JP2017129407A - Phase structure observation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase structure observation method for a polymer enabling an identification of a polymer component composing each phase structure without requiring a creation of a standard sample even if a sample has a similar area ratio obtained in a state without a swelling treatment.SOLUTION: A phase structure observation method is for a blend polymer containing two or more polymer components. The phase structure observation method includes: a swelling step of swelling the blend polymer with a solvent; and an observation step of using an atomic force microscope and observing the blend polymer swelled with the solvent.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for observing a phase structure of a polymer.

  In recent material developments, the importance of blended polymers is increasing to meet various needs. Many blend polymers have a phase structure consisting of phases of several nm to several hundred μm in size. Since the size and arrangement of each phase are affected by the blending polymer blend and thermal history, and additives such as reinforcing agents and colorants contained in the polymer, complex and diverse phase structures are formed. And since the phase structure affects the physical properties of the blend polymer, observing the phase structure accurately is an indispensable technique for material development by the blend polymer.

  Conventionally, a transmission electron microscope (TEM), a scanning electron microscope (SEM), an atomic force microscope (AFM), or the like is used as a method for observing the phase structure of a blend polymer as an image.

  For observation with TEM, it is necessary to cut a sample with a microtome or the like to prepare an ultrathin section. Samples that are not hard enough to cut at room temperature, such as rubber compositions, need to be frozen at a temperature below the glass transition point with liquid nitrogen, etc., and the pretreatment for observation is very complicated. There is a problem that. In addition, in both the TEM and SEM observation methods, when the difference in contrast between the observed images is small and the phase structure is difficult to observe, an etching process or a dyeing process for attaching heavy metals such as osmium and ruthenium is necessary. There is a problem that only a different state can be observed.

  AFM has the same resolution as TEM and does not require the creation of ultrathin sections. In the phase structure observation by AFM, the difference in hardness of the polymer components forming each phase is utilized. However, in the case of a blend polymer having a small difference in hardness, the contrast difference in the observed image is small, and the phase structure is difficult to observe.

  Therefore, the present inventor increases the difference in hardness by deteriorating before observing the phase structure by AFM, and more clearly observes the phase structure of the blend polymer without performing expensive equipment or complicated processing. The method to do is proposed (patent document 1).

JP 2014-190883 A

  In conventional phase observation of blend polymers by TEM, SEM, and AFM, especially in the phase structure observation of incompatible blend polymers that form sea-island structures, when the blend ratio is close, each phase (for example, sea phase and islands) It is difficult to determine the polymer component forming the phase. Therefore, there is a problem that it takes a lot of man-hours to observe the object, for example, it is necessary to prepare a standard sample with a different composition ratio in order to identify the polymer component. Therefore, the present invention can identify a polymer component that forms each phase structure without requiring preparation of a standard sample even if the sample has a comparable area ratio in a state where it is not swollen. An object is to provide a method for observing a phase structure of a polymer.

  The present invention is a method for observing a phase structure of a blend polymer containing two or more polymer components, a swelling step of swelling the blend polymer with a solvent, and an observation of observing the blend polymer after the solvent swelling with an atomic force microscope The present invention relates to a phase structure observation method including steps.

  Furthermore, it is preferable to include a comparison step of comparing the phase structure observation result obtained in the observation step with the phase structure observation result of the blend polymer that has not been swollen by an atomic force microscope.

  It is preferable that the observation in the observation step is observation by a tapping mode or a force volume mode of an atomic force microscope.

  The blend polymer is preferably a vulcanized rubber composition.

  According to the method for observing a phase structure of a blend polymer of the present invention, comprising a swelling step of swelling a blend polymer containing two or more polymer components, and an observation step of observing the blend polymer after the swelling treatment with an atomic force microscope , By immersing the sample in a solvent such as toluene to swell and swell each blended polymer at a different swelling rate, even if the area ratio obtained in the state that is not swell treatment is the same level, After swelling, the area ratio in the image can be changed. As a result, the composition of the polymer component can be clearly discriminated from the result obtained by measurement with an atomic force microscope.

It is a phase-structure observation result after a swelling process. It is a phase-structure observation result before a swelling process.

  The phase structure observation method of the present invention includes a swelling step in which a blend polymer containing two or more polymer components is swollen with a solvent, and an observation step in which the blend polymer after the solvent swelling is observed with an atomic force microscope. Is the method.

