Nonwoven fabric manufacturing method and manufacturing device

Abstract

To enable efficient manufacturing of a nonwoven fabric from which fiber falling is prevented both in dry and wet states by adopting air-laid method for adding fiber falling preventing agent and enable production by suppressing occurrence of malfunction of a device.SOLUTION: A manufacturing method of a nonwoven fabric formed so as to essentially include pulp fiber web manufactured by air-laid method includes a water flow interlacing step to apply a water flow interlacing processing to the pulp fiber web and an addition step to add a wet paper strengthening agent and anionic water soluble polymer to the pulp fiber web after the water flow interlacing step. The wet paper strengthening agent is polyamide-epichlorohydrin (PAE). In the addition step, addition is performed so that addition amount of the wet paper strengthening agent is 0.35 to 2.00% by weight and addition amount of the anionic water soluble polymer is 0.1 to 1.0% by weight to pulp fiber absolute dry weight of the pulp fiber web.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for manufacturing a nonwoven fabric formed by essentially containing pulp fibers, such as a nonwoven fabric formed only from pulp fibers, or a composite nonwoven fabric made of pulp fibers and a spunbonded nonwoven fabric. [Background technology]

[0002] For example, a composite nonwoven fabric made of a pulp fiber web and a spunbonded nonwoven fabric has both the liquid absorbency of the pulp fiber and the strength of the spunbonded nonwoven fabric, and is therefore widely used in a variety of applications, such as industrial wipers such as rags, and personal wipers such as hand towels and towels.

[0003] 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. Here, the spunbond nonwoven fabric has excellent strength and therefore functions as a backing layer for the manufactured 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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 2533260 Summary of the Invention [Problem to be solved by the invention]

[0005] The above-mentioned composite nonwoven fabric contains a pulp fiber web, which gives it excellent liquid absorption properties when in use. However, it has been recognized that reducing the amount of paper powder (also called fine fibers or lint) that falls off from the pulp fiber web when used in either a dry or wet state is an issue that needs to be addressed. In order to address this issue, it has been an easy idea to adapt a wet papermaking process to add a paper strength agent to produce a pulp fiber web. However, compared to the case of using an airlaid method, producing a pulp fiber web using a wet papermaking process requires larger production equipment, which increases production costs. Moreover, since it is not possible to completely remove foreign matter circulating in the white water during the papermaking process, foreign matter is likely to be mixed into the composite nonwoven fabric produced. Furthermore, when a pulp fiber web containing a paper strength agent is produced by a wet papermaking method, a large amount of the paper strength agent is unable to be fixed to the pulp and flows out into the white water, which causes a problem in that the yield of the paper strength agent is reduced (increasing costs). Therefore, there is a strong demand for the production of nonwoven fabrics using pulp fiber webs produced by the airlaid method, but there is a problem in that pulp fibers tend to fall off during processing and use. While it is conceivable to address this problem by adding chemicals, simply adding chemicals can cause problems in productivity, such as clogging and contamination of the equipment, and therefore an effective technology is desired.

[0006] Therefore, an object of the present invention is to provide a manufacturing method and manufacturing apparatus that employs an airlaid method and adds an agent to prevent fiber shedding, but that can produce a nonwoven fabric in which fiber shedding is suppressed in both a dry and wet state, and that can produce the fabric while suppressing the occurrence of equipment malfunctions. [Means for solving the problem]

[0007] The above object can be achieved by a method for producing a nonwoven fabric essentially containing a pulp fiber web produced by an airlaid method, the method comprising: a hydroentangling step of hydroentangling the pulp fiber web; and an addition step, subsequent to the hydroentangling step, of adding a wet strength agent and an anionic water-soluble polymer to the pulp fiber web, wherein the wet strength agent is polyamide epichlorohydrin (PAE), and the addition step adds the wet strength agent in an amount of 0.35 to 2.00 wt % and the anionic water-soluble polymer in an amount of 0.1 to 1.0 wt % relative to the bone dry weight of pulp fibers in the pulp fiber web.

[0008] The anionic water-soluble polymer can be carboxymethyl cellulose (CMC) or polyacrylamide (PAM). The carboxymethyl cellulose preferably has a degree of etherification (DS) of 0.75 or less.

[0009] In the adding step, a mixed additive obtained by mixing the wet strength agent and the anionic water-soluble polymer may be spray-coated onto the pulp fiber web.

