Laminated sealant film

Abstract

Provided is a laminated sealant film that is comprehensively and satisfactorily exceptional in terms of bag formation properties at low temperatures and all of rupture strength, heat resistance, stand-alone properties, and transparency after bag formation, the laminated sealant film satisfying all of the following conditions 1) to 9). 1) The laminated sealant film includes at least a laminate layer and a sealing layer. 2) The laminate layer comprises a resin composition having, as the main component, a polypropylene resin. 3) The sealing layer comprises a resin composition having, as the main component, a mixture of a polypropylene resin and a polyethylene resin. 4) With respect to 100 wt% of the mixture of the polypropylene resin and the polyethylene resin constituting the sealing layer, the polypropylene resin is contained in an amount of 1-95 wt% inclusive, and the polyethylene resin is contained in an amount of 5-99 wt% inclusive. 5) The polyethylene resin constituting the sealing layer contains 90 wt% or more of a straight-chain low-density polyethylene resin. 6) There is a difference of 15°C or more between the respective melting points of the straight-chain low-density polyethylene resin and the polypropylene resin of the sealing layer. 7) The ratio of the melt flow rate of the polypropylene resin to the melt flow rate of the straight-chain low-density polyethylene resin of the sealing layer is 0.8-2.0 inclusive. 8) The melt flow rates of the straight-chain low-density polyethylene resin and the polypropylene resin of the sealing layer are 9 g / 10 minutes or lower. 9) The longitudinal-direction tensile elastic modulus is 500 MPa or lower.

Description

Laminated Sealant Film

[0001] The present invention relates to a laminated sealant film having excellent bag-forming properties, low-temperature bag-forming properties, and excellent seal strength.

[0002] Packaging materials have been developed to suit the contents of many products, such as foods, beverages, pharmaceuticals, and chemicals. Packaging materials are used in various forms, such as pillow packaging, gusset packaging, and three-sided seal packaging, and the sealant films used in packaging materials also have the required functions depending on the application.

[0003] Sealant films are particularly suited to automatic bag-making processes for pillowcase packaging bags, gusset packaging bags, and three-sided sealed packaging bags while packaging the contents. The lower the temperature at which heat sealing can be performed, the lower the electricity bill and the greater the workability, as there is less risk of burns. Furthermore, heat sealing at low temperatures increases packaging and bag-making speed, reduces packaging material waste, and produces cleaner finished packaging bags. However, sealant films are also required to perform packaging and bag-making processes smoothly, and to provide various functions, such as sealing the resulting packaging bags with good sealing strength.

[0004] For example, when heavy contents are packaged in vertical pillowcases automatically, it is required that the seal strength be sufficient even immediately after heat sealing when the resin of the sealant film is in a molten state, and that the seal portion will not peel off even when subjected to the impact of pressure generated when the heavy contents are filled into the bag.

[0005] Furthermore, when the contents are automatically packaged in horizontal pillow packaging, it is required that the seal strength be sufficient even when the resin of the sealant film is in a molten state, and that the seal portion not peel off due to high-pressure gas (nitrogen flush) when filling the bag. None of the conventional sealant films comprehensively satisfied all of the following requirements: bag formability at low temperatures, burst strength after bag formation, heat resistance, self-supporting ability, and transparency (see, for example, Patent Documents 1 to 4).

[0006] JP 2000-272064 A JP 2000-272065 A JP 2002-241716 A JP 2020-192695 A

[0007] An object of the present invention is to provide a sealant film containing a propylene-based resin and a polyethylene-based resin, which has excellent low-temperature bag-forming properties and burst strength.

[0008] As a result of extensive research conducted to achieve this object, the present invention has succeeded in obtaining an excellent laminate sealant film that comprehensively satisfies all of the following requirements: bag formability at low temperatures, burst strength after bag formation, and the contradictory properties of heat resistance, self-supporting ability, and transparency, by controlling the raw material composition of each layer of the laminate sealant film and the elastic modulus of the entire film. That is, the laminate sealant film of the present invention has the following configuration.

[0009] [1] A laminated sealant film that satisfies all of the following requirements 1) to 9). 1) It includes at least a laminate layer and a seal layer. 2) The laminate layer is made of a resin composition primarily composed of a polypropylene-based resin. 3) The seal layer is made of a resin composition primarily composed of a mixture of a polypropylene-based resin and a polyethylene-based resin. 4) The seal layer contains 1% by weight or more and 95% by weight or less of a polypropylene-based resin and 5% by weight or more and 99% by weight or less of a polyethylene-based resin, relative to 100% by weight of the mixture of a polypropylene-based resin and a polyethylene-based resin. 5) The polyethylene-based resin that constitutes the seal layer contains 90% by weight or more of a linear low-density polyethylene resin. 6) The difference in melting point between the polypropylene-based resin and the linear low-density polyethylene resin in the seal layer is 15°C or more. 7) The ratio of the melt flow rate of the polypropylene-based resin to the melt flow rate of the linear low-density polyethylene resin in the seal layer is 0.8 or more and 2.0 or less. 8) The melt flow rates of the polypropylene-based resin and linear low-density polyethylene resin in the seal layer are 9 g / 10 min (load 2.16 kg) or less. 9) The tensile modulus in the longitudinal direction is 500 MPa or less. [2] The laminate sealant film according to [1] above, wherein the polypropylene-based resin in the laminate sealant seal layer is a propylene random copolymer. [3] The laminate sealant film according to [1] or [2], wherein the tensile modulus in the width direction of the laminate sealant film is 550 MPa or less. [4] The laminate sealant film according to any of [1] to [3], wherein the main peak of the melting point of the laminate sealant film is 120°C or higher. [5] The laminate sealant film according to any of [1] to [4], wherein the static friction coefficient between the seal layer surfaces of the laminate sealant film is 1.0 or less. [6] The laminate sealant film according to any of [1] to [5], wherein the kinetic friction coefficient between the seal layer surfaces of the laminate sealant film is 1.0 or less. [7] The laminate sealant film according to any one of [1] to [6], wherein the seal layer of the laminate sealant film contains silica particles. [8] The laminate sealant film according to any one of [1] to [7], wherein the seal layer of the laminate sealant film contains erucic acid amide.[9] The laminate sealant film according to any one of [1] to [8], wherein the sealing layer of the laminate sealant film contains organic particles.

[0010] The laminated sealant film of the present invention has excellent low-temperature bag-forming properties and is therefore suitable as a packaging material for many products, such as foods, beverages, pharmaceuticals, and chemicals. It is particularly suitable for automatic bag-forming processing into pillow packaging bags, gusset packaging bags, three-side seal packaging bags, etc. while packaging the contents.

[0011] The present invention will be described below. The laminated sealant film of the present invention includes at least a laminate layer and a sealing layer. The laminate layer and the sealing layer will be described in detail below.

[0012] (Sealing layer) The sealing layer in the present invention is made of a resin composition mainly composed of a mixture of polypropylene resin and polyethylene resin. Here, "main component" means that the mixture of polypropylene resin and polyethylene resin accounts for 90% by mass or more of the resin composition, more preferably 95% by weight or more, even more preferably 97% by weight or more, and even more preferably 99% by weight or more.

[0013] (Polypropylene-based resin) The polypropylene-based resin in the seal layer is a resin containing propylene as the main component, and examples thereof include propylene homopolymers, random copolymers and block copolymers of propylene with α-olefins such as ethylene, butene-1, pentene-1, hexene-1, 3-methylbutene-1, 4-methylpentene-1, and octene-1. The term "main component" means that propylene accounts for 90% by mass or more of the polypropylene resin, more preferably 95% by weight or more, even more preferably 97% by weight or more, and even more preferably 99% by weight or more. Polypropylene-based resins have a higher melting point and superior transparency than polyethylene-based resins.

