JPH08244041A - Washing of vulcanizing mold - Google Patents

Abstract

PURPOSE: To realize uniform ashing within a short time without applying restriction to the mold surface of a vulcanizing mold by constituting the reaction gas allowed to flow in a vacuum treatment tank of oxygen gas and halide gas and holding the pressure of the gas to low pressure within a predetermined range under the equilibrium of the inflow and outflow amts. of the gas. CONSTITUTION: One electrode 4 is allowed to protrude into a vacuum treatment tank 1 and an annular vulcanizing mold 15 is positioned around the electrode 4 as other electrode so as to be separated from the electrode 4 by a predetermined distance and plasma is generated only in the region between the surface of the vulcanizing electrode 15 to be cleaned and the surface of the electrode 4 and an insulator 8 is provided at the position covering the discharge region between both electrodes to prevent the generation of abnormal discharge. The reaction gas flowing in the vacuum treatment tank is constituted of oxygen gas and halide gas and the pressure of the gas in set to 0.1-10.0Torr under the equilibrium of the inflow and outflow amts. of the gas. By this constitution, the plasma region optimized to a tire tread pattern forming surface brings about uniform ashing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND 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 vibration-proof rubber and other plastic products as elastomers, and in the case of split molds, they are adjacent to each other. The method for cleaning the vulcanization mold to effectively remove the elastomer residue that is inevitably formed on the surface including the mating surface and the recesses and holes. The present invention relates to a method for cleaning a vulcanizing mold, which enables cleaning and 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, the object of the present invention is to improve the above-mentioned disadvantages and to bring about another disadvantageous abnormal phenomenon, and at a low cost without restricting the die-forming surface of the vulcanizing die. Another object of the present invention is to provide a method for cleaning a vulcanization mold, which can advantageously realize uniform ashing in a short processing time.

[0009]

In order to achieve the above object, a method for cleaning a vulcanization mold according to the present invention is to apply a plasma generated in a dilute reaction gas in a vacuum processing tank to the vulcanization mold, When removing the elastomer residue formed on the mold surface by repeated vulcanization molding of the elastomer by ashing, one electrode is projected into the processing tank, and the annular vulcanization mold is surrounded by the other electrode. As a result, the electrodes are positioned at a predetermined distance from the former electrodes, electric power is applied to these electrodes to generate plasma due to discharge between the electrodes, and an insulator is provided at a position covering the discharge region between the electrodes, whereby Oxygen gas and halide gas are used as reaction gases among the gases to be introduced into the vacuum treatment tank to prevent the discharge coupling phenomenon between the discharge region and the discharge in the voltage application side portion of the power supply, and the gas flow Characterized by holding the gas pressure under equilibrium amounts and runoff into the low pressure within a predetermined range.

In carrying out the present invention, the reaction gas pressure is in the range of 0.1 to 10.0 Torr, the insulator is a ceramic containing alumina as the main component, and oxygen gas and halide gas are used. To the reaction gas of
At least one of argon gas, helium gas, and nitrogen gas is added as a diluent gas, and oxygen gas and halide gas are added at the vicinity of the time including a nonuniform region in the plasma distribution between the electrodes. To the reaction gas with, adding at least one gas of argon gas, helium gas and nitrogen gas as a diluent gas,
The halide gas is a carbon tetrafluoride (CF ₄ ) gas, and the plasma distribution state between the electrodes and the abnormal discharge phenomenon are monitored by monitoring means, and the monitoring results are the reaction gas pressure, the reaction gas inflow amount, It is desirable to feed back to at least one of the control systems of the discharge power and the mold temperature, and to control at least one of the control systems based on this feedback.

