JP3319129B2 - Cleaning method for vulcanizing mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning dirt adhering to a mold used for vulcanizing and molding an elastomer such as a tire without being affected by attrition or corrosion.

[0002]

2. Description of the Related Art When vulcanizing and molding various elastomers such as rubber using a vulcanizing mold, organic substances and fillers contained in raw materials are repeatedly removed from the cavity surface of the mold, the inside of an air vent, and slits during repeated molding. Since it accumulates inside and adversely affects a molded product, it has been practiced to clean dirt accumulated on a mold after molding a predetermined number of times.

[0003] Conventionally, as a method for cleaning stains on a vulcanization mold of an elastomer article, there are a shot blast method in which plastic beads or the like are blown by air, and a liquid cleaning method in which the article is immersed in an acid or alkali solution. A method for cleaning mold dirt by a low-pressure plasma method in an oxygen gas or freon gas atmosphere has been proposed.

[0004]

However, the shot blasting method has a large cleaning effect on the die surface directly hit by the beads, but has a problem that the inside of the vent hole or the slit for venting air cannot be cleaned and the tire has a problem. Since the main material of the mold is aluminum, its strength is weak, and the letters and inscriptions on the mold become unclear due to abrasion and deformation of the edges, causing the pattern to lose sharpness. There is a problem that crushed beads of beads are clogged in the slit and hinder the function of air release. Further, the protruding rubber adhered to the edge of the mold cannot be removed.

In addition, the liquid cleaning method has the advantage that the aluminum material of the mold does not wear out and that the inside of the vent hole or slit for venting air can also be cleaned.

However, as inorganic acids, nitric acid, sulfuric acid, hydrochloric acid,
Alternatively, when caustic soda or the like is used as an inorganic alkali, they have a good cleaning effect on mold stains, but they have a problem of rapidly corroding aluminum of the mold material. In addition, when an organic alkaline amine-based cleaning agent is used, the cleaning effect of the mold dirt is good and the corrosion is small. However, since it belongs to the fourth class of dangerous goods, safety such as explosion proof of the cleaning device and securing of safety distance is required. In addition to the above problems, there are problems such as odor, wastewater treatment, and high cleaning cost. Another disadvantage of amine-based cleaning agents is that the silicone and Teflon films used for mold surface coating used for mold release are chemically stable, resulting in an insufficient cleaning effect. The problem is that the pattern remains mottled. In addition, the liquid cleaning method has a problem that the protruding rubber adhered to the edge of the mold cannot be removed in any case.

On the other hand, a method of cleaning mold dirt by a low-pressure plasma method in an oxygen gas or freon gas atmosphere can perform uniform cleaning with little processing unevenness, but the low-pressure plasma method is usually performed at a low pressure of 10 Torr or less. In order to carry out this process industrially, a large-sized vacuum device is required.In addition, equipment costs and processing costs are increased in order to perform continuous processing. In addition, such plasma processing generates heat during processing. When the mold is made of aluminum, the heat resistance is low, and the mold may be damaged.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and does not affect the vulcanizing mold made of aluminum or the like by abrasion, corrosion, or the like. It is an object of the present invention to provide a method for cleaning a vulcanization mold that can effectively and easily clean dirt attached to the inside.

[0009]

The present inventors have made intensive studies to achieve the above object, and as a result, have found that a method for cleaning the surface of a vulcanization mold used for vulcanization molding of an elastomer article has been disclosed. It has been found that a method of performing corona discharge in the presence of an atmosphere gas containing one or both of atoms and oxygen atoms and oxidatively decomposing a mold stain with a gas generated by the discharge is effective.

That is, according to this method, since the mold dirt treatment can be performed under the atmospheric pressure, a vacuum device is unnecessary, the device is simple, and not only the mold surface but also the air vent hole and the slit, and The organic material such as rubber protruding from the edge can be effectively ashed and cleaned, including a silicone or fluororesin film as a release film, and the processing temperature around the mold is as low as room temperature to about 200 ° C. Since it is a gas treatment, it wears out aluminum molds,
There is no possibility of affecting corrosion, heat distortion, etc.
Inorganic substances remain on the mold surface after such corona discharge treatment,
It has been found that cleaning of the mold can be performed almost completely and easily by performing a liquid cleaning by spraying the inorganic substance with high-pressure water or a mechanical cleaning method such as a brush.

