JP4288268B2 - Biodegradable laminated sheet - Google Patents

Description

  The present invention relates to a biodegradable laminated sheet-like material, and particularly relates to a biodegradable laminated sheet-like material having a barrier property such as a gas and a heat seal property.

Plastic films with excellent transparency and heat sealability may be required for plastic films for general packaging materials such as food storage bags, fishery, agricultural, architectural, and medical use. .
Many of plastic films and the like, in particular, plastic packaging materials are generally disposable, and are often discarded after use. General packaging plastics include polyethylene, polypropylene, polyethylene terephthalate (PET), and the like, but these materials generate a large amount of heat during combustion, which may damage the combustion furnace during the combustion process. Even today, polyvinyl chloride, which is used in large quantities, cannot be burned due to its self-extinguishing properties. Plastic products including such materials that cannot be incinerated are often buried in the soil, but these are chemically stable and non-biodegradable, so they remain and accumulate almost without being decomposed. For this reason, they not only scatter in the natural environment and contaminate the living environment of animals and plants, but also saturate the capacity of the land for garbage disposal in a short period of time.

  Therefore, a biodegradable material that has a low amount of combustion heat and is safe for the human body or the like is required, and many studies have been made. One of them is polylactic acid. Polylactic acid has a calorific value less than half that of polyethylene, and is naturally hydrolyzed in soil and water, and then becomes a harmless decomposition product by microorganisms. Development of films, sheets, containers (molded articles), etc. using polylactic acid has been actively conducted.

However, since polylactic acid does not have water vapor barrier properties and gas barrier properties, for example, when used as a packaging material, improvement of such barrier properties has been an important issue. For example, JP-A-8-290526 and JP-A-11-35058 disclose sheets laminated with an aluminum foil for imparting water vapor barrier properties, etc., but these sheets did not have sufficient heat sealability. .
In general, in order to impart heat sealability, a film made of a heat seal material such as polyethylene, polypropylene, ionomer, ethylene-vinyl acetate copolymer, aromatic-aliphatic polyester copolymer is provided. Since the sealing material is not biodegradable, environmental problems occurred during disposal.
Therefore, the appearance of a plastic material that satisfies all the requirements that the barrier properties such as water vapor and gas are good, the heat sealability is excellent, and does not cause environmental problems has been desired.

  The present invention has been made to solve the above-mentioned problems, and an object of the present invention is a plastic having good barrier properties such as water vapor and gas, excellent heat sealability, and biodegradability in a natural environment. The object is to provide a sheet.

As a result of intensive studies to solve the above problems, the present inventors have completed the present invention. That is, the biodegradable laminated sheet material of the present invention has a biaxially stretched sheet material A containing a polylactic acid-based polymer as a main component on one surface side of an aluminum layer and a polylactic acid-based material on the other surface side. A biodegradable laminated sheet material having a biaxially stretched sheet material B mainly composed of a polymer, the melting point of the biaxially stretched sheet material A composed mainly of the polylactic acid-based polymer, The difference between the melting point of the biaxially stretched sheet-like material B mainly composed of a polylactic acid polymer is 10 ° C. or more.
Here, among the biaxially stretched sheet A having the polylactic acid polymer as a main component and the biaxially stretched sheet B having the polylactic acid polymer as a main component, the higher melting point poly The biaxially stretched sheet-like material containing a lactic acid polymer as a main component can have a dynamic storage elastic modulus (E ′) at a frequency of 10 Hz and 120 ° C. measured by JIS K 7198 of 100 MPa or more.
Of the biaxially stretched sheet A having the polylactic acid polymer as a main component and the biaxially stretched sheet B having the polylactic acid polymer as a main component, the polylactic acid having a higher melting point. The amount of heat of crystallization and melting (ΔHm) of the biaxially stretched sheet-like product containing a polymer as a main component can be 20 J / g or more.

  The biodegradable laminated sheet material of the present invention is biodegradable because a polylactic acid polymer is used as a heat seal material instead of a normal plastic heat seal material, and is an environmental problem in disposal after use. Does not occur. Since the biodegradable laminated sheet material of the present invention has a biaxially stretched polylactic acid polymer layer (support layer) having a melting point higher than the material of the layer on the surface opposite to the layer to be heat sealed, Printing or the like can be performed without melting the support layer. Further, since the thin aluminum foil is used, it is naturally decomposed and does not cause environmental problems. Since the biodegradable laminated sheet material of the present invention uses a polylactic acid-based polymer, it is safe for the human body and can also be used when it comes into contact with food or the like.

