Manufacturing method for cellulose microfibers

Abstract

To provide a method for producing cellulose microfiber and a producing apparatus for producing cellulose microfiber that can produce homogeneous cellulose microfiber while avoiding clogging of pipes in a cellulose microfiber manufacturing apparatus.SOLUTION: This invention relates to a method for producing cellulose microfiber from cellulose pulp, in which the method comprises a step of flowing a cellulose-containing slurry through a channel system including a miniaturization device that renders the cellulose fibers fine and a flow meter, wherein the flow rate (B) of the cellulose-containing slurry supplied to the miniaturization device and / or the operating conditions of the miniaturization device are changed in accordance with variations in the flow rate (A) of the cellulose-containing slurry as measured by the flow meter.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a method for producing cellulose microfibers. [Background technology]

[0002] Traditionally, cellulose microfibers have been used as a plant resource with a wide range of applications, both from an environmental protection standpoint and from the perspective of exhibiting various distinctive properties. In recent years, their excellent properties, such as high elastic modulus and high thermal dimensional stability, have attracted attention for use as fillers in automotive composites and core materials for fiber-reinforced plastics. However, the production of cellulose microfibers requires special and complicated processes, and there are many challenges in producing them stably and inexpensively.

[0003] Patent Document 1 describes a cellulose nanofiber manufacturing apparatus for micronizing pulp fibers in a slurry, comprising a high-pressure homogenizer for micronizing the pulp fibers in the slurry, a tank for storing the slurry after the pulp fibers have been micronized using the high-pressure homogenizer, and piping connected to the high-pressure homogenizer and the tank, wherein the piping is sanitary piping connected via fittings fitted with gaskets. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2018-95987 [Overview of the project] [Problems that the invention aims to solve]

[0005] The apparatus described in Patent Document 1 aims to suppress clogging and contamination of pipes during the production of cellulose microfibers. However, this apparatus has the problem that it is difficult to precisely control the cellulose micronization process, resulting in insufficient homogeneity of the cellulose microfibers produced.

[0006] In cellulose microfiber manufacturing equipment, a cellulose-containing slurry is circulated through a flow system including a micronization device. However, the properties of the slurry, particularly its rheological properties, change significantly as the cellulose micronization progresses. Therefore, it is desirable that the operating conditions of elements such as pumps, valves, and micronization devices in the cellulose microfiber manufacturing equipment be controlled in a timely manner according to the degree of micronization. However, conventional technology has not focused on the importance of controlling operating conditions according to the degree of micronization, and a method for stably producing homogeneous cellulose microfibers has not yet been proposed.

[0007] One aspect of the present invention aims to provide a method for producing cellulose microfibers and a manufacturing apparatus that can solve the above problems and produce homogeneous cellulose microfibers while avoiding clogging of pipes in the cellulose microfiber manufacturing apparatus. [Means for solving the problem]

[0008] The present invention encompasses the following aspects. [1] A method for producing cellulose microfibers from cellulose pulp, The method includes a step of flowing a cellulose-containing slurry through a flow channel system that includes a micronizing device for micronizing cellulose and a flow meter, A method for changing the flow rate (B) of the cellulose-containing slurry supplied to the micronizing device and / or the operating conditions of the micronizing device in accordance with fluctuations in the flow rate (A) of the cellulose-containing slurry measured by the flow meter. [2] The method according to embodiment 1, wherein the flow rate (B) and / or the operating conditions of the miniaturization device are changed by one or more control modes selected from the group consisting of feedback control, cascade control, ratio control, program control, and sequence control, in response to fluctuations in the flow rate (A). [3] The method according to embodiment 1 or 2 above, wherein the flow meter is a vortex flow meter, differential pressure flow meter, turbine flow meter, area flow meter, positive displacement flow meter, Coriolis flow meter, electromagnetic flow meter, or ultrasonic flow meter. [4] The method according to embodiment 3, wherein the flow meter is an ultrasonic flow meter. [5] The flow path system further comprises a pump and / or a control valve located upstream of the miniaturization device, The flow meter is positioned downstream of the atomizing device. The method according to any one of embodiments 1 to 4 above, wherein the flow rate (B) is changed by changing the operating conditions of the pump and / or the control valve in accordance with the fluctuation of the flow rate (A). [6] The flow path system further comprises a first tank located upstream of the pump and / or the control valve, and a second tank located downstream of the flow meter, The cellulose-containing slurry is introduced from the first tank to the micronizing device via the pump and / or the control valve. In the aforementioned micronization apparatus, the cellulose in the cellulose-containing slurry is micronized. The method according to embodiment 5, wherein a cellulose-containing slurry is introduced from the micronization device to the second tank via the flow meter. [7] The flow path system further comprises a tank located upstream of the pump and / or the control valve, The cellulose-containing slurry is introduced from the tank to the micronization device via the pump and / or the control valve. In the aforementioned micronization apparatus, the cellulose in the cellulose-containing slurry is micronized. The method according to embodiment 5, wherein the cellulose-containing slurry is returned from the micronization device to the tank via the flow meter. [8] The flow path system further comprises a first tank and a second tank located upstream of the pump and / or the control valve, and a switching valve located downstream of the flow meter, which can switch the flow of cellulose-containing slurry from the flow meter to either the first tank or the second tank, by switching the switching valve, One or more first cycles in which a cellulose-containing slurry is introduced from the first tank to the micronizing device via the pump and / or the control valve, the cellulose in the cellulose-containing slurry is micronized in the micronizing device, and the cellulose-containing slurry is returned from the micronizing device to the first tank via the flow meter and the switching valve, The second cycle consists of one or more cycles of introducing a cellulose-containing slurry from the second tank to the micronizing device via the pump and / or the control valve, micronizing the cellulose in the cellulose-containing slurry in the micronizing device, and returning the cellulose-containing slurry from the micronizing device to the second tank via the flow meter and the switching valve, The method according to embodiment 5 above, wherein the steps are repeated alternately. [9] A apparatus for producing cellulose microfibers from cellulose pulp, A micronizing device for micronizing cellulose in a cellulose-containing slurry. A flow meter that measures the flow rate of a cellulose-containing slurry and, together with the aforementioned micronization device, constitutes a flow path system for circulating the cellulose-containing slurry, and A control mechanism that changes the flow rate (B) of the cellulose-containing slurry supplied to the micronizing device, and / or the operating conditions of the micronizing device, in accordance with fluctuations in the flow rate (A) of the cellulose-containing slurry measured by the flow meter. A manufacturing apparatus for cellulose microfibers, equipped with the following features.

[10] The apparatus for producing cellulose microfibers according to embodiment 9, wherein the control mechanism is a pump and / or a control valve, and the control mechanism changes the flow rate (B) in accordance with the fluctuation of the flow rate (A). [Effects of the Invention]

[0009] According to one aspect of the present invention, there can be provided a method and an apparatus for manufacturing cellulose microfibers, which can manufacture homogeneous cellulose microfibers while avoiding clogging of pipelines in the cellulose microfiber manufacturing apparatus.

