Mount for skin pack and skin pack package

Abstract

To provide a mount for a skin pack having good recycling properties and showing good strength even when wetted with water.SOLUTION: A mount for skin packaging having a thermoplastic resin layer on both surfaces of a paper base material, wherein the paper base material contains pulp, a sizing agent, and a polyacrylamide-based resin, a total content of the sizing agent and the polyacrylamide-based resin with respect to 100 parts by mass of the pulp is 0.15 parts by mass or more and 1.20 parts by mass or less, and a ratio by mass of a content of the sizing agent to a content of the polyacrylamide-based resin is 2.5 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a skin pack liner and a skin pack packaging body. [Background technology]

[0002] In the food packaging field, skin packs are used to maintain the freshness and long shelf life of food. The food is placed on a tray, and the tray and food are vacuum-packed using a barrier film. Skin packs, especially when used to package meat, can prevent dripping (water that escapes from food during storage), which can extend the shelf life and reduce food waste, so they are increasingly being used.

[0003] Patent Document 1 discloses a backing sheet including an innermost layer, a barrier layer, a bonding layer, a paper layer, and an outermost layer as a base material constituting a skin pack package. Contents such as fresh food and processed food are packaged in this skin pack package. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-123406 Summary of the Invention [Problem to be solved by the invention]

[0005] Depending on the contents, skin pack packages may be stored in a cold place such as a refrigerator. In this case, condensation occurs on the skin pack package, causing water to penetrate the backing paper, resulting in a decrease in the strength of the backing paper. In Patent Document 1, the outermost layer is made of a material with waterproof properties, thereby imparting water resistance to the mount. However, although this mount can maintain its strength if water adheres to the outermost layer, if water adheres to the edge surface, water will penetrate through the paper layer exposed to the edge surface, reducing its strength. In addition, recyclability is also required for mounts for skin packs.

[0006] An object of the present disclosure is to provide a skin pack mount that has good recyclability and exhibits good strength even when wet. [Means for solving the problem]

[0007] As a result of extensive research, the inventors of the present disclosure have found that in a skin pack liner having a thermoplastic resin layer on both sides of a paper base material, the above-mentioned problems can be solved by setting the contents and content ratio of the sizing agent and polyacrylamide resin in the paper base material within specific ranges.

[0008] [1] A skin pack mount having a thermoplastic resin layer on both sides of a paper base material, The paper base material contains pulp, a sizing agent, and a polyacrylamide resin, and satisfies the following requirements (A) and (B): (A) The total content of the sizing agent and the polyacrylamide resin relative to 100 parts by mass of the pulp is 0.15 parts by mass or more and 1.20 parts by mass or less. (B) The mass ratio of the content of the sizing agent to the content of the polyacrylamide resin is 2.5 or less. [2] The skin pack mount according to [1], wherein the paper substrate satisfies requirements (C) and (D). (C) The content of the sizing agent relative to 100 parts by mass of the pulp is 0.08 parts by mass or more and 0.80 parts by mass or less. (D) The content of the polyacrylamide resin relative to 100 parts by mass of the pulp is 0.05 parts by mass or more and 0.60 parts by mass or less. [3] The skin pack mount according to [1] or [2], wherein the ratio of the paper base material to the total mass of the skin pack mount is 50% by mass or more and 90% by mass or less. [4] The skin pack liner according to any one of [1] to [3], wherein the kink index of the pulp is 2,000 [1 / m] or more and 3,500 [1 / m] or less. [5] The skin pack mount has a basis weight of 300 g / m 2 The skin pack mount according to any one of [1] to [4] above. [6] The skin pack mount according to any one of [1] to [5], wherein the geometric mean of the wet stiffness in the longitudinal direction and the wet stiffness in the lateral direction of the skin pack mount is 19.0 mNm or more. [7] The skin pack mount according to any one of [1] to [6], wherein the sizing agent is at least one selected from the group consisting of rosin-based sizing agents and alkyl ketene dimer-based sizing agents. [8] A skin pack packaging body having the skin pack mount according to any one of [1] to [7], a contained item, and a resin film, A skin pack packaging body in which the stored item is stored between the skin pack mount and the resin film. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a skin pack mount that is highly recyclable and exhibits good strength even when wet. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of a skin pack mount according to the present embodiment. [Figure 2] FIG. 1 is a schematic diagram illustrating a method for evaluating the strength of a skin pack mount. DETAILED DESCRIPTION OF THE INVENTION

[0011] In the present disclosure, unless otherwise specified, the expressions "X or more and Y or less" and "X to Y" representing a numerical range mean a numerical range including the lower and upper limits, which are the endpoints. When the lower limit and upper limit of a numerical range are stated separately, the numerical range can be a combination of any lower limit and any upper limit.

[0012] In the present disclosure, a description such as "one or more selected from the group consisting of X, Y, and Z" means any of X, Y, Z, a combination of X and Y, a combination of X and Z, a combination of Y and Z, and a combination of X, Y, and Z. When X is a group, multiple Xs may be selected, and the same applies to Y and Z.

[0013] In the present disclosure, a description such as "X such as X1, X2, and X3" lists X1, X2, and X3 as examples of X, and does not mean that X is limited to X1, X2, and X3.

[0014] In the present disclosure, the "longitudinal direction" of the skin pack liner refers to the papermaking direction (M D) and is the direction in which the fibers are oriented. Also, "cross direction" is the direction perpendicular to the papermaking direction (CD).

[0015] 1. Skin pack mount A skin pack liner according to one embodiment of the present disclosure has a thermoplastic resin layer on both sides of a paper base material, the paper base material containing pulp, a sizing agent, and a polyacrylamide resin (hereinafter sometimes referred to as "PAM"), and satisfies the following requirements (A) and (B): (A) The total content of the sizing agent and the polyacrylamide resin relative to 100 parts by mass of the pulp is 0.15 parts by mass or more and 1.20 parts by mass or less. (B) The mass ratio of the content of the sizing agent to the content of the polyacrylamide resin is 2.5 or less.

[0016] The skin pack liner according to the present embodiment has good recyclability and good strength even when wetted by water because the contents and content ratios of pulp, sizing agent, and polyacrylamide resin contained in the paper base material are controlled within specific ranges. In particular, the skin pack liner according to the present embodiment can reduce the disadvantage of water penetration through the paper base material exposed at the end surface, resulting in a decrease in strength, and is therefore suitable for use in skin pack packages stored in a cool place such as a refrigerator or freezer.

[0017] An example of the layer structure of the skin pack liner according to this embodiment is shown in Figure 1. In Figure 1, the skin pack liner 1 has a paper base material 1a and thermoplastic resin layers 1b disposed on both sides of the paper base material 1a. The skin pack liner 1 may also have other layers, such as other layers (not shown) described below.

[0018] 1-1.Paper base material As long as the paper substrate contains pulp, a sizing agent, and a polyacrylamide resin so as to satisfy the above requirements (A) and (B), there are no particular limitations on the other constituent materials and layer structure.

[0019] (pulp) The paper substrate is not particularly limited as long as it is a commonly used paper, and is preferably paper whose main component is plant-derived pulp, and more preferably paper whose main component is wood pulp.

[0020] Specific examples of paper substrates include kraft paper, fine paper, (white) paperboard, paper container base paper, milk carton base paper, cup base paper, liner paper, coated paper, one-side glazed paper, glassine paper, and graphene paper. Among these, the paper substrate is preferably a paper selected from the group consisting of kraft paper, fine paper, (white) paperboard, paper container base paper, cup base paper, and one-side glazed paper, and from the standpoint of rigidity, among (white) paperboard, a paper selected from the group consisting of high-quality paperboard, special paperboard, cup base paper, and kraft paper is more preferred. Examples of kraft paper include bleached kraft paper, unbleached kraft paper, and one-side glazed bleached kraft paper. Of these, from the standpoint of print reproducibility and hygiene, the kraft paper is preferably a paper selected from the group consisting of bleached kraft paper and one-side glazed bleached kraft paper.

