Fiber laminate

Abstract

To provide a fiber laminate having low pressure loss and high dust retention capacity, in which a pre-collection layer and a collection layer are integrated without using an adhesive. A fiber laminate in which a pre-collection layer and a collection layer are laminated in this order, The pre-collection layer includes a plurality of fibers, The collection layer is a fiber laminate including a plurality of first fibers and a plurality of second fibers having an outer diameter smaller than that of the first fibers and supported by the first fibers in a dispersed state.

Description

[Technical Field]

[0001] The present disclosure relates to a fibrous laminate that may be used in an air filter. [Background technology]

[0002] Air filters are used to remove dust and fine particles from the air. The filter media for these air filters must have a high particle collection efficiency and also a low airflow resistance.

[0003] Patent Document 1 describes a filter having at least a first layer, a second layer, and an adhesive layer disposed between them. The second layer is made of fine fibers, etc., and the first layer is a pre-filter or a support layer.

[0004] Patent Document 2 discloses an air filter that is formed from a pre-filter, a medium-efficiency filter, a porous filter, and a HEPA filter or a ULPA filter, each of which is held by a holding frame. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 1,181,9790 [Patent Document 2] Japanese Patent Application Publication No. 2020-195941 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present disclosure is to provide a fiber laminate having low pressure loss and high dust retention capacity, in which a pre-collection layer and a collection layer are integrated without the use of adhesive. [Means for solving the problem]

[0007] As a result of extensive research to solve the above problem, the inventors discovered that the above problem can be solved by integrating a pre-collection layer and a collection layer containing first fibers and second fibers having an outer diameter smaller than that of the first fibers.

[0008] That is, the gist of the present disclosure is as follows. [1] A fiber laminate in which a pre-collection layer and a collection layer are laminated in order, The pre-collection layer includes a plurality of fibers, The collection layer is a fiber laminate including a plurality of first fibers and a plurality of second fibers having an outer diameter smaller than that of the first fibers and supported by the first fibers in a dispersed state. [2] The fiber laminate according to [1], wherein the thickness of the fiber laminate is 0.5 mm or more and 5 mm or less. [3] The basis weight of the fiber laminate is 80 g / m 2 More than 300g / m 2 The fiber laminate according to [1] or [2], which is as follows: [4] A fiber laminate according to any one of [1] to [3], wherein the pressure loss when air is passed through the fiber laminate in the thickness direction at a flow rate of 12.7 cm / sec is 3 Pa or more and 35 Pa or less. [5] The fiber laminate according to any one of [1] to [4], wherein the outer diameter of the plurality of fibers is 0.5 μm or more and 50 μm or less. [6] The fiber laminate according to any one of [1] to [5], wherein the ratio D1 / D2 of the outer diameter D1 of the first fibers to the outer diameter D2 of the second fibers is 15.0 or more and 1666.7 or less. [7] The fiber laminate according to any one of [1] to [6], wherein the collection layer contains resin granules. [8] The fiber laminate described in [7], wherein the pre-collection layer and the collection layer are bonded together by the resin granules. [9] The fiber laminate according to [7] or [8], wherein the resin granules comprise polytetrafluoroethylene, polypropylene, polyethylene, or polyamide.

[10] The fiber laminate according to any one of [7] to [9], wherein the resin granules contain polytetrafluoroethylene. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a fiber laminate having low pressure loss and high dust capacity in which a pre-collection layer and a collection layer are integrated without an adhesive layer. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of a fiber laminate according to one embodiment of the present disclosure. FIG. [Figure 2] FIG. 2 is a schematic diagram of a collection layer included in a fibrous laminate according to one embodiment of the present disclosure. [Figure 3] 1 is a schematic diagram of a fiber sheet manufacturing apparatus used to manufacture a fiber laminate according to an embodiment of the present disclosure. [Figure 4] 1 is a schematic diagram of a fiber article manufacturing apparatus used to manufacture a fiber laminate according to one embodiment of the present disclosure. [Figure 5] 1 is a schematic diagram of a fiber laminate manufacturing apparatus used to manufacture a fiber laminate according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Each configuration and combination thereof in each embodiment is merely an example, and additions, omissions, substitutions, and other modifications of configurations are possible as appropriate within the scope of the present disclosure. The present disclosure is not limited by the embodiments, but only by the scope of the claims. Furthermore, each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. Furthermore, in this disclosure, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits, and "A to B" means greater than or equal to A and less than or equal to B.

[0012] One embodiment of the present disclosure is a fiber laminate in which a pre-collection layer and a collection layer are laminated in order, The pre-collection layer includes a plurality of fibers, The collection layer is a fiber laminate including a plurality of first fibers and a plurality of second fibers having an outer diameter smaller than the first fibers and supported by the first fibers in a dispersed state.

[0013] FIG. 1 is a schematic diagram of a fiber laminate. The fiber laminate has at least a pre-collection layer 2 and a collection layer 3. The fiber laminate 1 shown in FIG. 1 is, for example, a filter member disposed in a flow path through which a predetermined fluid flows, and filters out impurities mixed in the fluid. The fluid passing through the interior of the fiber laminate 1 may be either a gas or a liquid, and is preferably a gas. For example, the gas is air. The pre-collection layer 2 is disposed on the upstream side of the flow path, i.e., on the side where the fluid flows into the fiber laminate 1. The collection layer 3 is disposed on the downstream side of the flow path, i.e., on the side where the fluid flows out of the fiber laminate 1.

[0014] In the fiber laminate of this embodiment, the pre-collection layer and the collection layer are integrally formed, so no frame is required for installing each layer, thereby saving space.

[0015] The fiber laminate 1 of this embodiment does not require an adhesive layer between the pre-collection layer 2 and the collection layer 3. This reduces the pressure loss of the filter medium. Furthermore, the adhesive step can be omitted, reducing manufacturing costs. It is believed that the resin granules 6 contained in the trapping layer 3 bond the pre-trapping layer 2 and the trapping layer 3 together, but this is not limiting.

[0016] The thickness of the fiber laminate 1 of this embodiment is not particularly limited, but is preferably 0.5 mm to 5 mm, more preferably 1 mm to 4 mm, and even more preferably 1.5 mm to 3 mm.

[0017] The basis weight of the fiber laminate 1 of this embodiment is not particularly limited, but is preferably 80 g / m 2 More than 300g / m 2 The preferred basis weight is 120 g / m2 More than 250g / m 2 Less than 150 g / m is more preferable. 2 More than 220g / m 2 It is more preferable that the basis weight is within the above range. When the basis weight is within the above range, the weight of the fiber laminate 1 can be reduced.

[0018] The fiber laminate 1 of this embodiment preferably exhibits a pressure loss of 3 Pa or more and 35 Pa or less when air is passed through it in the thickness direction at a flow rate of 12.7 cm / sec. The pressure loss is, for example, more preferably 10 Pa or more and 35 Pa or less, even more preferably 15 Pa or more and 35 Pa or less, and particularly preferably 20 Pa or more and 30 Pa or less. When the pressure loss is within the above range, clogging of the fiber laminate 1 during use can be prevented, and fluid can be efficiently circulated inside the fiber laminate 1. This prevents performance degradation associated with use of the fiber laminate 1.

[0019] This pressure loss is measured, for example, by the following procedure. A measurement sample is placed in a tube with an inner diameter of 113 mm (effective area as a filter medium: 100 cm 2 The sample is then set in a holder. The flow rate of the air flowing through the sample is adjusted to 12.7 cm / sec using a flow meter. The pressure difference between the upstream and downstream sides of the sample in the direction of air flow is measured using a manometer.

