Heat-seal sheet, method for manufacturing same, and sterile packaging

Abstract

The purpose of the present invention is to provide: a heat-seal sheet having sufficient heat adhesiveness and air permeability across the whole heat-seal surface, as well as high tear strength; a method for manufacturing the heat-seal sheet; and a sterile packaging using the heat-seal sheet.　This heat-seal sheet has at least a thermoplastic resin fiber nonwoven fabric layer A and a nonwoven fabric layer B. The thermoplastic resin fiber nonwoven fabric layer A contains thermoplastic resin fibers having a core-sheath structure, in which a sheath part is a polyolefin resin and a core part is made of a resin having a melting point higher than that of the sheath part by 20°C or higher. The nonwoven fabric layer B contains 10 mass % or more of pulp. The Oken-type air permeability of the heat-seal sheet, measured in accordance with JIS P 8117:2009, is 5–700 seconds, inclusive. The tear strength of the heat-seal sheet, measured in accordance with JIS P 8116:2000, is 700 mN or more.

Description

Heat seal sheet, manufacturing method thereof, and sterilized package

[0001] The present invention relates to a heat seal sheet, a method for producing the same, and a sterilization package.

[0002] Instruments used in surgery, treatment, etc. are sterilized by being placed in a sterile package before use. Sterilization methods used by hospitals, medical instrument manufacturers, etc. include placing scalpels, forceps, and other items to be sterilized in a sterile package, sealing it, and then sterilizing them using gas sterilization, autoclaving, radiation sterilization, etc. In gas sterilization, the package is placed in a pressure-resistant container, the pressure inside the container is reduced, the air inside the package is discharged, and then ethylene oxide gas (EOG) or the like is filled into the container to permeate the inside of the package and sterilize it. In autoclaving, the package is exposed to high-temperature steam using an autoclave or the like, and sterilized by repeatedly reducing and increasing the pressure. In radiation sterilization, sterilization is performed by irradiation with radiation. Of these, gas sterilization and autoclaving are commonly used due to their cost and simplicity.

[0003] Sterilized instruments are stored in this sterile packaging until they are used in surgery or other procedures, and are opened when they are used in surgery or treatment. Generally, a peel-open or tear-off method is used to open the packaging, making it easy for doctors and practitioners in hospitals to open even when wearing gloves. Peel-open sterile packaging is manufactured by peeling two rectangular sheets, one on the front and one on the back, and adhering them together. Tear-off sterile packaging is manufactured using an easily tearable (easy to tear open) sheet.

[0004] Sterilization packages used in the gas sterilization and high-pressure steam sterilization methods must be breathable due to the sterilization methods used. Sterilization packages used in radiation sterilization also preferably have breathability because residual solvents and odors contained in the contents may volatilize during the sterilization process. For this reason, breathable sheets are used for the sterilization packages.

[0005] Heat-sealable sheets that are sealed by thermocompression are used for bag- or container-shaped sterilization packages. For example, heat-sealable sheets that form lids for molded containers such as trays and cups are thermocompressed to the flange surrounding the opening to seal the container. Heat-sealable sheets are required to ensure breathability that allows for sterilization while achieving complete closure (maintaining the sterile state) after sterilization.

[0006] Patent Document 1 proposes a heat-sealable sheet in which the thermal adhesive layer is formed in a mesh-like pattern to ensure breathability. However, the flange portion to which the heat-sealable sheet is thermocompressed is usually narrow, and the mesh-like thermal adhesive layer raises questions about the integrity of the closure. Meanwhile, Patent Document 2 proposes a heat-sealable sheet in which a granular thermoplastic resin is incorporated into the thermal adhesive layer, enabling the thermal adhesive layer to be a solid coating while maintaining breathability. When these heat-sealable sheets use paper as the breathable substrate, the basis weight must be limited to ensure sufficient breathability, resulting in limitations in strength. Furthermore, there is a concern about lint generation due to detachment of pulp fibers. Therefore, while these heat-sealable sheets are applicable to the sterilization of small and lightweight medical instruments or general medical instruments, they are not currently applicable to heavy medical instruments, large medical instruments such as sheets and gowns, or advanced medical instruments such as catheters.

[0007] JP 2017-43866 A JP 2017-20130 A

[0008] An object of the present invention is to provide a heat seal sheet that has sufficient thermal adhesiveness and breathability over the entire heat seal surface and also has high tear strength, a method for producing the same, and a sterilized package using the same.

[0009] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by including a thermoplastic resin fiber nonwoven fabric layer A containing thermoplastic resin fibers with a specific core-sheath structure and a nonwoven fabric layer B containing a specific amount of pulp, and by having an Oken air permeability within a specific range and a tear strength equal to or greater than a specific value, thereby completing the present invention. <1> A heat-sealable sheet having at least a thermoplastic resin fiber nonwoven fabric layer A and a nonwoven fabric layer B, wherein the thermoplastic resin fiber nonwoven fabric layer A contains thermoplastic resin fibers with a core-sheath structure in which the sheath is made of a polyolefin resin and the core is made of a resin having a melting point 20°C or more higher than that of the sheath, the nonwoven fabric layer B contains 10% by mass or more of pulp, the heat-sealable sheet has an Oken air permeability measured in accordance with JIS P 8117:2009 of 5 seconds or more to 700 seconds or less, and the heat-sealable sheet has a tear strength measured in accordance with JIS P 8116:2000 of 700 mN or more. <2> The heat-sealable sheet according to <1>, further comprising a thermoplastic resin fiber nonwoven fabric layer C, in which the nonwoven fabric layer B / thermoplastic resin fiber nonwoven fabric layer A / thermoplastic resin fiber nonwoven fabric layer C are laminated in this order. <3> The heat-sealable sheet according to <2>, wherein the thermoplastic resin fiber nonwoven fabric layer C is a layer derived from thermoplastic resin fiber nonwoven fabric c, and the thermoplastic resin fiber nonwoven fabric c contains 25% by mass to 100% by mass of polyolefin hyperbranched fibers. <4> The heat-sealable sheet according to <2> or <3>, wherein the thermoplastic resin fiber nonwoven fabric layer C contains a low-melting-point polyester resin, polyester resin fibers, and a polyolefin resin. <5> The heat-sealable sheet according to any one of <2> to <4>, wherein the thermoplastic resin fiber nonwoven fabric layer C is a layer derived from thermoplastic resin fiber nonwoven fabric c, and the thermoplastic resin fiber nonwoven fabric c contains polyester resin fibers having a core-sheath structure. <6> The heat-sealable sheet according to any one of <2> to <5>, wherein the thermoplastic resin fiber nonwoven fabric layer C is a layer derived from thermoplastic resin fiber nonwoven fabric c, and the thermoplastic resin fiber nonwoven fabric c is a nonwoven fabric obtained by a wet paper-making method.<7> The heat-sealable sheet according to any one of <1> to <6>, wherein the thermoplastic resin fibers having a core-sheath structure used in the thermoplastic resin fiber nonwoven fabric layer A contain at least one resin selected from the group consisting of polypropylene resin, polyester resin, and polyamide resin. <8> The heat-sealable sheet according to any one of <1> to <7>, wherein the thermoplastic resin fiber nonwoven fabric layer A is a nonwoven fabric layer derived from at least one nonwoven fabric selected from the group consisting of spunbonded nonwoven fabrics, thermally bonded nonwoven fabrics, chemically bonded nonwoven fabrics, needle-punched nonwoven fabrics, spunlace nonwoven fabrics, melt-blown nonwoven fabrics, and wet-laid nonwoven fabrics. <9> The heat-sealable sheet according to any one of <1> to <8>, wherein the thermoplastic resin fiber nonwoven fabric layer A is a layer derived from a thermoplastic resin fiber nonwoven fabric a, and the thermoplastic resin fiber nonwoven fabric a contains thermoplastic resin fibers having a core-sheath structure, the sheath of which is a polyolefin resin and the core of which is made of a resin having a melting point 20°C or more higher than that of the sheath. <10> The heat seal sheet according to any one of <1> to <9>, wherein the heat seal sheet is heat-sealed to the polyethylene side of a laminated film of polyethylene terephthalate resin and polyethylene resin under conditions of 150°C, 0.2 MPa, and 1.0 second, and the heat-pressure-bonded product has a peel strength of 1.0 N / 15 mm or more and 15 N / 15 mm or less when peeled at a 180° angle at a peel rate of 300 mm / min in accordance with JIS P 8113:2006. <11> The heat seal sheet has a basis weight of 30 g / m. ２ 150g / m or more ２The heat seal sheet according to any one of <1> to <10>, wherein the thermoplastic resin fiber nonwoven fabric layer A and the nonwoven fabric layer B are disposed adjacent to each other. <12> The heat seal sheet according to any one of <1> to <11>, wherein the thermoplastic resin fiber nonwoven fabric layer A and the nonwoven fabric layer B are disposed adjacent to each other. <13> A sterilized package obtained by thermocompression bonding the heat seal sheet according to any one of <1> to <12> and a sterilized packaging material. <14> A method for producing the heat seal sheet according to any one of <1> to <12>, comprising the following steps 1 to 3 in this order: Step 1: preparing thermoplastic resin fiber nonwoven fabrics a and b; Step 2: stacking two or more layers of the thermoplastic resin fiber nonwoven fabrics a and b so as to include at least one layer each of the thermoplastic resin fiber nonwoven fabrics a and b; and Step 3: heat-sealing the product obtained in Step 2.