[0014] The polypropylene resin constituting the sealing layer preferably has a melt flow rate of 0.1 g / 10 min or more and 9 g / 10 min or less, more preferably 0.5 g / 10 min or more and 8 g / 10 min or less, and even more preferably 1 g / 10 min or more and 7 g / 10 min or less. The polypropylene resin constituting the sealing layer preferably has a melting point of 120 ° C or more, more preferably 125 ° C or more and 150 ° C or less, and even more preferably 130 ° C or more and 140 ° C or less. When the melting point of the polypropylene resin constituting the sealing layer is 120 ° C or more, it has excellent heat resistance such as retort resistance and self-supporting properties.

[0015] The polypropylene resin content is preferably 1% by weight or more and 95% by weight or less, and more preferably 5% by weight or more and 90% by weight or less, relative to 100% by weight of the mixture of polypropylene resin and polyethylene resin constituting the seal layer. When the polypropylene resin content is 1% by weight or more, the slipperiness is excellent and the ultimate heat seal strength is less likely to vary.

[0016] (Polyethylene Resin) The polyethylene resin in the seal layer is primarily composed of linear low-density polyethylene. In addition to linear low-density polyethylene, at least one ethylene homopolymer selected from the group consisting of high-pressure low-density polyethylene, medium-density polyethylene, and high-density polyethylene can be used. Furthermore, random or block copolymers containing ethylene as the main component and copolymerized with other monomers such as α-olefins (e.g., propylene, butene-1, pentene-1, hexene-1, 3-methylbutene-1, 4-methylpentene-1, and octene-1), vinyl acetate, (meth)acrylic acid, and (meth)acrylic acid esters, or mixtures thereof, can also be used. These may be crystalline, low-crystalline, or amorphous.

[0017] The polyethylene resin constituting the seal layer has a melt flow rate of 0.1 g / 10 min or more and 9 g / 10 min or less, preferably 0.5 g / 10 min or more and 8 g / 10 min or less, more preferably 1 g / 10 min or more and 7 g / 10 min or more. The polyethylene resin constituting the seal layer has a melting point of 100°C or more and 140°C or less, preferably 10°C or more and 135°C or less, more preferably 110°C or more and 130°C or less. The melting point of the polyethylene resin may show two or more melting endothermic peaks, and the peak with the highest melting temperature was defined as the main peak.

[0018] The polyethylene resin constituting the sealing layer preferably contains 90% by weight or more of straight-chain linear polyethylene resin, more preferably 95% by weight or more, even more preferably 97% by weight or more, and even more preferably 99% by weight or more.

[0019] The seal layer preferably contains 1% to 95% by weight of polypropylene resin and 5% to 99% by weight of polyethylene resin, with 20 to 90% being more preferred, based on 100% by weight of the mixture of polypropylene resin and polyethylene resin. If the polypropylene resin content is less than 1% by weight, delamination with the laminate layer is likely to occur, resulting in variations in burst strength and seal strength. If an intermediate layer is present between the laminate layer and the seal layer, delamination with the intermediate layer is likely to occur, resulting in variations in burst strength and seal strength. The difference in melting point between the polypropylene resin and polyethylene resin constituting the seal layer is preferably 15°C or more, more preferably 16°C or more, even more preferably 17°C or more, even more preferably 18°C ​​or more, and particularly preferably 19°C or more. When the difference in melting point between the polypropylene-based resin and the polyethylene-based resin is 15°C or more, low-temperature bag-forming properties are improved, and the polypropylene-based resin and the polyethylene-based resin are well mixed, reducing variations in burst strength and seal strength. The difference in melting point between the polypropylene-based resin and the polyethylene-based resin constituting the seal layer is preferably 50°C or less, with the upper limit of the melting point difference being preferably 50°C or less, more preferably 40°C or less, even more preferably 30°C or less, and most preferably 25°C or less. When the difference in melting point between the polypropylene-based resin and the polyethylene-based resin constituting the seal layer is 50°C or less, phase separation and peeling are less likely to occur within the seal layer, reducing variations in burst strength and seal strength. Furthermore, the arithmetic mean melting point of the polypropylene-based resin and the polyethylene-based resin constituting the seal layer is preferably 100°C or more, more preferably 112°C or more, even more preferably 116°C or more, even more preferably 116°C or more, and particularly preferably 121°C or more. When the arithmetic mean melting point of the polypropylene resin and the polyethylene resin is 100°C or higher, the heat resistance of the packaging material obtained by processing the laminated sealant film is improved. For example, when it is 100°C or higher, the boiling suitability is improved, when it is 105°C or higher, the semi-retort suitability is improved, when it is 116°C or higher, the retort suitability is improved, and when it is 121°C or higher, the high-retort suitability is improved.

[0020] (Anti-blocking agent) The resin composition of the sealing layer preferably contains an anti-blocking agent, and examples thereof include particles made of silica such as synthetic silica, inorganic particles such as diatomaceous earth, talc, and mica, and organic particles such as silicone particles, acrylic particles, nylon particles, and polyethylene particles. It is more preferable to contain silica particles or polyethylene particles. In particular, it is preferable to contain silica particles and polyethylene particles. The average particle size of the particles used in the present invention is preferably 2 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. Furthermore, the average particle size is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less.

[0021] The content of particles in the resin composition in the sealing layer is preferably 0.1 wt% or more, more preferably 0.3 wt% or more, and even more preferably 0.4 wt% or more, relative to the sealing layer of the film. Also, it is preferably 2 wt% or less, more preferably 1.5 wt% or less, and even more preferably 1.0 wt% or less. If the amount of particles added is less than 0.1 wt%, it becomes difficult to achieve a surface roughness Ra of 0.1 μm or more on at least one surface layer, making it difficult to obtain anti-blocking properties and slip properties. Furthermore, if the amount of particles added is more than 2 wt%, the number of surface protrusions increases, resulting in poor appearance and poor abrasion resistance.

[0022] (Organic Lubricant) The resin composition in the sealing layer preferably contains 0.01 wt% or more and 2.0 wt% or less of a fatty acid amide as an organic lubricant, more preferably 0.05 wt% or more and 1.5 wt% or less, and particularly preferably 0.1 wt% or more and 1.0 wt% or less. When the fatty acid amide is 0.01% or more, blocking between films is reduced, making it easier to handle the film. When the fatty acid amide is 2.0% or less by weight, the seal strength is less likely to decrease. Examples of fatty acid amides include erucic acid amide, ethylene bisoleic acid amide, and behenic acid amide, and these may be used in combination. In particular, erucic acid amide has a low melting point, is easy to bleed, and is easy to impart lubricity. The sealing layer more preferably contains silica particles as an antiblocking agent and erucic acid amide as an organic lubricant. The sealing layer more preferably contains polyethylene particles as an antiblocking agent and erucic acid amide as an organic lubricant. More preferably, the sealing layer contains silica particles and polyethylene particles as an antiblocking agent in combination with erucic acid amide as an organic lubricant.

[0023] The closer the ratio of the melt flow rate of the polypropylene-based resin to the melt flow rate of the linear low-density polyethylene resin in the seal layer is, the better the appearance will be. The ratio of the melt flow rate of the polypropylene-based resin to the melt flow rate of the linear low-density polyethylene resin in the seal layer is 0.8 or more, preferably 0.9 or more, more preferably 1.0 or more, even more preferably 1.1 or more, even more preferably 1.2 or more, and particularly preferably 1.4 or more. The ratio of the melt flow rate of the polypropylene-based resin to the melt flow rate of the linear low-density polyethylene resin in the seal layer is 2.0 or less, preferably 1.8 or less, more preferably 1.7 or less, and particularly preferably 1.6 or less. When the ratio of the melt flow rate of the polypropylene-based resin to the melt flow rate of the linear low-density polyethylene resin in the seal layer is 0.8 or more and 2.0 or less, the laminate sealant film is less likely to have poor appearance, such as misalignment of the layers, blemishes, or unevenness.

