JP5812947B2 - Method for producing polylactic acid and molded article thereof - Google Patents

Description

  The present invention relates to a method for producing polylactic acid and a molded body thereof.

  In recent years, interest in environmental protection has increased, and the promotion of the purchase of environmentally friendly materials by the Green Purchasing Law, and the promotion of recycling plastic materials and electrical appliances by the Containers and Packaging Recycling Law and the Home Appliance Recycling Law have emerged. In such a series of flows, expectations for biodegradable polymers with low environmental impact are increasing day by day.

  Polylactic acid, which is one of the biodegradable polymers, has high transparency, toughness, and has a property of easily hydrolyzing in the presence of water. When used as a general-purpose resin, it decomposes without contaminating the environment after disposal, and is environmentally friendly.When it is placed in the living body as a medical material, it is toxic to the living body after the purpose of the medical material is achieved. Because it is decomposed and absorbed in the living body without affecting the body, it is friendly to the living body.

  Polylactic acid is used in various applications such as films, sheets, molded products, foams, etc., but in order to realize the mechanical properties required for these applications, it is required to increase the molecular weight of the polymer. Various methods have been studied and proposed.

  Conventionally, as a method for obtaining a high molecular weight polylactic acid, a ring-opening polymerization method of lactic acid cyclic dimer (lactide) or a direct dehydration polycondensation method of lactic acid is known, but the ring-opening polymerization method is a raw material. There was a problem that the purification of lactide was complicated and not economical. Further, the direct dehydration polycondensation method is usually a reaction in an organic solvent, so that the volumetric efficiency is poor, and there is a problem that it is difficult to obtain a high molecular weight although it is economical compared with the ring-opening polymerization method.

  In contrast, a method of crystallizing low molecular weight polylactic acid obtained by direct dehydration polycondensation and then increasing the molecular weight in the solid phase has also been proposed. There is still room for improvement.

  On the other hand, the low molecular weight polylactic acid obtained by the direct dehydration polycondensation method is reacted with a chain extender such as an isocyanate compound at a temperature equal to or higher than the melting point of polylactic acid, for example, 210 to 215 ° C. to increase the molecular weight. A method has also been proposed. However, the molecular weight after chain extension is only about twice, and it has been difficult to increase the molecular weight more than twice (Patent Document 1). In addition, as a method for increasing the molecular weight of low-molecular-weight polylactic acid more than twice, a method of reacting telechelic polylactic acid of both terminal diols with diisocyanate has also been proposed, but the chain extension bond formed has low thermal stability. Because it is only a urethane bond, the resulting high molecular weight polylactic acid is prone to heat-breaking molecular chains at high temperatures, and there is a problem with heat resistance, and a method for reacting a dikelic acid telechelic polylactic acid with a bisoxazoline compound is also proposed However, there was an economic problem in that an expensive bisoxazoline compound was used (Non-patent Document 1).

  Furthermore, a high-molecular-weight polyester resin in which an aliphatic polyester resin (for example, polylactic acid) and an isocyanate compound are reacted in the presence of an amide catalyst and the chain is extended by an amide bond having high thermal stability has been proposed (Patent Document). 2). The polyester resin obtained by this method has a high molecular weight and excellent thermal stability. However, there has been a further demand for a production method having an economical advantage by a cheaper and simpler process.

JP-A-5-148352 International Publication WO2009 / 110472

Jukka Tuominen, CHAIN LINKED LACTIC ACID POLYMERS: POLYMERIZATION AND BIODEGRADATION STUDIES, Polymer Technology Publication Series Espoo 2003, Finland, Helsinki University of Tecnology, 2003.2.28, No. 25

  In order to solve the above-described problems, an object of the present invention is to provide a method for producing polylactic acid and a molded body thereof that are lower in cost and higher in productivity.

  As a result of diligent studies to solve the above problems, the present inventors have made a short reaction by reacting a water-controlled polylactic acid prepolymer with a polyisocyanate compound in the presence of an amidation catalyst and in the absence of a solvent. The inventors have found that a high molecular weight polylactic acid can be obtained in a time, and reached the present invention.

That is, the present invention
[1] A method for producing polylactic acid, which comprises reacting a polylactic acid prepolymer containing a lactic acid oligomer having a terminal carboxyl group ratio exceeding 80 mol% with a polyisocyanate compound in the presence of an amidation catalyst, A method for producing polylactic acid, in which, in the presence, the water concentration in the polylactic acid prepolymer is adjusted to 1 to 300 ppm and reacted.
And preferably any of the following.
[2] The method for producing polylactic acid, wherein the lactic acid oligomer is a mixture of an L-lactic acid oligomer and a D-lactic acid oligomer.
[3] The method for producing polylactic acid as described above, wherein the lactic acid oligomer is an L-lactic acid oligomer or a D-lactic acid oligomer, and an optical isomeric lactic acid polymer is further present.
[4] The method for producing polylactic acid as described above, wherein a twin-screw extruder and / or a static mixer is used.
[5] The method for producing polylactic acid as described above, wherein the total residence time of the resin in the twin-screw extruder and / or the static mixer is 5 minutes or more.
[6] The method for producing polylactic acid as described above, wherein the shear rate in the twin-screw extruder and / or the static mixer is 1,000 to 1,000,000 s ⁻¹ .
[7] The method for producing polylactic acid described above, wherein when the polyisocyanate compound and the polylactic acid prepolymer are mixed, a cooling layer is provided in the mixed portion.
[8] Polylactic acid produced by the method for producing polylactic acid described above.
[9] A molded body formed by molding the polylactic acid.

  Since the production method of the present invention is polymerization in the absence of a solvent, compared to polymerization in a solution state using a solvent, steps such as solvent recovery, crystallization, and drying can be omitted, and there is an equipment advantage. Have sex. Moreover, high molecular weight can be achieved in a short time, and productivity can be improved. Furthermore, since the polylactic acid obtained by the present invention has an amide bond in the molecular chain, has a practically sufficient high molecular weight, and has a high melting point and high thermal stability, the film, sheet, molded product, fiber It can be suitably used for applications that require mechanical properties such as heat resistance.

It is the schematic which shows an example of the structure of the mixing part of a twin-screw extruder. It is the schematic which shows an example of the structure of the mixing part of a twin-screw extruder. It is the schematic which shows an example of the structure of the mixing part of a twin-screw extruder.

Next, the present invention will be specifically described.
The present invention relates to a method for producing polylactic acid, in which a polylactic acid prepolymer containing a lactic acid oligomer having a terminal carboxyl group ratio exceeding 80 mol% and a polyisocyanate compound are reacted in the presence of an amidation catalyst. In the presence, the water concentration in the polylactic acid prepolymer is adjusted to 1 to 300 ppm, preferably 1 to 200 ppm, more preferably 1 to 100 ppm, and still more preferably 1 to 50 ppm. When the water concentration is within the above range, not only the polymerization time is shortened, but also high molecular weight is possible.

<Polylactic acid prepolymer>
The polylactic acid prepolymer used in the present invention is a lactic acid oligomer having a terminal carboxyl group ratio exceeding 80 mol%, or a mixture of a lactic acid oligomer and a lactic acid polymer having a terminal carboxyl group ratio exceeding 80 mol%. When the lactic acid polymer is mixed, the lactic acid polymer includes a lactic acid polymer having an optical isomer relationship with the lactic acid oligomer to be used.

《Lactic acid oligomer》
The lactic acid oligomer contained in the polylactic acid prepolymer used in the present invention is an L-lactic acid oligomer and / or a D-lactic acid oligomer, and 80 mol% or more of the structural unit is L-lactic acid or D-lactic acid. As long as it is less than 20 mol% and does not impair other optical isomers or the object of the present invention, other component units may be contained. The higher L-lactic acid content or D-lactic acid content is preferably 90 mol% or more, more preferably 95 mol% or more, and still more preferably 98 mol% or more. When the L-lactic acid content or D-lactic acid content is within the above range, the resulting polylactic acid tends to exhibit high crystallinity.

  Examples of other component units other than L-lactic acid or D-lactic acid include polyvalent carboxylic acids, polyhydric alcohols, hydroxycarboxylic acids, lactones, and the like, including initiators in the production method described below. Specifically, Polyvalent carboxylic 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 or the like Derivatives, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, neopentyl glycol, glycerin, trimethylolpropane, bisphenol and an aromatic polyhydride Dihydric alcohol, diethylene glycol , Polyhydric alcohols such as triethylene glycol, polyethylene glycol and polypropylene glycol or derivatives thereof, hydroxycarboxylic acids such as glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid and 6-hydroxycaproic acid And lactones such as glycolide, ε-caprolactone glycolide, ε-caprolactone, β-propiolactone, δ-butyrolactone, β- or γ-butyrolactone, pivalolactone, δ-valerolactone, and the like.

《Terminal carboxyl group of lactic acid oligomer》
The terminal functional group of the lactic acid oligomer used in the present invention is a carboxyl group in a proportion exceeding 80 mol%. Furthermore, the ratio of the terminal carboxyl group is preferably 90 mol% or more, and more preferably 95 mol% or more. As the proportion of terminal carboxyl groups increases, the proportion of chain extension bonds to amide bonds increases, and polylactic acid with better thermal stability can be obtained.

<< Method for producing lactic acid oligomer >>
The method for preparing the lactic acid oligomer used in the present invention is not particularly limited as long as it does not impair the purpose of the present invention. For example, L-lactic acid oligomer is L-lactic acid, and D-lactic acid oligomer is D-lactic acid. A direct polycondensation method in which each is directly dehydrated and condensed, and a ring-opening polymerization method in which L-lactide or D-lactide, which is once a cyclic dimer, is synthesized from L-lactic acid or D-lactic acid, respectively, and the lactide is subjected to ring-opening polymerization, And a method combining these and solid phase polymerization.

<Direct polycondensation method>
As a specific example of preparing the lactic acid oligomer used in the present invention by the direct polycondensation method, the raw material L-lactic acid or D-lactic acid is heated in an inert gas atmosphere, and the pressure is lowered to cause a polycondensation reaction. There is a method of obtaining an L-lactic acid oligomer or a D-lactic acid oligomer by conducting a polycondensation reaction under conditions of a predetermined temperature and pressure. At this time, by adding a polyvalent carboxylic acid or an acid anhydride or the like together with lactic acid as a raw material either in the initial stage, in the middle or later stage, an L-lactic acid oligomer in which the ratio of the carboxyl group in the terminal functional group exceeds 80 mol% Or the D-lactic acid oligomer in which the ratio of the carboxyl group in the terminal functional group exceeds 80 mol% can be prepared.

  The polycarboxylic acid component added during the direct polycondensation reaction is preferably a dicarboxylic acid. Examples of the dicarboxylic acid component include succinic acid, adipic acid, sebacic acid, fumaric acid, terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid. Acid, 5-sodium sulfoisophthalic acid, 5-tetrabutylphosphonium sulfoisophthalic acid and the like, and succinic acid is more preferable from the viewpoint of cost. Examples of the acid anhydride include succinic anhydride, phthalic anhydride, maleic anhydride, tetrabromophthalic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, or 2-dodecen-1-ylsuccinic anhydride, and succinic anhydride. Acid is preferred.

  When polyvalent carboxylic acid or acid anhydride is added during polymerization or in the initial stage, it may be added in accordance with the target weight average molecular weight in the L-lactic acid oligomer or D-lactic acid oligomer described later. Specifically, it is preferably 0.19 to 3.8 mol, more preferably 0.24 to 1.9 mol, and still more preferably 0.38 to 100 mol with respect to 100 mol of L-lactic acid or D-lactic acid used. 1.9 mol.

  When polyvalent carboxylic acid or acid anhydride is added in the latter stage of polymerization, the addition amount is preferably 0.19 to 7.2 moles, more preferably 100 moles of L-lactic acid or D-lactic acid used. Is 0.24 to 5.8 mol, more preferably 0.38 to 3.6 mol.

When the addition amount of the polyvalent carboxylic acid or acid anhydride added during the direct polycondensation reaction is in the above range, the molecular weight can be set to a desired range without requiring a long time for polymerization.
The polycondensation reaction may be performed in the presence of a catalyst for the purpose of shortening the polycondensation time, increasing the reaction rate with the acid anhydride, or shortening the reaction time. Examples of the catalyst include metals of Groups 2, 12, 13, 14, or 15 of the periodic table, or oxides or salts thereof. Specifically, metals such as zinc powder, tin powder, aluminum or magnesium, metal oxides such as antimony oxide, zinc oxide, tin oxide, aluminum oxide, magnesium oxide or titanium oxide, stannous chloride, stannic chloride , Stannous bromide, stannic bromide, antimony fluoride, zinc chloride, magnesium chloride, aluminum chloride and other metal halides, carbonates such as magnesium carbonate and zinc carbonate, tin acetate, tin octoate, tin lactate , Organic carboxylates such as zinc acetate or aluminum acetate, or organic sulfonates such as tin trifluoromethanesulfonate, zinc trifluoromethanesulfonate, magnesium trifluoromethanesulfonate, tin methanesulfonate or tin p-toluenesulfonate Can be given. In addition, organometallic oxides of the above metals such as dibutyltin oxide, metal alkoxides of the above metals such as titanium isopropoxide, alkyl metals of the above metals such as diethyl zinc, ion exchange resins such as dowex or amberlite, or the like And a protonic acid such as sulfuric acid, methanesulfonic acid, or p-toluenesulfonic acid, and a tin or zinc metal or a metal compound thereof, and a protonic acid, which can obtain a polymer having a high polymerization rate and a high molecular weight, are preferred. Furthermore, metal tin or tin compounds such as tin oxide and tin chloride and protonic acid are more preferred from the viewpoint of hue and catalytic activity.

Although the addition amount of a catalyst is not specifically limited, 0.01-2 mol is preferable with respect to 100 mol of L-lactic acid or D-lactic acid to be used, and 0.1-1 mol is more preferable.
If the amount of catalyst is less than 0.01 mol, the effect of shortening the polymerization time is reduced. May be damaged.

<Ring-opening polymerization method>
A ring-opening polymerization method is used to prepare an L-lactic acid oligomer in which the terminal functional group used in the present invention is a carboxyl group in excess of 80 mol% or a D-lactic acid oligomer in which the terminal functional group is a carboxyl group exceeds 80 mol%. As specific examples, L-lactide and D-lactide, which are the above-described lactic acid cyclic dimers, are used by using a compound containing two or more hydroxyl groups or amino groups in the molecule, a hydroxycarboxylic acid, water or the like. Examples thereof include a method obtained by adding an acid anhydride after ring-opening polymerization. Examples of the compound containing two or more hydroxyl groups or amino groups in the molecule include ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, neopentyl glycol, glycerin. , Trimethylolpropane, aromatic polyhydric alcohol obtained by addition reaction of ethylene oxide with bisphenol, polyhydric alcohol such as diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, ethylenediamine, 1,3-propanediamine, 1,4-butane Diamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, diethylenetriamine, polyamines such as melamine, glycolic acid, 3-hydroxybutyric acid, 4-hydro Shi acid, 4-hydroxyvaleric acid, etc. hydroxycarboxylic acids such as 6-hydroxycaproic acid. The amount of the initiator to be added is not particularly limited, but is preferably 0.38 to 7.7 moles per 100 moles of lactide (L-lactide or D-lactide) to be used, 3.84 mol is more preferable, and 0.77 to 3.84 mol is more preferable.

When the amount of the initiator used in the ring-opening polymerization is in the above range, the molecular weight can be set to a desired range.
Acid anhydrides added after ring-opening polymerization include succinic anhydride, phthalic anhydride, maleic anhydride, tetrabromophthalic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride or 2-dodecen-1-ylsuccinic anhydride. And succinic anhydride is preferable. The amount of the acid anhydride added is preferably 0.38 to 7.7 mol, more preferably 0.48 to 3.84 mol, based on 100 mol of L-lactide or D-lactide to be used, and 0.77 More preferred is ˜3.84 mol.

The ring-opening polymerization may be performed in the presence of a catalyst for the purpose of shortening the polymerization time, increasing the reaction rate with the acid anhydride, or shortening the reaction time. Examples of the catalyst include metals such as tin, zinc, lead, titanium, bismuth, zirconium, germanium, antimony, and aluminum, and derivatives thereof. Derivatives are preferably metal alkoxides, carboxylates, carbonates, oxides and halides. Specific examples include tin chloride, tin octylate, zinc chloride, zinc acetate, lead oxide, lead carbonate, titanium chloride, alkoxytitanium, germanium oxide, and zirconium oxide. Among these, a tin compound is preferable, and tin octylate is particularly preferable. Although the addition amount of a catalyst is not specifically limited, 0.01-2 mol is preferable with respect to 100 mol of L-lactide or D-lactide to be used, and 0.1-1 mol is more preferable.
If the amount of catalyst is less than 0.01 mol, the effect of shortening the polymerization time is lowered, and if it exceeds 2 mol, the molecular stability during the molding process of polylactic acid in the present invention and thermal stability such as thermal decomposition may be impaired.

