Anti-fog multilayer films, laminates, packaging materials, lids, and top-seal containers

Abstract

Provided is an antifogging multilayer film which has, in the following order, at least a layer (A) that has a linear polyethylene as a main resin component, an adhesive layer (B) that has a linear polyethylene and a polypropylene resin as main resin components and contains an antifogging agent, and a heat seal layer (C) that has a polypropylene resin as a main resin component and contains an antifogging agent, and which has a seal strength of 10-18 N / 15 mm at room temperature and a seal strength of 4-8 N / 15 mm at 100°C. Also provided are a laminate, a packaging material, a lid material, and a top seal container which use the antifogging multilayer film.

Description

[Technical Field]

[0001] The present invention relates to a multilayer film that is suitable for use as a lid material for food packaging containers, possessing both anti-fogging properties and easy-opening properties, and a laminate using the same. [Background technology]

[0002] Currently, top-seal containers are used as food packaging containers, which consist of a plastic container with a film lid (lid material). The lid material for top sealing requires anti-fogging properties to improve the visibility of the food contents. A multilayer film suitable for this purpose is known, which is a multilayer film in which a laminate layer (A) mainly composed of linear polyethylene (a) and without an anti-fogging agent, an intermediate layer (B) containing linear polyethylene (b1) and an anti-fogging agent (b2), and a heat-seal layer (C) containing polypropylene resin (c1) and an anti-fogging agent (c2) are laminated in the order of (A) / (B) / (C), the total mass of the anti-fogging agent (b2) and the anti-fogging agent (c2) is in the range of 0.8 to 1.6 mass% of the total mass of the multilayer film, the wettability of both outer surfaces of the multilayer film is in the range of 35 to 45 mN / m, and the total thickness of the multilayer film is 20 to 100 μm. (See, for example, Patent Document 1).

[0003] On the other hand, recently, there has been an increase in users directly heating top-seal containers in microwave ovens to heat the food inside. When top-seal containers are heated in a microwave oven, the contents become hot, posing a risk of burns. In addition, the large amount of steam generated makes it difficult to see the contents even if the container has anti-fog properties, and there is a risk of burns when opening the container. Furthermore, because the container itself becomes hot, its rigidity decreases, and it becomes difficult to open the container because it is hard to get a firm grip on the hot lid.

[0004] The anti-fog multilayer film described in Patent Document 1 was not designed for use as a top-seal container that is directly heated in a microwave oven, and there was still room for improvement. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] WO2015 / 046131 [Overview of the project] [Problems that the invention aims to solve]

[0006] The object of the present invention is to provide an anti-fog multilayer film suitable for direct microwave heating as a lid material for a top-seal container, a laminate obtained by laminating this multilayer film onto a base film, a packaging material using the same, and a top-seal container. [Means for solving the problem]

[0007] The inventors have discovered an anti-fog multilayer film suitable for use as a lid material for top-seal containers that are directly heated in a microwave oven. This film has sufficient sealing strength to withstand distribution and be opened before microwave heating, but during or immediately after heating, the sealing strength decreases to a level that allows the container to be easily opened even when it is hot.

[0008] In other words, the present invention provides an anti-fogging multilayer film having, in this order, at least a layer (A) mainly composed of linear polyethylene as the resin component, an adhesive layer (B) mainly composed of linear polyethylene and polypropylene resin and containing an anti-fogging agent, and a heat-seal layer (C) mainly composed of polypropylene resin and containing an anti-fogging agent, with a seal strength of 10 to 18 N / 15 mm at room temperature and a seal strength of 4 to 8 N / 15 mm at 100°C.

[0009] The present invention also provides a laminate containing the anti-fogging multilayer film described above.

[0010] The present invention also provides a packaging material containing the anti-fogging multilayer film described above.

[0011] The present invention also provides a lid material containing the anti-fogging multilayer film described above.

[0012] The present invention also provides a top-seal container containing the anti-fogging multilayer film described above.

Effects of the Invention

[0013] According to the present invention, an anti-fogging multilayer film suitable for direct microwave heating as a lid material for a top-seal container can be provided, and a laminate formed by laminating this multilayer film on a base film, a packaging material using this laminate, and a top-seal container can be provided.

Modes for Carrying Out the Invention

[0014] (Anti-fogging multilayer film) The anti-fogging multilayer film of the present invention has at least a layer (A) having linear polyethylene as a main resin component, an adhesive layer (B) having linear polyethylene and a polypropylene-based resin as main resin components and containing an anti-fogging agent, and a heat-sealing layer (C) having a polypropylene-based resin as a main resin component and containing an anti-fogging agent, in this order. When the anti-fogging multilayer film of the present invention is used as a lid material for a top-seal container, the heat-sealing layer (C) becomes the layer to be bonded to the container, and the layer (A) becomes the layer on the outside of the container.

[0015] [Layer (A)] The layer (A) in the present invention has linear polyethylene (a) as a main resin component (main ingredient). Also, as described later, the layer (A) in the present invention does not need to be composed of one layer, and may be one layer or a laminated structure of two or more layers. Even in the case of two or more layers, the main resin component is linear polyethylene (a).

[0016] Regarding the main resin component (main ingredient) in the present invention, it means containing a specific resin in an amount of 65% by mass or more, preferably 80% by mass or more, based on the total amount of the resin components forming the layer.

[0017] (Linear polyethylene (a)) As the linear polyethylene (a), it is obtained by copolymerizing ethylene monomer as the main component with α-olefins such as butene-1, hexene-1, octene-1, 4-methylpentene, etc. as comonomers by a low-pressure radical polymerization method using a single-site catalyst. The comonomer content is preferably in the range of 0.5 to 20 mol%, and more preferably in the range of 1 to 18 mol%.

