heated after the chemical conversion treatment using the conventional zinc phosphate chemical conversion treatment solution. According to this result, when pure water having a room temperature of 16 ° C. to 20 ° C. is accommodated in the water washing tank 16, an applied voltage of 110 V is necessary to obtain a standard electrodeposition film of 15 μm. Even when the temperature of pure water was increased to 27 ° C., the same voltage of 110 V had to be applied in order to obtain an electrodeposition film thickness of 15 μm. At this time, appearance defects occurred in the electrodeposition coating film.

  The apparatus that constitutes the chemical conversion treatment process B described above is a chemical conversion treatment apparatus.

  Returning to FIG. 1 and FIG. 2, after the pure water washing B2, an electrodeposition process C and an electrodeposition water washing process D are provided. In particular, in the pretreatment coating line of this example, the storage process of the body 4 is omitted between the chemical conversion treatment process B and the electrodeposition process C, and the body is allowed to flow directly to the electrodeposition process C even during lunch break or at the end of workday. I am going to do that. This also prevents rusting of the body 4 in addition to the pure water washing step B2 described above. Moreover, in order to maintain the temperature of the body 4 heated in the pure water washing process B2, from the outlet of the treatment tank 11 to the inlet of the electrodeposition tank 22, or from the outlet of the water washing tank 20 to the inlet of the electrodeposition tank 22 The space is a booth or a shelter (indicated by a dotted line 21 in FIG. 2) covering the side walls and the ceiling.

  The electrodeposition step C is a step of forming an electrodeposition coating film on the surface of the body 4 by the electrophoretic action of the electrodeposition solution. The electrodeposition step C has a boat-shaped electrodeposition tank 22 filled with the electrodeposition solution, and the coating hanger 3 The body 4 is immersed in the electrodeposition liquid in a state where the body 4 is mounted, and a high voltage is applied to a plurality of electrode plates (not shown) provided on the side wall and the bottom wall in the electrodeposition tank 22 and the body 4. Electrodeposition is applied by grounding the side. At this time, since the electrodeposition liquid enters the inside of the bag structure of the body 4, an electrodeposition coating film is also formed on the inner surface of the bag structure. As the electrodeposition liquid, the above-described cationic electrodeposition paint is preferably used for rust prevention, but an anionic electrodeposition paint that grounds the electrodeposition liquid side and applies a high voltage to the body 4 side may also be used. There is no problem.

  Subsequent to the electrodeposition step C, an electrodeposition water washing step D is provided in which excess electrodeposition liquid adhering to the body 4 is washed away and, if necessary, recovered. The electrodeposition rinsing process D of this example is composed of a preceding process of rinsing with industrial water and a subsequent process of rinsing with pure water, and FIG. The water washing process by the construction water is further constituted by full-dip washing and shower washing, a washing tank 23 filled with the construction water, a tank 24 in which the construction water is stored, and the construction water stored in the tank 24. Is pumped up and sprayed toward the body 4. Immediately after the shower type water washing process, although not shown in the drawing, similarly to the shower type water washing process, a tank for storing pure water and the pure water stored in the tank are pumped up by a pump. In addition, a pure water washing step having a nozzle that sprays in a mist toward the body 4 is provided.

  After the electrodeposition washing step D, as shown in FIG. 1, a drop lifter 27 is provided for transferring the body 4 mounted on the painting hanger 3 to the painting carriage, and the body transferred to the painting carriage here 4 is carried into the coating and drying furnace 28 by the floor conveyor 27, and is heated at 170 ° C. for 20 minutes, for example, so that the electrodeposition coating film applied to the body 4 is cured. This coating drying furnace 28 corresponds to the electrodeposition baking process E.

  After the electrodeposition baking process E, a storage process F is provided for temporarily storing the body 4 at lunch break or at the end of work. During the lunch break or at the end of work, the body assembly process before the drop lifter 1 and the sealing process G after the electrodeposition baking process E are interrupted. On the other hand, if the process is interrupted from the degreasing and washing process A to the electrodeposition baking process E, the quality is often affected. Therefore, even if the body assembly process or the sealing process G is interrupted, the process is continued. This storage process F is a line for temporarily storing the body 4 processed during that time and supplying the body 4 to the sealing process G when the operation is resumed. For this reason, it is usually preferable to have a storage capacity of the number of bodies that are present before the degreasing cleaning step A to the electrodeposition baking step E.

