Resin laminate for packaging materials

Abstract

[Problem] To provide a highly processable resin laminate for packaging materials, that is characterized in that a substrate layer and a sealant layer comprise the same material. [Solution] A resin laminate for packaging materials that is a resin laminate comprising at least a substrate layer and a sealant layer, wherein the main components of the resin compositions constituting the substrate layer and the sealant layer are composed of the same resin composition, and wherein the fusion initiation temperature (FIT-B) of the substrate layer and the seal initiation temperature (SIT-S) of the sealant layer satisfy formulas (1) to (3).　Formula (1): 50°C ≤ (FIT-B) - (SIT-S) ≤ 90 (°C); Formula (2): 90 ≤ (SIT-S) ≤ 120 (°C); Formula (3): 160 ≤ (FIT-B) ≤ 180 (°C)

Description

Resin laminate for packaging materials

[0001] The present invention relates to a heat-sealable resin laminate for packaging materials, which comprises a substrate layer and a sealant layer made of the same material.

[0002] Conventionally, packaging materials have been made by combining various resin film materials made from polyolefins, polyesters, etc. depending on the contents to be packaged and the application. For example, a low-melting-point unstretched polyethylene resin film is selected for a sealant film that requires heat sealing properties, while a biaxially oriented polyester film or polypropylene film is selected for a surface material that requires heat resistance, and these are laminated together.

[0003] In recent years, there has been a growing global demand for initiatives to create a recycling-oriented society, and with regard to packaging materials, there is a growing demand for "mono-material packaging" made from a single material that is easy to recycle, due to environmental considerations.

[0004] For example, Patent Document 1 proposes a packaging laminate in which the base layer and sealant layer are made of polyester film, Patent Document 2 proposes a packaging body in which the base layer and sealant layer are made of polyethylene, and Patent Document 3 proposes a packaging laminate in which the base layer and sealant layer are made of polypropylene.

[0005] On the other hand, while packaging materials have traditionally been designed by taking advantage of the characteristics of various materials, problems resulting from using a single material are also known. In particular, in heat sealing processing, using a single material can sometimes make it difficult to achieve both heat resistance and seal strength. For example, Patent Document 3 discloses a product using a biaxially oriented polypropylene film as the base layer and a non-oriented polypropylene film as the sealant. However, when the heat sealing temperature is high, the biaxially oriented polypropylene film as the base layer shrinks, making the appearance of the sealed area poor. Furthermore, there are problems such as the product being easily fused to the heat seal bar, making it difficult to process, and the heat seal strength being weak when heat sealing processing is performed at high speeds during bag production.

[0006] International Publication No. WO2020 / 262326 International Publication No. WO2021 / 054349 Japanese Patent Application Laid-Open No. 2020-157715 International Publication No. WO2020 / 080507

[0007] The object of the present invention is to solve the above-mentioned problems, and relates to a resin laminate for packaging materials which has good processability and is made of a resin composition in which the main components of the base layer and the sealant layer are the same type of resin.

[0008] As a result of extensive research into achieving this object, the present invention has been able to solve the above-mentioned problem by providing a resin laminate comprising at least a base layer and a sealant layer, wherein the base layer and the sealant layer are mainly composed of the same type of resin composition, and by controlling the fusion initiation temperature (FIT-B) of the base layer and the sealing initiation temperature (SIT-S) of the sealant layer to fall within a specific relationship and range.

[0009] That is, the present invention has the following configuration. [1] A resin laminate for packaging materials comprising at least a base material layer and a sealant layer, wherein the resin compositions constituting the base material layer and the sealant layer are mainly composed of the same resin composition, and the fusion-bonding initiation temperature (FIT-B) of the base material layer and the sealant layer are mainly composed of the same resin composition, and the fusion-bonding initiation temperature (FIT-B) of the base material layer and the sealant layer are mainly composed of the same resin composition. [1] The resin laminate for packaging materials according to [1], wherein the resin compositions constituting the base material layer and the sealant layer are mainly composed of propylene units, and the base material layer is a biaxially oriented polypropylene film. [3] The resin laminate for packaging materials according to [2], wherein the biaxially oriented polypropylene film of the base material layer has a heat shrinkage rate at 150°C of 6.5% or less in the longitudinal direction and 5.5% or less in the width direction. [4] The resin laminate for packaging materials according to [2] or [3], wherein the biaxially oriented polypropylene film of the base material layer has a Young's modulus of 2.0 GPa or more in the longitudinal direction and 3.5 GPa or more in the width direction. [5] The resin laminate for packaging materials according to any of [1] to [4], which has an adhesive layer between the base material layer and the sealant layer.

[0010] The resin laminate for packaging materials of the present invention is an easily recyclable "mono-material packaging material" made of a resin composition in which the main component of each layer is the same type. The base layer has high heat resistance, the difference between the fusion start temperature of the base layer and the sealing start temperature of the sealant layer is 50°C or more, and the fusion start temperature of the sealant layer is a specific temperature or lower, so that it is possible to achieve both heat seal strength and a beautiful finish during heat sealing processing.

[0011] The resin laminate for packaging materials according to the present invention will be described in more detail below. The resin laminate for packaging materials according to the present invention has a laminated structure of a substrate layer and a sealant layer, and is characterized in that the difference between the fusion initiation temperature of the substrate layer and the sealing initiation temperature of the sealant layer is 50°C or more. The present invention will be described in more detail below.

[0012] [Substrate Layer] The substrate layer in the present invention is a film whose main raw material resin is at least one resin selected from the group consisting of polypropylene, polyester, polyamide, etc., and is preferably a biaxially oriented film that has been biaxially stretched in terms of rigidity and heat resistance. Since polypropylene is often used as a material for sealant layers due to its low melting point, a biaxially oriented polypropylene film as the substrate layer in the present invention is suitable for use as a resin laminate for packaging materials, which uses a sealant layer made of a resin composition whose main component is polypropylene. The term "main component" as used herein refers to a resin that accounts for 50% by mass or more of the substrate layer.

