KR101237347B1 - Corrugation process for preparing carbon fiber sheet and corrugated carbon fiber sheet using the same - Google Patents

Abstract

Disclosed are a method of corrugating a carbon fiber sheet and a corrugated carbon fiber sheet obtained thereby.

The corrugating method of the carbon fiber sheet according to the present invention comprises: an impregnation step of impregnating a carbon fiber sheet with a composition for impregnation comprising a thermoplastic resin, a filler, and a solvent; Drying the carbon fiber sheet obtained by impregnation; And a waveform step of waveforming the carbon fiber sheet.

Description

Corrugation process for preparing carbon fiber sheet and corrugated carbon fiber sheet using the same}

1 shows a photograph after a long time elapse of the corrugated carbon fiber sheet according to Example 1. FIG.

2 shows a photograph of the corrugated carbon fiber sheet according to Comparative Example 1 after a long time.

The present invention relates to a method for producing a corrugated carbon fiber sheet, specifically, a carbon fiber sheet corrugation method that can maintain a uniform waveform even after the corrugation process despite the carbon fiber sheet having elasticity and using the same It relates to the obtained corrugated carbon fiber sheet.

Due to industrial development, the harmful substances such as dust (PM, Particulate Matter), soot, waste gas, smoke and volatile organic chemicals (VOC) generated from various engines such as industrial plants and automobiles are becoming more serious. In order to reduce such harmful substances, it is necessary to more actively suppress the release of the hazardous substances. In order to suppress the release of these harmful substances, some polymer filters are used, but polymer filters have weak problems in heat resistance, chemical resistance, abrasion resistance, and flame resistance. That is, a polymer filter using polyester shrinks at 150 ° C., and PTFE (Poltetrafluoroethylene, Teflon) having excellent heat resistance has only heat resistance of up to 250 ° C. In particular, the atmosphere of the process using industrial filters is a harsh environment in which dust, various types of waste gases, and moisture are generated at the same time.Non-woven filters of most polymer materials such as polyester, polypropylene, acrylic, polyamide, polyimide, and glass fiber If the dust adhering to the filter surface is shaken off by a jet pulse method or the like, the dust is dropped from the top to the bottom, and the surface wear of the filter due to the dust is more serious than expected, resulting in a problem of damaging the filter and shortening the use cycle of the filter.

In addition, if a spark occurs during the combustion process of each industry and is attached to the filter, the flame attached to the filter may lead to a fire or a hole in the filter, and in the case of waste incinerators, boilers, coal-fired power plants, and coal gasification combined cycle, There is a problem that the risk of exposure to the atmosphere is contrary to the tightening environmental regulations.

Above all, the development of transportation means that the number of automobiles is increasing rapidly, and the exhaust gas emitted from these vehicles has reached a serious level. As a result, regulations on emissions are becoming more difficult year after year in Europe, the United States, and Korea. Particularly, dust filtration filters (DPF, Diesel Particulate) are used to filter dust to suppress emissions of diesel engines. Research on filters is being actively conducted.

In order to be applied to the dust filter for diesel vehicles, heat resistance, thermal shock resistance, chemical resistance, thermal conductivity, porosity, and mechanical strength must be high, and extrusion of porous ceramic powder (cordierite, silicon carbide, etc.) that satisfies these characteristics to some extent is required. Molded honeycomb filters are often used.

Among them, DPF using silicon carbide powder has been spotlighted as the most promising DPF material in the future due to its excellent properties such as high thermal shock resistance and high thermal conductivity. However, the biggest problem to be solved in the silicon carbide extrusion DPF is that the porosity of the filter is low (about 50%), and in this case, the back pressure difference in the engine power unit may be high, which may overwhelm the engine. Will be lowered. In addition, when the soot or ash is laminated inside the filter and the process of regenerating it, local heat generation causes high temperature gradient inside the filter, causing cracks in the filter to crack or melt, making it impossible to perform the dust filtration function. . In addition, due to the development of engine technology of automobiles, the particle size of dust contained in exhaust gas is getting smaller and smaller, and even emits nanometer-sized dust, which is harmful to human body. To filter out these fine dusts, more meshed microstructures are required, and the cell structure must be further improved.

