Heat-seal sheet and sterilization package

Abstract

To provide a heat-seal sheet having suitable air permeability as sterilization paper, while retaining superior heat-sealability and easy peelability.SOLUTION: A heat-seal sheet comprises a breathable substrate and a heat-sealing layer provided on one surface of the breathable substrate, wherein the heat-sealing layer contains a thermoplastic resin and an antistatic agent comprising an imidazoline compound. It is preferable that the antistatic agent is present in an amount of 0.5 to 20 pts.mass relative to 100 pts.mass of the thermoplastic resin, and it is preferable that the Gurley air permeability is 700 seconds or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a heat-sealing sheet and a sterilized package.

Background Art

[0002] Instruments used in surgeries, treatments, etc. are sterilized before use while being stored in a sterilized package. Sterilization methods implemented in hospitals, etc. include, for example, after sealing the objects to be sterilized such as scalpels and forceps inside a sterilized package, using a gas sterilization method, a high-pressure steam sterilization method, a radiation sterilization method, etc. In the gas sterilization method, after reducing the pressure inside a pressure-resistant container containing the sterilized package, ethylene oxide gas (EOG), etc. is filled into the container, and thereby, the gas is allowed to penetrate into the sterilized package for sterilization. In the high-pressure steam sterilization method, the sterilized package is exposed to high-temperature steam using an autoclave, etc., and sterilization is performed by repeating pressure reduction and pressurization. In the radiation sterilization method, the sterilized package is irradiated with radiation for sterilization. Among these sterilization methods, due to the low cost required for sterilization and the simplicity of the work required for sterilization, the high-pressure steam sterilization method and the gas sterilization method are widely used.

[0003] On the other hand, a sterilized package containing the object to be sterilized is stored until used in a surgery, etc., and is opened when used in a surgery, etc. Therefore, so that even a doctor or operator wearing gloves can easily open it, the sterilized package has a property of being easily peelable or using a thin leaf body having a tear-openability that is easily tear-opened by mutually adhering two rectangular sheets or films, etc. of thin leaf bodies on the front and back. At the time of opening, generally, a peel-open method of peeling one thin leaf body from the other thin leaf body or a tearing method of tearing two thin leaf bodies is adopted.

[0004] When the adhered body is peeled from the sterilization paper in the above-described peel-open type sterilized package, paper powder, etc. caused by the destruction of the base material of the sterilization paper may scatter. Paper powder, etc. caused by the destruction of the base material becomes a factor for recontaminating the object to be sterilized such as medical instruments after sterilization. In a medical site that requires a high degree of cleanliness such as an operating room and the anteroom of the operating room, recontamination by paper powder may particularly become a problem.

[0005] Therefore, the required quality of the sterilization paper includes: (1) preventing the invasion of bacteria and having gas permeability that allows sterilization treatment; (2) having good heat sealability; (3) having easy peelability; and (4) suppressing scattered substances such as paper powder during peeling.

[0006] As an example of the above-described sterilization package, sterilization paper provided with a thermoplastic resin layer has been developed. For example, the configurations described in Patent Documents 1 to 8 are known. The sterilization package described in Patent Document 1 includes a thermoplastic resin layer on one side of a base paper. The sterilization package described in Patent Document 2 is obtained by coating a base paper containing aluminate with an acrylic copolymer. The sterilization package described in Patent Document 3 includes a thermoplastic resin layer containing a hollow polymer pigment on the surface of a base paper. The sterilization package described in Patent Document 4 is obtained by impregnating a low air permeability base paper of 10 seconds or less with an impregnating agent mainly composed of polyvinyl alcohol. Patent Document 5 includes a coating layer on at least one side of a base paper. The coating layer is mainly crosslinked polyvinyl alcohol and has a dry weight of 0.1 g / m 2 or more and 6 g / m 2 or less after coating. The sterilization package described in Patent Document 6 is obtained by impregnating a low air permeability base paper of 20 seconds or less with an impregnating agent mainly composed of an acrylic copolymer. The sterilization package described in Patent Document 7 provides a thermoplastic resin layer containing a polyolefin resin, an inorganic material, and a surfactant on one side of a base paper. Patent Document 8 is a heat seal sheet and a sterilization package provided with a heat fusion layer containing a thermoplastic resin and calcium fatty acid.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

[0008] A heat-seal sheet having good heat-sealability and easy-peelability may have insufficient air permeability. The present invention enables improvement of air permeability while maintaining good heat-sealability and easy-peelability. [Means for Solving the Problems]

[0009] As a result of intensive research, the present inventors have found that by using a combination of a heat-sealing agent and a specific antistatic agent in the heat-adhesive layer of a heat-seal sheet, a heat-seal sheet having appropriate air permeability as a sterilization paper can be obtained while maintaining good heat-sealability and easy-peelability.

