JP2022094613A - Nonwoven fabric, short-cut thermally bondable fiber, and filter - Google Patents

Abstract

To provide a nonwoven fabric suitable for filter material, having high collection efficiency, low pressure loss, small distortion under compression, and long life in practical use.SOLUTION: A nonwoven fabric includes a short-cut ultra fine fiber having a fiber diameter of 0.1 to 1 μm and an aspect ratio of 100 to 3000, and a short-cut thermally bondable fiber having a fiber diameter of 0.5 to 4 μm and an aspect ratio of 100 to 3000, and has a compressibility of 30% or less under a compression of 30 kPa.SELECTED DRAWING: Figure 1

Description

The present invention relates to non-woven fabrics, short-cut heat-adhesive fibers and filters using them.

Various filters made of non-woven fabric have been proposed so far. For example, a filter filter medium made of an air-laid non-woven fabric having a multi-layer structure with a gradient of fiber fineness (see, for example, Patent Document 1), or a general-purpose non-woven fabric in which ultrafine fibers obtained by an electrospinning method are laminated on the surface layer (for example). , Patent Document 2 and Patent Document 3) have been proposed.

Of these, the air-laid multilayer filter filter medium with a gradient of fiber fineness achieves low pressure loss and high filter life, but is insufficient to collect extremely fine dust. In addition, in a filter filter medium in which ultrafine fibers are laminated on the surface layer of a general-purpose non-woven fabric, the ultrafine fibers are coated in a planar manner, so that pressure loss tends to increase, and adhesion to the base material non-woven fabric is likely to occur. There was a problem that the sex was insufficient and the fibers were easily dropped.

Patent Document 4 proposes a filter filter medium composed of a short-cut ultrafine fiber having a fiber diameter of 100 to 1000 nm (0.1 to 1 μm) and a wet non-woven fabric containing a binder fiber having a single fiber fineness of 0.1 dtex or more. Although the collection efficiency will be better than before, the fineness of the binder fiber is limited, so in terms of further improving the collection efficiency for carbon fine particles such as those contained in automobile exhaust gas. It wasn't enough.

Further, Patent Document 5 is a filter filter medium using short-cut ultrafine fibers, which has a multi-layer structure of two or more layers and has no boundary surface between two adjacent layers of the multi-layer structure. Has been proposed. Although this is excellent in the balance of high collection efficiency, low pressure loss, and high filter life, as in the examples of Patent Document 4, only those having a single fiber fineness of 1.1 dtex are exemplified. However, there was room for improvement in improving the collection efficiency for nano-sized fine particles such as carbon in the exhaust gas.

Japanese Unexamined Patent Publication No. 2004-301121 Japanese Unexamined Patent Publication No. 2006-289209 Japanese Unexamined Patent Publication No. 2007-170224 International Publication No. 2008/13019 Pamphlet Japanese Unexamined Patent Publication No. 2013-126626

According to the studies by the present inventors, the fact that the deformation of the filter filter medium is small with respect to the external force applied to the filter filter medium by the medium and particles passing through the filter filter medium is an important factor for prolonging the practical filter life. Is.
An object of the present invention is to provide a nonwoven fabric having a high collection rate, a low pressure loss, little deformation during pressurization, and suitable as a filter medium having a long life in practical use.

The present invention comprises short-cut ultrafine fibers having a fiber diameter of 0.1 to 1 μm and an aspect ratio of 100 to 3000, and short-cut heat-adhesive fibers having a fiber diameter of 0.5 to 4 μm and an aspect ratio of 100 to 3000. It is a non-woven fabric characterized by having a compression ratio of 30% or less at the time of pressurizing 30 kPa.
The present invention is also a short-cut heat-adhesive fiber consisting only of polyester having a fiber diameter of 0.5 to 4 μm, an aspect ratio of 100 to 3000, and a heat-bonding component having a melting point of 250 ° C. or lower.

According to the present invention, it is possible to provide a nonwoven fabric having a high collection rate, a low pressure loss, little deformation during pressurization, and suitable as a filter medium having a long life in practical use.

It is sectional drawing of a part of an example of the spinning mouthpiece of the sea-island type composite fiber used for manufacturing the short-cut ultrafine fiber which is the material of this invention.

Hereinafter, embodiments of the present invention will be described in detail.

[Short cut ultrafine fiber]
The short-cut ultrafine fibers consist of fiber-forming thermoplastic polymers. The short-cut ultrafine fibers have a fiber diameter (D) of 0.1 to 1 μm, preferably 0.2 to 0.9 μm, and particularly preferably 0.3 to 0.8 μm. If the fiber diameter (D) exceeds 1 μm, the pore diameters of the holes appearing on the surface of the wet nonwoven fabric produced by the papermaking method may become non-uniform. On the other hand, if it is less than 0.1 μm, the short-cut ultrafine fibers may easily fall off from the mesh when the web is made by the papermaking method.

The aspect ratio of the short-cut ultrafine fibers (ratio of fiber length (L) to fiber diameter (D): L / D) is 100 to 3000, preferably 300 to 2500, and particularly preferably 500 to 2000. If the aspect ratio exceeds 3000, the fibers will be entangled with each other in water before the web is made by the papermaking method, resulting in poor dispersion. Therefore, the pore diameters appearing on the surface of the non-woven fabric manufactured by the papermaking method are non-uniform. There is a risk of becoming. On the other hand, if the aspect ratio is less than 100, the entanglement between the fibers becomes extremely weak, the transition from the wire part to the blanket becomes difficult after the web is formed, and the process stability may decrease.

Short-cut ultrafine fibers from the viewpoint of making the structure of the wet nonwoven fabric uniform when the nonwoven fabric is manufactured by the papermaking method, reducing the occurrence of defects, and improving the yield and manufacturing efficiency when manufacturing the nonwoven fabric by the papermaking method. The fiber length of the above is preferably 0.05 to 3 mm. As a method for obtaining short-cut ultrafine fibers cut to a predetermined length, a guillotine cutter type fiber bundle cutting device or a rotary cutter such as an Eastman type in which a large number of cutter blades are provided radially outward at equal intervals. Can be exemplified by the method of cutting ultrafine fibers using.

The fiber cross section of the short-cut ultrafine fiber may be a round cross section or a modified cross section.
As the polymer constituting the short-cut ultrafine fiber, a thermoplastic polymer can be preferably used, for example, a polyamide-based polymer, a polyester-based polymer, a polyolefin-based polymer, an acrylate-based polymer, or a polyphenylene sulfide-based polymer, and ultrafineness and molding are relatively easy. Therefore, a polyester polymer is preferable because it is excellent in strength and dimensional stability.

Among polyester polymers, polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, aromatic dicarboxylic acids such as isophthalic acid and 5-sulfoisophthalic acid metal salt, adipic acid, and sebacine having these as the main repeating units. Copolymers with aliphatic dicarboxylic acids such as acids and succinic acids, hydroxycarboxylic acid condensates such as ε-caprolactone, glycol components such as diethylene glycol, trimethylene glycol, tetramethylene glycol and hexamethylene glycol, polylactic acid, Polycaprolactone, polyhydroxybutyrate, polyethylene succinate, polybutylene succinate, and polybutylene succinate adipate are preferred.

As the polyamide polymer, aliphatic polyamides such as polyamide 6, polyamide 66, and polyamide 610 are preferable.

For polyolefin polymers, high-density polyethylene, medium-density polyethylene, high-pressure low-density polyethylene, linear low-density polyethylene, isotactic polypropylene, ethylene-propylene copolymer, ethylene copolymer of vinyl monomers such as maleic anhydride, Examples thereof include atactic polystyrene, isotactic polystyrene, and syndiotactic polystyrene. These are preferable because they are not easily attacked by acids, alkalis and the like, and because of their relatively low melting point, they can be used as a binder component after being taken out as ultrafine fibers.

Examples of the acrylate-based polymer include methyl polyacrylate, ethyl polyacrylate, sodium polyacrylate, methyl polymethacrylate, and an acrylamide crosslinked copolymer.

[Manufacturing method of short-cut ultrafine fibers]
The short-cut ultrafine fibers can be produced by a conventionally known method, for example, by the method disclosed in International Publication No. 2005/095686. In the present invention, it is preferable to use the one produced by this method. Hereinafter, a preferable method for producing short-cut ultrafine fibers will be described.