[0021] As mentioned above, the pulp constituting the paper base material is preferably wood pulp, and more preferably kraft pulp. Kraft pulp is classified into hardwood kraft pulp (LKP) and softwood kraft pulp (NKP) based on the difference in raw materials. As hardwood kraft pulp (LKP), hardwood bleached kraft pulp (LBKP) is preferred. As softwood kraft pulp (NKP), softwood bleached kraft pulp (NBKP) is preferred. Furthermore, as the difference in processing state, bleached kraft pulp (BKP), unbleached kraft pulp (UKP), and oxygen bleached kraft pulp (OKP) are listed, and from the viewpoint of print reproducibility, bleached kraft pulp is preferred. It is raft pulp (BKP).

[0022] Among these, the pulp is preferably one or more selected from the group consisting of hardwood kraft pulp (LKP) and softwood kraft pulp (NKP), and more preferably a mixture of hardwood kraft pulp (LKP) and softwood kraft pulp (NKP).

[0023] In the mixture, the mass ratio of hardwood kraft pulp (LKP) to softwood kraft pulp (NKP) (LKP / NKP) is not particularly limited as long as it is a ratio commonly used in paper, but is preferably 50 / 50 to 100 / 0, more preferably 70 / 30 to 98 / 2, even more preferably 80 / 20 to 97 / 3, and even more preferably 90 / 10 to 95 / 5. In other words, the content of hardwood kraft pulp (LKP) relative to the total amount of pulp is preferably 50 to 100% by mass, more preferably 70 to 98% by mass, even more preferably 80 to 97% by mass, and even more preferably 90 to 95% by mass. Furthermore, the content of softwood kraft pulp (NKP) relative to the total amount of pulp is preferably 0 to 50% by mass, more preferably 2 to 30% by mass, even more preferably 3 to 20% by mass, and even more preferably 5 to 10% by mass.

[0024] When the mass ratio (LKP / NKP) of hardwood kraft pulp (LKP) to softwood kraft pulp (NKP) is within the above range, it becomes easier to ensure the strength of the skin pack liner when wetted with water.

[0025] When the paper base material is an interleaf paper, for example, when paper base material A and paper base material B are used, the mass ratio (LKP / NKP) may be calculated for each paper base material.

[0026] The average fiber width of the pulp is preferably 12.0 to 30.0 μm, and more preferably 15.0 to 28.0 μm. The length-weighted average fiber length of the pulp is preferably 0.40 to 2.50 mm, and more preferably 0.50 to 1.80 mm.

[0027] The length-weighted average fiber length and average fiber width can be measured using a fiber length measuring instrument (Valmet FS-5 with UHD base unit, manufactured by Valmet Ltd.) in accordance with ISO 16065-2:2014 (Pulp - Determination of fiber length by automated photometric methods - Part 2: Non-polarized method, published January 14, 2014). In addition, the device can detect and measure each fiber using the attached camera, and meets ISO standards. In accordance with 16065-2:2014, images are taken within a measurement cell with a depth of field of 0.5 mm. The equipment captures images of fibers with a fiber length of 0.01 mm or more and 10.00 mm or less. Fibers with a fiber length of 0.2 mm or more and 7.0 mm or less are selected for the measurement of "fiber length" and "fiber width." The average fiber width is the arithmetic mean of the fiber widths of all the fibers obtained.

[0028] In this embodiment, the recyclability of the skin pack liner and its strength when wet can be improved by controlling the kink index of the pulp contained in the paper base material. The kink index is an index of the amount of bent fibers in the pulp fibers, and a higher kink index indicates that there are more bent fibers in the pulp fibers of the paper base material.

[0029] The kink index (1 / m) of pulp is Kibblewhite's kink index calculated by the following formula (1): The kink index of pulp is calculated by weighting the number of kinks in each angle range according to the increase in angle and dividing the weighted result by the sum of the fiber lengths.

[0030]

number

[0031] The symbols in formula (1) represent the following: n1 = Number of kinks (bends) between 21° and 45° in the measurement sample n2 = Number of kinks (bends) between 46° and 90° in the measurement sample n3 = Number of kinks (bends) between 91° and 180° in the measurement sample L c = Total fiber length of the measured sample (m)

[0032] The kink index of the pulp contained in the paper base material is preferably 2,000 to 3,500 [1 / m], more preferably 2,300 to 3,300 [1 / m], even more preferably 2,500 to 3,000 [1 / m], and even more preferably 2,700 to 2,800 [1 / m].

[0033] By setting the kink index of the pulp to the above lower limit or above, the fibers are less likely to swell in water, making it possible to provide a skin pack liner that exhibits good strength even when wet. Also, by setting the kink index of the pulp to the above upper limit or below, excessive entanglement between the pulp fibers is less likely to occur, increasing the defibration property and, as a result, improving the recyclability of the skin pack liner.

[0034] The kink index of the pulp can be controlled by the temperature when beating the pulp. The higher the temperature during beating, the smaller the kink index of the pulp, making it easier to control it within the above range. The kink index of the pulp can also be controlled by the pulp consistency when beating the pulp. Specifically, the higher the pulp consistency during beating, the higher the kink index of the pulp tends to be.

[0035] The kink index of pulp is measured in accordance with ISO 16065-2:2014 ("Pulp - Determination of fiber length by automated optical analysis - Part 2: Non-polarized method", published January 14, 2014). The specific procedure is described below.

[0036] When the paper base material is a slip sheet, the slip sheet is separated into its individual paper base materials, and the kink index of the pulp contained in each paper base material is measured. The weighted average value according to the basis weight of each paper base material is used as the kink index of the pulp for the entire slip sheet. For example, when the paper base material has paper base material A and paper base material B, the kink index is calculated using the following formula. Kink index [1 / m] when the paper substrate is a slip sheet = Kink index of paper base A × (basis weight of paper base A / sum of basis weight of paper base A and basis weight of paper base B) + Kink index of paper base material B × (basis weight of paper base material B / sum of basis weight of paper base material A and basis weight of paper base material B)

[0037] When the paper base material is an interleaf paper, the kink index of the pulp in the entire interleaf paper is preferably within the above range, and it is more preferable that the kink index of each paper base material included in the interleaf paper is within the above range. In other words, it is more preferable that the kink index of the pulp included in each paper base material in the interleaf paper is within the above range.

[0038] (internal additives) The paper base material contains pulp, a sizing agent, and a polyacrylamide resin in specific contents and content ratios. This allows the skin pack liner according to this embodiment to be easily recycled. The inventors of the present disclosure believe that the reason for this is as follows.

[0039] Polyacrylamide resins act as paper strength enhancers and can improve the strength of paper. Increasing the content of polyacrylamide resin in the paper base material can improve the strength of the paper base material, but if the content of polyacrylamide resin exceeds a certain amount, the recyclability of the skin pack liner tends to decrease. In addition, the sizing agent in the paper base material functions to suppress water penetration into the paper base material, thereby preventing the strength of the skin pack liner from decreasing when it becomes wet. Therefore, increasing the content of sizing agent in the paper base material can improve the water resistance of the paper base material. On the other hand, if the sizing agent is present in an amount exceeding a certain amount, it inhibits the adhesion of the polyacrylamide resin, which may prevent the polyacrylamide resin from fully exerting its effect. Therefore, the content and content ratio of sizing agent and polyacrylamide resin are factors that affect the strength of the skin pack liner when wet and the recyclability of the skin pack liner. If these are controlled within an appropriate range, these properties can be improved.

[0040] The ranges of the content and content ratio of the sizing agent and polyacrylamide resin suitable for improving the recyclability of the skin pack mount and its strength when wetted with water will be specifically described below.

[0041] The content of the sizing agent relative to 100 parts by mass of pulp is preferably 0.08 to 0.80 parts by mass, more preferably 0.10 to 0.60 parts by mass, even more preferably 0.12 to 0.45 parts by mass, even more preferably 0.15 to 0.40 parts by mass, and particularly preferably 0.18 to 0.35 parts by mass.

[0042] By setting the content of the sizing agent at or above the lower limit, the strength of the skin pack liner when wet can be further improved, while by setting the amount of the sizing agent at or below the upper limit, the recyclability of the skin pack liner can be further improved.

[0043] The content of the polyacrylamide resin relative to 100 parts by mass of pulp is preferably 0.05 to 0.60 parts by mass, more preferably 0.08 to 0.50 parts by mass, even more preferably 0.12 to 0.45 parts by mass, still more preferably 0.15 to 0.40 parts by mass, and particularly preferably 0.16 to 0.30 parts by mass.

