JPH11172230A - Sealant for automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealant for automobiles which does not contain a plasticizer, hence does not cause the yellowing and staining of a topcoating film, and enables a good appearance to be attained even without using a resin molding. SOLUTION: This sealant contains a mixture of an epoxy resin and a blocked isocyanate resin as the major component, has a viscosity of 10-60 Pa.s at a shear rate of 62 sec<-1> , and does not contain a plasticizer. Any epoxy resin, if it has at least two epoxy groups in the molecule, can be used, and a monoepoxy resin can also be used as a part of the epoxy resin. There is no limitation about the type of epoxy resin; a bisphenol A type, a novolak epoxy type, an ether ester type, an ester type, an aliph. type, a nitroge-contg. type, and modifications of these types can be used. Any blocked isocyanate resin can be used if it is the one prepd. by blocking molecular terminals of an urethane resin having at least two isocyanate groups with a blocking agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealant for automobiles, which is particularly suitable for use in a joint of a roof panel of an automobile.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 1, a joint portion between an automobile side panel and a roof panel, which is called a mohawk structure, is provided with a PVC-based sealing agent 4 at a spot weld 3 between the side panel 1 and the roof panel 2. Covering is performed to prevent water leakage and rust prevention at the spot welded portion 3 and to attach a resin molding 5 for the purpose of further improving the appearance of the panel.

[0003]

However, the above method is
An expensive resin molding is required to improve the appearance, and if the molding is made the same color as the panel, an extra cost is required.

[0004] In this case, if the finishing is performed only with the sealing agent without attaching the molding, the plasticizer usually contained in the sealing agent and other components that become a carrier of the plasticizer are transferred to the top coating film of the panel, and the top coating film is formed. Stain, yellowing and stickiness of the coating film occur.

Further, the above-mentioned method requires a repair work and a molding attaching work for preventing water leakage after application of the sealing agent, but it is particularly difficult to automate the molding attaching work.

[0006] The present invention is an improvement of the above circumstances, does not contain a plasticizer, can prevent yellowing and dirt of the overcoat film, can obtain a high appearance without using a resin molding. An object of the present invention is to provide an automotive sealing agent.

[0007]

Means for Solving the Problems and Embodiments of the Invention As a result of diligent studies to achieve the above object, the present inventor obtained a good appearance without using a resin molding. The main component is a mixture of an epoxy resin and a blocked isocyanate resin as a sealing agent composition not containing a plasticizer which causes the above, and at a shear rate of 62 sec ^{-1 at a} shear rate of 62 sec ^-1 from the viewpoint of usability.
Is adjusted to 10 to 60 Pa · s.

That is, the present invention comprises a mixture of an epoxy resin and a blocked isocyanate resin as a main component and a shear rate of 6%.
The viscosity at 2 sec ^-1 is 10 to 60 Pa · s,
An automotive sealing agent characterized by being free of a plasticizer.

Hereinafter, the present invention will be described in more detail.
The automotive sealing agent of the present invention contains a mixture of an epoxy resin and a blocked isocyanate resin as a main component.
As the epoxy resin used here, any resin having two or more epoxy resins in the molecule can be used, but if necessary, some compounds having one epoxy group in the molecule may be used. Can be used together. The type of epoxy resin is not particularly limited, and bisphenol A type, novolak epoxy type, ether ester type, ester type, aliphatic type, nitrogen-containing epoxy type and the like and modified products thereof can be used.

Next, as a blocked isocyanate resin,
Urethane resin with two or more isocyanate groups
Urethane resin whose terminal is blocked with a blocking agent
Any of them can be used. In this case,
There are no particular restrictions on the type of cyanate, TDI, MD
I, HDI, IPDI, XDI, H₆XDI, H ₁₂MD
I and modified products thereof can be used. Also, iso
Cyanate blocking agents include lactams, phenols
System, alcohol system, oxime system, ethyl acetoacetate, etc.
Can be used.

The epoxy resin and the blocked isocyanate resin can achieve an arbitrary elongation percentage depending on the modified content of the resin and the mixing ratio, but when used for a joint portion of a roof panel, the performance as a sealing agent is secured. For this purpose, the baking conditions of 140 ° C. × 20 minutes × 2
An elongation of 10 to 100% is required for each baking. If the elongation is less than 10%, there may be a problem in vibration durability. If the elongation is more than 100%, cracks may occur in the topcoat due to a difference in elongation from the topcoat. Therefore, it is preferable that the ratio between the epoxy resin and the blocked isocyanate resin is selected and mixed so as to give such an elongation.

The sealing agent of the present invention may further contain a curing agent, a filler and a solvent. As a curing agent,
A powder curing agent which is stable at room temperature and exerts a curing action by heating is effectively used, and a curing agent which can cure an epoxy resin or a blocked isocyanate resin in a temperature range of 60 to 200 ° C. is preferable. By using powder as a curing agent,
Since there is no migration from the sealing agent to the topcoat film, the coating film has very little yellowing, stickiness, peeling, dirt, etc., and a high appearance can be obtained. Examples of such a curing agent include dicyandiamide, dihydrazide, amine imide, tertiary amine salts, imidazole salts, and acid anhydrides, and one of them can be used alone or in combination of two or more. The amount used is the curing effective amount.

