JP2009125667A - Method for rust-proofing vehicle body member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To certainly form an efficient rust-proof film with high durability even with moisture in the places rust-proof to be required of a vehicle body. <P>SOLUTION: The rust-proof film is formed in the places rust-proof to be required by reaction with water present in the places rust-proof to be required by feeding a moisture-hardening-type film forming agent which reacts with water to the places rust-proof to be required of a vehicle body. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

    The present invention relates to a method for preventing rust of a vehicle body member.

    In order to extend the service life of the automobile or to maintain the appearance of the vehicle body, it is desirable to appropriately perform rust prevention treatment on the vehicle body. Particularly in cold regions, the necessity of this is high because the rock salt for preventing freezing sprayed on the road surface in winter tends to cause corrosion of the vehicle body. Conventionally, in car dealers and repair shops, as an anticorrosive treatment, an anticorrosive film is formed by applying or filling an anticorrosive wax to an anticorrosive portion (for example, a mating portion of a steel plate) of a vehicle body. .

In view of the fact that such a rust preventive wax does not have a long rust preventive effect and has low chipping resistance, a rust preventive paint having both chipping resistance and rust preventive properties has been developed. For example, Patent Document 1 describes a rust-preventing paint comprising petroleum sulfonate, lanolin fatty acid, hydrogenated castor oil, scaly filler and fibrous filler. This anti-corrosion paint is applied to the surface of vehicle exterior and vehicle parts with or without electrodeposition coating at a thickness of 50 μm to 200 μm and dried at 5 to 30 ° C. for 1 to 2 hours to form a reinforced anticorrosive film. Form.
JP-A-11-222565

    By the way, in the case of an automobile, painting is performed after assembling a panel, a frame, and the like for the main body of the vehicle body, and after assembling an inner panel and an outer panel for an opening / closing member such as a door. Therefore, even if the coating is performed with a paint having a high rust prevention performance as described above, for example, a coating film is formed on the surface side of the hemming portion on the periphery of the steel plate, but it is generated on the inside due to the folding by the hemming processing. The gap is normally closed with a sealer, the paint does not spread, and no coating film is formed on the inner surface.

    As a result, a gap generated in a joint portion between members constituting the vehicle body due to such hemming processing or panel assembly may be communicated to the outside due to deterioration of the sealer, an air vent hole, or the like. Therefore, water, outside air or salt may enter the gap, and the inner side surface may rust. Or even if it is the other part of a vehicle body, a coating film may be damaged and it may cause rusting.

    At present, the post-treatment when such rusting is found has to rely on the above-mentioned rust preventive wax. In the case of this rust preventive wax, although a temporary rust preventive effect is obtained by the water repellency of the formed film, since the film is soft, it is easily peeled off by water pressure at the time of car washing. Moreover, since the rust preventive wax generally has a high viscosity, the permeability to the mating portion of the vehicle body constituting member is not necessarily good. In addition, when there is moisture in the rust-preventive part of the vehicle body, it is not possible to form a film with the rust-proof wax.

    Therefore, an object of the present invention is to ensure that a highly durable rust preventive film can be reliably formed even when the rust required portion of the vehicle body is moist.

    In the present invention, the rust preventive film is formed by moisture existing in the desired part of the vehicle body in order to solve such a problem.

    The invention according to claim 1 supplies a moisture-curable film-forming agent that reacts with water to a rust-preventing location of a member constituting the vehicle body, and forms a rust-preventing coating by reaction with water present at the rust-preventing location. It is a rust-proofing method for a vehicle body member characterized by forming.

    Therefore, according to this rust prevention treatment method, the moisture curable film forming agent forms a rust prevention film by reaction with water. A rust film can be formed. Of course, even if there is little wetness of a rust prevention location, a rust prevention membrane | film | coat is formed with the water | moisture content in the air which exists in this obtained rust prevention location.

    The moisture curable film forming agent that reacts with water preferably has a functional group that reacts with water and polymerizes by reaction with water to form a resin film. For example, a polyisocyanate having two or more isocyanate groups per molecule, a polyurethane having a free isocyanate group at the terminal, a silane resin having a hydrolyzable silyl group, and the like can be mentioned. A resin film formed with such a moisture curable film forming agent is difficult to peel off even when subjected to an external force such as a car wash, and exhibits a rust prevention effect over a long period of time. In addition, calcium silicate, calcium aluminate, calcium aluminoferrite, calcium sulfate and the like that form a film by a hydration reaction may be employed as the moisture-curable film forming agent.

