Laminates for packaging materials and packaging containers

Abstract

The present invention provides laminates for packaging materials and packaging containers that, even when subjected to a chemical recycling process, pose little risk of reducing cracking efficiency. [Solution] A laminate for packaging materials and a packaging container for use in a chemical recycling process, comprising a base layer, an adhesive layer, and a sealant layer, with a nitrogen content of 200 ppm or less.

Description

[Technical Field]

[0001] This disclosure relates to laminates for packaging materials and packaging containers. [Background technology]

[0002] Various packaging containers are used to protect their contents, and in recent years, there has been a growing social demand for recycling used packaging containers. Recycling processes are broadly classified into chemical recycling and material recycling. Chemical recycling is a process in which waste plastics are chemically decomposed back into chemical raw materials such as decomposition oils, synthesis gases, and monomers, and converted into reusable substances. On the other hand, material recycling is a process in which waste plastics are physically crushed or otherwise used as raw materials for products. Patent document 1 discloses a technology that facilitates the material recycling of flexible packaging, which is a form of packaging container. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-171328 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] When the inventors considered subjecting a flexible package composed of laminates to a chemical recycling process, they became concerned that the nitrogen components in the laminates might cause catalyst poisoning during the cracking process of the package's decomposition oil, potentially reducing the catalyst's performance.

[0005] This disclosure aims to provide laminates for packaging materials and packaging containers that have little concern about reducing cracking efficiency even when the packages are subjected to a chemical recycling process. [Means for solving the problem]

[0006] One aspect of this disclosure is a laminate for packaging materials to be subjected to a chemical recycling process, comprising a base layer, an adhesive layer, and a sealant layer, with a nitrogen content of 200 ppm or less.

[0007] In one embodiment, the ratio of the basis weight of the adhesive layer to the total basis weight of the packaging laminate may be 0.00104 or less.

[0008] In one embodiment, the adhesive layer may be formed by coating an adhesive onto a substrate layer.

[0009] In one embodiment, the laminate for packaging material may be generated during the process of manufacturing the packaging container.

[0010] Another aspect of this disclosure is a packaging container comprising any of the packaging material laminates described above. [Effects of the Invention]

[0011] According to this disclosure, it is possible to provide laminates for packaging materials and packaging containers that have little concern about reducing the efficiency of cracking even when the packaging is subjected to a chemical recycling process. [Modes for carrying out the invention]

[0012] The embodiments described herein will be explained below.

[0013] [Laminated body for packaging materials] Embodiments of the packaging laminate of this disclosure will now be described. The packaging laminate can also be called a packaging film. The packaging laminate comprises a base layer, an adhesive layer, and a sealant layer. When a packaging container is made using the packaging laminate, the sealant layer comes into contact with the contents. Therefore, the direction in contact with the contents is sometimes called the contents side, and the opposite direction is sometimes called the outside. The packaging laminate may have an intermediate layer between the base layer and the sealant layer. Examples of intermediate layers include a gas barrier layer, a printing layer, and a second base layer to improve the strength of the laminate. In addition, a protective layer or a printing layer may be provided outside the base layer. Furthermore, when the packaging laminate is used in a tube container, a second sealant layer may be provided outside the base layer.

[0014] The laminate for packaging materials has a nitrogen content of 200 ppm or less. In the chemical recycling process, the laminate for packaging materials or packaging containers is thermally decomposed to produce decomposition oil, which is then cracked to produce monomers or oligomers, and the resulting monomers or oligomers are polymerized to produce polymers. If the nitrogen content is 200 ppm or less, the function of the catalyst used in the cracking process will not be reduced, and the decomposition oil obtained by decomposing the laminate for packaging materials can be efficiently monomerized. The laminate for packaging materials may contain nitrogen components if it is unavoidable in the manufacturing process and in an amount that does not hinder the cracking process. Furthermore, since the nitrogen content in the laminate becomes a problem in the process of cracking the decomposition oil in the chemical recycling process, a total nitrogen content of 200 ppm or less in the laminate for packaging materials means that the nitrogen content of the decomposition oil obtained by thermally decomposing the laminate for packaging materials of this embodiment is 200 ppm or less.