[0010] The present invention for solving the above problems has the following configuration. [1] A heat-seal sheet comprising a breathable substrate and a heat-adhesive layer provided on one surface of the breathable substrate, the heat-adhesive layer containing a heat-sealing agent and an antistatic agent containing an imidazoline-based compound. [2] The heat-seal sheet according to [1], wherein the antistatic agent is 0.5 to 20 parts by mass with respect to 100 parts by mass of the thermoplastic resin. [3] The heat-seal sheet according to [1] or [2], having a Gurley air permeability measured in accordance with JIS P 8121:2012 of 700 seconds or less. [4] The heat-seal sheet according to any one of [1] to [3], wherein the breathable substrate contains a polyacrylamide resin. [5] The heat-sealing strength when peeling the heat-sealed part where the heat-adhesive layer of the heat-sealing sheet and the polyvinyl chloride film are heat-sealed under the heat-sealing conditions of 150°C, 0.2 MPa, and 1.0 second at a peeling speed of 300 mm / min in accordance with JIS K 6854-3:1999 is 0.5 to 15 N / 15 mm, which is the heat-sealing sheet described in any one of [1] to [4]. [6] A sterilization package having at least a part of the heat-sealing sheet described in any one of [1] to [5]. [7] A sterilization package having a heat-sealed part formed by overlapping at least a part of the heat-adhesive layer of the heat-sealing sheet described in any one of [1] to [5] and at least a part of another base material and performing thermocompression bonding.

Brief Description of the Drawings

[0011]

Figure 1

Explanation of Reference Numerals

[0012] S... Space, 11... Package, 11E... Heat-sealed part, 21... Heat-sealing sheet, 22... Breathable base material, 23... Heat-adhesive layer, 31... Adherend, 31E... One end.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, one embodiment of the heat-sealing sheet and the sterilization package will be described with reference to FIG. 1. [Package 11] The package 11 includes a heat-sealing sheet (sterilization paper) 21 and an adherend 31. The heat-sealing sheet 21 includes a breathable base material 22 and a heat-adhesive layer 23 located on one surface of the breathable base material 22.

[0014] The adherend 31 is, for example, packaging paper, laminated paper, film, a molded container for sterilization, or the like. The material constituting the adherend 31 is at least one resin selected from the group consisting of polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, polyvinyl chloride, polyvinylidene chloride, polystyrene, ethylene-vinyl acetate copolymer resin, and ethylene-acrylic copolymer resin. Further, the adherend 31 may be constituted of a composite material in which these resins and other materials are laminated. The material constituting the adherend 31 may be a mixture of two or more different resins. The adherend 31 can also be embodied as a laminate in which two or more different resins form separate layers.

[0015] A sterilized package, which is an embodiment of the use of the sterilized paper of the present invention, will be described. The package 11 includes a heat-sealing portion 11E. The heat-sealing portion 11E has an annular shape in which the heat-sealing sheet 21 and the adherend 31 are heat-sealed to each other.

[0016] The package 11 includes a space S surrounded by the heat-sealing portion 11E between the heat-sealing sheet 21 and the adherend 31. The space S included in the sterilized package 11 is a space for accommodating an object to be sterilized such as a medical instrument. The sterilized package 11, for example, accommodates the object to be sterilized in the space S and, in that state, is subjected to sterilization treatments such as autoclaving, ethylene oxide gas (EOG) sterilization, electron beam sterilization, and gamma ray sterilization. When gas sterilization is performed, the sterilizing gas penetrates into the inside of the package 11 through the heat-sealing sheet 21. After the sterilization treatment, when the object to be sterilized is used, one end portion 31E of the adherend 31 separated from the heat-sealing sheet 21 is pulled up with respect to the air-permeable base material 22, and the adherend 31 is peeled off from the heat-sealing sheet 21. Then, the space S is released, and the object to be sterilized is exposed to the space where the sterilized package 11 is located. Note that the heat-sealing layer 23 can be formed on one surface of the air-permeable base material 22 where the adherend 31 is located and on the surface opposite to that surface.

[0017] [Heat-sealing layer 23] The heat-sealing layer 23 contains at least a heat-sealing agent and an antistatic agent containing an imidazoline-based compound. As the heat-sealing agent, a thermoplastic resin containing a polyolefin structure is preferable. Examples of the polyolefin structure include polyethylene and polypropylene. Further, copolymers of these polyolefins with one or more other copolymerizable monomers (for example, copolymers with (meth)acrylic acid or (meth)acrylic acid esters or vinyl acetate) can also be preferably applied. Commercially available products of the thermoplastic resin that can be used in the present invention include the Dick Seal E series manufactured by DIC Graphics Co., Ltd., the Chem Pearl series manufactured by Mitsui Chemicals, Inc., and the like. Since the heat-sealing layer 23 contains an antistatic agent containing a heat-sealing agent and an imidazoline-based compound, good heat-sealing properties with the adherend and easy-peel properties after heat adhesion can be obtained. In particular, even when the heat-sealing sheet is heat-sealed after being stored in a high-temperature environment, the heat-sealing sheet of the present invention can maintain good easy-peel properties. In addition, in the case where the adherend is polyvinyl chloride, the conventional heat-sealing sheet may have insufficient heat-adhesion strength or may not obtain easy-peel properties. However, the heat-sealing sheet of the present invention can obtain good heat-adhesion properties and easy-peel properties even when the adherend is polyvinyl chloride.

