JPS6213173B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a method for producing a composite by bonding a chemically crosslinked polyolefin foam and an adherend such as a nonwoven fabric to be superimposed on the foam. Cross-linked polyolefins in general, and cross-linked polyethylene foams in particular, are lightweight, have thermal insulation properties, cushioning properties,
Due to its properties such as closed cell properties, the demand for it has been increasing recently. Most of the applications use composites made of crosslinked polyolefin foam and other adherends such as nonwoven fabrics. Generally, methods for producing this composite include a method in which these two are bonded together using a solvent-type or hot-melt type adhesive, a powder lamination method in which thermoplastic powder is placed between the bonded materials, and a method in which thermoplastic powder is bonded using an extruder. This was done by the Ruderlami method, in which a molten resin was placed between the bonded materials, but in all of these methods adhesives or alternative adhesives were used to obtain composites. . There is also a method of bonding using heat, which uses an infrared lamp or a JIUBAN heater (a method of converting gas combustion heat into infrared heat) as a heat source for the adhesive surfaces to be bonded. It is something. Since these methods are indirect heating methods, there is a limit to the temperature of the surface of the adhered material. For example, when laminating foamed polyethylene (specific gravity 0.03 g/cc, thickness 2 mmt) and synthetic resin nonwoven fabric (nylon 66, basis weight 200 g/m ² , tricot fabric), the foamed polyethylene is heated. In the case of immediate pressure bonding with a roll or press, it was difficult to achieve sufficient heating using indirect heating using the above-mentioned infrared lamp, bank heater, or the like. The reason for this is that foamed polyethylene is an extremely good heat insulating material and has closed cells, so when it is heated for a long time, such as by indirect heating, the cells of the foamed polyethylene undergo thermal expansion, resulting in a volume change (dimensional change). On the other hand, the nonwoven fabric as the adherend is bonded to the expanded polyethylene whose volume has changed, and is cooled in that state. Therefore, only the foamed polyethylene shrinks significantly,
Wrinkles or large warps occur in the composite, resulting in a significant loss of commercial value. Incidentally, adherend materials such as nonwoven fabrics usually have a significantly smaller coefficient of thermal expansion than foamed polyethylene. The present invention has been made in view of the current situation, and as a result of extensive research, we have discovered a method for producing a composite of a polyolefin foam and an adherend material that has excellent adhesive strength and a beautiful appearance. That is, the present invention comprises a chemically crosslinked polyolefin, a paper to be laminated on the foam,
In a method of bonding to an adherend of either cloth or metal to form a composite, the surface of the polyolefin foam or both surfaces of the joint are heated and oxidized with flame to bond the adherend. It is characterized by this. The reason why the present invention is specifically limited to chemically crosslinked polyolefin foam is that the foam is made by mixing polyethylene with a chemical crosslinking agent, such as dicumyl peroxide, first heating it to the decomposition temperature of the crosslinking agent, and then increasing the temperature to the foaming temperature. Since it is crosslinked by heating, its gel fraction has a crosslinking rate of at least 60%. At the same time as having this high gel fraction, the surface of the foam is moderately oxidized by high-temperature and high-speed heating, and the foam has an extremely small coefficient of thermal expansion, and the high gel fraction effectively acts as an adhesive on oxidized surfaces. However, the obtained composite has a smooth and beautiful surface without wrinkles or warpage, and its adhesive surface has strong adhesive properties. On the other hand, non-crosslinked polyolefin foams do not meet the requirements for a high gel fraction as described above, so this cannot be applied, and when radiation crosslinked foams are used, the gel fraction is low. It is presumed that if it is less than 60% at most, and at the same time the surface of the foam is not oxidized, it will not be able to impart excellent adhesion to the adherend. In the present invention, the surface of the foam with a high gel fraction or both surfaces of the foam and the adherend are exposed to flame, thereby oxidizing the surface of the foam at high temperature and high speed to bring it into a slightly molten state. It has good adhesion. Therefore, since this adhesive layer is extremely thin, it does not act as a core that inhibits the flexibility of the composite, that is, it does not cause any discomfort, and there is very little decrease in thickness due to the pasting process before pasting the foam. It is something. As described above, in the present invention, by heating and oxidizing a foam having a high gel fraction at high temperature and high speed, it is possible to obtain remarkable effects not found in conventional composite manufacturing methods. In addition, in the present invention, as for the adherend, metal,
It may be made of cloth, paper, etc. Particularly suitable are nonwoven fabrics made of fibers such as nylon and polyethylene. Furthermore, when flame is applied to the surface of the polyolefin foam according to the present invention, the temperature is thought to be 800°C or higher, but in that case, lamination is carried out at an optimal temperature so as not to cause deformation in the thickness of the crosslinked polyolefin foam. It is necessary to. Note that when flames are applied to both sides of the crosslinked polyolefin foam and the adherend, the former foam is primarily heated, and the latter adherend is heated auxiliarily. Next, examples of the present invention will be described. Example 1 and Comparative Examples 1 and 2 As chemically crosslinked polyolefin foam, thickness 4
A chemically cross-linked polyethylene sheet (manufactured by Furukawa Electric Co., Ltd.) with a specific gravity of 0.03 g/cc was sliced into 2 mm thick pieces and cut in half. , weight 200
A composite according to the present invention was obtained by adhering G.g. That is, in the figure, 1 is a polyethylene foam sheet, 2 is a fabric, 3 is a pair of pressure rolls, and 4 is a lamination burner. (using gas) to heat and bond them together, where α is the distance between the burner and the foamed polyethylene sheet or fabric. As a comparative example, a 2 mm thick radiation-crosslinked polyethylene sheet (manufactured by Sekisui Chemical Co., Ltd.) (Comparative Example 1) and a 2 mm thick non-crosslinked polyethylene sheet (manufactured by Nippon Styrene Paper Co., Ltd.) were treated in the same manner as above. Each composite was obtained by pasting the fabric. Table 1 shows the results of measuring the optimal lamination speed, change in foam thickness after lamination, and adhesive strength for the composite obtained by the method of the present invention and the composite obtained by the comparative example. That's right.