  The biodegradable laminated sheet-like product of the present invention has good barrier properties such as water vapor and gas, is excellent in heat sealability, has biodegradability, and does not cause environmental problems.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is described in detail below.
The biodegradable laminated sheet material of the present invention has a biaxially stretched sheet material A containing a polylactic acid polymer as a main component on one side of an aluminum layer and a polylactic acid polymer as a main component on the other side. A biaxially stretched sheet B is provided.

  Here, the sheet-like material refers to a sheet or a sheet-like material. According to the definition in JIS, a sheet is a thin, generally flat product whose thickness is small compared to the length and width, and a film is extremely small compared to the length and width and has a maximum thickness. An arbitrarily limited thin flat product, usually supplied in the form of a roll (JIS K 6900). Therefore, it can be said that a particularly thin sheet is a film. However, since the boundary between the sheet and the film is not clear and it is difficult to distinguish clearly, in the present application, as described above, the term “sheet-like product” is used as a concept including both the sheet and the film. use.

The polylactic acid polymer used in the present invention is a polymer containing L-lactic acid, D-lactic acid or DL-lactic acid unit as a main component, or a mixture of these polymers. (For L-lactic acid, D-lactic acid can be copolymerized, and for D-lactic acid, L-lactic acid) can be copolymerized. The polylactic acid-based polymer may contain other hydroxycarboxylic acid or the like as a small amount of a copolymer component, and may contain a small amount of a chain extender residue.
Monomers such as copolymerization components copolymerized with polylactic acid include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2- Examples include bifunctional aliphatic hydroxycarboxylic acids such as hydroxy-3-methylbutyric acid, 2-methyllactic acid, and 2-hydroxycaproic acid, and lactones such as caprolactone, butyrolactone, and valerolactone.

  In the present invention, a known method such as a condensation polymerization method or a ring-opening polymerization method can be employed as the polymerization method. For example, in the condensation polymerization method, polylactic acid having an arbitrary composition can be obtained by directly dehydrating condensation polymerization of L-lactic acid, D-lactic acid, DL-lactic acid or the like. In the ring-opening polymerization method (lactide method), a polylactic acid-based polymer can be obtained by appropriately selecting and using a polymerization regulator, a catalyst, and the like as needed for lactide, which is a cyclic dimer of lactic acid. it can.

  The weight average molecular weight (Mw) of the polylactic acid polymer used in the present invention is preferably in the range of 60,000 to 700,000, more preferably 80,000 to 400,000, and particularly preferably 100,000 to 300,000. is there. If the weight average molecular weight of the polylactic acid-based polymer is 60,000 or more, practical mechanical properties and heat resistance can be exhibited. If the weight average molecular weight is 700,000 or less, the melt viscosity becomes high. It is not too inferior in moldability.

Biaxially stretched sheet-like material A (hereinafter sometimes referred to as “biaxially stretched sheet-like material A”) having a polylactic acid-based polymer as a main component, and biaxially-stretched sheet shape having a polylactic acid-based polymer as a main component In the product B (hereinafter also referred to as “biaxially stretched sheet-like product B”), the difference between the melting points of each biaxially stretched sheet-like product is 10 ° C. or more. In the biodegradable laminated sheet material of the present invention, the biaxially stretched sheet material having a lower melting point usually functions as a heat seal material, and the biaxially stretched sheet material having a higher melting point serves as a support layer and a protective layer. If the difference in melting point is smaller than 10 ° C., the biaxially stretched sheet having the higher melting point is also melted or semi-molten when the heat sealing material is heated and melted for sealing. It becomes a state, and a clean finish of the seal portion cannot be achieved. In the present invention, the difference in melting point between the biaxially stretched sheet A and the biaxially stretched sheet B is preferably 20 ° C. or higher, and more preferably 30 ° C. or higher.
In the present invention, the “melting point of the biaxially stretched sheet” means the melting point of the stretched sheet after biaxial stretching is performed on a sheet composed mainly of a polylactic acid polymer. The melting point is measured based on JIS K 7122 using, for example, a differential scanning calorimeter (DSC).

