JP5805043B2 - Degradation analysis method - Google Patents

Description

The present invention relates to a degradation analysis method for analyzing a degradation state of a polymer material.

In general, infrared spectroscopy (FT-IR), magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS) is used to evaluate changes in chemical state due to degradation of polymer materials containing one or more diene rubbers. ) Etc. are used. FT-IR and NMR can examine the detailed chemical state, but since the information obtained is bulk information, it is difficult to examine the detailed chemical state of deterioration that proceeds from the sample surface.

For this reason, it is desired to provide a method for investigating the deterioration state that progresses from the surface. For example, Patent Document 1 discloses that X-ray absorption is performed while irradiating a polymer material with high-intensity X-rays and changing X-ray energy. NEXAFS (Near Edge X-ray Absorption Fine Structure) that measures the X-ray absorption spectrum near the absorption edge of a specific element of interest using high-intensity X-rays ) Method using the method has been proposed.

In NEXAFS measurement, a method called an electron yield method for detecting a current flowing when a sample is irradiated with X-rays is often used. Therefore, it is usually necessary for the sample to be a conductive material. The polymer material is generally an insulator. For example, in the case of using rubber for tires, in particular, rubber with a sidewall, as a sample, the carbon black as a conductor is mixed in a large amount, so that the thickness is about 1 mm. Even with a relatively thick sample, conductivity is ensured and measurement is possible.

However, in recent years, there has been a tendency to reduce the fuel consumption of tires, so there is a tendency to reduce the amount of carbon black even in sidewall compounded rubber, and in tread compounded rubber, silica is compounded as a reinforcing agent to further reduce carbon black. Tend to. Thus, since it is difficult to secure the conductivity of a sample with a recent low fuel consumption compounded rubber, it is difficult to measure NEXAFS with a sample having a thickness of about 1 mm.

Moreover, in the said patent document 1, in order to implement | achieve the measurement with a high S / B ratio and S / N ratio, it is proposed to process (cut) a polymeric material into 100 micrometers or less by a microtome, Preferably it is 500 nm or less. Yes. However, since deterioration of the tire proceeds from the surface, it is necessary to cut the outermost surface and measure the surface side, but it is difficult to cut the outermost surface with a microtome. Furthermore, even if it can be cut, it is difficult to determine which of the sampled samples is on the surface side.

As described above, in the conventional method, it is difficult to perform the NEXAFS measurement on a sample having poor conductivity, such as a rubber compounded for tire with a small amount of carbon black, and to investigate in detail the deterioration state proceeding from the sample surface.

JP 2012-141278 A

An object of the present invention is to solve the above-mentioned problems and to provide a degradation analysis method capable of analyzing in detail the degradation state of the polymer material, particularly the degradation state of the surface state of the polymer material having low conductivity.

The present invention analyzes a polymer degradation state by irradiating a polymer material having a metal film with a thickness of 100 mm or less with high-intensity X-rays and measuring X-ray absorption while changing X-ray energy. The present invention relates to a deterioration analysis method.

The metal film is preferably a metal vapor deposition film.
The polymer material is preferably a tire rubber composition.
Here, the tire rubber composition preferably has a carbon black content of 50 parts by mass or less based on 100 parts by mass of the rubber component.

According to the present invention, a polymer material having a metal film with a thickness of 100 mm or less is irradiated with high-intensity X-rays, and the amount of X-ray absorption is measured while changing the energy of the X-rays. Therefore, the degradation state of the polymer material, particularly the degradation state of the surface state of the polymer material having low conductivity can be analyzed in detail. Therefore, regarding the deterioration of rubber compositions for tires such as rubber compounded with a small amount of carbon black and rubber compounded with silica, the degree of deterioration (%), contribution rate of oxygen deterioration and ozone deterioration, oxygen and ozone are bonded to the polymer material. Can be measured (degradation index).

