JP2017149051A - Layered body, fiber sheet for constituting layered body, method for producing layered body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a layered body having excellent shape stability in primary use and having excellent peelability in secondary use.SOLUTION: The layered body is provided by layering two or more fiber sheets in which fibers are assembled. Each of the breaking strength Sin a dry state and breaking strength Sin a wet state of the fiber sheets is 20 N/5 cm or more. The ratio A/Abetween adhesive strength Ain a dry state between two fiber sheets adjacent to each other and adhesive strength Ain a wet state between two fiber sheets adjacent to each other in at least one direction in the in-plane directions of the layered body is 5 or more.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a laminate, a fiber sheet for constituting the laminate, and a method for producing the laminate.

  Conventionally, a laminated body of fiber sheets formed by gathering fibers has been used as a wiper. In general, the wiper is required to be used for wiping off an object. Therefore, when the wiper is used, a frictional force is applied to the wiper. For this reason, the wiper is required to have a certain degree of form retention. For example, Japanese Patent Laying-Open No. 2005-160721 (Patent Document 1) discloses a wiper for a clean room in which a single fiber sheet made of a cellulose fiber nonwoven fabric is folded as a wiper having excellent shape retention.

JP 2005-160721 A

  By the way, after using the laminated body in the state of the thick laminated body itself as a primary use, the wiper is used as a secondary use in a state where the laminated body is separated for each fiber sheet. There is. In order for such a method of use to be carried out without stress by the user, it is difficult for the laminate to sway for primary use (morphological stability) and ease of peeling of the laminate for secondary use (peelability). Is required. In the prior art, a wiper that can satisfy such a requirement has not been developed. This is because the form stability and the peelability are contradictory.

  An object of the present invention is to provide a laminate capable of having excellent form stability in primary use and having excellent peelability in secondary use, a fiber sheet for constituting the laminate, and a laminate. It is to provide a manufacturing method.

  The present invention provides the following laminate, a fiber sheet for constituting the laminate, and a method for producing the laminate.

[1] A laminate in which two or more fiber sheets made of aggregated fibers are laminated, each of which has a breaking strength S _DRY in a dry state and a breaking strength S _WET in a wet state of 20 N / 5 cm. Thus, in at least one direction in the in-plane direction of the laminate, the adhesive strength A _DRY in the dry state between the two adjacent fiber sheets and the adhesive strength A _WET in the wet state between the two adjacent fiber sheets A laminate having a ratio A _DRY / A _WET of 5 or more.

  [2] At least a part of the fiber has a trunk part and a fibril part extending from the trunk part, and the fibril part in the one fiber sheet is between two adjacent fiber sheets of the laminate. The laminate according to [1], which has an inter-sheet network structure formed by hydrogen bonding to fibers in another fiber sheet.

  [3] The laminate according to [1] or [2], wherein the fiber sheet has an in-sheet network structure in which at least a part of a fibril part included in an arbitrary fiber is hydrogen-bonded to another fiber.

  [4] In the cross section parallel to the thickness direction of the laminate, when the direction parallel to the thickness direction is the vertical direction and the direction orthogonal to the thickness direction is the horizontal direction, at least two layers adjacent to the vertical region Of the fibril part that hydrogen-bonds the fiber of one fiber sheet and the fiber of the other fiber sheet when the section including the fiber sheets is observed and the width of the lateral region is 636 μm is observed. The laminate according to any one of [1] to [3], wherein the number is 30 or more.

  [5] In a cross-section parallel to the thickness direction of the laminate, when the direction parallel to the thickness direction is the vertical direction and the direction perpendicular to the thickness direction is the horizontal direction, When the section including the fiber sheets and having a lateral width of 636 μm is observed, the aspect ratio of the fibril part that hydrogen bonds the fibers of one fiber sheet and the fibers of the other fiber sheet is The laminate according to [1] to [4], which is 30 or more.

[6] fiber sheet has a basis weight of 10 to 500 g / m ^2, laminated body according to any one of [1] to [5].

[7] The laminate according to any one of [1] to [6], wherein the fiber is a cellulosic fiber.
[8] The laminate according to any one of [1] to [7], wherein 50% by mass or more of the fibers is Tencel (registered trademark).

  [9] The laminate according to any one of [1] to [8], wherein the laminate is a laminate used for a wiper.

[10] [1] - a fiber sheet for forming the laminate according to any one of [9], each 20 N / 5 cm of the breaking strength S _WET in breaking strength S _DRY and wet state in the dry state In the cross section parallel to the thickness direction of the fiber sheet, when the direction parallel to the thickness direction is the vertical direction and the direction orthogonal to the thickness direction is the horizontal direction, at least 2 adjacent to the vertical region. The number of fibril parts having an aspect ratio of 30 or more among the fibril parts raised from the surface of the fiber sheet when observing a section including the fiber sheets of the layers and having a lateral region width of 636 μm A fiber sheet.

  [11] A step of forming a sheet-like first precursor by assembling a plurality of fibers, and raising fibril parts from the fibers by applying cavitation energy from at least one side in the thickness direction of the first precursor The step of forming the second precursor, the step of forming the third precursor by performing a suction process on the second precursor, and the fourth precursor are formed by laminating the third precursor. The manufacturing method of a laminated body provided with a process and the process of heat-processing a 4th precursor.

  ADVANTAGE OF THE INVENTION According to this invention, while having the outstanding form stability in primary use, the laminated body which can have the outstanding peelability in secondary use can be provided.

It is a schematic diagram for demonstrating a peelability test, Fig.1 (a) is a typical perspective view which shows a laminated body, FIG.1 (b) is a schematic diagram which shows the laminated body for a peelability test. FIG. 1C is a schematic diagram showing the direction of the tensile force applied to the laminate for peelability test. It is another schematic diagram for demonstrating a peelability test. It is a scanning electron micrograph which shows the cross-section of the laminated body of this invention. It is a schematic diagram for demonstrating the network structure between sheets which a laminated body has. It is a scanning electron micrograph which shows the surface of a fiber sheet.

  Hereinafter, the present invention will be described in detail with reference to embodiments. In addition, in this specification, the notation of the format “A to B” means the upper and lower limits of the range (that is, A or more and B or less), the unit is not described in A, and the unit is described only in B. The unit of A is the same as the unit of B.

<Laminated body>
The present inventors have repeatedly studied to obtain a laminate having both characteristics of form stability at the time of primary use and peelability at the time of secondary use. Specifically, first, the present inventors paid attention to the state of the laminate during both primary use and secondary use. In many cases, the liquid component is not permeated into at least the outer edge portion of the laminate at the time of primary use, whereas when the laminate is peeled off during secondary use, the liquid component reaches the outer edge portion of the laminate. We focused on the penetration of the ingredients. That is, at the time of primary use, at least a part of the laminate is in a dry state, and in the secondary use, the entire laminate (or an area larger than that at the time of temporary use) is in a wet state.

Therefore, the present inventors have conducted intensive studies based on the above-mentioned attention points, and completed the laminate of the present invention. That is, the laminate of the present invention is a laminate satisfying the following (1) to (3).
(1) A laminated body in which two or more fiber sheets formed by collecting fibers are laminated.
(2) The fiber sheet has a breaking strength S _DRY in a dry state and a breaking strength S _WET in a wet state each of 20 N / 5 cm or more.
(3) In at least one direction in the in-plane direction of the laminate, an adhesive strength A _DRY in a dry state between two adjacent fiber sheets, and an adhesive strength A _WET in a wet state between two adjacent fiber sheets The ratio A _DRY / A _WET is 5 or more.

  With respect to (1) above, the “fiber sheet” is a collection of fibers, and specifically includes woven fabric (woven fabric), knitted fabric, lace, felt, nonwoven fabric, and the like. The fiber sheet can be appropriately selected according to the use. For example, if it is used repeatedly, it is preferable to select from a woven fabric and a knitted fabric from the viewpoint of durability. It is preferable to select.