[0044] By setting the polyacrylamide resin content at or above the lower limit, the strength of the skin pack liner when wet can be further improved, while by setting the polyacrylamide resin content at or below the upper limit, the recyclability of the skin pack liner can be further improved.

[0045] The total content of the sizing agent and polyacrylamide resin per 100 parts by mass of pulp is usually 0.15 to 1.20 parts by mass, preferably 0.18 to 1.00 parts by mass, more preferably 0.20 to 0.80 parts by mass, even more preferably 0.30 to 0.50 parts by mass, and even more preferably 0.35 to 0.40 parts by mass.

[0046] By setting the total content of the sizing agent and polyacrylamide resin at or above the lower limit, a skin pack liner that exhibits good strength even when wet can be provided. By setting the total content of the sizing agent and polyacrylamide resin at or below the upper limit, the recyclability of the skin pack liner can be improved.

[0047] The mass ratio of the sizing agent content to the polyacrylamide resin content (sizing agent / PAM) is usually 2.5 or less, preferably 0.1 to 2.5, and more preferably 0.3 to The range is preferably 2.1, more preferably 0.5 to 1.8, even more preferably 0.7 to 1.5, and particularly preferably 1.0 to 1.3.

[0048] By setting the sizing agent / PAM ratio within the above range, it is possible to provide a skin pack mount that is easy to recycle and has good strength when wet.

[0049] The sizing agent is not particularly limited, and examples thereof include rosin-based sizing agents, alkenyl succinic anhydride-based sizing agents, alkyl ketene dimer-based sizing agents, cationic polymer-based sizing agents, etc. Of these, from the viewpoint of further increasing the strength of the skin pack mount when wetted with water, the sizing agent is preferably one or more selected from the group consisting of rosin-based sizing agents and alkyl ketene dimer-based sizing agents, and more preferably a rosin-based sizing agent.

[0050] The polyacrylamide resin is an acrylamide polymer, and is preferably an acrylamide copolymer obtained by copolymerizing acrylamide with an anionic monomer such as acrylic acid and / or a cationic monomer such as 2-(dimethylamino)ethyl acrylate. The polyacrylamide resin may be one used as an internal paper strength enhancer. Examples of polyacrylamide resins commercially available as internal paper strength enhancers include the "Polystron" series manufactured by Arakawa Chemical Industries, Ltd.

[0051] The weight average molecular weight (Mw) of the polyacrylamide resin is not particularly limited, but is preferably 1,000,000 to 8,000,000, more preferably 2,000,000 to 6,000,000, and even more preferably 2,500,000 to 5,000,000. When the weight-average molecular weight of the polyacrylamide resin is within the above range, the pulp fibers and internal additives are uniformly distributed, making it easier to obtain a paper base material with good texture. Furthermore, the uniform distribution of the pulp fibers and internal additives suppresses variations in water penetration, making it possible to suppress a decrease in strength across the entire skin pack liner when it becomes wet with water.

[0052] The paper substrate may contain other internal additives as long as they do not impair the effects of the present disclosure. Examples of other internal additives include fixing agents, fillers, dry strength agents (excluding polyacrylamide resins), wet strength agents, retention aids, pH adjusters, drainage aids, water-resistant agents, softeners, antistatic agents, antifoaming agents, slime control agents, dyes, and pigments. Of these, the paper substrate preferably contains a fixing agent, and particularly when the sizing agent contains a rosin-based sizing agent, aluminum sulfate is preferably contained. Furthermore, preferred examples of dry strength agents other than polyacrylamide resins include starch-based strength agents such as starch, cationized starch, and oxidized starch.

[0053] (Layer composition) The paper base material may have a single-layer structure obtained by single-layer papermaking, or a multi-layer structure obtained by multi-layer papermaking. From the viewpoint of being able to freely adjust the raw material composition, basis weight, papermaking conditions, etc. of each layer, the paper base material preferably has a multi-layer structure. When the paper base material has a multi-layer structure, the number of layers constituting the paper base material is usually 2 to 10, preferably 3 to 9, more preferably 4 to 8, and even more preferably 4 to 6.

[0054] The paper base material may be a slip sheet containing two or more paper base materials, or may be a single sheet made of one paper base material. When the paper base material is a slip sheet, the number of paper base materials contained in the slip sheet is not particularly limited and may be, for example, 2 to 5, preferably 2 or 3, and more preferably 2. The paper base material preferably has a paper base material A, an adhesive layer, and a paper base material B in this order. The slip sheet having a paper base material A, an adhesive layer, and a paper base material B in this order may be a slip sheet made only of the paper base material A, the adhesive layer, and the paper base material B, or may be a slip sheet laminated with another paper base material via an adhesive layer. In this case, the paper base material B may be different from the paper base material A, or the same paper base material may be used. Furthermore, the other paper base material may be different from the paper base material A or the paper base material B, or the same paper base material may be used.

[0055] The basis weight A of the paper base material A is preferably 200 to 1,000 g / m 2 , more preferably 250 to 700 g / m 2 , and more preferably 300 to 600 g / m 2 , and even more preferably 300 to 500 g / m 2 is.

[0056] The basis weight B of the paper base material B is preferably 30 to 300 g / m 2 , more preferably 40 to 250 g / m 2 , and more preferably 50 to 200 g / m 2 , and even more preferably 60 to 150 g / m 2 is.

[0057] The basis weight of the entire paper base material is preferably 200 to 1,000 g / m 2 , more preferably 250 to 800 g / m 2 , and more preferably 300 to 700 g / m 2 , and even more preferably 350 to 600 g / m 2 , particularly preferably 350 to 450 g / m 2 is.

[0058] (adhesive layer) When the paper base material is a slip sheet, the adhesive layer that bonds the paper base materials, such as paper base material A and paper base material B, to each other is preferably a layer made of a material with adhesive properties, and preferably contains a thermoplastic resin. By using a thermoplastic resin, slip sheets can be easily obtained by coating at least one of the paper base materials with a heat-melted adhesive layer and laminating the other paper base material.

[0059] The thermoplastic resin preferably contains one or more selected from the group consisting of polyolefin-based resins, polyester-based resins, polylactic acid, styrene-based resins, and acrylic-based resins, and more preferably contains a polyolefin-based resin. Examples of polyolefin resins include polyethylene (low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), etc.), polypropylene (PP), and polymethylpentene.

[0060] Examples of polyester resins include polyethylene terephthalate and polybutylene terephthalate. Examples of the styrene resin include polystyrene, acrylonitrile styrene, and acrylonitrile butadiene styrene. Examples of acrylic resins include polymers and copolymers of acrylic monomers such as acrylic acid esters. Among these, the polyolefin resin is preferably one or more selected from the group consisting of polyethylene and polypropylene, more preferably one or more selected from the group consisting of LDPE and MDPE, and even more preferably MDPE.

[0061] The following adhesives may be used for the adhesive layer. The adhesive is not particularly limited, and may be a water-based adhesive, a solvent-based adhesive, a UV-based adhesive, or the like. Among these, the adhesive used for the adhesive layer is preferably a water-based adhesive. The water-based adhesive is preferably one or more selected from the group consisting of an acrylic adhesive, a polyurethane adhesive, and an isocyanate adhesive, and an acrylic adhesive is more preferred because of its ease of controlling adhesive strength and excellent heat resistance.

[0062] The amount of the adhesive layer per unit area is not particularly limited, but is preferably 1.0 g / m 2 More than 50.0g / m 2 or less, more preferably 1.0 g / m 2 More than 20.0g / m2 Below is When forming the adhesive layer, it is preferable to coat the adhesive on paper base A and / or paper base B so that the solid content is in this amount.

[0063] The adhesive layer may be formed as a single layer of a single resin, or as a single layer of a mixture of multiple resins, or as multiple layers of the same or different types of resins. The thickness of the adhesive layer is not particularly limited, but is preferably 5 to 100 μm, and more preferably 10 to 50 μm.

[0064] (Paper base ratio) The ratio of the mass of the paper substrate to the total mass of the skin pack mount (total mass if the skin pack mount has two or more paper substrates) is not particularly limited, but is preferably 50 to 90 mass%, more preferably 55 to 88 mass%, even more preferably 60 to 85 mass%, and even more preferably 70 to 75 mass%.

