JP4800598B2 - Manufacturing method of electret filter material made of pleated folded nonwoven fabric and filter material using the same - Google Patents

Description

  The present invention relates to a method for manufacturing a nonwoven fabric obtained by pleat folding an electret processed nonwoven fabric.

  Conventionally, as a general filter material, a nonwoven fabric obtained by electretizing a melt blown nonwoven fabric made of polypropylene resin has been used. Since melt blown nonwoven fabrics are not elastic, the melt blown nonwoven fabric is bonded to the melt blown nonwoven fabric, which is bonded to a rigid porous material such as a chemical bond bonded nonwoven fabric made of polyethylene terephthalate fiber or an opening material such as mesh. Fold the pleats. For this reason, a chemically bonded nonwoven fabric of polyethylene terephthalate fiber, in which polyester fiber with a glass transition point higher than room temperature is impregnated and bonded with a hard acrylic adhesive, has been used as a base fabric for folding electret polypropylene meltblown nonwoven fabrics. It was. Furthermore, in Japanese Unexamined Patent Application Publication No. 2004-66806 (Patent Document 1), a molded fibrous sheet is proposed in which a fibrous sheet having higher rigidity than a biodegradable electret fibrous sheet is bonded to the biodegradable electret fibrous sheet. Yes.

In addition, since the electretized polypropylene meltblown nonwoven fabric uses an electretization method by an ion implantation method, it cannot be said that the electret heat resistance is good. Generally, at 60 ° C., the disappearance of the electret begins. In general, the pin sonic method, which is not easily affected by heat, is also used. In general, in order to form and process a hard nonwoven fabric with good shape retention, thermoforming is usually used. However, since the conventional electret nonwoven fabric is vulnerable to heat, the electret nonwoven fabric has not been thermoformed.
JP 2004-66806 A

  The chemically bonded non-woven fabric bonded to the electret non-woven fabric or Patent Document 1 is a rigid non-woven fabric, so that it can be folded pleats with a feeling of being folded, the pleat folding is less likely to occur, and a sharp fold is formed. The meltblown non-woven fabric with no crack was covered with a folded surface, so the state of the crease was inconspicuous and was not sharp. In addition, non-woven fabrics made of polyolefin resin fibers are generally difficult to fold by pleats due to the rubber elasticity of polyolefin resin, and there is a problem in shape retention even if pleats are folded. It was done.

  An object of the present invention is to provide a method for producing a pleated folded nonwoven fabric excellent in pleat retention, which is an electret-processed nonwoven fabric, and a filter material using the same.

In order to solve such problems, the present inventors have examined the thermoformability in detail, and although it depends on the type of resin, it is 20 ° C. above the temperature at which the resin softens (hereinafter also referred to as “practical use temperature”). It has been found that a non-woven fabric can be permanently (permanently) thermoformed by applying a physical external force with a pleat folder at a low temperature or higher to cause thermoforming / deformation. That is, this invention is a manufacturing method of the electret filter material which consists of a pleated fold nonwoven fabric which pleat-folds the electret processed nonwoven fabric, Comprising: Resin which comprises the main electret fibers which comprise the said nonwoven fabric is polybutene-1 resin The polybutene-1 resin has a melting point (Tms: ° C.) of 115 <Tms <130, and the nonwoven fabric is pleated in a state of being heat-treated at a temperature of 60 to 100 ° C., or the nonwoven fabric The resin that constitutes the main electretized fibers constituting the fiber is a polypropylene resin, and the nonwoven fabric is pleated in a state of being heat treated at a temperature of 50 to 60 ° C., and the heat treatment is performed immediately before the pleat folding process. It is characterized by being.

  The filter material of the present invention is characterized in that the pleated folded nonwoven fabric produced by the above method is bonded and integrated with a frame.

  The filter material of the present invention is characterized in that the pleated folded nonwoven fabric produced by the above method is bonded and integrated with a frame.

  The present invention is a pleat folding process in a state where the temperature is 20 ° C. lower than the temperature at which the electretized fibers are softened, and is heat-treated in a range below the temperature at which at least 90% of the electret performance can be maintained. A pleated folded nonwoven fabric having high pleat retention can be obtained without losing the electret properties of the electret processed nonwoven fabric.

  In particular, the present invention includes a composite fiber in which polybutene-1 occupies 70% or more of the fiber surface as a main electret fiber constituting the nonwoven fabric, and is pleated in a state of being heat-treated in a range of 50 ° C. or more and 120 ° C. or less. By processing, a pleated folded nonwoven fabric having high pleat retention can be obtained without losing the electret property of the electret nonwoven fabric.

  In the filter material of the present invention, since the pleated folded nonwoven fabric produced by the above method is bonded and integrated with the frame, it has permanent pleat retention, and the pleated folding width is increased to increase the surface area. This can increase the filtration life.

  In general, it is well known that permanent shaping can be achieved when a polyolefin resin or fiber is thermoformed and deformed by applying a physical external force at a temperature higher than the practical use temperature. Polyolefin resins are excellent in disposal and recyclability. However, since they are soft and rich in rubber elasticity, non-woven fabric made of fibers has been generally recognized as a material that is inferior in rigidity and difficult to fold in pleats. Unlike other polyolefin fibers previously proposed by the present inventors, an electret comprising a composite fiber of polybutene-1, which is a rigid nonwoven fabric and can be used alone as a pleated folding filter, and polypropylene or polymethylpentene Even in the case of non-woven fabrics, especially when electret non-woven fabrics made entirely of polyolefin resin are pleated, due to the rubber elasticity that is characteristic of polyolefin resin, it tends to spread out even if it is folded, if it is removed, it assembles a pleated fold filter The work was complicated.

  The electret nonwoven fabric of polybutene-1 which is one form of the present invention has heat resistance in electret properties, enables thermoforming of pleats that could not be considered in conventional electret nonwoven fabrics of polypropylene fibers, and the electret properties are also impaired. It has been found that there is a wide range of thermoforming conditions for processing, and permanent pleating can be easily performed by pleating in a heat-treated state. As a result, it is possible to obtain a pleated filter made of only an electret material, without a pleated support that could not be considered with conventional electret nonwoven fabrics of polypropylene fibers. In particular, a filter made of an all-polyolefin resin does not emit black smoke like a polyethylene terephthalate resin even if it is incinerated, and is a filter excellent in disposal after use that is extremely easy to regenerate because of its non-hygroscopic property.

  The filter material of the present invention, when used as an all-olefin resin air filter, is easy to dispose of and does not contain any environmental hormones or other harmful substances as a material. Since it does not generate harmful gases such as hydrogen chloride, it is suitable as a filter material considering humans and the environment.

  The “temperature at which electretized fibers soften” in the present invention refers to a temperature (hereinafter referred to as “practical use temperature”) where the softening of the resin constituting the electretized fibers exceeds that. Specifically, in the polyolefin resin, the practical use temperature of the polypropylene resin is 70 ° C, the polybutene-1 resin is 100 ° C, and the polymethylpentene resin is 160 ° C.

