JP6416166B2 - Electrical property measuring apparatus, rubber composition inspection method, and rubber product manufacturing method - Google Patents

Description

  The present invention relates to an electrical property measuring device for measuring electrical properties of an unvulcanized rubber composition containing carbon black, a method for inspecting a rubber composition using the electrical property measuring device, and a rubber product using the inspection method It relates to the manufacturing method.

  In a rubber composition containing carbon black as a filler, the dispersion state of carbon black has a great influence on the quality of the resulting rubber product. For example, it is known that when the dispersibility of carbon black is low, mechanical strength such as tensile strength at break is reduced in the obtained rubber product. For these reasons, in the production process of rubber products containing carbon black, the dispersion state of carbon black in the rubber composition is set for setting the production conditions of the rubber product or for quality control of the obtained rubber product. It is very important to evaluate.

  As a method for evaluating the dispersion state of carbon black in the production process of rubber products, a method of measuring the electrical characteristics of a rubber composition and evaluating the dispersion state of carbon black from the measurement results is known. This is an evaluation method using the characteristic of the rubber composition that the electrical conductivity is lowered when the dependence of the carbon black in the rubber composition on the dispersibility and electrical characteristics, for example, the dispersibility of the carbon black is high.

  Conventionally, as an apparatus for measuring the electrical characteristics of an insulating material such as a rubber composition, an electrode electrically connected to one surface of a sheet-like insulating material, and an electrode electrically connected to the other surface of the insulating material There is known a device that includes a pair of electrodes and measures electrical characteristics of an insulating material interposed between the pair of electrodes (see Patent Document 1 and Patent Document 2).

  By the way, if the evaluation of the dispersion state of carbon black can be performed on the rubber composition before vulcanization in the rubber product manufacturing process, it is advantageous in manufacturing the rubber product. This is because, in an unvulcanized rubber composition, if it can be determined that the dispersion state of carbon black is poor, it is not necessary to subject the rubber composition to a subsequent molding step or vulcanization step. It is.

JP 2000-65875 A JP 2014-196956 A

However, it has been found that when the above-described electrical property measuring apparatus is used for evaluating the dispersion state of carbon black in an unvulcanized rubber composition, there are the following problems.
In order to measure the electrical properties of the rubber composition with high accuracy, the distance between the electrodes in contact with the rubber composition, the pressure acting on the rubber composition by the electrodes, the temperature of the rubber composition, and the like are controlled. is necessary. However, the above-mentioned electrical characteristics apparatus cannot control the pressure acting on the rubber composition, and the unvulcanized rubber composition is flexible, and it is easy to contact the electrode with a slight pressure. Therefore, it is difficult to control the distance between the electrodes by the pressure in the electrical characteristic device. Furthermore, when the rubber composition is produced, the rubber component and carbon black are kneaded while being heated. The temperature of the rubber composition immediately after the kneading varies greatly from batch to batch. Therefore, the electrical properties of the rubber composition immediately after kneading cannot be measured with high accuracy.

  The present invention has been made based on the circumstances as described above, and the object thereof is to measure the electrical characteristics of an unvulcanized rubber composition containing carbon black with high accuracy immediately after kneading. An object of the present invention is to provide an electrical property measuring device, a method for inspecting a rubber composition using the electrical property measuring device and a method for producing a rubber product.

An electrical property measuring device of the present invention is an electrical property measuring device for measuring electrical properties of an unvulcanized rubber composition containing carbon black,
A pair of electrodes arranged so as to oppose each other, and a rubber composition to be measured interposed therebetween,
Two insulating members having a recess on the surface that fits the outer shape of each of the pair of electrodes, and fixedly supported in a state where the electrode is accommodated in each of the recesses;
Two support plates, each having a concave shape conforming to the outer shape of each of the insulating members, and fixedly supported in a state where the insulating member is accommodated in each of the concave portions;
A spacer that is disposed so as to surround the rubber composition to be measured interposed between the pair of electrodes and regulates the distance between the pair of electrodes ; and a spacer separate from the support plate ;
A pressurizing mechanism for applying a pressing force at a specific pressure to at least one of the electrodes, with respect to the measurement target rubber composition interposed between the pair of electrodes;
A heating mechanism for heating the measurement target rubber composition interposed between the pair of electrodes to a specific temperature;
And a measuring instrument for measuring electrical characteristics of the measurement target rubber composition interposed between the pair of electrodes.

