JPH1119945A - Method for cleaning vulcanization mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to perform the uniform ashing treatment of a residue at a remarkably high efficiency without restricting the shape and the size of a face on which a mold is formed on a vulcanizing device by supplying a high-frequency electric power to a coil for induction bonding and at the same time, supplying a reactive gas to the center part of a vulcanization mold to product a plasma. SOLUTION: A mold 15 is stored in a jacket 17 for temperature regulation on a platen 16, then these are placed in a vacuum treatment tank 1, and containers 2-1, 2-2 are airtightly sealed and anchored to vacuumize the interior of the treatment tank 1. Further, a reactive gas is caused to flow into the hollow part 15a of the mold 15 as a mixed gas of O2 gas and CF4 gas to retain a plasma gas in the treatment tank 1 at a specified pressure level. In addition, a high frequency is output from a high frequency generation source 8, then is transmitted to a coil 7 for induction bonding through a matching box 6 to produced the plasma gas with the help of the coil 7, and in turn, the plasma composed mainly of an oxygen radical is caused to act upon the inner peripheral face 15a of the mold 15. Thus it is possible to perform the uniform ashing treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a vulcanization molding of rubber products such as rubber tires and vibration-isolating rubbers and other plastic products as an elastomer, which is used for the molding surface inside a mold which is used repeatedly, and in the case of a split mold. Regarding the cleaning method of the vulcanizing mold to advantageously remove the elastomer residue that is inevitably formed on the surface including the surface and the concave portions and holes, particularly without disadvantageous deterioration and damage to the vulcanizing mold, Also, the present invention relates to a method for cleaning a vulcanization mold capable of performing stable and uniform residue treatment without being bothered by formation of a non-uniform region of plasma distribution.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open No. Hei 6-285 by the present applicant has already been disclosed.
As described in detail in Japanese Patent Publication No. 868, elastomer products, especially rubber tire products (hereinafter simply referred to as tires), vibration-proof rubber products, and the like satisfy the required performance, and are crosslinked with natural rubber, synthetic rubber, or a blend rubber thereof. In addition to blending sulfur as an agent and carbon black as a reinforcing material,
It is necessary to incorporate a vulcanization accelerator and various chemicals for maintaining durability.

[0003] When vulcanizing and molding the unvulcanized rubber composition prepared as described above, a chemical reaction such as a crosslinking reaction generally occurs at a high temperature close to 200 ° C. Not only increase, but also gasify partly,
In addition to the molding surface of the vulcanizing mold, the rubber composition and its chemical reaction products are not only present in very small gaps in the mating surfaces of the molds, but also in holes such as so-called vent holes for air release. It is inevitable that they will adhere strongly as residue. By repeating this vulcanization molding many times, the residue is deposited with a thickness that cannot be overlooked. This occurs not only in the rubber composition but also in other elastomers in a similar manner.

[0004] Thick vulcanization residues firmly adhered and deposited on the vulcanization mold not only impair the appearance of the tire, but also adversely affect the excellent quality maintenance of the entire tire. Therefore, it is necessary to clean the vulcanization mold, which has been vulcanized and molded a predetermined number of times, as if it were a new one.As a method of this work, a shot blast cleaning method in which granules such as plastic beads and glass beads are sprayed with a high-pressure gas, Alternatively, the liquid cleaning method of immersing in a solution of an acid, an alkali, an amine or the like occupies the mainstream. 285868
A method for cleaning a vulcanizing mold by using a plasma described in Japanese Patent Application Laid-Open Publication No. H11-157, has been proposed, and a remarkably excellent effect has been obtained.

However, when these results were examined, it was found that there was room for further improvement in the following points.

That is, the first point is that, on the mold forming surface of the vulcanizing mold requiring cleaning, a large groove which is generally indispensable for sufficiently exhibiting the required characteristics for the tire, apart from the special tire type. , A large number of ribs and sipe (strips) for forming narrow grooves, slits, etc. in the tread portion are provided, and the plasma is blocked by these protrusions and covers the entire area of the clean surface target Uniform ashing (ashing) of the vulcanization residue tends to be impaired.

