Sheet for covering, and application method thereof

Abstract

To provide a sheet for covering, in which highly uneven distribution of impregnation liquid is achieved, having excellent use efficiency of impregnation liquid with good handleability.SOLUTION: A sheet for covering having a first surface and a second surface is used for covering a target surface to be contacted with the first surface. The sheet for covering is impregnated with an impregnation liquid. A first fiber layer including the first surface contains a hydrophilic fiber in an amount of 90 mass% or more. A second fiber layer including the second surface contains any one or both of the hydrophilic fiber and a hydrophobic fiber. The impregnation ratio of the first fiber layer is higher than the impregnation ratio of the second fiber layer.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a covering sheet used for covering a target surface and a method for using the same. [Background technology]

[0002] There are various known techniques for covering a target surface by contacting a sheet impregnated with a drug solution with the target surface. For example, Patent Document 1 describes a sheet comprising a first fiber layer containing hydrophilic fibers and a second fiber layer containing hydrophobic fibers that are more hydrophobic than the hydrophilic fibers contained in the first fiber layer, the sheet being formed by impregnating a liquid into a nonwoven fabric containing two or more types of hydrophobic fibers having different hydrophobicities. The sheet is used by contacting the first fiber layer with the skin.

[0003] Patent Document 2 describes a sheet impregnated with a liquid medicine on a nonwoven fabric having a two- or three-layer structure, the two- or three-layer structure including at least two types of fibers I and II having different fiber diameters, and 80% to 100% by mass of the fibers being cellulosic fibers. The document describes that the sheet has excellent handling properties, high liquid retention, low irritation to the skin, and excellent adhesion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-098464 A [Patent Document 2] Patent Publication No. 2022-061310 Summary of the Invention [Problem to be solved by the invention]

[0005] In the technology described in Patent Documents 1 and 2, and other sheets obtained by impregnating nonwoven fabric with a chemical solution, it is desirable to impregnate a large amount of the chemical solution in order to supply a sufficient amount of the chemical solution to the target surface for a long period of time. However, impregnating a large amount of the chemical solution is one of the causes of contamination of the manufacturing equipment and an increase in the cost of raw materials. In addition, a sheet impregnated with a large amount of the chemical solution may be significantly difficult to handle when used. Therefore, an object of the present invention is to provide a coating sheet which is excellent in the efficiency of use of an impregnation liquid and in which deterioration of handleability during use is suppressed. [Means for solving the problem]

[0006] The present invention has a first surface and a second surface opposite to the first surface, The first surface is brought into contact with a target surface to cover the target surface; A coating sheet impregnated with an impregnation liquid, the first fiber layer including the first surface contains 90% by mass or more of hydrophilic fibers; the second fibrous layer comprising the second surface comprises either or both of hydrophilic and hydrophobic fibers; The present invention provides a coating sheet in which the impregnation rate of the first fiber layer is at least 50% by mass higher than the impregnation rate of the second fiber layer.

[0007] The present invention further provides a method for using a covering sheet, which has a first surface and a second surface opposite to the first surface and is impregnated with an impregnation liquid, to cover a target surface with the first surface of the covering sheet and cool the target surface, comprising the steps of: the first fiber layer including the first surface contains 90% by mass or more of hydrophilic fibers; the second fibrous layer comprising the second surface comprises either or both of hydrophilic and hydrophobic fibers; The present invention provides a method for using a covering sheet, in which the impregnation rate of the first fiber layer is at least 50% higher by mass than the impregnation rate of the second fiber layer. Effect of the Invention

[0008] According to the present invention, there is provided a covering sheet in which the impregnation liquid is highly distributed unevenly within the sheet, the impregnation liquid is used with excellent efficiency, and the handling properties are excellent. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing an apparatus for measuring the frictional resistance value of a covering sheet. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described below based on its preferred embodiments. The coating sheet of the present invention is a wet sheet containing a base sheet and an impregnating liquid impregnated into the base sheet. The coating sheet has a first surface and a second surface located on the opposite side to the first surface. The coating sheet has a first fiber layer having a first surface and a second fiber layer having a second surface. That is, the coating sheet has a multi-layer structure. The coating sheet may have a two-layer structure consisting of a first fiber layer and a second fiber layer, or may have a three-layer structure having at least one other layer between the first fiber layer and the second fiber layer. In either case, the first fiber layer and the second fiber layer form the outermost surface of the coating sheet. In this specification, the term "coating sheet" may refer to the base sheet itself before being impregnated with the impregnating liquid, or may refer to the coating sheet obtained by impregnating the base sheet with the impregnating liquid, depending on the context.

[0011] In the coating sheet of the present invention, the first and second fiber layers are distinguished by the content and impregnation rate of hydrophilic fibers, but primarily by the sheet composition such as the thickness of the fibers that compose them. For example, the first and second fiber layers can be distinguished by the boundary surface where the fibers have different thicknesses as observed in an electron microscope image of a cross section of the coating sheet in the thickness direction.

[0012] The coating sheet of the present invention is used to coat a target surface. Specific examples of target surfaces will be described later. When coating a target surface with the coating sheet of the present invention, the first surface is brought into contact with the target surface to coat the target surface. Unless there are special circumstances, the second surface is not brought into contact with the target surface to coat the target surface.

