JP7145626B2 - Laminated film for packaging and package - Google Patents

Description

TECHNICAL FIELD The present invention relates to a laminated film for packaging an object to be packaged such as food, and a package in which the object to be packaged is wrapped with the laminated film.

Sliced cheese is usually sold as a package in which a plurality of individually packaged sliced cheese are bundled and packaged, but each individually packaged sliced cheese is wrapped with a film (inner film). directly packaged. Specifically, in the inner film of the individually packaged sliced cheese, the overlapped portion (back-pasted portion) where both ends of the film overlap and both sides of the film are sealed. The seal (center seal) of the back patch portion is normally sealed by a part coating method (a method of partially applying an adhesive to bond films together). On the other hand, both sides of the film are sealed (side seals) by thermal bonding (heat sealing).In recent years, the method of heat sealing has changed from the conventional method of using a metal heat seal bar to a 1 to 3 mm hole through which high pressure is applied. The method of heat sealing by blowing high temperature air is changing. In the method using a metal heat seal bar, there was a problem that the metal heat seal bar and the film were in close contact with each other, and high-speed packaging could not be achieved due to frictional resistance. Therefore, high-speed packaging is possible compared to the method using a metal heat seal bar. Therefore, in recent years, the method of blowing high-pressure, high-temperature air has become mainstream, and along with this high-speed packaging, the inner film is required to have heat-sealing properties at lower temperatures. Furthermore, sliced cheese is prepared by forming hot cheese into a sheet on a film and cooling it, but when the packaging film is peeled off after cooling, the surface layer of the cheese is peeled off at the same time as the packaging film, and the commercial value is lost. It may be damaged. Therefore, the inner film is also required to have excellent releasability (peelability) and to be easily unsealable.

As a packaging film that satisfies such properties, JP-A-2006-232345 (Patent Document 1) discloses a base layer made of a heat-sealable polyolefin resin and a film formed on the surface of the base layer. and a polyhydric alcohol fatty acid ester containing sucrose fatty acid ester, and a coating layer containing no sodium lauryl sulfate. In the examples of this document, a packaging film is produced by applying a coating agent prepared by dissolving a sucrose fatty acid ester in toluene to the non-corona discharge-treated surface of a coextruded polypropylene film and then drying it.

However, this packaging film has a low adhesive strength at a low temperature of 100° C. or less and does not have sufficient heat-sealing properties.

Japanese Patent Application Laid-Open No. 2014-181076 (Patent Document 2) discloses that a heat-adhesive layer containing a saturated copolyester and a release agent is directly or indirectly formed on at least one surface of a base film. A packaging film is disclosed. This document exemplifies sucrose fatty acid esters, lecithin, glycerin fatty acid esters, sorbitan fatty acid esters, stearic acid esters, oleic acid esters, and condensed ricinoleic acid esters as the release agent. In the examples, 1 part by weight of a releasing agent is mixed with 100 parts by weight of saturated copolyester, and a solution dissolved in a solvent is applied so as to have a dry weight of 2 g/m ² .

However, even with this packaging film, it was not possible to achieve both peelability (separability) from sliced cheese and heat-sealability at low temperatures. That is, since the sealability and releasability required for the inner film of sliced cheese are contradictory properties, it has been difficult to achieve both properties at the same time. Furthermore, if the heat-sealability at low temperatures is improved, the adhesiveness is likely to develop even in an unheated state. In addition, low-temperature heat-sealability and anti-blocking properties are also in a trade-off relationship, making it difficult to achieve both.

Japanese Patent Application Laid-Open No. 2006-232345 (claims 1 and 2, examples) JP 2014-181076 A (claims 1 and 7 to 8, examples)

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a laminated film for packaging that can improve the peelability of tightly wrapped objects and also improve the heat-sealing property at low temperatures, and a package in which the objects are packaged with this laminated film. is to provide

Another object of the present invention is to provide a laminated film for packaging that can improve heat-sealing properties at low temperatures and also improve anti-blocking properties, and a package in which an object to be packaged is packaged with this laminated film. .

Still another object of the present invention is to provide a laminated film for packaging that has an appropriate heat-sealing property and can easily open a sealed object, and a package in which the object is wrapped with this laminated film. That's what it is.

The present inventors have made intensive studies to achieve the above objects, and found that, on at least one surface of the base material layer, 100 parts by weight of a saturated copolymer polyester that combines a plurality of types with different glass transition temperatures, sucrose Detachment of tightly wrapped objects by laminating a heat seal layer containing 0.4 to 7 parts by weight of a release agent containing fatty acid ester and/or phospholipid at a weight of 0.4 to 1.3 g/m ² . The present inventors have found that the heat sealability can be improved and the heat sealability at low temperatures can also be improved, thus completing the present invention.

That is, the laminated film for packaging of the present invention is a laminated film for packaging comprising a substrate layer and a heat seal layer directly or indirectly laminated on at least one surface of the substrate layer, The heat seal layer comprises a saturated copolyester and a release agent, the saturated copolyester comprising a first saturated copolyester and a second saturated copolyester having a lower glass transition temperature than the first saturated copolyester. and a saturated copolyester of the release agent, the release agent comprises a sucrose fatty acid ester and/or a phospholipid, the weight of the heat seal layer is 0.4 to 1.3 g/m ² , and the release agent The proportion of the agent is 0.4 to 7 parts by weight per 100 parts by weight of the saturated copolyester. The mold release agent may comprise a sucrose fatty acid ester of HLB 2-8 (especially a sucrose saturated C _12-24 fatty acid ester). The phospholipid may be lecithin. The heat seal layer may be heat-bondable at 100° C. or less. The glass transition temperature of the first saturated copolyester may be 50 to 100°C. The glass transition temperature of the second saturated copolyester may be -30°C or higher and lower than 50°C. The weight ratio of the first saturated copolyester and the second saturated copolyester may be the former/the latter=80/20 to 10/90. The base material layer may contain polyester. The laminated film for packaging may be a film for individually packaging sliced cheese in close contact.

