Resin laminates for packaging materials

Abstract

A resin laminate for packaging material with good processability is provided, wherein the substrate layer and the sealing layer are formed from the same raw materials. The resin laminate for packaging material comprises at least a substrate layer and a sealing layer, wherein the main components of the resin compositions constituting the substrate layer and the sealing layer are composed of the same resin composition, and the welding initiation temperature (FIT-B) of the substrate layer and the sealing strength attainment temperature (SRT-S) of the sealing layer satisfy the following formulas (1) to (3): 50℃≤(FIT-B)-(SRT-S)≤90(℃) Formula (1) 90≤(SRT-S)≤120(℃) Formula (2) 160≤(FIT-B)≤180(℃) Formula (3)

Description

Technical Field

[0001] This invention relates to a heat-sealable resin laminate for packaging materials having a substrate layer and a sealing layer formed from the same raw materials. Background Technology

[0002] In the past, as a component of packaging materials, various resin film materials formed from polyolefins, polyesters, etc., were used in combination depending on the contents and purpose of the packaged materials.

[0003] For example, as a sealing film requiring heat sealing properties, a low-melting-point unstretched polyethylene resin film is selected; as a surface raw material requiring heat resistance, a biaxially stretched polyester film or a polypropylene film is selected, and they are laminated together for use.

[0004] In recent years, there has been a growing call worldwide to focus on a circular society. From an environmental perspective, there is also a demand for "monomaterial packaging materials" made from easily recyclable single raw materials.

[0005] For example, Patent Document 1 proposes a packaging laminate in which the substrate layer and the sealing layer are formed of polyester film.

[0006] Patent document 2 proposes a packaging body in which the substrate layer and sealing layer are made of polyethylene.

[0007] In addition, Patent Document 3 proposes a packaging laminate using polypropylene for both the substrate layer and the sealing layer.

[0008] On the other hand, packaging materials have been designed by effectively utilizing the characteristics of various raw materials in the past, but adverse effects caused by relying on a single raw material are also known.

[0009] Especially in heat sealing, it is difficult to balance heat resistance and sealing strength due to the reliance on a single raw material. For example, Patent Document 3 also discloses a technique that uses biaxially stretched polypropylene film for the substrate layer and unstretched polypropylene film for the sealing layer. However, if the heat sealing temperature is high, the biaxially stretched polypropylene film of the substrate layer shrinks, resulting in a poor appearance of the sealing area. This leads to the following problems: easy fusion with the heat sealing bar, making it difficult to process; and weak heat sealing strength during heat sealing in high-speed bag making.

[0010] Existing technical documents

[0011] Patent documents

[0012] Patent Document 1: International Publication No. WO2020 / 262326

[0013] Patent Document 2: International Publication No. WO2021 / 054349

[0014] Patent Document 3: Japanese Patent Application Publication No. 2020-157715

[0015] Patent Document 4: International Publication No. WO2020 / 080507 Summary of the Invention

[0016] The problem the invention aims to solve

[0017] The object of the present invention is to solve the above-mentioned problems and to provide a resin laminate for packaging materials with good processability, in which the main components of the substrate layer and the sealing layer are resin compositions of the same kind of resin.

[0018] Solution for solving the problem

[0019] In order to achieve the above-mentioned objectives, this invention has conducted in-depth research and found that, for a resin laminate having at least a substrate layer and a sealing layer, the main components of the aforementioned substrate layer and the aforementioned sealing layer are composed of the same type of resin composition, and by controlling the welding initiation temperature (FIT-B) of the aforementioned substrate layer and the sealing strength attainment temperature (SRT-S) of the sealing layer within a specific relationship and range, the above-mentioned problems can be solved. That is, this invention includes the following technical features. [1]

[0021] A resin laminate for packaging material, comprising at least a substrate layer and a sealing layer, wherein the main components of the resin composition constituting the substrate layer and the sealing layer are composed of the same type of resin composition, and the welding start temperature (FIT-B) of the substrate layer and the sealing strength reach temperature (SRT-S) of the sealing layer satisfy the following formulas (1) to (3).

[0022] 50℃≤(FIT-B)-(SRT-S)≤90(℃) Formula (1)

[0023] 90≤(SRT-S)≤120(℃) Equation (2)

[0024] 160≤(FIT-B)≤180(℃) Equation (3) [2]

[0026] According to the resin laminate for packaging materials described in [1], the main component of the resin composition constituting the aforementioned substrate layer and the aforementioned sealing layer is a propylene unit, and the substrate layer is a biaxially stretched polypropylene film. [3]

[0028] According to the resin laminate for packaging materials described in [2], the heat shrinkage rate of the biaxially stretched polypropylene film of the aforementioned substrate layer at 150°C is less than 6.5% in the length direction and less than 5.5% in the width direction. [4]

[0030] According to the resin laminate for packaging materials described in [2] or [3], the Young's modulus of the biaxially stretched polypropylene film of the aforementioned substrate layer is 2.0 GPa or more in the length direction and 3.5 GPa or more in the width direction. [5]

[0032] The resin laminate for packaging materials according to any one of [1] to [4] has an adhesive layer between the aforementioned substrate layer and the aforementioned sealing layer.

[0033] The effects of the invention

[0034] The packaging material of the present invention is a resin laminate in which each layer is formed by a resin composition in which the main components are the same type of resin, and is easy to recycle as a "single material packaging material". The substrate layer has high heat resistance, and the difference between the welding start temperature of the substrate layer and the sealing start temperature of the sealing layer is more than 50°C. In addition, the welding start temperature of the sealing layer is below a specific temperature. Therefore, it can take into account both the heat sealing strength and good finishability during heat sealing. Detailed Implementation

[0035] The following provides a more detailed description of the resin laminate for packaging materials of the present invention.

[0036] The resin laminate for packaging materials of the present invention is characterized in that it comprises a laminated structure of a substrate layer and a sealing layer, wherein the difference between the welding initiation temperature of the substrate layer and the sealing strength reaching temperature of the sealing layer is 50°C or more.

[0037] The present invention will now be described in more detail.

