JP2012192636A - Polylactic acid biaxially stretched film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film having superior gas barrier properties when imparting the vapor-deposited layer comprising a heat resistance property, heat sealability, silence, the metal or the inorganic oxide by a film combined with the acrylic resin and the polylactic acid resin, and extending in the biaxial direction.SOLUTION: A polylactic acid biaxially stretched film has an A layer that includes the acrylic resin and the non-crystalline polylactic acid resin, and a B layer including the polylactic acid resin.

Description

  The present invention relates to a polylactic acid biaxially stretched film excellent in heat resistance, heat sealability, silence, and gas barrier properties when a vapor deposition layer made of a metal or an inorganic oxide is applied.

  In recent years, due to increasing awareness of environmental issues, attention has been focused on soil pollution problems caused by the disposal of plastic products and global warming problems caused by increased carbon dioxide caused by incineration. As a measure against the former, various biodegradable resins, and as a measure against the latter, a resin made of biomass (plant-derived raw material) that does not give a new carbon dioxide load to the atmosphere even if it is incinerated has been extensively researched and developed. ing.

One example of a resin that satisfies the above-described characteristics is polylactic acid. Polylactic acid has a high melting point and is expected to be a practically excellent biodegradable polymer that can be melt-molded. For example, a polylactic acid film is said to have the highest tensile strength and elastic modulus among various biodegradable films, and is excellent in gloss and transparency. However, the film is inferior in gas barrier properties and has a problem of inferior heat resistance since the glass transition temperature of the polylactic acid resin is relatively low. (For example, see Non-Patent Document 1)
At present, the use of the polylactic acid film is expanding, but among them, it is particularly suitable for packaging materials. When used as part of a film of packaging material, higher functionality is required as a single film in order to be able to produce a commercially effective and cost-effective packaging product. For example, it may be heat sealability required for processing into a molded body, or gas barrier properties when a vapor deposition layer made of metal or an inorganic oxide is applied. In particular, regarding gas barrier properties, a very high level has recently been required. Furthermore, among packaging materials, when used in applications where there are many opportunities to touch or fold people's hands, such as for snack packaging, it is becoming more demanding that the film be quiet. . However, the polylactic acid film has a problem that it emits a peculiar harsh sound when external stresses such as stagnation and bending are applied, compared to other packaging thermoplastic resin films represented by polyolefin. .

  Various attempts have been made to solve the above requirements. For example, Patent Documents 1-3 disclose a film prepared by blending a polylactic acid resin and an acrylate resin. However, both are intended for use in decorative sheets and transparent optical film applications, and are technical ideas related to heat barrier properties and gas barrier properties when a vapor deposition layer made of metal or inorganic oxide is applied. Is not disclosed, and there is no suggestion of a solution. Further, for example, Patent Document 4 discloses a biaxially stretched polylactic acid film obtained by blending an amorphous polylactic acid resin and a crystalline polylactic acid resin. This is a film intended for gas barrier applications, but the technical idea regarding the film silence problem that a harsh sound peculiar to polylactic acid film is not disclosed, and furthermore, both silence and high gas barrier properties are achieved. No method is disclosed.

Mochizuki Masaaki et al., “Biodegradable Chemicals and Plastics”, CMC Corporation, 2000, p147

JP 2005-336054 A JP 2005-336054 A JP 2008-15408 A JP 2005-53223 A

  Therefore, the present invention has been made in view of the above-described problems, and is a polylactic acid system that is excellent in heat resistance, heat sealability, silence, and gas barrier properties when a vapor deposition layer made of metal or an inorganic oxide is applied. An object is to provide a biaxially stretched film.

In order to solve the above problems, the present invention has the following configuration. That is,
(1) A polylactic acid biaxially stretched laminated film having an A layer containing an acrylic resin and an amorphous polylactic acid resin and a B layer containing a polylactic acid resin.
(2) The polylactic acid biaxially stretched laminated film according to (1), wherein the thickness is 10 μm or more and 30 μm or less.
(3) The polylactic acid biaxially stretched laminated film according to (1) or (2), wherein the B layer contains a crystalline polylactic acid resin.
(4) The acrylic resin of the A layer is 20% by mass or more and 80% by mass or less with respect to 100% by mass of all the components of the A layer, according to any one of (1) to (3) Polylactic acid biaxially stretched laminated film.
(5) The B layer contains 50% by mass or more and 100% by mass or less of a crystalline polylactic acid-based resin in 100% by mass of all components of the B layer, and any one of (1) to (4) 2. A polylactic acid-based biaxially stretched laminated film described in 1.
(6) The polylactic acid biaxially stretched laminated film according to any one of (1) to (5), wherein the acrylic resin is polymethyl methacrylate.
(7) The polylactic acid biaxially stretched laminated film according to any one of (1) to (6), wherein the A layer, the B layer, and the A layer are directly laminated in this order.
(8) The polylactic acid biaxially stretched laminated film according to any one of (1) to (7), wherein the vapor deposition layer, the A layer, and the B layer are laminated in this order.

  According to the present invention, by producing a polylactic acid biaxially stretched laminated film having an A layer containing an acrylic resin and an amorphous polylactic acid resin and a B layer containing a polylactic acid resin, It is possible to provide a polylactic acid-based biaxially stretched film having excellent properties, heat sealability, quietness, and gas barrier properties when a vapor deposition layer made of metal or an inorganic oxide is applied.

  Hereinafter, the present invention will be described in detail together with preferred embodiments.

