JP5029038B2 - Method for producing polylactic acid plasticizer - Google Patents

Description

  The present invention relates to a method for producing a polylactic acid plasticizer obtained by polymerization reaction of lactide and polyether glycol. Specifically, it is a method for producing a polylactic acid-based plasticizer capable of suppressing the sublimation of lactide during the polymerization reaction and improving the productivity. The polylactic acid plasticizer obtained by the production method of the present invention has an extremely low lactide content, excellent hydrolysis resistance, quality stability during long-term storage, and good compatibility with polylactic acid. It can be suitably used for use. By blending the polylactic acid plasticizer obtained from the production method of the present invention with polylactic acid, the flexibility and impact resistance of molded products such as films and sheets are improved, and the resulting film and sheet are packaging wraps. It can be suitably used for applications such as films, plastic bags, and agricultural multi-sheets.

  In recent years, due to environmental problems and the like, research has been actively conducted to use biodegradable plastics that are decomposed by enzymes and microorganisms using plant-derived components as raw materials. Among them, polylactic acid is an example of a biodegradable aliphatic polyester that has recently been actively researched and developed.

  Polylactic acid is a polymer produced by producing lactic acid from starch or the like obtained from corn or moss, and using lactic acid as a monomer. Polylactic acid is excellent in mechanical properties, heat resistance, and transparency among aliphatic polyesters, and has been developed for various molded products such as films, sheets, tapes, fibers, nonwoven fabrics, and containers. . However, since polylactic acid is inherently a hard resin, the flexibility of a molded product is not sufficient depending on the application such as a packaging film, and a softening technique by adding a plasticizer has been studied.

  For example, Patent Document 1 discloses a technique for improving flexibility by adding lactic acid, a linear lactic acid oligomer, or a cyclic lactic acid oligomer to polylactic acid. Patent Document 2 discloses a technique for improving the flexibility of a composition by mixing a plasticizer containing polyalkylene ether as a main component in a copolymer of polylactic acid and polyalkylene ether.

  However, plasticizers of these polylactic acid oligomers or copolymers of polylactic acid and other polymers generally have low thermal stability during molding due to the raw material lactide remaining in the plasticizer. In addition, the molded product is easily hydrolyzed under normal use conditions. For this reason, when a molded product such as a film is produced from such a composition, the strength drops in a relatively short time, which may cause a problem in practical use of the molded product.

  This is because lactide remains in the polymer after the polymerization reaction. Since the polylactic acid synthesis method by ring-opening addition polymerization using lactide as a raw material is an equilibrium reaction of ring-opening addition-cyclization of lactide, the conversion rate of lactide to polymer does not reach 100%, and the polymerization reaction Even after completion, several percent of lactide remains. The lactide remaining in the polymer is hydrolyzed by moisture in the atmosphere to become lactic acid, which breaks the polymer chain and deteriorates the molded product.

  Therefore, in order to reduce the amount of residual lactide in a lactic acid polymer such as polylactic acid or a copolymer of polylactic acid and other monomers, a method of removing lactide from the lactic acid polymer has been studied. For example, Patent Document 3 discloses a method of removing lactide and a low polymer under reduced pressure while heating and melting the polymer with a twin screw extruder, and Patent Document 4 continuously extrudes the molten polymer into a pot under reduced pressure. A method for removing lactide and low polymer is disclosed.

  However, in these methods, since the polymerization catalyst remains active in the polymer, even if the lactide is removed once under reduced pressure and heating, if the polymer is remelted during molding, There was a problem that lactide in the polymer increased.

  Patent Document 5 describes a method for producing a polyester / polylactic acid copolymer comprising a dicarboxylic acid component and a diol component, and the polymerization catalyst is deactivated by adding alkyl phosphate and / or alkyl phosphonate. A method for removing lactide under reduced pressure is disclosed. However, a copolymer of polyester and polylactic acid composed of a dicarboxylic acid component and a diol component has not been sufficiently compatible with polylactic acid. In addition, with alkyl phosphate and alkyl phosphonate, the deactivation reaction with the catalyst is not sufficient, and by reducing the pressure inside the reaction system, the lactide content immediately after production can be temporarily reduced, but polymer remelting Occasionally, lactide in the polymer increased due to the reaction of forming lactide, and the hydrolysis resistance of the resulting polyester / polylactic acid copolymer was not satisfactory.