From the viewpoint of obtaining the desired fiber diameter and its uniformity, the short-cut ultrafine fiber has an island diameter (D) of 100 to 1000 nm (that is, 0.1 to 1 μm) made of a fiber-forming thermoplastic polymer constituting the short-cut ultrafine fiber. A sea-island type composite fiber having an island component, which is a sea component composed of a polymer that is more soluble in an alkaline aqueous solution than the above-mentioned fiber-forming thermoplastic polymer (hereinafter, also referred to as “alkali aqueous solution easily soluble polymer”). It is preferable that the sea components are bundled and cut as a fiber bundle (tow) and then subjected to an alkali weight loss process to dissolve and remove the sea component.

Here, the alkaline aqueous solution means an aqueous solution of an alkali metal such as potassium hydroxide and sodium hydroxide.
The island diameter can be measured by photographing the cross section of the sea-island type composite fiber with a transmission electron microscope. When the shape of the island is a modified cross section other than the round cross section, the diameter of the circumscribed circle is used as the island diameter (D).

The dissolution rate ratio of the aqueous alkaline aqueous solution easily soluble polymer forming the sea component to the fiber-forming thermoplastic polymer forming the island component is preferably 200 or more, more preferably 300 to 3000. Within this range, the island separability is good, which is preferable. If the dissolution rate is less than 200 times, the island component of the separated sea-island-type composite fiber cross-section surface layer is dissolved while the sea component in the center of the sea-island-type composite fiber cross-section is dissolved. Even though the amount equivalent to the sea has been reduced, the sea component in the center of the cross section of the sea-island type composite fiber cannot be completely dissolved and removed, leading to thickness spots on the island component and solvent erosion of the island component itself, resulting in uniform fiber. It is not preferable because it may not be possible to obtain short-cut ultrafine fibers with a diameter.

As the alkaline aqueous solution easily soluble polymer that forms the sea component of the sea-island type composite fiber, a polyester polymer, an aliphatic polyamide among polyamide polymers, and polyethylene or polystyrene among polyolefin polymers are preferable from the viewpoint of fiber formation. , Polylactic acid, ultrahigh molecular weight polyalkylene oxide condensate polymer, polyester polymer such as polyalkylene glycol compound and 5-sodium sulfoisophthalic acid copolymerized polyester are particularly preferable.

Among polyester polymers, polyethylene terephthalate having an intrinsic viscosity of 0.4 to 0.6 obtained by copolymerizing 6 to 12 mol% of 5-sodium sulfoisophthalic acid and polyethylene glycol having a molecular weight of 4000 to 12000 by 3 to 10% by mass. Polymerized polyester is preferred. Here, 5-sodium sulfoisophthalic acid contributes to the improvement of hydrophilicity and melt viscosity, and polyethylene glycol (PEG) improves the hydrophilicity. In addition, the larger the molecular weight of PEG, the more hydrophilicity it is thought to be due to its higher-order structure, but the reactivity deteriorates and it becomes a blend system, which causes problems in terms of heat resistance and spinning stability. there is a possibility. Further, if the copolymerization amount of PEG exceeds 10% by mass, there is an effect of lowering the melt viscosity, which is not preferable.

In the sea-island type composite fiber, it is preferable that the melt viscosity of the sea component at the time of melt spinning is larger than the melt viscosity of the island component polymer. In such a relationship, even if the composite mass ratio of the sea component is as small as less than 40%, it is unlikely that the islands will join each other or most of the island components will join, resulting in a sea-island type composite fiber. easy.

The melt viscosity ratio (sea / island) in the sea-island type composite fiber is preferably 1.1 to 2.0, and particularly preferably 1.1 to 1.5. If this ratio is less than 1.1 times, the island components tend to join during melt spinning, which is not preferable, while if it exceeds 2.0 times, the viscosity difference is too large and the spinning tone tends to deteriorate, which is not preferable.

The short-cut ultrafine fibers are derived from the island portion of the sea-island type composite fiber, and the number of islands in the cross section of the sea-island type composite fiber is preferably 100 or more, more preferably 300 to 1000. The sea-island composite mass ratio (sea: island), which is the mass ratio of the sea component and the island component, is preferably 5:95 to 95: 5. Within this range, the thickness of the sea component between the island component and other island components adjacent to it can be reduced, the dissolution and removal of the sea component becomes easy, and the conversion of the island component to ultrafine fibers is easy. It is preferable. If the proportion of the sea component exceeds 95%, the thickness of the sea component becomes too thick, while if it is less than 5%, the amount of the sea component becomes too small and bonding between islands is likely to occur.

As the mouthpiece used for melt spinning, any one can be used, such as one having a hollow pin group or a micropore group for forming an island component. For example, even with a spinneret such that an island component extruded from a hollow pin or a micropore and a sea component flow whose flow path is designed to fill the space between them are merged and compressed to form a sea island cross section. good. FIG. 1 shows an example of a base having a group of hollow pins.

In the spinneret 1 shown in FIG. 1, the melted island component polymer in the island component polymer reservoir 2 before distribution is placed in the island component polymer introduction passage 3 formed by a plurality of hollow pins. The distributed sea component polymer is introduced into the pre-distributed sea component polymer reservoir 5 through the sea component polymer introduction passage 4. The hollow pin forming the polymer introduction passage 3 for the island component penetrates the polymer reservoir 5 for the sea component, and is the center of each entrance of the plurality of core-sheath type composite diversion passages 6 formed below the hollow pin. It opens downward in the portion. From the lower end of the island component polymer introduction passage 3, the island component polymer flow is introduced into the central portion of the core-sheath type composite diversion passage 6, and the sea component polymer flow in the sea component polymer reservoir 5 is the core sheath. A core-sheath type composite flow is introduced into the type composite diversion passage 6 so as to enclose the island component polymer, and the core-sheath type composite flow is formed with the island component polymer flow as the core and the sea component polymer flow as the sheath, and a plurality of core-sheath type complex flows are formed. It is introduced into the funnel-shaped merging passage 7, and in the merging passage 7, the sheath portions of the plurality of core-sheath-type complex currents are close to each other to form a sea-island-type composite flow. While flowing down in the funnel-shaped merging passage 7, the sea-island type composite flow gradually decreases its horizontal cross-sectional area and is discharged from the discharge port 8 at the lower end of the merging passage 7.

The discharged sea-island type composite fiber is solidified by cooling air and is taken up by a rotating roller or ejector set to a predetermined take-up speed to obtain an undrawn yarn. This pick-up speed is preferably 200 to 5000 m / min. If it is less than 200 m / min, productivity is poor and it is not preferable. On the other hand, if it exceeds 5000 m / min, the spinning stability is poor, which is not preferable.

The obtained undrawn yarn may be used as it is in the cutting step depending on the use and purpose of the ultrafine fiber obtained after extraction and removal of sea components, and in order to obtain desired strength, elongation and heat shrinkage characteristics, It may be subjected to a cutting step after a stretching step or a heat treatment step. The stretching step may be a separate stretching method in which spinning and stretching are performed in separate steps, or a straight stretching method in which spinning is performed immediately after spinning in one step.

The sea-island type composite fiber is cut so that the aspect ratio (ratio of fiber length (L) to island diameter (D): L / D) of the short-cut ultrafine fiber made of the polymer of the island component is in the range of 100 to 3000. do. This cutting can be performed by cutting the undrawn yarn or the drawn yarn as it is or by making a tow bundled in units of tens to millions and cutting it with a guillotine cutter or a rotary cutter. Further, it may be cut after the sea component extraction / removal step. The sea component extraction / removal step is performed by alkali weight reduction processing.

In this sea component extraction / removal step, the ratio (bath ratio) of the sea-island type composite fiber to the alkaline aqueous solution is, for example, 0.1 to 5% by mass, preferably 0.4 to 3% by mass. If it is less than 0.1% by mass, there is a lot of contact between the fiber and the alkaline solution, but there is a possibility that processability such as drainage becomes difficult. On the other hand, if it exceeds 5% by mass, the amount of fibers is too large, so that there is a possibility that the fibers may be entangled with each other in the sea component extraction / removal step.

The bath ratio is defined by the following formula.
Bath ratio (mass%) = [sea island type composite fiber mass (g) / alkaline aqueous solution mass (g)] × 100

The treatment time for the alkali weight reduction process in the sea component extraction / removal step is, for example, 5 to 60 minutes, preferably 10 to 30 minutes. If it is less than 5 minutes, the alkali weight loss may be insufficient. On the other hand, if it exceeds 60 minutes, even the island component may be reduced.
The treatment temperature for the alkali weight loss process in the sea component extraction / removal step is, for example, 50 to 90 ° C, preferably 60 to 80 ° C.

