JP5391666B2 - Biaxially stretched film - Google Patents

Description

  The present invention provides a biaxially stretched film having a structure suitable for producing a polylactic acid film that is useful as a packaging material and has excellent processability and transparency, etc. with high productivity and operability. To do.

  Conventional polylactic acid is poor in thermal stability, and easily produces lactide during melt molding, fouling the machine base. A decrease in stretchability is observed. When a polytetramethylene glycol-containing resin is added, precipitation and volatilization of lactic acid oligomers and lactides can be suppressed even when produced under the same conditions as ordinary polylactic acid, and productivity can be improved.

Polylactic acid is attracting attention as a biomass-derived material, and is starting to be used for fibers, films, containers, and molding materials. Polylactic acid is generally melt-molded, but has poor thermal stability, producing lactide and lactic acid oligomers during melting, and causes problems such as fouling equipment when processed into films and fibers.
JP 2007-245710 A

  If you try to use high molecular weight polylactic acid to improve the mechanical properties of the film, the viscosity during melting will increase further and the melting temperature will increase, and in that case, thermal decomposition will occur. A lot of lactide adheres to the chill roll at the time of casting, the sheet surface gloss decreases, the stretchability decreases due to insufficient cooling, the peelability decreases from the chill roll due to unexpected cooling and breakage, etc. was there. For this problem, methods such as removal of residual catalyst and addition of a catalyst deactivator are used, but these methods are also insufficient.

  As described above, there is no prior art for improving the decrease in productivity due to lactide production in the conventional technique.

  It is an object of the present invention to provide a biaxially stretched film mainly composed of a polylactic acid resin suitable as a packaging material in which precipitation of oligomers and the like is suppressed in a molding process that is easy to produce with high productivity and operability. To do.

  The present inventor did not suppress lactide generated during melt molding, but studied an additive for preventing the generated lactide from precipitating out of the system. As a result, polytetramethylene glycol (PTMG) was added. It was found that precipitation outside the system was suppressed. However, mere addition of PTMG will bleed out to the surface over time and it will not withstand practical use. By copolymerizing with other components, it is possible to suppress oligomer precipitation and PTMG bleed out. Invented.

That is, this invention consists of the following structures.
1. A biaxially stretched film comprising a crystalline polylactic acid resin composition having an L-form / D-form ratio of 100/0 to 85/15, wherein the crystalline polylactic acid resin composition has a particle size of 0.1 to 10 μm. A biaxially stretched film comprising 100 to 10000 ppm of the total weight and 2 to 30% by weight of a thermoplastic resin containing a polytetramethylene glycol component based on the total weight.
2. The surface layer is composed of a crystalline polylactic acid resin composition having a L-form / D-form ratio of 100/0 to 85/15, and a lubricant having a particle diameter of 0.1 to 10 μm is 100 to 10,000 ppm with respect to the total weight. It has a resin layer made of a crystalline polylactic acid resin composition containing 2 to 30% by weight of the thermoplastic resin containing the component, and the inner layer is an aliphatic, alicyclic dicarboxylic acid component, or It has a layer made of a resin composition containing 50 to 100% by weight of a polyester resin containing hydroxycarboxylic acid as an essential component, the inner layer has a thickness of 10 to 80% of the total thickness, and a haze of 1 A biaxially stretched film characterized by being ˜10%.
2 . 2. The biaxially stretched film as described in the above item 1, wherein the thermoplastic-containing resin containing a polytetramethylene glycol component is a polyamide-based resin.
3 . 2. The biaxially stretched film as described in the above item 1, wherein the thermoplastic resin containing a polytetramethylene glycol component is a polyester resin.

  When the thermoplastic resin containing the PTMG component in the present invention is too compatible with the crystalline polylactic acid resin, the glass transition point of the crystalline polylactic acid resin is lowered, which causes a decrease in heat resistance. For this reason, as the resin for copolymerizing PTMG, a resin other than polylactic acid is preferable, and a polyamide resin and other polyester resins are preferable.

