KR100333590B1 - Deodorizer and method for deodorizing in light-regeneration mode - Google Patents

Abstract

PURPOSE: Provided are a deodorizer and a method for deodorizing using the deodorizer in a light-regeneration mode to decompose and remove bad odor generating materials by adsorption and/or using catalyst and to recover original deodorizing performance by radiation of visual or near-UV light. CONSTITUTION: The deodorizer comprises an adsorption material(A) having titanium oxide(IV) and porous material; another adsorption material(B) containing porous material carrying metallic oxides including one or more of iron, chromium, nickel, cobalt, manganese, copper, magnesium and calcium; UV enhancer to promote light oxidation of the titanium oxide by using activated molecules; at least one component selected from a group consisting of light-transmission ceramic and ceramic and light-transmission plastic. The adsorption agents(A,B) may be activated carbon, silica, activated alumina and/or zeolite.

Description

Photo Regenerative Deodorant and Deodorizing Method

The present invention relates to a deodorant for removing odor particles such as odor, and more particularly, it is possible to decompose and remove odorous substances by adsorption removal or catalytic reaction, and visible light such as sunlight when the adsorption performance and decomposition performance are reduced. Or a deodorant method using a photorenewable deodorant and a deodorant capable of restoring a deodorant function by irradiating near ultraviolet rays.

In general, air fresheners or deodorants are used to remove odorous substances present in an enclosed space, such as a room, a car, or a refrigerator for storing food, to maintain a clean state. Looking at the chemical composition of the malodorous gas, amines and mercaptans are the main components in food, and ammonia, lower aldehydes and lower carbonic acids in tobacco smoke.

As described above, a method of removing the malodorous component of the lower odorous compound is generally known, but the most widely used one is using an adsorbent such as activated carbon. Since adsorbents such as activated carbon are inexpensive in terms of price, they are widely used, but it is difficult to remove all kinds of malodorous gases only with adsorbents such as activated carbon.

On the other hand, an impregnated deodorant in which an alkaline substance or an acidic substance is supported on an adsorbent such as activated carbon is used. The impregnated deodorant is more effective in removing malodorous components than an adsorbent made of general activated carbon, but there is a problem in that adsorption removal is not effectively performed for all malodorous gases and the life of the deodorant is shortened. In addition, a method of supporting a catalyst material on an adsorbent is also known, but in the method using the catalyst as described above, there are many cases in which harmful odorous substances are generated due to side reactions such as the formation of disulfides from mercaptans.

In addition, a method of completely regenerating the deodorizing function and semi-permanently extending the life of the adsorbent by the method of completely oxidatively decomposing the malodorous component adsorbed, the deodorizing agent by such a method has a composition in which a noble metal compound is carried on the adsorbent. The deodorant is adsorbed by the odor gas, etc., and then heated at a high temperature of 100 ° C. or higher to regenerate and use the noble metal compound by oxidatively decomposing the odor component. However, this type of deodorant requires a heating source (energy) because it needs to be heated for regeneration. In addition, activated carbon, whose properties change at high temperatures, due to the high temperature of oxidative decomposition, cannot be used as an adsorbent for supporting precious metal compounds. Instead, a non-combustible adsorbent should be used, but the non-combustible adsorbents have a relatively low adsorption capacity.

Recently, a method of removing odorous substances using a photocatalyst represented by titanium oxide has been used as an oxidation catalyst for oxidatively decomposing odorous substances by irradiation with light at room temperature. The photocatalyst can exhibit its oxidative decomposition ability by irradiating light rays, especially near ultraviolet rays, and synthetic fiber products having a deodorizing function by incorporating such photocatalysts into synthetic resins have been developed. However, such a product has a problem that the synthetic resin is oxidized or deteriorated by the strong oxidizing power of titanium oxide during light irradiation.

In order to solve this problem, as shown in Japanese Patent Application Laid-Open No. 9-276706, a product having improved surface durability from oxidation or deterioration while maintaining a deodorizing ability by surface-treating ceramics having no photoactivity has been introduced. In addition, products that improve durability by pairing with inorganic carriers that are not oxidatively deteriorated instead of ceramics are being introduced. However, since the photocatalyst used in these products does not function properly without irradiating light, it can be used in a place where light exists, so it is inconvenient to make a separate light source in a limited or shaded environment. This happens.

