JPH09323067A - Method for assembling automotive body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To impart a high rest preventing property by pre-heating a coating part after applying a rust preventive at a prescribed site of a member, then assembling an automotive body by combining the members and forming a cured film by heating in a coating film drying furnace after moreover applying an electrodeposition. SOLUTION: Fluidity is controlled by imparting a pseudo-curing property by pre-heating the coating part after applying the rust preventive. A material having the pseudo-curing property, comprises a liq. epoxy resin, a powdery polymer consisting of an acrylate, a thermo-reactive type curing material and at least one kind selected among an reactive diluent, a plasticizer and a solvent as a diluent as main components. A spot welding to a coating steel sheet is possible by pressing at an automotive body assembling stage since the material has the pseudo-curing property, and also a bending work is possibly. Thereafter, the automotive body is assembled by combining the members, the cured film is formed by heating in the coating film drying furnace after applying the electrodeposition at the coating stage. In this way, high rust preventing property is imparted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of assembling an automobile body, and more specifically, a normal steel plate is used in place of the surface-treated steel plate, and a corrosive environment is severe due to the structure of the vehicle body.
In addition, the present invention relates to a method for assembling an automobile body for applying an anticorrosive agent only to a portion that is difficult to be coated, to impart an excellent antirust property to an automobile body at low cost.

[0002]

2. Description of the Related Art Conventionally, steel sheets used for parts that are required to have improved anticorrosion properties of automobile bodies and are required to have high anticorrosion properties, for example, fenders, doors, hoods, body sides, etc. Various surface-treated steel sheets having high rust prevention properties such as galvanized steel sheet, zinc-nickel plated steel sheet, and steel sheet obtained by coating an organic film on the plated steel sheet are used.

However, in recent years, the coating power of the paint has been improved by the improvement of the vehicle body structure, the electrodeposition paint, and the coating method, and the portion requiring the surface-treated steel sheet is, for example, in the case of the body side panel, It is only a sill called a bag structure, which is hard to paint due to the body structure.
Therefore, in such a case, there is a method of using the surface-treated steel plate only in the necessary part, but in many cases it is not possible to take the method of dividing the plate and joining it for design reasons, and many cars actually use it. The surface-treated steel sheet is used excessively, resulting in a large amount of waste. For this reason, there has been a strong demand for a technique of partially applying an anticorrosive agent to ordinary steel plates, and in fact, several inventions have been made.

As a method of applying a rust preventive agent and assembling,
For example, a method of spray-coating an epoxy resin adhesive containing silicic acid on a member and then assembling them to assemble a vehicle body (Japanese Patent Laid-Open No. 54-1630437), using a phenol resin and a cyclopentadiene-based polymer as a rust preventive agent. A method using a mixture of natural drying oil components (JP-A-56-163)
163).

[0005]

However, in the conventional method of assembling the ordinary steel sheet by applying the rust preventive agent, the workability is poor due to the high viscosity, and the oil surface adhesiveness of the rust preventive agent is low and peeling occurs. Therefore, there are problems such as low rust prevention. Further, since the fluidity is maintained even after the application, there is a problem that it may fall off or flow out in a spraying process such as degreasing or washing with water, resulting in contamination of the processing liquid or clogging of the spray nozzle.

Therefore, the present invention solves the above-mentioned drawbacks of the prior art and is a method for assembling a vehicle body for automobiles, which can be easily applied to a required portion of a normal steel plate and has a high rust preventive property. Is intended to provide.

That is, the present invention has been completed by overcoming the following problems with respect to the above objects. (1) It has high adhesiveness to a steel plate to which oil such as cleaning oil is attached, and can form a thin uniform coating film. (2) A method with excellent workability such as spraying or dipping can be adopted. (3) Spot welding is possible and contains almost no flammable solvent. (4) The coating agent does not fall off or flow out by spraying such as degreasing, acid treatment, and water washing in the coating process. (5) The cured film has excellent rust resistance. (6) It has excellent storage stability.

[0008]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors have found that after applying a rust preventive agent, the applied portion is preheated to have pseudo-curability and fluidity. Car body with high rust resistance by suppressing the heat treatment, then assembling the body by assembling the members, applying electrodeposition coating in the painting process, and then heating in a paint drying furnace to form a cured film. The present invention has been reached by finding the assembling method of the above.

