KR100415148B1 - Plastic cutting tool for preventing metal contamination and selecting method of material for making the same - Google Patents

Abstract

The present invention relates to a plastic cutting tool that can prevent metal contamination, and to a material selection method for the same, and more particularly, when cutting a sample of environmental field, such as filter paper for measuring the atmospheric environment for the purpose of testing a trace amount of metal components. It relates to a plastic cutting tool made of a polymer material containing a minimum amount of inorganic components in place of the metal cutting tool used. The present invention improves the Neutron Activation Analysis, which has been used for the analysis of trace elements of poorly soluble polymer materials, to solve the problem of damage to the sample container during contamination and neutron irradiation of metal components introduced from the outside during the pretreatment of the sample. The present invention provides a method for selecting the material of the plastic cutting tool by solving the inorganic component contained in the trace amount in the polymer material more accurately.

Description

Plastic cutting tool to prevent metal contamination and material selection method {PLASTIC CUTTING TOOL FOR PREVENTING METAL CONTAMINATION AND SELECTING METHOD OF MATERIAL FOR MAKING THE SAME}

The present invention relates to a plastic cutting tool that can prevent metal contamination and a material selection method therefor, and replaces the metal cutting tool used in the past with a plastic cutting tool, and improved neutron for the selection of the most suitable polymer material for this It is intended to apply the radiation analysis method.

Currently, all cutting tools such as punches and scissors used for cutting samples of environmental fields, such as filter paper, used for measuring the atmospheric environment, are metal products. When such metal products are used for the above-mentioned applications, contamination by metal components occurs and sometimes rusts on metal cutting tools, which causes a large test error in the environmental field where a small amount of metal components should be tested. When the metal cutting tool is replaced with the plastic cutting tool, the test error due to the contamination of the metal component can be excluded.

Plastic material is easy to process, so it can be manufactured with various sizes and shapes of cutting tools such as punchers and scissors. However, the plastic material to be used as the material of the cutting device should be selected by strictly measuring the physical properties such as appropriate strength and the chemical properties such as the type and content of the metal component (catalyst component, additive component, impurity component). That is, the material for making a plastic cutting tool should be high in strength and low in metal content. The strength of the material or the type of catalyst used in the synthesis can be determined by examining the material description or published data of the producing company. However, even in the same type of plastic, there are significant differences in the concentration of the catalyst component and the impurities such as the metal component according to the manufacturing company and the manufacturing method. Therefore, the candidate materials should be determined by using the physical properties of the plastic materials, and then the final candidate materials should be selected by precise testing of the metal components of these candidate materials. That is, the final plastic material for manufacturing the environmental sample cutting tool should be determined in consideration of the strength and the type and content of the metal component among the candidate materials. Metallic components contained in plastic materials can be classified into catalyst components, which are essential ingredients for synthesis, inorganic additives added to enhance the function of materials, and impurity components introduced from manufacturing processes or raw materials.

On the other hand, the analysis of inorganic components in the polymer material has been mainly used a solution analysis method such as AAS, ICP-AES and XRF method. However, in order to dissolve the polymer material, two steps of ashing and dissolution are required. This process is not only time-consuming and labor-intensive, but also has a high risk of contamination and loss, which is most concerned with the analysis of trace analytes. In terms of the XRF method, it must be manufactured in the form of discs or pellets, and thus, it is still necessary to overcome the disadvantages of contamination of impurities and deterioration of analytical sensitivity. Chemical Analysis (NAA) is a non-destructive and highly sensitive method for analysis without polymerizing or dissolving the polymer material, and does not need to be made of discs or pellets, and it is possible to measure the neutrons used for the radiation of a sample Since gamma rays pass through the sample medium almost completely, the disturbing effects of the medium can be almost neglected There are many advantages of such.

