JP7764210B2 - nonwoven fabric - Google Patents

Description

The present invention relates to nonwoven fabrics formed by essentially containing pulp fibers, such as nonwoven fabrics formed solely from a pulp fiber web and composite nonwoven fabrics made from a pulp fiber web and a spunbond nonwoven fabric.

For example, composite nonwoven fabrics made from a pulp fiber web and a spunbond nonwoven fabric have both the absorbency of the pulp fibers and the strength of the spunbond nonwoven fabric, and are therefore widely used in a variety of applications, including industrial wipers such as rags, and personal wipers such as hand towels and towels.

For example, as disclosed in Patent Document 1, a pulp fiber web and a spunbond nonwoven fabric are layered together and then integrated by a hydroentanglement process in which a high-pressure water jet (water flow) is sprayed onto them. The spunbond nonwoven fabric has excellent strength and therefore functions as a backing layer for the resulting composite nonwoven fabric. Meanwhile, the pulp fiber web has excellent liquid absorption properties. Therefore, such a composite nonwoven fabric can be offered to consumers as an excellent composite nonwoven fabric that combines the advantages of a pulp fiber web, which has good absorbency for both aqueous and oily liquids, and a spunbond nonwoven fabric, which has excellent strength.

Patent No. 2533260

The above-mentioned composite nonwoven fabric contains a pulp fiber web, and therefore has the characteristic of excellent liquid absorption when in use. However, the shedding of paper powder (fine fibers) from the pulp fiber web during both dry and wet use is recognized as a problem that needs to be improved.
In regard to this, it has been known that the falling off of paper powder can be suppressed by using a wet method or a press treatment, but this causes new problems such as a decrease in the liquid absorption capacity of the pulp fiber web.
Furthermore, although technology to suppress paper dust using chemicals is being established, the nonwoven fabric itself becomes hard, which causes a prickly feeling and a poor texture (hereinafter referred to as "smoothness"), making it unsuitable for wiping the human body and limiting its use to cleaning, etc. Furthermore, the increased stiffness also causes the problem of poor suitability for processing in interfolder processing machines, etc.
Naturally, the same problems arise in the case of a nonwoven fabric formed solely from a pulp fiber web.

The object of the present invention is therefore to provide a nonwoven fabric that suppresses paper dust, maintains sufficient liquid absorption, and has excellent smoothness and processability, regardless of whether it is used in a dry or wet state.

The object of the present invention is to provide a nonwoven fabric essentially containing a pulp fiber web produced by an airlaid method,
The pulp fiber web has a basis weight of 30 g/m ² or more and 80 g/m ² or less,
the pulp fiber web contains a wet strength agent and an anionic water-soluble polymer, the wet strength agent being polyamide epichlorohydrin (PAE);
the amount of the wet strength agent added is 0.35% by weight or more and the amount of the anionic water-soluble polymer added is 0.1% by weight or more relative to the bone dry weight of pulp fibers in the pulp fiber web;
This can be achieved by a nonwoven fabric characterized in that the rigidity of the pulp fiber web in the MD direction is 75 mm or less in length measured in accordance with the 45° cantilever method based on JIS L 1096.

The KES_MMD value, which is an index used to evaluate the smoothness of a nonwoven fabric, is preferably less than 0.0090, and more preferably 0.0060 or less.

The anionic water-soluble polymer is preferably carboxymethyl cellulose (CMC).
It is preferable that the water absorption (T.W.A.) is 300 g/m ² or more.

It can also be a composite type that further includes a spunbond nonwoven fabric, with the pulp fiber web laminated and integrated onto the spunbond nonwoven fabric.

The object of the present invention is to provide a method for producing a nonwoven fabric according to any one of the above-mentioned methods,
a hydroentangling step of subjecting the pulp fiber web to a hydroentangling treatment by spraying a water stream onto the pulp fiber web;
The object can also be achieved by a method for producing a nonwoven fabric, which comprises at least an addition step of adding the wet strength agent and the anionic water-soluble polymer to the pulp fiber web after the hydroentanglement step.

This invention suppresses the generation of paper dust in both dry and wet conditions, while maintaining sufficient liquid absorption, and provides a nonwoven fabric that is smooth and has excellent processability.

1 is a diagram showing an apparatus suitable for producing a nonwoven fabric according to the present invention.

