Breathable sheets and cushioning materials

Abstract

To provide a breathable sheet and cushioning material that can securely and reliably fix an object to be adsorbed by a vacuum adsorption device without impairing the smoothness of the object's surface, and that prevents the object from falling due to gravity. [Solution] The present invention provides a breathable sheet formed by laminating and integrating a porous sheet substrate and an ultrafine fiber sheet with an average fiber diameter of 1 μm or less, wherein the maximum pore diameter of the breathable sheet is 3 to 15 μm. Preferably, the constituent fibers of the ultrafine fiber sheet are bonded with a binder resin. Furthermore, it is preferable that the thickness of the breathable sheet is 300 μm or less. It is preferable that the cushioning material during vacuum adsorption is made of such a breathable sheet.

Description

[Technical Field]

[0001] The present invention relates to breathable sheets and cushioning materials. In particular, it relates to breathable sheets or cushioning materials that can be used on the suction surface of vacuum suction devices such as robot arms for transporting or fixing sheet-like objects to be suctioned, such as films, wafers, and glass. [Background technology]

[0002] In the precision cutting, processing, and transport of sheet-like objects such as films, semiconductor wafers, and LCD glass plates, or in the printing of electronic circuits onto these sheet-like objects, it is necessary to fix the objects in place to prevent them from shifting position. Vacuum suction devices are commonly used as fixing devices for this purpose.

[0003] Vacuum suction devices must securely and stably fix the object to be adsorbed. However, if the suction of the vacuum suction device is too strong, the area of ​​the object corresponding to the suction port of the vacuum suction device will become indented, impairing the smoothness of the surface and reducing the printability of the object's surface. Therefore, a method has been proposed to interpose a breathable sheet between the suction port of the vacuum suction device and the object to be adsorbed, thereby dispersing the suction force from the suction port and preventing damage to the smoothness of the object's surface.

[0004] For example, Japanese Patent Publication No. 2021-104652 (Patent Document 1) discloses "a breathable sheet used interposed between an adsorption stage and a substrate (corresponding to an object to be adsorbed) when printing on the surface of a substrate (corresponding to an object to be adsorbed) such as a film fixed by suction on an adsorption stage (corresponding to a vacuum adsorption device), the breathable sheet comprising a nonwoven fabric layer on the side in contact with the substrate and a support layer made of a nonwoven fabric or paper composed of an organic resin on the side in contact with the adsorption stage." Furthermore, Patent Document 1 discloses in an example a breathable sheet having an electrospun nonwoven fabric layer in which constituent fibers are bonded with an acrylic resin binder. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2021-104652 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] However, when the breathable sheet disclosed in Patent Document 1 was provided between the adsorbed object and the suction port of the vacuum suction device to transport or fix the adsorbed object, the decrease in the suction force was significant, and the adsorbed object could not be stably and reliably fixed, or the adsorbed object might fall due to gravity.

[0007] The present invention has been made under such circumstances, and an object thereof is to provide a breathable sheet and a cushioning material that can stably and reliably fix an adsorbed object by a vacuum suction device without impairing the smoothness of the surface of the adsorbed object, and prevent the adsorbed object from falling due to gravity. [Means for Solving the Problems]

[0008] The present invention is a breathable sheet in which a porous sheet base material and an ultrafine fiber sheet having an average fiber diameter of 1 μm or less are laminated and integrated, and the maximum pore diameter of the breathable sheet is 3 to 15 μm.

[0009] It is preferable that the constituent fibers of the ultrafine fiber sheet are adhered with a binder resin.

[0010] Moreover, it is preferable that the thickness of the breathable sheet is 300 μm or less.

[0011] It is preferable that it is a cushioning material during vacuum adsorption composed of such a breathable sheet. [Effects of the Invention]

[0012] The breathable sheet of the present invention has a maximum pore diameter of 3 to 15 μm, so that it can stably and reliably fix the adsorbed object by a vacuum adsorption device without impairing the smoothness of the surface of the adsorbed object and without reducing the suction force due to pressure loss, and the adsorbed object will not fall due to gravity.

[0013] In addition, when the ultrafine fiber sheet constituent fibers of the breathable sheet are adhered with a binder resin, since it has excellent abrasion resistance, even if the suction fixation and fixation release of the adsorbed object are repeated, the ultrafine fiber sheet constituent fibers are less likely to fluff due to friction, so the risk of soiling the adsorbed object is small.

[0014] Also, when the thickness of the breathable sheet is as thin as 300 μm or less, even if the breathable sheet is applied to an existing device such as a vacuum adsorption device, it will not inhibit the operation of the existing device, so it has excellent versatility.

[0015] Such a breathable sheet can stably and reliably fix the adsorbed object by a vacuum adsorption device without impairing the smoothness of the surface of the adsorbed object and without reducing the suction force due to pressure loss, and the adsorbed object will not fall due to gravity. Therefore, it is suitable as a buffer material during vacuum adsorption.

