JP2019171792A - Sealant film and packaging material - Google Patents

Abstract

To provide a sealant film that has excellent adhesion through heat sealing to a mold-releasable PET, can easily be peeled and exhibits a fine peeling appearance when opening a package hermetically sealed with a molded product by heat sealing and has good transparency.SOLUTION: The sealant film is composed of a seal layer 10 and a peeling layer 20 in contact with each other. The seal layer 10 comprises a polyester-based resin having a melt viscosity of 5,000 Pa sec or less and a storage elastic modulus E' of 1,000 MPa or more or the polyester-based resin and a surfactant and the peeling layer 20 comprises a modified ethylene-based copolymer having a melt viscosity of 1,500 Pa sec or less and a storage elastic modulus E' of 500 MPa or less. The surfactant is an anionic surfactant or an anionic surfactant and a nonionic surfactant. The content ratio of each of the anionic surfactant and the nonionic surfactant to the seal layer 10 is 0.1 mass% to less than 3.0 mass%.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sealant film and a packaging material used for heat sealing.

  Conventionally, container bottoms made of polyolefin resin have been used for individual packaging cup-shaped products that contain jelly, steamed rice bowls, side dishes, etc., as well as blister packs that contain medical supplies such as deep-drawn packaging and disposable syringes, daily necessities, and stationery. As the lid material, a film including a sealing layer made of a polyolefin resin having a melting point similar to that of the container bottom material has been used. For example, polyolefin resins such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer (EVA), and ethylene-acrylic acid ester copolymer have been widely used for the sealing layer of the lid film.

  In recent years, the bottom material of food packaging containers is also required to have high functionality, and amorphous polyethylene terephthalate (A-PET) from the viewpoints of transparency, heat resistance, oxygen gas barrier properties, non-adsorbability, fragrance retention, moldability, etc. In order to heat-seal the cover material against these, a film using a polyester resin as a sealing layer is used.

  Furthermore, in order to improve the sheet punching property and mold releasability when processing the A-PET sheet into a container bottom material, and the resistance against taking out one container bottom material from a plurality of stacked container bottom materials. In order to improve scratch resistance and to make it easy to take out contents such as foods, container bottom materials made of a releasable A-PET sheet coated with silicone have been frequently used. Therefore, when a film using the above-mentioned general-purpose polyolefin resin or polyester resin as the sealant film for the lid material is used, sufficient adhesion cannot be obtained due to the releasing action of silicone, resulting in a seal failure. . Therefore, the sealant film for the lid material is required to have a function having sufficient seal adhesion even when the release agent silicone is present on the surface of the container bottom material. On the other hand, even if the seal adhesion is strong, it is also important to provide an easy-open function that can be opened with a light force by human hands when opening.

As an easily openable film for a polyester resin container, for example, Patent Document 1 discloses a heat-sealable polyester layer having a breaking elongation of 30 to 100% and a thickness of 15 μm or less, and a copolymer resin of olefin and maleic anhydride. A three-layer coextruded film of a film layer and a polyolefin layer is disclosed.
However, in order to obtain the polyester constituting the heat-sealable polyester layer, it is an amorphous linear shape having a very low glass transition temperature for the purpose of improving the heat-sealability in a fused state with the target adherent polyester. Since saturated polyester, for example, Byron GM-900 (glass transition temperature-20 ° C.) manufactured by Toyobo Co., Ltd. is mixed, the film becomes opaque.

Patent Document 2 discloses an easy-open packaging material that is delaminated by a sealing layer containing crystalline polyester A having a glass transition temperature of 40 ° C. or lower and amorphous polyester B having a glass transition temperature of 45 ° C. to 90 ° C. ing.
However, in the case of such a seal layer, since the elastic modulus of the seal layer is low, the seal layer expands and breaks due to the stress at the time of opening and peeling, and the container bottom material generates a film residue and fluffing of the seal layer resin. There is a concern that

Patent Document 3 includes an ethylene-based copolymer of ethylene and (meth) acrylic acid alkyl ester or vinyl ester, a seal layer and a support layer containing a polyester resin, and an interface between the seal layer and the container body. An easy-open film that peels is disclosed.
However, in a seal layer containing an ethylene copolymer, adhesion cannot be obtained with respect to a PET container coated with a release agent. Also, since it is difficult to balance the seal adhesion strength between the seal layer and the container body and the interlayer adhesion strength between the seal layer and the support layer, the seal layer cannot be peeled off at the interface between the seal layer and the container body as intended, Elongation or film residue is likely to occur.

Patent Document 4 discloses a laminate layer (A) containing polyolefin as a main component and containing no antifogging agent, an intermediate layer (B) containing polyolefin and an antifogging agent, and an adhesive layer containing acid-modified polyolefin as a main component ( C), a multilayer film in which a heat-seal layer (D) containing a polyester resin and an antifogging agent is laminated in the order of (A) / (B) / (C) / (D). ing.
However, as the resin for the heat seal layer (D), only a wide variety of amorphous or low crystalline polyester resins are listed. For example, amorphous polyethylene terephthalate (Eastman) described in Example 1 is used. Chemical PETG6763) has insufficient seal adhesiveness with silicone-coated PET, and there is a concern that the sealing of the contents may be incomplete. In addition, when the crystalline polyester described in Example 8 (Toyobo's Byron GM-913) is used, the film becomes opaque, and the heat-seal layer expands when the container is opened from the bottom of the container, resulting in a film residue. .

Patent Document 5 discloses a sealing film including a sealing layer (A) made of an amorphous or low crystalline polyester coated with or containing an antifogging agent, an intermediate polyester layer (B), and an adhesive resin layer (C). Has been. Further, the intermediate layer (B) prevents the antifogging agent of the seal layer (A) from moving to the adhesive resin layer (C) and lowers the interlayer strength, and the intermediate layer (B ), The intermediate layer (B) is essentially required because it is designed with the technical idea of peeling the seal layer (A) having a high elongation at break from the adherend.
However, since the intermediate layer is essentially essential and the number of layers is large, the corresponding equipment is necessary, and due to the idea of peeling the seal layer from the adherend, film residue and fluffing of the seal layer are derived. There are concerns.