<Combination with solid phase polymerization>
As a method in which the direct polymerization method or the ring-opening polymerization method and the solid phase polymerization method are combined, the methods described in JP-A No. 2000-302852, JP-A No. 2001-122951, etc. can be used. Examples thereof include a method in which a crystallized lactic acid oligomer obtained by a direct polymerization method or a ring-opening polymerization method is heated in a solid phase in the presence of a catalyst, preferably in a flowing gas atmosphere, and subjected to dehydration polycondensation.

<< Molecular weight of lactic acid oligomer >>
The weight average molecular weight of the lactic acid oligomer used in the present invention is preferably 5,000 to 100,000, more preferably 10,000 to 80,000, and particularly preferably 10,000 to 50,000. preferable. It is preferable that the weight average molecular weight of the lactic acid oligomer is within the above range because the polymerization time is short and the manufacturing process time can be shortened. In the present invention, the weight average molecular weight (hereinafter also referred to as “Mw”) is determined by the measurement method described in the examples described later.

《Amount of catalyst residue of lactic acid oligomer》
In the lactic acid oligomer used in the present invention, the content of (heavy) metal derived from the catalyst in the lactic acid oligomer or the content of S derived from protonic acid is preferably 300 ppm or less, and preferably 100 ppm or less. More preferably, it is more preferably 50 ppm or less, and particularly preferably 30 ppm or less. The lower limit of the content is not particularly limited. When the content of the (heavy) metal derived from the catalyst in the lactic acid oligomer or the content of S is within the above range, a high molecular weight polylactic acid is obtained, and the thermal stability tends to increase. .

  Among the (heavy) metals, the Sn content is preferably 300 ppm or less, more preferably 100 ppm or less, still more preferably 50 ppm or less, and particularly preferably 30 ppm or less. The lower limit of the Sn content is not particularly limited. In particular, by controlling the Sn content within the above range, a high molecular weight polylactic acid can be obtained, and its thermal stability tends to increase. As a method for removing Sn contained in the lactic acid oligomer, a known method can be used, for example, a method of treating the lactic acid oligomer with hydrochloric acid / 2-propanol. In addition, (heavy) metals, such as Sn, and content of S are calculated | required with the measuring method described in the Example mentioned later.

《Lactic acid polymer》
The polylactic acid prepolymer used in the present invention may be a mixture of the lactic acid oligomer and the lactic acid polymer. The lactic acid polymer used in the present invention is an L-lactic acid polymer or a D-lactic acid polymer, and 80 mol% or more of the structural units is L-lactic acid or D-lactic acid. As long as it is less than 20 mol% and does not impair other optical isomers or the object of the present invention, other component units may be contained. The L-lactic acid content or the D-lactic acid content is preferably higher, preferably 90 mol% or more, more preferably 95 mol% or more, and particularly preferably 98 mol% or more. When the L-lactic acid content or D-lactic acid content is within the above range, the resulting polylactic acid tends to exhibit high crystallinity.
Examples of the component unit other than L-lactic acid or D-lactic acid include the same components as the specific examples of the other component units in the lactic acid oligomer described above.

<Ratio of terminal carboxyl group of lactic acid polymer>
The terminal functional group of the lactic acid polymer used in the present invention is not particularly limited, but is preferably a carboxyl group in a proportion exceeding 50 mol%, more preferably 80 mol% or more, and 90 mol% or more. Is more preferable, and it is especially preferable that it is 95 mol% or more. As the proportion of terminal carboxyl groups increases, the proportion of chain extension bonds to amide bonds increases, and polylactic acid with better thermal stability can be obtained.

<< Method for producing lactic acid polymer >>
If the lactic acid polymer used by this invention does not impair the objective of this invention, the preparation method will not be specifically limited, For example, the commercially available polylactic acid-type resin manufactured by the well-known method can be used.

On the other hand, as a method for preparing a lactic acid polymer in which the terminal functional group is a carboxyl group in a proportion exceeding 50 mol%, the same method as that for the lactic acid oligomer described above can be used. That is, in the L-lactic acid polymer, L-lactic acid, and in the D-lactic acid polymer, D-lactic acid is directly dehydrated and condensed, and L-lactic acid or D-lactic acid is a cyclic dimer once. There is a ring-opening polymerization method in which lactide or D-lactide is synthesized, and the lactide is subjected to ring-opening polymerization.
Further, a method in which a direct polymerization method or a ring-opening polymerization method and a solid phase polymerization method are combined can be used.

<Molecular weight of lactic acid polymer>
The weight average molecular weight of the lactic acid polymer used in the present invention is preferably 100,000 to 1,000,000, more preferably 120,000 to 700,000, and 150,000 to 500,000. More preferably. It is preferable in terms of moldability and mechanical strength that the weight average molecular weight of the lactic acid polymer is within the above range.

《Amount of catalyst residue of lactic acid polymer》
In the lactic acid polymer used in the present invention, the content of the (heavy) metal derived from the catalyst in the lactic acid polymer or the content of S derived from the protonic acid is preferably 300 ppm or less, and preferably 100 ppm or less. More preferably, it is more preferably 50 ppm or less, and particularly preferably 30 ppm or less. The lower limit of the content is not particularly limited. When the content of (heavy) metal derived from the catalyst in the lactic acid polymer or the content of S is within the above range, a high molecular weight polylactic acid is obtained, and the thermal stability tends to increase. .

  Among the (heavy) metals, the Sn content is preferably 300 ppm or less, more preferably 100 ppm or less, still more preferably 50 ppm or less, and particularly preferably 30 ppm or less. The lower limit of the Sn content is not particularly limited. In particular, by controlling the Sn content within the above range, a high molecular weight polylactic acid can be obtained, and its thermal stability tends to increase. Examples of the method for removing Sn contained in the lactic acid polymer include the same method as the method for removing Sn contained in the lactic acid oligomer described above. In addition, (heavy) metals, such as Sn, and content of S are calculated | required with the measuring method described in the Example mentioned later.

《Stereo Complex Polylactic Acid》
As a lactic acid oligomer in the polylactic acid prepolymer used in the present invention, an L-lactic acid oligomer and / or a D-lactic acid oligomer can be used. These may be used alone or in combination. In the case of using a mixture of L-lactic acid oligomer and D-lactic acid oligomer, the weight ratio is preferably 10:90 to 90:10, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40. . When the weight ratio is within this range, the resulting polylactic acid has a high melting point and excellent heat resistance by forming a stereocomplex.

  Further, when the polylactic acid prepolymer used in the present invention is a mixture of a lactic acid oligomer and a lactic acid polymer, it can also be obtained as a mixture of an L-lactic acid oligomer and a D-lactic acid polymer, or a mixture of a D-lactic acid oligomer and an L-lactic acid polymer. By forming a stereocomplex, polylactic acid has a high melting point and excellent heat resistance. The weight ratio when used in combination is preferably 10:90 to 90:10, more preferably 30:70 to 70:30, and still more preferably 40:60 to 60:40.

<Copolymerization component of polylactic acid prepolymer>
In addition to the lactic acid oligomer and the lactic acid polymer, the polylactic acid prepolymer used in the present invention may further contain a copolymer component as desired. The copolymer component is not particularly limited as long as it does not impair the object of the present invention, and can be used according to the object of improving physical properties. For example, polyhydroxycarboxylic acid other than polylactic acid, polyester, polyamide, polycarbonate and the like can be used.

  The content of the copolymer component is not particularly limited as long as the object of the present invention is not impaired, and is preferably 0 to 40 parts by weight, preferably 100 parts by weight of lactic acid oligomer or a mixture of lactic acid oligomer and lactic acid polymer. 5 to 20 parts by weight, more preferably 5 to 10 parts by weight.

  Specific examples of the polyhydroxycarboxylic acid in the copolymer component include polyglycolic acid, poly (3-hydroxybutyric acid), poly (4-hydroxybutyric acid), poly (2-hydroxy-n-butyric acid), poly (2-hydroxy- 3,3-dimethylbutyric acid), poly (2-hydroxy-3-methylbutyric acid), poly (2-methyllactic acid), poly (2-hydroxycaproic acid), poly (2-hydroxy-3-methylbutyric acid), poly (2-cyclohexyl glycolic acid), poly (mandelic acid), polycaprolactone, copolymers thereof and mixtures thereof.

  Examples of the polyester in the copolymer component include polyesters whose main components are represented by a repeating unit composed of a glycol component and a dicarboxylic acid component, but a copolymer of three or more components may be used, and a copolymer other than the glycol component and the dicarboxylic acid component may be used. Polymers may be included. Examples of the glycol component include ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, and 1,8-octanediol. 1,9-nonanediol, 1,10-decanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, glycerin, pentaerythritol, bisphenol A, polyethylene glycol, polypropylene glycol and polytetramethylene glycol These can be used, and one or more of these can be used.

  The dicarboxylic acid component in the polyester includes oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, phthalic acid, isophthalic acid, terephthalic acid, 5 -Methylisophthalic acid, 5-sodium sulfoisophthalic acid, 5-tetrabutylphosphonium isophthalic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, hexahydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, naphthalenedicarboxylic acid , Anthracene dicarboxylic acid, bis (p-carboxyphenyl) methane, 4,4'-diphenyl ether dicarboxylic acid, dicarboxylic acid such as diglycolic acid, and dimethyl ester thereof. To use Can.

  Further, as other copolymerization components in the polyester, hydroxycarboxylic acids such as glycolic acid, lactic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, and hydroxybenzoic acid may be included.

  Specific examples of the polyester in the copolymerization component include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polycyclohexanedimethylene terephthalate, polyethylene isophthalate, polypropylene isophthalate, polybutylene isophthalate, polyethylene naphthalate, polypropylene naphthalate, polybutylene. Naphthalate, polybisphenol A terephthalate, polybisphenol A isophthalate, polycyclohexanedimethylene isophthalate, polyethylene sulfoisophthalate, polypropylene sulfoisophthalate, polybutylene sulfoisophthalate, polyethylene sebacate, polypropylene sebacate, polybutylene sebacate, Poly-ε-caprolactone, poly Ethylene oxalate, polypropylene oxalate, polybutylene oxalate, polyneopentyl glycol oxalate, polyethylene succinate, polypropylene succinate, polybutylene succinate, polyethylene adipate, polypropylene adipate, polybutylene adipate.

  Examples of the polyamide in the copolymer component include amino acids, lactams, and polymers or copolymers mainly composed of diamine and dicarboxylic acid. Examples of amino acids include 6-aminocaproic acid, 11-aminoundecanoic acid, and 12-aminododecane. Examples include acids and paraaminomethylbenzoic acid, and examples of lactams include ε-caprolactam and ω-laurolactam.

  As diamine components in polyamide, 1,4-butanediamine, 1,6-hexanediamine, 1,11-undecanediamine, 1,12-dodecanediamine, 2,2,4-trimethyl-1,6-hexanediamine 2,4,4-trimethyl-1,6-hexanediamine, 5-methyl-1,9-nonanediamine, 2,4-dimethyl-1,8-octanediamine, metaxylylenediamine, paraxylylenediamine, 1 , 3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, 3,8-bis (aminomethyl) tricyclo Decane, bis (4-aminocyclohexyl) methane, bis (3-methyl-4-aminocyclohexyl) methane, , 2- bis (4-aminocyclohexyl) propane, bis and the like (aminopropyl) piperazine and aminoethyl piperazine.

  The dicarboxylic acid component in the polyamide includes oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, phthalic acid, isophthalic acid, terephthalic acid, 5 -Methylisophthalic acid, 5-sodium sulfoisophthalic acid, 5-tetrabutylphosphonium isophthalic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, hexahydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, naphthalenedicarboxylic acid , Anthracene dicarboxylic acid, bis (p-carboxyphenyl) methane, 4,4′-diphenyl ether dicarboxylic acid, diglycolic acid and the like.

  Specific examples of the polyamide in the copolymerization component include polycaproamide, polyhexamethylene adipamide, polytetramethylene adipamide, polyhexamethylene sebamide, polyhexamethylene dodecamide, polyundecamide, polydodecamide, polycaproamide / Polyhexamethylene terephthalamide copolymer, polyhexamethylene adipamide / polyhexamethylene terephthalamide copolymer, polyhexamethylene adipamide / polyhexamethylene isophthalamide copolymer, polyhexamethylene adipamide / polyhexamethylene isophthalamide / polycapro Amide copolymer, polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer, polyhexamethylene terephthalamide / polydodecamide copoly Chromatography, polyhexamethylene adipamide / polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer, poly-xylylene adipamide, polyhexamethylene terephthalamide / poly-2-methyl pentamethylene terephthalamide copolymers.

  The polycarbonate in the copolymerization component is a resin having a carbonate bond, and is a polymer or copolymer obtained by reacting an aromatic hydroxy compound or a small amount thereof with a carbonate precursor.

  Examples of the aromatic hydroxy compound include 2,2-bis (4′-hydroxyphenyl) propane (commonly referred to as bisphenol A), 2,2-bis (4′-hydroxyphenyl) methane, and 1,1-bis (4′-). Hydroxyphenyl) ethane, 1,1-bis (4′-hydroxyphenyl) cyclohexane, 2,2-bis (4′-hydroxy-3 ′, 5′-dimethylphenyl) propane, 2,2-bis (4′-) Hydroxy-3 ′, 5′-dibromophenyl) propane, 2,2-bis (4′-hydroxy-3′-methylphenyl) propane, bis (4′-hydroxyphenyl) sulfide, bis (4′-hydroxyphenyl) Sulfone, hydroquinone, resorcinol, 4,6-dimethyl-2,4,6-tri (4'-hydroxyphenyl) heptene, 2,4,6-dimethyl 2,4,6-tri (4'-hydroxyphenyl) heptane, 2,6-dimethyl-2,4,6-tri (4'-hydroxyphenyl) heptene, 1,3,5-tri (4 ' -Hydroxyphenyl) benzene, 1,1,1-tri (4'-hydroxyphenyl) ethane, 3,3-bis (4'-hydroxyphenyl) oxindole, 5-chloro-3,3-bis (4'- Hydroxyphenyl) oxyindole, 5,7-dichloro-3,3-bis (4′-hydroxyphenyl) oxyindole, 5-bromo-3,3-bis (4′-hydroxyphenyl) oxyindole, and the like. These may be used alone or in combination of two or more.

  As the carbonate precursor, carbonyl halide, carbonate ester, haloformate or the like is used, and specific examples include phosgene, diphenyl carbonate and the like.

  Although the terminal functional group of the copolymerization component of the polylactic acid prepolymer used in the present invention is not particularly limited, it is preferably a carboxyl group in a proportion exceeding 50 mol%, more preferably 80 mol% or more, More preferably, it is 90 mol% or more, and it is especially preferable that it is 95 mol% or more. As the proportion of terminal carboxyl groups increases, the proportion of chain extension bonds to amide bonds increases, and polylactic acid with better thermal stability can be obtained.

<Particle size of polylactic acid prepolymer>
The polylactic acid prepolymer used in the present invention may be in a molten state or a solid state. The particle diameter in the solid state is not particularly limited, but is preferably 10 μm to 20 mm in the case of powder, and is preferably 1 to 20 mm in the case of a lump.

<Water concentration in polylactic acid prepolymer>
Generally, moisture in the atmosphere is absorbed and adsorbed by the resin, and polylactic acid contains 1000 to 5000 ppm of moisture, although it depends on the particle size, temperature, and humidity in the solid state. When melted in a state containing moisture, not only does the resin hydrolyze and the weight average molecular weight decreases, but also the proportion of terminal carboxyl groups decreases, polymerization does not proceed, and high molecular weight polylactic acid is difficult to obtain. .

<< Drying method of polylactic acid prepolymer >>
The polylactic acid prepolymer used in the present invention is preferably used after being dried. The drying method is not particularly limited, but a hot air dryer that blows hot air to a solid to evaporate moisture, a dehumidifying dryer that blows dry gas to evaporate moisture, a vacuum dryer that evaporates moisture by heat transfer under reduced pressure conditions, etc. Can be used alone or in combination. Among these, a method of removing moisture while stirring at a temperature equal to or higher than the glass transition temperature (hereinafter also referred to as “Tg”) while flowing a small amount of dry nitrogen in the dryer under reduced pressure is preferable. Although depending on the particle size and bulk density in the solid state, the moisture concentration of the polylactic acid prepolymer can be reduced to 300 ppm or less by drying under reduced pressure at a temperature of 80 ° C. for 5 hours or more.

<Dry gas>
As the dry gas, an industrially produced and generally sold cylinder or a gas produced by a cryogenic separation method or the like can be used, and the dew point of the gas is −40 ° C. or less (moisture determined by calculation). It is preferable to use a gas having a concentration of 127 ppm or less, more preferably -50 ° C. or less (calculated water concentration of 39 ppm or less), and even more preferably -60 ° C. or less (calculated water concentration of 11 ppm or less). It is.