Brief Description of the Drawings

[0016] [Figure 1] Conceptual diagram of the device used to measure the adsorption force

Embodiments for Carrying out the Invention

[0017] The breathable sheet of the present invention is provided with a porous sheet base material that supports an ultrafine fiber sheet with an average fiber diameter of 1 μm or less, so it has excellent handleability. That is, an ultrafine fiber sheet with an average fiber diameter of 1 μm or less generally has weak strength and poor handleability, but by having a porous sheet base material, it has excellent handleability.

[0018] This porous sheet substrate only needs to be able to support an ultrafine fiber sheet and have breathability in the thickness direction. Its structure is not particularly limited, but it can be, for example, a nonwoven fabric, woven fabric, knitted fabric, paper, net, or foam. Among these, it is preferable to use a nonwoven fabric or paper, as the fibers can be arranged randomly, there are no bumps or irregularities due to the weave, and the material to be adsorbed can be randomly attracted, thus minimizing the impediment to the smoothness of the surface of the material to be adsorbed. Furthermore, since the porous sheet substrate is a nonwoven fabric or paper, it is less likely to crease or wrinkle even when external force is applied, resulting in excellent handling.

[0019] Furthermore, if the porous sheet substrate is made of an organic resin, it is preferable because it offers excellent handling characteristics for the breathable sheet. For example, it can be made of polyolefin resins (polyethylene, polypropylene, polymethylpentene, polyolefin resins with a structure in which part of the hydrocarbon is replaced with a cyano group or a halogen such as fluorine or chlorine), polyester resins (polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polycarbonate, polyarylate, all aromatic polyester resins, etc.), polyamide resins (e.g., aromatic polyamide resins, nylon resins, etc.), urethane resins, acrylic resins (e.g., polyacrylonitrile resins copolymerized with polyacrylonitrile, acrylic acid esters or methacrylic acid esters, etc., modacrylic resins copolymerized with acrylonitrile and vinyl chloride or vinylidene chloride, etc.), polyphenylene sulfide resins, etc.

[0020] When the porous sheet substrate is made of a suitable nonwoven fabric or paper, it may include single-component fibers made of one type of organic resin, composite fibers made of two or more types of organic resins, or mixed fibers made of two or more types of organic resins. As mentioned above, the porous sheet substrate provides support for the ultrafine fiber sheet in order to improve handling, so it is preferable that the porous sheet substrate has a certain level of strength or more. For this reason, it is preferable that the constituent fibers of the nonwoven fabric or paper include composite fibers made of two or more types of organic resins, or undrawn fibers that have not been sufficiently drawn after spinning and can be deformed by thermoplasticization, and that these fibers are bonded to each other by the fusion effect or thermoplastic deformation effect of these fibers.

[0021] Examples of the former type of composite fiber include low-melting-point polyester / polyester sheath-core composite fibers, polyethylene / polypropylene sheath-core composite fibers, low-density polyethylene / high-density polyethylene sheath-core composite fibers, polyethylene / polymethylpentene sheath-core composite fibers, and polypropylene / polymethylpentene sheath-core composite fibers. Examples of the latter type of undrawn fiber include undrawn polyester fiber, undrawn polypropylene fiber, and undrawn polyphenylene sulfide fiber. In the case of composite fibers, the arrangement of organic resins in the fiber cross-section is not particularly limited, but can be, for example, sheath-core type (including eccentric type), sea-island type, side-by-side type, orange type, etc. Among these, sheath-core type (including eccentric type) or sea-island type is preferred as it contains a large amount of organic resin that can participate in the fusion process.

[0022] When the porous sheet substrate is made of a suitable nonwoven fabric or paper, the fiber diameter of the constituent fibers is not particularly limited, but in order to ensure excellent form of the porous sheet substrate and not impair the surface smoothness of the adsorbed material, it is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 30 μm or less, and even more preferably 25 μm or less. On the other hand, in order to not impair the ultrafine fiber sheet support function of the porous sheet substrate, it is preferably greater than 1 μm, more preferably 3 μm or more, and even more preferably 6 μm or more.

[0023] In this invention, "fiber diameter" refers to the diameter of the fiber cross-section if it is circular, and if the fiber cross-section is not circular, the diameter of a circle having the same area as the cross-sectional area is considered to be the fiber diameter.

[0024] Furthermore, the fiber length of the constituent fibers is preferably 1 to 110 mm, more preferably 3 to 80 mm, and even more preferably 5 to 60 mm, in order to ensure excellent formation of the porous sheet substrate and not impair the surface smoothness of the adsorbed material.

[0025] The basis weight of the porous sheet substrate is not particularly limited, but it is 5 g / m² to ensure excellent support for the ultrafine fiber sheet. 2 Preferably, it is 10 g / m 2 It is more preferable to have a value of 15 g / m² or more. 2 The above is even more preferable. On the other hand, as the basis weight of the porous sheet substrate increases, the thickness tends to increase accordingly, and when a breathable sheet is applied to an existing device, air may leak from the edges of the breathable sheet, which may hinder the operation of the existing device. Therefore, 120 g / m 2 Preferably, it is 100g / m 2 It is more preferable that the following occur: 80 g / m 2 The following is even more preferable:

[0026] In this invention, "basis value" refers to the area of ​​the main surface, which is 1 m². 2 It refers to the mass per unit area.

