JPH0718870B2 - Testing device for calculating the distribution of vulcanization of rubber samples - Google Patents

Description

TECHNICAL FIELD The present invention relates to a test device for calculating a vulcanization degree distribution of a rubber sample.

Here, the vulcanization degree is, experimentally, according to the Aurenius equation. A: Constant (reaction index of rubber) E: Activation energy R: Gas constant T: Vulcanization temperature (absolute temperature K) T ₀ : Reference temperature (absolute temperature K) t: Reaction expressed as vulcanization time It is a measure of the state and is a function of the vulcanization temperature (T) and the vulcanization time (t). Therefore, the present invention provides a test device capable of calculating the vulcanization degree distribution of a rubber sample with high accuracy and with high efficiency, and finally identifying the blow point of the rubber with high accuracy. is there.

Further, the blow point is caused by insufficient vulcanization degree inside the article to be vulcanized at the end of the pressure vulcanization when vulcanizing rubber, a rubber-containing composite or the like under pressure. It means the minimum vulcanization degree (that is, the limit vulcanization degree) required for eliminating the presence of bubbles.

(Background Art) When vulcanizing rubber, a rubber-containing composite, or the like under pressure, when the pressure vulcanization is completed before the vulcanization target, particularly the central portion, reaches a certain degree of vulcanization, Since the center of the vulcanizate after vulcanization is in a foamed state, in many cases the degree of vulcanization should be determined in order to completely prevent the formation of such bubbles on the vulcanizate. Is going.

By the way, in producing a product having a short vulcanization time and no bubbles at all, it is extremely important to specify the blow point in order to determine the proper vulcanization degree of the material to be vulcanized.

Since this blow point differs depending on the composition of the rubber compound, kneading method, conditions, etc., it is extremely frequent to identify the blow point when performing quality control of the vulcanizate, development of the rubber composition, etc. It will be necessary to do.

Therefore, the plow point is required to be easily and quickly obtained with high accuracy.

(Prior Art) As described above, in order to calculate the foaming limit vulcanization degree, which is a blow point, as is clear from the formula (1), the vulcanization temperature (T) and the vulcanization time are calculated. It is necessary to obtain each (t), and conventionally, among these, the vulcanization time (t) can be determined by using a timer that operates in synchronization with the start of heating of the vulcanizate. It was general that the vulcanization temperature (T) inside the vulcanizate, which changes to, was measured by placing a temperature sensor inside the vulcanizate.

That is, conventionally, it has been widely general practice to create a sample corresponding to an actual material to be vulcanized and specify the blow point by variously changing the vulcanization degree for this sample. According to the above, although there is an advantage that highly accurate results can be obtained, there is a serious problem that the manufacturing man-hours of the sample and the test cost are significantly increased. A technique for identifying a blow point by using a test piece manufactured by using the above material as a sample is becoming widespread.

As a method for identifying blow points using test pieces as a sample, for example, “Determining the Blow Point in Tire Compounds” of “Rubber Age” February 1962 (RUBBER AGE, 1962, February).
(Determing the blow point in tire compounds: HAF
reeman: GOODYEAR TIRE and RUBBER CO.), one method is to vulcanize one rubber block with a large enough volume to identify the blow point, or to use multiple rubber blocks with a small volume. , There is a method to specify the blow point by vulcanizing by changing the vulcanization time. The former method is
As shown in FIG. 11, a plurality of pairs of thermocouples are embedded at predetermined intervals in respective parts a to e inside a large-volume rectangular parallelepiped rubber block, and the parts a to e during pressure vulcanization of the rubber book. The vulcanization degree of each part a to e is calculated by measuring the temperature of the above with a thermocouple over time, and then the vulcanization is terminated when the vulcanization degree inside the rubber block reaches a predetermined value. Furthermore, after cooling the rubber block that became a sample, cutting it and observing the foaming state inside, from the relationship between the vulcanization degree distribution in the sample calculated in advance and the foaming limit position of the sample It identifies the blow point.

In the latter method, a plurality of rectangular parallelepiped rubber blocks having a small volume as shown in FIG. 12 are prepared, and the relationship between the vulcanization degree and the vulcanization time of the central portion of the sample is obtained in advance for each rubber block. In the vulcanizing mold, pressure vulcanization is performed at different times, after allowing them to cool, each sample is cut and observed for the occurrence of bubbles, and the vulcanized samples are kept until no bubbles remain. The vulcanization degree is used as the blow point.

