JP5172781B2 - Ultrafine fiber composite nonwoven fabric and method for producing the same - Google Patents

Description

  The present invention relates to a composite nonwoven fabric in which ultrafine fibers and woven or knitted fabric are laminated and integrated, and is used in filters, wiping cloths, etc., and particularly suitable as a filter for removing fine dust, and has excellent shape retention and durability. The present invention relates to an ultrafine fiber composite nonwoven fabric and a method for producing the same.

  Conventional non-woven fabrics utilizing the characteristics of ultrafine fibers have been proposed. For example, there is a non-woven fabric for a filter as an application that makes use of the characteristics that ultrafine fibers remove fine dust. As such a nonwoven fabric, for example, there is a nonwoven fabric by a melt blow method. However, the ultrafine fibers formed by the melt-blowing method have a problem that they are not drawn and thus have low strength and cannot be put into practical use as they are. Further, since the strength is weak, when compressive force such as wind pressure is applied, the bulkiness is easily lost, and the dust holding capacity is reduced. In addition, the thickness of the ultrafine fiber is difficult to be uniform, and there is a problem that the filtration performance is not stable.

As a technique for improving such a nonwoven fabric by the melt blow method, a filter medium for a filter of Patent Document 1 has been proposed. According to this Patent Document 1, the bulk density is composed of 90 to 30% by weight of ultrafine fibers having a fiber diameter of 5 μm or less made of polyolefin or polyester, and 10 to 70% by weight of binder fibers having a fiber diameter of 12 to 30 μm made of polyolefin or polyester. A filter medium for a filter of 0.05 to 0.3 g / cm ³ has been proposed. In addition, as a method for producing the filter medium for a filter, a composite fiber using thermoplastic polyvinyl alcohol as a sea component of a sea-island cross-section composite fiber and a thermal binder fiber are used, and the form is maintained by thermally bonding the thermal binder fiber. A manufacturing method characterized by extracting and removing the thermoplastic polyvinyl alcohol from a dry nonwoven fabric is shown.

Further, it has been shown that it is preferable to use a filter in combination with a non-woven fabric such as a chemical binder type dry nonwoven fabric or a spunbond nonwoven fabric in order to make the filter stiff. The card web made of sea-island type raw cotton and binder fiber is laminated on a laminated nonwoven fabric made of polypropylene spunbond nonwoven fabric, meltblown nonwoven fabric, meltblown nonwoven fabric and spunbond nonwoven fabric (weight per unit area: 15 g / m ² , manufactured by Asahi Kasei Co., Ltd.) It is indicated that after embossing, polyvinyl alcohol of sea-island type raw cotton was extracted with hot water at 95 ° C. to obtain a filter medium. However, since this composite nonwoven fabric is embossed, the bonded portion is consolidated, and fluid does not pass through this portion, so there is a problem that pressure loss increases when used as a filter. .

  Further, in Example 10 of Patent Document 1, sea-island type raw cotton and binder fibers are mixed at a mixing ratio of 70:30, and after laminating on a laminated product composed of two melt blown nonwoven fabrics, It is shown that a filter medium composed of ultrafine fibers and binder fibers was obtained by heat bonding with hot air and hot water extraction at 95 ° C. However, since this composite nonwoven fabric is simply an airlaid nonwoven fabric containing binder fibers superimposed on a meltblown nonwoven fabric, the adhesive force between the nonwoven fabrics due to the binder fibers is small, and two layers There was a problem of easy peeling.

  Therefore, as a filter for removing particularly fine dust, an ultrafine fiber composite nonwoven fabric having a small pressure loss, a large dust holding capacity, and excellent shape retention and durability has been demanded.

JP 2005-319347 A

  The present invention relates to a composite nonwoven fabric in which ultrafine fibers and woven or knitted fabric are laminated and integrated to solve the above problems, and particularly suitable as a filter for removing fine dust, and has excellent shape retention and durability. It aims at providing a composite nonwoven fabric and its manufacturing method.

  Means for solving the above-mentioned problem is that, in the invention according to claim 1, the fiber web is an ultra-fine fiber composite nonwoven fabric in which the fiber web is laminated and integrated with a woven fabric or a knitted fabric, the fiber web comprising an alkali-insoluble resin component and an alkali-soluble resin. Containing the ultrafine fiber obtained by removing the alkali-soluble resin component of the composite fiber formed from the components, and the heat-adhesive fiber A, the woven fabric or knitted fabric contains the heat-adhesive fiber B, The fiber web is intertwined by a needle and bonded by the thermoadhesive fiber A, and the fiber web is intertwined by the woven or knitted fabric by a needle and bonded by the thermoadhesive fiber B. It is the ultrafine fiber composite nonwoven fabric characterized by the above-mentioned. According to the present invention, it is possible to provide an ultrafine fiber composite nonwoven fabric excellent in shape retention and durability, which is suitable as a filter for removing fine dust.

  In the invention which concerns on Claim 2, it is an air filter which consists of an ultrafine fiber composite nonwoven fabric of Claim 1.