In the electrical property measuring apparatus of the present invention, the specific pressure is preferably 0.1 to 1 MPa.
Moreover, it is preferable that the said specific temperature is 30-200 degreeC.

  The method for inspecting a rubber composition according to the present invention measures the electrical characteristics of an unvulcanized rubber composition containing carbon black using the electrical characteristics measuring apparatus described above, and based on the measured values, It is characterized by determining the quality of the dispersion state of carbon black.

The method for producing a rubber product of the present invention has a kneading step of kneading at least a rubber component, carbon black and a vulcanizing agent,
In the kneading step, a dispersion state inspection for determining whether the dispersion state of carbon black in the unvulcanized rubber composition is good or not is performed by the inspection method.

In the rubber product production method of the present invention, in the kneading step, a kneading operation A for kneading the rubber component and carbon black, and a kneading operation B for kneading the kneaded material obtained by the kneading operation A and the vulcanizing agent; It is preferable that the dispersion state inspection is performed between the kneading operation A and the kneading operation B.

In the electrical property measuring apparatus of the present invention, the distance between the pair of electrodes is regulated by the spacer, and a specific pressure is applied to the rubber composition interposed between the pair of electrodes by the pressurizing mechanism, The rubber composition interposed between the pair of electrodes is heated at a specific temperature by the heating mechanism.
Therefore, according to the electrical property measuring apparatus of the present invention, electrical properties of an unvulcanized rubber composition containing carbon black can be measured with high accuracy even immediately after kneading.

  According to the method for inspecting a rubber composition of the present invention, the electrical characteristics of an unvulcanized rubber composition containing carbon black can be measured with high accuracy, so that the dispersion state of carbon black in the rubber composition is good or bad. Can be reliably determined.

  According to the rubber product manufacturing method of the present invention, it is possible to reliably manufacture a rubber product in which carbon black is well dispersed. Further, since the dispersion state inspection is performed on the unvulcanized rubber composition, when it is determined that the dispersion state of the carbon black is poor, the rubber composition may be subjected to a subsequent process such as a molding process or a vulcanization process. Since it becomes unnecessary, productivity can be improved in the manufacture of rubber products.

It is sectional drawing for description which shows the structure in an example of the electrical property measuring apparatus of this invention. It is a top view which shows the upper side jig | tool and lower side jig | tool with a spacer in the electrical property measuring apparatus shown in FIG. It is a graph which shows the CV value of the measurement result of the electrical property of the sample A in an Example, and four measurement results. It is a graph which shows the CV value of the measurement result of the electrical property of the sample B in an Example, and four measurement results. It is a graph which shows the CV value of the measurement result of the electrical property of the sample C in an Example, and four measurement results. It is a graph which shows the CV value of the measurement result of the electrical property of the sample D in an Example, and four measurement results. It is a graph which shows the CV value of the measurement result of the electrical property of the sample E in an Example, and four measurement results.

Embodiments of the present invention will be described below.
[Electrical characteristics measuring device]
FIG. 1 is an explanatory cross-sectional view showing the configuration of an example of the electrical property measuring apparatus of the present invention. FIG. 2 is a plan view showing an upper jig and a lower jig in the electrical characteristic measuring apparatus shown in FIG. 1 together with spacers. This electrical property measuring apparatus measures electrical properties of an unvulcanized rubber composition containing carbon black.
In the electrical characteristic measuring apparatus shown in FIG. 1, a pair of disk-like electrodes 11 and 16 are provided so as to face each other at the time of measurement. Between the pair of electrodes 11 and 16, an unvulcanized rubber composition W which is a measurement target at the time of measurement is interposed.

Each of the pair of electrodes 11, 16 is accommodated in the respective recesses in plate-like insulating members 12, 17 having recesses on the surface that match the outer shapes of the electrodes 11, 16. Fixedly supported.
In addition, each of the insulating members 12 and 17 is housed in each of the recesses on the metal support plates 13 and 18 having recesses on the surface that fit the outer shapes of the insulating members 12 and 17. Fixed and supported in a state.
The electrodes 11 and 16, the insulating members 12 and 17, and the support plates 13 and 18 constitute an upper jig 10 and a lower jig 15, respectively.

