Method for manufacturing composite nonwoven fabrics

Abstract

To provide a method for manufacturing a conjugate-type nonwoven fabric that has suitable stiffness and can be wiped off while retaining shape, extremely reduces hooking of fibers when wiping off an irregular surface, can effectively suppress generation of paper powder after wiping off in wet state, and is excellent in processing suitability by adopting an air-laid method and adding a wet paper strengthening agent and anionic water soluble polymer.SOLUTION: A method for manufacturing a conjugate-type nonwoven fabric including a nonwoven fabric and at least pulp fiber web manufactured by air-laid method includes a water flow entanglement step and an addition step to add chemical liquid including a wet paper strengthening agent and anionic water soluble polymer to the pulp fiber web. The anionic water soluble polymer contains carboxymethyl cellulose. In the addition step, the chemical liquid is added so that ratio of addition amount of the anionic water soluble polymer to the wet paper strengthening agent is 1.00 or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing a composite non-woven fabric to which a wet paper strength agent and an anionic water-soluble polymer are added.

Background Art

[0002] In recent years, apart from paper products (sheets) consisting only of pulp fibers and non-woven fabric products consisting only of synthetic fibers, products of composite non-woven fabrics obtained by hydraulically entangling pulp fiber sheets and synthetic (long) fiber non-woven fabrics are being sold in the market.

[0003] In the production of composite non-woven fabrics obtained by entangling pulp fiber sheets and long fiber non-woven fabrics, when using wet sheets for the pulp fiber sheets, chemicals (additives) such as paper strength agents are added during the production (papermaking) of the pulp wet sheets.

[0004] On the other hand, when using a dry method (airlaid method) for forming pulp fiber webs (sheets), it is difficult to uniformly add chemicals to the pulp fibers. Therefore, when imparting functionalities such as texture, flexibility, and strength, chemicals and the like are added after water jet (hydraulic entanglement).

[0005] Due to the water jet, the pulp fibers enter between the long fibers and a structure in which both fibers are entangled is formed. Therefore, by adding chemicals thereafter, it becomes possible to add chemicals to the structure of the formed composite fibers.

[0006] As prior art documents relating to composite nonwoven fabrics, for example, Patent Document 1 discloses a nonwoven composite fabric with a high pulp content that is entangled by water pressure, characterized by comprising a nonwoven continuous filament support of about 30 weight percent or less and a fibrous portion made of pulp of about 70 weight percent or more. It also describes a method for manufacturing a nonwoven composite fabric, characterized by layering layers of pulp fibers on a nonwoven continuous filament support with a bond density of about 100 pin bond positions / square inch and a total bond area of ​​about 30 percent or less, entangling each layer by water pressure to form a composite material, and drying this composite material.

[0007] Furthermore, Patent Document 2 discloses a composite nonwoven fabric in which a pulp fiber web obtained by an airlaid method is laminated and integrated onto a spunbond nonwoven fabric, characterized in that the pulp fiber web contains a paper strength agent and an amphoteric resin, and the amount added, calculated as the solid content of the paper strength agent, is 0.04 to 1.0% of the solid weight of the pulp fiber web, and the amount added, calculated as the solid content of the amphoteric resin, is 0.06 to 1.5%. Furthermore, as a manufacturing apparatus for the composite nonwoven fabric, a suction device and a drying device are provided downstream of the water flow entanglement device to perform a dewatering treatment to suck and remove moisture remaining in the pulp fiber web, followed by a drying treatment to complete the manufacturing of the composite nonwoven fabric, and the suction device is, for example, a vacuum type that dewaters the composite nonwoven fabric after water flow entanglement from below, and a paper strength agent addition device is provided above the suction device with the conveyed composite nonwoven fabric in between. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Patent No. 2533260 [Patent Document 2] Japanese Patent Publication No. 2021-130888 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] However, with the composite nonwoven fabric manufactured by the above method, there was a problem in that paper dust would fall off the composite nonwoven fabric during wiping, actually soiling the area being wiped.

[0010] In composite nonwoven fabrics containing pulp fiber webs manufactured by the airlaid method, it has been found that by using a combination of a wetting force agent and an anionic water-soluble polymer, particularly carboxymethylcellulose (CMC), in the added chemical solution, the amount of paper dust that falls off can be suppressed, especially when wiping while wet. However, because the two additives cause condensation of the chemical solution when mixed, particular care was needed in terms of quality control and continuous operation, especially in airlaid equipment not specifically designed for chemical additives.

