JP2009107669A - Packaging bag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a packaging bag made of a film exhibiting excellence in printing performance and film-making operability, and exhibiting excellence in transparency, flexibility and seal strength. <P>SOLUTION: The packaging bag is formed by sealing a biaxially stretched polylactic acid-based film which is composed of a resin composition containing 50 to 90 mass parts of a polylactic acid (A) and 10 to 50 mass parts of a polylactic acid-based copolymer (B) containing 30 to 70 mass% of a lactic acid component, has not more than 0.5 mass% of a lactide content, has a tensile modulus of not more than 3.0 GPa, and shows a haze of not more than 10%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a packaging bag which is obtained from a polylactic acid-based film having transparency and flexibility and has excellent sealing strength.

  Films used as packaging materials for newspapers, magazines, foods and the like are desired to be formed from biodegradable polymers in accordance with the recent increase in social demand for environmental protection. Among them, polylactic acid, which is widely present in nature and harmless to animals, plants and animals, has a melting point of 140 to 175 ° C., sufficient heat resistance, extremely high transparency, and relatively inexpensive thermoplasticity. Since it is a resin and a plant-derived material, it has attracted a great deal of attention.

  However, since the film made of polylactic acid has very hard and brittle properties as it is, when it is used for conventionally known applications such as food film and industrial film, the machine is made by biaxial stretching. It is necessary to give physical properties. However, polylactic acid-based polymers originally have a high melting point among biodegradable polymers and tend to impair heat sealability when molecular orientation or orientation crystallization progresses by biaxial stretching, and further improvements in heat sealability are required. It has been.

Patent Document 1 discloses that the difference (ΔHm) between the amount of heat of crystal fusion ΔHm when the film is heated and the amount of heat of crystallization ΔHc caused by crystallization during the temperature increase when the plane orientation index ΔP is 3.0 × 10 ⁻³ or more. -ΔHc) is a package formed by fusing and sealing an oriented crystallized film made of a crystalline polylactic acid-based polymer, controlled to be 20 J / g or more and {(ΔHm-ΔHc) / ΔHm} to be 0.75 or more. A bag is disclosed. However, it was not excellent in flexibility as a packaging bag.

  Patent Document 2 discloses a technique of adding a plasticizer to impart flexibility to polylactic acid, and a film produced by this technique is imparted with flexibility without impairing transparency. . However, in order to obtain sufficient flexibility, it is necessary to add a large amount of a plasticizer. For this reason, there is a problem that the plasticizer tends to bleed out and impairs surface properties such as printability. Moreover, since there is also a problem that heat resistance is poor, it cannot be said that the film has suitability for a sealing machine when making a fusing sealing bag using a fusing sealing machine.

  In Patent Document 3, a polylactic acid polymer and a biodegradable aliphatic / aromatic polyester having a glass transition point Tg of 0 ° C. or lower are the main components, and [polylactic acid polymer] / [biodegradable fat]. Group / aromatic polyester] = 98/2 to 50/50, the tensile elongation in the MD direction of the biaxially stretched film is 100 to 200%, and the tensile elastic modulus is 3.0 GPa or less. A polylactic acid film excellent in fusing sealing performance is disclosed. However, when aliphatic / aromatic polyesters are mixed within the above range, the crystallinity increases and transparency is easily impaired. In particular, when biaxial stretching is performed, the decrease in transparency is remarkable due to crystallization and phase separation.

In Patent Document 4, a polylactic acid polymer and a biodegradable aliphatic polyester having a glass transition point Tg of 0 ° C. or lower are the main components, and polylactic acid polymer / biodegradable aliphatic polyester = 85/15. A transparent biodegradable bag obtained by fusing and sealing a laminated film of ˜50 / 50 is disclosed. However, when biaxial stretching was performed, crystallization and phase separation occurred, and transparency was not sufficient.
JP-A-9-77124 JP 2004-090522 A JP 2004-161925 A Japanese Patent Laid-Open No. 2004-082512

  The present invention solves the above-mentioned problems and provides a packaging bag excellent in film printability and film operability, and excellent in transparency, flexibility and seal strength.

