JP4411522B2 - Polylactic acid composition - Google Patents

Description

  The present invention relates to a polylactic acid composition excellent in heat resistance, impact resistance, flexibility, and gas barrier properties, and further relates to a molded article made of this composition.

  Polylactic acid, which can be synthesized from natural raw materials such as corn and has excellent transparency, biodegradability, and moldability, has attracted attention as an environmentally friendly resin, especially a molding resin. However, there are problems with brittleness and workability, so the industrial use is limited.

  As a method for improving these problems, for example, it has been reported that a biodegradable polyester resin composition containing polylactic acid, layered silicate and polyethylene glycol is excellent in mechanical strength and heat resistance ( For example, see Patent Document 1.)

  However, the biodegradable polyester resin composition is still not sufficient in terms of heat resistance, and depending on the composition ratio of the biodegradable polyester resin composition, the heat resistance of the composition may be significantly reduced. May cause. In addition, polyethylene glycol may bleed out from the surface of a molded product obtained using the biodegradable polyester resin composition. Also,

JP 2002-363393 A (Claim 1, paragraphs “0018” and “0030”)

An object of the present invention is to provide heat resistance, impact resistance, excellent flexibility, provides a bleed polylactic acid composition out capable to inhibit and molded product obtained by using the same from the surface of the molded product That is.

  The present inventors suppress the bleed out by using a block copolymer obtained by copolymerizing these in the presence of a layered silicate instead of a conventional mixture of polylactic acid and polyethylene glycol, The present inventors have found a polylactic acid composition that does not cause a significant decrease in heat resistance.

  That is, the present invention provides a weight average molecular weight obtained by copolymerizing a polyether polyol (I) having a weight average molecular weight of 500 to 250,000 and lactide (II) or polylactic acid (II ′) in the presence of a layered silicate. A polylactic acid composition comprising lactic acid block copolymer (IIIa) having 3000-250,000 and polylactic acid (IV), preferably the polylactic acid (IV) is modified with an acid anhydride Preferably, the weight ratio of the lactic acid block copolymer (IIIa) to the polylactic acid (IV) is from 3:97 to 50:50, and preferably has a Vicat softening point temperature of 70 ° C. or higher. Lactic acid composition.

  The present invention also provides a weight average molecular weight of 3000 obtained by copolymerizing a polyether polyol (I) having a weight average molecular weight of 500 to 250,000 and lactide (II) or polylactic acid (II ′) in the presence of carbon nanotubes. A polylactic acid composition comprising lactic acid block copolymer (IIIb) having a molecular weight of ˜250,000 and polylactic acid (IV), preferably the polylactic acid (IV) modified with an acid anhydride Preferably, the weight ratio of the lactic acid block copolymer (IIIb) to the polylactic acid (IV) is 3:97 to 50:50, and preferably has a Vicat softening point temperature of 70 ° C. or higher. It is a composition.

  The present invention also relates to a molded product obtained using the polylactic acid composition.

  The polylactic acid composition of the present invention is excellent in heat resistance and hardly causes bleed-out, and can exhibit excellent impact resistance, flexibility and gas barrier properties.

  The layered silicate is used for the purpose of improving the heat resistance, gas barrier property and mechanical strength of the polylactic acid composition. Polylactic acid is a polymer that is usually very slow to crystallize. For example, when molding with a mold heated to 70 to 130 ° C., it takes a long time to crystallize sufficiently. Further, when the temperature of the mold is cooled to room temperature or lower, the resulting molded product becomes amorphous. The polylactic acid composition of the present invention nanocomposited using a layered silicate has a high crystallization rate, and crystallization is sufficient when molded with a mold heated to a crystallization temperature (70 to 130 ° C.). It progresses and a molded article can be manufactured in a short time.

  The heat resistance temperature of the polylactic acid composition not using layered silicate, that is, Vicat softening point temperature, was 45 ° C. to less than 70 ° C., but can be improved to 70 ° C. or more by adding layered silicate, Can be improved to 100 ° C. or higher by adjusting the composition of the lactic acid block copolymer, the type and content of the layered silicate, the molding time, and the like. Furthermore, when layered silicate is used from the early stage of the production stage of lactic acid block copolymer (III), which will be described later, and layered silicate is dispersed, it is more efficient and finer than when blending layered silicate directly with polylactic acid. It is possible to disperse, and the amount of layered silicate used can impart at least excellent heat resistance. Accordingly, the loss of transparency can be suppressed.

  Moreover, gas barrier property can be provided to the polylactic acid composition of this invention by using layered silicate. The gas barrier property referred to here is a gas barrier property such as oxygen, nitrogen, carbon dioxide, water vapor, and the like, and its permeability can be reduced to about 1/2 to 1/5 when the layered silicate is not used. This is manifested by the so-called “detour theory” effect.

  In the detour theory, the finely dispersed layered silicate blocks a gas molecule permeation path, and the distance until the gas molecule permeates is increased by trying to bypass it.

  The layered silicate can impart a mechanical strength equal to or higher than that in the case of using a reinforcing material such as talc or glass fiber to the polylactic acid composition. The layered silicate is nano-sized and smaller than talc or glass fiber, and can have a functional group, so it can have a more complex structure with the polymer chain.

  As the layered silicate, for example, a 2: 1 type structure in which a single plate-like crystal layer is formed by overlapping a silicic acid tetrahedron sheet on top and bottom of an octahedron sheet containing elements such as aluminum, magnesium, and lithium. It is preferable to have an exchangeable cation between the plate-like crystal layers. The size of the plate-like crystal layer is preferably 0.05 to 0.5 μm in width and 6 to 15 Å in thickness.

  The cation exchange capacity of the exchangeable cation is preferably 0.2 to 3 meq / g, more preferably 0.8 to 1.5 meq / g.

  Specific examples of the layered silicate used in the present invention include, for example, smectite clay minerals such as montmorillonite, beidellite, nontronite, saponite, hectorite, and soconite, vermiculite, halloysite, kanemite, kenyanite, zirconium phosphate, and titanium phosphate. And various clay minerals, Li-type fluorine teniolite, Na-type fluorine teniolite, swellable mica such as Na-type tetrasilicon fluorine mica, Li-type tetrasilicon fluorine mica, and the like, which may be natural or synthesized. Among these, smectite clay minerals such as montmorillonite and hectorite, and swelling synthetic mica such as Na-type tetrasilicon fluorine mica and Li-type fluorine teniolite are preferable.

  The layered silicate is preferably subjected to an organic cation treatment in advance. In the organic cation treatment, the exchangeable cation of the layered silicate is ion-exchanged with the organic cation, thereby increasing the interlayer distance of the layered silicate, and improving the dispersibility of the layered silicate by delamination or intercalation of the polymer. It can be improved and a highly transparent polylactic acid composition can be produced.