The present invention also includes a package in which an object is packaged with the laminated film for packaging. The article to be packaged may be in close contact with the laminated film for packaging. The object to be packaged is sliced cheese, and may be an individual package of sliced cheese.

In the present invention, on at least one surface of the base material layer, 0 parts by weight of a release agent containing a sucrose fatty acid ester and/or a phospholipid is added to 100 parts by weight of a saturated copolyester combining a plurality of types with different glass transition temperatures. .4 to 7 parts by weight of the heat seal layer is laminated with a weight of 0.4 to 1.3 g/m ² , so that the peelability of tightly packed objects can be improved and the heat sealability at low temperatures can be improved. can also be improved. Moreover, the heat-sealing property at low temperatures can be improved, and the anti-blocking property can also be improved. Therefore, for example, if it is used as an inner film for individual packaging of sliced cheese, the sliced cheese can be easily separated from the body, and high-speed packaging is possible. . Furthermore, it has an appropriate heat-sealing property, so that the sealed package can be easily opened.

FIG. 1 is a schematic process diagram for explaining a method for measuring releasability of sliced cheese in Examples. FIG. 2 is a schematic process diagram for explaining the method for measuring heat-sealability in the examples.

[Base material layer]
The laminated film for packaging of the present invention includes a substrate layer. The substrate layer preferably contains a thermoplastic resin from the viewpoint of flexibility and moldability, and is usually a thermoplastic resin film. Examples of thermoplastic resins include polyolefins, styrene resins, vinyl resins (halogen-containing resins, vinyl ester resins, vinyl alcohol resins, etc.), fluororesins, polyesters, polycarbonates, polyamides, polyurethanes, cellulose esters, and the like. be done. These thermoplastic resins can be used alone or in combination of two or more. Among these thermoplastic resins, polyester is preferable from the viewpoint of excellent adhesion to the heat seal layer.

As polyester, for example, saturated homopolyester such as polyethylene terephthalate (PET), polypropylene terephthalate, polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate can be used. Of these, poly C _2-4 alkylene-C _6-10 arylates such as PET are preferred.

Polyester (especially saturated homopolyester) is preferably a crystalline resin, and has a melting point of, for example, 180 to 300°C, preferably 200 to 280°C, more preferably 240 to 270°C.

In this specification and claims, the melting point and glass transition temperature Tg of a resin can be measured using a differential scanning calorimeter (DSC).

The number average molecular weight (Mn) of polyester (especially saturated homopolyester) can be selected from the range of about 5000 to 1000000 in terms of polystyrene using GPC (gel permeation chromatography), for example 10000 to 500000, preferably 12000 to 300,000, more preferably about 15,000 to 100,000.

The substrate layer may be a single-layer film of the thermoplastic resin film, or may be a laminated film.

The substrate layer may be an unstretched thermoplastic resin film (especially polyester film), or may be a uniaxially or biaxially stretched film. In the case of a biaxially stretched film, the stretching ratios in the film take-up direction (MD direction) and the width direction (TD direction) may each be 1.5 times or more (eg, 1.5 to 10 times). to 8 times, preferably about 2 to 5 times.

The thermoplastic resin film may contain conventional additives in addition to the thermoplastic resin. Commonly used additives include, for example, stabilizers (heat stabilizers, antioxidants, ultraviolet absorbers, etc.), preservatives, bactericides, plasticizers, fillers, release agents, antiblocking agents, water repellents, Lubricants, crystal nucleus growth agents, coloring agents, viscosity modifiers, leveling agents, surfactants, antistatic agents, flame retardants and the like. These additives can be used alone or in combination of two or more. The proportion of the additive may be 30 parts by weight or less (for example, 0.1 to 10 parts by weight) with respect to 100 parts by weight of the thermoplastic resin.

The average thickness of the substrate layer is, for example, about 1 to 100 μm, preferably 5 to 50 μm, more preferably 10 to 30 μm (especially 12 to 20 μm).

In this specification and claims, the average thickness can be measured according to JIS K7130 (1999) A method.

The surface of the substrate layer (particularly, the contact surface with the heat seal layer) may be surface-treated (for example, corona discharge treatment, flame treatment, plasma treatment, ozone or ultraviolet irradiation treatment, etc.).

[Heat seal layer]
The laminated film for packaging of the present invention includes a heat seal layer laminated directly or indirectly on at least one surface of the substrate layer. The heat seal layer contains a saturated copolyester and a release agent. In the present invention, the heat-sealing layer contains a combination of a specific saturated copolyester and a specific release agent, so that both the peelability of the packaged object and the low-temperature heat-sealing property, which are in a trade-off relationship, can be achieved. .

(saturated copolyester)
The saturated copolyester may be a copolymer of dicarboxylic acid and diol, a copolymer of dicarboxylic acid, diol and hydroxycarboxylic acid, a copolymer of hydroxycarboxylic acid, or a copolymer of lactone. .

