JPH08216164A - Cleaning of vulcanizing mold - Google Patents

Abstract

PURPOSE: To advantageously realize uniform ashing within a short treatment time at a low cost by holding the pressure of a reaction gas to a low pressure within a predetermined range during a period when plasma distribution is uniform and reducing the same to a lower pressure as compared with the low pressure within the predetermined range in the vicinity of a point of time when a non-uniform region is generated. CONSTITUTION: When an elastomer residue formed on the surface of a mold is removed by ashing, a central electrode 4 is allowed to protrude into a treatment tank 1 and an annular vulcanizing mold 15 is positioned around the electrode 4 as other electrode so as to be spaced apart from the electrode 4 by a predetermined distance and power is applied across both electrodes 4, 15 to generate plasma by discharge. The pressure of the reaction gas from a reaction gas supply pipe 9 is held to a low pressure within a predetermined range from the start of discharge during a period when the plasma distribution between both electrodes 4, 15 is uniform in such a state that the inflow and outflow amts. of the reaction gas are well-balanced and, in the vicinity of a point of time when a non-uniform region is generated, the pressure of the reaction gas is reduced to lower pressure as compared with the low pressure within the predetermined range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding surface of a mold repeatedly used for vulcanization molding of rubber products such as rubber tires and anti-vibration rubber and other plastic products as elastomers, and a mating surface in the case of a split mold. Regarding the cleaning method of the vulcanizing mold for advantageously removing the elastomer residue that is inevitably formed on the surface including the surface and the recesses and holes, in particular, the effective utilization of plasma enables uniform and highly efficient cleaning in a shorter time, In addition, the present invention relates to a method for cleaning a vulcanization mold that enables low-cost cleaning by using a smaller amount of electric power and mainly applying a cheaper reaction gas.

[0002]

2. Description of the Related Art JP-A-6-2858 already filed by the present applicant.
As described in detail in Japanese Patent Publication No. 68, elastomer products, particularly rubber tire products (hereinafter simply referred to as tires), anti-vibration rubber products, and the like satisfy the required performance, and therefore natural rubber, synthetic rubber or blended rubbers thereof are cross-linked. In addition to blending sulfur as a component and carbon black as a reinforcing material, it is necessary to blend a vulcanization accelerator and various chemicals for maintaining various durability.

When the unvulcanized rubber composition thus prepared is vulcanized and molded, a chemical reaction such as a crosslinking reaction generally occurs at a high temperature close to 200 ° C., so that the rubber composition has fluidity. Not only does it increase, but it also partially gasifies, and as a result, not only the molding surface of the vulcanizing mold, but also the extremely narrow gaps in the mating surface of the mold and holes such as so-called vent holes for venting the rubber composition and its chemical composition. It is unavoidable that the reaction product adheres strongly as a residue, although it is a small amount, each time it is vulcanized and molded. By repeating this vulcanization molding a number of times, the residue is deposited in a thickness that cannot be overlooked. This applies not only to the rubber composition but also to other elastomers in the same manner and in different sizes.

The thick vulcanization residue firmly adhered and deposited on the vulcanization mold not only impairs the appearance of the tire, but also adversely affects the excellent quality maintenance of the entire tire. Therefore, it is necessary to clean the vulcanization mold that has been vulcanized and molded a predetermined number of times as if it was a new product.As this work method, a shot blast cleaning method in which granules such as plastic beads and glass beads are sprayed with high pressure gas, Alternatively, a liquid cleaning method of immersing in a solution of acid, alkali, amine or the like has predominantly been used. Since the various disadvantages of these cleaning methods are remarkably improved, the applicant of the present invention has described the above-mentioned JP-A-6- 285868
The method for cleaning a vulcanization mold by plasma described in Japanese Patent Publication has been proposed, and a remarkably excellent result has been obtained.

[0005]

However, upon examining this result, it was found that there is room for further improvement in the following points. That is, the first point is that the plasma region is excessively large with respect to the clean surface of the vulcanization mold, and as a result, a large amount of electric power and an excessive amount of reaction gas are required, resulting in high processing cost.

The second point is that, on the mold forming surface of the vulcanizing mold that needs to be cleaned, apart from special tire types, generally, the large grooves and fine grooves that are indispensable for sufficiently exhibiting the required characteristics of the tire are required. A large number of ribs and protrusions such as sipes (strips) for forming grooves and slits on the tread portion are provided, and the plasma is blocked by these protrusions and vulcanized over the entire area of the clean surface. This is because the uniform ashing (ashing) of the residue is impaired and tends to occur.

