JP2717641B2 - Rubber product manufacturing method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a rubber product, and more particularly, to applying an alternating current to a rubber compound to measure a dielectric loss tangent (tan δ) or a current value, and vulcanizing the rubber. The present invention relates to a method for measuring the progress of a reaction in real time.

[0002]

2. Description of the Related Art For example, vulcanization is performed to improve the physical properties of rubber to impart elasticity, tensile strength, wear resistance and the like. Regarding the degree of vulcanization, in the case of unvulcanized or overvulcanized, the quality of the product is deteriorated. Therefore, setting the optimum vulcanization conditions is important for ensuring the stability of product quality.

Heretofore, the setting of optimum vulcanization conditions has been carried out mainly by the following two methods. One method is to use a vulcanization tester such as a curastometer or a rheometer. A rubber compound obtained by mixing various materials (compounding agents) with rubber is applied to the above tester, and vulcanization tests are performed at various temperatures. In this method, optimal vulcanization conditions are set based on a heating time and a torque-time curve due to an increase in rubber viscosity. The other one is
In this method, a rubber product is manufactured by actually vulcanizing a rubber compound using a mold for product manufacture, and a performance test is performed to set optimum vulcanization conditions.

[0004]

However, optimum vulcanization conditions (vulcanization temperature, vulcanization temperature,
Vulcanization time), or vulcanizing the rubber compound with a production mold to produce a test piece, but if the test or production of the test piece with a vulcanization tester and the actual production of rubber products It is difficult to vulcanize under the same conditions.

[0005] One of the main causes is the non-uniformity of the dispersion state of the compounding agent in the rubber compound. In other words, it is difficult to uniformly disperse the compounding agent in the rubber having a high viscosity in the kneading process, and even if the optimum vulcanization conditions derived from a test machine or a test piece and the actual production conditions are the same,
When a rubber product is produced from a rubber compound in which the above-mentioned compounding agents are in a dispersion variation state, an unvulcanized or over-vulcanized state occurs depending on the product, resulting in a variation in product quality.

[0006] Another cause is a change in the heat history of the mold and its surroundings due to opening and closing of the mold. That is, when actually manufacturing a product, there is a step of opening the mold, taking out the product, and then closing the mold. The time during which the mold is open is not always constant. The longer the mold is open, the more it cools and the temperature of the mold changes. Then, even if the vulcanization time is the same, the vulcanization temperature does not become the same, and the heat history applied to the rubber differs every time. Therefore, even if the optimum vulcanization conditions derived from a test machine or a test piece are the same, unvulcanized or overvulcanized states occur, causing variations in product quality.

[0007] In order to prevent the occurrence of variations in product quality, the product may be manufactured under optimum vulcanization conditions for each rubber to be vulcanized. The present inventors have paid attention to the fact that the progress of the vulcanization reaction of rubber in a mold for actually producing a product is directly measured in real time, and if the product is taken out at the time of completion of the vulcanization, the variation in quality can be prevented.

The problem is how to determine the degree of vulcanization of the rubber during vulcanization. The present inventors have conducted further research on this point, and obtained a curve obtained by measuring the dielectric loss tangent (tan δ) or current value of the rubber to be vulcanized by applying an alternating current to the electrode attached to the mold and a test machine. It has been found that the heating time and the torque-time curve due to the increase in the viscosity of the rubber have a correlation, and the present invention has been completed based on this finding.

Accordingly, an object of the present invention is to measure the dielectric loss tangent (tan δ) or current value by applying a voltage to the rubber to be vulcanized, thereby measuring the progress of the rubber vulcanization reaction.
It is an object of the present invention to provide a method and an apparatus for producing a rubber product using the same.

[0010]

Means for solving the above problems and achieving the object are as follows. In the first means, an AC voltage is applied to an electrode provided on a mold.
The dielectric loss tangent (tan δ) of the rubber compound during the vulcanization reaction
Or by measuring the current value, the vulcanization
A method for producing a rubber product, comprising producing a rubber product while measuring a response .

