JP2006095379A - Manufacturing method of filter unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a filter unit constituted so as not only to prevent a rise in pressure loss and a fall in collection efficiency but also to simply and sufficiently seal the end part of a PTFE filter medium and a retaining frame. <P>SOLUTION: The end part of the PTFE filter medium including a polytetrafluoroethylene (PTFE) porous film and an air-permeable support is impregnated with an ultraviolet curable sealant including an ultraviolet curable resin and, after the impregnated PTFE filter medium is housed in the retaining frame, the ultraviolet curable resin solution infiltrated in the PTFE filter medium is cured to manufacture the filter unit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a filter unit using a filter medium including a PTFE porous membrane and a breathable support.

  A filter unit used for an air cleaner, a dust mask, or the like is required to have high dust collection efficiency and low ventilation resistance. In order to satisfy these characteristics, various studies have been made on the selection of filter media and the shape during attachment processing.

  Examples of the filter medium used for the air filter generally include paper made by adding a binder to glass fiber, and such a filter medium has some problems. For example, the presence of fibrils attached to the filter medium, the occurrence of self-dusting during bending, and the increase in pressure loss when the binder is increased to prevent self-dusting (see Patent Document 1).

  In order to solve these problems, use of an electret filter medium (see Patent Document 2), which is a synthetic fiber, has been proposed, but this also has a problem of attenuation of the electret.

  In recent years, a PTFE porous membrane has been used as a new filter medium. This PTFE porous membrane can be produced, for example, by preparing a sheet-like PTFE semi-fired body (see Patent Document 3) and biaxially stretching the resulting semi-fired body to make it porous (Patent Document 4). , See Patent Document 5). However, in the case of this production method, it is difficult to set production conditions for realizing a semi-baked state suitable for subsequent stretching, and particularly such a semi-fired state can be industrially realized because temperature conditions are narrow. very difficult. For this reason, it has been difficult to efficiently produce a useful PTFE porous membrane.

  Therefore, it has been newly proposed to stretch an unsintered PTFE sheet-like molded body and use the obtained PTFE porous membrane as a high-performance air filter medium (see Patent Document 6 and Patent Document 7). . There has also been proposed a filter medium that uses a PTFE porous membrane, in which a gas-permeable support is further interposed to improve the collection efficiency and reliability against leakage (see Patent Document 8).

  On the other hand, it is known that the pressure loss and the collection efficiency required for the filter unit are better as the filter medium area is larger. For this reason, when the filter medium is attached to the unit formwork, the filter medium is generally pleated in order to increase the area of the filter medium in the unit (see Patent Document 9).

The filter unit is generally manufactured by fitting the filter material having the shape processed as described above into a mold, and when fitting, the filter unit is closely attached so that no gap is generated between the filter medium and the mold. There is a need. However, since the shape of the filter medium and the shape of the filter unit are complicated, it takes much time to seal the filter medium and the formwork using an adhesive such as hot melt. Therefore, a method is disclosed in which a pressure is applied to the filter medium and the filter medium is fitted into a mold, and the filter medium is sandwiched by holding the filter medium in a state where a predetermined pressure is applied around the filter medium by the mold. (See Patent Document 9). In addition, there has been proposed a form shape for holding the filter medium (see Patent Document 10).
JP-A 63-16019 JP 54-53365 A JP 59-152825 A JP-A-3-221541 Japanese Patent Laid-Open No. 5-202217 International Publication No. WO94 / 16802 Japanese Patent Laid-Open No. 7-196831 JP-A-9-206568 JP 2000-153122 A Japanese Patent No. 3143879

  However, in order to prevent an increase in pressure loss, the air-permeable support itself in the PTFE filter medium generally has no collection performance or, if any, much lower than the PTFE porous membrane. . Then, when the filter medium is held by a mold in a state where pressure is applied to the filter medium as described above, the PTFE filter medium and the mold are in close contact with each other or a part of the PTFE filter medium is compressed. Become. However, in this case, the air-permeable support becomes a flow path, and dust or the like flows from the upstream side to the downstream side without passing through the PTFE porous membrane, and the collection efficiency may be reduced. In addition, when sealing between the two by hot melt, there are the following problems. The hot melt needs to be impregnated into the PTFE filter medium in a state where the viscosity is lowered by heating. However, since the temperature of the hot melt decreases and the viscosity increases during the impregnation, sufficient impregnation may not be performed. is there. In particular, such a problem becomes more prominent as the shape of the filter medium and the formwork becomes more complicated. For example, when the pleated filter medium as described above is impregnated with hot melt from the pleat peak side, the valley side of the pleat In some cases, the temperature drops before reaching the point, and sufficient sealing cannot be performed. Moreover, since a heating process is required, when a breathable support body contains a low melting-point polymer component like polyethylene (PE), there exists a possibility that a pressure loss may rise by melting.