Brief Description of the Drawings

[0010] [Figure 1] FIG. 1 is a schematic diagram for explaining a method and an apparatus for manufacturing cellulose microfibers according to one aspect of the present invention. [Figure 2] FIG. 2 is a schematic diagram for explaining a method and an apparatus for manufacturing cellulose microfibers according to one aspect of the present invention. [Figure 3] FIG. 3 is a schematic diagram for explaining a method and an apparatus for manufacturing cellulose microfibers according to one aspect of the present invention. [Figure 4] FIG. 4 is a diagram for explaining feedback control in a method and an apparatus for manufacturing cellulose microfibers according to one aspect of the present invention. [Figure 5] FIG. 5 is a diagram for explaining a combination of feedback control and feedforward control in a method and an apparatus for manufacturing cellulose microfibers according to one aspect of the present invention. [Figure 6] FIG. 6 is a diagram for explaining cascade control in a method and an apparatus for manufacturing cellulose microfibers according to one aspect of the present invention.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, exemplary embodiments of the present invention (hereinafter also referred to as the present embodiments) will be described, but the present invention is not limited to these embodiments.

[0012] ≪Method and Apparatus for Manufacturing Cellulose Microfibers≫ One aspect of the present invention provides a method for producing cellulose fine fibers from cellulose pulp. In one aspect, the method includes the step of flowing a cellulose-containing slurry through a flow channel system comprising a cellulose pulverizer and a flow meter. In one aspect, the flow rate (B) of the cellulose-containing slurry supplied to the cellulose pulverizer and / or the operating conditions of the cellulose pulverizer are changed in response to fluctuations in the flow rate (A) of the cellulose-containing slurry (hereinafter also simply referred to as flow rate (A)) measured by the flow meter.

[0013] One aspect of the present invention also provides a cellulose microfiber manufacturing apparatus for producing cellulose microfibers from cellulose pulp. In one embodiment, the manufacturing apparatus comprises a microfibering device for microfiberizing cellulose in a cellulose-containing slurry, a flow meter for measuring the flow rate of the cellulose-containing slurry and forming a flow path system for circulating the cellulose-containing slurry together with the microfibering device, and a control mechanism for changing the flow rate (B) of the cellulose-containing slurry supplied to the microfibering device and / or the operating conditions of the microfibering device in accordance with fluctuations in the flow rate (A) of the cellulose-containing slurry measured by the flow meter. In one embodiment, the method for manufacturing cellulose microfibers of this embodiment can be carried out using the cellulose microfiber manufacturing apparatus of this embodiment.

[0014] When cellulose-containing slurry is circulated through a flow system including a micronization device to produce cellulose microfibers from cellulose raw materials, problems such as fluctuations in slurry flow rate and pipe clogging are likely to occur due to the inherent tendency of cellulose fibers to entangle with each other and changes in the rheological properties of the slurry that occur as the cellulose micronization progresses. These problems can be particularly pronounced in the later stages of the process when the cellulose fibers become finer. Therefore, in order to uniformly and stably produce cellulose microfibers of the desired shape, it is important to flexibly and quickly change the process conditions according to the degree of micronization and the conditions inside the piping.

[0015] The inventors have found that by placing a flow meter in the flow path system through which cellulose-containing slurry flows through a micronizing device, the slurry flow rate information measured by the flow meter can be quickly reflected in the amount of cellulose-containing slurry supplied to the micronizing device and / or the operating conditions of the micronizing device, thereby enabling flexible and rapid control of the manufacturing process conditions for cellulose microfibers.

[0016] Figures 1-3 are schematic diagrams illustrating a method for producing cellulose microfibers and a production apparatus according to one aspect of the present invention. Referring to Figures 1-3, the cellulose microfiber production apparatus (hereinafter also simply referred to as the production apparatus) 100, 200, 300 comprises a micronizing device 104 for micronizing cellulose in a cellulose-containing slurry, a flow meter 105 that measures the flow rate of the cellulose-containing slurry and forms a flow path system for circulating the cellulose-containing slurry together with the micronizing device 104, and a control mechanism that changes the flow rate (B) of the cellulose-containing slurry supplied to the micronizing device 104 and / or the operating conditions of the micronizing device 104 in accordance with fluctuations in the flow rate (A) of the cellulose-containing slurry measured by the flow meter 105. Cellulose microfibers are produced by circulating the cellulose-containing slurry through such a flow path system comprising the micronizing device 104 and the flow meter 105. The micronizing device consists of a main body and a control unit that controls the operation of the main body. In one embodiment, the control mechanism is a pump 102 and / or a control valve 103, which also consists of a main body and a control unit that controls the operation of the main body. Figures 1-3 show examples where the manufacturing apparatus 100, 200, and 300 are equipped with both a pump 102 and a control valve 103. Both the pump 102 and the control valve 103 have the function of changing the flow rate (B) of the cellulose-containing slurry introduced into the micronizing apparatus 104 by changing their operating conditions. Therefore, the manufacturing apparatus 100, 200, and 300 preferably include both a pump 102 and a control valve 103, but may also include only one of them.

[0017] In one embodiment, the flow rate (B) of the cellulose-containing slurry supplied to the micronizing device 104 can be changed by increasing or decreasing the slurry discharge volume of the pump 102, and / or by increasing or decreasing the slurry flow rate at the outlet of the control valve 103 by opening or closing the control valve or adjusting the opening amount.

[0018] In one embodiment, the operating conditions of the micronization apparatus 104 can be changed by changing one or more of the following: slurry residence time in the apparatus, temperature in the apparatus, and defibration media conditions (for example, the inter-blade distance and rotation speed in the disc refiner described later, the inter-blade distance and rotation speed in the beater described later, the inter-valve distance and pressure in the high-pressure homogenizer described later, the gap distance and pressure in the water jet described later, the case (screen)-disk gap and rotation speed in the disc mill described later, the vessel rotation speed in the ball mill described later, the rotor rotation speed in the bead mill described later, the grinding wheel gap and rotation speed in the mascolloider described later, the rotation speed in the homomixer (high-shear homogenizer, disperser) described later, etc.).

[0019] Referring to Figures 1-3, a cellulose-containing slurry may be prepared by introducing cellulose, a dispersion medium, and optionally additional components as supply material a into tanks 101a, 201, and 301a. Alternatively, a pre-prepared cellulose-containing slurry may be introduced into tanks 101a, 201, and 301a as supply material a. For example, a cellulose-containing slurry may be prepared by dispersing cellulose raw material in water using a pulper, homomixer, etc., and then supplying this slurry to tanks 101a, 201, and 301a. The peripheral speed of the homomixer may be 10 m / sec or more, 20 m / sec or more, or 25 m / sec or more in one embodiment, and 90 m / sec or less, 80 m / sec or less, or 50 m / sec or less in another embodiment. By dispersing the cellulose raw material to reduce clumps, etc., a more homogeneous cellulose-containing slurry can be obtained. Note that the cellulose raw material may be pre-treated as described later.

[0020] Next, the cellulose-containing slurry in tanks 101a, 201, and 301a is introduced into the micronizer 104 via pump 102 and control valve 103, where the cellulose in the cellulose-containing slurry is micronized. The micronized cellulose-containing slurry then enters a flow meter 105 located downstream of the micronizer 104, where its flow rate (i.e., flow rate (A)) is measured.

[0021] In Figures 1-3, an example arrangement is shown where the pump 102, control valve 103, atomizer 104, and flow meter 105 are arranged in that order from upstream to downstream. However, in a flow path system, the order of these arrangements can be determined as appropriate depending on the purpose.

[0022] For example, in one embodiment, the arrangement of the pump 102, the atomizing device 104, and the flow meter 105 may be in the order of pump, atomizing device, and flow meter from upstream, or in another embodiment, the order may be flow meter, atomizing device, and pump from upstream.