[0010] In the adding step, the wet strength agent and the anionic water-soluble polymer may be separately prepared as separate additives and sprayed onto the pulp fiber web. In the adding step, after the wet strength agent, which is one of the individual additives, is spray-applied, the anionic water-soluble polymer, which is the other of the individual additives, may be spray-applied within 2 seconds.

[0011] Furthermore, any of the above-described nonwoven fabric manufacturing methods may be applied to a pulp fiber web manufactured by the airlaid method placed on a spunbond nonwoven fabric to produce a composite nonwoven fabric.

[0012] The above object can also be achieved by a nonwoven fabric manufacturing apparatus comprising: an airlaid apparatus for supplying a pulp fiber web; a hydroentangling apparatus for hydroentangling the pulp fiber web; and a dewatering apparatus downstream of the hydroentangling apparatus for dewatering the pulp fiber web from below, and an addition apparatus provided above the dewatering apparatus for adding a mixed additive comprising a wet strength agent and an anionic water-soluble polymer to the pulp fiber web, or adding separate additives comprising a wet strength agent and an anionic water-soluble polymer separately.

[0013] The object can also be achieved by a manufacturing apparatus for a composite nonwoven fabric, comprising: a spunbond nonwoven fabric supplying device for supplying a spunbond nonwoven fabric; an airlaid device for supplying a pulp fiber web; a hydroentangling device for hydroentangling the pulp fiber web placed on the spunbond nonwoven fabric from above to form a composite nonwoven fabric; and a dehydration device downstream of the hydroentangling device for dehydrating the composite nonwoven fabric from below, and an addition device provided above the dehydration device for adding a mixed additive comprising a wet strength agent and an anionic water-soluble polymer to the pulp fiber web of the composite nonwoven fabric, or adding individual additives comprising a wet strength agent and an anionic water-soluble polymer separately.

[0014] The nonwoven fabric manufacturing apparatus or composite nonwoven fabric manufacturing apparatus may be configured to spray the additive mixture or the additives individually at a discharge pressure of 0.1 to 1.5 MPa using a spray nozzle with a cat's-eye outlet, and to arrange a plurality of the spray nozzles in the width direction of the pulp fiber web so that the additive mixture or the additives are sprayed in a spray liquid form and uniformly applied to the pulp fiber web. Here, the additive in the form of a spray liquid may overlap each other at both ends, and the spray application may be performed by arranging a plurality of spray nozzles in a line along the width direction to produce a nonwoven fabric or a composite nonwoven fabric.

[0015] The nonwoven fabric manufacturing apparatus or composite nonwoven fabric manufacturing apparatus may also be configured such that a plurality of the spray nozzles are arranged at a predetermined interval and tilted with respect to the width direction, and the additives in the spray liquid form are spray-applied so as not to interfere with each other.

[0016] Furthermore, the nonwoven fabric manufacturing apparatus or composite nonwoven fabric manufacturing apparatus may be configured such that a plurality of the spray nozzles are arranged in multiple rows parallel to the width direction, alternately in front and behind, at predetermined intervals, and the additives in the spray liquid form are spray-applied so as not to interfere with each other. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a manufacturing method and manufacturing apparatus that can manufacture a nonwoven fabric in which fiber shedding is suppressed in both dry and wet states, and that can produce the fabric while suppressing the occurrence of equipment malfunctions. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a diagram showing an apparatus suitable for producing a nonwoven fabric according to the present invention. [Figure 2] FIG. 2 is a diagram for explaining the spray pattern of the additive produced by the additive adding device shown in FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0019] The method and apparatus for producing a nonwoven fabric according to the present invention will be described below. The present inventors have confirmed that fiber shedding (paper dust) can be suppressed when a pulp fiber web contains a wet strength agent and an anionic water-soluble polymer. They then designed conditions and equipment suitable for producing such a nonwoven fabric, leading to the present invention. The nonwoven fabric formed using the manufacturing method and apparatus of the present invention, including a pulp fiber web, can be a nonwoven fabric formed only from a pulp fiber web, or it can be a composite nonwoven fabric formed by including a spunbonded nonwoven fabric together with the pulp fiber web.