[0013] The coating sheet is a fiber sheet composed of fibers. In one embodiment, the constituent fibers of the coating sheet are entangled by hydroentanglement, thereby maintaining the sheet shape of the coating sheet. By hydroentangling the constituent fibers of the coating sheet, the coating sheet has a good feel, so that the coating sheet is less likely to cause discomfort when the coating sheet is used to cover a target surface, such as human skin. From this perspective, it is desirable that the constituent fibers of the coating sheet maintain the sheet shape only by hydroentanglement. However, as long as the feel is not impaired, the constituent fibers of the coating sheet may be fused at the intersections between the constituent fibers.

[0014] The first fiber layer in the coating sheet of the present invention contains hydrophilic fibers at 90% by mass or more, preferably 95% by mass or more, more preferably 98% by mass or more, and even more preferably the first fiber layer is made of hydrophilic fibers. When made of hydrophilic fibers, the first fiber layer is substantially composed of only hydrophilic fibers, except for hydrophobic fibers that are inevitably mixed in during the manufacturing process of the coating sheet. Examples of hydrophobic fibers that are inevitably mixed in during the manufacturing process of the coating sheet include hydrophobic fibers that may be contained in the second fiber layer described below. When the first fiber layer contains 90% by mass or more of hydrophilic fibers, it becomes easy for the first fiber layer to retain a sufficient amount of impregnating liquid, and as a result, by covering a target surface with the covering sheet so that the first surface of the covering sheet is in contact with the target surface, a sufficient amount of impregnating liquid can be supplied to the target surface. Incidentally, a part of the hydrophilic fibers constituting the first fiber layer may inevitably penetrate into the second fiber layer.

[0015] The hydrophilic fibers contained in the first fibrous layer may be staple fibers or continuous filaments, and the choice of which fiber to use may be determined depending on the method of manufacturing the coating sheet.

[0016] From the viewpoint of supplying a sufficient amount of impregnation liquid to the target surface, the average fiber diameter of the fibers constituting the first fiber layer is preferably 11.9 μm or less on the first surface. Hereinafter, such an average fiber diameter is also referred to as "average fiber diameter of fibers on the first surface." By using fibers having this average fiber diameter, a high capillary force is exerted, so that a sufficient amount of impregnation liquid can be retained in the first fiber layer. From the viewpoint of making this advantage more prominent, the average fiber diameter of the fibers constituting the first fiber layer is more preferably 11.5 μm or less on the first surface, and even more preferably 11.0 μm or less. From the viewpoint of exerting a high capillary force, it is desirable that the fibers constituting the first fiber layer are as thin as possible. However, from the viewpoint of cost, a thin fiber is disadvantageous. Therefore, in consideration of cost, the average fiber diameter of the fibers constituting the first fiber layer is preferably 7.0 μm or more on the first surface, more preferably 7.5 μm or more, and even more preferably 8.0 μm or more. Taking the above into consideration, the average fiber diameter of the fibers constituting the first fiber layer on the first surface is preferably 7.0 μm or more and 11.9 μm or less, more preferably 7.5 μm or more and 11.5 μm or less, and even more preferably 8.0 μm or more and 11.0 μm or less.

[0017] The average fiber diameter of the fibers on the first surface is measured by the following method. Observe the coating sheet from a direction perpendicular to the cross section in the thickness direction with a scanning electron microscope (SEM) at a magnification at which the fibers can be seen, and randomly select 20 fibers from the first surface and its vicinity. Measure the length of a line drawn perpendicular to the longitudinal direction of each fiber, and use this as the fiber diameter. The average fiber diameter is calculated by taking the arithmetic mean value of these fiber diameters.

[0018] From the viewpoint of supplying a sufficient amount of impregnation liquid to the target surface, the basis weight of the first fiber layer is set to 10 g / m 2It is preferable that the weight is 15 g / m or more. 2 More preferably, it is 20 g / m or more. 2 More preferably, the above is the case. In order to prevent excessive impregnation and improve the handling properties of the covering sheet, the basis weight of the first fiber layer is set to 60 g / m 2 Preferably, it is 55 g / m or less. 2 More preferably, it is 50 g / m or less. 2 It is even more preferable that: Taking the above into consideration, the basis weight of the first fiber layer is 10 g / m 2 More than 60g / m 2 It is preferable that the thickness is less than 15 g / m 2 More than 55g / m 2 More preferably, it is 20 g / m or less. 2 More than 50g / m 2 It is even more preferable that:

[0019] Next, the second fibrous layer in the coating sheet of the present invention will be described. The second fibrous layer contains either or both of hydrophilic and hydrophobic fibers. The second fiber layer is used for the purpose of retaining the impregnation liquid together with the first fiber layer. For this purpose, the second fiber layer preferably contains at least hydrophilic fibers. The type of hydrophilic fibers contained in the second fiber layer may be the same as or different from the type of hydrophilic fibers contained in the first fiber layer. Incidentally, a part of the hydrophilic fibers constituting the second fiber layer may inevitably penetrate into the first fiber layer.

[0020] The hydrophilic fibers contained in the second fibrous layer may be staple fibers or continuous filaments, and the choice of which fiber to use may be determined depending on the method of manufacturing the coating sheet.