  Patent Document 6 also discloses that the polymerization catalyst used during the polymerization of the lactic acid-based polyester is lost by melt-kneading the polyester composed of the dicarboxylic acid component and the diol component, and the lactic acid-based polyester with the chelating agent and the acidic phosphate ester. A method of activating is disclosed. However, chelating agents and acidic phosphoric acid esters not only act on polymerization catalysts for lactic acid-based polyesters but also on polyester polymerization catalysts composed of dicarboxylic acid components and diol components, so deactivation is insufficient. There was a case. Therefore, although the lactide content immediately after production can be reduced by reducing the pressure, the lactide may be regenerated at the time of remelting, and the resulting molded article may not be sufficiently resistant to hydrolysis.

Furthermore, in the production of these polylactic acid oligomers or copolymers of polylactic acid and other polymers, handling of lactide as a raw material has been a problem. Lactide as a raw material is a sublimable compound, and when heated under an inert gas at a melting point (95 ° C.) or higher, it partially melts and becomes sublimated at the same time. Since the raw material lactide is released from the reaction system by sublimation during the polymerization reaction, the yield of the polymerization reaction is lowered, or the sublimated lactide adheres to the polymerization reaction vessel or the piping of the decompression line. There was a problem that decreased.
JP-A-6-306264 JP-A-8-199052 European Patent No. 532154 JP-A-5-93050 JP-A-8-301993 Japanese Patent Laid-Open No. 9-104809

  The object of the present invention is to solve the above-mentioned problems of the prior art, and has a very low lactide content, excellent resistance to hydrolysis, quality stability during long-term storage, and compatibility with polylactic acid. It is another object of the present invention to provide a method for producing a polylactic acid-based plasticizer obtained by a polymerization reaction of lactide and polyether glycol with good productivity.

As described above, the object of the present invention is to produce a polylactic acid plasticizer having a number average molecular weight of 8000 to 20000 from lactide and polyether glycol, and in the presence of a catalyst, it exceeds 101.3 kPa and falls within the range of 304.0 kPa or less. After the polymerization deactivation, a catalyst deactivator is added, and after completion of the catalyst deactivation reaction, the temperature is 140 ° C. to 200 ° C., the pressure is 1.33 kPa to 1.33 Pa, and the time is 30 to 300 minutes. This can be achieved by a method for producing a polylactic acid plasticizer characterized by removing residual lactide and low molecular weight substances .

In the present invention, when a polylactic acid plasticizer having a number average molecular weight of 8000 to 20000 is produced by a polymerization reaction between lactide and polyether glycol, the catalyst is deactivated after the polymerization reaction is performed at a pressure within a specific range in the presence of a catalyst. Addition of an agent suppresses lactide sublimation during the polymerization reaction, improves productivity, and suppresses the regeneration of lactide, resulting in extremely low lactide content, hydrolysis resistance, and long-term storage quality A polylactic acid plasticizer excellent in stability can be obtained. Furthermore, the polylactic acid plasticizer obtained by the production method of the present invention is excellent in compatibility with polylactic acid and can be suitably used as a plasticizer for polylactic acid. By blending polylactic acid plasticizer obtained by the production method of the present invention with polylactic acid, using existing equipment used for general-purpose resins, extrusion molding, injection molding, inflation molding, laminate molding, press molding, etc. It is possible to form a sheet, a film, a container, etc. by various methods. Since the obtained molded product has excellent flexibility and impact resistance, it can be used in a wider field than before. As specific applications, for example, as film applications, bags such as garbage bags, plastic bags, general-standard bags, packaging materials for agricultural use, food use, industrial use, textile use, miscellaneous goods, binding tape, As agricultural multi-films, sheets, and injection molding, it is useful as agricultural, food, industrial sheets, trays, sundries, food containers, seedling pots, industrial materials, industrial products, and the like.

The plasticizer in the present invention is a polylactic acid plasticizer produced by a polymerization reaction between lactide and polyether glycol. The lactide of the present invention is a cyclic dimer of lactic acid, and lactic acid has optical isomers of L-lactic acid and D-lactic acid. The cyclic dimer lactide is also D-lactide, L-lactide, Although the meso-lactide optical isomer exists, the purity of the lactide optical isomer in the present invention is not particularly limited. The polylactic acid plasticizer of the present invention can control resin properties such as the melting point and crystallization temperature of the obtained polylactic acid plasticizer by adjusting the purity of the optical isomer of lactide. From the viewpoint of increasing the melting point of the polylactic acid-based plasticizer, imparting high crystallinity, or compatibility with polylactic acid, the lactide used preferably contains 75% by weight or more of L-lactide, more preferably 90% by weight or more.