[0020] Here, a method for producing a nonwoven fabric essentially containing a pulp fiber web produced by an airlaid method includes a hydroentanglement step of hydroentanglement-treating the pulp fiber web, and an addition step after the hydroentanglement step of adding a wet strength agent and an anionic water-soluble polymer to the pulp fiber web, wherein the wet strength agent is polyamide epichlorohydrin (PAE), and the addition step preferably includes adding the wet strength agent in an amount of 0.35 to 2.00 wt % and the anionic water-soluble polymer in an amount of 0.1 to 1.0 wt % relative to the bone dry weight of pulp fibers in the pulp fiber web. The anionic water-soluble polymer is preferably carboxymethyl cellulose (CMC) or polyacrylamide (PAM). The carboxymethyl cellulose preferably has a degree of etherification (DS) of 0.75 or less.

[0021] In the adding step, a mixed additive obtained by mixing the wet strength agent and the anionic water-soluble polymer may be spray-coated onto the pulp fiber web. In the adding step, the wet strength agent and the anionic water-soluble polymer may be spray-applied as separate additives to the pulp fiber web. In the adding step, it is preferable to spray-apply the anionic water-soluble polymer, which is the other of the individual additives, within 2 seconds, more preferably within 0.3 to 1.50 seconds, after spray-applying the wet strength agent, which is one of the individual additives.

[0022] The above-described method for manufacturing a nonwoven fabric using a pulp fiber web manufactured by the airlaid method can be carried out on the pulp fiber web manufactured by the airlaid method placed on a spunbond nonwoven fabric to produce a composite nonwoven fabric.

[0023] The nonwoven fabrics and composite nonwoven fabrics produced by the present invention contain a wet strength agent and an anionic water-soluble polymer on the pulp fiber web side. This not only imparts 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, which is thought to allow the wet strength agent to function (act) effectively, effectively inhibiting pulp fiber shedding while maintaining water absorption performance.

[0024] When the anionic water-soluble polymer is carboxymethyl cellulose (CMC), it is preferable to set the degree of etherification (DS) of the carboxymethyl cellulose to 0.75 or less. If the degree of etherification exceeds 0.75, the water solubility increases, and the CMC tends to be washed away while dissolved in water during the dehydration and drying processes, resulting in poor paper dust suppression effects. It is preferable to set the viscosity of this carboxymethyl cellulose at 20 mPa·s or less when preparing a 1% aqueous solution. If the viscosity exceeds 20 mPa·s, for example, when spraying with a spray nozzle, it becomes difficult to control the amount added at the appropriate pressure and concentration, making it difficult to apply the liquid uniformly to the nonwoven fabric. Furthermore, highly viscous liquids tend to accumulate during operation and become solidified stains, which can be a problem.

[0025] The manufacturing apparatus of the present invention will be further described below with reference to the drawings. Here, the manufacturing apparatus for a composite nonwoven fabric will be described, which can produce a composite nonwoven fabric by placing a pulp fiber web manufactured by an airlaid method on a spunbond nonwoven fabric, which is a preferred embodiment of the nonwoven fabric. A manufacturing apparatus suitable for manufacturing a composite nonwoven fabric will be described with reference to FIG.

[0026] The schematic configuration of a composite nonwoven fabric manufacturing apparatus 1 will now be described. The manufacturing apparatus 1 shown in Figure 1 is equipped 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 positioned below the airlaid device 2 so as to face it. In the web transport direction TD, 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 to perform 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 an example of a composite nonwoven fabric manufacturing apparatus that is equipped with a spunbond nonwoven fabric supplying device 3 and that can manufacture a composite nonwoven fabric by placing a pulp fiber web manufactured by an airlaid method on a spunbond nonwoven fabric. If the manufacturing apparatus is changed to one that supplies a pulp fiber web by an airlaid method directly onto a conveying wire without using a spunbond nonwoven fabric, it can be made into an apparatus for manufacturing a nonwoven fabric using only a pulp fiber web.

[0027] The airlaid device 2 includes a defibrator 21 that defibrates raw pulp RP, which is a sheet-like material made of densely packed fibers, into pulp fibers, and a duct 22 that is equipped with a blower (not shown) and transports the defibrated pulp fibers PF to an airlaid hopper 23.

[0028] 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 equipment 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.

[0029] 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) and production speed of the pulp fiber web PFW.

[0030] A transport wire 43 for transporting the web is disposed around the suction device 4. The transport wire 43 is arranged 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 from the explanation given below. 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).

[0031] A spunbond nonwoven fabric supplying device 3 is disposed below the airlaid device 2, upstream of the suction device 4. A roll of spunbond nonwoven fabric SW that has been prepared in advance is set in this spunbond nonwoven fabric supplying device 3. That is, as described above, the designed spunbond nonwoven fabric SW is wound up into a roll as it is manufactured, and this roll is pulled out from the spunbond nonwoven fabric supplying device 3 and transported to the layering position 24 on the transport wire 43 described above.