However, in analyzing the trace inorganic analysis in the polymer material using the above-described NAA method, the sample container may be damaged by the gas pressure generated due to the cleavage of the polymer chain and the oxidation reaction during the neutron irradiation. Since the size (12 mm ψ × 120 mm) is limited, the size of the sample must be cut accordingly. This process has a problem of being a contamination path by the cutting tool.

Therefore, the present inventors apply the freeze-crushing method using liquid nitrogen which is frequently used in biological sample grinding, thereby easily breaking the sample without using any metal tools and solving the problem of damage to the sample container. Through the selection of the plastic polymer materials currently on the market through to manufacture a plastic cutting tool that can prevent metal contamination and completed the present invention.

The object of the present invention is to solve the problems of the conventional neutron radiation analysis method when analyzing the trace amount of inorganic components contained in the polymer material as described above to block the contamination path of metal components introduced from the outside during the preparation of the sample Through this improved analytical method, it is possible to select polymer materials for plastic cutting tools that can be used for cutting of environmental samples that test trace metal components by measuring trace amounts of inorganic components contained in polymer materials more accurately. It is to make it possible.

Still another object of the present invention is to prepare a plastic cutting tool that can replace a metal cutting tool, using the polymer material selected according to the inorganic component content result in the polymer material found through the above analysis method.

Figure 1 shows the gamma-ray spectrum and representative nuclides obtained in each condition from children's toy products (polymer materials),

2 shows a pretreatment process of a sample according to the present invention,

3 shows an analysis process for selecting a polymer material according to the present invention.

In order to achieve the above object, in the present invention, as a method of selecting a material to be the material of the plastic cutting tool according to the results of the inorganic component analysis using the neutron radiation analysis method, (a) a liquid nitrogen material of the sample to be analyzed Freezing by using a plastic bag (bag) and crushed in a sealed state; (b) washing the crushed sample to remove contaminants remaining in the sample and dried; (c) the dried sample Is placed in a sample container for neutron radiation analysis, and making a small hole having a diameter of 0.5 mm or less for gas discharge on the top of the sample container; (d) irradiates neutrons to the sample in the sample container and emits gamma rays from radionuclides Preventing metal contamination, characterized in that using the improved neutron radiation analysis method comprising a; This material can be selected method is provided for plastic cutting mechanism.

In addition, the present invention provides a plastic cutting tool that can prevent metal contamination produced using the polymer material selected by the material selection method as described above.

Essential equipment for neutron emission analysis is the Neutron source and gamma detectors, and basic equipment such as PCs. Reactors were used as neutral resources for the radiation, and HPGe semiconductor detectors (EG G, ORTEC USA) and MCA (Multi Channel Analyzer) were used to measure gamma rays emitted from radionuclides.

Hereinafter, an analysis method for selecting a material of the present invention will be described in detail with reference to FIGS. 2 and 3.

(1) pretreatment step of the sample (FIG. 2)

1) Sample to be analyzed

In order to be used as the material of the cutting tool of the present invention, the polymer material should be excellent in physical properties such as strength, impact resistance and abrasion resistance.

In one embodiment of the present invention, as a result of examining the physical properties of various types of polymer material, it was confirmed that acetal material is most suitable as a candidate material, and these were used as samples.

2) washing and shredding

In one embodiment of the present invention, the polymer sample purchased using deionized water is thoroughly washed, soaked in liquid nitrogen for 30 minutes, taken out and sealed in a frozen polyethylene bag (Taglon) in a frozen state, and then Teflon. Crushing was carried out using the plastic hammer of the material (freeze-crushing method).

3) Pollutant removal and dry storage

To remove contaminants remaining in the shredded plastic sample, it is washed with 10% nitric acid solution and then dried in an oven or desiccator. After drying, store in a clean polypropylene bottle.

4) neutron flux measurement

The neutron flux measuring monitor is Au (Gold-aluminum alloy wire: 0.1274% of gold, Degusa, FRG) and Co (Cobalt-aluminum alloy wire: 0.0925% cobalt, Degusa, FRG) attached to both sides of the sample container and irradiated with neutron Place in container (HDPE rabbit).