In order to solve these problems, researches on the application of DPF using ceramic fibers have been actively conducted. The above-mentioned extrusions are made by using a sheet made of alumina fiber, alumina silicate fiber, etc., to form a honeycomb by corrugating it, or to make an extruded DPF structure by laminating the above sheets to make an extruded DPF structure. In order to compensate for the shortcomings as a DPF and to develop a high performance ceramic fiber DPF, research is being conducted.

The biggest problem with ceramic fiber DPFs, however, attempted above is the low mechanical strength after manufacturing from honeycomb. That is, since the material is a ceramic fiber sheet, not only the mechanical strength is low, but also the thermal conductivity is low due to the characteristics of the material, so it is easy to generate cracks due to the thermal shock. In order to improve such thermal properties, ceramic fiber DPFs using silicon carbide fiber sheets made of silicon carbide fibers have been proposed. Silicon carbide has emerged as a promising material for DPF due to its high thermal conductivity and high thermal shock resistance. However, silicon carbide fibers are very expensive and have a disadvantage of being inefficient for production applications. However, in order to solve the back pressure problem, which is the biggest problem in the development of the next generation diesel engine, ceramic fiber DPF has been proposed as an alternative, and active research is being conducted.

In order to manufacture the ceramic fiber DPF as described above, a method is known in which a ceramic fiber sheet is corrugated and then rolled into a honeycomb in a similar manner to a corrugated cardboard manufacturing method. First, a ceramic fiber is mixed with an additive to prepare a sheet. After making paper, corrugating and drying it, the honeycomb is manufactured by alternately bonding with a flat sheet. At this time, an inorganic adhesive and an inorganic sealant are used, of course.

At this time, the corrugation method allows the ceramic fiber sheet to pass through the gear rollers maintained at a constant temperature to obtain a corrugated shape, and to make the corrugation in a state containing a predetermined moisture to maintain a more efficient shape. A much better waveform shape can be obtained.

However, this method is applied to ceramic fiber sheets with very short (tens of 200 to 200 micrometers) ceramic fibers, and cannot be used for ceramic fibers, that is, carbon fiber sheets, which are longer than 1 to 200 mm in length. Ceramic fiber has a very large elasticity, so when a sheet made of a long fiber is corrugated in the same manner as above, the shape becomes uneven even after a predetermined time or becomes corrugated. This is because it is difficult to manufacture.

Therefore, there is still a need to develop a uniform and durable corrugated carbon fiber sheet to provide a honeycomb filter based on carbon fiber having the advantages of good adsorption, flexibility and tensile strength.

The technical problem to be achieved by the present invention is to produce a silicon carbide fiber DPF having a honeycomb structure, the carbon fiber sheet to be a material of the silicon carbide fiber, it is possible to maintain the waveform shape for a long time in a constant and stable form, In addition, it provides a method for increasing the conversion rate of carbon fibers to silicon carbide fibers.

Another technical problem to be achieved by the present invention is to provide a corrugated carbon fiber sheet produced by the manufacturing method for the manufacture of a dust filtration filter such as silicon carbide fiber DPF.

The present invention to achieve the first technical problem,

An impregnation step of impregnating the carbon fiber sheet with a composition for impregnation comprising a thermoplastic resin, a filler, and a solvent;

Drying the carbon fiber sheet obtained by impregnation; And

It provides a corrugation method of the carbon fiber sheet comprising a corrugation step of corrugating the carbon fiber sheet.

The present invention to achieve the above other technical problem,

It provides a corrugated carbon fiber sheet obtained by the above production method.

Hereinafter, the present invention will be described in more detail.

Although the method of corrugating the carbon fiber sheet according to the present invention basically has the advantages of excellent adsorption, flexibility and tensile strength, it is for facilitating the waveform of the carbon fiber sheet, which was difficult to be corrugated due to self-resilience. After impregnating and drying the carbon fiber sheet in the composition for impregnation comprising a thermoplastic resin, it is corrugated to produce a corrugated carbon fiber sheet.