[0018] In the present invention, an antistatic agent containing an imidazoline-based compound is used. However, within a range that does not impair the effects of the present invention, quaternary ammonium salts, pyridinium salts, cationic antistatic agents having cationic functional groups such as primary, secondary, and tertiary amino groups, anionic antistatic agents having anionic functional groups such as sulfonates, sulfate esters, phosphonates, and phosphate esters, amphoteric antistatic agents such as alkyl betaines and their derivatives, alanine and their derivatives, nonionic antistatic agents such as amino alcohols and their derivatives, and further, ion-conductive polymers obtained by polymerizing or copolymerizing monomers having the above cationic, anionic, and amphoteric ion conductivity can also be used. The antistatic agent can be used alone or in a mixture of two or more. Among these, it is preferable to contain an amphoteric antistatic agent.

[0019] The antistatic agent is preferably 0.5 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, and even more preferably 0.5 to 7 parts by mass with respect to 100 parts by mass of the thermoplastic resin. By setting it to 20 parts by mass or less, a decrease in peel strength can be suppressed. By setting it to 0.5 parts by mass or more, the effects of the present invention can be obtained.

[0020] The heat - adhesive layer may contain wax. Examples of the wax include animal - derived natural oil - based waxes such as paraffin wax and carnauba wax, and synthetic waxes such as polyethylene. The waxes can be used singly or in a mixture of two or more.

[0021] In the heat - adhesive layer, other materials can be included as long as the effects of the present invention are not impaired. Specifically, examples include auxiliary agents such as dispersants, water - retaining agents, and defoaming agents, and various inorganic pigments and organic pigments.

[0022] The heat - adhesive layer 23 is obtained, for example, by applying a heat - adhesive layer coating on one surface (the upper surface in the figure) of the breathable base material 22 and drying the applied heat - adhesive layer coating. The heat - adhesive layer coating contains a thermoplastic resin, an antistatic agent, other materials, and a liquid medium. Note that the heat - adhesive layer can also be provided with another heat - adhesive layer 23 on the surface opposite to one surface of the breathable base material 22. The heat - adhesive layer coating can be an aqueous coating or a solvent - based coating.

[0023] For the method of applying the heat - adhesive layer, various known wet - coating methods can be used. For example, an on - machine size press device of a paper - making machine, a transfer roll coater (such as a sim - size coater, a gate roll coater, etc.), a spray device, etc. can be used. Also, in an off - machine type device, general coating devices such as a blade coater, an air knife coater, a roll coater, a reverse roll coater, a sim - size coater, a gate roll coater, a bar coater, a curtain coater, a slot die coater, a gravure coater, a champlex coater, a brush coater, a two - roll coater, a bill blade coater, a short dwell coater, etc. can be used. From the viewpoint of reliably suppressing equipment contamination, it is preferable to use an air dryer or an infrared heater that does not come into contact with the coating surface for the drying equipment of the heat - adhesive layer paint. Incidentally, it is also possible to use a direct contact method with the coating surface by a cylinder dryer for the drying equipment of the heat - adhesive layer paint.

[0024] The coating amount of the heat - adhesive layer paint is, for example, 0.1 g / m 2 or more and 20 g / m 2 or less, preferably 0.5 g / m 2 or more and 12 g / m 2 or less, and more preferably 1.0 g / m 2 or more and 7.0 g / m 2 and is adjusted within the following range. When the coating amount of the heat - adhesive layer paint is 0.1 g / m 2 or more, it becomes possible to ensure the adhesive strength required for the heat - adhesive layer 23. Also, when the coating amount of the heat - adhesive layer paint is 20 g / m 2 or less, the air permeability required in the sterilization treatment of the sterilized package is ensured.

[0025] [Air - permeable substrate 22] The breathable substrate 22 is paper or a non-woven fabric. For example, the paper substrate includes paper and an undercoat layer provided as needed. The paper substrate is obtained by papermaking of a papermaking raw material containing pulp slurry. The pulp used in the pulp slurry is, for example, wood pulp or non-wood pulp. The wood pulp is at least one selected from the group consisting of, for example, softwood pulp and hardwood pulp. The cooking method and bleaching method of the wood pulp are not particularly limited. The non-wood pulp is at least one selected from the group consisting of, for example, hemp pulp, kenaf pulp, and bamboo pulp. The pulp slurry can contain materials other than pulp fibers, such as rayon fibers, nylon fibers, and other heat-fusible fibers, as auxiliary materials.

[0026] The pulp slurry is obtained by beating the pulp in the presence of water. As the beating method of the pulp and the beating device used therefor, for example, a double disk refiner (DDR) with high beating efficiency is preferably used. The beating of the pulp is carried out so that the freeness of the pulp (hereinafter also referred to as "standard freeness") measured according to JIS P 8121-2:2012 is 250 mL or more and 700 mL or less, more preferably 250 mL or more and 600 mL or less, and even more preferably 300 mL or more and 500 mL or less. When the standard freeness of the pulp is 250 mL or more, it is possible to ensure the air permeability of the paper. Also, when the standard freeness of the pulp is 250 mL or less, it is possible to improve the strength of the paper and improve the easy peelability.

