EP2914432A1

EP2914432A1 - Multi-layered film

Info

Publication number: EP2914432A1
Application number: EP13852187.7A
Authority: EP
Inventors: Gouhei Yamamura; Masayuki Hirota; Jun Sakamoto; Robert Loos; Jorg Auffermann; Xin Yang
Original assignee: BASF SE; Toray Industries Inc
Current assignee: BASF SE; Toray Industries Inc
Priority date: 2012-11-01
Filing date: 2013-10-18
Publication date: 2015-09-09
Also published as: CN104936779A; JP2015536255A; EP2914432A4; WO2014069379A1

Abstract

This invention relates to a multi-layered film that has high flexibility, tear resistance, heat sealability, interlayer contact strength, and biodegradability. The multi-layered film comprising layer (X) and layer (Y) which meet requirement (A): layer (X) comprises (a) lactic acid based resin, (b) biodegradable resin except lactic acid based resin, and (c) block copolymer resin of polyether segment and polylactic acid segment wherein resin (a), (b), and (c) account for 20-85 parts, 10-50 parts, and 5-30 parts by mass, respectively (resin (a), (b), and (c) in total account for 100 parts by mass) and requirement (B): layer (Y) comprises (d) aliphatic-aromatic polyester and resin (e) as defined below wherein resin (d) and (e) account for 30-100 parts and 0-70 parts by mass, respectively (resin (d) and (e) in total account for 100 parts by mass) Resin (e): at least one resin selected from the group consisting of lactic acid based resin, aliphatic polyester, polypropylene carbonate, and polyhydroxy alkanoate.

Description

[DESCRIPTION]

[Title of Invention]

Multi-layered film [Technical Field]

The present invention relates to a multi-layered film that has high flexibility, tear resistance, heat sealability, interlayer contact strength, and biodegradability.

[Background Art]

With the heightening of environment consciousness in recent years, attention is focused on soil contamination problems caused by waste plastic products, and attention is also focused on global petroleum resources depletion problems caused by manufacturing of oil-derived plastics.

Research and development studies have been performed actively on various biodegradable resins and plant-derived resins as means of solving the former and the latter problems, respectively.

In the resin film industry, efforts are being made for the replacement of conventional polyolefin based films such as polyethylene with, for instance, polylactic acid and aliphatic polyester. When used singly, however, these resins are poor in practical characteristics such as flexibility, tear resistance, and heat sealability. Various studies have been performed aiming to improve their characteristics.

In particular, there are proposals of laminated films consisting of two different resins that compensate for each other's disadvantages.

PTL 1, for instance, proposes a film with improved tear strength and impact strength that is composed of a layer of biodegradability polyester with a glass transition temperature of 10°C or less combined with polylactic acid and a seal layer of thermoplastic biodegradable resin.

PTL 2 proposes a film with improved flexibility and gas barrier properties that comprises a layer containing crystalline polylactic acid as primary component and a layer containing a crystalline resin composition as primary component.

The proposed film described in PTL 1, however, is poor in flexibility, tear resistance, and interlayer contact strength, although high in heat sealability.

The proposed film described in PTL 2 is also poor in tear resistance and interlayer contact strength, although improved in flexibility and heat sealability.

Thus, although studies have been made aiming to provide biodegradable resins and plant-derived resin that can replace conventional polyethylene and other polyolefin based resin films, they all have failed in providing films with required properties, and invention of films having practically high flexibility, tear resistance, heat sealability, and interlayer contact strength has not been achieved yet.

[Citation List] [Patent Literature]

[PTL 1] JP 2005-28615 A

[PTL 2] JP 2005-219487 A [Summary of Invention]

[Technical Problem]

In view of the above-mentioned issues, the present invention aims to provide a multi-layered film that is high in flexibility, tear resistance, heat sealability, interlayer contact strength, and biodegradability.

[Solution to Problem]

The multi-layered film according to the present invention that meet the above-mentioned aim has a constitution as described in undermentioned paragraph (1).

(1) A multi-layered film comprising layer (X) and layer (Y) wherein said layer (X) and said layer (Y) meet requirement (A) and requirement (B) given below, respectively.

Requirement (A): said layer (X) comprises a lactic acid based resin, biodegradable resin except a lactic acid based resin, and block copolymer resin of a polyether segment and a polylactic acid segment (hereinafter, said lactic acid based resin contained in said layer (X) is referred to as resin (a), said biodegradable resin except a lactic acid based resin contained in said layer (X) referred to as resin (b), and said block copolymer resin of a polyether segment and a polylactic acid segment contained in said layer (X) referred to as resin (c)) wherein said resin (a), said resin (b), and said resin (c) account for 20 to 85 parts by mass, 10 to 50 parts by mass, and 5 to 30 parts by mass, respectively, assuming that said resin (a), said resin (b), and said resin (c) in total account for 100 parts by mass.

Requirement (B): said layer (Y) comprises an aliphatic-aromatic polyester and resin (e) as defined below (hereinafter, said aliphatic-aromatic polyester contained in layer (Y) is referred to as resin (d)) wherein said resin (d) and said resin (e) account for 30 to 100 parts by mass and 0 to 70 parts by mass, respectively, assuming that said resin (d) and said resin (e) in total account for 100 parts by mass,

(Resin (e): resin (e) is at least one resin selected from the group consisting of lactic acid based resin, aliphatic polyester, polypropylene carbonate, and polyhydroxy alkanoate.)

The multi-layered film according to the present invention preferably has a constitution as described in any of paragraphs (2) to (15) given below.

(2) A multi-layered film as described in paragraph (1) wherein layer (X) contains 0.1 to 2 parts by mass of a component derived from a compatibilizer as defined below assuming that said resin (a), said resin (b), and said resin (c) in total account for 100 parts by mass.

Compatibilizer: a compound containing two or more functional groups selected from the group consisting of isocyanate, isocyanurate, oxazoline, carbodiimide, oxazine, epoxide, and carboxylic anhydride.

(3) A multi-layered film as described in either paragraph (1) or (2) wherein layer (Y) contains 0.1 to 2 parts by mass of a component derived from a compatibilizer as defined below assuming that said resin (d) and said resin (e) in total account for 100 parts by mass.

Compatibilizer: A compound containing two or more functional groups selected from the group consisting of isocyanate, isocyanurate, oxazoline, carbodiimide, oxazine, epoxide, and carboxylic anhydride. (4) A multi-layered film as defined in any of paragraphs (1) to (3) wherein said resin (b) is a polymer as defined below.

Resin (b): At least one resin selected from the group consisting of aliphatic-aromatic polyester, aliphatic polyester, polypropylene carbonate, and polyhydroxy alkanoate.

(5) A multi-layered film as defined in any of paragraphs (1) to (4) wherein said resin (b) and/or said resin (d) is a copolymerized polyester produced from an aliphatic dicarboxylic acid with a carbon number of 4 to 30, terephthalic acid, and a diol with a carbon number of 3 to 6.

(6) A multi-layered film as defined in any of paragraphs (1) to (5) wherein the polylactic acid segment accounts for 5 to 49 mass% assuming that the total quantity of the polymer in said resin (c) accounts for 100 mass%.

(7) A multi-layered film as defined in any of paragraphs (1) to (6) wherein the polyether segment in said resin (c) is a polyethylene glycol segment.

(8) A multi-layered film as defined in any of paragraphs (1) to (7) wherein, in cross sections of the film observed along the machine direction and the thickness direction, said layer (X) has a continuous phase comprising said resin (a) and said resin (c) and said continuous phase contains dispersed phases comprising said resin (b) that are dispersed over an elliptical area extended in the film's machine direction or over a layer-like area extended in the film's machine direction, said dispersed phases having a thickness of 150 to 600 nm.

(9) A multi -layered film as defined in any of paragraphs (1) to (8) wherein, in cross sections of the film observed along the machine direction and the thickness direction, said layer (Y) has a continuous phase comprising said resin (d) and said continuous phase contains dispersed phases of said resin (e) that are dispersed over an elliptical area extended in the film's machine direction or over a layer-like area extended in the film's machine direction, said dispersed phases having a thickness of 40 to 150 nm.

(10) A multi-layered film as defined in any of paragraphs (1) to (9) wherein at least either of the surface layers is constituted of said layer (Y) and said surface layer has a surface energy of 30 to 60 dyne/cm.

(11) A multi-layered film as defined in any of paragraphs (1) to (10) wherein said resin (b) has an orientation parameter of 0.8 to 2.0.

(12) A multi-layered film as defined in any of paragraphs (1) to (11) wherein said layer (Y), said layer (X), and said layer (Y) are directly stacked in this order. (13) A multi-layered film as defined in any of paragraphs (1) to (12) wherein the average of the tear strength in the film's machine direction and that in the film's crosswise direction 500 mN or more.

(14) A multi-layered film as defined in any of paragraphs (1) to (13) wherein the heat seal strength is 7 N or more.

(15) A multi-layered film as defined in any of paragraphs (1) to (14) that has a tensile modulus of 1,200 MPa or less.

[Advantageous Effects of Invention]

The present invention provides a multi-layered film that has high flexibility, tear resistance, heat sealability, interlayer contact strength, and biodegradability.

The multi-layered film according to the present invention is preferably uses as materials that mainly require flexibility, tear resistance, and heat sealability, including those for bags such as pouches, shopping bags, carry bags for vegetables, fruits, meat, fish, and other fresh products, as well as material for trash bag, manure bag, compost bag, other bags/packages, mulching film, other agricultural materials, and medical/hygienic materials.

[Description of embodiments]

The present invention is the first to solve the above problems by developing a multi-layered film comprising two layers of specific resins combined at a specific ratio based on intensive studies on multi-layered films that are high in flexibility, tear resistance, heat sealability, interlayer contact strength, and biodegradability.