  The laminated film of the present invention is a polylactic acid biaxially stretched laminated film having an A layer containing an acrylic resin and an amorphous polylactic acid resin, and a B layer containing a polylactic acid resin. To do.

  The A layer of the laminated film of the present invention contains an acrylic resin and an amorphous polylactic acid resin.

  Although there is no restriction | limiting in particular regarding content of the acrylic resin and amorphous polylactic acid-type resin in A layer, When content of all the components of A layer is 100 mass%, content of acrylic resin is 20 mass% or more 80 When the content is less than or equal to the mass%, it is preferable because it is particularly effective in improving transparency, stretchability, and heat resistance. By setting the content, a vapor deposition layer made of a metal or an inorganic oxide is applied to the surface layer of the A layer, and when a vapor deposition film is formed by vapor deposition, a desirable high layer is formed between the vapor deposition layer and the A layer. This is particularly effective for improving adhesion strength and gas barrier properties. On the other hand, when the content of the acrylic resin is less than 20% by mass in 100% by mass of all the components of the A layer, the harsh sound peculiar to the polylactic acid film is not reduced, and the quietness of the film is inferior. Moreover, in 100 mass% of all components of A layer, when it exceeds 80 mass%, the whole film will become weak, the elongation of a film will fall and it will be inferior to practicality. From the viewpoint of further improving the above properties, the content of the acrylic resin in 100% by mass of all components of the A layer is more preferably 25% by mass to 65% by mass, and further preferably 30% by mass to 50% by mass. is there.

  The acrylic resin in the present invention has at least one monomer selected from acrylate and methacrylate as a structural unit, and two or more monomers may be copolymerized and used. Examples of acrylates and methacrylates used to constitute the acrylic resin include acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, cyanoethyl acrylate, and cyanobutyl acrylate, and methyl methacrylate, ethyl methacrylate, Although methacrylates such as cyclohexyl methacrylate and 2-hydroxyethyl methacrylate can be mentioned, it is preferable to use polymethyl methacrylate in order to impart higher transparency and stretchability. The method for polymerizing or copolymerizing these monomers is not particularly limited, and known polymerization methods such as bulk polymerization, solution polymerization, and suspension polymerization can be used.

  The polylactic acid-based resin in the present invention means a polymer containing D-lactic acid and / or L-lactic acid as a main constituent component. In addition, the polylactic acid resin may contain a comonomer component other than lactic acid. Examples of the comonomer component include ethylene glycol, propylene glycol, butanediol, heptanediol, hexanediol, octanediol, nonanediol, decanediol, 1,4-cyclohexanedimethanol, neopentylglycol, glycerin, Glycol compounds such as pentaerythritol, bisphenol A, polyethylene glycol, polypropylene glycol and polytetramethylene glycol, oxalic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, cyclohexanedicarboxylic acid, terephthalate Acid, isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, bis (p-carboxyphenyl) methane, anthracene dicarboxylic acid, 4,4'-diphenyl ether di Dicarboxylic acids such as rubonic acid, 5-sodium sulfoisophthalic acid and 5-tetrabutylphosphonium isophthalic acid, glycolic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxybenzoic acid and other hydroxycarboxylic acids, caprolactone And lactones such as valerolactone, propiolactone, undecalactone, and 1,5-oxepan-2-one.

  Further, the polylactic acid resin contained in the A layer is an amorphous polylactic acid resin. By using a non-crystalline polylactic acid-based resin, a vapor deposition layer made of a metal or an inorganic oxide is applied to the surface layer of layer A, and when a vapor deposition film is formed by vapor deposition, the vapor deposition layer and the A layer A desirable high adhesion strength can be achieved between the two. This high adhesion strength reduces the number of defects (pinholes, scratches) in the deposited layer even when the deposited layer is contacted or rubbed with a processing tool such as a roll or cooling drum in the process after metallization. Particularly effective for improving gas barrier properties. Further, in the downstream processing process, various conveniences such as a wide sealing temperature range can be obtained, and high-productivity and cost-effective bag / pouch manufacturing becomes possible.

  In order to produce an amorphous polylactic acid-based resin, in addition to the method of copolymerizing the other monomer components described above, the content ratio of D-lactic acid and L-lactic acid in the amorphous polylactic acid-based resin is 10 : 90-15: 85, preferably 11: 89-13: 87. Preferable examples of the amorphous polylactic acid resin used for the A layer include, for example, Ingeo (trademark) 4060D (D-lactic acid = 12 mol%) manufactured by NatureWorks (registered trademark).

  The B layer of the present invention contains a polylactic acid resin. From the viewpoint of biodegradability and biomass properties, the B layer is preferably 70% by mass or more and 100% by mass or less, more preferably 75% by mass or more and 100% by mass or less, more preferably 100% by mass of all components of the B layer. Contains 80% by mass or more and 100% by mass or less of polylactic acid resin.

  In addition, the B layer is a crystalline polylactic acid-based resin for imparting rigidity, flatness and durability against mechanical load and heat treatment in a biaxial stretching process and in downstream processing processes such as lamination and bag molding. Is preferably contained. The content of the crystalline polylactic acid-based resin in the B layer is preferably 50% by mass or more and 100% by mass or less, more preferably 65% by mass or more and 100% by mass or less, and still more preferably in 100% by mass of all components of the B layer. Is 80 mass% or more and 100 mass% or less.