The nonwoven fabric according to the present invention will be described below.
The present inventors have confirmed that a nonwoven fabric designed by incorporating a predetermined amount of a wet strength agent and an anionic water-soluble polymer into a pulp fiber web having a relatively low basis weight and by designing the nonwoven fabric so that the rigidity in the MD direction (the machine direction during web production, i.e., the conveying direction during production) is a predetermined value or less in length measured in accordance with the 45° cantilever method based on JIS L 1096, can suppress fiber shedding (paper dust), maintain sufficient liquid absorbency, and also have excellent smoothness and processability, thereby arriving at the present invention.
The nonwoven fabric formed by essentially containing the pulp fiber web of the present invention may be a nonwoven fabric formed only from the pulp fiber web, or may be a composite nonwoven fabric containing a spunbond nonwoven fabric together with the pulp fiber web.

The basis weight of the pulp fiber web is preferably 30 g/ ^m2 or more and 80 g/ ^m2 or less. If the basis weight is less than 30 g/ ^m2 , the amount of pulp used is too small, resulting in noticeable unevenness and a poor surface condition. Conversely, if the basis weight is more than 80 g/ ^m2 , the thickness increases, making it difficult to adjust the stiffness within an appropriate range.

It is preferable that the wet strength agent is added in an amount of 0.35% by weight or more based on the bone dry weight of the pulp fibers in the pulp fiber web, and the anionic water-soluble polymer is added in an amount of 0.1% by weight or more based on the bone dry weight of the pulp fibers in the pulp fiber web.
More specifically, it is preferable that the amount of the wet strength agent added is 0.35 to 2.00 wt % and the amount of the anionic water-soluble polymer added is 0.1 to 1.00 wt % relative to the bone dry weight of the pulp fibers. If the amounts of the wet strength agent and the anionic water-soluble polymer added are too large and exceed the above ranges, the manufacturing equipment becomes noticeably soiled, making it difficult to stably supply and transport the nonwoven fabric during the manufacturing process.
The wet strength agent is preferably polyamide epichlorohydrin (PAE), which is known as a wet strength agent in the papermaking process, and the anionic water-soluble polymer is preferably carboxymethyl cellulose (CMC).

The nonwoven fabric of the present invention contains a wet strength agent and an anionic water-soluble polymer on the pulp fiber web side. This not only provides water resistance to cellulose (pulp fibers) through the commonly known self-crosslinking of the wet strength agent and strengthens hydrogen bonds between cellulose (pulp fibers) through the anionic water-soluble polymer, but also allows the wet strength agent and the anionic water-soluble polymer to form a crosslinked structure, allowing the wet strength agent to function (act) effectively, effectively preventing pulp fiber shedding while maintaining water absorption performance.

Furthermore, the pulp fiber web of the present invention also ensures suitability for processing by setting the rigidity in the MD direction to a predetermined value or less.
The pulp fiber web is preferably set so that the length measured in accordance with the cantilever method at an angle of 45° based on JIS L 1096 is 75 mm or less. Here, the measurement value by the cantilever method is the average value of the front and back of the pulp fiber web.
For nonwoven fabrics with a cantilever measurement of 75 mm or less, an upper limit on stiffness is set, so that the processability does not deteriorate when processed with an interfolder processing machine, etc. If the stiffness of the nonwoven fabric becomes higher than the preferred range, it becomes more likely to curl up on the cylinder of the processing machine, making it difficult to create uniform creases, and if the stiffness becomes excessively high, there will be a high incidence of defective processed products being mixed into the product.
The stiffness of the pulp fiber web in the MD direction can be adjusted by, for example, the type and basis weight of spunbond, the type and addition rate of chemicals used, the type of pulp, and the fiber orientation.