(2) Analysis of the polymer material using the neutron radiation analysis (Fig. 3)

1) Sample injection and hole formation on top of sample container

In the polyethylene sample container, 5g of short-lived nuclides and 10g of medium-long-lived nuclides are prepared and placed in the polyethylene sample container.Then, vessel damage caused by the gas (hydrogen, methane, etc.) generated from the sample itself during neutron irradiation is prepared. To solve this, make a small hole with a diameter of 0.5 mm or less on the top of the sample container.

2) neutron irradiation and gamma ray measurement

The neutron irradiation of the samples was carried out using a research reactor, and the thermal and neutron flux densities were 1.8 × 10 ¹³ and 7.5 × 10 ¹¹ n · cm ^-2 · s ^-1 , respectively. The samples for analysis of short-lived nuclides were neutron irradiated for 1 minute, and the samples for medium and long-lived nuclide analysis were irradiated for 30 minutes. In order to maximize the analytical sensitivity and analytical components of the short-lived nuclide, the optimum cooling condition for each component was obtained by repeating the neutron irradiation twice for 5 minutes and 120 minutes. Gamma-ray spectra were obtained by measuring samples after 2 days of neutron irradiation for mid-life nuclides and 20 days after long-life nuclides. Gamma-ray spectra were measured using an HPGe detector (energy resolution; 1.7 keV, measurement efficiency; 25%), and measurement times were performed at 500 seconds for short-lived nuclides, 2,000 seconds for mid-lived nuclides, and 4,000 seconds for long-lived nuclides. .

3) content determination

Gamma Vision (EG G ORTEC Inc., USA) was used for the processing and analysis of the gamma ray spectrum. Inorganic impurities contained in the sample were analyzed using a single comparison method (SCM-IF, absolute analysis method) that included analytical disturbance correction.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Example 1

Measurement conditions to maximize analysis sensitivity

In order to derive the optimal experimental conditions, the radionuclide intensity of the single half-life nuclides and the amount of attenuation according to the neutron irradiation time of the single-half-life nuclides are calculated by using the nuclear data of each component and the neutron flux characteristics of the reactor. A computer program was developed to determine the conditions under which Using this program, the optimum neutron irradiation time and radioactivity decay time were calculated according to the amount of analyte nuclei and the amount of interfering nuclides. Table 1 shows the optimum experimental conditions for the analysis of 33 inorganic components frequently observed in the polymer materials applied to the analysis. Figure 1 shows the gamma-ray spectrum and representative nuclides obtained under each condition from a toy product for children, one of the subject materials.

Optimum Conditions for Inorganic Elements in Polymeric Materials weight T _irrad T _cool T _count Nuclide 5g 1m 5 minutes 500 sec ²⁸ Al, ⁵¹ Ti, ²⁷ Mg, ⁵² V, ⁶⁶ Cu 120 minutes 500 sec ⁵⁶ Mn, ⁴⁹ Ca, ³⁸ Cl 10g 30m 2 days 2,000 seconds ²⁴ Na, ⁷⁶ As, ⁹⁹ Mo, ⁸² Br, ¹⁴⁰ La, ¹⁹⁸ Au, ⁴² K, ¹⁵³ Sm ¹⁸⁷ W, ⁷² Ga, ¹¹⁵ Cd 20 days 4,000 seconds ¹²⁴ Sb, ⁵⁹ Fe, ⁵¹ Cr, ¹⁸¹ Hf, ²⁰³ Hg, ⁶⁰ Co, ⁶⁵ Zn, ¹³⁴ Cs * T _irrad , T _cool and T _count represent irradiation time, cooling time and measurement time

Example 2

NAA Analysis of NIST 1632b Coal Standard Samples

In order to verify the analytical method of the present invention, a standard material was applied and tested. In the NAA aspect, the analytical method of the present invention was applied to a Coal standard (NIST SRM 1632b) similar to a polymer material (compounds containing carbon and hydrogen) in terms of NAA.

