JPH0675045B2 - Vulcanization mold for blow point measurement sample and blow point measurement method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vulcanization mold for a sample for measuring a blow point and an improvement in a blow point measuring method using the sample. It makes measurement possible.

Here, the blow point is caused by insufficient vulcanization degree inside the material to be vulcanized at the end of the pressure vulcanization when vulcanizing rubber, a composite containing rubber, etc. under pressure. It means the minimum vulcanization degree (that is, the foaming limit vulcanization degree) required to eliminate the presence of foam.

The vulcanization degree here 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).

(Background Art) When vulcanizing rubber, a composite containing rubber, etc. under pressure, when vulcanization of the vulcanizate is completed before the pressure vulcanization is completed without reaching a specific 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.

Here, the blow point differs depending on the composition of the rubber compound, the kneading method and conditions, etc.Therefore, the blow point should be measured very frequently when controlling the quality of the vulcanizate and developing the rubber composition. It will be necessary to do.

(Prior Art) In the past, therefore, it has been widely practiced to prepare a sample corresponding to an actual material to be vulcanized and measure the blow point by variously changing the vulcanization degree of the sample. Although this measurement method has an advantage that highly accurate results can be obtained, it has a serious problem that the number of man-hours for manufacturing a sample and the test cost are significantly increased. A technique of measuring a blow point using a test piece manufactured from a material used for a sulfide as a sample is becoming widespread.

Here, as a method of measuring the blow point using a test piece as a sample, for example, “Determining the Blow Point in Tire Compounds” of “Rubber Age” February 1962 (RUBBER AGE, 1962, February) ( Determining the blow point in tire compound
As described in s: H ・ A ・ Freeman: GOOD YEAR TIRE and RUBBER CO.) There is a method of measuring the blow point by vulcanizing a plurality of rubber blocks of different volumes at different vulcanization times, and the former method uses a predetermined volume inside a large rectangular parallelepiped rubber block as shown in Fig. 11. The vulcanization of the parts a to e was performed by embedding a plurality of pairs of thermocouples at intervals and measuring the temperature of the parts a to e during the pressure vulcanization of the rubber block with the thermocouples with time. The vulcanization degree is calculated when the vulcanization degree inside the rubber block reaches a predetermined value, and after the rubber block that has become a sample is allowed to cool, it is cut and the inside foamed state And vulcanization degree distribution in the sample calculated in advance, And measures the blow point from the relationship between the foam limit position of the sample. In the latter method, a plurality of small-volume rectangular parallelepiped rubber blocks as shown in Fig. 12 are prepared, and each rubber block is
The relationship between the degree of vulcanization at the center of the sample and the vulcanization time is calculated in advance in the vulcanization mold, which is pressure-vulcanized at different times, and after allowing them to cool, each sample is cut and foamed. The blow point is the vulcanization degree of the vulcanized sample until no bubbles remain.

(Problems to be solved by the invention) However, in the method of vulcanizing a large volume of a rectangular parallelepiped rubber block to measure the blow point, the man-hours for embedding the thermocouple and hence the rubber block are increased. However, there is a problem that the amount of rubber used for its production increases, and moreover, because the volume of the rubber block is large, as shown in the graph in FIG. There is a problem that the point measurement accuracy is low, and multiple rubber blocks with a small volume
In the method of measuring the blow point by vulcanizing by changing the vulcanization time, preparing a plurality of rubber blocks, and increasing the man-hour and time for vulcanizing each of them,
Since the amount of rubber used is large, and in addition, the vulcanization degree of each sample changes stepwise, there is a problem that an accurate blow point cannot be obtained.

The present invention advantageously solves the above problems of the prior art, and provides a vulcanization mold for a blow point measurement sample and a Plow point measurement method that enable accurate and rapid blow point measurement with a small volume sample. It is provided.

(Means for Solving Problems) The vulcanization mold of the sample for blow point measurement of the present invention is
In particular, the depth of the cavity formed by closing the upper and lower mold parts is increased continuously or stepwise from one end to the other.

In addition, the blow point measuring method using a sample manufactured by such a vulcanizing mold includes a step of vulcanizing the rubber for the sample in the cavity of the mold and an 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 of the part in progress is changed from the degree of vulcanization at each temperature measurement point when using a cavity that changes in stages, and when using a cavity that changes continuously. Sample estimated from the degree of vulcanization at the temperature measurement point Comprising a combination of a step of determining the degree of vulcanization of the parts.