【table】

[Table] As is clear from the above table, the composite obtained by the method of the present invention has almost no change in the thickness of the foam and has superior adhesive strength compared to the composite obtained by the comparative method. It is something. Example 2 and Comparative Examples 3 and 4 The same sheet and fabric as the chemically crosslinked polyethylene foam sheet in Example 1 were polyester nonwoven fabric (NW-160/011 manufactured by Nippon Vilene Co., Ltd.,
155 g/m ² ) by the method shown in FIG. 1 to obtain a composite according to the method of the present invention. Further, a radiation-crosslinked polyethylene sheet similar to Comparative Example 1 and a non-crosslinked polyethylene sheet similar to Comparative Example 2 were used, and a polyester nonwoven fabric similar to that described above was laminated to each of them by the method shown in FIG. Obtained a complex. For the composite obtained by the method of the present invention and the composite obtained by the comparative example, the optimum lamination speed, change in thickness of the foam after lamination, and adhesive strength were measured, and the results are shown in Table 2. It is.

【table】

[Table] As is clear from the above table, the composite obtained by the method of the present invention has almost no change in the thickness of the foam and has superior adhesive strength compared to the composite obtained by the comparative method. It is. Example 3 A sheet similar to the chemically crosslinked polyethylene foam sheet in Example 1 and kraft paper were laminated together by the method shown in FIG. 1 to obtain a composite according to the method of the present invention. The optimal lamination speed, thickness change after lamination, and adhesive strength of the composite were measured, and the results are shown in Table 2.

[Table] As detailed above, according to the method of the present invention, a chemically crosslinked polyolefin foam and an adherend can be easily bonded together through a simple process, and the adhesive strength is excellent without changing the thickness of the foam. It has remarkable effects such as not only making the composite material moist but also preventing wrinkles, shearing, etc. from occurring in the composite material.

[Brief explanation of the drawing]

The drawings are schematic illustrations for implementing the method of the present invention. 1...Chemically crosslinked polyolefin foam sheet,
2... Adherent sheet such as nonwoven fabric, 3... Roll,
4...Gas burner.

Claims (1)

[Claims] 1 In a method of forming a composite by bonding a chemically crosslinked polyolefin foam and an adherend of any one of metal, paper, or cloth to be superimposed on the foam, a gel is used as the chemically crosslinked polyolefin foam. 1. A method for producing a composite, which comprises using a polyolefin foam having a fraction of 60% or more, and bonding the surface of the foam or both surfaces of the foam and an adherend by heating and oxidizing the same with a flame.