JP6294623B2 - Life prediction method for polymer materials - Google Patents

Description

The present invention relates to a method for predicting the lifetime of a polymer material by analyzing the deterioration state of the polymer material.

As a method for predicting the life of polymer materials, conventionally, air heating aging test of JIS K6257, ozone deterioration test of JIS K6259, etc. have been carried out, and changes in physical properties such as execution time, temperature and tensile stress at that time are Arrhenius plot and Weibull In many cases, the deterioration rate was obtained by plotting, and the lifetime was calculated therefrom (Non-Patent Document 1).

However, for example, a product used in a region having a high ozone concentration and a region having a high temperature has different physical property changes of the polymer material in the market. Since the change in physical properties differs depending on the environment used in this way, it has been difficult to accurately predict the lifetime. In addition, even if the life can be predicted from the change in physical properties, it is difficult to determine which part has deteriorated, and it is difficult to take measures to extend the life of the product.

In general, polymer materials are often made by blending multiple polymers. For example, in the case of a material containing two or more types of diene polymers, the deterioration state of each rubber component is examined to predict the lifetime. It is important to do this, but it was difficult with the conventional method.

"Deterioration of rubber and elastomers and life prediction", Mitsuo Akiba and Shigeyoshi Hayashi, Rubber Digest, February 2000

An object of the present invention is to solve the above-mentioned problems and to provide a life prediction method that makes it possible to predict the life with higher accuracy than conventional life prediction methods for polymer materials.

The present invention irradiates a polymer material with high-intensity X-rays, measures the amount of carbon-carbon double bonds by measuring the amount of X-ray absorption while changing the energy of the X-ray, The present invention relates to a life prediction method for predicting the life of a polymer material by analyzing the degradation state of the polymer material from the consumption of carbon-carbon double bonds.

As the polymer material, it is preferable to use a rubber material containing one or more types of diene rubber, or a composite material in which the rubber material and one or more types of resins are combined.

As the polymer material, a rubber material containing at least two types of diene polymers is used, the amount of carbon-carbon double bonds is measured, and the obtained X-ray absorption spectrum is separated for each diene polymer. It is preferable to predict the life by analyzing the deterioration state every time.

As the polymer material, it is preferable to use a polymer material that has been accelerated or market deteriorated.

The lifetime prediction method is based on a graph in which the carbon-carbon double bond amount of the polymer material is Y, the elapsed time from the start of deterioration is T, the vertical axis is log _e Y, and the horizontal axis is T. The data obtained from the measurement of the amount of heavy bonds is plotted to calculate A and B in (Equation 1), and the lifetime is predicted from the time τ (half-life) at which Y becomes half in (Equation 1). Is preferred.
(Formula 1) log _e Y = A × T + B

The above life prediction method is based on a graph in which the carbon-carbon double bond amount of the polymer material is Y, the elapsed time from the start of deterioration is T, the vertical axis is Y, and the horizontal axis is T. It is preferable that the data obtained from the quantity measurement is plotted to calculate A and B in (Expression 2), and the time when Y = 0 is satisfied according to (Expression 2) is used.
(Formula 2) Y = A × T + B

When the present invention is used, the lifetime of the polymer material can be predicted with higher accuracy than the conventional method. Therefore, it is possible to greatly reduce the evaluation of deterioration resistance, which has taken several years to confirm the effect so far, and the human and material reduction effect produced by the promotion of development is great.
When the present invention is used, the lifetime of each diene polymer in the polymer material can also be calculated. Since the deterioration rate varies depending on the type of polymer as shown in FIGS. 1 and 2, there is an advantage that more specific measures against deterioration can be taken by obtaining the lifetime of each polymer in the polymer material. Moreover, the lifetime of the mixture containing 2 or more types of polymers can also be calculated | required like FIG.