  The inventors of the present invention have arrived at the present invention as a result of intensive studies to solve the above problems. That is, by adding a specific amount of a polylactic acid copolymer (B) containing a specific amount of a lactic acid component to polylactic acid (A), high transparency, flexibility and sealing properties can be imparted. And finding that the amount of lactide contained in the film is 0.5% by mass or less provides a packaging bag made of a polylactic acid-based film having excellent operability during film formation and excellent printability. It was.

  That is, the gist of the present invention is a resin composition containing 50 to 90 parts by mass of polylactic acid (A) and 10 to 50 parts by mass of a polylactic acid-based copolymer (B) containing 30 to 70% by mass of a lactic acid component. A polylactic acid-based biaxially stretched film comprising: a lactide amount of 0.5% by mass or less, a tensile modulus of 3.0 GPa or less, and a haze of 10% or less. This is a sealed packaging bag.

  The packaging bag of the present invention is a biaxially stretched polyacrylic acid (A) blended with a highly compatible polylactic acid copolymer (B) to maintain the inherent transparency of the polylactic acid film. Since a film is obtained, flexibility is imparted and surface printability is also excellent, and a packaging bag suitable for packaging foods, clothing, etc. using this film can be obtained. Moreover, since it is excellent in the operation stability at the time of film manufacture, it is industrially advantageous.

  The packaging bag of this invention can be manufactured with various sealing methods, and can obtain the sealing strength which is 15N / 15mm or more without a practical problem. In particular, it is excellent in suitability for a fusing and sealing machine, and if this method is used, it is possible to obtain a packaging bag with a more excellent appearance.

  Moreover, in the packaging bag of this invention, it is not necessary to dare to use a plasticizer, and if it does not use a plasticizer, printability will not be impaired by bleed-out.

  Furthermore, by making the surface specific resistance value LOG less than 14.0 as an antistatic property, the operability when printing on the film surface or making a bag is improved.

Hereinafter, the present invention will be described in detail.

  The packaging bag of this invention needs to be formed with the polylactic acid-type biaxially stretched film which consists of a resin composition which has polylactic acid (A) and a polylactic acid-type copolymer (B) as a structural component.

  The polylactic acid (A) is a poly L-lactic acid in which the structural unit of lactic acid is L-lactic acid, a poly D-lactic acid in which the structural unit is D-lactic acid, or a copolymer of L-lactic acid and D-lactic acid. Examples include poly DL-lactic acid or a mixture thereof. The weight average molecular weight is preferably in the range of 150,000 to 300,000, more preferably 160,000 to 200,000. When the weight average molecular weight of polylactic acid, which is the main component, is less than 150,000, the resulting film is inferior in mechanical properties. When the weight average molecular weight exceeds 300,000, the melt viscosity becomes too high and melt extrusion is difficult. It becomes.

  As for polylactic acid (A), crystalline polylactic acid and amorphous polylactic acid can be used in combination. However, in consideration of ensuring film formation stability and heat resistance by crystallization of polylactic acid, It is preferable to use it. The crystalline polylactic acid as used herein refers to a polylactic acid resin having a melting point in the range of 140 to 175 ° C., and the amorphous polylactic acid refers to a polylactic acid resin that does not substantially have a melting point. The blending ratio of crystalline polylactic acid and amorphous polylactic acid is in the range of (crystalline polylactic acid) / (amorphous polylactic acid) = 80/20 to 100/0 (mass%) by mass ratio. Is preferred. When the blending ratio of the crystalline polylactic acid and the amorphous polylactic acid is within this range, the seal portion is easily stretched and stress concentration is unlikely to occur. If the blending ratio of the crystalline polylactic acid is less than 80% by mass, stable film formation cannot be performed because the polylactic acid is inferior in crystallization.

  The polylactic acid copolymer (B) needs to contain 30 to 70% by mass of a lactic acid component. When the lactic acid component exceeds 70% by mass, it is necessary to use a large amount of the polylactic acid copolymer (B) in order to impart flexibility of the resulting film, which is not preferable. When the lactic acid component is less than 30% by mass, the compatibility between the polylactic acid (A) and the polylactic acid copolymer (B) is lowered, and the transparency of the resulting film is deteriorated, which is not preferable.

  The lactic acid component constituting the polylactic acid-based copolymer (B) may be any of L-lactic acid, D-lactic acid, and DL-lactic acid, but the lactic acid resin that is the main component of the polylactic acid (A). Those having the same structure as the structural unit are particularly preferred.

