JP7509539B2 - Composite nonwoven fabric and its manufacturing method - Google Patents

Description

The present invention relates to a composite nonwoven fabric obtained by hydroentangling a pulp fiber web and a spunbond nonwoven fabric.

Composite nonwoven fabrics made from pulp fiber webs and spunbond nonwoven fabrics have both the absorbency of pulp fibers and the strength of spunbond nonwoven fabrics, 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 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 functions as a backing layer for the composite nonwoven fabric produced. 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 that has good absorbency for both aqueous and oil-based liquids and a spunbond nonwoven fabric that has excellent strength.

By the way, it is preferable that the composite nonwoven fabric is designed so that the pulp fibers do not easily fall off when used. The composite nonwoven fabric is used as a wiper or the like in either a dry or wet state. If the pulp fibers fall off noticeably when used, the commercial value will decrease.
Incidentally, it is known that when a nonwoven fabric containing pulp fibers is manufactured by utilizing a sheet manufacturing technique based on a wet papermaking method, a paper strength agent is added sufficiently to the pulp fibers in advance (e.g., Patent Documents 2 and 3). In the pulp fiber web manufactured in this manner, the condition of the constituent fibers is stabilized, so that the fiber dropout can be suppressed.

Japanese Patent No. 2533260 JP 2012-211412 A JP 2018-535126 A

Regarding the pulp fiber web used in the composite nonwoven fabric consisting of a pulp fiber web and a spunbond nonwoven fabric, it is easily conceivable to use a pulp fiber web to which a paper strength agent has been added by a conventional wet papermaking method.
However, compared to when the airlaid method is used, producing a pulp fiber web by the wet papermaking method 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, there is a problem that foreign matter is easily mixed into the composite nonwoven fabric produced.

The main objective of the present invention is to provide a composite nonwoven fabric that can prevent pulp fibers from falling off even when using a pulp fiber web obtained by the airlaid method, has little foreign matter mixed in, and provides a good feel when used.

The above object can be achieved by a composite nonwoven fabric in which a pulp fiber web obtained by an airlaid method is laminated and integrated on a spunbonded nonwoven fabric, the composite nonwoven fabric having a strength agent added thereto, the composite nonwoven fabric having a basis weight of 51.0 g/ ^m2 or more and less than 85.0 g/ ^{m2 ,} a thickness of 0.28 mm or more and less than 0.48 mm, and an added amount of the strength agent calculated as a solid content is 0.1 to 2.0% of the solid weight of the pulp fiber web.

It is preferable that the strength agent is unevenly distributed so that it is concentrated on the surface layer side of the pulp fiber web.

It is also preferable that the drop water absorbency is 0.5 to 4.0 seconds, the water retention is 220 to 380 g/m ² , and the wet Taber value is at least 5 times.

It is also preferred that the spunbond nonwoven fabric has a basis weight of 7.0 to 20.0 g/ ^m2 , the spunbond nonwoven fabric includes a plurality of fusion points connecting the resin fibers forming the spunbond nonwoven fabric, the area of each fusion point is 0.10 to 0.50 ^mm2 , the area ratio of the fusion points per unit area is 7 to 20%, and the number of fusion points per unit area is 10 to 150/ ^cm2 .

The material of the spunbond nonwoven fabric can be one selected from the group consisting of nylon, vinylon, polyester, acrylic, polyethylene, polypropylene, and polystyrene, or a mixture of two or more selected materials.

It is preferable that the pulp fiber web has a basis weight of 40.0 to 70.0 g/ ^m2 , and the weight composition ratio of the spunbond nonwoven fabric to the pulp fiber web is 40/60 to 10/90 (wt %).

The pulp fiber web is preferably made of bleached softwood kraft pulp fibers selected from the group consisting of radiata pine, slash pine, southern pine, lodgepole pine, spruce and Douglas fir.

The above object can also be achieved by a manufacturing method for producing any of the above-mentioned composite nonwoven fabrics, in which a pulp fiber web supplied by an airlaid method is placed on a spunbond nonwoven fabric, followed by a hydroentanglement treatment, and after the hydroentanglement treatment, a paper strength agent is added to the pulp fiber web, thereby producing any of the above-mentioned composite nonwoven fabrics.
The strength agent is preferably added by spray application.

