Sealant film and laminate film

Abstract

The present invention provides a sealant film and a laminate film with excellent ease of handling while also containing a recycled material. More specifically, the present invention relates to: a sealant film 10 containing a recycled material using a laminate as a raw material, in which a plurality of resin layers consisting solely of a polyethylene resin film are laminated via an adhesive layer, the sealant film 10 having a multilayer structure of at least two layers, and the sealant film 10 having a virgin resin layer without the recycled material on at least one of end faces 14, 15 in the thickness direction; and a laminate film 16 in which a base material film 17 is laminated to the sealant film 10.

Description

Sealant and laminating films

[0001] The present invention relates to a sealant film and a laminating film.

[0002] Patent Document 1 describes a production method in which a synthetic resin containing aluminum foil pieces is fed into an extruder, the aluminum foil is crushed and kneaded to form pellets, and the pellets are then removed from cooling water and dehydrated and dried to a moisture content of 0.1% or less. Patent Document 2 describes a laminated film in which a recycled polyethylene layer is laminated with a linear low-density polyethylene layer.

[0003] Japanese Patent Publication No. 2009-073028 Japanese Patent Publication No. 2023-040660

[0004] Paragraph 0036 of Patent Document 1 describes the production of various molded products such as blocks, bricks, stakes, fences, boards, sheets, injection-molded products, and multilayer containers from recycled pellets, but does not describe their use as sealant films for packaging bags, etc. Paragraph 0044 of Patent Document 2 describes the use of a linear low-density polyethylene layer that does not contain recycled polyethylene as the innermost layer, and paragraph 0086 describes the production of synthetic resin products such as packaging bodies using a laminated film having a recycled polyethylene layer, but does not describe their use as sealant films for packaging bags, etc.

[0005] Sealant films are laminated with other resin films, such as base films, to produce packaging bags, but before laminating with other resin films, the sealant film is handled as a single film. Therefore, further improvements are needed to use laminated films with recycled polyethylene layers as sealant films. When horizontally recycling from one packaging bag to another, it is difficult to remove impurities such as adhesives, inks, and additives, and improvements are needed to ensure that the film is strong enough to be used as a sealant film even if these impurities are mixed in.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sealant film that contains recycled materials and yet has excellent handleability, and a laminate film that contains the sealant film.

[0007] In order to solve the above problems, one aspect of the present invention includes the following aspects.

[0008] The first aspect is a sealant film containing recycled material, which uses as its raw material a laminate in which multiple resin layers made only of polyethylene-based resin films are laminated via adhesive layers, and the sealant film has a multilayer structure of at least two layers, and has a virgin resin layer that does not contain the recycled material on at least one end surface in the thickness direction.

[0009] In a second aspect, in the first aspect, the sealant film has a virgin resin layer that does not contain recycled material on both end surfaces in the thickness direction of the sealant film.

[0010] A third aspect is the first or second aspect, wherein the density of the virgin resin contained in the sealant film is 0.910 g / cm ３ 0.930g / cm or more ３ The following is the result.

[0011] A fourth aspect is any one of the first to third aspects, wherein the content ratio of the recycled material to the total weight of the sealant film is 50% by weight or less.

[0012] A fifth aspect is any one of the first to fourth aspects, wherein the recycled material contains high-density polyethylene.

[0013] A sixth aspect is any one of the first to fifth aspects, wherein the recycled material contains a printing ink component or a urethane adhesive.

[0014] In the seventh aspect, in any one of the first to sixth aspects, the sealant film has a total light transmittance of 65 to 90%.

[0015] The eighth embodiment is a laminated film obtained by laminating a base film on the sealant film of any one of the first to seventh embodiments.

[0016] According to the present invention, it is possible to provide a sealant film and a laminate film that contain recycled materials and yet have excellent handleability.

[0017] 1 is a cross-sectional view showing an example of a sealant film of the present embodiment; FIG. 2 is a cross-sectional view showing an example of a laminate that is a raw material for recycled materials; and FIG. 3 is a cross-sectional view showing an example of a laminate film including the sealant film of the present embodiment.

[0018] The present invention will be described below based on preferred embodiments.

[0019] 1, the sealant film 10 of this embodiment has a multilayer structure of at least two layers. Methods for producing the multilayer structure include multilayer inflation molding, multilayer T-die molding, dry lamination, extrusion lamination, etc.

[0020] The illustrated multilayer structure includes terminal layers 11 and 13 facing both terminal surfaces in the thickness direction, respectively, and an intermediate layer 12 laminated between the terminal layers 11 and 13. The multilayer structure of at least two layers may be a two-layer multilayer structure consisting of the terminal layers 11 and 13, or may be a three-layer or more multilayer structure including one or more intermediate layers 12.

[0021] The sealant film 10, except for the end layers 11, 13 on at least one side, contains recycled material using polyethylene resin film as a raw material.