(Problems to be solved by the invention) However, in the method of vulcanizing a large volume of one rectangular parallelepiped rubber block to identify the blow point, the man-hours for embedding the thermocouple and hence the man-hours for manufacturing the rubber block increase, There is a problem in that the amount of rubber used for the rubber block increases, and because the volume of the rubber block is large, the slope of the vulcanization degree distribution curve becomes tight as shown in the graph in Fig. 11. However, there is a problem that the blow point identification accuracy is low, and in the method of vulcanizing multiple rubber blocks of small volume by changing the vulcanization time and identifying the blow point, prepare multiple rubber blocks. In addition to increasing the man-hours and time for vulcanizing each of them, the amount of rubber used also increases, and in addition, the vulcanization degree of each sample changes stepwise. There is a problem that can not be to obtain an accurate blow point.

The present invention advantageously solves the above problems of the prior art, and a rubber that enables a highly accurate calculation of the vulcanization degree distribution with a small volume sample, and at the same time enables accurate and rapid blow point identification. A test device for calculating the distribution of vulcanization degree of a sample is provided.

The method of previously embedding the temperature sensor inside the vulcanizate (sample) requires a lot of man-hours and is not efficient. Therefore, the method of inserting the temperature sensor inside the vulcanizate during temperature measurement is excellent in efficiency. However, in the temperature measurement by inserting the temperature sensor into the vulcanizate, the heat capacity of the temperature sensor itself, the amount of heat transferred from the vulcanization mold to the temperature sensor, and the temperature sensor mounting part Due to the influence of the amount of heat conducted to the temperature-sensitive part, it is virtually impossible to measure the true temperature inside the vulcanizate.
There is a problem that an accurate degree of vulcanization cannot be obtained.

That is, measuring the temperature by such an insertion method is extremely simple and efficient, but when measuring the internal temperature of the vulcanizate using such a method, There was a problem to mention. In other words, in FIG. 10 (a), the horizontal axis shows the vulcanization time and the vertical axis shows the vulcanization temperature, respectively. The temperature measured by the sensor becomes higher, and as a result, the vulcanization degree shown by the vertical axis in Fig. 10 (b) also shows the true vulcanization degree shown by the broken line and the calculated vulcanization shown by the solid line. It was quite different from the degree. Here, the true temperature is measured by, for example, preliminarily embedding and fixing an extremely thin thermocouple at a predetermined position of the vulcanization object so as not to be affected by heat transfer or the like to the vulcanization target. You can

This invention makes it possible to measure the true temperature inside the vulcanizate or a temperature as close to it as possible with a temperature sensor over time, and to sufficiently improve the accuracy of blow point identification. It is intended to provide a test device for
As shown as zone B in FIG. 5A, measures are taken against the difference between the measured temperature and the true temperature in the region where the temperature measured by the temperature sensor once falls and then rises again.

Here, as shown as zone A in FIG. 10 (a), after the start of vulcanization, when the flow of the material to be vulcanized almost stopped, it was heated under the influence of the temperature of the vulcanization mold. After inserting the temperature sensor into the vulcanizate, the temperature measured by the temperature sensor drops to near the internal temperature of the vulcanizate and reaches the lower limit temperature. The influence of the difference from the temperature on the vulcanization degree calculation accuracy can be completely eliminated by, for example, not sampling the measured temperature of the A zone as data.

