JPH0910703A - Mixing method for different plastic packaging materials - Google Patents

Abstract

(57) [Summary] [Purpose] For egg packs, multiple plastic packaging materials of the same type are stacked and supplied to the sorting process, such as egg packs, and within the overlap, materials other than the same packaging material are used. Check if the packaging materials of different plastics are mixed.
An object of the present invention is to provide a method capable of making a simple and quick determination without resorting to manual selection by observing the appearance of an operator. [Structure] For example, in an egg pack with 10 layers, P
When the ET pack is used as the target plastic packaging material and the PVC or PS pack is used as the different plastic packaging material, the overlapping of the egg packs is irradiated with light and the absorption spectrum of infrared light obtained from the transmitted light is measured by PET. And P
Absorbances b and h at wavelengths 1.675 and 1.738 μm, which are peculiar to VC, and a wavelength of 1.550 μ, which is deviated therefrom.
The absorbance a at m is measured, the ratio j = c / i between c = b−a and i = h−a is obtained, and it is determined that there is no mixture of different types of plastic packs under the condition of j ≧ 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the sorting of transparent or translucent plastic packaging materials such as egg packaging packs, vegetable and fruit packaging trays, and the like. Plural types of plastic packaging materials are stacked and supplied to the sorting process, and it is possible to easily and quickly determine whether or not different types of plastic packaging materials other than the same plastic packaging material are mixed in the overlap. On how to do.

[0002]

2. Description of the Related Art In daily life, transparent or translucent plastic packs and trays are widely used for packaging eggs, vegetables, and fruits. Various efforts have been made from the viewpoint of effective use of.

When the waste plastic packaging material is reused as a plastic raw material, it is important to prevent the mixing of different kinds of plastics, and it is necessary to sort the packaging material for each plastic material.

Among the plastics used for these packaging materials, PET (polyethylene terephthalate) is not only suitable as a packaging material for foods because it can obtain suitable packaging performance without adding a large amount of additives. , Its waste is also suitable for reuse as a PET raw material.

For these reasons, the packaging material for foods, such as egg packs, is gradually being switched from conventional PVC (polyvinyl chloride) or the like to PET packs.
In addition, the used egg packs have come to be collected through large-scale stores that sell the products.

[0006] The used egg pack is brought to the store where the consumer purchased the product and collected, but since the consumer does not know the material of the egg pack, it is different from PET purchased at other stores. A plastic material such as a PVC egg pack may be brought in, and a pack of a different material other than PET is mixed in the collected egg pack. Therefore, it is necessary to select PET packs from the collected egg packs.

[0007] Normally, the collected egg packs are sorted manually by a worker in a store or a specialized sorter. In order to improve the processing efficiency, manual selection is performed by stacking a plurality of egg packs, for example, 10 or less, and the operator looks at the egg packs stacked and the egg packs made of different materials other than PET To find out the mixture of the, by the difference in the appearance and texture.

If there are no different materials in the stack of egg packs, the stacked egg packs are collected for PET raw material. If different kinds of materials are mixed into the overlap of the egg packs, the egg packs of different materials are removed from the overlap, and the remaining egg packs are recovered for PET raw material.

However, it is complicated and very laborious to judge that the egg packs of different materials are mixed in the overlapping of the egg packs by such operator's observation, and improvement is desired. It was work.

As a method for discriminating plastics which does not require manual selection by an operator, a method utilizing absorption of X-rays is known. This discrimination method can be applied to PVC.
Only. Therefore, it is unsuitable for determining whether or not an egg pack made of a different material other than PET is mixed in the overlapping egg packs. Of course, since X-rays are used, it is troublesome in management.

[0011]

SUMMARY OF THE INVENTION
For various transparent or translucent plastic packaging materials such as egg packs, vegetables, and fruit trays, multiple plastic packaging materials of the same type are supplied to the sorting process, such as egg packs for egg packs, It is possible to easily and quickly determine whether or not the packaging materials of different plastics different from each other are mixed in the overlap in addition to the packaging materials of the same material, without performing manual selection by observing the appearance of the operator. A method was desired.

Therefore, an object of the present invention is to provide a method for determining the mixture of different types of plastic packaging materials having the above characteristics.