[0022] 2, the recycled material is produced using as a raw material a laminate 20 in which a plurality of resin layers 21, 22, 23 made only of polyethylene-based resin film are laminated via adhesive layers 24, 25. The number of resin layers 21, 22, 23 is not particularly limited, and may be two layers or four or more layers, rather than the three layers shown in the example.

[0023] At least one of the end layers 11, 13 is a virgin resin layer that does not contain recycled material. This allows at least one of the end surfaces 14, 15 to be formed from a virgin resin layer, which facilitates sanitation management of the surface that comes into contact with the contents and improves sealing performance when heat-sealing sealant films 10 together. It is preferable that both end layers 11, 13 are virgin resin layers and that both end surfaces 14, 15 do not contain recycled material.

[0024] Examples of polyethylene-based resins include linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), etc. The polyethylene-based resin may be a homopolymer of ethylene or a copolymer mainly composed of ethylene.

[0025] Examples of monomers (comonomers) other than ethylene include one or more of α-olefins such as 1-butene, 1-hexene, and 1-octene, cyclic olefins such as norbornene, and vinyl monomers such as vinyl acetate, vinyl chloride, and acrylic acid. When the polyethylene resin is copolymerized with a monomer having an ester group such as vinyl acetate, some of the ester groups may be saponified to form a copolymer containing vinyl alcohol.

[0026] The proportion of ethylene in the constituent monomers of polyethylene resins is preferably 50% by weight or more, and may be, for example, 80 to 100% by weight. Ethylene or comonomers may be compounds derived from fossil resources such as petroleum, compounds derived from biomass such as plants, or compounds obtained by chemical recycling. Chemical recycling refers to the process of producing compounds such as monomers by chemical treatment of raw materials of recycled materials.

[0027] The resin contained in the polyethylene-based resin layer may be polyethylene-based resin only, or may contain other resins. The polyethylene-based resin layer is preferably composed of 80 wt % or more, 90 wt % or more, or 95 wt % or more of polyethylene-based resin. Each polyethylene-based resin layer may be composed of one type of polyethylene-based resin, or two or more types of polyethylene-based resins.

[0028] The polyethylene resin may contain additives other than the resin. The additives are not particularly limited, but examples thereof include antioxidants, lubricants, antiblocking agents, flame retardants, UV absorbers, light stabilizers, antistatic agents, colorants, crosslinking agents, etc. The additives may be either components that are compatible with the resin or components that are not compatible with the resin.

[0029] The virgin resin layer is a polyethylene-based resin layer made of virgin polyethylene-based resin. Virgin polyethylene-based resin refers to a resin that is used in a product only after being industrially produced by polymerizing monomers, and may be simply referred to as "virgin resin" in the following explanation. The virgin resin may contain monomers obtained by the above-mentioned chemical recycling.

[0030] Virgin resins can be easily controlled in terms of composition, degree of polymerization, density, melting point, etc., so that they have desired physical properties. Therefore, virgin resins can be used stably, but compared to recycled materials, they impose a greater environmental burden in the processes of monomer production, polymerization, etc.

[0031] In the raw materials of the recycled material, the resin layers 21, 22, and 23 are polyethylene-based resin layers made of polyethylene-based resin. The polyethylene-based resin of the recycled material refers to a resin that is produced industrially by polymerization of a monomer, and then recovered after being used in a product or without being used in a product, and reused by processing such as crushing and dissolving without returning it to a monomer. In the following explanation, it may be simply referred to as "recycled material."

[0032] Examples of products using polyethylene resins include films, sheets, packaging bags, molded products, etc. Scraps of films, sheets, etc., used packaging films, packaging bags, etc. are used as raw materials for recycled materials. A laminate in which multiple resin layers made only of polyethylene resin films are laminated via adhesive layers may be used as the raw material for recycled materials, or other raw materials may be used in part. Examples of the proportion of other raw materials include 20% by weight or less, 10% by weight or less, etc.

[0033] Recycled materials are subjected to heat history during product processing before recycling, and are also subjected to heat history again during processes such as recovery, crushing, dissolution, and product processing after recycling. In addition, recycled materials are subjected to mechanical, optical, chemical, and other stresses during their history before and after recycling. For this reason, recycled materials may have inferior performance to virgin resins, even when processed from raw materials with relatively uniform properties, such as scraps and unused waste materials.

[0034] Furthermore, recycled materials may be processed in a mixed state of various raw materials during recycling. For example, polyethylene-based resins with different compositions, polymerization degrees, densities, melting points, etc. may not be sufficiently separated, and / or foreign matter such as additives, impurities, and deposits may not be sufficiently removed before processing. This may make it difficult to obtain stable performance, or foreign matter may affect the performance of the resin.

