JP4974162B2 - Cationic electrodeposition coating method for wheels - Google Patents

Description

  The present invention relates to a cationic electrodeposition coating method for a wheel and a wheel having a cured electrodeposition coating film obtained by this electrodeposition coating method.

  A wheel is attached to a wheel of a vehicle such as an automobile. Since this wheel is exposed to rain, snow, and the like, and is also exposed to impacts such as pebbles and mud, it is desirable to perform electrodeposition coating that can form a coating film having excellent corrosion resistance and durability. Electrodeposition coating is a coating method in which an object to be coated is immersed in an electrodeposition paint as an electrode and a voltage is applied, whereby an electrodeposition coating film is formed on the object to be coated.

  The electrodeposited wheel needs to heat and cure an uncured electrodeposition coating formed by electrodeposition coating. For such curing after painting, a hot-air heating furnace based on a hot-air heating system is generally used, and a method of heating and curing the entire object to be coated in the hot-air heating furnace is performed.

  However, such a hot-air heating furnace has a problem that it takes a long time to raise the temperature to a temperature required for heat-curing the coating film when heat-curing an object having a large heat capacity such as a wheel. There is. As a problem that it takes a long time to raise the temperature, the temperature rise time in the painting process becomes a loss time, and the cycle time of the painting process becomes longer, thereby reducing the painting efficiency. For example, in a process of heating and curing a wheel of an automobile, it takes about 10 to 20 minutes to raise the wheel to a curing temperature in a hot air heating furnace, about 10 to 30 minutes to heat and cure, and a cooling process to cool the wheel. It takes about 10 to 20 minutes, and it takes about 30 to 70 minutes from painting to cooling. Thus, much time is required to raise the temperature of the wheel to the curing temperature, and shortening of this time is desired.

  Such a hot-air heating furnace also needs to maintain the furnace temperature or hot-air temperature of the hot-air heating furnace at a temperature higher than the baking temperature of the coating film, so that a part of the coating object may be deteriorated by overheating. . Furthermore, in order to ensure cleanliness in the hot air heating furnace and to take into consideration the global environment, it is necessary to filter a large volume of hot exhaust hot air with a filter or the like, which increases the maintenance cost and running cost. There is a profit.

  By the way, a heating device using induction heating has been proposed as a method for heating a painted part having a large heat capacity to a temperature at which the painted paint can be heated in a short time. Japanese Patent Application Laid-Open No. 2000-239896 (Patent Document 1) discloses a step of immersing a traveling wire in an electrodeposition bath containing a coating material for coating, and a wire immersed in the electrodeposition bath by supplying power to the wire. Electrodeposition comprising a step of coating a surface with a paint, a step of inductively heating the wire after coating, and drying in a drying furnace; and a step of inductively heating the dried wire and firing in a firing furnace. The painting method is described. However, the object to be coated by this electrodeposition coating method is a wire having a certain shape with a small width and depth, and in this respect, the configuration and the required effect are different from the present invention.

  Japanese Patent Application Laid-Open No. 2004-2965 (Patent Document 2) discloses a coating film obtained by performing electrodeposition coating on a three-dimensional object to be coated made of metal, in particular, a three-dimensional object to be integrated of metal and plastic. The electrodeposition coating film forming method characterized by selectively drying by heating with a plurality of induction heating devices is described. However, this Patent Document 2 is different from the present invention in that it only describes a very general induction heating apparatus.

JP 2000-239896 A JP 2004-2965 A

  The present invention solves the above-mentioned conventional problems, and its object is to reduce the time required for the process of heat-curing the electrodeposition coating film applied to the wheel, and to reduce the time required for the cation electrode of the wheel. The object is to provide a method of coating.

The present invention
An electrodeposition coating process in which a cationic electrodeposition coating composition is electrodeposited on the wheel to form an uncured electrodeposition coating film, and the resulting uncured electrodeposition coating film is cured by heating in a heating device. To obtain a cured electrodeposition coating film, an electrodeposition coating film curing step,
A method of painting a wheel,
The heating device includes a first induction heating unit disposed close to the first surface to be connected to a rim portion of a wheel having an uncured electrodeposition coating film,
A relative position changing means capable of changing the relative position of the first surface with respect to the first induction heating unit;
The present invention provides a method for cationic electrodeposition coating of a wheel.

  The relative position changing means is preferably a relative position changing means capable of rotating the wheel about the annular axis of the rim portion when the first induction heating portion is in a heated state.

  Moreover, the said heating apparatus is the 2nd induction heating part arrange | positioned adjacently so that the 2nd surface which is a surface on the opposite side to the 1st surface connected with the rim | limb part of a wheel which has an uncured electrodeposition coating film may be opposed. It is preferable that it is a heating apparatus provided further.

  Further, in the electrodeposition coating step, it is preferable to form the electrodeposition coating film so that the thickness of the cured electrodeposition coating film is 5 to 50 μm.

  The cationic electrodeposition coating composition is preferably a cationic electrodeposition coating composition containing an amine-modified epoxy resin, a blocked isocyanate and a pigment.

  Furthermore, the electrodeposition coating film curing step for obtaining a cured electrodeposition coating film by heating and curing the obtained uncured electrodeposition coating film in a heating device is performed by the electrodeposition coating step using the heating device. The wheel is heated by the first induction heating unit disposed close to the first surface of the painted wheel, and in the heating state by the first induction heating unit, the relative induction is changed by the relative position changing unit. It is preferable that it is an electrodeposition coating film hardening process which changes the relative position of the 1st surface of the wheel with respect to a heating part.

  The present invention further provides a wheel having a cured electrodeposition coating film obtained by the cationic electrodeposition coating method for a wheel.

  By the method of the present invention, a wheel having a cured electrodeposition coating film excellent in corrosion resistance and durability can be heat-cured in a shorter time. Thereby, it becomes possible to manufacture a coating wheel in a shorter time. More specifically, the method of the present invention can shorten the temperature rising time of the wheel in the curing process, and therefore can shorten the baking and drying process after electrodeposition coating. In the present invention, a specific heating device having a relative position changing means and an induction heating unit is used for heating and curing an uncured electrodeposition coating film formed on the wheel, thereby heating the incomplete coating film. There is an advantage that a coating film having excellent durability and corrosion resistance can be formed on the wheel without such a problem. Furthermore, since the present invention can uniformly heat the wheel, it is possible to prevent the occurrence of spear due to overbaking. That is, it can be said that the present invention relates to a method using a heating device that can be particularly suitably used for electrodeposition coating of a wheel.

  Furthermore, by using a specific heating device having an induction heating unit in the present invention, there is an advantage that all the painting and baking hardening processes can be managed in a unified manner with electric power equipment. Electrodeposition coating is a coating method in which a coating film is formed on an object to be coated by applying a voltage, and is an application method that requires energization of the object to be coated in a coating process. On the other hand, the hot air heating furnace generally used in the curing process is often a gas facility because of energy efficiency. By this invention, it becomes possible to form a favorable coating film using the heating apparatus which has an induction heating part in coating-film heat-hardening. As a result, in the painting process and the heat curing process, it is possible to perform unified management of energizing equipment, and there is an advantage that convenience of painting management is improved. Further, by using a specific heating device having an induction heating unit in the present invention, there is an advantage that generation of radiant heat and combustion gas that can be generated in a hot air heating furnace can be suppressed.

The cationic electrodeposition coating method of the wheel in the present invention,
An electrodeposition coating process in which a cationic electrodeposition coating composition is electrodeposited on the wheel to form an uncured electrodeposition coating film, and the resulting uncured electrodeposition coating film is cured by heating in a heating device. To obtain a cured electrodeposition coating film, an electrodeposition coating film curing step,
Is included. And the heating device used in this electrodeposition coating film curing step, a first induction heating unit disposed close to the first surface connected to the rim portion of the wheel having an uncured electrodeposition coating film, And a relative position changing unit capable of changing a relative position of the first surface with respect to the first induction heating unit. Hereinafter, the cationic electrodeposition coating composition, the heating apparatus, and the method of the present invention used in the present invention will be described.

Wheel The object to be coated by the method of the present invention is a wheel used for a wheel of a vehicle such as an automobile. Since the method of the present invention involves electrodeposition coating, the material of the wheel to be coated is preferably a conductive material. Examples of such a wheel include a steel wheel mainly composed of iron, an aluminum wheel composed of an aluminum alloy, and a magnesium wheel composed of a magnesium alloy. These wheels may or may not be subjected to a chemical conversion treatment or the like. The method of chemical conversion treatment is not particularly limited, and examples thereof include general chemical conversion treatment methods such as zinc phosphate treatment or zirconium treatment.

