JP4880579B2 - Packaging film - Google Patents

Description

  The present invention is a packaging film mainly comprising a lactic acid-based polymer, which is a resin derived from a natural plant, and can be suitably used as a small wrap film used particularly in homes. About.

  A so-called “wrap film” (also referred to as “small roll wrap film” in the present invention to distinguish it from a commercial packaging film) is used as a film for packaging cooked foods on ceramics or plastic containers. Such a small roll wrap film is stored in a paper box provided with a cutter blade in a state of being wound around a cylinder, and when packaging, the film is drawn out from the paper box so as to cover the food, and the film is covered. The film is cut so that the tear propagates in the width direction by pressing against the cutter blade provided in the paper box, and making a perforated hole in the film with this cutter blade and tearing the film. It is common to use the packaging so that the part is in close contact with the container. For this reason, in addition to transparency, the small roll wrap film requires various properties such as adhesion to the container, drawability that allows the film to be pulled out smoothly from a paper box, and cutability when cutting the drawn film. It is said.

  The wrap film suitably used for the above-mentioned applications currently on the market is not only a film mainly composed of a stretched polyvinylidene chloride resin, but also an extruded cast polyethylene resin, plasticized polyvinyl chloride resin, poly 4- Examples thereof include a film mainly composed of methylpentene-1 resin.

  On the other hand, the effective use of depleting resources has become important due to increasing environmental problems, and natural plant-derived resins have attracted attention. Above all, lactic acid polymers are natural plant-derived resins obtained from starches such as corn and potatoes, and are not only mass-produced but also have excellent transparency, and are attracting attention as raw materials for packaging films. Research and development of packaging films using lactic acid polymers as raw materials has been conducted.

  For example, in Patent Document 1, as a biodegradable wrap film having cut suitability, packaging suitability, and heat resistance, which are the characteristics of a household wrap film, according to the dynamic viscoelasticity measurement method of JIS K-7198 A method, The value of storage elastic modulus at 40 ° C. measured at a frequency of 10 Hz and a strain of 0.1% is in the range of 100 MPa to 3 GPa, the value of storage elastic modulus at 100 ° C. is in the range of 30 MPa to 500 MPa, and the loss tangent (tan δ A lactic acid resin composition containing a lactic acid resin composition and a plasticizer in a mass ratio of 60:40 to 99: 1. A biodegradable wrap film containing as a main component is disclosed.

In Patent Document 2, the outermost layer is a layer mainly composed of a polyolefin-based resin in order to provide a shrinkable sheet-like material that can obtain a high shrinkage rate at a relatively low temperature by an inflation method having excellent productivity. A shrinkable sheet-like material having at least one layer mainly composed of polylactic acid between layers composed mainly of the polyolefin-based resin is disclosed. Further, it is disclosed that an acrylic-modified polyethylene resin is used as an adhesive layer between a layer mainly composed of a polyolefin resin and a layer mainly composed of polylactic acid.
WO / 2005/082981 JP 2002-19053 A

  However, as in Patent Document 1, in a system in which a plasticizer is blended with a lactic acid polymer, the glass transition point (Tg) of the lactic acid polymer is lowered to near room temperature, so that it is rapidly cooled by a casting method or the like. Then, when a wrap film is formed, the elastic modulus is lowered by sheeting with an amorphous material, and if it is wound as it is long, the problem is that the scroll is blocked due to the winding force or the like. There was a thing.

  In addition, as described above, in order to function as a small roll wrap film, in addition to transparency, adhesion to the container, drawability that allows the film to be pulled out smoothly from the paper box, cut suitability when cutting the drawn film However, it is not easy to produce a packaging film that satisfies such conditions using a lactic acid polymer as a main raw material. In a laminated film having a structure, it has been difficult to produce a film having excellent adhesion to a container.

  Therefore, the present invention is a packaging film made mainly of a lactic acid polymer, and does not cause blocking even when the formed film is stored in a rolled state, and the molecular weight of the lactic acid polymer is reduced. It is intended to provide a packaging film that can reduce the degree, yet satisfy the various conditions required for a small roll wrap film, with good cut suitability when cutting the drawn film in the film after the small roll change. It is.

  The present invention is a laminated film composed of at least three layers, and both surface layers contain a component (A) that is a polyolefin polymer as a main component, and the intermediate layer comprises a lactic acid polymer (B) and Storage elastic modulus (containing a glycerin fatty acid ester (C) having a molecular weight of 2000 or less including glycerin monoacetomonoester (C-1) as a main component and measured by dynamic viscoelasticity measurement at a frequency of 10 Hz and a temperature of 20 ° C. ( E ′) is 1 to 4 GPa, the loss tangent (tan δ) peak temperature is 20 to 70 ° C., and the peak value is in the range of 0.1 to 0.8. .

  In general, "film" is a thin flat product whose thickness is extremely small compared to the length and width and whose maximum thickness is arbitrarily limited, and is usually supplied in the form of a roll. (Japanese Industrial Standard JISK6900), and “sheet” generally refers to a product that is thin according to the definition in JIS, and whose thickness is usually small instead of length and width. However, since the boundary between the sheet and the film is not clear and it is not necessary to distinguish the two in terms of the present invention, in the present invention, even when the term “film” is used, the term “sheet” is included and the term “sheet” is used. In some cases, “film” is included.

In addition, in the present invention, the expression “main component” includes the intention to allow other components to be contained within a range that does not interfere with the function of the main component, unless otherwise specified. Although the content ratio of the components is not specified, the main component (when two or more components are the main components, the total amount thereof) is 50% by mass or more, preferably 70% by mass or more, particularly in the composition. It preferably includes 80% by mass or more (including 100%).
In addition, when described as “X to Y” (X and Y are arbitrary numbers), unless otherwise specified, “X or more and Y or less” is intended, and “intended to be larger than X and preferably smaller than Y” Is also included.

  Hereinafter, a packaging film (hereinafter referred to as “the packaging 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.