[0011]

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 in which the plasma distribution state is schematically illustrated in FIG.
Weaker plasma area than non-plasma area, which is weaker than plasma area (hatched area), which has suitable strength on a part of inner surface of
Is likely to occur during processing. In addition to the example shown in FIG.
A weak 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 process failure, a spark is generated between the two electrodes and the vulcanization mold and the center electrode are removed. 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 inevitably generated in plasma,
For example, local retention of F ⁻ and O ⁻ (especially F ⁻ is long residence time in the plasma, and this is likely to form a part that locally exhibits the state of an electron cloud, and this part is likely to be formed on both electrodes. (4) the central electrode is charged, or the elastomer residue (which is an insulator) on the inner surface of the vulcanization mold is charged.

In order to eliminate the above causes, (a) increase the power supply, (b) increase the degree of vacuum inside the processing tank, that is, decrease the inflow amount of the reaction gas and lower the pressure of the reaction gas. c) Then, it is effective to add an inert gas that facilitates discharge. Above all, further lowering the pressure of the reaction gas can be said to be an effective means because the mean free path of gas molecules becomes longer and the discharge tends to spread. However, if these plasma distribution equalizing means are easily applied, the abnormal discharge phenomenon as described below tends to occur, which is not preferable.

6 and 7 exemplify the cross sections of the vacuum processing tanks 1'and 1 ", and the state of the abnormal discharge phenomenon occurring inside the vacuum processing tanks will be described with reference to the respective drawings. A vulcanization mold 15 is positioned around the electrode 4 which is housed by projecting into the container 1 ', 1'. The vulcanization mold 15 is set on the upper surface of the surface plate 16, and these are carried by the wheel conveyor 17. The vacuum suction unit 3 is located below the container 2.

The vacuum processing tank 1'shown in FIG.
Is connected to the ground side, and electric power is supplied to the electrode 4 on the voltage applying side through the power transmission pipe 6. At this time, if the plasma distribution is made uniform by the above means, first, between the metal spacer 11 'for joining which is arranged between the insulator 8'and the metal pipe 10' for accommodating the power transmission pipe 6 and the upper portion of the insulator 8 '. An undesired discharge phenomenon appears due to the concentration of high-density electric lines of force, and this discharge is then combined with the plasma-generating discharge region between the electrode 4 and the vulcanization mold 15, as shown by the lattice pattern in the figure. It was confirmed that the abnormal discharge phenomenon progressed.

Under this abnormal discharge phenomenon, the desired discharge power between the electrode 4 and the inner surface of the vulcanization mold 15 is significantly reduced, and therefore the plasma density in the desired region is significantly reduced, and the ashing treatment capability is increased. It is inevitable that a decrease in In addition, this has the disadvantage that even the part of the vulcanization mold 15 where the discharge is not desired is included in the discharge area, which results in deterioration or damage to this part.

In the vacuum processing tank 1 "shown in Fig. 7, the electrode 4 is on the ground side, and power is supplied to the vulcanizing mold 15 on the voltage applying side through the power transmission pipe 6 '. This case is also shown above. Similar to the example, the abnormal discharge phenomenon occurs at the position shown by the lattice pattern in the figure, which causes the same disadvantages as described above.

However, by providing an insulator at a position covering both electrodes, that is, the discharge region between the electrode 4 and the vulcanization mold 15, the above-mentioned means for uniformizing the plasma distribution of the items (a) to (c) can be provided. When applied, it is possible to prevent abnormal discharge as described with reference to FIGS. The reason is as follows.

First, it has been described above that an undesired discharge that occurs at a portion where the voltage application side for supplying electric power to both electrodes and the ground side are relatively close to each other triggers the abnormal discharge. This is because in order to obtain a desired plasma density, it is necessary to apply high power, that is, high voltage, for example, 0.2 to 20 kV, and the electric field between the approaching portions is strengthened to reach the dielectric breakdown voltage, that is, the discharge start voltage. This is unavoidable in a low pressure reaction gas atmosphere, which should be called a vacuum state. This undesired discharge position is on both electrodes 4, 15
When the discharge area is relatively close to the desired discharge area between them, as in the example shown in FIG. 6, in the case where it reaches from the upper portion of the insulator 8'through the joining metal spacer to the joining flange of the metal pipe 10 ', this undesired discharge is generated. It tends to couple with the desired discharge area between both electrodes.