[0027] Generally, regarding the relationship between beating of pulp and paper strength, when beating is not advanced much, it is difficult to obtain paper strength. The reason is considered to be that the entanglement between pulp fibers is weak and the number of fiber-to-fiber bond (hydrogen bond) points is small. Paper strength improves by advancing beating to a certain extent. On the other hand, when beating is advanced, the entanglement between pulp fibers increases and the number of fiber-to-fiber bond points increases, so paper strength can be obtained, but the voids between fibers decrease and the air permeability of the paper base material decreases. In this regard, if the standard freeness of the pulp is in the range of 250 mL or more and 700 mL or less, it is possible to sufficiently increase the paper strength while maintaining the air permeability of the paper base material and thus the air permeability of the air-permeable base material 22. As a result, it becomes possible to further improve the easy-peel property of the heat-seal sheet 21.

[0028] The pulp slurry obtained by beating can, for example, use a papermaking raw material prepared by adding various internal additives for papermaking. The internal additives are, for example, various fixing agents such as sizing agents, paper strength enhancers, wet paper strength enhancers, sulfate bands, cationized starches, etc. In addition to these, as internal additives, it is also possible to arbitrarily blend a yield improver, an antifoaming agent, a filler, a coloring agent, etc. with respect to the papermaking raw material.

[0029] The paper strength enhancer contains at least one selected from, for example, polyacrylamide resins, cationized starches, and polyvinyl alcohols. Among these paper strength enhancers, by internally adding a polyacrylamide resin-based paper strength enhancer, the strength of the breathable base material can be more effectively improved, and the easy peelability can be further enhanced. Further, in order to exhibit the paper strength enhancing effect after adding the paper strength enhancer, it is preferably that the mass average molecular weight is 2 million (Mw) or more. Further, from the viewpoint of obtaining an appropriate viscosity during the operation of adding the paper strength enhancer and easy addition, it is preferably that the mass average molecular weight is 10 million (Mw) or less. The mass average molecular weight of the polyacrylamide resin is a polyethylene oxide conversion value measured by gel permeation chromatography (GPC). Further, as the polyacrylamide resin as the paper strength enhancer, for example, anionic, cationic, amphoteric, or nonionic polyacrylic resins can be used, and among these, it is particularly preferable to use an amphoteric polyacrylamide resin. The sizing agent contains at least one selected from the group consisting of, for example, alkenyl succinic acid, alkyl ketene dimer, and rosin. Further, the wet paper strength enhancer contains at least one selected from the group consisting of, for example, epichlorohydrin resin and melamine resin.

[0030] It is also possible to apply a primer, which is a coating liquid containing a polyacrylamide resin, to at least one surface of the breathable base material 22. By applying the primer, it is possible to further enhance the easy peelability. When the primer is applied to only one surface of the base material, the primer is applied to the surface on which the heat adhesive layer of the breathable base material is provided. The primer may be applied to both one surface of the base material and the surface opposite thereto.

[0031] The paper base material used for the breathable base material 22 is obtained, for example, by papermaking a prepared papermaking raw material by a conventional method. The basis weight of the breathable base material 22 can be appropriately set according to the basis weight of the paper base material and the coating amount of the primer.

[0032] The undercoat agent contains a polyacrylamide resin. The polyacrylamide resin is a polymer repeating (meth)acrylamide units. (Meth)acrylamide is a general term for acrylamide and methacrylamide. The polyacrylamide resin may have either acrylamide units or methacrylamide units, or both. The polyacrylamide resin may have other units other than (meth)acrylamide units.

[0033] The polyacrylamide resin contained in the undercoat agent is, for example, an anionic polyacrylamide resin, a cationic polyacrylamide resin, an amphoteric polyacrylamide resin, or a nonionic polyacrylamide resin. These undercoat agents are used as paper strengthening agents in the paper-making field. The polyacrylamide resin may be used alone or in combination of two or more. From the viewpoint of easy availability, an anionic polyacrylamide resin is preferred.

[0034] The anionic polyacrylamide resin contains, for example, anionic functional groups such as carboxy groups, sulfonic acid groups, phosphoric acid groups, or salts thereof. The anionic polyacrylamide resin is, for example, a copolymer of (meth)acrylamide and an anionic functional group-containing monomer such as acrylic acid, or a partial hydrolyzate of poly(meth)acrylamide.

[0035] The mass average molecular weight (Mw) of the polyacrylamide resin contained in the undercoat agent is preferably 50,000 or more and 2,000,000 or less, more preferably 50,000 or more and 500,000 or less, and even more preferably 50,000 or more and 300,000 or less. If the mass average molecular weight of the polyacrylamide resin contained in the undercoat layer is 50,000 or more and 2,000,000 or less, the effect of suppressing the fluffing on the surface of the breathable substrate 22 due to the peeling of the adherend 31 is more excellent. If the mass average molecular weight is 50,000 or more, the effect of suppressing the fluffing on the surface of the breathable substrate 22 when the thermal adhesive layer 23 peels off is easily obtained. If the mass average molecular weight is 2,000,000 or less, the low viscosity required for the application of the undercoat agent can be sufficiently obtained, and the preparation and application of the undercoat agent are easy. In addition, the concentration of the polyacrylamide resin contained in the undercoat agent can be increased within a desired viscosity range, and a desired coating amount can be easily obtained. The mass average molecular weight of the polyacrylamide resin is the polyethylene oxide conversion value measured by gel permeation chromatography (GPC).

