JP7471573B2 - High pressure injection treatment equipment - Google Patents

Description

The present invention relates to a method for circulating the jet flow from a high-pressure nozzle and a high-pressure jet processing device used when wet-micronizing raw materials.

Microparticles, especially nanoparticles, are being studied and used in various fields because their size on the order of nanometers (nm) gives them an extremely large surface area and they exhibit unique physical properties due to the quantum size effect. These particles are being used widely in various material fields, such as electronic parts, pigments, cosmetics, pharmaceuticals, food, and pesticides. In particular, nanoparticles tend to aggregate easily, so in order to effectively utilize the properties of nanoparticles, appropriate dispersion and micronization processing that suits the properties of the nanoparticles is necessary. In recent years, efficient fiber defibration technology for nanofiberization of cellulose and other materials has also become an important technology for the practical use of these materials. In these micronization processes, high-pressure injection processing equipment, which micronizes the particles themselves by high-pressure injection from a nozzle with a raw material liquid mixed with the raw material particles, has been widely used to disperse and micronize these particles.

However, there is no established method for on-site evaluation of the state of the liquid processed by the high-pressure jet processing device, making it extremely difficult to find the optimal conditions for the process. Until now, the liquid processed by the high-pressure jet processing device was sampled and analyzed with a laser particle size distribution device for evaluation. For this reason, it took a long time to find the conditions for the micronization process, and the high speed of this process could not be fully utilized compared to processes that require media such as a bead mill.
In addition, in conventional high-pressure injection processing, it is believed that the collision phenomenon of fluids in a low-pressure chamber is effective for microfabrication, and various chambers such as collision-type chambers and opposed chambers have been developed. However, microfabrication processing with these devices requires dozens of processes for some materials, and further efficiency improvements are required.

In light of this background, the present inventors have proposed and developed several monitoring methods and monitoring devices for high-pressure injection processing apparatuses used in wet-type pulverization of raw materials.
Patent Document 1 discloses a method for evaluating a high-pressure jet processing device equipped with a nozzle according to any one of claims 1 to 6, which performs high-pressure jet processing by high-pressure jetting such that the average velocity inside the nozzle is 300 m/s or more to finely pulverize or defibrate the raw material liquid, the method comprising attaching an AE sensor to the high-pressure jet processing device, detecting an AE signal, and evaluating the performance of the fine-pulverization characteristics from the magnitude of the AE signal.

Patent document 2 discloses "(Claim 1) A monitoring method for a high-pressure injection processing device that atomizes particles by high-pressure injection of raw material liquid from a high-pressure nozzle at a predetermined pressure, the monitoring method for the high-pressure injection processing device is characterized in that a signal caused by cavitation occurring in the high-pressure nozzle during an operation in which the operation of high-pressure injection of the raw material liquid is repeated multiple times is detected, the level of the signal is evaluated as an effective value within a predetermined time, and when the amount of change in the effective value before and after the high-pressure injection process falls within a set range, it is determined that the particles have been atomized" and "(Claim 2) The monitoring method for the high-pressure injection processing device described in claim 1, characterized in that an AE sensor is attached to the high-pressure injection processing device and an AE signal caused by cavitation with a frequency of 0.2 MHz or more occurring in the high-pressure nozzle during the high-pressure injection is detected."

In the non-patent literature, a paper on ultrasonic spectroscopy reports an example of the particle size of a _TiO2 slurry and the attenuation of ultrasonic waves propagating therethrough.

JP 2017-177037 A Patent No. 6221120

DUKHIN, A. S. , GOETZ, P. J. , (1996), Acoustic Spectroscopy for Concentrated Polydisperse Clados with High Density Contrast, Langmuir, 12, pp. 4987-4997

In conventional high-pressure injection processing, it is believed that the collision phenomenon of fluids in a low-pressure chamber is effective for microfabrication, and various chambers have been developed, such as collision-type chambers and opposed chambers. However, microfabrication with these devices requires some materials to be processed dozens of times, and further efficiency improvements are needed.
Cavitation used in high-pressure injection processing is a phenomenon in which localized low pressure areas are generated due to turbulence in the liquid flow, and when the low-pressure areas fall below the vapor pressure of the liquid, bubbles are generated, and when the bubbles contract and collapse, a large impact force is generated. Since this processing mainly applies cavitation to microparticulation, this method can obtain a larger destructive force by generating cavitation at as high a pressure as possible. By monitoring the state of the high energy generated at this time at high pressure, i.e., the high-frequency cavitation, the destruction process and the state of the raw solution containing the introduced particles can be evaluated (Patent Document 1).

The inventor has found through research that in order to increase the efficiency of the above-mentioned micro-refining by cavitation, it is best to generate cavitation in a high-pressure region with as much energy as possible. By changing the high-pressure nozzle from a single stage to a multi-stage configuration and forming a high-pressure cavitation region from the second stage onwards, the region related to micro-refining is expanded and efficiency is improved (Patent Document 1). However, there was a phenomenon in which particles were not micro-refined even though there was a lot of cavitation. From this experiment, it was discovered that there was an unused micro-refining region within the nozzle, and in order to further increase efficiency, a new nozzle was invented that utilizes the flow caused by the injection and has a mechanism for actively sending raw material to the micro-refining region within the nozzle that is not being used for micro-refining.

The object of the present invention is to provide a high-precision high-pressure nozzle jet flow circulation method and high-pressure jet processing device that enables further efficient fine fiberization and effective defibration.

The present invention is a method for circulating the jet flow of a high-pressure nozzle, which is characterized in that in a high-pressure nozzle that atomizes raw material liquid by high-pressure jetting, a return means is provided for returning a portion of the raw material liquid jetted from the through hole of the high-pressure nozzle to the through hole on the upstream side of the high-pressure nozzle, and the raw material liquid is jetted again at high pressure from the through hole of the high-pressure nozzle. The return means is a return passage formed to return a portion of the raw material liquid jetted from the through hole of the high-pressure nozzle to the through hole on the upstream side of the high-pressure nozzle by utilizing the reaction of the jet flow, and/or is provided with an aspulator mechanism for creating a reduced pressure state by the Venturi effect using the flow of the fluid. The return means is a return passage formed to return a portion of the raw material liquid jetted from the through hole of the high-pressure nozzle to the through hole on the upstream side of the high-pressure nozzle by utilizing the jet flow, and is a return passage provided in the vicinity of the through hole of the high-pressure nozzle, and a portion of the raw material liquid includes the jet liquid generated around the jetted raw material liquid, and this jet liquid is returned to the through hole on the upstream side of the high-pressure nozzle by the return passage provided in the vicinity of the through hole of the high-pressure nozzle. Here, "using the jet flow" may mean that the raw material liquid to be returned to the through hole is in the area inside the high-pressure nozzle, or that a high-pressure nozzle is placed in a low-pressure chamber and an aspulator mechanism is provided to return the raw material liquid jetted into the low-pressure chamber. The aspulator mechanism is a mechanism that uses the flow of a fluid to create a reduced pressure state by the Venturi effect, and the present invention uses the phenomenon in which the raw material liquid is drawn in by being caught up in the high-speed jet flow.

It is also preferable to provide the return passage on the outer peripheral wall of a nozzle case that houses a plurality of high-pressure nozzles each consisting of a nozzle tip and a nozzle holder, and to provide a communication passage leading to the through hole of the high-pressure nozzle on the side portion of the nozzle tip and/or the nozzle holder, or to provide a communication passage leading to the through hole of the high-pressure nozzle in the gap between the nozzle tip and the nozzle holder, or to interpose a spacer between the high-pressure nozzles and provide a communication passage in the spacer that leads to the through hole of the high-pressure nozzle.
According to the present invention, the efficiency of the micro-fine grains can be improved by supplying the raw material liquid to the area where cavitation occurs but the raw material does not flow in that area. Therefore, it is expected that the number of times of the micro-fine grains treatment, which has been required in the past, can be significantly reduced.