[0021] In the present invention, by creating a gradient of impregnation rate between the first and second sides of the covering sheet, that is, by increasing the uneven distribution of the impregnation liquid in the thickness direction of the covering sheet, a sufficient amount of impregnation liquid can be supplied to the target surface without excessively increasing the amount of impregnation liquid. For this purpose, in the present invention, the second fiber layer is used in combination with the first fiber layer to create a gradient of impregnation rate between the first and second sides of the covering sheet. From this viewpoint, it is preferable that the second fiber layer has a lower ability to retain the impregnation liquid than the first fiber layer. Therefore, in the present invention, it is advantageous to make the average fiber diameter of the fibers contained in the second fiber layer larger than the average fiber diameter of the fibers contained in the first fiber layer. This makes it easy to make the capillary force generated in the second fiber layer smaller than that of the first fiber layer. As a result, it is possible to make the retention of the impregnation liquid in the second fiber layer lower than that of the first fiber layer. From the viewpoint of making the average fiber diameter of the fibers contained in the first fiber layer smaller than the average fiber diameter of the fibers contained in the second fiber layer, it is preferable that the average fiber diameter of the fibers on the first surface of the first fiber layer be smaller than the average fiber diameter of the fibers on the second surface of the second fiber layer.

[0022] From the viewpoint of making the retention of the impregnation liquid in the second fiber layer lower than that of the first fiber layer, the average fiber diameter on the second surface of the fibers constituting the second fiber layer (hereinafter also referred to as "average fiber diameter of the fibers on the second surface") is preferably 7.5 μm or more, more preferably 8.0 μm or more, and even more preferably 8.5 μm or more. In addition, from the viewpoint of preventing the rigidity of the coating sheet from becoming excessively high and the feeling of use from being deteriorated, the average fiber diameter of the fibers on the second surface is preferably 35.0 μm or less, more preferably 34.0 μm or less, and even more preferably 33.0 μm or less. Taking the above into consideration, the average fiber diameter of the fibers in the second surface is preferably 7.5 μm or more and 35.0 μm or less, more preferably 8.0 μm or more and 34.0 μm or less, and even more preferably 8.5 μm or more and 33.0 μm or less. The average fiber diameter of the fibers on the second surface is measured in the same manner as the average fiber diameter of the fibers on the first surface.

[0023] When the second fiber layer contains hydrophilic fibers, from the viewpoint of making the retention of the impregnation liquid in the second fiber layer lower than that of the first fiber layer, the average fiber diameter of the hydrophilic fibers constituting the second fiber layer on the second surface (hereinafter also referred to as the "average fiber diameter of the hydrophilic fibers on the second surface") is preferably 12.0 μm or more and 27.0 μm or less, more preferably 12.5 μm or more and 26.0 μm or less, and even more preferably 13.0 μm or more and 25.0 μm or less, provided that it is larger than the average fiber diameter of the fibers constituting the first fiber layer on the first surface.

[0024] From the viewpoint of fully expressing the gradient of impregnation rate between the first side and the second side of the coating sheet, when the average fiber diameter of the hydrophilic fibers on the second side is D2 and the average fiber diameter of the hydrophilic fibers constituting the first fiber layer on the first side (hereinafter also referred to as "average fiber diameter of the hydrophilic fibers on the first side") is D1, the value of D1 / D2, which is the ratio of D1 to D2, is preferably 0.99 or less, more preferably 0.95 or less, and even more preferably 0.90 or less. From the viewpoint of preventing deterioration in the feeling of use of the application sheet, the value of D1 / D2 is preferably 0.10 or more, more preferably 0.15 or more, and even more preferably 0.20 or more. Taking the above into consideration, the value of D1 / D2 is preferably 0.1 or more and 0.99 or less, more preferably 0.15 or more and 0.95 or less, and even more preferably 0.20 or more and 0.90 or less. The average fiber diameter of the hydrophilic fibers on the first and second surfaces is measured by a method similar to the method for measuring the average fiber diameter of the fibers on the first surface.

[0025] From the same viewpoint as above, when the average fiber diameter of the fibers on the second surface is d2 and the average fiber diameter of the fibers on the first surface is d1, the ratio of d1 to d2, that is, d1 / d2, is preferably 0.99 or less, more preferably 0.95 or less, and even more preferably 0.90 or less. From the viewpoint of preventing deterioration in the feeling of use of the application sheet, the value of d1 / d2 is preferably 0.10 or more, more preferably 0.15 or more, and even more preferably 0.20 or more. Taking the above into consideration, the value of d1 / d2 is preferably 0.10 or more and 0.99 or less, more preferably 0.15 or more and 0.95 or less, and even more preferably 0.20 or more and 0.90 or less. The average fiber diameter d1 of the fibers on the first surface is substantially the same as the average fiber diameter D1 of the hydrophilic fibers on the first surface when the first fiber layer does not contain hydrophobic fibers. The average fiber diameter d2 of the fibers on the second surface is substantially the same as the average fiber diameter D2 of the hydrophilic fibers on the second surface when the second fiber layer does not contain hydrophobic fibers.