[0010] According to the present invention, there are provided a heat seal sheet having sufficient thermal adhesiveness and breathability over the entire heat seal surface and high tear strength, a method for producing the same, and a sterilized package using the same.

[0011] 1A-1C are cross-sectional views of one embodiment of a sterilization package, one embodiment of a heat seal sheet, another embodiment of a heat seal sheet, and another embodiment of a heat seal sheet.

[0012] In the present invention, "sheet" is a general term for thin sheets such as sheets, films, nonwoven fabrics, or laminates thereof. "Oken air permeability" is a value measured in accordance with JIS P 8117:2009. "Basis weight" is a value measured in accordance with JIS P 8124:2011. "Melting point" is the melting peak temperature measured in accordance with JIS K 7121:1987. "Tear strength" is the geometric mean value of the measured tear strengths in the longitudinal and transverse directions of the sheet measured in accordance with JIS P 8116:2000.

[0013] [Heat-sealable sheet and sterilized package] The heat-sealable sheet of this embodiment has at least a thermoplastic resin fiber nonwoven fabric layer A and a nonwoven fabric layer B. The thermoplastic resin fiber nonwoven fabric layer A contains a core-sheath thermoplastic resin fiber in which the sheath is a polyolefin resin and the core is a resin with a melting point 20°C or more higher than that of the sheath. The nonwoven fabric layer B contains 10% by mass or more of pulp. The Oken air permeability of the heat-sealable sheet measured in accordance with JIS P 8117:2009 is 5 seconds or more to 700 seconds or less, and the tear strength of the heat-sealable sheet measured in accordance with JIS P 8116:2000 is 700 mN or more. The heat-sealable sheet of this embodiment provides a heat-sealable sheet that has sufficient thermal adhesiveness and breathability over the entire heat-sealed surface and high tear strength. The detailed mechanism by which the above effects are achieved is unknown, but some of the following is thought to be the case. The thermoplastic resin fiber nonwoven fabric layer A contains thermoplastic resin fibers with a core-sheath structure in which the sheath is a polyolefin resin and the core is a resin with a melting point 20°C or more higher than that of the sheath, which is thought to cause the sheath to heat-fuse during heat sealing, imparting sufficient thermal adhesiveness to the entire heat-sealed surface. Furthermore, the thermoplastic resin fibers in the core retain their fibrous form during the preparation of the heat-sealed sheet and after heat sealing, which is thought to result in a heat-sealed sheet with high tear strength. Furthermore, the nonwoven fabric layer B contains 10% by mass or more of pulp, which is thought to result in a heat-sealed sheet with the desired air permeability. The reasons for the effects of this embodiment are not limited to those mentioned above.

[0014] An embodiment of the heat seal sheet and sterilization package of this embodiment will be described below with reference to FIGS. 1 to 4. As shown in FIG. 1, the sterilization package 11 of this embodiment includes the heat seal sheet 21 of this embodiment and an adherend 31. A portion of the heat seal sheet 21 and a portion of the adherend 31 are overlapped and heat-pressed together to form a space inside, thereby forming the sterilization package 11 in which the heat seal sheet 21 and the adherend 31 are heat-pressed together. Details of the adherend 31 will be described later, but it is preferably a thermoplastic resin sheet. As shown in FIG. 2, the heat seal sheet 21 has at least a thermoplastic resin fiber nonwoven fabric layer A 22 and a nonwoven fabric layer B 23. To achieve the desired air permeability and tear strength, the thermoplastic resin fiber nonwoven fabric layer A 22 and the nonwoven fabric layer B 23 are preferably disposed adjacent to each other. Alternatively, as shown in FIG. 3, the heat seal sheet 21 may have a thermoplastic resin fiber nonwoven fabric layer A 22 on both sides of the nonwoven fabric layer B 23.

[0015] Furthermore, as shown in Fig. 4, it is preferable that the heat seal sheet 21 further has a thermoplastic resin fiber nonwoven fabric layer C 24. When the thermoplastic resin fiber nonwoven fabric layer C is included, the heat seal sheet 21 is preferably formed by laminating nonwoven fabric layer B 23, thermoplastic resin fiber nonwoven fabric layer A 22, and thermoplastic resin fiber nonwoven fabric layer C 24 in this order. In the case of the heat seal sheet 21 shown in Fig. 4, it is preferable that the thermoplastic resin fiber nonwoven fabric layer C 24 and the adherend 31 are heat-sealed.

[0016] The thermoplastic resin fiber nonwoven fabric layer A is derived from the thermoplastic resin fiber nonwoven fabric a; similarly, the nonwoven fabric layer B is derived from the nonwoven fabric b; and the thermoplastic resin fiber nonwoven fabric layer C is derived from the thermoplastic resin fiber nonwoven fabric c. That is, when the heat seal sheet has the configuration shown in FIG. 2, it is produced by laminating the thermoplastic resin fiber nonwoven fabric a and the nonwoven fabric b and heat fusing them. When the heat seal sheet has the configuration shown in FIG. 3, it is produced by laminating the thermoplastic resin fiber nonwoven fabric a, the nonwoven fabric b, and the thermoplastic resin fiber nonwoven fabric a in this order and heat fusing them. When the heat seal sheet has the configuration shown in FIG. 4, it is produced by laminating the nonwoven fabric b, the thermoplastic resin fiber nonwoven fabric a, and the thermoplastic resin fiber nonwoven fabric c in this order and heat fusing them. Each layer and the nonwoven fabric from which each layer is derived are described in detail below.

[0017] <Thermoplastic resin fiber nonwoven fabric layer A and thermoplastic resin fiber nonwoven fabric a> In this embodiment, the thermoplastic resin fiber nonwoven fabric layer A contains thermoplastic resin fibers with a sheath-core structure, in which the sheath is a polyolefin resin and the core is made of a resin with a melting point 20°C or more higher than that of the sheath. By containing the thermoplastic resin fiber fibers with a sheath-core structure in the thermoplastic resin fiber nonwoven fabric layer A, a heat-sealable sheet with high tear strength can be obtained. Furthermore, the thermoplastic resin fiber nonwoven fabric a contains thermoplastic resin fibers with a sheath-core structure (hereinafter also referred to as "core-sheath structure thermoplastic resin fibers a") in which the sheath is a polyolefin resin and the core is made of a resin with a melting point 20°C or more higher than that of the sheath. When producing a heat-sealable sheet, it is preferable to heat-fuse the thermoplastic resin fiber nonwoven fabric a with another nonwoven fabric. During this process, it is thought that part of the sheath of the core-sheath structure thermoplastic resin fiber a in the thermoplastic resin fiber nonwoven fabric a will melt, but part of the sheath will remain, and it is thought that the thermoplastic resin fiber nonwoven fabric layer A also contains thermoplastic resin fibers with a core-sheath structure in which the sheath is a polyolefin resin and the core is made of a resin with a melting point 20°C or more higher than that of the sheath.