[0038] [Substrate Layer]

[0039] The substrate layer in this invention is a film made of at least one resin selected from the group consisting of polypropylene, polyester, polyamide, etc., as the main raw material resin. Considering rigidity and heat resistance, a biaxially oriented film that has undergone biaxial stretching is preferred. In particular, polypropylene, due to its low melting point, is mostly used as a raw material for sealing layers. Therefore, if the substrate layer in this invention is a biaxially oriented polypropylene film, it is suitable as a resin laminate for packaging materials using a sealing layer formed from a resin composition whose main component is propylene units. The term "main component" here refers to resin containing 50% by mass or more in the substrate layer.

[0040] (Characteristics of biaxially oriented polypropylene film as substrate layer)

[0041] The welding initiation temperature (hereinafter sometimes simply referred to as FIT-B) of the biaxially oriented polypropylene film, which is the substrate layer in this invention and has propylene units as the main component, is preferably 160°C or higher and 180°C or lower. More preferably, it is 163°C or higher and 175°C or lower.

[0042] If the welding initiation temperature (FIT-B) of the substrate layer is above 160°C, the substrate layer is less likely to deform due to heat shrinkage even under high-temperature heat sealing, thus reducing the risk of damage to the appearance of the packaging and preventing defects such as sticking to the conveyor rollers during processing. This is particularly useful in high-temperature heat sealing processes in high-speed automated packaging.

[0043] For the upper limit of the welding start temperature (FIT-B) of the substrate layer, a higher value is preferred for high-speed automated packaging, while a value below 180°C is suitable for industrial production.

[0044] The weld initiation temperature (FIT-B) of the biaxially oriented polypropylene film used in the substrate layer of this invention can be adjusted by using specific polypropylene resins described later as raw materials and by adopting specific film-forming conditions.

[0045] For the biaxially oriented polypropylene film with propylene units as the main component, which serves as the substrate layer in this invention, the heat shrinkage rate at 150°C is preferably 6.5% or less in the length direction and 5.5% or less in the width direction. More preferably, it is 6.0% or less in the length direction and 5.0% in the width direction, and even more preferably, it is 5.0% or less in the length direction and 3.0% or less in the width direction. If the heat shrinkage rate at 150°C is large, the substrate layer will shrink significantly during heat sealing, damaging the appearance of the packaging and causing defects such as heat seal peeling. On the other hand, if the heat shrinkage rate at 150°C is small, the heating temperature for heat sealing can be increased, thus enabling heat sealing in a short time and achieving high-speed bag making.

[0046] For the rigidity of the biaxially oriented polypropylene film, which uses propylene units as the main component and serves as the substrate layer in this invention, a Young's modulus of 2.0 GPa or more in the length direction and 3.5 GPa or more in the width direction is preferred. Furthermore, a length modulus of 2.5 GPa or more and a width modulus of 4.0 GPa or more are more preferable. By increasing the Young's modulus, the rigidity of the substrate layer is improved, making it less prone to wrinkling during processing such as bag making. Additionally, even when bags are formed, it is expected that the contents can easily enter and exit. Furthermore, by improving rigidity, the film thickness can be reduced. With a thinner substrate layer, heat is more easily transferred to the sealing layer during heat sealing, allowing for a lower heating temperature. This reduces shrinkage and wrinkling caused by heating and improves processing speed.

[0047] There is no particular limitation on the thickness of the biaxially oriented polypropylene film, which is the substrate layer in this invention and has propylene units as its main component. However, when the film is thin, the heat from the sealing rod is easily transferred to the sealing layer during heat sealing, so the heating temperature can be reduced. By reducing the heating temperature, wrinkles caused by heat shrinkage can be reduced, resulting in a better appearance and finish of the packaging, which is therefore preferred. In addition, reducing the heating temperature can also increase the processing speed.

[0048] On the other hand, if the thickness is too thin, the rigidity of the substrate layer may be insufficient. Insufficient rigidity of the substrate layer can lead to defects such as the product collapsing during display or wrinkles forming during processing. Taking the above into consideration, the thickness of the polypropylene film used as the substrate layer is preferably 3 to 50 μm, more preferably 10 to 35 μm, and even more preferably 12 to 19 μm. It is also preferable to select the thinnest possible film within a range that will not cause defects due to insufficient rigidity.

[0049] (Method for manufacturing biaxially oriented polypropylene film as substrate layer)

[0050] In order for the properties of the biaxially oriented polypropylene film, which uses propylene units as the main component and serves as the substrate layer in this invention, to be within the above-mentioned range, the following raw material composition and film-forming conditions are preferred.

[0051] As the main raw material resin for biaxially oriented polypropylene films, at least one polypropylene resin selected from the group consisting of propylene homopolymers, copolymers of propylene with ethylene and / or α-olefins having more than 4 carbon atoms, and mixtures thereof can be used.

[0052] Preferably, the propylene homopolymer is substantially free of ethylene and / or α-olefins having 4 or more carbon atoms. Even when it contains ethylene and / or α-olefins having 4 or more carbon atoms, 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 amount is more preferably 0.5 mol%, further preferably 0.3 mol%, and particularly preferably 0.1 mol%. Crystallinity is easily improved within the above range.

[0053] Examples of α-olefin components with 4 or more carbon atoms constituting such copolymers include, for example, 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. Polypropylene resins can be made from two or more different propylene homopolymers, copolymers of propylene with ethylene and / or α-olefins with 4 or more carbon atoms, and mixtures thereof.

[0054] The total amount of propylene homopolymer, copolymer of propylene with ethylene and / or α-olefin having 4 or more carbon atoms in the resin composition constituting the biaxially oriented polypropylene film is preferably 50% by weight or more, more preferably 60% by weight or more, further preferably 70% by weight or more, even more preferably 80% by weight or more, and particularly preferably 90% by weight or more.

[0055] The propylene unit, which is the main component of the resin composition constituting the biaxially oriented polypropylene film, is preferably 60 mol% or more, more preferably 70 wt% or more, further preferably 80 wt% or more, even more preferably 90 wt% or more, and particularly preferably 95 wt% or more relative to the total resin composition.

[0056] The percentage of meso-five-unit components ([mmmm]%), which is an indicator of the stereoregularity of the polypropylene raw material used as a raw material for 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%.

[0057] If the content is above 97.0%, the crystallinity of the polypropylene resin increases, improving the melting point, crystallinity, and crystal orientation of the crystals in the film, making it easier to obtain rigidity and heat resistance at high temperatures. If the content is below 99.9%, from the perspective of polypropylene resin manufacturing, it is easier to control costs and the film is less prone to breakage during film formation. Below 99.5% is preferred. The proportion of the racemic five-unit components was determined using nuclear magnetic resonance (NMR).