  The laminate in which two or more fiber sheets are laminated means a laminate in which fiber sheets are laminated in the thickness direction of the laminate. Needless to say, the laminate of the present invention may be composed of two or more fiber sheets, and may have three or more fiber sheets. Further, the fiber sheet may have directionality such as MD (machine) direction, CD (width) direction, etc., but when fiber sheets having such directionality are laminated, the direction of each fiber sheet The sexes may be matched or different. However, when used for a disposable use, it is preferable to match the directionality of each fiber sheet from the viewpoint of simple processing steps and good production efficiency.

  Here, as for the fiber sheet of 2 or more layers laminated | stacked in a laminated body, the part may be continuing. As a laminated body which has such a structure, the laminated body made into the laminated structure which bends one fiber sheet and consists of a fiber sheet of two or more layers is mentioned. In the present invention, a laminated structure in which one fiber sheet is bent and a laminated structure in which different fiber sheets are laminated may be combined. In addition, the upper limit of the number of stacked layers in the stacked structure is not particularly limited, but is 1000 layers or less from the viewpoint of manufacturability and the like.

Regarding (2) above, the breaking strength S _DRY and the breaking strength S _WET of the fiber sheet are measured as follows. First, a fiber sheet having a shape of 50 mm × 150 mm (width direction × length direction) is prepared. As this fiber sheet, you may use the fiber sheet produced in the middle of the manufacturing process of a laminated body, ie, the fiber sheet before lamination | stacking. This is because the physical properties of the fiber sheet before being laminated are maintained even after being laminated. Alternatively, a laminate obtained by wetting the laminate with water, peeling one fiber sheet from the wet laminate, and sufficiently drying the peeled fiber sheet may be used.

  The prepared fiber sheet is preliminarily dried at 50 ° C. for 1 hour and left in a standard state (temperature 20 ° C., relative humidity 65%) for 24 hours to obtain a dry fiber sheet. On the other hand, the prepared fiber sheet was immersed in water at 20 ° C. for 24 hours, and then the fiber sheet was taken out from the water, left on the fabric and drained to adjust the water content to 400% by weight of the fiber sheet. Is a wet fiber sheet. In the following description of the present specification, the “dry state” fiber sheet means the fiber sheet that has been subjected to the drying treatment, and the “wet state” fiber sheet means the fiber sheet that has been subjected to the wet treatment. .

Then, a tensile test based on JIS L1913 “General Short Fiber Nonwoven Fabric Test Method” was performed on each of the dried fiber sheet and the wet fiber sheet (executed five times with different samples), and the obtained results _These average values are defined as breaking strength S _DRY and breaking strength S _WET .

Here, the fiber sheet may have directionality as described above, but in the present invention, the breaking strength _SDRY and the breaking strength S in at least one of the in-plane directions (for example, the MD direction or the CD direction). _WET should satisfy the above value. However, the breaking strength S _DRY and the breaking strength S _WET in two directions (for example, the MD direction and the CD direction) orthogonal to the in-plane direction preferably satisfy the above values.

Regarding the above (3), the adhesive strength A _DRY and the adhesive strength A _WET of the laminate are measured as follows. First, as shown in FIG. 1 (a), a laminate 10 composed of two layers of fiber sheets 1a and 1b is prepared. When a laminated body consists of a fiber sheet of three or more layers, fiber sheets other than the two fiber sheets forming the interlayer to be measured are removed. As the removal method, a method of gently peeling the fiber sheet to be removed is preferable so that the shape of each fiber sheet in the dry state is not deformed. In addition, when the two-layer fiber sheet is continuous (in the case of a laminated structure in which one fiber sheet is bent), it is necessary to cut the continuous portion.

  Next, as shown in FIG. 1 (b), in the laminate 10, a part of each fiber sheet 1a, 1b (see FIG. 1) so that the area where the two fiber sheets 1a, 1b are in contact with each other is 50 mm × 50 mm. 1 (b) is removed to produce a stacked body 10A. In the laminated body 10A, the width D1 in the CD direction and the width D2 in the MD direction of the region where the fiber sheets 1a and 1b overlap each other are 50 mm.

  The prepared laminated body 10A is preliminarily dried at 50 ° C. for 1 hour and left in a standard state (temperature 20 ° C., relative humidity 65%) for 24 hours to obtain a laminated body in a dry state. On the other hand, the prepared laminate 10A was immersed in water at 20 ° C. for 24 hours, and then the laminate was taken out of the water, left on the fabric and drained to adjust the moisture content of the laminate to 400% by weight. This is a laminate in a wet state.

Then, a tensile test in accordance with JIS L1913 “General Short Fiber Nonwoven Fabric Test Method” was carried out on each of the laminated body 10A in the dry state and the laminated body 10A in the wet state (each five times with different samples), and obtained. Each average value of the obtained results is defined as an adhesive strength A _DRY and an adhesive strength A _WET . Specifically, using an autograph AGS-D device (manufactured by Shimadzu Corporation), as shown in FIG. 1 (c), one end 1bb of the laminated body 10A is illustrated in a state where the one end 1aa of the laminated body 10A is fixed. Pull in the direction of the arrow (matches the MD direction). And each average value of tensile force (N / 25cm < ² >) when the fiber sheets 1a and 1b peel is made into adhesive strength _ADRY and adhesive strength _AWET .

In the above description, the method of measuring the adhesive strength A _DRY and the adhesive strength A _WET in the MD direction has been described. However, for example, when the adhesive strength A _DRY and the adhesive strength A _WET in the CD direction are obtained, as shown in FIG. And a tensile test may be performed so that the fiber sheet is pulled in a direction (arrow direction in the figure) coinciding with the CD direction.

  By satisfying the above (1) to (3), the laminate of the present invention has excellent shape stability in a dry state (at the time of primary use), and excellent in a wet state (at the time of secondary use). It can have good peelability.

On the other hand, when each of the breaking strength S _DRY and the breaking strength S _WET is less than 20 N / 5 cm, sufficient form stability is hardly exhibited in both the dry state and the wet state. Each of the breaking strength S _DRY and the breaking strength S _WET is preferably 30 N / 5 cm or more, and more preferably 50 N / 5 cm or more. The upper limit values of the breaking strength S _DRY and the breaking strength S _WET are not particularly limited.

Further, when the ratio A _DRY / A _WET is less than 5, A _DRY tends to be too small or A _WET tends to be too large. If A _DRY is too small, the layered structure in the dry state will be insufficient, and the laminate will be liable to _move . If A _WET is too large, the peelability in the wet state tends to be insufficient. is there. The ratio A _DRY / A _WET is preferably 5 to 50, more preferably 6 to 30, and still more preferably 6 to 25.

Here, as described above, the fiber sheet may have an MD direction and a CD direction. Examples of such a fiber sheet include a spunlace nonwoven fabric formed by a spunlace method. In this case, it is preferable that at least the ratio A _DRY / A _WET in the MD direction satisfies the above range. This is because, in general, in a laminate having directionality such as MD direction and CD direction, when measuring the breaking strength in the CD direction, material breakage due to deformation of the fiber sheet is likely to occur, and the appropriate breaking strength is obtained. This is because measurement is difficult.

  As a laminate satisfying the above (1) to (3), at least a part of the fibers has a trunk portion and a fibril portion extending from the trunk portion, and between two adjacent fiber sheets in the laminate body. The laminated body which has the network structure between sheets in which the fibril part in the one fiber sheet is hydrogen-bonded to the fiber in the other fiber sheet is mentioned. Such a laminate will be described with reference to FIGS.

  FIG. 3 is a scanning electron micrograph (shooting magnification: 500 times) showing the cross-sectional structure of the laminate, and FIG. 4 is a schematic diagram for explaining the inter-sheet network structure of the laminate.

  As shown in FIGS. 3 and 4, the laminate 10 is a laminate 10 in which two or more fiber sheets 1 a and 1 b formed by gathering fibers 2 are laminated. At least a part of the fiber 2 has a trunk portion 2a and a fibril portion 2b extending from the trunk portion 2a.

  The fibril part 2b is a smaller fiber (small fiber) that is split (fibrillated) from the fiber 2 starting from a crack generated in the fiber 2, and is a so-called “microfibril” having a diameter of 0.005 μm or more and less than 0.05 μm, and It includes both so-called “macrofibrils” having a diameter of 0.05 to 5 μm. On the other hand, the trunk portion 2 a is a basic skeleton of the fiber 2 after the fibril portion 2 b is split from the fiber 2. Accordingly, the diameter of the trunk portion 2a can be regarded as a value obtained by subtracting the diameter of the fibril portion 2b split from the fiber from the diameter of the fiber.