[0018] The sheath of the core-sheath thermoplastic resin fiber (a) is a polyolefin, examples of which include polyethylene and polypropylene. Polyethylene is preferred due to its low melting point and excellent thermal fusion properties. The core is made of a resin with a melting point 20°C or more higher than that of the sheath. The resin of the core (the resin constituting the core) preferably includes at least one selected from the group consisting of polypropylene resin, polyester resin, and polyamide resin, and more preferably includes at least one selected from the group consisting of polypropylene resin and polyester resin. When the resin constituting the core is polypropylene resin, the resin constituting the sheath is preferably polyethylene. When the resin constituting the core is polyester resin, examples of the polyester resin include polyethylene terephthalate (PET) and polylactic acid (PLA). When the resin constituting the core is polyamide resin, examples of the polyamide resin include nylon resin, specifically nylon 6, nylon 6,6, nylon 11, and nylon 12.

[0019] The average fiber diameter of the core-sheath thermoplastic resin fiber a is not particularly limited, but from the viewpoint of facilitating the production of a nonwoven fabric and obtaining a heat-sealable sheet having high tear strength, it is preferably 1 μm or more and 300 μm or less, more preferably 3 μm or more, even more preferably 5 μm or more, and more preferably 100 μm or less, even more preferably 50 μm or less, and still more preferably 30 μm or less.

[0020] In the core-sheath thermoplastic resin fiber (a), the ratio of the mass of the core to the mass of the sheath (mass of the core / mass of the sheath) is not particularly limited, but is preferably 25 / 75 or more and 75 / 25 or less, more preferably 30 / 70 or more and 70 / 30 or less, and even more preferably 35 / 65 or more and 65 / 35 or less. A ratio of the mass of the core to the mass of the sheath of 25 / 75 or more is preferred because the amount of the core is large and the mechanical strength of the fiber is excellent. Furthermore, a ratio of 75 / 25 or less is preferred because the amount of the sheath, which is a thermally adhesive component, is sufficient and the thermal adhesiveness is excellent. As a result, a heat-sealable sheet with excellent tear strength can be obtained, and the adhesiveness and / or heat-sealability between nonwoven fabric layers can be excellent, which is preferred.

[0021] From the viewpoint of increasing the tear strength of the heat seal sheet, the thermoplastic resin fiber nonwoven fabric a is preferably at least one selected from the group consisting of spunbonded nonwoven fabric, thermalbonded nonwoven fabric, chemicalbonded nonwoven fabric, needlepunched nonwoven fabric, spunlace nonwoven fabric, meltblown nonwoven fabric, and wetlaid nonwoven fabric, more preferably at least one selected from the group consisting of spunbonded nonwoven fabric, thermalbonded nonwoven fabric, chemicalbonded nonwoven fabric, and needlepunched nonwoven fabric, and even more preferably a spunbonded nonwoven fabric. Spunbonded nonwoven fabrics are preferred because they are made of continuous fibers and therefore have high tear strength.

[0022] The thermoplastic resin fiber nonwoven fabric a contains at least the core-sheath thermoplastic resin fibers a described above and may contain other fibers and other components, but the content of the core-sheath thermoplastic resin fibers a in the thermoplastic resin fiber nonwoven fabric a is preferably 50% by mass or more and 100% by mass or less, more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and even more preferably 95% by mass or more. The thermoplastic resin fiber nonwoven fabric a may contain, as components other than the core-sheath thermoplastic resin fibers a, thermoplastic resin fibers other than the core-sheath thermoplastic resin fibers a, pulp, thermoplastic resin particles, etc.

[0023] The basis weight of the thermoplastic resin fiber nonwoven fabric a and the thermoplastic resin fiber nonwoven fabric layer A is not particularly limited, but from the viewpoint of obtaining sufficient heat sealability and high tear strength, it is preferably 5 g / m ２ More than 100g / m ２ More preferably, it is 10 g / m or less. ２ More preferably, 15 g / m ２ More preferably, it is 80 g / m or more. ２ More preferably 50 g / m or less ２ More preferably, 30 g / m or less ２ When the heat sealable sheet has two or more thermoplastic resin fiber nonwoven fabric layers A, the above-mentioned preferable range of basis weight is the preferable range of basis weight for each layer.

[0024] The thermoplastic resin fiber nonwoven fabric layer A contained in the heat seal sheet may be one layer or multiple layers. The thermoplastic resin fiber nonwoven fabric layer a may be a single layer or multiple layers, and the layering method with the nonwoven fabric b and the optional thermoplastic resin fiber nonwoven fabric c can be carried out in any order.

[0025] <Nonwoven fabric layer B and nonwoven fabric b> In this embodiment, nonwoven fabric layer B contains 10% by mass or more of pulp. When nonwoven fabric layer B contains 10% by mass or more of pulp, a desired air permeability can be obtained. Furthermore, nonwoven fabric b contains 10% by mass or more of pulp. When producing a heat-sealable sheet, nonwoven fabric b is preferably heat-fused to another nonwoven fabric. In this case, the pulp contained in nonwoven fabric b is not thermoplastic, and therefore exists in the form of pulp in nonwoven fabric layer B.

[0026] From the viewpoint of obtaining the desired air permeability, the pulp content in nonwoven fabric layer B and nonwoven fabric layer b is 10% by mass or more, preferably 15% by mass or more, more preferably 20% by mass or more, even more preferably 25% by mass or more, still more preferably 30% by mass or more, even more preferably 40% by mass or more, and even more preferably 50% by mass or more, and may be 100% by mass, but is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less.

[0027] Examples of pulp contained in nonwoven fabric layer B and nonwoven fabric b include chemical pulps such as bleached hardwood kraft pulp (LBKP) and bleached softwood kraft pulp (NBKP); mechanical pulps such as groundwood pulp (GP), pressure groundwood pulp (PGW), refiner mechanical pulp (RMP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), chemimechanical pulp (CMP) and chemiground pulp (CGP); recycled paper pulp; non-wood fiber pulps such as kenaf, bagasse, bamboo, hemp and cotton; synthetic pulp; and the like. These pulps may be used alone or in combination of two or more. In particular, from the viewpoint of obtaining a heat seal sheet having the desired air permeability and tear strength, it is preferable that the pulp contains at least one selected from the group consisting of LBKP and NBKP, and it is more preferable to use NBKP alone or in combination with LBKP. Examples of raw materials for LBKP include eucalyptus and acacia. Examples of raw materials for NBKP include radiata pine, lodgepole pine, Douglas fir, and spruce.

[0028] From the viewpoint of obtaining a heat-sealable sheet having the desired air permeability and excellent tear strength index, the Canadian Standard Freeness (CSF) of the fibers contained in nonwoven fabric b is preferably 250 mL or more and 750 mL or less, more preferably 300 mL or more, even more preferably 350 mL or more, still more preferably 380 mL or more, and more preferably 600 mL or less, even more preferably 500 mL or less, and still more preferably 450 mL or less. As will be described later, nonwoven fabric layer B and nonwoven fabric b may contain fiber components other than pulp, and in such cases, the CSF of the raw fiber material as a whole is preferably within the above-mentioned range.

[0029] Nonwoven fabric b preferably contains thermoplastic resin fibers (hereinafter, the thermoplastic resin fibers contained in nonwoven fabric b are also referred to as thermoplastic resin fibers b) in addition to pulp. The inclusion of thermoplastic resin fibers b is preferred because it imparts thermal fusion properties to nonwoven fabric b and improves adhesion to other nonwoven fabric layers.

[0030] The total content of thermoplastic resin fibers b in nonwoven fabric b is 0% by mass or more and 90% by mass or less, preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and preferably 85% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less, still more preferably 70% by mass or less, even more preferably 60% by mass or less, and even more preferably 50% by mass or less.