[0018] Examples of the single-site catalyst include various single-site catalysts such as metallocene catalyst systems which are combinations of metallocene compounds of transition metals of Group IV or V in the periodic table, organoaluminum compounds and / or ionic compounds. Also, since the active sites of the single-site catalyst are uniform, compared with multi-site catalysts with non-uniform active sites, the molecular weight distribution of the resulting resin becomes sharper. Therefore, when formed into a film, there is less precipitation of low molecular weight components, and a resin with excellent physical properties in terms of the stability of the adhesive strength between resin layers can be obtained, which is preferable.

[0019] The density of the linear polyethylene (a) used for layer (A) is preferably 0.920 to 0.950 g / cm 3 and more preferably in the range of 0.925 to 0.945 g / cm 3 and still more preferably in the range of 0.930 to 0.940 g / cm 3 If the density is within this range, it has appropriate rigidity, excellent mechanical strength such as pinhole resistance, and improved film-forming property, extrusion suitability, and heat resistance. Also, the melting point is preferably in the range of 60 to 130°C, and more preferably 70 to 125°C. If the melting point is within this range, the processing stability and the processability during co-extrusion with other layers are improved. Also, the MFR (190°C, 21.18 N) of the linear polyethylene (a) is preferably 2 to 20 g / 10 min, and more preferably 3 to 10 g / 10 min. If the MFR is within this range, the extrusion molding property of the film is improved.

[0020] As mentioned above, layer (A) is mainly composed of the linear polyethylene (a), but other resins may be used in combination when laminating with other substrates using adhesives, or when printing, for purposes such as improving adhesion with adhesives and inks. Other resins that can be used in combination at this time are preferably ethylene-based resins from the viewpoint of the transparency of the resulting multilayer film. Examples include branched polyethylene, ethylene-vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate (EMA) copolymer, ethylene-maleic anhydride copolymer (E-MAH), ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), and other ethylene-based copolymers; further, ionomers of ethylene-acrylic acid copolymer, ionomers of ethylene-methacrylic acid copolymer, and copolymers of monomers having a cyclic olefin structure such as norbornene monomers with ethylene, etc. These may be used individually or in combination of two or more.

[0021] Layer (A) may or may not contain the antifogging agent described later. If the antifogging agent is included, the content is preferably in the range of 0.2 to 1.5% by mass of the total mass of layer (A), and particularly preferably in the range of 0.4 to 1.0% by mass. The antifogging agent will be described later.

[0022] On the other hand, there are concerns about anti-fogging agents such as bleed-out. As mentioned above, layer (A) is the outer layer of the container, so it may be printed with lamination or direct ink for labeling. In this case, the anti-fogging agent that has bled out onto the surface may cause peeling of the lamination adhesive or ink, or cause printing defects. If there are such concerns, it is preferable to have a structure of two or more layers for layer (A), and to ensure that the outermost layer does not contain an anti-fogging agent.

[0023] Specifically, it is preferable to have two layers: a layer (A1) whose main resin component is linear polyethylene and which does not contain an antifogging agent, and a layer (A2) whose main resin component is linear polyethylene and which contains an antifogging agent. In this case, it is preferable that the layer (A1) which does not contain an antifogging agent becomes the outer layer of the container, and the layer (A2) which contains an antifogging agent is located between layer (A1) and the adhesive layer (B) described later. Hereafter, in layer (A), the layer that does not contain an anti-fogging agent may be referred to as "layer (A1)," and the layer that contains an anti-fogging agent may be referred to as "layer (A2)."

[0024] The amount of antifogging agent in the layer (A2) containing the antifogging agent is preferably in the range of 0.5 to 4.0% by mass of the total mass of the layer (A2), and particularly preferably in the range of 1.0 to 3.0% by mass. The antifogging agent will be described later.

[0025] There are no particular limitations on the thickness of layer (A), but the overall thickness of layer (A) is generally in the range of 15 to 70 μm, and more preferably in the range of 20 to 60 μm. In the case where layer (A) has a configuration of two or more layers, and the configuration includes two layers: a material layer (A1) that does not contain the antifogging agent and a layer (A2) that contains the antifogging agent, it is preferable that the thickness of layer (A1) is 5 to 40 μm and the thickness of layer (A2) is 5 to 40 μm.

[0026] [Adhesive layer (B)] The adhesive layer (B) in the present invention, which mainly consists of linear polyethylene and a polypropylene resin and contains an anti-fogging agent, mainly consists of linear polyethylene (b1) and a polypropylene resin (b2) and contains an anti-fogging agent.

[0027] (Linear polyethylene (b1)) The linear polyethylene (b1) in the present invention can be the same as the linear polyethylene (a) used in the aforementioned layer (A). The density of the linear polyethylene (b1) used in layer (B) is 0.920 to 0.950 g / cm³.3 Preferably, it is 0.925~0.945 g / cm³. 3 It is more preferable that the range be 0.930 to 0.940 g / cm³. 3 It is even more preferable that the density is within this range. If the density is within this range, it will have appropriate rigidity, excellent mechanical strength such as pinhole resistance, and improved film formation properties, extrusion suitability, and heat resistance. Furthermore, the melting point is preferably in the range of 60 to 130°C, and more preferably in the range of 70 to 125°C. A melting point within this range improves processing stability and processability when co-extruding with other layers. In addition, the MFR (190°C, 21.18N) of the linear polyethylene (a) is preferably 2 to 20 g / 10 min, and more preferably 3 to 10 g / 10 min. A MFR within this range improves the extrusion moldability of the film.