  In addition, since the polylactic acid resin is a biodegradable resin, a plant-derived resin, and a resin having a high glass transition point, it may be used by being laminated on the surface layer of another resin. For example, in the case of film formation of an aromatic-aliphatic polyester resin, the thermal stability during melting is poor as in the case of the polylactic acid resin, and the oligomer may precipitate. The glass transition point may be low and may have adhesiveness, and troubles that cannot be peeled off from the chill roll during casting may occur. In this case, by laminating the polylactic acid resin on the surface layer, precipitation of the oligomer derived from the aromatic-aliphatic polyester on the chill roll can be suppressed. However, by simply laminating ordinary polylactic acid, the oligomer derived from polylactic acid can be reduced. Precipitate. In such a case, various problems could be solved by adding a thermoplastic resin containing a PTMG component to the surface polylactic acid resin layer.

  According to the present invention, it is possible to provide a polylactic acid-based biaxially stretched film that can suppress problems such as precipitation of lactide that can maintain high productivity and operability.

Hereinafter, the present invention will be described in detail.
In the present invention, a resin obtained by copolymerizing a lubricant intended to impart slipperiness to a crystalline polylactic acid resin and a PTMG segment having a function of dissolving lactide and the like precipitated from the polylactic acid resin. It is preferable to add. The PTMG-containing resin in which lactide is dissolved preferably has a PTMG molecular weight in the range of 500 to 5000 and a copolymerization amount of 10 to 60% by weight. The resin to be copolymerized is not limited as long as it is a resin capable of copolymerizing PTMG, such as a polyester resin and a polyamide resin, but a polyester resin and a polyamide resin are preferable.

(Crystalline polylactic acid resin (A))
The crystalline polylactic acid resin (A) preferably used in the present invention is obtained by ring-opening polymerization of lactide using a compound having a hydroxyl group as an initiator in the presence of a suitable catalyst. The ratio of (hereinafter referred to as L-form) / D-lactic acid (hereinafter referred to as D-form) is preferably 100/0 to 85/15. If the L-form ratio is less than 85, the crystallinity is insufficient, the melting point is lowered, and the heat resistance is inferior. A preferred glass transition point in the present invention is 30 to 65 ° C., a melting point is preferably 120 to 170 ° C., and orientation crystallization is possible. The glass transition point and melting point can be obtained by a scanning calorimeter (DSC) or the like. The presence or absence of crystallinity can be confirmed by the presence or absence of a crystallization peak in the DSC temperature rising process or in the cooling process after melting. In the present invention, the preferred molecular weight is 30,000 to 200,000, more preferably 40,000 to 150000 in terms of weight average molecular weight. The weight average molecular weight can be obtained by gel permeation chromatography. If the molecular weight is less than 30000, it is brittle and a decrease in strength is observed. When the molecular weight exceeds 200,000, the viscosity at the time of melt molding becomes high, and a decrease in productivity is observed, and this is not preferable. Although what is contained in resin includes a polymerization catalyst, an oligomer, etc., the thing which removed the thing from the surface of thermal stability is desirable. As a method, there is a method of washing the pellet after polymerization with acetone or water. In the present invention, commercially available products satisfying the crystalline polylactic acid resin of L-form / D-form ratio = 100/0 to 85/5 include Lacia (registered trademark) H400, H100, H100E (Mitsui Chemicals), Levoda 101, 201 (manufactured by Kaisho Biological Material).

(Thermoplastic resin (B))
The thermoplastic resin (B) used in the present invention is a thermoplastic resin containing a PTMG component, and PTMG is preferably copolymerized in the resin. The molecular weight of the PTMG component of the present invention is preferably in the range of 500 to 5000. If the molecular weight is less than 500, the compatibility with the polylactic acid resin is well mixed, and the effect of suppressing the newly generated lactide during the process and precipitating out of the system is reduced. When the molecular weight exceeds 5,000, the size of phase separation of the PTMG component is increased, and haze and the like are lowered. The PTMG content and the copolymerization amount are preferably 10 to 60% by weight. When the copolymerization amount is less than 10% by weight, a large amount of addition is required for precipitation of lactide, and transparency is deteriorated. On the other hand, if it exceeds 60% by weight, the size of the phase separation of PTMG becomes large and the transparency is lowered, which is not preferable. The resin to be copolymerized is not limited as long as it is a resin capable of copolymerizing PTMG, such as a polyester resin and a polyamide resin, but polyester resin and polyamide resin are preferable in terms of transparency, transparency and thermal stability. In addition, polyalkylene glycol copolymers such as polyethylene glycol and polypropylene glycol other than PTMG described in Patent Document 1 have high compatibility with the polylactic acid of the polyethylene glycol component, so the lactide precipitation effect is low, and hydrophilicity Is not preferable because the film is whitened during moisture absorption.