The third point is that a lot of processing time is required in connection with the second point, so that the cleaning efficiency is lowered, and the fourth point is that the surface not to be cleaned is exposed to plasma. , Is to cause deterioration and damage to this surface portion.

Therefore, an object of the present invention is to improve the above-mentioned disadvantages, and to realize uniform ashing at a low cost and in a short processing time without restricting the mold forming surface of the vulcanizing mold. It is to provide a method of cleaning a vulcanization mold that can be performed.

[0009]

In order to achieve the above object, a method for cleaning a vulcanizing mold according to the first aspect of the present invention is to apply a plasma generated in a dilute reaction gas in a vacuum processing tank to a vulcanizing mold. Then, in order to ash and remove the elastomer residue formed on the mold surface by the repeated vulcanization molding of the elastomer, one electrode is projected into the treatment tank, and the annular vulcanization mold is surrounded around the projected electrode. The electrode is positioned at a predetermined distance from the former electrode, and electric power is applied to both electrodes to generate plasma due to discharge between both electrodes, and discharge is started under the balance of the inflow amount and outflow amount of the reaction gas. The reaction gas pressure is maintained at a low pressure within a predetermined range until the plasma distribution between the two electrodes is uniform, and the reaction gas pressure is set to the predetermined range at a time point near the time when the plasma distribution has a non-uniform region. Inside Wherein the depressurizing than than the pressure in the low pressure.

In carrying out one of the present inventions, the reaction gas pressure is 1.3 to 10.0 while the plasma distribution is uniform.
Within the range of Torr, the reaction gas pressure is set at 0.1 to around the time including the nonuniform region in the plasma distribution.
When the pressure is reduced within the range of less than 1.3 Torr, the reaction gas pressure is reduced within the range of 0.1 to less than 1.3 Torr, the discharge power output is also reduced, and the reaction gas pressure is reduced to 0.1. When the pressure is reduced within the range of less than 1.3 Torr, the amount of the reaction gas flowing into the processing tank is also reduced, and the reaction gas is at least one of oxygen gas and halide gas. Is desirable.

In the method for cleaning a vulcanizing mold according to the second aspect of the present invention, the plasma generated in the dilute reaction gas in the vacuum treatment tank is caused to act on the vulcanizing mold, and the mold surface is subjected to repeated vulcanization molding of the elastomer. When ashing and removing the elastomer residue formed on the one electrode, one electrode is projected into the processing tank, and the annular vulcanizing mold is used as the other electrode around the protruding electrode and is located at a predetermined distance from the former electrode. Then, electric power is applied to both electrodes to generate plasma due to discharge between the electrodes, and the reaction gas components consist of oxygen gas and halide gas, and the reaction gas flows under the balance of the inflow amount and the outflow amount of the reaction gas. It is characterized in that the pressure is maintained at a low pressure within a predetermined range.

In carrying out the second aspect of the present invention, the reaction gas pressure is in the range of 1.3 to 10.0 Torr, and the time point in the vicinity thereof, including the case where a non-uniform region occurs in the plasma distribution between the two electrodes, Then, the amount of the halide gas occupied in the reaction gas is reduced, and the reaction gas is only oxygen gas from the start of discharge between both electrodes until 10 to 30 minutes have passed, and thereafter, the halide gas is added to the oxygen gas. It is desirable to use the added mixed reaction gas.

Further, in carrying out the first and second aspects of the present invention, the halide gas is carbon tetrafluoride (CF ₄ ) gas, and the plasma distribution state between both electrodes and the normal discharge region between both electrodes are provided. The abnormal discharge phenomenon in the remaining area except for is monitored by the monitoring means, and the monitoring result is fed back to at least one control system of the reaction gas pressure, the reaction gas inflow amount, the discharge power and the mold temperature, It is desirable to be able to control at least one of the control systems based on the feedback.

[0014]

Operation: One electrode is projected into the processing tank, and an annular vulcanizing die is positioned around this electrode as the other electrode at a predetermined distance from the former electrode, so that cleaning is required first. It is only necessary to generate the plasma in the area between the surface of the metal mold and the electrode surface, and as a result, the plasma area can be optimized to the minimum required, and therefore, the extra power and the extra reaction gas consumption are required. And the processing cost can be reduced.