The polyether glycol in the present invention is not particularly limited, and examples thereof include polyethylene glycol, polypropylene glycol, polybutylene glycol, polypentanediol, polytetramethylene glycol, and block copolymers thereof. As for the above-mentioned polyether glycol component, only 1 type may be used and 2 or more types may be used together. Among these, polyethylene glycol is particularly preferable from the viewpoints of compatibility with polylactic acid, flexibility of the obtained molded product, and impact resistance.
The number average molecular weight of the polyether glycol is not particularly limited, but is preferably 2000 to 20000 from the viewpoint of flexibility and hydrolysis resistance of a molded product when a polylactic acid plasticizer is used as a plasticizer for polylactic acid. More preferably, it is 5000-10000. If the number average molecular weight is less than 2,000, hydrolysis resistance may decrease, and if the number average molecular weight exceeds 20,000, flexibility may be inferior.

The amount of such polyether glycol added is preferably 5 to 80% by weight, more preferably 30 to 80% by weight based on the polylactic acid-based plasticizer obtained from the viewpoint of compatibility with polylactic acid and flexibility. 70% by weight, more preferably 40 to 60% by weight. If it is less than 5% by weight, the impact resistance and flexibility may not be sufficient, and if it exceeds 80% by weight, the compatibility with polylactic acid and the biodegradability of the polylactic acid plasticizer may decrease. is there.
The water content of lactide and polyether glycol in the production method of the present invention is not particularly limited, but from the viewpoint of improving the polymerization reaction rate, it is preferable that at least one of lactide and polyether glycol has a water content of 3000 ppm or less. More preferably, both lactide and polyether glycol are 3000 ppm or less, and more preferably, both lactide and polyether glycol are 2000 ppm. When the water content of lactide and polyether glycol exceeds 3000 ppm, part of the polymerization catalyst is deactivated, so the progress of the polymerization reaction is hindered, or part of the lactide is hydrolyzed into lactic acid, resulting in polylactic acid The molecular weight of the plasticizer may decrease.

  The polymerization reaction of lactide and polyether glycol of the present invention must be carried out in the presence of a polymerization catalyst. Although it does not specifically limit as a polymerization catalyst, For example, derivatives, such as tin, zinc, lead, titanium, bismuth, zirconium, germanium, cobalt, can be mentioned, and as a derivative, a metal organic compound, carbonate, an oxide, And halides. From the viewpoint of high molecular weight and good color tone of the polylactic acid-based plasticizer obtained by the polymerization reaction, preferably, tin alkylate, tin chloride, zinc chloride, zinc acetate, lead oxide, lead carbonate, titanium chloride, Titanium alkoxide, germanium oxide alkoxide, and zirconium alkoxide, among which tin alkylate is preferable, and tin octylate is more preferable.

  The addition amount of the polymerization catalyst of the present invention is preferably 0.005 to 0.5% by weight with respect to the polylactic acid plasticizer obtained from the viewpoint of polymerization reactivity. If it is less than 0.005%, the polymerization reaction rate may be slow, and a high molecular weight polylactic acid plasticizer may not be obtained. On the other hand, if it exceeds 0.5%, the decomposition reaction of the polymer is promoted in parallel with the polymerization reaction, so that the color tone of the obtained polylactic acid-based plasticizer may deteriorate or the hydrolysis resistance may decrease. . More preferably, it is 0.02 to 0.3% by weight from the viewpoint of polymerization reaction rate and reaction rate.

  In the present invention, it is necessary to carry out a polymerization reaction of lactide and polyether glycol in the presence of a catalyst at a pressure of more than 101.3 kPa and not more than 304.0 kPa. However, the polymerization reaction here refers to the period from the addition of a polymerization catalyst to lactide and polyether glycol to the addition of a catalyst deactivator.