[0058] To ensure that the proportion of the meso-five-unit components of the polypropylene resin is within the above-mentioned range, it is preferable to use a method of washing the obtained polypropylene resin powder with a solvent such as n-heptane; and to appropriately select a catalyst and / or co-catalyst, and to select the components of the polypropylene resin composition, etc.

[0059] In addition, if it is within the scope that will not impair the effect of the present invention, various additives for improving quality, such as antistatic agents, antiblocking agents, heat stabilizers, antioxidants, and ultraviolet absorbers, can also be mixed into the biaxially oriented polypropylene film as the substrate layer.

[0060] From the viewpoint of imparting rigidity and heat resistance, the biaxially oriented polypropylene film used as the substrate layer in this invention is preferably a biaxially oriented film that has undergone biaxial stretching. It is known that biaxial stretching causes the polymer to crystallize, increasing the elastic modulus and melting point. As a method of biaxial stretching, any one of the following can be used: simultaneous biaxial stretching with inflation, simultaneous biaxial stretching with a tenter frame, sequential biaxial stretching with a tenter frame, or sequential biaxial stretching using both roller stretching and tenter frame stretching. However, from the viewpoint of film stability and thickness uniformity, sequential biaxial stretching with a tenter frame or sequential biaxial stretching using both roller stretching and tenter frame stretching is preferred. Particularly preferred is stretching in the length direction followed by stretching in the width direction; stretching in the width direction followed by stretching in the length direction is also acceptable.

[0061] As a film-forming method for increasing the welding initiation temperature of the biaxially oriented polypropylene film, which serves as the substrate layer in this invention, reducing the heat shrinkage rate at 150°C, and increasing Young's modulus to achieve high rigidity, the raw material resin is preferably selected as having high stereoregularity and high crystallinity. In addition, the stretching ratio is increased and the heat treatment temperature is increased during the stretching process of film formation.

[0062] As a particularly preferred film-forming method, the following method can be cited as an example: The raw material is a polypropylene resin with high stereoregularity, in which the proportion of meso-race five-unit components ([mmmm]%) is in the range of 97.0% to 99.9%. The resin is heated and melted at 230 to 270°C using an extruder. The molten polypropylene resin is extruded in sheet form through a T-die, and the molten sheet is brought into contact with a cooling roller at a temperature below 50°C. If necessary, the sheet is immersed in a water bath at a temperature below 30°C for rapid cooling to obtain an unstretched sheet. The unstretched sheet is then stretched 3.8 to 4.2 times in length direction using a roller stretching machine at 130 to 150°C. The two ends are then clamped, and the sheet is preheated at 170 to 175°C using a tenter frame. The sheet is then stretched more than 9 times in width direction at 150 to 160°C. The sheet is then heat-treated while being relaxed by 0 to 10% in width direction at 170 to 175°C.

[0063] [Sealing layer]

[0064] The sealing layer of the present invention is formed of a resin composition having at least one resin selected from the group consisting of polypropylene, polyester, polyamide, etc. as the main component, and is formed of a resin composition having a resin of the same kind as the main component of the resin composition constituting the substrate layer as the main component.

[0065] Since the sealing layer in this invention needs to have a lower melting point, it is preferable not to undergo stretching processes such as biaxial stretching. Furthermore, a polypropylene-based resin with a low melting point is preferred as the raw material. The term "main component" as used herein refers to a resin comprising 50% by mass or more in the sealing layer.

[0066] (Polypropylene film used as a sealing layer)

[0067] When using a film with propylene units as the main component as the sealing layer in this invention, the sealing strength reaching temperature (SRT-S) (hereinafter sometimes simply referred to as (SRT-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. If the sealing strength reaching temperature (SRT-S) is 120°C or lower, high-temperature heat sealing is not required, the substrate layer is less likely to deform due to heat shrinkage, and the appearance of the packaging is less likely to be damaged. In addition, when the welding initiation temperature is 90°C or higher, the heat resistance is improved, and it is less likely to cause defects such as sticking to the conveyor rollers during processing.

[0068] It is known that the sealing strength of a sealing layer with propylene units as the main component reaches its temperature of saturation (SRT-S) depending on the melting point of the resin components constituting the sealing layer. Therefore, it is also possible to mix various resins with different melting points to adjust the melting point to any desired temperature.

[0069] For the sealing layer, when propylene units are used as the main component, the main raw material resin 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.

[0070] Furthermore, the aforementioned copolymers can be any of random copolymers, block copolymers, and graft copolymers. The copolymer composition is not limited, and examples include lower α-olefins such as ethylene, butene, hepten, hexene, and octene, as well as dienes such as butadiene and isoprene. In the case of copolymer polymers, it can be a binary system or a multi-component system with the aforementioned composition.

[0071] Furthermore, there are no restrictions on the regularity of the structure; it can be isoregular, anaregular, or orthoregular. The appropriate type should be selected to meet market requirements. The preferred density is 870–912 kg / m³. 3 Therefore, the preferred density is 880–905 kg / m³. 3 Density less than 870 kg / m³ 3 At this point, rigidity, heat resistance, and anti-adhesion properties decrease, therefore it is not preferred. Conversely, a density exceeding 912 kg / m³... 3 In such cases, the heat-sealing performance deteriorates at low temperatures, therefore it is not the preferred option.

[0072] In polypropylene-based films where propylene units are the main component and serve as the sealing layer, polyethylene-based resins can be blended in to impart low-temperature sealing properties. The polyethylene-based resin is a resin with ethylene as the main component; for example, ethylene homopolymers such as high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE) can be used. Alternatively, random or block copolymers with monomers such as propylene, butene-1, pentene-1, hexene-1, 3-methylbutene-1, 4-methylpentene-1, octene-1, vinyl acetate, (meth)acrylic acid, and (meth)acrylate can be used. From the viewpoint of single-material compatibility, a lower blending amount of polyethylene-based resin is preferable.

[0073] Polypropylene-based films with propylene units as the main component, used as sealing layers, are preferably laminated films. For example, the sealing layer is preferably a heat-sealing layer / substrate layer (base layer) or a heat-sealing layer / substrate layer (base layer) / surface layer structure. The substrate (base layer) of the sealing layer can improve the overall rigidity of the sealing layer by increasing its rigidity. By providing a surface layer for the sealing layer, the smoothness of the sealing layer and the adhesion to the biaxially stretched polypropylene film of the substrate layer can be improved.