  And as FIG. 3 and FIG. 4 show, the laminated body 10 WHEREIN: Between the adjacent two-layer fiber sheets 1a and 1b, arbitrary fibril parts 2b in the one-layer fiber sheet 1a are other fiber sheets 1b. The inter-sheet network structure 3 formed by hydrogen bonding to the fibers 2 in FIG. It can confirm that the laminated body 10 has the network structure 3 between sheets by observing the cross section of the laminated body 10 using a scanning electron microscope. 3 indicates the thickness direction of the stacked body 10, and X in FIG. 3 indicates the in-plane direction of the stacked body 10. In FIG. 3, the distance (boundary) between the fiber sheets 1a and 1b can be determined by the presence or absence of the entanglement of the fibers 2 in the Z direction.

  The inventors of the present invention can satisfy the above-mentioned (1) to (3), and thus have a good shape stability in a dry state (at the time of primary use), and a wet state. The reason for having excellent peelability during secondary use will be considered as follows.

The laminated body 10 having the inter-sheet network structure 3 as described above tends to have a higher adhesive strength A _DRY than a conventional laminated body having no inter-sheet network structure 3. This is because the inter-sheet network structure 3 made of hydrogen bonds is strong in a dry state. On the other hand, when a liquid component containing moisture is applied to the inter-sheet network structure 3 including hydrogen bonds, that is, when the laminate 10 is wet, the hydrogen bonds constituting the inter-sheet network structure 3 are easily detached. For this reason, the adhesive strength A _WET tends to be lower than A _DRY . Therefore, in the laminated body 10, the ratio A _DRY / A _WET can show a high value of 5 or more, and as a result, the above effects can be exhibited.

In particular, in a cross section parallel to the thickness direction Z of the laminate 10, when the direction parallel to the thickness direction is the vertical direction and the direction orthogonal to the thickness direction is the horizontal direction, at least 2 adjacent to the vertical region. When a section including the fiber sheets of the layers and the width of the lateral region is 636 μm is observed, the fibers 2 of one fiber sheet 1a and the other fiber sheet 1b adjacent to the fiber sheet 1a are It is preferable that the number N ₁ of the fibril parts 2b to be bonded to the fibers 2 is 30 or more. Thereby, the hydrogen bond between the fiber sheets 1a and 1b of the laminated body 10 becomes a sufficient number, and therefore the adhesive strength A _DRY between the fiber sheets 1a and 1b can be designed to be larger, so the ratio A _DRY / A _WET is large. Will be.

Specifically, the number N ₁ can be obtained as follows. First, using a scanning electron microscope (preferably “S-3400N type”, manufactured by Hitachi High-Technologies Corporation), 10 sections of the section of the laminate 10 that satisfy the above are imaged. In addition, when the laminated body 10 has a several lamination | stacking number, there will be two or more "between fiber sheets", However, 10 places imaged are the same "between fiber sheets." Then, by observing the images, determine the number of fibrils portion 2b of hydrogen bonding between the fiber sheet 2 layers, the average value of the ten images, this value to the number N _1.

Here, there are the following forms (a) or (b) regarding the form considered to form the inter-sheet network structure by using the scanning electron microscope.
(A) The fibril part extended from the fiber which one fiber sheet has is hydrogen-bonded to the trunk of the fiber which the other fiber sheet has.
(B) The fibril part extended from the fiber which one fiber sheet has, and the fibril part extended from the fiber which the other fiber sheet has are hydrogen-bonded.

In the image of the scanning electron microscope, it is difficult to distinguish the above (a) and (b). For this reason, when calculating the number N ₁ , if one fiber sheet and another fiber sheet are hydrogen-bonded by the fibril part without distinguishing between (a) and (b) above, Count as "one".

In addition, when the imaging magnification of the scanning electron microscope is set to, for example, 5000 times or more, it can be observed that the fibril part 2b is further finely branched, and strictly speaking, a fibril part of several tens of nanometers can be observed. However, it is impossible to strictly count the number of them. Accordingly, the number N ₁ is taken at a magnification of 200 times using, for example, a scanning electron microscope, and only the fibril part 2b that is observed as one fibril part 2b from the image is counted.

Further, when there is directionality in the laminate performs equally determined for each direction of the cross-section that may different physical properties, it is preferable to set the average value as the number N _1. For example, when the laminate has an MD direction and a CD direction, and there is a difference in physical properties between them, the above measurement is performed 10 points each in the MD direction and the CD direction, and based on the measurement results of a total of 20 points. It is preferable to calculate the average value and set the value to the number N ₁ .

The number N ₁ is more preferably 50 or more, and still more preferably 100 or more. As the number N ₁ increases, the inter-sheet network structure becomes denser, thereby further increasing the ratio A _DRY / A _WET . The upper limit of the number N ₁ is not particularly limited, but is preferably 100,000 or less from the viewpoint of preventing the laminated body at the time of drying from being too hard or the form stability of the laminated body at the time of being wet from being too low. .

  In particular, in a cross section parallel to the thickness direction Z of the laminate 10, when the direction parallel to the thickness direction is the vertical direction and the direction orthogonal to the thickness direction is the horizontal direction, at least 2 adjacent to the vertical region. Bonding the fibers 2 of one fiber sheet 1a and the fibers 2 of another fiber sheet 1b when a section including the fiber sheets of the layers and having a lateral region width of 636 μm is observed. It is preferable that the aspect ratio of the fibril part 2b to be made is 30 or more. The fibril part 2b having such an aspect ratio is easy to extend from one fiber sheet to another fiber sheet located next to it, and hence is easy to hydrogen bond with another fiber sheet. There are advantages. For this reason, when such a fibril part 2b comprises the network structure between sheets, the adhesion structure between the fiber sheets by a hydrogen bond can be strengthened more. The aspect ratio is more preferably 50 to 100,000, and still more preferably 100 to 50,000.

  Here, the aspect ratio of the fibril part is the ratio of the length to the diameter of the fibril part (length / diameter), and can be determined as follows. First, fibril parts constituting the inter-sheet network structure are extracted from the scanning electron microscope image. And the thing in which both ends are confirmed is further extracted among this fibril part. In the above image, both end portions mean the joint portion observed to be coupled to one trunk portion and the joint portion observed to be coupled to another trunk portion. To do. Then, the length between the both ends of the fibril part is defined as the “length”, and the diameter of the fibril part (width perpendicular to the length direction observed in the image) is defined as the “diameter”. In this way, 100 fibril parts capable of calculating the aspect ratio are measured, and the average value is defined as the aspect ratio.

  Further, as shown in FIG. 3, in the laminate 10, in any fiber sheet 1 a, at least a part of the fibril part 2 b included in any fiber 2 is hydrogen-bonded to any other fiber 2. It is preferable to have a network structure 4. Thereby, the form stability of the fiber sheet 1a at the time of drying is improved, the form stability of the laminate 10 at the time of drying is improved, and the fibril part 2b of the fiber sheet 1a at the time of wetness is released from the combined state. Since one end becomes the free fibril part 2b, the flexibility of the fiber sheet at the time of secondary use improves.

  Note that whether the network structure observed in the image of the scanning electron microscope is an inter-sheet network structure or an in-sheet network structure is distinguished by a difference in the image. That is, when the cross-sectional structure of the laminate is observed, the fibril part that connects the fibers existing inside the fiber sheet, and the fibril part that connects one fiber sheet and the other fiber sheet, its state and arrangement, etc. Can be clearly distinguished.

  In the above description, the laminated body 10 having the two-layer structure has been described. However, as described above, the number of laminated bodies 10 is not limited thereto. In any layered structure 10, it is only necessary that the fibers 2 having the trunk portion 2 a and the fibril portion 2 b exist on the surface of at least one of the fiber sheets between the two fiber sheets. This is because the inter-sheet network structure 3 between the fiber sheets can be formed if at least one of the two adjacent surfaces has the fibril part 2b.

