JPS61278583A - Method of bonding coated steel plate - Google Patents

Abstract

PURPOSE:To obtain a coated steel molding having an excellent bond strength at its bonded portions, by activating a coating film surface of a coated steel by means of irradiation, applying an adhesive on the activated coating film surface, and bonding the coated steel. CONSTITUTION:A coating film layer 2 formed on a steel plate 1 is exposed to a radiation (e.g.: ultraviolet radiation or electron radiation) to excite molecules in the coating film layer 2 by the action of irradiation energy, causing degradation and activation. Oxygen contained in air present on the coating film surface is converted to active ozone by irradiation energy. As a result of a reaction between the activated molecules in the coating film and ozone, there occur polar radicals which serve to form an activated coating film surface 2a having an excellent affinity for an adhesive. An adhesive is applied on the activated coating film surface 2a to form an adhesive layer 3, which is bonded to a similarly treated coated steel plate 1, followed by pressing to bond completely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for adhering painted steel plates that have been previously painted on one or both sides. More specifically, the present invention relates to an industrially superior method for bonding coated steel plates, which allows production of coated steel plate moldings with adhesive portions firmly bonded.

[Conventional technology]

Figure 2 is a cross-sectional view showing the bonded area of painted steel plates bonded using the conventional method, where (1) is the steel plate and (2) is the painted film layer.

(3) is an adhesive layer.

Note that a coated steel plate is formed by the steel plate (1) and the paint film layer (2).

Next, the adhesion method will be explained. In the process of bonding coated steel plates cut and formed into predetermined dimensions and shapes with adhesive, the conventional method is to remove foreign matter adhering to the surface of the coating film layer (2) at the bonding area by using a dry cloth or impregnating it with a solvent. The surface was cleaned by wiping with a damp cloth, and then an adhesive was applied and allowed to dry and harden to adhere.

[Problem that the invention seeks to solve]

The above method does not activate the paint film surface, that is, add polar groups, so it has poor affinity with adhesives and only low adhesive strength can be obtained. There was a problem in that a coated steel plate with a layer formed thereon could only obtain an extremely low adhesive strength.

The present invention was made to eliminate such problems, and an object of the present invention is to provide a method for bonding coated steel plates with increased bonding strength.

[Means for solving problems]

The method for adhering painted steel sheets of the present invention is a method in which the painted steel sheet surface is activated by radiation irradiation, and then an adhesive is applied to the activated paint film surface to adhere the painted steel sheet.

[Effect]

The effect of radiation irradiation on the coating film surface of the adhesive part in this invention is as follows. That is, the molecules on the surface of the coating film are excited by the radiation energy, decompose and become activated. In addition, oxygen in the air existing at the paint film interface also receives radiation energy and generates active ozone. The active molecules on the surface of the coating film and ozone easily react to form polar groups, which promotes affinity with adhesives and increases adhesion.

[Example] FIG. 1 is a cross-sectional view of a bonded part of a painted steel plate according to an example of the present invention, and (1) to (3) are the same as the conventional one,
(2a) is the surface of the coating film activated by radiation irradiation.

Hereinafter, this invention will be explained in more detail with reference to Examples.

Example 1 A coating film layer consisting of 82% oil length, 8% by weight of coconut oil-modified alkyd resin Fewani, 18% by weight of butylated melamine resin varnish, and 29% by weight of rutile titanium oxide was applied to a 1.5 m thick steel plate (1). A coated steel plate composed of (2) is prepared, and the surface to which the above coating film layer adheres is cleaned with cotton cloth impregnated with ethyl alcohol.
, 5 Chiang's high-pressure mercury lamp (trade name: H2S-UVA, manufactured by Mitsubishi Electric) was irradiated for 1 minute from a distance of 10 cm to obtain an active layer (2a) on the coating film surface. After that, one liquid is applied to the painted film surface, mainly containing a polyisocyanate compound (product name: Takenate A).
28L (manufactured by Takeda Pharmaceutical) and a urethane resin adhesive (3
) was applied uniformly and bonded to a coated steel plate whose coated film surface had been treated with ultraviolet rays in the same manner as above, and the adhesive was cured at room temperature while being pressed at a pressure of 0.61. After sufficiently curing, the adhesive strength of the adhesive body was measured. In addition, the degree of activity of the painted film surface irradiated with ultraviolet rays was determined by the contact angle with respect to water.

