JPH0826298B2 - Hot melt molding sealer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a molded sealer used for waterproofing and rustproofing a joint portion of a vehicle body steel plate, for example.

[Prior Art] Conventionally, a paste-like sealer having an adhesive property is often used for this kind of application, and it is applied to the application site with a dedicated gun and then cured. There is a problem such as a sealer running out and coming off due to variations in
In addition, there is a defect that the appearance is deteriorated by correcting these defects.

Therefore, in recent years, a molding sealer in which the sealer is molded into a tape shape has been proposed, and a large area can be easily sealed,
Demand is increasing due to its good seal appearance.

[Problems to be Solved by the Invention] This molding sealer is classified into two types in terms of material.
The first is a thermosetting molding sealer, which has similar curing behavior to the baking paint used in vehicles, so cracking of the coating film is less likely to occur, but the fluidity (melt flow property) during heating is high. It is small, and the sealing properties and coating surface (skin) quality are lower than those of pasty sealers. Further, since it is a curable material, storage stability is extremely poor.

The other is a hot melt type molding sealer using a thermoplastic material, and is superior in sealing property, coating film quality and storage stability to the above thermosetting type molding sealer.

However, the hot-melt type molding sealer softens and flows every time heat is applied due to the property of thermoplasticity, and this tendency becomes remarkable especially by overbaking in a coating furnace. Therefore, for example, as shown in FIG. 3, when the sealer 3 is applied to the joint portion having the steps of the body steel plates 1 and 2, the sealer 3 melt-flows in the coating baking step, and the baking coating film 4 on the surface is formed. Cracks 5 and wrinkles 6 are likely to occur.

Therefore, the present invention provides a hot melt type molding sealer capable of controlling the melt flow property of the sealer by reheating while maintaining the advantages of the hot melt type molding sealer, and preventing the occurrence of coating film cracks and wrinkles. With the goal.

[Means for Solving the Problems] The inventors of the present invention have made extensive studies in view of the above circumstances, and as a result, 1 to 5 of whisker fibers was added to a mixture composed of a thermoplastic resin, a plasticizer, a filler and an adhesive component. It has been found that the above object can be achieved by using a hot melt type molding sealer formed by mixing 2% by weight and molding.

In the present invention, as the thermoplastic resin which is the base resin, specifically, a high molecular weight or low molecular weight ethylene-
Vinyl acetate resin and the like are preferably used.

Examples of the plasticizer added to the thermoplastic resin include naphthene-based, epoxy-based, polyester-based, urethane-based, paraffin-based plasticizers, and the like, and examples of the filler include calcium carbonate, silicic acid, Examples thereof include aluminum silicate, magnesium carbonate, magnesium silicate, antifoaming agent, pigment, petroleum resin and the like. As the adhesion component, acrylic and urethane type can be preferably used.

In the present invention, in order to control the melt flow property of the molding sealer, it is essential to mix whisker fibers in the mixture of these components. Examples of the whisker fibers used in the present invention include ceramic fibers such as boron carbide, silicon carbide, alumina and potassium titanate. The blending amount of the whisker fibers in the sealer should be in the range of 1 to 2% by weight. Here, if the blending amount is less than 1% by weight, it is difficult to control the flowability, and if it exceeds 2% by weight, the initial orientation becomes difficult to control, and the flowability in the initial stage of blending is deteriorated, resulting in a seal. Is not good.

The blending ratio of components other than whisker fibers is usually 20 to 50% by weight of thermoplastic resin, 5 to 15% by weight of plasticizer, 40 to 70% by weight of filler, and 5 to 15% by weight of adhesive component. Is desirable.

When the molded sealer of the present invention is manufactured, these various compounds and whisker fibers are added in a predetermined amount to the thermoplastic resin and sufficiently kneaded. The mixture thus obtained is
As shown in FIG. 1, the whisker fibers 7 are strongly entangled with each other, and good flowability cannot be obtained in this state. Then, the screw is extruded while heating. As a result, the entanglement between the whisker fibers 7 is released, and the molded sealer 3 in which the whisker fibers 7 are oriented along the flow of extrusion is obtained (Fig. 2). The heating temperature during this extrusion molding is usually preferably in the range of 50 to 60 ° C. Then, it is cut into a desired product shape to obtain the molded sealer of the present invention.

