JP5292775B2 - Method for producing polylactic acid resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for effectively producing polylactic acid-based resin having a high molecular weight, in favorable embodiments, having a high melting point, and excellent in thermal stability and hues. <P>SOLUTION: This method produces the polylactic acid-based resin through direct polycondensation using lactic acid as a main material, wherein solid phase polymerization is performed after polycondensation with the usage of a film evaporator, preferably in a state free from a solvent, and as a catalyst, at least one kind selected from a tin compound, a titanium compound, a lead compound, a zinc compound, a cobalt compound, an iron compound, a lithium compound, a rare earth compound, and a sulfonic acid compound is used. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a method for efficiently producing a polylactic acid-based resin having a high molecular weight and, in a preferred embodiment, having a high melting point and excellent thermal stability and hue.

  In recent years, polylactic acid has attracted attention as a plant-derived carbon neutral material from the viewpoint of environmental conservation. Polylactic acid has a high melting point of about 170 ° C. and can be melt-molded. Furthermore, since lactic acid, which is a monomer, has been produced at low cost by fermentation using microorganisms, it is a general-purpose plastic derived from petroleum raw materials. It is expected to be used as a biomass plastic that can be used as an alternative, and is gradually being used.

  The main production methods of polylactic acid include a ring-opening polymerization method in which lactide which is a dimer of lactic acid is ring-opened and polymerized, and a direct polycondensation method in which dehydration polycondensation is performed using lactic acid. Compared with the ring-opening polymerization method, it is said that polylactic acid can be produced at low cost because lactic acid can be directly used as a polymerization raw material without passing through a step of synthesizing lactide.

Patent Document 1 describes a direct polycondensation method using a thin film evaporator. However, the molecular weight and melting point are still low, mechanical properties such as strength cannot be satisfied, and there are problems that the polymerization time is long and further productivity needs to be improved.
JP-A-6-306149 (page 1-4)

  An object of the present invention is to provide a method for efficiently producing a polylactic acid-based resin having a high molecular weight, having a high melting point, and excellent in thermal stability and hue.

  The present invention has been studied to solve the above-mentioned problems, and as a result, has a high molecular weight, and in a preferred embodiment, efficiently produces a polylactic acid resin having a high melting point and excellent thermal stability and hue. The method has been found and the present invention has been reached.

That is, the method for producing the polylactic acid resin of the present invention comprises:
(1) A method for producing a polylactic acid resin by direct polycondensation using lactic acid as a main raw material, a low molecular weight body having a weight average molecular weight of 10,000 to 20,000 is prepared in advance, and the low molecular weight body is evaporated in a thin film. A method for producing a polylactic acid-based resin, characterized in that after a polycondensation is performed using a thin film evaporator, solid-phase polymerization is performed,
(2) The method for producing a polylactic acid-based resin according to (1), which is performed in the absence of a solvent,
(3) The method for producing a polylactic acid resin according to any one of (1) to (2), wherein a catalyst is used,
(4) One or more selected from a tin compound, a titanium compound, a lead compound, a zinc compound, a cobalt compound, an iron compound, a lithium compound, a rare earth compound, and a sulfonic acid compound are used as the catalyst. (1) A method for producing a polylactic acid resin according to any one of (3),
(5) The polylactic acid according to any one of (1) to (3), wherein at least one selected from tin compounds and at least one selected from sulfonic acid compounds are used as the catalyst. Resin production method,
(6) The tin compound is tin acetate (II) and / or tin (II) octylate, and the sulfonic acid compound is methanesulfonic acid and / or ethanesulfonic acid, A method for producing a polylactic acid resin ,
It is.

  An object of the present invention is to provide a method for efficiently producing a polylactic acid-based resin having a high molecular weight, having a high melting point, and excellent in thermal stability and hue.

  The present invention will be described in detail below.

  In the present invention, the polylactic acid-based resin is a polymer having L-lactic acid and / or D-lactic acid as a main component. When L-lactic acid is a main component, it is called poly-L-lactic acid, and D -When lactic acid is a main component, it is called poly-D-lactic acid.

  When the polylactic acid resin is poly-L-lactic acid, it preferably contains 70 mol% or more of L-lactic acid units, more preferably contains 90 mol% or more, and contains 95 mol% or more. It is more preferable that the content is 98 mol% or more.

  When the polylactic acid resin is poly-D-lactic acid, it preferably contains 70 mol% or more, more preferably 90 mol% or more, and more preferably 95 mol% or more D-lactic acid units. It is more preferable to contain 98 mol% or more.

  In this invention, the other component unit may be included in the range which does not impair the performance of the polylactic acid-type resin obtained by this invention. Examples of component units other than L-lactic acid or D-lactic acid units include polycarboxylic acids, polyhydric alcohols, hydroxycarboxylic acids, lactones, and the like. Specifically, succinic acid, adipic acid, sebacic acid, Polycarboxylic acids such as fumaric acid, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, 5-tetrabutylphosphonium sulfoisophthalic acid or their derivatives, ethylene glycol, propylene glycol, butane Diol, hexanediol, octanediol, neopentylglycol, glycerin, trimethylolpropane, pentaerythritol, trimethylolpropane, or polyhydric alcohol obtained by adding ethylene oxide or propylene oxide to pentaerythritol, Aromatic polyhydric alcohols obtained by addition reaction of phenol with ethylene oxide, polyhydric alcohols such as diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol or their derivatives, glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4 -Hydroxycarboxylic acids such as hydroxyvaleric acid, 6-hydroxycaproic acid, and glycolide, ε-caprolactone glycolide, ε-caprolactone, β-propiolactone, δ-butyrolactone, β- or γ-butyrolactone, pivalolactone, δ-valerolactone Examples include lactones such as lactones.

  The present invention is a method for producing a polylactic acid-based resin by direct polycondensation using lactic acid as a main raw material, wherein polycondensation is performed using a thin film evaporator, and then solid phase polymerization is performed. .

  In the present invention, the thin film evaporator is a reaction vessel having a decompression function, and may be either a vertical type or a horizontal type, but a vertical type is preferable in that it can efficiently remove volatile components and easily increase the molecular weight. A vertical stirring thin film evaporator is more preferable. When a raw material is introduced from the top of the vertical stirring thin film evaporator, a thin film of the raw material is formed by the natural fall of the raw material or forced scraping, and the volatile components contained in the raw material are reduced in pressure while moving to the bottom of the container. Means a device that is structured to be removed. There is no particular limitation as long as the apparatus satisfies such requirements. For example, the upper and lower rotary shafts provided on the central longitudinal axis, and the inner peripheral surface arranged on the outer peripheral side of the rotary shaft are heated and evaporated. A circular depressurized hermetic container body, a rotating dispersion unit attached to the upper rotating shaft, a thinning unit disposed below the dispersion unit, and a lower part of the hermetic container body It has a screw blade ejector attached to the lower rotary shaft located in the extension cylinder, and the upper rotary shaft and the lower rotary shaft are driven and rotated separately, and the bearing of the upper rotary shaft is a built-in bearing in the lower rotary shaft A thin film evaporator with a device structure arranged as is preferred.