  Generally, a wheel has a rim portion that holds a tire, a hub attachment portion that is attached to a hub of a vehicle, and a disk portion that has the hub attachment portion at its center and is connected to the rim portion at the outer periphery thereof. Depending on the shape (design) of the disc part, it is classified into a spoke wheel, a dish wheel, a mesh wheel, a fin wheel, and the like. In the present invention, the “first surface connected to the rim portion of the wheel” generally means a disc portion. FIG. 8 is a plan perspective view of the wheel. FIG. 8 shows an example of a spoke wheel. The wheel 100 shown in FIG. 8 is biased toward the substantially annular rim portion 102 and the first surface 120 side which is one surface of the annular rim portion 102. And a hub mounting portion 101 arranged radially extending from the outer periphery of the hub mounting portion 101, and an end portion in the vicinity of the first circumferential portion 102 a on the first surface (disk portion) 120 of the rim portion 102. And a spoke part 103 to be connected.

Cationic electrodeposition coating composition In the present invention, it is preferable to use a cationic electrodeposition coating composition. The cationic electrodeposition coating composition is preferably an aqueous solvent, a binder resin containing a cationic epoxy resin and a blocked isocyanate curing agent, neutralized acid, or organic solvent dispersed or dissolved in the aqueous solvent. The cationic electrodeposition coating composition may further contain a pigment, a catalyst, an additive and the like as necessary.

Cationic Epoxy Resin Cationic epoxy resins include amine-modified epoxy resins. Cationic epoxy resins typically open all of the epoxy rings of a bisphenol-type epoxy resin with an active hydrogen compound capable of introducing a cationic group, or some epoxy rings with other active hydrogen compounds. The ring is opened, and the remaining epoxy ring is produced by opening with an active hydrogen compound capable of introducing a cationic group.

  A typical example of the bisphenol type epoxy resin is a bisphenol A type epoxy resin or a bisphenol F type epoxy resin. As the former commercial product, there are Epicoat 828 (manufactured by Yuka Shell Epoxy Co., Epoxy Equivalent 180-190), Epicoat 1001 (Same, Epoxy Equivalent 450-500), Epicoat 1010 (Same, Epoxy Equivalent 3000-4000), etc. As the latter commercial product, there is Epicoat 807 (same as above, epoxy equivalent 170).

  These epoxy resins may be modified with suitable resins such as polyester polyols, polyether polyols, and monofunctional alkylphenols. In addition, the epoxy resin can be chain-extended using a reaction between an epoxy group and a diol or dicarboxylic acid.

  These epoxy resins are ring-opened with an active hydrogen compound so that an amine equivalent of 0.3 to 4.0 meq / g is obtained after ring opening, and more preferably 5 to 50% of them are occupied by primary amino groups. It is desirable to do.

  Active hydrogen compounds that can introduce a cationic group include primary amines, secondary amines, tertiary amine acid salts, sulfides and acid mixtures. When an amine is used as the active hydrogen compound, an amine-modified epoxy resin having a tertiary amino group can be obtained by reacting an epoxy resin with a secondary amine. Moreover, when an epoxy resin and a primary amine are reacted, an amine-modified epoxy resin having a secondary amino group is obtained. Furthermore, an amine-modified epoxy resin having a primary amino group can be prepared by using a compound having a primary amino group and a secondary amino group. Here, when preparing an amine-modified epoxy resin having a primary amino group using a compound having a primary amino group and a secondary amino group, the primary amino group of the compound is changed before reacting with the epoxy resin. It can be prepared by blocking with a ketone to form a ketimine, which is introduced into an epoxy resin and then deblocked.

  Specific examples of primary amine, secondary amine and ketimine include, for example, butylamine, octylamine, diethylamine, dibutylamine, methylbutylamine, monoethanolamine, diethanolamine, N-methylethanolamine, triethylamine hydrochloride, N, N- Examples include dimethylethanolamine acetate and diethyl disulfide / acetic acid mixture. In addition, there are secondary amines with blocked primary amines such as aminoethylethanolamine ketimine, diethylenetriamine diketimine. Two or more of these amines may be used in combination.

  As the cationic epoxy resin, an oxazolidone ring-containing epoxy resin described in JP-A-5-306327 and known may be used. As a method for introducing an oxazolidone ring into an epoxy resin, for example, a blocked isocyanate curing agent blocked with a lower alcohol such as methanol and a polyepoxide are heated and kept in the presence of a basic catalyst, and a by-product lower alcohol is formed in the system. It can be obtained by further distilling off. Specific examples and production methods of the oxazolidone ring-containing epoxy resin are described in, for example, paragraphs 0012 to 0047 of JP-A No. 2000-128959 and are publicly known.

Blocked isocyanate curing agent Polyisocyanate is used for the preparation of the blocked isocyanate curing agent. This polyisocyanate refers to a compound having two or more isocyanate groups in one molecule. The polyisocyanate may be any of aliphatic, alicyclic, aromatic and aromatic-aliphatic, for example.

  Specific examples of polyisocyanates include aromatic diisocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), p-phenylene diisocyanate, and naphthalene diisocyanate; hexamethylene diisocyanate (HDI), 2,2,4- C3-C12 aliphatic diisocyanates such as trimethylhexane diisocyanate and lysine diisocyanate; 1,4-cyclohexane diisocyanate (CDI), isophorone diisocyanate (IPDI), 4,4′-dicyclohexylmethane diisocyanate (hydrogenated MDI) , Methylcyclohexane diisocyanate, isopropylidene dicyclohexyl-4,4'-diisocyanate, and 1,3-diisocyanatomethylcyclo Carbon such as xane (hydrogenated XDI), hydrogenated TDI, 2,5- or 2,6-bis (isocyanatomethyl) -bicyclo [2.2.1] heptane (also referred to as norbornane diisocyanate). Aliphatic diisocyanates having a number of 5 to 18; aliphatic diisocyanates having an aromatic ring such as xylylene diisocyanate (XDI) and tetramethylxylylene diisocyanate (TMXDI); modified products of these diisocyanates (urethanes, carbodiimides, Uretdione, uretonimine, burette and / or isocyanurate modified product); These may be used alone or in combination of two or more.

  Adducts or prepolymers obtained by reacting polyisocyanates with polyhydric alcohols such as ethylene glycol, propylene glycol, trimethylolpropane and hexanetriol at an NCO / OH ratio of 2 or more may also be used as the block isocyanate curing agent.

  The blocking agent is added to a polyisocyanate group and is stable at ordinary temperature, but can regenerate a free isocyanate group when heated to a temperature higher than the dissociation temperature.

Pigment The cationic electrodeposition coating composition used in the method of the present invention may contain a pigment. Examples of pigments that can be used include commonly used inorganic pigments, for example colored pigments such as titanium white, carbon black and bengara; extender pigments such as kaolin, talc, aluminum silicate, calcium carbonate, mica and clay; Zinc phosphate, iron phosphate, aluminum phosphate, calcium phosphate, zinc phosphite, zinc cyanide, zinc oxide, aluminum tripolyphosphate, zinc molybdate, aluminum molybdate, calcium molybdate and aluminum phosphomolybdate, phosphomolybdic acid Examples include rust preventive pigments such as aluminum zinc.

  When a pigment is used as a component of an electrodeposition paint, generally, the pigment is dispersed in advance in an aqueous solvent at a high concentration to form a paste (pigment dispersion paste). This is because the pigment is in a powder form, and it is difficult to disperse in a single step in a low concentration uniform state used in the electrodeposition coating composition. Such a paste is generally called a pigment dispersion paste.

  The pigment dispersion paste is prepared by dispersing a pigment together with a pigment dispersion resin in an aqueous solvent. As the pigment dispersion resin, a cationic polymer such as a cationic or nonionic low molecular weight surfactant or a modified epoxy resin having a quaternary ammonium group and / or a tertiary sulfonium group is generally used. As the aqueous solvent, ion-exchanged water or water containing a small amount of alcohol is used. In general, the pigment dispersion resin is used in an amount of 20 to 100 parts by mass with respect to 100 parts by mass of the pigment. After the pigment dispersion resin and the pigment are mixed, the pigment is dispersed using a normal dispersing device such as a ball mill or a sand grind mill until the pigment in the mixture has a predetermined uniform particle size. A paste can be obtained.

  The pigment is generally contained in the cationic electrodeposition coating composition in an amount that occupies a lower limit of 1% by weight and an upper limit of 60% by weight with respect to the total solid content of the cationic electrodeposition coating composition. The upper limit is preferably 30% by weight.