Unlike the above, a deodorant that does not require a separate light source is newly showing. That is, as shown in Japanese Unexamined Patent Application Publication No. 1-234729, adsorbents are removed by adsorbing and removing odorous substances in a shaded environment by a combination of an adsorbent such as activated carbon and a photocatalyst. A regenerated adsorbent capable of regenerating was devised. In order to effectively operate an internal photocatalyst in combination with activated carbon in a state where light does not pass through, Japanese Unexamined Patent Application Publication No. 9-75434 proposes to form a shading plastic or the like. However, the regenerated adsorbent formed by the combination with the photocatalyst regardless of the kind of the adsorbent or the support of the catalyst deteriorates the original adsorption performance by the adsorbent, and thus, this method also did not have sufficient deodorization performance in the shading state.

In addition, in order to further improve the performance of the photocatalyst, Japanese Patent Application Laid-Open No. 8-196903 proposes a photocatalyst which coats the surface of a porous body with an oxide film having pores of uniform size, and then covers the surface with a metal film such as platinum. have. However, there is a problem in that the regenerative adsorption agent according to this method is not enough in deodorizing performance in the light shielding state, but also becomes cumbersome in the production of the catalyst.

On the other hand, there is a refrigerator as a representative example of the deodorizing operation in the shading state. As a representative method for deodorizing odorous substances in the refrigerator, conventionally, an inorganic adsorbent capable of regenerating activated carbon or a heater heat carrying a catalyst is used. However, activated carbon carrying a catalyst has excellent deodorizing ability, but also absorbs components such as water vapor and various organic substances that do not need to be removed. Therefore, various products generated by odorous substances or catalytic reactions, for example, methyl mercaptan The performance of removing dimethyl dioxide produced by the catalytic reaction may be further deteriorated. In addition, the regenerated inorganic adsorbent has a disadvantage that the deodorizing performance is not sufficient when odorous substances are generated in a large amount because the adsorption capacity is low and the amount of use is small as compared with catalytically activated carbon. In addition, since the refrigerator is substantially shielded from light, the photocatalyst cannot fully exhibit its performance. Therefore, a problem arises in that the refrigerator is not actually used in the refrigerator.

The present invention has been made to solve the above-mentioned problems, and as the deodorization performance in the shading state, which is a drawback of the conventional photocatalyst, is increased, a small amount of odor gas present in the living space, for example, is present in a refrigerator or an automobile. It is possible to sufficiently adsorb and remove odorous gases such as amines, ammonia, mercaptans, aldehydes, and lower carboxylic acids, even in a shaded state, and take them out of the shielding environment and adsorb them by irradiation with sunlight or fluorescent lamps. It is an object of the present invention to provide a regenerative deodorant which is capable of oxidatively decomposing odor components and recovers a deodorizing function and can be used semi-permanently, and a deodorizing method using such a deodorant.

According to a first aspect of the present invention for achieving the above object, the present invention is an adsorbent (A) carrying a titanium oxide (IV) and made of a porous material, iron, chromium, nickel, cobalt, manganese, copper, Adsorbent (B) consisting of a porous material carrying a metal oxide containing one or two or more kinds selected from the group of metals of magnesium and calcium, and molecules excited by light energy upon irradiation with titanium oxide An ultraviolet light sensitizer for promoting the photooxidation reaction (IV) and at least one component selected from the group consisting of light transmitting ceramics and light transmitting plastics.

The adsorbent (A) and the adsorbent (B) consist of at least one selected from the group consisting of activated carbon, silica, activated alumina and zeolite.

The titanium oxide (IV) is characterized by having an anatase crystal system.

The UV sensitizer consists of p-ethylaniline or p-ethylbiphenyl, and the light-transmissive ceramic consists of at least one of alumina, magnesium and yttrium, and the light-transmissive plastic consists of at least one of methyl polymethacrylate, polycarbonate and polyethylene. .

The optical regeneration deodorant and the deodorization method according to the present invention constituted as described above have the advantage that it can be used semi-permanently as well as improving the deodorization efficiency.

Hereinafter, the present invention having the above characteristics will be described in more detail. First, titanium (IV) is a photocatalyst which exhibits great high active oxidation power by irradiating near-ultraviolet wavelength of 300-400 nm. Titanium oxide (IV) as described above has the ability to oxidatively decompose all of the odorous gases present in the daily living space. Titanium oxide (IV) can be either anatase type or leukeru type, but it is more preferable to use anatase type with high photooxidation ability.