[0074] The main raw material resin for the heat-sealing layer, used as the sealing layer, 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. Furthermore, the aforementioned copolymers can be any of random copolymers, block copolymers, and graft copolymers. The copolymer composition is not limited, and examples include lower α-olefins such as ethylene, butene, heptene, hexene, and octene, and dienes such as butadiene and isoprene. In the case of copolymers, it can be a binary system or a ternary system or higher with the same composition. Furthermore, there is no limitation on stereoregularity; it can be any of isotactic, syndiotactic, or atactic. Appropriate characteristics can be selected to meet market requirements. The density is preferably 870–912 kg / m³. 3 Therefore, the preferred density is 880–905 kg / m³. 3 Density less than 870 kg / m³ 3 At this point, rigidity, heat resistance, and anti-adhesion properties decrease, therefore it is not preferred. Conversely, a density exceeding 912 kg / m³... 3 In such cases, the heat-sealing performance deteriorates at low temperatures, therefore it is not the preferred option.

[0075] The propylene unit, which is the main component of the resin composition constituting the heat-sealing layer of the sealing layer, is preferably 60% or more by mass, more preferably 70% or more by mass, and even more preferably 80% or more by mass relative to the total resin composition.

[0076] The main raw material resin for the substrate layer (base layer) of the sealing layer can be listed as at least one polypropylene resin selected from the group consisting of homopolymers of propylene, random copolymers of propylene and ethylene, butene-1, pentene-1, hexene-1, 3-methylbutene-1, 4-methylpentene-1, octene-1, and other α-olefins, and block copolymers. When using copolymers, copolymers with a lower copolymer content compared to the heat-sealing layer are preferred to improve rigidity.

[0077] The propylene unit, which is the main component of the resin composition constituting the base layer (base layer) of the sealing layer, is preferably 60% or more by mass, more preferably 70% or more by mass, further preferably 80% or more by mass, even more preferably 90% or more by mass, and particularly preferably 95% or more by mass relative to the total resin composition.

[0078] As the main component of the surface layer of the sealing layer, at least one polypropylene resin selected from the group consisting of propylene homopolymers, random copolymers of propylene and ethylene, butene-1, pentene-1, hexene-1, 3-methylbutene-1, 4-methylpentene-1, octene-1, and other α-olefins, and block copolymers can be used. When using copolymers, copolymers with a lower copolymer content compared to the heat-sealing layer are preferred to improve rigidity. Furthermore, a lubricant can be blended in to improve smoothness. Moreover, to maintain high rigidity and ensure good lamination strength of the biaxially oriented polypropylene film of the substrate layer and the sealing layer laminate, polypropylene resins copolymerized with a small amount of α-olefins can be blended in.

[0079] The propylene unit, which is the main component of the resin composition constituting the surface layer of the sealing layer, is preferably 60% or more by mass, more preferably 70% or more by mass, further preferably 80% or more by mass, even more preferably 90% or more by mass, and particularly preferably 95% or more by mass relative to the total resin composition.

[0080] Polypropylene films, with propylene units as the main component, used as sealing layers can be laminated films by using multiple extruders to melt various raw material resins, co-extruding them in sheet form through a T-die, cooling and curing them with cooling rollers, and then winding them into rolls to obtain, for example, a non-stretched polypropylene film for sealing layers containing a heat-sealing layer / substrate layer (base layer) / surface layer. Alternatively, without compromising heat-sealing properties, the film can be stretched along its length using a roller stretching machine until it is wound into rolls.

[0081] (Relationship between the weld initiation temperature (FIT-B) of the substrate layer and the seal strength attainment temperature (SRT-S) of the seal layer)

[0082] The following relationship is preferably present between the welding initiation temperature (FIT-B) of the substrate layer and the sealing strength arrival temperature (SRT-S) of the sealing layer.

[0083] 50℃≤(FIT-B)-(SRT-S)≤90(℃) Formula (1)

[0084] (FIT-B) is greater than (SRT-S), and the difference is 50°C or more, preferably 60°C or more. If the difference between (FIT-B) and (SRT-S) is 50°C or more, then in the case of high-temperature and high-speed bag making, the heat sealing bar can be set to a higher temperature, which can make bags at a higher speed, without wrinkles or deformation in the heat sealing part, and sufficient heat seal strength can be obtained.

[0085] The temperature difference between (FIT-B) and (SRT-S) is below 90°C. A larger difference between (FIT-B) and (SRT-S) is more advantageous for high-temperature, high-speed bag manufacturing. If the melting point of the substrate layer is low, and the temperature difference between (FIT-B) and (SRT-S) is below 90°C, the welding temperature of the sealing layer is not easily reduced, potentially leading to poor adhesion. Furthermore, in this invention, the main components of the resins constituting the substrate layer and the sealing layer must be of the same type, thus limiting the range of resin types that can be selected.

[0086] [Resin laminates for packaging materials]

[0087] (Lamination method of substrate layer and sealing layer)

[0088] The resin laminate for packaging materials of the present invention comprises a substrate layer and a sealing layer with the same main components. The substrate layer and the sealing layer are obtained in the form of their respective films, and therefore can be laminated by means of an adhesive. Furthermore, the substrate layer and the sealing layer can be laminated even by co-extrusion.

[0089] The packaging material resin laminate of the present invention comprises a two-layer structure of a substrate layer / sealing layer or a three-layer structure of a laminate (third layer) / substrate layer / sealing layer, etc., as long as the main components of each layer are the same, and its total thickness is not particularly limited, preferably about 30 to 200 μm, more preferably about 25 to 150 μm.

[0090] (The sealing strength of the laminate reaches the temperature)

[0091] The upper limit of the sealing strength temperature of the resin laminate for packaging materials of the present invention in both the length and width directions is preferably 120°C, more preferably 118°C, further preferably 116°C, and most preferably 114°C. If it is below 120°C, the sealing temperature when making packaging bags from the resin laminate for packaging materials can be reduced, thus reducing shrinkage and wrinkling caused by heat and producing packaging with a good appearance. The lower limit of the sealing strength temperature in both the length and width directions is 900°C, more preferably 95°C.

