Patent Publication Number: US-2020276544-A1

Title: Mixing apparatus

Description:
TECHNICAL FIELD 
     The present disclosure relates to a mixing apparatus for mixing materials together. 
     BACKGROUND ART 
     For example, Patent document 1 discloses mixing (the term “kneading” is used in this document) materials (called “rubber materials” in the document) in the presence of a supercritical fluid or a subcritical fluid (refer to paragraph 0040 of the document). This mixing is performed mechanically by a kneading member such as a rotor or a screw (refer to paragraphs 0027 and 0040 of the document). 
     CITATION LIST 
     Patent literature 
     Patent document 1: Japanese Patent No. 5,259,203 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the technique disclosed in the above document, a rotary blade (called “a kneading member” in the above document) of a rotor, a screw, or the like rotates with respect to a chamber (called “rubber kneading chamber” in the above document). Thus, energy for rotating the rotary blade is necessary. Usually, a motive power source for rotating the rotary blade is provided outside the chamber. As a result, a gap is formed between the chamber and a member that connects the motive power source and the rotary blade. Furthermore, the pressure of a supercritical fluid or a subcritical fluid is set higher than atmospheric pressure. This raises a problem of insufficient sealing performance of the chamber. 
     In view of the above, an object of the present disclosure is to provide a kneading apparatus capable of dispensing with energy for rotating a rotary blade and securing necessary sealing performance of a chamber. 
     Solution to Problem 
     A mixing apparatus according to the disclosure includes a mixer. The mixer mixes a material including a rubber or a resin in the presence of a working fluid that is in a supercritical state or a subcritical state. The mixer includes a chamber and a mixing blade. The chamber forms a flow passage for the working fluid and the material. The mixing blade is disposed in the chamber  51  and fixed to the chamber. 
     Advantageous Effects of Invention 
     The above configuration makes it possible to dispense with energy for rotating a rotary blade and secure necessary sealing performance of a chamber. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram of a mixing apparatus according to a first embodiment. 
         FIG. 2  is a sectional view, as viewed from a direction that is perpendicular to an axial direction X, of a mixer shown in  FIG. 1 . 
         FIG. 3  is a sectional view, as viewed from the axial direction X, of the mixer shown in  FIG. 2 . 
         FIG. 4  is a sectional view corresponding to  FIG. 3  of a case that two mixing blades like the one shown in  FIG. 2  are provided. 
         FIG. 5  is a sectional view corresponding to  FIG. 3  of a case that three mixing blades like the one shown in  FIG. 2  are provided. 
         FIG. 6  is a flowchart showing how the mixing apparatus shown in  FIG. 1  operates. 
         FIG. 7  is a block diagram, corresponding to  FIG. 1 , of a mixing apparatus according to a second embodiment. 
         FIG. 8  is a sectional view, corresponding to  FIG. 2 , of a mixer of a mixing apparatus according to a third embodiment. 
         FIG. 9  is a sectional view, taken along an arrowed line IX-IX, of  FIG. 8 . 
         FIG. 10  is a sectional view corresponding to  FIG. 9  in a case that two mixing blades like the one shown in  FIG. 9  are provided. 
         FIG. 11  is a sectional view, corresponding to  FIG. 2 , of a mixer of a mixing apparatus according to a fourth embodiment. 
         FIG. 12  is a sectional view, corresponding to  FIG. 2 , of a mixer of a mixing apparatus according to a fifth embodiment. 
         FIG. 13  is a sectional view, corresponding to  FIG. 2 , of a mixer of a mixing apparatus according to a sixth embodiment. 
         FIG. 14  is a block diagram, corresponding to  FIG. 1 , of a mixing apparatus according to a seventh embodiment. 
         FIG. 15  is a block diagram, corresponding to  FIG. 1 , of a mixing apparatus according to an eighth embodiment. 
         FIG. 16  is a graph showing temperatures T in a chamber shown in  FIG. 15 . 
         FIG. 17  is a block diagram, corresponding to  FIG. 1 , of a mixing apparatus according to a ninth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A mixing apparatus  1  according to a first embodiment is described with reference to  FIG. 1  to  FIG. 6 . 
     The mixing apparatus  1  (kneading apparatus, stirring apparatus) is an apparatus for mixing materials  21  using a working fluid  11 . The term “mixing” used above includes kneading and stirring. The mixing apparatus  1  includes a production unit  10 , a storage unit  20 , a dissolving unit  30 , a mixing unit  40 , a separation unit  70 , a carry-out unit  90 , and a control unit C. 
     The production unit  10  (supercritical production unit, subcritical production unit) is a unit for producing the working fluid  11 . The working fluid  11  is a fluid in a supercritical state (supercritical fluid) or a fluid in a subcritical state (subcritical fluid). The mixing apparatus  1  is a supercritical mixing apparatus or a subcritical mixing apparatus. The temperature and the pressure of the supercritical fluid are higher than or equal to a critical temperature (Tc) and a critical pressure (Pc), respectively. The supercritical fluid has characteristics of a liquid and a gas. The supercritical fluid has an ability to melt a solute like a liquid does (dissolving ability) and an ability to diffuse a solute like a gas does (diffusing ability). The characteristics (dissolving ability and diffusing ability) of the subcritical fluid are approximately the same as those of the supercritical fluid. For example, the temperature T and the pressure P of the subcritical fluid satisfy one of the following sets of conditions, The unit of temperatures T and critical temperatures Tc in the following examples is ° C. Example 1 of subcritical state: T∞Tc and P&lt;Pc. Example 2 of subcritical state: T&lt;Tc. P&lt;Pc, T being sufficiently higher than room temperature, and P being sufficiently higher than normal pressure (atmospheric pressure). Examples 3 of subcritical state: 0.5&lt;T/Tc&lt;1.0 and 0.5&lt;P/Pc. Example 4 of subcritical state: 0.5&lt;T/Tc and 0.5&lt;P/Pc&lt;1.0. Example 5 of subcritical state: 0.5&lt;P/Pc when the critical temperature Tc is lower than or equal to 0° C. 
     It is preferable that the substances constituting the working fluid  11  be substances that can be rendered in the supercritical fluid or the subcritical fluid as easily as possible. The difference between the polarity of the working fluid  11  and that of the materials  21  is so small that the materials  21  can be dissolved in the working fluid  11 . The substance that constitutes the working fluid  11  is carbon dioxide, for example. The critical temperature of carbon dioxide is 31° C. The critical pressure of carbon dioxide is 7.4 MPa. For example, carbon dioxide is in a subcritical state when its temperature is higher than or equal to 31° C. and its pressure is higher than or equal to 7.1 MPa. When its temperature is 20° C., carbon dioxide is in a subcritical state if its pressure is higher than or equal to 15 MPa. The substance that constitutes the working fluid  11  need not always be carbon dioxide and may be nitrogen, for example. In the following, the term “supercritical state or the like” may be used instead of the term “supercritical state or subcritical state.” The working fluid  11  is rendered in a supercritical state or the like when the materials  21  are dissolved in the working fluid  11  in the dissolving unit  30  and when the materials  21  are mixed together in a mixer  50  in the presence of the working fluid  11 , The working fluid  11  that is not in a supercritical state or the like (e.g., it is in the form of gas or liquid) is also referred to as a “fluid  12 .” 
     It is preferable that the working fluid  11  be in a supercritical state rather than a subcritical state. The materials  21  are mixed together more thoroughly when the working fluid  11  is in a supercritical state than when it is in a subcritical state. For example, where the materials  21  include a rubber (main material  21   a  described below), the quality of a rubber product(e.g., V-belt) manufactured through mixing by the mixing apparatus  1  may be evaluated by the wear rate of the rubber product. In this evaluation method, the wear rate increases (the quality degrades) in order of a case that the working fluid  11  being in a supercritical state is used, a case that the working fluid  11  being in a subcritical state is used, and a case that a fluid  12  at atmospheric pressure is used. For example, the production unit  10  includes a cooler  15 , a pump  16 , and a heater  17 . 