(Means for Solving Problems) The present invention proposes a temperature sensor insertion type temperature measurement, which may affect the above-mentioned temperature difference in the B zone of FIG. 10 (a). Of the heat capacity of a certain temperature sensor itself, the amount of heat transferred from the vulcanization mold to the temperature sensor, and the amount of heat transferred from the temperature sensor mounting part to the temperature sensing part of the temperature sensor, the one that has a large effect on the temperature difference is particularly important. The rubber according to the present invention was made by paying attention to the amount of heat transferred from the metal mold to the temperature sensor, and by making it possible to perform a highly accurate and highly efficient test by using a small volume sample. The test device for calculating the vulcanization degree distribution of a sample has a depth that changes from one end to the other end, and a cavity for fully accommodating the vulcanizate of the rubber sample and an interval in the direction in which the depth of this cavity changes are provided. Set aside A vulcanization mold having a plurality of through holes that communicate with the cavity, a heating source that heats the vulcanization mold from the depth direction of the cavity, and a hole in and out of the inside of each of the through holes. A plurality of temperature sensors that measure the temperature of each part inside the vulcanizate, and a thermal diffusivity that is placed in each of the through holes and that blocks heat transfer between the vulcanization mold and the temperature sensor is 20 mm ² Comprising a heat insulating member of / min or less, and means for putting in and taking out the temperature sensor, for the blow point identification of rubber, calculation of the vulcanization degree distribution inside the vulcanizate along the changing direction of the cavity depth It is characterized by enabling.

Here, in order to further reduce the temperature difference between the measured temperature and the true temperature, the diameter of the temperature sensor is made as thin as possible to reduce the heat capacity of the temperature sensor, and at the same time, from the vulcanization mold to the temperature sensor. To reduce the amount of heat transferred to the temperature sensor, to reduce the amount of heat transferred from the mounting part of the temperature sensor to the temperature sensing part of the sensor by configuring the temperature sensor outer skin and other materials with a low heat transfer coefficient, and It is preferable that at least one of the sensor and its mounting portion is directly or indirectly covered with, for example, asbestos, Teflon, or the like to insulate the radiant heat from the hot platen and the vulcanization mold and the like.

In carrying out the present invention, it is desirable that the depth change from one end to the other end of the cavity formed by closing the upper and lower mold parts is a continuous increase or a stepwise increase.

In addition, the blow point identification method using a sample manufactured by such a vulcanization mold is a step of vulcanizing the rubber for the sample in the cavity of the mold and the inside of the rubber being vulcanized. Measure the temperature at multiple points as needed over time, and calculate the degree of vulcanization at each point from this measurement result, and terminate the vulcanization when the calculated degree of vulcanization reaches a specified state. Then, the process of taking out the sample rubber from the cavity and the internal foaming state of the sample are observed in the direction in which the thickness changes, and vulcanization inside the sample is such that no bubbles remain inside. The degree of vulcanization in the progressing part is calculated from the degree of vulcanization at each temperature measurement point when using a stepped cavity, and from the temperature measurement point at each temperature measurement point when a continuous cavity is used. From the vulcanization degree of each part of the sample calculated from the vulcanization degree Comprising a combination of a step of determining Re respectively.

(Operation) In this device, the vulcanization mold is used to
A rubber sample, which can be used as a test piece, is vulcanized, and during this vulcanization, the vulcanization temperature of each part is precisely measured with time with a plurality of temperature sensors inserted to the predetermined position of the sample. This enables continuous calculation of the degree of vulcanization in the temperature-sensitive part of each sensor, and when the degree of vulcanization in each temperature-sensitive part reaches the required state, vulcanization is terminated and the temperature is Withdrawal of the sensor from the sample and removal of the sample from the vulcanization mold will result in a vulcanized blowpoint identifying sample that allows observation of blown development from subsequent samples.

That is, in this device, the thermal diffusivity around which the temperature sensor is located has a thermal insulation layer of 20 mm ² / min or less so that the temperature sensor is effectively insulated against the vulcanization mold, and the temperature sensor is inside the vulcanizate. The heat transfer from the vulcanization mold to the temperature sensor is reduced by the heat insulating member in the state where the vulcanization mold is inserted into the temperature sensing part such as a thermocouple arranged at the tip of the temperature sensor. The heat transfer is substantially blocked by the heat insulating member, so that the temperature measured by the temperature sensor is
Since the temperature is remarkably close to the true temperature, the calculated vulcanization degree is also very close to the true vulcanization degree, and even if there is a difference between both vulcanization degrees, this difference is within the tolerance range. It is a sufficiently small value included in.

The measured temperature and thus the degree of vulcanization in the sample thus obtained differ from part to part depending on the shape, wall thickness, etc. of the sample. By visually observing it, or by performing nondestructive inspection on it, the vulcanization degree at the boundary where vulcanization progressed until no bubbles remained in the sample, in other words, the foaming limit vulcanization degree, It is carried out by obtaining from the vulcanization degree distribution calculated in advance at the time of vulcanization.

