JP2016097576A - Laminate film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film excellent in moisture permeability, collapsibility, storage stability and membrane making stability.SOLUTION: The first form of the present invention is a laminate film having an A layer containing a polylactic acid resin and a B layer containing a polylactic resin and having weight average molecular weight of the A layer Mw(A) and weight average molecular weight of the B layer Mw(B) satisfying the formula (1) and hole rate of 10 to 80%. Mw(B)/Mw(A)≥1.2 Formula (1). The second form of the present invention is a laminate film having an A layer containing a polylactic acid resin and a B layer containing a polylactic resin and having carboxyl group terminal content of the A layer COOH(A) and carboxyl group terminal content of the B layer COOH(B) satisfying the formula (2) and hole rate of 10 to 80%. COOH(A)/COOH(B)≥1.2 Formula (2).SELECTED DRAWING: None

Description

  The present invention relates to a laminated film excellent in moisture permeability, disintegration, storage stability, and film formation stability.

  In recent years, with increasing environmental awareness, 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. As a resin that satisfies both of these requirements and is relatively advantageous in terms of cost, for example, a polylactic acid resin has attracted attention. When a polylactic acid resin is applied to a soft film represented by a polyolefin such as polyethylene, it lacks flexibility and impact resistance. In addition, there is a problem that it takes time to biodegrade the polylactic acid resin, and various attempts have been made to improve these properties and put them to practical use. For example, in the invention described in Patent Document 1, considering the use as sanitary materials such as diapers and liners, the decomposition of the film is divided into the volume reduction due to the collapse of the film and the subsequent biodegradation, and used in the desired application. A film that rapidly disintegrates when discarded in a water stream such as a flush toilet has been proposed.

JP 2014-173074 A

  In Patent Document 1, the molecular weight of the polylactic acid-based resin in the above-described film is set to be as low as 20,000 to 150,000 in order to rapidly proceed with disintegration. However, when the molecular weight is reduced as in Patent Document 1, the melt viscosity is reduced due to the molecular weight reduction, so that the stability during film formation is impaired and the thickness uniformity is impaired. There were problems such as winding misalignment. In the case of polylactic acid-based resins, it is generally known that embrittlement progresses due to a decrease in molecular weight accompanying biodegradation, but when the molecular weight is decreased as in Patent Document 1, In comparison, the embrittlement rate was increased, so that there was a problem that the storage stability was inferior until the film was used for a desired application after the film was prepared.

  Therefore, in view of the background of such conventional technology, the present invention is intended to provide a laminated film excellent in moisture permeability, disintegration, storage stability, and film forming stability.

  The first aspect of the present invention for solving the above problems is as follows.

  A film having an A layer containing a polylactic acid resin and a B layer containing a polylactic acid resin, wherein the weight average molecular weight Mw (A) of the A layer and the weight average molecular weight Mw (B) of the B layer are expressed by the formula ( 1. A laminated film satisfying 1) and having a porosity of 10 to 80%.

Mw (B) / Mw (A) ≧ 1.2 Formula (1)
The second aspect of the present invention is as follows.

  A film having an A layer containing a polylactic acid resin and a B layer containing a polylactic acid resin, wherein the carboxyl group terminal content COOH (A) of the A layer and the carboxyl group terminal content COOH (B of the B layer) ) Satisfies the formula (2) and has a porosity of 10 to 80%.

  COOH (A) / COOH (B) ≧ 1.2 Formula (2)

  ADVANTAGE OF THE INVENTION According to this invention, the laminated | multilayer film excellent in moisture permeability, disintegration, storage stability, and film forming stability is provided. Furthermore, the laminated film of the present invention can be preferably used for applications that mainly require moisture permeability. The laminated film of the present invention specifically includes agricultural materials such as multi-films, forestry materials such as fumigation sheets, sanitary materials such as paper diapers, napkins and liners, plastic bags, garbage bags, foods, and industrial products. It can be preferably used for various packaging materials.

  The present invention has an A layer containing a polylactic acid resin and a B layer containing a polylactic acid resin, and the porosity is 10 to 80%. In the first aspect, the weight average of the A layer The molecular weight Mw (A) and the weight average molecular weight Mw (B) of the B layer satisfy the formula (1). In the second embodiment, the carboxyl group terminal content COOH (A) of the A layer and the carboxyl group terminal of the B layer Content COOH (B) is a laminated film satisfying the formula (2).

Mw (B) / Mw (A) ≧ 1.2 Formula (1)
COOH (A) / COOH (B) ≧ 1.2 Formula (2)
Details of the present invention will be described below. In the following description, when the present invention is simply described, it means a general term for the first aspect of the present invention and the second aspect of the present invention.

(Polylactic acid resin)
The polylactic acid-based resin referred to in the present invention is a polymer mainly composed of an L-lactic acid unit and / or a D-lactic acid unit. Here, the main component means that the mass ratio of the lactic acid unit is the maximum in 100% by mass of the polymer. The mass ratio of the lactic acid unit is preferably 70% by mass to 100% by mass of the lactic acid unit in 100% by mass of the polymer.