More specifically, the elastomer article is a rubber product, a rubber composite made of organic fiber or steel cord, and examples thereof include a tire. When such a tire product is vulcanized and formed, stains such as black adhere to the surface of the mold. Table 1 shows the results of analysis of the stain deposits.

[0012]

[Table 1]

From the results of analysis in Table 1, it can be seen that carbon and organic substances other than zinc sulfide can be decomposed by an oxidation reaction, and the present invention can be obtained by corona discharging such oxidatively decomposable soil in the presence of the above-mentioned specific atmosphere gas. It is to be treated and removed by the gas.

Here, the normal oxidation reaction is combustion, and organic components and other carbon are decomposed into carbon dioxide gas and water by high-temperature combustion at 700 ° C. or higher. 550 ° C., which has an adverse effect on the mold.

On the other hand, corona discharge is a type of discharge obtained by applying a DC or AC voltage under a high pressure near or at atmospheric pressure. The oxidative decomposition is represented by the following equation. ^{_{C x H y + O * →}} CO + CO 2 + H 2 O (x, y represents a positive _{number) (C 2 X 6 + CX} 4 + COX 2 + HX) (O *: oxygen excited by corona discharge, in parentheses halogen It is an example of the product when it contains, and X shows fluorine, chlorine, bromine, and iodine.)

The corona discharge oxidizes and decomposes the organic component and the other carbon among the dirt adhering to the mold, leaving only white powdered zinc sulfide as the inorganic component. It is carried out at about ° C and does not require high-temperature oxidation. In addition, since the gas treatment is performed, the entire surface can be uniformly treated by entering the surface of a complicated shape, the vent hole for venting, and the inside of the slit. Therefore, after the corona discharge treatment, only the remaining zinc sulfide needs to be cleaned.

As described above, the method for cleaning a vulcanizing mold of the present invention is a cleaning method using a gas generated by corona discharge, and thus is suitable for cleaning an ordinary mold and especially an insert mold. This insert mold is composed of about nine split molds arranged along the periphery of the insert mold as described in, for example, Japanese Patent Application Laid-Open No. 4-223108. This is a pure-type mold that is composed of about several hundred pieces as a whole, and a gap of about 80 μm existing between the pieces functions as an air vent and has no air vent. In such an insert mold, since there are many gaps between the above-mentioned pieces, dirt and protrusion rubber clogged in the gaps exist, and in the past, the work of disassembling and cleaning several hundred pieces and reassembling them was carried out. In addition, since the deburring work is also required for the deformation burr of the edge portion, the workability is greatly deteriorated, but by employing the cleaning method of the present invention, such a problem can be solved. it can.

In this case, the vulcanizing mold to be particularly cleaned is placed 10 m away from the discharge portion between the electrodes forming the corona discharge region.
m or more, and an atmosphere gas containing halogen atoms and / or oxygen atoms was introduced between the electrodes and corona discharge was performed. The gas generated by this discharge was disposed at a position separated from the discharge portion. By treating the vulcanization mold, mold dirt can be reliably treated as described above, and since the vulcanization mold does not have to be disposed between the electrodes, it is necessary to expose the vulcanization mold to high temperatures. And the capacity of the discharge device can be reduced. The present invention has been made based on the above findings.

Hereinafter, the present invention will be described in more detail. The present invention relates to a method for cleaning the surface of a vulcanization mold used for vulcanization molding of an elastomer article, comprising one or both of a halogen atom and an oxygen atom. A method for cleaning a vulcanizing mold, comprising the steps of: performing a corona discharge in the presence of an atmosphere gas to be discharged, and oxidatively decomposing a mold stain with a gas generated by the discharge.