<Processing method after drying>
When the polylactic acid prepolymer used in the present invention is dried and then transferred to a container, a bag, or a hopper of a powder feeder, it is preferably handled in an atmosphere of a dry gas or an inert gas as much as possible. For example, although depending on the particle size in a solid state, the moisture concentration rises to about 400 ppm by simply leaving the polylactic acid prepolymer having a moisture concentration of 100 ppm or less dried under reduced pressure in the atmosphere for about 5 minutes. Therefore, when it is unavoidable to expose to the atmosphere, the moisture concentration can be reduced by shortening the time as much as possible and spraying the dry gas after the transfer. The container, bag, device, etc. to be transferred may be removed in advance by hot air drying, dehumidifying drying, reduced pressure drying, or the like.

<Moisture measurement method>
The water content of the polylactic acid prepolymer used in the present invention can be measured with a general moisture meter, and examples thereof include a drying method, Karl Fischer method, dielectric constant method, infrared absorption method, and neutron moisture meter. Among these, it is preferable to use a moisture meter by the Karl Fischer method. As a method of measuring the moisture of a solid with a Karl Fischer moisture meter, the solid is heated, the evaporated moisture is collected and titrated, or the solid is dissolved in a solvent. There are a calculation method and a method in which a solid is charged directly into a measurement cell. Any method may be used as long as an environment that does not absorb moisture in the atmosphere can be constructed.

<Polyisocyanate compound>
The polyisocyanate compound used in the present invention is a compound having two or more isocyanate groups, and is not particularly limited as long as the object of the present invention is not impaired. Examples of the polyisocyanate compound having 3 or more isocyanate groups include triisocyanates such as 1,6,11-undecane triisocyanate and polyisocyanate-substituted compounds such as polyphenylmethane polyisocyanate. The polyisocyanate compound is preferably a diisocyanate compound.

  Examples of the diisocyanate compound include 2,4-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, 1,1′-diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, 1 , 3-Xylylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, isophorone diisocyanate, 1,3-bis (isocyanato Methyl) cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane, 2,5-bis (isocyanatomethyl) bicyclo- [2,2,1] -heptane or bis (4'-isocyanatocyclohexyl) methane Raising More preferred examples include 1,3-xylylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, isophorone diisocyanate. 1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane, 2,5-bis (isocyanatomethyl) bicyclo- [2,2,1] -heptane or bis (4 '-Isocyanatocyclohexyl) methane and the like.

  Among these, 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, isophorone diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane 2,5-bis (isocyanatomethyl) bicyclo- [2,2,1] -heptane or bis (4′-isocyanatocyclohexyl) methane is more preferably one compound selected from the group consisting of Further, an aliphatic diisocyanate compound is more preferable, and 1,6-hexamethylene diisocyanate is further preferable. It is preferable that the polyisocyanate compound is an aliphatic diisocyanate because the resulting polylactic acid is less colored.

<Addition amount of polyisocyanate compound>
In the method for producing polylactic acid of the present invention, the addition amount of the polyisocyanate compound is determined based on the number of moles of terminal functional groups of the polylactic acid prepolymer. The number of moles of the terminal functional group of the polylactic acid prepolymer is calculated from the NMR data by the method described in the examples described later.

  In the method for producing polylactic acid according to the present invention, the polyisocyanate compound is preferably added in an amount of 0.8 to 2.0 times the mole of the terminal functional group of the polylactic acid prepolymer. It is more preferably 8 to 1.5 times mol, and further preferably 0.8 to 1.3 times mol. Here, “fold mole” is a unit of a value calculated by “number of moles of isocyanate group / number of moles of terminal functional group”.

  When the addition amount of the polyisocyanate compound is less than the lower limit, the addition effect of the polyisocyanate compound is small, and it may be difficult to obtain high molecular weight polylactic acid. On the other hand, when the upper limit is exceeded, the isocyanate may cause a side reaction such as a crosslinking reaction, and gel-like polylactic acid may be generated.

《Amidation catalyst》
The amidation catalyst that can be used in the method for producing polylactic acid of the present invention is a catalyst that reacts a terminal carboxyl group portion of the polylactic acid prepolymer containing the lactic acid oligomer with the polyisocyanate compound to form an amide bond. Say. By using an amidation catalyst, an amidation reaction can be carried out under mild conditions and side reactions can be suppressed, so that the desired polylactic acid can be produced with high purity.

  The amidation catalyst that can be used in the method for producing polylactic acid of the present invention preferably contains at least one metal selected from the group consisting of metals in Groups 1, 2 and 3 of the periodic table. When such a metal is contained, a catalyst having excellent reactivity can be obtained, and polylactic acid having a good color tone can be obtained.

  Examples of the amidation catalyst containing a Group 1 metal in the periodic table include organic metal compounds such as organic acid salts, metal alkoxides or metal complexes (acetylacetonato, etc.) of lithium, sodium, potassium, rubidium or cesium; An amidation catalyst containing a group 2 metal of the periodic table, and the like, and metal hydroxides, carbonates, phosphates, sulfates, nitrates, chlorides or fluorides; Are organic metal compounds such as organic acid salts, metal alkoxides or metal complexes (such as acetylacetonate) of beryllium, magnesium, calcium, strontium or barium; metal oxides, metal hydroxides, carbonates, phosphates, And inorganic metal compounds such as sulfates, nitrates, chlorides and fluorides. Furthermore, as the amidation catalyst containing the Group 3 metal of the periodic table, organometallic compounds such as scandium, ytterbium, yttrium or other rare earth organic acid salts, metal alkoxides, metal complexes (acetylacetonate, etc.) And inorganic metal compounds such as metal oxide, metal hydroxide, carbonate, phosphate, sulfate, nitrate, chloride or fluoride. These may be used alone or in combination of two or more. Among these metal compound catalysts, bis (acetylacetonato) magnesium, magnesium stearate, magnesium chloride, calcium stearate, ytterbium triflate and the like are preferable, magnesium compounds are more preferable, and bis (acetylacetonato) magnesium and magnesium stearate are preferable. Further preferred. Two or more of these catalysts can be used in combination.

<Addition amount of amidation catalyst>
In the method for producing polylactic acid of the present invention, the amount of the amidation catalyst added is preferably 0.001 to 0.24 mol, more preferably 100 mol of lactic acid component contained in the lactic acid oligomer in the polylactic acid prepolymer. The amount is 0.001 to 0.12 mol, more preferably 0.001 to 0.06 mol, and particularly preferably 0.001 to 0.03 mol.

  In the lactic acid oligomer contained in the polylactic acid prepolymer, the proportion of the terminal functional group being a carboxyl group exceeds 80 mol%, but the remaining terminal functional group may be a hydroxyl group. In that case, the hydroxyl group reacts with the polyisocyanate compound, thereby forming a urethane bond and increasing the weight average molecular weight. For example, by heat-treating the product after the melt reaction at around 100 ° C., urethane bonds can be formed and the weight average molecular weight can be increased.

<Production method of polylactic acid>
In conventional reactions in the presence of solvents, the viscosity of the mixture suddenly increased with the increase in the molecular weight of the reactants, and it was necessary to remove the solvent contained in the product. there were.
Since the present invention is a production method in which a water-controlled polylactic acid prepolymer and a polyisocyanate compound are reacted in the absence of a solvent, a solvent is unnecessary and the post-treatment of the product is simple and effective.

Here, “in the absence of a solvent” means that the solvent is contained in a proportion of less than 1% by weight.
Specifically, after an amidation catalyst is added to the polylactic acid prepolymer, it is dried by the above-described method, and the water concentration is controlled to 300 ppm or less. Next, after melting at a temperature equal to or higher than the melting point, a polyisocyanate compound is added and reacted at a predetermined temperature. Finally, polylactic acid can be obtained by decarboxylation of the obtained reaction product. The polyisocyanate compound is preferably a diisocyanate compound.
The timing for adding the amidation catalyst is not particularly limited, and may be before the reaction as described above or during the reaction or during the reaction.

<Melting temperature>
In the method for producing polylactic acid of the present invention, the state of the polylactic acid prepolymer at the time of melting is not particularly limited, but a part of the polylactic acid prepolymer is preferably in a molten state, and more preferably in a molten state. The temperature at the time of melting is not particularly limited as long as it is higher than the melting point of the lactic acid oligomer in the polylactic acid prepolymer or higher than the melting point of the stereocomplex mixture, but it is preferably as low as possible. Here, the stereocomplex mixture is a mixture of the L-lactic acid oligomer and the D-lactic acid oligomer, a mixture of the L-lactic acid oligomer and the D-lactic acid polymer, or the D-lactic acid oligomer and the L-lactic acid polymer. It is a mixture.

Specifically, when the melting temperature T ₁ and the melting point of the lactic acid oligomer or stereocomplex mixture which is a polylactic acid prepolymer is Tm, the melting temperature is preferably 0 ° C. ≦ (T ₁ −Tm) ≦ 50 ° C., more preferably 0 ° C. ≦ (T ₁ −Tm) ≦ 40 ° C., more preferably 5 ° C. ≦ (T ₁ −Tm) ≦ 35 ° C., and particularly preferably 10 ° C. ≦ (T ₁ −Tm) ≦ 30 ° C. Here, the melting point is the peak top value of the melting peak when the temperature is raised at a rate of temperature rise of 10 ° C./min by differential scanning calorimetry.

  Moreover, it is preferable that the time required for melting is short. If the heat history time is long, there is a possibility that the molecular weight may decrease or the proportion of the terminal carboxyl group may decrease due to thermal decomposition. The time required for melting is preferably 1 to 120 minutes, more preferably 1 to 90 minutes, still more preferably 1 to 60 minutes, and particularly preferably 1 to 30 minutes.

<Reaction temperature>
In the method for producing polylactic acid according to the present invention, the state of the polylactic acid prepolymer at the time of reaction is not particularly limited. The temperature during the reaction is not particularly limited as long as it is higher than the melting point of the lactic acid oligomer in the polylactic acid prepolymer or higher than the melting point of the stereocomplex mixture, but is preferably as low as possible.

Specifically, when the reaction temperature T ₂ and the melting point of the polylactic acid prepolymer lactic acid oligomer or stereo complex mixture is Tm, the reaction temperature is preferably 0 ° C. ≦ (T ₂ −Tm) ≦ 40 ° C., more preferably 0 ° C. ≦ (T ₂ −Tm) ≦ 35 ° C., more preferably 5 ° C. ≦ (T ₂ −Tm) ≦ 35 ° C., particularly preferably 10 ° C. ≦ (T ₂ −Tm) ≦ 30 ° C.

<Melting reactor>
Although the reaction apparatus used in the method for producing polylactic acid of the present invention is not particularly limited, a known melt polymerization reaction apparatus can be used. Specifically, kneading machines such as a vertical reaction tank equipped with a stirring blade, a static mixer, and an extruder can be used. Details of each of the melt reaction apparatuses will be described below, but the present invention is not limited thereto as long as the object of the present invention is not impaired.

<Vertical reaction tank>
Examples of the vertical reaction tank equipped with a stirring blade include a glass or SUS cylindrical reaction tube equipped with a stirring device and having two or more piping lines. Thereby, the carbon dioxide which is a by-product, and the water | moisture content contained in a raw material can be discharged | emitted out of the system, flowing inert gas etc.

<Static mixer>
In the case of using a static mixer, the number of elements may be adjusted for the purpose of adjusting the residence time after addition of polyisocyanate, and the number is not particularly limited. The residence time after addition of the polyisocyanate is preferably 1 to 60 minutes, more preferably 3 to 50 minutes, and even more preferably 5 to 40 minutes. If the residence time is too short, the polymerization does not proceed. If the residence time is excessively long, a decomposition reaction tends to occur, and the molecular weight decreases.

<Twin screw extruder>
In the method for producing polylactic acid of the present invention, various types of extruders can be used, but it is preferable to use a twin-screw extruder because the kneading effect is enhanced. The length / diameter ratio L / D of the screw to be used is preferably 20 or more, more preferably 30 or more, still more preferably 40 or more, and particularly preferably 50 or more, for the purpose of increasing the reaction time, that is, the residence time.

[Cylinder temperature]
The state of the polylactic acid prepolymer in the extruder is not particularly limited, but a part of the polylactic acid prepolymer is preferably in a molten state, and more preferably in a molten state. The barrel temperature is not particularly limited as long as it is equal to or higher than the melting point of the lactic acid oligomer and / or lactic acid polymer in the polylactic acid prepolymer, but is preferably as low as possible.

Specifically cylinder temperature T _3, when the melting point of the lactic acid oligomer and / or lactic acid polymers and Tm, preferred as cylinder temperature is _{0 ℃ ≦ (T 3 -Tm)} ≦ 50 ℃, more preferably 0 ° C. ≦ ( T ₃ −Tm) ≦ 40 ° C., more preferably 5 ° C. ≦ (T ₃ −Tm) ≦ 35 ° C., particularly preferably 10 ° C. ≦ (T ₃ −Tm) ≦ 30 ° C.

〔Residence time〕
In addition, the residence time after addition of the polyisocyanate is preferably 1 to 60 minutes, more preferably 3 to 50 minutes, and even more preferably 5 to 40 minutes. If the residence time is too short, the polymerization does not proceed. If the residence time is excessively long, a decomposition reaction tends to occur, and the molecular weight decreases.

  Examples of the method for controlling the residence time include a method of adjusting the feed amount of the polylactic acid prepolymer, and a method of controlling the screw element of the twin screw extruder by providing a kneading disk, a seal ring, and a reverse screw. Moreover, time can be adjusted by putting a mesh in a die | dye part and retaining resin.

[Resin pressure]
The resin pressure at the die portion varies depending on the number of meshes used, the die temperature, and the resin viscosity, but is preferably higher. Specifically, 0.1 to 10 MPa is preferable, 0.2 to 10 MPa is more preferable, and 0.3 to 10 MPa is more preferable. The resin pressure tends to increase as the weight average molecular weight of the resulting polylactic acid increases. On the other hand, when the die temperature increases, the resin viscosity decreases and the resin pressure tends to decrease.

[Shear rate]
Furthermore, the shear rate of the twin screw extruder is preferably 1,000 to 1,000,000 s ⁻¹ , more preferably 5,000 to 500,000 s ⁻¹ , and even more preferably 10,000 to 100,000 s ^−1. . If the shear rate is too slow, the polymerization does not proceed. If the shear rate is too fast, the decomposition reaction tends to occur, and the molecular weight decreases.

[Structure of mixed part]
The method of quantitatively feeding the polyisocyanate compound into the twin-screw extruder is not particularly limited, but when the polyisocyanate compound is solid, a method of premixing with the polylactic acid prepolymer can be mentioned. In the case where the polyisocyanate compound is liquid, for example, a method in which liquid is fed using a metering pump and inserted into a cylinder of a twin screw extruder can be mentioned. When a liquid polyisocyanate compound is inserted into a cylinder, as shown in FIG. 3, a pinhole is generally inserted into the cylinder, but the polyisocyanate compound undergoes self-condensation due to the heat transfer from the cylinder. The line may become blocked.

  In the method for producing polylactic acid according to the present invention, it is preferable to provide one or more cooling layers in the mixed portion in order to prevent heat transfer from the cylinder. Examples of the cooling layer in the mixed portion include a gas phase, a liquid phase, and a solid phase. In the case of the gas phase and the liquid phase, it is preferable to perform circulation cooling. In order to prevent heat transfer to the liquid feed line, it is preferable to provide a heat insulating layer.

  The direction of supply to the cylinder may be from any of the top, side, and bottom directions, and the resin pressure in the mixing part should be within the pressure range in which the liquid can be sent, that is, if the operating pressure of the liquid metering pump is higher than the resin pressure good. These are not limited as long as the purpose of preventing the self-condensation of the polyisocyanate compound is not impaired.

  More specifically, for example, a mixing part is provided in the upper part of the cylinder, a through hole having an area about the screw diameter is formed in the part, and a gas phase is provided as a cooling layer. Next, in order to prevent heat transfer, a resin sheet is piled up, a thin needle connected to the liquid feeding line is inserted from above, and the mixture is dropped and mixed, thereby preventing clogging and stable liquid feeding.

[Material of extruder]
The material of the resin contact part of the cylinder, screw and mixing part of the extruder used in the present invention is not particularly limited, but a metal having excellent corrosion resistance and wear resistance such as stellite, hastelloy, and kolmonoy is used. It is preferable. When a material having high corrosion resistance and wear resistance is used, the surface of the cylinder, screw, and mixing part is not easily eroded, and the number of foreign matters in the pellet is easily reduced. Further, the surface of the resin contact portion of the cylinder of the extruder and / or the screw and / or the mixing part may be subjected to titanium coating such as titanium carbide or titanium nitride, hard chrome plating or nickel plating. It is more preferable in that the effect is increased.

Although the example of the structure of the mixing part of the twin-screw extruder used suitably in the manufacturing method of the polylactic acid of this invention is shown in FIGS. 1-2, it is not necessarily limited to these.
FIG. 1 shows cylinder 1 / screw 2 / needle 3 / cooling layer (gas phase) 4 / connecting part (lower part) 5 / heat insulating layer 6 / connecting part (upper part) 5 ′ / fixing screw 7 / liquid feed line 8 FIG. 2 shows a mixing part including cylinder 1 / screw 2 / needle 3 / cooling layer (water phase) 4 ′ / connecting part 5 ″ / fixing screw 7 / feed line 8; In FIG. 3, the mixing part including cylinder 1 / screw 2 / connecting part 5 ″ ′ / fixing screw 7 / liquid feed line 8 is shown.