Further, the present applicant has disclosed in Japanese Patent Application Laid-Open No. Hei 8-20705.
No. 6, JP-A-8-216164 and JP-A-8-216164
In Japanese Patent Application Laid-Open No. -244041, one electrode for applying high-frequency power is formed in a cylindrical shape, or a structure provided with a plurality of fins on the outer peripheral surface thereof. An apparatus and a method for uniformly generating an incineration of the residue by generating plasma by electric discharge between the electrodes have been proposed.

However, the following points are disadvantages caused by locating the vulcanizing mold in the discharge area, that is, the second point is that a non-uniform discharge area is often formed and uniform ashing is performed. Processing is likely to be hindered,
The third point is that the temperature of the vulcanizing mold becomes higher than, for example, 200 ° C. based on the non-uniform electric discharge, and this causes deterioration of the accuracy of the mold, deterioration and damage of the mold. The fourth point is related to the third point, and it is difficult to control the temperature of the vulcanizing mold.The fifth point is that the surface outside the object of cleaning is exposed to the discharge area. To cause deterioration and damage.

In order to improve the first to fifth disadvantages, the present applicant further discloses in Japanese Patent Application Laid-Open No. Hei 8-300366 a plasma for supplying a neutral active species (radical) to a vacuum processing tank. A generating furnace and a microwave generator that uses a microwave discharge plasma as a gas containing a neutral active species as a reaction gas flowing into the furnace are provided, and the neutral active species generated in the plasma generating furnace is supplied through a conduit. Introduced into the processing tank,
A method was proposed in which the introduced neutral active species was uniformly ejected toward the entire residue surface of the vulcanizing mold, and the elastomer residue was ashed by the ejected neutral active species gas.

Although the cleaning of the vulcanizing mold by the above-mentioned new cleaning method has remarkably exerted an effect on improvement of the above disadvantages, it has become clear through the cleaning operation that further improvement is required. That is, in the above method, a part of the neutral active species is deactivated while the gas containing a large amount of neutral active species generated in the plasma generating furnace is supplied into the treatment tank through the conduit, so that the ashing efficiency is reduced. The disadvantage is that it decreases.

[0011]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to improve all of the disadvantages described above, without restricting the shape and size of the mold forming surface of the vulcanizing mold, and without reducing the shape. It is an object of the present invention to provide a method for cleaning a vulcanization mold capable of achieving uniform residue ashing under remarkably high efficiency without adversely affecting the mold.

[0012]

The present invention provides the following method for cleaning a vulcanizing mold in order to achieve the above object. Claim 1: An annular vulcanization mold is located in a vacuum processing tank,
In a method for cleaning a vulcanization mold, a plasma of a low-pressure reaction gas is applied to an elastomer residue formed on the inner surface of the mold by repeated vulcanization molding of the elastomer, and the residue is ashed and removed. A coil for inductive coupling is arranged in the hollow portion of the vulcanization mold so as to face the inner peripheral surface of the vulcanization mold, and high-frequency power is supplied to the coil from a high-frequency power supply, and the hollow of the vulcanization mold The reaction gas is supplied to the part, a plasma is generated, and the elastomer residue is ashed by at least one of the generated plasma gas and the neutral active species gas generated by the plasma. Cleaning method. In a preferred embodiment, the reactive gas comprises one of oxygen gas alone and a mixed gas with a halide gas containing oxygen gas as a main component. Claim 3: The vulcanizing mold in the vacuum processing tank is 100 to 1
The cleaning method according to claim 1, wherein the ashing is performed by heating and maintaining the temperature within a range of 80 ° C. 4.

According to the present invention, an inductive coupling coil is installed inside a vulcanizing mold installed in a vacuum processing tank, and inductively coupled plasma is generated at a location near the residue surface of the vulcanizing mold.
Since the ashing is performed using the plasma gas and the neutral active species gas, active species are hardly deactivated by transport, plasma can be generated uniformly and at a high density, and uniform and highly efficient ashing can be performed. In addition, since high-density plasma can be generated at a lower pressure than in the conventional method, the amount of process gas used can be reduced.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for cleaning a vulcanizing mold according to the present invention will be described in detail with reference to FIGS. FIG. 1 is a schematic sectional view of a cleaning apparatus used for carrying out the present invention, and the cleaning apparatus includes a vacuum processing tank 1. This vacuum processing tank 1
Comprises a container 2 having an upper container 2-1 and a lower container 2-2 which can be separated from each other at a lower position and which can be sealed, and the upper container 2-1 is detachable from the lower container 2-2. Can be moved upward and downward.