Other components When the cationic electrodeposition coating composition contains a dissociation catalyst for dissociating the blocking agent of the blocked isocyanate curing agent in addition to the above components, dibutyltin laurate, dibutyltin oxide, dioctyltin oxide, etc. Organic tin compounds, amines such as N-methylmorpholine, and metal salts such as strontium, cobalt and copper can be used. The concentration of the dissociation catalyst is 0.1 to 6 parts by mass with respect to 100 parts by mass of the total of the cationic epoxy resin and the blocked isocyanate curing agent in the cationic electrodeposition coating composition.

Preparation of cationic electrodeposition coating composition The cationic electrodeposition coating composition used in the present invention is prepared by dispersing the above-described cationic epoxy resin, blocked isocyanate curing agent, and pigment dispersion paste in an aqueous solvent. The Further, the aqueous solvent usually contains a neutralizing acid in order to neutralize the cationic epoxy resin and improve the dispersibility of the binder resin emulsion. The neutralizing acid is an inorganic or organic acid such as hydrochloric acid, nitric acid, phosphoric acid, formic acid, acetic acid, lactic acid.

  The amount of neutralizing acid used is preferably in the range of 10 to 25 mg equivalent to 100 g of binder resin solid content including a cationic epoxy resin and a blocked isocyanate curing agent. The lower limit is more preferably 15 mg equivalent, and the upper limit is more preferably 20 mg equivalent. If the amount of the neutralizing acid is less than 10 mg equivalent, the affinity for water is not sufficient and dispersion into water may not be possible, or the stability may be lost. On the other hand, if it exceeds 25 mg equivalent, the amount of electricity required for precipitation increases, the precipitation of paint solids decreases, and the throwing power may be inferior.

  The amount of the blocked isocyanate curing agent is sufficient to react with active hydrogen-containing functional groups such as primary, secondary amino groups, hydroxyl groups, etc. in the cationic epoxy resin during curing to give a good cured coating film. Needed. The amount of the blocked isocyanate curing agent is preferably 90/10 to 50/50, more preferably 80/20, expressed as a weight ratio of the cationic epoxy resin to the blocked isocyanate curing agent (cationic epoxy resin / curing agent). It is in the range of ~ 65/35. By adjusting the solid content ratio between the cationic epoxy resin and the blocked isocyanate curing agent, the fluidity and curing speed of the coating film (deposition film) during film formation are improved, and the smoothness of the coating film is improved.

  Examples of the organic solvent usually contained in the cationic electrodeposition coating composition include ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monoethyl hexyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, and propylene glycol monophenyl ether. Can be mentioned.

  In addition to the above, the cationic electrodeposition coating composition may contain conventional coating additives such as a plasticizer, a surfactant, an antioxidant, and an ultraviolet absorber. An amino group-containing acrylic resin, an amino group-containing polyester resin, and the like may be included.

Electrodeposition process Electrodeposition is usually carried out by applying a voltage of 50 to 450 V between the object to be coated (wheel) as the cathode and the anode. If the applied voltage is less than 50V, electrodeposition may be insufficient, and if it exceeds 450V, the coating film may be destroyed and an abnormal appearance may be obtained. At the time of electrodeposition coating, the bath temperature of the coating composition is usually adjusted to 10 to 45 ° C.

  The electrodeposition coating process involves immersing the object to be coated (wheel) in the cationic electrodeposition coating composition, and applying a voltage between the object to be coated (wheel) as the cathode and the anode to deposit a film. Process. Moreover, although the time which applies a voltage changes with electrodeposition conditions, generally it can be made into 2 to 4 minutes. Thus, an uncured electrodeposition coating film is formed on the wheel.

  The film thickness of the electrodeposition coating film is preferably 5 to 50 μm, more preferably 10 to 40 μm as a dry film thickness. If the film thickness is less than 5 μm, the rust prevention property may be insufficient.

  If necessary, a wheel having an uncured electrodeposition coating film may be washed with water after electrodeposition coating and before heat curing. By washing with water, the excess electrodeposition coating composition simply adhered on the wheel can be removed, and the appearance of the resulting cured electrodeposition coating film can be improved.

Electrodeposition coating curing step A cured electrodeposition coating is formed on the wheel by heating and curing the uncured electrodeposition coating formed on the wheel in the above-described electrodeposition coating step in a heating device. In the present invention, the heating device used in the electrodeposition coating film curing step is a first induction disposed so as to face the first surface connected to the rim portion of the wheel having the uncured electrodeposition coating film. It is a heating device provided with a heating part and relative position change means which can change the relative position of the 1st surface to this 1st induction heating part.

  In this heating apparatus, the wheel on which the uncured electrodeposition coating film is formed is induction-heated by the first induction heating unit. The wheel on which the uncured electrodeposition coating film is formed is induction-heated by the first induction heating unit and heated to a predetermined temperature, whereby the uncured electrodeposition coating film is cured, and the cured electrodeposition coating is applied. A film will be formed. Thereby, the wheel which has a hardening electrodeposition coating film will be obtained.

  The first induction heating unit is disposed in the vicinity of the first surface on which portions having a large heat capacity are concentrated. By heating the first surface side by the first induction heating unit, the part having the high heat capacity can be preferentially heated, and the rim part and the like connected to the first surface can be heated by heat conduction. It can be heated uniformly. Although the shape of a 1st induction heating part is not specifically limited, An electric wire, a hollow copper wire, etc. can be arrange | positioned and formed so that it may become substantially flat as a whole. For example, an induction heating unit obtained by winding a predetermined hollow copper wire in a flat shape can be exemplified. The first induction heating unit is preferably arranged substantially parallel to the first surface. Thereby, the 1st surface side in a wheel can be heated uniformly.

  The first induction heating unit can raise the temperature of the wheel to 120 to 200 ° C. in a short time by using the principle of induction heating. In addition, the temperature of the wheel before a heating start is normal temperature. Further, as described above, the entire portion of the wheel having a large heat capacity can be heated intensively by the first induction heating unit disposed in the vicinity of the portion having a large heat capacity, whereby the whole can be heated uniformly. Moreover, since the temperature of the part not directly heated by the heating part can be raised by heat conduction from the part heated by the first induction heating part, the whole temperature can be raised uniformly in a short time. .

  In the present specification, the proximity arrangement means that the first surface, which is a heating target by the first induction heating unit, is arranged at a position where induction heating is possible. Preferably, it arrange | positions by adjusting to the distance suitable for desired heating conditions.

  In the present invention, by using such a heating device having the first induction heating unit, the wheel can be uniformly heated in a short time to a temperature at which the uncured electrodeposition coating film is heated and cured. As a result, it is possible to shorten the time for painting and heat-curing the wheel, so that the working efficiency is improved and there is a merit in terms of cost.

  The relative position changing unit included in the heating device is a unit that can change the relative position of the first surface with respect to the first induction heating unit. Specifically, as will be described later, the wheel can be rotated around the annular axis of the rim portion of the wheel, or the wheel can be moved along the first induction heating unit. Moreover, you may comprise so that not a wheel but a 1st induction heating part may move.

  By using the heating device having the relative position changing means as described above, it becomes possible to change the relative position of the first surface with respect to the first induction heating unit, whereby the first induction heating unit can change the predetermined value of the first surface. It suppresses that a part is heated unevenly. That is, the part arrange | positioned at the 1st surface side can be heated uniformly by changing the relative position of the 1st surface with respect to a 1st induction heating part by a relative position change means. A general induction heating apparatus does not have such a relative position changing means, and therefore, a part of the object to be coated is heated by the induction heating unit in an uneven manner, resulting in incomplete heating and curing of the coating film. there were. In the present invention, by using such a heating device having the relative position changing means and the induction heating unit for heating and curing the uncured electrodeposition coating film formed on the wheel, heating of the incomplete coating film is performed. There is an advantage that a coating film having excellent durability and corrosion resistance can be formed on the wheel without causing a problem of curing. That is, it can be said that the heating device used in the present invention is particularly suitably used for electrodeposition coating of wheels.

  The relative position changing means is preferably means capable of changing the relative position of the first surface of the wheel when the first induction heating unit is in a heated state. Thereby, the uncured electrodeposition coating film formed on the wheel can be uniformly heated and cured.

  The relative position changing means is preferably means capable of moving the wheel in a direction substantially orthogonal to the annular axis in the rim portion. Thereby, for example, the wheel can be moved along the first induction heating unit formed in a substantially flat shape. For example, by continuously moving a plurality of wheels having an uncured electrodeposition coating film formed on the surface at a predetermined interval along the fixed first induction heating unit, the heat curing process of the wheel is continued. Can be done automatically.