[0035] Although it is possible to select raw materials depending on the intended use of the recycled material, it may be difficult to separate and separate the raw materials if they are composite materials. For example, a polyethylene resin film raw material may contain a laminate containing a relatively low-density resin such as LDPE or LLDPE and a relatively high-density resin such as HDPE or MDPE.

[0036] As described above, when the laminate 20 in which a plurality of resin layers 21, 22, 23 made only of polyethylene-based resin films are laminated via adhesive layers 24, 25 is used as a raw material, even if the resin layers 21, 22, 23 are different polyethylene-based resin layers, it is difficult to peel off the adhesive layers 24, 25 or separate the resin layers 21, 22, 23. For this reason, it is not easy to adjust the quality of the recycled material.

[0037] The density of the virgin resin contained in the sealant film 10 is 0.910 g / cm ３ 0.930g / cm or more ３ It is preferable that the density is less than 1 / 2 of the original density. This can improve the processability of recycled materials. If the density of the virgin resin is too low, blocking may occur easily. As the virgin resin used in the sealant film 10, resins with relatively low density such as LDPE and LLDPE are preferred.

[0038] The content of recycled material in the sealant film 10 is preferably 50% by weight or less relative to the total weight. By mixing virgin resin, which has properties suitable for a sealant, with recycled material, whose quality is difficult to adjust, it is possible to reduce the environmental impact while ensuring quality. The content of recycled material may have an upper or lower limit selected from at least one of 50% by weight, 40% by weight, 30% by weight, 20% by weight, 10% by weight, and 5% by weight.

[0039] From the viewpoint of quality control of the sealant film 10, it is preferable to use recycled materials with physical properties suitable for sealants, such as LDPE and LLDPE. However, raw materials for recycled materials are limited to scraps of sealant material, and it may be difficult to secure a sufficient quantity. For this reason, it is preferable that the recycled material contains HDPE.

[0040] HDPE is suitable as a base film for polyethylene-based resin films, so a composite film including a base film and a sealant film can be used as the raw material laminate 20.

[0041] From the perspective of quality control of the sealant film 10, it is preferable to thoroughly remove foreign materials such as printing ink components and urethane adhesives. However, this may complicate the processing of recycled materials and increase costs. For this reason, it is preferable that the recycled material contains printing ink components or urethane adhesives. The recycled material containing printing ink components may be a material with a lower total light transmittance than virgin resin. For example, the total light transmittance of the sealant film 10 may be 90% or less. However, compared to sealant films made only of recycled materials, the inclusion of a virgin resin layer that does not contain recycled materials can relatively increase the total light transmittance. For example, the total light transmittance of the sealant film 10 may be 65% or more. Furthermore, sealant films containing recycled materials have a lower total light transmittance than sealant films made only of virgin resin, resulting in excellent light-blocking and concealing properties.

[0042] The printing ink component is useful for ensuring a display surface and improving design when commercializing the polyethylene resin film, and the urethane adhesive is useful for bonding between the resin layers 21, 22, and 23. Therefore, a composite film including a printing layer (not shown) and adhesive layers 24 and 25 can be used as the raw material laminate 20.

[0043] The sealant film 10 can be laminated with a base film 17 to produce a laminate film 16. Since the sealant film 10 accounts for a large proportion of the laminate film 16, increasing the recycling rate of the sealant film 10 is advantageous for increasing the recycling rate of the laminate film 16.

[0044] The base film 17 is not particularly limited, but examples thereof include polyolefin resins such as polyethylene (PE) and polypropylene (PP), polyester resins such as polyethylene terephthalate (PET), and polyamide resins such as nylon (Ny). The base film 17 may be one layer or two or more layers. Furthermore, in consideration of subsequent recycling, the base film 17 is preferably a PE resin.

[0045] Although not specifically shown, the laminate film 16 may have at least one selected from a printed layer, an adhesive layer, a barrier resin layer such as an ethylene-vinyl alcohol copolymer (EVOH), a metal vapor deposition layer such as aluminum, a metal foil such as aluminum foil, an inorganic vapor deposition layer such as silica or alumina, an extruded resin layer such as PE, etc. The sealant film 10 and the base film 17 may be bonded together with a urethane adhesive.

[0046] The laminated film 16 may be used to manufacture packaging containers such as packaging bags. Specific examples of packaging bags include three-side sealed bags, four-side sealed bags, pillow bags, gusset bags, and standing pouches.

[0047] The dimensions of the packaging bag are not particularly limited. For example, in the case of use as a refill container, the vertical height is about 100 to 500 mm, the horizontal width is about 70 to 300 mm, and the filling amount is 100 cm ３ ~5000cm ３ It is preferable that the degree of

[0048] The packaging bag can be filled with a predetermined content and then sealed to obtain a desired packaged product (content-filled packaging bag). The state of the content is not particularly limited, but examples include fluids such as liquids, powders, and granules, and solids such as articles. The type of content is not particularly limited, but examples include detergents, medicines, cosmetics, pharmaceuticals, beverages, seasonings, inks, paints, fuels, etc.