  In the invention which concerns on Claim 3, the fiber web which consists of the composite fiber formed from the alkali-insoluble resin component and the alkali-soluble resin component, and the heat bondable fiber A is formed, and then the said fiber web and the heat bondable fiber B And then entangle the fiber web with a needle and entangle the fiber web with the woven or knitted fabric, and then the thermal adhesive fiber A and the thermal adhesive fiber. The ultrafine fiber composite, wherein the constituent fibers of the fiber web and the constituent fibers and the woven fabric or knitted fabric are bonded by heating B, and then the alkali-soluble resin component of the composite fiber is eluted with an alkaline solution. It is a manufacturing method of a nonwoven fabric. According to the present invention, it is possible to produce an ultrafine fiber composite nonwoven fabric excellent in shape retention and durability, which is suitable as a filter for removing fine dust.

  In the invention which concerns on Claim 4, the fiber web which consists of the composite fiber formed from the alkali-insoluble resin component and the alkali-soluble resin component, the heat-adhesive fiber A, and a hot-water melt | dissolution fiber is formed, Then, the said fiber web The fabric or knitted fabric containing the heat-adhesive fiber B is laminated, and then the fiber web is entangled with a needle and the fiber web and the woven or knitted fabric are entangled and integrated, and then the heat-adhesive fibers A and By heating the heat-adhesive fiber B, the constituent fibers of the fiber web, and the constituent fibers and the woven fabric or knitted fabric are bonded together, then the hot water-dissolved fibers are eluted with warm water, and then the composite with alkaline liquid It is a method for producing an ultrafine fiber composite nonwoven fabric characterized by eluting an alkali-soluble resin component of a fiber. According to the present invention, since the porosity of the ultrafine fiber composite nonwoven fabric can be increased, it is possible to obtain a filter having a smaller pressure loss and a larger dust holding capacity.

  To provide a composite nonwoven fabric in which ultrafine fibers and woven and knitted fabrics are laminated and integrated, and particularly to provide an ultrafine fiber composite nonwoven fabric excellent in shape retention and durability, which is suitable as a filter for removing fine dust, and a method for producing the same. Became possible.

Example of cross section of ultrafine fiber or composite fiber applied to the present invention (A) is another example of the cross section of the ultrafine fiber or composite fiber applied to the present invention, (b) is another example of the cross section of the ultrafine fiber or composite fiber applied to the present invention, and (c) is the present invention. (D) is a figure which shows another example of the cross section of the ultra fine fiber or composite fiber applied to this invention, (d).

  Hereinafter, preferred embodiments of the ultrafine fiber composite nonwoven fabric and the production method thereof according to the present invention will be described in detail. In addition, about the manufacturing method of an ultrafine fiber composite nonwoven fabric, it demonstrates in description of an ultrafine fiber composite nonwoven fabric.

  In the ultrafine fiber composite nonwoven fabric of the present invention, the fiber web is laminated and integrated with a woven fabric or a knitted fabric (hereinafter sometimes collectively referred to as a woven or knitted fabric). The fiber web consists essentially of alkali-insoluble fibers. Examples of alkali-insoluble fibers include polyamide fibers such as nylon 6 and nylon 66 formed from alkali-insoluble resin components, polyolefin fibers such as polypropylene and polyethylene, acrylic fibers such as polyacrylonitrile, and vinylon fibers. Can do. Moreover, a composite type fiber formed by combining two or more alkali-insoluble resin components can be given. Moreover, it is a core-sheath type composite fiber, and the composite fiber which has an alkali-insoluble resin component in a sheath part can be mentioned.

  Here, “substantially” means that, as will be described later, when forming the ultrafine fiber by removing the alkali-soluble resin component of the composite fiber formed from the alkali-insoluble resin component and the alkali-soluble resin component, It means that the soluble resin component includes a state in which it preferably remains less than 5% by mass, more preferably less than 3% by mass, and still more preferably less than 1% by mass.

  In this invention, the said fiber web contains the ultrafine fiber obtained by removing the alkali-soluble resin component of the composite fiber formed from the alkali-insoluble resin component and the alkali-soluble resin component, and the heat-adhesive fiber A. Here, examples of the form of the composite fiber formed from the alkali-insoluble resin component and the alkali-soluble resin component include, for example, sea-island type, orange type, multiple bimetal type, and the like. A sea-island type capable of generating fibers is preferred.

  As the sea-island type composite fiber, for example, there is a composite fiber composed of a resin component 1 that forms the sea and a resin component 2 that forms the island as illustrated in a cross section in FIG. Sea-island type composite fibers obtained by a composite spinning method such as a method of extruding and compounding island components by regulating the die can be applied. In addition, a sea-island type composite fiber obtained by a method of spinning after mixing a resin constituting an island component and a resin constituting a sea component, which is generally referred to as a mixed spinning method, is also possible. In the case of a composite fiber by the composite spinning method, there is an advantage that ultrafine fibers having the same fiber diameter can be obtained by dissolving and removing sea components. On the other hand, in the case of composite fibers obtained by the mixed spinning method, it is difficult to obtain ultrafine fibers having the same fiber diameter, but there is an advantage that it is possible to generate finer fibers. By forming the island component of the sea-island type composite fiber described above as an alkali-insoluble resin component, the sea component as an alkali-soluble resin component, and removing the sea-soluble alkali-soluble resin component, ultrafine fibers are formed from the island component. be able to.

