DK157710B - PROCEDURE FOR DETERMINING AND DISASSEMBLY OF AGED, NO LONGER USEFUL PLASTIC PRODUCTS - Google Patents

Description

DK 157710B

The invention relates to a method for detecting and disposing of aged, no longer usable plastic objects from the further use.

The invention aims at avoiding costly consequential damages that can be caused by old, no longer usable plastic objects.

As is well known, in {thermoplastic) plastic articles 10, a - chemical and physical - aging process is effected by the action of light radiation (in the visible or invisible area) in the presence of air (oxygen) and heat, namely on the surface of the objects. This aging process is independent of the age and, to a small extent, dependent on the frequency of use of the plastic articles due to the different extent of the effect of light, oxygen and heat on the plastic article. Therefore, based on the age of the objects, one cannot agree on anything about the aging state of the objects. This aging leads - from the surface of the objects - to make the plastic brittle and thus to reduce the usefulness of the article. that of plastic after irradiation with the xenon irradiator. The lightfastness of pigmented PVC profiles against natural and artificial weathering is investigated and the two methods are compared. The change in color is assessed visually with the blue scale and colorimetric using the triple photometer. The weathering in the zenotest allows a useful prediction of the behavior of weathering in the open.

Further, light fastness and mechanical properties of low-pressure ethylene are described after exposure in the xenotester. Stretch tension and elongation at tensile stress provide valuable information for the assessment of aging conditions following the influence in the xenotest, even when the tests do not allow

DK 157710 B

2 to recognize any noticeable color change in the visual assessment. By means of this degrading test, a change of material can already be detected before a change in color can be recognized. Thus, the degree of aging of the plastic article is not directly related to its reflectivity determined here.

If the visual assessment of the color is supplemented by a measurement on the photometer, it has proved appropriate to constant the color value proportions X and Y and to take the color value Y into consideration as a measure of brightness. These sizes are the usual colorimetric feature sizes for assessing color and color differences.

DIN 5035, leaf 2 (March 1972) defines concepts in the area 15 regarding aging of high polymer materials. The aging phenomenon is indicated, among other things, the color change - especially the yellowing. According to the German industry standard, color change and yellowing are one of several possible aging phenomena. The industry standard does not indicate any coherent relationship between, on the one hand, aging and, on the other, color change and yellowing. As shown in Kunststoffe 60 (1970) (see above), the plastic may already be aged before a color change can be recognized.

In the case of plastic articles for repeated use, e.g.

25 multi-way bottle transport boxes are of mass-colored polyolefins, consequential damage is caused by a sufficiently large aging. These can manifest themselves as significant disruptions in the automatic filling in the beverage industry or as collapse of box stacks or pallet stacks in stock or during transportation.

The aging state and thus the usefulness after a certain useful life can be ascertained by various chemical or mechanical methods. These are always time-consuming and mostly not devastating and therefore only applicable to individual plastic objects. The known methods without destructive effect can also not be routinely used in the case of very large pieces of plastic articles. There- 3

DK 157710B

so far, a method without degrading effect has been lacking, in which the state of aging of plastic articles can be determined in a simple manner and by means of a very large number of uniform articles it is possible to ascertain and separate those objects which, as a result of advanced aging, no longer exist. are usable.

The object of the invention is to determine the aging state of plastic objects - irrespective of their age - by means of a degradation-free measurement method without contact for the sorting of no longer usable objects from several similar objects.

This is achieved according to the invention by: - illuminating the plastic objects with a light source that emits light in the total visible spectral range (white light), - measuring the reflection at at least one critical point on the surface of the plastic objects in a region of the spectrum of the plastic objects color which is outside the color region of the plastic article, and - the removal of all plastic objects whose reflection lies outside a predetermined calculated range.

White lamps, halogen lamps or Xenon high-pressure lamps are suitable as light sources. No color filter is inserted into the illumination beam path. The wavelength range of the light reflected from the surface of the plastic article must, for a large part, be contained in the light emitted from the light source.

The reflectance is measured by one of the known methods using a commercially available color measurement apparatus and taking into account the convenience required for optical examinations' From the reflected light whose spectral range 4

DK 157710B

and intensity depends on the color of the plastic article and the state of the surface, an appropriate spectral range is filtered out by means of a color filter in the reflection beam path, thereby making the method sufficiently sensitive.

5

The calculated area in which the reflection from the still usable objects should lie is in accordance with the requirements specific to the usefulness of the present plastic article.

The method according to the invention depends on the relationship between the aging state of the plastic article and the reflection of the surface. The measure of the aging state is the difference between the reflectance figures for the surface of a completely unused plastic article and of the aged plastic article of the same species 15 and color in a selected wavelength range which is outside the wavelength range in which the plastic article exhibits the greatest reflection, the measurement conditions of the two objects are identical. Given the particulars in Kunststoffe £ 0 (1970), this connection is surprising.

20

Critical places on the surface of the plastic articles are those which are subject to the effects of light, oxygen and heat, as well as mechanical pull, pressure and bending effects, and do not exhibit any mechanical damage or alteration (such as scratches, abrasions). - or scouring tracks, adhesives, adhesives, foreign matter, imprints, embossings).

