JPS59501080A - Method and device for measuring the degree of crosslinking of plastics - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Method and device for measuring the degree of crosslinking of plastics This invention is applicable to plastics, especially polyethylene. The present invention relates to a method and apparatus for continuously measuring the degree of crosslinking of urethane without taking samples.

As is well known, plastics have applications in a variety of different fields. Especially Polie Chyrene has a variety of important technical applications, most notably for high-voltage power lines. Applications include insulation and water and sewer pipes. polyethylene chemistry ・The mechanical durability is excellent, and the mechanical strength is at least satisfactory. It is. If polyethylene is used as a pipe material for hot water, must be able to withstand temperatures above and exhibit similar durability. It is clear that The so-called crosslinking point has a heat resistance of well over 100℃. Polyethylene does not exceed 80°C unless it is polyethylene or 1-pExj (trade name). It tends to soften when heated.

Polyethylene products are made by the so-called extrusion method, where the molten plus The tick is pressurized through an orifice into its final form, e.g. tube or wire sheathing. molded into an insulator for use. It is then heat treated or vulcanized, but in this process the polyethylene During the process, many intermolecular cross-bonds are formed between adjacent carbon chains; This is called cross-linking. This bond further increases the strength and durability of polyethylene. This makes it possible to use it, for example, as a material for water pipes. Depending on the extrusion method When making pipes, it is easy to determine how well the crosslinks are formed. It was extremely difficult to know. During production, we first collect a sample and test it. The test results must be taken to a laboratory, and test results are only known several hours later.

The degree of vulcanization of PEX is indicated by the degree of crosslinking.

For example, in the case of water pipes, the degree of crosslinking must be at least 70% for practical purposes. stomach. In recent years, the degree of crosslinking of PEX has been measured using various chemical and physical methods. Among them, the so-called steeping method and Infrared analytical methods are the most important. In either method, the initiation of crosslinking is determined by the amount of residual peroxide. Measure as. These methods are laboratory methods, and samples cannot be collected after production. It is used only when collected and tested in a laboratory.

PEX is made by continuous extrusion, so there is no need to interrupt production to take samples. is impossible. Therefore, from a technical and economic point of view, the degree of crosslinking of PEX was changed. It was necessary to develop a meter that could measure directly on the line during production. this If possible, the quality of the final product will be consistently uniform and pass the quality standards. If you check that, you should be able to do it. This meter measures the absolute value of crosslinking It is not necessary to monitor changes in the degree of crosslinking, and it is sufficient to monitor changes in the degree of crosslinking. Therefore, the quality can be maintained above the target value.

The purpose of this invention is to provide a method for measuring the degree of crosslinking of PEX (and other plastics). , continuous type, online meter that can measure without touching the sample. It is in the provision of meters. The device according to the invention directly measures the degree of crosslinking and reports the results. Although it is taken out electronically, the degree of crosslinking can also be displayed digitally if necessary. .

However, this means that the device needs to be calibrated with known samples. Taste. Since the device does not measure the absolute value of the degree of crosslinking, the resulting electronic signal The verification is corrected so that an alarm will be activated when the value falls below a preset value. Should. This format also achieves excellent guarantees in quality control in production. It will be done. This meter also supports the production of water pipes and wire sheathing. It has been found to be particularly suitable for monitoring. Test results to date show that high-density This device has been successfully applied not only to plastics but also to low-density plastics. ing. Works easily on PEX for high voltage electric wires with choke. On the other hand, Satisfactory results have not been obtained in the case of carbon-filled wire coatings.

The device of this invention shows that the fluorescence intensity of PEX plastic increases as the degree of crosslinking increases. It is based on the observation that In tests conducted at this company, non-crosslinked polyethylene The fluorescence is only slight; however, its intensity varies approximately as a function of the degree of crosslinking. increases linearly. The spectrum of the fluorescent light also seems to change slightly, but the intensity can be monitored. ter gives the best results.