  In the organic cation treatment, for example, an organic cation is added in the form of a salt to a dispersion of a layered silicate in water or alcohol, and the mixture is stirred and mixed to exchange the cation of the layered silicate with the organic cation. Then, it is a method of filtering, washing, and drying, and it is preferable to use a layered silicate that has been converted into an organic onium salt.

  Examples of the organic cation include primary or tertiary amines and salts thereof, quaternary ammonium salts, and organic phosphonium salts. Examples of the primary amine include octylamine, dodecylamine, octadecylamine and the like. Examples of the tertiary amine include trioctylamine, dimethyldodecylamine, didodecylmoomethylamine and the like. Examples of the quaternary ammonium ion include tetraethylammonium, octadecyltrimethylammonium, dimethyldioctadecylammonium, dihydroxyethylmethyloctadecylammonium, methyldodecylbis (polyethylene glycol) ammonium, methyldiethyl (polypropyleneglycol) ammonium and the like. Examples of organic phosphonium ions include tetraethylphosphonium, tetrabutylphosphonium, hexadecyltributylphosphonium, tetrakis (hydroxymethyl) phosphonium, 2-hydroxyethyltriphenylphosphonium, and the like. These organic cations may be used alone or in combination of two or more.

  As the layered silicate, those having a hydroxyl group or a carboxyl group are preferably used. A layered silicate having a hydroxyl group is preferable because it improves the affinity with the polyether polyol (I) and relaxes aggregation of the layered silicate. Moreover, the layered silicate having a carboxyl group can be bonded to the terminal hydroxyl group of the polyether polyol (I) and can be uniformly dispersed.

  The number of carbon atoms of the first and second organic onium salts that can be used in the present invention is preferably 6 or more. When the carbon number is 6 or more, the interlayer distance of the layered silicate can be sufficiently widened, and the dispersibility can be improved.

  The layered silicate is preferably used in an amount of 0.1 to 20% by weight with respect to the polylactic acid composition of the present invention, more preferably in the range of 0.5 to 10% by weight, and 1 to 5% by weight. The range of is more preferable. By using in such a range, it is possible to obtain a sufficient effect of promoting the crystallization speed, further facilitates molding, does not cause a decrease in the molecular weight of the polylactic acid composition component, and stability of mechanical properties over a short period and a long period. However, in view of the transparency of the polylactic acid composition of the present invention, it is preferably as small as possible.

  The layered silicate is used in the process of reacting the later-described polyether polyol (I) with lactide (II) or polylactic acid (II '). By using the layered silicate in such a process, finer dispersion can be achieved than in the case where the lactic acid block copolymer (III) and the layered silicate are mixed as in the prior art.

  The layered silicate may be used again after polymerizing the lactic acid block copolymer (III). It can also be used again when melt blending lactic acid block copolymer (III) and polylactic acid (IV). In that case, since it is difficult to uniformly disperse the layered silicate in the polylactic acid composition at a nano level, there is a device such as using a screw with high kneading ability or increasing the number of revolutions if it is a twin screw extruder. is necessary.

  Next, the carbon nanotube that can be used in the present invention will be described.

  Carbon nanotubes are used for the purpose of improving the heat resistance, gas barrier properties and mechanical strength of the polylactic acid composition of the present invention, as in the case of the above-mentioned layered silicate. Functions such as electrical conductivity, thermal conductivity, and electromagnetic wave shielding properties can be imparted to the polylactic acid composition of the present invention.

  Polylactic acid is a polymer that is usually very slow to crystallize. For example, when molding with a mold heated to 70 to 130 ° C., it takes a long time to crystallize sufficiently. Further, when the temperature of the mold is cooled to room temperature or lower, the resulting molded product becomes amorphous. The polylactic acid composition of the present invention nanocomposited using carbon nanotubes has a high crystallization speed, and crystallization proceeds sufficiently when it is molded with a mold heated to a crystallization temperature (70 to 130 ° C.). And a molded article can be manufactured in a short time.

  Carbon nanotubes are tube-shaped molecules with a diameter of 1 nm to several tens of nm and a length of about 0.1 to several μm, and there are single-wall type and multi-wall type depending on the number of wall layers forming a hollow structure. Any can be used in the invention. Carbon nanotubes have the advantages of being extremely fine and long, having high mechanical strength, excellent electrical conductivity, and high structural stability.

  Carbon nanotubes are usually in the form of a powder composed of a lump in which carbon nanotubes are entangled, and in order to disperse the carbon nanotubes, it is preferable to use those having functional groups on the surface of carbon nanotubes. The carbon nanotube having a functional group on the surface is a carbon nanotube having at least one kind of functional group on the outer surface of the carbon nanotube, and the kind of the functional group is not particularly limited, and examples thereof include a hydroxyl group, a carbonyl group, and a carboxyl group. , A nitro group, a sulfone group, an ether group, and the like.

  By using such carbon nanotubes, the functional groups present on the outer surface of the carbon nanotubes repel each other and the entangled carbon nanotubes are loosened. As a result, in the process of producing the lactic acid block copolymer (III) Dispersibility can be improved.

  Examples of the method for imparting a functional group to the surface of the carbon nanotube include a method using a carboxyl group generated at a site where the structure bond is broken, a method using high-temperature fluorine, a defect generation method using ultrasonic treatment in polymethyl methacrylate, an aromatic There are modification methods with group molecules, plasma treatment, etc.

  In the present invention, it is necessary to polymerize polyether polyol (I) and lactide (II) or polylactic acid (II ′) in the presence of carbon nanotubes. In this case, the resulting sulfuric acid block copolymer is obtained. When (III) coats the carbon nanotube surface, when the polylactic acid composition is used, the aggregation between the carbon nanotubes is suppressed, so the aggregation between the carbon nanotubes can be suppressed in the polylactic acid composition of the present invention, and melt kneading In the case of mechanical dispersion such as the above, excellent dispersibility can be expressed.

  Since the carbon nanotube has a high aspect ratio, it can be used in a small amount as compared with talc, glass fiber, and carbon black (for example, carbon fiber) as in the case of the layered silicate, and 0.1% with respect to the polylactic acid composition of the present invention. It is preferable to use it so that it may become -20 weight%, The range of 0.5-10 weight% is more preferable, The range of 0.5-5 weight% is further more preferable. By using in such a range, it is possible to obtain a sufficient effect of promoting the crystallization rate, further facilitates molding, does not cause a decrease in molecular weight of the polymer composition component, and stability of mechanical properties over a short period and a long period. However, in view of the transparency of the polylactic acid composition of the present invention, it is preferably as small as possible.

  Next, the polyether polyol (I) used in the present invention will be described.