In the second means, a method for producing a rubber product
Method, and the dielectric loss tangent (tan δ) of the rubber
Alternatively, measure the time change of the current value and set the optimal vulcanization conditions.
The step of constant, dielectric loss tangent (tan to the optimum vulcanization conditions
δ) When the current value is measured, stop vulcanization and remove the mold.
Step to set control conditions to open, in the mold
Apply AC voltage to electrodes while molding and vulcanizing rubber compound
And the dielectric loss tangent (tan δ) or current value of the rubber compound
Measurement step, preset dielectric loss tangent from measured value
(Tanδ) or when the current value is obtained, stop vulcanization and
Characterized in that it comprises the steps of obtaining a rubber product by opening the mold
This is a method for producing a rubber product.

The third means is a method for producing a rubber product, which comprises filling a rubber compound in a mold and measuring the dielectric loss tangent (tan δ) or the current value of the rubber compound while molding and vulcanizing. Step, preset dielectric loss tangent (tan δ)
Or stopping the molding vulcanization when the current value is measured.

According to a fourth means, there is provided an apparatus for molding and vulcanizing a rubber compound in a mold, and an electrode for measuring a dielectric loss tangent (tan δ) or a current value of the rubber compound in the mold. An apparatus for manufacturing a rubber product, wherein the apparatus is provided.

In the fifth means, the tip of the injection molding apparatus is provided.
Located on the end side, it consists of a fixed mold and a movable mold.
Molding mold that is provided, provided in the above mold,
A measuring unit provided with an electrode, wherein the electrode comprises a measuring unit.
Characterized by being electrically connected to the control unit via
This is a rubber product manufacturing device.

The tan δ is obtained as the ratio (ε ″ / ε ′) between the permittivity ε ′ of the real part of the complex permittivity (ε ^* ) and ε ″ of the imaginary part. In addition, as a means for measuring the progress of the vulcanization reaction of rubber, a method utilizing a DC leakage current method, a DC superposition method, a low frequency superposition method, or a DC component method may be used.

[0016]

The optimum vulcanization condition of a rubber compound is measured in advance by a tester, and the dielectric loss tangent (tan) of the rubber compound is measured.
δ) or the current value is measured. An AC voltage is applied to the rubber compound while molding and vulcanizing the rubber compound, and the dielectric loss tangent (tan δ) or the current value of the rubber compound is measured.
When the measured value reaches a preset dielectric loss tangent (tan δ) or current value, vulcanization is stopped, whereby a rubber product optimally vulcanized can be obtained.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail with reference to the embodiments shown in the drawings. FIG. 1 is an explanatory view of a mold equipped with electrodes. The mold is composed of an upper mold 11 and a lower mold 12. A flat cavity 13 is formed in the center of the upper surface of the lower mold 12.

Electrodes 14 and 15 are embedded in the center of the upper mold 11 and the center of the lower mold 12, respectively, with their surfaces exposed. The electrodes 14 and 15 are insulated from the surroundings by an insulator (Teflon) 16. Reference numeral 17 denotes a thermocouple for measuring the temperature of rubber and a mold, and R denotes rubber.

FIG. 2 is a diagram showing the time change of torque with the progress of the vulcanization reaction after vulcanizing NBR rubber having the composition shown in Table 1 below. A vulcanization tester (MDR200 manufactured by Monsanto Co., Ltd.) which is an established method for tracking the vulcanization reaction
It measured at 150 degreeC of vulcanization temperature using 0). From 3 minutes after the start of the vulcanization, there is a sharp increase in the torque, and the subsequent stabilization is observed. Five minutes after the start of vulcanization, the change in torque became small, indicating that vulcanization proceeded sufficiently.