[0036] The liquid medium contained in the undercoat agent preferably dissolves the polyacrylamide resin, for example, water. The undercoat agent can also contain other components other than the polyacrylamide resin as long as the easy peelability is not impaired. The other components are, for example, water-soluble polymer compounds, aqueous polymer compounds, release agents, defoaming agents, dispersants, wetting agents, colored dyes, colored pigments, and white pigments. Any one of these may be used alone, or two or more kinds may be used in combination. Examples of the water-soluble polymer compound include starch, modified starch, polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, diisobutylene-maleic anhydride copolymer salt, and styrene-maleic anhydride copolymer salt. Examples of the aqueous polymer compound include styrene-butadiene copolymer emulsion, acrylic ester copolymer emulsion, urethane resin, urea resin, styrene-acrylic resin emulsion, and ethylene-acrylic resin emulsion.

[0037] The content (concentration) of the polyacrylamide resin contained in the primer is preferably 50% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 100% by mass or less, based on the total solid content (100% by mass) in the primer. If the content of the polyacrylamide resin is 50% by mass or more, the easy peelability of the sterilized paper 21 can be further enhanced. The total solid content is the total amount obtained by removing the liquid medium from the primer, and when other components other than the polyacrylamide resin are included, it is the sum of the polyacrylamide resin and other components.

[0038] The coating amount of the primer on the breathable substrate is appropriately set according to the content of the polyacrylamide resin contained in the primer. The coating amount of the primer on the surface of the breathable substrate on the side where the heat adhesive layer 23 is located, in terms of the amount of the polyacrylamide resin, is 0.05 g / m 2 or more and 20 g / m 2 or less, preferably 0.1 g / m 2 or more and 15 g / m 2 or less, more preferably 0.2 g / m 2 or more and 10 g / m 2 or less. If the coating amount of the polyacrylamide resin is 0.05 g / m 2 or more, when peeling the adherend 31 from the sterilized paper 21, the breathable substrate 22 and the heat adhesive layer 23 are peeled well, and fluffing on the surface of the breathable substrate 22 due to this peeling and breakage of the breathable substrate 22 are less likely to occur. Also, if the coating amount of the polyacrylamide resin is 20 g / m 2 or less, when heat-sealing the sterilized paper 21, uneven adhesion can be suppressed, and for example, it can be applied substantially uniformly over the entire surface of the breathable substrate 22 on the side where the heat adhesive layer 23 is located. On the other hand, the primer may be applied, for example, on the surface of the breathable substrate 22 on the side where the heat adhesive layer 23 is provided, so as to have a predetermined pattern.

[0039] The components of the undercoat layer may also include components other than the polyacrylamide resin. The other components are at least one selected from the group consisting of, for example, starch, resins such as polyvinyl alcohol and styrene-butadiene resin, and pigments such as kaolin, talc, calcium carbonate, and white carbon. Note that the polyacrylamide resin contained in the undercoat agent applied to one side may be, for example, the same as the polyacrylamide resin contained in the undercoat agent applied to the other side, or they may be different from each other. When applying the undercoat agent to the other side of the paper substrate, the coating amount of the undercoat agent is, for example, in terms of solid content, 0.01 g / m 2 or more and 20 g / m 2 or less, and preferably 0.01 g / m 2 or more and 5 g / m 2 or less, more preferably 0.01 g / m 2 or more and 3 g / m 2 or less, and even more preferably 0.1 g / m 2 or more and 2 g / m 2 or less. If the coating amount of the undercoat agent is 20 g / m 2 or less, the air permeability of the sterilized paper 21 can be kept good. Also, by adjusting the coating amount of the undercoat agent on the other side of the paper substrate in this way, it becomes easy to appropriately adjust the concentration of the polyacrylamide resin on one side, the other side, and in the middle between one side and the other side of the paper substrate. Note that when applying the undercoat agent to each of one side and the other side of the paper substrate, for example, it is preferable that the ratio of the coating amount on one side to the coating amount on the other side is 3:7 to 7:3. With such a ratio of the coating amounts, it becomes even easier to make the concentration of the polyacrylamide resin in the substrate larger on one side and the other side of the substrate than in the middle therebetween. From the viewpoint of reducing the manufacturing cost of the sterilized paper 21, the case where the undercoat agent is not applied to the other side of the paper substrate can be adopted as an example of a preferable embodiment.

[0040] As the method for applying the undercoat agent, various known wet coating methods can be used. For example, an on-machine size press device of a paper machine, a transfer roll coater (such as a simcizer, a gate roll coater, etc.), a spray device, etc. can be used as the method for applying the undercoat agent. Also, in the case of an off-machine type device, general coating devices such as a blade coater, an air knife coater, a roll coater, a reverse roll coater, a simcizer, a gate roll coater, a bar coater, a curtain coater, a slot die coater, a gravure coater, a champlex coater, a brush coater, a two-roll coater, a bill blade coater, a short dwell coater, etc. can be used. From the viewpoint of improving operability and productivity, it is preferable to use an on-machine type for the application and drying of the undercoat agent. As the type of paper machine for papermaking the paper base material, those equipped with a coating machine on the machine, such as a long wire paper machine, a short wire paper machine, a cylinder paper machine, etc. are preferable. The content of the polyacrylamide resin in the breathable base material 22 is, for example, 1.0 mass% or more and 30 mass% or less.