     The cooler  15  (heat exchanger) converts the fluid  12  into a liquid by cooling a gas-form fluid  12 . Where the fluid  12  is carbon dioxide, the cooler  15  converts a carbon dioxide gas at atmospheric pressure (0.1 MPa), for example, into a liquid. 
     The pump  16  sends out the working fluid  11  (causes it to flow) to the mixer  50 . The pump  16  increases the pressure of a liquid-form fluid  12 . Where the pump  16  increases the pressure of a liquid-form fluid  12 , the size of the pump  16  can be made smaller than in a case that it increases the pressure of a gas-form fluid  12 . Where the fluid  12  is carbon dioxide, the pump  16  increases its pressure to 2 to 3 MPa, for example. 
     The heater  17  (heat exchanger) evaporates the fluid  12  by heating a liquid-form fluid  12 . The heater  17  pressurizes the fluid  12  by evaporating it in a container. As a result, the fluid  12  is rendered in a supercritical state or a subcritical state. Where the fluid  12  is carbon dioxide, the heater  17  pressurizes the fluid  12  to 7 to 8 MPa, for example. 
     The storage unit  20  (material storage unit) is a unit for storing materials  21 . The storage unit  20  has outlets through which materials  21  are fed into the dissolving unit  30 . The materials  21  include plural kinds of materials. For example, the materials  21  include a main material  21   a  (main row material) and an auxiliary material  21   b  (auxiliary row material, additive agent, additive). The main material  21   a  includes a polymeric material. The main material  21   a  includes a rubber or a resin. The auxiliary material  21   b  is a filler, for example. The auxiliary material  21   b  may include an inorganic substance or an organic substance. For example, the auxiliary material  21   b  may include a natural material-based material, a plant-origin material, a fiber material, or cellulose nanofiber (CNF) or the like. For example, the mixing apparatus  1  is a rubber mixing (kneading) apparatus, a resin mixing (kneading) apparatus, or the like. 
     The dissolving unit  30  is a unit for dissolving the materials  21  in the working fluid  11 . The materials  21  are fed into the dissolving unit  30  from the storage unit  20 . The working fluid  11  flows into the dissolving unit  30  from the production unit  10 . Then the materials  21  are dissolved in the working fluid  11  in the dissolving unit  30 . The materials need not always be dissolved fully in the working fluid  11 , that is, only a part of the materials  21  may be dissolved in the working fluid  11 . 
     The mixing unit  40  (kneading unit, stirring unit) is a unit for mixing the materials  21  together. The mixing unit  40  is provided downstream of the dissolving unit  30 . The term “downstream” used above means the destination side of a flow of the working fluid  11  and the materials  21  (likewise, the term “upstream” means the source side of a flow of the working fluid  11  and the materials  21 ). The mixing unit  40  includes a mixer  50  and a degree-of-opening adjustment valve  60 . 
     The mixer  50  (kneader, stirrer) mixes the materials  21  together in the presence of the working fluid  11  being in a supercritical state or a subcritical state (supercritical atmosphere or subcritical atmosphere). The mixer  50  mixes the main material  21   a  and the auxiliary material  21   b  together. Since this mixing is performed in the presence of the working fluid  11  being in a supercritical state or the like, the dispersion of the auxiliary material  21   b  and the mixing of the main material  21   a  and the auxiliary material  21   b  are accelerated more than in a case that they are mixed together in the presence of the fluid  12  that is not in a supercritical state or the like. The mixer  50  includes a chamber  51 , a mixing blade  53 , and a support structure  55  that are shown in  FIG. 2  and sensors  57  shown in  FIG. 1 . The axial direction X is defined as the direction of a center axis of the chamber  51 . Where the center axis of the chamber  51  is not straight (see  FIG. 12 ), the axial direction X is defined as the direction of a straight line that passes through the center of an entrance and the center of an exit of the chamber  51 . 
     As shown in  FIG. 2 , the chamber  51  is a container in which the materials  21  are mixed together. A flow passage (mixing flow passage) for the working fluid  11  and the materials  21  is formed inside the chamber  51 . The chamber  51  is shaped like a pipe that is long in the axial direction X. In  FIG. 2 , a part of arrows indicating flow directions of the working fluid  11  and the materials  21  are given symbols of the working fluid  11  and the materials  21 . 
     The chamber  51  (mixer  50 ) has an entrance-side portion and an exit-side portion. The entrance-side portion is a portion located upstream of the center of the chamber  51  in the axial direction X. The exit-side portion is a portion located downstream of the center of the chamber  51  in the axial direction X. As a result, the lengths of the entrance-side portion and the exit-side portion in the axial direction X are ½ of the overall length of the chamber  51  in the axial direction X. The length of at least one of the entrance-side portion and the exit-side portion in the axial direction X may be shorter than or equal to ⅓, ⅕, or 1/10 of the overall length of the chamber  51  in the axial direction X. 
     The mixing blade  53  (kneading blade, stirring blade) is a blade for mixing the materials  21  together. The materials  21  are mixed together because shearing forces act between the mixing blade  53  and the inner surface (wall surface) of the chamber  51 . The mixing blade  53  is disposed inside the chamber  51 . The mixing blade  53  extends in the axial direction X. The mixing blade  53  is fixed to the chamber  51 . The mixing blade  53  is of a static mixer, that is, it is a static blade. The mixing blade  53  is a non-rotary blade that does not rotate with respect to the chamber  51 . The mixing blade  53  is fixed to the chamber  51  via support structures  55 . Since the mixing blade  53  is fixed to the chamber  51 , it is not necessary to provide devices and members (rotary shaft etc.) for rotating the mixing blade  53 . The mixing blade  53  has a shaft portion  53   a  and a blade portion  53   b . The shaft portion  53   a  extends in the axial direction X and is shaped like a cylinder, for example. The blade portion  53   b  projects from the shaft portion  53   a  outward in the radial direction X (see  FIG. 3 ). The blade portion  53   b  is shaped spirally, for example. Flowing alongside the mixing blade  53 , the working fluid  11  and the materials  21  form a swirling flow, for example. As a result, the mixing of the materials  21  are accelerated. In  FIG. 2  etc., the mixing blade  53  is shown in a simplified manner (the same is true of the support structures  55 ). 
     Only one mixing blade  53  may be provided (one axis). Alternatively, plural mixing blades  53  may be provided (plural axes; two axes, three axes, or the like) (refer to  FIG. 4  and  FIG. 5 ). Where plural mixing blades  53  are provided, the materials  21  can be mixed more thoroughly than in the case where only one mixing blade  53  is provided. As shown in  FIG. 3 , an outer circumferential portion of the mixing blade  53  as viewed from the axial direction X (hereinafter referred to as an “outer circumferential portion of the mixing blade  53 ”) and the inner surface of a cross section of the chamber  51  as viewed from the axial direction X (hereinafter referred to as a “cross-section inner surface of the chamber  51 ”) have corresponding shapes (paired shapes). A gap is formed between the outer circumferential portion of the mixing blade  53  and the cross-section inner surface of the chamber  51 . For example, the outer circumferential portion of the mixing blade  53  is shaped like a circle, an ellipse, or a shape that is close to a circle or an ellipse. The cross-section inner surface of the chamber  51  is shaped as follows. Example 1: Where only one mixing blade  53  is provided, the shape of the cross-section inner surface of the chamber  51  is similar to the shape of the outer circumferential portion of the mixing blade  53 , for example, a circle, an ellipse, or a shape that is close to a circle or an ellipse. Example 2: Where plural mixing blades  53  are provided, the shape of the cross-section inner surface of the chamber  51  is a shape of an outer circumferential portion obtained by connecting outer circumferential portions of the plural mixing blades  53  in an overlapped manner, For example, the shape of the cross-section inner surface of the chamber  51  is a shape of an outer circumferential portion obtained by connecting plural circles, ellipses, or shapes that are close to circles or ellipses in an overlapped manner. 