In the pulp fiber web of the present invention, the KES (Kawabata Evaluation System)_MMD value, which is an index for judging the smoothness of a nonwoven fabric, is set to less than 0.0090, and more preferably 0.0060 or less. KES is a system developed by Dr. Toshio Kawabata, and is an effective index for distinguishing "smoothness (also known as "handle")," the sensation felt by people when they touch something. It is a technology that can measure the smoothness of a nonwoven fabric by replacing subjective and vague judgments of physical properties with objective numerical data that can be shared by anyone.
In the present invention, the KES MMD (mean deviation of the coefficient of friction) is used to evaluate the smoothness of a pulp fiber web. This KES_MMD indicates the degree of variation in the coefficient of friction; a high value indicates a large variation in the coefficient of friction, meaning that there are many smooth and non-smooth areas. On the other hand, a low value indicates a small variation in the coefficient of friction, meaning that the surface is relatively uniform, i.e., smooth. By achieving a uniform surface, it is believed that prickly sensations such as fuzzing are reduced.
The KES_MMD value can be measured, for example, using a "KES-SE (friction feel tester)" tester manufactured by Kato Tech Co., Ltd., and the KES_MMD value can be adjusted to be less than 0.0090 by, for example, subjecting the pulp fiber web to a calendar treatment to smooth the surface so that it is uniform.

A composite nonwoven fabric formed by including a spunbond nonwoven fabric together with a pulp fiber web will be described below as a preferred embodiment of the nonwoven fabric of the present invention.
A manufacturing apparatus suitable for manufacturing a composite nonwoven fabric will be described with reference to FIG.
The schematic configuration of a composite nonwoven fabric manufacturing apparatus 1 will be described. The manufacturing apparatus 1 shown in Figure 1 is provided with an airlaid device 2 for supplying a pulp fiber web on the upstream side, a spunbond nonwoven fabric supplying device 3 for supplying a spunbond nonwoven fabric, and a suction device 4. The suction device 4 is disposed below the airlaid device 2 so as to face it.
In the web conveyance direction MD, downstream of these devices 2, 3, and 4 are arranged, in this order from the upstream side, a hydroentangling device 5 that sprays water jets for hydroentangling, a suction device 6 that performs dehydration, and a dryer 7. Downstream of the dryer 7 is provided a winding device 8 for winding up the continuously produced composite nonwoven fabric (hereinafter also referred to as composite nonwoven fabric WP).
1 shows a preferred example in which a spunbond nonwoven fabric supplying device 3 is provided to produce a composite nonwoven fabric using a spunbond nonwoven fabric. However, the present invention is not limited to this example, and it is also possible to obtain a nonwoven fabric made only of a pulp fiber web by changing the design of the equipment so that pulp fibers are supplied directly onto the conveying wire without using a spunbond nonwoven fabric.

The airlaid device 2 includes a defibrator 21 that defibrates raw pulp RP, which is a sheet of densely packed fibers, into pulp fibers, and a duct 22 equipped with a blower (not shown) that transports the defibrated pulp fibers PF to an airlaid hopper 23.

An airlaid hopper 23 is disposed downstream of the duct 22. Inside the airlaid hopper 23, the pulp fibers in a defibrated state descend while being dispersed, and are designed to gradually pile up at a stacking position 24 set on the bottom surface to form a pulp fiber web PFW.
As described above, the airlaid apparatus 2 is equipment capable of supplying a pulp fiber web by a dry process, and can reduce equipment costs compared to an apparatus that produces a pulp fiber web by a wet process using a wet papermaking method. Furthermore, in the airlaid apparatus 2, the entire process from pulp defibration to dispersion and descent is a closed space, preventing the inclusion of foreign matter, and therefore the inclusion of foreign matter can be kept significantly lower than when a pulp fiber web is supplied by a wet papermaking method.

A suction device 4 is disposed below and facing the stacking position 24. More specifically, the suction device 4 has a suction section 42 on the upper surface of a device body 41, and the suction section 42 is set with respect to the stacking position 24 so as to apply a suction force (negative pressure) to the pulp fiber web PFW.
1 illustrates an example in which the pulp fiber web PFW is formed by arranging one airlaid hopper 23 and one suction device main body 41 in a single stage. However, the present invention is not limited to this, and the airlaid hopper 23 and the suction device main body 41 may be arranged in two or more stages depending on the basis weight (basis weight) of the pulp fiber web PFW and the production speed.

A transport wire 43 for transporting the web is disposed around the suction device 4. The transport wire 43 is disposed so that the pulp fiber web PFW, on which the pulp fibers PF have been accumulated at the stacking position 24, can be placed and transports the web downstream. However, the pulp fiber web PFW is not placed directly on the transport wire 43. This will become clear in the following description.
The conveying wire 43 is formed in an open mesh form so that the suction force of the suction portion 42 reaches the opposite side (upper side).