[0013] (Characteristics of Biaxially Oriented Polypropylene Film as Base Layer) The fusion initiation temperature (hereinafter sometimes abbreviated as FIT-B) of the biaxially oriented polypropylene film containing propylene units as the base layer in the present invention is preferably 160°C or higher and 180°C or lower. More preferably, it is 163°C or higher and 175°C or lower. When the fusion initiation temperature (FIT-B) of the base layer is 160°C or higher, the base layer is less likely to deform due to heat shrinkage even when heat-sealed at high temperatures, the appearance of the package is less likely to be damaged, and problems such as sticking to the conveying roll during processing are less likely to occur. This is particularly useful in high-temperature heat-sealing processing in high-speed automatic packaging. The upper limit of the fusion initiation temperature (FIT-B) of the base layer is preferably higher for high-speed automatic packaging, and a temperature of 180°C or lower allows industrial production. The fusion initiation temperature (FIT-B) of the biaxially oriented polypropylene film used in the base layer of the present invention can be adjusted by using a specific polypropylene resin described below as a raw material and adopting specific film-forming conditions.

[0014] The biaxially oriented polypropylene film containing propylene units as a main component as the base layer in the present invention preferably has a heat shrinkage rate at 150°C of 6.5% or less in the longitudinal direction and 5.5% or less in the width direction. More preferably, it is 6.0% or less in the longitudinal direction and 5.0% or less in the width direction, and even more preferably, it is 5.0% or less in the longitudinal direction and 3.0% or less in the width direction. If the heat shrinkage rate at 150°C is large, the base layer will shrink significantly during heat sealing, not only damaging the appearance of the package but also causing problems such as peeling of the heat seal. On the other hand, if the heat shrinkage rate at 150°C is small, the heating temperature for heat sealing can be increased, enabling heat sealing in a short period of time and high-speed bag production.

[0015] The rigidity of the biaxially oriented polypropylene film containing propylene units as the base layer in the present invention preferably has a Young's modulus of 2.0 GPa or more in the longitudinal direction and 3.5 GPa or more in the width direction. More preferably, it is 2.5 GPa or more in the longitudinal direction and 4.0 GPa or more in the width direction. Increasing the Young's modulus improves the rigidity of the base layer, which is expected to reduce wrinkles during processing such as bag making, and to facilitate the insertion and removal of contents into the bag. Furthermore, improving the rigidity allows the film thickness to be reduced. Reducing the thickness of the base layer facilitates heat transfer to the sealant layer during heat sealing, allowing the heating temperature to be lowered, reducing shrinkage wrinkles due to heating, and improving the processing speed.

[0016] The thickness of the biaxially oriented polypropylene film primarily composed of propylene units used as the base layer in the present invention is not particularly limited. However, a thinner film allows for easier transfer of heat from the seal bar to the sealant layer during heat sealing, thereby enabling a lower heating temperature. Lowering the heating temperature reduces wrinkles due to thermal shrinkage, which is preferable because it improves the appearance and finish of the package. Lowering the heating temperature also makes it possible to increase the processing speed. On the other hand, if the thickness is too thin, there is a concern that the base layer may lack rigidity. Insufficient rigidity of the base layer can cause problems such as collapse when packed and displayed with products or wrinkles during processing. Taking the above into consideration, the thickness of the polypropylene film used as the base layer is preferably 3 to 50 μm, more preferably 10 to 35 μm, and even more preferably 12 to 19 μm. Furthermore, it is preferable to select a film as thin as possible within a range that does not cause problems due to insufficient rigidity.

[0017] (Method for manufacturing biaxially oriented polypropylene film as base layer) In order to achieve the above-described ranges for the properties of a biaxially oriented polypropylene film containing propylene units as a base layer in the present invention, the following raw material composition and film-forming conditions are preferably used. The main raw material resin for the biaxially oriented polypropylene film can be at least one polypropylene resin selected from the group consisting of propylene homopolymers, copolymers of propylene with ethylene and / or α-olefins having 4 or more carbon atoms, and mixtures thereof. Propylene homopolymers that are substantially free of ethylene and / or α-olefins having 4 or more carbon atoms are preferred. Even if ethylene and / or α-olefins having 4 or more carbon atoms are contained, the amount of ethylene and / or α-olefins having 4 or more carbon atoms is preferably 1 mol% or less. The upper limit of the component amount is more preferably 0.5 mol%, even more preferably 0.3 mol%, and particularly preferably 0.1 mol%. Crystallinity is likely to be improved within the above range. Examples of the α-olefin component having 4 or more carbon atoms that constitutes such a copolymer include 1-butene, 1-pentene, 3-methylpentene-1, 3-methylbutene-1, 1-hexene, 4-methylpentene-1, 5-ethylhexene-1, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, and 1-eicosene. The polypropylene resin may be a copolymer of two or more different propylene homopolymers, a copolymer of propylene with ethylene and / or an α-olefin having 4 or more carbon atoms, or a mixture thereof. In the resin composition that constitutes the biaxially oriented polypropylene film, the total content of the propylene homopolymer and the copolymer of propylene with ethylene and / or an α-olefin having 4 or more carbon atoms is preferably 50% by weight or more, more preferably 60% by weight or more, even more preferably 70% by weight or more, even more preferably 80% by weight or more, and particularly preferably 90% by weight or more.The propylene unit, which is the main component of the resin composition constituting the biaxially oriented polypropylene film, is preferably 60 mol% or more of the entire resin composition, more preferably 70 mass% or more, even more preferably 80 mass% or more, even more preferably 90 mass% or more, and particularly preferably 95 mass% or more.