As the adsorbent made of a porous material, any material having a large specific surface area and capable of strongly acting as a Vander wall force and having high physical adsorption can be used. For example, activated carbon, silica, activated aluminum, zeolite, and the like. As can be seen from the fact that these adsorbents have a large specific surface area, not only the externally observable surface but also the inside of the material can provide a large specific surface area by micropores, macropores or cracks. Among the adsorbents described above, preferably, activated carbon having excellent adsorption performance of malodorous substances is used. On the other hand, the adsorbent (A) carrying titanium oxide (IV) and the adsorbent (B) carrying metal oxide may use the same thing in said adsorbent, or may use 2 or more types of different adsorbents.

Activated carbon used in the present invention is usually several hundred square meters per 1g Or it can use widely if it is a carbon material which has a large specific surface area or more and shows high adsorption property. As a raw material of the activated carbon to be used, carbides or coal such as coconut shell or wood are usually used. The activated carbon may also be obtained by any method such as an activation method that is activated at high temperature by steam or carbon dioxide gas, or a chemical treatment method which is treated with a chemical such as zinc chloride, phosphoric acid, or concentrated acid.

The silica used in the present invention is an adsorbent prepared by coagulating a silicate colloidal solution. The main component is silicate-based pore structure and has a specific surface area of 90-500㎡ / g and high adsorption. The pore volume is not particularly limited but is preferably 0.3 ml / g or more in order to have sufficient adsorption performance.

The zeolite used in the present invention is a crystalline aluminate, which is composed of a three-dimensional skeleton and has a pore structure through the inside. In particular, zeolites have a high specific surface area of 500 m 2 / g or more, and have high adsorptivity based thereon. The composition and structure of the zeolite are not particularly limited, and any natural or synthetic product can be used. The pore volume is not particularly limited but is preferably 0.3 ml / g or more in order to have sufficient adsorption performance.

The adsorbent described above can also use a general commercial item. The adsorbent may be used as it is in particle or powder form. It is also possible to process and use various shapes according to a binder as mentioned later. Basically, it is dry-formed, plate-, block-, pipe-, sheet- and paper-like, or wet-forming with liquids such as water, sheet-like, paper-like or corrugated. I can process it and use it. These molding methods can use a well-known method. In addition, it can also apply and apply to a glass tube, a metal plate, etc.

Next, a method of supporting the photocatalyst in the adsorbent as described above will be described. First, the method of supporting a photocatalyst on an adsorbent can also use a conventionally well-known method. That is, a method using a colloidal solution of titanium oxide adjusted in an organic solvent, or a method using a commercially available titanium oxide dispersion liquid or a solution in which commercially available powdered titanium oxide is dispersed in water can be used.

In order to prevent the photocatalyst from falling off during the production process or during use, a small amount of a binder capable of forming a film may be added to these colloidal solutions. The film-forming binder can be used as long as it can dissolve or disperse in water and form a film after drying to fix the photocatalyst. For example, water-soluble high molecular compounds, latex, emulsions, water-soluble inorganic compounds and the like can be used. Examples of the water-soluble high molecular compound include polyacrylamide, polyacrylate, polyethyleneimine, polyvinyl alcohol, polyvinylpyridine, starch, gelatin, carboxymethyl cellulose, acrylic acid ester emulsion, salt vinyl copolymer emulsion, and the like. Examples of the water-soluble inorganic compound include aluminum polyphosphate.

In the present invention, an adsorbent (B) made of a porous material carrying a metal oxide containing at least one or two or more kinds of metals selected from the group of metals of iron, chromium, nickel, cobalt, manganese, copper magnesium and calcium may be used. It is necessary to stick about 0.1-20%. The appropriate concentration for adhering the metal oxide to the adsorbent described above is 0.1-3, preferably 0.5-1, in which a predetermined amount of the metal salt is dissolved in an acid solution, the adsorbent is added to the solution and stirred, and the metal salt is sufficiently adsorbed. The solution is then liquefied and dried at 200 ° C. Next, the metal salt adhered to the carrier is decomposed by heat treatment to make a metal oxide. The supporting amount of the metal oxide is appropriately about 0.1-20%, and preferably, the supporting amount is about 0.5-2%.