The high-pressure injection process has two types of effects. One is "shear" caused by a large speed difference near the boundary of the high-speed flow inside the nozzle due to high-pressure injection. The other is "cavitation" (a physical phenomenon in which bubbles are generated and disappear in a short time due to pressure differences in a liquid flow) caused by negative pressure caused by the high-speed fluid due to high-pressure injection. Since "shear" is based on the speed difference, it only occurs at the interface of the fluid injected at high speed and high pressure. Therefore, its effect is difficult to extend to the entire liquid, and the micronization characteristics are not very good. On the other hand, cavitation often occurs in a cloud state on the outside of the flow injected from the through hole, so by making good use of that part, it is possible to make the effect more likely to extend to the entire liquid. Therefore, in order to make effective use of cavitation, we aimed to improve the micronization characteristics by devising a nozzle structure.
The inventors of the present application improved the efficiency of cavitation by increasing the number of stages of the high-pressure nozzle, which was previously a single nozzle, and realized a configuration with improved micronization performance. They then attempted to make further improvements, but the measurement data from the above monitoring showed that although cavitation occurred frequently, there were some results in which the efficiency of micronization did not improve. In other words, it was thought that there was an area in the nozzle where high-energy cavitation was occurring but where it was not acting on the raw material liquid. It was thought that this area was inside the high-pressure nozzle, and the efficiency of micronization was greatly improved by supplying material to this area through a return passage. Specifically, a prototype device was made with a multi-stage nozzle and a return passage (return means), and the experimental results were examined.

Specific actions of atomization include: 1. atomization by shear in the region with a large velocity gradient near the boundary of the jet flow (region (a) in Figure 11); and 2. atomization by high-pressure cavitation in the region outside the jet flow where the pressure is high (region (b) in Figure 11). In the case of a single nozzle, the pressure in region (b) is slightly higher near the nozzle tip, but the cavitation energy is not high enough to atomize the raw material liquid, so it is thought that the raw material liquid is not atomized. Therefore, a multi-stage high-pressure nozzle configuration is used to expand the high-pressure region, and a mechanism for replenishing the raw material to the high-pressure portion is formed, that is, a return passage is formed to return the raw material liquid sprayed from the through hole Na of the high-pressure nozzle case back to the through hole Na in the high-pressure nozzle case, and a part of the sprayed raw material liquid is returned to the through hole on the upstream side of the high-pressure nozzle for high-pressure spraying. At this time, it is important that the return passages Nt1 and Nt2 have an aspirator mechanism that uses the fluid to create a reduced pressure state through the Venturi effect, and that the liquid returns to the nozzle due to the reaction of the flow.

(Effect of aspulator on multi-stage nozzle)
Based on the research of the inventors of the present application, the flow of liquid in a nozzle is considered. There are three types of flow: laminar flow, turbulent flow, and jet flow. When the injection speed increases, the flow moves to the latter type. In the device for atomization of the present invention, the flow injected at high pressure becomes a jet flow, so there is a large velocity gradient at the boundary, but the inside has an almost uniform velocity. Therefore, large shear forces hardly act in this jet flow. On the other hand, large shear forces act on the boundary part of the flow. Also, when the velocity difference becomes large under a certain pressure, cavitation occurs outside. Generally, a phenomenon called cavitation cloud occurs. In this state, there are two types of regions where atomization occurs: (a) the boundary part with large shear forces and (b) cavitation occurring outside the flow. Important conditions from the viewpoint of atomization are given below (see FIG. 11).
(a) In order to enlarge the boundary area with large shear force, it is necessary to keep the flow speed as low as possible. In other words, it is important to avoid creating any part that acts as resistance to the flow so that a fast flow can occur.
(b) In order to enhance the destruction or atomization caused by cavitation, it is necessary to cause cavitation at a high speed and in a region of as high pressure as possible.
The above (a) requires that there be no obstacles and that a flow with excellent linearity be generated, and that the nozzle diameter be adjusted to prevent laminar flow, etc. For example, there is a restriction on the size of the diameter.
In addition, in the case of (b) above, a structure in which the high-pressure portion is expanded as much as possible (a multi-stage nozzle structure in which the through holes become larger toward the discharge side) is effective in preventing the pressure from dropping.
However, simply configuring high-pressure nozzles in multiple stages increases the area where high-energy cavitation occurs, but due to the structure, there is no circulation of the raw material to be atomized in that area, and efficiency may not increase simply because of damage to the nozzle holder, etc.
For example, in the case of the high-pressure injection device (multi-stage structure) shown in Fig. 9, it is conceivable that the raw material may enter the nozzle outlet on the low-pressure chamber side slightly due to the negative pressure caused by the flow, but almost no raw material enters the nozzle where the high-pressure cavitation works. Therefore, it was assumed that the efficiency of micronization could be improved by providing an aspulator As for returning the raw material liquid remaining in the low-pressure chamber after injection to the through hole of the high-pressure nozzle and injecting it again at high pressure.

In the present invention, it is possible to divide the high-pressure nozzle using an aspirator mechanism or a structure that applies a reaction force to the flow, and return the air from the low-pressure chamber to the through hole of the high-pressure nozzle through the divided gap, and then spray it again at high pressure. In addition, the return passage can be easily manufactured by dividing the high-pressure nozzle and using the divided gap to connect the nozzle through hole and the return passage.

The high-pressure nozzle of the present invention is a multi-stage type in which a plurality of high-pressure nozzles, each of which is composed of a nozzle tip and a nozzle holder, is connected together, and is provided with a nozzle case that houses the plurality of connected high-pressure nozzles. The nozzle case is provided with a return passage, and the raw material liquid in the area adjacent to the through hole provided in the Nth nozzle holder is returned to a position immediately behind the first high-pressure nozzle on the most upstream side.
In addition, it is preferable that the high-pressure nozzle of the present invention is a multi-stage type, and spacers are interposed between the multiple high-pressure nozzles, and communication passages are provided by providing notches or grooves in the spacers, or by opening through holes or dividing the spacers, and these are connected to the return passages of the nozzle case to form a return means (aspulator) that returns the raw material to the through holes Na of the high-pressure nozzle (Figure 5 (b)). In this case, the nozzle diameter on the low-pressure side is made larger than that on the high-pressure side so as not to affect the high-speed flow, and the return passages and communication passages that constitute the return means (aspulator) are preferably installed axially symmetrically with respect to the flow direction so as not to affect the jet flow.
According to the present invention, in the case of a multi-stage system using multiple high-pressure nozzles, a part of the raw material liquid remaining in the low-pressure chamber is returned from the low-pressure chamber to the through-hole of the high-pressure nozzle by the return means, which enables processing in the cavitation region that could not be used before. In addition, by bending the flow path (by providing a corner in the return passage), it becomes possible to apply a large shear force to the raw material (see FIG. 28(a)). These actions enable efficient fine reduction and defibration. However, in order to achieve this effect, it is important not to interfere with the linear flow, for example by providing the communication passage constituting the return means immediately before the nozzle tip.

The present invention is characterized in that the through hole of the high pressure nozzle is formed in the center of the high pressure nozzle, and the return passage is provided in a plurality of positions symmetrically around the outer periphery of the through hole of the high pressure nozzle with the high pressure nozzle as an axis. Here, it is preferable that the return passages are arranged in a plurality of positions symmetrically around the through hole of the high pressure nozzle, and that the total diameter of the return passages is larger than the high pressure nozzle diameter Dnm.
According to the present invention, in addition to the amount that can be processed through the high-pressure nozzle hole, the enlarged nozzle hole portion on the downstream side increases the volume that is subjected to the micronizing effect such as cavitation, making it possible to efficiently micronize and defibrate the raw material.

According to the present invention, high-energy cavitation occurs, but efficient micronization can be achieved by using a return means to supply raw material to areas that have not been used for micronization. Therefore, compared to conventional cases where a circulation path is formed outside the device and multiple micronizations are performed, extremely efficient micronization is achieved, and one micronization with the high-pressure injection device of the present invention is equivalent to multiple conventional injections, making more uniform micronization possible. As a result, the production of monodispersed suspensions and uniform fibers can be easily achieved.