[0023] Furthermore, the arrangement of the control valve 103, the atomizing device 104, and the flow meter 105 may, in one embodiment, be in the order of control valve, atomizing device, and flow meter from the upstream side, or in another embodiment, be in the order of flow meter, atomizing device, and control valve from the upstream side.

[0024] When both the pump 102 and the control valve 103 are present, the pump may be positioned upstream or downstream of the control valve, but from the viewpoint of better control of the slurry flow rate, it is preferably positioned upstream of the control valve. On the other hand, if the desired slurry flow rate can be controlled by increasing or decreasing the slurry discharge amount of the pump (i.e., the flow rate of slurry delivered from the pump), the control valve may be omitted.

[0025] In a preferred embodiment, the flow path system includes a pump 102 and / or a control valve 103 located upstream of the micronizing device 104, and a flow meter 105 located downstream of the micronizing device 104. In this case, the flow rate (B) may be changed by changing the operating conditions of the pump and / or control valve in response to fluctuations in the flow rate (A). The placement of the pump and / or control valve upstream of the micronizing device and the placement of the flow meter downstream of the micronizing device are preferred from the viewpoint of more precise control of the slurry volume in the micronizing device and therefore further homogenization of the cellulose fine fibers.

[0026] The cellulose microfiber manufacturing apparatus may be a one-pass system (i.e., a system in which the cellulose-containing slurry is passed through the micronizer only once) or a multi-pass system (i.e., a system in which the cellulose-containing slurry is passed through the micronizer two or more times) equipped with one or more tanks. The cellulose microfiber manufacturing apparatus is preferably a one-pass system or a multi-pass system equipped with multiple tanks, and more preferably a multi-pass system equipped with multiple tanks, in terms of having good efficiency in manufacturing cellulose microfibers.

[0027] Figure 1 shows an example of a one-pass manufacturing apparatus equipped with multiple tanks. The flow path system of the manufacturing apparatus 100 includes a first tank (tank 101a) located upstream of the pump 102 and control valve 103, and a second tank (tank 101b) located downstream of the flow meter 105. The manufacturing apparatus 100 is configured to introduce cellulose-containing slurry from the first tank (tank 101a) to the micronizing device 104 via the pump 102 and control valve 103, where the cellulose in the cellulose-containing slurry is micronized, and then the cellulose-containing slurry is introduced from the micronizing device 104 to the second tank (tank 101b) via the flow meter 105. After storage in the second tank (tank 101b) for a desired time, the cellulose-fine fiber-containing slurry b is removed from the system.

[0028] Figure 2 shows an example of a multi-path manufacturing apparatus with one tank. The flow path system of the manufacturing apparatus 200 includes a tank 201 located upstream of the pump 102 and control valve 103 and downstream of the flow meter 105. A switching valve 206 is provided between the tank 201 and the pump 102, and is configured to allow switching between a flow path from the tank 201 to the pump 102 and a flow path from the tank 201 to the outside of the system.

[0029] The manufacturing apparatus 200 is configured to introduce cellulose-containing slurry from tank 201 to micronizer 104 via switching valve 206, pump 102, and control valve 103, micronize the cellulose in the cellulose-containing slurry in the micronizer 104, and return the cellulose-containing slurry from the micronizer 104 to tank 201 via flow meter 105. When the desired micronization is complete, the switching valve 206 is switched and the cellulose-fine fiber-containing slurry b is removed from the system.

[0030] Figure 3 shows an example of a multi-path manufacturing apparatus equipped with multiple tanks. The flow path system of the manufacturing apparatus 300 includes a switching valve 307 located downstream of the flow meter 105, and a first tank (tank 301a) and a second tank (tank 301b) located upstream of the pump 102 and control valve 103, and downstream of the flow meter 105 and switching valve 307. The switching valve 307 is configured to allow switching between a flow path from the flow meter 105 to the first tank (tank 301a) and a flow path from the flow meter 105 to the second tank (tank 301b). A switching valve 306 is provided between the second tank (tank 301b) and the pump 102, and is configured to allow switching between a flow path from the second tank (tank 301b) to the pump 102 and a flow path from the second tank (tank 301b) to the outside of the system.

[0031] The manufacturing apparatus 300 is operated by switching the switching valve 307. The first cycle consists of one or more times in which a cellulose-containing slurry is introduced from the first tank (tank 301a) to the micronizer 104 via pump 102 and control valve 103, the cellulose in the cellulose-containing slurry is micronized in the micronizer 104, and the cellulose-containing slurry is returned from the micronizer 104 to the first tank (tank 301a) via flow meter 105 and switching valve 307, The cellulose-containing slurry is introduced from the second tank (tank 301b) to the micronizer 104 via pump 102 and control valve 103, the cellulose in the cellulose-containing slurry is micronized in the micronizer 104, and the cellulose-containing slurry is returned from the micronizer 104 to the second tank (tank 301b) via flow meter 105 and switching valve 307. This second cycle is repeated once or multiple times. The system is configured to repeat the process alternately. When the desired leveling is complete, the switching valve 306 is switched and the cellulose fine fiber-containing slurry b is removed from the system.

[0032] The following describes illustrative embodiments of each element of a cellulose microfiber manufacturing apparatus.

[0033] [tank] The tank should be made of a material and be of a size that can accommodate the cellulose-containing slurry. In one embodiment, the tank is preferably one in which the inner wall surface is coated or lined with fluororesin, or buffed or electropolished. Among these, the one coated with fluororesin is preferred because it reduces the adhesion of cellulose fine fibers. Furthermore, it is preferable to provide baffles to maintain stirring uniformity.

[0034] [pump] As for the pump, a pump with slurry discharge capacity capable of circulating cellulose-containing slurry within the flow path system at a desired flow rate can be used, and examples include axial flow type, centrifugal type, reciprocating type, vane type, screw type, and gear type. Among these, centrifugal, reciprocating, and gear types are preferred from the viewpoint of quantitatively and stably delivering high-pressure, high-viscosity slurry. Furthermore, to prevent fiber clogging and to perform more precise liquid delivery, a reciprocating type is preferred, and among reciprocating types, the diaphragm type is more preferred.

[0035] [Adjustment valve] Examples of control valves include swing valves, gate valves, globe valves, butterfly valves, ball valves, diaphragm valves, and pinch valves. While all of these are applicable to the method and apparatus of this embodiment, they tend to exhibit the following characteristics: Swing valves are usable, but their accuracy tends to be lower compared to other types of valves. Gate valves and globe valves are on / off controlled and therefore not finely adjustable; therefore, valves that allow fine adjustment are more preferable. Butterfly valves allow for continuous flow control, albeit with low accuracy. Ball valves, diaphragm valves, and pinch valves allow for continuous flow control with high accuracy. From the above viewpoint, the control valve is preferably a gate valve, globe valve, butterfly valve, ball valve, diaphragm valve, or pinch valve, more preferably a butterfly valve, ball valve, diaphragm valve, or pinch valve, and particularly preferably a ball valve, diaphragm valve, or pinch valve.

[0036] [Miniaturization device] Examples of micronization equipment include beaters, disc refiners, high-pressure homogenizers, water jets, disc mills, ball mills, bead mills, mascolloiders, and homomixers. Micronization may be performed in one stage or multiple stages. In the case of multiple stages, this may involve repeatedly passing a cellulose-containing slurry through one micronization device, sequentially passing a cellulose-containing slurry through multiple micronization devices, or a combination thereof. When micronization is performed in multiple stages, two or more micronization devices with different micronization mechanisms and / or micronization performance (e.g., design shear rate) may be combined. Examples of multi-stage micronization include multi-stage beating using multiple disc refiners with different disc configurations, and multi-stage beating in which beating is performed in a high-pressure homogenizer after beating in a disc refiner.