[0026] In order to provide the covering sheet with sufficient strength, the basis weight of the second fiber layer is 10 g / m 2 It is preferable that the weight is 15 g / m or more. 2 More preferably, it is 20 g / m or more. 2 More preferably, the above is the case. In order to prevent the stiffness of the covering sheet from becoming excessively high, the basis weight of the second fiber layer is set to 60 g / m 2 Preferably, it is 55 g / m or less. 2 More preferably, it is 50 g / m or less. 2 It is even more preferable that: Taking the above into consideration, the basis weight of the second fiber layer is 10 g / m 2 More than 60g / m 2 It is preferable that the thickness is less than 15 g / m 2 More than 55g / m 2 More preferably, it is 20 g / m or less. 2 More than 50g / m 2It is even more preferable that:

[0027] As described above, the second fiber layer preferably contains at least hydrophilic fibers. The proportion of hydrophilic fibers in the second fiber layer is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, from the viewpoint of ensuring the impregnation rate of the entire coating sheet with the impregnation liquid. There is no particular upper limit to the proportion of hydrophilic fibers contained in the second fiber layer, and 100% of the constituent fibers of the second fiber layer may be hydrophilic fibers.

[0028] The second fibrous layer may include hydrophobic fibers, which has the advantage of reducing the frictional resistance of the second surface and improving the feel against the skin, and also has the advantage of promoting a gradient of wet pick-up between the first surface and the second surface. When the second fibrous layer contains hydrophobic fibers, a part of the hydrophobic fibers may inevitably be embedded in the first fibrous layer. When the second fiber layer contains hydrophobic fibers, there are no particular restrictions on the average fiber diameter D3 of the hydrophobic fibers at the second surface. However, in relation to the average fiber diameter D2 of the hydrophilic fibers at the second surface contained in the second fiber layer, it is preferable that the value of D3 / D2 is preferably 0.15 or more and 3.00 or less, more preferably 0.20 or more and 2.90 or less, and even more preferably 0.25 or more and 2.80 or less, since this reduces the frictional resistance of the second surface and has a significant advantage of promoting the gradient of the impregnation rate between the first surface and the second surface.

[0029] The hydrophobic fibers additionally contained in the second fibrous layer may be staple fibers or continuous filaments, and the choice of which fiber to use may be determined depending on the method of manufacturing the covering sheet.

[0030] In this specification, a fiber is defined as a hydrophobic fiber if the contact angle between the fiber surface and water is 90 degrees or more when a droplet of pure water is dropped onto the fiber in an environment of 25° C., and a fiber is defined as a hydrophilic fiber if the contact angle between the fiber surface and water is less than 90 degrees. The contact angle can be measured, for example, according to the method described in JP 2015-142721 A.

[0031] The hydrophilic fibers contained in the first fiber layer and / or the second fiber layer refer to both fibers whose fiber surfaces are inherently hydrophilic, and fibers whose fiber surfaces are inherently hydrophobic but have been subjected to a hydrophilization treatment to be rendered hydrophilic. Examples of fibers whose fiber surface is inherently hydrophilic include natural cellulose fibers such as rayon, cotton, cupra, lyocell, and wood pulp, regenerated cellulose fibers, and silk. These fibers can be used alone or in combination of two or more. In particular, rayon is preferred because it greatly improves flexibility in a wet state and improves adhesion between the covering sheet and the target surface. Although the fiber surface is inherently hydrophobic, examples of fibers that have been subjected to hydrophilic treatment to be rendered hydrophilic include fibers made of thermoplastic resins having fiber-forming ability, such as polyolefin resins, acrylic resins, and polyester resins, on the surface of which a hydrophilizing agent has been applied.

[0032] Examples of the hydrophobic fibers additionally contained in the second fiber layer include fibers made of thermoplastic resins having fiber-forming ability, such as polyolefin resins, acrylic resins, and polyester resins.

[0033] Comparing the first fiber layer with the second fiber layer, as described above, it is preferable that the fibers constituting the first fiber layer have a smaller average fiber diameter than the fibers constituting the second fiber layer. In addition, it is preferable that the first fiber layer has a higher fiber density than the second fiber layer. In other words, it is preferable that the first fiber layer is in a state where thin fibers are densely present. On the other hand, the second fiber layer preferably has a lower fiber density than the first fiber layer, that is, the second fiber layer preferably has thick fibers sparsely present. Due to the first and second fiber layers being in these states, the impregnation liquid impregnated in the covering sheet is more likely to migrate from the second surface side to the first surface side. As a result, in the covering sheet, the impregnation rate of the first fiber layer is higher than that of the second fiber layer, and this effectively creates an impregnation rate gradient between the first surface and the second surface. In other words, the impregnation rate of the first surface is higher than that of the second surface.

[0034] The degree of fiber density in the first fiber layer and the second fiber layer can be evaluated by fiber fixation. Fiber fixation is a parameter indicating the degree of difficulty in removing fibers from the covering sheet, and high fiber fixation means that the fibers are less likely to be removed. As described above, the first fiber layer preferably has a higher fiber density than the second fiber layer, so that in terms of fiber fixation, it is preferable that the fiber fixation of the first surface is higher than that of the second surface.

[0035] As will be apparent from the method for measuring fiber fixation, which will be described in the Examples below, fiber fixation is represented by the amount (mg) of fibers that have come off from the first and second sides. When the amount of fibers that have come off from the first side is S1 and the amount of fibers that have come off from the second side is S2, from the viewpoint of providing a large gradient in the impregnation rate between the first and second sides, the value of S2 / S1, which is the ratio of S2 to S1, is preferably 5 or more and 300 or less, more preferably 10 or more and 250 or less, and even more preferably 17 or more and 200 or less.

