JPS6058440A - Uncrosslinked polyethylene foam of low expansion ratio - Google Patents

Abstract

PURPOSE:The titled foam of specific expansion ratio, obtained by incorporating a linear low-density polyethylene with low-density high-pressure polyethylene, having improved toughness, abrasion and heat resistance, and suitable to packaging materials, etc. CONSTITUTION:An uncrosslinked polyethylene foam, obtained by melt incorporating 15-75wt% linear low-density polyethylene, preferably a copolymer of ethylene and octene-1 having 0.3-3.0 melt index and 0.915-0.930 resin density with 25-85wt% high-density high-pressure polyethylene, preferably having 0.1- 3.0 melt index and 0.915-0.930 resin density, and expanding the resultant mixture, and having <=3 expansion ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to non-crosslinked polyethylene low modulus foams having improved strength properties and heat resistance.

Conventionally, foams based on high-pressure low-density polyethylene (hereinafter referred to as PLDPE) and polystyrene have been commercialized as low-modulus foams (with an expansion ratio of 3 times or less), but the former The latter has problems in heat resistance and toughness, and is subject to many practical restrictions.

In addition, linear low density polyethylene (LLDPFI:
) has higher toughness, heat resistance,
Although it has excellent abrasion resistance, it has not been utilized as a non-crosslinked low foam material because the poor foam moldability caused by its unique melting properties cannot be overcome.

The present inventors used LLDPE to create a low-foaming product in the above-mentioned situation, which is economical because it does not require complicated processes such as crosslinking, and has low-rate foaming that has excellent starting properties and heat resistance. [Tension of the melt that occurs when drawing the molten resin at the nozzle outlet at a constant speed (approximately 7.s5 m/min) using a melt index measuring device (based on ASTM-DI23g)] means. ], and as a result of examining the case where HPLDPE is blended, we found that LLDPE3 [(The melt tension shows an extremely large value when the amount concentration is around 20 coefficients, and even if LLDPFJ is at a high concentration, LLDPE This shows that the melt tension - (two-rise effect) is larger than that of the melt tension alone.When the melt tension is large, there is an effect of preventing excessive foaming due to cell rupture, and it is easy to obtain a homogeneous foam. The present invention has been completed.

That is, the present invention is a non-crosslinked polyethylene low-ratio foam with an expansion ratio of 3 or less, which is composed of 15-75% by weight of linear low-density polyethylene and 25-85% by weight of high-pressure low-density polyethylene. The LLDPE used is not restricted by its manufacturing method, and is a copolymer of ethylene and α-olefin, with an α-olefin content of 20% by weight or less, and the α-olefins include butene-1, pentene-1, heptene-1
, 4 methylintene-1, hexene-1, octene-1
etc.

Octene-1 is particularly preferred from the viewpoint of improving foam moldability and physical properties.

The melt index (hereinafter abbreviated as Ml), which is a basic characteristic of LLDPE, is 0.1 to 10. It is 0.3~3
．． It is 0.

If the MIIO is higher than that, no-pull formation during inflation molding and foaming moldability will be reduced, and if the MI is lower than 0.1, the extrusion moldability will be significantly lowered.

A resin density of 0.915 to 0.940 is commonly used, but from the viewpoint of foam moldability and improvement of physical properties, it is particularly 0.915 to 0.93.
0 is preferred.

The HPLDPE used in the present invention is not restricted by its manufacturing method, and has a resin density of 0.915 to 0.930 g/c,
rd.

It is commonly used for extrusion molding of MIO, 1 to 30.

An ethylene-vinyl acetate copolymer having an arsenic content of 10% by weight or less is also applicable.

When combined with LLDPE-r, HPLDPE
The MI of I is the combination partner composition, and the MI of LDPE
, it is more effective to improve foam moldability.

There are no particular restrictions on the chemical blowing agent used in the present invention, but
N! Diazocaramide-based foaming agents, dinitrone bentamethylenetetramine, etc., which are generating and high-temperature decomposition type blowing agents, are useful.

It is also possible to use it in combination with a nucleating agent and an auxiliary agent.

The low ratio foam of the present invention has LLDPE 15 to 75 weight ratio,
25-85% by weight of HPLDPE and 0.2-85% chemical blowing agent
2. PHR is mixed by the triblend method or by granulation into a uniform mixture using a known melt mixing device, and then put into a melt mixing device and foamed while being continuously extruded from an annular mold. In addition, the chemical blowing agent is
A master no-matched version may also be used. LLDP
When I is less than 15% by weight, strength characteristics, heat resistance, etc. are not exhibited. Further, if the amount exceeds 75%, the foaming moldability is poor and it is difficult to obtain a uniform foam.

The low-modulus foam of the present invention has excellent toughness, abrasion resistance, and heat resistance, and has cushioning properties, so it can be used as packaged feed, and since it can be easily heat-sealed, it is also useful as a bag. Furthermore, it can also be used as a shrink label.

The present invention will be explained below with reference to Examples and Comparative Examples.

Examples 1 to 12 and Comparative Examples 1 to 14 Using the LLDPE%HPDPE and foaming agent shown in Table 1, a low percentage foam was produced at the blending ratio shown in Table 1.

Manufacturing, melt tension, foam moldability, foaming condition and ASTM
Impact strength was measured using D1709.

The results are shown in Table-1.

Note that foaming was performed using a blown film forming device (Modern Machinery EA-so), with screw L/D=
28, compression ratio 35, spiral type annular gooey 1 as gooey
00 ψ, gap 1. It was conducted in OB.

(Margin below)

[Brief explanation of the drawing]

The drawings are diagrams showing the relationship between resin blending ratio and melt tension in Examples and Comparative Examples of the present invention. Patent applicant Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] Non-crosslinked polyethylene low ratio foam with a foaming ratio of 3 times or less, consisting of linear low density polyethylene 15 to 75% by weight and high pressure processed low density polyethylene 25 to 85% by weight