The term "pseudo-curability" as used herein refers to the property of solidifying to a non-adhesive state or an adhesive state under heating conditions lower than the heating conditions under which a liquid or paste resin composition is thermoset. Due to this property, in the car body assembly process, it is possible to spot weld to the coated steel sheet by applying pressure, and it is also possible to bend it, and at the same time, degreasing in the coating process, acid treatment, spraying of the coating part by spraying with water etc. Prevents falling off and scattering, and prevents contamination of the processing liquid and clogging of the spray nozzle.

The present inventors have made earnest studies as a material having such a pseudo-curing property and satisfying the above-mentioned various performances. As a result, a liquid epoxy resin, a powder polymer made of acrylate, and a heat-activatable curing type. We have found a rust preventive agent containing, as a main component, at least one selected from the group consisting of a reactive diluent, a plasticizer and a solvent as an agent and a diluent.

Hereinafter, the present invention will be described in more detail. As a method of ensuring rust-preventive properties of the mating part, narrow part, bag structure part and its surroundings where the throwing power of the electrodeposition coating is low, it is a member that can be applied to the above-mentioned parts and is easy to apply. It is best applied at the level. After application, spot welding is possible, and preheating is indispensable to prevent the coating film from falling off or flowing out during the coating process. The coating film is cured in a drying oven in the coating process, such as an electrodeposition coating drying oven.

By applying to the members, preheating, joining and assembling the members, electrodeposition coating and heating in a drying furnace, a rust preventive film can be formed by this assembling method to secure the rust preventive property of the vehicle body. At this time, the applied film thickness is 50 to 300.
It is preferably in the range of μm. Coating thickness is 50 μm
If it is less than the above range, the permeation of water cannot be prevented due to the deterioration of the film and the existence of pinholes due to the thin film, and the rust preventive property is remarkably poor. On the other hand, when the film thickness exceeds 300 μm, the impact resistance decreases, the film peels off and cracks occur, and rust progresses from that part, and the rust prevention property decreases.

Preheating requires a temperature and time at which the powdered polymer made of the acrylate blended absorbs the epoxy resin and swells to exhibit pseudo-curability, and the surface temperature of the coated part is 80 to 200 ° C. It is preferable to carry out in the range for 0.5 to 20 minutes. Preheating is 80 ℃,
If it is less than 0.5 minutes, the pseudo-curability will not appear. In this case, when the vehicle body is assembled, the protrusion from the joint, the rust preventive agent may drop off or be washed away in the painting process, the treatment liquid may be contaminated, and the nozzle may be clogged. On the contrary, the preheating is 200 ℃,
If it exceeds 20 minutes, the heat-activatable curing agent reacts to form a cured film, making spot welding difficult.

The liquid epoxy resin as a rust preventive agent has a function of enhancing the adhesiveness to the oil-surfaced steel plate on which rust preventive oil or cleaning oil is adhered, preventing moisture from entering the coated surface and maintaining the rust preventive property. ing. Specific examples thereof include liquid epoxy resins having at least one epoxy group in the molecule, such as bisphenol A type epoxy resin and bisphenol F type epoxy resin.

The powder polymer made of acrylate functions to enhance the adhesiveness of the oil-faced steel sheet, absorb the epoxy resin by preheating and swell, and give pseudo-hardening to the coated part. Specific examples thereof include (a) one or more alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, methyl methacrylate, and stearyl methacrylate; and methyl acrylate, butyl acrylate, and alkyl glycol (meth) methacrylate. Polymer resin particles using
Examples include (b) core-shell type polymer resin particles made of the above-mentioned polymer, and polymer resin particles obtained by ion-crosslinking the surface of the polymer resin particles of (c) (a) or (b). Among these, the polymer resin particles of (b) and (c) are particularly preferable.