(Operation) According to the vulcanization mold of the present invention, the vulcanization is performed inside one sample by manufacturing the sample in the cavity whose depth increases continuously from one end to the other end. Since the degree changes continuously in the direction in which its thickness changes,
By producing one sample having a portion where bubbles remain inside and a portion where it does not remain, it becomes possible to find the foaming limit position by eye or by nondestructive inspection very accurately, and As a result, the man-hours and time required for various operations and the amount of rubber used are significantly reduced.

The degree of vulcanization at the foaming limit position thus found can be determined by comparison with the degree of vulcanization of each part of the sample which is obtained in advance.

Further, in the measuring method of the present invention, this is also preferably during vulcanization of the sample rubber by the vulcanizing mold as described above, while measuring the internal temperature of the rubber at a plurality of locations as required over time, By calculating the vulcanization degree from each measurement result, the change in the vulcanization degree of each part of the sample can be continuously detected, and the vulcanization is finished when the calculated vulcanization degree reaches a predetermined state. Then, after taking out the sample rubber from the cavity and allowing it to cool for a certain period of time, the internal foaming state of the sample is cut by cutting the sample whose vulcanization degree continuously changes from one end to the other, or Without cutting, observing in the direction in which the thickness changes, the position where vulcanization inside the sample is progressing to the extent that no bubbles remain inside, in other words, the foaming limit position is accurately found, That place By determining the vulcanization degree of the final vulcanization degree at each temperature measurement point and the vulcanization degree of each part of the sample estimated from these vulcanization degrees, it is possible to extremely accurately identify the foaming limit position and continuously change it. Based on the degree of vulcanization
The blow point can be measured with high accuracy.

Therefore, here, as described above, by producing one sample having a portion where bubbles remain and a portion where it does not remain inside, extremely quickly under a small number of working steps and rubber usage, And the blow point can be measured accurately.

Here, in the case of using a vulcanizing mold in which the depth of the cavity changes step by step, find a step in which the vulcanization progresses to such an extent that no bubbles of the sample remain after the vulcanization is completed. At the same time, the blow point can be quickly measured by obtaining the vulcanization degree of the step from the final vulcanization degree of each step calculated in advance.

In addition, in this measurement method, especially when pressure vulcanizing rubber in a 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 measurement temperature can be effectively removed, and the temperature change based on the heat quantity transferred to the inside of the rubber from the vertical direction 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 estimated with high accuracy, and therefore,
Blow point measurement accuracy can be improved.

Further, in this measurement method, in addition to the above, the thicknesses of both ends of the temperature-measuring region of the rubber during vulcanization, h ₁₀ and h ₂₀
The relationship between the vulcanization temperature (hot platen set temperature) of 170 ° C and the relationship between the thicknesses h ₁₀ and h ₂₀ and the length l of the temperature measurement region
When set to ~ 190 ℃, And, and And when the vulcanization temperature (hot platen set temperature) was set to 130 ° C to 150 ° C, And, and It is preferable that

Ie average thickness When the value is smaller than the above-mentioned minimum value, when vulcanization is completed 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 It is not possible to raise it sufficiently, which causes deformation of the sample when taking it out of the vulcanization mold, and it becomes extremely difficult to accurately identify the foaming limit position, so the blow point measurement accuracy decreases. And on the other hand,
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 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 larger than the value, the difference in vulcanization degree in the proper temperature measurement region becomes too large, so the measurement error of the probe point caused by the judgment error of the foaming limit position of the sample becomes significantly large and the measurement accuracy decreases. There was a problem of doing.

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

FIG. 1 is a partial cross-sectional side view illustrating a manufacturing apparatus for a blow point measurement sample, in which 1 is a base frame and 2 is a pressurizing cylinder provided above the base frame 1 at a distance from each other. , 3 also shows the vulcanization molds 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 reliably position the spacer 8 screwed on 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, and the guide rod 10 includes a sliding member 12 provided on a lower end flange 8a of the spacer 8 and a sliding member 12 provided on the lower end flange 8a. It guides the up-and-down movement of each member attached to the rod (2a) in surface contact over a half circumference. Further, the column 11 acts to support the upper and lower limit switches 13 and 14 at predetermined positions in the length direction thereof, and the respective limit switches 13 and 14 of these limit switches 13 and 14 are supported.
Is also a dog 15 provided on the lower end flange 8a of the spacer 8.
When they are actuated by the above, stop signals for raising and lowering the rod 2a are generated respectively.

