JPH08309902A - Production of laminate - Google Patents

Abstract

PURPOSE: To prevent the generation of the rupture of a foamed sheet at a time of bending processing by irradiating an extruded sheet formed from a foamable polyolefinic resin compsn. with electron beam to crosslink the same and forming a high density polyethylene resin layer on the single surface of the crosslinked sheet and heating the whole to foam the sheet and bonding a metal plate to the foamed sheet layer. CONSTITUTION: A compd. obtained by adding a foaming agent to a polyolefinic resin is melted and kneaded to prepare a foamable polyolefinic resin compsn. and this compsn. is extruded to form a sheet which is, in turn, irradiated with electron beam. Next, a high density polyethylene resin layer is formed on at least the single surface of the crosslinked sheet by extrusion lamination and the crosslinked sheet is heated to decompose the foaming agent to form a foamed sheet 2. Finally, a metal plate 4 is laminated to the foam layer of the obtained foamed sheet 1 through an adhesive layer 3 to obtain a laminate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a laminate comprising a metal plate and a polyolefin resin foam sheet. Such a laminate is used, for example, as a roofing material because the foam sheet is lightweight, has excellent heat insulating properties, and has good workability.

[0002]

2. Description of the Related Art Conventionally, a laminate comprising a metal plate and a polyolefin resin foam sheet such as a foam polyethylene sheet has been manufactured by bonding a foam polyethylene sheet to a metal plate via an adhesive. This is followed by roll forming or press forming at 90 ° or more depending on the application in the processing step,
In some cases, a 180 ° bending process is performed.

In the above-mentioned laminate, the expanded polyethylene sheet was obtained by an electron beam cross-linking method, that is, a method of forming an extruded sheet containing a foaming agent, cross-linking it by electron beam irradiation, and then foaming it by heating. When the laminated body is bent, the foam sheet of the laminated body may be broken by a working die (see Japanese Utility Model Laid-Open No. 6-81731).

On the other hand, the foamed polyethylene sheet is obtained by a chemical cross-linking method, that is, a method in which an extruded sheet containing a foaming agent and a cross-linking agent is molded and then heated to simultaneously perform cross-linking and foaming. In this case, the surface friction coefficient of the foam sheet was 0.5 or less and the slip property was good, and the foam polyethylene sheet layer did not break, but
There is a problem that it is difficult to adjust the degree of crosslinking and control the temperature conditions.

[0005]

In view of the above points, the present invention does not cause breakage of the foam sheet during bending of the laminate, and has a degree of crosslinking at the time of manufacturing the foam sheet. It is an object of the present invention to provide a method for producing a laminated body which does not have any difficulty in preparation of the composition and control of temperature conditions.

[0006]

Means for Solving the Problems The method for producing a laminate according to the present invention is a method in which an extruded sheet formed from a foamable polyolefin resin composition is irradiated with an electron beam to crosslink, and then at least one surface of the crosslinked sheet obtained. A high-density polyethylene resin layer is formed on the above, and then the crosslinked sheet is heated to foam, and a metal plate is bonded to the foam side of the obtained foam sheet.

The expandable polyolefin resin composition is mainly composed of a polyolefin resin and a foaming agent.

Examples of the polyolefin resin include homopolymers of olefin monomers such as ethylene, propylene and butene-1: ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, ethylene-vinyl chloride copolymer, ethylene-acrylic acid. Copolymers based on olefins such as copolymers: One polyolefin-based resin with other polyolefin-based resin blocked, random block, random copolymerized: Chlorinated polyethylene, chlorinated polypropylene, etc. Substituted polyolefin: Polyolefin-based Examples thereof include those obtained by blending another resin such as ethylene-vinyl acetate copolymer or polyvinyl chloride, or rubber such as chloroprene rubber. As a polyolefin resin, melt index (MI) 1-1
It is preferably 0, particularly preferably a polyethylene resin.