Examples of dicarboxylic acids include C _8-20 aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2,7-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid and 2,5-naphthalenedicarboxylic acid, adipic acid, Examples include C _4-12 alkanedicarboxylic acids such as azelaic acid and sebacic acid, and C _4-12 cycloalkanedicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid.

Diols include, for example, C _2-10 alkanediols such as ethylene glycol, propylene glycol, butanediol and neopentyl glycol; poly-C _2-4 alkylene glycols such as diethylene glycol and polyethylene glycol; and 1,4-cyclohexanedimethanol. C _4-12 cycloalkanediols, aromatic diols such as bisphenol A, bisphenol A-alkylene oxide adducts, and the like.

Hydroxycarboxylic acids include, for example, p-hydroxybenzoic acid and p-hydroxyethoxybenzoic acid.

Lactones include, for example, _C4-8 lactones such as β-butyrolactone, δ-valerolactone and ε-caprolactone.

The saturated copolyester includes a plurality of types of saturated copolyester prepared by appropriately combining these polymerization components. Specifically, by adjusting the glass transition temperature, the first saturated copolyester, and a second saturated copolyester having a glass transition temperature lower than that of the first saturated copolyester. In the present invention, by combining saturated copolyesters having different glass transition temperatures, it is possible to achieve both heat sealability and releasability at low temperatures.

The glass transition temperature of the saturated copolyester is adjusted to the desired range, and the combination of the polymerization components is not limited. A copolymer using a plurality of types of polymerization components may also be used. The saturated copolyester may be an amorphous polyester.

Such a saturated copolyester may be a copolymer having a poly C _2-4 alkylene-C _6-10 arylate skeleton as a main skeleton _. , a part of C _2-4 alkylene glycol, polyoxy C _2-4 alkylene glycol, C _5-10 alkylene glycol, alicyclic diol (cyclohexanedimethanol, hydrogenated bisphenol A, etc.), aromatic diol (bisphenol A, copolyesters substituted with other diols such as bisphenol A-alkylene oxide adducts), some of the symmetrical aromatic dicarboxylic acids such as terephthalic acid, asymmetric aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, adipic acid, etc. may also be copolyesters substituted with other dicarboxylic acids such as aliphatic C _6-12 dicarboxylic acids of. The molar ratio of the C _2-4 alkylene glycol and the other diol can be selected from the range of the former/latter = about 99/1 to 10/90, for example 95/5 to 20/80, preferably 90/10 to 30. /70, more preferably about 80/20 to 50/50. The molar ratio between the symmetrical aromatic dicarboxylic acid and the other dicarboxylic acid can be selected from the range of the former/latter = about 99/1 to 10/90, for example 95/5 to 20/80, preferably 90/10 to 30. /70, more preferably about 80/20 to 50/50.

The method for adjusting the glass transition temperature of the copolyester is not particularly limited, and as described above, it may be adjusted by appropriately selecting the proportion and type of the copolymerization component, and further polyols (glycerin, trimethylolpropane, trimethylolethane, pentaerythritol, etc.) and/or polyvalent carboxylic acid (trimellitic acid, pyromellitic acid, etc.), and the molecular weight may be adjusted.

The glass transition temperature Tg of the first saturated copolyester may be 50° C. or higher. More preferably, it is about 60 to 80°C (especially 65 to 70°C). If the glass transition temperature of the first saturated copolyester is too low, the sealability may deteriorate, and if it is too high, the heat sealability at low temperatures may deteriorate.

The number average molecular weight (Mn) of the first saturated copolyester can be selected from the range of about 3000 to 50000 in terms of polystyrene using GPC, for example 5000 to 30000, preferably 10000 to 25000, more preferably 15000 to 20000. degree. If the molecular weight is too small, the sealability may deteriorate, and if it is too high, the heat sealability at low temperatures may deteriorate.

The hydroxyl value of the first saturated copolyester is, for example, about 1 to 50 mgKOH/g, preferably about 2 to 30 mgKOH/g, more preferably about 3 to 20 mgKOH/g (especially about 4 to 10 mgKOH/g).

The glass transition temperature Tg of the second saturated copolyester may be less than 50° C., but from the viewpoint of suppressing blocking, for example, −30° C. or more and less than 50° C., preferably −20 to 30° C. (for example, −15 to 20°C), more preferably about -10 to 10°C (especially 0 to 5°C). If the glass transition temperature of the second saturated copolyester is too low, blocking may occur.

The number average molecular weight (Mn) of the second saturated copolyester can be selected from a range of about 5,000 to 100,000 in terms of polystyrene using GPC, for example, 10,000 to 50,000, preferably 15,000 to 30,000, more preferably 20,000 to 25,000. degree. If the molecular weight is too small, blocking may occur.

The hydroxyl value of the second saturated copolyester is, for example, about 1 to 50 mgKOH/g, preferably about 2 to 30 mgKOH/g, more preferably about 3 to 20 mgKOH/g (especially about 4 to 10 mgKOH/g).

The weight ratio of the first saturated copolyester and the second saturated copolyester can be selected from the range of former/latter=90/10 to 5/95, for example, 80/20 to 10/90 (for example, 70/30 to 15/85), preferably 60/40 to 20/80, more preferably 50/50 to 30/70 (especially 45/55 to 35/65). If the proportion of the first saturated copolyester is too low, the sealability may be deteriorated or blocking may occur.