  In addition, orange type and multiple bimetal type composite fibers include, for example, chrysanthemum type fibers having a cross-sectional shape in which one component is arranged radially between other components, and bimetallic type fibers having a cross-sectional shape in which different components are alternately laminated in layers. Specifically, for example, a composite fiber composed of a resin component 1 and a resin component 2 is exemplified as shown in cross sections in FIGS. 2 (a), (b), (c), and (d). it can. In FIG. 2A, the resin component 1 can be an alkali-insoluble resin component, and the resin component 2 can be an alkali-soluble resin component. By dissolving and removing the resin component 1 or the resin component 2 of the splittable composite fiber having such a cross-sectional shape using an alkaline solution, an ultrafine fiber having a flat cross-sectional shape can be formed. In addition, since it is an ultrafine fiber obtained by removing the alkali-soluble resin component, it is an ultrafine fiber that is almost completely divided, unlike the ultrafine fiber that is generated by simply splitting with a water stream, and can fully exhibit the effect as an ultrafine fiber. There is an advantage.

  The fiber diameter of the ultrafine fiber is preferably 0.1 to 7 μm, more preferably 0.2 to 3 μm, and still more preferably 0.3 to 1 μm. If it exceeds 7 μm, the effect of removing fine dust may be reduced. Moreover, if it is less than 0.1 micrometer, the intensity | strength of an ultrafine fiber will fall and, as a result, durability of a nonwoven fabric may fall.

  The fiber diameter of the ultrafine fiber can be represented by a diameter that can be confirmed by a plane or cross-sectional image of a scanning electron microscope. When there is a variation in diameter, it can be represented by, for example, an arbitrary number average value of 100 images. When the cross-sectional shape of the fiber is not circular, it can be represented by the diameter of a circle having the same area as the fiber cross-section. In addition, when the fineness (decitex) of the raw material used is known, it can represent with the fiber diameter obtained by following Formula.

D = (4d / π · 10 ⁶ · ρ) ^0.5 · 10 ⁴
(Here, D: Fiber diameter (μm), ρ: Density of polymer (g / cm ³ ) constituting the fiber, d: Fiber fineness (decitex), π: Circumferential ratio)

  The proportion of the ultrafine fibers in the fiber web is preferably 50 to 95% by mass, more preferably 55 to 90% by mass, and still more preferably 55 to 85% by mass. If the amount is less than 50% by mass, the effect of removing fine dust may not be sufficiently exhibited when used in a filter. If the amount exceeds 95% by mass, the proportion of adhesive fibers decreases, and the fibers and fibers And the porous support may be insufficiently bonded, and the structure of the ultrafine fiber composite nonwoven fabric may be easily broken.

  In the present invention, the fiber web further includes a heat-adhesive fiber A. As the heat-adhesive fiber A, a heat-adhesive fiber composed of a single component having the lowest melting point among the melting points of the constituent fibers of the fiber web is applicable, and the lowest melting point among the melting points of the constituent fibers. And a high melting point component having a higher melting point than this low melting point component (preferably a melting point higher by 10 ° C. or higher, more preferably a melting point higher by 20 ° C. or higher). Composite-type heat-bondable fibers such as side-by-side and core-sheath types are possible. The bonding temperature of the heat-adhesive fiber A is lower by 10 ° C. or more than the melting point of the ultrafine fiber so that the ultrafine fiber is not deformed or thermally contracted when the constituent fibers containing the ultrafine fiber are bonded together. Is more preferable, and it is more preferable that the temperature is lower by 20 ° C. or more.

  Examples of the heat-adhesive fiber composed of the above-mentioned single component include fibers mainly composed of resins such as polyethylene, polypropylene, polyamide, polyvinyl chloride, and polyurethane. As the resin component of the composite-type heat-adhesive fiber, 6 nylon / Examples include, but are not limited to, polyethylene, polypropylene / polyethylene, polypropylene / ethylene-vinyl acetate copolymer, 6 nylon / 66 nylon, high density polyethylene / low density polyethylene, and the like.

  Moreover, it is preferable that the ratio which occupies in the constituent fiber of the said heat bondable fiber A is 5-50 mass%, It is more preferable that it is 10-45 mass%, It is still more preferable that it is 15-45 mass%. . If the amount is less than 5% by mass, the constituent fibers may not be sufficiently bonded, resulting in an inferior durability ultrafine fiber composite nonwoven fabric. If the amount exceeds 50% by mass, the effect of removing fine dust from the ultrafine fiber composite nonwoven fabric is reduced. There is a case.

  In the present invention, the fiber web is not limited to the ultrafine fiber and the heat-bondable fiber A. For the purpose of adding other functionality, other alkali-insoluble fibers may be used as long as the characteristics of the present invention are not greatly deteriorated. It is also possible to contain.

  In addition, as the fiber length of the constituent fibers, a length suitable for forming a fiber web in each method of manufacturing a nonwoven fabric can be applied. For example, as a staple fiber supplied to a card machine in a dry method or an air lay method, It is preferable that it is 15-110 mm suitable, and if it is a spunbond method, a continuous long fiber is applicable. Among these manufacturing methods, if the dry method or air lay method is used, the sea-island type composite fiber, the splittable composite fiber, and the thermal adhesive fiber A can be uniformly mixed as compared with the spunbond method. In comparison, it is preferable in that the strength of the ultrafine fiber composite non-woven fabric is more excellent. From this point, it can be said that a preferable fiber length is 15 to 110 mm.