[0037] Examples of disc refiners include single disc refiners, double disc refiners, and conical refiners. To highly control the beating process, a single disc refiner with high precision in clearance control between the fixed blade and the rotating blade is preferred.

[0038] A disc refiner has blades and grooves, and the design of the blade width, groove width, and the value obtained by dividing the blade width by the groove width (hereinafter referred to as the blade-to-groove ratio) affects the degree of cellulose refinement, i.e., the shape of the resulting cellulose microfibers. Appropriate design of the disc refiner is advantageous, for example, in reducing the number of long fibers that cause aggregation in the resin when compounding cellulose microfibers with resin, and in obtaining cellulose microfibers with a low fibril content. In the beating process in a disc refiner, controlling the distance between the two blades (clearance) is particularly advantageous in terms of producing homogeneous cellulose microfibers with good mechanical properties as fillers. When adjusting the blade distance, it is preferable to gradually reduce the blade distance from a wider distance while keeping the current value of the device below a certain level. By controlling it in this way, clogging and overload of the device can be prevented, and highly homogeneous cellulose microfibers can be obtained.

[0039] The shape of cellulose microfibers can also be controlled by the number of times the cellulose-containing slurry passes between the rotating blade and the stationary blade (hereinafter referred to as the number of passes). By increasing the number of passes, cellulose microfibers with uniform fiber diameter and fiber length can be obtained. Here, the number of passes refers to the number of times the cellulose-containing slurry passes between the rotating blade and the stationary blade after the desired blade distance has been set.

[0040] The number of passes for the disc refiner is preferably 5 or more, more preferably 20 or more, and even more preferably 40 or more. A higher number of passes is preferable because the distribution of fiber shapes gradually converges to a constant level as the number of passes increases, but considering productivity, the upper limit of the number of passes is preferably 300 or less.

[0041] In one embodiment, the micronization apparatus may be a combination of a disc refiner and a high-pressure homogenizer. In one embodiment, the cellulose-containing slurry is passed through the disc refiner and then the high-pressure homogenizer. The high-pressure homogenizer has a greater effect on thinning fibers compared to the disc refiner. The processing pressure of the high-pressure homogenizer is preferably 30 MPa or higher, more preferably 50 MPa or higher, and more preferably 80 MPa or higher. Due to the characteristics of the apparatus, the upper limit of the pressure is preferably 300 MPa or lower, more preferably 250 MPa or lower, and even more preferably 150 MPa or lower.

[0042] Examples of high-pressure homogenizers include the NS-type high-pressure homogenizer from Nilo Soavi GmbH (Italy), the Lanier-type (R model) pressure homogenizer from SMT Corporation, the high-pressure homogenizer from Sanwa Machinery Co., Ltd., and ultra-high-pressure homogenizers such as the microfluidizer from Mizuho Industries Co., Ltd., the nanomizer from Yoshida Machinery Industry Co., Ltd., and the ultimateizer from Sugino Machine Co., Ltd., which are high-pressure impact type beating machines. Other devices that perform miniaturization with a mechanism similar to these devices can also be used.

[0043] [Flowmeter] Examples of flow meter types include vortex flow, differential pressure, turbine, area, volumetric, Coriolis, electromagnetic, and ultrasonic types. While all of these are applicable to the method and apparatus of this embodiment, they tend to exhibit the following characteristics: Specifically, vortex flow meters tend to decrease in measurement accuracy as cellulose fineness increases and slurry viscosity rises. Differential pressure and turbine flow meters experience less of a decrease in measurement accuracy due to increased slurry viscosity compared to vortex flow meters, but are more prone to fiber clogging within the flow meter. Area and volumetric flow meters, although less severe than differential pressure and turbine flow meters, are still prone to a decrease in measurement accuracy due to increased slurry viscosity and fiber clogging within the flow meter. Coriolis flow meters are less susceptible to a decrease in measurement accuracy due to increased slurry viscosity, but are more prone to pressure increases due to pipe resistance. Electromagnetic flow meters require the medium to be an electrolyte, and therefore have the limitation of not being applicable to slurries where the medium is, for example, pure water. On the other hand, the ultrasonic type does not have any of the weaknesses exemplified above, and can measure the slurry flow rate with high accuracy regardless of the slurry properties, the degree of cellulose refinement, etc. From the above viewpoint, the type of flow meter is preferably a differential pressure type, turbine type, area type, volume type, Coriolis type, electromagnetic type, or ultrasonic type, more preferably an area type, volume type, Coriolis type, electromagnetic type, or ultrasonic type, even more preferably a Coriolis type, electromagnetic type, or ultrasonic type, and particularly preferably an ultrasonic type.

[0044] [Switching valve] As the switching valve, any valve of the type exemplified as the control valve described above that can switch between desired flow paths in a branching section where the flow path branches in three or more directions can be used, for example, a three-way valve. The switching valve may be a ball valve, solenoid valve, hydraulic valve, electromagnetic valve, gate valve, change valve, spool, relief valve, etc., and preferably a ball valve, hydraulic valve, electromagnetic valve, and change valve.

[0045] [Control Mode] In one embodiment, the control method for changing the flow rate (B) of the cellulose-containing slurry introduced into the micronizer and / or the operating conditions of the micronizer in response to fluctuations in the flow rate (A) measured by a flow meter may include one or more selected from the group consisting of feedback control, cascade control, ratio control, program control, and sequence control. Examples of program control and sequence control include, for example, pre-programming the operating conditions based on predictions of the amount of change over time when the slurry properties (viscosity, temperature, etc.) change over time, or pre-programming a sequence of such operating conditions. Feedback control, cascade control, etc., may be applied to adjust the amount of change in operating conditions during these controls. The control method preferably includes feedback control, cascade control, or a combination of feedback control and feedforward control, more preferably includes cascade control, or a combination of feedback control and feedforward control, and particularly preferably includes a combination of feedback control and feedforward control, as it enables rapid and precise control.

[0046] Figure 4 illustrates a method for producing cellulose microfibers and a manufacturing apparatus according to one aspect of the present invention, illustrating feedback control in the manufacturing apparatus. Referring to Figure 4, the control valve control unit 41 performs feedback control to change the valve opening / closing state of the control valve body 42 based on the difference between the set slurry flow rate at a predetermined flow meter location and the slurry flow rate measurement value obtained by the flow meter and output to the control valve control unit 41, thereby increasing or decreasing the flow rate (B). The change in the valve opening / closing state is performed by on / off control in the case of gate valves or globe valves, for example, and by proportional control in the case of swing valves, butterfly valves, ball valves, diaphragm valves or pinch valves.

[0047] Figure 5 illustrates a combination of feedback control and feedforward control in a method and apparatus for manufacturing cellulose microfibers according to one aspect of the present invention. Referring to Figure 5, the first control valve control unit 51 performs feedforward control to adjust the valve opening / closing state of the control valve body 53 based on a predetermined set slurry flow rate at the control valve outlet. The second control valve control unit 52 performs feedback control to adjust the valve opening / closing state of the control valve body 53 based on the difference between a predetermined set slurry flow rate at the flow meter and a slurry flow rate measurement value obtained by the flow meter and output to the control valve control unit 52. The set slurry flow rate at the flow meter may be set based on a predetermined relationship formula between the set slurry flow rate at the control valve outlet and the set slurry flow rate at the flow meter.