The graph which shows the deterioration degree of the butadiene rubber (BR) in use in the market with respect to elapsed years. The graph which shows the deterioration degree of the natural rubber (NR) in use in the market with respect to elapsed years. The graph which shows the deterioration degree of the mixture of the butadiene rubber (BR) / natural rubber (NR) in use in the market with respect to elapsed years. The graph which showed the NEXAFS measurement result in the carbon K shell absorption edge vicinity of isoprene rubber (IR) and butadiene rubber (BR). The graph which showed the NEXAFS measurement result in the carbon K shell absorption edge vicinity of the ozone deterioration goods of the rubber | gum which blended isoprene rubber (IR) and butadiene rubber (BR). The graph which showed the NEXAFS measurement result of the K-shell absorption edge of the carbon atom of the new article of butadiene rubber (BR), the sample which carried out ozone degradation for 7 hours, and the sample which carried out oxygen degradation for one week (before standardization). The graph which showed the NEXAFS measurement result of the K-shell absorption edge of the carbon atom of the new article of butadiene rubber (BR), the sample which carried out ozone degradation for 7 hours, and the sample which carried out oxygen degradation for one week (after normalization). The graph which showed the NEXAFS measurement result of K-shell absorption edge vicinity of the carbon atom of isoprene rubber (IR) and butadiene rubber (BR). The graph which showed the NEXAFS measurement result of the K-shell absorption edge of the carbon atom of the new article of the rubber which blended isoprene rubber (IR) and butadiene rubber (BR), and the deteriorated article which carried out ozone degradation for 1 hour (before normalization). The graph which showed the NEXAFS measurement result of the K-shell absorption edge of the carbon atom of the new article which blended isoprene rubber (IR) and the butadiene rubber (BR), and the deteriorated article which carried out ozone degradation for 1 hour (after normalization). The graph which separated the waveform of the NEXAFS measurement result of the K-shell absorption edge of the carbon atom after normalization about the new rubber blended with isoprene rubber (IR) and butadiene rubber (BR). The graph which isolate | separated the NEXAFS measurement result of the K-shell absorption edge of the carbon atom after normalization about the deterioration goods which implemented ozone deterioration of the rubber which blended isoprene rubber (IR) and butadiene rubber (BR) for 1 hour. The graph which shows the correlation diagram with the grade which attached | subjected the crack of the surface called the cracking degree of rubber | gum and Superficial Cracking (SFC) visually.

In the lifetime prediction method of the present invention, a high-intensity X-ray is irradiated on a polymer material, and the amount of carbon-carbon double bonds is measured by measuring the amount of X-ray absorption while changing the energy of the X-ray. This is a method for predicting the lifetime of a polymer material by analyzing the degradation state of the polymer from the consumption of carbon-carbon double bonds to the polymer material.

The lifetime prediction method of the present invention focuses on the use of high-intensity X-rays for examining the chemical state in more detail than conventional methods such as FT-IR, NMR, Raman spectroscopy, XPS, etc. By irradiating each high-molecular material with high-intensity X-rays while changing the energy, and measuring the X-ray absorption amount, the spectra obtained are analyzed to analyze the degradation state of the polymer material after degradation. In this way, the lifetime of the polymer material can be predicted with higher accuracy than before.
In general, the polymer material is often produced by blending a plurality of polymers. With this method, the measured carbon-carbon double bond amount can be separated for each blended polymer. Therefore, it is possible to predict the life by analyzing the deterioration state for each polymer.

Specifically, an X-ray absorption spectrum near the absorption edge of a particular element of interest is measured using high-intensity X-rays (NEXAFS (X-ray absorption fine structure near the absorption edge): Near Edge X-ray Absorption Fineline. (Structure) method can be adopted, and soft X-rays absorb light elements, so that the chemical state of the soft material can be analyzed in detail.

The NEXAFS method scans with X-ray energy, so the light source requires a continuous X-ray generator, and X-ray absorption spectra with high S / N ratio and S / B ratio are measured to analyze the detailed chemical state. There is a need to. Therefore, the X-ray emitted from the synchrotron has a brightness of at least 10 ¹⁰ (photons / s / mrad ² / mm ² /0.1% bw) and is a continuous X-ray source. Ideal for. Note that bw represents the band width of X-rays emitted from the synchrotron.

The luminance (photons / s / mrad ² / mm ² /0.1% bw) of the high-intensity X-ray is preferably 10 ¹⁰ or more, more preferably 10 ¹² or more. Although an upper limit is not specifically limited, It is preferable to use the X-ray intensity below the extent that there is no radiation damage.