  The term “poly L-lactic acid” as used in the present invention refers to those having a content of L-lactic acid units of more than 50 mol% and not more than 100 mol% in 100 mol% of all lactic acid units of the polylactic acid resin. On the other hand, the poly-D-lactic acid referred to in the present invention refers to those having a D-lactic acid unit content of more than 50 mol% and not more than 100 mol% with respect to 100 mol% of all lactic acid units of the polylactic acid resin.

  As the polylactic acid resin, a crystalline polylactic acid resin or an amorphous polylactic acid resin can be used alone or in combination.

  The content of the polylactic acid resin in the A layer of the present invention is not particularly limited, but from the viewpoint of dealing with environmental burdens, the content of the polylactic acid resin is 10 to 60 in 100% by mass of all components of the A layer. It is preferably mass%, more preferably 15 to 50 mass%, still more preferably 20 to 40 mass%. The content of the polylactic acid resin in the B layer is the same as that in the A layer.

(Porosity)
It is important that the laminated film of the present invention has pores and the porosity is 10 to 80%. When the laminated film has pores and the porosity is 10 to 80%, moisture permeability can be imparted to the laminated film.

  When the porosity of the laminated film of the present invention is less than 10%, a practical level of moisture permeability cannot be imparted. On the other hand, when the porosity exceeds 80%, a practical film elongation cannot be maintained. A more preferable porosity is 20 to 75%, and further preferably 30 to 70%.

  The achievement means for setting the porosity of the laminated film of the present invention to 10 to 80% is a combination of the above-described polylactic acid-based resin in the A layer and the B layer, and a filler described later, in a preferable type and a mixing ratio, The method of obtaining a film by the film forming method mentioned later can be mentioned. In the stretching method to be described later, the porosity can be controlled to be small by reducing the stretching ratio, and the porosity can be controlled to be large by increasing the stretching ratio.

(Weight average molecular weight ratio of layer A and layer B)
In the first aspect of the laminated film of the present invention, it is important that the weight average molecular weight Mw (A) of the A layer and the weight average molecular weight Mw (B) of the B layer satisfy the formula (1).

Mw (B) / Mw (A) ≧ 1.2 Formula (1)
Disintegration, which is one of the problems of the present invention, is closely related to the brittleness of the laminated film of the present invention. The lower the weight average molecular weight of the A layer and the B layer, the more remarkable the brittleness. In the present invention, the weight average molecular weights of the A layer and the B layer are represented by the formula (1), so that the A layer exhibiting a relatively low weight average molecular weight and consequently high brittleness is collapsed of the laminated film of the present invention. As a result, it becomes possible to impart high disintegration to the laminated film of the present invention.

  On the other hand, the weight average molecular weights of the A layer and the B layer in the laminated film of the present invention are closely related to the melt viscosity, and the higher the weight average molecular weight, the more remarkable the film forming stability. In the present invention, by setting the weight average molecular weights of the A layer and the B layer to the relationship of the formula (1), the B layer showing a relatively high weight average molecular weight and consequently a high melt viscosity is supported during film formation. As a result, it becomes possible to impart high film forming stability to the laminated film of the present invention.

When Mw (A) and Mw (B) do not satisfy the relationship of the formula (1), the A layer and the B layer have almost the same Mw. Both sex characteristics cannot be expressed effectively. More preferably about Mw (A) and Mw (B),
Mw (B) / Mw (A) ≧ 1.5
More preferably, Mw (B) / Mw (A) ≧ 2
It is.

  As a method for Mw (A) and Mw (B) satisfying the formula (1), there are various methods. For example, while selecting a polylactic acid resin raw material having a low weight average molecular weight as a raw material for the A layer, As a raw material for the B layer, a method of using a polylactic acid raw material having a high weight average molecular weight can be mentioned. The upper limit of Mw (B) / Mw (A) is not particularly limited, but considering the problem of processing suitability such as generation of flow marks due to the difference in melt viscosity between the raw material of layer A and the raw material of layer B, Mw The upper limit of (B) / Mw (A) is preferably 20 or less.

  In the second embodiment of the laminated film of the present invention, it is preferable to satisfy the relationship of the weight average molecular weight ratio between the A layer and the B layer described here. That is, in the second aspect of the laminated film of the present invention, it is preferable that the weight average molecular weight Mw (A) of the A layer and the weight average molecular weight Mw (B) of the B layer satisfy the formula (1).

Mw (B) / Mw (A) ≧ 1.2 Formula (1)
(Weight average molecular weight of layer A)
The layer A in the laminated film of the present invention preferably has a weight average molecular weight Mw (A) of 20,000 to 150,000. When the Mw (A) of the A layer is 20,000 or more, workability can be imparted, and when it is 150,000 or less, high disintegration property can be imparted. The weight average molecular weight Mw (A) of the A layer is preferably 30,000 or more and 140,000 or less, and more preferably 40,000 or more and 130,000 or less.

  The measurement of Mw (A) and Mw (B) in the present invention is carried out in a hexafluoroisopropanol solvent by gel permeation chromatography (GPC), although a specific method will be described later. The molecular weight is obtained by conversion from a calibration curve of a standard sample of polymethyl methacrylate, and the weight average molecular weight value calculated from the range corresponding to the molecular weight of 1,000 to 10,000,000 is the weight of the layer referred to in the present invention. The average molecular weight is Mw.