[0036] In order to control the degree of fiber density in the first fiber layer and the second fiber layer and achieve desired fiber fixation on the first surface and the second surface, for example, the conditions for producing the base sheet that constitutes the coating sheet may be appropriately controlled.

[0037] In order to cover a target surface with the coating sheet of the present invention and successfully supply the impregnating liquid impregnated in the coating sheet to the target surface, it is preferable that the first surface, which is the surface facing the target surface, adheres closely to the target surface. On the other hand, it is preferable that the second surface located on the opposite side to the target surface has low adhesion in terms of improving the handling of the coating sheet. As a result of the study by the present inventor, it was found that the degree of adhesion can be evaluated by the friction resistance values ​​(friction resistance values ​​in a wet state) of the first and second surfaces. In detail, the higher the friction resistance value, the higher the adhesion can be evaluated. From this viewpoint, in the coating sheet of the present invention, it is preferable that the friction resistance value F1 of the first surface is higher than the friction resistance value F2 of the second surface. Specifically, the value of F1 / F2, which is the ratio of the friction resistance value F1 of the first surface to the friction resistance value F2 of the second surface, is preferably 1.0 to 24, more preferably 1.5 to 22, and even more preferably 2.0 to 20. Here, the frictional resistance value is measured by bringing a coating sheet impregnated with 400% by mass of the impregnation solution into contact with a model skin. The method for measuring the frictional resistance value will be described in detail in the Examples below.

[0038] In order to increase the frictional resistance of the first side, the first fiber layer may be made of fibers having a small diameter and the first fiber layer may have a high impregnation rate with the impregnation liquid, whereas in order to decrease the frictional resistance of the second side, the second fiber layer may be made of fibers having a large diameter and the second fiber layer may have a low impregnation rate with the impregnation liquid. In addition, the low frictional resistance value of the second surface is advantageous in that, for example, when the coating sheet of the present invention is used to cover human skin, friction between the coating sheet and clothing is reduced, making it less likely for the coating sheet to shift position during coverage.

[0039] The impregnating liquid contained in the coating sheet of the present invention is selected from those having an appropriate composition depending on the type of the target surface to be coated with the coating sheet. In terms of ease of handling and safety, the impregnating liquid is preferably an aqueous liquid that uses water as a medium. When the impregnation liquid is an aqueous liquid, the proportion of water in the impregnation liquid is preferably 50% by mass or more and 99.9% by mass or less from the viewpoints of handling property, safety, and the like. Examples of components other than water contained in the aqueous liquid include water-soluble organic solvents, various surfactants, fragrances, cooling ingredients, preservatives, oils, thickeners, and pH adjusters. Examples of water-soluble organic solvents include lower alcohols, propylene glycol, polyethylene glycol, and propylene glycol monomethyl ether. When the aqueous liquid contains ethanol, the target surface can be effectively cooled when the target surface is covered with the covering sheet, which is preferable. When the target surface is human skin, the target surface can be given a sufficient cooling sensation.

[0040] The degree of the impregnation liquid contained in the covering sheet, in other words, the impregnation rate represented by the ratio of the impregnation liquid to the base sheet, is preferably 200% by mass or more and 700% by mass or less, more preferably 250% by mass or more and 650% by mass or less, and even more preferably 300% by mass or more and 600% by mass or less, from the viewpoint of the supply of the impregnation liquid to the target surface and the handling of the covering sheet. In the present invention, since a gradient is generated in the impregnation rate of the impregnation liquid in the thickness direction of the covering sheet, a sufficient amount of the impregnation liquid can be supplied to the target surface without excessively increasing the impregnation rate of the covering sheet as a whole.

[0041] The impregnation rate of the entire coating sheet is as described above, and the impregnation rate of the first fiber layer is preferably 300% by mass or more, more preferably 320% by mass or more, and even more preferably 350% by mass or more, from the viewpoint of supplying a sufficient amount of impregnation liquid to a target surface. From the viewpoint of handling of the covering sheet, the impregnation rate in the first fiber layer is preferably 800% by mass or less, more preferably 750% by mass or less, and even more preferably 700% by mass or less. Taking the above into consideration, the impregnation rate in the first fiber layer is preferably 300% by mass or more and 800% by mass or less, more preferably 320% by mass or more and 750% by mass or less, and even more preferably 350% by mass or more and 700% by mass or less. On the other hand, from the viewpoints of sufficiently supplying the impregnation liquid to the first fiber layer and of the ease of handling the covering sheet, the impregnation rate in the second fiber layer is preferably 10% by mass or more, more preferably 50% by mass or more, and even more preferably 100% by mass or more, provided that it is lower than the impregnation rate in the first fiber layer. From the viewpoint of providing a sufficient gradient in the impregnation rate of the impregnation liquid in the thickness direction of the covering sheet, the impregnation rate of the second fiber layer is preferably 650% by mass or less, more preferably 600% by mass or less, and even more preferably 550% by mass or less. Taking the above into consideration, the impregnation rate in the second fiber layer is preferably 10% by mass or more and 650% by mass or less, more preferably 50% by mass or more and 600% by mass or less, and even more preferably 100% by mass or more and 550% by mass or less.