[0028] (Polypropylene resin) The polypropylene resin (b2) in the present invention is not particularly limited as long as it can be laminated with the aforementioned layer (A), and examples include propylene homopolymers, propylene-α-olefin random copolymers, such as propylene-ethylene copolymers, propylene-butene-1 copolymers, propylene-ethylene-butene-1 copolymers, and metallocene catalyst-based polypropylenes. These may be used individually or in combination of two or more. Preferably, it is a propylene-α-olefin random copolymer, and as mentioned above, a propylene-α-olefin random copolymer polymerized using a metallocene catalyst is particularly preferred.

[0029] Furthermore, the polypropylene resin (b2) preferably has an MFR (230°C) of 0.5 to 30.0 g / 10 min and a melting point of 110 to 165°C, and more preferably has an MFR (230°C) of 2.0 to 15.0 g / 10 min and a melting point of 115 to 162°C. If the MFR and melting point are within this range, the shrinkage of the film during heat sealing is reduced, and the film-forming properties of the film are also improved.

[0030] The ratio of linear polyethylene (b1) and polypropylene resin (b2) used in the adhesive layer (B) is preferably in the range of 90:10 to 50:50 per 100 parts by mass of the resin, and more preferably 80:20 to 60:40. If the mass ratio is within this range, both layer (A) and heat seal layer (C) will have good adhesive strength.

[0031] (Anti-fogging agent) In the present invention, the antifogging agent is not particularly limited as long as it is generally known to be added to olefin resins to impart antifogging properties. For example, anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, etc., can be used, and it is preferable to use a nonionic surfactant.

[0032] Specifically, sorbitan-based surfactants such as sorbitan monostearate, sorbitan distearate, sorbitan monopalmitate, sorbitan dipalmitate, sorbitan monobehenate, sorbitan dibehenate, sorbitan monolaurate, sorbitan dilaurate; glycerin-based surfactants such as glycerin monolaurate, glycerin dilaurate, diglycerin monopalmitate, diglycerin dipalmitate, glycerin monostearate, glycerin distearate, diglycerin monostearate, diglycerin distearate, diglycerin monolaurate, diglycerin dilaurate; and polyethylene glycol monostearate. Examples include polyethylene glycol-based surfactants such as polyethylene glycol monopalminate; trimethylolpropane-based surfactants such as trimethylolpropane monostearate; diethanolalkylamine-based and diethanolalkylamide-based surfactants such as lauryldiethanolamine, oleyldiethanolamine, stearyldiethanolamine, lauryldiethanolamide, oleyldiethanolamide, and stearyldiethanolamide; pentaerythritol-based surfactants such as pentaerythritol monopalmitate; and polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan distearate, and mono and distearates of sorbitan-diglycerin condensates. These can be used individually or in combination of two or more.

[0033] The proportion of the antifogging agent used in the adhesive layer (B) is preferably in the range of 0.5 to 5.0% by mass of the total mass of the layer, and particularly preferably in the range of 1.0 to 4.5% by mass. By using the antifogging agent within this range, it is easy to maintain good antifogging properties as a film even if migration to the aforementioned layer (A) occurs. Furthermore, it does not affect the interlayer strength between layer (A) and the heat-seal layer (C).

[0034] [Heat seal layer (C)] In the present invention, the heat-seal layer (C), which mainly consists of a polypropylene resin and contains an anti-fogging agent, must use a polypropylene resin (c1) in order to facilitate the development of heat-seal properties when used as a lid material for a container or a packaging bag.

[0035] The polypropylene resin (c1) is not particularly limited as long as it can be laminated with the aforementioned layer (A) and adhesive layer (B), and examples include propylene homopolymer, propylene-α-olefin random copolymer, for example, propylene-ethylene copolymer, propylene-butene-1 copolymer, propylene-ethylene-butene-1 copolymer, and metallocene catalyst-based polypropylene. These may be used individually or in mixtures of two or more. Preferably, it is a propylene-α-olefin random copolymer, and as mentioned above, a propylene-α-olefin random copolymer polymerized using a metallocene catalyst is particularly preferred. By using these propylene resins as the resin for the heat seal layer (C), they can be suitably used as lid material for packaging containers, particularly when the sealing surface of the packaging container is a resin layer containing a polypropylene resin. Furthermore, it is preferable that the heat-seal layer (C) contains a polypropylene-butene-1 copolymer in an amount ranging from 10% to 30% by mass.

[0036] Furthermore, the polypropylene resin (c1) is preferably one with an MFR (230°C) of 0.5 to 30.0 g / 10 min and a melting point of 110 to 165°C, and more preferably one with an MFR (230°C) of 2.0 to 15.0 g / 10 min and a melting point of 115 to 162°C. If the MFR and melting point are within this range, the shrinkage of the film during heat sealing is reduced, and the film-forming properties of the film are also improved.

[0037] In the heat-seal layer (C), it is preferable that the polypropylene resin (c1) is the main component, and more preferably that it is contained in an amount of 85% by mass or more. Other resins that can be used in combination are the same as those exemplified as resins that can be used in combination in layer (A).

[0038] Any of the anti-fogging agents exemplified above can be used as the anti-fogging agent for the heat seal layer (C), and the same applies to preferred agents.

[0039] The antifogging agent used in the aforementioned layer (A2) and the adhesive layer (B) may be the same or different from the antifogging agent used in the heat-seal layer (C). When using a masterbatch-formed antifogging agent, from the viewpoint of compatibility, it is preferable that the base resin is a polyethylene-based resin for the aforementioned layer (A2) and the adhesive layer (B), and a polypropylene-based resin for the heat-seal layer (C).