  Accordingly, an object of the present invention is to provide a method for producing a filter unit in which the end of a filter medium is easily sealed with a mold without causing an increase in pressure loss and a decrease in collection efficiency.

  In order to achieve the above object, the present invention provides a method of manufacturing a filter unit in which a PTFE filter medium including a PTFE porous membrane and a breathable support is housed in a mold, and an optical filter is formed on an end of the PTFE filter medium. An impregnation step (a) for impregnating a photocurable sealant containing a curable resin, a storage step (b) for accommodating the PTFE filter medium in a mold, and a curing for curing the photocurable resin solution impregnated in the PTFE filter medium It is a manufacturing method of the filter unit characterized by including a process (c).

  As described above, if a photocurable sealing agent containing a photocurable resin is used, the PTFE porous membrane and the air-permeable support can be provided at the end of the PTFE filter medium without being affected by the temperature as in the case of the hot melt described above. Both the body and the photocurable sealant can be sufficiently impregnated. For this reason, if the impregnated photocurable resin is cured, the filter medium and the mold can be reliably sealed. The filter unit thus obtained has a PTFE porous membrane reliably present in the air flow path with a sufficient seal, so that it is possible to prevent the collection efficiency from being lowered, and unlike the hot melt, the heating step is Since it is unnecessary, it is possible to prevent an increase in pressure loss of the breathable support.

  In the present invention, the thickness of the PTFE porous membrane is not particularly limited, but is preferably in the range of 1 to 100 μm, more preferably in the range of 1 to 30 μm.

  An example of a method for producing the PTFE porous membrane layer is shown below. First, a liquid lubricant is added to unfired PTFE fine powder and mixed uniformly. The PTFE fine powder is not particularly limited, and a commercially available product can be used. The liquid lubricant is not particularly limited as long as it can wet the PTFE fine powder and can be removed later, hydrocarbon oils such as naphtha, white oil, liquid paraffin, toluene, xylene, alcohols, Solvents of ketones and esters can be used. These may be used alone or in combination of two or more.

  The addition ratio of the liquid lubricant to the PTFE fine powder is appropriately determined depending on the type of the PTFE fine powder, the type of the liquid lubricant, the sheet molding conditions described later, and the like. For example, for 100 parts by weight of the PTFE fine powder The liquid lubricant is in the range of 15 to 35 parts by weight.

  Next, the mixture is formed into a sheet in an unfired state. Examples of the method include a rolling method in which the mixture is extruded into a rod shape and then rolled with a pair of rolls, and an extrusion method in which the mixture is extruded into a plate shape to form a sheet. Moreover, you may combine both methods. Although the thickness of this sheet-like molded object is suitably determined by the conditions of the extending | stretching performed later, etc., it is the range of 0.1-0.5 mm, for example.

  The liquid lubricant contained in the obtained sheet-like molded body is preferably removed by a heating method or an extraction method before the subsequent stretching step. The solvent used in the extraction method is not particularly limited, and examples thereof include normal decane, dodecane, naphtha, kerosene, and sumoyl.

  Next, it extends | stretches with respect to the said sheet-like molded object. The said sheet-like molded object is stretched by uniaxial stretching or biaxial stretching at a temperature not higher than the melting point (327 ° C.) of PTFE to make it porous. For example, in the longitudinal direction of the sheet-like molded body, it is stretched at a temperature of 150 to 327 ° C. so that its length is in the range of 2 to 60 times, and subsequently in the width direction of the sheet-like molded body, The film is stretched at a temperature of 40 to 150 ° C. so that the length is in the range of 10 to 60 times. After the stretching, the stretched state may be maintained and heated to a temperature equal to or higher than the melting point (327 ° C.) of PTFE and fired to improve mechanical strength and increase dimensional stability. Thus, a PTFE porous membrane can be produced.

