Method for peeling off plate-like particles

Abstract

To provide a method for peeling tabular particles, which can peel off a large amount of particles without requiring cost or effort.SOLUTION: A method for peeling tabular particles includes: a peeling step (step S2) of peeling off the particles by kneading a high-viscosity composite material comprising, as a primary component, a polymeric material and filled with the tabular particles, by using a two-roll kneader 10 that includes a first roll 11 and a second roll 12 arranged adjacent to and parallel to the first roll 11, and that can adjust rotational speed of the first roll 11 and the second roll 12.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for exfoliating plate-like particles having plate-like crystal flakes stacked thereon. [Background technology]

[0002] Conventionally, a method for exfoliating plate-like particles has been known in which plate-like particles of boron nitride are mixed with an epoxy monomer to produce a slurry-like composite material, and then kneaded using a three-roll mill to exfoliate the boron nitride particles (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2017-510540 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the three-roll mill used in conventional exfoliation methods is a kneading device generally suited to low-viscosity materials. Typically, the greater the amount of boron nitride particles mixed, the higher the viscosity of the resulting composite material. Therefore, conventional exfoliation methods using a three-roll mill have the problem of being difficult to knead composite materials containing a large amount of platelet-like particles, making them unsuitable for mass processing.

[0005] It is also possible to exfoliate plate-like particles using kneading devices such as wet jet mills, rotary disk mills, planetary homogenizers, high-pressure homogenizers, and ultrasonic mills. However, for example, ultrasonic mills require the use of large amounts of expensive ionic solutions and long processing times, making any of these kneading devices a labor-intensive and cost-intensive method. For this reason, no exfoliation method applicable to industrial fields has been established.

[0006] The present invention has been made in view of the above-mentioned problems, and has as its object to provide a method for peeling off plate-like particles, which can peel off a large amount of plate-like particles without requiring cost or labor. [Means for solving the problem]

[0007] In order to achieve the above object, the method for exfoliating plate-like particles of the present invention comprises the steps of: a step of filling plate-like particles into a material selected from epoxy resin, silicone resin, polyethylene, polypropylene, or rubber as a main material, and generating a composite material in which the amount of the plate-like particles added to the main material is set to 20 to 90 vol%; A rotary kiln comprising a first roll and a second roll arranged adjacent to the first roll and parallel to the axis thereof, and capable of adjusting the rotation speeds of the first roll and the second roll. Batch type For two-roll kneaders a step of adding a predetermined amount of the composite material to the batch-type two-roll kneader; Therefore, The aforementioned a peeling step of peeling off the plate-like particles by kneading the composite material; and a step of discharging the kneaded composite material after the kneading for a predetermined time has been completed. Equipped with. [Effects of the Invention]

[0008] The method for peeling off plate-like particles of the present invention makes it possible to peel off a large amount of plate-like particles without requiring cost or labor. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic plan view showing a continuous two-roll kneader used in the method for exfoliating plate-like particles in Example 1. [Figure 2] 1 is a flowchart showing the procedure of the method for peeling off plate-like particles in Example 1. [Figure 3] FIG. 2 is a schematic diagram illustrating the peeling of plate-like particles. [Figure 4] 1(a) is an image showing the state of kneading using a kneader without grooves on the roll surface, and FIG. 1(b) is an image showing the state of kneading using the two-roll kneader of Example 1. [Figure 5] 1 is an image of boron nitride particles contained in a composite material before compounding. [Figure 6] 1 is an image of boron nitride particles contained in the composite material after kneading using the two-roll kneader of Example 1. [Figure 7]1 is a graph showing the measurement frequency for each thickness size of boron nitride particles contained in a composite material before kneading, and the measurement frequency for each thickness size of boron nitride particles contained in a composite material after kneading using the two-roll kneader of Example 1. [Figure 8] 1A shows a batch-type two-roll kneader used in the method for exfoliating plate-like particles of the present invention, in which (a) is a schematic plan view, (b) is a schematic front view, and (c) is a schematic cross-sectional view taken along the line AA. [Figure 9] 1 is a table showing processing results when kneading is performed under different operating conditions using a batch-type two-roll kneader. [Figure 10] 1 is a table showing processing results when composite materials with different physical properties are mixed using a batch-type two-roll mixer. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment for carrying out the method for peeling off plate-like particles of the present invention will be described based on Example 1 shown in the drawings.

[0011] In the method for exfoliating plate-like particles of Example 1, a two-roll kneader 10 shown in Figure 1 is used. The two-roll kneader 10 is an apparatus that kneads a slurry-like material (material to be pulverized) that is fed between two cylindrical rolls (first and second rolls 11 and 12) that rotate in opposite directions, by compressing and shearing the material between the rolls. Here, the two-roll kneader 10 shown in Figure 1 is a continuous two-roll kneader that simultaneously feeds materials and discharges the kneaded material. In the two-roll kneader 10 of Example 1, the two rolls continue to rotate when feeding materials and discharging the kneaded material.

[0012] The two-roll kneader 10 comprises a cylindrical first roll 11 and a cylindrical second roll 12 disposed adjacent to the first roll 11 with its axial direction parallel (axially parallel). The first roll 11 and the second roll 12 are disposed with a small gap 13 between them and are supported at the same height by a base (not shown). The size of the gap 13 is adjustable.

[0013] The first roll 11 is rotatably supported via bearings 51 and 52, and the second roll 12 is rotatably supported via bearings 53 and 54. The first roll 11 and the second roll 12 are driven to rotate in opposite directions by a driving device (not shown), such as an electric motor, and rotate in directions from top to bottom in the gap 13. Note that an operator mainly operates from the side of the first roll 11.

[0014] The first roll 11 and the second roll 12 may be rotated and driven separately by two drive devices, or one roll may be rotated and driven by one drive device and the other roll may be rotated and driven by a transmission device such as a gear. The rotation speeds (number of rotations) and rotation speed ratio of the first and second rolls 11 and 12 can be adjusted as desired. In the two-roll kneader 10, the rotation speed of the first roll 11 is set to be faster than that of the second roll 12, so that the material to be processed can be wrapped around only the first roll 11 and kneaded.