[0065] By setting the mass ratio of the paper base material at or above the lower limit, not only can the environmental impact be reduced, but the paper base material is easily separated from the thermoplastic resin layer during recycling, and the paper base material can be sufficiently separated, improving the recyclability of the skin pack liner. Furthermore, by setting the mass ratio of the paper base material at or below the upper limit, the area occupancy rate of the paper base material at the edge surface does not become excessively large, thereby suppressing water penetration and making it possible to suppress a decrease in strength across the entire skin pack liner when it becomes wet with water.

[0066] (Oken smoothness of paper substrate) The Oken smoothness of the paper substrate is preferably 5 seconds or more, more preferably 10 to 1,500 seconds. The Oken smoothness of the paper substrate is measured in accordance with JIS P 8155:2010 ("Paper and paperboard - Smoothness test method - Oken method", published February 22, 2010).

[0067] (75° gloss of paper substrate) From the viewpoint of print reproducibility, the 75° gloss of the paper substrate is preferably 5% or more, more preferably 10 to 70%.

[0068] 1-2.Thermoplastic resin layer The skin pack liner has a thermoplastic resin layer on both sides of a paper base material. The thermoplastic resin layer on the front side (the side facing the stored item) protects the surface of the skin pack liner from the stored item, such as food, and protects the stored item from external stimuli such as oxygen. Furthermore, for example, when the stored item is sandwiched between the skin pack liner and a resin film, the thermoplastic resin layer serves to adhere to the resin film. The thermoplastic resin layer on the back side (the side opposite the stored item) serves to make the paper base material less susceptible to water wetting.

[0069] The thermoplastic resin layer on the front side may be a single layer of thermoplastic resin or a laminate containing a thermoplastic resin, but is preferably a laminate containing a barrier layer, and particularly preferably a laminate having a barrier layer between thermoplastic resin layers, such as "thermoplastic resin layer / barrier layer / thermoplastic resin layer." The thermoplastic resin layer on the front side may also be a laminate layer.

[0070] When the thermoplastic resin layer is a laminate having a barrier layer, the barrier layer is not particularly limited as long as it is a layer that can barrier oxygen and / or water vapor, and may have a single-layer structure or a multi-layer structure of two or more layers.

[0071] Specifically, the resin forming the barrier layer is made of polyamide resin, polyvinyl alcohol, ethylene-vinyl alcohol copolymer (EVOH), and polyvinylidene chloride resin. The barrier layer is preferably one or more selected from the group consisting of polyamide resins, polyvinyl alcohol, and ethylene-vinyl alcohol copolymers, and more preferably one or more selected from the group consisting of polyamide resins, polyvinyl alcohol, and ethylene-vinyl alcohol copolymers. The polyamide resin is preferably an aromatic polyamide, and more preferably polyamide MXD6. The barrier layer may further contain one or more other resins, such as biomass resins and biodegradable resins. Alternatively, the barrier layer may be a metal layer.

[0072] The thickness of the barrier layer is not particularly limited, but is preferably 1 to 100 μm, more preferably 3 to 50 μm, and even more preferably 5 to 30 μm.

[0073] The thermoplastic resin used for the front thermoplastic resin layer is preferably one that can be laminated onto a paper substrate. The thermoplastic resin may be appropriately selected from any thermoplastic resin, such as a known thermoplastic resin or a thermoplastic resin equivalent thereto. Specific examples include polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactic acid, and polybutylene succinate; polyolefin resins such as polyvinyl chloride, polyvinylidene chloride, polybutene, polybutadiene, ethylene-vinyl acetate copolymer, polyethylene, polypropylene, ethylene-vinyl alcohol copolymer, ethylene-propylene copolymer, and polymethylpentene; polycarbonate; polyurethane; polyamides such as nylon 6; polyacrylonitrile; and poly(meth)acrylate.

[0074] Among these thermoplastic resins, the thermoplastic resin used in the laminate layer is preferably one or more selected from the group consisting of polyethylene (PE) and polypropylene (PP), more preferably PE or PP, because of its excellent lamination properties and barrier properties. PE is preferably one or more selected from the group consisting of low-density polyethylene (LDPE) and medium-density polyethylene (MDPE), more preferably MDPE, because of its excellent lamination properties.

[0075] Commercially available resin laminates (laminate films) suitable for use as the front thermoplastic resin layer include a PE (polyethylene) / EVOH (ethylene-vinyl alcohol copolymer) / PP (polypropylene) film (trade name: Diamiron YF1966, 40 μm thick) manufactured by Mitsubishi Chemical Corporation, a PE (polyethylene) / EVOH (ethylene-vinyl alcohol copolymer) / PP (polypropylene) film (trade name: Diamiron MF F903, 40 μm thick) manufactured by Mitsubishi Chemical Corporation, a PP (polypropylene) / PVOH (polyvinyl alcohol) / PP three-layer film (trade name: ECO-B, 20 μm thick) manufactured by Futamura Chemical Industry Co., Ltd., a NY6 (nylon 6) / EVOH (ethylene-vinyl alcohol copolymer) / NY6 three-layer film (trade name: Heptax HP, 17 μm thick) manufactured by Gunze Limited, and a NY6 / MXD6 (polyamide MXD6) / NY6 three-layer film (trade name: Embron M, 15 μm thick) manufactured by Unitika Ltd.

[0076] The thickness of the thermoplastic resin layer on the front side is not particularly limited, but is preferably 1 to 300 μm, more preferably 5 to 200 μm, even more preferably 10 to 100 μm, still more preferably 20 to 80 μm, and particularly preferably 25 to 60 μm.

[0077] The thermoplastic resin layer on the back side may be a single layer of thermoplastic resin or a laminate containing thermoplastic resin, but is preferably a single layer of thermoplastic resin.

[0078] The thermoplastic resin used for the backside thermoplastic resin layer is preferably one that can be laminated to a paper substrate. The thermoplastic resin may be appropriately selected from any thermoplastic resin, such as known thermoplastic resins and thermoplastic resins equivalent thereto. Specific examples include polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactic acid, and polybutylene succinate; polyolefin resins such as polyvinyl chloride, polyvinylidene chloride, polybutene, polybutadiene, ethylene-vinyl acetate copolymer, polyethylene, polypropylene, ethylene-vinyl alcohol copolymer, ethylene-propylene copolymer, and polymethylpentene; polycarbonate; polyurethane; polyamides such as nylon 6; polyacrylonitrile; and poly(meth)acrylate.

[0079] Of these, the thermoplastic resin is preferably one or more selected from the group consisting of polyethylene (PE) and polypropylene (PP) because of its excellent lamination properties and waterproofing. PE is preferably one or more selected from the group consisting of low-density polyethylene (LDPE) and medium-density polyethylene (MDPE), and more preferably MDPE, because of its excellent lamination properties.

[0080] The thickness of the thermoplastic resin layer on the back side is not particularly limited, but is preferably 1 to 300 μm, more preferably 10 to 240 μm, even more preferably 40 to 210 μm, still more preferably 70 to 180 μm, and particularly preferably 100 to 150 μm.

[0081] The total thickness of the front and back thermoplastic resin layers is not particularly limited, but is preferably 10 to 400 μm, more preferably 40 to 300 μm, even more preferably 60 to 250 μm, still more preferably 80 to 200 μm, and particularly preferably 100 to 180 μm.

[0082] (Adhesive layer) When the surface of the thermoplastic resin layer has adhesive properties, the thermoplastic resin layer may be directly adhered to the surface of the paper substrate, but it is preferable to have an adhesive layer between the paper substrate and the thermoplastic resin layer to prevent peeling during production, transportation, and display of the skin pack packaging. The adhesive constituting the adhesive layer is not particularly limited, but is preferably a resin-based adhesive suitable for dry lamination and wet lamination. Specifically, the adhesive constituting the adhesive layer can be of various types, such as water-based, solvent-based, and UV-based adhesives, among which water-based adhesives are preferred. Among the water-based adhesives, at least one selected from the group consisting of acrylic adhesives, polyurethane adhesives, and isocyanate adhesives is preferred, with acrylic adhesives being more preferred.

[0083] The amount of adhesive layer per unit area is 1 to 50 g / m 2 is preferable, and more preferably 1 to 20 g / m 2 It is preferable to coat the pressure-sensitive adhesive layer on the surface of the paper substrate or the surface of the thermoplastic resin layer so that the solid content is within this range. For coating, it is preferable to use a coating liquid containing the pressure-sensitive adhesive.