The only suitable intensity for reliable observation of fluorescent light is from laser light. It was also found that it was necessary to use excited laser light. Besides, Since the spectral distribution of the laser light is narrow enough, a desirable fluorescence spectrum can be obtained. Ru. When testing with an ordinary fluorescent lamp, first the intensity of the ordinary fluorescent lamp was It is inconvenient to focus the weakly fluctuating and rapidly generated light beam on the desired point. The light beam is easy to guide, and its spectral distribution is wide and filterable. The lifespan of a fluorescent lamp is significantly shorter than that of a laser light source. Therefore, measurement was extremely troublesome. UV fluorescent lamps can also be used in testing rooms. However, it is nearly impossible to apply it to production sites. Therefore, it is recommended to use a racer. It will be done. Monitoring narrow laser beams is rather inconvenient near fragile production equipment. It is advantageous.

In the apparatus of this invention, a PEX specimen is passed through a rotating chopper using a HeCd laser. Irradiate with a light beam. At this time, the PEX test piece is intensity modulated to a predetermined frequency f. Irradiated by optically modulated light. PEX tends to emit fluorescence under the influence of excitation light. However, the fluorescence at this time occurs at the same frequency f as the incident modulated light. Fluorescence Changes in the degree of crosslinking can be detected by monitoring the strength and changes in Ru. Fluorescence occurs at a predetermined frequency f, so it can be detected by a photodetector. It is possible to create an electronic amplifier tuned to the same frequency f as the fluorescence emitted. It's easy. At the same time, interference light generated at other frequencies is filtered by this amplifier. - to do. The intensity of the fluorescence is monitored by a photodetector, which may be a photomultiplier tube. Any of the semiconductor detectors can be.

The front surface of this photodetector must have a surface that efficiently absorbs a specific wavelength of the excitation laser light. The method is to install an optical filter that allows only fluorescent light to pass through.

Argon laser or UV type laser can also be used, but HeCcl laser Best results are obtained with light from When crosslinking occurs, there are many Several cross-links are formed. The creation of a union is a new energy level means the creation of As the cross-linking increases, the number of energy levels increases accordingly will also increase. And the number of fluorescence levels also increases. Various plastics emit fluorescent light. It is known that fluorescence increases as a function of the degree of crosslinking. The discovery of new facts constitutes the purpose of this invention.

This principle can also be applied when chalk is used as a filler, but charcoal It cannot be applied to plastics filled with elementary substances.

U.S. Patent No. 4,107,245 describes the use of chemical dyes for plastics. It is disclosed that the degree of crosslinking of polyethylene can be measured by adding In this case, the color properties change as the degree of crosslinking increases. on the other hand, Add some kind of dyed assay tape to the plastic and this color change indicates cross-linking. It is possible to find out the degree of First, the dye components must be measured reliably. Note that it must be evenly distributed in the plastic to the extent that Should. Second, if dyed tape is used, the tape should be visible. In order to do so, the plastic article must be cut open. In the end, consumers will Don't be interested in plastics that are changing.

The method of this invention is free from such drawbacks. Moreover, the accuracy of measurements made by this invention is good. The accuracy is better than the standard chemical stapling method. In good condition. The correlation coefficient is therefore higher than 0.94 in the required measurement range.

West German patent no. An apparatus for measuring chemical properties is disclosed. The claims disclose detection of fluorescence. However, the relationship with cross-linking is not mentioned.

Advantageous embodiments of the invention will now be described in more detail with reference to the accompanying drawings, in which: The invention is not limited exclusively to this embodiment.

FIG. 1 is a diagram showing the generation of fluorescence and its observation.

FIG. 2 is an explanatory diagram showing the principle of construction of the apparatus of the present invention.

Figure 1 shows the results when a laser beam with a narrow spectral distribution is used as the excitation light. This shows the generation of fluorescence. UV lamps do not give the same good results. .