The invention according to claim 2 is the invention according to claim 1,
The moisture curable film-forming agent contains, as a main component, a polyisocyanate that forms a rust-proof film by polymerization by reaction with water.

    That is, a polyisocyanate having two or more isocyanato groups per molecule is polymerized by reaction with water to form a resin film having water repellency. Therefore, high rust prevention performance is obtained. In addition, by adding a solvent, the viscosity of the moisture-curing film-forming agent can be lowered, and the injection property (penetration) into the mating part of the vehicle body constituent member can be increased, so that a rust-proof film can be reliably formed. Become advantageous.

    As said polyisocyanate, what has three or more isocyanato groups in 1 molecule like an isocyanurate type isocyanate and biuret type isocyanate is further more preferable.

The invention according to claim 3 is the invention according to claim 2,
The moisture curable film forming agent further contains a curing accelerator that accelerates the curing of the rust preventive film.

    Therefore, the hardening of the rust preventive film can be accelerated and the time required for the rust preventive treatment can be shortened.

    As such a curing accelerator, there is a polyol, a polymerization catalyst, or another isocyanate having a higher reactivity with water than a polyisocyanate whose main component is a curing accelerator.

    In the case of a polyol, the hydroxyl group reacts with an isocyanate isocyanato group, which is a main component, to accelerate the curing of the rust preventive film. In addition, the introduction of polyol increases the elongation of the resulting rust preventive film, which is advantageous in avoiding cracks in the rust preventive film due to vibration during use of an automobile. However, the amount of polyol is less than the stoichiometric ratio of 100% of the hydroxyl group (OH group) of the polyol and the NCO group of the isocyanate, and some of the isocyanate reacts with the water present in the rust-preventive area. To polymerize. Thereby, a rust prevention membrane | film | coat can be formed, absorbing the water of a rust prevention location.

    Moreover, also when the diisocyanate higher than the polyisocyanate which has a reactivity with water as a main component is used as a hardening accelerator, it becomes possible to enlarge the elongation rate of a rust preventive film.

The invention according to claim 4 is the invention according to claim 2 or claim 3,
The moisture curable film-forming agent further contains a hygroscopic agent.

    This makes it possible to remove excess moisture with a hygroscopic agent and form an expected rust-preventive film even when there is a lot of moisture in the rust-requiring part of the vehicle body or when rust prevention treatment is performed in a high humidity environment. it can.

The invention according to claim 5 is any one of claims 1 to 4,
The moisture curable film forming agent is supplied into a gap between members constituting the vehicle body.

    That is, the gap between the members constituting the vehicle body is a site where the paint is not spread through the painting process after the vehicle body member is assembled and a coating film is difficult to be formed. Therefore, effective rust prevention of the vehicle body can be achieved by subjecting such a portion to rust prevention treatment according to the present invention.

    As described above, according to the present invention, the moisture curable film-forming agent that reacts with water is supplied to the rust-preventing portion of the member constituting the vehicle body, and is prevented by the reaction with water existing at the rust-preventing portion. Since the rust film is formed, the rust preventive film can be surely formed even when the rust-preventive portion of the vehicle body is moist, and the rust preventive effect can be exhibited over a long period of time.

    Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the following description of the preferred embodiment is merely illustrative in nature, and is not intended to limit the present invention, its application, or its use.

    FIG. 1 shows an example of a rust-preventing portion of a vehicle body member to which the vehicle body member rust prevention method according to the present invention is applied. That is, in the figure, reference numeral 1 denotes an outer panel of an automobile door, and 2 denotes an inner panel thereof. A sealer 4 is interposed between the peripheral edge of the outer panel 1 and the peripheral edge of the inner panel 2. A portion of the outer panel 1 that protrudes outward from the inner panel 2 and the sealer 3 is folded back by hemming so as to sandwich the periphery of the inner panel 2, and the folded portion 1 a is a surface of the inner panel 2 (vehicle It is superimposed on the room side surface. By this hemming process, a small cavity (gap) 4 is formed between the folded back portion of the outer panel 1 and the end surfaces of the inner panel 2 and the sealer 3.