[0020] <Pre-collection layer> The pre-collection layer 2 of this embodiment contains a plurality of fibers and has a nonwoven fabric structure. Examples of nonwoven fabrics include short fiber nonwoven fabrics, long fiber nonwoven fabrics, spunbond nonwoven fabrics, meltblown nonwoven fabrics, spunlace nonwoven fabrics, thermal bond (air-through) nonwoven fabrics, needle-punched nonwoven fabrics, point-bond nonwoven fabrics, and laminated nonwoven fabrics (such as SMS nonwoven fabrics or SMMS nonwoven fabrics in which a meltblown layer is sandwiched between spunbond layers).

[0021] The fibers contained in the pre-collection layer 2 preferably include fibers made of rayon, polypropylene (PP), polyethylene terephthalate (PET), polyacrylonitrile, nylon 6, cellulose acetate, or rayon, and more preferably include fibers made of cellulose acetate (hereinafter sometimes referred to as "cellulose acetate fibers"). Such materials can improve the strength of the fiber laminate.

[0022] The outer diameter of the plurality of fibers contained in the pre-collection layer 2 is, for example, preferably 0.5 μm or more and 50 μm or less, more preferably 10 μm or more and 30 μm or less, and even more preferably 15 μm or more and 25 μm or less.

[0023] The thickness of the pre-collection layer 2 is not particularly limited, but is preferably 0.5 mm to 3.0 mm. The thickness of the pre-collection layer 2 is more preferably 1.0 mm to 2.5 mm, and even more preferably 1.5 mm to 2.0 mm. By keeping the thickness within the above range, the pre-collection layer 2 can be made lighter and more compact.

[0024] The basis weight of the pre-collection layer 2 is not particularly limited, but is preferably 50 g / m 2 More than 200g / m 2 The preferred basis weight is 75 g / m 2 More than 175g / m 2 The following is more preferred: 00g / m 2 More than 150g / m 2 It is more preferable that the basis weight is not more than 1000. When the basis weight is within the above range, the weight of the pre-collection layer 2 can be reduced.

[0025] The pre-collection layer 2 of this embodiment preferably exhibits a pressure loss of 0.5 Pa or more and 8.0 Pa or less when air is passed through it in the thickness direction at a flow rate of 12.7 cm / sec. The pressure loss is, for example, more preferably 0.5 Pa or more and 6.0 Pa or less, even more preferably 0.5 Pa or more and 4.0 Pa or less, and particularly preferably 0.5 Pa or more and 2.0 Pa or less. When the pressure loss is within the above range, clogging of the pre-collection layer 2 during use can be prevented, allowing fluid to circulate efficiently inside the pre-collection layer 2. This prevents performance degradation associated with use of the pre-collection layer 2. The pressure loss can be measured in the same manner as for the fiber laminate 1.

[0026] <Collection layer> The trapping layer includes a plurality of first fibers and a plurality of second fibers having an outer diameter smaller than the first fibers and supported by the first fibers in a dispersed state.

[0027] 2 is a schematic diagram of the trapping layer 3. In FIG. 2, an enlarged view showing the internal structure of the trapping layer 3 is also shown.

[0028] The trapping layer 3 is sheet-shaped and includes a plurality of first fibers 4 and a plurality of second fibers 5 that have a smaller outer diameter than the first fibers 4 and are supported in a dispersed state by the first fibers 4. The trapping layer 3 may also include resin granules 6.

[0029] The trapping layer 3 has fiber gaps formed by the plurality of first fibers 4 and the plurality of second fibers 5. The trapping layer 3 preferably has a mesh structure made up of the plurality of first fibers 4 and the plurality of second fibers 5. In the trapping layer 3 of this embodiment, the second fibers 5 are fixed to the first fibers 4, so that the mesh structure is less likely to be destroyed even when an external force is applied to the trapping layer 3, and the filtering performance of the trapping layer 3 can be stably maintained.

[0030] Furthermore, inside the trapping layer 3, the second fibers 5 are entangled with and supported by the first fibers 4. Therefore, even if the outer diameter D2 of the second fibers 5 is smaller than the outer diameter D1 of the first fibers 4, damage such as breakage of the second fibers 5 can be prevented. In other words, the functions of the second fibers 5 can be maintained for a long period of time.

[0031] Generally, when a fiber sheet is continuously produced by a papermaking method or a spinning method, most of the fibers constituting the fiber sheet are oriented in the fiber sheet's conveying direction on the production line. Therefore, in the width direction, which is perpendicular to the fiber sheet's conveying direction, there is relatively little fiber entanglement, and the strength is low. Hereinafter, the direction perpendicular to the thickness direction of the trapping layer 3, in which the tensile strength of the trapping layer 3 is minimum, will be referred to as the minimum strength direction (hereinafter also referred to as the "first direction"). As described above, the minimum strength direction usually corresponds to the width direction perpendicular to the conveying direction of the fiber sheet (hereinafter also simply referred to as the "fiber sheet"), which is an intermediate product of the trapping layer 3 before cutting, on a production line that continuously produces the trapping layer 3. Meanwhile, the direction perpendicular to the thickness direction that is perpendicular to the minimum strength direction will be referred to as the "second direction" below.

[0032] In the trapping layer 3, for example, uneven distribution of the inter-fiber gaps between the plurality of first fibers 4 and the plurality of second fibers 5 is suppressed in a first direction and a second direction extending perpendicular to each other in a plane perpendicular to the thickness direction. As a result, the trapping layer 3 has abundant inter-fiber gaps formed by the plurality of first fibers 4 and the plurality of second fibers 5. As a result, when the trapping layer 3 is disposed in the flow path and a fluid is circulated through the trapping layer 3, the fluid comes into uniform contact with the first fibers 4 and the second fibers 5, and the functions of the first fibers 4 and the second fibers 5 are easily exerted. Furthermore, the formation of the mesh structure in the trapping layer 3 maintains the shape of the trapping layer 3, and the filtering performance of the trapping layer 3 is stably maintained. can.

[0033] The trapping layer 3 of this embodiment has a nonwoven fabric structure. The first fibers 4 are, for example, short fibers having a length of 10 mm or more and 100 mm or less. The first fibers 4 have, for example, a higher strength (e.g., tensile strength) than the second fibers 5. Also, for example, the first fibers 4 are longer than the second fibers 5. This allows the first fibers 4 to stably support the abundant second fibers 5 even if the number of first fibers 4 is relatively small.

[0034] In this embodiment, the first fibers 4 are crimped, for example. By using a plurality of crimped first fibers 4, the fiber density of the trapping layer 3 is reduced compared to when a plurality of uncrimped first fibers 4 is used. Furthermore, the trapping layer 3 is configured to be bulkier than when the first fibers 4 are uncrimped. This allows for abundant fiber gaps formed by the plurality of first fibers 4 to be arranged in the trapping layer 3. This not only reduces the weight and compactness of the trapping layer 3, but also increases the contact area between the first fibers 4 and the second fibers 5 and the fluid, making it easier for the first fibers 4 and the second fibers 5 to perform their respective functions.