[0011] Regarding the problem of chemical solution aggregation, by reducing the amount of carboxymethylcellulose (CMC) added and adjusting the ratio of the wet-strengthening agent to the amount of carboxymethylcellulose (CMC) added, it is possible to create a composite nonwoven fabric that maintains a soft texture, prevents paper dust from falling off when wiping wet objects, and eliminates contamination of equipment. However, due to its soft texture, it was difficult to apply only the desired surface to the object during wiping, resulting in the material curling up during use. Additionally, when wiping uneven surfaces, the fibers would catch on the surface, causing paper dust to fall off. Furthermore, while adding carboxymethylcellulose (CMC) could harden the texture, this also presented the challenge of compromising the suitability of the hard composite nonwoven fabric for subsequent folding processes.

[0012] Therefore, the object of the present invention is to provide a method for producing a composite nonwoven fabric using an airlaid method, in which a wetting paper strength agent and an anionic water-soluble polymer (carboxymethylcellulose) are added in combination to a chemical solution, the composite nonwoven fabric having appropriate stiffness, being able to be wiped while maintaining its shape, significantly reducing fiber snagging when wiping uneven surfaces, effectively suppressing the generation of paper dust after wiping when wet, and having excellent processability. [Means for solving the problem]

[0013] The inventors conducted diligent research and have completed the present invention, which provides a method for producing a composite nonwoven fabric comprising at least a nonwoven fabric and a pulp fiber web manufactured by an airlaid method, wherein the method involves a water flow entanglement step and an addition step in which a chemical solution containing a wet paper strength agent and an anionic water-soluble polymer is added to the pulp fiber web, the wet paper strength agent being polyamide epichlorohydrin (PAE) and the anionic water-soluble polymer being carboxymethylcellulose (CMC), and by adjusting the ratio of the amounts of the wet paper strength agent and the anionic water-soluble polymer added, and the addition rate of the anionic water-soluble polymer relative to the oven-dry weight of the pulp fiber web, to within predetermined numerical ranges, the present invention provides a composite nonwoven fabric that has appropriate stiffness, can be wiped while maintaining its shape, has significantly less fiber snagging when wiping uneven surfaces, can effectively suppress the generation of paper dust after wiping when wet, and has excellent processability. In other words, the present invention provides the following.

[0014] (1) A first aspect of the present invention is a method for producing a composite nonwoven fabric, comprising at least a nonwoven fabric and a pulp fiber web produced by an airlaid method, comprising: a water flow entanglement step of treating the nonwoven fabric and the pulp fiber web with water flow entanglement; and an addition step of adding a chemical solution containing a wet strength agent and an anionic water-soluble polymer to the pulp fiber web after the water flow entanglement step, wherein the wet strength agent contains polyamide epichlorohydrin (PAE) and the anionic water-soluble polymer contains carboxymethylcellulose (CMC), and in the addition step, the chemical solution is added to the pulp fiber web such that the ratio of the amount of anionic water-soluble polymer added to the amount of wet strength agent added is 1.00 or more, and the addition rate of the anionic water-soluble polymer to the oven-dry weight of the pulp fiber web is 0.50% or more and 3.50% or less.

[0015] (2) A second aspect of the present invention is a method for producing a composite nonwoven fabric as described in (1), characterized in that, in the addition step, the chemical solution is added to the pulp fiber web such that the addition rate of the anionic water-soluble polymer to the oven-dry weight of the pulp fiber web is 1.00% or more and 3.50% or less.

[0016] (3) A third aspect of the present invention is a method for producing a composite nonwoven fabric as described in (1), characterized in that, in the addition step, the chemical solution is added to the pulp fiber web such that the ratio of the amount of anionic water-soluble polymer added to the amount of wet paper strength agent added is 1.10 or more.

[0017] (4) A fourth aspect of the present invention is a method for producing a composite nonwoven fabric as described in (1), wherein the addition step includes a pre-addition dewatering step in which the composite nonwoven fabric is dewatered by a dewatering device provided below it, and a chemical solution addition step in which the chemical solution is added to the pulp fiber web by spray spraying using an addition device provided downstream of the dewatering device.

[0018] (5) The fifth aspect of the present invention is the method for manufacturing the composite nonwoven fabric according to (4), wherein in the chemical solution addition step, the chemical solution is divided into two times and both are added by spray spraying, and the chemical solution is added to the pulp fiber web by the addition device provided downstream of the dehydration device both for the first liquid and the second liquid.

[0019] (6) The sixth aspect of the present invention is the method for manufacturing the composite nonwoven fabric according to (4), wherein in the chemical solution addition step, the chemical solution is a mixture of the wet strength agent and the anionic water-soluble polymer, and is added to the pulp fiber web by spray spraying by the addition device.

[0020] (7) The seventh aspect of the present invention is the method for manufacturing the composite nonwoven fabric according to (4), wherein in the chemical solution addition step, the chemical solution is two chemical solutions containing the wet strength agent and the anionic water-soluble polymer separately without mixing, and are added to the pulp fiber web by spray spraying by different addition devices respectively.