[0018] The mesopentad fraction ([mmmm]%), which is an index of the stereoregularity of the polypropylene raw material used to make the biaxially oriented polypropylene film, is in the range of 97.0 to 99.9%, preferably in the range of 97.5 to 99.7%, more preferably in the range of 98.0 to 99.5%, and particularly preferably in the range of 98.5 to 99.3%. When it is 97.0% or higher, the crystallinity of the polypropylene resin is enhanced, and the melting point, crystallinity, and crystalline orientation of the crystals in the film are improved, making it easier to obtain rigidity and heat resistance at high temperatures. When it is 99.9% or lower, it is easier to reduce costs in terms of the production of the polypropylene resin and makes it less likely to break during film formation. A mesopentad fraction of 99.5% or lower is more preferable. The mesopentad fraction is measured by nuclear magnetic resonance (NMR) spectroscopy. In order to set the mesopentad fraction of the polypropylene resin within the above range, a method of washing the obtained polypropylene resin powder with a solvent such as n-heptane, a method of appropriately selecting a catalyst and / or a co-catalyst, and a method of appropriately selecting the components of the polypropylene resin composition are preferably employed.

[0019] Furthermore, as long as the effects of the present invention are not impaired, various additives for improving quality, such as antistatic agents, antiblocking agents, heat stabilizers, antioxidants, and ultraviolet absorbers, can also be blended into the biaxially oriented polypropylene film used as the base layer.

[0020] In the present invention, the biaxially oriented polypropylene film used as the base layer is preferably a biaxially oriented film that has been biaxially stretched from the viewpoint of imparting rigidity and heat resistance. It is known that biaxial stretching causes crystalline orientation of polymers, increasing the modulus of elasticity and melting point. As a biaxial stretching method, any of simultaneous inflation biaxial stretching, simultaneous tenter biaxial stretching, sequential tenter biaxial stretching, and sequential biaxial stretching by roll stretching and tenter stretching can be used. However, from the viewpoint of film formation stability and thickness uniformity, it is preferable to employ sequential tenter biaxial stretching or sequential biaxial stretching by roll stretching and tenter stretching. It is particularly preferable to stretch the film in the longitudinal direction and then in the width direction, but a method in which stretching in the width direction is followed by stretching in the longitudinal direction may also be used.

[0021] In the present invention, as a film-forming method for increasing the fusion initiation temperature of the biaxially oriented polypropylene film used as the base layer, reducing the heat shrinkage rate at 150°C, and increasing the Young's modulus to achieve high rigidity, it is preferable to select a raw material resin that has high stereoregularity and high crystallinity, and to increase the stretching ratio and heat treatment temperature in the stretching step during film formation. A particularly preferred film-forming method includes, for example, using a highly stereoregular polypropylene resin having a mesopentad fraction ([mmmm]%) in the range of 97.0 to 99.9% as a raw material, heating and melting the resin in an extruder at 230 to 270°C, extruding the molten polypropylene resin into a sheet from a T-die, contacting the molten sheet with a cooling roll at 50°C or less, and optionally immersing it in a water bath at 30°C or less to rapidly cool it to obtain an unstretched sheet, stretching the unstretched sheet 3.8 to 4.2 times in the longitudinal direction at 130 to 150°C in a roll stretching machine, clamping both ends with clips, preheating in a tenter at 170 to 175°C, stretching the sheet widthwise at 150 to 160°C or more at 9 times, and then heat-treating the sheet widthwise at 170 to 175°C while relaxing it by 0 to 10%.

[0022] [Sealant Layer] The sealant layer of the present invention is made of a resin composition whose main raw material resin is at least one resin selected from the group consisting of polypropylene, polyester, polyamide, etc., and is made of a resin composition whose main component is the same type of resin as the main component of the resin composition constituting the base layer. Since the sealant layer of the present invention needs to have a low melting point, it is preferable that it is not subjected to a stretching process such as biaxial stretching. Furthermore, a polypropylene-based resin with a low melting point is preferable as the material. The main component here means a resin that is contained in the sealant layer at 50% by mass or more.

[0023] (Polypropylene Film as Sealant Layer) When a polypropylene film primarily composed of propylene units is used as the sealant layer in the present invention, the seal initiation temperature (SIT-S) (hereinafter sometimes abbreviated as SIT-S) is 90°C or higher and 120°C or lower, more preferably 100°C or higher and 115°C or lower, and even more preferably 105°C or higher and 110°C or lower. A seal initiation temperature (SIT-S) of 120°C or lower eliminates the need for heat sealing at high temperatures, the base layer is less likely to deform due to thermal shrinkage, and the appearance of the package is less likely to be damaged. Furthermore, a seal initiation temperature (SIT-S) of 90°C or higher is less likely to cause problems such as sticking to conveyor rolls during processing. This is particularly useful for heat sealing in high-speed automated packaging. It is known that the seal initiation temperature (SIT-S) of a sealant layer primarily composed of propylene units depends on the melting point of the resin component constituting the sealant layer. Therefore, the melting point can be adjusted to any desired temperature by mixing various resins with different melting points.

