WET-LAID NON-WOVEN FABRIC FOR HYDROCARBON TRAP OF AIR CLEANER FOR GASOLINE ENGINE AND MANUFACTURING METHOD THEREOF

Abstract

The present invention provides a wet-laid non-woven fabric for a hydrocarbon trap of an air cleaner or gasoline engine, wherein powdery activated carbon having specific physical properties, pulp, a synthetic fiber having specific physical properties and a carbon binder are used as basic materials to prepare a web type non-woven fabric; and this fabric is formed into a wet-laid non-woven fabric having a predetermined thickness through compressing, so that: when using the fabric in an air cleaner, this may adsorb volatile oil vapor such as hydrocarbon contained in evaporation gases generated from a fuel of the engine, and then, desorb the same when driving the engine, thereby preventing outflow of the hydrocarbon as a main cause of air pollution to an outside; and further, damage to a passenger in a vehicle due to hydrocarbon gas may be minimized, and a manufacturing method thereof.

Claims

1. A wet-laid non-woven fabric for a hydrocarbon trap of an air cleaner for a gasoline engine, which is installed in the air cleaner for a gasoline engine to capture hydrocarbon in evaporation gases generated from a fuel in a combustion chamber of an engine or a fuel storage tank during driving or stoppage of a vehicle, or to recover the captured hydrocarbon to the engine so as to be reburned therein, the wet-laid non-woven fabric comprising: basic materials including powdery activated carbon, pulp, a synthetic fiber and a carbon binder, wherein the powdery activated carbon has an average particle size in a range of 20 to 150 m and contains 45 to 90% of meso-structure, and the synthetic fiber has a diameter of 30 m or less and a melting point of 110 C. to 270 C.

2. The wet-laid non-woven fabric according to claim 1, wherein the synthetic fiber includes at least one synthetic fiber selected from an ultra-fine fiber, a fine fiber, a split fine type fiber, and a sea-island type fiber; or at least one selected from sheath/core or side by side type composite melting point fibers which are selected from PP/PE, PET/PE, PET/PP and PET/Nylon.

3. The wet-laid non-woven fabric according to claim 1, wherein the basic materials include 45 to 80 wt. % of the powdery activated carbon, 3 to 13 wt % of the pulp, 10 to 30 wt. % of the synthetic fiber and 3 to 12 wt. % of the carbon binder.

4. The wet-laid non-woven fabric according to claim 3, further comprising: in addition to the basic materials, at least one of 0.05 to 2.0 wt. % of a dispersant, 0.2 to 1.0 wt. % of a water repellent agent, 0.05 to 1 wt. % of a carbon fixing agent and 0.05 to 1.0 wt. % of a dehydration enhancer based on a total composition of the non-woven fabric.

5. The wet-laid non-woven fabric according to claim 1, wherein the powdery activated carbon has a specific surface area of 1,000 to 3,000 m.sup.2/g.

6. A method for manufacturing a wet-laid non-woven fabric for a hydrocarbon trap of an air cleaner for a gasoline engine, which is installed in the air cleaner for a gasoline engine to capture hydrocarbon in evaporation gases generated from a fuel in a combustion chamber of an engine or a fuel storage tank during driving or stoppage of a vehicle or to recover the captured hydrocarbon to the engine so as to be rebumed therein, the method comprising: preparing basic materials which include powdery activated carbon, pulp, a synthetic fiber and a carbon binder, wherein the powdery activated carbon used herein has an average particle size in a range of 20 to 150 m and contains 45 to 90% of meso-structure, and the synthetic fiber used herein has a diameter of 30 m or less and a melting point of 110 C. to 270 C.; passing the basic materials through a suspension process to prepare a suspension; subjecting the basic materials passed through the suspension process to a web formation process to form a web type product; subjecting the web type product to a water removal process; drying the web type product in a drying process after the water removal process; and subjecting the web type product after the drying process to a heat compressing process to conduct heat compressing and molding, so as to form a sheet type or roll type fabric.

7. The method according to claim 6, wherein the synthetic fiber uses at least one synthetic fiber selected from an ultra-fine fiber, a fine fiber, a split fine type fiber, and a sea-island type fiber; or at least one selected from sheath/core or side by side type composite melting point fibers which are selected from PP/PE, PET/PE, PET/PP and PET/Nylon.

8. The method according to claim 6, wherein the basic materials include 45 to 80 wt. % of the powdery activated carbon, 3 to 13 wt % of the pulp, 10 to 30 wt. % of the synthetic fiber and 3 to 12 wt. % of the carbon binder.

9. The method according to claim 7, wherein the wet-laid non-woven fabric further comprises, in addition to the basic materials, at least one of 0.05 to 2.0 wt. % of a dispersant, 0.2 to 1.0 wt. % of a water repellent agent, 0.05 to 1 wt. % of a carbon fixing agent and 0.05 to 1.0 wt. % of a dehydration enhancer based on a total composition of the non-woven fabric.

10. The method according to claim 6, wherein the heat compressing process is a process of heat pressing and molding the product that has a weight of 300 to 800 g/m.sup.2 and a thickness of 2.2 to 3.6 mm through the heat compressing process so as to have a thickness of 0.6 to 1.8 mm while maintaining the same weight of 300 to 800 g/m.sup.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0044] FIG. 1 is a block diagram illustrating a process of manufacturing a wet-laid non-woven fabric for a hydrocarbon trap of an air cleaner for a gasoline engine according to the present invention;

[0045] FIG. 2A is a photograph illustrating a size distribution of structures of activated carbon for each pore size according to the present invention;

[0046] FIG. 2B is a partially enlarged photograph illustrating a pore structure of the activated carbon according to the present invention;

[0047] FIG. 2C is a graph illustrating an increase or a decrease (that is, variation) in a pore volume depending on a distribution of meso-structure and micro-structure pores of the activated carbon according to the present invention; and

[0048] FIG. 3 is views illustrating cross-sectional structures of fibers preferably applied to a synthetic fiber according to the present invention, which is views conceptually illustrating a variety of shapes of sheath/core or side by side type composite melting point fibers.