(Release agent)
Release agents include sucrose fatty acid esters and/or phospholipids. In the present invention, the release agent contains a sucrose fatty acid ester and / or a phospholipid, so that the peelability of the tightly packed packaged product can be improved, and the combination with the saturated copolymer polyester improves the peelability and low temperature It can be compatible with sealing performance.

Fatty acids constituting the sucrose fatty acid ester may be saturated fatty acids or unsaturated fatty acids. Saturated fatty acids include, for example, _C4-30 saturated fatty acids such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, and behenic acid. Unsaturated fatty acids include, for example, C _10-30 unsaturated fatty acids such as palmitoleic acid, oleic acid and erucic acid. The sucrose fatty acid ester may be an ester of a single fatty acid or a mixed acid ester (or mixed fatty acid ester, eg mixed fatty acid ester of saturated and unsaturated fatty acids).

Among these fatty acids, C _12-24 saturated or unsaturated fatty acids (eg at least one C _14-22 saturated or unsaturated fatty acid selected from lauric acid, palmitic acid, stearic acid, oleic acid and erucic acid) are preferred, and C _12-24 saturated fatty acids (preferably C _14-22 saturated fatty acids, more preferably C _16-20 saturated fatty acids) such as stearic acid are particularly preferred.

Typical sucrose fatty acid esters include, for example, sucrose saturated fatty acid esters [e.g., mono-sucrose to octacaprylate, mono-sucrose to octalaurate, mono-sucrose to octapalmitate, mono-sucrose mono- to octaesters of sucrose and _C8-24 saturated fatty acids (especially _C10-22 saturated fatty acids) such as octastearate, sucrose mono- to octabehenate], sucrose unsaturated fatty acid esters [e.g. , mono- to octaesters of sucrose and C _12-24 unsaturated fatty acids (especially C _16-22 unsaturated fatty acids) such as sucrose mono- to octaoleic acid esters). These sucrose fatty acid esters may be used alone or in combination of two or more. For example, a mixture of sucrose fatty acid esters with different degrees of esterification may be used.

In particular, sucrose fatty acid esters include sucrose mono- to octa-C12, such as sucrose monostearate, sucrose distearate, sucrose tristearate, sucrose tetrastearate, and sucrose _hexastearate . _-24 saturated fatty acid esters (particularly sucrose mono- to hexa C _14-22 saturated fatty acid esters) and mixtures thereof.

When the sucrose fatty acid ester is a mixture of sucrose fatty acid esters with different degrees of esterification, the monoester content in the sucrose fatty acid ester may be 80% by weight or less, for example 5 to 60% by weight, preferably It is about 8 to 50% by weight (eg, 10 to 40% by weight), more preferably about 12 to 30% by weight (especially 15 to 25% by weight).

The hydrophilic-lipophilic balance (HLB) of the sucrose fatty acid ester can be selected from the range of about 1 to 16, and from the viewpoint of achieving both peelability and low-temperature sealability, for example, 1.5 to 10, preferably 2 to 7. (for example, 2.2 to 5), more preferably about 2.5 to 4 (especially 2.8 to 3.5). In addition, in this specification and claims, the HLB value can be measured according to the Griffin method.

Phospholipids include glycerophospholipids and sphingophospholipids, and glycerophospholipids are preferred because of their excellent releasability. Glycerophospholipids include, for example, phosphatidic acid, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, lysophosphatidylcholine and the like. These glycerophospholipids can be used alone or in combination of two or more. Among these, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and phosphatidylserine are preferred, and phosphatidylcholine is particularly preferred.

Glycerophospholipids may be lecithins derived from natural products such as soybean lecithin and egg yolk lecithin, or may be fractionated lecithins (functionally modified lecithins) in which specific glycerophospholipid concentrations in these lecithins are adjusted.

Among these, fractionated lecithins are preferred, and fractionated lecithins with a high phosphatidylcholine content are particularly preferred. The phosphatidylcholine content in the fractionated lecithin is, for example, 30% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more (for example, about 60 to 80% by weight) from the viewpoint of improving the heat-sealing property at low temperatures. There may be.

Among these, sucrose fatty acid esters are preferable because they have a large effect of improving heat sealability at low temperatures, and sucrose fatty acid esters of HLB 2 to 8 (in particular, HLB 3 to Sucrose-saturated C _12-24 fatty acid esters of 7) are particularly preferred.

The mold release agent may contain other mold release agents in addition to sucrose fatty acid and/or phospholipids. Other release agents include, for example, fatty acid esters, fatty acid amides, propylene glycol fatty acid esters, (poly)glycerin fatty acid esters, sorbitan fatty acid esters, silicone resins, silicone oils and waxes. These other release agents can be used alone or in combination of two or more. The proportion of the other release agent is, for example, 30% by weight or less, preferably 10% by weight or less, more preferably 5% by weight or less, in the release agent.

In the present invention, the total proportion of sucrose fatty acid ester and phospholipid in the release agent may be 50% by weight, for example 70% by weight or more, preferably 90% by weight or more, more preferably 95% by weight or more. and may be 100% by weight of sucrose fatty acid ester and/or phospholipid. If the total ratio of the sucrose fatty acid ester and the phospholipid in the release agent is too small, there is a possibility that the peelability of the closely-packaged product may deteriorate.