Next, the optimization of the plasma region has the advantages that the processing time can be shortened at a low cost, and that a defect that deteriorates the surface not to be cleaned can be avoided. Also, the optimized plasma region for the tire tread surface having a fairly complex and diverse morphology provides uniform ashing.

From the beginning of the cleaning process to the end of the process,
The plasma density distribution between both electrodes (hereinafter abbreviated as plasma distribution) cannot always be said to be uniform. This state is shown, for example, in a plan view of both electrodes 4 and 15 schematically illustrated in FIG.
The plasma area with a lower density or the non-plasma area, that is, the non-discharge area (both white areas) is in the middle of processing, compared to the plasma area (hatched area) that has a suitable density on a part of the inner peripheral surface of the It is easy to occur in. In addition to the example shown in FIG. 5, a low-density plasma region or non-plasma region is often formed in the vertical direction between both electrodes.

If the ashing process is continued under the above-mentioned non-uniform plasma distribution, in addition to problems such as a decrease in process efficiency and a process failure, a spark is generated between the two electrodes to cause the vulcanization mold and the center electrode to move. There is a disadvantage of being damaged.

Then, when the cause of the non-uniform plasma distribution was sought, (1) the radial distance between the central electrode and the vulcanization mold was not constant or uniform when viewed around the circumference, and Since the inner shape of the vulcanization mold is curved in a direction orthogonal to (vertical direction), there is a difference in the distance between the center electrode and the vulcanization mold in the vertical direction. In the case of, the degree of temperature rise of the vulcanization mold due to discharge differs for each segment, and the temperature distribution is not uniform. (3) Negative ions in plasma, such as F ⁻ , O ⁻
Remain locally, (4) the central electrode is charged, or the elastomer residue on the inner surface of the vulcanization mold (this is an insulator)
Have found that there is a charge. The present invention will be described below in its first and second parts.

1. Regarding the first aspect of the present invention; Therefore, the reaction gas pressure is set to a low pressure in the vicinity of the time when the plasma distribution has an inhomogeneous region, including the time when the plasma distribution between the electrodes is uniform. By reducing the pressure to a lower pressure than the reaction gas pressure, the degree of vacuum can be further increased and the mean free path of the electrons can be further extended. As a result, the electrons can be more easily diffused. This means that the causes of (1) to (4) above are removed or the action of the causes is weakened, and as a result, uniform plasma distribution can be realized.

By setting the reaction gas pressure during the uniform plasma distribution from the beginning of cleaning to within the range of 1.3 to 10.0 Torr, a large amount of power can be supplied, thereby obtaining a uniform plasma distribution. It contributes to the realization of highly efficient ashing, and the reaction gas pressure is 0.1 to 1.
By reducing the pressure within the range of less than 3 Torr, it is possible to further enhance the effect for preventing the non-uniformity of the plasma distribution.

When the pressure of the above-mentioned reaction gas is reduced, the discharge power of the discharge is also lowered to avoid the murmur of the abnormal discharge, and if the power drop causes the generation of nonuniform plasma. The reaction gas pressure may be further reduced within the above range. By repeating this, it is possible to prevent abnormal discharge and non-uniform plasma, respectively.

Further, when the reaction gas pressure is reduced, it is advantageous in terms of cost to reduce the inflow amount of the reaction gas at the same time, which is useful for reducing the load on the vacuum pump, and a stable reaction gas pressure can be obtained. Contribute to that. Further, the reaction gas is at least one of oxygen gas (O ₂ ) and halide gas (particularly CF ₄ gas), that is, O ₂ gas or C.
F ₄ gas or (O ₂ + CF ₄ ) gas is useful for achieving effective and proper cleaning.

As the halide gas, any gas containing F (fluorine), Cl (chlorine), Br (bromine), I (iodine), etc. can be used. Further, since it only needs to be supplied as a gas to the vacuum processing tank, it does not necessarily have to be a gas in a standard state (25 ° C., 1 atm), and may be in a liquid state, for example. In particular, chlorofluorocarbon, NF ₃ , and SF ₆ are preferably used, and CF ₄ is particularly effective.

