Sample preparation method

Abstract

To provide a sample preparation method which enables preparation of an ultrathin section (sample) of a rubber-metal wire composite body while preventing separation between rubber and a metal wire.SOLUTION: A sample preparation method for analyzing a bonding interface between rubber and a metal wire of a rubber-metal wire composite body is provided, the method involving adjusting the width of the rubber to 40% or less of a total width of a sample on a surface thereof.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for preparing a sample. [Background technology]

[0002] The adhesive state between the rubber and metal wire is extremely important in terms of tire durability, etc. While the elemental composition of the adhesive interface can sometimes be analyzed using EDS (energy dispersive X-ray spectroscopy) with an electron microscope, the state of chemical bonds must be analyzed using EELS (electron energy loss spectroscopy). EELS measurement requires ultrathin sectioning of the sample, but because the sample is a composite of rubber and metal wire, sample preparation is not easy (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-100068 [Patent Document 2] Patent Publication No. 2021-85750 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 discloses a method of cutting a rubber-metal wire composite with a wire saw, but it is difficult to prepare a sample of a size suitable for analysis with a transmission electron microscope using a wire saw.

[0005] Patent Document 2 discloses a method for producing a smooth surface or an ultrathin slice of a sample by irradiating the sample with an ion beam, but the use of an ion beam changes the surface condition of the sample.

[0006] The present invention aims to solve the above-mentioned problems and provide a method for producing a sample that can produce an ultrathin section (sample) of a rubber and metal wire composite in which peeling between the rubber and metal wire is prevented. [Means for solving the problem]

[0007] The present invention relates to a method for preparing a sample for analyzing the adhesive interface between rubber and a metal wire in a rubber and metal wire composite, characterized in that the ratio of the width of the rubber to the width of the entire sample on the surface of the sample is adjusted to 40% or less. [Effects of the Invention]

[0008] According to the present invention, there is provided a method for preparing a sample for analyzing the adhesive interface between rubber and metal wire in a rubber and metal wire composite, characterized in that the ratio of the width of the rubber to the overall width of the sample on the surface of the sample is adjusted to 40% or less.Therefore, there is provided a method for preparing a sample that can produce ultrathin sections (samples) in which peeling between the rubber and metal wire is prevented in a rubber and metal wire composite. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an example of a schematic diagram of rubber and metal wires occupying the surface of a sample. [Figure 2] FIG. 10 is a diagram showing the cutting direction of a composite of rubber and metal wire. [Figure 3] 1 shows a TEM image of an ultrathin section prepared in an example. [Figure 4] 1 is a TEM image of an ultrathin section prepared in a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0010] The above-mentioned sample preparation method is a method for preparing a sample for analyzing the adhesive interface between rubber and metal wire in a rubber-metal wire composite (hereinafter also referred to as a rubber-metal wire composite), characterized by adjusting the ratio of the width of the rubber to the overall width of the sample surface to 40% or less. Using this preparation method, it is possible to prepare an ultrathin section sample that sufficiently prevents delamination between the rubber and metal wire in the rubber-metal wire composite and maintains the state of the adhesive interface between the rubber and metal wire in the rubber-metal wire composite. Therefore, for example, by analyzing the prepared sample using electron energy loss spectroscopy (EELS), it is possible to accurately analyze the chemical bonding state of the adhesive interface.

[0011] In the above sample preparation method, the ratio of the width of the rubber to the overall width of the sample on the surface of the sample is adjusted to 40% or less. By adjusting the ratio within this range, peeling between the rubber and the metal wire can be prevented. In addition, a sufficient adhesive interface layer is present within the sample, allowing for suitable analysis of the chemical bonding state. The ratio of the width of the rubber is preferably 30% or less, more preferably 20% or less. There is no particular lower limit, but it is preferably 5% or more.

[0012] In this specification, the ratio of the width of the rubber to the width of the entire sample refers to the ratio of the width of the rubber to the width of the entire sample in a direction including the rubber and metal wire on the surface of a sample (ultrathin section) made of rubber and metal wire. For example, in the case of a sample prepared by cutting using an ultramicrotome or the like in a direction that allows simultaneous cutting of the rubber and metal wire, the ratio of the width of the rubber to the width of the entire sample is the ratio of the width of the rubber in a direction approximately perpendicular to the cutting direction. The ratio of the width of the rubber to the width of the entire sample is the average value of the ratio of the width of the rubber at each point on the surface of the sample in the cutting direction, etc.

[0013] In the above sample, the width of the rubber is preferably 1 μm or more, more preferably 2 μm or more, taking into consideration the thickness of the adhesive layer. There is no particular upper limit, but it is preferably 40 μm or less, more preferably 10 μm or less. The width of the rubber is also an average value of the ratio of the width of the rubber at each point, similar to the ratio of the width of the rubber to the width of the entire sample.