Therefore, in order to prevent abnormal discharge, it is necessary to increase the above-mentioned dielectric breakdown voltage or discharge start voltage, but this alone cannot be said to be perfect. Therefore, even if an undesired discharge occurs, it is possible to prevent the discharge between both electrodes. By providing an insulator at a position that covers the discharge region, preferably by providing an insulator that covers the discharge region at least at the voltage application side position of the upper and lower sides of the discharge region, the insulator surface facing the discharge region is Since it is charged by the action of plasma, the undesired discharge in the voltage application side portion is not coupled to the discharge region between both electrodes, and it becomes possible to completely prevent the occurrence of the abnormal discharge phenomenon. As a result, the phenomenon that the plasma region diffuses upward or downward can also be prevented.

By applying the means as described above, it becomes possible to make the plasma distribution uniform without the occurrence of abnormal discharge. That is, the reaction gas among the gases flowing into the vacuum processing tank is oxygen gas and halide gas,
By maintaining the gas pressure at a low pressure within a predetermined range under the equilibrium of the gas inflow amount and the gas outflow amount, as described above in (a) to (c), the power supply is increased and the pressure of the reaction gas is increased. And it is possible to add an inert gas that facilitates discharge. As a result, a uniform plasma can be generated between both electrodes from the beginning to the end of discharge, resulting in uniform cleaning and treatment time. It is possible to realize reduction of cost and cost.

Oxygen gas and 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, so that the negative ions are locally retained in the plasma, and electrons required for discharge are discharged. Supply is interrupted, and as a result, a non-uniform region is formed in the plasma distribution. By keeping the oxygen gas and the halide gas at low pressure, it is possible to suppress the generation amount of these negative ions and mitigate the discharge interruption effect. Therefore, uniform plasma processing can be obtained.

The reaction gas pressure is 0.1 to 10.0 Torr.
Within the range, it contributes to further enhancing the above effect. If the insulator is a ceramic containing alumina as a main component, it is effective for preventing the occurrence of abnormal discharge, and it is also effective to apply an insulating resin such as Teflon.

At least one of argon (Ar) gas, helium (He) gas, and nitrogen (N ₂ ) gas, optimally Ar gas as a diluent gas, is added to the reaction gas of oxygen gas and halide gas. By doing so, it is possible to further smooth the discharge between both electrodes and contribute to obtaining a uniform plasma distribution. Also, when a sign that a non-uniform region is generated in the plasma distribution is observed or after that, at least one gas of Ar gas, He gas and N ₂ gas, optimally Ar gas as a diluent gas, is added. For example, the problem of non-uniformity can be solved and the amount of expensive Ar gas used can be reduced, which is useful for cost reduction.

Further, the halide gas is replaced by tetrafluoride gas (C
F ₄ ) contributes to highly efficient ashing. As a halide gas, F (fluorine), Cl (chlorine), Br
Any gas having (bromine), I (iodine), etc. in the compound can be applied. Further, since it is sufficient that these compounds can be supplied as a gas into the vacuum processing tank, they do not necessarily have to be gases in a standard state (25 ° C., 1 atm), and may be in a liquid state, for example. Freon, NF ₃ , and SF ₆ are particularly preferably used, and among them CF ₄
Is valid.

Further, the plasma distribution state and the abnormal discharge phenomenon are monitored by the monitoring means, and the monitoring result is displayed in at least one of the control systems of the reaction gas pressure, the reaction gas inflow amount, the discharge power and the vulcanization mold temperature. The feedback controllability contributes to the advantageous and appropriate realization of the above-mentioned various operational effects.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described in detail below with reference to FIGS. FIG. 1 is an explanatory view 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. Applies to 1-3.

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 diameter of the electrode 4 can be freely expanded and reduced, and in this case, the radial (horizontal) distance between the inside of the vulcanization mold 15 and the outside of the electrode 4 which will be 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 tank 5 through the conductor plate 4a, and the cooling tank 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 is on the ground side and the power transmission pipe 6 is on the voltage application side.