Examples of the heat-activatable curing agent used in the present invention include organic acid hydrazides such as adipoyldihydrazide and isophthaloyldihydrazide which are stable during storage and active at high temperatures, and derivatives thereof, dicyandiamide, diaminodiphenylsulfone, 2-methylimidazole,
Examples thereof include imidazole derivatives having a triazine ring such as triazine salts, N, N-dialkylurea derivatives, and acid anhydrides such as trimellitic anhydride. These heat-activatable curing agents may be used alone or in combination of two or more. Among these heat-activatable curing agents, dicyandiamide is particularly preferable from the viewpoint of storage stability after dispersion and compounding and oil surface adhesiveness.

The diluent is necessary for reducing the viscosity of the rust preventive agent and maintaining good coating workability in spray coating and the like.
Specific examples of the reactive diluent include mono-, di- or triepoxyside compounds such as n-butyl glycidyl ether, allyl glycidyl ether, diglycidyl ether and (poly) ethylene glycol diglycidyl ether. . Further, examples of the plasticizer include dioctyl phthalate, dibutyl phthalate, tricresyl phosphate and the like. When a large amount of the plasticizer is used, the adhesiveness to the steel plate is deteriorated, so it is preferable to keep the amount of the plasticizer small. In addition, examples of the solvent include xylene and toluene, but it is preferable to use only a small amount because they volatilize at the time of application and deteriorate the working environment.

As the diluent, at least one selected from the group consisting of a reactive diluent, a plasticizer and a solvent can be used in combination. The diluent is preferably contained in the range of 10 to 150 parts by weight with respect to 100 parts by weight of the liquid epoxy resin. If the amount of the diluent exceeds 150 parts by weight, the adhesiveness after curing will be reduced and the rust resistance will be reduced.
If it is less than 0 parts by weight, the viscosity becomes high and the coating operation becomes difficult.

In the present invention, a filler can be blended if necessary. Specific examples of this filler include:
Examples thereof include at least one selected from the group consisting of fused silica, crystalline silica, mica, alumina, calcium carbonate, calcium silicate, talc, barium sulfate, magnesium oxide, titanium oxide and aluminum hydroxide. Further, the surface of the filler may be treated with a silane coupling agent, a titanium coupling agent, a fatty acid, a surfactant or the like. Further, a rust-preventive pigment such as aluminum phosphates may be added in order to further enhance the rust-preventive property.

[0020]

EXAMPLES The present invention will now be described in more detail by way of examples, which should not be construed as limiting the invention.

The coated products were evaluated by the following methods. (1) Evaluation of Adhesiveness to Oil Surface Steel Plate After applying a steel plate cleaning oil (trade name of Idemitsu Kosan Co., Ltd .: Daphne Coat NR3), it was held vertically for 5 hours, and the amount of adhered oil was about 1 g / m ² . Steel plate (25 W, 100 L, 0.
8t), a rust inhibitor is applied to a thickness of 200 μm, preheated, degreased, phosphoric acid film treated, electrodeposition coated, dried at 170 ° C. for 30 minutes, and then shear strength Was subjected to an adhesion test according to JIS K6850.

(2) Evaluation of coating workability Using a 30: 1 airless pump manufactured by Graco Co., Ltd., the rust preventive agent temperature was maintained at 40 ° C., and the air pressure was 5.0 kg / c.
It was evaluated whether it could be atomized with an airless spray by applying m ² .

(3) Evaluation of pseudo-curability After coating in an inverted L-shape and preheating, it was held at an angle of 70 degrees for 1 hour, and the presence or absence of deviation and sagging was measured. ○: No deviation or sagging occurred ×: Deviation or sagging occurred

(4) Evaluation of anticorrosion property A coated product was prepared by the same process as in (1) except that the coating was carried out by airless spraying using a 75 W, 150 L, 0.8 t ordinary steel plate. The presence or absence of rusting after 200 cycles was evaluated under the conditions. 1 cycle: 5% salt water spray (35 ° C, 4h) → dry (6
0 ℃, 2h) → Wet (50 ℃, 95% RH, 2h)

(5) Impact resistance evaluation According to JIS K5400, a coated product having exactly the same specifications as in the rust prevention evaluation and having the same film thickness adjusted by the DuPont method at a height of 30
The weight was dropped from cm to evaluate the impact resistance.

