JPS622965B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering or recycling plastics, and in particular to a method for recovering or recycling plastics consisting of multiple layers.

Conventionally, products made of single-layer plastic are crushed into small particles, then heated and melted using an extruder, etc., crushed into particles, heated and melted using an extruder, etc., and extruded into a certain shape for recovery and recycling. and has been put to appropriate use again.

In recent years, different types of plastics have been laminated in multiple layers and molded into containers and the like. A technology for so-called multilayer plastics has been developed, and along with this, a technology for separating and recycling each layer of multilayer plastics is required, and the development of this technology is awaited.

That is, if multilayer plastics are recycled in the same way as single-layer plastic products, only a mixture of different resins will be obtained. In many cases of multilayer plastics, resins that are incompatible with each other are usually applied to each layer, so recycled plastics obtained by mixing these incompatible resins are significantly different from the plastic before recycling or the resins in each layer. The properties are different from, and the properties are inferior to. For example, when two types of resins with different melting points are mixed, molding must be performed at the molding temperature of the resin with a higher melting point, which means that molding must be performed at a temperature that is not originally required, resulting in problems with the quality of the product. There are problems with productivity and stability.

The present invention has been developed in view of the above circumstances, and its purpose is to separate each layer of a multilayer plastic and recover the resin corresponding to each layer without mixing the resins of different layers.

That is, the present invention reduces shearing force,
Each layer of resin is peeled off by impact force, tearing force, etc., and the peeled resin mixture of each layer is dropped onto a net-like conveyor and while being moved, air is blown from the bottom of the conveyor to float the resin mixture above the conveyor. This plastic collection method is characterized by blowing air from the side of the conveyor to blow off only resins of a shape and size that are easily blown away by the wind from the conveyor.

According to the method of the present invention, each layer of a multilayer plastic can be peeled cleanly from the adhesive surface. When using impact force, etc., the pulverized product after peeling is a mixture of resin particles or tangible objects corresponding to each layer, so in order to recover each resin, it is necessary to further collect each resin particle or tangible object. must be separated.

Hereinafter, a more detailed explanation will be given according to examples.

Example A blow-molded product having a two-layer structure consisting of an outer layer of polyamide resin and an inner layer of low-density polyethylene was heated to about 140° C. in an oven and immediately pulverized using a rotary shear pulverizer.

The polyamide resin and polyethylene resin had been previously colored in different colors with a coloring agent, and they were manually sorted according to this color.

From the weight of the obtained polyamide resin alone, the separation rate is calculated according to the following formula.

(Separation rate) = (weight of peeled polyamide single product) / (weight of sample) x 1 / (weight ratio of polyamide in molded product) x
100 The calculated separation rate is close to 100%. This separation rate is about 5% at room temperature, but increases rapidly from around 80℃, and when heated to 200℃ or higher, the crushed products may fuse and form lumps.
It is preferable to apply the present invention between. FIG. 1 shows a method of separating resins based on their size and shape. For example, peeled polyamide has a thin leaf-like shape and is easier to blow away in the wind compared to particle polyethylene. A resin mixture is dropped from a hopper 1 onto a mesh conveyor 2, and while moving on the conveyor, air is blown from a lower air outlet 3 to float the resin mixture. At this time, since the polyamide floats at a high position, air is blown from the air outlet 4 on the side of the conveyor 2, and only the polyamide is blown off the conveyor and then collected.

Since the present invention has the above-described configuration, it is possible to efficiently recover a single resin powder from plastic made by laminating different types of resins, and to efficiently collect each resin as a single resin powder without contamination with different types of resins. . Further, since the recycled plastic thus obtained has almost the same composition as the plastic before use, the present invention has remarkable effects such as being able to be used for appropriate purposes again.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram for explaining the method of separating exfoliated resin according to the present invention. 1...hopper, 2...conveyor, 3,4...
Air outlet.

Claims (1)

[Claims] 1. When recycling multilayer plastic made of polyamide and polyolefin, the plastic is crushed under heating to peel it into thin leaf-like polyamide and granular polyolefin, and the peeled resin mixture of each layer is transferred onto a mesh conveyor. This method of collecting plastics is characterized by blowing air from the underside of the conveyor while moving the plastics to float the resin mixture above the conveyor, and further blowing air from the side of the conveyor to blow only the polyamide off the conveyor.