The lower container 2-2 includes a suction unit 3 connected to a vacuum pump (not shown). Prior to starting the cleaning operation of the vulcanizing mold 15, the vacuum pump is operated to exhaust air in the container 2 through the suction unit 3 in the direction of arrow A in FIG. 10 ^-1 to 1
0 to ^-5 Torr called in vacuum to high vacuum. In addition,
In the illustrated example, the vacuum processing tank 1 fixedly supports the lower container 2-2 together with the wheel conveyor 5 on a floor surface Fs or the like by, for example, a plurality of columns 4 (only two columns are shown). The wheel conveyor 5 holds an annular vulcanizing mold 15 to be cleaned, which is set on a surface plate 16.

In the hollow portion 15a of the vulcanizing mold 15, an inductive coupling coil 7 is disposed so as to face the inner peripheral surface 15s of the mold 15, and the coil 7 is provided with a matching box 6
Is connected to the high-frequency generation source 8 via the.

The high frequency generator 8 has a frequency of 300 KHz to 3 KHz.
Within the range of 00 MHz, desirably 1 MHz to 100 MH
A high frequency within the range of z is generated and output, and this high frequency output is matched by a matching box 6 and supplied to the inductive coupling coil 7.

The inductive coupling coil 7 has two windings in FIGS. 1 and 2, but is not limited thereto.
It may be wound or three or more. Further, as shown in FIG. 4, a plurality of coils can be connected in parallel. Furthermore, the coil can be cooled by forming the inductive coupling coil with a hollow pipe and flowing a cooling medium inside.

Reference numeral 10 denotes a hollow portion 15a of the mold 15 described above.
It is a pipe for ejecting the reaction gas arranged in the inside. A plurality of pipes 10 are arranged between the mold 15 and the coil 7 at predetermined intervals (preferably at equal intervals). Although not shown, these pipes 10 communicate with one annular pipe. A reaction gas introduction pipe 10a is connected to the annular pipe, and a reaction gas is supplied from the reaction gas introduction pipe 10a to each pipe 10 through the annular pipe. A small hole provided in each pipe 10 faces the inner peripheral surface 15 s of the mold 15 so as to blow toward the inner peripheral surface 15 s of the mold 15.

When the inner peripheral surface of the vulcanizing mold 15 is cleaned by using the above-described cleaning device, the high-frequency generator 8 is operated, and the inductive coupling coil 7 is passed through the matching box 6.
Supply high frequency power to Thereby, the high frequency generation source 8
The high-frequency wave transmitted from the coil 15 forms an electromagnetic field in the hollow portion 15a of the mold 15 by the inductive coupling coil 7. At the same time, when the reaction gas is ejected from each pipe 10, the reaction gas is turned into plasma by the energy of the electromagnetic field, and a high-density plasma gas and a neutral active species gas having a sufficient concentration are generated.

Since the neutral active species gas reaches the inner surface of the residue of the mold to be cleaned without passing through an extra path, the neutral active species gas is very little deactivated on the way. In addition, since the plasma generating portion and the inner surface of the mold to be processed are close to each other, the plasma gas itself also reaches the surface to be processed, and can contribute to the ashing action. In addition, since the mold is not used as an electrode, abnormal discharge does not occur, all disadvantages associated with abnormal discharge can be eliminated, and a uniform plasma gas can be produced without consuming extra electric power. It is possible to generate the gas at a high density together with the gas, and as a result, it is possible to realize an ashing effect on the vulcanization residue with a high degree of efficiency.

In this case, by applying a negative bias voltage to the vulcanizing mold in the vacuum chamber, an even faster ashing action can be realized. The bias voltage may be either DC or AC.

Here, if the reaction gas is composed of any one of oxygen gas alone and a mixed gas with a halide gas containing oxygen gas as a main component, it contributes to further improvement of the ashing processing efficiency. Here, the oxygen gas of the reaction gas is O
Both ₂ and O ₃ are suitable, and the halide gases include F (fluorine), Cl (chlorine), Br (bromine),
Any gas containing (iodine) or the like can be used. Further, since it is sufficient that the gas can be supplied to the vacuum processing tank 1, the gas does not always need to be in a standard state (25 ° C., 1 atm), and may be in a liquid state, for example.
In particular, Freon, NF ₃ and SF ₆ are preferably used, and CF ₄ (carbon tetrafluoride) is particularly effective.