DETAILED DESCRIPTION OF THE INVENTION

[0049] Hereinafter, a method for manufacturing a wet-laid non-woven fabric for a hydrocarbon trap of an air cleaner for a gasoline engine, as well as the wet-laid non-woven fabric for a hydrocarbon trap manufactured by the same will be described in detail with reference to accompanying drawings by means of an embodiment.

[0050] FIG. 1 is a block diagram illustrating a process for manufacturing a wet-laid non-woven fabric for a hydrocarbon trap of an air cleaner for a gasoline engine according to the present invention.

[0051] Referring to FIG. 1, the method for manufacturing a wet-laid non-woven fabric for a hydrocarbon trap of an air cleaner for a gasoline engine according to a preferred embodiment of the present invention is illustrated. Herein, the method for manufacturing a wet-laid non-woven fabric is described for each step, wherein the wet-laid non-woven fabric is installed in the air cleaner to capture hydrocarbon in evaporation gases generated from a fuel in a combustion chamber of an engine or a fuel storage tank during driving or stoppage of a vehicle, or to recover the captured hydrocarbon to the engine so as to be rebumed therein.

[0052] FIG. 2A is a photograph illustrating a size distribution of a meso-structure of activated carbon structures according to the present invention, FIG. 2B is a partially enlarged photograph illustrating a pore structure of the activated carbon according to the present invention, and FIG. 2C is a graph illustrating an increase or a decrease (that is, variation) in a pore volume depending on a distribution in pore sizes of meso-structure and micro-structure pores of the activated carbon according to the present invention.

[0053] Referring to FIGS. 2A to 2C, if the distribution of the meso-structure in the activated carbon components according to the preferred embodiment of the present invention is higher, repeatedly using the non-woven fabric is advantageous. Therefore, the above non-woven fabric may be semi-permanently used in repeat processes of absorption-desorption-adsorption-desorption.

[0054] FIG. 3 is views conceptually illustrating a variety of shapes of sheath/core or side by side type composite melting point fibers preferably applied to a synthetic fiber according to the present invention.

[0055] Referring to FIG. 3, as the synthetic fiber according to the present invention, when using a synthetic fiber having a diameter of 30 m or less and a composite melting point fiber, powdery activated carbon may be adhered and bonded to the melting point fiber while isolating the activated carbon between the fibers, so as to prevent release of the activated carbon and allow the activated carbon to be bonded to a specific synthetic fiber, and thereby decreasing a content of the used carbon binder.

[0056] Further, the wet-laid non-woven fabric for a hydrocarbon trap of an air cleaner for a gasoline engine, which is produced by the method for manufacturing a wet-laid non-woven fabric for a hydrocarbon trap of an air cleaner for a gasoline engine may be installed in the air cleaner, in particular, may be fixed and mounted on a housing of the air cleaner through ultrasonic fusion.

[0057] In this case, the wet-laid non-woven fabric for a hydrocarbon trap of an air cleaner for a gasoline engine according to the present invention may include basic materials including powdery activated carbon, pulp, a synthetic fiber and a carbon binder. Further, the basic material may include at least one additive selected from a dispersant, a water repellent agent, a carbon fixing agent and a dehydration enhancer.

[0058] Meanwhile, in order to produce a wet-laid non-woven fabric, the method for manufacturing the same may include: a suspension process S110 of mixing the basic materials described above and the additive as necessary to prepare a suspension; a web formation process S120 of forming the suspension into a web type product; a water removal process S130 performed on the web type product to discharge water; a drying process S140 of drying the same; and a heat compressing process S150 of heat compressing and molding the product after the drying process S140, thereby forming a sheet type or roll type fabric.

[0059] According to the preferred embodiment of the present invention, the basic materials may have the most preferable composition of components such as 45 to 80 wt. % of powdery activated carbon, 3 to 13 wt. % of pulp, 10 to 30 wt. % of a synthetic fiber, and 3 to 12 wt. % of a carbon binder.

[0060] Further, the additive further included in the basic material preferably may include: 0.05 to 0.2 wt. % of a dispersant; 0.2 to 1.0 wt. % of a water repellent agent; 0.05 to 1.0 wt. % of a carbon fixing agent; and 0.05 to 1.0 wt. % of a dehydration enhancer based on a total composition of the wet-laid non-woven fabric.

[0061] According to the preferred embodiment of the present invention, the powdery activated carbon used herein may have an average particle size in a range of 20 to 150 m. If the particle size is too small, adsorption efficiency is low and it becomes much dusty during production, thus not being preferable. On the other hand, if the particle size is too large, overall adsorption effects may be reduced and the activated carbon powders may be possibly released during the manufacturing process or when using the activated carbon by applying to the trap.

[0062] In addition, if the particle size of the activated carbon is less than 20 m, the activated carbon in a wire suction process to remove water from the suspension for wet-laid non-woven fabric may be drained quite a lot along with the water. Further, if the activated carbon having a particle size of 20 m is too much, a suction pressure is considerably higher and may make it impossible to manufacture the wet-laid non-woven fabric.

[0063] Further, when using the activated carbon having an average particle size of more than 150 m in a hydrocarbon trap (HC Trap), the activated carbon particles may adversely affect the engine if the activated carbon particles are mixed up into the engine upon occurring vibration after mounting the same in an engine air cleaner.