The number of photons (photons / s) of the high-intensity X-ray is preferably 10 ⁷ or more, more preferably 10 ⁹ or more. Although an upper limit is not specifically limited, It is preferable to use the X-ray intensity below the extent that there is no radiation damage.

The energy range scanned using the high-intensity X-ray is preferably 4000 eV or less, more preferably 1500 eV or less, and still more preferably 1000 eV or less. When it exceeds 4000 eV, there is a possibility that the deterioration state analysis in the target polymer material cannot be performed. The lower limit is not particularly limited.

The measurement can be carried out by irradiating a sample placed in an ultra-high vacuum with soft X-rays to emit photoelectrons, and in order to compensate for this, electrons flow from the ground, and the sample current is measured. Therefore, although it is sensitive to the surface, the conditions of the sample that can be measured include the fact that it does not emit gas in a vacuum and that it is electrically conductive. There has been little research on rubber samples that are likely to be removed and that are insulators.

However, ESCA, which is the same surface sensitive technique, looks at the inner shell of the atom, so it is difficult to separate the degradation state of the polymer in detail, whereas NEXAFS looks at the outer shell affected by the atom and atom. As compared with ESCA, it is greatly affected by the element bonded to the element to be investigated, so that it is possible to separate individual molecular states, and it is possible to predict the lifetime using this, leading to the present invention. .

Specifically, it can be carried out by the method described below.
After the sample is attached to the sample holder, it is placed in a vacuum chamber for performing X-ray absorption measurement. Thereafter, the continuous X-rays radiated from the synchrotron are monochromatic with a spectroscope and irradiated on the sample. At this time, secondary electrons and photoelectrons escape from the sample surface into the vacuum, but electrons are replenished from the ground to compensate for the lost electrons. Here, the current flowing from the ground is X-ray absorption intensity I, the current of the gold mesh installed in the optical system of the beam line is incident X-ray intensity I _0, and the X-ray absorption μL is calculated from the following (Equation 3). Obtained (electron yield method). In this method, the Lanbert-Beer equation can be applied, but in the case of the electron yield method, it is considered that (Equation 3) is approximately established.

The following three methods are typically used for the NEXAFS measurement method. In the embodiment of the present invention, the electron yield method was used. However, the present invention is not limited to this, and various detection methods may be used, or simultaneous measurement may be performed in combination.

(Transmission method)
This is a method for detecting the X-ray intensity transmitted through a sample. For measurement of transmitted light intensity, a photodiode array detector or the like is used.

(Fluorescence method)
This is a method for detecting fluorescent X-rays generated when a sample is irradiated with X-rays. In the case of the transmission method, when X-ray absorption measurement of an element having a small content in a sample is performed, the background is increased due to the X-ray absorption of an element having a small content and a large content, so that the S / B ratio is poor. It becomes a spectrum. On the other hand, in the fluorescence method (especially when an energy dispersive detector or the like is used), it is possible to measure only the fluorescent X-rays from the target element, so that the influence of the element having a large content is small. Therefore, it is effective when measuring an X-ray absorption spectrum of an element having a small content. In addition, since fluorescent X-rays have strong penetrating power (low interaction with substances), it is possible to detect fluorescent X-rays generated inside the sample. Therefore, this method is the most suitable method for obtaining bulk information after the transmission method.

(Electron yield method)
This is a method for detecting a current flowing when a sample is irradiated with X-rays. Therefore, the sample needs to be a conductive material. Since the polymer material is an insulator, until now, the X-ray absorption measurement of the polymer material has mostly used a sample with a sample placed on a substrate by vapor deposition or spin coating, but in the present invention, A high S / B ratio and S / N ratio measurement can be realized by processing (cutting) the polymer material into a microtome of 100 μm or less, preferably 10 μm or less, more preferably 1 μm or less, and even more preferably 500 nm or less.

Another characteristic of the electron yield method is that it is surface sensitive (information on the surface of the sample about several nm). When the sample is irradiated with X-rays, electrons escape from the element, but electrons have a strong interaction with the substance, so that the mean free path in the substance is short.