[0024] When the sealant layer is primarily composed of propylene units, the primary raw material resin may be at least one polypropylene-based resin selected from the group consisting of propylene homopolymers, copolymers of propylene with ethylene and / or α-olefins having 4 or more carbon atoms, and mixtures thereof. The copolymer may be a random copolymer, a block copolymer, or a graft copolymer. The copolymer components are not limited, and examples include lower α-olefins such as ethylene, butene, heptene, hexene, and octene, and dienes such as butadiene and isoprene. Copolymers may be binary systems with the components, or multi-component systems of ternary or higher components. The stereoregularity is also not limited, and may be isotactic, syndiotactic, or atactic. The stereoregularity may be appropriately selected to meet the desired characteristics. The density is 870 to 912 kg / m. ３ Furthermore, the density is preferably 880 to 905 kg / m ３ Preferably, the density is 870 kg / m ３ If the density is less than 912 kg / m, the rigidity, heat resistance and blocking resistance will decrease, which is not preferable. ３ If it exceeds this value, the low-temperature heat sealability will be deteriorated, which is not preferable.

[0025] The polypropylene film containing propylene units as a main component as the sealant layer is preferably a laminate film. For example, the sealant layer preferably has a layer structure of heat seal layer / substrate layer (base layer) or heat seal layer / substrate layer (base layer) / surface layer. By increasing the rigidity of the substrate (base layer) of the sealant layer, the rigidity of the entire sealant layer can be increased. By providing a surface layer on the sealant layer, the slipperiness of the sealant layer and the adhesion of the substrate layer to the biaxially oriented polypropylene film can be improved.

[0026] The main raw material resin of the heat seal layer of the sealant layer may be at least one polypropylene-based resin selected from the group consisting of propylene homopolymers, copolymers of propylene with ethylene and / or α-olefins having 4 or more carbon atoms, and mixtures thereof. The copolymer may be a random copolymer, a block copolymer, or a graft copolymer. The copolymer components are not limited, and examples include lower α-olefins such as ethylene, butene, heptene, hexene, and octene, and dienes such as butadiene and isoprene. The copolymer may be a binary system with the components, or a ternary or higher multi-component system. The stereoregularity is also not limited, and may be isotactic, syndiotactic, or atactic. It can be selected appropriately to meet the characteristics required in the market. The density is 870 to 912 kg / m. ３ Furthermore, the density is preferably 880 to 905 kg / m ３ Preferably, the density is 870 kg / m ３ If the density is less than 912 kg / m, the rigidity, heat resistance and blocking resistance will decrease, which is not preferable. ３ If the content exceeds this range, the low-temperature heat sealability will deteriorate, which is not preferred. The content of propylene units, which are the main component of the resin composition constituting the heat seal layer of the sealant layer, is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, based on the total resin composition.

[0027] The main raw material resin for the substrate layer (base layer) of the sealant layer can be at least one polypropylene-based resin selected from the group consisting of propylene homopolymers, random copolymers of propylene with α-olefins such as ethylene, butene-1, pentene-1, hexene-1, 3-methylbutene-1, 4-methylpentene-1, and octene-1, and block copolymers. When a copolymer is used, it is preferable to use a copolymer with a lower copolymerization amount than that of the heat seal layer in order to increase rigidity. The propylene unit, which is the main component of the resin composition constituting the substrate layer (base layer) of the sealant layer, is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, of the entire resin composition.

[0028] The main raw material resin for the surface layer of the sealant layer may be at least one polypropylene-based resin selected from the group consisting of propylene homopolymers, random copolymers of propylene with α-olefins such as ethylene, butene-1, pentene-1, hexene-1, 3-methylbutene-1, 4-methylpentene-1, and octene-1, and block copolymers. When using a copolymer, it is preferable to use a copolymer with a lower copolymerization amount than that of the heat seal layer to increase rigidity. A lubricant can also be added to improve slipperiness. Furthermore, to improve the laminate strength of the laminate of the biaxially oriented polypropylene film of the base layer and the sealant layer while maintaining high rigidity, a polypropylene resin copolymerized with a small amount of α-olefin can be added. The propylene unit, which is the main component of the resin composition constituting the surface layer of the sealant layer, is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, of the entire resin composition.

[0029] In the case of a laminated film, a polypropylene film having propylene units as a main component for the sealant layer is produced by melting the respective raw resins using multiple extruders, co-extruding them into a sheet from a T-die, cooling and solidifying them with a cooling roll, and then winding them into a roll to obtain, for example, an unstretched polypropylene film for the sealant layer having a structure consisting of a heat seal layer / substrate layer (base layer) / surface layer. In this case, the film can also be stretched in the longitudinal direction using a roll stretching machine before being wound into a roll, as long as the heat sealability is not impaired.

[0030] (Relationship between the fusion initiation temperature (FIT-B) of the base material layer and the sealing initiation temperature (SIT-S) of the sealant layer) The fusion initiation temperature (FIT-B) of the base material layer and the sealing initiation temperature (SIT-S) of the sealant layer preferably have the following relationship: 50°C≦(FIT-B)−(SIT-S)≦90(°C) Equation (1) (FIT-B) is greater than (SIT-S), and the difference between them is 50°C or more, preferably 60°C or more. If the difference between (FIT-B) and (SIT-S) is 50°C or more, the heat seal bar can be set to a higher temperature when forming bags at high temperatures and high speeds, making it possible to form bags at a higher speed, preventing wrinkles and deformation in the heat-sealed portion, and achieving sufficient heat seal strength. The difference between (FIT-B) and (SIT-S) is 90°C or less. The greater the difference between (FIT-B) and (SIT-S), the more advantageous it is for high-temperature, high-speed bag production, but if the melting point of the base layer is low, the fusion temperature of the sealant layer is unlikely to be low and blocking may be unlikely to occur if the difference between (FIT-B) and (SIT-S) is 90°C or less. Furthermore, in the present invention, the main components of the resins constituting the base layer and the sealant layer must be the same type of resin, so the range of resin types that can be selected is unlikely to be narrowed.