[0064] In other words, if a weight of the activated carbon is low, butane adsorption capacity is also low while a filtration area is increased, and a large amount of the activated carbon is required due to a small space of a housing of the engine air cleaner. On the other hand, if the weight of the activated carbon is too high, an amount of the activated carbon is increased to cause a deterioration in ultrasonic adhesiveness to the housing of the engine air cleaner, and it is difficult to form a housing structure of the engine air cleaner in a plate or circular shape.

[0065] The present invention uses pulp. Due to a strong hydrogen bond, the pulp allows smooth transportation of a filter medium in a wet state. Further, powdery activated carbon may be substantially adhered to a plate-shaped pulp structure. Therefore, if an amount of pulp used herein is too small, activated carbon adhesion efficiency is low. On the other hand, if the amount thereof is too large, a high vacuum pressure occurs during a water removal process although the activated carbon is adhered well. As a result, the water is not removed, thereby causing a deterioration in overall adsorption/desorption effects.

[0066] According to the preferred embodiment of the present invention, the pulp may typically include NBK (CANFOR Pulp and Paper Co.), but it is not limited thereto.

[0067] Further, according to the preferred embodiment of the present invention, powdery activated carbon having a particle size in a range of 20 to 150 m may be used. In this case, the powdery activated carbon preferably has a specific surface area of 1,000 to 3,000 m.sup.2/g, and more preferably, 2,000 to 3,000 m.sup.2/g. If the specific surface area thereof is too small, excess of activated carbon should be used. In particular, at largest 2-fold content of the activated carbon needs to be included, thus causing a difficulty in manufacturing a wet-laid non-woven fabric. Further, if the specific surface area thereof is larger than 3,000 m.sup.2/g, an apparent density of the activated carbon is increased and a volume thereof becomes large to cause an increase in a thickness of the wet-laid non-woven fabric to be produced. For this reason, a mixing ratio of the melting point fine fibers or a content of the synthetic fiber should be considerably increased more than 30%. In addition, a temperature and a pressure should be further increased in a heat compressing process of the wet-laid non-woven fabric, thus not being preferable.

[0068] A fine fiber generally refers to a thread having a thickness of 1 denier (5 m) or less. Typically, the fine fiber is a fiber developed to have very soft and smooth touch feel. Depending upon splitting a spun fiber, finest fibers with maximum 0.001 denier may be fabricated, which are generally used for artificial suede requiring softness or a cloth for cleaning a lens such as glasses.

[0069] In the present disclosure, a melting point fine fiber commonly refers to fibers fabricated using a fine fiber, an ultra-fine fiber, a split fine type fiber, and a sea-island type fiber, etc, which have a melting point of 110 to 270 C. and a diameter of 30 m or less. Any synthetic fiber may be used without particular limitation thereof so far as it can satisfy the above-described melting point and thickness.

[0070] The powdery activated carbon used in the present invention should have the above-described specific surface area. Nevertheless, it is preferable that the powdery activated carbon in the present invention has a specific pore structure. The pore structure of the activated carbon used in the present invention may include a meso-structure of 45 to 90%, and preferably, 60 to 90%. If the content of the meso-structure in the powdery activated carbon is less than the above range, an adsorption capacity of the volatile oil vapor is drastically reduced. If the above content is too much, there is a difficulty in production of the activated carbon without any economic advantage. Furthermore, the volatile oil vapor is not adsorbed but may remain after adsorption of the same without further increasing the adsorption capacity.

[0071] Herein, the meso-structure means that the activated carbon has a pore size in a range of 2 nm to 50 nm. The present invention may use the powdery activated carbon having the meso-structure in a specific range to remarkably improve characteristics of repetitive adsorption-desorption-adsorption-desorption of volatile oil vapor.

[0072] In this regard, FIG. 2A illustrates a distribution of the meso-structure among the pore structures of the activated carbon. In consideration of using the characteristics of repetitive adsorption-desorption-adsorption-desorption of volatile oil vapor by the activated carbon, the distribution of the meso-structure is more significant in the present invention than the micro-structure or meso-structure itself.

[0073] In particular, referring to FIG. 2C, it can be seen that that the distribution of the meso-structure in the activated carbon is significant, wherein the graphs illustrate results of experiments for the micro- and meso-pore structures to the activated carbon obtained by using a specific surface area measurement method developed by Brunauer, Emmett and Teller (BET). Among the graphs in FIG. 2C, a dotted line shows the micro-pore structure while a solid line shows the meso-pore structure. Therefore, it could be confirmed that the activated carbon including 45 to 90% of the meso-structure indicated by a longitudinal solid line, which is within a range of hydrocarbon trap (HC Trap), had excellent adsorption/desorption effects.

[0074] According to the present invention, the content of the above-described meso-structure in the powdery activated carbon is not absolutely proportional to the specific surface area. Even when the specific surface area is small, the content of the meso-structure may be increased depending on a formation ratio of the macro-structure having a larger diameter than the meso-structure or the micro-structure having a smaller diameter than the meso-structure. On the other hand, even if the specific surface area is large, the meso-structure may be included in a small quantity. A distribution of the content of the meso-structure in the powdery activated carbon and the content of macro- or micro-structure may be varied to a great extent according to a production process and conditions of the activated carbon as well as raw materials thereof.

[0075] Therefore, according to the present invention, it is expected that, only when using the powdery activated carbon containing the meso-structure in a content of 45 to 90% among the powdery activated carbons used as the basic materials, synergistic effects for the adsorption/desorption effects of volatile oil vapor may be achieved by other components to be blended, that is, a specific synthetic fiber and an entire composition of the basic materials such as pulp and a carbon binder.