  In addition, the manufacturing method of a PTFE porous membrane layer is not limited to the above-mentioned method. In addition to such a method, for example, a PTFE fine powder having a different molecular weight mixed with a liquid lubricant is subjected to paste extrusion into multiple layers, rolled, and further stretched (Japanese Patent Publication No. 7-8926). A method of rolling and stretching a PTFE rolled sheet containing a lubricant (Japanese Examined Patent Publication No. 3-58291), laminating unfired PTFE porous structures having different pore diameters by pressure bonding, and having a melting point higher than that of PTFE A method of baking at a temperature (Japanese Patent Laid-Open No. 54-97686) can also be employed.

  The thickness of the breathable support is not particularly limited and can be selected according to the required filter medium performance. From the viewpoint of strength, the thickness is preferably, for example, in the range of 0.05 to 1 mm, more preferably 0.05 to 0.5 mm.

  The shape of the breathable support is not particularly limited, and for example, woven fabric, non-woven fabric, metal or plastic mesh, metal or plastic net, plastic foam, and the like can be used. In addition, it is preferable to use a nonwoven fabric for the said air-permeable support body from the point of cost. When the air-permeable support is a fiber material, for example, polyolefin such as polyethylene or polypropylene, synthetic fiber such as polyamide, polyester, aromatic polyamide, acrylic or polyimide, or a composite material thereof is used. be able to. A core-sheathed spunbonded nonwoven fabric such as PE (polyethylene) / PET (polyethylene terephthalate) spunbonded nonwoven fabric, polyester / polyethylene spunbonded nonwoven fabric, or the like can also be used.

  The PTFE filter medium can be obtained by bonding and integrating the PTFE porous membrane and a breathable support. The bonding method is not particularly limited, but for example, a method of laminating with a hot-melt net or mesh sandwiched, a method of applying and bonding an adhesive in fine dots or lines, a hot melt adhesive Examples include a method of bonding. As the adhesive, a two-component mixed type or a self-crosslinking type adhesive by heat can be used. As the two-component mixed type, an epoxy resin is preferable, and as the self-crosslinking type by heat, a vinyl acetate-ethylene copolymer, an ethylene-vinyl chloride copolymer, or the like is preferable.

  Considering from the viewpoint of cost, the method of laminating a non-woven fabric having thermal adhesiveness beforehand to the PTFE porous membrane layer is most preferably used. When a non-woven fabric made of a thermoplastic resin such as polyethylene is laminated with a PTFE porous membrane layer with appropriate heat and pressure, a part of the material melts and the PTFE porous Adhere to the membrane layer. Since this adhesion is limited to the non-woven fiber, air permeability is ensured in the part without fiber. The PTFE porous membrane and the air permeable support are preferably such that the PTFE porous membrane is upstream and the air permeable support is downstream with respect to the direction of air passing through the filter medium. Moreover, the said air permeable support body may be laminated | stacked on both surfaces of a PTFE porous membrane, respectively.

The thickness of the PTFE filter medium is not particularly limited, but is, for example, 0.05 to 3 mm, and preferably 0.05 to 1 mm.
Further, the PTFE filter medium may be folded as described above. Examples of the folding process include pleating and the like, and the pleating is performed using a reciprocating method, a rotary method, or the like. Note that the number of pleats, the size, and the like can be appropriately determined according to the use of the filter unit.

  The photo-curing type sealant contains a photo-curing resin that can be cured by light irradiation, and is not particularly limited as long as it has a shape (for example, liquid) that can be impregnated with a PTFE filter agent. Mold sealant and the like. If a photocurable sealing agent containing a photocurable resin is used in this way, for example, it is not thermally reactive like an isocyanate-based adhesive or a peroxide-based adhesive, so there is no need to consider pot life, Like hot melt, temperature adjustment for maintaining a viscosity suitable for coating is not necessary. As a specific example of the sealing agent containing the photocurable resin, for example, a photoinitiator can be added and adjusted to one or two or more known photopolymerizable oligomers or photopolymerizable monomers blended. . The form of the photo-curing resin is preferably liquid. Moreover, you may add another additive to the sealing compound containing the said photocurable resin as needed.

  Examples of the photopolymerizable oligomer include oligomers having two or more methacrylate groups such as polyester methacrylate, epoxy methacrylate, and urethane methacrylate.

