Method for treating nonwoven fabric sheet by combination of activation and bonding

Abstract

The present invention relates to a method for producing a nonwoven sheet comprising a combined activation and bonding step, and further relates to the application of this method to the production of elastically extensible nonwoven laminate sheets, sheets produced by such a method, and uses of such sheets.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a nonwoven sheet including a step of combining activation and bonding. The present invention further relates to applying this method to the manufacture of an elastically stretchable nonwoven sheet, a sheet manufactured by such a method, and the use of such a sheet.

Background Art

[0002] In the hygiene industry, nonwoven sheets are widely used as materials for manufacturing baby diapers and similar products. In many cases, for example, an elastically stretchable material is required to make the rear ear part of an open-type diaper or the belt part of a pants-type baby diaper. However, standard nonwoven sheets do not meet this requirement.

[0003] Traditional methods to address this problem of limited elastic stretch of nonwoven sheets include providing an elastic film between layers of nonwoven material. The resulting laminate may have good elastic properties, but the elastic film does not allow air to pass through and can be uncomfortable for the wearer. Other methods consist of including elastic threads, typically those called Lycra threads, in the sheet. The drawbacks of this method are that the local elastic force can also be uncomfortable for the wearer and that the threads are prone to breakage during manufacturing.

[0004] In addition, by using an elastic film or thread, the sheet obtains elasticity, but only within the limit of the maximum elongation of the nonwoven material with the elastic film or thread. The elongation at break of most common nonwoven materials is at most 50 - 80% in the machine direction (MD) and 70 - 100% in the cross-machine direction (CD) (WSP 110.4), and is usually even smaller. That is, it can only stretch a very limited amount before breaking. However, in the application fields specified above, the sheet is required to elastically stretch to 150% of its original dimensions (becoming 250% of its original dimensions), and depending on the individual application field, it may be required for either the machine direction or the cross-machine direction. For example, in a typical manufacturing process for making a general open-type or tape-type baby diaper, the material used for the rear ear laminate is required to exhibit the above-mentioned degree of elastic elongation in the CD. On the other hand, for making adult or baby diaper pants, in a typical manufacturing process, the material used for elastic applications such as belts is required to exhibit the same degree of elastic elongation in the MD.

[0005] A common way to address the problem of limited elongation of nonwoven materials is to provide pleats in the nonwoven material laminated to the elastic film or thread. In this way, the lack of elongation of the nonwoven material itself is compensated for by the additional material stored in each pleat. However, the drawback of providing pleats is that more materials are required for manufacturing, and the final product becomes thicker. This increases the heat insulation property and makes it more conspicuous, which causes dissatisfaction among consumers.

[0006] A nonwoven sheet that can elastically stretch as an inherent property is disclosed in WO 2020 / 187540 A1. These sheets comprise an elastic spunbond web made of elastic fibers and a spunbond carrier layer of a nonwoven sheet made of crimped fibers, and are pre-stretched by passing them through an activation unit comprising an interacting pair of corrugated rollers. The elastic web can be non-bonded, but the bonding of the carrier layer is necessary to provide a useful nonwoven material. At the same time, due to the necessity of bonding the carrier layer, the degree to which these layers can be pre-stretched without being broken is greatly limited. This is because the bonding fixes the position of the fibers and limits the possibility of repositioning. By using an open dot bonding pattern and crimped fibers, the carrier layer becomes more flexible than a general nonwoven. For example, an elastic elongation of about 250% of the original dimensions can be achieved at least in the CD direction, meeting industrial requirements, but the elastic elongation in the MD direction in these sheets is more limited.

[0007] Another corresponding method for manufacturing a nonwoven sheet that can elastically stretch as an inherent property is disclosed in EP 3 715 517 A1. The method disclosed in this document depends on an in-line process and bonding a carrier layer and an elastic layer, which is done prior to the activation of the already bonded sheet. Despite the use of crimped fibers in this fabric, since the carrier layer is bonded before activation, the degree to which this sheet can be pre-stretched without being broken is limited.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] Therefore, in the hygiene industry, there is a need for nonwoven sheets that can be elastically stretched even more significantly as an inherent property, particularly in the machine direction, but also in the machine cross direction.