According to the present invention, even when using a pulp fiber web obtained by the airlaid method, it is possible to prevent the pulp fibers from falling off, and it is possible to provide a composite nonwoven fabric that is less likely to be contaminated with foreign matter and has a good feel when used.

FIG. 1A is a diagram showing the cross-sectional structure of a composite nonwoven fabric WP according to the present invention, and FIG. 1B is a diagram showing the cross-sectional structure of a composite nonwoven fabric using a pulp fiber web produced by utilizing sheet manufacturing technology using a wet papermaking method. FIG. 1 is a diagram showing an apparatus suitable for producing a composite nonwoven fabric according to the present invention.

Hereinafter, a composite nonwoven fabric according to one embodiment of the present invention will be described.
FIG. 1(a) is a diagram showing a schematic cross-sectional structure of a composite nonwoven fabric WP according to the present invention.
The composite nonwoven fabric WP has a structure in which a pulp fiber web PFW is laminated and integrated onto a spunbond nonwoven fabric SW. This structure can be formed by a hydroentanglement treatment, as described later.

The composite nonwoven fabric WP has a basis weight of 51.0 g/ ^m2 or more and less than 85.0 g/ ^m2 and a thickness of 0.28 mm or more and less than 0.48 mm. This composite nonwoven fabric WP is designed as a relatively low basis weight and thin nonwoven fabric compared to conventional composite nonwoven fabrics. Such a low basis weight composite nonwoven fabric WP is ideal for wiping off liquids with various viscosities used in households, food factories, etc., and has the advantages of being comfortable to wipe and being able to wipe off cleanly even with a relatively weak force.

The upper pulp fiber web PFW was obtained by the airlaid method. When the pulp fiber web PFW is supplied by the airlaid method, the production cost can be reduced and the inclusion of foreign matter can be prevented, compared with the case where the pulp fiber web PFW is produced by utilizing a wet papermaking method.
On the other hand, as mentioned above, there is a concern that fibers may fall off from pulp fiber webs provided by the airlaid method, but the inventors have confirmed that fiber fall off can be effectively prevented by adding a strength agent to the pulp fiber web, and have arrived at the present invention.
As the paper strength agent, it is desirable to use a so-called wet paper strength agent, and for example, polyamide epichlorohydrin-based, polyamide epoxy-based, polyamide polyamine-based, etc. The amount of the paper strength agent added, calculated as the solid content, is preferably 0.1 to 2.0%, more preferably 0.3 to 1.5%, based on the solid weight of the pulp fiber web.
By setting the amount of the strength agent in the above range, it is possible to suppress the shedding of pulp fibers and to provide a composite nonwoven fabric with a soft wiping feel (if too much strength agent is added, the fabric becomes hard and the feel of use becomes poor). The amount of strength agent added can be measured using a trace nitrogen meter.
In addition, the amount of strength agent added to the pulp fibers in the finished composite nonwoven fabric can be confirmed, for example, by the following steps.
1) Solid weight of pulp: Cellulase or the like is applied to the product to dissolve and remove the pulp.
The weight of the pulp is determined by subtracting the weight of the remaining nonwoven fabric from the weight of the product.
2) Amount of strength agent added: The amount of strength agent added is confirmed by measuring the pulp portion with a "trace nitrogen meter."
3) From the above 1) and 2), confirm the amount of the strength agent added, calculated as the solid content relative to the solid weight of the pulp fiber web.

Fig. 1(b) is a schematic diagram showing a composite nonwoven fabric obtained by using a pulp fiber web obtained by utilizing a sheet manufacturing technology using a wet papermaking method, for comparison with the composite nonwoven fabric WP according to the present invention shown in Fig. 1(a). In the composite nonwoven fabric shown in Fig. 1(b), fiber shedding is suppressed in a state where a paper strength agent SA is added to the entire pulp fiber web. However, as mentioned above, there is a problem of foreign matter being mixed in.
In contrast, the composite nonwoven fabric WP of the present invention shown in FIG. 1(a) can simultaneously prevent fiber shedding and the inclusion of foreign matter by adding a paper strength agent SA to the pulp fiber web PFW obtained by the airlaid method.