[0084] The thickness of the pressure-sensitive adhesive layer is not particularly limited, but from the viewpoint of moldability, it is preferably 5 to 100 μm, more preferably 8 to 30 μm.

[0085] 1-3. Other layers The skin pack mount according to this embodiment may have layers other than those described above at any position within the scope that does not impair the effects of the present disclosure. Examples of such layers include a laser-printed layer that can be printed by ultraviolet laser printing. Furthermore, the skin pack mount according to this embodiment may have another paper substrate (preferably one made of the same material and with the same properties as the above-described paper substrate) as another layer.

[0086] (Laser printing layer) The laser printing layer is a printing layer containing titanium oxide. When the laser printing layer is irradiated with an ultraviolet laser, the titanium oxide in the printing layer changes color from white to black, and characters, patterns, etc. are printed. The discoloration of titanium oxide is thought to occur when the ionic valence of the titanium oxide contained in the printing layer changes from tetravalent to trivalent, causing oxygen defects.

[0087] The laser printing layer can be provided on the surface of the thermoplastic resin layer opposite the paper substrate, between the thermoplastic resin layer and the paper substrate, etc. Alternatively, the paper substrate may contain titanium oxide, so that the paper substrate also serves as the laser printing layer.

[0088] The method for forming the laser printing layer is not particularly limited, and may be a coating method or a lamination method, but a coating method is preferred because it is easy to provide the printing layer only in the desired locations and is easy to manufacture.

[0089] The content of titanium oxide in the laser printing layer is preferably 0.1 to 10 g / m 2 , more preferably 0.2 to 7.5 g / m 2 , and more preferably 0.3 to 5.0 g / m 2 , and even more preferably 0.4 to 3.5 g / m 2 is.

[0090] By ensuring that the titanium oxide content is equal to or greater than the lower limit, sufficient print density can be obtained. On the other hand, by ensuring that the titanium oxide content is equal to or less than the upper limit, print spots with excellent print clarity can be obtained, and cost increases due to the inclusion of more titanium oxide than necessary due to the print density reaching a plateau can be suppressed, and the amount of smoke generated during ultraviolet laser irradiation (printing) can be suppressed.

[0091] If smoke occurs during irradiation with an ultraviolet laser, which is thought to be due to the scattering of titanium oxide, there is a risk that the discolored titanium oxide will fall off from the laser-printed layer, and if the discolored titanium oxide falls off from the laser-printed layer, the print clarity will tend to decrease. However, by setting the content of titanium oxide in the laser-printed layer to the above-mentioned upper limit or less, such smoke generation tends to be suppressed.

[0092] Furthermore, when a laser printing layer is provided between the thermoplastic resin layer and the paper substrate, the thermoplastic resin layer functions as a protective layer, which suppresses the generation of smoke associated with ultraviolet laser irradiation and also suppresses the detachment of titanium oxide associated with the generation of smoke, and this tends to result in a printed image with high print density and excellent print clarity for each point, which is even more effective.

[0093] 1-4. Characteristics of skin pack mount (Wet stiffness) The wet stiffness in the longitudinal direction of the skin pack mount is preferably 28.0 to 60.0 mNm, more preferably 30.0 to 55.0 mNm, even more preferably 33.0 to 50.0 mNm, and even more preferably 39.0 to 50.0 mNm.

[0094] The wet stiffness in the lateral direction of the skin pack mount is preferably 13.0 to 40.0 mNm, more preferably 15.0 to 35.0 mNm, even more preferably 17.0 to 30.0 mNm, and even more preferably 20.0 to 25.0 mNm.

[0095] The geometric mean of the wet stiffness in the vertical direction and the wet stiffness in the horizontal direction of the skin pack mount ((wet stiffness in the vertical direction x wet stiffness in the horizontal direction) 1 / 2 (hereinafter sometimes referred to as "geometric mean wet stiffness") is preferably 19.0 mNm or more, more preferably 19.0 to 45.0 mNm, even more preferably 20.0 to 40.0 mNm, still more preferably 26.0 to 38.0 mNm, and particularly preferably 30.0 to 35.0 mNm.

[0096] When the wet stiffness in the longitudinal direction, the wet stiffness in the transverse direction, and the geometric mean of the wet stiffness of the skin pack mount are within the above ranges, the strength of the skin pack mount when wetted with water also tends to be good.

[0097] Wet stiffness is measured in accordance with JIS P 8125-2:2017 (Paper and paperboard - Bending resistance test methods - Part 2: Taber type tester method, established on March 21, 2017) after conditioning the skin pack liner in a humidity-controlled environment as specified in JIS P 8111:1998 ("Paper, paperboard and pulp - Standard conditions for humidity conditioning and testing", revised on September 20, 1998) and immersing it in ion-exchanged water at 23°C for 60 seconds. The specific procedure is described below.

[0098] (Basic weight) The basis weight of the skin pack mount is not particularly limited, but is preferably 250 g / m 2 or more than 300g / m 2 or more, more preferably 300 to 1,000 g / m 2 , and more preferably 400 to 800 g / m 2 , and even more preferably 500 to 700 g / m 2 , particularly preferably 550 to 600 g / m 2 is.

[0099] The basis weight of the skin pack liner is measured in accordance with JIS P 8124:2011 ("Paper and paperboard -- Determination of basis weight," revised March 22, 2011). The specific procedure is described below.

[0100] (Thickness) The thickness of the skin pack mount is not particularly limited, but is preferably 300 to 900 μm, more preferably 400 to 800 μm, and even more preferably 500 to 700 μm.

[0101] (density) The density of the skin pack mount is not particularly limited, but is preferably 0.60 to 1.10 g / cm 3 and more preferably 0.70 to 1.00 g / cm 3 and more preferably 0.80 to 0.90 g / cm 3 is.

[0102] The density of the skin pack mount can be determined by dividing the basis weight measured by the above method by the thickness.

[0103] 2. Manufacturing method of skin pack mount The method for producing the skin pack mount according to the present embodiment is not particularly limited, and any method such as a known method or a method based thereon can be used. An example of the production method is shown below.

[0104] (Preparation of paper substrate) When the paper base material is a single sheet, a paper layer having a single layer or multilayer structure can be prepared by single-layer or multi-layer papermaking of the paper material, and this paper layer can be used as the paper base material. When the paper base material is a slip sheet, the paper base material can be prepared by bonding the above paper layers together with an adhesive layer or the like.

[0105] The stock contains pulp, a sizing agent, and a polyacrylamide resin. The contents of the pulp, sizing agent, and polyacrylamide resin in the stock may be selected so that the resulting paper base material satisfies the above requirements (A) and (B), preferably the above requirements (A) to (D). The stock may also contain other internal additives as described above.

[0106] To obtain the desired pulp, wood chips are cooked. The wood chips may be appropriately selected depending on the desired pulp. The cooking method is not particularly limited, and any method such as a known method or a method based thereon may be used.

[0107] The freeness (freeness) of the pulp in the paper stock is preferably 300 to 700 mL, more preferably 350 to 600 mL, and even more preferably 400 to 600 mL. Here, freeness refers to the Canadian standard freeness (CSF) measured in accordance with JIS P8121-2:2012 ("Pulp - Freeness test methods - Part 2: Canadian standard freeness method", established June 20, 2012). The method of beating the pulp to adjust the freeness is not particularly limited, and any method such as a known method or a method based thereon can be used.

[0108] From the viewpoint of adjusting the kink index within the above range, the temperature during beating is preferably 20 to 70°C, more preferably 30 to 60°C, and even more preferably 40 to 60°C.

[0109] Any wet paper machine can be appropriately selected and used for making the paper stock, including a twin-wire paper machine, a Fourdrinier paper machine, a gap former paper machine, a cylinder paper machine, and a short-wire paper machine.

[0110] The paper produced by the paper machine is preferably transported on a felt and dried in a dryer. A multi-stage cylinder dryer may be used as a pre-dryer before the paper is dried in the dryer.

[0111] The resulting paper may be subjected to a surface treatment using a calendar to make the thickness and smoothness uniform. Any suitable calendaring machine can be used for the calendaring treatment.