  The copolymer component other than the lactic acid component is preferably a polyester composed of a dicarboxylic acid and a diol, or a polyether.

  The dicarboxylic acid component constituting the polyester is not particularly limited, but oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, dimer acid, terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalene Examples include dicarboxylic acid, 5-sodium sulfoisophthalic acid, maleic anhydride, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, cyclohexanedicarboxylic acid and other dicarboxylic acids, 4-hydroxybenzoic acid, and ε-caprolactone. Can do. A dicarboxylic acid having 10 or less carbon atoms is preferable from the viewpoint of compatibility with polylactic acid.

  The diol component constituting the polyester is not particularly limited, but ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, Examples include 1,6-hexanediol, cyclohexanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene oxide adducts of bisphenol A and bisphenol S, and the like. In view of compatibility with polylactic acid, glycol having 10 or less carbon atoms is preferred.

  Examples of the polyether include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. The weight average molecular weight of the polyether is preferably 200 to 5,000. Within this range, flexibility can be imparted to polylactic acid without lowering the compatibility with polylactic acid.

  The polylactic acid copolymer (B) may further contain a small amount of a trifunctional compound such as trimellitic acid, trimesic acid, pyromellitic acid, trimethylolpropane, glycerin, and pentaerythritol.

  Two or more of the above-mentioned copolymerization components in the polylactic acid copolymer (B) may be used in combination.

  The weight average molecular weight of the polylactic acid copolymer (B) is preferably in the range of 10,000 to 100,000, more preferably 20,000 to 80,000. When the weight average molecular weight is less than 10,000, not only the strength of the resulting film is remarkably lowered, but also the melt viscosity difference is too large when the film is formed, and the kneadability may be poor. On the other hand, if the weight average molecular weight exceeds 100,000, the softening effect of the polylactic acid-based copolymer (B) is lowered, and sufficient flexibility may not be imparted to the resulting packaging bag.

  In consideration of flexibility, the glass transition temperature of the polylactic acid copolymer (B) is preferably 40 ° C. or less, and more preferably in the range of 0 to 30 ° C.

  The blending ratio of the polylactic acid (A) and the polylactic acid copolymer (B) is (polylactic acid (A)) / (polylactic acid copolymer (B)) (parts by mass / 90 parts by mass). It is necessary to be in the range of 10-50 / 50, 85 / 15-60 / 40 is preferable, and 85 / 15-70 / 30 is a more preferable range. If the polylactic acid (A) component exceeds 90 parts by mass, the stiffness of the film becomes too strong, that is, the tensile elastic modulus of the film becomes high, so stress concentrates on the seal part and bag breakage tends to occur. When the polylactic acid (A) component is less than 50 parts by mass, the operability including stretchability and slipperiness deteriorates, and the film easily stretches too much. Invite defects.

  The resin composition obtained from the polylactic acid (A) and the polylactic acid copolymer (B) preferably has a weight average molecular weight of 100,000 or more, more preferably 120,000 to 200,000. When the weight average molecular weight is less than 100,000, the strength may be inferior when used as a packaging material.

  In the present invention, the amount of lactide contained in the polylactic acid-based biaxially stretched film is required to be 0.5% by mass or less, and preferably 0.1 to 0.4% by mass. When the amount of lactide exceeds 0.5% by mass, smoke generation during film formation is remarkable, and equipment near the die is contaminated. In severe cases, the film is transferred to the film surface via a cast roll. Gets worse.

  As a method for reducing the amount of lactide, when polymerizing the polylactic acid (A) or the polylactic acid copolymer (B), it is removed by reducing the pressure at a temperature equal to or higher than the melting point, or polylactic acid (A) or polylactic acid. Examples include a method of gasifying and removing the pellets after polymerization of the system copolymer (B) under high temperature and reduced pressure, and a method of extracting and removing by immersion in warm water.