MEANS FOR SOLVING THE PROBLEM

[0009] To solve this problem, not only was the problem solved, but the idea in the treatment of nonwoven fabrics, which is also applicable to other aspects, was developed.

[0010] Specifically, the present invention proposes a method for manufacturing a nonwoven fabric sheet. The method includes a step (a) of preparing a precursor sheet. Further, the method includes a step (b) of obtaining a nonwoven fabric sheet by simultaneously activating and bonding the precursor sheet. The activation includes passing the precursor sheet between a pair of activation rollers having a plurality of meshing ribs and grooves arranged in parallel on cooperating surfaces, thereby stretching the precursor sheet in a direction perpendicular to the ribs and grooves. And the bonding includes embossing bonding points on the precursor sheet while it is stretched. The embossing is performed by embossing protrusions arranged along the tops of the ribs and / or grooves of the activation rollers.

[0011] In one embodiment, the ribs and grooves are arranged in the machine direction and extend annularly on the surface of the roller, whereby the precursor sheet is stretched in the machine cross direction.

[0012] In another embodiment, the ribs and grooves are arranged in the machine cross direction and extend axially on the surface of the roller, whereby the precursor sheet is stretched in the machine direction.

[0013] The precursor sheet may be bonded to a nonwoven material having one or more layers. In a preferred embodiment, it may be a calender-bonded material.

[0014] Alternatively, the precursor sheet may be an unbonded fiber web. Such a web is an unbonded precursor of solidified fibers that becomes a nonwoven material. The fibers constituting the web are not bonded by calendar embossing and preferably are not bonded by other bonding processes such as needling or spunlace. Thus, they are still highly mobile and have a much higher potential for rearrangement within the web compared to the fibers of the bonded layers such as the sheet of WO 2020 / 187540 A1. From this, it is possible to further pre-stretch much more greatly compared to the bonded precursor material, and it is possible to exceed 150% for both MD and CD if necessary, without the structure breaking.

[0015] Most preferably, the nonwoven material or fiber web comprises at least one spunbond layer. Examples include single-layer S material, multi-layer Sn material, or SM- or SMS-type laminated fabrics that combine a spunbond layer and a meltblown layer.

[0016] In a preferred embodiment, the method is a method for manufacturing an elastically stretchable sheet, the sheet comprising a first nonwoven carrier layer, an elastic nonwoven layer containing elastic fibers, and optionally a second nonwoven carrier layer, and the precursor sheet prepared in step (a) is a first carrier structure that is a precursor of the first nonwoven carrier layer in the sheet to be formed, an elastic structure that is a precursor of the elastic nonwoven layer in the sheet to be formed and contains elastic fibers, and optionally a second carrier structure that is a precursor of the optional second nonwoven carrier layer in the sheet to be formed.

[0017] In one variation of this embodiment, the first carrier structure is an unbonded fiber carrier web, the elastic structure is an unbonded elastic layer precursor web containing elastic fibers, and any second carrier structure is a second unbonded fiber carrier web, and none of the fiber webs are bonded by calendar embossing.

[0018] In this modification example, by joining the webs simultaneously in a pre - advanced state, the need for joining the webs to form a firm non - woven fabric material can be satisfied, and it does not prevent the ability of the carrier web to stretch to the extent of pre - stretching later. On the other hand, if the joining is performed as a separate process after the precursor sheet has shrunk to its original dimensions due to the elastic force of the elastic layer, this ability is generally lost. This is because the fibers are joined at the positions in the shrunk state.

[0019] In another modification example of this embodiment, the first carrier structure is a joined non - woven carrier layer, the elastic structure is a joined non - woven carrier layer containing elastic fibers, the second carrier structure which may optionally be included is a joined non - woven carrier layer, and all non - woven layers are joined by calendar embossing.

