The present invention relates to an ozone decomposing agent for decomposing ozone which is formed, for instance, in a corona charger for electrophotographic copying machines and laser printers, and in the apparatus for purifying water and air in which ozone is employed for such purification.
Ozone is formed by the action of sunlight, ultraviolet light or sparks of thunder on oxygen of the air. It is also formed when electrical apparatus for industrial use produces sparks in the air. For instance, a corona charger employed in copying machine ionizes the ambient air when it is in operation, and such ionization promotes the formation of ozone. Ozone is toxic to human beings and lower animals when breathing air containing more than 0.1 ppm of ozone for long periods of time. According to the safety standards for ozone to human beings proposed by Japan Association of Industrial Health, ACGIH (American Conference of Governmental Industrial Hygienists), and OSHA (Occupational Safety and Health Administration), the permissible maximum average concentration of ozone in the air is 0.1 ppm when breathing the air for 8 hours. Many apparatus for industrial use are produced by observing these standards. Ozone has a characteristic, pungent odor, and the odor is noticeable even at concentrations as low as 0.01 to 0.02 ppm. Some operators of an industrial apparatus which forms ozone at such concentrations may complain about the odor. When the concentration amounts to about 0.05 ppm, it has an unpleasant odor, and when the concentration exceeds 0.1 ppm, it is irritating to mucous membranes of the eyes and respiratory organs.
Further, ozone is a powerful oxidizing agent which oxidizes and deteriorates organic materials. Therefore, it is desirable that the concentration of ozone be as low as possible, not only to human beings, but also to industrial apparatus and devices.
Ozone is employed at concentrations as high as 500-2500 ppm for sterilization of water and for treatment of raw sewage by deodorization and decolorization thereof. For example, when water is sterilized by ozone, 1 to 3 g of ozone is blown into 1 m.sup.3 of water. Most of the ozone blown into water is decomposed in the water, but some of the remaining ozone is discharged from the water into the air. However, since the concentration of the thus discharged ozone in the air is usually as high as 1 ppm, it is necessary to decompose the discharged ozone before it spreads into the air for the safety to human beings and for the protection of environment.
Since ozone is toxic to human beings when its concentration in the air is high, various methods have been proposed to decrease the concentration of ozone.
For example, filters made of an organic hydrocarbon such as activated carbon are employed for sewage purification.
Filters comprising Hopcalite catalyst, such as metal oxides of manganese, copper, silver and cobalt, are also employed for decomposition of ozone. In addition to this, a method of using a paint containing a variety of organic materials has been proposed, although the decomposition efficiency is not high enough for use in practice.
In Japanese Laid-Open Patent Application No. 49-87334, there is proposed a method of decomposing ozone by using a rubber olefin polymer containing double-bond groups with which ozone may react, which method is for use in an electrophotographic copying machine.
In Japanese Laid-Open Patent Application No. 61-64315 there is proposed a method of removing ozone by using terpenoide.
When any of filters containing activated carbon or Hopcalite catalyst is employed, if the density of the filter is high, the absorption of ozone thereto and the ozone decomposition efficiency can be increased. However, the flow rate of the air through the filter decreases and accordingly the pressure loss of the air increases. The result is that the temperature within the apparatus in which such filter is employed may increase and the life of the apparatus may be accordingly shortened. On the contrary, if the density of the filter is decreased, the absorption of ozone and the ozone decomposition efficiency are decreased. In any event, a suction device is necessary for causing the air containing ozone to pass through such filters, and in some cases, a cooling apparatus may become necessary for not raising the temperature within the apparatus. The result is that the entire price of the apparatus becomes high.
When purifying water, a large quantity of activated carbon has to be used so that this method is expensive. Furthermore, the ozone decomposition power of activated carbon significantly decreases when activated carbon comes into contact with an organic solvent such as acetone.
When a rubber olefin polymer is employed for decomposition of ozone, since the reaction of decomposition of ozone is of a solid-to-gas reaction type, the decomposition efficiency is not only low, but also it loses its decomposition power in a short time.
In addition to the above ozone decomposing agents, the following ozone decomposing agents are known: terpenoides capable of decomposing ozone, such as linalool, linalool ester and citral, dissolved in alcohol; natural essential oils containing, for instance, linalool; terpenoids; terpenoids absorbed in an absorbent such as porous silica powder. From these ozone decomposing agents, a terpenoide vaporizes and spreads into the air to react with ozone in the air, thereby decomposing ozone. In these ozone decomposing agents, however, the vaporization rate is not constant and it is difficult to continue the vaporization with a constant rate over a long period of time. More specifically, it has a tendency that it vaporizes very quickly in the beginning, and immediately the varporization drastically decreases. In order to continue the vaporization over a long period of time, a large amount of the ozone decomposing agents is required and therefore these ozone decomposing agents are expensive.