  The polyester resin used in the present invention is preferably a normal dicarboxylic acid-diol type polyester, particularly preferably a polyester resin mainly composed of an aromatic dicarboxylic acid and an aliphatic diol, and more preferably an aromatic dicarboxylic acid and a fatty acid. Polyester resin mainly composed of a mixture of aliphatic or alicyclic dicarboxylic acids and an aliphatic diol. The polyester resin of the present invention can be obtained by adding PTMG to this raw material system for polymerization. A known method can be used as the polymerization method. A preferred molecular weight in the present invention is a weight average molecular weight in the range of 5000 to 200,000, and if it is less than 5000, there are many hydroxyl groups and carboxyl groups at the terminal, which is not preferable because the polylactic acid resin is decomposed. It can be used if the terminal functional group is blocked. When the molecular weight exceeds 200,000, the melt viscosity becomes too high and it is difficult to uniformly mix with the polylactic acid resin, which is not preferable. Although there is no restriction | limiting about the glass transition point of the polyester resin used in this invention, It is necessary to fuse | melt at the melting temperature of a polylactic acid resin, and it is preferable that melting | fusing point and softening temperature are 170 degrees C or less at that point.

  The polyamide resin used in the present invention is preferably a normal lactam polyamide or dicarboxylic acid-diamine type polyamide, particularly preferably a lactam polyamide resin, more preferably a polyamide resin mainly composed of a lactam having 10 or more carbon atoms. It is. The polyamide resin of the present invention can be obtained by adding PTMG to this raw material system for polymerization. A known method can be used as the polymerization method. In the present invention, the preferred molecular weight is a weight average molecular weight in the range of 5000 to 200,000, and if it is less than 5000, there are many carboxyl groups and amino groups at the terminal, which is not preferable because the polylactic acid resin is decomposed. It can be used if the terminal functional group is blocked. When the molecular weight exceeds 200,000, the melt viscosity becomes too high and it is difficult to uniformly mix with the polylactic acid resin, which is not preferable. Although there is no restriction | limiting about the glass transition point of the polyamide resin used in this invention, It is necessary to fuse | melt at the melting temperature of a polylactic acid resin, and it is preferable that the melting | fusing point and softening temperature are 170 degrees C or less at that point.

  In addition, as a commercial product of PTMG copolymer resin that can be suitably used in the present invention, as long as it is a polyester resin, Perprene (registered trademark) GP301 (manufactured by Toyobo), Hytrel (registered trademark) (produced by Toray Dubon) , Arnitel (trade name, manufactured by DSM), Byron (registered trademark) GM915, GM920, GM980, GM990, etc. (manufactured by Toyobo), Primalloy (registered trademark) (manufactured by Mitsubishi Chemical), and polyamide resins, And PEBAX (registered trademark) 4033 (manufactured by Arkema).

(Lubricant)
The active agent particles used in the present invention preferably have a particle size of 0.1 to 10 μm. If the particle diameter is less than 0.1 μm, the particle diameter is too small for imparting slipperiness and the effect for imparting roughness is reduced, which is not preferable. When it exceeds 10 μm, a decrease in transparency is observed, which is not preferable. The added amount is preferably 100 to 10,000 ppm with respect to the total weight. If the addition amount is 100 ppm, the effect on slipperiness is small, and if it exceeds 10000 ppm, a decrease in transparency is observed, which is not preferable. As the lubricant, both inorganic and organic can be used. Examples of the inorganic particles include silica, alumina, titanium dioxide, calcium carbonate, kaolin, and barium sulfate. Examples of the organic particles include acrylic resin particles, melamine resin particles, silicone resin particles, and crosslinked polystyrene particles. Preferably, the use of silica is preferable in terms of economy and thermal stability. Illustrative examples include silica particles (manufactured by Fuji Silysia Chemical, Silicia 310).