  In order to make the polylactic acid resin crystalline, the content ratio of D-lactic acid and L-lactic acid in the polylactic acid resin is preferably 0: 100 to 10:90. Even if the polylactic acid resin essentially contains only L-lactic acid, it will not be a serious problem, but if the amount of the crystalline polylactic acid resin is too large, the film production process can be poor, A more preferable content ratio of D-lactic acid and L-lactic acid is 1:99 to 5:95, and a more preferable ratio is 2:98 to 4:96. Preferred examples of the crystalline polylactic acid resin that can be used for the B layer include, for example, Ingeo (trademark) 4032D (D-lactic acid = 1.4 mol%), 4042D (D-lactic acid = 4.2 mol) manufactured by NatureWorks (registered trademark). %). The D-L ratio can be adjusted to a predetermined level by mixing these components or by mixing with a brand having a high D component ratio such as Ingeo ™ 4060D (D-lactic acid = 12 mol%).

  The layer structure of the laminated film of the present invention may be any layer structure as long as the effects of the present invention are not impaired. Examples of the layer structure include, for example, A layer / B layer, A layer / B layer / A layer, etc. Is mentioned. Particularly preferred is an embodiment in which the A layer, the B layer, and the A layer are directly laminated in this order. As will be described later, when the film of the present invention has a vapor deposition layer, the vapor deposition layer, the A layer, and the B layer are preferably laminated in this order.

  Although there is no restriction | limiting in particular in the thickness of the laminated | multilayer film of this invention, it is preferable that it is 10 micrometers or more and 30 micrometers or less from a viewpoint of the handleability at the time of processing into a packaging material, More preferably, it is 13-27 micrometers, More preferably, 16- 24 μm.

  Moreover, it is preferable to adjust the relationship between each thickness of A layer and B layer in this invention. If the total thickness of the A layer is too large, or if the B layer is too thin, the flatness of the profile of the film is deteriorated and the thermal stability is lowered. A preferable range of (total thickness of layer A / total thickness of layer B) is 0.6 or less, more preferably 0.45 or less, and still more preferably 0.3 or less. When this ratio exceeds 0.6, the flatness of the film profile becomes poor due to heat applied in the film production process, the processing process, etc., and the thermal stability is lowered.

  In order to impart favorable handling properties to the film and achieve functional friction coefficient properties, it is preferable that the A layer contains inorganic or organic particles.

  The average particle diameter of the layer A is preferably 0.1 to 3 μm, more preferably 0.5 to 2 μm. Content of the particle | grains A added to A layer becomes like this. Preferably it is 0.01-0.3 mass% of a skin layer, More preferably, it is 0.01-0.1 mass%. If the particles of layer A are larger than the above ranges (in terms of size and content), for example, when vapor deposition is performed to form a vapor deposition film, transfer defects (eg, scratches) on the vapor deposition layer due to too many large protrusions. Gas barrier properties may be impaired by the occurrence of scratches or pinholes. If the particles in layer A are smaller than the above ranges (in terms of size and / or content), they cannot fully contribute to the required handling and are also wound, metallized, slitted, laminated May cause blocking during the process.

  As long as the effective range and processability of the film are maintained, suitable inorganic particles include, for example, zeolite, calcium carbonate, magnesium carbonate, alumina, silica, aluminum silicate, barium hydroxide, kaolin, kaolinite, talc, clay, Examples include diatomaceous earth, montmorillonite, titanium oxide, and mixtures thereof. Suitable organic particles include, for example, crosslinked polymer particles such as polymethoxysilane compounds, polystyrene compounds, acrylic compounds, polyurethane compounds, polyester compounds, fluorine compound crosslinked particles, and mixtures thereof.

  Preferred particles are aluminum silicate particles. Aluminum silicate shows good compatibility with polylactic acid-based resin. In particular, when the A layer is relatively thin and the surface structure can be kept uniform, the processing apparatus is prevented from being contaminated by the dropped particles. be able to. Such compatibility reduces film haze as voids around the particles are reduced. Preferable examples of aluminum silicate used in these films include, for example, the Shiruton (trademark) JC series and Shiruton (trademark) AMT series manufactured by Mizusawa Chemical.

  Preferred ranges of the surface roughness of the A layer are SRa (surface average roughness) of 10 to 100 nm, SRz (5 highest peaks and lowest points) of less than 2000 nm, more preferably SRa of 20 to 60 nm and SRz of less than 1500 nm. It is. If the SRa on the surface of the A layer is less than 10 nm, the adhesiveness of the film becomes excessive, and blocking, winding failure, surface static electricity, and the like are generated. If the surface roughness of the surface of the A layer is larger than 100 nm in SRa or higher than 2000 nm in SRz, the size or number of protrusions is increased and the film becomes too rough. Accordingly, when a vapor deposition layer made of a metal or an inorganic oxide is applied to the surface layer of the A layer, and the laminated film of the present invention is formed by vapor deposition, the gas barrier property is lowered.

  Other additives can be added to the laminated film of the present invention as long as the desired properties are not impaired. Other additives that can be used include flame retardants, heat stabilizers, light stabilizers, antioxidants, hydrophobics, debonding agents, coupling agents, chain extenders, end group capping agents, oxygen absorbers, There are hygroscopic agents, anti-coloring agents, ultraviolet absorbers, antistatic agents, plasticizers, nucleating agents, lubricants, adhesion improvers, pigments and the like. The general amount of such additives is 0-5% by weight of the total polymer component amount in each layer.