In the alkali weight reduction process of the sea component extraction / removal step, the alkali concentration of the alkaline aqueous solution is preferably 2 to 10% by mass. If it is less than 2% by mass, the alkali becomes insufficient and the weight loss rate may become extremely slow, which is not preferable. On the other hand, if it exceeds 10% by mass, the amount of alkali is reduced too much, and the amount may be reduced to the island portion, which is not preferable.

As a method for reducing the amount of alkali in the sea component extraction / removal step, the sea-island type composite fiber is put into an alkaline solution, treated under predetermined conditions for a predetermined time, then once subjected to a neutralization step, and then put into water again to acetic acid. , A method of neutralizing and diluting with an organic acid such as oxalic acid and finally dehydrating can be used.

Further, a method can be used in which the treatment is performed for a predetermined time, the neutralization treatment is performed, water is further injected to proceed with dilution, and then dehydration is performed. In these cases, since the former is processed in a batch manner, it can be manufactured (processed) in a small amount, but it takes time for the neutralization treatment, so that the productivity is slightly poor. The latter allows semi-continuous production, but requires a large amount of acid-based aqueous solution during the neutralization process and a large amount of water for dilution.

The processing equipment is a mesh-like material having an aperture ratio (the area of the opening portion per unit area) of 10 to 50% as disclosed in Japanese Patent No. 36785511 from the viewpoint of preventing fibers from falling off during dehydration. It is preferable to apply (for example, a non-alkali hydrolyzable bag). In this case, if the aperture ratio is less than 10%, moisture escape is extremely poor and unfavorable, while if it exceeds 50%, ultrafine fibers may fall off, which is not preferable.

After the sea component extraction and removal step, a dispersant (for example, Meikasurf manufactured by Meisei Kagaku Kogyo Co., Ltd.) was applied to the surface of the short-cut ultrafine fibers in order to enhance the dispersibility of the short-cut ultrafine fibers, 0.1 to the fiber mass. It is preferable to adhere to ~ 5.0% by mass.

By subjecting the short-cut fiber obtained by cutting the sea-island type composite fiber to a predetermined length to the sea component extraction / removal step described above, the sea-island type composite fiber is converted into the short-cut ultrafine fiber of the present invention composed of the island component. To. At that time, when the island component is made of a polyester-based polymer, a short-cut ultrafine fiber made of polyester can be obtained.

[Short-cut heat-adhesive fiber]
In the present invention, the short-cut heat-adhesive fiber is used as a binder fiber for maintaining the short-cut ultrafine fiber in the form of a non-woven fabric. By using the short-cut heat-adhesive fiber, it is possible to remarkably improve the collection efficiency of fine particle size particles when the non-woven fabric is used as a filter filter medium.

The fiber diameter (D) of the short-cut heat-adhesive fiber is 0.5 to 4 μm, preferably 0.8 to 3 μm, and more preferably 1.0 to 2.8 μm. If the fiber diameter (D) is less than 0.5 μm, the rigidity of the fiber itself may be low and the structure of the filter filter medium may be difficult to maintain, which is not preferable. On the other hand, when it exceeds 4 μm, the number of short-cut heat-adhesive fibers occupying the filter filter medium decreases, the number of adhesive points decreases, the rigidity decreases, the pore size of the filter filter medium increases, and the collection efficiency of fine particle size particles decreases. It is not preferable because there is a risk of

The aspect ratio of the short-cut heat-adhesive fiber (ratio of fiber length (L) to single fiber diameter (D): L / D) is 100 to 3000, preferably 300 to 2500, and particularly preferably 500 to 2000. If the aspect ratio is less than 100, the entanglement between the fibers becomes extremely weak, the transition from the wire part to the blanket becomes difficult after the web is formed, and the process stability may decrease. On the other hand, when the aspect ratio exceeds 3000, the fibers are entangled with each other in water before the web is made by the papermaking method, resulting in poor dispersion. Therefore, the pore diameters appearing on the surface of the wet nonwoven fabric are non-uniform (that is, average). The ratio of the hole diameter to the maximum hole diameter is large).

The fiber length of the short-cut heat-adhesive fiber is preferably 0.05 to 10 mm from the viewpoint of the uniformity of the structure of the wet nonwoven fabric, the occurrence of few defects, defects in the manufacture of the wet nonwoven fabric, and the yield / production efficiency.

As a method for obtaining short-cut heat-adhesive fibers of a predetermined length, a guillotine cutter type fiber bundle cutting device or a rotary cutter such as an Eastman type in which a large number of cutter blades are provided radially outward at equal intervals is used. The method used can be applied.

One of the preferred embodiments of the short-cut heat-adhesive fiber is a mode in which the short-cut heat-adhesive fiber occupies 20 to 80% by mass of the fiber-forming component and 80 to 20% by mass of the heat-adhesive component. ,
In this embodiment, the fiber-forming component is a polyester having a melting point of 180 ° C. or higher, and the heat-adhesive component is a polyester having a melting point 20 ° C. or higher lower than the melting point of the fiber-forming component.

If the short-cut heat-adhesive fiber is less than 20% by mass, the nonwoven fabric cannot retain its shape under a predetermined pressure, which is not preferable. On the other hand, if it exceeds 80% by weight, the flow portion of the heat-adhesive component increases, the space volume for capturing the collected material decreases, which leads to a decrease in collection efficiency and filter life, which is not preferable.

The fiber-forming component in the short-cut heat-adhesive fiber is a polyester having an alkylene terephthalate having a melting point of 180 ° C. or higher, preferably a melting point of 190 to 270 ° C. as a main repeating component. If the melting point of this polyalkylene terephthalate polyester is less than 180 ° C., not only is it difficult to stably produce the composite fiber, but also the dimensional stability during the heat bonding treatment is lowered, which is not preferable. On the other hand, if the melting point exceeds 270 ° C., it becomes difficult to make ultrafine particles, which is not preferable.

As the polyalkylene terephthalate polyester having this fiber-forming component, polyethylene terephthalate, polytrimethylene terephthalate, and polybutylene terephthalate are preferable, and polyethylene terephthalate is particularly preferable because it is inexpensive and versatile. In addition, in order to improve the fiber moldability for ultrafineness, isophthalic acid, 5-sulfoisophthalic acid metal salt, 5-sulfoisophthalic acid organic phosphorus salt, 2,6-dinaphthalene acid, adipic acid, sebacic acid, Adipic acid, dodecanoic acid, ε caprolactone, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, diethylene glycol, polyalkylene glycol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, trimethylene glycol , Tetramethylene glycol, hexamethylene glycol, triethylene glycol, tetraethylene glycol, and the like may be copolymerized within a range in which the melting point is within a predetermined range.

The heat-adhesive component of the short-cut heat-adhesive fiber is preferably polyester having a melting point of 20 ° C. or higher lower than that of the fiber-forming component. In this case, the polyester is preferably a polyalkylene terephthalate polyester having a melting point of 250 ° C. or lower. Since the melting point of the heat-adhesive component is 20 ° C. or higher lower than that of the fiber-forming component, good adhesive force with short-cut ultrafine fibers can be obtained. Since the heat-adhesive component is a polyalkylene terephthalate polyester having a melting point of 250 ° C. or lower, it is possible to obtain elasticity and rigidity in which the space inside the nonwoven fabric is not easily crushed even under good adhesive force and pressure.

As the polyalkylene terephthalate polyester having a heat adhesive component, a polyalkylene polyester having ethylene terephthalate, trimethylene terephthalate, butylene terephthalate, and hexamethylene terephthalate as the main repeating units is preferable, and heat adhesion temperature adjustment, crimping temperature / pressure are preferable. Isophthalic acid, 5-sulfoisophthalic acid metal salt, 5-sulfoisophthalic acid organic phosphorus salt, 2,6-dinaphthalene acid, adipic acid, sebacic acid in order to improve fiber moldability for adjustment and ultrafineness. , Azelaic acid, dodecanoic acid, ε caprolactone, 1,3-cyclohexanedicarboxylic acid, dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, diethylene glycol, polyalkylene glycol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedi. A diol component such as methanol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, triethylene glycol, or tetraethylene glycol may be copolymerized.

The above-mentioned composite fiber needs to be composited so that the heat-adhesive component is exposed on the surface of the composite fiber in order to heat-bond the composite fibers to each other. As this embodiment, for example, a concentric structure in which a heat-adhesive component and a fiber-forming component are combined in a parallel type (side-by-side type), or a concentric structure in which the heat-adhesive component is used as a sheath component and the fiber-forming component is used as a core component. Examples thereof include a core-sheath type composite fiber and an eccentric core-sheath composite fiber, and among them, a concentric core-sheath type composite fiber is preferable. Concentric core-sheath type composite fibers can obtain better adhesion points between short-cut ultrafine fibers or short-cut heat-adhesive fibers, and the interfiber distance, which affects the pore size, which is important for filter performance, is uniform. In addition, it is good in terms of dimensional stability under high temperature and high pressure. Even if it is a concentric core sheath type composite fiber, there is no problem even if the center of gravity of the core and the center of gravity of the sheath are deviated within a range that does not hinder, and unless the structure is intentionally eccentric, the concentric core sheath It shall be regarded as a type composite fiber.