Japanese Patent Laid-Open No. 4-94933 JP 2001-328221 A JP 2006-116700 A WO2015 / 046132 JP 2004-25825 A

The present invention has been made in view of the above problems, and is a releasable polyester resin molded body (hereinafter referred to as “release PET”) in which a release agent such as silicone is applied to a surface of a sheet made of a polyester resin. It can be easily peeled when opening a package sealed with a molded body and a heat seal, and the resin remains at the opening after peeling. Provided is a sealant film which can form a beautiful peeling surface (peeling appearance) without causing film residue and fuzzing, and has good transparency.
In addition, a molded object means the film, sheet | seat, container bottom material, plate etc. which shape | mold a polyester-type resin. The molded body may be entirely formed of a polyester-based resin, the inner layer on the content side may be formed of a polyester-based resin in a multilayer structure, or at least heat-sealed with a sealant film. The seal portion may be formed of a polyester resin.

  As a result of intensive studies, the present inventors have made the sealing layer have a function capable of firmly heat-sealing with the release PET, and the release layer is disposed in direct contact with the seal layer, and the release layer has a layer interface with the seal layer. The following sealant film having a function capable of peeling (interlaminating) and a packaging material using the film have been devised, and the above problems have been solved.

The first aspect of the present invention is a sealant film having at least a seal layer and a release layer,
The seal layer and the release layer are in contact with each other,
Polyester resin in which the sealing layer has a melt viscosity of 5,000 Pa · sec or less at a set temperature of 180 ° C., a shear rate of 100 sec ⁻¹ , and a storage elastic modulus E ′ at 20 ° C. of 1,000 MPa or more, or the polyester Consisting of a resin and a surfactant,
The release layer is composed of a modified ethylene copolymer having a melt viscosity at a set temperature of 180 ° C., a shear rate of 100 sec ⁻¹ of 1,000 Pa · sec or less, and a storage elastic modulus E ′ at 20 ° C. of 1,500 MPa or less. ,
The surfactant is an anionic surfactant or an anionic surfactant and a nonionic surfactant, and each content ratio of the anionic surfactant and the nonionic surfactant to the seal layer is 0. It is a sealant film characterized by being not less than 1% by mass and less than 3.0% by mass.

  In the first invention, the breaking elongation of the sealing layer is preferably 10% or less.

  In the first aspect of the present invention, the polyester resin is preferably an amorphous resin.

  In 1st this invention, it is preferable to have a support layer on the opposite side to the surface which the sealing layer of the said peeling layer contacts.

  The haze of the sealant film of the first invention is preferably 20% or less.

2nd this invention is a packaging material formed by heat-sealing the sealant film of 1st this invention, and the container bottom material which consists of polyester-type resin.
“Container bottom material made of polyester resin” means that at least a portion to be heat-sealed with a sealant film is formed of polyester resin. For example, a container made of a laminated film having a heat seal layer made of polyester resin Including bottom material. Moreover, it is preferable that this polyester-type resin is mold release PET with which silicone was apply | coated, and the sealant film of this invention exhibits favorable heat-sealing property also with respect to this mold release PET.

According to the present invention, it is possible to provide a sealant film that can be firmly adhered to a polyester-based resin molded body (for example, a container bottom material) coated with a silicone release agent, so that the content is moisture such as yogurt, jelly, sugar beet, etc. Even if there is a possibility that the seal setting part may get wet or a minute contaminant may exist in the seal setting part, the sealant film and the molded body are surely sealed. be able to.
Also, when opening after packaging, it has easy peelability (easy peel property) that allows delamination at the interface between the seal layer and the release layer. Therefore, when taking out the contents, the contents can be taken out without being caught at the seal portion. In addition, since the resin of the seal layer is hardly broken, it is possible to prevent the broken resin from being mixed into the contents as a foreign substance.
Furthermore, since it is a transparent sealant film, the contents are highly visible, and it is effective in enhancing the aesthetics of the product and improving the product value.

(A)-(b) is a schematic diagram which shows the layer structure of the sealant film of this invention.

  Hereinafter, the sealant film of the present invention (hereinafter referred to as “the present film”) as an example of the embodiment of the present invention will be described. However, the scope of the present invention is not limited to the embodiments described below.

<Sealant film>
As shown in FIGS. 1A to 1C, the sealant film 100 of the present invention has at least a seal layer 10 and a release layer 20.

(Sealing layer 10)
The sealing layer 10 of the present film is disposed at the position of the outermost surface on one side of the present film for the purpose of heat sealing with the adherend. Further, the sealing layer 10 of the present film is a polyester resin having a melt viscosity of 5,000 Pa · sec or less at a set temperature of 180 ° C., a shear rate of 100 sec ⁻¹ , and a storage elastic modulus E ′ of 20 MPa at 1,000 ° C. or more. Consists of.
Since the seal layer 10 has a function of having both a seal adhesiveness and an easy-opening property with a polyester resin molded body to which a silicone release agent is applied (hereinafter sometimes referred to as “release PET”). First, in order to require sufficient seal adhesion with respect to the release PET, the viscosity of the polyester-based resin constituting the seal layer 10 in a high-temperature molten state may be lowered. Secondly, when the seal layer 10 is opened in a room temperature environment, the seal layer 10 is stored in the release layer 20 in order to be peeled off at the interface with the release layer 20 while remaining in close contact with the release PET. It is better to increase the elastic modulus.

The polyester resin constituting the seal layer 10 has a melt viscosity at a set temperature of 180 ° C. and a shear rate of 100 sec ⁻¹ of preferably 5,000 Pa · sec or less, more preferably 4,000 Pa · sec or less, and 3,500 Pa. -Sec or less is more preferable. 180 ° C. is an example of a general-purpose sealing temperature condition when the polyester-based resin molded body and the sealant film are heat-sealed. Therefore, the conditions necessary for defining the characteristics of the resin constituting the sealing layer 10 When the heat sealing is performed under a lower temperature condition, it is preferable that the melt viscosity at a set temperature of 160 ° C. and a shear rate of 100 sec ⁻¹ is in the above range, for example.