It has been found appropriate to measure the reflection at two critical sites of the surface of the plastic article, which is equal to two approx. perpendicular to each other exterior surfaces of an object which, when using the article according to its determination, is exposed to light. If necessary, the reflection can be measured on more than 35 two or all sides of the object. In these cases, more light sources and a receiver are required for each of the sides of the object to be measured.

5

DK 157710B

A plastic article is filtered out and excluded from further use if the reflection from one or more than one critical location is outside the calculated area dependent on the plastic object.

The method according to the invention offers the following advantages: 10 - It is practically independent of the fluctuations in the pigment content of the plastic articles.

- It is devoid of destructive effects and is without touch and 15 associated with acceptable tenders.

- It can easily be put into use in devices already available for handling the plastic objects.

20 - It enables the aging state of the objects to be ascertained, although several objects of the same kind are virtually indistinguishable visually, and thus also when the color measurement according to DIN 5033, leaf 6, shows no change in color.

25 - It works automatically and can be used continuously especially in case of large pieces of plastic articles.

- It is free from subjective influences.

30

The process of the invention can be used for mass pigmented plastic articles. The objects can be of different shape and color and used for different purposes.

35 Aged multi-way bottle transport boxes of, for example, polydefines presenting too high a safety risk for further use are characterized by the following reflection (measured in relation to MgO white standard in a spectral photometer with post-shot Ulbricht sphere) in 6

DK 157710B

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For bottle transport boxes colored with other pigments, or for such boxes of other plastics or for plastic objects for other uses, calculated or desired areas may also be indicated for selected spectral areas in which the reflection of an aged plastic object must lie before the object is to be sorted.

Example

For example, for the detection and sorting of aged and no longer usable multi-way bottle transport boxes of poly = 10 ethylene, which are colored in the mass dark red with cadmium-selenide, proceed as follows.

After the washing process, the cleaned, dry bottle transport boxes pass the measuring zone on the conveyor belt to the box filling station. This measuring zone consists of a lighting device with white fluorescent lamps as a light source placed above the conveyor band within a shield. The shield keeps unwanted light effects away. The power supply for the fluorescent lamps is stabilized. The fluorescent tubes preferably illuminate the upper orbital rim of the bottle boxes in a direction that slopes somewhat with respect to the surface normals.

As a color measuring device, a commercially available device with color video camera is used. The axis of the reflection beam is perpendicular to the measuring surface of the bottle box. The measuring surface is located 25 on a vertical outside of the bottle boxes approximately, in the middle of the upper, circumferential U-rim. A blue filter is inserted in front of the color measuring device's video camera.

Each of the bottle boxes running over the conveyor belt in the usual way passes through the measuring zone, whereby the reflection of the measuring surface 30 is measured. If the reflection value of a bottle box is outside the calculated range /

DK 157710 B

8 applicable box is automatically pushed away from the conveyor belt.

Since a relative measurement is sufficient for this method, the color measuring device is set as follows: 5 The color measuring device's display device is set to zero by means of an unused bottle box in the measuring zone by means of apparatus setting. Then a bottle box of the same kind that is no longer usable is shot into the measurement zone. Hereby, for example, the color measuring device's display apparatus shows 2.3 mV. The apparatus for dispensing the bottle boxes with a reflection outside the calculated range from the measuring surface is automatically triggered by the color measuring device as soon as the display device shows more than 2.3 mV.

15 The zero adjustment of the pointer and the setting of the automatic release of the pointer can be repeated arbitrarily as needed by means of the unused and no longer usable bottle box,

The reflection from the no longer usable bottle transport box used to adjust the color measuring device was previously measured on a spectral photometer with post-injected Ulbricht sphere relative to the MgO white standard. The measuring surface at the critical site of this bottle box showed a mean reflection of 10% in the spectral range 400-500 25 nm. Thus, this box's reflection lies on the boundary of the calculated range for aged, yet usable bottle boxes.

Claims (4)

A method for detecting the aging state 5 of mass-colored plastic articles by means of a degradation-free and non-contact measuring method for separating no longer usable objects from several similar objects, characterized by: 10. illumination of the plastic articles with a light emitting light. the total visible spectral range, - measuring the reflection from at least one critical site on the surface of the plastic article in an area of the spectrum that is outside the color region of the plastic object, and - sorting out all plastic objects whose reflection is outside a predetermined desired range. A method according to claim 1, characterized by measuring the reflection at two critical locations of the surface of the plastic articles, which is at about 2 cm. perpendicular to each other, sides of an object which, in accordance with its provision 25, are subjected to light by the use of the object. Method according to claim 1 or 2, applied to multi-way plastic bottle transport boxes, characterized by measuring the reflection from one or more measuring fields 30. the upper part of one or two of the vertical outer sides of the bottle box. Method according to claim 1 used for multi-way bottle transport boxes of polyethylene colored dark red 35 with CdSe, characterized by DK 157710 B: ι t - measuring the reflection on at least one vertical side of the bottle box in the upper part of the spectral range from 400 -500 nm, and - filtering out all bottles whose reflection (measured in relation to MgO 5) is more than 10%. 15 20 25 30 35