[0027] Furthermore, the thickness of the porous sheet substrate is preferably 300 μm or less, more preferably 250 μm or less, even more preferably 200 μm or less, and even more preferably 150 μm or less, so that when a breathable sheet is applied to an existing device, air does not leak from the edges of the breathable sheet, thus hindering the operation of the existing device. On the other hand, if the thickness is too thin, the strength of the porous sheet substrate decreases, and consequently the strength of the breathable sheet decreases, which tends to make it difficult to handle. Therefore, the thickness is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more.

[0028] In this invention, "thickness" refers to the arithmetic mean of measurements taken at five points on a porous sheet substrate under a 500g load using a thickness measuring instrument (Digimatic Standard Outside Micrometer (MDC-MJ / PJ) 1 / 1000mm (Mitutoyo Corporation)).

[0029] Such porous sheet substrates can be manufactured by conventional methods. For example, if the porous sheet substrate is made of a suitable nonwoven fabric, a fiber web can be formed by a dry method, a wet method, or a spunbond method. The nonwoven fabric can then be manufactured by bonding the fibers together through the fusion action of the composite fibers constituting the fiber web, the thermoplastic deformation action of the undrawn fibers, the entanglement action of fluid flow such as needles or water flow, the adhesive action of an emulsion binder, or a combination of these actions. Among these, nonwoven fabrics in which the fibers are bonded together through the fusion action of the composite fibers constituting the fiber web or the thermoplastic deformation action of the undrawn fibers are preferred because they have excellent strength and provide excellent support for ultrafine fiber sheets.

[0030] The breathable sheet of the invention, in addition to the porous sheet substrate described above, is equipped with an ultrafine fiber sheet with an average fiber diameter of 1 micron m or less. By adjusting the maximum pore diameter of the breathable sheet to 3 to 15 μm, the object to be adsorbed can be stably and reliably fixed by a vacuum adsorption device without impairing the smoothness of the surface of the object to be adsorbed or reducing the suction force due to pressure loss, and the object to be adsorbed will not fall due to gravity.

[0031] The average fiber diameter of the ultrafine fiber sheet is 1 μm or less so that the surface of the breathable sheet is smooth. However, if the average fiber diameter is too small, it tends to fray due to friction and easily contaminate the adsorbed material. Therefore, it is preferable that it be 50 nm or more, more preferably 100 nm or more, and even more preferably 300 nm or more.

[0032] In this invention, "average fiber diameter" refers to the arithmetic mean of the fiber diameters of 50 fibers.

[0033] The embodiments of the ultrafine fiber sheet of the present invention are not particularly limited, but can be, for example, nonwoven fabric, woven fabric, knitted fabric, or paper. Among these, it is preferable that the sheet be made of nonwoven fabric or paper, in which the fibers can be arranged randomly, there are no bumps or irregularities due to the weave, the surface is smooth, and as a result the smoothness of the surface of the object to be adsorbed is not easily impaired when the object to be adsorbed is attracted.

[0034] Furthermore, if the ultrafine fiber sheet is composed of organic resin fibers, it is preferable because it offers excellent handling characteristics for a breathable sheet. The organic resin fibers constituting this ultrafine fiber sheet can be, for example, the same organic resin fibers (excluding the average fiber diameter) that can constitute a porous sheet substrate, or they can be organic resin fibers made of one or more types of organic resins, such as styrene resins, polyether resins (polyetheretherketone, polyacetal, phenolic resins, melamine resins, urea resins, epoxy resins, modified polyphenylene ether, aromatic polyetherketone, etc.), polyimide resins, polyamideimide resins, epoxy resins, polysulfone resins (polysulfone, polyethersulfone, etc.), fluorine resins (polytetrafluoroethylene, polyvinylidene fluoride, etc.), and polybenzimidazole resins.

[0035] The fiber length of the fibers constituting the ultrafine fiber sheet of the present invention is not particularly limited, but it is preferably 1 to 110 mm in terms of having excellent texture and smoothness. On the other hand, considering the case where the ultrafine fiber sheet comes into direct contact with an object to be adsorbed, it is preferable that the fibers be continuous in order to prevent fuzzing and to have excellent abrasion resistance.

[0036] Furthermore, it is preferable that the constituent fibers of the ultrafine fiber sheet of the present invention are bonded with a binder resin. This is because bonding with a binder resin provides excellent abrasion resistance, and even with repeated suction and release of the object to be adsorbed, the constituent fibers of the ultrafine fiber sheet are less likely to fray due to friction, thus reducing the risk of contaminating the object to be adsorbed. In addition, the binder resin is bonded in a state where a film is formed at the intersections of the constituent fibers of the ultrafine fiber sheet, which also has the advantage of being able to adjust the maximum pore size of the ultrafine fiber sheet and, consequently, the breathable sheet.