The composite nonwoven fabric WP according to the present invention shown in Fig. 1(a) is manufactured by applying a liquid strength agent SA from the pulp fiber web PFW side. This results in a state in which the strength agent SA is present in greater amounts on the surface side of the pulp fiber web PFW, that is, the strength agent SA is unevenly distributed on the surface side of the pulp fiber web PFW as shown in Fig. 1(a). The state shown in Fig. 1(a) suppresses fiber shedding with the use of a relatively smaller amount of strength agent than the state shown in Fig. 1(b).
Therefore, the composite nonwoven fabric WP according to the present invention efficiently uses the strength agent SA, which also contributes to reducing manufacturing costs.

The composite nonwoven fabric WP preferably has a water drop absorbency of 0.5 to 4.0 seconds, a total water absorbency (TWA) of 220 to 380 g/ ^m2 , and a wet Taber value in the Taber test of at least 5, preferably 5 or more.
The composite nonwoven fabric WP that satisfies the above-mentioned condition range can satisfy the water retention and durability required for products such as wipers.

The basis weight of the spunbonded nonwoven fabric SW contained in the composite nonwoven fabric WP of the present invention is preferably 7.0 to 20.0 g/ ^m2 . The spunbonded nonwoven fabric SW includes a plurality of fusion points that connect the resin fibers forming the spunbonded nonwoven fabric, and each fusion point has an area of 0.10 to ^0.50 mm2, the area ratio of the fusion points per unit area is 7 to 20%, and the number of fusion points per unit area is preferably 10 to 150/ ^cm2 . The spunbonded nonwoven fabric SW that satisfies these conditions can stably maintain the shape of the composite nonwoven fabric WP. The shape of the fusion points is not limited, but may be, for example, a circle, an ellipse, a polygon, or the like.
If the composite nonwoven fabric WP is made using a spunbond nonwoven fabric that satisfies the above-mentioned condition range, it will have a moderate strength, be soft, and be excellent in feel when used.

The material of the spunbond nonwoven fabric SW may be one selected from the group consisting of nylon, vinylon, polyester, acrylic, polyethylene, polypropylene, and polystyrene, or a mixture of two or more selected materials. It is preferable to use polypropylene.

The pulp fiber web PFW preferably has a basis weight of 40.0 to 70.0 g/ ^m2 , and is desirably designed so that the weight composition ratio of the spunbond nonwoven fabric SW to the pulp fiber web PFW is 40/60 to 10/90 (wt%).
The pulp fiber web PFW is preferably composed of bleached softwood kraft pulp fibers selected from the group consisting of radiata pine, slash pine, southern pine, lodgepole pine, spruce and Douglas fir.
The composite nonwoven fabric of the present invention, which is formed so as to satisfy the above conditions, can prevent the fall-off of pulp fibers even when using a pulp fiber web obtained by the airlaid method, and is also expected to prevent the inclusion of foreign matter and reduce manufacturing costs.

A manufacturing apparatus suitable for manufacturing the composite nonwoven fabric of the present invention will now be described with reference to FIG.
First, a schematic configuration of a composite nonwoven fabric manufacturing apparatus 1 will be described. The manufacturing apparatus 1 shown in Figure 2 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 transport direction TD, downstream of these devices 2, 3, and 4 are arranged, in this order from the upstream side, a hydroentanglement device 5 that sprays water jets for hydroentanglement, a suction device 6 for dehydration, and a drying device 7. Downstream of the drying device 7 is provided a winding device 8 for winding up the composite nonwoven fabric WP that is continuously produced.

The airlaid device 2 includes a defibrator 21 that defibrates the 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.