Although the mechanism is not known, the polyester resin of the sealing layer 10 is melted when the film is heated in the heat sealing process because the melt viscosity at the heat sealing temperature is 5,000 Pa · sec or less. Thus, it is considered that the surface area of the adherend is wetted and spreads to every corner of the unevenness, and the contact surface area can be maximized, the anchor effect function can be achieved, and high adhesion can be achieved. Moreover, when the melt viscosity is 5,000 Pa · sec or less, the silicone of the release PET is easily taken into the polyester resin layer melted in the heat seal, and the polyester resin of the seal layer 10 and the container bottom material It is conceivable that the polyester resin is easily fused. Although a minimum is not specifically limited, 500 Pa.sec or more is preferable from the relationship with the melt tension required at the time of film forming.
The melt viscosity of the polyester-based resin was measured based on JIS K 7199 using a capillary die having an inner diameter of 1 mm and a length of 10 mm under a set temperature of 180 ° C. and a shear rate of 100 sec ⁻¹ .

The 20 ° C. storage elastic modulus E ′ of the polyester resin constituting the seal layer is preferably 1,000 MPa or more, and more preferably 2,000 MPa or more. When it is 1,000 MPa or more, when the film is peeled off from the release PET in the room temperature environment and opened, the seal layer is firmly adhered to the release PET and peeled off at the layer interface with the release layer, and then opened. Can do. Since the difference in storage elastic modulus between the seal layer 10 and the release layer 20 is 500 MPa or more, the interlayer strength between the seal layer 10 and the release layer 20 is sufficiently smaller than the adhesion strength between the seal layer 10 and A-PET (release PET). Thus, the delamination between the seal layer 10 and the release layer 20 is improved. Although an upper limit is not specifically limited, 5,000 Mpa or less is preferable from the point of the softness | flexibility of a film and the difficulty of a crack.
The storage elastic modulus of the polyester-based resin was calculated as a storage elastic modulus at 20 ° C. by measuring the temperature dispersion of a tensile vibration having a frequency of 10 Hz based on the JIS K 7244-4 method.

The breaking elongation of the seal layer 10 is preferably 10% or less. When the film is 10% or less, when the film is peeled off at the interface between the peeling layer 20 and the sealing layer 10, the sealing layer 10 that is in close contact with the adherend is not easily stretched by being pulled toward the peeling layer. Therefore, easy peelability becomes good. The lower limit is not particularly limited, but is generally 1% or more.
The breaking elongation of the seal layer 10 was measured at a speed of 200 mm / sec based on JIS K7127. Further, the measurement may be performed by peeling off the sealing layer 10 from the film 100 and measuring the sealing layer 10 alone, or by molding the polyester resin constituting the sealing layer 10 into a single film.

  The melt viscosity, storage elastic modulus, and elongation at break of the polyester resin are each affected by the copolymer composition, molecular weight, molecular weight distribution, molecular structure such as branching, and three-dimensional structure such as crystallinity and orientation.

The intrinsic viscosity of the polyester resin (IV) is preferably not more than 0.10 m ³ / kg in terms of adhesion and co-extruded film formability for the release PET, more preferably at most 0.09 m ³ / kg.
The glass transition temperature of the polyester-based resin is preferably 20 ° C. or higher and 100 ° C. or lower, and more preferably 30 ° C. or higher and 80 ° C. or lower from the viewpoint of delamination with the seal layer 20. If the glass transition temperature of the polyester-based resin is 20 ° C. or higher, the resin is glassy at room temperature. Therefore, the peeling behavior between the seal layer 20 and the peeling layer 10 becomes good, and the film residue hardly occurs.

The type of polyester resin constituting the seal layer 10 of the present film is not particularly limited as long as it satisfies the above-described physical property ranges of melt viscosity and storage modulus. From the viewpoint of these physical properties, amorphous polyester or low crystalline polyester is preferable. For example, as the dibasic acid component, phthalic acid, terephthalic acid, isophthalic acid, adipic acid, sevansinic acid, naphthalenedicarboxylic acid, 4,4′-diphenylsulfone dicarboxylic acid, 4,4′-biphenyldicarboxylic acid, 1,4- Cyclohexanedicarboxylic acid, 1,3-phenylenedioxydiacetic acid, and structural isomers thereof, dicarboxylic acid such as malonic acid, succinic acid, adipic acid or derivatives thereof, p-hydroxybenzoic acid, p-hydroxybenzoic acid esters A component selected from oxyacids such as glycolic acid or derivatives thereof, and glycol components such as ethylene glycol, diethylene glycol, neopentyl glycol, hexanediol, 1,2-propanediol, 1,3-propanediol, 1,4 -Butanediol, pentamethyle One or a plurality of components selected from aliphatic glycols such as glycol, alicyclic glycols such as cyclohexanedimethanol, and aromatic dihydroxy compound derivatives such as bisphenol A and bisphenol S. The dibasic acid component and the glycol component can be transesterified or esterified, and then obtained by a melt polycondensation reaction.
The sealing layer 10 may be formed using two or more kinds of polyester resins. In that case, each resin has a melt viscosity of 5,000 Pa · s at a set temperature of 180 ° C. and a shear rate of 100 sec ⁻¹ . The one having a storage elastic modulus E ′ of 1,000 MPa or more at 20 ° C. or less is used.
From the viewpoint of the transparency of the sealing layer 10 and thus the transparency of the film, it is preferable to form the sealing layer 10 using one kind of polyester resin. Moreover, when using 2 or more types of polyester resins, it is preferable to combine highly compatible polyester resins. When using two or more types of polyester resins that are incompatible with each other, it is preferable to combine the types having a small difference in refractive index, or to disperse the resins by combining polyester resins having a small viscosity difference at the extrusion molding temperature. It is preferable to make it good.