  The electret performance of the polyolefin resin can be maintained up to 50 ° C. with electret polypropylene fibers obtained by a general ion implantation method with heating for 6 minutes, but rapidly loses when the temperature exceeds 60 ° C. In a composite fiber having polybutene-1 electretized by heat electret processing as the fiber surface, the fiber is stable up to 110 ° C., and when it exceeds 120 ° C., the loss starts gradually. Polymethylpentene resin is stable up to 160 ° C. and starts to lose at temperatures above this. The propylene copolymer depends on the copolymerization ratio, but is generally below the temperature of the polypropylene resin described above. It has been found that the electret stability of the polyolefin resin has a strong relationship with the practical use temperature which has a strong relationship with the fluidity of the molecule. Of course, it goes without saying that there is a strong relationship between the product of the heating temperature and the exposure time at that temperature and the electret stability. Therefore, permanent permanent pleats can be obtained by pleating the electret nonwoven fabric under the conditions above the minimum permanent thermoforming temperature and below the maximum temperature and heating time at which electret stability can be ensured. Can be processed. Specifically, by performing pleat folding in a state where the temperature is 20 ° C. lower than the practical use temperature and the temperature is not more than 90% of the electret performance, it is permanently A pleated folded nonwoven fabric having a permanent can be obtained. After the pleating process, it is better to cool to room temperature by cooling. In the present invention, “maintain at least 90% of electret performance” is measured according to JIS-B-9908 (performance test method for ventilation air filter unit / ventilation electric dust collector) described later. The rate at which the collection efficiency changes before and after the pleat folding, that is, the collection efficiency after the pleat folding is divided by the collection efficiency before the pleat folding, and a value multiplied by 100 is expressed as the electret performance retention rate I will do it.

  The “heat-treated state” as used in the present invention refers to a state in which the electret-processed nonwoven fabric is heat-treated and maintained at a temperature within a predetermined temperature range. And it is preferable that the said heat processing is the process immediately before in a pleat folding process (henceforth "preheating process"). Examples of the preheating treatment include a method of contacting with a heating plate, a method of heating with a hot air heating box, a method of contacting with a hot roll, and a method of heating with an infrared heater.

  For example, a conventional electretized polypropylene meltblown nonwoven fabric is obtained by performing pleat folding at a temperature that is higher than the practical use temperature (70 ° C) -20 ° C of polypropylene resin and lower than 60 ° C at which the electret performance is reduced. The pleated folded nonwoven fabric of the invention can be obtained. A nonwoven fabric comprising an electretized composite fiber composed of a polybutene-1 resin as one component is obtained by subjecting a pleat fold process to a practical use temperature (100 ° C.)-40 ° C. higher than 60 ° C. and lower than 120 ° C. The pleated folded nonwoven fabric of the invention can be obtained. In this way, the main electretized fiber is heated under heat processing that can maintain at least 90% of its electret performance, and is plied in a softened state, and after permanent pleating, after the pleats are stretched, Even if it is released and relaxed, it is possible to obtain a novel pleated folded non-woven fabric that is almost restored to the heat-set pleated shape and is rich in pleat restoration.

  Furthermore, it is also preferable that the pleats are heat-set by further heating at least the ridge line portion of the pleated nonwoven fabric because permanent pleatability can be enhanced. Specifically, there is a method in which after the pleat folding process, in the folded state, heat exposure below the heat treatment condition is performed, and the ridge line portion of the pleat is mainly exposed to heat.

  In addition, the pleat folding machine used in the present invention is roughly classified into two processing methods. One is a reciprocating pleated folder that does not choose the thickness of the nonwoven fabric. The other is a rotary pleat folding machine of a roller nip method in which the thickness of the nonwoven fabric that can be processed is limited. At present, since a rotary unit is set on an impregnated base fabric made of polyethylene terephthalate fiber, which is widely used with thickness, it is necessary to match the thickness of the filter material not using the base fabric.

  The electret-processed nonwoven fabric (hereinafter referred to as “electret nonwoven fabric”) that can be used in the present invention has a fiber material layer intended to be electretized. Specific examples of fibers that can be electretized include a meltblown nonwoven fabric made of polypropylene resin, or a meltblown nonwoven fabric of a composite fiber having a core component made of polypropylene resin and a sheath component made of polybutene-1 resin. 70% or more of the fibers are made of a polyolefin resin mainly composed of propylene, butene-1 or methylpentene, and are mainly non-woven fabrics fiberized by a melt blow method, a spun bond method or a split yarn method preferable.

  Based on a polypropylene spunbond nonwoven fabric, which is one of the present invention, which has the advantage of easy disposal after use and is composed entirely of polyolefin resin, the meltblown nonwoven fabric of polybutene-1 composite fiber has a fiber mass It is preferable that many are scattered in the nonwoven fabric. By increasing the thickness of the non-woven fabric, the bulk of the fiber mass can be increased. An electret nonwoven fabric in which a large number of fiber lumps are dispersed in the nonwoven fabric has a structure in which a large gap is formed between the fibers collected around the fiber lumps. Furthermore, by collecting fibers from the top, it is possible to create a three-dimensional accumulation condition in the thickness direction and actively perform fiber accumulation to lower the density. As a result, it is possible to widen the inter-fiber gap and improve fluid permeability. It was. In other words, the electret filter material has an effect of reducing the pressure loss and has a lower pressure loss.

One of the preferred forms of the electretized non-woven fabric is produced by a melt-blowing method in which a composite fiber is composed of two or more thermoplastic resin components having different melting points and the low melting point component occupies most of the fiber surface. A large number of fiber lumps in which a plurality of constituent fibers are partially aggregated and fused to form a convex portion on the nonwoven fabric surface, and there are fiber lumps around the fiber lumps. The nonwoven fabric has a bulkiness (thickness μm / g / m ² per unit area) of 8 or more, characterized in that the gap between the constituent fibers spreads from the unexposed portion and the fiber density decreases.

  The electret fiber has an average fiber diameter (d: μm) of 0.3 <d <200, and in the case of a composite fiber, each of a plurality of constituent thermoplastic resin components has a melting point (Tm: ° C.) of 60. ≦ Tm <270, melt flowability melt flow rate (MFR: g / 10 min; measurement temperature is 230 ° C. when Tm ≦ 200, 290 ° C. when 200 <Tm, weight is 2.169 Kg, JIS-K- 6760) is preferably a thermoplastic synthetic resin in which 5 <MFR <200.

The thermoplastic resin component of the composite fiber is a polybutene having a low melting point component having a density (D: g / cm ³ ) of 0.905 ≦ D <0.930 and a melting point (Tms: ° C.) of 115 <Tms <130. 1 and the other is preferably polypropylene.

