JPH11165363A - Plastic foamed sheet suited for incineration treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the formation of dioxins contained in an exhaust gas thru further enhancing the burning characteristics by adding a specific weight percent of iron oxide powder to a plastic. SOLUTION: The burning characteristics of polyethylene or the like are enhanced by a catalytic action peculiar to an oxide of iron as a transition metal element by adding 0.1 wt.% or more of the iron oxide to a foamed sheet material such as polyethylene. The upper limit of the addition is to be 10 wt.% from the viewpoint of a cost effect and plastic workability. In addition, calcium carbonate CaCO3 is decarboxylated as quick lime CaO through burning the calcium carbonate CaCO3 by adding 1-30 wt.% of calcium carbonate powder, and thereby, an acidic substance such as chlorine, hydrogen chloride, sulfur oxide or nitrogen oxide contained in a combustion exhaust gas is fixed. Thus it is possible to burn the plastic under such conditions that dioxins contained in the exhaust gas are limited to a comparatively lower level and remove harmful components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a plastic foam sheet, and provides a plastic foam sheet suitable for disposal by incineration.

[0002]

2. Description of the Related Art A plastic bubble sheet (hereinafter referred to as a plastic foam sheet) formed by bonding a flat plastic back film to the bottom surface of a projection of a plastic cap film provided with a number of projections to form a number of sealed air bubbles. “Aerated sheet” is widely used as a cushioning material, mainly in the field of packaging.

[0003] This kind of bubble sheet can be reused several times depending on how it is used, but if it becomes dirty or bubbles are crushed, it must be discarded. The fact that disposal is bulky is almost always done by incineration. Since the plastics used as the material of the foam sheet are mainly polyolefins such as polyethylene, those generated by combustion are limited to water and carbon dioxide, and the combustion exhaust gas can be said to be relatively clean. This point is somewhat advantageous when compared to the fact that so-called foamed plastics contain chlorofluorocarbons and hydrocarbons inside the cells, and there is a possibility that undesired components may be generated in the exhaust gas by combustion. In addition, since the content of the bubbles is air, which also assists the combustion of the bubble sheet as a source of oxygen, the bubble sheet is generally good in combustibility, and the incineration process should not be so problematic. .

[0004] However, the actual incineration is performed not only with the bubble sheet alone but also with other substances such as dust, so that the high flammability of the bubble sheet is not always utilized.

On the other hand, as a material for the garbage bag, a polyethylene film mixed with a large amount of calcium carbonate is used. This calcium carbonate aims to protect the incinerator by suppressing heat generation during incineration. However, in fact, the mixing of calcium carbonate inevitably increases the thickness of the film, increasing the amount of polyethylene to be incinerated. Has been pointed out.

An important problem with refuse incinerators is that they must be operated under conditions that produce as little poisonous dioxins as possible. From this viewpoint, it is advantageous to perform combustion at a relatively high temperature. Therefore, it is desirable to further increase the flammability of the bubble sheet for incineration of refuse.

[0007]

SUMMARY OF THE INVENTION The basic object of the present invention is to provide a plastic foam sheet which is originally rather suitable for incineration, because it has a higher flammability than conventional products and is therefore mixed with dust. It is still another object of the present invention to provide a bubble sheet suitable for incineration, which can be easily incinerated and reduces the generation of dioxins in exhaust gas. A secondary object of the present invention is to provide a bubble sheet in which the cushioning effect of the bubbles is maintained and the above basic effects can be maintained.

[0008]

SUMMARY OF THE INVENTION A plastic foam sheet suitable for incineration according to the present invention is a plastic cap provided with a number of projections as shown in a plan view in FIG. 1 and a cross section in FIG. In a plastic bubble sheet formed by adhering a flat plastic back film (2) to the bottom surface of the projection of the film (1) to form a number of closed cells (3), the plastic is made of iron oxide powder ( 4) is added in an amount of 0.1 to 10% by weight.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The iron oxide suitable for use in the present invention is a finely powdered and highly reactive iron oxide used in hand warmers and the like. Those marketed under the name "active ferroxide" or the like can advantageously be used. It is considered that the reason why the flammability of polyethylene and the like is further enhanced by the addition of iron oxide is due to the catalytic action of the oxide of iron as a transition element. In order to clearly obtain the effect of improving flammability, it is usually necessary to add iron oxide in an amount of 0.1% by weight or more to a foam sheet material such as polyethylene. Addition of a large amount is disadvantageous because it does not provide an effect corresponding to the increase in cost and impairs the processability of the plastic. For this reason, an upper limit of 10% by weight was set.
If the amount of addition is within this range, the foam sheet can be manufactured without making any other changes to the conventional technology. The preferred range of the amount of iron oxide to be added varies slightly depending on the physical properties of the plastic material to be used and the specifications of the foam sheet to be produced, in particular, the thickness of the film. % By weight.