Blend polymer The blend polymer is a blend polymer containing two or more kinds of polymer components, and a blend containing two or more kinds of incompatible polymer components from the viewpoint that the effects of the present invention are effectively exhibited. A polymer is preferable, and a blend polymer containing two or more polymer components that form a sea-island structure is more preferable.

  The polymer component is not particularly limited. For example, polyethylene, polypropylene, polybutadiene, polyisoprene, ethylene-propylene copolymer, polystyrene, styrene-butadiene copolymer, acrylonitrile-styrene copolymer, polyvinyl chloride, poly Various polymers such as acrylic acid, polymethacrylic acid, polyamide, polyurethane, polyethylene terephthalate, polybutylene terephthalate, polytetrafluoroethylene, polycarbonate, polysulfone, polyethersulfone, various resins such as epoxy resin, urethane resin, unsaturated polyester resin, Modified natural rubber such as natural rubber (NR) and epoxidized natural rubber (ENR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR) Butyl rubber (IIR), brominated product of isobutylene-p-methylstyrene copolymer, acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), ethylene-propylene rubber (EPM), ethylene-propylene-diene copolymer rubber (EPDM) ), Styrene-isoprene rubber, styrene-isoprene-butadiene copolymer rubber (SIBR), isoprene-butadiene rubber, chlorosulfonated polyethylene (CSM), acrylic rubber (ACM, ANM), epichlorohydrin rubber (CO, ECO, GECO), Examples thereof include rubber components such as polysulfide rubber (T), silicone rubber (Q), fluorine rubber (FKM), and urethane rubber (U).

  As described above, a blend polymer containing two or more incompatible polymer components is preferable, and a blend polymer containing two or more polymer components forming a sea-island structure is more preferable. Here, incompatible means that different types of polymers are not uniformly mixed at the molecular level. In a blend polymer including a plurality of polymers that are incompatible with each other, a phase structure is formed by phase separation of each polymer, and in some cases, a sea-island structure is formed. Specific combinations of polymer components that can form a sea-island structure include combinations of NR and BR, NR and SBR, NR and EPDM, SBR and NBR.

  The blend polymer is preferably a vulcanized rubber composition. The vulcanized rubber composition contains the rubber component as a polymer component and can be obtained by crosslinking reaction. In the case of an unvulcanized rubber composition, some polymer components may be dissolved in a swelling solvent.

  The blend polymer is a compounding agent generally used in the production of rubber compositions, for example, fillers such as carbon black and silica, zinc oxide, stearic acid, processing aids, anti-aging agents, oils, waxes, Sulfur, a vulcanization accelerator, etc. can be mix | blended suitably.

  The carbon black is not particularly limited, and examples thereof include carbon black such as furnace black, acetylene black, thermal black, channel black, and graphite. The silica is not particularly limited, and examples thereof include dry method silica and wet method silica.

  0-50 mass parts is preferable and, as for the total content with respect to 100 mass parts of blend polymers of carbon black and silica, 0-20 mass parts is more preferable. When the amount exceeds 50 parts by mass, the observation visual field is covered with carbon black or silica, and the polymer morphology may not be observed.

Swelling step The swelling step is a step of swelling by immersing a blend polymer containing two or more polymer components in a solvent. Since the swelling rate with respect to each solvent differs for each polymer component, a difference can be caused in the phase structure after swelling by subjecting the blend polymer containing two or more polymer components to swelling treatment. Thereby, even if it is a sample which shows the phase structure of the comparable area ratio before a swelling process, the composition of a polymer component can be discriminate | determined clearly.

  A method for swelling the blend polymer is not particularly limited, and a conventional swelling method can be adopted. For example, a method of immersing the blend polymer in a sufficient amount of solvent for a predetermined time or more can be mentioned.

  The amount of the solvent in which the blend polymer is immersed is preferably at least 100 times the volume of the blend polymer because it can sufficiently swell, and prevents the solvent from volatilizing and decreasing during immersion to affect the degree of swelling. 1000 times or more is more preferable. Further, the upper limit of the amount of the solvent is not particularly limited, but is preferably 5000 times or less, more preferably 3000 times or less, of the blend polymer volume from the viewpoint of workability.

  The time for immersing the blend polymer is preferably 24 hours or more, and more preferably 48 hours or more, from the reason that the blend polymer can be sufficiently swollen. In addition, from the viewpoint of workability and the reason that the degree of swelling does not change after a certain time or longer, 120 hours or shorter is preferable, and 72 hours or shorter is more preferable.