Example 2 The coating film layer in Example 1 was made of thermosetting acrylic resin varnish 46.7% by weight and butylated melamine resin varnish 20.7% by weight.
Adhesion was carried out in the same manner as in Example 1, except that it was made of 88.8% by weight of rutile-type titanium oxide, and the adhesive strength and contact angle of the painted film surface with respect to water were determined. The results are shown in the table.

Example 8 The same painted steel plate as in Example 1 was prepared, and after cleaning the surface to which the paint film layer adhered with cotton cloth impregnated with ethyl alcohol, an 18-inch electro curtain (product name: ESI 18 inch electro curtain, Energy Science Co., Ltd. 80
The active layer (2a) was obtained on the surface of the coating film by irradiation for seconds. After that, the same urethane resin adhesive as in Example 1 (3
) was applied uniformly, and the painted steel plate was treated with electron beam irradiation in the same manner as above, and the coated steel plates were bonded together in the same manner as in Example 1, and the adhesive strength and the contact angle of the painted film surface with respect to water were determined. Ta. The results are shown in the table.

Example 4 Painted steel plates similar to those in Example 2 were prepared and adhered in the same manner as in Example 8 to determine the adhesive strength and the contact angle of the painted film surface to water. The results are shown in the table.

Comparative Example 1 A painted steel plate with the same paint film layer as in Example 1 was created,
Immediately after cleaning the painted film surface with a real cotton cloth impregnated with ethyl alcohol, the same adhesive as in Example 1 was applied to the painted film surface and bonded under the same curing conditions as in Example 1 to determine the adhesive strength. In addition, after cleaning the paint film surface, the contact angle of the paint film surface with water was determined and the results are shown in the table.

Comparative Example 2 Adhesion was performed in the same manner as in Comparative Example 1, except that the same coated steel plate as in Example 2 was used, and the adhesive strength and contact angle with respect to water were determined. The results are shown in the table.

*λ: Material failure, B: Cohesive failure of adhesive.

C: Interfacial destruction between adhesive and painted surface In addition, in the above examples, examples were shown in which a combination of melamine alkyd resin and acrylic melamine resin coated steel sheets and urethane resin adhesives were used, but in addition to this, coated steel sheets Examples include vinyl chloride resin coating film, urethane resin coating film, polyester resin coating film, epoxy resin coating film, vinyl acetate resin coating film, etc. As the adhesive, egixy resin adhesive and polyester resin adhesive may be used. Furthermore, the surface of the coating film may be irradiated with radiation other than ultraviolet rays and electron beams, and even if two or more types of radiation are irradiated, the same effects as in the above embodiments can be obtained.

〔Effect of the invention〕

As explained above, this invention activates the coating film surface of a painted steel plate by radiation irradiation, and then applies an adhesive to the activated coating film surface to adhere the coated steel plate.
A method for bonding painted steel plates with increased bonding strength can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a bonded portion of a coated steel plate according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of a bonded portion of a coated steel plate according to a conventional method. In the figure, (1) is a steel plate, (2) is a paint film layer, (2a
) is the activated paint film surface, and (3) is the adhesive layer. Note that the same reference numerals in each figure indicate the same or equivalent parts.

Claims (3)

[Claims] (1) A method for adhering painted steel plates, in which the painted steel plate surface is activated by radiation irradiation, and then an adhesive is applied to the activated paint film surface to adhere the painted steel plate. (2) The method for adhering painted steel sheets according to claim 1, wherein the radiation is ultraviolet rays. (3) The method for adhering painted steel sheets according to claim 1 or 2, wherein the radiation is an electron beam.