[0042] From the viewpoint of providing a sufficient gradient in the impregnation rate of the impregnation liquid in the thickness direction of the coating sheet, the impregnation rate of the first fiber layer is preferably at least 50% by mass higher than the impregnation rate of the second fiber layer, more preferably at least 100% by mass higher, even more preferably at least 130% by mass higher, and even more preferably at least 200% by mass higher. On the other hand, from the viewpoint of continuously supplying a sufficient amount of impregnation liquid to the target surface, the impregnation rate of the first fiber layer is preferably at most 600% by mass higher than the impregnation rate of the second fiber layer, more preferably at most 500% by mass higher, even more preferably at most 450% by mass higher, and even more preferably at most 400% by mass higher. Taking the above into consideration, the impregnation rate of the first fiber layer is preferably 50% by mass or more and 600% by mass or less, more preferably 100% by mass or more and 500% by mass or less, even more preferably 130% by mass or more and 450% by mass or less, and even more preferably 200% by mass or more and 400% by mass or less, higher than the impregnation rate of the second fiber layer. From the viewpoints of supplying a sufficient amount of the impregnation liquid to the target surface and providing a sufficient gradient in the impregnation rate of the impregnation liquid in the thickness direction of the covering sheet, the value of P1 / P2, which is the ratio of the impregnation rate P1 in the first fiber layer to the impregnation rate P2 in the second fiber layer, is preferably 1.05 or more and 3.1 or less, more preferably 1.10 or more and 3.0 or less, and even more preferably 1.15 or more and 2.9 or less.

[0043] When the impregnating liquid contained in the coating sheet of the present invention is an aqueous liquid, the aqueous liquid is supplied to the target surface by covering the target surface with the coating sheet, and the target surface is cooled. When the target surface is human skin, the coating sheet can be used to give the target a cooling sensation. In other words, the coating sheet of the present invention can be used as a cooling sheet. The degree of cooling of the target surface by the coating sheet of the present invention can be evaluated by the heat flux maximum value Qmax. Qmax is the maximum value of the heat flow when heat is stored in a hot plate such as a metal plate with a temperature sensor, the temperature of the hot plate is set higher than the temperature of the measurement target, the hot plate is brought into contact with the surface of the measurement target, and the heat stored in the hot plate immediately after the contact is transferred to the measurement target on the low temperature side. The larger the value of Qmax, the higher the degree of cooling of the target surface can be evaluated.

[0044] As a result of the study by the inventor, it was found that the value of Qmax is correlated with the impregnation rate of the impregnation liquid, and the higher the impregnation rate, the higher the Qmax can be. From this viewpoint, it is advantageous to increase the degree of cooling of the target surface by increasing the impregnation rate of the impregnation liquid. However, there is a limit to increasing the impregnation rate of the impregnation liquid, and increasing the impregnation rate tends to reduce the handleability of the covering sheet. Therefore, in the present invention, as described above, by providing a gradient of the impregnation rate between the first surface and the second surface of the covering sheet, the apparent impregnation rate is increased and Qmax is increased without excessively increasing the actual impregnation rate.

[0045] From the above viewpoint, the maximum heat flux Qmax (W / cm2) on the first surface when the surface is impregnated with 400 mass% of the impregnating liquid is 2) is the maximum heat flux Qmax (W / cm2) on the second surface 2 ) is preferably at least 0.15 W / cm 2 More than 1.3W / cm 2 More preferably, it is 0.2 W / cm or less. 2 More than 1.2W / cm 2 It is more preferable that the temperature is higher than this.

[0046] From the viewpoint of further increasing the degree of cooling of the target surface by the coating sheet of the present invention, the maximum heat flux Qmax on the first surface in a state where the sheet is impregnated with 400% by mass of the impregnation liquid is 0.85 W / cm 2 It is preferable that the value is equal to or higher than 0.85 W / cm 2 More than 1.4W / cm 2 More preferably, it is 0.87 W / cm or less. 2 More than 1.3W / cm 2 It is even more preferable that: From the same viewpoint, the maximum heat flux Qmax on the second surface is set to 0.70 W / cm2, provided that the maximum heat flux Qmax on the first surface is smaller than the maximum heat flux Qmax on the second surface. 2 It is preferable that the value is less than 0.05 W / cm 2 More than 0.70W / cm 2 More preferably, it is 0.1 W / cm or less. 2 More than 0.68W / cm 2 It is even more preferable that: From the same viewpoint, the ratio of the heat flux maximum value Qmax on the first surface to the heat flux maximum value Qmax on the second surface is preferably 1.1 or more and 7.0 or less, more preferably 1.1 or more and 6.5 or less, and even more preferably 1.2 or more and 6.0 or less. The maximum heat flux value Qmax can be measured in accordance with JIS L 1927 under the condition that the temperature difference between room temperature and the heat source plate is 10° C. A specific measurement method will be described in the examples described later.

[0047] Next, a preferred method for producing the coating sheet of the present invention will be described. As described above, in one embodiment of the coating sheet of the present invention, the sheet shape is maintained by hydroentangling the constituent fibers. From this viewpoint, it is preferable that the base sheet constituting the coating sheet is produced by the spunlace method. In other words, it is preferable that the base sheet is a spunlace nonwoven fabric.