When the pressure of the polymerization reaction is 101.3 kPa or less, lactide continuously sublimates during the polymerization reaction. Lactide is a highly sublimable compound, and when heated to normal temperature, for example, 110 ° C., about 8% in 2 hours and about 10% in 3 hours are lost from the reaction system due to sublimation. Sublimation of lactide not only reduces the yield of the polymerization reaction, but also the sublimated lactide adheres to the wall of the polymerization reaction vessel, the polymerization reaction vessel and the vacuum pump, the pipe connecting the condenser, etc. The efficiency of removing lactide and low molecular weight substances from the polymer under reduced pressure cannot be reduced, and the amount of lactide in the polylactic acid-based plasticizer cannot be reduced. As long as the pressure during the polymerization reaction is in the range of more than 101.3 kPa and not more than 304.0 kPa, it may be constant or may vary, but the yield of the polymerization reaction and the resistance of the polylactic acid-based plasticizer to be obtained From the viewpoint of hydrolyzability, the pressure during the polymerization reaction is preferably higher than the vapor pressure of lactide at the polymerization reaction temperature, specifically, it is preferably in the range of more than 101.3 kPa and 250.0 kPa or less. More preferably, it is more than 101.3 kPa and 160.0 kPa or less.
The polymerization reaction temperature is not particularly limited, but is preferably 100 to 180 ° C. from the viewpoint of polymerization reactivity and hydrolysis resistance of the obtained polylactic acid plasticizer. More preferably, it is 145-170 degreeC from the point of the molecular weight fall suppression by heat deterioration. If the temperature exceeds 180 ° C., the polymerization-cyclization equilibrium of lactide is biased toward the cyclization side, the equilibrium concentration of lactide becomes extremely high, and the resulting polylactic acid plasticizer has hydrolysis resistance and quality stability during long-term storage. May decrease. In order to suppress hydrolysis of lactide and polyether glycol and deactivation of the polymerization reaction catalyst, the atmosphere during the polymerization reaction is preferably a dry inert gas, particularly preferably nitrogen or argon gas under pressure. The polymerization reaction time is not particularly limited, but is preferably 1 to 10 hours from the viewpoint of the molecular weight of the polylactic acid plasticizer and the compatibility with polylactic acid.

  In the production method of the present invention, it is necessary to use a catalyst deactivator that reduces the activity of the polymerization catalyst. The type of the catalyst deactivator varies depending on the polymerization catalyst and is not particularly limited, and examples thereof include phosphorus compounds, carboxylic acids and derivatives thereof, sulfuric acid and derivatives thereof, nitric acid and derivatives thereof, and the like. Among these, phosphorus compounds are preferable from the viewpoint of reactivity with the polymerization catalyst and heat resistance of the obtained polylactic acid-based plasticizer and suppression of lactide regeneration, and phosphoric acid, and esters and inorganic metal salts thereof are more preferable. preferable. Specific structures include phosphoric acid, phosphorous acid, monomethyl phosphate, dimethyl phosphate, monoethyl phosphate, diethyl phosphate, monopropyl phosphate, dipropyl phosphate, monoisopropyl phosphate, diisopropyl phosphate, monobutyl phosphate, dibutyl phosphate, monobutyl phosphate Pentyl phosphate, dipentyl phosphate, monohexyl phosphate, dihexyl phosphate, monooctyl phosphate, dioctyl phosphate, monoethylhexyl phosphate, diethylhexyl phosphate, monodecyl phosphate, didecyl phosphate, monoisodecyl phosphate, diisodecyl phosphate, monoundecyl phosphate Decyl phosphate, monododecyl phosphate Fate, didodecyl phosphate, monotetradecyl phosphate, ditetradecyl phosphate, monohexadecyl phosphate, dihexadecyl phosphate, monooctadecyl phosphate, dioctadecyl phosphate, monophenyl phosphate, diphenyl phosphate, monobenzyl phosphate, dibenzyl phosphate, monomethyl Methyl phosphonate, monoethyl ethyl phosphonate, monopropyl propyl phosphonate, mono isopropyl isopropyl phosphonate, monobutyl butyl phosphonate, monopentyl pentyl phosphonate, monohexyl hexyl phosphonate, mono octyl octyl phosphonate, monoethyl hexyl ethyl hexyl phosphonate, monodecyl decyl phosphonate, monoisodecyl Isodecylphosphonate, monoundecylundecylphosphonate, monododecyldodecylphosphonate, monotetradecyltetradecylphosphonate, monohexadecylhexadecylphosphonate, monooctadecyloctadecylphosphonate, monophenylphenylphosphonate, monobenzylbenzylphosphonate, dimethylphosphonate, diethylphosphonate , Dipropyl phosphonate, diisopropyl phosphonate, dibutyl phosphonate, dipentyl phosphonate, dihexyl phosphonate, dioctyl phosphonate, diethyl hexyl phosphonate, didecyl phosphonate, diisodecyl phosphonate, diundecyl phosphonate, didodecyl phosphonate, ditetradecyl phosphonate, dihexadecyl phosphonate, di Examples include octadecyl phosphonate, diphenyl phosphonate, dibenzyl phosphonate, and inorganic metal salts thereof. These may be used alone or in combination of two or more. Among these, phosphoric acid or phosphorous acid is more preferable from the viewpoint of the heat resistance of the polylactic acid plasticizer and the effect of suppressing lactide, and particularly preferably, the purity is 98 from the viewpoint of hydrolysis resistance of the polylactic acid plasticizer. % High purity phosphoric acid or high purity phosphorous acid in a crystalline state.