As another form of the short-cut heat-adhesive fiber, a fiber composed of a single component of polyester having a heat-adhesive component of the short-cut heat-adhesive fiber having a melting point of 250 ° C. or less may be used. In this case, by heat-sealing or crimping the short-cut heat-adhesive fibers to each other or the short-cut ultrafine fibers, the pore diameter is conventionally known in combination with the fineness of the short-cut heat-adhesive fibers of the present invention. It can be smaller than the heat-adhesive fibers that are present. In order to do so, it is preferable that the melting point of the short-cut heat-adhesive fiber is 5 ° C. or more lower than the melting point of the short-cut ultrafine fiber.
The fiber cross-sectional shape of the short-cut heat-adhesive fiber is arbitrary, and examples thereof include a round cross section, a hollow cross section, a cross section, a flat cross section, and a cross section having fins.

Among the above-mentioned polymers, various stabilizers, ultraviolet absorbers, thickening branching agents, thickening agents, matting agents, colorants, antibacterial agents, deodorants, carbon blacks, hydrophilic agents, water repellent agents, etc. Metal fine particles, metal oxides, antioxidants, light stabilizers, fluorescent whitening agents, and various other improving agents may also be blended as needed.

[Manufacturing method of short-cut heat-adhesive fiber]
The ultrafine short-cut heat-adhesive fiber having a fiber diameter of 0.5 to 4 μm in the present invention can be produced, for example, by the following method.

When the short-cut heat-adhesive fiber is a composite fiber composed of a fiber-forming component and a heat-adhesive component, the polymer constituting the above-mentioned heat-adhesive component and the fiber-forming component is formed into chips, and these are heated or dehumidified, respectively. After drying under the nitrogen or air atmosphere or under vacuum, it is melted and introduced into the composite yarn base, extruded as a molten composite fiber thread, cooled and solidified at a position 15 to 100 mm below the mouthpiece, and the spinning speed is 300 to 1000 m /. Undrawn yarn is obtained in minutes. As the composite spinneret, a known one can be used.

When the heat-adhesive component of the short-cut heat-adhesive fiber is composed of a single component of a polyalkylene terephthalate polyester having a melting point of 250 ° C. or less, the polymer constituting the heat-adhesive component is formed into a chip, and the same as described above. It is dried and melted, introduced into a spinneret for a single component having a known single-hole nozzle, cooled and solidified, and taken up to obtain an undrawn yarn.

As a method for obtaining short-cut heat-adhesive fibers having a desired fiber diameter, undrawn yarn is flow-drawn to draw at a high magnification of 5 times or more without changing the orientation and crystallization of the amorphous part in the undrawn yarn as much as possible. Then, if necessary, a method of performing high-magnification stretching of 10 times or more in total can be used by further increasing the stretching ratio until the unstretched portion disappears by neck stretching.

At this time, it is preferable to impart a polyether / polyester copolymer to the surface of the undrawn yarn. The flow drawing is performed in warm water 5 to 50 ° C. higher than the glass transition temperature of the heat-adhesive component and the fiber-forming component of the undrawn yarn, whichever is higher, and the polyether / polyester copolymer is used in the undrawn yarn. This is because, when applied to the surface, a film is formed on the surface of the undrawn yarn, so that fusion and adhesion between the fibers are less likely to occur during flow drawing in hot water at high temperature.

Further, when a wet nonwoven fabric is obtained from the obtained fiber by a papermaking method, the polyether / polyester copolymer adheres to the fiber, so that the dispersibility of the fiber in water is improved. When the polyether / polyester copolymer is applied to the undrawn yarn, it is applied by an oiling device immediately after the undrawn yarn is spun, or it is applied by being included in a hot water bath in the flow drawing step. Is desirable.

Subsequently, the undrawn yarn is flow-stretched, neck-stretched or subjected to a limited heat shrinkage treatment in a relaxed state as necessary, and then a fiber treatment agent according to the molding process and the imparting function of the non-woven fabric is applied, and then the guillotine. A desired short-cut heat-adhesive fiber can be obtained by cutting with a cutter, a rotary cutter, or the like.

When the non-woven fabric is a wet non-woven fabric, a wet web forming step is carried out by applying an aqueous emulsion of a polyether / polyester copolymer similar to that applied to the undrawn yarn as a fiber treatment agent after stretching or before and after cutting. The dispersibility of the fiber in water is further improved. In this case, the polyether / polyester copolymer may be attached in an amount of 0.03 to 10.0% by mass per 100% by mass of the short-cut heat-adhesive fiber. If it is less than 0.03% by mass, the dispersion of the fibers in water in the papermaking process is insufficient, which is not preferable. On the other hand, if it exceeds 10.0% by mass, the adhesiveness between the fibers tends to be impaired. However, a large amount of the polyether / polyester copolymer is not preferable because it increases the water quality load on the circulating water in the wet web forming step.

The above-mentioned polyether / polyester copolymer consists of terephthalic acid and / or isophthalic acid, lower alkylene glycol and polyalkylene glycol and / or monoether thereof. Examples of the lower alkylene glycol preferably used include ethylene glycol, propylene glycol and tetramethylene glycol. On the other hand, examples of the polyalkylene glycol include polyethylene glycol having an average molecular weight of 600 to 6000, a polyethylene glycol / polypropylene glycol copolymer, and polypropylene glycol. Further, examples of the monoether of polyalkylene glycol include monomethyl ethers such as polyethylene glycol and polypropylene glycol, monoethyl ethers and monophenyl ethers.

The above-mentioned polyether / polyester copolymer preferably has a molar ratio of terephthalate unit to isophthalate unit in the range of 95: 5 to 40:60 from the viewpoint of dispersibility in water, but alkali metal salts sulfoisophthalic acid, adipic acid, etc. A small amount of sebacic acid or the like may be copolymerized.

The average molecular weight of the polyether / polyester copolymer depends on the molecular weight of the polyalkylene glycol used, but is usually 1000 to 20000, preferably 3000 to 15000. If the average molecular weight is less than 1000, the effect of improving the dispersibility in water is not sufficient, while if it exceeds 20000, it becomes difficult to emulsify and disperse the polymer.

In order to improve the flow stretchability and obtain an ultrafine short-cut heat-adhesive fiber having a fiber diameter of 0.5 to 4 μm, the short-cut heat-adhesive fiber is made of polyester, and the polyester has a terephthalic acid component of 60 to 90 mol. % And 10 to 40 mol% of the isophthalic acid component is preferably a copolymerized polyester containing a dicarboxylic acid component.

By copolymerizing the isophthalic acid component with polyester in the range of 10 to 40 mol%, the flow draw ratio can be significantly improved. In the case of isophthalic acid copolymerization, the magnification can be improved up to about 20 to 200 times, whereas in the case of no copolymerization, the magnification remains 10 times or less. The reason for this is not clear, but it is possible to reduce the molecular orientation of amorphous and amorphous fibers in undrawn yarns and fibers after flow stretching, and depending on the copolymerization, increase the molecular weight. However, it is possible because the free volume (excluded volume) around the molecule during flow stretching becomes large, the molecular chain moves easily at a temperature higher than the glass transition temperature, and the molecular weight can be increased enough to secure sufficient entanglement of the molecular chain. It is estimated that the draw ratio will be improved.

If the copolymerization amount of the isophthalic acid component is less than 10 mol%, the flow draw ratio decreases, and it becomes difficult to obtain short-cut heat-adhesive fibers having a fiber diameter of 4 μm or less, which is not preferable. On the other hand, if the copolymerization amount of the isophthalic acid component exceeds 40 mol%, it becomes difficult to suppress fusion between the fibers during flow stretching, and it is also difficult to produce desired ultrafine fibers uniformly and stably, which is not preferable. The copolymerization amount of the isophthalic acid component is more preferably 15 to 35 mol%, particularly preferably 20 to 30 mol% based on the total dicarboxylic acid component.

When the short-cut heat-adhesive fiber is in the form of a composite fiber, it is preferable that the isophthalic acid component is copolymerized with both the fiber-forming component and the heat-adhesive component, and the copolymerization amount of the isophthalic acid component is the amount of fiber formation. The sex component and the heat-adhesive component may differ, but even in that case, the copolymerization amount of the isophthalic acid component on the load average of both (that is, the fiber as a whole) may be in the range of 10 to 40 mol%. preferable.