  This packaging film has a molecular weight of 2000 or less including <surface layer> containing a polyolefin-based polymer (A) as a main component, a lactic acid-based polymer (B), and a glycerin monoacetomonoester (C-1). It is a laminated film including an <intermediate layer> containing glycerin fatty acid ester (C) as a main component.

  Hereinafter, the surface layer and the intermediate layer constituting the packaging film will be described, and then the laminated structure, characteristic values, and manufacturing method of the packaging film will be described in this order.

<Surface layer>
In this packaging film, it is important that the main component of the inner and outer surface layers (hereinafter simply referred to as “surface layer”) is the polyolefin polymer (A).

(Polyolefin polymer (A))
Examples of polyolefin polymers (A) include ethylene polymers, butylene polymers, propylene polymers such as polypropylene and ethylene-propylene copolymers, poly-4-methylpentene, polybutene, and ethylene-vinyl acetate copolymers. And so on. These resins may be one type of the resins listed above, or may be a mixed resin composed of two or more types of resins.
As these polyolefin polymers (A), polyolefin thermoplastic elastomers in which ethylene / propylene rubber or the like is dispersed and composited can also be used.

  Among the above, the role of the surface layer, that is, blocking of the packaging film, an appropriate balance between slip and surface adhesiveness, surface properties such as antifogging properties, stability of molding processing during film formation, and further by hydrolysis It is a layer that can play a role such as suppression of a temporal decrease in the molecular weight of the lactic acid-based polymer (B), and considering these roles, the main component of the surface layer is preferably an ethylene-based polymer.

As the ethylene polymer, one type of ethylene polymer selected from low density polyethylene, linear low density polyethylene, linear ultra low density polyethylene, medium density polyethylene and high density polyethylene, or a combination of two or more of these Or a copolymer containing ethylene as a main component, that is, ethylene and 3 to 10 carbon atoms such as propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1, etc. Α-olefins of vinyl acetate, vinyl esters such as vinyl acetate and vinyl propylene acid; unsaturated carboxylic acid esters such as methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate; unsaturated such as conjugated and non-conjugated dienes A copolymer with one or more comonomers selected from compounds, or It can is mentioned multicomponent copolymer or the ethylene-based polymer, the copolymer, a mixed resin of two or more kinds of combinations of the multicomponent copolymer. The ethylene unit content of these ethylene polymers is usually more than 50% by mass.
Among them, 1 selected from low density polyethylene, linear low density polyethylene, linear ultra low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer and ethylene-methacrylic acid ester copolymer A mixed resin composed of a kind of ethylene polymer or a combination of two or more of these is particularly preferred.
Examples of the acrylic acid ester of the ethylene-acrylic acid ester copolymer include methyl acrylate and ethyl acrylate. Examples of the acrylic acid ester of the ethylene-methacrylic acid ester copolymer include methyl methacrylate. And ethyl methacrylate.

Among the ethylene-based polymers, when importance is attached to surface properties such as balance of surface tackiness, antifogging properties, and molding processing stability during film formation, the vinyl acetate content is 10 to 60% by mass, The rate (hereinafter sometimes abbreviated as “MFR”. MFR measurement conditions are 190 ° C., load 21.18 N based on JIS K 7210, and other MFRs are also the same). An ethylene-vinyl acetate copolymer that is / 10 minutes is particularly preferred.
In this ethylene-vinyl acetate copolymer, if the vinyl acetate content is 10% by mass or more, the film is not hard because the crystallinity is low, the flexibility and elastic recovery are good, and surface tackiness is also exhibited. It is preferable in that it is easy. On the other hand, if it is 60% by mass or less, heat resistance, film strength, etc. can be secured, bleed-out can be suppressed even if an antifogging agent is added, and the film is unwound because the surface tackiness is not too strong. It is preferable at the point that property and an external appearance can be made favorable. From such a viewpoint, the vinyl acetate content of the ethylene-vinyl acetate copolymer is more preferably 10 to 58% by mass, and particularly preferably 12 to 56% by mass.
Further, if the MFR of the ethylene-vinyl acetate copolymer is 0.2 g / 10 min or more, the extrusion processability is stable, and if it is 20 g / 10 min or less, stable film formation at the time of molding becomes possible. It is preferable because thickness unevenness, decrease in mechanical strength, variation, and the like are reduced. From such a viewpoint, the MFR of the ethylene-vinyl acetate copolymer is more preferably 0.5 to 18 g / 10 minutes, and more preferably 1 to 15 g / 10 minutes.

On the other hand, when importance is attached to microwave heat resistance that can withstand microwave heating, linear low density polyethylene having a density of 0.90 to 0.95 g / cm ³ and an MFR of 0.2 to 20 g / 10 min is used. Particularly preferred.
If the density of the ethylene polymer is within such a range, the film does not become hard because it has appropriate crystallinity, and the flexibility and elastic recovery are good. Since the temperature will be higher than the operating temperature range, specifically the atmospheric temperature when heated in a microwave oven, etc., the food will be packaged with the resulting film, and even when heated in a microwave oven etc., the film will melt and stick to the food container etc. This is preferable because it does not cause a problem of sticking.
From this point of view, more preferably the density of the ethylene-based polymer is 0.90~0.94g / cm ^3, and even more preferably among them 0.91~0.94g / cm ^3.
If the MFR of the ethylene polymer is 0.2 g / 10 min or more, the extrusion processability is stable, and if it is 20 g / 10 min or less, stable film formation is possible at the time of molding. It is preferable because the decrease in strength, variation, and the like are reduced. From such a viewpoint, the MFR of the ethylene-based polymer (A) is more preferably 0.5 to 18 g / 10 minutes, and particularly preferably 1 to 15 g / 10 minutes.

  The method for producing the ethylene polymer is not particularly limited, and a known polymerization method using a known olefin polymerization catalyst, for example, a multisite catalyst represented by a Ziegler-Natta type catalyst or a metallocene catalyst. Examples thereof include a slurry polymerization method, a solution polymerization method, a bulk polymerization method, a gas phase polymerization method using a single site catalyst, and a bulk polymerization method using a radical initiator.

<Intermediate layer>
Next, constituent components of the intermediate layer will be described.