Various modes are possible for the plastic foam sheet of the present invention. For example, an example of a plastic material is a material obtained by adding 1 to 30% by weight of calcium carbonate powder in addition to iron oxide. This calcium carbonate CaCO3
Is decarbonated by combustion to form quicklime CaO, and has a function of fixing acidic substances such as chlorine, hydrogen chloride, sulfur oxides, and nitrogen oxides in the combustion exhaust gas to make the female girl.

Another variation is to enclose oxygen-enriched air in a bubble. Needless to say, the oxygen in the bubbles participates in the combustion, and the combustion of the bubble sheet proceeds more intensely.
Encapsulation of oxygen-enriched air in bubbles can be easily performed by replacing the atmosphere on the cap film surface with oxygen-enriched air when forming a cap film usually performed by vacuum forming.

[0012] If the plastic film forming the gas bubbles is easily permeated, gas molecules are exchanged between the inside and the outside of the film, and the gas enclosed in the gas bubbles is exchanged. As the proportion of oxygen in the air decreases, the bubbles collapse. By avoiding this, it is desired to secure the buffering capacity of the bubbles for a long period of time and to suppress exchange of gas molecules as much as possible so that high flammability is maintained during incineration. For this purpose, it is recommended to use a plastic film as a laminate of two or more layers, one of which is a gabarrier material. As a representative of the gas barrier plastic film, an ethylene-vinyl acetate copolymer is preferable, and it is recommended to use a film obtained by laminating ordinary polyethylene by coextrusion. Instead of the gas barrier layer, a plastic film having a surface coated with a coating containing mica powder may be used.

[0013]

EXAMPLE A low-density polyethylene kneaded with 0.9% by weight of "activated ferroxide" was used as a material to form a two-layer polyethylene film foam sheet having an air chamber height of 4 mm and a diameter of 10 mm. Manufactured.

On a steel sheet placed on a sheathed heater, the temperature was increased at a constant speed while heating the bubble sheet while being in contact with air, and the situation of disappearance by combustion was observed. When the temperature exceeded 400 ° C., it ignited at once and combustion proceeded, and when the temperature reached 450 ° C., the material of the bubble sheet almost disappeared. For comparison, a polyethylene foam sheet containing no iron oxide, which was burned under the same conditions, ignited at about the same temperature and started burning, but continued burning to a temperature exceeding 500 ° C., and took several times as long. Cost me.

[0015]

Since the plastic foam sheet of the present invention has high flammability, it burns quickly and completely even when incinerated alone or when mixed with various refuse. Such a manner of combustion facilitates incineration under conditions where the content of dioxins in exhaust gas is kept relatively low.

In the embodiment in which calcium carbonate is added, calcium oxide produced by incineration reacts with acidic substances such as chlorine and hydrogen chloride in exhaust gas to fix them, thereby removing harmful components. Help.

The effect of improving the combustibility can be further enhanced if the gas sealed in the bubbles is oxygen-enriched air. The effect of this aspect can be enjoyed for a long time by using a gas barrier material as the material of the plastic film.

The addition of iron oxide makes the foam sheet brown. This is useful when it is desired to prevent the package from being deteriorated by sunlight.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a plastic foam sheet of the present invention.

FIG. 2 is a sectional view taken along the line II of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cap film 2 Back film 3 Bubbles 4 Iron oxide powder

Claims (4)

[Claims] 1. A plastic foam sheet comprising a plastic cap film provided with a large number of projections and a flat plastic back film bonded to the bottom surface of the projections to form a large number of sealed air bubbles. A plastic foam sheet, characterized in that iron oxide powder is added in an amount of 0.1 to 10% by weight. 2. The plastic foam sheet according to claim 1, wherein the plastic material is further added with 1 to 30% by weight of calcium carbonate powder. 3. The plastic foam sheet according to claim 1, wherein oxygen-enriched air is used for forming the cap film, and oxygen-enriched air is enclosed in bubbles. 4. The plastic foam sheet according to claim 3, wherein the plastic film is a laminated material of two or more layers, and one of the laminated materials is a gas barrier material.