     As shown in  FIG. 3 , the support structures  55  are structures for fixing the mixing blade  53  to the chamber  51  and having the former be supported by the latter. For example, the support structures  55  are members that extend inward in the radial direction (i.e., toward the shaft portion  53   a ) from the inner surface of the chamber  51 . 
     As shown in  FIG. 1 , the sensors  57  detect inside states of the mixer  50 . The sensors  57  are used for detecting a state of the working fluid  11  (i.e., whether it is in a supercritical state or a subcritical state). The sensors  57  may be used for detecting an amount (presence/absence, mixing state) of the materials  21  in the mixer  50 . The sensors  57  may be used for controlling (adjusting) the flow rate Q of the working fluid  11  and the materials  21  in the mixer  50 . The sensors  57  include pressure gauges and thermometers. The sensors  57  include a mixer entrance pressure gauge  57   p   1 , a mixer exit pressure gauge  57   p   2 , a mid-mixer pressure gauge  570 , a mixer entrance thermometer  57   t   1 , a mixer exit thermometer  57   t   2 , a mid-mixer thermometer  57   t   3 . The mixer entrance pressure gauge  57   p   1  detects a pressure P 1  at the entrance-side portion of the mixer  50 . The mixer exit pressure gauge  57   p   2  detects a pressure P 2  at the exit-side portion of the mixer  50 . The mid-mixer pressure gauge  57   p   3  detects a pressure P 3  at a portion (called a “middle portion”) located downstream of the mixer entrance pressure gauge  57   p   1  and upstream of the mixer exit pressure gauge  57   p   2 . Mid-mixer pressure gauges  57   p   3  may be provided at plural positions (the same is true of mid-mixer thermometers  57   t   3 ). The plural mid-mixer pressure gauges  57   p   3  may be provided at positions that are spaced from each other in the axial direction X (the same is true of mid-mixer thermometers  57   t   3 ). The mixer entrance thermometer  57   t   1  detects a temperature T 1  at the entrance-side portion of the mixer  50 . The mixer exit thermometer  57   t   2  detects a temperature T 2  at the exit-side portion of the mixer  50 . The mid-mixer thermometer  57   t   3  detects a temperature T 3  at the portion (called the “middle portion”) located downstream of the mixer entrance thermometer  57   t   1  and upstream of the mixer exit thermometer  57   t   2 . 
     The degree-of-opening adjustment valve  60  is used for controlling (adjusting) the pressure and the flow rate in the mixer  50 . The degree-of-opening adjustment valve  60  adjusts the degree of opening of a flow passage for a fluid (working fluid  11  and materials  21 ) that is ejected from the mixer  50 . For example, the degree-of-opening adjustment valve  60  may be provided at the exit of the chamber  51 , downstream of the chamber  51 , or in a flow passage that is connected to the exit of the chamber  51 . Either one or plural degree-of-opening adjustment valves  60  may be provided. 
     The separation unit  70  is a unit for separating the working fluid  11  (fluid  12 ) from the materials  21  dissolved in the working fluid  11 . The separation unit  70  is provided downstream of the mixing unit  40 , the mixer  50 , and the degree-of-opening adjustment valve  60 . The separation unit  70  includes a separator  71  and a pressure adjustment valve  73 . 
     The separator  71  separates the working fluid  11  from the materials  21  (devolatilization). The separator  71  separates the working fluid  11  from the materials  21  by lowering the pressure of the working fluid  11  and the materials  21  and thereby vaporizing the working fluid  11  (producing a gas-form fluid  12 ). As a result, the separator  71  deposits the materials  21 . The separator  71  includes an opening portion  71   a . The opening portion  71   a  ejects the materials  21  from which a working fluid  11  has been separated. The opening portion  71   a  is a lid, capable of being opened and closed (movable opening/closing portion), of the separator  71 . When the opening portion  71 a is closed, it is airtight. The opening portion  71   a  ejects the materials  21  intermittently (described later in detail). The opening portion  71   a  ejects the materials  21  downward (i.e., drops materials  21 ). 
     The pressure adjustment valve  73  adjusts the degree of opening of the flow passage through which a working fluid  11  (i.e., gas-form fluid  12 ) separated from the materials  21  passes, The pressure adjustment valve  73  adjusts the pressure at a position upstream of itself . The pressure adjustment valve  73  adjusts the pressure in the separator  71 . For example, the pressure adjustment valve  73  may be provided at the exit of the separator  71 , downstream of the separator  71 , or in the flow passage (devolatilization flow passage) that is connected to the exit of the separator  71 . Either only one or plural pressure adjustment valves  73  may be provided. It is preferable that a gas-form fluid  12  that has passed through the pressure adjustment valve  73  flow into the production unit  10  (e.g., cooler  15 ) (so as to be used again). 
     The carry-out unit  90  is a unit for carrying out the materials  21  to the next process. The next process is a process located next to the process using the mixing apparatus  1 . The carry-out unit  90  may include a belt conveyor, for example, For example, the apparatus of the next process may be an apparatus for manufacturing pellets (i.e., pelletizer) or an apparatus for manufacturing sheets (e.g., sheet extruder). The materials  21  may be carried out to the next process directly from the separation unit  70 , that is, without passing through the carry-out unit  90 . 
     The control unit C performs input/output of signals, computation (judgment, calculation, etc.), control of devices, etc. Detection results of the sensors  57  are input to the control unit C. For example, the control unit C controls the operations of the production unit  10 , the storage unit  20 , the dissolving unit  30 , the mixing unit  40 , the separation unit  70 , and the carry-out unit  90 . 
     (Operations) 
     How the mixing apparatus  1  operates is described by mainly referring to a flowchart shown in  FIG. 6 . The individual constituent elements of the above-described mixing apparatus  1  is described by mainly referring to  FIG. 1 . In the following, how the mixing apparatus  1  operates is described in order. The order of operations may be changed. 
     (Dissolving of Materials  21  in Working Fluid  11  and Related Operations) 
     The pump  16  is driven and materials  21  are fed into the dissolving unit  30  (step S 11 ). The details of this step are as follows. When the pump  16  is driven, a working fluid  11  flows into the dissolving unit  30  from the production unit  10  (through pressurization) Furthermore, materials  21  are fed into the dissolving unit  30  through the outlets of the storage unit  20 . At this time, the degree-of-opening adjustment valve  60  is closed fully. The pressures in the dissolving unit  30  and the mixing unit  40  are increased by increasing the rotation speed of the pump  16 . 