  In the present invention, the thin film evaporator may be used in the entire process of polycondensation, or may be used in some steps. When used in some steps, for example, a low molecular weight body having a weight average molecular weight of less than 30,000, preferably 10,000 to 20,000 is prepared in advance, and the low molecular weight body is supplied to a thin film evaporator and subjected to polycondensation. A method can be mentioned.

  In the present invention, the temperature of polycondensation using a thin film evaporator is not particularly limited, but is preferably 100 to 240 ° C., and a polylactic acid resin having a high melting point and excellent hue can be obtained. It is more preferable that it is 120-200 degreeC at a point, and it is still more preferable that it is 140-190 degreeC. The temperature may be one step or may be two or more steps, but it is preferably two or more steps from the viewpoint that the melting point can be increased. For example, the reaction is performed at a temperature of 100 to 140 ° C. And a method in which the reaction is carried out at a temperature of 140 to 240 ° C.

  In the present invention, the pressure of polycondensation using a thin film evaporator is not particularly limited, and may be any of reduced pressure, normal pressure and pressurized conditions, but has a high molecular weight and a high melting point, and is stable in heat and hue. In terms of being able to obtain an excellent polylactic acid-based resin, it is preferably a reduced pressure condition, more preferably 0.1 Pa to 100 kPa, still more preferably 1 Pa to 13000 Pa, and 1 Pa to 1300 Pa. Is particularly preferable, and is most preferably 1 Pa to 800 Pa. Further, the pressure may be one stage or may be two or more stages, but is preferably two or more stages in terms of high molecular weight and excellent hue, for example, 13 kPa to 100 kPa. Examples include a method in which the reaction is performed at a pressure of 0.1 to 13 kPa after the reaction is performed at a pressure. When it is carried out under normal pressure conditions, it is preferably carried out under an inert gas stream such as dry nitrogen.

  In the present invention, a solvent may or may not be used, but it is preferably carried out without a solvent in that the process can be simplified and a polylactic acid resin can be obtained efficiently.

  In the present invention, a catalyst may or may not be used, but it has a high molecular weight, and in a preferred embodiment, a polylactic acid-based resin having a high melting point and excellent thermal stability and hue can be obtained. It is preferable to use a catalyst because it can be used.