[0024] (Laminate Layer) The laminate layer in the present invention is made of a resin composition mainly composed of a polypropylene resin. Here, "main component" means that the proportion of the polypropylene resin in the resin composition is 90% by mass or more, more preferably 95% by weight or more, even more preferably 97% by weight or more, and even more preferably 99% by weight or more.

[0025] (Polypropylene Resin) The polypropylene resin in the laminate layer is a resin containing propylene as a main component, and examples thereof include propylene homopolymers, random copolymers and block copolymers of propylene with α-olefins such as ethylene, butene-1, pentene-1, hexene-1, 3-methylbutene-1, 4-methylpentene-1, and octene-1. Among these, random copolymers and / or block copolymers of propylene with α-olefins such as ethylene, butene-1, pentene-1, hexene-1, 3-methylbutene-1, 4-methylpentene-1, and octene-1 are preferred. Note that "main component" means that propylene accounts for 90% by mass or more of the polypropylene resin, more preferably 95% by weight or more, even more preferably 97% by weight or more, and even more preferably 99% by weight or more.

[0026] The polypropylene resin constituting the laminate layer preferably has a melt flow rate (JIS K7112) of 0.1 g / 10 min or more and 9 g / 10 min or less, more preferably 0.5 g / 10 min or more and 8 g / 10 min or less, and even more preferably 1 g / 10 min or more and 7 g / 10 min or less.

[0027] The upper limit of the melting point (JIS K7121) of the polypropylene resin constituting the laminate layer is preferably 150°C, more preferably 145°C or less, and even more preferably 140°C. When the melting point (JIS K7121) of the polypropylene resin constituting the laminate layer is 150°C or less, the tensile modulus of the laminate sealant film is easily controlled to 500 MPa or less. The lower limit of the melting point (JIS K7121) of the polypropylene resin constituting the laminate layer is preferably 120°C, more preferably 125°C, and even more preferably 130°C. When the melting point (JIS K7121) of the polypropylene resin constituting the laminate layer is 120°C or more, the laminate sealant film is less likely to wrinkle, for example, when subjected to retort treatment, and transparency is easily maintained. Furthermore, when laminated with a stretched polypropylene film, it is possible to obtain packaging bags made of the same material, and the laminate sealant film can be used for applications that could not be achieved with a sealant film made of a polyethylene resin. This is useful as a so-called monomaterial film.

[0028] In addition to polypropylene-based resins, the resin composition of the laminate layer can include at least one ethylene homopolymer selected from the group consisting of high-pressure low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, and high-density polyethylene. Furthermore, random or block copolymers composed primarily of ethylene and copolymerized with other monomers, such as α-olefins (e.g., propylene, butene-1, pentene-1, hexene-1, 3-methylbutene-1, 4-methylpentene-1, and octene-1), vinyl acetate, (meth)acrylic acid, and (meth)acrylic acid esters, or mixtures thereof, can also be used. These copolymers may be crystalline, low-crystalline, or amorphous. The content of polymers other than these polypropylene-based resins in the laminate layer is preferably 20% by weight or less, more preferably 15% by weight or less, even more preferably 10% by weight or less, and particularly preferably 5% by weight or less.

[0029] The polyethylene resin constituting the laminate layer preferably has a melt flow rate (JIS K7112) of 0.1 g / 10 min or more and 9 g / 10 min or less, more preferably 0.5 g / 10 min or more and 8 g / 10 min or less, and even more preferably 1 g / 10 min or more and 7 g / 10 min or less. The polyethylene resin constituting the laminate layer preferably has a melting point (JIS K7121) of 100°C or more and 140°C or less, more preferably 105°C or more and 135°C or less, and even more preferably 110°C or more and 130°C or less. The melting point of the polyethylene resin may show two or more melting endothermic peaks, and the peak with the highest melting temperature was defined as the main peak.

[0030] (Anti-blocking agent) The resin composition of the laminate layer preferably contains an anti-blocking agent, and examples thereof include silica particles such as synthetic silica, inorganic particles such as diatomaceous earth, talc, and mica, and organic particles such as silicone particles, acrylic particles, nylon particles, and polyethylene particles. It is more preferable to contain silica particles or polyethylene particles. It is particularly preferable to contain silica particles and polyethylene particles. The average particle size of the particles used in the present invention is preferably 2 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. The average particle size is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less.

[0031] The content of particles in the resin composition in the laminate layer is preferably 0.1 wt% or more, more preferably 0.3 wt% or more, and even more preferably 0.4 wt% or more, based on the sealing layer of the film. Also, it is preferably 2 wt% or less, more preferably 1.5 wt% or less, and even more preferably 1.0 wt% or less. Furthermore, when the amount of particles added is 2 wt% or less, the number of protrusions on the surface is not too large, and poor appearance and abrasion resistance are unlikely to occur.

[0032] (Organic Lubricant) The resin composition in the laminate layer preferably contains 0.01 wt% or more and 2.0 wt% or less of a fatty acid amide as an organic lubricant, more preferably 0.05 wt% or more and 1.5 wt% or less, and particularly preferably 0.1 wt% or more and 1.0 wt% or less. When the fatty acid amide is 0.01 wt% or more, blocking between films is not too strong, and the film handling is likely to be satisfactory. When it is 2.0 wt% or less, the seal strength is unlikely to decrease. Examples of fatty acid amides include erucic acid amide, ethylene bisoleic acid amide, and behenic acid amide, and these may be used in combination.

[0033] The closer the melt flow rates of the resin compositions or raw resins constituting the laminate layer, the better the appearance. The ratio of the melt flow rates of the raw resins mixed in the seal layer is preferably 0.5 to 2.0, more preferably 0.8 to 1.8, and even more preferably 1.0 to 1.6. When the melt flow rate ratio is within this range, poor appearance such as layer misalignment, blemishes, and unevenness is less likely to occur.

[0034] (Intermediate layer) The laminated sealant film of the present invention may include an intermediate layer between the laminate layer and the seal layer. The intermediate layer in the present invention is made of a resin composition mainly composed of a polypropylene resin. The term "main component" means that the proportion of the polypropylene resin in the resin composition is 90% by mass or more, more preferably 95% by weight or more, even more preferably 97% by weight or more, and even more preferably 99% by weight or more.

[0035] (Polypropylene Resin) The polypropylene resin in the intermediate layer is a resin containing propylene as a main component, and examples thereof include propylene homopolymers, random copolymers and block copolymers of propylene and an α-olefin such as ethylene, butene-1, pentene-1, hexene-1, 3-methylbutene-1, 4-methylpentene-1, and octene-1. Among these, random copolymers of propylene and an α-olefin such as ethylene, butene-1, pentene-1, hexene-1, 3-methylbutene-1, 4-methylpentene-1, and octene-1 are preferred. Note that "main component" means that propylene accounts for 90% by mass or more of the polypropylene resin, more preferably 95% by weight or more, even more preferably 97% by weight or more, and even more preferably 99% by weight or more.

[0036] The polypropylene resin constituting the intermediate layer preferably has a melt flow rate of 0.1 g / 10 min or more and 9 g / 10 min or less, more preferably 0.5 g / 10 min or more and 8 g / 10 min or less, and even more preferably 1 g / 10 min or more and 7 g / 10 min or less. The upper limit of the melting point (JIS K7121) of the polypropylene resin constituting the intermediate layer is preferably 150°C, more preferably 145°C or less, and even more preferably 140°C. If the melting point (JIS K7121) of the polypropylene resin constituting the laminate layer is 150°C or less, the tensile modulus of the laminate sealant film is easily set to 500 MPa or less. The lower limit of the melting point (JIS K7121) of the polypropylene resin constituting the intermediate layer is preferably 120°C, more preferably 125°C, and even more preferably 130°C. When the melting point (JIS K7121) of the polypropylene resin constituting the laminate layer is 120°C or higher, the laminate sealant film is less likely to wrinkle when subjected to, for example, retort processing, and transparency is easily maintained. Furthermore, it can be used in applications that could not be handled with sealant films made of polyethylene resins, such as laminating it with an OPP (oriented polypropylene) film to form a mono-material film.