  Furthermore, a surface nonwoven fabric layer made of fibers having a fiber diameter of 15 μm or more is arranged on at least one surface of the composite fiber nonwoven fabric made of polybutene-1 and polypropylene, and depends on at least the low melting point component of the composite fiber constituting the composite fiber nonwoven fabric. A composite nonwoven fabric integrated by thermal bonding is preferred.

One of the preferable forms of the composite nonwoven fabric is a composite nonwoven fabric having a basis weight of 30 to 400 g / m ² . If the basis weight exceeds 400 g / m ² , electret processing becomes extremely difficult, and the heat pleat set may be difficult due to its thickness.

  Most preferably, the surface non-woven fabric layer is a single component fiber or a composite fiber in which the fibers are made of only a polyolefin resin. The single component fiber includes a mixed polymer fiber, a polymer alloy fiber, an inorganic material added fiber, and the like, and any of them is preferable. The form of the fiber is preferably a hollow fiber or a modified cross-section fiber. Specifically, a homopolymer mainly composed of propylene, a spunbond nonwoven fabric of single component fibers or composite fibers, and / or polypropylene, comprising at least one polyolefin resin among copolymers mainly composed of propylene. A majority of the fiber surface is covered with a propylene-based copolymer propylene or polybutene-1, and a composite fiber heat-bonded nonwoven fabric or hydroentangled nonwoven fabric with polymethylpentene as the core component is preferred.

  Further, one surface of the surface nonwoven fabric layer is a fiber made of polyethylene terephthalate resin. After the fiber is physically entangled and integrated with the above-described spunbond nonwoven fabric by needle punching or hydroentanglement treatment, For the purpose of improving rigidity and nonwoven fabric strength, it is a composite fiber that is bonded and integrated by impregnation with acrylic resin, one surface is a polyethylene terephthalate fiber layer, the middle layer is a spunbond nonwoven fabric layer, and is the main body of the electret function It is also preferable that the non-woven fabric layer is a composite non-woven fabric forming another surface.

  Further, the composite fiber composed of polybutene-1 and polypropylene has an average fiber diameter (d: μm) of 0.00 on the composite fiber nonwoven fabric having an average fiber diameter (d: μm) of 10 <d <200. It is preferable that the above-mentioned composite fiber nonwoven fabric having a composite fiber of 3 <d <20 as a constituent fiber is disposed, and a layer between the nonwoven fabric layers is a composite nonwoven fabric that is thermally bonded and integrated by a low melting point component of the composite fiber.

  One of the preferred embodiments of the present invention is a composite nonwoven fabric in which the composite nonwoven fabric is electret-processed and composite fibers made of at least polybutene-1 and polypropylene are electretized.

  Moreover, since it is a composite nonwoven fabric processed by electret, one of the preferable forms is that at least one surface of the nonwoven fabric layer is not attached with a hydrophilic chemical substance such as a surfactant that may adversely affect the effect of the electret. It is preferably composed of polypropylene fiber or polyethylene fiber, and further, this surface nonwoven fabric layer is disposed on both sides, and is a composite fiber comprising the polybutene-1 and polypropylene according to one embodiment of the present invention The non-woven fabric is a composite non-woven fabric that is integrated by thermal bonding with at least a low melting point component of the composite fiber constituting the composite fiber non-woven fabric, and is electretized.

  One of the preferred embodiments of the present invention is a composite comprising the composite fiber nonwoven fabric in which a surface nonwoven fabric layer made of fibers having a fiber diameter of 15 μm or more is disposed on at least one surface of the composite fiber nonwoven fabric made of polybutene-1 and polypropylene. One or more selected from polypropylene fiber having a fiber diameter of 5 μm or more, rayon fiber, vinylon fiber or acrylic fiber on the composite fiber nonwoven fabric surface side of the composite nonwoven fabric integrated by thermal bonding with at least a low melting point component of the fiber This is a composite nonwoven fabric in which a hydrophilic fiber layer made of the above fibers is laminated and integrated by thermal bonding using at least a low melting point component of the composite fiber and is electretized. Furthermore, the hydrophilic fiber layer is water-soluble or hydrophilic, for example, antibacterial, bactericidal, antibacterial, such as copper compounds such as copper sulfate, zinc compounds, metal phthalocyanine derivatives, and natural useful products such as salmon thiol. It is also preferable to impregnate or fix an agent having odor or aromatherapy properties.

  One of the preferred embodiments of the present invention is a composite comprising the composite fiber nonwoven fabric in which a surface nonwoven fabric layer made of fibers having a fiber diameter of 15 μm or more is disposed on at least one surface of the composite fiber nonwoven fabric made of polybutene-1 and polypropylene. A laminated nonwoven fabric composed of three layers of a rayon fiber layer, an activated carbon fiber layer, and a polypropylene spunbond nonwoven fabric layer is formed on at least one surface of a composite nonwoven fabric integrated by thermal bonding with at least a low melting point component of the fiber. It is a composite non-woven fabric that is integrated by heat bonding with components and is electretized.

Moreover, one of the preferable forms of this invention is the said composite nonwoven fabric in which the fiber of nonwoven fabric layers other than a melt blown nonwoven fabric is flame-retarded.
Hereinafter, the present invention will be specifically described.

  Examples of the electret non-woven fabric include a melt-blown non-woven fabric made of polypropylene and a melt-blown non-woven fabric made of a composite fiber using polybutene-1. Since the former method for making a melt-blown nonwoven fabric made of polypropylene is known, it will be omitted. The melt-blown nonwoven fabric composed of the latter composite fiber is composed of two or more thermoplastic resin components having different melting points, and preferably the two components as shown in FIG. The fiber has a cross-sectional structure like a three-layer type in which components are separated into two by other components, and the low melting point component occupies most of the fiber surface. In addition, multi-core type, three-layer type, and the fiber cross-section that is divided into at least a plurality of components and divided by other components are split fiber types such as mandarin orange type and windmill type, and the fiber shape is circle or ellipse Although it is basically a circular shape, there may be a variant with a rounded corner.

  Further, the average fiber diameter (d: μm) of the electretized fibers is generally 0.3 <d <200, and when intentionally forming a fiber lump, thick fibers of 20 μm or more are efficient and economical. In the case of adhering to a polypropylene spunbonded nonwoven fabric, the above-mentioned thick fibers are convenient because of their large adhesive strength for fixing or fusion bonding. Of course, in order to efficiently capture fine particles, it is preferable to accumulate a large number of finer fibers, and it is generally desirable that the nonwoven fabric of the present invention has a configuration of polypropylene spunbond nonwoven fabric / thick fibers / fine fibers. Whether or not the thick fiber layer has a fiber lump is selected depending on the filter performance specifications such as the thickness of the nonwoven fabric to be produced and the airflow pressure loss.