  In addition, when the resin constituting the layer is a mixture, the weight average molecular weight distribution obtained by molecular weight measurement is a curve in which each resin overlaps, but in the present invention, the weight average obtained from the overlap curve Adopt molecular weight. Furthermore, if the filler contained in layer A does not dissolve in the solvent hexafluoroisopropanol, it will be removed when preparing the GPC measurement sample or by a prefilter in the GPC device, but the effect of removing the filler is ignored. It shall be.

(Carboxyl group terminal content ratio of A layer and B layer)
In the second aspect of the laminated film of the present invention, it is important that the carboxyl group terminal content COOH (A) of the A layer and the carboxyl group terminal content COOH (B) of the B layer satisfy the formula (2). is there.

COOH (A) / COOH (B) ≧ 1.2 Formula (2)
The carboxyl group terminal content is known to be closely related to the hydrolysis rate of polylactic acid resin, and the lower the content, the lower the molecular weight decrease due to hydrolysis and the progress rate of embrittlement and the higher storage Stability can be imparted.

  By making the carboxyl group terminal content of A layer and B layer into the relationship of Formula (2) in this invention, the B layer which has a relatively low carboxyl group terminal content and the hydrolysis was suppressed becomes a support layer. As a result, high storage stability can be imparted to the laminated film of the present invention.

On the other hand, the carboxyl group terminal has an effect of increasing the affinity of the polylactic acid resin and water by polarity. As a result, when the laminated film of the present invention is discarded into a water stream such as a flush toilet, the molecular weight reduction due to hydrolysis is promoted in the A layer having a relatively high carboxyl group terminal content and consequently high affinity with water, As a result, it becomes possible to impart disintegration to the laminated film of the present invention. When COOH (A) and COOH (B) do not satisfy the relationship of the formula (2), the A layer and the B layer have almost the same carboxyl group terminal content, so the A layer which is the object of the present invention Therefore, it is impossible to effectively exhibit both the characteristics of disintegration due to high COOH and storage stability due to low COOH in the B layer. More preferably,
COOH (A) / COOH (B) ≧ 1.5
More preferably, COOH (A) / COOH (B) ≧ 2
It is.

  In addition, although the upper limit of COOH (A) / COOH (B) is not specifically limited, when practical storage stability is considered, it is preferable that the upper limit of COOH (A) / COOH (B) is 200 or less.

  There are various methods for COOH (A) and COOH (B) to satisfy the formula (2). For example, while selecting a polylactic acid resin having a high carboxyl group terminal content as a raw material for the A layer, A method of using a polylactic acid resin having a high carboxyl group terminal content as a raw material for the B layer is mentioned. Further, it is known that the carboxyl group terminal content COOH of the polylactic acid-based resin can be controlled by using a terminal reactive compound capable of reacting with the carboxyl group terminal, and this terminal reactive compound is used as a raw material for the B layer. There is also a method of satisfying the formula (2) by using no terminal reactive compound as the raw material of the A layer.

  The term “terminal reactive compound” as used herein refers to a compound that undergoes an addition reaction or condensation reaction at the carboxyl group terminal of the polylactic acid-based resin to block the carboxyl group terminal. Known compounds can be used as the terminal reactive compound, and it is preferable to use a compound containing one or more functional groups selected from the group consisting of a glycidyl group, a carbodiimide group, an isocyanate group, and an oxazoline group.

  Among these, a terminal reactive compound having a carbodiimide group is particularly preferable, and commercially available products include “Carbodilite” (registered trademark) series of Nisshinbo Co., Ltd., “STABAXOL” (registered trademark) series of Rhein Chemie. Etc.

  The addition amount of the terminal reactive compound is preferably 0.1% by mass or more and 10% by mass or less, assuming that all the components of the raw material of the layer B of the present invention are 100% by mass.

  Further, as shown in the formula (2), in view of increasing the amount of COOH (A) relative to COOH (B), it is particularly necessary to add a terminal reactive compound to the raw material of the A layer. However, in the case of adding a terminal reactive compound to the raw material of the A layer in order to give higher storage stability, as in the case of adding to the raw material of the B layer, all the components of the raw material of the A layer are set to 100. It is preferable to set it as 0.1 mass% or more and 10 mass% or less when setting it as the mass%.

  In addition, also in the 1st aspect of the laminated | multilayer film of this invention, it is suitable to satisfy | fill the relationship of the carboxyl group terminal content ratio of A layer mentioned here and B layer. That is, in the first aspect of the laminated film of the present invention, the carboxyl group terminal content COOH (A) of the A layer and the carboxyl group terminal content COOH (B) of the B layer satisfy the formula (2). preferable.

COOH (A) / COOH (B) ≧ 1.2 Formula (2)
(Terminal carboxyl group content of layer A)
The layer A in the laminated film of the present invention preferably has a carboxyl group terminal content COOH (A) of 20 to 200 eq / ton. When COOH (A) is 20 eq / ton or more, disintegration is good, and when COOH (A) is 200 eq / ton or less, workability is good. COOH (A) is more preferably 40 to 180 eq / ton, further preferably 60 to 160 eq / ton, and particularly preferably 80 to 140 eq / ton.