[0021] (8) The eighth aspect of the present invention is that in the chemical solution addition step according to (7), after one chemical solution containing the wet strength agent is added to the pulp fiber web by spray spraying by the addition device, the other chemical solution containing the anionic water-soluble polymer is added to the pulp fiber web by spray spraying by the addition device within 2 seconds.

[0022] (9) The ninth aspect of the present invention is the method for manufacturing the composite nonwoven fabric according to (1), wherein the nonwoven fabric is a spunbond nonwoven fabric, and the water flow entanglement step is to perform water flow entanglement treatment on the spunbond nonwoven fabric and the pulp fiber web manufactured by the airlaid method placed thereon.

Advantages of the Invention

[0023] According to the present invention, in a method for producing a composite nonwoven fabric using an airlaid method and adding a wetting paper strength agent and an anionic water-soluble polymer (carboxymethylcellulose) to a chemical solution, it is possible to provide a method for producing a composite nonwoven fabric that has appropriate stiffness, can be wiped while maintaining its shape, has significantly less fiber snagging when wiping uneven surfaces, can effectively suppress the generation of paper dust after wiping when wet, and has excellent processability. [Brief explanation of the drawing]

[0024] [Figure 1] This is a schematic diagram of a manufacturing apparatus for carrying out the manufacturing method of composite nonwoven fabric according to this embodiment. [Modes for carrying out the invention]

[0025] The following describes in detail embodiments for carrying out the present invention (hereinafter simply referred to as "this embodiment"). This embodiment is illustrative for explaining the present invention and is not intended to limit the present invention to the following content. The present invention can be implemented by modifying it as appropriate within the scope of its gist.

[0026] In the drawings, identical elements will be denoted by the same reference numeral, and redundant explanations will be omitted. Furthermore, unless otherwise specified, positional relationships such as top, bottom, left, and right shall be based on those shown in the drawings. Additionally, the dimensional ratios in the drawings are not limited to those shown. Furthermore, in composite nonwoven fabrics, the MD direction refers to the conveying direction (Machine Direction) during the manufacturing of the composite nonwoven fabric, while the CD direction refers to the width direction (Cross Direction) perpendicular to the conveying direction.

[0027] A method for manufacturing a composite nonwoven fabric according to one embodiment of the present invention is a method for manufacturing a composite nonwoven fabric that includes at least a nonwoven fabric and a pulp fiber web manufactured by an airlaid method. The nonwoven fabric is not particularly limited, but is preferably a spunbond nonwoven fabric. Figure 1 shows a manufacturing method and apparatus for producing a composite nonwoven fabric by placing a pulp fiber web supplied by an airlaid device onto a spunbond nonwoven fabric, and then subjecting it to a water entanglement treatment using a water entanglement device. A method for manufacturing a composite nonwoven fabric using a manufacturing apparatus suitable for producing a composite nonwoven fabric according to the present invention will be described below with reference to Figure 1.

[0028] <Manufacturing equipment for composite nonwoven fabrics> As shown in Figure 1, the composite nonwoven fabric WP manufacturing apparatus (hereinafter also simply referred to as the manufacturing apparatus) 1 according to this embodiment is equipped with an airlaid device 2 for supplying pulp fiber web PFW on the upstream side, a spunbond nonwoven fabric supply device 3 for supplying spunbond nonwoven fabric SW, and a suction device (hereinafter also referred to as the dewatering device) 4 for dewatering. The suction device 4 is provided facing the lower side of the airlaid device 2. In the web transport direction MD, downstream of these devices, from upstream to downstream, are a water flow entanglement device 5 that sprays water jets for water flow entanglement treatment, a suction device 6 for dewatering treatment, and a drying device 7. Downstream of the drying device 7 is a winding device 8 for winding up the continuously manufactured composite nonwoven fabric WP.

[0029] (Lamination process) The airlaid apparatus 2 described above includes a defibrator 21 that defibrates the raw material pulp RP, which is densely packed with fibers and forms a sheet, into pulp fibers PF, and a duct 22 equipped with a blower (not shown) that transports the defibrated pulp fibers PF to the airlaid hopper 23.

[0030] Furthermore, an airlaid hopper 23 is located downstream of the duct 22. Inside this airlaid hopper 23, pulp fibers PF in a defibrated state descend while dispersing, and are designed to gradually accumulate at the stacking position 24 located on the lower surface, forming a pulp fiber web PFW. As described above, the airlaid apparatus 2 is a device that can supply pulp fiber webs (PFW) in a dry manner, and can reduce equipment costs compared to devices that manufacture pulp fiber webs in a wet manner by applying the wet papermaking method. In addition, the airlaid apparatus 2 is a closed system from pulp defibration to dispersion and descent, so the inclusion of foreign matter is prevented, and the amount of foreign matter contamination can be kept overwhelmingly low compared to when pulp fiber webs are supplied by the wet papermaking method.