  In order to impart gas barrier properties to the laminated film of the present invention, a vapor deposition layer made of a metal or an inorganic oxide can be included in the surface layer of the A layer. The metal or inorganic oxide used for the vapor deposition layer is not particularly limited, and examples thereof include aluminum, aluminum oxide, silicon oxide, silicon oxynitride, cerium oxide, calcium oxide, diamond-like carbon film, and a mixture thereof. Can be mentioned. In order to improve gas barrier properties while maintaining or improving productivity, aluminum, aluminum oxide, and silicon oxide are more preferably used. A vapor deposition layer using aluminum is preferable because it is excellent in economy and gas barrier performance, and a vapor deposition layer using aluminum oxide or silicon oxide is preferable in terms of cost and transparency.

  A vacuum process is used as a method for forming the vapor deposition layer. Although it does not specifically limit as a vacuum process, For example, a vacuum evaporation method, sputtering method, an ion plating method, a chemical vapor deposition method etc. are used preferably. For example, in order to provide an inorganic oxide vapor deposition layer, a reactive vapor deposition method is more preferably used in terms of productivity and cost.

In the vacuum process, the surface of the vapor deposition layer is preferably subjected to plasma treatment or corona treatment in order to further improve the gas barrier property. Processing strength when subjected to corona treatment is preferably 5～50W · min / ^{m 2,} more preferably a 10～45W · min / ^{m 2.} In addition, it is preferable to provide a cored metal vapor deposition layer under plasma discharge before providing a vapor deposition layer made of metal or an inorganic oxide from the viewpoint of improving the adhesion of the vapor deposition layer and, consequently, improving the gas barrier property. In this case, plasma discharge is preferably performed in an oxygen and / or nitrogen gas atmosphere, and copper is preferably used as the cored metal.

To deposit aluminum oxide by reactive vapor deposition, aluminum metal and alumina are evaporated by resistance heating boat method, crucible high frequency induction heating, electron beam heating method, and aluminum oxide is deposited on the film in an oxidizing atmosphere. A method is preferably employed. Oxygen is used as a reactive gas for forming an oxidizing atmosphere, but a gas mainly composed of oxygen and added with water vapor or a rare gas may be used. Further, ozone may be added or a method for promoting a reaction such as ion assist may be used in combination. In order to form a silicon oxide vapor deposition layer by a reactive vapor deposition method, a method of evaporating Si metal, SiO or SiO ₂ by an electron beam heating method and depositing silicon oxide on a film in an oxidizing atmosphere is employed. The method described above is used as a method of forming the oxidizing atmosphere.

  Further, the A layer and the B layer may contain other thermoplastic resins as long as the effects of the present invention are not impaired. Examples of other thermoplastic resins include ultra low density polyethylene, linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, polypropylene, ethylene / propylene rubber, ethylene / vinyl acetate copolymer, ethylene / vinyl acetate, Polyolefins such as acrylic acid ester copolymers and ionomers; Polyesters such as polyethylene terephthalate and polyethylene naphthalate; Polystyrene resins such as polystyrene, high-impact polystyrene, styrene / butylene / styrene block copolymers, and hydrogenation; Hard poly Polyvinyl chloride resins such as vinyl chloride and soft polyvinyl chloride; polycarbonate, polyamide, polyurethane, ethylene / vinyl alcohol copolymer, polyvinylidene chloride resin and the like are preferable.

  Although it does not specifically limit in order to produce the laminated | multilayer film of this invention, Well-known biaxial stretching methods, such as a sequential biaxial stretching method and a simultaneous biaxial stretching method, or the method that combined them can be used.

  Below, the manufacturing method of the laminated | multilayer film of this invention in which A layer and B layer were directly laminated | stacked in this order is described.

  Each extruder is melt-extruded with the resin composition used for the A layer and the B layer, and after removing foreign substances with a filter and adjusting the flow rate with a gear pump, it is supplied to a multi-manifold die or a feed block installed on the upper part of the die. . The multi-manifold base or the feed block needs to be provided with a desired number of channels having a desired shape in accordance with a required film layer configuration. The molten resin extruded from each extruder is merged by the multi-manifold die or the feed block as described above, and coextruded into a sheet form from the die. The sheet is brought into close contact with the casting drum by an air knife or a system such as electrostatic application, and is cooled and solidified to form an unstretched sheet.

  Here, in order to prevent surface roughness due to foreign matters such as gels and thermally deteriorated products, it is preferable to use a filter obtained by sintering and compressing stainless steel fibers having an average opening of 5 to 90 μm as a filter during film formation. Further, after the filter in which the stainless steel fiber is sintered and compressed, a filter in which a stainless steel powder having an average opening of 10 to 70 μm is sintered is continuously filtered in this order, or the two kinds of filters are put in one capsule. It is preferable to use a composite filter that is also used because gels and thermally deteriorated materials can be efficiently removed, and it is desirable because of the cost merit that the film forming edge and the core part can be reused.

  Next, in order to sequentially biaxially stretch the unstretched sheet thus obtained, the unstretched sheet is preheated by passing through a roll, and subsequently passed between rolls having a difference in peripheral speed, and stretched in the longitudinal direction. Immediately after cooling to room temperature, the longitudinally uniaxially stretched film is guided to a tenter and stretched in the transverse direction, and then it is heat-set while being relaxed in the transverse direction. In this way, the laminated film of the present invention is produced.

  From the viewpoint of obtaining a film having good stretchability and flatness, the longitudinal and lateral stretching temperatures of the laminated film of the present invention are preferably 70 to 105 ° C or less, more preferably 75 to 100 ° C, and still more preferably. 80 ° C to 95 ° C. The stretching ratio is preferably 2.0 to 10.0 times, more preferably 2.2 to 8.0 times, and still more preferably 2.5 to 5.0 times for each of the longitudinal and lateral stretching.

