JPH0251451B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a laminated polyester molded article with good adhesive properties, and more particularly to a method for obtaining the polyester molded article by controlling changes in the atomic composition of the surface layer of the molded article by corona discharge treatment. Furthermore, the present invention provides a molded product with even better adhesiveness without impairing the heat resistance, transparency, and mechanical properties of the base layer by laminating a highly adhesive layer on all or part of the surface of the base layer. This is how you can get it. Surface modification of plastic molded articles by corona discharge is generally known as a treatment technique for films, and has had substantial effects such as improved adhesion due to surface activation. However, the results are not completely satisfactory. The present inventors particularly focused on polyester molded products, and for example, when subjecting a polyester film to corona discharge treatment to improve its surface (particularly improve adhesion), it was possible to achieve treatment efficiency that was sufficiently satisfactory at the actual production level. I wanted to establish a method that would allow me to do so. For example, as a corona discharge treatment method for plastic molded products, there is a technique that promotes chemical changes on the discharge surface by supplying an organic solvent to the discharge area, as shown in Japanese Patent Publication No. 17747/1982. It is difficult to apply it to the molded products in question. or
Journal of Applied Polymer Science, Vol.15,
P.1365-1375 (1971) describes a technique for performing corona discharge treatment in an inert gas atmosphere, and suggests that the treatment atmosphere may have an effect on activation or deterioration. Techniques have also been proposed that replace the process with . However, this type of conventional method requires a large amount of inert gas, resulting in high costs.Furthermore, corona discharge technology for running films under an inert atmosphere eliminates atmospheric air entrained by the film. A special shield structure is required to shut off, making the equipment complex, and even then, a complete or almost complete inert atmosphere is not guaranteed, and in reality, only a low-oxygen atmosphere is created. I had to settle for a low processing level. The reason why conventional improvement processing methods cannot achieve sufficient results can be considered as follows. In other words, the key to increasing processing efficiency is thought to be the gas atmosphere in the discharge processing section, but conventional improvement methods only address the gas atmosphere within the processing system or chamber; This seems to be because shielding failure due to accompanying flow (outside air) is not taken into account. Therefore, if processing was carried out in a batch-type stationary state, the above-mentioned problems would be alleviated, but this would significantly reduce industrial productivity and increase market prices, making it practical only for limited applications. cannot be converted into Moreover, if we try to increase the processing effect through continuous processing as described above, the processing speed will have to be drastically reduced, but this will damage the surface of the processed object and cause problems such as poor appearance, poor adhesion, and increased blocking. is derived. In the conventional corona discharge treatment in the atmospheric atmosphere, the surface of the object to be treated is oxidized and oxidized deterioration products are generated on the surface, so even if the degree of treatment is increased, the adhesion cannot be improved beyond a certain level. . The inventors of the present invention have been concerned about this situation for some time, and have initially conducted research aimed at improving the corona discharge treatment technology itself, as usual. As a result, when nitrogen gas or a nitrogen-containing composite composition gas with an oxygen content of 20% by volume or less is sprayed onto the treated surface, the amount of oxygen gas on the surface of the molded product is extremely small, and the process is mainly affected by the direct influence of nitrogen gas. The present invention was completed after realizing that this effect can be obtained. The reason why the corona discharge surface becomes strongly affected mainly by the nitrogen gas when nitrogen gas or a nitrogen-containing composite composition gas with an oxygen content of 20% by volume or less is sprayed has not been fully elucidated. No, but you can think of it as follows. In other words, on the surface of the molded product transferred to the corona discharge section,
Although it varies depending on the surface properties and the transport speed, a considerable amount of air is present, and the composition is generally 21% by volume of oxygen and 78% by volume of nitrogen. On the other hand, the composition of the entrained air on the surface of the molded product cannot be easily changed by the above-mentioned ordinary means, such as adjusting the atmosphere in the chamber, but when the above-mentioned blowing means according to the present invention is adopted, the blowing gas is Since part or all of the entrained air layer is expelled and replaced, the composition of the entrained air layer changes. This change is caused by oxygen
This is because 21% by volume of air is replaced by a blown gas containing less than 20% by volume of oxygen, so the oxygen concentration decreases relatively and the effect of nitrogen gas, which is present as the main component, increases. As a result, effects that cannot be obtained with conventional corona discharge treatment in an atmospheric environment are exhibited. As mentioned in the above discussion, there is a point in spraying nitrogen gas or a nitrogen-containing gas with an oxygen content of 20% by volume or less, so gas components other than oxygen and nitrogen include argon gas, Regardless of whether it is helium gas, carbon dioxide gas, etc., the influence of nitrogen gas will be significant in any case. When we attempted to apply the improved corona discharge treatment technology to polyester molded products as described above, we found that there were no inconveniences in terms of blocking or slipping, and the adhesion was significantly improved. It was confirmed that the adhesiveness did not deteriorate even under high temperature and high humidity, and the present invention was completed. That is, the gist of the present invention resides in the following points. 25 to 25 to
A polyester obtained by reacting a dibasic acid residue consisting of 85 mol% terephthalic acid with an alkylene glycol residue and a dialkylene glycol residue.