  The polylactic acid biaxially stretched film used in the present invention preferably has a glass transition temperature of 40 to 55 ° C. From the viewpoint of flexibility, the glass transition temperature is preferably low, but in the present invention, it is not preferable to lower it to less than 40 ° C. When the glass transition temperature is lowered, the cast roll temperature during film formation needs to be lowered accordingly, but in the case of a polylactic acid resin, there are problems such as precipitation of lactide on the film surface and adhesion to the cast roll. Therefore, the temperature of the cast roll is preferably 30 ° C. or higher, and accordingly, the glass transition temperature is preferably 40 ° C. or higher. On the other hand, when the glass transition temperature exceeds 55 ° C., the softening effect of the polylactic acid film is small.

  The melting point of the polylactic acid biaxially stretched film used in the present invention is preferably 140 ° C. or higher, and particularly preferably 150 ° C. or higher. If the melting point is less than 140 ° C., heat resistance may be insufficient when heat treatment such as sealing at the time of bag making, printing or laminating is required.

  In addition, the resin composition constituting the polylactic acid-based biaxially stretched film is used in combination with a crosslinking agent such as an organic peroxide and a crosslinking aid for the purpose of suppressing a decrease in melt tension during film formation. Then, the resin composition may be subjected to slight crosslinking.

  The polylactic acid-based biaxially stretched film constituting the packaging bag of the present invention preferably has antistatic properties. Polylactic acid resin is highly hydrophobic and has the property of being easily charged. Therefore, after forming it into a film, it is given antistatic properties in order to avoid static electricity trouble when it is used for secondary processing such as printing and bag making. Is important. More specifically, when the film is charged, the roll is likely to be wound or wrinkled during roll running such as winding of the film, slitting, and subsequent printing and bag making. Further, ink repels at the time of printing, is scattered when the contents are packaged in the package, and the contents and debris other than the contents are attached to the inside and outside of the package. In addition, when the charging is severe, a spark due to static electricity may occur during roll running. As an index for imparting antistatic properties, the surface specific resistance value LOG is preferably less than 14.0 [Ω]. By setting the surface specific resistance value LOG to less than 14.0, it is possible to suppress various problems derived from charging as described above, and improve operability during secondary processing such as bag making and printing.

  Examples of the method for imparting antistatic properties to the film include a method in which an antistatic agent is kneaded into the resin constituting the film, or a method in which an antistatic agent is coated on the film surface, and is not particularly limited in the present invention. The method is a preferable method because it is not necessary to coat and can simplify the production process, and there is no deterioration in the working environment derived from the coating, and there are no quality problems such as interference fringes and blocking.

  As an antistatic agent used in the kneading method, an anionic or cationic ionic type and a nonionic type can be used, but if an ionic antistatic agent is used for polylactic acid, it is thermally decomposed in an extruder. There is a problem that the molecular weight is lowered, and in particular, although a cationic system can obtain a high antistatic effect even in a small amount, it is extremely difficult to use due to a significant decrease in molecular weight due to thermal decomposition. Therefore, in the present invention, it is preferable to use a nonionic antistatic agent. The amount of the antistatic agent kneaded is suitably in the range of about 0.1 to 5.0 parts by mass per 100 parts by mass of the resin composition constituting the film.

  Nonionic antistatic agents include fatty acid amines or amides. In particular, the combined use of an aliphatic amine or amide and a reaction product of a higher fatty acid ester and boric acid (hereinafter referred to as boric acid ester) is preferable. By using a fatty acid amine or amide in combination with a boric acid ester, a high antistatic effect can be obtained with a small amount while suppressing a decrease in the molecular weight of polylactic acid.

  The aliphatic amine or amide fatty acid has 1 to 30 carbon atoms, preferably one or more fatty acids having 8 to 30 carbon atoms, but is not particularly limited.

  The boric acid ester is obtained by esterifying a polyhydric alcohol and a higher fatty acid to obtain a higher fatty acid ester and then reacting it with boric acid. Polyhydric alcohols used in higher fatty acid esters include glycerin, diglycerin, triglycerin, polyglycerin, arabitol, sorbitol, pentaerythritol, glucose, lactose, monosaccharides, or ethylene glycol, propylene glycol, butylene glycol, etc. Although it is mentioned, it is not specifically limited. The higher fatty acid has 1 to 30 carbon atoms, may be a saturated fatty acid or an unsaturated fatty acid, and may be linear or branched, but preferably has 8 to 24 carbon atoms. The amount of boric acid added is preferably 0.1 to 2.0 mol, particularly preferably 0.5 to 1.0 mol, relative to 1 mol of the higher fatty acid ester. When the amount of boric acid added is large and the amount of unreacted residue is large, it bleeds out during storage of the stretched film and turns into white powder.