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 lower surface to form a pulp fiber web PFW.
As described above, the airlaid apparatus 2 is equipment capable of supplying a pulp fiber web in a dry manner, and can reduce equipment costs compared to an apparatus that produces a pulp fiber web in a wet manner by applying a wet papermaking method. Furthermore, in the airlaid apparatus 2, the process from pulp defibration to dispersion and descent is a closed space, preventing the inclusion of foreign matter, so the inclusion of foreign matter can be kept overwhelmingly low compared to 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.
2 illustrates an example in which the pulp fiber web PFW is formed by arranging the airlaid hopper 23 and the 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.

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 are 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 description below.
The conveying wire 43 is formed in an open mesh shape so that the suction force of the suction portion 42 extends to the opposite side (upper side).

A spunbond nonwoven fabric supplying device 3 is disposed below the airlaid device 2 and upstream of the suction device 4. A roll of spunbond nonwoven fabric SW is prepared in advance and set in this spunbond nonwoven fabric supplying device 3. That is, as described above, the designed spunbond nonwoven fabric SW is wound up in a roll during production, and this is pulled out from the spunbond nonwoven fabric supplying device 3 and transported to the stacking position 24 on the transport wire 43 described above.

The above-mentioned pulp fiber web PFW is placed on the spunbond nonwoven fabric SW located at the stacking position 24. At this time, the suction force by 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.
When the preliminary laminate PWeb is formed as described above, it is desirable to design the composite nonwoven fabric manufactured by this device so that the basis weight of the pulp fiber web PFW contained in the composite nonwoven fabric manufactured by this device is, for example, 40.0 to 70.0 g/m ² by controlling the amount of the pulp fiber web PFW supplied onto the spunbond nonwoven fabric SW, so that the ratio of the pulp fiber web is higher than that of conventional composite nonwoven fabrics. The basis weight of the spunbond nonwoven fabric SW is, for example, 7.0 to 20.0 g/m ² , and the composite nonwoven fabric manufactured (spunbond nonwoven fabric SW + pulp fiber web PFW) is 51.0 g/m ² or more and less than 85.0 g/m ^2. The conveying speed of the pulp fiber web and the supply amount per hour of the pulp fiber web PFW can be appropriately adjusted, and the basis weight of the pulp fiber web PFW of the manufactured composite nonwoven fabric can be confirmed, so that the basis weight is set to be within the desired range. The transport speed of the pulp fiber web is preferably, for example, 150 to 300 m/min.

The above-mentioned preliminary laminate PWeb is maintained in a laminated state by being sucked and 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 fed into the downstream hydroentangling device 5 in this state, there is a risk that a part of the pulp fibers PF will be blown up by the water jet (high-pressure water flow).
Therefore, in the present manufacturing apparatus 1, there are provided clamping rollers 28 for sandwiching the preliminary laminate PWeb from above and below to stabilize the placement state of the pulp fiber web PFW on the spunbond nonwoven fabric SW, and a pre-wetting device 30 for applying moisture to prevent the fibers from 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 the underside of the preliminary laminate PWeb (i.e., the underside of the pulp fiber web PFW).

2 shows an example in which the pre-wetting device 30 is provided as a new device before the hydroentanglement device 5 as described above, but the present invention is not limited to this. The design of the hydroentanglement device 5 may be modified so that the first set of a plurality of 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 a pre-wetting device as described above is effective in reducing equipment costs.

In the hydroentangling device 5, the entanglement of the pulp fibers is promoted by spraying a high-pressure water jet onto the preliminary laminate PWeb that has been treated by the clamping rollers 28 and the pre-wetting device 30, which are the pre-treatment devices. This promotes integration of the pulp fiber web PFW layer located on the upper side and the spunbond nonwoven fabric SW layer located on the lower side (hydroentangling treatment).
The hydroentangling device 5 exemplarily shown in FIG. 2 has water jet heads 51 arranged in multiple stages (four stages are shown in FIG. 2) along the conveyance direction TD.
2 does not show the nozzles provided on the water jet head 51 extending in the direction perpendicular to the transport direction TD (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 the water jet nozzles is preferably 0.06 to 0.15 mm. The interval between the water jet nozzles is preferably 0.4 to 1.0 mm.