Table 2 shows the results of NAA analysis of NIST 1632 coal standard samples. Except for Sr and V among the 27 components analyzed, it was confirmed that the coincidence within the deviation of less than 10%.

Example 3

Selection of Polymer Materials for Plastic Cutters

As a result of applying the improved NAA of the present invention to the precise analysis of the inorganic component of the standard material in Example 2 it was confirmed that can be analyzed accurately. The analytical method was applied to an acetal material having physical properties such as strength, impact resistance, and abrasion resistance suitable for use in a polymer material of a plastic cutting tool capable of preventing metal contamination, thereby obtaining the results as shown in Table 3 below.

element NIST (ppm) Analysis result of the present invention uncertainty Al 0.86 ± 0.02 0.90 ± 0.04 5.2 Ca 0.20 ± 0.01 0.21 ± 0.01 3.3 Fe 0.76 ± 0.05 0.77 ± 0.08 1.2 K 0.075 ± 0.003 0.076 ± 0.005 1.1 Na 0.052 ± 0.001 0.053 ± 0.002 2.3 Ti 0.045 ± 0.002 0.046 ± 0.002 2.1 As 3.7 ± 0.1 3.9 ± 0.1 3.4 Ba 68 ± 2 69 ± 4 2.7 Co 2.3 ± 0.2 2.3 ± 0.1 2.1 Mn 12 ± 1 13 ± 1 2.2 Rb 5.1 ± 0.1 5.4 ± 0.3 6.5 Th 1.3 ± 0.1 1.4 ± 0.2 6.2 U 0.44 ± 0.01 0.48 ± 0.08 10 Zn 12 ± 1 13 ± 2 5.5 Sb 0.24 0.25 ± 0.02 2.1 Br 17 18 ± 2 5.8 Ce 9 9.7 ± 1.1 8.1 Cs 0.44 0.46 ± 0.03 4.9 Cl 1300 130 ± 16 1.7 Cr 11 12 ± 2 8.3 Eu 0.17 0.18 ± 0.02 7.4 Hf 0.43 0.47 ± 0.04 10 La 5.1 5.4 ± 0.5 5.6 Sm 0.87 0.90 ± 0.09 2.9 Sc 1.9 1.9 ± 0.3 1.2 Sr 100 110 ± 23 11 V 14 16 ± 2 13

NAA analysis result of 7 kinds of cutter candidate materials (polyacetal) (unit: ppm) Inorganic elements A B C D E F G Na 0.71 (16) 0.88 (23) 47 (2.3) 4.2 (5.4) 3.2 (6.4) 3.9 (5.4) 69 (2.2 Mg 320 (2.1) 410 (2.0) 6.9 (11) 1.2 (14) <0.61 <0.49 360 (1.9) Al 0.31 (5.4) 3.1 (2.3) 0.36 (13) 0.32 (4.3) 0.41 (4.1) 0.20 (4.8) 1.3 (2.5) Cl 0.62 (13) 0.45 (19) <0.22 4.1 (5.4) 4.1 (5.4) 4.8 (4.9) 0.60 (31) Ca 16 (18) 170 (5.4) <1.3 <1.7 11 (20) 10 (20) 42 (39) Ti 0.84 (31) 0.77 (40) 0.26 (69) <0.082 <0.15 <0.061 <0.076 V (PPb) 11 (6.6) 20 (6.5) <0.63 0.90 (69) <0.11 0.96 (37) 2.3 (40) Mn (PPb) 51 (17) 160 (8.0) <2.7 10 (28) 10 (28) 8.2 (28) 65 (18) Sc (PPb) 0.12 (16) 0.68 (5.7) 0.082 (24) <0.019 0.064 (29) <0.011 0.11 (15) Ca 6.5 (56) 31 (29) 7.8 (56) <4.6 <4.9 <4.3 <1.3 Cr (PPb) 35 (13) 75 (7.9) 36 (14) 6.0 (57) 12 (29) <2.1 31 (13) Fe <0.17 4.5 (11) 1.7 (40) <0.18 0.36 (55) 0.22 (52) 1.5 (18) Co (PPb) 1.3 (43) 3.2 (20) 1.5 (58) 1.1 (54) 1.8 (32) 1.6 (52) 1.8 (28) Zn (PPb) 52 (44) 68 (38) 63 (51) <9.8 <16 <3.9 49 (16) Sb (PPb) 1.8 (43) 2.8 (32) <0.89 <0.18 1.7 (56) <0.35 <0.25 * Unit ppm = parts per million, μg / g, 1ppm = 0.0001%, 1ppb = 0.001 ppm The number in () is the% analysis error symbol <is the detection limit, and if <x, the sample contains less than x. Meaning