[0076] Further, as the specific surface area and the meso-structure of the activated carbon are larger, absorption/desorption abilities of butane are more excellent. Furthermore, if the specific surface area is small and the meso-structure is developed, a weight of the required activated carbon is increased. Therefore, a method for preparation of the activated carbon containing more than 90% meso-structure has no economic advantage, such that there is no effectiveness for accomplishing the objects of the present invention.

[0077] Accordingly, the present invention uses the powdery activated carbon having an average particle size in a range of 20 to 150 m and a specific surface area in a range of 1,000 to 3,000 m.sup.2/g, as well as forms a wet-laid non-woven fabric wherein a structure of the activated carbon includes 45 to 90% of meso-structure. Therefore, when using the wet-laid non-woven fabric for a hydrocarbon trap, hydrocarbon contained in evaporation gases generated from a fuel in a combustion chamber of the engine or a fuel storage tank during stoppage of the engine in a vehicle may be efficiently captured and easily desorbed with regard to an entire size regardless of the size of the hydrocarbon.

[0078] As such, the evaporation gas generated during startup stoppage of an engine may be formed from the residual fuel around a fuel injector after the startup stoppage of the engine, or the fuel in the combustion chamber of the engine or the fuel storage tank. The evaporation gas includes hydrocarbon gas which is necessary to be captured. According to the present invention, when using a wet-laid non-woven fabric manufactured by using the powdery activated carbon which includes 45 to 90% of meso-structure and has a particle size in a range of 20 to 150 hydrocarbon may be more efficiently captured with regard to an entire size regardless of the size of the hydrocarbon itself.

[0079] According to the present invention, the average particle size of the above-described powdery activated carbon and the distribution characteristic of the meso-structure in the same are very important factors in relation to an entire volatile oil vapor adsorption ability of the wet-laid non-woven fabric and quality of hydrocarbon trap. In particular, these factors may also serve as conditions for expecting selective characteristics of the synthetic fiber to be described below as well as synergistic effects of overall quality and adsorption/desorption effects of volatile oil vapor, thus being of great significance.

[0080] According to the preferred embodiment of the present invention, the synthetic fiber used herein may have a diameter of 30 m or less, preferably, 10 m or less, and a melting point of 110 C. to 270 C. If the diameter thereof is too large or the melting point thereof is not defined within the above range, when the synthetic fiber is used for manufacturing a wet-laid non-woven fabric which in turn is applied to the hydrocarbon trap, release of the activated carbon particles may occur, in the manufacturing of a non-woven fabric by heat pressing, the pressing is not well performed. Further, capturing effects such as prevention of release of the activated carbon particles may be hardly expected. Accordingly, desired quality may not be achieved.

[0081] According to the preferred embodiment of the present invention, the synthetic fiber used herein may include, for example, at least one selected from an ultra-fine fiber, a fine fiber, a split fine type fiber, and a sea-island type fiber; or at least one selected from sheath/core or side by side type composite melting point fibers which have a melting point of 110 C. to 270 C. and are selected from PP/PE, PET/PE, PET/PP and PET/Nylon.

[0082] Herein, PP, PE and PET refer to polypropylene, polyethylene and polyethylene terephthalate, respectively.

[0083] In this regard, FIG. 3 shows a variety of sheath/core type or side by side type composite melting point fibers, in particular, fibers having a fiber diameter of 10 m, to conceptually illustrate cross-sectional structures of the composite melting point fibers. The synthetic fiber usable in the present invention is not particularly limited thereto, instead, other similar type composite melting point fibers or composite melting point fibers including other similar components may also be used.

[0084] Further, according to the present invention, other synthetic fibers may also be used so far as they have a diameter and a melting point within the above-described ranges.

[0085] The reason for using the above-described synthetic fibers is that these can prevent release of the powdery activated carbon used together and minimize an amount of the used carbon binder, such that the carbon binder does not hinder the meso-structure of the activated carbon, thus to improve a performance of the BWC. Further, in order to allow the powdery activated carbon to be stably present in the non-woven fabric with being adhered and/or captured therein, the above-described optional characteristics of the synthetic fiber according to the present invention are significant. As a result, adsorption/desorption effects may be markedly increased and stable effects of capturing the activated carbon may be achieved. Therefore, synergistic effects of the synthetic fiber and the powdery activated carbon may be expected.

[0086] As such, the present invention preferably uses the above-described specific synthetic fiber, such that it is possible to surprisingly exhibit advantageous effects such as a prevention of release of the activated carbon, a control of a thickness during the heat compressing process, and an execution of smooth ultrasonic fusion of the engine air cleaner.

[0087] According to the preferred embodiment of the present invention, the specific synthetic fiber may be used in a composition of 10 to 30% by weight (wt. %). If an amount of the synthetic fiber used herein is too small, the activated carbon could not be sufficiently applied. When an excess of the synthetic fiber is used, a content of the activated carbon per unit volume is decreased in inverse proportion, and therefore, improvement of the adsorption/desorption effects may not be expected.

[0088] According to the preferred embodiment of the present invention, if using the melting point fine fiber among the synthetic fibers, it is preferable to add a water repellent agent having good dispersion to the melting point fine fiber, in order to improve dispersion of the melting point fine fiber and to prevent inflow of moisture into the powdery activated carbon. In this case, the water repellent agent may be one that does not block a pore structure of the activated carbon and can minimize suppression of water absorption.

[0089] Further, the present invention uses a carbon binder. This is used for adhering and fixing the powdery activated carbon to the synthetic fiber and for preventing release of the same. For example, the carbon binder used herein may include, for example, at least one selected from an acryl resin, a polyvinyl acetate (PVAC) resin, a polyvinyl alcohol (PVA) resin or powders, a starch (CMC), phenol resin, an ethylvinyl acetate (EVA) resin or powders, and polyethylene (PE) powders.