[0015] The first roll 11 and the second roll 12 are each equipped with a heating means (not shown) and are set to a surface temperature suitable for kneading the material to be processed. The heating means is generally a mechanism using thermal oil or an electric heater. The heating means is capable of adjusting the surface temperatures of the first and second rolls 11 and 12.

[0016] Furthermore, in the two-roll kneader 10 of Example 1, spiral grooves 14 are formed on the surface of the first roll 11. Furthermore, spiral grooves 15 are formed on the surface of the second roll 12. Here, the twist direction of the grooves 14 formed on the first roll 11 and the twist direction of the grooves 15 formed on the second roll 12 are set to be opposite to each other. Furthermore, when the first roll 11 and the second roll 12 rotate, the grooves 14 and the grooves 15 move the material to be processed introduced between the rolls in the same direction, that is, from one end 16a to the other end 16b.

[0017] Furthermore, the grooves 14 are formed over the entire length of the first roll 11. Therefore, there is no smooth area on the first roll 11 where the grooves 14 are not provided. Moreover, the grooves 15 are formed over the entire length of the second roll 12. Therefore, there is no smooth area on the second roll 12 where the grooves 15 are not provided.

[0018] The shapes of the grooves 14 and 15 can be appropriately set depending on the model of the two-roll kneader 10, and are set, for example, so that the depth is 3 / 1000 to 2 / 100 of the roll diameter, the width is 1 / 1000 to 6 / 100 of the roll diameter, and the product of the width and the number of grooves is 1 / 6 to 1 / 5 of the roll circumference. The grooves 14 and 15 are preferably shaped to facilitate cleaning after kneading the material to be treated. Furthermore, by making the grooves 14 and 15 a multi-thread screw with two or more threads, the material to be treated can be fed quickly and reliably.

[0019] A scraper 30 is disposed in the vicinity of the two-roll kneader 10. The scraper 30 is driven by a drive unit (not shown) from the side of the first roll 11 to approach or move away from the first roll 11. The scraper 30 can appropriately bring its tip 31 into contact with the first roll 11. As a result, the material to be treated that has wrapped around the first roll 11 is cut by the scraper 30 and peeled off from the surface of the first roll 11.

[0020] The procedure of the method for peeling off the plate-like particles in Example 1 will be described below with reference to the flowchart shown in FIG.

[0021] In step S1, a polymeric material as a main material and plate-like particles (filler) as an additive are fed from separate feeds into a continuous two-roll kneader 10 shown in FIG. 1, and the process proceeds to step S2.

[0022] The polymeric material and plate-like particles fed into the two-roll kneader 10 are mixed between the rolls to form a composite material in which the plate-like particles are filled with the polymeric material as the main material. The two-roll kneader 10 rotates the first roll 11 and the second roll 12 before the polymeric material and the plate-like particles are fed. Therefore, the polymeric material and the plate-like particles are fed toward the gap (gap 13) between the rotating first roll 11 and second roll 12.

[0023] Here, the polymer material is a material composed of a polymer compound with a relatively large molecular weight, and in Example 1, a liquid epoxy resin containing a curing agent is selected as the polymer material. The polymer material can be appropriately selected depending on the plate-like particles and the specifications of the two-roll kneader 10. For example, the polymer material may be a thermosetting resin such as an epoxy resin or a silicone resin, or a thermoplastic resin such as polyethylene or polypropylene. Furthermore, the polymer material may be rubber.

[0024] The plate-like particles are a substance in which plate-like crystal flakes are stacked, and in Example 1, hexagonal boron nitride particles (boron nitride particles) are selected as the plate-like particles. Boron nitride is a layered substance with a structure similar to that of graphite, but the interaction between the crystal flakes (the bonding force between the layers of the crystal flakes) is stronger than the van der Waals force between the layers of graphite. The type of plate-like particles is not particularly limited, and graphite, talc, mica, etc. may be selected.

[0025] When the plate-like particles are filled into the polymer material, the amount of the plate-like particles added to the polymer material is set to 20 to 90 vol %. The amount of the boron nitride particles added to the liquid epoxy resin is preferably set to 50 to 70 vol %, and in Example 1, it is set to 60 vol %.

[0026] Furthermore, a composite material in which the amount of plate-like particles added to the polymer material is set to 20 to 90 vol % is a composite material in which the amount of plate-like particles added to the polymer material is large, and the plate-like particles are highly filled. Here, the composite material produced by filling a polymer material with plate-like particles has a higher viscosity as the amount of plate-like particles added to the polymer material increases (the higher the filling). Therefore, a composite material in which the amount of plate-like particles added to the polymer material is set to 20 to 90 vol % is a high-viscosity composite material. In other words, in Example 1, a high-viscosity composite material in which a polymer material is the main material and is highly filled with plate-like particles is fed into the two-roll kneader 10.

[0027] In step S2 (peeling step), following the introduction of the polymeric material and plate-like particles in step S1, a high-viscosity composite material containing a polymeric material as the main component and plate-like particles filled with plate-like particles is kneaded using a continuous two-roll kneader 10 shown in FIG. 1, and the plate-like particles are then peeled off and the process proceeds to the end. Because a continuous two-roll kneader 10 is used, the introduction of the polymeric material and plate-like particles, the kneading of the composite material, and the discharge of the composite material (kneaded product) are all performed simultaneously. That is, the polymeric material and plate-like particles introduced into the two-roll kneader 10 are mixed together to form a composite material, which is compressed and sheared between the first roll 11 and the second roll 12 and then moved from one end 16a to the other end 16b by the grooves 14 and 15. During this process, the plate-like particles are gradually peeled off. Then, the two-roll kneader 10 continuously discharges the composite material from which the plate-like particles have been peeled off from the other end 16b while the first roll 11 and the second roll 12 are kept rotating.