  In the laminate of the present invention described in detail above, the fiber sheet is preferably a nonwoven fabric. This is because when the fiber sheet is formed of a non-woven fabric, there are advantages such as easy formation of voids between the fibers and low-cost production compared to the case of forming the fiber sheet other than the non-woven fabric. Especially, it is preferable that a fiber sheet is a spunlace nonwoven fabric. In the spunlace nonwoven fabric, it is not necessary to use an adhesive component such as a thermoplastic resin in order to obtain the form and strength as a sheet as compared with the case where the nonwoven fabric is formed by a method other than the spunlace, and has, for example, fibrils. There is an advantage that the blending ratio of the fibers can be freely set.

  The thickness of the laminate of the present invention is preferably 0.1 to 50 mm, more preferably 0.5 to 20 mm, and still more preferably 1.0 to 10 mm. The laminate having such a thickness is suitably used for a personal wiper. Moreover, the thickness of the fiber sheet which comprises the laminated body of this invention becomes like this. Preferably it is 0.05-10 mm.

In the laminate of the present invention, the adhesive strength A _DRY is preferably 3.0 to 20, and the adhesive strength A _WET is preferably 0.5 to 2.0. This is to avoid that the laminated body when dried is too hard or the form stability of the laminated body when wet is too low. These values may also be satisfied in at least one direction in the in-plane direction of the laminate, and particularly in the case where there is directionality, it is preferable that the values are satisfied in the MD direction.

Moreover, in the fiber sheet (dry state) constituting the laminate of the present invention, the elongation at break E _DRY in at least one direction (for example, MD direction or CD direction) in the in-plane direction is preferably 10% or more, More preferably, it is 30% or more, More preferably, it is 35% or more. Among them, two directions (e.g., MD direction and CD direction) perpendicular in-plane direction the breaking elongation E _DRY at preferably satisfies this. When such a fiber sheet is used as a wiper, the fiber sheet can locally expand to absorb force even if the fiber sheet is caught during wiping. Thereby, damages such as peeling of the laminate and tearing of the fiber sheet can be reduced.

Also in the fiber sheet (wet state) constituting the laminate of the present invention, the elongation at break E _WET in at least one direction (for example, MD direction or CD direction) in the in-plane direction is preferably 10% or more, More preferably, it is 30% or more, More preferably, it is 35% or more. Especially, it is preferable that each breaking elongation _EWET satisfy _| fills this in two directions (for example, MD direction and CD direction) orthogonal to an in-plane direction. Such a fiber sheet is flexible and excellent in handleability when used as a wiper.

  In the fiber sheet constituting the laminate of the present invention, the porosity is preferably 75% or more, more preferably 80% or more, and further preferably 90% or more. When the porosity of the fiber sheet is less than 75%, the voids are too small and the liquid retention capacity may not be sufficient. In the fiber sheet, the porosity is preferably 97% or less, more preferably 95% or less. When the porosity of the fiber sheet exceeds 97%, the fiber density of the fiber sheet is small, and it may be difficult to maintain its shape (for example, a sheet shape). The porosity of the fiber sheet can be calculated using the basis weight, thickness, and average specific gravity of the fiber sheet.

Also in the fiber sheet constituting the laminate of the present invention, the apparent density is preferably 0.015~0.45g / cm ^3, more preferably from 0.045~0.37g / cm ^3, more preferably Is 0.08 to 0.30 g / cm ³ . In the conventional technique, high adhesive strength A _DRY cannot be realized in such a low-density fiber sheet. However, according to the present invention, high adhesive strength A _DRY is realized even at such low density. be able to. The apparent density is determined by calculating the basis weight (g / m ² ) and thickness (mm) according to JIS L 1913 “General Nonwoven Test Method” and dividing the basis weight by the thickness.

  In the laminate of the present invention, the fiber is not particularly limited, but is preferably a fiber having fibrils. This is because a fiber sheet as described above can be formed. Examples of fibers having fibrils include cellulosic fibers (such as “Tencel (registered trademark)” manufactured by Lenzing, “Cupra” manufactured by Asahi Kasei Co., Ltd., “NANOVAL” manufactured by Nanobar), para-aramid fibers (polyparaphenylene terephthalamide fibers ( "Kevlar (registered trademark)" manufactured by Toray DuPont, "Twaron" manufactured by Teijin Aramid); copolyparaphenylene-3,4-diphenyl ether terephthalamide fiber ("Technora (registered trademark)" manufactured by Teijin Techno Products) ), Polyparaphenylene benzobisoxazole fibers (such as “Zeylon” manufactured by Toyobo Co., Ltd.), wholly aromatic polyester fibers (such as “Vectran” manufactured by Kuraray), polyketone fibers (such as “Cybalon” manufactured by Asahi Kasei), super High molecular weight polyethylene fiber ("Dyneema" manufactured by Toyobo Co., Ltd.) "Spectra" manufactured by Neuer), meta-aramid fibers (polymetaphenylene isophthalamide fiber ("Dome" "Nomex", Teijin Techno Products "Conex")), polyvinyl alcohol fiber (Kuraray "Kuraron") ]). These fibers are preferred fibers because they are highly oriented fibers.

  Cellulosic fibers (fibers made from cellulose) are preferred because the fibers having the fibrils described above are advantageous in that the liquid can be suitably diffused and absorbed, and they are advantageous in that they are general-purpose fibers that are readily available and inexpensive. Preferred examples of the cellulose fiber include natural cellulose fiber, regenerated cellulose fiber, and purified cellulose fiber. Specific examples include natural cellulose fibers such as cotton, hemp, and pulp, regenerated cellulose fibers such as rayon and cupra, and purified cellulose fibers such as Tencel (registered trademark). Among them, Tencel (registered trademark) is preferable in that it has high strength due to its high molecular weight, and the strength hardly decreases even when wet. Specifically, it is preferable that 50% by mass or more of the fibers constituting the fiber sheet of the present invention is Tencel (registered trademark), and that all the fibers (100% by mass) are Tencel (registered trademark). More preferred.

  In the laminate of the present invention, the fiber having fibrils is preferably solvent-spun cellulose fiber produced by solvent spinning. As such solvent-spun cellulose fibers, wood pulp is dissolved in NMMO (N-methylmorpholine-N-oxide) as a solvent and dissolved at a blending ratio of NMMO / water / cellulose = 80% / 10% / 10%. The above-mentioned TENCEL (registered trademark), which is a processed fiber, is mentioned.

  The fineness of the fiber having fibrils is not particularly limited, but is preferably in the range of 0.01 to 5.5 dtex. This is because when the fineness of the fiber is less than 0.01 dtex, the strength of the fiber sheet tends to decrease due to the low fiber strength, and when the fineness exceeds 5.5 dtex, the fiber sheet This is because the network structure tends to be difficult to be formed because the distance between the fibers becomes large. The fiber fineness is more preferably in the range of 0.7 to 5.0 dtex, and particularly preferably in the range of 1.3 to 3.8 dtex, because the strength and the appropriate fiber space (void) can be suitably formed.

  Moreover, it is preferable that the fibril part which the fiber contained in the fiber sheet of a laminated body has has an aspect ratio of 30 or more. Such a fibril part has the advantage that it is easy to form an inter-sheet network structure due to its sufficient length. The aspect ratio is more preferably 50 to 100,000, and still more preferably 100 to 50,000.

  The fiber length of the fibers constituting the laminate of the present invention is not particularly limited, but is preferably 20 mm or more, for example. A fiber sheet using such long fibers can be produced as a nonwoven fabric by, for example, a spunlace method. When the fiber length is less than 20 mm, the density of the fiber sheet to be formed becomes high, so that it is difficult to secure a gap between fibers necessary for network formation by fibrils. The fiber length is more preferably 25 to 60 mm, and further preferably 32 to 51 mm.

  In addition, in the laminated body of this invention, as long as there exists the above-mentioned effect, fibers other than the fiber which has the above-mentioned fibril may be contained. Fibers other than the fibers having fibrils can be freely selected according to the purpose, and are not particularly limited, and examples thereof include synthetic fibers. Moreover, in order to make it bulky, you may make it mix a polyester fiber as another fiber. Furthermore, you may make it use the conventionally well-known appropriate composite fiber which has a core-sheath structure as another fiber.

