JP6422407B2 - Evaluation method for cationic electrodeposition coatings - Google Patents

Description

  The present invention relates to irregularities that occur on the electrodeposition coating film in the electrodeposition coating process, which is one of the painting processes of automobile bodies and parts, and that occurs mainly with iron powder such as welded spatter pieces. The present invention relates to a method for evaluating the superiority or inferiority of ease of use between paints.

  Traditionally, reducing the number of bumps on the electrodeposition coating, which is one of the typical problems in the painting process of automobile bodies and parts, has been one of the major improvement themes in the painting line. There are various types of deposits on electrodeposition coatings, such as those based on paint-derived resin components and pigment components, and dust deposits from dust in the line process. Among these, sputtered pieces generated during body welding. Since there are a large number of defects in the main parts (hereinafter referred to as “iron irons”) mainly composed of iron powder such as metal scrap generated at the time of body forming, reducing these problems is highly effective in reducing the defects.

  Until now, improvements and improvements have been made mainly by painting equipment and painting conditions in order to reduce iron dust. In addition, as an evaluation method, the actual situation was reproduced using a real apparatus of a coating apparatus or a large-scale apparatus close to the actual apparatus, and the superiority or inferiority was evaluated by the appearance of the object to be coated. On the other hand, with respect to the characteristics of the electrodeposition paint, no physical property value has been found so far that leads to the generation of iron defects. Moreover, as prior art documents regarding the evaluation method of appearance defects such as blisters in the electrodeposition coating process, there are Patent Documents 1 to 5, but the superiority or inferiority of the occurrence of iron blisters due to the paint composition is detected using a small lab scale device. It does not propose an evaluation method for this purpose.

  However, recent studies have revealed that the occurrence of iron fouling in the electrodeposition coating process is affected not only by the coating equipment and coating conditions, but also by the composition of the coating itself and the coating properties. As an example, the contact angle and surface tension value of the paint related to the wettability of the paint can be cited, and these differences affect the difficulty of iron powder slipping on the substrate and the difficulty of loosening the aggregation of iron powder. As a result, it has become clear that this has led to an increase in iron. Up to now, no attention has been paid to such paint properties with respect to the generation of iron irregularities, and therefore an evaluation method for the generation of iron irregularities by a small lab-scale device has not been considered.

JP 7-216594 A JP 2005-49236 A JP 2005-126778 A JP 2008-7831 A JP 2012-92293 A

  The present invention has been made in view of the current state of the prior art, and an object of the present invention is to evaluate a method for evaluating the superiority or inferiority of iron deposits of a cationic electrodeposition paint in an electrodeposition coating line with a small scale and a small device. It is to provide.

  As a result of intensive studies to achieve the above object, the present inventors have paid attention to the wettability of the paint to the iron powder (surface composition = iron oxide), and the slip of the iron powder in the paint due to this difference in properties. As a result, it was found that the superiority or inferiority of these characteristics can be evaluated on a small scale by using a device configuration and evaluation conditions suitable for evaluation of property and looseness.

  That is, in the present invention, an iron powder group containing iron powder having a particle size distribution ranging from 10 μm to 500 μm in diameter on a test plate tilted in a range of 3 degrees to 20 degrees with respect to a horizontal plane is preliminarily set as water. In the presence of the mixture, after flowing a cationic electrodeposition paint in a range of flow rate from 3 cm / second to 20 cm / second, an electrodeposition coating with a standard film thickness is performed with the same paint, It is an evaluation method for cationic electrodeposition paints, characterized by evaluating the superiority or inferiority of the occurrence of iron flaws in the electrodeposition coating process by comparing the number of iron powders remaining after baking with water between the paints .