  Among these, an amorphous polyester resin is preferable from the viewpoint of sealing properties with respect to the release PET. Further, polyethylene terephthalate (hereinafter sometimes referred to as “IPA copolymerized PET”) comprising an isophthalic acid component and a terephthalic acid component as the dibasic acid component and ethylene glycol as the glycol component is preferred, and transparency and moldability are preferred. Is also good.

The seal layer 10 of the present film can contain a surfactant.
When this film is used as a cover for other bottom material containers, for example, in the case of water such as jelly or steamed tea in the bottom material container, or a product packaged in a full or full form, the cover material Since this film does not require antifogging properties, the seal layer does not contain a surfactant. On the other hand, when the content contains some moisture and there is a space between the content in the bottom material container and the lid, the content-side surface of the lid, that is, the seal, depends on the outside air temperature. The surface of the layer 10 is clouded by the moisture of the contents, and the visibility of the contents is deteriorated.

  Therefore, conventionally, the application of an antifogging agent to the surface of the sealing layer and the mixing of the antifogging agent into the polyester resin layer constituting the sealing layer as in Patent Document 5 have been proposed. The kneading of the antifogging agent into the system resin layer has the disadvantage that the seal layer becomes opaque and sufficient antifogging properties are not exhibited from the point of compatibility of both. Therefore, also in patent document 5, in the Example, the method of apply | coating an antifogging agent solution to the polyester resin layer surface is used instead of kneading an antifogging agent.

  In this film, the antifogging property and transparency of the film can be combined by containing a specific type of surfactant with respect to the polyester resin having a predetermined melt viscosity and storage elastic modulus. Furthermore, it has an excellent antifogging property (low temperature antifogging property) that the film surface does not become clouded even at low temperature storage in a refrigerator or the like.

In general, a nonionic surfactant is often used as an antifogging agent for a resin film for packaging from the viewpoint of compatibility with a resin, but a seal composed of a polyester resin having the above-mentioned melting characteristics and elastic characteristics. As the surfactant to be kneaded into the layer, an anionic surfactant is preferable.
As the anionic surfactant, alkylsulfonic acid, alkylarylsulfonic acid, arylsulfonic acid, alkylsulfuric acid, alkylarylsulfuric acid, alkali metal salt of arylsulfuric acid, or alkaline earth metal salt is desirable. Among them, metal salts such as alkylsulfonic acid, alkylarylsulfonic acid, alkylsulfuric acid sodium, potassium, lithium, magnesium, or calcium having 8 to 30 carbon atoms, more preferably 12 to 16 carbon atoms, are preferable. It is preferable to use a salt. In addition, these anionic surfactants may be used alone or in combination of two or more.

  In order to improve the transparency of the sealing layer 10 and thus the film 100, it is preferable to use an anionic surfactant and a nonionic surfactant in combination. Specifically, increasing the content of an anionic surfactant in the seal layer to improve anti-fogging properties may reduce seal strength, peelability, and transparency. By using an agent and a nonionic surfactant in combination, it is possible to combine antifogging properties with seal strength, peelability, and transparency.

As a nonionic surfactant used for this film, an ethylene oxide adduct and polyethylene glycol are preferable, and 1 type may be used and 2 or more types may be used.
The ethylene oxide adduct is a compound in which ethylene oxide is added to alcohol, fatty acid, esters thereof, fats and oils, etc., and by adjusting the chain length of the polymerized portion of ethylene oxide, a desired lipophilic hydrophilic parameter ( HLB). Specific examples of the ethylene oxide adduct include polyoxyethylene alkyl ether, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene fatty acid ester and the like. Polyethylene glycol has a structure in which ethylene glycol is polymerized and has a structure similar to that of polyethylene oxide. Polyethylene glycol has a molecular weight of up to about 20,000, whereas polyethylene oxide has a molecular weight of tens of thousands or more.
Among them, the use of polyoxyethylene alkyl ether is preferable in terms of combining antifogging properties and transparency in combination with an anionic surfactant, and the alkyl group has more preferably 8 to 30 carbon atoms, and 12 to 12 carbon atoms. 16 is more preferred.

In the case where only an anionic surfactant is used as the surfactant, or when the anionic surfactant and the nonionic surfactant are used in combination, the anionic surfactant and the nonionic surfactant in the seal layer 10 are used. Each content ratio of is preferably 0.1% by mass or more and less than 3% by mass. The lower limit is more preferably 0.2% by mass or more, further preferably 0.3% by mass or more, and the upper limit is more preferably 2.5% by mass or less. When the content of the surfactant is 0.1% by mass or more, even when the moisture-containing contents are packaged with this film and stored in a refrigerated environment, the moisture inside the package will drop on the surface of the sealant film. It is easy to form a uniform water film. Thus, since it is excellent in anti-fogging property from normal temperature to low temperature, the visibility of the content is favorable, and the aesthetics of goods are used suitably. Moreover, since the antistatic effect is also excellent, troubles in film formation such as blocking and frictional charging can be suppressed. If it is less than 3% by mass, the transparency tends to be good.
In addition, since an anionic surfactant has low compatibility with the polyester-based resin constituting the seal layer 10, when the content is 3% by mass or more, transparency, seal strength, and peelability are caused by bleeding out of the anionic surfactant. May decrease. On the other hand, since the nonionic surfactant has a relatively high compatibility with the polyester-based resin, transparency and sealing strength can be achieved even if less than 3% by weight of the nonionic surfactant is added to less than 3% by weight of the anionic surfactant. In addition, it is possible to achieve both releasability and improved antifogging property.
When both an anionic surfactant and a nonionic surfactant are contained, the content ratio of the anionic surfactant and the nonionic surfactant is preferably about 1: 0.5 to 1: 1.