[0020]

[Table 1]

FIG. 3 is a diagram showing a dielectric loss tangent (tan δ) -time curve. The mold shown in FIG. 1 was filled with NBR rubber having the composition shown in Table 1, and an AC voltage of 200 V was applied.
Vulcanized at 150 ° C. Tan after 2-3 minutes from the start of vulcanization
The rapid rise in δ and subsequent stabilization is similar to the torque-time curve shown in FIG. 2 and the ability to track the vulcanization reaction by measuring the dielectric tangent (tan δ) to obtain optimal vulcanization conditions. I understand.

FIG. 4 is a diagram showing a change in current-vulcanization time. The mold shown in FIG. 1 was filled with NBR rubber having the composition shown in Table 1, and an AC voltage of 120 V was applied thereto, followed by vulcanization at 150 ° C. The current increased rapidly after 5 minutes from the start of vulcanization and increased to 1
After one minute, it becomes almost constant and its shape is very similar to FIG. In other words, it can be seen that the vulcanization reaction can be tracked by measuring the value of the current flowing in the rubber compound to obtain optimum vulcanization conditions.

FIG. 5 is a diagram showing the time change of the tensile strength with the progress of the vulcanization reaction. The tensile strength increased with time until the vulcanization reaction was almost completed up to a vulcanization time of 10 minutes, but thereafter decreased substantially or slightly. It can be seen that they correspond well to the graphs showing the change in the dielectric loss tangent (tan δ) -time curve and the current-vulcanization time.

[0024]

Comparative Example FIG. 6 is a graph showing a dielectric loss tangent (tan δ) -time curve of a rubber compound containing neither sulfur nor a vulcanizing agent. It can be seen that the dielectric loss tangent (tan δ) only increases gradually, and no vulcanization reaction has occurred.

FIG. 7 is a diagram showing the correlation between t ₉₀ (torque) and t ₉₀ (tan δ) obtained from the tan δ-time curve. Generally, the 90% vulcanization time t ₉₀ (torque) obtained from the torque-time curve of FIG. 2 is adopted as the optimum vulcanization time. There is a correlation between t ₉₀ (torque) and t ₉₀ (tan δ) obtained from the tan δ-time curve, and very good linearity is observed.

FIG. 8 is a diagram showing the correlation between t ₉₀ (torque) and t ₉₀ (current) obtained from the current-time curve. A linear relationship is observed at a vulcanization temperature of 140 to 170 ° C. As described above, the torque-time curve, the tan δ-time curve, and the current-time curve have an extremely good correlation.

FIG. 9 is a partial sectional view showing a main part of a molding apparatus according to the present invention. Reference numeral 80 denotes a screw of an injection molding apparatus (a view of the entire apparatus is omitted), and a die 81 is provided on a tip side thereof. The mold 81 includes a fixed mold 82 and a movable mold 83.

Mold 81 (fixed mold 82 and movable mold 83)
A measuring section 85 is formed outside of the forming section 84 in FIG. The forming section 84 and the measuring section 85 are in communication. The fixed mold 82 and the movable mold 83 related to the measuring section 85 are provided with electrodes 86 and 87, respectively. The electrodes 86 and 87 are a measuring unit 88
Are electrically connected to the control unit 89 via the.

[0029]

(1) The dielectric loss tangent (tan) of the rubber compound R is determined in advance.
δ) or the time change of the current value is measured, and the optimum vulcanization conditions are set by this apparatus. When the control unit 89 measures the dielectric loss tangent (tan δ) or the current value which is the optimum vulcanization condition, the control condition is set so that the vulcanization is stopped and the mold 81 is opened. (2) The screw 80 is operated, and the forming portion 8 of the mold 81 is formed.
4 is filled with a rubber compound R. A part of the rubber compound R filled in the molding section 84 flows into the measuring section 85. (3) While molding and vulcanizing the rubber compound R in the mold 81, an AC voltage is applied to the electrodes 86 and 87, and the dielectric loss tangent (tan δ) or the current value of the rubber compound in the measuring section 85 is measured. (4) Dielectric tangent (tan δ) preset from measured values
Alternatively, when the current value is obtained, vulcanization is stopped and the mold 81 is opened, so that a rubber product having undergone optimal vulcanization can be obtained. Note that the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims.