[0040] The proportion of antifogging agent used in the heat-seal layer (C) is preferably in the range of 1.0 to 6.0% by mass relative to the total mass of the layer, and particularly preferably in the range of 2.0 to 5.0% by mass. By using the antifogging agent within this range, it is easy to obtain a film with good antifogging properties and antifogging durability.

[0041] [Composition of anti-fog multilayer film] Specific embodiments of the anti-fogging multilayer film of the present invention are shown below. Layer (A) / Adhesive layer (B) / Heat seal layer (C) Layer (A1) / Layer (A2) / Adhesive layer (B) / Heat seal layer (C)

[0042] [Seal strength of anti-fog multilayer film] A key feature of the anti-fogging multilayer film of the present invention is that its seal strength differs between room temperature and high temperature. The seal strength decreases at high temperatures. Specifically, under condition (X), the seal strength at room temperature is 10-18 N / 15 mm, and the seal strength at 100°C is 4-8 N / 15 mm. In this invention, "room temperature" is defined as a range of 20°C plus or minus 15°C (5-35°C) (JIS Z 8703[4]). Condition (X) is the following condition:

[0043] (Condition X) (1) A laminate is created by bonding the anti-fogging multilayer film of the present invention and a 15 μm biaxially oriented nylon film with a polyurethane adhesive, and then aged at 40°C for 48 hours. (2) The heat seal layer (C) of the laminate and a 0.3 mm thick polypropylene sheet are placed facing each other and overlapped. The upper heat seal bar of the heat seal tester, which is adjusted to a temperature of 180°C, is set so that it is on the outermost layer opposite to the heat seal layer (C) of the laminate, and heat seal is performed under conditions of 0.2 MPa and 1 second. (3) Using a tensile testing machine, the polypropylene sheet and the laminate are each held in place by fixtures, and the seal strength, which is the maximum strength when peeled off at a speed of 300 mm / min using the tensile testing machine, is measured. The peeled surface at this time is between the adhesive layer (B) and the heat seal layer (C), and the seal strength of this interface is measured.

[0044] In the present invention, the polyurethane adhesive in (1) above is "DIC Dry LX500 / KR90S", a urethane-based reactive adhesive manufactured by DIC Corporation. Furthermore, the heat seal tester used in (2) was a "Precision Heat Sealer manufactured by Tester Industries."

[0045] The seal strength at room temperature is in the range of 10-18 N / 15 mm, which reduces the likelihood of contents leaking due to bag breakage during distribution. Furthermore, the seal strength at 100°C is in the range of 4-8 N / 15 mm, which is particularly suitable for easy opening even after microwave heating, when the container's rigidity decreases at high temperatures or when the container or lid cannot be gripped firmly. In addition, the low seal strength reduces the risk of spilling contents by allowing for faster opening.

[0046] In this invention, the factors that cause a decrease in the seal strength of the anti-fogging multilayer film at high temperatures are estimated to be as follows. Thermoplastic resins such as polyethylene, polypropylene, and their copolymers soften at temperatures above their glass transition point. Therefore, it is known that their seal strength decreases at high temperatures compared to room temperature. Furthermore, it is known that steam emitted from the contents during microwave heating can reach temperatures of around 100°C. In conventional technology, seal strength was often adjusted solely by copolymer resins such as propylene-butene-1 copolymer, making it difficult to control seal strength at both room temperature and high temperature. By incorporating a heat-resistant polypropylene resin into the heat-seal layer, the adhesive layer, or both, and by increasing the density of linear polyolefins in layer (A) and the adhesive layer (B), the anti-fogging multilayer film of the present invention suppresses the decrease in seal strength at high temperatures, enabling strength control at both room temperature and high temperature.

[0047] The total thickness of the anti-fogging multilayer film of the present invention is preferably in the range of 20 to 100 μm, and more preferably in the range of 25 to 80 μm, because it facilitates lamination when used in combination with other substrates and provides suitable heat sealability and anti-fogging properties.

[0048] Furthermore, regarding the ratio of each layer in the multilayer film, from the viewpoint of sealing properties, ease of opening, and lamination properties, it is preferable that the thickness ratio of layer (A) is in the range of 60-90%, the thickness ratio of the adhesive layer (B) is in the range of 5-20%, and the thickness ratio of the heat seal layer (C) is in the range of 5-18%.

[0049] The total amount of antifogging agent contained in the entire antifogging multilayer film of the present invention is preferably 0.8 to 2.5% by mass, and particularly preferably in the range of 1.0 to 2.0% by mass, from the viewpoint of good film formation, the emergence of antifogging properties, and the duration of antifogging.

[0050] Each layer (A), layer (B), and layer (C) of the anti-fogging multilayer film of the present invention may contain components such as antistatic agents, heat stabilizers, nucleating agents, antioxidants, lubricants, antiblocking agents, mold release agents, ultraviolet absorbers, and colorants, to the extent that they do not impair the objectives of the present invention. In particular, in order to provide processing suitability during film molding and lamination, and packaging suitability for packaging machines, the coefficient of friction of the film surface is preferably 1.5 or less, and more preferably 1.0 or less. Therefore, it is preferable to appropriately add lubricants, antiblocking agents, and antistatic agents to the resin layer corresponding to the surface layer of the multilayer film.