The schematic diagram of the sample in which the metal film was formed. The graph which showed the sample electric current of the sample which vapor-deposited Au with the thickness of 8 to the tire tread compounding sample, and the sample which has not performed metal vapor deposition. The graph which showed the X-ray-absorption spectrum of the polybutadiene rubber from which thickness which vapor-deposited Au differs (not specified). NEXAFS measurement of K-shell absorption edge of carbon atoms of a new side wall compounded rubber, a sample subjected to ozone degradation for 48 hours, and a sample subjected to oxygen degradation for 1 week by Au deposition. Graph showing results (before standardization). NEXAFS measurement of K-shell absorption edge of carbon atoms of a new side wall compounded rubber, a sample subjected to ozone degradation for 48 hours, and a sample subjected to oxygen degradation for 1 week by Au deposition. Graph showing results (after normalization). NEXAFS in the vicinity of the K-shell absorption edge of oxygen atoms in a new side wall compounded rubber sample, a sample subjected to ozone degradation for 48 hours, and a sample subjected to oxygen degradation for one week, which was prepared by Au deposition. The graph which showed the measurement result. The graph which showed the NEXAFS measurement result of the K-shell absorption edge vicinity of the oxygen atom of the Au vapor deposition film | membrane formation sample produced by carrying out composite degradation (oxygen degradation and ozone degradation) of the side wall compound rubber, and performing Au vapor deposition. The graph which showed the NEXAFS measurement result of the Au vapor deposition film | membrane formation sample produced by performing Au vapor deposition to each of the sidewall compounded rubber which carried out ozone degradation for 24 hours and 48 hours (after normalization).

In the degradation analysis method of the present invention, a polymer material having a metal film with a thickness of 100 mm or less is irradiated with high-intensity X-rays, and the amount of X-ray absorption is measured while changing the energy of the X-rays. This is a method of analyzing the deterioration state. Known degradation factors for polymer materials such as rubber include degradation of polymer molecular chains due to ultraviolet rays, oxygen, ozone, heat, etc., and degradation of the cross-linked structure. Which factor can be used to improve degradation resistance? It is important to know how the polymer molecular chain and the cross-linked structure change depending on.

In this regard, the above degradation analysis method uses a high-intensity X for each of a new material and a deteriorated polymer material (sample) having a predetermined thickness by previously forming a metal film by a metal vapor deposition method or the like to improve conductivity. This is a method in which the deterioration state of the polymer material after deterioration can be analyzed by irradiating the line while changing the energy and comparing each spectrum obtained by measuring the amount of X-ray absorption.

Specifically, an X-ray absorption spectrum in the vicinity of the absorption edge of a particular element of interest is measured using high-intensity X-rays for a polymer material on which a metal film having a predetermined thickness is formed (NEXAFS (absorption edge) (Near Edge X-ray Absorption Fine Structure) method can be employed, and soft X-rays absorb light elements, so that the chemical state of the soft material can be analyzed in detail.

In other words, in the present invention, a metal film is formed on the surface of the sample and the surface is prevented from being charged, so that NEXAFS measurement is possible even for polymer materials with poor conductivity, such as compound rubber with a small amount of carbon black, silica compound rubber, etc. At the same time, by setting the film thickness of the metal film to 100 mm or less and minimizing the influence of the metal film, it is possible to carry out deterioration analysis of the polymer material itself.

The polymer material (sample) provided for the present invention is one in which a metal film having a predetermined film thickness is formed on the sample surface. Thereby, the electroconductivity of a polymeric material (sample) can be improved in the range in which degradation analysis is possible. The method for forming the metal film is not particularly limited as long as it can be formed on the sample surface, and a metal vapor deposition method or the like can be suitably used.

There are various methods such as resistance heating type, electron beam type, high frequency induction type, laser type, etc. for metal vapor deposition. A thin film is formed on the surface of a sample placed at a distant position. Any method is possible, but considering the possibility that the vapor deposition material is ionized and damages the sample, it is desirable to adopt a resistance heating type vacuum vapor deposition method in which heating is performed by passing an electric current through the vapor deposition material.

The thickness of the metal film formed on the polymer material surface is 100 mm or less, preferably 50 mm or less, more preferably 10 mm or less. When it exceeds 100%, there is a tendency to be greatly affected by the deposited metal. In particular, since the NEXAFS method is a surface sensitive measurement, if the thickness of the deposited metal is thick, there is a possibility that accurate chemical information of the sample itself cannot be obtained. As long as conductivity is ensured, the lower limit is not particularly limited, but is preferably at least 1 mm, more preferably at least 3 mm, and even more preferably at least 5 mm.

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. 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 these upper limits are 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 degradation state analysis in the target polymer composite 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.