(B) is continuously transferred to a corona discharge treatment device comprising at least one pair of electrodes facing each other to perform corona discharge treatment on the laminated surface. Spray nitrogen gas or a nitrogen-containing composite composition gas with an oxygen content of 20% by volume or less onto the corona discharge-treated surface of the object to determine the oxygen index and nitrogen index in a thin layer within 100 Å of the surface of the object before the corona discharge treatment.・The ratio of each amount of change after [Δ oxygen index / Δ nitrogen index] is 1.5 to -3.5, and the nitrogen index after corona discharge treatment in the thin layer part within 100 Å from the outermost surface of the object to be treated is 3 or more. A method for producing a laminated highly adhesive polyester molded product, characterized by: (However, the oxygen index and nitrogen index are determined by the following method: ESCA spectrometer ES-200
The integrated intensity obtained from the 1s orbital spectrum of carbon on the surface of the molded product using a mold (manufactured by Kokusai Denki Co., Ltd.),
Calculate the ratio of the integrated intensity obtained from the peak corresponding to the binding energy of organic nitrogen from the 1s orbital spectrum of oxygen, and calculate the carbon number 100 based on the integral ratio.
The number of oxygen per individual is determined and this value is defined as the oxygen index. Regarding the nitrogen index, the number of nitrogen per 100 carbon atoms is determined by the same method, and this is defined as the nitrogen index. ) One of the polyesters (A) of the laminated polyesters that are the object of the present invention is a dibasic acid (80 mol% or more of the dibasic acid is terephthalic acid)
It is a polyester composed of residues and alkylene glycol residues. This dibasic acid residue is mainly a terephthalic acid residue, but other dibasic acid residues of up to 20 mol% include isophthalic acid, phthalic acid, adipic acid, sebacic acid, succinic acid, oxalic acid, etc. groups, and also residues of oxyacids such as p-hydroxybenzoic acid can be used. In addition, glycol residues are ordinary alkylene glycol residues, and examples include residues such as ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, and hexamethylene glycol. ethylene glycol and tetramethylene glycol residues are used. A very practical polymer is polyethylene terephthalate or polytetramethylene terephthalate. On the other hand, the other polyester (B) is a polyester in which 25 to 85 mol% of the dibasic acid component is terephthalic acid and the remainder is dibasic acid. Adhesion can be improved by laminating the polyester (B), but if the content of terephthalic acid is less than 25 mol%, it becomes too soft and difficult to handle, and if it is more than 85 mol%, sufficient adhesion is not achieved. cannot be granted. As the remaining dibasic acid, the acid components exemplified in the description of the polyester (A), such as isophthalic acid and phthalic acid, are used to constitute the acid component. On the other hand, the glycol component is a mixture of alkylene glycol and dialkylene glycol, and examples of the alkylene glycol include those exemplified in the explanation of polyester (A), such as ethylene glycol, propylene glycol, trimethylene glycol, etc. It can be raised again. On the other hand, examples of the dialkylene glycol include diethylene glycol and dipropylene glycol. Note that the ratio of alkylene glycol to dialkylene glycol used is not particularly limited. However, in general, the mol% ratio of the former to the latter is (1 to
99):(99-1) preferably (95-30):(5-70)
It is recommended that it be used within the range. When layering polyester (B) on polyester (A), the thickness of the latter layer is not particularly limited, but when the layer thickness of polyester (A) itself is thin like a film or sheet, the characteristics of both layers In order to ensure that the polyester (A) thickness ratio is not less than 5% and the polyester (B) thickness ratio is
It is recommended that it not fall below 10%.