Inside the power transmission pipe 6, a cooling medium such as a liquid for cooling the electrode 4 (for example, cooling water at about 20 ° C. or similar cooling oil) or a gas is supplied to the cooling tank 5 for cooling with a smaller diameter. 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. The power supply can be direct current or alternating current, and the discharge type can be appropriately selected depending on the frequency. In addition to the above-mentioned high frequency, low frequency or microwave discharge is well known as the AC discharge.

A vertically long insulator, for example, an insulator 8 made of ceramics 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 a cylinder 10 made of a metal, for example, stainless steel, which extends vertically upward similarly to the insulator 8 are provided.
And the flange portion of the above are joined to each other in a completely sealed state via a metal connecting spacer 11 having a sufficient thickness. Of course, the inside of the metal 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. Metal cylinder 1
0 is fixed to the upper part 2-1 of the container or movably attached.

At this time, the insulator 8 and the connecting spacer 11
In the cross section of FIG. 1, the intersection of the straight line represented as the coupling line and the power transmission pipe 6 is point X, and the end of the lower coupling surface of the coupling spacer 11 is pointed. Y
Respectively, and preferably the distance L between both points X and Y is 50
mm or more. As a result, it is possible to effectively prevent the occurrence of undesired discharge near the point Y (actually, the circumferential edge).

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 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 vulcanization 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.

A plate-like insulator 12 that projects like a top lid of the vulcanization mold 15 is provided below the insulator 8. The plate-shaped insulator 12 has a shape or dimension that covers at least the plasma region generated between the electrode 4 and the vulcanization mold 15, and one plate surface is exposed to this plasma and charged. It is placed and positioned so as to prevent diffusion of the plasma towards the upper region. The material of the plate-like insulator 12 is preferably Teflon or ceramics, especially alumina ceramics, and a material having excellent corrosion resistance against plasma of CF ₄ or O ₂ is suitable.

By providing the plate-shaped insulator 12 at the above position, even if the undesired discharge occurs near the point Y described above, this discharge is coupled to the desired discharge region between the electrodes 4 and 15. It is possible to eliminate defects. See also FIG.
As shown in, by arranging the solid insulator 13 covering the periphery from the upper portion of the tubular insulator 8 to the middle portion of the metal cylinder 10,
Distance Z from the above point Y to the outer surface of the covering insulator 13
Even if the lines of electric force are concentrated within (for example, 10 to 300 mm), the discharge phenomenon does not occur due to the enhancement of the covering insulator 13. Further, since the electric field is significantly weakened around the coated insulator 13, it is possible to sufficiently suppress the generation of the undesired discharge coupled to the desired discharge region.

In the vulcanization mold 15, 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 used as a steel holding member. It is attached to form the above-mentioned segment, and 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 on the same wheel conveyor (not shown) to the position shown in the drawing, and at the same time, centering is performed. This centering accuracy is the amount of misalignment, and is desirably 3c.
m or less, more preferably 5 mm or less.

After the surface plate 16 is conveyed to a predetermined position, the surface plate 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, this apparatus is equipped with means for monitoring the plasma distribution state and abnormal discharge phenomenon, and the plasma emission spectrum, electron temperature and electron density (probe measurement), vulcanization mold temperature are monitored. (Thermocouple, infrared thermometer) and the like, and other windows that allow visual observation and video camera photography are provided in the container 2 to allow external observation and image analysis. Based on the monitoring results by these monitoring, the reaction gas pressure, the reaction gas inflow amount,
Properly control discharge power and vulcanization mold temperature.