  The intermediate layer contains a lactic acid-based polymer (B) and a glycerin fatty acid ester (C) having a molecular weight of 2000 or less containing a glycerin monoacetomonoester (C-1) as main components. What contains as a main component the glycerin fatty acid ester (C) whose molecular weight is 2000 or less including the mixture of a polymer (B), glycerol monoacetomonoester (C-1), and glycerol diacetomonoester (C-2). More preferred.

(Lactic acid polymer (B))
As the lactic acid polymer (B), poly (L-lactic acid) whose structural unit is L-lactic acid, poly (D-lactic acid) whose structural unit is D-lactic acid, structural units that are L-lactic acid and D-lactic acid Poly (DL-lactic acid), a mixture thereof, or a copolymer containing these can be used.
However, poly (L-lactic acid) or poly (D-lactic acid) referred to here is ideally a polymer comprising 100% of L-lactic acid or D-lactic acid, but inevitably different lactic acid is included in the polymerization. Since there is a possibility, it contains 98% or more of L-lactic acid or D-lactic acid.

The ratio (molar ratio) of D-lactic acid (D-form) to L-lactic acid (L-form) in the lactic acid-based polymer (B) is L-form / D-form = 100/0 to 85/15, or L-form / D. It is preferable that it is 0 / 100-15 / 85, More preferably, L-form / D-form = 99.5 / 0.5-85 / 15 or L-form / D-form = 0.5 / 99.5 15/85. If it exists in this range, the heat resistance of the film obtained will not be impaired.
In addition, you may blend the lactic acid-type polymer from which the copolymerization ratio of L body and D body differs. In that case, it is preferable that the average value of the copolymerization ratios of the L-form and D-form of a plurality of lactic acid polymers falls within the above range.

  From the viewpoint of suppressing bleed-out of a plasticizer or the like, it is preferable that the lactic acid polymer (B) has low crystallinity. Therefore, polylactic acid having a lower crystallinity than poly (L-lactic acid), such as poly (D- The main component is preferably lactic acid), poly (DL-lactic acid), or a mixture thereof. The ratio of D-form to L-form in the poly (DL-lactic acid) or the mixture is L-form / D-form = 85/15 to 95/5, or L-form / D-form = 5/95 to 15/85. Is preferred. If it exists in this range, since the crystallinity of a lactic acid-type polymer (B) is low, bleeding out, such as a plasticizer, can be suppressed.

  In consideration of the balance between suppression of bleeding out of plasticizers and the like and heat resistance (depending on the type of polyolefin polymer (A) which is the main component of both surface layers), the D-form content is 0. .5-5 mol% poly (L-lactic acid) (hereinafter sometimes abbreviated as “B-1 component”) and D-form content 10-15 mol% poly (D, L-lactic acid) (hereinafter “ The mixed resin composition may be abbreviated as “B-2 component”), and among them, the mixing mass ratio of the component (B-1) and the component (B-2) is preferably (B-1) / (B-2) = 10/90 to 60/40 is particularly preferable, and among them, a mixed resin composition having (B-1) / (B-2) = 20/80 to 55/45 is more preferable. .

  The lactic acid polymer (B) may contain other hydroxycarboxylic acid or the like as a small amount of a copolymer component, and may contain a small amount of a chain extender residue.

As a polymerization method for the lactic acid-based polymer (B), a condensation polymerization method, a ring-opening polymerization method, and other known polymerization methods can be employed.
For example, in the condensation polymerization method, L-lactic acid, D-lactic acid, or a mixture thereof can be directly subjected to dehydration condensation polymerization to obtain a lactic acid polymer having an arbitrary composition.
In the ring-opening polymerization method (lactide method), lactide, which is a cyclic dimer of lactic acid, has an arbitrary composition and crystallinity using an appropriate catalyst while using a polymerization regulator or the like as necessary. A lactic acid polymer can be obtained.
Lactide includes L-lactide, which is a dimer of L-lactic acid, D-lactide, which is a dimer of D-lactic acid, or DL-lactide composed of L-lactic acid and D-lactic acid. Accordingly, a lactic acid polymer having any composition and any crystallinity can be obtained by mixing and polymerizing.

  The weight average molecular weight of the lactic acid polymer (B) is preferably in the range of 50,000 to 400,000, and more preferably in the range of 100,000 to 250,000. If the weight average molecular weight of the lactic acid polymer (B) is 50,000 or more, practical properties such as mechanical properties and heat resistance can be secured, and if it is 400,000 or less, the melt viscosity is too high and the moldability is high. There is no inferiority.

  As the lactic acid polymer (B) used for the packaging film, a commercially available lactic acid polymer can be used. For example, the product name “Lacia” series (manufactured by Mitsui Chemicals, Inc.), the product name “Nature Works” series (manufactured by NatureWorks), the product name “U'z series” (manufactured by Toyota Motor Corporation), and the like can be mentioned.

(Glycerin fatty acid ester (C))
The glycerin fatty acid ester (C) can play a role of plasticizing the lactic acid polymer (B).
As such glycerin fatty acid ester (C), it is important that glycerin monoacetomonoester (C-1) having a molecular structure as shown in Chemical Formula 1 below is contained. Glycerin monoaceto monoester (C-1) has good plasticization performance, and can substantially reduce the number of added plasticizers to the resin to be mixed. Bleed out can be suppressed by reducing the number of added parts.

The glycerin monoacetomonoester (C-1) is a case where R1 is an alkyl group in the above chemical formula 1, one of R2 and R3 is an acetyl group, and the other is hydrogen.
The number of carbon atoms of the alkyl group of R1 is not particularly limited and is appropriately selected so that the objectives of improving adhesion and flexibility are achieved, but it is generally preferably 6-20.

  In order to obtain good compatibility with the lactic acid polymer (B), the molecular weight of the glycerin fatty acid ester (C) is 2,000 or less, and particularly preferably 1,500 or less.