[0049] While the present invention has been described above based on preferred embodiments, the present invention is not limited to the above-described embodiments and various modifications can be made without departing from the spirit of the present invention. Modifications include addition, substitution, omission, and other changes of components.

[0050] The present invention will be specifically described below with reference to examples.

[0051] A sealant film 10 having three layers, an outer (terminal layer 13), a middle (intermediate layer 12), and an inner (terminal layer 11), was produced by multi-layer inflation using the layer configuration and layer ratio shown in Table 1. The layer ratio is the relative weight ratio determined according to the product of the thickness and density of each layer. The recycling rate is the weight ratio (wt%) of recycled material used in each layer. "R" in the layer configuration represents a layer with a recycling rate greater than 0 wt%, and "V" represents a virgin resin layer with a recycling rate of 0 wt%.

[0052] The recycled material used was a polyethylene resin obtained by repelletizing a laminate obtained by laminating an HDPE layer and an LLDPE layer with a printing ink layer and a urethane adhesive layer interposed therebetween, as a raw material.

[0053] The virgin resin used was C6LLDPE copolymerized with a comonomer having 6 carbon atoms. The density of the virgin resin is shown in Table 1.

[0054]

[0055] The evaluation results of the sealant film are shown in Table 2. The evaluation methods were as follows.

[0056] (Recycling rate) The recycling rate of the entire sealant film is calculated by dividing the layer ratio of each layer of the sealant film (A 外 , A 中 , A 内 ) and recycling rate (B 外 , B 中 , B 内 ) and calculated using the following formula: "Overall recycling rate" = (A 外 B 外 +A 中 B 中 +A 内 B 内 ) / (A 外 +A 中 +A 内 )

[0057] (Processability) The processability was evaluated for film-forming ability and blocking according to the following criteria. For film-forming ability, stable bubbles were evaluated as "○", stable bubbles were evaluated as "△", and unstable bubbles were evaluated as "×". For blocking, no sticking to the inner surface of the tube was evaluated as "○", some sticking to the inner surface of the tube but easy peeling was evaluated as "△", and sticking to the inner surface of the tube and not easy peeling was evaluated as "×".

[0058] (Dart Impact Test) The dart impact test was performed in accordance with JIS K7124-1 Staircase A Method. A dart was dropped onto the sealant film from a predetermined height of 0.66 m, and the impact fracture mass (g) was measured. When the impact fracture mass was 1200 g or more, it was recorded as 1200 or more.

[0059] (Gelbo Flex Test) The Gelbo Flex test was performed using a BE-1005 Gelbo Flex Tester manufactured by Tester Sangyo Co., Ltd., and the number of pinholes that occurred after bending the sealant film 500 times or 1000 times was counted and evaluated. In Table 2, "-" indicates that no measurement was performed.

[0060] (Total Light Transmittance) The total light transmittance was measured in accordance with JIS K7361 using NDH4000 manufactured by Nippon Denshoku Industries Co., Ltd.

[0061]

[0062] As shown in Table 2, at least good results were obtained for the sealant films of Examples 1 to 8. Excellent results were also obtained for the sealant films of Examples 4 to 8. This shows that the present invention improves film-forming properties and flex resistance.

[0063] 10...sealant film, 11, 13...end layer, 12...intermediate layer, 14, 15...end surface, 16...laminated film, 17...substrate film, 20...laminated body, 21, 22, 23...resin layer, 24, 25...adhesive layer

Claims

A sealant film containing recycled materials using as a raw material a laminate in which a plurality of resin layers made of only polyethylene-based resin films are laminated via adhesive layers, The sealant film has a multi-layer structure of at least two layers, and has a virgin resin layer not containing the recycled material on at least one end surface in the thickness direction.

2. The sealant film according to claim 1, further comprising a virgin resin layer not containing the recycled material on both end surfaces in the thickness direction of the sealant film. 　 The density of the virgin resin contained in the sealant film is 0.910 g / cm ３ 0.930g / cm or more ３ The sealant film according to claim 1 or 2, characterized in that:

4. The sealant film according to claim 1, wherein the content of the recycled material relative to the total weight of the sealant film is 50% by weight or less. 　 The sealant film according to any one of claims 1 to 4, characterized in that the recycled material contains high density polyethylene. 　 The sealant film according to any one of claims 1 to 5, wherein the recycled material contains a printing ink component or a urethane adhesive.

7. The sealant film according to claim 1, wherein the sealant film has a total light transmittance of 65 to 90%. 　 A laminate film comprising the sealant film according to any one of claims 1 to 7 and a base film laminated thereon.

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