  Examples of the photopolymerizable monomer include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, t-butyl group, isobutyl group, amyl group, isoamyl group, hexyl group, cyclohexyl group, 2 -Acrylic acid or methacrylic acid having linear or branched alkyl groups such as ethylhexyl group, octyl group, isooctyl group, nonyl group, isononyl group, decyl group, undecyl group, lauryl group, tridecyl group, tetradecyl group, stearyl group, octadecyl group, etc. Examples thereof include monofunctional or polyfunctional acrylic acid alkyl esters containing esters such as acids.

  Examples of the photoinitiator include benzoin ethers such as benzoin methyl ether and benzoin isopropyl ether; substituted benzoin ethers such as anisole methyl ether; 2, 2-diethoxyacetophenone, and 2, 2-dimethoxy-2-phenylacetophenone. Substituted acetophenones; substituted alpha-ketols such as 2-methyl-2-hydroxypropiophenone; aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride; 1-phenyl-1, 1-propanedione-2- (o-ethoxycarbonyl) And photoactive oximes such as) -oxime. The content rate of a photoinitiator is not restrict | limited in particular, According to the kind and desired viscosity of a photocurable sealing agent, it can determine suitably.

  The viscosity of the photocurable sealing agent is, for example, preferably 100 Pa · s or less, more preferably 0.01 to 40 Pa · s, and particularly preferably 1 to 40 Pa · s. Within such a range, for example, both the PTFE porous membrane constituting the PTFE filter medium and the breathable support can be sufficiently impregnated, and dripping can be sufficiently prevented. In addition, the viscosity of a photocurable sealing agent can be adjusted as follows, for example.

  The photocurable sealing agent containing the photopolymerizable monomer generally has a lower viscosity than the hot melt (usually about 1 Pa · s or less), and therefore impregnates PTFE filter media (PTFE porous membrane and breathable support). Easy to make. Also, before the photo-curable sealing agent is impregnated into the PTFE filter medium, for example, if the photo-polymerizable monomer is partially polymerized by ultraviolet irradiation, the viscosity of the photo-curable sealing agent can be increased. . In the curing by ultraviolet irradiation, the reaction can be stopped by interrupting the irradiation, so that the viscosity can be easily adjusted by stopping the irradiation when the desired viscosity is reached. On the other hand, in the case of a photocurable sealing agent containing a photopolymerizable oligomer, for example, the viscosity is generally lowered by adding a monomer having a low viscosity, the viscosity is raised by partial polymerization as described above, etc. Viscosity can be adjusted easily. In addition, a viscosity can be suitably determined according to the fabric weight, thickness, etc. of a breathable support body, for example.

  In addition, the photo-curing type sealing agent not only serves to eliminate a gap between the PTFE filter medium and the mold (so-called sealing), but also adheres the two by, for example, imparting adhesiveness to itself. You can also. In this case, as the photopolymerizable monomer contained in the photocurable sealing agent, for example, a conventionally known monomer having a glass transition temperature (Tg) of room temperature or lower (for example, 25 ° C. or lower), preferably 0 ° C. or lower is used. For example, a photocurable sealing agent that is a pressure-sensitive adhesive can be prepared by using a conventionally known blending method. Further, for example, depending on the desired elastic modulus after curing, the type and content ratio of the monomer or oligomer to be used can also be determined.

  Next, although the manufacturing method of the filter unit of this invention is demonstrated with a specific example, it is not restrict | limited to these.

  As a first manufacturing method, (impregnation step a) impregnating the end portion of the PTFE filter medium with a photocurable sealing agent containing a photocurable resin, and (curing step c) curing the photocurable resin, Step b) An example of a method for storing the PTFE filter medium in a mold will be described.

  First, the PTFE filter medium as described above is prepared, and the end portion thereof is impregnated with the photocurable sealing agent.

  The impregnation method is not particularly limited, and examples thereof include a method in which the end portion is applied with a nozzle, a brush, a sponge, and the like, and a method in which only the end portion is immersed in the photocurable sealing agent. These methods can be selected depending on the ease of supply according to, for example, the viscosity of the photocurable sealing agent. For example, when the viscosity is relatively high, supply with a nozzle is preferable, When the viscosity is low, application with a brush or a sponge is preferred.