[0015] The nitrogen component in the laminate for packaging materials can be nitrogen atoms contained in the polymer of the resin constituting the laminate, nitrogen atoms derived from impurities contained in the resin constituting the laminate, or nitrogen atoms contained in the adhesive. Since nylon, which is often used for laminates for packaging materials, contains a large amount of nitrogen atoms in the polymer, in the laminate for packaging materials in the present disclosure, it is preferable not to include a layer containing nylon. The layer containing nylon can be a layer composed of nylon or a layer in which nylon is dispersed in another type of resin.

[0016] (Base material layer) As the base material layer, resin materials commonly used in the field of packaging containers can be used. Examples of such resin materials include polyolefin, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc. However, nylon is not preferable as the material for the base material layer for the reasons described above. Polyolefin is, for example, polyethylene or polypropylene. The resin material used for the base material layer may be a petroleum-derived resin, a plant-derived resin, or a recycled resin as long as the content ratio of the nitrogen component in the entire laminate is 200 ppm or less. The recycled resin may be a mechanical recycled resin or a chemical recycled resin.

[0017] The base material layer may contain materials other than those described above as impurities. Further, the base material layer may further contain additives such as fillers, antistatic agents, plasticizers, lubricants, light-shielding pigments, and antioxidants, if necessary. When the base material layer contains a light-shielding pigment, the base material layer also functions as a light-shielding layer.

[0018] The thickness of the base material layer is not particularly limited, but may be, for example, 10 μm or more and 100 μm or less, or may be 15 μm or more and 40 μm or less. The basis weight of the base material layer is 8.0 g / m 2 or more and 80.0 g / m 2 or less, may be 8.0 g / m 2 or more and 30.0 g / m 2 or less, may be 8.0 g / m 2 or more and 20.0 g / m2 The following may be applicable. Also, the base material layer may be a single layer or a multilayer structure. When the base material layer has a multilayer structure, all the layers may be composed of the same material or different materials.

[0019] When providing an adhesive layer on the surface of the base material layer, in order to enhance the adhesion with the adhesive layer, various pretreatment such as corona treatment, plasma treatment, ozone treatment, flame treatment, etc. may be performed on the surface on the adhesive layer side, or a coating layer such as an easy-adhesion layer may be provided. Also, the base material layer may be stretched or non-stretched.

[0020] (Adhesive layer) The adhesive layer is disposed between the base material layer and the sealant layer. The adhesive layer is a layer formed using an adhesive. That is, the adhesive layer is a layer composed of a cured product of the adhesive. The adhesive layer may be formed by coating the adhesive on the base material layer. Alternatively, the adhesive layer may be formed by extruding a molten resin between two layers to be laminated. As the adhesive, for example, known adhesives containing a nitrogen component such as two-component curable urethane adhesives, isocyanate adhesives, and two-component curable epoxy adhesives, as well as known adhesives not containing a nitrogen component such as modified polyolefin adhesives and butadiene adhesives can be used. The adhesive may be a gas barrier adhesive. As the gas barrier adhesive, for example, an epoxy-based gas barrier adhesive or a urethane-based gas barrier adhesive may be used. Examples of the epoxy-based gas barrier adhesive include polyamine adhesives. Examples of the gas barrier adhesive include Maxseal (registered trademark, manufactured by Mitsubishi Gas Chemical Co., Inc.) and Paslim (registered trademark, manufactured by DIC Corporation).

[0021] The two-component curable urethane adhesive containing a nitrogen component contains a polyol component as the main agent and a polyisocyanate component as the curing agent.

[0022] The polyol component is one or more selected from the group consisting of polyester polyols, polyether polyols, polyether ester polyols, and polyurethane polyols, and the ends of the polyols are partially acid-modified. The terminal hydroxyl groups of the polyol component are partially acid-modified, for example, so that their valency is between 2 and 20.