(Laminated structure)
The laminated film of the present invention is not particularly limited as long as it has an A layer and a B layer, but the A layer and the B layer are directly laminated without any other layer, and the A layer is at least one of the layers. It is preferably located on the surface. When the layer A having disintegration is located on at least one surface of the laminated film of the present invention, when the laminated film of the present invention is disposed in an environment where stress is applied such as in a water stream, the layer is first laminated. The layer A located on the surface layer of the film easily causes a collapse. As a result, the disintegration propagates to the B layer starting from the trigger, and it becomes possible to impart high disintegration to the laminated film of the present invention.

  Furthermore, it is more preferable that the laminated film of the present invention has a configuration in which the A layer is located on both surfaces, such as A layer / B layer / A layer. With this configuration, the area that can cause the collapse is doubled, so that it is possible to impart higher disintegration properties.

  In this invention, it is preferable that ratio Xa of the thickness of A layer is 5 to 50% with respect to 100% of the thickness of the whole laminated film. When Xa is 5 to 50%, practically sufficient disintegration can be obtained. Further preferable Xa is 10 to 40%. Here, Xa means the ratio of the thickness of the A layer to the total thickness of the film. That is, in the case of a film laminated in order of three layers, A layer / B layer / A layer, Xa (%) = [total thickness of two A layers] / [total thickness of film] × 100, It is.

(Thickness)
The laminated film of the present invention preferably has a thickness of 5 to 200 μm. By setting the thickness to 5 μm or more, the firmness of the film becomes strong, the handleability is excellent, and the roll winding shape and unwinding property are good. By setting the thickness to 200 μm or less, the decomposability and moisture permeability are excellent. The thickness of the film of the present invention is more preferably 7 to 150 μm, further preferably 10 to 100 μm, and still more preferably 12 to 50 μm.

(filler)
The laminated film of the present invention preferably contains a filler in order to improve moisture permeability. That is, the A layer and the B layer preferably contain a filler in order to improve moisture permeability. Here, the filler refers to a substance added as a base material for improving various properties, or an inert substance added for the purpose of increasing the amount, increasing the volume, reducing the cost of the product, or the like. As long as this definition is satisfied, the filler may have other functions such as an antioxidant function and an ultraviolet absorption function. That is, the filler may correspond to an antioxidant, and the filler may correspond to an ultraviolet stabilizer.

  Such fillers can include inorganic fillers and / or organic fillers.

  Further, the content of the filler in each layer constituting the laminated film of the present invention is not particularly limited, but the content of the filler is preferably 10 to 70% by mass in 100% by mass of all components in each layer. More preferably, it is 15-60 mass%, and it is more preferable that it is 20-40 mass%. In each layer such as the A layer and the B layer, by setting the filler content to 10% by mass or more, the porosity of the laminated film of the present invention can be made 10% or more to easily impart moisture permeability. Further, in each layer such as the A layer and the B layer, by making the filler content 70% by mass or less, the filler can be uniformly dispersed in the laminated film, and stable melt moldability can be imparted. It becomes possible.

  Examples of inorganic fillers include carbonates such as calcium carbonate, magnesium carbonate, and barium carbonate; sulfates such as magnesium sulfate, barium sulfate, and calcium sulfate; zinc oxide, silicon oxide (silica), zirconium oxide, magnesium oxide, and oxide. Metal oxides such as calcium, titanium oxide, magnesium oxide, iron oxide, and alumina; hydroxides such as aluminum hydroxide; complex oxides such as silicate minerals, hydroxyapatite, mica, talc, kaolin, clay, montmorillonite, and zeolite A phosphate such as lithium phosphate, calcium phosphate or magnesium phosphate; a metal salt such as lithium chloride or lithium fluoride can be used.

  Among these fillers, calcium carbonate, barium sulfate, barium sulfate, calcium sulfate, silicon oxide (silica) are used from the viewpoints of improving the moisture permeability of laminated films, maintaining mechanical properties such as strength and elongation, and reducing costs. Titanium oxide, mica, talc, kaolin, clay and montmorillonite are preferred.

  Although the average particle diameter of a filler is not specifically limited, 0.01-10 micrometers is preferable. When the average particle size is 0.01 μm or more, the film can be highly filled with the filler, and as a result, the film has high potential for increasing the porosity and moisture permeability of the film. When the average particle size is 10 μm or less, the stretchability of the film becomes good, and as a result, the film has a high potential for increasing the porosity and moisture permeability of the film. The average particle diameter is more preferably 0.1 to 8 μm, further preferably 0.5 to 5 μm, and most preferably 1 to 3 μm. Here, the average particle diameter is a 50% cumulative distribution average particle diameter measured by a laser diffraction scattering method.