Further, in the device of the present invention, the depth of vulcanization changes from one end to the other end, and preferably, the vulcanization degree within one sample is increased by manufacturing the sample in a cavity that continuously increases. Since the thickness changes continuously in the changing direction, it is possible to manufacture one sample having a part where bubbles remain inside and a part where it does not remain, and the foaming limit position is visually or Non-destructive inspection makes it possible to find out very accurately, and also brings about a significant reduction in the man-hours and time of various operations therefor and the amount of rubber used.

The degree of vulcanization at the foaming limit found in this way is
It can be obtained by comparison with the degree of vulcanization of each part of the sample obtained in advance.

And here, during vulcanization of the sample rubber by the vulcanization mold as described above, the internal temperature of the rubber is measured at a plurality of points as required over time, and the vulcanization degree is calculated from each measurement result. By doing so, it is possible to continuously detect the change in the vulcanization degree of each part of the sample, and when the calculated vulcanization degree reaches a predetermined state, the vulcanization is terminated and the rubber used as the sample is After being taken out of the cavity and allowed to cool for a certain period of time, the internal foaming state of the sample can be measured by cutting the sample with or without cutting the vulcanization degree continuously changing from one end to the other. The vulcanization inside the sample is the position where the vulcanization progresses to the extent that no bubbles remain inside, that is, the foaming limit position is accurately found, and the vulcanization degree at that position is determined. , Each temperature measurement point By obtaining the final vulcanization degree and the vulcanization degree of each part along the change direction of the sample thickness obtained by interpolation of the vulcanization degree at each of these points, it is possible to specify the foaming limit position extremely accurately and continuously change. Based on the vulcanization degree distribution, the blow wind can be specified with high accuracy.

Therefore, here, as described above, by producing one sample having a portion in which bubbles do not remain when they remain inside, extremely quick and accurate operation can be achieved under a small number of working steps and a small amount of rubber. The blow point can be specified.

Here, when a vulcanization mold in which the depth of cavities is changed stepwise is used, the step of vulcanization of the sample after completion of vulcanization is performed to the extent that no bubbles remain at all. The blow point can be rapidly identified by finding the vulcanization degree of the step and the final vulcanization degree of each step calculated in advance.

In addition, here, in particular, when the rubber is pressure-vulcanized in the cavity where the depth continuously increases from one end to the other end, the temperature measurement region of the rubber during vulcanization is set to the depth of the cavity. In the direction in which the direction changes, the central region is separated from each edge of the rubber by at least three times the rubber thickness at each edge, so that it is transmitted from the side wall portion of the vulcanization mold to the inside of the rubber. The effect of the heat quantity on the measured temperature can be effectively removed, and the temperature change based on the heat quantity transferred from the vertical direction to the inside of the rubber can be measured sufficiently accurately. By performing the temperature measurement only in the area, the vulcanization degree of each part of the sample can be calculated with high accuracy, and therefore the accuracy of identifying the blow point can be increased.

Further, here, in addition to the above, here, the relative relationship between the thicknesses h ₁₀ and h ₂₀ at both ends of the temperature measurement region of the rubber during vulcanization and the thicknesses h ₁₀ and h ₂₀ and the length of the temperature measurement region are described. When the vulcanization temperature (hot platen set temperature) is 170 ° C to 190 ° C, And, and And when the vulcanization temperature (hot platen set temperature) was set to 130 ° C to 150 ° C, And It is preferable that

Ie average thickness When the value is smaller than the above-mentioned minimum value, when the vulcanization is terminated in a state where bubbles remain in at least a part of the sample, the vulcanization time of the sample becomes too short, so that the hardness of the surface layer part is sufficiently high. I ca n’t raise it,
Therefore, when the sample is taken out from the vulcanization mold, the sample is deformed, and it becomes extremely difficult to accurately identify the foaming limit position, so that there is a problem that the blow point identification accuracy is lowered. When the average thickness is made larger than the above-mentioned maximum value, there is a problem that the sample volume becomes too large and the vulcanization time, the measurement man-hours, etc. increase remarkably.