The corrugating method of the carbon fiber sheet according to the present invention comprises: an impregnation step of impregnating a carbon fiber sheet with a composition for impregnation comprising a thermoplastic resin, a filler and a solvent; Drying the carbon fiber sheet obtained by impregnation; And a waveform step of waveforming the carbon fiber sheet.

The corrugated carbon fiber sheet obtained by the above method can maintain a uniform waveform even after a long time despite the restoring force of the carbon fiber itself, so that it can be usefully used as a constituent of the honeycomb filter for removing various harmful substances and dust. have.

In the method for producing a corrugated carbon fiber sheet according to the present invention, after impregnating the impregnating composition, the process of leveling the carbon fiber sheet prior to corrugating the dried carbon fiber sheet may be further proceeded. This makes it possible to form the waveform state more homogeneously.

The carbon fiber sheet is impregnated with a composition for impregnation comprising a thermoplastic resin in a carbon fiber sheet having a basic elastic force, the thermoplastic resin penetrates into the carbon fiber sheet to offset the restoring force of the carbon fiber sheet during the corrugation process It will play a role. Such an impregnating composition includes a thermoplastic resin, a filler, and a solvent, and may include 0 to 500 parts by weight of a filler, and 100 to 3000 parts by weight of a solvent, based on 100 parts by weight of the thermoplastic resin.

In addition, the impregnating composition may be used as needed, various additives such as a reaction initiator, a curing accelerator, a curing delay agent, and their content may be used in an amount of 0.1 to 30 parts by weight based on 100 parts by weight of the thermoplastic resin.

The thermoplastic resin, which is the subject of the composition for impregnation, may be used without limitation as long as it is a polymer material that softens at high temperature and hardens upon cooling, that is, a resin having thermoplastics. In the present invention, polyvinyl alcohol, polyvinylacetate or Preference is given to using mixtures.

Silicon may be used as the filler, and as such a filler, silicon is dispersed in a thermoplastic resin solution and impregnated at the same time because the conversion of carbon fibers to silicon carbide fibers results in as many silicon components as possible in as many processes as possible. It is necessary to supply a high silicon carbide conversion rate and to produce good silicon carbide fibers. In fact, in the silicon slurry impregnation process, which is part of the process of manufacturing the silicon carbide fiber honeycomb filter, in order to supply silicon and convert it to 100%, the silicon content of the silicon slurry needs to be added in excess. This is because aggregation occurs and uniform dispersion between carbon fibers becomes difficult. Therefore, when silicon is pre-injected into the composition for impregnation, silicon is infiltrated in advance between the carbon fibers, so that an appropriate amount of silicon can be applied in the subsequent silicon slurry impregnation process. Dispersion leads to homogeneous silicon carbide (SiC) fibers. The filler may be used in an amount of 10 to 500 parts by weight, preferably 100 to 200 parts by weight, based on 100 parts by weight of the thermoplastic resin, and when the content exceeds 500 parts by weight, impregnation during the corrugation process due to agglomeration of the silicon powder. There is a problem that the sheet may be broken by lowering the elastic force of the sheet, and even if the silicon powder is not added, there is no difficulty in obtaining the effect of the present invention. It is desirable to do it.

As the filler, components having various particle diameters may be used, and certain components may have the same particle diameter, or may be used by mixing the same components having different particle diameters. The particle diameter of the filler is preferably 0.1 to 100 μm, and the manufacturing cost may increase when the particle size of the filler is less than 0.1 μm. In the case of more than 100 μm, there is a problem in that the carbon fiber sheet may not be uniformly distributed in the carbon fiber sheet and thus the carbon fiber may not be uniformly converted into silicon carbide.

As a solvent used in the impregnating composition for the corrugation method according to the present invention, water, alcohols, ethers or a mixture thereof may be used, and as the alcohols, for example, methanol, ethanol, isopropyl alcohol. , Butyl alcohol, octyl alcohol, benzyl alcohol, cyclohexanol, ethylene glycol, glinerol, diethylene glycol, and the like can be used, the ethers can be used cellosolve, butyl cellosolve and the like.

