JPH01129042A - Crosslinked polyolefin resin foam - Google Patents

Abstract

PURPOSE:To obtain the title foam excellent in adhesiveness and mechanical strength, by foaming and crosslinking a polyolefin resin mainly consisting of linear low-density PE and an ethylene/acrylic copolymer. CONSTITUTION:A polyolefin resin (A) is obtained by mixing linear low-density PE (a) of a density of 0.915-0.940g/cm<3> and an MI of 0.5-50g/10min, preferably, 1.0-10.0g/10min with an ethylene/acrylic acid copolymer (b) of an acrylic acid content of 5-30wt.% in a component (a) to component (b) ratio of 9-1:1-9 and, optionally, another polyolefin (c). Component A is mixed with a blowing agent (B), and the resulting mixture is melt-kneaded at a temperature at which component B does not substantially decompose and an elevated pressure, and molded into a sheet, which is crosslinked by irradiation with an ionizing radiation, and expanded by heating to a temperature higher than the decomposition temperature of component B.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a crosslinked 4-lyoretzine resin foam that has excellent adhesion and mechanical strength.

(Prior Art) Cross-linked foams of low-density polyethylene have been known as foams having uniform, fine closed cells and having excellent mechanical strength and heat resistance, and are used for various purposes.

However, when the above-mentioned crosslinked foam is bent into a composite plate with a steel plate, it does not have sufficient mechanical strength, and when used as a base material around an adhesive tube, it does not have sufficient adhesion, so a large amount of brimer is required. It was intended to be.

In order to improve these mechanical strengths, for example, add linear low density to 100 parts by weight of low density lyethylene. Liethylene 1
Cross-linked polyethylene foam CI containing 0 to 70 parts by weight
! #Kokai No. 58-53929) or crosslinked 4-lyethylene containing linear low-density polyethylene and ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer (
JP-A No. 59-41338) has been proposed.

However, although the former foam has improved mechanical strength, its flexibility decreases, making it particularly difficult to use as a base material around adhesive tubes. Although the latter foam has improved flexibility, its adhesion is insufficient, and when it is laminated to a steel plate and used as a heat insulating material for folded plates, a portion of the foam exhibits a phenomenon of peeling off from the steel plate.

(Problems to be Solved by the Invention) The present invention has been made as a result of extensive research in view of the current situation, and has developed a crosslinked polyolefin resin foam that has excellent flexibility, adhesiveness, and mechanical strength.

(Means for solving the problem) That is, the present invention provides linear low density - lyethylene and ethylene -
This is a crosslinked polyolefin resin foam made by crosslinking and foaming a monoolefin resin mainly composed of a mixture of acrylic acid co-blocker.

In the present invention, linear low-density polyethylene refers to ethylene, propylene,
butene-1, (butene-1, hexene-1, octene-1)
By combining a small amount of α-olefin such as 1,4-methylpentene-1, an appropriate number of short chain branches are introduced into the linear backbone polymer, thereby increasing the density to that of conventional high-pressure low-density polyethylene. It is preferably a polymer with a density of 0.915 to 0.940 II/crn'' and a melt flux of 0.5 to 50,9710 minutes, more preferably 1.0 to 10.0 g. /l 0 minutes.

In the present invention, the ethylene-acrylic acid copolymer is a copolymer of ethylene and acrylic acid, and those with an acrylic acid content of 5 to 30 vt% improve the flexibility, adhesiveness, and moldability of the foam. It is preferable from this point of view that if the content of acrylic acid is small, the adhesiveness and flexibility of the foam will decrease, and if the content is large, the moldability of the foam will become difficult. Further, the amount of the mixture of linear low density polyethylene and ethylene-acrylic acid copolymer is preferably at least 50% of the pace polymer.

Furthermore, the mixing ratio of linear low density polyethylene and ethylene-acrylic acid copolymer is in the range of 9:1 to 1:9, particularly preferably in the range of 4:1 to 1:4, in order to improve the mechanical strength of the foam. , preferred in terms of flexibility, adhesiveness, and moldability. In this case, if the amount of linear low-density polyethylene is too small, mechanical strength such as tensile strength will be poor, and if it is too large, flexibility and adhesiveness will be reduced.