[0037] In addition to polypropylene-based resins, the resin composition of the intermediate layer can include at least one ethylene homopolymer selected from the group consisting of high-pressure low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, and high-density polyethylene. Furthermore, random or block copolymers containing ethylene as the main component and copolymerized with other monomers, such as α-olefins such as propylene, butene-1, pentene-1, hexene-1, 3-methylbutene-1, 4-methylpentene-1, and octene-1, vinyl acetate, (meth)acrylic acid, and (meth)acrylic acid esters, or mixtures thereof, can also be used. These copolymers may be crystalline, low-crystalline, or amorphous. The content of these polymers other than polypropylene-based resins in the laminate layer is preferably 20% by weight or less, more preferably 15% by weight or less, even more preferably 10% by weight or less, and particularly preferably 5% by weight or less.

[0038] The polyethylene resin constituting the intermediate layer preferably has a melt flow rate of 0.1 g / 10 min or more and 9 g / 10 min or less, more preferably 0.5 g / 10 min or more and 8 g / 10 min or less, and even more preferably 1 g / 10 min or more and 7 g / 10 min or less. The polyethylene resin constituting the intermediate layer preferably has a melting point of 100°C or more and 140°C or less, more preferably 105°C or more and 135°C or less, and even more preferably 110°C or more and 130°C or less. The melting point of the polyethylene resin may show two or more melting endothermic peaks, and the peak with the highest melting temperature was defined as the main peak.

[0039] (Anti-blocking Agent) The resin composition of the intermediate layer may contain an anti-blocking agent, such as silica particles (e.g., synthetic silica), inorganic particles (e.g., diatomaceous earth, talc, and mica), or organic particles (e.g., silicone particles, acrylic particles, nylon particles, and polyethylene particles). Silica particles or polyethylene particles are particularly preferred. Silica particles and polyethylene particles are particularly preferred. The resin composition of the intermediate layer may contain inorganic particles (e.g., synthetic silica, diatomaceous earth, talc, and mica), or organic particles (e.g., silicone particles, acrylic particles, nylon particles, and polyethylene particles). The average particle size of the particles used in the present invention is preferably 2 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. The average particle size is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less.

[0040] The content of particles in the resin composition in the intermediate layer is preferably 2% by weight or less, more preferably 1.5% by weight or less, and even more preferably 1.0% by weight or less, based on the weight of the seal layer of the film.

[0041] (Organic Lubricant) The resin composition of the intermediate layer may contain a fatty acid amide, preferably at 2.0 wt % or less, more preferably at 1.5 wt % or less, and particularly preferably at 1.0 wt % or less. Examples of fatty acid amides include erucic acid amide, ethylene bisoleic acid amide, and behenic acid amide, and these may be used in combination.

[0042] The closer the melt flow rates of the resin compositions or raw resins constituting the intermediate layer, the better the appearance. The ratio of the melt flow rates of the raw resins mixed in the seal layer is preferably 0.5 to 2.0, more preferably 0.8 to 1.8, and even more preferably 1.0 to 1.6. When the melt flow rate ratio is within this range, poor appearance such as layer misalignment, blemishes, and unevenness is less likely to occur.

[0043] (Layer Structure) Examples of the layer structure of the laminate sealant film of the present invention include laminate layer / sealing layer, laminate layer / intermediate layer / sealing layer, and laminate layer / intermediate layer 1 / intermediate layer 2 / sealing layer. It is preferable to provide an intermediate layer between the laminate layer and the seal layer, as this reduces peeling between the laminate layer and the seal layer and makes it easier to use recycled raw materials. The raw material composition of the intermediate layer is preferably intermediate between the laminate layer and the seal layer, in order to reduce peeling between the laminate layer and the seal layer. The thickness of the laminate layer is preferably 3 μm or more, more preferably 5 μm or more. The thickness of the seal layer is preferably 3 μm or more, more preferably 5 μm or more. The thickness of the intermediate layer is preferably 3 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, and particularly preferably 15 μm or more. The thickness of the laminate layer is preferably 12 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less. The thickness of the sealing layer is preferably 12 μm or less, more preferably 10 μm or more, and even more preferably 8 μm or less. The thickness of the intermediate layer is preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 20 μm or less. The ratio of the thickness of the intermediate layer to the thickness of the laminate layer is preferably 1.0 or more, more preferably 1.5 or more, and even more preferably 2.0 or more. The ratio of the thickness of the sealing layer to the thickness of the laminate layer is preferably 0.3 or more and 1.5 or less, and preferably 0.5 or more and 1.2 or less. The ratio of the thickness of the intermediate layer to the thickness of the sealing layer is preferably 1.0 or more, more preferably 1.5 or more, and even more preferably 2.0 or more.

[0044] The greater the difference in melt flow rate between the raw material resins of adjacent layers and / or the greater the difference in melt flow rate between the raw material resins mixed in each layer, the more poor the appearance becomes. The ratio of the melt flow rates of the raw material resins of adjacent layers is preferably 0.5 or more and 2.0 or less. When the melt flow rate ratio is within this range, poor appearance such as layer misalignment, blemishes, and unevenness is less likely to occur. Furthermore, the main peak of the melting point of the laminated sealant film of the present invention is preferably 121°C or more, more preferably 130°C or more, and even more preferably 140°C or more. When the main peak of the melting point of the film is 121°C or more, the high retort suitability is further improved.

[0045] (Method for producing laminate sealant film) The method for producing the laminate sealant film of the present invention will be described in detail below, but is not limited thereto. The resin compositions for the laminate layer, intermediate layer, and seal layer may be prepared by blending the above-mentioned resin raw materials and, if necessary, various additives in a mixer such as a Henschel mixer, a Banbury mixer, or a tumbler mixer, and then pelletizing the mixture using a single- or twin-screw extruder to form a film. Alternatively, the components may be blended together and fed to a film-forming machine.

[0046] (Melt Extrusion Process) The mixed resin composition is melted, for example, under conditions of a resin temperature of 110°C or higher and 300°C or lower, and melt-extruded into a sheet form, for example, through a T-die, cast onto a cooling roll, and cooled and solidified to obtain an unstretched sheet. A specific method for this is preferably casting onto a cooling roll. Multilayering can be achieved using a multilayering device such as a multilayer feed block, a static mixer, or a multi-manifold die. For example, resins delivered from different flow paths using two or more extruders can be laminated into multiple layers using a multilayer feed block or a multi-manifold die. Examples of methods include melt-extruding a melt-kneaded laminated resin composition sheet and forming it into a film using a T-die method or an inflation method. However, the T-die method is particularly preferred because it allows for a high resin melt temperature.

[0047] (Cooling and Solidification Process) For example, it is preferable to cast a sheet melt-extruded from a T-die onto a chill roll and cool it. The lower limit of the chill roll temperature is preferably 10°C. If the temperature is lower than this, not only may the crystallization suppression effect saturate, but problems such as condensation may also occur, which is undesirable. The upper limit of the chill roll temperature is preferably 70°C or lower. If the temperature exceeds this range, crystallization will progress and transparency will deteriorate, which is undesirable. Furthermore, when the chill roll temperature is within the above range, it is preferable to reduce the humidity of the environment near the chill roll to prevent condensation. During casting, the surface temperature of the chill roll rises because the hot resin comes into contact with the surface. Typically, chill rolls are cooled by flowing cooling water through piping inside. However, it is necessary to reduce the temperature difference across the width of the chill roll surface by ensuring a sufficient amount of cooling water, optimizing the piping arrangement, and performing maintenance to prevent sludge from adhering to the piping. In this case, the thickness of the unstretched sheet is preferably in the range of 3 μm to 200 μm. The thickness of the film is preferably in the range of 5 μm or more and 100 μm or less, more preferably 10 μm or more and 80 μm or less.