  Of the biaxially stretched sheet-like material A and the biaxially stretched sheet-like material B, the biaxially stretched sheet-like material having a higher melting point (tentatively referred to as the biaxially stretched sheet-like material A) is defined in JIS-K-7198. Based on this, the dynamic storage elastic modulus (E ′) measured at a frequency of 10 Hz and a temperature of 120 ° C. is preferably 100 MPa or more. When the dynamic storage elastic modulus (E ′) is 100 MPa or more, the heat resistance of the biaxially stretched sheet A that functions as a protective layer is sufficient when the biodegradable laminated sheet is heat sealed. It does not stick to the heating plate (heating bar). Therefore, the biaxially stretched sheet A can be easily peeled off from the heating plate without damaging the surface, and a clean finish of the seal portion can be achieved. The dynamic storage elastic modulus (E ′) is a value that varies depending on the crystallinity of the polylactic acid polymer. The higher the crystallinity, the larger the dynamic storage elastic modulus (E ′) when compared at the same temperature. Become. Actually, the upper limit of the dynamic storage elastic modulus (E ′) at 120 ° C. of the stretched sheet-like material made of a polylactic acid polymer is 350 MPa.

  The biaxially stretched sheet material A and the biaxially stretched sheet material B are a sheet or cylinder obtained by extruding a resin composition mainly composed of a polylactic acid polymer from a T die, an I die, a round die, or the like. A sheet-like product is rapidly cooled with a cooling cast roll, water, compressed air, or the like, solidified in a state close to an amorphous state, and then stretched biaxially by a roll method, a tenter method, a tubular method, or the like. . In general, biaxial stretching of a sheet-like material is performed by a sequential biaxial stretching method in which longitudinal stretching is performed by a roll method and a lateral stretching is performed by a tenter method, or by a simultaneous biaxial stretching method in which stretching is performed by a tenter at the same time.

  As stretching conditions, the stretching temperature is 55 to 90 ° C., preferably 65 to 80 ° C., the longitudinal stretching ratio is 1.5 to 5 times, preferably 2 to 4 times, and the transverse stretching ratio is 1.5 to 5 times. The stretching speed is 10 to 100,000% / min, preferably 100 to 10,000% / min. However, the appropriate range of stretching conditions varies depending on the composition of the polylactic acid-based polymer and the thermal history of the unstretched sheet-like material, and is thus determined as appropriate while looking at the in-plane orientation index and the plane orientation index of the sheet-like material.

After stretching, the stretched sheet-like material is subjected to heat treatment. In order to suppress the thermal contraction of the stretched sheet-like material, it is necessary to perform heat treatment while holding the stretched sheet-like material. In the tenter method, stretching is usually performed while a sheet-like material is held by a clip, and thus heat treatment can be performed as it is after stretching.
The heat treatment conditions depend on the melting point of the polylactic acid polymer to be used, but the heat treatment temperature is 100 ° C. or higher and the melting point of the polylactic acid polymer or lower and the heat treatment time is 3 seconds or more. Is preferred. If the heat treatment conditions are within such a range, the thermal contraction rate of the sheet-like material becomes small, and problems due to the shrinkage of the sheet-like material do not occur in the secondary processing step of the sheet-like material. The thermal contraction rate for preventing such a problem is that the thermal contraction rate of the sheet-like material after being immersed in warm water of 80 ° C. for 10 seconds is 5% or less, preferably 3% or less. is there.
Further, if the heat treatment temperature is not higher than the melting point of the polylactic acid polymer, the sheet-like material does not melt or break during the heat treatment.

In the present invention, among the biaxially stretched sheet A and the biaxially stretched sheet B, the material of the sheet having the lower melting point is, for example, first selecting the sheet having the higher melting point, Next, a material having a melting point lower by 10 ° C. or more can be arbitrarily selected from the sheet-like material.
The biaxially stretched sheet A and the biaxially stretched sheet B have a heat stabilizer, a light stabilizer, a light absorber, a lubricant, a plasticizer, an inorganic filler, a colorant, for the purpose of adjusting various physical properties. A pigment or the like can also be added. Furthermore, by applying a corona treatment to one or both surfaces of the sheet-like material A and / or the sheet-like material B, it is possible to improve adhesion and printability.