  Since the solvent temperature during the immersion changes the degree of swelling of the solvent with respect to the polymer depending on the temperature, the solvent temperature during the immersion is preferably kept constant, and the temperature is preferably 20 ° C. or higher, more preferably 25 ° C. or higher. Moreover, 40 degreeC or less is preferable and 35 degrees C or less is more preferable from the reason that the solvent volatilizes and decreases near the boiling point of the solvent.

Observation Step The observation step is a step of observing the blend polymer after the swelling treatment with an atomic force microscope (AFM), and the phase structure of the blend polymer after the swelling treatment can be observed. In TEM and SEM in which the sample needs to be placed under vacuum conditions during observation, the swelling solvent is volatilized and the swollen state cannot be maintained, so it is difficult to apply the observation method of the present invention.

  The shape and size of the sample piece used for observation with an atomic force microscope are not particularly limited as long as it can be placed on the AFM sample stage. For forming the blend polymer, a knife, scissors, razor, cryomicrotome or the like can be used as appropriate. Since a smooth surface suitable for observation by AFM is formed, it is preferable to use a cryomicrotome.

  The AFM includes a cantilever with a probe attached to the tip. The probe scans the surface of the sample piece, and the movement of the probe is detected by the cantilever. The AFM image is obtained by imaging the movement of the probe detected by the cantilever. In AFM, the three-dimensional shape of the surface of the sample piece, the mechanical properties such as the hardness of the surface of the sample piece, and the frictional force can be measured. Examples of the AFM that can be used in the observation method of the present invention include MultiMode 8 manufactured by Bruker AXS, E-sweep manufactured by Hitachi High-Tech Science, and the like. AFM measurement conditions are appropriately selected according to the type of specimen and the surface condition. A probe made of tungsten, iridium, silicon nitride or the like can be used.

  The observation by the AFM in the present invention is observed in an appropriate measurement mode provided in the AFM. An appropriate measurement mode is appropriately selected according to the type of polymer component contained in the blend polymer and the surface state of the sample piece subjected to AFM observation. A typical measurement mode of AFM includes a contact mode, a tapping mode, and a non-contact mode. A force modulation mode in which the hardness of a minute region on the surface of the sample piece is measured, or a force volume mode in which the elastic modulus and Young's modulus distribution on the surface of the sample piece can be measured may be selected. A preferable measurement mode is a tapping mode suitable for measurement of a soft sample piece and a force volume mode capable of imaging a difference in mechanical characteristics of a micro area of the sample piece with a short contact time between the probe and the sample piece.

Comparison process When the difference in the swelling rate of the polymer components in the blend polymer is known, the phase structure observation result after the swelling treatment obtained in the observation step is compared with the phase structure observation result before the swelling treatment. Even in the case of samples having the same area ratio before the swelling treatment, the polymer components forming each phase can be clearly discriminated. For example, in the observation of the phase structure before the swelling treatment of the blend polymer containing 50% by mass of the polymer component X and the polymer component Y that are incompatible with each other, even when the area ratio of each phase is the same, By swelling the blend polymer, in the observation results after the swelling treatment, the area ratio of the polymer layer formed by the polymer component having the higher swelling ratio is further increased. Can be determined. If the swelling rate is not known, a sample using only each polymer component is similarly swelled to calculate the swelling rate, and the difference in swelling rate of each polymer component can be determined.

  As a phase structure observation result before the swelling treatment of the blend polymer, a phase structure observation result by a conventional TEM, SEM, AFM, or the like can be used. Especially, the blend polymer after swelling treatment is easy because the correspondence between each polymer phase (each domain) in the observation result before swelling treatment and each polymer phase (each domain) in the observation result after swelling treatment is easy to understand. Similar to the observation method, it is preferable to use the observation result by AFM.

  The blend polymer before the swelling treatment may be a blend polymer after the deterioration treatment described in JP 2014-190883 A. The deterioration treatment is treatment for forming a plurality of phases having different hardnesses in the blend polymer, and specific treatment methods include heat treatment and chemical treatment. The heat treatment includes treatment with an existing apparatus such as an oven, a thermostatic bath, and a dryer, and the chemical treatment includes treatment with an acid or alkali.

  According to the method for observing the phase structure of the blend polymer of the present invention, the composition of the polymer component can be clearly discriminated even in the case of a sample having the same area ratio obtained without being subjected to the swelling treatment.