A spunbond nonwoven fabric supplying device 3 is located below the airlaid device 2, upstream of the suction device 4. A roll of pre-prepared spunbond nonwoven fabric SW is set in this spunbond nonwoven fabric supplying device 3. As mentioned above, the designed spunbond nonwoven fabric SW is wound into a roll during production, and this roll is pulled out of the spunbond nonwoven fabric supplying device 3 and transported to the stacking position 24 on the transport wire 43 described above.

The pulp fiber web PFW described above is placed on the spunbond nonwoven fabric SW located at the stacking position 24. At this time, the suction force from the suction section 42 of the suction device 4 passes through the conveying wire 43 at the stacking position 24 and acts on the spunbond nonwoven fabric SW and the pulp fiber web PFW thereon. Thus, the preliminary laminate PWeb (laminate web) in which the spunbond nonwoven fabric SW and the pulp fiber web PFW are laminated is conveyed downstream.
By controlling the amount of pulp fiber web PFW supplied onto the spunbond nonwoven fabric SW when the preliminary laminate PWeb is formed as described above, the basis weight of the pulp fiber web PFW included in the composite nonwoven fabric produced by this apparatus is set to, for example, 30.0 to 80.0 g/ ^m² , which is lower than the basis weight of the pulp fiber web in conventional composite nonwoven fabrics. The basis weight of the spunbond nonwoven fabric SW is, for example, 10.0 to 40.0 g/ ^m² , and the composite nonwoven fabric (spunbond nonwoven fabric SW + pulp fiber web PFW) produced has a basis weight of, for example, 40.0 to 120.0 g/ ^m² . The basis weight can be set to fall within the desired range by appropriately adjusting the conveying speed of the pulp fiber web and the hourly supply amount of the pulp fiber web PFW, and checking the basis weight of the pulp fiber web PFW of the produced composite nonwoven fabric. The transport speed of the pulp fiber web is preferably set to, for example, 150 to 300 m/min.

The above-described preliminary laminate PWeb is maintained in a laminated state by being suction-compressed by the suction force of the suction device 4. At this time, the fibers of the upper pulp fiber web PFW are in a dense state. However, if the preliminary laminate PWeb is transported and introduced into the downstream hydroentangling device 5 in this state, there is a risk that some of the pulp fibers PF will be blown up by the water jet (high-pressure water flow).
Therefore, the present manufacturing apparatus 1 is provided with clamping rollers 28 for sandwiching the preliminary laminate PWeb from above and below to stabilize the state in which the pulp fiber web PFW is placed on the spunbond nonwoven fabric SW, and a pre-wetting device 30 for applying moisture to prevent fiber scattering upstream of the hydroentangling device 5. The pre-wetting device 30 preferably includes a spray nozzle 31 for spraying water mist from above the preliminary laminate PWeb, and a suction device 32 for applying suction force from below the preliminary laminate PWeb (i.e., the lower surface of the pulp fiber web PFW).

1 illustrates the case where the pre-wetting device 30 is provided as a new device before the hydroentangling device 5 as described above, but the present invention is not limited to this. The hydroentangling device 5 may be designed so that the first set of multiple sets, each consisting of a water jet head 51 and a suction device 52 (described later), is used as the pre-wetting device 30. In this case, adjustments may be made so that low-pressure water mist is sprayed from the first water jet head 51.
In the case of a hydroentanglement device 5 that has a sufficient number of sets of water jet heads 51 and suction devices 52 to perform hydroentanglement processing, using the leading water jet head 51 and suction device 52 as pre-wetting devices as described above is effective in reducing equipment costs.

The hydroentangling device 5 promotes entanglement of the pulp fibers by spraying high-pressure water jets onto the preliminary laminate PWeb, which has been processed by the clamping rollers 28 and the pre-wetting device 30, which serve as the pre-treatment section. This promotes integration of the upper pulp fiber web PFW layer and the lower spunbond nonwoven fabric SW layer (hydroentangling treatment).
The hydroentangling device 5 exemplarily shown in FIG. 1 has water jet heads 51 arranged in multiple stages (four stages are shown in FIG. 1) along the conveyance direction MD.
1 does not show the nozzles provided on the water jet head 51 extending in a direction perpendicular to the conveying direction MD (the width direction CD of the web), but multiple water jet nozzles are arranged at appropriate positions in the width direction. The hole diameter φ of these water jet nozzles is preferably 0.06 to 0.15 mm. The spacing between the water jet nozzles is preferably 0.4 to 1.0 mm.

