JPH04249143A - Synthetic-resin laminated foam and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide the above synthetic-resin laminated foam, in which the adhesive properties between layers are improved and which has fine appearance, by simple operation. CONSTITUTION:A synthetic-resin laminated foam is manufactured in such a manner that a plurality of foamable synthetic resin composition sheets containing a pyrolysis type foaming agent are superposed, heated and contact- bonded and crosslinked and foamed, and the synthetic-resin laminated foam is obtained through said method.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a synthetic resin laminated foam and a method for producing the same, and more specifically, a synthetic resin laminated foam with improved interlayer adhesion and a simplified manufacturing method, and a method for producing the same. Regarding.

0002

[Prior Art] Conventionally, for example, two layers with different expansion ratios were used.
As a method for manufacturing a synthetic resin laminated foam such as a laminated foam having more than one layer or a laminated foam having two or more different types of synthetic resin foam layers, each foam is created in advance and then laminated. method is known.

[0003] As a laminating method, a method of heat-sealing a plurality of foam bodies is usually adopted. However, in the conventional heat fusion method, as shown in Figure 2, a clear fused layer is formed at the laminated interface (between layers) of each layer, resulting in an unsightly cross section and the occurrence of quality defects such as poor fusion. can be seen. In addition, a process of heat-sealing is required after each foam is manufactured separately, which is time-consuming and costly. Furthermore, there are problems such as the difficulty of laminating thin foams. Ta.

0004

SUMMARY OF THE INVENTION An object of the present invention is to provide a synthetic resin laminated foam that can be easily operated, has good adhesion between layers, and has a beautiful appearance. Another object of the present invention is to provide a method for easily producing a laminated foam even if it is thin.

[0005] As a result of intensive research in order to overcome the problems of the prior art, the inventor of the present invention conducted heat-pressure bonding of multiple types of sheets to laminate them at the stage of forming a foamable synthetic resin composition sheet before foaming. However, it was discovered that the above object could be achieved by crosslinking and foaming the material.
Based on this knowledge, we have completed the present invention.

[0006]

[Means for Solving the Problems] Thus, according to the present invention, a plurality of foamable synthetic resin composition sheets containing a pyrolyzable foaming agent are superimposed and bonded under heat, and then crosslinked and foamed. Provided is a method for producing a synthetic resin laminated foam characterized by the following. Further, according to the present invention, there is provided a synthetic resin laminated foam manufactured by the above method. The present invention will be explained in detail below.

(Foamable synthetic resin composition) Examples of the synthetic resin used in the present invention include low density polyethylene, medium to
High-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-vinyl chloride copolymer, ethylene-methacrylate copolymer, ethylene-
Ethylene polymers such as ethyl acrylate copolymers,
Examples include polypropylene polymers such as polypropylene, butene-propylene copolymer, and ethylene-propylene copolymer, olefin resins such as chlorinated polyethylene, ionomers, chlorosulfonated polyethylene, and mixtures thereof.

[0008] The foamable synthetic resin composition contains as an essential component a thermally decomposable blowing agent that is varied depending on the desired expansion ratio in the synthetic resin, and when crosslinking with an organic peroxide, the organic peroxide is used as the crosslinking agent. In addition, a foaming aid, a crosslinking aid, a flame retardant, an antioxidant, a filler, a coloring agent, etc. are added as necessary.

Examples of the thermally decomposable blowing agent used in the present invention include azodicarbonamide, dinitrosopentamethylenetetramine, oxybisbenzenesulfonyl hydrazide, azobisisobutyronitrile, and 4,4'-oxybisbenzenesulfonyl. Examples include various blowing agents that decompose with heat and generate gas, such as hydrazide. The proportion of the pyrolytic blowing agent used varies depending on the desired magnification, but
Generally, the amount is 1 to 25 parts by weight per 100 parts by weight of the synthetic resin.

Examples of organic peroxides used in crosslinking with organic peroxides include 1,1-bis(t-butylperoxy)cyclohexane, t-butylperoxymaleic acid, t-butylperoxy- 3,5,5-trimethylhexane, cyclohexane peroxide, t-butylperoxyallyl carbonate, t-butylperoxyisopropyl carbonate, 2,5-dimethyl-2
, 5-di(benzoylperoxy)hexane, 2,2-
Bis(t-butylperoxy)octane, t-butylperoxyacetate, 2,2-bis(t-butylperoxy)butane, t-butylperoxybenzoate, n
-butyl-4,4-bis(t-butylperoxy)berlate, di-t-butylperoxyisophthalate, methyl ethyl ketone peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butyl) (peroxy)hexane, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, t-butylcumyl peroxide, di-t-butyl peroxide, and the like. When using an organic peroxide, the proportion is usually preferably 0.3 to 5 parts by weight per 100 parts by weight of the synthetic resin.

The foamable synthetic resin composition of the present invention includes, for example, foaming aids such as fatty acid metal salts and zinc white, and crosslinking agents such as divinylbenzene, trimethylolpropane trimethacrylate, diethylene glycol dimethacrylate, and 1,4-polybutadiene. Auxiliary agents, flame retardants, fillers, antioxidants, colorants, etc. can be added.