[0037] Examples of binder resins include vinyl acetate resin, ethylene vinyl acetate copolymer (EVA), acrylic resins (such as acrylic acid esters), urea resins, melamine resins, chloroprene rubber, nitrile rubber, polyamide resins, and polyester resins. To ensure excellent abrasion resistance, the glass transition temperature of the binder resin is preferably 0°C or higher, more preferably 20°C or higher, even more preferably 30°C or higher, and even more preferably 40°C or higher. The upper limit of the glass transition temperature is preferably 120°C, more preferably 90°C, and even more preferably 70°C.

[0038] In this invention, the glass transition temperature refers to the temperature obtained by measuring the binder resin using a differential scanning calorimeter in accordance with JIS K 7121 (1987), and reading the extrapolation glass transition onset temperature (Tig) from the resulting DSC curve.

[0039] Note that the binder resin can adhere the ultrafine fiber sheet constituent fibers with the binder resin by applying an emulsion-type binder in which the binder resin is dispersed, a solvent-type binder in which the binder resin is dissolved, or a hot-melt binder in which the binder resin is melted to the ultrafine fiber sheet. Examples of the application method include a method of applying or spraying the binder resin to the ultrafine fiber sheet, a method of immersing the ultrafine fiber sheet in a binder resin bath, and the like. Further, when using an emulsion-type binder, the emulsion-type binder may contain an antistatic agent so as not to be easily charged by friction with the adsorbed material, a penetrant so that the emulsion-type binder easily penetrates into the internal voids of the ultrafine fiber sheet, and the like.

[0040] The basis weight of the ultrafine fiber sheet of the present invention is not particularly limited as long as the maximum pore diameter of the breathable sheet can be 3 to 15 μm, but it is preferably 1 to 12 g / m 2 and more preferably 1.5 to 10, and even more preferably 2 to 8 g / m 2 is even more preferable.

[0041] Further, the thickness of the ultrafine fiber sheet is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less so that the pore diameter does not become too small and the suction force does not decrease. On the other hand, if the thickness is too thin, the roughness of the porous sheet affects the surface smoothness of the breathable sheet and tends to decrease. Therefore, it is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more. It can be manufactured. For example, a nonwoven fabric can be manufactured by a wet method, a melt blow method, an electrospinning method, a method of accumulating fibers spun by applying a gas in parallel to a spinning solution discharged using a spinning device as disclosed in JP-A-2009-287138, and the like. Among these, the ultrafine fiber sheet manufactured by the electrospinning method is suitable because the constituent fibers are continuous fibers, the fiber diameters are uniform, the fluffing is less likely to occur, and the surface is smooth.

[0042] The breathable sheet of the present invention is in a state in which the aforementioned porous sheet substrate and the ultrafine fiber sheet are laminated and integrated, and the ultrafine fiber sheet is supported by the porous sheet substrate, resulting in an enhanced strength.

[0043] This laminated integrated state is not particularly limited as long as the ultrafine fiber sheet is supported by the porous sheet substrate and its strength is enhanced, but for example, it can be bonded with a binder resin, and / or bonded by thermal fusion or thermoplastic deformation of the porous sheet substrate or the constituent materials of the ultrafine fiber sheet. In the former case, where it is bonded with a binder resin, the constituent fibers of the ultrafine fiber sheet are also bonded and fixed by the binder resin, making it less prone to fraying due to friction, and the maximum pore diameter of the breathable sheet is also adjusted, making it a preferred embodiment. This preferred binder resin can be the same binder resin that can be applied to the ultrafine fiber sheet, and it can be bonded in the same way. The amount of binder resin is not particularly limited as long as the maximum pore diameter of the breathable sheet is 3 to 15 μm.

[0044] The breathable sheet of the present invention basically consists of a porous sheet substrate and an ultrafine fiber sheet. However, when using the breathable sheet, it is necessary to fix the breathable sheet to a suction part having a suction port of a vacuum adsorption device, so an adhesive layer can be provided on the surface of the porous sheet substrate. Examples of this adhesive layer include adhesives made of hot melt resin, particles, fibers, or fiber sheets such as nonwoven fabrics, or adhesives intermittently applied in the shape of dots or stripes.

[0045] The breathable sheet of the present invention has the structure described above, and because the maximum pore diameter is 3 to 15 μm, the object to be adsorbed can be stably and reliably fixed by a vacuum adsorption device without impairing the smoothness of the surface of the object to be adsorbed, and without reducing the suction force due to pressure loss, and the object to be adsorbed will not fall due to gravity. In other words, if the maximum pore diameter is smaller than 3 μm, the suction force tends to weaken due to pressure loss, making it difficult to stably and reliably fix the object to be adsorbed. For this reason, the maximum pore diameter is 3 μm or more, preferably 3.2 μm or more, and more preferably 4 μm or more. On the other hand, if the maximum pore diameter is larger than 15 μm, the smoothness of the surface of the breathable sheet is low and it is in a state of microscopic irregularity, which tends to cause various problems such as poor printability. For this reason, the maximum pore diameter is 15 μm or less, preferably 14 μm or less, and more preferably 13.5 μm or less.