The amount of carbon-carbon double bonds (%) can be analyzed by measuring and analyzing the X-ray absorption spectrum of the polymer material using the above-mentioned electron yield method. Hereinafter, the carbon-carbon double bond amount analysis method will be described.

As the carbon-carbon double bond amount analysis method, for example, an X-ray absorption spectrum obtained by scanning the necessary range of the K-shell absorption edge of carbon atoms in the high-intensity X-ray energy range of 260 to 400 eV. Based on the above, the normalization constants α and β are calculated by the following (Equation 4), and the X-ray absorption spectrum of the K-shell absorption edge of the carbon atom corrected using the normalization constants α and β is separated into waveforms. A method of obtaining the carbon-carbon double bond amount by the following (formula 5) using the obtained peak area attributed to the π ^* transition near 285 eV can be mentioned.
(Formula 4)
[Total area of X-ray absorption spectrum of measurement range in sample before deterioration] × α = 1
[Total area of X-ray absorption spectrum in the measurement range of the sample after deterioration] × β = 1
(Formula 5)
[[(Peak area of π ^* after degradation) × β] / [(Peak area of π ^* before degradation) × α]] × 100 = Carbon-carbon double bond amount (%)

When the high-intensity X-ray irradiation is performed, as shown in FIG. 4, the peak energy attributed to the π ^* transition varies depending on the type of polymer, and as shown in FIG. 5, it belongs to the π ^* transition near 285 eV. By separating the peaks in the waveform, the amount of carbon-carbon double bonds for each polymer can be determined for a polymer material in which a plurality of polymers are blended.
In this case, for example, based on the X-ray absorption spectrum obtained by scanning the necessary range of the K-shell absorption edge of the carbon atom in the range of 260 to 400 eV for the energy of the high-intensity X-ray, Normalization constants α and β are calculated, and the X-ray absorption spectrum of the K-shell absorption edge of the carbon atom corrected using the normalization constants α and β is separated into waveforms, and the obtained each polymer around 285 eV is obtained. The method of calculating | requiring the amount of carbon-carbon double bonds by the following (Formula 5 ') using the peak area attributed to (pi) ^* transition is mentioned.
(Formula 5 ')
[[(Π ^* peak area of each polymer after degradation) × β] / [(π ^* peak area of each polymer before degradation) × α]) × 100 = carbon-carbon double bond amount (%)

By the above method, the carbon-carbon double bond amount (%) after deterioration is obtained. Here, in the method for obtaining the carbon-carbon double bond amount, it is preferable that the energy of the high-intensity X-ray is set in a range of 260 to 350 eV. In addition, in the method of calculating | requiring the said carbon-carbon double bond amount, before performing operation of said (Formula 4), it evaluates from the slope before an absorption edge and draws a background.

In the method for determining the amount of carbon-carbon double bonds, the total area of the X-ray absorption spectrum in (Equation 4) is obtained by integrating the spectrum within the measurement range, and the energy range can be changed depending on the measurement conditions and the like. it can.

The polymer material used in the method for determining the carbon-carbon double bond amount may be a polymer material that has been actually used and deteriorated (market deterioration), or may be a polymer material that has been accelerated and deteriorated. . By appropriately selecting the conditions for accelerated deterioration, the state of market deterioration can be reproduced, so by finding the accelerated deterioration conditions that reproduce the market deterioration for a specified number of years, It is also possible to predict the lifetime of the polymer material.
The method of accelerated deterioration is not particularly limited, and ozone deterioration, oxygen deterioration, a combination thereof, and the like can be used.