[0028] Here, "exfoliating plate-like particles" refers to kneading plate-like particles β, which have a structure in which multiple plate-like crystal flakes α are stacked, in a two-roll kneader 10, as shown schematically in FIG. 3, and then thinly peeling off the overlapping crystal flakes α into layers (cleavage treatment). By peeling off the stacked crystal flakes, the plate-like particles have a high aspect ratio. This facilitates efficient contact between the plate-like particles in the composite material, allowing the properties of the plate-like particles to be efficiently exploited. For example, the hexagonal boron nitride particles selected as the plate-like particles in Example 1 have high thermal conductivity, but exfoliation facilitates the formation of a heat conduction network. As a result, a composite material with high thermal conductivity can be obtained even when the amount of plate-like particles (boron nitride particles) added is reduced.

[0029] In Example 1, when kneading the composite material, the spacing dimension of gap 13 (roll spacing) is set to 0.1 mm to 0.7 mm. If the spacing dimension of gap 13 is too wide (for example, about 0.8 mm), the composite material to be processed may not be wound around first roll 11 or second roll 12. If the spacing dimension of gap 13 is too narrow (for example, less than 0.1 mm), the composite material to be processed may get stuck between the rolls and may not be properly kneaded. In Example 1, the spacing dimension of gap 13 is set to 0.3 mm, which allows the composite material to be wound around first roll 11 or second roll 12 and be properly kneaded.

[0030] Whether the composite material is wound around the first or second roll 11, 12 is determined by the rotational speed ratio (ratio of rotational speeds) between the first and second rolls 11, 12 and the surface temperature. In Example 1, while the composite material is being kneaded, the first roll 11 is set to a rotational speed equal to or higher than the rotational speed of the second roll 12. This allows the two-roll kneader 10 to knead the composite material while it is wound around the first roll 11. The speed ratio between the rotational speed of the first roll 11 and the rotational speed of the second roll 12 is preferably set in the range of 1:0.5 to 1:1. In Example 1, the rotational speed of the first roll 11 is set to 20 min -1The rotation speed of the second roll 12 is set to 16 min -1 and the speed ratio between the first roll 11 and the second roll 12 is set to 1:0.8.

[0031] Furthermore, the two-roll kneader 10 creates a temperature difference between the surface temperature of the first roll 11 and the surface temperature of the second roll 12 while kneading the composite material. That is, in Example 1, the surface temperature of the first roll 11 is set to a temperature higher than the surface temperature of the second roll 12. This allows the two-roll kneader 10 to knead the composite material while it is wrapped around the first roll 11.

[0032] Furthermore, when the composite material contains a thermosetting resin, that is, when a thermosetting resin is selected as the polymer material, the surface temperatures of the first roll 11 and the second roll 12 during kneading of the composite material are set to a temperature lower than the temperature at which the thermosetting resin contained in the composite material begins to harden. Furthermore, when the composite material contains a thermoplastic resin, that is, when a thermoplastic resin is selected as the polymer material, the surface temperatures of the first roll 11 and the second roll 12 are set to a temperature higher than the temperature at which the thermoplastic resin contained in the composite material melts.

[0033] In Example 1, the liquid epoxy resin selected as the polymer material is a thermosetting resin, and therefore the surface temperatures of the first roll 11 and the second roll 12 are set to be lower than the temperature at which the liquid epoxy resin begins to harden.

[0034] If the surface temperatures of the first and second rolls 11 and 12 rise during kneading, the temperature is lowered, for example, by passing water through the inside of the second roll 12. This suppresses hardening of the polymer material (liquid epoxy resin in Example 1) contained in the composite material, and stabilizes the state in which the composite material is wrapped around the first roll 11.

[0035] The difference between the kneading action by the two-roll kneader 10 used in the method for peeling off plate-like particles in Example 1 and the kneading action by the three-roll kneader will be described below.

[0036] A three-roll kneader has three cylindrical rolls arranged closely parallel to each other, which rotate in opposite directions to each other, compressing and shearing the material to be processed between the rolls in turn.

[0037] In a three-roll kneader, no grooves are formed on the surface of any of the rolls, and all of the rolls have a smooth surface. The three-roll kneader performs batch processing by kneading the material to be processed while moving it around the rolls. Three-roll kneaders are generally used to knead relatively low-viscosity materials such as ink and paint. Furthermore, the L / D ratio (L: effective length of the rolls, D: diameter of the rolls) in a three-roll kneader is generally smaller than that of the two-roll kneader 10 of Example 1. The roll spacing is, for example, several tens of μm, the roll rotation speed is, for example, 25 to 180 rpm, and the rotation ratio of the three rolls is set to, for example, 1:3:9, assuming that the rotation speed of the roll into which the material is fed is "1."

[0038] Here, in order to improve the dispersibility of the slurry-like material when it is kneaded, it is important to increase the shear stress generated between two adjacent rolls. The shear stress can be calculated using the following formula (1). From the following formula (1), it can be considered that the shear stress acting on the slurry-like material is proportional to the product of the viscosity of the material and the velocity gradient of the roll rotation speed.

number

[0039] In contrast, three-roll kneaders are generally used to process low-viscosity materials, as described above. When the viscosity of the material being processed is low, the roll rotation speed gradient must be increased to increase the shear stress. That is, when using a three-roll kneader, the roll spacing is reduced and the roll rotation speed and roll rotation ratio are increased to increase the roll rotation speed gradient and increase the shear stress. However, with a three-roll kneader, the roll rotation speed gradient is large, which can result in excessive torque acting on the rolls and potentially damage to the equipment. Furthermore, when attempting to process high-viscosity materials with a three-roll kneader, the torque acting on the rolls can be excessively large, potentially resulting in damage to the equipment. Furthermore, composite materials containing a polymeric material as the main component and plate-like particles have a higher viscosity as the amount of plate-like particles added increases (the more highly packed the plate-like particles are). Therefore, it is difficult to exfoliate high-viscosity composite materials containing a large amount of plate-like particles using a three-roll kneader.