The water pressure of the jets used in the hydroentanglement process is preferably set taking into account the basis weights of the pulp fiber web PFW and the spunbond nonwoven fabric SW. For example, it is preferable to select a pressure in the range of 1 to 30 MPa.

A suction device 52 is disposed opposite the water jet head 51. A 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 believed that the combined action of the water jet head 51 and the suction device 52 creates a state in which the pulp fibers on the pulp fiber web PFW side penetrate into the spunbond nonwoven fabric SW located below, or penetrate through the spunbond nonwoven fabric SW to the opposite side. This action promotes integration of the two layers.

A conveying wire 55 is also provided in the hydroentangling device 5. The conveying wire 55 receives the preliminary laminate PWeb downstream of the pre-treatment units 28 and 30 and conveys it into the hydroentangling device 5. The conveying wire 55 is provided so as to pass between the water jet head 51 and the suction device 52 of the hydroentangling device 5 from the upstream side to the downstream side.
Therefore, the preliminary laminate PWeb transported on the transport wire 55 undergoes more hydroentangling treatment as it moves downstream in the transport direction MD, and by the time it leaves the hydroentangling device 5, sufficient entangling treatment is achieved between the upper pulp fiber web PFW layer and the lower spunbond nonwoven fabric SW layer.
Immediately after leaving the hydroentangling device 5, the composite nonwoven fabric is in a wet state, and the bonds between the pulp fibers etc. are not yet sufficiently established.

1, a suction device 6 and a dryer 7 are provided downstream of the hydroentanglement device 5 to perform a dehydration process to suck and remove moisture remaining in the pulp fiber web, followed by a drying process to complete the production of the composite nonwoven fabric WP. By performing the dehydration process and drying process using the suction device 6 and the dryer 7 in this manner in the latter stages of the production of the composite nonwoven fabric WP, the composite nonwoven fabric can be produced efficiently, and the dried composite nonwoven fabric can be produced without applying a large external pressure to the hydroentangled composite nonwoven fabric to be produced.
However, as previously pointed out, it is necessary to produce a composite nonwoven fabric that can reliably prevent fine pulp fibers (paper dust) from falling off from the pulp fiber web on the composite nonwoven fabric WP. For this reason, the manufacturing apparatus 1 is provided with an additive device 9 for adding an agent to prevent the pulp fibers from falling off.

The suction device 6 is, for example, a vacuum type, and dehydrates the hydroentangled composite nonwoven fabric from below. An addition device 9 for adding a wet strength agent is disposed above the suction device 6, with the composite nonwoven fabric WP being conveyed between them.
The adding device 9 adds a mixed additive, which is a mixture of a wet strength agent and an anionic water-soluble polymer, to the upper side of the composite nonwoven fabric WP after compounding in the hydroentanglement device 5, i.e., the pulp fiber web PWF. Because the mixed additive is added from the outside to the surface of the pulp fiber web of the composite nonwoven fabric after compounding, the mixed additive acts efficiently to connect the pulp fibers together. Because a drying process is performed downstream of the adding device 9, there is no waste such as the added mixed additive being washed away.
In addition, the presence of a suction device on the lower side facilitates the penetration of the mixed additive into the pulp fiber web, thereby more reliably preventing the pulp fibers from falling off. The addition is performed by spray application, which further facilitates the penetration of the mixed additive in the form of a sprayed liquid into the pulp fiber web. Furthermore, the addition device 9 also makes it easy to check the state of the composite nonwoven fabric WP being produced and control the amount of mixed additive.
It is preferable to adjust the moisture content of the pulp fiber web PWF (inlet moisture % immediately before entering the adding device 9) to 120 to 400% when the mixed additive is sprayed in the adding device 9.