Although the addition amount of the catalyst deactivator of the present invention is not particularly limited, it is preferably 1 to 20 times the mol of the polymerization catalyst from the viewpoint of reactivity, heat resistance, and hydrolysis resistance. When the addition amount of the catalyst deactivator with respect to the polymerization catalyst is less than 1 mol, the deactivation of the polymerization catalyst may be insufficient or the hydrolysis resistance of the polylactic acid plasticizer may be lowered. On the other hand, if it exceeds 20 moles, the reaction rate of the subsequent batch may decrease due to the residue in the polymerization reaction can when continuously producing the polylactic acid plasticizer. More preferably, it is 3-10 times mole.
Although the temperature which adds the catalyst deactivator in this invention is not specifically limited, 100-190 degreeC is preferable from the point of polymerization reactivity and the hydrolysis resistance of the polylactic acid-type plasticizer obtained. More preferably, it is 145-170 degreeC from the point of the molecular weight fall by heat deterioration and the color tone of a polylactic acid-type plasticizer. If it exceeds 190 ° C., the polylactic acid plasticizer may be thermally deteriorated and the color tone may be deteriorated.
The catalyst deactivation reaction time is not particularly limited, but is preferably 5 minutes to 2 hours from the viewpoint of hydrolysis resistance and color tone of the polylactic acid plasticizer. If it exceeds 2 hours, the color tone of the polylactic acid-based plasticizer may deteriorate.

In the production method of the present invention to remove the residual lactide and the low molecular weight material in the polymer, in order to improve the hydrolysis resistance of the polylactic acid-based plasticizer, after completion of catalyst deactivation reactions, it is an under reduced pressure . Temperature to remove the lactide and the low molecular weight polymer under reduced pressure, lactide was efficiently removed, and, from the point of suppressing the thermal decomposition of the polylactic acid-based plasticizer, and 1 40 ℃ ~200 ℃. Pressure, and 1.33kPa~1.33Pa, decompression time shall be the 30 to 300 minutes.
In the production method of the present invention, the polylactic acid plasticizer in which the residual lactide is reduced by decompression can be taken out from the polymerization can and formed into a desired shape such as a block shape, a sheet shape, a gut shape, or a pellet shape. it can. The molding method is not particularly limited, but in order to avoid moisture absorption of the obtained polylactic acid-based plasticizer, the molten polylactic acid-based plasticizer is taken out in a humidity and temperature controlled atmosphere and quickly cooled and crystallized. Is preferred. When moisture is absorbed, the lactide slightly remaining in the polylactic acid-based plasticizer is hydrolyzed to become lactic acid, which accelerates the hydrolysis of the polymer, and the quality stability of the polylactic acid-based plasticizer during long-term storage may be poor. Since the polylactic acid plasticizer obtained by the polymerization reaction with lactide and polyether glycol has a very high hygroscopic property, it is important to prevent moisture absorption during molding. The atmosphere for taking out the polylactic acid plasticizer after the devolatilization reaction is preferably controlled to a relative humidity of 65% or less, more preferably 50% or less. When the relative humidity is higher than 65%, the polylactic acid plasticizer absorbs moisture during cooling and crystallization, and the storage stability of the polylactic acid plasticizer may be lowered.

  Furthermore, it is preferable to store the polylactic acid-based plasticizer formed into a desired shape such as pellets, sheets, and films in a humidity-controlled atmosphere as in the case of molding.

