US20130165601A1 - Polylactic acid block copolymer - Google Patents

Polylactic acid block copolymer Download PDF

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US20130165601A1
US20130165601A1 US13/819,879 US201113819879A US2013165601A1 US 20130165601 A1 US20130165601 A1 US 20130165601A1 US 201113819879 A US201113819879 A US 201113819879A US 2013165601 A1 US2013165601 A1 US 2013165601A1
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lactic acid
poly
block copolymer
acid
polylactic acid
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Yoshitake Takahashi
Takuma Naotsuka
Ken Sudo
Hiroyuki Ome
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Toray Industries Inc
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Toray Industries Inc
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Assigned to TORAY INDUSTRIES, INC. reassignment TORAY INDUSTRIES, INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: NAOTSUKA, TAKUMA, OME, HIROYUKI, SUDO, KEN, TAKAHASHI, YOSHITAKE
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G81/00—Macromolecular compounds obtained by interreacting polymers in the absence of monomers, e.g. block polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
    • C08G63/06—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from hydroxycarboxylic acids
    • C08G63/08—Lactones or lactides
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
    • C08G63/06—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from hydroxycarboxylic acids
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/78—Preparation processes
    • C08G63/80—Solid-state polycondensation
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/78—Preparation processes
    • C08G63/82—Preparation processes characterised by the catalyst used
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/78—Preparation processes
    • C08G63/82—Preparation processes characterised by the catalyst used
    • C08G63/823—Preparation processes characterised by the catalyst used for the preparation of polylactones or polylactides
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/91—Polymers modified by chemical after-treatment
    • C08G63/912—Polymers modified by chemical after-treatment derived from hydroxycarboxylic acids
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
    • C08L67/04—Polyesters derived from hydroxycarboxylic acids, e.g. lactones
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G2261/00—Macromolecular compounds obtained by reactions forming a carbon-to-carbon link in the main chain of the macromolecule
    • C08G2261/10—Definition of the polymer structure
    • C08G2261/12—Copolymers
    • C08G2261/126—Copolymers block
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2205/00—Polymer mixtures characterised by other features
    • C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
    • C08L2205/025—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group containing two or more polymers of the same hierarchy C08L, and differing only in parameters such as density, comonomer content, molecular weight, structure
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2205/00—Polymer mixtures characterised by other features
    • C08L2205/05—Polymer mixtures characterised by other features containing polymer components which can react with one another

Definitions

  • This disclosure relates to a polylactic acid block copolymer that forms a polylactic acid stereocomplex excellent in transparency, heat resistance and mechanical properties.
  • Polylactic acid is a macromolecule which can be practically subjected to melt molding, and, because of its biodegradable property, it has been developed as biodegradable plastics that are degraded, after use, under a natural environment to be released as carbon dioxide gas and water.
  • the raw material of polylactic acid itself is a renewable resource (biomass) originated from carbon dioxide and water, release of carbon dioxide after its use neither increases nor decreases carbon dioxide in the global environment.
  • biomass biomass
  • lactic acid which is the monomer for polylactic acid
  • polylactic acid can be inexpensively produced by fermentation methods using microorganisms in recent years, and polylactic acid is therefore being studied as a material alternative to general-purpose polymers made of petroleum-based plastics.
  • polylactic acid has lower heat resistance and durability, and also has lower productivity due to its lower crystallization rate. Therefore, its practical use is largely restricted at present.
  • a polylactic acid stereocomplex is formed by mixing optically active poly-L-lactic acid (hereinafter referred to as PLLA) and poly-D-lactic acid (hereinafter referred to as PDLA), and its melting point reaches 220° C., which is 50° C. higher than the melting point of a polylactic acid homopolymer, 170° C. Therefore, attempts are being made to apply polylactic acid stereocomplexes to production of fibers, films and resin molded articles having high melting points and high crystallinities.
  • PLLA optically active poly-L-lactic acid
  • PDLA poly-D-lactic acid
  • a polylactic acid stereocomplex is formed by mixing PLLA and PDLA in the solution state or by melt mixing of PLLA and PDLA under heat.
  • the method by mixing of PLLA and PDLA solutions requires evaporation of the solvent after the mixing and the production process is therefore laborious, resulting in high cost of the polylactic acid stereocomplex, which is problematic.
  • melt mixing of PLLA and PDLA under heat these need to be mixed at a temperature that allows sufficient melting of the polylactic acid stereocomplex, but such a temperature also causes thermal degradation reaction of polylactic acid, leading to decreased physical properties of the molded article, which is problematic.
  • Examples of the polylactic acid stereocomplex obtained by melt mixing under heat include the polylactic acid stereocomplex obtained in JP 2003-96285 A by melt mixing of high-molecular-weight PLLA and low-molecular-weight PDLA having a difference in the weight average molecular weight between the PLLA and PDLA of not less than 50,000. This technique achieves higher stereocomplexation and enables production of a polylactic acid stereocomplex having excellent heat resistance and crystallinity.
  • polylactic acid block copolymers composed of PLLA segments and PDLA segments have been disclosed (JP 2003-238672 A, JP 2006-28336 A and JP 2006-307071 A).
  • JP 2003-238672 A relates to a polylactic acid block copolymer obtained by preparing PLLA and PDLA by ring-opening polymerization or direct polycondensation and melt-mixing the prepared PLLA and PDLA under heat to prepare a mixture, followed by subjecting the mixture to solid-phase polymerization.
  • JP 2006-28336 A relates to a polylactic acid block copolymer obtained by preparing PLLA and PDLA by melt polymerization and melt-mixing the prepared PLLA and PDLA under heat, followed by subjecting the resulting mixture to solid-phase polymerization.
  • JP 2006-307071 A relates to a polylactic acid block copolymer obtained by mixing PLLA and PDLA having different molecular weights at a temperature close to the melting point and subjecting the resulting mixture to solid-phase polymerization in the presence of crystals of the polylactic acids alone.
  • the kneaded mixture comprises low molecular weight components and the mixture has a large polydispersity as a whole so that the polylactic acid stereocomplex shows low mechanical properties, which is problematic.
  • the polylactic acid block copolymer obtained by the technique described in JP 2006-28336 A shows a melting point derived from stereocomplex crystals, it has high heat resistance, but its low molecular weight leads to low mechanical properties, which is problematic. The problem remains to be solved for practical use of the block copolymer.
  • the weight average molecular weight after solid-phase polymerization tends to be as high as not less than 100,000, but the polylactic acid block copolymer comprises a low molecular weight component and the polydispersity is as high as not less than 2.7, resulting in low mechanical properties, which is problematic.
  • polylactic acid block copolymer constituted by a poly-L-lactic acid segment(s) containing as a major component L-lactic acid and a poly-D-lactic acid segment(s) containing as a major component D-lactic acid, the polylactic acid block copolymer satisfying Inequalities (1) and (2):
  • ⁇ Hh represents the heat of fusion of stereocomplex crystals in DSC measurement wherein the temperature is increased at a heating rate of 20° C./min. (J/g); and ⁇ Hl represents the heat of fusion of crystals of poly-L-lactic acid alone and crystals of poly-D-lactic acid alone in DSC measurement wherein the temperature is increased at a heating rate of 20° C./min. (J/g)
  • Tm represents the melting point of polylactic acid block copolymer observed in DSC measurement wherein the temperature is increased at a heating rate of 40° C./min.
  • Tms represents the beginning temperature of melting of polylactic acid block copolymer observed in DSC measurement wherein the temperature is increased at a heating rate of 40° C./min.
  • Tme represents the end temperature of melting of polylactic acid block copolymer observed in DSC measurement wherein the temperature is increased at a heating rate of 40° C./min.
  • a molded product comprising the above polylactic acid block copolymer, the molded product having a relative degree of crystallinity of not less than 90% and comprising a part having a haze value of not more than 30% when the thickness of the molded product is 100 ⁇ m.
  • the ratio of molecular weights of not less than 100,000 is preferably not less than 40%.
  • the cooling crystallization temperature is preferably not less than 130° C. when the temperature of the polylactic acid block copolymer is increased to 250° C. and then kept constant for 3 minutes, followed by decreasing the temperature at a cooling rate of 20° C./min.
  • the polydispersity represented by the ratio between the weight average molecular weight and the number average molecular weight is preferably not more than 2.7.
  • the average sequence length of the L-lactic acid units and D-lactic acid units in the polylactic acid block copolymer is preferably not less than 20.
  • the weight ratio between the L-lactic acid component and the D-lactic acid component in the polylactic acid block copolymer is preferably within the range of 80/20 to 60/40 or within the range of 40/60 to 20/80.
  • the polylactic acid block copolymer preferably has a weight average molecular weight of not less than 100,000.
  • the polylactic acid block copolymer is preferably obtained by mixing poly-L-lactic acid and poly-D-lactic acid one of which has a weight average molecular weight of 60,000 to 300,000 and the other of which has a weight average molecular weight of 10,000 to 50,000 to obtain a mixture having a weight average molecular weight of not less than 90,000 and satisfying Inequality (3):
  • ⁇ Hh represents the heat of fusion of stereocomplex crystals in DSC measurement wherein the temperature is increased at a heating rate of 20° C./min. (J/g); and ⁇ Hl represents the heat of fusion of crystals of poly-L-lactic acid alone and crystals of poly-D-lactic acid alone in DSC measurement wherein the temperature is increased at a heating rate of 20° C./min. (J/g)
  • J/g the heat of fusion of stereocomplex crystals in DSC measurement wherein the temperature is increased at a heating rate of 20° C./min.
  • the polylactic acid block copolymer of the present invention is preferably obtained by mixing poly-L-lactic acid and poly-D-lactic acid in which the ratio of the weight average molecular weight of the polylactic acid having a higher weight average molecular weight with respect to the weight average molecular weight of the polylactic acid having a lower weight average molecular weight is not less than 2 and less than 30, to obtain a mixture having a weight average molecular weight of not less than 90,000 and satisfying Inequality (3):
  • ⁇ Hh represents the heat of fusion of stereocomplex crystals in DSC measurement wherein the temperature is increased at a heating rate of 20° C./min. (J/g); and ⁇ Hl represents the heat of fusion of crystals of poly-L-lactic acid alone and crystals of poly-D-lactic acid alone in DSC measurement wherein the temperature is increased at a heating rate of 20° C./min. (J/g)
  • J/g the heat of fusion of stereocomplex crystals in DSC measurement wherein the temperature is increased at a heating rate of 20° C./min.
  • the total number of the segment(s) composed of L-lactic acid units and segment(s) composed of D-lactic acid units contained per one molecule of the polylactic acid block copolymer is preferably not less than 3.
  • the polylactic acid block copolymer means a polylactic acid block copolymer in which a segment(s) composed of L-lactic acid units and a segment(s) composed of D-lactic acid units are covalently bonded to each other.
  • the segment composed of L-lactic acid units herein means a polymer containing L-lactic acid as a major component and containing not less than 70 mol % of L-lactic acid units.
  • the segment comprises more preferably not less than 80 mol %, still more preferably not less than 90 mol %, especially preferably not less than 95 mol %, most preferably not less than 98 mol % of L-lactic acid units.
  • the segment composed of D-lactic acid units herein means a polymer containing D-lactic acid as a major component and containing not less than 70 mol % of D-lactic acid units.
  • the segment comprises more preferably not less than 80 mol %, still more preferably not less than 90 mol %, especially preferably not less than 95 mol %, most preferably not less than 98 mol % of D-lactic acid units.
  • the segment composed of L-lactic acid units or D-lactic acid units may comprise other component units as long as the performance of the obtained polylactic acid block copolymer is not adversely affected.
  • component units other than L-lactic acid and D-lactic acid units include polycarboxylic acid, polyalcohol, hydroxycarboxylic acid and lactone, and specific examples of the component units include:
  • polycarboxylic acids such as succinic acid, adipic acid, sebacic acid, fumaric acid, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, 5-tetrabutylphosphonium sulfoisophthalic acid, and derivatives thereof;
  • polyalcohols such as ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, octanediol, neopentyl glycol, glycerin, trimethylolpropane, pentaerythritol, polyalcohol prepared by addition of ethylene oxide or propylene oxide to trimethylolpropane or pentaerythritol, aromatic polyalcohol prepared by addition reaction of bisphenol with ethylene oxide, diethylene glycol, triethylene glycol, polyethylene glycol and polypropylene glycol, and derivatives thereof;
  • hydroxycarboxylic acids such as glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid and 6-hydroxycaproic acid;
  • lactones such as glycolide, ⁇ -caprolactone glycolide, ⁇ -caprolactone, ⁇ -propiolactone, ⁇ -butyrolactone, ⁇ - or ⁇ -butyrolactone, pivalolactone and ⁇ -valerolactone.
  • stereocomplex formation allows the polylactic acid block copolymer to have a melting point derived from stereocomplex crystals of 190 to 230° C.
  • the polylactic acid block copolymer has higher heat resistance compared to polylactic acid homopolymers.
  • the melting point derived from stereocomplex crystals is preferably 200° C. to 230° C., more preferably 205° C. to 230° C., especially preferably 210° C. to 230° C.
  • the polylactic acid block copolymer needs to have a degree of stereocomplexation (Sc) of not less than 80% in view of the heat resistance.
  • the degree of stereocomplexation is more preferably 85 to 100%, especially preferably 90 to 100%.
  • the degree of stereocomplexation herein means the ratio of stereocomplex crystals with respect to the total crystals in the polylactic acid. More particularly, it can be calculated according to Equation (4), wherein ⁇ Hl represents the heat of fusion of crystals of poly-L-lactic acid alone and crystals of poly-D-lactic acid alone and ⁇ Hh represents the heat of fusion of stereocomplex crystals as measured with a differential scanning calorimetry (DSC) by increasing the temperature from 30° C. to 250° C. at a heating rate of 20° C./min.
  • DSC differential scanning calorimetry
  • the polylactic acid block copolymer further needs to satisfy Inequality (5).
  • Tm represents the melting point measured with a differential scanning calorimetry (DSC) by increasing the temperature of the polylactic acid block copolymer at a heating rate of 40° C./min. from 30° C. to 250° C.
  • Tms represents the beginning temperature of melting measured with a differential scanning calorimetry (DSC) by increasing the temperature of the polylactic acid block copolymer at a heating rate of 40° C./min. from 30° C. to 250° C.
  • Tme represents the end temperature of melting measured by measured with a differential scanning calorimetry (DSC) by increasing the temperature of the polylactic acid block copolymer at a heating rate of 40° C./min. from 30° C. to 250° C.
  • a range of 1 ⁇ (Tm ⁇ Tms)/(Tme ⁇ Tm) ⁇ 1.6 is preferred, and a range of 1 ⁇ (Tm ⁇ Tms)/(Tme ⁇ Tm) ⁇ 1.4 is more preferred.
  • the cooling crystallization temperature (Tc) is preferably not less than 130° C. in view of the moldability and the heat resistance of the polylactic acid block copolymer.
  • the cooling crystallization temperature (Tc) of the molded product herein means the crystallization temperature derived from polylactic acid crystals measured with a differential scanning calorimetry (DSC) by increasing the temperature at a heating rate of 20° C./min. from 30° C. to 250° C. and keeping the temperature constant for 3 minutes at 250° C., followed by decreasing the temperature at a cooling rate of 20° C./min.
  • the crystallization temperature (Tc) is not restricted, and preferably not less than 130° C., more preferably not less than 132° C., especially preferably not less than 135° C. in view of the heat resistance and the transparency.
  • the weight average molecular weight of the polylactic acid block copolymer is not restricted, and preferably not less than 100,000 and less than 300,000 in view of the moldability and the mechanical properties.
  • the weight average molecular weight is more preferably not less than 120,000 and less than 280,000, still more preferably not less than 130,000 and less than 270,000, especially preferably not less than 140,000 and less than 260,000.
