JPS5853929A - Crosslinked polyethylene resin foam - Google Patents

Abstract

PURPOSE:To obtain the titled foam having excellent mechanical properties such as tensile strength, elongation, peeling strength, etc. and suitable as the substrate of pressure-sensitive adhesive tape, heat-insulating material for laminating to steel sheet, etc., by adding a specific amount of a linear low-density polyethylene to a low-density polyethylene, and foaming and crosslinking the mixture. CONSTITUTION:100pts.wt. of (A) a low-density polyethylene (preferably having a density of 0.91-0.93g/cm<3> and a melt index of 1-10g/10min) is mixed with 10-70pts.wt. of (B) a linear low-density polyethylene (preferably having a density of 0.915-0.94g/cm<3> and a melt index of 1.0-10g/10min). A foaming agent such as azodicarbonamide is added to the mixture, and mixed homogenously. The mixture is molten and kneaded at a temperature below the decomposition point of the foaming agent, formed to a sheet, and crosslinked by irradiation with ionizing radiations such as beta-ray, gamma-ray, etc. at a dose not e.g. 0.5-20 Mrad to obtain the objective crosslinked foam.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crosslinked polyethylene resin foam with excellent mechanical strength.

Cross-linked low-density polyethylene foams have been known as foams that have uniform, fine closed cells, have a certain degree of mechanical strength, and have excellent heat insulation properties, and are used for a variety of purposes, including those for adhesive tapes. Mechanical strengths such as tensile strength, elongation, and peel strength were not sufficient for applications that require special mechanical strength, such as insulation materials for folding plates that are bonded to base materials and steel plates and then bent. . In order to improve their mechanical strength, a method of reinforcing the skin layer by laminating polyethylene films, etc., is shown in Table 1.
111 Either a method of adjusting the degree of crosslinking of the skin layer was used, sufficient mechanical strength was not obtained, manufacturing was complicated, manufacturing cost was high, etc., and in either case, there was no definitive solution. I hadn't reached it yet.

An object of the present invention is to provide a crosslinked polyethylene resin foam that has even better mechanical strengths such as tensile strength, elongation, and peel strength than conventional crosslinked low-density polyethylene foams.

The gist of the present invention resides in a special bridge polyethylene resin foam characterized by containing 10 to 70 parts by weight of linear low density polyethylene per 100 parts by weight of low density polyethylene.

The low-density polyethylene used in the present invention is a conventional low-density polyethylene that has irregular long chain branches and is manufactured by radical polymerization reaction under high pressure, and has a density of α91-o, 9ar/ ct/l and a melt index of 1 to 10 t/10 minutes are preferred.

The linear low-density polyethylene used in the present invention is melted, for example, by an ionic polymerization reaction under medium and low pressure to produce propylene, butene-1, pentene-1, hexene-1, etc.
1. By copolymerizing a small amount (approximately 1 to 10 mol%) of α-olefin such as octene-1,4-methylbentene-1, an appropriate number of short chain branches are introduced into the straight chain polymer. This is a polymer whose density has been lowered to the range of ordinary high-pressure low-density polyethylene, with a density of 0.91.
5-α94 r /ctA, melt index 0.5
A melt index of ~50 F/10 minutes is preferable, more preferably a melt index of 10 to 1 (LOP/10 minutes, such as Ultzex-3021F, 202OL).
(manufactured by Mitsui Ishiura Chemical), DNGA7342, GR3
Examples include N7345 (manufactured by Union Carbide).

In the present invention, a crosslinked foam is produced by mixing 10 to 70 parts by weight of linear low density polyethylene with 100 parts by weight of the above low density polyethylene. A method similar to the manufacturing technique of crosslinked foam of low density polyethylene can be used. For example, a blowing agent is blended into the above resin mixture, the mixture is uniformly mixed using a ribbon blender, etc., and the mixture is cross-melted using an extruder or calendar roll at a temperature and pressure that does not substantially decompose the blowing agent to form a sheet. A method of obtaining a crosslinked foam by molding the sheet-like molded product into a shape, crosslinking it by irradiating the sheet-like molded product with ionizing radiation, and then heating it to a temperature higher than the decomposition temperature of the foaming agent, or adding a foaming agent to the resin mixture. , a cross-linking agent is blended, and the mixture is uniformly mixed using an extruder or calendar roll to cross-melt it at a temperature and pressure that does not substantially decompose the foaming agent and cross-linking agent, and form it into a sheet. Examples include a method of crosslinking by heating to a temperature at which the crosslinking agent decomposes, and then obtaining a crosslinked foam by further heating to a temperature higher than the decomposition temperature of the blowing agent.