In the present invention, the surface density of the fiber web is preferably 7 to 90 g / m ² , more preferably 10 to 75 g / m ² , and still more preferably 10 to 60 g / m ² . If it is less than 7 g / m ² , the entanglement by the needle is insufficient and the durability may be inferior. If it exceeds 90 g / m ² , the rigidity becomes too high or the pressure loss becomes high when used as a filter. It may be too much.

Further, the surface density of the previous fiber web eluting the alkali-soluble resin component from the composite fibers is preferably from 50 to 300 g / ^{m 2,} more preferably 60~250g / ^{m 2,} more preferably 70~200g / ^{m 2} It is. When it is less than 50 g / m ² , the entanglement with the needle is insufficient and the durability may be inferior, and when it exceeds 300 g / m ² , the alkali-soluble resin component cannot be sufficiently eluted from the composite fiber. There is. Also, the rigidity of the ultrafine fiber composite nonwoven fabric may become too high, or when used as a filter, the pressure loss may become too high.

  In the present invention, the fiber web is laminated and integrated with the woven or knitted fabric, but the woven or knitted fabric is not particularly limited as long as long fibers or yarns are woven or knitted, and may be a net. It is. The fibers constituting the woven or knitted fabric are substantially composed of alkali-insoluble fibers. Moreover, the fiber which comprises the said woven / knitted fabric contains the heat bondable fiber B. FIG. For example, in the case of a woven fabric, a knitted fabric, or a net, two or more types of filaments in which long fibers and monofilaments contain composite heat-bondable fibers B such as side-by-side type and core-sheath type, or yarns having different melting points Or it is formed from staple fibers. Specifically, as the thermal adhesive fiber B, a low melting point component having the lowest melting point among the melting points of the constituent fibers of the fiber web, and a melting point higher than this low melting point component (preferably a melting point higher by 10 ° C. or more). In addition, a composite-type heat-bondable fiber such as a side-by-side type or a core-sheath type made of two or more kinds of resin components is possible.

As a preferred embodiment of the woven or knitted fabric, for example, a polyolefin resin net in which a core-sheath monofilament having a core component made of polypropylene and a sheath component made of polyethylene is plain-woven (for example, a product name “Literon Net” manufactured by Chisso Corporation). ”, Mesh: 17 / inch, surface density 54 g / m ² or 38 g / m ² ) is preferably used.

Although the surface density of the woven or knitted fabric is not particularly limited, it is preferably 15 to 140 g / m ² , more preferably 20 to 100 g / m ² , and still more preferably 30 to 70 g / m ² . Moreover, although the thickness of the woven or knitted fabric is not limited, it is preferably 0.1 to 0.8 mm, more preferably 0.15 to 0.6 mm, and still more preferably 0.2 to 0.5 mm. In addition, the thickness of the woven or knitted fabric is expressed by a thickness at a load of 20 g per 1 cm ² .

In the present invention, the fiber web is intertwined by the needle and bonded by the thermal adhesive fiber A, and the fiber web is intertwined by the woven or knitted fabric by the needle and the thermal adhesive fiber B. Are bound by. Entangling with a needle can be performed by a known method, for example, using a needle for needle punching, under conditions of a needle depth of 1 to 20 mm and a needle density of 100 to 1000 / m ^2. It is. Specifically, for example, a fiber web composed of a composite fiber formed from an alkali-insoluble resin component and an alkali-soluble resin component and a heat-adhesive fiber A is formed, and then the fiber web and the heat-adhesive fiber B are formed. It can be carried out by laminating the woven or knitted fabric to be contained, and then entangled the fiber web with a needle and entangled and integrated the fiber web and the woven or knitted fabric.

  In the present invention, it is necessary that the fiber web is bonded by the thermal adhesive fiber A and the fiber web is bonded by the woven or knitted fabric by the thermal adhesive fiber B. In this bonding, the heat-adhesive fiber A and the heat-adhesive fiber B are heat-treated at a temperature equal to or higher than the melting point of the low-melting-point component, so that the low-melting-point component is fused to other fibers. Bonding occurs. This heat treatment is preferably performed after entanglement with the needle and before the dissolution treatment of the alkali-soluble resin component with the alkaline liquid, and by such a method, the fiber structure is prevented from collapsing, There is an advantage that an ultrafine fiber composite non-woven fabric having excellent flexibility and excellent durability after the dissolution treatment of the alkali-soluble resin component can be obtained. That is, first, the adhesive fibers A are securely bonded to each other at the intersection of the fibers, and are also bonded and fixed to the woven or knitted fabric with the adhesive fibers B contained in the woven or knitted fabric, thereby forming a strong and durable fiber structure skeleton. To do.