The water pressure during the hydroentanglement process is preferably set taking into consideration 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 on the upper side, while the suction force of the suction device 52 is applied to the lower side 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 located on the lower side, or penetrate through the spunbond nonwoven fabric SW to reach the opposite side. This action promotes integration of the two layers.

The hydroentangling device 5 is also provided with a conveying wire 55. 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 disposed 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 hydroentanglement treatment as it moves downstream in the transport direction TD, and by the time it leaves the hydroentanglement device 5, sufficient entanglement treatment is achieved between the upper pulp fiber web layer PFW 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.

2, a suction device 6 and a dryer 7 are provided downstream of the hydroentanglement device 5 to perform a dehydration process for sucking and removing the water 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 the drying process by 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 composite nonwoven fabric can be produced by drying the composite nonwoven fabric after hydroentanglement without applying a large external pressure to the composite nonwoven fabric produced.
The composite nonwoven fabric WP of the present invention is designed to prevent pulp fibers from coming off the pulp fiber web PFW. For this purpose, the manufacturing apparatus 1 is provided with a paper strength agent adding device 9 for adding a paper strength agent.

The suction device 6 is, for example, of a vacuum type, and dehydrates the composite nonwoven fabric after hydroentanglement from below. A paper strength agent adding device 9 is disposed above the suction device 6 with the composite nonwoven fabric WP being transported therebetween.
The strength agent adding device 9 sprays and applies the strength agent to the upper side of the composite nonwoven fabric WP after compounding in the hydroentanglement device 5, i.e., the pulp fiber web PWF side. Since the strength agent is applied from the surface side of the pulp fiber web of the composite nonwoven fabric after compounding is completed, the strength agent is unevenly distributed so that it is more abundant on the surface layer side of the pulp fiber web PWF. Therefore, a relatively small amount of strength agent acts efficiently to connect the pulp fibers together compared to when it is applied or impregnated over the entire surface. Since the strength agent is dried downstream of the strength agent adding device 9, there is no waste such as the sprayed strength agent being washed away and washed away.
Since there is a suction device on the lower side, the sprayed liquid paper strength agent is advantageously allowed to penetrate into the pulp fiber web, which makes it possible to more reliably prevent the pulp fibers from falling off. In addition, the paper strength agent adding device 9 can easily control the amount of paper strength agent by checking the state of the composite nonwoven fabric WP being produced.

It is preferable to adjust the moisture content of the pulp fiber web PWF portion when the strength agent is spray-applied by the strength agent adding device 9 (the inlet moisture content % immediately before entering the strength agent adding device 9) to, for example, 120 to 400%. When the traveling pulp fiber web has an appropriate moisture content within the above range, scattering of the strength agent during spray application is suppressed, the yield of the strength agent is increased, and the strength agent becomes more easily compatible with the pulp fiber web, thereby more effectively preventing fiber shedding.
In addition, it is preferable to perform dehydration treatment within 10 seconds after spray application of the paper strength agent. That is, as explained with reference to FIG. 2 above, dehydration may be performed immediately below spray application of the paper strength agent, or at a position slightly away from spray application (a position within 10 seconds of conveying time). In short, the optimal time (within 10 seconds after spray application) may be appropriately determined by checking the penetration and diffusion state of the chemical solution into the pulp fiber web PWF when the paper strength agent is spray applied. By performing the dehydration process simultaneously with spray application of the paper strength agent or within 10 seconds after spray application, the components of the paper strength agent can easily penetrate into the inside of the pulp fiber web, and the effect of preventing fiber shedding can be more effectively exhibited.
In the above, spray application has been described as a form of adding the paper strength agent to the pulp fiber web PWF, but the addition is not limited to this, and size press, roll coating, gravure coating, rod bar coating, air knife coating, etc. may also be used as the addition form.