<Molecular weight of polylactic acid>
The weight average molecular weight of the polylactic acid produced by the present invention is preferably 150,000 to 1,000,000, more preferably 175,000 to 700,000, and 200,000 to 500,000. More preferably. It is preferable in terms of moldability and mechanical strength that the weight average molecular weight of the polylactic acid is within the above range.

<Melting point of polylactic acid <Tm>
The polylactic acid composed of L-lactic acid oligomer or D-lactic acid oligomer has a melting peak peak top (hereinafter also referred to as “Tm”) of 140 ° C. ≦ when heated at a rate of temperature increase of 10 ° C./min by differential scanning calorimetry. Tm ≦ 180 ° C. is preferable, 140 ° C. ≦ Tm ≦ 170 ° C. is more preferable, and 150 ° C. ≦ Tm ≦ 170 ° C. is further preferable.

Polylactic acid composed of L-lactic acid oligomer and D-lactic acid oligomer, polylactic acid composed of L-lactic acid oligomer and D-lactic acid polymer, or polylactic acid composed of D-lactic acid oligomer and L-lactic acid polymer are 180 ° C. ≦ Tm ≦ 230 ° C. is preferable, 190 ° C. ≦ Tm ≦ 230 ° C. is more preferable, and 200 ° C. ≦ Tm ≦ 230 ° C. is further preferable. It is preferable in terms of heat resistance that the Tm of the polylactic acid is within the above range.
The value of Tm is a value obtained by the measurement method described in Examples described later.

<Polylactic acid composition>
The polylactic acid produced by the present invention can be made into a polylactic acid composition by adding ordinary additives or resins other than the polylactic acid produced by the present invention to the extent that the object of the present invention is not impaired. .

<Stabilizer>
The polylactic acid produced in the present invention may contain a stabilizer, and preferably contains 0.001 to 5 parts by weight of stabilizer per 100 parts by weight of polylactic acid. More preferably, it is 0.001 to 1 part by weight, and particularly preferably 0.005 to 1 part by weight. From the viewpoint of cost and resin appearance, the stabilizer is preferably within the above range.

  The method of adding the stabilizer to polylactic acid is not particularly limited, but it is mixed with pellets after melt polymerization, kneaded again and pelletized, added during melt polymerization, or mixed with polylactic acid prepolymer. And melt polymerization.

  Stabilizers include phenolic compounds (hindered phenolic compounds), thioether compounds, vitamin compounds, triazole compounds, polyvalent amine compounds, hydrazine derivative compounds, phosphorus compounds, etc. May be used. Among them, it is preferable to include at least one phosphorus compound, and it is more preferable to use a phosphate compound or a phosphite compound. Preferred examples are “ADEKA STAB” AX-71 (dioftademil phosphate) manufactured by ADEKA, PEP-8 (distearyl pentaerythritol diphosphite), PEP-36 (cyclic neopentatetrayl bis (2,6-t-butyl). -4-methylphenyl) phosphite). The phosphorus stabilizer is considered to act as a deactivator for the amidation catalyst and / or a deactivator for the catalyst used for the preparation of the polylactic acid prepolymer, and the catalyst deactivator in the production of polylactic acid in the present invention. It is effective as

  Specific examples of the phenol compound 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-hydro) Xylphenyl) -propionate], tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane, 3,9-bis [2- {3- (3-t -Butyl-4-hydroxy-5-methylphenyl) propionyloxy} -1,1-dimethylethyl] 2,4,8,10-tetraoxaspiro (5,5) undecane, N, N′-bis-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionylhexamethylenediamine, N, N′-tetramethylene-bis-3- (3′-methyl-5′-t-butyl-4) '-Hydroxyphenol) propionyldiamine, N, N'-bis- [3- (3,5-di-tert-butyl-4-hydroxyphenol) propionyl] hydrazine, N-salicyloyl-N'-salicy Lidenhydrazine, 3- (N-salicyloyl) amino-1,2,4-triazole, N, N′-bis [2- {3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy } Ethyl] oxyamide, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], N, N′-hexamethylenebis- (3,5-di-t- And butyl-4-hydroxy-hydrocinnamide, preferably triethylene glycol-bis- [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) -propionate], tetrakis [methylene -3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane, 1,6-hexanediol-bis- [ -(3,5-di-t-butyl-4-hydroxyphenyl) -propionate], pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], N, N'-hexamethylenebis- (3,5-di-tert-butyl-4-hydroxy-hydrocinnamide.

  Specific product names of the phenolic compounds include “ADEKA STAB” AO-20, AO-30, AO-40, AO-50, AO-60, AO-70, AO-80, AO-330 manufactured by ADEKA, Ciba "Irganox" 245, 259, 565, 1010, 1035, 1076, 1098, 1222, 1330, 1425, 1520, 3114, 5057 manufactured by Specialty Chemicals, "Sumilyzer" BHT-R, MDP-S, BBM- manufactured by Sumitomo Chemical S, WX-R, NW, BP-76, BP-101, GA-80, GM, GS, “Sianox” CY-1790 manufactured by Cyanamid and the like.

  Specific examples of the thioether compound include dilauryl thiodipropionate, ditridecyl thiodipropionate, dimyristyl thiodipropionate, distearyl thiodipropionate, pentaerythritol tetrakis (3-lauryl thiopropionate) Pentaerythritol-tetrakis (3-dodecylthiopropionate), pentaerythritol-tetrakis (3-octadecylthiopropionate), pentaerythritol-tetrakis (3-myristylthiopropionate), pentaerythritol-tetrakis (3- Stearyl thiopropionate).

  Specific product names of thioether compounds include “ADEKA STAB” A0-23, AO-412S, AO-503A manufactured by ADEKA, “Irganox” PS802 manufactured by Ciba Specialty Chemicals, “Sumilyzer” TPL-R, TPM manufactured by Sumitomo Chemical. , TPS, TP-D, DSTP manufactured by API Corporation, DLTP, DLTOIB, DMTP, Cylin Kasei "Sinox" 412S, Cyamide "Syanox" 1212, and the like.

  Specific examples of the vitamin compound include d-α-tocopherol acetate, d-α-tocopherol succinate, d-α-tocopherol, d-β-tocopherol, d-γ-tocopherol, d-δ-tocopherol, d- Natural products such as α-tocotrienol, d-β-tocofetrienol, d-γ-tocofetrienol, d-δ-tocofetrienol, dl-α-tocopherol, dl-α-tocopherol acetate, succinic acid Examples thereof include synthetic products such as dl-α-tocopherol calcium and dl-α-tocopherol nicotinate.

Specific product names of vitamin compounds include “Tocopherol” manufactured by Eisai, “Irganox” E201 manufactured by Ciba Specialty Chemicals, and the like.
Specific examples of the triazole compound include benzotriazole and 3- (N-salicyloyl) amino-1,2,4-triazole.

  Specific examples of the polyvalent amine compound 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 salt (Li, Na, K) of ethylenediamine-tetraacetic acid, N, N′-disalicylidene-ethylenediamine, N, N′-disalicylidene-1 , 2-propylenediamine, N, N ″ -disalicylidene-N′-methyl-dipropylenetriamine, 3-salicyloylamino-1,2,4-triazole.

  Specific examples of the hydrazine derivative-based compound include decamethylene dicarboxyl acid-bis (N′-salicyloyl hydrazide), bis (2-phenoxypropionyl hydrazide) isophthalate, N-formyl-N′-salicyloyl hydrazine. 2,2-oxamide bis- [ethyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], oxalyl-bis-benzylidene-hydrazide, nickel-bis (1-phenyl-3- Methyl-4-decanoyl-5-pyrazolate), 2-ethoxy-2′-ethyloxanilide, 5-t-butyl-2-ethoxy-2′-ethyloxanilide, N, N-diethyl-N ′, N′-diphenyl oxamide, N, N′-diethyl-N, N′-diphenyl oxamide, oxalic acid (Benzylidene hydrazide), thiodipropionic acid-bis (benzylidene hydrazide), bis (salicyloyl hydrazine), N-salicylidene-N′-salicyloyl hydrazone, N, N′-bis [3- (3 5-Di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine, N, N′-bis [2- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] ethyl] Oxamide is mentioned.

  Examples of phosphorus compounds include phosphite compounds and phosphate compounds. Specific examples of such 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-di-carboxylic acid-di-salicylo Ruhydrazide-diphosphite, tetrakis [2-tert-butyl-4-thio (2′-methyl-4′-hydroxy-5′-tert-butylphenyl) -5-methylphenyl] -di (hydroxyethylcarbonyl) hydrazide Diphosphite, tetrakis [2-t-butyl-4-thio (2′-methyl-4′-hydroxy-5′-t-butylphenyl) -5-methylphenyl] -N, N′-bis (hydroxyethyl) oxamide -Diphosphite is preferable, and at least one PO bond is more preferably bonded to an aromatic group. Specific examples include tris (2,4-di-t-butylphenyl) phosphite, tetrakis (2,4-di-t-butylphenyl) 4,4′-biphenylene phosphonite, bis (2,4-di-t-butylphenyl) pentaeri Thritol-di-phosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol-di-phosphite, 2,2-methylenebis (4,6-di-t-butylphenyl) octyl Phosphite, 4,4′-butylidene-bis (3-methyl-6-tert-butylphenyl-di-tridecyl) phosphite, 1,1,3-tris (2-methyl-4-ditridecyl phosphite-5 -T-butyl-phenyl) butane, tris (mixed mono and di-nonylphenyl) phosphite, tris (nonylphenyl) phosphite, 4,4'-isopropylidenebis (phenyl-dialkyl phosphite), Tris (2,4-di-t-butylphenyl) phosphite, 2,2-methylenebis (4,6-di-t-butylpheny ) Octyl phosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol-di-phosphite, tetrakis (2,4-di-t-butylphenyl) -4,4′-biphenylene Phosphonite and the like can be preferably used. Specific product names of phosphite compounds include “ADEKA STAB” C, PEP-4C, PEP-8, PEP-11C, PEP-24G, PEP-36, HP-10, 2112, 260, 522A, manufactured by ADEKA, 329A, 1178, 1500, C, 135A, 3010, TPP, Ciba Specialty Chemical "Irgafos" 168, Sumitomo Chemical "Smilizer" P-16, Clariant "Sand Stub" PEPQ, GE "Weston" 618, 619G 624 and the like.

  Specific examples of the phosphate compound include monostearyl acid phosphate, distearyl acid phosphate, methyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, octyl acid phosphate, isodecyl acid phosphate, among them monostearyl acid phosphate, Distearyl acid phosphate is preferred. Specific product names of phosphate compounds include “Irganox” MD1024 from Ciba Specialty Chemicals, “Inhibitor” OABH from Eastman Kodak, “Adekastab” CDA-1, CDA-6, AX-71 from ADEKA, etc. Can be mentioned.

<Other additives>
In addition to the stabilizer, the polylactic acid produced according to the present invention includes conventional additives such as fillers (glass fiber, carbon fiber, metal fiber, natural fiber, organic fiber, etc. as long as the object of the present invention is not impaired. Fibers, glass flakes, glass beads, ceramic fibers, ceramic beads, asbestos, wollastonite, talc, clay, mica, sericite, zeolite, bentonite, montmorillonite, synthetic mica, dolomite, kaolin, fine silicic acid, feldspar powder, titanic acid Potassium, shirasu balloon, calcium carbonate, magnesium carbonate, barium sulfate, calcium oxide, aluminum oxide, titanium oxide, aluminum silicate, silicon oxide, gypsum, novaculite, dosonite or clay, ultraviolet absorbers (resorcinol, salicylate, benzotria) , Benzophenone, etc.), heat stabilizers (such as hindered phenols, hydroquinones, phosphites and their substitutes), lubricants, mold release agents (montanic acid and its salts, its esters, their half esters, stearyl alcohol, Colorants including stearamide and polyethylene wax), dyes (such as nigrosine) and pigments (such as cadmium sulfide, phthalocyanine), anti-coloring agents (such as phosphite, hypophosphite), flame retardants (red phosphorus, phosphoric acid) Ester, brominated polystyrene, brominated polyphenylene ether, brominated polycarbonate, magnesium hydroxide, melamine and cyanuric acid or salts thereof, conductive agent or colorant (carbon black, etc.), sliding property improver (graphite, fluorine resin) ), Crystal nucleating agent (talc Inorganic nucleating agents, organic amide compounds such as ethylenebislauric acid amide, ethylenebis-12-dihydroxystearic acid amide and trimesic acid tricyclohexylamide, pigment nucleating agents such as copper phthalocyanine and pigment yellow 110, organic carboxylic acids 1 type, or 2 or more types of additives, such as a metal salt, zinc phenylphosphonate, and an antistatic agent, can be added.

<Blend with resin>
In addition, the polylactic acid produced by the present invention can further contain at least one or more resins such as other thermoplastic resins or thermosetting resins within a range not impairing the object of the present invention. Examples of thermoplastic resins include polyethylene, polypropylene, acrylic resin, polyamide, polyphenylene sulfide resin, polyether ether ketone resin, polyester, polysulfone, polyphenylene oxide, polyacetal, polyimide, polyether imide, soft thermoplastic resin (for example, ethylene) / Glycidyl methacrylate copolymer, polyester elastomer, polyamide elastomer, ethylene / propylene terpolymer, ethylene / butene-1 copolymer, etc.). Examples of thermosetting resins include phenolic resins, melamine resins, polyester resins, silicone resins, and epoxy resins.

  The content of the other thermoplastic resin or thermosetting resin is not particularly limited as long as it does not impair the object of the present invention, but is 0 to 50 parts by weight per 100 parts by weight of polylactic acid. Preferably there is.

<Polylactic acid molding process and application>
The method for molding polylactic acid produced in the present invention is not particularly limited. Specifically, injection molding, extrusion molding, inflation molding, extrusion hollow molding, foam molding, calendar molding, blow molding, balloon molding, vacuum molding. And molding methods such as spinning. Among these, injection molding, foam molding, and spinning that make use of the characteristics of polylactic acid are preferably applied. In addition, the polylactic acid produced by the present invention can be produced by, for example, a writing tool member such as a ballpoint pen, a mechanical pencil, or a pencil, a stationary member, a golf tee, or a ball for fuming golf ball by an appropriate molding method. Capsules for oral pharmaceuticals, suppositories for anal and vaginal suppositories, carriers for skin and mucous membranes, pesticide capsules, fertilizer capsules, seedling capsules, compost, fishing line spools, fishing floats, fake fishing bait, lures, Fishing buoys, hunting decoys, hunting shot capsules, camping equipment such as tableware, nails, piles, binding materials, antiskid materials for muddy / snowy roads, blocks, lunch boxes, tableware, lunch boxes and prepared food containers, chopsticks, Chopsticks, forks, spoons, skewers, toothpicks, cup ramen cups, cups used in beverage vending machines, fresh fish, meat, fruits and vegetables, tofu, prepared dishes, etc. Food containers and trays, trobaco used in the fresh fish market, bottles for dairy products such as milk, yogurt and lactic acid bacteria beverages, soft drink bottles such as carbonated drinks and soft drinks, beer and whiskey Bottles for alcoholic drinks, bottles with or without pumps for shampoos and liquid soaps, toothpaste tubes, cosmetic containers, detergent containers, bleach containers, cold boxes, flower pots, water purifier cartridge casings, artificial kidneys and Casings such as artificial livers, syringe barrels, cushioning materials for use in transporting home appliances such as televisions and stereos, cushioning materials for use in transporting precision machines such as computers, printers, and watches, glass, Can be used as cushioning material for transporting ceramic products such as ceramics, but has high heat resistance and gas barrier properties Utilizing the heat container such as a microwave oven, the fiber can be suitably used to applications such as a film. Also, automotive material parts such as front doors and foil caps that require heat resistance and impact resistance, automotive interior parts such as car seats for automobiles, housing parts for products such as personal computers, headphone stereos, mobile phones, etc. It can be suitably used for electric home appliance material parts and OA equipment material parts or electric / electronic material parts such as reflective material films / sheets and polarizing films / sheets.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not limited to these Examples at all.
Each measurement method in this example is shown below.

<Weight average molecular weight (Mw)>
10 g of a mixed solvent of chloroform / hexafluoroisopropanol = 99/1 (weight ratio) was added to 10 mg of the sample to be measured, and the sample was completely dissolved, and then gel permeation chromatography (GPC, manufactured by JASCO Corporation, detector) RI: RI2031plus manufactured by JASCO Corporation, column: LF-G, LF-804 manufactured by SHODEX, Inc. (column temperature 40 ° C., flow rate 1 mL / min, chloroform solvent), which was obtained by comparison with a polystyrene standard sample.