[0041] The basis weight of the breathable base material 22 is, for example, 30 g / m 2 or more, preferably 40 g / m 2 or more, more preferably 45 g / m 2 or more. If the basis weight of the breathable base material 22 is 30 g / m 2 or more, it is easy to obtain the strength in the breathable base material 22 that can withstand peeling the adherend 31 from the breathable base material 22, and breakage of the breathable base material 22 during peeling is less likely to occur. Also, since the generation of pinholes can be suppressed, it is preferable from the viewpoint of bacterium barrier property.

[0042] The upper limit of the basis weight of the breathable base material 22 is not particularly limited, but from the viewpoint of obtaining breathability during the sterilization treatment, it is preferably 300 g / m 2 or less, more preferably 250 g / m 2 or less, still more preferably 200 g / m 2 or less. The basis weights of the breathable base material 22 and the paper base material are measured in accordance with, for example, JIS P 8124:2011.

[0043] The density of the breathable substrate 22 is, for example, 0.60 g / cm 3 or more and 1.20 g / cm 3 or less, preferably 0.70 g / cm 3 or more and 1.10 g / cm 3 or less. If the density of the breathable substrate 22 is 0.60 g / cm 3 or more, it is easy to obtain a strength that can withstand easy peel, and breakage of the breathable substrate 22 during peeling is less likely to occur. If the density of the substrate 22 is 1.20 g / cm 3 or less, air permeability can be maintained. The density of the breathable substrate 22 is obtained by calculation from the measured values of thickness and basis weight, for example, by measuring the thickness in accordance with JIS P 8118:1998.

[0044] [Heat-seal sheet 21] The heat-seal sheet 21 preferably has a Gurley air permeability of 700 seconds or less, more preferably 500 seconds or less, and particularly preferably 200 seconds or less, as measured in accordance with JIS P 8117:2009. If the sterilization paper 21 has a Gurley air permeability within this range, the air permeability of the sterilization paper 21 can be effectively improved. On the other hand, the lower limit value of the Gurley air permeability can be, for example, 5 seconds. The Gurley air permeability of the sterilization paper 21 can be adjusted, for example, by appropriately selecting the freeness of the pulp, the basis weight of the breathable substrate 22, the coating amount of the undercoat agent, etc.

[0045] The heat-sealing surface of the sterilization paper 21, which is the surface of the heat-adhesive layer 23, is preferably, for example, 50 seconds or more as the Gurley smoothness measured in accordance with JIS P 8155:2010, because it can reduce the variation in seal strength and can also cope with short-time heating. As a method for adjusting the smoothness of the heat-sealing surface, the breathable substrate 22 may be smoothed by various known methods, or the smoothing treatment may be performed after forming the heat-adhesive layer 23.

[0046] The sterilized package 11 obtained by thermally bonding the heat-sealing sheet 21 and the adherend 31 preferably has a peel strength of, for example, 0.5 N / 15 mm or more and 15 N / 15 mm or less when the adherend 31 is peeled at 180° at a peel rate of 300 mm / min according to JIS P 8113:2006. If the sterilized paper 21 has a peel strength within this range, a sterilized package 11 with an extremely excellent balance between easy peelability and thermal adhesion can be obtained. Further, from the viewpoint of more effectively improving the balance between easy peelability and thermal adhesion, it is more preferable that the peel strength is 0.5 N / 15 mm or more and 7.0 N / 15 mm or less, and even more preferably 1.0 N / 15 mm or more and 4.0 N / 15 mm or less. The peel strength can be appropriately adjusted, for example, by selecting the type and coating amount of the thermal adhesive layer 23.

[0047] [Function] The heat-sealing sheet 21 is excellent in easy peelability and temperature stability by containing a thermoplastic resin and an antistatic agent in the thermal adhesive layer 23. For example, after the heat-sealing sheet 21 is thermally bonded to the film-shaped adherend 31, when the heat-sealing sheet 21 is peeled from the adherend 31, the thermal adhesive layer 23 remains attached to the adherend 31 and is easily peeled from the interface with the breathable base material 22, and the breathable base material 22 is not easily torn. Further, since the thermal adhesive layer 23 can be visually recognized on the adherend 31, it can be easily confirmed that the adhesion is uniform before peeling. Further, the heat-sealing sheet 21 maintains its easy peelability even when stored in a high-temperature environment before being thermally bonded, and due to the stabilization of the easy peelability, the fluffing and peeling of paper pieces are stably suppressed, so that lint falling off from the fluffed portion and peeled paper pieces can be prevented from adhering to the adherend 31 or the contained object. As a result, it is possible to provide a heat-sealing sheet 21 that suppresses fluffing during peeling and can be used in an operating room with a high degree of cleanliness.

[0048] The sterilization method of the sterilized package 11 includes several sterilization methods such as autoclave, ethylene oxide gas (EOG) sterilization, and gamma-ray sterilization. In particular, EOG sterilization requires gas replacement after sterilization. The heat-sealing sheet 21 can be made to have excellent air permeability depending on the freeness of the pulp used in the production of the breathable base material 22 and the basis weight of the breathable base material 22. By increasing the air permeability of the heat-sealing sheet 21, the time for replacing the sterilization gas with air after sterilization can be shortened. Therefore, it is possible to realize a heat-sealing sheet 21 that is particularly suitable for EOG sterilization. Thus, the heat-sealing sheet 21 is extremely useful in practice, having an excellent balance between easy peelability and air permeability.