  Between each of the support plates 13 and 18, a rubber composition in which a frame plate-like spacer 20 that restricts the distance between the pair of electrodes 11 and 16 at the time of measurement is interposed between the pair of electrodes 11 and 16. It is arranged so as to surround W.

  One electrode 11 is electrically connected to a power source P by a conducting wire 21. The other electrode 16 is electrically connected to the power source P via a measuring instrument 25 by a conducting wire 22. The conducting wires 21 and 22 are connected to the electrodes 11 and 16, respectively, in a state of being insulated from the support plates 13 and 18, respectively.

  The measuring instrument 25 measures the electrical characteristics of the rubber composition W interposed between the pair of electrodes 11 and 16. As the types of electrical characteristics, a current value, a voltage value, a volume specific resistance of the rubber composition W, an electrical conductivity, etc. that flow through the rubber composition W when a constant DC voltage is applied between the pair of electrodes 11 and 16. Can be selected.

In this electrical characteristic measuring apparatus, a pressurizing mechanism 30 is provided that applies a pressing force to the rubber composition W interposed between the pair of electrodes 11 and 16 at a specific pressure by at least one of the electrodes. The pressurizing mechanism 30 in the illustrated example has a pair of press plates 31 and 32 provided on the back surfaces of the support plates 13 and 18. Of these press plates 31, 32, for example, the upper press plate 31 presses the support plate 13 in the thickness direction.
The support plates 13 and 18 of this example incorporate an electric heater (not shown) as a heating mechanism that heats the rubber composition W interposed between the pair of electrodes 11 and 16 to a specific temperature. Yes.

The material which comprises each of a pair of electrodes 11 and 16 will not be specifically limited if it has electroconductivity, As a specific example, metal materials, such as stainless steel, are mentioned.
The diameter of the surface of the pair of electrodes 11 and 16 is, for example, 20 to 100 mm.
As the material constituting the insulating members 12 and 17, a heat-resistant material is used, and a specific example thereof is a fluororesin.
As the metal material constituting the support plates 13 and 18, it is preferable to use a material having good thermal conductivity, and specific examples thereof include aluminum.

As a material constituting the spacer 20, stainless steel or the like can be used.
The thickness of the spacer 20 is preferably 1.0 to 10.0 mm. When this thickness is too small, there is a possibility that a short circuit will occur due to contact when foreign matter is mixed. On the other hand, if this thickness is excessive, it may be difficult to stabilize the temperature of the rubber composition W in a short time due to temperature control.
As the measuring device 25, a device that measures a current value between terminals at both ends to which the conducting wire 22 is connected, a device that measures a voltage value, or the like can be used.

  In the electrical characteristic measuring apparatus, first, with the upper jig 10 removed from the lower jig 15, the unvulcanized rubber to be measured is placed on the surface of the electrode 16 in the lower jig 15. Composition W is placed. Thereafter, the upper jig 10 is disposed on the lower jig 15 with the spacers 20 interposed therebetween so that the pair of electrodes 11 and 16 face each other. Next, the rubber composition W is heated to a specific temperature by a heating mechanism (electric heater), and a certain direct current is applied to the pair of electrodes 11 and 16 while a specific pressure is applied to the rubber composition by the pressurizing mechanism 30. A voltage is applied. The measuring device 25 measures the characteristics of electricity flowing between the pair of electrodes 11 and 16.

  In the above, the volume of the rubber composition W that is the measurement target is 1.5 times or more the volume of the space between the pair of electrodes 11 and 16 (the surface area of the electrode × the volume corresponding to the thickness of the spacer). It is preferable. When the volume of the rubber composition W is too small, the contact area between each of the pair of electrodes 11 and 16 and the rubber composition W is not stable, and it may be difficult to measure the electrical characteristic value with high accuracy. There is.

  Moreover, it is preferable that the specific temperature which heats the rubber composition W with a heating mechanism is 30-200 degreeC, More preferably, it is 50-120 degreeC. When this temperature is too low, when the temperature of the rubber composition W is higher, it may take a long time to adjust the temperature. On the other hand, if this temperature is too high, the polymer in the rubber composition W may be destroyed and the physical properties may change.