Furthermore, it is preferable to perform dehydration treatment within 10 seconds after spray application of the mixed additive. That is, dehydration may be performed immediately after spray application of the mixed additive as described above with reference to Fig. 1, or at a position slightly away from the spray application (a position within 10 seconds of conveyance time). In short, the optimal time (however, within 10 seconds after spray application) can be appropriately determined by checking the penetration and diffusion state of the chemical solution into the pulp fiber web PWF when the mixed additive is spray applied.
The additive mixture can be added using known devices such as spray coating, size press, roll coating, gravure coating, rod bar coating, air knife coating, etc., as the adding device 9. Although not particularly limited, spray coating is preferred.
The above-described application device 9 has been described as a preferred example in which a mixed additive, in which a wet strength agent and an anionic water-soluble polymer are premixed, is applied to the pulp fiber web PWF. However, the application method is not limited to this. The wet strength agent and the anionic water-soluble polymer may be applied separately to the pulp fiber web PWF. In this case, the application device 9 is configured as an apparatus including both a first application device for applying the wet strength agent and a second application device for applying the anionic water-soluble polymer. Here, the first application device and the second application device may simultaneously apply their respective chemicals (wet strength agent and anionic water-soluble polymer), or the first application device and the second application device may be slightly offset from each other in the web transport direction. In this case, spray application is also preferred.

The wet strength agent and the anionic water-soluble polymer are preferably added to the pulp fiber web PWF so that the amount of each added, calculated as a solid content, falls within a predetermined range relative to the bone-dry weight of the pulp fibers in the pulp fiber web PWF. Specifically, the amount of the wet strength agent added is 0.35% by weight or more, preferably 0.35 to 2.00% by weight, relative to the bone-dry weight of the pulp fibers in the pulp fiber web. The amount of the anionic water-soluble polymer added is 0.1% by weight or more, preferably 0.1 to 1.0% by weight, more preferably 0.2 to 0.8% by weight, relative to the bone-dry weight of the pulp fibers in the pulp fiber web.
By setting an upper limit for the amount of chemicals to be added as described above, it is possible to prevent the problem of chemicals accumulating on the manufacturing equipment and causing worsening contamination.
Furthermore, when spray-applied, the mixed additive is preferably sprayed onto the pulp fiber web PWF at a concentration of 0.1 to 2.5%, more preferably 0.7 to 1.5%, and at a discharge pressure of 0.1 to 1.5 MPa, more preferably 0.3 to 0.8 MPa. If the pressure is too low, the mixed additive will be scattered by the wind generated by the pulp fiber web being transported, reducing yield and making it difficult to effectively suppress paper dust shedding. On the other hand, if the pressure is too high, the mixed additive will bounce off the surface of the pulp fiber web being transported, which also reduces yield and reduces the effectiveness of suppressing paper dust shedding.
As described above, it is preferable to use polyamide epichlorohydrin (PAE), which is known as a wet strength agent in the papermaking process, as the wet strength agent. The solids concentration of polyamide epichlorohydrin (PAE) in this wet strength agent is 10 to 40 wt%, more preferably 20 to 30 wt%. Other wet strength agents that can be used include melamine resins.
As mentioned above, it is preferable to use carboxymethyl cellulose (CMC) as the anionic water-soluble polymer. By using these two types, fiber shedding can be effectively prevented and a composite nonwoven fabric with sufficient water absorbency can be obtained.

A drying device 7 is further installed downstream of the suction device 6 and the adding device 9, where the composite nonwoven fabric WP including the pulp fiber web PWF spray-coated with the mixed additive is dried. The drying device 7 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 a cylindrical body with a number of through-holes on its circumferential surface, and hot air heated by a heat source (not shown) is preferably sucked from the periphery toward the center of the dryer body.
The composite nonwoven fabric WP thus continuously produced is dried and then wound around the roll 81 of the winding device 8.
As described above, a composite nonwoven fabric according to the present invention that exhibits minimal pulp fiber shedding and maintains sufficient water absorption can be obtained by using the manufacturing apparatus 1. The thickness of the finished nonwoven fabric is preferably 0.20 mm or more and 0.75 mm or less for a basis weight of, for example, 40.0 to 120.0 g/ ^m2 .
As shown in Fig. 1, a calendering device CA may be further disposed between the drying device 7 and the winding device 8 so that the pulp fiber web can be calendered. By calendering the pulp fiber web, the smoothness of the nonwoven fabric described above can be increased. Although the calendering may be performed by a separately provided calendering device, the online arrangement shown in Fig. 1 is advantageous in terms of equipment costs and production costs.