[0020] In this modification example, by using a relatively open joining pattern within the structure, stability and processability can be enhanced while maintaining a certain degree of mobility within the pre - stretched structure. The joining points applied in step (b) where activation and joining are performed simultaneously are superimposed on the joining points existing in the supplied structure.

[0021] Due to the pre - stretching of the precursor sheet, the microscopic fiber configuration of the material changes locally. In the embodiments including the elastic and carrier layers described above, this change mainly occurs in the carrier structure which is generally non - elastic. Specifically, the microscopic fiber configuration changes back and forth along a regular repeating pattern that reflects the arrangement of the ribs and grooves on the roller surface, that is, a pattern of parallel stripes. If the ribs and grooves are oriented in the machine direction, the microscopic fiber configuration of the structure changes back and forth along a regular repeating pattern in the cross - machine direction of the fabric and is constant along the lines in the machine direction. If the ribs and grooves are oriented in the cross - machine direction, the microscopic fiber configuration of the structure changes back and forth along a regular repeating pattern in the machine direction of the fabric and is constant along the lines in the cross - machine direction.

[0022] Microscopic changes in the fiber structure are related in particular to the average fiber orientation and fiber density. Generally, the elongation is not large in some regions, for example, along the top lines of ribs and grooves, and is large in other regions, for example, in the regions adjacent to the top lines. In the regions where the elongation is larger, the average fiber orientation changes more greatly along the direction of elongation, and the fiber density becomes lower.

[0023] Since the embossing protrusions are arranged along the top of the rib or groove, the bonding points are embossed side by side along the stripes of the pattern where the local fiber structure is the same. Assuming that the ribs and grooves are oriented in the machine direction, the bonding points are embossed along the lines parallel to the machine direction where the local fiber structure is the same. Assuming that the ribs and grooves are oriented in the cross-machine direction, the bonding points are embossed along the lines parallel to the cross-machine direction where the local fiber structure is the same. Assuming that the elongation is minimal along the top line, the bonding points are embossed within the stripe pattern range in the fabric, and this range has the highest fiber density on average and the most fibers in the length direction of the stripes on average.

[0024] Specifically described in the above-described embodiments for the stretchable nonwoven sheet including the elastic layer and the carrier layer, due to the shrinkage of the sheet produced after the preliminary stretching during the simultaneous activation and bonding, the microscopic fiber structure within the stripe pattern range between the rows of bonding points in the product sheet has changed compared to the stretched structure. Therefore, in the product sheet, it is not necessarily true that the fiber density is the highest or the average fiber orientation is the most obvious along the row of bonding points. Nevertheless, in the product sheet, the fiber structure changes back and forth along the regular repeating pattern of parallel stripes, and the bonding points are arranged side by side along the stripes of the pattern where the local fiber structure is the same.

[0025] Assuming that a second carrier structure is present in the precursor, the elastic structure is sandwiched between the two carrier structures. Similarly, in the product sheet, if there is a second carrier layer, the elastic layer is sandwiched between the two carrier layers. There may be more than three layers by having additional elastic layers, additional carrier layers, or non-elastic layers. Also, in each layer, there may be two or more identical or similar sub-layers, each formed at different fiber laying stages of the manufacturing process.

[0026] Returning to a more general context, in one embodiment, steps (a) and (b) are carried out continuously in-line. Such an overall in-line configuration is extremely advantageous in terms of manufacturing efficiency.

[0027] In other embodiments, steps (a) and (b) are carried out offline on a different line. On one line, the precursor sheet is prepared on one line in step (a), then wound up and transported to another line where a combination of activation and bonding is carried out according to step (b). In the above-described embodiment including the elastic layer and the carrier layer, the unbonded precursor sheet obtained in step (a) is stable enough to be manipulated without the layers peeling off. This is due to the inherent adhesiveness of the elastic fibers formed from the thermoplastic elastic material.

