Patent Publication Number: US-2021162632-A1

Title: Quality Inspection Method and Quality Inspection System for Unvulcanized Rubber Material, and Production Method and Production System for Unvulcanized Rubber Material

Description:
TECHNICAL FIELD 
     The present technology relates to a quality inspection method and a quality inspection system for unvulcanized rubber material, and a production method and a production system for unvulcanized rubber material. 
     BACKGROUND ART 
     Producing a rubber product such as a tire or the like includes a step of kneading an unvulcanized rubber and a compounding agent using a mixer (mixing machine) or a rubber extruder to produce an unvulcanized rubber material. In this production step, the compounding agent is added at a compounding ratio set for the unvulcanized rubber. If the compounding ratio of the actually added compounding agent deviates from the reference range, the quality of the produced unvulcanized rubber material will be affected. This also affects the quality of the rubber product produced using this unvulcanized rubber material. 
     An oxygen flask combustion method or a sodium peroxide melting method have been are known as methods for inspecting the compounded amount of sulfur in an unvulcanized rubber material. However, in these inspection methods, procedures and preparations are complex, and time required for inspection is long. In addition, these inspection methods require complicated procedures and preparations and cannot perform inspection on the production line for the unvulcanized rubber material, failing to produce the unvulcanized rubber material of predetermined quality with good productivity. 
     As a method for determining the quality of an unvulcanized rubber material, a method has been proposed in which ultrasonic waves (0.5 MHz to 20 MHz) are transmitted to the extruded unvulcanized rubber material, and an attenuation amount of the strength of the ultrasonic waves transmitted through the unvulcanized rubber material (see Japan Unexamined Patent Publication No. 2014-521948). The proposed method can recognize the presence or absence of contaminants in the unvulcanized rubber material, and the relative change in the content of the contaminants on the basis of the attenuation amount of the strength of the ultrasonic waves, but does not determine whether or not the compounding ratio of the compounding agent in the unvulcanized rubber material is appropriate. 
     A method for measuring the concentration, the content rate, and the like of the chloride in concrete, although not unvulcanized rubber material, has been known (for example, see Japan Unexamined Patent Publication No. 2006-214941). 
     SUMMARY 
     The present technology provides a quality inspection method and a quality inspection system for unvulcanized rubber material that can easily and quickly determine the acceptability of the compounding ratio of a compounding agent in the unvulcanized rubber material. Another object of the present technology is to provide a production method and a production system for unvulcanized rubber material that can produce the unvulcanized rubber material on the production line for the unvulcanized rubber material with good productivity, with a compounding agent of predetermined type being mixed with unvulcanized rubber at an appropriate compounding ratio. 
     A quality inspection method for unvulcanized rubber material according to the present technology includes: based on a dielectric constant of an unvulcanized rubber material in which a compounding agent of predetermined type is mixed with unvulcanized rubber, calculating a compounding ratio of the compounding agent to the unvulcanized rubber material by a calculator; and determining whether or not the calculated compounding ratio is within a preset compounding reference range by the calculator. 
     A quality inspection system for unvulcanized rubber material according to the present technology including: 
     a dielectric constant measurement device configured to detect a dielectric constant of an unvulcanized rubber material obtained by mixing a compounding agent of predetermined type to unvulcanized rubber; and 
     a calculator configured to receive an input of the dielectric constant detected by the dielectric constant measurement device, wherein 
     the calculator calculates a compounding ratio of the compounding agent in the unvulcanized rubber material based on the dielectric constant, and determines whether or not the calculated compounding ratio is within a compounding reference range input to the calculator. 
     According to the present technology, a production method for unvulcanized rubber material for feeding a primary rubber material that is a mixture of unvulcanized rubber and an unvulcanizing compounding agent of predetermined type, and a vulcanizing compounding agent of predetermined type into an extruder, and perform mixing to continuously produce a final rubber material includes: calculating a compounding ratio of the vulcanizing compounding agent to the final rubber material by a final calculator based on a dielectric constant of the final rubber material extruded from the extruder; and adjusting a ratio of the vulcanizing compounding agent fed to the extruder to the unvulcanized rubber such that the calculated compounding ratio is within a preset vulcanizing compounding reference range. 