  Examples of the polyether polyol (I) include those obtained by polymerizing alkylene oxides such as ethylene oxide, propylene oxide, and tetramethylene oxide. Specifically, polyethylene glycol, polypropylene glycol, polyethylene glycol and polypropylene are used. Examples include block copolymers such as glycol, polytetramethylene glycol, and the like. Among these, polyethylene glycol is most preferably used because it has the highest compatibility with polylactic acid (IV) described later, and can impart flexibility and transparency to the polylactic acid composition of the present invention. Polypropylene glycol is preferably used because it has a methyl group as a side chain and can impart impact resistance to the polylactic acid composition, and is also liquid at room temperature and has good transparency. Polytetramethylene glycol is preferably used because it has a long methylene chain and can impart an excellent plasticizing effect, that is, flexibility even at a low temperature of 0 ° C. or lower.

  The molecular weight of the polyether polyol (I) is 500 to 250,000 in terms of weight average molecular weight, considering the molecular weight of the polyether polyol (I) currently sold. The longer it is, the better the impact resistance is, and the shorter the flexibility, the lower the molecular weight, the easier it is to cause bleed-out, while the higher the molecular weight, the more dispersed the layered silicate or carbon nanotube. The properties are reduced and the physical properties are difficult to express. In view of these, the weight average molecular weight is preferably 1,000 to 100,000, more preferably 2,000 to 30,000, and still more preferably 2,000 to 20,000.

  Next, lactide (II) and polylactic acid (II ′) copolymerized with the polyether polyol (I) will be described.

  Lactide (II) is a compound in which two molecules of lactic acid are cyclic dimerized by dehydration condensation, and is a monomer having a stereoisomer, L-lactide comprising two molecules of L-lactic acid, and D- comprising two molecules of D-lactic acid. Examples include lactide and meso-lactide composed of D-lactic acid and L-lactic acid. A copolymer containing only L-lactide or D-lactide is crystallized and has a high melting point, and preferable resin characteristics can be realized by combining these three types of lactide in various proportions depending on the application. Further, when the constituent ratio of L-lactide and D-lactide in lactide (II) and the constituent ratio of D-lactic acid and L-lactic acid in polylactic acid (IV) are extremely different, for example, lactide (II) is D-lactide. When the polylactic acid (IV) is poly (L-lactic acid), the polylactic acid composition forms a stereocomplex, which is preferable because it has a high melting point and is excellent in heat resistance and mechanical properties.

  Polylactic acid (II ′) is poly (L-lactic acid) whose structural unit is L-lactic acid, poly (D-lactic acid) whose structural unit is D-lactic acid, and whose structural units are L-lactic acid and D-lactic acid. It refers to poly (DL-lactic acid) and mixtures thereof. Further, when the constituent ratio of D-lactic acid and L-lactic acid in polylactic acid (II ′) and the constituent ratio of D-lactic acid and L-lactic acid in polylactic acid (IV) are extremely different, for example, polylactic acid (II ′) Is poly (D-lactic acid) and polylactic acid (IV) is poly (L-lactic acid), the polylactic acid composition forms a stereocomplex, which has a high melting point and excellent heat resistance and mechanical properties. Therefore, it is preferable.

  The polylactic acid (II ') described above preferably has a weight average molecular weight of 50,000 to 400,000, more preferably 100,000 to 250,000. By using polylactic acid having a weight average molecular weight in such a range, it is possible to express practical physical properties such as mechanical properties and heat resistance, and further, since it has an appropriate melt viscosity, a lactic acid block copolymer excellent in molding processability ( III) can be obtained.

  Polylactic acid (II ′) is modified with an acid anhydride such as maleic anhydride, pyromellitic anhydride, or trimellitic anhydride for the purpose of improving compatibility with the layered silicate or carbon nanotube. May be. The addition amount of the acid anhydride is preferably 0.01 to 10% by weight, more preferably 0.05 to 5% by weight, and particularly preferably 0.1 to 3% by weight with respect to the polylactic acid (IV). . By adding an amount in such a range, the molecular weight of polylactic acid can be maintained and compatibility with the layered silicate or carbon nanotube can be expressed. There are various methods for the modification, but usually reactive processing using a twin screw extruder is used.

  For the polylactic acid (II ′), a small amount of chain extender, for example, a diisocyanate compound such as hexamethylene diisocyanate or toluene diisocyanate, an epoxy compound or the like can be used for the purpose of increasing the molecular weight.

  Next, the lactic acid block copolymers (IIIa) and (IIIb) used in the present invention (in the present invention, the lactic acid block copolymers (IIIa) and (IIIb) are combined together to form a “lactic acid block copolymer (III ) "And abbreviated.).

  Next, the lactic acid block copolymer (III) used in the present invention will be described. The lactic acid block copolymer (III) used in the present invention imparts impact resistance, flexibility and heat resistance to the polylactic acid composition of the present invention by adding to the polylactic acid (IV) described above. Which can be copolymerized with lactide (II) or polylactic acid (II ′) and polyether polyol (I) having a weight average molecular weight of 500 to 250,000 in the presence of layered silicate or carbon nanotube. A block copolymer comprising a polylactic acid segment and a polyether polyol segment. Here, it is important that the lactic acid block copolymer (III) used in the present invention is a block copolymer. When this is a random copolymer, there is no lactic acid block that is a compatible component with polylactic acid (IV), so the adhesion between the lactic acid block copolymer (III) of the present invention and polylactic acid is improved. The mechanism that suppresses the interfacial peeling is not effective, causes bleed-out, and also negatively improves the impact resistance.

  The weight average molecular weight of the lactic acid block copolymer (III) is 3000 to 250,000, preferably 10,000 to 250,000, more preferably 20000 to 200,000, still more preferably 30000 to 150,000. When the weight average molecular weight is less than 3000, it is difficult to impart impact resistance. When the weight average molecular weight exceeds 250,000, the melt viscosity is increased and the dispersibility in polylactic acid (IV) is deteriorated.

  The average chain length of the polylactic acid segment of the lactic acid block copolymer (III) is preferably as long as possible. However, in view of its production method, the lactic acid residue is essentially the lactic acid residue excluding the lactic acid hydroxyl group H and the carboxyl group OH. Is preferably 5 to 3000 units, more preferably 10 to 2000 units, still more preferably 50 to 1000 units, and still more preferably 100 to 1000 units. By preparing in such a range, the polylactic acid segment becomes more compatible with polylactic acid (IV), and the adhesion at the interface between the lactic acid block copolymer (III) and polylactic acid (IV) is improved. Interfacial peeling can be suppressed, and furthermore, bleeding out can be prevented and the viscosity can be maintained at an appropriate level. Therefore, the lactic acid block copolymer (III) can be uniformly dispersed in the polylactic acid (IV). In order to convert the above-mentioned unit into a number average molecular weight, the molecular weight of one unit of lactic acid residue is (72) × the number of units. For example, 10 units has a number average molecular weight of 720.