(Thermoplastic resin other than polylactic acid resin)
The laminated film of the present invention preferably contains a thermoplastic resin other than a polylactic acid-based resin in order to improve moisture permeability. That is, the A layer and the B layer preferably contain a thermoplastic resin other than the polylactic acid-based resin in order to improve moisture permeability. The thermoplastic resin other than the polylactic acid resin is not particularly limited, but polyacetal, polyethylene, polypropylene, poly (meth) acrylate, polyester, polyurethane, polyisoprene, polysulfone, polyphenylene oxide, polyimide, polyetherimide, ethylene / glycidyl. Methacrylate copolymers, polyester elastomers, polyamide elastomers, ethylene / glycidyl methacrylate copolymers, ethylene / propylene polymers, polymers containing starch, and the like can be used. Of these, polyesters (other than polylactic acid resins) are preferred as thermoplastic resins other than polylactic acid resins because they have good compatibility with polylactic acid resins. When using polyester as a thermoplastic resin other than polylactic acid-based resin, aliphatic polyester or aliphatic aromatic polyester is preferable from the viewpoint of improving flexibility. Among these, aliphatic polyesters are particularly preferable as thermoplastic resins other than polylactic acid resins from the viewpoint that aliphatic polyesters are particularly highly compatible with polylactic acid resins and have excellent film-forming stability.

  Furthermore, the laminated film of the present invention is a block copolymer having a polylactic acid segment and a polyether segment, or a block copolymer having a polylactic acid segment and a polyester segment, together with the aliphatic polyester or the aliphatic aromatic polyester. It is also preferable to contain. These block copolymers can act as a plasticizer for the polylactic acid resin. In particular, when the block copolymer is a block copolymer having a polyethylene glycol segment and a polylactic acid segment, particularly excellent flexibility is imparted to the laminated film of the present invention due to the plasticizing effect of the polyether segment portion. It becomes possible. Furthermore, since the polylactic acid segment portion has an affinity for the polylactic acid resin of the laminated film of the present invention, the bleedout of the block copolymer is suppressed and flexibility can be maintained.

  The total content of the thermoplastic resin other than the polylactic acid-based resin in the A layer constituting the laminated film of the present invention is preferably 10 to 60% by mass in 100% by mass of all components in the A layer. More preferably, it is 20-40 mass%.

(Additive)
The laminated film of the present invention may contain various additives as long as the effects of the present invention are not impaired. For example, antioxidants, UV stabilizers, anti-coloring agents, matting agents, antibacterial agents, deodorants, weathering agents, antistatic agents, antioxidants, ion exchange agents, tackifiers, antifoaming agents, Color pigments and dyes can be used.

(Production method)
Next, the method for producing the laminated film of the present invention will be specifically described, but the present invention is not limited to this.

  The composition constituting the laminated film of the present invention, that is, the composition containing the polylactic acid resin for producing the A layer (raw material of the A layer), and the composition containing the polylactic acid resin for producing the B layer The product (the raw material of the B layer) may contain other components as necessary, and in obtaining these compositions, a melt-kneading method in which the components are produced by melt-kneading each component is preferable. . The melt kneading method is not particularly limited, and a known mixer such as a kneader, roll mill, Banbury mixer, single-screw or twin-screw extruder can be used. Among these, from the viewpoint of productivity, it is preferable to use a single screw or twin screw extruder.

  The temperature at the time of melt kneading is preferably in the range of 150 ° C. to 240 ° C., and more preferably in the range of 170 ° C. to 210 ° C. from the viewpoint of preventing the deterioration of the polylactic acid resin.

  The laminated film of the present invention can be obtained by an existing film production method such as a known inflation method, a tubular method, or a T-die cast method, for example, using the composition obtained by the above-described method.

  Furthermore, in order to improve moisture permeability and disintegration, the laminated film obtained by the above-mentioned method is uniaxially or biaxially stretched to produce pores in the A layer and the B layer, and the porosity of the laminated film is increased. It is preferable to set it as 10 to 80%.

  When carrying out longitudinal uniaxial stretching by conveying on a heating roll, the preferable range of extending | stretching temperature is 50-100 degreeC, More preferably, it is 55-97 degreeC. The non-oriented film heated in this way is stretched in one stage, or two or more stages in the longitudinal direction of the film using a difference in peripheral speed between heating rolls. The total draw ratio is preferably 3 to 10 times, more preferably 4 to 9 times, and still more preferably 5 to 8 times.

  If necessary, after the film uniaxially stretched in this manner is once cooled, the both ends of the film may be held by clips and guided to a tenter, and stretched in the width direction.

  Next, this stretched film is heat-treated. The preferable heat treatment temperature varies depending on the resin constituting the laminated film. For example, when an aliphatic aromatic polyester-based resin is included, the heat treatment temperature is 90 to 150 ° C, more preferably 100 to 140 ° C, and still more preferably 110 to 130 ° C. is there. Moreover, when aliphatic polyester is included, it is 50 to 130 degreeC, More preferably, it is 60 to 120 degreeC, More preferably, it is 70 to 110 degreeC.

  Subsequently, the laminated film is cooled and wound up to obtain a desired laminated film.