  And when a composite fiber is a sea-island type composite fiber, while the composite fiber becomes ultrafine by alkali treatment in the skeleton, the adhesion intersection between fibers disappears, and the freedom degree of a fiber increases. At the same time, the voids become larger and the dispersion of the ultrafine fibers is promoted. Further, the subsequent neutralization and heat drying after washing with water again cause an adhesion intersection between the fibers to fix the fiber structure and prevent the fibers from being detached. In this way, the dust holding capacity is increased and the capacity for capturing dust is increased.

  Further, when the conjugate fiber is a splittable conjugate fiber, the conjugate fiber becomes ultrafine by the alkali treatment in the skeleton, thereby causing dispersion and increasing the degree of freedom of the fiber. Further, the adhesive intersection made of the fusion resin formed by fusing the adhesive fiber A to the composite fiber becomes a small adhesion intersection with the ultrafine fiber made of the alkali-insoluble resin component by the alkali treatment, that is, the fusion resin. When a part of the resin is peeled off to become a small fusion resin, the degree of freedom of the fibers is increased, the voids are increased, the dust holding capacity is increased, and the capacity for capturing dust is increased.

The surface density of the ultrafine fiber composite nonwoven fabric of the present invention is preferably 30 to 160 g / m ² , more preferably 40 to 130 g / m ² , and still more preferably 50 to 100 g / m ² . If it is less than 30 g / m ² , the entanglement with the needle is insufficient and the durability may be inferior. If it exceeds 160 g / m ² , the rigidity becomes too high, or when used as a filter, the pressure loss increases. It may be too much.

Moreover, 0.2-1.3 mm is preferable, as for the thickness of the ultrafine fiber composite nonwoven fabric of this invention, 0.3-1.1 mm is more preferable, and 0.4-0.8 mm is still more preferable. When it is less than 0.2 mm, when used as a filter, the filtration performance may be reduced or the dust holding capacity may be reduced. Moreover, when it exceeds 1.3 mm, when used as a filter, processing such as folding may become difficult. Further, in the filter element or filter unit in which the frame material is attached after being folded, the storage filtration area per unit volume may be reduced and the pressure loss may be increased. The thickness is expressed as a thickness at a load of 20 g per 1 cm ² .

Further, the apparent density of the ultrafine fiber composite nonwoven fabric of the present invention is preferably 0.04~0.35g / cm ^3, more preferably 0.06~0.25g / cm ^3, 0.08~0.18g / cm ³ is more preferable. If it is less than 0.04 g / cm ³ , the fiber structure may be easily collapsed. If it exceeds 0.35 g / cm ³ , the rigidity becomes too high, or the pressure loss becomes too high when used as a filter. There is.

  Applications of the ultrafine fiber composite nonwoven fabric of the present invention include filters such as an air filter and a liquid filter in that the features of the ultrafine fibers can be sufficiently exhibited and the durability is excellent. As an air filter, the use of the medium-high performance air filter evaluated especially by the counting method can be mentioned.

  The first ultrafine fiber composite nonwoven fabric production method of the present invention comprises forming a fiber web comprising a composite fiber formed from an alkali-insoluble resin component and an alkali-soluble resin component, and a heat-bondable fiber A, and then the fiber The web and the woven or knitted fabric containing the heat-adhesive fiber B are laminated, and then the fiber web and the woven or knitted fabric are intertwined and integrated with each other by a needle, and then the heat-adhesive fibers A and By heating the heat-adhesive fiber B, the constituent fibers of the fiber web, and the constituent fibers and the woven or knitted fabric are bonded together, and then the alkali-soluble resin component of the composite fiber is eluted with an alkaline solution. To do. By this first production method, the ultrafine fiber composite nonwoven fabric of the present invention can be produced.

  The above description can be applied as it is to “a fiber web composed of a composite fiber formed of an alkali-insoluble resin component and an alkali-soluble resin component and a heat-bondable fiber A”. Further, “the fiber web and the woven or knitted fabric containing the heat-adhesive fiber B are laminated, and then the fiber web and the woven or knitted fabric are intertwined and integrated with each other by a needle, and then the heat The above description can be applied as it is to “bonding the constituent fibers of the fiber web and the constituent fibers and the woven or knitted fabric by heating the adhesive fibers A and the thermoadhesive fibers B”.

  In the production method of the present invention, the constituent fibers of the fiber web and the constituent fibers and the woven or knitted fabric are bonded together by heating the thermal adhesive fibers A and the thermal adhesive fibers B. The alkali-soluble resin component of the composite fiber is eluted. As the alkaline solution, an alkaline aqueous solution is preferably used, and the entangled / bonded fiber web integrated with the woven or knitted fabric is immersed in the alkaline aqueous solution to elute and remove the alkali-soluble resin component. In this treatment, if the alkali-soluble resin component is a polyester resin component, for example, a 6% aqueous solution of sodium hydroxide is heated to 95 ° C. and immersed in the aqueous solution for 30 minutes, so that it is almost 100% dissolved. Removal is possible.

  In addition, after elution of the alkali-soluble resin component with an alkaline solution, a drying process is performed. As a temperature condition for this drying process, the heat-adhesive fiber is particularly required when flexibility is required for the ultrafine fiber composite nonwoven fabric. It is preferable to perform the drying treatment at a temperature lower than the melting point of the low melting point resin component. In particular, when durability is required for the ultrafine fiber composite nonwoven fabric, it is preferable to perform the drying treatment at a temperature equal to or higher than the melting point of the low melting point resin component of the heat-adhesive fiber.