When the supported amount of the metal oxide is 0.1% or less, the catalytic activity is insufficient, and when the supported amount of the metal oxide is 20% or more, the adhesion amount is large and the catalytic performance is not relatively improved, and the adsorption performance of the adsorbent itself as a carrier is impaired. Considering these points, the amount of loading needs to be 20% or less. The carrying amount adjustment of the metal oxide is performed by changing the comparison between the amount of the metal salt in the acid aqueous solution and the amount of the adsorbent. Usually, the metal salts in solution are almost completely adsorbed by the adsorbent. By heat-processing this at the temperature of about 200 degreeC, the adsorbent which immobilized the metal oxide is produced.

In addition, the ultraviolet sensitizer used in the present invention needs to be a substance having an effect of promoting the photooxidation reaction of titanium oxide (IV) by molecules excited to an active state by light energy upon irradiation with ultraviolet rays. For example, p-ethylaniline, p-ethylbiphenyl, etc. can be used.

On the other hand, the light-transmissive plastic needs to have a property of guiding the light to be split due to high light transmittance into the molding. In other words, it is necessary to have a function of guiding a light beam irradiated to the surface of the molded product deep inside the molded product and promoting a photochemical reaction. For example, polymethyl methacrylate, polycarbonate, polyethylene, etc. are preferable. The light transmitting plastics, the light transmitting ceramics, and the ultraviolet sensitizer may also be mixed with other molding binders such as polyethylene powder, carboxymethyl cellulose, and silica adhesives.

In the present invention, as the light-transmitting ceramic, a ceramic having a property of guiding a high light-transmitting ray into the molding may be widely used. In particular, a material having low light reflectance and low light reflectance may be used. For example, light-transmissive alumina, magnesium, yttrium and the like can be used. These ceramics have a function of guiding light rays irradiated to the surface of the molding deep inside the molding and promoting photochemical reaction.

The amount of titanium oxide supported on the adsorbent (A) is preferably supported on the pore inlet and outer portions of the adsorbent from the viewpoint of the performance preservation of the adsorbent and the effective use of the irradiated light beam. Thus selected. That is, when the adsorbent is a particle, the amount of titanium oxide that can be supported is selected according to the degree of particle size, but in order to improve the photoregeneration effect, it is not necessarily effective to increase the amount of the adsorbent (A) supported. It is more preferable to increase the addition of the adsorbent (A) carrying an amount of titanium oxide. In addition, in order to improve the adsorption performance of the malodorous substance in the light shielding state which is the subject of the present invention, it is preferable to increase the composition of the adsorbent (B).

In addition, an ultraviolet sensitizer, a translucent ceramic, and a translucent plastic may be used together, and you may use two or one type in between. As a result, the photocatalyst of the present invention can be used by adding a platinum compound having better oxidation catalytic properties or an oxide such as nickel or iron. In addition, for example, quartz glass fiber or the like may be used, which is a material having a suitable shape for guiding the light rays into the molded product and having a high light transmittance and preferably a high light transmittance of near ultraviolet rays.

The shape of the deodorant according to the present invention may be used in the form of particles or powder, as described with respect to the adsorbent described above, but the form mainly used is a lattice, plate, block, pipe, sheet formed using a binder or an adhesive. It is often used in the form of phase, ground or wave shape.

The deodorant of the present invention has a function of substantially removing a small amount of odor gas present in the light shielding space. For example, a small amount of amines, ammonia, mercaptans, aldehydes, and the like present in the interior of a refrigerator or an automobile, and After adsorption and removal of malodorous gases such as lower carboxylic acids, there is an effect of oxidatively decomposing malodorous components adsorbed into odorless components by irradiating light rays. As the analyzed component is released, the function of removing the odor gas of the deodorant is regenerated and it is possible to use it semipermanently. This is the biggest feature of the present invention deodorant.

In particular, the deodorant of the present invention improves the ability of the conventional photocatalyst to adsorb and remove malodorous gas in a shielded state, and furthermore, it has a sufficient photoregeneration function even with a smaller amount of photocatalyst and is excellent in durability. The malodorous gas adsorbed is regenerated as it is oxidatively decomposed by lighting of direct or indirect sunlight or ultraviolet lamps during the day. The content of the adsorbent (A) carrying the photocatalyst and the adsorbent (B) carrying the metal oxide and made of a porous material is selected by the balance between the adsorption capacity and the regeneration ability at the time of shading, depending on the use or purpose.