     A production system for unvulcanized rubber material according to the present technology includes: an extruder configured to mix a primary rubber material that is a mixture of unvulcanized rubber and an unvulcanizing compounding agent of predetermined type, and a vulcanizing compounding agent of predetermined type, and extrude a final rubber material; a vulcanizing compounding agent supply unit configured to feed the vulcanizing compounding agent into the extruder; a final dielectric constant measurement device configured to detect a dielectric constant of the final rubber material; a final calculator configured to receive an input of the dielectric constant detected by the final dielectric constant measurement device; and a final controller configured to control the vulcanizing compounding agent supply unit, wherein a compounding ratio of the vulcanizing compounding agent to the final rubber material is calculated by the final calculator based on the dielectric constant, the vulcanizing compounding agent supply unit is controlled by the final controller based on comparison of the calculated compounding ratio and a preset vulcanizing compounding reference range, and a ratio of the vulcanizing compounding agent fed to the extruder to the unvulcanized rubber is adjusted such that the compounding ratio calculated by the final calculator is within the vulcanizing compounding reference range. 
     In the quality inspection method and the quality inspection system for the unvulcanized rubber material according to the present technology, by detecting the dielectric constant of the unvulcanized rubber material, and performing calculation based on the dielectric constant by the calculator, the compounding ratio of the compounding agent of the unvulcanized rubber material may be calculated to rapidly determine the acceptability of the compounding ratio. Moreover, since it is no need to acquire data using various solutions, inspection may be easily performed. 
     In the production method and the production system for unvulcanized rubber material according to the present technology, by detecting the dielectric constant of the final rubber material extruded from the extruder, and performing calculation based on the dielectric constant by the final calculator, the compounding ratio of the vulcanizing compounding agent to the final rubber material may be calculated to determine the acceptability of the compounding ratio easily and rapidly. Therefore, by adjusting the ratio of the vulcanizing compounding agent fed to the extruder to the unvulcanized rubber based on the determination result, it is possible to acquire an unvulcanized rubber material in which the vulcanizing compounding agent is mixed with the unvulcanized rubber at an appropriate compounding ratio within the vulcanizing compounding reference range. Moreover, since the acceptability of the compounding ratio may be determined on the production line of the unvulcanized rubber material, the unvulcanized rubber material of predetermined quality may be produced with good productivity. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an explanatory diagram illustrating a quality inspection system for unvulcanized rubber material according to the present technology. 
         FIG. 2  is a graph schematically illustrating the relationship between each of the compounding ratio of carbon black and the compounding ratio of a master batch and the dielectric constant of the unvulcanized rubber material. 
         FIG. 3  is an explanatory diagram illustrating contents (change in the compounding ratio of the compounding agent over time) displayed on a monitor. 
         FIG. 4  is an explanatory diagram illustrating another type of contents (the dispersion of the compounding agent) displayed on a monitor. 
         FIG. 5  is an explanatory diagram illustrating a production system for unvulcanized rubber material according to the present technology. 
         FIG. 6  is a partial enlarged diagram illustrating the production system of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     A quality inspection method and a quality inspection system for unvulcanized rubber material according to the present technology will be described below based on the illustrated embodiments. 
     A quality inspection system  1  for unvulcanized rubber material (hereinafter referred to as the inspection system  1 ) according to the present technology in  FIG. 1  includes a dielectric constant measurement device  5 , a calculator  6  that receives an input of the dielectric constant detected by the dielectric constant measurement device  5 , and a monitor  8  connected to the calculator  6  in a wired or wireless manner. The present technology may inspect, as an unvulcanized rubber material R, both a primary rubber material R 1  in which an unvulcanized rubber M and an unvulcanizing compounding agent Ac of predetermined type are mixed, and a final rubber materials R 2  in which the primary rubber material R 1  and a vulcanizing compounding agent As of predetermined type are mixed. In this embodiment, the final rubber material R 2  just extruded by the extruder  4  is used as the inspection target. 
     Examples of the unvulcanizing compounding agent Ac include carbon black and silica. Examples of the vulcanizing compounding agent As include at least one of a vulcanization activator, a vulcanization accelerator, and sulfur. A master batch in which the vulcanization activator, the vulcanization accelerator, and the sulfur are mixed at prescribed ratios may be used as the vulcanizing compounding agent As. 
     An extruder  4  includes a cylinder  4   a  provided with a rotationally-driven screw, a material feeding port  4   b  formed on a top surface of a rear end of the cylinder  4   a , a hopper  4   d  disposed on the material feeding port  4   b , and an extrusion port  4   c  formed on the tip of the cylinder  4   a . A conveyance means such as a conveyor extends in front of the extrusion port  4   c . Additionally, a compounding agent supply unit  7  that feeds the vulcanizing compounding agent As of predetermined type to the material feeding port  4   b  via the hopper  4   d  is provided. 