  Moreover, it is preferable that the specific pressure which acts on the rubber composition W by the pressurization mechanism 30 is 0.1-1 MPa. When the pressure is too small, the rubber composition W is not sufficiently pressurized, and it becomes difficult to control the thickness of the rubber composition W by the spacer 20, and it is difficult to measure the electrical property value with high accuracy. There is a risk of becoming. On the other hand, when the applied pressure is excessive, an excessive pressure resistance specification is required as the electrical characteristic measuring device, and the risk of work itself may increase.

  Moreover, it is preferable that the voltage applied to the pair of electrodes 11 and 16 has an upper limit of 500V.

In such an electrical characteristic measuring apparatus, the distance between the pair of electrodes 11 and 16 is regulated by the spacer 20, and the rubber composition W interposed between the pair of electrodes 11 and 16 is further regulated by the pressurizing mechanism 30. A specific pressure is applied, and the rubber composition W interposed between the pair of electrodes 11 and 16 is heated at a specific temperature by the heating mechanism.
Therefore, according to the electrical property measuring apparatus, the electrical property of the unvulcanized rubber composition W containing carbon black can be measured with high accuracy even immediately after kneading.

[Inspection method of rubber composition]
The method for inspecting a rubber composition according to the present invention comprises measuring the electrical characteristics of an unvulcanized rubber composition containing carbon black using the electrical characteristics measuring apparatus described above, and based on the measured values, carbon in the rubber composition. The quality of the black dispersion state is judged.
Specifically, a reference electrical characteristic value (hereinafter referred to as “reference value”) is set in advance, and the reference value and the measured value are compared to determine whether the carbon black dispersion state is good or bad. . For example, when the electrical characteristic value is a current value, it is determined that the dispersion state is good when the measured value is less than the reference value, and it is determined as defective when the measured value is greater than or equal to the reference value.

  According to such a method for inspecting a rubber composition, the electrical property of the unvulcanized rubber composition containing carbon black can be measured with high accuracy by the above electrical property measuring apparatus. It is possible to reliably determine whether the carbon book is in a dispersed state.

[Production method of rubber products]
The method for producing a rubber product of the present invention includes a kneading step of kneading at least a rubber component, carbon black, and a vulcanizing agent.
In the kneading step, a kneading operation A for kneading the rubber component and carbon black and a kneading operation B for kneading the kneaded material obtained by the kneading operation A and the vulcanizing agent are performed.
Examples of the kneader used in the kneading step include open or closed kneaders such as a plast mill, a Banbury mixer, a roll, and an internal mixer.

As the rubber component, a vulcanizable rubber material is used, and other rubber materials may be used in combination as necessary.
Specific examples of the rubber component include polybutadiene rubber, styrene-butadiene copolymer rubber, natural rubber, isoprene rubber, butyl rubber, ethylene-α-olefin copolymer rubber, ethylene-α-olefin-diene copolymer rubber, acrylonitrile-butadiene copolymer. Examples thereof include polymer rubber, chloroprene rubber, halogenated butyl rubber, hydrogenated modified products thereof, and mixtures thereof.

As carbon black, what is generally used as a filler can be used. The use ratio of carbon black is, for example, 20 to 80 parts by mass with respect to 100 parts by mass of the rubber component.
As the vulcanizing agent, sulfur is usually used. The use ratio of the vulcanizing agent is, for example, 1 to 3 parts by mass with respect to 100 parts by mass of the rubber component.

In the kneading operation A, a rubber component excluding a vulcanizing compound such as a vulcanizing agent and a vulcanization accelerator, a filler such as carbon black, and the like can be added.
In the kneading operation B, the remaining rubber components not added in the kneading operation A, a vulcanizing compound, and the like can be added.

The vulcanization accelerator is not particularly limited, and dibenzothiazyl disulfide, tetramethylthiuram disulfide, N-cyclohexyl-2-benzothiazolylsulfenamide and the like can be used. The use ratio of the vulcanization accelerator is, for example, 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the rubber component.
As the vulcanization acceleration aid, zinc oxide, stearic acid, or the like can be used. The use ratio of the vulcanization acceleration aid is, for example, 1 to 10 parts by mass with respect to 100 parts by mass of the rubber component.

The kneading temperature in the kneading operation A is, for example, 60 to 200 ° C.
The kneading temperature in the kneading operation B is, for example, 60 to 130 ° C.