  In particular, when a vapor deposition layer made of a metal or an inorganic oxide is added to the surface layer of layer A of the laminated film of the present invention to form a vapor deposition film, the longitudinal and lateral stretching temperatures are 80 to 95 ° C. The range is most preferable. By forming a film at the stretching temperature, it is possible to produce a film with small stretching unevenness and good flatness. In addition, the number of defects (pinholes, scratches) in the vapor deposition layer can be reduced by vapor deposition on the surface layer of a film having a small stretch unevenness and good flatness, resulting in having a high barrier. Is possible. On the other hand, since the glass transition temperature of the polylactic acid resin is lower than that of the acrylic resin, in the laminated film not containing the acrylic resin in the A layer, when the film is formed at the stretching temperature, the longitudinal stretching roll The layer A resin adheres to the surface and the surface becomes extremely rough, or the film-forming property is remarkably deteriorated in the tenter, the flatness is low, and the thickness unevenness of the whole film is large.

  In addition, after stretching, it is preferable to perform relaxation heat treatment at a temperature lower by 10 ° C. or more than the melting point of at least one layer constituting the A layer and the B layer, and then cool. After proper stretching, a film having good flatness can be obtained by subjecting to relaxation heat treatment under such conditions.

Moreover, when the vapor deposition layer which consists of a metal or an inorganic oxide was provided to the A layer of the laminated | multilayer film of this invention produced by the said method, and it was set as the vapor deposition processed vapor deposition film, water vapor permeability is 1 It is preferably 0.0 g / m ² / day or less. When the water vapor permeability exceeds 1.0 g / m ² / day, the water vapor barrier property is poor, and when the laminated film is processed into a package using the packaging film, the freshness of the contents may be poor. The vapor permeability of the vapor-deposited film is more preferably 0.5 g / m ² / day or less, more preferably 0.25 g / m ² / day or less, most preferably for applications that require better water vapor barrier properties. Preferably it is 0.1 g / m ² / day or less. In addition, water vapor | steam barrier property is so preferable that it is preferable, and especially a minimum is not provided, but it is guessed that about 0.01 g / m < ² > / day is a minimum which can be implement | achieved. Note that the water vapor transmission rate is the average surface roughness of the layer on which the deposited layer is formed, the type of metal or inorganic oxide in the deposited layer, the thickness of the deposited layer, and the amount of defects (pinholes, scratches, etc.) in the deposited layer. It can be controlled by the metal adhesion between the deposited layer and the film. The oxygen permeability is preferably 1.0 cc / m ² / day / atm or less. When the oxygen permeability of the vapor deposition film exceeds 1.0 cc / m ² / day / atm, the oxygen barrier property is inferior, and when the vapor deposition film is processed into a package using the packaging material, the freshness of the contents is maintained. May be inferior. The oxygen permeability of the vapor-deposited film is more preferably 0.5 cc / m ² / day / atm or less, more preferably 0.25 cc / m ² / day / for applications where better oxygen barrier properties are required. It is atm or less, and most preferably 0.1 cc / m ² / day / atm or less. In addition, although oxygen barrier property is so preferable that it is favorable, especially a minimum is not provided, but about 0.01 cc / m < ² > / day / atm is guessed as a feasible minimum. The oxygen permeability of the deposited film is determined by the average surface roughness of the layer on which the deposited layer is formed, the thickness of the gas barrier resin layer, the type of metal or inorganic oxide in the deposited layer, the thickness of the deposited layer, the thickness of the deposited layer, It can be controlled by the amount of defects (pinholes, scratches, etc.).

  The laminated film of the present invention can be produced using the above method. According to the present invention, by producing a polylactic acid biaxially stretched laminated film having an A layer containing an acrylic resin and an amorphous polylactic acid resin and a B layer containing a polylactic acid resin, It is possible to provide a polylactic acid-based biaxially stretched film having excellent properties, heat sealability, quietness, and gas barrier properties when a vapor deposition layer made of metal or an inorganic oxide is applied. In addition, the laminated film of the present invention is stretched in the range of 80 to 95 ° C. in the longitudinal and lateral directions, and a deposition layer made of a metal or an inorganic oxide is provided on the surface layer of the layer A, and the deposition film is subjected to a deposition process. In this case, the number of defects (pinholes, scratches) in the vapor deposition layer can be suppressed, and as a result, a high barrier can be provided.

Next, an Example is given and the laminated film of this invention is demonstrated concretely.
[Measurement and evaluation method]
The characteristic evaluation method used in the present invention is as follows.

1. The thickness of each layer The sample was cut out from the center part of the horizontal direction of a laminated | multilayer film. Ultra-thin slices were collected at −100 ° C. using an ultramicrotome method by the resin embedding method using an epoxy resin so that the cross-section in the longitudinal direction-thickness direction of the sample piece was the observation surface. A thin film section of this laminated film cross section was photographed with a scanning electron microscope at a magnification of 1000 times (the magnification can be adjusted as appropriate), and the thickness of each layer was measured. The same measurement was performed with 10 observation points changed, and the average value of the obtained values was defined as the thickness (μm) of each layer.

2. Film thickness Using a dial gauge thickness gauge (JIS B7503 (1997), PURICOCK UPRIIGHT DIAL GAUGE (0.001 × 2 mm), No. 25, measuring element 5 mmφ flat type) at intervals of 10 cm in the vertical and horizontal directions. Ten points were measured at a time, and the average value was taken as the film thickness (μm).