[0090] According to the present invention, if an amount of the used carbon binder is too small, release of the activated carbon particles may occur. When the amount thereof is too much, adsorption efficiency may be considerably reduced due to blocking of the pores in the activated carbon.

[0091] Preferably, the present invention may minimize a content of the above-described carbon binder. The reason is that the powdery activated carbon as well as the synthetic fiber having specific physical properties may be desirably selected and used as described above, and thereby manufacturing the inventive fabric with the desired composition having a reduced amount of the carbon binder used herein to a minimum.

[0092] According to the preferred embodiment of the present invention, in addition to the basic materials, an additive such as a dispersant may be included in an amount of 0.05 to 0.2 wt. % based on a total composition of the wet-laid non-woven fabric. The dispersant used herein may be a modified starch or any one of other typical dispersants. Further, the water repellent agent used as the additive may include, for example, any typical water repellent agent such as silane, siloxane, and siliconate-based agents, etc., which may be used in an amount of 0.2 to 1.0 wt. %.

[0093] Further, according to the preferred embodiment of the present invention, in order to reduce a loss rate of the activated carbon and improve the activated carbon adsorption/desorption effects, a carbon fixing agent and a dehydration enhancer may be further used as additional components. The carbon fixing agent used herein is preferably an amine-based polymer such as 1,2-ethane diamine. Such a carbon fixing agent may be contained in an amount of 0.05 to 1.0 wt. % based on a total composition of the wet-laid non-woven fabric. If the amount thereof used herein is too small, no particular effect is achieved by adding the same. When the amount thereof used herein is too large, adsorption/desorption effects may be inhibited.

[0094] Furthermore, the dehydration enhancer also useable as the additive may include, for example, amides such as polyacryl amide and a content thereof used herein may range from 0.05 to 1.0 wt. %. In this case, if an amount thereof used herein is too small, dehydration enhancing effects cannot be expected. On the other hand, if the amount thereof used herein is too large, adsorption/desorption effects may be rather inhibited.

[0095] According to the preferred embodiment of the present invention, in the method for manufacturing the wet-laid non-woven fabric for a hydrocarbon trap of an air cleaner for a gasoline engine according to the present invention as described above, a sheet type or roll type fabric is formed through the heat compressing process S150 using a rolling roller, such that a product having a weight of 300 to 800 g/m.sup.2 and a thickness of 2.2 to 3.6 mm immediately before the heat compressing process S150 is preferably pressed and molded so as to have a thickness of 0.6 to 1.8 mm whiling maintaining the same weight of 300 to 800 g/m.sup.2 through the heat compressing process S150. This means that the product is pressed so as to reduce the volume its original size through heat pressing with no change in weight. If the pressing is conducted too much, absorption/desorption effects may be rather reduced.

[0096] Alternatively, the method for manufacturing the wet-laid non-woven fabric for a hydrocarbon trap of an air cleaner for a gasoline engine according to the present invention may include closely adhering a dry non-woven fabric made of a synthetic fiber to any one surface of the wet-laid non-woven fabric, and then forming the same into a sheet type or roll type synthetic non-woven fabric through the heat compressing process S150.

[0097] According to the preferred embodiment of the present invention, while closely adhering the dry non-woven fabric to any one surface of the wet-laid non-woven fabric for a hydrocarbon trap of an air cleaner for a gasoline engine as described above, the above fabric may undergo the heat compressing process S150 so as to be formed in a sheet type or roll type synthetic non-woven fabric. In this case, the fabric may be configured so as to be installed in the air cleaner. Further, the fabric may be more stably fused and fixed on the housing of the air cleaner through ultrasonic fusion.

[0098] According to the preferred embodiment of the present invention, in consideration of the loss rate of activated carbon and butane working capacity (BWC) of the wet-laid non-woven fabric for a hydrocarbon trap, on which the processes from the suspension process S110 to the drying process S140 are completed, it is preferable to use powdery activated carbon having specific physical properties, in which the meso-structure as described above is contained in a specific range.

[0099] Further, in a case of the air cleaner for a gasoline engine, the engine may be damaged when particles having a particle size of 200 m inflow into the engine, therefore, the powdery activated carbon having a particle size of 20 to 150 m is used. During water suction through a mesh net in the suspension process S110, the powdery activated carbon may come out along with the water to increase the loss rate thereof. Therefore, in order to reduce the loss rate of the powdery activated carbon, additionally using a carbon fixing agent is preferably considered. As such, the additive additionally used in the present invention may partially serve to further improve the physical properties of the wet-laid non-woven fabric.

[0100] In addition, according to the preferred embodiment of the present invention, with regard to the heat compressing process S150, when using the activated carbon, pulp, the synthetic fiber and the carbon binder and/or any other additional components, the raw materials mixed with the additives listed above have a problem in which these components are not completely combined after drying the resulting fabric. Therefore, during the fabric is mounted and used in the air cleaner for a gasoline engine, it is necessary to prevent desorption of the raw materials which were used in manufacturing the wet-laid non-woven fabric. For this purpose, it is preferable to conduct the heat compressing process. However, if the fabric has a high thickness after the heat compressing process, pressure loss in a flow path is increased to increase consumption of the fuel. Therefore, it is preferable to reduce the thickness to a minimum by performing the heat compressing process.

[0101] An example according to the present invention is to prepare a fabric using the basic materials of the present invention through suspension and web forming processes. If the fabric is formed in a paper formation mode, a dehydration time is less involved therein. On the other hand, a succession of lines in a mechanical mode has a limitation in suction. Thus, it is possible to manufacture the fabric when increasing a suction capacity. Further, according to another preferred example, it is preferable that bi-fold fabrics are at first prepared, respectively, and then combined together.