[0035] The outer diameter D2 of the second fibers 5 is smaller than the outer diameter D1 of the first fibers 4. Therefore, the trapping layer 3 has a composite structure of fibers with different diameters. The second fibers 5 are supported by the first fibers 4 while being dispersed in the trapping layer 3. At least a portion of the second fibers 5 is attached to the first fibers 4. For example, the ratio D1 / D2 of the outer diameter D1 of the first fibers 4 to the outer diameter D2 of the second fibers 5 is 15.0 or more and 1666.7 or less. Thus, for example, the trapping layer 3 of this embodiment includes first fibers 4 with a large outer diameter D1 and second fibers 5 with an outer diameter D2 that is significantly smaller than the outer diameter D1.

[0036] The ratio D1 / D2 is, for example, preferably 15.0 or more and 1300.0 or less, more preferably 15.0 or more and 714.3 or less, and even more preferably 15.0 or more and 300.0 or less.

[0037] In another example, the ratio D1 / D2 is preferably, for example, 60.0 or more and 1666.7 or less, more preferably 60.0 or more and 1300.0 or less, even more preferably 60.0 or more and 714.3 or less, and even more preferably 60.0 or more and 300.0 or less.

[0038] When the ratio D1 / D2 is 15.0 or more, for example, in the trapping layer 3, the first fibers 4 and the second fibers 5, which have different outer diameters, can easily exhibit their respective functions. Furthermore, when the ratio D1 / D2 is 1666.7 or less, for example, it is easy to encircle the second fibers 5 around the first fibers 4 while suppressing an increase in the outer diameter D1 of the first fibers 4. Furthermore, by maintaining the outer diameter D2 at a relatively large value, it is easy to form the second fibers 5. Furthermore, when the ratio D1 / D2 is 60.0 or more and 1666.7 or less, the filtering performance of the trapping layer 3 can be improved while the amount of the second fibers 5 used can be reduced, thereby reducing the production cost of the trapping layer 3.

[0039] The outer diameter D1 is, for example, preferably 5.0 μm or more and 50.0 μm or less, more preferably 10.0 μm or more and 40.0 μm or less, and even more preferably 20.0 μm or more and 30.0 μm or less. Within this range, the first fibers 4 stably support the second fibers 5, while multiple second fibers 5 are easily arranged abundantly around the first fibers 4. At the same time, excessively large inter-fiber gaps in the trapping layer 3 can be prevented. Furthermore, even if an external force acts on the trapping layer 3 during use, damage to the first fibers 4 and the second fibers 5 in the trapping layer 3 can be prevented. Therefore, the functions of the first fibers 4 and the second fibers 5 can be exhibited over a long period of time, resulting in stable filter performance.

[0040] The outer diameter D2 is, for example, preferably 30.0 nm or more and 1.0 μm or less, more preferably 30.0 nm or more and 800 nm or less, and even more preferably 30.0 nm or more and 166.7 nm or less. In another example, the outer diameter D2 is preferably, for example, 50.0 nm or more and 800.0 nm or less. Within this range, the ratio D1 / D2 can be sufficiently increased while preventing the outer diameter D2 of the second fibers 5 from becoming excessively thin. As a result, a trapping layer 3 containing a large number of second fibers 5 can be stably formed.

[0041] When the outer diameter D1 of the first fibers 4, the outer diameter D2 of the second fibers 5, and the ratio D1 / D2 are within the above ranges, both relatively large fiber gaps formed by a plurality of first fibers 4 and relatively small fiber gaps formed by a plurality of second fibers 5 can be formed abundantly in the trapping layer 3. As a result, even when the thickness or basis weight of the trapping layer 3 is relatively small, the first fibers 4 and the second fibers 5, which have a predetermined difference in outer diameter, can easily exhibit their respective functions with respect to the fluid flowing inside the trapping layer 3.

[0042] In the trapping layer 3, the ratio V1 / V2 of the total volume V1 of the first fibers 4 to the total volume V2 of the second fibers 5 and the resin granules 6 is preferably 1.9 or more and 124.0 or less. The ratio V1 / V2 is more preferably 20.0 or more and 124.0 or less. When the ratio V1 / V2 is within this range, the functions of the first fibers 4 and the second fibers 5 can be easily exhibited.

[0043] The collection layer 3 has a basis weight of 60 g / m 2 More than 300g / m 2 or less (for example, 152 g / m 2 ) is preferable. The basis weight is, for example, 60 g / m 2 More than 250g / m 2 Less than 60 g / m is more preferable. 2 More than 200g / m 2 In another example, the basis weight is 80 g / m or less. 2 More than 200g / m 2 Preferably less than 100 g / m 2 More than 200g / m 2 It is more preferable that the basis weight is not more than 1000. When the basis weight is within the above range, the weight of the trapping layer 3 can be reduced.

[0044] The tensile strength of the trapping layer 3 in the direction perpendicular to the thickness direction, i.e., the minimum strength direction, where the tensile strength is at its smallest, is preferably at least 0.8 N / 10 mm. The unit "N / 10 mm" indicates how many N of load the trapping layer 3 can withstand per 10 mm of measurement width. If the tensile strength is within the above range, the shape of the trapping layer 3 is likely to be maintained even when an external force is applied to the trapping layer 3 during use. Therefore, a trapping layer 3 with stable filtering performance can be obtained. To manufacture a trapping layer having a tensile strength of at least 0.8 N / 10 mm in the minimum strength direction, for example, the manufacturing method described below can be used.

[0045] Furthermore, the tensile strength of the trapping layer 3 in the direction of minimum strength is preferably 100 N / 10 mm or less. If the tensile strength in the direction of minimum strength is within this range, for example, excessive increase in the tensile strength of the trapping layer 3 can be prevented, making it easier to manufacture the trapping layer 3. The tensile strength of the trapping layer 3 of this embodiment in the direction of minimum strength is preferably 0.8 N / 10 mm or more and 100 N / 10 mm or less. The range of the tensile strength in the direction of minimum strength is, for example, more preferably 1 N / 10 mm or more and 100 N / 10 mm or less, and even more preferably 5 N / 10 mm or more and 100 N / 10 mm or less. In another example, the range of the tensile strength in the direction of minimum strength is, for example, preferably 8 N / 10 mm or more and 100 N / 10 mm or less, and even more preferably 10 N / 10 mm or more and 100 N / 10 mm or less.

[0046] Furthermore, the trapping layer 3 of this embodiment preferably has a tensile elongation of 5% or more relative to the natural state in the direction of minimum strength. Furthermore, the trapping layer 3 of this embodiment preferably has a tensile elongation of 250% or less. That is, the tensile elongation of the trapping layer 3 of this embodiment is preferably 5% or more and 250% or less. When the tensile elongation is within this range, the trapping layer 3 is less likely to break even when an external force acts in the direction of minimum strength. The tensile elongation is, for example, more preferably 10% or more and 250% or less, and even more preferably 20% or more and 250% or less. In another example, the tensile elongation is, for example, preferably 30% or more and 250% or less, and even more preferably 40% or more and 250% or less.