  Examples of the catalyst used in the present invention include tin compounds, titanium compounds, lead compounds, zinc compounds, cobalt compounds, iron compounds, lithium compounds, rare earth compounds, and the types of compounds include metal alkoxides, metal halogen compounds, and organic compounds. Carboxylate, carbonate, sulfate, oxide and the like are preferable. Specifically, tin powder, tin (II) chloride, tin (IV) chloride, tin (II) bromide, tin (IV) bromide, ethoxy tin (II), t-butoxy tin (IV), isopropoxy Tin (IV), tin acetate (II), tin acetate (IV), tin octylate (II), tin (II) laurate, tin (II) myristate, tin (II) palmitate, tin stearate (II) ), Tin (II) oleate, tin (II) linoleate, tin (II) acetylacetone, tin (II) oxalate, tin (II) lactate, tin (II) tartrate, tin (II) pyrophosphate, p- Phenol sulfonate tin (II), bis (methane sulfonate) tin (II), tin sulfate (II), tin oxide (II), tin oxide (IV), tin sulfide (II), tin sulfide (IV), oxidation Dimethyltin (IV), methylphenyltin (IV) oxide, dibutyltin (IV) oxide, dioctyltin (IV) oxide, diphenyltin (IV) oxide, tributyltin oxide, triethyltin hydroxide (IV) , Triphenyltin hydroxide (IV), tributyltin hydride, monobutyltin (IV) oxide, tetramethyltin (IV), tetraethyltin (IV), tetrabutyltin (IV), dibutyldiphenyltin (IV), tetraphenyl Tin (IV), tributyltin acetate (IV), triisobutyltin acetate (IV), triphenyltin acetate (IV), dibutyltin diacetate, dibutyltin dioctanoate, dibutyltin dilaurate (IV), dibutyltin maleate (IV), dibutyltin bis (acetylacetonate), tributyltin chloride (IV), dibutyltin dichloride, monobutyltin trichloride, dioctyltin dichloride, triphenyltin chloride (IV), tributyltin sulfide, tributyltin sulfate , Tin (II) trifluoromethanesulfonate, ammonium hexachlorotin (IV), dibutyltin sulfide, diphenyltin sulfide, triethyltin sulfate, Tin compounds such as and phthalocyanine tin (II), and among them, a tin compound other than tin (II) chloride are preferred. Also, titanium methoxide, titanium propoxide, titanium isopropoxide, titanium butoxide, titanium isobutoxide, titanium cyclohexyl, titanium phenoxide, titanium chloride, titanium diacetate, titanium triacetate, titanium tetraacetate, titanium (IV) oxide, etc. Titanium compounds, lead diisopropoxy (II), lead monochloride, lead acetate, lead (II) octylate, lead (II) isooctanoate, lead (II) isononanoate, lead (II) laurate, lead oleate (II), lead compounds such as lead (II) linoleate, lead naphthenate, lead (II) neodecanoate, lead oxide, lead (II) sulfate, zinc powder, methyl propoxy zinc, zinc chloride, zinc acetate, octylic acid Zinc (II), zinc naphthenate, zinc carbonate, zinc oxide, zinc sulfate and other zinc compounds, cobalt chloride, cobalt acetate, octi Cobalt (II) phosphate, cobalt (II) isooctanoate (II), isononanoate (II), cobalt laurate (II), cobalt oleate (II), cobalt linoleate (II), cobalt naphthenate, cobalt neodecanoate ( II), cobalt compounds such as cobaltous carbonate, cobaltous sulfate, cobalt oxide (II), iron chloride (II), iron acetate (II), iron octylate (II), iron naphthenate, iron carbonate (II) ), Iron compounds such as iron (II) sulfate, iron (II) oxide, lithium compounds such as propoxylithium, lithium chloride, lithium acetate, lithium octylate, lithium naphthenate, lithium carbonate, dilithium sulfate, lithium oxide, triiso Propoxy europium (III), triisopropoxyneodymium (III), triisopropoxylantan, triisopropoxysamarium (III ), Triisopropoxy yttrium, isopropoxy yttrium, dysprosium chloride, europium chloride, lanthanum chloride, neodymium chloride, samarium chloride, yttrium chloride, dysprosium triacetate (III), europium triacetate (III), lanthanum acetate, neodymium triacetate, Samarium acetate, yttrium triacetate, dysprosium carbonate (III), dysprosium carbonate (IV), europium carbonate (II), lanthanum carbonate, neodymium carbonate, samarium carbonate (II), samarium carbonate (III), yttrium carbonate, dysprosium sulfate, sulfuric acid Examples include rare earth compounds such as europium (II), lanthanum sulfate, neodymium sulfate, samarium sulfate, yttrium sulfate, europium dioxide, lanthanum oxide, neodymium oxide, samarium (III) oxide, yttrium oxide. . Other potassium compounds such as potassium isopropoxide, potassium chloride, potassium acetate, potassium octylate, potassium naphthenate, tert-butyl potassium carbonate, potassium sulfate, potassium oxide, copper (II) diisopropoxide, copper chloride (II), copper acetate (II), copper octylate, copper naphthenate, copper sulfate (II), copper compounds such as dicopper carbonate, nickel chloride, nickel acetate, nickel octylate, nickel carbonate, nickel sulfate (II) , Nickel compounds such as nickel oxide, tetraisopropoxyzirconium (IV), zirconium trichloride, zirconium acetate, zirconium octylate, zirconium naphthenate, zirconium carbonate (II), zirconium carbonate (IV), zirconium sulfate, zirconium oxide (II ) Zirconium compounds such as triisopropoxy Antimony compounds such as antimony, antimony fluoride (III), antimony fluoride (V), antimony acetate, antimony (III) oxide, magnesium, magnesium diisopropoxide, magnesium chloride, magnesium acetate, magnesium lactate, magnesium carbonate, sulfuric acid Magnesium compounds such as magnesium and magnesium oxide, calcium compounds such as diisopropoxy calcium, calcium chloride, calcium acetate, calcium octylate, calcium naphthenate, calcium lactate and calcium sulfate, aluminum, aluminum isopropoxide, aluminum chloride, aluminum acetate , Aluminum compounds such as aluminum octylate, aluminum sulfate, aluminum oxide, germanium, tetraisopropoxygermane, germanium oxide Germanium compounds such as nium (IV), triisopropoxymanganese (III), manganese trichloride, manganese acetate, manganese octylate (II), manganese naphthenate (II), manganese compounds such as manganous sulfate, bismuth chloride ( III), bismuth powder, bismuth oxide (III), bismuth acetate, bismuth octylate, bismuth neodecanoate, and the like. Also, sodium stannate, magnesium stannate, potassium stannate, calcium stannate, manganese stannate, bismuth stannate, barium stannate, strontium stannate, sodium titanate, magnesium titanate, aluminum titanate, potassium titanate, Compounds composed of two or more metal elements such as calcium titanate, cobalt titanate, zinc titanate, manganese titanate, zirconium titanate, bismuth titanate, barium titanate and strontium titanate are also preferred. Moreover, an acid catalyst can also be mentioned, and it can be a Bronsted acid as a proton donor, a Lewis acid as an electron pair acceptor, or an organic acid or an inorganic acid. For example, monocarboxylic acid compounds such as formic acid, acetic acid, propionic acid, heptanoic acid, octanoic acid, octylic acid, nonanoic acid, isononanoic acid, trifluoroacetic acid and trichloroacetic acid, oxalic acid, succinic acid, maleic acid, tartaric acid and malonic acid Dicarboxylic acid compounds such as citric acid and tricarballylic acid, benzenesulfonic acid, n-butylbenzenesulfonic acid, n-octylbenzenesulfonic acid, n-dodecylbenzenesulfonic acid, pentadecylbenzenesulfonic acid, 2 , 5-dimethylbenzenesulfonic acid, 2,5-dibutylbenzenesulfonic acid, o-aminobenzenesulfonic acid, m-aminobenzenesulfonic acid, p-aminobenzenesulfonic acid, 3-amino-4-hydroxybenzenesulfonic acid, 5 -Amino-2-me Rubenzenesulfonic acid, 3,5-diamino-2,4,6-trimethylbenzenesulfonic acid, 2,4-dinitrobenzenesulfonic acid, p-chlorobenzenesulfonic acid, 2,5-dichlorobenzenesulfonic acid, cumenesulfonic acid , Xylenesulfonic acid, o-cresolsulfonic acid, m-cresolsulfonic acid, p-cresolsulfonic acid, p-toluenesulfonic acid, 2-naphthalenesulfonic acid, 1-naphthalenesulfonic acid, isopropylnaphthalenesulfonic acid, dodecylnaphthalenesulfonic acid , Dinonylnaphthalenesulfonic acid, dinonylnaphthalenedisulfonic acid, anthraquinone-2-sulfonic acid, m-benzenedisulfonic acid, 2,5-diamino-1,3-benzenedisulfonic acid, aniline-2,4-disulfonic acid, anthraquinone -1,5- Aromatic sulfonic acids such as disulfonic acid and polystyrene sulfonic acid, methanesulfonic acid, ethanesulfonic acid, 1-propanesulfonic acid, n-octylsulfonic acid, pentadecylsulfonic acid, trifluoromethanesulfonic acid, trichloromethanesulfonic acid, 1, 2-aliphatic sulfonic acids such as ethanedisulfonic acid, sulfonic acid compounds such as cyclopentanesulfonic acid, cyclohexanesulfonic acid and alicyclic sulfonic acids such as camphorsulfonic acid, acidic amino acids such as aspartic acid and glutamic acid, ascorbic acid, retinoin Phosphoric acid monoesters such as acid, phosphoric acid, metaphosphoric acid, phosphorous acid, hypophosphorous acid, polyphosphoric acid, monododecyl phosphate and monooctadecyl phosphate, diesters such as didodecyl phosphate and dioctadecyl phosphate And phosphoric acid compounds such as phosphorous acid monoester and phosphorous acid diester, boric acid, hydrochloric acid, sulfuric acid and the like. Further, the shape of the acid catalyst is not particularly limited, and any of a solid acid catalyst and a liquid acid catalyst may be used. For example, as the solid acid catalyst, acidic clay, kaolinite, bentonite, montmorillonite, talc, zirconium silicate and Natural minerals such as zeolite, oxides such as silica, alumina, titania and zirconia or oxide composites such as silica alumina, silica magnesia, silica boria, alumina boria, silica titania and silica zirconia, chlorinated alumina, fluorinated alumina, positive Examples thereof include ion exchange resins. In the case where polymerization is carried out using a racemic compound, which is an equal mixture of L-lactic acid and D-lactic acid, using a catalyst having stereoselective polymerizability, poly-L-lactic acid and poly-D-lactic acid are used. Can be manufactured simultaneously.