(Example)
Examples and comparative examples in which the nonwoven fabric according to the present invention is a composite nonwoven fabric containing a spunbonded nonwoven fabric will be described below.
The wet strength agent added to the pulp fiber web of the composite nonwoven fabric was polyamide epichlorohydrin (PAE), and the anionic water-soluble polymer was carboxymethyl cellulose (CMC). The amounts of each added, as well as the basis weight, measurements taken using a 45° cantilever method (average values of the front and back surfaces), and KES_MMD values were as shown in Table 1 for the composite nonwoven fabrics of Examples 1 to 6, and for Comparative Examples 1 to 8, as shown in Table 2. The amount of paper powder, processability (number of times curling occurred), smoothness, and liquid absorption performance (amount of water absorbed) were confirmed and comprehensively evaluated.

1) Amount of paper dust after wiping in a dry state (visual inspection)
The generation of paper dust was evaluated by 10 monitors.
The amount of residual paper dust is small and good (Excellent ◎)
The amount of residual paper dust is worse than excellent, to the point where some users may judge it to be unusable (good).
The amount of residual paper dust is noticeable and it is unsuitable for use (Not acceptable).
2) Amount of paper dust after wiping in a wet state (visual inspection)
The generation of paper dust was evaluated by 10 monitors.
The amount of residual paper dust is small and good (Excellent ◎)
The amount of residual paper dust is worse than excellent, to the point where some users may judge it to be unusable (good).
The amount of residual paper dust is noticeable and it is unsuitable for use (Not acceptable).

3) A sample that showed less than one curl per minute (<1) on the processing machine was judged to be suitable for processing. A sample with a cantilever measurement of 75 mm or less was deemed to be suitable for processing.
4) The smoothness of the nonwoven fabric was evaluated by sensory testing. Nonwoven fabrics rated as smooth had a KES_MMD value of less than 0.0090, while those rated as even smoother had a KES_MMD value of 0.0060 or less.
It feels smooth to the touch and is not prickly (Excellent)
The prickly feeling on the skin when touched is reduced (OK)
It feels prickly when you touch it (poor △)

5) Liquid absorption performance was evaluated by preparing test pieces from the nonwoven fabric and evaluating the amount of water absorbed.
The water absorption (T.W.A.) was determined as follows. First, a nonwoven fabric was cut into a 75 x 75 mm square to prepare a sample piece, and its dry weight was measured. Next, this sample piece was immersed in distilled water for 2 minutes, and then hung in a steam-saturated container in a stretched state (100% RH) with one corner of the sample piece positioned at the top, and this top and the two adjacent corners supported. After leaving for 30 minutes, the weight after draining was measured. Paper towels cut to 3 x 38 mm were used for draining. The measured value was then converted into the water retention capacity (g/ ^m2 ) per 1 ^m2 of the sample piece. Nonwoven fabrics with a water absorption capacity of less than 300 g/ ^m2 were considered to have insufficient water absorption.

6) Overall Evaluation In the evaluation items 1) to 5) above, if the nonwoven fabric was judged to be × with noticeable paper dust, the cantilever measurement value exceeding 75 mm and the number of curls was high (poor processability), the KES_MMD value exceeded 0.0090 (smoothness evaluation was (poor △)), or the water absorption performance was poor, the overall evaluation was ×, and the nonwoven fabric was deemed unsuitable for use.
In relation to the above, if there were no negative evaluations in the evaluation items and the overall evaluation was ⊚ or ◯, the nonwoven fabric was judged to be suitable for use.

As shown in Table 1, in Examples 1 to 6, the basis weight of the pulp fiber web in the nonwoven fabric was 30 g/m² or ^more and 80 g/m² ^or less, the amount of wet strength agent (PAE) added was 0.35 wt% or more, the amount of anionic water-soluble polymer (CMC) added was 0.1 wt% or more, and the stiffness in the MD direction measured using the 45° cantilever method was 75 mm or less. The nonwoven fabrics of Examples 1 to 6 suppressed paper dust and maintained sufficient liquid absorbency whether used in a dry or wet state, and were also nonwoven fabrics with excellent smoothness and processability. Note that calendering was performed in Examples 2 to 4.