[0047] Here, tensile strength is measured using, for example, a Tensilon universal material testing machine (manufactured by A&D Corporation), a tensile testing machine conforming to JIS B 7721:2018. In this case, a test specimen molded to a width of 10 mm and a length of 60 mm is used. This test specimen is pulled at a chuck distance of 40 mm and a pulling speed of 200 mm / min, and the maximum tensile load until break is measured as the tensile strength. The tensile elongation is calculated using the following formula (1) under the same conditions as in the tensile strength measurement. Here, "elongation" refers to the difference between the length at break of the test specimen and the length before the tensile test. When measuring the maximum tensile load, the test specimen is conditioned at 23°C and 50% relative humidity for 24 hours. Tensile elongation (%) = elongation (mm) / chuck distance (mm) × 100 (Equation 1)

[0048] Furthermore, in this embodiment, the trapping layer 3 has a thickness of, for example, less than 3.0 mm (for example, 1.1 mm). The thickness of the trapping layer 3 is, for example, 0.1 mm or more and less than 3.0 mm. This thickness is, for example, preferably 0.1 mm or more and 2.5 mm or less, and more preferably 0.1 mm or more and 2.0 mm or less. In another example, this thickness is, for example, preferably 0.5 mm or more and 2.5 mm or less, and more preferably 1.0 mm or more and 2.5 mm or less. In this disclosure, the "thickness" of the trapping layer 3 refers to the thickness of the trapping layer 3 in its natural state. If the thickness of the trapping layer 3 is within this range, the fiber laminate can be configured to be thin and lightweight.

[0049] Furthermore, the trapping layer 3 of this embodiment has, as an example, a PF value of 16 or more and 84 or less (e.g., 64). The PF value refers to a value calculated based on the following formulas 2, 3, and 4. When calculating the transmittance (%) in formula 2, NaCl particles having a particle diameter of 0.4 μm are used, which are generated in accordance with the method described in JIS B9928 Appendix 5 (regulations) NaCl aerosol generation method (pressure spray method). Air containing these NaCl particles is passed through the trapping layer 3 in the thickness direction at a flow rate of 5.3 cm / sec, and the number of NaCl particles before and after passing through is measured using a particle counter. The transmittance (%) is calculated based on these measurements. Transmittance (%)=(CO2 / CI2)×100 (Formula 2) Here, CO2 is the number of NaCl particles after passing through the trapping layer 3. CI2 is the number of NaCl particles before passing through the trapping layer 3. Collection efficiency (%) = 100 - transmittance (%) (Equation 3) PF value = {-log(100-collection efficiency (%)) / 100} / (pressure loss (Pa) / 1000) (Equation 4)

[0050] The PF value is, for example, preferably 16 or more and 70 or less, and more preferably 16 or more and 60 or less. In another example, for example, it is preferably 20 or more and 84 or less, and more preferably 25 or more and 84 or less. By setting the PF value within the above range, it is possible to achieve a good balance between collection efficiency and pressure loss while achieving weight reduction and improved strength.

[0051] The trapping layer 3 of this embodiment preferably has a trapping efficiency calculated by Equation 3 of 35% to 95% (for example, 61%). This trapping efficiency is, for example, preferably 35% to 85% and more preferably 35% to 75%. In another example, it is, for example, preferably 40% to 90% and more preferably 45% to 90%.

[0052] The trapping layer 3 of this embodiment preferably exhibits a pressure loss of 3 Pa or more and 35 Pa or less (6 Pa, for example) when air is passed through it in the thickness direction at a flow rate of 5.3 cm / sec. This pressure loss is, for example, more preferably 3 Pa or more and 25 Pa or less, and even more preferably 3 Pa or more and 15 Pa or less. In another example, it is preferably 6 Pa or more and 35 Pa or less, and even more preferably 9 Pa or more and 35 Pa or less. When the pressure loss is within the above range, This prevents clogging of the trapping layer 3 during use and allows the fluid to circulate efficiently inside the trapping layer 3. This prevents performance degradation that accompanies use of the trapping layer 3. The pressure loss can be measured in the same way as for the fiber laminate 1, except that the air flow velocity was set to 5.3 cm / sec.

[0053] The material of the first fibers 4 can be selected as appropriate. When the trapping layer 3 is manufactured, for example, an aqueous dispersion containing the resin granules 6 (hereinafter simply referred to as aqueous dispersion) is applied to the first fibers 4, thereby attaching the resin granules 6 to the first fibers 4. In this case, in order to increase the affinity of the first fibers 4 for the aqueous dispersion, the material of the first fibers 4 is preferably one that has a relatively low water contact angle θ1 immediately after water droplets are dropped on the surfaces of the first fibers 4. Specifically, the water contact angle θ1 is preferably 10° or more and 40° or less, and more preferably 20° or more and 35° or less.

[0054] The first fibers 4 preferably contain fibers made of rayon, polypropylene (PP), polyethylene terephthalate (PET), polyethylene (PE), or cellulose acetate, and more preferably contain fibers made of cellulose acetate. Such materials result in a relatively low water contact angle θ1. The multiple first fibers 4 contained in the trapping layer 3 can be obtained by crimping and opening a tow (tow band) containing cellulose acetate fibers. By obtaining multiple first fibers 4 in this manner, the bulk of the trapping layer 3 tends to be the desired value.

[0055] Next, the second fibers 5 will be described in detail. The first fibers 4 and the second fibers 5 have good affinity with each other. In this embodiment, the second fibers 5 are attached to the first fibers 4 by, for example, van der Waals forces. The second fibers 5 are attached to the first fibers 4 in a state where they intersect with each other.

[0056] In this embodiment, the second fibers 5 are formed from resin granules 6 attached to the first fibers 4 during the production of the trapping layer 3. The resin granules 6 are, for example, extrusion molded bodies produced by a paste extrusion molding method. The resin granules 6 contain a polymer that can be made into a fiber. That is, the second fibers 5 also contain a polymer that can be made into a fiber.

[0057] The resin granules 6 contain a lamellar structure. In this disclosure, the term "lamellar structure" refers to a structure in which polymer chains constituting the resin of the resin granules 6 are connected and folded. Specifically, the lamellar structure contained in the resin granules 6 is composed of fine fibers formed by these polymer chains being connected in ribbon shapes in the millions. These fine fibers are folded and stored inside the resin granules 6.

[0058] The resin granules 6 have an average particle size of, for example, 100 nm or more and 100 μm or less. For example, the average particle size is preferably 200 nm or more and 700 nm or less, and more preferably 250 nm or more and 400 nm or less. In this disclosure, the average particle size refers to the median diameter (cumulative 50% diameter (D50)) calculated from the results of measurements using dynamic light scattering. For example, the resin granules 6 are molded by paste extrusion molding.

[0059] The resin granules 6 are primary particles. When the resin granules 6 are attached to a plurality of first fibers 4, a first external force is applied to the resin granules 6 in a direction that compresses (reduces) the interstices between the first fibers 4 (i.e., the direction of minimum strength), and the plurality of resin granules bond together to form secondary particles. When a second external force is applied to the two bonded resin granules 6 in a direction that pulls them apart, the fine fibers of the resin granules 6 are pulled outward, and second fibers 5 are formed.

[0060] The second fibers 5 are also formed when the first external force applied to the resin granules 6 is relaxed and the inter-fiber spaces between the first fibers 4 are enlarged. By applying a second external force to the oil granules 6, abundant second fibers 5 are actively formed. Also, as shown in the enlarged view in Figure 2, some resin granules 6 may remain in the trapping layer 3 after production.

[0061] By applying the first external force and the second external force sequentially to the resin granules 6, the fine fibers extend from the inside of the resin granules 6 toward the outside.

[0062] As a polymer that can be made into a fiber, the second fibers 5 preferably contain fibers made of polytetrafluoroethylene (hereinafter also referred to as PTFE), polypropylene (PP), polyethylene (PE), or polyamide (PA). The second fibers 5 of this embodiment preferably contain PTFE as a main component. In other words, the second fibers 5 preferably contain PTFE in an amount greater than 50% by weight of the total weight of the second fibers 5. That is, the second fibers 5 of this embodiment are preferably ultrafine fibers of PTFE. The raw material of the resin granules 6 may also be the same as that of the second fibers 5.

