JP2011000770A - Packaging film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packaging film which is superior in blocking resistance, and durability capable of suppressing hydrolysis of a lactic acid-based polymer, and has a various characteristics required for a small wrap film roll.SOLUTION: The packaging film includes both surface layers comprising a surface layer forming composition containing an olefin-based polymer (A), and any one kind or two kinds or more of the following (a)-(d), and an intermediate layer comprising an intermediate layer forming composition containing the lactic acid-based polymer (B) as a main component, and includes an adhesive layer comprising an adhesive forming composition containing an olefin-based polymer (A) and the lactic acid-based polymer (B) as main components between the surface layer and the intermediate layer. The (a)-(d) include: (a) a block copolymer of a vinyl aromatic compound and a conjugate diene or the hydrogenated derivative thereof, (b) a random copolymer of a vinyl aromatic compound and a conjugate diene or the hydrogenated derivative thereof, (c) petroleum resins, and (d) at least one kind of liquid additive selected from a liquid polybutene or a liquid polyisobutylene.

Description

  The present invention is a packaging film using a lactic acid polymer, which is a resin derived from a natural plant, as one of the main raw materials, and is housed in a box equipped with a cutter blade and used at home, etc. The present invention relates to a packaging film that can be suitably used as a small roll film.

A so-called “wrap film” (also referred to as a “small roll wrap film” in the present invention to distinguish it from a commercial stretch wrap film) is used as a film for packaging cooked foods on earthenware or plastic containers. Yes.
Such a small wrap film is usually stored in a state of being wound around a cylinder in a paper box having a cutter blade. When packaging, pull the film out of the paper box to cover the food, press the film against the cutter blade provided in the paper box, open a perforated hole in the film with this cutter blade, and tear the film The film is cut so as to propagate the tear in the width direction, and the end of the film is used in close contact with the container for packaging. For this reason, in addition to transparency, the small roll wrap film is required to have various properties such as adhesion to the container and cut suitability when the film drawn from the box is cut.

Many of the wrapping films currently on the market are films mainly composed of stretched polyvinylidene chloride resin, extruded polyethylene resin, plasticized polyvinyl chloride resin, poly-4-methylpentene-1 system A film mainly composed of resin or the like.
In recent years, 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 potato, and are not only mass-produced but also excellent in transparency, so they are also attracting attention as raw materials for packaging films. Research and development of packaging films using lactic acid-based polymers as raw materials has been conducted.

For example, in Patent Document 1, cut suitability, packaging suitability, which are characteristics of a household wrap film,
As a biodegradable wrap film having heat resistance at the same time, a storage elastic modulus value at 40 ° C. measured at a frequency of 10 Hz and a strain of 0.1% by a dynamic viscoelasticity measurement method of JIS K-7198 A method is 100 MPa. A lactic acid resin composition in a range of ˜3 GPa, a storage elastic modulus at 100 ° C. in a range of 30 MPa to 500 MPa, and a loss tangent (tan δ) peak value in a range of 0.1 to 0.8, For example, a biodegradable wrap film containing a lactic acid resin composition containing a lactic acid polymer and a plasticizer in a mass ratio of 60: 1 to 99: 1 as a main component is disclosed.

  In Patent Document 2, the outermost layer is a layer mainly composed of an olefin polymer, and a layer mainly composed of polylactic acid (lactic acid polymer) between the layers mainly composed of the olefin polymer. A shrink sheet-like material having at least one layer is disclosed, and an adhesive layer made of an acrylic-modified polyethylene resin is provided between a layer mainly composed of an olefin polymer and a layer mainly composed of polylactic acid. It is also disclosed that it can intervene.

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 sheet is kept amorphous and the elastic modulus is lowered. If the wrap film is wound as it is, the roll may be blocked.
In addition, when the lactic acid polymer is exposed on the front and back layers of the wrap film, the molecular weight of the lactic acid polymer decreases with time due to hydrolysis, and thus there is a problem that blocking is more likely to occur.
Furthermore, in order to function as a small roll wrap film, as described above, in addition to transparency, various properties such as adhesion to the container and cut suitability when cutting the drawn film are required. It is not easy to produce a packaging film satisfying such various characteristics using as a main raw material, and in particular, in a multilayer film having a multilayer structure as in Patent Document 2, adhesion to a container is not possible. It has not been easy to produce a film that excels.

  Therefore, in a packaging film that uses a lactic acid polymer as one of the main raw materials, blocking does not occur even when the formed film is stored in a wound state, and the degree of molecular weight reduction of the lactic acid polymer is reduced. The following packaging film has been proposed as a packaging film that can be reduced and yet satisfy various properties required for a small roll wrap film (Patent Document 3).

  That is, Patent Document 3 discloses a packaging film composed of a laminated film of five or more layers having at least a surface layer / adhesive layer / intermediate layer / adhesive layer / surface layer in this order. The intermediate layer contains a lactic acid polymer as a main component, both adhesive layers contain an adhesive resin as a main component, and the adhesive resin contains a modified olefinic polymer. A polymer, a copolymer of a soft aromatic hydrocarbon and a conjugated diene hydrocarbon, a hydrogenated derivative of these copolymers, or an ethylene-vinyl acetate copolymer having a vinyl acetate content of 30 to 80% by mass Acrylic block copolymer having a polymer or a lactic acid polymer, a polymer block mainly composed of an acrylate unit, and a polymer block mainly composed of a methacrylic ester unit Any one of the lactic acid-acrylic mixed resin, or packaging film which is a resin composed of two or more thereof is disclosed having a.

WO / 2005/082981 JP 2002-19053 A WO / 2008/004510

  As disclosed in Patent Document 3, from a laminated film having an adhesive layer between a surface layer mainly composed of an olefin polymer and an intermediate layer mainly composed of a lactic acid polymer to a packaging film When manufacturing the film, the important issues are ensuring the transparency of the adhesive layer, preventing delamination due to the difference in the melt viscosity of the resins that make up each layer, and providing adhesion to the container in the laminated film there were. Moreover, when creating a laminated film having a surface layer mainly composed of an olefin polymer, if the film is uniaxially stretched for the purpose of imparting cutability as a wrap film, there is a problem of tearing the film in the stretching direction. It was a problem to occur.

  Therefore, the present invention further improves a packaging film having a laminated structure including an adhesive layer between a surface layer mainly composed of an olefin polymer and an intermediate layer mainly composed of a lactic acid polymer. Therefore, even when the film formed is stored in a wound state, blocking does not occur, the degree of decrease in the molecular weight of the lactic acid polymer can be reduced, and various characteristics required for a small-wrap film can be obtained. In addition, it can prevent delamination while ensuring the transparency of the adhesive layer, has excellent adhesion to the container, and even if it is uniaxially stretched during film formation, it does not easily cause troubles in tearing the film in the stretching direction. It is intended to provide a new packaging film.