3. Water vapor permeability Under conditions of a temperature of 38 ° C. and a humidity of 90% RH, using a water vapor permeability measuring device (model name, “Permatran” (registered trademark) W3 / 31) manufactured by MOCON, USA It measured based on B method (infrared sensor method) as described in JIS K7129 (2008). Further, the measurement was performed by applying a water vapor flow to the film and detecting on the opposite side, and the measurement was performed four times, and the average value was taken as the water vapor transmission rate (g / m ² / day) of the sample.

4). Oxygen permeability Under the conditions of a temperature of 23 ° C. and a humidity of 0% RH, an oxygen permeability measuring device (model name, “Oxytran” (registered trademark) (“OXTRAN” 2/20)) manufactured by MOCON, USA. It was measured based on the electrolytic sensor method described in JIS K7126-2 (2006). Further, the measurement was carried out by applying a water vapor flow to the film and detecting on the opposite side, and the measurement was performed four times. The average value was defined as the oxygen permeability (cc / m ² / day / atm) of the sample.

5. The heat seal strength of the film was measured using a heat seal machine (TP-701S HEAT SEAL TESTER, TESTER SANGYO CO, LTD) at a residence time of 2.1 kgf / cm ² for 1 second. It was performed with a heated flat top seal fixture coated with a registered trademark and a non-heated bottom seal fixture made of rubber and glass cloth. The film was heat-sealed on the sealing material sides in a predetermined sealing temperature range (for example, increments of 10 ° C. in the range of 90 to 160 ° C.), and the respective seal strengths were measured with a tensile tester manufactured by Daiei Kagaku Seisakusho . Cut the heat-sealed sample into a 25 mm wide strip, attach the two unsealed ends to the upper and lower clamps of the Instron machine, and the sealed ends against the two unsealed ends Support at an angle of 90 ° and perform a 90 ° T-peel test. The lowest temperature at which a seal strength of 200 g / 25 mm or more can be achieved was defined as the heat seal start temperature, and the heat sealability was judged according to the following criteria. Δ or more is a practically usable range.
A: Heat seal start temperature is 95 ° C. or higher and lower than 115 ° C. ○: Heat seal start temperature is 115 ° C. or higher and lower than 135 ° C. Δ: Heat seal start temperature is 135 ° C. or higher and lower than 155 ° C. x: 200 g / 25 mm or higher at any seal temperature The seal strength cannot be achieved.

6). The vapor deposition film obtained by forming the vapor deposition layer on the metal adhesion strength measurement film and the longitudinal direction of the unstretched polypropylene film (CPP) were aligned and dry laminated under the following conditions.
・ CPP: “Torayfan” NO # 60 ZK93KM manufactured by Toray Film Processing Co., Ltd.
・ Adhesive: Toyo Morton Co., Ltd. AD503 / cat10
-Blending amount: AD503 / cat10 / ethyl acetate = 20/1/20% by mass
-Application | coating: The adhesive agent was apply | coated to the corona treatment surface side of CPP using the metabar # 12.
Drying: 80 ° C., 45 seconds Lamination: After drying, the coated surface on the CPP was laminated on the deposited layer of the film.
Curing: 40 ° C., 48 hours A test piece having a width of 15 mm was taken out from the obtained sample, and a peel test was performed under the following conditions. In the peeling force curve, the upper limit value and the lower limit value after the start of peeling were read and used as the metal adhesion strength of the film.
・ Peel tester: Tensile Seiki Seisakusho tensile tester ・ Peel angle: 180 °
・ Peeling speed: 200 mm / min ・ Chart speed: 20 mm / min ・ Peeling direction: Longitudinal direction ・ Sample width: 15 mm
Three test pieces were collected from the same sample, and the same measurement was performed three times. The average value of the obtained values was defined as the metal adhesion strength (g / 15 mm).

7). Tensile elongation, tensile modulus measurement Tensile elongation (%)
Stress-strain measurement at 23 ° C. was performed using TENSILON UCT-100 manufactured by Orientec Corp. equipped with a thermostatic chamber, and the elongation in the length direction and the width direction at 23 ° C. was measured.

  Specifically, a sample was cut into a strip shape having a length of 150 mm and a width of 10 mm in the measurement direction, and in a thermostatic chamber adjusted to 23 ° C., the distance between the initial tensile chucks was 50 mm and the tensile speed was 200 mm / min. Measurement was carried out according to the method specified in -7127 (1999), and the average elongation (%) of 10 measurements was determined in the length direction and width direction.

Tensile modulus (GPa)
Using the method described above, the stress-strain measurement at 23 ° C. is performed, and using the first linear portion of the stress-strain curve, the stress difference between the two points on the straight line is the same as the strain difference between the two points. The tensile modulus was calculated. The measurement was performed 10 times in total, and the average value was adopted. This was calculated for each of the length direction and the width direction.

8). Silentness Evaluation of Film Silentness of the film was measured and evaluated by the following method using iPhone 3G software Sonic Scan [(C) 2009 Welbony Software].
With the iPhone 3G fixed, hold the end of the film cut to a size of 15 cm square with one hand at a position 10 cm away from the iPhone 3G microphone and handshake for 30 seconds. The handshake is performed at a rate of 3 times per second with a swing width of 15 cm. The measurement was performed in a soundproof room in order to shut down the external sound. An average noise level (dB) for 30 seconds was collected, the same measurement was performed three times, and the average value obtained was taken as the noise level (dB) of the film. In addition, the quietness was judged according to the following criteria. Δ or more is a practically usable range.
A: The noise level is less than 91 dB, the harsh sound peculiar to the polylactic acid film is greatly reduced, and the noise is extremely excellent.
A: The noise level is 91 dB or more and less than 93 dB, the harsh sound peculiar to the polylactic acid film is reduced, and the silence is excellent.
(Triangle | delta): A noise level is 93 dB or more and less than 95 dB, the unpleasant sound peculiar to a polylactic acid film is not reduced, and is unpleasant.
X: The noise level is 95 dB or more, the harsh sound peculiar to polylactic acid film is increased, and it is very uncomfortable.