[0028] In an embodiment, the amount of (preliminary) stretching of the precursor sheet during step (b) determines the amount by which the product fabric can elastically stretch in a direction perpendicular to the direction of the stripes. It is desired that the product fabric can stretch to 150%, preferably 200%, of its original dimensions in the corresponding direction. Thus, in one embodiment, in step (b), the precursor sheet is stretched to 150%, preferably 200%, of its original dimensions in a direction perpendicular to the ribs and grooves.

[0029] The elongation during activation is controlled by the distance between adjacent ribs / grooves, the depth to which the rib of one roller meshes with the groove of another roller (meshing depth), and the width of these structures. In an exemplary embodiment, the distance between adjacent ribs / grooves is 1 to 12 mm, preferably 3 to 10 mm, more preferably 4 to 8 mm. The meshing depth is between 1 and 10 mm, preferably between 3 and 7 mm. The width of the rib / groove is 0.5 to 3 mm, preferably about 1 mm.

[0030] The pattern of the stripes in the product sheet generally corresponds to the sum of the distance between adjacent ribs / grooves and the width of the rib / groove, with the local fiber configuration repeating. Thus, in one embodiment, it may repeat every 1 to 12 mm, preferably every 3 to 10 mm. If one row of bonding points is embossed once per repetition, the distance between the rows of bonding points is 2 to 15 mm, preferably 5 to 10 mm.

[0031] Referring again to the above-described embodiment of the stretchable nonwoven sheet having an elastic layer and a carrier layer, the basis weight of each carrier precursor structure in the precursor sheet and the basis weight of the corresponding carrier layer in the product sheet are between 5 and 40 g / m 2 preferably between 8 and 30 g / m 2 more preferably between 10 and 25 g / m 2 even more preferably between 15 and 20 g / m 2 between. The basis weight of the elastic layer is between 10 and 140 g / m 2 preferably between 20 and 120 g / m 2 more preferably between 20 and 12 g / m 2 between. Setting these basis weights has been found to be useful in terms of the feel, elastic properties, and stability of the fabric.

[0032] Returning again to a more general context, the embossing protrusions are preferably heated to a temperature above 50°C, preferably above 80°C, and it is preferable to melt the fibers of the precursor sheet together under local pressure. Usually, the preferred temperature is even higher than 80°C. The exact temperature selection depends on the type of polymer material used. In this context, the temperature of the embossing protrusions may coincide with at least the glass transition temperature of the polymer used, or may exceed the glass transition temperature of the polymer used by at least 10°C or at least 20°C. The heating of the protrusions may be achieved by heating the entire surface of the activation roller, or may be achieved by locally heating only the peripheral region of the embossing protrusions or the embossing protrusions themselves. In other embodiments, ultrasonic embossing is used. That is, the embossing protrusions are vibrated at an ultrasonic frequency to melt the fibers in the structure of the precursor sheet together. This option is particularly suitable when the difference in the melting points of the respective materials between the carrier structure and the elastic structure is relatively large. The local impact can be realized by the superposition of interlocking independent ultrasonic waves by each embossing protrusion. The temperature and ultrasonic vibration can also be used in combination.

[0033] Coating the activation roller in the vicinity of the embossing protrusions with an inert material such as a fluoropolymer, for example PTFE, can improve the accuracy and regularity of the embossing process in some cases, especially when using thermal embossing.

[0034] Returning again to the above-described embodiments specific to the stretchable nonwoven sheet having an elastic layer and a carrier layer, in one embodiment, the elastic layer precursor structure is composed of a thermoplastic elastomer material, preferably endless fibers of spunbonded fibers. In other embodiments, meltblown can be used instead of spunbonded to form the endless fibers of the elastic layer precursor structure. Correspondingly, in the product sheet, the elastic nonwoven structure in one embodiment is a spunbonded or meltblown structure and includes elastic endless fibers made of a spunbonded or meltblown formed from a thermoplastic elastomer polymer material.