Specifically, the present invention provides a multi-layered film comprising layer (X) and layer (Y) wherein layer (X) comprises a lactic acid based resin, biodegradable resin, and block copolymer of a polyether segment and a polylactic acid segment (hereinafter, the lactic acid based resin contained in layer (X) is referred to as resin (a), the biodegradable resin contained in layer (X) referred to as resin (b), and the block copolymer resin of a polyether segment and a polylactic acid segment contained in layer (X) referred to as resin (c)), said resin (a), said resin (b), and said resin (c) accounting for 20 to 85 parts by mass, 10 to 50 parts by mass, and 5 to 30 parts by mass, respectively, assuming that said resin (a), said resin (b), and said resin (c) in total account for 100 parts by mass, while layer (Y) comprises an aliphatic-aromatic polyester and a resin (e) as defined below (hereinafter, the aliphatic-aromatic polyester contained in layer (Y) is referred to as resin (d)), said resin (d) and said resin (e) accounting for 30 to 100 parts by mass and 0 to 70 parts by mass, respectively, assuming that said resin (d) and said resin (e) in total account for 100 parts by mass.

The multi-layered film according to the present invention is described in detail below.

A lactic acid based resin as referred to for the present invention is a polymer containing an L-lactic acid unit and/or a D-lactic acid unit that account for more than 80 mass% and 100 mass% or less per 100 mass% of the polymer.

A poly-L-lactic acid as referred to for the present invention is a lactic acid based resin in which the poly-L-lactic acid accounts for more than 50 mol% and 100 mol% or less of the total lactic acid units, which account for 100 mol%. On the other hand, a poly-D-lactic acid as referred to for the present invention is a lactic acid based resin in which the poly-D-lactic acid accounts for more than 50 mol% and 100 mol% or less of the total lactic acid units, which account for 100 mol%.

A poly-L-lactic acid changes in resin crystallinity depending on the content of D-lactic acid units. Specifically, a poly-L-lactic acid material decreases in crystallinity and increases in amorphousness with an increasing content of D-lactic acid units in the poly-L-lactic acid material while the poly-L-lactic acid material increases in crystallinity with a decreasing content of D-lactic acid units in the poly-L-lactic acid material. Similarly, a poly-D-lactic acid changes in the resin crystallinity depending on the content of L-lactic acid units. Specifically, a poly-D-lactic acid material decreases in crystallinity and increases in amorphousness with an increasing content of L-lactic acid units in the poly-D-lactic acid material while the poly-D-lactic acid material increases in crystallinity with a decreasing content of L-lactic acid units in the poly-D-lactic acid material.

A crystalline lactic acid based resin as referred to for the present invention is a lactic acid based resin that releases heat of crystal fusion attributed to polylactic acid components as determined by subjecting the polylactic acid resin to differential scanning calorimetry (DSC) in an appropriate temperature range after heating it to ensure adequate crystallization.

An amorphous lactic acid based resin as referred to for the present invention, on the other hand, is a lactic acid based resin that does not show a distinct melting point when subjected to similar observation.

A lactic acid based resin to be used for the present invention may be a copolymer containing monomer units other than lactic acid. Such other monomers include glycol compounds such as ethylene glycol, propylene glycol, butanediol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, and naphthalene dicarboxylic acid; hydroxycarboxylic acids such as glycolic acid, hydroxypropionic acid, and hydroxybutyric acid; and lactones such as caprolactone. Said other monomer units in the copolymer preferably account for 0 to 20 mol%, more preferably 0 to 10 mol%, of the total monomer units, which account for 100 mol% of the lactic acid based resin polymer. Of the monomer units given above, it is preferable to use biodegradable ones, depending on uses.

To meet practical mechanical characteristics, a lactic acid based resin to be used for the present invention preferably has a mass average molecular weight of 50,000 to 500,000, more preferably 80,000 to 400,000, and still more preferably 100,000 to 300,000.

It is important for layer (X) in the multi-layered film according to the present invention to contain a lactic acid based resin. Hereinafter, the lactic acid based resin contained in layer (X) is referred to as resin (a).

It is important for said resin (a) in layer (X) of the multi-layered film according to the present invention to account for 20 to 85 parts by mass assuming that resin (a), resin (b), and resin (c), the latter two being described in detail later, in total account for 100 parts by mass. If it is less than 20 parts by mass, the film will not be sufficiently high in processability, handleability, and interlayer contact strength, whereas if it is more than 85 parts by mass, the film will lack in flexibility, tear resistance, and interlayer contact strength.

Resin (a) preferably accounts for 30 parts by mass or more, more preferably 40 parts by mass or more, assuming that resin (a), resin (b), and resin (c) in total account for 100 parts by mass. Resin (a) preferably accounts for 75 parts by mass or less, more preferably 65 parts by mass or less, assuming that resin (a), resin (b), and resin (c) in total account for 100 parts by mass.

Said resin (a), furthermore, preferably accounts for 20 to 80 mass% of layer (X), which accounts for 100 mass%, in view of the processability, handleability, interlayer contact strength, flexibility, and tear resistance of the film. It is more preferable that said resin (a) accounts for 25 mass% or more, more preferably 35 mass% or more, of layer (X), which accounts for 100 mass%. It is more preierable, furthermore, that said resin (a) accounts for 70 mass% or less, more preferably 60 mass% or less, of layer (X), which accounts for 100 mass%.

Of the various lactic acid based resins, it is preferable that resin (a) for the present invention is poly-L-lactic acid and/or poly-D-lactic acid. If a poly-L-lactic acid is to be used as said resin (a), it is preferable that said poly-L-lactic acid is block-copolymerized with a poly-D-lactic acid or that said poly-L-lactic acid is mixed with a poly-D-lactic acid. If a poly-D-lactic acid is to be used as said resin (a), it is preferable that said poly-D-lactic acid is block-copolymerized with a poly-L-lactic acid or that said poly-D-lactic acid is mixed with a poly-L-lactic acid. This is because stereocomplex crystals thus formed have a higher melting point than common polylactic acid crystals (a-crystals), and form a film with improved heat resistance.

It is preferable that resin (a) for the present invention is a fully amorphous lactic acid based resin or a mixture of a crystalline lactic acid based resin and an amorphous lactic acid based resin. Assuming that the total quantity of resin (a) used for the present invention accounts for 100 mass% (assuming that the total quantity of crystalline lactic acid based resin and amorphous lactic acid based resin accounts for 100 mass%), it is preferable that the amorphous lactic acid based resin accounts for 60 to 100 mass%, more preferably 70 to 100 mass%, and still more preferably 80 to 100 mass%. This is because the use of a mixture of crystalline lactic acid based resin and amorphous lactic acid based resin as resin (a) can combine the advantages of crystalline and amorphous lactic acid based resins. A film containing crystalline lactic acid based resin as resin (a) has high heat resistance. A film containing amorphous lactic acid based resin as resin (a), on the other hand, has high interlayer contact strength and flexibility.

In the crystalline lactic acid based resin to be used as resin (a) for the present invention, the L-lactic acid units in the poly-L-lactic acid or the D-lactic acid units in the poly-D-lactic acid preferably accounts for 98 to 100 mol%, more preferably 99 to 100 mol%, of the total lactic acid units, which account for 100 mol%, from the viewpoint of improving tear resistance.

<Resin (b) (i.e., the biodegradable resin except a lactic acid based resin contained in layer (X))> It is important for layer (X) in the multi-layered film according to the present invention to contain biodegradable resin except a lactic acid based resin. Hereinafter, the biodegradable resin except a lactic acid based resin contained in layer (X) is referred to as resin (b).

Biodegradable resin as referred to for the present invention is defined as one that reaches a biodegradability degree of 60% or more within 180 days compared with cellulose as measured according to IS014855-1 (2005). However, the lactic acid based resin that corresponds to resin (a) and the block copolymer of a polyether segment and a polylactic acid segment that corresponds to resin (c) are excluded from the biodegradable resin in the present invention.

For the present invention, resin (b) may be a single resin or a mixture of two or more resins, and specific examples include aliphatic aromatic polyester, aliphatic polyester, polypropylene carbonate, polyhydroxyalkanoate, thermoplastic starch, thermoplastic-starch-containing resin, and thermoplastic cellulose.

Of these, said resin (b) is preferably at least one resin selected from the group consisting of aliphatic aromatic polyester, aliphatic polyester, polypropylene carbonate, and polyhydroxyalkanoate.

In particular, it is most preferable that said resin (b) is an aliphatic aromatic polyester.

Aliphatic-aromatic polyesters preferred as said resin (b) are copolymerized polyesters produced from an aliphatic dicarboxylic acid with a carbon number of 4 to 30, terephthalic acid, and a diol with a carbon number of 3 to 6. Specific examples include polybutylene succinate-co-terephthalate and polybutylene adipate-co-terephthalate.

Specific examples of preferred aliphatic polyesters to be used as said resin (b) include polycaprolactone, polybutylene succinate, and polybutylene succinate-co-adipate.

Specific examples of preferred polypropylene carbonate can be used as disclosed in International publication WO2006/061237.

Specific examples of preferred polyhydroxyalkanoates to be used as said resin (b) include polyglycolic acid, poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3 -hydroxy valerate ), and poly(3-hydroxybutyrate-co-4- hydroxybutyrate) .

It is important for resin (b) in layer (X) of the multi-layered film according to the present invention to account for 10 to 50 parts by mass assuming that resin (a), resin (b), and resin (c), which is described in detail later, in total account for 100 parts by mass. If it is more than 50 parts by mass, the film will not be sufficiently high in stiffness, whereas if it is less than 10 parts by mass, the film will lack in flexibility, tear resistance, and interlayer contact strength.