(Resin composition)
In the present invention, the ratio between the polylactic acid resin (A) and the thermoplastic resin (B) is preferably 98/2 to 70/30 (weight ratio). When the ratio of (A) is more than 98%, the effect of addition of (B) is small, which is not preferable. When the ratio of (B) exceeds 30%, the effect of adding (B) is saturated, which is not economical.

  In addition, other resins and additives may be added to the above resin composition. In particular, in terms of thermal stability, it is preferable to add a phosphorus compound for the purpose of catalyst deactivation. Moreover, it is one of preferable embodiments that the collection film manufactured by this patent is used as part or all of the polylactic acid film from the viewpoint of economy. As other resins, known resins such as other polyester resins, polyurethane resins, acrylic resins, polycarbonate resins, polyolefin resins, polyester elastomer resins, and polyamide elastomer resins can be used, but are not limited thereto.

(Structure of the film)
The biaxially stretched film of the present invention is not particularly limited, whether it is a single layer structure or a multilayered film. The thickness of the film after biaxial stretching is preferably 5 to 40 μm. If it is thinner than 5 μm or thicker than 40 μm, it is not preferable because it becomes difficult to handle as a normal packaging material. In the case of a multilayer structure, the polylactic acid-based resin composition containing PTMG in the present invention can be used as a surface layer or an inner layer, but as described later, it can be used as a surface layer. By using it as a surface layer of a resin from which various heat-degraded products are deposited due to low thermal stability, dirt on the chill roll can be solved, which is one of preferred embodiments in the present invention.

  The resin composition of the present invention can be obtained by processing into an unstretched sheet by various methods and then biaxially stretching. As a method for producing an unstretched sheet, in addition to solution casting, a method by melt extrusion can be used, and the melt extrusion method is suitable in the present invention.

  The melting of the resin composition in the present invention is preferably in the range of 150 to 250 ° C, more preferably 180 to 240 ° C. At 150 ° C., the melt viscosity is high and the productivity is lowered, which is not preferable. If it exceeds 250 ° C., the polylactic acid resin is liable to undergo thermal degradation, which is not preferable.

  The die temperature at the time of melt extrusion is the same as described above, but is preferably in the range of 150 to 300 ° C, preferably 170 to 290 ° C, more preferably 180 to 240 ° C. If the temperature is too low, the melt viscosity becomes too high and the surface becomes rough and the appearance deteriorates. If the temperature is too high, thermal decomposition of the resin occurs, which is not preferable.

(Stretching method)
The biaxially stretched film of the present invention can be stretched by sequential biaxial stretching and simultaneous biaxial stretching of an unstretched sheet melt-extruded from a T-die, and other methods such as a tubular system can be used. For this purpose, a method using a biaxial stretching machine is preferred. A preferable method from the standpoints of characteristics and economy includes a method of stretching in the longitudinal direction with a roll type stretching machine and then stretching in the transverse direction with a tenter type stretching machine (sequential biaxial stretching method). As for MD (longitudinal) stretching, it is preferable to use MD multistage stretching in order to improve the bowing after TD (transverse) stretching.

  A substantially unoriented polylactic acid resin sheet obtained by melt extrusion from a T-die is a glass transition temperature Tg ° C. or higher of the polylactic acid resin (A), and a temperature rising crystallization temperature (Tc) +20 of the polylactic acid resin (A). After stretching 2.5 to 10 times in the machine direction at a temperature of ℃ or lower, the obtained longitudinally stretched film is further heated to 3.0 to 10 at a temperature of 50 ℃ or higher and the melting point (Tm) of the polylactic acid resin (A) -20 ℃ or lower. It is preferable to obtain the biaxially stretched polylactic acid resin film by heat-fixing in the temperature range of 90 to 180 ° C.