[0092] (The heat-sealing strength of the laminate)

[0093] The lower limit of the length direction of the resin laminate for packaging materials of the present invention reaching heat-sealing strength is preferably 5 N / 15 mm, more preferably 8 N / 15 mm, further preferably 10 N / 15 mm, even more preferably 12 N / 15 mm, and particularly preferably 15 N / 15 mm. A value of 5 N / 15 mm or higher can reduce the likelihood of bag breakage in packaging bags made from the resin laminate for packaging materials. The upper limit of the length direction is not particularly limited, but a practical value is 30 N / 15 mm, preferably 25 N / 15 mm or less.

[0094] (High-temperature heat-sealing finish)

[0095] When evaluating the appearance of the sealed portion when heat-sealed at the temperature at which the sealing strength of the aforementioned laminate is reached, and the appearance of the sealed portion when heat-sealed at a temperature 10°C higher than the temperature at which the sealing strength is reached, based on the degree of peeling and wrinkling of the substrate film in the following three levels, it is preferable that no peeling or / and significant wrinkling of the entire substrate film occurs, more preferably that wrinkling occurs only in a part of the substrate film, and even more preferably that no peeling or wrinkling of the substrate film occurs.

[0096] (Heat sealing process)

[0097] In order to form bags for packaging food and the like using the resin laminate of the packaging material of the present invention, the packaging material of the present invention is used to form a bag with an opening, then the contents are filled, and the opening is heated to weld the sealing layer for sealing. Furthermore, this process is generally performed in the same way when filling the bag with food.

[0098] To manufacture bags, the following process is typically used: a sealing layer is laminated onto a substrate layer, and a heat-sealing process is performed to fuse the substrate layer and sealing layer together by heating from the substrate layer side. During heat sealing, pressure is applied to the film from the substrate layer side using a heated plate to seal it. Since the substrate layer is directly heated, if its heat resistance is low, wrinkles due to shrinkage and fusion of the substrate layer with the heat-sealing rod can occur. Fewer wrinkles are better for bag durability and to increase sales appeal. Furthermore, fusion can soil the outer surface of the bag, and in the case of printing, ink peeling can significantly impair the design.

[0099] Furthermore, the desire to increase bag-making speed is increasing, which requires heat-sealing at higher temperatures and thinning of the substrate layer. The process of welding the bag opening after filling the contents also requires heat-sealing at even higher temperatures. Preferably, even in this case, shrinkage is minimal and there is no welding of the substrate layer to the heat-sealing bar.

[0100] Example

[0101] The present invention will be described in detail below using examples. It should be noted that the characteristics were measured and evaluated using the following methods.

[0102] (1) Meso-five-unit component ratio

[0103] The determination of the meso-five-unit component ratio ([mmmm]%) of polypropylene resin was performed using... 13 The C-NMR was performed. The proportions of the racemic pentagonal components were calculated according to the method described in Zambelli et al., Macromolecules, Vol. 6, p. 925 (1973). 13 C-NMR determination was performed using an Avance 500 instrument manufactured by BRUKER. 200 mg of the sample was dissolved in an 8:2 mixture of o-dichlorobenzene and deuterated benzene at 135 °C, and the determination was carried out at 110 °C.

[0104] (2) Film thickness

[0105] The thickness of the thin film was measured using a Millitron 1202D meter manufactured by Seiko EM.

[0106] (3) Thermal shrinkage rate of the substrate layer

[0107] The following method was used to determine the thermal shrinkage rate of the substrate layer according to JIS Z 1712: The film was cut into sections with a width of 20 mm and a length of 200 mm in both the length and width directions, and then suspended in a hot air oven at 150°C for 5 minutes. The length after heating was measured, and the thermal shrinkage rate of the substrate layer was calculated as the ratio of the shrunken length to the original length.

[0108] (4) Young's modulus of the substrate layer

[0109] The Young's modulus of the film in both the longitudinal and transverse directions was determined according to JIS K 7127 at 23°C. Samples were cut from the film at dimensions of 15 mm × 200 mm and mounted on a tensile testing machine (Instron 5965, a dual-column benchtop testing machine manufactured by Instron Japan Company, Limited) with a chuck width of 100 mm. Tensile tests were conducted at a tensile speed of 200 mm / min. The Young's modulus of the substrate layer was determined from the slope of the linear portion in the initial stage of elongation using the obtained deformation-stress curve.

[0110] (5) Welding initiation temperature of the substrate layer (FIT-B)

[0111] Two 300mm × 100mm long polyethylene terephthalate films (manufacturer: Toyobo Co., Ltd., trademark: E5100, thickness: 12μm) used in the examples and comparative examples were sandwiched between two corona-treated surfaces, with the surfaces facing each other. The samples were heat-sealed at 0.2MPa × 1 second using a hot tilting roller (manufactured by Toyo Seiki Co., Ltd.), and a 15mm wide sample was cut out. The T-peel seal strength (N / 15mm) in the length direction was measured using a tensile testing machine (Shimadzu Autograph universal testing machine, model: S-100-D) at a speed of 200mm / min.

[0112] For the welding initiation temperature of the substrate layer, plot a graph with the horizontal axis set as the sealing temperature and the vertical axis set as the sealing strength. The temperature at which the sealing strength reaches 1N / 15mm is set as the welding initiation temperature (FIT-B) (°C) of the substrate layer.

[0113] (6) The sealing strength of the sealing layer reaches the temperature (SRT-S).

[0114] Two 300mm × 100mm long polyethylene terephthalate films (manufacturer: Toyobo Co., Ltd., trademark: E5100, thickness: 12μm) used in the examples and comparative examples were sandwiched between each other in a 300mm × 60mm long direction sealing layer (sealing surface when the sealing layer is multi-layered). The layers were heat-sealed at 0.2MPa × 1 second using a hot tilting roller (manufactured by Toyo Seiki Co., Ltd.). A 15mm wide sample was cut out, and the T-peel seal strength (N / 15mm) in the length direction was evaluated using a tensile testing machine (Shimadzu Autograph universal testing machine, model: S-100-D) at a speed of 200mm / min. A graph was plotted with the sealing strength reaching temperature (SRT-S) of the sealing layer, with the horizontal axis representing the sealing temperature and the vertical axis representing the sealing strength. The temperature at which the sealing strength reaches 5N / 15mm was defined as the sealing strength reaching temperature (SRT-S) (°C).