Judgment as to whether the conditions for the accelerated deterioration are appropriate can be made as follows.
(1) The degree of market deterioration (reduction amount of carbon-carbon double bonds) and elapsed time are measured in advance using the same polymer material, and the relationship between the deterioration rate and elapsed time is calculated from the degree (formula 1 described later). Or, formula 2) is calculated.
(2) From the amount of carbon-carbon double bonds of the polymer material that has been accelerated and the formula 1 or formula 2 calculated in advance from the polymer material that has been market-degraded, the accelerated degradation is a deterioration of the years of market degradation. To determine whether the conditions for accelerated deterioration are appropriate.
For example, when a carbon-carbon double bond content of a test piece that has been accelerated and deteriorated using a mixture of butadiene rubber (BR) / natural rubber (NR) is 100%, the elapsed year of 0 to 1.4 years in FIG. Although it corresponds to the degree, it is in a range where the deterioration has not progressed, and is inappropriate as a condition for accelerated deterioration. Similarly, when the carbon-carbon double bond content of the accelerated and deteriorated test piece is 0%, it is in the range where the progress of the deterioration is completed, and it is inappropriate as the condition for the accelerated deterioration.
In this way, if an appropriate condition for reproducing the market deterioration for a given year is found for a certain polymer material, the same condition is adopted for other polymer materials, and the market deterioration for the given year is obtained. Can be reproduced. Thereby, about other polymeric materials, Formula 1 or Formula 2 can be created only by accelerated deterioration, and a lifetime can be estimated.

The method for obtaining the carbon-carbon double bond amount will be specifically described with reference to an example using a new BR, a sample subjected to ozone degradation for 7 hours, and a sample subjected to oxygen degradation for one week.
The NEXAFS measurement results of the K-shell absorption edge of carbon atoms of these samples are shown in FIG. As shown in FIG. 6, in the deteriorated sample, the peak of π ^* near 285 eV is smaller than that of a new product, but it is difficult to measure the absolute value in the NEXAFS method. The reason is that subtle changes such as the distance of the sample from the light source affect the magnitude of the X-ray absorption spectrum. For the above reasons, the NEXAFS measurement result of the K-shell absorption edge of carbon atoms cannot be simply compared between samples.

Therefore, in order to compare the measured X-ray absorption spectra between samples, normalization was performed as follows (the X-ray absorption spectra of each sample were corrected so that they could be directly compared). Since the X-ray absorption amount of the carbon shell does not change before and after deterioration, the above (Equation 4) is used to normalize the peak area of the K-shell absorption edge of carbon atoms to 1. That is, first, normalization constants α and β are calculated based on (Expression 4) for an X-ray absorption spectrum before normalization, and then corrected to a spectrum obtained by multiplying the X-ray absorption spectrum before normalization by α and β ( By normalization, the π ^* peaks between samples can be directly compared.

The spectrum of the K-shell absorption edge of the carbon atom after normalization obtained in this way is shown in FIG. The amount of carbon-carbon double bonds is determined from the normalized spectrum using the above (formula 5). The amount of carbon-carbon double bonds is the residual ratio of the peak of π ^* from before deterioration to after deterioration, and when the amount of carbon-carbon double bonds contained in the polymer material at the time of a new product is 100% The carbon-carbon double bond residual ratio (%) of the sample is shown.

Next, regarding the method of obtaining the carbon-carbon double bond amount for each polymer of a polymer material blended with two or more kinds of polymers, a new rubber blended with IR and BR, and a deteriorated product subjected to ozone degradation for 1 hour. This will be specifically described using an example using a sample.

NEXAFS measurement is performed in advance near the K-shell absorption edge of each carbon atom of IR and BR. FIG. 8 shows the measurement result, and both IR and BR have a π ^* transition peak (also referred to as a π ^* _{(C = C)} peak) attributed to C = C (carbon-carbon double bond) in the vicinity of 285 eV. However, the energy of the peak top of IR is around 285.4 eV, the energy of the peak top of BR is around 284.9 eV, and there is a difference in the energy of the peak top depending on the type of diene polymer (molecular difference). It is shown.

In FIG. 8, examples of IR and BR are shown. However, the present invention can be applied without particular limitation to the polymer type when the energy of each peak top of the blend polymer is different, for example, styrene. Since the energy of the peak top of butadiene rubber (SBR) is around 285.0 eV, and there is a difference in energy as well, the same method can be adopted for blend rubber containing SBR. Natural rubber (NR) has the same peak top energy as IR, and can be handled in the same manner as IR.