  The thermoplastic resin that forms such a composite fiber uses a resin having a higher melt flowability than the melt viscosity of a general staple composite fiber, and the melt flow rate is an index of the melt flowability. (MFR: g / 10 min; measurement temperature is 230 ° C. when Tm ≦ 200, 290 ° C. when 200 <Tm, weight is 2.169 Kg, according to JIS-K-6760), but 5 <MFR <1000 It is a certain thermoplastic synthetic resin. In addition, in the nonwoven fabric in which the fiber lump is scattered, the fiber having a large fiber diameter is ejected from the nozzle, and the adjacent fibers of the spun composite fiber are partially brought into contact with each other during the ejection to have the fiber lump in the structure. Form. Naturally, it is preferable to use a resin having a large MFR for fine fibers of 1 μm or less, and a resin having a low MFR for thick fibers exceeding 5 μm. Usually, it is economically convenient to select the resin from 50 to 1000 for the former and from 5 to 200 for the latter.

  By producing a melt-blown nonwoven fabric having a fiber mass, a nonwoven fabric having a thickness of 20 to 100% can be obtained from a melt-blown nonwoven fabric having the same basis weight produced by using the same thermoplastic resin by a conventional melt-blowing method. In the present invention, the thickness of the nonwoven fabric was measured by the JIS L-1913-6.1.2A method.

  The electret composite fiber constituting the electret non-woven fabric preferably has a melting point (Tm: ° C.) of the thermoplastic resin, and the resin covering the majority of the fiber surface (the melting point is Tms: ° C.) has a low melting point. , 60 ≦ Tms <170 is convenient. If the melting point is less than 60 ° C., it is not preferable because it is too fused and difficult to control. Further, if the temperature is 170 ° C. or higher, the combination with the thermoplastic resin that is the core component of the fiber is limited, which is not preferable. The melting point of the core component thermoplastic resin (whose melting point is Tmc: ° C.) is not preferable because it has a temperature restriction of the melt blow equipment used. In a practical range, less than 270 ° C. is appropriate. The relationship between the resin covering the majority of the fiber surface (the melting point is Tms: ° C.) and the melting point of the core component resin is preferably Tms + 20 ≦ Tmc.

  “Thermal bonding” in the present invention means that a low melting point thermoplastic resin is heated to a melting point or higher and melts and adheres, but when the heating temperature is low, the low melting point component maintains the shape of the fiber surface. It fuses to the adjacent fibers that come into contact. As the heating temperature becomes higher than the melting point, the low melting point component is completely melted and aggregates at the bonding point, and the adjacent fibers covering the bonding point are more firmly bonded and integrated.

  In the pleated folded nonwoven fabric having heat setting and permanent pleat retention according to the present invention, the electret nonwoven fabric is most preferably a hard and rigid nonwoven fabric. For rigid non-woven fabrics, it is particularly convenient to use a low MFR resin as the resin used for the fibers. In the present invention, a high MFR resin is used only when producing fine fibers of 5 μm or less, but fibers of 1 μm or more are used. In this case, in order to obtain a rigid nonwoven fabric that meets the object of the present invention by spinning rigid fibers, the staple fibers are not intended to be made finer by using a low-viscosity resin, unlike conventional meltblown nonwoven fabrics. For the purpose of producing a nonwoven fabric composed of fibers having the characteristics of stiffness and hardness, the resin used in the present invention is preferably a resin having the same melt viscosity as that for producing staple fibers. Regarding the melting point of the resin used, if the temperature is too high, the conveyor just below the nozzle is overheated, which is undesirable for nonwoven fabric formation. Unlike staple fibers, this point is not a facility restriction unlike when melt spinning fibers. As a result, the temperature of the hot air to be used cannot be raised unnecessarily, and a limitation of 270 ° C. is provided. Even if there is no restriction on equipment, a higher temperature such as 350 ° C. is also possible.

  The melt fluidity of the resin used mainly in the present invention, excluding fine fibers, is in the range of 5 to 200 g / 10 minutes when expressed in terms of the melt flow rate, and whether or not the measurement temperature is sufficiently melted at 230 ° C. In some cases, the melt fluidity at the melt temperature at the time of actual melt spinning does not match. The melt fluidity preferred for melt spinning varies depending on the resin, and the most preferred melt fluid state of polyethylene terephthalate or polymethylpentene is around 100 g / 10 minutes, and polypropylene is lower than this.

  For the above reasons, the thermoplastic resin used in the present invention can be used generally conveniently if the resin used in the conventional staple fiber is devised. 270 ° C polyolefin resin, polyester resin including low melting point ester copolymer and aliphatic polyester, polyamide resin such as polyamide and polyimide, polycarbonate resin and thermoplastic elastomer resin with melting point read as flow start temperature can be used. A modified resin by polymer alloy, graft polymerization, low-temperature plasma treatment or the like. Further, if the melting point is 60 ° C. or higher, for example, UCC microbial disintegrating polyester TONE (trade name) having a melting point of 60 ° C. is devised for cooling after it is made into a nonwoven fabric, but can be used in the present invention. However, as the resin used as the electret material that covers most of the fiber surface, a polyolefin resin having a monomer having 3 or more carbon atoms is conveniently used.

  In particular, polyolefin resin is particularly preferable for the electret nonwoven fabric, and polybutene-1 is particularly preferable as the electret material. Polybutene-1 is a specific resin whose crystal form changes over time from a soft state to a hard and brittle form, but can be spun as a composite fiber with polypropylene. Further, the exclusion of the resin having a lower melting point is a practical problem of the nonwoven fabric, and there is no other reason. In addition, it is needless to say that the polypropylene referred to in the present invention includes a copolymer such as ethylene, but polybutene-1 also has a limited density and melting point. However, polybutene-1 containing as much butene-1 as possible is preferable as an electret material. However, it is not limited depending on the application. In particular, a resin that is easily fused between fibers is a copolymer or an amorphous resin such as ethylene or propylene, and a resin that exhibits flexibility under heating such as semi-melting. Propylene-rich ethylene-propylene copolymer, ethylene-octene copolymer, polymethylpentene, low-density polyethylene, and the like are preferably used.

  The electret nonwoven fabric that can be used in the present invention is preferably a nonwoven fabric composed entirely of polyolefin resin, which has the advantage of easy disposal after use. For example, a composite nonwoven fabric in which a polypropylene spunbond nonwoven fabric is used as a base fabric and a melt blown nonwoven fabric of composite fibers containing polybutene-1 as one component is laminated and integrated. This is because polybutene-1 can be subjected to heat electret processing and is excellent in heat resistance of the electret. The processing temperature in the heat electret processing is preferably in the range of 80 ° C. or higher and 150 ° C. or lower.

  In the melt blown nonwoven fabric of composite fibers containing polybutene-1 as a component, it is preferable that a large number of fiber masses are scattered in the nonwoven fabric. This is because the fiber lump portion can be made bulky by increasing the thickness of the nonwoven fabric accordingly. An electret nonwoven fabric in which a large number of fiber lumps are dispersed in the nonwoven fabric has a structure in which a large gap is formed between the fibers collected around the fiber lumps. Furthermore, by collecting fibers from the top, it is possible to create a three-dimensional accumulation condition in the thickness direction and actively perform fiber accumulation to lower the density. As a result, the gap between fibers can be widened to improve fluid permeability It was. That is, an effect of reducing the pressure loss is produced, and an electret filter material having a lower pressure loss can be obtained.