[0048] The obtained unstretched sheet may be stretched, but the stretching ratio is preferably less than 2 times, since stretching to 2 times or more will result in a tensile modulus of elasticity exceeding 500 MPa.

[0049] (Film characteristics) The film characteristics of the present invention will be described. Note that the "longitudinal direction" of the laminated sealant film of the present invention is the direction corresponding to the flow direction in the film production process, and the "width direction" is the direction perpendicular to the flow direction in the film production process. Hereinafter, the "longitudinal direction" may be abbreviated as the "MD direction" and the "width direction" may be abbreviated as the "TD direction".

[0050] (Tensile Modulus) The upper limit of the tensile modulus in the longitudinal direction of the laminate sealant film of the present invention is preferably 500 MPa, more preferably 480 MPa, even more preferably 460 MPa, even more preferably 440 MPa, particularly preferably 420 MPa, and most preferably 400 MPa. When the tensile modulus in the longitudinal direction is 500 MPa or less, the low-temperature sealing effect at the sealing initiation temperature is improved. The lower limit of the tensile modulus in the longitudinal direction of the laminate sealant film of the present invention is preferably 200 MPa, more preferably 250 MPa, even more preferably 300 MPa, and even more preferably 325 MPa. When the tensile modulus in the longitudinal direction is 200 MPa or more, bag-making processing is easier. The upper limit of the tensile modulus in the width direction of the laminate sealant film of the present invention is preferably 550 MPa, more preferably 530 MPa, even more preferably 500 MPa, even more preferably 480 MPa, and particularly preferably 440 MPa. When the tensile modulus in the width direction is 550 MPa or less, the low-temperature sealing effect at the sealing initiation temperature is improved. The lower limit of the tensile modulus in the width direction of the laminated sealant film of the present invention is preferably 200 MPa, more preferably 250 MPa, even more preferably 300 MPa, and even more preferably 325 MPa. When the tensile modulus in the width direction is 200 MPa or more, bag-making processing is easier.

[0051] The upper limit of the sum of the longitudinal tensile modulus and the width tensile modulus of the laminated sealant film of the present invention is preferably 1050 MPa, more preferably 1000 MPa, even more preferably 950 MPa, even more preferably 900 MPa, particularly preferably 850 MPa, and most preferably 800 MPa. When the longitudinal tensile modulus is 1050 MPa or less, the low-temperature sealing effect at the seal initiation temperature is improved. The lower limit of the sum of the longitudinal tensile modulus and the width tensile modulus of the laminated sealant film of the present invention is preferably 400 MPa, more preferably 500 MPa, even more preferably 600 MPa, and even more preferably 650 MPa. When the sum of the longitudinal tensile modulus and the width tensile modulus is 400 MPa or more, bag-making processing is easier. The upper limit of the average of the longitudinal and width tensile moduli of the laminate sealant film of the present invention is preferably 500 MPa, more preferably 480 MPa, even more preferably 460 MPa, even more preferably 440 MPa, and particularly preferably 420 MPa. When the average of the longitudinal and width tensile moduli is 500 MPa or less, the low-temperature sealing effect of the seal initiation temperature is improved. The lower limit of the average of the longitudinal and width tensile moduli of the laminate sealant film of the present invention is preferably 200 MPa, more preferably 250 MPa, even more preferably 300 MPa, and even more preferably 325 MPa. When the longitudinal tensile modulus is 200 MPa or more, bag-making processing is easier.

[0052] (Haze) The haze of the laminate sealant film of the present invention is preferably 10% or less, more preferably 9% or less, even more preferably 8% or less, even more preferably 7% or less, and particularly preferably 5% or less. If the haze exceeds 10%, the film often has streaks or scratches, and the contents become difficult to see. The haze of the laminate sealant film of the present invention is preferably 1% or more, more preferably 2% or more, and even more preferably 3% or more. If the haze is 1% or more, the coefficient of friction is less likely to increase.

[0053] (Appearance Unevenness) The laminated sealant film of the invention has better appearance unevenness, particularly when the melt flow rates of the raw resins of the resin composition constituting the seal layer are closer, and the more widely separated they are, the more likely appearance unevenness occurs.

[0054] (Delamination) The delamination of the laminate sealant film of the present invention means, for example, delamination between the seal layer and the intermediate layer when measuring the flat seal initiation temperature, the hermetic seal initiation temperature, or the burst strength. If delamination occurs, it becomes difficult to remove the contents, so it is preferable that delamination does not occur. Delamination is likely to occur when the components or component ratios of the resin compositions of the seal layer and the intermediate layer and / or the intermediate layer and the laminate layer are significantly different.

[0055] (Flat seal initiation temperature) The flat seal initiation temperature of the laminated sealant film of the present invention is preferably 60°C or higher and 150°C or lower, more preferably 70°C or higher and 140°C or lower, and even more preferably 80°C or higher and 130°C or lower. The flat seal initiation temperature is preferably set at a lower limit of a temperature 30°C or higher than the lowest melting point of the polyethylene resin and / or polypropylene resin in the seal layer, and at an upper limit of a temperature 10°C or higher than the highest melting point of the polyethylene resin and / or polypropylene resin in the laminate layer. The low-temperature sealing effect of the flat seal initiation temperature is evaluated based on the flat seal initiation temperature in Comparative Example 1 described below, based on the degree of decrease in the flat seal initiation temperature. The low-temperature sealability of the flat seal initiation temperature is preferably 5°C or higher, more preferably 10°C or higher, even more preferably 15°C or higher, even more preferably 20°C or higher, particularly preferably 25°C or higher, and most preferably 27°C or higher.

[0056] (Hard seal initiation temperature) The hard seal initiation temperature of the laminated sealant film of the present invention is preferably 60°C or higher and 150°C or lower, more preferably 70°C or higher and 140°C or lower, and even more preferably 80°C or higher and 130°C or lower. The hard seal initiation temperature is preferably set at a lower limit of 30°C or higher than the lowest melting point of the polyethylene resin and / or polypropylene resin in the seal layer, and at an upper limit of 10°C or higher than the highest melting point of the polyethylene resin and / or polypropylene resin in the laminate layer. The low-temperature sealing effect of the hard seal initiation temperature is evaluated based on the degree of reduction in the hard seal initiation temperature, using the hard seal initiation temperature in Comparative Example 1 described below as a reference. The low-temperature sealability of the hard seal initiation temperature is preferably above 10°C, more preferably 11°C or higher, even more preferably 12°C or higher, particularly preferably 15°C or higher, and most preferably 20°C or higher.

[0057] (Hot tack property) The hot tack property of the laminated sealant film of the present invention is desirably such that the tack peel distance is 20 mm or less at a lower temperature. Here, good hot tack property means that the seal strength between sealant films is sufficient even when the resin of the sealant film is in a molten state. The low-temperature sealing effect of hot tack property is evaluated by the degree of decrease in hot tack temperature, based on the hot tack temperature in Comparative Example 1 described below. The low-temperature sealing property of hot tack property is preferably 5°C or higher, more preferably 10°C or higher, even more preferably 15°C or higher, even more preferably 18°C ​​or higher, and particularly preferably 20°C or higher.

[0058] The sealing properties of the present invention (flat seal initiation temperature, hermetic seal initiation temperature, and hot tack temperature) are such that, in order to exhibit low-temperature sealing properties compared to conventional techniques, the sealing layer contains an ethylene-based resin with a low melting point, and is a mixture with a polypropylene-based resin to prevent delamination between the sealing layer and adjacent layers, and the laminate layer and intermediate layer are made primarily of a propylene-based resin to maintain the heat resistance of the laminated sealant film.

[0059] (Impact Strength) It is preferable that the impact strength of the laminate sealant film of the present invention is less likely to decrease even at a low temperature of 5° C. or less compared to the impact strength at room temperature. In particular, the higher the mixing ratio of the polyethylene resin constituting the seal layer, the less likely the impact strength at low temperatures to decrease.