On the other hand, in Comparative Examples 1 to 8, the amount of paper powder was large or noticeable, the processing suitability was poor, the smoothness was poor, or the liquid absorption performance was poor, so the overall evaluation was "x," making it difficult to provide the nonwoven fabric to users.
In Comparative Example 1, since no anionic water-soluble polymer was added, paper powder was noticeable in a wet state, and the KES_MMD value exceeded 0.0090, indicating a lack of smoothness.
In Comparative Examples 2 and 3, the basis weight exceeded 80 g/ ^m2 , and the measured value by the cantilever method exceeded 75 mm, so the rigidity was high and the processability was poor, and the KES_MMD value exceeded 0.0090, so the smoothness was insufficient.
In Comparative Example 4, the addition rate of the anionic water-soluble polymer was increased, so that the measurement value by the cantilever method exceeded 75 mm, the rigidity was high, and the processability was poor. In addition, the KES_MMD value exceeded 0.0090, so that the smoothness was insufficient.
In Comparative Example 6, the amount of wet strength agent added was insufficient, resulting in noticeable paper powder in a dry state; in Comparative Example 7, the amount of anionic water-soluble polymer added was insufficient, resulting in noticeable paper powder in a wet state; and in Comparative Example 8, the basis weight was 28.2 g/ ^m2 and the KES_MMD value was 0.0090, resulting in a lack of smoothness and water absorption performance.

The above-described examples demonstrate the paper dust suppression effect, water absorbency, processability, and smoothness of a composite nonwoven fabric made of a pulp fiber web to which a predetermined amount of wet strength agent and anionic water-soluble polymer has been added and a spunbond nonwoven fabric. However, it goes without saying that similar effects can be expected from a nonwoven fabric formed only from a pulp fiber web.
This concludes the description of the embodiment, but it goes without saying that the present invention is not limited to the above embodiment, and can be implemented with various modifications within the scope of the gist of the present invention.

REFERENCE SIGNS LIST 1 Composite nonwoven fabric manufacturing apparatus 2 Airlaid apparatus 3 Spunbond nonwoven fabric supply apparatus 4 Suction device 5 Hydroentanglement device 6 Suction device 7 Drying device 8 Winding device 9 Addition device 21 Defibrator 22 Duct 23 Airlaid hopper 24 Stacking position 28 Nipping roller 30 Pre-wetting device 31 Spray nozzle 32 Suction device 41 Suction device main body 42 Suction section 43 Conveying wire 51 Water jet head 52 Suction device 55 Conveying wire SW Spunbond nonwoven fabric PF Pulp fiber PFW Pulp fiber web PWeb Preliminary laminate (laminated web)
WP Composite nonwoven fabric MD Transport direction CD Width direction CA Calendering device

Claims (5)

A nonwoven fabric essentially comprising a pulp fiber web manufactured by an airlaid method,
The pulp fiber web has a basis weight of 30 g/m ² or more and 80 g/m ² or less,
the pulp fiber web contains a wet strength agent and carboxymethyl cellulose (CMC) , the wet strength agent being polyamide epichlorohydrin (PAE);
the amount of the wet strength agent added is 0.35% by weight or more and the amount of carboxymethyl cellulose (CMC) added is 0.1% by weight or more relative to the bone dry weight of pulp fibers in the pulp fiber web;
A nonwoven fabric characterized in that the rigidity of the pulp fiber web in the MD direction, as measured in accordance with the 45° cantilever method based on JIS L 1096, is 75 mm or less. The nonwoven fabric according to claim 1, characterized in that the KES_MMD value, an index for evaluating the smoothness of a nonwoven fabric, is less than 0.0090. 3. The nonwoven fabric according to claim 1 , wherein the water absorption (T.W.A.) is 300 g/m ² or more. 4. The nonwoven fabric according to claim 1 , further comprising a spunbond nonwoven fabric, wherein the pulp fiber web is laminated on and integrated with the spunbond nonwoven fabric to form a composite. A method for producing the nonwoven fabric according to any one of claims 1 to 4 ,
a hydroentangling step of subjecting the pulp fiber web to a hydroentangling treatment by spraying a water stream onto the pulp fiber web;
a method for producing a nonwoven fabric, comprising at least an addition step of adding the wet strength agent and carboxymethyl cellulose (CMC) to the pulp fiber web after the hydroentanglement step.