In view of such a problem, the present invention comprises both an olefin polymer (A) and a surface layer forming composition containing any one of the following (a) to (d) or two or more of them. A surface layer and an intermediate layer comprising an intermediate layer-forming composition containing a lactic acid polymer (B) as a main component, and the olefin polymer (A) and the lactic acid heavy polymer between the surface layer and the intermediate layer. The packaging film provided with the contact bonding layer which consists of a contact bonding layer forming composition which contains a unification | combination (B) as a main component is proposed.
(A) Block copolymer of vinyl aromatic compound and conjugated diene or hydrogenated derivative thereof (b) Random copolymer of vinyl aromatic compound and conjugated diene or hydrogenated derivative thereof (c) Petroleum resins (d ) At least one liquid additive selected from liquid polybutene or liquid polyisobutylene

  If it is a film for packaging provided with such a configuration, since it has both surface layers mainly composed of the olefin polymer (A), it can be stored in a state in which the formed film is wound. Without causing blocking, the degree of decrease in the molecular weight of the lactic acid polymer can be reduced. In addition, since the adhesive layer is formed with the olefin polymer (A) and the lactic acid polymer (B) as the main components, each of the surface layers, the adhesive layer, the intermediate layer, and the adhesive layer is composed of each layer. Difference in melt viscosity of resin can be reduced, for example, delamination at the time of small rewinding can be prevented, film forming stability can be improved, and even the film edge can be finished to a good appearance Can do. Moreover, since it is a laminated film composed of at least 5 layers, both surface layers can contain any one of the compositions (a) to (d) and additives such as an antifogging agent. In addition to improving the adhesion and anti-fogging properties of the film, it is possible to obtain a film that is less likely to cause tearing troubles even when stretched.

  Furthermore, the lactic acid polymer (B) to be mixed by regulating the crystallization heat amount of the olefin polymer (A), particularly the olefin polymer (A) forming the adhesive layer, to 5 J / g to 80 J / g. And the refractive index difference can be reduced, and the transparency can be increased to 3% or less of the total haze value of the packaging film. And it can build in so that the various characteristics calculated | required by a small volume wrap film can be acquired.

  Furthermore, if the adhesive layer forming composition is constituted by using the surface layer forming composition and the intermediate layer forming composition, the difference in the melt viscosity of the resin constituting each layer can be further reduced. It is possible to further prevent delamination at the time of small rewinding, to further improve the film-forming stability, and to achieve a better appearance up to the film end. In addition, since product loss such as trimming loss (chips) can be used as a raw material for the adhesive layer forming composition, a packaging film can be manufactured at a lower cost.

  Hereinafter, a packaging film (hereinafter referred to as “the present packaging film”) as an example of an 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 is a laminated film composed of at least five layers, and comprises a surface layer forming composition containing an olefin polymer (A) and predetermined additives ((a) to (d)). Both surface layers, an intermediate layer composed of an intermediate layer forming composition containing a lactic acid polymer (B) as a main component, an olefin polymer (A) and a lactic acid polymer (B) as main components It is a packaging film provided with the contact bonding layer which consists of a contact bonding layer formation composition.

  In this section, the olefin polymer (A), the additives ((a) to (d)) added to the surface layer forming composition, and the lactic acid polymer (B) will be described in order, and then the surface layer, intermediate The layer and the adhesive layer will be described, and then the laminated structure, physical characteristics, manufacturing method and the like of the packaging film will be described.

<Olefin polymer (A)>
The olefin polymer (A) is a main component of the surface layer and the adhesive layer. The olefin polymers (A) in both layers may be of different types, but from the viewpoint of reducing the difference in melt viscosity between layers, it is preferable to use the same type, particularly the same resin.

The olefin polymer (A) used in the packaging film, particularly the olefin polymer (A) constituting the adhesive layer, preferably has a crystallization heat amount ΔHc = 5 J / g to 80 J / g.
In this packaging film, since the mixed resin of the olefin polymer (A) and the lactic acid polymer (B) is a main component of the adhesive layer, the mixed resin needs to have excellent transparency.
Transparency in the polymer blend is affected by the particle size of the dispersed phase and the average refractive index difference between the dispersed phase and the matrix phase. When the particle size of the dispersed phase is smaller than the visible light region, the resin composition exhibits excellent transparency. On the other hand, when the particle size of the dispersed phase is larger than the visible light region, the transparency is better as the difference in average refractive index between the dispersed phase and the matrix phase is smaller. In general, the transparency of the resin composition and film obtained from the olefin polymer (A) and the lactic acid polymer (B) is greatly influenced by the difference in the average refractive index of both components.
Since the refractive index of a general olefin polymer is higher than that of a lactic acid polymer and the difference in refractive index between the two is large, a mixture of an olefin polymer (A) and a lactic acid polymer (B) is mixed. The transparency of the resin is not preferred. Therefore, in this packaging film, by using an olefin polymer having a crystallization heat amount lower than that of a general olefin polymer, the difference in refractive index from the lactic acid polymer (B) is reduced, and the olefin polymer weight is reduced. The transparency of the mixed resin composed of the coalescence (A) and the lactic acid polymer (B) is enhanced.
Therefore, from the viewpoint of transparency, the crystallization heat amount of the olefin polymer (A) is preferably 5 J / g to 80 J / g, particularly 5 J / g to 60 J / g, and especially 5 J / g. More preferably, it is -40J / g.

On the other hand, when this packaging film is used as a small roll film, heat resistance is required because it may be heated in a microwave oven or the like. In order to improve heat resistance, it is preferable that the heat of crystallization is high, and it is particularly preferable that the heat of crystallization of the olefin polymer (A) constituting the surface layer is high.
Therefore, when the same olefin polymer (A) is used for the surface layer and the adhesive layer, the crystallization heat amount of the olefin polymer (A) is 20 J in consideration of both ensuring transparency and heat resistance. / G to 80 J / g, preferably 30 J / g to 60 J / g.

  The crystallization heat amount ΔHc of the olefin polymer (A) can be measured using a differential scanning calorimeter. Specifically, it can be expressed as the amount of heat when the temperature is raised to 200 ° C. at a heating rate of 10 ° C./min, held at 200 ° C. for 5 minutes, and then lowered to room temperature at a cooling rate of 10 ° C./min.

The average refractive index of the olefin polymer (A) is preferably 1.48 to 1.49.
As described above, the transparency of the packaging film is greatly affected by the difference in average refractive index between the olefin polymer (A) and the lactic acid polymer (B). In general, the average refractive index of a lactic acid polymer is about 1.45 to 1.46, and the average refractive index of a general olefin polymer is about 1.50 to 1.51, so the absolute value of the difference Is about 0.04 to 0.06. When this value exceeds 0.04, the resulting resin composition and film tend to become cloudy.
In contrast, the olefin polymer (A) is a relatively low crystalline olefin polymer and has an average refractive index of 1.48 to 1.49. The average refractive index difference is small, and the transparency of the mixed resin composed of the olefin polymer (A) and the lactic acid polymer (B) can be enhanced. If the absolute value of the average refractive index difference between the olefin polymer (A) and the lactic acid polymer (B) is 0.04 or less, a resin composition and a film excellent in transparency can be obtained. It is more preferable if it is 0.02 or less, and it is further preferable because the transparency is further improved.
Incidentally, the average refractive index of an olefin polymer is affected by its crystallinity, and the olefin polymer having a lower crystallization heat quantity ΔHc tends to decrease.

  Examples of the olefin polymer (A) include ethylene polymers, butylene polymers, propylene polymers such as polypropylene and ethylene-propylene copolymers, poly-4-methylpentene, polybutene, and ethylene-vinyl acetate copolymer. Examples of the polymer include an ethylene polymer, a propylene polymer, or a mixture thereof having a crystallization heat amount ΔHc in the above range from the viewpoints of mechanical properties and moldability of flexibility and transparency. It is preferable to use it.

In the case of an olefin polymer, as a means for setting the crystallization heat amount ΔHc in the above range, a method of making a copolymer, a method of reducing stereoregularity, or the like is preferably used.
As the copolymer, a propylene-α-olefin copolymer or an ethylene-α-olefin copolymer is preferably used. Preferred examples of the α-olefin include those having 2 to 20 carbon atoms such as ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene and the like. It can be illustrated. In this case, the α-olefin to be copolymerized may be used alone or in combination of two or more.
Specifically, from the viewpoint of low crystallinity and heat resistance, one propylene polymer selected from propylene-ethylene random copolymer, propylene-ethylene-butene-1 copolymer, and polypropylene elastomer, Alternatively, it is preferable to use a mixed resin composed of a combination of two or more of these.
Among them, a propylene-ethylene random copolymer is particularly preferable because of its low crystallinity, balance between flexibility and heat resistance, and industrial availability at a relatively low cost.