    In the door, the outer panel 1 and the inner panel 2 are assembled, and after the sash is further assembled, the anticorrosion coating is performed. For this reason, although the coating film 5 is formed in the surface exposed to the exterior of both panels 1 and 2, and the surface exposed to the door interior space, the folding | returning part 1a of the inner surface of the said cavity 4, the outer panel 1, and an inner panel In the part where 2 and the sealer 3 are interposed, the coating film by the antirust coating is not formed.

    Therefore, in the case of this door, the part in which the said coating film 5 is not formed turns into a rust prevention location. Therefore, a liquid moisture-curing film forming agent, which will be described later, is applied by an arrow in FIG. 1 along the portion (gap) where the sealer 3 is interposed between the outer panel 1 and the inner panel 2 by a spray gun. As shown, spray supply is performed from the interior space side of the door, and a rust-preventing film is formed at the rust-preventing location. In this case, the film forming agent penetrates into the cavity 4 by capillary action from the portion where the sealer 3 between the panels 1 and 2 is interposed, and further, the folded portion 1a of the outer panel 1 and the inner panel 2 And the surface where the sealer 3 of both panels 1 and 2 is interposed, the inner surface of the cavity 4, and the surface where the folded portion 1a of the outer panel 1 and the inner panel 2 overlap are prevented. A rust film is formed.

<About moisture-curing film-forming agent>
A preferred moisture curable film forming agent is to contain polyisocyanate as a main component. Preferred polyisocyanates are Chemical Isocyanurate type isocyanate (HMDI isocyanurate) and Chemical Formula 2 biuret type isocyanate having three or more isocyanato groups per molecule.

    In this case, polyamine and carbon dioxide gas are produced by the reaction of polyisocyanate and water, and the polyamine further reacts with polyisocyanate to obtain a polyurea resin film.

    In order to increase the permeability of the moisture curable film-forming agent, an organic solvent is mixed with the polyisocyanate. Various organic solvents such as ethyl acetate, butyl acetate, toluene and xylene can be used.

    To the moisture curable film forming agent, a polyol, a diisocyanate having a higher reactivity than the main component polyisocyanate, or a polymerization catalyst can be added as a curing accelerator for the rust preventive film, and a moisture absorbing agent is further added. be able to.

    As the polyol, acrylic polyol, polyester polyol, polyether polyol, polyurethane polyol and the like can be adopted, and acrylic polyol is particularly preferable. In this case, a part of the polyisocyanate reacts with the polyol to produce a polyurethane resin.

    As the diisocyanate, MDI of Chemical Formula 3 is preferable. As the polymerization catalyst, an organotin catalyst such as DBTL (dibutyltin dilaurate) is preferable. As the hygroscopic agent, for example, PTSI (p-toluenesulfonyl isocyanate) may be employed. Two or more curing accelerators can be used in combination, and both a curing accelerator and a hygroscopic agent can be added.

<Comparison between the method of the present invention and the conventional method>
A test piece having a hemming structure shown in FIG. 1 was prepared, and the antirust effect was evaluated when the method of the present invention was applied and when a conventional antirust wax was applied. In the method of the present invention, a moisture curable film forming agent obtained by mixing butyl acetate with the isocyanurate type isocyanate of Chemical Formula 1 was employed. In the conventional method, a commercially available rust preventive wax (“NOX RUST 712AM” manufactured by Parker Kosan Co., Ltd.) was employed.

    The evaluation test is to apply the method of the present invention and the conventional method at the time when 10 cycles of the cyclic corrosion test are performed on the rust-preventive portion of the test piece, and then continue the cyclic corrosion test. is there. In the cyclic corrosion test, one cycle corresponds to three cycles of JISK5600-7-9 cycle A. Further, 10 cycles of this cycle corrosion test correspond to 1 year use of the automobile. In the evaluation test, the coating progresses along the surface of the inner panel 2 along the passenger compartment side from the time when the folded plate 1a of the outer panel 1 and the inner panel 2 are joined together (point A in FIG. 1) every five cycles. The blister width (blister) was measured.

    A test result is shown in FIG. 2 with the case without rust prevention construction. Without rust prevention, the swelling of the coating proceeds from around 10 cycles. In the conventional rust preventive wax construction, the progress of the swelling of the coating film is delayed compared to the case without construction, and it starts from the 20th cycle. The big difference is gone.