[0112] (Formation of thermoplastic resin layer) A skin pack mount can be produced by providing a thermoplastic resin layer on the obtained paper substrate. The thermoplastic resin layer may be directly adhered to the paper substrate, or may be adhered to the paper substrate via an adhesive layer. In the latter case, it is preferable to apply a coating liquid containing an adhesive to the surface of the thermoplastic resin layer, and then laminate the thermoplastic resin layer on the surface of the paper substrate via the adhesive layer. In this case, a film may be attached to the paper substrate as the thermoplastic resin layer.

[0113] When the paper substrate is a single sheet, a skin pack mount can be produced by providing a thermoplastic resin layer on the single sheet.

[0114] When the paper substrate is a slip sheet, a skin pack liner may be prepared by providing a thermoplastic resin layer on the slip sheet, or by providing a thermoplastic resin layer on one paper substrate and then laminating the first paper substrate to another paper substrate. Lamination of paper substrates can be performed, for example, by coating the surface of one paper substrate with an adhesive and then laminating the other paper substrate to the coated surface. The adhesive coating may be performed by applying an adhesive liquid containing an adhesive resin, or by applying a heat-melted adhesive resin. If necessary, a printed layer may be provided on the surface of the paper substrate either before or after lamination of the paper substrates. The printed layer may be provided, for example, by printing or laminating a printed layer.

[0115] (processing) The skin pack mount obtained as described above may be cut to an appropriate size taking into consideration the size and shape of the contents to be contained, and suitability for transportation and display. From the viewpoint of efficiently obtaining skin pack mounts of the same shape, cutting is preferably performed by punching. The punching process is preferably carried out using a high-speed automatic punching machine, a flat-bed punching machine, or a rotary punching machine, and more preferably a high-speed automatic punching machine. By performing punching using a high-speed automatic punching machine or a flat-bed punching machine, skin pads having shapes such as a rectangle, a rounded rectangle, an oval, etc. can be produced. Therefore, the mount for the ink can be obtained easily and efficiently.

[0116] 3. Skin pack packaging A skin pack packaging according to another embodiment of the present disclosure includes the skin pack liner, a storage item, and a resin film, with the storage item stored between the skin pack liner and the resin film. The skin pack packaging according to this embodiment is preferably one that hermetically stores the storage item. Skin pack packaging may be performed by any known means or equivalent means.

[0117] The resin film can be appropriately selected depending on the type and shape of the stored items, but preferably has excellent adhesiveness and is releasable when the stored items are removed, since it must be adhered to the thermoplastic resin layer of the skin pack mount to store the stored items. Therefore, the resin film is preferably made of the thermoplastic resin used in the thermoplastic resin layer described above, and more preferably has a barrier layer when the contents are food, etc. The barrier layer used in the thermoplastic resin layer described above is preferably used as the barrier layer.

[0118] The stored items are not particularly limited, and examples thereof include food and daily necessities. Since the skin pack packaging can hermetically store the stored items, it is suitable for storing foods such as fresh foods such as vegetables, meat, and fresh fish, as well as processed foods thereof. [Example]

[0119] The present disclosure will be explained in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present disclosure. Therefore, the scope of the present disclosure should not be interpreted as being limited by the specific examples shown below.

[0120] Example 1 (Preparation of paper substrate) 90 parts by mass of bleached hardwood kraft pulp (LBKP) and 10 parts by mass of bleached softwood kraft pulp (NBKP) were beaten at a temperature of 40°C to a Canadian Standard Freeness (CSF) of 500 mL to obtain a pulp slurry. A double-disc refiner was used for the beating. 0.80 parts by mass (solids equivalent) of aluminum sulfate (liquid aluminum sulfate manufactured by Asahi Chemical Industries Co., Ltd.) and 0.80 parts by mass (solids equivalent) of polycarbonate were added to 100 parts by mass of pulp (solids equivalent) in the obtained pulp slurry. By adding 0.08 parts by mass (solids equivalent) of an acrylamide resin (Polystron 1430 manufactured by Arakawa Chemical Industries, Ltd.), 0.10 parts by mass (solids equivalent) of a rosin-based sizing agent (Sizepine N-817 manufactured by Arakawa Chemical Industries, Ltd.), and 0.20 parts by mass (solids equivalent) of internally added cationized starch (P-3 manufactured by Piraab Starch), paper stock for five layers was prepared: for the surface layer, the undersurface layer, the middle layer, the undersurface layer, and the back layer. This paper stock was used to make a five-layer paper using a twin-wire paper machine. At this time, the basis weight per layer was 84 g / m 2 The total weight of the five layers is set to 420±5g / m 2 Thereafter, a calendering treatment was carried out so that the thickness became 510±5 μm, thereby obtaining a paper substrate.

[0121] (Lamination of thermoplastic resin layer and paper substrate) A thermoplastic resin layer of MDPE ("8010" manufactured by ENEOS NUC Corporation) was attached to the back side of the paper substrate by melt extrusion lamination so that the dry film thickness was 120±3 μm. Next, a reverse roll coater was used to coat one side of a barrier film (Diamilon YF1966 manufactured by Mitsubishi Chemical Corporation; film thickness 40 μm) with a coating weight of 6.0 g / m2 after heat drying. 2 A water-based acrylic adhesive (Arakawa Paint Co., Ltd. "Polystick EM-57 5") was coated onto the paper substrate. A barrier film was then attached to the front side of the paper substrate via a water-based acrylic adhesive.

[0122] <Example 2> In preparing the paper stock, the paper base material was obtained in the same manner as in Example 1, except that the amount of polyacrylamide resin ("Polystron 1430" manufactured by Arakawa Chemical Industries, Ltd.) added was changed to 0.20 parts by mass (solid content equivalent) and the amount of rosin sizing agent ("Sizepine N-817" manufactured by Arakawa Chemical Industries, Ltd.) added was changed to 0.25 parts by mass (solid content equivalent). Using the obtained paper base material, a skin pack mount was obtained in the same manner as in Example 1.

[0123] Example 3 In preparing the paper stock, the paper base material was obtained in the same manner as in Example 1, except that the amount of polyacrylamide resin ("Polystron 1430" manufactured by Arakawa Chemical Industries, Ltd.) added was changed to 0.40 parts by mass (solid content equivalent) and the amount of rosin sizing agent ("Sizepine N-817" manufactured by Arakawa Chemical Industries, Ltd.) added was changed to 0.50 parts by mass (solid content equivalent). Using the obtained paper base material, a skin pack mount was obtained in the same manner as in Example 1.

[0124] Example 4 In preparing the paper stock, the paper base material was obtained in the same manner as in Example 1, except that the amount of polyacrylamide resin ("Polystron 1430" manufactured by Arakawa Chemical Industries, Ltd.) added was changed to 0.14 parts by mass (solid content equivalent) and the amount of rosin sizing agent ("Sizepine N-817" manufactured by Arakawa Chemical Industries, Ltd.) added was changed to 0.28 parts by mass (solid content equivalent). Using the obtained paper base material, a skin pack mount was obtained in the same manner as in Example 1.

[0125] <Example 5> In preparing the paper stock, the paper base material was obtained in the same manner as in Example 1, except that the amount of polyacrylamide resin ("Polystron 1430" manufactured by Arakawa Chemical Industries, Ltd.) added was changed to 0.25 parts by mass (solid content equivalent) and the amount of rosin sizing agent ("Sizepine N-817" manufactured by Arakawa Chemical Industries, Ltd.) added was changed to 0.17 parts by mass (solid content equivalent). Using the obtained paper base material, a skin pack mount was obtained in the same manner as in Example 1.

[0126] Example 6 The set basis weight for papermaking is 520±5g / m 2 A paper base material was obtained in the same manner as in Example 2, except that the paper obtained by papermaking was subjected to a calendar treatment so that the thickness became 630±5 μm. In addition, a skin pack backing was obtained in the same manner as in Example 1, except that when MDPE ("8010" manufactured by ENEOS NUC Corporation) was laminated to the paper substrate by melt extrusion lamination, the dry film thickness of the MDPE was set to 15±3 μm.

[0127] Example 7 The set basis weight for papermaking is 340±5g / m 2 A paper base material was obtained in the same manner as in Example 2, except that the paper obtained by papermaking was subjected to a calendar treatment so that the thickness became 420±5 μm. In addition, a skin pack backing was obtained in the same manner as in Example 1, except that when MDPE ("8010" manufactured by ENEOS NUC Corporation) was laminated to the paper substrate by melt extrusion lamination, the dry film thickness of the MDPE was set to 200±3 μm.