  The PTFE filter medium is usually used by laminating a PTFE porous membrane and a breathable support and then cutting out to a desired size. The photocurable sealing agent is impregnated from the cut surface (side surface) of the end. It is preferable to make it. This is because, by impregnating from the side, the photocurable sealing agent surely permeates both the PTFE porous membrane and the air-permeable support. Further, the end portion of the PTFE filter medium may be impregnated with a photocurable sealing agent from the surface of the PTFE filter medium. In this case, the photocurable sealing agent is applied to the outermost part of the PTFE filter medium (that is, the outermost part of the breathable support), the sealing agent is allowed to permeate the breathable support, and the sealing agent is made of PTFE porous material. By reaching the membrane, the interface between the air-permeable support and the PTFE porous membrane can be adhered.

  The PTFE filter medium is generally subjected to pleating as described above, but the impregnation with the photocurable sealing agent may be performed before or after the processing. Alternatively, the raw material of the PTFE filter medium before cutting may be pleated and cut, and then impregnated at the end. In that case, it can also apply | coat, for example by winding the PTFE filter material which gave the pleating process around a roll, and immersing only the edge part of a roll-shaped PTFE filter medium in the said photocurable sealing agent.

  The width of the end portion of the PTFE filter material impregnated with the photocurable sealing agent is not particularly limited. For example, at least the PTFE filter material may be impregnated in a portion in contact with the mold, and the PTFE porous material may be porous. It is preferable to carry out so that it may become more than the thickness of a membrane. Usually, since the PTFE porous membrane used for the filter medium has a thickness of several μm to several tens of μm, the impregnation width is preferably 0.01 mm or more, and more preferably about 0.1 mm. Moreover, in order to ensure the sealing property with a formwork, it is preferable that the width is preferably a formwork width, more preferably an impregnation width equal to or greater than the formwork width.

  It is sufficient that the photocurable sealing agent is impregnated not only in the PTFE porous membrane but also in the air-permeable support. For example, the photocurable sealing agent is raised to about 1 mm from the surface of the PTFE filter medium. For example, the height at which sealing can be performed can be selected in a timely manner in accordance with the meshing accuracy of the formwork. In this case, the viscosity of the photocurable seal is preferably in the range of 10 to 100 Pa · s, for example. This form will be described later.

  Next, the PTFE filter medium is stored in a mold.

  The mold is not particularly limited, and a conventionally known one can be used. For example, a mold having a form in which an upper member and a lower member are fitted is generally used.

  An example of a formwork is shown in the perspective view of FIG. As shown in the figure, a pair of side surfaces includes a frame-shaped upper member 30a and a lower member 30b having comb-shaped protrusions. When the upper member 30a and the lower member 30b are fitted together, combs on both side surfaces are formed. The protrusions of the mold are engaged with each other. Note that the upper member 30a and the lower member 30b are in mesh with each other on the other side surface. Then, as shown in the perspective view of FIG. 4 (a), for example, a pleated PTFE filter medium is disposed between the upper member 30a and the lower member 30b so as to extend along the comb-shaped protrusion, and both the members 30a, If 30b is engaged, as shown in FIG. 4B, the PTFE filter medium can be clamped by the engagement of both the members 30a and 30b.

  In the case of such a form, the PTFE filter medium is an engagement portion between the upper member and the lower member, and comes into contact therewith, so that the contact portion may be impregnated with the photocurable sealing agent (see FIG. 3 and FIG. 3). In FIG. 4, a photocurable sealing agent is not shown).

  Subsequently, the PTFE filter medium housed in the mold is irradiated with light to cure the photocurable sealing agent.

  As described above, the end portion of the PTFE filter medium accommodated in the mold, that is, at least the portion in contact with the mold is impregnated with the photocurable sealing agent. Therefore, for example, compared with the case where the sealant is not impregnated and stored in the mold, the sealant, as well as the inside of the PTFE filter medium, at the end, the mold and the PTFE filter medium The gap is filled, that is, in a sealed state. Therefore, the adhesiveness between the PTFE filter medium and the mold can be reliably maintained by further curing the photocurable resin by light irradiation.

  In addition, as described above, if the photocurable sealing agent is raised from the surface of the PTFE filter medium, the raised portion plays a role like packing, so that the adhesion between PTFE and the mold is further increased. It can be said that it can be improved. For example, in the case of the mold shown in FIG. 3, the photo-curing sealant portion is compressed between the upper member and the lower member, so that even if the engagement accuracy of the both members is low The gap generated between the two members can be filled by the raised portion. Further, the adhesion can be reliably maintained by further curing.