[0051] Furthermore, in the anti-fogging multilayer film of the present invention, corona treatment may be performed as needed to impart wettability. Examples of methods for imparting wettability include surface oxidation treatments such as corona discharge treatment, plasma treatment, flame treatment, and ozone / ultraviolet treatment, but corona discharge treatment is preferred. By performing such a surface treatment, when subsequent processes such as applying ink or adhesive to layer (A) of the multilayer film and laminating it with a substrate are carried out, the coatability of ink or adhesive is improved, the adhesion with ink, adhesive, anchor coating agent, etc. is excellent, and problems such as detachment or delamination of ink, adhesive, or vapor-deposited aluminum are easily avoided. When laminating by extrusion lamination, there is no particular problem even if the surface of layer (A) of the multilayer film is not treated with corona. The method for corona discharge treatment is not particularly limited, and known methods can be used.

[0052] The method for manufacturing the anti-fogging multilayer film of the present invention is not particularly limited, but for example, a co-extrusion method is used in which each resin or resin mixture used for layer (A), adhesive layer (B), and heat seal layer (C) is heated and melted in separate extruders, and then laminated in the order of (A) / (B) / (C) or (A1) / (A2) / (B) / (C) in the molten state using methods such as the co-extrusion multilayer die method or the feed block method, and then formed into a film using methods such as inflation or the T-die chill roll method. This co-extrusion method is preferred because it is possible to adjust the ratio of the thickness of each layer relatively freely, and a multilayer film with excellent hygiene and cost performance can be obtained. Among these, the T-die chill roll method is preferred because it is easy to suppress deterioration of the film appearance when co-extruding resins with different melting points and Tg, and to form a uniform layer structure, making it easy to obtain a film with suitable transparency and gloss. The inflation method is also preferred because the equipment is simple and it is suitable for small-batch, high-mix production.

[0053] Since the anti-fogging multilayer film of the present invention is obtained as a substantially unstretched multilayer film by the above manufacturing method, secondary molding such as deep drawing by vacuum forming and embossing is also possible.

[0054] The anti-fogging multilayer film of the present invention can also be used in combination with other substrates. While there are no particular limitations on the other substrates that can be used, from the viewpoint of easily exhibiting the effects of the present invention, it is preferable to use a thermoplastic resin film having high rigidity and high gloss, particularly a biaxially oriented resin film. Furthermore, for applications where transparency is not required, aluminum foil can be used alone or in combination with other materials.

[0055] Examples of stretched resin films include biaxially oriented polyester (PET), biaxially oriented polypropylene (OPP), biaxially oriented polyamide (PA), co-extruded biaxially oriented polyamide (ONY) with ethylene vinyl alcohol copolymer (EVOH) as the core layer, biaxially oriented ethylene vinyl alcohol copolymer (EVOH), and co-extruded biaxially oriented polypropylene coated with polyvinylidene chloride (PVDC). These may be used individually or in combination.

[0056] The laminate of the present invention is a laminate film obtained by laminating the thermoplastic resin film onto the anti-fogging multilayer film obtained as described above. Examples of lamination methods include dry lamination, wet lamination, non-solvent lamination, and extrusion lamination.

[0057] Examples of adhesives used in the dry lamination include polyester-polyurethane adhesives. Various adhesives can also be used, but pressure-sensitive adhesives are preferred. Examples of pressure-sensitive adhesives include rubber-based adhesives obtained by dissolving polyisobutylene rubber, butyl rubber, or mixtures thereof in organic solvents such as benzene, toluene, xylene, or hexane; or rubber-based adhesives obtained by compounding these with tackifiers such as rosin aviethylene acid ester, terpene-phenol copolymer, or terpene-indene copolymer; or acrylic-based adhesives obtained by dissolving acrylic copolymers with a glass transition temperature of -20°C or lower, such as 2-ethylhexyl acrylate-n-butyl acrylate copolymer or 2-ethylhexyl acrylate-ethyl acrylate-methyl methacrylate copolymer, in an organic solvent.

[0058] The applications of the laminate of the present invention are not particularly limited, but it can be suitably used as a lid material for packaging containers used for food, pharmaceuticals, industrial parts, general merchandise, magazines, etc. In particular, it is preferable from the viewpoint of balancing ease of opening and seal strength that the outermost layer of the packaging container (the part that adheres to the heat-seal layer of the multilayer film of the present invention) contains various propylene-based resins.

[0059] (lid material) The anti-fogging multilayer film and laminate of the present invention can be used as container lids for plastic containers of food, pharmaceuticals, and other products. When used as a lid, they may be used alone or as a laminated film, depending on the contents, usage environment, and usage form, and the layer configuration may change. It is preferable that the outermost layer of the packaging container (the part that adheres to the heat-seal layer of the multilayer film of the present invention) contains various propylene-based resins, from the viewpoint of balancing ease of opening and seal strength.

[0060] (Top-seal container) The top-seal container equipped with the anti-fog multilayer film or laminate of the present invention as a sealing lid is a container in which a flange protrudes from the outer circumference of the opening of the container body filled with solid or liquid food contents, and this opening is sealed by the sealing lid via this flange. As described above, the anti-fog multilayer film or laminate of the present invention has sufficient sealing strength to withstand distribution but can be opened before microwave heating of the top-seal container. However, during or immediately after heating, the sealing strength decreases to a level that allows the container to be easily opened even when it is hot, thereby reducing the risk of burns to the user and enabling the safe provision of food. As for the container material of the top-seal container, it is preferable that the outermost layer (the part that adheres to the heat-seal layer of the multilayer film of the present invention) contains various propylene-based resins, from the viewpoint of balancing ease of opening and seal strength. [Examples]

[0061] Next, the present invention will be described in more detail with reference to examples and comparative examples. Hereinafter, unless otherwise specified, "parts" refers to parts by mass.