  In MD stretching, when the temperature of the film is less than the glass transition temperature Tg ° C. of the polylactic acid resin (A), problems such as breakage due to orientation crystallization due to stretching and thickness unevenness are not preferable. On the other hand, when the temperature of the film exceeds the temperature rising crystallization temperature (Tc) + 20 ° C. of the polylactic acid resin (A), it is not preferred because breakage is likely to occur due to crystallization by heat. Further, when the draw ratio in MD stretching is less than 1.1 times, there are problems such as poor quality such as thickness spots and insufficient strength in the machine direction, and when it exceeds 10 times, subsequent TD stretching becomes difficult. A preferable draw ratio is 2.0 to 6.0 times.

  Furthermore, when the temperature of the film in TD stretching is a low temperature of less than 50 ° C., the TD stretchability is poor and breakage occurs, and the thickness variation in the TD direction due to neck stretching increases, which is not preferable. When the temperature is higher than (Tm) −20 ° C., thick spots increase, which is not preferable. In addition, when the TD stretch ratio is less than 1.1 times, the thickness variation in the TD direction increases, which is not preferable, and in addition to the point where the strength in the TD direction is lowered, the plane orientation is lowered and the pinhole resistance and the piercing strength are lowered. Therefore, it is not preferable. Further, when the TD stretch ratio is higher than 10 times, it is substantially difficult to stretch.

(Heat fixing)
In the present invention, it is preferable to perform heat setting in a temperature range of 90 to 180 ° C. When the heat setting temperature is lower than 90 ° C., the film has poor dimensional stability due to heat and is inappropriate. On the other hand, at a high temperature exceeding 180 ° C, holes are formed in the film, which is inappropriate. In the heat setting after TD stretching, the density increase due to crystallization and the accompanying volume shrinkage occur, and rapid heating causes stress in the MD direction and breaks. For this reason, as a heating method at the time of heat setting, it is preferable to increase the amount of heat in a stepwise manner to suppress the generation of a rapid contraction stress. As a specific method, there are methods such as gradually increasing the temperature or increasing the air volume from the vicinity of the entrance of the heat setting zone to the vicinity of the exit, and gradually reducing the air volume in terms of the heat shrinkage rate after stretching and heat setting. The heat setting method which raises is preferable.

  Regarding the relaxation treatment, it is preferable to determine the relaxation rate in consideration of the balance with the thermal contraction rate in the vertical direction. In the present invention, since the longitudinal dimension change in moisture absorption is small, the relaxation rate is preferably in the range of 0 to 5%. If it exceeds 5%, the effect for reducing the thermal shrinkage in the width direction is small, which is not preferable.

(Resin preferably used for inner layer of multilayer structure film)
The present invention also provides a film having a laminated structure in which a polylactic acid resin composition containing PTMG is arranged on the surface layer for the purpose of improving productivity. In addition to resins that have a low glass transition point and do not peel from chill rolls in the usual melt casting method, various resins that have been deteriorated due to poor thermal stability during melt molding are preferred as resins used for the inner layer. Raw materials that are easy to produce can be used. Specific examples of the former include polycaprolactone and polyhydroxybutyrate, and examples of the latter include Apexa (registered trademark) 4024 (manufactured by DuPont). The polyester resin according to the present invention is characterized in that it is a resin composition containing 50 to 100% by weight in the inner layer. If the polyester resin is less than 50%, the necessity for providing a surface layer is low and it is not economical. In the present invention, the inner layer occupies 10 to 80% of the total thickness. If the inner layer is less than 10%, the contribution of the characteristics derived from the inner layer is small, which is not preferable. If the inner layer exceeds 80%, the effect of suppressing the precipitation of the surface layer is small, which is not preferable.

  In the present invention, the biaxially stretched laminated film in which a resin containing a PTMG component is added to the surface layer and the above resin is added to the inner layer preferably has a haze of 1 to 10%. If the haze is less than 1%, it is difficult to achieve compatibility with slipperiness, and it is not preferable because stable productivity is taken into consideration. On the other hand, if it exceeds 10%, there are problems such as poor aesthetics and difficult to see contents.

(Film characteristics-haze)
The haze of the biaxially stretched film in the present invention is preferably in the range of 0.1 to 10.0% including that of a single layer. If the haze is less than 0.1%, it is difficult to produce stably, which is not preferable. If the haze exceeds 10%, it is not preferable because the design properties are deteriorated in addition to the contents and the like during use being difficult to see.