As the foaming agent, azodicarbonamide,
An organic decomposition type foaming agent such as dinitrosopentamethylenetetramine, allophanic acid amide, p, p′-oxybisbenzenesulfonyl hydrazide, or an inorganic decomposition type foaming agent such as sodium bicarbonate can be appropriately used. Among these, azodicarbonamide or the one based on it is preferable. In order to accelerate the decomposition of the foaming agent, a known decomposition aid such as zinc oxide or zinc stearate may be appropriately added.

The amount of the foaming agent added is the polyolefin resin 1
10 to 50 parts by weight, preferably 20 to 100 parts by weight
30 parts by weight. If the amount of the foaming agent added is less than 10 parts by weight with respect to 100 parts by weight of the polyolefin resin, the crosslinked product in a molecularly fixed state cannot be sufficiently expanded due to the three-dimensional network, so that the desired foaming is achieved. Magnification cannot be obtained. On the other hand, if the amount of the foaming agent added exceeds 50 parts by weight, the cell membrane is broken due to an increase in the internal pressure, and conversely the foaming ratio decreases.

A cross-linking aid such as a polyfunctional monomer may be used in combination for increasing the cross-linking efficiency. As the cross-linking aid, for example, divinylbenzene, diallylbenzene, divinylnaphthalene, polyethylene dimethacrylate,
Bifunctional monomers such as 1,9-nonanediol dimethacrylate and diallyl phthalate, trimethylolpropane trimethacrylate, triallyl isocyanurate,
Trifunctional monomers such as triallyl trimellitate are used. These crosslinking aids may be used alone or in combination of two or more.

The amount of the crosslinking aid added is preferably 0.01 to 30 parts by weight, more preferably 0.05 to 15 parts by weight, based on 100 parts by weight of the polyolefin resin.

The expandable polyolefin resin composition includes
Additives such as an antioxidant, a heat stabilizer, a metal damage inhibitor, an ultraviolet absorber and a pigment can be added if necessary.

According to the method of the present invention, first, a foaming agent is added to a polyolefin resin, and if necessary, a crosslinking aid and various additives are added, and the resulting mixture is melt-kneaded to form a foamable polyolefin. A resin composition is prepared, a sheet is formed from this composition, and the obtained sheet is crosslinked by irradiation with ionizing radiation. The above-mentioned sheet is formed as follows.
Using a general-purpose kneading device such as a single-screw extruder, a twin-screw extruder, a Henschel mixer, a Banbury mixer, a kneader mixer, and a mixing roll, the mixture is melt-kneaded at a temperature lower than the decomposition temperature of the pyrolytic foaming agent, The kneaded material obtained is formed into a sheet. Sheet width is preferably 300-10
00 cm, and the thickness is preferably 1 mm to 5 mm.

As a crosslinking method, an electron beam crosslinking method can be applied. In the electron beam cross-linking method, ionizing radiation such as α rays, β rays, γ rays, X rays and ultraviolet rays is used. Irradiation dose is usually 1
~ 50.0 Mrad.

Next, a high density polyethylene resin layer is formed on at least one side of the obtained crosslinked sheet. The high density polyethylene resin layer is preferably formed by extrusion lamination. The thickness of the high-density polyethylene resin layer is preferably about 80 to 200 μm.

High density polyethylene resin (density 0.94 g
/ Cm ³ or more), MI = 5 to 15 is preferable.

Next, the crosslinked sheet is heated to decompose the foaming agent to foam the foamed sheet.

As a heating means for foaming, hot air, infrared ray or electric heater, steam heating, ultrasonic heating or a combination thereof is used. The heating temperature depends on the type of polyolefin resin or foaming agent, but is usually around 250 ° C.

The expansion ratio of the foam sheet thus obtained is usually 10 to 50 times, and the thickness is usually 2 to 10 m.
m. The thickness of the high density polyethylene resin layer after foaming is preferably about 5 to 20 μm.

