ABSORBENT BODY PRODUCTION DEVICE AND ABSORBENT BODY PRODUCTION METHOD

An absorbent body production device and an absorbent body production method can suppress scattering of an absorbing substance during spraying of the absorbing substance to a substrate. A substrate is conveyed along a rotating outer circumferential surface of a conveyance drum. A granular absorbing substance is discharged from a spray port of a spray apparatus facing the outer circumferential surface of the conveyance drum, and the absorbing substance is sprayed to the substrate which is conveyed along the outer circumferential surface of the conveyance drum. The spray position at which the absorbing substance is sprayed to the substrate is controlled. For example, the position of the spray port of the spray apparatus, or the angle at which the absorbing substance is discharged from the spray port of the spray apparatus is controlled.

TECHNICAL FIELD

The present invention relates to an absorbent body production device and an absorbent body production method, and more specifically, relates to a technology of producing an absorbent body by spraying an absorbing substance to a substrate.

BACKGROUND ART

An absorbent body containing an absorbing substance capable of absorbing and holding liquid is used for absorbent articles such as disposable diapers, disposable shorts, sanitary napkins and incontinence pads.

The absorbent body is produced, for example, by using an absorbent body production device shown in a schematic configuration view ofFIG.6. As shown inFIG.6, a substrate101is conveyed along an outer circumferential surface141of a rotating conveyance drum104. The conveyance drum104sucks air from the outside toward the inside through the outer circumferential surface141. A granular absorbing substance103is stored in a tank105of a spray apparatus, and is dropped little by little toward the conveyance drum104. The absorbing substance 8 is sprayed to the substrate101when the substrate101passes an area104where the absorbing substance 8 drops. A coating sheet102is overlaid on the substrate101to which the absorbing substance 8 has been sprayed, and the coating sheet102and the substrate101are ultrasonically joined together by an ultrasonic horn193, thereby forming an absorbent body120(for example, see Patent Literature 1).

CITATION LIST

Patent Literature

SUMMARY OF THE INVENTION

Problem to Be Solved by the Invention

In a case where the absorbent body is produced by spraying the absorbing substance to the substrate being conveyed by the conveyance drum as described above, the suction pressure is adjusted in a manner that the absorbing substance having reached the substrate is trapped.

However, when the reaching position (spray position) of the absorbing substance is inappropriate, there are cases where the absorbing substance is bounced off the substrate and this makes it impossible to suppress scattering of the absorbing substance even if the suction pressure is adjusted.

Moreover, for example, when the rotation speed of the conveyance drum is increased, there are cases where the absorbing substance is bounced off the substrate by a shift of the reaching position (spray position) of the absorbing substance caused by an air flow occurring in the rotation direction of the drum and this makes it impossible to suppress scattering of the absorbing substance even if the suction pressure is adjusted.

In view of such circumstances, a problem to be solved by the present invention is to provide an absorbent body production device and an absorbent body production method that make it possible to suppress scattering of the absorbing substance during spraying of the absorbing substance to the substrate.

Means for Solving the Problem

To solve the above-mentioned problem, the present invention provides an absorbent body production device structured as follows:

The absorbent body production device is provided with (a) a conveyance drum having a rotating cylindrical outer circumferential surface and conveying a substrate along the outer circumferential surface, (b) a spray apparatus having a spray port facing the outer circumferential surface of the conveyance drum, discharging a granular absorbing substance from the spray port and spraying the absorbing substance to the substrate being conveyed along the outer circumferential surface of the conveyance drum, and (c) spray position control means for controlling a spray position at which the absorbing substance is sprayed to the substrate.

According to the above-described structure, the discharge position at which the absorbing substance is sprayed to the substrate can be controlled in a manner that scattering of the absorbing substance is suppressed during spraying of the absorbing substance to the substrate.

In the above-described structure, the absorbing substance may be sprayed to an area where the outer circumferential surface of the conveyance drum moves downward or the absorbing substance may be sprayed to an area where the outer circumferential surface of the conveyance drum moves upward.

Preferably, the spray position control means controls the spray position in a manner that, when an angle formed by a horizontal plane and a straight line vertical to a rotation center line of the conveyance drum and passing the spray position is θ, the angle θ is within a predetermined range satisfying 0°≤θ≤60°.

In this case, it is easy to trap the sprayed absorbing substance in the substrate.