  The blending ratio of the aliphatic amine or amide (a) and the boric acid ester (b) is preferably 30 to 90/70 to 10% by mass, particularly 50 to 80/50 to 20% by mass in (a) / (b). preferable. When the aliphatic amine or amide is less than 30% by mass, the antistatic performance when the stretched film is formed is inferior, and when it is 90% by mass or more, the molecular weight may decrease.

  When a mixture of an aliphatic amine or amide and a borate ester is used, 0.1 to 3.0 parts by mass, preferably 0.5 to 2.0 parts by mass are added per 100 parts by mass of the resin composition constituting the film. Is preferred. By setting the addition amount in this range, the surface specific resistance LOG can be made less than 14.0 [Ω], and good antistatic properties are imparted.

  In addition, the resin composition constituting the polylactic acid-based biaxially stretched film used in the present invention includes an ultraviolet ray preventive agent, a light stabilizer, an antifogging agent, an antifogging agent, a flame retardant, a color preventing agent, an oxidation agent, depending on the application Additives other than the above, such as inhibitors, fillers and pigments, can also be added.

  Next, the manufacturing method of the polylactic acid-type biaxially stretched film which comprises the packaging bag of this invention is demonstrated.

  The method for forming the resin composition into a film is not particularly limited, and examples thereof include a T-die method, an inflation method, a calendar method, and the like. Among these, the T-die method is preferable. In the T-die method, a resin composition containing polylactic acid (A) and a polylactic acid copolymer (B) is supplied to an extruder hopper, melted and kneaded, extruded, and cooled by a cast roll. A sheet is obtained. At this time, as temperature conditions, the cylinder temperature is suitably 180 to 250 ° C., and the T die temperature is suitably 200 to 250 ° C. The cast roll is suitably controlled at 20 to 40 ° C. According to this method, an unstretched sheet having a thickness of 100 to 600 μm is obtained.

  A biaxially stretched film is obtained by biaxially stretching an unstretched sheet. Examples of the stretching method include a roll method and a tenter method, and either a sequential biaxial stretching method or a simultaneous biaxial stretching method may be employed. Moreover, it is preferable that the surface magnification in biaxial stretching is 6 to 16 times. If the surface magnification is less than 6 times, the mechanical properties of the resulting film, particularly the tensile strength, is low and may not be practically used. On the other hand, if the surface magnification exceeds 16 times, the film may not be able to withstand the stretching stress during stretching and may be broken.

  The thickness of the obtained stretched film is preferably 10 to 50 μm. When the thickness is less than 10 μm, the packaging bag is not stiff, and when it is thicker than 50 μm, it is disadvantageous in terms of cost, which is not preferable.

  As extending | stretching temperature, 50-90 degreeC is preferable and 60-80 degreeC is further more preferable. When the stretching temperature is less than 50 ° C., the film is broken at the initial stage of stretching due to insufficient heat for stretching. On the other hand, when the temperature exceeds 90 ° C., heat is excessively applied to the film, and draw stretching tends to occur, resulting in frequent occurrence of stretch spots.

  A coating agent can also be coated on the unstretched sheet before the stretching step, if necessary. The coating method is not particularly limited, and examples include gravure roll coating, reverse roll coating, wire bar coating, lip coating, air knife coating, curtain flow coating, spray coating, and dip coating.

  Moreover, you may implement a thermal relaxation process after extending | stretching in order to provide dimensional stability to a biaxially stretched film. As a method of thermal relaxation treatment, a method of blowing hot air, a method of irradiating infrared rays, a method of irradiating microwaves, a method of contacting on a heat roll, etc. can be selected, and a method of blowing hot air in that it can be heated uniformly and accurately Is preferred. In that case, it is preferable that it is 1 second or more in the range of 80-160 degreeC, and it is preferable to implement on the conditions of a 2-8% relaxation rate.

  Even if the film of the present invention is a single layer, a good package can be obtained, but other resins may be laminated in accordance with the contents, the storage method, and the bag making method. Examples of the lamination method include coating, direct lamination, extrusion lamination, and the like, and can be appropriately selected according to required performance.