  This relative position changing means is preferably means capable of moving the wheel in a predetermined direction with the distance from the first surface to the first induction heating unit kept substantially the same. Thereby, since a heating state can be kept substantially the same, the 1st surface side in a wheel can be heated uniformly.

  The relative position changing means is preferably means capable of rotating the wheel around the annular axis. Thereby, the 1st surface side in a wheel can be heated uniformly. In addition, the first surface side of the wheel can be uniformly heated without making the first induction heating unit have a size or shape that covers the entire first surface. For example, the first induction heating unit can be made compact. In addition, for example, when the wheel is moved in a predetermined direction while rotating, the wheel heat curing step can be continuously performed by the compact first induction heating unit.

  The first induction heating unit included in the heating device used in the present invention is disposed so as to cover at least a part of the hub mounting part, a part of the spoke part, and a part of the first circumferential part in the rim part. It is preferable. Thereby, for example, the first surface side can be heated by changing the relative position by the relative position changing means. Specifically, the first surface side can be heated uniformly by moving or rotating the wheel according to the shape and arrangement of the first induction heating unit.

  The heating device used in the present invention may further include a second induction heating unit that is disposed in close proximity so as to face a second surface that is a surface opposite to the first surface in the rim portion. By including the second induction heating unit in the heating device, it is possible to heat a portion that is the most distant from the first surface and has a large heat capacity, and the wheel can be heated uniformly in a shorter time.

  Hereinafter, a heating apparatus that can be used in the present invention will be described more specifically with reference to the drawings. First, the 1st embodiment of a heating apparatus is described according to FIGS.

[1.1] First Embodiment [1.1.1] Outline of Heating Device The heating device 1 shown in FIGS. 1 to 3 includes a first induction heating unit 2 and a horizontal position (not shown) that is a relative position changing unit. A moving unit and a rotating unit 511. This 1st induction heating part 2 is adjoined so that it may oppose the 1st surface 120 in the wheel 100 in which the uncured electrodeposition coating film was formed.

  According to the heating apparatus 1, the wheel 100 can be heated in a very short time to a temperature at which the uncured electrodeposition coating film is heat-cured, thereby reducing the heat-curing time of the uncured electrodeposition coating film. It can be greatly shortened.

[1.1.2] Induction Heating Unit As shown in FIGS. 1 to 3, the first induction heating unit 2 includes a first strip-shaped induction heating unit 2 a disposed with the center of the hub attachment unit 101 interposed therebetween, And a two-band induction heating unit 2b. The first induction heating unit 2 is an induction heating unit formed by winding a predetermined hollow copper wire in a flat shape. Cooling water or the like for suppressing the temperature rise of the copper wire can be passed through the hollow portion formed in the copper wire. The 1st strip | belt-shaped induction heating part 2a and the 2nd strip | belt-shaped induction heating part 2b are each formed with the same hollow copper wire. The first induction heating unit 2 heats the wheel 100 according to electric power supplied from a power source (not shown).

  For example, the first induction heating unit 2 can be formed in a substantially flat shape while continuously winding a hollow copper wire in a spiral shape or a spiral shape. Moreover, it can also form with two or more hollow copper wires. In this case, the power output to the first hollow copper wire and the power output to the second hollow copper wire can be controlled separately.

  The heating apparatus 1 according to the present embodiment further includes a second induction heating unit 3 that is disposed in close proximity to the second surface 130 that is a surface opposite to the first surface 120 of the rim unit 102. Similar to the first induction heating unit 2, the second induction heating unit 3 is an induction heating unit formed by winding a predetermined hollow copper wire in a flat shape. The second induction heating unit 3 includes a third strip-shaped induction heating unit 3a and a fourth strip-shaped induction heating unit 3b that are arranged with the center of the hub attachment unit 101 interposed therebetween. The 3rd strip | belt-shaped induction heating part 3a and the 4th strip | belt-shaped induction heating part 3b are each formed with the same hollow copper wire. The third belt-like induction heating unit 3 a and the fourth belt-like induction heating unit 3 b are wound so as to form a substantially U-shape in a direction substantially perpendicular to the second induction heating unit 3 in order to form the opening 10. It is continuous via the connecting part 23.

  The 1st induction heating part 2 is arrange | positioned adjacent to the 1st surface 120 where the site | part with a large heat capacity is concentrated and arrange | positioned. Specifically, the portion having a large heat capacity is the first circumferential portion 102 a in the hub attachment portion 101, the spoke portion 103, and the rim portion 102. Here, the proximity arrangement means that the first induction heating unit 2 is arranged at a position where the first surface 120 to be heated can be induction heated. For example, the distance from the first induction heating unit 2 to the first surface 120 can be exemplified by 5 mm to 20 mm, but is not limited to this condition.

  By heating the first surface 120 side by the first induction heating part 2, the hub mounting part 101, the spoke part 103 and the first circumferential part 102a of the rim part 102 having a high heat capacity can be heated preferentially, and the The side surface portion of the rim portion 102 continuous with the first surface 120 can be heated by heat conduction. As a result, the first induction heating unit 2 can uniformly heat the entire wheel 100.

  As shown in FIGS. 1 to 3, in the present embodiment, the first induction heating unit 2 is disposed substantially parallel to the first surface 120. Thereby, the 1st surface 120 side in the wheel 100 can be heated uniformly.

  Further, as shown in FIGS. 1 and 3, in the present embodiment, the first induction heating unit 2 includes at least a part of the hub attachment part 101, a part of the spoke part 103, and a first circle in the rim part 102. It arrange | positions so that a part of periphery part 102a may be covered. Thereby, the 1st surface 120 side can be heated uniformly, for example by changing the relative position of the 1st induction heating part 2 and the 1st surface 120 by the relative position change means mentioned below. Specifically, the first surface 120 side can be uniformly heated by horizontally moving or rotating the wheel 100 according to the shape and arrangement of the first induction heating unit 2.

  For example, the first induction heating unit 2 can raise the temperature of the wheel to 120 to 200 ° C. in a short time by using the principle of induction heating. Furthermore, as described above, the first circumferential portion 102a of the hub mounting portion 101, the spoke portion 103, and the rim portion 102 having a large wheel heat capacity is provided by the first induction heating portion 2 disposed in the vicinity of the portion having a large heat capacity. By heating intensively, the whole can be heated uniformly. Further, the temperature of the side surface of the rim portion 102 not directly heated by the first induction heating unit 2 and the second induction heating unit 3 is increased by heat conduction from the portion heated by the first induction heating unit 2. Can do. Thereby, the whole wheel can be heated uniformly in a short time. For this reason, the wheel 100 on which the uncured electrodeposition coating film is formed can be heated to 120 to 200 ° C. in a short time. Thereby, the uncured electrodeposition coating film formed on the surface of the wheel 100 can be uniformly heat-cured in a short time.

  Moreover, according to the heating apparatus 1 of this embodiment, since the wheel 100 whole can be heated uniformly in a short time, the coating film which has a favorable coating-film external appearance can be formed. Specifically, since the temperature is raised not from the surface side of the electrodeposition coating film but from the wheel 100 side which is the inner surface of the electrodeposition coating film, the coating that may occur when heated from the outside with conventional hot air is applied. There is no problem that only the film surface is cured. Accordingly, since the coating film is uniformly heated and cured, a coating film having a good coating film appearance can be formed. In addition, since the heat curing time is short and it is not necessary to blow hot air on the coating film, it is unlikely that dust and dirt will adhere to the surface of the uncured coating film and the coating film appearance will be damaged. This also contributes to the formation of a coating film having a good coating film appearance.

[1.1.3] Relative Position Changing Unit As shown in FIGS. 1 and 3, in the heating apparatus 1, the wheel 100 on which the uncured electrodeposition coating film is formed by the relative position changing unit is It is moved in the direction and rotated in the direction of arrow R. Specifically, it is horizontally moved in the direction of arrow T by a horizontal movement unit (not shown) which is a relative position changing means, and in the direction of arrow R about the annular axis of the rim portion 102 by the rotation movement unit 511. It is rotated. The rotation by the rotation moving unit 511 is, for example, 0.5 to 20 rpm, and particularly preferably 0.5 to 10 rpm.

  More specifically, the wheel 100 on which the uncured electrodeposition coating film is formed is disposed in a state where the wheel 100 is positioned at an unillustrated disposition portion formed on the wheel 100 side of the holding member 513. The holding member 513 that positions and holds the wheel 100 is moved in the direction of the arrow T by a horizontal movement unit (not shown).