The number average molecular weight of the polylactic acid type plasticizer obtained by the production method of the present invention, 8 is 000 to 20,000, the compatibility with the polylactic acid, more preferably from flexibility point is 10,000 to 15,000. If the number average molecular weight is less than 8000, the heat resistance may decrease. When the number average molecular weight exceeds 20000, flexibility may be inferior.

The melting point of the polylactic acid-based plasticizer obtained by the production method of the present invention is not particularly limited, but is preferably 120 to 180 ° C, more preferably 130 to 150 ° C from the viewpoint of flexibility and molding processability. If it is lower than 120 ° C, the heat resistance may be inferior, and if it is 180 ° C or higher, flexibility may be reduced.
The amount of residual lactide of the polylactic acid-based plasticizer obtained by the production method of the present invention is 3.0% by weight or less based on the polylactic acid-based plasticizer from the viewpoint of hydrolysis resistance and long-term storage quality stability. Preferably, it is 2.5 wt% or less. If the amount of residual lactide exceeds 3.0%, the hydrolysis resistance of the polylactic acid plasticizer and the quality stability during long-term storage may decrease.

  The polylactic acid plasticizer obtained by the production method of the present invention preferably has an acid value of 120 equivalent / t or less. The acid value increases depending on the amount of lactic acid obtained by hydrolyzing the remaining lactide and the deactivator added excessively to the polymerization catalyst. If the acid value exceeds 120 equivalents / t, the quality stability during long-term storage may deteriorate.

  The water content of the polylactic acid plasticizer obtained by the production method of the present invention is preferably 5000 ppm or less, more preferably 2000 ppm or less, from the viewpoint of hydrolysis resistance and quality stability during long-term storage. If it exceeds 5000 ppm, the quality stability during long-term storage may be poor.

Hereinafter, the present invention will be described in more detail with reference to examples. In addition, the physical-property value in an Example was measured by the method described below.
-Yield The weight of the polylactic acid-type plasticizer taken out from the polymerization reaction can was measured, and the reaction yield was calculated from the following formula (1).

(Weight of polylactic acid-based plasticizer (kg)) / (Total of input amounts of lactide, polyether glycol, polymerization catalyst, catalyst deactivator (kg)) * 100 (1)
(2) Moisture content The moisture content of polyether glycol, lactide, and polylactic acid plasticizer is measured using a Karl Fischer moisture meter MKC-510 (manufactured by Kyoto Electronics Industry Co., Ltd.) at a measurement temperature of 120 ° C. under nitrogen. It was measured.
(3) Number average molecular weight The molecular weight of the polyether glycol and the polylactic acid plasticizer was measured using gel permeation chromatography (GPC) with polystyrene standards.

A tetrahydrofuran solution of polyether glycol or polylactic acid plasticizer adjusted to 0.1% by weight is injected into a gel permeation chromatography (Shimadzu LC-10A) with a column temperature of 30 ° C., and the retention time is determined by RI detection. It was measured. Tetrahydrofuran was used as the solvent, and SHODEX KF-806L and KF-804L manufactured by Showa Denko KK were connected in series as the column. The number average molecular weight was calculated from a calibration curve calculated from the measured retention time and the separately measured retention time of the polystyrene standard.
(4) Melting point The melting point was measured using a differential scanning calorimeter (Seiko Denshi Kogyo RDC220). Using 5 mg of a polylactic acid-based plasticizer, measurement was carried out at a temperature rising rate of 20 ° C./min under 20 to 200 ° C., and the endothermic peak was taken as the melting point. However, when a plurality of endothermic peaks exist, the peak temperature of the endothermic peak on the highest temperature side was taken as the melting point.
(5) Lactide content (a) Adjustment of sample solution About 1 g of pulverized sample was weighed and separately prepared internal standard mother liquor (2,6-dimethyl-γ-pyrone in methylene chloride solution (0.1 mg / ml)) Add 1 ml and fill up to 20 ml with methylene chloride to prepare the lysate. Next, 1 ml of the solution and 3 ml of acetone are weighed in a volumetric flask, and cyclohexane is added dropwise with ultrasonic stirring to fill up. As a result, the block copolymer composed of polylactic acid and polyether glycol precipitates and precipitates, so it is filtered through a disk filter (PTEE 0.45 μm) to prepare a sample solution.