[0023] Polyester polyols are, for example, esterification products of polycarboxylic acids, dialkyl esters of polycarboxylic acids, and mixtures thereof with glycol-based solvents. Examples of polycarboxylic acids include succinic acid, glutaric acid, isophthalic acid, terephthalic acid, adipic acid, pimelic acid, corticic acid, azelaic acid, sebatic acid, dodecanedioic acid, and dimer acids. Examples of glycol-based solvents include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butylene glycol, neopentyl glycol, and 1,6-hexanediol.

[0024] Polyether polyols are polymers of, for example, oxirane compounds and low molecular weight polyols. Oxirane compounds include, for example, ethylene oxide, propylene oxide, butylene oxide, and tetrahydrofuran. Low molecular weight polyols include water, ethylene glycol, propylene glycol, trimethylolpropane, and glycerin.

[0025] Polyether ester polyols are obtained, for example, by the reaction of polycarboxylic acids, dialkyl esters of polycarboxylic acids, and mixtures thereof with polyether polyols. Polyurethane polyols are reaction products of polyester polyols, polyether polyols, polyether ester polyols, and polyisocyanate monomers.

[0026] The polyisocyanate component is a mixture of aliphatic polyisocyanates and aromatic polyisocyanates. Aliphatic polyisocyanates include, for example, polyisocyanate monomers, polyisocyanate derivatives, and polyisocyanate-terminated prepolymers. Examples of polyisocyanate monomers include tetramethylene diisocyanate, isopropyl diisocyanate, 1,6-hexamethylene diisocyanate, dodecamethylene diisocyanate, and trimethylhexamethylene diisocyanate. Examples of polyisocyanate monomers include 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, lysine diisocyanate, and isophorone diisocyanate.

[0027] Aromatic polyisocyanates include, for example, polyisocyanate monomers, polyisocyanate derivatives, and polyisocyanate-terminated prepolymers. Examples of polyisocyanate monomers include tolylene diisocyanate, phenylene diisocyanate, diphenylmethane diisocyanate, and naphthalene diisocyanate. Examples of polyisocyanate monomers include xylylene diisocyanate and tetramethylxylylene diisocyanate.

[0028] Polyisocyanate derivatives are, for example, isocyanurates derived from polyisocyanate monomers. Polyisocyanate-terminated prepolymers are difunctional polyisocyanates containing terminal isocyanate groups obtained by reacting polyisocyanate monomers with difunctional polyol compounds such as polypropylene glycol. Polyisocyanate-terminated prepolymers are also polyfunctional polyisocyanates containing terminal isocyanate groups obtained by reacting polyisocyanate monomers with trifunctional or higher polyol compounds such as trimethylolpropane.

[0029] As a nitrogen-free butadiene-based adhesive, for example, EL451 (manufactured by Toyo Ink Co., Ltd.) can be used. As a nitrogen-free modified polyolefin-based adhesive, for example, Aron Base (registered trademark) SD-5200 (manufactured by Unitika Ltd.), Unistol (registered trademark) R-300 (manufactured by Mitsui Chemicals, Inc.), or Auroren (registered trademark) 350S (manufactured by Nippon Paper Industries Co., Ltd.) can be used.

[0030] From the viewpoint of easily making the content ratio of the nitrogen component in the laminate 200 ppm, the coating amount of the adhesive is preferably 0.15 g / m 2 or less, more preferably 0.08 g / m 2 or less, still more preferably 0.06 g / m 2 or less, still more preferably 0.05 g / m 2 or less is still more preferable. In order to prevent the nitrogen component from inhibiting the cracking process in the chemical recycling process, the coating amount of the adhesive layer with respect to the total thickness of the laminate for packaging materials is important. Therefore, when the total thickness of the laminate is large, that is, when the basis weight is large, a larger coating amount of the adhesive is allowed. However, increasing the thickness of the laminate without reason will only require more resin materials. For these reasons, the coating amount of the adhesive is preferably within the above range.

[0031] The ratio of the basis weight of the adhesive layer to the total basis weight of the laminate for packaging materials is preferably 0.00104 or less. This makes it easy to make the content ratio of the nitrogen component in the entire laminate for packaging materials 200 ppm or less.