1 is a conceptual diagram showing cavitation occurring in a high-pressure nozzle of a high-pressure injection processing device according to an embodiment of the present invention. FIG. 1 is a flow chart showing the procedure of a monitoring method for a high-pressure injection treatment device according to an embodiment of the present invention. 1A to 1C are diagrams illustrating a process in which particles in a raw material liquid injected at high pressure are atomized by cavitation collapse. FIG. 2 is a cross-sectional view showing a schematic diagram of a multi-stage high-pressure nozzle in a high-pressure injection treatment device. 1A and 1B are schematic diagrams showing a single high-pressure nozzle in a high-pressure injection processing device, in which (a) is a cross-sectional view showing the nozzle N1, and (b) is an example in which the ratio (Wn/Dn) of the thickness Wn to the diameter Dn of the nozzle tip through hole is 10. FIG. 2 is a perspective view showing a high-pressure nozzle used in the first embodiment to which the present invention is applied. FIG. 2 is a perspective view showing the configuration of only a multi-stage high-pressure nozzle used in the above embodiment to which the present invention is applied. FIG. 2 is a development view showing the configuration of only the multi-stage high-pressure nozzle used in the above embodiment to which the present invention is applied. FIG. 2 is a perspective view showing a nozzle case that houses a multi-stage high-pressure nozzle used in the above embodiment to which the present invention is applied and has a return passage. FIG. 2 is a diagram showing a state in which a multi-stage high-pressure nozzle is housed in a nozzle case used in the above embodiment to which the present invention is applied. FIG. 1 is a schematic diagram showing the flow of the jet liquid around a single high-pressure nozzle and the atomized region. FIG. 2 is a schematic diagram showing the multi-stage high-pressure nozzle of the above embodiment to which the present invention is applied and the circulation state of the jet flow. FIG. 2 is a schematic diagram showing the multi-stage high-pressure nozzle of the above embodiment to which the present invention is applied and the circulation state of the jet flow. FIG. 13 is a diagram showing the magnitude of AE and the viscosity η of the treatment liquid when a single nozzle is used in an experiment according to the present invention. FIG. 13 is a diagram showing AE and η when a multi-stage high-pressure nozzle is used in an experiment in the present invention. FIG. 13 is a diagram showing AE and η when a multi-stage high-pressure nozzle in which one aspulator is disposed between N2 and N3 is used in an experiment in the present invention. FIG. 13 is a diagram showing AE and η when a multi-stage high-pressure nozzle having one aspulator disposed between N1 and N2 is used in an experiment according to the present invention. FIG. 13 is a diagram showing AE and η when a multi-stage high-pressure nozzle having two aspulators arranged between N2 and N3 is used in an experiment according to the present invention. FIG. 13 is a diagram showing AE and η when a multi-stage high-pressure nozzle having two aspulators arranged between N1 and N2 is used in an experiment of the present invention. FIG. 13 is a diagram showing AE and η when an aspulator is used as a multi-stage high-pressure nozzle having an intermediate body disposed between N1 and N2 in an experiment according to the present invention. FIG. 13 is a diagram showing AE and η when an aspulator is used in an experiment of the present invention, in which an intermediate aspulator is disposed between N1 and N2 and a multi-stage high-pressure nozzle in which two aspulators are disposed immediately before N2 is used. FIG. 13 is a graph showing AE and η when an intermediate body is disposed between N1 and N2 and a multi-stage high-pressure nozzle having two aspulators disposed on the intermediate body is used in an experiment according to the present invention. FIG. 13 is a diagram showing AE and η when a multi-stage high-pressure nozzle having a five-stage structure is used in an experiment in the present invention. FIG. 13 is a diagram showing AE and η when two aspulators are arranged between N1-N2 of a five-stage multi-stage high-pressure nozzle in an experiment according to the present invention. 1 is a microscope image of a raw material before being pulverized, used in an experiment in the present invention. 1 is a microscope image of a feedstock atomized using a single high pressure nozzle in an experiment according to the present invention. 1 is a microscope image of a raw material pulverized using a multi-stage high-pressure nozzle (three stages) in an experiment of the present invention. This is a microscope image of a raw material that was pulverized using a multi-stage high-pressure nozzle (3 stages) with two aspirators arranged between N1 and N2 in an experiment of the present invention. FIG. 11 is a diagram summarizing the results of an experiment in the present invention, showing the number of treatments Np and the viscosity η of the treatment liquid for each type of nozzle used. FIG. 2 is a schematic diagram showing a location where atomization occurs inside a multi-stage high-pressure nozzle. FIG. 2 is a schematic diagram showing an effective arrangement position of an aspulator in a multi-stage high-pressure nozzle according to an embodiment of the present invention. FIG. 11 is a diagram showing a multi-stage high-pressure nozzle according to another embodiment of the present invention. FIG. 11 is a diagram showing a multi-stage high-pressure nozzle according to another embodiment of the present invention. FIG. 11 is a diagram showing a multi-stage high-pressure nozzle according to another embodiment of the present invention. FIG. 11 is a diagram showing a multi-stage high-pressure nozzle according to another embodiment of the present invention. FIG. 11 is a diagram showing a multi-stage high-pressure nozzle according to another embodiment of the present invention.

The following describes in detail an embodiment of the present invention with reference to the drawings.

(Configuration of the high-pressure injection treatment device used in the present invention)
FIG. 1 is a block diagram showing a schematic configuration of a high-pressure chamber 500, a low-pressure chamber 40, and a high-pressure nozzle 400 (nozzle case 100) and its surroundings of the high-pressure injection processing device of the present invention.
The direction of movement of the raw material liquid 10 will be described in detail below, with the high pressure chamber side of the high pressure injection processing device being the upstream side and the low pressure chamber side being the downstream side.
In the present invention, the high-pressure injection processing device is a device equipped with a drive control unit for pressurizing the raw material liquid to 100 MPa or more by driving and controlling the high-pressure pump, a high-pressure pump for pressurizing the raw material liquid 10 to 100 MPa or more, a raw material tank for introducing the raw material liquid 10, and a high-pressure chamber. The raw material liquid 10 (and the particles 1a in 10) introduced and pressurized to 100 MPa or more is accelerated around the high-pressure nozzle 400, and becomes a high-speed flow, i.e., a jet flow, when passing through the nozzle, and cavitation occurs around it. The particles in the raw material liquid are finely divided by the cavitation. After that, in the low-pressure chamber 40, a supercavitation state with many bubbles is created, and a suspension 20 containing stirred and finely divided particles is generated and discharged from the outlet 402. This process is repeated. The number of injections is represented by N _P , and a high processing effect means that the N _P required to obtain fine particles of the same diameter is small.
The low pressure chamber 40 includes a single nozzle chamber, an oblique collision chamber, a ball collision chamber, etc., and houses and arranges the high pressure nozzle 400 (nozzle case 100).

(About ingredients)
The raw material mixture 10 is, for example, a mixture of particles 1a (raw material) and water or an organic solvent. A surfactant may be included depending on the application. In the present invention, the particles 1a (raw material) contained in the raw material mixture 10 include titanium oxide, barium titanate, ferrite, alumina, silica, PZT (lead zirconate titanate), and other known metal, oxide, and carbide fine particles. It is also possible to use fiber-shaped materials such as cellulose and carbon nanotubes (CNT). The raw material mixture 10 is a suspension-like liquid containing the fine particles and their aggregates.

(About AE signals)
In order to evaluate the state of miniaturization, it is possible to attach a monitoring device 1 for the high-pressure injection processing device to the high-pressure injection processing device and perform performance evaluation of the device such as the high-pressure nozzle and the high-pressure chamber. In this case, the device is provided with an AE sensor 9 attached to the high-pressure injection processing device and a signal processing and evaluation means 8 for processing the AE signal detected by the AE sensor 9 and judging the performance evaluation of the device.
As mentioned above, the micronization phenomenon in high-pressure injection processing is mainly caused by cavitation occurring in the high-pressure part. Cavitation occurring in the high-pressure injection processing device is classified into (1) low-energy cavitation occurring on the low-pressure side such as the low-pressure chamber and (2) high-energy cavitation occurring in the high-pressure nozzle. Since the micronization of the raw material liquid particles is an impact based on the collapse of the cavitation (2) mentioned above, the degree of micronization of the particles and the crushing force due to the flow can be evaluated by measuring the AE signal due to the high-energy cavitation (2), i.e., the high-frequency signal (0.2 MHz or more), using an AE sensor.