  The blending amount of the lactic acid polymer (B) and the glycerin fatty acid ester (C) is preferably blended so that the mass ratio is (B) / (C) = 90 / 10-60 / 40. By setting it within the above range, it is possible to suppress the bleed-out in which the glycerin fatty acid ester (C) is transferred to the surface with time and the surface becomes sticky by providing flexibility.

  The blending amount of the glycerin fatty acid ester (C) is preferably small from the viewpoint of processability. Especially, the glycerin fatty acid ester (C) is 1 to 20 parts by mass, especially 1 with respect to 100 parts by mass of the lactic acid polymer (B). It is even more preferable to mix so as to include ˜15 parts by mass, particularly 2 to 15 parts by mass. By making the mixing amount of the glycerin fatty acid ester (C) 20 parts by mass or less, the melt viscosity of the lactic acid-based resin composition (B) as a mixture is not excessively decreased, and with the fluidity with the surface layer. The difference in elastic modulus can be reduced. That is, at the time of film formation, the workability at the time of co-pressing with the surface layer (for example, the polyolefin polymer (A)) is improved, and a film excellent in appearance without striped pattern or whitening can be obtained. In addition, even when the film is stretched, it becomes easy to match the elastic modulus in a wide temperature range with the surface layer (for example, the polyolefin polymer (A)), and since the stretching conditions can be set widely, the workability during stretching is also good. .

As the glycerin fatty acid ester (C), other glycerin fatty acid ester may be added besides glycerin monoacetomonoester (C-1). The type is not particularly limited, and examples thereof include monoglyceride, diglyceride, triglyceride, glycerin diacetate monoester, and polyglycerin fatty acid esters such as diglycerin, triglycerin, and tetraglycerin. In this invention, it is preferable that it is a mixture of glycerol monoacetomonoester (C-1) and glycerol diacetomonoester (C-2).
The glycerin diacetate monoester (C-2) is a case where R1 is an alkyl group and R2 and R3 are acetyl groups in the above Chemical Formula 1. Glycerine diacetomonoester (C-2) is preferable in that it can suppress the volatilization of the plasticizer when mixed with the resin, and by using it together with the glycerin monoacetomonoester (C-1), the volatilization of the plasticizer can be prevented. Good plasticization performance can be exhibited while suppressing.

Here, each mixing ratio can be appropriately selected depending on the application and the required function.
Especially, the mixing ratio of glycerol monoacetomonoester (C-1) and glycerol diacetomonoester (C-2) is preferably (C-1) / (C-2) = 10/90 to 100/0. More preferably, it is 10 / 90-60 / 40, More preferably, it is 20 / 80-50 / 50. It is preferable that the mixing ratio of (C-1) and (C-2) be within the above range because the suppression of volatilization of the plasticizer and the plasticizing performance can be adjusted with good balance.
As the glycerin fatty acid ester (C) used for the packaging film, Riken Vital “Riquemar PL819” can be obtained commercially.

(Other ingredients)
The intermediate layer of the packaging film may contain a polyolefin polymer (E) in addition to the lactic acid resin composition (B).

  The polyolefin polymer (E) may be the same polyolefin polymer as the polyolefin polymer (A) constituting the surface layer or may be a different polyolefin polymer, but preferably the same polyolefin polymer. It may be a polymer. If the polyolefin polymer (E) and the polyolefin polymer (A) constituting the surface layer are the same polyolefin polymer, the adhesion between the intermediate layer and the surface layer can be improved, In addition to improving mechanical properties, for example, trimming loss that occurs when trimming by trimming both ends of the formed film can be prepared by adding it as a constituent material of the intermediate layer, eliminating waste of materials. The material cost can be reduced.

  As the most preferred polyolefin polymer (E), an ethylene-vinyl acetate copolymer having a vinyl acetate content of 10 to 60% by mass can be mentioned. This ethylene-vinyl acetate copolymer can be suitably used as a polyolefin polymer (A) which is a main component of the surface layer, and is transparent when a recycled resin generated from trimming loss is added. There are no practical problems in terms of properties, mechanical properties, and material costs, and they can be stably obtained as industrial materials.

  The blending ratio of the polyolefin polymer (E) is (B) :( E) = 1: 99 to 50:50, particularly 5:95 to 50 in the mass ratio with the lactic acid polymer (B) in the intermediate layer. : 50, particularly preferably 10:90 to 45:55.

In the intermediate layer of the packaging film, a heat stabilizer, an antioxidant, a UV absorber, an anti-blocking agent, a light stabilizer, a nucleating agent, a hydrolysis inhibitor, a deodorant, as long as the effects of the invention are not impaired. Additives such as agents can be formulated.
For example, in order to maintain the practical properties of the packaging film, the carbodiimide compound is preferably 0.1 to 3 parts by mass, more preferably 0.5 to 1 part by mass with respect to 100 parts by mass of the lactic acid resin composition. By blending, the weight average molecular weight can be increased. Below this range, the effect of increasing the weight average molecular weight is often insignificant, and above this range, fish eyes and gels may be produced during film formation, which is not preferred.

(Other additives)
In the surface layer and / or intermediate layer of this packaging film, various additives such as the following can be appropriately blended in order to impart performance such as antifogging property, antistatic property, slipperiness, and adhesiveness. .
For example, an aliphatic alcohol fatty acid ester which is a compound of an aliphatic alcohol having 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms and a fatty acid having 10 to 22 carbon atoms, preferably 12 to 18 carbon atoms, specifically, Monoglycerin oleate, polyglycerin oleate, polyglycerin polyricinoleate, glycerin triricinoleate, glyceryl acetyl ricinoleate, polyglyceryl stearate, polyglyceryl laurate, methyl acetyl lysylate, ethyl acetyl lysylate, butyl acetyl lysylate, Propylene glycol oleate, propylene glycol laurate, pentaerythritol oleate, polyethylene glycol oleate, polypropylene glycol oleate, sorbitan oleate, sorbitan laurate, polyethylene glycol Sorbitan oleate, polyethylene glycol sorbitan laurate, and the like, and polyalkylene ether polyols, specifically, polyethylene glycol, polypropylene glycol, etc., and at least one compound selected from paraffinic oil and the like constitute various types. 0.1 to 12 parts by mass can be added to 100 parts by mass of the resin component, and preferably 1 to 8 parts by mass is preferably added.