[0063] PTFE is, for example, a high-molecular-weight PTFE obtained by emulsion polymerization or suspension polymerization of tetrafluoroethylene (TFE). The high-molecular-weight PTFE may be either modified PTFE or homo-PTFE. The modified PTFE includes, for example, TFE units based on TFE and monomer units other than TFE, such as modified monomers. Generally, modified PTFE refers to, but is not limited to, those uniformly modified with modified monomer units and those modified at the initial or final stage of the TFE polymerization reaction. The monomer units other than TFE, such as modified monomers, may be modified monomer units based on modified monomers. In the present disclosure, the "modified monomer units" are part of the molecular structure of modified PTFE and are derived from the modified monomer. The modified monomer is not particularly limited as long as it can be copolymerized with TFE.

[0064] In this disclosure, the term "high molecular weight" in high molecular weight PTFE refers to a molecular weight that is easily fibrous during production of the trapping layer 3, yields long fibrils, has a standard specific gravity (SSG) of 2.130 or more and 2.230 or less, and does not substantially melt flow due to a high melt viscosity. For details about PTFE that can be fibrous, see, for example, WO 2013 / 157647.

[0065] When the aqueous dispersion is used in producing the trapping layer 3, it is preferable that the water contact angle θ2 immediately after a water droplet is dropped on the surface of the trapping layer 3 be a relatively low value in order to increase the affinity of the trapping layer 3 for the aqueous dispersion. In this case, it is preferable that the water contact angle θ2 be the same as the water contact angle θ1.

[0066] The water contact angles θ1 and θ2 can be measured, for example, by observing the surface of an object onto which a water droplet has been dropped from the side of the water droplet using a microscope. The water contact angles θ1 and θ2 can be calculated, for example, by using a commercially available contact angle meter (contact angle meter "DMs-401" manufactured by Kyowa Interface Science Co., Ltd.) to drop a water droplet onto the object and measure the contact angle at five points, and then calculating the average of the measured values.

[0067] In this embodiment, the water contact angles θ1 and θ2 are relatively low to increase the affinity of the first fibers 4 for the aqueous dispersion, but the water contact angles θ1 and θ2 may be relatively high to match the characteristics of the dispersion in which the resin granules 6 are dispersed. Furthermore, the dispersion containing the dispersed resin granules 6 may be adjusted to have a low contact angle with the surface of the first fibers 4 to increase the affinity of the dispersed resin granules 6 for the first fibers 4. When the trapping layer 3 is manufactured without using a dispersion, for example, by attaching powdered resin granules 6 to the first fibers 4, the water contact angles θ1 and θ2 are not limited to the above-described preferred ranges.

[0068] <Method of manufacturing fiber laminate> The fiber laminate 1 of this embodiment can be produced by a production method including a step of laminating the pre-trapping layer 2 and the trapping layer 3. The production method may include a step of producing the trapping layer.

[0069] The trapping layer can be manufactured by the following first to third steps. In the first step, a fiber sheet containing a plurality of first fibers is conveyed in a predetermined conveying direction while a plurality of resin granules containing a fibrous polymer are attached to the fiber sheet. In the second step, a first external force is applied to the fiber sheet to which the plurality of resin granules are attached so as to reduce the interstices between the first fibers while conveying the fiber sheet. In the third step, the applied first external force is relaxed, and a second external force is applied to the fiber sheet conveyed in the conveying direction so as to expand the interstices between the plurality of first fibers at least in the width direction of the fiber sheet. This forms a plurality of second fibers thinner than the first fibers from the plurality of resin granules, thereby forming a fiber composite containing the plurality of first fibers and the plurality of second fibers. The fiber composite is used as the trapping layer as is or after being cut to a predetermined size. In the first step, a nonwoven fabric is preferably used as the fiber sheet. The fiber sheet used in the first step can be manufactured, for example, using a fiber sheet manufacturing apparatus 7 described below.

[0070] [Fiber sheet manufacturing equipment] FIG. 3 is a schematic diagram of a fiber sheet manufacturing apparatus 7 (hereinafter also referred to as the "manufacturing apparatus 7"). As shown in FIG. 3, a packaging box B containing a bale-shaped raw web 50 folded, compressed, and packed is supplied to the manufacturing apparatus 7. The raw web 50 includes first fibers 51, which are a plurality of long fibers. The manufacturing apparatus 7 continuously pays out the raw web 50 from the packaging box B. The manufacturing apparatus 7 manufactures a fiber sheet 60 from a plurality of short fibers 52 formed from the plurality of first fibers 51. The manufacturing apparatus 7 of this embodiment also functions as a nonwoven fabric manufacturing apparatus. The fiber sheet 60 of this embodiment is a nonwoven fabric. In this disclosure, nonwoven fabric refers to a nonwoven fabric conforming to JIS L 0222:2001. As an example, in this embodiment, the fiber sheet 60, which is a nonwoven fabric, is manufactured using a spunlace method. The method for manufacturing a nonwoven fabric is not limited to the spunlace method, and other known methods such as a needlepunch method may also be used. The fiber sheet 60 is conveyed in a predetermined conveying direction P. The fiber sheet 60 is long and has a longitudinal direction that is the machine direction P, and a width direction that is perpendicular to the thickness direction and orthogonal to the machine direction P.

[0071] For example, the first fibers 51 contained in the raw web 50 are crimped. This gives the raw web 50 flexibility. The raw web 50 immediately after being unwound from the packaging box B has multiple first fibers 51 intertwined. For example, the first fibers 51 are crimped cellulose acetate fibers, and the raw web 50 is a tow band containing the first fibers 51. For example, the cellulose acetate fibers are spun by a dry spinning method. The spinning method is not limited to the dry spinning method. The cellulose acetate fibers are crimped by a primary crimp, which is the smallest crimp unit, and also by a secondary crimp, which is a crimp unit larger than the primary crimp. The cellulose acetate fibers may also be crimped by a higher-order crimp, which is a crimp unit larger than the secondary crimp. The cross-sectional shape of the first fibers 51 may be, for example, a circular shape, a Y-shape, or an irregular shape.

[0072] The total denier of the raw roll 50 and the single fiber denier can be set as appropriate. For example, the total denier of the raw roll 50 is in the millions, hundreds of thousands, tens of thousands, or thousands. In another example, the total denier of the raw roll 50 is preferably 3 million or more and 5 million or less, and more preferably 1 million or more and 2 million or less. In yet another example, the total denier of the raw roll 50 is preferably 100,000 or more and 700,000 or less, and more preferably 100,000 or more and 300,000 or less. In yet another example, the total denier of the raw roll 50 is preferably 5,000 or more and 100,000 or less, and more preferably 10,000 or more and 50,000 or less.

[0073] As an example, the single fiber denier of the raw roll 50 is 20 or less. In another example, the single fiber denier of the raw roll 50 is preferably 1 or more and 15 or less, more preferably 1 or more and 10 or less, and more preferably 1 or more and 15 or less. When the manufacturing apparatus 7 of this embodiment is driven, the raw web 50 is conveyed while being subjected to a relatively weak tension (load) of 2 mgf (approximately 0.0196 mN) or more and 50 mgf (approximately 0.490 mN) or less per denier in the conveyance direction P.