  In these copolymers, the content of α-olefin, particularly ethylene, is preferably 1.0% by mass or more from the viewpoints of crystallization heat quantity, flexibility, transparency, etc., among which 2.0-15% by mass. % Is particularly preferred. However, when the content of α-olefin, particularly ethylene, is increased, the refractive index tends to increase. When the content of α-olefin, particularly ethylene, exceeds 50% by mass, the refractive index becomes too high, which is not preferable.

  The melt flow rate (MFR) of the olefin polymer (A) is not particularly limited, but usually MFR (JISK7210, temperature: 230 ° C., load: 21.2 N) is 0.2 g / 10 min. As mentioned above, Preferably, they are 0.5g / 10min-18g / 10min, and it is more preferable that they are 1g / 10min-15g / 10min.

  The production method of the olefin polymer (A) 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 system. Examples include a slurry polymerization method, a solution polymerization method, a bulk polymerization method, a gas phase polymerization method and the like using a single site catalyst typified by a catalyst, and a bulk polymerization method using a radical initiator.

<Additives (a) to (d)>
Additives (a) to (d) are mixed with the olefin polymer (A) to improve the adhesion of the film to the container when the packaging film is used as a wrapping film for food packaging. be able to. In addition, the additive (a) and the additive (b) are mixed with the olefin polymer (A), so that even if uniaxial stretching is performed during film formation, there is no problem of tearing the film after film formation. It can be made difficult to occur.

(Additive (a))
The additive (a) is a block copolymer of a vinyl aromatic compound and a conjugated diene or a hydrogenated derivative thereof.

Styrene is a typical vinyl aromatic compound, but styrene homologues such as α-methylstyrene can also be used.
On the other hand, examples of the conjugated diene include 1,3-butadiene, isoprene, 1,3-pentadiene, and the like. These can be used alone or in combination of two or more. .
Further, as the third component, a small amount of components other than the vinyl aromatic compound and the conjugated diene may be contained. However, the thermal stability and weather resistance when a double bond mainly consisting of vinyl bonds in the conjugated diene moiety remains are extremely poor. To improve this, 80% or more, preferably 95% of the double bonds. It is preferable to use one added with hydrogen.

  The ratio between the vinyl aromatic compound and the conjugated diene is preferably 3/97 to 40/60 by weight. Here, if the vinyl aromatic compound in the copolymer composition is less than 3% by weight, the polymerization productivity such as the rigidity of the copolymer itself is too low and pelletization becomes difficult, and on the other hand, 40% by mass. If it exceeds 1, the rigidity of the copolymer itself becomes high, and the effect of suppressing the instantaneous restoration behavior of the film, which is the purpose of adding the additive (a), tends to be insufficient.

  Specific examples of the additive (a) include styrene-butadiene block copolymer elastomer (Asahi Kasei Kogyo Co., Ltd., trade name “Tufprene”), hydrogenated derivative of styrene-butadiene block copolymer (Asahi Kasei Kogyo Co., Ltd.) Name "Tuftec", Shell Japan Co., Ltd. trade name "Clayton G"), Hydrogenated derivative of styrene-isoprene block copolymer (Kuraray Co., Ltd. trade name "Septon"), Styrene-vinylisoprene block copolymer elastomer (Kuraray brand name "Hibler") etc. are marketed.

  The addition amount of the additive (a) is preferably 5 to 50% by mass, particularly 10 to 30% by mass of the olefin polymer (A). If the content of the additive (a) is within 50% by mass, the waist of the resulting film can be retained, it can be prevented from becoming too soft and the waist is lost, and cut properties, heat resistance Sex can also be maintained. If content of an additive (a) is 5 mass% or more, the softness | flexibility of the film obtained can be maintained and container adhesiveness can be hold | maintained.

(Additive (b))
The additive (b) is a random copolymer of a vinyl aromatic compound and a conjugated diene or a hydrogenated derivative thereof.
The kind of vinyl aromatic compound and conjugated diene component, and the weight ratio thereof are the same as those of the additive (a) described above, but the styrene content is particularly 5 to 25% by mass, and the vinyl bond of the conjugated diene moiety. A styrene / conjugated diene random copolymer having an amount exceeding 50%, preferably 60 to 90% of a hydrogenated derivative of a styrene / conjugated diene random copolymer is finely dispersed in the olefin polymer (A) ( It is particularly suitable from the viewpoints of compatibility and transparency improvement.

As a specific example of such an additive (b), it is marketed as a hydrogenated derivative of a styrene-butadiene random copolymer (trade name “DYNARON”, JSR Corporation).
Details of the hydrogenated derivative of the styrene / conjugated diene random copolymer and the production method thereof are disclosed in JP-A-2-15843, JP-A-2-305814 and JP-A-3-72512. ing. As a specific example of such a copolymer, a hydrogenated styrene butadiene rubber structure is used, and a material called abbreviation of HSBR is commercially available under the trade name “Dynalon 1320P”.

  The addition amount of the additive (b) is preferably 5 to 50% by mass, particularly 10 to 30% by mass of the olefin polymer (A). If the content of the additive (b) is within 50% by mass, the waist of the resulting film can be maintained, it can be prevented from becoming too soft and the waist is lost, and the cut property, heat resistance Sex can also be maintained. If content of an additive (b) is 5 mass% or more, the softness | flexibility of the film obtained can be maintained and container adhesiveness can be hold | maintained.

A copolymer of the additive (a) and the additive (b) or a mixture of the additive (a) and the additive (b) can also be suitably used.
Under the present circumstances, it is preferable that the addition amount of the copolymer of an additive (a) and an additive (b) and a mixture shall be 5-50 mass% of an olefin type polymer (A), especially 10-30 mass%. . If the content of the additive (b) is 50% by mass or less, the waist of the resulting film can be retained, it can be prevented from becoming too soft and the waist is lost, and cut properties, heat resistance Sex can also be maintained. On the other hand, if it is 5 mass% or more, the flexibility of the resulting film can be maintained and the container adhesion can be maintained.

(Additive (c))
The additive (c) is a petroleum resin.
Although additive (c) can also be used independently, the further improvement of container adhesiveness can be aimed at by using together with additive (a) or additive (b).

Examples of petroleum resins include petroleum resins, terpene resins, coumarone-indene resins, rosin resins, and hydrogenated derivatives thereof.
Examples of the petroleum resin include cyclopentadiene or an alicyclic petroleum resin derived from a dimer thereof and an aromatic petroleum resin derived from a C9 component, and examples of the terpene resin include terpene resins and terpene-phenol resins derived from β-pinene. Examples of the rosin resin include rosin resins such as gum rosin and wood rosin, and esterified rosin resins modified with glycerin, pentaerythritol, and the like. The petroleum resins are preferably hydrogenated derivatives in terms of color tone, thermal stability, and compatibility.
In addition, petroleum resins having various softening temperatures are mainly obtained depending on the molecular weight, and those having a softening temperature of 100 to 150 ° C, preferably 110 to 140 ° C are preferably used.
Specifically, Mitsui Chemicals' product names “Hilets” and “Petrogin”, Arakawa Chemical Industries' product name “Arcon”, Yashara Chemicals' product name “Clearon”, Idemitsu Petrochemical Co., Ltd. ) And trade name “Escolez” of Tonex Co., Ltd. can be used.