The signal processing and judgment means is a device that can output a signal from an AE sensor so that the frequency and level can be determined, and can also judge whether the signal is good or bad. Examples of the signal processing and judgment means include an AE tester, an FFT analyzer, a spectrum analyzer, a digital oscilloscope, and other devices that calculate and record effective values. The AE tester is a device that combines a preamplifier, a filter, a discriminator, and a rate meter, and a commercially available product can be used.

The high-pressure injection processing device can be configured to include a resonant AE sensor for executing the monitoring method and a signal processing and judgment means for processing and judging a signal from the resonant AE sensor, and in an operation in which the work of high-pressure injection of the raw material liquid is repeated multiple times, the high-pressure injection process can be repeated until the signal processing and judgment means judges that the particle micronization process is complete. In an operation in which the work of high-pressure injection of the raw material liquid is repeated multiple times, the level of the AE signal can be evaluated as an effective value within a predetermined time, and when the amount of change in the effective value before and after the high-pressure injection process falls within a set range, it can be judged that the particle micronization process is complete.

(Regarding the monitoring method of the present invention)
FIG. 2 is a flow diagram showing the procedure of the monitoring method of the high-pressure injection processing device according to the embodiment of the present invention. In this embodiment, first, the AE sensor is attached to a location where ultrasonic waves generated by the high-pressure nozzle of the high-pressure injection processing device can be detected (step S1). If the high-frequency ultrasonic waves generated by the nozzle pass through the suspension (slurry) and are propagated by the members constituting the high-pressure chamber, the high-pressure nozzle, and the low-pressure chamber, the AE sensor may be attached to any of them. Next, the raw material mixture is subjected to high-pressure injection processing at a predetermined pressure from the high-pressure nozzle of the high-pressure injection processing device (step S2). Then, the AE sensor detects ultrasonic waves having a frequency of 0.2 MHz or more generated in the nozzle during the high-pressure injection processing, and the signal level from the AE sensor is evaluated (step S3). Then, it is determined whether or not to repeat the high-pressure injection processing (step S4). If there is a change in the signal level in step S4, it is determined that the particles have not yet been sufficiently atomized, and the high-pressure injection processing is repeated. If there is no change in the signal level in step S4, or if the signal level reaches a predetermined level, it is determined that the particles have been atomized, and the processing is terminated.

(Regarding the monitoring device of the present invention)
1 is a conceptual diagram showing a signal generated by cavitation detected by a monitoring device of a high-pressure jet processing device according to an embodiment of the present invention. The signal includes a cavitation signal AE _s generated from the liquid due to the flow, a cavitation signal AE _p generated from the particles, and the propagation characteristics (attenuation rate) _Attu of those ultrasonic waves. This embodiment is a monitoring device 1 for a high-pressure jet processing device that high-pressure jets a raw material liquid 10 from a high-pressure nozzle 400 at a predetermined pressure to micronize particles, and includes an AE sensor 9 attached to the high-pressure jet processing device and a signal processing and judgment means 8 that processes and judges the AE signal detected by the AE sensor 9. The AE sensor 9 is a resonant type AE sensor with a resonant frequency of 0.5 MHz. The signal processing and judgment means 8 can be, for example, an AE tester, an FFT analyzer, a spectrum analyzer, a digital oscilloscope, or other effective value calculation and recording display device.

The flow velocity of the liquid in the high-pressure nozzle 400 can be accurately determined from the nozzle diameter and the signal generation time of the AE sensor 9. Near the outlet of the high-pressure nozzle 400, σ _c is 0.6 or less, which is considered to be a state of supercavitation, that is, a state in which there are many bubbles on the side of the nozzle and a strong stirring effect can be obtained.
On the other hand, in the region from the high-pressure nozzle 400 into the low-pressure chamber 40, the cavitation collapse energy also decreases rapidly in the reduced pressure atmosphere. In this region, the effect of fine particle breakage due to strong cavitation collapse cannot be obtained. The occurrence of cavitation continues for a while from the supercavitation until the flow velocity settles to near zero, and finally disappears. Therefore, the high-energy cavitation occurring inside the high-pressure nozzle 400 disappears in a short time, but low-pressure cavitation occurs for a while in the low-pressure chamber. As a result, the low-frequency AE signal continues to be generated for a while, as if it has a lingering effect, even after the end of injection. The low-pressure chamber is a component indicated by the symbol 40, and houses the high-pressure nozzle (FIG. 1).

In the case of raw material liquid (slurry) containing large particles with a particle size of several microns in the high-pressure nozzle 400, a signal _AEp due to cavitation is generated from the particles. This shows different sizes depending on the number and particle shape. Cavitation occurs when a part that becomes negative pressure when a fluid flows on a solid surface is generated and the pressure drops below the vapor pressure of the fluid. Therefore, it is considered that the negative pressure part that is the source of bubbles becomes larger as the particle size increases, and therefore the energy, i.e., the signal level of the high-frequency AE signal, becomes larger. From this signal level, the particle size in the slurry can be estimated. This is because cavitation is more likely to occur in the slurry than in the case of only the fluid, and this signal begins to be generated near the entrance of the high-pressure nozzle 400.

In actual measurements, as shown in FIG. 1, there may be considered an AE signal of ultrasonic waves propagating from the direction of the low pressure chamber 40 and an AE signal of ultrasonic waves propagating through the liquid material 10 in the direction of the high pressure chamber 500.
Next, the generated signal and its propagation path will be described. From the change in the cavitation number, cavitation occurs in the middle of the nozzle, and then becomes supercavitation. Since the latter half of the nozzle is in a state of supercavitation and there are many large low-pressure cavitations in the direction of the low-pressure chamber 40, there is a large difference in acoustic impedance between the raw material liquid in this part and this part. As a result, the ultrasonic waves that are largely reflected and generated are difficult to propagate in the direction of the low-pressure chamber 40. Therefore, it is considered that the ultrasonic waves measured as AE signals propagate in the liquid where cavitation is not occurring in the opposite direction to the traveling direction of the high-pressure nozzle 400. When the propagation speed of the ultrasonic waves in the solution is calculated, the propagation speed of the ultrasonic waves is 1500 m/s, which is greater than the flow speed of 400 m/s, so they propagate efficiently in this direction.

In the high pressure nozzle 400, the AE signal has sources of _AEp and _AEs , and when the AE sensor 9 is attached, many signals propagating through the suspension (slurry) 10 are detected. This is naturally influenced by the propagation characteristics (attenuation rate). The propagation characteristics (attenuation characteristics) are said to be highly dependent on the particle size, and it is shown that ultrasonic attenuation is large in a slurry containing particles of 1 micron or more.

As described above, the measured AE signal _AEm is the sum of the fluid cavitation signal _AEs generated from the solvent and the particle cavitation signal _AEp generated from the particles in the high-pressure nozzle, and reflects the ultrasonic propagation characteristic (attenuation rate) _Attu . Therefore, the measured signal strength _AEm is expressed by the following equation: _AEm = ( _AEs + _AEp ) x _Attu .
In this formula, when the slurry concentration is high, _AEp becomes large and the change in particle size can be accurately captured. On the other hand, when the slurry concentration is low, _AEs becomes large and _AEp , which contains information on particle size, is buried. As a result, accurate evaluation cannot be performed.

Fig. 3 is a schematic diagram showing cavitation occurring in the raw material liquid 10 injected at high pressure and the resulting atomization. In Fig. 3, reference numeral 1a denotes raw material particles immediately before atomization, reference numeral 1b denotes particles in the middle of the atomization process, and reference numeral 1c denotes atomized particles.
When considering the flow, the way in which cavitation occurs also depends greatly on the particle shape. For example, as shown in Fig. 3(a), if the particles 1a in the raw material liquid 10 have a distorted shape such as an aggregate, negative pressure is likely to occur at the part where the curvature suddenly becomes small, and cavitation 700 occurs starting from that point, causing the particles to collapse. During this contraction process, the pressure that draws in the particles in contact and the impact of the collapse are applied to that part. In other words, more effective micronization can be achieved with distorted particles that have undergone necking.
On the other hand, as shown in FIG. 3(b), when the particles 1b are spherical, the areas that are easily subject to negative pressure are reduced. In other words, the size of the cavitation 700 is reduced, and the collapse energy is also reduced. As shown in FIG. 3(c), when the particles 1c are in a minute spherical shape, the cavitation size is reduced, and the collapse energy is also reduced. As a result, it is considered that the impact due to the collapse does not exceed the stress required to destroy the particles 1c, and the micronization does not proceed. This state means that the micronization process is completed. Due to this effect, the high-pressure injection process can produce a monodisperse slurry with a uniform particle size.