    On the other hand, in the isocyanate construction of the present invention, the swelling of the coating film is finally seen from the 30th cycle, and the swelling width is about 3 mm even at the 50th cycle, which shows that the antirust effect is high. This is because, in the case of the method of the present invention, even when there is moisture at a rust-preventive location, the moisture-curing film-forming agent is polymerized by reaction with water to reliably form a rust-proof film, and the rust prevention It is recognized that the film is a resin film and has a high antirust effect.

<Effect of adding polyol to moisture curable film-forming agent>
As the polyol for accelerating film hardening, an acrylic polyol resin solution and a polyester diol resin solution mixed at a mass ratio of 57: 5 and further added with about 20% by mass of an organic solvent are employed. A plurality of moisture curable film forming agents having different component ratios were prepared. Butyl acetate was used as the organic solvent. The polyol has a mass average molecular weight Mw of 4600, a hydroxyl value of 170, and a volatile content concentration NV of 47%. The isocyanate has an NCO% of 16.5% and a volatile content concentration NV of 75%.

    Then, each moisture curable film forming agent having a different component ratio was applied to a degreased cold-rolled steel sheet (flat plate), and the film curing time and rust prevention performance were examined, and the film flexibility was examined. The curing time is the time until no sag occurs in the film. Rust prevention performance was evaluated by measuring the area ratio of rusting at the 15th cycle of the above-described cycle corrosion test using image analysis software. The film flexibility is measured by measuring the elongation of the film according to JISK5400 (measurement conditions: 23 ± 2 ° C., 50 ± 10% RH, tensile speed: 5 ± 1 mm / min), and the elongation when the polyol component ratio is zero is the standard. And evaluated by the degree of improvement in elongation. Moreover, each moisture hardening type film-forming agent from which the said component ratio differs was applied to the test piece of the structure shown in FIG. 1, and the swelling width | variety from the A point was calculated | required at the time of board alignment after a cycle corrosion test (70 cycles). The results are shown in Table 1.

    According to the table, as the polyol ratio increases, the curing time is shortened and the elongation of the film is improved. However, even if the polyol ratio is higher than the component ratio “8: 2”, the curing time is not shortened. Regarding rust prevention performance, as the polyol ratio increases, the rusting area ratio decreases, but the swollen width from the time of joining the plates deteriorates when the polyol ratio becomes higher than the component ratio “8: 2”. Yes (the blister width is larger). The cause of this deterioration is that the higher the polyol ratio, the less the isocyanate groups that react with the water present in the rust-preventing location (such as the cavity 4 in FIG. 1), and the more likely that the rust-preventing film is difficult to form. It is done.

    FIG. 3 is a graph showing the curing time of Table 1 and the swollen width from the time of plate alignment. From the viewpoint of promptly performing rust-proofing and ensuring the durability of the rust-proofing effect, the curing time is preferably 4 hours or less, and the swollen width after joining the plates is preferably 7 mm or less. According to the figure, it can be seen that when the component ratio of isocyanate: polyol is in the range of “8: 0.6” to “8: 4”, both requirements can be satisfied.

<Addition effect of MDI to moisture curable film-forming agent>
A plurality of moisture curable film forming agents having different component ratios prepared by mixing the isocyanate of Chemical Formula 1 and the MDI (Film Curing Accelerator) of Chemical Formula 3 were prepared. Butyl acetate was used as the organic solvent. Using each of the moisture curable film forming agents having different component ratios, the film curing time, film flexibility (improvement of elongation) and rust prevention performance were examined. The antirust performance was evaluated by applying each moisture-curing film-forming agent to a cold-rolled steel sheet (flat plate) degreased and measuring the foaming rate of the obtained antirust film with image analysis software. The results are shown in Table 2.

    According to the table, as the MDI ratio increases, the curing time is shortened and the elongation of the film is improved. However, with respect to rust prevention performance, the foaming rate increases as the MDI ratio increases. This is because the amount of carbon dioxide gas generated by the reaction between MDI and water increases, and it becomes a film containing bubbles, which is disadvantageous in terms of rust prevention.

    FIG. 4 is a graph showing the curing time and the foaming rate in Table 2. From the viewpoint of promptly performing the rust prevention construction and ensuring the rust prevention performance, the curing time is preferably 4 hours or less, and the foaming rate is preferably 30% or less. According to the figure, it is understood that both requirements can be satisfied when the component ratio of isocyanate: MDI is in the range of “4: 1” to “4: 2”.