  Next, a packaging bag is manufactured using the obtained polylactic acid type biaxially stretched film.

  Various automatic bag making machines are used for making a film. Examples thereof include various automatic bag making machines such as a side weld automatic bag making machine, a three-way press seal automatic bag making machine, a press center seal automatic bag making machine, and a side seal automatic bag making machine. By these bag making machines, bags such as various standard bags, carrying bags, shopping bags and the like are produced at high speed. A film made by a bag making machine is folded into one side and heat-sealed in two directions or heat-sealed in three directions without being folded into a bag for storing a storage object in a plane.

  As a bonding method in bag making, a heat sealing method, an impulse sealing method, a fusing sealing method, an impulse fusing sealing method, an ultrasonic sealing method, a high frequency sealing method, or the like is used. Of these, the heat sealing method, the impulse sealing method, and the fusing sealing method are generally used. The polylactic acid-based biaxially stretched film of the present invention can use each of the above-mentioned sealing methods and has a good sealing strength, but when performing a treatment involving crystallization such as stretching, the impulse sealing method, the fusing sealing method, the impulse fusing Sealing method, ultrasonic sealing method and high frequency sealing method can be used. The sealing strength in the packaging bag is generally good if it is 15 N / 15 mm or more, and it is considered that there is no problem in practical use. This sealing strength can be achieved by any of the above methods.

  Among the sealing methods described above, the fusing seal has a neat appearance because the fused portion (seal portion) has no width and a linear appearance, and the fusion remains in a very narrow local area. This is a preferable sealing method because the coalescence can be sufficiently melted and the film characteristics are hardly adversely affected. The fusing and sealing temperature varies depending on the melting point of the polymer and the fusing and sealing time, but a range of 180 to 400 ° C. is suitable.

  In the fusing seal, the angle of the tip of the fusing blade greatly affects the bag-making property. In general, if the tip angle is acute, the film can be cut smoothly, but the sealing strength is weakened. Conversely, if the tip angle is obtuse, the film is difficult to cut, but the sealing strength is increased. When fusing and sealing a lactic acid polymer film as in the present invention, the angle of the tip of the fusing blade is preferably 45 degrees or more and 120 degrees or less, more preferably 60 degrees or more and 90 degrees or less.

  In manufacturing a packaging bag, a conventionally known method can be applied without hindrance. For example, a long oriented crystallized film can be fed in two layers or fed as a half-folded film folded from the center and sealed with a rotating ring-shaped sealing blade, a heating wire that moves up and down, or a fusing blade. it can. Further, the packaging bag can be made in advance with one side opening and the contents can be packed later, or the contents can be packed simultaneously with the bag making. Moreover, if it is a small quantity, it can also package, making a bag manually using what is called an L-type sealer.

  As for the form of the packaging bag, it is usual to seal three sides (before storing the contents) or four sides (after storing the contents) around the bag, but the peelable adhesive on the opening side for storing the contents Agents can also be used. Alternatively, the film can be sealed in the length direction to form a cylinder, and twisted 90 degrees so that the seal comes to the center.

  The obtained packaging bag has a high strength at its sealing part as described above, and has a good appearance with reduced wrinkles due to heat shrinkage, so that it can be used as a packaging bag for food, clothing, various prizes, etc. It can be used suitably.

  Hereinafter, the present invention will be specifically described based on examples.

  The raw materials of the film and the method for measuring the characteristic values in the examples and comparative examples are as follows.