  Furthermore, the average fiber diameter (d: μm) of the composite fiber composed of polybutene-1 and polypropylene is 10 <d <200, and the average fiber diameter (d: μm) is 0.3 <d <20. The composite nonwoven fabric is preferably a composite nonwoven fabric in which a nonwoven fabric having a composite fiber as a constituent fiber is disposed, and the layers between the nonwoven fabrics are thermally bonded and integrated by a low melting point component of the composite fiber.

  Most preferably, the surface non-woven fabric layer is a single component fiber or a composite fiber in which the fibers are made of only a polyolefin resin. The single component fiber includes a mixed polymer fiber, a polymer alloy fiber, an inorganic material added fiber, and the like, and any of them is preferable. The form of the fiber is preferably a hollow fiber or a modified cross-section fiber. Specifically, a homopolymer mainly composed of propylene, a spunbond nonwoven fabric of single component fibers or composite fibers, and / or polypropylene, comprising at least one polyolefin resin among copolymers mainly composed of propylene. A majority of the fiber surface is covered with a propylene-based copolymer propylene or polybutene-1, and a composite fiber heat-bonded nonwoven fabric or hydroentangled nonwoven fabric with polymethylpentene as the core component is preferred.

  Moreover, in the case of the electret fiber material layer which consists of composite fiber using the highly electret polybutene-1, a surface nonwoven fabric layer uses a polypropylene spunbond nonwoven fabric in order to ensure releasability from the conveyor electrode at the time of electret processing. It is very convenient to use the nonwoven fabric of the present invention. When pleating using a rotary pleat folding machine, it is necessary to secure a thickness and foldability of a polyethylene terephthalate fiber chemical bond nonwoven fabric with a polypropylene spunbond nonwoven fabric that can be easily secured in thickness. It is convenient to use it accordingly.

When the composite nonwoven fabric is composed only of polyolefin fibers, it is most economical to use a polypropylene spunbond nonwoven fabric for the surface nonwoven fabric layer, but when seeking thickness and more pleated shape retention, It is most preferable to use a hydroentangled nonwoven fabric or a spunbonded nonwoven fabric of a composite fiber using a sheath component as a propylene copolymer and polymethylpentene as a core component. In addition, using a polypropylene spunbond nonwoven fabric for the surface nonwoven fabric layer, the fiber material layer for electretization for rotary pleat folding has a fiber lump in which a plurality of constituent fibers are partially agglomerated and thermally bonded. There are a large number of protrusions on the surface of the nonwoven fabric, and the periphery of the fiber lump is characterized by a gap between the constituent fibers extending from the part where the fiber lump is not present and the fiber density is reduced, It is also very convenient to use it as a bulky nonwoven fabric made of a composite fiber having a thickness μm / g / m ² ) of 8 or more.

Specifically, the bulky melt blown nonwoven fabric, which is one of the preferred embodiments of the present invention, is a composite fiber composed of two or more thermoplastic resin components having different melting points, and the low melting point component occupies most of the fiber surface. A non-woven fabric manufactured by a melt-blowing method for forming a constituent fiber, wherein a plurality of fiber lumps in which a plurality of constituent fibers are partially aggregated and fused exist in the non-woven fabric to form convex portions on the surface of the non-woven fabric. The thickness (μm) / weight per unit area (g / m ² ) is 8 or more, characterized in that the gap between the constituent fibers is widened around the lump and the fiber density is lower than the part where the lump is not present. It is a composite fiber nonwoven fabric. In this case, it is a thick fiber, so it does not become partly agglomerated and heat-bonded fiber mass, but by examining the equipment and fiberization process using the melt-blow technique, the fiber mass is finer, apart from extremely thin fibers. It can be made intentionally regardless of the desired condition, and the use of a resin that is easily heat-bonded is desirable for the sheath component. It was. For low-pressure-loss filter applications, a nonwoven fabric composed of at least two layers of a thick fiber layer composed of fibers thicker than 10 μm and a thin fiber layer composed mainly of fibers smaller than 20 μm mainly having a filter function is convenient. Of course, the constituent fibers are thicker than the fibers constituting the fine fiber layer.

The composite fiber nonwoven fabric is obtained by melting and blowing directly from a nozzle to a conveyor and peeling it off the conveyor belt at the outlet. At this time, when a thin base fabric such as a spunbond nonwoven fabric is supplied on the conveyor in advance and the composite fiber is melt blown thereon, it is convenient to smoothly peel the nonwoven fabric from the conveyor belt. In addition, the base fabric is a non-stretched fiber that forms the meltblown nonwoven fabric, and the orientation crystallization of the fiber has not progressed so much that the fiber is brittle and assists the low strength point. It is also effective for increasing the stiffness of the nonwoven fabric and the waist. As the nonwoven fabric to be such a base fabric, a point-bonded spunbond nonwoven fabric, a meltblown nonwoven fabric, a spunlace nonwoven fabric, a heat-bonded nonwoven fabric, a needle punched nonwoven fabric, or a resin-impregnated bonded nonwoven fabric is convenient. Among them, the spunbond nonwoven fabric also serves to improve the peelability from the conveyor when it is an electret nonwoven fabric, and is particularly convenient for an electret nonwoven fabric, having a fineness of 2 to 20 dtex and a basis weight of 10 to 60 g / m. ² is particularly preferable. Although such a base fabric nonwoven fabric is not limited to a fiber material, it is made of a polyolefin resin in consideration of its adhesiveness because it is melt-blown and simultaneously bonded to or fixed to the base fabric nonwoven fabric by melt blowing polyolefin fibers that are electret materials. Nonwoven fabrics are preferred and are particularly preferred for disposal.

  In electret processing, it is preferable to use a fiber having a fiber diameter larger than 15 μm because of the demand for low-pressure loss mainly for filter applications. However, even thinner fibers are not inconvenient depending on the application. In addition, electret nonwoven fabric with nonwoven fabric on both sides is intended for curtains, wall hangings and wallpaper for dust absorption, and the composite fiber of the present invention is assumed to be polyolefin fiber. A non-woven fabric in which polyolefin fibers are at least partially arranged on the surface to be bonded is used.

When the composite nonwoven fabric obtained by bonding and integrating the composite fiber nonwoven fabric layer in which the fiber lumps of the thick fibers are dispersed on the base fabric is electret processed, it becomes difficult to electret the conventional electret nonwoven fabric without the fiber lumps, and the basis weight is 90 g. / M ² , it can be processed under a strong electric field, and it can be obtained by laminating fine fibers. When the majority of the fibers are thick fibers, electretization is not impossible even at 400 g / m ² . In addition, a composite nonwoven fabric in which a thick fiber composite fiber nonwoven fabric layer is bonded and integrated has a lower stiffness than a conventional composite nonwoven fabric, becomes a hard nonwoven fabric, can be easily pleated, and has a high shape retention effect. It was.