Finally, a metal plate is adhered to the obtained foam sheet with an adhesive. As a metal plate, thickness 0.5
A steel plate of about 1.0 mm is preferable. The adhesive is preferably a chloroprene adhesive, but is not limited to this.

[0022]

In the method of the present invention, since the high-density polyethylene resin layer is formed on at least one side of the electron beam cross-linked polyolefin resin sheet and the cross-linked sheet is then foamed by heating, the high-density polyethylene layer has a uniform thickness. At the same time, it does not peel off from the obtained foam sheet.

Further, since the foam sheet is protected by the high-density polyethylene layer covering the foam sheet, the foam sheet does not break during bending of the laminate, and the surface of the high-density polyethylene layer is not broken. The static friction coefficient and dynamic friction coefficient are low.

[0024]

EXAMPLES Next, examples of the present invention will be described.

Example 1 Polyethylene resin (MI: 4, density: 0.921 g /
cm ³ ) 100 parts by weight was mixed with 15 parts by weight of azodicarbonamide as a foaming agent, and the mixture was melt-kneaded at 140 ° C. using an extruder, and the obtained kneaded product was extruded into a sheet by a T-die method. Molded to obtain a foamable sheet having a thickness of 2.00 mm.

Next, the foamable sheet was crosslinked by irradiation with ionizing radiation (irradiation dose of 4.0 Mrad).

Thereafter, a high density polyethylene resin (density: 0.965 g / cm ³ , M
I: 13) is extruded and laminated to obtain a thickness of 1
A resin layer of 00 μm was formed.

Next, the crosslinked sheet was heated in a vertical foaming machine at a temperature of 240 ° C. to decompose the foaming agent and foamed to obtain a foamed sheet.

The foam sheet thus obtained had an expansion ratio of 30 and a thickness of 4.15 mm, and the foamed high density polyethylene resin layer had a thickness of 9 μm. Finally, a steel plate having a thickness of 0.7 mm was bonded to the obtained foam sheet with a chloroprene-based adhesive to obtain a laminate composed of the steel plate and the foam sheet.

The laminated structure of the laminate thus obtained is shown in FIG. 1 attached. This laminate has a high-density polyethylene resin layer (1) laminated on one side of a foam sheet (2) and a steel plate (4) bonded on the other side via an adhesive layer (3). Is.

Comparative Example 1 A laminate comprising a steel sheet and a foam sheet was obtained in the same manner as in Example 1 except that the high density polyethylene resin layer was not formed on one surface of the crosslinked sheet.

Comparative Example 2 A steel plate and a foam were prepared in the same manner as in Example 1 except that a low density polyethylene resin (density: 0.923 g / cm ³ , MI: 4) was used instead of the high density polyethylene resin. A laminated body including a body sheet was obtained.

Performance Test The static friction coefficient and dynamic friction coefficient of each laminate obtained in the examples and comparative examples were measured. In addition, each laminate was subjected to bending at 90 ° by roll forming, and the presence or absence of breakage of the foam sheet of the laminate and the presence or absence of peeling of the high-density polyethylene resin layer from the foam sheet were examined. Table 1 shows the results.

[0034]

[Table 1] As can be seen from Table 1, in the laminates obtained in the examples, the foam sheet did not tear, and the high-density polyethylene resin layer did not peel off from the foam sheet.

[0035]

Since the method for producing a laminate according to the present invention is constructed as described above, it is possible to produce a laminate in which the foam sheet does not break during bending.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a laminated structure of a laminated body obtained in an example.

[Explanation of symbols]

 1: High-density polyethylene resin layer 2: Foam sheet 3: Adhesive layer 4: Steel plate

Claims (1)

[Claims] 1. An extruded sheet formed from a foamable polyolefin resin composition is irradiated with an electron beam to crosslink it,
A laminate characterized in that a high-density polyethylene resin layer is formed on at least one surface of the obtained crosslinked sheet, the crosslinked sheet is then heated to foam, and a metal plate is bonded to the foam side of the obtained foam sheet. Body manufacturing method.