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

In the sample manufacturing apparatus configured as described above, here, the vulcanization mold 3 for vulcanizing the sample is shown in FIG.
As illustrated in (b) respectively, the lower die portion 3a and the upper die portion 3b, both of which have a rectangular planar contour, are formed, and the bolts are inserted into the four corners of the lower die and upper die portions 3a, 3b. Bolt holes 17 and 18 are provided to allow the above. Further, here, in the central portion of the lower mold portion 3a, a recess 19 whose planar contour is also rectangular is formed, and in the central portion of the upper mold portion 3b, an apex is fitted into the recess 19, which will be described later. Each of the protrusions 20 that contributes to the structure of the cavity is provided, and further, one side wall of the lower mold portion 3a, which is a high mold portion, has a plurality of through holes 21 that penetrate therethrough to reach the cavity 19 and reach the cavity. Are provided at the required intervals in the same horizontal plane, and the other side wall is provided with a vent hole 22 for allowing 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 is formed between both mold parts. In addition, here, each through hole 21 provided in one side wall of the lower mold portion 3a has a depth of each portion of the cavity 25.
It is located at the point of 1/2, and this is the same in any part in the long side direction.

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). The same is true for.

Further, as shown in FIG. 4, the sensor unit 16 driven to move back and forth with respect to the cavity 25 of the vulcanizing mold 3 is, for example, a sensor holder made of cloth-filled bakelite.
26 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). Here, a plurality of such sensor units 16 are shown. Then, four of them are arranged so as to face the respective through holes 21 provided in one side wall of the lower mold part 3a, and are held by one sliding member 28 extending in the horizontal direction. This sliding member 28 is connected to a cylinder rod 30a of an air cylinder 30 fixed to an elevating plate 29, and based on the operation of the air cylinder 30, the sensor unit 16 and thus the temperature sensor 27, and the guide rod.
Under the guidance of 31, it moves back and forth with respect to the cavity 25 through the through hole 21.

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. By rotating the support column 32 on the basis of the screwing, the position corresponding to the level of the vulcanization mold 3 together with the sensor unit 16, the sliding member 28 and the guide rod 31, that is, the axial position of the temperature sensor 27, is obtained. It is moved up and down to a height that coincides with the axis of the through hole 21.

Further, as the temperature detecting means of the temperature sensor 27 here, a resistance change element, a thermocouple or the like can be selected. In particular, when the thermocouple is selected, the tip portion of the temperature sensor 27 is It is preferable to configure as shown in the sectional view. That is, for example, a stainless steel inner cylinder containing a thermocouple 33 made of copper-constantan.
Magnesium oxide 35 acting as a heat-resistant material, a heat insulating material and an insulating material is filled in 34, and an air layer 36 as a heat insulating layer is provided outside the inner cylinder 34 to form an outer cylinder 37 also made of stainless steel. The thermocouples 33 are arranged and closed at their tips with a conical temperature sensing part 38 which can be made of a brazing material or other material having a high thermal conductivity, and the coupling part of the thermocouple 33 is placed in the temperature sensing part 38. Is preferably completely embedded.

According to such a temperature sensor 27, its radial heat transfer is caused by the air layer 36 and the magnesium oxide 35.
Further, the heat transfer in the length direction is effectively prevented by the stainless steel inner and outer cylinders 34 and 37 and the magnesium oxide 35, which have lower thermal conductivity than other metals, so that the thermocouple 33 is The temperature of the temperature sensing section 38 can be detected sufficiently accurately based on the thermoelectromotive force generated in the coupling section without being affected by the amount of heat transferred from the.

Then, in order to bring the temperature measured by the temperature sensor 27 closer to the true temperature, the temperature sensor 27 should be placed in the cavity.
Provided that it can be accurately inserted into the vulcanizate in 25, its outer diameter, for example, by a small diameter of about 1-2 mm, of the sensor 27 due to the decrease in the heat capacity of the temperature sensor 27, It is desirable to improve the ability to follow the temperature of the material to be vulcanized and to reduce the amount of heat transferred from the vulcanization mold 3 to the temperature sensor 27. Furthermore, the temperature sensor 27 and the sensor holder as its mounting portion are desirable. 26
It is preferable to cover at least one of the above with a heat insulating layer to prevent radiant heat and the like from being transmitted to them.