[0032] (Sealant layer) The sealant layer is a layer that forms a seal by melting during the manufacturing of a laminate for packaging materials. As the sealant layer, resin materials commonly used in the field of packaging containers can be used. Examples of such resin materials include polyolefins and polyethylene terephthalate (PET). Polyolefins include, for example, polyethylene and polypropylene. The resin material used in the sealant layer may be petroleum-derived resin, plant-derived resin, or recycled resin, as long as the nitrogen content of the entire laminate is 200 ppm or less. Recycled resin may be mechanically recycled resin or chemically recycled resin. However, if there are concerns about psychological resistance from consumers, it is preferable to use petroleum-derived resin or plant-derived resin instead of recycled resin.

[0033] The sealant layer may be colored white or the like. For example, a white sealant containing a titanium dioxide-based white pigment can be used as the sealant layer.

[0034] The thickness of the sealant layer is not particularly limited, but may be, for example, 10 μm to 100 μm, or 40 μm to 80 μm. The basis weight of the sealant layer is 20.0 g / m². 2 More than 100.0g / m 2 The following may be used: 30.0 g / m 2 More than 70.0g / m 2 The following may be used: 40.0 g / m 2 More than 60.0g / m 2 The following may apply. The sealant layer may be a single layer or a multilayer structure. If the sealant layer is a multilayer structure, all layers may be made of the same material or different materials.

[0035] The sealant layer may be formed by applying an adhesive to the substrate layer and then laminating a sealant film via an extruded resin, or by applying an adhesive to the substrate layer and then extruding a resin for forming the sealant layer onto it.

[0036] If the laminate for packaging material includes a second sealant layer, it can have the same configuration as the sealant layer described above.

[0037] (Gas barrier layer) The packaging laminate may include a gas barrier layer as an intermediate layer. The gas barrier layer has barrier properties against gases such as water vapor and oxygen. Examples of the gas barrier layer include a vapor-deposited layer of a metal such as aluminum, or a vapor-deposited layer of an inorganic oxide such as aluminum oxide or silicon oxide. The gas barrier layer may be formed directly on the substrate layer, or via an anchor coat layer or the like, or the gas barrier layer may be formed on a substrate for forming the gas barrier layer, and then these laminates may be laminated on the substrate layer.

[0038] Each of the above layers may be composed of recycled resin. The recycled resin may be post-industrial resin (PIR) generated during the process of manufacturing the packaging container, or post-consumer resin (PCR) generated from waste after the contents have been filled and used. PIR is preferred because it is less affected by the contents and there is less concern that it will reduce the efficiency of cracking even when subjected to a chemical recycling process.

[0039] [Packaging container] Next, embodiments of the packaging container of this disclosure will be described. The packaging container is a container made using the laminate for packaging material described above. That is, it comprises a laminate for packaging material. The packaging container is made by a sealing process in which the sealant layers of the laminate for packaging material are placed facing each other, the sealant layers are melted, and pressure is applied. It may be formed by folding one laminate for packaging material in the middle, or it may be formed using a pair of laminates for packaging material. The form of the packaging container may be a sachet, a gusset, various pouches such as three-sided pouches, four-sided pouches, standing pouches, retort pouches, tubes such as laminate tubes, pillow packaging, etc. It may further have a spout or a zipper.

Claims

1. A laminate for packaging materials to be subjected to a chemical recycling process, comprising a base layer, an adhesive layer, and a sealant layer, with a nitrogen content of 200 ppm or less.

2. The packaging laminate according to claim 1, wherein the ratio of the basis weight of the adhesive layer to the total basis weight of the packaging laminate is 0.00104 or less.

3. The laminate for packaging material according to claim 1, wherein the adhesive layer is formed by coating the substrate layer with an adhesive.

4. A laminate for packaging material according to claim 1, which is generated in the process of manufacturing a packaging container.

5. A packaging container comprising a laminate for packaging material according to any one of claims 1 to 3.