This means that the smaller the particle diameter, the more difficult it becomes for this high-pressure injection device to produce the micronization phenomenon, and only the effect of strong stirring by low-energy cavitation and supercavitation occurring in the low-pressure chamber 40 can be utilized. Due to this destructive force--the limit of micronization, there is no change in the particle diameter or shape in the slurry. This is the limit of the micronization process by high-pressure injection, and indicates that the process has ended.
In addition, although the impact on the particle surface with this high-pressure injection device does not directly lead to finer particles, it is much stronger than ultrasonic cleaning, etc., and it is expected to have the effect of removing contaminants from the particle surface and making the particle into a spherical shape. These are the features of high-pressure injection processing.

(About the viscosity of the suspension)
In addition to the AE signal, the refining of the raw material can also be evaluated by the viscosity η of the suspension after the high-pressure injection process. For example, in the case of a refining process to turn cellulose into nanofibers, the process starts with the refining of the raw material particles, followed by nanofiberization of the produced fine particles, forming nanofiber aggregates. Furthermore, as the process proceeds, the produced aggregates also go through a process of becoming smaller (the length of the nanofibers becomes shorter). This change is related to the entanglement of the aggregates, so the refining performance can be measured as a change in viscosity. In other words, the refining performance can be evaluated by the magnitude of the maximum viscosity and the number of treatments N _P at that time.
As the viscometer, a general rotational or vibration type viscometer can be used.

(Multi-stage high-pressure nozzle)
FIG. 4 is a cross-sectional view showing the multi-stage high-pressure nozzle N2.
The high-pressure nozzle according to the embodiment of the present invention is composed of a single nozzle holder Nh and a nozzle tip Nn. It has been found that for micro-finishing, a nozzle in which Dn of the nozzle tip is small, Wn is as thick as possible, and Wn/Dn is 10 or more is effective (see FIG. 5(b)). However, it is very difficult to form a small Dn when Wn is thick in the material of the nozzle tip, such as single crystal diamond, sintered diamond, or polycrystalline diamond.
Therefore, the high pressure nozzle of the present invention is formed by combining a plurality (multi-stage) of nozzle tips Nn _m (m=1, 2, . . . , M) and a plurality (multi-stage) of nozzle holders Nh _m (m=1, 2, . . . , M).

The multi-stage high-pressure nozzle is composed of multiple nozzle tips Nn _m (m = 1, 2, ..., M) and multiple nozzle holders Nh _m (m = 1, 2, ..., M), which are attached in a line from the upstream side to the downstream side in the order Nn ₁ , Nh ₁ , Nn ₂ , Nh ₂ , Nn ₃ , Nh ₃ , ..., Nn _M , Nh _M , and the through holes of the nozzle tips Nn _m and the nozzle holders Nh _m are all formed so as to be coaxial with each other.
The number M of nozzle tips Nn _m (m=1, 2, . . . , M) and nozzle holders Nh _m (m=1, 2, . . . , M) is preferably two or more, and more preferably three.
A cylindrical through-hole is provided at the center of the nozzle tip Nn _m (m=1, 2, ..., M). The material of the nozzle tip Nn _m is single crystal diamond, sintered diamond, polycrystalline diamond, or the like.
The nozzle holder _Nhm is a holder for fixing the nozzle tip _Nnm , and is attached to the high pressure chamber 500 on the upstream side and connected to the low pressure chamber 40 on the downstream side. A cylindrical through hole is provided in the center of the nozzle holder _Nhm as in the nozzle tip _Nnm (m = 1, 2, ..., M). The material of the nozzle holder _Nhm is a SUS-based metal such as SUS630.
The nozzle tip _Nn1 located on the most upstream side is an inlet for high-pressure spraying of the pressurized raw material mixture 10 toward the low-pressure chamber 40 on the downstream side, and is housed and attached in a nozzle holder _Nh1 .
The diameter Dn _m (m = 1, 2, ..., M) of the through hole of the nozzle tip Nn _m is preferably 0.2 mm or less in order to achieve a high flow rate in the multi-stage high pressure nozzle. The diameter Dn ₁ of the through hole of the nozzle tip Nn ₁ located most upstream is set to be the smallest, and the diameters Dn ₂ , Dn ₃ , ..., Dn _M of the through holes of the other nozzle tips Nn ₂ , Nn ₃ , ..., Nn _M are set to be larger than the diameter Dn ₁ .

Diameter Dn ₁ is 0.1 mm to 0.16 mm (0.16 mm or less), and other Dn _m (m
= 2, ..., M) is preferably 0.16 mm or more and 0.8 mm or less, and more preferably 0.2 mm.
In addition, the thickness _Wnm (m = 1, 2, ..., M) of the through hole of the nozzle chip _Nnm is made sufficiently larger than the diameter _Dn1 of the through hole of the nozzle chip _{Nn1 , as shown in (Equation 4) (the ratio of the diameter Dn1 of the through hole of the nozzle chip Nn1 to the sum of the thicknesses Wnm (m = 1, 2, ..., M) of the through hole of the nozzle chip Nnm is made 10 or more} ).

By using the multi-stage high-pressure nozzle, efficient micro-processing can be achieved by combining multiple nozzle tips with short holes, placing the nozzle with the smallest diameter hole on the most upstream side, and making the diameter of the holes in the other nozzles somewhat larger, without forming a nozzle tip with a small diameter and long holes. In other words, it is possible to obtain the same effect as when a nozzle tip with a long hole is used in the area where the shear force is applied. Furthermore, the multi-stage type makes it possible to increase the volume of the high-pressure cavitation area, further improving processing efficiency. In addition, when making the nozzle, there is no need to drill long small holes in the hard material that will become the nozzle tip, such as single crystal diamond, sintered diamond, or polycrystalline diamond, making it easier to manufacture.

(First embodiment of the present invention)
As the high-pressure injection treatment device, a Starburst Mini HJP-25001 manufactured by Sugino Machine Co., Ltd. was used, and as the low-pressure chambers 40, ball collision chambers were used.

6 to 10 are diagrams showing the details of the multi-stage high-pressure nozzle of this embodiment.
FIG. 6 is a cross-sectional perspective view of the high-pressure nozzle 400, showing that the nozzle tip Nn is incorporated into the nozzle holder Nh, and that the nozzle tip Nn and the nozzle holder Nh are respectively provided with through holes Nan and Nah on the same axis.
Figure 7 is an oblique view showing the structure of a multi-stage high-pressure nozzle in which multiple high-pressure nozzles 400 are arranged, and shows that three high-pressure nozzles are arranged (N1, N2, N3 from the upstream side) and a first spacer 5A and a second spacer 5B are interposed between the high-pressure nozzles from the upstream side.
FIG. 8 is a development view of the multi-stage high-pressure nozzle shown in FIG. 7, and the first spacer 5A is provided with two grooves as communication passages, vertically symmetrical with respect to the axis of the through hole.
FIG. 9 is a cross-sectional perspective view of a nozzle case 100 that houses a multi-stage high-pressure nozzle, and is provided with a through hole Nac through which the raw material liquid is sprayed at high pressure, and a pair of return passages Nt1, Nt2 for returning the suspension remaining in the low-pressure chamber 40 after high-pressure spraying to the high-pressure nozzle.
The pair of return passages Nt1 and Nt2 are provided at symmetrical positions with respect to the through hole Nac as an axis, and are connected to the communication passage provided in the first spacer shown in FIG.
These return passages Nt1, Nt2 and communication passages may be provided in a plurality of symmetrical positions with respect to the through hole as an axis, or may be provided in a cross shape or radially at finer intervals.
Figure 10 is a cross-sectional perspective view (a) showing three high-pressure nozzles (N1, N2, N3) and a first spacer 5A and a second spacer 5B interposed between the high-pressure nozzles stored in a nozzle case 100, and a cross-sectional view (b) showing the relationship between the spray flow of the raw material liquid and the flow of the suspension returning to the high-pressure nozzle after spraying.
In addition, the multi-stage high-pressure nozzle of the actual device is stored by being pushed into the high-pressure chamber 500 of the high-pressure injection processing device via a circular sealing member (packing) arranged on the upstream surface of N1 to prevent leakage, but this is not shown in the figure to clarify the drawing.