[0040] In contrast, the two-roll kneader 10 of Example 1 is generally used to knead materials with relatively high viscosity, such as resins and rubbers. Furthermore, the L / D value of the two-roll kneader 10 is generally larger than that of a three-roll kneader.

[0041] For this reason, the two-roll kneader 10 is capable of kneading a material with a higher viscosity than a three-roll kneader, and because the viscosity of the material is high, sufficient shear stress can be obtained even with a small roll rotation speed gradient. In other words, the two-roll kneader 10 does not require a large roll rotation speed gradient, and can prevent the torque acting on the rolls from becoming too large. Furthermore, since the two-roll kneader 10 can thus suppress the torque acting on the rolls, it is possible to appropriately knead even a composite material with a large amount of plate-like particles and a high viscosity (a composite material highly filled with plate-like particles). Therefore, the two-roll kneader 10 is more suitable than a three-roll kneader for exfoliating a high-viscosity composite material with a large amount of plate-like particles.

[0042] Furthermore, because the torque acting on the rolls is large, the deflection of each roll cannot be ignored in a three-roll kneader. For this reason, three-roll kneaders often employ crown rolls, which are curved in a gentle arc from the center of the roll to both ends. In contrast, in the two-roll kneader 10, the torque acting on the first roll 11 and the second roll 12 can be reduced, so there is no need to consider the deflection of the first and second rolls 11 and 12, and therefore crown rolls do not need to be employed.

[0043] Moreover, the two-roll kneader 10 of Example 1 is a continuous two-roll kneader that simultaneously inputs materials and discharges the kneaded product. Specifically, the two-roll kneader 10 of Example 1 has spiral grooves 14 formed on the surface of the first roll 11 and spiral grooves 15 formed on the surface of the second roll 12. Furthermore, in the peeling treatment using the two-roll kneader 10 of Example 1, the first roll 11 and the second roll 12 are rotated in opposite directions in advance. Then, the polymeric material and the plate-like particles are individually introduced between the first roll 11 and the second roll 12, which are rotating in opposite directions. Thus, the two-roll kneader 10 mixes and kneads the individually introduced polymeric material and plate-like particles, and simultaneously moves (transports) them in the axial direction. Furthermore, the two-roll kneader 10 can discharge the processed product while the first and second rolls 11 and 12 continue to rotate.

[0044] Furthermore, as shown in Figure 4(a), if neither of the two rolls (R1 and R2 in Figure 4(a)) that knead the material to be processed has grooves, in the bank section B that is generated during kneading, no exchange of material X to be processed is observed between the center and surface sections of bank section B. Note that bank section B is the section where material X, which has been introduced between the two rolls R1 and R2, accumulates and rises up between the rolls before flowing into gap S.

[0045] On the other hand, in the two-roll kneader 10 of Example 1, as shown in Figure 4(b), the material X (composite material) undergoes convection in the bank section B, and the material X in the center and the material X in the surface layer section are constantly replaced. As a result, the two-roll kneader 10 of Example 1 can knead the material X even in the center of the bank section B, and the material X is automatically turned over. For this reason, a three-roll kneader without grooves, unlike the two-roll kneader 10, requires manual turning over of the material to be treated.

[0046] In this way, in the two-roll kneader 10 of Example 1, the material to be treated is subjected to compression and shearing action in the process of being moved (conveyed) in the axial direction due to the action of the grooves 14 and 15, and furthermore, macro-mixing is performed by convection in the bank section B, thereby allowing kneading to proceed. In other words, the two-roll kneader 10 of Example 1 can effectively obtain the repeated action of compression and folding, which is the basic element of kneading, rather than simply mixing the material to be treated by switching it over.

[0047] The results of kneading the composite material using the two-roll kneader 10 of Example 1 will be described below.

[0048] Fig. 5 shows an image of boron nitride particles contained in a composite material before it is kneaded by the two-roll kneader 10, and Fig. 6 shows an image of boron nitride particles contained in a composite material kneaded by the two-roll kneader 10. Note that both the images shown in Fig. 5 and Fig. 6 are images of boron nitride particles contained in a composite material produced by adding 50 to 70 vol% of hexagonal boron nitride particles selected as plate-like particles to a liquid epoxy resin, a curing agent, a curing accelerator, and a reactive diluent as polymer materials (main materials).

[0049] As shown in Figure 5, the boron nitride particles contained in the composite material before kneading are thick, with crystal flakes stacked on top of each other. In contrast, as shown in Figure 6, the boron nitride particles contained in the composite material after kneading appear to have become thinner due to the crystal flakes peeling off. This shows that the composite material is subjected to shearing and compressive forces when kneaded using the two-roll kneader 10 of Example 1, causing the plate-like particles to peel off.

[0050] 7 is a graph showing the measurement frequency for each thickness size of boron nitride particles contained in the composite material before kneading, and the measurement frequency for each thickness size of boron nitride particles contained in the composite material after kneading using the two-roll kneader 10. The measurement targets shown in FIG. 7 are boron nitride particles contained in a composite material produced by adding 50 to 70 vol% of hexagonal boron nitride particles selected as plate-like particles to a polymer material (main material) that includes a liquid epoxy resin, a curing agent, a curing accelerator, and a reactive diluent.

[0051] The graph shown in Fig. 7 shows that the measurement frequency of plate-like particles having a small thickness increases before and after kneading the composite material using the two-roll kneader 10 of Example 1. In other words, the graph shown in Fig. 7 also shows that kneading the composite material using the two-roll kneader 10 caused the exfoliation of the plate-like particles to progress.

[0052] Thus, the method for peeling off plate-like particles of Example 1 includes a peeling step (step S2) in which a high-viscosity composite material containing a polymer material as the main material and filled with plate-like particles is kneaded using the two-roll kneader 10 of Example 1, which is equipped with a first roll 11 and a second roll 12 arranged adjacent to the first roll 11 and parallel to the axis, and which is capable of adjusting the rotation speeds of the first roll 11 and the second roll 12, thereby peeling off the plate-like particles.