[0031] [Resin laminate for packaging material] (Method of laminating substrate layer and sealant layer) The resin laminate for packaging material of the present invention is composed of a substrate layer and a sealant layer having the same main component. The substrate layer and sealant layer can be obtained as separate films and then laminated via an adhesive. The substrate layer and sealant layer can also be laminated by co-extrusion. The resin laminate for packaging material of the present invention has a layer structure of two layers (substrate layer / sealant layer) or three layers (laminate material (third layer) / substrate layer / sealant layer), as long as the main component of each layer is the same. The total thickness is not particularly limited, but is preferably about 30 to 200 μm, and more preferably about 25 to 150 μm.

[0032] (Seal strength temperature of laminate) The upper limit of the seal strength temperature of the resin laminate for packaging materials of the present invention in the longitudinal and width directions is preferably 120°C, more preferably 118°C, even more preferably 116°C, and most preferably 114°C. If the temperature is 120°C or less, the sealing temperature when producing a packaging bag from the resin laminate for packaging materials can be lowered, reducing shrinkage wrinkles due to heat and allowing the production of a package with good appearance. The lower limit of the seal strength temperature in the longitudinal and width directions is 900°C, more preferably 95°C.

[0033] (Ultimate Heat Seal Strength of Laminate) The lower limit of the ultimate heat seal strength of the resin laminate for packaging materials of the present invention in the longitudinal direction is preferably 5 N / 15 mm, more preferably 8 N / 15 mm, even more preferably 10 N / 15 mm, still more preferably 12 N / 15 mm, and particularly preferably 15 N / 15 mm. If it is 5 N / 15 mm or more, the breakage of packaging bags made from the resin laminate for packaging materials can be reduced. There is no particular preferred upper limit in the longitudinal direction, but a realistic value is 30 N / 15 mm, and preferably 25 N / 15 mm or less.

[0034] (High-temperature heat seal finish) When the appearance of the sealed portion of the laminate when heat-sealed at the seal strength temperature of the laminate is evaluated on the following three-point scale based on the degree of peeling and wrinkling of the base layer film, it is preferable that there is no peeling or / and no significant wrinkling of the base layer film, it is more preferable that wrinkles occur only in a part of the base layer film, and it is even more preferable that there is no peeling or wrinkling of the base layer film.

[0035] (Heat Sealing) To form a bag for packaging food or the like using the resin laminate for packaging materials of the present invention, the resin laminate for packaging materials of the present invention is formed into a bag with an opening, the contents are filled, and the opening is heated to fuse and seal the sealant layer. The same process is often used when forming a bag while filling it with food. Generally, bag production involves laminating a sealant layer to a substrate layer and then performing a heat sealing process in which the sealant layers of the substrate layer and sealant layer laminate are fused together by heating from the substrate layer side. In the heat sealing process, a heating plate applies pressure from the substrate layer side to hold down the film and seal it. However, since the substrate layer is directly heated during this process, if its heat resistance is low, wrinkles due to shrinkage and fusion of the substrate layer to the heat seal bar may occur. Fewer wrinkles are preferable for bag durability and to increase consumer interest. Furthermore, fusion can cause staining of the outer surface of the bag, and if printed, can cause ink peeling, significantly impairing the design. In addition, there is a growing demand for faster bag manufacturing processes, which requires higher-temperature heat sealing and thinner base layers, and in the process of sealing the opening of the bag after filling it with the contents, heat sealing at even higher temperatures is required. Even in this case, it is preferable that shrinkage is small and that the base layer does not fuse to the heat seal bar.

[0036] The present invention will be described in detail below with reference to examples. The properties were measured and evaluated by the following methods. (1) Mesopentad fraction The mesopentad fraction ([mmmm]%) of a polypropylene resin was measured by the following method. １３The mesopentad fraction was calculated according to the method described in Zambelli et al., Macromolecules, Vol. 6, p. 925 (1973). １３ C-NMR measurement was performed using an AVANCE 500 manufactured by BRUKER, by dissolving 200 mg of a sample in a 8:2 mixture of o-dichlorobenzene and deuterated benzene at 135°C and at 110°C.

[0037] (2) Film Thickness The film thickness was measured using a Millitron 1202D manufactured by Seiko EM Corporation.

[0038] (3) Heat shrinkage of base layer This was measured according to JIS Z1712 by the following method. The film was cut into pieces of 20 mm width and 200 mm length in both the longitudinal and transverse directions of the film, and then hung in a hot air oven at 150°C for 5 minutes. The length after heating was measured, and the heat shrinkage of the base layer was calculated as the ratio of the shrunk length to the original length.

[0039] (4) Young's modulus of base layer The Young's modulus of the film in the longitudinal and transverse directions was measured at 23°C in accordance with JIS K 7127. Samples of 15 mm x 200 mm were cut out of the film and set in a tensile tester (Instron 5965, a dual-column tabletop tester manufactured by Instron Japan Co., Ltd.) with a chuck width of 100 mm. A tensile test was carried out at a tensile speed of 200 mm / min. The Young's modulus of the base layer was determined from the slope of the linear portion of the obtained strain-stress curve at the beginning of elongation.

[0040] (5) Fusion Initiation Temperature of Base Material Layer (FIT-B) Two 300 mm × 60 mm long base material layers used in the Examples and Comparative Examples were sandwiched between two 300 mm × 100 mm long polyethylene terephthalate films for preventing adhesion (manufacturer: Toyobo Co., Ltd., brand: E5100, thickness: 12 μm) with the corona-treated surfaces facing each other, and heat-sealed at 0.2 MPa × 1 second using a thermal gradient sealer (manufactured by Toyo Seiki Seisaku-sho), and a 15 mm wide sample was cut out, and the longitudinal T-peel seal strength (N / 15 mm) was measured using a tensile tester (Shimadzu Corporation, autograph, model: S-100-D) at a speed of 200 mm / min. The fusion initiation temperature of the base material layer was determined by plotting a graph with the sealing temperature on the horizontal axis and the sealing strength on the vertical axis, and the temperature at which the sealing strength reached 1 N / 15 mm was defined as the fusion initiation temperature of the base material layer (FIT-B) (°C).