  In the present embodiment, a horizontal movement unit (not shown) moves the wheel 100 in a direction substantially orthogonal to the annular axis of the rim unit 102. Further, a horizontal movement unit (not shown) moves the wheel 100 in the direction of the arrow T in a state where the distance from the first surface 120 to the first induction heating unit 2 is kept substantially the same. That is, a horizontal movement unit (not shown) horizontally moves the wheel 100 along the first induction heating unit 2.

  In the present embodiment, the rotational movement unit 511 rotates the wheel 100 about the annular axis in the rim portion 102. Furthermore, the wheel 100 can be rotated around the annular axis of the rim portion 102 by the rotational movement portion 511 while the wheel 100 is horizontally moved in the direction of the arrow T by the horizontal movement portion (not shown).

  Here, in the present embodiment, horizontal movement by a horizontal portion (not shown) which is a relative position changing unit and rotational movement by the rotational movement unit 511 can be suitably performed even in a heating state by the first induction heating unit 2.

  In the present embodiment, the plurality of wheels 100 held by the holding member 513 from the opening 10 can be continuously inserted so that the first induction heating unit 2 is disposed close to the first surface 120. The wheel 100 inserted from the opening 10 is moved in the direction of the arrow T at a predetermined speed by a horizontal movement unit (not shown) and is rotated by a rotation movement unit 511. Thereby, the heating apparatus 1 in this embodiment can perform the heat-hardening process of a some wheel continuously.

  As described above, the relative position changing unit can change the relative position of the first surface 120 with respect to the first induction heating unit 2. Thus, by making the relative position changeable, the first induction heating unit 2 can uniformly heat the predetermined part of the first surface 120. That is, the part arrange | positioned at the 1st surface 120 side can be heated uniformly by changing the said relative position by a relative position change means.

[1.2] Second Embodiment A heating apparatus 1A according to a second embodiment of the present invention will be described with reference to FIG. As shown in FIG. 4, the heating device 1 </ b> A in the second embodiment is a heating device in which the form of the first induction heating unit 2 in the heating device 1 of the first embodiment is different.

  Specifically, 1 A of heating apparatuses differ in arrangement | positioning of the 1st induction heating part 2 with respect to the 1st surface 120 of the wheel 100. FIG. That is, the first induction heating unit 2 is disposed on one side with respect to the center of the hub attachment unit 101. Specifically, the first strip-shaped induction heating unit 2 a and the second strip-shaped induction heating unit 2 b are arranged on one side with respect to the center of the hub attachment unit 101.

  Thus, even if the first induction heating unit 2 is disposed only on one side of the first surface 120 of the wheel 100 in the radial direction, the circular movement of the rim unit 102 is performed by a rotation moving unit (not shown) that is a relative position changing unit. By rotating in the direction of arrow R about the ring axis, the entire first surface 120 can be heated uniformly. Moreover, in the heating state by the 1st induction heating part 2, like the above-mentioned 1st Embodiment, the heating hardening process of a some wheel is carried out by moving the wheel 100 to the arrow T direction by the horizontal movement part not shown. Can be done continuously.

[1.3] Third Embodiment A heating apparatus 1B according to a third embodiment of the present invention will be described with reference to FIG. As illustrated in FIG. 5, the heating device 1 </ b> B in the third embodiment is a heating device in which the aspect of the relative position changing unit in the heating device 1 of the first embodiment is different.

  Specifically, the heating device 1B is a heating device that does not have a horizontal moving part. That is, in the heating state by the first induction heating unit 2, the wheel 100 is rotated about the annular axis of the rim unit 102 by a rotation moving unit (not shown) that is a relative position changing unit, but does not move in the horizontal direction. In other words, the wheel 100 is rotationally moved by a rotational movement unit (not shown) which is a relative position changing unit in a state where the wheel 100 is positioned at the approximate center of the enclosure 300 in the heating state of the first induction heating unit 2.

  In this way, the entire first surface 120 can be uniformly heated by rotating in the direction of the arrow R about the annular axis of the rim portion 102 by a rotational movement unit (not shown) that is a relative position changing means. . Moreover, in the heating state by the 1st induction heating part 2, since the wheel 100 cannot be moved to the arrow T direction by a horizontal movement part not shown, the heat hardening process of a some wheel similarly to the above-mentioned 1st Embodiment. Can not be carried out continuously, but the wheel heating and curing step can be carried out semi-continuously by the so-called batch continuous method. That is, the wheel 100 on which the uncured electrodeposition coating film is formed is moved in the direction of the arrow S1 and positioned from the opening 15 to the approximate center of the enclosure 300. Then, in the heating state by the first induction heating unit 2, the positioned wheel 100 is rotated in the direction of the arrow R by a rotation moving unit (not shown) to heat and cure the paint. After the heat curing, the wheel 100 can be moved semi-continuously by moving the wheel 100 in the direction of the arrow S2 and continuously performing this series of operations.

[1.4] Fourth Embodiment A heating apparatus 1C according to a fourth embodiment of the present invention will be described with reference to FIG. As shown in FIG. 6, the heating device 1 </ b> C in the fourth embodiment is a heating device in which the form of the first induction heating unit 2 in the heating device 1 </ b> B of the third embodiment is different.

  Specifically, the arrangement of the first induction heating unit 2 with respect to the first surface 120 of the wheel 100 is different. That is, the first induction heating unit 2 covers only one end portion in the radial direction of the wheel 100. However, the first induction heating unit 2 can heat the entire first surface 120 by rotating around the annular axis of the rim unit 102 in the direction of the arrow R by a rotation moving unit (not shown). Further, as in the case of the third embodiment, the wheel heat curing step can be performed semi-continuously by a so-called batch continuous method.

[1.5] Applied Embodiment A heating apparatus 1D in the applied embodiment will be described with reference to FIG. As shown in FIG. 7, the heating device 1D includes a first induction heating unit 2, a second induction heating unit 3, a horizontal movement unit 500 and a rotation movement unit 511 that are relative position changing means, a holding member 513, An arrangement unit 515 and a power source 301 that supplies power to the first induction heating unit 2 and the second induction heating unit 3 are provided.

  The 1st induction heating part 2 and the 2nd induction heating part 3 are the heating parts formed in the long flat shape of a predetermined direction, respectively by the some hollow copper wire. The first induction heating unit 2 and the second induction heating unit 3 are electrically connected to a power source 301, and the wheel 100 is induction-heated by electric power supplied from the power source 301.

  The wheel 100 is positioned by an arrangement portion 515 formed on the other end side of the holding member 513 that is rotatably connected to the rotational movement portion 511 at one end side. The wheel 100 is rotationally moved about the annular axis of the rim part 102 by the rotational movement part 511 via the holding member 513.

  Further, since the rotational movement unit 511 is disposed on the upper side of the horizontal movement unit 500, the wheel 100 is moved in the arrow T direction via the rotational movement unit 511 and the holding member 513. That is, the horizontal moving unit 500 horizontally moves the wheel 100 along the first induction heating unit 2 and the second induction heating unit 3 in the arrow T direction. As a result, the wheel 100 on which the uncured electrodeposition coating film is formed is suitably heat-cured, whereby a cured electrodeposition coating film can be obtained.

  For example, the holding member 513 and the placement unit 515 are moved by the horizontal moving unit 500 so as to circulate in the order of the arrow T, the arrow T1, the arrow T2, and the arrow T3. Here, the wheel 100 is disposed on the placement unit 515 in front of one end side of the first induction heating unit 2 (arrow K1), and is removed from the placement unit 515 on the other end side of the first induction heating unit 2 (arrow K2). By repeating the above, the wheel heat curing step can be continuously performed.

Electrodeposition Film Curing In the present invention, the wheel having an uncured electrodeposition film is heated by using the above-described heating device to cure the electrodeposition film (electrodeposition film curing step). In this step, the wheel 100 is heated to a predetermined temperature by the first induction heating unit 2 so that the uncured electrodeposition coating film is cured by heating, whereby a cured electrodeposition coating film is obtained. It becomes. In the electrodeposition coating film curing step, the heating device is used to heat the wheel by the first induction heating unit disposed close to the first surface of the wheel painted by the electrodeposition coating step, and In the heating state by the first induction heating unit, it is preferable that the relative position changing unit is a curing step in which the relative position of the first surface of the wheel with respect to the first induction heating unit is changed.

  The 1st induction heating part 2 is arrange | positioned adjacent to the 1st surface 120 where the site | part with a large heat capacity is concentrated and arrange | positioned. By heating the first surface 120 side by the first induction heating unit 2, it is possible to preferentially heat the portion having the high heat capacity and to heat the rim portion 102 and the like connected to the first surface 120 by heat conduction. The entire wheel 100 can be heated uniformly. Although the shape of the 1st induction heating part 2 is not specifically limited, An electric wire, a hollow copper wire, etc. can be arrange | positioned and formed so that it may become substantially flat as a whole. For example, an induction heating unit obtained by winding a predetermined hollow copper wire in a flat shape can be exemplified.