[Embodiment 1] According to FIG. 1, the electrode 4 has a cylindrical shape, and its dimensions are 480 mm in outer diameter and 22 in height.
It is 0 mm. The vulcanization mold 15 has eight segments and a maximum inner diameter of 550 mm. As the reaction gas, a mixed gas of CF ₄ gas and O ₂ gas was used, and the ratio of the inflow amounts of these gases was CF ₄ : O ₂ = 1: 2. 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 90 minutes and the reaction gas pressure (Torr) and the discharge power (KW) is shown as a diagram in which the former is a series of triangles and the latter is a series of circles. Collectively shown in FIG. When a vulcanization mold of the same size to which the polymer residue of the same degree as in Example 1 was attached was subjected to a cleaning treatment with a uniform plasma distribution, using a treatment tank from which the plate-shaped insulator 12 was removed for comparative evaluation. When compared with the treatment completion time of Example 1, it was about 90 of Example 1.
It was found that it takes about 150 minutes for the compared mold.

The reason is that, as shown in FIG. 2, the initial electric power could be increased up to 8 kW in Example 1 because there was no suspicion of abnormal discharge, whereas in the case of the comparative mold, abnormal discharge was possible. This is because the initial power of the limit that does not generate is only 6 kW. Further, the pressure reduction operation of the reaction gas pressure for securing a more uniform plasma region was performed twice in the comparative mold, whereas in Example 1, it was sufficient only once, and the pressure was reduced in accordance with the pressure reduction. Regarding the electric power after that, 5 in Example 1
This is because the compared mold was about 4 KW against KW. The circles in the figure represent electric power, and the triangles represent reaction gas pressure.

Example 2 Vulcanization used for cleaning in Example 1
All except for the use of a mold with a larger amount of residue deposits than mold 15.
The same vulcanization mold 15 was subjected to plasma treatment. Processing tank 1
Are the same. However, as the gas to flow into the processing tank 1,
CF of reaction gas from the beginning of discharge_FourGas and O ₂Ar to gas
Gas is added, and the mixing ratio of these gases is CF_Four: O₂: A
Set r = 1: 2: 3 and keep this ratio constant until the end of processing.
While maintaining the gas pressure at 1.6 Torr,
Was a constant 8 kW except at the beginning of discharge. This is
Figure 3 is shown as a diagram. The circles shown in the figure
Indicates electric power and triangular marks indicate gas pressure (the same applies hereinafter).

By adding Ar gas from FIG. 3,
It is understood that it is possible to keep the gas pressure constant without impairing the uniform plasma distribution from the start of discharge to the end of discharge at which sufficient ashing is achieved. Example 1
Compared with the above, it can be understood that it is necessary to extend the processing time, but since it is possible to discharge at high power throughout the period except when the discharge starts, it takes about 60 minutes.

[Embodiment 3] The same vulcanization mold 15 as in Embodiment 2
The inflow gas from the start of discharge to the lapse of about 25 minutes was CF ₄ gas and O ₂ gas (CF ₄ : O _{2) which} were reaction gases.
= 1: 2) only, and after that, by adding Ar gas, the inflowing gas is changed to CF ₄ : O ₂ : Ar = 1: 2: Three
And The gas pressure was kept at 1.5 Torr throughout. This state is shown in FIG. 4 as a diagram, and the right vertical axis in the figure is the inflow ratio of Ar gas.

In the third embodiment, the occurrence of the non-uniform plasma distribution state is detected promptly by monitoring, and at this point A
The operation of starting the additional inflow of r gas was carried out. As a result, the plasma distribution showed a uniform state throughout, and the processing completion time could be shortened to about 60 minutes.

In addition to the above-mentioned comparison object, as a comparative example, a vulcanization mold of the same eight segments as in each example was positioned between both electrodes of the conventional case, and the reaction gas was CF ₄ gas with an electric power of 6 KW. A mixed gas with an O ₂ gas (inflow ratio 1: 2) was applied, and the reaction gas pressure was kept at 1.5 Torr for plasma treatment. The evaluation items were the temperature at the time of completion of processing of each segment, and the visual judgment as to whether the clean state was good or bad. The amount of residue adhered in the comparative example was about the same as in Example 1. The results of temperature measurement are shown in Table 1. In Table 1, the segment No. Are sequentially attached clockwise. The value is No. It is better to be uniform between 1 and 8.