The solvent is preferably included in an amount of 100 to 3000 parts by weight based on 100 parts by weight of the thermoplastic resin.

When the content of the solvent is less than 100 parts by weight, the viscosity of the thermoplastic resin solution is too high, and uniform mixing and dispersion of silicon powder in the thermoplastic resin solution is not possible, so that uniform impregnation of the carbon fiber sheet is impossible. In addition, since the thermoplastic resin blocks pores in the carbon fiber sheet, there is a problem in that uniform impregnation of the silicon slurry does not occur during the subsequent silicon slurry impregnation process. When the content is more than 3000 parts by weight, the viscosity of the thermoplastic resin solution is too low, that is, the content of the thermoplastic resin is too low, it is not desirable to exhibit the shape holding force required for the waveform shape maintenance during hot waveform.

The carbon fiber sheet that can be used in the corrugation method may include carbon fiber prepared from various raw materials such as polyacrylonitrile, rayon, and pitch, and all porous structures having pores supporting the composition may be used. It is possible to use, preferably the porosity of 50 to 99% can be used, it is preferable to use a carbon fiber length of 1 to 50mm. As for the shape of such a carbon fiber sheet, it is more preferable in the application of this invention to use paper, a nonwoven fabric, a woven fabric, etc.

In the case of the paper, the honeycomb structure formed by laminating it has good heat resistance and corrosion resistance, and is lighter and has higher porosity than that formed by extrusion molding, so the pressure loss of the exhaust gas is small, so that the catalyst for gas phase reaction, heat exchange element, and dust for diesel engine Attention as a filtration filter.

In other words, since paper is a sheet of paper, carbon fiber is easily formed, embossed, or bonded by a conventional paper processing method, and thus, development as a structure utilizing heat resistance, electrical properties, porosity, and adsorption functions has been actively conducted. In addition, the honeycomb structure manufactured through corrugate processing to corrugate is particularly preferable in the present invention because it can be used as a heat exchanger, a catalyst carrier, a dehumidifier, a filter for an environmental purifier, a heat insulating material, and the like.

The nonwoven fabric is formed by combining short fibers with an adhesive on the basis of a web or sheet-like fiber aggregate, bonding the fibers using thermoplastic fibers, or entangles the fibers by needle punching or sewing. .

The woven fabric is manufactured by spinning, weaving, cotton, or the like, and is preferably woven loosely for supporting the slurry, and includes sufficient pores for supporting the slurry in the woven fabric.

The impregnating composition impregnated in the carbon fiber sheet may be a method of applying the composition to the sheet, impregnating the sheet into the composition, or spraying the composition onto the sheet, and adhering, fusing, After the preparation in the form of a sheet to be produced through sewing, self-bonding, or molding using a mold, the composition may be impregnated.

In particular, the sheet contains a sufficient composition, and the process of impregnating and squeezing the sheet in the composition is repeated 1 to 5 times or the process of applying or spraying and squeezing the composition to the sheet is repeated 2 to 5 times It is more preferable that the composition is sufficiently loaded in the filter.

When the sheet is chopped or molded to a predetermined size and then supported on the composition, the drying step may be immediately performed. If the sheet is not chopped or molded to a predetermined size, the step of forming the sheet into a shape suitable for the purpose is added. Can be carried out.

The content of the composition impregnated in the carbon fiber sheet and the properties of the honeycomb filter made of the corrugated carbon fiber sheet according to the present invention are affected by the porosity of the carbon fiber sheet. The porosity of the carbon fiber sheet is preferably 50 to 99%. When the porosity is less than 50%, the impregnating composition may not be sufficiently supported. If the porosity is greater than 99%, the mechanical durability of the carbon fiber sheet may be lowered, which is not preferable.

