JPS62164742A - Crosslinked polyethylene resin foam having improved elasticity - Google Patents

Abstract

PURPOSE:To provide the titled foam having excellent elasticity, flexibility and heat resistance, by molding and expanding a polymer blend of a PVC resin and a specified PE resin. CONSTITUTION:10-80wt% PVC resin (A) having a chlorine content of 5-50wt%, ppref. 20-40wt%, a density of 1.03-1.23 and an MI of 20-50g/10min is mixed with 80-20wt% PE resin (B) having a density of 0.910-0.950g/cc, pref. 0.915-0.930g/cc. If desired, a lubricant, an antioxidant, an ultraviolet absorber, a colorant, an antistatic agent, a flame retarder, etc., are added thereto to obtain a polymer blend. The polymer is blended with a heat-decomposable blowing agent (e.g., uzodicarbonamide) and a crosslinking agent capable of generating a radical by heating. The mixture is molded and crosslinked to such an extent that the product has a gel fraction of 15-45%. The product is heated in a hot air atmosphere or on a salt bath to expand it.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a foam made of a polyolefin resin blend polymer containing chlorinated polyethylene and a polyethylene resin as essential components, and more specifically, The present invention relates to a foam made of the above-mentioned blended polymer, which is rich in elasticity and has excellent flexibility and heat resistance.

[Conventional technology]

Conventionally, polyolefin resin foams such as polyethylene resin foams have been used for many purposes due to their excellent heat insulation and silane properties, but they are also used as underlays for sports mats, artificial turf, carpets, etc. When used as a base material, it has insufficient flexibility and elasticity and is prone to injury, and there is a strong demand for improvement. In response to these demands, a foam made of ethylene-vinyl acetate copolymer has been proposed as a flexible foam, but this foam has a softening point of ethylene-vinyl acetate copolymer. As a result, there was a problem of poor thermal properties such as dimensional stability and heat resistance.

[Problem to be solved]

In order to solve the above-mentioned drawbacks and problems, the present inventors have conducted intensive studies on foams made of blended polymers whose main component is polyethylene resin (hereinafter abbreviated as PE), and found that We have discovered that the above drawbacks and problems can be significantly improved by blending chlorinated polyethylene, which has been said to be difficult to form, with PH,
This led us to propose the present invention.

That is, the object of the present invention is to provide a polyethylene resin foam that has high elasticity, flexibility, and dimensional stability without substantially impairing the excellent properties of the polyethylene resin foam. It is an object of the present invention to provide a foam that exhibits excellent properties, particularly for use in underlays.

[Means for solving problems]

The purpose of such invention is to reduce the chlorine content from 5 to 50% by weight.
A cross-linked polyethylene resin with improved elasticity consisting of a blend polymer of 10 to 80% by weight of a chlorinated polyethylene resin with a density of 0.910 to 0.950 g/cc and 80 to 20% by weight of a polyethylene resin with a density of 0.910 to 0.950 g/cc. This can be achieved by foam.

In the present invention, the chlorinated polyethylene resin preferably contains chlorine in the range of 5 to 50% by weight, preferably 20 to 40%, and if the chlorine content is less than 5%, the flexibility may be reduced. The improvement effect is small, and when it exceeds 50%, heat resistance decreases, so it is not preferred.

Examples of such chlorinated polyethylene resin include, but preferably, a crystalline chlorine content of 20 to 40% and a polymer density of 1.03 to 1.23.
, M120 to 50 g/10 minutes is preferable.

On the other hand, the polyethylene resin constituting the foam of the present invention preferably has a density of 0.910 to 0.950 g/cc, preferably 0.915 to 0.930 g/cc; If the density is lower than 910 g/cc, the strength of the cell membrane of the foam will be weak and it will easily collapse, which is undesirable. If the density exceeds 0.950 g/cc, the rigidity of the polymer will be strong and the flexibility of the present invention will not be sufficient. This is not preferable because it cannot be applied to

As polyethylene having such a density range, for example, high pressure process low density polyethylene density 0.923 g/cc
MI3.7 (manufactured by Mikata) Low pressure method - low density polyethylene - density 0.930g/cc
Examples include MIB, 0 (manufactured by Showden).

In the present invention, the blending ratio of the chlorinated polyethylene resin needs to be 80 to 20% by weight, preferably 50 to 30%, based on the polymer blend.

In other words, if the amount of chlorinated polyethylene resin is less than 20%, that is, if the amount of polyethylene resin is more than 80%, sufficient flexibility will not be obtained, and the foam made of low-density polyethylene alone will not change. It is not preferable in terms of properties (hardness), and if it exceeds 80%, it is not preferable because a foam that can be used for practical purposes cannot be obtained.