Here, in the cleaning method of the present invention, the corona discharge is performed in the presence of an atmosphere gas containing one or both of a halogen atom and an oxygen atom. In this case, the halogen atom-containing gas may be F ₂ ,
Simple gases such as Cl ₂ , Br ₂ , I ₂ , HF, HCl, HB
r, hydrogen halide such as HI, CF ₄ , CHClF ₂ , C
Freon such as ClF ₃ , CCl ₂ F ₂ , C ₂ F ₆ , halon such as CBrF ₃ , CHCl ₃ , CH ₂ Cl ₂ , CH ₃ CCl ₃ , C
Examples include halogenated hydrocarbons such as Cl ₄ , SF ₆ , NF _{3 and the} like. Of these, CFCs, halons and halogenated hydrocarbons are preferably used from the viewpoint of easy handling. Also,
Air, O ₂ , H ₂ are gases composed of oxygen atom-containing molecules.
Examples include gases such as O and CO ₂ , and gases of oxygen-containing organic substances such as alcohols, ketones, and ethers. Of these, air and O ₂ are particularly preferably used.

The mixed gas of the halogen atom-containing gas and the oxygen atom-containing gas is preferably an oxygen gas, especially a mixture of air and a small amount of a halogen atom-containing gas. In this case, the mixing ratio of the halogen atom-containing gas is , 0-100
%, Preferably about 0.1 to 80% by volume, and more preferably about 0.5 to 20% by volume. Specifically, the following is preferable as a mixed gas of oxygen (air) and a gas containing a halogen atom.

O ₂ + CCl ₂ F ₂ , O ₂ + CCLF ₃ , O ₂ +
CHClF ₂ , O ₂ + CBrF ₃ , O ₂ + CF ₄ , O ₂ + CF
₄ + CHCl ₃ , O ₂ + CF ₄ + CH ₂ Cl ₂ , O ₂ + CF ₄ +
CCl ₄ , O ₂ + CF ₄ + CH ₃ CCl ₃

When the above-mentioned reaction gas is used, it is preferable to dilute the above-mentioned reaction gas with another gas. Examples of such a gas include general-purpose gases such as nitrogen and hydrogen, rare gases such as argon, and various organic gases. One or a mixture of two or more gases such as a gas can be used. Of these, nitrogen is particularly preferably used. However, when a gas containing a halogen atom is used by mixing with air, it is not always necessary to dilute the gas.
The dilution ratio can be selected from the range of 0.1 to 100%.

These gases do not necessarily need to be in a gaseous state at room temperature, and the method of supply is selected depending on the discharge area temperature, the state at room temperature (solid, liquid, gas) and the like. That is,
If it is gaseous at the temperature of the discharge region or at room temperature, it can be flowed into the processing vessel as it is, and if it is liquid, if its vapor pressure is relatively high, it can be flowed as it is. Alternatively, the liquid may be introduced by bubbling with an inert gas or the like. On the other hand, when it is not gaseous and the vapor pressure is relatively low, it can be used in a gaseous or vapor pressure state by heating.

As a method of generating corona discharge according to the present invention, any method can be employed as long as it can generate corona discharge. The method of applying a voltage can be roughly classified into two types, DC and AC. However, industrially, AC discharge is easier.

When an internal electrode type AC discharge is adopted, it is recommended to coat at least one of the electrodes with an insulator in order to easily obtain a stable discharge. In the present invention, since corrosive gas is generated, both electrodes are preferably covered with an insulator for the purpose of suppressing corrosion of the electrode material. As the insulating material, any generally known material can be used. In particular, ceramics such as mica, alumina, artificial synthetic mica having excellent withstand voltage, and plastics such as silicone rubber and fluororesin are preferably used. .

On the other hand, in the case of DC discharge, a DC corona is formed by direct inflow of electrons from the electrodes, and therefore neither the high-voltage application side electrode nor the ground side electrode is covered with an insulator. In both cases of direct current and alternating current, the electrode material is not particularly limited as long as it has conductivity.

The material of the processing chamber used for corona discharge is not particularly limited, but includes metals such as stainless steel and aluminum, and insulators such as plastic, glass and ceramics. The treatment chamber is not limited as long as it can generate a discharge corona and can arrange the electrodes and the object to be treated, and any material such as a size and a shape can be used.