[0048] Figure 6 illustrates a cascade control in a method for producing cellulose microfibers and a manufacturing apparatus according to one aspect of the present invention. Referring to Figure 6, the first control valve control unit 61 performs feedback control to determine the set slurry flow rate at the control valve outlet based on the difference between the set slurry flow rate at a predetermined flow meter location and the slurry flow rate measurement value acquired by the flow meter and output to the first control valve control unit 61. The second control valve control unit 62 performs feedback control to adjust the valve opening / closing state of the control valve body 63 based on the difference between the set slurry flow rate at the control valve outlet determined above and the slurry flow rate measurement value at the control valve outlet acquired at the outlet of the control valve and output to the second control valve control unit 62. Changing the valve opening / closing state of the control valve body 63 changes the slurry flow rate at the control valve outlet, and therefore changes the flow rate of slurry supplied to the micronization apparatus (flow rate (B) in this disclosure). The flow rate (B) is changed by program control based on the relationship between a predetermined amount of change in the flow rate (B) and the amount of change in the operating conditions of the miniaturization device body 64, thereby changing the operating conditions of the miniaturization device body 64 (for example, slurry residence time).

[0049] <Cellulose-containing slurry> The cellulose-containing slurry supplied to the cellulose microfiber manufacturing apparatus may contain cellulose raw materials, a medium, and optionally additional components (e.g., additives such as dispersants).

[0050] [Cellulose raw material] While there are no particular limitations on the cellulose raw material, coniferous tree chips, hardwood chips, or non-wood cellulose raw materials (such as those derived from cotton, hemp, bagasse, kenaf, bamboo, or straw) can be used. However, it is preferable to use a cellulose raw material with a high degree of type I crystallinity.

[0051] Furthermore, in order to suppress discoloration and deterioration of physical properties due to heat when compounding cellulose microfibers with resin, the glucose content of the cellulose raw material in this embodiment, as determined by constituent sugar analysis, is preferably 90% by mass or more, more preferably 91% by mass or more, and even more preferably 93% by mass or more. There is no particular upper limit to the glucose content, but considering the limits of impurities (for example, components other than polysaccharides, such as oil components, various contaminants, etc.) that may be mixed in during the harvesting or purification process of the cellulose raw material, or during the manufacturing process of cellulose microfibers, it is preferable that it be 99.5% by mass or less. In cellulose raw materials, a high glucose content usually indicates high cellulose purity. Cellulose microfibers obtained using high-cellulose-purity cellulose raw materials have the advantage of having low amounts of lignin and hemicellulose, which are components that can reduce elastic modulus and heat resistance.

[0052] The method for measuring glucose content in structural sugar analysis is as follows. Structural sugar analysis can be performed according to the analytical procedure of the National Renewable Energy Laboratory (NREL), USA, 2008. (Sluiter, A., Hames, B., Ruiz, R., Scarlata, C., Sluiter, J., Templeton, D., Crocker, D.: Determination of structural carbohydrates and lignin in biomass. National Renewable Energy Laboratory (NREL), USA, 2008.) Add 3 ml of 72% sulfuric acid to 200 mg of the sample and swell at 30°C for 1 hour. Then, pour the mixture into a 125 ml pressure-resistant bottle with 84 ml of pure water and hydrolyze at 120°C for 1 hour. After that, suction filtration is performed while the sample is still hot using a 1G-3 glass filter (weighed constant at 105°C), and after solid-liquid separation, the filtrate is diluted to 100 ml, and the constituent sugars can be quantified by high-performance liquid chromatography (HPLC) (FL detection method).

[0053] As a refined cellulose raw material, refined pulp or cotton-like refined product can be used, obtained from the aforementioned cellulose raw materials, such as coniferous tree chips, hardwood chips, or non-wood cellulose raw materials (derived from cotton, hemp, bagasse, kenaf, bamboo, straw, etc.), through a purification process and bleaching process aimed at deligninization by pulping and removal of hemicellulose. Furthermore, cut yarn of regenerated cellulose fibers and cut yarn of regenerated cellulose obtained by the electrospinning method can also be used as a refined cellulose raw material. It is preferable to set appropriate purification conditions (e.g., pulping temperature, alkali concentration during pulping, bleaching agent concentration, or bleaching time) according to the type of cellulose raw material to produce refined cellulose fibers that maintain high cellulose purity and use them as a raw material. On the other hand, recycled materials such as recycled cotton and recycled wood can also be used as cellulose raw materials.

[0054] Among these, cellulose raw materials derived from cotton (cotton lint or cotton linter) are preferred in terms of high cellulose purity, industrial availability, and quality stability, and cotton linter pulp is particularly preferred.

[0055] Applying heat treatment, alkali treatment, enzyme treatment, etc., to the cellulose raw material can also be effective in obtaining high-purity purified cellulose raw material. In particular, combining several of these treatments is especially preferable.

[0056] Furthermore, the glucose content determined by the above-mentioned constituent sugar analysis is preferably high not only in cellulose raw materials but also in cellulose microfibers. The glucose content of cellulose microfibers is preferably 85% or more, more preferably 90% or more, and there is no particular upper limit, but in one embodiment it is 99.5% by mass or less.

[0057] (Fiber length distribution of cellulose raw materials) In one embodiment, the cellulose raw material may have an average fiber length (specifically, the length-weighted average fiber length described later) of 3 mm or less as measured by an automated fiber shape analyzer, and / or the number percentage of fibers with a fiber length of 3 mm or more may be 20% or less. Having a specific fiber length distribution in the cellulose raw material improves energy transfer in the micronization device and reduces clogging within the device, allowing for stable micronization even in slurries with a high solid content, for example.

[0058] The average fiber length is more preferably 2.5 mm or less, even more preferably 2.0 mm or less, and particularly preferably 1.6 mm or less. Since the above effects are enhanced as the average fiber length decreases, there is no particular lower limit, but considering the mechanical properties when using cellulose microfibers as a resin filler, it is preferably 0.1 mm or more, and more preferably 0.5 mm or more.

[0059] The percentage of fibers with a length of 3 mm or more is more preferably 15% or less, and even more preferably 10% or less. The lower limit is not particularly limited, as a smaller value enhances the above-mentioned effects, but a range of 0.5% or more and more preferably 1% or more is preferable for practical pretreatment.

[0060] The fiber length of the cellulose raw material mentioned above can be measured using an automated fiber shape analyzer (Morfi Neo, manufactured by Techpap). The measurement procedure is described below.

[0061] Disperse the cellulose raw material in pure water to prepare a 1 L aqueous dispersion. Here, the final solid content concentration of the cellulose raw material should be 0.003 to 0.005 mass%. If the cellulose raw material before dilution is an aqueous dispersion of less than 2 mass%, it is sufficient to simply mix it with a spatula or the like. However, if it is an aqueous dispersion of 2 mass or more, a hydrated cake, or a powder, the dispersion treatment should be performed using a high-shear homogenizer (IKA, product name "Ultra-Turrax T18") under the following conditions: rotation speed 25,000 rpm for 5 minutes. If dispersed in a medium other than water, the medium is dispersed in a sufficient amount of pure water using a high-shear homogenizer (IKA, product name "Ultra-Turrax T18") under the following conditions: rotation speed 25,000 rpm for 5 minutes. After dispersing, the medium is removed by means of suction filtration or other means. Then, the medium is dispersed again in pure water using the high-shear homogenizer (IKA, product name "Ultra-Turrax T18") under the following conditions: rotation speed 25,000 rpm for 5 minutes, so that the final solid content concentration is 0.003 to 0.005 mass%, thereby replacing the medium with water.