9. Biomass degree The whole resin composition which comprises a polylactic acid-type biaxially stretched film was made into 100 mass%, the content rate (mass%) of the polylactic acid-type resin was calculated | required, it was set as the biomass degree, and the following reference | standard judged. However, the particles were excluded because the content in the entire film was less than 0.1% by mass.
A: Biomass degree is 100% by mass
○: Biomass degree is 70% by mass or more and less than 100% by mass Δ: Biomass degree is 50% by mass or more and less than 70% by mass ×: Biomass degree is less than 50% (Example)
The raw materials used in the production examples, examples, and comparative examples of the present invention are as follows. In the production examples, examples, and comparative examples, the following abbreviations may be used.
[CPLA]
Crystalline poly-L-lactic acid (“Ingeo” 4032D manufactured by Nature Works; D-form amount = 1.4 mol%, melting point = 168 ° C., Tg = 58 ° C.) dried at 100 ° C. for 4 hours in a rotary vacuum dryer.
[CPLA-MB1]
A cPLA-MB1 chip was prepared by blending 95% by mass of the above cPLA and 5% by mass of “Silton” JC-30 manufactured by Mizusawa Chemical Co., Ltd. and drying at 100 ° C. for 5 hours.
[APLA]
Amorphous poly-L-lactic acid (“Ingeo” 4060D manufactured by Nature Works; D body amount = 12 mol%, Tg = 58 ° C.) dried for 8 hours at 50 ° C. in a rotary vacuum dryer.
[APLA-MB2]
In the aPLA, 95% by mass of the aPLA and 5% by mass of “Silton” JC-30 manufactured by Mizusawa Chemical Co., Ltd. were blended, and the chip dried at 50 ° C. for 5 hours was designated as aPLA-MB2.
[APLA-MB3]
In the aPLA, 90% by mass of the aPLA and 10% by mass of “Silton” JC-30 manufactured by Mizusawa Chemical Co., Ltd. were blended, and the chip dried at 50 ° C. for 5 hours was designated as aPLA-MB3.
[PMMA]
Polymethylmethacrylate (VS-100 manufactured by Arkema) dried at 80 ° C. for 8 hours in a stationary vacuum dryer.

The present invention will be described based on examples. In addition, in order to obtain a desired thickness configuration, the polymer extrusion amount of each extruder was adjusted to a predetermined value unless otherwise specified.
Example 1
To the single-screw extruder (A), as a resin composition of the A layer, 30% by mass of aPLA, 30% by mass of aPLA-MB2, and 40% by mass of PMMA are mixed in advance and extruded at 220 ° C. The polymer was filtered through a filter obtained by sintering and compressing stainless steel fibers having an average opening of 65 μm, and supplied to a multi-manifold die of a two-kind / three-layer stacking type. In addition, 100% by mass of cPLA is supplied to the single-screw extruder (B) as a resin composition of the B layer, extruded at 220 ° C., and the average opening is 65 μm in a flow path different from the extruder (A). After the polymer is filtered through a filter in which stainless steel fibers are sintered and compressed, the polymer is supplied to the multi-manifold die and laminated in the order of extruder (A) / extruder (B) / extruder (A). They were merged in the multi-manifold die and co-extruded into a sheet form from the die. At this time, the extruded sheet was cast on a mirror metal drum having a temperature of 30 ° C. and cooled and solidified into a sheet.

  The obtained unstretched sheet was stretched 3 times in the longitudinal direction at 75 ° C. with a roll stretching machine, and immediately cooled to room temperature. Next, the obtained uniaxially stretched film was introduced into a tenter, stretched 3 times in the transverse direction at 75 ° C. while holding both edges with clips, and subsequently heat treated at 140 ° C. while giving 3% relaxation in the transverse direction. After cooling, it was wound up.

The obtained biaxially stretched film was 20 μm, and the thickness configuration was A layer / B layer / A layer = 1/3/1. In addition, after the aging of the biaxially stretched film for 24 hours, the surface of layer A was subjected to corona treatment in a nitrogen atmosphere at a treatment strength of 30 W · min / m ² , and then in a vacuum deposition apparatus equipped with a film running apparatus. Set. After making it the high pressure reduction state of 1.00 * 10 ^<-2 > Pa, it was made to run on a 0 degreeC cooling metal drum. At this time, the aluminum metal was evaporated by heating to form a vapor deposition layer on the A layer to obtain a vapor deposition film.