And also the gradient of the sample With respect to the above, when it is made smaller than the above-mentioned minimum value, the difference in vulcanization degree at both end portions of the length l of the proper temperature measurement region of the sample becomes too small,
It is extremely difficult to generate a region where the foaming limit position can be determined by one-time vulcanization, and as a result, there is a problem that the number of vulcanizations and the number of measurements are increased. When the value is made larger, the difference in vulcanization degree in the proper temperature measurement region becomes too large, so that the blow point identification error caused by the determination error of the foaming limit position of the sample becomes significantly large and the identification accuracy decreases. There is a problem.

(Example) Hereinafter, the present invention will be described based on illustrated examples.

FIG. 1 is a partial sectional view showing an embodiment of the present invention,
In the figure, 1 is a base frame, 2 is a pressurizing cylinder provided above the base frame 1 at a distance, and 3 is a vulcanizing mold attached to each of them.

Here, the lower mold part 3a of the vulcanizing mold 3 is attached to the base frame 1 via the lower heating plate 4 and the heat insulating plate 5, and the upper mold part 3b of the vulcanizing mold 3 is connected to the upper heating plate 6. , And is fixed to the rod end of the pressurizing cylinder 2 via the heat insulating board 7 and the spacer 8.

In the figure, 9 indicates a lock nut.
Serves to surely position the spacer 8 screwed onto the rod 2a of the pressurizing cylinder 2 at a predetermined position of the rod 2a.

Further, 10 and 11 respectively indicate a vertically extending guide rod and a support column for mounting a limit switch. The guide rod 10 includes a sliding member 12 provided on a lower end flange 8a of a spacer 8 and It guides the up-and-down movement of each member attached to the rod (2a) by making surface contact over almost half the circumference. The guide rod 10 is also provided on the back side of the vulcanization mold 3 and operates in the same manner. In addition, the column 11 has two limit switches 13, 14 at the upper and lower positions at predetermined positions in the length direction.
The respective limit switches 13 and 14 stop the rising and lowering operations of the rod 2a by being actuated by the dog 15 provided on the lower end flange 8a of the spacer 8 as well. Generate signals respectively.

Further, reference numeral 16 in the figure denotes a sensor unit connected to a temperature detector (not shown) and driven to move in and out of the cavity of the vulcanization mold 3, and this sensor unit 16 has a temperature sensor at its tip. .

In the vulcanization degree distribution calculation test device configured as described above, the vulcanization mold 3 for vulcanizing the vulcanization target (sample) is illustrated in FIGS. 2 (a) and 2 (b), respectively. It is composed of a lower part 3a and an upper mold part 3b whose plane contours are both rectangular, and bolt holes 17 and 18 which allow the insertion of bolts, respectively, at the four corners of the lower mold part and the upper mold parts 3a and 3b. Set up. Further, here, in the central portion of the lower portion 3a, a recess 19 whose planar contour is also rectangular is formed, and in the central portion of the upper mold portion 3b, the recess 19 is just fitted into the cavity 19 to be described later. Each of the protrusions 20 that contributes to the structure of the lower mold portion 3a is formed on one side wall of the lower mold portion 3a, which is a high mold portion, and penetrates therethrough to reach the recess 19 and thus the cavity (four in this example). ) Through hole 21 in the same horizontal plane,
A vent hole 22 is provided on the other side wall at a required interval to allow the surplus vulcanizate to flow out of the mold as a spew.

Such a vulcanizing mold 3 has a lower heating plate 4 with a lower mold portion 3a by means of bolts 23 inserted into bolt holes 17 thereof, as is clear from the cross section in the longitudinal direction of FIG. 3 (a). With the upper mold part 3b clamped to the upper heating plate 6 with the bolts 24 inserted into the bolt holes 18,
By closing them, a cavity 25 whose cross-sectional shape is a sideways isosceles trapezoid whose depth changes from one end to the other is formed between both mold parts. In this case, the axis of each through hole 21 provided on one side wall of the lower mold portion 3a is located at a half point of the depth of each portion of the cavity 25.

On the other hand, the cross section of the cavity 25 in the short side direction has a uniform depth in each part as is clear from the view shown in FIG. 3 (b), which means that in any part in the long side direction. Is also the same.