Furthermore, it is particularly preferred if the proportion of sucrose fatty acid ester in the release agent is 50% by weight. The proportion of sucrose fatty acid ester in the release agent may be 70% by weight or more, preferably 90% by weight or more, more preferably 95% by weight or more, and 100% by weight of sucrose fatty acid ester (sucrose fatty acid ester only).

In the present invention, the proportion of the release agent (sucrose fatty acid ester and/or phospholipid) should be adjusted to 0.4 to 7 parts by weight with respect to 100 parts by weight of the saturated copolyester. The proportion of the release agent is preferably 0.6 to 5 parts by weight, more preferably 0.8 to 3 parts by weight, and most preferably 1 to 2 parts by weight. , for example, 0.8 to 6 parts by weight, preferably 1 to 5 parts by weight, more preferably 1.5 to 4 parts by weight (especially 2 to 3 parts by weight). If the proportion of the release agent is too small, the peelability of the packaged product will be reduced, and if it is too large, the heat sealability will be reduced.

(other additives)
The heat seal layer may further contain other additives in addition to the saturated copolyester and the release agent. Examples of other additives include additives exemplified as conventional additives added to the thermoplastic resin film of the base material layer. The above additives can be used alone or in combination of two or more. The proportion of other additives may be 30 parts by weight or less, preferably 10 parts by weight or less (for example, 0.1 to 10 parts by weight) per 100 parts by weight of the saturated copolyester.

(Characteristics of heat seal layer)
As described above, the heat seal layer is a combination of a specific copolysaturated polyester and a specific release agent, so heat sealability at low temperatures is possible, preferably 100 ° C. or less (for example, 70 to 100 °C). In addition, not only the heat-sealing property at a low temperature but also the part to be packaged can be stably sealed after sealing, and the opening is easy. Furthermore, despite the excellent sealability, the peelability of the packaged object is also excellent, and even if sliced cheese is sealed and packaged, for example, it is easy to separate when the package is opened.

The heat-sealing layer may be directly or indirectly laminated on at least one surface of the base material layer, and may be laminated on both sides, but is usually laminated on one side. Furthermore, when the heat-seal layer is laminated on one side of the base material layer, the region where the heat-seal layer is laminated may be at least partially laminated, and can be appropriately selected according to the type of package. , sliced cheese, etc., may be laminated on the entire surface of one side.

The weight of the heat seal layer (the weight of one side when laminated on both sides of the substrate layer) should be adjusted to 0.4 to 1.3 g/m ² . The weight of the heat seal layer is preferably 0.42 to 1 g/m ² (eg 0.45 to 0.8 g/m ² ), more preferably 0.5 to 0.7 g/m ² (especially 0.55 to 0.8 g/m 2 ). 0.65 g/m ² ). If the weight is too small, sealing properties such as low-temperature heat-sealing properties will be reduced. .

(anchor layer)
When the heat-sealing layer is indirectly laminated on at least one surface of the base material layer, an adhesive is provided between the base material layer and the heat-sealing layer in order to adjust the adhesiveness between the heat-sealing layer and the base material layer. , an anchor layer may be interposed. The anchor layer may be an easily adhesive layer formed on a commercially available base material layer.

The anchor layer may contain a conventional adhesive component. Usual adhesive components include, for example, vinyl adhesives, polyolefin adhesives, polyamide adhesives, polyester adhesives, urethane adhesives (thermoplastic polyurethane adhesives, two-component curing polyurethane resins, etc.). , cellulose-based adhesives, rubber-based adhesives, and the like. When the substrate layer is a polyester film, the adhesive component may be a polyester-based adhesive such as low-molecular-weight polyester, aliphatic polyester, or amorphous polyester.

The anchor layer may further contain other additives in addition to the adhesive component. Examples of other additives include additives exemplified as conventional additives added to the thermoplastic resin film of the base material layer. The above additives can be used alone or in combination of two or more. The proportion of other additives may be 30 parts by weight or less, preferably 10 parts by weight or less (for example, 0.1 to 10 parts by weight) per 100 parts by weight of the adhesive component.

In the present invention, when the base material layer is a polyester film, the heat seal layer contains a saturated copolyester and has excellent adhesion to the base material layer. Sufficient adhesiveness can be ensured even if the layers are laminated directly. Therefore, it is preferable to laminate the heat seal layer directly on the substrate layer.

The average thickness of the anchor layer is, for example, about 0.01 to 5 μm, preferably 0.05 to 2.5 μm, more preferably about 0.1 to 1.5 μm.

(other layers)
In the laminated film for packaging of the present invention, when the heat seal layer is laminated only on one surface of the substrate layer, a conventional functional layer may be laminated on the other surface. In particular, when packaging an item such as sliced cheese, the laminated film for packaging is usually folded back to seal the item. gluing). Therefore, a release layer and/or an adhesive layer may be laminated as a functional layer for the purpose of adjusting the adhesion between the base material layer and the heat seal layer.

The release layer may contain a release agent exemplified as a release agent for the heat seal layer, and may contain, for example, a curable silicone resin. The release layer may contain additives exemplified as conventional additives added to the thermoplastic resin film of the base layer, and may further contain an antiblocking agent such as silica particles. . The release layer may be formed on a part of the other surface or may be formed on the entire surface. The average thickness of the release layer is, for example, about 0.01 to 5 μm, preferably about 0.05 to 3 μm, more preferably about 0.1 to 2 μm.