  Next, the weight ratio of the aforementioned lactide (II) or polylactic acid (II ′) to the polyether polyol (I) varies depending on how much impact resistance and flexibility are desired, but at least lactide. (II): Polyether polyol (I) or Polylactic acid (II ′): Polyether polyol (I) = 10: 90 to 90:10, preferably 25:75 to 70:30, More preferably, it is 30: 70-60: 40, More preferably, it is 40: 60-60: 40. By adjusting to such a range, bleeding out can be suppressed and impact resistance, flexibility, etc. can be sufficiently imparted. When you want to give a large impact resistance and flexibility, naturally it is desirable to increase the amount of polyether polyol (I).

Next, the manufacturing method of lactic acid-type block copolymer (III) is demonstrated. The production method is not particularly limited as long as it is a production method capable of obtaining a block copolymer composed of a lactic acid segment and a polyester segment.
(1) A method of reacting lactide (II) and polyether polyol (I) in the presence of a layered silicate or carbon nanotube using a polymerization catalyst,
(2) A method in which polylactic acid (II ′), polyether polyol (I), and layered silicate or carbon nanotube are melt-mixed and then dehydrated and polycondensed under reduced pressure in the presence of an esterification or transesterification catalyst.
(3) Add polylactic acid (II '), polyether polyol (I), layered silicate or carbon nanotube to high boiling point solvent, use transesterification catalyst, and perform azeotropic dehydration polycondensation, ie direct polymerization, under reduced pressure. Examples include a condensation reaction method.

  First, (1) a method for copolymerizing lactide (II) and polyether polyol (I) will be described. The reaction temperature is preferably 220 ° C. or lower, preferably 200 ° C. or lower, more preferably 190 ° C. or lower in terms of preventing the coloration and decomposition of lactide (II), and the presence of moisture in the reaction system is not preferable. The polyether polyol (I) needs to be sufficiently dried. Under such conditions, lactide (II) and polyether polyol (I) are mixed and dissolved at 100 ° C to 220 ° C. Under the present circumstances, you may use 1-30 weight part non-reactive solvent, such as toluene with respect to these total weight as needed. Furthermore, a polymerization catalyst (for example, tin octoate) is added and polymerized in an inert gas atmosphere such as nitrogen or argon at 140 to 220 ° C. with respect to the total amount of lactide and polyether polyol.

  As the polymerization catalyst, any of catalysts generally known as esterification catalysts, transesterification catalysts, and ring-opening polymerization catalysts can be used. For example, Sn, Ti, Zr, Zn, Ge, Co, Fe, Al, Mn, Examples thereof include alkoxides such as Hf, acetates, oxides and chlorides. Among these, tin powder, tin 2-ethylhexylate, dibutyltin dilaurate, tetraisopropyl titanate, tetrabutoxy titanium, titanium oxyacetylacetonate, iron (III) acetylacetonate, iron (III) ethoxide, aluminum isopropoxide, aluminum Acetylacetonate is preferred because of its fast reaction.

  Next, (2) a copolymerization method of polylactic acid (II ′) and polyether polyol (I) will be described. After melt-mixing polylactic acid (II ′) and polyester (I), a lactic acid block copolymer polyester (III) can be obtained by performing a reduced pressure polycondensation reaction in the presence of a catalyst. Before the polyester (I) is melt-mixed with the polylactic acid (II ′), it is preferable to remove the catalyst used in the synthesis of the polyester (I) or to deactivate the catalyst with a catalyst deactivator. The reason for this is that the residual active catalyst of polyester acts as a transesterification catalyst of polylactic acid, thereby excessively cutting the polylactic acid molecular chain, greatly reducing the molecular weight of polylactic acid at the start of polymerization, and obtained after completion of the polycondensation reaction. This is because the molecular weight of the resulting lactic acid block copolymer polyester (III) is unnecessarily lowered. When the polymerization temperature is too high, polylactic acid is decomposed into lactide by thermal decomposition, and is preferably 170 to 220 ° C, more preferably 180 to 210 ° C. The higher the degree of vacuum, the faster the polymerization proceeds, and it is preferably 2 kPa or less, more preferably 1 kPa or less, and even more preferably 0.5 kPa or less.

  As the polymerization catalyst, the same ones as described above can be used. Among them, tetraisopropyl titanate, tetrabutoxy titanium, titanium oxyacetylacetonate, iron (III) acetylacetonate, aluminum acetylacetonate, zirconium tetrachloride, zirconium tetrachloride, 2THF complex, hafnium chloride, hafnium chloride, 2THF complex Aluminum acetylacetonate, zirconium tetrachloride, zirconium tetrachloride, 2THF complex, hafnium chloride, tetrachlorohafnium, 2THF complex are more preferred because the resulting polymer is less colored. The amount of catalyst used is preferably 50 to 500 ppm of the total amount of polylactic acid and polyester.

  (3) A method of carrying out an azeotropic dehydration polycondensation reaction, that is, a direct polycondensation reaction under reduced pressure using a transesterification catalyst in the coexistence of polylactic acid (II ′), polyether polyol (I) and a high boiling point solvent is xylene The same conditions as in (2) except that a high boiling point solvent such as diphenyl ether is used. However, since it is necessary to finally remove the solvent as compared with (2), it is preferable to apply the method (1) or (2) as the production method.

  Furthermore, the storage stability of the lactic acid block copolymer (III) is further improved by extracting the polymerization catalyst with a solvent after the polymerization is completed, or by deactivating the polymerization catalyst with the catalyst deactivator described above. Can be made.

  As such a catalyst deactivator, chelating agents and / or acidic phosphates are particularly preferable. Although it does not specifically limit as a chelating agent, For example, ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid disodium, oxalic acid, phosphoric acid, pyrophosphoric acid, alizarin, acetylacetone, diethylenetriaminepentaacetic acid, triethylenetetramine hexaacetic acid, catechol, 4- t-butylcatechol, L (+)-tartaric acid, DL-tartaric acid, glycine, chromotropic acid, benzoylacetone, citric acid, gallic acid, dimercaptopropanol, triethanolamine, cyclohexanediaminetetraacetic acid, ditoluoyltartaric acid, dibenzoyltartaric acid Can be mentioned.

  In addition, the acidic phosphate esters are those that form a complex with the metal ion of the catalyst contained in the hydroxycarboxylic acid polyester, lose the catalytic activity, and show the effect of inhibiting the cleavage of the polymer chain. Known acidic phosphoric acid esters, phosphonic acid esters, alkylphosphonic acid and the like, and mixtures thereof may be mentioned, for example, 2-ethylhexane phosphate. The above-described acidic phosphoric acid esters are excellent in workability because of good solubility in organic solvents, excellent in reactivity with lactic acid-based polyesters, and excellent in deactivation of the polymerization catalyst.

  Next, the polylactic acid composition of the present invention will be described.

  The polylactic acid composition contains a lactic acid block copolymer (III) and polylactic acid (IV), and the weight ratio thereof may be adjusted depending on how much impact resistance and flexibility are desired. The larger the amount of the lactic acid-based block copolymer (III) used, the greater the impact resistance and flexibility, and the lower the viscosity of the polylactic acid composition. Is polylactic acid (IV): lactic acid block copolymer (III) = 97: 3 to 40:60, more preferably 95: 5 to 50:50, still more preferably 95: 5 to 60:40.