In the rubber product manufacturing method of the present invention, in the kneading step, a dispersion state inspection is performed to determine whether the dispersion state of the carbon black in the unvulcanized rubber composition is good or bad by the above rubber composition inspection method.
The dispersion state inspection may be performed between the kneading operation A and the kneading operation B, or may be performed after the kneading operation B is completed, but may be performed between the kneading operation A and the kneading operation B. preferable.
By performing the dispersion state inspection between the kneading operation A and the kneading operation B, it is possible to identify a dispersion failure at an earlier stage of the manufacturing process, and thus it is possible to reduce the manufacturing cost.

  And the target rubber product is obtained by shape | molding the unvulcanized rubber composition obtained by the kneading | mixing process in a required shape, and vulcanizing the obtained molded object.

  According to such a method for producing a rubber product, a rubber product in which carbon black is well dispersed can be reliably produced. Further, since the dispersion state inspection is performed on the unvulcanized rubber composition, when it is determined that the dispersion state of the carbon black is poor, the rubber composition may be subjected to a subsequent process such as a molding process or a vulcanization process. Since it becomes unnecessary, productivity can be improved in the manufacture of rubber products.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made.
For example, in the electrical characteristic measuring apparatus shown in FIG. 1, as a heating mechanism, electric heaters may be incorporated in the press plates 31 and 32 instead of the support plates 13 and 18.
In addition, as a power source for applying a voltage between the pair of electrodes 11 and 16, an AC power source can be used instead of the DC power source.
In the rubber product manufacturing method, the kneading step may be performed by a single kneading operation without being divided into the kneading operation A and the kneading operation B. In this case, the dispersion state inspection is performed after the end of the single kneading operation.

  Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to the following examples.

[Electrical characteristics measuring device]
In accordance with the configuration shown in FIG. 1, an electrical property measuring apparatus having the following specifications was produced.
A pair of electrodes (11, 16): material = stainless steel, diameter = 30 mm, thickness = 2.0 mm Insulating member (12, 17): material = fluororesin, thickness (parts other than the recess) = 10 mm
Support plate (13, 18): material = aluminum, thickness (other than the recess) = 28 mm
Spacer (20): material = stainless steel, opening size = 80 mm × 80 mm, thickness = 2 mm
Measuring instrument (25): Ammeter

[Preparation of rubber composition]
100 parts by mass of acrylonitrile butadiene rubber (“N230S” manufactured by JSR Corporation) as a rubber component, 20 parts by mass of carbon black (“SEAST 3H” manufactured by Tokai Carbon Co., Ltd.), 1 part by mass of dibenzothiazyl disulfide as a vulcanization accelerator, tetra Mixture of 1 part by weight of methylthiuram disulfide and 1 part by weight of N-cyclohexyl-2-benzothiazolylsulfenamide, a mixture of 5 parts by weight of zinc oxide and 1 part by weight of stearic acid as a vulcanization accelerator, and a parallel vulcanizing agent 1 part by mass of sulfur was prepared.
Next, the rubber component was masticated with a closed biaxial kneader (Sumitomo Heavy Industries, 1 L capacity) under the conditions of a rotation speed of 10 rpm and a temperature of 60 ° C. or less. Thereafter, a vulcanization acceleration aid, a vulcanization accelerator and a vulcanizing agent were added and kneaded in this order into the rubber component, and carbon black was further added and kneaded. A part of the rubber composition was sampled from the kneader when the kneading time after the addition of carbon black reached 10, 20, 40, 60 and 90 minutes.

  Hereinafter, sample A is a rubber composition sampled at a kneading time of 10 minutes, sample B is a rubber composition sampled at a kneading time of 20 minutes, sample C is a rubber composition sampled at a kneading time of 40 minutes. The rubber composition sampled in 60 minutes is designated as sample D, and the rubber composition sampled in 90 minutes in kneading time is designated as sample E.