[0032] 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 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. When the preliminary laminate PWeb is formed as described above, the amount of the pulp fiber web PFW supplied onto the spunbond nonwoven fabric SW is controlled, so that the basis weight of the pulp fiber web PFW contained in the composite nonwoven fabric produced by this apparatus can be set to, for example, 30.0 to 125.0 g / m 2 It is desirable to design the spunbond nonwoven fabric SW so that the ratio of the pulp fiber web is higher than that of conventional general composite nonwoven fabrics. The basis weight of the spunbond nonwoven fabric SW is, for example, 10.0 to 40.0 g / m 2 The composite nonwoven fabric (spunbond nonwoven fabric SW + pulp fiber web PFW) produced has a weight of, for example, 40.0 to 165.0 g / m 2 The basis weight can be set to fall within a desired range by appropriately adjusting the conveying speed of the pulp fiber web and the amount of pulp fiber web PFW supplied per hour, and checking the basis weight of the pulp fiber web PFW of the manufactured composite nonwoven fabric. The conveying speed of the pulp fiber web is preferably, for example, 150 to 300 m / min.

[0033] The above-mentioned 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 underside of the pulp fiber web PFW).

[0034] 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.

[0035] Then, in the hydroentangling device 5, the pulp fibers are entangled by spraying a high-pressure water jet 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 TD. 1 does not show the nozzles provided on the water jet head 51 extending in a direction perpendicular to the conveyance direction TD (web width direction CD), but multiple water jet nozzles are arranged at appropriate positions in the width direction. The water jet nozzle hole diameter φ is preferably 0.06 to 0.15 mm. The interval between the water jet nozzles is preferably 0.4 to 1.0 mm.

[0036] The water pressure during the hydroentanglement treatment is preferably set in consideration of the basis weights of the pulp fiber web PFW and the spunbond nonwoven fabric SW, and is preferably selected within the range of, for example, 1 to 30 MPa.

[0037] 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 on the upper side, while the suction force of the suction device 52 is applied to the underside of the spunbond nonwoven fabric SW located on the lower side. It is presumed that the cooperative 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 on the lower side, or penetrate through the spunbond nonwoven fabric SW to the opposite side. This action promotes integration of the two layers.

[0038] 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, 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 TD, and by the time it leaves the hydroentangling device 5, sufficient entanglement 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.

[0039] 1, a suction device 6 and a dryer 7 are provided downstream of the hydroentanglement device 5 to perform a dehydration treatment to suck out and remove moisture remaining in the pulp fiber web, followed by a drying treatment to complete the production of the composite nonwoven fabric WP. By performing the dehydration treatment and drying treatment by the suction device 6 and the dryer 7 in this way 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 addition device 9 for adding an agent to prevent the pulp fibers from falling off.

[0040] 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 transported composite nonwoven fabric WP in between. 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 ​​(addition step). 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 content immediately before entering the adding device 9) to 120 to 400% when the mixed additive is spray-applied in the adding device 9. The reason for this is that if the moisture content is too low, the coating may not be applied evenly during spray coating, resulting in unevenness. Conversely, if the moisture content is too high, a large amount of moisture may be carried over to the subsequent process, increasing the drying load and possibly causing stains.

[0041] 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 explained above with reference to Fig. 1, or dehydration may be performed 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 state of penetration and diffusion of the chemical solution into the pulp fiber web PWF ​​when the mixed additive is spray applied. The mixed additives 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-mentioned adding device 9 has been described as a suitable example in which a mixed additive in which a wet paper strength agent and an anionic water-soluble polymer are pre-mixed is applied to a pulp fiber web PWF, but the form of application is not limited to this.

[0042] The wet strength agent and the anionic water-soluble polymer may be spray-applied to the pulp fiber web PWF ​​as separate additives. When separate additives are used, the application device 9 may be configured as an apparatus equipped with both a first applicator for applying the wet strength agent and a second applicator for applying the anionic water-soluble polymer. The first applicator and the second applicator may simultaneously apply the respective chemicals (wet strength agent and anionic water-soluble polymer), or the first applicator and the second applicator may be slightly offset from each other in the web transport direction. When applying the individual additives in a staggered manner, it is preferable to spray the anionic water-soluble polymer, which is the other individual additive, within 2 seconds, more preferably within 0.3 to 1.50 seconds, after spraying the wet strength agent, which is one of the individual additives. This is because optimizing the time until the two are sprayed can be expected to have the technical effect of more effectively building a crosslinked structure between the wet strength agent and the anionic water-soluble polymer.

