JP2006028579A - Pre-coating treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pre-coating treatment method capable of preventing the occurrence of a chemical conversion defect by appropriately removing an oil-component carried into a chemical conversion treatment process before electrodeposition coating. <P>SOLUTION: In the pre-coating treatment method of forming the chemical conversion coating on a surface of a body 4 by immersing the body 4 into a chemical conversion treatment liquid after a degreasing/cleaning process and prior to the electrodeposition coating process, the treatment is applied to the body 4 by immersing the body in the chemical conversion treatment liquid in the state of suspending an oil adsorptive resin block 17 in a chemical conversion treatment vessel 11 filled with the chemical conversion treatment liquid. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pretreatment method 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.

  For this reason, it is also proposed to omit the surface adjustment step and the treatment of the chemical conversion sludge by improving the chemical conversion treatment liquid.

  Also, in the water washing step after the degreasing treatment, the oil-containing water collected by the water washing tank or spray water washing is once collected in the tank, and the oil adsorption belt is partially immersed in the surface and rotated, and the oil content is scraped off and collected. It has also been proposed to extract water from the bottom of the tank and reuse it as flush water (see Patent Document 1).

However, if an oil component that could not be degreased in the degreasing / cleaning step, for example, an oil component remaining on the mating surface or narrow portion of the panel of the automobile body, is brought into the chemical conversion treatment step, there is a risk of poor chemical conversion. In particular, this problem becomes prominent when the surface adjustment step and the previous cleaning step are omitted or shortened in order to simplify the chemical conversion treatment step.
JP-A-10-324997

An object of this invention is to provide the coating pre-processing method which can remove suitably the oil introduced in the chemical conversion treatment process before electrodeposition coating, and can prevent generation | occurrence | production of a chemical conversion defect.
In order to achieve the above object, according to the present invention, after the degreasing / cleaning step and before the electrodeposition coating step, the surface of the object to be treated is immersed in the chemical conversion solution. In the pre-coating treatment method for forming a chemical conversion coating, the treatment object is immersed in the chemical conversion treatment solution in a state where the oil-adsorbing resin mass is suspended in the chemical conversion treatment tank filled with the chemical conversion treatment solution. There is provided a pre-painting method characterized by applying.

  In the present invention, since the object to be treated is immersed in the chemical treatment liquid in a state where the oil-adsorbing resin mass is suspended in the chemical conversion treatment tank, even if the oil component of the previous process is brought in by the object to be treated, It can adsorb | suck with a lump, and can prevent generation | occurrence | production of the poor chemical conversion caused by oil by this.

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 the pre-painting treatment method of the present invention is applied, and FIG. 2 is a side view showing an embodiment of a pre-painting processing apparatus to which the pre-painting processing method of the present invention is applied. FIG. 3 (A) is a side view showing an embodiment of a chemical conversion treatment apparatus according to the pre-painting treatment method of the present invention, and FIG. 3 (B) is a plan view.

  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 29.

  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 the figure, the degreasing and cleaning step A is mainly performed in the preliminary degreasing step A1 and the main degreasing step A2 for removing oil, and the degreasing liquid and 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 process B of this example is composed of a chemical conversion film forming process B1 and a pure water washing process B2 for preventing rusting by the chemical conversion liquid, and no surface adjustment process is 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. A chemical conversion treatment liquid containing 1 to 5 g / liter of a solid content concentration of one or more types of silica sols. 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 chemical conversion treatment tank 11 through which the body 4 mounted on the coating hanger passes, and the body 4 is also up and down as the overhead conveyor 2 is raised and lowered. The body 4 can be immersed in the filled chemical conversion liquid. Although the so-called full-dip type chemical conversion treatment tank 11 is shown in the same figure, the half-dip type in which only the lower part of the body 4 is immersed and the upper part of the body 4 is showered, or the whole body 4 is chemically converted by the shower method. It is also possible to adopt.