The above-mentioned copolymerized polyester contains alkylene terephthalate as a main repeating component, and the repeating unit is preferably ethylene terephthalate, trimethylene terephthalate, butylene terephthalate, or hexamethylene terephthalate. Then, it is preferable to use an aliphatic diol as the diol component of the copolymerized polyester.

Among the above-mentioned co-weighted polyesters, isophthalic acid copolymerized polyalkylene terephthalate-based polyesters containing ethylene terephthalate as a main repeating unit are most preferable. In addition to isophthalic acid, bifunctional carboxylic acids such as adipic acid, sebacic acid, and sodium 3-5-dicarboxybenzene sulfonate, in order to adjust the melting point and adhesive strength of the flow stretchability and heat-adhesive components, Diethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, polyethylene glycol and other diols may be copolymerized together.

[Non-woven fabric]
The nonwoven fabric of the present invention contains short-cut ultrafine fibers and short-cut heat-adhesive fibers as defined above, and if necessary, contains other short-cut fibers, and after forming a web, the nonwoven fabric is in the form of a nonwoven fabric by heating or pressurizing. It can be obtained by molding into.

Examples of the method for forming the web include a carding method, an airlaid method, and a papermaking method, and it is particularly preferable to use a wet non-woven fabric by the papermaking method. Examples of the web joining method include an air-through method, an embossing method, a yanky dryer method, a multi-cylinder dryer method, a calendar method, a resin bond method, and a water jet method, and in particular, a calendar method and a water jet method (spun race method, water flow). The entanglement method and the hydroentangle method) are preferable.

In the nonwoven fabric of the present invention, the mass ratio of the short-cut ultrafine fibers to the total mass of the nonwoven fabric is preferably 0.5 to 50% by mass, more preferably 1 to 40% by mass, and particularly preferably 3 to 30% by mass. If the short-cut ultrafine fibers are less than 0.5% by mass, not only a satisfactory collection efficiency cannot be obtained, but also formation spots as a wet non-woven fabric may occur, which is not preferable. On the other hand, if it exceeds 50% by mass, the filter filter medium (wet non-woven fabric) becomes too dense, so that the drainage in the papermaking process becomes extremely poor, the productivity deteriorates, and the pressure loss becomes too large. Not preferable.

Further, in the nonwoven fabric of the present invention, the mass ratio of the short-cut heat-adhesive fiber to the total mass of the nonwoven fabric is preferably 10 to 99.5% by mass, more preferably 10 to 95.5% by mass, still more preferably 15 to 90. It is by mass, particularly preferably 20 to 85% by mass. If the short-cut ultrafine fiber is less than 10% by mass, the thermal adhesiveness is small, the strength of the non-woven fabric and the pressure deformation are insufficient, a uniform pore diameter cannot be obtained, and the collection efficiency and filter life are inferior. Not only is it stable in quality, but it is also unsuitable because it may cause texture spots as a wet non-woven fabric. On the other hand, if it exceeds 95.5% by mass, the effect of the short-cut ultrafine fibers is insufficient, and the filtration performance (collection efficiency) is inferior to that of the conventional technique using ultrafine fibers.

The non-woven fabric of the present invention has a form as a filter filter medium by using short-cut heat-adhesive fibers having a small fiber diameter to increase the number of adhesion points of the heat-adhesive components and by making the distance between fibers uniform. It is a major feature that it is maintained, is not easily crushed by pressure, has high collection efficiency, low pressure loss, and high filter life.

In the nonwoven fabric of the present invention, if it is 50% by mass or less with respect to the total mass of the nonwoven fabric, various synthetic fibers (polyethylene terephthalate, polytrimethylene terephthalate) can be used as fibers other than the short-cut ultrafine fibers and short-cut heat-adhesive fibers. , Polybutylene terephthalate, nylon, olefin-based, aramid-based), natural pulp such as wood pulp and linter pulp, synthetic pulp containing aramid and polyethylene as main components, and the like may be mixed. In particular, polyethylene terephthalate staples made of stretched polyethylene terephthalate having a single fiber fineness of 0.01 to 0.6 dtex and a fiber length of 1 to 10 mm are preferable from the viewpoint of dimensional stability and the like.

If the non-woven fabric of the present invention satisfies the requirements including short-cut ultrafine fibers and short-cut heat-adhesive fibers, the short-cut ultrafine fibers and short-cut heat-adhesive fibers may have different fiber diameters and polymers, respectively, depending on the purpose. It may be in the form of a mixture of two or more types of short-cut fibers having different types and compositions. Further, the nonwoven fabric may be a single layer having a uniform mixing ratio as a whole, but may be composed of two or more layers depending on the purpose. In that case, in order to use it as a filter filter medium, it is necessary that the mixing ratio and the fiber density in which there is no boundary surface between adjacent layers have a structure in which the fiber density is inclined in the thickness direction of the nonwoven fabric (the mixing ratio and the fiber density gradually increase or decrease). Preferably, in such a form, in the process of forming the web, a plurality of carding machines, air-laid web manufacturing devices, and paper machines are arranged, layers having different mixing ratios and fiber types are laminated, and then the fibers are heat-bonded or heat-bonded. It is possible by fixing the space. Further, when the structure is composed of two or more layers, if the mixing ratio of the short-cut ultrafine fibers is large or the average fiber diameter of the entire composed fibers is small, the density is large and the through pores can be made small. By providing the density difference for each web layer in this way, it is possible to design a filter having high collection efficiency and low pressure loss and having a long filter life. The density of the web layer may be designed to increase in the filtration direction, may be designed to be small, or may be in a laminated state in which large and small are mixed, and may be freely designed according to the purpose. good.

In addition, depending on the purpose, the non-woven fabric of other materials is laminated for the purpose of the tensile strength and hardness of the filter, further improvement of the filter life like a pre-filter for coarse dust, pleated stability and adhesiveness of other materials. May be good. For example, other materials include spunbonded non-woven fabric, melt blown non-woven fabric, heat-bonded non-woven fabric, needle punched non-woven fabric, spunlaced non-woven fabric, air-laid non-woven fabric, resin-bonded non-woven fabric, stitch-bonded non-woven fabric, tow-open fiber non-woven fabric, burst fiber non-woven fabric, and these non-woven fabrics. A composite laminate or other woven or knitted fabric may be laminated.

The basis weight of the nonwoven fabric of the present invention is preferably 1 to 500 g / m ² , more preferably 3 to 400 g / m ² , and particularly preferably 5 to 300 g / m ² . If the basis weight is less than 1 g / m ² , the strength of the non-woven fabric is weakened because the non-woven fabric is too thin, and spots are likely to occur on the papermaking, which may cause defects or breakage through the substance to be filtered when the filter is used. On the other hand, if it exceeds 500 g / m ² , it becomes difficult for water to drain during papermaking, and problems are likely to occur in terms of manufacturing and cost.

The thickness of the nonwoven fabric of the present invention is preferably 0.01 to 3.0 mm, more preferably 0.5 to 3.0 mm, and particularly preferably 1.0 to 2.5 mm. If the thickness is less than 0.01 mm, the strength of the filter medium is insufficient, which is not preferable. On the other hand, if it exceeds 3.0 mm, the compactness as a filter filter medium is lowered, and it is particularly difficult to mold the pleating process (zigza-folded structure) performed to increase the filtration area, which is not preferable.

In the nonwoven fabric of the present invention, the average pore diameter of the penetrating pores is preferably 0.1 to 10.0 μm, more preferably 0.3 to 5.0 μm, and even more preferably 0.5 to 2.5 μm. If the average pore diameter is less than 0.1 μm, the pressure loss of the filter filter medium becomes too high, and the air flow rate after filter filtration decreases, which is not preferable. On the other hand, if it exceeds 10.0 μm, the fineness of the filter filter medium is lowered and the collection rate of fine particles is lowered, which is not preferable.

Further, in the nonwoven fabric of the present invention, the maximum pore diameter / average pore diameter (value obtained by dividing the maximum pore diameter by the average pore diameter) of the through pores is preferably 1.0 to 2.5, preferably 1.0 to 2. It is 3.3. A maximum pore diameter / average pore diameter of 1.0 indicates that the through-pore diameter of the nonwoven fabric is uniform, which is most preferable. If the maximum pore diameter / average pore diameter exceeds 2.5, the density as a filter filter medium is lowered, and the collection rate of fine particles is lowered, which is not preferable. If the hole shape is not a perfect circle, the major axis is the hole diameter.