  The relative position changing means can change the relative position of the first surface 120 with respect to the first induction heating unit 2 when the first induction heating unit 2 is in a heated state. Specifically, as described later, the wheel 100 can be moved along the first induction heating unit 2, or the wheel 100 can be rotated around the annular axis of the rim portion 102 in the wheel 100. Moreover, you may comprise so that not the wheel but the 1st induction heating part 2 may move.

  Thus, by changing the relative position of the first surface of the wheel in the heating state by the first induction heating unit 2, the predetermined part of the first surface 120 is biased and heated by the first induction heating unit 2. Suppress. That is, the part arrange | positioned at the 1st surface 120 side can be heated uniformly by changing the relative position of the 1st surface of a wheel in a heating state by a relative position change means.

  Here, the proximity arrangement means that the first induction heating unit 2 is arranged at a position where the first surface 120 to be heated can be induction heated. Preferably, it arrange | positions by adjusting to the distance suitable for desired heating conditions.

  In the electrodeposition coating film curing step, the wheel 100 is moved in a direction substantially orthogonal to the annular axis of the rim portion 102 by the relative position changing means. Thereby, for example, the wheel 100 can be moved along the first induction heating unit 2 formed in a substantially flat and flat shape. For example, the heat curing process of the wheel is performed by continuously moving the plurality of wheels 100 having the uncured electrodeposition coating film formed on the surface thereof at a predetermined interval along the fixed first induction heating unit 2. Can be performed continuously.

  In the electrodeposition coating film curing step, the wheel 100 is moved in a predetermined direction by the relative position changing means while keeping the distance from the first surface 120 to the first induction heating unit 2 substantially the same. Thereby, since a heating state can be kept substantially the same, the 1st surface 120 side in the wheel 100 can be heated uniformly.

  In the electrodeposition coating film curing step, the wheel 100 is rotated around the annular axis in the heating step by the relative position changing means. Thereby, the 1st surface 120 side in the wheel 100 can be heated uniformly. Moreover, the 1st surface 120 side of the wheel 100 can be heated uniformly by the 1st induction heating part 2 which is not the magnitude | size and shape which cover the whole 1st surface 120. FIG. For example, the compact first induction heating unit 2 can be used. In addition, for example, when the wheel 100 is moved in a predetermined direction while rotating, the wheel heat curing process can be continuously performed by the compact first induction heating unit 2.

  As described above, the uncured electrodeposition coating film is cured by heating, and a cured electrodeposition coating film is obtained. As heating conditions in the electrodeposition coating film curing step, for example, a heating time of 1 to 10 minutes, preferably 1 to 6 minutes, and heating of the uncured electrodeposition coating film for raising the temperature of the wheel to 120 to 200 ° C. A condition that the curing time is 5 to 30 minutes can be mentioned.

  By the method of the present invention, a wheel having a cured electrodeposition coating film excellent in corrosion resistance and durability can be heated to a heat curing temperature in a shorter time. Thereby, it becomes possible to manufacture a coating wheel in a shorter time. In addition, the method of the present invention has a high thermal efficiency in the curing step of the electrodeposition coating film because the heating time of the wheel in the curing step is shortened, so that the energy cost can be reduced. Further, since it is not necessary to use hot air, it is possible to reduce exhaust maintenance costs such as installation and replacement of exhaust filters.

  And in this invention, the heating of an incomplete coating film is used by using the specific heating apparatus which has a relative position change means and an induction heating part for the heat curing of the uncured electrodeposition coating film formed on the wheel. There is an advantage that a coating film having excellent durability and corrosion resistance can be formed on the wheel without causing a problem of curing. That is, it can be said that the present invention relates to a method using a heating device that can be particularly suitably used for electrodeposition coating of a wheel.

  In the present invention, since a specific induction heating device suitable for heating the wheel is used, there is an advantage that the entire wheel can be heated uniformly. In the conventional hot air heating apparatus, in order to prevent the occurrence of an uncured coating film, generally, the set baking temperature is set as the baking minimum temperature, and the heat curing is performed at a temperature exceeding that temperature. In particular, if there is a difference in the thickness (thickness) of the object itself depending on the shape of the object to be coated, the temperature of the thick part does not rise sufficiently, so that the electrodeposition coating on that part Therefore, it was necessary to raise the apparatus temperature to a temperature that greatly exceeded the set baking temperature so as not to be uncured. However, in such a hot air heating method, there is a problem that the thin portion of the wheel or other portion is excessively heated above the set baking temperature, that is, overbaking occurs. . There is a problem that this overbaking is accompanied by the occurrence of scum. By the method of the present invention, such an overbaking problem has been solved, and it has become possible to prevent the occurrence of excessive scum.

  Furthermore, by using a specific heating device having an induction heating unit in the present invention, there is an advantage that all the painting and baking hardening processes can be managed in a unified manner with electric power equipment. Electrodeposition coating is a coating method in which a coating film is formed on an object to be coated by applying a voltage, and is a coating method that requires energization in the coating process. On the other hand, the hot air heating furnace generally used in the curing process is often a gas facility because of energy efficiency. By this invention, it becomes possible to form a favorable coating film using the heating apparatus which has an induction heating part in coating-film heat-hardening. As a result, in the painting process and the heat curing process, it is possible to perform unified management of energizing equipment, and there is an advantage that convenience of painting management is improved. Further, by using a specific heating device having an induction heating unit in the present invention, there is an advantage that generation of radiant heat and combustion gas that can be generated in a hot air heating furnace can be suppressed. Furthermore, since it is not necessary to install a hot-air heating furnace, it is possible to reduce the frequency of occurrence of defects in coating film appearance deterioration due to the occurrence of spear and soot in the furnace. In particular, it is possible to reduce the trouble of removing and cleaning these spears and soot, including the above-mentioned spear generation prevention effect.

  The following examples further illustrate the present invention, but the present invention is not limited thereto. In the examples, “parts” and “%” are based on weight unless otherwise specified.

Preparation of cationic electrodeposition coating composition
Production Example 1 Production of amine-modified epoxy resin 2,4- / 2,6-tolylene diisocyanate (weight ratio = 8/2) 92 was placed in a flask equipped with a stirrer, a cooling tube, a nitrogen introduction tube, a thermometer and a dropping funnel. Part, 95 parts of methyl isobutyl ketone (hereinafter abbreviated as MIBK) and 0.5 part of dibutyltin dilaurate were charged. While stirring the reaction mixture, 21 parts of methanol was added dropwise. The reaction was started from room temperature and heated to 60 ° C. due to heat generation. Then, after continuing reaction for 30 minutes, 50 parts of ethylene glycol mono-2-ethylhexyl ether was dripped from the dropping funnel. Further, 53 parts of a bisphenol A-propylene oxide 5 mol adduct was added to the reaction mixture. The reaction was mainly carried out in the range of 60 to 65 ° C. and continued until absorption based on the isocyanate group disappeared in the measurement of IR spectrum.

  Next, 365 parts of epoxy resin with an epoxy equivalent of 188 synthesized from bisphenol A and epichlorohydrin by a known method was added to the reaction mixture, and the temperature was raised to 125 ° C. Thereafter, 1.0 part of benzyldimethylamine was added and reacted at 130 ° C. until the epoxy equivalent was 410.

  Subsequently, 61 parts of bisphenol A and 33 parts of octylic acid were added and reacted at 120 ° C., resulting in an epoxy equivalent of 1190. Thereafter, the reaction mixture was cooled, 11 parts of diethanolamine, 24 parts of N-ethylethanolamine and 25 parts of 79 wt% MIBK solution of ketimine product of aminoethylethanolamine were added and reacted at 110 ° C. for 2 hours. Then, it diluted with MIBK until it became non-volatile content 80%, and the amine modified epoxy resin (resin solid content 80%) was obtained.

Production Example 2 Production of Blocked Isocyanate Curing Agent 1250 parts of diphenylmethane diisocyanate and 266.4 parts of MIBK were charged into a reaction vessel, which was heated to 80 ° C., and then 2.5 parts of dibutyltin dilaurate was added. A solution prepared by dissolving 226 parts of ε-caprolactam in 944 parts of butyl cellosolve was added dropwise at 80 ° C. over 2 hours. Furthermore, after heating at 100 degreeC for 4 hours, in the measurement of IR spectrum, it confirmed that the absorption based on an isocyanate group disappeared, and after standing to cool, MIBK 336.1 parts was added and the block isocyanate hardening | curing agent was obtained.