[0031] The thermoplastic resin fibers b contained in the nonwoven fabric b are not particularly limited. However, from the viewpoint of forming a nonwoven fabric with pulp, thermoplastic resin fibers suitable for wet papermaking are preferred. Furthermore, from the viewpoint of imparting heat-sealing properties, thermoplastic resin fibers with a low melting point are preferred. From the above viewpoints, polyolefin hyperbranched fibers are preferred as the thermoplastic resin fibers b. Examples of polyolefin hyperbranched fibers obtained by pseudo-pulping polyolefins include the SWP (registered trademark) series manufactured by Mitsui Chemicals, Inc. Furthermore, the thermoplastic resin fibers b contained in the nonwoven fabric b may be core-sheath fibers whose sheath melting point is lower than the thermal lamination temperature during the production of the heat-sealable sheet. Specific examples include core-sheath structure fibers in which the sheath resin is a polyethylene resin or a low-melting-point polyester resin and the core resin is a polypropylene resin or a polyester resin. Using core-sheath structure fibers as the thermoplastic resin fibers b is preferred because at least a portion of the sheath melts during the production of the heat-sealable sheet, thereby suppressing fuzzing on the surface of the nonwoven fabric layer B.

[0032] The basis weight of the nonwoven fabric layer B and the nonwoven fabric b is not particularly limited, but from the viewpoint of obtaining a heat sealable sheet having the desired air permeability, it is preferably 5 g / m ２ More than 300g / m ２ More preferably, it is 10 g / m or less. ２ More preferably, 20 g / m ２ More preferably, 30 g / m ２ More preferably 40 g / m ２ More preferably, it is 200 g / m or more. ２ More preferably, 100 g / m or less ２More preferably, 80 g / m or less ２ When the heat seal sheet has two or more nonwoven fabric layers B, the above-mentioned preferable range of basis weight is the preferable range of basis weight for each layer.

[0033] The nonwoven fabric layer B contained in the heat seal sheet may be one layer or multiple layers. The nonwoven fabric b may be a single layer or multiple layers, and the thermoplastic resin fiber nonwoven fabric a and the optional thermoplastic resin fiber nonwoven fabric c may be laminated in any order.

[0034] <Thermoplastic Resin Fiber Nonwoven Fabric Layer C and Thermoplastic Resin Fiber Nonwoven Fabric C> The heat-sealable sheet of this embodiment preferably further includes a thermoplastic resin fiber nonwoven fabric layer C in addition to the thermoplastic resin fiber nonwoven fabric layer A and nonwoven fabric layer B described above. The thermoplastic resin fiber nonwoven fabric layer C preferably contains a low-melting-point polyester resin, polyester resin fiber, and a polyolefin resin. The heat-sealable sheet preferably includes a thermoplastic resin fiber nonwoven fabric layer C, particularly on the surface where heat sealing with the adherend is performed. This is preferable because it provides the desired peel strength suitable for easy peeling in the thermocompression-bonded product. When the thermoplastic resin fiber nonwoven fabric layer C is not included, it is preferable to use the thermoplastic resin fiber nonwoven fabric layer A as the heat-sealable surface with the adherend. However, using the thermoplastic resin fiber nonwoven fabric layer C on the heat-sealable surface is preferable compared to the thermoplastic resin fiber nonwoven fabric layer A, as it provides a peel strength more suitable for easy peeling. The thermoplastic resin fiber nonwoven fabric layer C is a layer derived from the thermoplastic resin fiber nonwoven fabric c, and one or more types of thermoplastic resin fibers can be used as the thermoplastic resin fibers c constituting the thermoplastic resin fiber nonwoven fabric c. For the purpose of adhesion to the thermoplastic resin fiber nonwoven fabric layer A after thermal lamination and for the development of heat sealability of the heat seal sheet, the thermoplastic resin fibers c preferably contain fibers having a melting point of less than 150°C.

[0035] The thermoplastic resin fiber c may have a single structure or a core-sheath structure of two or more layers. When the thermoplastic resin fiber c has a core-sheath structure, the melting point of the resin in the sheath portion is preferably less than 150°C, and the melting point of the resin in the core portion may be 150°C or higher.

[0036] Examples of thermoplastic resin fibers c include various polyolefin resin fibers, polyethylene-vinyl acetate ester resin fibers, low-melting point polyester resin fibers, composite fibers with a core-sheath structure in which the core is made of a normal polyester resin and the sheath is made of the various polyethylene resin fibers described above, polyethylene-vinyl acetate ester resin fibers, and composite resins with a core-sheath structure in which the core is made of a normal polyester resin and the sheath is made of a low-melting point polyester resin. These thermoplastic resin fibers may also have a multi-branched structure.

[0037] Among these, from the viewpoint of thermal lamination properties and heat sealing properties with the thermoplastic resin fiber nonwoven fabric a or b, preferred thermoplastic resin fibers c are polyester resin fibers and polyolefin resin fibers with a sheath-core structure using a low-melting-point polyester resin as the sheath and a conventional polyester resin as the core, and more preferred are polyester resin fibers and polyolefin hyperbranched fibers with the above-mentioned sheath-core structure. Here, in polyester resin fibers with a sheath-core structure using a low-melting-point polyester resin as the sheath and a conventional polyester resin as the core, the low-melting-point polyester resin used in the sheath preferably has a melting point below 150°C, more preferably 140°C or less, even more preferably 130°C or less, and even more preferably 120°C or less. Meanwhile, the polyester resin used in the core preferably has a melting point above 150°C, more preferably 180°C or more, even more preferably 200°C or more, and even more preferably 240°C or more. An example of a polyester resin used in the core is polyethylene terephthalate.

[0038] The melting point of the polyolefin resin fiber is preferably 150°C or lower, more preferably 140°C or lower. The polyolefin resin fiber is preferably a polyolefin hyperbranched fiber obtained by pseudo-pulping polyolefin, since this allows the thermoplastic resin fiber nonwoven fabric (c) to be produced by wet papermaking. Preparing the thermoplastic resin fiber nonwoven fabric (c) by wet papermaking is preferred because it results in a more excellent texture, high uniformity, and dense nonwoven fabric. When the thermoplastic resin fiber nonwoven fabric (c) is a nonwoven fabric obtained using a core-sheath polyester resin fiber in which a low-melting-point polyester resin is used as the sheath and a conventional polyester resin is used as the core, and polyolefin fiber, the thermoplastic resin fiber nonwoven fabric layer (C) after lamination and heat fusion with the thermoplastic resin fiber nonwoven fabrics (a) and (b) does not necessarily retain its fibrous shape because the low-melting-point polyester resin and polyolefin fiber in the sheath of the core-sheath polyester resin fiber are partially or completely melted. The low-melting-point polyester resin and polyolefin fiber do not necessarily have to be completely melted; at least a portion of them must be melted.

[0039] The thermoplastic resin fiber nonwoven fabric (c) is preferably a nonwoven fabric (wet nonwoven fabric) obtained by a wet papermaking method, and more preferably obtained by wet papermaking a polyester resin fiber having a core-sheath structure in which the low-melting-point polyester resin is used as the sheath and a conventional polyester resin is used as the core, and a polyolefin hyperbranched fiber. When the thermoplastic resin fiber nonwoven fabric (c) contains a polyester resin fiber having a core-sheath structure in which the low-melting-point polyester resin is used as the sheath and a conventional polyester resin is used as the core, the content thereof is preferably 5% by mass or more and 75% by mass or less, more preferably 10% by mass or more, even more preferably 15% by mass or more, still more preferably 20% by mass or more, and more preferably 60% by mass or less, even more preferably 50% by mass or less, and even more preferably 40% by mass or less. The mass ratio of the sheath to the core (sheath / core) is preferably 20 / 80 or more and 80 / 20 or less, more preferably 30 / 70 or more and 70 / 30 or less, and even more preferably 40 / 60 or more and 60 / 40 or less. Examples of polyester resin fibers having a core-sheath structure in which a low-melting-point polyester resin is used for the sheath and a normal polyester resin is used for the core include the Tepyrus series manufactured by Teijin Frontier Co., Ltd. and PET-based binder fibers manufactured by Kuraray Co., Ltd.

[0040] The content of polyolefin hyperbranched fibers in the thermoplastic resin fiber nonwoven fabric c is preferably 25% by mass or more and 100% by mass or less, more preferably 40% by mass or more, even more preferably 50% by mass or more, still more preferably 60% by mass or more, and more preferably 95% by mass or less, even more preferably 90% by mass or less, still more preferably 85% by mass or less, even more preferably 80% by mass or less, and even more preferably 75% by mass or less. Examples of polyolefin hyperbranched fibers obtained by pseudo-pulping polyolefin include the SWP (registered trademark) series manufactured by Mitsui Chemicals, Inc.