Specifically, it can be carried out by the method described below.
A sample on which a metal film having a predetermined thickness is formed is attached to a sample holder, and then placed in a vacuum chamber for performing X-ray absorption measurement. In addition, FIG. 1 shows the schematic diagram of the sample in which the metal film was formed. 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 defined as the X-ray absorption intensity I, the current of the gold mesh installed in the beam line optical system is defined as the incident X-ray intensity I _0, and the X-ray absorption amount μL is obtained from the following (formula). (Electron yield method). In this method, the Lanbert-Beer equation can be applied. However, in the case of the electron yield method, it is considered that the following equation 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. This is effective when measuring an X-ray absorption spectrum of an element having a small content. In addition, fluorescent X-rays have a strong transmission power and can detect fluorescent X-rays generated inside the sample, which is an optimal method for obtaining bulk information.

(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. In this invention, electroconductivity is securable by forming a metal membrane | film | coat. A high S / B ratio and S / N ratio measurement is 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. It is also possible. Moreover, in order to ensure conduction | electrical_connection with a board | substrate and a sample, you may use the tape which has electroconductivity and can be used in a vacuum, such as a carbon tape and a silver tape.

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. Furthermore, since the energy of X-rays used in the NEXAFS method is relatively low, the kinetic energy of escaped electrons is small. For this reason, electrons that can jump out of the sample surface become a part of the extreme surface layer of the sample, and this detection method is a surface-sensitive method.

Here, it will be specifically described with reference to FIGS. 2 to 3 that X-ray absorption can be measured by forming a metal film on the sample surface, and that the film thickness of the metal film affects the deterioration analysis of the sample. explain.

FIG. 2 shows sample currents of a sample obtained by vapor-depositing Au with a thickness of 8 mm on a tire tread compound sample and a sample not subjected to metal vapor deposition. The sample without metal vapor deposition has a negative value in the broken line and the X-ray absorption could not be measured, whereas the sample with Au vapor deposition had a positive sample current and X-ray absorption. It has been shown that the measurement of absorption was possible. Thus, by forming a metal film having a predetermined thickness on the sample, X-ray absorption can be measured even for a polymer material having poor conductivity.

The metal to be deposited is preferably a metal that does not have X-ray absorption in the energy range to be measured. For example, when measuring in the vicinity of the carbon K absorption edge (270 eV to 320 eV), gold (Au) having no absorption in this energy region can be suitably used.

FIG. 3 shows an X-ray absorption spectrum of a sample in which an Au vapor deposition film having a different film thickness is formed on polybutadiene rubber. Since a cast film is used and even a sample not subjected to metal vapor deposition can be measured, the thickness of vapor deposition is changed, and the change in the X-ray absorption spectrum is examined. It shows that the larger the change, the greater the influence of the deposited metal, and the more likely it is that accurate degradation analysis cannot be performed.

The X-ray absorption spectrum of FIG. 3 is affected by the vapor deposition film from the spectrum of the sample on which the Au vapor deposition film is not formed, and the shape of the spectrum gradually changes as the film thickness of the vapor deposition film increases. It shows that. That is, in the sample in which the Au vapor-deposited film having a thickness of 8 mm is formed, the spectrum and the shape of the sample in which the vapor-deposited film is not formed are hardly changed. It has been shown that there is a risk of being slightly affected by the deposited film. Although the accuracy is slightly inferior even at a thickness of 20 mm, deterioration analysis is possible.

Furthermore, by using the above-mentioned electron yield method, the degree of deterioration (%) is measured by analyzing the X-ray absorption spectrum of a polymer material (hereinafter also referred to as a metal film-forming sample) on which a metal film having a thickness of 100 mm or less is formed. ), Contribution rate (%) of oxygen deterioration and ozone deterioration, and the combined amount of oxygen and ozone (deterioration index). Each will be described below.

As the degradation analysis method, for example, the following (formula) is 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. The normalization constants α and β are calculated according to 1), 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 π around 285 eV is obtained. ^* Using the peak area attributed to the transition, a method of obtaining the degree of deterioration by the following (Formula 2) is mentioned.
(Formula 1)
[Total area of X-ray absorption spectrum in measurement range in metal film-formed sample before deterioration] × α = 1
[Total area of X-ray absorption spectrum in the measurement range in the metal film-formed sample after deterioration] × β = 1
(Formula 2)
[1-[(Peak area of π ^* after degradation) × β] / [(Peak area of π ^* before degradation) × α]] × 100 = Degree of degradation (%)
Thereby, the deterioration degree (%) of the polymer after deterioration is obtained, and the deterioration rate can be analyzed. Here, in the method for determining the degree of deterioration, it is preferable that the energy of the high-intensity X-ray is in a range of 260 to 350 eV. In the method for obtaining the degree of deterioration, the background is drawn by evaluating from the slope before the absorption end before performing the operation of (Equation 1).