[0074] As a specific example, the manufacturing apparatus 7 includes a feed roll pair 8 that guides the raw web 50 unwound from the packaging box B, multiple guide members G1 to G3, and a cutter 11 that forms multiple short fibers 52 from the multiple first fibers 51 of the raw web 50. The feed roll pair 8 has a pair of feed rolls 9 and 10. The guide members G1 to G3 include, for example, multiple guide rolls. The manufacturing apparatus 7 also includes a conveying device 12 that conveys the multiple short fibers 52 discharged from the cutter 11, and a packaging device 13 that compresses and packages the multiple short fibers 52 conveyed by the conveying device 12. The packaging device 13 forms a fiber block 53 in which the multiple short fibers 52 are compressed and packaged into a predetermined shape. The fiber block 53 is used in the next process. The feed roll pair 8 is not essential and may be omitted.

[0075] The manufacturing apparatus 7 also includes a blowing machine 14 that removes impurities from the fiber block 53 and arranges the staple fibers 52, a blower BL that transports the staple fibers 52 that have passed through the blowing machine 14 in the transport direction P, a measuring feeder 15 that weighs the staple fibers 52 transported by the blower BL and supplies them in predetermined amounts, and at least one carding machine 16 that cards the staple fibers 52 supplied from the measuring feeder 15. The carding machine 16 forms a nonwoven fabric intermediate 54 containing the staple fibers 52.

[0076] The length of the staple fibers 52 can be set as appropriate. For example, the length of the staple fibers 52 is 10 mm or more and 100 mm or less. In another example, the length of the staple fibers 52 is 30 mm or more and 100 mm or less. For example, when the length of the staple fibers 52 is 100 mm or less, unnecessary entanglement of the staple fibers 52 with the carding machine 16 can be suppressed. Furthermore, when the length of the staple fibers 52 is 10 mm or more, crimped staple fibers 52 can be easily entangled with one another. This allows for the production of a fiber sheet 60, which is a bulky nonwoven fabric with abundant inter-fiber gaps. Furthermore, a fiber article 62 (see FIG. 4) having a reduced fiber density can be obtained compared to when non-crimped staple fibers are used.

[0077] The manufacturing apparatus 7 also includes an entanglement machine 19 that entangles the plurality of short fibers 52 of the nonwoven fabric intermediate 54 discharged from the carding machine 16 to form a fiber sheet 60 that is a nonwoven fabric, a dryer 20 that dries the fiber sheet 60 discharged from the entanglement machine 19, and a winder 21 that winds up the fiber sheet 60 that has passed through the dryer 20. The entanglement machine 19, for example, sprays a high-pressure water stream onto the nonwoven fabric intermediate 54, and entangles the plurality of short fibers 52 in the nonwoven fabric intermediate 54 by the pressure of the water stream.

[0078] The manufacturing apparatus 7 also includes a supply device 18. The supply device 18 supplies a second intermediate 59, which is a nonwoven fabric intermediate containing a plurality of fibers, to a first intermediate 56, which is a nonwoven fabric intermediate 54 discharged from the carding machine 16. The second intermediate 59 contains short fibers 52 or fibers different from the short fibers 52. As an example, the second intermediate 59 contains pulp fibers or synthetic fibers. The second intermediate 59 is unwound from a supply roll R1 provided in the supply device 18 and arranged so as to be overlapped on the first intermediate 56. The intermediates 56 and 59 are transported in an overlapping state and introduced into the entanglement machine 19. The entanglement machine 19 entangles the plurality of fibers of the intermediates 56 and 59. As a result, a fiber sheet 60, which is a composite sheet and nonwoven fabric in which the intermediates 56 and 59 are arranged overlapping each other, is formed.

[0079] The fiber sheet 60 may include a plurality of first intermediates 56 and at least one second intermediate 59. In this case, the second intermediate 59 may be disposed between the plurality of first intermediates 56. The second intermediate 59 may be further disposed in the laminate including the plurality of first intermediates 56. Alternatively, the first intermediates 56 and at least one second intermediate 59 may be integrally entangled. The manufacturing apparatus 7 may be configured without the supply device 18. In this case, the fiber sheet 60 is configured only by the first intermediates 56.

[0080] The fiber sheet 60 discharged from the intertwining machine 19 is dried by the dryer 20. The dried fiber sheet 60 is wound around a winding roll R2 of a winding machine 21. The winding roll R2 is used in the next step.

[0081] [Textile manufacturing equipment] FIG. 4 is a schematic diagram of a fiber article manufacturing apparatus 22 (hereinafter also referred to as "manufacturing apparatus 22") capable of manufacturing a trapping layer from a fiber sheet. A fiber sheet 60 containing a plurality of first fibers 51 (here, short fibers 52) is supplied to the manufacturing apparatus 22 from a winding roll R2. As will be described in detail below, the manufacturing apparatus 22 applies a predetermined first external force and a second external force while conveying the fiber sheet 60 to which a plurality of resin granules are attached, thereby forming abundant second fibers from the resin granules. This forms a fiber composite 61 containing the first fibers 51 and the second fibers.

[0082] As a specific example, the manufacturing apparatus 22 includes a plurality of guide members G4 to G7 that guide the fiber sheet 60 in the conveying direction P, an applicator 25 that applies an applicator liquid 90 containing a plurality of resin granules to the fiber sheet 60, and a dryer 26 that dries the fiber sheet 60 to which the applicator liquid 90 has been applied. As an example, the guide members G4 to G7 include a plurality of guide rolls. The manufacturing apparatus 22 also includes a pair of pressure rolls 27 that apply pressure to the dried fiber sheet 60, and a stretching device 30 that stretches in a predetermined direction a plurality of first fibers 51 (short fibers 52) contained in the fiber sheet 60 that has passed through the pair of pressure rolls 27. The pair of pressure rolls 27 includes a pair of pressure rolls 28 and 29. The manufacturing apparatus 22 also includes a winder 31 that winds up the fiber composite 61 discharged from the stretching device 30.

[0083] As an example, the applicator 25 includes a storage section 32 that stores the impregnating liquid 90 and an applicator roll 33 that applies the impregnating liquid 90 in the storage section 32 to the short fibers 52 (first fibers 51) of the fiber sheet 60 via the peripheral surface thereof. The applicator 25 also includes a liquid collector 34 that collects the impregnating liquid 90 discharged from the storage section 32, and a pump 35 that circulates the collected impregnating liquid 90 back to the storage section 32. The configuration of the applicator 25 is not limited. For example, the applicator 25 may include one or more nozzles that spray the impregnating liquid 90 onto the fiber sheet 60 and a housing that accommodates the nozzles. As an example, the impregnating liquid 90 is a water-based impregnating liquid. Using a water-based impregnating liquid allows the impregnating liquid 90 to be produced relatively inexpensively. Furthermore, the impregnating liquid 90 can be easily handled. The impregnating liquid 90 may contain a liquid other than water.

[0084] The resin granules are primary particles. Secondary particles are formed when multiple resin granules are bonded to each other. When the impregnation liquid 90 is impregnated onto the first fibers 51, multiple resin granules are dispersed and impregnated onto the surfaces of the multiple first fibers 51. As an example, multiple secondary particles of the resin granules are impregnated onto the surfaces of the first fibers 51.