In Figure 1, spectral line 1 shows the excitation light, which comes from the laser. It is extremely narrow.

Spectrum 2 is the generated fluorescence spectrum, which has a longer wavelength than the excitation light. It shows what is on the side. Fluorescence occurs immediately without delay. Remove excitation light The absorption spectrum 3 of the filter effectively absorbs the excitation light in front of the photodetector. It is clear that it is collected.

This allows the detector to observe only the fluorescent light. The spectral distribution of laser light is Because of the extremely narrow filter area, only the smallest fraction of the fluorescence is masked by the excitation light. It is.

FIG. 2 details the principle and design diagram of the method of operating the device of this invention. Leh The light beam 11 from the laser 10 is modulated by means of a chopper 12 and Therefore, the sample 13 is irradiated with the light beam 14 having the modulation frequency f. It has become. The electro-optical blueprint for stabilizing the intensity of light is also known. However, they are not shown because they are not directly related to this invention. to crosslink The fluorescent light 15 thus generated and modulated at frequency f is observed by a photodetector 16. A filter 17 for absorbing excitation light is disposed in front of the filter. The filter itself does not emit any fluorescent light. After photodetector 16 An electronic detector and amplifier [8] is installed in the section and is tuned to the frequency r. Degree of crosslinking The output from the detector 18 is some kind of function of the microprocessor board, e.g. computer or other required control or alarm device 19 and 20. You may be forced to do so. A known phase detector may be used for the phase detector 18. However, there is no direct connection with this invention.

The method of the present invention can be used in electric wire manufacturing equipment and PEX tube manufacturing equipment. It can be used for measurements on production lines that perform cross-linking of ticks, but at the same time Attached to machines and equipment that manufacture various hoards, bunts, or PEX coatings. Can be used.

FIG.I FIG.2 international search report

Claims (1)

[Claims] 1 Continuously measure the degree of crosslinking of plastics, especially polyethylene, without contacting the sample A method of The intensity of the fluorescent radiation (15) generated in the plastic when irradiated with A method characterized in that it is a function of the degree of crosslinking of the stick. 2 The degree of crosslinking of plastics, especially the degree of crosslinking of wire insulation made of polyethylene, is An apparatus based on the method according to claim 1 for continuous measurement, the apparatus comprising: A modulated laser light beam (14) that generates fluorescent light is transmitted into a wire manufacturing machine. A laser (]0) is used to irradiate the wire in a concentrated manner, and a positive laser beam on the wire is used. an electronic photodetector (16) for detecting the fluorescent radiation (15) emitted by the tic; It consists of a filter (17) for absorbing excitation light disposed in front of the photodetector (16). In this case, the electronic signal supplied by the photodetector (16) is The electronic signal proportional to the degree of cross-linking is transmitted to electronic amplifiers (8) and other signal processing systems. (]9.20) to retrieve the crosslinking degree data of the wire coating plastic. A device that allows you to do this. 3 Continuously check the degree of crosslinking of plastics, especially the degree of crosslinking of pipes made of polyethylene. An apparatus based on the method according to claim 1 for measuring A modulated laser light beam (4) that generates fluorescence is transmitted into a pipe manufacturing machine. A laser (]0) that focuses on the pipe and the fluorescent light emitted by the pipe. an electronic photodetector (16) for detecting radiation (15); and a filter (17) for absorbing excitation light disposed in the front part of the filter. At this time, the electronic signal supplied by the photodetector (16) is proportional to the degree of crosslinking. transmitting electronic signals to electronic amplifiers (18) and other signal processing systems (19, 20). This is a device that allows data on the degree of crosslinking of pipes to be retrieved. 4 Claims for continuously measuring the degree of crosslinking of plastics, especially polyethylene The apparatus according to item 2 or 3, wherein the sample (13) to be measured is made of polyester. A patent characterized in that it is a board, film or coating made of tyrene.