  • the polydispersity of the polylactic acid block copolymer is preferably 1.5 to 3.0 in view of the mechanical properties.
  • the polydispersity is more preferably 1.8 to 2.7, especially preferably 2.0 to 2.4 in view of the moldability and mechanical properties.
  • the ratio of molecular weights of not less than 100,000 is preferably not less than 40% and up to 100% in view of the mechanical properties.
  • the ratio is more preferably not less than 45% and up to 100%, and especially preferably not less than 50% and up to 100% in view of the mechanical properties.
  • the ratio of molecular weights of not less than 100,000 (Mwp) can be calculated according to Equation (6), wherein (c) represents the area of the whole molecular weight distribution curve and (d) represents the area of the portion corresponding to molecular weights of not less than 100,000.
  • the weight average molecular weight, polydispersity and molecular weight distribution are values measured by gel permeation chromatography (GPC) using hexafluoroisopropanol or chloroform as a solvent and calculated in terms of poly(methyl methacrylate) standards.
  • the average sequence length of the polylactic acid block copolymer is preferably not less than 20.
  • the average sequence length is more preferably not less than 25, and an average sequence length of not less than 30 is especially preferred in view of the mechanical properties of the molded product.
  • the average sequence length of the polylactic acid block copolymer can be calculated by 13 C-NMR measurement according to Equation (7), wherein (a) represents the integrated value of the peak at about 170.1 to 170.3 ppm among the peaks of carbon belonging to carbonyl carbon and (b) represents the integrated value of the peak at about 169.8 to 170.0 ppm.
  • the weight ratio between the total segment(s) composed of L-lactic acid units and the total segment(s) composed of D-lactic acid units is preferably 90:10 to 10:90.
  • the weight ratio is more preferably 80:20 to 20:80, especially preferably 75:25 to 60:40 or 40:60 to 25:75.
  • a polylactic acid stereocomplex is likely to be formed, resulting in a sufficiently large increase in the melting point of the polylactic acid block copolymer.
  • the total number of the segment(s) composed of L-lactic acid units and the segment(s) composed of D-lactic acid units per one molecule of the polylactic acid block copolymer is preferably not less than 3 in view of easily forming a polylactic acid stereocomplex having a high melting point and obtaining a molded article having high heat resistance.
  • the total number is more preferably not less than 5, especially preferably not less than 7.
  • the method for producing a polylactic acid block copolymer is not restricted, and conventional methods for producing polylactic acid may be used.
  • the method include the lactide method wherein either cyclic dimer L-lactide or D-lactide produced from raw material lactic acid is subjected to ring-opening polymerization in the presence of a catalyst and the lactide with the optical isomer to the polylactic acid above described is further added, followed by subjecting the resulting mixture to ring-opening polymerization, to obtain a polylactic acid block copolymer (Production Method 1); a method wherein each of poly-L-lactic acid and poly-D-lactic acid is polymerized by respectively direct polymerization of the raw material or by ring-opening polymerization via lactide, and the obtained poly-L-lactic acid and poly-D-lactic acid are then mixed, followed by obtaining a polylactic acid block copolymer by solid-phase polymerization (Production Method 2); a method wherein poly-L-lactic acid and poly-
  • any of the production methods may be used, and the method by mixing poly-L-lactic acid and poly-D-lactic acid followed by solid-phase polymerization is preferred since, in this method, the total number of the segment(s) composed of L-lactic acid units and segment(s) composed of D-lactic acid units contained per one molecule of the polylactic acid block copolymer is not less than 3, and a polylactic acid block copolymer having all of excellent heat resistance, crystallinity and mechanical properties can be obtained as a result.
  • the poly-L-lactic acid herein means a polymer containing L-lactic acid as a major component and containing not less than 70 mol % L-lactic acid units.
  • the poly-L-lactic acid comprises preferably not less than 80 mol %, more preferably not less than 90 mol %, still more preferably not less than 95 mol %, especially preferably not less than 98 mol % L-lactic acid units.
  • the poly-D-lactic acid herein means a polymer containing D-lactic acid as a major component and containing not less than 70 mol % D-lactic acid units.
  • the poly-D-lactic acid comprises preferably not less than 80 mol %, more preferably not less than 90 mol %, still more preferably not less than 95 mol %, especially preferably not less than 98 mol % D-lactic acid units.
  • Examples of the method wherein a polylactic acid block copolymer is obtained by ring-opening polymerization include a method wherein one of L-lactide and D-lactide is subjected to ring-opening polymerization in the presence of a catalyst and the lactide with the other optical isomer to the polylactic acid above described is added, followed by subjecting the resulting mixture to ring-opening polymerization, to obtain a polylactic acid block copolymer.
  • the ratio between the weight average molecular weight of the segment(s) composed of L-lactic acid units and the weight average molecular weight of the segment(s) composed of D-lactic acid units contained per one molecule of the polylactic acid block copolymer obtained by the ring-opening polymerization is preferably not less than 2 and less than 30 in view of the heat resistance, and the transparency of the molded product.
  • the ratio is more preferably not less than 3 and less than 20, especially preferably not less than 5 and less than 15.
  • the ratio between the weight average molecular weight of the segment(s) composed of L-lactic acid units and the weight average molecular weight of the segment(s) composed of D-lactic acid units can be controlled by the weight ratio between L-lactide and D-lactide used upon polymerization of the polylactic acid block copolymer.
  • the total number of the segment(s) composed of L-lactic acid units and segment(s) composed of D-lactic acid units contained per one molecule of the polylactic acid block copolymer obtained by the ring-opening polymerization is preferably not less than 3 in view of improvement of the heat resistance and the crystallinity.
  • the total number is more preferably not less than 5, especially preferably not less than 7.
  • the weight average molecular weight per segment is preferably 2,000 to 50,000.
  • the weight average molecular weight per segment is more preferably 4,000 to 45,000, especially preferably 5,000 to 40,000.
  • the optical purity of the L-lactide and D-lactide to be used in the ring-opening polymerization is preferably not less than 90% ee in view of improvement of the crystallinity and the melting point of the polylactic acid block copolymer.
  • the optical purity is more preferably not less than 95% ee, especially preferably not less than 98% ee.
  • the amount of water in the reaction system is preferably not more than 4 mol % with respect to the total amount of L-lactide and D-lactide in view of obtaining a high molecular weight product.
  • the amount of water is more preferably not more than 2 mol %, especially preferably not more than 0.5 mol %.
  • the amount of water is a value measured by coulometric titration using the Karl-Fischer method.
  • Examples of the polymerization catalyst used for production of the polylactic acid block copolymer by the ring-opening polymerization method include metal catalysts and acid catalysts.
  • Examples of the metal catalysts include tin compounds, titanium compounds, lead compounds, zinc compounds, cobalt compounds, iron compounds, lithium compounds and rare earth compounds.
  • Preferred examples of the types of the compounds include metal alkoxides, halogen metal compounds, organic carboxylates, carbonates, sulfates and oxides.
  • tin compounds include tin powder, tin(II) chloride, tin(IV) chloride, tin(II) bromide, tin(IV) bromide, ethoxytin(II), t-butoxytin(IV), isopropoxytin(IV), stannous acetate, tin(IV) acetate, stannous octoate, tin(II) laurate, tin(II) myristate, tin(II) palmitate, tin(II) stearate, tin(II) oleate, tin(II) linoleate, tin(II) acetylacetonate, tin(II) oxalate, tin(II) lactate, tin(II) tartrate, tin(II) pyrophosphate, tin(II) p-phenolsul
  • titanium compounds include titanium methoxide, titanium propoxide, titanium isopropoxide, titanium butoxide, titanium isobutoxide, titanium cyclohexide, titanium phenoxide, titanium chloride, titanium diacetate, titanium triacetate, titanium tetraacetate and titanium(IV) oxide.
  • the lead compounds include diisopropoxylead(II), lead monochloride, lead acetate, lead(II) octoate, lead(II) isooctoate, lead(II) isononanoate, lead(II) laurate, lead(II) oleate, lead(II) linoleate, lead naphthenate, lead(II) neodecanoate, lead oxide and lead(II) sulfate.
  • the zinc compounds include zinc powder, methylpropoxy zinc, zinc chloride, zinc acetate, zinc(II) octoate, zinc naphthenate, zinc carbonate, zinc oxide and zinc sulfate.
  • cobalt compounds include cobalt chloride, cobalt acetate, cobalt(II) octoate, cobalt(II) isooctoate, cobalt(II) isononanoate, cobalt(II) laurate, cobalt(II) oleate, cobalt(II) linoleate, cobalt naphthenate, cobalt(II) neodecanoate, cobalt(II) carbonate, cobalt(II) sulfate and cobalt(II) oxide.
  • iron compounds include iron(II) chloride, iron(II) acetate, iron(II) octoate, iron naphthenate, iron(II) carbonate, iron(II) sulfate and iron(II) oxide.
  • lithium compounds include lithium propoxide, lithium chloride, lithium acetate, lithium octoate, lithium naphthenate, lithium carbonate, dilithium sulfate and lithium oxide.
  • rare earth compounds include triisopropoxyeuropium(III), triisopropoxyneodymium(III), triisopropoxylanthanum, triisopropoxysamarium(III), triisopropoxyyttrium, isopropoxyyttrium, dysprosium chloride, europium chloride, lanthanum chloride, neodymium chloride, samarium chloride, yttrium chloride, dysprosium(III) triacetate, europium(III) triacetate, lanthanum acetate, neodymium triacetate, samarium acetate, yttrium triacetate, dysprosium(III) carbonate, dysprosium(IV) carbonate, europium(II) carbonate, lanthanum carbonate, neodymium carbonate, samarium(II) carbonate, samarium(III) carbonate, yttrium carbonate, dysprosium chloride,
  • metal catalysts include potassium compounds such as potassium isopropoxide, potassium chloride, potassium acetate, potassium octoate, potassium naphthenate, potassium t-butyl carbonate, potassium sulfate and potassium oxide; copper compounds such as copper(II) diisopropoxide, copper(II) chloride, copper(II) acetate, copper octoate, copper naphthenate, copper(II) sulfate and dicopper carbonate; nickel compounds such as nickel chloride, nickel acetate, nickel octoate, nickel carbonate, nickel(II) sulfate and nickel oxide; zirconium compounds such as tetraisopropoxyzirconium(IV), zirconium trichloride, zirconium acetate, zirconium octoate, zirconium naphthenate, zirconium(II) carbonate, zirconium(IV) carbonate, zirconium sulfate and
  • the metal catalysts include compounds composed of two or more kinds of metallic elements, such as sodium stannate, magnesium stannate, potassium stannate, calcium stannate, manganese stannate, bismuth stannate, barium stannate, strontium stannate, sodium titanate, magnesium titanate, aluminum titanate, potassium titanate, calcium titanate, cobalt titanate, zinc titanate, manganese titanate, zirconium titanate, bismuth titanate, barium titanate and strontium titanate.
  • the acid catalyst may be either a Br ⁇ nsted acid as a proton donor or a Lewis acid as an electron-pair acceptor, and may be either an organic acid or an inorganic acid.
  • the acid catalyst include monocarboxylic acid compounds such as formic acid, acetic acid, propionic acid, heptanoic acid, octanoic acid, octylic acid, nonanoic acid, isononanoic acid, trifluoroacetic acid and trichloroacetic acid; dicarboxylic acid compounds such as oxalic acid, succinic acid, maleic acid, tartaric acid and malonic acid; tricarboxylic acid compounds such as citric acid and tricarballylic acid; sulfonic acid compounds such as aromatic sulfonic acids including benzenesulfonic acid, n-butylbenzenesulfonic acid, n-octylbenzenesulfonic acid, n-dodecylbenzenesulfonic acid, pentadecylbenzenesulfonic acid, 2,5-dimethylbenzenesulfonic acid, 2,5-dibut
  • the form of the acid catalyst is not restricted, and may be either a solid acid catalyst or a liquid acid catalyst.
  • the solid acid catalyst include natural minerals such as acid clay, kaolinite, bentonite, montmorillonite, talc, zirconium silicate and zeolite; oxides such as silica, alumina, titania and zirconia; oxide complexes such as silica alumina, silica magnesia, silica boria, alumina boria, silica titania and silica zirconia; chlorinated alumina; fluorinated alumina; and positive ion exchange resins.
  • the polymerization catalyst for the ring-opening polymerization method is preferably a metal catalyst, and among metal catalysts, tin compounds, titanium compounds, antimony compounds and rare earth compounds are more preferred.
  • tin compounds and titanium compounds are more preferred.
  • tin-based organic carboxylates and tin-based halogen compounds are preferred, and stannous acetate, stannous octoate and tin(II) chloride are more preferred.
  • the amount of the polymerization catalyst to be added for the ring-opening polymerization is not restricted, and preferably not less than 0.001 part by weight and not more than 2 parts by weight, especially preferably not less than 0.001 part by weight and not more than 1 part by weight with respect to 100 parts by weight of the raw materials used (L-lactic acid, D-lactic acid and/or the like).
  • the amount of catalyst is within the above-described preferred range, the effect of reducing the polymerization time can be obtained, and the molecular weight of the polylactic acid block copolymer finally obtained tends to be high.
  • the total amount of the catalysts added is preferably within the above-described range.
  • the timing of addition of the polymerization catalyst in the ring-opening polymerization is not restricted, and the catalyst is preferably added after melting of the lactide under heat in view of uniform dispersion of the catalyst in the system and enhancement of the polymerization activity.
  • poly-L-lactic acid and poly-D-lactic acid are mixed and solid-phase polymerization is then carried out to obtain a polylactic acid block copolymer (Production Method 2) will now be described below.
  • the method of production of poly-L-lactic acid and poly-D-lactic acid may be carried out by either the ring-opening polymerization method or the direct polymerization method.
  • one of the poly-L-lactic acid and poly-D-lactic acid preferably has a weight average molecular weight of 60,000 to 300,000 and the other preferably has a weight average molecular weight of 10,000 to 50,000 in view of increasing the weight average molecular weight and the degree of stereocomplexation after the solid-phase polymerization. More preferably, one of the polylactic acids has a weight average molecular weight of 100,000 to 270,000 and the other has a weight average molecular weight of 15,000 to 45,000.
  • one of the polylactic acids has a weight average molecular weight of 150,000 to 240,000 and the other has a weight average molecular weight of 20,000 to 40,000.
  • the combination of the weight average molecular weights of the poly-L-lactic acid and poly-D-lactic acid is preferably appropriately selected such that the weight average molecular weight after mixing is not less than 90,000.
  • the ratio of the polylactic acid having a higher weight average molecular weight with respect to the polylactic acid having a lower average molecular weight is preferably not less than 2 and less than 30.
  • the ratio is more preferably not less than 3 and less than 20, most preferably not less than 5 and less than 15.
  • the combination of the weight average molecular weights of the poly-L-lactic acid and poly-D-lactic acid is preferably appropriately selected such that the weight average molecular weight after mixing is not less than 90,000.
  • Each of the amount of lactide and the amount of oligomers contained in poly-L-lactic acid or poly-D-lactic acid is preferably not more than 5%.
  • the amount is more preferably not more than 3%, especially preferably not more than 1%.
  • the amount of lactic acid contained in poly-L-lactic acid or poly-D-lactic acid is preferably not more than 2%.
  • the amount is more preferably not more than 1%, especially preferably not more than 0.5%.
  • the acid value of one of the poly-L-lactic acid and poly-D-lactic acid is preferably 100 eq/ton.
  • the value is more preferably not more than 50 eq/ton, still more preferably not more than 30 eq/ton, especially preferably not more than 15 eq/ton.
  • the acid value of the other of the poly-L-lactic acid and poly-D-lactic acid to be mixed is preferably not more than 600 eq/ton.