[0060] (Improvement in cold resistance) The improvement in cold resistance of impact strength of the laminate sealant film of the present invention is evaluated by the difference from the impact strength at 5° C. in Comparative Example 1 described later as a standard. The improvement in cold resistance of impact strength is preferably 0.05 J or more, more preferably 0.10 J or more, even more preferably 0.15 J or more, even more preferably 0.20 J or more, and particularly preferably 0.25 J or more.

[0061] (Burst Strength) The burst strength of the laminate sealant film of the present invention is evaluated using bags made from the laminate sealant film. When high burst strength is required, such as for retort sterilization, it is preferably 20 kPa or more, more preferably 30 kPa or more, and even more preferably 35 kPa or more. By optimizing the melting point of the sealing layer and the elastic modulus of the film, the laminate sealant film of the present invention has been confirmed to achieve low-temperature sealing effects in terms of the flat seal initiation temperature, hermetic seal initiation temperature, and hot tack temperature, as well as to improve its burst strength. This is thought to be due to the fact that the bag becomes more easily deformed by optimizing the elastic modulus in particular, thereby improving its burst strength.

[0062] (Static and dynamic friction coefficients) The static and dynamic friction coefficients between the seal layer surfaces of the laminated sealant film of the present invention at a load of 0.5 kgf are preferably 2.0 or less, more preferably 1.0 or less, and even more preferably 0.5 or less. If the static and / or dynamic friction coefficients are 2.0 or more, the slipperiness between the films becomes insufficient, resulting in unsatisfactory handling properties as a packaging material.

[0063] (Melting Point of Resin) The melting point of the resin was measured in accordance with JIS K7121 using a differential scanning calorimeter (Seiko Instruments Inc., DSC60). Specifically, about 5 mg of a sample was packed into an aluminum pan, heated from room temperature to 200°C at a heating / cooling rate of 10°C / min, held at 200°C for 3 minutes, cooled to 23°C, held at 23°C for 3 minutes, and then heated again to 200°C. The temperature of the highest melting endothermic peak was taken as the melting point. When there were two or more melting endothermic peaks, the highest melting endothermic peak was taken as the melting point.

[0064] (Melt Flow Rate) In accordance with JIS K7112, measurements were made using a thermal flow evaluation device (Shimadzu Corporation, Capillary Rheometer, CFT-500D) under a load of 2.16 kg at a temperature of 230°C for polypropylene-based resins and at a temperature of 190°C for polyethylene-based resins such as L-LDPE.

[0065] (Average particle size of particles) Inorganic particles or polyethylene particles were dispersed in ion-exchanged water stirred at a predetermined rotation speed (about 5000 rpm) using a high-speed stirrer, and the resulting dispersion was added to Isotone (physiological saline) and further dispersed using an ultrasonic disperser. The particle size distribution was then determined by the Cole counter method, and the volume average particle size was calculated. The refractive indexes used were 1.30 for physiological saline, 1.457 for synthetic silica and diatomaceous earth, and 1.54 for polyethylene.

[0066] (Flat seal initiation temperature) A laminated sealant film and a biaxially oriented polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., Toyobo Ester (registered trademark), E5100, 12 μm) were overlapped, folded in half so that the seal layers of the laminated sealant film faced each other, and heat-sealed using a thermal gradient tester (Toyo Seiki Seisakusho Co., Ltd., model: HG-100-2) at a sealing pressure of 0.2 MPa, a sealing time of 1.0 second, and a heat-sealing temperature of 70 to 160 ° C. at 5 ° C. intervals. The heat-sealed sample was cut into strips with a heat-seal width of 15 mm and set in a universal material testing machine (Instron Japan Company Limited, 68TM-5 model). The maximum strength of the peeled seal between the seal layers at a speed of 200 mm / min was measured with n = 3, and the heat-sealing strength and heat-sealing temperature at each temperature were plotted. The heat seal temperature at which the strength reached 4.9 N / 15 mm was read from a graph connecting each plot with a straight line, and this was taken as the flat seal initiation temperature.

[0067] (Low-temperature sealing effect of flat seal initiation temperature) The low-temperature sealing effect of the flat seal initiation temperature is evaluated by the difference (°C) in the flat seal initiation temperature, based on the flat seal initiation temperature in Comparative Example 1 described below. Specifically, the low-temperature sealability evaluation of Example 3 is (flat seal initiation temperature in Comparative Example 1: 130°C) - (flat seal initiation temperature in Example 3: 118°C) = 12°C.

[0068] (Preparation of Laminated Product) A laminated product of a laminated sealant film and a biaxially oriented polypropylene film (Pylen (registered trademark), P2161, 20 μm, manufactured by Toyobo Co., Ltd.) was prepared as follows: A dry laminating adhesive (TM569, CAT-10L, manufactured by Toyo-Morton Co., Ltd.) was applied to the corona surface of the biaxially oriented polypropylene film at a solid content of 3 g / m ２ The solvent was evaporated and removed in an oven at 80° C., and then the corona surface of the laminated sealant film and the adhesive-coated surface were nipped and laminated with a temperature-controlled roll at 60° C. This laminated laminated sealant film was left standing at 40° C. for 2 days.

[0069] (Sealing Initiation Temperature) This laminated sealant film was made into bags using a horizontal pillow packaging machine (Fujikikai Co., Ltd., FW3301 II / B BD100). The conditions were set to a cut length of 250 mm, a height of 45 mm, and a rotation speed of 40 rpm. A sponge scrubber (Kikuron Co., Ltd., Kikuron A (size: 75 × 115 × 36 mm)) was used as the contents. The bag was made at the same temperature for the center seal and end seal portions, and the temperature was lowered in 5°C increments from 160°C. For evaluation, one bag was first cut into two so as to obtain two complete end seal portions. Next, several drops of an evaluation liquid (Kobayashi Create Co., Ltd., self-recording ink RED1812E) were placed in each half bag, and the bag was visually evaluated by rubbing it with a finger to determine whether the evaluation liquid penetrated through the overlapping area between the center seal and end seal portions. The lowest heat seal temperature at which the test liquid did not penetrate was determined as the seal initiation temperature.

[0070] (Low-temperature sealing effect of sealing start temperature) The low-temperature sealing effect of sealing start temperature is evaluated by the difference (°C) in sealing start temperature based on the sealing start temperature in Comparative Example 1 described below. Specifically, the low-temperature sealability evaluation of Example 3 is (sealing start temperature in Comparative Example 1: 150°C) - (sealing start temperature in Example 3: 135°C) = 15°C.

[0071] (Hot tack temperature) The laminated sealant films were stacked with the sealant surfaces facing each other, and subjected to hot tack at temperatures of 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, and 160°C under a pressure of 2 kg / cm ２ After heat sealing for 1 second at a pressure of 1000 kJ / s, a load of 46 g was applied and the distance the sealed portion peeled off was measured. The device used was a HEAT SEAL TESTER, TP-701-B, manufactured by Tester Sangyo Co., Ltd. The temperature at which the peeled distance of the sealed portion was 20 mm or less was defined as the hot tack temperature.

[0072] (Low-temperature sealing effect of hot tack temperature) The low-temperature sealing effect of the hot tack temperature is evaluated by the difference in hot tack temperature (°C) based on the hot tack temperature in Comparative Example 1 described below. Specifically, the low-temperature sealing effect evaluation of Example 3 is (hot tack temperature in Comparative Example 1: 140°C) - (hot tack temperature in Example 1: 130°C) = 10°C.