2. Regarding the second aspect of the present invention; the reaction gas components are composed of oxygen gas and halide gas, and the reaction gas pressure is maintained at a low pressure within a predetermined range, so that the partial pressures of the respective gases are adjusted as needed. Therefore, it is possible to eliminate the causes (1) to (4) described above, or to alleviate the action based on these causes, and it is also possible to perform uniform cleaning from the start to the end of the cleaning process. Plasma processing becomes possible.

This is because the oxygen gas and the halide gas are apt to become negative ions in the plasma, and in particular, the ions of the latter gas have a long staying life in the plasma, and thus locally form a state like an electron cloud. The part to be exposed is formed for a long time, and this part acts to interrupt the discharge between both electrodes, resulting in the formation of a non-uniform region in the plasma distribution. By holding it, it is possible to suppress the amount of generation of these negative ions and alleviate the discharge interruption effect,
This is because uniform plasma processing becomes possible.

The reaction gas pressure is 1.3 to 10.0 Torr.
Within the range, it contributes to further enhancing the above effect. Also, by reducing the amount of halide gas occupying in the vicinity of the time, including when a non-uniform region occurs in the plasma distribution between both electrodes, the non-uniform region is eliminated and the plasma distribution becomes uniform. It also has the advantage of reducing the amount of expensive gas used.

From the start of discharge to the lapse of 10 to 30 minutes, only O ₂ gas is used, and thereafter, a mixed gas in which a halide gas, preferably CF ₄ gas is added to O ₂ gas is used. After 30 minutes, the vulcanization mold shows a high temperature, which means an efficient ashing reaction occurs.
This means that _four gases are added, which enables highly efficient cleaning, while also suppressing the amount of expensive CF ₄ gas used, leading to cost reduction. The substances compatible with the halide gas are as described above.

Through the first and second aspects of the present invention, the plasma distribution state and the abnormal discharge phenomenon are monitored by the monitoring means, and the monitoring results are the reaction gas pressure, the reaction gas inflow amount,
Feeding back control to at least one of the control systems for controlling the discharge power and the temperature of the vulcanization mold contributes to realizing the above-mentioned various effects advantageously and accurately.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The first and second embodiments of the present invention will be described in detail below with reference to FIG. FIG. 1 is an explanatory diagram showing a cross section of a main part of a side surface of a vacuum processing tank 1 used for cleaning a vulcanizing mold together with a simplified cross section of a vulcanizing mold.

In FIG. 1, a vacuum processing tank 1 is a container upper part 2 which is vertically separable and sealable at a lower position.
-1 and a container lower part 2-2, and a suction part 3 that is connected to a vacuum pump (not shown) in the container lower part 2-2.
It is equipped with. Prior to starting the cleaning work of the vulcanization mold, the vacuum pump is operated to adjust the air pressure inside the container 2 to a so-called medium vacuum to high vacuum of, for example, 10 ^-1 to 10 ^-5 Torr. In the vacuum processing tank 1 of the illustrated example, the container lower part 2-2 side is fixed to the floor surface Fs or the like by a plurality of columns 2-2a (only one is shown in the figure), and the container upper part 2-1 side is fixed. The container lower part 2-2 is detachably provided upward.

As shown in FIG. 1, the electrode 4 on one side is arranged so as to project from the upper side into the container 2 in a suspended state. This arrangement position may be movable in the vertical direction in the figure or may be fixed to the container upper part 2-1. The electrode 4 in the illustrated example has a cylindrical outer periphery, and is of a type in which the middle of the cylinder is electrically and mechanically joined by a conductor plate (disc) 4a. It is not necessary to limit the outer shape of the electrode 4 of this kind to a cylinder. For example, it is possible to form a polygon of pentagon or more, and in order to improve the discharge efficiency, a large number of fins are arranged side by side along the outer circumference of the electrode. They can be arranged or arranged vertically.

Further, the electrode 4 can be constructed so that its diameter can be expanded and contracted freely. In this case, the radial (horizontal) distance between the inside of the vulcanization mold 15 and the outside of the electrode 4 described later is reduced. It is adjustable and has the advantage of being useful for selecting the optimum distance and applying various vulcanization dies with greatly different inner diameters.