[0053] Therefore, the plate-like particle exfoliation method of Example 1 can properly knead the composite material and exfoliate the plate-like particles, even if the composite material has a high viscosity and a large amount of plate-like particles added to the polymer material. As a result, the plate-like particle exfoliation method of Example 1 can exfoliate a large amount of plate-like particles without requiring cost or effort.

[0054] Furthermore, the exfoliation method of Example 1 uses a continuous two-roll kneader as the two-roll kneader 10, which simultaneously inputs materials and discharges the kneaded product. Therefore, the exfoliation of the plate-like particles with stacked crystal flakes and the kneading of the composite material can proceed simultaneously. In other words, the plate-like particle exfoliation process and the composite material kneading process do not need to be performed separately. The exfoliation of the plate-like particles and the kneading of the composite material can be simultaneously performed using a single two-roll kneader 10, thereby reducing the number of manufacturing steps. Furthermore, the exfoliation method of Example 1 allows the first and second rolls 11 and 12 to continue rotating without stopping the two-roll kneader 10 from the time the materials are input until the time the kneaded product is discharged. This reduces the effort and cost required for the process compared to using a batch kneader.

[0055] Furthermore, in the peeling method of Example 1, the two-roll kneader 10 used for kneading has spiral grooves 14, 15 formed on the surfaces of the first roll 11 and the second roll 12, respectively. Therefore, the two-roll kneader 10 can smoothly move the composite material in the axial direction, enabling continuous kneading processing. Furthermore, as shown in Figure 4(b), the material X to be processed can also be kneaded in the center of the bank section B, and the material X to be processed can be automatically cut back and forth.

[0056] In the peeling method of Example 1, the polymer material and the plate-like particles are separately introduced between the first roll 11 and the second roll 12, which are rotating in opposite directions, and the polymer material and the plate-like particles are mixed and kneaded. This allows the peeling of the plate-like particles and the kneading of the composite material to proceed simultaneously, enabling continuous kneading processing.

[0057] In the method for exfoliating plate-like particles in Example 1, the plate-like particles to be exfoliated are added to the polymer material. Therefore, if it is desired to extract only the exfoliated plate-like particles, the plate-like particles can be easily extracted by volatilizing the polymer material in the composite material after kneading using the two-roll kneader 10.

[0058] Furthermore, in the exfoliation method of Example 1, when a composite material is produced, the amount of plate-like particles added to the polymer material is set to 20 to 90 vol%. Therefore, the exfoliation method of Example 1 can increase the proportion of plate-like particles in the composite material to be kneaded, resulting in a high-viscosity composite material. This allows the exfoliation method of Example 1 to increase the production yield of exfoliated plate-like particles. Furthermore, by highly filling the plate-like particles to produce a high-viscosity composite material, the shear force that the composite material receives increases. As a result, the exfoliation method of Example 1 can further promote the exfoliation of the plate-like particles.

[0059] Furthermore, since the exfoliation method of Example 1 can promote the exfoliation of the plate-like particles as described above, it is possible that the functions of the plate-like particles can be exhibited even when the amount of the plate-like particles is small. Furthermore, if the amount of plate-like particles contained in the composite material is reduced, it is possible to reduce the weight and cost of the composite material. In other words, the composite material kneaded by the exfoliation method of Example 1 can be expected to be lightweight and cost-effective.

[0060] In the exfoliation method of Example 1, boron nitride particles are selected as the plate-like particles, and when producing a composite material, the amount of boron nitride particles added to the polymer material is set to 50 to 70 vol %. Therefore, the exfoliation method of Example 1 can highly fill the polymer material with boron nitride particles, thereby producing a composite material with high thermal conductivity.

[0061] Furthermore, in the exfoliation method of Example 1, when the composite material is kneaded by the two-roll kneader 10, the speed ratio between the rotation speed of the first roll 11 and the rotation speed of the second roll 12 is set to 1:0.5 to 1:1. As a result, the exfoliation method of Example 1 can adjust the shear force generated between the first roll 11 and the second roll 12, and can exfoliate the plate-like particles while suppressing crushing of the crystal flakes.

[0062] Furthermore, in the peeling method of Example 1, the two-roll kneader 10 is capable of adjusting the distance of the gap 13 set between the first roll 11 and the second roll 12. When the composite material is kneaded by the two-roll kneader 10, the distance of the gap 13 is set to 0.1 mm to 0.7 mm. This allows the two-roll kneader 10 to appropriately knead the composite material while it is wound around the first roll 11 or the second roll 12.

[0063] Furthermore, in the peeling method of Example 1, the two-roll kneader 10 is capable of adjusting the surface temperatures of the first roll 11 and the second roll 12. A liquid epoxy resin, which is a thermosetting resin, is selected as the polymer material, and when the composite material is kneaded by the two-roll kneader 10, the surface temperatures of the first roll 11 and the second roll 12 are set to a temperature lower than the temperature at which the liquid epoxy resin begins to harden. As a result, the peeling method of Example 1 can prevent the viscosity of the composite material, which contains the liquid epoxy resin, which is a thermosetting resin, from increasing during kneading, and can suppress the torque acting on the first and second rolls 11 and 12.

[0064] In the peeling method of Example 1, when a thermoplastic resin is selected as the high-molecular-weight material and the composite material contains a thermoplastic resin, the surface temperatures of the first roll 11 and the second roll 12 are set to a temperature higher than the temperature at which the thermoplastic resin contained in the composite material melts. Therefore, the peeling method of Example 1 reduces the viscosity of the composite material containing a thermoplastic resin during kneading, and can suppress the torque acting on the first and second rolls 11 and 12.

[0065] The method for exfoliating plate-like particles of the present invention has been described above based on Example 1, but the specific configuration is not limited to this Example, and design changes and additions are permitted as long as they do not deviate from the gist of the invention as defined in each claim of the patent.