[0073] (Burst Strength) A horizontal pillow packaging machine (Fujikikai Co., Ltd., FW3301 II / B BD100) was used, with a cut length of 250 mm, a height of 45 mm, and a rotation speed of 40 rpm. A sponge scrubber (Kikuron Co., Ltd., Kikuron A (size: 75 x 115 x 36 mm)) was used as the contents, and the temperatures of the center seal portion and the end seal portion were set to the sealing start temperature of each. A laminated laminated sealant film was produced into a bag. Evaluation was performed by burst strength (JIS Z0238 Test method for heat-sealed flexible packaging bags and semi-rigid containers). The burst strength was measured using a seal strength / burst strength measuring instrument (Sun Scientific Co., Ltd., SEAL TESTER, FKT-100-J).

[0074] (Tensile modulus) Measurement was performed in accordance with JIS K7127 under the following conditions: The tensile modulus of the laminated sealant film in the machine direction (MD) and the transverse direction (TD) of the film was measured three times with a sample length of 100 mm, a sample width of 15 mm, a chuck distance of 20 mm, and a speed of 200 mm / min, and the average value was taken as the tensile modulus in each direction.

[0075] (Interlayer Delamination) Interlayer delamination of the laminated sealant film of the present invention means the case where delamination occurs between the seal layer and the intermediate layer and / or between the intermediate layer and the laminate layer when the flat seal initiation temperature, the hermetic seal initiation temperature or the burst strength is measured.

[0076] (Appearance Unevenness) Appearance unevenness of the laminated sealant film of the present invention was evaluated by visually inspecting the film for the presence or absence of defects in appearance such as layer misalignment, spots, and unevenness.

[0077] (Impact Strength) Measurement was performed according to ASTM D3420 under the following conditions. The laminate sealant film was cut out to ensure an outer diameter of 100 mm, and after leaving it to stand for one day and night at a measurement temperature of 23°C or 5°C, five measurements were made on test pieces with a diameter of 80 mm, and the average value was used as the impact strength. The impact strength was measured using a film impact tester (Yasuda Seiki Seisakusho Co., Ltd.) installed at the same measurement temperature as the film.

[0078] (Improvement in cold resistance) The improvement in cold resistance of the impact strength of the laminate sealant film of the present invention is evaluated by the difference from the impact strength at 5° C. in Comparative Example 1 described below as the standard. Specifically, the improvement in cold resistance in Example 3 is evaluated as (impact strength at 5° C. in Example 3: 0.20 J) - (impact strength at 5° C. in Comparative Example 1: 0.01 J) = 0.19 J.

[0079] (Haze) The haze of the laminate sealant film was measured in accordance with JIS K8701 using a turbidity meter (manufactured by Nippon Denshoku Industries Co., Ltd., model: ZE2000).

[0080] (Static and Dynamic Friction Coefficients) The static and dynamic friction coefficients were determined in accordance with JIS K7125 under the following conditions in an environment of 23°C and 65% RH. The load was 0.5 kgf, and the tensile speed was 200 mm / min. The measurement surfaces were the opposing seal layer surfaces (B / B) of the laminate sealant film itself, or the seal layer surface and laminate layer surface (F / B). The laminated laminate sealant film was the opposing seal layer surfaces of the laminate sealant film (CP / CP), or the laminate layer surface of the laminate sealant film and a biaxially oriented polypropylene film (OP / CP). The measurement device used was a TENSILON STM-T-50BP manufactured by Toyo Baldwin Co., Ltd.

[0081] (Propylene-based copolymers) 1) FL8115A (manufactured by Sumitomo Chemical Co., Ltd., Noblen (registered trademark), propylene-ethylene-butene random copolymer, melting point 148°C, melt flow rate 7.0 g / 10 min, flexural modulus 1,000 MPa) 2) FL6745A (manufactured by Sumitomo Chemical Co., Ltd., Noblen (registered trademark), propylene-ethylene-butene random copolymer, melting point 130°C, melt flow rate 6.0 g / 10 min, flexural modulus 700 MPa)

[0082] (Ethylene-based polymers) 1) FV401 (manufactured by Sumitomo Chemical Co., Ltd., Sumikathene (registered trademark) E, linear low-density polyethylene resin, melting point 112°C, melt flow rate 3.8g / 10min, flexural modulus 80MPa) 2) FV405 (manufactured by Sumitomo Chemical Co., Ltd., Sumikathene (registered trademark) E, linear low-density polyethylene resin, melting point 118°C, melt flow rate 3.8g / 10min, flexural modulus 220MPa) 3) FV103 (manufactured by Sumitomo Chemical Co., Ltd., Sumikathene (registered trademark), linear low-density polyethylene resin, melting point 115°C, melt flow rate 1.2g / 10min, flexural modulus 80MPa) 4) 015AN (manufactured by Ube Maruzen Polyethylene Co., Ltd., Yumerit (registered trademark), metallocene linear low-density polyethylene resin, melting point 103°C, melt flow rate 14g / 10min, flexural modulus 210MPa) 5) 031GLD (manufactured by Ube Maruzen Polyethylene Co., Ltd., Yumerit (registered trademark), metallocene linear low-density polyethylene resin, melting point 104°C, melt flow rate 9g / 10min, flexural modulus 220MPa)

[0083] (Butene polymer) BL2491M (manufactured by Mitsui Chemicals, Inc., Tafmer (registered trademark), butene resin, melting point 100°C, melt flow rate 4.0 g / 10 min, tensile modulus 260 MPa)

[0084] (Anti-blocking agent) 1) Synthetic silica: KMP130-2 (average particle size 2 μm, Shin-Etsu Chemical Co., Ltd.) 2) Synthetic silica: KMP130-4 (average particle size 4 μm, Shin-Etsu Chemical Co., Ltd.) 3) Ultra-high molecular weight polyethylene particles: PM200 (average particle size 10 μm, manufactured by Mitsui Chemicals, Inc.)

[0085] (Organic lubricants) 1) Erucic acid amide: Brand name Diamid L-200 (melting point 81°C, manufactured by Mitsubishi Chemical Corporation) 2) Behenic acid amide: Brand name D1007 (melting point 110°C, manufactured by Tokyo Chemical Industry Co., Ltd.)

[0086] (Masterbatches) 1) Silica masterbatch: Noblen (registered trademark) FL6745A manufactured by Sumitomo Chemical Co., Ltd. was mixed with silica (KMP-130-2 manufactured by Shin-Etsu Chemical Co., Ltd., average particle size 2 μm) to prepare a masterbatch containing 15% by weight of silica. 2) Silica masterbatch: Noblen (registered trademark) FL6745A manufactured by Sumitomo Chemical Co., Ltd. was mixed with silica (KMP-130-4 manufactured by Shin-Etsu Chemical Co., Ltd., average particle size 4 μm) to prepare a masterbatch containing 12% by weight of silica. 3) Ultra-high molecular weight polyethylene particle masterbatch: Noblen (registered trademark) FL6745A manufactured by Sumitomo Chemical Co., Ltd. was mixed with ultra-high molecular weight polyethylene particles (Mipelon PM200 manufactured by Mitsui Chemicals, Inc., average particle size 10 μm) to prepare a masterbatch containing 10% by weight of ultra-high molecular weight polyethylene particles. 4) Erucamide masterbatch: A masterbatch containing 5% by weight of erucamide was prepared by mixing erucamide with Noblen (registered trademark) FL6745A manufactured by Sumitomo Chemical Co., Ltd. 5) Behenamide masterbatch: A masterbatch containing 2% by weight of behenamide was prepared by mixing behenamide with Noblen (registered trademark) FL6745A manufactured by Sumitomo Chemical Co., Ltd.