[0043] The wet strength agent and the anionic water-soluble polymer are preferably added to the pulp fiber web PWF ​​in amounts calculated on a solids basis 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 is 0.35 to 2.00 wt %, preferably 0.50 to 1.50 wt %, relative to the bone-dry weight of the pulp fibers in the pulp fiber web. The amount of the anionic water-soluble polymer is 0.1 to 1.0 wt %, preferably 0.35 to 0.80 wt %, relative to the bone-dry weight of the pulp fibers in the pulp fiber web. The weight ratio of the anionic water-soluble polymer to the wet strength agent, ie, (anionic water-soluble polymer / wet strength agent) is preferably 10 to 100% by weight. If the amount of the wet strength agent and anionic water-soluble polymer added is too small, the effect of preventing fiber shedding will decrease, and conversely, if too much is added, the effect relative to the addition rate will remain constant, but there is a concern that excess chemicals will accumulate around the equipment, worsening soiling.

[0044] 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 may be scattered by the wind generated by the pulp fiber web being transported, which may reduce yield and reduce the effectiveness of preventing paper dust from falling off. On the other hand, if the pressure is too high, the mixed additive may bounce off the surface of the pulp fiber web being transported, which may also reduce yield and reduce the effectiveness of preventing paper dust from falling off. 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 and the like. As the anionic water-soluble polymer, it is preferable to use carboxymethyl cellulose (CMC) or polyacrylamide (PAM) as described above. By using the above two types in a predetermined ratio, clogging of the nozzle of the adding device and contamination of surrounding equipment during production can be suppressed, and composite nonwoven fabric can be produced continuously and efficiently.Furthermore, the composite nonwoven fabric produced is prevented from fiber shedding and has sufficient water absorbency.

[0045] A drying device 7 is further installed downstream of the suction device 6 and the adding device 9, where the composite nonwoven fabric WP comprising the pulp fiber web PWF ​​spray-coated with the mixed additive is dried. The drying device 7 here is preferably a non-compression type dryer, preferably an air-through dryer. In FIG. 1, the rotatable air-through dryer body 71 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 of the dryer body toward the center. The composite nonwoven fabric WP is continuously produced in this manner while preventing clogging of the nozzle of the adding device and contamination of surrounding equipment, and is wound around the roll 81 of the winding device 8 after drying. As described above, the composite nonwoven fabric produced by the production apparatus 1 according to the present invention is one in which the shedding of pulp fibers is suppressed.

[0046] Furthermore, the shape of the spray nozzle and the spray conditions that can be employed in the spray application by the above-mentioned adding device 9 will be described with reference to FIG. As shown in FIG. 2(a), it is preferable to spray the liquid using a spray nozzle having a cat's eye-shaped outlet so that the shape of the spray liquid becomes a cat's eye shape CS. 2(b) shows an example in which the horizontally elongated cat's-eye shaped nozzles CS are set so that both ends overlap each other so that the spray liquid is evenly applied to the pulp fiber web PWF ​​along the width direction CD, which is perpendicular to the conveying direction TD of the pulp fiber web. In this case, an addition device 9 is used in which multiple spray nozzles with cat's-eye shaped outlets corresponding to the spray liquid shape are arranged linearly at predetermined intervals in the width direction CD.

[0047] Next, in Figure 2(c), the cat's-eye-shaped spray nozzles CS are tilted relative to the cross direction CD, with a slight distance between them. This arrangement is preferable because the sprays do not interfere with each other. In Figure 2(c), there are gaps between adjacent cat's-eye-shaped spray nozzles CS. However, in an actual manufacturing apparatus 1, the pulp fiber web PWF ​​on the composite nonwoven fabric WP is transported in the TD direction. As a result, the spray nozzle can be uniformly applied across the entire width of the pulp fiber web PWF. To form the spray nozzle shape shown in Figure 2(c), an application device 9 is used, in which spray nozzles with cat's-eye-shaped nozzles are tilted relative to the cross direction CD and arranged at a predetermined interval in the cross direction CD.