Molded products other than films and sheets include fibers,
Examples include molded products such as pipes, tapes, textiles, and nonwoven fabrics. When obtaining a laminate molded product using the above-mentioned polyester (A) and polyester (B), other polymers may be further blended as long as the properties of each are not adversely affected. For example, polyester (A) , (B) may be mixed with each other. In this case, if the mixing ratio exceeds 60%, the properties of the base polymer will be impaired. When blending polymers other than polyester, it is desirable that the content be 20% or less so as not to impair the properties of the polyester. In addition to polymer components, stabilizers, lubricants, anti-blocking agents, anti-fog agents, ultraviolet absorbers, flame retardants, clarifying agents, antioxidants, light stabilizers, antistatic agents, Additives such as dyes and pigments may be contained, and all additives that do not adversely affect the implementation of corona discharge are included as objects of the present invention, whether alone or in combination. In producing polyester molded articles using a polyester composition made of the above-mentioned materials, it is sufficient to follow a known method for each molded article. will not deviate from the scope. Therefore, the method for producing the molded article may be freely selected, but since a typical molded article to which the present invention is applied is a film, the method for producing the film will be explained as follows. That is, an unstretched film is first formed by forming the above-mentioned composition raw material into a film by a normal polyester film forming method, such as a T-die method or an inflation method. If this is stretched uniaxially or biaxially, a film with satisfactory strength can be obtained. The corona discharge treatment described below may be performed as one of the entire film forming process at the latter stage of the stretching process, and in some cases, the corona discharge treatment may be carried out while the once-rolled product is being re-rolled. In some cases, a method of applying In the present invention, the above-mentioned polyester molded product is treated, and the molded product is continuously transferred to a corona discharge treatment device having at least one pair of electrodes facing each other to obtain the laminated surface, that is, the surface of the laminated polyester (B). During this treatment, the surface to be treated is treated with nitrogen gas or a nitrogen-containing complex gas with an oxygen content of 20% by volume or less [specifically, air with an appropriate amount of oxygen removed]. , air with an appropriate amount of something other than oxygen added, or N ₂ alone or added with H ₂ , Ar, CO ₂ , Xe, Kr, Cl ₂ , NH ₃ ,
Spray a mixture of inert gas such as NOX or ionic gas (hereinafter abbreviated as inert gas for convenience). The spraying speed is not particularly limited, but is preferably 1% of the transfer speed of the polyester molded material.
The above shall apply. As will be detailed later, by strictly specifying the relationship between the oxygen index and nitrogen index before and after corona discharge treatment in the thin layer within 100 Å from the outermost surface of the surface to be treated, various materials (such as metal It is possible to obtain polyester molded articles having extremely excellent adhesion to various inks, especially cellulose inks and water-based inks; resins, such as vinylidene chloride homopolymers or copolymers, functional group-containing resins, etc.). The structure and effects of the present invention will be clarified below based on the drawings of the embodiments, but the structure and arrangement of the discharge side electrodes and the shape of the cover shown in the drawings are only representative examples. Since the above is merely an example of application to plastic film, it is within the technical scope of the present invention to change the design on the condition that it does not go against the spirit of these descriptions. FIG. 1 is a sectional view of the main parts showing the implementation concept of the present invention,
FIG. 2 is a perspective view showing a part of the discharge side electrode, in which 1 is a metal drum, 2 is an electrode cover, and 3 is a perspective view showing a part of the discharge side electrode.
Reference numeral indicates a discharge side electrode, 4 indicates a gas supply pipe, 5 indicates a gas outlet, and 6 indicates a running film. That is, the film 6 is introduced from the direction of arrow B into the metal drum 1 rotating in the direction of arrow A, and is further pulled out in the direction of arrow C. , applying a high voltage of several thousand to tens of thousands of V at a high frequency of several hundred KC/S between the metal drum 1 covered with polyester, epoxy resin, ceramic, chlorosulfonated polyethylene, EP rubber, silicone rubber, etc. For example, in the natural atmosphere, ozone and nitrogen oxide are generated under the influence of high-pressure corona generated by the film 6, and carbonyl groups and carboxyl groups are generated on the surface of the film 6, thereby polarizing the surface. On the other hand, in the conventional example, oxygen in the atmosphere generates oxidized deterioration products on the film surface that inhibit adhesion. However, in this example, the entire atmosphere of corona discharge is isolated from the atmosphere by the electrode cover 2, and
Since the discharge side electrode 3 is provided with a gas outlet 5 and configured to spray inert gas toward the surface of the film 6, the oxygen content in the accompanying air layer is substantially reduced, thereby reducing the The above-mentioned problems are eliminated, and the effect of nitrogen gas is greatly increased, so that the corona discharge effect on the surface layer of the film 6 is maximized. This situation will be explained in more detail as follows.