     (Judgment of State of Working Fluid  11 ) 
     Then it is judged whether the working fluid  11  is in a supercritical state or the like (step S 21 ). This judgment is made by the control unit C. Likewise, other judgments are made by the control unit C. The following description is made of a case that a state of the working fluid  11  at the exit-side portion of the mixer  50  is judged. A state of the working fluid  11  at a portion other than the exit-side portion of the mixer  50  may be judged. It is preferable that judgment be made at more portions. It is judged (through comparison) whether the pressure P 2  is higher than or equal to a desired pressure Pa and the temperature T 2  is higher than or equal to a desired temperature Ta. The desired pressure Pa and the desired temperature Ta are set in the control unit C in advance. Where the working fluid  11  should be rendered in a supercritical state, the desired pressure Pa is the critical pressure and the desired temperature Ta is the critical temperature. Where the working fluid  11  should be rendered in a subcritical state, the desired pressure Pa and the desired temperature Ta are a pressure and a temperature at which the working fluid  11  is rendered in a subcritical state. If the pressure P 2  is higher than or equal to the desired pressure Pa and the temperature T 2  is higher than or equal to the desired temperature Ta (yes), it is judged that the working fluid  11  is in a supercritical state or the like and the process moves to the next step S 23 . If the pressure P 2  is lower than the desired pressure Pa or the temperature T 2  is lower than the desired temperature Ta (no), it is judged that the working fluid  11  is not in a supercritical state or the like. In this case, the pressure and the temperature of the working fluid  11  are increased until the pressure P 2  becomes higher than or equal to the pressure Pa and the temperature T 2  becomes higher than or equal to the temperature Ta. More specifically, the rotation speed of the pump  16  is increased (step S 22 ). 
     (Start of Flowing of Materials  21  etc.) 
     Subsequently, the degree-of-opening adjustment valve  60  is set to an open state (step S 23 ). It is preferable that at this time the degree-of-opening adjustment valve  60  is opened gradually from the closed state. The term “open state”means a state that degree-of-opening adjustment valve  60  is on the open side of the fully closed state; for example, the open state may be a fully open state or a state between the fully open state and the fully closed state. When the degree-of-opening adjustment valve  60  is rendered in an open state, the materials  21  are mixed together while flowing downstream through the mixer  50  and then flow into the separator  71  from the mixer  50 . 
     (Deposition of Materials  21 ) 
     The working fluid  11  and the materials  21  flow into the separator  71  with the opening portion  71   a  of the separator  71  and the pressure adjustment valve  73  closed. Then the pressure adjustment valve  73  is rendered in an open state. As a result, the working fluid  11  is vaporized and the working fluid  11  (fluid  12 ) is devolatilised from the materials  21 . It is preferable that at this time the pressure adjustment valve  73  be opened gradually. With this measure, the pressure in the separator  71  lowers gradually. As a result, bubble formation due to quick pressure reduction and resulting generation of noise can be suppressed. The opening portion  71   a  is thereafter opened. As a result, deposited materials  21  (i.e., materials  21  from which a working fluid  11  has been separated) are ejected from the separator  71 . The opening portion  71   a  is then closed. In this manner, the opening portion  71   a  ejects materials  21  intermittently (what is called a semi-batch type operation), 
     (Judgment of State of Working Fluid  11 ) 
     As described above, the pressure in the mixer  50  lowers when each of the degree-of-opening adjustment valve  60  and the pressure adjustment valve  73  is rendered in an open state. If at this time the state that the working fluid  11  is in a supercritical state or the like is canceled, materials  21  are deposited in the mixer  50  and the flow passage in the mixer  50  may be clogged. To prevent the flow passage in the mixer  50  from being clogged, the working fluid  11  needs to be kept in a supercritical state or the like. Thus, the state of the working fluid  11  is judged again (step S 31 ). This judgment is made at least at one of the entrance-side portion, the middle portion, and the exit-side portion. For example, the same judgment as made at step S 21  is made. If the pressure P 2  is higher than or equal to the desired pressure Pa and the temperature T 2  is higher than or equal to the desired temperature Ta (yes), it is judged that the working fluid  11  is in a supercritical state or the like and the process moves to the next step S 41 . If the pressure P 2  is lower than the desired pressure Pa or the temperature T 2  is lower than the desired temperature Ta (no), it is judged that the working fluid  11  is not in a supercritical state or the like. in this case, the pressure and the temperature of the working fluid  11  are increased until the pressure P 2  becomes higher than or equal to the pressure Pa and the temperature T 2  becomes higher than or equal to the temperature Ta (step S 32  which is the same as step S 22 ). 
     (Judgment of Differential Pressure ΔP and Flow Rate Q) 
     A flow rate of the working fluid  11  and the materials  21  flowing through the mixer  50  is judged (step S 41 ). More specifically, a flow rate Q is calculated on the basis of the differential pressure ΔP between the pressure P 1  and the pressure P 2 . It is then judged whether the flow rate Q is within a prescribed range (the term “prescribed range”means a predetermined proper range (regular range); the same applies to the following description). Whether the differential pressure ΔP is within a prescribed range may be judged without calculating a flow rate Q. The prescribed range of the flow rate Q (or the prescribed range of the differential pressure ΔP) is set in the control unit C in advance. The prescribed range is set to a range where the working fluid  11  can be kept in a supercritical state or the like. More specifically, for example, it is judged whether the flow rate Q is within a range of the desired flow rate Qa±10% (prescribed range). Alternatively, it may be judged whether the differential pressure ΔP is within a range of a desired differential pressure ±10%. If the flow rate Q (or differential pressure ΔP) is within the prescribed range (yes), the process moves to the next step S 43 . If the flow rate Q (or differential pressure ΔP) is not within the prescribed range (no), the next control is performed. In this case, the differential pressure ΔP is controlled so as to fall within the prescribed range. As a result, the flow rate Q is controlled so as to fall within the prescribed range. The differential pressure ΔP is controlled (the flow rate Q is controlled) by controlling the degree of opening of the degree-of-opening adjustment valve  60 . The differential pressure ΔP may be controlled by controlling the rotation speed of the pump  16  in place of or in addition to the control of the degree of opening of the degree-of-opening adjustment valve  60 . 
     (Judgment of Residual Materials  21 ) 
     An amount of materials  21  remaining in the mixer  50  is judged (step S 43 ). More specifically, the amount of materials  21  remaining in the mixer  50  (residual materials) becomes small when the mixing in the mixer  50  has come close to the end. As a result, the sectional area of the flow passage in the mixer  50  increases, the pressure loss in the mixer  50  decreases, and the differential pressure ΔP becomes small. Thus, it is judged whether the differential pressure ΔP is smaller than or equal to a desired differential pressure ΔPa. The desired differential pressure ΔPa is set in the control unit C in advance. If the differential pressure ΔP is larger than the desired differential pressure ΔPa (no), it is judged that an amount of materials  21  remaining in the mixer  50  is larger than a prescribed amount. In this case, the flow rate Q is adjusted as necessary (step S 44  which is the same as step S 42 ) and the mixing is continued. In this case, for example, the process returns to step S 31 . If the differential pressure ΔP is larger than the desired differential pressure ΔPa (yes), it is judged that an amount of materials  21  remaining in the mixer  50  is smaller than or equal to the prescribed amount. In this case, the mixing in the mixer  50  is finished (step S 51 ). More specifically, the degree-of-opening adjustment valve  60  is closed and the pump  16  is stopped. 
     (Comparison with Rotary Blade) 
     An apparatus that mixes materials together without using a supercritical fluid or the like has the following problems, for example. In such apparatuses, a rotary blade is rotated with respect to a chamber and shearing forces are applied to the materials, whereby the materials are caused to heat (shearing heating) and melt and melted materials are mixed together, In this case, shearing heat generated in the materials causes problems that the materials are degraded and the energy efficiency is low. For example, where the materials include a polymer (rubber, resin, or the like) that is formed by entangled molecular chains, molecular chains of the materials may be cut when the materials receive strong shearing forces. Cuffing of molecular chains leads to degradation of the materials. On the other hand, in apparatuses that mix materials together using a supercritical fluid or the like, it is not necessary to melt the materials by shearing heating because the materials are melted in the supercritical fluid or the like. Thus, such apparatuses are free of the problems that the materials are degraded and the energy efficiency is low. 