[0048] When manufacturing a base sheet by the spunlace method, a first web as a raw material for the first fiber layer and a second web as a raw material for the second fiber layer are prepared. The first web is made of hydrophilic fibers. The second web contains hydrophilic fibers with a larger diameter than the hydrophilic fibers contained in the first web, and may additionally contain hydrophobic fibers. Both the first web and the second web can be manufactured by, for example, a carding machine.

[0049] The first and second webs are superimposed on each other to form a laminated web, and water is sprayed onto the laminated web, whereby the constituent fibers of the first web, the constituent fibers of the second web, and the constituent fibers of the first web and the second web are hydroentangled, resulting in a base sheet made of a spunlace nonwoven fabric having a first fiber layer formed from the first web and a second fiber layer formed from the second web.

[0050] After the base sheet is obtained by the above method, the desired covering sheet is obtained by impregnating the base sheet with a predetermined amount of impregnation liquid. Since the base sheet has a first fiber layer and a second fiber layer each containing fibers with different average fiber diameters, if the base sheet is kept stationary after being impregnated with the impregnation liquid, a gradient in the impregnation rate occurs.

[0051] The covering sheet thus obtained is used to cover various target surfaces. For example, the covering sheet can be used to cover human skin to give a cooling sensation. Therefore, the covering sheet of the present invention is useful, for example, when one wants to relieve heat when going out in hot weather. In this case, the covering sheet is used so that the first surface is in contact with the skin and the second surface faces outward. The first surface side of the covering sheet, i.e., the first fiber layer, holds the impregnating liquid at a high impregnation rate, so that the impregnating liquid is smoothly supplied to the skin through the first surface, enhancing the cooling effect. On the other hand, the second surface side of the covering sheet, i.e., the second fiber layer, has a low impregnation rate of the impregnating liquid, which is advantageous in that clothes are less likely to become wet with the impregnating liquid. When the frictional resistance value of the second surface is lower than that of the first surface, the frictional force generated between the outwardly facing second surface and clothing can be reduced, which has the advantage that the covering sheet is less likely to shift in position due to friction between the covering sheet and clothing. Also, when the frictional resistance value of the first surface is higher than that of the second surface, the adhesion between the first surface and the skin is improved, improving the cooling effect.

[0052] The present invention has been described above based on its preferred embodiment, but the present invention is not limited to the above embodiment. For example, in the above embodiment, the application of the coating sheet of the present invention to cool human skin is described as an example, but the cooling target is not limited to human skin, and may be other target surfaces. In addition, the coating sheet of the present invention is not limited to being used as a cooling sheet to cool a target surface, but can also be used to cover a target surface for the purpose of, for example, a face mask, a compress, water absorption, oil absorption, and cleaning of a hard surface. EXAMPLES

[0053] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, "%" means "% by mass".

[0054] [Examples 1 to 8 and Comparative Examples 1 and 2] The fibers constituting the first fiber layer including the first side and the fibers constituting the second fiber layer including the second side were shown in Table 1 below in the compositions shown in the same table, and a base sheet was produced by the spunlace method. The obtained base sheet was impregnated with 400% by mass of an impregnation liquid to produce a coating sheet. The impregnation liquid used was an aqueous liquid containing 0.1% by mass of a nonionic surfactant (polyoxyethylene lauryl ether, Emulgen (registered trademark) 108 from Kao Corporation). The average fiber diameters D1 and D2 of the hydrophilic fibers on the first and second sides of the obtained coating sheet, as well as the average fiber diameter d1 on the first side and the average fiber diameter d2 on the second side were measured by the methods described above. Furthermore, for the obtained coating sheet, the impregnation rates of the first and second fiber layers, the Qmax of the first and second sides, the frictional resistance values ​​of the first and second sides, and the fiber fixation properties of the first and second sides were measured by the following methods. Furthermore, the obtained coating sheets were evaluated for the fit of the first side and the wetness of the first and second sides by the following methods. The results are shown in Table 1.

[0055] [Impregnation rate of the first fibrous layer and the second fibrous layer] The base sheet before impregnated with the impregnation liquid was peeled into the first fiber layer and the second fiber layer, and the initial mass of each was measured. The first fiber layer and the second fiber layer were stacked as they were before and placed in a storage bag, and the impregnation liquid was impregnated in the bag at 400% by mass. The base sheet was then pressed with a 1 kg roller so that the impregnation liquid was spread over the entire base sheet, and a covering sheet was obtained. After leaving the covering sheet with the first surface facing down for 12 hours or more, the masses of the first fiber layer and the second fiber layer were measured, and the impregnation rates of the first fiber layer and the second fiber layer were calculated using the following formula (1). Impregnation rate = (mass after impregnation - initial mass) / initial mass x 100 (1)

[0056] [Qmax of the first and second surfaces] The covering sheet was left for 12 hours or more with the first surface facing down. The first surface and the second surface were used as the measurement surfaces, and the Qmax was measured using a Kato Tech KES-F7. The measurement environment was room temperature 23°C and relative humidity 50%, and a measurement plate heated to +10°C (ΔT=10°C) from room temperature was brought into contact with the sample that had been fully acclimated to the measurement environment to measure the Qmax.