  As described above, in the present embodiment, the automobile body 4 is completely submerged in pure water heated to a temperature equivalent to the electrodeposition liquid temperature in the treatment tank 16 of the pure water washing step B2. Since the electrodeposition liquid is heated to the electrodeposition liquid temperature and electrodeposition coating is performed in this state, it is possible to improve the reversibility with electrodeposition and to improve the quality of the coating film. In addition, since the electrodeposition voltage can be set low in a portion having an excessive electrodeposition film thickness, the running cost of the electrodeposition process can be reduced.

  In addition, according to the present embodiment, the surface conditioning is performed before the chemical conversion treatment step B by using the chemical conversion treatment liquid that contains zirconium ions and / or titanium ions and fluorine ions and does not substantially contain phosphate ions. A process becomes unnecessary and the chemical water treatment process after the chemical conversion treatment process B becomes unnecessary, so that the chemical conversion treatment process can be simplified.

  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 a plane layout figure which shows an example of the coating process to which the coating pre-processing method and coating pre-processing apparatus of this invention are applied. It is a side view which shows one Embodiment of the coating pre-processing method and coating pre-processing apparatus of this invention. It is an apparatus block diagram which shows one Embodiment of the chemical conversion treatment apparatus which concerns on the coating pre-processing method and coating pre-processing apparatus of this invention. It is a graph which shows the relationship between the pure water washing temperature at the time of processing using a zinc-phosphate type | system | group chemical conversion treatment liquid, and an electrodeposition film thickness. It is a graph which shows the relationship between the pure water washing temperature at the time of processing using a zirconium ion containing chemical conversion treatment liquid, and an electrodeposition film thickness.

Explanation of symbols

A ... Degreasing cleaning process B ... Chemical conversion film formation process B1 ... Chemical conversion film formation process B2 ... Pure water washing process C ... Electrodeposition process D ... Electrodeposition water washing process E ... Electrodeposition baking process F ... Storage process G ... Sealing process 4 ... Automobile Body (object to be processed)

Claims (12)

In the pre-painting treatment method for forming a chemical conversion film on the surface of an automobile body that is an object to be treated before electrodeposition coating, the automobile body is subjected to a degreasing treatment and a washing treatment, and after being subjected to a chemical conversion treatment with a chemical conversion treatment liquid, A pre-painting method characterized in that an automobile body is heated to a temperature equivalent to the electrodeposition liquid at the time of electrodeposition coating. The coating pretreatment method according to claim 1, wherein the chemical conversion treatment liquid contains zirconium ions. The method of pre-painting treatment according to claim 1 or 2, wherein the heating of the automobile body before the electrodeposition coating is performed by washing the automobile body with a cleaning liquid adjusted to a temperature equivalent to the temperature of the electrodeposition liquid. The pre-painting treatment method according to claim 3, wherein the heating of the automobile body before the electrodeposition coating is performed by immersing and washing the automobile body in a cleaning liquid adjusted to a temperature equivalent to the temperature of the electrodeposition liquid. The coating pretreatment method according to claim 3 or 4, wherein the cleaning liquid is heated by waste heat of an electrodeposition drying furnace. The coating pretreatment method according to any one of claims 3 to 5, wherein the temperature of the cleaning liquid is controllable according to the atmospheric temperature. A coating pretreatment apparatus installed in a pre-process of an electrodeposition coating apparatus, which is provided with a degreasing and cleaning apparatus for performing a degreasing process and a cleaning process on an automobile body that is an object to be processed, and a chemical conversion process A chemical conversion treatment bath in which the automobile body is filled with the liquid and the chemical conversion treatment bath is provided after the chemical conversion treatment bath, and the automobile body is heated to a temperature equivalent to the electrodeposition liquid temperature during the electrodeposition coating. A pre-coating apparatus comprising: a heating means; The coating pretreatment apparatus according to claim 7, wherein the chemical conversion treatment liquid contains zirconium ions. 9. The coating pretreatment method according to claim 7, wherein the heating means is a washing means for washing the automobile body with a washing liquid adjusted to a temperature equivalent to the electrodeposition liquid temperature. The heating unit includes a cleaning tank in which a cleaning liquid is filled and the automobile body is immersed, and a cleaning liquid temperature adjusting unit that adjusts the cleaning liquid to a temperature equivalent to the electrodeposition liquid temperature. 9. The pre-painting method according to 9. The coating pretreatment method according to claim 9 or 10, wherein the cleaning liquid temperature adjusting means adjusts the temperature of the cleaning liquid by heat exchange between the cleaning liquid and waste heat of the electrodeposition drying furnace. The pretreatment method for coating according to any one of claims 9 to 11, wherein the cleaning liquid temperature adjusting means controls the temperature of the cleaning liquid in accordance with an ambient temperature.

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