     Even among apparatuses that mix materials together using a supercritical fluid or the like, apparatuses that mix materials together by a rotary blade that rotate with respect to a chamber have the following problem, for example. In such apparatuses, a drive device for rotating the rotary blade is provided outside the chamber. It is conceivable that the drive device outside the chamber and the rotary blade in the chamber are connected to each other by, for example, a shaft portion of the rotary blade. Thus, there is a problem of fluid leakage through, for example, the gap between the chamber and the shaft portion of the rotary blade (the problem relating to sealing performance). The problem relating to sealing performance is particularly serious because the inside of the chamber is in a high pressure state (i.e., a state that the pressure is higher than atmospheric pressure) such as a supercritical state or the like. On the other hand, in this embodiment, since the mixing blade  53  is fixed to the chamber  51 , it is possible to avoid the above problem relating to sealing performance. The mixing apparatus  1  according to this embodiment may be provided with a rotary blade (refer to a ninth embodiment), 
     (Rotation Speed of Pump  16 ) 
     It is preferable that the rotation speed of the pump  16  can be varied (i.e., increased and decreased). It is preferable the control of the rotation speed of the pump  16  be inverter control. Where the rotation speed of the pump  16  is varied, the working fluid  11  and the materials  21  are compressed and expanded repeatedly (causing a pressure variation and a pumping effect). This makes it possible to cause an extensional flow in addition to a shear flow in the working fluid  11  and the materials  21  and hence to mix the materials  21  more thoroughly. For example, where the materials  21  include a fiber material (e.g., CNF), entangled fibers can be defibrated by the above-mentioned pumping effect. 
     The mixing apparatus  1  shown in  FIG. 1  provides the following advantages. 
     (Advantages of First Aspect of Invention) 
     The mixing apparatus  1  includes the mixer  50 , The mixer  50  mixes materials  21  including a rubber or a resin in the presence of a working fluid  11  being in a supercritical state or a subcritical state. The mixer  50  includes the chamber  51  and the mixing blade  53 . The chamber  51  forms a flow passage for the working fluid  11  and the materials  21 . 
     [Configuration 1] The mixing blade  53  is disposed in and fixed to the chamber  51 . 
     The mixing apparatus  1  has the above [Configuration 1]. Thus, the mixing apparatus  1  can dispense with energy for rotating the mixing blade  53  with respect to the chamber  51 . Furthermore, it is not necessary to form a gap between members for rotating the mixing blade  53  with respect to the chamber  51  and the chamber  51 . This makes it possible to give necessary sealing performance to the chamber  51 . 
     The above [Configuration 1] may provide the following advantages. The heat generated by the friction between the mixing blade  53  and the materials  21  can be made smaller than in a case that the mixing blade  53  is rotated with respect to the chamber  51 . Thus, the temperature increase of the materials  21  being mixed together can be suppressed. As a result, the degradation of the materials  21  by heat can be suppressed. This makes it possible to increase the kinds of materials  21  that can be mixed together. More specifically, for example, even materials that are less resistant to heat (e.g., plant-origin materials such as CNF) than metal materials etc. can be subjected to mixing by the mixer  50 . Furthermore, where the mixing blade  53  is formed so as to rotate the working fluid  11 , the following advantages may be provided. Since the heat generated by the friction between the mixing blade  53  and the materials  21  is reduced, the rotation speed during kneading can be increased to raise the kneading efficiency of the materials  21 . 
     (Advantage of Second Aspect of Invention) 
     [Configuration 2] The mixing apparatus  1  includes the separator  71 . The separator  71  is disposed downstream of the mixer  50  and separates the working fluid  11  (fluid  12 ) from the materials  21 . 
     The above [Configuration 2] makes it possible to deposit materials  21  in the separator  71  which is disposed downstream of the mixer  50 . Thus, it is not necessary to separate (devolatilize) the working fluid  11  from the materials  21  in the mixer  50 . 
     The details of this advantage are as follows. Where the materials  21  are mixed together by a rotary blade that rotates with respect to the chamber  51  unlike in the embodiment, deposited materials  21  can be pushed out to the downstream side by the rotary blade even if devolatilization is performed in the mixer  50 . Thus, deposited materials  21  do not clog the mixer  50 . On the other hand, in the embodiment, the mixing blade  53  is fixed to the chamber  51  (above [Configuration 11]). Thus, if devolatilization is performed in the mixer  50 , deposited materials  21  may clog in the mixer  50 . However, since the mixing apparatus  1  has the above [Configuration 2]. It is not necessary to perform volatilization in the mixer  50 . Thus, clogging of the mixer  50  by deposited materials  21  can be suppressed. 
     The above [Configuration 2] may provide the following advantage. A working fluid  11  (fluid  12 ) separated by the separator  71  is reused easily. 
     (Advantages of Third Aspect of Invention) 
     [Configuration 3] The mixing apparatus  1  includes the pressure adjustment valve  73 . The pressure adjustment valve  73  adjusts the degree of opening of the flow passage through which a working fluid  11  (fluid  12 ) separated from the materials  21  is to pass. 
     The above [Configuration 3] makes it possible to adjust the pressure in the separator  71 . Thus, the use of the pressure adjustment valve  73  makes it possible to lower the pressure of the working fluid  11  and the materials  21  gradually (smoothly) and to cause devolatilization gradually. This makes it possible to suppress bubble formation due to quick pressure reduction (i.e., volatilization in a short time) and resulting generation of noise. Furthermore, energy loss (useless energy consumption) due to generation of noise can be suppressed. 
     (Advantage of Fourth Aspect of Invention) 
     [Configuration 4] The separator  71  includes the opening portion  71   a  for ejecting the materials  21  intermittently from which a working fluid  11  has been separated. 
     The above [Configuration 4] makes it easier to eject the materials  21  from the separator  71  after devolatilization is completed properly. 
     (Advantages of Fifth Aspect of Invention) 
     [Configuration 5] The mixing apparatus  1  includes the degree-of-opening adjustment valve  60  for adjusting the degree of opening of the flow passage through which a fluid (working fluid  11  and materials  21 ) ejected from the mixer  50  is to pass. 
     The above [Configuration 5] makes it possible to adjust the flow rate of the working fluid  11  and the materials  21  in the mixer  50 , 
     (Advantages of Sixth Aspect of Invention) 
     [Configuration 6] The mixer  50  includes the mixer entrance pressure gauge  57   p   1 , the mixer entrance thermometer  57   t   1 , the mixer exit pressure gauge  57   p   2 , and the mixer exit thermometer  57   t   2 . The mixer entrance pressure gauge  57   p   1  detects a pressure at the entrance-side portion of the mixer  50 . The mixer entrance thermometer  57   t   1  detects a temperature at the entrance-side portion of the mixer  50 . The mixer exit pressure gauge  57   p   2  detects a pressure at the exit-side portion of the mixer  50 . The mixer exit thermometer  57   t   2  detects a temperature at the exit-side portion of the mixer  50 . 
     With the above [Configuration 6], pressures P 1  and P 2  and temperatures T 1  and T 2  in the mixer  50 , that is, at the entrance-side portion and the exit-side portion of the mixer  50 , are detected. Thus, states of the working fluid  11  (i.e., whether the working fluid  11  is in a supercritical state or the like) at the entrance-side portion and the exit-side portion of the mixer  50  can be judged. Furthermore, with the above [Configuration 6], since pressures P 1  and P 2  at the entrance-side portion and the exit-side portion of the mixer  50  are detected, respectively, a differential pressure ΔP between the pressures P 1  and P 2  at the entrance-side portion and the exit-side portion of the mixer  50  can be detected, as a result of which a flow rate Q in the mixer  50  can be detected. Thus, information relating to the flow rate Q can be used for controlling the flow rate Q in the mixer  50 . The detection of a differential pressure ΔP also makes it possible to detect an amount of materials  21  remaining in the mixer  50 . 