  The production method of the second ultrafine fiber composite nonwoven fabric of the present invention forms a fiber web composed of a composite fiber formed from an alkali-insoluble resin component and an alkali-soluble resin component, a heat-adhesive fiber A, and a hot water-dissolved fiber. Then, the fiber web and the woven or knitted fabric containing the heat-adhesive fiber B are laminated, then the fiber web is entangled with a needle and the fiber web and the woven or knitted fabric are entangled and integrated. By heating the adhesive fiber A and the heat-adhesive fiber B, the constituent fibers of the fiber web and the constituent fibers and the woven or knitted fabric are bonded together, then the hot water-dissolved fibers are eluted with warm water, and then an alkaline solution The alkali-soluble resin component of the composite fiber is eluted at

  Here, the hot water-soluble fiber means a fiber that dissolves in water at a temperature of 15 to 100 ° C., and the hot water-soluble fiber is, for example, partially saponified polyvinyl alcohol having a melting temperature of 40 to 100 ° C. Can be mentioned. By using such hot water-dissolved fibers, when the fiber web is entangled with the needle and the fiber web and the woven or knitted fabric are entangled and integrated, the surface density of the fiber web increases, and the entanglement effect Can be increased. That is, if the total amount of the composite fiber and the adhesive fiber A is small, the woven or knitted fabric may not be sufficiently entangled. In such a case, there is an effect as a fiber extender for promoting entanglement. Furthermore, by promoting the entanglement of the fiber and removing it as an excess before the alkali treatment, the voids in the fiber web increase as a result, the alkali treatment becomes easier and the degree of freedom of the fiber increases, There is also an effect that it helps to improve the dispersibility of the ultrafine fibers generated by the treatment. Moreover, since the porosity of the ultrafine fiber composite nonwoven fabric finally obtained can be increased, there is an effect that a filter having a smaller pressure loss and a large dust holding capacity can be obtained.

  The proportion of the warm water-dissolved fiber in the fiber web before dissolution is preferably 15 to 70% by mass, and more preferably 20 to 65% by mass. If it is less than 15% by mass, the effect as a fiber extender for promoting the entanglement described above may be reduced, and the effect of providing voids in the fiber web may be reduced. Moreover, when it exceeds 70 mass%, the space | gap in a fiber web will become large too much, and durability may fall.

  In the second production method, such hot water-dissolved fibers are added in advance to the fiber web, and the entangled / bonded fibers are integrated with the woven or knitted fabric in water heated (or heated) to 40 to 100 ° C. The hot water-dissolved fiber is eluted by immersing the web, and then the alkali-soluble resin component of the composite fiber is eluted with an alkaline solution in the same manner as in the first production method. According to this second manufacturing method, the effect as a fiber extender for promoting entanglement works as compared with the first manufacturing method, and an ultrafine fiber composite nonwoven fabric excellent in durability can be obtained. . Moreover, it is easy to disperse | distribute ultrafine fiber uniformly, and the ultrafine fiber composite nonwoven fabric of a uniform structure can be obtained. Moreover, since the porosity of the ultrafine fiber composite nonwoven fabric can be increased, it is possible to obtain a filter having a smaller pressure loss and a larger dust holding capacity.

  Examples of the present invention will be described below, but these are only suitable examples for facilitating the understanding of the present invention, and the present invention is not limited to the contents of these examples.

(Filtration performance evaluation method for ultrafine fiber composite nonwoven fabric)
In the test method specified in JIS B9908 type 1, the wind speed is 50 cm / sec. And the atmospheric dust collection efficiency in the range of 1 to 2 μm in particle size.

(Fiber non-release test method)
3000 cc of a 6% NaOH aqueous solution is put in a sealed container, and a 1 m ² test piece wound around a cylindrical porous body is immersed in the aqueous solution. Next, the aqueous solution is heated to 95 ° C. and subjected to an alkali extraction treatment for 30 minutes while rotating forward and backward. Next, the aqueous NaOH solution is filtered, and the presence or absence of detached fibers in the aqueous NaOH solution is visually confirmed. As a result, it is evaluated as ◯ when no detached fiber is recognized, and × when it is recognized.

