JPH0543731A - Olefin resin crosslinked foam - Google Patents

Abstract

(57) [Summary] [Purpose] To provide an olefin resin crosslinked foam having a high expansion ratio, high skin strength and bending rigidity, and good workability such as film lamination. [Structure] 90 to 40 parts by weight of polyethylene having a density of 0.926 g / cm ³ or more, and a density of 0.918 to 0.940 g /
cm ³ linear low density polyethylene (L-LDPE) 1
A foaming resin composition containing 0 to 60 parts by weight and a pyrolytic foaming agent is molded, irradiated with ionizing radiation to be crosslinked, and then foamed by heating to have a foaming ratio of 30 cc.
/ G or more olefin resin crosslinked foam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an olefin resin crosslinked foam, and more specifically, it is required to have rigidity and mechanical strength even at a high expansion ratio and to have cushioning properties such as slats and heat insulating properties. The present invention relates to an olefin-based crosslinked foam suitable for the field.

[0002]

2. Description of the Related Art Conventionally, an olefin resin foam has been used as a bath drainboard, and a film is usually laminated on the surface thereof. Since it is required that the drainboard for a bath has particularly good heat insulating properties and cushioning properties, a foam having a high expansion ratio and a low apparent density is desirable. However, when the apparent density of the foam becomes smaller than a certain level, when laminating the film on the surface of the foam, so-called raindrops and air squeeze phenomenon occur, and air enters between the foam and the film and adheres. Not doing so, detracts from the product value.

For example, low density polyethylene, medium / high density polyethylene, etc. are cross-linked by electron beam irradiation,
When a cross-linked foam with a high ratio is created, the expansion ratio of the skin layer becomes too high, the skin strength decreases, the rigidity is impaired, and when laminating the film on the surface,
Raindrops and air spillover phenomena are more likely to occur.

On the other hand, when linear low density polyethylene (L-LDPE) is used in order to obtain a foam having good mechanical strength, the foam becomes too soft due to the low crystallinity of the polymer. The workability is reduced when making a saw.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an olefin resin crosslinked foam having a high expansion ratio, high skin strength and bending rigidity, and good workability for film laminating and the like. .

As a result of earnest studies, the present inventors have made an olefin resin suitable as a bath drainboard by forming a crosslinked foam using a resin raw material containing polyethylene having a specific density and L-LDPE. The inventors have found that a crosslinked foam can be obtained, and have completed the present invention based on the findings.

[0007]

The gist of the present invention is that 90 to 40 parts by weight of polyethylene having a density of 0.926 g / cm ³ or more and linear low-density polyethylene having a density of 0.918 to 0.940 g / cm ³ ( L-LDPE) 10 to 60 parts by weight, and a foamable resin composition containing a pyrolyzable foaming agent are molded, irradiated with ionizing radiation to crosslink, and then,
An olefin resin crosslinked foam having a foaming ratio of 30 cc / g or more obtained by heating and foaming.

The present invention will be described in detail below. In the present invention, as the olefin resin, (a) density 0.926 g
/ Cm ³ or more, preferably 0.926 to 0.940 g /
cm ³ polyethylene 90 to 40 parts by weight, preferably 8
0 to 50 parts by weight, and (b) density 0.918 to 0.940
10 to 60 parts by weight, preferably 20 to 50 parts by weight of L-LDPE of g / cm ³ are used.

By combining these two types of polyethylene in a specific blending ratio, a crosslinked foam having good skin strength and bending rigidity, and therefore mechanical strength without impairing the feeling of rigidity can be obtained.

Examples of the thermal decomposition type foaming agent used in the present invention include azodicarbonamide, oxybenzenesulfonyl hydrazide, azobisisobutyronitrile, barium azodicarboxylic acid, dinitrosopentamethylenetetramine and hydrazodicarbonamide. The compound which decomposes | disassembles by the heat of and generate | occur | produces a gas can be mentioned.

The addition ratio of the heat-decomposable foaming agent can be appropriately determined according to the desired expansion ratio, but the resin component 10
It is usually 2 to 30 parts by weight, preferably 5 to 25 parts by weight, relative to 0 parts by weight.

As the crosslinking aid, for example, a polyfunctional monomer represented by divinylbenzene, trimethylolpropane triacrylate, ethylene glycol dimethacrylate, etc., and a polymer having an unsaturated double bond represented by 1.4 polybutadiene, etc. You may use together. The addition ratio of these cross-linking aids can be appropriately determined according to the desired degree of cross-linking, but usually 1 to 10 parts by weight in the case of a polyfunctional monomer, relative to 100 parts by weight of the resin component. In the case of a polymer having a saturated double bond, 4 to
A range of 20 parts by weight is preferred.