[0046] The breathable sheet of the present invention preferably has an average pore diameter of 1 to 12 μm so that the object to be adsorbed can be stably and reliably fixed by a vacuum adsorption device without impairing the smoothness of the surface of the object to be adsorbed and without reducing the suction force due to pressure loss, and so that the object to be adsorbed does not fall due to gravity. If the average pore diameter is smaller than 1 μm, the suction force tends to weaken due to pressure loss, making it difficult to stably and reliably fix the object to be adsorbed, so the average pore diameter is more preferably 1.5 μm or more, and even more preferably 2 μm or more. On the other hand, if the average pore diameter is larger than 12 μm, the smoothness of the surface of the breathable sheet is low and it is in a state of microscopic irregularity, so various problems tend to occur, such as poor printability, so the average pore diameter is more preferably 11 μm or less, and even more preferably 10.5 μm or less.

[0047] In this invention, "maximum pore diameter" and "average pore diameter" refer to values ​​measured by the bubble point method using a porometer (manufactured by Coulter).

[0048] The basis weight of the breathable sheet of the present invention is not particularly limited, but if the basis weight is high, the thickness will also be high, which may interfere with the operation of existing devices such as vacuum suction devices when applied to them. Therefore, 132 g / m² is used. 2 Preferably, it is 70 g / m 2 It is more preferable to be 60 g / m² 2 It is even more preferable that the amount be less than 55 g / m². 2 It is even more preferable that it be less than 50 g / m². 2 The following is even more preferable. On the other hand, if the basis weight is too low, the strength will be weak and it may be difficult to handle, so 6g / m 2 Preferably, the amount is 11.5 g / m² or more. 2 It is more preferable to have a value of 17 g / m² or more. 2 It is even more preferable if the above conditions are met.

[0049] Furthermore, the thickness of the breathable sheet is preferably 300 μm or less, more preferably 250 μm or less, even more preferably 200 μm or less, and even more preferably 150 μm or less, so as not to hinder the operation of the existing equipment when applied to it. On the other hand, the breathable sheet is preferably 30 μm or more, more preferably 40 μm or more, and even more preferably 50 μm or more, so as to have excellent strength.

[0050] Furthermore, the porosity of the breathable sheet is preferably 45-95%, more preferably 50-90%, and even more preferably 55-85%. This is because if the porosity is less than 45%, the breathability of the breathable sheet tends to be low, and the suction and fixation performance of the adsorbed material tends to be poor. If the porosity exceeds 95%, the surface of the breathable sheet tends to be rough and the surface smoothness is poor.

[0051] In this invention, the porosity (P) refers to the value obtained from the following formula. P = 100 - [(M / T) / SG] × 100

[0052] Here, M is the basis weight of the breathable sheet (unit: g / m²). 2), T is the thickness of the breathable sheet (unit: μm), and SG is the average density of the material constituting the breathable sheet (unit: g / cm³). 3 These terms represent the respective terms, and the average density is the value obtained from the following formula. SG = SG1 × P1 + SG2 × P2 + ... + SG n ×P n

[0053] Here, SG n This refers to the density (unit: g / cm³) of the n component that makes up the breathable sheet (e.g., porous sheet substrate constituent material, ultrafine fiber sheet constituent fiber, etc.). 3 ), Pn represents the mass ratio of the n component in the breathable sheet.

[0054] Furthermore, while the breathability of the breathable sheet is not particularly limited, it should be 0.5 cm² to ensure excellent suction and fixation performance of the object to be adsorbed. 3 / cm 2 Preferably, it should be 1.0 (cm) or more. 3 / cm 2 It is more preferable to be 1.5 (cm) or more. 3 / cm 2 It is even more preferable that the permeability is 20 (cm²) or higher. While there is no particular upper limit to the permeability of the breathable sheet, if the permeability is too high, the surface of the breathable sheet tends to be rough and lacks smoothness, so 20 (cm²) is preferable. 3 / cm 2 It is preferable that it be less than or equal to / s.

[0055] In this invention, the degree of air permeability refers to the value measured by the Frazier method specified in JIS L 1913.

[0056] Furthermore, while the rigidity of the breathable sheet is not particularly limited, it is preferable that it be a breathable sheet with good firmness and handling properties, making it easy to attach to a vacuum suction device, with a rigidity of 2 mN·cm or more, more preferably 4 mN·cm or more, even more preferably 6 mN·cm or more, even more preferably 8 mN·cm or more, and even more preferably 10 mN·cm or more.

[0057] In this invention, the rigidity and flexibility refer to the values ​​measured by the 41.5° cantilever method specified in JIS L 1913.