The present invention also provides the above-mentioned linear low density polyethylene and ethylene-
In addition to the mixture with the acrylic acid copolymer, ordinary polyolefins such as low density polyethylene may be blended, thereby imparting chemical resistance properties or improving extrusion processability.

The method for manufacturing the foam of the present invention is similar to the conventional method for manufacturing low-density polyethylene crosslinked foam. That is, a blowing agent is blended into the resin mixture, cross-melted using an extruder at a temperature and pressure that does not substantially decompose the blowing agent, and formed into a sheet, which is then crosslinked by irradiating it with ionizing radiation. Thereafter, a method of obtaining a crosslinked foam by foaming by heating above the decomposition temperature of the blowing agent, or a method of blending a blowing agent and a crosslinking agent into the above resin mixture and using an extruder etc. to remove the blowing agent and crosslinking agent at a practical cost. After cross-melting at a temperature and pressure that does not cause decomposition and forming it into a sheet, this is crosslinked by heating to a temperature at which the crosslinking agent decomposes, and then crosslinked by heating to a temperature above the decomposition temperature of the blowing agent. There is a way to obtain foam.

(Example) Example (1) Density 0.920.9/work 3, melt index 1.0
g/10 min linear low density/IJ ethylene 20 parts by weight,
Acrylic acid content 81 Melt index 5.5fi/
80 parts by weight of a 10-minute ethylene-acrylic acid copolymer, 8 parts by weight of a blowing agent (azodicalcareamide), and 2.0 parts by weight of an auxiliary agent (fatty acid ester) were mixed together and formed into a sheet using an extruder. After molding, 4 Mrad with an electron beam irradiation machine
The material was crosslinked by irradiation with an electron beam, and then introduced into a hot air oven at 230° C., and heated and foamed by passing through it continuously to obtain a foamed sheet of the present invention having a thickness of about 2.0 fl.

Example (2) Same linear low density as Example (1), j? 20 parts by weight of IJ ethylene, 60 parts by weight of the same ethylene-acrylic acid copolymer as in Example (1), density 0.921. jil/c
m', 20 parts by weight of low-density polyethylene with a melt index of 2.5.9/10, 8 parts by weight of a blowing agent (azodical♂apore), 20 parts by weight of a blowing agent and an auxiliary agent (fatty acid ester), and carried out. Crosslinking and foaming were carried out under the same conditions as in Example 1 to obtain a foamed sheet of the present invention having a thickness of about 2.0 mm.

Comparative Example (1) 818 parts of a blowing agent (azodicardenamide) and an auxiliary agent (
Example (1)
Cross-linking and foaming were performed under the same conditions as above to a thickness of approximately 2.0 fl.
A comparative foam sheet was obtained.

Comparative Example (2) Same linear low density as Example (1)? 30 parts by weight of polyethylene, ethylene-vinyl acetate copolymer (VA content 10 parts by weight)
wt%, MI 3.0 p710 min), 8 parts by weight of blowing agent and 0.5 parts by weight of auxiliary agent were mixed, and Example (
Cross-linking foaming was carried out under the same conditions as in 1), and the thickness was 2. O
A comparative foam sheet of U was obtained.

The performance of the thus obtained foamed sheets of the present invention and comparative foamed sheets was measured. The results are shown in Table 1.

(Effects) As described in detail above, the polyolefin resin foam of the present invention has excellent mechanical properties and adhesive properties, and is therefore useful for composite plates with steel plates or the like, adhesive plates, etc.

Claims (2)

[Claims] (1) A crosslinked polyolefin resin foam obtained by crosslinking and foaming a polyolefin resin mainly composed of a mixture of linear low density polyethylene and an ethylene-acrylic acid copolymer. (2) The crosslinked polyolefin resin according to claim 1, characterized in that the mixing ratio of linear low density polyethylene and ethylene acrylic acid copolymer is in the range of 9:1 to 1:9. foam.