The strength agent is preferably added in an amount calculated based on the solid content of the pulp fiber web PWF of 0.1 to 2.0% of the solid weight of the pulp fiber web PWF, and more preferably 0.3 to 1.5% of the solid weight of the pulp fiber web PWF. If the amount of strength agent added is too small, the effect of preventing fiber shedding is reduced, and conversely, if the amount is too large, the fiber shedding can be prevented, but the feeling of use (softness) will be deteriorated.
The strength agent is preferably sprayed onto the pulp fiber web PWF at a concentration of 0.5 to 2.0%, more preferably 0.7 to 1.5%, and at a discharge pressure of 0.1 to 1.0 MPa, more preferably 0.3 to 0.8 MPa. If the pressure is too low, the strength agent will be scattered by the wind generated by the transported pulp fiber web, resulting in a decrease in yield. On the other hand, if the pressure is too high, the agent will bounce off the surface of the transported pulp fiber web, which also results in a decrease in yield.
The strength agent may be at least one selected from polyamide epichlorohydrin, polyamide epoxy, polyamide polyamine, etc. It is preferable to use a polyamide epichlorohydrin-based agent, and for example, wet strength agents WS4030, WS4038, WS4027, etc. manufactured by Seiko PMC Co., Ltd. By using a polyamide epichlorohydrin-based strength agent, the effect of preventing fiber shedding can be suitably obtained, and the use feeling of the composite nonwoven fabric can be improved.

A drying device 7 is further installed downstream of the suction device 6 and the paper strength agent adding device 9, and the composite nonwoven fabric WP including the pulp fiber web PWF sprayed with the paper strength agent is dried. The drying device 7 here is preferably a non-compression type dryer, preferably an air-through dryer. In Fig. 2, the rotatable dryer body 71 of the air-through dryer is a cylindrical body, and a number of through holes are provided on its peripheral surface, and it is preferable that hot air heated by a heat source (not shown) is sucked from the outer periphery of the dryer body toward the center.
The composite nonwoven fabric WP thus continuously produced is wound around the roll 81 of the winding device 8 after drying.

The composite nonwoven fabric manufacturing apparatus 1 described above can produce a composite nonwoven fabric with little fiber shedding, even when using a pulp fiber web produced by the airlaid method. In addition, the yield of the strength agent used can be increased compared to conventional methods, and the strength agent can be used efficiently to reduce manufacturing costs. In addition, the inclusion of foreign matter in the composite nonwoven fabric WP can be suppressed.

(Example)
The composite nonwoven fabrics of the examples produced by the above-mentioned production apparatus will be described below.
The composite nonwoven fabric was specified in terms of basis weight, thickness, drop absorbency, water retention (TWA), wet Taber value (number of times), and amount of strength agent added. The spunbond nonwoven fabric SW was specified in terms of basis weight, area of fusion points, area ratio, number and material. Furthermore, the pulp fiber web PFW was specified in terms of basis weight, and the weight composition of the spunbond nonwoven fabric SW and pulp fiber web PFW was specified.
The drop water absorbency was measured according to the Pulp and Paper Technology Association's J. TAPPI No. 32-2:2000 (Paper-Water Absorption Test Method-Part 2: Drop Method). The wet Taber value was measured using a Taber tester with friction wheel H-18 in accordance with the Taber type method described in the fabric test method for woven and knitted fabrics specified in JIS L 1096, and the value (number of times) was measured when a nonwoven fabric in a wet state was tested.
As shown in Table 1 below, composite nonwoven fabrics of Examples 1 to 3 and Comparative Examples 1 to 3 were manufactured, and the composite nonwoven fabrics were subjected to sensory evaluations during use regarding the amount of fallen fibers (ability to prevent fallen fibers), foreign matter contamination, and usability (softness). Seiko PMC's WS4030 (polyamide epichlorohydrin type) was used as the paper strength agent in both the airlaid method and the wet papermaking method. Southern pine was used for the pulp fiber web in all composite nonwoven fabrics.
1) Few fallen fibers: Few fallen fibers when using composite nonwoven fabric Almost no fallen fibers were observed (Excellent ◎)
Although some fiber has fallen out, it is still usable without any problems (Good).
Too much fiber falling out, difficult to use (Not good)
2) Foreign matter contamination: No foreign matter was found on the surface of the composite nonwoven fabric within an area of 1m x 1m (Good).
One or more foreign objects of a color other than white, measuring ^1mm2 or more, are found within an area of 1m x 1m (Failed x)
3) Feel (softness): Feel and softness when using the composite nonwoven fabric for wiping purposes Soft and good feel (Excellent ◎)
It feels a little hard, but it can be used without any problems (Good)
Hard and poor usability (Not acceptable)