In the method for determining the degree of deterioration, the total area of the X-ray absorption spectrum in (Equation 1) is obtained by integrating the spectrum in the measurement range, and the energy range can be changed depending on the measurement conditions and the like.

The method for determining the degree of deterioration will be specifically described using an example using a new sidewall-blended rubber, a sample subjected to ozone deterioration for 48 hours, and a sample subjected to oxygen deterioration for one week.
FIG. 4 shows the NEXAFS measurement results of the K-shell absorption edge of the carbon atom of the Au deposited film-formed sample prepared by performing Au deposition on each of the new product, ozone-degraded sample, and oxygen-degraded sample. As shown in FIG. 4, 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 1) 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 1) 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 degree of deterioration is determined from the normalized spectrum using the above (Equation 2). The degree of deterioration is a reduction rate of the peak of π ^* from before deterioration to after deterioration, and indicates the deterioration rate (%) of the sample.

Note that, in the method for obtaining the degree of deterioration, the degree of deterioration can be obtained in the same manner even if the peak intensity is used in place of the peak area in (Equation 2).

Further, as the degradation analysis method, the X-ray absorption spectrum at the K-shell absorption edge of oxygen atoms obtained by scanning the high-intensity X-ray energy in the range of 500 to 600 eV is separated into waveforms, and the peak top energy is obtained. The low energy side peak in the range of 532 to 532.7 eV is oxygen degradation, the high energy side peak in the range of 532.7 to 534 eV is ozone degradation, and the contribution ratio of oxygen degradation and ozone degradation by the following (Equation 3) There is also a method for calculating.
(Formula 3)
[Peak area of oxidation degradation] / [(Peak area of ozone degradation) + (Peak area of oxidation degradation)] × 100 = Oxygen degradation contribution rate (%)
[Ozone degradation peak area] / [(ozone degradation peak area) + (oxidation degradation peak area)] × 100 = ozone degradation contribution rate (%)
Thereby, the contribution rate (%) of oxygen deterioration and ozone deterioration in the polymer material after deterioration can be obtained, and the contribution rate of each deterioration factor can be analyzed. In the method of calculating the contribution rate, the background is drawn by evaluating from the slope before the absorption edge before performing the operation of (Equation 3).

The method for calculating the contribution rate will be specifically described with reference to an example using a new sidewall compounded rubber, a sample subjected to ozone deterioration for 48 hours, and a sample subjected to oxygen deterioration for one week.
First, FIG. 6 shows the result of NEXAFS measurement in the vicinity of the K-shell absorption edge of oxygen atoms of an Au deposited film-formed sample prepared by performing Au deposition on each of an ozone-degraded sample and an oxygen-degraded sample. Thus, the ozone-degraded sample has a peak at 532.7 to 534 eV, the oxygen-degraded sample has a peak at 532 to 532.7 eV, and the peak on the high energy side of the two peaks is ozone-degraded and low. The energy peak is attributed to oxygen degradation.

Further, FIG. 7 shows NEXAFS measurement results of the Au vapor deposition film-formed sample prepared by performing composite vapor deposition (oxygen degradation and ozone degradation) and performing Au vapor deposition. As shown in FIG. 7, a peak having two shoulders at 532 to 534 eV was detected. This is considered that the low energy side peak (532-532.7 eV) resulting from oxygen deterioration and the high energy side peak (532.7-534 eV) resulting from ozone deterioration overlap. Therefore, after peak separation, the contribution ratio of oxygen deterioration and ozone deterioration was determined using the above (Formula 3). Thereby, it is possible to analyze the oxygen deterioration rate and the ozone deterioration rate of both deterioration factors for the sample in which both oxygen and ozone deterioration have progressed.

In the method of calculating the contribution rate, the deterioration contribution rate of oxygen deterioration and ozone deterioration can be obtained in the same manner even when the peak intensity is used instead of the peak area in (Equation 3).

Further, as the degradation analysis method, a normalization constant γ is obtained by the following (Equation 4) based on the X-ray absorption spectrum of the K-shell absorption edge of the carbon atom after degradation, and the following equation is obtained using the normalization constant γ. There is also a method of obtaining the amount of oxygen and ozone bound to the polymer material by correcting the total peak area of the K-shell absorption edge of oxygen atoms according to (5).
(Formula 4)
[Total area of X-ray absorption spectrum of K-shell absorption edge of carbon atom] × γ = 1
(Formula 5)
[Peak area of K-shell absorption edge of oxygen atom] × γ = Amount of oxygen and ozone combined (index)
Thereby, the amount of oxygen / ozone bonded to the polymer material due to deterioration is measured and can be used as a deterioration index.