The adhesive layer may contain an adhesive component exemplified as the adhesive component of the anchor layer. The adhesive layer is often formed on a partial region of the other surface, and in particular, may be formed on a portion of the region that comes into contact with the heat seal layer on the back surface in the packaged state. The average thickness of the adhesive layer is, for example, about 0.01 to 5 μm, preferably about 0.05 to 3 μm, more preferably about 0.1 to 2 μm.

A printed layer may be laminated as a functional layer for the purpose of decoration. The print layer may be a layer formed of a conventional ink composition containing pigments. The printed layer may be formed on a part of the other surface or may be formed on the entire surface. The average thickness of the printed layer is, for example, about 0.1 to 3 μm, preferably about 0.3 to 2 μm, more preferably about 0.5 to 1.5 μm.

[Laminated film for packaging and package]
The laminated film for packaging of the present invention has excellent heat-sealing properties between the substrate layer and the heat-sealing layer at low temperatures, and the substrate layer and the heat-sealing layer are sealed at a temperature of 90° C. under a load of 1 kg/cm ² for 1 second. The peel strength between layers thermally adhered with may be 40 to 150 g/15 mm, preferably 50 to 130 g/15 mm, more preferably 60 to 120 g/15 mm (especially 80 to 100 g/15 mm). If the peel strength between the layers is too low, the sealability may deteriorate.

The laminated film for packaging of the present invention has excellent peelability (mold releasability) of the heat seal layer from the packaged object, and the peel strength at 5 ° C. from the heat-adhered sliced cheese is 4.2 g / 15 mm or less. It may be, preferably 4 g/15 mm or less, more preferably 3.9 g/15 mm or less (for example, 3.5 to 3.9 g/15 mm). If the peel strength is too high, there is a risk that the peelability from the packaged material will be reduced.

The laminated film for packaging of the present invention is also excellent in transparency, and may have a total light transmittance of 30% or more, preferably 30 to 100%, more preferably 40 to 98% (especially 50 to 95%). %). In this specification and claims, the total light transmittance can be measured according to JIS K7105.

The laminated film for packaging of the present invention can be produced by a conventional method, for example, it may be produced by coating a base layer with a liquid composition for forming a heat-sealable layer, followed by drying. This liquid composition may contain a solvent capable of dissolving or dispersing the saturated copolyester in addition to the saturated copolyester for forming the heat seal layer and the release agent.

Examples of solvents include alcohols (e.g., aliphatic alcohols such as methanol, ethanol, propanol and isopropanol, alicyclic alcohols such as cyclohexanol, etc.), ketones (e.g., dialkyl alcohols such as acetone and methyl ethyl ketone). ketone, cyclohexanone, etc.), esters (methyl acetate, ethyl acetate, butyl acetate, etc.), ethers (chain ethers such as diethyl ether, cyclic ethers such as dioxane, tetrahydrofuran, etc.), hydrocarbons [e.g. group hydrocarbons (hexane, isohexane, heptane, octane, etc.), alicyclic hydrocarbons (cyclohexane, methylcyclohexane, etc.), aromatic hydrocarbons (toluene, xylene, etc.), amides (dimethylformamide, etc.), etc. mentioned. These solvents can be used alone or in combination of two or more. Among these, ketones such as methyl ethyl ketone and aromatic hydrocarbons such as toluene are commonly used, and mixed solvents of ketones and aromatic hydrocarbons are preferred. When ketones and aromatic hydrocarbons are mixed, the proportion of aromatic hydrocarbons is 10 to 100 parts by weight, preferably 20 to 80 parts by weight, more preferably 30 to 100 parts by weight per 100 parts by weight of ketones. It is about 50 parts by weight.

The proportion of the solvent is, for example, 100 to 5000 parts by weight, preferably 300 to 3000 parts by weight, more preferably 500 to 2000 parts by weight (especially 1000 to 1500 parts by weight) with respect to 100 parts by weight of the saturated copolyester. .

As the coating method, conventional coating means such as spray, roll coater, gravure roll coater, knife coater and dip coater can be used. Also, if necessary, a hot melt coater may be used. Further, if desired, the liquid composition may be coated multiple times.

The drying method may be natural drying, but heat drying is preferable from the viewpoint of productivity. The heating temperature may be 50°C or higher, for example, 50 to 150°C, preferably 60 to 130°C, more preferably about 80 to 120°C.

The laminated film for packaging thus obtained can be used for packaging various objects to be packaged. is preferred. Furthermore, since the laminated film for packaging of the present invention can seal the base material layer and the heat seal layer at a low temperature, it is particularly preferable to use it as a film (inner film) for individually packaging sliced cheese in close contact. The planar shape of the film can be appropriately selected according to the type of the item to be packaged, and may be circular, square, or the like. In the case of sliced cheese, it is rectangular.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited by these examples. The materials used in Examples and Comparative Examples are as follows, and the properties of the laminated films for packaging obtained in Examples and Comparative Examples were evaluated by the following methods.