[Electrical characteristics measurement]
Using the above-described electrical property measuring apparatus, electrical properties of samples A to D were measured under the following conditions.
Volume of measurement sample: about 3.0 cm ³
Heating temperature by heating mechanism: 70 ° C
Pressure by pressure mechanism: 0.8 MPa
Applied voltage: 250V (DC)
Measurement time: 3 minutes Number of measurements: 4 times

FIG. 3 is a graph showing the measurement results of the electrical characteristics of the sample A and the CV values of the four measurement results. FIG. 4 is a graph showing the measurement results of the electrical characteristics of the sample B and the CV values of the four measurement results. 5 is a graph showing the measurement results of the electrical characteristics of the sample C and the CV values of the four measurement results. FIG. 6 is a graph showing the measurement results of the electrical characteristics of the sample D and the CV of the four measurement results. FIG. 7 is a graph showing the measurement results of the electrical characteristics of the sample E and the CV values of the four measurement results.
In Samples A to E, the average value of the measurement results 3 minutes after the start of measurement is 106.2 μA for Sample A, 95.6 μA for Sample B, 94.3 μA for Sample C, 118.6 μA for Sample D, In sample E, it was 121.5 μA.

It is considered that the lower the average value of the measurement results and the smaller the dispersion of the four measurement results, the better the dispersibility of the carbon black.
Therefore, from the above results, it is understood that the dispersibility of the carbon black in Sample B and Sample C is good, and the kneading time is appropriately 20 to 40 minutes.

[Mechanical strength of rubber products]
Using samples A to E, a rubber sheet was prepared by vulcanizing at 150 ° C. with a press. Each of the obtained rubber sheets was punched with a dumbbell cutter to produce a total of eight No. 3 dumbbell-shaped test pieces. About the obtained test piece, the tension test was done with "Tensilon universal testing machine RGT130 (made by A &D)." The average value of each test result is shown in Table 1 below.

From the results of Table 1, it is understood that Sample B and Sample C show high values for both the tensile strength at break and the tensile elongation at break, and the carbon black is well dispersed.
From the above, it was confirmed that there is a correlation between the electrical characteristics of the unvulcanized rubber composition and the strength of the rubber product obtained from the rubber composition.

DESCRIPTION OF SYMBOLS 10 Upper side jig | tool 11 Electrode 12 Insulation member 13 Support plate 15 Lower side jig | tool 16 Electrode 17 Insulation member 18 Support plate 20 Spacer 21, 22 Conductor 25 Measuring instrument 30 Pressurization mechanism 31, 32 Press plate P Power supply W Rubber composition

Claims (6)

An electrical property measuring device for measuring electrical properties of an unvulcanized rubber composition containing carbon black,
A pair of electrodes arranged so as to oppose each other, and a rubber composition to be measured interposed therebetween,
Two insulating members having a recess on the surface that fits the outer shape of each of the pair of electrodes, and fixedly supported in a state where the electrode is accommodated in each of the recesses;
Two support plates, each having a concave shape conforming to the outer shape of each of the insulating members, and fixedly supported in a state where the insulating member is accommodated in each of the concave portions;
A spacer that is disposed so as to surround the rubber composition to be measured interposed between the pair of electrodes and regulates the distance between the pair of electrodes ; and a spacer separate from the support plate ;
A pressurizing mechanism for applying a pressing force at a specific pressure to at least one of the electrodes, with respect to the measurement target rubber composition interposed between the pair of electrodes;
A heating mechanism for heating the measurement target rubber composition interposed between the pair of electrodes to a specific temperature;
An electrical property measuring apparatus comprising: a measuring instrument that measures electrical properties of a measurement target rubber composition interposed between the pair of electrodes.   The electrical characteristic measuring apparatus according to claim 1, wherein the specific pressure is 0.1 to 1 MPa.   The electrical characteristic measuring device according to claim 1 or 2, wherein the specific temperature is 30 to 200 ° C.   The electrical property of the unvulcanized rubber composition containing carbon black is measured by the electrical property measuring device according to any one of claims 1 to 3, and based on the measured value, A method for inspecting a rubber composition, wherein the quality of a dispersed state of carbon black is judged. Having a kneading step of preparing a rubber composition for kneading at least a rubber component, carbon black and a vulcanizing agent;
A method for producing a rubber product, characterized in that, in the kneading step, a dispersion state inspection is performed by the inspection method according to claim 4 to determine whether the dispersion state of carbon black in the unvulcanized rubber composition is good or bad. In the kneading step, the kneading operation A kneading the rubber component and carbon black, and a kneaded product and curing agent obtained by kneading operation A performs the kneading operation B of kneading, the dispersion state examination, the kneading 6. The method for producing a rubber product according to claim 5, which is performed between the operation A and the kneading operation B.

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