In other words, a slight accompanying air layer is formed on the surface of the film 6 that enters at a fairly high speed along the direction of arrow B, and even if the atmosphere in the corona discharge area is replaced by an inert gas, The surface of the film 6 itself remains in an atmospheric atmosphere. Therefore, in carrying out the present invention, as shown in FIG. The gas composition in the air layer 7 is changed to increase the proportion of nitrogen gas. In some cases, the surface is almost completely replaced with an inert gas. The flow velocity of the jet stream 8 necessary to burst and disperse the entrained air layer 7 to obtain the above effect cannot be determined uniformly because it varies depending on the shape and size of the object to be treated, the speed at which it is carried into the processing equipment, etc. As a result of experiments, it was found that it is most preferable to set the speed based on the speed of entry of the accompanying air layer 7 (in other words, the speed of transport of the material to be treated). In other words, by setting the inert gas jet velocity to 1% or more, preferably 10% or more, and even more preferably 40% or more of the conveyance speed of the material to be treated, the air layer 7 can be reduced to a level where there is no practical problem. It can be destroyed and dispersed. The angle at which the ejected gas is blown onto the film can be freely selected depending on the effective angle. The loading speed of the processed material is generally 1~
The speed is about 500m/min. By adopting such conditions, it becomes possible to destroy and disperse the accompanying air layer, and at the same time, it becomes possible to protect the vicinity of the corona discharge part with an inert gas atmosphere. The electrode cover 2 shown in the figure has a primary function of protecting the electrode 3 from mechanical shock rather than an atmosphere maintenance function, and a secondary function of suppressing the accompanying flow. Become. Therefore, when carrying out the present invention, the electrode cover 2 may be removed from time to time, but in order to suppress the consumption of inert gas, it is desirable to reconsider its function for maintaining the atmosphere. As shown in FIG. 4, if the lower end (film side) of the cover 2 is squeezed and at the same time inert gas is introduced into the cover 2 from the conduit 10, the gas will be converged along the inner surface of the slope 9 in the direction indicated by the arrow. direction, and a gas curtain effect is exerted at the inlet of the cover 2. That is, the intrusion of the entrained air layer is blocked on the inlet side, and the value of the electrode cover 2 is further improved. Furthermore, as shown in FIG. 5, if an extension cover 11 is provided especially at the inlet and brought close to the surface of the molded product, the inert gas leaking from inside the cover 2 will be absorbed by the extension cover 1.
Since the inside of the cover 1 is filled with air, the accompanying air layer that has entered through the cover 11 is also destroyed and dispersed little by little as it progresses inside the cover 11. Therefore, upon reaching the corona discharge atmosphere, the degree of substitution with the inert gas becomes extremely high, and the effects of the present invention are more significantly exhibited. Furthermore, when using the apparatus shown in Fig. 5, inert gas can be sprayed from the extension cover 11, and the spraying angle in this case can be freely selected, but in any case, the inert gas can be sprayed directly at the film introduction part. Since it is sprayed, the replacement efficiency for the accompanying air layer is extremely high. On the other hand, on the exit side of the film 6 (the right side in Fig. 4), the gas inside the cover 2 is discharged along with the traveling film 6, so the sealing performance or air infiltration barrier properties should be given the same consideration as on the entrance side. Although not necessary, it is meaningful to take the same consideration as on the inlet side in terms of reducing the amount of inert gas consumed as described above. In order to achieve the above-mentioned sealing function on the inlet and outlet sides of the cover 2 to the minimum extent possible, it is necessary to release it onto the film surface at a speed of at least 0.2% or more, preferably 10% or more relative to the film running speed. is desired. Regarding the ejection speed of the inert gas, only the lower limit side has been described for both the gas ejection port 5 and the inlet/outlet of the cover 2, but there is no practical need to set an upper limit on the ejection speed, and it is based on economic efficiency and the required quality of the final product. It should be decided appropriately based on the balance. By setting the processing conditions as described above, the processing effect of corona discharge is enhanced and the adhesion is greatly improved. We proceeded with further research, believing that it was necessary to quantitatively understand the surface characteristics before and after. As a result, (1) the ratio of changes in the oxygen index and nitrogen index before and after corona discharge treatment in a thin layer within 100 Å of the surface of the workpiece [Δoxygen index/Δnitrogen index], and (2) By strictly controlling the nitrogen index after corona discharge treatment in a thin layer within 100 Å of the surface,
It has been found that a high degree of adhesion can be guaranteed. In other words, the above-identified fact is that regarding (1) above, [Δoxygen index/Δnitrogen index] is 1.5 to -3.5.