In the method for determining the combined amount, the total peak area 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.

The method for obtaining the combined amount will be specifically described with reference to an example using a sample of a sidewall compounded rubber that has been ozone-degraded for 24 hours and 48 hours.
FIG. 8 shows the result of NEXAFS measurement of Au vapor deposition film-formed samples prepared by performing Au vapor deposition on each of these. This is based on the X-ray absorption spectrum of the K-shell absorption edge of the carbon atom, and the normalization constant γ is obtained using the above (Equation 4) and normalized as described above. The peak area at the K-shell absorption edge of the normalized oxygen atom is considered to be the combined amount of oxygen and ozone. As shown in FIG. 8, since the area deteriorated for 48 hours is larger than the sample deteriorated for 24 hours, this value can be used as an index of deterioration. The larger the deterioration index number, the greater the amount of oxygen bound to the polymer material due to deterioration. Thereby, the deterioration rate by oxygen and ozone couple | bonding with a polymeric material can be measured by the increase rate of the peak area of the K-shell absorption edge of an oxygen atom.

The above-described method of the present invention can be performed, for example, at the BL12 beam line of the Saga Kyushu Synchrotron Light Research Center.

Further, the polymer material applicable to the present invention is not particularly limited and includes conventionally known materials. For example, a rubber material containing one or more types of diene rubber, the rubber material and one or more types of resins. 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 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 present invention can be applied to any material having high conductivity or low material without particular limitation. For example, the polymer material includes a rubber component and a rubber for a tire including a filler such as silica and carbon black. It can be suitably applied to the composition. Examples of the rubber component include the diene rubber. Carbon black and silica are not particularly limited, and those commonly used in the tire field can be used.

Since the present invention is a method applicable to any conductive polymer material, the amount of carbon black blended in the rubber composition for tires is not particularly limited. In particular, from the viewpoint of ensuring conductivity by a metal film, a rubber composition with a carbon black content of 50 parts by mass or less with respect to 100 parts by mass of the rubber component can be applied. Applicable.

In addition, since the present invention can be applied to a low-conductivity silica-containing rubber, the amount of silica in the tire rubber composition is not particularly limited, but is preferably 5 to 90 parts by mass, and more preferably 10 -60 mass parts.

In the tire rubber composition, in addition to the above components, compounding agents generally used in the production of rubber compositions, for example, reinforcing fillers such as clay, silane coupling agents, zinc oxide, stearic acid, various Antiaging agents, oils, waxes, vulcanizing agents, vulcanization accelerators, and the like can be appropriately blended.

The rubber composition for tires is manufactured by a general method. That is, it can be produced by a method of kneading the above components with a Banbury mixer, a kneader, an open roll or the like and then vulcanizing. The rubber composition can be used for each member of a tire, and in particular, can be suitably used for a tread, a sidewall, and the like.

Moreover, this invention is applicable also to the pneumatic tire produced by the normal method using the said rubber composition for tires. A pneumatic tire is a tire molding machine that extrudes a rubber composition for a tire containing the above components in accordance with the shape of each tire member such as a sidewall and a tread at an unvulcanized stage, together with other tire members. It can be manufactured by forming an unvulcanized tire by molding in the usual manner and heating and pressurizing the unvulcanized tire in a vulcanizer.

The method of the present invention can be applied to, for example, a tire rubber composition and a sample in which a metal film having a predetermined thickness is formed on a sample (polymer material) prepared by sampling from each member of a tire using the rubber composition. Here, the thickness of the sample is not particularly limited, but is preferably 10 nm to 1 mm, and more preferably 50 nm to 100 μm.

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

[Manufacture of test tires]
(Process 1)
According to the formulation shown in Tables 1-2, materials other than sulfur and a vulcanization accelerator 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)
Sulfur and a vulcanization accelerator are added to the kneaded product obtained in Step 1, and kneaded for 3 minutes under the condition of 80 ° C. using an open roll, and each unvulcanized rubber composition for sidewall and tread is used. The thing (sidewall 1-2, tread 1-2) was obtained.
(Process 3)
The unvulcanized rubber composition of the sidewall 1 obtained in step 2 is formed into a sidewall shape, the unvulcanized rubber composition of the tread 1 is formed into a tread shape, and bonded to another tire member to form a tire, A test tire 1 was manufactured by vulcanization at 160 ° C. for 20 minutes. A test tire 2 was produced in the same manner except that the sidewall 2 was used instead of the sidewall 1 and the tread 2 was used instead of the tread 1.