[0013]

The above object can be achieved by the method for determining the mixing of different kinds of plastic packaging materials according to the present invention. In summary, the present invention is a method for discriminating the mixing of different types of plastic packaging materials with respect to the target plastic packaging material of a plurality of types of plastic packaging materials of different materials. Of different types of plastics by irradiating and measuring the absorption spectrum of infrared light obtained from the transmitted light to determine the presence or absence of mixing of different types of plastics within the overlap of multiple packaging materials. This is a method for determining the mixture of packaging materials. According to the present invention, a plurality of types of plastic packaging materials are PE
There may be five types of packaging materials of T, PVC, PS, PP and PE.

Preferably, the plurality of types of plastic packaging materials are three types of packaging materials of PET, PVC and PS. When the PET packaging material is the target plastic packaging material and the PVC and PS packaging materials are different plastic packaging materials, the absorption spectrum of infrared light is
By measuring the absorbance at the wavelength peculiar to T and the wavelength peculiar to PVC, and obtaining the ratio of these absorbances and comparing it with a predetermined reference value, the packaging material of different plastics within the overlap of a plurality of packaging materials The presence / absence of the mixture is determined. When the PVC packaging material is the target plastic packaging material and the PET and PS packaging materials are different plastic packaging materials, the PS packaging material is the target plastic packaging material and the PET and PVC packaging materials are different plastic materials. In the case of a packaging material, it is possible to determine whether or not the packaging material of different kinds of plastic is mixed by a method according to this.

Preferably, the absorbance ratio of the packaging material and its reference value are obtained by subtracting the absorbance at a wavelength that does not depend on the material of the packaging material from the absorbance of the packaging material. As the wavelength peculiar to the material of the packaging material, a wavelength giving a maximum absorbance peculiar to the material of the packaging material or a wavelength in the vicinity thereof can be used. The packaging material can be stacked with 10 sheets or less. To measure the absorbance at a wavelength peculiar to the material of the packaging material, irradiate natural light or white light from a white light source on the packaging material that is stacked multiple layers, and the infrared of the wavelength peculiar to the material of the packaging material in the transmitted light. It can be performed by receiving light, or by irradiating a plurality of packaging materials with infrared light having a wavelength peculiar to the material of the packaging material and receiving the transmitted light. be able to. In addition, instead of the absorbance at the wavelength peculiar to the material of the packaging material, use the intensity measured at the wavelength peculiar to the material of the packaging material for the spectrum obtained by the first derivative or second derivative of the absorption spectrum of infrared light. You can

[0016]

EXAMPLES The present invention will be described with reference to examples.

Example 1 In this example, a PET (polyethylene terephthalate) egg pack was used as a target plastic packaging material, and a PVC (polyvinyl chloride) or PS (polystyrene) packaging material was used as a different plastic packaging material. The case where it is determined whether or not the packaging material of different plastics is mixed in the overlap of the egg packs is shown.

FIG. 1 is an infrared absorption spectrum of the plastic used in the discrimination method of the present invention. PET, PV
Each of the absorption spectra of C and PS was obtained by irradiating white light from a halogen lamp on the overlap of 10 egg PET, PVC, and PS egg packs, and continuously measuring the absorbance of infrared light in the obtained transmitted light. Measured, of which about 1.3
The range from 5 μm to about 2.1 μm is displayed. As shown in FIG. 1, the infrared absorption by PET has a wavelength of 1.675.
There is a maximum value in μm, and similarly PVC is 1.738μ.
m and PS have maximum values at 1.709 μm.

In the present invention, with respect to this infrared absorption spectrum, the absorbance at a wavelength peculiar to the plastic material is measured, and it is judged whether or not the different plastic packaging material is mixed with the target plastic packaging material based on the measured absorbance. As the wavelength peculiar to, the PET uses a wavelength of 1.675 μm or its vicinity that gives the maximum value. Similarly, PVC uses a wavelength having a maximum value of 1.738 μm or its vicinity, and PS uses a wavelength having a maximum value of 1.709 μm or its vicinity.

Table 1 shows the relationship between the number of PVC packs mixed in the PET egg pack and the absorbance, Table 2 shows the relationship between the number of PS packs mixed and the absorbance, and the number of PVC packs and PS packs mixed. Table 3 shows the relationship with the absorbance.

In Tables 1 to 3, the absorbance a is PET,
Absorbance measured at an arbitrary wavelength of 1.550 μm far from the wavelengths peculiar to PVC and PS, 1
Seed blank. Absorbance b is the overlap of egg packs measured at a PET maximum wavelength of 1.675 μm, and absorbance h is a PVC maximum wavelength of 1.738 μm.
Is the measurement of the overlap of the egg packs. Also,
j = c / i is c = ba obtained by subtracting a from the absorbance b.
And i = h−a obtained by subtracting a from the absorbance h.