  • the value is more preferably not more than 300 eq/ton, still more preferably not more than 150 eq/ton, especially preferably not more than 100 eq/ton.
  • the amount of water in the reaction system is preferably not more than 4 mol % with respect to the total amount of L-lactide and D-lactide in view of obtaining a high molecular weight product.
  • the amount of water is more preferably not more than 2 mol %, especially preferably not more than 0.5 mol %.
  • the amount of water is a value measured by coulometric titration using the Karl-Fischer method.
  • Examples of the polymerization catalyst used for production of poly-L-lactic acid or poly-D-lactic acid by the ring-opening polymerization method include the same metal catalysts and acid catalysts as in Production Method 1.
  • the amount of the polymerization catalyst to be added for the ring-opening polymerization is not restricted, and preferably not less than 0.001 part by weight and not more than 2 parts by weight, especially preferably not less than 0.001 part by weight and not more than 1 part by weight with respect to 100 parts by weight of the raw materials used (L-lactic acid, D-lactic acid and/or the like).
  • the amount of catalyst is within the above-described preferred range, the effect of reducing the polymerization time can be obtained, and the molecular weight of the polylactic acid block copolymer finally obtained tends to be high.
  • the total amount of the catalysts added is preferably within the above-described range.
  • the timing of addition of the polymerization catalyst in the ring-opening polymerization is not restricted, and the catalyst is preferably added after melting of the lactide under heat in view of uniform dispersion of the catalyst in the system and enhancement of the polymerization activity.
  • Examples of the polymerization catalyst used for production of poly-L-lactic acid or poly-D-lactic acid by the direct polymerization method include metal catalysts and acid catalysts.
  • Examples of the metal catalysts include tin compounds, titanium compounds, lead compounds, zinc compounds, cobalt compounds, iron compounds, lithium compounds and rare earth compounds.
  • Preferred examples of the types of the compounds include metal alkoxides, halogen metal compounds, organic carboxylates, carbonates, sulfates and oxides.
  • tin compounds include tin powder, tin(II) chloride, tin(IV) chloride, tin(II) bromide, tin(IV) bromide, ethoxytin(II), t-butoxytin(IV), isopropoxytin(IV), stannous acetate, tin(IV) acetate, stannous octoate, tin(II) laurate, tin(II) myristate, tin(II) palmitate, tin(II) stearate, tin(II) oleate, tin(II) linoleate, tin(II) acetylacetonate, tin(II) oxalate, tin(II) lactate, tin(II) tartrate, tin(II) pyrophosphate, tin(II) p-phenolsul
  • titanium compounds include titanium methoxide, titanium propoxide, titanium isopropoxide, titanium butoxide, titanium isobutoxide, titanium cyclohexide, titanium phenoxide, titanium chloride, titanium diacetate, titanium triacetate, titanium tetraacetate and titanium(IV) oxide.
  • the lead compounds include diisopropoxylead(II), lead monochloride, lead acetate, lead(II) octoate, lead(II) isooctoate, lead(II) isononanoate, lead(II) laurate, lead(II) oleate, lead(II) linoleate, lead naphthenate, lead(II) neodecanoate, lead oxide and lead(II) sulfate.
  • the zinc compounds include zinc powder, methylpropoxy zinc, zinc chloride, zinc acetate, zinc(II) octoate, zinc naphthenate, zinc carbonate, zinc oxide and zinc sulfate.
  • cobalt compounds include cobalt chloride, cobalt acetate, cobalt(II) octoate, cobalt(II) isooctoate, cobalt(II) isononanoate, cobalt(II) laurate, cobalt(II) oleate, cobalt(II) linoleate, cobalt naphthenate, cobalt(II) neodecanoate, cobalt(II) carbonate, cobalt(II) sulfate and cobalt(II) oxide.
  • iron compounds include iron(II) chloride, iron(II) acetate, iron(II) octoate, iron naphthenate, iron(II) carbonate, iron(II) sulfate and iron(II) oxide.
  • lithium compounds include lithium propoxide, lithium chloride, lithium acetate, lithium octoate, lithium naphthenate, lithium carbonate, dilithium sulfate and lithium oxide.
  • rare earth compounds include triisopropoxyeuropium(III), triisopropoxyneodymium(III), triisopropoxylanthanum, triisopropoxysamarium(III), triisopropoxyyttrium, isopropoxyyttrium, dysprosium chloride, europium chloride, lanthanum chloride, neodymium chloride, samarium chloride, yttrium chloride, dysprosium(III) triacetate, europium(III) triacetate, lanthanum acetate, neodymium triacetate, samarium acetate, yttrium triacetate, dysprosium(III) carbonate, dysprosium(IV) carbonate, europium(II) carbonate, lanthanum carbonate, neodymium carbonate, samarium(II) carbonate, samarium(III) carbonate, yttrium carbonate, dysprosium chloride,
  • metal catalysts include potassium compounds such as potassium isopropoxide, potassium chloride, potassium acetate, potassium octoate, potassium naphthenate, potassium t-butyl carbonate, potassium sulfate and potassium oxide; copper compounds such as copper(II) diisopropoxide, copper(II) chloride, copper(II) acetate, copper octoate, copper naphthenate, copper(II) sulfate and dicopper carbonate; nickel compounds such as nickel chloride, nickel acetate, nickel octoate, nickel carbonate, nickel(II) sulfate and nickel oxide; zirconium compounds such as tetraisopropoxyzirconium(IV), zirconium trichloride, zirconium acetate, zirconium octoate, zirconium naphthenate, zirconium(II) carbonate, zirconium(IV) carbonate, zirconium sulfate and
  • the metal catalysts include compounds composed of two or more kinds of metallic elements, such as sodium stannate, magnesium stannate, potassium stannate, calcium stannate, manganese stannate, bismuth stannate, barium stannate, strontium stannate, sodium titanate, magnesium titanate, aluminum titanate, potassium titanate, calcium titanate, cobalt titanate, zinc titanate, manganese titanate, zirconium titanate, bismuth titanate, barium titanate and strontium titanate.
  • the acid catalyst may be either a Br ⁇ nsted acid as a proton donor or a Lewis acid as an electron-pair acceptor, and may be either an organic acid or an inorganic acid.
  • the acid catalyst include monocarboxylic acid compounds such as formic acid, acetic acid, propionic acid, heptanoic acid, octanoic acid, octylic acid, nonanoic acid, isononanoic acid, trifluoroacetic acid and trichloroacetic acid; dicarboxylic acid compounds such as oxalic acid, succinic acid, maleic acid, tartaric acid and malonic acid; tricarboxylic acid compounds such as citric acid and tricarballylic acid; sulfonic acid compounds such as aromatic sulfonic acids including benzenesulfonic acid, n-butylbenzenesulfonic acid, n-octylbenzenesulfonic acid, n-dodecylbenzenesulfonic acid, pentadecylbenzenesulfonic acid, 2,5-dimethylbenzenesulfonic acid, 2,5-dibut
  • the form of the acid catalyst is not restricted, and may be either a solid acid catalyst or a liquid acid catalyst.
  • the solid acid catalyst include natural minerals such as acid clay, kaolinite, bentonite, montmorillonite, talc, zirconium silicate and zeolite; oxides such as silica, alumina, titania and zirconia; oxide complexes such as silica alumina, silica magnesia, silica boria, alumina boria, silica titania and silica zirconia; chlorinated alumina; fluorinated alumina; and positive ion exchange resins.
  • tin compounds, titanium compounds, antimony compounds, rare earth compounds and acid catalysts are preferred, and, in consideration of the melting point of the produced polylactic acid, tin compounds, titanium compounds and sulfonic acid compounds are more preferred.
  • tin-based organic carboxylates and tin-based halogen compounds are preferred, and stannous acetate, stannous octoate and tin(II) chloride are more preferred; and, in the case of an acid catalyst, mono- and disulfonic acid compounds are preferred, and methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, propanedisulfonic acid, naphthalenedisulfonic acid and 2-aminoethanesulfonic acid are more preferred.
  • the catalyst may be of a single type, or two or more types of catalysts may be used in combination.
  • two or more types of catalysts are preferably used in combination.
  • one or more selected from tin compounds and/or one or more selected from sulfonic acid compounds is/are preferably used.
  • stannous acetate and/or stannous octoate in combination with any one or more of methanesulfonic acid, ethanesulfonic acid, propanedisulfonic acid, naphthalenedisulfonic acid and 2-aminoethanesulfonic acid
  • stannous acetate and/or stannous octoate in combination with any one of methanesulfonic acid, ethanesulfonic acid, propanedisulfonic acid and 2-aminoethanesulfonic acid.
  • the amount of polymerization catalyst to be added is not restricted, and preferably not less than 0.001 part by weight and not more than 2 part by weight, especially preferably not less than 0.001 part by weight and not more than 1 part by weight with respect to 100 parts by weight of the raw materials used (L-lactic acid, D-lactic acid and/or the like).
  • the amount of catalyst is less than 0.001 part by weight, the effect of reducing the polymerization time decreases, and, in cases where the amount is more than 2 parts by weight, the molecular weight of the polylactic acid block copolymer finally obtained is less likely to increase.
  • the total amount of the catalysts added is preferably within the above-described range.
  • the weight ratio between the tin compound(s) and the sulfonic acid compound(s) is preferably 1:1 to 1:30 in view of maintenance of high polymerization activity and suppression of coloring, and is preferably 1:2 to 1:15 in view of achievement of excellent productivity.
  • the timing of addition of the polymerization catalyst is not restricted, and, especially in cases where the polylactic acid is polymerized by the direct polymerization method, an acid catalyst is preferably added to the raw material or before dehydration of the raw material in view of achievement of excellent productivity.
  • a metal catalyst is preferably added after dehydration of the raw material in view of increasing the polymerization activity.
  • poly-L-lactic acid and poly-D-lactic acid are mixed and the resulting mixture is subjected to solid-phase polymerization to obtain a polylactic acid block copolymer
  • the degree of stereocomplexation (Sc) of the mixture is more preferably within the range of 15% to 99%, still more preferably within the range of 20% to 95%.
  • the degree of stereocomplexation (Sc) of the kneaded mixture is preferably higher than 60%.
  • the degree of stereocomplexation (Sc) is more preferably within the range of 70 to 99%, especially preferably within the range of 80 to 95%.
  • the degree of stereocomplexation herein means the ratio of stereocomplex crystals contained with respect to the total crystals in the polylactic acid.
  • Equation (8) wherein ⁇ Hl represents the heat of fusion of crystals of poly-L-lactic acid alone and crystals of poly-D-lactic acid alone and ⁇ Hh represents the heat of fusion of stereocomplex crystals as measured with a differential scanning calorimetry (DSC) by increasing the temperature from 30° C. to 250° C. at a heating rate of 20° C./min.
  • DSC differential scanning calorimetry
  • poly-L-lactic acid and poly-D-lactic acid to be used for the mixing are crystallized is not restricted, and either poly-L-lactic acid and poly-D-lactic acid in the crystallized state may be mixed, or poly-L-lactic acid and poly-D-lactic acid in the molten state may be mixed.
  • specific examples of the method thereof include a method wherein the polylactic acids are maintained at a crystallization treatment temperature in the gas phase or liquid phase, a method wherein poly-L-lactic acid and poly-D-lactic acid in the molten state are retained in a melting apparatus at a temperature between the melting point ⁇ 50° C.
  • Crystallization treatment temperature herein is not restricted as long as the temperature is higher than the glass-transition temperature and lower than the melting point of the polylactic acid having a lower melting point selected from the poly-L-lactic acid and the poly-D-lactic acid mixed as described above.
  • the crystallization treatment temperature is more preferably between the heating crystallization temperature and the cooling crystallization temperature as measured with a differential scanning calorimetry (DSC) in advance.
  • DSC differential scanning calorimetry
  • the crystallization in the gas phase or liquid phase may be carried out under any of the conditions of reduced, normal and increased pressures.
  • the crystallization period in the gas phase or liquid phase is not restricted, and the crystallization can be sufficiently achieved within 3 hours, and a length of time of not more than 2 hours is also preferred.
  • the melting apparatus is not restricted as long as shearing or pressurization is possible therewith.
  • the melting apparatus which may be used include polymerization reactors, kneaders, Banbury mixer, single screw extruders, twin screw extruders and injection molding machines, and the melting apparatus is preferably a single screw extruder or twin screw extruder.
  • the crystallization treatment temperature is preferably between the melting point ⁇ 50° C. and the melting point+20° C. of the poly-L-lactic acid and poly-D-lactic acid to be mixed.
  • the crystallization temperature is more preferably between the melting point ⁇ 40° C. and the melting point, especially preferably between the melting point ⁇ 30° C. and the melting point ⁇ 5° C.
  • the temperature of the melting apparatus is conventionally set to a temperature of not less than the melting point+20° C.
  • the melting point herein means the crystal melting temperature measured by differential scanning calorimetry by increasing the temperature from 30° C. to 250° C. at a heating rate of 20° C./min.
  • the crystallization treatment time is preferably 0.1 minute to 10 minutes, more preferably 0.3 to 5 minutes, especially preferably 0.5 minute to 3 minutes. In cases where the crystallization treatment time is within the preferred range, crystallization sufficiently occurs, and thermal degradation is unlikely to occur.
  • the molecules in molten resin tend to be oriented under shearing in the melting apparatus, and this allows a remarkable increase in the crystallization rate as a result.
  • the shear rate in this step is preferably 10 to 400/second. In cases where the shear rate is within the preferred range, the crystallization rate is sufficiently large, and thermal degradation due to shear heating is unlikely to occur.
  • Crystallization tends to be promoted also under pressure, and the pressure is especially preferably 0.05 to 10 MPa for obtaining crystallized polylactic acid having both good fluidity and crystallinity. In cases where the pressure is within the preferred range, the crystallization rate is sufficiently high.
  • the crystallization rate is even higher, which is especially preferred.
  • the method for mixing poly-L-lactic acid and poly-D-lactic acid is not restricted, and examples of the method include a method wherein poly-L-lactic acid and poly-D-lactic acid are melt-mixed at a temperature of not less than the end of melting point of the component having a higher melting point, a method wherein mixing in a solvent is followed by removal of the solvent, and a method wherein at least one of poly-L-lactic acid and poly-D-lactic acid in the molten state is retained in a melting apparatus at a temperature between the melting point ⁇ 50° C. and the melting point+20° C. under shearing, followed by mixing such that crystals of the mixture composed of poly-L-lactic acid and poly-D-lactic acid remain.
  • the melting point herein means the temperature at the peak top of the peak due to melting of crystals of polylactic acid alone as measured with a differential scanning calorimetry (DSC), and the end of melting point means the temperature at the end of the peak due to melting of crystals of polylactic acid alone as measured with a differential scanning calorimetry (DSC).
  • Examples of the method wherein melt mixing is performed at a temperature of not less than the end of melting point include a method wherein poly-L-lactic acid and poly-D-lactic acid are mixed by a batch method or continuous method, either of which may be employed for the mixing.
  • Examples of the extruder include single screw extruders, twin screw extruders, plastomill, kneaders and stirring-vessel-type reactors equipped with a pressure reducing device. In view of enabling uniform and sufficient kneading, a single screw extruder or twin screw extruder is preferably used.
  • poly-L-lactic acid and poly-D-lactic acid are preferably melt-mixed at a temperature of not less than the end of melting point of the component having a higher melting point.
  • the temperature is preferably 140° C. to 250° C., more preferably 160° C. to 230° C., especially preferably 180° C. to 210° C.
  • the mixing temperature is within the preferred range, the mixing can be carried out in the molten state, and the molecular weight is unlikely to decrease during the mixing. Further, the fluidity of the mixture can be kept constant and a remarkable decrease in the fluidity is unlikely to occur.