  The compounding of the surfactant into the polyester resin constituting the sealing layer 10 can be performed by a known method. For example, a master surfactant having a high surfactant concentration prepared by kneading a polyester resin and a surfactant in advance with a twin screw extruder or the like and a polyester resin may be dry blended and used at a predetermined concentration. You may use the produced masterbatch. Further, in an extruder for forming a film, the polyester resin and the surfactant may be directly dry blended. From the viewpoint of the dispersibility of the surfactant with respect to the polyester-based resin, it is preferable to prepare a master batch with a twin screw extruder.

(Peeling layer 20)
The release layer 20 of the present film exists in direct contact with the seal layer 10, has a melt viscosity at a measurement temperature of 180 ° C., a shear rate of 100 sec ⁻¹ of 1500 Pa · sec or less, and a storage elastic modulus E ′ at 20 ° C. of 500 MPa or less. It consists of a certain modified ethylene copolymer.
First, the release layer 20 needs to have a low viscosity in a high-temperature molten state because it requires sufficient adhesion with the seal layer 10 during film formation. Secondly, since the release layer 20 is peeled from the interface between the two layers with respect to the seal layer 10 that is kept in close contact with the release PET at the time of opening in a room temperature environment, the storage elastic modulus of the release layer is changed to the seal layer. On the other hand, it should be lower than a predetermined value.

The melt viscosity of the modified ethylene copolymer constituting the release layer 20 at a measurement temperature of 180 ° C. and a shear rate of 100 sec ⁻¹ is preferably 1,500 Pa · sec or less, and more preferably 1,000 Pa · sec or less. 180 ° C. is an example of general-purpose sealing temperature conditions when heat-sealing the polyester-based resin molded body and the sealant film, and therefore is a necessary condition for defining the characteristics of the resin constituting the release layer 20. When the heat sealing is performed under a lower temperature condition, it is preferable that the melt viscosity at a set temperature of 160 ° C. and a shear rate of 100 sec ⁻¹ is in the above range, for example.
When the melt viscosity is 1,500 Pa · sec or less, the interlayer adhesion of the release layer 20 to the seal layer 10 is improved when the film is formed. The lower limit is not particularly limited, but is preferably 10 Pa · sec or more from the viewpoint of delamination with the seal layer.

  The 20 ° C. storage elastic modulus E ′ of the modified ethylene copolymer constituting the release layer 20 is preferably 500 MPa or less, more preferably 300 MPa, and even more preferably 100 MPa or less. When it is 500 MPa or less, the release layer 20 peels off at the layer interface with the seal layer 10 while the seal layer 10 is firmly adhered to the release PET when the film is peeled off from the release PET and opened in a room temperature environment. Can be opened easily. When the storage elastic modulus of the release layer 20 is 500 MPa or more lower than the storage elastic modulus of the seal layer 10, the interlayer strength between the seal layer 10 and the release layer 20 is sufficiently smaller than the adhesion strength between the seal layer 10 and A-PET. And the peelability between the release layer 20 are improved. Although a minimum is not specifically limited, Generally 10 Mpa or more is preferable.

The melt viscosity and storage elastic modulus of the modified ethylene copolymer are affected by the copolymer composition, degree of modification, molecular weight, molecular weight distribution, molecular structure such as branching, and three-dimensional structure such as crystallinity and orientation, respectively. .
The melt viscosity of the modified ethylene copolymer was measured under the conditions of a set temperature of 180 ° C. and a shear rate of 100 sec ⁻¹ using a capillary die having an inner diameter of 1 mm and a length of 10 mm based on JIS K 7199.
As for the storage elastic modulus of the modified ethylene copolymer, the storage elastic modulus at 20 ° C. was calculated by temperature dispersion measurement of tensile vibration at a frequency of 10 Hz based on JIS K7244-4 method.

Preferably the density of the modified ethylene-based copolymer is 920 kg / ^{m 3} or less, 910 kg / ^{m 3} or less is more preferable. When the density is 920 kg / m ³ or less, the crystal component in the modified ethylene copolymer is reduced, and the coextrusion adhesion with the adjacent layer is improved.

The type of the modified ethylene copolymer constituting the release layer 20 of the present film is not particularly limited as long as it satisfies the above-described physical property ranges of melt viscosity and storage modulus.
Examples of the monomer used for the ethylene copolymer include alkenes having 2 to 8 carbon atoms such as ethylene, propylene, and butene, and may contain a (meth) acrylic acid ester component. (Meth) acrylic acid ester components include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, (meth) acrylic acid Examples include octyl, decyl (meth) acrylate, lauryl (meth) acrylate, octyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, and the like. Similarly, it may contain a vinyl acetate component, a vinyl alcohol component, or the like. These may be used alone or in combination of two or more.

The modification is preferably acid modification with an unsaturated carboxylic acid component. Examples of unsaturated carboxylic acid components include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, crotonic acid, and the like, as well as unsaturated dicarboxylic acid half esters and half amides. It is done. Of these, acrylic acid, methacrylic acid, maleic acid, and maleic anhydride are preferable, and maleic anhydride is particularly preferable. The unsaturated carboxylic acid component may be copolymerized with the ethylene monomer, and its form is not limited. Examples of the copolymerization state include random copolymerization, block copolymerization, and graft copolymerization. Polymerization etc. are mentioned. These may be used alone or in combination of two or more.
The acid modification rate is preferably from 0.1 to 10%, more preferably from 0.2 to 5% from the viewpoint of good adhesiveness.

  The release layer 20 may be mixed with other resins as long as the interlayer adhesion and easy peelability are not significantly impaired or improved. Polyolefin resins modified or copolymerized with polyethylene or maleic anhydride are preferred from the viewpoints of miscibility with the modified ethylene copolymer and coextrudability of film formation. The mixing ratio of other resins in the release layer 20 is less than 50% by mass.