Resin (b) preferably accounts for 45 parts by mass or less, more preferably 40 parts by mass or less, assuming that resin (a), resin (b), and resin (c) in total account for 100 parts by mass. Said resin (b) preferably accounts for 15 parts by mass or more, more preferably 20 parts by mass or more, assuming that resin (a), resin (b), and resin (c) in total account for 100 parts by mass.

It is important for layer (X) in the multi-layered film according to the present invention to contain a block copolymer of a polyether segment and a polylactic acid segment. Hereinafter, the block copolymer resin of a polyether segment and a polylactic acid segment contained in layer (X) is referred to as resin (c).

A block copolymer of a polyether segment and a polylactic acid segment to be used as resin (c) is a polymer containing an L-lactic acid unit and/or a D-lactic acid unit that account for 1 mass% or more and 80 mass% or less per 100 mass% of the polymer.

Specific examples of said polyether segment in resin (c) include segments comprising polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyethylene glycol/polypropylene glycol copolymer. Of these, it is particularly preferable that the polyether segment is a polyethylene glycol segment, which ensures high affinity with resin (a) and high modification efficiency.

It is preferable that the polylactic acid segments in total account for 5 to 49 mass% of the total polymer content in resin (c) for the present invention, which accounts for 100 mass%.

If it is 5 mass% or more, the material will be high in affinity with resin (a) and resistance to bleed-out, while if it is 49 mass% or less, addition in small amounts will achieve the intended modification effect. It is preferable that the polylactic acid segments in total account for 10 mass% or more, more preferably 20 mass% or more, of the total polymer content in resin (c) for the present invention, which accounts for 100 mass%. It is preferable that the polylactic acid segments in total account for 45 mass% or less, more preferably 40 mass% or less, of the total polymer content in resin (c) for the present invention, which accounts for 100 mass%.

It is preferable that each polyether segment in each molecule of a block copolymer resin of a polyether segment and a polylactic acid segment used as resin (c) has a number average molecular weight of 400 to 20,000. If the number average molecular weight is 400 or more, addition in smaller amounts is likely to achieve the intended modification effect, depending on its ratio to the number average molecular weight of the polylactic acid segment. If the number average molecular weight is 20,000 or less, it ensures adequately high affinity with resin (a), high modification efficiency, and high biodegradability. The number average molecular weight of each polyether segment in each molecule of resin (c) is more preferably 1,200 to 15,000, still more preferably 2,000 to 10,000.

It is preferable that each polylactic acid segment in each molecule of resin (c) has a number average molecular weight of 200 to 5,000. If the number average molecular weight is 200 or more, the material will be high in affinity with resin (a) and resistance to bleed-out. If the number average molecular weight is 5,000 or less, addition in smaller amounts is likely to achieve the intended modification effect, depending on its ratio to the number average molecular weight of the polyether segment. The number average molecular weight of each polylactic acid segment in each molecule of resin (c) is more preferably 1,000 to 4,000, still more preferably 2,000 to 3,000. To depress the bleed-out, in particular, it is preferable that L-lactic acid accounts for 95 to 100 mass% or D-lactic acid accounts for 95 to 100 mass% of the polylactic acid segment in resin (c).

It is preferable that resin (c) has a number average molecular weight of 1,000 to 20,000. If the number average molecular weight is 1,000 or more, it serves to depress the overall melt viscosity of the composition that constitutes layer (X). If its number average molecular weight is 20,000 or less, it will have high affinity with resin (a) and high biodegradability. It is more preferable that resin (c) has a number average molecular weight of 5,000 to 18,000, still more preferably 10,000 to 16,000.

There are no specific limitations on the order of said polyether segment and polylactic acid segment or on the number of blocks, but it is preferable that at least one end is terminated with a polylactic acid segment to ensure high affinity with resin (a) and high resistance to bleed-out. It is more preferable that both ends are terminated with a polylactic acid segment.

It is important for resin (c) in layer (X) of the multi-layered film according to the present invention to account for 5 to 30 parts by mass assuming that resin (a), resin (b), and resin (c) in total account for 100 parts by mass. If it is more than 30 parts by mass, the film will not be sufficiently high in processability, handleability, interlayer contact strength, and tear resistance, whereas if it is less than 5 parts by mass, the film will lack in flexibility and tear resistance. Resin (c) preferably accounts for 25 parts by mass or more, more preferably 20 parts by mass or more, assuming that resin (a), resin (b), and resin (c) in total account for 100 parts by mass. Resin (c) preferably accounts for 10 parts by mass or less, more preferably 15 parts by mass or less, assuming that resin (a), resin (b), and resin (c) in total account for 100 parts by mass.

It is important for layer (Y) in the multi-layered film according to the present invention to contain an aliphatic-aromatic polyester. Hereinafter, the aliphatic-aromatic polyester contained in layer (Y) is referred to as resin (d).

For the present invention, there are no specific limitations on resin (d) as long as it is an aliphatic-aromatic polyester, but it is preferably a copolymerized polyester produced from an aliphatic dicarboxylic acid with a carbon number of 4 to 30, terephthalic acid, and a diol with a carbon number of 3 to 6. Specific examples include polybutylene succinate-co-terephthalate and polybutylene adipate-co-terephthalate.

It is important for said resin (d) in layer (Y) of the multi-layered film according to the present invention to account for 30 to 100 parts by mass assuming that resin (d) and resin (e), which is described in detail later, in total account for 100 parts by mass. If it is less than 30 parts by mass, the resin will lack in flexibility, tear resistance, heat sealability, and interlayer contact strength. Resin (d) preferably accounts for 40 parts by mass or more, more preferably 50 parts by mass or more, assuming that resin (d) and resin (e) in total account for 100 parts by mass. Resin (d) preferably accounts for 95 parts by mass or less, more preferably 90 parts by mass or less, assuming that resin (d) and resin (e) in total account for 100 parts by mass.

Said resin (d), furthermore, preferably accounts for 25 to 95 mass% of layer (Y), which accounts for 100 mass%, in view of the processability, handleability, interlayer contact strength, flexibility, and tear resistance of the film. It is more preferable that resin (d) accounts for 35 mass% or more, more preferably 45 mass% or more, of layer (Y), which accounts for 100 mass%. It is more preferable, furthermore, that resin (d) accounts for 90 mass% or less, more preferably 85 mass% or less, of layer ( Y), which accounts for 100 mass%.

It is important for layer (Y) in the multi-layered film according to the present invention to contain resin (e). Thus, for the multi-layered film according to the present invention, resin (e) is an optional component of layer (Y) and may not be contained, but in a preferred embodiment of this invention, layer (Y) contains resin (e). Here, resin (e) is at least one resin selected from the group consisting of lactic acid based resin, aliphatic polyester, polypropylene carbonate, and polyhydroxy alkanoate. In the lactic acid based resin to be used as resin (e) for the present invention, the L-lactic acid units in the poly-L-lactic acid or the D-lactic acid units in the poly-D-lactic acid preferably accounts for 60 to 96 mol%, more preferably 70 to 93 mol%, and still more preferably 80 to 90 mol%, of the total lactic acid units, which account for 100mol%. If it is 60 mol% or more, the resin will have high heat resistance, whereas if it is 96 mol% or less, the resin will have high heat sealability and interlayer contact strength.

The specific examples of aliphatic polyester, polypropylene carbonate, and polyhydroxy alkanoate given above for resin (b) may also be mentioned as specific examples of resin (e) to be used for the present invention.

It is important for said resin (e) in layer (Y) of the multi-layered film according to the present invention to account for 0 to 70 parts by mass assuming that resin (d) and resin (e) in total account for 100 parts by mass. If it is more than 70 parts by mass, the resin will lack in flexibility, tear resistance, heat sealability, and interlayer contact strength. Resin (e) preferably accounts for 5 parts by mass or more, more preferably 10 parts by mass or more, assuming that resin (d) and resin (e) in total account for 100 parts by mass. Resin (e) preferably accounts for 60 parts by mass or less, more preferably 50 parts by mass or less, assuming that resin (d) and resin (e) in total account for 100 parts by mass. It should be noted that for the content of resin (e), the description that it is 0 to 70 parts by mass assuming that resin (d) and resin (e) in total account for 100 parts by mass means that the case where it is 0 part by weight is included in the present invention. Thus, even though the expression "contained" is used in requirement (B) in paragraph (1) above, it is "not contained" in a precise sense when the content is 0 part by weight, but it should be assumed herein that such cases are included in the present invention.

Layer (X) and/or layer (Y) in the multi-layered film according to the present invention preferably contains a portion derived from a compatibilizer as defined below.

It is more preferable, furthermore, that layer (X) and/or layer (Y) in the multi-layered film according to the present invention preferably has a portion derived from a compatibilizer as defined below.

Compatibilizer: a compound containing two or more isocyanates^ two or more isocyanurates, two or more oxazolines, two or more carbodiimides, two or more oxazines, two or more epoxides, or two or more carboxylic anhydrides.

Such a compatibilizer is more preferable because if different functional groups coexist in a compatibilizer, such different functional groups may react with each other to prevent the compound from acting as compatibilizer, but such problem will not take place in the case of a compatibilizer that contains a plurality of the same kind of functional groups.

Specific examples of compounds having two or more epoxides that work as compatibilizer include glycidyl ether compounds, glycidyl ester compounds, glycidyl amine compounds, glycidyl imide compounds, glycidyl (meth)acrylate compounds, and alicyclic epoxy compounds. Examples of commercial products include Biomax Strong series (trade name) supplied by DuPont and LOTADER series (trade name) supplied by Arkema (copolymers of an ethylene, acrylate, and glycidyl (meth)acrylate), Joncryl series (trade name) supplied by BASF (glycidyl-group-containing (meth)acrylic/styrene based copolymers), Rezeda series (trade name) and Arufon series (trade name) supplied by Toagosei Co., Ltd., and Tepic series (trade name) supplied by Nissan Chemical Industries, Ltd.