[Materials used]
PET film: “FE2001” manufactured by Futamura Chemical Co., Ltd., thickness 16 μm
First saturated copolyester: "Vylon (registered trademark) 200" manufactured by Toyobo Co., Ltd., Tg 67°C, Mn 17000, hydroxyl value 6 mgKOH/g
Second saturated copolyester: Toyobo Co., Ltd. "Vylon (registered trademark) 50DS", Tg 4 ° C., Mn 23000, hydroxyl value 5 mg KOH / g, solution dissolved in solvent (solid content 41% by weight)
PVDC: vinylidene chloride resin, "PVDC latex L-509" manufactured by Asahi Kasei Corporation
Sucrose fatty acid ester (HLB3): Mitsubishi Chemical Foods Co., Ltd. "Ryoto (registered trademark) sugar ester S-370", HLB about 3, monoester content about 20%
Sucrose fatty acid ester (HLB5): Mitsubishi Chemical Foods Co., Ltd. "Ryoto (registered trademark) sugar ester S-570", HLB about 5, monoester content about 30%
Sucrose fatty acid ester (HLB7): Mitsubishi Chemical Foods Co., Ltd. "Ryoto (registered trademark) sugar ester S-770", HLB about 7, monoester content about 40%
Lecithin A: "SLP-PC70" manufactured by Tsuji Oil Co., Ltd., phosphatidylcholine content 70%
Lecithin B: "SLP-PI Powder A" manufactured by Tsuji Oil Co., Ltd.
Lecithin C: "SLP-White" manufactured by Tsuji Oil Co., Ltd.
Glycerol fatty acid ester: "Ryoto (registered trademark) polyglyester B-100D" manufactured by Mitsubishi Chemical Foods Co., Ltd.
Sorbitan fatty acid ester: Sorbitan trioleate, manufactured by Wako Pure Chemical Industries, Ltd. Stearic acid ester: Tetraglycerin pentaester, manufactured by Sakamoto Pharmaceutical Co., Ltd. "SY Glister TS-3S"
Oleic acid ester: tetraglycerin pentaester, "SY Glister PO-3S" manufactured by Sakamoto Yakuhin Kogyo Co., Ltd.
Condensed ricinoleic acid ester: tetraglycerin ester, "SY Glister CR-310" manufactured by Sakamoto Yakuhin Kogyo Co., Ltd.
Commercially available sliced cheese: “Meiji Hokkaido Tokachi Cheese” manufactured by Meiji Dairies Co., Ltd.

[Mold Releasability (Cheese Releasability)]
Evaluation of releasability of the sliced cheese packaging film was performed by the following method.
(1) Cut the films of Examples and Comparative Examples into a size of 250 mm×100 mm.
(2) Commercially available sliced cheese stored in a refrigerator is taken out of the packaging film and repackaged with the laminated film for packaging obtained in Examples and Comparative Examples. Specifically, as shown in step (A) of FIG. 1, one end of the sliced cheese is aligned with the longitudinal center line (folding line) 1a of the laminated film for packaging 1, and the heat seal layer of the laminated film for packaging 1 is formed. Place sliced cheese on top. Next, after folding the laminated film for packaging 1 along the folding line 1a to sandwich the sliced cheese, as shown in step (B), the three sides of the opening of the folded laminated film were subjected to a load of 1 kg/cm ² and a temperature of 1 kg/cm 2 . The sliced cheese is sealed in the laminated film by heat-sealing at a width of 1 cm (three-point heat-sealing) at 90° C. for 1 second. That is, the sliced cheese 2 is packaged by folding the laminated packaging film 1, and as shown in step (C), the heat-sealed layers facing each other by folding are integrated by thermal bonding of the opening to form a heat-sealed portion 1b. forming
(3) The packaged sliced cheese individual package is placed in an oven with a weight of 300 g placed thereon and heated at 70° C. for 3 minutes.
(4) The heated sliced cheese individual packages are left in a refrigerator (5°C) for one hour.
(5) Take out the sliced cheese individual packaging that has been left in the refrigerator (5 ° C.) for one hour, and along the longitudinal direction of the laminated film (laminated film before folding) as shown by the broken line shown in step (C) in FIG. Cut into 15mm width.
(6) The heat-sealed portion 1b of the sliced cheese individual package cut to a width of 15 mm (the portion where the laminated films are in close contact with each other due to the folding of the laminated film) is peeled off by hand (with the heat-sealed portion 1b removed in advance, the tester ), using a tensile tester (“AGS-X” manufactured by Shimadzu Corporation), a load is applied to the peeled film edge at a tensile speed of 300 mm / min, and the laminated film is peeled off from the sliced cheese. measure the force required to Furthermore, it is visually observed whether sliced cheese adheres to the peeled laminated film.

[Thermal adhesion strength (heat seal strength)]
Evaluation of the thermal adhesive strength at low temperature of the laminated film for packaging was performed without sandwiching the cheese between the laminated films, as shown below. The reason for this is that when the cheese is sandwiched between the laminated films, a slight amount of the cheese intervenes between the laminated films of the heat-sealed portion, resulting in variations in the thermal adhesive strength value.
(1) Cut the laminate film for packaging obtained in Examples and Comparative Examples into a size of 250 mm×100 mm.
(2) The laminate film for packaging was folded and heat-sealed at one point in the vicinity of the folding line in the same manner as in the evaluation of cheese peelability, except that sliced cheese was not sandwiched. Specifically, as shown in step (a) of FIG. 2, the laminated film for packaging 11 is folded along the folding line 11a, and as shown in step (b), a 10 mm gap is provided from the folding line 11a, and the folded film is folded along the folding line. They are heat-sealed in parallel with a width of 1 cm (single-point heat-sealing) to form a heat-sealed portion 11b as shown in step (c).
(3) Cut the folded laminated film to a width of 15 mm along the longitudinal direction of the laminated film (laminated film before folding) along the dashed line shown in step (c) of FIG.
(4) The open end of the laminated film cut to a width of 15 mm (the end on the opposite side or the opposite side of the folded end) is set in a tensile tester, and the peel strength (g /15 mm).