(Method for producing a synthetic resin laminated foam) A synthetic resin composition containing a pyrolytic blowing agent is heated to a temperature above the temperature at which the synthetic resin melts, and the pyrolytic blowing agent or crosslinking agent (organic peroxide) is Knead at a temperature below decomposition temperature and form into a sheet using a sheet molding machine. The resulting multiple sheets were heated to a temperature below the temperature at which the pyrolytic foaming agent and crosslinking agent decompose (
The laminate is bonded under heat at a temperature of about 90 to 140° C. to form a laminate having a predetermined thickness. Examples of the compression bonding method include a method using a press or a calendar machine.

FIG. 3 is a perspective view showing a method of heat-pressing in a hydraulic press. FIG. 4 is a front view. A plurality of stacked foamable synthetic resin composition sheets 5 are placed on a press stand on which an aluminum spacer 4 is placed, and when pressed with presses 3, 3, the desired thickness (thickness of the spacer) is achieved. A laminated sheet can be obtained. Note that each foamable sheet is heated to a temperature below the temperature at which the pyrolyzable foaming agent and the crosslinking agent decompose.

Next, the laminated sheet is irradiated with ionizing radiation (electron beam or radiation) to give the resin crosslinking that provides the viscoelasticity necessary for foaming, and then the pyrolytic foaming agent is thermally decomposed to form a gas. is generated in the resin and foamed to obtain a crosslinked laminated foam. When crosslinking with an organic peroxide, the laminated sheet is preheated before foaming to give the resin the viscoelasticity necessary for foaming, and then heated and foamed, or simultaneously crosslinked and foamed to form a crosslinked laminated foam. obtain.

FIG. 1 is a schematic representation of a laminated foam obtained by the method of the invention. Since the foam is heat-pressed and laminated in advance and then cross-linked and foamed, it is possible to create a beautiful laminated foam without a heat-adhesive layer, and the adhesion between the layers is good due to the cross-linking between the layers. It is.

[0016]

[Examples] The present invention will be specifically explained below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Example 1] Low density polyethylene (MI=
2.5, density = 0.922) 15 parts by weight of azodicarbonamide as a pyrolytic blowing agent,
1 part by weight of zinc white was added as a foaming aid and mixed using a Henschel mixer. This mixture was put into an extruder with a diameter of 65 mm (L/D=26), melt-kneaded, and extruded from a T-die to create a foamable synthetic resin composition sheet (A) with a thickness of 1.80 mm and a width of 450 mm. The temperature conditions of the extruder are:
The temperature was 130°C, 135°C, and 140°C from the compound input side, the temperature of the mold was 125°C, and the extrusion rate was 45 kg/hour. In the same manner, a foamable sheet (B) having a thickness of 1.35 mm was created.

[0018] Cut out the foam sheets A and B, and
After heating to 0° C., it was placed on a press shown in FIG. 3, and pressed using a spacer having a thickness of 2.5 mm. The obtained foamable laminated sheet was irradiated with an electron beam (200K
eV, 4 Mrad) for crosslinking, and then introduced into an oven heated to 230° C. and heated and foamed. The foaming ratio of the obtained laminated foam is 30cc for both layers A and B.
/g. The interlayer adhesion of laminated foam is good;
Even when I tried to forcefully pull it off by hand, it did not come off.

[Examples 2 to 4] Laminated foams were produced in the same manner as in Example 1, except that the synthetic resins shown in Table 1 were used and the thickness and/or expansion ratio (amount of foaming agent added) was changed. Created. The results are shown in Table 1. In addition, PE-EVA is
It is a 1:1 mixture of polyethylene (PE) and ethylene-vinyl acetate copolymer (EVA; vinyl acetate content 19%, MI=2.5).

[0020]

[Table 1] As is clear from Table 1, not only the same resins but also
As in Example 2, good adhesion was observed even between different types of resins.

In Example 3, the compression width in crimping is 2
．． Adhesion was good although the distance was small, from 7 mm to 2.5 mm.

In Example 4, although the foaming ratios of Sheet A and Sheet B are different, good adhesion was obtained without peeling at the interface (adhesive surface). This indicates that slight variations in the foaming ratios of laminated sheets do not pose a problem in the laminated foaming method of the present invention.

[0023]

[Effects of the Invention] According to the method for producing a laminated foam of the present invention, since there is no fused layer between the layers, the laminated interface is more beautiful than that produced by conventional heat fusion, and the laminated foam has a more beautiful appearance between the layers. Since crosslinking has occurred, it has sufficient practical performance in terms of strength. Furthermore, it is possible to laminate thin materials, which is difficult with conventional heat fusion methods.

Moreover, compared to conventional methods, only one foaming step is required, making it possible to reduce the number of steps, time, and cost required for manufacturing.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional perspective view of a laminated foam obtained by the present invention.

FIG. 2 is a cross-sectional perspective view of a laminated foam obtained by conventional heat fusion.

FIG. 3 is a perspective view of a thermocompression bonding device used in the present invention.

FIG. 4 is a front view of the thermocompression bonding device used in the present invention.

[Explanation of symbols]

1 Adhesive surface of the laminated foam obtained by the present invention, 2
Fused layer of laminated foam obtained by conventional heat fusing method, 3 Hydraulic press used for heat compression bonding, 4 Thickness 2
．． 5mm aluminum spacer, 5 Layered foamable synthetic resin sheets A and B before foaming.

Claims (2)

[Claims] 1. A method for producing a synthetic resin laminated foam, which comprises stacking a plurality of sheets of a foamable synthetic resin composition containing a pyrolyzable foaming agent, heat-pressing them, and then crosslinking and foaming them. . 2. A synthetic resin laminated foam obtained by the manufacturing method according to claim 1.