<Effect of addition of catalyst DBTL to moisture curable film forming agent>
A plurality of moisture curable film forming agents having different component ratios obtained by adding DBTL (film hardening accelerator) to the isocyanate of Chemical Formula 1 were prepared. Butyl acetate was used as the organic solvent. Using each of the moisture curable film forming agents having different component ratios, the film curing time and the film foaming rate were measured. The results are shown in Table 3.

    According to the table, the curing time is shortened as the DBTL addition amount is increased, but the foaming rate of the film is increased. This is because the amount of carbon dioxide generation increased by the addition of DBTL. In the case where the component ratio was “isocyanate: DBTL = 100: 5”, DBTL bleed was observed in the rust preventive film.

    FIG. 5 is a graph showing the curing time and the foaming rate in Table 3. From the viewpoint of promptly performing the rust prevention construction and ensuring the rust prevention performance, the curing time is preferably 4 hours or less, and the foaming rate is preferably 30% or less. According to the figure, it is understood that both requirements can be satisfied when the component ratio of isocyanate: DBTL is in the range of “100: 0.4” to “100: 5”.

<Effect of adding a moisture absorbent to a moisture curable film-forming agent>
A plurality of moisture-curing film forming agents having different component ratios obtained by adding PTSI as a hygroscopic agent to the isocyanate of Chemical Formula 1 were prepared. Butyl acetate was used as the organic solvent. Using each of the moisture curable film forming agents having different component ratios, the film curing time, the film strength (tensile strength), and the film foaming rate when applied in an atmosphere of 50 ° C. and 95% RH were measured. The tensile strength was measured according to JISK5400. The results are shown in Table 4.

    According to the table, the effect of the PTSI addition amount is not exerted on the curing time, but the effect is exerted on the tensile strength and the foaming rate. That is, as the PTSI addition amount increases, the tensile strength decreases while the foaming rate decreases. Since PTSI is a monofunctional isocyanate, it removes moisture and suppresses the generation of carbon dioxide gas (decreases the foaming rate), but remains as a fine particle in the polyisocyanate film without forming a film. Therefore, when the PTSI addition amount is increased, the tensile strength of the film is lowered.

    FIG. 6 is a graph showing the foaming rate and the tensile strength in Table 4. From the viewpoint of securing the rust prevention performance while securing the film strength, the tensile strength is preferably 10 MPa or more, and the foaming rate is preferably 30% or less. According to the figure, it is understood that both requirements can be satisfied when the component ratio of isocyanate: PTSI is in the range of “80: 1” to “80: 3”.

It is sectional drawing which shows an example of the rust prevention location of a vehicle body member. It is a graph which shows the rust prevention effect of the isocyanurate construction of this invention, and each of the conventional rust prevention wax construction compared with no rust prevention construction. It is a graph which shows the influence which the component ratio of an isocyanate and a polyol has on film hardening time and a rust prevention effect. It is a graph which shows the influence which the component ratio of isocyanate and MDI has on film hardening time and a film | membrane foaming rate. It is a graph which shows the influence which the component ratio of isocyanate and DBTL exerts on film hardening time and a film | membrane foaming rate. It is a graph which shows the influence which the component ratio of isocyanate and PTSI has on the film foaming rate and tensile strength.

Explanation of symbols

1 Outer panel 2 Inner panel 3 Sealer 4 Cavity 5 Coating film

Claims (5)

    A vehicle body characterized in that a moisture curable film forming agent that reacts with water is supplied to a rust-preventive portion of a member constituting the vehicle body, and a rust-proof film is formed by reaction with water existing in the rust-preventive portion. Rust prevention treatment method for members. In claim 1,
The moisture curable film-forming agent contains, as a main component, a polyisocyanate that polymerizes by reaction with water to form a rust-proof film. In claim 2,
The moisture curable film-forming agent further contains a curing accelerator that accelerates the curing of the rust-proof film. In claim 2 or claim 3,
The moisture curable film forming agent further contains a hygroscopic agent. In any one of Claims 1 thru | or 4,
A rust preventive treatment method for a vehicle body member, characterized in that the moisture curable film-forming agent is supplied to a gap between members constituting the vehicle body.

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