In addition, regarding (2) above, by strictly controlling the treatment conditions and treatment atmosphere of corona discharge so that the nitrogen index after treatment is 3 or more, it is possible to apply etc.), the adhesion to various synthetic resins such as vinylidene chloride alone or copolymer resins, functional group-containing resins, etc. can be dramatically improved, and will be described in more detail below. First, a polyester molded product that satisfies the requirement of [nitrogen index ≧3] specified in the present invention can sometimes be obtained using conventional processing conditions, and can also be obtained by known corona discharge treatment in a nitrogen gas atmosphere. It is possible. However, as explained earlier, in order to ensure the above-mentioned high level of nitrogen index using the conventional method, which is intended for continuous processing at least, large-scale equipment is required, making it difficult to put it into practical use on an industrial scale. Ta. On the other hand, if the method of the present invention is adopted,
The nitrogen index can be easily increased to 3 or more with relatively simple equipment. On the other hand, there are also reports that the adhesion of plastic materials to various materials is simply determined by the nitrogen index determined by the ESCA method.
However, such reports capture only one aspect of the influence on adhesion. By the way, if you blend N components into the material, the nitrogen index will increase, but if you consider the fact that just mixing antistatic agents and lubricants, which are N-containing components, will not improve the adhesion, but will actually decrease it, the nitrogen index will increase. It is clear that an increase in index does not directly correlate with adhesion. Therefore, we also investigated other factors that affect adhesion, and found that the value calculated by [Δoxygen index/Δnitrogen index] almost accurately represents the effect of corona discharge treatment, that is, the effect of improving adhesiveness. It has been confirmed that products that have been treated so that this value is between 1.5 and -3.5 exhibit a high level of adhesion that meets the intended purpose. By the way, even if the nitrogen index within 100 Å of the surface layer after treatment is 3 or more, [Δoxygen index/Δnitrogen index]
If it exceeds 1.5, the corona discharge treatment effect is insufficient and a high level of adhesion cannot be obtained. In this sense, the treatment method of the present invention is adopted, and the nitrogen index is 3 or more, [Δoxygen index/Δnitrogen index]
It is essential to control the processing conditions so that the value is between 1.5 and -3.5. Note that it was practically extremely difficult to reduce this ratio to less than -3.5. By the way, regarding [Δ oxygen index / Δ nitrogen index], oxygen atoms constituting polyester, oxygen atoms in other polymers that may be blended, or specific oxygen atoms in various additives are released and removed by inert gas. As mentioned above, a negative value may be shown as a result due to the nitrogen atoms in the inert gas being replaced or removed by nitrogen atoms in the inert gas. In this negative range, generally in the range of -1.0 to 0, favorable results can be obtained in that the change in adhesive strength over time is extremely small and the blocking resistance is improved. The present invention is roughly constructed as described above, and the corona discharge treatment conditions are specified, and the treatment effect is constantly grasped from the amount of change in the oxygen index and nitrogen index of the surface layer before and after treatment. It has become possible to reliably obtain polyester molded products with excellent adhesiveness to various materials. In particular, the effect of improving adhesion is exhibited even after long-term exposure to high temperature and high humidity, and the surface layer with improved adhesion is not easily peeled off from the base layer, so for example, molded When it is a film, there is no possibility that the above-mentioned surface layer will be transferred to the back side during winding and storage, and there is no worry that the printing ink will peel off when it is actually applied as a film package. Furthermore, since the adhesion to other film base materials is improved, there is no possibility that the laminated films will peel off after long-term storage. Next, experiments will be carried out to clarify the effects of the present invention. The method for evaluating surface properties adopted in the experimental examples is as follows. (A) Haze Measured according to JIS-K-6714 (B) Lamination strength After printing with cellophane ink, coating with polyethyleneimine and drying at 290℃
Low-density polypropylene is laminated using melt extrusion method to a thickness of 30 μm. Immediately after storage or treatment under various conditions, the film and polypropylene layer are peeled off and the adhesive strength is measured. The peeling conditions are 180 degree peeling and speed.