[0066] In the method for exfoliating plate-like particles in Example 1, an example was shown in which a composite material was kneaded using a continuous two-roll kneader 10 that simultaneously charges materials and discharges the kneaded product. However, as the two-roll kneader for kneading a composite material, a batch-type two-roll kneader 10A (see FIGS. 8(a) to (c)) that charges a predetermined amount of materials, performs the necessary kneading, and then discharges the kneaded product may also be used.

[0067] As shown in Figures 8(a) to 8(c), the batch-type two-roll kneader 10A includes a first roll 11A and a second roll 12A. The second roll 12A is arranged adjacent to the first roll 11A, axially parallel to the first roll 11A, with a small gap 13 between them. The size of the gap 13 is adjustable. The first roll 11A is rotatably supported via bearings 51 and 52. The second roll 12A is rotatably supported via bearings 53 and 54. The rotation and temperature control of the first roll 11A and second roll 12A are the same as in the continuous two-roll kneader 10 of Example 1. Furthermore, a scraper 30 is arranged near the batch-type two-roll kneader 10A.

[0068] On the other hand, the batch-type two-roll kneader 10A includes a pair of regulating members 40a, 40b arranged side by side at a predetermined interval along the axial direction of the first roll 11A and the second roll 12A. As shown in FIG. 8(c), two arc-shaped curved surfaces 41a, 41b are formed on the lower surface of one of the regulating members 40a. One curved surface 41a contacts the surface of the first roll 11A, and the other curved surface 41b contacts the surface of the second roll 12A. The other regulating member 40b also has two arc-shaped curved surfaces (not shown) formed on the lower surface, each of which contacts the surfaces of the first and second rolls 11A, 12A, respectively. The pair of regulating members 40a, 40b are movable in the axial direction of the first and second rolls 11A, 12A while contacting the surfaces of the first and second rolls 11A, 12A. The first and second rolls 11A and 12A are rotatable while being in contact with the pair of regulating members 40a and 40b.

[0069] The pair of regulating members 40a, 40b contact the first and second rolls 11A, 12A, so that the material to be processed that is fed between the pair of regulating members 40a, 40b is kneaded without going beyond the regulating members 40a, 40b. In other words, the area sandwiched between the pair of regulating members 40a, 40b becomes a kneading area 42 where the material to be processed is kneaded.

[0070] Furthermore, as shown in FIG. 8(b), the base (not shown) is provided with a moving means 43 that moves each of the regulating members 40a and 40b along the axial direction. The moving means 43 includes a first arm 43a to which one of the regulating members 40a is fixed at its tip, and a second arm 43b to which the other of the regulating members 40b is fixed at its tip. As the first arm 43a moves in the horizontal direction, one of the regulating members 40a is moved along the axial direction while in contact with the first and second rolls 11A and 12A. As the second arm 43b moves in the horizontal direction, the other regulating member 40b is moved along the axial direction while in contact with the first and second rolls 11A and 12A.

[0071] Here, the moving means 43 can move the first arm 43a and the second arm 43b separately. Therefore, the moving means 43 moves the first arm 43a and the second arm 43b in the same direction, thereby moving the pair of regulating members 40a, 40b along the axial direction of the first and second rolls 11A, 12A with a predetermined gap between them. As a result, the kneading region 42 moves along the axial direction of the first and second rolls 11A, 12A.

[0072] Furthermore, the moving means 43 can move the pair of regulating members 40a, 40b in the same direction simultaneously, by the same distance, and at the same speed. In this case, the distance between the pair of regulating members 40a, 40b is maintained, and the kneading region 42 moves while maintaining a constant size.

[0073] Furthermore, the moving means 43 moves the first arm 43a and the second arm 43b simultaneously in opposite directions to move the pair of regulating members 40a, 40b closer to or farther apart. In other words, the moving means 43 can adjust the width of the gap between the pair of regulating members 40a, 40b. This allows the size of the kneading region 42 to be changed without moving it in the axial direction. In this way, the batch-type two-roll kneader 10A can control the size and position of the kneading region 42 by controlling the positions of the pair of regulating members 40a, 40b.

[0074] When the moving means 43 does not move the first and second arms 43a, 43b, the movement of the pair of regulating members 40a, 40b stops, and the size and position of the kneading region 42 are maintained. The moving means 43 may automatically move the first and second arms 43a, 43b using an electric motor or the like, or the first and second arms 43a, 43b may be moved manually by an operator.

[0075] Furthermore, in the batch-type two-roll kneader 10A, the surface of the first roll 11A is formed as a smooth surface without grooves. Also, spiral grooves 20 are formed on the surface of the second roll 12A. The grooves 20 include a first groove 21 formed on the surface from one end 12x of the second roll 12A to the center, and a second groove 22 formed on the surface from the other end 12y of the second roll 12A to the center.

[0076] The first grooves 21 are grooves that feed the material to be processed from the center toward one end 12x when the second roll 12A rotates. The second grooves 22 are set to have a twist direction opposite to that of the first grooves 21, and are grooves that feed the material to be processed from the center toward the other end 12y when the second roll 12 rotates. In the batch-type two-roll kneader 10A, the first grooves 21 and the second grooves 22 are continuous at the center of the second roll 12A, and the twist directions of the grooves 20 are opposite at the center. In other words, the grooves 20 are formed over the entire length of the second roll 12A, and there are no smooth areas on the surface of the second roll 12A where the grooves 20 are not provided.

[0077] The first and second grooves 21, 22 can be appropriately shaped, for example, to have a width of 5 mm and a depth of 1 mm, and are preferably shaped to facilitate cleaning after the material to be processed has been mixed. Furthermore, the first and second grooves 21, 22 can be threaded with two or more threads, allowing the material to be fed quickly and reliably.

[0078] When the plate-like particles are peeled off using the batch-type two-roll kneader 10A, a high-viscosity composite material is first produced in advance before the materials are added, with the composite material being primarily made of a polymer material and filled with plate-like particles (filler). Next, a predetermined amount of the produced composite material is fed into the kneading region 42 defined by the regulating members 40a and 40b. After the composite material has been fed into the kneading region 42, the first roll 11A and the second roll 12A of the batch-type two-roll kneader 10A are rotated to knead the composite material and peel off the plate-like particles. After the predetermined period of kneading is completed, the processed product (kneaded composite material) is discharged.