[0041] The thermoplastic resin fiber nonwoven fabric layer C derived from the thermoplastic resin fiber nonwoven fabric c obtained using these thermoplastic resin fibers c preferably contains a low-melting-point polyester resin, polyester resin fibers, and polyolefin resin. The polyester resin fibers are referred to as "polyester resin fibers" because they are preferably in a fibrous form. Meanwhile, the low-melting-point polyester resin and polyolefin resin constituting the thermoplastic resin fibers c are referred to as "low-melting-point polyester resin" and "polyolefin resin," respectively, because they may be at least partially molten and not in a fibrous form. When a low-melting-point polyester resin is contained, the content of the low-melting-point polyester resin is preferably 1.0 parts by mass or more and 60.0 parts by mass or less, more preferably 3.0 parts by mass or more, even more preferably 6.0 parts by mass or more, even more preferably 10 parts by mass or more, and more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less, based on the total amount of the low-melting-point polyester resin, polyester resin fibers, and polyolefin resin taken as 100 parts by mass. As mentioned above, the low-melting-point polyester resin is a polyester resin with a melting point of less than 150°C. Furthermore, when polyester resin fibers are contained, the content of the polyester resin fibers is preferably 1.0 part by mass or more and 60.0 parts by mass or less, more preferably 3.0 parts by mass or more, even more preferably 6.0 parts by mass or more, still more preferably 10 parts by mass or more, and more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, and still more preferably 20 parts by mass or less, when the total amount of the low-melting-point polyester resin, polyester resin fiber, and polyolefin resin is taken as 100 parts by mass. In this embodiment, the "polyester resin fiber" has a melting point of 150°C or more, preferably 180°C or more, more preferably 200°C or more, and even more preferably 240°C or more, and an example of this is polyethylene terephthalate fiber.Furthermore, when the total amount of the low-melting point polyester resin, polyester resin fiber, and polyolefin resin is 100 parts by mass, the content of the polyolefin resin is preferably 25 parts by mass or more and 100 parts by mass or less, preferably 40 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 60 parts by mass or more, and more preferably 90 parts by mass or less, even more preferably 85 parts by mass or less, and even more preferably 80 parts by mass or less.

[0042] The total content of the low-melting-point polyester resin, polyester resin fiber, and polyolefin resin in the thermoplastic resin fiber nonwoven fabric layer C is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 85% by mass or more, with the upper limit being 100% by mass or less. Furthermore, as long as the object of the present invention is not impaired, natural pulp fiber, recycled fiber, or other chemical fiber can also be used in combination as the thermoplastic resin fiber c.

[0043] The fiber diameter of the fibers used in the thermoplastic resin fiber nonwoven fabric c is not particularly limited, but is preferably 1 μm or more and 60 μm or less, and more preferably 1 μm or more and 40 μm or less.

[0044] The basis weight of the thermoplastic resin fiber nonwoven fabric layer C and the thermoplastic resin fiber nonwoven fabric layer C is not particularly limited, but from the viewpoint of obtaining sufficient thermal adhesiveness, breathability, and tear strength, it is preferably 5 g / m ２ More than 100g / m ２ More preferably, it is 10 g / m or less. ２ More preferably, 15 g / m ２ More preferably, it is 80 g / m or more. ２ More preferably 60 g / m or less ２ When the heat seal sheet has two or more thermoplastic resin fiber nonwoven fabric layers C, the above-mentioned preferable range of basis weight is the preferable range of basis weight for each layer.

[0045] The thermoplastic resin fiber nonwoven fabric layer C may be a single layer or a multi-layer structure of two or more layers. The thermoplastic resin fiber nonwoven fabric layer A and the nonwoven fabric layer B may be laminated in any order.

[0046] Various known methods can be used to manufacture the thermoplastic resin fiber nonwoven fabric (c), but wet papermaking is preferred because it is easy to obtain good formation even at low basis weights and is less likely to produce pinholes that impair the antibacterial properties of the heat-sealable sheet. Examples of wet papermaking methods include those using a Fourdrinier paper machine, a short-wire paper machine, a cylinder paper machine, and an inclined paper machine. Of these, cylinder paper machines and inclined paper machines are preferred because they can use materials with relatively long fiber lengths, and inclined paper machines are more preferred. Various dispersants, surfactants, thickeners, and other internal additives can also be added to the raw material slurry to improve formation.

[0047] The method for drying the thermoplastic resin fiber nonwoven fabric c after wet papermaking is not particularly limited, and a multi-cylinder dryer, Yankee dryer, hot air dryer, infrared dryer, etc. can be used. When a multi-cylinder dryer or Yankee dryer is used, it is preferable to set the drying temperature to a value equal to or lower than the melting point of the thermoplastic resin fiber, or to coat the surface of the multi-cylinder dryer or Yankee dryer with a fluororesin in order to prevent surface contamination due to adhesion of the thermoplastic resin.

[0048] [Method for manufacturing a heat seal sheet] The method for manufacturing a heat seal sheet of this embodiment preferably comprises the following steps 1 to 3 in this order: Step 1: A step of preparing a thermoplastic resin fiber nonwoven fabric a and a nonwoven fabric b; Step 2: A step of stacking (laminating) two or more layers of thermoplastic resin fiber nonwoven fabric a and nonwoven fabric b so as to include at least one layer each; Step 3: A step of heat-sealing the product (laminate) obtained in step 2

[0049] <Step 1> Step 1 is a step of preparing thermoplastic resin fiber nonwoven fabrics a and b. Thermoplastic resin fiber nonwoven fabrics a and b may be prepared by the method described above. When the heat-sealable sheet has a thermoplastic resin fiber nonwoven fabric layer C, in step 1, a thermoplastic resin fiber nonwoven fabric c is prepared in addition to the thermoplastic resin fiber nonwoven fabrics a and b.

[0050] <Step 2> Step 2 is a step of overlaying (laminating) two or three or more layers so as to include at least one layer of thermoplastic resin fiber nonwoven fabric a and one layer of nonwoven fabric b. When the laminate obtained in step 2 is two layers, thermoplastic resin fiber nonwoven fabric a and nonwoven fabric b are laminated. When the laminate obtained in step 2 is three layers and consists of thermoplastic resin fiber nonwoven fabric a and nonwoven fabric b, the laminate is an a / b / a or b / a / b laminate. Of these, an a / b / a laminate is preferred because the thermoplastic resin fiber nonwoven fabric a, which has better heat-sealing properties, is heat-sealed to the adherend. Furthermore, when the laminate obtained in step 2 is three-layered and consists of thermoplastic resin fiber nonwoven fabric a, nonwoven fabric b, and thermoplastic resin fiber nonwoven fabric c, the stacking order may be any of a / b / c, a / c / b, c / b / a, or c / a / b. However, from the viewpoint of suppressing the generation of fluff when peeling the laminate from the adherend after adhesion, it is preferable that the heat-sealable layer between the adherend and the nonwoven fabric layer C is the thermoplastic resin fiber nonwoven fabric layer. Furthermore, from the viewpoint of improving the adhesion between the layers in the heat-sealable sheet, it is preferable that the intermediate layer is the thermoplastic resin fiber nonwoven fabric layer A derived from the thermoplastic resin fiber nonwoven fabric a. Therefore, the stacking order from the heat-sealable layer side is preferably c / a / b, but is not limited to this. A laminate structure of four or more layers may be used, but from the viewpoint of ease of manufacture, a two- or three-layer structure is preferable, and a three-layer structure is more preferable.

[0051] <Step 3> Step 3 is a step of heat-sealing the laminate obtained in step 2. In step 3, the thermoplastic resin fiber nonwoven fabric a, nonwoven fabric b, and optionally the thermoplastic resin fiber nonwoven fabric c that constitute the laminate are heat-sealed (heat-laminated). The heat-sealing step can be carried out by passing the laminate obtained in step 2 between two heated rolls or by pressing the laminate between two hot plates.