  In the present invention, a tin compound, a titanium compound, a lead compound, a zinc compound, a cobalt compound, an iron compound, a lithium compound, a rare earth compound, an antimony compound, in that a polylactic acid resin having a high molecular weight and a high melting point can be obtained. , Bismuth compounds, acid catalysts are preferred, and tin compounds, titanium compounds, lead compounds, zinc compounds, cobalt compounds, iron compounds, lithium compounds, rare earth compounds, sulfonic acid compounds, and phosphorus compounds are more preferred in terms of excellent productivity. More preferred are tin compounds, titanium compounds, rare earth compounds, sulfonic acid compounds, and phosphorus compounds. In addition, a tin-based organic carboxylate having two ligands is more preferable in that a polylactic acid resin excellent in thermal stability and hue can be obtained, and tin (II) acetate, octylic acid is more preferable. Tin (II) is particularly preferred. Further, the catalyst may be used alone or in combination of two or more, but it is preferable to use two or more in combination in that a polylactic acid resin having a high molecular weight and a high melting point can be obtained. It is preferable to use at least one selected from tin compounds and at least one selected from sulfonic acid compounds from the viewpoint of excellent properties. Tin (II) acetate and / or tin (II) octylate and methanesulfone are preferable. It is more preferable to use an acid and / or ethanesulfonic acid, and it is more preferable to use tin (II) acetate and / or tin (II) octylate and ethanesulfonic acid.

  The addition amount of the catalyst used in the present invention is 100 weights of raw materials (L-lactic acid and / or D-lactic acid, etc.) used in that a polylactic acid resin having a high molecular weight and a high melting point can be obtained efficiently. 0.001 to 2 parts by weight with respect to parts, 0.001 to 1 parts by weight being more preferred, and 0.001 in that a polylactic acid resin excellent in thermal stability and hue can be obtained. -0.5 weight part is further more preferable, and 0.01-0.3 weight part is especially preferable. In terms of increasing the molecular weight, the catalyst is preferably added in advance by preparing a low molecular weight material having a weight average molecular weight of less than 30,000, adding the catalyst thereto, and supplying the low molecular weight material to a thin film distiller.

  In the present invention, it is preferable to produce a prepolymer having a weight average molecular weight of 30,000 or more and less than 130,000 by polycondensation using a thin film evaporator, and a polylactic acid resin having a high molecular weight can be obtained efficiently. Therefore, it is preferable to produce a prepolymer having a weight average molecular weight of 40,000 to 90,000, more preferably a prepolymer having a weight average molecular weight of 50,000 to 80,000, and a weight average molecular weight of 60,000 to 70,000. It is further preferred to produce a prepolymer. The weight average molecular weight is a value of weight average molecular weight in terms of standard polymethyl methacrylate as measured by gel permeation chromatography (GPC) using hexafluoroisopropanol as a solvent.

  In the present invention, solid phase polymerization is characterized by using a prepolymer obtained by polycondensation using a thin film evaporator and performing solid phase polymerization at a temperature below the melting point of the prepolymer, and has a weight average molecular weight of 100,000. It is preferable to produce the above polymer.

  In the present invention, the solid phase polymerization is preferably performed at a temperature of 120 to 160 ° C. in that a polylactic acid resin having a high molecular weight and a high melting point and excellent in hue can be efficiently obtained. It is more preferable to carry out at a temperature of 140 to 160 ° C, and it is more preferable to carry out at a temperature of 145 to 155 ° C. In addition, the temperature of the solid phase polymerization may be one step or may be two or more steps, but it may be set to two or more steps in terms of easy high molecular weight in a short time and excellent hue. Preferably, it is more preferable to raise the temperature stepwise as the reaction proceeds. For example, a method of reacting at a temperature of 120 to 140 ° C and then reacting at a temperature of 140 to 160 ° C can be mentioned.

  In the present invention, solid-phase polymerization is a reaction time of 1 to 100 hours in that a polylactic acid-based resin having a high molecular weight and a high melting point, and excellent in thermal stability and hue can be obtained efficiently. It is preferably carried out, and it is preferably carried out with a reaction time of 3 to 80 hours, more preferably with a reaction time of 5 to 50 hours, in that a polylactic acid resin excellent in hue can be obtained efficiently. The reaction time is preferably 10 to 30 hours, and more preferably.

  Moreover, when performing the temperature of solid-phase polymerization in multiple steps | paragraphs of two or more steps, it is 1 to 50 hours at the temperature of 120-140 degreeC as a 1st stage, and the temperature of 140-160 degreeC as a 2nd stage, for example. The method performed for 50 hours is mentioned, It is easy to make high molecular weight in a short time, and is excellent also in hue, From the point of 120 to 140 degreeC as a 1st stage, it is 5 to 20 hours, and 140 to 150 degreeC as a 2nd stage. More preferably, the temperature is 5 to 20 hours, and the third stage is 150 to 160 ° C. for 10 to 30 hours. In addition, even if it is a case where temperature is performed by the multistage of 2 steps or more, the total of the reaction time of solid-phase polymerization is 1 to 100 hours.

  In the present invention, the pressure condition of the solid phase polymerization is not particularly limited, and any of the reduced pressure condition, the normal pressure condition and the pressurized condition may be used, but a polylactic acid resin having a high molecular weight can be efficiently obtained. From the viewpoint of being able to do so, it is preferable to be under reduced pressure conditions or normal pressure conditions. When it carries out on pressure reduction conditions, it is preferable to carry out by the pressure of 0.13-13000Pa. In addition, it is preferably performed at a pressure of 1 to 1300 Pa, more preferably a pressure of 10 to 900 Pa, and a pressure of 100 to 800 Pa in that a polylactic acid resin having excellent hue can be efficiently obtained. It is more preferable to carry out at a pressure of 500 to 700 Pa. Further, the pressure of the solid phase polymerization may be one step or may be two or more steps, but it is preferably two or more steps in terms of high molecular weight and excellent hue. Examples include a method of reacting at a pressure of 0.13 to 700 Pa after reacting at a pressure of 700 to 1300 Pa. When it is carried out under normal pressure conditions, it is preferably carried out under an inert gas stream such as dry nitrogen.

  In the present invention, when solid phase polymerization is carried out, the shape of the prepolymer is not particularly limited and may be any of agglomerates, films, pellets, powders, etc., but solid phase polymerization is efficiently advanced. It is preferable to use pellets or powders in that they can be produced. As a method for forming pellets, a melted prepolymer is extruded into strands, pelletized with a strand cutter, dropped into droplets using a dropping nozzle, and contacted with a gas or liquid to form pellets Etc. Moreover, as a method of making into powder, the method of grind | pulverizing using a mixer, a blender, a ball mill, and a hammer grinder is mentioned. In the case of powder, the average particle diameter is preferably 0.01 to 3 mm, more preferably 0.1 to 1 mm, from the viewpoint that solid-phase polymerization can be efficiently performed.

  In the present invention, the solid phase polymerization may be a batch method or a continuous method, and the reaction vessel may be a stirring vessel type reaction vessel, a mixer type reaction vessel, a tower type reaction vessel, or the like. Two or more types can be used in combination.