[0041] (6) Sealing initiation temperature of sealant layer (SIT-S) Two 300 mm × 60 mm sealant layers (sealing surfaces when the sealant layer is multilayered) used in the examples and comparative examples were sandwiched between two 300 mm × 100 mm long polyethylene terephthalate films for preventing adhesion (manufacturer: Toyobo Co., Ltd., brand: E5100, thickness: 12 μm) so that they faced each other, and heat-sealed at 0.2 MPa × 1 second using a thermal gradient sealer (manufactured by Toyo Seiki Seisaku-sho), and a 15 mm wide sample was cut out and evaluated for longitudinal T-peel seal strength (N / 15 mm) at a speed of 200 mm / min using a tensile tester (Shimadzu Corporation, autograph, model: S-100-D) The seal strength attainment temperature (SIT-S) of the sealant layer was determined by plotting a graph with the seal temperature on the horizontal axis and the seal strength on the vertical axis, and the temperature at which the seal strength reached 3 N / 15 mm was taken as the seal initiation temperature (SIT-S) (°C) of the sealant layer.

[0042] (7) Temperature at which seal strength of laminated body is reached A laminate of a base layer and a sealant layer was produced using a continuous dry laminator as follows: First, an adhesive was applied to the corona-treated surface of the biaxially oriented polypropylene film obtained in the Examples and Comparative Examples in a dry coating amount of 3.0 g / m. ２After gravure coating to obtain a uniform thickness, the laminate was introduced into a drying zone and dried at 80°C for 5 seconds. Subsequently, the sealant layer was bonded to the adhesive-coated surface between rolls installed downstream (roll pressure: 0.2 MPa, roll temperature: 60°C). The resulting laminate was wound up and aged for 3 days at 40°C. The adhesive used was a dry lamination adhesive obtained by mixing 28.9% by mass of base agent (TM569, manufactured by Toyo-Morton Co., Ltd.), 4.00% by mass of curing agent (CAT10L, manufactured by Toyo-Morton Co., Ltd.), and 67.1% by mass of ethyl acetate. Next, a measurement sample measuring 15 mm wide x 200 mm long in the longitudinal direction was cut out from the prepared laminate, and the sealant layers of two laminate samples were heat-sealed together at 0.2 MPa x 1 second using a thermal gradient sealer (manufactured by Toyo Seiki Co., Ltd.). The laminate was heat-sealed at 5°C intervals from 90°C, and a 15mm wide sample was cut out. The measurement sample was set in a tensile tester (Tensilon, manufactured by Orientec Co., Ltd.) with an initial chuck distance of 100mm, and the peel strength in the longitudinal direction at time T was measured at a tensile speed of 200mm / min. A graph was plotted with the heat-sealing temperature on the horizontal axis and the seal strength on the vertical axis, and the temperature at which the seal strength reached 5N / 15mm was recorded as the seal strength temperature (°C) of the laminate.

[0043] (8) Final heat seal strength of laminate In the graph obtained in (7) with the heat seal temperature on the horizontal axis and the seal strength on the vertical axis, the value at which the maximum strength was reached was taken as the final heat seal strength of the laminate.

[0044] (9) High-Temperature Heat-Seal Finish The appearance of the sealed portion of the laminate when heat-sealed at the seal strength temperature of the laminate was evaluated according to the following three levels based on the degree of peeling and wrinkling of the base layer. ◯: No peeling or wrinkling of the base layer film. Δ: Wrinkling occurred in part of the base layer film. ×: Peeling occurred entirely and / or significant wrinkling occurred in the base layer film.

[0045] Example 1 A packaging resin laminate was produced by laminating the following biaxially oriented polypropylene film as the base layer and the following unoriented polypropylene film as the sealant layer using the method described above. The biaxially oriented polypropylene film of the base layer had a thickness of 16 μm, a fusion initiation temperature (FIT-B) of 166°C, a 150°C heat shrinkage rate of 4.5% in the longitudinal direction and 0.8% in the width direction, and a Young's modulus of 2.2 GPa in the longitudinal direction and 3.6 GPa in the width direction. The sealant layer had a thickness of 30 μm and a seal initiation temperature (SIT-S) of 110°C, with a difference between (FIT-B) and (SIT-S) of 56°C. The seal strength attainment temperature of the laminated packaging resin laminate was 125°C, and the attained heat seal strength was 8.0 N / 15 mm. The heat seal finish was good, with no peeling or wrinkles. Base material layer: As a polypropylene resin, 80 parts by mass of propylene homopolymer PP-1 having MFR = 7.5 g / 10 min, [mmmm] = 98.9%, Tc = 116 ° C., Tm = 163 ° C. and 20 parts by mass of propylene homopolymer PP-2 having MFR = 3.0 g / 10 min, [mmmm] = 98.4%, Tc = 116 ° C., Tm = 163 ° C. were blended to form a polypropylene resin composition, which was then heated and melted at 250 ° C. in an extruder. The molten polypropylene resin composition was extruded into a sheet from a T-die at 250 ° C., and the molten sheet was brought into contact with a cooling roll at 37 ° C. and then placed directly in a water bath at 29 ° C. to obtain an unstretched sheet. The unstretched sheet was then stretched 4.0 times in the longitudinal direction at 140°C using two pairs of rolls, then both ends were clamped with clips and introduced into a hot air oven (tenter), where it was preheated at 174°C, stretched 10 times in the width direction at 160°C, and then heat-treated while relaxing by 7% in the width direction at 174°C. One surface of the obtained biaxially oriented polypropylene film was subjected to a corona treatment at 13 W / m using a corona treatment machine manufactured by Kasuga Electric Co., Ltd. ２The film was subjected to a corona treatment under conditions of 0.5 min and then wound up on a winder to obtain a biaxially oriented polypropylene film with a thickness of 16 μm. Sealant layer: A non-oriented polypropylene film consisting of a propylene homopolymer and a propylene-ethylene copolymer (manufactured by Toyobo Co., Ltd., Pylen (registered trademark) CT P1162, thickness 30 μm, seal initiation temperature (SIT-S) = 110°C) was used. The amount of propylene units in the sealant layer was 70 mass% or more.