  In the chemical conversion treatment process using the above-described chemical conversion treatment solution containing zirconium ions, so-called chemical conversion sludge does not occur, and therefore it is not necessary to provide a special sludge removal device in the chemical conversion treatment 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 chemical conversion treatment tank 11 and stirring the chemical conversion treatment liquid. Here, as shown in FIGS. 2A and 2B, the suction port 16 of the circulation pipe 15 is provided at a height relatively close to the liquid level of the chemical conversion treatment tank 11, and the discharge nozzle 14 is also the chemical conversion treatment tank 11. The height is relatively close to the liquid level. A plurality of suction ports 16 of the circulation pipe 15 can be provided at the inlet side of the chemical conversion treatment tank 11. In addition, by providing a plurality of discharge nozzles 14 substantially uniformly in the width direction on the outlet side of the treatment tank 11, the chemical conversion liquid forms a liquid flow from the vicinity of the liquid surface on the outlet side of the chemical conversion treatment tank 11 toward the inlet side. . Thereby, even if an oil component is brought into the chemical conversion treatment tank 11 by the body 4, it is returned to the inlet side of the chemical conversion treatment tank 11, and the floating oil component is prevented from being taken out when the body 4 is discharged. .

  In particular, in this example, a resin lump 17 having oil adsorbability is provided on the side of the chemical conversion treatment tank 11 so as to float on the liquid surface. The resin agglomerate 17 having oil adsorbability is composed of fibers such as polypropylene fibers, and is composed of an occlusion-type agglomerate that adsorbs oil to the gaps between the fibers using a capillary phenomenon, or a hydrocarbon polymer such as polystyrene. In addition, a type in which oil is taken in between molecules and adsorbed and gelled can be used. Since this kind of oil-absorbing resin is hydrophobic, only the oil is selectively adsorbed without sucking moisture, so that the oil that has been brought into the chemical conversion treatment tank 11 and floated on the liquid surface is efficiently removed. can do. The shape of the oil-adsorbing resin mass 17 is not particularly limited, and it can be formed into a spherical shape, a column shape, a mat shape, or the like. Moreover, although a magnitude | size is not specifically limited, When a to-be-processed object is a motor vehicle body, it is preferable that it is about 10 mm-1000 mm.

  The oil-adsorbing resin mass 17 can be simply floated on the liquid surface of the chemical conversion treatment tank 11, but is fixed to the treatment tank 11 side with a fixture 18 or the like so as not to enter the body 4 and take it out. It is more preferable to keep it. Further, the installation location of the oil-adsorbing resin mass 17 is not particularly limited, but as shown in FIG. 5B, it is a side portion that does not obstruct the course of the body 4 and particularly near the suction port 16 of the circulation pipe 15. It is also desirable to install it in

  Although not limiting the present invention, a rubberizer (registered trademark, hydrocarbon polymer manufactured by HAZ-MAT Co., Ltd., specific gravity 0.4, absorption capacity 5 times / volume) is 150 mm × 500 mm × as the oil adsorbing resin mass 17. What was formed in the magnitude | size (0.05 kg / piece) of 70 mm was used, and this is fixed to the both sides of the chemical conversion treatment tank 11 by 10 m on one side at 1 m pitch. As a result, the total volume of the oil-adsorbing resin mass 17 is 105 liters, so that the adsorption capacity is 525 liters. When the amount of oil brought in by the body 4 is 5 ml / unit, 105,000 units of oil can be removed.

  Returning to FIG. 3, a pure water washing step B2 is provided subsequent to the chemical conversion film forming step B1, and this pure water washing step B2 pumps the pure water stored in the tank 19 as shown in FIG. This is a so-called shower-type liquid contact method in which the water is pumped up at 20 and sprayed in a mist form from the nozzle 21 toward the body 4. This pure water washing process B2 is for preventing the generation | occurrence | production of rust on a body by this by this, when the pH of a chemical conversion liquid is 2-5 and acidic as above-mentioned. Therefore, it is possible to omit the pure water washing step or reduce the spray amount as necessary.

  In particular, in this example, an overflow pipe 22 that collects pure water sprayed on the body 4 in the tank 19 and guides the overflow water from the tank 19 to the chemical conversion treatment tank 11 is provided. When the automobile body 4 is immersed in the chemical conversion treatment tank 11 and the chemical conversion treatment is performed, in addition to the chemical conversion treatment liquid used for the treatment, there are not a few chemical conversion treatment liquids taken out to the next process by the body 4 as in this example. In addition, the chemical conversion treatment liquid taken out from the treatment layer 11 is collected into the tank 19 in the pure water washing step B2, and the overflowed liquid (chemical conversion treatment liquid + pure water) is returned to the chemical conversion treatment tank 11. Then, the shortage in the chemical conversion treatment tank 11 is replenished from a supply chemical conversion treatment liquid tank (not shown), and the shortage in the pure water tank 19 is supplied from a replenishment pure water tank (not shown). Thereby, the waste water treatment system of chemical conversion film formation process B1 and pure water washing process B2 is closed.

