JP2021081335A - Analytical method of rubber composition - Google Patents

Abstract

To provide an analytical method of a rubber composition, which analyzes a dispersion state of elements contained in the rubber composition.SOLUTION: In an analytical method of a rubber composition, a primary ion beam with a beam spot of 0.25 μm2 or less is applied to a vulcanized rubber with a thickness of 500 μm or less and an arithmetic average height of the surface of 1.5 μm or less, and a generated secondary ion is measured so that a dispersion state of elements contained in the rubber composition is analyzed.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for analyzing a rubber composition.

The physical properties of the rubber composition are affected by the dispersibility of additives such as reinforcing fillers and vulcanizing agents. Therefore, there is a demand for a method for analyzing the dispersed state of additives such as a reinforcing filler and a vulcanizing agent in a rubber composition.

Reference 1 describes a method for evaluating the cross-linking density of a cross-linked rubber by a small-angle X-ray scattering method or a small-angle neutron scattering method.

In Reference 2, a polymer composite material containing a vulcanization-based material is irradiated with high-intensity X-rays, and the amount of X-ray absorption in a minute region of the polymer composite material is measured while changing the X-ray energy. A vulcanization material analysis method capable of observing and analyzing the dispersed state and chemical state of the vulcanization material is described.

Japanese Patent No. 6376758 JP-A-2017-2017252 Japanese Unexamined Patent Publication No. 2018-141750

However, further improvement in measurement accuracy is required.

In view of the above points, an object of the present invention is to provide a method for analyzing a rubber composition, which analyzes a dispersed state of elements contained in the rubber composition.

In addition, although the cited document 3 describes the method of determining the time when a foreign substance is mixed by the imaging mass spectrometry method, the foreign substance mixed in the food and drink is analyzed, and the method relating to the analysis method of the rubber composition is not applicable. Absent.

The method for analyzing a rubber composition according to the present invention was generated by irradiating a vulcanized rubber having a thickness of 500 μm or less and an arithmetic mean height of a surface of 1.5 μm or less with a primary ion beam at a beam spot of 0.25 μm ^{2 or less.} By measuring the secondary ions, the dispersed state of the elements contained in the rubber composition shall be analyzed.

The method for analyzing the rubber composition can be measured after extracting volatile low molecules contained in the vulcanized rubber with a solvent.

According to the present invention, the dispersed state of the elements contained in the rubber composition can be analyzed.

The schematic diagram of the measuring apparatus used in the analysis method of one Embodiment of this invention.

Hereinafter, matters related to the practice of the present invention will be described in detail.

In the method for analyzing a rubber composition according to the present embodiment, a vulcanized rubber having a thickness of 500 μm or less and an arithmetic mean height of a surface of 1.5 μm or less is irradiated with a ^{primary ion beam at a beam spot of 0.25 μm 2 or less.} The dispersed state of the elements contained in the rubber composition is analyzed by measuring the secondary ions.

As such an analysis method, a secondary ion mass spectrometry (SIMS) is known. In particular, dynamic SIMS is preferable, and by irradiating the sample surface with a continuous beam of chemically active primary ions in a vacuum, atoms near the surface are ejected as secondary ions (so-called sputtering). The content of the target element can be determined by analyzing the secondary ions that have popped out.

As the ion species used for the primary ion beam, oxygen, cesium and the like can be used.

The irradiation amount of the primary ion beam is not particularly limited, but is preferably ^{30 ions / cm 2 or more.}

The beam spot of the primary ion beam is 0.25 μm ² or less, preferably 0.1 μm ² or less. When the beam spot is 0.25 μm ² or less, the spatial resolution is high and the measurement result can be obtained with higher accuracy than the conventional measurement method.

The target element is not particularly limited, and examples thereof include carbon, sulfur, oxygen, nitrogen, and silicon.

In addition, mass spectrometry can be performed by scanning within a predetermined region on the sample, and the detection intensity of the target element obtained as a result of mass spectrometry and its measurement position are displayed on the optical image of the sample. It is possible to image the dispersed state of the elements contained in the vulcanized rubber. Such imaging is performed using analysis software built into the mass spectrometer or analysis software such as MALDISION (registered trademark) (Netwell Co., Ltd.), BioMap (Novartis) MATLAB (MathWorks), ImageJ, etc. be able to.

When displaying the detection intensity of the target element obtained as a result of mass spectrometry and its measurement position on the optical image of the sample, the detection intensity of each element may be displayed on the optical image, but other elements (preferably). The detection intensity ratio (content ratio) of the target element to carbon) may be displayed on the optical image.