[0035] The thermoplastic elastomer material includes thermoplastic polyolefin elastomer (TPE-o), preferably a thermoplastic polyolefin elastomer containing a propylene-α-olefin copolymer. Instead of this, or in addition, that is, as a mixture, other thermoplastic elastomer materials such as thermoplastic polyurethane (TPU) or styrene block copolymer (TPE-s) may be used. In one embodiment, up to 20% by weight, preferably up to 10% by weight, of a thermoplastic olefin such as homopolypropylene may be included in the thermoplastic elastomer and then in the thermoplastic elastomer material.

[0036] In one embodiment, a two-component elastic fiber composed of two different thermoplastic elastomers, for example, arranged in an adjacent configuration or a core-sheath structure, may be formed.

[0037] The first and optionally the second carrier layer precursor structures are of a spunbond structure. Instead of this, a meltblown fiber structure or a staple fiber structure such as a carded structure may also be used as the carrier layer precursor.

[0038] In one embodiment, the two carrier layer precursor structures on different surfaces of the elastic layer precursor structure are of different natures. For example, one of the carrier layer precursor structures is composed of spunbond fibers, and the other carrier layer precursor structure is composed of different spunbond fibers or meltblown or carded fibers. Correspondingly, in the product sheet, the two nonwoven carrier layers on different surfaces of the elastic nonwoven layer are of different natures. For example, one of the nonwoven carrier layers is a spunbond nonwoven, and the other nonwoven carrier layer is a different spunbond nonwoven or a meltblown or carded nonwoven.

[0039] In baby diapers or adult incontinence products, while it is desired that the inner surface of the product has a certain elasticity and adhesiveness to the skin to prevent displacement of the worn product, it is desired that the outer surface has as little adhesiveness to clothes as possible. In this case, it is preferable that a spunbond carrier nonwoven / precursor structure is provided in one of the elastic nonwoven / precursor structures, and a meltblown carrier nonwoven / precursor structure is provided in the other of the elastic nonwoven / precursor structures. Since meltblown nonwoven generally has higher affinity for skin and other materials than spunbond nonwoven, such a structure can satisfy the requirements described above.

[0040] Endless fibers may also be referred to as filaments in this technology. However, here, the term fiber is used for both endless fibers produced, for example, by spunbond and staple fibers that can have a specific length from 1 cm to several cm.

[0041] In one embodiment, all precursor structures are spunbond structures, and all layers of the product sheet are spunbond nonwovens.

[0042] As long as the carrier precursor structure / layer is spunbond fiber, these fibers can be crimped multi-component fibers. However, in contrast to the technology disclosed in WO 2020 / 187540 A1, crimped fibers are not essential to obtain a predetermined stretchability. However, in the context of the present invention, crimped fibers are also useful, for example, to enhance the loftiness and flexibility of the product.

[0043] However, in a preferred embodiment, at least one carrier layer is composed of non-crimped single-component fibers. This is because in any case, loftiness and flexibility are obtained by activation, the carrier layer composed of non-crimped single-component fibers is more stable, and non-crimped single-component fibers are easier to manufacture and more cost-effective.

[0044] Generally, the fibers of the carrier precursor structure / layer preferably consist of a thermoplastic polymer material, particularly a polyolefin such as polypropylene (PP), polyethylene (PE) or polypropylene-ethylene copolymer (co-PP).

[0045] Returning again to the general context, the plurality of layers of the precursor sheet may all be formed inline, for example, by spinning a plurality of structures onto a common conveyor belt. In other embodiments, the sheet is a pre-manufactured material and may be supplied, for example, by unwinding rolls manufactured at different lines, or even different locations.

[0046] In one embodiment, the precursor sheet supplied in step (a) may be pre-compressed by passing between a pair of pre-compression rollers having a flat surface before performing the combination of bonding and activation in step (b).

[0047] In one embodiment, the bonding area in the pre-stretched sheet may be between 2% and 15%, preferably between 4% and 8% (for the bonding points provided in step (b) where the combination of bonding and activation is performed). The number of bonding points is between 2 and 15, preferably between 4 and 8 (again, for the bonding points provided in step (b) where the combination of bonding and activation is performed). When the product sheet shrinks from the pre-stretched state to a relaxed state later, the bonding area and the number of such bonding points per unit area increase correspondingly. In this case, in the product sheet, in one embodiment, the corresponding bonding area is between 5% and 25%, preferably between 10% and about 20%. The number of corresponding bonding points is between 5 and 25, preferably between 10 and 20.