(material)
(A) Polylactic acid 4032D manufactured by Nature Works, D-form content 1.2 mol%, residual lactide amount 0.22 mass%, weight average molecular weight 200,000.
(B) Polylactic acid copolymer (B-1): Dainippon Ink Pramate PD350, lactic acid component content 50 mass%, melting point 158 ° C., glass transition temperature 18 ° C., weight average molecular weight 50,000, lactide content 2.02 mass%.
(B-2): B-1 was heat-treated at 110 ° C. under a reduced pressure of 0.5 mmHg or less for 24 hours to reduce the lactide amount to 0.54% by mass.
(C) Polyester (C-1): Bionore # 3001, manufactured by Showa Polymer Co., Ltd., melting point 95 ° C., glass transition temperature −45 ° C. It is an aliphatic polyester that does not contain a polylactic acid component.
(C-2): Ecoflex F manufactured by BASF, melting point 105, glass transition temperature -30 ° C. It is an aliphatic-aromatic polyester containing no polylactic acid component.
(D) Plasticizer RIKEN Vitamin Co., Ltd. Poem G-038
(E) Antistatic agent (E-1): Palm oil diethanolamide (Semiyo Kasei Chemistat 2500)
(E-2): Reaction product of glycerin stearic acid ester and boric acid A glass autoclave was charged with 1.0 mol of glycerin and 1.0 mol of stearic acid, and while introducing N ₂ gas, under a basic catalyst, The temperature was raised to 220 to 250 ° C. and esterification was performed for 5 hours to synthesize glycerin monostearate. Subsequently, 0.5 mol of boric acid is added to 1.0 mol of the glycerin monostearate ester synthesized, gradually heated and dehydrated to 130 to 135 ° C., and then gradually heated to 230 ° C. A reaction product of monostearic acid ester and boric acid was obtained.

(Measurement method)
(1) Lactide amount Measured using HP-6890 Series GC System manufactured by Hewlett Packard Co. and column 30m × 0.25mm ID DB-17 capillary column (0.25 μm ft.) As a carrier gas. .
(2) Weight average molecular weight GPC apparatus LC-VP manufactured by Shimadzu Corporation was used as the eluent tetrahydrofuran, and measurement was performed at a temperature of 40 ° C. and a flow rate of 1 mL / min to obtain a molecular weight distribution curve. The molecular weight was evaluated in terms of polystyrene based on a calibration curve using 6 standard polystyrene samples having a molecular weight in the range of 1,000 to 3,000,000.
(3) Melting point, glass transition temperature (° C)
Using a differential scanning calorimeter DSC-7 manufactured by Perkin Elmer, the heating rate was measured at 20 ° C./min.
(4) Extrusion operability After the continuous film formation for 3 hours, the contamination near the T-die, the state of smoke generation, and the degree of dirt on the cast roll were visually evaluated according to the following criteria.
○: There is little contamination and smoke generation, and the cast roll is not soiled.
Δ: Slightly contaminated / smoke occurred, and cast roll was slightly dirty.
X: Contamination / smoke occurred and the cast roll was dirty.
(5) Haze (transparency)
It measured according to JIS-K7105. In the present invention, 10% or less was accepted. It is more preferable in practical use to be 5% or less.
(6) Tensile modulus (GPa), tensile strength (MPa) and tensile elongation (%)
The measurement was performed according to the method described in JIS K-7127.
(7) Bleed property The stretched film was left in an atmosphere of 50 ° C. and 40% RH for 30 days, and judged according to the following criteria.
○: No bleed out was observed.
Δ: Slightly bleed out was observed, but there was no practical problem.
X: Bleed-out was noticeable.
(8) Surface resistivity value:
The film after production was allowed to stand at 23 ° C. and 50% RH for 1 day, and then measured according to JIS-K6911.
(9) Printability After printing on the corona-treated surface of the film with a flexographic printing machine, the film was dried with hot air at 40 ° C. The printing state was visually observed in a range of 3 m in length, and then a cellophane tape having a width of 15 mm and a length of 50 mm was applied to the printing surface of the normal part, and then the cellophane tape was peeled off, and judged according to the following criteria. .
◎: No print missing visually, and no ink was peeled off by tape peeling ○: Printing missing was observed visually, but no ink was peeled by tape peeling ×: Ink was removed by tape peeling Peeled off (10) Fusing seal strength Using a three-way side seal machine (HK-40V manufactured by Totani Giken Kogyo Co., Ltd.) equipped with a hot blade with a blade angle of 90 °, with a seal temperature of 380 ° C., a pitch of 200 mm, and a shot number of 100 rpm A test piece having a seal width of 15 mm was cut out from the sealed portion of the bag made and subjected to a tensile test by 180 ° peeling at a tensile speed of 300 mm / min.
(11) Evaluation of packaging bag A packaging bag was produced by the method described in (10) above, and a product with a good seal portion appearance was marked with ◯, and a wrinkle or whiskers with poor appearance was marked with ×.
(12) Comprehensive evaluation The above evaluation items were comprehensively evaluated and evaluated according to the following criteria.
○: There is no problem in each evaluation item, and it is an excellent practical level.
X: There is at least one problem of each evaluation item, and it is not a practical level.