As described above, the carbon fiber sheet subjected to the impregnation process evaporates the solvent through a drying process. Such drying may be performed by natural drying, hot air drying, sun drying, or shading drying, and in particular, shortening drying time. In order to prevent deformation and cracking of the carbon fiber sheet, it is preferable to set appropriate drying conditions. This will suppress product damage due to the sheet in the manufacture of honeycomb filters later.

Such a drying process is preferably carried out for 30 minutes to 2 hours at a temperature condition of room temperature to 150 ℃ bar, when the temperature exceeds 150 ℃ there is a possibility that deformation and cracks of the sheet may occur, which is not preferable. If the drying time is less than 30 minutes, sufficient drying cannot be obtained. If the drying time is more than 2 hours, deformation and cracking of the sheet may similarly occur, which is not preferable.

After the drying process, the process of planarizing the carbon fiber sheet on which the composition for impregnation is carried out can be additionally performed. Such a planarization process may be performed prior to the corrugation process of the carbon fiber sheet, thereby helping to obtain a more homogeneous waveform. Such flattening is achieved by pressing a dried sheet, which is obtained by passing carbon fiber between two pressurized rollers. In this case, the pressure applied may be influenced by the thickness or size of the carbon fiber, and the compression to the extent that the porosity of the carbon fiber sheet is lowered is not preferable, and the compression to the extent that causes cracking of the internal thermoplastic resin or the filler is also preferable. Not. Therefore, it is preferable to perform the pressing of the carbon fiber sheet by maintaining an appropriate gap between the two rollers.

It is also preferable that the planarization step is performed by hot pressing in addition to simple pressing. Hot pressing may soften the carbon fiber sheet as the thermoplastic resin softens at a high temperature, so that the carbon fiber sheet may be flattened more efficiently, and heat is applied to the carbon fiber sheet through two rollers. The temperature at the time of hot pressing is preferably 150 to 200 ° C.

By such a flattening process, a carbon fiber sheet having a uniform thickness and a uniform flatness is obtained. Such a planarization process is performed before the corrugation step, but is not necessarily performed, and a waveform of uniform quality cannot be obtained, the thickness is irregular, or a resin aggregate is generated on the surface by the corrugation process alone. Optionally, it can be usefully used to improve the quality of the sheet itself.

The carbon fiber sheet subjected to the selective planarization process is finally subjected to the corrugation step. Such waveforming may be performed by passing a corrugator in which two gears are engaged in a roller form, and the two gears provided in the corrugator may have various shapes according to a waveform to be obtained. That is, when the waveform to be obtained is an angular triangle shape, the gear also has an angular triangle shape, and when it is desired to obtain a rounded waveform, it is possible to shape the shape of the gear into a round shape.

In the corrugation process, as in the planarization process, heat may be applied to the gear to soften the thermoplastic resin at a high temperature so that the carbon fiber sheet may be formed into a gear-shaped corrugation. In this case, the appropriate gear temperature of the waveformer is 150 to 200 ° C. When the carbon fiber sheet is passed through the engagement gear of the corrugator heated to the above temperature, the thermoplastic resin is softened at high temperature, and the carbon fiber sheet is molded into a gear-shaped corrugated form. Will be maintained.

The corrugated carbon fiber sheet obtained by the corrugation process as described above may be useful in forming various filters such as honeycomb filters by maintaining a uniform waveform even after a long time.

In particular, among the ceramic fiber DPFs that can cope with increasingly demanding environmental regulations and are proposed as alternatives to high-power DPFs for next-generation diesel engines, silicon carbide fiber DPFs, which are known to have the highest thermal characteristics but are very expensive, are low-cost carbon. By using a chemical reaction (conversion) of the fiber and the silicon powder, and by using a honeycomb filter using the corrugated carbon fiber sheet according to the present invention, it is possible to produce silicon carbide fiber DPF more economically.

For example, the method of manufacturing the silicon carbide fiber DPF is as follows.