Example 1
1.5 decitex compound spinning type sea-island fiber (fiber length 38 mm, sea component is polyethylene terephthalate resin, island component is polypropylene resin) 43% by mass, 0.88 dtex thermal adhesive fiber (fiber length 38 mm, core component) 10% by mass of a core-sheath type composite fiber of which the sheath component is made of polyethylene and 47% by mass of 1.7 dtex hot-water-soluble fiber (fiber length 51 mm, partially saponified polyvinyl alcohol that dissolves in water at 100 ° C.) Then, it was put into a card machine to form a fiber web.
Next, this fiber web is a woven fabric in which a core-sheath monofilament having a core component made of polypropylene and a sheath component made of polyethylene is plain-woven, a polyolefin resin net (manufactured by Chisso Co., Ltd .: trade name “Literon Net”, Placement on 17 mesh / inch, surface density 54 g / m ² ), and this laminated fiber web is subjected to needle processing (needle: No. 40, needle depth: 8 mm, needle density 200 / cm) ² ) and the fiber web and the woven fabric were entangled and integrated.
Next, the intertwined fiber web is put into a dryer at 145 ° C. and heat treated to bond the constituent fibers of the fiber web with the heat-adhesive fibers contained in the fiber web and the fabric, and the fiber web and the fabric. Thus, a composite fiber sheet (surface density: 154 g / m ² , thickness 2.3 mm, apparent density 0.067 g / cm ³ ) was obtained.
Next, the composite fiber sheet is immersed in boiling water for 30 minutes to dissolve and remove the hot water-dissolved fibers. After dehydration, the composite fiber sheet is wound around a PP cylindrical porous body, and remains in this wound state. Then, it was immersed in an aqueous NaOH solution (6% by mass) at 95 ° C. for 30 minutes to elute almost 100% of the polyethylene terephthalate resin component. Subsequently, an ultrafine fiber composite nonwoven fabric was obtained through steps of neutralization, washing with water, dehydration, and drying (145 ° C.) with acetic acid.
When the cross section of the obtained ultrafine fiber composite nonwoven fabric was observed with a scanning electron microscope image, it was confirmed that 600 nm ultrafine fibers were generated from the island components of the sea-island fibers.
The ultrafine fiber composite nonwoven fabric has an areal density of 79 g / m ² (fiber web has a surface density of 25 g / m ² ), a thickness of 0.65 mm, and an apparent density of 0.12 g / cm ³ . Yes, the ratio of ultrafine fibers in the fiber web was 60% by mass, and the ratio of heat-adhesive fibers was 40% by mass. In addition, the pressure loss was 35 Pa, the particle collection efficiency by the counting method was 72%, and the result of the non-detachment test of the fibers was o that no fibers were observed.

(Example 2)
In Example 1, 43 mass% of 1.5 dtex compound spinning type sea-island fiber, 5 mass% of 0.88 dtex thermal adhesive fiber, and 52 mass% of 1.7 dtex hot water dissolving fiber were mixed. The composite fiber sheet (surface density: 154 g / m ² , thickness 2.1 mm, apparent density 0. 1) was passed through the same steps as in Example 1 except that it was put into a card machine and a fiber web was formed. 073 g / cm ³ ) and an ultrafine fiber composite nonwoven fabric were obtained.
When the cross section of the obtained ultrafine fiber composite nonwoven fabric was observed with a scanning electron microscope image, it was confirmed that 600 nm ultrafine fibers were generated from the island components of the sea-island fibers.
In addition, this ultrafine fiber composite nonwoven fabric has a surface density of 74 g / m ² (a fiber web has a surface density of 20 g / m ² ), a thickness of 0.62 mm, and an apparent density of 0.12 g / cm ³ . Yes, the proportion of ultrafine fibers in the fiber web was 75% by mass, and the proportion of thermally adhesive fibers was 25% by mass. Further, the pressure loss was 30 Pa, the particle collection efficiency by the counting method was 77%, and the result of the fiber non-detachment test was o that no fiber was observed.

(Example 3)
In Example 1, 70% by mass of a 1.5 dtex compound spinning type sea-island fiber, 5% by mass of 0.88 dtex thermal adhesive fiber, and 25% by mass of 1.7 dtex hot water-dissolved fiber were mixed. The composite fiber sheet (surface density: 154 g / m ² , thickness 1.95 mm, apparent density 0. 10 mm) was obtained through the same steps as in Example 1 except that the fiber web was formed by loading the card machine. 079 g / cm ³ ) and an ultrafine fiber composite nonwoven fabric.
When the cross section of the obtained ultrafine fiber composite nonwoven fabric was observed with a scanning electron microscope image, it was confirmed that 600 nm ultrafine fibers were generated from the island components of the sea-island fibers.
Further, this ultrafine fiber composite nonwoven fabric has an areal density of 84 g / m ² (fiber web has a surface density of 30 g / m ² ), a thickness of 0.69 mm, and an apparent density of 0.12 g / cm ³ . Yes, the proportion of ultrafine fibers in the fiber web was 83% by mass, and the proportion of thermally adhesive fibers was 17% by mass. Further, the pressure loss was 42 Pa, the particle collection efficiency by the counting method was 83%, and the result of the non-detachment test of the fibers was o that no fibers were observed.

Example 4
In Example 1, 35 mass% of 1.5 dtex complex spinning type sea-island fiber, 5 mass% of 0.88 dtex thermal adhesive fiber, and 60 mass% of 1.7 dtex hot water dissolving fiber were mixed. A polyolefin resin net, which is a woven fabric in which a core web is formed by plain weaving into a card machine and forming a fiber web, and a core-sheath monofilament having a core component made of polypropylene and a sheath component made of polyethylene. Except that it was placed on (made by Chisso Corporation: trade name “Light Ronnet”, scale: 17 / inch, surface density 38 g / m ² ), the same steps as in Example 1 were performed. A composite fiber sheet (surface density: 118 g / m ² , thickness 1.84 mm, apparent density 0.064 g / cm ³ ) and an ultrafine fiber composite nonwoven fabric were obtained.
When the cross section of the obtained ultrafine fiber composite nonwoven fabric was observed with a scanning electron microscope image, it was confirmed that 600 nm ultrafine fibers were generated from the island components of the sea-island fibers.
Further, this ultrafine fiber composite nonwoven fabric has an areal density of 52 g / m ² (fiber web has a surface density of 14 g / m ² ), a thickness of 0.47 mm, and an apparent density of 0.11 g / cm ³ . Yes, the proportion of ultrafine fibers in the fiber web was 71% by mass, and the proportion of thermally adhesive fibers was 29% by mass. Further, the pressure loss was 24 Pa, the particle collection efficiency by the counting method was 51%, and the result of the fiber non-detachment test was o that no fiber was observed.