The above-mentioned angle θincludes not only the angle θ shown in a first and second embodiments described later but also the angle θ′ shown in a first modification described later.

More preferably, the spray position control means controls the spray position in a manner that θ=45° is included within the predetermined range of the angle θ.

In this case, it is easier to trap the sprayed absorbing substance in the substrate.

Preferably, the spray position control means controls a position of the spray port of the spray apparatus or a discharge angle at which the absorbing substance is discharged from the spray port of the spray apparatus.

In this case, it is easy to control the spray position of the absorbing substance.

Moreover, to solve the above-mentioned problem, the present invention provides an absorbent body production method structured as follows:

The absorbent body production method is provided with (i) a conveyance step of conveying a substrate along a rotating outer circumferential surface of a conveyance drum and (ii) a spray step of discharging a granular absorbing substance from a spray port facing the outer circumferential surface of the conveyance drum and spraying the absorbing substance to the substrate being conveyed along the outer circumferential surface of the conveyance drum. At the spray step, a spray position at which the absorbing substance is sprayed to the substance is controlled.

According to the above-described method, the spray position at which the absorbing substance is sprayed to the substrate can be controlled in a manner that scattering of the absorbing substance is suppressed during spraying of the absorbing substance to the substrate.

In a preferred mode, the outer circumferential surface of the conveyance drum is air-permeable. The substrate includes (a) an air-permeable support sheet conveyed along the outer circumferential surface of the conveyance drum and (b) a pulp layer where pulp crushed and conveyed by a duct is sucked and fiber-laminated in a predetermined pattern on the support sheet. At the spray step, the absorbing substance is sprayed to the pulp layer.

In another preferred mode, the substrate includes a nonwoven fiber sheet conveyed along the outer circumferential surface of the conveyance drum. At the spray step, the absorbing substance is sprayed to one main surface of the nonwoven fabric sheet. At the conveyance step, the nonwoven fabric sheet includes a bulky structure constituting at least part of the one main surface and having a gap for the absorbing substance to enter.

Effects of the Invention

According to the present invention, scattering of the absorbing substance can be suppressed during spraying of the absorbing substance to the substrate.

MODE FOR CARRYING OUT THE INVENTION

<First embodiment> An absorbent body production device10and an absorbent body production method according to the first embodiment will be described with reference toFIGS.1to3.

FIG.1is a schematic view showing the structure of the absorbent body production device10.FIG.2is a relevant part schematic view of the absorbent body production device10. As shown inFIGS.1and2, in the absorbent body production device10, a duct22for forming a pulp layer2band a spray apparatus30that sprays a granular absorbing substance8to the formed pulp layer2bare disposed around a conveyance drum12. The conveyance drum12conveys in the direction indicated by the arrow12r, a first and second sheets2aand4are conveyed in the directions indicated by the arrows2xand4x, and an absorbent body6is conveyed in the direction indicated by the arrow6x.

The conveyance drum12has a cylindrical outer circumferential surface12s, and is disposed in a manner that the rotation center line12xextends horizontally. The outer circumferential surface12sof the conveyance drum12is air-permeable; for example, a large number of suction holes (not shown) are formed in a predetermined area of the outer circumferential surface12s. A non-illustrated suction box is disposed inside the conveyance drum12, and air is sucked from the outside toward the inside through the outer circumferential surface12sof the conveyance drum12in a predetermined range (for example, a range of substantially 180° of the upper half of the conveyance drum12).

The first sheet2ais wound on the outer circumferential surface12sof the conveyance drum12through a first guide roll14, and is conveyed along the outer circumferential surface12sof the conveyance drum12.

The duct22has an opening24facing the outer circumferential surface12sof the conveyance drum12at one end thereof, a crusher20is connected to the other end thereof, and pulp (not shown) crushed by the crusher20is conveyed to the opening24through the duct22. After discharged from the opening24, the crushed pulp is sucked in a predetermined pattern on the first sheet2abeing conveyed along the outer circumferential surface12sof the conveyance drum12, thereby forming a fiber-laminated pulp layer2b(seeFIG.2). The first sheet2aand the pulp layer2bare a substrate2, and are conveyed integrally. The first sheet2ais a support sheet2athat supports the pulp layer2b.