[0062] Next, the aqueous dispersion prepared above is subjected to an autosampler and measured. The obtained measurement results are output in txt format (or csv format), and each shape parameter is extracted or calculated from the measurement results. The following values ​​from the measurement results will be used for each parameter.

[0063] 1) Length-weighted average fiber length: [μm] 2) Percentage of fibers with a fiber length of 3 mm or more: From the histogram of the fiber length distribution in 1), the percentage of fibers with a fiber length of 3 mm or more out of the total number of fibers is calculated using the following formula. Percentage of fibers with a length of 3 mm or more (%) = Number of fibers with a length of 3 mm or more / Total number of measured fibers x 100 3) Mean fiber width [μm]

[0064] (Pretreatment of cellulose raw materials) The cellulose raw material supplied to the cellulose fine fiber manufacturing method or manufacturing apparatus of this embodiment may be subjected to one or more pretreatments selected from crushing, grinding, and classification in order to control the fiber length distribution within a specific range. Crushing is a process of crushing the cellulose raw material dry, and as the crusher, a coarse crusher, an intermediate crusher, a fine crusher, etc., can be used. Grinding is a process of dispersing the cellulose raw material in an aqueous medium and subjecting the aqueous dispersion to a grinding treatment, and is distinguished from the above-mentioned crushing treatment in that it is a wet process. Examples of grinders include rotary millstones, grinders, planetary mixers, single-screw extruders, twin-screw extruders, bead mills, etc. Classification is an operation of separating the cellulose raw material by fiber length in order to standardize the fiber length, and either dry classification or wet classification can be used. Dry classification methods include gravity field classification, inertial force field classification, and centrifugal force field classification (natural vortex type or forced vortex type), while wet classification methods include gravity field classification, centrifugal force field classification (free vortex type), and centrifugal force field classification (forced vortex type). Classification using mesh sizes of sieves, screens, wires (edge ​​wires), nets, etc., and classification by centrifugal separation can also be used.

[0065] (Chemical modification of cellulose raw materials) In one embodiment, the cellulose microfibers produced by the method or apparatus of this embodiment are chemically modified cellulose microfibers. In this disclosure, chemically modified cellulose microfibers mean cellulose microfibers in which at least a portion of the three hydroxyl groups contained in the glucopyranose units in the cellulose molecular backbone present in the cellulose fiber are chemically modified. Here, "a portion" means that at least one hydroxyl group of at least one glucopyranose unit in the cellulose structure formed by the polymerization of multiple glucopyranose units is chemically modified. In a typical embodiment, the entire cellulose is not chemically modified, and the chemically modified cellulose microfibers retain the crystalline structure of the cellulose before chemical modification. For example, the crystalline structure of cellulose type I can be confirmed when analyzed by X-ray diffraction (XRD).

[0066] The cellulose raw material may be chemically modified before defibration. This chemical modification may be carried out before or after the above-mentioned pretreatment, but it is easier and preferable to carry it out after the pretreatment.

[0067] Methods of chemical modification include esterification, etherification, and urethaneification, but esterification is preferred. Among these, saturated monocarboxylic acid esterification such as acetate esterification (acetylation), propionic acid esterification, pentanoic acid (valeric acid) esterification, and hexanoic acid (caproic acid) esterification is preferred. Of these, acetate esterification (acetylation) is preferred due to the heat resistance of the cellulose microfibers after chemical modification, but esterification using dicarboxylic acids such as phthalic acid esterification may also be used. For chemical modification, general esterification reaction methods using saturated carboxylic acids or their acid anhydrides or acid chlorides, or saturated monocarboxylate vinyls such as vinyl acetate and vinyl propionate can be used.

[0068] When chemically modifying cellulose raw materials before micronization, it is preferable to perform the chemical modification in a solvent that swells the cellulose raw materials well in order to chemically modify the fiber surface inside the cellulose raw materials. In one embodiment, the solvent that swells the pulp well is an aprotic polar solvent, and dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and mixtures of any of these are preferred.

[0069] In another embodiment, the cellulose raw material may be chemically modified after being micronized using the micronization apparatus of this embodiment. In this case, the cellulose microfibers are concentrated by suction filtration or the like to form a moist cake, which is then diluted and dispersed in a solvent for chemical modification. The method of chemical modification may be the same as that for chemical modification of the cellulose raw material. However, when chemically modifying the cellulose microfibers, if they are dried too much, aggregation of the cellulose microfibers will occur, so the solid content concentration is preferably 30% by mass or less, and more preferably 20% by mass or less. On the other hand, since the esterifying agent also reacts with water, it is better to have less water introduced, so the lower limit of the solid content concentration is preferably 5% by mass or more, and more preferably 10% by mass or more. If chemical modification is difficult due to the presence of water, it is preferable to repeat the operation of suction filtration of the dispersion slurry diluted and dispersed in the above solvent, and then adding more solvent to reduce the amount of water in the system before performing chemical modification. Also, when chemically modifying cellulose after micronization, it is preferable to use a solvent that swells the cellulose raw material well in order to perform homogeneous chemical modification, but since the surface of the cellulose microfibers is exposed, it is not limited to the solvent mentioned above and can be used.

[0070] [Characteristics of cellulose raw materials and cellulose microfibers] (Degree of substitution of cellulose raw materials and cellulose microfibers) In one embodiment, the chemically modified group may be an acyl group. The degree of substitution (DS) of the acyl group in the cellulose raw material or cellulose microfiber is preferably 0.5 or higher, more preferably 0.6 or higher, and even more preferably 0.7 or higher. The upper limit is preferably 1.3 or lower, more preferably 1.1 or lower, and even more preferably 1.0 or lower, because if the DS is too high, the degree of crystallinity decreases, and the mechanical properties of the resin composition obtained by compounding the cellulose microfiber with the resin decrease.

[0071] The degree of acyl substitution (DS) can be calculated from the reflectance infrared absorption spectrum of esterified cellulose fibers based on the peak intensity ratio between the peak derived from the acyl group and the peak derived from the cellulose skeleton. The peak of the C=O absorption band based on the acyl group is at 1730 cm⁻¹. -1 The peak of the CO absorption band based on the cellulose backbone chain appears at 1030 cm⁻¹. -1 It appears in [location]. The DS of esterified cellulose fibers is obtained by creating a correlation graph between the DS obtained from solid-state NMR measurements of esterified cellulose fibers (described later) and the modification rate (IR index 1030), which is defined as the ratio of the peak intensity of the absorption band of C=O based on the acyl group to the peak intensity of the absorption band of CO in the cellulose backbone chain, and a calibration curve calculated from the correlation graph. Degree of substitution DS = 4.13 × IR index (1030) This can be obtained by using [this method].