[0087] Examples 1-12: The laminate layer and intermediate layer were made from FL6745A. The seal layer was made from the resins and additives listed in Tables 1 and 2, and appropriate masterbatches were used. The resins were melted at 240°C in three extruders, filtered through a sintered filter with a filtration accuracy of 60 μm, and then co-extruded into a sheet from a T-die. The laminate layer, intermediate layer, and seal layer were melt-extruded to a thickness ratio of 20:60:20 vol.%, cooled and solidified on a cooling roll at 30°C, and then wound into a roll at a speed of 20 m / min. A laminate sealant film with a total thickness of 30 μm (laminate layer thickness: 6 μm, intermediate layer thickness: 12 μm, seal layer thickness: 6 μm) and a laminate layer wet tension of 45 mN / m was obtained. The content ratios of polypropylene-based resin and polyethylene-based resin in each layer are based on the total content of polypropylene-based resin and polyethylene-based resin. The evaluation results are shown in Tables 1 and 2.

[0088] (Example 13) A laminate sealant film was obtained in the same manner as in Example 5, except that the laminate layer was made of FL8115A. The laminate sealant films obtained in Examples 1 to 13 had a high low-temperature sealing effect at the flat seal initiation temperature due to the low melting point of the seal layer, an excellent low-temperature sealing effect at the hermetic seal initiation temperature due to the low elastic modulus, and further exhibited excellent impact strength due to the inclusion of a polyethylene resin. Furthermore, the films exhibited sufficiently low coefficients of static and dynamic friction as well as good appearance due to the inclusion of a suitable antiblocking agent and organic lubricant. Of course, there were no problems with film formation processability, and sufficient burst strength was obtained.

[0089] Comparative Examples 1 to 8 Laminated sealant films were obtained in the same manner as in Example 1, except that masterbatches were appropriately used to make the laminate layer, intermediate layer, and seal layer using the resins and additives shown in Table 3 as raw materials. The evaluation results are shown in Table 3.

[0090] The film obtained in Comparative Example 1 is a single polypropylene resin film, and has poor low-temperature sealing effect at the flat seal initiation temperature and the hermetic seal initiation temperature. The films obtained in Comparative Examples 2 to 7 have poor low-temperature sealing effect at the hermetic seal initiation temperature. The film obtained in Comparative Example 8 has poor low-temperature sealing effect at the hermetic seal initiation temperature, and interlayer delamination was observed between the seal layer and the intermediate layer. The films in Comparative Examples 1 to 8 have high tensile modulus of elasticity, and are particularly poor in low-temperature sealing effect at the hermetic seal initiation temperature.

[0091] (Comparative Examples 9 to 16) Laminated sealant films were obtained in the same manner as in Example 1, except that masterbatches were used appropriately to make the laminate layer, intermediate layer, and seal layer from the resins and additives shown in Table 4. The evaluation results are shown in Table 4. The film obtained in Comparative Example 9 is a single polypropylene resin film, and has poor low-temperature sealing effects at flat seal initiation temperature and hermetic seal initiation temperature. The films obtained in Comparative Examples 10 to 15 are inferior in low-temperature sealing effects at hermetic seal initiation temperature. The film obtained in Comparative Example 16 exhibited interlayer delamination between the seal layer and intermediate layer.

[0092] (Comparative Examples 17 to 22) Laminated sealant films were obtained in the same manner as in Example 1, except that masterbatches were used appropriately to make the laminate layer, intermediate layer, and seal layer from the resins and additives shown in Table 5. The evaluation results are shown in Table 5. The films obtained in Comparative Examples 17 to 22 had a large melt flow rate ratio between the propylene-based copolymer and the ethylene-based polymer in the seal layer, and had uneven lamination and poor appearance.

[0093] (Comparative Example 23) A laminated sealant film was obtained in the same manner as in Example 1, except that a masterbatch was appropriately used to make the laminate layer, intermediate layer, and seal layer using the resins and additives shown in Table 5 as raw materials. The evaluation results are shown in Table 5. The film obtained in Comparative Example 23 had a high tensile modulus of elasticity and was poor in low-temperature sealing effect at the hermetic seal initiation temperature.

[0094] (Comparative Example 24) A laminated sealant film was obtained in the same manner as in Example 1, except that a masterbatch was appropriately used to make the laminate layer, intermediate layer, and seal layer from the resins and additives shown in Table 5. The evaluation results are shown in Table 5. The film obtained in Comparative Example 24 is a polyethylene film, which has a low tensile modulus and is poor in handleability and self-supporting ability as a packaging material. The film obtained in Comparative Example 24 has a low melting point for the film and the seal layer, and is prone to wrinkling and adhesion during retort treatment.

[0095] (Comparative Example 25) A laminated sealant film was obtained in the same manner as in Example 1, except that a masterbatch was appropriately used to make the laminate layer, intermediate layer, and seal layer from the resins and additives shown in Table 5. The evaluation results are shown in Table 5. The film obtained in Comparative Example 25 was made of a linear low-density polyethylene resin, and the melting points of the film and the seal layer were low, so that wrinkles were likely to occur during retort treatment, and there was a risk of the films sticking to each other.

[0096] (Comparative Examples 26 and 27) Laminated sealant films were obtained in the same manner as in Example 1, except that masterbatches were used appropriately to make the laminate layer, intermediate layer, and seal layer from the resins and additives shown in Table 5. The evaluation results are shown in Table 5. The films obtained in Comparative Examples 26 and 27 had a large ratio of the melt flow rate of the polypropylene resin to the melt flow rate of the linear low-density polyethylene resin in the seal layer, which made them prone to causing misalignment of the layers of the laminated sealant film and poor appearance such as blemishes and unevenness.

[0097]

[0098]

[0099]

[0100]

[0101]

[0102] The laminated sealant film of the present invention has excellent low-temperature bag-forming properties and is therefore suitable as a packaging material for many products, such as foods, beverages, pharmaceuticals, and chemicals. In particular, it can be suitably used for automatically forming pillow packaging bags, gusset packaging bags, three-side seal packaging bags, and the like while packaging the contents.

Claims

1. A laminated sealant film that satisfies all of the following requirements 1) to 9). 1) It includes at least a laminate layer and a seal layer. 2) The laminate layer is made of a resin composition containing a polypropylene-based resin as a main component. 3) The sealing layer is made of a resin composition containing as a main component a mixture of a polypropylene-based resin and a polyethylene-based resin. 4) The sealing layer contains 1% by weight or more and 95% by weight or less of polypropylene resin and 5% by weight or more and 99% by weight or less of polyethylene resin, based on 100% by weight of the mixture of polypropylene resin and polyethylene resin constituting the sealing layer. 5) The polyethylene resin constituting the sealing layer contains 90% by weight or more of linear low-density polyethylene resin. 6) The difference in melting point between the polypropylene resin and the linear low-density polyethylene resin in the sealing layer is 15° C. or more. 7) The ratio of the melt flow rate of the polypropylene resin to the melt flow rate of the linear low density polyethylene resin in the sealing layer is 0.8 or more and 2.0 or less. 8) The melt flow rate of the polypropylene resin and linear low-density polyethylene resin in the sealing layer is 9 g / 10 min (load 2.16 kg) or less. 9) The tensile modulus in the longitudinal direction is 500 MPa or less.

2. 2. The laminate sealant film according to claim 1, wherein the polypropylene resin is a propylene random copolymer.

3. 3. The laminate sealant film according to claim 1, wherein the laminate sealant film has a tensile modulus in a width direction of 550 MPa or less.

4. 3. The laminate sealant film according to claim 1, wherein the laminate sealant film has a main peak of a melting point of 120°C or higher.

5. 3. The laminate sealant film according to claim 1, wherein the coefficient of static friction between the surfaces of the seal layers of the laminate sealant film is 1.0 or less.

6. 3. The laminate sealant film according to claim 1, wherein the coefficient of dynamic friction between the surfaces of the seal layers of the laminate sealant film is 1.0 or less.

7. 3. The laminate sealant film according to claim 1 or 2, wherein the sealing layer of the laminate sealant film comprises silica particles.

8. 3. The laminate sealant film according to claim 1, wherein the sealing layer of the laminate sealant film comprises erucamide.

9. The laminate sealant film according to claim 1 or 2, wherein the sealing layer of the laminate sealant film contains organic particles.