[0062] (Preparation of anti-fogging agent) Regarding the antifogging agent, a masterbatch was prepared by mixing 20 parts by mass of the antifogging agent with any one of the resins that make up the layer to be used, and then melt-kneading the mixture in an extruder.

[0063] (Example 1) As the resin for the heat-sealing layer (C), 30 parts of a propylene-butene-1 copolymer (1) with a density of 0.885 g / cm 3 and an MFR (230 °C) of 7.0 g / 10 min, 50 parts of a polypropylene (1) with a density of 0.900 g / cm 3 and an MFR (230 °C) of 7.0 g / 10 min, and 20 parts of an anti-fogging agent (1) adjusted with polypropylene (1) were mixed and used. At this time, the anti-fogging agent concentration in the heat-sealing layer (C) was 4.0% by mass. As the resin for the adhesive layer (B), 65 parts of an LLDPE (1) with a density of 0.937 g / cm 3 and an MFR of 4.0 g / 10 min, 15 parts of polypropylene (1), and 20 parts of an anti-fogging agent (2) adjusted with an LDPE (1) with a density of 0.919 g / cm 3 and an MFR of 7.0 g / 10 min were mixed and used. At this time, the anti-fogging agent concentration in the adhesive layer (B) was 4.0% by mass. As the resin for the layer (A1) that does not contain an anti-fogging agent, 80 parts of LLDPE (1) and 20 parts of LDPE (1) were mixed and used. Resin was supplied to each of the extruders for the heat-sealing layer (C), the adhesive layer (B), and the layer (A), and extruded from a T-die at an extrusion temperature of 250 °C by a co-extrusion method so that the thicknesses of the respective layers of (A) / (B) / (C) were 20 μm / 6 μm / 4 μm, and cooled with a water-cooled metal cooling roll at 40 °C. Next, corona discharge treatment was performed, wound around a roll, and aged in an aging chamber at 38 °C for 24 hours to obtain a multilayer film having a layer structure of (A) / (B) / (C) with a total thickness of 30 μm. Thereafter, the obtained co-extruded film and a biaxially stretched nylon film of 15 μm were bonded together with a polyurethane-based adhesive [Dick Dry LX500 / KR90S manufactured by DIC Corporation] to obtain a laminate.

[0064] (Example 2) As the resin for the layer (A2) containing an anti-fogging agent, LLDPE (1), LDPE (1), and the anti-fogging agent (2) were mixed and used so that the mass ratio was 80 / 18 / 2. At this time, the anti-fogging agent concentration in the layer (A2) was 0.4% by mass. Apart from these points, the laminate of Example 2 was obtained in the same manner as in Example 1.

[0065] (Example 3) The resin used for the adhesive layer (B) has a density of 0.931 g / cm³. 3 A mixture of 65 parts of LLDPE(2) with an MFR of 6.0 g / 10 min, 15 parts of polypropylene(1), and 20 parts of anti-fogging agent(2) was used. The anti-fogging agent concentration in the adhesive layer(B) at this time was 4.0% by mass. For the layer (A1) that does not contain an anti-fogging agent, a mixture of 80 parts LLDPE(2) and 20 parts LDPE(1) was used as the resin. Apart from these points, the laminate of Example 3 was obtained in the same manner as in Example 1.

[0066] (Example 4) For the heat seal layer (C), a mixture of propylene-butene-1 copolymer (1), 58 parts of polypropylene (1), and an antifogging agent (1) was used in a mass ratio of 30 / 58 / 12. The antifogging agent concentration in the heat seal layer (C) at this time was 2.4% by mass. For the adhesive layer (B), LLDPE (1), LDPE (1), polypropylene (1), and antifogging agent (2) were mixed in a mass ratio of 63 / 12 / 15 / 10. The antifogging agent concentration in the adhesive layer (B) at this time was 2.0% by mass. For the layer (A1) that does not contain an anti-fogging agent, LLDPE(1) and LDPE(1) were mixed in a mass ratio of 80 / 20 and used as the resin. For the anti-fogging layer (A2), LLDPE(1), LDPE(1), and anti-fogging agent (2) were mixed in a mass ratio of 80 / 10 / 10 and used as the resin. The anti-fogging agent concentration in layer (A2) at this time was 2.0% by mass. The laminate of Example 4 was obtained in the same manner as in Example 1, except that resin was supplied to the extruder for the heat-seal layer (C), the extruder for the adhesive layer (B), the extruder for layer (A1), and the extruder for layer (A2), and the layers (A1) / (A2) / (B) / (C) were extruded from the T-die by co-extrusion at an extrusion temperature of 250°C so that the thicknesses of each layer were 10 μm / 12 μm / 4 μm / 4 μm.

[0067] (Example 5) LLDPE(1) was used as the resin for the layer (A1) that does not contain an anti-fogging agent. For the anti-fogging layer (A2), LLDPE (1) and the anti-fogging agent (2) were mixed in a mass ratio of 90 / 10 and used as the resin. The anti-fogging agent concentration in layer (A2) at this time was 2.0% by mass. Aside from these points, the laminate of Example 5 was obtained in the same manner as in Example 4.