[0085] The pressure roll pair 27 applies a first external force to the first fibers 51 and the resin granules in the fiber sheet 60 to which the resin granules are attached and which is being conveyed, so as to reduce the interfiber spaces between the first fibers 51. The pressure roll pair 27 is, for example, a pair of thermocompression rolls that thermocompress the fiber sheet 60. The heating temperature at which the first fibers 51 and the resin granules are heated by the thermocompression roll pair can be adjusted as appropriate. For example, the heating temperature is higher than 25°C and lower than 200°C. The heating temperature is, for example, preferably 50°C or higher and 200°C or lower, more preferably 70°C or higher and 200°C or lower, and even more preferably 90°C or higher and 200°C or lower. In another example, the heating temperature is preferably 110°C or higher and 200°C or lower. The heating temperature is preferably 150° C. or higher and 200° C. or lower. The heating temperature may be, for example, lower than the melting point of each material of the first fibers 51 and the resin granules, or lower than the decomposition temperature of each material.

[0086] The stretching device 30 applies a second external force to the fiber sheet 60 being transported in the transport direction P, so that the first external force is relaxed after the first external force is applied, thereby expanding the inter-fiber spaces between the first fibers 51 in at least the width direction W (the direction perpendicular to the paper surface in FIG. 4 ) of the fiber sheet 60. As an example, the stretching device 30 applies the second external force to the transported fiber sheet 60 in both the transport direction P and the width direction W. As an example, the stretching device 30 is a known simultaneous biaxial stretching device. The configuration of a simultaneous biaxial stretching device can be found in, for example, Japanese Patent No. 4224241. Alternatively, a known sequential biaxial stretching device may be used as the stretching device.

[0087] When the manufacturing apparatus 22 is in operation, the fiber sheet 60 to which the impregnation liquid 90 has been applied by the applicator 25 is sent to the dryer 26. The fiber sheet 60 is dried as the solvent component of the impregnation liquid 90 evaporates. The dried fiber sheet 60 is introduced into the pair of pressure rolls 27. When the fiber sheet 60 passes through the nip point of the pair of pressure rolls 27, a first external force is applied to the multiple first fibers 51 and multiple resin granules of the fiber sheet 60. In one example, the multiple first fibers 51 and multiple resin granules are heated by the pair of pressure rolls 27 when the first external force is applied. The first fibers 51 are plasticized by being heated. Therefore, the first external force makes it easier for the gaps between the fibers to shrink. When the fiber sheet 60 passes through the nip point of the pair of pressure rolls 27, the first external force applied to the multiple first fibers 51 and multiple resin granules is alleviated.

[0088] The first external force may be applied to the plurality of first fibers 51 and the plurality of resin granules by a configuration other than a pair of pressure rolls. The first external force may also be applied to the plurality of first fibers 51 and the plurality of resin granules by a configuration other than a pair of thermocompression rolls. In this case, for example, the manufacturing apparatus 22 may include a pair of pressure rolls that does not have a heating function.

[0089] The fiber sheet 60, from which the first external force has been relaxed, is introduced into the stretching device 30. In the stretching device 30, a second external force may be applied to the fiber sheet 60 in the conveying direction P and the width direction W so as to expand the inter-fiber spaces between the plurality of first fibers 51. At this time, the second external force is applied to the plurality of first fibers 51 and the plurality of resin granules so as to separate the resin granules that are adhered to each other between the plurality of first fibers 51. As a result, the fine fibers of the resin granules are stretched outward, and second fibers are formed so as to bridge different plurality of first fibers 51. As a result, a fiber composite 61 is formed that contains a plurality of first fibers 51 and an abundant plurality of second fibers.

[0090] Here, the second fibers are also formed when the first external force applied to the fiber sheet 60 is relaxed, expanding the interstices between the first fibers 51. However, in this embodiment, the interstices between the first fibers 51 can be expanded in a desired direction by actively applying a second external force to the first fibers 51 and the resin granules. This allows for the formation of more abundant second fibers. Furthermore, for example, the thickness or number of the second fibers formed can be adjusted by adjusting at least one of the strength of the second external force and the temperature at which the second external force is applied. This allows for the adjustment of each characteristic of the trapping layer within a certain range.

[0091] Furthermore, in the fiber sheet 60, after the first external force applied to the plurality of first fibers 51 and the plurality of resin granules is relaxed, the fiber gaps between the plurality of first fibers 51 in the thickness direction naturally expand due to a restoring force. In contrast, in the fiber sheet 60, the fiber gaps between the plurality of first fibers 51 in both the conveying direction P and the width direction W are expanded by the application of a second external force. As a result, in the fiber sheet 60, for example, the fiber gaps in two directions that are perpendicular to the thickness direction and perpendicular to each other are formed wider than the gaps in the thickness direction. The "fiber gaps in two directions" referred to here refers to the gaps in the conveying direction P and the width direction W. It corresponds to the direction P and the width direction W.

[0092] The fiber composite 61 is wound around a winding roll R3 of the winding machine 31. The fiber composite 61 can be processed into a fiber article 62 by cutting it to a predetermined size. This produces a fiber article 62 in which the occurrence of unevenness in the fiber gaps between the plurality of first fibers 51 and the plurality of second fibers in the two-directional fiber gaps is suppressed. The fiber article 62 has a configuration in which the fiber gaps in the two directions are formed wider than the fiber gaps in the thickness direction. This configuration allows, for example, a relatively small basis weight, and can suppress an increase in pressure loss over time in use. The fiber composite 61 or the fiber article 62 can be used as the trapping layer of this embodiment.

[0093] Thus, the method for manufacturing the trapping layer includes a first step of attaching a plurality of resin granules containing a fiberizable polymer to a fiber sheet 60 that includes a plurality of first fibers 51 and is transported in a predetermined transport direction P. It also includes a second step of applying a first external force to the plurality of first fibers 51 and the plurality of resin granules in the transported fiber sheet 60 to which the plurality of resin granules are attached so as to reduce the inter-fiber gaps between the first fibers 51.

[0094] The manufacturing method also has a third step of applying a second external force to the fiber sheet 60, which is conveyed after the first external force has been applied and the first external force has been relaxed, so as to expand the fiber gaps between the multiple first fibers 51 in at least the width direction W of the fiber sheet 60, thereby forming second fibers having an outer diameter smaller than the first fibers 51 from the multiple resin granules, and forming a fiber composite 61 containing the first fibers 51 and the second fibers.

[0095] In addition, in the third step, as an example, a second external force is applied to the fiber sheet 60 in multiple directions including the width direction W. In addition, as an example, in the third step, the second external force is simultaneously applied to the fiber sheet 60 in multiple directions including the width direction W.

[0096] Furthermore, for example, by adjusting at least one of the strength of the second external force and the temperature when the second external force is applied, it is possible to adjust the fiber gaps between the plurality of first fibers 51 and the plurality of second fibers, the number of second fibers, the outer diameter D2, and the length of the second fibers. For example, by increasing the second external force within a certain range, it is possible to set the outer diameter D2 small. Also, by decreasing the second external force within a certain range, it is possible to set the outer diameter D2 large.

[0097] This allows the production of a trapping layer whose basis weight, tensile strength in the minimum strength direction, tensile elongation relative to the natural state in the minimum strength direction, PF value, thickness, pressure loss, and trapping efficiency are within desired ranges. Specifically, by increasing the second external force within a certain range, the basis weight and thickness in the natural state of the trapping layer decrease. Furthermore, by reducing the second external force within a certain range, the basis weight and thickness in the natural state of the trapping layer increase. Furthermore, by increasing the second external force within a certain range, an abundant amount of second fibers is formed. Furthermore, for example, as the number of second fibers increases, the tensile elongation of the trapping layer relative to the natural state decreases. Furthermore, for example, as the number of second fibers increases, the tensile strength of the trapping layer increases.