The electrode 4 is electrically and mechanically joined to the conductor cooling bath 5 through the conductor plate 4a, and the cooling bath 5 is electrically and mechanically connected to the slightly large diameter transmission pipe 6 (for example, a copper pipe). To join. Of course, the conductor plate 4a and the cooling tank 5 are mutually sealed to prevent the cooling medium from flowing out. The power transmission pipe 6 is arranged in the center of the container 2 and is fixed by insulation above the container upper portion 2-1. In this example, the container 2 was on the ground side.

Inside the power transmission pipe 6, a cooling medium having a smaller diameter is supplied to the cooling tank 5 by supplying a cooling medium such as a liquid for cooling the electrode 4 (for example, cooling water of about 20 ° C. or similar cooling oil) or gas to the cooling tank 5. The pipe 7 is accommodated. The pipe 7 opens into the cooling tank 5 to release the cooling medium, and the released cooling medium plays its role, and then passes between the power transmission pipe 6 and the cooling pipe 7 and moves upward in the drawing. And then discharged. The internal pressure between the power transmission pipe 6 and the cooling pipe 7 is kept substantially equal to the atmospheric pressure.

In this way, the electrode 4 is fixedly supported on the container 2 as a central electrode at the central position of the vertical axis, and electric power is supplied to the electrode 4 through the cooling tank 5 and the power transmission pipe 6, and at the same time, the electrode 4 is operated. The overheating of the electrode 4 is suppressed and the electrode 4 is maintained at an appropriate temperature. Although not shown in the figure, the power supply power source transmits high-frequency power called radio waves having a frequency of 13.56 MHz in this example. In another example, it may be a DC power supply or a microwave power supply.

A vertically long insulator, for example, a ceramic insulator 8 such as alumina is fixed to the upper portion of the cooling tank 5 at its lower portion. The insulator 8 has a hollow portion, and this hollow portion has a space for accommodating the power transmission pipe 6 and the reaction gas supply pipe 9. Further, the upper portion of the insulator 8 and the flange portion of the cylinder 10 extending vertically upward like the insulator 8 are joined together in a sealed state. Of course, the inside of the cylinder 10 has a sufficient space for accommodating both pipes 6 and 9. The space of the insulator 8 connected to this space is opened to the atmosphere, and therefore the cooling tank 5 and the insulator 8 are coupled to each other in a sufficiently sealed state.
The cylinder 10 is fixed to the upper part 2-1 of the container or is movably attached.

The reaction gas extends laterally in the insulator 8 at the lower end of the supply pipe 9 in a completely sealed state, and then passes through a connecting pipe 9-1 extending downward inside the electrode 4 to the pipe 9-. An annular pipe 9 connected to the lower end of 1
-2, and is supplied into the processing tank 1 from a large number of discharge ports (not shown) formed in the pipe 9-2 at substantially equal intervals. At this time, the flow of the reaction gas is blocked by the plate 4a of the electrode 4 and once goes upward, and then the container 2 is filled.

An annular vulcanizing mold 15 is positioned around the central electrode 4. Although the vulcanization mold 15 is shown as one body,
In this example, a large number, for example, 3 to 20, of the so-called split mold, which divides the outer peripheral side, are formed on the upper surface of the supporting and transporting platen 16 which is also made of metal, for example, steel and which also serves as an electric conductor during actual use. The figure shows a temporary assembly in the same state as.

An aluminum alloy is generally applied to the tread portion of the tire where treads and various grooves and slits are formed. When actually used, this alloy portion is attached to a steel holding member to form the above-mentioned segment. In the present invention, both the case of only the alloy portion and the case of the segment are referred to as a vulcanization mold.

When the vulcanization mold 15 is a split mold, a pair of side molds are combined above and below the segment mold shown in the figure to form a mold body. This mold body can be used as a vulcanizing mold 15 for plasma cleaning, and the present invention can be applied to a so-called split mold having a divided surface on the circumference.

Although not shown in the drawings, the surface plate 16 is a mechanism for setting a group of segments or a set of these molds at a predetermined position when temporarily assembling a large number of segments or when placing a split mold body or a split mold. Further, the surface plate 16 is provided with a mechanism for centering the vulcanizing mold 15 as an assembly or the vulcanizing mold 15 as these molds with respect to the central electrode 4. The latter mechanism is centeringly engaged with a centering device provided on a wheel conveyor 17 supporting the vulcanizing mold 15 and the surface plate 16.