[0031] A suction device 4 is positioned opposite the stacking position 24. More specifically, the suction device 4 has a suction section 42 on the upper surface of the suction device body 41, and the suction section 42 is set relative to the stacking position 24 to apply suction force (negative pressure) to the pulp fiber web PFW. In Figure 1, the airlaid hopper 23 and the suction device body 41 are arranged in a single-stage configuration to form a pulp fiber web (PFW). However, the arrangement is not limited to this configuration, and the airlaid hopper 23 and the suction device body 41 may be changed to a multi-stage configuration of two or more stages depending on the basis weight (grammage) and manufacturing speed of the pulp fiber web (PFW).

[0032] Furthermore, a transport wire 43 for transporting the web is arranged around the suction device 4. The transport wire 43 is positioned to allow the pulp fiber web PFW, on which pulp fibers PF have accumulated at the stacking position 24, to be placed and to transport it downstream. However, the pulp fiber web PFW is not placed directly on the transport wire 43. This will be explained later. The conveying wire 43 is formed in a mesh shape such that the suction force of the suction section 42 extends to the opposite side (upper side).

[0033] Below the airlaid device 2 described above, upstream of the suction device 4, is a spunbond nonwoven fabric supply device 3. This spunbond nonwoven fabric supply device 3 is set with pre-prepared spunbond nonwoven fabric SW in roll form. That is, as mentioned above, the designed spunbond nonwoven fabric SW is wound into a roll form during manufacturing, and this is drawn out from the spunbond nonwoven fabric supply device 3 and transported to the lamination position 24 on the transport wire 43 described above.

[0034] In this way, the pulp fiber web PFW described above is placed on top of the spunbond nonwoven fabric SW located at the lamination position 24. At the lamination position 24, the suction force from the suction section 42 of the suction device 4 passes through the conveyor wire 43 and acts on the spunbond nonwoven fabric SW and pulp fiber web PFW above it. As a result, the preliminary laminate PWeb (laminated web), in which the spunbond nonwoven fabric SW and pulp fiber web PFW are laminated, is conveyed downstream.

[0035] As described above, when the preliminary laminate PWeb is formed, the basis weight of the pulp fiber web PFW contained in the composite nonwoven fabric WP produced by this apparatus can be controlled by controlling the amount of pulp fiber web PFW supplied onto the spunbond nonwoven fabric SW. It is preferable to design the basis weight of the pulp fiber web PFW contained in the composite nonwoven fabric WP to have a higher ratio of pulp fiber web PFW than conventional composite nonwoven fabrics, for example, 30 g / m². 2 More than 130g / m 2 Preferably, it is 54 g / m 2 More than 73g / m 2 The following is more preferable: By setting the basis weight of the pulp fiber web (PFW) within the above numerical range, a composite nonwoven fabric (WP) that exhibits strength can be obtained. Furthermore, the basis weight of the spunbond nonwoven fabric SW is, for example, 8.0 g / m². 2 More than 40.0g / m 2Preferably, the basis weight of the composite nonwoven fabric WP (spunbond nonwoven fabric SW + pulp fiber web PFW) produced is, for example, 38.0 g / m². 2 More than 170.0g / m 2 The following is preferable. Each basis weight shall be measured in accordance with JIS P 8124. Furthermore, by appropriately adjusting the conveying speed of the pulp fiber web (PFW) and the hourly supply rate of the pulp fiber web (PFW), and by checking the basis weight of the pulp fiber web (PFW) of the manufactured composite nonwoven fabric (WP), the basis weight can be set to fall within the desired range. The conveying speed of the pulp fiber web (PFW) is preferably 100 m / min to 300 m / min, for example, the same as the conveying speed when adding the chemical solution described later.

[0036] (hydraulic entanglement process) Then, in the water flow entanglement device 5, a water flow entanglement process is performed in which the spunbond nonwoven fabric SW and the pulp fiber web PFW manufactured by the airlaid method, which is placed on top of it, are subjected to water flow entanglement. Specifically, a high-pressure water jet is applied to the preliminary laminate PWeb, which has been processed by the airlaid device 2, which serves as the pre-processing unit, thereby promoting entanglement between pulp fibers and facilitating integration between the upper pulp fiber web PFW layer and the lower spunbond nonwoven fabric SW layer (water jet entanglement treatment). The water flow entanglement device 5 shown exemplified in Figure 1 has water jet heads 51 arranged in multiple stages (four stages in Figure 1) along the transport direction MD.

[0037] Although Figure 1 does not show the nozzles on the water jet head 51 extending in a direction perpendicular to the transport direction MD (web width direction CD), multiple water jet nozzles are arranged at appropriate positions in the width direction CD. The hole diameter φ of these water jet nozzles is preferably 0.06 mm to 0.15 mm. Furthermore, the spacing between the water jet nozzles is preferably 0.4 mm to 1.0 mm. The water pressure used when performing the above-described water entanglement treatment should preferably be set considering the basis weight of the pulp fiber web (PFW) and the spunbond nonwoven fabric (SW), and is preferably selected within the range of 1 MPa to 30 MPa.