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

The various chemicals used in the examples are summarized below.
NR: TSR20
BR: BR150B manufactured by Ube Industries, Ltd.
Oil: Process X-140 manufactured by Japan Energy Co., Ltd.
Zinc oxide: Silver candy R made by Toho Zinc Co., Ltd.
Stearic acid: Agate wax manufactured by NOF Corporation: Ozoace 0355 manufactured by Nippon Seiwa Co., Ltd.
Anti-aging agent: NOCRACK 6C (N-1,3-dimethylbutyl-N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Sulfur: 5% oil-treated powder sulfur manufactured by Tsurumi Chemical Co., Ltd. (soluble sulfur containing 5% oil content)
Vulcanization accelerator: Noxeller NS (N-tert-butyl-2-benzothiazylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Preparation of Vulcanized Rubber Composition According to the formulation shown in Table 1, rubber components, anti-aging agents, wax, stearic acid, zinc oxide and oil were manufactured by Kobe Steel Co., Ltd. so that the filling rate would be 58%. .7L Banbury was filled and kneaded at 80 rpm until reaching 140 ° C. An unvulcanized rubber composition was obtained by blending the obtained kneaded material with the amounts of sulfur and vulcanization accelerator shown in Table 1 and further kneading. And the obtained unvulcanized rubber composition was shape | molded and each vulcanized rubber composition was obtained by vulcanizing for 20 minutes at 160 degreeC.

Swelling treatment A 20 mm ³ test piece cut out from each vulcanized rubber composition was immersed in 50 ml of toluene and allowed to stand for 48 hours at a solvent temperature of 25 ° C. to swell. Table 1 shows the swelling ratio (volume after swelling treatment / volume before swelling treatment) (%) of Production Examples 2 and 3.

Observation of the phase structure From the vulcanized rubber composition of Production Example 1 before the swelling treatment and the vulcanized rubber composition of Production Example 1 after the swelling treatment, a small piece was cut out using a razor and cut with a cryomicrotome to obtain a smooth surface. It was created. The phase structure of the created smooth surface was observed by AFM (MultiMode 8, manufactured by Bruker AXS, tapping mode, cantilever: 40 N / m (spring constant), frequency: 5 Hz, measurement range: 1 μm × 1 μm). In order to prevent the solvent from volatilizing the sample after the swelling treatment, an O-ring that is slightly larger than the sample is placed on the disk on which the sample is fixed, and the swollen solvent is dropped therein to form a sealed system. Observation was performed using a cell dedicated for measurement in liquid. The observation results after the swelling treatment are shown in FIG. 1, and the observation results before the swelling treatment are shown in FIG.

  Since the swelling rate of toluene in Production Example 2 (NR simple) and Production Example 3 (BR simple) shown in Table 1 was 550% and 420%, respectively, which was higher in Production Example 2, the swelling treatment was performed. A domain in which the area ratio is increased in the phase image of the obtained NR / BR blend can be considered as NR.

  The phase image obtained by measuring the production example 1 (NR / BR blend) not subjected to the swelling treatment in the tapping mode (FIG. 2) clearly distinguishes the rubber components constituting the sea layer and the island layer. Since the area ratios of the yellow domain (A in FIG. 2) and the brown domain (B in FIG. 2) are almost equal, it is difficult to determine the composition. However, it can be seen from the result of FIG. 1 that the swelling process is performed that the size of the yellow domain (A in FIG. 1) is increased. Furthermore, from the results of Table 1, it can be seen that the yellow domain in which the area ratio increases is NR, so that the yellow domain A in FIG. 2 is NR and the brown domain B is BR.

  As described above, according to the phase structure observation method of the present invention, each phase can be obtained without preparing a standard sample with a changed composition ratio, even in the case of a sample having a similar area ratio in a state where it is not swollen. The polymer components that form the structure can be identified.

A yellow domain B brown domain

Claims (4)

A method for observing a phase structure of a blend polymer containing two or more polymer components,
A phase structure observation method including a swelling step of swelling the blend polymer with a solvent and an observation step of observing the blend polymer after the solvent swelling with an atomic force microscope. Furthermore, the phase structure observation method of Claim 1 including the comparison process which compares the phase structure observation result obtained at the said observation process with the phase structure observation result by the atomic force microscope of the blend polymer which is not swollen. The phase structure observation method according to claim 1 or 2, wherein the observation in the observation step is observation in a tapping mode or a force volume mode of an atomic force microscope. The phase structure observation method according to claim 1, wherein the blend polymer is a vulcanized rubber composition.