  In the present invention, a volatile component generated in the entire process of polycondensation and solid-phase polymerization is separated, and a vaporization part having a function of removing a part of the volatile component out of the reaction system and a part of the volatile component in the reaction system It is preferable to use an apparatus having a condensing part that has the function of returning to water. Specifically, among volatile components, water is removed, and lactic acid and lactide or their low molecular weight polymers are subjected to a thin film evaporator or polycondensation reaction. Any device can be used as long as it is returned to the tank. Here, as a condenser which comprises a condensation part, methods, such as a double tube type, a multi-tube type, a coil type, a plate type, a plate fin type, a spiral type, and a jacket type, can be mentioned, for example. In the present invention, in order to efficiently return lactic acid and lactide or their low molecular weight polymer to the reaction vessel, the condenser temperature may be set to be equal to or higher than the melting point of lactic acid and lactide or their low molecular weight polymer. Preferably, it is 90 degreeC or more, It is more preferable that it is 100-160 degreeC, It is especially preferable that it is 105-140 degreeC. Further, as a method for removing moisture, for example, after volatile components are liquefied, a desiccant is passed through to remove only moisture.

  In the present invention, when solid phase polymerization is carried out, the prepolymer is preferably crystallized, and it is more preferable to perform crystallization treatment after completion of polycondensation using a thin film evaporator.

  The method for crystallization is not particularly limited, and a known method can be used. For example, a method of treating at a crystallization temperature in a gas phase or a liquid phase, a method of volatilizing a solvent after dissolving the prepolymer in a solvent, a method of bringing the prepolymer into contact with the solvent, and a molten prepolymer Examples of the method include cooling and solidifying while performing stretching or shearing operations. From the viewpoint of easy operation, a method of treating at a crystallization temperature in a gas phase or a liquid phase is preferable.

  The crystallization temperature as used herein is not particularly limited as long as it is higher than the glass transition temperature of the prepolymer that can be obtained by polycondensation using a thin film evaporator and lower than the melting point. It is more preferable that the temperature is within the range of the temperature rising crystallization temperature and the temperature falling crystallization temperature measured by a differential scanning calorimeter (DSC), and a polylactic acid resin having a high molecular weight and a high melting point and excellent in hue is efficiently used. It is more preferable that it is 30-170 degreeC at the point that it can obtain, It is especially preferable that it is 50-150 degreeC, It is most preferable that it is 100-140 degreeC.

  Further, the time for crystallization is not particularly limited, but it is sufficiently crystallized within 3 hours, and preferably within 2 hours. The pressure condition in the crystallization process may be any of reduced pressure, normal pressure and increased pressure.

  In the present invention, the shape of the prepolymer at the time of crystallization treatment is not particularly limited, and any of a lump, a film, a pellet, and a powder may be used, but the pellet or the powder can be efficiently crystallized. Is preferably used. As a method for forming pellets, a melted prepolymer is extruded into strands, pelletized with a strand cutter, dropped into droplets using a dropping nozzle, and contacted with a gas or liquid to form pellets Etc. Moreover, as a method of making into powder, the method of grind | pulverizing using a mixer, a blender, a ball mill, and a hammer grinder is mentioned. In the case of powder, the average particle diameter is preferably 0.01 to 3 mm, more preferably 0.1 to 1 mm, in that it can be efficiently crystallized.

  When producing a polylactic acid resin using the present invention, it is prepared in advance using lactic acid and other copolymer components supplied to the thin film evaporator. The low molecular weight production step, the step of increasing the molecular weight by passing through a thin film evaporator, and the step of solid phase polymerization may be performed in a consistent continuous process or a batch process. The batch method is effective in the case of producing a small amount of other varieties, but the continuous method is preferable when the same varieties are produced over a long period of time.

  Furthermore, in the present invention, by adding a melt extruder after the thin film evaporator, various additives and fillers are continuously blended, and a resin composition containing a polylactic acid resin is obtained in a process continuous with polymerization. It can also be manufactured.

  The weight average molecular weight of the polylactic acid resin obtained by the method of the present invention is not particularly limited, but is preferably 100,000 or more in view of mechanical properties. In particular, it is preferably 100,000 to 1,200,000, more preferably 120,000 to 500,000, and even more preferably 140,000 to 350,000 in terms of excellent moldability and mechanical properties. The weight average molecular weight is a value of weight average molecular weight in terms of standard polymethyl methacrylate as measured by gel permeation chromatography (GPC) using hexafluoroisopropanol as a solvent.

  When using a catalyst in the present invention, it is preferable to add a catalyst deactivator from the viewpoint of excellent thermal stability. When the polymerization catalyst remains, the polylactic acid-based resin may be thermally decomposed during melt kneading and melt molding by the remaining catalyst, and by adding a catalyst deactivator, thermal decomposition can be suppressed, Stability can be improved.

  Examples of the catalyst deactivator used in the present invention include hindered phenol compounds, thioether compounds, vitamin compounds, triazole compounds, polyvalent amine compounds, hydrazine derivative compounds, phosphorus compounds, and the like. You may use together. 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. As further preferred examples of specific examples, “ADEKA STAB” AX-71 (dioctadecyl phosphate), PEP-8 (distearyl pentaerythritol diphosphite), PEP-36 (cyclic neopentatetrayl bis (2,6) manufactured by ADEKA) -T-butyl-4-methylphenyl) phosphite).

  Specific examples of the hindered 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-hexane Diol-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-hydroxyphenyl) -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-t-butyl-4-hydroxyphenol) propionyl] Dorazine, N-salicyloyl-N′-salicylidenehydrazine, 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′-hexamethylene Bis- (3,5-di-t-butyl-4-hydroxy-hydrocinnamide) and the like. Preferably, triethylene glycol-bis- [3- (3-t-butyl-5-methyl- 4-hydroxyphenyl) -propionate], tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate Acid] methane, 1,6-hexanediol-bis- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) -propionate], pentaerythrityl-tetrakis [3- (3,5- Di-t-butyl-4-hydroxyphenyl) propionate], N, N′-hexamethylenebis- (3,5-di-t-butyl-4-hydroxy-hydrocinnamide). Specific product names of the hindered phenol compounds include “ADEKA STAB” AO-20, AO-30, AO-40, AO-50, AO-60, AO-70, AO-80, AO-330 manufactured by ADEKA. “Irganox” 245, 259, 565, 1010, 1035, 1076, 1098, 1222, 1330, 1425, 1520, 3114, 5057, manufactured by Ciba Specialty Chemicals, “Sumilyzer” BHT-R, MDP-S, manufactured by Sumitomo Chemical Co., Ltd. Examples include BBM-S, WX-R, NW, BP-76, BP-101, GA-80, GM, GS, “Sianox” CY-1790 manufactured by Cyanamid.