As shown in Table 1 above, Examples 1 to 3 were suitable for provision as products, whereas Comparative Examples 1 to 3 were unsatisfactory in terms of fiber shedding prevention, foreign matter contamination, or sensory evaluation of usability.
In all of the above Examples 1 to 3, the basis weight was 51.0 g/ ^m2 or more and less than 85.0 g/ ^m2 , the thickness was 0.28 mm or more and less than 0.48 mm, and the amount of the strength agent added, calculated as the solid content, was within the range of 0.1 to 2.0% of the solid weight of the pulp fiber web.

This concludes the explanation of the embodiment, but it goes without saying that the present invention is not limited to the above embodiment and can be modified in various ways without departing from the spirit of the invention.

LIST OF SYMBOLS 1 Composite nonwoven fabric manufacturing device 2 Airlaid device 3 Spunbond nonwoven fabric supply device 4 Suction device 5 Water flow entanglement device 6 Suction device 7 Drying device 8 Winding device 9 Strength agent addition device 21 Defibrator 22 Duct 23 Airlaid hopper 24 Stacking position 28 Grip 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 TD Transport direction CD Width direction SA Paper strength agent

Claims (7)

A composite nonwoven fabric in which a pulp fiber web obtained by an airlaid method is laminated on and integrated with a spunbond nonwoven fabric,
A paper strength agent is added to the pulp fiber web,
the paper strength agent is unevenly distributed on the surface layer side of the pulp fiber web,
The composite nonwoven fabric has a basis weight of 51.0 g/ ^m2 or more and less than 85.0 g/ ^m2 , a thickness of 0.28 mm or more and less than 0.48 mm, and an added amount of the paper strength agent calculated as a solid content is 0.1 to 2.0% based on the solid weight of the pulp fiber web. 2. The composite nonwoven fabric according to claim 1, which has a water drop absorbency of 0.5 to 4.0 seconds, a water retention capacity of 220 to 380 g/m ² and a wet Taber value of at least 5 times. The spunbond nonwoven fabric has a basis weight of 7.0 to 20.0 g/ ^m2 ;
The composite nonwoven fabric according to claim 1 or 2, characterized in that the spunbonded nonwoven fabric includes a plurality of fusion points that connect the resin fibers forming the spunbonded nonwoven fabric, the area of each of the fusion points is 0.10 to 0.50 ^mm2 , the area ratio of the fusion points per unit area is 7 to 20%, and the number of the fusion points per unit area is 10 to 150/ ^cm2 . The composite nonwoven fabric according to any one of claims 1 to 3, characterized in that the material of the spunbond nonwoven fabric is one selected from the group consisting of nylon, vinylon, polyester, acrylic, polyethylene, polypropylene and polystyrene, or a mixture of two or more selected materials. The pulp fiber web has a basis weight of 40.0 to 70.0 g/ ^m2 ;
5. The composite nonwoven fabric according to claim 1, wherein a weight ratio of said spunbond nonwoven fabric to said pulp fiber web is 40/60 to 10/90 (wt %). The composite nonwoven fabric according to any one of claims 1 to 5, characterized in that the pulp fiber web is made of fibers of bleached softwood kraft pulp selected from the group consisting of radiata pine, slash pine, southern pine, lodgepole pine, spruce and Douglas fir. 7. A method for producing a composite nonwoven fabric according to claim 1, comprising: placing a pulp fiber web supplied by an airlaid method on a spunbond nonwoven fabric, subjecting the spunbond nonwoven fabric to a hydroentanglement treatment, and spraying a strength agent onto the pulp fiber web from the surface layer side of the pulp fiber web after the hydroentanglement treatment to produce the composite nonwoven fabric according to any one of claims 1 to 6.

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