A preferred example of an apparatus used for carrying out the cleaning method according to the present invention will be described. A vulcanization mold may be arranged between an applied electrode and a ground electrode.
The following devices are preferred. The apparatus shown in FIG. 1 accommodates a vulcanizing mold 2 in a processing chamber 1 in which a corona discharge region is formed, and contains an oxygen atom-containing gas, a halogen atom-containing gas, and a gas for diluting the gas in the processing chamber 1. A gas is supplied from the gas supply pipe 3 and a mold treatment is performed by forming a corona discharge region c between the electrodes 4 and 4. In this case, the vulcanization mold 2 is connected to the electrodes 4 and 4. The processing is performed in a state where the corona discharge processing area c between the four is separated and arranged. The electrodes 4, 4
Are covered with an insulator and are disposed opposite to each other with a predetermined distance therebetween. An AC power supply 5 is connected to one electrode 4 and the other electrode 4 is grounded.
The vulcanizing mold 2 is disposed at a position separated from the discharge portion between the four and the processing is performed. In this case, the electrodes 4, 4
The distance between the vulcanization mold 2 and the vulcanizing mold 2 is preferably 10 mm or more, more preferably 10 mm to several tens m, further preferably 50 mm to 10 m, and most preferably 100 mm to 1 m.
m is desirable. Reference numeral 6 denotes a gas exhaust pipe (exhaust system).

FIG. 2 shows the processing chamber 1 in FIG. 1 in which a discharge chamber 7 is separated from a processing chamber 8, and gas generated by corona discharge in the discharge chamber 7 is introduced into the processing chamber 8 through a gas introduction pipe 9. The surface treatment of the vulcanizing mold 2 arranged in 8 is performed. In this case, the distance between the electrodes 4 and 4 and the vulcanizing mold 2 is preferably the same as above.

FIG. 3 shows that the upper and lower surfaces of the discharge chamber 7 are electrodes 4,
4 is also shown. In this case, it is preferable to cool the electrodes 4 and 4, and the treatment of the vulcanizing mold 2 is performed in the same manner as using the apparatus shown in FIG. 2 and 3, the same components as those in FIG. 1 are denoted by the same reference numerals.
The description is omitted.

Any electrode can be used as long as it can perform corona discharge.
The shape shown in FIG. 1 can be used. 4 is a parallel plate electrode, FIG. 5 is an approximate Rogowski electrode, FIG. 6 is a coaxial cylindrical electrode, FIG. 7 is a sphere electrode, FIG. 8 is a sphere-plate electrode, and FIG.
FIG. 10 shows a needle-plate electrode, and FIG. 11 shows a wire-plate electrode.

As described above, the vulcanizing mold cleaning method of the present invention can remove the organic component of the mold dirt with the gas subjected to the corona discharge treatment. This corona discharge treatment alone is sufficient, but when an inorganic component is contained, it is necessary to perform a post-treatment.

Therefore, the post-treatment depends on the type of the inorganic component.
Preferably, such post-treatments include high pressure
Water spray method, air blow, vacuum suction method, interface
Method of cleaning with water containing activator, water cleaning using ultrasonic
Method, method of rubbing the surface with a rotating brush, acid or alkali
And a method of washing with a liquid.
It can be performed in combination of more than one species. Elastomer
If the article is a rubber product such as a tire, 20 to 200 kg /
cm^Two A washing method using moderately high pressure water is recommended.

[0035]

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

Surface dirt of a mold (insert mold, made of aluminum) used for vulcanization molding of rubber is treated with a gas subjected to corona discharge treatment under the following conditions in the presence of an atmosphere gas shown in Table 2, and post-treatment. And high pressure water washing was performed. The results are also shown in Table 2. Corona discharge conditions: Apparatus: FIG. 3 Electrode: 70 mm × 150 mm, gap 1 mm Frequency: 20 kHz Power: 700 W Pressure: 1 atm

[0037]

[Table 2]

According to the results shown in Table 2, CF was added to air (N ₂ + O ₂ ).
It is recognized that the addition of a freon gas such as ₄ or R22 (CHClF ₂ ) significantly improves the oxidation effect. This is due to the change in color tone (gray when carbon remains, otherwise white with zinc sulfide only) and oxidative decomposition index (approximately 6
Times). Ashing was also observed in the protruding rubber adhered to the edge of the mold.