  • the mixing time is preferably 0.1 minute to 10 minutes, more preferably 0.3 minute to 5 minutes, especially preferably 0.5 minute to 3 minutes.
  • the mixing time is within the preferred range, poly-L-lactic acid and poly-D-lactic acid can be uniformly mixed, and thermal degradation due to mixing is unlikely to occur.
  • the pressure conditions for the mixing at a temperature of not less than the end of melting point is not restricted, and the mixing may be carried out either in the air or under an atmosphere of an inert gas such as nitrogen.
  • Specific examples of the method for mixing poly-L-lactic acid and poly-D-lactic acid prepared by crystallizing poly-L-lactic acid and poly-D-lactic acid in a melting apparatus under shearing and/or pressure include mixing by a batch method or continuous method, and either method may be used for the mixing.
  • the degree of stereocomplexation of the mixture of poly-L-lactic acid and poly-D-lactic acid after mixing can be controlled by a method wherein poly-L-lactic acid and poly-D-lactic acid in the molten state are retained in a melting apparatus under shearing at a temperature between the melting point ⁇ 50° C. and the melting point+20° C.
  • poly-L-lactic acid and poly-D-lactic acid in the molten state are retained in a melting apparatus under pressure at a temperature between the melting point ⁇ 50° C. and the melting point+20° C. of the polylactic acid having a lower melting point.
  • the degree of stereocomplexation herein means the ratio of stereocomplex crystals with respect to the total crystals in the polylactic acid. More particularly, it can be calculated according to Equation (9), wherein ⁇ Hl represents the heat of fusion of crystals of poly-L-lactic acid alone and crystals of poly-D-lactic acid alone and ⁇ Hh represents the heat of fusion of stereocomplex crystals as measured with a differential scanning calorimetry (DSC) by increasing the temperature from 30° C. to 250° C. at a heating rate of 20° C./min.
  • DSC differential scanning calorimetry
  • the degree of stereocomplexation can also be calculated from the ratio between crystals of polylactic acid alone and stereocomplex crystals as measured by X-ray diffraction, the value calculated as described above based on the amount of heat due to melting of crystals measured by DSC is employed in the present invention.
  • the temperature during mixing is preferably between the melting point ⁇ 50° C. and the melting point+20° C. of the mixture of poly-L-lactic acid and poly-D-lactic acid.
  • the mixing temperature is more preferably between the melting point ⁇ 40° C. and the melting point, especially preferably between the melting point ⁇ 30° C. and the melting point ⁇ 5° C.
  • the temperature of the melting apparatus is conventionally preferably set to a temperature of not less than the melting point+20° C. for melting the resin to allow achievement of good fluidity, but, in cases where the mixing temperature is set within the above-described preferred range, the fluidity does not decrease too much, and produced crystals are unlikely to be remelted.
  • the melting point herein means the crystal melting temperature measured with a differential scanning calorimetry (DSC) by increasing the temperature from 30° C. to 250° C. at a heating rate of 20° C./min.
  • Poly-L-lactic acid and poly-D-lactic acid prepared by crystallizing poly-L-lactic acid and poly-D-lactic acid in a melting apparatus under shearing and/or pressure are preferably mixed at a shear rate 10 to 400/second.
  • shear rate is within the preferred range
  • poly-L-lactic acid and poly-D-lactic acid can be uniformly mixed while the fluidity and crystallinity are maintained, and thermal degradation due to shear heating is unlikely to occur during the mixing.
  • the pressure during the mixing is preferably 0.05 to 10 MPa. In cases where the pressure is within the preferred range, poly-L-lactic acid and poly-D-lactic acid can be uniformly mixed while the fluidity and crystallinity are maintained.
  • the method for supplying polylactic acid is not restricted, and examples of possible methods thereof include a method wherein poly-L-lactic acid and poly-D-lactic acid are supplied at once from a resin hopper, and a method wherein, using a side resin hopper as required, poly-L-lactic acid and poly-D-lactic acid are separately supplied via a resin hopper and a side resin hopper.
  • the polylactic acid may also be supplied in the molten state to the extruder directly after the step of producing the polylactic acid.
  • the screw element of the extruder is preferably equipped with a kneading element in the mixing section such that the poly-L-lactic acid and poly-D-lactic acid can be uniformly mixed to form stereocomplexes.
  • the mixing weight ratio between the poly-L-lactic acid composed of L-lactic acid units and the poly-D-lactic acid composed of D-lactic acid units is preferably 90:10 to 10:90.
  • the mixing weight ratio is more preferably 80:20 to 20:80, especially preferably 75:25 to 60:40 or 40:60 to 25:75.
  • a polylactic acid stereocomplex is likely to be formed, resulting in a sufficient increase in the melting point of the polylactic acid block copolymer.
  • the mixing weight ratio between the poly-L-lactic acid and poly-D-lactic acid is other than 50:50, it is preferred to blend the poly-L-lactic acid or poly-D-lactic having a higher weight average molecular weight than the other in a larger amount.
  • the mixing step it is preferred to include a catalyst in the mixture for efficiently promoting the subsequent solid-phase polymerization.
  • the catalyst may be the residual component(s) of the catalyst(s) used for producing the poly-L-lactic acid and/or poly-D-lactic acid, and/or one or more selected from the above-described catalysts may be further added in the mixing step.
  • the content of the catalyst for efficient promotion of solid-phase polymerization is not restricted, and preferably not less than 0.001 part by weight and not more than 1 part by weight, especially preferably not less than 0.001 part by weight and not more than 0.5 part by weight with respect to 100 parts by weight of the mixture of the poly-L-lactic acid and poly-D-lactic acid.
  • the amount of catalyst is within the above-described preferred range, the effect of reducing the reaction time of solid-phase polymerization can be obtained, and the molecular weight of the polylactic acid block copolymer finally obtained tends to be high.
  • the weight average molecular weight (Mw) of the mixture of poly-L-lactic acid and poly-D-lactic acid after the mixing is preferably not less than 90,000 and less than 300,000 in view of the mechanical properties of the mixture.
  • the weight average molecular weight is more preferably not less than 120,000 and less than 300,000, especially preferably not less than 140,000 and less than 300,000.
  • the polydispersity of the mixture of poly-L-lactic acid and poly-D-lactic acid after mixing is preferably 1.5 to 4.0.
  • the polydispersity is more preferably 2.0 to 3.7, especially preferably 2.5 to 3.5.
  • the polydispersity herein means the ratio of the weight average molecular weight with respect to the number average molecular weight of the mixture, and is more particularly a value measured by gel permeation chromatography (GPC) using hexafluoroisopropanol or chloroform as a solvent and calculated in terms of poly(methyl methacrylate) standards.
  • GPC gel permeation chromatography
  • Each of the amount of lactide and the amount of oligomers contained in poly-L-lactic acid or poly-D-lactic acid is preferably not more than 5%.
  • the amount is more preferably not more than 3%, especially preferably not more than 1%.
  • the amount of lactic acid contained in poly-L-lactic acid or poly-D-lactic acid is preferably not more than 2%.
  • the amount is more preferably not more than 1%, especially preferably not more than 0.5%.
  • the form of the mixture of poly-L-lactic acid and poly-D-lactic acid is not restricted, and the mixture may be in the form of a block(s), film(s), pellet(s), powder or the like.
  • a pellet(s) or powder is/are preferably used. Examples of the method for forming the mixture into a pellet(s) include a method wherein the mixture is extruded into a strand-like shape and pelletized, and a method wherein the mixture is extruded into water and pelletized using an underwater cutter.
  • Examples of the method for forming the mixture into powder include a method wherein the mixture is pulverized using a pulverizer such as a mixer, blender, ball mill or hammer mill.
  • a pulverizer such as a mixer, blender, ball mill or hammer mill.
  • the method for carrying out the solid-phase polymerization step is not restricted, and either a batch method or continuous method may be employed.
  • the reactor may be a stirring-vessel-type reactor, mixer-type reactor, column reactor or the like, and two or more types of these reactors may be used in combination.
  • the mixture of poly-L-lactic acid and poly-D-lactic acid is preferably crystallized.
  • crystallization of the mixture of poly-L-lactic acid and poly-D-lactic acid is not necessarily required for carrying out the solid-phase polymerization, but performing crystallization allows further enhancement of the efficiency of solid-phase polymerization.
  • the method of crystallization is not restricted, and a known method may be employed.
  • Examples of the method include a method by maintaining the polylactic acid at a crystallization treatment temperature in the gas phase or liquid phase and a method by cooling and solidifying a molten mixture of poly-L-lactic acid and poly-D-lactic acid while carrying out the operation of stretching or shearing.
  • the method by maintaining the polylactic acid at a crystallization treatment temperature in the gas phase or liquid phase is preferred.
  • the crystallization treatment temperature herein is not restricted as long as the temperature is higher than the glass-transition temperature and lower than the melting point of the polylactic acid having a lower melting point selected from the poly-L-lactic acid and the poly-D-lactic acid mixed as described above.
  • the crystallization treatment temperature is more preferably between the heating crystallization temperature and the cooling crystallization temperature preliminarily measured with a differential scanning calorimetry (DSC).
  • DSC differential scanning calorimetry
  • the crystallization may be carried out under any of the conditions of reduced, normal and increased pressures.
  • the crystallization period is not restricted, and the crystallization can be sufficiently achieved within 3 hours, and a length of time of not more than 2 hours is also preferred.
  • a temperature of not more than the melting point of the mixture of poly-L-lactic acid and poly-D-lactic acid is preferred. Since the mixture of poly-L-lactic acid and poly-D-lactic acid has a melting point of 190 to 230° C. derived from stereocomplex crystals due to stereocomplex formation and a melting point of 150° C. to 185° C. derived from crystals of poly-L-lactic acid alone and crystals of poly-D-lactic acid alone, solid-phase polymerization is preferably carried out at a temperature lower than these melting points. More specifically, the temperature is preferably not less than 100° C.
  • the temperature is more preferably not less than 110° C. and not more than 200° C., still more preferably not less than 120° C. and not more than 180° C., especially preferably not less than 130° C. and not more than 170° C.
  • the temperature is preferably increased stepwise or continuously as the reaction proceeds.
  • the temperature conditions for increasing the temperature stepwise during the solid-phase polymerization are preferably 120 to 145° C. for 1 to 15 hours in the first step, 135° C. to 160° C. for 1 to 15 hours in the second step, and 150° C. to 175° C. for 10 to 30 hours in the third step; more preferably 130 to 145° C. for 2 to 12 hours in the first step, 140° C. to 160° C. for 2 to 12 hours in the second step, and 155° C. to 175° C. for 10 to 25 hours in the third step.
  • the temperature is preferably increased from an initial temperature of 130° C. to 150° C. to a temperature of 150° C. to 175° C. continuously at a rate of 1 to 5° C./min. Further, combination of stepwise temperature increase and continuous temperature increase is also preferred in view of efficient promotion of the solid-phase polymerization.
  • the step is preferably performed under vacuum or under the flow of an inert gas such as dry nitrogen.
  • the degree of vacuum during the solid-phase polymerization under vacuum is preferably not more than 150 Pa, more preferably not more than 75 Pa, especially preferably not more than 20 Pa.
  • the flow rate during the solid-phase polymerization under the flow of an inert gas is preferably 0.1 to 2,000 mL/min., more preferably 0.5 to 1,000 mL/min., especially preferably 1.0 to 500 mL/min., per 1 g of the mixture.
  • the yield of the polymer after the solid-phase polymerization is preferably not less than 90%.
  • the yield is more preferably not less than 93%, especially preferably not less than 95%.
  • the yield of the polymer herein means the ratio of the weight of the polylactic acid block copolymer after the solid-phase polymerization with respect to the weight of the mixture before the solid-phase polymerization. More specifically, the yield can be calculated according to Equation (10), wherein Wp represents the weight of the mixture before the solid-phase polymerization and Ws represents the weight of the polymer after the solid-phase polymerization.
  • the polydispersity of the mixture preferably decreases. More specifically, the polydispersity preferably changes from a value 1.5 to 4.0, which is for the mixture before the solid-phase polymerization, to a value 1.5 to 2.7, which is for the polylactic acid block copolymer after the solid-phase polymerization.
  • the polydispersity more preferably decreases from a value 2.0 to 3.7, which is for the mixture before the solid-phase polymerization, to a value 1.8 to 2.6, which is for the polylactic acid block copolymer after the solid-phase polymerization.
  • the polydispersity especially preferably changes from a value 2.5 to 3.5, which is for the mixture before the solid-phase polymerization, to a value 2.0 to 2.5, which is for the polylactic acid block copolymer after the solid-phase polymerization.
  • one of the poly-L-lactic acid and poly-D-lactic acid preferably has a weight average molecular weight of 60,000 to 300,000 and the other preferably has a weight average molecular weight of 10,000 to 50,000 in view of achieving a high degree of stereocomplexation after melt mixing. More preferably, one of the polylactic acids has a weight average molecular weight of 100,000 to 270,000 and the other has a weight average molecular weight of 15,000 to 45,000. Especially preferably, one of the polylactic acids has a weight average molecular weight of 150,000 to 240,000 and the other has a weight average molecular weight of 20,000 to 40,000.
  • the combination of the weight average molecular weights of the poly-L-lactic acid and poly-D-lactic acid is preferably appropriately selected such that the weight average molecular weight after mixing is not less than 90,000.
  • Examples of the method for melt-mixing at a temperature of not less than the end of melting point for a long time include a method wherein poly-L-lactic acid and poly-D-lactic acid are mixed by a batch method or continuous method, either of which may be employed for the mixing.
  • Examples of the extruder include single screw extruders, twin screw extruders, plastomill, kneaders and stirring-vessel-type reactors equipped with a pressure reducing device. In view of enabling uniform and sufficient kneading, a single screw extruder or twin screw extruder is preferably used.
  • the mixing needs to be carried out at a temperature of not less than the end of melting point of the component having a higher melting point selected from the poly-L-lactic acid and poly-D-lactic acid.
  • the temperature is preferably 140° C. to 250° C., more preferably 160° C. to 230° C., especially preferably 180° C. to 210° C.
  • the mixing temperature is within the above-described preferred range, the fluidity does not decrease too much and the molecular weight of the mixture is unlikely to decrease.
  • the length of time is of preferably 0.1 to 30 minutes, more preferably 0.3 to 20 minutes, especially preferably 0.5 to 10 minutes.
  • the mixing time is within the above-described preferred range, the poly-L-lactic acid and poly-D-lactic acid can be uniformly mixed, and thermal degradation is less likely to occur by the mixing.
  • the pressure conditions during the mixing are not restricted, and the mixing may be carried out either in the air or under an atmosphere of an inert gas such as nitrogen.
  • the mixing weight ratio between the poly-L-lactic acid composed of L-lactic acid units and the poly-D-lactic acid composed of D-lactic acid units to be mixed is preferably 80:20 to 20:80, more preferably 75:25 to 25:75, still more preferably 70:30 to 30:70, especially preferably 60:40 to 40:60.
  • the weight ratio of the poly-L-lactic acid composed of L-lactic acid units is within the above-described preferred range, a polylactic acid stereocomplex is likely to be formed, resulting in a sufficient increase in the melting point of the polylactic acid block copolymer finally obtained.
  • a catalyst is preferably included in the mixture.
  • the catalyst may be the residual component(s) of the catalyst(s) used for producing the poly-L-lactic acid and/or poly-D-lactic acid, and/or a catalyst(s) may be further added in the mixing step.
  • the content of the catalyst is not restricted, and preferably not less than 0.001 part by weight and not more than 1 part by weight, especially preferably not less than 0.001 part by weight and not more than 0.5 part by weight with respect to 100 parts by weight of the mixture of the poly-L-lactic acid and poly-D-lactic acid.