  The apparatus constituting the chemical conversion treatment process B described above is the chemical conversion treatment apparatus B.

  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. However, a storage process can be provided as necessary.

  The electrodeposition process C is a process of forming an electrodeposition coating film on the surface of the body 4 by the electrophoretic action of the electrodeposition liquid. The electrodeposition process C has a boat-shaped electrodeposition tank 23 filled with the electrodeposition liquid, 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 low wall in the electrodeposition tank 23 and the body 4 is applied. 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 using the industrial water is further constituted by full-dip water washing and shower water washing. The water washing tank 24 filled with the industrial water, the tank 25 in which the industrial water is stored, and the industrial water stored in the tank 25. A nozzle 26 for pumping up the water and spraying it toward the body 4 is provided. 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 29 by the floor conveyor 28, 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, according to the present embodiment, the body 4 is immersed in the chemical conversion treatment liquid in a state where the oil-adsorbing resin mass 17 is suspended in the treatment tank 1, so that oil from the previous process is brought into the body 4. However, it can be adsorbed by the oil adsorbing mass 17, thereby preventing the occurrence of poor chemical conversion due to the oil.

  Further, in this example, by using a chemical conversion treatment solution that contains zirconium ions and / or titanium ions and fluorine ions and does not substantially contain phosphate ions, a surface adjustment step is not required before chemical conversion treatment step B. Moreover, the water-washing process by industrial water becomes unnecessary after the chemical conversion treatment process B, and the chemical conversion treatment process can be simplified.

  Moreover, at this time, the drainage system of the chemical conversion treatment process B can be closed by returning the recovered overflow liquid of the pure water washing process B2 after the chemical conversion film forming process B1 to the chemical conversion treatment tank 11. Moreover, since there is no problem even if the pure water sprayed in this pure water washing process is brought into the electrodeposition process of the next process, it is not necessary to provide a draining and drying furnace in the chemical conversion treatment process B. It will function as pure water for replenishment of electrodeposition paint.

  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 of this invention is applied. It is a side view which shows one Embodiment of the coating pre-processing apparatus with which the coating pre-processing method of this invention is suitable. (A) is a side view which shows one Embodiment of the chemical conversion treatment apparatus which concerns on the coating pre-processing method of this invention, (B) is a top view.

Explanation of symbols

A ... Degreasing cleaning process B ... Chemical conversion treatment process C ... Electrodeposition process D ... Electrodeposition washing process E ... Electrodeposition baking process F ... Storage process G ... Sealing process 4 ... Automobile body (object to be treated)
11 ... Chemical conversion treatment tank 17 ... Oil-adsorbing resin mass

Claims (8)

In the pre-painting treatment method, a chemical conversion film is formed on the surface of the treatment object by immersing the treatment object in a chemical conversion treatment solution after the degreasing / washing step and before the electrodeposition coating step. A pretreatment method for coating, wherein the treatment object is immersed in a chemical conversion treatment liquid in a state where the oil-adsorbing resin mass is suspended in a chemical conversion treatment tank filled with the treatment liquid. After the degreasing / washing step, the chemical conversion treatment is performed without performing a surface conditioning treatment, and then the electrodeposition coating is performed without performing a water washing treatment with industrial water and a drying treatment of an object to be treated. The coating pretreatment method according to claim 1. The coating pretreatment method according to claim 2, wherein the chemical conversion treatment liquid contains zirconium ions. 4. The pre-painting treatment method according to claim 2, wherein after the chemical conversion treatment, the object to be treated is washed with pure water. The average diameter of the oil-adsorptive mass is 10 mm to 1000 mm, The coating pretreatment method according to any one of claims 1 to 4. The pretreatment method for coating according to any one of claims 1 to 5, wherein the oil-adsorbing mass is fixed to the chemical conversion treatment tank. The coating pretreatment method according to any one of claims 1 to 6, wherein a surface flow from the outlet side to the inlet side of the chemical conversion treatment tank is formed. The coating pretreatment method according to any one of claims 1 to 7, wherein the oil-adsorbing mass is disposed in the vicinity of a suction port for a chemical conversion treatment liquid in the chemical conversion treatment tank.

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