As described above, the ash residue of the mold stain after the corona discharge treatment is a white powder containing zinc sulfide as a main component. Therefore, cleaning was easily performed by high-pressure water washing in the post-treatment. In addition, the ash residue that could not be washed with high-pressure water remaining in the vent hole or slit inside the air vent inside the mold was washed with an acid that easily dissolves zinc sulfide, such as hydrochloric acid, sulfuric acid, nitric acid, etc. Also, the residue existing deep inside the mold could be discharged outside the mold.

In addition, ashing was also observed in the silicone resin and the fluororesin coated on the surface of the mold for releasing the mold from the elastomer article.

Further, the corona discharge treatment can be carried out at room temperature when the mold is not exposed to electric discharge, and the temperature rises only up to about 200 ° C. even when exposed to electric discharge. This is slightly higher than the tire vulcanization temperature of 150 to 180 ° C., and is not affected by the thermal strain of the aluminum mold.
Further, no influence of corrosion of the mold material on aluminum or iron was observed.

[0042]

According to the method for cleaning a vulcanizing mold of the present invention,
It is possible to easily remove dirt generated by molding not only on the surface of the mold but also on the inside of the vent hole for venting air and the inside of the slit without affecting the mold material such as abrasion and corrosion.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a corona discharge device used in an embodiment of the present invention.

FIG. 2 is a schematic view showing another example of a corona discharge device used in an embodiment of the present invention.

FIG. 3 is a schematic view showing another example of the corona discharge device used in the embodiment of the present invention.

FIG. 4 is a schematic view showing an example of a parallel plate electrode of the corona discharge device.

FIG. 5 is a schematic view showing an example of an approximate Rogowski electrode of the corona discharge device.

FIG. 6 is a schematic diagram showing an example of a coaxial cylindrical electrode of the corona discharge device.

FIG. 7 is a schematic view showing an example of a spherical electrode of the corona discharge device.

FIG. 8 is a schematic view showing an example of a sphere-plate electrode of the corona discharge device.

FIG. 9 is a schematic view showing an example of a needle-needle electrode of the corona discharge device.

FIG. 10 is a schematic view showing an example of a needle-plate electrode of the corona discharge device.

FIG. 11 is a schematic view showing an example of a wire-plate electrode of the corona discharge device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Processing chamber 2 Processing object 3 Gas supply pipe 4 Electrode 5 AC power supply c Corona discharge area

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Toshio Naito 969-1 Magin, Miyamae-ku, Kawasaki City, Kanagawa Prefecture (56) References JP-A-62-44410 (JP, A) (58) Fields investigated (Int. . ^7, DB name) B29C 33/00 - 33/76

Claims (3)

(57) [Claims] 1. A method for cleaning a surface of a vulcanization mold used for vulcanization molding of an elastomer article, wherein corona discharge is performed in the presence of an atmosphere gas containing one or both of a halogen atom and an oxygen atom. A method for cleaning a vulcanizing mold, comprising a step of oxidatively decomposing mold stains with a gas generated by the discharge. 2. A vulcanizing mold according to claim 1, wherein a vulcanizing mold to be cleaned is disposed at a position at least 10 mm away from the discharge portion between the electrodes forming the corona discharge area to perform mold stain treatment. Cleaning method for metal mold. 3. After the step of treating a mold stain according to claim 1 or 2, the residue after the treatment is sprayed with high-pressure water, air blow, vacuum suction, cleaning with water containing a surfactant, and ultrasonic cleaning. A method for cleaning a vulcanizing mold, wherein the vulcanizing mold is removed by any one of a cleaning method of rotary brush cleaning, acid solution cleaning and alkali solution cleaning.