     (Advantage of Seventh Aspect of Invention) 
     [Configuration 7] The mixing apparatus  1  (control unit C) controls the differential pressure ΔP between a pressure P 1  detected by the mixer entrance pressure gauge  57   p   1  and a pressure P 2  detected by the mixer exit pressure gauge  57   p  so that the differential pressure ΔP falls within a prescribed range. 
     With the above [Configuration 7], the differential pressure ΔP between the pressures P 1  and P 2  at the entrance-side portion and the exit-side portion of the mixer  50  falls within a prescribed range. This makes it possible to have the flow rate Q in the mixer  50  fall within a prescribed range. 
     (Advantages of Eighth Aspect of Invention) 
     [Configuration 8] The mixer  50  includes the mid-mixer pressure gauge  57   p   3  and the mid-mixer thermometer  57   t   3 . The mid-mixer pressure gauge  57   p   3  detects a pressure at the portion (middle portion) located downstream of the mixer entrance pressure gauge  57   p   1  and upstream of the mixer exit pressure gauge  57   p   2 . The mid-mixer thermometer  57   t   3  detects a temperature at the portion (middle portion) located downstream of the mixer entrance thermometer  57   t   1  and upstream of the mixer exit thermometer  57   t   2 . 
     The above [Configuration 8] makes it possible to detect whether the working fluid  11  is in a supercritical state or the like at the entrance-side portion, the exit-side portion, and the middle portion of the mixer  50 . Furthermore, the above [Configuration 8] makes it possible to detect the differential pressure between a pressure P 1  at the entrance-side portion and a pressure P 3  at the middle portion of the mixer  50  and the differential pressure between the pressure P 3  at the middle portion and a pressure P 2  at the exit-side portion of the mixer  50 . As a result, a flow rate Q in the mixer  50  can be detected with higher accuracy. 
     Furthermore, an amount of materials  21  remaining in the mixer  50  can be detected with higher accuracy, 
     (Advantages of Ninth Aspect of Invention) 
     [Configuration 9] The mixing apparatus  1  includes the pump  16  for sending out the working fluid  11  to the mixer  50 . The rotation speed of the pump  16  is inverter-controlled. 
     The above [Configuration 9] makes it possible to vary the rotation speed of the pump  16  easily. When the rotation speed of the pump  16  is varied, the working fluid  11  and the materials  21  are compressed and expanded repeatedly (causing a pressure variation and a pumping effect). This makes it possible to cause an extensional flow in addition to a shear flow in the working fluid  11  and the materials  21  and hence to mix the materials  21  more thoroughly. This may provide the following advantage. For example, where the materials  21  include a fiber material (e.g., CNF), entangled fibers can be defibrated by the above-mentioned pumping effect. 
     Second Embodiment 
     Differences of a mixing apparatus  201  according to a second embodiment from the mixing apparatus according to the first embodiment is described with reference to  FIG. 7 . Constituent elements, having the same ones in the first embodiment, of the mixing apparatus  201  according to the second embodiment is not described by, for example, giving the former the same symbols as the latter. Likewise, common constituent elements is not described in the other embodiments. A dissolving unit  230  and a mixer  250  are inclined with respect to the horizontal direction. 
     The mixer  250  is inclined with respect to the horizontal direction (hereinafter referred to simply as “inclined”) so that the materials  21  go down from the upstream side to the downstream side of the working fluid  11  and the materials  21 . The chamber  51  (see  FIG. 2 ) and the mixing blade  53  (see  FIG. 2 ) are inclined. Either the whole of the mixer  250  or only a part of it may be inclined. A dissolving unit  230  is inclined like the mixer  250 . Where the mixer  250  is inclined, the dissolving unit  230  need not always be inclined. Although in the example shown in  FIG. 7  neither the mid-mixer pressure gauge  57   p   3  (see  FIG. 1 ) nor the mid-mixer thermometer  57   t   3  (see  FIG. 1 ) is provided, they may be provided. 
     The mixing apparatus  201  shown in  FIG. 7  provides the following advantages. 
     (Advantages of 10th Aspect of Invention) 
     [Configuration 10] The mixer  250  is inclined respect to the horizontal direction so that the materials  21  go down from the upstream side to the downstream side of the materials  21 . 
     With the above [Configuration 10], the materials  21  tend to flow toward the downstream side in the mixer  250  due to gravity (i.e., their own weights). The details of this advantage are as follows. Where unlike in this embodiment materials are mixed together by a rotary blade that rotates with respect to a chamber, materials are not prone to be left in the mixer because the rotary blade can carry the materials toward the downstream side. On the other hand, in this embodiment, the mixing blade  53  is fixed to the chamber  51  (refer to the above [Configuration 1]). Thus, materials  21  may remain in the mixer  250 . In view of this, the mixing apparatus  201  has the above [Configuration 10]). As a result, materials  21  are not prone to remain in the mixer  250 . 
     Furthermore, since the materials  21  tend to flow toward the downstream side in the mixer  250 , the motive power for causing the working fluid  11  and the materials  21  to flow toward the downstream side (e.g., the motive power of the pump  16 ) can be suppressed. 
     Third Embodiment 
     Differences of a mixer  350  of a mixing apparatus  301  according to a third embodiment from the mixer employed in the first embodiment is described with reference to  FIGS. 8 to 10 . As shown in  FIG. 8 , the mixer  350  includes mixing acceleration members  355 . 
     The mixing acceleration members  355  are members for accelerating the mixing of materials  21 . The mixing acceleration members  355  are fixed to the chamber  51 , block a part of the flow passage in the chamber  51 , and are provided separately from the mixing blade  53 . The mixing acceleration members  355  are shaped like plates (mixing acceleration plates), for example. In this case, the thickness direction of the plate-like mixing acceleration members  355  is the axial direction X of the chamber  51 , for example. The mixing acceleration members  355  need not always be shaped like plates and may be shaped like blocks, for example. For example, the mixing acceleration members  355  project from the inner surface of the chamber  51  toward the center axis of the chamber  51 . The mixing acceleration members  355  may project from a top portion of the inner surface of the chamber  51  toward its bottom portion (see  FIG. 9 ) or from a bottom portion of the inner surface of the chamber  51  toward its top portion. As shown in  FIG. 10 , the mixing acceleration members  355  may project from the inner surface of the chamber  51  from the outside toward the inside in the horizontal direction. 
     As shown in  FIG. 8 , because of the provision of the mixing acceleration members  355 , the working fluid  11  and the materials  21  come to flow clear of the mixing acceleration members  355 . As a result, the flow passage in the mixer  350  tends to become complex (the flow passage tends to vary and replacement of materials  21  is accelerated), whereby the materials  21  are mixed together more thoroughly. For example, assume that the materials  21  flow through the mixer  350  so as to rotate spirally alongside the mixing blade  53 . In this case, the materials  21  tend to be distributed (i.e., gather) more in the vicinity of the inner surface of the chamber  51  because of centrifugal force and flow near and alongside the inner surface of the chamber  51 . When flowing in this manner and coming close to a mixing acceleration member  355 , materials  21  then flow clear of the mixing acceleration member  355 . Thus, the materials  21  move toward the center axis of the chamber  51 . In this manner, the flowing direction of the materials  21  vary in a complicated manner in the vicinity of the mixing acceleration members  355 , whereby mixing of the materials  21  is accelerated. 