     A sheet-like primary rubber material R 1  is continuously fed into the cylinder  4   a  of the extruder  4  from the material feeding port  4   b  via the hopper  4   d . In addition, the vulcanizing compounding agent As of predetermined type is continuously fed from the material feeding port  4   b  via the hopper  4   d  by the compounding agent supply unit  7 . The vulcanizing compounding agent As is set to be fed at a predetermined ratio preset for 100 weight parts of the unvulcanized rubber M. 
     The fed primary rubber material R 1  and the vulcanizing compounding agent As move forward while being mixed and kneaded in the cylinder  4   a  by the rotating screw. Then, the final rubber material R 2  formed into a sheet form is continuously extruded from the extrusion port  4   c.    
     The dielectric constant measurement device  5  may use equipment various known specifications. Preferable equipment is capable of irradiating the inspection target (unvulcanized rubber material R) with ultrasonic waves and detecting the dielectric constant in a non-contact manner. For example, the dielectric constant measurement device  5  sequentially detects the dielectric constant in the range through which the final rubber material R 2  passes while being extruded. 
     Not only a single but a plurality of dielectric constant measurement devices  5  may be aligned in the width direction of the final rubber material R 2 . Alternatively, the dielectric constant measurement device  5  may be configured to be movable in the width direction of the final rubber material R 2 . By employing these configurations, the substantially entire width of the final rubber material R 2  can be inspected. 
     As illustrated in  FIG. 2 , correlation data between the compounding ratio of the vulcanizing compounding agent As of predetermined type in the final rubber material R 2  and the dielectric constant of the final rubber material R 2  are input to the calculator  6 . Specifically, as the compounding ratio of the master batch used as the vulcanizing compounding agent As increases, the dielectric constant of the final rubber material R 2  tends to decrease. The calculator  6  calculates a compounding ratio D 1  of the vulcanizing compounding agent As in the final rubber material R 2  on the basis of the correlation data and the sequentially-input dielectric constant. 
     In this embodiment, correlation data between the compounding ratio of the unvulcanizing compounding agent Ac of predetermined type in the primary rubber material R 1  and the dielectric constant of the primary rubber material R 1  is also input to the calculator  6 . Specifically, as the compounding ratio of carbon black used as the unvulcanizing compounding agent Ac increases, the dielectric constant of the primary rubber material R 1  tends to increase. According to the type of the compounding agents A (Ac, As), the correlation between the compounding ratio and the dielectric constant of the unvulcanized rubber material R mixed with the compounding agent A (which the dielectric constant increases or decreases proportionally, the degree of change in the dielectric constant) varies, and therefore, for each compounding agent A, the correlation data is previously acquired and input to the calculator  6 . 
     A compounding reference range C 1  indicating the appropriate compounding ratio for each type of the vulcanizing compounding agent As is also input to the calculator  6 . As illustrated in  FIG. 3 , the calculator  6  sequentially compares the calculated compounding ratio D 1  with the compounding reference range C 1 , and sequentially determines whether or not the compounding ratio D 1  is within the compounding reference range C 1 . 
     The determination result of the calculator  6  is sequentially displayed on the monitor  8 . The displayed determination result may be a warning simply indicating that the calculated compounding ratio D 1  is out of the range of the compounding reference range C 1 , or a change in the compounding ratio D 1  over time illustrated in  FIG. 3  may be sequentially displayed. 
     As described above, according to the present technology, by detecting the dielectric constant of the final rubber material R 2  and performing calculation based on the dielectric constant to calculate the compounding ratio of the vulcanizing compounding agent As in the final rubber material R 2 , the acceptability of the compounding ratio can be rapidly determined by the non-destructive inspection. Moreover, unlike the known inspection method, there is no need to acquire data using various solutions, achieving simple inspection. 
     Even when the vulcanizing compounding agent As is added to the primary rubber material R 1  at a compounding ratio within the compounding reference range C 1 , unless the vulcanizing compounding agent As is sufficiently dispersed and mixed with the unvulcanized rubber M (primary rubber material R 1 ), the quality of the final rubber material R 2  produced is disadvantageously affected. Therefore, it is more preferable to determine the acceptability of the dispersion of the vulcanizing compounding agent As as well. 