  After forming into a laminated film, various surface treatments may be applied for the purpose of improving printability, laminate suitability, coating suitability, and the like. Examples of the surface treatment method include corona discharge treatment, plasma treatment, flame treatment, and acid treatment. Any of these methods can be used, but the corona discharge treatment can be exemplified as the most preferable one because it can be continuously processed and the apparatus can be easily installed in an existing film forming facility and the processing is simple.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited thereto.

[Measurement and evaluation method]
Measurements and evaluations shown in the examples were performed under the following conditions.

(1) Porosity (%)
The laminated film was cut into a size of 30 mm × 40 mm and used as a sample. Using an electronic hydrometer (SD-120L manufactured by Mirage Trading Co., Ltd.), the specific gravity of the sample was measured in an atmosphere having a room temperature of 23 ° C. and a relative humidity of 65%. The measurement was performed three times, and the average value was defined as the specific gravity ρ of the film.

Next, the measured film was hot-pressed at 280 ° C. and 5 MPa, and then rapidly cooled with methanol cooled with dry ice to prepare a non-porous sheet. The specific gravity of the non-porous sheet was measured in the same manner as described above, and the average value was defined as the specific gravity (d) of the resin. From the specific gravity (ρ) of the laminated film and the specific gravity (d) of the resin, the porosity was calculated by the following formula.
Porosity (%) = [(d−ρ) / d] × 100
(2) Moisture permeability Moisture permeability (g / (m ² · day)) was measured with a constant temperature and humidity apparatus set at 25 ° C. and 90% RH according to the method defined in JIS Z0208 (1976).

Using the value of moisture permeability, the evaluation was made according to the following criteria.
A: 1,000 g / (m ² · day) or more B: 350 g / (m ² · day) or more and less than 1,000 g / (m ² · day) C: 100 g / (m ² · day) or more 350 g / (m Less than ² · day) D: Less than 100 g / (m ² · day).

  The moisture permeability is good in A, B, and C, and A is the best among them.

(3) Layer A thickness ratio (Xa)
The cross-section of the laminated film was photographed with transmitted light using a metal microscope Leica DMLM manufactured by Leica Microsystems Co., Ltd., and the thickness of each layer was measured. The thickness ratio (Xa) of A layer was calculated | required from the thickness of each obtained layer.

(4) Storage stability First, a sample of a laminated film was attached to an aluminum frame frame in a tension state, and fixed using a plurality of double clips for stationery. Subsequently, the laminated film was forcibly deteriorated under the following conditions.
Equipment used: Constant temperature and constant humidity conditions in the tank: 40 ° C, 75% RH
Forced deterioration time: 4 weeks Subsequently, the laminated film sample immediately after film formation, and the laminated film sample after forced deterioration according to the above-described method, using TENSILON UCT-100 manufactured by Orientec, room temperature 23 ° C., relative humidity 65% The elongation was measured in the atmosphere.

  Specifically, a sample was cut into a strip shape having a length of 150 mm and a width of 10 mm in the film forming direction (hereinafter referred to as the machine direction) of the laminated film of the present invention, and the initial tensile chuck distance was 50 mm and the tensile speed was 200 mm / min. In accordance with the method defined in JIS K-7127 (1999), ten measurements were performed, and the average value of the elongation was taken as the elongation in the machine direction of the sample. By this method, the elongation (S) in the machine direction immediately after film formation and the elongation (Sx) in the machine direction after forced deterioration were measured, and Sx / S × 100 = elongation retention (%) was obtained. .

Based on the obtained elongation retention, the storage stability was evaluated according to the following criteria.
A: Elongation retention is 80% or more B: Elongation retention is 50% or more and less than 80% C: Elongation retention is less than 50% Storage stability is proportional to elongation retention, and A is the most Excellent storage stability.

(5) Disintegration Put 800 ml of water in a 2000 ml beaker, put four test pieces cut into 5 cm × 5 cm, and take out the laminated film from the beaker after stirring for 48 hours at 23 ° C. and 500 rpm rotation speed with a magnetic stirrer. The number of test pieces after stirring was observed.
Evaluation was performed according to the following criteria using the number of the test pieces.
A: 17 or more B: 14 or more and 16 or less C: 11 or more and 13 or less D: 8 or more and 10 or less E: 7 or less Disintegration is proportional to the number of test pieces, and A is the most disintegrated. Excellent in properties.

(6) DSC (melting point)
The melting point of the polylactic acid resin used as the raw material of the film is that the polylactic acid resin is heated in a hot air oven at 100 ° C. for 24 hours, and a differential scanning calorimeter RDC220 manufactured by Seiko Instruments Inc. is used. The temperature was set in a saucer, and the peak temperature of the crystal melting peak when the temperature was raised from 25 ° C. to 250 ° C. at a heating rate of 20 ° C./min was used.

(7) Weight average molecular weight The layer A was scraped from the laminated film of the present invention, and about 4 mg of the collected sample was added about 4 mL of hexafluoroisopropanol to which 5 mM sodium trifluoroacetate was added as a solvent, and gently stirred at room temperature. Any insoluble matter was removed by filtration through a 0.45 μm filter to prepare a measurement sample.