[0115] (7) The sealing strength of the laminate reaches the temperature

[0116] The laminate of the substrate layer and the sealing layer was fabricated using a continuous dry laminator as follows. First, the corona-treated surface of the biaxially oriented polypropylene film obtained in the examples and comparative examples was coated with an amount of 3.0 g / m² when dry. 2After the adhesive is applied using a gravure printing method, it is guided to a drying area and dried at 80°C for 5 seconds. Next, the sealing layer is bonded to the adhesive-coated surface between rollers located on the downstream side (roller pressure 0.2 MPa, roller temperature: 60°C). The resulting laminate is then cured at 40°C for 3 days while in a wound state.

[0117] It should be noted that the adhesive used is a dry lamination adhesive obtained by mixing 28.9% by mass of the main agent (Toyo-Morton, Ltd., TM569), 4.00% by mass of the curing agent (Toyo-Morton, Ltd., CAT10L) and 67.1% by mass of ethyl acetate.

[0118] Next, a measurement sample with a width of 15mm and a length of 200mm was cut from the prepared laminate. The sealing layers of the two laminate samples were then heat-sealed together at 0.2MPa for 1 second using a hot tilting roller (manufactured by Toyo Seiki Co., Ltd.).

[0119] The test samples, cut to a width of 15 mm, were heat-sealed at 90°C in 5°C intervals and mounted on a tensile testing machine (manufactured by TENSILON or ORIENTEC CO.,LTD.) with an initial chuck spacing of 100 mm. The T-peel strength in the length direction was measured at a tensile speed of 200 mm / min. A graph was plotted with the horizontal axis representing the heat-sealing temperature and the vertical axis representing the sealing strength. The temperature at which the sealing strength reaches 5 N / 15 mm was set as the sealing strength attainment temperature (°C) of the laminate.

[0120] (8) The heat seal strength of the laminate

[0121] In the graph obtained in (7), with the horizontal axis set as heat sealing temperature and the vertical axis set as sealing strength, the value of the maximum strength will be set as the heat sealing strength reached by the laminate.

[0122] (9) High-temperature heat-sealing finish

[0123] The appearance of the sealed portion when heat-sealed at the temperature at which the sealing strength of the aforementioned laminate is reached, and the appearance of the sealed portion when heat-sealed at a temperature 10°C higher than the temperature at which the sealing strength is reached, are evaluated by the degree of peeling and wrinkling of the substrate layer using the following three levels.

[0124] ○: No peeling or wrinkling of the substrate layer film occurred.

[0125] △: A portion of the substrate layer film is wrinkled.

[0126] ×: This indicates peeling and / or significant wrinkling of the entire substrate layer film.

[0127] (Example 1)

[0128] A packaging resin laminate is prepared by laminating a biaxially stretched polypropylene film as the substrate layer and a non-stretched polypropylene film as the sealing layer using the aforementioned method. The biaxially stretched polypropylene film of the substrate layer has a weld initiation temperature (FIT-B) of 166°C, a heat shrinkage rate of 4.5% in the length direction and 0.8% in the width direction at 150°C, and a Young's modulus of 2.2 GPa in the length direction and 3.6 GPa in the width direction. The non-stretched polypropylene film of the sealing layer has a seal strength reach temperature (SRT-S) of 111°C, which is 55°C different from the weld initiation temperature (FIT-B) of the substrate layer.

[0129] For the heat-sealing finish of laminated resin laminates for packaging, there is no peeling or wrinkling, and the results are good.

[0130] Substrate layer: As polypropylene resin, 80 parts by weight of propylene homopolymer PP-1 with MFR=7.5g / 10min, [mmmm]=98.9%, Tc=116℃, Tm=163℃ and 20 parts by weight of propylene homopolymer PP-2 with MFR=3.0g / 10min, [mmmm]=98.4%, Tc=116℃, Tm=163℃ are mixed to form a polypropylene resin composition. The composition is heated and melted at 250℃ using an extruder. The molten polypropylene resin composition is extruded in sheet form through a T-die at 250℃, and the molten sheet is brought into contact with a cooling roller at 37℃ and directly immersed in a water bath at 29℃ to obtain an unstretched sheet. Then, the unstretched sheet is stretched 4.0 times in length at 140°C using two pairs of rollers. The two ends are then clamped and guided into a hot air oven (stenter). After preheating at 174°C, it is stretched 10 times in width at 160°C. Then, it is heat-treated while being relaxed by 7% in width at 174°C.

[0131] The single-sided surface of the obtained biaxially oriented polypropylene film was treated with a corona treatment machine manufactured by Kasuga Electric Co., Ltd. at 13W / m. 2 After corona treatment for 1 minute, the film is wound up using a winding machine to obtain a 16μm thick biaxially oriented polypropylene film for use.

[0132] Sealing layer: Using three extruders, the film is melted at 240°C and co-extruded in sheet form through a T-die. After being cooled and solidified by a cooling roller at 30°C, it is wound in rolls at a speed of 150 m / min to obtain a non-stretched polypropylene film for sealing layer with a thickness ratio of 1 / 2 / 1 for the base layer (base layer) / surface layer containing heat-sealing layer / sealing layer and a thickness of 30 μm.

[0133] It should be noted that, as the heat-sealing layer raw material, a resin composition is prepared by mixing 55% by mass of propylene-ethylene-butene random copolymer (FL6745 manufactured by Sumitomo Chemical Co., Ltd., melting point 130°C, MFR: 7g / 10min) and 45% by mass of linear low-density polyethylene resin (Evolue SP2040 manufactured by Prime Polymer Co., Ltd., melting point 112°C, melt flow rate 3.8g / 10min). As the surface layer raw material on the opposite side of the substrate layer (base layer) and the heat-sealing layer, a propylene-ethylene-butene random copolymer (melting point 148°C, MFR 7.0g / 10min) is used.

[0134] The propylene unit component of the sealing layer is more than 70% by mass.

[0135] (Example 2)

[0136] Similar to Example 1, a biaxially stretched polypropylene film as the substrate layer and a non-stretched polypropylene film as the sealing layer were laminated using the aforementioned method to produce a resin laminate for packaging. The biaxially stretched polypropylene film of the substrate layer has a thickness of 16 μm, a weld initiation temperature (FIT-B) of 165°C, a heat shrinkage rate of 4.7% in the length direction and 2.0% in the width direction at 150°C, and a Young's modulus of 2.3 GPa in the length direction and 4.0 GPa in the width direction. The non-stretched polypropylene film of the sealing layer has a seal strength reach temperature (SRT-S) of 111°C, which is 54°C different from the weld initiation temperature (FIT-B) of the substrate layer.