[0068] (Example 6) The resin used for the adhesive layer (B) has a density of 0.944 g / cm³. 3 A mixture of 63 parts of LLDPE(3) with an MFR of 4.0 g / 10 min, 12 parts of LDPE(1), 15 parts of polypropylene(1), and 10 parts of anti-fogging agent(2) was used. The anti-fogging agent concentration in the adhesive layer (B) at this time was 2.0% by mass. LLDPE (3) was used as the resin for the layer (A1) that does not contain an anti-fogging agent. For the anti-fogging layer (A2), LLDPE (3) and the anti-fogging agent (2) were mixed in a mass ratio of 90 / 10 and used as the resin. The anti-fogging agent concentration in layer (A2) at this time was 2.0% by mass. Apart from these points, the laminate of Example 6 was obtained in the same manner as in Example 4.

[0069] (Example 7) For the adhesive layer (B), LLDPE (1), LDPE (1), propylene-butene-1 copolymer (2), and antifogging agent (2) were mixed in a mass ratio of 63 / 12 / 15 / 10. The antifogging agent concentration in the adhesive layer (B) at this time was 2.0% by mass. Apart from these points, the laminate of Example 7 was obtained in the same manner as in Example 4.

[0070] (Example 8) For the heat seal layer (C), a mixture of propylene-butene-1 copolymer (1), 58 parts of polypropylene (1), and an antifogging agent (1) was used in a mass ratio of 10 / 78 / 12. The antifogging agent concentration in the heat seal layer (C) at this time was 2.4% by mass. Apart from these points, the laminate of Example 8 was obtained in the same manner as in Example 4.

[0071] (Example 9) For the heat seal layer (C), a mixture of propylene-butene-1 copolymer (1), 58 parts of polypropylene (1), and an antifogging agent (1) was used in a mass ratio of 15 / 73 / 12. The antifogging agent concentration in the heat seal layer (C) at this time was 2.4% by mass. Apart from these points, the laminate of Example 9 was obtained in the same manner as in Example 4.

[0072] (Comparative Example 1) For the heat seal layer (C), a mixture of 88 parts propylene (1) and 12 parts antifogging agent (1) was used. The antifogging agent concentration in the heat seal layer (C) at this time was 2.4% by mass. The resin used for the adhesive layer (B) has a density of 0.886 g / cm³. 3 A mixture of 48 parts of ethylene-butene-1 copolymer (1) with an MFR of 4.0 g / 10 min, 42 parts of LDPE (1), and 10 parts of anti-fogging agent (2) was used. The anti-fogging agent concentration in the adhesive layer (B) at this time was 2.0% by mass. Apart from these points, the laminate of Comparative Example 1 was obtained in the same manner as in Example 4.

[0073] (Comparative Example 2) For the heat seal layer (C), a mixture of propylene-butene-1 copolymer (1) and polypropylene (1) was used in a mass ratio of 70 / 30. For the adhesive layer (B), LLDPE(1), LDPE(1), and propylene(1) were mixed in a mass ratio of 65 / 20 / 15 and used as the resin. Apart from these points, the laminate of Comparative Example 2 was obtained in the same manner as in Example 1.

[0074] (Comparative Example 3) As a resin for the heat seal layer (C), density 0.890 g / cm³ 3 A mixture of 88 parts of propylene-ethylene copolymer (1) at MFR (230℃) 7.0 g / 10 min and 12 parts of anti-fogging agent (3) prepared with propylene-ethylene copolymer (1) was used. The anti-fogging agent concentration in the heat seal layer (C) at this time was 2.4% by mass. The resin used for the adhesive layer (B) has a density of 0.933 g / cm³. 3 80 parts of LLDPE(4) with an MFR of 5.0 g / 10 min and a density of 0.905 g / cm³ 3 Twenty parts of an anti-fogging agent (4) prepared with LLDPE (5) at an MFR of 4.0 g / 10 min were mixed and used. The anti-fogging agent concentration in the adhesive layer (B) at this time was 4.0% by mass. For the layer (A2) containing the antifogging agent, a mixture of 80 parts LLDPE (4) and 20 parts antifogging agent (4) was used as the resin. The antifogging agent concentration in layer (A2) at this time was 4.0% by mass. LLDPE (4) was used as the resin for the layer (A1) that does not contain an anti-fogging agent. Apart from these points, the laminate of Comparative Example 3 was obtained in the same manner as in Example 4.

[0075] (Comparative Example 4) As a resin for the heat seal layer (C), density 0.890 g / cm³ 3 A propylene-butene-1 copolymer (3) was used, prepared at MFR (230℃) 4.0g / 10min. For the layer (A1) that does not contain an anti-fogging agent, the resin has a density of 0.935 g / cm³. 3 A mixture of 80 parts of LLDPE (6) with an MFR of 4.5 g / 10 min and 20 parts of propylene-butene-1 copolymer (3) was used. A laminate of Comparative Example 4 was obtained in the same manner as in Example 1, except that resin was supplied to the extruder for the heat-seal layer (C) and the extruder for the layer (A1), and the layers (A1) and (C) were extruded from the T-die by co-extrusion at an extrusion temperature of 250°C so that the thickness of each layer was 25 μm / 5 μm.

[0076] Unless otherwise specified, MFR values ​​are measured at 190°C.

[0077] (Evaluation method) (Film appearance evaluation) The appearance of the film samples extruded from the T-die by co-extrusion was visually inspected after aging at 38°C for 24 hours. ○: No whitening due to anti-fogging agent bleed-out, etc. was observed. ×: Whitening due to anti-fogging agent bleed-out, etc., resulting in deterioration of film transparency.

[0078] (Laminate strength evaluation) The behavior of the laminate strength between biaxially oriented nylon film and films obtained by co-extrusion was evaluated using a tensile testing machine (manufactured by A&D Co., Ltd.) at a peeling speed of 300 mm / min, according to the following criteria. ○: Strong adhesion was confirmed between the biaxially oriented nylon film and the film obtained by co-extrusion, due to the maintenance of sufficient lamination strength. ×: Due to insufficient lamination strength, easy delamination was observed between the biaxially oriented nylon film and the film obtained by co-extrusion.