[0057] [Friction resistance value of the first and second surfaces] The covering sheet cut into a size of 40 x 80 mm was placed in a pillow bag made of a composite sheet laminated with aluminum foil and left for 12 hours or more with the first surface facing down. The covering sheet was cut so that its MD direction was the same as the longitudinal direction. The frictional resistance value was measured using the device shown in Fig. 1. In the figure, reference numeral 10 denotes a fixing plate, on which model skin 11 was placed. A covering sheet 12 was placed on the model skin 11, and a weight of 500 g was placed on top of the covering sheet 12. The covering sheet 12 was placed on the model skin 11 so that the surface for measuring the frictional resistance value faced the model skin 11. An acrylic plate 14 was placed between the covering sheet 12 and the weight so that the load was applied to the entire area of ​​the covering sheet 12. As the model skin 11, a pore 3D skin model (product number: NO. 351), which is a skin model made by Bealux Co., Ltd., was used. After applying a load with the weight 13 for 10 seconds, the weight 13 and the acrylic plate 14 were removed, and the frictional resistance value (maximum static friction force (N)) when the covering sheet 12 was pulled horizontally at a speed of 100 mm / min was measured with a digital force gauge 15. The covering sheet 12 and the digital force gauge 15 were connected with a clip 16. The digital force gauge used was the ZTS-50N manufactured by Imada Co., Ltd. The measurement environment was a temperature of 23°C and a relative humidity of 50%.

[0058] [Fibre fixation on the first and second surfaces] An adhesive tape (KK-18D from Nichiban Co., Ltd.) with a width of 18 mm and a length of 70 mm was attached along the MD direction of the base sheet, and a load of 1 kg was applied and pressed for 20 seconds. After removing the weight, the adhesive tape was peeled off along the MD direction. The mass of the adhesive tape after peeling was measured. The measurement environment was a temperature of 23°C and a relative humidity of 50%. The mass of the removed fiber was calculated by subtracting the mass of the adhesive tape before attachment from the mass, and this value was taken as the fiber fixation.

[0059] [Fit of the first surface and wet feel of the first and second surfaces] The covering sheet was left for 12 hours or more with the first surface facing down. At 25°C, the inside of the forearm of one expert monitor was covered with the covering sheet. At this time, the first surface was made to face the inside of the forearm. Under this condition, the expert monitor evaluated the fit and wetness according to the following criteria. <Fit of the first surface> 4: I feel a strong fit. 3: The fit feels a little tight. 2: The fit feels a little weak. 1: The fit feels weak. <Wet feeling on the first side> 4: Feels very wet. 3: Feels slightly wet. 2: The wet feeling is slightly weak. 1: Feels slightly wet. <Wet feeling on the second side> 4: Almost no wetness. 3: Doesn't feel very wet. 2: Feels slightly wet. 1: Feels wet.

[0060] [Table 1]

[0061] As is clear from the results shown in Table 1, the application sheets obtained in the respective Examples had excellent fit and wet feeling on the first side, and low wet feeling on the second side. [Explanation of symbols]

[0062] 10 Fixed plate 11 Model Skin 12 Covering sheet 13 Weight 14 Acrylic plate 15 Digital Force Gauge 16 clips

Claims

1. a first surface and a second surface located opposite the first surface; The first surface is brought into contact with a target surface to coat the target surface; A coating sheet impregnated with an impregnation liquid, the first fiber layer including the first surface contains 90% by mass or more of hydrophilic fibers; the second fibrous layer comprising the second surface comprises either or both of hydrophilic and hydrophobic fibers; A covering sheet, wherein the impregnation rate of the first fiber layer is at least 50% by mass higher than the impregnation rate of the second fiber layer.

2. The coating sheet according to claim 1, wherein the impregnation rate of the second fiber layer is 650 mass % or less.

3. The coating sheet according to claim 1 or 2, wherein the average fiber diameter of the fibers on the first surface of the first fiber layer is smaller than the average fiber diameter of the fibers on the second surface of the second fiber layer.

4. The coating sheet according to claim 1 or 2, wherein the average fiber diameter of the fibers constituting the first fiber layer is 11.9 μm or less on the first surface.

5. The coating sheet according to claim 1 or 2, wherein the first surface has a higher fiber fixation property than the second surface.

6. The coating sheet according to claim 1 or 2, wherein the frictional resistance value of the first surface is higher than the frictional resistance value of the second surface.

7. When the impregnation liquid is impregnated at 400 mass %, the maximum heat flux value Qmax on the first surface is 0.15 W / cm 2 higher than the maximum heat flux value Qmax on the second surface. ２ The coating sheet according to claim 1 or 2, wherein the coating sheet has a viscosity of 1000 MPa or more.

8. 3. The coating sheet according to claim 1, wherein the target surface is human skin, and the coating sheet is used to cover the skin and provide a cooling sensation.

9. A method for using a covering sheet, which has a first surface and a second surface opposite to the first surface and is impregnated with an impregnation liquid, to cover a target surface with the first surface of the covering sheet and cool the target surface, comprising: the first fiber layer including the first surface contains 90% by mass or more of hydrophilic fibers; the second fibrous layer comprising the second surface comprises either or both of hydrophilic and hydrophobic fibers; A method for using a covering sheet, wherein the impregnation rate of the first fiber layer is at least 50% by mass higher than the impregnation rate of the second fiber layer.

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