     Thus, the extruded final rubber material R 2  is divided into multiple segments in a plan view, and the dielectric constant is detected for each divided segment. Then, based on the magnitude of a variation in the detected dielectric constants of the segments, the calculator  6  calculates a degree of dispersion D 2  of the vulcanizing compounding agent As in the final rubber material R 2 . 
     A dispersion reference range C 2  indicating the appropriate degree of dispersion D 2  for each type of the vulcanizing compounding agent As is input to the calculator  6 . Then, the calculator  6  sequentially compares the calculated degree of dispersion D 2  with the dispersion reference range C 2 , and determines whether or not the degree of dispersion D 2  is within the dispersion reference range C 2 . 
     For example, a reference dielectric constant Cd is set, and a value acquired by averaging absolute values of differences between the reference dielectric constant Cd and the dielectric constants of the segments in a predetermined area range (per unit area) is defined as the degree of dispersion D 2 . As the degree of dispersion D 2  is larger, dispersion of the vulcanizing compounding agent As becomes worse, and thus, a preset average allowable range is previously set to the dispersion reference range C 2 , and it is determined that the dispersion is poor when the degree of dispersion D 2  is greater than the dispersion reference range C 2 . 
     Also when the dielectric constant is locally too large or too small, it can be deemed that the vulcanizing compounding agent As is not well dispersed. Thus, a preset local allowable range is set to the dispersion reference range C 2 , and it may be determined that the dispersion is poor when a segment where the degree of dispersion D 2  is larger than the dispersion reference range C 2  is present. At least one of the above-mentioned average allowable range and local allowable range may be adopted as the dispersion reference range C 2 , but both are preferably adopted. 
     The determination result of the calculator  6  is sequentially displayed on the monitor  8 . The displayed determination result may be a warning that simply indicates that the calculated degree of dispersion D 2  is outside the range of the dispersion reference range C 2 , but as illustrated in  FIG. 4 , the dispersion of the dielectric constant (or the compounding ratio D 1 ) may be displayed. 
     In displaying as illustrated in  FIG. 4 , the segments are categorized into a plurality of ranks (for example, an index such as less than 85, 85 to 95, . . . ) by the calculator  6  according to the magnitude of the dielectric constant. Each segment is then displayed on the monitor  8  such that its rank is distinguishable. In  FIG. 4 , the categorized ranks are distinguishable using blank and line patterns, but may be distinguishable using the difference in color or shade of color. With such display, the acceptability of the dispersion of the vulcanizing compounding agent As may be easily recognized by simply looking at the monitor  8 . 
     The contents described above may be applied to the primary rubber material R 1  as well. In other words, by detecting the dielectric constant of the primary rubber material R 1  and performing calculation based on the dielectric constant, the compounding ratio of the unvulcanizing compounding agent Ac in the primary rubber material R 1  and the acceptability of the compounding ratio may be rapidly determined. Additionally, the acceptability of the dispersion of the unvulcanizing compounding agent Ac in the primary rubber material R 1  may be determined in the same manner as in the final rubber material R 2 . 
     Next, a production method and a production system for unvulcanized rubber material according to the present technology will be described with reference to the illustrated embodiment. 
     A production system  2  for unvulcanized rubber material (hereinafter referred to as production system  2 ) according to the present technology illustrated in  FIGS. 5 and 6  utilizes the above-described inspection system  1  according to the present technology. The production system  2  includes an extruder  4  that extrudes the final rubber material R 2 , a vulcanizing compounding agent supply unit  7   b  that feeds the vulcanizing compounding agent As into the extruder  4 , a final dielectric constant measurement device  5   b , a final calculator  6   b  that receives an input of the dielectric constant detected by the final dielectric constant measurement device  5   b , and a final controller  9  that controls the vulcanizing compounding agent supply unit  7   b . The final dielectric constant measurement device  5   b  is intended to inspect the final rubber material R 2  just extruded by the extruder  4 . The final rubber material R 2  is formed by mixing the primary rubber material R 1  and the vulcanizing compounding agent As of predetermined type, and the primary rubber material R 1  is formed by mixing unvulcanized rubber M and the unvulcanizing compounding agent Ac of predetermined type. The final calculator  6   b  is connected to the final controller  9  in a wired or wireless manner. 