[0079] Here, in the batch-type two-roll kneader 10A, the size of the kneading region 42 (the pair of regulating members 40a, 40b and the distance between them) is set to, for example, 100 mm to 150 mm. During kneading of the composite material, the moving means 43 moves the pair of regulating members 40a, 40b at a speed of 0.5 mm / sec, respectively, in the same direction and at the same timing along the axial direction of the first and second rolls 11A, 12A. This causes the kneading region 42 to move a predetermined distance along the axial direction while maintaining its size. Here, the moving distance of the regulating members 40a, 40b can be set to 50 mm to 70 mm.

[0080] Furthermore, it is desirable that the moving means 43 repeats two to four reciprocating movements of the regulating members 40a, 40b along the axial direction of the rolls by 50 to 70 mm, followed by 50 to 70 mm in the opposite direction during kneading of the composite material. By repeatedly performing multiple reciprocating movements of the regulating members 40a, 40b along the axial direction, the batch-type two-roll kneader 10A can lengthen the time that the composite material is subjected to shear force compared to when reciprocating movements are not performed, thereby accelerating the peeling of the plate-like particles.

[0081] During the kneading of the composite material, any composite material that falls from the kneading region 42 due to being scraped off by the regulating members 40a, 40b is manually returned to the kneading region 42 and continues to be kneaded. When the plate-like particles are peeled off using the batch-type two-roll kneader 10A, after the reciprocating movement of the regulating members 40a, 40b is completed, the pair of regulating members 40a, 40b is moved to move the kneading region 42 to the center of the rolls, and then the movement of the regulating members 40a, 40b is stopped. The batch-type two-roll kneader 10A kneads the composite material for a predetermined time (e.g., 1 minute) without moving the position of the kneading region 42, and then stops the rotation of the first roll 11A and the second roll 12A, thereby completing the kneading. The total processing time from the introduction of the composite material to the stopping of the rotation of the first and second rolls 11A, 12A is approximately 10 to 15 minutes.

[0082] FIG. 9 shows the processing results when the same composite material was mixed under different operating conditions using the batch-type two-roll mixer 10A. The composite material used for the mixing shown in FIG. 9 was produced by adding 50 to 60 vol% of hexagonal boron nitride particles selected as plate-like particles to a liquid epoxy resin, curing agent, curing accelerator, and reactive diluent as the polymer material (main material). Furthermore, under all operating conditions, the specific surface area of ​​the plate-like particles was larger after mixing than before mixing. Furthermore, under the first to third conditions, the aspect ratio of the plate-like particles was larger after mixing than before mixing. In other words, under all operating conditions, the plate-like particles were exfoliated by mixing using the batch-type two-roll mixer 10A.

[0083] Comparing the first and second operating conditions, the second operating condition requires four more reciprocating movements. In this case, the kneading time is longer when kneading is performed under the second operating condition than under the first operating condition. Furthermore, the specific surface area and aspect ratio of the crystal flakes of the plate-like particles are larger when kneading is performed under the second operating condition than when kneading is performed under the first operating condition. This is thought to be because the plate-like particles are subjected to a shear force from the two-roll kneader 10A for a longer period of time when the operating conditions are set to the second operating condition.

[0084] Furthermore, when comparing the operating conditions under the first and third conditions, the rotational speed ratio between the first roll 11A and the second roll 12A is smaller under the third condition. That is, under the third condition, the rotational speeds of the first and second rolls 11A and 12A are the same, while under the first condition, the rotational speed of the first roll 11A is slower than that of the second roll 12A. In this case, when kneading is performed under the operating condition under the third condition, the specific surface area and aspect ratio of the crystal flakes are smaller than when kneading is performed under the operating condition under the first condition. This is thought to be because the shear force that the plate-like particles receive from the two-roll kneader 10 is smaller when the operating condition is set to the third condition.

[0085] Furthermore, when comparing the operating conditions under conditions 1 and 4, the addition rate of plate-like particles under condition 4 was lower, resulting in a smaller amount of plate-like particles. In other words, under condition 4, the amount of polymer material contained in the composite material was greater than under condition 1. In this case, when kneading was performed under operating conditions under condition 1, the aspect ratio was larger than before kneading, but when kneading was performed under operating conditions under condition 4, no significant difference in the aspect ratio was observed before and after kneading. This is thought to be because when the operating conditions were set to condition 4, the amount of polymer material increased, reducing the shear force acting directly on the plate-like particles.

[0086] As described above, when kneading is performed using the two-roll kneader 10A, there are many factors that can adjust the shear force that the plate-like particles receive from the two-roll kneader 10A. Therefore, by kneading a composite material using the two-roll kneader 10A, it becomes possible to peel off the plate-like particles in a state that suits the purpose. Even when a composite material is kneaded using the continuous two-roll kneader 10 and the plate-like particles are peeled off, there are many factors that can adjust the shear force that the plate-like particles receive from the continuous two-roll kneader 10, and it is possible to peel off the plate-like particles in a state that suits the purpose.

[0087] Fig. 10 shows the results of mixing composite materials with different physical properties in a batch-type two-roll mixer 10A. Samples 1 to 3 shown in Fig. 10 are all composite materials produced by adding 50 to 60 vol% of hexagonal boron nitride particles selected as plate-like particles to a polymeric material (main material) consisting of a liquid epoxy resin, a curing agent, a curing accelerator, and a reactive diluent, but the specifications of the added boron nitride particles differ. The operating conditions of the two-roll mixer 10A when mixing each of Samples 1 to 3 were the first conditions shown in Fig. 9.