[0079] (Confirmation and evaluation of anti-fogging effect after lamination) The resulting laminate was aged at 40°C for 48 hours, then cut into 8cm x 8cm pieces. After heat sealing with a φ71 injection molded container (manufactured by Toko Co., Ltd.) containing 30ml of 40°C water (pressure 64kgf / cup, temperature 160°C, time 1.0 second), the laminate was stored in a low-temperature room at 3°C ​​for 3 hours using the following criteria for visual inspection to confirm its anti-fogging effect. ○: A continuous water film is formed on the film surface, resulting in good visibility. △: Even with fine water droplets on the film surface, visibility remains good. ×: Water droplets present, reduced visibility

[0080] (Confirmation and evaluation of anti-fogging effect after microwave heating) The resulting laminate was aged and heat-sealed under the above conditions, then stored in a low-temperature chamber at 3°C ​​for 3 hours. After that, a portion of the lid was opened and the laminate was heated in a microwave oven (Iris Ohyama IMB-F186-W) at 500W for 1 minute, and the appearance immediately after heating was checked. ○: A continuous water film is formed on the film surface, resulting in good visibility. △: Even with fine water droplets on the film surface, visibility remains good. ×: Water droplets present, reduced visibility

[0081] (Creating a heat seal sample) After aging the resulting laminate under the above conditions, it was placed on top of a 0.3 mm thick polypropylene sheet with the heat-sealing surface facing the polypropylene sheet. Using a heat seal tester (precision heat sealer manufactured by Tester Industries), the upper heat seal bar, adjusted to a temperature of 180°C, was set to face the outermost layer of the laminate, and heat-sealed under conditions of 0.2 MPa and 1 second.

[0082] (Evaluation of seal strength) A 15mm wide strip of sample was cut perpendicular to the heat-sealed portion, and the maximum strength when peeled at a speed of 300mm / min using a tensile testing machine (manufactured by A&D Co., Ltd.) was defined as the peel strength. In the 100°C environment test, the peel strength was measured after being held in a constant temperature bath adjusted to 100°C for 5 minutes.

[0083] (Evaluation of ease of opening after microwave heating) The resulting laminate was aged and heat-sealed under the above conditions, then stored in a low-temperature chamber at 3°C ​​for 3 hours. After that, a portion of the lid was opened and heated in a microwave oven (Iris Ohyama IMB-F186-W) (500W, 1 minute). Immediately after heating, the entire lid was opened, starting from the previously opened location, and inspected. ○: No film residue or delamination occurs, and it has moderate strength and is easy to open. △: Has moderate strength and opening strength, but some film residue or delamination may occur. ×: Film residue or delamination may occur, or the opening strength may be weak and the package may open all at once.

[0084] Tables 1-3 show the layer structure and evaluation results of the anti-fogging multilayer film. Blank spaces indicate the absence of a specific compound.

[0085] [Table 1]

[0086] [Table 2]

[0087] [Table 3]

[0088] As a result, it is clear that the anti-fog multilayer film of the example has sufficient seal strength to withstand distribution and be opened before microwave heating, but during or immediately after heating, the seal strength decreases to a level that allows the container to be easily opened even when it is hot.

Claims

1. At a minimum, the structure comprises, in this order, a layer (A) whose main resin component is linear polyethylene (a), an adhesive layer (B) whose main resin components are linear polyethylene (b1) and polypropylene resin (b2) and which contains an anti-fogging agent, and a heat-seal layer (C) whose main resin component is polypropylene resin (c1) and which contains an anti-fogging agent. The density of the linear polyethylene (a) is 0.920 to 0.950 g / cm³. The density of the linear polyethylene (b1) is 0.920 to 0.950 g / cm³. The ratio of the linear polyethylene (b1) and the polypropylene resin (b2) used is in the range of a mass ratio of 90:10 to 50:

50. The proportion of the anti-fogging agent used in the adhesive layer (B) is 0.5 to 5.0% by mass relative to the total mass of the adhesive layer (B). The proportion of the anti-fogging agent used in the heat-seal layer (C) is 1.0 to 6.0% by mass relative to the total mass of the heat-seal layer (C). An anti-fogging multilayer film characterized by having a seal strength of 10 to 18 N / 15 mm at room temperature and a seal strength of 4 to 8 N / 15 mm at 100°C.

2. The anti-fogging multilayer film according to claim 1, wherein the density of linear polyethylene contained in the layer (A) and the adhesive layer (B) is 0.930 or higher, and the density of the layer (A) is higher than the density of the adhesive layer (B) and the density of the heat-seal layer (C).

3. The anti-fogging multilayer film according to claim 1, wherein the heat-seal layer (C) contains a polypropylene-butene-1 copolymer in an amount of 10 to 30% by mass.

4. The anti-fogging multilayer film according to claim 1, wherein the layer (A) comprises two layers: a base layer (A1) mainly composed of linear polyethylene and not containing an anti-fogging agent, and a base layer (A2) mainly composed of linear polyethylene and containing an anti-fogging agent.

5. A laminate containing the anti-fogging multilayer film described in any one of claims 1 to 4.

6. A packaging material containing an anti-fogging multilayer film according to any one of claims 1 to 4.

7. A lid material containing an anti-fogging multilayer film according to any one of claims 1 to 4.

8. A top-seal container containing an anti-fogging multilayer film according to any one of claims 1 to 4.

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