  • the amount of catalyst is within the above-described preferred range, the frequency of transesterification of the mixture is sufficiently high, and the molecular weight of the polylactic acid block copolymer finally obtained tends to be high.
  • the method wherein a polyfunctional compound(s) is/are mixed with poly-L-lactic acid and poly-D-lactic acid to cause covalent bonding of poly-L-lactic acid and poly-D-lactic acid by the polyfunctional compound(s) to obtain a polylactic acid block copolymer (Production Method 4) will now be described.
  • the poly-L-lactic acid and poly-D-lactic acid to be used in this production method may be produced by either the ring-opening polymerization method or the direct polymerization method.
  • one of the poly-L-lactic acid and poly-D-lactic acid has a weight average molecular weight of 30,000 to 100,000 and the other has a weight average molecular weight of 10,000 to 30,000 in view of increasing the degree of stereocomplexation. More preferably, one of the polylactic acids has a weight average molecular weight of 35,000 to 90,000 and the other has a weight average molecular weight of 10,000 to 25,000. Especially preferably, one of the polylactic acids has a weight average molecular weight of 40,000 to 80,000 and the other has a weight average molecular weight of 10,000 to 20,000.
  • the ratio between the weight average molecular weight of the poly-L-lactic acid and the weight average molecular weight of the poly-D-lactic acid used in the above-described mixing is preferably not less than 2 and less than 10 in view of increasing the degree of stereocomplexation.
  • the ratio is more preferably not less than 3 and less than 10, especially preferably not less than 4 and less than 10.
  • polyfunctional compound(s) to be used herein is/are not restricted, and examples thereof include polycarboxylic anhydrides, polycarboxylic acid halides, polycarboxylic acids, polyisocyanates, polyamines, polyalcohols and polyepoxy compounds.
  • polyfunctional compound(s) include polycarboxylic anhydrides such as 1,2-cyclohexanedicarboxylic anhydride, succinic anhydride, phthalic anhydride, trimellitic anhydride, 1,8-naphthalenedicarboxylic anhydride and pyromellitic anhydride; polycarboxylic acid halides such as isophthalic acid chloride, terephthalic acid chloride and 2,6-naphthalenedicarboxylic acid chloride; polycarboxylic acids such as succinic acid, adipic acid, sebacic acid, fumaric acid, terephthalic acid, isophthalic acid and 2,6-naphthalenedicarboxylic acid; polyisocyanates such as hexamethylene diisocyanate, 4,4′-diphenylmethane diisocyanate and toluene-2,4-diisocyanate; polyamines such as ethylenediamine, hexanediamine and di
  • the polyfunctional compound(s) is/are preferably a polycarboxylic anhydride(s), polyisocyanate(s), polyalcohol(s) and/or polyepoxy compound(s), and is/are especially preferably a polycarboxylic anhydride(s), polyisocyanate(s) and/or polyepoxy compound(s).
  • a polycarboxylic anhydride(s), polyisocyanate(s) and/or polyepoxy compound(s) One of these or a combination of two or more of these may be used.
  • the amount of the polyfunctional compound(s) to be mixed is not restricted, and is preferably not less than 0.01 part by weight and not more than 20 parts by weight, more preferably not less than 0.1 part by weight and not more than 10 parts by weight with respect to 100 parts by weight of the total of poly-L-lactic acid and poly-D-lactic acid. In cases where the amount of the polyfunctional compound(s) added is within the above-described preferred range, the effect of forming covalent bonds can be sufficiently produced.
  • a reaction catalyst(s) may be added for promoting the reaction of poly-L-lactic acid and poly-D-lactic acid with the polyfunctional compound(s).
  • the reaction catalyst(s) include alkali metal compounds such as sodium hydroxide, potassium hydroxide, lithium hydroxide, cesium hydroxide, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate, potassium carbonate, lithium carbonate, sodium acetate, potassium acetate, lithium acetate, sodium stearate, potassium stearate, lithium stearate, sodium borohydride, lithium borohydride, sodium phenylborate, sodium benzoate, potassium benzoate, lithium benzoate, disodium hydrogenphosphate, dipotassium hydrogenphosphate, dilithium hydrogenphosphate, disodium salt of bisphenol A, dipotassium salt of bisphenol A, dilithium salt of bisphenol A, sodium salt of phenol, potassium salt of phenol, lithium salt of phenol and cesium salt of phenol;
  • the amount of the catalyst(s) to be added is not restricted, and is preferably not less than 0.001 part by weight and not more than 1 part by weight with respect to 100 parts by weight of the total of poly-L-lactic acid and poly-D-lactic acid. In cases where the amount of the catalyst(s) is within the above-described preferred range, the effect of promoting the reaction can be obtained, and the molecular weight of the polylactic acid block copolymer finally obtained tends to be high.
  • the method of reacting the poly-L-lactic acid and poly-D-lactic acid with the polyfunctional compound(s) is not restricted, and examples of the method include a method wherein melt mixing is performed at a temperature of not less than the end of melting point of the component having a higher melting point selected from the poly-L-lactic acid and poly-D-lactic acid.
  • Examples of the method wherein melt mixing is performed at a temperature of not less than the end of melting point include a method wherein poly-L-lactic acid and poly-D-lactic acid are mixed by a batch method or continuous method, either of which may be employed.
  • Examples of the extruder include single screw extruders, twin screw extruders, plastomill, kneaders and stirring-vessel-type reactors equipped with a pressure reducing device. In view of enabling uniform and sufficient kneading, a single screw extruder or twin screw extruder is preferably used.
  • the melt mixing is preferably carried out at a temperature of not less than the end of melting point of the component having a higher melting point selected from the poly-L-lactic acid and poly-D-lactic acid.
  • the temperature is preferably 140° C. to 250° C., more preferably 160° C. to 230° C., especially preferably 180 to 210° C.
  • the mixing temperature is within the above-described preferred range, the fluidity does not decrease too much, and the molecular weight of the mixture is unlikely to decrease.
  • the length of time is preferably 0.1 to 30 minutes, more preferably 0.3 to 20 minutes, especially preferably 0.5 to 10 minutes.
  • the mixing time is within the above-described preferred range, the poly-L-lactic acid and poly-D-lactic acid can be uniformly mixed, and thermal degradation is less likely to occur during the mixing.
  • the pressure conditions during the melt mixing are not restricted, and the mixing may be carried out either in the air or under an atmosphere of an inert gas such as nitrogen.
  • the mixing weight ratio between the poly-L-lactic acid composed of L-lactic acid units and the poly-D-lactic acid composed of D-lactic acid units to be mixed is preferably 90:10 to 10:90, more preferably 80:20 to 20:80.
  • the mixing weight ratio is especially preferably 75:25 to 60:40 or 40:60 to 25:75.
  • a polylactic acid stereocomplex is likely to be formed, resulting in a sufficient increase in the melting point of the polylactic acid block copolymer finally obtained.
  • polylactic acid block copolymer obtained by mixing a polyfunctional compound(s) with poly-L-lactic acid and poly-D-lactic acid is a high molecular weight product because of covalent bonding of poly-L-lactic acid and poly-D-lactic acid caused by the polyfunctional compound(s)
  • solid-phase polymerization may also be carried out by the above-mentioned method after the mixing.
  • a catalyst deactivating agent(s) is/are preferably added after the polylactic acid block copolymer was obtained.
  • the residual catalyst may cause thermal degradation of the polylactic acid block copolymer during melt mixing or melt molding.
  • the catalyst deactivating agent examples include hindered phenol compounds, thioether compounds, vitamin compounds, triazole compounds, polyamine compounds, compounds of hydrazine derivatives and phosphorous compounds, and these may also be used in combination.
  • at least one of phosphorous compounds is preferably contained, and the phosphorous compound(s) is/are more preferably a phosphate compound(s) and/or phosphite compound(s).
  • Still more preferred specific examples of the compounds include “Adekastab” AX-71 (dioctadecyl phosphate), PEP-8 (distearyl pentaerythritol diphosphite) and PEP-36 (cyclic neopentatetraylbis(2,6-t-butyl-4-methylphenyl)phosphite) manufactured by ADEKA Corporation.
  • hindered phenol compounds include n-octadecyl-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)-propionate, n-octadecyl-3-(3′-methyl-5′-t-butyl-4′-hydroxyphenyl)-propionate, n-tetradecyl-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)-propionate, 1,6-hexanediol-bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate], 1,4-butanediol-bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate], 2,2′-methylenebis-(4-methyl-t-butylphenol), triethylene glycol-bis-[3-(3-t-butyl-5-methyl-4-hydroxy
  • Preferred examples of the hindered phenol compounds include triethylene glycol-bis-[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)-propionate], tetrakis[methylene-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate]methane, 1,6-hexanediol-bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate], pentaerythrityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] and N,N′-hexamethylenebis(3,5-di-t-butyl-4-hydroxy-hydrocinnamide).
  • hindered phenol compounds include “Adekastab” AO-20, AO-30, AO-40, AO-50, AO-60, AO-70, AO-80 and AO-330 manufactured by ADEKA Corporation; “Irganox” 245, 259, 565, 1010, 1035, 1076, 1098, 1222, 1330, 1425, 1520, 3114 and 5057 manufactured by Ciba Specialty Chemicals; “Sumilizer” BHT-R, MDP-S, BBM-S, WX-R, NW, BP-76, BP-101, GA-80, GM and GS manufactured by Sumitomo Chemical Co., Ltd.; and “Cyanox” CY-1790 manufactured by Saianamido Inc.
  • thioether compounds include dilauryl thiodipropionate, ditridecyl thiodipropionate, dimyristyl thiodipropionate, distearyl thiodipropionate, pentaerythritol-tetrakis(3-laurylthiopropionate), pentaerythritol-tetrakis(3-dodecylthiopropionate), pentaerythritol-tetrakis(3-octadecylthiopropionate), and pentaerythritol-tetrakis(3-myristylthiopropionate) and pentaerythritol-tetrakis(3-stearylthiopropionate).
  • thioether compounds include “Adekastab” AO-23, AO-412S and AO-503A manufactured by ADEKA Corporation; “Irganox” PS802 manufactured by Ciba Specialty Chemicals; “Sumilizer” TPL-R, TPM, TPS and TP-D manufactured by Sumitomo Chemical Co., Ltd.; DSTP, DLTP, DLTOIB and DMTP manufactured by API Corporation; “Seenox” 412S manufactured by Shipro Kasei Kaisha, Ltd.; and “Cyanox” 1212 manufactured by Saianamido Inc.
  • polyamine compounds include 3,9-bis[2-(3,5-diamino-2,4,6-triazaphenyl)ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane, ethylenediamine-tetraacetic acid, alkali metal (Li, Na, K) salts of ethylenediamine-tetraacetic acid, N,N′-disalicylidene-ethylenediamine, N,N′-disalicylidene-1,2-propylenediamine, N,N′′-disalicylidene-N′-methyl-dipropylenetriamine and 3-salicyloylamino-1,2,4-triazole.
  • hydrazine derivatives include decamethylenedicarboxylic acid-bis(N′-salicyloyl-hydrazide), isophthalic acid bis(2-phenoxypropionylhydrazide), N-formyl-N′-salicyloylhydrazine, 2,2-oxamidobis-[ethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], oxalyl-bis-benzylidene-hydrazide, nickel-bis(1-phenyl-3-methyl-4-decanoyl-5-pyazolate), 2-ethoxy-2′-ethyloxanilide, 5-t-butyl-2-ethoxy-2′-ethylanilide, N,N-diethyl-N′,N′-diphenyloxamide, N,N′-diethyl-N,N′-diphenyloxamide, oxalic acid-bis(benz
  • Examples of the phosphorous compounds include phosphite compounds and phosphate compounds.
  • Specific examples of the phosphite compounds include tetrakis[2-t-butyl-4-thio(2′-methyl-4′-hydroxy-5′-t-butylphenyl]-5-methylphenyl]-1,6-hexamethylene-bis(N-hydroxyethyl-N-methylsemicarbazide)-diphosphite, tetrakis[2-t-butyl-4-thio(2′-methyl-4′-hydroxy-5′-t-butylphenyl)-5-methylphenyl]-1,10-decamethylene-di-carboxylic acid-di-hydroxyethylcarbonylhydrazide-diphosphite, tetrakis[2-t-butyl-4-thio(2′-methyl-4′-hydroxy-5′-t-butylphenyl)-5-methylphenyl]-1,10-decamethylene-d
  • phosphite compounds include tris(2,4-di-t-butylphenyl)phosphite, tetrakis(2,4-di-t-butylphenyl)4,4′-biphenylenephosphonite, bis(2,4-di-t-butylphenyl)pentaerythritol-di-phosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol-di-phosphite, 2,2-methylenebis(4,6-di-t-butylphenyl)octylphosphite, 4,4′-butylidene-bis(3-methyl-6-t-butylphenyl-di-tridecyl)phosphite, 1,1,3-tris(2-methyl-4-ditrid
  • Tris(2,4-di-t-butylphenyl)phosphite, 2,2-methylenebis(4,6-di-t-butylphenyl)octylphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol-di-phosphite, tetrakis(2,4-di-t-butylphenyl)-4,4′-biphenylenephosphonite and the like may be preferably used.
  • phosphite compounds include “Adekastab” C, PEP-4C, PEP-8, PEP-11C, PEP-24G, PEP-36, HP-10, 2112, 260, 522A, 329A, 1178, 1500, C, 135A, 3010 and TPP manufactured by ADEKA Corporation; “Irgafos” 168 manufactured by Ciba Specialty Chemicals; “Sumilizer” P-16 manufactured by Sumitomo Chemical Co., Ltd.; “Sandostab” PEPQ manufactured by Clarinat International Ltd.; and “Weston” 618, 619G and 624 manufactured by GE.
  • the phosphate compounds include monostearyl acid phosphate, distearyl acid phosphate, methyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, octyl acid phosphate and isodecyl acid phosphate, and, among these, monostearyl acid phosphate and distearyl acid phosphate are preferred.
  • Specific examples of trade names of the phosphate compounds include “Irganox” MD1024 manufactured by Ciba Specialty Chemicals; “Inhibitor” OABH manufactured by Eastman Kodak; and “Adekastab” CDA-1, CDA-6 and AX-71 manufactured by ADEKA Corporation.
  • the amount of the catalyst deactivating agent to be added is not restricted, and is preferably 0.001 to 2 parts by weight, more preferably 0.01 to 1 part by weight, still more preferably 0.05 to 0.5 part by weight, most preferably 0.08 to 0.3 part by weight with respect to 100 parts by weight of the polylactic acid block copolymer in view of the thermal stability.
  • the catalyst deactivating agent it is preferably added after the polylactic acid block copolymer was obtained, in view of maintaining a high molecular weight product.
  • a catalyst deactivating agent(s) may be added in the step of mixing polylactic acid in view of obtaining a polylactic acid block copolymer having a high melting point and a high molecular weight.
  • the catalyst deactivating agent(s) is/are preferably added before addition of the catalyst for solid-phase polymerization.