[0058] The breathable sheet of the present invention can securely and reliably fix an object to be adsorbed by a vacuum adsorption device without impairing the smoothness of the object's surface or reducing the suction force due to pressure loss, and the object will not fall due to gravity. Therefore, it can be suitably used as a cushioning material during vacuum adsorption of robot arms and the like. The breathable sheet of the present invention is a laminated and integrated structure of a porous sheet substrate and an ultrafine fiber sheet. Since the ultrafine fiber sheet tends to have a smoother surface, the breathable sheet can be used so that the ultrafine fiber sheet side is in contact with the object to be adsorbed. However, since the ultrafine fiber sheet may become fuzzy and the ultrafine fibers may fall off when the ultrafine fiber sheet side is in contact with the object to be adsorbed, it is preferable that the ultrafine fiber sheet is made of ultrafine fibers bonded together with a binder resin.

[0059] The breathable sheet of the present invention is formed by laminating a porous sheet substrate and an ultrafine fiber sheet into a single integrated structure. For example, after manufacturing the porous sheet substrate and the ultrafine fiber sheet separately by the method described above, the porous sheet substrate and the ultrafine fiber sheet are laminated together, and an emulsion-type binder in which a binder resin is dispersed or a solvent-type binder in which a binder resin is dissolved is applied to the laminate, and the sheet is dried to produce the breathable sheet. This manufacturing method is preferable because it can produce a breathable sheet in which the ultrafine fiber sheet is bonded with a binder resin, even if the ultrafine fiber sheet is not bonded with a binder resin.

[0060] Furthermore, after manufacturing a porous sheet substrate and an ultrafine fiber sheet using the method described above, a breathable sheet can be manufactured by laminating them with a hot-melt binder (a molten binder resin) interposed between the porous sheet substrate and the ultrafine fiber sheet, and then pressurizing the resulting laminate.

[0061] Alternatively, after manufacturing a porous sheet substrate and an ultrafine fiber sheet separately using the method described above, the porous sheet substrate and the ultrafine fiber sheet are laminated together, and the laminate is heat-treated under conditions that cause the materials constituting the porous sheet substrate and / or the ultrafine fiber sheet to be thermally fused or thermoplastically deformed, thereby producing a breathable sheet.

[0062] In any of the above cases, an ultrafine fiber sheet may also be formed by directly accumulating ultrafine fibers dispersed in white water, melt-blown ultrafine fibers, electrospun ultrafine fibers, or ultrafine fibers spun by applying gas parallel to a spinning solution discharged using a spinning apparatus such as the one disclosed in Japanese Patent Application Publication No. 2009-287138, onto a porous sheet substrate.

[0063] Furthermore, in any of the above cases, the sheet can be pressurized using a calender or other pressurizing means to adjust the maximum pore diameter and the thickness of the sheet. Heating can also be done simultaneously with pressurization.

[0064] Furthermore, if the breathable sheet has an adhesive layer in addition to the porous sheet substrate and the ultrafine fiber sheet, for example, hot melt resin particles, hot melt resin fibers, or a hot melt resin fiber sheet can be laminated onto the porous sheet substrate side surface and fused by heating to form an adhesive layer. Alternatively, molten hot melt resin particles, hot melt resin fibers, or a hot melt resin fiber sheet can be applied to the porous sheet substrate side surface and pressed if necessary to form an adhesive layer. Or, an adhesive can be applied intermittently to the porous sheet substrate side surface using a gravure roll or the like in a textured, dotted, or striped pattern, while ensuring the breathability of the breathable sheet and forming an adhesive layer. [Examples]

[0065] Examples of the present invention are described below, but the present invention is not limited to these examples.

[0066] (Preparation of porous sheet substrate) 1. Preparation of porous sheet substrate A; A wet-laid fiber web was formed using a mixture of 80 mass% of a sheath-core composite fiber (fiber diameter: 15 μm, fiber length: 5 mm) with a low-melting-point polyester as the sheath component (melting point: 150°C) and polyester as the core component (melting point: 260°C), and 20 mass% of polyester fiber (fiber diameter: 8 μm, fiber length: 5 mm), dispersed in white water.

[0067] After dehydration and drying, the sheath components of the sheath-core composite fiber are heat-fused by passing it through a hot air dryer set to 155°C, resulting in a heat-fused nonwoven fabric (= porous sheet base material A, basis weight: 30g / m²). 2 A product with a thickness of 130 μm was manufactured.

[0068] 2. Preparation of porous sheet substrate B; A dry fiber web was formed by blending 65 mass% of drawn polyester fibers (fiber diameter: 12 μm, fiber length: 38 mm) with 35 mass% of undrawn polyester fibers (fiber diameter: 24 μm, fiber length: 38 mm), and then opening the fibers using a carding machine.

[0069] Subsequently, the dry fiber web is passed between a steel roll heated to 215°C and an elastic roll, and pressurized with a linear pressure of 90 kN / m to thermoplasticize and deform the undrawn polyester fibers, resulting in a heat-deformed nonwoven fabric (= porous sheet base material B, basis weight: 15 g / m²). 2 We manufactured a product with a thickness of 40 μm.

[0070] 3. Preparation of porous sheet substrate C; A wet fiber web was formed using 100 mass% of a sheath-core composite fiber (fiber diameter: 10 μm, fiber length: 5 mm) in which high-density polyethylene was used as the sheath component (melting point: 135°C) and polypropylene was used as the core component (melting point: 160°C).