The spray apparatus30has a spray port32(seeFIG.2) facing the outer circumferential surface12sof the conveyance drum12, and discharges, from the spray port32, the granular absorbing substance8(seeFIG.2) capable of absorbing and holding liquid. The absorbing substance8is, for example, powdery or granular SAP (Superabsorbent polymer). The granular absorbing substance8discharged from the spray port32is sprayed to the pulp layer2b. The spray apparatus30may be structured as appropriate; for example, it may be structured so as to discharge a mixture of two or more kinds of absorbing substances.

A second sheet4is overlaid on the pulp layer2bto which the granular absorbing substance8has been sprayed, through a second guide roll16and a compression roll17, thereby forming the absorbent body6where the pulp layer2bto which the absorbing substance8has been sprayed is sandwiched between the first sheet2aand the second sheet4. The absorbent body6is compressed in the thickness direction when passing between the conveyance drum12and the compression roll17, and then, conveyed to the post-process through a third guide roll18.

FIG.3is a block diagram of the absorbent body production device10. As shown inFIG.3, in the absorbent body production device10, the following are connected to a control device50that supervises the control of the overall absorbent body production device10: a conveyance motor52that rotates the conveyance drum12; a suction motor54; a spray motor56that drives the spray apparatus30; and an operation device58for operating the absorbent body production device10. Further, a spray position change device60, a detection device62and a storage device64described later are connected to the control device50. The control device50is, for example, a control computer such as a sequencer.

As shown inFIG.1, the spray position of the granular absorbing substance8can be defined by an angle θ. The angle θ is an angle formed by a horizontal plane H and a straight line L vertical to the rotation center line12xof the conveyance drum12and passing a point P within the spray position. The spray position of the absorbing substance8, that is, the angle θ is preferably within a predetermined range satisfying 0°≤θ≤60°, and is most preferably θ=45°.

The absorbent body production device10which is provided with spray position control means for controlling the spray position of the absorbing substance8is capable of controlling the spray position of the granular absorbing substance8according to the production condition of the absorbent body6.

For example, the spray position control means controls the position of the spray port32of the spray apparatus30or the discharge angle at which the absorbing substance8is discharged from the spray port32of the spray apparatus30. In this case, the spray position control means includes (a) the spray position change device60(seeFIG.3) that changes the spray position of the granular absorbing substance8, (b) the detection device62(seeFIG.3) that detects the spray position or the spray condition of the absorbing substance8and (c) the control device50.

The spray position change device60changes the position of the spray port32of the spray apparatus30with respect to the outer circumferential surface12sof the conveyance drum12or the discharge angle at which the absorbing substance8is discharged from the spray port32of the spray apparatus30to the outer circumferential surface12sof the conveyance drum12. In a case where the position of the spray port32of the spray apparatus30is changed, the spray position change device60may move at least the spray port32of the spray apparatus30in the vertical direction Z and/or the horizontal direction Y shown inFIG.1, may move it in a diagonal direction intersecting the vertical direction Z and the horizontal direction Y, or may move it arcuately around the conveyance drum12.

The detection device62is, for example, a camera that images the spray position of the absorbing substance8and its surroundings, or a sensor that detects the range where the absorbing substance8is sprayed (for example, the above-mentioned angle θ of the spray position of the absorbing substance8) by sensor light passing near the spray position of the absorbing substance8.

The control device50controls the spray position change device60in a manner that the angle θ of the spray position of the absorbing substance8is within the predetermined range satisfying 0°≤θ≤60° while monitoring the spray position or the spray condition of the absorbing substance8detected by the detection device62.

For example, the control device50controls the spray position change device60in a manner that the angle θ of the spray position of the absorbing substance8is not more than 45° when the rotation speed of the conveyance drum12is V1.

When the rotation speed of the conveyance drum12is changed to V2(V2>V1) in a manner that the angle θ of the spray position of the absorbing substance8is decreased to not more than 30°, the control device50controls the spray position change device60in a manner that the angle θ of the spray position of the absorbing substance8is not more than 45°.

By thus controlling the spray position of the absorbing substance8by the spray position control means, scattering of the absorbing substance8during spraying of the absorbing substance8to the substrate2can be suppressed, so that the spraying condition of the absorbing substance8is stabilized.

The spray position control means may automatically control the spray position of the absorbing substance8according to the production condition of the absorbent body6.