[0102] Further, it is preferable to press the fabric by a multi-stage press in both the paper fabrication mode and the mechanical mode to decrease the thickness thereof.

[0103] In this case, according to the preferred embodiment of the present invention, the thickness of the fabric should be decreased at least by its original thickness during the heat compressing process. Basically, since it is a limited to decrease the thickness even after the suction process, using the synthetic fiber under specific conditions according to the present invention may achieve the desired results. For example, a melting point fine fiber or the synthetic fibers selected and used according to the present invention as illustrated above are preferably used. In order to prevent release of the activated carbon in the fabric manufacturing process, the heat compressing process is preferably conducted at a high temperature of 150 C. to 260 C. with a high pressure of 30 N/cm.sup.2 to 300 N/cm.sup.2 to compress the fabric.

[0104] As such, the wet-laid non-woven fabric for a hydrocarbon trap of an air cleaner for a gasoline engine, which is manufactured by the above-described manufacturing method, may capture hydrocarbon in evaporation gases generated from a fuel in a combustion chamber of an engine or a fuel storage tank during driving or stoppage of a vehicle, or to recover the captured hydrocarbon to the engine so as to be rebumed therein, therefore, may be applied to a hydrocarbon trap equipped for adsorption/desorption of volatile oil vapor in an air cleaner for an engine of a vehicle by any typical method.

[0105] Therefore, the present invention includes a hydrocarbon trap for an air cleaner in a gasoline engine, which includes the above-described wet-laid non-woven fabric for a hydrocarbon trap of an air cleaner for a gasoline engine according to the present invention.

[0106] Hereinafter, the present invention will be described in detail by means of the following examples, however, it is not limited thereto.

[0107] Hereinafter, various tests are performed on an air cleaner to which the wet-laid non-woven fabrics manufactured in each of the examples and comparative examples are applied as follows: an activate carbon performance test of the powdery activated carbon in regard to the above air cleaner (Experimental Example 1); an experimental test for assessing the loss rate of activated carbon of the wet-laid non-woven fabric for a hydrocarbon trap obtained after completing the processes from the suspension process S110 to the drying process S140 (Experimental Example 2); a BWC test for assessing the butane working capacity (BWC) efficiency (Experimental Example 3); and an ultrasonic fusion test (Experimental Example 4), in regard to the wet-laid non-woven fabric for a hydrocarbon trap obtained after completing the entire manufacturing process from the suspension process S110 to the heat compressing process S150, etc., which will be described below for each step.

PREPARATIVE EXAMPLES 1 TO 6, AND COMPARATIVE PREPARATIVE EXAMPLES 1 TO 4

[0108] With the configurations shown in Table 1 below, powdery activated carbon used for manufacturing a wet-laid non-woven fabric for a hydrocarbon trap of an air cleaner for a gasoline engine was prepared.

Experimental Example 1: Activated Carbon Performance Test of Powdery Activated Carbon

[0109] In order to conduct a performance test of adsorption/desorption abilities on the powdery activated carbon prepared in each of the preparative examples and comparative preparative examples, baking was performed at 110 C. for 3 hours before the test, and by using a standard jig for test, 500 ml of activated carbon was filled at room temperature under normal pressure (25 C.2 C., 1 atm) and 505% RH. Then, after loading 250 cc/min of N2 gas and 250 cc/min of butane gas, it was subjected to measurement until saturation, followed by purging the same with 25.5 l/min to reach a minimum mass. Results of the above procedures are shown in Table 1 below.

TABLE-US-00001 TABLE 1 BWC Meso- Specific adsorption/ structure surface area BWC mass/ desorption Section (%) (m.sup.2/g) Carbon mass Efficiency (%) Preparative 88.1 2,500 0.23 95.81 Example 1 Preparative 80.0 2,393 0.22 93.79 Example 2 Preparative 75.3 2,100 0.19 89.00 Example 3 Preparative 54.0 1,800 0.18 84.80 Example 4 Preparative 45.3 1,500 0.17 83.10 Example 5 Preparative 80.0 1,800 0.19 85.12 Example 6 Comparative 92.1 2,500 0.23 93.90 Preparative Example 1 Comparative 30.2 1,500 0.09 45.21 Preparative Example 2 Comparative 25.5 1,100 0.05 36.60 Preparative Example 3 Comparative 50.5 800 0.11 57.36 Preparative Example 4

[0110] Referring to activated carbon performance test of the powdery activated carbon described above (Experimental Example 1), it could be seen that, as the specific surface area of the activated carbon and the content of meso-structure in the activated carbon were larger, butane gas adsorption ability was higher and, when the content of meso-structure was decreased, the butane gas adsorption ability was reduced. Further, in consideration of adsorption/desorption abilities in the composition of the wet-laid non-woven fabric, it is advantageous if the specific surface area of the powdery activated carbon is larger. However, it was found that the content of meso-structure was much more effective than the specific surface area upon the adsorption/desorption abilities.

[0111] That is, as a butane gas capture weight (g) per 1 g of activated carbon is higher, the capture ability is more excellent.

[0112] For reference, the wet-laid non-woven fabric is mounted in the air cleaner for a gasoline engine to conduct adsorption during stoppage of a vehicle and desorption during driving, and therefore, is semi-permanently used until the vehicle is scrapped. Thereby, it is ideal that a sum of adsorption efficiency and desorption efficiency thereof is close to 99%.

[0113] In addition, with reduced adsorption/desorption abilities, the butane gas remains with being captured in the activated carbon and is not completely desorbed. Therefore, in order to use the fabric semi-permanently, a hydrocarbon trap (HC) which repeats completely desorbing the butane gas and then adsorbing the same again still has a limitation.