(Support layer 30)
The sealant film 100 of the present invention only needs to have a sealing layer 10 located on the outermost surface on one side of the film and a peeling layer 20 that is in contact with the sealing layer 10, and the two-layer configuration of the sealing layer 10 and the peeling layer 20. Alternatively, the seal layer 10 and the support layer 30 that supports the release layer 20 may be provided on the release layer 20 side (FIG. 1B). Moreover, the structure which has the support layer 30 of two or more layers may be sufficient (FIG.1 (c)).
As the support layer 30, for example, depending on the film application and required characteristics such as oxygen gas barrier property, water vapor barrier property, impact resistance, pinhole property, handling property during production and transportation in food packaging applications, the resin layer It is good to configure. For example, one or two resin layers of polyolefin resin such as polyethylene resin, polypropylene resin, polystyrene resin and ethylene copolymer, and gas barrier resin such as polyamide resin, polyester resin and ethylene-vinyl acetate copolymer A combination of the above can be used. Among the polyethylene resins, a low density polyethylene resin and a linear low density polyethylene resin are preferable in terms of interlayer adhesion.

Specific examples of the layer configuration include the following layer configurations. Note that an adhesive layer, a vapor deposition layer, a printed layer, a coat layer, and the like can be appropriately provided between the release layer 20 and the support layer 30 and between the support layers 30.
・ Seal layer / Peel layer / Polyethylene resin layer / Seal layer / Peel layer / Polypropylene resin layer / Seal layer / Peel layer / Polyamide resin layer / Seal layer / Peel layer / Polyamide resin layer / Polyolefin resin layer / Seal layer / Release layer / Polyamide resin layer / Polyester resin layer / seal layer / Peel layer / Polyamide resin layer / Ethylene-vinyl acetate copolymer layer / Polyolefin resin layer

Further, in terms of film strength and pinhole resistance, it is preferable to use a biaxially stretched film as the support layer 30, which is laminated on the side of the support layer 30 made of the above resin layer.
Examples of the biaxially stretched film include a biaxially stretched polyethylene terephthalate film (OPET), a biaxially stretched nylon film (ONy), a biaxially stretched polypropylene film (OPP), and a biaxially stretched polystyrene film (OPS).

<Thickness of each layer and film>
The thickness of the seal layer 10 and the thickness of the release layer 20 of this film satisfy the heat seal adhesion with the release PET, the easy peel property, and the transparency based on the balance between the total thickness of the film and the thickness of other layers. If it does, it will not specifically limit, However, About 1-50 micrometers is preferable for both layers, respectively. The lower limit is more preferably 2 μm or more, further preferably 3 μm or more, and the upper limit is more preferably 40 μm or less, still more preferably 30 μm or less. If it is 1 micrometer or more, film-forming property is good, and if it is 20 micrometers or less, it is preferable at the point of economical efficiency.
The total thickness of the film is preferably 10 to 100 μm, the lower limit is more preferably 15 μm or more, and the upper limit is more preferably 50 μm or less. If the total thickness of this film is 10 μm or more, sufficient film strength is obtained, and if it is 100 μm or less, it is preferable in terms of heat transfer in the heat sealing process and transparency of the film.

(Other ingredients)
Each layer of this film should just have each above-mentioned component as a main component, and may contain other resin or the following additives in the range which does not inhibit the function of this invention. Here, the main component is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 90% by mass or more, and particularly preferably 100% by mass.
The present film can contain various additives as long as the properties of each layer are not impaired. For example, coloring agents, inorganic fillers, organic fillers, ultraviolet absorbers, light stabilizers, heat stabilizers, antioxidants, lubricants, hydrolysis inhibitors, plasticizers, flame retardants and the like can be mentioned. The addition amount of these additives is not particularly limited, and can be appropriately determined within a range that does not hinder the desired physical properties of the present invention.

<Method for producing sealant film>
The method for producing the present film is not particularly limited as long as the sealing layer 10 is located on the outermost surface on one side of the film and can be produced so that the sealing layer 10 and the release layer 20 are disposed in direct contact with each other.
For example, the seal layer 10 and the release layer 20 may be co-extruded by a feed block method, a multi-manifold method, or a combination thereof by a known T-die method or inflation method, or after each layer is manufactured as a single layer film Thermal lamination may be performed, and the other may be extrusion laminated to one layer.

The support layer 30 may be co-extruded together with the seal layer 10 and the release layer 20, or the support layer 30 may be dry laminated, wet laminated, or sand laminated with respect to the seal layer 10 / release layer 20 film. Alternatively, it may be formed by a heat laminating method or an extrusion laminating method. When laminating, surface treatment such as anchor coating, plasma or corona discharge may be performed as necessary. In dry lamination and wet lamination, various types of adhesives such as known urethane adhesives, acrylic adhesives, and polyester adhesives can be used.
Alternatively, the sealing layer 10 / release layer 20 / support layer 30 may be produced by co-extrusion, and the biaxially stretched film described above as the support layer 30 may be further laminated on the support layer 30 side. The laminating method and the surface treatment method are as described above.
The film may be unstretched, may be uniaxially stretched or biaxially stretched by a known method, and biaxial stretching may be simultaneous stretching or sequential stretching. Moreover, when laminating a biaxially stretched film as the support layer 30 as described above, the film may be stretched as necessary before laminating.

<Heat seal adhesion, easy peelability>
The sealant film 100 of the present invention is an easy-peel sealant film having excellent heat-seal adhesion to release PET and having excellent easy-peeling properties by peeling between the seal layer 10 and the release layer 20 when opened.
For example, it is preferable to exhibit good seal adhesion at a heat seal setting temperature of 180 ° C. with respect to the release PET, and it is more preferable to exhibit seal adhesion at a lower temperature of 160 ° C. The lower limit of the delamination strength of the seal layer 10 / release layer 20 is preferably 10 N / 15 mm width or more, and more preferably 12 N / 15 mm width or more. The upper limit is preferably 30 N / 15 mm width or less, and more preferably 20 N / 15 mm width or less. If it has such a range of peel strength, it is in close contact with the adherend with sufficient strength and can be easily peeled and opened by hand. Furthermore, the present film is less likely to cause film residue, fluffing, and resin fragmentation that remain indefinitely on the two-layer release surfaces after peeling, and provides a good peel appearance.
The peel strength is the maximum test force measured when the present film and the adherend are subjected to a 180 degree peel test at a speed of 200 mm / min.