<Laminated structure>
In this packaging film, both surface layers contain (A), which is a polyolefin polymer, as a main component, and the intermediate layer contains a lactic acid polymer (B) and glycerin monoacetomonoester (C-1). It may be a laminated film composed of at least three layers having an intermediate layer mainly composed of a mixture of glycerin fatty acid ester (C) having a molecular weight of 2000 or less, and within a range not exceeding the gist of the present invention, mechanical properties Other layers (hereinafter sometimes abbreviated as P layer) may be appropriately introduced as necessary, such as improvement of interlayer adhesion, etc., but preferably an adhesive layer or / and a reproduction layer are preferable. Here, the surface layer (hereinafter sometimes abbreviated as S layer) may have the same layer other than both surface layers, that is, an intermediate layer. Further, the intermediate layer (hereinafter sometimes abbreviated as “M layer”) may have at least one layer between both surface layers, and may have two or more layers. For example, a three-layer structure composed of (S layer) / (M layer) / (S layer), a four-layer structure composed of (S layer) / (P layer) / (M layer) / (S layer), (S layer) 5 layers consisting of / (P layer) / (M layer) / (P layer) / (S layer), (S layer) / (M layer) / (P layer) / (M layer) / (S layer) A typical configuration can be given. In this case, the resin composition and thickness ratio of each layer may be the same or different.

  When the adhesive layer is used for the P layer, the resin to be used is not particularly limited. For example, a copolymer of a soft aromatic hydrocarbon and a conjugated diene hydrocarbon or a hydrogenated derivative of these copolymers An ethylene-vinyl acetate copolymer having a vinyl acetate content of 30 to 80% by mass, a modified polyolefin resin, a lactic acid polymer, a polymer block copolymer mainly composed of an acrylate unit, and a methacrylate unit. It is more preferable to contain as a main component a resin composed of any one kind or a combination of two or more kinds of lactic acid / acrylic mixed resins which are mixed resins with an acrylic block copolymer having a main polymer block.

When an adhesive layer is used for the P layer, the packaging film of the present invention can have a reproduction layer containing a surface layer, an intermediate layer, and the like. These can use, for example, trimming loss that occurs when the film is trimmed by trimming both ends of the film, eliminating material waste and reducing material cost.
The reproduction layer can be provided not only between the surface layer and the intermediate layer, but also between the surface layer and the adhesive layer, and between the intermediate layer and the adhesive layer. For example, the surface layer, the intermediate layer, or the adhesive layer has a two-layer configuration, and one layer is formed using trimming loss at both ends of the film, so that not only the surface layer and the intermediate layer but also the surface A reproduction layer can be provided between the layer and the adhesive layer, and between the intermediate layer and the adhesive layer. In this case, in addition to the thickness ratio and composition ratio of each layer, the mixing ratio of these components can be adjusted depending on whether the layer containing the trimming loss is based on the surface layer, the intermediate layer, or the adhesive layer.
Moreover, you may use the mixture containing a polyolefin-type polymer (A) and a lactic acid-type polymer (B) as an alternative of a reproduction | regeneration layer.

In the packaging film, the thickness ratio of the intermediate layer to the total thickness of the film is preferably 35 to 90%. If the thickness ratio of the intermediate layer is within such a range, it becomes easy to design a film that satisfies the above characteristic values (E ′, tan δ) due to the dynamic viscoelasticity. For example, when the film is formed by the T-die method Stable film-forming stability can be obtained, and mechanical properties for expressing a suitable cutting property for wrapping films for food packaging and relaxation properties for developing container adhesion can be imparted relatively easily. Can do. In addition, even when stored in a state where the formed film is wound, blocking does not occur, antifogging properties and container adhesion are good, and in addition to being difficult to cause molecular weight reduction due to hydrolysis over time, It can be set as the packaging film which has favorable adhesiveness between layers.
Furthermore, when more importance is attached to stable film forming processability and flexibility, the thickness ratio of the intermediate layer to the total thickness of the film is preferably 35 to 65%, and more preferably 35 to 60%. preferable.
Further, in the case where importance is attached to the cut property and the adhesion to the container, and further, the degree of planting, that is, CO ₂ reduction, the thickness ratio of the intermediate layer to the total thickness of the film is preferably 60 to 90%, particularly More preferably, it is 65 to 90%.
When there are two or more intermediate layers as described above, the thickness ratio may be calculated using the total thickness of all the intermediate layers.

  The total thickness of the packaging film may be a range used as a food packaging wrap film, specifically 6 to 30 μm, and preferably 10 to 20 μm.

<Characteristic value>
The packaging film has (1) a storage elastic modulus (E ′) measured by dynamic viscoelasticity measurement at a frequency of 10 Hz and a temperature of 20 ° C. of 1 to 4 GPa, and (2) a peak temperature of loss tangent (tan δ). Can be prepared such that the peak value is in the range of 0.1 to 0.8, and all such conditions (1), (2), and (3) can be prepared. It is preferable that the film is prepared so as to satisfy the above.

If the storage elastic modulus (E ′) is less than 1 GPa, the film is too soft and the stress is too small for deformation, so that for example, the cutability when pulled out from a paper box and cut may be deteriorated. On the other hand, when the storage elastic modulus (E ′) exceeds 4 GPa, the film becomes hard and hardly stretched, and the drawability when drawn from the paper box may be deteriorated.
In addition, if the peak temperature of loss tangent (tan δ) is 60 ° C. or less and the peak value is 0.1 or more, the restoring behavior against deformation of the film does not occur instantaneously, so the film is packaged in a container. When doing, it is preferable because the film is not restored in a short time and the adhesion to the container is improved. In addition, if the peak temperature of loss tangent (tan δ) is 20 ° C. or higher and the peak value is 0.8 or lower, plastic deformation does not occur. It is preferable because it is not.
The loss tangent (tan δ) is the ratio of the loss elastic modulus (E ″) to the storage elastic modulus (E ′), that is, the loss tangent (tan δ = E ″ / E ′). This means that the loss elastic modulus (E ″) of the material, that is, the contribution ratio of viscosity is large among the viscoelastic properties. By evaluating the value of this loss tangent (tan δ) and the temperature range showing a high value, It is a great measure for judging the adhesion to the container during packaging and the stress relaxation behavior of the film in the packaging process.