  The fineness of other fibers is not particularly limited, but is preferably in the range of 0.1 to 5.5 dtex, more preferably in the range of 0.5 to 3.8 dtex, and in the range of 1.3 to 3.8 dtex. Further preferred. When the fineness of the other fibers is less than 0.1 dtex, the density of the fiber sheet becomes high, so that there is a tendency that a gap between fibers necessary for forming a network structure by fibrils cannot be secured. When the fineness of other fibers exceeds 5.5 dtex, the distance between the fibers of the fiber sheet becomes large, so that it tends to be difficult to form a network structure by fibrils. Further, the fiber length of other fibers is not particularly limited, and can be set to 20 mm or more in the same manner as the fibers having fibrils described above.

  When other fibers are mixed, it is preferable to mix other fibers because it easily acts to create a void in the fiber sheet of the present invention. On the other hand, when the mixing ratio of other fibers is increased, formation of a network structure by fibrils is preferable. Work in a difficult direction. For this reason, it is preferable that the fiber which has a fibril by weight ratio occupies 20% or more among the fiber which has the said fibril, and other whole fibers, and it is more preferable to occupy 50% or more. This is because when the fiber having fibrils is less than 20%, it is difficult to form the network structure as described above.

  The laminate of the present invention described in detail above is suitably used as a laminate for wipers. Specifically, at the time of primary use (i.e., at least when the outer edge is in a dry state), for example, the surface of the object to be wiped can be removed without causing kinking of the laminated body in order to have high dimensional stability. Can be wiped off. On the other hand, at the time of secondary use (that is, when the entire laminate is in a wet state), the fiber sheet can be easily peeled off. Examples of the wiper include an industrial wiper, an industrial waste, kitchen paper, a face mask, cotton, a care wiper, and an antiperspirant sheet. Among these, from the viewpoint of touch, it is suitable for interpersonal wipers such as a face mask, cotton, a care wiper, and an antiperspirant sheet.

  In the laminate of the present invention, primary use is not limited to consumer use. For example, the following usage methods can be mentioned. At the time of primary use, merchandise processing, for example, package processing in the state of a laminated body is easily performed, and later encapsulated with a liquid. At the time of secondary use, a consumer peels a fiber sheet from a laminated body, and uses each fiber sheet.

  Moreover, in the laminated body of this invention, the fibril part which is an ultrafine fiber is extended from the trunk | trunk part which is a thick fiber with respect to this. That is, one end of the fibril part is a trunk part (continuous to the trunk part), and thus has an advantage that it is difficult to generate fuzz as occurs in a laminated body in which, for example, thick fibers and ultrafine fibers are mixed. Note that the observed ultrafine fiber is a fibril part in which one end is continuous with a thick fiber (that is, the ultrafine fiber and the thick fiber are not separate), for example, by using a scanning electron microscope. When both ends of the ultrafine fiber are observed at a magnification of 2000 times or more, it is confirmed that one end of the ultrafine fiber is structurally connected to the fiber trunk.

<Fiber sheet for constituting a laminate>
The present invention is a fiber sheet for constituting the above laminate, each having a breaking strength S _DRY in a dry state and a breaking strength S _WET in a wet state of 20 N / 5 cm or more, and in the thickness direction of the fiber sheet. In a parallel cross section, when the direction parallel to the thickness direction is the longitudinal direction and the direction orthogonal to the thickness direction is the transverse direction, the longitudinal width includes at least the surface of the fiber sheet, and the lateral width is 636 μm. When a certain section is observed, among the fibril parts raised from the surface of the fiber sheet, the number N ₂ of fibril parts having an aspect ratio of 30 or more is also related to the fiber sheet.

The breaking strength S _DRY and breaking strength S _WET of the fiber sheet can be measured by the same method as described above. In the fiber sheet, the breaking strength _SDRY and the breaking strength _SWET in at least one of the in-plane directions (for example, the MD direction or the CD direction) may satisfy the above values. However, the breaking strength S _DRY and the breaking strength S _WET in two directions (for example, the MD direction and the CD direction) orthogonal to the in-plane direction preferably satisfy the above values. Here, the breaking strength S _DRY and the breaking strength S _WET of the fiber sheet coincide with the breaking strength S _DRY and the breaking strength S _{WET of the} fiber sheet constituting the laminate. This is because the physical properties of the fiber sheet are still taken over even if the laminate is constituted.

The number N _{2 of the} fibril parts can be obtained as follows. First, using a scanning electron microscope (preferably, “S-3400N type”, manufactured by Hitachi High-Technologies Corporation), 10 sections of a section satisfying the above conditions are imaged in the cross section in the thickness direction of the fiber sheet. Then, by observing the images, the aspect ratio is calculated by determining the number of 30 or more fibrils unit calculates an average value of the number of each fibril portions obtained, this value and the number N _2. As described above, it is preferable to set the imaging magnification to 200 times. The method for obtaining the aspect ratio is the same as described above. Note that the fibril part may be free (not hydrogen-bonded) at the end or may be hydrogen-bonded.

Further, when there is directionality in the fiber sheet, subjected to equally determined for each direction of the cross-section that may different physical properties, it is preferable to set the average value as the number N _2. For example, when the laminate has an MD direction and a CD direction, and there is a difference in physical properties between them, the above measurement is performed 10 points each in the MD direction and the CD direction, and based on the measurement results of a total of 20 points. It is preferable to calculate an average value and set the value to the number N ₂ .

  As shown in FIG. 5, the fiber sheet as described above has many thin and long fibril parts 2 b on the surface thereof, and therefore when laminated with other fiber sheets (or folded and laminated). A dense inter-sheet network structure can be formed between the surfaces of adjacent fiber sheets.

  Since the other structure of the fiber sheet of this invention is the same as that of the fiber sheet demonstrated in <laminate>, the description is not repeated. This is because the physical properties of the fiber sheet alone before lamination and the physical properties of the fiber sheet contained in the laminated body after lamination are generally the same.

<Method for producing laminate>
The manufacturing method of the laminated body which concerns on this invention is demonstrated. Here, the manufacturing method of the laminated body 10 of a two-layer structure is demonstrated.

  The manufacturing method of the laminated body which concerns on this embodiment at least one regarding the process (fiber sheet formation process) which aggregates several fibers and forms a sheet-like 1st precursor, and the thickness direction of a 1st precursor. By applying cavitation energy from the side, the fibril portion is raised from the fiber to form the second precursor (fibrillation step), and the second precursor is subjected to suction treatment to form the third precursor. A step of forming (fibril drawing step), a step of laminating the third precursor to form a fourth precursor (lamination step), and a step of heat-treating the fourth precursor (heat treatment step).

(Fiber sheet forming process)
In the manufacturing method of the present embodiment, first, a plurality of fibers are assembled to form a sheet-like first precursor. The first precursor is obtained by using the above-described fiber as a preferable fiber having fibrils, or, in some cases, mixing the above-described fiber as a preferable other fiber, and by using existing processing technology (woven fabric, knitting, A lace, a felt, and a nonwoven fabric (a method for producing either dry or wet) may be used without particular limitation. The first precursor is preferably a nonwoven fabric in which fibers are three-dimensionally entangled with a spunlace (water flow).

(Fibrillation process)
Next, cavitation energy is applied to the obtained first precursor from at least one side in the thickness direction. This step may be performed by forming the first precursor in the above-described step and may be performed as it is, or may be performed by taking out the first precursor once wound after the formation. Thereby, the 2nd precursor in which the fibril part was raised from the fiber is formed.

  As a method of giving cavitation energy, there is a method of giving cavitation energy by applying ultrasonic waves to the first precursor while immersing the first precursor in a liquid (generally water is used) as a medium. . In the case of applying ultrasonic energy, there is a method in which the first precursor is placed in the medium in the vicinity of a horn that converts electrical energy generated from the ultrasonic oscillator into mechanical vibration energy and exposed to ultrasonic waves. The vibration direction of the ultrasonic waves is preferably longitudinal vibration that is perpendicular to the first precursor. The distance between the first precursor and the horn is preferably less than about 1 mm and is disposed at a wavelength distance of ¼ from the horn. However, the first precursor may be disposed in contact with the horn.