[0071] After dehydration and drying, the sheath component of the sheath-core composite fiber is heat-fused by passing it through a hot air dryer set to 140°C. Next, it is passed between a steel roll heated to 40°C and an elastic roll, and pressurized with a linear pressure of 50kN / m to create a heat-fused nonwoven fabric (=porous sheet base material C, basis weight: 43g / m²). 2 A product with a thickness of 130 μm was manufactured.

[0072] 4. Preparation of porous sheet substrate D; Weight: 60g / m 2 A heat-sealable nonwoven fabric (=porous sheet substrate D) was manufactured in the same manner as porous sheet substrate A, except that the thickness was set to 250 μm.

[0073] (Preparation of ultrafine fiber sheets) 1. Ultra-fine continuous fiber sheet a; Using a spinning solution containing dissolved polyethersulfone resin, the fibers are spun by electrospinning, and the resulting ultrafine continuous fibers are directly accumulated on a conveyor to form an ultrafine continuous fiber sheet a (basis weight: 2g / m²). 2 A material with a thickness of 10 μm and an average fiber diameter of 1 μm was manufactured.

[0074] 2. Ultra-fine continuous fiber sheet b; Basis weight 5g / m 2 Except for the above, ultrafine continuous fiber sheet b (thickness: 23 μm, average fiber diameter: 1 μm) was manufactured in the same manner as ultrafine continuous fiber sheet a.

[0075] 3. Ultra-fine continuous fiber sheet c; Using a spinning solution containing dissolved polyacrylonitrile resin, the fibers are spun by electrospinning, and the resulting ultrafine continuous fibers are directly accumulated on a conveyor to form an ultrafine continuous fiber sheet c (basis weight: 16.5 g / m²). 2 A material with a thickness of 80 μm and an average fiber diameter of 0.5 μm was manufactured.

[0076] (Prepare the binder) 1. An acrylic acid ester emulsion binder I was prepared, containing an antistatic agent, a penetrating agent, and an acrylic acid ester (glass transition temperature: 60°C).

[0077] 2. An acrylic acid ester emulsion binder II was prepared, containing an antistatic agent, a penetrating agent, an acrylic acid ester (glass transition temperature: 60°C), and an oxazoline-based crosslinking agent.

[0078] 3. An acrylic acid ester emulsion binder III was prepared, containing an antistatic agent, a penetrating agent, and an acrylic acid ester (glass transition temperature: -5°C).

[0079] (Preparation of breathable sheets) (Examples 1-6, Comparative Examples 1-3) The porous sheet substrates and ultrafine fiber sheets described above were combined as shown in Table 1, or they were not combined at all to form the breathable sheet substrate 1.

[0080] Furthermore, when using porous sheet substrates A, C, or D, after overlapping the porous sheet substrate and the ultrafine continuous fiber sheet, the sheet is passed through the surface of a glass roll heated to a temperature 5°C higher than the melting point of the sheath component, so that the surface of the ultrafine continuous fiber sheet is in contact with it. This causes the sheath component constituting the porous sheet substrates A, C, or D to fuse together, thereby laminating and integrating with the ultrafine continuous fiber sheet a or ultrafine continuous fiber sheet b to form a breathable sheet substrate 1.

[0081] Furthermore, when using porous sheet substrate B, the spun ultrafine continuous fibers were directly accumulated and integrated onto the porous sheet substrate B, which was stacked on a conveyor, to form a breathable sheet substrate 1.

[0082] This breathable sheet substrate 1 was immersed in the binder bath described in Table 1, squeezed with a rubber roller, dried with a can dryer, and then bonded with the amount of binder resin described in Table 1, or left unbonded, to become breathable sheet substrate 2.

[0083] Subsequently, the breathable sheet substrate 1 or breathable sheet substrate 2 was passed through a calender roll consisting of a steel roll at the temperature shown in Table 1 and a rubber roll at room temperature, or without passing through the calender roll, to form breathable sheet substrate 3.

[0084] Then, as shown in Table 1, a hot melt resin nonwoven fabric made of copolymerized polyamide (basis weight: 20 g / m²) is placed on the porous sheet substrate side of the breathable sheet substrate 3. 2 A breathable sheet was manufactured by laminating these materials and heating them to 80°C to fuse them to the porous sheet substrate, thereby forming an adhesive layer, or without forming an adhesive layer. The physical properties of these breathable sheets are shown in Table 1.

[0085] [Table 1]

[0086] The breathability sheets of Examples 1-6 and Comparative Examples 1-3 were evaluated using the following method.

[0087] (Adsorption power) The adsorption force was measured using the apparatus shown in Figure 1.

[0088] In other words, a suction box (SB) was prepared in which 1.5 mm diameter through-holes (TH) were arranged in a grid pattern at 10 mm intervals within a 140 mm square area in the center of the top surface of a rectangular box [225 through-holes (15 rows, 15 columns)]. A suction fan (SF) and a differential pressure gauge (DP) were connected to the side wall of the suction box (SB) to measure the internal pressure of the suction box.