  In a preferred embodiment of the method of the present invention, the number of iron powders to be compared is at least one iron selected from the group consisting of the number of total iron powders, the number of aggregated iron powders, and the number of iron powders that can be touched. The number of powders. Further, in a preferred embodiment of the method of the present invention, in order to prevent the iron powder group mixed and aggregated with water from excessively adhering on the test plate, the portion on the test plate where the iron powder group exists is PTFE. Covered with tape. Furthermore, in a preferred embodiment of the method of the present invention, in order to prevent the flow of the cationic electrodeposition paint flowing on the test plate from being interrupted, it is downstream from the point of dropping of the paint on the test plate, A weir having a height ranging from 2 mm to 10 mm is installed at a location upstream from the position where the powder group is present.

  According to the evaluation method of the present invention, it is possible to grasp in advance the influence on the iron surface property at the time of introducing a new paint regarding the generation of the iron surface in the automobile body painting line or the part painting line. In addition, according to the evaluation method of the present invention, it is easy to grasp the relationship between the composition factor of the electrodeposition paint and the iron occurrence property.

It is an example of the apparatus (no dam) which can be used with the evaluation method of this invention. It is an example of the apparatus (with a weir) which can be used with the evaluation method of the present invention.

  In the method of the present invention, an iron powder group collected in an actual coating line or an iron powder group having a similar particle size distribution is placed on a test plate fixed at a specific range of angles, and water is dropped on the iron powder group. Agglomerates of iron powder group and water mixed are present on the test plate, and a certain amount of paint is allowed to flow there at a constant speed, and the iron powder remaining on the coating film after electrodeposition, water washing and baking Confirm the number (total number of iron powders, number of aggregated iron powders, number of iron powders that can be touched), and compare the number of each paint to determine the superiority or inferiority of the occurrence of iron flaws in the coating process. It is something to evaluate.

  The test plate used in the present invention is not particularly limited as long as it is a material for an automobile body capable of electrodeposition coating. For example, a cold-rolled steel plate (SPCC material) or alloying used as a steel plate for automobiles is used. Either a hot-dip galvanized steel plate (GA material) or an aluminum plate (AL material) can be used, and it can be left untreated or subjected to any chemical conversion treatment as necessary.

  Further, when observing iron bumps in an actual automobile body painting line, a shape in which a plurality of iron powders having a diameter of about 10 μm to about 500 μm are gathered together is seen in the bumps. In these cases, iron powders are aggregated by the influence of water at the time before entering the electrodeposition tank, and they remain until the end of energization without being loosened in the electrodeposition paint. Accordingly, the iron powder used in the present invention is a group of iron powders whose main component (50 wt% or more, preferably 80 wt% or more) having a particle size distribution in the range of about 10 μm or less to 500 μm in diameter. is necessary. In this case, it is preferable to contain 50% by weight or more of an iron powder group having a particle size distribution in the range of 10 μm or more and less than 100 μm. Actually, it is preferable to degrease and use the iron powder group collected by suction from the automobile body before the degreasing washing process. At this time, it is preferable to remove dust other than metal powder and large particles having a diameter of 500 μm or more. Moreover, since the iron powder group collect | recovered with the magnet is tinged with magnetic force, it cannot be used for the evaluation method of this invention.

  The paint used in the present invention is a cationic electrodeposition paint, and can be used as a resin system in any of an epoxy system and an acrylic system. For example, Saxade # 80V manufactured by Shinto Axalta Coating Systems Co., Ltd. can be used for epoxy, and Shinto Saxade # 3500 made by Shinto Paint can be used for acrylic.

  The method of flowing the paint at a constant flow rate on the test plate according to the method of the present invention is not particularly limited, but the viscosity of the paint is the same because the standard and size are available all over the world and there is little variation in the flow rate. It is preferable to drop the paint from a Ford cup or DIN cup used for the measurement onto a tilted test plate. In addition, on the test plate, a weir is placed at a location downstream of the paint drop point and upstream of the position where the iron powder group exists in order to make the flow more uniform. It is desirable to install and ensure that the paint over the weir flows evenly across the width of the test plate. In this case, the height of the weir is 2 mm to 10 mm, preferably 3 mm to 9 mm, more preferably 3 mm to 7 mm, and still more preferably 3 mm to 6 mm. The distance from the weir to the position where the iron powder group is present is 15 mm to 60 mm, preferably 20 mm to 50 mm. The test plate has an angle of 3 ° to 20 ° with respect to the horizontal plane, preferably an angle of 4 ° to 18 °, more preferably an angle of 4 ° to 17 °, and the paint flow rate on the test plate is 3 cm / sec to 20 cm / sec. , Preferably 4 cm / second to 18 cm / second, more preferably 5 cm / second to 17 cm / second.