Here, the high-pressure nozzles (N1, N2, N3) are each composed of a nozzle tip provided with a through hole Nan and a nozzle holder provided with a through hole Nah, and the through hole diameter Dn of the nozzle tip Nn is smaller than the through hole diameter Dh of the nozzle holder Nh. Also, the return passages Nt1, Nt2 are arranged in a plurality of positions symmetrically about the through hole axis in the nozzle case 100, and the cross-sectional area of the total diameters of these is larger than the difference between the cross-sectional area of the maximum through hole diameter Dnm of the high-pressure nozzle and the cross-sectional area of the minimum through hole diameter Dnm.
For example, in the multi-stage high-pressure nozzle, it is preferable to return the suspension after high-pressure injection to the nozzle through hole Na between the first nozzle N1 and the second nozzle N2 on the upstream side via the return passage and the communication passage. If the return passages Nt1 and Nt2 are provided on the nozzle case side of the boundary between the nozzle case 100 and the high-pressure nozzle 400, it is relatively easy to manufacture.

Hereinafter, the mechanism for returning the suspension in the low-pressure chamber to the high-pressure nozzle, which is composed of the return passage Nt and the communication passage 5c, will be described as an aspulator As.
(About the aspirator effect in multi-stage nozzles)
Based on previous research, we consider the flow of injected liquid inside a high-pressure nozzle. The inside of a flow (jet flow) injected at high pressure has an almost uniform velocity, so large shear forces are unlikely to act there. On the other hand, there is a large velocity gradient at the outer boundary of the flow, so large shear forces act there. Furthermore, if the velocity gradient in that area becomes large, cavitation will spread to the far outside (Figure 11).
Considering this phenomenon, there are two types of regions where the micro-dispersion occurs: (a) boundary areas where there is a large shear force, and (b) cavitation that occurs outside the flow.
(a) In order to maximize the particle size reduction effect at the boundary where there is a large shear force, it is necessary to keep the flow speed as low as possible. In other words, a linear flow is more effective than a diffusing flow.
(b) To increase the micronization effect of cavitation, it is necessary to cause cavitation at a high speed and in a pressure range as high as possible. For (a) above, a high-pressure nozzle capable of generating a flow with excellent linearity is preferable. For (b) above, a structure in which the high-pressure portion is as wide as possible (multi-stage high-pressure nozzle structure) is effective in preventing pressure drop.
However, simply adopting a multi-stage structure increases the area where high-energy cavitation occurs, but due to the structure, there is no supply of raw material to be finely divided in that area, and the processing efficiency does not increase, as the high-pressure nozzle is simply damaged.
For example, in the case of the multi-stage structure shown in Fig. 12, it is possible that a small amount of raw material may enter the outlet of the high-pressure nozzle on the low-pressure side due to the negative pressure caused by the flow, but almost no raw material enters the high-pressure nozzle where the high-pressure cavitation for fine particle size works. Therefore, it is considered that the efficiency of fine particle size can be improved by providing a return means (aspulator) that returns the raw material from the low-pressure chamber 40 to the high-pressure nozzle. Experiments were carried out with the following nozzle structure to examine its effects.

(Experimental details)
A 2% raw material solution of crystalline cellulose powder was prepared, and various prototype nozzles were attached to a Starburst Mini HJP-25001 manufactured by Sugino Machine Co., Ltd., and the solution was sprayed at high pressure at 200 MPa. The AE signal during the process and the viscosity after the process were measured. The viscometer was a vibration viscometer VM-10A manufactured by Sekonic Co., Ltd. The cellulose particles were finely divided and nanofiberization was further promoted in this high-pressure spray process. Therefore, as the amount of nanofibers in the liquid increases, the viscosity of the liquid increases. As the nanofibers are further reduced in length (more precisely, as agglomerates of nanofibers) the viscosity tends to decrease. Therefore, the micronization performance of the device can be evaluated by the number of times that a large viscosity is reached with as few treatments as possible, and the magnitude of that viscosity.
In order to investigate the effect of the aspulator As, the following experiment was carried out. The notation of the multi-stage high-pressure nozzle is, for example, "M010202" when the through-hole diameter _Dn1 of the upstream first nozzle N1 is 0.1 mm, the through-hole diameter _Dn2 of the second nozzle N2 is 0.2 mm, and the through-hole diameter _Dn3 of the downstream third nozzle N3 is 0.2 mm, and the experiment was carried out by arranging the aspulator As between the high-pressure nozzles. Here, in the multi-stage high-pressure nozzle M010202, the insertion position of the aspulator As is indicated as "A", and when there are two insertion positions (arranged symmetrically around the through-hole), it is indicated as "AA". That is, FIG. 13 is a schematic diagram for explaining the principle of the high-pressure injection device of the present invention, and is indicated as "M01AA0202".

The contents of the experiment are as follows:
Experiment A - When there is one aspulator As High pressure nozzle (N1: _Dn1 = 0.1 mm + _Dh1 = 0.8 mm, N2: _Dn2 = 0.2 mm + _Dh2 = 0.8 mm, N3: _Dn3 = 0.2 mm + _Dh3 = 0.8 mm
(a) M010202: No aspirator As.
(b) M0102A02: One aspulator As was placed between the high-pressure nozzles N2 and N3.
(c) M01A0202: One aspulator As was placed between the high-pressure nozzles N1 and N2.

Experiment B - When there are two aspirators As, high pressure nozzle (same conditions as Experiment A)
(d) M0102AA02: Two aspulators As were placed between nozzles N2 and N3.
(e) M01AA0202: Two aspulators As were placed between the nozzles N1 and N2.

Experiment C - When there are two aspirators As, positioned at the middle part and just before the nozzle tip High pressure nozzle (N1: _Dn1 = 0.1 mm + _Dh1 = 0.8 mm, middle part with through hole diameter of 0.8 mm, same as _Dh1 of N1, N2: _Dn2 = 0.2 mm + _Dh2 = 0.8 mm)
(f) M010802: Without aspirator As.
(g) M0108AA02: Two aspirators As were placed immediately before the high pressure nozzle N2.
(h) M01AA0802: Two aspulators As were placed between the high-pressure nozzles N1 and N2.
Experiment D - When there are two aspirators As and the rear stage is extended, high pressure nozzle (N1 under the same conditions as in Experiment A, and four N2 under the same conditions as in Experiment A (N3, N4, N5))
(i) M0102020202: No aspulator As is inserted.
(j) M01AA02020202: Two aspulators As were placed between nozzles N1 and N2, and the latter stage was made longer.

Here, in order to make the aspurator As work fully, when the diameter _dA converted into the diameter of a single nozzle from the total cross-sectional area value of the return passages Nt1 and Nt2 is calculated, it must be larger than the diameter of the through hole of the largest nozzle on the low pressure side. It is also important that the pressure in the nozzle holder part on the high pressure side does not drop as much as possible. Therefore, if the diameter of the first nozzle is _d1 and the diameter of the smallest nozzle thereafter is _d2 , the following relationship is required.

In this case, the condition that _d1 is smaller than _d2 is added, and it is preferable to set _dA to as small a value as possible in the above formula 1. In the experiment, _dA was set to about 1 mm due to the relationship with the processing accuracy.

(Single nozzle)
For reference, the relationship between the size of the AE and the viscosity η of the treatment liquid when a single nozzle is used is shown in FIG.
The single nozzle is designated "S01N" and a commercially available nozzle tip with a through-hole diameter Dn of 0.1 mm was used. As the number of treatments N _P increased, η and the AE signal V _AE tended to increase, but even after 120 treatments, η was only 500 mPa sec.