  • one or more of normal additives such as fillers (glass fibers, carbon fibers, metal fibers, natural fibers, organic fibers, glass flakes, glass beads, ceramic fibers, ceramic beads, asbestos, wollastonite, talc, clay, mica, sericite, zeolite, bentonite, montmorillonite, synthetic mica, dolomite, kaolin, silicic acid fine powder, feldspar powder, potassium titanate, shirasu balloon, calcium carbonate, magnesium carbonate, barium sulfate, calcium oxide, aluminum oxide, titanium oxide, aluminum silicate, silicon oxide, plaster, novaculite, dawsonite, white clay and the like), ultraviolet absorbers (resorcinol, salicylate, benzotriazole, benzophenone and the like), heat stabilizers (hindered phenol, hydroquinone, phosphites and substituted bodies thereof, and the like), lubricants, releasing agents (montanic acid and salt
  • fillers glass fibers, carbon fiber
  • the polylactic acid block copolymer obtained by the production method may additionally comprise at least one of other thermoplastic resins (polyethylene, polypropylene, polystyrene, acrylic resins, acrylonitrile/butadiene/styrene copolymers, polyamide, polycarbonate, polyphenylene sulfide resins, polyether ether ketone resins, polyester, polysulfone, polyphenylene oxide, polyacetal, polyimide, polyetherimide, cellulose esters and the like), thermosetting resins (phenol resins, melamine resins, polyester resins, silicone resins, epoxy resins and the like), soft thermoplastic resins (ethylene/glycidyl methacrylate copolymers, polyester elastomers, polyamide elastomers, ethylene/propylene terpolymers, ethylene/butene-1 copolymers and the like) and the like as long as the product is not adversely affected.
  • other thermoplastic resins polyethylene, polypropylene
  • preferred examples of the resin generally include acrylic resins containing as a major component (meta)alkyl acrylate units having a C 1 -C 4 alkyl group(s). Further, the (meta)alkyl acrylate having a C 1 -C 4 alkyl group(s) may be copolymerized with another alkyl acrylate having a C 1 -C 4 alkyl group(s) or an aromatic vinyl compound such as styrene.
  • Examples of the (meta)alkyl acrylate having an alkyl group(s) include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, cyclohexyl acrylate and cyclohexyl methacrylate.
  • polymethyl methacrylate composed of methyl methacrylate is especially preferred.
  • the polylactic acid block copolymer has a property that easily allow formation of a polylactic acid stereocomplex having a high melting point even after heat melting and solidification upon processing of the block copolymer into a molded article or the like.
  • the molded product comprising the polylactic acid block copolymer is characterized in that it has a portion having a relative degree of crystallinity of not less than 90%, which portion also has a haze value of not more than 30% when the thickness of the molded product is 100 ⁇ m.
  • the relative degree of crystallinity herein can be calculated according to Equation (11), wherein ⁇ Hm represents the melting enthalpy of crystals in the molded product and ⁇ Hc represents the crystallization enthalpy of crystals in the molded product upon temperature increase.
  • the relative degree of crystallinity is preferably not less than 90%, more preferably not less than 92%, especially preferably not less than 94%.
  • ⁇ Hc herein means the crystallization enthalpy of crystals in molded product as measured with differential scanning calorimeter (DSC) upon temperature increase at a heating rate of 20° C./min.
  • ⁇ Hm means the melting enthalpy of crystals in the molded product measured with DSC at a heating rate of 20° C./min., which the melting enthalpy of crystals as measured by increasing the temperature at a heating rate of 20° C./min. from 30° C. to 250° C. during the first temperature increase and then decreasing the temperature at a cooling rate of 20° C./min. to 30° C., further followed by increasing the temperature at a heating rate of 20° C./min. from 30° C. to 250° C. during the second temperature increase.
  • the haze value means a value obtained by measurement according to JIS K 7105 with a molded product having a thickness of 100 ⁇ m, and, in view of the transparency, the haze value is preferably not more than 30%, more preferably not more than 20%, especially preferably not more than 10%.
  • the lower limit is not restricted, and the haze value is not less than 0%.
  • the molded product preferably has a haze value of not more than 20% when the thickness is 250 to 750 ⁇ m.
  • the haze value is more preferably not more than 10%, and especially preferably not more than 5% in view of the transparency.
  • the lower limit is not restricted, and the haze value is not less than 0%.
  • the molded product has a haze value of preferably not more than 30%, more preferably not more than 20%, still more preferably not more than 10%, still more preferably not more than 7%, especially preferably not more than 5% when the thickness is 0.75 to 1.25 mm. Further, even in cases where a nuclear agent to be used for improvement of the transparency is not contained, the molded product has a haze value of preferably not more than 30%, more preferably not more than 20%, especially preferably not more than 10%.
  • the polylactic acid block copolymer contained in the molded product preferably has a cooling crystallization temperature (Tc) of not less than 130° C. in view of the heat resistance and the transparency.
  • the cooling crystallization temperature (Tc) of the molded product herein means the crystallization temperature derived from polylactic acid crystals as measured with a differential scanning calorimetry (DSC) by increasing the temperature from 30° C. to 250° C. at a heating rate of 20° C./min. and then keeping the temperature constant at 250° C. for 3 minutes, followed by decreasing the temperature at a cooling rate of 20° C./min.
  • the crystallization temperature (Tc) is not restricted, and is preferably not less than 130° C., more preferably not less than 132° C., especially preferably not less than 135° C. in view of the heat resistance and the transparency.
  • the polylactic acid block copolymer contained in the molded product has a degree of stereocomplexation (Sc) of preferably not less than 80%, more preferably 85 to 100%, especially preferably 90 to 100%.
  • the degree of stereocomplexation herein means the ratio of stereocomplex crystals with respect to the total crystals in the polylactic acid. More particularly, it can be calculated according to Equation (12), wherein ⁇ Hl represents the heat of fusion of crystals of poly-L-lactic acid alone and crystals of poly-D-lactic acid alone and ⁇ Hh represents the heat of fusion of stereocomplex crystals as measured with a differential scanning calorimetry (DSC).
  • the polylactic acid block copolymer contained in the molded product preferably has a total number of the segment(s) composed of L-lactic acid units and segment(s) composed of D-lactic acid units of not less than 3 per one molecule of the polylactic acid block copolymer in view of the fact that a polylactic acid block copolymer which is likely to form a polylactic acid stereocomplex having a high melting point can be obtained.
  • the molecular weight per segment is preferably 2,000 to 50,000.
  • the molecular weight per segment is more preferably 4,000 to 45,000, especially preferably 5,000 to 40,000 in view of the mechanical properties.
  • the polylactic acid block copolymer contained in the molded product preferably has an average sequence length of not less than 20.
  • the average sequence length is more preferably not less than 25, especially preferably not less than 30 in view of the mechanical properties of the molded product.
  • the average sequence length of the molded product can be calculated by 13 C-NMR measurement according to Equation (13), wherein (a) represents the integrated value of the peak at about 170.1 to 170.3 ppm among the peaks of carbon belonging to carbonyl carbon and (b) represents the integrated value of the peak at about 169.8 to 170.0 ppm.
  • the weight average molecular weight of the polylactic acid block copolymer in the molded product is not restricted, and the weight average molecular weight is preferably not less than 90,000 and less than 300,000 in view of the mechanical properties.
  • the weight average molecular weight is more preferably not less than 100,000 and less than 290,000, still more preferably not less than 120,000 and less than 280,000, especially preferably not less than 140,000 and less than 260,000 in view of the moldability and the mechanical properties.
  • the polydispersity of the polylactic acid block copolymer in the molded product is preferably 1.5 to 3.0 in view of the mechanical properties.
  • the polydispersity is more preferably 1.8 to 2.7, especially preferably 2.0 to 2.4 in view of the moldability and the mechanical properties.
  • the weight average molecular weight and the polydispersity are values which are measured by gel permeation chromatography (GPC) using hexafluoroisopropanol or chloroform as a solvent and calculated in terms of poly(methyl methacrylate) standards.
  • the polylactic acid resin composition constituting the molded product is preferably a polylactic acid resin composition comprising at a ratio of not less than 60% the polylactic acid block copolymer constituted by a segment(s) composed of L-lactic acid units and segment(s) composed of D-lactic acid units.
  • the ratio is more preferably not less than 70%, especially preferably not less than 80%.
  • Each of the amount of lactide and the amount of oligomers contained in the polylactic acid block copolymer constituting the molded product is preferably not more than 5%.
  • the amount is more preferably not more than 3%, especially preferably not more than 1%.
  • the amount of lactic acid contained in the poly-L-lactic acid or poly-D-lactic acid is preferably not more than 2%.
  • the amount is more preferably not more than 1%, especially preferably not more than 0.5%.
  • Examples of the method for producing a molded product comprising the polylactic acid block copolymer include known molding methods such as injection molding, extrusion molding, blow forming, vacuum forming and press forming. In view of transparency and heat resistance, injection molding, blow forming, vacuum forming and press forming are preferred.
  • examples of the method include a method in which a molten polylactic acid resin composition comprising the polylactic acid block copolymer is extruded through a die having a predetermined thickness to obtain a sheet, and a method in which a molten polylactic acid resin composition comprising the polylactic acid block copolymer is sandwiched between predetermined metal molds to obtain a sheet. Further, the obtained sheet may be subjected to heat treatment at a predetermined temperature for a predetermined length of time to increase the degree of crystallinity.
  • Specific examples of the production method include a method in which melting at 240° C. for 2 minutes is followed by pressing at a press metal mold temperature of 80° C.
  • a press sheet having a thickness of 100 ⁇ m which is then subjected to heat treatment under a nitrogen atmosphere at 110° C. for 30 minutes, and a method in which melting under heat at 240° C. for 2 minutes is followed by pressing at a press temperature of 40° C. to prepare a press sheet having a thickness of 1 mm, which is then subjected to heat treatment under a nitrogen atmosphere at 80° C. for 5 minutes and at 110° C. for 30 minutes.
  • the mold temperature is preferably set within the temperature range from the glass-transition temperature to the melting point of the polylactic acid block copolymer, more preferably 60° C. to 220° C., still more preferably 70° C. to 200° C., still more preferably 80° C. to 180° C., and each molding cycle in the injection molding is preferably operated for not more than 150 seconds, more preferably not more than 90 seconds, still more preferably not more than 60 seconds, still more preferably not more than 50 seconds.
  • examples of the method include a method in which the polylactic acid block copolymer is molded by injection molding according to the above method into a closed-end tubular molded product (parison) having a degree of crystallinity that allows blow forming, and transferred to a metal mold for blow forming whose temperature was set within the range from the glass-transition temperature to the glass-transition temperature+80° C., preferably 60° C. to 140° C., more preferably 70° C. to 130° C., followed by stretching with a stretching rod while compressed air is supplied from an air nozzle, to obtain a molded product.
  • a closed-end tubular molded product having a degree of crystallinity that allows blow forming
  • examples of the method include, in view of transparency and heat resistance, a method in which a sheet or film having a degree of crystallinity that allows molding is once obtained and then heated with a heater such as a hot plate or hot air to 60° C. to 150° C., preferably 65° C. to 120° C., more preferably 70° C. to 90° C., followed by bringing the sheet into close contact with a metal mold which was set to a mold temperature of 30 to 150° C., preferably 40° C. to 100° C., more preferably 50° C. to 90° C. while the pressure inside the metal mold is reduced, to perform molding.
  • a heater such as a hot plate or hot air to 60° C. to 150° C., preferably 65° C. to 120° C., more preferably 70° C. to 90° C.
  • examples of the method include a method in which a sheet or film having a degree of crystallinity that allows molding is once obtained and then heated with a heater such as a hot plate or hot air to 60° C. to 150° C., preferably 65° C. to 120° C., more preferably 70° C. to 90° C., followed by bringing the sheet into close contact with a metal mold composed of a male mold and female mold which was set to a mold temperature of 30 to 150° C., preferably 40° C. to 100° C., more preferably 50° C. to 90° C., and pressurizing the sheet to perform mold clamping.
  • a heater such as a hot plate or hot air to 60° C. to 150° C., preferably 65° C. to 120° C., more preferably 70° C. to 90° C.
  • the molded product comprising the obtained polylactic acid block copolymer has transparency even in cases where stretching treatment was not carried out so that it is not necessary to perform stretching treatment to give transparency to the product.
  • stretching treatment it is also possible to perform stretching treatment as required.
  • the shape of the molded product to be subjected to stretching treatment is preferably a film or a sheet.
  • stretching is preferably carried out within the range from the glass-transition temperature to the melting point of the polylactic acid stereocomplex, more preferably 60° C. to 170° C., still more preferably 70° C. to 150° C.
  • the polylactic acid block copolymer and the molded product comprising the polylactic acid block copolymer may be used as a film, sheet, fiber/cloth, non-woven fabric, injection-molded article, extrusion-molded article, vacuum pressure-molded article, blow-molded article, complex with another/other material(s), and the like, and are useful for uses such as agricultural materials, garden materials, fishery materials, civil engineering and construction materials, stationery, medical supplies, automobile parts, electrical/electronic components and optical films.
  • Examples of the uses include electrical/electronic components such as relay cases, coil bobbins, optical pickup chassis, motor cases, housings and internal parts for laptop computers, housings and internal parts for CRT displays, housings and internal parts for printers, housings and internal parts for mobile terminals including mobile phones, mobile computers and handheld-type mobiles, housings and internal parts for recording media (e.g., CD, DVD, PD and FDD) drives, housings and internal parts for copiers, housings and internal parts for facsimile devices, and parabolic antennas.
  • electrical/electronic components such as relay cases, coil bobbins, optical pickup chassis, motor cases, housings and internal parts for laptop computers, housings and internal parts for CRT displays, housings and internal parts for printers, housings and internal parts for mobile terminals including mobile phones, mobile computers and handheld-type mobiles, housings and internal parts for recording media (e.g., CD, DVD, PD and FDD) drives, housings and internal parts for copiers, housings and internal parts for facs
  • parts for home and office electric appliances such as VTR parts, television parts, iron parts, hair driers, rice cooker parts, microwave oven parts, acoustic parts, parts for video equipments including video cameras and projectors, substrates for optical recording media including Laser discs (registered trademark), compact discs (CDs), CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-R, DVD-RW, DVD-RAM and Blu-ray disks, illumination parts, refrigerator parts, air conditioner parts, typewriter parts and word processor parts.
  • VTR parts television parts, iron parts, hair driers, rice cooker parts, microwave oven parts, acoustic parts
  • parts for video equipments including video cameras and projectors
  • substrates for optical recording media including Laser discs (registered trademark), compact discs (CDs), CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-R, DVD-RW, DVD-RAM and Blu-ray disks, illumination parts, refrigerator parts, air conditioner parts, typewriter parts and word processor parts.
  • the polylactic acid block copolymer and the molded product comprising the polylactic acid block copolymer are also useful for, for example, housings and internal parts for electronic musical instruments, home game machines and portable game machines; electrical/electronic components such as various gears, various cases, sensors, LEP lamps, connectors, sockets, resistors, relay cases, switches, coil bobbins, condensers, cases for variable condensers, optical pickups, oscillators, various terminal blocks, transformers, plugs, printed circuit boards, tuners, speakers, microphones, headphones, small motors, magnetic head bases, power modules, semiconductors, liquid crystals, FDD carriages, FDD chassis, motor brush holders, transformer members and coil bobbins; building components such as sash rollers, blind curtain parts, pipe joints, curtain liners, blind parts, gas meter parts, water meter parts, water heater parts, roof panels, adiabatic walls, adjusters, plastic floor posts, ceiling hangers, stairs, doors and floors; fishery-related members such as bait bags; civil
  • the weight average molecular weight, polydispersity and molecular weight distribution are values which are measured by gel permeation chromatography (GPC) and calculated in terms of poly(methyl methacrylate) standards.
  • GPC gel permeation chromatography
  • the GPC measurement was carried out using: as a detector, WATERS 410, which is a differential refractometer manufactured by WATERS; as a pump, MODEL 510 manufactured by WATERS; and, as a column, Shodex GPC HFIP-806M and Shodex GPC HFIP-LG which are linearly connected.
  • the flow rate was 0.5 mL/min.
  • hexafluoroisopropanol was used as a solvent, and 0.1 mL of a solution having a sample concentration of 1 mg/mL was injected.
  • the total area (c) and the area (d) corresponding to molecular weights of not less than 100,000 were calculated, and the ratio of molecular weights of not less than 100,000 (Mwp) was calculated according to the Equation (14) below.