[0046] Example 2 Similar to Example 1, a packaging resin laminate was produced by laminating the following biaxially oriented polypropylene film as the base layer and the following unoriented polypropylene film as the sealant layer using the method described above. The biaxially oriented polypropylene film of the base layer had a thickness of 16 μm, a fusion initiation temperature (FIT-B) of 165°C, a 150°C heat shrinkage rate of 4.7% in the longitudinal direction and 2.0% in the width direction, and a Young's modulus of 2.3 GPa in the longitudinal direction and 4.0 GPa in the width direction. The sealant layer was 30 μm thick, and the seal initiation temperature (SIT-S) was 110°C, with a difference between (FIT-B) and (SIT-S) of 55°C. The seal strength attainment temperature of the laminated packaging resin laminate was 125°C, and the attained heat seal strength was 7.5 N / 15 mm. The heat seal finish was good, with no peeling or wrinkles. Base layer: A biaxially oriented polypropylene film with a thickness of 16 μm was obtained and used in the same manner as in Example 1, except that the relaxation rate during heat treatment was changed to 6.0%. Sealant layer: A non-oriented polypropylene film composed of a propylene homopolymer and a propylene-ethylene copolymer (manufactured by Toyobo Co., Ltd., Pylen (registered trademark) CT P1162, thickness 30 μm, seal initiation temperature (SIT-S) = 110°C) was used.

[0047] Example 3 A packaging resin laminate was prepared by laminating in the same manner as in Example 1, except that the following biaxially oriented polypropylene film was used as the base layer and the following unstretched polypropylene film was used as the sealant layer. The biaxially oriented polypropylene film of the base layer had a thickness of 16 μm, a fusion initiation temperature (FIT-B) of 164°C, a 150°C heat shrinkage rate of 5.0% in the longitudinal direction and 4.7% in the width direction, and a Young's modulus of 2.0 GPa in the longitudinal direction and 4.2 GPa in the width direction. The sealant layer was 30 μm thick and had a seal initiation temperature (SIT-S) of 110°C, with a difference between (FIT-B) and (SIT-S) of 54°C. The seal strength attainment temperature of the laminated packaging resin laminate was 125°C, and the attained heat seal strength was 8.0 N / 15 mm. The heat seal finish was good, with no peeling or wrinkles. Base layer: A biaxially oriented polypropylene film with a thickness of 16 μm was obtained and used in the same manner as in Example 2, except that the heat treatment temperature was changed to 172° C. Sealant layer: A non-oriented polypropylene film composed of a propylene homopolymer and a propylene-ethylene copolymer (manufactured by Toyobo Co., Ltd., Pylen (registered trademark) CT P1162, thickness 30 μm, seal initiation temperature (SIT-S) = 110° C.) was used.

[0048] Example 4 A packaging resin laminate was prepared by laminating in the same manner as in Example 1, except that the following biaxially oriented polypropylene film was used as the base layer and the following unstretched polypropylene film was used as the sealant layer. The biaxially oriented polypropylene film of the base layer had a thickness of 16 μm, a fusion initiation temperature (FIT-B) of 161°C, a 150°C heat shrinkage rate of 6.1% in the longitudinal direction and 5.5% in the width direction, and a Young's modulus of 2.2 GPa in the longitudinal direction and 4.3 GPa in the width direction. The sealant layer was 30 μm thick and had a seal initiation temperature (SIT-S) of 110°C, with a difference between (FIT-B) and (SIT-S) of 51°C. The seal strength attainment temperature of the laminated packaging resin laminate was 125°C, and the attained heat seal strength was 5.0 N / 15 mm. The heat seal finish was good, with no peeling or wrinkles. Base layer: A biaxially oriented polypropylene film having a thickness of 16 μm was obtained in the same manner as in Example 1, except that the longitudinal stretching ratio was changed to 4.5 times and the heat treatment temperature was changed to 170° C. Sealant layer: A film consisting of a propylene homopolymer and a propylene-ethylene copolymer (CT P1162, thickness 30 μm, seal initiation temperature (SIT-S) = 110° C.) was used.