[0014] Figure 1 shows an example of a schematic diagram of the rubber and metal wire occupying the surface of a sample. Figure 1(a) shows the surface of a sample prepared by simultaneously cutting the rubber and metal wire from a rubber-metal wire composite, as shown, and is a schematic diagram of the sample surface where the width of the rubber is greater than the width of the metal wire. Figure 1(b) shows the surface of a sample prepared by similarly simultaneously cutting the rubber and metal wire from a rubber-metal wire composite, and is a schematic diagram of the sample surface where the ratio of the rubber width to the total width of the sample is 40% or less. By adjusting the width of the rubber to 40% or less of the total width of the sample, as in Figure 1(b), peeling between the rubber and the metal wire can be prevented.

[0015] The method for adjusting the ratio of the width of the rubber to the overall width of the sample to 40% or less can be any method that allows adjustment within this range. For example, ultrathin sections of the sample adjusted to the above ratio can be suitably prepared by cutting in a direction that allows simultaneous cutting of the rubber and metal wire. In particular, by simultaneously cutting the rubber and metal wire of a rubber-metal wire composite using an ultramicrotome, a sample can be prepared with a cut surface that prevents peeling between the rubber and metal wire.

[0016] Ultramicrotomes are used as a well-known method for preparing thin sections (ultrathin sections) for observation under electron microscopes or optical microscopes. Methods for preparing thin sections include embedding the sample completely in resin or the like, fixing it to the arm of the ultramicrotome, and cutting it with a diamond or glass knife by moving the arm up and down.

[0017] When cutting the rubber-metal wire composite using an ultramicrotome, the cutting conditions may be appropriately set in consideration of the state of separation between the rubber and the metal wire. For example, the cutting temperature is preferably −80° C. or higher, more preferably −70° C. or higher, even more preferably −60° C. or higher, and is preferably −20° C. or lower, more preferably −30° C. or lower, even more preferably −40° C. or lower. The cutting speed is preferably 0.10 mm / sec or less, more preferably 0.08 mm / sec or less, and even more preferably 0.05 mm / sec or less. The sample feed is preferably 20 nm or more, more preferably 40 nm or more, and even more preferably 50 nm or more, and is preferably 100 nm or less, more preferably 80 nm or less, and even more preferably 70 nm or less.

[0018] For ultrathin sections (thin sections) cut with an ultramicrotome, for example, a dry collection method can be used, in which the ultrathin sections are directly picked up with an eyelash probe and placed directly on a TEM grid. It is also possible to collect the ultrathin sections using an eyelash probe in a wet state. The tip of the eyelash probe is thin and moderately flexible, making it ideal for transferring ultrathin sections. Among these, it is desirable to employ the dry recovery method in order to prevent separation of the rubber from the metal wire.

[0019] In the above sample preparation method, from the viewpoint of preventing peeling between the rubber and the metal wire, it is desirable that the rubber-metal wire composite (sample) be cut to a cutting size of 200 μm or less in both length and width (200 μm or less × 200 μm or less × thin thickness). The length × width size is preferably 100 to 150 μm × 70 to 100 μm, more preferably 20 to 100 μm × 20 to 70 μm.

[0020] The thickness of the rubber-metal wire composite (sample) is preferably 10 nm or more, more preferably 20 nm or more, and even more preferably 30 nm or more from the viewpoint of ease of handling, and is preferably 500 nm or less, more preferably 200 nm or less, and even more preferably 100 nm or less from the viewpoint of electron permeability.

[0021] The rubber (rubber composition) constituting the rubber-metal wire composite is not particularly limited, and any rubber known in the field of tires, etc., can be used. For example, a rubber composition containing a rubber component and other materials can be used.

[0022] Examples of the rubber component include diene rubbers such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), and styrene isoprene butadiene rubber (SIBR), and non-diene rubbers such as butyl rubber (IIR) and halogenated butyl rubber (X-IIR). These may be used alone or in combination of two or more.

[0023] Examples of the other materials include fillers such as carbon black and silica, zinc oxide, stearic acid, antioxidants, wax, oil, vulcanizing agents such as sulfur, vulcanization accelerators, and other conventional compounding agents used in the rubber field.

[0024] The rubber composition can be produced, for example, by kneading the above-mentioned components using a rubber kneading device such as an open roll or a Banbury mixer, followed by vulcanization.

[0025] The metal wire (metal cord) is not particularly limited, and examples thereof include steel cord.

[0026] Examples of the steel cord include a steel cord made by twisting together a plurality of brass-plated steel wires, and a steel cord made of a single steel wire. Examples of the steel cord include belt cords and carcass cords for tires.

[0027] The rubber-metal wire composite may be a composite of a rubber composition and a metal wire, and specific examples thereof include a belt and a carcass for a tire.