The addition amount of the additive (c) is preferably 5 to 30% by mass, particularly 10 to 25% by mass, of the olefin polymer (A).
If the content of petroleum resins is 30% by mass or less, the mechanical strength and low temperature characteristics can be maintained, and the film can be prevented from being easily broken, and the petroleum resins bleed on the surface over time. Or, when it is a scroll, problems such as blocking between films can be reduced.

(Additive (d))
The additive (d) is at least one liquid additive selected from liquid polybutene or liquid polyisobutylene.
The additive (d) is compatible with the film made of the polyolefin polymer (A), can be uniformly dispersed in the structure, and can impart wettability to the surface. As a result, the adhesion of the container can be improved.
In addition, the liquid additive preferably has a number average molecular weight of 100 to 3000, preferably 300 to 1500, from the viewpoint of more easily expressing the tackiness imparted to the film. Is done.
Specifically, commercially available products such as “Nissan Polybutene” from Nichiyu Co., Ltd., “Nisseki Polybutene” from Nippon Oil Corporation, “Nisseki Polyisobutylene”, and the like can be used.

  The addition amount of the additive (d) is preferably 5 to 30% by mass, particularly 10 to 20% by mass, of the olefin polymer (A). If the content of petroleum resins is 30% by mass or less, polybutene or polyisobutylene can be prevented from bleeding on the surface over time, and the film can be prevented from blocking when it is used as a scroll. Can do. Moreover, if content is 5 mass% or more, adhesiveness can be provided.

<Lactic acid polymer (B)>
The lactic acid polymer (B) is a main component of the intermediate layer and the adhesive layer. The lactic acid polymers (B) in both layers may be of different types, but from the viewpoint of reducing the difference in melt viscosity between layers, it is preferable to use the same type, particularly the same resin.

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 composed of 100% 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 plasticizers and the like, it is preferable that the crystallinity of the lactic acid polymer is low. Therefore, polylactic acid having a lower crystallinity than poly (L-lactic acid), such as poly (D-lactic acid), It is preferable to use poly (DL-lactic acid) or a mixture thereof as a main component. 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 is low, bleeding out, such as a plasticizer, can be suppressed.

  Also, considering the balance between suppression of bleeding out of plasticizers and the like, heat resistance and cutability (depending on the type of olefin polymer (A) which is the main component of both surface layers), D Poly (L-lactic acid) having a body content of 0.5 to 5 mol% (hereinafter sometimes abbreviated as “B-1 component”) and poly (D, L-lactic acid) having a D body content of 10 to 15 mol% It is preferable to use a mixed resin composition (hereinafter sometimes abbreviated as “B-2 component”). Among them, the mixing mass ratio of the component (B-1) and the component (B-2) is (B− 1) / (B-2) = 10/90 to 80/20 is particularly preferable, and among them, (B-1) / (B-2) = 50/50 to 70/30 is particularly preferable. Is more preferable.

  The lactic acid-based polymer 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, 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 or 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 mass average molecular weight of the lactic acid polymer is preferably in the range of 50,000 to 400,000, more preferably in the range of 100,000 to 250,000. If the mass average molecular weight of the lactic acid polymer 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 molding processability may be inferior. Absent.

  A commercially available lactic acid polymer can be used as the lactic acid polymer used for the packaging film. For example, a brand name “Lacia” series (manufactured by Mitsui Chemicals, Inc.), a brand name “Nature Works” series (manufactured by NatureWorks), a brand name “U′z series” (manufactured by Toyota Motor Corporation), and the like can be given.

<Surface layer>
Both the inner and outer surface layers (hereinafter simply referred to as “surface layer”) are formed from a surface layer forming composition containing the olefin polymer (A) and predetermined additives ((a) to (d)). Can do.

  In addition to the above-mentioned olefin polymer (A), the surface layer can enhance the antifogging property of the film by blending an antifogging agent, and further improve the adhesion of the film by blending an adhesive. Can be increased.

More specifically, in order to further improve performances such as antifogging property, antistatic property, slipperiness, and adhesiveness, the following various additives can be appropriately blended.
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, glycerin acetyl ricinoleate, polyglycerin stearate, polyglycerin laurate, glyceryl acetyl laurate, methyl acetyl lysylate, ethyl acetyl lysylate, Butylacetyl lysylate, propylene glycol oleate, propylene glycol laurate, pentaerythritol oleate, polyethylene glycol oleate, polypropylene glycol oleate, sorbitan oleate, sorbitan la Rate, 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 oils, 0.1 to 12 parts by mass can be blended with respect to 100 parts by mass of resin components constituting various types, and preferably 1 to 8 parts by mass is blended.

  The surface layer has a heat stabilizer, an antioxidant, a UV absorber, an anti-blocking agent, a light stabilizer, a nucleating agent, a hydrolysis inhibitor, a deodorant, etc. as long as the function of the packaging film is not impaired. These additives can be appropriately blended.

<Intermediate layer>
The intermediate layer can be formed from an intermediate layer forming composition containing the lactic acid polymer (B) as a main component.

  In addition to the lactic acid polymer (B), it is preferable to contain a plasticizer capable of plasticizing the lactic acid polymer (B).

  Examples of the plasticizer include phthalic acid esters, adipic acid esters, trimellitic acid esters, phosphoric acid esters, adipic acid polyesters, glycerin fatty acid ester, and other plasticizers. From the viewpoint of good compatibility with the polymer, it is preferable to use glycerin fatty acid ester (C). Hereinafter, this glycerol fatty acid ester (C) is demonstrated.

(Glycerin fatty acid ester (C))
The glycerin fatty acid ester (C) can plasticize the lactic acid polymer (B). Such glycerin fatty acid esters are not particularly limited in their types, and examples include monoglycerides, diglycerides, triglycerides, acetylated monoglycerides, and polyglycerin fatty acid esters such as diglycerin, triglycerin, and tetraglycerin. Can do. Among them, an acetylated monoglyceride having a molecular structure represented by the following chemical formula (1) is particularly preferable from the viewpoint of good compatibility with a lactic acid polymer and high plasticizing ability.

  In the chemical formula (1), R1 represents an alkyl group, and R2 and R3 each represents an acetyl group or hydrogen. The number of carbon atoms of these alkyl groups is not particularly limited and is appropriately selected so as to achieve the purpose of improving adhesion and flexibility. In general, it is preferably 6 to 20.

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

  Among the glycerin fatty acid esters, a mixture of glycerin monoacetomonoester and glycerin diacetate monoester is preferable. Glycerin monoaceto monoester has good plasticizing performance and can substantially reduce the number of plasticizers added to the resin to be mixed. On the other hand, glycerin diacetate monoester can suppress volatilization of a plasticizer when mixed with a resin, and can exhibit stable plasticization performance. Therefore, the number of added parts can be determined and added depending on the application and the function required.

  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.

  In addition, from the viewpoint of processability, since it is preferable that the blending amount of glycerin fatty acid ester (C) is small, 1 to 20 parts by mass of glycerin fatty acid ester (C) with respect to 100 parts by mass of lactic acid polymer (B), Among these, it is more preferable to mix so as to include 3 to 18 parts by mass, particularly 5 to 18 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 polymer (B) is not excessively decreased, and the difference in elastic modulus with the fluidity between the front and back layers. Can be reduced. That is, at the time of film formation, the processability at the time of co-extrusion with the front and back layers (for example, the olefin polymer (A)) is improved, and a film having an excellent appearance without striped pattern or whitening can be obtained.