[0052] The temperature of the heating roll or hot plate is adjusted to be equal to or higher than the melting point of the thermoplastic resin fiber with the lowest melting point used in the thermoplastic resin fiber nonwoven fabric a. When the temperature of the heating roll or hot plate is not lower than the melting point of the thermoplastic resin fiber with the lowest melting point used in the thermoplastic resin fiber nonwoven fabric a, the interlayer adhesion of the heat-sealable sheet is excellent. Furthermore, it is preferable to coat the surface of the heating roll or hot plate with a fluororesin to prevent surface contamination due to the adhesion of the thermoplastic resin.

[0053] The surface temperatures of the upper and lower heating rolls or hot plates may be the same or different. Heat fusion may be performed with one nip or two or more nips. When two or more nips are used, heat fusion may be performed in one pass or two or more passes. When the laminate obtained in step 2 has three or more layers, heat fusion may be performed on all layers simultaneously, or a portion may be heat fused first, followed by the addition of another layer. During heat fusion, a step of preheating the thermoplastic resin fiber nonwoven fabric a and / or nonwoven fabric b using a preheater before pressure application may be added before contacting the thermoplastic resin fiber nonwoven fabric a and / or nonwoven fabric b with the heating roll. Other known techniques may also be applied.

[0054] [Characteristics of Heat Seal Sheet] (Basis Weight) The basis weight of the heat seal sheet of the present embodiment is preferably 30 g / m from the viewpoints of ease of production, appropriate heat seal strength, and tear strength. ２ More preferably, 50 g / m ２ More preferably, 70 g / m ２ and preferably 300 g / m ２ or less, more preferably 200 g / m ２ More preferably 150 g / m or less ２ The basis weight of the heat seal sheet can be adjusted to a desired range by adjusting the basis weights of the thermoplastic resin fiber nonwoven fabric a, nonwoven fabric b, and thermoplastic resin fiber nonwoven fabric c to appropriate ranges.

[0055] (Oken air permeability) The Oken air permeability of the heat seal sheet of this embodiment, measured in accordance with JIS P 8117:2009, is 5 seconds or more and 700 seconds or less. An Oken air permeability of 5 seconds or more is preferable because a sterilized state can be maintained after sterilization treatment, and an Oken air permeability of 700 seconds or less is preferable because ethylene oxide gas sterilization treatment can be applied. The Oken air permeability of the heat seal sheet is more preferably 10 seconds or more, even more preferably 25 seconds or more, and more preferably 300 seconds or less, even more preferably 150 seconds or less, still more preferably 100 seconds or less, and even more preferably 50 seconds or less.

[0056] (Tear Strength) The tear strength of the heat seal sheet of this embodiment, measured in accordance with JIS P 8116:2000, is 700 mN or more. A tear strength of 700 mN or more is preferable because it can be used as a sterilization packaging material for relatively large medical devices or heavy medical instruments. The tear strength of the heat seal sheet is more preferably 800 mN or more, even more preferably 1,000 mN or more, even more preferably 1,500 mN or more, and even more preferably 1,800 mN or more. The upper limit of the tear strength is not particularly limited, but from the viewpoint of ease of production, it is preferably 12,000 mN or less, more preferably 10,000 mN or less. When the heat seal sheet has anisotropy, the tear strength is the geometric mean value of the tear strength in the longitudinal direction (papermaking direction, MD direction, T direction) and the tear strength in the transverse direction (direction perpendicular to the papermaking direction, CD direction, Y direction). When the papermaking direction is unknown, the tear strength is measured in one arbitrary direction and in a direction perpendicular to the direction, and the geometric mean value is calculated.

[0057] (Peel Strength) The heat seal sheet of this embodiment has a peel strength of preferably 1.0 N / 15 mm or more and 25 N / 15 mm or less, more preferably 2.0 N / 15 mm or more, even more preferably 3.0 N / 15 mm or more, more preferably 20.0 N / 15 mm or less, even more preferably 15.0 N / 15 mm or less, still more preferably 12.0 N / 15 mm or less, and even more preferably 9.0 N / 15 mm or less, when heat-sealed at 150° C. under conditions of 0.2 MPa for 1.0 second to the polyethylene side of a laminate film of polyethylene terephthalate resin and polyethylene resin and peeled at 180° at a peel rate of 300 mm / min in accordance with JIS P 8113:2006. Peel strengths within the above ranges are preferred because, when used to form a sterilized package, the resulting sterilized package has sufficient heat sealability and excellent openability.

[0058] [Effects] The heat-sealable sheet of this embodiment is obtained by thermally fusing (thermal laminating) thermoplastic resin fiber nonwoven fabrics a and b, and has sufficient thermal adhesiveness and breathability over the entire heat-sealed surface, as well as high strength, making it an excellent sterilized medical packaging material. Furthermore, by including thermoplastic resin fiber nonwoven fabric layer C derived from thermoplastic resin fiber nonwoven fabric c, fluffing after peeling can be suppressed, and the amount of lint generated can be kept low.

[0059] [Uses] The heat seal sheet of this embodiment is suitable for use in, for example, sterilization packaging. A portion of the heat seal sheet is overlapped with a portion of an adherend, such as wrapping paper, laminated paper, film, or a sterilization-use molded container, so as to form a space inside, and then heat-pressed to form a sterilization packaging in which the heat seal sheet and the adherend are heat-pressed together. Examples of films or sterilization-use molded containers include films or sterilization-use molded containers made of polyolefins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate, polyvinyl chloride, polyvinylidene chloride, polystyrene, ethylene-vinyl acetate copolymer resins, ethylene-acrylic copolymer resins, or laminates thereof. A sterilization-use molded container typically has one or more recesses for containing contents. In this case, the heat seal sheet is typically used as a lid material to seal the opening of the one or more recesses. A sterilization-use molded container is preferred as the adherend to be heat-pressed to the heat seal sheet, as it is required to have sufficient peel strength without causing substrate damage even with a relatively narrow seal width.

[0060] In the sterilization package, a space for containing an item such as a medical instrument is formed by a heat seal sheet and an adherend that are heat-pressed together. The heat seal sheet and the adherend are heat-pressed together after the item is contained. The medical instrument as the contained item is not particularly limited as long as it is a medical instrument that requires sterilization before use. Specific examples include injection needles, syringes, catheters, gloves, scalpels, forceps, forceps, scissors, gauze, adhesive bandages, etc.

[0061] The sterilization package is subjected to a sterilization treatment while containing the contents. For example, the sterilization treatment is carried out by a sterilization method such as autoclave, ethylene oxide gas (EOG) sterilization, electron beam sterilization, or gamma ray sterilization. When the contents are to be used, the heat seal sheet is peeled off from the adherend to remove the contents. The use of the heat seal sheet is not limited to sterilization packages, but can also be used for packaging food, various freshness-preserving agents such as desiccants and oxygen absorbers, general industrial products, etc. In addition, it is possible to apply a printing process to either the front or back surface, or to the outermost surface of both surfaces.

[0062] In a sterilized package of a heat-sealable sheet and an adherend, the peel strength when the heat-sealable sheet and the adherend are peeled at a 180° angle at a peel speed of 300 mm / min is preferably 1.0 N / 15 mm or more and 25 N / 15 mm or less, more preferably 1.5 N / 15 mm or more, even more preferably 2.0 N / 15 mm or more, still more preferably 3.0 N / 15 mm or more, even more preferably 4.0 N / 15 mm or more, even more preferably 4.5 N / 15 mm or more, even more preferably 5.0 N / 15 mm or more, and more preferably 20.0 N / 15 mm or less, even more preferably 15.0 N / 15 mm or less, still more preferably 12.0 N / 15 mm or less, even more preferably 10.5 N / 15 mm or less, even more preferably 9.0 N / 15 mm or less, and even more preferably 7.5 N / 15 mm or less. A peel strength within the above range provides an excellent balance between easy-peel properties and heat-sealability. The heat-seal peel strength is measured by the method described in the Examples. The heat-seal peel strength can be adjusted to a desired range by adjusting the basis weight of the thermoplastic resin fiber nonwoven fabric layer A, nonwoven fabric layer B, or thermoplastic resin fiber nonwoven fabric layer C that constitutes the heat-seal surface, the polyethylene resin content in the layer that constitutes the heat-seal surface, the heat-sealing conditions in the heat-sealing step of the laminate when producing the heat-sealable sheet, and the heat-sealing conditions with the adherend within appropriate ranges.