[0089] Furthermore, a laminate (150 mm square) was prepared by layering polyester film (PF), rubber sheet (RB), and acrylic plate (AB) in that order, and integrating each material with adhesive. A hook (H) for tension measurement was attached to the acrylic plate (AB) that constitutes this laminate to create an adsorbed object (AD).

[0090] Next, the polyester film (PF) surface of the object to be adsorbed (AD) was placed in contact with the top surface of the adsorption box (SB) so as to cover all the through holes (TH), and then the suction fan (SF) was adjusted so that the internal pressure of the adsorption box (SB) was -2.82 kPa.

[0091] Subsequently, a breathable sheet (AS) (150 mm square) from either Examples 1-6 or Comparative Examples 1-3 was placed between the top surface of the adsorption box (SB) and the polyester film (PF) surface of the object to be adsorbed (AD), covering all the through-holes (TH). After adsorbing the object to be adsorbed (AD) under the adjusted conditions, the hook (H) of the object to be adsorbed (AD) was pulled perpendicular to the top surface of the adsorption box (SB), and the force at which the adsorption of the object to be adsorbed (AD) was broken was measured. Then, after subtracting the weight of the object to be adsorbed (AD) from the force at which it broke, the area of ​​the object to be adsorbed (AD) (0.025 m²) was used. 2 The force was obtained by dividing by ( ). This force was measured five times, and the arithmetic mean was taken as the force.

[0092] (handling) In the (adhesion force) test described above, when placing the breathable sheet (AS) on the upper surface of the adhesion box (SB), a "○" was given if it was rigid, could be easily repositioned with one hand, and did not tear or fray, while a "×" was given if it was not rigid, could not be easily repositioned with one hand, or torn or frayed.

[0093] (Abrasion resistance) Using a Japan Society for the Promotion of Science (JSPS) type friction tester, the surface condition was evaluated after 50 reciprocating passes of a friction element fitted with cotton (Kanakin No. 3) on the ultrafine fiber sheet surface of a breathable sheet (on the porous sheet substrate C surface in Comparative Example 3) according to the following criteria.

[0094] ○: No pilling or shedding of the ultrafine fiber sheet. △: There is some fuzziness, but no missing ultrafine fiber sheets. ×: There is some pilling and some of the microfiber sheet is missing.

[0095] (smoothness) A 150mm square polyester film (subject to be adsorbed) was fixed to an adsorption box (SB) via a breathable sheet (AS). Using a screen printing plate, a solid color print was applied to a 65mm square area in the center of the polyester film (subject to be adsorbed), and the finish was evaluated. Color unevenness due to through-holes was evaluated as "×", and the absence of color unevenness due to through-holes was evaluated as "〇".

[0096] As shown in Examples 1-6, breathable sheets with a maximum pore diameter in the range of 3-15 μm exhibited excellent suction power, with a suction force of 2.0 kPa or higher.

[0097] Furthermore, a comparison of Example 1 and Example 3 revealed that when the constituent fibers of the ultrafine fiber sheet are bonded with a binder resin, the abrasion resistance is superior.

[0098] Furthermore, a comparison of Examples 1-6 with Comparative Example 2 revealed that the porous sheet substrate provides superior handling characteristics.

[0099] Furthermore, a comparison of Examples 1-6 with Comparative Example 3 revealed that the presence of an ultrafine fiber sheet resulted in a maximum pore diameter of 15 μm or less, excellent adsorption capacity, and a smooth, breathable surface.

[0100] Furthermore, a comparison of Examples 1 and 2 with Example 4 revealed that when the glass transition temperature of the binder resin used to bond the ultrafine fiber sheet components is 40°C or higher, the fibers are less prone to fraying and exhibit superior abrasion resistance. [Industrial applicability]

[0101] The breathable sheet of the present invention can securely and reliably fix an object to be adsorbed by a vacuum adsorption device without impairing the smoothness of the object's surface or reducing the suction force due to pressure loss, and the object will not fall due to gravity. Therefore, it can be suitably used as a cushioning material during vacuum adsorption, a backing sheet during printing or stamping, or a smoothing sheet applied to smooth rough surfaces. [Explanation of symbols]

[0102] SB Suction Box TH Through Hole SF Suction Fan DP differential pressure gauge AD Adsorbed object PF polyester film RB rubber sheet AB Acrylic Sheet H hook AS breathable sheet

Claims

1. A breathable sheet characterized by having a porous sheet substrate and an ultrafine fiber sheet with an average fiber diameter of 1 μm or less laminated together, wherein the maximum pore diameter of the breathable sheet is 3 to 15 μm.

2. The breathable sheet according to claim 1, characterized in that the constituent fibers of the ultrafine fiber sheet are bonded together with a binder resin.

3. The breathable sheet according to claim 1, characterized in that the thickness of the breathable sheet is 300 μm or less.

4. A cushioning material for vacuum adsorption, comprising a breathable sheet as described in any one of claims 1 to 3.

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