  The strength of cavitation and the time of exposure to cavitation are preferably adjusted according to the type of fiber and the degree of fibrillation in the first precursor. The higher the strength of cavitation, the faster the fibril part generation rate, and the easier it is to produce fibril parts that are thinner and have a high aspect ratio (for example, 300 or more). The ultrasonic vibration frequency is usually 10 to 500 kHz, preferably 10 to 100 kHz, and more preferably 10 to 40 kHz.

  The temperature of the medium is not particularly limited and is preferably 10 to 100 ° C. The treatment time varies depending on the type of fiber in the first precursor, the shape of the target fiber sheet, and the fineness of the fiber. The treatment time is from 0.005 seconds to less than 10 minutes, preferably from 0.01 seconds to less than 2 minutes, and more preferably from 0.02 seconds to less than 1 second. Similar to the processing time, the density of the network structure can be adjusted by the number of processing times. The number of times of treatment is not particularly limited, but it is preferable to perform treatment twice or more.

  As long as the first precursor is impregnated with a liquid, the cavitation treatment using ultrasonic waves may be performed in the atmosphere. However, if the first precursor is sonicated in the atmosphere, the liquid will be released like a spray, so after sonicating for several seconds, repeatedly impregnating the liquid with the first precursor, A method is preferred in which the first precursor is subjected to ultrasonic treatment while the liquid always flows down the first precursor. In this case, longitudinal vibration is particularly preferred in which the vibration direction of the ultrasonic wave is perpendicular to the first precursor.

  This step may be performed repeatedly. For example, after applying cavitation energy from one surface side of the first precursor, cavitation energy may be applied from the other surface side of the first precursor. In this case, many fibril parts can be raised on both surfaces of the second precursor. In the present specification, the surface in which the fibril portion is raised on the surface of the surface when cavitation energy is applied is also referred to as a “cavitation treated surface”.

(Fibril drawing process)
Next, with respect to the second precursor in which the fibril part is raised, the fibril part to be raised is further pulled out from the surface of the fiber sheet, and the direction of the second precursor is made closer to the thickness direction of the second precursor. A suction process is performed in the thickness direction. Specifically, first, of the second precursor, the second precursor is placed on the support so that the cavitation-treated surface is in contact with the surface of the metal porous support. Then, suction processing is performed such that air flows from the back surface (the surface opposite to the cavitation processing surface) side of the second precursor toward the cavitation processing surface. Thereby, the fibril part which exists in a cavitation process surface will be pulled out so that it may expose outside from the surface of a 2nd precursor.

The suction conditions at this time are preferably, for example, temperature: 10 to 40 ° C. and suction pressure: 300 to 3500 mmH ₂ O. As a result, the fibril portion raised on the surface of the second precursor is pulled out in the thickness direction of the second precursor, so the fibril portion is raised in the thickness direction of the second precursor and extends longer. Will be. For example, a third precursor having 300 or more fibril parts with an aspect ratio of 30 or more raised on the surface is obtained. This third precursor corresponds to the <fiber sheet> described above. Hereinafter, in the present specification, a surface that is a cavitation processing surface and from which fibrils have been extracted in the fibril extraction step is also referred to as a “suction processing surface”.

(Drying process)
Although the 3rd precursor which passed through the suction process in said fibrillation process may be used for the lamination process mentioned later as it is, after using this 3rd precursor for a drying process, it is preferable to use for a lamination process. Thereby, since a 3rd precursor becomes a fiber sheet of the state dried enough, it becomes easy to carry out the lamination process mentioned below. The method of the drying process is not particularly limited. For example, the drying process is performed by placing the third precursor on the drying drum at 100 to 150 ° C. so that the suction processing surface is in contact with the surface of the drying drum. Can do.

(Lamination process)
Next, a third precursor is laminated. The lamination method is not particularly limited. In addition, with respect to the stacking direction, the fourth precursor (laminated structure) is stacked by stacking so that at least one of the two surfaces of the two third precursors that are in contact with each other is a suction treatment surface. Make it. For example, the fourth precursor can be produced by winding the third precursor onto a cylindrical support to create a wound body (roll) and unwinding the fiber sheet from each of the plurality of wound bodies. it can.

(Heat treatment process)
Next, the fourth precursor is heat treated. The method for the heat treatment is not particularly limited, and for example, hot air may be blown onto the fourth precursor. In at least one of the surfaces adjacent to each other in the fourth precursor, many long and thin (high aspect ratio) fibril portions are raised. Such fibril parts can form hydrogen bonds with high frequency with respect to the fibers constituting other adjacent surfaces. Thereby, the laminated body 10 is produced.

  The temperature of the heat treatment is appropriately adjusted depending on the type of fiber, the basis weight of the third precursor, the amount of medium (water content), and the like, but preferably 100 to 150 ° C., for example. Also, the processing time required for the heat treatment is appropriately adjusted depending on the type of fiber, the basis weight of the second precursor, the amount of water, etc., but is preferably 30 seconds to 10 minutes.

  Moreover, it is preferable to implement this heat processing process in the state which included 50 to 500% of water | moisture content uniformly with respect to the areal weight with respect to a 4th precursor. Thereby, the hydrogen bond by a fibril part can be formed more uniformly, and, thereby, the network structure between sheets can be formed more uniformly. The method for adding moisture to the fourth precursor is not particularly limited, and examples thereof include a method of filling a water tank with water and immersing the fourth precursor in this water. The fourth precursor after immersion is lifted from the water tank and appropriately dehydrated so that the water content of the fourth precursor can be adjusted within the above range.

  According to the manufacturing method detailed above, the laminate of the present invention can be manufactured. Further, for example, when a two-layer laminate is formed using two fiber sheets (third precursor), when two surfaces in contact with each other are suction treatment surfaces after cavitation treatment, the inter-sheet network There can be more fibrils to form the structure. For this reason, the network structure between sheets formed between both fiber sheets can become denser.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. In addition, the measuring method of each physical-property value in a following example and a comparative example is as follows.

[1] Weight per unit area of fiber sheet (g / m ² )
In accordance with JIS L 1906, a fiber sheet test piece is allowed to stand for 24 hours in a standard state at a temperature of 20 ° C. and a humidity of 65%, and then a sample measuring 1 m in the width direction and 1 m in the length direction is taken and weight (g) is used. Measure. The weight (g) obtained was rounded off to the second decimal place to obtain a basis weight.

[2] Fiber sheet thickness (mm)
Using a razor ("Feather Shaving Blade S Single Blade" manufactured by Feather Safety Razor Co., Ltd.), the sample was cut in the MD direction perpendicular to the surface, and a digital microscope [Digital Microscope manufactured by Keyence Co., Ltd.] (DIGITALMICROSCOPE) VHX-900] was used to observe the cross section of the sample and measure the thickness.

[3] Apparent density of fiber sheet (g / cm ³ )
The apparent density was determined by dividing the basis weight (g / m ² ) by the thickness (mm).

[4] Porosity of fiber sheet (%)
From the basis weight F (g / m ² ), thickness G (μm) and average specific gravity H (g / cm ² ) of the fiber, the following formula: porosity (%) = 100 − ((F / G / H) × 100)
Was used to calculate the porosity (%).

[5] Breaking strength S of fiber sheet (N / 5cm)
According to JIS L 1913 “General Short Fiber Nonwoven Fabric Test Method”, the breaking strengths in the dry state and wet state were measured in the MD direction and CD direction of the fiber sheet.

[6] Elongation at break E (%) of fiber sheet
According to JIS L 1913 “General Short Fiber Nonwoven Fabric Test Method”, the breaking elongations in the dry state and the wet state were measured with respect to the machine direction (MD) and the width direction (CD) of the fiber sheet.

[7] Number N ₂ in fiber sheet
Using a scanning electron microscope (“S-3400N type”, manufactured by Hitachi High-Technologies Corporation), the cross section in the thickness direction of the fiber sheet includes the space between the two layers of fiber sheets adjacent to the longitudinal region, and the lateral direction ( Ten sections (imaging magnification: 200 times) were imaged in a section where the width of the region in the MD direction was 636 μm. Each image was observed to obtain the number of fibril parts having an aspect ratio of 30 or more. Further, in the cross section in the thickness direction of the fiber sheet, 10 sections are imaged (imaging magnification: Similarly, the number of fibril parts having an aspect ratio of 30 or more was determined. Then, the average value of the number of the fibrils portion and the number N ₂ at positions total 20.