  The light irradiation can be performed according to, for example, the type of the photocurable sealing agent. For example, in the case of an ultraviolet curable sealing agent containing an ultraviolet curable resin, it is preferable to irradiate ultraviolet rays. The light irradiation conditions are not particularly limited, and can be determined according to, for example, the type of the photo-curing sealant used, and can usually be performed using a high-pressure mercury lamp.

  As a second production method, (impregnation step a) impregnating the end portion of the PTFE filter material with a photocurable sealant, (storage step b) after storing the PTFE filter material in a mold, (curing step c) A method for curing the photo-curing resin is exemplified. This method can be performed in the same manner as in the first manufacturing method, except that curing is performed after storage. Thus, the method of hardening after storage is preferable, for example, when the gap of a formwork is narrow. This is because the compressive stress after curing does not increase and the generation of repulsive force is suppressed, so that the shape can be sufficiently retained without generating extra stress when fitted in the mold.

  As a third manufacturing method, (housing step b) after the PTFE filter medium is housed in a mold, (impregnation step a) an end portion of the PTFE filter medium is impregnated with a photocurable sealing agent containing a photocurable resin. (Curing step c) A method of curing the photo-curing resin is exemplified. As described above, when impregnated with a photocurable sealing agent after being stored in the mold, the impregnation surely introduces the sealing agent between the PTFE filter medium and the mold and cures it. Thus, the adhesion between the two is ensured.

  After the PTFE filter medium is housed in the mold, for example, the photocurable sealant is applied to the exposed end of the PTFE filter medium from the outside of the mold to impregnate the seal material. it can. Moreover, you may impregnate the said photocurable sealing agent from the inner side of a formwork. This is because, unlike a conventional hot melt or the like, for example, since there is almost no change in viscosity, the valleys can be sufficiently impregnated. As another method, it is also possible to apply the photo-curing sealant to a portion of the mold that is in contact with the PTFE filter medium, and perform the storing step and the impregnation step almost simultaneously.

EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not restrict | limited by a following example.
(Preparation of PTFE filter media)
100 parts by weight of PTFE (trade name Fluorone CD-123, manufactured by Asahi Glass Co., Ltd.) and 30 parts by weight of a liquid lubricant (liquid paraffin) were uniformly mixed, and this mixture was preformed under the condition of 20 kg / cm ² . The preform was extruded into a rod shape, and the obtained rod-shaped product was passed between a pair of metal rolling rolls to obtain a long sheet-shaped molded product having a thickness of 0.2 mm. Next, the liquid lubricant was removed from the sheet-shaped molded body by an extraction method using normal decane, and the sheet-shaped molded body was wound around a tubular core body in a roll shape. Furthermore, this sheet-like molded body is stretched at 320 ° C. in the longitudinal direction by a roll stretching method (stretching ratio 20 times), and then stretched at 90 ° C. in the width direction using a tenter (stretching ratio 60 times). A PTFE porous membrane was prepared. The obtained PTFE porous membrane had a thickness of 3 μm.

  Next, the PTFE porous membrane and the spunbond nonwoven fabric were thermally laminated to prepare two types of PTFE filter media. As the spunbonded nonwoven fabric, a commercial product (trade name Elves, manufactured by Unitika Co., Ltd.) formed of a composite fiber having a polyester / polyethylene core-sheath structure having a basis weight of 15 g, 30 g, and 70 g, respectively, was used. The structures of the two types of produced filter media are shown in the cross-sectional views of FIGS. 1 (a) and 1 (b). The first filter medium shown in FIG. 1 (a) includes one layer of PTFE porous membrane 10 and two nonwoven fabrics 20, and three layers of nonwoven fabric 20 having a basis weight of 30 g laminated on both sides of the PTFE porous membrane 10. Structure. The second filter medium shown in FIG. 1 (b) includes two porous membranes 10, two nonwoven fabrics 21 having a basis weight of 15 g, and one nonwoven fabric 22 having a basis weight of 70 g. A nonwoven fabric 21 with a basis weight of 15 g is arranged on both surfaces of the porous membrane 10, and a nonwoven fabric 22 with a basis weight of 70 g is further arranged on one nonwoven fabric 21 via the second porous membrane 10, and these are laminated. It has a five-layer structure. The first filter medium and the second filter medium were bonded together by overlapping each other on a 145 ° C. hot roll.