In this embodiment, in order to improve the accuracy of discrimination, the absorbances b and P at the PET wavelength of 1.675 μm are used.
VC = 1.78 μm, the absorbance h at the wavelength of 1.738 μm was subtracted from the absorbance a, and c = b−a and i = ha were used for the determination. However, it is not always necessary to subtract the blank absorbance a, and in some cases, the absorbance b. , H can be used as they are.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

As shown in Table 1, when the 10 egg packs consisted only of the target PET pack and no PVC pack was mixed, the absorbance ratio j was 2.230, but P
When even one VC pack is mixed, the ratio j becomes smaller than 1.887. Similarly, as shown in Table 2, when even one PS pack is mixed in 10 egg packs, the absorbance ratio j becomes 1.990 or less. When PVC pack and PS pack were mixed in 10 egg packs, the absorbance ratio j was further decreased.
T / PVC / PS = 8/1/1 (sheets) is 1.68 at maximum
2. Therefore, whether or not the ratio j of the absorbances exceeds the reference value can be used to determine whether or not there is a PVC or PS pack of a different plastic other than the PET pack in the overlap of the 10 egg packs. it can.

In the present embodiment, from the above, 2 is selected in consideration of the safety of the absorbance ratio j, and if the condition j ≧ 2, then 10 is selected.
The overlapping of the egg packs was determined to be all PET packs without inclusion of PVC or PS packs.

Example 2 In this example, a PVC egg pack is used as a target plastic packaging material, and a PET or PC packaging material is used as a different plastic packaging material. The case where it is determined whether or not the material is mixed is shown.

In this embodiment, the wavelength peculiar to the material used for the measurement of the absorbance is the same as that of the first embodiment except for PVC.
The maximum value of C was 1.738 μm, but the wavelength of 1.668 μm at the intersection of the absorption spectrum of PET and the absorption spectrum of PS was used for PET and PS. This is because the intersection of these absorption spectra is PET and PS.
This is because they exhibit both absorption characteristics of.

Table 4 shows the relationship between the number of PET packs mixed in the overlap of PVC egg packs and the absorbance, Table 5 shows the relationship between the number of PS packs mixed and the absorbance, and the number of PVC packs and PS packs mixed. Table 6 shows the relationship with the absorbance.

In Tables 4 to 6, the absorbance d is the overlap of egg packs measured at a wavelength of 1.668 μm at the intersection of PET and PS. The absorbance h is obtained by measuring the overlap of egg packs at a wavelength of 1.738 μm, which is the maximum value of PVC. k = i / e is i = h-a obtained by subtracting a from the absorbance h and e = d obtained by subtracting a from the absorbance d.
It is a ratio with −a.

Since the mixing of the PET pack into the PVC pack is the same as the case of mixing the PVC pack into the PET pack, the absorbance h in Table 4 is the value of h in Table 1. The absorbance a is also the value in Table 1. Since the absorbance d was also measured for the object for which the absorbance h in Table 1 was measured, the absorbance a is the value in Table 1 for the absorbance d.

[0033]

[Table 4]

[0034]

[Table 5]

[0035]

[Table 6]

As shown in Table 4, when the 10 egg packs consisted of only the target PVC pack and no PET pack was mixed, the absorbance ratio k was 8.967, but P
If even one ET pack is mixed, the absorbance ratio k will be 5.5.
It becomes smaller than 32. Similarly, when even one PS pack is mixed into 10 egg packs, the absorbance ratio k becomes 5.172 or less as shown in Table 5, and PE
When the T pack and the PS pack were mixed, the absorbance ratio k was further decreased, and in Table 6, PET / PVC /
The maximum value of PS = 1/8/1 (sheets) is 3.584.

Therefore, in this embodiment, 6 is selected in consideration of the safety of the absorbance ratio k, and if the condition k ≧ 6, there is no mixture of PET or PS in the overlap of 10 egg packs. All were judged to be PVC packs.

Example 3 In this example, a PS egg pack was used as a target plastic packaging material, and a PET or PVC packaging material was used as a different plastic packaging material within the overlap of 10 egg packs.
A case is shown in which it is determined whether or not a packaging material of a different plastic other than the target plastic is mixed.

Therefore, in this embodiment, the wavelength of the maximum value of PS is 1.709 μm and the wavelength of the maximum value of PET is 1.67.
5 μm, and PVC maximum wavelength 1.738 μm
Then, the absorbance of the absorption spectrum was measured.