  Regarding the morphology of polylactic acid (IV) and lactic acid block copolymer (III) described above, polylactic acid (IV) is in the sea phase, whereas lactic acid block copolymer (III) is in the island phase. However, when the particle size of the island is small, the flexibility and transparency are excellent, and when the island phase is large, the impact resistance is excellent. That is, when the average particle size is relatively large as 0.20 to 2 μm, the impact resistance and the interfacial adhesion between the polylactic acid (IV) and the lactic acid block copolymer (III) are excellent, more preferably 0.2. It is -1 micrometer, More preferably, it is 0.3 micrometer-1 micrometer, More preferably, it is 0.5 micrometer-1 micrometer.

On the other hand, when the average particle size of the islands is relatively small, such as 0.2 μm or less, flexibility and transparency are preferably maintained, more preferably 0.1 μm or less, still more preferably 0.01 Of course, it is most preferable if it is compatible. In addition, the average particle diameter said by this invention means the average value of the length of the long axis of a island phase, and a short axis.

  As for the relationship between the island diameter and the polyether polyol, the island diameter increases when the molecular weight is high. If the type is increased, polytetramethylene glycol is large, followed by polypropylene glycol, poly (ethylene glycol-propylene glycol) copolymer, The tendency becomes stronger in the order of polyethylene glycol.

Since the polylactic acid composition of the present invention contains the lactic acid block copolymer (III), it exhibits excellent impact resistance and flexibility. Moreover, it is excellent in heat resistance by presence of a layered silicate or a carbon nanotube. Furthermore, it has excellent gas barrier properties, and for example, the oxygen permeability is reduced to about 1/3 to 1/4 compared with a polylactic acid composition in which no layered silicate or carbon nanotube is present. Further, by adjusting the addition amount of the lactic acid-based block copolymer (III), it is 3 (kJ / m ² ) or more, preferably 4 to 20 (kJ / m ² ), by the method described in Examples. It preferably has an IZOD impact strength of 5 to 20 (kJ / m ² ), particularly preferably 7 to 20 (kJ / m ² ). Alternatively, it has a DuPont impact strength of 0.2 J or more, preferably 0.3 to 5 J with an unstretched film or a stretched film, or a film impact of 1 J or more, preferably 1 to 10 J with a stretched heat set film.

  Furthermore, by adjusting the addition amount of the lactic acid block copolymer (III), it exhibits excellent flexibility, for example, a polylactic acid composition is formed into a film and measured at 20 ° C. measured with RSAII manufactured by Rheometrics Co., Ltd. The storage elastic modulus (E ′) at 1 Hz is in the range of 0.5 to 5.0 GPa, more excellent is 0.6 to 3 GPa, and more excellent is 0.6 to 2.5 GPa. Show.

  Moreover, since the polylactic acid composition of the present invention is finely dispersed during polymerization of the lactic acid block copolymer (III) when the amount of layered silicate or carbon nanotube used is small, in the polylactic acid composition, Since it disperses better than mechanical kneading, it becomes difficult to impair transparency. In this case, the transparency refers to a polylactic acid composition having a thickness of 200 μm and a haze value of 35% or less, more preferably 1 to 30%, still more preferably 1 to 25%, and even more preferably 1 to 20 %.

  The polylactic acid composition of the present invention includes antioxidants such as 2,6-di-t-butyl-4-methylphenol (BHT) and butyl hydroxyanisole (BHA), salicylic acid derivatives, benzophenone series, benzotriazole It is also possible to improve the thermal stability during polymerization or molding by using a UV absorber such as a phosphor and a stabilizer such as phosphate ester, isocyanate, carbodiimide, carbodilite. The addition amount of these stabilizers is not particularly limited as long as the effect of the present invention is not impaired, but is usually added in an amount of 0.01 to 10% with respect to the addition target polymer. Is preferred.

  Also, metal soaps such as zinc stearate, magnesium stearate, calcium stearate, mineral oil, liquid paraffin, lubricants such as ethylene bisstearyl amide, nonionic systems such as glycerin fatty acid ester and sucrose fatty acid ester, alkyl sulfonates, etc. The addition of a surfactant such as an ionic type, a colorant such as titanium oxide or carbon black, a flame retardant such as a phosphorus type, bromine type, or silicone type may be added.

  Also, plasticizers often used for vinyl chloride resins such as dioctyl adipate (DOA), acetyl tributyl acetyltributyl citrate (ATBC), dioctyl sebacate (DOS), trimellitic acid plasticizer, adipic acid polyester, etc. A low molecular plasticizer may be used. This addition particularly improves the tensile elongation and further improves the flexibility. When the amount of the low molecular plasticizer used is too large, the heat resistance is greatly lowered, so that it is preferably 0.5 to 30% by weight, more preferably 1 to 20% by weight, based on the polylactic acid composition. More preferred is weight percent.

  Addition of inorganic foaming agents such as sodium bicarbonate and ammonium bicarbonate, organic foaming agents such as azodicarbonamide, azobisisobutyronitrile and sulfonyl hydrazide, or foaming agents such as pentane, butane and freon Can be made into a foam by impregnating the polymer with the present invention in advance or by directly feeding it into the extruder during the extrusion process. It can also be laminated with paper, aluminum foil or other degradable polymer films by extrusion lamination, dry lamination or coextrusion.

  The molded product using the above-described polylactic acid composition of the present invention is molded by the molding method shown below. For such molded product or film (10 × 10 cm square, 250 μm thick), 35 ° C. When left in a constant temperature and humidity chamber with a humidity of 80%, the bleed product does not appear from the surface of the molded product for 60 days or more, preferably 180 days or more.

  Examples of the molded product made of the polylactic acid composition of the present invention include injection molded products, fibers, or films formed by extrusion molding such as T-die casting or inflation molding. It is also possible to carry out a multilayered film by a plurality of extruders. In addition, although the sheet | seat and the film are conventionally used properly by normal thickness, in order to avoid confusion in this invention, it shall generically call it a film. The thickness of the film of the present invention is not particularly limited, but generally refers to 5 μm to 2 mm.

  Moreover, there exists the method of annealing a polylactic acid composition at crystallization temperature in the shaping | molding method of the polylactic acid composition of this invention. For example, in the case of vacuum molding, compressed air molding, injection molding, blow molding and compression molding, the mold temperature is set within the range of the crystallization start temperature to the end temperature when DSC falls, and the composition of the present invention is placed in the mold. To crystallize. By this method, a heat-resistant lactic acid polymer molded product having excellent heat resistance and impact strength can be obtained. Mold temperature is 70-130 degreeC, 80-120 degreeC is preferable, 80-110 degreeC is more preferable, 90-110 degreeC is more preferable. Within this temperature range, it can be easily crystallized, and after molding, when the molded product is taken out from the mold, it can be solidified to obtain a molded product with good dimensional accuracy. If the temperature is out of this temperature range, the crystallization speed may be slow, and the solidified time of the molded product is required, so that the practicality may be inferior. The crystallization time is from 1 second to 10 minutes, but when practicality such as productivity is considered, this time is preferably as short as possible. Therefore, it is preferably 1 second to 3 minutes, more preferably 1 second to 1 minute. is there.