     The production system  2  in the embodiment includes equipment for the primary rubber material R 1 , which is similar to the above-mentioned equipment for the final rubber material R 2 . Specifically, the production system includes an extruder  3  that extrudes the primary rubber material R 1 , an unvulcanizing compounding agent supply unit  7   a  that feeds the unvulcanizing compounding agent Ac into the extruder  3 , a primary dielectric constant measurement device  5   a , a primary calculator  6   a  that receives an input of the dielectric constant detected by the primary dielectric constant measurement device  5   a  is input, and a primary controller  9  that controls the unvulcanizing compounding agent supply unit  7   a . The primary dielectric constant measurement device  5   a  is intended to inspect the primary rubber material R 1  just extruded by the extruder  3 . The primary calculator  6   a  is connected to the primary controller  9  in a wired or wirelessly manner. 
     In this embodiment, one controller  9  is shared by the primary controller  9  and the final controller  9 , but the controllers may be individually provided. In addition, in this embodiment, the primary calculator  6   a  and the final calculator  6   b  are separately provided, but one calculator may be shared. Alternatively, the primary calculator  6   a , the final calculator  6   b , and the controller  9  may be integrated into a single computer, for example. 
     In addition, in the present technology, to produce the primary rubber material R 1 , various kneading means (for example, a mixer) capable of mixing the unvulcanized rubber M and the unvulcanizing compounding agent Ac of predetermined type to produce the primary rubber material R 1  may be used in place of the extruder  3 . In this embodiment, one monitor  8  connected to the controller  9  in a wired or wirelessly manner is provided. In the configuration in which the primary controller  9  and the final controller  9  are separately provided, the controllers may be connected to the primary monitor  8  and the final monitor  8 , respectively. 
     The extruder  4  has the configuration described in the previous embodiment, and the sheet-like primary rubber material R 1  is continuously fed into the cylinder  4   a  from the material feeding port  4   b  via the hopper  4   d . In addition, the vulcanizing compounding agent As of predetermined type is continuously fed from the material feeding port  4   b  via the hopper  4   d  by the vulcanizing compounding agent supply unit  7   b . The vulcanizing compounding agent As is set to be fed at a predetermined ratio preset for 100 weight parts of the unvulcanized rubber M. 
     The fed primary rubber material R 1  and the vulcanizing compounding agent As move forward while being mixed and kneaded in the cylinder  4   a  by the rotating screw. Then, the final rubber material R 2  formed into a sheet form is continuously extruded from the extrusion port  4   c.    
     The final dielectric constant measurement device  5   b  may use equipment various known specifications. Preferable equipment is capable of irradiating the inspection target (final rubber material R 2 ) with ultrasonic waves and detecting the dielectric constant in a non-contact manner. For example, the final dielectric constant measurement device  5   b  sequentially detects the dielectric constant in the range through which the final rubber material R 2  passes while being extruded. 
     Not only a single but a plurality of final dielectric constant measurement devices  5   b  may be aligned in the width direction of the final rubber material R 2 . Alternatively, the final dielectric constant measurement device  5   b  may be configured to be movable in the width direction of the final rubber material R 2 . By employing these configurations, the substantially entire width of the final rubber material R 2  can be inspected. The dielectric constant in a specific range in the width direction of the final rubber material R 2  may be detected, but the dielectric constant is preferably detected over the entire width and the entire length of the final rubber material R 2 . 
     As illustrated in  FIG. 2 , correlation data between the compounding ratio of the vulcanizing compounding agent As of predetermined type in the final rubber material R 2  and the dielectric constant of the final rubber material R 2  are input to the final calculator  6   b . The final calculator  6   b  calculates the compounding ratio D 1  of the vulcanizing compounding agent As in the final rubber material R 2  on the basis of the correlation data and the sequentially-input dielectric constant. 
     In this embodiment, as illustrated in  FIG. 2 , correlation data between the compounding ratio of the unvulcanizing compounding agent Ac of predetermined type in the primary rubber material R 1  and the dielectric constant of the primary rubber material R 1  is also input to the primary calculator  6   a . According to the type of the compounding agents A (Ac, As), the correlation between the compounding ratio and the dielectric constant of the unvulcanized rubber material R mixed with the compounding agent A (which the dielectric constant increases or decreases proportionally, the degree of change in the dielectric constant) varies, and therefore, for each compounding agent A, the correlation data is previously acquired and input to the primary calculator  6   a  or the final calculator  6   b.    
     A compounding vulcanizing reference range C 1  indicating the appropriate compounding ratio for each type of the vulcanizing compounding agent As is also input to the final calculator  6   b . As illustrated in  FIG. 3 , the final calculator  6   b  sequentially compares the calculated compounding ratio D 1  with the vulcanizing compounding reference range C 1 , and sequentially determines whether or not the compounding ratio D 1  is within the vulcanizing compounding reference range C 1 . 