(Experiment A)
The magnitude of the AE signal and the change in viscosity of the cellulose suspension treated using the M010202 three-stage nozzle are shown in Figure 15. With this configuration, the AE signal was larger than with a single nozzle, and η was also larger, reaching 600 mPa·sec at an N _P of 10. The AE when spraying only water was also larger than with a single nozzle. It can be seen that a lot of cavitation occurs inside the nozzle.
(M0102A02 multi-stage nozzle + 1 aspirator)
When a single aspulator As was disposed between N2-N3 of the M010202 and a three-stage nozzle of M0102A02 was used, the AE signal became even larger and η showed a slightly larger value (FIG. 16).
(M01A0202 multi-stage nozzle + 1 aspirator)
On the other hand, when a single aspulator As is disposed between N1 and N2 of M010202, and a three-stage nozzle of M01A0202 is used, it can be seen that η is larger than that of the above-mentioned M0102A02 (FIG. 17).
This experiment A demonstrated that the AE signal value and η value were both higher for the multi-stage nozzle (3 stages) than for a single nozzle, and for the multi-stage nozzle (3 stages) + one aspulator than for the multi-stage nozzle (3 stages), thereby improving the micro-fineness performance.

(Experiment B)
Next, in the case of the three-stage nozzle of M010202, in which two aspulators As are arranged symmetrically around the axis of the through hole, the AE signal initially decreased, but as the cellulose was refined, the AE signal tended to increase.
That is, by arranging two aspulators As, the back pressure of the nozzle before the aspulators is reduced and the AE signal falls, but as the miniaturization progresses, the η of the raw material increases, the pressure inside the nozzle rises, and the AE becomes larger.
As described above, even when two aspulators were arranged, differences could be seen depending on their arrangement (return position). The highest viscosity (900 mPa sec) was achieved with the M01AA0202 configuration (Figure 19), in which the absolute value of AE was not larger than that of the M0102AA02 configuration (Figure 18). This is thought to be the result of the raw material liquid (suspension) being most effectively supplied to the cavitation region, which has the energy necessary to micronize the cellulose.

(Experiment C)
The nozzle tip used in the experiment had a through hole diameter Dn of 0.1 mm or 0.2 mm, and the nozzle holder had a through hole diameter Dh of 0.8 mm, so a nozzle was created in which an intermediate portion with a through hole diameter of 0.8 mm was placed between the first nozzle N1 and the second nozzle N2.
This nozzle is referred to as M010802. In this case, there was no aspulator As, and large cavitation occurred after the first nozzle N1. The magnitude of AE was almost constant regardless of _NP . η was large, similar to M010202. This result shows that, although cavitation contributes to the atomization of the raw material to some extent in this configuration, there is a lot of unused cavitation (Figure 20).
Therefore, when an experiment was conducted with the three-stage nozzle M0108AA02, in which two aspulators As were placed symmetrically around the axis of the through hole just before the 0.2 mm nozzle tip, the AE of water alone was smaller than that of the single nozzle, but a very large AE was generated by adding a cellulose suspension. This AE is thought to be coming from the finely refined cellulose. In this case, the flow rate did not decrease, and high fineness performance was obtained. In addition, up to N _P 3, the largest η was shown among all the treatments, but after that, the η and AE began to decrease quickly. It was found that when the aspulator As was placed at a place where the diameter of the through hole changed, the decrease in η from the maximum value became faster (Figure 21).
Next, the micronization characteristics of the three-stage nozzle M01AA0802, which is configured when two aspulator As are arranged in the middle part, are shown. With this nozzle configuration, the AE of water alone is large, but the AE of the cellulose suspension does not increase much. Furthermore, since η does not increase, it can be seen that the micronization did not progress very much. There was also no correlation between AE and η. This lack of correlation indicates that the flow state changed significantly at N _P. Therefore, when the flow velocity was calculated from the AE data, it was lower than that of M010802. In particular, in the case of water alone, the flow velocity decreased rapidly at low pressures of 100 Pa or less. It is believed that these results occurred because the linear flow in the nozzle holder was disturbed by placing the aspulator As away from the second high-pressure nozzle and midway between N1 and N2. In other words, it was found that it is important to place the aspulator As so as not to disturb the jet flow in the nozzle, and it is preferable to place it just before the second high-pressure nozzle (nozzle tip). From these results, the state of the jet flow is shown in Figure 22.

(Experiment D)
A five-stage structure M01020202 was produced by adding two high-pressure nozzles with a nozzle tip through-hole diameter Dn of 0.2 mm to the rear stage of the three-stage nozzle M010202, and its micronization performance was evaluated.
The AE signal was smaller than that of M010202, and the increase in η was also slightly worse than that of M010202. In this case, the flow resistance increased and the flow velocity decreased, which is thought to have resulted in worse refinement performance than M010202 (Figure 23).
Next, two aspulators As were placed on the five-stage nozzle M0102020202, and the atomization characteristics of M01AA02020202 were evaluated. In this case, the addition of the aspulators As increased η, but the magnitude of η was smaller than that of the three-stage nozzle M01AA0202, so the atomization characteristics of the device deteriorated. This is also thought to be due to the longer rear stages and the reduced flow rate (Figure 24).

Next, optical microscope images of the raw material before micronization are shown (Figure 25), and images of cellulose microparticles and cellulose nanofiber (CNF) aggregates processed with the standard nozzles S01N and M010202, and the M01AA0202 nozzle equipped with an aspulator As are shown (Figures 26 to 28).
With the S01N nozzle, many cellulose fine particles were present that had not been converted into nanofibers, forming large aggregates of several hundred μm. Even when the N _P was increased to 30, many fine particles remained, and the suspension was cloudy. In contrast, with the M010202 nozzle, cellulose fine particles of several μm and cellulose nanofiber (CNF) aggregates of several tens of μm were observed, and when the N _P was increased to 30, the cellulose fine particles that appeared black became smaller, and the CNF aggregates that appeared lighter also became smaller, and the transparency of the suspension increased significantly.
Furthermore, with the M01AA0202 nozzle equipped with an aspulator As, the number of black cellulose fine particles of several μm observed was extremely small, and the size of the faintly visible CNF aggregates was also small at several tens of μm, and the suspension showed very high transparency. From the above results, it was confirmed that the micronization performance was greatly improved by using a multi-stage nozzle configuration and adding an aspulator As.
From the above, it was found that the nanofiberization of cellulose using a high-pressure injection device is as follows. First, the raw material particles are refined, then the fine particles produced are converted into nanofibers, and CNF aggregates are formed. As the process proceeds, the CNF aggregates produced also go through a process of becoming smaller. Changes in the morphology of these aggregates and their entanglement can be measured as changes in viscosity. In other words, the refinement performance can be evaluated by the magnitude of the maximum viscosity and the number of treatments N _P at that time, and it was confirmed that the multi-stage nozzle configuration and the addition of the aspulator As achieved significantly higher refinement performance than a conventional single nozzle.

(Experimental Verification)
The change in viscosity caused by the treatment of a cellulose suspension with various multi-stage high-pressure nozzle configurations is summarized in Figure 29. The structures in which two aspulators As are arranged symmetrically around the axis of the through hole between the nozzles N1 and N2, such as M01AA0202 and M0108AA02, showed the highest refining performance.
From the above results, the effect of the arrangement of the aspulator As in the multi-stage high-pressure nozzle system can be summarized as follows.

By arranging an aspulator As in a multi-stage high-pressure nozzle, a cellulose nanofiber (CNF) suspension with high viscosity was obtained even with fewer treatments compared to a single nozzle or a multi-stage high-pressure nozzle without an aspulator, and the micronization performance was significantly improved. In addition, by arranging an aspulator, the initial AE signal became smaller, but as the N _P was increased and the micronization proceeded, the AE signal tended to become larger. In particular, the viscosity increase was large when the N _P was 10 or less, and the strong cavitation generated by the high pressure was successfully applied to the raw material liquid, allowing for micronization.
The results are shown in Fig. 30. The raw material liquid is high-pressure injected from the upstream side (left) of the high-pressure chamber to the downstream side (right) of the low-pressure chamber. The hatched area in the figure is the area where it is assumed that the atomization action such as cavitation is working, but since the raw material liquid does not circulate in that area, it is shown that the whole raw material liquid is not atomized. In this case, atomization mainly occurs only in the vicinity of the jet flow near the nozzle outlet (a). If an aspulator As or the reaction of the flow in the low-pressure chamber is used there, the raw material is supplied to the inside of the second nozzle with a larger diameter where high-pressure cavitation and shear are working (b). It is believed that this has significantly improved the atomization performance.