[0028] The sample (ultrathin section) prepared by the above sample preparation method is used to analyze the adhesive interface between the rubber and the metal wire, and the analysis is carried out using, for example, electron energy loss spectroscopy (EELS). EELS is well known and is usually used in combination with a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM). TEM-EELS and STEM-EELS can be carried out by a conventional method using products from JEOL Ltd. or the like. The energy resolution of these is preferably 1 eV or less, more preferably 0.5 eV or less. There is no particular lower limit, but it is usually 0.1 eV or more.

[0029] The above sample preparation method adjusts the ratio of the rubber width to the overall width of the sample to 40% or less, preventing separation between the rubber and the metal wire. This allows analysis while maintaining the adhesive interface between the rubber and metal wire in the rubber-metal wire composite, enabling accurate analysis of the chemical bonding state at the adhesive interface. [Example]

[0030] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0031] Ultrathin sections were prepared according to the following procedure.

[0032] <Production of rubber-metal wire composite> A monofilament metal wire was embedded in a rubber composition (unvulcanized) having the following composition, and vulcanized at 160°C for 20 minutes to prepare a rubber-metal wire composite. (Rubber composition) Natural rubber: 100 parts by mass Carbon black: 60 parts by mass Sulfur: 6 parts by mass Vulcanization accelerator: 1 part by mass Zinc oxide: 10 parts by mass Cobalt stearate: 0.1 parts by mass

[0033] <Preparation of ultrathin sections> Using nippers or the like, the rubber-metal wire composite prepared above was cut and resin-embedded to facilitate handling. The cross-section of the rubber-metal wire composite and the side surface of the metal wire were shaved with sandpaper. Using a cryo-ultramicrotome, mirror polishing, trimming, and preparation of ultra-thin sections were performed using a diamond knife. Trimming was performed so that the size of the entire section was 70 μm or less in width and 100 μm or less in length. The set thickness of the ultra-thin section was 50 nm. (Equipment used) Cryo-ultramicrotome: Ultra-microtome FC7 manufactured by Leica (using a diamond knife manufactured by Diatome for both trimming and preparation of ultra-thin sections) (Cutting conditions for preparation of ultra-thin sections) Temperature: -60 to -40 °C Speed: 0.05 to 0.07 mm / sec Feed: 50 to 70 nm Recovery of ultra-thin sections: Placed directly on a TEM grid using a eyelash probe

[0034] (Examples) In the preparation of ultra-thin sections according to the above procedure, ultra-thin sections (width of rubber: 1 μm or more) were prepared on the surface of the sample with the ratio of the width of the rubber to the width of the entire sample adjusted to 40% or less. Figure 2 shows the cutting direction of the composite of rubber and metal wire.

[0035] (Comparative examples) In the preparation of ultra-thin sections according to the above procedure, ultra-thin sections (width of rubber: 1 μm or more) were prepared on the surface of the sample with the ratio of the width of the rubber to the width of the entire sample adjusted to more than 40%.

[0036] <STEM-EELS measurement> STEM-EELS: JEM-ARM200F ACCELARM manufactured by JEOL Ltd. Energy resolution: 0.3 eV Accelerating voltage: 200 kV Beam current: 500 pA Exposure time: 0.5 s Pixel size: 1.5nm Under the above conditions, the ultrathin sections prepared in the example and comparative example were observed using STEM-EELS, and the TEM images shown in FIG. 3 and FIG. 4 were obtained.

[0037] It can be seen that in the sample of the comparative example, the metal wire and the rubber are separated, whereas in the sample of the example, the metal wire and the rubber are not separated.

[0038] The present invention (1) is a method for preparing a sample for analyzing an adhesive interface between rubber and a metal wire in a composite of rubber and a metal wire, comprising: This is a sample preparation method characterized by adjusting the ratio of the width of the rubber to the entire width of the sample on the surface of the sample to 40% or less.

[0039] The present invention (2) is a method for preparing a sample according to the present invention (1), in which the composite is cut using an ultramicrotome to prepare ultrathin sections.

[0040] The present invention (3) is a method for preparing a sample according to the present invention (1) or (2), in which cutting is performed in a direction that allows cutting the rubber and the metal wire simultaneously.

[0041] The present invention (4) is a method for producing a sample in any combination with any of the present inventions (1) to (3), in which the composite is cut to a cutting size of 200 μm or less both vertically and horizontally.

Claims

1. A method for preparing a sample for analyzing an adhesive interface between rubber and a metal wire in a rubber and metal wire composite, comprising: A sample preparation method characterized in that the ratio of the width of the rubber to the width of the entire sample on the surface of the sample is adjusted to 40% or less.

2. 2. The method for preparing a sample according to claim 1, wherein the composite is cut using an ultramicrotome to prepare ultrathin sections.

3. 3. The method for preparing a sample according to claim 1, wherein cutting is performed in a direction that allows cutting of the rubber and the metal wire simultaneously.

4. 3. The method for preparing a sample according to claim 1, wherein the composite is cut to a cutting size of 200 μm or less in both the length and width directions.

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