     Furthermore, the provision of the mixing acceleration members  355  causes pressure losses in the flow passage in the mixer  350  and a pumping effect (mentioned above) on the working fluid  11  and the materials  21 . This makes it possible to cause an extensional flow in addition to a shear flow in the working fluid  11  and the materials  21 , whereby the materials  21  can be mixed together more thoroughly. For example, where the materials  21  include a fiber material (e.g., CNF), the above pumping effect makes it possible to defibrate entangled fibers. 
     The mixing apparatus  301  shown in  FIG. 8  provides the following advantages. 
     (Advantages of 11th Aspect of Invention) 
     [Configuration 11] The mixer  350  includes the mixing acceleration members  355 . The mixing acceleration members  355  are fixed to the chamber  51 , block a part of the flow passage in the chamber  51 , and is provided separately from the mixing blade  53 . 
     With the above [Configuration  11 ], the flow passage for the materials  21  can be made complex, whereby the materials  21  can be mixed together more thoroughly. 
     Fourth Embodiment 
     Differences of a mixer  450  of a mixing apparatus  401  according to a fourth embodiment from the mixer employed in the first embodiment is described with reference to  FIG. 11 . The mixer  450  of the mixing apparatus  401  includes a chamber  451 . 
     The sectional area of the chamber  451  as viewed from the axial direction X varies depending on the position in the axial direction X. For example, a portion where the sectional area of the chamber  451  decreases gradually and a portion where the sectional area of the chamber  451  increases gradually are arranged alternately from the upstream side to the downstream side in the axial direction X. In this case, the working fluid  11  and the materials  21  are compressed and expanded repeatedly (a pumping effect occurs) and they accelerate and decelerate repeatedly. This makes it possible to cause an extensional flow in addition to a shear flow in the working fluid  11  and the materials  21 , whereby the materials  21  can be mixed together more thoroughly. For example, where the materials  21  include a fiber material (e.g., CNF), the above pumping effect makes it possible to defibrate entangled fibers. 
     The mixing apparatus  401  shown in  FIG. 11  provides the following advantages. 
     (Advantages of 12th Aspect of Invention) 
     [Configuration 12] The sectional area of the chamber  451  as viewed from the axial direction X of the chamber  451  varies depending on the position in the axial direction X in the chamber  451 . 
     With the above [Configuration 12], the pressure acting on the materials  21  varies as the working fluid  11  and the materials  21  flow through the chamber  451 . As a result, the materials  21  can be mixed together more thoroughly. 
     Fifth Embodiment 
     Differences of a mixer  550  of a mixing apparatus  501  according to a fifth embodiment from the mixer employed in the first embodiment is described with reference to  FIG. 12 . The mixer  550  of the mixing apparatus  501  includes a chamber  551 . 
     A line obtained by connecting the centers of cross sections, as viewed from the axial direction X, of the chamber  51  is referred to as a cross section center line  551   a . The cross section center line  551   a  is shaped like a curved line or a polygonal line. At least one of the vertical position and the horizontal position of the cross section center line  551   a  varies depending on the position in the axial direction X. For example, the cross section center line  551   a  snakes in the vertical direction. For example, the cross section center line  551   a  may snake in the horizontal direction. The cross section center line  551   a  may snake in a direction that is inclined with respect to the vertical direction and the horizontal direction. The cross section center line  551   a  may be shaped like a spiral. The cross section center line  551   a  need not always snake. Where the cross section center line  551   a  is shaped like a curved line or a polygonal line, the sectional area, as viewed from the axial direction X, of the chamber  551  may either vary depending on the position in the axial direction X or kept the same (kept constant). 
     The mixing apparatus  501  shown in  FIG. 12  provides the following advantages. 
     (Advantages of 13th Aspect of Invention) 
     [Configuration 13] The line (cross section center line  551   a ) obtained by connecting the centers of cross sections, as viewed from the axial direction X of the chamber  551 , of the chamber  551  is shaped like a curved line or a polygonal line. 
     With above [Configuration 13], a flow passage for the materials  21  is made more complex than in the case where the cross section center line  551   a  is straight, whereby the materials  21  can be mixed together more thoroughly. 
     Sixth Embodiment 
     Differences of mixing blades  653  etc. of a mixer  650  of a mixing apparatus  601  according to a sixth embodiment from the mixing blade etc. employed in the first embodiment is described with reference to  FIG. 13 . 
     The mixing blades  653  are arranged at intervals in the axial direction X. The mixing blades  653  are arranged in the axial direction X in such a manner that intervals (gap regions A) are formed between them. In each gap region A, a flow passage for the materials  21  tends to become complex (the flow passage tends to vary and replacement of materials is accelerated). In  FIG. 13 , the support structures  55  (see  FIG. 2  etc.) are not shown. The mixing acceleration members  355  (see  FIG. 1 ) may be disposed in the respective gap regions A. In this case, the mixing acceleration members  355  can be disposed in the respective gap regions A easily. The mixing apparatus  601  shown in  FIG. 13  provides the following advantages. 
     (Advantages of 14th Aspect of Invention) 
     [Configuration 14] The mixing blades  653  are arranged at intervals in the axial direction X of the chamber  51 . 
     With the above [Configuration 14], a flow passage for the materials  21  can be made complex in the regions (gap regions A) formed between the mixing blades  653  in the axial direction X. As a result, the materials  21  can be mixed together more thoroughly. 
     Seventh Embodiment 
     Differences of a mixing apparatus  701  according to a seventh embodiment from the mixing device according to the first embodiment is described with reference to  FIG. 14 . The mixer  50  of the mixing apparatus  701  includes heaters  759 . 
     The heaters  759  heat the inside of the chamber  51  (see  FIG. 2 ; this also applies to the following). The heaters  759  heat the working fluid  11  and the materials  21  existing in the chamber  51 . Although in the example shown in  FIG. 14 , the heaters  759  are disposed at three positions, the heater(s)  759  may be disposed at one position, two positions, or four or more positions. 
     The heaters  759  are used for maintaining a state (e.g., supercritical state or the like) of the working fluid  11 . As a control for maintaining a state of the working fluid  11 , a temperature control is easier than a pressure control. More specifically, the difference between a pressure of the working fluid  11  being in a supercritical state or the like and atmospheric pressure is large (the former is about  74  times or more as high as the latter in the case of carbon dioxide, for example). Thus, it is more difficult to fine-adjust the pressure of the working fluid  11  than its temperature. Furthermore, energy consumed by a pressure control may be larger (a motive power loss may be larger) than that consumed by a temperature control. In view of the above, in this embodiment, a control is performed using the heaters  759  so that a state (e.g., supercritical state or the like) of the working fluid  11  is maintained. As a modification, the pressure of the working fluid  11  may be controlled to maintain a state of the working fluid  11 . 
     The heaters  759  are used to control the progress of a chemical reaction of the materials  21  in the mixer  50  (in the chamber  51 ). Incidentally, the heaters  759  may be used for only one of the controls for maintaining a state of the working fluid  11  and the control of the progress of a chemical reaction of the materials  21 . 
     The mixing apparatus  701  shown in  FIG. 14  provides the following advantages. 
     (Advantages of 15th Aspect of Invention) 
     [Configuration 15] The mixer  50  includes the heaters  759  for heating the inside of the chamber  51 . 
     The temperature in the mixer  50  (in the chamber  51 ) can be controlled by the heaters  759  of the above [Configuration 15]. 
     The above [Configuration 15] nay provide the following advantages. A state (e.g., supercritical state or the like) of the working fluid  11  can be maintained by controlling the temperature in the mixer  50 . Furthermore, the progress of a reaction of the materials  21  can be controlled by controlling the temperature in the mixer  50 . Where materials  21  are mixed together by a rotary blade that rotates with respect to a chamber, it is not necessary to provide heaters because usually the materials can be heated by heat generated by friction between the rotary blade and the materials. 