  In the method of the present invention, after the coating material is poured on the test plate as described above, electrodeposition coating is performed with the same coating material to obtain a standard film thickness, followed by washing with water and baking. Then, by comparing the number of iron powders remaining on the test plate between the paints, the superiority or inferiority of the occurrence of defects in the paint in the electrodeposition coating process is evaluated. The method for evaluating the number of iron powders is not limited. For example, the number of iron powders can be generally visually observed, or can be performed with a magnifying glass or a microscope having a magnification of about 50 times together with observation of the aggregation state. The number of iron powders that can be touched can be evaluated based on the number of iron powders that are detected by hand sensation while wearing nylon inspection gloves.

  The total number of iron powders on the test plate obtained by the above method, the number of agglomerated iron powders (that is, a state in which a plurality of iron powders are gathered together) and the number of iron powders that can be touched are compared between paints. By this, it is possible to easily determine the superiority or inferiority of the occurrence of iron flaw failure between paints.

  Next, an apparatus that can be used in the evaluation method of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram of an example of such an apparatus. The test plate uses the above-mentioned materials for automobile bodies that can be electrodeposited, but a certain length and area are required to evaluate the flowability of iron powder due to the flow rate of the paint. X A length of 20 cm or more is preferable, and more preferably a width of 7 cm x length of 25 cm in view of the space and the amount of paint used. Moreover, it is preferable to attach the wall for preventing the protrusion of the paint which causes the variation of a test result to the both ends of a test board. The material of the wall is not particularly limited as long as it is a non-conductive material, but is preferably made of hard vinyl chloride from the viewpoint of workability and handling. The amount of paint used in the test is preferably 500 ml or more and 1500 ml or less, and more preferably 500 ml or more and 1000 ml or less. The diameter of the paint outlet, which is one of the factors that determine the paint flow rate, is preferably 2 to 9 mm, and more preferably 3 to 7 mm. The height from the test plate to the paint outlet is preferably 30 to 160 mm, more preferably 40 to 140 mm. Furthermore, the installation angle of the test plate is 3 to 20 degrees with respect to the horizontal plane, preferably 4 to 18 degrees, and more preferably 5 to 15 degrees. For these conditions, if the value is less than the lower limit, the number of remaining iron powders is too large, making it difficult to compare between paints. Conversely, if the value exceeds the upper limit, the number of remaining iron powders is too small, making comparisons between paints difficult. It becomes. FIG. 2 is the same as FIG. 1 except that a weir is installed at a location downstream of the paint drop point on the test plate and upstream of the position where the iron powder group exists. It is the schematic of an example of an apparatus.

  About the iron powder used for the evaluation method of the present invention, as described above, the iron powder collected with an aspirator so as not to become magnetized from the automobile body before the degreasing process is degreased and washed in a laboratory, and the diameter is 500 μm. It is preferable to use a product obtained by removing dust other than the large iron powder and the obvious iron powder. Alternatively, an iron powder group having the same particle size distribution may be artificially made and used. In order to mix the iron powder group with water to form an agglomerated state, the particle size thereof needs to be a group of iron powders having a wide particle size distribution from 10 μm to 500 μm in diameter. When 3 mg of the iron powder sample collected from the sample was weighed, the breakdown of the particle size distribution was about 75% by weight from 10 μm to less than 100 μm, about 15% by weight from 100 μm to less than 150 μm, 5% by weight from 150 μm to less than 200 μm, 200 μm More than 500 μm is about 5% by weight. These particle sizes were determined by screening the iron powder actually weighed and measuring the number of particles by visual observation, and then measuring the particle size with a microscope. Therefore, it is preferable to use a material mainly composed of an iron powder group having a wide particle size distribution with a diameter of 10 μm to 500 μm.

