JPH0321682A - Bonding and sealing method using hot melt - Google Patents

Abstract

PURPOSE:To prevent foam from staying in the interface between a plastic and hot melt by using the hot melt degassed under reduced pressure when a plastic generating gas by heating is bonded and sealed. CONSTITUTION:A plastic such as polycarbonate or acrylic resin generating gas by heating is bonded and sealed using a hot melt degassed by reducing pressure by >=500mm Hg. As the above-mentioned hot melt, a heat meltable composition obtained by properly adding tackiness providing agent, wax, plasticizer, filler and stabilizer, etc., to a base polymer consisting of ethylene/vinyl acetate copolymer, low molecular PE or styrene/isopropylene block copolymer, etc., is preferably used.

Description

[Detailed Description of the Invention] Industrial Application Fields The present invention relates to a method for adhesively sealing plastics such as polycarbonate and acrylic resin using hot melt, and more specifically, to a method for adhesively sealing plastics such as polycarbonate and acrylic resin using hot melt. This invention relates to an adhesive sealing method that does not allow air bubbles to remain in the area.

(Conventional technology) Polycarbonate has extremely high mechanical strength including impact strength, is stable to heat, has excellent electrical properties and weather resistance, is highly transparent, can be colored freely, and has a wide range of dimensions. Due to its excellent stability, it is used in mechanical parts, electrical parts, lighting equipment parts, household goods, etc.

Generally, an adhesive or sealant called hot melt is used for adhesion or sealing of polycarbonate, and the hot melt is melted with an applicator and applied to the polycarbonate, and the hot melt is sticky. They are pasted together and polycarbonate is glued or sealed in between.

By the way, when polycarbonate is bonded or sealed using such conventional methods and heated to 60 to 120°C, low-molecular compounds such as H20 and CO2 are generated from the polycarbonate, as shown in Figure 1. , stays as bubbles 3 at the interface between polycarbonate 1 and hot melt 2,
These air bubbles 3 caused a decrease in adhesive strength and sealing performance.

A similar phenomenon was also observed when acrylic resin plastics were bonded and sealed using hot melt.

Problems to be Solved by the Invention> As mentioned above, when bonding and sealing plastics such as polycarbonate and acrylic resin using hot melt, in the conventional method, air bubbles derived from the plastic are trapped at the interface between the plastic and the hot melt. This caused a decline in adhesive strength and sealing performance.

Therefore, as a countermeasure, a hot melt that easily permeates gases such as H20 and CO2 was proposed.

However, even if such a hot melt is used, it is not possible to completely prevent the accumulation of bubbles. Therefore, at present, by heating and drying in advance, H20
This is handled by using polycarbonate from which low-molecular compounds such as and CO are emitted.

The present invention has been made in view of the above facts, and provides a method for adhesively sealing plastics such as polycarbonate and acrylic resin using hot melt without causing air bubbles to remain at the interface between the plastic and hot melt. The purpose is to provide. Means for Solving the Problems> The present invention provides hot melt adhesive sealing for plastics that generate gas when heated.
The present invention provides an adhesive sealing method using a hot melt, which is characterized by using a hot melt that has been degassed by reducing the pressure to Hg or more.

Degassing is preferably performed when the hot melt is melted or after the hot melt is melted and before the hot melt is applied to the plastic.

The present invention will be explained in detail below.

Adhesive sealing of plastics using hot melt is usually performed in the following order: ■ Melting the hot melt by heating ■ Applying the hot melt to the adhesive seal area of the adherend ■ Adhering or sealing the adherend .

In the method of the present invention, in the middle of such a series of work steps, the pressure is further reduced by 500 ■Hg or more. The process includes the step of degassing the furnace. By adding this degassing step, the accumulation of air bubbles at the interface between the adherend plastic and the hot melt is eliminated.

Although the theoretical background of this is not clear, degassed hot melt melts into H, O, which is generated from plastic when heated.
Hot melt, which is not degassed, already contains constant gas in a saturated state, and therefore cannot absorb gases generated from plastic. It is thought that the particles are retained at the interface.

Degassing is performed under reduced pressure of 500 mmHg or more.

This is because if the degree of pressure reduction is less than 500 mm}Ig, it will not be possible to perform sharp air sufficiently.