[0137] For the heat-sealing finish of laminated resin laminates for packaging, there is no peeling or wrinkling, and the results are good.

[0138] Substrate layer: The relaxation rate was changed to 6.0% during heat treatment, and otherwise the same procedure was performed as in Example 1 to obtain a biaxially oriented polypropylene film with a thickness of 16 μm for use.

[0139] Sealing layer: Use a 30 μm unstretched polypropylene film with the same thickness as in Example 1.

[0140] (Example 3)

[0141] Similar to Example 1, a biaxially stretched polypropylene film as the substrate layer and a non-stretched polypropylene film as the sealing layer were laminated using the aforementioned method to produce a resin laminate for packaging. The biaxially stretched polypropylene film of the substrate layer has a thickness of 16 μm, a weld initiation temperature (FIT-B) of 164°C, a heat shrinkage rate of 5.0% in the length direction and 4.7% in the width direction at 150°C, and a Young's modulus of 2.0 GPa in the length direction and 4.2 GPa in the width direction. The non-stretched polypropylene film of the sealing layer has a seal strength reach temperature (SRT-S) of 111°C, which is 53°C different from the weld initiation temperature (FIT-B) of the substrate layer.

[0142] For the heat-sealing finish of laminated resin laminates for packaging, there is no peeling or wrinkling, and the results are good.

[0143] Substrate layer: The heat treatment temperature was changed to 172°C, and otherwise the same procedure was performed as in Example 2 to obtain a biaxially oriented polypropylene film with a thickness of 16 μm.

[0144] Sealing layer: Use a 30 μm unstretched polypropylene film with the same thickness as in Example 1.

[0145] (Example 4)

[0146] Similar to Example 1, a biaxially stretched polypropylene film as the substrate layer and a non-stretched polypropylene film as the sealing layer were laminated using the aforementioned method to produce a resin laminate for packaging. The biaxially stretched polypropylene film of the substrate layer has a thickness of 16 μm, a weld initiation temperature (FIT-B) of 161°C, a heat shrinkage rate of 6.1% in the length direction and 5.5% in the width direction at 150°C, and a Young's modulus of 2.2 GPa in the length direction and 4.3 GPa in the width direction. The non-stretched polypropylene film of the sealing layer has a seal strength reach temperature (SRT-S) of 111°C, which is 50°C different from the weld initiation temperature (FIT-B) of the substrate layer.

[0147] For the heat-sealing finish of the laminated resin laminate for packaging, there is no peeling or wrinkling at the temperature where the sealing strength is reached, which is good. However, at a sealing temperature 10°C higher than the temperature where the sealing strength is reached, wrinkles occur in a portion of the film.

[0148] Substrate layer: The stretch ratio in the length direction was changed to 4.5 times and the heat treatment temperature was changed to 170°C. Otherwise, it was carried out in the same way as in Example 1 to obtain a biaxially oriented polypropylene film with a thickness of 16 μm for use.

[0149] Sealing layer: Use a 30 μm unstretched polypropylene film with the same thickness as in Example 1.

[0150] (Comparative Example 1)

[0151] Similar to Example 1, a biaxially stretched polypropylene film as the substrate layer and a non-stretched polypropylene film as the sealing layer were laminated using the aforementioned method to produce a resin laminate for packaging. The biaxially stretched polypropylene film of the substrate layer has a thickness of 16 μm, a weld initiation temperature (FIT-B) of 152°C, a heat shrinkage rate of 15.5% in the length direction and 22.7% in the width direction at 150°C, and a Young's modulus of 1.8 GPa in the length direction and 2.9 GPa in the width direction. The non-stretched polypropylene film of the sealing layer has a seal strength reach temperature (SRT-S) of 111°C, which is 41°C different from the weld initiation temperature (FIT-B) of the substrate layer.

[0152] For heat-sealing finishing of laminated resin laminates for packaging, significant peeling and wrinkling of the substrate layer surface are observed, resulting in defects.

[0153] Substrate layer: As polypropylene resin, a propylene homopolymer with MFR = 2.5 g / 10 min, [mmmm] = 96.5%, Tc = 116 °C, and Tm = 163 °C is melted at 250 °C using an extruder. The molten polypropylene resin composition is extruded in sheet form through a T-die at 250 °C, and the molten sheet is brought into contact with a cooling roller at 37 °C and directly immersed in a water bath at 29 °C to obtain an unstretched sheet. Then, the unstretched sheet is stretched 4.5 times in length direction at 140 °C using two pairs of rollers. The two ends are then clamped and guided into a hot air oven (stenter). After preheating at 174 °C, it is stretched 10 times in width direction at 160 °C. Then, it is heat-treated while relaxing by 6.7% in width direction at 165 °C.

[0154] The single-sided surface of the obtained biaxially oriented polypropylene film was treated with a corona treatment machine manufactured by Kasuga Electric Co., Ltd. at 13W / m. 2 After corona treatment for 1 minute, the film is wound up using a winding machine to obtain a 16μm thick biaxially oriented polypropylene film for use.

[0155] Sealing layer: Use a 30 μm unstretched polypropylene film with the same thickness as in Example 1.

[0156] (Comparative Example 2)

[0157] As the substrate layer, a biaxially stretched polypropylene film as described below is used; as the sealing layer, a non-stretched polypropylene film as described below is used. Otherwise, a resin laminate for packaging is fabricated using the same method as in Example 1. The biaxially stretched polypropylene film of the substrate layer has a thickness of 16 μm, a weld initiation temperature (FIT-B) of 165°C, a heat shrinkage rate of 4.7% in the length direction and 2.0% in the width direction at 150°C, and a Young's modulus of 2.3 GPa in the length direction and 4.0 GPa in the width direction.

[0158] The sealing strength reach temperature (SRT-S) of the unstretched polypropylene film of the sealing layer is 143°C, which is 22°C different from the weld initiation temperature (FIT-B) of the substrate layer.

[0159] For heat-sealing finishing of laminated resin laminates for packaging, significant peeling and wrinkling of the substrate layer surface are observed, resulting in defects.