Specific examples of compounds having two or more carboxylic anhydrides that work as compatibilizer include compounds having, for instance, succinic anhydrides, maleic anhydrides, or phthalic anhydrides. Examples of commercial products include Bondine series (trade name) supplied by Arkema (copolymers of an ethylene, acrylate, and maleic anhydride), Orevac series (trade name) supplied by Arkema, Bynel series supplied by DuPont (graft polymers of maleic anhydride), and Yumex series (trade name) supplied by Sanyo Chemical Industries Ltd., and Kraton series (trade name) supplied by Kraton (maleic anhydride-copolymerized SEBS).

Specific examples of compounds having two or more carbodiimides that work as compatibilizer include Carbodilite series (trade name) supplied by Nisshinbo Industries, Inc. and Stabaxol series (trade name) supplied by Rhein Chemie.

As a compatibilizer an aromatic or aliphatic diisocyanates might be used. However, it is also possible to use isocyanates of higher functionality. Examples are tolylene 2,4-diisocyanate, tolylene 2,6-diisocyanate, diphenylmethane 2,2'-diisocyanate, diphenylmethane 2,4'-diisocyanate, diphenylmethane 4,4'-diisocyanates; especially any of the linear or branched alkylene diisocyanates or cycloalkylene diisocyanates having from 2 to 20 carbon atoms, preferably from 3 to 12 carbon atoms, examples being hexamethylene 1 ,6-diisocyante, isophorone diisocyanate, or methylenebis (4-isocyanatocyclohexane).

Among the preferred isocyanurates are the aliphatic isocyanurates that derive from alkylene diisocyanates or from cycloalkylene diisocyanates, where these have from 2 to 20 carbon atoms, preferably from 3 to 12 carbon atoms, examples being isophorone diisocyanate or methylenebis(4-isocyanatocyclohexane). Theses alkylene diisocyanates can be either linear or branched compounds. Particular preference is given to isocyanurates based on n-hexamethylene diisocyanate, examples being cyclic trimers, pentamers, or higher oligomers of hexamethylene 1 ,6-diisocyanate.

Bisoxazolines are generally obtainable by the process disclosed in Angew. Chem. Int. Ed., vol. 11 (1972), pp.287-288. Particularly preferred bisoxazolines and bisoxazolines are those in which the bridging member is a single bond, a (C¾ )z-alkylene group, where z=2,3, or 4, e.g. methylene, ethane- 1,2-diyl, propane- 1,3 -diyl, or propane- 1,2-diyl, or a phenylene group. Particularly preferred bisoxazolines that may be mentioned are 2,2'-bis(2-oxazoline), bis(2-oxazolinyl)methane, 1 ,2-bis(2-oxazolinyl)ethane, l,3-bis(2-oxazolinyl) propane or 1 ,4-bis(2-oxazolinyl)butane, in particular 1 ,4-bis(2-oxazolinyl) benzene, 1 ,2-bis(2-oxazolinyl)benzene or l,3-bis(2-oxazolinyl)benzene. Further examples are :2,2'-bis(2-oxazoline), 2,2'bis(4-methyl-2-oxazoline), 2,2'-bis(4,4'-dimethyl-2-oxazoline), 2,2'-bis(4-ethyl-2-oxazoline), 2,2 ' -bis(4,4' -diethyl-2-oxazoline), 2,2 ' -bis(4-propyl-2-oxazoline), 2,2 ' -bis(4-butyl-2-oxazoline), 2,2'-bis(4-hexyl-2-oxazoline), 2,2' -bis(4-phenyl-2-oxazoline), 2,2' -bis(4-cyclohexyl-2-oxazoline), 2,2'-bis(4-benzyl-2-oxazoline), 2,2'-p-phenylenebis(4-methyl-2-oxazoline), 2,2'-p-phenylenebis(4,4'-dimethyl-2-oxazoline), 2,2'-m-phenylenebis(4-methyl-2-oxazoline), 2,2 ' -m-phenylenbis(4,4 ' -dimethyl-2-oxazoline), 2,2 '-hexamethylenebis(2-oxazoline),

2,2'-octamethylenebis(2-oxazoline), 2,2'-decamethylenebis(2-oxazoline), 2,2' -ethylenebis(4-methyl-2-oxazoline), 2,2' -tetramethylenebis(4,4' -dimethyl-2-oxazoline),

2,2'-9,9'-diphenoxyethanebis(2-oxazoline), 2,2'-cyclohexylenebis(2-oxazoline), and

2,2 ' -diphenylenbis(2-oxazoline).

Preferred bisoxazines are 2,2'-bis(2-oxazine), bis(2-oxazinyl)methane, 1 ,2-bis(2-oxazinyl)ethane, l,3-bis(2-oxazinyl)propane, or 1 ,4-bis(2-oxazinyl)butane, in particular l,4-bis(2-oxazinyl)benzene, 1 ,2-bis(2-oxazinyl) benzene, or 1,3- bis(2-oxazinyl) benzene.

With respect to the content of the compatibilizer-derived portion in layer (X), the compatibilizer-derived portion in layer (X) preferably accounts for 0.1 to 2 parts by mass of the total of resin (a), resin (b), and resin (c) which accounts for 100 parts by mass. If it is 0.1 part by mass or more, the compatibilizer can have adequate effect to ensure high tear resistance, whereas if it is 2 parts by mass or less, the resins can be prevented from being cured due to excess reaction. It is more preferable that the compatibilizer-derived portion in layer (X) accounts for 0.2 part by mass or more, still more preferably 0.5 part by mass or more, of the total of resin (a), resin (b), and resin (c) which accounts for 100 parts by mass. It is more preferable, furthermore, that the compatibilizer-derived portion in layer (X) accounts for 1.8 part by mass or more, still more preferably 1.5 parts by mass or less, of the total of resin (a), resin (b), and resin (c) which accounts for 100 parts by mass.

The compatibilizer-derived portion in layer (Y) preferably accounts for 0.1 to 2 parts by mass of the total of resin (a), resin (b), and resin (c) which accounts for 100 parts by mass. If it is 0.1 part by mass or more, the compatibilizer can have adequate effect to ensure high tear resistance, whereas if it is 2 parts by mass or less, the resins can be prevented from being cured due to excess reaction. It is more preferable that the compatibilizer-derived portion in layer (Y) accounts for 0.2 part by mass or more, still more preferably 0.5 part by mass or more, of the total of resin (d) and resin (e), which accounts for 100 parts by mass. It is more preferable that the compatibilizer-derived portion in layer (Y) accounts for 1.8 parts by mass or less, still more preferably 1.5 parts by mass or less, of the total of resin (d) and resin (e), which accounts for 100 parts by mass.

<Cross-sectional structure of layer (X)>

For the multi-layered film according to the present invention, it is preferable, from the viewpoint of tear resistance and interlayer contact strength, that in cross sections of the film observed along the machine direction and the thickness direction, layer (X) has a continuous phase comprising resin (a) and resin (c) and said continuous phase contains dispersed phases of resin (b) that are dispersed over an elliptical area extended in the film's machine direction or over a layer-like area extended in the film's machine direction, said dispersed phases having a thickness (the thickness of the dispersion layer in layer (X) is hereinafter referred to as dispersion layer thickness Tx of layer (X)) that meet the following equation: 150 nm < T x <600 nm. Here, the dispersion layer thickness Tx of layer (X) refers to the thickness in the thickness direction of the multi-layered film and is defined as the average single layer thickness that is calculated over the plurality of dispersed layers, as defined later.

It is more preferable that the thickness Tx of said dispersed phases is 200 nm or more, still more preferably 250 nm or more. It is more preferable that the thickness Tx of said dispersed phases is 550 nm or less, more preferably 500 nm or less.

Regarding said continuous phase and dispersed phases, the sea and the islands in a so-called sea-island structure correspond to the continuous phase and the dispersed phases, respectively. For the multi-layered film according to the present invention, it is sometimes difficult to distinguish between the continuous phase and a dispersed phase because dispersed phases are extended in the film's machine direction. In such a case, the field of view in observation of the dispersion structure by transmission electron microscopy (TEM) is shifted in the film's machine direction to find an edge of an island, which is then regarded as a dispersed phase, as described later.

Here, said continuous phase comprising resin (a) and resin (c) is defined as one in which the sum of the mass of resin (a) and the mass of resin (c) is larger than the sum of the mass of any other two components of the continuous phase. This means that the continuous phase comprising resin (a) and resin (c) may contain components other than resin (a) and resin (c), such as, for instance, various additives, organic lubricants, and particles. Similarly, a dispersed phase comprising resin (b) is defined as one in which the mass of resin (b) is larger than the mass of any other component of the dispersed phase. This means that a dispersed phase comprising resin (b) may contain components other than resin (b).

The meanings of the expressions "elliptical" and "layer-like" are as follows: when a film is observed by transmission electron microscopy as described later at a magnification that allows the entire thickness of the film can be seen, an area is referred to as elliptical if its both ends along the machine direction can be identified while it is referred to as layer-like if at least one end along the machine direction cannot be identified.

There are no specific limitations on the means of controlling the dispersed phase thickness Tx of layer (X) at 150 to 600 nm, but as described later, this may be achieved by forming a film in a blow-extrusion apparatus equipped with a spiral-type ring die under any of the following conditions: adjusting the number of flow channel overlaps to a preferred range, adjusting the ring die lip clearance to a preferred range, adjusting the stretching ratio (blow ratio, draw ratio) between the machine direction and the crosswise direction during film production to a preferred range, or a combination thereof.