  When placing iron powder directly on the test plate and dropping the water for aggregation onto the test plate, when the iron powder group is placed on the test plate, the iron powder and the test plate are in close contact with each other, causing the paint to flow. The evaluation of how the iron powder is caused to flow due to the wettability of the paint may not be correct. Therefore, in order to prevent excessive adhesion between the iron powder group and the test plate, it is preferable to cover the test plate on which the iron powder group exists with a tape made of PTFE (polytetrafluoroethylene) which is a material having a high surface tension. By doing so, the iron powder easily moves when the paint is poured, and the difference in the wettability of the paint is more easily detected. In order to make the iron powder move more easily when the paint is poured, the paint may be further dropped on the mixture of the iron powder and water. In this case, the ratio of the paint to the amount of water is preferably 100% or less, and more preferably 50% or less. Specifically, 2 drops of water and 1 drop of paint are preferable with a 5 ml dropper for 3 mg of the iron powder group.

  For electrodeposition after the paint has been poured onto the test plate, leave the wall and PTFE tape attached to the test plate as they are, place them horizontally in an empty container for electrodeposition, and connect them with a power cable. Pour the paint gently. The container is a non-conductive material, and the material and capacity are not particularly limited as long as the test plate can be accommodated, but a commercially available hard vinyl chloride or polyethylene container of about 4 L can be used. A stainless steel electrode plate is set, and a direct current from a rectifier is applied under a constant voltage condition with the electrode plate as an anode and the test plate as a cathode. Electrodeposition coating is performed at an arbitrary bath temperature, voltage, and energization time to obtain a standard film thickness of about 15 μm, washed with water, set, and baked in a hot air circulating drying oven. At this time, since the water pressure condition at the time of washing affects the number of iron powders finally remaining, the washing conditions within the same test are made as much as possible.

  The evaluation of iron brittleness is performed by the number of remaining iron powder after baking. Specifically, the total number of iron powders was visually measured, the number of aggregated iron powders was measured by magnifying or microscopic observation, and the number of iron powders that could be touched with a nylon glove for inspection was measured. By comparing these values between paints, the superiority or inferiority of the occurrence of iron flaws is judged. For example, poor paints that are prone to iron defects tend to increase the number of iron powders that can be touched and the number of agglomerated iron powders.

  The effect of the evaluation method of the present invention will be shown by examples, but the present invention is not limited to these examples.

Examples 1 to 13, Comparative Examples 1 and 2
Based on saxade # 80V, a cationic electrodeposition paint manufactured by Shinto Axalta Coating Systems Co., Ltd., the dynamic surface tension and contact angle to iron oxide are adjusted by varying the amount of nonionic surfactant added. Paint A (dynamic surface tension = 41 mN / m, contact angle with iron oxide = 43 degrees) and paint B (dynamic surface tension = 45 mN / m, contact angle with iron oxide = 52 degrees) were prepared. Using these paints, Examples 1 to 8 and Comparative Examples 1 and 2 using the apparatus shown in FIG. 2 and Examples 9 to 13 using the apparatus shown in FIG. The height of the weir installed on the test plate (a), the distance from the weir to the iron powder (b), the amount of paint (c), the diameter of the paint outlet (d), the paint flow velocity (e), the cup height (F), the test plate angle (g), the type of iron powder group (particle size distribution), and the presence or absence of premixing of the iron powder group and water were evaluated. The total number of iron powders was evaluated visually, the number of aggregated iron powders was evaluated with a Pentax magnifier (magnification × 50), and the number of iron powders that could be touched was evaluated with nylon gloves for inspection. . The electrodeposition coating conditions were evaluated at a bath temperature of 28 ° C., a voltage of 200 V, an energization time of 3 minutes, and a film thickness of about 20 μm. Washing with water was carried out at a pressure of ² kg / cm ² for 5 seconds, and baking was carried out by holding at 170 ° C. for 20 minutes in a hot air circulating furnace (PHH-201 manufactured by Tabai Espec). The dynamic surface tension was measured by the maximum bubble pressure method using BP-2 manufactured by KRUSS, and the surface tension value at 24 ° C. and 6 Hz was defined as the dynamic surface tension value. Also, the contact angle is obtained by degreasing a commercially available untreated iron oxide plate SS-400 (manufactured by Nippon Test Panel, length 150 mm × width 70 mm × thickness 3 mm) using DM-501 manufactured by Kyowa Interface Science Co., Ltd. The measurement was carried out under the conditions of measurement at 20 ° C. and 20 seconds after dropping. The number of iron powders was measured five times for each example and comparative example, and the average and standard deviation of the five evaluation results were calculated.