  Subsequently, molecular weight measurement was performed using a gel permeation chromatograph (GPC). The measurement conditions were a column temperature of 40 ° C., an injection volume of 0.2 mL, and a flow rate of 0.5 mL / min. Conversion to molecular weight was performed using a calibration curve of a standard sample of polymethyl methacrylate.

  The weight average molecular weight value calculated from the range corresponding to a molecular weight of 1,000 to 10,000,000 (rounded down to the next two digits) is the weight average molecular weight Mw (A) of the A layer in the present invention. did. Similarly, the B layer was scraped from the laminated film of the present invention, and the obtained weight average molecular weight value was defined as the weight average molecular weight Mw (B) of the B layer.

  The equipment and standard samples used in the measurement are as follows.

Detector: differential refractive index detector Waters manufactured RI-2414 type, sensitivity 256
Liquid feed pump: Waters Model 515 HPLC PUMP
Injector: Autosampler AS-8020 manufactured by Tosoh Column: Shodex HFIP-806M (2) (manufactured by Showa Denko)
Standard samples: monodisperse polymethyl methacrylate (Showa Denko) (weight average molecular weights: 1,050,000, 608,000, 218,000, 732,000, 276,000, 206,000, 0.683 million, 0.00 (1850,000, 0.0850,000, 0.0645 million)
(8) Carboxyl group terminal content (COOH amount) (eq / ton)
Remove layer A from the laminated film of the present invention, add 25 mL of chloroform as a solvent to about 0.3 g of the collected sample, gently stir at room temperature, and filter with a 0.45 μm filter if insolubles are present. The sample for measurement was prepared. After adding 7 drops of a bromophenol red / methanol 1 wt% solution as an indicator to this solution, titration was performed with a 0.005 N KOH ethanol solution to obtain a titer (a) (mL) required for neutralization. Similarly, the titration amount (b) (mL) required for neutralization of only the solvent was determined, and the carboxyl group terminal content was determined by the following formula. The measurement was performed twice for each sample, and the average value was defined as the carboxyl group terminal content COOH (A) of the A layer.

COOH (A) (eq / ton) = (ab) × 0.005 × 1000 / c
a: Titration volume (mL) required for sample neutralization (2nd decimal place)
b: Titration amount (mL) required for neutralization of solvent only (2nd decimal place)
c: Mass of sample (g) (3rd decimal place)
The layer B was scraped from the laminated film of the present invention, and the carboxyl group terminal content obtained in the same manner was defined as the carboxyl group terminal content COOH (B) of the layer B.

  At the time of titration, an oligomer such as lactide, which is a cyclic dimer of lactic acid, is hydrolyzed to generate a carboxyl group terminal, so that the carboxyl group terminal of the polymer, the carboxyl group terminal derived from the monomer, and the carboxyl group terminal derived from the oligomer The total value was defined as the carboxyl group terminal content in the present invention.

(9) Film-forming stability in the inflation method When forming an unstretched film by the inflation method, the stability of the bubble width shape when it was made into a bubble was visually evaluated, and the following determination was made.
A: No fluctuation in bubble width B: Some fluctuation in bubble width occurs C: The fluctuation in bubble width is severe and wrinkles occur in the film as well as wrinkles.

  A is the most excellent film forming stability.

[Polylactic acid resin (A)]
(A1)
Polylactic acid-based resin (NatureWorks, trade name "Ingeo ^TM biopolymer4032D"), weight average molecular weight = 200,000, terminal carboxyl group content (COOH weight) = 30 eq / ton
(A2)
Polylactic acid-based resin (NatureWorks, trade name "Ingeo ^TM biopolymer6250D"), weight average molecular weight = 110,000, terminal carboxyl group content (COOH weight) = 33eq / ton
(A3)
In a reaction vessel equipped with a stirrer and a reflux device, 50% by mass of a 90% by mass L-lactic acid aqueous solution was brought to a temperature of 150 ° C., and the reaction was carried out for 3.5 hours while gradually reducing the pressure to distill off water. did. Thereafter, the pressure was increased to normal pressure in a nitrogen atmosphere, 0.02% by mass of tin (II) acetate was added, and a polymerization reaction was performed for 7 hours while gradually reducing the pressure to 170 Pa at 170 ° C. Subsequently, after performing a crystallization treatment at 110 ° C. for 1 hour in a nitrogen atmosphere, solid-phase polymerization was performed at a pressure of 60 Pa for 3 hours at 140 ° C., 3 hours at 150 ° C., and 6 hours at 160 ° C. Resin (A3) was obtained. Weight average molecular weight = 31,000, carboxyl group terminal content (COOH amount) = 71 eq / ton
[Thermoplastic resin other than polylactic acid resin (B)]
(B1)
Polybutylene succinate resin (trade name “GSPla” (registered trademark) FZ91PN, manufactured by Mitsubishi Chemical Corporation) Weight average molecular weight = 200,000, carboxyl group terminal content (COOH amount) = 25 eq / ton
(B2)
62 parts by mass of polyethylene glycol having a number average molecular weight of 8,000, 38 parts by mass of L-lactic acid and 0.05 parts by mass of tin octylate are mixed and polymerized in a reaction vessel equipped with a stirrer at 160 ° C. for 3 hours in a nitrogen atmosphere. Thus, a block copolymer plasticizer D1 having poly L-lactic acid segments having a number average molecular weight of 2,500 at both ends of polyethylene glycol having a number average molecular weight of 8,000 was obtained. Weight average molecular weight = 15,000, carboxyl group terminal content (COOH amount) = 60 eq / ton
[Filler (C)]
(C1)
Calcium carbonate (manufactured by Sankyo Seimitsu Co., Ltd., trade name “Top Flow H200” (registered trademark), average particle size 1.7 μm)
[Terminal Reactive Compound (D)]
(D1)
Carbodiimide compound (“STABAXOL (registered trademark) I”, monomer type, manufactured by Rhein Chemie)
[Create film]
Example 1
The polylactic acid-based resin listed in the table is supplied to a twin screw extruder with a vacuum vent of 44 mm and a cylinder diameter of 180 ° C. at a ratio of each mass% listed in the table, and melted while degassing the vacuum vent part. After kneading, homogenizing, and pelletizing, composition A was obtained.