In this case, the spray position control means includes, for example, the storage device64(seeFIG.3) prestoring optimum spray positions of the absorbing substance8, that is, spray position information in association with production conditions of the absorbent body6. Examples of the production conditions of the absorbent body6include the rotation speed of the conveyance drum12, the kind, spray amount and spray pattern of the absorbing substance8to be sprayed and the kind (for example, fluff where crushed pulp or the like is fiber-laminated or a nonwoven fabric sheet processed so as to be bulky) and characteristics (for example, the thickness and the density) of the substrate to which the absorbing substance8is to be sprayed.

When the operation device58accepts an input of a production condition such as the rotation speed of the conveyance drum12, the control device50of the spray position control means reads, from the storage device64, the spray position information prestored in association with the production condition the input of which is accepted, and controls the spray position change device60in a manner that the absorbing substance8is sprayed to the optimum spray position indicated by the read spray position information while monitoring the spray position or the spray condition of the absorbing substance8detected by the detection device62.

Automatically controlling the spray position of the absorbing substance8according to the production condition of the absorbent body6as described above makes it easy to change the production condition of the absorbent body6.

The spray position control means may be capable of manually controlling the spray position by the operation device58.

Next, an absorbent body production method of the first embodiment1using the absorbent body production device10will be described.

The absorbent body production method of the first embodiment is provided with (i) a conveyance step of conveying the substrate2along the rotating outer circumferential surface12sof the conveyance drum12and (ii) a spray step of discharging the granular absorbing substance8from the spray port32facing the outer circumferential surface12sof the conveyance drum12and spraying the absorbing substance8to the substrate2being conveyed along the outer circumferential surface12sof the conveyance drum12. At the spray step, the spray position at which the absorbing substance8is sprayed to the substrate2is controlled.

According to the above-described method, the spray position of the absorbing substance8can be controlled in a manner that scattering of the absorbing substance8is suppressed during spraying of the granular absorbing substance8to the substrate2.

Specifically, the outer circumferential surface of the conveyance drum is air-permeable. The substrate2includes (a) the air-permeable first sheet2aconveyed along the outer circumferential surface12sof the conveyance drum12and (b) the pulp layer2bwhere pulp crushed and conveyed by the duct22is sucked and fiber-laminated in a predetermined pattern on the first sheet2a. At the spray step, the absorbing substance8is sprayed to the pulp layer2b.

<Second embodiment> An absorbent body production device10aand an absorbent body production method of the second embodiment using a nonwoven fabric as the substrate will be described with reference toFIG.4. In the following, components the same as those of the first embodiment are denoted by the same reference numerals, and differences from the first embodiment will be described mainly.

As shown inFIG.4, in the absorbent body production device10aof the second embodiment, as in the first embodiment, a spray apparatus31is disposed around the conveyance drum12.

Unlike the first embodiment, a nonwoven fabric sheet3is conveyed along the outer circumferential surface12sof the conveyance drum12, and the granular absorbing substance8is sprayed to one main surface3sof the nonwoven fabric sheet3. The other main surface3tof the nonwoven fabric sheet3is supported by the outer circumferential surface12sof the conveyance drum12.

The nonwoven fabric sheet3previously includes a bulky structure3kconstituting at least part of the one main surface3sand having a gap for the granular absorbing substance8to enter. For example, the nonwoven fabric sheet3is napped along the one main surface3sby a non-illustrated napping device, thereby forming the bulky structure3k. While an appropriate kind of nonwoven fabric sheet is used as the nonwoven fabric sheet3, for example, an air-through nonwoven fabric is used. The nonwoven fabric sheet3may be a composite sheet where two or more nonwoven fabric sheets are pasted together.

As in the first embodiment, the spray apparatus31discharges the granular absorbing substance8from a non-illustrated spray port facing the outer circumferential surface12sof the conveyance drum12. While spray apparatus31may be structured as appropriate, for example, it may be structured so as to discharge a mixture of two or more kinds of absorbing substances. The discharged absorbing substance8is sprayed to the one main surface3sof the nonwoven fabric sheet3being conveyed by the conveyance drum12. At least some of the sprayed absorbing substance8enters the bulky structure3kof the nonwoven fabric sheet3from the one main surface3sof the nonwoven fabric sheet3.

Although the sprayed absorbing substance8enters the bulky structure3kof the nonwoven fabric sheet3even if the structure is not employed where air is sucked from the outside toward the inside through the outer circumferential surface12sof the conveyance drum12, a structure where the outer circumferential surface12sof the conveyance drum12is air-permeable and air is sucked from the outside toward the inside through the outer circumferential surface12sof the conveyance drum12is preferable because the sprayed absorbing substance8readily enters the bulky structure3kof the nonwoven fabric sheet3.