[0063] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these examples. Unless otherwise specified, % means % by mass and parts means parts by mass.

[0064] [Examples 1 to 10, Comparative Examples 1 to 8] <Preparation of Thermoplastic Resin Fiber Nonwoven Fabric a> For each of the Examples and Comparative Examples, the thermoplastic resin fiber nonwoven fabric a shown in Table 1 was prepared.

[0065]

[0066] In Table 1, thermoplastic resin fiber nonwoven fabric a (I) is a spunbond nonwoven fabric made of thermoplastic resin fibers with a core-sheath structure, where the sheath is polyethylene resin (melting point 135°C) and the core is polyester resin (polyethylene terephthalate, melting point 260°C). Thermoplastic resin fiber nonwoven fabric a (II) is a spunbond nonwoven fabric made of thermoplastic resin fibers with a core-sheath structure, where the sheath is polyethylene resin (melting point 135°C) and the core is polypropylene resin (melting point 160°C). Thermoplastic resin fiber nonwoven fabric a (III) is a spunbond nonwoven fabric made of polyester resin fiber (polyethylene terephthalate fiber). Thermoplastic resin fiber nonwoven fabric a (IV) is a wet-laid nonwoven fabric made of polyester resin fiber (polyethylene terephthalate fiber). Thermoplastic resin fiber nonwoven fabric a (V) is a spunbond nonwoven fabric made of polypropylene resin fiber.

[0067] <Production of Nonwoven Fabric b> Polyolefin hyperbranched fiber (trade name: SWP (registered trademark) E400, melting point 135°C, average fiber length 0.9 mm, fiber diameter approximately 1 to 30 μm, manufactured by Mitsui Chemicals, Inc.) and softwood bleached kraft pulp (NBKP) (Canadian standard freeness (freeness) as described in JIS P 8121-2:2012: 556 mL) were mixed in the predetermined ratios shown in Table 2, and the mixture was beaten in a DDR (double disc refiner) to a Canadian standard freeness (freeness) as described in JIS P 8121-2:2012 of 410 mL to obtain a raw material slurry. In Comparative Examples 7 and 8, a core-sheath polyester resin fiber (trade name: Tepyrus (registered trademark) TJ04CN, fineness 1.1 dtex, fiber length 5 mm, fiber diameter approximately 10 μm, sheath melting point 110°C, core (polyethylene terephthalate) melting point 260°C, sheath / core mass ratio = 55 / 45, manufactured by Teijin Frontier Co., Ltd.) was used instead of softwood bleached kraft pulp (NBKP). The raw material slurry was paper-formed using a Fourdrinier paper machine to a predetermined basis weight, and then calendered to obtain nonwoven fabric b. The air permeability of the obtained nonwoven fabric b is shown in Table 2.

[0068] <Production of Thermoplastic Resin Fiber Nonwoven Fabric c> 70 parts by mass of polyolefin hyperbranched fiber (trade name: SWP (registered trademark) E400, melting point 135°C, average fiber length 0.9 mm, fiber diameter approximately 1 to 30 μm, manufactured by Mitsui Chemicals, Inc.) and 30 parts by mass of core-sheath structured polyester resin fiber (trade name: Tepyrus (registered trademark) TJ04CN, fineness 1.1 dtex, fiber length 5 mm, fiber diameter approximately 10 μm, sheath melting point 110°C, core (polyethylene terephthalate) melting point 260°C, sheath / core mass ratio = 55 / 45, manufactured by Teijin Frontier Co., Ltd.) were mixed and stirred to obtain a raw material slurry. The raw material slurry was paper-formed using a wet inclined papermaking machine and dried in a Yankee dryer at a surface temperature of 105°C to obtain a paper having a basis weight of 35 g / m ２ Thus, a thermoplastic resin fiber nonwoven fabric c was obtained.

[0069] <Production of heat seal sheet> The thermoplastic resin fiber nonwoven fabrics a, b, and c obtained above were stacked in the order shown in Table 2, and subjected to a thermal lamination treatment using a thermal laminator having heating rolls with fluorine-coated surfaces, with the roll temperatures of the upper and lower rolls set to 150°C, to obtain heat seal sheets of Examples 1 to 10 and Comparative Examples 1 to 8.

[0070] [Comparative Example 9] <Preparation of Paper Base> Hardwood bleached kraft pulp (LBKP) was beaten in a DDR (double disc refiner) to a Canadian standard freeness (freeness) of 390 mL as described in JIS P 8121-2: 2012 to obtain a pulp slurry. The pulp slurry was internally added with the following chemicals per 100 parts by mass of pulp: 0.5 parts by mass of aluminum sulfate on an oven-dry basis, 0.05 parts by mass of an alkenyl succinic anhydride sizing agent dispersion previously dispersed in cationized starch, as the solid content of the alkenyl succinic anhydride sizing agent, 0.7 parts by mass of an amphoteric polyacrylamide resin paper strength enhancer (PAM) (trade name: Polystron OFT-3, manufactured by Arakawa Chemical Industries, Ltd., weight average molecular weight 3,000,000), and 0.4 parts by mass of an epichlororesin wet strength enhancer (trade name: WS4024, manufactured by Seiko PMC Corporation), to obtain a papermaking raw material. The papermaking raw material was made into a breathable substrate using a Fourdrinier paper machine. The basis weight of the breathable substrate was 60 g / m ２The "alkenyl succinic anhydride sizing agent dispersion previously dispersed in cationized starch" was prepared as follows: A 2% by mass aqueous solution of cationized starch (Pillar 3YK, manufactured by Pillar Starch Co., Ltd.) was prepared, and an alkenyl succinic anhydride sizing agent (Fibran 81K, manufactured by Arakawa Chemical Industries, Ltd.) was added thereto so that the solids concentration was 4 / 1 (cationized starch (Pillar 3YK, manufactured by Pillar Starch Co., Ltd.) / alkenyl succinic anhydride sizing agent). 0.05 parts by mass of the aqueous solution prepared as described above was added as a solid content of alkenyl succinic anhydride.

[0071] <Preparation of paint for thermal adhesive layer> 138 parts of EVA dispersion (Chemipearl V200, manufactured by Mitsui Chemicals, Inc., EVA particle average particle size 7 μm, minimum film formation temperature 85° C., solid content 40%), PE dispersion (Chemipearl W400, manufactured by Mitsui Chemicals, Inc., PE particle average particle size 4 μm, solid content 40%, PE density 920 kg / m ３ 90 parts of a rosin emulsion (Sizepine N775, manufactured by Arakawa Chemical Industries, Ltd., softening point less than 100°C, solids concentration 50%), 18 parts of a reinforced rosin emulsion (Sizepine N775, manufactured by Arakawa Chemical Industries, Ltd., softening point less than 100°C, solids concentration 50%), and 154 parts of dilution water were mixed and stirred to obtain a coating material for a thermal adhesive layer with a solids concentration of 25%.

[0072] <Production of heat seal sheet> The above-mentioned coating material for the thermal adhesive layer was applied to one surface of the breathable substrate obtained above using a bar coater, and then dried in a blower dryer at 100°C for 1 minute to form a thermal adhesive layer. Here, the coating amount of the coating material for the thermal adhesive layer after drying was 2.0 g / m ２ In this way, a heat seal sheet of Comparative Example 9 was obtained.

[0073] [Measurement Methods] The heat seal sheets obtained in the Examples and Comparative Examples were evaluated as follows: <Basis Weight> Basis weight was measured in accordance with JIS P 8124:2011.

[0074] <Measurement of Oken air permeability> The Oken air permeability of the heat seal sheet was measured in accordance with JIS P 8117:2009. An air permeability of 700 seconds or less is preferable because ethylene oxide gas sterilization treatment can be applied. An air permeability of more than 700 seconds is unpreferable because the penetration speed of ethylene oxide gas decreases and the sterilization efficiency decreases.