  Further, since the polylactic acid composition of the present invention is easily hydrolyzed due to its high hygroscopicity, in the processing of injection molding, fiber or film packaging material, etc., in order to avoid hydrolysis in the molding machine or extruder. It is preferable to perform dehumidification drying in advance with a vacuum dryer or the like to suppress the moisture in the raw material to 50 ppm or less.

  Next, regarding the film obtained using the polylactic acid composition of the present invention, the extruder screw used for film formation is usually the length (L) of the kneading part of the screw and the diameter of the kneading screw ( A full flight type having an L / D ratio of about 20 to 50, or a vent may be provided. The appropriate extrusion temperature varies depending on the molecular weight, composition, and viscosity of the polylactic acid composition to be used, but is preferably equal to or higher than the flow start temperature.

  The melting temperature when forming a polylactic acid composition into a film by T-die casting is not particularly limited, but is usually a temperature 10 to 60 ° C. higher than the melting point of polylactic acid (VI). The melt-extruded film is usually cast so as to have a predetermined thickness, and cooled if necessary. At that time, when the film is thick, a touch roll, an air knife, and when it is thin, electrostatic pinning is properly used to form a uniform film.

  The formed film can be stretched uniaxially and biaxially by a tenter method or an inflation method at a temperature not lower than the glass transition temperature and not higher than the melting point. Further, by performing a stretching treatment, molecular orientation can be generated, and physical properties such as impact resistance, rigidity, and transparency can be improved.

  In the case of uniaxial stretching, it is preferable to stretch 1.3 to 10 times in the longitudinal direction or the transverse direction by longitudinal stretching by a roll method or transverse stretching by a tenter. In the case of biaxial stretching, longitudinal stretching by a roll method and transverse stretching by a tenter can be mentioned. As the method, the first-axis stretching and the second-axis stretching may be performed sequentially or simultaneously. The draw ratio is preferably 1.3 to 6 times in the longitudinal direction and the transverse direction. If the draw ratio is lower than this, it is difficult to obtain a film having a sufficiently satisfactory strength, and if it is high, the film will be broken during stretching. In addition, when shrinkage | contraction property especially at the time of heating is requested | required, such as a shrink film, high magnification extending | stretching of 3-6 times etc. to a uniaxial or biaxial direction is preferable.

  The stretching temperature is preferably in the range of glass transition temperature (hereinafter referred to as Tg) to (Tg + 50) ° C. of the polylactic acid composition, and particularly preferably in the range of Tg to (Tg + 30) ° C. By setting the stretching temperature within such a range, the film can be sufficiently stretched, and the strength by stretching can be improved.

  In addition, in order to further improve the heat resistance of the film obtained using the polylactic acid composition of the present invention, when heat setting treatment (crystallization treatment) is performed under tension immediately after stretching, strain is removed or crystallized. The heat resistance can be improved by promoting. The heat setting temperature is 70 to 130 ° C, preferably 70 to 120 ° C, more preferably 80 ° C to 110 ° C, and more preferably 90 to 110 ° C. If it is performed in such a range, not only heat resistance but also other film physical properties such as tensile elongation are improved. In this case, the heat setting treatment time is usually 1 second to 3 minutes, preferably 1 second to 1 minute, and more preferably 1 second to 30 seconds.

  As the secondary processing method of the film of the present invention, a vacuum forming method, a pressure forming method, a vacuum pressure forming method, or the like can be used. The polylactic acid composition of the present invention can be formed into a film using an existing apparatus used for film production of general-purpose resins.

  Regarding the film forming method, in the case of vacuum forming or vacuum / pressure forming, plug assist forming may be performed. The stretched film is preferably subjected to pressure forming. In addition, the heating and cooling of the mold can be arbitrarily used at the time of molding. In particular, the heat resistance can be improved by heating the mold above the crystallization temperature and actively proceeding with crystallization.

  Inflation molding can be easily performed with a molding device equipped with a normal circular die and air ring, and no special accessory device is required. At this time, in order to avoid uneven thickness, the die, air ring or winder may be rotated.

  Regarding the production of the film, it can be easily heat-sealed by a normal bag making machine such as a horizontal pillow bag making machine, a vertical pillow bag making machine, a twist back bag making machine, etc. to obtain a bag-like product.

  When a processed product other than these films is obtained, a mold such as a container can be obtained without problems using a normal injection molding machine.

  Blow molding is also easy, and single layer and multilayer bottles can be easily molded by using an existing molding machine. There is no particular problem with press molding, and a single layer or a laminated product can be obtained with an ordinary molding machine.

  Applications of the polylactic acid composition of the present invention include various molded products, molding resins, packaging materials, paint resins, ink resins, toner resins, adhesive resins, sanitary materials, medical materials, and fiber materials. It is useful as agricultural material, fishery material, lamination material for paper, foamed resin material, etc. More specifically, for example, as various molded articles, trays, cups, dishes, blisters, blow molded articles, shampoo bottles, cosmetic bottles, beverage bottles, oil containers, injection molded articles (golf tees, cotton swab cores, candy sticks) , Brushes, toothbrushes, helmets, syringes, dishes, cups, combs, razor handles, tape cassettes and cases, disposable spoons, forks, stationery such as ballpoint pens, etc.). Packaging materials include sheet materials, film materials, and more specifically shrink film, vapor deposition film, wrap film, food packaging, other general packaging, garbage bags, plastic bags, general standard bags, heavy bags, etc. Bags, hygiene materials such as disposable diapers, sanitary products, medical materials such as wound dressings and sutures, textile materials such as woven and knitted fabrics, lace, braids, nets, felts, non-woven fabrics, and other agricultural materials As germination film, seed string, agricultural multi-film, slow-acting agricultural chemical and fertilizer coating agent, bird-proof net, curing film, seedling pot, etc. as fishing materials, fishing net, nori culture net, fishing line, ship bottom paint, etc. In addition, paper lamination products include trays, cups, dishes, megaphones, etc., as well as tie tapes (tie bands), prepaid cards, balloons, panties Tokkingu, hair caps, sponges, cellophane tape, umbrellas, raincoat, plastics gloves, hair caps, ropes, tubes, foam trays, foam cushioning materials, cushioning materials, packaging materials, tobacco filters, etc., include a wide variety of applications.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely using an Example and a comparative example, this invention is not limited to these Examples at all.