[0098] As described above, the manufacturing apparatus 22 can be used to manufacture the trapping layer.

[0099] [Fiber laminate manufacturing equipment] 5 is a schematic diagram of a fiber laminate manufacturing apparatus 36 (hereinafter also referred to as "manufacturing apparatus 36"). As shown in FIG. 5, a fiber composite 61 is supplied to the manufacturing apparatus 36 from a winding roll R3, and a prefilter precursor 63 is supplied from a winding roll R4. The manufacturing apparatus 36 is provided with a pressing roll pair 37 that presses the fiber composite 61 and the prefilter precursor 63 together. The pressing roll pair 37 has a pair of pressing rolls 38 and 39. The manufacturing apparatus 36 also includes a winder 40 that winds up the fiber laminate 64 discharged from the pressing roll pair 37.

[0100] The pair of pressure-bonding rolls 37 is, for example, a pair of thermocompression rolls that thermocompresses the fiber composite 61 and the prefilter precursor 63 together. The heating temperature of the pair of thermocompression rolls can be adjusted as appropriate. For example, the heating temperature is higher than 25°C and lower than 200°C. For example, the heating temperature is preferably higher than 25°C and lower than 150°C, more preferably higher than 25°C and lower than 100°C, and even more preferably higher than 25°C and lower than 50°C. When the heating temperature is equal to or lower than the upper limit, the pressure loss is likely to be low.

[0101] The fiber laminate 64 wound around the winding roll R5 of the winding machine 40 can be cut to a predetermined size as needed and used as an air filter medium. [Example]

[0102] The present disclosure will be specifically described below with reference to examples, but the present disclosure is not limited to the aspects of the following examples.

[0103] (Comparative Examples 1 to 4) As comparative examples, a PTFE filter medium (hereinafter sometimes referred to as "PTFE HEPA") manufactured by Daikin Industries, Ltd. and a glass fiber filter medium (H820, H840, or H8185) were used as the collection layer. The pre-collection layer was a PET / PE composite fiber filter medium "020-076-2307" (basis weight 120 g / m) manufactured by Daikin Industries, Ltd. 2 The trapping layer and pre-collection layer were laminated using a fiber laminate manufacturing device 36. A pair of thermocompression rolls was used as the compression roll pair 37, and the heating temperature was set to 30°C.

[0104] (Examples 1 and 2) A fiber sheet 60 was prepared, including a plurality of first fibers 51 (short fibers 52) that were crimped cellulose acetate fibers. A plurality of resin granules containing PTFE were also prepared. A fiber article including the first fibers and second fibers was manufactured by performing the first to third steps. In the first step, the plurality of resin granules were attached to the plurality of first fibers 51 (short fibers 52) based on an impregnation method. A nonwoven fabric manufactured by a spunlace method was used as the fiber sheet 60. In the second step, the heating temperature of the pressure roll pair 27 was set to 110°C. The nip pressure as the first external force of the pressure roll pair 27 was set to 2 MPa. The manufactured fiber article and a pre-collection layer were laminated using a fiber laminate manufacturing device 36. A thermo-compression roll pair was used as the pressure roll pair 37, and the heating temperature was set to 30°C. The pre-collection layer was made of Daikin Industries' PET / PE composite fiber filter media "020-076-2307" (basis weight 120 g / m 2 , thickness 2.0 mm) or PP / polyacrylonitrile composite fiber filter media "6224PMHM11" (basis weight 55 g / m 2 , thickness 1.2 mm) was used.

[0105] For each comparative example and example, measurements were made of basis weight, thickness, pressure loss when air was passed through in the thickness direction at a flow rate of 12.7 cm / sec, and dust amount at 700 Pa. In each example, a pre-collection layer was placed on the upstream side (inlet side).

[0106] The dust amount at 700 Pa was measured using the following procedure. Based on the method conforming to item 9.2 "Dust Load" of the General Ventilation Filter Test (JIS B 9908-3:2019), the dust load (g / m) when the pressure loss at the end of the test is 700 Pa 2 The test wind speed was 12.7 cm / s.

[0107] The results are shown in Table 1.

[0108] [Table 1]

[0109] As is clear from Table 1, the fiber laminate according to one embodiment of the present disclosure has lower pressure loss and significantly higher dust capacity than the comparative examples using PTFE or glass fiber as the trapping layer. Furthermore, by pressing the layers together using a pair of pressing rolls without using an adhesive, a fiber laminate in which the trapping layer and pre-trapping layer are integrated can be obtained. [Explanation of symbols]

[0110] 1: fiber laminate, 2: pre-collection layer, 3: collection layer, 4: first fiber, 5: second fiber, 6: resin granules, 7: fiber sheet manufacturing device, 8: feed roll pair, 9, 10: feed roll, 11: cutter, 12: conveying device, 13: packaging device, 14: mixing and punching machine, 15: measuring feeder, 16: carding machine, 18: feeding device, 19: entangling machine, 20: dryer, 21: winding machine, 22: fiber article manufacturing device, 25: applicator, 26: dryer, 27: pressure roll pair, 28, 29: pressure roll, 30: drawing device, 31: winding machine, 32: storage section , 33: impregnation roll, 34: liquid collection section, 35: pump, 36: fiber laminate manufacturing apparatus, 37: pair of pressure rolls, 38, 39: pressure rolls, 40: winder, 50: raw roll, 51: first fiber, 52: short fiber, 53: fiber block, 54: nonwoven fabric intermediate, 56: first intermediate, 59: second intermediate, 60: fiber sheet, 61: fiber composite, 62: fiber article, 63: prefilter precursor, 64: fiber laminate, 90: impregnation liquid, B: packaging box, BL: blower, G1 to G7: guide members, R1: supply roll, R2 to R5: winding roll

Claims

1. A fiber laminate in which a pre-collection layer and a collection layer are laminated in order, The pre-collection layer includes a plurality of fibers, The collection layer is a fiber laminate including a plurality of first fibers and a plurality of second fibers having an outer diameter smaller than that of the first fibers and supported by the first fibers in a dispersed state.

2. The fiber laminate according to claim 1 , wherein the thickness of the fiber laminate is 0.5 mm or more and 5 mm or less.

3. The basis weight of the fiber laminate is 80 g / m ２ Above, 300g / m ２ 3. The fiber laminate according to claim 1 or 2, wherein:

4. 3. The fiber laminate according to claim 1, wherein a pressure loss when air is passed through the fiber laminate in a thickness direction at a flow rate of 12.7 cm / sec is 3 Pa or more and 35 Pa or less.

5. 3. The fiber laminate according to claim 1, wherein the outer diameter of the plurality of fibers is 0.5 μm or more and 50 μm or less.

6. The fiber laminate according to claim 1 or 2, wherein a ratio D1 / D2 of an outer diameter D1 of the first fibers to an outer diameter D2 of the second fibers is 15.0 or more and 1666.7 or less.

7. 3. The fiber laminate according to claim 1, wherein the collection layer comprises resin particles.

8. The fiber laminate according to claim 7 , wherein the pre-collection layer and the collection layer are bonded together by the resin granules.

9. 8. The fibrous laminate of claim 7, wherein the resin particles comprise polytetrafluoroethylene, polypropylene, polyethylene, or polyamide.

10. 8. The fibrous laminate of claim 7, wherein the resin particles comprise polytetrafluoroethylene.

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