[0049] As described above, the heat-sealing sheet 21 is not limited to the above-described embodiment. Each configuration in the above-described embodiment and combinations thereof are merely examples, and additions, omissions, substitutions, and other modifications of the configuration are possible without departing from the spirit of the present invention. For example, another layer may be provided between the breathable base material 22 and the heat-adhesive layer 23 of the heat-sealing sheet 21. Examples of the other layer include a water vapor barrier layer, an oxygen barrier layer, a printing layer, a printing suitability improvement layer, an overprint layer, and a light-shielding layer. The other layer located between the base material 22 and the heat-adhesive layer 23 may be one layer or two or more layers. Note that, without departing from the spirit of the present invention, a printing layer may be provided on both surfaces of the breathable base material 22. An overprint layer may be further provided on the printing layer.

Example

[0050] An example of the above-described embodiment will be described below. <Example 1> [Production of breathable substrate 22] Hardwood bleached kraft pulp (LBKP) was beaten by a double disc refiner (DDR) to obtain a pulp slurry having a Canadian standard freeness of 400 mL as described in JIS P 8121-2: 2012. Then, an internal additive was added to the pulp slurry to obtain a papermaking raw material. The internal chemicals, in terms of the amount added on an absolute dry basis relative to the mass of pulp, were 0.5% aluminum sulfate, 0.05% alkenyl succinic acid sizing agent (Fibran 81K, National Starch) previously dispersed with cationic starch (Pillar 3YK, Pillar Starch), 0.7% amphoteric polyacrylamide resin paper strength enhancer (PAM) (product name: Polystron OFT-3, Arakawa Chemical Industries, mass average molecular weight 3 million), and 0.4% polyamine-polyamide epichlorohydrin resin wet strength enhancer (WS4024, Seiko PMC). Next, the raw paper was made into base paper on a Fourdrinier papermaking machine, and then the following paint A was applied to both sides at 29 mL / m using a size press coater attached to the papermaking machine. 2 After coating and drying, the Oken smoothness of the base paper surface, measured in accordance with JIS P 8155:2010 using an on-machine calendar attached to the papermaking machine, is adjusted to 100 seconds, and the basis weight is 60 g / m 2 and its density is 0.8g / cm 3 Thus, the breathable substrate 22 of Example 1 was obtained. [Paint A] An aqueous solution of anionic polyacrylamide resin (mass average molecular weight 200,000) (Polymerset (registered trademark) 512 manufactured by Arakawa Chemical Industries, Ltd. was diluted with water to adjust the anionic polyacrylamide resin concentration to 7 mass %).

[0051] [Production of heat seal sheet] 100 parts by mass of olefin-based water-based emulsion (manufactured by Mitsui Chemicals) as a thermoplastic resin and 1 part by mass of Electrostripper AC (manufactured by Kao Corporation) as an antistatic agent containing an imidazoline-based compound were adjusted to a solid content concentration of 25%, to obtain a thermal adhesive layer coating material. Next, a coating amount of 3 g / m2 after drying was applied to one side of the breathable substrate 22 of Example 1 using a bar coater. 2The thermal adhesive layer paint was applied and dried so as to form the thermal adhesive layer 23 of Example 1. In this way, a heat seal sheet 21 including the breathable substrate 22 of Example 1 and the thermal adhesive layer 23 of Example 1 was obtained.

[0052] Example 2 A heat seal sheet 21 of Example 2 was produced in the same manner as in Example 1, except that in the production of the heat seal sheet 21 of Example 1, the amount of Electrostripper AC was changed to 3 parts by mass.

[0053] Example 3 A heat seal sheet 21 of Example 3 was produced in the same manner as in Example 1, except that in the production of the heat seal sheet 21 of Example 1, the amount of Electrostripper AC was changed to 5 parts by mass.

[0054] Comparative Example 1 The heat seal sheet 21 of Comparative Example 1 was produced in the same manner as in Example 1, except that Electrostripper AC was not used.

[0055] <Comparative Example 2> The heat seal sheet 21 of Comparative Example 2 was produced in the same manner as in Example 1, except that in the production of the heat seal sheet 21 of Example 1, the antistatic agent was changed to another antistatic agent, Electrostripper F (manufactured by Kao Corporation, an anionic antistatic agent containing a phosphate ester salt).

[0056] <Evaluation> The following measurements and evaluations were carried out for each of the heat seal sheets of Examples 1 to 4 and Comparative Examples 1 to 3. Table 1 shows the formulation of the thermal adhesive layer of each heat seal sheet and the results of the measurements and evaluations.

[0057] [Oken air permeability measurement] The Oken air permeability of each sterilized paper was measured according to JIS P 8117: 2009. If the Oken air permeability is 700 seconds or less, it can be said to be suitable as a sterilization packaging material.