  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- Stearylthiopropionate). Specific trade names of thioether compounds include “ADEKA STAB” AO-23, AO-412S, AO-503A from ADEKA, “Irganox” PS802 from Ciba Specialty Chemicals, “Sumilyzer” TPL-R from Sumitomo Chemical, Examples thereof include TPM, TPS, TP-D, DSTP manufactured by API Corporation, DLTP, DLTOIB, DMTP, “Sinox” 412S manufactured by Cypro Kasei, and “Sianox” 1212 manufactured by Cyamide.

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 Synthetic products such as dl-α-tocopherol calcium and dl-α-tocopherol nicotinate can be mentioned. 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, 3- (N-salicyloyl) amino-1,2,4-triazole, and the like.

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) salt 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 and the like.
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′-diphenyloxamide, N, N′-diethyl-N, N′-diphenyloxamide, oxalic acid-bis ( Nidylidenehydrazide), thiodipropionic acid-bis (benzylidenehydrazide), bis (salicyloylhydrazine), N-salicylidene-N′-salicyloylhydrazone, N, N′-bis [3- (3,5 -Di-tert-butyl-4-hydroxyphenyl) propionyl] hydrazine, N, N′-bis [2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] ethyl] oxamide Etc.

  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-tert-butyl-4-thio (2'-methyl-4'-hydroxy-5'-tert-butylphenyl) -5-methylphenyl] -1,10-decamethylene-di-carboxylic acid-di-hydroxyethylcarbonylhydrazide-diphosphite, tetrakis [2-tert-butyl-4-thio (2'-methyl-4'-hydroxy-) 5'-t-butylphenyl) -5-methylphenyl] -1,10-decamethylene-di-carboxylic acid di-sali Roylhydrazide-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 and the like are mentioned, and those in which at least one PO bond is bonded to an aromatic group are more preferable. 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) Pentaerythritol-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) and the like Tris (2,4-di-t-butylphenyl) phosphite, 2,2-methylenebis (4,6-di) t-butylphenyl) octyl phosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol-di-phosphite, tetrakis (2,4-di-t-butylphenyl) -4, 4′-biphenylenephosphonite 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, “Irgaphos” 168, manufactured by Ciba Specialty Chemicals, “Sumilyzer” P-16, manufactured by Sumitomo Chemical, “Sand Stub” manufactured by Clariant, P-EPQ, “Weston” manufactured by GE 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, etc., among which 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.

  The addition amount of the catalyst deactivator is not particularly limited, but is preferably 0.001 to 2 parts by weight with respect to 100 parts by weight of the polylactic acid resin in terms of excellent thermal stability. It is more preferably ˜1 part by weight, still more preferably 0.05 to 0.5 part by weight, and most preferably 0.08 to 0.3 part by weight.

  The timing of adding the catalyst deactivator is not particularly limited, but at the end of polycondensation using a thin film evaporator and / or the end of solid-phase polymerization in that a high melting point, high molecular weight polylactic acid resin can be obtained. It is preferably added occasionally, and it is also preferable to add in two or more times during the polycondensation because it is excellent in hue. In addition, when adding at the time of polycondensation, it is preferable to add the catalyst for solid-phase polymerization after adding a catalyst deactivator.

  Further, in terms of excellent thermal stability, 0.001 to 1 part by weight may be added to 100 parts by weight of the polylactic acid resin at each stage at the end of the polycondensation and at the end of the solid phase polymerization. In terms of excellent productivity, it is more preferable to add 0.01 to 0.5 parts by weight, and more preferable to add 0.01 to 0.1 parts by weight.

  In the present invention, the method of adding the catalyst deactivator is not particularly limited, and examples thereof include a method of melt kneading above the melting point of the polylactic acid resin and a method of removing the solvent after being dissolved and mixed in the solvent. However, a method of melt-kneading at a melting point or higher of the polylactic acid resin is preferable in that it can be produced efficiently. The melt-kneading method may be a batch method or a continuous method. As the apparatus, a single-screw extruder, a twin-screw extruder, a multi-screw extruder, a plastmill, a kneader, a stirring reactor equipped with a decompression device, or the like is used. It is preferable to use a single screw extruder or a twin screw extruder in that it can be kneaded efficiently and uniformly.

  In the present invention, the temperature at which the catalyst deactivator is added is preferably from 180 to 250 ° C., and more preferably from 190 to 230 ° C. in terms of excellent mechanical properties.

  In the present invention, the pressure at which the catalyst deactivator is added may be any of reduced pressure, normal pressure, and increased pressure, and is preferably reduced in that the generated gas can be removed during melt-kneading.

  In the present invention, the atmospheric conditions at the time of melt kneading may be either an air atmosphere or an inert gas atmosphere such as nitrogen, but in an inert gas atmosphere in that the amount of gas generated at the time of melt kneading can be reduced. It is preferable to carry out with.

  When mixing in a solvent, a solvent in which the polymer and the monomer are dissolved is used. As the solvent, for example, chloroform, methylene chloride, acetonitrile and the like can be used. The method for removing the solvent when it is necessary to remove the solvent after mixing is not particularly limited. For example, the solvent is volatilized at room temperature and the solvent is volatilized at a temperature equal to or higher than the boiling point of the solvent under reduced pressure. Or the like can be used.

  In the polylactic acid-based resin obtained by the production method of the present invention, ordinary additives such as fillers (glass fiber, carbon fiber, metal fiber, natural fiber, organic fiber, organic fiber, Glass flakes, glass beads, ceramic fibers, ceramic beads, asbestos, wollastonite, talc, clay, mica, sericite, zeolite, bentonite, montmorillonite, synthetic mica, dolomite, kaolinite, 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, benzo) Lyazole, benzophenone, etc.), heat stabilizer (hindered phenol, hydroquinone, phosphites and their substitutes, etc.), lubricant, mold release agent (montanic acid and its salt, its ester, its half ester, stearyl alcohol, stearamide) And polyethylene waxes), colorants including dyes (such as nigrosine) and pigments (such as cadmium sulfide and phthalocyanine), anti-coloring agents (such as phosphites and hypophosphites), flame retardants (red phosphorus, phosphate esters) , Brominated polystyrene, brominated polyphenylene ether, brominated polycarbonate, magnesium hydroxide, melamine and cyanuric acid or salts thereof, conductive agent or colorant (carbon black, etc.), slidability improver (graphite, fluororesin, etc.) ), Crystal nucleating agent (t Inorganic nucleating agents such as bismuth, 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 1 type, or 2 or more types, such as a carboxylic acid metal salt, zinc phenylphosphonate, and an antistatic agent, can be added.

  In addition, the polylactic acid resin obtained by the production method of the present invention includes other thermoplastic resins (for example, polyethylene, polypropylene, acrylic resin, polyamide, polyphenylene sulfide resin, polyether) within the range not impairing the object of the present invention. Ether ketone resin, polyester, polysulfone, polyphenylene oxide, polyacetal, polyimide, polyetherimide, etc.) or thermosetting resin (eg phenol resin, melamine resin, polyester resin, silicone resin, epoxy resin, etc.) or soft thermoplastic resin ( For example, ethylene / glycidyl methacrylate copolymer, polyester elastomer, polyamide elastomer, ethylene / propylene terpolymer, ethylene / butene-1 copolymer, etc.) It may further contain a.