[0048] The sheet produced according to the present invention can be used in the production of sanitary products. For example, the sheet can be used in the production of tape-type diapers using the sheet as a material for the elastic rear ear part. In the current typical manufacturing process for this application in the industry, it is required that the material be elastically stretchable in the CD. In other examples, the sheet can be used in the production of diaper pants including the sheet as an elastic waist part material. In the current typical manufacturing process for this application in the industry, it is required that the material be elastically stretchable in the MD.

[0049] Further details and advantages of the present invention will become clearer by the figures and the examples that follow. The figures are as follows.

Brief Description of the Drawings

[0050]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0051] FIG. 1 shows a schematic cross-section of an elastically stretchable nonwoven sheet 100 according to the present invention. The elastic nonwoven sheet is sandwiched between first and second carrier layers 120 and includes an elastic nonwoven layer 130 containing elastic fibers.

[0052] An example of the machinery for manufacturing the elastically stretchable nonwoven sheet 130 according to the present invention is shown in FIG. 2.

[0053] The equipment includes a conveyor belt 10 and a total of three spunbonding devices 20, 30, and 40 arranged side by side on the conveyor belt.

[0054] In each spunbonding device, the molten thermoplastic polymer is extruded through the die holes. The extruded fiber yarns are then quenched and stretched to form endless fibers, which are placed on the conveyor belt 10 or on the web that has already been deposited thereon.

[0055] The first spunbonding device 20 deposits a first carrier layer precursor web made of ordinary polypropylene endless fibers on the conveyor belt 10. The middle spunbonding device 30 deposits an elastic carrier layer precursor web made of endless fibers of a thermoplastic elastomer on the first carrier layer precursor web. The last spunbonding device 40 deposits a second carrier layer precursor web made of ordinary polypropylene endless fibers again on the elastic carrier layer precursor web.

[0056] After the spunbonding devices 20, 30, and 40, there are provided pre-compression roller pairs 21, 31, and 41 for pre-compressing each web.

[0057] The key feature of the present invention is the unit 50 that simultaneously bonds and activates the three-layer precursor sheet formed earlier in the spunbonding device. This unit has a plurality of meshing ribs and grooves arranged parallel to the cooperating surfaces, and is equipped with activation roller pairs 51, 52 that rotate in opposite directions to each other, and embossing protrusions are arranged along the tops of the ribs. The unit 50 will be described in more detail below.

[0058] At the end of the overall in-line process, the product sheet is collected on the product roll 60.

[0059] Figure 3 shows an embodiment of the activation rollers 51, 52 of the unit 50, by which the precursor sheet formed by the spunbond apparatuses 20, 30, and 40 is stretched in the machine cross direction. The right figure is an enlarged cross section by an axial plane.

[0060] Both rollers 51 and 52 are provided with a plurality of annular ribs 53 arranged at regular intervals on the functional surface, and grooves 54 are formed therebetween. The width of the rib 53 is denoted by the letter "a", the depth of engagement is denoted by the letter "b", and the distance between adjacent ribs is denoted by the letter "c". The stretching in the machine cross direction during activation is controlled by these three parameters. In an exemplary embodiment, the distance "c" between adjacent ribs 53 may be about 6 mm. The depth of engagement "b" may be about 5 mm. The width "a" of the rib may be about 1 mm.

[0061] Another embodiment of the activation rollers 51, 52 will be described with reference to FIG. 4. The embodiment of FIG. 4 is set to stretch the precursor sheet formed by the spunbond apparatuses 20, 30, and 40 in the machine direction. Shown in FIG. 4 is an enlarged cross section by a radial plane perpendicular to the axis of the roller.