The measurements performed in the examples are as follows.
(Molecular weight measurement)
It measured by the comparison with a polystyrene standard sample with the gel permeation chromatography measuring apparatus (Hereafter, it abbreviates as GPC. HLC-8020 by Tosoh Corporation, column temperature 40 degreeC, tetrahydrofuran solvent).

(Thermal properties measurement)
Using a differential scanning calorimeter (hereinafter abbreviated as DSC; DSC220C manufactured by Seiko Denshi Kogyo Co., Ltd.), a range of −100 to 200 ° C. was measured at a temperature rising rate of 10 ° C./min.

(Vicat softening point temperature)
Using a heat starter manufactured by Toyo Seiki Co., Ltd., a test piece after molding was measured under the conditions of a load of 1 kgf and a temperature increase rate of 50 ° C./hour in accordance with ASTM-D1525.

(Storage elastic modulus (E ′); hereinafter abbreviated as DMA)
Using a Rheometrics RSAII, a film having a thickness of 200 μm × width 5 mm × length 35 mm was measured by FILM TEXTURE geometry under conditions of 22.4 mm between chucks, 6.28 rad, −50 to 120 ° C.

(Transparency measurement; hereinafter abbreviated as “haze”)
A 10 cm long × 10 cm wide film was cut into 5 cm long × 5 cm wide and measured with a turbidimeter (ND-1001DP manufactured by Nippon Denshoku Industries Co., Ltd.).

(Izod impact test; hereinafter abbreviated as IZOD)
It was measured by an Izod impact test method (notched) according to JIS K 7110.

(DuPont impact strength test)
Using the DuPont impact strength measurement method of JIS K 5400, the weight of the weight having a constant weight was changed and dropped, and the 50% fracture energy of the obtained film was determined depending on the presence or absence of breakage. The striking portion with the film is made of steel, and is a smooth hemisphere (manufactured by Uesima Seisakusho) with a radius of 6.3 mm.

(Film impact test)
It measured by the method based on ASTMD-3420.

(Tensile test)
It measured according to JIS-K7127 using Shimadzu Tensilon. The test piece was made with a JIS No. 2 dumbbell and a tensile speed of 5 mm / min.

(Production Example 1) (Synthesis of modifier A-1)
1.40 kg of polyethylene glycol having a number average molecular weight of 2,000 (PEG-2000 manufactured by Sanyo Chemical Co., Ltd., hereinafter abbreviated as PEG2000) and 3.27 kg of polylactic acid (H-400 manufactured by Mitsui Chemicals, hereinafter abbreviated as PLA) Then, 0.33 kg of layered silicate (SAN manufactured by Coop Chemical Co., hereinafter abbreviated as SAN) was charged into a 10 L reaction kettle, stirred and melted at 190 ° C., 100 ppm of titanium tetrabutoxide was added as a catalyst, and 0.1 kPa Polymerization was performed for 5 hours under reduced pressure. Thereafter, 100 ppm of ethylenediaminetetraacetic acid (hereinafter abbreviated as EDTA) was added as a catalyst deactivator, and the residual lactide was devolatilized under a reduced pressure of 0.1 kPa for 1 hour to complete the polymerization to obtain a modifier (A-1). . Note that the glass transition point (Tg) overlaps with the melting point peak of PEG and is unknown.

(Production Example 2) (Synthesis of modifier A-2)
Similar to Production Example 1 using 3.27 kg of polyethylene glycol having a number average molecular weight of 20,000 (PEG-20000 manufactured by Sanyo Kasei Co., Ltd., hereinafter abbreviated as PEG 20000), 1.40 kg of PLA, and 0.33 kg of SAN. Polymerization was performed under various conditions to obtain a modifier (A-2). Note that Tg is unclear with the melting point peak of PEG.

(Production Example 3) (Synthesis of modifier A-3)
3.15 kg of polyprolene glycol having a number average molecular weight of 3,000 (Sanix PP-3000 manufactured by Sanyo Kasei Co., Ltd., hereinafter abbreviated as PPG) and 1. L-lactide (Purac Co., Ltd., hereinafter abbreviated as L-LD). 35 kg and 0.50 kg of layered silicate (ME100 manufactured by Coop Chemical Co., hereinafter abbreviated as ME100) were charged into a 10 L reaction kettle and dissolved at 185 ° C. in a nitrogen atmosphere. After the solution became homogeneous, 250 ppm of tin octoate was added, and after stirring at 185 ° C. for 3 hours, 200 ppm of 2-ethylhexyl acid phosphate (AP-8 manufactured by Daihachi Chemical Co., Ltd.) was added as a catalyst deactivator, 0.1 kPa The residual lactide was devolatilized under reduced pressure for 1 hour to obtain a modifier (A-3).

(Production Example 4) (Synthesis of modifier A-4)
A polyethylene glycol-polyprolene glycol-polypropylene glycol block copolymer having a number average molecular weight of 4,000 (Sanyo Kasei New Pole PE-75, hereinafter abbreviated as PE75) and 0.86 kg of L-LD and 0.87 kg, respectively. Polymerization was carried out under the same conditions as in Production Example 3 except that 0.27 kg of carbon nanotubes (manufactured by Hyperion) was used to obtain a modifier (A-4).

(Production Example 5) (Synthesis of modifier A-5)
Polymerization was carried out under the same conditions as in Production Example 1 using 0.90 kg of PE-75, 0.90 kg of PLA, and 0.40 kg of ME100 to obtain a modifier (A-5).

(Production Example 6) (Synthesis of modifier A-6)
1.95 kg of polytetramethylene glycol having a number average molecular weight of 3,000 (PTMG 3000 manufactured by Mitsubishi Chemical Corporation, hereinafter abbreviated as PTMG), 1.95 kg of PLA, 0.10 kg of carbon nanotubes (manufactured by Hyperion), and as a catalyst Polymerization was carried out under the same conditions as in Production Example 1 except that 100 ppm of zirconium tetrachloride · 2THF was used, to obtain a modifier (A-6).

(Comparative Production Example 1) (Synthesis of modifier HA-1)
Polymerization was carried out under the same conditions as in Production Example 1 using 1.50 kg of PEG2000 and 3.50 kg of PLA to obtain a modifier (HA-1).

(Comparative Production Example 2) (Synthesis of modifier HA-2)
Polymerization was performed under the same conditions as in Production Example 1 using 3.5 kg of PPG and 1.5 kg of L-LD to obtain a modifier (HA-2).

(Example 1) (Preparation of polymer blend P-1)
After dry blending 3.50 kg of PLA and 1.50 kg of modifier (A-1), it was melt kneaded at a cylinder temperature of 200 ° C. with a 35 mm twin screw extruder (Toshiba Machine Co., Ltd.) with L / D = 36. A compounded pellet (P-1) was obtained.

(Example 2) (Preparation of polymer blend P-2)
Pellets (P-2) were obtained under the same conditions as in Example 1 using 0.10 kg of maleic anhydride, 3.40 kg of PLA, and 1.50 kg of modifier (A-2).