[0075] <Measurement of tear strength> The tear strength of the heat seal sheet was measured in the longitudinal and transverse directions of the sheet in accordance with JIS P 8116:2000, and the geometric mean of these values ​​was calculated. A tear strength of 700 mN or more is preferable because it can be used as a sterilization packaging material for relatively large medical devices or heavy medical instruments. If the tear strength is less than 700 mN, when a relatively large medical device or heavy medical instrument is contained inside, the sterilized medical packaging material may tear during transportation or if accidentally dropped, and the sterilization state inside the package may not be maintained.

[0076] <Measurement of heat seal peel strength> Each heat seal sheet obtained in the examples and comparative examples was overlapped with a laminate film of polyethylene terephthalate resin (PET) and PE (a laminate film dry-laminated between a 50 μm thick polyethylene film and a 12 μm thick PET film) as an adherend, so that the surface of the heat seal sheet on the thermal adhesive layer side (thermal adhesive surface) was in contact with the surface of the laminate film on the PE side, and a heat press tester was used to heat press bond the sheets under heat pressing conditions of 150°C, 0.2 MPa, and 1.0 second to produce a heat press bonded product. The heat press bonded product produced by the above method was cut to a width of 15 mm to produce a sample for measuring peel strength. The peel strength (N / 15 mm) of the obtained sample for peel strength measurement was measured in accordance with JIS P 8113:2006 using a tensile tester (model: Tensilon RTC-1250A, manufactured by Orientec Co., Ltd.) by chucking each end of the composite film and heat seal sheet of the sample and peeling them at a peel rate of 300 mm / min by the 180° peel method.

[0077]

[0078] The heat-sealable sheets of Examples 1 to 10 exhibited low air permeability (seconds), suggesting their applicability to ethylene oxide gas sterilization. Furthermore, their tear strength was sufficiently high, suggesting their applicability to sterilization of large or relatively heavy medical instruments. Furthermore, in Examples 1 to 6, 9, and 10, in which the thermoplastic resin fiber nonwoven fabric c or nonwoven fabric b was used for heat sealing with the adherend, peel strength within the desired range was achieved. On the other hand, when the thermoplastic resin fiber nonwoven fabric layer A was not present, as in Comparative Example 1, sufficient tear strength was not obtained. Furthermore, when the nonwoven fabric layer B was not present, as in Comparative Examples 2 and 6, the air permeability was less than 5 seconds. Furthermore, in Comparative Example 3, in which a polyester spunbonded nonwoven fabric was used as the thermoplastic resin fiber nonwoven fabric a, Comparative Example 4, in which a polyester wet-laid nonwoven fabric was used, and Comparative Example 5, in which a polypropylene spunbonded nonwoven fabric was used, when the thermoplastic resin fiber nonwoven fabric c / thermoplastic resin fiber nonwoven fabric a / nonwoven fabric b were laminated and heat-melted in this order, the polyester resin and polypropylene resin in the thermoplastic resin fiber nonwoven fabric a did not melt, and a heat-sealable sheet could not be obtained. Furthermore, in Comparative Examples 7 and 8, in which a core-sheath polyester resin fiber was used instead of pulp, the air permeability was less than 5 seconds, and the desired air permeability was not obtained. In Comparative Example 9, when a thermal adhesive layer was provided on the paper substrate, sufficient tear strength was not obtained.

[0079] The heat sealable sheet of the present invention has sufficient thermal adhesiveness and breathability over the entire heat seal surface, and is also strong, making it an excellent sterilized medical packaging material.

[0080] 11...sterilized package, 21...heat seal sheet, 22...thermoplastic resin fiber nonwoven fabric layer A, 23...nonwoven fabric layer B, 24...thermoplastic resin fiber nonwoven fabric layer C, 31...adherend

Claims

1. A heat-sealable sheet having at least a thermoplastic resin fiber nonwoven fabric layer A and a nonwoven fabric layer B, wherein the thermoplastic resin fiber nonwoven fabric layer A contains thermoplastic resin fibers with a core-sheath structure in which the sheath is made of a polyolefin resin and the core is made of a resin with a melting point 20°C or more higher than that of the sheath, the nonwoven fabric layer B contains 10% by mass or more of pulp, the Oken air permeability of the heat-sealable sheet measured in accordance with JIS P 8117:2009 is 5 seconds or more and 700 seconds or less, and the tear strength of the heat-sealable sheet measured in accordance with JIS P 8116:2000 is 700 mN or more.

2. The heat-sealable sheet according to claim 1, wherein the heat-sealable sheet further comprises a thermoplastic resin fiber nonwoven fabric layer C, and the nonwoven fabric layer B, the thermoplastic resin fiber nonwoven fabric layer A, and the thermoplastic resin fiber nonwoven fabric layer C are laminated in this order.

3. A heat seal sheet as described in claim 2, wherein the thermoplastic resin fiber nonwoven fabric layer C is a layer derived from a thermoplastic resin fiber nonwoven fabric C, and the thermoplastic resin fiber nonwoven fabric C contains 25% by mass or more and 100% by mass or less of polyolefin hyperbranched fibers.

4. The heat seal sheet according to claim 2, wherein the thermoplastic resin fiber nonwoven fabric layer C contains a low melting point polyester resin, polyester resin fibers, and a polyolefin resin.

5. A heat-sealable sheet as described in claim 2, wherein the thermoplastic resin fiber nonwoven fabric layer C is a layer derived from a thermoplastic resin fiber nonwoven fabric C, and the thermoplastic resin fiber nonwoven fabric C contains polyester resin fibers having a core-sheath structure.

6. A heat-sealable sheet according to claim 2, wherein the thermoplastic resin fiber nonwoven fabric layer C is a layer derived from a thermoplastic resin fiber nonwoven fabric C, and the thermoplastic resin fiber nonwoven fabric C is a nonwoven fabric obtained by a wet papermaking method.

7. The heat-sealable sheet according to claim 1, wherein the resin of the core portion of the thermoplastic resin fiber of a core-sheath structure used in the thermoplastic resin fiber nonwoven fabric layer A comprises at least one resin selected from the group consisting of polypropylene resin, polyester resin, and polyamide resin.

8. The heat seal sheet according to claim 1, wherein the thermoplastic resin fiber nonwoven fabric layer A is a nonwoven fabric layer derived from at least one nonwoven fabric selected from the group consisting of spunbonded nonwoven fabric, thermally bonded nonwoven fabric, chemically bonded nonwoven fabric, needle-punched nonwoven fabric, spunlaced nonwoven fabric, melt-blown nonwoven fabric, and wet-laid nonwoven fabric.

9. A heat seal sheet according to claim 1, wherein the thermoplastic resin fiber nonwoven fabric layer A is a layer derived from thermoplastic resin fiber nonwoven fabric a, and the thermoplastic resin fiber nonwoven fabric a contains thermoplastic resin fibers having a core-sheath structure in which the sheath is made of a polyolefin resin and the core is made of a resin having a melting point 20°C or more higher than that of the sheath.

10. The heat seal sheet according to claim 1, wherein the heat seal sheet is heat sealed to the polyethylene side of a laminated film of polyethylene terephthalate resin and polyethylene resin under conditions of 150°C, 0.2 MPa, and 1.0 second, and the peel strength of the heat seal sheet when peeled at 180° at a peel rate of 300 mm / min in accordance with JIS P 8113:2006 is 1.0 N / 15 mm or more and 15 N / 15 mm or less.

11. Basis weight: 30 g / m ２ 150g / m or more ２ 2. The heat seal sheet according to claim 1, wherein:

12. The heat sealable sheet according to claim 1, wherein the thermoplastic resin fiber nonwoven fabric layer A and the nonwoven fabric layer B are disposed adjacent to each other.

13. A sterilization package obtained by thermocompression bonding the heat seal sheet according to any one of claims 1 to 12 to a sterilization packaging material.

14. A method for producing a heat-sealable sheet according to any one of claims 1 to 12, comprising the following steps 1 to 3 in this order: Step 1: A step of preparing a thermoplastic resin fiber nonwoven fabric a and a nonwoven fabric b. Step 2: A step of stacking two or three or more layers of the thermoplastic resin fiber nonwoven fabric a and the nonwoven fabric b so as to include at least one layer each. Step 3: A step of heat-sealing the products obtained in Step 2.

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