<Ratio of terminal carboxyl group and number of terminal functional groups>
The terminal functional group of the lactic acid oligomer or lactic acid polymer in the present invention includes a lactic acid-derived carboxyl group (S _COOH ), a carboxyl group obtained by reacting lactic acid-derived hydroxyl group with succinic acid or succinic anhydride (S succinic acid). Acid) and unreacted lactic acid-derived hydroxyl groups (S _OH ), and the ratio of S _COOH , S succinic acid, and S _OH can be expressed as follows.
S _COOH : 50 mol%
S succinic acid: 50 mol% x (terminal reaction rate)
_SOH : 50 mol% x {1- (terminal reaction rate)}

The term “terminal reaction rate” as used herein refers to the rate at which the lactic acid-derived hydroxyl group reacts with succinic acid or succinic anhydride, and was determined by the following method.
50 mg of lactic acid oligomer or lactic acid polymer was dissolved in 1.0 g of deuterated chloroform, and ¹ H-NMR (device: ECA500 manufactured by JEOL Ltd., internal standard tetramethylsilane: δ = 0 ppm) was measured. In this spectrum,
I Succinic acid: Integral value of methylene chain hydrogen derived from succinic acid or succinic anhydride (δ = 2.61 to 2.72 ppm, multiplet, 4H) in lactic acid oligomer or lactic acid polymer I-terminal _OH : lactic acid oligomer or lactic acid Assuming that the integral value of methine hydrogen at the α-position of the terminal hydroxyl group in the polymer (δ = 4.36 ppm J = 6.92, quartet, 1H), the terminal reaction rate can be obtained from the following equation.
(Terminal reaction rate) = (I succinic acid / 4) / {(I succinic acid / 4) + I-terminal _OH }

S succinic acid (mol%) was determined from the terminal reaction rate, and the ratio of terminal carboxyl groups was determined from the following formula.
Terminal carboxyl group ratio (mol%) = S _COOH (mol%) + S succinic acid (mol%)

<Number average molecular weight (Mn) and number of terminal functional groups>
In the aforementioned ¹ H-NMR measurement spectrum,
I Main chain methine: When the integral value of main chain methine hydrogen (δ = 4.9 to 5.7 ppm, quartet) in a lactic acid oligomer or lactic acid polymer is taken, the average degree of polymerization of the lactic acid unit can be determined from the following equation: .
(Average degree of polymerization) = (I main chain methine) / {(I succinic acid / 4) + I terminal _OH }

Using the following formula, the number average molecular weight (Mn) and the number of terminal functional groups (mol / g) were determined from the average degree of polymerization.
Number average molecular weight (Mn) = (average degree of polymerization) × 72 + 18
Number of terminal functional groups (mol / g) = 2 / {number average molecular weight (Mn)}

<Identification of amide bond of polylactic acid resin>
¹³ C-NMR (apparatus: ECA500 manufactured by JEOL Ltd., internal standard chloroform-d: δ = 77 ppm) of a polylactic acid resin obtained by reacting polylactic acid and hexamethylene diisocyanate was measured. In this spectrum, the presence or absence of an amide bond in polylactic acid was confirmed by the presence or absence of the following peak.
δ = 39 ppm:
Derived from the α-position carbon of the hexamethylene unit adjacent to the amide bond

<Measurement method of Sn>
After wet digestion of the sample with sulfuric acid and hydrogen peroxide, 1 ml of the resulting degradation product was made up to a constant volume and diluted 40-fold with hydrochloric acid to obtain an ICP emission spectroscopic analyzer (ICPS-8100 manufactured by SHIMADZU). Was used to measure the content of heavy metals such as Sn. The detection limit of the content of heavy metals such as Sn by the measurement method is less than 4 ppm.

<Measurement method of S>
The sample was precisely weighed on a quartz sample board and burned and decomposed at 900 ° C. (combustion furnace set temperature) in an Ar / O ₂ stream. The generated gas was absorbed into the absorbing solution and the volume was adjusted with pure water. SO ₄ in this test solution was quantified by ion chromatography (device: DX-500 manufactured by Dionex, column: IonPac AS12A manufactured by Dionex), and S was converted from SO ₄ and obtained. Dilution treatment was performed as appropriate.

<Method of measuring water content of polylactic acid prepolymer>
In a nitrogen atmosphere, the sample was placed in a vacuum-dried sample bottle and precisely weighed. Further, dehydrated chloroform was added and precisely weighed. The water content of the solution was determined using the Karl Fischer moisture meter (apparatus: AQ-2000, manufactured by Hiranuma Sangyo Co., Ltd., generated solution: Aqualite RS / chloroform = 1/1 (volume ratio) mixed solution, counter electrode solution: Aqualite CN) It was measured by. The amount of water (A ₁ ) contained in the sample was determined from the following calculation formula.
A ₁ : Water content of the sample (ppm)
A ₀ : Water content of chloroform (ppm)
A: Water content of the solution (ppm)
R ₁ : weight ratio of sample R ₀ : weight ratio of chloroform,
From A = A ₀ × R ₀ + A ₁ × R ₁ ,
A ₁ = (A−A ₀ × R ₀ ) / R ₁
here,
B ₁ : Weight of sample (g)
B ₀ : weight of chloroform (g),
From R ₀ = B ₀ / (B ₁ + B ₀ ), R ₁ = B ₁ / (B ₁ + B ₀ ),
A ₁ = {A−A ₀ × B ₀ / (B ₁ + B ₀ )} / {B ₁ / (B ₁ + B ₀ )}

<Melting point (Tm)>
Melting | fusing point (Tm) was calculated | required from the peak top of the melting peak using the differential scanning calorimeter (DSC apparatus RDC220 by SII). A sample was weighed 5 to 6 mg, weighed into a nitrogen-sealed pan, and placed in a DSC measuring unit that was previously nitrogen-sealed and set at 25 ° C. Next, the temperature was raised to 240 ° C. at a temperature raising rate of 10 ° C./min (first temperature raising process), and subsequently held at 240 ° C. for 10 minutes, and then the temperature was lowered to 0 ° C. at a temperature lowering rate of 99.9 ° C./min. Held for a minute. Subsequently, the temperature was raised again from 0 ° C. to 240 ° C. at a temperature raising rate of 10 ° C./min (second temperature raising process), and then the temperature was lowered to 25 ° C. at a temperature lowering rate of 99.9 ° C./min. The melting points in the first temperature raising process and the second temperature raising process were Tm ₁ and Tm ₂ , respectively.

<Tensile strength, tensile modulus>
It measured based on JIS-K 7161.

Lactic acid oligomers were produced by the method shown in the production examples below.
[Production Example 1]
Purac's 90% by weight L-lactic acid (L-form 99.5 mol% lactic acid) 500 g (5.0 mol) and reagent tin (II) chloride dihydrate (Wako Pure Chemical Industries) 1.18 g ( 0.005 mol) and 12.51 g (0.13 mol) of succinic anhydride were charged into a 1000 ml round bottom flask equipped with a Dean-Stark trap. After the atmosphere in the flask was replaced with nitrogen, the temperature was raised to 130 ° C. with an oil bath heated to 150 ° C. under normal pressure and nitrogen atmosphere. The inside of the flask was gradually depressurized and held at 50 mmHg for 2 hours. Next, after releasing the inside of the flask to normal pressure, 40 g of xylene was added to the flask. The Dean Stark trap was then replaced with a Dean Stark trap filled with xylene. Next, the oil bath temperature was raised to 180 ° C., the pressure in the flask was reduced to 500 mmHg, and the reaction solution temperature was maintained at 150 ° C. for 30 hours to obtain a transparent L-lactic acid oligomer. About this L-lactic acid oligomer, it was 10,000 when the weight average molecular weight (Mw) was measured. Thereafter, the inside of the flask was released to normal pressure, 300 g of xylene was added to the obtained oligomer for dilution, and the resulting solution was extracted, and the xylene was air-dried under a nitrogen stream. The solid after air drying was washed twice with 1.0 L of 2-propanol containing 1% of 35% hydrochloric acid and filtered, and the residue was further washed several times with methanol and dried under reduced pressure at 50 ° C. 302 g of L-lactic acid oligomer [PLLA (1)] was obtained. About this PLLA (1), when the weight average molecular weight (Mw), the ratio of a terminal carboxyl group, the number average molecular weight (Mn), the number of terminal functional groups, and Sn content were measured, they were 10,000, 98 mol%, 2704,7. 396 × 10 ⁻⁴ (mol / g) and 5 ppm or less. Moreover, it was 151 degreeC when melting | fusing point (Tm1) in the _1st temperature rising process was measured.

[Production Example 2]
Purac's 90% by weight L-lactic acid (L-form 99.5 mol% lactic acid) 500 g (5.0 mol) and reagent tin (II) chloride dihydrate (Wako Pure Chemical Industries) 1.18 g ( 0.005 mol) was charged into a 1000 ml round bottom flask equipped with a Dean-Stark trap. After the atmosphere in the flask was replaced with nitrogen, the temperature was raised to 130 ° C. with an oil bath heated to 150 ° C. under normal pressure and nitrogen atmosphere. The inside of the flask was gradually depressurized and held at 50 mmHg for 2 hours. Next, after releasing the inside of the flask to normal pressure, 40 g of xylene was added to the flask. The Dean Stark trap was then replaced with a Dean Stark trap filled with xylene. Next, the oil bath temperature was raised to 180 ° C., the pressure in the flask was reduced to 500 mmHg, and the reaction solution temperature was maintained at 150 ° C. for 20 hours to obtain a transparent L-lactic acid oligomer. It was 20000 when the weight average molecular weight (Mw) was measured about this L-lactic acid oligomer.

Furthermore, 6.55 g (0.065 mol) of succinic anhydride was added to the flask, and the mixture was stirred at an oil bath temperature of 150 ° C. for 2 hours. Then, the obtained solution was extracted, and xylene was air-dried under a nitrogen stream. The solid after air drying was washed twice with 1.0 L of 2-propanol containing 1% of 35% hydrochloric acid and filtered, and the residue was further washed several times with methanol and dried under reduced pressure at 50 ° C. 340 g of L-lactic acid oligomer [PLLA (2)] was obtained. The PLLA (2) was measured for weight average molecular weight (Mw), terminal carboxyl group ratio, number average molecular weight (Mn), number of terminal functional groups and Sn content. It was 955 * 10 < ^-4 > (mol / g) and 5 ppm or less. Moreover, it was 159 degreeC when melting | fusing point (Tm1) in the _1st temperature rising process was measured.

[Production Example 3]
800 g (8.0 mol) of 90 wt% L-lactic acid (99.5 mol% of L form) from Purac, 3.53 g (0.037 mol) of methanesulfonic acid (manufactured by Wako Pure Chemical Industries) as a reagent, and The reagent, succinic acid (manufactured by Junsei Co., Ltd.), 9.44 g (0.08 mol), was charged into a 1000 ml round bottom flask equipped with a Dean-Stark trap. After the atmosphere in the flask was replaced with nitrogen, the temperature was raised to 130 ° C. with an oil bath heated to 150 ° C. under normal pressure and nitrogen atmosphere. The inside of the flask was gradually depressurized and held at 50 mmHg for 2 hours. Next, after releasing the inside of the flask to normal pressure, 40 g of xylene was added to the flask. The Dean Stark trap was then replaced with a Dean Stark trap filled with xylene. Next, the oil bath temperature was raised to 180 ° C., the pressure in the flask was reduced to 500 mmHg, and the reaction solution temperature was maintained at 150 ° C. for 15 hours for polymerization. Thereafter, the inside of the flask was released to normal pressure, and 320 g of xylene was added to the obtained oligomer for dilution. The resulting solution was extracted, and the xylene was air-dried under a nitrogen stream. The solid after air drying was dried under reduced pressure at 50 ° C. to obtain 566 g of a white L-lactic acid oligomer. It was 15000 when the weight average molecular weight (Mw) was measured about this L-lactic acid oligomer.

The white solid was put into a dryer having a volume of 27 L, and solid state polymerization was performed at 140 ° C. for 72 hours while flowing 2.8 L / min of nitrogen. Furthermore, solid phase polymerization was performed at a nitrogen flow rate of 14 L / min for 24 hours to obtain 535 g of a white L-lactic acid oligomer [PLLA (3)]. The PLLA (3) was measured for weight average molecular weight (Mw), terminal carboxyl group ratio, number average molecular weight (Mn), number of terminal functional groups, and S content. 671 × 10 ⁻⁴ (mol / g) and 43 ppm. Moreover, it was 160 degreeC when melting | fusing point (Tm1) in the _1st temperature rising process was measured.

[Production Example 4]
800 g (8.0 mol) of 90 wt% L-lactic acid (99.5 mol% L form) from Purac, 3.53 g (0.037 mol) of methanesulfonic acid (manufactured by Wako Pure Chemical Industries) as a reagent, and The reagent, succinic acid (manufactured by Junsei Chemical Co., Ltd.) 4.72 g (0.04 mol) was charged into a 1000 ml round bottom flask equipped with a Dean-Stark trap. After the atmosphere in the flask was replaced with nitrogen, the temperature was raised to 130 ° C. with an oil bath heated to 150 ° C. under normal pressure and nitrogen atmosphere. The inside of the flask was gradually depressurized and held at 50 mmHg for 2 hours. Next, after releasing the inside of the flask to normal pressure, 40 g of xylene was added to the flask. The Dean Stark trap was then replaced with a Dean Stark trap filled with xylene. Next, the oil bath temperature was raised to 180 ° C., the pressure in the flask was reduced to 500 mmHg, and the reaction solution temperature was maintained at 150 ° C. for 15 hours for polymerization. Thereafter, the inside of the flask was released to normal pressure, and 320 g of xylene was added to the obtained oligomer for dilution. The resulting solution was extracted, and the xylene was air-dried under a nitrogen stream. The solid after air drying was dried under reduced pressure at 50 ° C. to obtain 560 g of a white L-lactic acid oligomer. It was 20000 when the weight average molecular weight (Mw) was measured about this L-lactic acid oligomer.

The white solid was put into a dryer having a volume of 27 L, and solid state polymerization was performed at 140 ° C. for 72 hours while flowing 2.8 L / min of nitrogen. Furthermore, solid phase polymerization was performed at a nitrogen flow rate of 14 L / min for 24 hours to obtain 530 g of a white L-lactic acid oligomer [PLLA (4)]. The PLLA (4) was measured for weight average molecular weight (Mw), terminal carboxyl group ratio, number average molecular weight (Mn), number of terminal functional groups, and S content. 353 × 10 ⁻⁴ (mol / g) and 37 ppm. Moreover, it was 166 degreeC when melting | fusing point (Tm1) in the _1st temperature rising process was measured.

[Production Example 5]
In Production Example 3, instead of using 9.44 g (0.08 mol) of succinic acid (manufactured by Junsei Chemical Co., Ltd.), L-lactic acid oligomer [ PLLA (5)] was obtained. The PLLA (5) was measured for a weight average molecular weight (Mw), a terminal carboxyl group ratio, a number average molecular weight (Mn), a terminal functional group number, and an S content to be 80000, 99 mol% or more, 30075, 0 665 × 10 ⁻⁴ (mol / g) and 32 ppm. Moreover, it was 169 degreeC when melting | fusing point (Tm1) in the _1st temperature rising process was measured.

[Production Example 6]
Purac's 90% by weight L-lactic acid (L-form 99.5 mol% lactic acid) 500 g (5.0 mol) and reagent tin (II) chloride dihydrate (Wako Pure Chemical Industries) 1.18 g ( 0.005 mol) was charged into a 1000 ml round bottom flask equipped with a Dean-Stark trap. After the atmosphere in the flask was replaced with nitrogen, the temperature was raised to 130 ° C. with an oil bath heated to 150 ° C. under normal pressure and nitrogen atmosphere. The inside of the flask was gradually depressurized and held at 50 mmHg for 2 hours. Next, after releasing the inside of the flask to normal pressure, 40 g of xylene was added to the flask. The Dean Stark trap was then replaced with a Dean Stark trap filled with xylene. Next, the oil bath temperature was raised to 180 ° C., the pressure in the flask was reduced to 500 mmHg, and the reaction solution temperature was maintained at 150 ° C. for 20 hours to obtain a transparent L-lactic acid oligomer. Thereafter, the inside of the flask was released to normal pressure, 300 g of xylene was added for dilution, the resulting solution was extracted, and xylene was air-dried under a nitrogen stream. The solid after air drying was washed twice with 1.0 L of 2-propanol containing 1% of 35% hydrochloric acid and filtered, and the residue was further washed several times with methanol and dried under reduced pressure at 50 ° C. 310 g of L-lactic acid oligomer [PLLA (6)] was obtained. About this PLLA (6), when the weight average molecular weight (Mw), the ratio of the terminal carboxyl group, the number average molecular weight (Mn), the number of terminal functional groups, and Sn content were measured, 20000, 50 mol%, 5464, 3. It was 660 × 10 ⁻⁴ (mol / g) and 5 ppm or less. Moreover, it was 158 degreeC when melting | fusing point (Tm1) in the _1st temperature rising process was measured.