[0048] Furthermore, Figure 2(d) illustrates a case where multiple rows are formed parallel to the cross direction CD, and the cat's eye shape CS of the spray liquid is staggered in two rows, one in front and one in back. In this case, the sprayed liquid does not interfere with each other, and the spray liquid can be uniformly applied across the entire width of the pulp fiber web PWF. To form the spray liquid shape shown in Figure 2(d), it is preferable to use an addition device 9 in which multiple spray nozzles with cat's eye-shaped outlets are arranged in multiple rows parallel to the cross direction CD, staggered at predetermined intervals.

[0049] It is preferable to carry out spray application with the wet strength agent concentration of 0.1 to 2.5% and the discharge pressure of 0.1 to 1.5 MPa, and with the anionic water-soluble polymer concentration of 0.20 to 2.00% and the discharge pressure of 0.1 to 1.5 MPa.

[0050] (Example) Hereinafter, examples and comparative examples will be described in which a manufacturing method is carried out using a manufacturing apparatus according to the present invention to manufacture a composite nonwoven fabric containing a spunbond nonwoven fabric. 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) or polyacrylamide (PAM). The amounts and mixing ratios of the wet strength agent and anionic water-soluble polymer added to the pulp fiber web of the composite nonwoven fabric were as shown in Table 1. The composite nonwoven fabrics of Examples 1 to 7 were produced using the additive amounts and mixing ratios shown in Table 1, and the composite nonwoven fabrics of Comparative Examples 1 to 4 were produced using the additive amounts and mixing ratios shown in Table 2. The amount of paper powder that fell off the composite nonwoven fabrics produced, the occurrence of nozzle clogging as a problem that occurred during production, and the degree of contamination during operation were confirmed and comprehensively evaluated. In this example, the spray pattern by the additive device was produced in two cases: a mixed additive in which the wet strength agent and the anionic water-soluble polymer were mixed, and an individual additive in which the wet strength agent and the anionic water-soluble polymer were mixed separately. These are shown as "mixed" and "individual" in Tables 1 and 2 below. The discharge pressure, chemical concentration, and nozzle arrangement (two staggered rows used here, see Figure 2(d)) for the mixed additive are shown. For the individual additives, the discharge pressure, chemical concentration, nozzle arrangement, and the time (sec) between spray (1) and spray (2) for the first applicator (spray (1)) and the second applicator (spray (2)) are also shown.

[0051] 1) Amount of paper powder falling off during drying (visual observation) The nonwoven fabric was shaken ten times on black paper in a dry state, and the amount of paper powder that fell off was visually evaluated. The amount of residual paper dust is small and good (Excellent ◎). The amount of residual paper dust is less than excellent, but still usable (passable). The amount of residual paper dust is noticeable, making it unsuitable for use (Not acceptable). 2) Amount of paper dust after wiping (visual inspection) The generation of paper dust under dry and wet conditions 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 (passable). The amount of residual paper dust is noticeable, making it unsuitable for use (Not acceptable).

[0052] 3) Occurrence of nozzle clogging (visual inspection) The level of each example and comparative example was evaluated visually at the time of sampling to determine the condition of the spray nozzle. No nozzle clogging (Excellent ◎) Minor nozzle clogging (OK) Nozzle clogging (not possible)

[0053] 4) Operational conditions (visual inspection) The level of contamination of the equipment was visually evaluated at the time of sampling for each example and comparative example. Equipment contamination is within the range of normal operation (Excellent ◎) Equipment is less dirty than normal (OK) The equipment is so dirty that it is difficult to continue operation (Unacceptable ×)

[0054] 5) Overall rating All evaluation items were scored based on the following criteria. An overall score of 3 or above was considered a pass mark, indicating good quality and a level at which continuous operation was possible. The operating conditions are poor, and it is difficult to supply nonwoven fabrics (1 point) Although there are some issues with paper dust reduction, the operational status is above 0 (2 points) All ratings are 〇 or above, and there are 3 ◎ ratings (3 points) All ratings are 〇 or above, with 4 ◎ ratings (4 points) All ratings are ◎ (5 points)

[0055] [Table 1]

[0056] [Table 2]