[0128] Example 8 A paper base material was obtained in the same manner as in Example 2, except that in preparing the pulp slurry, the beating temperature was changed to 50°C. Using the obtained paper base material, a skin pack mount was obtained in the same manner as in Example 1.

[0129] Example 9 A paper base material was obtained in the same manner as in Example 2, except that in preparing the pulp slurry, the beating temperature was changed to 30°C. Using the obtained paper base material, a skin pack mount was obtained in the same manner as in Example 1.

[0130] Example 10 The set basis weight for papermaking is 340±5g / m 2 A paper base material was obtained in the same manner as in Example 2, except that the paper obtained by papermaking was subjected to a calendar treatment so that the thickness became 420±5 μm. In addition, a skin pack backing sheet was obtained in the same manner as in Example 1, except that when MDPE ("8010" manufactured by ENEOS NUC Corporation) was laminated to the paper substrate by melt extrusion lamination, the dry film thickness of the MDPE was set to 105±3 μm.

[0131] Example 11 The set basis weight for papermaking is 265±5g / m 2A paper base material was obtained in the same manner as in Example 2, except that the paper obtained by papermaking was subjected to a calendar treatment so that the thickness became 330±5 μm. In addition, a skin pack backing was obtained in the same manner as in Example 1, except that when MDPE ("8010" manufactured by ENEOS NUC Corporation) was laminated to the paper substrate by melt extrusion lamination, the dry film thickness of the MDPE was set to 50±3 μm.

[0132] <Comparative Example 1> In preparing the paper stock, the paper base material was obtained in the same manner as in Example 1, except that the amount of polyacrylamide resin ("Polystron 1430" manufactured by Arakawa Chemical Industries, Ltd.) added was changed to 0.05 parts by mass (solid content equivalent) and the amount of rosin sizing agent ("Sizepine N-817" manufactured by Arakawa Chemical Industries, Ltd.) added was changed to 0.07 parts by mass (solid content equivalent). Using the obtained paper base material, a skin pack mount was obtained in the same manner as in Example 1.

[0133] <Comparative Example 2> In preparing the paper stock, the paper base material was obtained in the same manner as in Example 1, except that the amount of polyacrylamide resin ("Polystron 1430" manufactured by Arakawa Chemical Industries, Ltd.) added was changed to 0.75 parts by mass (solid content equivalent) and the amount of rosin sizing agent ("Sizepine N-817" manufactured by Arakawa Chemical Industries, Ltd.) added was changed to 1.00 parts by mass (solid content equivalent). Using the obtained paper base material, a skin pack mount was obtained in the same manner as in Example 1.

[0134] <Comparative Example 3> In preparing the paper stock, the paper base material was obtained in the same manner as in Example 1, except that the amount of polyacrylamide resin ("Polystron 1430" manufactured by Arakawa Chemical Industries, Ltd.) added was changed to 0.10 parts by mass (solid content equivalent) and the amount of rosin sizing agent ("Sizepine N-817" manufactured by Arakawa Chemical Industries, Ltd.) added was changed to 0.30 parts by mass (solid content equivalent). Using the obtained paper base material, a skin pack mount was obtained in the same manner as in Example 1.

[0135] The physical properties of the skin pack mounts and paper substrates prepared in the Examples and Comparative Examples were measured and evaluated by the following methods. The results are shown in Tables 1 and 2.

[0136] <Basic weight> The basis weight of the skin pack liner, paper base material and thermoplastic resin layer is measured in accordance with JIS P 8124:2011 ("Paper and paperboard - Method of measurement of basis weight", revised March 22, 2011). did.

[0137] (basis weight of paper base material) The paper base materials (paper base materials A and B in the case of interleaf paper) were separated from the skin pack mount, and their basis weights were measured. The specific procedure was as follows. The skin pack backing was placed in a beaker containing xylene heated to 100°C and left to stand in the xylene for 30 minutes to dissolve the thermoplastic resin. The remaining thermoplastic resin on the surface of the paper substrate was then wiped off with a cloth. If the thermoplastic resin could not be completely removed from the surface of the paper substrate, the above procedure was repeated until the thermoplastic resin was completely removed from the paper substrate. The paper substrate from which the thermoplastic resin had been removed was dried in a draft or similar container to thoroughly volatilize the xylene. The paper substrate thus separated from the skin pack liner was conditioned in a humidity-conditioning environment specified in JIS P 8111:1998 ("Paper, paperboard and pulp -- Standard conditions for humidity conditioning and testing", revised September 20, 1998), and then its basis weight was measured.

[0138] (Basis weight of thermoplastic resin layer) The thermoplastic resin layer (MDPE and barrier film) was separated from the skin pack mount and its basis weight was measured. The specific procedure is as follows. The skin pack backing was carefully peeled by hand into the paper substrate and the thermoplastic resin layer. If part of the paper substrate adhered to the thermoplastic resin layer, the thermoplastic resin layer with the paper substrate adhered thereto was immersed in a 4% by mass cellulase solution at 40°C for 30 minutes to dissolve the paper substrate. If the paper substrate remained on the surface of the thermoplastic resin, the above procedure was repeated by immersing it again in the cellulase solution and rubbing it by hand until the paper substrate was completely removed. After the paper substrate was removed, the thermoplastic resin layer was washed with water and wiped dry with a cloth. The thermoplastic resin layer thus separated from the skin pack liner was conditioned in a humidity-conditioning environment specified in JIS P 8111:1998 ("Paper, paperboard and pulp -- Standard conditions for humidity conditioning and testing", revised September 20, 1998), and then its basis weight was measured.

[0139] <Paper base ratio> From the measured basis weights of the skin pack backing and paper base material, the basis weight of the paper base material (g / m 2 ) ÷ Basis weight of skin pack backing paper (g / m 2 The ratio of the paper substrate was calculated using the formula: ) × 100.

[0140] <Thickness> The thicknesses of the skin pack liner, paper substrate, and thermoplastic resin layer were measured in accordance with JIS P 8118:2014 ("Paper and paperboard -- Test methods for thickness, density, and specific volume," revised November 20, 2014) after conditioning in the humidity-controlled environment specified in JIS P 8111:1998 ("Paper, paperboard, and pulp -- Standard conditions for conditioning and testing," revised September 20, 1998).

[0141] The thickness of the paper substrate and the thermoplastic resin layer was measured using the paper substrate and the thermoplastic resin layer separated from the skin pack mount by the method described in the <basis weight> section.

[0142] The measuring device used was a paper thickness meter (No. 132 manufactured by Toyo Seiki Seisakusho, Ltd.) Measurements were made with n=10, and the arithmetic mean value was taken as the thickness.

[0143] <density> From the measured basis weight and thickness, the basis weight (g / m 2 The density was calculated using the formula: )÷thickness (μm).

[0144] <Kink index> The paper substrate was separated from the skin pack mount by the method described in the <Basis Weight> section. The separated paper substrate was cut into 4 cm squares, immersed in ion-exchanged water, adjusted to a solids concentration of 2%, and left to stand for 24 hours. Subsequently, in accordance with JIS P 8220-1:2012 ("Pulp - Disintegration methods - Part 1: Disintegration of chemical pulp", established April 20, 2012), the paper substrate was processed using a standard disintegrator (manufactured by Kumagai Riki Kogyo Co., Ltd.) until no undisintegrated fibers remained, thereby disintegrating the pulp into fibers. The disintegrated slurry (dispersion of pulp fibers) was adjusted to a solids concentration of 0.1% by mass, and the pulp solids concentration was calculated in accordance with JIS P 8225:2003 ("Method for measuring solids concentration in pulp - paper stock", established on May 20, 2003). The disintegrated slurry was adjusted to a solids concentration of 0.004% by mass, and 500 g of slurry was obtained, and the amount taken was recorded. The dry weight of the sample was calculated using the solids concentration and the amount of slurry taken. The obtained slurry was used to measure the kink index of the pulp using a fiber length measuring device (Valmet FS-5 (with UHD base unit) manufactured by Valmet Co., Ltd.).