In cleaning the vulcanizing mold, the high frequency and the amount of power supplied to the high frequency generator 8 and the inflow of the reaction gas are set so that the density of the plasma gas and / or the neutral active species gas becomes a desired value. (SCCM). In this case, oxygen (O, O ₂ , O ₃ ) radicals are used as a reaction gas, either oxygen gas alone or a mixed gas of a main component oxygen gas and a subcomponent halide gas, preferably a CF ₄ gas. , CF ₄ radicals. In addition, during the ashing process, the vacuum pump is operated to constantly operate the suction unit 3.
It is preferable that the gas in the vacuum processing tank 1 is continuously exhausted, and the pressure inside the processing tank 1 is constantly maintained at a constant pressure in the range of 0.001 to 10 Torr.

In FIG. 1, reference numeral 17 denotes a temperature adjusting jacket as a heating source for heating the mold 15, and a heating medium such as a high-temperature gas or steam is supplied to an inner space 17j of the jacket 17; Mold 15 from 100
Heat to a desired temperature within the range of 180 ° C. and maintain. If the mold 15 is kept at this high temperature, the ashing reaction speed is further increased, which contributes to greatly shortening the plasma ashing processing time. Although illustration is omitted,
The mold 15 includes a temperature measurement sensor, and controls the temperature and / or flow rate of the heating medium and the temperature of the mold 15 outside the processing tank 1.

Although the mold 15 is shown as an integral part in the figure, in this example, a so-called split mold is formed by dividing a large number, for example, 3 to 20 segments of the outer peripheral side of a so-called split mold with a metal, for example, steel. On the upper surface of the base plate 16 for supporting and transporting made in the same state as in actual use.

In general, an aluminum alloy is applied to a portion where a tread portion and various grooves and slits are formed in a tread portion of a tire, and when actually used, this alloy portion is attached to a steel holding member to attach the above-described segment to the above-mentioned segment. In the present invention, the mold 15 includes both the case of only the alloy portion and the case of the segment.

If the mold 15 is a split mold, a pair of side molds are combined above and below the segment mold shown to form a mold body. This mold body can be subjected to plasma cleaning as a vulcanizing mold 15,
Further, the present invention can be applied to any one of a so-called upper and lower two-piece mold and a large number of segment molds each having a dividing surface on the circumference.

Although not shown, the platen 16 is used for temporarily assembling a large number of segments or for placing the split mold body or the upper and lower two-piece mold together, for assembling the segments or placing these molds at predetermined positions. The platen 16 further includes a mechanism for centering the molds 15 as an assembly or the molds 15 as these molds with respect to the central axis of the concave portion 2c. The latter mechanism is mold 15
And a centering device provided on the wheel conveyor 5 supporting the surface plate 16 for centering engagement.

The mold 15 is introduced into the processing tank 1 by moving the upper container 2-1 upward and moving the mold 15 temporarily assembled or set on the platen 16 outside the processing tank 1 in advance. Surface plate 1
Along with 6, it is conveyed to the position shown on another similar wheel conveyor (not shown), and is simultaneously centered.

[0031]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

According to FIGS. 1 to 3, a mold 15 having a maximum inner diameter of 550 mm comprising eight segments is accommodated in a temperature adjusting jacket 17 on a surface plate 16, and these are placed in a vacuum processing tank 1. After the containers 2-1 and 2-2 are hermetically sealed, the vacuum pump is operated to reduce the pressure inside the processing tank 1 to 1
The pressure was reduced to × 10 ^-4 Torr.

The reaction gas is O_TwoGas and CF_FourGas mixing gas
And O_TwoGas is 1000 SCCM, CF_Four50 for gas
At a rate of 0 SCCM, it flows into the hollow portion 15a of the mold 15.
And the plasma gas pressure in the processing tank 1 is set to 1 × 10^-1Tor
r. 13.56M frequency from high frequency source 8
Hz high frequency and output this high frequency
To the inductive coupling coil 7 through the
Plasma is generated by the coil 7 and mainly oxygen radicals
Plasma acting on the inner peripheral surface 15s of the mold 15
Was. The outer diameter of the inductive coupling coil 7 is 400 mm.
And two turns.