That is, composite fibers having different fiber diameters are arranged on a nonwoven fabric (base fabric) layer made of fibers having a fiber diameter of 15 μm or more. In the first stage, a thick composite fiber having a fiber diameter (d: μm) of 10 <d <200 is arranged on the base fabric, but the thick fiber is made of a thick composite fiber having a fiber diameter of 50 to 10 μm. It is most preferable to stack the layers so that the distance between the melt blow nozzle and the base fabric is close to be gathered so that the basis weight is 5 to 15 g / m ^2, and then the composite fibers having a large desired fiber diameter are accumulated. Thus, the thick composite fiber constituting the thick fiber layer is not inconvenienced even if it is an accumulation of fibers having a plurality of fiber diameters.

The distance between the nozzle and the base fabric is preferably about 5 to 25 cm. This is a closer distance in the normal melt blow spinning process. The reason for close-up and accumulation is that the thick fibers infiltrate the base fabric, facilitate physical entanglement with the thick fibers, and enhance the fusion bonding effect between the base fabric fibers and the thick fibers. . However, it is natural to set the distance between the nozzle and the base fabric so that the base fabric does not melt with the hot air of melt blow spinning. However, if the operation is continued for a long time, the temperature of the circulating conveyor belt rises, A problem that a part of the resin melts or forms a film is not preferable. In order to prevent this phenomenon, the above-described range using thick fibers having a basis weight of 5 to 15 g / m ^{2 and} a fiber diameter of 50 to 10 μm is most convenient. If the basis weight is less than 5 g / m ² , the adhesion to the base fabric is weak, and if it exceeds 15 g / m ² , the problem of melting or film formation tends to occur. If the fiber diameter of the thick fiber exceeds 50 μm, partial melting of the fibers constituting the base fabric is likely to occur, and if it is less than 10 μm, the fiber accumulation effect on the surface of the base fabric is large, and the penetration of the thick fibers into the base fabric layer occurs. Less is less preferred because the physical entanglement effect of the thick fibers is reduced.

  Originally, thicker fibers are better for bulkiness, lower pressure loss and higher hardness of the nonwoven fabric (higher nonwoven fabric and higher pleat foldability are better). It is extremely convenient to laminate and integrate the fibers while fusing or fusing them with a low melting point resin that occupies the majority of the fiber surface.

  When the composite nonwoven fabric of the present invention is used for filter applications, a filter is formed by laminating a fine fiber layer containing finer composite fibers for obtaining a function of mainly collecting dust on the above-described base fabric and thick fiber accumulation layer. Give the function as. The fiber diameter (d: μm) of the finer composite fiber is 0.3 <d <20, and the fiber diameter is arbitrarily selected according to the purpose.

  The fiber diameter referred to in the present invention means a number average fiber diameter, and the nonwoven fabric of the present invention uses a heat-adhesive conjugate fiber and is arbitrarily partially fused and bonded. Since the dispersion and distribution of the fiber diameter were wide and the fiber diameter was determined by microscopic observation, it was described as a number average. A lump or fiber bundle that was fused and bonded was counted as one.

  When making the raw fabric of the pleated folded nonwoven fabric of the present invention, it is very convenient in production to have a surface nonwoven fabric layer as a base fabric. As a specific example, a polypropylene spunbond nonwoven fabric of 17 dtex or 6 dtex, or 6 dtex of These polypropylene spunbond nonwoven fabrics are made by using a chemically bonded composite nonwoven fabric as a base fabric, in which polyethylene terephthalate fibers of 5 dtex are spunlaced into a polypropylene spunbond nonwoven fabric and then entangled with an acrylic adhesive. In addition, a sheath-core type composite fiber having 5 dtex polybutene-1 as a sheath component and polypropylene as a core component is ejected and laminated by a melt blow technique, and the sheath component polybutene-1 is fusion-bonded to the fibers of the spunbond nonwoven fabric. Let After the both layers is bonded and integrated, further laminated, by bonding and integrating the combined non-woven fabric by the sheath-core type composite fibers thin the 0.5~2dtex jetted by meltblowing techniques. For example, an electret nonwoven fabric obtained by subjecting this to an electret processing machine equipped with an electrode capable of generating a high electric field inside and outside a conveyor mesh-made conveyor dryer heated to 120 ° C. and outside the dryer. And In addition, a composite nonwoven fabric in which a melt-blown nonwoven fabric made of polypropylene fibers having an average fiber diameter of 1 μm is bonded and integrated with a chemical bond nonwoven fabric made of polyethylene terephthalate fibers of 6 dtex with a hot melt adhesive at room temperature or low temperature, a direct current plasma electret The raw material is made into an electret non-woven fabric by ion implantation using a crystallization apparatus.

  The electret non-woven fabric of the composite fiber containing the former polybutene-1 resin as one component is subjected to pleat folding in a state where it is heat-treated at a practical use temperature (100 ° C.)-50 ° C. to a temperature of 50 ° C. to 120 ° C. The nonwoven fabric of this invention can be obtained. The range of preferable heat processing temperature is 60-120 degreeC, More preferably, it is 70-110 degreeC. Specifically, for example, when sliding on an iron plate heated to 60 to 80 ° C. with a contact time of several tens of seconds, and then pleating with a reciprocating pleat folding machine, the folded state is maintained for several tens of seconds or more. Even if the pleats that have been made permanent pleats are stretched, when they are released, a new pleated folded nonwoven fabric having a high pleat restoration property can be obtained that returns almost to the heat-set pleated shape. Furthermore, when the pleat ridgeline is heated for a short time so that the surface temperature of the nonwoven fabric becomes 70 to 110 ° C. in the folded state of the pleats, the pleated folded nonwoven fabric of the present invention having more pleat restoration properties can be obtained. .

  The composite nonwoven fabric obtained by adhering the latter conventional electret polypropylene meltblown nonwoven fabric to the chemical bond nonwoven fabric has a practical use temperature (70 ° C.) of the polypropylene resin of −20 ° C. higher than 50 ° C. and lower than 60 ° C., that is, 50 ° C. Slip on an iron plate heated to -60 ° C, fold the pleats with a reciprocating pleat folder and keep it folded for several tens of seconds. If the pleats are stretched, they will be released. A new pleated folded nonwoven fabric that is slightly inferior to the former electrified nonwoven fabric of a composite fiber containing polybutene-1 resin as one component, but returns to a heat-set pleated shape, but is rich in pleat resilience. .