The place of use of the deodorant of the present invention is not particularly limited, but a place where it is easy to take out for regeneration and at the same time has a high deodorizing effect is preferred. If the shading environment has a circulation function of air, it is preferable to install at the inlet or outlet of the circulation device or the circulation device to improve the deodorizing performance. In addition, it is preferable to use a suitable protective water for the installation of the deodorant, it is possible to easily remove from the protective water so that regeneration is easily achieved, or it is also possible to use a transparent material if not removed.

Ultraviolet lamps, high-pressure mercury lamps, and the like can also be used as light sources of near-ultraviolet light for regeneration. However, these lamps are expensive and consume extra energy. It is preferable to take out and expose to sunlight. In this case, in order to effectively use the near-ultraviolet rays contained in these light rays, it is preferable to use a ultraviolet sensitizer and to use a binder having high light transmittance.

The photocatalyst used in the present invention usually has a sufficient deodorizing performance even at room temperature, but when a nonflammable light-transmitting ceramic such as alumina is formed as a binder by using a non-flammable zeolite as an adsorbent, the photocatalyst can be used at a high temperature of 200 ° C or higher.

Next, a preferred embodiment of the deodorant preparation according to the present invention will be described in more detail.

As the adsorbent, activated carbon having a particle size of 32-60 mesh obtained by using a palm shell as a raw material was used. 30 ml of tetraisopropoxytitanium titanium was dripped gradually in 90 ml of 1 mol of nitric acid aqueous solutions, stirring at room temperature, and stirring was continued for about 3 hours, and transparent titanium oxide was prepared. Furthermore, 600 ml of distilled water was added, 1 mol of sodium hydroxide aqueous solution was added, it adjusted to pH3, and the colloidal solution of titanium oxide was prepared.

Add 100 g of coconut shell activated carbon to this colloidal solution and stir for 1 hour. The titanium oxide-supported activated carbon was washed with distilled water until the pH of the washing liquid became 6 or more. This was vacuum dried at room temperature, and then calcined at 300 ° C. for 1 hour to prepare titanium (IV) supported activated carbon. Furthermore, it was confirmed that titanium oxide obtained by hydrolyzing tetraisopropoxytitanium under the same conditions without adding activated carbon had an anatase crystal system by XRD (X-Ray diffraction) measurement.

In addition, 50 g of activated carbon (KURARAY CHEMICAL Co., Ltd. product name "KURARAY COAL-GW") of particle size 32-60 mesh obtained by using a palm shell as a raw material was added to 200 ml of 0.5 normal acid solution containing 1.0 g of metal salts, and stirred well, After standing for 3 hours, water was cut off, washed with 100 ml of pure water, and dried at 200 ° C. to obtain a metal oxide-bonded activated carbon having a metal oxide deposition amount of 2.0 wt%.

20 g of the titanium oxide-supported coconut shell activated carbon prepared in this way, 30 g of metal oxide-impregnated activated carbon, and 27 g of activated carbon (KURARAY CHEMICAL Co., Ltd.) "KURARAY COAL-GW" with a particle size obtained by using palm shell as raw materials After mixing 1 g of zein p-nitroaniline, 2 g of translucent alumina powder, and 20 g of polyethylene powder binder, the mixture is filled into a mold, heated to 130 ° C., cooled under pressure, and cooled to 200 mm in thickness, 7 mm in diameter, and 4 mm holes. Nine lattice shapes were obtained.

One of these plate-shaped molded bodies was put in a desiccator having a capacity of 3.8 liters, and a odor gas removal test was performed. As the odor gas, methyl mercaptan and trimethylamine, which are main components of the odor gas generated in the refrigerator, were used. The malodorous gas was injected so as to have an initial concentration of 500 ppm, and the residual concentration of methyl mercaptan after 3 hours and trimethylamine after 4 hours were measured. In addition, the test was performed with the alumina foil around the desiccator and the light from outside. Photoregeneration was carried out for 1 day in daylight by removing the deodorant. After photoregeneration, the same test was repeated to evaluate the regeneration effect.