  The pellets of the composition A were vacuum-dried at a temperature of 80 ° C. for 5 hours using a rotary drum type vacuum dryer.

  Similarly, the polylactic acid-based resin described in the table is melt-kneaded at the ratio of each mass% described in the table under the same extruder and conditions as the composition A, homogenized, and then pelletized to obtain the composition B It was.

  The pellets of the composition B were vacuum-dried at a temperature of 50 ° C. for 5 hours using a rotary drum type vacuum dryer.

  Subsequently, the pellet of the composition A was fed to a single screw extruder with a screw diameter of 60 mm as a layer A at a cylinder temperature of 200 ° C. and melted. At the same time, the pellet of the composition B was separated into another cylinder temperature of 200 ° C. as a layer B. Then, the two types of melt-kneaded compositions were fed into a single screw extruder having a screw diameter of 60 mm, and a two-layer / three-layer laminated type, a diameter of 250 mm, a lip clearance of 1.0 mm, and a temperature set at 155 ° C. Then, it was extruded upward in a bubble shape at a blow ratio of 2.0 by an inflation method, air-cooled by a cooling ring, taken up while being folded by a nip roll above the die, and wound into a roll shape. By adjusting the take-off speed, an unstretched film of 100 μm was obtained. This unstretched film was longitudinally stretched 5.5 times in a longitudinal direction at a temperature of 97 ° C. by a roll-type stretching machine. The uniaxially oriented film was once cooled on a chill roll and then heat treated at 110 ° C. for 5 seconds to obtain a film having a thickness of 20 μm. The physical properties of the obtained film are shown in the table.

  In Examples 2 to 7 and Comparative Examples 1 to 3, laminated films were obtained in the same manner as in Example 1 except that the compositions of the A layer and the B layer were changed as shown in the table. The physical properties of the obtained laminated film are shown in the table.

  The film of the present invention relates to a film excellent in moisture permeability and decomposability. According to the present invention, a film excellent in moisture permeability and decomposability is provided. Furthermore, the film of the present invention can be preferably used for applications that mainly require moisture permeability and flexibility. The film of the present invention specifically includes agricultural materials such as multi-films, forestry materials such as fumigation sheets, sanitary materials such as paper diapers, napkins and liners, plastic bags, garbage bags, foods, industrial products, etc. It can be preferably used for various packaging materials.

Claims (9)

A film having an A layer containing a polylactic acid resin and a B layer containing a polylactic acid resin, wherein the weight average molecular weight Mw (A) of the A layer and the weight average molecular weight Mw (B) of the B layer are expressed by the formula ( 1. A laminated film satisfying 1) and having a porosity of 10 to 80%.
Mw (B) / Mw (A) ≧ 1.2 Formula (1) The laminated film according to claim 1, wherein the carboxyl group terminal content COOH (A) of the A layer and the carboxyl group terminal content COOH (B) of the B layer satisfy the formula (2).
COOH (A) / COOH (B) ≧ 1.2 Formula (2) A film having an A layer containing a polylactic acid resin and a B layer containing a polylactic acid resin, wherein the carboxyl group terminal content COOH (A) of the A layer and the carboxyl group terminal content COOH (B of the B layer) ) Satisfies the formula (2) and has a porosity of 10 to 80%.
COOH (A) / COOH (B) ≧ 1.2 Formula (2) The laminated film according to claim 3, wherein the weight average molecular weight Mw (A) of the A layer and the weight average molecular weight Mw (B) of the B layer satisfy the formula (1).
Mw (B) / Mw (A) ≧ 1.2 Formula (1)   Mw (A) is 20,000-150,000, The laminated film of Claim 1, 2, or 4 characterized by the above-mentioned.   The laminated film according to any one of claims 2 to 4, wherein the carboxyl group terminal content COOH (A) of the A layer is 20 to 200 eq / ton.   The A layer and the B layer are directly laminated without interposing other layers, and the A layer is located on at least one surface. Laminated film.   The laminated film according to claim 1, comprising a thermoplastic resin other than a filler and a polylactic acid resin.   The film according to claim 8, wherein the thermoplastic resin other than the polylactic acid resin is an aliphatic polyester.