The materials used for the sidewalls 1 and 2 and the treads 1 and 2 are as follows.
(material)
Natural rubber (NR): TSR20
Butadiene rubber (BR): BR150B manufactured by Ube Industries, Ltd.
Styrene butadiene rubber (SBR): Nipol 1502 manufactured by Nippon Zeon Co., Ltd.
Carbon Black N351: Show Black N351 (N ₂ SA: 71 m ² / g) manufactured by Cabot Japan
Silica: Ultrasil VN3 from Degussa
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
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: Agate powder sulfur manufactured by Nippon Oil & Fats Co., Ltd. (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]
After sampling the test tire 1 that has been deteriorated due to market running, the sidewall 1 and the tread 1, and the deteriorated test tire 2 from the sidewall 2 and the tread 2, about 2 mm × 1 mm × 0.5 mm, respectively, According to 4, an Au vapor deposition film was formed on the sample surface by a resistance heating type vacuum vapor deposition method to prepare a test sample. After that, the sample was stored in a vacuum desiccator so that the influence of oxygen other than deterioration did not appear.

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

Using NEXAFS, the degree of deterioration (%) was measured for each sample by performing the following deterioration rate analysis. Moreover, oxygen and ozone deterioration contribution rate (%) were measured by implementation of the following deterioration contribution rate analysis. Further, the degradation index (index) was measured by carrying out the following degradation index measurement.
The measurement conditions for 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

(Deterioration rate analysis)
High energy X-ray energy was scanned in the range of 260 to 400 eV to obtain an X-ray absorption spectrum of the K-shell absorption edge of the carbon atom. Normalization constants α and β were calculated from (Equation 1) based on the necessary range of 260 to 350 eV in this spectrum, and the spectrum was normalized (corrected) using these constants. The normalized spectrum was separated into waveforms, and the degree of deterioration (%) was obtained from (Equation 2) based on the peak area attributed to the π ^* transition near 285 eV.

(Deterioration contribution analysis)
High energy X-ray energy was scanned in the range of 500 to 600 eV to obtain an X-ray absorption spectrum of the K-shell absorption edge of oxygen atoms. This spectrum is waveform-separated, and the low energy peak at the peak top of 532 to 532.7 eV is defined as oxygen degradation, and the high energy peak at 532.7 to 534 eV is defined as ozone degradation. The contribution rate of deterioration was calculated.

(Deterioration index measurement)
Based on the X-ray absorption spectrum at the K-shell absorption edge of the deteriorated carbon atom obtained by the deterioration rate analysis, the normalization constant γ was determined from (Equation 4). Using this constant, the total peak area at the K-shell absorption edge of oxygen atoms was corrected (normalized), and the amount of oxygen and ozone bound to the polymer material (degradation index) was determined from (Equation 5).

The results obtained from the above analysis are shown in Tables 3-4.

In the sample in which the Au vapor deposition film was not formed and the sample in which the Au vapor deposition film having a thickness of 500 mm was formed, none of ozone and oxygen degradation contribution rate, degradation degree, and degradation index (index) of the degraded sample could be analyzed. On the other hand, in the example using the sample in which the Au vapor deposition film having a thickness of 8 mm was formed, any analysis was possible by using NEXAFS. Therefore, the effectiveness of the evaluation method of the present invention was proved.

Claims (4)

A degradation analysis method for analyzing the degradation state of a polymer by irradiating a polymer material having a metal film with a thickness of 100 mm or less with high-intensity X-rays and measuring the X-ray absorption while changing the energy of the X-rays Because
The measurement of the X-ray absorption amount is a deterioration analysis method performed by NEXAFS measurement using an electron yield method . The deterioration analysis method according to claim 1, wherein the metal film is a metal vapor deposition film. The deterioration analysis method according to claim 1 or 2, wherein the polymer material is a tire rubber composition. The deterioration analysis method according to claim 3, wherein the tire rubber composition has a carbon black content of 50 parts by mass or less based on 100 parts by mass of the rubber component.

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