[0038] A suction device 52 is positioned opposite the water jet head 51. The high-pressure water jet from the water jet head 51 is sprayed onto the pulp fiber web PFW located above, while the suction force of the suction device 52 is applied to the underside of the spunbond nonwoven fabric SW located below. It is presumed that the cooperative action of the water jet head 51 and the suction device 52 creates conditions in which the pulp fibers PF on the pulp fiber web PFW side penetrate into the spunbond nonwoven fabric SW below, or penetrate the spunbond nonwoven fabric SW and reach the opposite side. This action promotes the integration of the two layers.

[0039] A conveyor wire 55 is also installed in the water flow entanglement device 5. The conveyor wire 55 receives the preliminary laminate PWeb downstream of the airlaid device 2 and conveys it into the water flow entanglement device 5. The conveyor wire 55 is arranged to pass between the water jet head 51 and the suction device 52 of the water flow entanglement device 5 from upstream to downstream. Therefore, the preliminary laminate PWeb being transported on the transport wire 55 undergoes more water entanglement treatment as it moves downstream in the transport direction MD, and sufficient entanglement treatment is achieved between the upper pulp fiber web PFW layer and the lower spunbond nonwoven fabric SW layer when it leaves the water entanglement device 5.

[0040] (addition process) Immediately after exiting the water flow entanglement device 5, the composite nonwoven fabric WP is in a wet state, and the bonding between pulp fibers and other components is not yet fully established. Therefore, as shown in Figure 1, a suction device 6 and a drying device 7 are provided downstream of the water flow entanglement device 5 to perform a dewatering treatment to suck and remove moisture remaining in the pulp fiber web PFW, followed by a drying treatment to complete the production of the composite nonwoven fabric WP. By performing the dewatering treatment and drying treatment using the suction device 6 and drying device 7 in the later stages of the production of the composite nonwoven fabric WP in this way, the composite nonwoven fabric WP can be produced efficiently, and the composite nonwoven fabric WP produced after water flow entanglement can be dried without applying large external pressure.

[0041] However, as previously noted, it is necessary to create a composite nonwoven fabric WP that can reliably suppress the detachment of pulp fibers PF from the pulp fiber web PFW on the composite nonwoven fabric WP. For this reason, the manufacturing apparatus 1 is equipped with an additive device 9 for adding a chemical solution containing a wet paper strength agent and an anionic water-soluble polymer in order to suppress the detachment of pulp fibers PF (paper dust).

[0042] The manufacturing process for composite nonwoven fabric WP includes an additive step in which, after a water flow entanglement step using a water flow entanglement device 5, a chemical solution containing a wet paper strength agent and an anionic water-soluble polymer is added to the pulp fiber web PFW using an additive device 9. Furthermore, the addition process preferably includes a pre-addition dewatering step in which the composite nonwoven fabric WP (pulp fiber web PFW) described above is dewatered by a dewatering device (suction device 6) located below it, and a chemical solution addition step in which the chemical solution is added to the pulp fiber web PFW by spraying using a chemical solution addition device 9 (hereinafter also referred to as addition device 9) located downstream of the dewatering device (suction device 6).

[0043] Specifically, the suction device 6 is preferably a vacuum type that dewaters the composite nonwoven fabric WP from below after water flow entanglement, and it is preferable that an additive device 9 is provided further downstream of the suction device 6. Furthermore, in order to improve manufacturing efficiency, it is preferable that the location where the water flow entanglement device 5 is provided and the locations where the suction device 6 and additive device 9 are provided are separate. Thus, an additive device 9 is provided downstream of the suction device 6. That is, after the water flow entanglement treatment, a dewatering treatment is performed to adjust the moisture content of the composite nonwoven fabric WP, and then by adding the chemical solution to the composite nonwoven fabric WP, the fixation of the wet paper strength agent and anionic water-soluble polymer can be made uniform, and the yield of the composite nonwoven fabric WP can be ensured. Furthermore, it is possible to produce a composite nonwoven fabric WP that develops strength efficiently. Note that there may be two suction devices 6, or there may be more than two stages.

[0044] In this case, the added chemical solution contains a wetting agent and an anionic water-soluble polymer, wherein the wetting agent contains polyamide epichlorohydrin (PAE) and the anionic water-soluble polymer contains carboxymethylcellulose (CMC). By containing a wetting agent, particularly polyamide epichlorohydrin (PAE), and an anionic water-soluble polymer, particularly carboxymethylcellulose (CMC), the generation (detachment) of paper dust can be effectively suppressed when using composite nonwoven fabric WP, especially during wet wiping. As a wet-strength agent, in addition to polyamide epichlorohydrin (PAE), polyacrylamide (PAM), polyamide epoxy, and polyamide polyamine may also be included, and the anionic water-soluble polymer may contain polyacrylamide (PAM) or other materials in addition to carboxymethylcellulose (CMC). As a polyamide epichlorohydrin-based wet-strength agent, for example, paper strength agents WS4030, WS4038, WS4027 manufactured by Seikoh PMC Co., Ltd. can be used, and as carboxymethylcellulose (CMC), Sunrose manufactured by Nippon Paper Industries Co., Ltd. can be used.