Table 7 shows the relationship between the number of PET packs and the absorbance in the overlap of PS egg packs, Table 8 shows the relationship between the number of PVC packs and the absorbance, and the number of PET and PVC packs mixed. Table 9 shows the relationship with the absorbance
Shown in

In Tables 7 to 9, the absorbance f is the overlap of egg packs measured at a wavelength of PS maximum value of 1.709 μm. In addition, since the mixing of the PET pack into the PS pack is the same as the case of mixing the PS pack into the PET pack, the absorbances a, b, and h in Table 7 are shown in Table 2. It is the stated value,
In Table 8, absorbances a and h are values described in Table 5, and in Table 9, absorbances a, b and h are values described in Table 3.

Further, l = g / c is g = f-a obtained by subtracting a from the above-mentioned absorbance f and the absorbance b for PET.
The ratio of c = b−a obtained by subtracting a from m, g = i is
Absorbance g of the above deduction and absorbance h of PVC
Is the ratio of i = ha minus a.

[0043]

[Table 7]

[0044]

[Table 8]

[0045]

[Table 9]

As the number of PET packs mixed into the target PS pack out of 10 egg packs increased, as shown in Table 7, the absorbance ratios l and m decreased, and PV ratio
As the number of C packs mixed increases, as shown in Table 8,
The absorbance ratio 1 becomes large and m becomes small, and when the PET pack and the PVC pack are mixed with the target PS pack, the absorbance ratios 1 and m are different.

If standard values of 2.5 and 1.5 are selected for the absorbance ratios 1 and m, respectively, l ≧ 2.5 and m ≧
Satisfying both of the conditions of 1.5 is PET / Table 7
PS = 1/9 (sheets) and PVC / PS = 1/9 in Table 8
The case of (sheets) is not excluded. Therefore, if the number of stacked egg packs is reduced and measurement is performed, l ≧ 2.5 and m ≧ 1.5
Depending on the conditions of PET or PV
There is no mixture of C packs, and it can be determined that they are all PS packs.

In the above embodiments, PET, PVC, PC
It was determined whether or not one of the two plastic packs other than the target plastic pack was mixed in the overlap of 10 egg packs with one of the above plastics as the target plastic. Is not limited to these, but in addition to these three types of plastics, transparent or translucent plastics such as PP (polypropylene) and P
Even if E (polyethylene) is added, it is possible to determine whether or not a pack of different plastics other than the target plastic pack is mixed in the overlapping egg packs.

The infrared absorption spectra of PP and PE are
The infrared absorption spectrum of PET and the like are shown in FIG. P
P has a maximum at a wavelength of 1.745 μm, and PE has a maximum at a wavelength of 1.752. As described above, PP has a maximum value of 1.745 as a wavelength peculiar to the material.
The wavelength of μm or its vicinity may be used, and the wavelength of 1.752 μm or its vicinity giving the maximum value in PE may be used.

The number of overlapping egg packs is not limited, and may be 10, 5, or 15, but is preferably 10 or less for easy handling.

Further, the overlapping of the egg pack was irradiated with white light, and the absorption spectrum of infrared light obtained from the transmitted light was measured for the absorbance at a wavelength peculiar to the plastic material. You may make it receive the infrared light of the wavelength peculiar to. Also, from the beginning, the infrared light of the wavelength peculiar to the plastic material is selectively irradiated,
The transmitted light may be received. A halogen lamp was used to illuminate white light, but natural light can also be used.

The plastic packaging materials that can be the subject of the present invention are not limited to egg packs, but include various forms such as vegetable and fruit trays, packaging bags, and the like. It is possible to determine whether or not the packaging material of different kinds of plastic is mixed.

Further, instead of the absorbance at the wavelength peculiar to the material of the packaging material, the spectrum obtained by first-derivative or second-derivative absorption spectrum of infrared light is measured at the wavelength peculiar to the material of the packaging material. Signals can be used.

[0054]

As described above, according to the present invention,
If it's an egg pack, stack multiple plastic packaging materials of the same type, such as an egg pack, irradiate white light on the overlap of the packaging materials, and compare the absorption spectrum of infrared light obtained from the transmitted light with the target plastic and material. By measuring the absorbance at the wavelengths peculiar to different types of different plastics, and calculating the ratio of the absorbances and comparing it with the reference value, the packaging materials of different types of plastic other than the packaging material of the target plastic can be found in the overlap of the packaging materials. Since it is discriminated whether or not they are mixed, it is possible to discriminate easily and quickly without resorting to manual selection by observing the appearance of the operator.