[0114] Moreover, as the meso-structure and the specific surface area is increased, the butane adsorption capacity is increased, and adsorption/desorption abilities are also increased. However, it was found that, even though the meso-structure is larger than 90%, further improvement in adsorption/desorption abilities was not substantially expected. The above experimental results indicate that unfavorable results may be caused in consideration of non-economic advantage in production of the powdery activated carbon containing more than 90% of meso-structure.

[0115] In fact, the inventive fabric should be used semi-permanently as a hydrocarbon trap (HC Trap) component provided in the air cleaner for an engine in a vehicle. For this purpose, the fabric continuously conducts adsorption and desorption.

[0116] That is, since adsorption is again performed when the engine is stopped, while butane is again sucked into the engine by inflow of air into the engine during driving, 100% adsorption/desorption efficiency is most ideally preferred. However, in terms of the production and structure of activated carbon, it is not possible to produce activate carbon including 100% meso-structure.

[0117] In particular, even though the powdery activated carbon includes more than 90% meso-structure, functional effects are not much improved, whereas the product has no economic advantage due to difficulties in production and high production costs. Therefore, it could be found that the activated carbon with 90% or less of meso-structure was preferably used.

EXAMPLES 1 TO 4

[0118] Basic materials used in these examples are as follows: 340 g/m.sup.2 of the powdery activated carbon having a particle size of 90 m prepared in Preparative Example 2; 15 g/m.sup.2 of pulp; 80 g/m.sup.2 of melting point fine fiber (10 m) at 110 C.; 1.3 g/m.sup.2 of a water repellent agent; 45 g/m.sup.2 of a carbon binder (Hercopuls 125 of Ashland Co.); and 20 g/m.sup.2 of a non-woven fabric support. Further, other additives are also used in these examples. The above basic materials were subjected to a suspension process S110 of preparing a suspension by mixing the basic materials, followed by a web formation process S120 to form a web type product. Then, the web product was dried in a drying process S140 after passing through a water removal process S130. Herein, among the additives, a carbon fixing agent or a dehydration enhancer was used in Examples 1 to 4, while including the basic materials, respectively. The carbon fixing agent used herein was SY CHEM SB-50N (manufactured by SY CHEM Co.), and the dehydration enhancer was SY CHEM C-100 (manufactured by SY CHEM Co.). According to the above procedures, wet-laid non-woven fabrics for a hydrocarbon trap of an air cleaner for a gasoline engine, which have the compositions listed in Table 2 below, were manufactured.

Experimental Example 2: Test for Assessing Loss Rate of Activated Carbon of Wet-Laid Non-Woven Fabric For a Hydrocarbon Trap, on Which Processes from the Suspension Process S110 to the Drying Process S140 are Completed

[0119] With regard to the fabrics manufactured in each of the examples 1 to 4, a difference (that is, deviation) between a weight before introduction and a weight after introduction was used to measure loss of the activated carbon. Results thereof are shown in Table 2 below.

TABLE-US-00002 TABLE 2 Example 1 Example 2 Carbon fixing Carbon fixing agent 0.6% + agent 0% + Example 3 Example 4 dehydration Dehydration Carbon fixing Dehydration Section enhancer 0.5% enhancer 0% agent 0.8% enhancer 0.5% Dehydration 4.5 6.8 5.40 5.2 time (sec) Weight of fabric 500.4 510.4 506.2 520.1 (g/m.sup.2) Weight of loss 14.96 68.68 45.9 29.92 (g/m.sup.2) Loss of activated 4.4 20.2 13.5 8.8 carbon (%)

EXAMPLES 5 TO 8, AND COMPARATIVE EXAMPLES 1 AND 2

[0120] After preparing the fabrics according to the same procedures as described in Example 2, the prepared fabrics were subjected to a heat compressing process S150 to undergo heat compressing and molding under conditions of 150 C. to 230 C. with 30 N/cm.sup.2 to 160 N/cm.sup.2, thereby manufacturing wet-laid non-woven fabrics. As a result, wet-laid non-woven fabrics for a hydrocarbon trap of an air cleaner for a gasoline engine, which have the compositions listed in Table 3 below, were manufactured.

[0121] As comparative examples, wet-laid non-woven fabrics were manufactured in a method using different contents of meso-structure in the activated carbon, different contents of activated carbon and different thicknesses of the fabrics.

Experimental Example 3

[0122] BWC performance test for reviewing butane working capacity (BWC) efficiency performed on the wet-laid non-woven fabric for a hydrocarbon trap, on which manufacturing processes from the suspension process S110 to the heat compressing process S150 are finally competed.

[0123] With regard to the fabrics manufactured in Examples 5 to 8 and Comparative Examples 1 to 2, Butane Working Capacity (BWC) performance test was conducted by the following processes: the fabric in a volume of 0.031 m.sup.2, was stabilized by suction of dry and clean air at 28.50.5 l/min using a standard jig for test in a forced convection oven at 1105 C. for 3 hours, followed by termination when a change in a weight is less than 0.1 g/10 min; the treated product was loaded by suction of a sample in a butane suction device (50% butane+50% nitrogen) at 176 ml/min, followed by termination when a change in a weight is less than 0.01 g/10 min and measurement of the weight; the treated product was subjected to desorption through suction (i.e., purging) of a dry and clean air at 42 l/min, followed by termination when a change in the weight is less than 0.01 g/10 min and measurement of the weight. These procedures were repeated three times to obtain an average. Results of the present experiment are shown in Table 3 below.