[0062] Also in this embodiment, both rollers 51 and 52 are provided with a plurality of ribs 53 arranged at regular intervals on the functional surface, and grooves 54 are formed therebetween. However, in contrast to FIG. 3, the ribs 53 of this embodiment face the machine cross direction and extend axially on the surfaces of the rollers 51 and 52.

[0063] Also in this embodiment, the width "a" of the rib 53, the depth of engagement "b", and the distance "c" between adjacent ribs 53 control the stretching in the machine direction in this case during activation. Also in this case, in an exemplary embodiment, the distance "c" between adjacent ribs 53 may be about 6 mm. The depth of engagement "b" may be about 5 mm. The width "a" of the rib may be about 1 mm.

[0064] In both embodiments of FIGS. 3 and 4, there are rows of embossing protrusions 59 on the top lines of each rib 53 of both rollers 51 and 52 for joining the precursor web during stretching, in other words, for joining the fabric simultaneously with stretch activation.

[0065] FIG. 5 shows a photograph of the top line of the rib 53 of the activation rollers 51 and 52. It is schematically shown in FIG. 4, and the rib 53 is provided with embossing protrusions on its top line.

[0066] The embossing protrusions 59 may have a height of about 0.2 to 0.5 mm, preferably about 0.3 mm, at the top line of the rib 53. These may generally be quadrilateral as shown in FIG. 5, or may also be circular, elliptical, rectangular, rhombic, etc. The bonding area may be, for example, 1 mm 2 or so, and the quadrilateral embossing protrusion 59 shown in FIG. 5 may be 1 mm × 1 mm. The distance between the bonding points may be about 1 to 5 mm, preferably 2 to 4 mm, more preferably 2.5 to 3 mm.

[0067] Considering the above dimensions, the resulting bonding area on the pre-stretched web is between about 4% and about 8%, and 4 to 8 bonding points are distributed per cm 2 These bonding areas and the number of bonds per unit area increase proportionally after the product sheet contracts from the pre-stretched state to the relaxed state. Each of the two rollers 51 and 52 produces half of the bonding points by the provided embossing protrusions 59.

[0068] Figure 6 shows the unit of FIG. 4 in an operating state. From left to right in FIG. 6, a precursor sheet consisting of two carrier layer precursor webs and an elastic layer precursor web sandwiched therebetween, which is unbonded and not yet activated, enters a combined process of activation and bonding. As the precursor sheet enters between two rollers 51, 52, the activation process starts between the meshing ribs 53. In an exemplary embodiment, the distance from the top line of one rib 53 provided on the first roller 51 to the top line of the nearest rib 53 provided on the second roller 52 may be about 2 mm when the precursor sheet enters the activation process. As the ribs 53 gradually mesh into the grooves 54, this distance gradually increases and, at the central position where the ribs 53 and the grooves 54 are fully meshed, it is about 5.2 mm in an exemplary embodiment. The elastic layer precursor web is stretched by its elastic properties in this process. In contrast, the essentially inelastic fibers of the carrier layer precursor web are repositioned, creating a high-density region A around the top line of each rib 53 and a low-density region B therebetween.

[0069] At the central position where the meshing of the rollers 51, 52 is maximum, the embossing protrusions 59 on the rib 53 of one roller (here roller 51) contact the opposing groove 54 of the opposing roller (here roller 52) and form a row of bonding points along the top line of the rib 53, that is, along the stripe-shaped high-density region A in the pre-stretched precursor sheet.

[0070] As the pre-stretched and bonded material exits the unit 50 as described, the elastic fibers in the elastic nonwoven layer 120 in the product sheet 100 contract, the stretching of the material returns to its original state, and it returns to its original length in the machine direction. The portions of the fibers in the carrier layers 110 and 130 that are not attached to the bonding points are repositioned / or crimped during the relaxation process but always maintain the ability to stretch in the machine direction up to the extent pre-stretched in the unit 50.