In consideration of the required basis weight of the individual layers as described above, the basis weight of the nonwoven fabric of the present invention will depend on the application, preferably 30 to 400 g / m ^2, and poor penetration conditions of the hot air exceeds 400 g / m ² If it is less than 30 g / m ^2, it is not convenient because the required weight of each constituent layer cannot be secured. For pleated fold filter applications, 60 g / m ² or more is preferable in view of its rigidity. Moreover, even in electret processing, the basis weight of the electret processed nonwoven fabric layer made of polyolefin resin or the like can be 30 to 400 g / m ² , but the polyolefin fiber to be electret processed has high electrical insulation, and the basis weight is high. In the case of 200 to 400 g / m ² , when the polyolefin fiber alone is used, the nonwoven fabric is generally limited to a nonwoven fabric made of thick and coarse fibers, and is bonded to a chemical bond nonwoven fabric using fibers having low electrical insulation properties such as polyethylene terephthalate fiber. Electret processing is limited to above, and if it exceeds 400 g / m ² , electret processing becomes extremely difficult, which is not preferable. In the nonwoven fabric of the present invention, the basis weight of the polyolefin fiber layer to be mainly electret processed is preferably 30 to 200 g / m ² , and the polyolefin fiber layer has a small porosity and is mainly composed of fine fibers. Is particularly preferred.

  An embodiment of the present invention, in which a thick fiber layer and a thin fiber layer are integrated in a layer shape, solves the above-mentioned problems in electret processing and can reduce the pressure loss of the fluid. The layer configuration is particularly preferred.

  The composite nonwoven fabric that can be used in the present invention can be applied to various uses by selecting the fibers to be used. For example, an electret non-woven fabric in which both sides of a polybutene-1 / polypropylene composite fiber as an intermediate layer are occupied by an olefin non-woven fabric to which a hydrophilic substance such as a surfactant is not attached, and also relates to a non-woven fabric convenient for a dust-absorbing curtain or the like. .

  In addition, the melt blown nonwoven fabric that can be used in the present invention has a phenomenon that a hole is quickly opened when it hits itself, and is excellent in flame retardancy, but a composite nonwoven fabric bonded with a polypropylene spunbond nonwoven fabric is The flame blown nonwoven fabric has good flame retardancy when exposed to flame, but the spunbond nonwoven fabric has inferior flame retardancy, and the polypropylene resin that makes up the spunbond nonwoven fabric is difficult for Ciba Specialty Chemicals. The composite non-woven fabric made of spunbond non-woven fabric by adding at least 0.5% by weight of the flame retardant “Flem Stub CGL-116” (trade name) is always flame retardant evaluation method JIS regardless of which side is exposed to flame. . Since it becomes possible to obtain flame retardant grade 3 by the L1091, A-1 method, it is further optimal as an air filter material. The flame retardant effect agent “CGL-116” is a derivative of a Halus stabilizer which is a normal weathering stabilizer of polypropylene. Even in combination with the Halus stabilizer and other stabilizers, environmental hormones and harmful It is environmentally friendly because it contains no substances.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an example of a cross-sectional shape of a composite fiber that is a constituent fiber of a composite fiber nonwoven fabric that can be used in the present invention. FIG. 1A shows a cross-sectional shape that is a core component generally called a cat eye, in which a high-melting-point component (1) is elliptical, and a low-melting-point component (2) that is a sheath component surrounds the periphery. FIG. 1B shows a concentric core-sheath structure in which the core is the high melting point component (1) and the sheath is the low melting point component (2). FIG. 1C shows a three-layer structure in which a high melting point component (1) is sandwiched between low melting point components (2).

  FIG. 2 shows a preferred 1 of the nonwoven fabric layer that can be used in the present invention in which the electret nonwoven fabric layer is made bulky to reduce the electretization efficiency and the airflow pressure loss and the fiber masses with improved rigidity are scattered. It is a form.

  Next, the effects of the present invention will be specifically described with reference to examples and comparative examples. In addition, the melt blown nonwoven fabric of the composite fiber which uses polybutene-1 as the sheath component and polypropylene as the core component, which is one embodiment of the present invention, will be mainly described. Finally, the melt blown nonwoven fabric of polypropylene fiber is hot as a chemical bond nonwoven fabric. A non-woven fabric bonded with a melt adhesive will also be described. Needless to say, other types of composite fiber nonwoven fabrics and composite nonwoven fabrics can also be easily produced by referring to the examples.

(Preparation of polymer)
Resins used in Examples and Comparative Examples are as shown in Table 1. PP is polypropylene, PB is polybutene-1 (Mitsui Chemicals Tafmer, density D: 0.92 g / cm ³ ), PE is high-density polyethylene, and PET is polyethylene terephthalate (resin with a conventional critical viscosity IV value of 0.64). Use), PMP was polymethylpentene (Mitsui Chemicals TPX), and EP was an ethylene-propylene copolymer having an excess of propylene (ethylene content of 6 to 8 mass%). The composite ratio of the sheath and the core component is 1: 1, and the melt flowability MFR is measured at 290 ° C. for PET and PMP and at 230 ° C. for others, and the unit is g / 10 minutes. The Q value is a ratio of weight average molecular weight / number average molecular weight.

(Production of composite nonwoven fabric)
A composite nonwoven fabric was prepared by laminating a composite fiber nonwoven fabric produced by a melt blow technique on a spunbond nonwoven fabric. First, individual thermoplastic resins are extruded from two extruders, and quantitatively supplied by a gear pump, and using a composite nozzle with a width of less than 70 cm capable of forming a composite fiber, a high-speed heated air flow from a row of orifices At the same time as discharging into the fiber, it is made into a fiber that is basically continuous by elongating with the airflow, and is accumulated on a net conveyor equipped with a suction facility to produce a composite fiber nonwoven fabric that is fiberized by a melt blow technique, A polypropylene spunbonded non-woven fabric preheated at 140 ° C. is positioned on the conveyor, and a weight of 15 g / m ² of thick fibers having an average fineness of 6 to 10 dTex (23 to 38 μmφ) is obtained on the spunbonded non-woven fabric by a melt blow method. And then change the traveling angle of the net conveyor each time to add the desired thick or fine fibers. To prepare a combined non-woven fabric of the present invention by laminating superposed layers. Each layer was accumulated by intersecting at an angle of at least 30 degrees.

  The non-woven fabric of the composite fiber having polybutene-1 as a constituent element is continuously conveyed in a dryer at 120 ° C. and allowed to cool while being conveyed by a stainless mesh conveyor. An electric field was generated, and an electret nonwoven fabric was formed by heat electret processing in the electric field.

  The electret nonwoven fabric is brought into contact with a stainless steel heating plate (T ° C.) heated to the temperature shown in Table 2 as preheating for 20 seconds, and is used as a pleated folded nonwoven fabric having a pitch of 30 mm with a reciprocating pleated folding machine. It was.