TABLE-US-00003 TABLE 3 Comparative Comparative Section Example 5 Example 1 Example 6 Example 7 Example 8 Example 2 Weight of fabric 500 500 550 550 550 330 (g/m.sup.2) Thickness of 1.4 1.4 1.6 1.6 2.6 0.7 fabric (mm) Weight of 340 (68%) 340 (68%) 340 (61.8%) 300 (54.5%) 300 (54.5%) 214.5 (65%) activated carbon (g/m.sup.2) Specific surface 2,390 1,501 2,389 2,395 2,393 2,396 area (m.sup.2/g) Meso-structure 80 30 80 80 80 80 (%) Test filtration area 0.031 (m.sup.2) BWC (g) 3.45 1.52 3.33 3.01 3.04 1.78

[0124] As a result of analyzing the above experimental results, in consideration of the results as well as the experimental results in Experimental Example 1 proposed by the above preparative examples, it was confirmed that, if selecting the powdery activated carbon containing meso-structure in a specific range and using it a predetermined range, test results of BWC performance exhibited remarkably excellent characteristics.

[0125] Further, the heat compressing process S150 allows the fabric to be used at a typical flow rate of 2.8 m.sup.2/min for a gasoline engine since the activated carbon, pulp, the synthetic fiber, the carbon binder and the additive are not completely combined after drying, and further allows the fabric to be mounted in an air cleaner for a gasoline engine to prevent desorption of the fuel. Furthermore, since a pressure loss in a flow path is increased to cause an increase in combustion of the fuel if the fabric has a large thickness, it was confirmed that the heat compressing process was preferably conducted to minimize the thickness.

EXAMPLE 9, AND COMPARATIVE EXAMPLES 3 TO 6

[0126] The same activated carbon as Example 2, and a melting point fine fiber having a diameter of 30 m or less or a melting point of 110 C. as a synthetic fiber were used. For comparative examples, other different synthetic fibers (or fibers having a diameter of more than 30 m or different melting points or physical properties) were used, and under the conditions shown in Table 4 below, respective wet-laid non-woven fabrics were manufactured.

Experimental Example 4: Ultrasonic Fusion Test

[0127] An experiment of release and adhesion of HC Trap fabric to a housing of the engine air cleaner was executed by an ultrasonic fusion test of the wet-laid non-woven fabrics produced in Example 9 and Comparative Examples 3 to 6.

[0128] Then, in order to assess whether the HC Trap fabric can be semi-permanently used, physical properties thereof were measured. The test was conducted according to a vehicle standard ESIR breakaway test method. While altering a weight of the fabrics and a thickness of the fabrics, ultrasonic fusion strengths were measured. Results of the measurement are shown in Table 4 below.

TABLE-US-00004 TABLE 4 Comparative Comparative Comparative Comparative Section Example 9 Example 3 Example 4 Example 5 Example 6 Synthetic fiber Melting point Melting point Melting point Normal fiber Inorganic fiber 110 C. 90 C. 280 C. 35 m 30 m Microfiber Microfiber Microfiber 80 g/m.sup.2 80 g/m.sup.2 10 m 10 m 10 m 80 g/m.sup.2 45 g/m.sup.2 80 g/m.sup.2 Weight of fabric 500 465 500 500 500 (g/m.sup.2) Thickness of fabric 1.4 1.3 1.8 2.4 2.8 (mm) Weight of activated 340 (68%) carbon (g/m.sup.2) Ultrasonic fusion 8.0 5.2 4.3 2.0 0.5 strength (kgf/35 mm)

[0129] Referring to the above experiment, it could be seen that using the melting point fine fiber within the corresponding range as a synthetic fiber (Example 9) exhibited superior and excellent bonding characteristics, as compared to cases of not using the same (Comparative Examples 3 to 6). Such a result demonstrated that the wet-laid non-woven fabric has excellent effects of preventing release of powdery activated carbon and excellent product reliability. Therefore, it is evident that, when applying the present product to a hydrocarbon trap, improvement of volatile oil vapor adsorption/desorption effects may also be sustained for a long period of time.

[0130] As described above, according to the wet-laid non-woven fabric for a hydrocarbon trap of an air cleaner for a gasoline engine, basic materials such as powdery activated carbon, pulp, a synthetic fiber and a carbon binder are used, and if necessary, additives such as a dispersant, a water repellent agent, a carbon fixing agent, etc. may be added. Through the compressing process, a wet-laid non-woven fabric having a predetermined thickness is manufactured and installed in an air cleaner for a gasoline engine, in order to capture hydrocarbon gas contained in evaporation gases generated from a fuel in a combustion chamber of the engine or a fuel storage tank during stoppage of the engine on a side of the wet-laid non-woven fabric for a hydrocarbon trap, as well as, recover the hydrocarbon captured in the wet-laid non-woven fabric for hydrocarbon during stoppage of the engine into the engine with a negative pressure at startup of the engine when the vehicle is driven, so as to be rebumed in the engine.

[0131] Moreover, since the wet-laid non-woven fabric is composed of the basic materials such as powdery activated carbon, pulp, a synthetic fiber and a carbon binder, as well as additives such as a dispersant, a water repellent agent, a carbon fixing agent and a dehydration enhancer, and is formed into a wet-laid non-woven fabric having a predetermined thickness through the compressing process, the fabric may capture hydrocarbon in evaporation gases discharged during driving or stoppage of the vehicle so as to prevent release of the hydrocarbon which is a main cause of air pollution to an outside, and damage caused by the hydrocarbon to a passenger in the vehicle may be minimized.

[0132] While the present invention has been described with reference to the specific examples, the present invention is not limited thereto, and it will be understood by those skilled in the related art that various modifications and variations may be made therein without departing from the scope of the present invention as defined by the appended claims, as well as these modifications and variations will be included in the scope of the present invention.