[0072] The method for calculating the DS of esterified cellulose fibers using solid-state NMR is as follows: For freeze-pulverized esterified cellulose fibers... 13 The following formula can be used to determine the signal intensity (Inf) from a single carbon atom derived from the modifying group, based on the total area intensity (Inp) of the signals attributed to carbon atoms C1-C6 derived from the pyranose ring of cellulose, which appear in the range of 50 ppm to 110 ppm. DS = (Inf) × 6 / (Inp) For example, if the modifying group is an acetyl group, you can use the 23 ppm signal assigned to -CH3.

[0073] used 13 The conditions for C solid NMR measurement are as follows, for example. Apparatus: Bruker Biospin Avance500WB Frequency: 125.77 MHz Measurement method: DD / MAS method Waiting time: 75 sec NMR sample tube: 4 mm φ Number of integrations: 640 times (about 14 Hr) MAS: 14,500 Hz Chemical shift standard: glycine (external standard: 176.03 ppm)

[0074] (Crystallinity of cellulose raw material and cellulose microfibrils) The crystallinity of the cellulose raw material or cellulose microfibrils is preferably 55% or more. When the crystallinity is within this range, the mechanical properties (strength, dimensional stability) of the cellulose itself are high. Therefore, when the cellulose microfibrils are dispersed in the resin, the strength and dimensional stability of the resin composition tend to be high. The lower limit of the more preferable crystallinity is 60%, even more preferably 70%, and most preferably 80%. There is no particular limitation on the upper limit of the crystallinity of the cellulose raw material or cellulose microfibrils, and a higher value is preferable, but from the perspective of production, the preferable upper limit is 99%.

[0075] The crystallinity referred to here, when the cellulose is cellulose I type crystal (derived from natural cellulose), is determined by the Segal method from the diffraction pattern (2θ / deg. is 10 - 30) when the sample is measured by wide-angle X-ray diffraction, according to the following formula. Crystallinity (%) = [I (200) -I (amorphous) / I (200) ×100 I (200) : Diffraction peak intensity by the 200 plane (2θ = 22.5°) in cellulose I type crystal I (amorphous): The halo peak intensity due to amorphous material in type I cellulose crystals, specifically the peak intensity at an angle 4.5° lower than the diffraction angle of the 200 plane (2θ = 18.0°).

[0076] Furthermore, if the cellulose is a type II cellulose crystal (derived from regenerated cellulose), the degree of crystallinity can be determined by the following formula using wide-angle X-ray diffraction, from the absolute peak intensity h0 at 2θ=12.6°, which is attributed to the (110) plane peak of the type II cellulose crystal, and the peak intensity h1 from the baseline at this interplanar spacing. Crystallinity (%) =h1 / h0 ×100

[0077] Known crystalline forms of cellulose include Type I, Type II, Type III, and Type IV. Among these, Type I and Type II are particularly widely used, while Type III and Type IV, although obtained on a laboratory scale, are not widely used on an industrial scale. The cellulose raw material or cellulose microfibers of this disclosure have relatively high structural mobility, and by dispersing the cellulose microfibers in a resin, a resin composition with a lower coefficient of thermal expansion and superior strength and elongation during tensile and bending deformation can be obtained. Therefore, materials containing Type I or Type II cellulose crystals are preferred, and materials containing Type I cellulose crystals with a crystallinity of 55% or higher are more preferred.

[0078] [Medium] The medium may be an aqueous medium. Examples of aqueous mediums include water itself, or a mixture of water and one or more organic solvents, such as alcohols (ethanol, n-propanol, isopropanol, butanol, etc.), polyhydric alcohols (ethylene glycol, diethylene glycol, glycerin, etc.), ketones (acetone, etc.), nitrile solvents (acetonitrile, etc.), and pyrrolidone solvents. The proportion of the organic solvent in the above-mentioned mixture of organic solvent and water is preferably less than 50% by mass, more preferably 30% by mass or less, and particularly preferably 20% by mass or less. The higher the water ratio, the better the defibrillation, and the higher the organic solvent ratio, the more the aggregation of fine fibers in the drying process after defibrillation is suppressed. Therefore, the ratio of the organic solvent is preferably set in consideration of the balance between defibrillation and aggregation suppression.

[0079] The solid content of the cellulose-containing slurry (typically, the content of cellulose raw materials) may, in one embodiment, be 0.5% by mass or more, or 0.8% by mass or more, or 1.0% by mass or more, and in one embodiment, it may be 6% by mass or less, or 3.5% by mass or less, or 3% by mass or less.

[0080] <Cellulose microfibers> [Shape of cellulose microfibers] (Average fiber length) The cellulose microfibers produced by the method or apparatus of this embodiment are preferable when they have a longer average fiber length, as this improves their mechanical properties when used as a reinforcing material for resins, etc. That is, when the fiber length is long, the fibers intertwine with each other when compounded with resin, allowing the cellulose microfibers to be uniformly dispersed in the resin without forming aggregates. This improves the stress transmission of the resin composition, increasing its strength and fracture strain. The average fiber length is preferably 400 μm or more, more preferably 500 μm or more, even more preferably 600 μm or more, and particularly preferably 700 μm or more, as measured by the length-weighted average fiber length in an automated fiber shape analyzer. The length-weighted average fiber length is defined in ISO / FDIS 16065-2:2006 and is the average value of the fiber length corresponding to the actual fiber length considering the bending shape of the bent fiber. The longer the fiber length, the greater the above-mentioned effect, so there is no particular upper limit, but a preferred range is 1000 μm or less.

[0081] (Average fiber diameter) In this embodiment, the cellulose microfibers preferably have an average fiber diameter of 300 nm or less as measured by an automated fiber shape analyzer. Having an average fiber diameter within this range makes it easy to sufficiently increase the L / D ratio of individual cellulose fibers. A high L / D ratio causes entanglement among the cellulose microfibers within the resin, thereby increasing the strength of the resin composition. The average fiber diameter of the cellulose microfibers is more preferably 200 nm or less, even more preferably 150 nm or less, and most preferably 130 nm or less. While a thinner average fiber diameter is preferable because it allows for a higher L / D ratio, the lower limit is not particularly limited. However, a certain thickness is desirable to achieve high flexural elasticity of the resin composition, so it is preferably 10 nm or more, more preferably 40 nm or more.

[0082] (Coefficient of variation (CV) of average fiber length) In the cellulose microfibers of this embodiment, when the variation in fiber length is small, it is preferable that the anisotropy of the mechanical properties (tensile strength, flexural strength, tensile modulus, flexural modulus, thermal expansion coefficient, etc.) is small among the reinforcing effects when added to the resin. The variation in fiber length is expressed as the coefficient of variation CV by the following formula. CV(%) = (Standard deviation of fiber length (μm) / Average fiber length (μm)) x 100 The coefficient of variation (CV) is preferably 20% or less, more preferably 15% or less, and particularly preferably 12% or less. Since a lower value increases the aforementioned effect, there is no particular lower limit, but in practice, 1% or more is preferable.

[0083] (Concentration and drying of cellulose microfibers) The cellulose microfibers of this embodiment can be obtained in the form of a wet molded body (wet cake) by dewatering the slurry using a filter or a paper machine. Among these methods, the papermaking method using a paper machine is advantageous in that it reduces drying shrinkage between the cellulose microfibers. In one embodiment, dewatering is performed by filtering the slurry on a porous substrate. In the papermaking method, any paper machine equipped with wires of a mesh size that allows the cellulose microfibers to remain after dewatering the slurry can be used. As for the papermaking apparatus, when obtaining a composite molded body in the shape of a flat sheet, an inclined wire paper machine, a long wire paper machine, or a cylinder wire paper machine can be used.