(6) Evaluation of spot weldability and spray resistance The spot weldability is the same as in (1) up to preheating, and the welding current is applied to the joint portion coated to a thickness of about 200 μm. 7KA, pressure 200kgf / cm
^2. Weldability was evaluated at an energization time of 0.1 seconds. Also,
If the rust preventive agent comes off or flows out during the spraying process of coating, it will come off through a process that simulates a line at a water temperature of 65 ° C and a water pressure of 0.2 MPa for the coated product that has been treated in exactly the same way as in (1) up to preheating. The presence or absence of leakage was evaluated.

Examples 1 to 11 Epicoat 828 (trade name, manufactured by Yuka Shell Epoxy Co., Ltd.) as a liquid epoxy resin, dicyandiamide as a heat-activatable curing agent, and a core-shell type methacrylate polymer as a powder polymer made of acrylate. Some F
-351 (manufactured by Nippon Zeon Co., Ltd.), n-butyl glycidyl ether as a reactive diluent, dioctyl phthalate as a plasticizer, and xylene as a solvent, respectively, and surface-treated as a filler. Example samples 1 to 1 with the composition shown in Table 1 using calcium carbonate
11 was prepared.

Using the above-prepared example samples 1 to 11, the adhesiveness evaluation sample was a spatula, and the other evaluation samples were applied by the above-mentioned airless spray, preheating, degreasing, phosphoric acid film treatment, A coated product was prepared by electrodeposition coating and drying. The anti-rust agent or the coated product was used to evaluate the adhesiveness to oil surface steel plate, coating workability, pseudo-hardening property, anti-rust property, impact resistance, spot welding property and spray resistance. The preheating was performed using a hot air drying oven under the conditions shown in Table 1, and the drying after the electrodeposition coating was 17
The treatment was performed at 0 ° C. for 30 minutes. Table 1 shows the evaluation results.

[0029]

[Table 1]

Comparative Examples 1 to 9 Comparative Example Samples 1 to 9 were prepared according to the formulations shown in Table 1, and the prepared samples were applied and evaluated in the same manner as in the Examples. In Comparative Example 3, a product prepared by coating with a spatula was used, and in other Comparative Examples, a product coated by airless spray was prepared. The results are shown in Table 2.

[0031]

[Table 2]

[0032]

According to the present invention, a plain steel plate is used in place of the surface-treated steel plate, and after the rust preventive agent is applied, the applied portion is preheated to have a pseudo hardening property, and then the members are joined to assemble the vehicle body. A method of assembling an automobile body showing high rust prevention by heating in a coating process to form a cured film. Also,
The method for assembling an automobile body of the present invention can be applied to a place where a surface-treated steel sheet is used in order to maintain rustproofing, in addition to the automobile body.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryuzo Uemura 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd.

Claims (7)

[Claims] 1. A method of assembling a vehicle body by combining a plurality of members, wherein after applying a rust preventive agent to a predetermined portion of the members,
A method for assembling an automobile body, characterized in that the coating portion is preheated, then the members are combined to assemble the vehicle body, the electrodeposition coating is applied, and then the coating film is heated in a coating drying furnace to form a cured film. . 2. The method for assembling an automobile body according to claim 1, wherein the rust preventive cured film thickness is in the range of 50 to 300 μm. 3. The method for assembling an automobile body according to claim 1, wherein the surface temperature of the coated portion is in the range of 80 to 200 ° C. and preheating is performed for 0.5 to 20 minutes. 4. The assembly of an automobile body according to claim 1, wherein the coating portion is an inner surface of the mating portion and / or an inner surface of the narrow portion and / or an inner surface of the bag structure portion and / or a peripheral portion thereof. Method. 5. A rust preventive agent containing a liquid epoxy resin, a powder polymer of acrylate, a heat-activatable curing agent, and a diluent as main components is applied. Assembly method of car body. 6. The method for assembling an automobile body according to claim 5, wherein the diluent contains at least one selected from the group consisting of a reactive diluent, a plasticizer and a solvent as a main component. 7. With respect to 100 parts by weight of the liquid epoxy resin,
7. The method for assembling an automobile body according to claim 5, wherein the diluent is contained in an amount of 10 to 150 parts by weight, preferably 10 to 150 parts by weight.