Production Example 3 Production of Pigment Dispersing Resin First, 222.0 parts of isophorone diisocyanate (hereinafter abbreviated as IPDI) was placed in a reaction vessel equipped with a stirrer, a cooling pipe, a nitrogen introduction pipe and a thermometer. After dilution, 0.2 part of heredibutyltin dilaurate was added. Then, after heating this to 50 degreeC, 131.5 parts of 2-ethylhexanol was dripped over 2 hours in dry nitrogen atmosphere, stirring. The reaction temperature was maintained at 50 ° C. by cooling appropriately. As a result, 2-ethylhexanol half-blocked IPDI (resin solid content: 90.0%) was obtained.

  Next, 87.2 parts of dimethylethanolamine, 117.6 parts of 75% aqueous lactic acid solution, and 39.2 parts of ethylene glycol monobutyl ether are added to a suitable reaction vessel in this order, and the mixture is stirred at 65 ° C. for about half an hour to form quaternization. An agent was prepared.

  Next, 710.0 parts of EPON 829 (bisphenol A type epoxy resin manufactured by Shell Chemical Company, epoxy equivalent 193 to 203) and 289.6 parts of bisphenol A were charged into a suitable reaction vessel, and the reaction was conducted under a nitrogen atmosphere. When heated to 150 to 160 ° C., an initial exothermic reaction occurred. The reaction mixture was reacted at 150-160 ° C. for about 1 hour, then cooled to 120 ° C., and 498.8 parts of 2-ethylhexanol half-blocked IPDI (MIBK solution) prepared above was added.

  The reaction mixture is kept at 110-120 ° C. for about 1 hour, then 463.4 parts of ethylene glycol monobutyl ether are added, the mixture is cooled to 85-95 ° C. and homogenized, and then the quaternizing agent 196 prepared above is used. 7 parts were added. After maintaining the reaction mixture at 85 to 95 ° C. until the acid value becomes 1, 964 parts of deionized water is added to finish quaternization in the epoxy-bisphenol A resin, and a pigment dispersion having a quaternary ammonium salt portion A resin was obtained (resin solid content 50%).

Production Example 4-1 Production of Pigment Dispersion Paste (1) 120 parts of resin for pigment dispersion obtained in Production Example 3 in a sand grind mill, 2.0 parts of carbon black, 100.0 parts of kaolin, 80.0 parts of titanium dioxide Then, 18.0 parts of aluminum phosphomolybdate and 221.7 parts of ion-exchanged water were added and dispersed until the particle size became 10 μm or less to obtain a pigment dispersion paste (solid content 48%).

Production Example 4-2 Production of Pigment Dispersion Paste (2) 54 parts of pigment dispersion resin obtained in Production Example 3 in a sand grind mill, 3.0 parts of carbon black, 38 parts of kaolin, 5.0 parts of aluminum phosphomolybdate And 100 parts of ion-exchanged water was added and dispersed until the particle size became 10 μm or less to obtain a pigment dispersion paste (solid content 50%).

Production Example 5-1 Production of Cationic Electrodeposition Coating Composition (1) The amine-modified epoxy resin obtained in Production Example 1 and the blocked isocyanate curing agent obtained in Production Example 2 are uniformly at a solid content ratio of 80/20. It mixed so that it might become. Glacial acetic acid was added so that the milligram equivalent (MEQ (A)) of the acid per 100 g of resin solids was 30, and ion-exchanged water was slowly added to dilute. By removing MIBK under reduced pressure, an emulsion having a solid content of 36% was obtained.

  Mixing 1500 parts of this emulsion and 540 parts of pigment dispersion paste (1) obtained in Production Example 4-1, 1920 parts of ion-exchanged water, 40 parts of 10% aqueous cerium acetate solution and 10 parts of dibutyltin oxide, A cationic electrodeposition coating composition (1) having a content of 20% by weight was obtained.

Production Example 5-2 Production of Cationic Electrodeposition Coating Composition (2) The amine-modified epoxy resin obtained in Production Example 1 and the blocked isocyanate curing agent obtained in Production Example 2 are uniformly at a solid content ratio of 80/20 It mixed so that it might become. Glacial acetic acid was added so that the milligram equivalent (MEQ (A)) of the acid per 100 g of resin solids was 30, and ion-exchanged water was slowly added to dilute. By removing MIBK under reduced pressure, an emulsion having a solid content of 36% was obtained.

  1500 parts of this emulsion and 540 parts of pigment dispersion paste (2) obtained in Production Example 4-2, 1920 parts of ion-exchanged water, 40 parts of 10% aqueous cerium acetate solution and 10 parts of dibutyltin oxide were mixed to form a solid. A cationic electrodeposition coating composition (2) having a content of 20% by weight was obtained.

  First, the following reference example will be described as to whether or not a good cured electrodeposition coating film can be formed by baking an electrodeposited article using the general induction heating apparatus shown in FIG. Confirmed by

Reference example 1
A galvanized steel sheet (JIS G3302 standard product, 150 × 70 × 0.8 mm) treated with zinc phosphate was coated with the cationic electrodeposition coating composition (1) obtained in Production Example 5-1, with a dry coating film of 17 μm. Electrodeposition coating was performed to form an uncured electrodeposition coating film.

  The uncured electrodeposition coating film formed on the steel plate was heat-cured under the following conditions in a heating apparatus having the structure shown in FIG. 12 to obtain a cured electrodeposition coating film.

Heat curing conditions / induction heating part Electric wire, etc .: hollow copper wire, diameter φ10 mm (hollow part for water conduction: φ6 mm)
・ Placement of steel plate Distance from induction heating unit 2 to steel plate: 5 cm
-Heating conditions for induction heating section: Temperature is raised from room temperature to 170 ° C (1 minute), then 170 ° C is held for 20 minutes

Reference example 2
As heating conditions, after raising the temperature from room temperature to 170 ° C. (1 minute), the heating of the induction heating unit was interrupted, and the hot air at 170 ° C. was supplied for 20 minutes instead, as in Example 1, A cured electrodeposition coating was obtained.

Reference example 3
As a heating condition, a cured electrodeposition coating film was obtained in the same manner as in Example 1 except that the temperature was raised from room temperature to 200 ° C. (1 minute) and then maintained at 200 ° C. for 5 minutes.

Comparative Reference Example 1
A galvanized steel sheet (JIS G3302 standard product, 150 × 70 × 0.8 mm) treated with zinc phosphate was coated with the cationic electrodeposition coating composition (1) obtained in Production Example 5-1, with a dry coating film of 17 μm. Electrodeposition coating was performed to form an uncured electrodeposition coating film.

  The uncured electrodeposition coating film formed on the steel plate was heat-cured under the following conditions in a hot air heating furnace to obtain a cured electrodeposition coating film.

Heat curing conditions Temperature rise from room temperature to 170 ° C (5 minutes), then keep 170 ° C for 20 minutes

  The cured electrodeposition coating films formed according to Reference Examples 1 to 3 and Comparative Reference Example 1 were evaluated as follows.

Measurement of Ra Value The Ra value of the obtained cured electrodeposition coating film was measured using an evaluation type surface roughness measuring machine (manufactured by Mitutoyo, SURFTEST SJ-201P) in accordance with JIS-B0601-2001. Measurement was performed 7 times as a 0.8 mm width cut-off (number of sections: 5), and an Ra (0.8 mm) value was obtained by an average of vertical erase. Moreover, it measured 7 times as a 2.5mm width cut-off (5 divisions), and obtained Ra (2.5mm) value by the vertical erase average. The obtained results are shown in Table 1. In addition, these Ra values show that there are few unevenness | corrugations on the coating-film surface, and a coating-film external appearance is so favorable that a value is small.

Pencil Hardness Test The pencil hardness of the obtained cured electrodeposition coating film was measured according to JIS K5600-5-4 (1999) and scratch hardness (pencil method). The obtained results are shown in Table 1.

  As shown in Table 1 above, in Reference Examples 1 and 2, the temperature rising time was as short as 1 minute. The cured electrodeposition coating film obtained in Reference Examples 1 and 2 was confirmed to be as excellent as the cured electrodeposition coating film of Comparative Reference Example 1 that was heat-cured by hot air heating, which is the current process method. It was done. On the other hand, in Comparative Reference Example 1, even if it was a hot dip galvanized steel sheet having a size of 150 × 70 × 0.8 mm, the temperature raising time required 5 minutes. The temperature raising time of Comparative Reference Example 1 is five times longer than that of the example. Furthermore, in Reference Example 3, even when the baking temperature (heating holding temperature) was raised to 200 ° C., the temperature could be raised in only 1 minute. It was confirmed that the method of the present invention raises the temperature to such a high temperature in a short time. Under such a high temperature, a cured electrodeposition coating film having the same hardness as the conventional one can be obtained even if the heat holding time is shortened to 5 minutes, which is significantly shorter than the normal heat holding time. Was confirmed.