The configuration of the measuring device is not particularly limited, but for example, as shown in FIG. 1, a sample introduction chamber 1, an ion source 2, an analysis chamber 3, an energy analyzer 4, a mass spectrometer 5, and a detector 6 are used. And can have. After being introduced into the sample introduction chamber 1, the measurement sample is carried to the analysis chamber 3 by a sample moving mechanism (not shown). The analysis chamber 3 is in a vacuum state by a vacuum pump (not shown). Then, the primary ion beam is irradiated from the ion source 2 to the sample in the analysis chamber 3. The secondary ions generated from the sample surface by the irradiation of the primary ion beam are carried to the detector 6 via the energy analyzer 4 and the mass spectrometer 5.

As the mass spectrometer 5, for example, a quadrupole mass spectrometer, a sector magnetic field mass spectrometer, a time-of-flight mass spectrometer (TOF-MS), or the like can be used. The mass spectrometer 5 can deliver the target element to the detector 6 by the magnetic field based on the mass of the element and the ionic charge.

The measuring device is not particularly limited, but "NanoSIMS 50L" manufactured by CAMECA Co., Ltd. can be used.

The thickness of the vulcanized rubber sample used for the analysis is 500 μm or less, preferably 300 μm or less. When the thickness of the vulcanized rubber sample is 500 μm or less, the vibration of the sample can be suppressed even if the irradiation with the primary ion beam is performed, and the blurring of the imaging image can be suppressed.

In the present specification, the "thickness" of the vulcanized rubber sample is a value measured by a thickness gauge.

The arithmetic mean height of the surface of the vulcanized rubber sample used for the analysis is 1.5 μm or less, preferably 1.0 μm or less. Here, the arithmetic mean height of the surface is a parameter representing the surface roughness obtained by extending the arithmetic average height (Ra) of the line to the surface, and the difference in height of each point with respect to the average surface of the surface. Shows the average of absolute values. Since the arithmetic mean height of the surface is 1.5 μm or less, it is easy to obtain a clearer distribution image of the elements.

In the present specification, the "arithmetic mean height of the surface" can be measured using, for example, "Shape Analysis Laser Microscope VK-X150 / X160" manufactured by KEYENCE CORPORATION.

The arithmetic mean height of the surface of the vulcanized rubber sample can be adjusted by adjusting the surface roughness of the mold used when preparing the sample. Specifically, for example, two metal plates having a predetermined surface roughness are used as a mold to sandwich the rubber composition, and vulcanization is performed while pressurizing in the thickness direction so as to have a predetermined thickness. , Samples can be prepared.

It is desirable that the vulcanized rubber sample be extracted with a solvent to remove volatile small molecules before measurement. Since the inside of the analysis chamber 3 of the measuring device has a high vacuum, if volatile molecules are contained in the sample, the degree of vacuum cannot be maintained and measurement may not be possible.

The amount of solvent used for extraction is not particularly limited, but is preferably 0.1 mL or more with respect to 1 mg of the vulcanized rubber sample. Further, as an extraction method, it is preferable to immerse the vulcanized rubber sample in a solvent at a temperature of 40 ° C. or lower for 12 hours or more. As the drying performed after the extraction, it is preferable to dry the vulcanized rubber sample for 8 hours or more under the conditions of 40 ° C. or lower and 2000 Pa or less. Here, the method of immersing the vulcanized rubber sample in a solvent has been described, but the present invention is not limited to this, and extraction methods such as Soxhlet and high-speed solvent extraction can also be applied.

The solvent is not particularly limited, and examples thereof include toluene, acetone, chloroform, benzene, acetonitrile, tetrahydrofuran (THF), dioxane and the like.

The rubber composition used for the measurement is not particularly limited, and is a reinforcing filler such as carbon black or silica used in the ordinary rubber industry, process oil, zinc oxide, stearic acid, softener, plasticizer, wax. , Anti-aging agents, vulcanizing agents, vulcanization accelerators and other compounding chemicals can be appropriately compounded within the usual range, but it is desirable that they do not contain volatile low molecules.

Examples of the rubber component include natural rubber (NR), butadiene rubber (BR), styrene butadiene rubber (SBR), isoprene rubber (IR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, and styrene-. It may further contain isoprene-butadiene copolymer rubber, or modified rubber in which a part of the terminal or main chain thereof is modified.

The rubber composition according to the present embodiment can be produced by kneading according to a conventional method using a commonly used mixer such as a Banbury mixer, a kneader, or a roll. That is, in the first step (non-professional kneading step), other additives other than the vulcanizing agent and the vulcanization accelerator are added and mixed with the rubber component, and the obtained mixture is mixed with the final step (professional kneading step). A rubber composition can be prepared by adding a vulcanizing agent and a vulcanization accelerator and mixing them.

