Mold is an important tool used in the tire vulcanization process. During the use of the mold, the mold is inevitably contaminated by the comprehensive deposition of rubber, compounding agents, and mold release agents used in the vulcanization process (the main pollutants are sulfides, inorganic oxides, silicone oil, carbon black, etc.). Caused some patterns to pollute the dead zone. Therefore, the mold must be cleaned frequently to ensure the cleanliness of its surface, so as to ensure the quality of the tire and the life of the mold. In view of this, the development of tire mold cleaning technology has received much attention from the industry.
1. Traditional cleaning methods
There are two types of traditional cleaning methods for tire molds:
(1) Mechanical cleaning method
Using a manual abrasive cloth or steel wire physical grinding and dry sandblasting, different combinations can be selected for cleaning according to needs. The mechanical cleaning method is a mature technology widely used by the tire industry. This method has the advantages of being simple and easy to implement, and has low requirements on equipment and tools; but also has insurmountable defects: it can cause mechanical damage to the mold and shorten the life of the mold; sandblasting can easily block the exhaust hole of the mold, and clear the exhaust after sandblasting The work volume of the stomata is very large; the mold must be disassembled, resulting in high labor intensity and a long cleaning cycle.
(2) Chemical cleaning method
The chemical cleaning method mainly includes the organic solvent method, melting method, pickling method, alkaline washing method, etc.
These methods are easy to use and have low cost, but long-term use of the above methods will cause mold corrosion, which directly affects the appearance and quality of the product; at the same time, these pharmaceutical raw materials pollute the environment and damage the health of the operator, and must have complete labor protection methods and pollutants Processing equipment. At present, the law is mainly used for small rubber products enterprises.
With the continuous development of science and technology, some new technologies have been continuously developed and applied. These cleaning technologies will bring a "revolution" to the tire mold cleaning industry, which has attracted much attention. But whether these higher-invested technologies can be accepted by the market needs to be tested.
The following will focus on introducing several new technologies that have been industrialized.
2. New cleaning technology
(1) Laser cleaning technology
Laser cleaning technology is a new type of cleaning technology that has developed rapidly in the past 10 years. It has gradually replaced the traditional cleaning process in many fields with its own many advantages.
Laser cleaning technology refers to the use of high-energy laser beam to irradiate the surface of the workpiece so that the dirt, rust or coating on the surface can be evaporated or peeled off instantly, and the attachment or surface coating on the surface of the cleaning object can be effectively removed at high speed to achieve a clean process. It is a new technology based on the interaction effect of laser and substance. Unlike the traditional mechanical cleaning method, chemical cleaning method and ultrasonic cleaning method (wet cleaning process), it does not need to use any organic solvent that destroys the ozone layer, no pollution, No noise, no harm to the human body and the environment, is a "green" cleaning technology.
As far as the mechanism of laser cleaning is concerned, laser cleaning uses a cleaning substrate (also called a matrix) and surface attachments (dirt) to have a very different absorption coefficient for a certain wavelength of laser energy. Most of the laser energy radiated to the surface is absorbed by the surface attachments, causing it to be heated or vaporized or evaporated, or instantaneously expanded, and driven by the steam flow formed on the surface, detaching from the surface of the object for cleaning purposes.
It is specifically used for tire mold cleaning. The mold absorbs laser light of a specific wavelength. The energy is extremely small and will not cause damage. The dirt on the surface of the mold (sulfide, an inorganic oxide, silicone oil, carbon black, etc.) absorbs a lot of energy and is instantly expanded. Vaporization and evaporation, take away from the mold surface, so as to achieve the cleaning effect.
The main methods of laser cleaning are:
1) Laser dry cleaning method. That is, using pulsed laser direct radiation decontamination;
2) Laser + liquid film method. That is, first deposit a liquid film on the surface of the substrate, and then use laser radiation to decontaminate;
3) Laser + inert gas method, that is, at the same time of laser radiation, sweep the surface of the substrate with inert gas. When the dirt is peeled from the surface, it will be blown away by the gas immediately to avoid the surface from being contaminated and oxidized again;
4) After using the laser to loosen the dirt, clean it with a non-corrosive chemical method.
At present, the first three methods are commonly used, and the fourth method is only found in the cleaning of stone cultural relics.
The advantages of laser cleaning are: high efficiency, speed, low cost, small thermal and mechanical load on the mold, will not damage the workpiece being cleaned; waste can be recycled, no environmental pollution; safe and reliable, does not damage the health of the operator; Can remove all kinds of dirt with different thickness and different composition; the cleaning process is easy to realize automatic control, remote cleaning and so on.
Disadvantages of laser cleaning: high equipment investment, high maintenance, and use requirements, technology monopolized by foreign countries, subject to technical services, and parts supply.
(2) Dry ice cleaning technology
Dry ice cleaning technology began in the late 1980s and was first applied in the domestic industrial field in the United States. After more than 20 years of development, both in technology, equipment, and applications have been gradually improved and developed and has become a practical cleaning technology.
1) Brief introduction of dry ice cleaning technology
Dry ice cleaning technology is to make liquid CO2 into dry ice spherical particles of a certain size (2-14mm value diameter) through a dry ice preparation machine (granulator), using compressed air as a power source, and spray dry ice washing machine to compare dry ice spherical particles High-speed injection onto the surface of the object to be cleaned (the working principle is similar to the principle of the sandblasting process). The dry ice particles not only have a grinding and impact effect on the dirt surface, but more importantly, the low-temperature effect and sublimation effect of the dry ice particles make the dirt quickly Freeze and embrittlement, and then produce different cold shrinkage effects with the materials it contacts, thereby reducing the adhesion of dirt on the surface of the material, plus the grinding and impact of dry ice particles, the blowing, and shearing of compressed air, The dirt is stripped from the surface to be cleaned in a solid form, and the purpose of removing the dirt is achieved.
2) Dry ice cleaning method
The dry ice cleaning system consists of two parts: the first part is the dry ice granulation system, which functions to solidify the liquid CO2 into dry ice and make it into high-density, equal-size dry ice particles; the second part is the dry ice spray cleaning system, which uses air The compressed air supplied by the press or the factory itself sprays the high-density dry ice particles loaded into the jet cleaning machine with the compressed air through the spray gun to the surface of the workpiece to be cleaned.
The jet cleaning machine can be equipped with a variety of spray guns to clean a variety of dirt and various surfaces. The dry ice granulator and dry ice blasting machine can be assembled together for on-site use, or the dry ice can be pre-granulated, stored in a plastic sealed container, transported to the cleaning construction site, and loaded into the jet cleaning machine for cleaning construction. Generally, the pre-made dry ice particles stored in a sealed container can be kept for 7-10 days.
3) Technical characteristics and process parameters
Dry ice as the cleaning medium of this cleaning technology, its unique physical properties, and process technology determine the following technical characteristics of cleaning tire molds: the hot tire molds that have just been used can be cleaned directly on the vulcanizer without cooling and without removing the mold The cleaning task can be completed; online cleaning can be achieved without damaging the mold and leaving no residue; the small exhaust holes can be cleaned, which is impossible for other cleaning methods; it does not pollute the environment and is non-toxic and non-toxic to the operator Irritation; low labor intensity and short cleaning cycle.