[0071] The dimensions of the ribs 53 and the grooves 54, particularly the parameters "a", "b" and "c", may vary as required based on the stretching properties required in the product sheet. According to the values of these parameters exemplified in the descriptions of FIGS. 4 to 6, the preliminary stretching in the machine direction results in about 160% (from 2.0 mm to about 5.2 mm). Since most current hygiene products require the ability to enable elastic stretching of about 100 to 150%, this design that stretches 160% is suitable for the requirements in most cases.

Claims

1. A method for manufacturing a nonwoven fabric sheet, comprising: a step (a) of preparing a precursor sheet; and a step (b) of obtaining a nonwoven fabric sheet by simultaneously bonding and activating the precursor sheet, wherein the activation includes passing the precursor sheet between a pair of activation rollers having a plurality of meshing ribs and grooves arranged in parallel on cooperating surfaces, thereby stretching the precursor sheet in a direction perpendicular to the ribs and grooves, and the bonding includes embossing bonding points on the precursor sheet while it is stretched, and the embossing is performed by embossing protrusions arranged along the tops of the ribs and / or grooves on the surface of the activation roller. A method for manufacturing a nonwoven fabric sheet.

2. In the method of Claim 1, the method is a method for manufacturing an elastically stretchable nonwoven fabric sheet, the nonwoven fabric sheet includes a first nonwoven carrier layer, an elastic nonwoven layer containing elastic fibers, and optionally a second nonwoven carrier layer, the precursor sheet prepared in the step (a) includes a first carrier structure that is a precursor of the first nonwoven carrier layer in the nonwoven fabric sheet to be formed, an elastic structure that is a precursor of the elastic nonwoven layer in the nonwoven fabric sheet to be formed and contains elastic fibers, and optionally a second carrier structure that is a precursor of the second nonwoven carrier layer, which may be optionally included, in the nonwoven fabric sheet to be formed. A method for manufacturing a nonwoven fabric sheet.

3. In the method of Claim 2, the first carrier structure is a fiber carrier web without bonding, the elastic structure is an elastic layer precursor web without bonding containing elastic fibers, and the optional second carrier structure, if any, is a second fiber carrier web without bonding, and none of the fiber webs are bonded by calendar embossing. A method for manufacturing a nonwoven fabric sheet.

4. In the method of Claim 2, the first carrier structure is a bonded nonwoven carrier layer, the elastic structure is a bonded nonwoven layer containing elastic fibers, and the optional second carrier structure, if any, is a bonded nonwoven carrier layer, and all the nonwoven layers are bonded by calendar embossing. A method for manufacturing a nonwoven fabric sheet.

5. In any one of the methods of Claims 1 to 4, A method for manufacturing a nonwoven fabric sheet, wherein the ribs and grooves are arranged in the machine direction and extend annularly on the surface of the activation roller, whereby the precursor sheet is stretched in the cross-machine direction.

6. In the method according to any one of Claims 1 to 4, A method for manufacturing a nonwoven fabric sheet, wherein the ribs and grooves are arranged in the cross-machine direction and extend axially on the surface of the activation roller, whereby the precursor sheet is stretched in the machine direction.

7. In the method according to any one of Claims 1 to 6, In the step (b), a method for manufacturing a nonwoven fabric sheet, wherein the precursor sheet is stretched in a direction perpendicular to the ribs and grooves up to 150% of its original dimensions.

8. In the method according to any one of Claims 1 to 6, In the step (b), a method for manufacturing a nonwoven fabric sheet, wherein the precursor sheet is stretched in a direction perpendicular to the ribs and grooves up to 200% of its original dimensions.

9. In the method according to any one of Claims 2 to 4, A method for manufacturing a nonwoven fabric sheet, wherein the embossing protrusions are vibrated at a heating and / or ultrasonic frequency to melt the fibers of the first carrier structure of the precursor sheet, the second carrier structure that may optionally be included, and the elastic structure together under local pressure.

10. In the method according to any one of Claims 1 to 9, A method for manufacturing a nonwoven fabric sheet, wherein one or both of the activation roller pairs are coated with an inert material in the vicinity of the embossing protrusions, and the inert material is a fluoropolymer.

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