[0030]

According to the present invention, the voltage is applied to the rubber to be vulcanized to measure the dielectric loss tangent (tan δ) or the current value, thereby measuring the progress of the rubber vulcanization reaction in real time. be able to. Further, by using the above-mentioned measuring method, automatic control of the vulcanization molding apparatus becomes possible, and thus, the rubber molding process can be automated.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a mold equipped with electrodes.

FIG. 2 is a diagram showing the time change of torque with the progress of the vulcanization reaction after vulcanizing NBR rubber having the composition shown in Table 1.

FIG. 3 is a diagram showing a dielectric loss tangent (tan δ) -time curve.

FIG. 4 is a diagram showing a change in current-vulcanization time.

FIG. 5 is a diagram showing a temporal change in tensile strength as the vulcanization reaction proceeds.

FIG. 6 is a graph showing a dielectric loss tangent (tan δ) -time curve of a rubber compound not containing sulfur and a vulcanizing agent.

FIG. 7 is a diagram showing a correlation between 90% vulcanization time t ₉₀ (torque) and 90% vulcanization time t ₉₀ (tan δ).

FIG. 8 is a diagram showing a correlation between 90% vulcanization time t ₉₀ (torque) and 90% vulcanization time t ₉₀ (current).

FIG. 9 is a partial cross-sectional view showing a main part of a molding apparatus according to the present invention.

[Explanation of symbols]

 81 mold 82 fixed mold 83 movable mold 85 measuring section 86, 87 electrode

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication location G01R 27/26 G01R 27/26 T // B29K 21:00 105: 24 (56) References JP JP-A-8-285802 (JP, A) JP-A-2-275349 (JP, A) JP-A-7-198642 (JP, A) JP-A-3-7309 (JP, A) JP-A-60-223828 (JP) , A) JP-A-58-139057 (JP, A)

Claims (5)

(57) [Claims] 1. An AC voltage is applied to an electrode provided on a mold.
Loss tangent (tan) of the rubber compound during the vulcanization reaction
δ) or by measuring the current value,
A method for producing a rubber product, comprising producing a rubber product while measuring a vulcanization reaction . 2. A method for producing a rubber product, comprising: determining a dielectric loss tangent (tan δ) or a current value of a rubber compound in advance.
Measure the time change and set the optimal vulcanization conditions.
Flop, the optimum vulcanization conditions dielectric loss tangent (tan [delta) or current
Control is performed to stop vulcanization and open the mold.
Setting step, AC voltage is applied to the electrode while molding and vulcanizing the rubber compound in the mold.
To determine the dielectric loss tangent (tan δ) or
Measuring the flow value, a preset dielectric loss tangent (tan δ) from the measured value or
When the current value is obtained, stop vulcanization, open the mold and open the rubber product
A method for producing a rubber product. 3. A method for producing a rubber product, comprising: filling a rubber compound in a mold and measuring a dielectric loss tangent (tan δ) or a current value of the rubber compound while molding and vulcanizing; Stopping the molding vulcanization when a tangent (tan δ) or a current value is measured, a method for producing a rubber product. 4. An apparatus for molding and vulcanizing a rubber compound in a mold, the dielectric tangent (tan) of the rubber compound being added to the mold.
δ) An apparatus for producing a rubber product, comprising an electrode for measuring a current value. 5. An injection molding apparatus, comprising:
And a fixed mold (82) and a movable mold (83).
A molding die (81), The electrodes (86, 8) are provided on the mold (81).
A measuring unit (85) having 7); Including The electrodes (86, 87) are controlled via a measuring unit (88).
And electrically connected to the control unit (89).
, Rubber product manufacturing equipment.