In the nonwoven fabric of the present invention having the above-mentioned basis weight and thickness, the breathability is preferably 0.5 to 10 cm ³ / cm ² / sec, more preferably 0.7 to 5 cm ³ / cm ² / sec, and particularly preferably 1 to 1. It is 4 cm ³ / cm ² / sec. If the air permeability is less than 0.5 cm ³ / cm ² / sec, the pressure loss of the filter becomes too high and the air flow rate after filter filtration decreases, which is not preferable. On the other hand, if the air permeability exceeds 10 cm ³ / cm ² / sec, the fineness of the filter filter medium is lowered and the collection efficiency is lowered, which is not preferable.

The non-woven fabric of the present invention has a compressibility of 30% or less, preferably 26% or less when pressurized at 30 kPa, which is calculated by the following formula. When the compressibility at the time of pressurizing 30 kPa exceeds 30%, the non-woven fabric as the filter medium is crushed by the pressure when used as a filter, the density becomes high, and the life is shortened.
Compressibility during pressurization (%) = Filter media thickness during compression (mm) / Filter media thickness before compression (mm)

[Manufacturing method of non-woven fabric]
The non-woven fabric of the present invention is produced by a normal long net paper machine, a short net paper machine, a circular net paper machine, or a combination of a plurality of these machines to make a multi-layer paper machine to obtain a wet non-woven fabric, and then heat-treat the non-woven fabric. be able to.

The heat treatment step is performed after the web forming step by the papermaking method, and either the Yankee dryer or the air through dryer can be applied to the heat treatment. The heat treatment temperature is usually 100 to 140 ° C., preferably 110 to 130 ° C., and the heat treatment time is, for example, 30 to 300 seconds, preferably 60 to 180 seconds. If necessary, the nonwoven fabric may be subjected to calendar processing, embossing processing, or flat plate heat pressing processing. In the case of calendar processing, the temperature of the calendar roller is, for example, 140 to 250 ° C., and the linear pressure between the rollers is, for example, 1 to 100 kN / m.

〔filter〕
The non-woven fabric of the present invention uses short-cut ultrafine fibers for short-cut and heat-adhesive fibers with a very fine fiber diameter, and has a high collection rate, low pressure loss and long life when used as a filter filter medium. You can get a filter that satisfies all of the above.

The filter made of the non-woven fabric of the present invention can be suitably used for, for example, a chemical filter, an air filter, a liquid filter, and an oil filter.
Since the nonwoven fabric of the present invention is homogeneous and has an extremely small pore diameter, it can be suitably used not only as a filter but also as a base paper for stencil printing, a wiper, a battery separator, artificial leather and the like.

Next, examples and comparative examples of the present invention will be described in detail. In addition, each measurement item in an Example was measured by the following method.

(1) Intrinsic Viscosity 0.12 g of a polymer sample was dissolved in 10 mL of a tetrachloroethane / phenol mixed solvent (volume ratio 1/1), and the intrinsic viscosity (dL / g) at 35 ° C. was measured.

(2) Melting point A melting peak was determined by measuring at a heating rate of 20 ° C./min using a thermal differential analyzer 990 manufactured by DuPont. When the melting temperature was not clearly observed, a micro melting point measuring device (manufactured by Yanagimoto Seisakusho) was used, and the temperature at which the polymer softened and started to flow (softening point) was used as the melting point. In each case, the number of samples to be measured was set to 5, and the average value was calculated.

(3) Melt Viscosity The test polymer is dried, set in an orifice set at the melt temperature of a melt spinning extruder, held in a melted state for 5 minutes, and then extruded under a predetermined level of load. Shear rate and melt viscosity were plotted. The above operation was repeated under a load of multiple levels. Based on the above data, a shear rate-melt viscosity relationship curve was created. On this curve, the melt viscosity was estimated when the shear rate was 1000 seconds ^-1 .

(4) Measurement of dissolution rate Each of the polymers for both sea and island components is extruded through a spinneret for manufacturing sea-island type composite fibers having 24 discharge holes with a hole diameter of 0.3 mm and a land length of 0.6 mm, and 1000 to 2000 m / It was wound at a rate of minutes and the fibers were stretched. The cutting elongation was controlled within the range of 30 to 60% to produce a multifilament of 75 dtex / 24 filaments. This multifilament was dissolved in a solvent at a predetermined temperature at a bath ratio of 50, and the weight loss rate was calculated from the dissolution time and the dissolution amount at this time.

(5) Fiber length L
The length of 100 single yarn fibers was measured using a Keyence digital microscope (VHX-5000), and the average value was defined as the fiber length L (unit: mm).

(6) Fiber diameter D (in the case of short-cut ultrafine fibers)
Using a transmission electron microscope TEM (with a length measuring function), a cross-sectional photograph of the fiber was taken and measured at a magnification of 30,000 times. For the fiber diameter D, the diameter of the circumscribed circle in the cross section of the single fiber was used (mean value of 5 samples).

(7) Fiber diameter D (for other than short-cut ultrafine fibers)
It was calculated by the following formula from the single yarn fineness d (dtex) and the density ρ (g / cm ³ ) (unit: μm). Here, π is the pi.
D (μm) = 20 × (d / πρ) ^1/2

(8) Single yarn fineness (d) (for other than short-cut ultrafine fibers)
A 2000 mm fiber bundle after stretching was collected and dried in a hot air dryer at 120 ° C. for 40 minutes, and then the measured absolute dry mass was multiplied by 5000 to measure the total fineness (unit: dtex) of the fiber bundle. The single yarn fineness d (unit: dtex) was calculated by dividing the obtained total fineness by the number of constituent single yarn fibers.

(9) Fiber density (for other than short-cut ultrafine fibers)
The fiber density ρ (unit: g / cm ³ ) was measured using the density gradient tube method described in JIS L1015: 2010 8.14.2.

(10) Aspect ratio (L / D)
Using the values of fiber diameter D (unit: mm) and fiber length L (unit converted from μm to mm) calculated from single yarn fineness, the ratio of fiber length (L) / fiber diameter (D) is aspected. The ratio (L / D) was used.

(11) Metsuke It was carried out based on JIS P8124: 2011 (paper and paperboard-measurement method of basis weight).

(12) Thickness Performed based on JIS P8118: 2014 (paper and paperboard-test method for thickness, density and specific volume).

(13) Nonwoven fabric density This was carried out based on JIS P8118: 2014 (paper and paperboard-test method for thickness, density and specific volume).

(14) Breathability Performed based on JIS L1913: 2010 (general non-woven fabric test method) 6.8.

(15) Specific tensile strength Based on JIS P8113: 2006 (paper and paperboard-test method for tensile properties-Part 2: constant velocity elongation method), the direction of paper passing through the dryer (MD) at the time of sample preparation and orthogonal to it. Each direction (CD) was measured and converted into specific tensile strength. (Unit: N ・ m / g)

(16) 30 kPa compressibility Performed based on JIS L1913: 2010 (general non-woven fabric test method) 6.14.

(17) Two circular samples having a pore diameter of 2.5 cm were randomly collected from the non-woven fabric, and the average pore diameter, the minimum pore diameter, and the maximum pore diameter (a pore diameter distribution measuring instrument manufactured by PMI) were used. Unit: μm) was measured. Moreover, the value of the maximum pore diameter / the average pore diameter was calculated.

(18) Atmospheric dust collection rate Adjust so that the wind speed is 5.1 cm / sec, count the atmospheric dust before and after the sample with a particle counter (KC-03B manufactured by Rion Co., Ltd.), and calculate the collection rate based on the ratio. did.
Atmospheric dust collection rate (%) = (1- (Number of atmospheric dust after passing sample / Number of atmospheric dust before passing sample)) x 100

(19) Pressure loss The pressure before and after passing through the test piece at the time of measuring the air dust collection rate (wind speed 5.1 cm / sec) was measured, and the pressure difference was determined as the pressure loss.

(20) Filter life When eight types of JIS Z 8901 are used as test dust, the flow velocity when passing through the sample is 16.7 cm / sec, the dust concentration is 1 g / m ³ , and the increase in pressure loss is 2 kPa. The amount of dust collected (mass increase) was measured (g / m ² ).