  The biaxially stretched film of the present invention may be subjected to corona treatment, coating treatment or flame treatment in order to improve adhesion and wettability depending on applications. In the coating process, an in-line coating method in which a film coated during film formation is stretched is one preferred embodiment. In general, the film of the present invention is further subjected to processing such as printing, vapor deposition, and laminating according to the application.

  The biaxially stretched film of the present invention has a hydrolysis resistance improver, antioxidant, colorant (pigment, dye), antistatic agent, conductive agent, flame retardant, reinforcing agent, filler, inorganic lubricant, organic lubricant, core An agent, a release agent, a plasticizer, an adhesion aid, a pressure-sensitive adhesive, and the like can be optionally contained.

  The biaxially stretched film of the present invention can be suitably processed into a bag shape and used. Various methods other than the fusing method can be used. The biaxially stretched film of the present invention is suitably used as a composite film in which a sealant layer such as polyethylene is laminated on the surface layer. For the lamination of the sealant layer, a melt extrusion lamination method can be used in addition to the dry lamination method. From the viewpoint of extrusion lamination suitability, the biaxially stretched film of the present invention preferably has a thermal shrinkage rate at 120 ° C. of 5% or less for both MD and TD.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not restrict | limited at all to these examples, unless the summary is exceeded. The measurement method used in the present invention is shown below.

(1) Haze
The sample was measured at three different locations using a haze meter (Nippon Denshoku, NDH2000) by a method according to JISK7105, and the average value was defined as haze.

(2) Glass transition temperature (Tg) measurement and low-temperature crystallization temperature (Tc) measurement An unoriented polyamide resin sheet is frozen in liquid nitrogen, decompressed and thawed, using a DSC manufactured by Seiko Denshi Co., Ltd. Measured with

(3) Molecular weight measurement PLA as an average molecular weight sample of PLA is dissolved in chloroform to prepare a solution having a concentration of about 0.2% by weight, and gel permeation chromatography (manufactured by Showa Denko KK, model: GPC-SYSTEM21) , Hereinafter referred to as GPC). The weight average molecular weight (Mw) was calculated using polystyrene as a standard substance.

(4) Mechanical properties (elastic modulus, breaking strength)
Conforms to JIS K 7113. A sample having a width of 10 mm and a length of 100 mm in the longitudinal direction and the width direction of the film was cut out using a razor as a sample. The measurement was performed under the conditions of a distance between chucks of 40 mm and a pulling speed of 200 mm / min, and an average value of five measurement results was used. As a measuring device, an autograph AG5000A manufactured by Shimadzu Corporation was used.

(5) Pinhole resistance (bending fatigue resistance test)
Using a gelbo flex tester manufactured by Rigaku Corporation, the bending fatigue resistance was measured by the following method. The test was conducted using a gelbo flex tester (manufactured by Riken Corporation). First, the obtained film sample was formed into a cylindrical shape on a fixed head having a diameter of 8.89 cm (3.5 inches) and a movable head having the same diameter disposed in parallel at a distance of 17.78 cm (7 inches) from the fixed head. Attached. A shaft attached in the middle of the movable head controls the movement of the movable head. First, move the movable head 440 degrees closer to the fixed head 8.89 cm (3.5 inches), then move it closer to the fixed head 6.35 cm (2.5 inches) in a horizontal motion, Returned to the state. One cycle of this cycle was performed 1000 times at a rate of 40 times / minute at 23 ° C. and 60% RH. The number of pinholes after 1000 repetitions was measured.

(6) Gloss The glossiness (gross) is 20 according to JIS K8741 using a gloss tester (gloss meter model 1001DP (manufactured by Nippon Denshoku Industries Co., Ltd.)). The specular gloss was measured.

(7) Evaluation of oligomer precipitation (gloss of cast sheet)
Pellets of polylactic acid resin (Mitsui Chemicals Lacia (registered trademark) H-400) and resin are mixed, put into an extruder, melted at 220 ° C, and T-die in sheet form on a cooling roll adjusted to 20 ° C The unstretched sheet was produced by extruding from the above and solidifying by cooling. Casting speed is 4m / min, the surface of the cooling roll after casting for 30 minutes is confirmed, and 5 samples are collected from the center of the obtained sheet in the width direction. The situation was evaluated.