The intermediate layer of the packaging film has a heat stabilizer, antioxidant, UV absorber, anti-blocking agent, light stabilizer, nucleating agent, hydrolysis inhibitor, thickening, as long as the function of the packaging film is not impaired. Additives such as agents and deodorants can be formulated.
For example, in order to maintain the practical properties of the packaging film, the carbodiimide compound is preferably blended in an amount of 0.1 to 3 parts by weight, more preferably 0.5 to 1 part by weight, based on 100 parts by weight of the lactic acid polymer. Thus, the mass average molecular weight can be increased. Below this range, the effect of increasing the mass average molecular weight is often small, and above this range, fish eyes and gels may be produced during film formation, which is not preferred.

<Adhesive layer>
The adhesive layer of this packaging film can be formed from an adhesive layer forming composition containing an olefin polymer (A) and a lactic acid polymer (B) as main components.
Among them, the surface layer forming composition and the intermediate layer forming composition may be used, that is, only the surface layer forming composition and the intermediate layer forming composition may be used, or compatible with the surface layer forming composition and the intermediate layer forming composition. It is preferable that other materials such as an agent are added to form the adhesive layer forming composition. The reason is that if the surface layer forming composition and the intermediate layer forming composition are used to form the adhesive layer forming composition, the difference in melt viscosity between the surface layer, the adhesive layer, and the constituent resin between the intermediate layer and the adhesive layer. Therefore, it is possible to obtain more preferable film-forming stability, and, for example, use trimming loss that occurs when trimming is performed by cutting both ends of the formed film as a raw material for the adhesive layer forming composition. This is because the waste of material can be eliminated and the cost can be reduced.

The mixing ratio of the olefin polymer (A) and the lactic acid polymer (B), and the mixing ratio of the surface layer forming composition and the intermediate layer forming composition surface layer component are 70/30 to 40/60. Preferably, it is 65/35 to 50/50. Within this range, the peel strength between the surface layer and the intermediate layer can be kept good.
In order to adjust to such a mixing ratio, when trimming loss is used, a resin having an insufficient component may be added according to the component composition of the trimming loss. If the entire trimming loss cannot be used up as the adhesive layer, the surplus may be provided as the reproduction layer. Moreover, you may use the mixture containing an olefin polymer (A) and a lactic acid-type polymer (B) as an alternative of trimming loss.

In addition, the adhesive layer forming composition can be blended with a compatibilizing agent as long as it does not impair the function of the packaging film, and imparts antifogging properties, antistatic properties, slipping properties, adhesive properties, and the like. In order to do so, the following various additives can be appropriately blended.
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, glycerin acetylricinoleate, glycerin monoacetomonostearate, glycerin diacetomonolaurate, glycerin diacetomonooleate, polyglycerin stearate, polyglycerin Laurate, methyl acetyl lysylate, ethyl acetyl lysylate, butyl acetyl lysylate, propylene glycol oleate, propylene glycol laurate, pentaerythritol oleate, polyethylene glycol acrylate , Polypropylene glycol oleate, sorbitan oleate, sorbitan laurate, polyethylene glycol sorbitan oleate, polyethylene glycol sorbitan laurate, etc., and polyalkylene ether polyols, specifically polyethylene glycol, polypropylene glycol, etc., and paraffinic oils , At least one compound selected from polybutene, terpene resin, petroleum resin, and the like can be blended in an amount of 0.1 to 30 parts by mass with respect to 100 parts by mass of various resin components, preferably 3 to It is preferable to add 25 parts by mass.

  The thickness of the adhesive layer is preferably 0.3 μm to 5 μm because of its function. If the thickness of the adhesive layer is within such a range, the adhesiveness between the two surface layers and the intermediate layer can be expressed, and film forming stability is obtained during film formation, which is preferable. When it is desired to further secure the thickness ratio of the intermediate layer, the thickness is more preferably 0.5 μm to 3 μm.

<Laminated structure>
This packaging film is a laminated film comprising both surface layers, an intermediate layer, and an adhesive layer, and is a laminated film of 5 or more layers having at least surface layer / adhesive layer / intermediate layer / adhesive layer / surface layer in this order. Any other layer may be introduced as needed, such as improvement of mechanical properties and interlayer adhesion. Further, a reproducing layer can be provided between the surface layer and the adhesive layer, or between the intermediate layer and the adhesive layer.

  For example, a layer having the same composition as the surface layer may be interposed in addition to both surface layers, and two or more layers having the same composition as the intermediate layer may be interposed between both surface layers. It doesn't matter. Specifically, in addition to a five-layer structure comprising surface layer / adhesive layer / intermediate layer / adhesive layer / surface layer, surface layer / adhesive layer / intermediate layer / intermediate layer / adhesive layer / surface layer, surface layer / regeneration layer / Adhesive layer / intermediate layer / adhesive layer / surface layer, surface layer / adhesive layer / reproduction layer / intermediate layer / adhesive layer / surface layer, etc., surface layer / adhesive layer / intermediate layer / surface layer / intermediate Layer / adhesive layer / surface layer, surface layer / adhesive layer / intermediate layer / adhesive layer / intermediate layer / adhesive layer / surface layer, surface layer / reproduction layer / adhesive layer / intermediate layer / adhesive layer / reproduction layer / surface layer, A seven-layer structure composed of surface layer / adhesive layer / reproduction layer / intermediate layer / reproduction layer / adhesion layer / surface layer and the like can be exemplified. In this case, the resin composition and thickness ratio of each layer may be the same or different.

In this packaging film, it is preferable that the thickness ratio of the intermediate | middle layer with respect to the thickness of the whole film is 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 In addition to providing stable film-forming stability, it is relatively easy to impart mechanical properties for expressing cut properties suitable for food packaging wrap films and relaxation properties for expressing container adhesion. it can. 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, in the case where more importance is attached to stable film forming workability and flexibility, the thickness ratio of the intermediate layer to the total film thickness is preferably 35 to 65%, more preferably 35 to 60%. preferable.
On the other hand, when more importance is attached to cutability and adhesion to a container, and further, the degree of planting, that is, CO ₂ reduction, the thickness ratio of the intermediate layer to the thickness of the entire film is preferably 60 to 90%. 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.

(Reproduction layer)
As described above, the packaging film can have a reproduction layer as long as the effects of the present invention are not impaired. This is because, for example, trimming loss that occurs when trimming by trimming both ends of the formed film, it is possible to use a surplus after molding for the adhesive layer, defective molding, etc., eliminating waste of materials, Material costs can be reduced.
The reproduction layer can be provided between the surface layer and the adhesive layer, or between the intermediate layer and the adhesive layer. For example, the surface layer, the intermediate layer, or the adhesive layer is configured to have a two-layer configuration, and the trimming loss at both ends of the film is returned to one layer, so that the intermediate layer and the adhesive layer are between the surface layer and the adhesive layer. A reproducing layer can be provided between the two. In this case, in addition to the thickness ratio and composition ratio of each layer, the mixing ratio of the three components can be adjusted depending on whether the layer containing the return is based on the surface layer, the intermediate layer, or the adhesive layer.

  The thickness (whole) of this packaging film should just be the range used as a food packaging wrap film, specifically 6 micrometers-30 micrometers, Preferably it is 8 micrometers-20 micrometers.

<Physical characteristics of this packaging film>
Next, physical characteristics of the packaging film will be described.

(Total haze value)
The packaging film preferably has a total haze value of 3% or less in order to be suitably used as a small roll wrap film for home use, and the total haze value of the packaging film can be 3% or less. .

  If the total haze value of the film exceeds 3%, the packaged contents become difficult to see, and the value as a packaging film is lost. Therefore, the preferable total haze value is 2% or less, and more preferably 1.5% or less. In order to make the total haze value of the film within such a range, it can be adjusted by reducing the difference in refractive index between the olefin polymer (A) and the lactic acid polymer (B) as described above.