  In order to produce a film that satisfies all of the above conditions (1) to (3), for example, selection of constituent components in the intermediate layer, the surface layer, and the adhesive layer (in some cases, the reproduction layer) (the type of resin as the main component) , Molecular weight and Tg, presence / absence and type of plasticizer, mixing ratio of components, LD ratio of lactic acid polymer, etc.), thickness ratio of intermediate layer, surface layer, and adhesive layer (recycled layer in some cases) It can be produced by appropriately adjusting the method and processing conditions (for example, heat treatment conditions after film formation, etc.) in a well-balanced manner.

In this packaging film, both surface layers are formed with a polyolefin polymer (A) as a main component, while the intermediate layer has a molecular weight containing a lactic acid polymer (B) and glycerin monoacetomonoester (C-1). Of glycerin fatty acid ester (C) having a molecular weight of 2000 or less, and a storage elastic modulus (E ′) measured by dynamic viscoelasticity measurement at a frequency of 10 Hz and a temperature of 20 ° C. is 1.0 to 4.0 GPa. Yes, by making a packaging film so that the peak temperature of loss tangent (tan δ) is 20 to 70 ° C. and the peak value is in the range of 0.10 to 0.80, Required conditions, ie transparency, adhesion to containers, drawability to smoothly pull out the film from the paper box, cut when cutting the drawn film Packaging film that can satisfy the various conditions such as positive can provide, can function suitably as a small roll wrap film. At this time, by forming both surface layers with the polyolefin copolymer (A) as a main component, even if the film thus formed is stored in a rolled state, the decrease in the molecular weight of the lactic acid resin composition is suppressed. It is possible to eliminate the problem of film sticking by suppressing blocking of the film.
Furthermore, since the anti-fogging agent etc. can be included in both surface layers by setting it as the laminated film comprised from at least 3 layers, the anti-fogging property etc. of a film can also be improved.

<Manufacturing method>
Although the manufacturing method of this packaging film is demonstrated, it is not limited to the following manufacturing method.

  First, when the constituent material of each layer is a mixed composition, the constituent material of each layer is preferably mixed in advance and pelletized as necessary. As a mixing method at this time, for example, it may be pre-compounded in advance using a same-direction twin-screw extruder, a kneader, a Hayshell mixer or the like, or each raw material is dry blended and directly a film extruder. You may make it throw in. In any mixing method, it is necessary to consider a decrease in molecular weight due to decomposition of the raw material, but pre-compounding is preferable for uniform mixing. For example, in the case of an intermediate layer, the lactic acid polymer (B) and the additive as necessary are sufficiently dried to remove moisture, and then melt-mixed using a twin-screw extruder, from the vent port. A pellet may be produced by extruding into a strand shape while adding a predetermined amount of plasticizer.

Next, the constituent materials of each layer may be separately put into an extruder, melt extruded, and coextruded by T-die molding or inflation molding to be laminated.
At this time, it is preferable to form a film by practically pulling the melt extruded from the T die as it is while rapidly cooling it with a casting roll or the like.

When emphasizing the heat resistance and cutability of the film, after the melt-extruded sheet is cooled and solidified by a cooling roll, it is heated below the crystallization temperature of the resin, and the difference in speed between the nip rolls is used in the longitudinal direction of the film. It is preferable to employ a longitudinal stretching method in which the film is stretched 1.2 to 5.0 times, or a flat stretching method in which biaxial stretching and / or simultaneous biaxial stretching is sequentially performed 1.2 to 5.0 times in both the longitudinal and lateral directions of the film.
As the stretching temperature, the temperature of the extruded sheet is preferably set in the range of 30 to 90 ° C, and more preferably in the range of 40 to 90 ° C. If the stretching temperature is within such a range, it is preferable because both the lactic acid resin composition (B) of the intermediate layer and the polyolefin copolymer (A) of the surface layer can be made close to the elastic modulus suitable for stretching. . The draw ratio is preferably in the range of 1.2 to 5.0 times, and more preferably in the range of 1.5 to 4.0 times. As long as the draw ratio is within this range, the cut property can be improved without causing troubles such as breakage and whitening of the extruded sheet.

  Moreover, when importance is attached to productivity and / or economy, it is preferable to melt-extrude the material resin from an annular die and perform inflation molding. Moreover, as a cooling method in that case, either the method of cooling from the outer surface of the tube, or the method of cooling from both the outer surface and the inner surface of the tube may be used.

The film thus obtained is reduced in heat shrinkage rate and natural shrinkage rate, depending on the purpose such as suppression of occurrence of width shrinkage, longitudinal stretching between heating rolls as required, various heat setting, Heat treatment such as aging may be performed.
As the heat treatment conditions, the heat treatment temperature is preferably set in the range of 40 to 100 ° C, and more preferably in the range of 60 to 90 ° C. If the heat treatment temperature is 40 ° C. or higher, the effect of the heat treatment can be sufficiently obtained, and if it is 100 ° C. or lower, the problem of formability such as stickiness of the film on the roll does not occur.

  Further, for the purpose of imparting and promoting antifogging properties, antistatic properties, adhesiveness, and the like, treatments such as corona treatment and aging, and surface treatments and surface treatments such as printing and coating may be performed.

  It should be noted that the upper and lower limits of the numerical range in the present invention are those of the present invention as long as they have the same operational effects as those in the numerical range even if they are slightly outside the numerical range specified by the present invention. It is included in the equivalent range.

Hereinafter, although an Example and a comparative example demonstrate in more detail, this invention does not receive a restriction | limiting at all.
In addition, the various measured value and evaluation about the film displayed in this specification were performed as follows. Here, the flow direction of the film from the extruder is referred to as the vertical direction (hereinafter sometimes referred to as “MD”), and the perpendicular direction thereof is referred to as the horizontal direction (hereinafter sometimes referred to as “TD”).