The hot melt may be sharpened during the adhesive sealing process described above, but preferably, it is performed during the melting of the hot melt, or after the hot melt is melted and before the hot melt is applied to the plastic. go to

FIG. 2 shows an example of a hot melt discharging apparatus for carrying out the method of the present invention. That is, FIG. 2 shows a hot melt dispensing device in which an automatic gun 9 or a hand gun 10 is connected to a hot melt applicator 4.

The method of the present invention will be explained based on FIG. 2. Hot melt is melted in a hot melt applicator 4, degassed under reduced pressure at the same time, then conveyed through an automatic gun hose 5 or a hand gun hose 6, and discharged from a nozzle 7. do. In this way, when degassing is performed at the same time as melting, the pressure reducing section 8 is not necessary.

Alternatively, the hot melt is melted in the hot melt applicator 4, conveyed in the automatic gun hose 5 or hand gun hose 6, decompressed and degassed in the decompression section 8, and then conveyed again in the automatic gun hose 5 or hand gun hose 6, Discharge from nozzle 7.

Alternatively, a device (not shown) in which a nozzle is directly connected to a pressure reducing section may be used, and the product may be discharged from the nozzle immediately after depressurization and degassing.

As for the pressure reduction method, any known normal method may be used.

By the way, examples of plastics to which the adhesive sealing method of the present invention can be effectively applied include plastics that generate gas when heated, such as Gt, polycarbonate, and acrylic resin.

In addition, the hot melt used in the adhesive sealing method of the present invention includes, for example, ethylene/vinyl acetate copolymer (EVA), low molecular weight polyethylene (LDPE), ethylene/ethyl acrylate copolymer ( EEA), thermoplastic block copolymers (e.g., styrene-isoprene block copolymers (SIS)
), styrene-butadiene block copolymer (SBS)
, and its hydrogenated products (SEBS), etc.) Butyl rubber (
IIR), etc., and add a tackifier (e.g.
rosin-based, terpene-based, petroleum resin-based compounds, etc.), waxes (e.g., paraffin wax, microcrystalline wax, Fischer-Tropsch wax, etc.)
, plasticizers (e.g., phthalate esters, glycol esters, hydrocarbon plasticizers, etc.), fillers (e.g., calcium carbide, talc, white carbon, etc.), stabilizers (antioxidants, ultraviolet absorbers, etc.), etc. A hot-melt type composition in which the additive is added as appropriate is suitable.

Table 1 &: shows. As is clear from Table 1, if the hot melt is degassed under reduced pressure under the conditions specified by the method of the present invention, no air bubbles remain at the interface between the hot melt and the polycarbonate plate.

Table 1 Example The present invention will be specifically described below based on Examples.

(Example 1) 100 g of rubber-based hot melt adhesive M-1000 (manufactured by Yokohama Rubber ■) was melted at 190°C, and after vacuuming under the conditions shown in Table 1, it was immediately applied on a polycarbonate plate, It was air cooled and then heated at 100° C. for 4 hours.

Regarding these, the presence or absence of air bubbles at the interface between the hot melt and the polycarbonate plate was observed. As a result, the effects of the invention> The present invention allows polycarbonate, acrylic resin, etc. A method of adhesively sealing plastics using hot melt is provided.

When adhesion and sealing are performed using the method of the present invention, air bubbles do not remain at the interface between the plastic and the hot melt, resulting in high adhesive strength and sealing performance.

Furthermore, since there is no need to heat and dry the plastic in advance, work efficiency increases.

7... Nozzle, 8... pressure reduction section, 9... automatic gun, 10...hand gun

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a state in which polycarbonate is bonded by hot melt using a conventional method. FIG. 2 is a schematic diagram showing an example of a hot melt discharging device.

Claims (3)

[Claims] (1) An adhesive sealing method using a hot melt, which is characterized in that when adhesively sealing a plastic that generates gas when heated, the hot melt is degassed by reducing the pressure to 500 mmHg or more. (2) The adhesive sealing method using a hot melt according to claim 1, wherein the degassing is performed when the hot melt is melted. (3) The adhesive sealing method using a hot melt according to claim 1, wherein the deaeration is performed after melting the hot melt and before applying the hot melt to the plastic.