The vulcanization mold 15 is introduced into the processing tank 1 with the upper part 2-1 of the container and the central electrode 4 being moved upward.
The vulcanization mold 15 temporarily assembled or set aside on the surface plate 16 outside the processing tank 1 is conveyed together with the surface plate 16 to the position shown on another similar wheel conveyor (not shown), and at the same time, centering is performed. . The centering accuracy, which is the amount of misalignment, is preferably 3 cm or less, and more preferably 5 mm or less.

After the platen 16 is conveyed to a predetermined position, the platen 16 is temporarily fixed by a fixing means (not shown) provided on the wheel conveyor 17. After fixing, the electrical contact 18 provided on the upper end of the rod 19 connected to the elevating means 20 is raised to make contact with the surface plate 16. The electrical contact 18 is connected to the ground side of the power supply for power supply via the rod 19. That is, in this example, the vulcanization mold 15 is on the ground side, but in another example, it can be on the voltage application side.

Thereafter, the container upper part 2-1 and the central electrode 4 are lowered to be brought into contact with and engage with the container lower part 2-2.
2-2 is fixed in a hermetically sealed state, and then a vacuum pump (not shown) is operated to bring the inside of the container 2 into the predetermined medium to high vacuum state described above through the suction section 3. Then, the reaction gas is caused to flow in from the discharge port of the annular pipe 9-2. In addition, in order to smooth the balance between the air discharge and the inflow and outflow of the reaction gas, it is preferable that the surface plate 16 corresponding to the position of the suction port of the suction unit 3.
Provide a plurality of through holes at the positions. The reaction gas pressure measurement position may be any position except the suction port of the suction unit 3 and its vicinity.

Although not shown in the drawing, this apparatus is provided with means for monitoring the plasma distribution state and abnormal discharge phenomenon, and the plasma emission spectrum as the monitoring target,
Electron temperature and electron density (probe measurement), vulcanization mold temperature (thermocouple, infrared thermometer), etc. In addition, a window that allows visual observation and video camera shooting is provided in the container 2 for external observation and image analysis. It is possible. Based on the monitoring results of these monitoring, the control of the reaction gas pressure, the reaction gas inflow amount, the discharge power and the vulcanization mold temperature is properly performed.

[Embodiment 1] According to FIG. 1, the electrode 4 has a cylindrical shape, and its dimensional specifications include an outer diameter of 480 mm and a height of 22.
It is 0 mm. The vulcanization mold 15 has eight segments and a maximum inner diameter of 550 mm. The reaction gas is O ₂ gas and C
A mixed gas of F ₄ gas was used, and the ratio of the inflow amounts of these gases was set to O ₂ : CF ₄ = 2: 1. In detail, O ₂ is 500S
CCM and CF ₄ are 250 SCCM.

The relationship between the elapsed time during the discharge time of about 150 minutes and the reaction gas pressure (Torr) and the supplied power (KW) is shown as a diagram in which the former is a series of triangle marks and the latter is a series of circle marks. Collectively shown in FIG.

In FIG. 2, since the plasma distribution is uniform from the start of discharge to the time point indicated by symbol A (after a lapse of about 50 minutes), the reaction gas pressure is maintained at 1.5 Torr, and at the time point A, the plasma distribution around the circumference is maintained. At that time, the reaction gas pressure was gradually reduced, and at point B, it was confirmed that this tendency had completely disappeared and a uniform distribution was obtained, and the depressurization operation was stopped. After that, a similar tendency was observed again at time C (about 100 minutes after the start of discharge), so the depressurization operation was performed until time D when the plasma distribution became completely uniform, and after time D, the pressure became almost uniform until the treatment was completed. Held The inflow amount of the reaction gas after the time point D was set to about 60% of the initial amount.

The electric power initially held 6 kW,
If the high-voltage state is continued under the reduced pressure of the reaction gas, there is a gratification that abnormal discharge (coupling) occurs between the ground side and the voltage-applying side of the vulcanization mold 15 except for the inner side surface thereof. The supply power was decreased at the time point X near the time point C of the reaction gas. By the above operation, the elastomer residue of the vulcanization mold 15 is uniformly and sufficiently ashed over the entire surface under normal discharge and uniform plasma distribution, and the mold is as good as new without any other adverse effect. I was able to get an inner skin.