[Production Example 7]
In Production Example 1, instead of using 90% by weight of L-lactic acid, 90% by weight of D-lactic acid (hydrolyzed D-lactide made by Purac, lactic acid having a D form of 99.5 mol% or more) is used. Except that, D-lactic acid oligomer [PDLA (1)] was obtained in the same manner as in Production Example 1. About this PDLA (1), when the weight average molecular weight (Mw), the ratio of the terminal carboxyl group, the number average molecular weight (Mn), the number of terminal functional groups, and Sn content were measured, it was 10,000, 98 mol%, 2686,7. 445 × 10 ⁻⁴ (mol / g) and 5 ppm or less. Moreover, it was 150 degreeC when melting | fusing point (Tm1) in the _1st temperature rising process was measured.

[Production Example 8]
In Production Example 2, instead of using 90 wt% L-lactic acid, 90 wt% D-lactic acid (hydrolyzed D-lactide manufactured by Purac, lactic acid having a D form of 99.5 mol% or more) is used. Except that, D-lactic acid oligomer [PDLA (2)] was obtained in the same manner as in Production Example 2. About this PDLA (2), when the weight average molecular weight (Mw), the ratio of the terminal carboxyl group, the number average molecular weight (Mn), the number of terminal functional groups, and Sn content were measured, 20000, 95 mol%, 5180,3. 861 × 10 ⁻⁴ (mol / g) and 5 ppm or less. Moreover, it was 157 degreeC when melting | fusing point (Tm1) in the _1st temperature rising process was measured.

[Production Example 9]
In Production Example 4, instead of using 90% by weight L-lactic acid, 90% by weight D-lactic acid (hydrolyzed D-lactide made by Purac, lactic acid having a D form of 99.5 mol% or more) was used. However, instead of performing solid phase polymerization while flowing 2.8 L / min of nitrogen in a 27 L capacity dryer, using the 96 L capacity dryer, solid phase polymerization is performed while flowing 16 L / min of nitrogen. D-lactic acid oligomer [PDLA (3)] was obtained in the same manner as in Example 4. About this PDLA (3), when the weight average molecular weight (Mw), the ratio of the terminal carboxyl group, the number average molecular weight (Mn), the number of terminal functional groups, and S content were measured, 25000, 86 mol%, 9901,2. 020 × 10 ⁻⁴ (mol / g) and 37 ppm. Moreover, it was 162 degreeC when melting | fusing point (Tm1) in the _1st temperature rising process was measured.

[Production Example 10]
In Production Example 4, instead of using 90% by weight L-lactic acid, 90% by weight D-lactic acid (hydrolyzed D-lactide made by Purac, lactic acid having a D form of 99.5 mol% or more) was used. Except that, D-lactic acid oligomer [PDLA (4)] was obtained in the same manner as in Production Example 4. With respect to the PDLA (4), the weight average molecular weight (Mw), the ratio of terminal carboxyl groups, the number average molecular weight (Mn), the number of terminal functional groups and the S content were measured to be 40000, 94 mol%, 13899, 1. 439 × 10 ⁻⁴ (mol / g) and 40 ppm. Moreover, it was 165 degreeC when melting | fusing point (Tm1) in the _1st temperature rising process was measured.

[Production Example 11]
90 g of D-lactic acid (hydrolyzed D-lactide manufactured by Purac, lactic acid having a D-form of 99.5 mol% or more) 500 g (5.0 mol) and the reagent tin (II) chloride dihydrate ( 0.340 g (0.0015 mol) manufactured by Wako Pure Chemical Industries, Ltd. was charged into a 1000 ml round bottom flask equipped with a Dean-Stark trap. After the atmosphere in the flask was replaced with nitrogen, the temperature was raised to 130 ° C. with an oil bath heated to 150 ° C. under normal pressure and nitrogen atmosphere. The inside of the flask was gradually depressurized and held at 50 mmHg for 2 hours. Next, after releasing the inside of the flask to normal pressure, 40 g of xylene was added to the flask. The Dean Stark trap was then replaced with a Dean Stark trap filled with xylene. Next, the oil bath temperature was raised to 180 ° C., the pressure in the flask was reduced to 500 mmHg, and the reaction solution temperature was maintained at 150 ° C. for 50 hours to obtain a transparent D-lactic acid oligomer. The D-lactic acid oligomer was measured to have a weight average molecular weight (Mw) of 22,000.

Furthermore, 6.55 g (0.065 mol) of succinic anhydride was added to the flask, and the mixture was stirred at an oil bath temperature of 150 ° C. for 2 hours. Then, the obtained solution was extracted, and xylene was air-dried under a nitrogen stream. It dried under reduced pressure at 50 degreeC and obtained 342g of white D-lactic acid oligomer [PDLA (5)]. About this PDLA (5), when the weight average molecular weight (Mw), the ratio of the terminal carboxyl group, the number average molecular weight (Mn), the number of terminal functional groups, and Sn content were measured, 23000, 92 mol%, 7000, 2. 857 × 10 ⁻⁴ (mol / g) and 300 ppm. Moreover, it was 160 degreeC when melting | fusing point (Tm1) in the _1st temperature rising process was measured.

[Production Example 12]
In Production Example 6, instead of using 90% by weight L-lactic acid, 90% by weight D-lactic acid (hydrolyzed D-lactide made by Purac, lactic acid having a D-form of 99.5 mol% or more) was used. Except that, D-lactic acid oligomer [PDLA (6)] was obtained in the same manner as in Production Example 6. About this PDLA (6), when the weight average molecular weight (Mw), the ratio of a terminal carboxyl group, the number average molecular weight (Mn), the number of terminal functional groups, and Sn content were measured, 20000, 50 mol%, 5359,3. It was 732 * 10 < ^-4 > (mol / g) and 5 ppm or less. Moreover, it was 158 degreeC when melting | fusing point (Tm1) in the _1st temperature rising process was measured.

  Table 1 shows the weight average molecular weight (Mw), the ratio of terminal carboxyl groups, the number average molecular weight (Mn), the number of terminal functional groups, and the Sn or S content of the lactic acid oligomers obtained in Production Examples 1 to 12.

［実施例１−１］
製造例１で合成したＰＬＬＡ（１）３０．０ｇ、ステアリン酸マグネシウム３７ｍｇ（０．０６２ｍｍｏｌ）とを、８０℃で１２時間以上減圧乾燥した後、大気下、２本の枝管が付いた２００ｍｌのガラス製シュレンク管に装入した。該フラスコ内を窒素置換後、再度８０℃で２時間減圧乾燥を行った。この時のポリ乳酸プレポリマーの水分濃度は２９０ｐｐｍだった。その後オイルバスを１８０℃まで昇温し、ＰＬＬＡ（１）を溶解させた。次に、該フラスコ内にヘキサメチレンジイソシアネート１．９５７ｇ（１１．６５ｍｍｏｌ、末端官能基数に対しイソシアネート基が１．０５倍モル）を加え、内温１７５℃で１時間反応させた。反応開始２０分後に得られたポリ乳酸の重量平均分子量を測定したところ、１４００００であった。また、得られたポリ乳酸の重量平均分子量の最大値は、２２００００（３０分後）だった。¹³C-NMR測定により、得られたポリ乳酸のアミド結合の含有を確認した。

[Example 1-1]
30.0 g of PLLA (1) synthesized in Production Example 1 and 37 mg (0.062 mmol) of magnesium stearate were dried under reduced pressure at 80 ° C. for 12 hours or more, and then 200 ml of two branch pipes attached in the atmosphere. The glass Schlenk tube was charged. After the atmosphere in the flask was replaced with nitrogen, it was again dried under reduced pressure at 80 ° C. for 2 hours. At this time, the water concentration of the polylactic acid prepolymer was 290 ppm. Thereafter, the temperature of the oil bath was raised to 180 ° C. to dissolve PLLA (1). Next, 1.957 g of hexamethylene diisocyanate (11.65 mmol, 1.05 times mole of isocyanate group with respect to the number of terminal functional groups) was added to the flask, and reacted at an internal temperature of 175 ° C. for 1 hour. The weight average molecular weight of the polylactic acid obtained 20 minutes after the start of the reaction was measured and found to be 140,000. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 220,000 (after 30 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-2]
In Example 1-1, instead of using PLLA (1) synthesized in Production Example 1, the same operation as Example 1-1 except that 30.0 g of PLLA (2) synthesized in Production Example 2 was used. The mixture was reacted at a moisture concentration of 250 ppm, hexamethylene diisocyanate 0.782 g (4.65 mmol, 1.05 mol of isocyanate group based on the number of terminal functional groups), and an internal temperature of 175 ° C. for 1 hour. The weight average molecular weight of the polylactic acid obtained 20 minutes after the start of the reaction was measured and found to be 229000. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 262000 (after 30 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-3]
In Example 1-1, instead of using PLLA (1) synthesized in Production Example 1, the same operation as Example 1-1 except that 30.0 g of PLLA (3) synthesized in Production Example 3 was used. Water concentration 270 ppm, hexamethylene diisocyanate 0.707 g (4.21 The reaction was carried out at an internal temperature of 175 ° C. for 1 hour. It was 152000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the reaction start was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 270000 (after 60 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-4]
In Example 1-1, instead of using PLLA (1) synthesized in Production Example 1, the same operation as Example 1-1 except that 30.0 g of PLLA (4) synthesized in Production Example 4 was used. The reaction was carried out at a water concentration of 280 ppm, hexamethylene diisocyanate 0.358 g (2.13 mmol, 1.05 times mol of isocyanate groups with respect to the number of terminal functional groups), and an internal temperature of 175 ° C. for 1 hour. It was 171000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the start of reaction was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 281000 (after 60 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-5]
30.0 g of PLLA (4) synthesized in Production Example 4 and 37 mg (0.062 mmol) of magnesium stearate were dried under reduced pressure at 80 ° C. for 12 hours or more, and then 200 ml of two branches attached in the atmosphere. The glass Schlenk tube was charged. After the atmosphere in the flask was replaced with nitrogen, it was again dried under reduced pressure at 80 ° C. for 2 hours. At this time, the water concentration of the polylactic acid prepolymer was 250 ppm. Thereafter, the temperature of the oil bath was raised to 190 ° C. to dissolve PLLA (4). Next, 0.358 g of hexamethylene diisocyanate (2.13 g) was put into the flask. The isocyanate group was added in an amount of 1.05 times the number of mmol and terminal functional groups, and the mixture was reacted at an internal temperature of 190 ° C. for 1 hour. The weight average molecular weight of the polylactic acid obtained 20 minutes after the start of the reaction was measured and found to be 227,000. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 277000 (after 60 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-6]
In Example 1-5, the same operation as in Example 1-5 was carried out except that the reaction was carried out at an internal temperature of 220 ° C. instead of the reaction at an internal temperature of 190 ° C., and a water concentration of 280 ppm and hexamethylene diisocyanate of 0.358 g. (2.13 mmol, 1.05 times mole of isocyanate group with respect to the number of terminal functional groups), and reaction was performed at an internal temperature of 220 ° C. for 1 hour. It was 217000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the reaction start was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 230000 (after 30 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-7]
In Example 1-5, instead of reacting at an internal temperature of 190 ° C., the same operation as in Example 1-5 was performed except that the reaction was performed at an internal temperature of 230 ° C., and a moisture concentration of 260 ppm and hexamethylene diisocyanate of 0.358 g The reaction was carried out at an internal temperature of 230 ° C. for 1 hour (2.13 mmol, 1.05 times mole of isocyanate group with respect to the number of terminal functional groups). The weight average molecular weight of the polylactic acid obtained 20 minutes after the start of the reaction was measured and found to be 176000. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 176000 (after 20 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-8]
In Example 1-5, instead of using 0.358 g of hexamethylene diisocyanate (2.13 mmol, 1.05 times mole of isocyanate group based on the number of terminal functional groups), 0.300 g of hexamethylene diisocyanate (1.79 mmol, terminal) The same operation as in Example 1-5 was performed except that the isocyanate group was used in an amount of 0.88 moles of the functional group. The water concentration was 250 ppm. It was 174000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the reaction start was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 197000 (after 30 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-9]
In Example 1-5, instead of using 0.358 g of hexamethylene diisocyanate (2.13 mmol, 1.05 mol of the isocyanate group based on the number of terminal functional groups), 0.402 g (2.39 mmol, terminal of hexamethylene diisocyanate) was used. The same operation as in Example 1-5 was performed except that 1.18 moles of isocyanate groups were used relative to the number of functional groups. The water concentration was 260 ppm. It was 208000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the reaction start was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 273000 (after 60 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-10]
In Example 1-5, instead of using 0.358 g of hexamethylene diisocyanate (2.13 mmol, 1.05 mol of the isocyanate group based on the number of terminal functional groups), 0.477 g (2.84 mmol, terminal of hexamethylene diisocyanate) was used. The same operation as in Example 1-5 was performed except that the isocyanate group was used in an amount of 1.40 times mol of the functional group. The water concentration was 270 ppm. The weight average molecular weight of the polylactic acid obtained 20 minutes after the start of the reaction was measured and found to be 195,000. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 195000 (after 20 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-11]
In Example 1-5, instead of using 37 mg (0.062 mmol) of magnesium stearate, the same operation as in Example 1-5 was performed, except that 18 mg (0.031 mmol) of magnesium stearate was used. The reaction was carried out at a concentration of 260 ppm, hexamethylene diisocyanate 0.358 g (2.13 mmol, 1.05 times moles of isocyanate groups relative to the number of terminal functional groups), and an internal temperature of 190 ° C. for 1 hour. The weight average molecular weight of the polylactic acid obtained 20 minutes after the start of the reaction was measured and found to be 156,000. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 292000 (after 60 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-12]
In Example 1-5, instead of using 37 mg (0.062 mmol) of magnesium stearate, 18 mg (0.031 mmol) of magnesium stearate was used, and instead of reacting at an internal temperature of 190 ° C, an internal temperature of 220 ° C was used. Except for the reaction, the same operation as in Example 1-5 was performed, and the water concentration was 280 ppm, hexamethylene diisocyanate 0.358 g (2.13 mmol, 1.05 mol of isocyanate group with respect to the number of terminal functional groups), internal temperature The reaction was carried out at 220 ° C. for 1 hour. It was 187000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the reaction start was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 214000 (after 30 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-13]
In Example 1-5, instead of using 37 mg (0.062 mmol) of magnesium stearate, the same operation as in Example 1-5 was performed except that 74 mg (0.124 mmol) of magnesium stearate was used. Concentration 250 ppm, hexamethylene diisocyanate 0.358 g (2.13 The reaction was carried out at an internal temperature of 190 ° C. for 1 hour. The weight average molecular weight of the polylactic acid obtained 20 minutes after the start of the reaction was measured and found to be 224,000. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 242000 (after 30 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-14]
30.0 g of PLLA (4) synthesized in Production Example 4 and 37 mg (0.062 mmol) of magnesium stearate were dried under reduced pressure at 80 ° C. for 12 hours or more, and then 200 ml of two branches attached in the atmosphere. The glass Schlenk tube was charged. While nitrogen was blown into the polylactic acid prepolymer of the flask, it was again dried under reduced pressure at 80 ° C. for 12 hours. Next, the temperature of the oil bath was raised to 240 ° C. to dissolve PLLA (4), and then the temperature was lowered to 220 ° C. Next, 0.358 g of hexamethylene diisocyanate (2.13 g) was put into the flask. The isocyanate group was added in an amount of 1.05 times the number of mmol and the number of terminal functional groups, and reacted at an internal temperature of 220 ° C. for 1 hour. It was 191000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the start of reaction was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 205000 (after 30 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-15]
In Example 1-5, instead of using 0.358 g of hexamethylene diisocyanate (2.13 mmol, 1.05 times mol of the isocyanate group based on the number of terminal functional groups), 0.401 g of 1,3-xylylene diisocyanate (2 Except for using .13 mmol and 1.05 times mole of isocyanate group with respect to the number of terminal functional groups), the same operation as in Example 1-5 was performed, and the mixture was reacted for 1 hour at a water concentration of 250 ppm and an internal temperature of 190 ° C. The weight average molecular weight of the polylactic acid obtained 20 minutes after the start of the reaction was measured and found to be 360000. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 426000 (after 30 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-16]
In Example 1-5, instead of using PLLA (4) synthesized in Production Example 4, the same procedure as in Example 1-5 except that 30.0 g of PLLA (5) synthesized in Production Example 5 was used. The operation was performed, and the reaction was performed at a water concentration of 270 ppm, hexamethylene diisocyanate 0.176 g (1.05 mmol, 1.05 times mole of isocyanate group with respect to the number of terminal functional groups), and an internal temperature of 190 ° C. for 1 hour. It was 230,000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the reaction start was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 292000 (after 60 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-17]
In Example 1-1, the same procedure as in Example 1-1 was used except that 30.0 g of PDLA (1) synthesized in Production Example 7 was used instead of using PLLA (1) synthesized in Production Example 1. The operation was carried out, and the reaction was carried out at a water concentration of 290 ppm, hexamethylene diisocyanate 1.970 g (11.73 mmol, 1.05 times moles of isocyanate groups with respect to the number of terminal functional groups), and an internal temperature of 175 ° C. for 1 hour. It was 112000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the reaction start was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 210000 (after 60 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-18]
In Example 1-1, the same procedure as in Example 1-1 was used except that 30.0 g of PDLA (2) synthesized in Production Example 8 was used instead of using PLLA (1) synthesized in Production Example 1. Operation was carried out, moisture concentration 260 ppm, hexamethylene diisocyanate 1.022 g (6.08) The reaction was carried out at an internal temperature of 175 ° C. for 1 hour. The weight average molecular weight of the polylactic acid obtained 20 minutes after the start of the reaction was measured and found to be 130,000. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 219000 (after 60 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-19]
In Example 1-5, instead of using PLLA (4) synthesized in Production Example 4, 30.0 g of PDLA (2) synthesized in Production Example 8 was used, and 0.358 g of hexamethylene diisocyanate (2.13). The same operation as in Example 1-5 except that 1.144 g of 1,3-xylylene diisocyanate (6.08 mmol, 1.05 times mole of isocyanate group with respect to the number of terminal functional groups) was used in place of mmol). And reacted for 1 hour at a water concentration of 280 ppm and an internal temperature of 190 ° C. It was 239000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the reaction start was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 259000 (after 30 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-20]
In Example 1-1, the same procedure as in Example 1-1 was used except that 30.0 g of PDLA (3) synthesized in Production Example 9 was used instead of using PLLA (1) synthesized in Production Example 1. The operation was carried out, and the reaction was carried out at a water concentration of 250 ppm, 0.534 g of hexamethylene diisocyanate (3.18 mmol, 1.05 times mol of isocyanate groups with respect to the number of terminal functional groups), and an internal temperature of 175 ° C. for 1 hour. The weight average molecular weight of the polylactic acid obtained 20 minutes after the start of the reaction was measured and found to be 119000. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 204000 (after 60 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-21]
Instead of using PLLA (1) synthesized in Production Example 1 in Example 1-1, instead of using 30.0 g of PDLA (4) synthesized in Production Example 10 and reacting at an internal temperature of 175 ° C., The same operation as in Example 1-1 was performed except that the reaction was performed at an internal temperature of 210 ° C., and a water concentration of 300 ppm, hexamethylene diisocyanate 0.381 g (2.27 mmol, 1.05 times the number of functional groups on the terminal functional group) Mol) and an internal temperature of 210 ° C. for 1 hour. The weight average molecular weight of the polylactic acid obtained 20 minutes after the start of the reaction was measured and found to be 156,000. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 185000 (after 45 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-22]
After 30.0 g of PDLA (4) synthesized in Production Example 10 and 37 mg (0.062 mmol) of magnesium stearate were dried under reduced pressure at 80 ° C. for 12 hours or more, 200 ml of two branches were attached in the atmosphere. The glass Schlenk tube was charged. While nitrogen was blown into the polylactic acid prepolymer of the flask, it was again dried under reduced pressure at 80 ° C. for 12 hours, and then taken out from the dryer and subjected to nitrogen flow for 2 hours. When the water concentration of the polylactic acid prepolymer was measured, it was 120 ppm. Next, the oil bath was heated to 240 ° C. to dissolve PDLA (4), and then cooled to 210 ° C. Next, 0.381 g of hexamethylene diisocyanate (2.27 mmol, 1.05 times mole of isocyanate group with respect to the number of terminal functional groups) was added to the flask and reacted at an internal temperature of 210 ° C. for 1 hour. The weight average molecular weight of the polylactic acid obtained 20 minutes after the start of the reaction was measured and found to be 162,000. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 219000 (after 60 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 1-23]
Example 1-5 was the same as Example 1-5 except that 30.0 g of PDLA (5) synthesized in Production Example 11 was used instead of using PLLA (4) synthesized in Production Example 4. The operation was performed, and the reaction was carried out for 2 hours at a moisture concentration of 250 ppm, hexamethylene diisocyanate 0.756 g (4.50 mmol, 1.05 times moles of isocyanate groups with respect to the number of terminal functional groups), and an internal temperature of 190 ° C. It was 78000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the reaction start was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 160000 (after 120 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Comparative Example 1-1]
30.0 g of PLLA (4) synthesized in Production Example 4 and 37 mg (0.062 mmol) of magnesium stearate were dried under reduced pressure at 80 ° C. for 12 hours or more, and then 200 ml of two branches attached in the atmosphere. The glass Schlenk tube was charged. The polylactic acid prepolymer in the flask was left in the atmosphere for 2 hours. When the water concentration of the polylactic acid prepolymer was measured, it was 1750 ppm. Next, the temperature of the oil bath was raised to 240 ° C. to dissolve PLLA (4), and then the temperature was lowered to 220 ° C. Next, 0.358 g of hexamethylene diisocyanate (2.13 mmol, 1.05 times mole of isocyanate group with respect to the number of terminal functional groups) was added to the flask, and reacted at an internal temperature of 220 ° C. for 1 hour. The weight average molecular weight of the polylactic acid obtained 20 minutes after the start of the reaction was measured and found to be 137,000. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 137000 (after 20 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Comparative Example 1-2]
In Example 1-5, instead of using PLLA (4) synthesized in Production Example 4, the same procedure as in Example 1-5 except that 30.0 g of PLLA (6) synthesized in Production Example 6 was used. The operation was carried out, and the reaction was carried out for 1 hour at a water concentration of 270 ppm, hexamethylene diisocyanate 0.968 g (5.76 mmol, 1.05 times moles of isocyanate groups with respect to the number of terminal functional groups) and an internal temperature of 190 ° C. It was 55000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the reaction start was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 55000 (after 20 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Comparative Example 1-3]
Example 1-5 was the same as Example 1-5 except that 30.0 g of PDLA (6) synthesized in Production Example 12 was used instead of using PLLA (4) synthesized in Production Example 4. The operation was carried out, and the reaction was carried out at a moisture concentration of 280 ppm, hexamethylene diisocyanate 0.987 g (5.88 mmol, 1.05 mol of the isocyanate group relative to the number of terminal functional groups), and an internal temperature of 190 ° C. for 1 hour. It was 51000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the reaction start was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 51000 (after 20 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Comparative Example 1-4]
30.0 g of PLLA (3) synthesized in Production Example 3 and 22 mg (0.037 mmol) of magnesium stearate were charged into a separable flask and dried under reduced pressure at 80 ° C. for 12 hours or more. After setting the flask, nitrogen was passed through the system for 12 hours or more. When the water concentration of the polylactic acid prepolymer was measured, it was 200 ppm. Next, 30 g of dehydrated orthodichlorobenzene was charged into the flask, the oil bath was heated to 190 ° C. to dissolve PLLA (3), and then 0.707 g (4.21 mmol, 4.21 mmol, hexamethylene diisocyanate was dissolved in the flask. The isocyanate group was added in an amount of 1.05 times the mole of the terminal functional group, and the mixture was reacted at an internal temperature of 180 ° C. for 6 hours. The weight average molecular weight of the polylactic acid obtained 20 minutes after the start of the reaction was measured and found to be 53,000. The weight average molecular weight of the polylactic acid obtained 60 minutes and 180 minutes after the start of the reaction was 122,000 and 198,000, respectively, and the maximum value of the weight average molecular weight of the obtained polylactic acid was 226000 (after 300 minutes). It was. After reacting for 360 minutes, 240 g of xylene was charged, allowed to cool to room temperature, the deposited precipitate was filtered, and dried under reduced pressure at 60 ° C. for 24 hours. The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.
The above results are shown in Table 2-1 and Table 2-2.

