JPH0613194B2 - Resin parts joining method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a resin component joining method. More specifically, the present invention relates to improvement of curing history of an adhesive in a method of joining a resin component such as a resin outer plate to an adherend with an adhesive in an automobile production process.

(Prior Art) In recent years, from the viewpoint of energy saving, weight reduction of automobiles and improvement of aerodynamic characteristics have been achieved to improve fuel efficiency, and material conversion in exterior materials has been actively promoted. As an alternative material to replace the steel material, a synthetic resin material such as fiber reinforced resin and polymer alloy is mentioned as one of the most promising materials.

However, when such a synthetic resin-based member is used, joining with an inner reinforcing member and a metal part such as a steel plate forming a vehicle body may occur as a problem. Conventionally, a mechanical method using a screw, a rivet or the like and a method using an adhesive have been used to bond such a resin member to an adherend such as an inner reinforcing material and a vehicle body. Is not so favored from the viewpoint of productivity, and it is desirable to perform bonding with an adhesive by reducing the number of bonding sites by the method as much as possible.

As a method of joining the resin component and the adherend such as the inner reinforcing material and the vehicle body with the adhesive, (1) the resin component and the adherend are completely cured at a place different from the production process line. , And then assembling it to the vehicle body in the main line of vehicle body assembly, (2) Temporarily fixing resin parts and adherends by partially curing the adhesive partially by high-frequency baking etc. in the sub-line of vehicle body assembly However, there is used a method of completely curing the remaining adhesive by using heat during baking of the paint in the painting process after assembling to the car body in the main line of car body assembly (JP-A-54-16).
0,435).

(Problems to be Solved by the Invention) However, in the case of the method (1), it is necessary to completely cure the adhesive in the sub-line, which requires not only heating equipment but also time, so the productivity is low.

On the other hand, in the case of the method (2), since the other parts are uncured except the part where the adhesive is hardened by the high frequency baking, the parts formed by the resin parts and the steel material are exposed to the high temperature of baking. When the body and the body are thermally expanded, the adhesive follows the expansion and slips between the phases to flow. Therefore, the adhesive cures without distortion in a state where a difference due to the difference in thermal expansion occurs between the resin component and the adherend. However, since the adhesive is partially completely cured, the adhesive has a softening transition point (hereinafter, “softening transition point” means a dynamic setting in the thermosetting adhesive when the temperature is lowered after baking. Temperature at which physical properties such as Young's modulus change rapidly, to be precise, loss tangent tan
δ indicates the vicinity of the peak point. ) Is reached, shear stress is rapidly generated in the joint due to the difference in heat shrinkage between the resin part and the adherend, and the adhesive layer cannot absorb the shear stress, resulting in a defective appearance such as a dent in the resin part. There was fear.

(Means for Solving Problems) The present invention has been made by paying attention to the problems of such a conventional method. First, an adhesive agent for adhering a resin component and an adherend is 1 to 20 kg / Incompletely cured to a bonding strength of cm ² ,
After that, the above problems are solved by advancing the curing by heating at the time of baking the paint in the painting process in the automobile production process.

(Function) According to the resin component joining method of the present invention, the adhesive for first adhering the resin component and the adherend is 1 to 20 kg / cm.
^In order to achieve incomplete curing up to the joint strength of ² , due to the heating during coating baking in the painting process, the resin component and the adherend composed of steel material etc. thermally expand and heat is generated between the resin component and the adherend. Even if the difference due to the difference in expansion occurs, the adhesive layer is not completely hardened yet and is distorted within the elastic limit. Therefore, no slippage occurs at the interface between the resin component or the adherend and the adhesive layer. For this reason, the shear stress applied to the adhesive layer due to heat shrinkage at the time of temperature decrease during coating baking is smaller than that when the adhesive layer is slipped and cured, and even if the transverse shear elastic modulus of the adhesive layer increases as curing progresses. The elasticity of the adhesive layer can absorb the shear stress. Further, since the adhesive is incompletely hardened, no sudden shear stress is generated during joining when the temperature is lowered after baking. From the above, the appearance of defects such as dents does not occur in the resin component. Here, the adhesive strength of the adhesive when the incompletely cured was 1~20Kg / cm ² is practical occur misalignment between components when conveyed is less than 1Kg / cm ² by the line Further, if it exceeds 20 kg / cm ² , the shear strength applied to the adhesive is high, and therefore the effect of preventing the occurrence of dents in the resin parts cannot be expected. In the joining method of the present invention, the adhesive agent is finally completely cured after a lapse of time after the finish of baking the coating.

As the resin component used in the present invention, any resin can be used as long as it can be adhered to the adhesive used, but as an example, a resin component reinforced with glass fiber, carbon fiber, boron fiber or the like can be used. There are molded parts such as saturated polyester resin, epoxy resin, phenol resin, etc., particularly, molded parts such as sheet molding compound (SMC) and bulk molding compound (BMC).

Further, it is desirable that the incomplete curing of the adhesive is performed under low temperature conditions and in a short time so that the difference in thermal expansion due to the difference in linear expansion coefficient between the resin component and the adherend is minimized. For this purpose, for example, in the adhesive composition, it is desirable to add a curing catalyst or the like that sufficiently acts even in a low temperature range.