[0145] The kink index of pulp was calculated by dividing the number of kinks in each angle range by the total fiber length, weighting the number according to the angle. Measurements were performed in accordance with ISO 16065-2:2014 ("Pulp - Determination of fiber length by automated photometric methods - Part 2: Non-polarized light method", published January 14, 2014). The device also uses an attached camera to detect and measure each individual fiber, taking pictures within a measurement cell with a depth of field of 0.5 mm. Fibers with lengths between 0.01 mm and 10.00 mm were photographed using the device.

[0146] <Sizing agent content> The paper substrate was separated from the skin pack mount by the method described in the <Basis Weight> section. After collecting 150 μg of the paper base material, the content of the sizing agent was measured by mass spectrometry using a gas chromatography (GC / MS) analyzer (Shimadzu Corporation, "GC-2025") under the following measurement conditions: The values ​​represent the content (parts by mass) relative to 100 parts by mass of the pulp that constitutes the paper base material.

[0147] (Measurement conditions) Sample: Sizepine N-817 manufactured by Arakawa Chemical Industries, Ltd. Column: Agilent Technologies HP-5MS (length 30 m, inner diameter 0.25 μm, outer diameter 0.25 mm) Carrier gas: Nitrogen Measurement temperature conditions: 100°C to 325°C at a rate of 15°C / min, held at 325°C for 5 minutes Pyrolysis equipment: Frontier Labs PY-2010SL ·Pyrolysis furnace temperature: 450℃

[0148] <Polyacrylamide resin content> The paper substrate was separated from the skin pack mount by the method described in the <Basis Weight> section. After collecting 150 μg of the paper base material, the polyacrylamide resin content was measured by mass spectrometry using a pyrolysis GC / MS analyzer (Shimadzu Corporation, "GC-2025") under the following measurement conditions: The values ​​represent the content (parts by mass) per 100 parts by mass of the pulp that makes up the paper base material.

[0149] (Measurement conditions) Standard: Arakawa Chemical Industries, Ltd. "Polystron 1430" Column: Agilent Technologies HP-INNOWAX (length 30 m, inner diameter 0.25 μm, outer diameter 0.25 mm) Carrier gas: Helium Measurement temperature conditions: 50°C to 200°C at a rate of 10°C / min, then 200°C to 240°C Heat at 5°C / min, then heat from 240°C to 260°C at 10°C / min, and hold at 260°C for 15 minutes Pyrolysis equipment: Frontier Labs PY-3030D ·Pyrolysis furnace temperature: 500℃

[0150] <Wet stiffness> The skin pack liner was cut into a length of 70 mm and a width of 38 mm to obtain a sample. The sample was conditioned in a humidity-controlled environment according to JIS P 8111:1998 ("Paper, paperboard, and pulp -- Standard conditions for humidity control and testing," revised September 20, 1998), and then immersed in ion-exchanged water at 23°C for 60 seconds. The water on the sample was then wiped off with a cloth, and the longitudinal stiffness was immediately measured according to JIS P 8125-2:2017 ("Paper and paperboard -- Bending resistance test method -- Part 2: Taber tester method," established March 21, 2017). This value was used as the longitudinal wet stiffness of the skin pack liner. The wet stiffness in the lateral direction of the skin pack mount was measured in the same manner as above, except that the skin pack mount was cut into a size of 38 mm lengthwise and 70 mm widthwise to prepare a sample.

[0151] The measuring device used was a Taber stiffness meter (digital Taber stiffness tester manufactured by Toyo Seiki Seisakusho, Ltd.) Measurements were carried out for an n number of 5, and the arithmetic mean value was taken as the wet stiffness of the skin pack mount in the longitudinal or transverse direction.

[0152] <Evaluation of strength when wet> The skin pack mount was punched into a rectangle measuring 280 mm long x 180 mm wide to obtain a sample. For punching, an automatic flat-plate punching machine ("Carton Master" manufactured by Asahi Machinery Co., Ltd.) was used. AP-1300-TSG-8).

[0153] The obtained samples were placed in a condensation cycle tester (Espec DCTH-201) and subjected to five cycles, each consisting of 60 minutes at 35°C and 90% RH and 60 minutes at -5°C. One minute after the test was completed, the following evaluations were performed under conditions of 23°C and 50% RH.

[0154] First, the sample was fixed onto four rectangular parallelepiped stands. Specifically, as shown in Figure 2A, sample 11 was placed on four rectangular parallelepiped stands 13 so that each of the four corners of sample 11 rested on each stand, measuring 1 cm x 1 cm. Next, as shown in Figures 2B and 2C, a 200 g weight 15 (oval shape with a major axis of 150 mm and a minor axis of 100 mm) was placed in the center of sample 11, and the degree of deflection was confirmed. The number of millimeters that sample 11 sunk in both the vertical and horizontal directions was measured, and the strength of the skin pack mount was evaluated based on the larger deflection using the following criteria.

[0155] Evaluation criteria S: Deflection less than 15mm A: Deflection is 15mm or more and less than 20mm B: Deflection is 20mm or more and less than 25mm C: Deflection of 25mm or more

[0156] <Recyclability evaluation> 60 g (bone dry mass) of skin pack backing paper was cut into 3 cm squares and diluted with tap water at 20°C to a solids concentration of 3% by mass. A standard disintegrator (manufactured by Kumagaya Riki Kogyo Co., Ltd.) was used to disintegrate the material at 3,000 rpm for 15 minutes to obtain a slurry. The resulting slurry was passed through a flat screen (manufactured by Kumagaya Riki Kogyo Co., Ltd.) equipped with a 6-cut (slit width: 0.15 mm) screen plate and refined for 15 minutes in a water flow of 10 L / min. The undisintegrated material remaining on the screen plate was collected and dried in an oven at 105°C to measure the bone dry mass. The recycling rate (%) was calculated from the measured value by 100 × {bone dry mass (g) of the backing paper used in the test - bone dry mass (g) of the undisintegrated material} ÷ bone dry mass (g) of the backing paper used in the test. The recyclability of the skin pack mount was evaluated according to the following criteria.

[0157] Evaluation criteria S: Recycling rate is 70% or more A: Recycling rate is between 55% and 70% B: Recycling rate is 40% or more but less than 55% C: Recycling rate is less than 40%

[0158] [Table 1]

[0159] [Table 2] [Explanation of symbols]

[0160] 1 Skin pack mount 1a Paper base material 1b Thermoplastic resin layer 11 Sample 13 units 15 weights

Claims

1. A skin pack mount having a thermoplastic resin layer on both sides of a paper base material, The paper base material contains pulp, a sizing agent, and a polyacrylamide resin, and satisfies the following requirements (A) and (B): (A) The total content of the sizing agent and the polyacrylamide resin relative to 100 parts by mass of the pulp is 0.15 parts by mass or more and 1.20 parts by mass or less. (B) The mass ratio of the content of the sizing agent to the content of the polyacrylamide resin is 2.5 or less.

2. The skin pack mount according to claim 1, wherein the paper substrate satisfies requirements (C) and (D). (C) The content of the sizing agent relative to 100 parts by mass of the pulp is 0.08 parts by mass or more and 0.80 parts by mass or less. (D) The content of the polyacrylamide resin relative to 100 parts by mass of the pulp is 0.05 parts by mass or more and 0.60 parts by mass or less.

3. The skin pack liner according to claim 1, wherein the ratio of the paper base material to the total mass of the skin pack liner is 50% by mass or more and 90% by mass or less.

4. 2. The skin pack liner according to claim 1, wherein the pulp has a kink index of 2,000 [1 / m] or more and 3,500 [1 / m] or less.

5. The skin pack mount has a basis weight of 300 g / m ２ The skin pack mount according to claim 1, wherein the skin pack mount is as described above.

6. 2. The skin pack mount according to claim 1, wherein the geometric mean of the wet stiffness in the longitudinal direction and the wet stiffness in the lateral direction of the skin pack mount is 19.0 mNm or more.

7. 2. The skin pack liner according to claim 1, wherein the sizing agent is at least one selected from the group consisting of rosin-based sizing agents and alkyl ketene dimer-based sizing agents.

8. A skin pack packaging body comprising the skin pack mount according to any one of claims 1 to 7, a contained item, and a resin film, A skin pack packaging body in which the stored item is stored between the skin pack mount and the resin film.

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