As the blowing agent, chemical blowing agents such as azodicarbonamide and N-N'-dinitrosopentamethylenetetramine, which generate decomposed gas when heated, are preferable because they do not require special equipment for use.

When using ionizing radiation as a means for crosslinking the resin, beta rays, gamma rays, neutrons, electron beams, etc. are used, and the irradiation dose is preferably in the range of t-ja 5 to 20 Mrad. In addition, when using a crosslinking agent as a means for crosslinking the resin, dicumyl peroxide, 2.5
-Dimethyl-2-5-ditertiary-peroxyhexane, ditertiary-butyl perterephthalate, and other organic peroxides are used.

The cross-linked foam obtained by mixing 10 to 70 parts by weight of linear low-density polyethylene with 100 parts by weight of low-density polyethylene has higher tensile strength, elongation, and peeling than the conventional cross-linked foam made of low-density IW polyethylene. This results in a loss of mechanical strength such as strength.

When the linear low-density polyethylene has less than 10 fold failure points, no significant improvement in mechanical strength is observed compared to conventional low-density polyethylene crosslinked foam, and the linear low-density polyethylene
If the overlap exceeds 0, it becomes difficult to produce a crosslinked foam having uniform and fine closed cells.

In addition, in producing the crosslinked foam of the present invention, in addition to the above resin, blowing agent, and crosslinking agent, stabilizers, ultraviolet absorbers, lubricants,
It is of course possible to mix commonly used additives and auxiliary materials such as pigments, antistatic agents, fillers, and reinforcing agents. Furthermore, it is also possible to add resins such as high-density polyethylene, ethylene-vinyl acetate copolymer, and ethylene-propylene copolymer.

Since the crosslinked polyethylene resin foam of the present invention is constructed as described above, it has uniformly dispersed fine closed cells and has higher tensile strength and higher elongation than conventional low density polyethylene crosslinked foams. It exhibits mechanical strength such as high peel strength and high peel strength, and can be suitably used for heat insulating materials, cushioning materials, packaging materials, particularly base materials for adhesive tapes, heat insulating materials for folding plates, and the like.

The crosslinked polyethylene resin foam of the present invention will be explained below with reference to Examples.

Example: 70 parts by weight of low density polyethylene with density α923, melt index tar/10 minutes and density Q, 918, melt index 2. Of /10 minutes linear low density polyethylene 30 parts by weight and blowing agent (abdicarbonamide) 15
Mix 53 parts by weight of the auxiliary material and extrude to a thickness of 8 parts by weight.
Extruded into a simple sheet, then exposed to 5Mr using an electron beam irradiation machine.
crosslinking by irradiating ad electron beam, then crosslinking at 200C to 300C
The foamed sheet was heated and foamed through an oven that was continuously heated in the range of 0.degree. C. to obtain a foamed sheet having a thickness of about 21111 mm.

The resulting foam sheet had uniformly dispersed closed cells.

Comparative Example A foamed sheet with a thickness of about 2 cm was obtained in the same manner as in the example except that the resin used in the example was changed to 100 parts by weight of low density polyethylene instead of using linear low density polyethylene.

Table 1 shows the results of comparing the mechanical properties of the foamed sheets of the above examples and comparative examples.

Table 1 (Measurement method is based on JIS K-6767) 1st
As is clear from the table, the foamed sheet 1 of the example containing linear low density 1 (polyethylene) has significantly superior mechanical strength compared to the foamed sheet of the comparative example.

Claims (1)

[Scope of Claims] 1. A crosslinked polyethylene resin foam characterized by containing 10 to 70 parts by weight of linear low-density polyethylene per 100 parts by weight of low-density polyethylene. 2 Low density polyethylene has a density of Q91 to a931/c
tll, melt index 1 to 10r/10min, linear low density polyethylene has density ac+xs
~o, 949/6A, melt index a5~50r
1. The crosslinked polyethylene resin foam according to claim 1, which has a polyethylene resin foam of /10 minutes.