(1) E ′, tan δ
According to the dynamic viscoelasticity measurement method described in JIS K-7198 A method, the vibration frequency is measured in the transverse direction (TD) of the film using a dynamic viscoelasticity measurement device “DVA-200” manufactured by IT Measurement Control Co., Ltd. Measured from −50 ° C. to 150 ° C. at a rate of temperature rise of 1 ° C./min at 10 Hz and a strain of 0.1%. From the obtained data, the storage elastic modulus (E ′) at a temperature of 20 ° C. and the loss tangent The peak temperature of (tan δ) and its peak value were determined.

(2) Molecular weight retention (wet heat durability)
The obtained film was placed in a constant temperature and humidity machine LH-112 made by Tabay Espec adjusted to 40 ° C. × 90% by weight for 1 month. The weight average molecular weight of the film before and after the test was mounted on a gel permeation chromatography HLS-8120GPC manufactured by Tosoh Corporation and a chromatographic column Shim-Pack series GPC-800CP manufactured by Shimadzu Corporation. Measurement was performed at a solution concentration of 0.2 wt / vol% by weight, a solution injection amount of 200 μl, a solvent flow rate of 1.0 ml / min, and a solvent temperature of 40 ° C., and a weight average molecular weight was calculated in terms of polystyrene. The weight average molecular weight of the standard polystyrene used is 20000, 670000, 110,000, 35000, 10,000, 4000, 600. The molecular weight retention rate (% by weight) was calculated from the calculated weight average molecular weights before and after the test, and the following determinations were made.
○: The molecular weight retention is 60% by weight or more and 100% by weight or less and the molecular weight after aging is 100,000 or more. X: The molecular weight retention is 0% by weight or more and less than 60% by weight. Whose molecular weight is less than 100,000

(3) Film-forming stability When a film was formed by the T-die forming method, the stability of casting and the degree of sticking to a roll were observed and evaluated according to the following criteria.
◎: Extremely stable ○: Stable ×: Unstable

(4) Blocking resistance The obtained roll of film is stored in a temperature-controlled room at a temperature of 43 ° C. and a relative humidity of 40% for 5 days, and the subsequent surface condition and roll-back property are observed and evaluated according to the following criteria. did.
◎: Level where there is no blocking between films ○: Level where there is a little blocking between films, but there is no practical problem ×: Level where the film cannot be peeled off due to blocking between films, and rewinding is impossible, causing a practical problem

(5) Container Adhesion The adhesion to a container when packaged in a bowl-shaped ceramic container having a diameter of 10 cm and a depth of 5 cm was evaluated according to the following criteria.
◎: Level that can be packaged moderately ○: Level that spreads slightly from the shape of the container, but no problem for practical use ×: Level that causes practical problem because the film spreads along the container

(6) Anti-fogging property The film is pasted on the opening on one side of a cylinder made of SUS304 having a diameter of 50 mm and a height of 80 mm, and the film is pasted in an environment with an outside temperature of 0 to 5 ° C. The cylindrical end 30 mm on the open side was immersed in water at a water temperature of 20 ° C., and after 1 hour from the start of immersion, the antifogging property was visually observed and evaluated according to the following criteria.
◎: Water film with uniform moisture and no water droplets ○: Water film with uniform moisture content, but there are fine water droplets in some places ×: Water droplets with a diameter of about 3 mm

(7) Cut property The formed film was put into a carton box with a metal saw blade, and the film was pulled out and cut, and the ease of cutting at that time was evaluated according to the following criteria.
◎: Level that can be used comfortably when cutting ○: Level that feels some resistance when cutting, but no problem in practical use ×: Level that wraps into the metal saw blade and feels excessive resistance when cutting

Example 1
About the resin composition which forms both surface layers, an ethylene-vinyl acetate copolymer “LV440” (vinyl acetate content: 15% by mass, MFR: 2.2 g / m) manufactured by Nippon Polyethylene Co., Ltd. as a polyolefin polymer (A). 10 minutes) 100 parts by mass (hereinafter abbreviated as “A-1”) and 5.0 parts by mass of diglycerin monooleate “DGO-1” manufactured by Riken Vitamin Co., Ltd. as an antifogging agent are set at an extrusion temperature of 180 to 200. It put into the same direction twin screw extruder set to ° C, and melt kneaded.
On the other hand, for the resin composition forming the intermediate layer, “Nature Works 4032D” (L-form / D-form = 98.6 / 1.4, weight average molecular weight: 200,000) manufactured by NatureWorks as the lactic acid polymer (B). (Hereinafter abbreviated as “B-1”), and put into the same direction twin screw extruder set at the extrusion set temperature of 180 ° C. Subsequently, as glycerol fatty acid ester (C), the mixing ratio of glycerol monoacetomonoester (C-1) and glycerol diacetomonoester (C-2) is (C-1) / (C-2) = 50/50. The mixture to be melt-kneaded while injecting the mixture from the first vent port of the extruder using a metered liquid feed pump so that the component (C) is 15 parts by mass with respect to 100 parts by mass of B-1 Then, the resin composition for forming both surface layers melted and kneaded as described above and the resin composition for forming the intermediate layer are merged from separate extruders, respectively, and the three-layer T die temperature is 200 ° C. and the die gap is 2 mm. The film for packaging having a total thickness of 12 μm (surface layer / intermediate layer / surface layer = 1.5 μm / 9 μm / 1.5 μm) was obtained by quenching with a cast roll set at a temperature of 30 ° C. The results of evaluating the obtained film are shown in Table 1.

(Example 2)
In Example 1, the same procedure was performed except that the component (A) was changed to Nippon Unicar's linear low density polyethylene “NUCG5225” (MFR: 2.0 g / 10 min) (hereinafter abbreviated as A-2). A packaging film having a total thickness of 12 μm (surface layer / intermediate layer / surface layer = 1.5 μm / 9 μm / 1.5 μm) was obtained. The results of evaluating the obtained film are shown in Table 1.