In addition, in this device, a tubular heat insulating layer 39 that allows the temperature sensor 27 and the tip of the temperature sensor 27 to enter the cavity 25 is fitted and fixed in each through hole 21 of the lower die portion 3a. 39 effectively prevents heat conduction from the lower mold part 3a to the tip of the temperature sensor. Incidentally, here, the tubular heat insulating layer 39, when inserting the temperature sensor tip portion into the inside and the sensor tip portion into the vulcanizate,
It has a shoulder portion for preventing it from coming out to the recess side of the lower mold portion 3a.

Further, here, in order for the tubular heat insulating layer 39 to sufficiently exert its intended heat insulating action, a = K / cρ (mm ² / min) (2) a: thermal diffusivity K: heat conduction It is preferable that the thermal diffusivity a represented by degree c: specific heat ρ: density is 20 or less.

Further, in the device of this example, as is apparent from FIGS. 3 (b) and 4, the temperature sensor is attached to the lower mold part 3a.
A Teflon plate 40 that allows the penetration of 27 is fixed, and this Teflon plate 40 supports the temperature sensor 27 and guides its forward / backward movement, and further from the vulcanization mold 3 and the heating plates 4 and 6. , Mainly radiant heat temperature sensor 2
Effectively prevent transmission to 7. Here, the Teflon plate 40 is made as thick as possible in order to more fully exert its heat insulating function. In addition, as shown in FIG. When the molds of 3b and 3a are closed, it is preferable to make the height as high as possible as long as it does not interfere with the upper and lower heating plates 6 and 4.

When manufacturing a blow point measurement sample by the above-mentioned apparatus, first, the cavity 25 of the vulcanization mold 3 is filled with the sample rubber and vulcanization is started, and the flow of the rubber is almost stopped. At this stage, the four temperature sensors 27 are moved forward by the action of the air cylinder 30, for example, from the retracted position where the leading edge of the sensor 27 is aligned with the peripheral wall of the recess of the lower mold part 3a.
Insert the 27 horizontally to the required position of the rubber, then measure the temperature of each temperature sensitive part 38 with each temperature sensor 27 over time, and add the temperature of each temperature measurement point from this measurement result and vulcanization time. The degree of sulfur is calculated continuously.

Then, by the continuous vulcanization of the rubber, when the calculated vulcanization degree reaches a predetermined state, the vulcanization is terminated, after the backward movement of the temperature sensor 27 and the opening and closing of the upper and lower mold parts 3b, 3a, etc. Take out the rubber that has become a trapezoidal sample from the cavity and allow it to cool for a certain period of time.

Further, after such cooling of the sample, the foaming state inside the sample is observed in a direction in which the thickness of the sample changes by a nondestructive inspection or by cutting and visually observing it as shown in FIG. Then, the foaming limit position where the vulcanization inside thereof progressed to such an extent that no bubbles remained at all was found, and the vulcanization degree at this position was determined by the final vulcanization at each temperature measurement point as shown in FIG. It is determined from the degree of vulcanization and the degree of vulcanization of each part of the sample estimated from these degrees of vulcanization. So in this example,
As shown in Fig. 6, the final vulcanization degree at each temperature measurement point a, b, c, d is plotted on the graph in relation to the distance (x) from the edge where the sample thickness is thinnest. In addition, by connecting each of these points with a single line, the vulcanization degree of each part in the length direction of the sample is obtained in advance, while the sample thickness at the foaming limit position found by observing the sample is the thinnest. The Plow point is measured by measuring the distance x ₁ from the edge and reading the degree of vulcanization at that distance x ₁ from the vulcanization degree curve of the graph.

In the examples described above, the internal temperature of the rubber during vulcanization was described as being measured by the temperature sensor 27 that is inserted therein afterwards, but the internal temperature was previously embedded in the rubber. It is also possible to measure with a plurality of pairs of thermocouples.In this case, when pre-molding the unvulcanized sample rubber according to the shape and size of the cavity 25, the thermocouples are embedded in a plurality of places inside the rubber. , And the temperature of each part during pressure vulcanization of the rubber was measured with each thermocouple over time, and from these measurement results,
Calculate the degree of vulcanization.

When the rubber is pressure-vulcanized in the cavity whose depth continuously increases from one end to the other as in this embodiment, the temperature measurement region of the rubber during vulcanization is set to As shown in FIG. 7, it is preferable to make a central region of a length l away from each edge of the rubber and at least three times the rubber thickness h ₁ and h ₂ at each edge, and to set the temperature measuring region to With this setting, as is clear from the graph shown in FIG. 7, the temperature measurement can be performed with little or no effect on the amount of heat transferred from the side wall of the vulcanizing mold 3 to the inside of the rubber. As a result, the degree of vulcanization can be measured, and
The vulcanization degree curve in the central area can be very easily and
Since it can be created with sufficient accuracy, the accuracy of blow point measurement can be effectively improved by performing temperature measurement in the central area even when there are few temperature measurement points.