  The polylactic acid-based resin obtained by the production method of the present invention has a high molecular weight even after it is once melted and solidified when it is processed into a molded product or the like, and in a preferred embodiment, has a high melting point, It is easy to form a polylactic acid resin having excellent thermal stability and hue.

  The polylactic acid resin obtained by the production method of the present invention can be widely used as a molded product. Examples of molded products include films, sheets, fibers / clothes, non-woven fabrics, injection molded products, extrusion molded products, vacuum / pressure molded products, blow molded products, and composites with other materials. The article is useful for agricultural materials, horticultural materials, fishery materials, civil engineering / architectural materials, stationery, medical supplies, automotive parts, electrical / electronic components or other uses.

  Hereinafter, the present invention will be described specifically by way of examples. Here, the number of parts in the examples indicates parts by weight.

(1) Weight average molecular weight (Mw)
It is a value of weight average molecular weight in terms of standard polymethyl methacrylate measured by gel permeation chromatography (GPC). GPC measurement was performed using a WATERS differential refractometer WATERS410 as a detector, a MODEL510 high performance liquid chromatography as a pump, and a column with Shodex GPC HFIP-806M and Shodex GPC HFIP-LG connected in series. It was. The measurement conditions were a flow rate of 0.5 mL / min, hexafluoroisopropanol was used as a solvent, and 0.1 mL of a solution having a sample concentration of 1 mg / mL was injected.

(2) Melting point This is a value measured by a differential scanning calorimeter (DSC), and a DSC7 manufactured by PerkinElmer was used, and the measurement conditions were 10 mg of a sample in a nitrogen atmosphere at a heating rate of 20 ° C./min.

(3) Thermal stability This is a value measured with a thermogravimetric measuring device (TGA), using TGA7 manufactured by PerkinElmer, and as a measurement condition, the weight is retained when the sample is held at 220 ° C. for 30 minutes in a nitrogen atmosphere. Judged from the rate. It can be said that the greater the weight retention, the better the thermal stability.

(4) Hue Judging from visual judgment, the following criteria were used.
5: Uncolored 4: Intermediate between 3: 3 and 5: Slightly yellow colored 2: Intermediate between 2: 1 and 3: Large colored [Reference Example 1]
In a reaction vessel equipped with a stirrer and a reflux device, 100 parts of a 90% L-lactic acid aqueous solution was added, the temperature was adjusted to 160 ° C., and the pressure was gradually reduced to 800 Pa. The reaction was performed for 4 hours while removing water, A low molecular weight substance I (A-1) having Mw 4000 was obtained. Thereto, 0.5 part of tin (II) acetate was added as a catalyst and reacted at 170 ° C. and 600 Pa for 4 hours to obtain a low molecular weight substance II (B-1) having an Mw of 18000.

[Reference Example 2]
In a reaction vessel equipped with a stirrer and a reflux device, 100 parts of a 90% L-lactic acid aqueous solution was added, the temperature was adjusted to 160 ° C., and the pressure was gradually reduced to 800 Pa. The reaction was performed for 4 hours while removing water, A low molecular weight substance I (A-2) having Mw 4000 was obtained. Thereto, 0.5 part of samarium acetate tetrahydrate was added as a catalyst and reacted at 170 ° C. and 600 Pa for 4 hours to obtain a low molecular weight substance II (B-2) having Mw 17000.

[Reference Example 3]
In a reaction vessel equipped with a stirrer and a reflux device, 100 parts of a 90% L-lactic acid aqueous solution was added, the temperature was adjusted to 160 ° C., and the pressure was gradually reduced to 800 Pa. The reaction was performed for 4 hours while removing water, A low molecular weight substance I (A-3) having Mw 4000 was obtained. Thereto, 0.5 part of cobalt (II) acetate was added as a catalyst and reacted at 170 ° C. and 600 Pa for 4 hours to obtain a low molecular weight substance II (B-3) having an Mw of 12000.

[Reference Example 4]
In a reaction vessel equipped with a stirrer and a reflux device, 100 parts of a 90% L-lactic acid aqueous solution was put, the temperature was adjusted to 140 ° C., the pressure was gradually reduced to 800 Pa, and the reaction was carried out for 2 hours while removing water. Next, the temperature was raised to 160 ° C., followed by reaction for 2 hours to obtain a low molecular weight substance I (A-4) having Mw 4500. Thereto, 0.2 parts of tin (II) acetate and 0.8 part of ethanesulfonic acid were added as catalysts and reacted at 170 ° C. and 600 Pa for 4 hours to obtain a low molecular weight substance II (B-4) having an Mw of 15000. .

[Reference Example 5]
In a reaction vessel equipped with a stirrer and a reflux device, 100 parts of a 90% L-lactic acid aqueous solution was put, the temperature was adjusted to 140 ° C., the pressure was gradually reduced to 800 Pa, and the reaction was carried out for 2 hours while removing water. Next, the temperature was raised to 160 ° C., followed by reaction for 2 hours to obtain a low molecular weight substance I (A-5) having Mw 4500. Thereto, 0.2 parts of tin (II) octylate and 0.8 part of ethanesulfonic acid were added as catalysts and reacted at 170 ° C. and 600 Pa for 4 hours to obtain a low molecular weight substance II (B-5) having Mw 17000. It was.

[Reference Example 6]
In a reaction vessel equipped with a stirrer and a reflux device, 100 parts of a 90% L-lactic acid aqueous solution was put, the temperature was adjusted to 140 ° C., the pressure was gradually reduced to 800 Pa, and the reaction was carried out for 2 hours while removing water. Next, the temperature was raised to 160 ° C., followed by reaction for 2 hours to obtain a low molecular weight substance I (A-6) having Mw 4500. Thereto, 0.2 parts of tin (II) octylate and 0.8 part of methanesulfonic acid were added as catalysts and reacted at 170 ° C. and 600 Pa for 4 hours to obtain low molecular weight substance II (B-6) having Mw 16000. It was.

[Example 1]
A vertical stirring thin film evaporator comprising the low molecular weight body II (B-1) obtained in Reference Example 1 comprising a cylinder having an inner diameter of 155 mmφ × height of 430 mm and an inclined multi-stirring blade rotating while maintaining a clearance of 2 mm from the inner wall of the cylinder. (Resin temperature: 170-180 ° C., degree of vacuum: 50-600 Pa, stirring blade rotation speed: 800-1000 rpm), polymerization was carried out by treatment in a molten state and under reduced pressure, and then 30 mmφ, L / D = 42 twin screw extruder to obtain a pellet-shaped prepolymer (C-1). The pellets were crystallized at 120 ° C. for 2 hours using a hot air dryer, and then solid-phase polymerized using a vacuum dryer at 145 ° C. and 50 Pa for 30 hours to obtain a polylactic acid resin. (D-1) was obtained. The results are shown in Table 1.