<Cross-sectional structure of layer (Y)>

For the multi-layered film according to the present invention, it is preferable, from the viewpoint of tear resistance and interlayer contact strength, that in cross sections of the film observed along the machine direction and the thickness direction, layer (Y) has a continuous phase comprising resin (d) and the thickness direction of the film and said continuous phase contains dispersed phases of resin (e) that are dispersed over an elliptical area extended in the film's machine direction or over a layer-like area extended in the film's machine direction, said dispersed phases having a thickness (the thickness of the dispersion layer in layer (Y) is hereinafter referred to as dispersion layer thickness Ty of layer (Y)) of 40 to 150 nm.

It is more preferable that the thickness of the dispersed phases in layer (Y) is 50 nm or more, more preferably 60 nm or more. It is more preferable that the thickness Ty of said dispersed phases is 120 nm or less, more preferably 90 nm or less.

Here, said continuous phase comprising resin (b) is defined as one in which the mass of resin (d) is larger than the mass of any other component of the continuous phase. This means that a continuous phase formed of resin (d) may contain components other than resin (d), such as, for instance, various additives, organic lubricants, and particles.

Similarly, a dispersed phase comprising resin (e) is defined as one in which the mass of resin (e) is larger than the mass of any other component of the dispersed phase. This means that a dispersed phase formed of resin (e) may contain components other than resin (e).

There are no specific limitations on the means to take for controlling the dispersed phase thickness Ty of layer (Y) in the range of 40 to 150 nm, but as described later, it can be achieved, for instance, by adjusting the relation in melt viscosity between resin (d) and resin (e) to an preferable range or by adjusting the stretching ratio (blow ratio, draw ratio) between the machine direction and the crosswise direction during film production to a preferable range.

For the multi-layered film according to the present invention to have a dispersed phase thickness Ty of layer (Y) in the range of 40 to 150 nm, it is preferable to meet the following equation: 0.7 < r]d/r|e < 1.2 where nd denotes the melt viscosity of the material for resin (d) (feedstock for producing resin (d) before film formation) at a temperature of 200°C and a shear velocity of 100 sec^"1, and ne denotes the melt viscosity of the material for resin (e) (feedstock for producing resin (e) before film formation) at a temperature of 200°C and a shear velocity of 100 sec^"1. The range is more preferably 0.8 < d/ne < 1.1 , still more preferably 0.9 < nd/ne < 1.0.

It is important for the multi-layered film according to the present invention to comprise layer (X) and layer (Y), but as long as this requirement is met, there are no other specific limitations on the laminated structure. For instance, it may consist of two layers (layer (X) and layer (Y)), three layers (layer (X)/layer (Y)/layer (X) or layer (Y)/layer (X)/layer (Y)), or more layers. Or, it may contain a third layer other than layer (X) and layer (Y). If a third layer is contained, furthermore, it may be located between layer (X) and layer (Y) or at a position other than between layer (X) and layer (Y). From the viewpoint of tear resistance, heat sealability, and film production, in particular, it is preferable that layer (Y), layer (X), and layer (Y) are directly stacked in this order, thus forming a layer (Y)/layer (X)/layer (Y) structure with no other layer existing between layer (X) and layer (Y). For the multi-layered film according to the present invention, the proportion of the thickness of layer (Y) (the total thickness of layer (Y) if two or more of layer (Y) exist; hereinafter the same) to the total thickness of layer (X) and layer (Y) is preferably in the range of 1 to 50% to allow both' layers to work effectively. It is preferable that the thickness of layer (Y) accounts for 1 to 50% of the total thickness of said layer (X) and layer (Y) because both high tear resistance and heat sealability can be achieved simultaneously. The proportion of the thickness of layer (Y) to the total thickness of layer (X) and layer (Y) is more preferably 5% or more, still more preferably 10% or more. The proportion of the thickness of layer (Y) to the total thickness of layer (X) and layer (Y) is more preferably 40% or less, more preferably 30% or less.

It is preferable that the multi-layered film according to the present invention has a film thickness of 5 to 200 μπι. Maintaining a film thickness of 5 μηι or more ensures that the resulting film will have high bending strength, high handleability, good roll appearance, and good unwinding properties. Maintaining a film thickness of 200 μηι or less ensures that the resulting film will have improved flexibility and high handleability in various uses, and when processed by blow extrusion, it will not suffer from unstable bubble formation due to its own weight. Said film thickness is more preferably 7 μιη or more, still more preferably 10 μηι or more, and most preferably 12 μιη or more. Furthermore, said film thickness is more preferably 150 μιη or less, still more preferably 100 μηι or less, and most preferably 50 μπι or less. <Particles>

The multi-layered film according to the present invention may contain particles aiming to improve the blocking resistance and handleability.

Such particles may be either inorganic particles or organic particles, and usable particle materials include silicon oxides such as silica; various carbonates such as calcium carbonate, magnesium carbonate, and barium carbonate; various sulfates such as calcium sulfate and barium sulfate; various composite oxides such as zepiolite and zeolite; various phosphates such as calcium phosphate and magnesium phosphate; various oxides such as titanium oxide and zinc oxide; various hydrides such as aluminum hydroxide and magnesium hydroxide; and various salts such as lithium fluoride. These particles may be surface-treated as required.

For the multi-layered film according to the present invention, said particles are preferably contained at least in either of the surface layers of the film and they are more preferably contained in both surface layers. It is preferable that these particles account for 1 to 10 mass%, more preferably 3 to 5 mass%, assuming that all the layers in total account for 100 mass%.

The multi-layered film according to the present invention may contain an organic lubricant. Said organic lubricant is preferably contained at least in either of the surface layers in the film and they are more preferably contained in both surface layers. It is preferable that said organic lubricant accounts for 0.1 to 5 mass%, more preferably 0.5 to 2 mass%, assuming that all the layers in total account for 100 mass%. In such cases, it is possible to prevent blocking from taking place in the film after being wound up. Furthermore, it will be possible to prevent a decrease in melt viscosity and deterioration in processability due to excessive addition of an organic lubricant, and the resulting film will not suffer from significant defects in appearance such as bleed-out of the organic lubricant and poor transparency. If the process for producing the multi-layered film according to the present invention comprises a step of pelletizing a composition, followed by drying, re-melt-kneading, extrusion, and film production, as described below, blocking among pellets will be prevented to ensure high handleability.

There are no specific limitations on the type of organic lubricant to be used, and various ones including, for instance, fatty acid amide based organic lubricants can be used. In particular, organic lubricants with a relatively high melting point such as ethylene bis-stearamide, ethylene bis-oleamide, and ethylene bis-lauramide are preferable from the viewpoint of develop high blocking resistance.

The multi-layered film according to the present invention may contain additives other than those described above as long as they do not impair the effect of the multi-layered film according to the present invention. Examples include, for instance, conventionally known ones such as end-capping agent, crystal nucleating agent, antioxidant, ultraviolet ray stabilization agent, color protection agent, delustering agent, deodorant, flame retardant, weathering agent, antistatic agent, antioxidant, ion exchange agent, tackifier, antifoaming agent, color pigment, and dye.

Preferable examples of said end-capping agent include monocarbodiimide compounds.

Preferable organic crystal nucleating agents include aliphatic amide compound, melamine based compound, metallic phenylphosphonate, benzenecarbamide derivative, aliphatic/aromatic carboxylic acid hydrazide, sorbitol based compound, amino acid, polypeptide, and metal phthalocyanine. Preferable inorganic crystal nucleating agents include talc, clay, mica, kaolinite, other silicate minerals, and carbon black.

Preferable antioxidants include hindered phenolic ones and hindered amine based ones.

Preferable color pigments include inorganic pigments such as carbon black and iron oxide, and organic pigments such as cyanine based ones.

To have adequate flexibility, it is preferable that the multi-layered film according to the present invention has a tensile modulus of 1 ,200 MPa or less in either the film's machine direction (MD) or the film's crosswise direction (CD, the direction perpendicular to the machine direction). The tensile modulus is more preferably 1,000 MPa or less, still more preferably 800 MPa or less. Rather than meeting the above-mentioned numerical requirement for tensile modulus in either direction, it is particularly preferable for the tensile modulus to meet said numerical requirement in both the film's machine direction and the film's crosswise direction. There are no specific limitations on the lower limit of tensile modulus, but practically it is about 100 MPa.

Depressing the tensile modulus to 1,200 MPa or less in either the machine direction or the crosswise direction can be achieved by, for instance, adjusting the types and the contents of the resins that constitute layer (X) and layer (Y) to the preferable ranges described above, or adjusting the stretching ratio (blow ratio, draw ratio) between the machine direction and the crosswise direction during film production to the preferable ranges described below.

It is preferable that the multi-layered film according to the present invention has an average tear strength between the machine direction (MD) and the crosswise direction (CD) of 500 mN or more. If the average tear strength between MD and CD is more preferably 1,000 mN or more, still more preferably 1,500 mN or more. Here, said average tear strength is preferably as high as possible, but the practically achievable upper limit is considered to be about 5,000 mN.

If the tear strength is 500 mN or more, the multi -layered film according to the present invention will have adequately high tear resistance to ensure high resistance to breakage and high practical performance when used in various applications.

Methods to allow the average tear strength between MD and CD to be 500 mN or more include, for instance, adjusting the types and the contents of the resins that constitute layer (X) and layer (Y) to the preferable ranges described above, adjusting the stretching ratio (blow ratio, draw ratio) between the machine direction and the crosswise direction during film production to the preferable ranges described below, forming layer (X) and/or layer (Y) so that their cross sections along the film's machine direction and the thickness direction have preferable structures as described above, or adjusting the orientation parameter of resin (b) to the preferable range described below.