[0084] When cellulose microfibers are used as a dry filler, they can be dried using known drying equipment such as a hot air dryer or spray dryer. Cellulose tends to aggregate during the drying process and is difficult to redisperse afterward, so it is preferable to use a dispersant. By improving redispersibility, the mechanical properties and stability of the resin composition obtained by compounding cellulose microfibers with resin can be improved. It is desirable to add a dispersant to an aqueous cellulose dispersion and then dry it while applying shear to obtain cellulose powder. The dispersant can be at least one selected from the group consisting of surfactants, organic compounds with a boiling point of 100°C or higher, and resins having a chemical structure that can highly disperse cellulose.

[0085] (Applications of cellulose microfibers) The cellulose microfibers produced by the method or apparatus of this embodiment may, in one embodiment, have a moderate fineness that is neither too coarse nor too fine, and may also have good homogeneity. The cellulose microfibers can be suitably used as a reinforcing filler for fiber-reinforced resins. Furthermore, they can be used as a prepreg material by molding them into a sheet and impregnating them with resin, or used in building materials such as concrete, etc.

[0086] Cellulose microfibers may be compounded with thermosetting resins, photocurable resins, or thermoplastic resins to constitute a resin composition. Since the cellulose microfibers of this embodiment have excellent heat resistance, it is preferable that they be compounded with thermoplastic resins. The cellulose microfibers of this embodiment can also be suitably compounded with resins having a melting point of 200°C or higher and a melt-mixing temperature of 250°C or higher. The thermoplastic resin is one or more selected from the group consisting of polyolefins (polyethylene, polypropylene, etc.), polyesters (polyethylene terephthalate, polylactic acid, etc.), polyamides (PA6, PA66, PA4, PA12, aromatic polyamides, etc.), polyacrylonitrile, polymethyl methacrylate, polystyrene, polyvinyl alcohol, polyphenylene ether, polyoxymethylene, and polyphenylene sulfide. These thermoplastic resins may be used individually or in combination of two or more.

[0087] (Cellulose microfiber content in resin composition) The content of cellulose microfibers in the resin composition is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and even more preferably 20% by mass or more. From the viewpoint of avoiding performance degradation due to the disruption of the continuous layer of the resin and molding defects due to reduced fluidity during molding of the resin composition, it is preferable that the content of cellulose microfibers is not too high, and the upper limit of the content is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less.

[0088] The resin content in the resin composition is preferably 50% by mass or more, or 60% by mass or more. From the viewpoint of obtaining a good reinforcing effect by the cellulose microfibers without reducing the cellulose microfiber content too much, it is preferably 99% by mass or less, or 95% by mass or less, or 90% by mass or less. [Industrial applicability]

[0089] According to one aspect of the present invention, a method and apparatus for producing cellulose microfibers make it possible to produce homogeneous cellulose microfibers that can be useful for various applications. [Explanation of symbols]

[0090] 100, 200, 300 Cellulose Microfiber Manufacturing Equipment 101a, 101b, 201, 301a, 301b Tanks 102 pump 103 Adjustment valve 104 Miniaturization equipment 105 Flow meter 206, 306, 307 Switching valve

Claims

1. A method for producing cellulose microfibers from cellulose pulp, The method includes a step of flowing a cellulose-containing slurry through a flow channel system that includes a micronizing device for micronizing cellulose and a flow meter, The flow rate of the cellulose-containing slurry from the micronization apparatus is measured using the flow meter. The cellulose-containing slurry is passed through the micronization apparatus two or more times. A method for changing the flow rate (B) of the cellulose-containing slurry supplied to the micronizing device and / or the operating conditions of the micronizing device in accordance with the time-dependent fluctuation of the flow rate (A) of the cellulose-containing slurry, as measured by the flow meter, due to changes in the rheological properties of the slurry that occur as the micronization of cellulose progresses.

2. The method according to claim 1, wherein the flow rate (B) and / or the operating conditions of the miniaturization device are changed by one or more control modes selected from the group consisting of feedback control, cascade control, ratio control, program control, and sequence control, in response to fluctuations in the flow rate (A).

3. The method according to claim 1 or 2, wherein the flow meter is a vortex flow meter, differential pressure flow meter, turbine flow meter, area flow meter, positive displacement flow meter, Coriolis flow meter, electromagnetic flow meter, or ultrasonic flow meter.

4. The method according to claim 3, wherein the flow meter is an ultrasonic flow meter.

5. The flow path system further comprises a pump and / or a control valve located upstream of the miniaturization device, The flow meter is positioned downstream of the atomizing device. The method according to any one of claims 1 to 4, wherein the flow rate (B) is changed by changing the operating conditions of the pump and / or the control valve in accordance with the fluctuation of the flow rate (A).

6. The flow path system further comprises a first tank located upstream of the pump and / or the control valve, and a second tank located downstream of the flow meter. The cellulose-containing slurry is introduced from the first tank to the micronization device via the pump and / or the control valve. In the aforementioned micronization apparatus, the cellulose in the cellulose-containing slurry is micronized. The method according to claim 5, wherein a cellulose-containing slurry is introduced from the micronization device to the second tank via the flow meter.

7. The flow path system further comprises a tank located upstream of the pump and / or the control valve, The cellulose-containing slurry is introduced from the tank to the micronization device via the pump and / or the control valve. In the aforementioned micronization apparatus, the cellulose in the cellulose-containing slurry is micronized. The method according to claim 5, wherein the cellulose-containing slurry is returned from the micronizing device to the tank via the flow meter.

8. The flow path system further comprises a first tank and a second tank located upstream of the pump and / or the control valve, and a switching valve located downstream of the flow meter that can switchly guide the cellulose-containing slurry flow from the flow meter to either the first tank or the second tank, and by switching the switching valve, The first cycle consists of one or more times in which a cellulose-containing slurry is introduced from the first tank to the micronizing device via the pump and / or the control valve, the cellulose in the cellulose-containing slurry is micronized in the micronizing device, and the cellulose-containing slurry is returned from the micronizing device to the first tank via the flow meter and the switching valve, The second cycle consists of one or more cycles of introducing a cellulose-containing slurry from the second tank to the micronizing device via the pump and / or the control valve, micronizing the cellulose in the cellulose-containing slurry in the micronizing device, and returning the cellulose-containing slurry from the micronizing device to the second tank via the flow meter and the switching valve, The method according to claim 5, wherein the steps are repeated alternately.

9. A apparatus for producing cellulose microfibers from cellulose pulp, A micronizing apparatus for micronizing cellulose in a cellulose-containing slurry, wherein the cellulose-containing slurry is arranged to flow through the micronizing apparatus two or more times. A flow meter that measures the flow rate of the cellulose-containing slurry from the aforementioned micronization device and constitutes a flow path system for circulating the cellulose-containing slurry together with the micronization device, and A control mechanism that changes the flow rate (B) of the cellulose-containing slurry supplied to the micronizing device, and / or the operating conditions of the micronizing device, in accordance with the time-dependent fluctuation of the flow rate (A) of the cellulose-containing slurry measured by the flow meter, due to changes in the rheological properties of the slurry that occur as the micronization progresses. A manufacturing apparatus for cellulose microfibers, equipped with the following features.

10. The apparatus for producing cellulose microfibers according to claim 9, wherein the control mechanism is a pump and / or a control valve, and the control mechanism changes the flow rate (B) in accordance with the fluctuation of the flow rate (A).

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