Further, here, the relative relationship between the thicknesses h ₁₀ and h ₂₀ at both ends of the central area and the relationship between the thicknesses h ₁₀ and h ₂₀ and the length 1 of the central area of the sample are described as follows. 1
When the temperature is 70 ℃ -190 ℃, And, and In addition, when the vulcanization temperature is 130 ℃ ~ 150 ℃, And, and It is preferable that

Ie the average thickness of the sample Is smaller than the above-mentioned minimum value, at least a part of the sample, preferably when the vulcanization is finished in a state where the bubbles remain in the position biased to the thickness side, the vulcanization time of the sample If it is too short, the hardness of the surface layer of the sample cannot be increased to 10 parts, which causes the sample to be deformed when the sample is taken out from the vulcanization mold, and the blow point should be measured with sufficient accuracy. There is a problem that can not be performed, on the other hand, when the average thickness is larger than the maximum value described above, the sample volume becomes too large,
There is a problem that the molding man-hours, vulcanization time, measuring man-hours, etc. of the rubber for samples are significantly increased.

Also, the sample gradient Is smaller than each of the above-mentioned minimum values, the difference in the degree of vulcanization at both ends of the length l of the central region of the sample, which is the proper temperature measurement region, becomes too small, so that one vulcanization results in It becomes extremely difficult to generate a region in which the foaming limit position can be determined. On the contrary, when the gradient is made larger than the above-mentioned maximum values, the difference in vulcanization degree in the central region of the length l is Is too large, the measurement error of the probe point due to the determination error of the foaming limit position of the sample becomes significantly large.

Here, suitable values of such average thickness and gradient of the sample will be determined according to the respective vulcanization temperatures. In other words, when the actual material to be vulcanized is, for example, a tire, the vulcanization temperature is generally 12
It is appropriately selected within the range of 0 ° C to 200 ° C, and there will be a suitable average thickness and gradient for each selected temperature.

In addition, in order to observe the internal foaming state of the sample manufactured by the vulcanization mold according to the present invention, in the width direction of the sample, the central portion in the short side direction in this example, that is, the heat from the side wall It is preferable to set the foaming state judgment region in the vicinity of the part where the influence of the vulcanization degree in the width direction is minimal, in terms of the judgment accuracy of the foaming limit position, and on the other hand, for example, 5 to 20 mm width. Placing the temperature sensor 27 or the tip of the thermocouple in the judgment area that can be done makes the insertion mark or the embedding mark confuse with a bubble and causes the judgment of the foaming limit position to be erroneous. It is not preferable. Therefore, it is necessary to dispose the temperature sensor 27 or the tip of the thermocouple at a position that approaches the determination area but does not enter the inside thereof.

By the way, in the case where the temperature sensor 27 or the thermocouple is arranged in this way, when the width B of the sample is smaller than the wall thickness h thereof as shown in FIG. 8 (a),
The vulcanization degree at both end portions in the width direction of the sample is affected by the heat from the side wall of the vulcanization mold 3, and is considerably advanced from that in the foaming state determination region w at the center portion of the sample. As shown in the graph of FIG. 8 (a), the vulcanization degree curve has a very steep rising slope on both sides of the foamed state determination region w, and therefore, for example, a temperature sensor arranged adjacent to the determination region w is used. A considerably large difference occurs between the degree of vulcanization calculated from the side temperature result of the temperature detector 27 (point f) and the degree of vulcanization in the judgment region w. Therefore, if the vulcanization degree calculated from the side temperature result is the vulcanization degree of the determination region w, the accuracy of the probe point measurement will be significantly reduced.

Therefore, here, the position adjacent to the determination area w (point f)
The deviation between the degree of vulcanization calculated from the side temperature result in Fig. 8 and the degree of vulcanization in the judgment area w is not so large as in the case of the vulcanization degree curve shown in the graph in Fig. 8 (b). Determine the sample width B within, in other words B ≧ 4h
It is preferable that

The present invention has been described above with respect to the case where the cavity depth of the vulcanizing mold is linearly increased from one end to the other end, but in the present invention, the depth of the cavity 25 is changed from one end to the other end. It is also possible to gradually increase in a curvilinear manner toward, and to increase the depth stepwise from one end to the other end, in other words, the vulcanized sample in the cavity 25 It is also possible to change the cavity depth so as to form a step shape as shown in FIGS. 9 (a) and 9 (b).