Further, as shown in FIG. 4, a sensor unit 16 driven into and out of the cavity 25 of the vulcanizing mold 3 is provided with a sensor holder 26 made of, for example, bakelite with cloth.
And a temperature sensor 27 fixed to the tip of the holder 26 and connected to a temperature detector via a flexible cord (not shown).
And a plurality of such sensor units 16, here four in the figure, are arranged so as to face the respective through holes 21 provided in one side wall of the lower mold part 3a and extend in the horizontal direction. It is held by one existing sliding member 28. This sliding member 28 is connected to a cylinder rod 30a of an air cylinder 30 fixed to an elevating plate 29, so that the sensor unit 16 and thus the temperature sensor 27 are guided by a guide rod 31 based on the operation of the air cylinder 30. Under the through hole 21
To move in and out of the cavity 25 via.

Here, one end of the guide rod 31 is attached to the lift plate 29,
The other ends are connected to the side walls of the lower mold part 3a, respectively, and the lifting plate 29, as is clear from the view shown in FIG. The support unit 32 is rotated based on the screwing of the sensor unit 16, the sliding member 28, and the guide rod.
Along with 31, the position corresponding to the level of the vulcanizing mold 3, that is, the height of the temperature sensor 27 and the axis of the through hole 21 are moved up and down.

Further, as the temperature detecting means of the temperature sensor 27 here,
A variable resistance element, a thermocouple, etc. can be selected. In particular, when the thermocouple is selected, the temperature sensor 27
It is preferable that the tip end portion of the is configured as shown in the sectional view of FIG. That is, for example, in a stainless steel inner cylinder 34 accommodating a thermocouple 33 made of copper-constantan,
While filling magnesium oxide 35 acting as a heat resistant material, a heat insulating material and an insulating material, an outer cylinder 37 made of stainless steel is arranged outside the inner cylinder 34 with an air layer 36 as a heat insulation layer interposed therebetween. The tip of the cone-shaped temperature sensing part 38 can be composed of a brazing material or other material with high thermal conductivity.
It is preferable that the thermocouple 33 is completely closed and the coupling portion of the thermocouple 33 is completely embedded in the temperature sensitive portion 38.

According to such a temperature sensor 27, the heat transfer in the radial direction is due to the air layer 36 and the magnesium oxide 35, and the heat transfer in the length direction is lower in thermal conductivity than other metals. Since the stainless steel inner and outer cylinders 34 and 37 and the magnesium oxide 35 are effectively prevented from each other, the thermocouple 33 changes the temperature of the temperature sensing portion 38 to the coupling portion without being affected by the amount of heat transferred from the outside. It can be detected with sufficient accuracy based on the thermoelectromotive force generated in the.

And in order to bring the temperature measured by the temperature sensor 27 closer to the true temperature, the temperature sensor 27 can be accurately inserted into the relative vulcanizate in the cavity 25,
By setting the outer diameter to a small diameter of, for example, about 1 to 2 mm, the sensor caused by the decrease in the heat capacity of the temperature sensor 27
It is preferable to improve the followability of the specific vulcanizate temperature of 27 and to reduce the amount of heat transferred from the vulcanization mold 3 to the temperature sensor 27. Furthermore, the temperature sensor 27 and a sensor as a mounting portion thereof are preferable. At least one of the holders 26 is preferably covered with a heat insulating layer to prevent the transmission of radiant heat or the like to them.

In addition, in this device, a heat insulating member that allows the temperature sensor 27 and further the tip of the temperature sensor 27 to move into and out of the cavity 25 in each through hole 21 of the lower mold portion 3a, and in this example, a tubular heat insulating member 39 is fixed by fitting. , The lower mold part by this tubular heat insulating member 39
Effectively prevents heat conduction from 3a to the tip of the temperature sensor.
Here, the tubular heat insulating member 39 prevents the temperature sensor tip portion from slipping out to the recessed side of the lower mold portion 3a when the temperature sensor tip portion is inserted into the inside and the sensor is inserted into the vulcanized material. Have a shoulder for.