[Example 1]
Polyethylene terephthalate (intrinsic viscosity 0.64 dL / g, melting point 256 ° C) with an island component having a melt viscosity at 285 ° C. of 120 Pa · sec, and a sea component with a melt viscosity at 285 ° C. of 135 Pa · sec, with an average molecular weight of 4000. Modified polyethylene terephthalate (intrinsic viscosity 0.39 dL / g, melting point 226 ° C.) obtained by copolymerizing 4% by mass of polyethylene glycol and 9 mol% of 5-sodium sulfoisophthalic acid was used, and the mass ratio of sea: island = 10:90. Then, spinning was performed using a sea-island type composite fiber spinning base having 400 islands having the structure shown in FIG. 1, and the viscosity was taken up at a spinning speed of 1500 m / min. The difference in alkali weight loss rate between the island component and the sea component was 1000 times.

This was stretched 3.9 times and then cut to a fiber length of 1 mm with a guillotine cutter to obtain a composite fiber for short-cut ultrafine fiber A. When this was reduced by 10% at 75 ° C. with a NaOH aqueous solution having a concentration of 4% by mass, ultrafine staple fibers having a relatively uniform fiber diameter and fiber length were produced. This was designated as a short-cut ultrafine fiber A. The obtained short-cut ultrafine fiber A had a fiber diameter of 0.75 μm, a fiber length of 0.8 mm, and an aspect ratio of 1067.

On the other hand, the fiber-forming component is isophthalic acid 20 mol% copolymerized polyethylene terephthalate (intrinsic viscosity 0.64 dL / g, melting point 202 ° C.), and the heat-adhesive component is isophthalic acid 40 mol% -diethylene glycol 4 mol% copolymerized polyethylene. A core-sheath type composite fiber having a terephthalate (intrinsic viscosity 0.55 dL / g, melting point (softening point) 110 ° C.), a fiber-forming component as a core, and a heat-adhesive component as a sheath (core: sheath = 50: 50 mass ratio) was prepared.

The content of the isophthalic acid component, which is a copolymerization component contained in the core-sheath type composite fiber, is 10 mol% (20 mol% × 50%) contained in the fiber-forming component of the core and the thermal adhesiveness of the sheath. The sum of 20 mol% (40 mol% × 50%) contained in the components was 30 mol%.

In order to obtain a core-sheath type composite fiber, the fiber-forming component and the heat-adhesive component are melted by separate vent type twin-screw extruders, the fiber-forming component is used as the core component, and the heat-adhesive component is used as the sheath component. A capillary having a hole diameter of 0.3 mm was combined with a known core-sheath type composite spinneret having 1336 holes so that the mass ratio was core: sheath = 50:50, and melt-discharged in the form of threads. At this time, the base temperature was 290 ° C. and the discharge rate was 430 g / min.

Further, the discharged yarn is cooled and solidified by cooling air at 25 ° C. at a position 31 mm below the mouthpiece, and at the lower part, an aqueous emulsion of a polyether / polyester copolymer is applied in an amount of 0.5% by mass of solid content, and 500 m / m /. It was wound in minutes to obtain an undrawn yarn.

The undrawn yarn was stretched 63 times in warm water at 82 ° C., and then doubled in warm water at 70 ° C. A short-cut heat-adhesive fiber with a fiber length of 0.051 dtex (fiber diameter 2.3 μm, fiber length 3 mm, aspect ratio 1328) cut to a fiber length of 3 mm after applying an aqueous solution of a polyether / polyester copolymer to the fiber surface. B was obtained.

In addition to this, as other fiber C, polyethylene terephthalate short fiber (Teijin Frontier Co., Ltd. Tepilus TA04PN SD0.1 × 3 (intrinsic viscosity 0.47 dL / g, melting point 256 ° C., fineness 0.1 dtex, fiber diameter 4 μm, fiber length) 3 mm, aspect ratio 750) was used.

Short-cut ultrafine fiber A, short-cut heat-adhesive fiber B and other fiber C are mixed in a predetermined mass ratio (short-cut ultrafine fiber A / short-cut heat-adhesive fiber B / other fiber C = 15/40/45). After stirring, paper was made by TAPPI (square sheet machine manufactured by Kumagai Riki Kogyo) with a grain size of 100 g / m ² , and then dried (120 ° C. × 2 minutes) with a Yankee dryer to obtain a wet non-woven fabric. The physical characteristics of the obtained nonwoven fabric (filter medium) are shown in Tables 1 and 2.

[Example 2]
A wet nonwoven fabric was obtained in the same manner as in Example 1 except that the basis weight was 300 g / m ² in the papermaking of Example 1. The physical characteristics of the obtained nonwoven fabric (filter medium) are shown in Tables 1 and 2.

[Example 3]
As the short-cut heat-adhesive fiber B, the short-cut fiber of the core-sheath type composite fiber described below was used, and a wet nonwoven fabric was obtained by the same method as in Example 1 except that the dryer temperature was changed to 150 ° C. The physical characteristics of the obtained nonwoven fabric (filter medium) are shown in Tables 1 and 2.

The fiber-forming component is 20 mol% isophthalic acid copolymerized polyethylene terephthalate (inherent viscosity 0.64 dL / g, melting point 202 ° C.), and the heat-adhesive component is 20 mol% isophthalic acid-1,4 butanediol 65 mol% copolymerized polyethylene. Short-cut thermal adhesion using a core-sheath type composite fiber having a terephthalate (inherent viscosity 0.62 dL / g, melting point (softening point) 155 ° C.) and having a fiber-forming component as a core and a heat-adhesive component as a sheath. Sex fiber B was prepared.

The copolymerized isophthalic acid component contained in the short-cut heat-adhesive fiber B is 10 mol% (50% of 20 mol%) contained in the fiber-forming component and 10 mol contained in the heat-adhesive component. The sum of% (50% of 20 mol%) was 20 mol%.

In order to obtain the short-cut heat-adhesive fiber B, the fiber-forming component and the heat-adhesive component are melted by separate vent type twin-screw extruders, the fiber-forming component is used as the core component, and the heat-adhesive component is used. As a sheath component, a capillary having a hole diameter of 0.3 mm was combined with a known core-sheath type composite spinneret having 1336 holes so that the mass ratio was core: sheath = 50:50, and melted and discharged in the form of threads. At this time, the base temperature was 290 ° C. and the discharge rate was 430 g / min.

Further, the discharged yarn is cooled and solidified by cooling air at 25 ° C. at a position 42 mm below the mouthpiece, and at the lower part, an aqueous emulsion of a polyether / polyester copolymer is applied in an amount of 0.5% by mass of solid content, and 500 m / m /. It was wound in minutes to obtain an undrawn yarn.

This undrawn yarn was stretched 28 times in warm water at 82 ° C. and then 2.9 times in warm water at 70 ° C. A short-cut heat-adhesive fiber with a fineness of 0.079 dtex (fiber diameter 2.8 μm, fiber length 3 mm, aspect ratio 1067) cut to a fiber length of 3 mm after applying an aqueous solution of a polyether / polyester copolymer to the fiber surface. B was obtained.

[Example 4]
A wet nonwoven fabric was obtained in the same manner as in Example 3 except that the basis weight was 300 g / m ² in the papermaking of Example 3. The physical characteristics of the obtained nonwoven fabric (filter medium) are shown in Tables 1 and 2.

[Examples 5 and 6]
20 mol% isophthalic acid copolymerized polyethylene terephthalate (intrinsic viscosity 0.64 dL / g, melting point 202 ° C.) is melted with a vent type twin-screw extruder, and spinning for a known single component having 1192 pores of a capillary with a pore diameter of 0.18 mm. It was melted and discharged in the form of threads from the mouthpiece. At this time, the base temperature was 290 ° C. and the discharge rate was 200 g / min.

Further, the discharged yarn is cooled and solidified by cooling air at 25 ° C. at a position 26 mm below the mouthpiece, and at the lower part, 0.5% by mass of a water-based polyether / polyester copolymer emulsion is applied in terms of the amount of solid content adhered to 500 m /. It was wound in minutes to obtain an undrawn yarn. The undrawn yarn was stretched 68 times in warm water at 82 ° C., and then doubled in warm water at 70 ° C. After applying an aqueous solution of a polyether / polyester copolymer to the fiber surface, the fiber is cut to a fiber length of 3 mm, and only from the heat-adhesive component having a fineness of 0.025 dtex (fiber diameter 1.6 μm, fiber length 3 mm, aspect ratio 1897). A short-cut heat-adhesive fiber B was obtained. The copolymerized isophthalic acid component contained in the short-cut heat-adhesive fiber B was 20 mol%.

In Examples 1 and 2, the short-cut thermoadhesive fiber B was replaced with the above-mentioned one, and after papermaking and drying by the same method as in Examples 1 and 2, a hydraulic clearance embossing machine (Yuri Roll Co., Ltd.) A wet non-woven fabric was obtained by thermocompression bonding at 190 ° C., 29 kN / m and a speed of 2 m / min. The physical characteristics of the obtained nonwoven fabric (filter medium) are shown in Tables 1 and 2 and Tables 3 and 4.