FIG. 9 shows the NEXAFS measurement result of the K-shell absorption edge of the carbon atoms of the new and deteriorated samples (ozone deterioration). As shown in FIG. 9, in the deteriorated sample, the peak of π ^* near 285 eV is smaller than that of the new product. However, as described above, since the NEXAFS method is difficult to measure the absolute value, the above equation (4) is used. Then, normalization is performed so that the peak area of the K-shell absorption edge of carbon atoms is 1, so that the π ^* peaks between samples can be directly compared. The spectrum of the K-shell absorption edge of the carbon atom after normalization obtained in this way is shown in FIG.

For each of the new and deteriorated samples, the π ^* _{(C = C)} peak in the spectrum of the K-shell absorption edge of the carbon atom after normalization in FIG. 10, the IR near the peak top energy of 285.4 eV, the peak top The waveform is separated into each peak attributed to BR near 284.9 eV. FIGS. 11-12 have shown the figure which isolate | separated the waveform into IR and BR about each of a new article and a deteriorated article. A Gauss function can be used as a waveform separation method for separating each peak attributed to each polymer component. Moreover, you may use the Lorenz function or the arbitrary functions which added and added the Gauss function and the Lorenz function with the weight as needed.

The peak area attributed to the IR of the new article in FIG. 11 and the deteriorated article in FIG. 12 is used to determine the amount of carbon-carbon double bonds in IR by using the equation (5 ′). Similarly for BR, the amount of carbon-carbon double bond of BR is determined by using the formula (5 ').

In addition, in the method for obtaining the carbon-carbon double bond amount, the carbon-carbon double bond amount is similarly obtained even if the peak intensity is used instead of the peak area in the above (Formula 5) or (Formula 5 ′). Can do.

In the above description, ozone-degraded products and oxygen-degraded products have been described. However, degraded products degraded by both ozone and oxygen can be analyzed by the same method, and the amount of carbon-carbon double bonds for each polymer component can be calculated. It is possible to ask.

When measuring the amount of carbon-carbon double bonds, it is difficult to accurately determine the amount of carbon-carbon double bonds if the bloom on the polymer surface is left as it is. It is preferred to remove the bloom before measuring the amount.
As a method for removing blooms, a Soxhlet extraction method according to JIS K6229 can be used.

The above-described measurement of the carbon-carbon double bond amount can be performed, for example, at the BL12 beam line of the Saga Prefectural Kyushu Synchrotron Light Research Center.

The lifetime prediction method of the present invention is based on the amount of carbon-carbon double bonds determined by the above formula 4, formula 5 and formula 5 ′, that is, the residual ratio of carbon-carbon double bonds in the polymer material. This is a method for predicting the lifetime of molecular materials.
Specifically, it is preferable to use one of the following methods. When the polymer material is a blend of a plurality of polymers, the life prediction for each polymer can be performed by using the following method for each polymer. Moreover, the lifetime of the whole blend can be predicted.
(Method 1)
Obtained from the measurement of carbon-carbon double bond amount on a graph where the carbon-carbon double bond amount of the polymer material is Y, the elapsed time from the start of deterioration is T, the vertical axis is log _e Y, and the horizontal axis is T. A method of plotting the obtained data, calculating A and B in (Expression 1), and predicting the life from the time τ (half-life) at which Y becomes half in (Expression 1).
(Formula 1) log _e Y = A × T + B
(Method 2)
The carbon-carbon double bond amount of the polymer material was Y, the elapsed time from the start of deterioration was T, the vertical axis was Y, and the horizontal axis was T. A method of plotting data, calculating A and B in (Expression 2), and setting the time when Y = 0 according to (Expression 2) as the lifetime.
(Formula 2) Y = A × T + B

1-3 is a figure which showed the deterioration degree of the market use goods with respect to elapsed years. According to conventional knowledge, it has been said that a change in physical properties has occurred from the beginning. However, when the carbon-carbon double bond on the surface of the market-use product was measured, it was found that there was a period when it did not deteriorate so much from a new one, but then it decreased rapidly. The reason why the carbon-carbon double bond does not decrease from the time of new article to about 1.8 years is considered to be that the anti-aging agent in the rubber is always deposited on the surface to prevent deterioration.
Therefore, in the above method 1 and method 2, graphs as described in method 1 and method 2 are prepared and the measurement data is plotted, and regarding the region where the carbon-carbon double bond decreases rapidly, the equation 1 or the equation 2 Draw an approximate line such as 2 to calculate A and B to predict the life.