In the present invention, an aluminum layer is laminated in order to provide barrier properties such as water vapor and gas. Aluminum is oxidized in a natural environment, and thin ones eventually collapse. In the present invention, an aluminum layer having a thickness of about 0.02 μm to about 100 μm is preferably laminated.
As the aluminum layer, an aluminum foil or the like conventionally used for a packaging material or the like can be used. For example, an aluminum foil having a thickness of 2 to 100 μm can be used. In addition to the aluminum foil, an aluminum layer can be formed by aluminum deposition or the like. In this case, the thickness of the aluminum layer is, for example, about 0.02 μm to about 0.2 μm, preferably about 0.04 μm. ~ 0.1 μm.
In order to laminate the aluminum layer, a publicly known method can be used. For example, an aluminum foil or the like may be laminated on the biaxially stretched sheet A or the like using an adhesive. Aluminum may be deposited on the axially stretched sheet A or the like.
The aluminum layer may be subjected to various surface treatments such as corona treatment as necessary.

The biodegradable laminated sheet material of the present invention is not limited to a three-layer structure. That is, even if the biaxially stretched sheet A and / or the biaxially stretched sheet B is directly provided on the aluminum layer, it is provided via another layer (for example, an adhesive layer) therebetween. Further, on the biaxially stretched sheet A and / or the biaxially stretched sheet B, other layers (for example, a coat layer, a skin layer, and a print layer) may be provided. Good.
That is, the layer structure of the biodegradable laminated sheet material of the present invention may be a three-layer structure such as biaxially stretched sheet material A / aluminum layer / biaxially stretched sheet material B, or biaxially stretched. A five-layer structure such as sheet-like material A / adhesive layer / aluminum layer / adhesive layer / biaxially stretched sheet-like material B, or skin layer / biaxially stretched sheet-like material A / aluminum layer / biaxially stretched sheet shape A four-layer structure like the object B may be used.

  For example, in the case of forming a package using the biodegradable laminated sheet material of the present invention, the biaxially stretched one of the biaxially stretched sheet material A and the biaxially stretched sheet material B having the higher melting point. The sheet-like material is used as an outer layer, and the biaxially stretched sheet-like material having a lower melting point is placed on the inside to be bonded as a heat seal layer. The biaxially stretched sheet-like material of the outer layer is usually a layer on which reverse printing is performed, and the inner biaxially stretched sheet-like material is a layer in contact with the contents to be packaged. In the present invention, since the material of the portion in contact with the inner contents is formed of polylactic acid, food or the like can be packaged.

As the adhesive, vinyl-based, acrylic-based, polyamide-based, polyester-based, rubber-based and urethane-based adhesives can be generally used, but the adhesive can also be made biodegradable. As the biodegradable adhesive, polysaccharides such as starch, amylose, and amylopectin, proteins and polypeptides such as glue, gelatin, casein, zein, and collagen, unvulcanized natural rubber, and aliphatic polyester are preferable. Used.

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
The melting point (Tm), crystallization heat of fusion (ΔHm), and dynamic storage modulus (E ′) were determined under the following conditions.

Melting point (Tm) and heat of crystallization melting (ΔHm)
Using a differential scanning calorimeter “DSC-7” (manufactured by PerkinElmer), the heat of fusion was measured based on JIS K7121 and JIS K7122. That is, 10 mg of a test piece was cut out from the prepared biaxially stretched sheet-like material, and after adjusting the state in a standard state, the temperature was raised to 200 ° C. at a nitrogen gas flow rate of 25 ml / min and a heating temperature of 10 ° C./min. The endothermic peak and its area were read from the DSC curve drawn in between, and were taken as the melting point (Tm) and the heat of crystallization and melting (ΔHm), respectively.

Dynamic storage elastic modulus at 120 ° C (E ')
Using a dynamic viscoelasticity measuring device “VES-II type” (manufactured by Iwamoto Seisakusho Co., Ltd.), based on JIS K 7198, the temperature rising rate is within the range of room temperature or higher and below the melting temperature of the polylactic acid polymer. Measurements were made at 1 ° C./min and a frequency of 10 Hz. The dynamic storage elastic modulus (E ′) at 120 ° C. was determined from the obtained viscoelastic curve.

