JP2000304616A - Vinyl chloride discriminating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vinyl chloride discriminating method capable of discriminating vinyl chloride simply and precisely from other plastics and the like. SOLUTION: Waste plastic material containing vinyl chloride is irradiated with a plurality of lights different in wavelength, and intensities of the reflected lights are measured. By obtaining the correlation of the index of the reflected light intensity and the wavelength of the reflected light, negative correlation of at least 98% is recognized in only the vinyl chloride material. By using the correlation, vinyl chloride is discriminated from other plastic material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for sorting waste plastic, and more particularly to a method for identifying vinyl chloride from waste plastic.

[0002]

2. Description of the Related Art Hitherto, there has been proposed a technique of identifying a predetermined plastic material from waste plastics, selecting the same, and recycling the same.

As a method for sorting such waste plastics, for example, wind sorting or sedimentation sorting has been performed by utilizing a difference in specific gravity depending on the type of material. But,
In the sorting method using such a difference in specific gravity, materials having substantially the same specific gravity cannot be identified, and a desired plastic material cannot be efficiently sorted. For this reason, a technique has been proposed in which a desired plastic material is identified by irradiating near infrared light or the like and measuring the absorbance or the like. For example, Japanese Patent Application Laid-Open No. Hei 10-24414 discloses that waste plastic is irradiated with near-infrared light having a predetermined wavelength,
A technique for discriminating a PET bottle and a PVC bottle from the absorbance is disclosed.

[0004]

However, in the above-mentioned conventional technology, a waste plastic is irradiated with light of a specific wavelength, and a desired plastic material is identified from the absorbance. There is a problem that the accuracy of identification cannot be increased.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a vinyl chloride identification method capable of easily and accurately identifying vinyl chloride from other plastics. .

[0006]

In order to achieve the above object, the present invention relates to a method for identifying vinyl chloride from waste plastic, which comprises irradiating waste plastic with a plurality of lights having different wavelengths. The method is characterized in that the intensity of the reflected light is measured, and vinyl chloride is identified from a correlation coefficient between the wavelength of the specific reflected light and the intensity of the reflected light.

In the above-mentioned vinyl chloride identification method, the correlation coefficient is negative, and the correlation coefficient is 9
8% or more.

[0008]

Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

FIG. 1 shows the relationship between the wavelength of light reflected from the waste plastic material and the intensity of the reflected light when the waste plastic material is irradiated with a plurality of lights having different wavelengths.

As can be seen from FIG. 1, the pattern of the relationship between the wavelength of the reflected light and the intensity of the reflected light is different for each plastic material. The comparison allows the identification of the plastic material. Certainly, PVC powder, PVC transparent plate, and rigid PVC pipe, which are vinyl chloride materials, have a large difference in the pattern of reflected light intensity from materials other than vinyl chloride such as PET, PP, and ABS. Easy. However, when the surface of the vinyl chloride material is soiled, the degree of absorption of the irradiated light differs, and the difference in the pattern of the reflected light intensity from the material other than vinyl chloride may not always be large.
Further, in the case of a dark blue hard PVC tube, since the entire wavelength of the irradiated light is absorbed, there is no difference in the pattern of the reflected light intensity from PET, PP, ABS, etc., and it is more difficult to identify.

As described above, it is not always easy to identify the vinyl chloride material directly from the reflected light intensity, and the identification accuracy cannot be improved. Therefore, the present inventors irradiate a plurality of lights having different wavelengths to waste plastic containing vinyl chloride, measure the intensity of reflected light, and obtain a relationship with the wavelength of the reflected light. As a result, in the case of vinyl chloride, it was found that there was a strong negative correlation between a specific wavelength of reflected light and the reflected light intensity.

FIGS. 2 and 3 show regression lines obtained by using the least squares method to obtain the relationship between the wavelengths of the reflected light beams a, b, c and d in FIG. FIG.
This is a regression line for vinyl chlorides, and a strong negative correlation is found between the wavelength of each reflected light and the intensity of the reflected light, and the correlation coefficient is 98%. Therefore, in the case of vinyl chloride, it is possible to identify with an absolute value without comparing with a database of a relation pattern between the reflected light wavelength and the reflected light intensity.