Further, various additives such as an antioxidant, an antiaging agent, an ultraviolet absorber, an antistatic agent, a pigment and the like can be added if necessary.

In the present invention, polyethylene, LL
A composition containing DPE and a heat-decomposable foaming agent is melt-kneaded at a temperature below the temperature at which the foaming agent decomposes, for example, using a Banbury mixer, a single-screw extruder, a twin-screw extruder, etc., and a desired shape such as a sheet shape. To mold.

The resulting molded product of the expandable resin composition contains α
Cross-linking is carried out by irradiation with ionizing radiation such as rays, β rays, γ rays and electron rays. The irradiation dose of ionizing radiation is usually 0.1 to
It is about 50 Mrad, preferably about 0.5 to 20 Mrad.

After irradiating with ionizing radiation, the foaming agent is heated above the decomposition temperature to foam. This heat foaming is performed using, for example, a vertical foaming furnace, a horizontal foaming furnace, or the like.

The expansion ratio of the crosslinked foam is 30 cc / g or more, preferably 35 cc / g or more, more preferably 40.
It is cc / g or more. With a high expansion ratio, functions such as cushioning properties and heat insulating properties can be obtained.

The olefin resin crosslinked foam of the present invention is
It has a high expansion ratio, a large skin strength and a high bending rigidity, and even if a film is laminated, the phenomenon of air squeezing does not occur.

[0019]

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 20 parts by weight of L-LDPE having a density of 0.920 was mixed with 80 parts by weight of polyethylene (PE) having a density of 0.930, and further, a resin component 100 was added.
22 parts by weight of azodicarbonamide was added to parts by weight, and the mixture was molded into a sheet by an extruder.

The resulting foamable sheet (thickness: 1.6 mm)
Then, an electron beam of 4 Mrad was irradiated with an electron beam irradiator to cross-link and then introduced into a vertical foaming furnace heated at 250 ° C. to foam. The obtained co-foam had a thickness of 4.0 mm and an expansion ratio of 40.6 cc / g.

When a film was laminated on the surface of this crosslinked foamed product, it was possible to obtain a beautiful laminated body without air squeezing.

(Example 2) A crosslinked foam was obtained in the same manner as in Example 1 except that 50 parts by weight of L-LDPE having a density of 0.920 was mixed with 50 parts by weight of PE having a density of 0.930. .

(Comparative Example 1) 10 PE having a density of 0.930
A crosslinked foam was obtained in the same manner as in Example 1 except that 0 part by weight was used.

Comparative Example 2 A crosslinked foam was obtained in the same manner as in Example 1 except that 100 parts by weight of low density polyethylene having a density of 0.920 was used.

The physical properties of the foams obtained in the above Examples and Comparative Examples were measured, and then a film was laminated on each foam to evaluate the workability. The results are shown in Table 1. In addition, the measuring method and evaluation method of each physical property are as follows.

<Surface Strength> A cloth tape having a width of 25 mm is applied to the surface of the foam, and a roll of 4 kg is reciprocated twice on the foam tape, and the tape and the skin are peeled off by a tensile tester, and the strength at that time is measured.

<Bending rigidity> Using a taper type stiffener tester, the initial stiffness is measured.

<Expansion ratio> A sample was cut into a 10 cm square, its weight and thickness were measured, and the volume was calculated from the thickness.
Calculate by volume / weight.

<Lamination Property> ○: No air sticking ×: Air sticking

[0031]

[Table 1]

Slatels were prepared from the crosslinked foamed raw fabrics obtained in Examples 1 and 2 and practically evaluated. As a result, cushioning properties and appropriate rigidity were obtained, and good practical performance was obtained. there were.

[0033]

EFFECTS OF THE INVENTION According to the present invention, since a foam having a feeling of rigidity and a high mechanical strength can be obtained, it is possible to provide a molded product having a higher expansion ratio and excellent cushioning property and heat insulating property. . Workability such as film lamination is also good, and cost can be reduced. Since the elongation percentage is good, it is possible to provide a molded product that has a wide range of applications for molding and has a sense of rigidity.

Claims (1)

[Claims] 1. 90 to 40 parts by weight of polyethylene having a density of 0.926 g / cm ³ or more, and a density of 0.918 to 0.940.
g / cm ³ linear low density polyethylene (L-LDP
E) A foaming resin composition containing 10 to 60 parts by weight and a pyrolyzable foaming agent is molded, irradiated with ionizing radiation to be crosslinked, and then heat-foamed to give a foaming ratio of 30.
Olefin-based resin crosslinked foam having a cc / g or more.