[0058] [Adhesion to the adherend] A polyvinyl chloride film (manufactured by Mitsubishi Chemical Corporation, C-416) was used as the adherend. The heat-sealing sheet was overlaid so that the surface on the heat-adhesive layer side was in contact with the film, and heat-pressed under the heat-adhesive conditions of 150 °C, 0.2 MPa, and 1.0 second using a hot press tester to obtain a heat-adhesive sample. In addition, in order to secure a portion to be chucked by a tensile tester in the "Measurement of peel strength" described later, a portion where the adherend and the sterilization paper were not heat-adhered was left at the end of the heat-adhesive sample.

[0059] [Measurement of peel strength] The heat-adhesive sample obtained in the above "Adhesion to the adherend" was cut to be able to correspond to a measurement clearance with a width of 15 mm and a length of 100 mm to prepare a sample for measuring peel strength. The peel strength (N / 15 mm) of each sample for measuring peel strength was measured in accordance with JIS K 6854-3:1999. At this time, using a tensile tester (model: Tensilon RTC-1250A, manufactured by Orientec Co., Ltd.), one end portion 31E of the adherend and one end portion of the heat-sealing sheet 21 were chucked and measured at a peel rate of 300 mm / min by the 180-degree peel method. In addition, when measuring the peel strength, those in which the substrate was broken instead of peeling at the heat-adhesive layer or the interface between the heat-adhesive layer and the adherend were recorded as "substrate breakage" instead of the measured value. If the peel strength is 0.5 N / 15 mm or more, there is no practical problem as a sterilized package. Also, if the peel strength is 6.0 N / 15 mm or less, it can be said that it is suitable for easy peelability.

[0060] [Measurement of temperature stability] After storing the heat-sealing sheets of Examples 1 to 3 and Comparative Example 1 under the following two conditions, the measurement was carried out by the method described in the above "Measurement of peel strength". (Condition 1) Store in a thermostat at 60 °C for 30 days (Condition 2) Store in a thermostat at 80 °C for 1 day. If the peel strength is maintained in the range of 0.5 to 4.5 N / 15 mm after storage under Condition 1, it can be said that the durability under high-temperature environment is excellent. If the peel strength after storage under Condition 1 and the peel strength after storage under Condition 2 are both maintained in the range of 0.5 to 4.5 N / 15 mm, it can be said that the durability under high-temperature environment is very excellent.

[0061]

Table 1

[0062] As shown in Table 1, the heat-seal sheets of Examples 1 to 3 maintained the peel strength in the range of 0.5 to 4.5 N / 15 mm before and after storage under the above Conditions 1 and 2, and it was confirmed that they were excellent in easy peelability and temperature stability of easy peelability. On the other hand, the heat-seal sheet of Comparative Example 1 had no easy peelability immediately after production, and the easy peelability remained impaired even after storage in a high-temperature environment. Also, the heat-seal sheet of Comparative Example 2 lost its easy peelability after storage under the above Conditions 1 and 2.

[0063] As described above, according to the above embodiment, the following effects can be obtained. By containing an antistatic agent containing a thermoplastic resin and an imidazoline-based compound in the heat-adhesive layer, when the heat-seal sheet and the adherend are heat-sealed, sufficient adhesive strength can be obtained for packaging the contents, and at the time of peeling, one can be easily peeled from the other with an appropriate force between the base material and the heat-adhesive layer (easy peelability). Furthermore, even after storing the heat-seal sheet before heat adhesion in a high-temperature environment and then heat-sealing the heat-seal sheet and the adherend, the easy peelability can be maintained.

Industrial Applicability

[0064] The present invention can provide an excellent heat-seal sheet having heat-sealability and easy peelability, and capable of maintaining the easy peelability even when the heat-seal sheet and the adherend are heat-sealed after storing the heat-seal sheet before heat adhesion in a high-temperature environment.

Claims

1. A breathable substrate, and a heat-sealing sheet provided with a heat-adhesive layer on one surface of the breathable substrate, the heat-adhesive layer containing an antistatic agent containing a thermoplastic resin and an imidazoline-based compound.

2. The heat-sealing sheet according to Claim 1, wherein the antistatic agent is 0.5 to 20 parts by mass with respect to 100 parts by mass of the thermoplastic resin.

3. The heat-sealing sheet according to Claim 1 or 2, wherein the Gurley air permeability measured in accordance with JIS P 8121:2012 is 700 seconds or less.

4. The heat-sealing sheet according to any one of Claims 1 to 3, wherein the breathable substrate contains a polyacrylamide resin.

5. The 180° peel strength when peeling the heat-adhesive portion obtained by heat-adhering the heat-adhesive layer of the heat-sealing sheet and a polyvinyl chloride film under heat-adhesive conditions of 150°C, 0.2 MPa, and 1.0 second at a peel rate of 300 mm / min in accordance with JIS K 6854-3:1999 is 0.5 to 15 N / 15 mm. The heat-sealing sheet according to any one of Claims 1 to 4.

6. A sterilization package having at least a part of the heat-sealing sheet according to any one of Claims 1 to 5.

7. A sterilization package having a heat-adhesive portion obtained by overlapping and thermocompression-bonding at least a part of the heat-adhesive layer of the heat-sealing sheet according to any one of Claims 1 to 5 and at least a part of another substrate.

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