[Embodiment 2] Referring to FIG.
Vulcanization mold 1 having the same electrode 4 and 8 segments
5, and the reaction gas is O₂Gas and CF_FourApply gas
Was. Keep the reaction gas pressure at 1.5 Torr from beginning to end
25 minutes have passed since the start (code G₁ Reaction gas up to
O₂Apply gas only, G₁ CF from the moment_FourAdd gas
And made into mixed gas. About 5 minutes after the start of addition
End time G₂Ratio of gas inflow at ₂: CF_FourIs 2: 1
And This operation state is shown as a diagram in FIG. Right vertical axis
Represents the ratio of the inflow amount of the reaction gas.

This is because the ashing reaction does not proceed so much until the temperature of the vulcanization mold 15 reaches a sufficiently high temperature, so that the application of expensive CF ₄ gas is avoided until the temperature reaches a predetermined temperature from the start of discharge. Therefore, the processing cost can be reduced. With the same intention, as shown in FIG. 3, the electric power was set to 4 KW at the start of discharge, increased to 8 KW until the time point Y when about 10 minutes had elapsed, and kept at this value until the end of the treatment. As a result, the same ashing effect as in Example 1 could be obtained.

[Embodiment 3] Referring to FIG.
Vulcanization mold 1 having the same electrode 4 and 8 segments
5, the reaction gas was O ₂ gas and CF from the beginning of discharge.
A mixed gas with ₄ gases was applied, and the pressure as a reaction gas was kept at 1.5 Torr from beginning to end. The operation state is shown in FIG. 4 as in FIG.

As shown in FIG. 4, at the time point H ₁ (after about 25 minutes), there was a sign that a non-uniform region was generated in the plasma distribution. Therefore, the reaction gas was changed from the time point H _{1 to the} time point H _2. The flow rate of CF ₄ gas was reduced while the pressure was kept at 1.5 Torr. As a result, the generation of the non-uniform plasma region was prevented, the amount of expensive CF ₄ gas used could be reduced, and the same ashing effect as in Example 1 could be obtained.

Comparisons were made to evaluate the effects of Examples 1 to 3.
As an example, the same eight segment segments as those in each embodiment are provided between the two conventional electrodes.
The vulcanization mold of the component is positioned, and the reaction gas is generated with the power of 6KW.
Is O ₂Gas and CF_FourMixed gas with gas (ratio of inflow
O₂: CF_Four2: 1) and the reaction gas pressure is 1.
The plasma treatment was performed while holding at 5 Torr. Evaluation item
Is the temperature immediately after processing each segment of the vulcanization mold,
This was based on the visual judgment of the clean state. Example 1
The degree of contamination of the vulcanization mold (residual thickness) is
Most noticeable, and Examples 2 and 3 had relatively lighter stains.
It was in a state. The results of temperature measurement are shown in Table 1. Table 1 Smell
Segment No. Are sequentially attached clockwise. Value is N
o. It is better to be uniform between 1 and 8.

[0055]

[Table 1]

From Table 1, Examples 1 to 3 show that there is little temperature variation between the segments and uniform cleaning can be achieved, whereas in Comparative Example, the ratio of the maximum temperature to the minimum temperature is 2 It is more than double that, which means that a non-uniform region appears in the plasma distribution. When the vulcanizing mold was taken out and observed after the plasma treatment was completed, in each of the examples, uniform and sufficient residue cleaning was achieved over the entire inner surface of the mold. 5 and 6 were not cleaned sufficiently. Further, no damage was found in the vulcanization mold in each of the examples, whereas in the comparative example, the high temperature segment No. There was a damaged part that could not be overlooked in 1.

[0057]

According to the present invention, the elastomer residue formed on the surface of the mold by the repeated vulcanization molding of the elastomer is not accompanied by a disadvantage such as damage to the vulcanization mold and the vulcanization mold. Without any restrictions on the mold forming surface of
It is possible to provide a method of cleaning a vulcanizing mold that can be uniformly and advantageously ashed at a low cost with a short processing time.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a side surface of a vacuum processing tank according to an embodiment used in a cleaning method according to the present invention.

FIG. 2 is a diagram showing the relationship between discharge time and electric power and reaction gas pressure according to an embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a discharge time and an electric power and a reaction gas inflow ratio according to an embodiment of the present invention.

FIG. 4 is a diagram showing the relationship between the discharge time and power and reaction gas inflow ratio of another embodiment according to the present invention.