[0057] As shown in Table 1, in Examples 1 to 7, nonwoven fabrics were produced using wet strength agents in amounts of 0.35 to 2.00% by weight and anionic water-soluble polymers in amounts of 0.1 to 1.0% by weight. This resulted in the composite nonwoven fabrics suppressing the amount of paper dust after wiping in both dry and wet states. Furthermore, there were no problems with nozzle clogging or serious contamination around the device, which would hinder production, and the overall evaluation was 3 points or higher. In Example 1, the application interval between spray (1) and spray (2) is slightly long, so the paper dust suppression effect is slightly reduced, but this does not affect the manufacturing process. Example 2 is a mixed additive, which tends to clog the nozzle and stain the area around the device compared to the individual additives, but does not impede continuous production, and the resulting nonwoven fabric suppresses paper dust. The conditions of Example 3 were all rated as excellent, which is the best mode. In Example 4, the application interval between spray (1) and spray (2) is slightly short, so the paper dust suppression effect is slightly reduced, but this does not cause any problems in the manufacturing process. In Example 5, the anionic water-soluble polymer was changed from CMC to PAM, which slightly reduced the paper dust suppression effect, but the nonwoven fabric was still effective in suppressing paper dust. Because a mixed additive was used, there was a tendency for nozzle clogging and contamination around the device, but this did not hinder continuous production. In Example 6, the anionic water-soluble polymer was changed from CMC to PAM, and the paper dust suppression effect was slightly reduced, but the nonwoven fabric was still effective in suppressing paper dust. There was a tendency for the area around the device to become dirty, but this did not hinder continuous production. In Example 7, the degree of CMC etherification is high, so the paper dust suppression effect is slightly reduced, but the nonwoven fabric is still effective in suppressing paper dust.Since a mixed additive is used, there is a tendency for nozzle clogging and dirt around the equipment to occur, but this does not hinder continuous production.

[0058] On the other hand, in Comparative Examples 1 to 4, the amount of wet strength agent added was outside the range of 0.35 to 2.00 wt%, or the amount of anionic water-soluble polymer added was outside the range of 0.1 to 1.0 wt%. When nonwoven fabrics were produced under these conditions, they either resulted in nonwoven fabrics with insufficient paper dust suppression (evaluated as "X"), or nozzle clogging occurred during the production process or the surrounding area of ​​the equipment was contaminated (evaluated as "X" for the operating conditions).

[0059] The above-described examples have been described with respect to the case where a composite nonwoven fabric is produced from a pulp fiber web and a spunbond nonwoven fabric by adding a predetermined amount of a wet strength agent and an anionic water-soluble polymer. However, it goes without saying that the same effects as those described above can be expected when a nonwoven fabric is produced from a pulp fiber web alone. 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. [Explanation of symbols]

[0060] 1. Composite nonwoven fabric manufacturing equipment 2 Airlaid equipment 3 Spunbond nonwoven fabric supply device 4 Suction device 5 Hydro-entangling device 6 Suction device 7 Drying equipment 8 Winding device 9 Addition device 21 Fiberizer 22 Duct 23 Air Raid Hopper 24 Stacking position 28 clamping 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 Carrying wire SW spunbond nonwoven fabric PF pulp fiber PFW Pulp Fiber Web PWeb Pre-Laminate (Laminate Web) WP composite nonwoven fabric TD conveying direction CD width direction CS Cat's Eye Shape

Claims

1. A method for producing a nonwoven fabric essentially containing a pulp fiber web produced by an airlaid method, comprising: a hydroentangling step of hydroentangling the pulp fiber web; and adding, after the hydroentanglement step, a mixed additive obtained by mixing a wet strength agent and an anionic water-soluble polymer, or separate additives obtained by separately preparing the wet strength agent and the anionic water-soluble polymer, to the pulp fiber web by spray coating, wherein the wet strength agent is polyamide epichlorohydrin (PAE), In the adding step, the amount of the wet strength agent added is 0.35 to 2.00% by weight, and the amount of the anionic water-soluble polymer added is 0.1 to 1.0% by weight, relative to the bone dry weight of pulp fibers in the pulp fiber web, and the weight ratio of the anionic water-soluble polymer to the wet strength agent is 10 to 100% by weight, A method for producing a nonwoven fabric, comprising: setting a discharge pressure of the mixed additive or the individual additive at 0.1 to 1.5 MPa; using a spray nozzle having a cat's-eye discharge port; and arranging a plurality of the spray nozzles in the width direction of the pulp fiber web so that the mixed additive or the individual additive is sprayed in a spray liquid form and uniformly applied to the pulp fiber web.

2. The method for producing a nonwoven fabric according to claim 1, wherein the anionic water-soluble polymer is carboxymethyl cellulose (CMC).