  • 13 C-NMR measurement was carried out using an NMR apparatus AL-400 manufactured by Japan Electro Optical Laboratory, followed by calculation according to the Equation (15) below, wherein (a) represents the integrated value of the peak at about 170.1 to 170.3 ppm among the peaks of carbon belonging to carbonyl carbon and (b) represents the integrated value of the peak at about 169.8 to 170.0 ppm.
  • Hydrogenated chloroform containing 10% hexafluoroisopropanol was used as a solvent in the measurement.
  • a sample solution was prepared by dissolving 50 mg of the sample in 0.7 ml of the solvent, and the resulting solution was subjected to the measurement at a measurement temperature of 27° C. and a measurement frequency of 125 MHz.
  • the melting point, the end of melting point and the amount of heat due to melting were measured with a differential scanning calorimetry (DSC) manufactured by Perkin-Elmer Corp.
  • DSC differential scanning calorimetry
  • measurement was carried out with 5 mg of the sample under a nitrogen atmosphere at a heating rate of 20° C./min.
  • the melting point herein means the temperature at the peak top of the peak due to melting of crystals, and the end of melting point means the temperature at the end of the peak due to melting of crystals.
  • a melting point of not less than 190° C. and less than 250° C. was judged to be due to formation of a polylactic acid stereocomplex, and a melting point of not less than 150° C. and less than 190° C. was judged to be due to nonoccurrence of formation of a polylactic acid stereocomplex.
  • the melting point of the mixture herein means the melting point measured by increasing the temperature at a heating rate of 20° C./min. from 30° C. to 250° C.
  • the melting point of the polylactic acid block copolymer after solid-phase polymerization means the melting point measured by increasing the temperature at a heating rate of 20° C./min. from 30° C. to 250° C. during the first temperature increase and then decreasing the temperature at a cooling rate of 20° C./min. to 30° C., further followed by increasing the temperature at a heating rate of 20° C./min. from 30° C. to 250° C. during the second temperature increase.
  • Tm represents the melting point derived from stereocomplex crystals of the polylactic acid block copolymer or the mixture of poly-L-lactic acid and poly-D-lactic acid (peak top temperature in the peak due to melting of crystals); Tms represents the beginning temperature of melting of stereocomplex crystals of the polylactic acid block copolymer or the mixture of poly-L-lactic acid and poly-D-lactic acid; and Tme represents the end temperature of melting of the polylactic acid block copolymer or the mixture of poly-L-lactic acid and poly-D-lactic acid.
  • DSC differential scanning calorimetry
  • the measured value was obtained by increasing the temperature at a heating rate of 40° C./min. from 30° C. to 250° C. during the first temperature increase and then decreasing the temperature at a cooling rate of 40° C./min. to 30° C., further followed by increasing the temperature at a heating rate of 40° C./min. from 30° C. to 250° C. during the second temperature increase.
  • ⁇ Hl represents the heat of fusion of crystals of poly-L-lactic acid alone and crystals of poly-D-lactic acid alone, which appears at not less than 150° C. and less than 190° C.
  • ⁇ Hh represents the heat of fusion of stereocomplex crystals, which appears at not less than 190° C. and less than 250° C.
  • the degree of stereocomplexation in the mixture was calculated for the peak due to melting of crystals measured with a differential scanning calorimetry (DSC) during the first temperature increase, and the degree of stereocomplexation of the polylactic acid block copolymer after solid-phase polymerization was calculated for the peak due to melting of crystals measured by increasing the temperature at a heating rate of 20° C./min. from 30° C. to 250° C. during the first temperature increase and then decreasing the temperature at a cooling rate of 20° C./min. to 30° C., further followed by increasing the temperature at a heating rate of 20° C./min. from 30° C. to 250° C. during the second temperature increase.
  • DSC differential scanning calorimetry
  • Wp represents the weight of the mixture before solid-phase polymerization
  • Ws represents the weight of the polylactic acid block copolymer after solid-phase polymerization
  • the cooling crystallization temperatures of the polylactic acid block copolymer and the polylactic acid stereocomplex were measured with a differential scanning calorimetry (DSC) manufactured by Perkin-Elmer Corp. More specifically, the temperature of 5 mg of each sample was increased with a differential scanning calorimetry (DSC) under a nitrogen atmosphere at a heating rate of 20° C./min from 30° C. to 250° C., and the temperature was then kept constant at 250° C. for 3 minutes, followed by decreasing the temperature at a cooling rate of 20° C./min. while measuring the temperature at the crystallization peak top to obtain the cooling crystallization temperature.
  • DSC differential scanning calorimetry
  • the haze value was measured.
  • a sheet-shaped molded product having a thickness of 0.1 mm was subjected to measurement of the haze value using a haze meter NDH-300A manufactured by Nippon Denshoku Industries, according to JIS K 7105.
  • the storage modulus was measured.
  • the central portion of a sheet-shaped molded product having a thickness of 0.1 mm was cut into a piece having a size of 40 mm ⁇ 2 mm to provide a strip-shaped sample, and the sample was subjected to measurement of the dynamic viscoelasticity using a Dynamic viscoelasticity apparatus (DMS6100 manufactured by Seiko Instruments Inc.) under a nitrogen atmosphere at a heating rate of 2° C./min. at a frequency of 3.5 Hz, to measure the storage modulus at 130° C. It can be said that the higher the modulus, the higher the heat resistance.
  • DMS6100 Dynamic viscoelasticity apparatus
  • the central portion of a sheet-shaped molded product having a thickness of 0.1 mm was cut into a piece having a size of 40 mm ⁇ 2 mm to provide a strip-shaped sample, and the sample was subjected to measurement of the tensile strength according to ASTM D882.
  • PLA1 poly-L-lactic acid
  • the weight average molecular weight of PLA1 was 18,000; the polydispersity was 1.5; the melting point was 149° C.; and the end of melting point was 163° C.
  • PLA1 obtained in Reference Example 1 was subjected to crystallization treatment under a nitrogen atmosphere at 110° C. for 1 hour, and then to solid-phase polymerization under a pressure of 60 Pa at 140° C. for 3 hours, at 150° C. for 3 hours and then at 160° C. for 5 hours, to obtain poly-L-lactic acid (PLA2).
  • the weight average molecular weight of PLA2 was 43,000; the polydispersity was 1.8; the melting point was 159° C.; and the end of melting point was 176° C.
  • PLA1 obtained in Reference Example 1 was subjected to crystallization treatment under a nitrogen atmosphere at 110° C. for 1 hour, and then to solid-phase e polymerization under a pressure of 60 Pa at 140° C. for 3 hours, at 150° C. for 3 hours and then at 160° C. for 12 hours, to obtain poly-L-lactic acid (PLA3).
  • the weight average molecular weight of PLA3 was 137,000; the polydispersity was 1.8; the melting point was 168° C.; and the end of melting point was 189° C.
  • PLA1 obtained in Reference Example 1 was subjected to crystallization treatment under a nitrogen atmosphere at 110° C. for 1 hour, and then to solid-phase polymerization under a pressure of 60 Pa at 140° C. for 3 hours, at 150° C. for 3 hours and then at 160° C. for 18 hours, to obtain poly-L-lactic acid (PLA4).
  • the weight average molecular weight of PLA4 was 203,000; the polydispersity was 1.9; the melting point was 170° C.; and the end of melting point was 189° C.
  • PLA5 poly-L-lactic acid
  • the weight average molecular weight of PLA5 was 262,000; the polydispersity was 2.1; the melting point was 171° C.; and the end of melting point was 191° C.
  • PDA1 obtained in Reference Example 7 was subjected to crystallization treatment under a nitrogen atmosphere at 110° C. for 1 hour, and then to solid-phase polymerization under a pressure of 60 Pa at 140° C. for 3 hours, at 150° C. for 3 hours and then at 160° C. for 3 hours, to obtain poly-D-lactic acid (PDA2).
  • the weight average molecular weight of PDA2 was 29,000; the polydispersity was 1.6; the melting point was 150° C.; and the end of melting point was 168° C.
  • PDA1 obtained in Reference Example 7 was subjected to crystallization treatment under a nitrogen atmosphere at 110° C. for 1 hour, and then to solid-phase polymerization under a pressure of 60 Pa at 140° C. for 3 hours, at 150° C. for 3 hours and then at 160° C. for 6 hours, to obtain poly-D-lactic acid (PDA3).
  • the weight average molecular weight of PDA3 was 42,000; the polydispersity was 1.6; the melting point was 158° C.; and the end of melting point was 176° C.
  • PDA1 obtained in Reference Example 7 was subjected to crystallization treatment under a nitrogen atmosphere at 110° C. for 1 hour, and then to solid-phase polymerization under a pressure of 60 Pa at 140° C. for 3 hours, at 150° C. for 3 hours and then at 160° C. for 18 hours, to obtain poly-D-lactic acid (PDA4).
  • the weight average molecular weight of PDA4 was 198,000; the polydispersity was 2.0; the melting point was 170° C.; and the end of melting point was 191° C.
  • a plasticization part set to a temperature of 180° C.
  • the weight average molecular weight of the mixture was as high as not less than 100,000 in Examples 1 to 7 and Comparative Example 5, while the weight average molecular weight upon mixing was as low as less than 100,000 in Comparative Examples 1 to 4.
  • the degree of stereocomplexation was as high as not less than 60% in Examples 1 to 7 and Comparative Examples 1 to 4, but the degree of stereocomplexation was low in Comparative Example 5, wherein a combination of poly-L-lactic acid and poly-D-lactic acid each having a molecular weight of not less than 100,000 was mixed.
  • Each mixture obtained in (1) was subjected to solid-phase polymerization. More specifically, solid-phase polymerization was carried out in a vacuum drier at 140° C. under a pressure of 13.3 Pa for 4 hours. Subsequently, the temperature was increased to 150° C. and solid-phase polymerization was carried out for 4 hours, and the temperature was then further increased to 160° C. and solid-phase polymerization was carried out for 10 hours. By this, a polylactic acid block copolymer having more than 3 segments was obtained.
  • the weight average molecular weight increased to not less than 100,000 after solid-phase polymerization in any of Examples 1 to 7 and Comparative Example 5. Further, the ratio of molecular weights of not less than 100,000 in the molecular weight distribution curve was not less than 50% in any of these cases. Since the polydispersity after solid-phase polymerization was lower than the polydispersity upon mixing and less than 3.0, it could be confirmed that the polymerization proceeded and polylactic acid block copolymer was obtained. In contrast, in Comparative Examples 1 to 4, the weight average molecular weight after solid-phase polymerization was not more than 100,000, and the ratio of molecular weights of not less than 100,000 in the molecular weight distribution curve was less than 40%.
  • the average sequence length of the polymer observed after solid-phase polymerization was as high as not less than 30 in Examples 1 to 7 and Comparative Examples 5 and 6.
  • the yield after solid-phase polymerization was as high as not less than 90% in any of Examples 1 to 7 and Comparative Examples 1 to 3 and 5 wherein high molecular weight segments were used as the polylactic acid to be mixed, but the yield after solid-phase polymerization was as low as less than 90% in Comparative Example 4 wherein a combination of poly-L-lactic acid and poly-D-lactic acid having molecular weights of as low as not more than 100,000 was used in the mixing.
  • the parameter of thermal properties is less than 1.8 only in the cases of polylactic acid block copolymers shown in Examples having both high molecular weights and high heat resistance.
  • Examples 1 to 7 and Comparative Example 4 showed values of not less than 130° C., which indicate excellent crystallization properties, while Comparative Examples 1 to 3 and 5 showed values of less than 130° C., which indicate poor crystallization properties.
  • the weight average molecular weight upon mixing was 84,000.
  • an increase in the melting point due to stereocomplex formation was partially observed.
  • the polymer since blending in the mixing step was carried out at a temperature of not more than the end of melting point of PLA6, the polymer only partially melted and crystals of the polylactic acid alone remained, resulting in a degree of stereocomplexation of as low as 26%.
  • the mixture obtained in (1) was subjected to heat treatment under a pressure of 66.6 Pa at 110° C. for 2 hours, and then heated at 130° C. for 5 hours and at 140° C. for 25 hours (30 hours in total) to perform solid-phase polymerization, thereby preparing a polylactic acid block copolymer having not less than 3 segments.
  • the molecular weight was 151,000 and the average sequence length was 52 after solid-phase polymerization, but the yield after solid-phase polymerization was as low as not more than 90%. Further, the polydispersity was as large as 2.9 and the ratio of molecular weights of not less than 100,000 was as low as 36% after solid-phase polymerization, so that it could be confirmed that the polymer contained a large amount of low molecular weight components. In terms of the thermal properties after solid-phase polymerization, an increase in the melting point due to stereocomplex formation was observed, and the degree of stereocomplexation was high.
  • the parameter of thermal properties (Tm ⁇ Tms)/(Tme ⁇ Tm) was 2.0, which was higher than the parameter values for the polylactic acid block copolymers in Examples having low polydispersities after solid-phase polymerization. Further, the cooling crystallization temperature after solid-phase polymerization was 124° C., which was lower than the values of not less than 130° C. shown in the Examples.
  • Poly-L-lactic acid and poly-D-lactic acid were mixed in the same manner as in Example 1.
  • the melting point was 162° C./215° C. and an increase in the melting point due to stereocomplex formation (Sc, 95%) was observed, but the parameter of thermal properties (Tm ⁇ Tms)/(Tme ⁇ Tm) was 2.2, which was larger than the value for the polylactic acid block copolymer in Example 1.
  • the cooling crystallization temperature was 112° C., which was lower than in Example 1 wherein solid-phase polymerization was carried out under reduced pressure.
  • Poly-L-lactic acid and poly-D-lactic acid were mixed using a batch-type twin screw extruder (Labo Plastomill) manufactured by Toyo Seiki Co., Ltd. to obtain mixtures of poly-L-lactic acid and poly-D-lactic acid.
  • the test conditions were as follows: kneading temperature, 245° C.; kneading rotation speed, 120 rpm; kneading time, 10 minutes (Comparative Examples 8 and 11) or 60 minutes (Comparative Examples 9 and 12).
  • the combinations of poly-L-lactic acid and poly-D-lactic acid were as shown in Table 2.
  • the weight average molecular weight of the mixture of poly-L-lactic acid and poly-D-lactic acid was as high as not less than 100,000 in Comparative Examples 8 and 11, but was not more than 100,000 and tended to be low in Comparative Examples 9 and 12 wherein the kneading time was as long as 60 minutes.
  • the total number of the segment(s) composed of L-lactic acid units and segment(s) composed of D-lactic acid units contained per one molecule of the mixture of poly-L-lactic acid and poly-D-lactic acid was 1.
  • the melting point of the mixture of poly-L-lactic acid and poly-D-lactic acid was not less than 200° C.
  • Poly-L-lactic acid and poly-D-lactic acid were prepared by kneading poly-L-lactic acid and poly-D-lactic acid using a batch-type twin screw extruder under the same conditions as in Comparative Examples 9 and 12 for 60 minutes and then adding 10 parts by weight of a plasticizer, followed by further kneading the resulting mixture for 5 minutes.
  • the combinations of poly-L-lactic acid, poly-D-lactic acid and the plasticizer were as shown in Table 2.
  • the weight average molecular weights of the mixtures of poly-L-lactic acid and poly-D-lactic acid in Comparative Example 10 and 13 were 84,000 and 51,000, respectively, and the molecular weight tended to be low due to kneading for a long time as in the cases of Comparative Examples 9 and 12.
  • the total number of the segment(s) composed of L-lactic acid units and segment(s) composed of D-lactic acid units contained per one molecule of the mixture of poly-L-lactic acid and poly-D-lactic acid was 1.