[Brief description of the drawings]

FIG. 1 is a diagram showing an infrared absorption spectrum of a plastic used in the determination method of the present invention.

FIG. 2 is a diagram in which an infrared absorption spectrum of PP and PE is added to the infrared absorption spectrum of FIG.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G01N 21/35 B09B 5/00 P

Claims (12)

[Claims] 1. A method for discriminating the mixing of a packaging material of a different type of plastic into a packaging material of a target plastic among a plurality of types of plastic packaging materials of different materials, which comprises irradiating a plurality of packaging materials with light. By measuring the absorption spectrum of infrared light obtained from the transmitted light, it is possible to determine the presence / absence of mixing of different types of plastic packaging materials within the overlap of a plurality of packaging materials. Mixing determination method. 2. A plurality of types of plastic packaging materials are PE
The mixing determination method according to claim 1, wherein the mixing determination method is five types of packaging materials of T, PVC, PS, PP and PE. 3. A plurality of types of plastic packaging materials are PE
The mixing determination method according to claim 2, wherein the mixing determination method is three types of packaging materials of T, PVC, and PS. 4. The PET wrapping material is a target plastic wrapping material, and the PVC and PS wrapping materials are different plastic wrapping materials, and the infrared absorption spectrum is unique to PET and PVC. Claims for determining the presence or absence of mixing of different types of plastic packaging material within the overlap of a plurality of packaging materials by measuring the absorbance at the wavelength of, and comparing the absorbance ratio with a predetermined reference value. Mixing determination method of 3. 5. The PVC packaging material is a target plastic packaging material, and the PET and PS packaging materials are different plastic packaging materials, and the absorption spectrum of infrared light has a wavelength peculiar to PVC and PET and PS. By measuring the absorbance at the wavelengths peculiar to and and comparing the absorbances with a predetermined reference value, it is possible to determine whether or not the packaging materials of different plastics are mixed in the overlap of multiple packaging materials. The method for determining mixture according to claim 3, wherein 6. The PS wrapping material is a target plastic wrapping material, and the PET and PVC wrapping materials are different plastic wrapping materials, and the absorption spectrum of infrared light is peculiar to PS, peculiar to PET. Wavelength and PV
The absorbance at the wavelength peculiar to C is measured, and the ratio of the absorbance at the wavelength peculiar to PS and the wavelength peculiar to PET and the ratio of the absorbance at the wavelength peculiar to PS and the wavelength peculiar to PVC are obtained, and 4. The mixture discriminating method according to claim 3, wherein it is discriminated whether or not the packaging material of different kinds of plastic is mixed in the overlap of a plurality of packaging materials by comparing the ratio of the above with a predetermined reference value. 7. The mixing ratio according to claim 4, 5 or 6, wherein the absorbance ratio of the packaging material and its reference value are obtained by subtracting the absorbance at a wavelength that does not depend on the material of the packaging material from the absorbance of the packaging material. Method. 8. The mixing determination method according to claim 4, wherein the wavelength peculiar to the material of the packaging material is a wavelength giving a maximum absorbance peculiar to the material of the packaging material or a wavelength in the vicinity thereof. 9. The mixing determination method according to claim 3, 4, 5, 6, 7, or 8, wherein the packaging materials are stacked with 10 sheets or less. 10. The measurement of the absorbance at a wavelength peculiar to the material of the packaging material is performed by irradiating a plurality of packaging materials with natural light or white light from a white light source, and peculiar to the material of the packaging material in the transmitted light. 10. The mixing determination method according to claim 3, 4, 5, 6, 7, 8 or 9, which is performed by receiving infrared light having a different wavelength. 11. The measurement of the absorbance at a wavelength peculiar to the material of the packaging material is performed by selectively irradiating a plurality of packaging materials with infrared light having a wavelength peculiar to the material of the packaging material and transmitting the infrared light. Claims 3, 4, 5, 6, 7, which are performed by receiving light.
8 or 9 mixing discrimination method. 12. A spectrum which is obtained by irradiating light on a packaging material having a plurality of layers and deriving an absorption spectrum of infrared light obtained from the transmitted light by a first derivative or a second derivative at a wavelength peculiar to the material of the packaging material. The measured intensity is used instead of the absorbance at a wavelength peculiar to the material of the packaging material.
6, 7, 8 or 9 mixture discrimination method.