For the multi-layered film according to the present invention to have improved heat sealability, it is preferable that at least either of the surface layers comprises layer (Y) with a surface energy of 30 to 60 dyne/cm. The surface energy is more preferably 35 dyne/cm or more, more preferably 40 dyne/cm or more.

Methods to allow layer (Y) at the surface to have a surface energy of 30 to 60 dyne/cm include adjusting the types and the contents of the resins that constitute layer (Y) to the preferable ranges described above, and treating the surface by, for instance, corona discharge treatment or plasma treatment.

For the multi-layered film according to the present invention to have an intended tear resistance, it is preferable that resin (b) has an orientation parameter of 0.8 to 2.0 in either MD or CD. The orientation parameter of resin (b) is more preferably 1.8 or less, still more preferably 1.6 or less. Rather than meeting the above-mentioned numerical requirement for orientation parameter in either direction, it is particularly preferable for the orientation parameter to meet said numerical orientation parameter requirement in both the film's machine direction and the film's crosswise direction.

Here, the orientation parameter can be determined from polarized Raman spectra from the film's cross sections measured by Raman spectroscopy as described later. The orientation parameter is equal to 1.0 in a non-oriented state, and the orientation in the film's cross-sectional direction increases with a decreasing parameter below 1 while the orientation perpendicular to the film's cross section increases with an increasing parameter above 1.

Methods to controlling the orientation parameter of resin (b) to 0.8 to 2.0 in either MD or CD include adjusting the ring die lip clearance and the stretching ratio (blow ratio, draw ratio) between the machine direction and the crosswise direction during film production to preferable ranges as described below.

It is preferable that the multi-layered film according to the present invention has a heat seal strength of 7 N or more. It is more preferably 11 N or more, still more preferably 15 N or more.

A method to control the heat seal strength at 7 N or more is stacking layers so that layer (Y) is located at the outermost position and works as heat sealing surface, and adjusting the types and contents of the resins that constitute said layer (Y) and the surface energy of said layer (Y) to preferable ranges as described above. Here, there are no specific limitations on the upper limit of said heat seal strength of the multi-layered film according to the present invention, but to the knowledge of the present inventors, it is roughly 80 N to 100 N.

<Multi-layered film production method according to the present invention>

In the next place, the multi-layered film production method according to the present invention is described in detail, but it should be understood that the invention is not construed as being limited thereto.

A lactic acid based resin used for the present invention can be prepared, for instance, by direct dehydration and condensation of a material mainly comprising a lactic acid component such as L-lactic acid and D-lactic acid, or by ring-opening polymerization of a cyclic ester intermediate, such as lactide and glycolide, formed from hydroxycarboxylic acid.

Compositions to constitute layer (X) and layer (Y) of the multi-layered film according to the present invention can be produced by dissolving and uniformly mixing required components in a solvent to produce a solution and removing the solvent to produce a composition, but it is preferable to adopt the melt-kneading method because it is free from steps such as dissolving feedstock in a solvent and removing the solvent, and accordingly very practical. There are no specific limitations on the melt-kneading method, and generally-used, commonly-known mixers including kneader, roll mill, Banbury mixer, and uniaxial or twin screw extruder may be used. In particular, it is preferable to use a uniaxial or twin screw extruder from the viewpoint of productivity.

If the melt-kneading method is adopted, it is preferable that all component to be used as feedstock are processed in advance, for instance, by drying to adjust the moisture content to 500 ppm or less, more preferably 200 ppm or less, still more preferably 100 ppm or less. If the moisture content is 500 ppm or less for all components, it will be possible to prevent each layer from suffering from a decrease in melt viscosity and prevent the film from suffering from deterioration in mechanical properties. From a similar point of view, it is preferable to perform melt-kneading using a vent-type twin screw extruder to remove moisture and volatile components such as low molecular weight substances.

Melt-kneading is performed more preferably in the temperature range of 150°C to 250°C, and it is still more preferably in the range of 160°C to 210°C to prevent degradation of lactic acid based resin.

The multi-layered film according to the present invention can be produced by conventionally-known existing film production methods including blow extrusion, tubular film extrusion, and T-die casting, of which the blow extrusion method is preferable from the viewpoint of the formation of a preferable dispersion structure in the multi-layered film according to the present invention as well as production cost.

If the multi-layered film according to the present invention is produced by blow extrusion, a composition prepared as described above may be fed directly to a ring die, or a composition prepared as described above may be pelletized first and then fed to an extruder equipped with a ring die. If it is pelletized first, it is preferable that pellets are treated in advance, for instance, by drying them to adjust their moisture content to 500 ppm or less, more preferably 200 ppm or less, and still more preferably 100 ppm or less, as described above. If an extruder equipped with a ring die is used, it is also preferably a vent-type twin screw extruder.

Each composition that constitutes layer (X) and layer (Y) produced by a method as described above is fed to a multi-layered ring die, and the molten resin extruded through a ring-like lip clearance is subjected to cooling air supplied from an air ring while supplying dry air inside the tube to form bubbles. While being folded flat by a nip roll, the resulting film is taken up at a predetermined take-up speed and, after cutting either end or both ends open if required, wound up to provide the multi-layered film according to the present invention.

For the multi-layered film according to the present invention, it is important to adjust the blow ratio and the draw ratio properly during blow extrusion for film production. Here, the blow ratio is defined as the ratio of stretching in the crosswise direction of a film, which is calculated as (size in the crosswise direction of a film wound up after an end is cut open) / (diameter of the ring die). The draw ratio, on the other hand, is the ratio of stretching in the machine direction of a film, which is represented as (wind-up speed) / (speed of discharge from the ring die) but practically calculated as (lip clearance of the ring die) / {(film thickness after completion of film production) ^χ (blow ratio)}.

For the multi-layered film according to the present invention, the blow ratio is preferably 1.6 to 4.0 and the draw ratio is preferably 5 to 40 to allow a preferable dispersed state to be formed in cross sections of layer (X) and/or layer (Y). The blow ratio is more preferably 2.2 to 3.8, most preferably 2.8 to 3.6. The draw ratio is more preferably 10 to 30, most preferably 15 to 20.

The lip clearance (mm) of the ring die may be adjusted so that that the resulting film has an intended thickness when produced at a preferable blow ratio and draw ratio as described above, but normally, it is 0.2 to 1.8 (mm), preferably 0.3 to 1.4 (mm), and most preferably 0.4 to 1.0 (mm). It is preferable to use a spiral-type ring die from the viewpoint of thickness accuracy and uniformity, and it is preferable to use a rotary ring die from a similar point of view.

When using a spiral-type ring die, it is preferable that there are 2 to 8 flow channel overlaps on the side face of the die. The number of overlaps is calclulated as (number of spiral flow channels in the die) ^χ (number of rotations per flow channel).

The number of flow channel overlaps for the resin that constitutes layer (X) in particular is more preferably 2 to 6, still more preferably 3 to 5, to allow a preferable dispersed state to be formed in cross sections of layer (X).

When a biodegradable film for the present invention is produced by blow extrusion, the extrusion temperature is commonly in the range of 140 to 240°C, preferably 150 to 200°C, and the ring die temperature is commonly in the range of 140 to 190°C, preferably 150 to 180°C.

The film thus produced may be heat-treated on a heating roller or in an oven to prevent heat shrinkage of the film. Other various surface treatments such as corona discharge treatment and plasma treatment may be performed to improve printing properties, lamination suitability, coating suitability, and the like.

[Examples]

The multi-layered film according to the present invention will be illustrated below in greater detail with reference to Examples, but it should be understood that the invention is not construed as being limited thereto. <Measurement and evaluation method>

Measurements and evaluations made in Examples were carried out under the following conditions.

(1) Tensile modulus (MPa)

Tensilon (registered trademark) UCT-T00 supplied by Orientec Co., Ltd., was used in an atmosphere of room temperature of 23 °C and a relative humidity of 65% for tensile modulus determination. Specifically, strip specimens with a length of 150 mm in the measuring direction and a width of 10 mm were cut out, and 10 measurements were made in MD with an initial tensile chuck distance of 50 mm and a tension speed of 200 mm/min according to the method specified in JIS K-7127 (1999), followed by averaging them to represent their tensile modulus. The same procedure was carried out for CD.

(2) Heat seal strength (N)

Heat sealing strength measurements were performed using a Kopp-Labormaster 3000 with integrated Laboratory- Sealer SGPE 3000. Measurements were performed at a pressure of 150N and at a temperature of 90°C (higher temperatures led to severe blocking). A sealing time of 0.5 seconds and a cooling time of 3 seconds were used. Higher Pressure or longer cooling times were tested but resulted in almost identical values. The tensile test was performed at a speed of 0.2 m/min and the value was recorded in Newton. A minimum of 5 film samples was measured and the average value is reported.

(3) Dispersed phase thickness Tx (nm) in layer (X) and dispersed phase thickness Ty (nm) in layer GO

A film was dyed with ruthenium acid, embedded in epoxy resin, and cut with an ultramicrotome in the direction that is parallel to the machine direction of the film and perpendicular to the film surface to prepare ultrathin sections. Using a transmission electron microscope (H-7100, supplied by Hitachi, Ltd.) at an accelerating voltage of 100 kV, the cut surface was first observed at a magnification that enables the observation of the entire cross section of the film in the thickness direction, and through-thickness center portions of three regions defined by equally dividing each layer into three in the thickness direction were photographed at a magnification of 50,000x. Thus, three photographs were taken for each layer.