Examples 1-13
Mix 40 parts by weight of the first saturated copolyester, 60 parts by weight of the second saturated copolyester (converted to solid content) and 0.5 to 5 parts by weight of the release agent shown in Table 1, and dissolve in methyl ethyl ketone and toluene. The solution (solvent amount in the solution: 860 parts by weight of methyl ethyl ketone, 340 parts by weight of toluene) was applied to one side of the PET film so that the dry weight was 0.6 to 1.3 g/m ² , and the temperature was maintained at 100°C for 30 seconds. After drying, a laminated film for packaging sliced cheese having a heat adhesive layer (heat seal layer) on one side was produced.

Comparative Examples 1-11
A mixed resin of 40 parts by weight of the first saturated copolyester and 60 parts by weight of the second saturated copolyester or PVDC is mixed with 0.3 to 10.0 parts by weight of the release agent shown in Table 1, and methyl ethyl ketone is mixed. and a solution dissolved in toluene (amount of solvent in solution: 860 parts by weight of methyl ethyl ketone, 340 parts by weight of toluene) was applied to one side of a PET film so that the dry weight was 0.3 to 1.5 g/m ² , and 100 C. for 30 seconds to produce a laminated film for packaging sliced cheese having a heat adhesive layer (heat seal layer) on one side.

Table 1 shows the evaluation results of the laminated films obtained in Examples and Comparative Examples.

As is clear from the results in Table 1, the laminated films obtained in Examples were excellent in cheese peeling property and had an appropriate range of heat seal strength at low temperatures. In particular, the examples in which the sucrose fatty acid ester was blended were able to stably balance both characteristics compared to the examples in which lecithin was blended.

On the other hand, the laminated films obtained in the comparative examples could not satisfy both properties.

In addition, the laminated film obtained in Comparative Example 4 had too high a heat seal strength and was difficult to open. Blocking has occurred.

Furthermore, the laminated film obtained in Comparative Example 5 had a mottled pattern and poor appearance.

INDUSTRIAL APPLICABILITY The laminated film for packaging of the present invention is excellent in releasability (or releasability) from the object to be packaged, and is useful for packaging various objects to be packaged. That is, the laminated film for packaging of the present invention can be used as a packaging film for packaging (and unpacking) by bringing the heat-seal layer into contact with an object to be packaged. The object to be packaged is not particularly limited, and depending on the type and function of the base material layer (e.g., gas barrier property, etc.), for example, foods [e.g., processed meat products (ham, sausage, bacon, grilled pork, chicken, etc.) ), steamed buns (steamed buns, Chinese buns, etc.), rice balls, confectionery, sweet pastries, castella, sliced cheese, chocolate, caramel, bean paste, etc.], pharmaceuticals or chemicals (e.g., medicines or medicines, etc.), etc. can. The packaged item may be solid, semi-solid or fluid at room temperature. In addition, the form of packaging may be individual packages such as steamed buns, sponge cake, sliced cheese, and the like.

Among these objects to be packaged, the laminated film for packaging of the present invention can be suitably used as a film for packaging food (food packaging film), and in particular, has a melted state and fluidity when heated. It can be preferably used for foods (sliced cheese, chocolate, kamaboko, etc.) that are tightly packed after cooling and solidifying, and sliced cheese is particularly preferably used.

DESCRIPTION OF SYMBOLS 1, 11... Laminated film for packaging 1a, 11a... Folding line 1b, 11b... Heat seal part 2... Sliced cheese

Claims (8)

A laminated film for packaging comprising a substrate layer and a heat seal layer laminated directly or indirectly on at least one surface of the substrate layer,
The heat seal layer contains a saturated copolyester and a release agent,
The saturated copolyester comprises a first saturated copolyester and a second saturated copolyester having a lower glass transition temperature than the first saturated copolyester,
The glass transition temperature of the first saturated copolyester is 50 to 100° C., the glass transition temperature of the second saturated copolyester is -30° C. or more and less than 50° C.,
The weight ratio of the first saturated copolyester and the second saturated copolyester is the former/latter = 80/20 to 10/90,
The release agent contains a sucrose fatty acid ester of HLB 2-8,
The heat seal layer has a weight of 0.4 to 1.3 g/m ² ,
A laminated film for packaging, wherein the release agent is present in an amount of 0.4 to 7 parts by weight per 100 parts by weight of the saturated copolyester. 2. The laminated film for packaging according to claim 1, wherein the sucrose fatty acid ester of HLB 2-8 is a sucrose saturated C _12-24 fatty acid ester. The laminated film for packaging according to claim 1 or 2, wherein the heat-sealable layer is heat-bondable at 100°C or less. The laminated film for packaging according to any one of claims 1 to 3 , wherein the base layer contains polyester. The laminated film for packaging according to any one of claims 1 to 4 , which is a film for individually packaging sliced cheese in close contact. A package in which an object is packaged with the laminated film for packaging according to any one of claims 1 to 5 . 7. The package according to claim 6 , wherein the item to be packaged is in close contact with the laminated packaging film. 8. The package according to claim 6 or 7 , wherein the item to be packaged is sliced cheese, and the sliced cheese is individually packaged.

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