Example 1
After weighing 85% by mass of A and 15% by mass of B-2, they are dry blended and melt-extruded at a T-die temperature of 230 ° C using a 90mmΦ single-screw extruder, and closely attached to a cast roll whose temperature is controlled at 35 ° C. After cooling, an unstretched sheet having a thickness of 240 μm was obtained. Next, the end of the unstretched film was held by a clip of a tenter type simultaneous biaxial stretching machine, and after running through a preheating zone at 70 ° C., the temperature was 68 ° C. and 3.0 times MD and 3.3 TD. At the same time biaxial stretching. Then, after a heat treatment for 4 seconds at a temperature of 140 ° C. with a TD relaxation rate of 5%, the film was cooled to room temperature and wound up to obtain a biaxially stretched film having a thickness of 25 μm. The obtained biaxially stretched film was evaluated by the measuring methods (1) to (12).

Examples 2-5, Comparative Examples 1-6
The raw material resins and additives were changed as shown in Table 1, and various films were obtained in the same manner as in Example 1.

As shown in Examples 1 to 5, those in the range specified by the present invention have high transparency with a haze of 5% or less, excellent elasticity with a tensile modulus of 3.0 GPa or less, and made of a film. It was a packaging bag with excellent printability with little change in storage performance such as operability during filming and bleeding.

  As shown in Examples 4 and 5, the addition of an antistatic agent reduces the surface resistivity, and in particular, the antistatic agent having the composition used in Example 4 reduces the molecular weight and other performances of the film. It was possible to impart an antistatic effect without causing it to occur. On the other hand, in Example 5, since the content of the fatty acid amide in the antistatic agent was large, the molecular weight of the film was lowered, and the strength was lowered accordingly. Moreover, since the surface specific resistance value was falling in Examples 4 and 5, compared with Examples 1-3, there was no omission of printing due to the chargeability, and the printability was excellent.

  In Comparative Example 1, since the addition amount of the polylactic acid copolymer (B) was small, the flexibility of the film was inferior, and the obtained packaging bag was also inferior in the fusing seal strength.

  In Comparative Example 2, since the amount of lactide in the film was large, the operability was inferior, and wrinkles and whiskers were generated at the time of fusing sealing, and the appearance of the packaging bag was not excellent.

  In Comparative Example 3, because the polylactic acid copolymer (B) was added in a large amount, the film was excellent in flexibility and the resulting packaging bag was excellent in fusing seal strength. Beard was generated and the appearance of the packaging bag was not excellent. Furthermore, the molecular weight of the film was low, and the tensile strength did not reach a practical level.

  In Comparative Example 4, since the addition amount of the polylactic acid copolymer (B) was small, flexibility was imparted with a low molecular plasticizer, but the obtained packaging bag was inferior in bleed property and excellent in printability. There wasn't.

  In Comparative Example 5, since an aliphatic polyester not containing a polylactic acid component was used instead of the polylactic acid copolymer (B), the compatibility with polylactic acid (A) was poor, and the resulting packaging bag was Although it had excellent fusing seal strength and flexibility, it had high haze and was inferior in transparency.

In Comparative Example 6, since an aliphatic-aromatic polyester not containing a polylactic acid component was used instead of the polylactic acid copolymer (B), the compatibility with polylactic acid (A) was poor, and the resulting packaging Although the bag was excellent in fusing seal strength and flexibility, it had high haze and was inferior in transparency.

Claims (4)

A polylactic acid-based resin composed of a resin composition containing 50 to 90 parts by mass of polylactic acid (A) and 10 to 50 parts by mass of a polylactic acid copolymer (B) containing 30 to 70% by mass of a lactic acid component. A packaging bag formed by sealing a polylactic acid biaxially stretched film which is an axially stretched film and has a lactide amount of 0.5% by mass or less, a tensile elastic modulus of 3.0 GPa or less, and a haze of 10% or less. The packaging bag according to claim 1, wherein the sealing method is a fusing seal. The packaging bag according to claim 1, wherein the sealing strength is 15 N / 15 mm or more. The packaging bag according to claim 1, wherein the surface specific resistance LOG is less than 14.0 [Ω].