Further, here, in order for the tubular heat insulating member 39 to sufficiently exert its intended heat insulating action, a = K / cρ (mm ² / min) (2) a: thermal diffusivity K: heat conduction It has been confirmed by experiments that a material having a thermal diffusivity a represented by a degree c: specific heat ρ: density needs to be 20 or less. That is, the outer diameter of the tip of the temperature sensor is 1.8φ, the insertion depth of the temperature sensor 27 into the vulcanizate is 15 mm, the thickness of the tubular heat insulating member 39 is 7 mm, and the vulcanization is performed at 145 ° C. for 20 minutes. , When the true vulcanization degree of the vulcanizate becomes 0.20, the tubular heat insulating member is made of a plurality of types of substances having different thermal diffusivities a.
The measurement result of the difference between the measured vulcanization degree and the true vulcanization degree when 39 is constituted is as shown in FIG. 6, and according to the graph of FIG. 6, the thermal diffusivity a is 20%. It is understood that when the tubular heat insulating member 39 made of a larger substance is applied, the ratio between the measured vulcanization degree and the true vulcanization degree cannot be set to 1.10 or less, which is a general allowable limit error. The thermal diffusivity a of each substance shown in the figure is about 5 (mm ² / mi) for butyl rubber.
n), Teflon is about 10 (mm ² / min), silicone rubber is about
20 (mm ² / min), ceramics about 100-200 (mm ² / mi
n), iron is about 700 (mm ² / min).

Also, in the apparatus of this example, as is clear from FIGS. 3 (b) and 4, the temperature sensor 27 is attached to the lower mold part 3a.
The Teflon plate 40 that allows the penetration of the Teflon plate 40 is fixed, and the Teflon plate 40 supports the temperature sensor 27 and guides the movement in and out of the temperature sensor 27. , Mainly radiant heat temperature sensor 27
Effectively prevent transmission to. Here, in order to make the Teflon plate 40 more fully exhibit its heat insulating function, the thickness of the Teflon plate 40 should be as thick as possible,
As shown in Fig. (B), when the upper and lower mold parts 3b and 3a are closed, as long as they do not interfere with the upper and lower heating plates 6 and 4,
It is preferable to make the height as high as possible.

When manufacturing the blow point specifying sample by the above-described apparatus, first, the cavity 5 of the vulcanization mold 3 is filled with unvulcanized rubber as a substance to be vulcanized to start vulcanization, When the flow of the rubber is almost stopped, the four temperature sensors 27 are moved forward by the action of the air cylinder 30 from the retracted position where the tip edge of the sensor 27 is aligned with the peripheral wall of the recess of the lower mold part 3a. Operate each temperature sensor 27
Rubber is inserted horizontally to the required position of the rubber, then the temperature of each temperature sensitive portion 38 is measured with each temperature sensor 27 over time, and the degree of vulcanization is continuously measured from this measurement result and the vulcanization time. calculate.

In this temperature measurement here, the heat conduction from the vulcanization mold 3 to the temperature sensor 27 is mainly due to the thermal diffusivity of 20 mm ² / mi.
Since it is effectively blocked by the action of the tubular heat insulating member of n or less, the temperature measured by each temperature sensor 27 comes close enough to the true temperature, and as a result, the calculated vulcanization is performed. The degree is also very close to the true degree of vulcanization.

Therefore, after that, it was confirmed from the calculated vulcanization degree that the vulcanization degree distribution of each part of the rubber reached the required state, and the blow point specifying sample obtained by stopping the vulcanization The true vulcanization degree also becomes a value extremely close to the calculated vulcanization degree.

Then, the blow points for the blow point specifying sample taken out from the vulcanization mold 3 are specified by, for example, determining the final calculated vulcanization degree at each temperature measurement point for each measurement point as shown in FIG. , A, b, c, d are plotted, and each point is connected by an interpolation line to calculate the vulcanization degree of each part in the length direction of the sample, and then the length is calculated. While observing the sample cut in the direction, find the position where the degree of vulcanization inside progresses to such an extent that no bubbles remain at all, while determining the degree of vulcanization at that position from the above calculated degree of vulcanization Done by

The blow point obtained in this way is a value determined by the rubber type, composition, kneading conditions, etc., so by applying it to the actual vulcanization of the vulcanizate, in addition to foam generation An excellent vulcanized product free of vulcanization can be obtained.

The present invention has been described above based on the illustrated embodiment. However, in another embodiment, the cavity 25 of the vulcanization mold 3 is not
A shape for producing a vulcanization degree distribution calculation sample having a shape as shown in the perspective views of FIGS.
From vulcanization and samples in those cavities,
The blow point can be obtained in substantially the same manner as described above. Here, the blow point can be specified for the stepwise sample as follows.