FIG. 5 is an explanatory diagram of plasma distribution.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum processing tank 2 Container 2-1 Container upper part 2-2 Container lower part 3 Suction part 4 Electrode 4a Conductor plate 5 Cooling tank 6 Power transmission pipe 7 Refrigerant sending pipe 8 Insulator 9 Reactive gas supply pipe 9-1 Connection pipe 9- 2 circular pipe 10 cylinder 15 vulcanization mold 16 supporting and transporting surface plate 17 wheel conveyor 18 electrical contact point 19 rod 20 lifting means

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location B29K 105: 24 (72) Inventor Koji Hirose 1-4445 Ogawamachi, Kodaira-shi, Tokyo Garden Heights Kodaira 1- 612

Claims (11)

[Claims] 1. When removing plasma by causing plasma generated in a dilute reaction gas in a vacuum treatment tank to act on a vulcanizing mold to ash and remove elastomer residue formed on the mold surface by repeated vulcanization molding of elastomer , One electrode is projected into the treatment tank, and the annular vulcanizing die is positioned around the projected electrode as the other electrode at a predetermined distance from the former electrode, and electric power is applied to both electrodes to apply both electrodes. Plasma is generated by the discharge in the meantime, and under the balance of the inflow and outflow of the reaction gas, the reaction gas pressure is kept at a low pressure within a predetermined range from the start of the discharge until the plasma distribution between both electrodes is uniform. The method for cleaning a vulcanization mold is characterized in that the pressure of the reaction gas is reduced to a lower pressure than the low pressure within the above-mentioned predetermined range at a time point in the vicinity of the time when the plasma distribution has a non-uniform region. 2. The reaction gas pressure while the plasma distribution is uniform is within the range of 1.3 to 10.0 Torr, and the reaction gas pressure is 0 at a time point near the time when the nonuniform region is generated in the plasma distribution. The cleaning method according to claim 1, wherein the pressure is reduced within a range of 0.1 to less than 1.3 Torr. 3. The reaction gas pressure is 0.1 to 1.3 Torr.
The cleaning method according to claim 2, wherein when the pressure is reduced within the range of less than, the output of the discharge power is also reduced. 4. The reaction gas pressure is 0.1 to 1.3 Torr.
The cleaning method according to claim 2 or 3, wherein when the pressure is reduced within the range of less than, the amount of reaction gas flowing into the processing tank is also reduced. 5. The reaction gas is at least one of oxygen gas and halide gas.
The cleaning method described in any one of 1. 6. When removing plasma by causing plasma generated in a dilute reaction gas in a vacuum treatment tank to act on a vulcanization mold and ashing the elastomer residue formed on the mold surface by repeated vulcanization molding of the elastomer. , One electrode is projected into the treatment tank, and the annular vulcanizing die is positioned around the projected electrode as the other electrode at a predetermined distance from the former electrode, and electric power is applied to both electrodes to apply both electrodes. Plasma is generated by electric discharge in the meantime, the reaction gas component consists of oxygen gas and halide gas, and the reaction gas pressure is maintained at a low pressure within a predetermined range under the balance of the reaction gas inflow amount and outflow amount. Cleaning method for vulcanizing mold. 7. The reaction gas pressure is 1.3 to 10.0 Tor.
The cleaning method according to claim 6, which is within the range of r. 8. The cleaning method according to claim 6, wherein the amount of the halogenide gas in the reaction gas is reduced at a time point near the nonuniform region in the plasma distribution between the electrodes, including the time when the nonuniform region occurs. 9. The reaction gas for 10 to 30 minutes after the start of discharge between both electrodes is only oxygen gas, and thereafter is a mixed reaction gas obtained by adding a halide gas to oxygen gas. The cleaning method described in. 10. The halide gas is carbon tetrafluoride (C
The cleaning method according to claim 5 or any one of claims 6 to 9, which is F ₄ ) gas. 11. The plasma distribution state between both electrodes and the abnormal discharge phenomenon in the remaining region excluding the normal discharge region between both electrodes are monitored by a monitoring means, and the monitoring results are used as the reaction gas pressure, the reaction gas inflow amount, and the discharge. Feedback to at least one control system of each control system of electric power and mold temperature,
The cleaning method according to claim 1, wherein at least one of the control systems can be controlled based on this feedback.