(Comparative Example 1)
A fiber web was formed in the same manner as in Example 1.
Next, the fiber web was entangled by needle processing (needle: No. 40, needle depth: 8 mm, needle density: 200 / cm ² ) without being placed on the woven fabric.
Next, the entangled fiber web is put into a dryer at 145 ° C. and subjected to heat treatment, and the constituent fibers of the fiber web are bonded by the heat-adhesive fibers contained in the fiber web to obtain a fiber sheet (surface density: 100 g / m ^2). And a thickness of 1.9) mm and an apparent density of 0.053 g / cm ³ ).
Next, the fiber sheet is immersed in boiling water for 30 minutes to dissolve and remove the hot water-dissolved fibers, and after dehydration, the fiber sheet is wound around a cylindrical porous body made of PP. When immersed in an aqueous NaOH solution (6% by mass) at 30 ° C. for 30 minutes to elute almost 100% of the polyethylene terephthalate resin component, the shape of the fiber sheet collapsed and a nonwoven fabric composed of ultrafine fibers could not be obtained. .

(Comparative Example 2)
In Example 1, a polyolefin resin net (manufactured by Chisso Co., Ltd .: trade name “Lightlon Net”, mesh size: 17 / inch, surface density, which is a woven fabric obtained by plain weaving monofilaments made of polypropylene. 54 g / m ² ), and the laminated fiber web is entangled by needle processing (needle: No. 40, needle depth: 8 mm, needle density: 200 / cm ² ), and the fiber web A composite fiber sheet (surface density: 154 g / m ² , thickness 2.3 mm, apparent density 0.067 g / cm ³⁾ was obtained through the same steps as in Example 1 except that the woven fabric and the fabric were entangled and integrated. )
When the cross section of the obtained ultrafine fiber composite nonwoven fabric was observed with a scanning electron microscope image, it was confirmed that 600 nm ultrafine fibers were generated from the island components of the sea-island fibers.
The ultrafine fiber composite nonwoven fabric has an areal density of 79 g / m ² (fiber web has a surface density of 25 g / m ² ), a thickness of 0.65 mm, and an apparent density of 0.12 g / cm ³ . Yes, the ratio of ultrafine fibers in the fiber web was 60% by mass, and the ratio of heat-adhesive fibers was 40% by mass. The pressure loss was 35 Pa, and the particle collection efficiency by the counting method was 72%. However, the result of the non-leaving property test of the fiber was x where the detached fiber was recognized.

1 Resin component 2 Other resin component

Claims (4)

  An ultra-fine fiber composite nonwoven fabric in which a fiber web is laminated and integrated with a woven fabric or a knitted fabric, and the fiber web is obtained by removing an alkali-soluble resin component of a composite fiber formed from an alkali-insoluble resin component and an alkali-soluble resin component. The woven fabric or knitted fabric contains a heat-adhesive fiber B, and the fiber web is intertwined with a needle and the heat-adhesive fiber A. And the fiber web is intertwined with the woven fabric or knitted fabric by a needle and bonded by the heat-adhesive fiber B.   An air filter comprising the ultrafine fiber composite nonwoven fabric according to claim 1.   Forming a fiber web composed of a composite fiber formed of an alkali-insoluble resin component and an alkali-soluble resin component and a heat-adhesive fiber A, and then a woven or knitted fabric containing the fiber web and the heat-adhesive fiber B; The fibers are laminated by entanglement of the fiber web with a needle and entangle the fiber web with the woven fabric or knitted fabric, and then heat the heat-adhesive fiber A and the heat-adhesive fiber B. A method for producing an ultrafine fiber composite nonwoven fabric, wherein constituent fibers of a web, and constituent fibers and the woven fabric or knitted fabric are bonded together, and then the alkali-soluble resin component of the composite fiber is eluted with an alkaline solution.   A fiber web composed of a composite fiber formed from an alkali-insoluble resin component and an alkali-soluble resin component, a heat-adhesive fiber A, and a hot water-dissolved fiber is formed, and then the fiber web and the heat-adhesive fiber B are contained. A woven fabric or a knitted fabric is laminated, and then the fiber web is entangled with a needle and the fiber web and the woven fabric or knitted fabric are entangled and integrated, and then the thermal adhesive fiber A and the thermal adhesive fiber B are heated. By combining the constituent fibers of the fiber web and between the constituent fibers and the woven fabric or knitted fabric, the hot water-soluble fiber is eluted with warm water, and then the alkali-soluble resin component of the composite fiber is eluted with an alkaline solution. A method for producing an ultra-fine fiber composite nonwoven fabric.

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