Sheet-like product No. 1-No. 5 (1) Sheet-like material No. 5 1
100 parts by weight of polylactic acid having a weight average molecular weight of about 200,000 (melting point: 175 ° C.) and granular silicon dioxide (silica) having an average particle size of about 2.5 μm (trade name “Silysia 430”, manufactured by Fuji Silysia Chemical Co., Ltd.) 1 part by weight is dried to remove water sufficiently, and then put into a twin screw extruder with a diameter (Φ) of 40 mm, melted and mixed at about 200 ° C., extruded into a strand, and cooled. Cut into pellets. The pellets were dried again as a master batch, mixed at a rate of 10% with the above-mentioned polylactic acid dried in the same manner, put into a co-directional twin screw extruder with a diameter (Φ) of 40 mm, and set temperature 210 ° C. After extruding into a sheet, the mixture was quenched and solidified with a rotating cooling drum to obtain a substantially amorphous sheet.
However, the obtained sheet-like material is heated in combination with an infrared heater while being brought into contact with a hot water circulating roll, and is 2.4 times at 70 ° C. in the longitudinal direction between the peripheral speed difference rolls, and then this longitudinally stretched sheet-like material. The film is guided to a tenter while being gripped with a clip, stretched 2.7 times at 70 ° C. in the direction perpendicular to the film flow, and then heat-treated at 130 ° C. for about 25 seconds to form a biaxially stretched sheet (sheet) having a thickness of 25 μm. Article No. 1) was produced.
The obtained sheet No. For 1, the melting point (Tm), the heat of crystallization and fusion (Hm), and the dynamic storage modulus (E ′) at 120 ° C. were determined. The results are shown in Table 1.

(2) Sheet-like product No. 2-No. 4
Sheet-like product No. In the preparation of 1, the content of D-lactic acid in the polylactic acid polymer was changed to prepare unstretched sheet-like materials of the polylactic acid polymer. In addition, using the obtained unstretched sheet-like material, the sheet-like material No. 1 except that the longitudinal stretching and transverse stretching temperatures and stretch ratios and the heat treatment conditions were changed as shown in Table 1. In the same manner as in the preparation of No. 2-No. 4 biaxially stretched sheet-like material was prepared.

(3) Sheet-like product No. 5
Sheet-like product No. In the production of sheet No. Using the raw material No. 4, an unstretched sheet of polylactic acid polymer was prepared. Here, the sheet-like material that has not been stretched and is still unstretched is referred to as a sheet-like material No. 5 was used. However, the thickness of the sheet was 25 μm.
Sheet-like product No. No. 5 is a biaxially oriented sheet-like product No. 5 using the same raw material. Unlike 4, the melting point (Tm) could not be observed by DSC measurement. That is, the sheet-like product No. Since No. 5 has a considerably lower crystallinity than the biaxially stretched sheet-like material and is substantially in an amorphous state, it softens at a temperature exceeding the glass transition point. Even in the dynamic viscoelasticity measurement, measurement in the region of 120 ° C. could not be performed. That is, at 120 ° C., the dynamic storage elastic modulus (E ′) is significantly lower than 100 MPa.

(Example 1)
Sheet-like material No. 2 cut out to A4 size. Corona treatment was applied to one surface of 1 at a strength of 50 W / m ² / min to improve the wetting tension on the surface of the sheet. In addition, wetting tension can be improved as the strength of the corona treatment increases, but if it is too high, problems such as melting of the surface of the sheet-like material during the corona treatment occur, and the appearance is impaired. A corona treatment strength of 50 W / m ² / min is expected to be most effective as long as the appearance of the sheet is not impaired. For reference, the strength of the corona treatment of the polyolefin-based sheet is generally 20 to 40 W / m ² / min, and at most 500 W / m ² / min.
A 7 μm thick aluminum foil is cut into A4 size, and the surface of this aluminum foil is an adhesive for aliphatic polyester-based dry laminate, trade name “Takelac A-315” (manufactured by Takeda Pharmaceutical Co., Ltd.) and products. A mixture of the name “Takenate A-50” (manufactured by Takeda Pharmaceutical Co., Ltd.) at a ratio of 15: 1 was applied using a Mayer bar to a thickness of about 3 μm. Immediately after coating, the sheet-like material No. The surface subjected to the corona treatment 1 was bonded to the adhesive surface. However, this sheet was used as a support layer.
Next, the sheet-like material No. 1 cut out to A4 size on the other surface of the aluminum foil. 2 were bonded in the same manner. This sheet-like product No. 2 was a heat seal layer.
The obtained biodegradable laminated sheet was aged at 40 ° C. for 2 days, and then evaluated as follows. The results are shown in Table 2.