[0058]

[Table 1]

From Table 1, Examples 1 to 3 show that the temperature difference between the segments is small and that the treatment under a uniform plasma distribution can be achieved, whereas the Comparative Example shows the highest temperature and the lowest temperature. This proves that the ratio with temperature reached more than twice, and the non-uniform region appeared in the distribution. Therefore, when the vulcanization mold was taken out after the plasma treatment and observed in detail,
In each of the examples, the entire inner surface of the vulcanizing mold was uniformly and sufficiently cleaned of the residue, while in the comparative example, the segment No. 5 and 6 were not cleaned sufficiently. Further, no damage was found on the vulcanization mold in any of the examples, whereas in the comparative example, the high temperature of segment No. No. 1 had a damaged part that could not be overlooked.

[0060]

According to the present invention, the elastomer residue, which is inevitably formed on the inner surface of the mold by the repeated vulcanization molding of the elastomer, does not have a disadvantage such as damage to the vulcanization mold. Further, it is possible to provide a method for cleaning a vulcanizing mold that can be ashed uniformly and advantageously at low cost and in a short processing time without applying any restriction to the mold forming surface of the vulcanizing mold.

[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 the relationship between discharge time and power and reaction gas pressure in another embodiment according to the present invention.

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

FIG. 5 is an explanatory diagram of plasma distribution.

FIG. 6 is a side sectional view of another vacuum processing tank for explaining the operation of the present invention.

FIG. 7 is a sectional view of another side of the vacuum processing tank for explaining the operation of the present invention.

[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 5 Cooling tank 6 Power transmission pipe 7 Refrigerant sending pipe 8 Insulator 9 Reactive gas supply pipe 9-1 Connecting pipe 9-2 Circular pipe 10 Metal Cylinder 11 Connection Spacer 12 Plate Insulator 13 Solid Cover Insulator 15 Vulcanizing Mold 16 Supporting Transport Surface Plate 17 Wheel Conveyor 18 Electrical Contact 19 Rod 20 Elevating Means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Hirose 1-445-1 Ogawamachi, Kodaira-shi, Tokyo Garden Heights 1-612 Kodaira

Claims (7)

[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. A plasma is generated by a discharge between the electrodes, and an insulator is provided at a position covering the discharge region between the two electrodes to prevent a discharge coupling phenomenon between the discharge region and the discharge in the voltage application side portion of the power supply. Of the gases introduced into the vacuum treatment tank, the reaction gas is oxygen gas and halide gas, and the gas pressure is maintained at a low pressure within a predetermined range under the balance of the gas inflow and outflow. Cleaning method for vulcanizing mold. 2. The reaction gas pressure is 0.1 to 10.0 Tor.
The cleaning method according to claim 1, which is within the range of r. 3. The cleaning method according to claim 1, wherein the insulator is a ceramic containing alumina as a main component. 4. The reaction gas of oxygen gas and halide gas, at least one gas of argon gas, helium gas and nitrogen gas is added as a diluent gas.
The cleaning method described in any one of 3 to 3. 5. The reaction gas of oxygen gas and halide gas is at least one of argon gas, helium gas, and nitrogen gas at a time point near the time when a nonuniform region is generated in the plasma distribution between the electrodes. The cleaning method according to any one of claims 1 to 4, wherein the gas of (1) is added as a diluent gas. 6. The carbon tetrafluoride (CF) is used as the halide gas.
₄ ) The cleaning method according to claim 1, wherein the cleaning method is gas. 7. A plasma distribution state between the both electrodes and the abnormal discharge phenomenon are monitored by a monitoring means, and the monitoring result is at least one of control systems of reaction gas pressure, reaction gas inflow amount, discharge power and mold temperature. 7. Feedback is provided to one control system, and at least one control system among the control systems can be controlled based on this feedback.
The cleaning method described in.