The filler is not particularly limited, and for example, calcium carbonate, barium sulfate, talc, clay, silica and the like can be used. The compounding amount of the filler can be in the range of 10 to 60% by weight of the whole, and the viscosity of the sealing agent can be adjusted by selecting the compounding amount of the filler.

As the solvent, a solvent which does not dissolve the curing agent,
For example, aliphatic hydrocarbons and the like are preferably used. The amount of the solvent can be 0 to 30% by weight of the whole, and the viscosity of the sealing agent can be adjusted by selecting the amount of the solvent used.

Here, the sealing agent of the present invention is preferably formed as a one-pack type thermosetting sealing agent obtained by mixing a powdery curing agent, a filler and a solvent into an epoxy resin and a blocked isocyanate resin. However, the viscosity of the sealing agent of the present invention at a shear rate of 62 sec ^-1 is 10 to 60.
Pa · s (20 ° C.). That is, for example, the sealing at the joint between the roof panel and the side panel is discharged by an airless pump, but if it is lower than 10 Pa · s, the dripping property is poor, and if it is higher than 60 Pa · s, the leveling property is poor. Therefore, for viscosity adjustment, the amount of solvent as described above,
It is desirable to select the amount of the filler and the like.

The sealing agent of the present invention is suitably used particularly for sealing a joint between an automobile side panel and a roof panel. The method of using the sealing agent is the same as that of a conventional sealing agent such as discharging by an airless pump. Method can be used.

According to the present invention, after the application of the sealing agent, it has a good appearance without attaching a resin molding, and does not contaminate the top coat. Further, since the resin molding work can be eliminated, automation is possible.

[0018]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Examples and Comparative Examples Sealing agents were obtained by using the components shown in Table 1 in the proportions shown in the same table. Next, the following items were evaluated for the obtained sealing agent. The results are also shown in Table 1.

[0020] The pressure Shikimi multiplied viscometer (Meiho Inc.) used as the Evaluation method] The viscosity viscometer, 6
The viscosity at 2 sec ^-1 was measured at 20 ° C. After applying the sealing agent in the groove-type panel 10 shown in sagging Figure 2, tilting the panel at an angle 15 °, it was measured sagging length after 10 minutes. Leveling Property After applying a sealing agent to the grooved panel of FIG. 2, the leveling property was visually determined. After the test panels fabricated in the topcoat yellowing following steps [1], and left at 100 ° C. atmosphere for 10 days, confirmed the varying topcoating yellowing on sealant visually. Procedure [1] Apply a sealing agent to a 150 × 70 mm electrodeposited plate with a width of 50 ×
Applied to length 50 x thickness 8mm Bake at 95 ° C x 10 minutes Middle coat 35 µm Middle coat dry 140 ° C 18 minutes Top coat Base 15 µm, clear 30 µm Top coat dry 140 ° C x 18 minutes Top coat stickiness Prepare test panel by the above procedure [1] Thereafter, stickiness was evaluated by finger erosion. Test panels were prepared by overcoating stain resistance above procedure [1]. Then, add 0.25% by weight of soiled substance-dispersed water (carbon / clay = 1/1 mixed to deionized water) and adjust the pH with sulfuric acid.
(Adjusted to 2.8). Leave at room temperature for 17 hours. After performing the sunshine weatherometer for 6 hours (black panel 63 ° C., with rainfall) for 4 times, the coating film stain on the sealing agent was evaluated. After preparing the test panel in the above procedure [1], a cross-cut peeling test was performed (2 × 2 mm, 100 pieces). [Evaluation criteria] ○: very good △: normal ×: bad

[0021]

[Table 1] (1) Epoxy resin: bisphenol A type epoxy resin, epoxy equivalent 190 (2) blocked isocyanate resin: aromatic isocyanate prepolymer blocked with a phenolic blocking agent, NCO equivalent 2000 (3) vinyl chloride resin: homopolymer , Average degree of polymerization 16
(4) Curing agent: modified polyamine-based curing agent, melting point 100 ° C. (5) Solvent: aliphatic hydrocarbon-based solvent, average molecular weight 19
0 (6) plasticizer: DINP (7) adhesion-imparting agent: modified polyamidoamine, amine value 2
00 (8) Antifoaming agent: CaO

[0022]

According to the present invention, the use of a sealing agent containing no plasticizer prevents yellowing and dirt of the overcoating film, and a high appearance can be obtained without using a resin molding. And the operation can be automated.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a sealing agent application mode at a joint between a side panel and a roof panel.

FIG. 2 is a perspective view of a grooved panel used for evaluation of sagging property and leveling property of a sealing agent.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Side panel 2 Roof panel 3 Spot welding part 4 Sealant 5 Resin molding

Claims (1)

[Claims] An automotive sealing agent characterized by comprising a mixture of an epoxy resin and a blocked isocyanate resin as a main component, having a viscosity of 10 to 60 Pa · s at a shear rate of 62 sec ⁻¹ and containing no plasticizer. .