As can be seen from the results of Table 3, it can be seen that the difference in concentration of each inorganic component is great even in the same polymer material acetal (acetal). In order to minimize metal contamination, the concentration of inorganic components should be as low as possible, and depending on the purpose of the cutting tool, the type of inorganic components contained is also important.

For example, a material such as B contains more than 100 ppm of Mg, Ca, etc., and thus, it can be seen that the cutting tool for the analysis of trace elements is the most unsuitable among the seven candidate materials. On the other hand, D material is the most candidate material that can prevent the contamination of metals considering the comprehensive inorganic components because the content of most inorganic components is lower than the other six species. However, it can be seen that A material is suitable when the main components of the sample to be analyzed are Na and Cl.

As such, when the cutter is manufactured by accurately measuring the type and concentration of the inorganic component contained in the material, contamination of the metal component may be minimized.

Example 4

Manufacture of plastic cutter tool

According to the result of Example 3, the scissors and the puncher were manufactured by using the conventional cutting tool manufacturing method using A and D materials as the polymer material to be used for the production of the plastic cutting tool which can prevent metal contamination.

As described above, the neutron radiation analysis method of the present invention uses the freeze-crushing method to prevent metal contamination during the pretreatment of the sample, solve the breakage problem of the sample container when analyzing the polymer material, and the high sensitivity analysis characteristics are the biggest problems in the trace amount analysis. It can solve the complexity of sample processing and consequent analysis inaccuracy, so it is very suitable for the analysis of trace inorganic substances in poorly soluble solid materials such as polymer materials, and it can be used to determine the accuracy of other inorganic analysis methods. It may also be used.

In the present invention, by using the improved analysis method as a material selection method for the plastic cutting tool that can prevent metal contamination, the cutting tool is manufactured to obtain an effect of greatly improving the accuracy of the analysis result of the atmospheric environmental measurement sample. .

Claims (6)

As a method of selecting the material of the plastic cutting tool according to the results of the inorganic component analysis using the neutron radiation analysis method, (A) freezing the polymer material of the sample to be analyzed using liquid nitrogen, and then crushed in a sealed state in a bag (bag); (b) washing the crushed sample to remove contaminants remaining in the sample and drying it; (c) placing the dried sample in a sample container for neutron radiation analysis, and making a small hole having a diameter of 0.5 mm or less for discharging gas at the top of the sample container; (d) a neutron radiation analysis step of irradiating a sample in the sample container with neutrons and measuring gamma rays emitted from radionuclides; Material selection method for a plastic cutting tool that can prevent metal contamination, characterized in that using the improved neutron radiation analysis method comprising a. The method of claim 1, The crushing is a material selection method for a plastic cutting tool that can prevent metal contamination, characterized in that using a plastic hammer. delete Plastic cutting tool that can prevent metal contamination, characterized in that manufactured using the polymer material selected by the material selection method of claim 1. The method of claim 4, wherein The polymer material is a plastic cutting tool that can prevent metal contamination, characterized in that the acetal (acetal) material. The method according to claim 4 or 5, The plastic cutting tool is a plastic cutting tool that can prevent metal contamination, characterized in that the scissors or puncher.