Table 1 and Table 2 show the results of the deodorization test at 25 ° C. for methyl mercaptan and trimethylamine.

TABLE 1

Deodorization performance of methyl mercaptan (residual concentration after 3 hours, unit ppm)

TABLE 2

Deodorization performance of trimethylamine (residual concentration after 4 hours, unit ppm)

Example 2 A slurry obtained by mixing 1 g of commercially available titanium dioxide (Sukwon Industrial Co., Ltd. product name "ST-21") and 20 g of water as a photocatalyst was activated carbon having a particle size of 30-60 mesh obtained by using coconut shell as a raw material (KURARAY). 30 g of CHEMICAL Co., Ltd. brand name "KURARAY COAL-GW") and 20 g of polyethylene powder binder were used, and the odor gas removal test was done like Example 1 using the plate-shaped molded object produced like Example 1 above. The result is combined with Table 1 and Table 2, and is shown.

(Comparative Examples 1 and 2) The odor gas removal test was conducted in the same manner as in Example 1 except that the plate-shaped molded bodies prepared in Examples 1 and 2 were used as photocatalysts and photoregenerated and tested in the dark room. The results are also shown in Table 1 and Table 2 together.

(Comparative Example 3) Except that 80 g of the photocatalyst impregnated carbon obtained in Example 2 and 20 g of polyethylene powder binder were used, the plate-shaped molded product produced in the same manner as in Example 2 was used, and the odor gas was removed in the same manner as in Example 1. The result is combined with Table 1 and Table 2, and is shown.

(Example 3) The molded product of the photocatalyst impregnated coal obtained in Example 2 was put into 3.8 liter of desiccant, and the odor gas removal test was done. As the odor gas, dimethyl disulfide, the main component of the odor gas generated in the refrigerator, was used. The odor gas was injected at an initial concentration of 3000 ppm and the residual concentration was measured after 2 hours. Furthermore, during the test, the surroundings of the desigate were covered with alumina foil, and the light from outside was blocked. Photoregeneration was carried out by daytime sunlight by taking out the deodorant. After photoregeneration, the same test was repeated to evaluate the photoregeneration effect.

(Comparative Example 4) The deodorizing performance was evaluated in the same manner as in Example 3 except that the test was conducted in the dark room and was not regenerated.

Table 3 shows the results of the deodorization test at 7 ° C for Example 3 and Comparative Example 4.

TABLE 3

Deodorization performance of dimethyl disulfide (residual concentration after 2 hours, unit ppm)

As shown in the above experimental results, by using the deodorant according to the present invention even in a shading space having less effect when using a conventional photocatalyst, not only the odor gas removal performance is excellent but also the deodorization performance can be reproduced by irradiation of light after use. It is possible to use semi permanently. That is, the deodorizing agent according to the present invention as described above adsorbs odorous gases such as trace amounts of amines, ammonia, mercaptans, aldehydes and lower carbon acids present in a substantially shielded space such as a refrigerator or a car interior. By simply exposing it to sunlight or the like, the odor component is oxidized and decomposed to become an odorless component, and thus, the deodorizing performance is regenerated so that it can be used almost semipermanently.

Claims (4)

An adsorbent (A) carrying titanium oxide (IV) and made of a porous material; An adsorbent (B) made of a porous material carrying a metal oxide containing one or two or more selected from a metal group consisting of iron, chromium, nickel, cobalt, manganese, copper, magnesium and calcium; An ultraviolet sensitizer in which molecules excited to light state by irradiation with ultraviolet rays promote the photooxidation reaction of titanium oxide (IV); An optical regeneration type deodorant comprising at least one component selected from the group consisting of a light transmitting ceramic and a ceramic and a light transmitting plastic. The optical regeneration type deodorant according to claim 1, wherein the adsorbent (A) and the adsorbent (B) are at least one selected from the group consisting of activated carbon, silica, activated alumina and zeolite. The optical regeneration type deodorant according to claim 2, wherein the titanium (IV) oxide has an anatase crystal system. The method of claim 1, wherein the ultraviolet sensitizer is composed of p-ethylaniline or p-ethylbiphenyl, the light-transmissive ceramic consists of at least one of alumina, magnesium and yttrium, the light-transmissive plastic is polymethyl methacrylate, polycarbonate , Optical regeneration deodorant characterized in that made of at least one of polyethylene.