FIG. 13 shows a correlation diagram between the degree of deterioration and a score obtained by visually observing a surface crack called Superficial Cracking (SFC). Thus, it is known that there is a high correlation with the correlation coefficient r = 0.84. Similarly, TGC is considered to have a correlation. Since the degree of deterioration can be measured by the amount of carbon-carbon double bond reduction, the amount of carbon-carbon double bonds (the amount of carbon-carbon double bonds relative to the amount of carbon-carbon double bonds of the polymer material at the time of a new article) The calculation of the elapsed time in the market using the formula (4), the formula (5), and the formula (5 ′) from the residual ratio) is extremely useful for obtaining the lifetime of the deterioration of the polymer material, particularly the surface crack. Is important to.

The polymer material applicable to the present invention is not particularly limited and may be a conventionally known material. For example, a rubber material containing one or more types of diene rubber, the rubber material and one or more types of resins may be used. A composite material that is composited can be suitably used. Examples of the diene rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), Examples thereof include polymers having a carbon-carbon double bond such as halogenated butyl rubber (X-IIR) and styrene isoprene butadiene rubber (SIBR).

The resin is not particularly limited, and examples thereof include those widely used in the rubber industry field, and examples thereof include petroleum resins such as C5 aliphatic petroleum resins and cyclopentadiene petroleum resins. The degradation analysis method of the present invention can be suitably applied to these materials.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

(Manufacture of rubber composition)
Process 1
The rubber component, anti-aging agent, stearic acid and zinc oxide described in the following materials are filled in a 1.7 L Banbury manufactured by Kobe Steel Co., Ltd. so that the filling rate is 58%, and reaches 140 ° C. at 80 rpm. Until kneaded.
Process 2
The kneaded product obtained in step 1 was blended with sulfur and a vulcanization accelerator in the amounts shown in Table 1, and kneaded at 80 ° C. for 5 minutes to obtain an unvulcanized rubber composition.
Process 3
The test tire was manufactured by shape | molding the unvulcanized rubber composition obtained at the process 2 in the shape of a side wall, bonding together with another tire member, shape | molding it to a tire, and vulcanizing at 160 degreeC for 20 minute (s).

(material)
Natural rubber (NR): TSR20
Butadiene rubber (BR): BR150B manufactured by Ube Industries, Ltd.
Carbon Black N351: Show Black N351 (N2SA: 71m2 / g) manufactured by Cabot Japan
Oil: Process X-140 manufactured by Japan Energy Co., Ltd.
Phenylenediamine-based anti-aging agent: NOCRACK 6C (N-1,3-dimethylbutyl-N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Wax: Ozoace 0355 manufactured by Nippon Seiwa Co., Ltd.
Zinc oxide: Silver candy R made by Toho Zinc Co., Ltd.
Stearic acid: Koji powder sulfur manufactured by NOF Corporation (containing 5% oil): 5% oil-treated powder sulfur manufactured by Tsurumi Chemical Co., Ltd. (soluble sulfur containing 5% by mass of oil)
Vulcanization accelerator: Noxeller CZ (N-cyclohexyl-2-benzothiazylsulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.

Examples and comparative examples (sample preparation)
Sample the sidewall piece of the test tire as a test sample, perform the ozone deterioration test of JIS K6259 or the air heat aging test of JIS K6257, sample about 2 mm x 1 mm x 0.5 mm, and sample oxygen other than the deterioration. The sample was stored in a vacuum desiccator after the sample was prepared so that no influence would appear.
Since the degree of deterioration cannot be accurately calculated if the bloom on the sample surface is left as it is, the sample was sampled, and then the bloom was removed using an extraction operation according to the Soxhlet extraction method according to JIS K6229.