[8] Weight per unit area of laminate (g / m ² )
In accordance with JIS L 1906, a fiber sheet test piece is allowed to stand for 24 hours in a standard state at a temperature of 20 ° C. and a humidity of 65%, and then a sample measuring 1 m in the width direction and 1 m in the length direction is taken and weight (g) is used. Measure. The weight (g) obtained was rounded off to the second decimal place to obtain a basis weight.

[9] Ratio A _DRY / A _WET of adhesive strength A _DRY and adhesive strength A _{WET in} the laminate
From the laminate, a test piece in a dry state and a test piece in a wet state were prepared according to the method described above. When the laminate has a three-layer structure or more, a structure having a two-layer structure of a fiber sheet constituting the outermost layer and a fiber sheet adjacent to the fiber sheet is taken out from the laminate (other than this) The layer was removed) and a test piece was prepared using this. And according to JIS L1913 "General short fiber nonwoven fabric test method" with respect to each of the test piece in a dry state and the test piece in a wet state, the above-mentioned tension | pulling is performed using an autograph AGS-D type | mold apparatus (made by Shimadzu Corporation). The test was conducted. From the obtained results, the above ratio A _DRY / A _WET was determined. However, in each example and each comparative example, only the adhesive strength A _DRY and the adhesive strength A _{WET in} the MD direction were obtained.

[10] Number N ₁ in the laminate
Using a scanning electron microscope (“S-3400N type”, manufactured by Hitachi High-Technologies Corporation), in the thickness direction of the laminate, between the two layers of fiber sheets adjacent to the vertical region, and in the transverse direction (MD direction) ) 10 sections were captured (imaging magnification: 200 times). And each image was observed and the number of fibril parts which hydrogen-bond between two layers of fiber sheets was calculated | required. Further, in the cross section in the thickness direction of the fiber sheet, 10 sections are imaged (imaging magnification: including a space between the two layers of fiber sheets adjacent to the longitudinal region and the width of the lateral (CD direction) region is 636 μm. In the same manner, the number of fibril parts that hydrogen bond between the two fiber sheets was determined. Then, the average value of the number of the fibrils portion to the number N ₁ in place a total of 20.

[11] Sensory evaluation 1 (primary use)
A laminated sheet in which the laminate was cut to 15 cm × 15 cm (MD direction × CD direction) was produced and placed on an acrylic plate that does not absorb moisture. Next, 3 ml of ion-exchanged water was dropped onto the central portion of the placed laminated sheet. Sixty subjects rubbed their arms using the laminated sheet 60 seconds after the dropping, and the sense of unity of the laminated sheet at that time was subjected to sensory evaluation according to the following three criteria.
AAA: It feels that the handleability is good without the laminated sheet peeling off.
AA: A part of the laminated sheet is peeled off and feels poor in handling.
A: The laminated sheet is completely peeled off and the laminated state cannot be maintained, and the handleability feels very bad.

And the sensory evaluation result was determined based on the following criteria.
+++: AAA evaluation is 6 or more.
++: AAA evaluation is 1 to 5 people.
+: No AAA rating.

[12] Sensory evaluation 2 (secondary use)
First, the laminated sheet evaluated as “++++” in sensory evaluation 1 was placed in a plastic vat and 100 ml of water was poured. Next, 10 test subjects picked up one by one from the outermost surface of the laminated sheet and peeled the laminated sheet. The peelability of the laminated sheet at that time was subjected to sensory evaluation according to the following criteria.
BBB: It was possible to cleanly peel one by one from the outermost surface of the laminated sheet and pick it up.
B: The outermost surface of the laminated sheet did not peel and remained in a laminated state.

And the sensory evaluation result was determined based on the following criteria.
+++: BBB evaluation is 6 or more.
++: BBB evaluation is 1 to 5 people.
+: No BBB rating.

  Here, the laminate according to each example described in detail below is a laminate manufactured by the above-described manufacturing method including the first to fourth steps, and the laminate according to each comparative example is the above-described second step. It is the laminated body manufactured by the manufacturing method which does not implement. [1] to [7] are the physical properties of the fiber sheet, and [8] to [10] are the physical properties of the laminate. 7], a fiber sheet obtained by subjecting the fiber sheet (third precursor) after the third step to hot air treatment at 130 ° C. for 3 minutes was used.

<Example 1>
(Fiber sheet forming process)
A semi-random web was prepared by CAD using Tencel (registered trademark) (manufactured by Lenzing) having a fineness of 1.7 dtex and a fiber length of 38 mm. Subsequently, the three-dimensional entanglement process by a water flow was performed. Specifically, first, the web was placed on a metal porous support member, and using two rows of nozzles each having an injection hole having a diameter of 0.10 mm provided at intervals of 0.6 mm in the width direction of the web, The water flow was jetted in the order of water pressure of 3 MPa and 5 MPa, respectively, and entangled (first entanglement process). Further, the front and back of the web are reversed by a conveyor, and placed on a polyester plain weave mesh (manufactured by Nippon Filcon Co., Ltd., OP-76) support. Three-dimensional entanglement was performed (second entanglement process). A series of these treatments was performed at a speed of 5 m / min to obtain a spunlace nonwoven fabric (first precursor).

(Fibrillation process)
Next, on a support made of nylon plain weave mesh (wire diameter 160 μm, # 200) manufactured by Kansai Wire Mesh Co., Ltd. on one side of a spunlace nonwoven fabric using an ultrasonic processing machine manufactured by Seidensha Electronics Industry Co., Ltd. The output was 1200 W, the frequency was 20 kHz, the water temperature was 25 ° C., and the treatment was performed for 0.2 seconds by water bath ultrasonic processing. This obtained the fiber sheet (2nd precursor) in which the fibril part raised.

(Fibril drawing process)
Next, in the fiber sheet after the fibrillation step, the fiber sheet was placed on the punching drum so that the cavitation treatment surface was in contact with the punching drum. Then, suction treatment was performed at a temperature of 25 ° C. and a suction pressure of 2000 mmH ₂ O so that air flows from the back surface (the surface that is not the cavitation treatment surface) side of the spunlace nonwoven fabric toward the cavitation treatment surface side. Thereby, the fiber sheet (3rd precursor) after the cavitation process surface and the suction process surface corresponded and the suction process was performed was produced.

(Drying process)
Next, the fiber sheet after the suction treatment was subjected to a drying treatment by being subjected to a 130 ° C. drying drum. The fiber sheet (third precursor) after the drying treatment was continuously wound around a wound body. In this way, five wound bodies were produced.

(Lamination process)
Next, a laminated structure (fourth precursor) having a five-layer structure was produced while unwinding the fiber sheet from the five wound bodies. At this time, it arrange | positioned so that all the surfaces where a fibril part raises may be located in the one surface side of a laminated structure. The laminated structure produced while being unwound in this manner is immersed in a water tank filled with water at 25 ° C. as it is, and then the laminated structure lifted from the water tank is dehydrated with a dehydrating mangle, and the laminated structure is obtained. The amount of water with respect to the basis weight was about 500%.

(Heat treatment process)
And the laminated structure was dried by spraying a 130 degreeC hot air with respect to the laminated structure after dehydration for 5 minutes. Finally, the laminated structure was cut in the MD direction to produce a laminated body (MD direction × CD direction: 100 cm × 50 m) according to Example 1.

<Example 2>
Tencel (registered trademark) (manufactured by Lenzing) having a fineness of 1.3 dtex and a fiber length of 38 mm was used. Moreover, the laminated body which concerns on Example 2 was produced by the method similar to Example 1 except performing the fibril process with respect to both surfaces of the 1st precursor, and making the laminated structure into the 3 layer structure.

  Here, in Example 2, the cavitation treatment was performed on both surfaces (front and back surfaces) of the fiber sheet, and the suction treatment was performed only on the (surface) of the fiber sheet. And in producing a laminated structure, three fiber sheets were laminated | stacked so that the surface of a fiber sheet might face the back surface of an adjacent fiber sheet.