(Viscoelastic properties)
This 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 GPa to 4 GPa, and (2) a peak temperature of loss tangent (tan δ). 20 ° C. to 70 ° C. (3) It can be prepared so that its peak value is in the range of 0.1 to 0.8.
Incidentally, if it is a film provided with all of (1) to (3), it can be used as a small roll wrap film for home use.

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 E ′ exceeds 4 GPa, the film becomes hard and hardly stretched, and the drawability when pulled out from the paper box may deteriorate.
In addition, when the peak temperature of tan δ is 70 ° C. or lower and the peak value is 0.10 or higher, the restoring behavior against deformation of the film does not occur instantaneously. It is preferable because the film is not restored and the adhesion to the container is improved. In addition, if the peak temperature of tan δ is 20 ° C. or higher and the peak value is 0.80 or lower, plastic deformation is not exhibited, and this is not a problem in a normal usage method.
The tan δ (loss tangent) 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 the viscosity is large among the viscoelastic properties. By evaluating the peak value and the peak temperature of tan δ, This is a great measure for judging the adhesiveness and 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), film formation 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.

<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. 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-based polymer and additives as necessary are sufficiently dried to remove moisture, and then melt-mixed using a twin screw extruder, and a plasticizer is removed from the vent port. What is necessary is just to produce a pellet by extruding into a strand shape while adding a predetermined amount.

  The constituent raw materials for each layer are as described above, and as the raw material for the adhesive layer forming resin, the trimming loss of the packaging film can be used as it is or pellets obtained by adjusting the components can be used.

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. Flat stretching method in which longitudinal stretching (uniaxial stretching) for stretching 1.2 to 5.0 times is performed, or sequential biaxial stretching and / or simultaneous biaxial stretching is performed 1.2 to 5.0 times in both longitudinal and transverse directions of the film. Is preferably adopted. In order to improve the cut property, it is preferable to perform uniaxial stretching.
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 60 ° C. If the stretching temperature is within such a range, both the lactic acid polymer (B) in the intermediate layer and the ethylene copolymer (A) in the surface layer can be made close to the elastic modulus suitable for stretching, which is preferable. 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. As a cooling method in that case, either a method of cooling from the outer surface of the tube, or a 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 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.

  The obtained film is trimmed at both ends, and then cut into a desired size to produce a product.

<Explanation of terms>
In the present invention, the “main component” includes the meaning of allowing other components to be contained within a range that does not interfere with the function of the main component, unless otherwise specified. At this time, the content ratio of the main component is not specified, but the main component (when two or more components are main components, the total amount thereof) is 50% by mass or more, particularly 70% by mass in the composition. %, More preferably 90% by mass or more (including 100%).

  In general, “sheet” is a thin product as defined by JIS and generally has a thickness that is small and flat instead of length and width. In general, “film” refers to length and width. A thin flat product having an extremely small thickness and an arbitrarily limited maximum thickness, usually supplied in the form of a roll (Japanese Industrial Standard JISK6900). For example, in terms of thickness, in the narrow sense, a film having a thickness of 100 μm or more is sometimes referred to as a sheet, and a film having a thickness of less than 100 μm is sometimes referred to as a film. 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 the present invention, when expressed as “X to Y” (X and Y are arbitrary numbers), “X is preferably greater than X” and “preferably Y”, with the meaning of “X to Y” unless otherwise specified. It means “smaller”.
Further, in the present invention, when expressed as “X or more” (X is an arbitrary number), it means “preferably larger than X” unless otherwise specified, and “Y or less” (Y is an arbitrary number). ) Includes the meaning of “preferably smaller than Y” unless otherwise specified.

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 values 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) Heat of crystallization (ΔHc)
According to JIS K7121, 10 mg of olefin polymer was heated to 200 ° C. at a heating rate of 10 ° C./min using Pyris1 DSC manufactured by PerkinElmer Co., Ltd., held at 200 ° C. for 5 minutes, and then cooled at a rate of 10 The heat of crystallization ΔHc (J / g) was determined from the thermogram measured when the temperature was lowered to room temperature at ° C / min.

(2) Transparency Based on JISK7105, the total haze value of the film was measured at a film thickness of 10 μm.

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

(4) Molecular weight retention (wet heat durability)
The obtained film was allowed to stand for 1 month in a constant temperature and humidity machine LH-112 manufactured by Tabay Espec adjusted to 40 ° C. × 90 mass%.
Gel Permeation Chromatography HLS-8120GPC manufactured by Tosoh Corporation is equipped with GPC-800CP of Shimadzu Corporation chroma column Shim-Pack series, solvent chloroform, solution concentration 0.2 wt / vol mass%. The mass average molecular weight of the film before and after the test (that is, before and after standing for 1 month) was measured under the conditions of a solution injection amount of 200 μl, a solvent flow rate of 1.0 ml / min, and a solvent temperature of 40 ° C. Molecular weight was calculated.
The mass average molecular weights of the standard polystyrene used are 20000, 670000, 110000, 35000, 10,000, 4000, 600.

The molecular weight retention rate (% by mass) was calculated from the calculated mass average molecular weight before and after the test, and the determination was made according to the following criteria.
○: The molecular weight retention is 60% by mass or more and 100% by mass or less, and the molecular weight after aging is 100,000 or more.
X: The molecular weight retention is 0% by mass or more and less than 60% by mass, and the molecular weight after aging is less than 100,000.

(5) Film-forming stability When the 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.
A: Extremely stable.
○: Stable.
X: Unstable.

(6) Production stability Production stability when the examples and comparative examples were implemented was observed and evaluated according to the following criteria.
A: During production, there was no thickness unevenness or breakage due to the difference in fluidity during extrusion of each layer, and stable production was possible.
A: During production, there was a thickness unevenness due to the difference in fluidity during extrusion of each layer, but a film could be formed without causing breakage.
X: During production, thickness unevenness was remarkable due to the difference in fluidity during extrusion of each layer, and breakage occurred frequently.

(7) Blocking resistance The obtained roll of film was stored in a temperature-controlled room under conditions of a temperature of 43 ° C. and a relative humidity of 40% for 5 days, and then the surface condition and roll-back property were observed and evaluated according to the following criteria. .
A: Level where there is no blocking between films.
○: A level where there is a little blocking between films, but does not cause a problem in practical use.
X: Level at which the film cannot be peeled off due to blocking between the films and cannot be rewound to cause a practical problem.

(8) Adhesion of container 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.
(Double-circle): The level which can be packaged moderately.
○: Slightly widening from the shape of the container, but at a level where there is no practical problem.
X: Level at which the film spreads out of the container and causes a practical problem.

(9) Small rewinding suitability The rewinding test of the film formed was performed at a winding speed of 200 m / min to 600 m / min, and the small rewinding suitability was evaluated according to the following criteria.
A: Small rewinding was possible without problems even at a winding speed of 600 m / min.
○: Small rewinding was possible without a problem at a winding speed of 200 m / min or more and less than 600 m / min.
X: 200 m / min or more and less than 600 m / min In the course of rewinding, delamination and film breakage occurred.

(10) Cutability 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 without a sense of incompatibility when cutting.
○: A level where there is a slight practical resistance but no problem in practice.
X: Level at which the wrap bites into the metal saw blade and feels excessive resistance when cutting.

(11) Tearability The formed film was put into a carton box with a metal saw blade, and the film was pulled out and cut. The tearability in the film feeding direction at that time was evaluated according to the following criteria.
A: Level where there is almost no tearing in the feeding direction during cutting.
○: Some tearing in the feeding direction is seen at the time of cutting, but there is no practical problem.
×: Level at which the lap cannot be cut well by tearing in the feeding direction during cutting.