  From Tables 2-1 and 2-2, by controlling the water content of the polylactic acid prepolymer and the terminal carboxylic acid ratio, polylactic acid having a high weight average molecular weight can be obtained, and in the absence of a solvent. It can be seen that a high molecular weight can be achieved in a short time by reacting with.

[Example 2-1]
After 2.0 kg of PLLA (4) synthesized in Production Example 4 and 2.45 g (4.15 mmol) of magnesium stearate were mixed and dried under reduced pressure at 80 ° C. for 72 hours, they were placed in an aluminum zip so as not to be in the atmosphere as much as possible. Moved. Next, nitrogen was blown into the raw lactic acid oligomer in the aluminum zip and dried for 48 hours. The water content of the raw lactic acid oligomer at this point was measured and found to be 40 ppm. The aluminum zip sealed with the raw material was transferred into an enclosure of an enclosure weight control feeder [KF-M2500, manufactured by Kubota Corp.] with a gas inlet and kept in a nitrogen atmosphere. After confirming that the oxygen concentration was 0%, the aluminum zip was opened and the raw lactic acid oligomer was charged into the hopper. Further, nitrogen was blown into the raw lactic acid oligomer in the hopper and dried for 48 hours. The water content of the raw lactic acid oligomer at this point was measured and found to be 25 ppm.

The lactic acid oligomer was fed to a twin screw extruder having a feed amount of 250 g / hr and a diameter of 15 mmΦ. As the extruder, a 15 mm same-direction meshing twin screw extruder [KZW15TW manufactured by Technobel Co., Ltd.] was used. The extruder was composed of 8 temperature-controlled zones and a die part, and a screw length / diameter ratio L / D of 60 was used. Next, hexamethylene diisocyanate was charged at a rate of 2.98 g / hr (isocyanate group 1.05 times mol with respect to the number of terminal functional groups) in the middle of the cylinder using the connecting part shown in FIG. Extrusion polymerization was performed at 0 ° C. and a screw rotation speed of 80 rpm. As a polyisocyanate compound feed pump, a Waters 515 HPLC pump was used and charged from the third temperature control zone from the feed port. When the residence time from the start of the feed was confirmed, it was about 15 minutes. The discharged strand was air-cooled on a belt conveyor, cut with a pelletizer, and dried under reduced pressure at 50 ° C. or lower. The weight average molecular weight of this sample was 185000, and the melting point (Tm ₁ ) in the first temperature raising process was 159 ° C.

[Example 2-2]
In Example 2-1, instead of feeding the oligomer at a feed rate of 250 g / hr, it was fed at 200 g / hr, and instead of charging hexamethylene diisocyanate at 2.98 g / hr, 2.39 g / hr (number of terminal functional groups) Extrusion polymerization was carried out in the same manner as in Example 2-1, except that the isocyanate group was charged at 1.05 moles relative to the other. When the residence time from the start of the feed was confirmed, it was about 20 minutes. The discharged strand was air-cooled on a belt conveyor, cut with a pelletizer, and dried under reduced pressure at 50 ° C. or lower. The weight average molecular weight of this sample was 214,000, and the melting point (Tm ₁ ) in the first temperature raising process was 160 ° C.

[Example 2-3]
2.0 kg of PLLA (2) synthesized in Production Example 2 and 2.45 g (4.15 mmol) of magnesium stearate are mixed and dried under reduced pressure at 80 ° C. for 72 hours, and then placed in an aluminum zip so as not to be in the atmosphere as much as possible. Moved. Next, nitrogen was blown into the raw lactic acid oligomer in the aluminum zip and dried for 48 hours. The water content of the raw lactic acid oligomer at this point was measured and found to be 120 ppm. The aluminum zip sealed with the raw material was transferred into a weight-controlled feeder enclosure maintained in a nitrogen atmosphere. After confirming that the oxygen concentration was 0%, the aluminum zip was opened and the raw lactic acid oligomer was hopperd. I was charged. Further, nitrogen was blown into the raw lactic acid oligomer in the hopper and dried for 48 hours. The water content of the raw lactic acid oligomer at this point was measured and found to be 40 ppm.

The lactic acid oligomer was fed to a twin screw extruder having a feed amount of 250 g / hr and a diameter of 15 mmΦ. Next, hexamethylene diisocyanate was charged into the cylinder halfway using a connecting part shown in FIG. 1 at 6.00 g / hr (isocyanate group 1.07 times mol with respect to the number of terminal functional groups). Extrusion polymerization was performed at 0 ° C. and a screw rotation speed of 80 rpm. When the residence time from the start of the feed was confirmed, it was about 15 minutes. The discharged strand was air-cooled on a belt conveyor, cut with a pelletizer, and dried under reduced pressure at 50 ° C. or lower. The weight average molecular weight of this sample was 210000, and the melting point (Tm ₁ ) in the first temperature raising process was 156 ° C.

[Example 2-4]
Example 2-3 was carried out in the same manner as in Example 2-3 except that the oligomer was fed at 200 g / hr instead of 250 g / hr. The amount of hexamethylene diisocyanate was 6.00 g / hr The isocyanate group was charged at 1.34 times the number of groups, and extrusion polymerization was performed. When the residence time from the start of the feed was confirmed, it was about 20 minutes. The discharged strand was air-cooled on a belt conveyor, cut with a pelletizer, and dried under reduced pressure at 50 ° C. or lower. The weight average molecular weight of this sample was 150,000, and the melting point (Tm ₁ ) in the first temperature raising process was 157 ° C.

[Comparative Example 2-1]
2.0 kg of PLLA (2) synthesized in Production Example 2 and 2.45 g (4.15 mmol) of magnesium stearate are mixed and dried under reduced pressure at 80 ° C. for 72 hours, and then placed in an aluminum zip so as not to be in the atmosphere as much as possible. After the transfer, it was opened, and the raw lactic acid oligomer was charged into the hopper under the atmosphere. Nitrogen was passed through the enclosure of the weight controlled feeder. The water content of the raw lactic acid oligomer at this time was measured and found to be 600 ppm.

The lactic acid oligomer was fed to a twin screw extruder having a feed amount of 250 g / hr and a diameter of 15 mmΦ. Next, hexamethylene diisocyanate was charged into the cylinder halfway at 5.89 g / hr (isocyanate group 1.05 moles relative to the number of terminal functional groups), and extrusion polymerization was performed at a cylinder temperature of 180 ° C. and a screw rotation speed of 80 rpm. went. When the residence time from the start of the feed was confirmed, it was about 15 minutes. The discharged strand was air-cooled on a belt conveyor, cut with a pelletizer, and dried under reduced pressure at 50 ° C. or lower. The weight average molecular weight of this sample was 115000, and the melting point (Tm ₁ ) in the first temperature raising process was 159 ° C.
The above results are shown in Table 3.

  From Table 3, it can be seen that by controlling the water content of the polylactic acid prepolymer (lactic acid oligomer), it is possible to increase the molecular weight with a twin screw extruder.