[0160] Substrate layer: Biaxially stretched polypropylene film prepared in Example 2.

[0161] Sealing layer: Uses unstretched polypropylene film manufactured by Toyobo Co., Ltd. (PYLEN (registered trademark) CT P1128, thickness 30μm, sealing strength reach temperature (SRT-S) = 143℃).

[0162] It should be noted that the propylene unit content of the sealing layer is more than 70% by mass.

[0163] (Comparative Example 3)

[0164] As the substrate layer, a biaxially stretched polypropylene film as described below is used; as the sealing layer, a non-stretched polypropylene film as described below is used. Otherwise, a resin laminate for packaging is fabricated using the same method as in Example 1. The biaxially stretched polypropylene film of the substrate layer has a thickness of 16 μm, a weld initiation temperature (FIT-B) of 165°C, a heat shrinkage rate of 4.7% in the length direction and 2.0% in the width direction at 150°C, and a Young's modulus of 2.3 GPa in the length direction and 4.0 GPa in the width direction. The non-stretched polypropylene film of the sealing layer has a seal strength reach temperature (SRT-S) of 125°C, which is 40°C different from the weld initiation temperature (FIT-B) of the substrate layer.

[0165] For heat-sealing finish of laminated resin laminates for packaging, no peeling or wrinkling occurs at the temperature where the sealing strength is achieved, which is good. However, at a sealing temperature 10°C higher than the temperature where the sealing strength is achieved, peeling and wrinkling of the substrate layer surface also occur significantly, which is poor.

[0166] Substrate layer: Biaxially stretched polypropylene film prepared in Example 2.

[0167] Sealing layer: Uses unstretched polypropylene film manufactured by Toyobo Co., Ltd. (PYLEN (registered trademark) CT P1162, thickness 30μm, sealing strength reaching temperature (SRT-S) = 125℃).

[0168] It should be noted that the propylene unit content of the sealing layer is more than 70% by mass.

[0169] (Refer to Example 1)

[0170] Similar to Example 1, a packaging resin laminate was prepared by laminating the following biaxially stretched polyethylene terephthalate film as the substrate layer and the following unstretched polypropylene film as the sealing layer using the aforementioned method. The biaxially stretched polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., E5100, 12 μm thickness) as the substrate layer has a weld initiation temperature (FIT-B) higher than 200°C, a heat shrinkage rate of 1.4% in the length direction and 0.2% in the width direction at 150°C, and a Young's modulus of 3.9 GPa in the length direction and 4.0 GPa in the width direction. The sealing strength reach temperature (SRT-S) of the unstretched polypropylene film as the sealing layer is 111°C, and the difference between it and the weld initiation temperature (FIT-B) of the substrate layer is greater than 89°C.

[0171] The laminated resin laminate for packaging reaches a heat-sealing temperature of 160℃ and a heat-sealing strength of 5.0 N / 15 mm. Regarding heat-sealing finish, there is no peeling or wrinkling on the substrate layer surface, indicating good performance.

[0172] Substrate layer: Biaxially stretched polyethylene terephthalate film (TOYOBOESTER Film (registered trademark) E5100, 12μm thick) manufactured by Toyobo Co., Ltd.

[0173] Sealing layer: Use a 30 μm unstretched polypropylene film with the same thickness as in Example 1.

[0174] [Table 1]

[0175]

[0176] Industrial availability

[0177] The resin laminate for packaging materials of the present invention can be suitably used as a single-material packaging material that can be heat-sealed at high temperature and high speed, similar to a resin laminate for packaging materials that uses polyester (PET) film as the base layer and polyolefin film as the sealing layer.

Claims

1. A resin laminate for packaging materials, comprising at least a substrate layer and a sealing layer, wherein the main components of the resin compositions constituting the substrate layer and the sealing layer are composed of the same resin composition, and the welding initiation temperature FIT-B of the substrate layer and the sealing strength reaching temperature SRT-S of the sealing layer satisfy the following formulas (1) to (3). 50℃≤(FIT-B)-(SRT-S)≤90℃ Formula (1) 90℃≤(SRT-S)≤120℃ Equation (2) 160℃≤(FIT-B)≤180℃ Equation (3), wherein Two 300mm × 60mm substrate layers are sandwiched between two 12μm thick polyethylene terephthalate films of 300mm × 100mm, with the sealing layer surfaces facing each other. The films are heat-sealed using a hot tilting roller at 0.2MPa × 1 second. A 15mm wide sample is cut out, and the T-peel seal strength in the length direction (in N / 15mm) is measured using a tensile testing machine at a speed of 200mm / min. A graph is plotted with the horizontal axis set as the sealing temperature and the vertical axis as the sealing strength. The temperature at which the sealing strength reaches 1N / 15mm is set as the welding initiation temperature FIT-B of the substrate layer. Two 300mm × 60mm sealing layers are sandwiched between two 12μm thick polyethylene terephthalate films of 300mm × 100mm, with the sealing surfaces facing each other. When the sealing layers are multi-layered, they are sandwiched with the sealing surfaces facing each other. Heat sealing is performed using a hot tilting roller at 0.2MPa × 1 second. A 15mm wide sample is cut out, and the T-peel seal strength in the length direction in N / 15mm is evaluated using a tensile testing machine at a speed of 200mm / min. A graph is plotted with the horizontal axis set as the sealing temperature and the vertical axis as the sealing strength. The temperature at which the sealing strength reaches 5N / 15mm is set as the sealing strength reaching temperature SRT-S of the sealing layer.

2. The resin laminate for packaging materials according to claim 1, wherein The resin constituting the substrate layer and the sealing layer is mainly composed of propylene units, and the substrate layer is a biaxially stretched polypropylene film.

3. The resin laminate for packaging materials according to claim 2, wherein The thermal shrinkage rate of the biaxially stretched polypropylene film of the substrate layer at 150°C is less than 6.5% in the length direction and less than 5.5% in the width direction.

4. The resin laminate for packaging materials according to claim 2, wherein The Young's modulus of the biaxially stretched polypropylene film of the substrate layer is greater than 2.0 GPa in the length direction and greater than 3.5 GPa in the width direction.

5. The resin laminate for packaging materials according to any one of claims 1 to 4, wherein an adhesive layer is provided between the substrate layer and the sealing layer.

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