(8) MD heat shrinkage rate In the longitudinal direction and the width direction of the film, a strip sample having a length of 150 mm and a width of 20 mm, respectively, is cut out, and two marks are provided at intervals of 100 mm in the length direction of each sample,
The distance A between the two marks was measured under no load. Subsequently, after gripping one side of each strip-shaped sample and leaving it in an oven under no load at 120 ° C. for 30 minutes, the sample was taken out,
After leaving at room temperature for 30 minutes, the interval B of each sample was read. From reading intervals A and B,
The thermal shrinkage rate at 120 ° C. of each sample was calculated by the following formula.
MD thermal shrinkage (%) = ((A−B) / A) × 100

(9) TD thermal contraction rate It evaluated by the method similar to MD contraction | shrinkage rate except having cut out the strip-shaped sample of length 20mm and width 150mm with respect to the longitudinal direction and the width direction of a film, respectively. The calculation formula is as follows (similar to MD thermal shrinkage).
TD heat shrinkage (%) = ((A−B) / A) × 100

(Production Example 1)
A 4-necked flask was charged with 900 parts of L-lactide, 100 parts of polytetramethylene glycol (PTG1000SN manufactured by Hodogaya Chemical Co., Ltd.) having a molecular weight of 1000, and 1 part by mass of tin octylate as a ring-opening polymerization catalyst. Resin (resin 1) was obtained by ring-opening polymerization by heating and melting for a period of time, and distilling off the residual lactide under reduced pressure. The weight average molecular weight by GPC was 12000.

(Production Example 2)
80 parts of a polyester polyol with a molecular weight of 2000 (DIC, OD-X-2044) and 10 parts of a polytetramethylene glycol with a molecular weight of 1000 (PTG1000SN made by Hodogaya Chemical) are charged into a four-necked flask and dissolved in 300 parts of methyl ethyl ketone under reflux. It was. Here, 10 parts of diphenylmethane diisocyanate (manufactured by Sumika Bayer Urethane, Desmodule 44) and 1 part by mass of dibutyltin laurate as a polymerization catalyst were polymerized by heating and melting under reflux in a nitrogen atmosphere for 3 hours. On the way, the increase in solution viscosity was confirmed, and MDI was appropriately added to adjust the molecular weight. After completion of the polymerization, reprecipitation with ethanol and drying under reduced pressure gave a resin (resin 2). The weight average molecular weight by GPC was about 8000.

(Production Example 3)
A 4-necked flask was charged with 900 parts of L-lactide, 100 parts of polyethylene glycol having a molecular weight of 1000 (PEG-20 manufactured by NOF Corporation), and 1 part by mass of tin octylate as a ring-opening polymerization catalyst, and at 180 ° C. for 3 hours under a nitrogen atmosphere. The resin (resin 3) was obtained by ring-opening polymerization by heating and melting, and distilling off the residual lactide under reduced pressure. The weight average molecular weight by GPC was 15000.

( Reference Example 1 )
Lubricant (manufactured by Fuji Silysia Chemical, Silicia 310) and polylactic acid resin (Laisia (registered trademark) H400 manufactured by Mitsui Chemicals) are mixed with an extruder at 220 ° C, adjusted to a lubricant concentration of 200 ppm, dried and crystallized. Polylactic acid resin pellets and polyether amide resin (PEBAX4033, manufactured by Arkema) were mixed at a weight ratio of 95/5, introduced into an extruder, melted at 220 ° C, and sheeted on a cooling roll adjusted to 20 ° C. An unstretched sheet was produced by extruding from a T-die and cooling and solidifying. The casting speed was 4 m / min, the contamination of the surface of the cooling roll after casting for 30 minutes was confirmed, and the gloss of the obtained sheet was evaluated to evaluate the state of oligomer precipitation. The thickness of the unstretched sheet was 200 μm. This sheet was pre-heated at a temperature of 60 ° C., then MD stretched at a stretching temperature of 80 ° C. at a deformation rate of 5000% / min, quadrupled MD, and the sheet was continuously led to a tenter, and the residual heat zone of 70 ° C. TD-stretched 5 times at 85 ° C in the stretching zone, heat-fixed at 150 ° C and 5% transverse relaxation treatment, cooled, cut and removed both edges, and biaxially stretched polylactic acid with a thickness of 15μm A system film was obtained. Table 1 shows the film physical properties at this time.