Example wheel (steel wheel, hub central portion (D portion in FIG. 9) φ170 mm, first circumferential portion (outer end portion) φ475 mm, second circumferential portion (inner end portion) φ475 mm, height: 205 mm, mass : 10 kg, spokes: 7) were subjected to zinc phosphate treatment. Next, the cationic electrodeposition coating composition (2) obtained from Production Example 5-2 was electrodeposited so that the dried coating film had a thickness of 17 μm, thereby forming an uncured electrodeposition coating film.
The uncured electrodeposition coating film formed on the wheel was cured by heating under the following conditions in the heating apparatus 1 shown in FIGS. The temperature of the wheel during heating by the heating device 1 was measured at points A to F shown in FIG. The measurement results are shown in the graph of FIG.

Heat curing conditions : 1st induction heating part and 2nd induction heating part Electric wire, etc .: Hollow copper wire
Diameter φ10mm (Hollow for water conveyance: φ6mm)
Arrangement 15 mm from the first induction heating unit 2 to the first surface 120
Distance from second induction heating unit 3 to second surface 130 10 mm
・ Movement Rotation movement: 1rpm
Horizontal movement: Enter from the opening 10 to the position shown in FIG. 1 (only rotational movement thereafter)
・ Power supply / transmitter / operation unit (manufactured by Shimada Rika Kogyo Co.)
Output 200KW, 10KHz
・ Temperature measurement The temperature of each point is measured with thermography TVS-600 (Nippon Avionics).

  In FIG. 10, A: upper rim (first circumferential portion), B: spoke, C: outer peripheral portion of hub mounting portion, D: central portion (a part of hub mounting portion), E: rim in the embodiment The result of having measured the temperature in the middle of a part, F: 2nd circumference part is shown. The positions of points A to F are as shown in FIG. 9 for the embodiment.

Comparative Example The wheel electrodeposited in the same manner as in the example was heated with hot air in a heating furnace under the following conditions. The temperature of the wheel during this heating was measured in the same manner as in the example. The measurement results are shown in the graph of FIG. In addition, since the wheel is heated slowly over a long time in the heating furnace, the temperatures at a plurality of spaced points on the wheel are not substantially different and are substantially the same. Therefore, the temperature only at the point D in FIG. The measurement result which measured was shown.

Heat-curing conditions Wheels under the same conditions as in the above examples were heated with the atmospheric temperature in the hot stove maintained at 170 ° C.

  The Examples and Comparative Examples were evaluated as follows.

  The wheel temperature rise of the examples and comparative examples was evaluated. When the temperature rise of the wheel of an Example and the temperature rise of the wheel of a comparative example are compared by FIG.10 and FIG.11, the wheel heated with the heating apparatus in an Example is the wheel heated with the hot air in the heating furnace in a comparative example. In comparison, it was found that the temperature was raised in an extremely short time. According to the heating device of the present invention, it was found that the wheel can be heated to a high temperature of 170 ° C. in 6 minutes. On the other hand, it was found that it took about 45 minutes to heat the wheel to 170 ° C. in the comparative example. Moreover, it turned out that the said heating apparatus 1 in an Example can heat a wheel uniformly uniformly. It was found that the temperature difference depending on the wheel position was small, and the heat curing could be performed while maintaining a uniform temperature distribution as a whole.

  Table 2 shows the measurement results of the Ra value and pencil hardness of the cured electrodeposition coating film in each of the above portions A to F of the painted wheel obtained in the examples. These measurement methods are the same as described above.

＊ＤおよびＦにおけるＲａ値の「−」は、その部位のホイール形状により、Ｒａ値を測定することが不可能であったことを示す。

* "-" Of Ra value in D and F indicates that it was impossible to measure Ra value due to the wheel shape of the part.

  As shown in Table 2, the cured electrodeposition coating film formed on the wheel according to the example has a good coating film hardness in any of A to F, and there are few irregularities on the coating film surface. It was confirmed that the appearance of the coating film was good.

  From the above, it was found that the heating apparatus 1 can heat the wheel in a shorter time than the heating by the hot stove, and can uniformly heat the whole. Moreover, as Table 2 showed, it turned out that the coating wheel in which the coating-film of the outstanding quality with favorable coating-film smoothness and coating-film hardness was formed can be manufactured.

  By the method of the present invention, a wheel having a cured electrodeposition coating film excellent in corrosion resistance and durability can be heat-cured in a shorter time. Thereby, a coating wheel can be manufactured in a shorter time. In addition, the method of the present invention has a high thermal efficiency in the curing step of the electrodeposition coating film because the heating time of the wheel in the curing step is shortened, so that the energy cost can be reduced. Further, since it is not necessary to use hot air, it is possible to reduce exhaust maintenance costs such as installation and replacement of exhaust filters. In addition, the method of the present invention has the advantage that all the painting and baking and curing processes can be managed in a unified manner with electric power equipment, and that the energization equipment can be centrally managed in the painting and heating and curing processes.

It is a perspective view explaining the 1st embodiment of the heating device which can be used by the present invention. It is a side view explaining the 1st embodiment of the heating device which can be used by the present invention. It is a top view explaining 1st Embodiment of the heating apparatus which can be used by this invention. It is a top view explaining 2nd Embodiment of the heating apparatus which can be used by this invention. It is a top view explaining 3rd Embodiment of the heating apparatus which can be used by this invention. It is a top view explaining 4th Embodiment of the heating apparatus which can be used by this invention. It is a perspective view explaining application embodiment of the heating apparatus which can be used by this invention. It is a top perspective view of a wheel. It is a plane perspective view of a wheel explaining a temperature measurement point. It is a graph which shows the measurement result of the temperature in an Example. It is a graph which shows the measurement result of the temperature in a comparative example. It is a schematic perspective view explaining the induction heating apparatus used in Reference Examples 1-3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heating device 2 1st induction heating part 3 2nd induction heating part 100 Wheel 101 Hub attachment part 102 Rim part 102a 1st circumference part 102b 2nd circumference part 103 Spoke part 120 1st surface 130 2nd surface 201 Matching device 203 Power supply 205 Induction heating unit 207 Object to be coated (test piece)

Claims (4)

An electrodeposition coating process in which a cationic electrodeposition coating composition is electrodeposited on the wheel to form an uncured electrodeposition coating film, and the resulting uncured electrodeposition coating film is cured by heating in a heating device. To obtain a cured electrodeposition coating film, an electrodeposition coating film curing step,
A method of painting a wheel,
The heating device includes a first induction heating unit disposed in close proximity to face a first surface connected to a rim portion of a wheel having an uncured electrodeposition coating film;
A second induction heating unit disposed close to the second surface that is opposite to the first surface;
Relative position changing means capable of changing the relative position of the first surface with respect to the first induction heating unit, wherein the first induction heating unit is arranged to cover at least a part of the hub mounting portion of the wheel. And
When the first induction heating unit is in a heated state, the relative position changing unit rotates the wheel about the annular axis in the rim portion, and moves the wheel along the first induction heating unit. A relative position changing means capable of
Heating apparatus Der comprising is,
The cationic electrodeposition coating composition is a cationic electrodeposition coating composition comprising an amine-modified epoxy resin, a blocked isocyanate and a pigment.
Cationic electrodeposition coating method for wheels. In the electrodeposition coating step, the electrodeposition coating film is formed so that the thickness of the cured electrodeposition coating film is 5 to 50 μm.
A method for cationic electrodeposition coating of a wheel according to claim 1 . The electrodeposition coating film curing step for obtaining a cured electrodeposition coating film by heating and curing the obtained uncured electrodeposition coating film in a heating device is applied by the electrodeposition coating step using the heating device. The wheel is heated by the first induction heating unit disposed close to the first surface of the wheel, and the first induction heating unit is heated by the relative position changing means in the heating state by the first induction heating unit. The method of cationic electrodeposition coating of a wheel according to claim 1 or 2 , which is an electrodeposition coating curing step of changing the relative position of the first surface of the wheel with respect to the wheel. Claim 1-3 obtainable by cationic electrodeposition coating process of the wheel according to any wheel having a cured electrodeposited coating.

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