Example 1
For the surface layer forming composition, as a olefin polymer (A), a propylene / ethylene random copolymer “Novatech PP MG3F” manufactured by Nippon Polypro Co., Ltd. (ethylene content: 3 mass%, average refractive index 1.49, MFR) : 9 g / 10 min) (hereinafter abbreviated as “A-1”) and Kuraray styrene-vinylisoprene block copolymer elastomer “Hibler 7311” as additive (a), mass ratio A-1 / (A) = 80/20 and weigh and mix, then, as antifoggant mainly composed of diglycerin oleate with respect to the total of A-1 and (a) (100 parts by mass) “MJ-1” manufactured by Riken Vitamin Co., Ltd. was weighed and mixed so as to be 5.0 parts by mass, and these were put into a twin-screw extruder in the same direction set at an extrusion setting temperature of 170 to 190 ° C. and melt kneaded. Prepared.

  On the other hand, for the intermediate layer forming composition, “Nature Works 4032D” (L-form / D-form = 98.6 / 1.4, average refractive index 1.46, mass average, as a lactic acid polymer (B) manufactured by NatureWorks (Molecular weight: 200,000) (hereinafter abbreviated as “B-1”) and “NatureWorks 4060D” manufactured by NatureWorks (L-form / D-form = 87/13, average refractive index 1.46, mass-average molecular weight: 200,000) (below) "B-2") is weighed so that the mass ratio is B-1 / B-2 = 60/40, and these are mixed and the same direction biaxial extrusion set at an extrusion set temperature of 180 ° C Glycerin diacetomonoester (molecular weight 330) and glycerin monoacetomonoester (molecular weight 310) as glycerin fatty acid ester (C) A compound (average molecular weight 320, hereinafter abbreviated as “C-1”) was weighed so that C-1 was 17 parts by mass with respect to the total of B-1 and B-2 (100 parts by mass). The mixture was prepared by melt-kneading while injecting from the first vent port of the extruder using a fixed liquid feed pump.

  Further, the above-mentioned A-1, B-1, and C-1 were previously added to the extruder for the adhesive layer at a mass ratio of A-1 / B-1 / C-1 = 50 / 42.5 / 7.5. A resin composition pre-compounded with a directional twin screw extruder was charged to prepare an adhesive layer forming composition.

Then, the surface layer forming composition, the intermediate layer forming composition, and the adhesive layer forming composition obtained as described above are merged from separate extruders, respectively, and a five-layer T die temperature of 190 ° C. is set. By co-extrusion with a gap of 2 mm and quenching with a cast roll set at a temperature of 30 ° C., the total thickness was 30 μm (surface layer / adhesive layer / intermediate layer / adhesive layer / surface layer = 4.8 μm / 2.25 μm / 15. A raw film of 9 μm / 2.25 μm / 4.8 μm was obtained.
Next, the film was uniaxially stretched in MD by roll stretching at a stretching temperature of 60 ° C., a heat treatment temperature of 90 ° C. and a stretching ratio of 3 times, and a thickness of 10 μm (surface layer / adhesive layer / intermediate layer / adhesive layer / surface layer = 1.6 μm / A packaging film of 0.75 μm / 5.3 μm / 0.75 μm / 1.6 μm) was obtained. The results of evaluating the obtained film are shown in Table 1.

(Example 2)
Regarding the surface layer forming composition, the above-mentioned “A-1” as the olefin polymer (A) and the hydrogenated derivative “Dynalon 1320P” of a styrene-butadiene random copolymer manufactured by JSR as the additive (b) Example 1 except that these were weighed so that the mass ratio A-1 / (b) = 80/20, and these were mixed and put into a co-directional twin-screw extruder set at an extrusion set temperature of 180 ° C. Coextrusion and stretching were performed in the same manner as above to obtain a packaging film having a thickness of 10 μm. The results of evaluating the obtained film are shown in Table 1.

(Example 3)
Regarding the surface layer forming composition, the above-mentioned “A-1” as the olefin polymer (A) and the hydrogenated derivative “Dynalon 1320P” of a styrene-butadiene random copolymer manufactured by JSR as the additive (b) The hydrogenated petroleum resin “Alcon P125” manufactured by Arakawa Chemical Co., Ltd. as additive (c) was weighed so that A−1 / (b) / (c) = 70/20/10 and mixed. Then, co-extrusion and stretching were carried out in the same manner as in Example 1 except that it was put into a same-direction twin-screw extruder set at an extrusion set temperature of 180 ° C. to obtain a packaging film having a thickness of 10 μm. The results of evaluating the obtained film are shown in Table 1.

Example 4
About the surface layer forming composition, 100 parts by mass of the “A-1” as the olefin polymer (A) and 13 parts by mass of liquid polybutene “HV-100” manufactured by Nippon Oil Corporation as the additive (d), 3 parts by mass of “Rikemar DO-100” manufactured by Riken Vitamin Co., Ltd. as an antifogging agent mainly composed of diglycerin monooleate, and Riken Vitamin Co., Ltd. as an antifogging agent composed mainly of glycerin diacetomonolaurate 3 parts by weight of “Poem G-002” was put into the same direction twin-screw extruder set at an extrusion set temperature of 170 to 190 ° C., melt-kneaded and prepared in the same manner as in Example 1, Stretching was performed to obtain a packaging film having a thickness of 10 μm. The results of evaluating the obtained film are shown in Table 1.

(Comparative Example 1)
The surface layer forming composition was coextruded and stretched in the same manner as in Example 1 except that 100 parts by mass of “A-1” was obtained, thereby obtaining a packaging film having a thickness of 10 μm. The results of evaluating the obtained film are shown in Table 1.

(Comparative Example 2)
Co-extrusion and stretching were carried out in the same manner as in Example 1 except that the resin charged into the adhesive layer extruder was changed to “Tuftec H1041” (styrene-ethylene-butadiene block copolymer) manufactured by Asahi Kasei Corporation. A packaging film having a thickness of 10 μm was obtained. The results of evaluating the obtained film are shown in Table 1.

(Comparative Example 3)
In the extruder for the surface layer, a linear low density polyethylene “NUCG5361” (MFR: 4.0 g / 10 min, average refractive index 1.51) (hereinafter abbreviated as “A-2”) manufactured by Nihon Unicar Co., Ltd. and “NUCG5371” (MFR: 12.0, average refractive index: 1.51) or less, abbreviated as “A-3”) is weighed so that the mass ratio is A−2 / A−3 = 50/50 While mixing and feeding, the A-2, A-3, B-1 and C-1 were added to the extruder for the adhesive layer A-2 / A-3 / B-1 / C-1 = 19 / Co-extrusion and stretching were carried out in the same manner as in Example 1 except that the adhesive layer-forming composition was prepared and charged in advance in a same-direction twin-screw extruder at a ratio of 19/53/9. 10 μm (surface layer / adhesive layer / intermediate layer / adhesive layer / surface layer = 1.6 μm / 0.75 μm / 5.3 μm / 0.75 μm /1.6 μm) was obtained. The results of evaluating the obtained film are shown in Table 1.

(Comparative Example 4)
The same procedure as in Example 1 was performed except that pellets pre-compounded to have the same composition as that of the intermediate layer forming composition of Example 1 were put into the adhesive layer extruder in order to obtain a substantially three-layer film. Thus, a packaging film having a total thickness of 10 μm (surface layer / intermediate layer / surface layer = 1.6 μm / 6.8 μm / 5.3 μm) was obtained. The results of evaluating the obtained film are shown in Table 1.