[0045] Furthermore, it is preferable that the chemical solution containing the wet-strength agent is added (sprayed) to the pulp fiber web PFW by spraying from the addition device 9, as shown in Figure 1. By adding the chemical solution containing the wet-strength agent to the pulp fiber web PFW by spraying, the generation of paper dust in the composite nonwoven fabric WP to be manufactured can be effectively suppressed, while also maintaining a soft texture. Furthermore, the transport speed of the pulp fiber web (PFW) when adding the chemical solution is preferably between 100 m / min and 300 m / min.

[0046] Furthermore, in the chemical solution addition step, the ratio of the amount of anionic water-soluble polymer added to the amount of wet paper strength agent added is preferably 1.00 or more, and more preferably 1.10 or more. When the chemical solution consists of two solutions as described later, the two solutions come into contact with each other via the first adding device 91 and the second adding device 92, which may result in the accumulation of dirt in the suction device 6 and the drying device 7. However, as long as the ratio is within the above numerical range, there will be no precipitate generated by the chemical solutions coming into contact and coagulating during operation, and a soft composite nonwoven fabric WP can be manufactured without impairing the tactile feel of the composite nonwoven fabric WP. Note that the amounts of the wet paper strength agent and the anionic water-soluble polymer added are both amounts added relative to the oven-dry weight of the pulp fiber web PFW.

[0047] Then, in the chemical solution addition process, the chemical solution is added to the pulp fiber web (PFW) such that the addition rate of the anionic water-soluble polymer relative to the oven-dry weight of the pulp fiber web (PFW) is between 0.50% and 3.50%. If the addition rate is less than 0.50%, the manufactured composite nonwoven fabric is too soft, and when wiping uneven surfaces, the fibers catch on the uneven surface, making it easy for paper dust to fall off. If the addition rate exceeds 3.50%, the manufactured composite nonwoven fabric is too stiff and unsuitable for folding and other processing. Furthermore, it is preferable that the addition rate of the anionic water-soluble polymer to the oven-dry weight of the pulp fiber web (PFW) be between 1.00% and 3.50%.

[0048] Furthermore, it is preferable that the addition rate of the wet paper strength agent relative to the oven-dry weight of the pulp fiber web (PFW) be 2.50% or less. If the addition rate exceeds 2.50%, the nozzle is more likely to clog during the chemical solution addition process. Furthermore, it is more preferable that the addition rate of the wet paper strength agent to the oven-dry weight of the pulp fiber web (PFW) be between 0.45% and 2.40%.

[0049] Furthermore, in the drug solution addition step, it is preferable to spray the drug solution in two separate applications, as shown in Figure 1. In other words, it is preferable that both the first and second chemical solutions are added to the pulp fiber web (PFW) by spray spraying using an additive device 9 (first additive device 91 and second additive device 92) located downstream of the suction device 6. The spray spraying of the chemical solution may be in one stage (one solution) or in two or more stages (two or more solutions). In particular, in the case of adding two solutions (divided into two stages), although a large amount of chemical solution flows out without settling, nozzle clogging is reduced because the chemical solution is dispersed, and composite nonwoven fabric (WP) can be manufactured efficiently.

[0050] Furthermore, in the chemical solution addition step in which the chemical solution is added to the pulp fiber web PFW by spray spraying using the addition device 9, the chemical solution to be sprayed may be a mixture of a wetting force agent and an anionic water-soluble polymer, or it may be two chemical solutions containing the wetting force agent and the anionic water-soluble polymer separately without mixing. Furthermore, if there are two chemical solutions, in the two-step spray application described above, it is preferable to add one chemical solution containing a wetting paper strength agent to the pulp fiber web (PFW) by spray application using the first adding device 91, and then, within 2 seconds, add the other chemical solution containing an anionic water-soluble polymer to the pulp fiber web (PFW) by spray application using the downstream second adding device 92. By keeping the addition interval to within 2 seconds, the two types of chemical solutions can be effectively retained within the nonwoven fabric.