The vapor deposition film thus obtained was aged for 48 hours to obtain a vapor deposition layer on the A layer. In addition, the optical density of the vapor deposition film was confirmed online during vapor deposition, and the vapor deposition thickness was controlled to be 2.5.
The

The characteristic values of the obtained film were as shown in Table 2-1, and the water vapor barrier property, oxygen barrier property, and quietness were all excellent.
(Example 2)
A film produced in the same manner as in Example 1 was used in Example 2 except that the resin used for the A layer was changed to a blend raw material in which 15% by mass of aPLA-MB3 and 85% by mass of PMMA was previously mixed. The characteristic values of the obtained film are as shown in Table 2-1, and although the water vapor barrier property, the oxygen barrier property, and the silence are excellent, the film itself is very brittle because of the large PMMA content in the surface layer. It was. For this reason, the elongation at break decreased and the practicality was slightly inferior.
(Example 3)
Example 3 A film produced in the same manner as in Example 1 except that the resin used for the A layer was changed to a blend raw material in which aPLA was 10% by mass, aPLA-MB3 was 15% by mass, and PMMA was 75% by mass. It was. The characteristic values of the obtained film were as shown in Table 2-1, and the water vapor barrier property, oxygen barrier property, and quietness were all excellent.
Example 4
A film produced in the same manner as in Example 1 was used in Example 4 except that the resin used in the B layer was changed to a blend raw material in which 45% by mass of cPLA and 55% by mass of aPLA were mixed in advance. The characteristic values of the obtained film are as shown in Table 2-1, and although the water vapor barrier property, the oxygen barrier property, and the quietness are excellent, the tensile modulus of elasticity, The tensile elongation was low and the practicality was slightly inferior.
(Example 5)
A film produced in the same manner as in Example 1 was used in Example 5 except that the resin used for the B layer was changed to a blend raw material in which 55% by mass of cPLA and 45% by mass of aPLA were mixed in advance. The characteristic values of the obtained film are as shown in Table 2-2. Compared with the film of Example 4, the tensile modulus and tensile elongation were improved and the film was excellent in practicality.
(Example 6)
A film produced in the same manner as in Example 1 except that the transverse stretching temperature was changed to 90 ° C. was defined as Example 6. The characteristic values of the obtained film were as shown in Table 2-2, and the quietness was excellent. Further, the number of defects (pinholes and scratches) in the deposited layer was remarkably reduced, and the water vapor barrier property and oxygen barrier property were very excellent.
(Example 7)
Example 7 A film produced in the same manner as in Example 1 except that the resin used in the A layer was changed to a blend raw material in which 55% by mass of aPLA, 30% by mass of aPLA-MB2 and 15% by mass of PMMA was premixed. It was. The characteristic values of the obtained film are as shown in Table 2-2. Because the PMMA content in the A layer is small, the harsh sound peculiar to the polylactic acid film is not reduced and the quietness is slightly inferior. It was.
(Comparative Example 1)
A film produced in the same manner as in Example 1 except that aPLA was changed to 70% by mass and aPLA-MB2 was changed to 30% by mass was used as Comparative Example 1. The characteristic values of the obtained film were as shown in Table 2-2. When the film was touched or folded, the harsh sound peculiar to the polylactic acid film was increased, and the film was inferior in silence.
(Comparative Example 2)
A film produced in the same manner as in Example 1 except that aPLA was changed to 70% by mass, aPLA-MB2 was changed to 30% by mass, and the transverse stretching temperature was changed to 90 ° C. did. However, because the transverse stretching temperature was too high, the film forming property was remarkably deteriorated, and tearing occurred frequently in the tenter. Although it was difficult to collect with a roll, only a part of the film was evaluated, and the obtained characteristic values are shown in Table 2-2. Water vapor barrier properties, oxygen barrier properties, and quietness were all inferior. Moreover, many defects (pinholes and scratches) were confirmed in the deposited layer of the obtained film.
(Comparative Example 3)
A film produced in the same manner as in Example 1 except that the resin used for the layer A was changed to a blend raw material in which cPLA was 30% by mass, cPLA-MB1 was 30% by mass, and PMMA was 40% by mass. It was. The characteristic values of the obtained film are shown in Table 2-2. Many defects (pinholes and scratches) were confirmed in the deposited layer of the film, and the water vapor barrier property and oxygen barrier property were inferior. Moreover, since cPLA was used for the surface layer, both heat seal strength and metal adhesion strength were inferior.

  The present invention relates to a polylactic acid biaxially stretched film excellent in heat resistance, heat sealability, silence, and gas barrier properties when a vapor deposition layer made of a metal or an inorganic oxide is applied. In addition, the laminated film of the present invention is suitably used as a packaging material for applications where gas barrier requirements are particularly severe among various packaging materials.

Claims (8)

  A polylactic acid biaxially stretched laminated film having an A layer containing an acrylic resin and an amorphous polylactic acid resin, and a B layer containing a polylactic acid resin.   The polylactic acid biaxially stretched laminated film according to claim 1, wherein the thickness is 10 μm or more and 30 μm or less.   The polylactic acid biaxially stretched laminated film according to claim 1 or 2, wherein the B layer contains a crystalline polylactic acid resin.   The polylactic acid biaxial according to any one of claims 1 to 3, wherein the acrylic resin of the A layer is 20% by mass to 80% by mass with respect to 100% by mass of all components of the A layer. Stretched laminated film.   5. The polylactic acid according to claim 1, wherein the B layer contains a crystalline polylactic acid-based resin in an amount of 50% by mass to 100% by mass with respect to 100% by mass of all components of the B layer. Biaxially stretched laminated film.   The polylactic acid biaxially stretched laminated film according to any one of claims 1 to 5, wherein the acrylic resin is polymethyl methacrylate.   The polylactic acid biaxially stretched laminated film according to any one of claims 1 to 6, wherein the A layer, the B layer, and the A layer are directly laminated in this order.   The polylactic acid-based biaxially stretched laminated film according to any one of claims 1 to 7, wherein the deposited layer, the A layer, and the B layer are laminated in this order.