<Transparency>
The transparency of the sealant film 100 is preferably 20% or less, more preferably 10% or less, from the viewpoints of the visibility, aesthetics, and design of the contents. The lower limit is not particularly limited, and a smaller value is preferable because transparency is good. The haze is a total haze value measured based on JIS K7136.

<Wettability>
The wettability of the surface of the seal layer 10 of the sealant film 100 is that, from the point of anti-fogging property of the film, a drop of 1 μL of distilled water is dropped on the surface of the seal layer at 23 ° C., and the contact angle after 20 seconds is It is preferably 30 ° or less, and more preferably 20 ° or less. The lower limit of the contact angle is not particularly limited, and a smaller value is preferable because it means that water wets and spreads on the surface of the seal layer.

<Anti-fogging property>
The sealant film 100 exhibits excellent antifogging properties by containing an antifogging agent in the seal layer 10. Furthermore, it exhibits good antifogging properties even in a refrigerated environment.
For example, 100 mL of room temperature distilled water is placed in a polypropylene cylindrical container having a bottom diameter of 50 mm and a depth of 80 mm, and this film is sealed with a double-sided tape attached to the opening of the container with the seal layer 10 facing the container, Even when it is allowed to stand at 5 ° C. for 6 hours in a thermostatic bath, water vapor does not condense on the surface of the film seal layer. Alternatively, even when moisture condenses on the film surface, a uniform water film is formed without forming a lens shape, so that the contents can be clearly confirmed.

The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited by the following examples.
Films were prepared by the following raw materials and methods, tested and evaluated, and the results are summarized in Table 1.

<Raw materials>
(Seal layer; polyester resin)
PEs-1: Polyethylene terephthalate / isophthalate copolymer (180 ° C. melt viscosity: 3,100 Pa · sec, 20 ° C. storage modulus: 2,400 MPa, elongation at break: 3%, intrinsic viscosity: 0.086 m ³ / kg Glass transition temperature: 73 ° C., melting point: none)
PEs-2: Polyethylene terephthalate / isophthalate copolymer (180 ° C. melt viscosity: 2,600 Pa · sec, 20 ° C. storage elastic modulus: 2,200 MPa, elongation at break: 2%, intrinsic viscosity: 0.083 m ³ / kg Glass transition temperature: 71 ° C., melting point: none)
PEs-3: Polybutylene terephthalate-polytetramethylene ether glycol copolymer (180 ° C. melt viscosity: 650 Pa · sec, 20 ° C. storage elastic modulus 33 MPa, breaking elongation 800%, intrinsic viscosity: 0.150 m ³ / kg, glass Transition temperature: -70 ° C, melting point: 126 ° C)
PEs-4: glycol modified polyethylene terephthalate (melt viscosity: 5,700 Pa · sec, 20 ° C. storage elastic modulus: 1,400 MPa, elongation at break 280%, intrinsic viscosity: 0.106 m ³ / kg, glass transition temperature: 71 ° C. , No melting point)

(Seal layer; surfactant)
AS-1: alkylsulfonic acid sodium salt (alkyl group having 12 to 16 carbon atoms),
AS-2: alkyl sulfate sodium salt (alkyl group having 12 to 16 carbon atoms),
NS-1: polyoxyethylene alkyl ether (ethylene oxide addition number: 5 mol%, alkyl group carbon number 12-16),
NS-2: polyethylene glycol (number average molecular weight 8600),

<Peeling layer>
APE-1: maleic anhydride modified ethylene-propylene-butene copolymer (180 ° C. melt viscosity: 830 Pa · sec, 20 ° C. storage elastic modulus: 64 MPa, density: 903 kg / m ³ )
APE-2: maleic anhydride modified ethylene-propylene-butene copolymer (180 ° C. melt viscosity: 860 Pa · sec, 20 ° C. storage elastic modulus: 25 MPa, density: 888 kg / m ³ ),
APE-3: ethylene-acrylic acid ester copolymer (180 ° C. melt viscosity: 640 Pa · sec, 20 ° C. storage elastic modulus 38 MPa, density: 942 kg / m ³ ),

<Support layer>
SL-1: linear low density polyethylene (C6),
SL-2: polyamide 6,66 copolymer,
OPET: biaxially stretched polyethylene terephthalate film (12 μm thick),

(Examples 1-9, Comparative Examples 1-5)
The raw materials having the composition shown in Table 1 are supplied to each extruder, and extruded by contacting each layer of the seal layer, the release layer and the support layer under the condition of an extrusion temperature of 220 ° C. by a T-die coextrusion method, and a water-cooled metal at 40 ° C. It was cooled with a cooling roll to obtain a coextruded film. The thickness of the seal layer / release layer / support layer was 5 μm / 10 μm / 15 μm.
Next, the surface of the coextruded support layer was subjected to corona discharge treatment, and then OPET was dry-laminated using an ether-based polyurethane adhesive.

<Evaluation method>
The samples obtained in Examples and Comparative Examples were measured and evaluated by the following methods, and the results are shown in Table 1.

(1) Heat seal test, peel test A-PET sheet (Mitsubishi Chemical Co., Ltd. Novaclear SR006, 200 μm thickness) coated with silicone was used as the adherend, and the films obtained in Examples and Comparative Examples on the silicone coated surface The seal layer surfaces were stacked facing each other, and one end thereof was heat sealed using a heat sealing machine under the conditions of a load of 2 kg / cm ² and a heat sealing time of 1 second. The test was conducted at two preset temperatures of 160 ° C and 180 ° C.
After that, it was cut into a strip shape having a length of 100 mm and a width of 15 mm, and the ends of the A-PET sheet and the film were attached to the gripping tool of a tensile tester with the heat seal portion at the center, a peeling angle of 180 degrees, and a peeling speed of 200 mm / Under the condition of minutes, the strip was pulled in the longitudinal direction until it peeled or broken, and the measured maximum stress was measured as the peel strength.
A film having a peel strength of 10 N / 15 mm or more at a set temperature of 180 ° C. was determined to have good adhesion. Moreover, it peeled at the interface of a peeling layer / seal layer, and the thing of 30 N / 15mm width or less was judged to be easy to peel.