[0088] As shown in Fig. 10, in all of Samples 1 to 3, kneading with the two-roll kneader 10A increased the specific surface area of ​​the crystal flakes of the plate-like particles by 1.1 to 1.8 times. Furthermore, in all of Samples 1 to 3, kneading with the two-roll kneader 10A increased the aspect ratio of the crystal flakes of the plate-like particles by 1.2 to 1.6 times. This shows that, although the aspect ratio of the crystal flakes after kneading varies depending on the physical properties of the composite material, kneading with the two-roll kneader 10A causes the plate-like particles to peel off regardless of the physical properties of the composite material.

[0089] In this way, by using a two-roll kneader, whether continuous or batch type, to knead a high-viscosity composite material containing a polymer material as the main material and filled with plate-like particles, it is possible to exfoliate a large amount of plate-like particles without incurring costs or labor.

[0090] In the method for exfoliating plate-like particles using a batch-type two-roll kneader 10A, the two-roll kneader 10A for kneading the composite material is provided with a pair of regulating members 40a, 40b that are arranged at a predetermined distance along the axial direction of the first roll 11A and the second roll 12A and are movable in the axial direction while in contact with the first roll 11A and the second roll 12A. The composite material is introduced into a kneading region 42 provided between the pair of regulating members 40a, 40b.

[0091] Therefore, in the method for peeling plate-like particles using the batch-type two-roll kneader 10A, it is possible to prevent the composite material from spreading in the axial direction of the rolls during kneading, and to allow the composite material to be subjected to an appropriate kneading action. Also, it is possible to control the kneading state of the composite material in the two-roll kneader 10A by controlling, for example, the size and position of the kneading region 42 and the moving (conveying) speed of the composite material.

[0092] Furthermore, in the method for peeling plate-like particles using the batch-type two-roll kneader 10A, when the composite material is kneaded using the two-roll kneader 10A, the pair of regulating members 40a, 40b are moved back and forth multiple times along the axial direction while maintaining the distance between them. As a result, in the method for peeling plate-like particles using the batch-type two-roll kneader 10A, the composite material can be subjected to a shear force for a longer period of time than when the pair of regulating members 40a, 40b are not moved back and forth. This allows the peeling of the plate-like particles to proceed further.

[0093] In the example shown in FIG. 8, the grooves 20 formed in the second roll 12A include a first groove 21 and a second groove 22 that divide the second roll 12A in half. However, the shape of the grooves 20 is not limited to this. For example, the grooves 20 may be composed of only either the first groove 21 or the second groove 22. Furthermore, a plurality of first grooves 21 and a plurality of second grooves 22 may be formed alternately along the axial direction of the second roll 12A. Furthermore, the positions at which the first grooves 21 and the second grooves 22 are formed may be set opposite to the positions shown in FIG. 8. Furthermore, the first grooves 21 and the second grooves 22 do not necessarily need to be continuous, and a smooth surface where no grooves 20 are formed may be provided on part of the surface of the second roll 12A.

[0094] Furthermore, in the above-described method for peeling plate-like particles using the batch-type two-roll kneader 10A, an example has been shown in which the pair of regulating members 40a, 40b are moved back and forth while maintaining the size of the kneading region 42 during kneading of the composite material, but the movement of the pair of regulating members 40a, 40b during kneading is not limited to this. For example, the pair of regulating members 40a, 40b may move while widening or narrowing the size of the kneading region 42 during kneading of the composite material. Furthermore, the direction and speed of movement of the pair of regulating members 40a, 40b can be set as appropriate. [Explanation of symbols]

[0095] 10. Continuous two-roll kneader 11 Roll 1 12 Roll 2 13 Gap 14 groove 15 groove 10A Batch type two-roll kneader 11A Roll 1 12A Roll 2 40a, 40b Regulating member 42 Mixing area 20 grooves 21 First groove 22 Second groove

Claims

1. A process for producing a composite material, the process comprising filling plate-like particles into a material selected from epoxy resin, silicone resin, polyethylene, polypropylene, or rubber as a main material, and setting the amount of the plate-like particles to be added to the main material to be 20 to 90 vol%; a step of introducing a predetermined amount of the composite material into a batch-type two-roll kneader including a first roll and a second roll arranged adjacent to the first roll and parallel to the axis of the first roll, the batch-type two-roll kneader being capable of adjusting the rotation speeds of the first roll and the second roll; a peeling step of kneading the composite material with the batch-type two-roll kneader to peel off the plate-like particles; and a step of discharging the kneaded composite material after the kneading for a predetermined time has been completed. A method for peeling off plate-like particles, comprising:

2. The method for peeling off plate-like particles according to claim 1, The batch-type two-roll kneader includes a pair of regulating members arranged side by side at a predetermined interval along the axial direction of the first roll and the second roll, In the step of feeding the composite material, the composite material is fed into a kneading region defined by the pair of regulating members. A method for peeling off plate-like particles, comprising:

3. A method for peeling off plate-like particles according to claim 1 or claim 2, Boron nitride particles are selected as the plate-like particles, In the step of producing the composite material, the amount of the boron nitride particles added to the main material is set to 50 to 70 vol %. A method for peeling off plate-like particles, comprising:

4. The method for peeling off plate-like particles according to any one of claims 1 to 3, In the peeling step, the rotational speed ratio between the first roll and the second roll is set to 1:0.5 to 1:

1. A method for peeling off plate-like particles, comprising:

5. The method for peeling off plate-like particles according to any one of claims 1 to 4, the batch-type two-roll kneader is configured so that the surface temperatures of the first roll and the second roll are adjustable; The epoxy resin or the silicone resin, which is a thermosetting resin, is selected as the main material; In the peeling step, the surface temperatures of the first roll and the second roll are set to a temperature lower than the temperature at which the thermosetting resin starts to harden. A method for peeling off plate-like particles, comprising:

6. The method for peeling off plate-like particles according to any one of claims 1 to 4, the batch-type two-roll kneader is configured so that the surface temperatures of the first roll and the second roll are adjustable; The polyethylene or polypropylene, which is a thermoplastic resin, is selected as the main material, In the peeling step, the surface temperatures of the first roll and the second roll are set to a temperature higher than the temperature at which the thermoplastic resin melts. A method for peeling off plate-like particles, comprising:

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