The two types of filter media are subjected to pleating using a reciprocating pleating machine at a blade temperature of 90 ° C., and two types of pleated PTFE filter media having a pleat crest interval of 10 mm (pleated first PTFE filter media, pleated first pleated media) 2PTFE filter medium) was obtained.
(Example 1)
90 parts by weight of 2-ethylhexyl acrylate (manufactured by Wako Pure Chemical Industries), 10 parts by weight of acrylic acid (98% by weight acrylic acid, manufactured by Toagosei Co., Ltd.) and 2,2-dimethoxy-2-phenylacetophenone (trade name Irgacure 184, 1 part by weight of Ciba Specialty Chemicals Co., Ltd. was blended to prepare an ultraviolet curable resin solution as a photo-curable sealant. The viscosity of the ultraviolet curable resin solution was 0.01 Pa · s or less.

As shown in the perspective view of FIG. 2, the above-mentioned two types of pleated PTFE filter media were each cut so as to have a width of 60 mm and a length of 15 pleated peaks. 2 to 5, the number of pleat peaks is omitted. Then, the periphery of the PTFE filter medium, that is, an end portion of about 2 mm from the cut portion was immersed in the ultraviolet curable resin solution, and only the end portion was impregnated with the solution. Subsequently, the PTFE filter medium was irradiated with ultraviolet rays (irradiation amount: 3000 mj / cm ² ) using a high-pressure mercury lamp having a light intensity of 100 mW / cm ² to cure the ultraviolet curable resin.

Then, the PTFE filter medium was sandwiched between cases to obtain a filter unit. As shown in the perspective view of FIG. 3, the case is composed of two frame-shaped members (30a, 30b) whose pair of side surfaces are comb-shaped protrusions, 30a being an upper member, and 30b being a lower member. When the upper member 30a and the lower member 30b are combined, the comb-shaped protrusions on the side surfaces of both are engaged with each other. In addition, as for the shape of the side surfaces of both members (30a, 30b), the interval between the peaks and valleys is 10 mm, and the number of peaks in the lower member (30b) is 15. Specifically, the PTFE filter medium is disposed on the lower member 30b so that the peak portion is along the peak portion on the side surface of the lower member 30b. Further, the upper member 30a is disposed on the PTFE filter medium 1, and the lower member 30b and the upper member 30a are meshed. Schematic diagrams of the obtained filter unit are shown in FIGS. FIG. 4A is a perspective view showing the filter unit disassembled for each constituent member, and FIG. 4B is a perspective view of the filter unit 3. FIG. 5 is a cross-sectional view of the filter unit 3 of FIG. 4B as seen from the II direction. 1 to 5, the same portions are denoted by the same reference numerals.
(Example 2)
A PTFE filter medium and a filter unit were manufactured in the same manner as in Example 1 except that the viscosity of the ultraviolet curable resin solution was 10 Pa · s. In order to adjust the viscosity, first, an ultraviolet curable resin solution is put into a flask, a nitrogen purge is performed for 30 minutes, and then ultraviolet rays are irradiated through quartz glass, and the viscosity is detected by the torque of a stirring blade, and a target is obtained. When the viscosity (10 Pa · s) was reached, ultraviolet irradiation was stopped.
(Example 3)
A PTFE filter medium and a filter unit were manufactured in the same manner as in Example 1 except that the PTFE filter medium impregnated with the ultraviolet curable resin solution was sandwiched between cases and irradiated with ultraviolet light.
(Comparative Example 1)
A PTFE filter medium and a filter unit were manufactured in the same manner as in Example 1 except that the pleated PTFE filter medium was not directly impregnated with the ultraviolet curable resin solution but directly sandwiched between cases.
(Comparative Example 2)
Example: Except that the pleated PTFE filter medium was directly sandwiched between cases without impregnating the UV curable resin solution, then hot melt was applied along the end of the PTFE filter medium from the outside of the case and sealed. In the same manner as in Example 1, a PTFE filter medium and a filter unit were manufactured. The temperature condition when applying the hot melt was 180 ° C., and the viscosity of the hot melt at that time was 5 Pa · s.
(Comparative Example 3)
A PTFE filter medium and a filter unit were manufactured in the same manner as in Comparative Example 2 except that the pleated PTFE filter medium on the downstream side of the airflow was sealed with hot melt from one surface side.