* 1 Type of iron powder: Iron powder group 1 = Iron powder group having a wide particle size distribution with a diameter of 10 μm or more to 500 μm (10 μm or more and less than 100 μm: 75 wt%, 100 μm or more and less than 150 μm: 15 wt%, 150 μm or more and 200 μm Less than: 5% by weight, 200 μm or more and 500 μm or less: 5% by weight)
Iron powder group 2 = iron powder group having a narrow particle size distribution with a diameter of 300 to 500 μm (300 μm or more and less than 400 μm: 50% by weight, 400 μm or more and 500 μm or less: 50% by weight)
* 2 Paint A: Dynamic surface tension = 41 mN / m, contact angle to iron oxide = 43 degrees * 3 Paint B: Dynamic surface tension = 45 mN / m, contact angle to iron oxide = 52 degrees * 4 Judgment propriety: ○ = Can be judged between paints A and B, △ = Can be judged between paints A and B, but the difference between paints is small, x = The difference between paints A and B is not significant and cannot be judged

  From the test results in Table 1, in all of Examples 1 to 13, the number of total iron powder, the number of agglomerated iron powder, and palpation remaining between paint A with good wettability and paint B with poor wettability A clear difference was observed in the number of possible iron powders. Moreover, Examples 1-8 which installed the weir downstream from the paint dropping point on the test plate and upstream from the place where the iron powder group exists are compared with Examples 9-13 where no weir is installed. As a result, the total standard deviation indicating the variation in the measured values was reduced. On the other hand, about the comparative examples 1 and 2, even if the number of iron powder changed the state of the iron powder, the difference was not recognized and it became the result which cannot judge the superiority or inferiority of the occurrence of iron defects.

  According to the evaluation method of the present invention, it is possible to quickly and accurately evaluate the superiority or inferiority of the occurrence of defects in the iron line, which may become a problem in the painting line, and accordingly, the proper electrodeposition paint composition can be quickly determined. Can be determined.

Claims (4)

  Pre-mixed iron powder containing iron powder with a particle size distribution in the range of 10 μm to 500 μm in diameter on a test plate tilted in the range of 3 to 20 degrees with respect to the horizontal plane Then, after the cationic electrodeposition paint was flowed in the range of flow rate from 3 cm / sec to 20 cm / sec, electrodeposition coating with a standard film thickness was carried out with the same paint, and after washing with water and baking, A method for evaluating a cationic electrodeposition paint, wherein the number of remaining iron powders is compared between paints to evaluate the superiority or inferiority of the occurrence of iron flaws in the paint coating process.   The number of iron powders to be compared is the number of at least one iron powder selected from the group consisting of the number of total iron powders, the number of aggregated iron powders, and the number of iron powders that can be touched. The evaluation method according to claim 1.   The evaluation method according to claim 1 or 2, wherein a portion of the test plate on which the iron powder group is present is covered with a PTFE tape.   A weir having a height ranging from 2 mm to 10 mm is installed at a location downstream of the point of paint drop on the test plate and upstream of the position where the iron powder group exists. The evaluation method according to claim 1.