JPS608227B2 - Honeycomb core joining method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for joining a honeycomb core and a substrate.

Honeycomb cores are used as lightweight reinforcing materials in composite panels bonded in a sandwich between substrates, and some are made of paper or some are made of aluminum.

Additionally, the following method has been proposed and implemented as a method for bonding the honeycomb core and the substrate. '1} Apply liquid adhesive to the substrate and then attach it to the honeycomb core.

An adhesive sheet is interposed between the '21 substrate and the honeycomb core to bond them together.

{3} After electrostatically coating the honeycomb core with powder adhesive, bring it into contact with the substrate and heat it to bond.

In order to obtain strong adhesion between the honeycomb core and the substrate,
It is desirable that the adhesive layer thickens in the honeycomb-shaped part, that is, the fillet forming ability is large, but the above '1} and {2}
With this method, strong adhesive strength cannot be obtained unless a thick adhesive is applied to the entire surface of the substrate or a specially formulated adhesive layer is used to improve the fillet forming ability.
There were drawbacks such as a decrease in the stability of adhesive strength.

In addition, in method {3', the adhesive is attached only to the honeycomb-shaped part, so there is no loss of adhesive as in method '2', but since the powder adhesive is applied using electrostatic coating, It cannot be applied unless it is a metal honeycomb core such as a honeycomb core, and it is not practical because the coating efficiency on the inner surface of the core is poor due to the Faraday cage effect.

In view of this situation, the present inventors conducted research on a method of joining that can be applied to honeycomb cores made of paper or metal and that can effectively use an adhesive, and as a result, the present invention was achieved.

That is, the present invention provides a honeycomb core wet-treated with a primer having a viscosity of 400 poise or less at room temperature.
The present invention relates to a method for joining honeycomb cores, which comprises applying a heat-melting powder adhesive having a fluidity index of 2 to 20 when heated, and then heating the adhesive in contact with a substrate.

According to the present invention, the heat-melting powder adhesive can be applied only to the honeycomb-shaped portion in an amount sufficient to form a fillet without being affected by the material of the honeycomb core, so that the adhesive can be used effectively.

The primer is used for the purpose of attaching a heat-meltable powder adhesive, and a primer having a viscosity of 400 poise or less at room temperature is used. The reason for using a primer of 400 poise or less is that powder adhesion performance deteriorates if it is 400 poise or more.

The primer layer is usually used at a thickness of 2 to 20 mm. If the film thickness is 20 μm or more, a large amount of primer will be mixed in during heat bonding, which tends to cause a decrease in adhesive strength or poor appearance such as foaming, and if the film thickness is less than 2 μm, the powder adhesion performance will decrease. The primer used is a solvent, a liquid compound, or a solution thereof. As the solvent, water, alcohols, halogenated hydrocarbons, ketones, etc. are used, and as the liquid compound, amines, acids, and liquid resins such as epoxy resins, polyester resins, and aryl resins are used. In order to form a primer layer having a film thickness of 2 to 20 mm, it is preferable to use an ordinary liquid compound diluted with an easily volatile solvent among the above-mentioned solvents to an appropriate concentration.

As the heat-meltable powder adhesive used in the present invention, thermoplastic resins and thermosetting resins are used alone or in combination. (approximately 120 to 200 qo) with a flowability index of 2 to 20.

What is the flowability index here? Heat-melt powder adhesive with a temperature of 0.5 mm is molded into a tablet with a diameter of 13 mm using 100 k9 mm, and is placed on a hot plate set at a bonding temperature (joining temperature) and tilted at 60 degrees. When the above-mentioned tablet is placed, the distance a melted and flowed and the thickness h of the tablet are the values expressed in 3 and a half 3. If the flowability index during heating is less than 2, the ability to form fillets is poor, and if it is more than 20, it will flow too much and fillet formation will also be insufficient. In addition, even for heat-fusible powders with a flowability index of 20 or more, convenient conditions can be selected by shortening the heating time (in the case of thermoplastic resin alone) or lowering the heating temperature. Needless to say. The particle size of the heat-meltable powder adhesive is usually 42 mesh pass.

In order to attach powder to the honeycomb core, first, the honeycomb core is wet-treated with a primer, and the powder is attached using the adhesive force of the primer. At this time, the powder and the wet-treated honeycomb core can be brought into contact and adhered by the fluidized bonding method or the spreading method, so it can be applied not only to metal honeycomb cores but also to paper honeycomb cores. be able to. When the honeycomb core with the powder attached is brought into contact with a predetermined substrate and heated to a temperature such that the flowability index of the heat-melting powder adhesive is 2 to 20, the powder adhesive melts and forms an adhesive layer. do. In the present invention, the first step is to attach a primer layer to the honeycomb core, but it should be noted that this step is fundamentally different from attaching a solution-type adhesive or a solvent-free liquid adhesive. .

The purpose of the primer treatment of the present invention is to form 2 to 20 mm particles and impart powder collection ability, so the primer has a low viscosity and good workability, but the solution-type adhesive treatment However, in the case of a solvent-free liquid adhesive, the film must be thick and adhered to the honeycomb core, so there is a difference in that it has poor liquid drainage and exhibits system forming properties, resulting in significantly inferior workability. The details of the present invention will be explained in Examples.

EXAMPLE A brimer having a concentration of 15% was prepared by dissolving Epikot #828 (liquid epoxy resin manufactured by Yuka Shellepoxy Co., Ltd., viscosity 100 poise at 2520) in trichlorethane.

Further, 0.1, 0.4, 0.7, and 1.5 parts by weight of 2-methylimidazole were melt-mixed to 100 parts by weight of Epikot #1002 (solid epixy resin manufactured by Yuka Shell Shepoxy Co., Ltd.), and then cooled and pulverized to 60% by weight. A hot-melt powder adhesive of ~200 mesh was prepared.

The flowability index of each powder adhesive is 2 at 150℃.
It was 5 10, 5, 1.

Approximately 3 end faces of the paper honeycomb core were soaked in the primer at room temperature for about 5 seconds, and then brought into contact with each of the powder adhesives described above in a fluidized bonding tank to adhere the powder to the honeycomb core. Ta.

Next, the honeycomb core was placed on a dull steel plate with a thickness of 1.2 and heated in a 150q◯ heating furnace to perform a melting and hardening reaction of the powder adhesive, thereby bonding the dull steel plate and the honeycomb core.
Powder adhesives with a flowability index of 10 and 5 have good fillet formation and adhesive strength of 3.2k9, respectively.
However, those with flowability indexes of 25 and 1 used for comparison had poor fillet formation properties and adhesive strength of 1.2k9/ground and 0.8k9/mm, respectively. As a model, an aluminum plate having a thickness of 0.6 mm was treated with the above primer, and the thickness of the primer film was examined in terms of weight, and it was found to be about 6 mm.

Claims (1)

[Claims] 1. A hot-melt powder adhesive with a flowability index of 2 to 20 when heated is applied to a honeycomb core that has been wet-treated with a primer having a viscosity of 400 poise or less at room temperature, and then brought into contact with a substrate. A honeycomb core joining method characterized by heating.