( Reference Examples 2-6, Comparative Examples 1-3)
In the same manner as in Reference Example 1, a biaxially stretched polylactic acid film was obtained with the formulation shown in Table 1.

(Example 1 )
Lubricant (manufactured by Fuji Silysia Chemical, Silicia 310) and polylactic acid resin (Laisia (registered trademark) H400 manufactured by Mitsui Chemicals) are mixed with an extruder at 220 ° C, adjusted to a lubricant concentration of 200 ppm, dried and crystallized. A polylactic acid resin composition in which a pellet of polylactic acid resin and a pellet of polyetheramide resin (manufactured by Arkema, PEBAX (registered trademark) 4033) are mixed at a weight ratio of 95/5, and biodegradable polyester resin (manufactured by DuPont, APEXA (registered trademark) 4024) is put into two extruders and melted at 220 ° C and 240 ° C, respectively, and the polylactic acid resin composition is the surface layer and the biodegradable polyester resin is the inner layer with 2 types and 3 layers As a sheet having a structure, an unstretched sheet was produced by extruding from a T-die into a cooling roll adjusted to 20 ° C. and cooling and solidifying. The thickness configuration of the multilayer sheet was surface layer / inner layer / surface layer = 10/80/10 from the discharge amount. The casting speed was 4 m / min, the contamination of the surface of the cooling roll after casting for 30 minutes was confirmed, and the gloss of the obtained sheet was evaluated to evaluate the state of oligomer precipitation. The thickness of the unstretched sheet was 200 μm. This sheet was pre-heated at a temperature of 60 ° C., then MD stretched at a stretching temperature of 80 ° C. at a deformation rate of 5000% / min, quadrupled MD, and the sheet was continuously led to a tenter, and the residual heat zone of 70 ° C. , TD stretched 5 times at 85 ° C in the stretching zone, heat-fixed at 210 ° C and 5% transverse relaxation treatment, then cooled, both edges were cut and removed, and a biaxially stretched laminated film with a thickness of 15 μm Got. Table 2 shows the film physical properties at this time.

(Examples 2 to 5 and Comparative Examples 4 to 5)
A biaxially stretched laminated film was obtained with the formulation shown in Table 2 in the same manner as in Example 1 .

H400: Mitsui Chemicals polylactic acid resin Lacia (registered trademark) H400
H100: Polylactic acid resin Lacia (registered trademark) H100 manufactured by Mitsui Chemicals

ECOFLEX®: BASF biodegradable polyester
RV630: Toyobo Byron (registered trademark)
PCL: Placel (registered trademark) H1P manufactured by Daicel Chemical

  According to the present invention, a biaxially stretched film using a polylactic acid-based resin that can be produced with high productivity and operability, is useful as a packaging material, has excellent processing suitability, and has excellent transparency and the like. It was possible to provide.

Claims (3)

It is a crystalline polylactic acid resin composition with a L / D ratio of 100/0 to 85/15 on the surface layer , and a lubricant having a particle size of 0.1 to 10 μm is 100 to 10,000 ppm with respect to the total weight, polytetramethylene glycol It has a resin layer made of a crystalline polylactic acid resin composition containing 2 to 30% by weight of the thermoplastic resin containing the component, and the inner layer is an aliphatic, alicyclic dicarboxylic acid component, or It has a layer made of a resin composition containing 50 to 100% by weight of a polyester resin containing hydroxycarboxylic acid as an essential component, the inner layer has a thickness of 10 to 80% of the total thickness, and a haze of 1 A biaxially stretched film characterized by being ˜10%. The biaxially stretched film according to claim 1, wherein the thermoplastic-containing resin containing a polytetramethylene glycol component is a polyamide-based resin. The biaxially stretched film according to claim 1, wherein the thermoplastic resin containing a polytetramethylene glycol component is a polyester resin.