[Examples 1-21, Comparative Examples 1-2]
As the composite fiber nonwoven fabric, the resin shown in Table 1 was used, and the composite nonwoven fabric was formed under the conditions shown in Tables 2 and 3 in the above process. The spinning temperature refers to the nozzle temperature, which is ejected using high-pressure hot air at the same temperature, sucked at a suction amount of 5 times or more of the ejected hot air amount, and about 7 dTex with a basis weight of 15 g / m ^2. Thus, the pleated folded nonwoven fabrics of Examples and Comparative Examples were obtained.

  In Examples 7 to 9, a fine composite fiber melt blown nonwoven fabric using a high MFR resin is laminated on the thick fiber melt blown nonwoven fabric of Example 6. The indication of the fiber component indicates the additional layer.

The fiber diameters in Table 2 and Table 3 are number average fiber diameters (μm), and fused fibers were excluded. Each fiber layer has a number of times of accumulation of at least 2 times, is indicated by its basis weight (g / m ² ), and the thickness was measured by the JIS-L-1913-6.1.2A method. The thickness of the thick fiber meltblown layer is indicated by the thickness including the base fabric.

  The collection efficiency is in accordance with JIS-B-9908. Instead of the filter unit, the nonwoven fabric of each example is attached, and atmospheric dust is removed at a surface speed of 5.3 cm / second by measuring with a filtration surface of 100 mmφ. Filtration was performed to fractionate 0.3 to 0.5 μm particles before and after filtration, and the number was counted and calculated.

The shape retention of the pleats was evaluated by whether or not the folds were folded to a folding width of 30 mm and stretched to half of the total length and recovered instantaneously.
X: Same as the conventional non-preheated one, but slightly returned or stretched, and the crease is not sharp.
Excellent: Sharp creases and instant resilience.
Good: The crease is sharp, but the resilience recovery is slightly slow.

Base cloth used in Examples 1 to 12 are polypropylene spun-bonded nonwoven fabric having a basis weight of 15 g / m ^2, Examples 13 to 16, the spunlaced the 6dtex polyethylene terephthalate fibers having a basis weight of 30 g / m ² on the spunbonded nonwoven fabric What was processed and pre-entangled and made into a chemical bond nonwoven fabric with an acrylic adhesive was used as a base fabric. The display was PET. The total basis weight was 50 g / m ² , and the meltblown nonwoven fabric layer was sprayed to the spunbond nonwoven fabric side to be fused and adhered to the spunbond nonwoven fabric layer. In Examples 17 to 20, the fine fiber meltblown nonwoven fabric was further sprayed and laminated on the thick fiber meltblown nonwoven fabric of Comparative Example 1.

  In any of the pleated folded nonwoven fabrics of Examples 1 to 21, the pleated shape retention was high, the electret performance was not lost, and the collection efficiency was high. On the other hand, the pleated folded nonwoven fabric of Comparative Example 1 had low pleat shape retention, the electret performance was lost, and the collection efficiency was low. Under the conditions of Comparative Example 2, a nonwoven fabric could not be formed.

[Example 22]
Two non-woven fabrics of Example 6 are stacked so that the meltblown non-woven fabric layer side is in contact with each other, and bonded with a hot air processing machine at 140 ° C. while being rubbed with a bar, and then the same as in Example 1. Heat electret processing was performed to make an electret nonwoven fabric, which was then pleated. When it was put in a box in which atmospheric dust was diffused, atmospheric dust was adsorbed remarkably, and the spunbond nonwoven fabric on the surface became grayish.

[Example 23]
An activated carbon fiber nonwoven fabric obtained by firing a 6 dTex rayon hydroentangled nonwoven fabric with a basis weight of 60 g / m ² under anaerobic conditions at 650 to 700 ° C. was placed on the 7 dTex spunbond nonwoven fabric used in Example 1, and The hydroentangled nonwoven fabric obtained by placing a web of 30 g / m ² of rayon fiber of ² dTex on the basis of hydroentanglement treatment and hydroentangled with the rayon fiber to form the hydroentangled nonwoven fabric of Example 1 was used. Instead, the melt-blown nonwoven fabric was laminated in the same manner as in Example 1 with the spunbond nonwoven fabric layer on top, and electret processing and pleat folding were performed as a composite nonwoven fabric in the same manner as in Example 1. The composite nonwoven fabric retained at least the ability to collect hydrogen sulfide.

[Example 24]
A polypropylene melt blown nonwoven fabric with a basis weight of 40 g / m ² and a 2 μm polypropylene melt blown nonwoven fabric was pinsonically bonded to the chemical bond nonwoven fabric of Example 13, and pleated with a preheated pleat folding machine in the same manner as in Example 1. It was foldable, bent more sharply than the one not preheated, and improved pleat retention.

  The pleated folded nonwoven fabric obtained by the production method of the present invention is useful as a material for building air-conditioning filters, dust-absorbing curtains, masks and the like. In addition, the filter material of the present invention is bonded and integrated with a frame, and filters such as building air conditioners, home air conditioners, air purifiers, automobile cabin filters, electronic equipment air conditioning equipment, clean room dust removal filters, etc. Useful as a material.

A, B, and C in FIG. 1 are examples of a cross-sectional view of a composite fiber constituting the composite fiber nonwoven fabric of the present invention. It is an enlarged view of the side sectional view of the composite nonwoven fabric used in the present invention.

Explanation of symbols

1 High melting point component 2 Low melting point component 3 Fiber mass 4 Thick fiber 5 Fine fiber 6 High fiber density part

Claims (4)

A method for producing an electret filter material comprising a pleated folded nonwoven fabric for pleating a nonwoven fabric subjected to electret processing,
The resin constituting the main electret fibers constituting the nonwoven fabric is polybutene-1 resin, and the melting point (Tms: ° C.) of the polybutene-1 resin is 115 <Tms <130, and the nonwoven fabric is 60-100 ° C. Pleats folded in a state of being heat treated at a temperature of
The resin constituting the main electret fibers constituting the nonwoven fabric is a polypropylene resin, and the nonwoven fabric is pleated in a state of being heat-treated at a temperature of 50 to 60 ° C.,
The method for producing an electret filter material comprising a pleated folded nonwoven fabric, characterized in that the heat treatment is performed immediately before the pleat folding process.   The manufacturing method of the electret filter material which consists of a pleated folding nonwoven fabric of Claim 1 in which the ridgeline part of the pleating in the said nonwoven fabric folded by the pleat is further heated.   The electret-processed non-woven fabric is produced by a melt-blowing method, is composed of two or more thermoplastic resin components having different melting points, and a low-melting point component that occupies 70% or more of the fiber surface contains polybutene-1 as an electret fiber The manufacturing method of the electret filter material which consists of a pleated folding nonwoven fabric of Claim 1 or 2 which is a nonwoven fabric contained as.   The manufacturing method of the electret filter material which consists of a pleated fold nonwoven fabric of Claim 1 or 2 with which the said electret processed nonwoven fabric is heat electret-processed in the atmosphere within the range of 80 degreeC or more and 150 degrees C or less.

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