<Example 3>
Tencel (registered trademark) with a fineness of 1.7 dtex and a fiber length of 38 mm (manufactured by Lenzing) and viscose rayon with a fineness of 1.7 dtex and a fiber length of 40 mm (Corona, manufactured by Ohmi Kenshi) by weight ratio. Fibers uniformly mixed so as to be 50:50 were used. Further, in each of the first entanglement process and the second entanglement process, Example 3 is performed in the same manner as in Example 1 except that the water flow is 5 MPa, 8 MPa, 10 MPa, and the laminated structure is a two-layer structure. A laminate was produced.

<Example 4>
Tencel (registered trademark) (manufactured by Lenzing) having a fineness of 1.7 dtex and a fiber length of 38 mm was used. Moreover, the laminated body which concerns on Example 4 was produced by the method similar to Example 1 except the water flow of the 1st entanglement process having been 3 Mpa, and the water flow of the 2nd entanglement process having been 4 Mpa.

<Comparative Example 1>
As the fibers, Tencel (registered trademark) (manufactured by Lenzing) with a fineness of 1.7 dtex and a fiber length of 38 mm, and a core-sheath composite fiber (core: polypropylene, sheath: polyethylene, “HR-NTW” with a fineness of 1.7 dtex and a fiber length of 51 mm. “, Ube Nitto Co., Ltd.)” was used, and the fiber was uniformly mixed so that the weight ratio was 75:25. Moreover, the laminated body was produced by the method similar to Example 1 except not having implemented the 2nd process and having made the conditions of the drying process in a 3rd process into 135 degreeC and 5 minutes.

<Comparative example 2>
A laminate was produced in the same manner as in Example 1 except that the second step was not carried out.

<Comparative Example 3>
By the same method as in Example 1 except that a split fiber having a fineness of 3.8 dtex and a fiber length of 51 mm (mass ratio of nylon 6 and polyethylene terephthalate: 33/67, “WRAMP W102”, manufactured by Kuraray Co., Ltd.) was used. A laminate was produced.

<Comparative Example 4>
As the fiber, Tencel (registered trademark) (manufactured by Lenzing Co., Ltd.) having a fineness of 1.7 dtex and a fiber length of 38 mm was used. Moreover, the laminated body which concerns on the comparative example 4 was produced by the method similar to Example 1 except the water flow of the 1st entanglement process having been 1 MPa, and the water flow of the 2nd entanglement process having been 1 MPa.

Table 1 shows the physical properties of the laminates produced in each example and each comparative example, and the physical properties of the fiber sheet used in the laminate. In Table 1, “number N ₂ (front surface)” means a surface that is a cavitation treatment surface and is a suction treatment surface, and “number N ₂ (back surface)” is a surface that is a cavitation treatment surface. Means a surface that is not a suction processing surface, or a surface that is not subjected to any processing.

With reference to Table 1, it was confirmed that the laminated body of Examples 1-4 satisfy | fills said (1)-(3). In particular, according to the laminates of Examples 1 to 4, it is understood that since A _WET is smaller than A _DRY , it is difficult to peel off when dried and easily peeled off when wet. In the laminated body of Example 2, the number N ₁ exceeded 100. This is considered to be due to the fact that the number of fibers on the surface was relatively increased due to the small fineness of the tencel and that both surfaces were subjected to cavitation treatment.

  On the other hand, it was confirmed that the laminated bodies of Comparative Examples 1 to 4 do not satisfy the above (3). In particular, in the laminate of Comparative Example 1, the sheath component of the core-sheath composite fiber constituting the fiber sheet was melted in the drying step, and the fiber sheet was fixed by bonding the core-sheath composite fibers together. . For this reason, in the comparative example 1, the lamination sheet which is hard to peel at the time of drying was obtained. However, the laminated sheet of Comparative Example 1 could not be peeled even when wet.

  Moreover, it was confirmed that the laminated body of the comparative example 4 does not satisfy | fill said (2) further. The layered product of Comparative Example 4 is likely to have insufficient shape stability of the layered product in a dry state. For example, the material of the layered product is different from the layers of the layered product only by holding the layered product with both hands and bending it at 90 degrees. It broke and peeled.

  Moreover, it turned out that the laminated body of Examples 1-4 is excellent in the form stability at the time of primary use, and the peelability at the time of secondary use from the result of the sensory evaluation 1 and the sensory evaluation 2 of Table 1. In Comparative Examples 2 to 4, since the result of the sensory evaluation 1 was “+”, the sensory evaluation 2 was not performed.

  The embodiments and examples disclosed herein are illustrative in all respects and should not be construed as being restrictive. The scope of the present invention is shown not by the embodiments and examples described above but by the scope of claims, and is intended to include meanings equivalent to the scope of claims and examples, and all modifications within the scope. The

  10 laminate, 1a, 1b fiber sheet, 1aa, 1bb end, 2 fibers, 2a trunk, 2b fibril part, 3 sheet network structure, 4 sheet network structure.

Claims (11)

A laminate in which two or more layers of fiber sheets formed by gathering fibers are laminated,
The fiber sheet has a breaking strength S _DRY in a dry state and a breaking strength S _WET in a wet state of 20 N / 5 cm or more,
In at least one direction in the in-plane direction of the laminate, an adhesive strength A _DRY in a dry state between two adjacent fiber sheets, and an adhesive strength A _WET in a wet state between two adjacent fiber sheets, A laminate having a ratio A _DRY / A _WET of 5 or more. At least a part of the fiber has a trunk part and a fibril part extending from the trunk part,
The inter-sheet network structure in which the fibril portion in one fiber sheet has hydrogen bonds to the fibers in the other fiber sheet between two adjacent fiber sheets in the laminate. The laminated body of description.   The laminate according to claim 1 or 2, wherein in the fiber sheet, at least a part of a fibril part included in an arbitrary fiber has an in-sheet network structure formed by hydrogen bonding to another fiber.   In the cross section parallel to the thickness direction of the laminate, when the direction parallel to the thickness direction is the vertical direction and the direction orthogonal to the thickness direction is the horizontal direction, at least two adjacent regions in the vertical direction are adjacent to each other. Fibrils that hydrogen bond the fibers of one fiber sheet and the fibers of another fiber sheet when a section including the fiber sheets of the layers and having a width of 636 μm in the lateral direction is observed. The laminated body of any one of Claims 1-3 whose number of parts is 30 or more.   In the cross section parallel to the thickness direction of the laminate, when the direction parallel to the thickness direction is the vertical direction and the direction orthogonal to the thickness direction is the horizontal direction, at least two adjacent regions in the vertical direction are adjacent to each other. Fibrils that hydrogen bond the fibers of one fiber sheet and the fibers of another fiber sheet when a section including the fiber sheets of the layers and having a width of 636 μm in the lateral direction is observed. The laminate according to any one of claims 1 to 4, wherein the aspect ratio of the part is 30 or more. The fiber sheet has a basis weight of 10 to 500 g / m ^2, laminated body according to any one of claims 1 to 5.   The laminate according to any one of claims 1 to 6, wherein the fibers are cellulosic fibers.   The laminated body according to any one of claims 1 to 7, wherein 50% by mass or more of the fibers is Tencel (registered trademark).   The said laminated body is a laminated body of any one of Claims 1-8 which is a laminated body used for a wiper. A fiber sheet for constituting the laminate according to any one of claims 1 to 9,
Each of the breaking strength S _DRY in the dry state and the breaking strength S _WET in the wet state is 20 N / 5 cm or more,
In a cross section parallel to the thickness direction of the fiber sheet, when the direction parallel to the thickness direction is the vertical direction and the direction perpendicular to the thickness direction is the horizontal direction, the width in the vertical direction is at least of the fiber sheet. When the section including the surface and having a lateral width of 636 μm is observed,
Of the fibril parts raised from the surface of the fiber sheet, the fiber sheet has 300 or more fibril parts having an aspect ratio of 30 or more. A step of collecting a plurality of fibers to form a sheet-like first precursor;
With respect to the thickness direction of the first precursor, by providing cavitation energy from at least one side, the fibril portion is raised from the fiber to form the second precursor;
Performing a suction process on the second precursor to form a third precursor;
Laminating the third precursor to form a fourth precursor;
And a step of heat-treating the fourth precursor.