(Comparative Example 5)
In Comparative Example 4, comparison was performed except that the pellets pre-compounded in advance so as to have the same composition as the intermediate layer forming composition of Example 1 were put into the extruder for the surface layer to make a substantially single layer film. In the same manner as in Example 4, a packaging film having a total thickness of 10 μm was obtained. The results of evaluating the obtained film are shown in Table 1.

(Comparative Example 6)
In Comparative Example 4, the pre-compounded pellets were added to the extruder for the intermediate layer in advance so as to have the same composition as the surface layer forming composition of Example 1 to obtain a substantially single layer film. A packaging film having a total thickness of 10 μm was obtained in the same manner as in Comparative Example 3. The results of evaluating the obtained film are shown in Table 1.

From Table 1, the films obtained in Examples 1 to 4 can suppress the molecular weight of the packaging film from decreasing over time, and blocking occurs even when the formed film is stored in a wound state. Furthermore, it was confirmed that the container adhesion was also good. In addition, it was confirmed that by providing a specific adhesive layer, a packaging film excellent in small rewinding suitability, a transparent packaging film having a good film appearance was obtained. Furthermore, by performing the stretching process, the cutting properties were particularly excellent, while tearing troubles in the stretching direction at the time of cutting were less likely to occur.
On the other hand, in Comparative Examples 1-6, when the front and back layers are made of only the olefin polymer (A) (Comparative Example 1), the container adhesion is not excellent, and tearing in the stretching direction occurs during cutting. This was a problem in practical use. When a styrene elastomer is used as the adhesive layer between the front and back layers and the intermediate layer (Comparative Example 2), film perforations and the like are observed because the fluidity of each layer does not match during film formation. When linear low density polyethylene was used for the layer and the adhesive layer (Comparative Example 3), it was confirmed that the transparency (total haze value) was insufficient. Moreover, when it does not have adhesive layer resin (comparative example 4), it is confirmed that a problem arises in small rewinding suitability, and when it does not have front and back layer resin (comparative example 5), after film formation The blocking was remarkable, and the decrease in molecular weight with time was also significant. In the case where an intermediate layer containing a lactic acid polymer as a main component was not present (Comparative Example 6), the blocking and film-forming stability were good, but the container adhesion was insufficient.

The amount of crystallization ΔHc of the olefin polymer (A) used in Examples 1 and 2 was 60 J / g, and sufficient transparency was obtained, whereas the linear low density used in Comparative Example 2 was obtained. The heat of crystallization ΔHc of polyethylene was 100 J / g, and sufficient transparency was not obtained. Thus, from the viewpoint of transparency, the crystallization heat amount ΔHc of the olefin polymer (A) is preferably 80 J / g or less, particularly 5 J / g to 60 J / g, and especially 5 J / g to 40 J / g. It is considered particularly preferable.
However, since it is preferable that the amount of crystallization heat is high in order to improve heat resistance, the crystallization heat amount of the olefin polymer (A) is 20 J / g to 80 J / g in consideration of both ensuring transparency and heat resistance. It is preferable that it is 30 J / g to 60 J / g.

  A block copolymer of a vinyl aromatic compound and a conjugated diene or a hydrogenated derivative thereof (addition) such as “styrene-vinylisoprene block copolymer elastomer” added to the surface layer forming composition in Example 1 Agent (a)) generally has rubber elasticity and is flexible and can be blended with the olefin polymer (A) to lower the crystallinity of the olefin polymer (A). Effectively reduces the tensile elastic modulus (storage elastic modulus E ′) of the olefin polymer (A). Accordingly, since the value of the loss elastic modulus (E ″) increases, the peak value of the loss tangent (tan δ = loss elastic modulus E ″ / storage elastic modulus E ′) can be increased. If the peak value of tan δ can be increased, the restoring behavior against deformation of the film does not occur instantaneously, and hence the adhesion to the container is further improved. In addition, when uniaxial stretching is performed when forming the packaging film, blending with the olefin polymer (A) suppresses the molecular chain orientation to some extent by stretching the olefin polymer (A). It can be considered that tearing troubles in the stretching direction of the film after film formation can be suppressed.

  A random copolymer of a vinyl aromatic compound and a conjugated diene or a hydrogenated derivative thereof (additive (b)) such as “styrene-butadiene random copolymer” added to the surface layer forming composition in Example 2. With regard to)), it can be considered that the same effect as the additive (a) can be obtained from the viewpoint of composition and structure. Moreover, when the copolymerization form of the vinyl aromatic compound and the conjugated diene is “random”, an effect of further reducing the crystallinity of the olefin polymer (A) can be obtained.

  In Example 3, a hydrogenated derivative (additive (b)) of a random copolymer of a vinyl aromatic compound and a conjugated diene was used in combination with a hydrogenated petroleum resin (additive (c)) to form a surface layer. It is added to the composition. Thus, a block copolymer of a vinyl aromatic compound and a conjugated diene or a hydrogenated derivative thereof (additive (a)), a random copolymer of a vinyl aromatic compound and a conjugated diene or a hydrogenated product thereof By using petroleum derivatives such as hydrogenated petroleum resin (additive (c)) in combination with the derivative (additive (b)), the container adhesion can be further improved.

  In Example 4, the container adhesion was improved by adding liquid polybutene to the surface layer forming composition. Thus, liquid polybutene or liquid polyisobutylene (additive (d)) was added to the surface layer forming composition. Can be uniformly dispersed in the olefin polymer (A), the wettability of the film surface of the olefin polymer (A) can be improved, and tackiness can be imparted, resulting in improved container adhesion. Can be made.

Claims (9)

Both surface layers composed of a surface layer forming composition containing the olefin polymer (A) and any one of the following (a) to (d) or two or more of these, and a lactic acid polymer ( An intermediate layer comprising an intermediate layer-forming composition containing B) as a main component, and containing an olefin polymer (A) and a lactic acid polymer (B) as main components between the surface layer and the intermediate layer A packaging film provided with an adhesive layer made of an adhesive layer forming composition.
(A) Block copolymer of vinyl aromatic compound and conjugated diene or hydrogenated derivative thereof (b) Random copolymer of vinyl aromatic compound and conjugated diene or hydrogenated derivative thereof (c) Petroleum resins (d ) At least one liquid additive selected from liquid polybutene or liquid polyisobutylene   The packaging film according to claim 1, wherein the olefin polymer (A) has a crystallization heat amount of 5 J / g to 80 J / g.   The packaging film according to claim 1 or 2, wherein the total haze value is 3% or less.   The film for packaging according to any one of claims 1 to 3, wherein the adhesive layer forming composition comprises a surface layer forming composition and an intermediate layer forming composition.   The film for packaging according to any one of claims 1 to 4, wherein the intermediate layer-forming composition contains a glycerin fatty acid ester (C) having a molecular weight of 2000 or less.   6. The packaging film according to claim 5, wherein the intermediate layer forming composition contains 1 to 20 parts by mass of the glycerin fatty acid ester (C) with respect to 100 parts by mass of the lactic acid polymer (B).   The packaging film according to any one of claims 1 to 6, wherein the lactic acid polymer (B) is a mixed resin of two or more lactic acid polymers having different LD ratios.   The olefin polymer (A) is one propylene polymer selected from propylene-ethylene random copolymer, propylene-ethylene-butene-1 copolymer and polypropylene elastomer, or two or more thereof. The packaging film according to claim 1, which is a mixed resin comprising a combination of the above. As measured by dynamic viscoelasticity, the storage elastic modulus (E ′) measured at a frequency of 10 Hz and a temperature of 20 ° C. is 1 GPa to 4 GPa, the peak temperature of loss tangent (tan δ) is 20 to 70 ° C., and the peak value is 0.00. It is in the range of 1-0.8, The packaging film in any one of Claims 1-8 characterized by the above-mentioned.