(Measurement of carbon-carbon double bond amount and lifetime prediction)
The X-ray absorption spectrum near the absorption edge of a specific element is measured (NEXAFS (Near Edge X-ray Absorption Fine Structure) method). The sample was measured, and the amount of carbon-carbon double bonds in the polymer portion was determined from the peak area of the X-ray absorption spectrum at the K-shell absorption edge of the carbon atom. Then, the graph of the carbon-carbon double bond amount with respect to an elapsed year was created, the correlation formula of the part in which the carbon-carbon double bond amount reduces rapidly was calculated | required, and the deterioration rate A was computed. For comparison, measurement by the XPS method was also performed. Waveform separation of peaks for each polymer contained in the sample, and graphs of carbon-carbon double bond amounts with respect to the elapsed years for each polymer are shown in Figs. FIG. 3 shows a graph of the carbon-carbon double bond amount with respect to the elapsed years for the whole polymer.

NEXAFS measurement was performed on the sample subjected to the ozone deterioration test or the air heating aging test, and the carbon-carbon double bond amount was measured. From the measured amount of carbon-carbon double bonds and the deterioration rate A of Equation 2 obtained using the above-mentioned market-degraded samples, it was calculated how many years of accelerated deterioration each corresponded to market deterioration. The results are shown in Tables 2-5.
The amount of carbon-carbon double bonds in Tables 2 to 5 is the carbon-carbon double bond residual ratio (%) after each elapsed time when the carbon-carbon double bond amount of the polymer at the time of a new product is taken as 100%. ).

(Device used)
NEXAFS: SEX Prefectural Kyushu Synchrotron Light Research Center NEXAFS measurement system attached to BL12 beam line XPS: AXIS Ultra manufactured by Kratos

The measurement conditions of NEXAFS were as follows.
Luminance: 5 × 10 ¹² photons / s / mrad ² / mm ² /0.1% bw
Number of photons: 2 × 10 ⁹ photons / s
Scanned energy range: 260-400 eV

In the XPS method, the amount of carbon-carbon double bonds in the sample could not be measured, whereas in the example using the NEXAFS method, the amount of carbon-carbon double bonds in the sample could be measured. It was possible to predict the life by graphing the measurement results. Moreover, the carbon-carbon double bond amount measurement and lifetime prediction for each polymer contained in the sample were possible.

Claims (5)

High-intensity X-rays are irradiated onto the polymer material, and the amount of carbon-carbon double bonds is measured by measuring the amount of X-ray absorption while changing the energy of X-rays. A life prediction method for predicting the life of a polymer material by analyzing the degradation state of the polymer material from the consumption of heavy bonds,
Obtained from the measurement of carbon-carbon double bond amount on a graph where the carbon-carbon double bond amount of the polymer material is Y, the elapsed time from the start of deterioration is T, the vertical axis is log _e Y, and the horizontal axis is T. a the obtained data are plotted (equation 1) to calculate the B, life prediction how to predict the lifetime from (equation 1) by the time Y is halved tau (half-life).
(Formula 1) log _e Y = A × T + B High-intensity X-rays are irradiated onto the polymer material, and the amount of carbon-carbon double bonds is measured by measuring the amount of X-ray absorption while changing the energy of X-rays. A life prediction method for predicting the life of a polymer material by analyzing the degradation state of the polymer material from the consumption of heavy bonds,
The carbon-carbon double bond amount of the polymer material was Y, the elapsed time from the start of deterioration was T, the vertical axis was Y, and the horizontal axis was T. data are plotted in (equation 2) a, and calculates the B, life prediction method shall be the (formula 2) by Y = 0 and becomes time life.
(Formula 2) Y = A × T + B The life prediction method according to claim 1 or 2, wherein a rubber material containing one or more types of diene rubber or a composite material in which the rubber material and one or more types of resin are combined is used as the polymer material. As the polymer material, a rubber material containing at least two types of diene polymers is used, the amount of carbon-carbon double bonds is measured, and the obtained X-ray absorption spectrum is separated for each diene polymer. The life prediction method according to claim 1 or 2, wherein the life state is predicted by analyzing the deterioration state. The life prediction method according to any one of claims 1 to 4, wherein an accelerated deterioration or a market deteriorated polymer material is used as the polymer material.

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