  • the parameter of thermal properties (Tm ⁇ Tms)/(Tme ⁇ Tm) was not less than 2.0 in both cases and higher than in Examples.
  • the cooling crystallization temperature was 103° C. and 120° C. in Comparative Examples 10 and 13, respectively, and almost the same as in Comparative Examples 9 and 12.
  • Poly-L-lactic acid and poly-D-lactic acid were prepared by kneading using a twin screw extruder in the same manner as in Examples 1 to 7. All of poly-L-lactic acid, poly-D-lactic acid and the nuclear agent were fed to the twin screw extruder from the resin hopper, and the kneading temperature was set to 240° C. for carrying out kneading.
  • the combinations of poly-L-lactic acid, poly-D-lactic acid and the nuclear agent were as shown in Table 2.
  • the polylactic acid mixtures obtained by kneading had weight average molecular weights of 110,000 to 120,000 in Comparative Examples 14 to 16, while the molecular weight in Comparative Example 17 was 65,000 and tended to be low.
  • the total number of the segment(s) composed of L-lactic acid units and segment(s) composed of D-lactic acid units contained per one molecule of the polylactic acid stereocomplex was 1.
  • the melting points of the polylactic acid mixtures observed were not less than 200° C. due to stereocomplex formation, but the cooling crystallization temperature could be observed only in Comparative Examples 14 to 16 wherein a nuclear agent was used in combination.
  • N2 Phosphate ester sodium salt (“NA-11” manufactured by ADEKA CORPORATION).
  • N3 Phosphate ester aluminum salt (“NA-71” manufactured by ADEKA CORPORATION)
  • Plasticizer P1 Polyglyceryl fatty acid ester (“Chirabazol” manufactured by Tolyo Kagaku Co., Ltd.)
  • the polylactic acid block copolymers obtained in Examples 1 to 7 and Comparative Examples 1 to 6 (SB1 to SB7 and SB8 to SB13) and the polylactic acid mixture obtained in Comparative Example 7 (SB14) were subjected to melt mixing using a twin screw extruder with 0.05 part of a phosphorus catalyst deactivating agent at 240° C. to perform catalyst deactivation. Subsequently, each mixture was melted by heating at 240° C. for 2 minutes, and pressed at a pressing temperature of 80° C. to prepare a pressed sheet having a thickness of 0.1 mm (100 ⁇ m). Thereafter, the pressed sheet was subjected to heat treatment under a nitrogen atmosphere under the heat treatment conditions of 110° C. for 30 minutes, to prepare a sheet-shaped molded product for various kinds of measurement.
  • the values of various physical properties measured after sampling the central portion of the sheet-shaped molded product were as shown in Table 3.
  • the relative degree of crystallinity of the sheet-shaped molded product was 100%.
  • the haze value was measured for the sample prepared by cutting out a piece having a size of 5 cm ⁇ 5 cm from the central portion of the sheet-shaped molded product, and, as a result, it was found that the sheet-shaped molded products in Examples 8 to 14 have haze values of less than 10% and are excellent in transparency.
  • the haze values of the sheet-shaped molded products of Comparative Examples 18 to 24 were not less than 10% except for the sheet-shaped molded product of Comparative Example 21, which had a haze value of less than 10%.
  • each sheet-shaped molded product was cut into a piece having a size of 40 mm ⁇ 2 mm to provide a strip-shaped sample, and the sample was subjected to measurement of the storage modulus at 130° C. according to viscoelasticity.
  • any of the sheet-shaped molded products of Examples 8 to 14 had a storage modulus of not less than 2 GPa, and was excellent in heat resistance. Measurement of the tensile strength of the strip-shaped samples revealed that any of these has a value of not less than 60 MPa.
  • each sheet-shaped molded product was heated using a vacuum forming machine under the conditions of a heating temperature of 100° C. and heating time of 60 seconds, and brought into close contact with a metal mold at a mold temperature of 40° C. while the pressure inside the metal mold was reduced, to obtain a cylindrical container having an inner diameter of 6 cm and a depth of 10 cm.
  • This cylindrical container was subjected to heat treatment under a nitrogen atmosphere under the heat treatment conditions of 110° C. for 30 minutes.
  • the container was then filled with water and the lid was closed. Thereafter, the container was dropped onto concrete from a height of 2 m with its bottom facing downward, and the number of times of this operation was counted until the container was broken due to the drop impact to cause leakage of water.
  • all of the samples of Examples 8 to 14 were confirmed to have good impact resistance.
  • breakage of the container and leakage of water were observed after less than 5 times of the dropping.
  • sheets were obtained in the same manner as in Examples 8 to 10 except that the press temperature was 40° C.; sheet thickness was 1 mm; and heat treatment was carried out at 80° C. for 5 seconds and at 110° C. for 30 seconds.
  • the haze values of the resulting sheets were not more than 20% in all cases.
  • the polylactic acid block copolymer obtained by solid-phase polymerization in Example 1 was subjected to catalyst deactivation before preparation of a sheet-shaped molded product.
  • the method of catalyst deactivation was the same as in Examples 8 to 14.
  • the polylactic acid block copolymer subjected to catalyst deactivation was melted by heating at 240° C. for 2 minutes, and then pressed at a press temperature of 80° C. to prepare a press sheet having a thickness of 0.1 mm, followed by cooling the sheet in ice water, to provide a sheet-shaped molded product for various kinds of measurement.
  • the methods of measurement of various kinds of physical properties of the sheet-shaped molded product were the same as in Examples 8 to 14.
  • the relative degree of crystallinity of the sheet-shaped molded product of Comparative Example 25 was as low as 10% since heat treatment of the molded product was not carried out. Further, the haze value of the molded product having a thickness of 100 ⁇ m was 2% since heat treatment was not carried out, and the transparency was high. However, the tensile strength and impact resistance of the sheet-shaped molded product were lower than those in Examples 8 to 14, and the storage modulus at 130° C. could not be measured because the molded product was broken in the process of temperature increase during the measurement.
  • Example 1 The mixture of poly-L-lactic acid and poly-D-lactic acid SC1 obtained in Example 1 was subjected to catalyst deactivation before preparation of a sheet-shaped molded product.
  • the method of catalyst deactivation was the same as in Examples 8 to 14.
  • a molded product for measuring various kinds of physical properties was prepared using the SC1 after catalyst deactivation.
  • the method of preparation of the molded product and the methods of measurement of physical properties were the same as in Examples 8 to 14.
  • the relative degree of crystallinity of the sheet-shaped molded product of Comparative Example 26 was 100%.
  • the haze value of the molded product at a thickness of 100 ⁇ m was 14%, and the transparency was therefore high.
  • the storage modulus of the sheet-shaped molded product at 130° C. was as high as 2.4 GPa, but the tensile strength and the impact resistance were inferior to those of Examples 8 to 14.
  • the polylactic acid mixtures obtained in Comparative Examples 8, 9, 11 and 12 were subjected to catalyst deactivation before preparation of sheet-shaped molded products.
  • the method of catalyst deactivation was the same as in Examples 13 to 24.
  • a molded product for measuring various kinds of physical properties was prepared using each of the polylactic acid mixtures after catalyst deactivation.
  • the method of preparation of the molded product for measuring various kinds of physical properties and the methods of measurement of physical properties were the same as in Examples 8 to 14.
  • Comparative Examples 28, 30 and 31 each showed a value of 100%, but Comparative Example 27 showed a value of as low as 78%.
  • Comparative Example 31 showed a value of 22%, but Comparative Examples 27, 28 and 30 showed values of not less than 40%, having lower transparency compared to Examples 8 to 14.
  • the storage moduli of the sheet-shaped molded products at 130° C. were not more than 2 GPa, indicating lower rigidity at high temperature.
  • Comparative Example 27 wherein the molecular weight of the molded product was high, showed excellent values, but Comparative Examples 28, 30 and 31 showed lower values compared to Examples 8 to 14.
  • the polylactic acid mixtures obtained in Comparative Examples 10 and 13 were subjected to catalyst deactivation before preparation of sheet-shaped molded products.
  • the method of catalyst deactivation was the same as in Examples 13 to 24.
  • a molded product for measuring various kinds of physical properties was prepared using each of the polylactic acid mixtures after catalyst deactivation.
  • the method of preparation of the molded product for measuring various kinds of physical properties and the methods of measurement of physical properties were the same as in Examples 8 to 14.
  • the relative degree of crystallinity of the sheet-shaped molded product was 100% in each Comparative Example.
  • the haze value of the molded product at a thickness of 100 ⁇ m was lower than in Comparative Examples 23 and 26 due to addition of a plasticizer, resulting in improved transparency, but the tensile strength of the molded product tended to be low due to addition of the plasticizer.
  • the polylactic acid obtained in Reference Example 13 (PLA8) and the polylactic acid mixtures obtained in Comparative Examples 14 to 17 (SC20 to SC23) were subjected to catalyst deactivation before preparation of sheet-shaped molded products.
  • the method of catalyst deactivation was the same as in Examples 13 to 24.
  • a molded product for measuring various kinds of physical properties was prepared using each of the polylactic acid mixtures after catalyst deactivation.
  • the relative degree of crystallinity of the sheet-shaped molded product of any of the Comparative Examples was 100%.
  • Comparative Examples 33 and 34 showed values of not less than 50%, having low transparency
  • Comparative Examples 35 to 37 showed values of as low as 13 to 15% due to combined use of a nuclear agent.
  • any of the products showed a lower value compared to Examples 8 to 14, and both the tensile strength and the impact resistance tended to be even lower in Comparative Example 37 wherein the molecular weight was especially low.
  • the obtained reaction product was dissolved in chloroform, and unreacted monomers were removed by allowing reprecipitation with stirring in methanol (5 times the amount of chloroform), to obtain a polylactic acid block copolymer (LD-1) in which a segment composed of D-lactic acid units is bound to PLA9 composed of L-lactic acid units, which polylactic acid block copolymer has 2 segments.
  • the molecular weight of LD-1 was 148,000, and the melting point was 210° C.
  • the obtained reaction product was dissolved in chloroform, and unreacted monomers were removed by allowing reprecipitation with stirring in methanol (5 times the amount of chloroform), to obtain a polylactic acid block copolymer (LD-2) in which segments composed of D-lactic acid units are bound to both terminal groups of PLA10 composed of L-lactic acid units, which polylactic acid block copolymer has 3 segments.
  • the molecular weight of LD-2 was 150,000, and the melting point was 210° C.
  • a twin screw extruder 50 parts of the poly-L-lactic acid (PLA4) obtained in Reference Example 4 and 50 parts of the poly-D-lactic acid (PDA1) obtained in Reference Example 7 were mixed, and the resulting mixture was subjected to solid-phase polymerization, to obtain a polylactic acid block copolymer (LD-3) having more than 3 segments.
  • the mixing method and the method of phase polymerization were the same as in Examples 8 to 14.
  • the polylactic acid block copolymer obtained by solid-phase polymerization was subjected to melt mixing using a twin screw extruder with 0.05 part of a phosphorus catalyst deactivating agent at 240° C. to perform catalyst deactivation.
  • the molecular weight of the obtained LD-3 was 125,000; the melting point was 221° C.; and the degree of stereocomplexation was 100%.
  • the relative degree of crystallinity of the molded product of LD-1 obtained in Reference Example 13 was 100%.
  • a high melting point was observed at 208° C., and the degree of stereocomplexation was 100%.
  • the parameter of thermal properties (Tm ⁇ Tms)/(Tme ⁇ Tm) was 1.9 and the cooling crystallization temperature was 110° C., indicating lower crystallization properties than in Examples 1 to 7.
  • the haze value of the molded product at a thickness of 100 ⁇ m was 34%, which was higher than in Examples 8 to 14, and, in terms of the mechanical properties, both the tensile strength and the impact resistance were the same as in Examples 8 to 14.
  • Polylactic acid and polylactic acid block copolymers were mixed at ratios shown in Table 4, and the resulting mixtures were subjected to melt mixing using a single screw extruder having a diameter of 40 mm at a cylinder temperature of 240° C. and a rotation speed of 50 rpm, to obtain polylactic acid resin compositions.
  • the relative degree of crystallinity of the molded product in both Comparative Examples 39 and 40 was 100%.
  • a high melting points was observed at about 210° C., and the degree of stereocomplexation was 68% and 89, respectively, indicating that the higher the content of the polylactic acid block copolymer, the higher the degree of stereocomplexation.
  • the cooling crystallization temperature was 103° C. and 105° C. in Comparative Examples 39 and 40, respectively, suggesting lower crystallization properties compared to Examples 1 to 7.
  • the haze value of the molded product at a thickness of 100 ⁇ m was 35% and 32% in Comparative Examples 39 and 40, respectively, suggesting poorer transparency compared to Examples 8 to 14.
  • both the tensile strength and the impact resistance were the same as in Examples 8 to 14.
  • the relative degree of crystallinity of the molded product was 100%. In terms of the thermophysical properties of the molded product, a high melting point was observed at 212° C., and the degree of stereocomplexation was 92%. The cooling crystallization temperature was 130° C., indicating excellent crystallization properties. The haze value of the molded product at a thickness of 100 ⁇ m was 15%, indicating excellent transparency. In terms of the mechanical properties of the molded product, both the tensile strength and the impact resistance were the same as in Examples 8 to 14.
  • the conditions for melt mixing were the same as in Comparative Examples 39 and 40.
  • the relative degree of crystallinity of the polylactic acid resin composition contained in the molded product of Example 16 was 100%.
  • a high melting point was observed at about 210° C., and the degree of stereocomplexation was 80%.
  • the cooling crystallization temperature was 128° C., which was almost the same as in Example 15.
  • the haze value of the molded product at a thickness of 100 ⁇ m was 8%, which indicates excellent transparency.
  • both the tensile strength and the impact resistance were equivalent to those in Examples 8 to 14.
  • the polylactic acid block copolymer was excellent in heat resistance, crystallinity, transparency and mechanical properties also as a molded product.
  • Example 16 Poly lactic acid L-4 (Parts by weight) 70 30 30 20 LD-1 (Parts by weight) 100 LD-2 (Parts by weight) 30 70 LD-3 (Parts by weight) 70 60 Poly methylmethacrylate (Parts by weight) 20 Mw ratio between segment composed of L- 1.0 1.0 1.0 13.5 13.5 lactic acid units and segment composed of D-lactic acid units in polylactic acid block copolymer Molded Mw ⁇ 10 4 14.6 15.3 16.3 16.5 14.9 product Mp 62 65 65 61 61 Polydipersity 1.6 1.6 1.6 1.6 1.6 Average sequence length 31 32 28 30 23 Relative crystallinity degree (%) 100 100 100 100 100 100 100 100 Melting point (° C.) 208 170/208 169/208 171/212 167/210 (Tm-Tms)/(Tme-Tm) 1.9 1.5 1.5 1.2 1.2 Sc (%) 100 68 89 92 80 Cooling crystallization 110
  • a A A A L-4 Poly-L-lactic acid by ring-opening polymerization; Mw 201,000; Mp 173° C.
  • LD-1 Poly lactic acid diblock copolymer by ring-opening polymerization; Mw 135,000; Mp 208° C.
  • LD-2 Poly lactic acid triblock copolymer by ring-opening polymerization; Mw 150,000; Mp 210° C.
  • LD-3 Poly lactic acid block copolymer by direct polycondensation; Mw 125,000; Mp 221° C. Poly methylmethacrylate: Mw 100,000 Tg 90° C., Syndiotacticity 39% (“SUMIPEX” LG35 manufactured by Sumitomo Chemical Co., Ltd.)
  • the polylactic acid block copolymer has a high molecular weight, high melting point and excellent transparency, it can be suitably applied to fields in which use of polylactic acid homopolymers has been difficult because of requirement of heat resistance and transparency.

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