[Operation] When the molded sealer of the present invention thus obtained is used in the coating sealer process of a vehicle, first, the molded sealer of the present invention is placed at a predetermined sealing portion and heated and dried in a sealer drying furnace. To do. In this step, the whisker fibers in the molding sealer are oriented in a certain direction, so that the whisker fibers exhibit good melt flow properties and closely adhere to the joints of the steel plates to seal them. At the same time, the whisker fibers that had been oriented until now are entangled. Therefore, in the subsequent coating baking step, the flow of the sealer is suppressed by the entanglement of the whisker fibers, and the generation of cracks and wrinkles of the coating film is suppressed.

[Examples] Hereinafter, the present invention will be described in detail with reference to Examples. In addition,
The present invention is not limited to these examples as long as the gist thereof is not exceeded.

Examples 1 and 2 Polymeric ethylene-vinyl acetate resin (EVA) and low molecular weight EVA were used as the thermoplastic resins, and various components and whisker fibers (fiber diameter with potassium titanate whiskers were used).
0.2-0.5 μm, fiber length 10-20 μm) was added and kneaded at the compounding ratio shown in Table 1, and the obtained mixture was screw-extruded to obtain a tape-shaped molded sealer.

A seal test of a steel plate joint portion was performed using the obtained molding sealer. The performance evaluation was carried out on the three points of the melt flow property of the molded sealer in the sealer process, the coating appearance in the coating process after sealing, the presence or absence of wrinkles, and the productivity, and the results are also shown in Table 1. As is clear from the table, the molded sealer of this example containing 1% by weight or 2% by weight of the whisker fibers had good flowability, coating appearance and productivity.

Comparative Examples 1 to 4 Molded sealers were obtained without adding the whisker fibers and changing the compounding amounts of calcium carbonate or thermoplastic resin as shown in Table 1, respectively. The performance was evaluated in the same manner as in Example 1 above, and the results are also shown in Table 1.

As is apparent from the table, Comparative Example 1 has almost the same composition as in Example 1 except that the whisker fiber is not added, but the sealer melt-flows in the coating process, cracks and wrinkles occur in the coating film. The paint appearance is inferior. In Comparative Example 2 in which the blending amount of the high-molecular thermoplastic resin was increased, the initial hardness was increased, but there was no effect in reducing coating film cracks and wrinkles. In addition, Comparative Example 3 in which a crosslinking agent is added is effective in reducing coating film cracks and wrinkles, but melt flowability and productivity deteriorate. Furthermore, in Comparative Example 4 in which the amount of calcium carbonate added was significantly increased, not only the effect of improving the coating appearance was not obtained, but also the flowability and productivity were poor.

Comparative Example 5 A molded sealer obtained by adding glass fibers in place of the whisker fibers in the molded sealer having the composition of Example 2 was obtained. The performance was evaluated in the same manner, and the results are also shown in Table 1.

As is apparent from the table, the use of glass fiber improves the coating appearance, but it is difficult to control the flowability and productivity.

Comparative Example 6 A molded sealer having the same composition as in Example 1 was obtained except that the content of whisker fibers was increased to 2.5% by weight and the content of calcium carbonate was decreased accordingly. The performance was evaluated in the same manner as in Example 1 above, and the results are also shown in Table 1.

As is clear from the table, when the content of the whisker fiber is more than 2% by weight, the flowability is deteriorated. It is considered that this is because the whisker fibers are difficult to be oriented in the molding process and the initial flowability cannot be obtained due to the entanglement of the whisker fibers.
It can be seen that the range of 2% by weight is suitable.

EFFECTS OF THE INVENTION As described above, the hot-melt type molding sealer of the present invention is
By blending a certain amount of whisker fibers, the melt flow property of the sealer is controlled by reheating in the coating baking process,
It is possible to prevent the coating film from cracking and wrinkles. Therefore, the coating appearance can be remarkably improved while maintaining the excellent sealing property.

[Brief description of drawings]

1 and 2 are views showing a manufacturing process of the forming sealer of the present invention, and FIG. 3 is a cross-sectional view of a steel plate joining portion to which a conventional forming sealer is applied. 3 …… Molding sealer 4 …… Coating film 7 …… Whisker fiber

Claims (1)

[Claims] 1. A whisker fiber in an admixture comprising a thermoplastic resin, a plasticizer, a filler and an adhesive component, in an amount of 1 to 2% by weight.
A hot-melt type molding sealer characterized by being mixed and molded.