In the method for producing the foam of the present invention, the chlorine content is 5.
A polymer blend containing a chlorinated polyethylene resin of ~50% by weight and a polyethylene resin with a density of 0.910~0.950 g/cc is added with a known thermally decomposable blowing agent, such as azodicarbonamide or dinitroso. Pentamethylenetetramine and the like and, if necessary, a crosslinking agent that generates radicals upon heating are mixed, held at a temperature at which the foaming agent and crosslinking agent do not decompose, and molded, for example, into a sheet shape. This formed sheet material is cross-linked by applying any known method such as ionizing radiation cross-linking method or chemical cross-linking method so that the gel fraction becomes 15 to 45%, preferably 20 to 40%. do.

More specifically, in the case of the ionizing radiation crosslinking method, α, β, T, X-rays, electron beams, neutron beams, etc. are used as high-energy rays, and a high-energy electron beam irradiation machine is usually used. Crosslinking is achieved by irradiating the sheet with an electron beam at a dose of ~50 Mrad. In this case, 0.1 to 10!1 parts of various known crosslinking aids, such as divinylbenzene, diallyl phthalate, trimethylolpropane triacrylate, etc., are added to the blend polymer of the present invention for electron beam crosslinking. Good too.

Instead of this radiation irradiation, it is also possible to add an ultraviolet sensitizer such as benzophenone and crosslink by irradiating ultraviolet rays.

In addition, in the case of chemical crosslinking method, dicumic peroxide,
A cross-linking method using an organic peroxide such as ditertiary butyl peroxide, and a silane cross-linking method in which a vinyl silane such as vinyltrimethoxysilane is kneaded with these cross-linking agents to form a graft, and then cross-linked by a siloxane condensation reaction are used as appropriate. Can be applied.

The molded product thus obtained is heated in a hot air atmosphere or on a melt bath to rapidly decompose the foaming agent contained within the molded product, thereby converting it into a foam.

In addition, to the extent that the object of the present invention is not impaired, the composition used for producing the foam of the present invention may include lubricants, antioxidants,
Ultraviolet absorbers, colorants, antistatic agents, flame retardants, and other various additives can be blended within the range that can achieve the desired purpose.

Furthermore, the chlorinated polyolefin resin foam of the present invention can be laminated with an adhesive applied to one side by corona discharge treatment, coating, etc. to improve its workability. In other words, various processing techniques can be applied, such as laminating plastic films or sheets, other foam sheets, or metal foils, or imparting a composite structure by extrusion lamination.

〔Effect of the invention〕

The crosslinked polyolefin resin foam of the present invention not only has excellent heat insulation properties, but also has excellent elasticity (cushioning properties), flexibility, dimensional stability, etc., and meets the requirements for these properties. It greatly improves the performance and quality of its uses, such as underlays for athletic mats, artificial turf, carpets, etc.

The effects of the present invention will be explained in more detail below based on Examples.

In the present invention, (specify the method for measuring necessary physical properties such as melting point (Tm), drawing ratio (K), gel fraction, surface roughness, etc.) is a value measured by the following method.

Tm: DSC method forming drawing ratio: Displayed as the (depth/diameter) ratio when vacuum forming using the female cup method with a diameter of 50 m.

Gel fraction: When extracted with tetralin at 135°C, expressed as [(weight after extraction, g))/(sample amount, g)) x100.

Surface roughness: Measured using a surface roughness meter using the stylus method.

Example 1 Chlorine content is 45χ, melt index is 17.0,
Add 15 parts by weight of azodicarbonamide to 100 parts by weight of a mixture consisting of 50 parts by weight of polyethylene with a density of 0.955 and 50 parts by weight of low-density polyethylene with a melt index of 3.7 and a density of 0.923, and mix uniformly. After that, a sheet having a thickness of 2.5 mm was formed using an extruder.

Place this sheet on a salt bath heated to 230°C.
It was irradiated with a Mrad electron beam to form a foam, thereby obtaining a foam.

The resulting foam has a thickness of 5.0 m and a density of 0.031
g/cc, the hardness measured using an Asker type rubber hardness meter was 10 or less, and it was rich in flexibility with fine bubbles.

In contrast, the hardness of the foam obtained from the commercially available low-density polyethylene alone was 15, indicating that the foam of the present invention has significantly superior flexibility.

Example 2 and Comparative Examples Table 1 shows the flexibility, elasticity, etc. of foams prepared in the same manner as in Example 1 with different blending ratios.

Table 2 shows the elasticity and flexibility of foams prepared in the same manner as in Example 1 using chlorinated polyethylenes having different densities.

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Claims (1)

[Claims] A chlorinated polyethylene resin having a chlorine content of 5 to 50% by weight, 10 to 80% by weight, and a density of 0.910 to 0.5% by weight.
A crosslinked polyethylene resin foam with improved elasticity consisting of a blended polymer with 80-20% by weight of a polyethylene resin of 950 g/cc.