(Example 3)
In Example 2, the mass of B-1 and NatureWorks 4060D "(L-form / D-form = 97/13, weight average molecular weight: 200,000) (hereinafter abbreviated as B-2) is the mass of polylactic acid (B) component. A packaging film having a total thickness of 12 μm (surface layer / intermediate layer / surface layer = 1.5 μm / 9 μm / 1.5 μm) was obtained in the same manner except that the ratio was B-1 / B-2 = 60/40. . The results of evaluating the obtained film are shown in Table 1.

Example 4
In Example 3, as glycerol fatty acid ester (C), the mixing ratio of glycerol monoacetomonoester (C-1) and glycerol diacetomonoester (C-2) is (C-1) / (C-2) = A total thickness of 12 μm (surface layer / intermediate layer) was similarly obtained except that the mixture of 50/50 was changed so that the amount of (C) added was 12 parts by mass with respect to 100 parts by mass of (B). / Surface layer = 1.5 μm / 9 μm / 1.5 μm). The results of evaluating the obtained film are shown in Table 1.

(Example 5)
In Example 3, as the glycerin fatty acid ester (C) which is the same component (C), the mixing ratio of glycerin monoacetomonoester (C-1) and glycerin diacetate monoester (C-2) is (C-1 ) / (C-2) = 27/73 A total thickness of 12 μm (surface layer) except that the amount of (C) added was 13 parts by mass with respect to 100 parts by mass of (B) / Intermediate layer / surface layer = 1.5 μm / 9 μm / 1.5 μm). The results of evaluating the obtained film are shown in Table 1.

(Example 6)
In Example 4, the film was coextruded with the same configuration to obtain a raw film having a total thickness of 36 μm (surface layer / adhesive layer / intermediate layer / adhesive layer / surface layer = 4.5 μm / 27 μm / 4.5 μm). Subsequently, the film was uniaxially stretched in the MD by roll stretching at a stretching temperature of 70 ° C., a heat treatment temperature of 90 ° C., and a stretching ratio of 3 times to obtain a packaging film having a thickness of 12 μm. The results of evaluating the obtained film are shown in Table 1.

(Comparative Example 1)
In Example 1, instead of A-1 as the resin composition for forming both surface layers and the antifogging agent, a resin composition having the same composition as the resin composition for forming the intermediate layer is pre-compounded to form pellets. A packaging film having a total thickness of 12 μm was obtained in the same manner as in Example 1 except that this pellet was put into an extruder for both surface layers to make a substantially single layer film.

(Comparative Example 2)
In Example 2, a packaging film having a total thickness of 12 μm was obtained in the same manner as in Example 2 except that A-2 was charged into an intermediate layer extruder to obtain a substantially single layer film. The results of evaluating the obtained film are shown in Table 1.

(Comparative Example 3)
In Example 1, the glycerin fatty acid ester (C) was not injected from the first vent of the extruder, that is, melt-kneaded without containing the glycerin fatty acid ester (C). A surface layer / intermediate layer / surface layer = 1.5 μm / 9 μm / 1.5 μm) packaging film was obtained. The results of evaluating the obtained film are shown in Table 1.

(Table 1)

From Table 1, the films obtained in Examples 1 to 6 can suppress the molecular weight of the packaging film from decreasing with time, and block even if the formed film is stored in a wound state. It was confirmed that the antifogging property and the container adhesion were also good.
On the other hand, in the case of Comparative Examples 1 to 3, when there is no intermediate layer mainly composed of a lactic acid polymer resin composition (Comparative Example 2), blocking, antifogging, The film stability was good, but the container adhesion was insufficient. Further, when the surface layer mainly composed of a polyolefin-based polymer was not provided (Comparative Example 1), the container adhesion was good, but the film-forming stability, blocking, and antifogging properties were insufficient. In addition, the molecular weight decreased due to hydrolysis over time, which was a problem due to insufficient practical characteristics. Moreover, when the peak temperature of loss tangent was higher than the range of 20-70 degreeC (comparative example 3), although blocking and anti-fogging property were favorable, container adhesiveness was inadequate.
Further, in Examples 4 and 5, since the glycerin fatty acid ester (C) is a mixture of glycerin monoacetomonoester and glycerin diacetate monoester, the physical properties equivalent to those of Examples 1 to 3 are obtained even when the addition amount is small. It was confirmed that it was obtained.
Furthermore, Example 6 was excellent in cut property by performing a drawing process.

Claims (5)

  A packaging film having at least three layers, both surface layers containing a polyolefin polymer (A) as a main component, and an intermediate layer comprising a lactic acid polymer (B) and a glycerin monoacetomonoester ( C-1) containing glycerin fatty acid ester (C) having a molecular weight of 2000 or less as a main component, and storage elastic modulus (E ′) measured at a frequency of 10 Hz and a temperature of 20 ° C. by dynamic viscoelasticity measurement is 1 to 1. 4 GPa, loss tangent (tan δ) peak temperature is 20 to 70 ° C., and the peak value is in the range of 0.1 to 0.8.   The glycerin fatty acid ester (C) having a molecular weight of 2000 or less containing glycerin monoacetomonoester (C-1) is a mixture of glycerin monoacetomonoester (C-1) and glycerin diacetomonoester (C-2). The packaging film according to claim 1.   The intermediate layer contains 1 to 20 parts by mass of a glycerin fatty acid ester (C) having a molecular weight of 2000 or less including glycerol monoacetomonoester (C-1) with respect to 100 parts by mass of the lactic acid polymer (B). The packaging film according to claim 1, wherein the packaging film is a film.   The packaging film according to any one of claims 1 to 3, wherein the lactic acid polymer (B) is a mixed resin of two or more lactic acid polymers having different LD ratios. The polyolefin copolymer (A) is selected from low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, and ethylene-methacrylic acid ester copolymer. The packaging film according to any one of claims 1 to 4, wherein the packaging film is a mixed resin comprising at least one ethylene polymer or a combination of two or more thereof.