A coating sheet5is overlaid on the nonwoven fabric sheet3to which the absorbing substance8has been sprayed, through a first guide roll16aand a compression roll17a. An adhesive is previously applied to the main surface of the coating sheet5facing the nonwoven fabric sheet3by a first adhesive application device40disposed on the upstream side of the compression roll17ain the conveyance direction. The nonwoven fabric sheet3and the coating sheet5are compressed when passing between the conveyance drum12and the compression roll17a, so that an absorbent body7is formed where the coating sheet5is bonded to the one main surface3sof the nonwoven fabric sheet3to which the absorbing substance8has been sprayed.

For example, the width of the coating sheet5is larger than that of the nonwoven fabric sheet3, and the coating sheet5is overlaid on the nonwoven fabric sheet3in such a manner that the coating sheet5protrudes on one side or on both sides in the width direction of the nonwoven fabric sheet3. On the absorbent body7, an adhesive is applied to the part of the coating sheet5protruding from the nonwoven fabric sheet3by a second adhesive application device42. Then, the part of the coating sheet5protruding from the nonwoven fabric sheet3is folded so as to overlap the other main surface3tof the nonwoven fabric sheet3by a folding device44. Then, the absorbent body7is compressed in the thickness direction when passing between a pair of compression rolls46pand46qin the directions indicated by the arrows46mand46n.

The absorbent body7may be produced by overlaying the coating sheet5on the nonwoven fabric sheet3in a manner that the coating sheet5does not protrude in the width direction of the nonwoven fabric sheet3.

Like the absorbent body production device10of the first embodiment, the absorbent body production device10aof the second embodiment is provided with the spray position control means for controlling the spray position of the absorbing substance8and is capable of controlling the spray position of the absorbing substance8. Consequently, scattering of the absorbing substance can be suppressed during spraying of the absorbing substance to the substance.

Next, an absorbent body production method of the second embodiment using the absorbent body production device10awill be described.

The absorbent body production method of the second embodiment is provided with the conveyance step and the spray step the same as those of the absorbent body production method of the first embodiment, and at the spray step, the spray position at which the absorbing substance is sprayed to the substrate is controlled. However, unlike the absorbent body production method of the first embodiment, the substrate3includes the nonwoven fabric sheet3conveyed along the outer circumferential surface12sof the conveyance drum12. At the spray step, the absorbing substance8is sprayed to the one main surface3sof the nonwoven fabric sheet3. At the conveyance step, the nonwoven fabric sheet3includes the bulky structure3kconstituting at least part of the one main surface3sand having a gap for the absorbing substance8to enter.

<First modification>FIG.5is an explanatory view of the spray position. While in the first and second embodiments, a case is shown where, as shown inFIG.5, the absorbing substance is sprayed to an area where the outer circumferential surface12sof the conveyance drum12rotating in the direction indicated by the arrow12rmoves downward (for example, within a predetermined range satisfying 0°≤θ≤60° where θ is an angle formed by the horizontal plane H and the straight line L vertical to the rotation center line12xof the conveyance drum12and passing the point P within the spray position), the absorbing substance may be sprayed to an area where the outer circumferential surface12sof the conveyance drum12moves upward.

In the case where the absorbing substance is sprayed to the area where the outer circumferential surface12sof the conveyance drum12moves upward, as in the first and second embodiments, the spray position of the granular absorbing substance can be defined by an angle θ′. The angle θ′ is an angle formed by the horizontal plane H and a straight line L′ vertical to the rotation center line12xof the conveyance drum12and passing a point P′ within the spray position. The spray position of the absorbing substance, that is, the angle θ′ is preferably within a predetermined range satisfying 0°≤0′≤60°, and is most preferably θ′=45°.

<Summary> As described above, scattering of the absorbing substance8can be suppressed during spraying of the absorbing substance8to the substrate2or3by controlling the spray position of the absorbing substance8.

The present invention is not limited to the above-described embodiments and may be variously modified when carried out.

For example, the absorbing substance8may be sprayed intermittently. In this case, by cutting the absorbent body6or7in an area where no absorbing substance8is sprayed, individual pieces of the absorbent body6or7with no spill of the absorbing substance8can be formed.

Moreover, an absorbent body6may be produced in which one side or both sides in the width direction of the first sheet2aand/or the second sheet4of the first embodiment are folded.