[0051] (Drying and winding process) Further downstream of the suction device 6 and additive device 9, a drying device 7 is installed to dry the composite nonwoven fabric WP, which has a pulp fiber web PFW to which a wet paper strength agent has been added. The drying device 7 here is preferably a non-compression type dryer, preferably an air-through dryer. In Figure 1, the rotatable dryer body 71 of the air-through dryer is cylindrical, and numerous through holes are provided on its circumferential surface, and it is preferable that hot air heated by a heat source (not shown) is drawn in from the outer circumference of the dryer body 71 toward the center. In this way, the composite nonwoven fabric WP, which is continuously manufactured, is wound onto the roll 81 of the winding device 8 after drying.

[0052] As described above, according to this embodiment, in a method for manufacturing a composite nonwoven fabric that employs an airlaid method and adds a wetting paper strength agent and an anionic water-soluble polymer (carboxymethylcellulose) to a chemical solution, it is possible to provide a method for manufacturing a composite nonwoven fabric that has appropriate stiffness, can be wiped while maintaining its shape, has significantly less fiber snagging when wiping uneven surfaces, can effectively suppress the generation of paper dust after wiping when wet, and has excellent processability. [Examples]

[0053] The present invention will be described in more detail by the following examples and comparative examples, but the present invention is not limited in any way by the following examples.

[0054] Under the conditions shown in Tables 1 and 2, composite nonwoven fabrics for Examples 1-6 and Comparative Examples 1-6 were manufactured and evaluated as follows.

[0055] In addition to the evaluations below, the proportion of gel-like precipitates generated when the sprayed chemical solutions were mixed was measured. The proportion of gel-like precipitates was quantified by preparing chemical solutions (1) and (2) adjusted to the "spray chemical addition concentrations" shown in Tables 1 and 2, mixing 100g of each, stirring with a stirrer, and then letting it stand for 5 minutes before the gel substance was generated. Percentage of gel-like precipitate (%) = Weight of the gel-like precipitate that was generated (g) ÷ (100g of solution (1) adjusted to the concentration of spray chemical added + 100g of solution (2) adjusted to the concentration of spray chemical added) × 100

[0056] (1) Operability (gel formation during mixing) In the manufacturing of composite nonwoven fabrics, the (continuous) operability was evaluated in terms of gel generation during mixing when a wetting force agent and an anionic water-soluble polymer were used as chemicals. Excellent (◎): No gel-like precipitate is generated, and continuous operation is possible. Acceptable (○): Minor gel-like precipitate formation is observed. Unacceptable (×): Gel-like precipitates will form, increasing the burden of cleaning.

[0057] (2) Nozzle clogging During the manufacturing of composite nonwoven fabrics, operability was evaluated in terms of the clogging of spray nozzles when chemicals were added. Excellent (○): No nozzle clogging occurs, and continuous operation is smooth. Not possible (×): Nozzle clogging is likely to occur, requiring the machine to be stopped to resolve the issue.

[0058] (3) Processing suitability The processing suitability of the manufactured composite nonwoven fabric for folding was evaluated. Excellent (○): It has just the right amount of stiffness and can be folded without any problems. Unacceptable (×): It's too stiff to be folded.

[0059] (4) Appropriate hardness when wiping The manufactured composite nonwoven fabric was used as a wiper, and its workability when wiping objects was (sensory) evaluated. Excellent (◎): This composite nonwoven fabric has good resilience and excels at wiping objects on the target surface. Acceptable (○): This is a composite nonwoven fabric that has some stiffness and does not easily curl up when wiping objects. Unsuitable (×): This composite nonwoven fabric is not suitable for wiping objects because it lacks stiffness, tends to curl up, and is not suitable for that purpose.

[0060] (5) Amount of paper dust after wiping when wet The generation of paper dust after wiping in a wet state of the manufactured composite nonwoven fabric was visually evaluated. Excellent (◎): The amount of residual paper dust is low and the quality is good. Acceptable (○): The amount of residual paper dust is worse than the "Excellent" condition, and some users may deem it unusable. Unacceptable (×): The amount of residual paper dust is noticeably high, making it unsuitable for use.

[0061] (6) Amount of paper dust after wiping the uneven surface The generation of paper dust after wiping the uneven surface of the manufactured composite nonwoven fabric was visually evaluated. Excellent (◎): The amount of residual paper dust is low and the quality is good. Acceptable (○): The amount of residual paper dust is worse than the "Excellent" condition, and some users may deem it unusable. Unacceptable (×): The amount of residual paper dust is noticeably high, making it unsuitable for use.

[0062] (7) Overall evaluation For all evaluation items, the manufacturing methods of each example and comparative example were scored on a four-point scale based on the following criteria. A total evaluation of 3 or higher was considered a passing grade, as it indicates a manufacturing method capable of providing composite nonwoven fabrics with good yield. 1 point: Manufacturing method that makes continuous operation impossible 2 points: The nonwoven fabric manufacturing method has good continuous operation capabilities, but other evaluation items are unsatisfactory. 3 points: A nonwoven fabric manufacturing method that allows for continuous operation. 4 points: Excellent for continuous operation, but slightly inferior for wiping uneven surfaces. 5 points: A nonwoven fabric manufacturing method that exhibits excellent continuous operation and excels in all other evaluations.