The vulcanization conditions are not particularly limited, but may be, for example, vulcanization at 140 to 180 ° C. for 5 to 120 minutes.

Hereinafter, examples of the present invention will be shown, but the present invention is not limited to these examples.

In the non-professional kneading step, 2 parts by mass of zinc oxide and 1 part by mass of stearic acid are added and mixed with 100 parts by mass of isoprene rubber (discharge temperature = 150 ° C.), and 0.5 parts by mass of sulfur is added in the professional kneading step. A rubber composition was prepared by adding and mixing 1 part by mass of a vulcanization accelerator (discharge temperature = 90 ° C.).

Details of each of the above components are as follows.
-Isoprene rubber: "IR2200" manufactured by JSR Corporation
・ Zinc Oxide: “Zinc Oxide No. 3” manufactured by Mitsui Mining & Smelting Co., Ltd.
-Stearic acid: "Lunac S-20" manufactured by Kao Corporation
・ Sulfur: "Powdered sulfur" manufactured by Tsurumi Chemical Industry Co., Ltd.
-Vulcanization accelerator: "Noxeller CZ-G" manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.

The obtained rubber composition was vulcanized at 160 ° C. using metal plates having different surface roughness as a mold while pressurizing in the thickness direction so as to have a predetermined thickness, and a 6 cm × 4 cm cm vulcanized rubber sample. It was created. As the vulcanization time, the 90% vulcanization time (t90) described in JIS K6300-2 was applied.

The thickness and surface roughness of each of the obtained vulcanized rubber samples were measured. The measurement method is as follows.
-Thickness: Measure with a thickness gauge.
-Surface roughness (arithmetic mean height Sa (μm) of the surface): Measured using "Shape Analysis Laser Microscope VK-X150 / X160" manufactured by KEYENCE CORPORATION and an objective lens 100 times.

Next, each of the obtained vulcanized rubber samples was immersed in toluene at 40 ° C. or lower for 12 hours or more, and then the sample was placed on a silicon wafer and dried at 40 ° C. or lower and 2000 Pa or lower for 8 hours or longer. Next, gold was deposited on the surface of the vulcanized rubber sample.

Using "NanoSIMS 50L" manufactured by CAMECA, Inc., measurement was performed under the following measurement conditions in an arbitrary measurement range (8 μm × 8 μm) of the vulcanized rubber sample.
[Measurement condition]
Primary ion species: Cesium ion (Cs ⁺ )
Beam spot: 0.1 μm ²
Number of integrations: 20 times 1 pixel beam irradiation time: 1 msec

Based on the measurement results, the suitability of the sample was evaluated based on the following indicators.
◯: Since a clear image was obtained, it is suitable as a sample.
Δ: Although there is a part of the image that is not clear, a clear image was obtained as a whole, so that it is suitable as a sample.
X: The image is not clear as a whole, so it is not suitable as a sample.

The results are as shown in Table 1, and in Examples 1 to 3 using a sample having a thickness of 500 μm or less and an arithmetic mean height of the surface of 1.5 μm or less, whether the obtained image is clear or not. Even if there is an unclear part, it is only a part, so it is evaluated as suitable as a rubber sample used for the measurement method of irradiating the ^{primary ion beam with a beam spot of 0.25 μm 2 or less and measuring the generated secondary ion.} did it.

In Comparative Example 1 using a sample whose surface arithmetic mean height was not 1.5 μm or less, the obtained image was not clear as a whole, so a primary ion beam was ^{irradiated at a beam spot of 0.25 μm 2} or less, and the second was generated. It was unsuitable as a rubber sample used in the measurement method for measuring the next ion.

The rubber composition analysis method of the present invention can be used for analysis of various rubber compositions such as tire rubber compositions.

1 ... Sample introduction room 2 ... Ion source 3 ... Analysis room 4 ... Energy analyzer 5 ... Mass spectrometer 6 ... Detector

Claims (2)

A rubber composition is obtained by irradiating a vulcanized rubber having a thickness of 500 μm or less and an arithmetic mean height of a surface of 1.5 μm or less with a primary ion beam at a beam spot of 0.25 μm ² or less and measuring the generated secondary ions. A method for analyzing a rubber composition, which analyzes the dispersed state of the elements contained therein. The method for analyzing a rubber composition according to claim 1, wherein the volatile low molecules contained in the vulcanized rubber are extracted with a solvent and then measured.

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