The speed shall be 200mm/min. However, boiling water treated and retort treated products are laminated using isocyanate adhesive, and after lamination
Evaluation was performed after aging at 40°C for 2 days. Film production example (A) Polyethylene terephthalate (intrinsic viscosity 0.65
dl/g) (B) Both polyesters produced by adding ethylene glycol (70 mol%) and diethylene glycol (30 mol%) as alcohol components to terephthalic acid are formed into a film by coextrusion method, and then an unstretched film is formed. Stretched 3.2 times in the longitudinal direction at 90°C and 3.5 times in the transverse direction at 95°C, and further heat-set at 230°C for 3 seconds to a thickness of 12 μm [(A) component: 10 μm, (B) component:
2 μm] was obtained. The (B) component side of the film obtained above was subjected to corona discharge treatment under the conditions shown in Invention Examples 1 to 3 in Table 1. Moreover, Comparative Example 1 in Table 1 is a case where the corona discharge part is simply protected with a nitrogen gas atmosphere, and Comparative Example 1
Comparative Example 2 in the table is a case where the corona discharge section was placed in the air atmosphere. ESCA values are also listed in Table 1. When the haze and lamination strength of the corona discharge treated film were determined, the results shown in Table 2 were obtained.

【table】

【table】

[Table] As shown in Tables 1 and 2, the corona discharge treated film of the present invention has a [Δoxygen index/Δnitrogen index].
It is 1.5 or less (especially a negative value), which means that the laminate strength has been significantly improved.

[Brief explanation of drawings]

Figure 1 is a conceptual diagram showing the implementation status of the present invention, Figure 2
The figure is a sketch diagram illustrating the discharge-side electrode used in the present invention, FIG. 3 is an explanatory diagram showing the state of destruction of the accompanying air layer, and FIGS. 4 and 5 are explanatory diagrams showing an example of the electrode cover. 1...metal drum, 2...electrode cover, 3...
Discharge side electrode, 5... gas jet port, 6... film.

Claims (1)

[Scope of Claims] 1 All or part of the surface of polyester (A) composed of dibasic acid residues and alkylene glycol residues, of which 80 mol% or more is composed of terephthalic acid,
A laminated molded product made by laminating a polyester (B) obtained by reacting a dibasic acid residue composed of 25 to 85 mol% of terephthalic acid with an alkylene glycol residue and a dialkylene glycol residue, When the laminated surface of the molded product is continuously transferred to a corona discharge treatment device comprising at least one pair of electrodes facing each other and subjected to corona discharge treatment, nitrogen gas or oxygen content is applied to the corona discharge treated surface of the molded article. 20% capacity
The following nitrogen-containing composite composition gas was sprayed, and the ratio of the amount of change in the oxygen index and nitrogen index before and after corona discharge treatment in a thin layer within 100 Å of the surface of the treated object [Δoxygen index/Δnitrogen index] was calculated. 1.5 to -
3.5. A method for producing a laminated highly adhesive polyester molded product, which is characterized in that the thin layer within 100 Å from the outermost surface of the object to be treated has a nitrogen index of 3 or more after corona discharge treatment. (However, the oxygen index and nitrogen index are determined by the following method: ESCA spectrometer ES-200
The integrated intensity obtained from the 1s orbital spectrum of carbon on the surface of the molded product using a mold (manufactured by Kokusai Denki Co., Ltd.),
Calculate the ratio of the integrated intensity obtained from the peak corresponding to the binding energy of organic nitrogen from the 1s orbital spectrum of oxygen, and calculate the carbon number 100 based on the integral ratio.
The number of oxygen per individual is determined and this value is defined as the oxygen index. Regarding the nitrogen index, the number of nitrogen per 100 carbon atoms is determined by the same method, and this is defined as the nitrogen index. )