After impregnating and drying the polymer aqueous solution in which the silicon powder was uniformly dispersed in the carbon fiber sheet, corrugating and flattening, and cutting to a certain size, these sheets were alternately laminated using a ceramic sealant and a ceramic adhesive. A honeycomb block made of carbon fiber is manufactured. The honeycomb block is impregnated and dried in a second polymer resin solution in which silicon powder is uniformly dispersed, and then subjected to a degreasing step, followed by heat treatment in a non-oxidizing atmosphere of 1600 ° C or higher. This converts the carbon fibers into beta silicon carbide (β-SiC) by reacting with the silicon powder, thereby producing a ceramic fiber honeycomb filter block made of silicon carbide fibers. The honeycomb block manufactured as described above is externally processed in a predetermined form, and subjected to an external wall treatment with a silicon carbide-based ceramic paste, followed by heat treatment in an oxidizing atmosphere to finally complete a ceramic fiber honeycomb filter made of silicon carbide fiber material.

The present invention will be described in more detail with reference to the following Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1

100 parts by weight of polyvinyl alcohol resin, 2000 parts by weight of water, and 200 parts by weight of silicon were added to the mixer, followed by mixing in a mixer to prepare a composition for impregnation. After impregnating the composition so that the carbon fiber sheet of carbon fiber sheet having a length of 0.5 to 50mm is sufficiently supported, it is dried by hot air, and the dried carbon fiber sheet is passed between two rollers to perform a hot pressing process. Hot pressed sheets were obtained.

Thereafter, the compressed carbon fiber sheet was passed through an interlocking gear of the corrugating apparatus heated to 200 ° C., and naturally cooled to obtain a corrugated carbon fiber sheet. A photograph of the obtained corrugated carbon fiber sheet stored for a long time in a constant humidity environment is shown in FIG. 1, and as shown in FIG. 1, the corrugated carbon fiber sheet obtained by the manufacturing method according to the present invention is maintained even after a long time. It can be seen that the waveform is uniform and there is no change in shape.

Comparative Example 1

A corrugated carbon fiber sheet was prepared in the same manner as in Example 1, except that the composition for impregnation was not used in Example 1.

After the corrugated carbon fiber sheet obtained in Comparative Example 1 for a long time in a constant humidity environment is shown in Figure 2, as can be seen in Figure 2 the waveform is uneven due to the restoring force of the carbon fiber sheet after a long time It can be seen that the waveform becomes flat.

In the manufacturing method of the corrugated carbon fiber sheet according to the present invention, the thermoplastic resin impregnated in the carbon fiber sheet is softened by heat treatment by a corrugator, the sheet is molded in the form of a gear of the corrugator, and then cooled to room temperature When the thermoplastic resin is cured, a sheet having a stable and uniform corrugated shape may be provided even after a long time elapses, and the honeycomb type diesel engine exhaust gas purification filter (DPF) is formed using the obtained corrugated sheet. Can be provided. In particular, the present invention provides a silicon carbide fiber DPF, which is known to have the best thermal properties but is very expensive, by using a chemical reaction (conversion) of inexpensive carbon fiber and silicon powder more economically.

Claims (9)

An impregnation step of impregnating the carbon fiber sheet with a composition for impregnation comprising a thermoplastic resin, silicon powder and a solvent; Drying the carbon fiber sheet obtained by impregnation; And Corrugation method of the carbon fiber sheet comprising the waveform step of corrugating the carbon fiber sheet. The method of claim 1, And a flattening step of hot pressing the dried carbon fiber sheet to flatten it before the corrugating step. The method of claim 1, The impregnating composition comprises 100 parts by weight of a thermoplastic resin, 10 to 200 parts by weight of a filler and 100 to 2000 parts by weight of a solvent. The method of claim 1, The thermoplastic resin is a polyvinyl alcohol, polyvinyl acetate or a mixture thereof, characterized in that the waveform of the carbon fiber sheet. delete The method of claim 1, The particle size of the silicon powder is 0.1 to 100㎛ waveform of the carbon fiber sheet, characterized in that. The method of claim 1, And the solvent is water, methanol, ethanol or a mixture thereof. The method of claim 1, The porosity of the carbon fiber sheet is 50 to 99%, the length of the carbon fiber sheet is a waveform of the carbon fiber sheet, characterized in that 0.5 to 50mm. delete

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