After incomplete curing until a bond strength of 1 to 20 kg / cm ² is obtained in this way, the bonded resin component and adherend are
It is attached to the car body. This assembling may be performed before the coating process, that is, before the pretreatment performed before the electrodeposition coating, or before the intermediate coating process in the coating process, that is, after the electrodeposition coating and after drying / baking, or the top coating process. It may be performed before drying, that is, after the intermediate coating, and after baking. In this way, the adhesive for adhering the resin parts assembled to the vehicle body is then heated by the coating baking process in the coating process. Undercoat (electrodeposition) paint bake, intermediate coat paint bake and top coat paint bake when assembled to vehicle body before painting process, and intermediate coat paint bake if assembled to vehicle body before intermediate coat process When the top coat is baked, and when it is assembled to the vehicle body before the top coat process, the top coat paint is baked respectively, but in both cases, the adhesive is complete after the finish of the top coat paint (in the automobile production process). It is necessary to properly adjust the adhesive composition so that it cures.
The heating by such a baking treatment promotes the curing of the adhesive, and finally an adhesive strength of 40 kg / cm ² or more is obtained.

(Examples) Examples 1 and 2 and Comparative Example 1 Using 500 g of three kinds of one-pack type epoxy resin adhesives having different composition amounts of the curing agent having the composition shown in Table 1, a width of 1
40 cm, 120 cm long, 2.5 mm thick SMC board with a width of 1
35cm, 110cm long, 0.8mm thick steel plate,
The temperature was raised from room temperature to 120 ° C. in 2 minutes, kept at 120 ° C. for 10 minutes, and then lowered to room temperature in 5 minutes to perform calcination and incomplete curing. At this time, the shear strengths of the adhesive layers of Examples 1 and 2 and Comparative Example 1 were 13, 15, and 2, respectively.
It was 6 kg / cm ² . Furthermore, this adhesive is 140 ° C. for 10 minutes from room temperature, assuming a top coat baking process.
The temperature was raised to 140 ° C. for 20 minutes, and then baked in an oven for 15 minutes to cool to room temperature. The shear strength of the adhesive layer in the obtained adhesive body was completely cured at 40 kg / cm ² or more after the lapse of 24 hours after the finish of baking the coating, but in Examples 1 and 2, a comparison was made in which no dent was generated. Regarding Example 1, a dent is generated.

Examples 3 to 4 and Comparative Example 2 An SMC plate was used as a steel plate in the same manner as in Example 1 by using 500 g of two kinds of two-component epoxy resin adhesives having different composition amounts of the curing agent having the compositions shown in Table 2. Adhesion was performed, the temperature was raised from room temperature to 120 ° C. in 2 minutes, the temperature was maintained at 120 ° C. for 3 minutes, and the temperature was lowered to room temperature in 10 minutes to perform calcination and incomplete curing. At this time, the shear strengths of the adhesive layers of Examples 3 to 4 and Comparative Example 2 were 10, 20, and 30 kg / cm ² , respectively. Further, this adhesive was baked under the same conditions as in Example 1, assuming the baking treatment of the top coat. The shear strength of the adhesive layer in the obtained adhesive body was completely cured at 24 kg / cm ² or more after 24 hours, but in Example 3.4, no dent was generated but Comparative Example 2 was used. There is a dent.

Examples 5 to 6 and Comparative Example 3 An SMC plate was used as a steel plate in the same manner as in Example 1 by using 500 g of two kinds of two-component urethane resin adhesives having different composition amounts of the curing agent having the composition shown in Table 3. Bonding was performed, the temperature was raised from room temperature to 120 ° C. in 3 minutes, the temperature was maintained at 120 ° C. for 5 minutes, and then the temperature was lowered to room temperature in 10 minutes to perform calcination. At this time, the shear strengths of the adhesive layers of Examples 5 to 6 and Comparative Example 3 were 10, 15, and 30 kg / cm ² , respectively. Further, this adhesive was baked under the same conditions as in Example 1, assuming the baking treatment of the top coat. The shear strength of the adhesive layer in the obtained adhesive body was completely cured at 40 kg / cm ² or more after 24 hours. In Example 5.6, no dent was generated but Comparative Example 3 had a dent. It has occurred.

(Effects of the Invention) As described above, the present invention is a method of joining a resin component to an adherend composed of different materials in an automobile production process by an adhesive, and first, the resin component and the adherend are joined together. A method of joining resin parts, characterized in that the adhesive to be joined is incompletely cured to a joint strength of 1 to ²⁰ kg / cm ² , and then the curing is advanced by heating during coating baking in the automobile manufacturing process. Therefore, it is possible to perform automobile production with excellent productivity and without causing a defective appearance such as a dent in the resin part or reducing adhesive strength.

Claims (1)

[Claims] 1. In a method of joining a resin component to an adherend by an adhesive in an automobile production process, an adhesive for first adhering the resin component and the adherend is used up to a joint strength of 1 to ²⁰ kg / cm ^2. A method for joining resin parts, which comprises completely curing and then proceeding with curing by heating during baking for painting in an automobile production process.