In this embodiment, the temperature of the mold 15 is not controlled by the jacket 17 at all, and the temperature of the mold 15 is left to rise naturally by the energy of the plasma.
The ashing processing time was two types of 60 minutes and 120 minutes. The incineration at the end of the treatment was visually evaluated and scored by a 5-point method (the larger the value, the better the score out of 5).
The treated surface was washed with water to remove ash (inorganic metal salt having little adhesion to metal, for example, ZnSO ₄ ), and then scored according to the above five-point method.

In order to verify the effect of the embodiment, Japanese Patent Laid-Open No.
An ashing process according to a comparative example according to Japanese Patent Publication No. 300366 was performed. The processing conditions of the comparative examples were all in accordance with the examples, and the evaluation items and the determination method were also in accordance with the examples. The processes of the example and the comparative example were each performed 10 times, and each time,
An evaluation was performed. The results are summarized in Table 1.

[0036]

[Table 1]

From Table 1, it can be seen that both the ashing property and the degree of cleaning of the examples show markedly superior values as compared with those of the comparative example at the same treatment time. This is a testament to the fact that the method for cleaning the vulcanization residue of the mold according to the present invention has remarkably improved processing efficiency as compared with the method according to the earlier application.

[0038]

According to the present invention, the following advantages can be obtained. Since the vulcanization mold is not used as an electrode, a non-uniform discharge region is not formed, and uniform ashing can be performed. Further, the temperature control of the vulcanizing mold becomes easy, and deterioration and damage of the mold can be suppressed. Since at least one of the plasma gas and the neutral active species gas is directly blown onto the residue surface, disadvantages such as a decrease in the density of the plasma gas and the deactivation of the neutral active species are eliminated, and under a high power efficiency. It is possible to ashing the residue uniformly and effectively in a short processing time. As described above, since the mold is not used as an electrode, an arbitrary DC or AC bias voltage can be applied to the mold, thereby increasing the ashing reaction speed and shortening the ashing processing time. Compared with the conventional method, high-density plasma can be generated at a low pressure, so that a sufficient ashing speed can be obtained with a small amount of gas, which is industrially advantageous.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a cleaning device used for carrying out the present invention.

FIG. 2 is a perspective view of an inductive coupling coil used in the example.

FIG. 3 is a cross-sectional view of a main part of the same example.

FIG. 4 is a perspective view showing another example of the inductive coupling coil.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum processing tank 2 Vessel 2c Depression 2-1 Upper vessel 2-2 Lower vessel 3 Suction part 4 Prop 5 Wheel conveyor 6 Matching box 7 Inductive coupling coil 8 High frequency generation source 10 Reaction gas ejection pipe 10a Reaction gas introduction pipe 10 -1 Neutral activated species ejection container (plasma generating furnace) 11 Window member 12 Coupling slot 15 Vulcanizing mold 15a Hollow portion 15s Inner peripheral surface 16 Surface plate 17 Jacket A

Claims (3)

[Claims] An annular vulcanizing mold is positioned in a vacuum processing tank, and plasma of a low-pressure reaction gas is caused to act on an elastomer residue formed on an inner surface of the mold by repeated vulcanization molding of the elastomer. In the method of cleaning a vulcanizing mold for removing a residue by ashing, an inductive coupling coil is disposed in a hollow portion of the vulcanizing mold in the treatment tank so as to face the inner peripheral surface of the vulcanizing mold, A high-frequency power is supplied to the coil from a high-frequency power source, and a reactive gas is supplied to the hollow portion of the vulcanizing mold to generate plasma, and the generated plasma gas and neutral active species gas generated by the plasma are generated. A method for cleaning a vulcanizing mold, comprising ashing an elastomer residue with at least one gas. 2. The cleaning method according to claim 1, wherein the reaction gas is one of oxygen gas alone and a mixed gas with a halide gas containing oxygen gas as a main component. 3. A vulcanizing mold in a vacuum processing tank is set to 100
The cleaning method according to claim 1, wherein the ashing process is performed while maintaining the temperature at a temperature within a range of from about 180 ° C. to about 180 ° C. 4.