[0063] The results of each of the above evaluations are shown in Tables 1 and 2. [Table 1]

[0064] [Table 2]

[0065] Based on the above, it has been confirmed that, according to the manufacturing method of this embodiment, even when an airlaid method is adopted and a wetting paper strength agent and an anionic water-soluble polymer (carboxymethylcellulose) are added to the chemical solution in combination, a composite nonwoven fabric can be obtained that has appropriate stiffness, can be wiped while maintaining its shape, has significantly less fiber snagging when wiping uneven surfaces, can effectively suppress the generation of paper dust after wiping when wet, and has excellent processability. [Explanation of Symbols]

[0066] 1. Manufacturing equipment (for composite nonwoven fabrics) 2. Air Raid Device 3. Spunbond nonwoven fabric feeding device 4, 6, 52 Suction device 5 Hydro-entangling device 7 Drying equipment 8 Winding device 9, 91, 92 Addition equipment 21. Fiber defibring machine 22 ducts 23 Air Raid Hopper 24 Stacking position 41 Suction device body 42 Suction section 43, 55 Conveyor wire 51 Water Jet Head 71 Hair dryer unit 81 rolls SW Spunbond Nonwoven Fabric PF pulp fiber PFW pulp fiber web PWeb (Preliminary Stacked Web) WP composite nonwoven fabric MD transport direction CD width direction

Claims

1. A method for producing a composite nonwoven fabric, comprising at least a nonwoven fabric and a pulp fiber web manufactured by an airlaid method, A water flow entanglement step in which the nonwoven fabric and the pulp fiber web are subjected to water flow entanglement treatment, The addition step includes, after the water flow entanglement step, adding a chemical solution containing a wet paper strength agent and an anionic water-soluble polymer to the pulp fiber web. The wet-strength agent contains polyamide epichlorohydrin (PAE), and the anionic water-soluble polymer contains carboxymethylcellulose (CMC). A method for producing a composite nonwoven fabric, characterized in that, in the addition step, the ratio of the amount of anionic water-soluble polymer added to the amount of wet paper strength agent added is 1.00 or more, and the addition rate of the anionic water-soluble polymer to the oven-dry weight of the pulp fiber web is 0.50% or more and 3.50% or less, by which time the chemical solution is added to the pulp fiber web.

2. The method for producing a composite nonwoven fabric according to claim 1, characterized in that, in the addition step, the chemical solution is added to the pulp fiber web such that the addition rate of the anionic water-soluble polymer relative to the oven-dry weight of the pulp fiber web is 1.00% or more and 3.50% or less.

3. A method for producing a composite nonwoven fabric according to claim 1, characterized in that, in the addition step, the chemical solution is added to the pulp fiber web such that the ratio of the amount of anionic water-soluble polymer added to the amount of wet paper strength agent added is 1.10 or more.

4. The aforementioned addition step includes a pre-addition dewatering step in which the composite nonwoven fabric is dewatered by a dewatering device provided on the lower side, A method for producing a composite nonwoven fabric according to claim 1, characterized by comprising a chemical solution addition step of adding the chemical solution to the pulp fiber web by spraying using an additive device provided downstream of the dewatering device.

5. In the aforementioned chemical solution addition step, the chemical solution is added in two separate steps, both by spray application. The method for producing a composite nonwoven fabric according to claim 4, characterized in that both the first and second chemical solutions are added to the pulp fiber web by the addition device provided downstream of the dewatering device.

6. The method for producing a composite nonwoven fabric according to claim 4, characterized in that, in the chemical solution addition step, the chemical solution is a mixture of the wetting paper strength agent and the anionic water-soluble polymer, and is added to the pulp fiber web by spray spraying using the addition device.

7. The method for producing a composite nonwoven fabric according to claim 4, characterized in that, in the chemical solution addition step, the chemical solution consists of two chemical solutions, each containing the wetting paper strength agent and the anionic water-soluble polymer separately without being mixed, and each is added to the pulp fiber web by spray spraying using a separate addition device.

8. The method for producing a composite nonwoven fabric according to claim 7, characterized in that, in the chemical solution addition step, one chemical solution containing the wetting paper strength agent is added to the pulp fiber web by spray spray using the addition device, and then within 2 seconds, the other chemical solution containing the anionic water-soluble polymer is added to the pulp fiber web by spray spray using the addition device.

9. The aforementioned nonwoven fabric is a spunbond nonwoven fabric. The method for producing a composite nonwoven fabric according to claim 1, characterized in that the water flow entanglement step involves subjecting the spunbond nonwoven fabric and the pulp fiber web manufactured by the airlaid method, which is placed thereon, to a water flow entanglement treatment.

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