Here, the probe point can be measured in the same manner as in the above-mentioned example for the sample whose thickness changes in a curve, and in the following manner for the sample having the step-like shape.

First, as shown in Fig. 10, the vulcanization degree at the central position of each step at the end of vulcanization, i, ii, ii, and ii, was determined, and then the state of foam generation in each step of the sample was indirectly determined. Alternatively, by directly observing, a step in which vulcanization is progressing to the extent that no bubbles remain is found, and the vulcanization degree at the central position of the step, in the figure, is the blow point.

(Comparative Example) Below, the blow point measurement using the mold and method according to the present invention and the blow point measurement according to the conventional technique are compared in terms of dimensions, effects and the like.

In this table, focusing attention on Examples 1 to 3 and Comparative Example 9, in Examples 1 to 3, the required amount of rubber and the number of measurement steps were remarkably reduced, and the blow point measurement accuracy was significantly improved. In addition, Examples 4 and 5 and Comparative Example 1
Focusing on 0, it can be seen that the measurement man-hours and accuracy are dramatically improved.

Further, here, as shown in Comparative Examples 1 to 8, the average thickness of the samples And slope It is clear that the blow point cannot be measured with sufficient accuracy when is outside the appropriate range.

(Effect) Therefore, according to the vulcanization mold of the present invention, by manufacturing a sample in the cavity whose depth increases continuously or stepwise from one end to the other end, The vulcanization degree will change continuously or stepwise in the direction in which the thickness changes, and it is possible to form both a portion where bubbles remain and a portion where bubbles do not remain in one sample, Judgment of the foaming limit position becomes extremely easy,
The work man-hours for measuring the blow point and the amount of rubber used will be significantly reduced.

Further, according to the method of the present invention, it becomes possible to measure the blow point extremely accurately and promptly in relation to the vulcanization mold.

[Brief description of drawings]

1 is a partial cross-sectional side view illustrating a sample manufacturing apparatus, FIG. 2 is a plan view showing a lower mold part and an upper mold part of a vulcanization mold, and FIG. 3 is a long side direction and a short side of the vulcanization mold. FIG. 4 is a partial sectional plan view showing the relationship between the lower end portion of the vulcanizing mold and the sensor unit, FIG. 5 is an enlarged sectional view illustrating the tip of the temperature sensor, and FIG. The figure which shows the measuring point of the blow point, the figure 7 which shows the proper temperature measurement territory of the sample, the figure 8 which shows the relationship between sample width and thickness, Figure 9 shows the sample shape of other example FIG. 10 is a perspective view, FIG. 10 is a view showing a temperature measurement region of a blow point for the sample shown in FIG. 9, and FIGS. 11 and 12 are views showing conventional blow point measurement procedures. 3 ... Vulcanizing mold, 3a ... Lower mold part 3b ... Upper mold part, 16 ... Sensor unit 19 ... Dimple, 20 ... Projection 25 ... Cavity, 27 ... Temperature sensor

Claims (3)

[Claims] 1. A vulcanization mold comprising an upper mold part and a lower mold part, wherein the depth of the cavity formed by closing the upper and lower mold parts is continuous or stepwise from one end to the other. Vulcanization mold for sample for blow point measurement, which is increased in quantity. 2. A step of pressurizing and vulcanizing rubber for a sample in a cavity whose depth increases continuously from one end to the other end, or an internal temperature of the rubber during vulcanization. The process of measuring the vulcanization degree at each location based on the measurement results over time, and the vulcanization is completed when the calculated vulcanization degree reaches a predetermined state. The process of taking out the rubber from the cavity and the internal foaming state of the sample were observed in the direction in which the thickness changed, and the vulcanization inside the sample proceeded to such an extent that no bubbles remained inside. The blow-point measuring method is a combination of a vulcanization degree of a part to be measured and a step of obtaining from the vulcanization degree of each temperature measurement point or the vulcanization degree of each part of the sample estimated from the vulcanization degree of each temperature measurement point. 3. A rubber for a sample is pressure-vulcanized in a cavity whose depth continuously increases from one end to the other, and the temperature measurement region of the rubber during vulcanization is set to the depth of the cavity. From the respective edges of the rubber in the direction
A method according to claim 2, which is a central area separated by at least three times the rubber thickness at each edge thereof.