     The final controller  9  controls the vulcanizing compounding agent supply unit  7   b  based on comparison between the calculated compounding ratio D 1  and a vulcanizing compounding reference range C 21 . Under this control, the ratio of the vulcanizing compounding agent As fed into the extruder  4  to the unvulcanized rubber M is adjusted such that the compounding ratio D 1  of the vulcanizing compounding agent As, which is calculated by the final calculator  6   b , is within the preset vulcanizing compounding reference range C 1 . 
     The determination result of the final calculator  6   b  is sequentially displayed on the monitor  8 . The displayed determination result may be a warning simply indicating that the calculated compounding ratio D 1  is out of the range of the vulcanizing compounding reference range C 1 , or a change in the compounding ratio D 1  over time illustrated in  FIG. 4  may be sequentially displayed. 
     As described above, according to the present technology, by detecting the dielectric constant of the final rubber material R 2  and performing calculation based on the detected dielectric constant to calculate the compounding ratio of the vulcanizing compounding agent As in the final rubber material R 2 , the acceptability of the compounding ratio can be determined easily and rapidly by the non-destructive inspection. Therefore, by adjusting the ratio of the vulcanizing compounding agent As fed into the extruder  4  to the unvulcanized rubber M based on the determination result, it possible to obtain the final rubber material R 2  in which the vulcanizing compounding agent As is mixed with the unvulcanized rubber M at an appropriate compounding ratio within the vulcanizing compounding reference range C 1 . Moreover, since the acceptability of the compounding ratio may be determined on the production line of the unvulcanized rubber material R, the final rubber material R 2  of predetermined quality may be produced with good productivity. 
     As described in the previous embodiments, it is more preferable to determine the acceptability of the dispersion of the vulcanizing compounding agent As as well. That is, the extruded final rubber material R 2  is divided into multiple segments in a plan view, and the dielectric constant is detected for each divided segment. Then, based on the magnitude of a variation in the detected dielectric constants of the segments, the final calculator  6   b  calculates a degree of dispersion D 2  of the vulcanizing compounding agent As in the final rubber material R 2 . 
     A vulcanizing dispersion reference range C 2  indicating the appropriate degree of dispersion D 2  for each type of the vulcanizing compounding agent As is input to the final calculator  6   b . Then, the final calculator  6   b  sequentially compares the calculated degree of dispersion D 2  with the vulcanizing dispersion reference range C 2  to determine whether or not the degree of dispersion D 2  is within the vulcanizing dispersion reference range C 2 . Specifically, the degree of dispersion D 2  described in the previous embodiment may be used. Then, the acceptability of the dispersion is determined based on the degree of dispersion D 2 . 
     The determination result of the final calculator  6   b  is sequentially displayed on the monitor  8 . The displayed determination result may be a warning that simply indicates that the calculated degree of dispersion D 2  is outside the range of the vulcanizing dispersion reference range C 2 , but as illustrated in  FIG. 4 , the dispersion of the dielectric constant (or the compounding ratio D 2 ) may be displayed. Then, the contents described in the previous embodiment are displayed on the monitor  8 . 
     When the final rubber material R 2  includes a portion having an inadequate compounding ratio or the dispersion, the portion may be removed by a cutting machine such as a cutter installed on the production line. As a result, only the final rubber material R 2  that satisfy predetermined quality is transported to the subsequent step of the production line, and the final rubber material R 2  that satisfies the predetermined quality is excluded from the production line. 
     The contents described above may be applied to the primary rubber material R 1  as well. In other words, by detecting the dielectric constant of the primary rubber material R 1  and performing calculation based on the detected dielectric constant, the compounding ratio of the unvulcanizing compounding agent Ac in the primary rubber material R 1  may be calculated to rapidly determine the acceptability of the compounding ratio. By adjusting the ratio of the unvulcanizing compounding agent Ac fed into the extruder  3  to the unvulcanized rubber M based on this determination result, it is possible to obtain the primary rubber material R 1  in which the unvulcanizing compounding agent Ac is mixed with the unvulcanized rubber M at an appropriate compounding ratio within the unvulcanizing compounded reference range. Additionally, the acceptability of the dispersion of the unvulcanizing compounding agent Ac in the primary rubber material R 1  may be determined in the same manner as in the final rubber material R 2 .