Evaluation of heat sealability (adhesiveness), evaluation of change of support layer during heat seal The obtained biodegradable laminated sheet was cut into a width of 150 mm and a length of 128 mm. The two cut sheet-like materials were superposed so that the lower melting point sheet-like materials (heat seal materials) face each other and contact each other. Three sides of the overlapped sheet were heat-sealed. However, the heat sealing was performed by pressing a heating plate having a heating bar width of 5 mm at a pressure of 1.5 kgf / cm ² for 5 seconds and then allowing to cool. The heat sealing temperature was appropriately set within a range of 80 to 170 ° C. so that the heat sealing material was fused. In addition, the standard of the setting of heat seal temperature is making it more than melting | fusing point of a heat seal material.
After heat sealing, the heat sealability (adhesiveness) of the heat seal part was evaluated visually and by touch. That is, “◯” indicates that the adhesion is good, and “x” indicates that the adhesion is insufficient.
In addition, the sheet having the higher melting point that becomes the support layer (printing layer) at the time of heat sealing is heated and sticks to the heating bar, or the surface of the support layer melts and the finish is poor. The support layer was slightly changed, and “△” indicates a slightly poor finish, and “◯” indicates a fine finish.

(Examples 2 and 3 and Comparative Examples 1 to 3)
A biodegradable laminated sheet material was produced in the same manner as in Example 1 except that the support material and the sheet material of the heat seal layer bonded to aluminum were changed as shown in Table 2 in Example 1. The obtained biodegradable laminated sheet was evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Example 4)
Using an electron beam heating type vacuum vapor deposition machine (manufactured by Reybold Co., Ltd.), a corona-treated sheet-like material No. 1 was prepared using aluminum (Al) as a raw material in an air atmosphere with a degree of vacuum of 5 × 10 ⁻⁵ . The vapor deposition process was continuously given to one side of 1.
Next, on the surface of the sheet-like material on which the aluminum was not deposited, the sheet-like material No. 1 cut into A4 size in the same manner as in Example 1. 4 was laminated to make a laminated sheet. The obtained laminated sheet was evaluated in the same manner as in Example 1. The results are shown in Table 2.

As is clear from Tables 1 and 2, Examples 2 to 4 showed good heat sealability. Further, in Example 1 in which the melting point of the sheet-like material bonded to both surfaces of aluminum was relatively close, although the finish was slightly inferior, there was no problem in heat sealability.
On the other hand, in Comparative Example 1, although there was heat sealing (adhesion) property, the support layer melted out at the time of heat sealing, and it did not finish cleanly by sticking to the heating bar. Comparative Example 2 is a laminate having the same configuration as Comparative Example 1, but the heat seal temperature was lowered, so the support layer did not melt out but could not be sealed. In Comparative Example 3, sealing was attempted in the heat seal temperature range of 80 to 170 ° C., but the surface of the support layer was fused to the seal bar and could not be finished cleanly.
The sheet-like material of the present invention was excellent in water vapor and gas barrier properties.

Claims (3)

  Biaxially stretched sheet-like material A having a polylactic acid polymer as a main component on one surface side of the aluminum layer, and biaxially stretched sheet material having a polylactic acid polymer as a main component on the other surface side A biodegradable laminated sheet material having B, wherein the biaxially stretched sheet material A and the biaxially stretched sheet material B are not the same, and are biaxially composed mainly of the polylactic acid-based polymer. The difference between the melting point of the stretched sheet A and the melting point of the biaxially stretched sheet B mainly composed of the polylactic acid polymer is 10 ° C. or more, and the biaxially stretched sheet A and A biodegradable laminated sheet material, wherein the surface of the biaxially stretched sheet material B on the side in contact with at least one aluminum layer is subjected to corona treatment.   Of the biaxially stretched sheet material A having the polylactic acid polymer as a main component and the biaxially stretched sheet material B having the polylactic acid polymer as a main component, the polylactic acid heavy material having the higher melting point. 2. The biaxially stretched sheet-like material composed mainly of a coalescence has a dynamic storage elastic modulus (E ′) at a frequency of 10 Hz and 120 ° C. measured by JIS K 7198 of 100 MPa or more. The biodegradable laminated sheet material described in 1.   Of the biaxially stretched sheet material A having the polylactic acid polymer as a main component and the biaxially stretched sheet material B having the polylactic acid polymer as a main component, the polylactic acid heavy material having the higher melting point. The biodegradable laminated sheet-like material according to claim 1 or 2, wherein the biaxially stretched sheet-like material containing the coalescence as a main component has a heat of crystallization and melting (ΔHm) of 20 J / g or more.