FIGS. 2A to 2D are diagrams showing the relationship between the wavelength and the intensity of the reflected light from various vinyl chloride materials. The light used in this case has a wavelength a of 1685 nm,
Wavelength b is 1694 nm, wavelength c is 1704 nm, wavelength d
Are four types of light of 1714 nm. FIG.
The vertical axis of (d) shows the intensity of the reflected light. Further, the horizontal axis indicates the measured light wavelength. In addition, 1685n
m to 1714 nm is near-infrared light, and this embodiment will be described using near-infrared light as an example.

As shown in FIGS. 2A to 2D, P
It can be seen that there is a high negative correlation in any of the VC powder, the PVC transparent plate, the light gray hard PVC pipe, and the dark blue hard PVC pipe. When the correlation coefficients in this case are calculated, they are all 98% or more.

On the other hand, FIGS. 3A to 3C show materials other than vinyl chloride, specifically, FIG. 3A shows an ABS plate, FIG. 3B shows a PP plate, and FIG. Is a measurement result of the correlation between the intensity of the reflected light and the wavelength of the reflected light in the case of a PET plate. 3A to 3C, the horizontal axis represents the wavelength, and the vertical axis represents the intensity.

As shown in FIGS. 3A to 3C, in the case of a plastic material other than vinyl chloride, a correlation coefficient between the wavelength and the intensity of the reflected light is 98% or more. There is no correlation. Therefore, by irradiating the waste plastic material with light having the above-described wavelength and examining the relationship between the intensity of the reflected light and the wavelength of the reflected light, it is easy to determine whether or not the material is vinyl chloride based on the difference in the correlation coefficient. And can be identified with high accuracy.

As described above, in the present invention, the correlation between the wavelength and the intensity of the reflected light is obtained instead of identifying vinyl chloride by comparing each wavelength of the reflected light from the plastic material and the pattern of the intensity of the reflected light. Therefore, even if the plastic material is colored or the surface is slightly contaminated, and even if it is a colored vinyl chloride material, the discrimination error from other plastic materials can be reduced.

For example, the dark blue hard PVC shown in FIG.
As described above, in the tube, the pattern of the reflected light intensity is not different from that of other plastic materials. However, the reflected light intensity of the above four wavelengths is constant at a certain rate with the increase of the wavelength, similarly to other PVC materials. Is decreasing. Therefore, when the reflected light intensity is indexed and the relationship between the index and the wavelength is observed, a high negative correlation is recognized. In this way, when the reflected light intensity is expressed as an index, even if the value of the raw reflected light intensity cannot discriminate vinyl chloride from other plastic materials, highly accurate identification becomes possible.

[0019]

As described above, according to the present invention,
By irradiating the waste plastic material with light and identifying the vinyl chloride by the correlation between the wavelength of the reflected light and the index of the reflected light intensity, even if the vinyl chloride is colored or the surface is dirty, It is possible to accurately identify vinyl chloride.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the wavelength of reflected light from various waste plastic materials and the intensity of reflected light.

FIG. 2 is a diagram showing a relationship between wavelength and intensity of light reflected from a vinyl chloride material.

FIG. 3 is a diagram showing a relationship between wavelength and intensity of reflected light from a plastic material other than vinyl chloride.

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Claims (2)

[Claims] 1. A method for identifying vinyl chloride from waste plastic, comprising irradiating waste plastic with a plurality of lights having different wavelengths, measuring the intensity of reflected light for each light, and determining a specific wavelength of the reflected light. A vinyl chloride identification method characterized in that vinyl chloride is identified from a correlation coefficient between the intensity and reflected light intensity. 2. A vinyl chloride identification method according to claim 1, wherein said correlation coefficient is 98% or more, which is negative.