The sample of the filter unit thus prepared was subjected to measurement of pressure loss and collection efficiency, and the deterioration of characteristics of the PTFE filter medium was examined. The comparison results are shown in Table 1.
(Pressure loss)
The sample (filter unit) is set in a circular holder having an effective area of 100 cm ² , while supplying atmospheric dust from the inlet side, a pressure difference is applied between the inlet side and the outlet side, and the air permeation speed is set to 5. The atmospheric dust was adjusted to 3 cm / sec and the pressure loss (unit Pa) was measured with a pressure gauge (manometer). The measurement was performed at five locations per sample, and the average of each measurement value was taken as the pressure loss of the sample. The term “air dust” refers to dust floating in the atmosphere.
(Collection efficiency)
Using the same apparatus as the pressure loss measurement, the air permeation flow rate is 5.3 cm / sec, and 10 ⁷ polydispersed dioctyl phthalate (DOP) particles having a particle size of 0.1 μm to 0.15 μm are located upstream of the sample. The particle concentration on the upstream side and the concentration on the downstream side that has permeated the sample are measured with a particle counter (trade name KC-80, manufactured by Rion Co., Ltd.) and captured based on the following formula. The collection efficiency (%) was determined.
Collection efficiency (%) = [1− (Downstream concentration / Upstream concentration)] × 100
Unit of particle concentration downstream: Particles / liter Unit of particle concentration upstream: Particles / liter
(Weight amount)
The nonwoven fabric made of the PE / PET core-sheath fiber was sampled at 100 cm ² , and the weight was measured with an electronic balance to determine the mass per 1 m ² .

  As shown in Table 1, the pressure loss was reduced and the collection efficiency was sufficiently maintained in the examples, but in the comparative example, the adhesion between the filter medium and the case was probably insufficient. There was a decrease in the collection efficiency that was thought to be caused by

  As described above, according to the present invention, by using the ultraviolet curable resin solution, there is no increase in pressure loss and no decrease in collection efficiency, and the end of the filter medium and the mold can be easily and sufficiently sealed. Therefore, it can be said that this is a very useful production method.

FIG. 1 is a cross-sectional view showing an example of a PTFE filter medium in the filter unit of the present invention. FIG. 2 is a perspective view of another example of the PTFE filter medium in the filter unit of the present invention. FIG. 1 is a perspective view showing an example of a mold in the filter unit of the present invention. FIG. 4A is a perspective view showing an example of the filter unit of the present invention in a state in which constituent members are disassembled, and FIG. 4B is a perspective view showing an example of the filter. It is sectional drawing of the said filter unit.

Explanation of symbols

1, 2 PTFE filter medium 3 Filter unit 10 PTFE porous membrane 20, 21, 22 Breathable support 30a Upper member 30b Lower member

Claims (9)

A method of manufacturing a filter unit that contains a PTFE filter medium including a polytetrafluoroethylene (PTFE) porous membrane and a breathable support in a mold, and a photocuring that includes a photocurable resin at an end of the PTFE filter medium An impregnation step (a) for impregnating a mold sealant, an accommodating step (b) for accommodating the PTFE filter medium in a mold, and a curing step (c) for curing the photocurable resin solution impregnated in the PTFE filter medium. A method for manufacturing a filter unit comprising: The manufacturing method of Claim 1 which implements the said hardening process (c) after the said impregnation process (a) and the said accommodation process (b). The manufacturing method of Claim 1 which implements the said accommodation process (b) after the said impregnation process (a) and the said hardening process (c). The manufacturing method of Claim 1 which implements the said impregnation process (a) and the said hardening process (c) after the said storage process (b). The manufacturing method according to any one of claims 1 to 4, wherein in the impregnation step, a photocurable sealing agent containing the photocurable resin is impregnated from the PTFE porous membrane side of the PTFE filter medium. The manufacturing method according to claim 1, wherein the photocurable sealing agent has a viscosity of 100 Pa · s or less. The said air-permeable support body is a nonwoven fabric, The manufacturing method as described in any one of Claims 1-6. The manufacturing method according to claim 1, wherein the PTFE filter medium is a folded filter medium. The filter unit obtained by the manufacturing method of the filter unit as described in any one of Claims 1-8.

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