First, as shown in FIG. 9, the degree of vulcanization of the central parts a, b, c, and d of each step at the end of vulcanization is obtained, and then the generation state of bubbles in each step of the sample is indirectly or directly determined. The step where vulcanization is progressing to such an extent that no bubbles remain at all is found, and the vulcanization degree at the central portion of the step, in the figure, is the blow point.

(Comparative Example) The following table shows the test results regarding the effectiveness of the tubular heat insulating member in the present invention.

Here, the outer diameter of the temperature sensor was 1.5φ and the insertion depth was 20 mm.

According to this test result, the cylindrical heat insulating member has a thermal diffusivity of 20.
By using a substance of mm ² / min or less, it is possible to remarkably improve the reliability of the measured temperature and thus the calculated vulcanization degree, and the vulcanization degree ratio is a general allowable marginal error.
It turns out that it can be well within 1.10.

(Effect of the Invention) Therefore, according to the present invention, in particular, by using the vulcanizing mold whose depth changes from one end to the other end, the foamed portion and the non-foamed portion are provided inside one small amount rubber sample. And can be generated simultaneously, and the thermal diffusivity is 20 mm ² / min
By effectively preventing the heat conduction from the vulcanization mold to the plug-in type temperature sensor by the action of the following tubular heat insulating member, the measured temperature and thus the calculated vulcanization degree can be made sufficiently close to the true value. This makes it possible to significantly improve the accuracy of identifying the blow point in the sample.By vulcanizing the actual vulcanizate using this blow point as a guide, it is possible to prevent internal foaming, overvulcanization, etc. It is possible to prevent and extremely efficiently provide a vulcanized product of excellent quality at all times, and it is possible to remarkably reduce the number of man-hours for the blow-point specifying work that needs to be performed frequently.

[Brief description of drawings]

FIG. 1 is a partial sectional view showing an embodiment of the present invention, FIG. 2 is a plan view showing a lower mold part and an upper mold part of a vulcanizing mold, and FIG. Sectional view in the direction of the short side, FIG. 4 is a plan view showing the relationship between the lower part of the vulcanizing mold and the temperature sensor, FIG. 5 is an enlarged sectional view illustrating the tip of the temperature sensor, and FIG. FIG. 7 is a graph showing the influence of the calculation of the thermal diffusivity of the cylindrical heat insulating member on the vulcanization degree, FIG. 7 is a view illustrating the procedure for identifying the blow point, FIG. 8 is an inclined view illustrating another shape of the sample, and FIG. The figure shows the procedure for specifying the blow point for the sample shown in FIG. 8, and FIG. 10 shows the difference between the measured temperature and the true temperature and the difference between the calculated vulcanization degree and the true vulcanization degree according to the prior art. Graphs and FIGS. 11 and 12 are diagrams showing conventional blow point specifying regions, respectively. 3 ... Vulcanizing mold, 3a ... Lower mold part 3b ... Upper mold part, 4 ... Lower heating plate 6 ... Upper heating plate, 16 ... Sensor unit 21 ... Through hole, 22 ... Vent hole 25 …… Cavity, 26 …… Sensor holder 27 …… Temperature sensor, 28 …… Sliding member 30 …… Air cylinder, 38 …… Temperature sensing part 39 …… Cylindrical heat insulating member

Claims (2)

[Claims] 1. A cavity, the depth of which changes from one end to the other, to accommodate a vulcanizate of a rubber sample, and the cavities which are spaced apart in a direction in which the depth of the cavity changes. A vulcanization die having a plurality of through holes communicating with the heating source; a heating source for heating the vulcanization die in the depth direction of the cavity; A plurality of temperature sensors that measure the temperature of each part inside the vulcanizate, and arranged in each of the through holes, the thermal diffusivity to prevent heat transfer between the vulcanization mold and the temperature sensor is 20 mm ² / min It is equipped with the following heat insulating member and means for putting in and taking out the temperature sensor, and it is possible to calculate the vulcanization degree distribution inside the vulcanizate along the changing direction of the cavity depth for identifying the blow point of rubber. Vulcanization of rubber samples characterized by Test device for calculating degree distribution. 2. The apparatus according to claim 1, wherein the depth change from one end of the cavity to the other end is an increase in either a continuous increase or a stepwise increase.