[0049] Comparative Example 1 A packaging resin laminate was prepared by laminating in the same manner as in Example 1, except that the following biaxially oriented polypropylene film was used as the base layer and the following unstretched polypropylene film was used as the sealant layer. The biaxially oriented polypropylene film of the base layer had a thickness of 16 μm, a fusion initiation temperature (FIT-B) of 152°C, a 150°C heat shrinkage rate of 15.5% in the longitudinal direction and 22.7% in the width direction, a Young's modulus of 1.8 GPa in the longitudinal direction and 2.9 GPa in the width direction, a sealant layer of 30 μm as shown below, a seal initiation temperature (SIT-S) of 110°C, and a difference between (FIT-B) and (SIT-S) of 42°C. The seal strength ultimate temperature of the laminated packaging resin laminate was 125°C, and the ultimate heat seal strength was 7.5 N / 15 mm. The heat seal finish was poor, with peeling of the base layer surface and significant wrinkling. Base material layer: A propylene homopolymer having an MFR of 2.5 g / 10 min, [mmmm] of 96.5%, a Tc of 116°C, and a Tm of 163°C was used as the polypropylene resin. The propylene homopolymer was heated and melted at 250°C in an extruder, and the molten polypropylene resin composition was extruded into a sheet from a T-die at 250°C. The molten sheet was contacted with a cooling roll at 37°C and then placed in a water bath at 29°C to obtain an unstretched sheet. The unstretched sheet was then stretched 4.5 times in the longitudinal direction at 140°C using two pairs of rolls, then clamped at both ends with clips and introduced into a hot air oven (tenter). After preheating at 174°C, it was stretched 10 times in the width direction at 160°C, and then heat-treated while relaxing by 6.7% in the width direction at 165°C. One side of the obtained biaxially oriented polypropylene film was treated with a corona treatment machine manufactured by Kasuga Electric Co., Ltd. at 13 W / m ２ After corona treatment under conditions of 0.5 min, the film was wound up on a winder to obtain a biaxially oriented polypropylene film with a thickness of 16 μm. Sealant layer: A non-oriented polypropylene film consisting of a propylene homopolymer and a propylene-ethylene copolymer (manufactured by Toyobo Co., Ltd., Pylen (registered trademark) CT P1162, thickness 30 μm, seal initiation temperature (SIT-S) = 110°C) was used.

[0050] Comparative Example 2 A packaging resin laminate was prepared by laminating in the same manner as in Example 2, except that the following biaxially oriented polypropylene film was used as the base layer and the following unstretched polypropylene film was used as the sealant layer. The biaxially oriented polypropylene film of the base layer had a thickness of 16 μm, a fusion initiation temperature (FIT-B) of 165°C, a 150°C heat shrinkage rate of 4.7% in the longitudinal direction and 2.0% in the width direction, and a Young's modulus of 2.3 GPa in the longitudinal direction and 4.0 GPa in the width direction. The sealant layer was 30 μm thick, and the seal initiation temperature (SIT-S) was 128°C, with a difference between (FIT-B) and (SIT-S) of 37°C. The seal strength attainment temperature of the laminated packaging resin laminate was 143°C, and the attained heat seal strength was 5.0 N / 15 mm. The heat seal finish was poor, with peeling of the base layer surface and significant wrinkling. Base layer: The biaxially oriented polypropylene film prepared in Example 2 was used. Sealant layer: An unstretched polypropylene film consisting of a propylene homopolymer and a propylene-ethylene copolymer (manufactured by Toyobo Co., Ltd., Pylen (registered trademark) CT P1128, thickness 30 μm, seal initiation temperature (SIT-S) = 128°C) was used. The amount of propylene units in the sealant layer was 70 mass% or more.

[0051] Reference Example 1: In the same manner as in Example 1, a packaging resin laminate was produced by laminating the following biaxially oriented polyethylene terephthalate film as the base layer and the following unstretched polypropylene film as the sealant layer using the method described above. The biaxially oriented polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., E5100, thickness 12 μm) as the base layer had a fusion initiation temperature (FIT-B) higher than 200°C, a 150°C heat shrinkage rate of 1.4% in the longitudinal direction and 0.2% in the width direction, and a Young's modulus of 3.9 GPa in the longitudinal direction and 4.0 GPa in the width direction. The sealant layer was 30 μm thick, and the seal initiation temperature (SIT-S) was 110°C, with the difference between (FIT-B) and (SIT-S) being greater than 90°C. The seal strength ultimate temperature of the laminated packaging resin laminate was 125°C, and the ultimate heat seal strength was 8.0 N / 15 mm. The heat seal finish was good, with no peeling or wrinkles on the surface of the base layer. Base layer: A biaxially oriented polyethylene terephthalate film (Toyobo Ester Film (registered trademark) E5100, thickness 12 μm) manufactured by Toyobo Co., Ltd. was used. Sealant layer: A non-oriented polypropylene film composed of a propylene homopolymer and a propylene-ethylene copolymer (Toyobo Pylen (registered trademark) CT P1162, thickness 30 μm, seal initiation temperature (SIT-S) = 110°C) was used.

[0052]

[0053] The resin laminate for packaging materials of the present invention can be suitably used as a mono-material packaging material that can be heat-sealed into bags at high temperature and high speed, similar to a resin laminate for packaging materials that uses a polyester (PET) film as a base layer and a polyolefin film as a sealant layer.

Claims

1. A resin laminate for packaging materials comprising at least a base layer and a sealant layer, wherein the base layer and the sealant layer are made of the same resin composition as a main component, and the fusion initiation temperature (FIT-B) of the base layer and the sealing initiation temperature (SIT-S) of the sealant layer satisfy the following formulas (1) to (3): 50℃≦(FIT-B)-(SIT-S)≦90(℃) Formula (1) 90≦(SIT-S)≦120(℃) Formula (2) 160≦(FIT-B)≦180(℃) Formula (3)

2. 2. The resin laminate for packaging materials according to claim 1, wherein the main component of the resin composition constituting the base layer and the sealant layer is a propylene unit, and the base layer is a biaxially oriented polypropylene film.

3. 3. The resin laminate for packaging materials according to claim 2, wherein the biaxially oriented polypropylene film of the base material layer has a heat shrinkage rate at 150°C of 6.5% or less in the longitudinal direction and 5.5% or less in the width direction.

4. 4. The resin laminate for packaging materials according to claim 2 or 3, wherein the biaxially oriented polypropylene film of the base layer has a Young's modulus of 2.0 GPa or more in the longitudinal direction and 3.5 GPa or more in the width direction.

5. The resin laminate for packaging materials according to claim 1 or 2, further comprising an adhesive layer between the base material layer and the sealant layer.