[Example 2]
The same procedure as in Example 1 was performed except that the low molecular weight substance II (B-2) obtained in Reference Example 2 was used. The results are shown in Table 1.

[Example 3]
The same procedure as in Example 1 was performed except that the low molecular weight substance II (B-3) obtained in Reference Example 3 was used. The results are shown in Table 1.

[Example 4]
The same operation as in Example 1 was carried out except that the low molecular weight substance II (B-4) obtained in Reference Example 4 was used. The results are shown in Table 1.

[Example 5]
The same operation as in Example 1 was carried out except that the low molecular weight substance II (B-5) obtained in Reference Example 5 was used. The results are shown in Table 1.

[Example 6]
The same operation as in Example 1 was carried out except that the low molecular weight substance II (B-6) obtained in Reference Example 6 was used. The results are shown in Table 1.

[Example 7]
This was carried out in the same manner as in Example 4 except that solid-phase polymerization was carried out at 155 ° C. for 30 hours under atmospheric pressure and nitrogen flow using a tower reactor. The results are shown in Table 1.

[Example 8]
To 100 parts of the polylactic acid resin obtained after solid phase polymerization, 0.5 part of a catalyst deactivator (AX-71) is melt-kneaded using a 30 mmφ, L / D = 42 twin screw extruder, The same procedure as in Example 7 was performed except that the pellet-shaped polylactic acid resin (E-8) was used. The results are shown in Table 1.

[ Reference Example 7 ]
In a reaction vessel equipped with a stirrer and a reflux device, 100 parts of a 90% L-lactic acid aqueous solution was put, the temperature was adjusted to 140 ° C., the pressure was gradually reduced to 800 Pa, and the reaction was carried out for 2 hours while removing water. Next, the temperature was raised to 160 ° C., and the mixture was reacted for 2 hours to obtain a low molecular weight substance I (A-9) having Mw 4500. Thereto, 0.2 part of tin (II) octylate and 0.8 part of ethanesulfonic acid were added as catalysts, and the uniformly mixed liquid was connected in series with the vertical stirring thin film evaporator used in Example 1. The first unit is made to react at a resin temperature: 160 to 170 ° C., the degree of vacuum: 50 to 600 Pa, and the stirring blade rotation speed: 800 to 1000 rpm, and the second unit is made of resin. Temperature: 170 to 180 ° C., degree of vacuum: 50 to 600 Pa, stirring blade speed: 800 to 1000 rpm, and after polymerization by treatment in a molten state and under reduced pressure, 30 mmφ, L / D = 42 It supplied to the twin-screw extruder and obtained the pellet-form prepolymer (C-9). The pellets were crystallized at 120 ° C. for 2 hours using a hot air dryer, and then solid-phase polymerized at 155 ° C. for 30 hours under atmospheric pressure and nitrogen flow using a tower reactor. A resin (D-9) was obtained. Further, using a 30 mmφ, L / D = 42 twin screw extruder, 100 parts of polylactic acid resin (D-9) was melt-kneaded with 0.5 part of catalyst deactivator (AX-71). A pellet-shaped polylactic acid resin (E-9) was obtained. The results are shown in Table 1.

[Comparative Example 1]
In a reaction vessel equipped with a stirrer and a reflux device, 100 parts of a 90% L-lactic acid aqueous solution was added, the temperature was adjusted to 160 ° C., and the pressure was gradually reduced to 800 Pa. The reaction was performed for 4 hours while removing water, A low molecular weight substance I (CA-1) having Mw 4000 was obtained. Thereto, 0.5 part of tin (II) acetate was added as a catalyst, reacted at 170 ° C. and 600 Pa for 10 hours, then supplied to a 30 mmφ, L / D = 42 twin screw extruder, and Mw 40000 pellet low Molecular weight body II (CB-1) was obtained. This low molecular weight substance II (CB-1) was crystallized at 120 ° C. for 2 hours using a hot air dryer, and then solid-phased at 145 ° C. and 50 Pa for 30 hours using a vacuum dryer. Polymerization was performed to obtain a polylactic acid resin (CD-1). The results are shown in Table 1.

[Comparative Example 2]
In a reaction vessel equipped with a stirrer and a reflux device, 100 parts of a 90% L-lactic acid aqueous solution was added, the temperature was adjusted to 160 ° C., and the pressure was gradually reduced to 800 Pa. The reaction was performed for 4 hours while removing water, A low molecular weight substance I (CA-2) having Mw 4000 was obtained. Thereto, 0.5 part of tin (II) acetate was added as a catalyst and reacted at 170 ° C. and 600 Pa for 4 hours to obtain a low molecular weight substance II (CB-2) having an Mw of 18000. This low molecular weight II (CB-2) was connected to three vertical agitating thin film evaporators consisting of a cylinder having an inner diameter of 155 mmφ × height of 430 mm, an inner wall of the cylinder and an inclined multi-stirring blade rotating while maintaining a clearance of 2 mm. Polylactic acid resin is introduced into the apparatus, polymerized by reacting at a resin temperature of 170 to 180 ° C., a pressure reduction degree of 50 to 600 Pa, a stirring blade rotation speed of 800 to 1000 rpm, and processing in a molten state and under reduced pressure. (CC-2) was obtained. The results are shown in Table 1.

  From the results of Table 1, a polylactic acid resin having a high molecular weight, having a high melting point, and excellent in thermal stability and hue is obtained by the method for producing a polylactic acid resin of the present invention. You can see that

Claims (6)

This is a method for producing polylactic acid resin by direct polycondensation using lactic acid as the main raw material. A low molecular weight body having a weight average molecular weight of 10,000 to 20,000 is prepared in advance, and the low molecular weight body is supplied to a thin film evaporator. A method for producing a polylactic acid-based resin, comprising performing polycondensation using a thin film evaporator and then solid-phase polymerization. The method for producing a polylactic acid resin according to claim 1, wherein the method is performed in the absence of a solvent. The method for producing a polylactic acid resin according to claim 1, wherein a catalyst is used. 4. The catalyst according to claim 3, wherein at least one selected from a tin compound, a titanium compound, a lead compound, a zinc compound, a cobalt compound, an iron compound, a lithium compound, a rare earth compound, and a sulfonic acid compound is used. The manufacturing method of polylactic acid-type resin as described in any one of. The method for producing a polylactic acid resin according to claim 3, wherein at least one selected from a tin compound and at least one selected from a sulfonic acid compound are used as the catalyst. 6. The polylactic acid system according to claim 5, wherein the tin compound is tin (II) acetate and / or tin (II) octylate, and the sulfonic acid compound is methanesulfonic acid and / or ethanesulfonic acid. Manufacturing method of resin.