Each photograph thus taken was placed with the length of the film in the longitudinal direction, and cut into 15 cm xl5 cm squares, and a line that crosses the lengthwise center was drawn (specifically, the line thus drawn equally divides the square into upper and lower halves). On the basis of the intersections between this line and boundaries of dispersed phases that are in an elliptical form extended in the machine direction of the film or in a layer-like form extended in the machine direction of the film, the thickness of all dispersed phases excluding those at the right and left edges was measured to the nearest 0.1 mm. Similarly, the thickness of dispersed phases was measured using three photographs for each layer, and the average was calculated for all layers, followed by calculating the thickness (nm) of dispersed phases by assuming 1 mm in observations corresponds to 20 nm (rounded off to the nearest whole number).

When it is difficult to distinguish between the continuous phase and a dispersed phase because dispersed phases are extended in the film's machine direction, the field of view in observation of the dispersion structure by transmission electron microscopy (TEM) is shifted in the film's machine direction to find an edge of an island, which is then regarded as a dispersed phase.

(4) Melt viscosity (Pa - s)

A CFT-500A flow tester supplied by Shimadzu Corporation (die diameter 1 mm, die length 10 mm, and plunger cross section 1 cm²) was used to measure the melt viscosity (Pa* s) (rounded off to the nearest ten) under the conditions of a temperature of 200°C and preheat time of 3 min, and measurements at a shear velocity of 100 sec^"1 were adopted.

(5) Surface energy

Four measurement liquids with a known surface energy and components thereof (dispersion force, polar force, hydrogen bonding strength) (values of water, formamide, ethylene glycol, methylene iodide given in J. Panzer, J. Colloid Interface Sci., 44, 142 (1973) were used for the present invention) were prepared, and the contact angle of each liquid on a film specimen was measured using a CA-D type contact angle gauge (supplied by Kyowa Interface Science Co., Ltd.) under the conditions of a temperature of 23 °C and a relative humidity of 65%. Measurements were made at five randomly selected positions on the film specimen, and their average was taken to represent the contact angle. This value of contact angle was put in the following equation, which is derived from extended Fowkes equation and Young's equation, to calculate each component.

(YSSLT² + (Ys^P - YL^P)^1/2 + (YSNLV⁷² = YL(1 + cos9)/2

(In the equation, γ_δ = Ys^d + Ys^p + Ys^h, YL = YL^D + YL^P + YL'¹, where y_s, Ys^d, Ys^p, and Ys'¹ denote the surface energy, dispersion force component, polar force component, and hydrogen bonding strength component of the film, respectively, while YL, γιΛ YL^p, and denote the surface energy, dispersion force component, polar force component, and hydrogen bonding strength component of the measurement liquid used, respectively. And Θ denotes the contact angle of the measurement liquid on the film.)

The measurements of Θ obtained for each liquid, the surface energy and its components for the measurement liquid were put in the equations given above, and the surface energy of the film was calculated by solving the simultaneous equations.

(6) Tear strength (mN)

The Elmendorf tear resistance was determined according to EN ISO 6383-2:2004. Film samples with a constant radius were prepared and measured using a Pro Tear Electronic Elmendorf tear Tester Model 60-2200. For every film orientation (machine direction and cross direction) 10 film samples each were measured and the average value determined by the Tear Tester in mN. The average Elmendorf tear given in the tables was calculated using the formula Tear Strength = (Tear strength at MD + Tear strength at CD)/2.

(7) Interlayer contact strength The surface of a film was subjected to corona treatment, and a polyurethane based adhesive (Takelac 971, supplied by Mitsui Chemicals Polyurethanes, Inc. / Takenate A3, supplied by Mitsui Chemicals Polyurethanes, Inc. / ethyl acetate (9:1:10)) was applied, followed by combining the surface with a corona treated surface of a biaxially orientated polypropylene film with a thickness of 20 μηι and ageing them at 40°C for 48 hours to prepare a composite film. The film was subjected to peeling test using a Tensilon tester supplied by Toyo Baldwin, and evaluated in terms of the weight required for peeling according to the following five-stage criteria.

film width: 25.4 mm

peeling speed: lOO mm/min

peeling angle: 90° peeling

peel load less than 10 g: 1

10 g or more, less than 30 g: 2

30 g or more, less than 50 g: 3

50 g or more, less than 100 g: 4

100 g or more, or film breakage: 5

(8) Orientation parameter of resin (b)

Measurements were made by Raman spectroscopy using the following equipment under the following conditions.

^• Equipment: T-64000 (supplied by Jobin Yvon)

^• Conditions: Measurement mode; micro-Raman spectroscopy

objective lens; xlOO

beam diameter; 1 μιτι

light source; argon ion laser / 514.5 nm

laser power; 100 mW

diffraction grating; Single 600 gr/mm

Slit; 100 μηι

detector; CCD / Jobin Yvon 1024x256

A film to be used for measurement was sampled, embedded in epoxy resin, and cut with an ultramicrotome to prepare a section of the film. Here, five sections having a surface perpendicular to the machine direction of the film and another five sections having a surface perpendicular to the crosswise direction were prepared, and measurements were made at the center of layer (X) of each specimen.

Laser beam (incident beam) used for the measurement was polarized using a polarizer. The polarizer was arranged so that its polarization direction is parallel to the polarization direction of the incident beam, and the beam passing through the polarizer was detected, following by determining the Raman band intensity. For layer (X) of each specimen, spectra were obtained with the specimen placed so that its machine direction or its crosswise direction are parallel to the polarization direction of the laser beam (incident beam), and then spectra were also obtained with the specimen placed so that its machine direction or its crosswise direction are perpendicular to the polarization direction of the laser beam (incident beam).

When resin (b) was polybutylene adipate · terephthalate, the orientation parameter O was calculated by the following equation. Five measurements were made and averaged, and then rounded off to one decimal place to represent the orientation parameter. It was calculated for sections with a surface parallel to the film's machine direction and those with a surface parallel to the film's crosswise direction.

O (orientation parameter) = Ii₆₁₂parallel / Ii₆i₂perpendicular

Ii6i₂parallel: 1612 cm^"1 Raman band intensity in Raman spectrum observed with a beam polarized parallel to the machine direction or the crosswise direction.

Ii₆i₂perpendicular: 1612 cm^"1 Raman band intensity in Raman spectrum observed with a beam polarized perpendicular to the machine direction or the crosswise direction.

It is important that the Raman band selected to determine the Raman band intensity to be used for calculation of the orientation parameter of resin (b) is a Raman spectral band that is inherent in resin (b), and an appropriate band may be selected arbitrarily as long as it overlaps only slightly with other bands and can be intensified largely by controlling the polarization direction of the incident beam on the specimen. If polybutylene adipate 'terephthalate resin is used as resin (b), for instance, the C=C stretching band at 1612 cm^"1 can be used.

If the vibration direction of the band thus selected is perpendicular to the molecular chain, the orientation parameter of a specimen with a cross section parallel to the film's machine direction is calculated by dividing the Raman band intensity measured with a laser beam polarized in a direction perpendicular to the machine direction by a Raman band intensity measured with a laser beam polarized in a direction parallel to the machine direction, or the orientation parameter of a specimen with a cross section parallel to the film's crosswise direction is calculated by dividing the Raman band intensity measured with a laser beam polarized in a direction perpendicular to the crosswise direction by a Raman band intensity measured with a laser beam polarized in a direction parallel to the crosswise direction.

On the contrary, if the vibration direction of the band thus selected is parallel to the molecular chain, the orientation parameter of a specimen with a cross section parallel to the film's machine direction is calculated by dividing the Raman band intensity measured with a laser beam polarized in a direction parallel to the machine direction by a Raman band intensity measured with a laser beam polarized in a direction perpendicular to the machine direction, or the orientation parameter of a specimen with a cross section parallel to the film's crosswise direction is calculated by dividing the Raman band intensity measured with a laser beam polarized in a direction parallel to the crosswise direction by a Raman band intensity measured with a laser beam polarized in a direction perpendicular to the crosswise direction.

(9) Mass average molecular weight, and number average molecular weight

Measurements were made with a chloroform solvent using a Waters 2690 gel permeation chromatography (GPC) supplied by Nihon Waters K.K. at a column temperature of 40°C, and calculations were made with the polymethyl methacrylate conversion method.

The following three lactic acid based resins Al, A2, and A3 were prepared.

Lactic acid based resin Al :

Homopolylactic acid having a mass average molecular weight of 175,000, D-form content of 12.0 mol%, no melting point, melt viscosity of 1,250 Pa- s at a temperature of 200°C and shear velocity of 100 sec^"1

Lactic acid based resin A2:

Homopolylactic acid having a mass average molecular weight of 200,000, D-form content of 1.4 mol%, melting point of 170°C, melt viscosity of 1,400 Pa' s at a temperature of 200°C and shear velocity of 100 sec^"1

Lactic acid based resin A3:

Homopolylactic acid having a mass average molecular weight of 200,000, D-form content of 5.0 mol%, melting point 150°C, melt viscosity of 1,400 Pa* s at a temperature of 200°C and shear velocity of lOOsec^"1

The above measurements of mass average molecular weight were made with a chloroform solvent using Warters 2690 supplied by Nihon Waters K.K. at a column temperature 40°C along with polymethyl methacrylate as the standard.

To determine the melting point of a lactic acid based resin, it was first heated for 24 hours in a hot air oven at 100°C, and then a 5 mg specimen was taken on the aluminum tray of an RDC 220 differential scanning calorimeter supplied by Seiko Instruments Inc. and heated from 25°C up to 250°C at a heating rate of 20°C/min while measuring the temperature of the crystal melting peak. <Biodegradable resin>

The following four biodegradable resins Bl, B2, B3, and B4 were prepared.