(Example 3) (Preparation of polymer blend P-3)
Using 9.00 kg of PLA and 1.00 kg of modifier (A-3), pellets (P-3) were obtained under the same conditions as in Example 1.

(Example 4) (Preparation of polymer blend P-4)
Pellets (P-4) were obtained under the same conditions as in Example 1 using 3.50 kg of PLA and 1.50 kg of the modifier (A-4).

(Example 5) (Preparation of polymer blend P-5)
Using 2.00 kg of PLA, 1.25 kg of PLA modified with 3 wt% maleic anhydride in advance using a twin screw extruder, 1.50 kg of modifier (A-5), and 0.25 kg of SAN, Pellets (P-5) were obtained under the same conditions as in Example 1.
(Example 6) (Preparation of polymer blend P-6)
Implemented using 2.00 kg of PLA, 0.95 kg of PLA modified with 3 wt% maleic anhydride in advance using a twin screw extruder, 2.00 kg of modifier (A-6), and 0.05 kg of carbon nanotubes Pellets (P-6) were obtained under the same conditions as in Example 1.

(Comparative Example 1) (Preparation of polymer blend HP-1)
Using 3.50 kg of PLA and 1.50 kg of modifier (HA-1), pellets (HP-1) were obtained under the same conditions as in Example 1.

(Comparative Example 2) (Preparation of polymer blend HP-2)
Using 9.00 kg of PLA and 1.00 kg of a modifier (HA-2), pellets (HP-2) were obtained under the same conditions as in Example 1.

(Comparative Example 3) (Preparation of polymer blend HP-3)
Using 29.1 kg of PLA100 and 0.9 kg of SAN, pellets (HP-3) were obtained under the same conditions as in Example 1.

(Test Example 1) (Evaluation of polymer blend (crystallization temperature))
About each polymer blend obtained in Examples 1-6 and Comparative Examples 1-3, the crystallization temperature was measured by DSC, and the result was put together in Tables 3-5.

(Test Example 2) (Injection molding and evaluation of polymer blend)
Each polymer blend obtained in Examples 1 to 6 and Comparative Examples 1 to 3 was dried under reduced pressure at 100 ° C. for 6 hours, injection-molded with a 1 ounce injection molding machine, and then heated in a mold adjusted to 90 ° C. Crystallization was performed for 30 seconds to obtain an IZOD test piece. These Vicat softening point temperatures and IZOD impact strength (notched) were measured, and the results are summarized in Tables 3-5.

(Test Example 3) (Film formation and evaluation of 200 μm heat set film)
Each polymer blend obtained in Examples 1 to 6 and Comparative Examples 1 to 3 was dried under reduced pressure at 100 ° C. for 6 hours, then L / D = 36 50 mm single screw extruder (manufactured by Tanabe Plastics), cylinder temperature 220. The mixture was melt-kneaded at 0 ° C. and extruded from a die into a sheet having a width of 30 cm and a thickness of 200 μm. For the cooling of the sheet thermally melted at the die outlet, a touch roll was used for Examples 4 to 7, and an air knife was used otherwise. The film was crystallized by heat setting at 100 ° C. for 1 minute. The obtained 200 μm film was measured for DuPont impact value, haze, tensile modulus, tensile elongation, and storage modulus at 20 ° C. in DMA, and the results are summarized in Tables 3 to 5.

(Test Example 4) (Biodegradability test of film)
The films of Examples 1 to 6 obtained in Test Example 3 were sandwiched with a wire mesh and left in an electric composting apparatus maintained at 45 ° C. Stirring was performed every few hours to avoid an anaerobic environment. When the film was taken out after 30 days, it was tattered and hardly kept its original shape. After 60 days, the film disappeared and could not be confirmed.

(Test Example 5) (Film formation and evaluation of biaxially stretched heat set film)
Each polymer blend obtained in Examples 1 to 6 and Comparative Examples 1 to 3 was melt-kneaded at a cylinder temperature of 220 ° C. with a L / D = 36 50 mm single screw extruder (manufactured by Tanabe Plastics Co., Ltd.). The sheet was extruded into a sheet having a thickness of 30 cm and a thickness of 100 μm. An air knife was used to cool the sheet melted at the die outlet. Furthermore, after stretching to twice the longitudinal and lateral same ratio by successive stretching at a stretching temperature condition of 70 ° C. and a stretching speed of 10 mm / second, heat setting was performed at 140 ° C. for 50 seconds, and a biaxial stretching heat of 25 μm in thickness. A set film was obtained. About this, the film impact, haze, the tensile elasticity modulus, and the tensile elongation were measured, and the result was put together in Tables 3-5, and was shown.

(Test Example 6) (Bleed-out evaluation of film)
In addition, the films obtained in Tests 3 and 5 were left in a constant temperature and humidity chamber PR-2F manufactured by Tabay Espec Corp. maintained at 35 ° C. and a humidity of 80%. The state of the film was observed every day, and evaluated by the number of days when the bleed-out started. The results are summarized in Tables 3 to 5. During the evaluation, no bleed out occurred.

In contrast to the Vicat softening point temperatures of Comparative Examples 1 and 2 of 70 ° C. or lower, the polylactic acid composition of the present invention shows high heat resistance of 80 ° C. or higher, and the impact resistance or flexibility is equal or higher. The numerical value of is realized. In Comparative Example 3, the Vicat softening point temperature is 85 ° C., but the IZOD impact strength, the DuPont impact value, and the impact resistance value of the film impact are all lower than those of the Examples, and the tensile modulus or storage modulus is high. Poor flexibility.

Claims (7)

Lactic acid having a weight average molecular weight of 3000 to 250,000 obtained by copolymerization of polyether polyol (I) having a weight average molecular weight of 500 to 250,000 and lactide (II) or polylactic acid (II ′) in the presence of a layered silicate. A polylactic acid composition comprising a system block copolymer (IIIa) and polylactic acid (IV). Lactic acid series having a weight average molecular weight of 3000 to 250,000 obtained by copolymerizing polyether polyol (I) having a weight average molecular weight of 500 to 250,000 and lactide (II) or polylactic acid (II ′) in the presence of carbon nanotubes A polylactic acid composition comprising block copolymer (IIIb) and polylactic acid (IV). The polylactic acid composition according to claim 1, wherein a weight ratio of the lactic acid block copolymer (IIIa) and the polylactic acid (IV) is from 3:97 to 50:50. The polylactic acid composition according to claim 2, wherein a weight ratio of the lactic acid-based block copolymer (IIIb) to the polylactic acid (IV) is 3:97 to 50:50. The polylactic acid composition according to any one of claims 1 to 4, which has a Vicat softening point temperature of 70 ° C or higher. The polylactic acid composition according to any one of claims 1 to 5, wherein the polylactic acid (IV) is modified with an acid anhydride. A molded article obtained using the polylactic acid composition according to any one of claims 1 to 6.