[Comparative Example 1]
A wet nonwoven fabric was obtained in the same manner as in Example 1 except that the core-sheath type composite fiber described below was used as the short-cut heat-adhesive fiber B. The physical characteristics of the obtained nonwoven fabric (filter medium) are shown in Tables 3 and 4.

The fiber-forming component is polyethylene terephthalate (intrinsic viscosity 0.64 dL / g, melting point 256 ° C.), and the heat-adhesive component is isophthalic acid 40 mol% -diethylene glycol 4 mol% copolymerized polyethylene terephthalate (intrinsic viscosity 0.55 dL / g, melting point). A short-cut heat-adhesive fiber B was prepared by using a core-sheath composite fiber having a fiber-forming component as a core and a heat-adhesive component as a sheath at (softening point) 110 ° C.).

As a method for producing a core-sheath type composite fiber, the fiber-forming component and the heat-adhesive component are melted by separate vent type biaxial extruders, the fiber-forming component is used as the core component, and the heat-adhesive component is used as the sheath component. A capillary having a hole diameter of 0.3 mm was combined with a known core-sheath type composite spinneret having 1336 holes so that the mass ratio was core: sheath = 50:50, and the fibers were melt-discharged in the form of threads. At this time, the base temperature was 290 ° C. and the discharge rate was 600 g / min.

Further, the discharged yarn is cooled and solidified by cooling air at 25 ° C. at a position 56 mm below the mouthpiece, and at the lower part, 0.5% by mass of a water-based polyether / polyester copolymer emulsion is applied in terms of the amount of solid content adhered to 1350 m /. It was wound in minutes to obtain an undrawn yarn. The undrawn yarn was stretched 2.6 times in warm water at 58 ° C. and then 1.15 times in warm water at 56 ° C. After applying an aqueous solution of a polyether / polyester copolymer to the fiber surface, the fiber is cut to a fiber length of 5 mm and has a fineness of 1.1 dtex (fiber diameter 10.5 μm, fiber length 5 mm, aspect ratio 477). B was obtained.

The copolymerized isophthalic acid component contained in the short-cut heat-adhesive fiber B is 0 mol% (50 parts by mass of 0 mol%) contained in the fiber-forming component and 20 mol contained in the heat-adhesive component. The sum of% (50 parts by mass of 40 mol%) was 20 mol%.

[Comparative Example 2]
A wet nonwoven fabric was obtained in the same manner as in Comparative Example 1 except that the basis weight was 300 g / m ² in the papermaking of Comparative Example 1. The physical characteristics of the obtained nonwoven fabric (filter medium) are shown in Tables 3 and 4.

[Comparative Examples 3 and 4]
Wet nonwoven fabrics were obtained in the same manner as in Examples 5 and 6 using the short-cut heat-adhesive fiber B, which is a fiber composed of a single component of the heat-adhesive component described below. The physical characteristics of the obtained nonwoven fabric (filter medium) are shown in Tables 3 and 4.

Heat-adhesive component In order to obtain a fiber consisting of a single component, 20 mol% isophthalic acid copolymerized polyethylene terephthalate (intrinsic viscosity 0.64 dL / g, melting point 202 ° C.) was melted with a bent twin-screw extruder to have a pore size of 0. A .18 mm capillary was melt-discharged in the form of a thread from a known single-component spinneret having 1192 holes. At this time, the base temperature was 285 ° C. and the discharge rate was 180 g / min.

Further, the discharged yarn is cooled and solidified by cooling air at 25 ° C. at a position 25 mm below the mouthpiece, and at the lower part, 0.5% by mass of a water-based polyether / polyester copolymer emulsion is applied in terms of the amount of solid content adhered to 1350 m /. It was wound in minutes to obtain an undrawn yarn. This undrawn yarn is not drawn, but a polyether / polyester copolymer aqueous solution is applied to the fiber surface, and then the yarn is cut to a fiber length of 5 mm and has a fineness of 1.1 dtex (fiber diameter 10.5 μm, fiber length 5 mm, aspect ratio). A short-cut heat-adhesive fiber B composed of a single component of the heat-adhesive component of 477) was obtained. The amount of the copolymerized isophthalic acid component contained in the short-cut heat-adhesive fiber B was 20 mol%.

The numbers in parentheses in the melting point column represent softening points.
Tables 1 to 4 are collectively listed below as Table 5.

The nonwoven fabric of the present invention can be suitably used as a filter filter medium. Since this filter has high collection efficiency, low pressure loss, and a long filter life, it can be suitably used as an air filter for an internal combustion engine for intake air. Of course, air filters, microfilters and liquid filters for other applications such as indoor air conditioners, air conditioners, heaters (electric type, kerosene type, etc.), automobile air conditioners, air purifiers, clean rooms, indoor humidifiers, etc. It can be used as an air conditioner.

1 Spinning cap 2 Island component polymer reservoir 3 Island component polymer introduction passage 4 Sea component polymer introduction passage 5 Sea component polymer reservoir 6 Core-sheath type composite diversion passage 7 Confluence passage 8 Discharge port

Claims (11)

30 kPa including short-cut microfibers having a fiber diameter of 0.1 to 1 μm and an aspect ratio of 100 to 3000 and short-cut thermally adhesive fibers having a fiber diameter of 0.5 to 4 μm and an aspect ratio of 100 to 3000. A non-woven fabric characterized by a compression ratio of 30% or less when pressurized. The nonwoven fabric according to claim 1, wherein the short-cut heat-adhesive fiber is made of a polyester, and the polyester is a copolymerized polyester containing 60 to 90 mol% of a terephthalic acid component and 10 to 40 mol% of an isophthalic acid component as a dicarboxylic acid component. .. The short-cut heat-adhesive fiber is a composite fiber composed of a fiber-forming component and a heat-adhesive component, in which the fiber-forming component accounts for 20 to 80% by mass and the heat-adhesive component accounts for 80 to 20% by mass. The nonwoven fabric according to claim 1 or 2, wherein the fiber-forming component is a polyester having a melting point of 180 ° C. or higher, and the heat-adhesive component is a polyester having a melting point of 20 ° C. or higher lower than the melting point of the fiber-forming component. The nonwoven fabric according to claim 3, wherein the composite fiber is a core-sheath type composite fiber having a fiber-forming component as a core and a heat-adhesive component as a sheath. The nonwoven fabric according to claim 1 or 2, which comprises only polyester having a melting point of 250 ° C. or lower as a heat-adhesive component. A short-cut heat-adhesive fiber consisting only of polyester having a fiber diameter of 0.5 to 4 μm, an aspect ratio of 100 to 3000, and a heat-adhesive component having a melting point of 250 ° C. or less. The short-cut heat according to claim 6, wherein the polyester constituting the short-cut heat-adhesive fiber is a copolymerized polyester containing 60 to 90 mol% of a terephthalic acid component and 10 to 40 mol% of an isophthalic acid component as a dicarboxylic acid component. Adhesive fiber. It is a short-cut heat-adhesive fiber composed of a fiber-forming component and a heat-adhesive component. In the short-cut heat-adhesive fiber, the fiber-forming component accounts for 20 to 80% by mass, and the heat-adhesive component accounts for 80 to 80 to 80%. Claim 6 or 7, wherein the fiber-forming component is a polyester having a melting point of 180 ° C. or higher, and the heat-adhesive component is a polyester having a melting point of 20 ° C. or higher lower than the melting point of the fiber-forming component, which accounts for 20% by mass. The short-cut heat-adhesive fiber described. The 6th or 7th claim, wherein the short-cut heat-adhesive fiber is composed of only a heat-adhesive component, and the heat-adhesive component of the short-cut heat-adhesive fiber is composed of a single component of polyester having a melting point of 250 ° C. or lower. Short cut heat adhesive fiber. Short cut with a fiber diameter of 0.1 to 1 μm and an aspect ratio of 100 to 3000 The content of ultrafine fibers is 0.5 to 50% by mass, and the fiber diameter is 0.5 to 4 μm and the aspect ratio is 100 to 3000. The content of the cut heat-adhesive fiber is 10 to 99.5% by mass, the grain size is 1 to 500 g / m ² , the thickness is 0.01 to 3.0 mm, and the average pore diameter is 0.1 to 10.0 μm. The non-woven fiber according to any one of claims 1 to 5, wherein the maximum pore diameter / average pore diameter is 1.0 to 2.5. A filter using the nonwoven fabric according to any one of claims 1 to 5 and claim 10.

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