Biodegradable resin B 1 :

Polybutylene adipate-terephthalate resin (Ecoflex (trade name) FBX7011 supplied by BASF) with a melt viscosity of 1,200 Pa- s at a temperature of 200°C and shear velocity of 100 sec^"1

Biodegradable resin B2:

Polybutylene succinate - adipate based resin (Bionolle (trade name, registered trademark) #3001 supplied by Showa Highpolymer Co., Ltd.), with a melt viscosity of 1,250 Pa- s at a temperature of 200°C and shear velocity of 100 sec^'1

Biodegradable resin B3 :

Poly(3-hydroxybutyrate · 3 -hydroxy hexanoate) (Aonilex (trade name) supplied by Kaneka Corporation) with a melt viscosity of 800 Pa - s at a temperature of 200°C and shear velocity of 100 sec

Biodegradable resin B4:

Polybutylene adipate-terephthalate resin (Ecoflex (trade name) FBX7020 supplied by BASF) with a melt viscosity of 650 Pa* s at a temperature of 200°C and shear velocity of 100 sec^"1

The following two block copolymer resins CI and C2, each comprising a polyether segment and a polylactic acid segment, were prepared. Block copolymer CI of a polyether segment and a polylactic acid segment:

In a reaction container equipped with a stirrer, 62 parts by mass of polyethylene glycol with a number average molecular weight 8,000, 38 parts by mass of L-lactide, and 0.05 part by mass of tin octylate were mixed and polymerized in a nitrogen atmosphere at 160°C for 3 hours to produce a block copolymer CI having a polylactic acid segment with a number average molecular weight 2,500 at each end of polyethylene glycol with a number average molecular weight of 8,000. The mass content of the polylactic acid segment was 38 mass% in the entire CI, which accounted for 100 mass%. Block copolymer C2 of a polyether segment and a polylactic acid segment:

In a reaction container equipped with a stirrer, 62 parts by mass of polyethylene glycol with a number average molecular weight 4,000, 38 parts by mass of L-lactide, and 0.05 part by mass of tin octylate were mixed and polymerized in a nitrogen atmosphere at 160°C for 3 hours to produce a block copolymer CI having a polylactic acid segment with a number average molecular weight 2,500 at each end of polyethylene glycol with a number average molecular weight of 4,000. The mass content of the polylactic acid segment was 56 mass% in the entire C2, which accounted for 100 mass%.

The following two compatibilizers Dl and D 2 were prepared.

Compatibilizer D 1 :

An epoxy-containing styrene/acrylate copolymer (Joncryl ADR-4368, supplied by BASF, a compound having two or more epoxides)

Compatibilizer D2:

Polycarbodiimide (Carbodilite LA-1, supplied by Nisshinbo Industries, Inc., a compound having two or more carbodiimides)

The following one type of particles El was prepared.

Particles El :

Calcium carbonate (Caltex (trade name) R, supplied by Maruo Calcium Co., Ltd., average particle diameter 2.8 um, surface treated with fatty acid containing stearic acid as primary component, surface treatment agent accounting for 3 mass% or less)

<Multi-layered film production>

[Example] [Comparative example 1]

As feedstock for producing layer (X), 45 parts by mass of lactic acid based resin (Al) and 55 parts by mass of biodegradable resin (Bl) were fed to a vacuum venting type twin screw extruder with a cylinder temperature of 190°C, screw diameter of 30 mm, and L/D of 30, and melt-kneaded while degasing the equipment from vacuum vent ports. As feedstock for producing layer (Y), 55 parts by mass of biodegradable resin (Bl) and 45 parts by mass of lactic acid based resin (Al) were fed to a vacuum venting type twin screw extruder with a cylinder temperature of 190°C, screw diameter of 30 mm, and L/D of 30, and melt-kneaded while degasing the equipment from vacuum vent ports.

These two melt-kneading resins were fed to a spiral -type two-resin three-layer ring die with a diameter of 250 mm, lip clearance of 1.0 mm, four flow channel overlaps for the resin to constitute layer (X) (the number being denoted by X), four flow channel overlaps for the resin to constitute layer (Y)) (the number being denoted by Y), and temperature of 160°C so as to form a laminated film consisting of layer (Y)/layer (X)/layer (Y) with a lamination ratio of 1/8/1. While cooling air was blown from an air ring to the molten resin extruded from the lip clearance, drying air was supplied into the tube to form bubbles at a blow ratio of 3.0, and then the resulting film was folded flat by a nip roll with the discharge rate and the take-up speed being adjusted so as to achieve a draw ratio of 17 and final thickness of 20 μηι, followed by cutting open both ends with an edge cutter to produce two film strips, which were wound up separately. The structures and physical properties of the resulting films are given in Table 1.

Examples 1 to 34, Comparative examples 2 to 6

In Examples 1 to 34 and Comparative examples 2 to 6, the same procedure as in Comparative example 1 except for changes in the feedstock compositions for layer (X) and layer (Y), lip clearance of the ring die, number (X) of flow channel overlaps for the resin to constitute layer (X), blow ratio, and draw ratio as described in Tables 1 to 4 was carried out to produce a film with a final thickness of 20 μιη. The structures and physical properties of the resulting films are given in Tables 1 to 4.

[Table 1]

[Table 2]

Table 3

[Table 4]

[Industrial applicability]

The multi-layered film according to the present invention has high flexibility, tear resistance, heat sealability, interlayer contact strength, and biodegradability, can be used preferably as materials that mainly require including those for bags such as pouches, shopping bags, carry bags for vegetables, fruits, meat, fish, and other fresh products, as well as material for trash bag, manure bag, compost bag, other bags/packages, mulching film, other agricultural materials, and medical/hygienic materials.

Claims

[Claim 1]

A multi-layered film comprising layer (X) and layer (Y) wherein said layer (X) and said layer (Y) meet requirement (A) and requirement (B) given below, respectively:

Requirement (A): said layer (X) comprises a lactic acid based resin, biodegradable resin except a lactic acid based resin, and block copolymer resin of a polyether segment and a polylactic acid segment (hereinafter, said lactic acid based resin contained in said layer (X) is referred to as resin (a), said biodegradable resin except a lactic acid based resin contained in said layer (X) referred to as resin (b), and said block copolymer resin of a polyether segment and a polylactic acid segment contained in said layer (X) referred to as resin (c)) wherein said resin (a), said resin (b), and said resin (c) account for 20 to 85 parts by mass, 10 to 50 parts by mass, and 5 to 30 parts by mass, respectively, assuming that said resin (a), said resin (b), and said resin (c) in total account for 100 parts by mass,

[Claim 2]

A multi-layered film as described in claim 1 wherein layer (X) contains 0.1 to 2 parts by mass of a component derived from a compatibilizer as defined below assuming that said resin (a), said resin (b), and said resin (c) in total account for 100 parts by mass:

[Claim 3]

A multi-layered film as described in either claim 1 or 2 wherein layer (Y) contains 0.1 to 2 parts by mass of a component derived from a compatibilizer as defined below assuming that said resin (d) and said resin (e) in total account for 100 parts by mass:

[Claim 4]

A multi-layered film as defined in any of claims 1 to 3 wherein said resin (b) is a polymer as defined below:

[Claim 5]

A multi-layered film as defined in any of claims 1 to 4 wherein said resin (b) and/or said resin (d) is a copolymerized polyester produced from an aliphatic dicarboxylic acid with a carbon number of 4 to 30, terephthalic acid, and a diol with a carbon number of 3 to 6.

[Claim 6]

A multi-layered film as defined in any of claims 1 to 5 wherein the polylactic acid segment accounts for 5 to 49 mass% assuming that the total quantity of the polymer in said resin (c) accounts for l00 mass%.

[Claim 7]

A multi-layered film as defined in any of claims 1 to 6 wherein the polyether segment in said resin (c) is a polyethylene glycol segment.

[Claim 8]

A multi-layered film as defined in any of claims 1 to 7 wherein, in cross sections of the film observed along the machine direction and the thickness direction, said layer (X) has a continuous phase comprising said resin (a) and said resin (c) and said continuous phase contains dispersed phases comprising said resin (b) that are dispersed over an elliptical area extended in the film's machine direction or over a layer-like area, extended in the film's machine direction said dispersed phases having a thickness of 150 to 600 nm.

[Claim 9]

A multi-layered film as defined in any of claims 1 to 8 wherein, in cross sections of the film observed along the machine direction and the thickness direction, said layer (Y) has a continuous phase comprising said resin (d) and said continuous phase contains dispersed phases of said resin (e) that are dispersed over an elliptical area extended in the film's machine direction or over a layer-like area extended in the film's machine direction, said dispersed phases having a thickness of 40 to 150 nm.

[Claim 10]

A multi-layered film as defined in any of claims 1 to 9 wherein at least either of the surface layers comprises said layer (Y) and said surface layer has a surface energy of 30 to 60 dyne/cm.

[Claim 11]

A multi-layered film as defined in any of claims 1 to 10 wherein said resin (b) has an orientation parameter of 0.8 to 2.0.

[Claim 12]

A multi-layered film as defined in any of claims 1 to 11 wherein said layer (Y), said layer (X), and said layer (Y) are directly stacked in this order to form a multi-layered structure.

[Claim 13]

A multi-layered film as defined in any of claims 1 to 12 wherein the average between the tear strength in the film's machine direction and that in the film's crosswise direction is 500 mN or more.

[Claim 14]

A multi-layered film as defined in any of claims 1 to 13 that has a heat seal strength of 7 N or more.

[Claim 15]

A multi-layered film as defined in any of claims 1 to 14 that has a tensile modulus of 1,200 MPa or less.