In the experiment, the position of the aspulator As was the best when it was placed between the high pressure nozzles N1 and N2 (just before N2), and this structure was suitable for efficient atomization of the raw material liquid. It is particularly important that the increase in viscosity was large when the number of treatments N _P was as small as 1 to 5.
A single standard nozzle requires an _NP of 120 or more to exceed 500 mPa·sec in viscosity, whereas the three-stage M010202 high-pressure nozzle exceeded 500 mPa·sec at an Np of 10, and the M01AA0202, which had two aspulators As placed between the high-pressure nozzles N1 and N2, symmetrically about the axis of the through-hole, far exceeded that value at an _NP of 5. When the raw material was water alone, the pressure at the location of the aspulator As was reduced as expected, and the AE value became smaller. However, when cellulose powder was added to the raw material liquid, the AE value increased rapidly at an _NP of 5 to 10 when the aspulator As was placed between the high-pressure nozzles N2 and N3, and increased rapidly at an _NP of 2 or more when the aspulator As was placed between the high-pressure nozzles N1 and N2. This is thought to be because when the fiber is finely divided to a certain extent, large cellulose nanofiber (CNF) aggregates are formed, and the pressure inside the aspirator passage increases as the aggregates fill up, causing the AE signal to increase.
In addition, in the configuration of M01AA0202, the direction of the flow of the raw material supplied from the aspulator As changes when the nozzle diameter changes from 0.1 to 0.2 mm, along with the increase in AE due to cavitation, so it is considered that the shear force applied to the CNF aggregates also increases. Therefore, it was most efficiently refined and showed a high η, but since the effect of refining the aggregates also increased, η rapidly decreased after reaching a maximum value.
In this way, by creating a thin jet stream with the first nozzle and configuring the second and subsequent nozzles so as not to reduce the pressure, high micronization performance was achieved. Furthermore, by adding the aspulator As, it was possible to give as much cavitation effect as possible to the raw material liquid, and it became clear that the micronization processing efficiency was improved. However, at this time, it was necessary not to reduce the speed of the jet stream in order to avoid a decrease in the micronization performance.

In summary, it was found that the micro-refining performance can be significantly improved by adding an aspulverizer mechanism to the multi-stage high-pressure nozzle part of the high-pressure injection device and by not reducing the injection speed of the raw material liquid.
In addition, in the high-pressure injection device, the CNFs are refined in the above process, but when large CNF aggregates are formed along the way, if the flow path is changed by 90 degrees at the aspulator As (see FIG. 31(a)), the aggregates enter a fast-flowing area as soon as they enter the inlet, so part of the aggregate is pressed against the nozzle, and a very high shear force acts on the entire aggregate. On the other hand, if this part is provided in front of the nozzle, the aggregates are no longer held down by the nozzle, so a large shear force is not applied to the aggregates as in the former case (see FIG. 31(b)). Comparing the two, the refinement performance is improved when the aspulator As is placed just before the nozzle tip.
In other words, the position of the aspulator As is also an important parameter related to the micronization performance, and this embodiment can be said to be an excellent micronization method that enhances cavitation and shear force.

(Another embodiment of the present invention)
In the above experimental results, the best experimental results were obtained for the first embodiment in which the communication passage 5c is provided on the downstream side of the first spacer 5A (just before the N2 nozzle tip), but other embodiments are shown below (Figures 32 to 36 ).
32(a) and (b) are diagrams showing a multi-stage high-pressure nozzle structure in which a plurality of high-pressure nozzles 400 (N1, N2, N3) are arranged as in the first embodiment, and a plurality of high-pressure nozzles are housed in a nozzle case 101. Spacers 5A and 5B are interposed between the high-pressure nozzles, and a communication passage 5c (the spacer 5B has a communication passage in the figure) or a through hole (not shown) is formed by cutting out a part of the spacer 5A or 5B, and is connected to return passages Nt1 and Nt2 formed symmetrically above and below the through hole provided in the nozzle case 101, forming an aspulator As. Therefore, by high-pressure injection, the raw material liquid remaining in the low-pressure chamber is returned to the through hole Na via the return passage Nt and the communication passage 5c, and is injected again at high speed.

FIG. 33 is a diagram showing how a through hole is provided in the nozzle holder Nh constituting the high-pressure nozzle 400 to serve as a communication passage 5c, which is connected to a return passage provided in the nozzle case to form an aspulator As.
In this embodiment, the position of the communication passage 5c provided in the nozzle holder Nh may be anywhere within the range A-A as shown in Figures 42 (a) and (b), and if it is provided at the downstream side end of the nozzle holder Nh, it may be provided by cutting out.

In addition, the aspulator As, which is composed of a return passage and a communication passage, may be provided symmetrically with respect to the nozzle through hole Na as an axis and formed in a cross shape (FIGS. 34(a) and (b)), or the number of aspulators may be increased radially.
Furthermore, as shown in FIG. 35, the spacer 5A (or 5B) can be divided, and the central gap formed by the division can be used as a communication passage 5c and a through hole, which can be connected to the return passage Nt to form an aspulator As.

In Figure 36, of the multiple high-pressure nozzles, the upstream high-pressure nozzle N1 is housed from the upstream side of the nozzle case 102, and the downstream high-pressure nozzles N2 and N3 are housed from the downstream side of the nozzle case 102, and are screwed together without any gaps by the screw groove Ny arranged in the nozzle case 102 and the screw-in holding member Nj.
In addition, the nozzle case 102 is provided with a partition wall 40a that separates the high-pressure nozzles N1, N2, and N3, and a communication passage 5c is formed therein, which is connected to the return passages Nt1 and Nt2. In other words, this is an example in which an aspulator As is formed by return passages and communication passages throughout the entire nozzle case 102.

In the above embodiments, a multi-stage high-pressure nozzle is configured with holes and communication passages in the nozzle holder, nozzle case, and spacer, and the raw material liquid remaining in the low-pressure chamber is returned to the holes, but the present invention is not limited to these embodiments and can be widely applied to multi-stage high-pressure nozzles.

400, N1, N2, N3 high pressure nozzle,
Nn, _Nn1 , _Nn2 , _Nn3 , _NnM nozzle tips,
Nh, Nh ₁ , Nh ₂ , Nh ₃ , Nh _M nozzle holder,
Nt, Nt1, Nt2 return passages,
100, 101, 102 nozzle case,
Nan nozzle tip through hole,
Nah: nozzle holder through hole,
NAC nozzle case through hole,
5A first spacer,
5B second spacer,
5c Connecting passage,
8 signal processing and determination means,
9 AE sensor,
10 Raw material liquid,
1a, 1b Aggregates of fine particles (slurry),
1c microparticles,
20 suspensions,
40 low pressure chamber,
40a Partition wall,
402 outlet from low pressure chamber;
500 high pressure chamber,
600 AE signal propagation path,
AE _m is the measured AE signal strength,
AE _p signal due to particle cavitation,
As Aspulator,
Att _u Ultrasonic propagation characteristics (attenuation rate),
Np: number of injections of high pressure injection treatment,
_Vrms AE signal voltage

Claims (3)

A high-pressure injection treatment apparatus for injecting a raw material liquid at a predetermined pressure from a through hole of a high-pressure nozzle into a low-pressure chamber to reduce particles in the raw material liquid, the high-pressure nozzle being formed so that the through hole diameter on the upstream side thereof is smallest, the high-pressure injection treatment apparatus being equipped with a return passage for returning a portion of the raw material liquid injected into the low-pressure chamber side to the upstream side of the high-pressure nozzle by utilizing the injection flow, and a communication passage for connecting the return passage to a portion of the high-pressure nozzle downstream of the portion with the smallest through hole diameter.
The high-pressure nozzle is a multi-stage type in which a plurality of high-pressure nozzles are connected together, the high-pressure nozzles being composed of nozzle tips and nozzle holders to which the nozzle tips are fixed and having a larger through-hole diameter than the nozzle tips, and the return passage is connected to a communication passage provided between the upstream Nth high-pressure nozzle and the next N+1th high-pressure nozzle, or the return passage is connected to a communication passage provided between the upstream Nth nozzle tip and the N+1th nozzle tip.
3. The high-pressure injection treatment device according to claim 2, wherein the communication passage is formed immediately before an (N+1)th nozzle tip constituting the high-pressure nozzle and returns to the through hole.