(2) Peeling state evaluation The peeling surface after the said peeling test was observed and evaluated on the following reference | standard.
○: Delamination is neatly performed at the interface between the release layer and the seal layer.
Δ: Delamination occurs at the peeling layer / seal layer interface, but part of the peeling layer remains on the seal layer surface.
(Triangle | delta): There exists a part peeled in the interface of a seal layer / adhered body other than the part which peeled between the peeling layer / sealing layer, and the peeling surface is disordered.
X: Peeling at the interface between the seal layer and the adherend.

(3) Transparency Based on JIS K7136, total light transmittance and total haze were measured.
A sample having a total haze of 20% or less was regarded as acceptable.

(4) Wettability A drop of 1 μL of distilled water was dropped on the surface of the seal layer at 23 ° C., and the contact angle after 20 seconds was measured.
A contact angle of 30 ° or less was accepted.

(5) Anti-fogging property in a low temperature environment 100 mL of room temperature distilled water is put into a polypropylene cylindrical container having a bottom diameter of 50 mm and a depth of 80 mm, and then the seal layer side of the film is directed to the container and the container opening with a double-sided tape. The film was affixed and sealed, and allowed to stand at 5 ° C. for 6 hours in a thermostatic bath. The degree of cloudiness of the film was observed and evaluated according to the following criteria.
A: Moisture spreads evenly over the entire content-side surface of the film, and the content can be clearly seen.
◯: The moisture content does not become water droplets but the surface of the content side of the film is wet (there is unevenness), and the content can be visually recognized.
X: Water condenses on the content-side surface of the film to form fine water droplets, and the film becomes cloudy and the content cannot be visually recognized.

  From Table 1, the films described in Examples 1 to 9 have sufficient adhesion, release property by delamination and good peeling appearance when heat sealed at a set temperature of 180 ° C. with release mold, and further good Transparency could be obtained. Further, Examples 1, 2, 4 to 9 were excellent in that a good peel appearance was obtained even in heat sealing at a set temperature of 160 ° C.

Since the film of Comparative Example 1 contains 3% by mass of the anionic surfactant in the seal layer, the surfactant is excessively deposited on the surface of the seal layer, and the heat seal adhesion with the release PET is poor. The peel strength was low and the transparency was poor.
Since the film of Comparative Example 2 was a resin in which the release layer resin was not modified such as acid modification, the peel strength was low because the adhesive strength of the release layer was weak with respect to the seal layer adhered to the adherend, A film residue also occurred.

In the film of Comparative Example 3, since the surfactant used for the seal layer was only the nonionic surfactant, the surfactant is difficult to deposit on the seal layer surface, and the antifogging property on the seal layer surface can be expressed. could not. Further, a film residue was generated on the layer interface peeling surface between the seal layer and the peeling layer.
Since the film of Comparative Example 4 is a very soft resin material having a 20 ° C. storage elastic modulus of 33 MPa of the polyester-based resin of the seal layer, the peel strength is low because the film stretches at the time of peeling. Also, the transparency was extremely bad.
In the film of Comparative Example 5, since the 180 ° C. melt viscosity of the resin of the seal layer is as high as 5,700 Pa · sec, the adhesion of the seal layer to the adherend is weak in the heat sealing process, and the interface between the seal layer and the adherend And the peeled surface was disturbed.

  Moreover, about the antifogging evaluation of the example containing surfactant, Examples 2-9 contained a predetermined amount of predetermined surfactant in the seal layer, and the content visibility was favorable. Examples 3 and 5-9 were evaluated as “◎”, and Examples 2 and 4 were evaluated as “◯”. The antifogging properties of Comparative Examples 1, 4, and 5 were evaluated as “◎”, and Comparative Example 2 was evaluated as “◯”. However, the adhesion was poor, and Comparative Examples 1 and 4 were further poor in transparency. Comparative Example 3 contained a surfactant, but only a nonionic surfactant, and therefore the antifogging property was evaluated as “x”.

This sealant film has good heat-seal adhesion, easy-openability, and transparency with respect to the release PET, so that content visibility and aesthetics are important. Food, pharmaceuticals, medical products, industrial Suitable for packaging parts.
As a form of packaging, it is suitable as a cover material for container bottoms such as cups, deep-drawn bodies, blister packs formed of release PET, and can also be used as a sealant film for bags such as pouches.

Claims (6)

In a sealant film having at least a seal layer and a release layer,
The seal layer and the release layer are in contact with each other,
Polyester resin in which the sealing layer has a melt viscosity at a set temperature of 180 ° C., a shear rate of 100 sec ⁻¹ of 5000 Pa · sec or less, and a storage elastic modulus E ′ of 20 ° C. of 1,000 MPa or more, or the polyester resin And a surfactant,
The release layer is composed of a modified ethylene copolymer having a melt viscosity at a set temperature of 180 ° C., a shear rate of 100 sec ⁻¹ of 1,500 Pa · sec or less, and a storage elastic modulus E ′ at 20 ° C. of 500 MPa or less,
The surfactant is an anionic surfactant or an anionic surfactant and a nonionic surfactant, and each content ratio of the anionic surfactant and the nonionic surfactant to the seal layer is 0. A sealant film characterized by being 1% by mass or more and less than 3.0% by mass.   The sealant film according to claim 1, wherein the breaking elongation of the seal layer is 10% or less.   The sealant film according to claim 1 or 2, wherein the polyester resin is an amorphous resin.   The sealant film according to any one of claims 1 to 3, further comprising a support layer on a side opposite to a surface of the release layer that contacts the seal layer.   The sealant film according to any one of claims 1 to 4, wherein the haze of the sealant film is 20% or less.   A packaging material formed by heat-sealing the sealant film according to claim 1 and a container bottom made of a polyester resin.

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