3. 3. The method for producing a nonwoven fabric according to claim 2, wherein the carboxymethyl cellulose has a degree of etherification (D.S) of 0.75 or less.

4. 2. The method for producing a nonwoven fabric according to claim 1, wherein, in the adding step, after the wet strength agent, which is one of the individual additives, is spray-applied, the anionic water-soluble polymer, which is the other of the individual additives, is spray-applied within 2 seconds.

5. A method for producing a composite nonwoven fabric, comprising carrying out the method for producing a nonwoven fabric according to any one of claims 1 to 4 on a pulp fiber web produced by the airlaid method and placed on a spunbond nonwoven fabric, to produce a composite nonwoven fabric.

6. an airlaid device that supplies a pulp fiber web; a hydroentangling device for subjecting the pulp fiber web to a hydroentangling treatment; A dewatering device is provided downstream of the hydroentanglement device to dewater the pulp fiber web from below, and an addition device is provided above the dewatering device to add a mixed additive comprising a wet strength agent and an anionic water-soluble polymer to the pulp fiber web, or to add individual additives comprising a wet strength agent and an anionic water-soluble polymer separately, the adding device adds the wet strength agent in an amount of 0.35 to 2.00 wt % and the anionic water-soluble polymer in an amount of 0.1 to 1.0 wt % relative to the bone dry weight of pulp fibers in the pulp fiber web, and the weight ratio of the anionic water-soluble polymer to the wet strength agent is 10 to 100 wt %, A composite nonwoven fabric manufacturing device characterized in that the discharge pressure of the mixed additive or the individual additive is set to 0.1 to 1.5 MPa, a spray nozzle having a cat's-eye outlet is used, and a plurality of the spray nozzles are arranged in the width direction of the pulp fiber web to spray the mixed additive or the individual additive into an atomized liquid form so that the mixed additive or the individual additive is uniformly applied to the pulp fiber web.

7. a spunbond nonwoven fabric supplying device that supplies a spunbond nonwoven fabric; an airlaid device that supplies a pulp fiber web; a hydroentangling device that hydroentangles the pulp fiber web placed on the spunbond nonwoven fabric from above to form a composite nonwoven fabric; A dewatering device is provided downstream of the hydroentanglement device to dewater the composite nonwoven fabric from below, and an addition device is provided above the dewatering device to add a mixed additive comprising a wet strength agent and an anionic water-soluble polymer to the pulp fiber web of the composite nonwoven fabric, or to add individual additives comprising a wet strength agent and an anionic water-soluble polymer separately, the adding device adds the wet strength agent in an amount of 0.35 to 2.00 wt % and the anionic water-soluble polymer in an amount of 0.1 to 1.0 wt % relative to the bone dry weight of pulp fibers in the pulp fiber web, and the weight ratio of the anionic water-soluble polymer to the wet strength agent is 10 to 100 wt %, A composite nonwoven fabric manufacturing device characterized in that the discharge pressure of the mixed additive or the individual additive is set to 0.1 to 1.5 MPa, a spray nozzle having a cat's-eye outlet is used, and a plurality of the spray nozzles are arranged in the width direction of the pulp fiber web to spray the mixed additive or the individual additive into an atomized liquid form so that the mixed additive or the individual additive is uniformly applied to the pulp fiber web.

8. The nonwoven fabric manufacturing apparatus or composite nonwoven fabric manufacturing apparatus according to claim 7, characterized in that the mixed additive or the individual additives in the spray liquid form overlap each other at both ends, and are spray-applied by arranging a plurality of the spray nozzles in a line along the width direction.

9. The nonwoven fabric manufacturing apparatus or composite nonwoven fabric manufacturing apparatus according to claim 7, characterized in that the plurality of spray nozzles are arranged at a predetermined interval and tilted with respect to the width direction, and the mixed additive or the individual additives in the spray liquid form are spray-applied so as not to interfere with each other.

10. The nonwoven fabric manufacturing apparatus or composite nonwoven fabric manufacturing apparatus according to claim 7, characterized in that the plurality of spray nozzles are arranged in multiple rows parallel to the width direction, alternately in front and behind at predetermined intervals, and the mixed additive or the individual additives in the spray liquid form are spray-applied so as not to interfere with each other.

11. The method for producing a nonwoven fabric according to claim 1 , wherein in the adding step, polyacrylamide (PAM) is used instead of the anionic water-soluble polymer.

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