     Eighth Embodiment 
     Differences of a mixing apparatus  801  according to an eighth embodiment from the mixing device according to the first embodiment is described with reference to  FIGS. 15 and 16 . The mixer  50  of the mixing apparatus  801  is provided with a cooler  859 . The cooler  859  cools the working fluid  11  and the materials  21  in the chamber  51 . The cooler  859  is disposed downstream of heaters  759 . 
     Where the mixer  50  includes the cooler  859  and the heaters  759 . the temperature in the mixer  50  can be controlled more finely than in the case where the mixer  50  includes only the heaters  759 . For example, where the mixer  50  includes only the heaters  759 , it is conceivable to, for example, control the temperature in the mixer  50  by on/off-switching the heaters  759  (on/off control). The temperature in the mixer  50  can be controlled more finely by cooling the inside of the mixer  50  with the cooler  859  in addition to on/off-controlling the heaters  759 . As a result, energy that is necessary for the temperature control in the mixer  50  can be suppressed, 
     Furthermore, the pressure of the working fluid  11  can he lowered smoothly by cooling the inside of the mixer  50  with the cooler  859 . More specifically, the pressure of the working fluid  11  can be controlled by the pressure adjustment valve  73 . However, there may occur a case that the pressure of the working fluid  11  cannot be controlled finely only by the pressure adjustment valve  73 . In view of this, in addition to controlling (lowering) the pressure of the working fluid  11  by the pressure adjustment valve  73 , the pressure of the working fluid  11  is controlled (lowered) by the cooler  859 . This makes it possible to change the state of the working fluid  11  smoothly from a supercritical state or a subcritical state to a high-pressure gas, then to a middle-pressure gas, and finally to a low-pressure gas. 
     The cooler  859  is used for controlling the progress of a chemical reaction of the materials  21 . More specifically, for example, a following control can he performed using the cooler  859 .  FIG. 16  shows a relationship between the distance in the axial direction X from the entrance of the chamber  51  (horizontal axis) and the temperature T in the chamber  51  (vertical axis). In the following, individual elements of the mixing apparatus  801  is described with reference to  FIG. 15 . The working fluid  11  and the materials  21  flow from the entrance of the chamber  51  to its downstream side and are heated by the heaters  759 . As a result, the temperature T in the mixer  50  is increased to a temperature Tb (desired temperature) that is necessary for a chemical reaction of the materials  21 . After the chemical reaction of the materials  21  has proceeded properly (after the reaction has completed), the temperature in the mixer  50  is lowered by the cooler  859 . At this time, for example, the temperature T in the mixer  50  is lowered to a temperature (normal mixing temperature Tn) of a case that none of the heaters  759  and the cooler  859  are provided. Degradation of the materials  21  can be suppressed by the above controls. 
     As a modification, the cooler  859  may be provided in a case that no heaters  759  are provided. 
     The mixing apparatus  801  shown. in  FIG. 15  provides the following advantages, 
     (Advantages of 16th Aspect of Invention) 
     [Configuration 16] The mixer  50  includes the cooler  859  for cooling the inside of the chamber  51 . 
     The temperature in the chamber  51  can be controlled by the cooler  859  of the above [Configuration 16]. 
     The above [Configuration 16] may provide the following advantages. The progress of a reaction of the materials  21  can be controlled while the working fluid  11  is kept in a supercritical state or the like by controlling the temperature in the mixer  50 . Furthermore, the pressure of the working fluid  11  can be lowered smoothly. Thus, the state of the working fluid  11  (fluid  12 ) can be changed smoothly from a supercritical state or a subcritical state to a gas. This makes it possible to suppress bubble formation due to quick pressure reduction and hence to suppress noise generated by bubble formation. Furthermore, energy loss due to generation of noise can be suppressed. 
     Ninth Embodiment 
     Differences of a mixing apparatus  901  according to a ninth embodiment from the mixing device according to the first embodiment is described with reference to  FIG. 17 . The separation unit  70  of the mixing apparatus  901  includes an auxiliary mixer  980 . 
     The auxiliary mixer  980  (auxiliary mixing apparatus, auxiliary kneading apparatus) is an apparatus for exerting force to the materials  21 . More specifically, the separator  71  can separate the working fluid  11  (fluid  12 ) from the materials  21  by lowering the pressure of the working fluid  11  and the materials  21  to (approximately) atmospheric pressure, for example. However, only with the devolatilization using the separator  71 , there may occur a case that a fluid  12  remains in, for example, gaps in the materials  21 . In view of this, the auxiliary mixer  980  exerts force on the materials  21 . This force is a force that is produced by a pressure that is at least higher than atmospheric pressure. In this manner, the auxiliary mixer  980  closes gaps in the materials  21  and thereby separate a fluid  12  from the materials  21 . The auxiliary mixer  980  exerts a shearing force on the materials  21 . In this case, the auxiliary mixer  980  can adjust the molecular weights of the materials  21  and hence makes it possible to, for example, manage the quality of rubber. The auxiliary mixer  980  is disposed downstream of the mixer  50  and the separator  71 . The auxiliary mixer  980  exerts force on the materials  21  using, for example, a rotary blade (i.e., a blade that rotates with respect to a chamber). 
     The mixing apparatus  901  shown in  FIG. 17  provides the following advantages. 
     (Advantages of 17th Aspect of Invention) 
     [Configuration 17] The mixing apparatus  901  includes the auxiliary mixer  980 . The auxiliary mixer  980  is disposed downstream of the mixer  50  and exerts a pressure that is higher than atmospheric pressure on the materials  21 . 
     The above [Configuration 17] makes it possible to separate the working fluid  11  (fluid  12 ) from the materials  21  reliably. As a result, for example, the quality of the materials  21  can be made higher. 
     (Modifications) 
     The above-described embodiments may be modified in various manners. For example, constituent elements of different embodiments may be combined together. For example, the positions and shapes of individual constituent elements may be changed. For example, the number of constituent elements may be changed and part of the constituent elements may be omitted. 
     For example, the mixer  250  shown in  FIG. 7  that is inclined with respect to the horizontal direction may be applied to the second and fourth to ninth embodiments. For example, the sensors  57  shown in  FIG. 1  may be omitted. For example, the center axis of the mixing blade  53  shown in  FIG. 12  etc. may be curved (e.g., shaped like a spiral). Where the center axis of the mixing blade  53  is curved, the cross section center line  551   a  of the chamber  51  may either be curved or be straight. 
     The present application is based on Japanese Patent Application No. 2017-214760 filed on Nov. 7, 2017, the disclosure of which is incorporated herein by reference. 
     DESCRIPTION OF SYMBOLS 
     
         
           1 ,  201 ,  301 ,  401 ,  501 ,  601 ,  701   801 ,  901 : Mixing apparatus 
           11 : Working fluid 
           16 : Pump 
           21 : Materials 
           50 ,  250 ,  350 ,  450 ,  550 ,  650 : Mixer 
           51 :  451 ,  551 : Chamber 
           53 ,  553 .  653 : Mixing blade(s) 
           57   p   1 : Mixer entrance pressure gauge 
           57   p   2 : Mixer exit pressure gauge 
           57   p   3 : Mid-mixer pressure gauge 
           57   t   1 : Mixer entrance thermometer 
           57   t   2 : Mixer exit thermometer 
           57   t   3 : Mid-mixer thermometer 
           60 : Degree-of-opening adjustment valve 
           71 : Separator 
           71   a : Opening portion 
           73 : Pressure adjustment valve 
         b  355 : Mixing acceleration member 
           551   a : Cross section center line 
           759 : Heater 
           859 : Cooler 
           980 : Auxiliary mixer 
         X: Axial direction