[Example 3-1]
After 15.0 g of PLLA (4) synthesized in Production Example 4, 15.0 g of PDLA (4) synthesized in Production Example 10 and 37 mg (0.062 mmol) of magnesium stearate were dried under reduced pressure at 80 ° C. for 12 hours or more. In the atmosphere, it was charged into a 200 ml glass Schlenk tube with two branch tubes. After the atmosphere in the flask was replaced with nitrogen, it was again dried under reduced pressure at 80 ° C. for 2 hours. At this time, the water concentration of the polylactic acid prepolymer was 250 ppm. Next, the temperature of the oil bath was raised to 240 ° C., PLLA (4) and PDLA (4) were dissolved, and then the temperature was lowered to an internal temperature of 210 ° C. Next, 0.369 g of hexamethylene diisocyanate (2.20 mmol, 1.05 times moles of isocyanate groups with respect to the number of terminal functional groups) was added to the flask, and reacted at an internal temperature of 210 ° C. for 1 hour. It was 190,000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the reaction start was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 213000 (after 45 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 3-2]
In Example 3-1, instead of using 0.369 g (2.20 mmol) of hexamethylene diisocyanate, 0.412 g of hexamethylene diisocyanate (2.45 mmol, 1.17 times mol of isocyanate groups relative to the number of terminal functional groups) was used. Instead of using and reacting at an internal temperature of 210 ° C., the same operation as in Example 3-1 was performed except that the reaction was performed at an internal temperature of 220 ° C. . It was 152000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the reaction start was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 169000 (after 30 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 3-3]
After 15.0 g of PLLA (4) synthesized in Production Example 4, 15.0 g of PDLA (4) synthesized in Production Example 10 and 37 mg (0.062 mmol) of magnesium stearate were dried under reduced pressure at 80 ° C. for 12 hours or more. In the atmosphere, it was charged into a 200 ml glass Schlenk tube with two branch tubes. While nitrogen was blown into the polylactic acid prepolymer of the flask, it was again dried under reduced pressure at 80 ° C. for 12 hours, and then taken out from the dryer and subjected to nitrogen flow for 2 hours. When the water concentration of the polylactic acid prepolymer was measured, it was 70 ppm. Next, the temperature of the oil bath was raised to 240 ° C., PLLA (4) and PDLA (4) were dissolved, and then the temperature was lowered to 210 ° C. Next, 0.369 g of hexamethylene diisocyanate (2.20 mmol, 1.05 times moles of isocyanate groups with respect to the number of terminal functional groups) was added to the flask, and reacted at an internal temperature of 210 ° C. for 1 hour. It was 182000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the reaction start was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 218000 (after 45 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 3-4]
In Example 3-3, instead of using 37 mg (0.062 mmol) of magnesium stearate, the same operation as in Example 3-3 was performed except that 18 mg (0.031 mmol) of magnesium stearate was used. The reaction was carried out at a concentration of 70 ppm, hexamethylene diisocyanate 0.369 g (2.20 mmol, 1.05 moles of isocyanate groups with respect to the number of terminal functional groups), and an internal temperature of 210 ° C. for 1 hour. The weight average molecular weight of the polylactic acid obtained 20 minutes after the start of the reaction was measured and found to be 162,000. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 231000 (after 60 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 3-5]
In Example 3-3, instead of using 37 mg (0.062 mmol) of magnesium stearate, the same operation as in Example 3-3, except that 14 mg (0.063 mmol) of bis (acetylacetonato) magnesium was used The mixture was reacted at a moisture concentration of 80 ppm, hexamethylene diisocyanate 0.369 g (2.20 mmol, 1.05 times mole of isocyanate group with respect to the number of terminal functional groups), and an internal temperature of 210 ° C. for 1 hour. It was 185000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the start of reaction was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 263000 (after 60 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 3-6]
In Example 3-3, instead of using 37 mg (0.062 mmol) of magnesium stearate, the same operation as in Example 3-3, except that 28 mg (0.126 mmol) of bis (acetylacetonato) magnesium was used. The mixture was reacted at a moisture concentration of 70 ppm, hexamethylene diisocyanate 0.369 g (2.20 mmol, 1.05 moles of isocyanate groups with respect to the number of terminal functional groups), and an internal temperature of 210 ° C. for 1 hour. It was 212000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the reaction start was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 239000 (after 45 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 3-7]
As L-lactic acid polymer, LACEA manufactured by Mitsui Chemicals, Inc., H400PW (Lot No. 07D1L01T, weight average molecular weight 223000, terminal functional group number 0.238 × 10 ⁻⁴ (mol / g)) 15.0 g, Production Example 10 After 15.0 g of synthesized PDLA (4) and 28 mg (0.126 mmol) of bis (acetylacetonato) magnesium were dried under reduced pressure at 80 ° C. for 12 hours or more, 200 ml of two branches were attached in the atmosphere. The glass Schlenk tube was charged. While nitrogen was blown into the polylactic acid prepolymer of the flask, it was again dried under reduced pressure at 80 ° C. for 12 hours, and then taken out from the dryer and subjected to nitrogen flow for 2 hours. When the water concentration of the polylactic acid prepolymer was measured, it was 80 ppm. Next, the temperature of the oil bath was raised to 240 ° C., H400PW and PDLA (4) were dissolved, and then the temperature was lowered to 210 ° C. Next, 0.254 g of hexamethylene diisocyanate (1.51 mmol, 1.20-fold mole of isocyanate group with respect to the number of terminal functional groups) was added to the flask and reacted at an internal temperature of 210 ° C. for 1 hour. The weight average molecular weight of the polylactic acid obtained 20 minutes after the start of the reaction was measured and found to be 255000. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 259000 (after 30 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 3-8]
PLLA (4) 15.0 g synthesized in Production Example 4, D-lactic acid polymer, manufactured by Purac, PDLA High IV (Lot No. 0701001661, weight average molecular weight 229000, terminal functional group number 0.232 × 10 ⁻⁴ (mol / g)) 15.0 g and 14 mg (0.063 mmol) of bis (acetylacetonato) magnesium were dried under reduced pressure at 80 ° C. for 12 hours or more, and then 200 ml of glass Schlenk with two branch pipes in the atmosphere. The tube was charged. While nitrogen was blown into the polylactic acid prepolymer of the flask, it was again dried under reduced pressure at 80 ° C. for 12 hours, and then taken out from the dryer and subjected to nitrogen flow for 2 hours. When the water concentration of the polylactic acid prepolymer was measured, it was 60 ppm. Next, the temperature of the oil bath was raised to 240 ° C., PLLA (4) and PDLA High IV were dissolved, and then the temperature was lowered to 230 ° C. Next, 0.210 g of hexamethylene diisocyanate (1.25 mmol, 1.05 times the number of isocyanate groups with respect to the number of terminal functional groups) was added to the flask and reacted at an internal temperature of 230 ° C. for 1 hour. It was 190,000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the reaction start was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 190000 (after 20 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 3-9]
PLLA (4) 15.0 g synthesized in Production Example 4, PDLA (4) 15.0 g synthesized in Production Example 10, Teijin Chemicals Co., Ltd. polycarbonate resin panlite (L-1225Y, injection molding) Grade, weight average molecular weight 50000, terminal functional group number 0.800 × 10 ⁻⁴ (mol / g)) 3.0 g, bis (acetylacetonato) magnesium 14 mg (0.063 mmol), reduced pressure at 80 ° C. for 12 hours or more After drying, it was placed in a 200 ml glass Schlenk tube with two branch tubes in the atmosphere. While nitrogen was blown into the polylactic acid prepolymer of the flask, it was again dried under reduced pressure at 80 ° C. for 12 hours, and then taken out from the dryer and subjected to nitrogen flow for 2 hours. When the water concentration of the polylactic acid prepolymer was measured, it was 50 ppm. Next, the temperature of the oil bath was raised to 240 ° C., PLLA (4), PDLA (4) and panlite were dissolved, and then the temperature was lowered to 230 ° C. Next, 0.391 g of hexamethylene diisocyanate (2.33 mmol, 1.05 moles of isocyanate groups with respect to the number of terminal functional groups) was added to the flask and reacted at an internal temperature of 230 ° C. for 1 hour. It was 181000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the reaction start was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 181000 (after 20 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 3-10]
In Example 3-3, instead of using PLLA (4) 15.0 g and PDLA (4) 15.0 g, implementation was performed except that PLLA (4) 10.0 g and PDLA (4) 20.0 g were used. The same operation as in Example 3-3 was performed, and the reaction was carried out at a moisture concentration of 80 ppm, hexamethylene diisocyanate 0.373 g (2.22 mmol, 1.05 times mole of isocyanate group with respect to the number of terminal functional groups), and an internal temperature of 210 ° C. for 1 hour. It was. The weight average molecular weight of the polylactic acid obtained 20 minutes after the start of the reaction was measured and found to be 172,000. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 215000 (after 60 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 3-11]
In Example 3-3, instead of using PLLA (4) 15.0 g and PDLA (4) 15.0 g, implementation was performed except that PLLA (4) 20.0 g and PDLA (4) 10.0 g were used. The same operation as in Example 3-3 was performed, and the reaction was performed at a water concentration of 80 ppm, hexamethylene diisocyanate 0.366 g (2.18 mmol, 1.05 times moles of isocyanate groups with respect to the number of terminal functional groups), and an internal temperature of 210 ° C. for 1 hour. It was. It was 192000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the start of reaction was measured. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 223000 (after 45 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Example 3-12]
In Example 3-3, in addition to PLLA (4) 15.0 g and PDLA (4) 15.0 g, 0.15 g of “ADEKA STAB” PEP-36 made by ADEKA as a stabilizer, “Irganox made by Ciba Specialty Chemicals” “The same operation as in Example 3-3 was performed except that 0.15 g of 1010 was used, and a moisture concentration of 80 ppm, hexamethylene diisocyanate 0.369 g (2.20 mmol, 1.05 times the number of isocyanate groups relative to the number of terminal functional groups). Mol) and an internal temperature of 210 ° C. for 1 hour. The weight average molecular weight of the polylactic acid obtained 20 minutes after the start of the reaction was measured and found to be 159000. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 220,000 (after 60 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Comparative Example 3-1]
After 15.0 g of PLLA (4) synthesized in Production Example 4, 15.0 g of PDLA (4) synthesized in Production Example 10 and 37 mg (0.062 mmol) of magnesium stearate were dried under reduced pressure at 80 ° C. for 12 hours or more. In the atmosphere, it was charged into a 200 ml glass Schlenk tube with two branch tubes. After the inside of the flask was purged with nitrogen, the water concentration of the polylactic acid prepolymer was measured and found to be 400 ppm. Next, the temperature of the oil bath was raised to 240 ° C., PLLA (4) and PDLA (4) were dissolved, and then the temperature was lowered to an internal temperature of 230 ° C. Next, 0.369 g of hexamethylene diisocyanate (2.20 mmol, 1.05 times mole of isocyanate group with respect to the number of terminal functional groups) was added to the flask and reacted at an internal temperature of 230 ° C. for 1 hour. The weight average molecular weight of the polylactic acid obtained 20 minutes after the start of the reaction was measured and found to be 128,000. Moreover, the maximum value of the weight average molecular weight of the obtained polylactic acid was 128000 (after 20 minutes). The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.

[Comparative Example 3-2]
PLLA (4) synthesized in Production Example 4 (15.0 g), PDLA (4) synthesized in Production Example 10 (15.0 g) and magnesium stearate (22 mg, 0.037 mmol) were charged into a separable flask at 80 ° C. And dried under reduced pressure for 12 hours or more. After setting the flask, nitrogen was passed through the system for 12 hours or more. When the water concentration of the polylactic acid prepolymer was measured, it was 200 ppm. Next, 30 g of dehydrated orthodichlorobenzene was charged into the flask, the oil bath was heated to 190 ° C. to dissolve PLLA (4) and PDLA (4), and then 0.369 g of hexamethylene diisocyanate was added to the flask. (2.20 mmol, 1.05 times mole of isocyanate group with respect to the number of terminal functional groups) was added and reacted at an internal temperature of 180 ° C. for 6 hours. It was 50000 when the weight average molecular weight of the polylactic acid obtained 20 minutes after the reaction start was measured. The weight average molecular weights of the polylactic acid obtained 60 minutes and 180 minutes after the start of the reaction were 115000 and 185000, respectively, and the maximum value of the weight average molecular weight of the obtained polylactic acid was 196000 (after 300 minutes). It was. After reacting for 360 minutes, 240 g of xylene was charged, allowed to cool to room temperature, the deposited precipitate was filtered, and dried under reduced pressure at 60 ° C. for 24 hours. The content of amide bond in the obtained polylactic acid was confirmed by ¹³ C-NMR measurement.
The results are shown in Table 4.

  From Table 4, it is possible to obtain polylactic acid with a high weight average molecular weight by controlling the water content of the polylactic acid prepolymer, and it is possible to increase the molecular weight in a short time by reacting in the absence of a solvent. It turns out that it is. Furthermore, it can be seen that polylactic acid having a high weight average molecular weight can be obtained even if the component ratio in the polylactic acid prepolymer is changed.

[Example 4-1]
PLLA (4) 1.0 kg synthesized in Production Example 4, 1.0 kg of PDLA (4) and 1.832 g (8.23 mmol) of bis (acetylacetonato) magnesium were mixed and dried under reduced pressure at 80 ° C. for 72 hours. Later, it was moved to an aluminum zip so as not to be in the atmosphere as much as possible. Next, nitrogen was blown into the polylactic acid prepolymer in the aluminum zip and dried for 48 hours. The water content of the polylactic acid prepolymer at this time was measured and found to be 80 ppm. The aluminum zip sealed with the polylactic acid prepolymer was transferred into an enclosure of an enclosure weight control feeder [KF-M2500, manufactured by Kubota Corp.] with a gas inlet and maintained in a nitrogen atmosphere. After confirming that the oxygen concentration was 0%, the aluminum zip was opened and the polylactic acid prepolymer was charged into the hopper. Further, nitrogen was blown into the polylactic acid prepolymer in the hopper and dried for 48 hours. The water content of the polylactic acid prepolymer at this time was measured and found to be 60 ppm.

  The polylactic acid prepolymer was fed to a twin screw extruder having a feed amount of 250 g / hr and a diameter of 15 mmΦ. As the extruder, a 15 mm same-direction meshing twin screw extruder [KZW15TW manufactured by Technobel Co., Ltd.] was used. The extruder was composed of 8 temperature-controlled zones and a die part, and a screw length / diameter ratio L / D of 60 was used. Next, hexamethylene diisocyanate was charged into the cylinder at 3.08 g / hr (isocyanate group 1.05 times mol with respect to the number of terminal functional groups) using the connecting part shown in FIG. Extrusion polymerization was performed at 0 ° C. and a screw rotation speed of 80 rpm. As a polyisocyanate compound feed pump, a Waters 515 HPLC pump was used and charged from the third temperature control zone from the feed port. When the residence time from the start of the feed was confirmed, it was about 15 minutes. The discharged strand was air-cooled on a belt conveyor, cut with a pelletizer, and dried under reduced pressure at 50 ° C. or lower. The weight average molecular weight of this sample was 211,000, and the melting point in the first temperature raising process was 205 ° C. Although the operation was continued for 5 hours, clogging of the hexamethylene diisocyanate feeding line did not occur. The surface temperature of the upper surface of the mixing component (5 ′) at this time was 115 ° C.

[Example 4-2]
In Example 4-1, instead of feeding the polylactic acid prepolymer at a feed rate of 250 g / hr, it was fed at 200 g / hr, and instead of charging hexamethylene diisocyanate at 2.98 g / hr, 2.46 g / hr ( Extrusion polymerization was carried out in the same manner as in Example 4-1, except that the isocyanate group was charged at 1.05 times the mole of the terminal functional group. When the residence time from the start of the feed was confirmed, it was about 20 minutes. The discharged strand was air-cooled on a belt conveyor, cut with a pelletizer, and dried under reduced pressure at 50 ° C. or lower. This sample had a weight average molecular weight of 222,000 and a melting point of 206 ° C. in the first heating step. Although the operation was continued for 5 hours, clogging of the hexamethylene diisocyanate feeding line did not occur. The surface temperature of the upper surface of the mixing component (5 ′) at this time was 115 ° C.

[Example 4-3]
In Example 4-1, extrusion polymerization was performed in the same manner as in Example 4-1, except that instead of using the components shown in FIG. 1 for the liquid addition part of the twin screw extruder, the connection components shown in FIG. 3 were used. Went. When the residence time from the start of the feed was confirmed, it was about 15 minutes. The discharged strand was air-cooled on a belt conveyor, cut with a pelletizer, and dried under reduced pressure at 50 ° C. or lower. This sample had a weight average molecular weight of 210000 and a melting point of 205 ° C. in the first temperature raising step. The pressure of the liquid feeding line started to increase 50 minutes after the start of the charging of hexamethylene diisocyanate, and the liquid feeding line was blocked after 60 minutes and the operation could not be continued. At this time, the surface temperature of the upper surface of the connecting component (5 ″ ′) was 210 ° C.
The results of Example 4-1 and Example 4-2 are shown in Table 5.

  From Example 4-1, Example 4-2, and Example 4-3, in extrusion polymerization under a high temperature condition, a liquid feeding line is provided by providing a cooling layer on the connection component when charging the polyisocyanate compound. It can be seen that stable extrusion polymerization can be achieved.

(Press molding)
The samples obtained in Example 2-1 to Example 2-4 were dried under reduced pressure at 80 ° C. for 5 hours, preheated at 205 ° C. for 5 minutes under reduced pressure, and then hot pressed at 2 MPa for 1 minute. The sheet was rapidly cooled to obtain a sheet having a thickness of 0.2 mm. Table 6 shows the results of tensile strength and tensile modulus of each sheet.

  The samples obtained in Example 4-1 and Example 4-2 were dried under reduced pressure at 80 ° C. for 5 hours, then preheated at 230 ° C. under reduced pressure for 5 minutes, and then hot pressed at 2 MPa for 1 minute. This was followed by rapid cooling to obtain a sheet having a thickness of 0.2 mm. Table 6 shows the results of tensile strength and tensile modulus of each sheet.

  Since the production method of the present invention is polymerization in the absence of a solvent, the equipment is simplified and the cost can be reduced as compared with polymerization in a solution state using a solvent. Moreover, high molecular weight can be achieved in a short time, and productivity can be improved.

1 Cylinder 2 Screw 3 Needle 4 Cooling layer (gas phase)
4 'Cooling layer (water phase)
5 Connecting parts (bottom)
5 'connection parts (top)
5 "Connection part 5"'Connection part 6 Thermal insulation layer (Teflon sheet)
7 Fixing screw 8 Liquid feed line

Claims (7)

  A method for producing polylactic acid, in which a polylactic acid prepolymer containing a lactic acid oligomer having a terminal carboxyl group ratio exceeding 80 mol% and a polyisocyanate compound are reacted in the presence of an amidation catalyst, in the absence of a solvent, A method for producing polylactic acid, wherein the water concentration in the polylactic acid prepolymer is adjusted to 1 to 300 ppm and reacted.   The method for producing polylactic acid according to claim 1, wherein the lactic acid oligomer is a mixture of an L-lactic acid oligomer and a D-lactic acid oligomer.   The method for producing polylactic acid according to claim 1, wherein the lactic acid oligomer is an L-lactic acid oligomer or a D-lactic acid oligomer, and an optical isomeric lactic acid polymer is further present.   The method for producing polylactic acid according to any one of claims 1 to 3, wherein a twin-screw extruder and / or a static mixer is used.   The method for producing polylactic acid according to claim 4, wherein the total residence time of the resin in the twin-screw extruder and / or the static mixer is 5 minutes or more. 6. The production of polylactic acid according to claim 4 or 5, wherein the shear rate in the twin screw extruder and / or the static mixer is 1,000 to 1,000,000 s- ^1. Method.   The method for producing polylactic acid according to any one of claims 4 to 6, wherein when the polyisocyanate compound and the polylactic acid prepolymer are mixed, a cooling layer is provided in the mixed portion.

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