(B) Measurement 1 μl of the sample solution of (a) was injected into a gas chromatograph measuring apparatus (manufactured by Shimadzu Corporation, GC-17A), and the temperature was raised from 80 ° C. to 200 ° C. at a temperature rising rate of 10 ° C./min.
(6) It measured using the acid value neutralization titration method. A 0.2 g sample was weighed and dissolved in chloroform, and then a few drops of an indicator (1% bromophenol red) were dropped and titrated with a 0.02 mol / L ethanolic potassium hydroxide solution. A 0.02 mol / L ethanolic potassium hydroxide solution was titrated until the color changed from orange to blue, and the acid value was calculated using the following formula (2).

[KOHmg / g] = {(A−B) × f × 1/25 × 56.11} / W
Acid value [eq / t] = [KOHmg / g] × 1000 / 56.11 Formula (2)
A: Sample titration (ml)
B: Reagent blank titration (ml)
f: Potency of ethanolic potassium hydroxide solution W: Reagent collection amount (g)
(7) Compatibility with polylactic acid A mixture of 30 parts by weight of a polylactic acid-based plasticizer and 70 parts by weight of a polylactic acid resin (Cargill Dow Co., Ltd .: number average molecular weight 130,000) was dried under reduced pressure at 100 ° C. for 6 hours, and then cylinder temperature 220 The mixture was fed to a biaxial kneading extruder at 0 ° C. and kneaded to obtain a composition formed into pellets. Using the obtained composition, it was formed into a sheet having a thickness of 150 μm by hot pressing at 200 ° C. The obtained sheet was stored at a relative humidity of 65% and a temperature of 25 ° C. for 1 week. The sheet surface (100 cm ² ) after storage was observed with a digital microscope VH (450 times) manufactured by Keyence Corporation, and the number of precipitates of 10 μm or more was used as a compatibility index.

○ ... 0 to 10 precipitates Δ ... 11 to 30 precipitates × ... 30 or more precipitates (8) Long-term storage of polylactic acid plasticizer Quality stability over time The polylactic acid plasticizer was stored for 1 month in a refrigerator with a relative humidity of 65% and 5 ° C. Quality stability was judged from the difference in molecular weight and acid value before and after storage.

  ◎ ・ ・ ・ A decrease in molecular weight after 1 month of storage is less than 10%, and an increase in acid value is less than 10%.

  ○: Molecular weight decrease after 10 months storage is 10% or more and less than 20%, and acid value increase is 10% or more and less than 50%.

  X: The decrease in molecular weight after one month of storage is 20% or more, and the increase in acid value is 50% or more.

Example 1
After adding 59 parts by weight of polyethylene glycol (number average molecular weight: 8300) to the polymerization reaction can, it was heated and melted at 140 ° C., and water was removed at 160 ° C. and 1.33 kPa for 90 minutes with stirring. The water content of polyethylene glycol at this time was 850 ppm.

  Thereafter, the pressure is returned to normal pressure with dry nitrogen, and 41 parts by weight of an L-lactide / D-lactide mixture having a moisture content of 500 ppm (manufactured by Nature Works, L-lactide content 95%) is added and mixed and melted in polyether glycol. I let you. Next, 0.1 part by weight of tin octylate was added as a polymerization catalyst, and a polymerization reaction was carried out at a reaction temperature of 160 ° C. and a reaction pressure of 140.0 kPa.

  After 3 hours from the start of the polymerization reaction, the polymerization reaction was completed, the pressure inside the polymerization reaction vessel was normal, the temperature inside the polymerization reaction vessel was 160 ° C., and 0.1 wt. Part of the mixture was added and stirred for 30 minutes under a dry nitrogen atmosphere to carry out a deactivation reaction of tin octylate as a polymerization catalyst.

  Subsequently, the pressure was reduced to about 1.33 kPa or less over about 10 minutes, and while maintaining this state, the pressure was reduced for 3 hours to remove lactide and the low polymer. Subsequently, the reaction can was returned to normal pressure with dry nitrogen, taken out from the polymerization reaction can in an atmosphere with a relative humidity of 40%, cooled, crystallized, and molded on a pellet to obtain a polylactic acid plasticizer. The yield of the polylactic acid plasticizer was 95.2%.

  The evaluation results of the obtained polylactic acid plasticizer are shown in Table 3. The number average molecular weight was 13500 and the melting point was 139 ° C. The lactide content was as good as 1.8%. The moisture content was 1200 ppm and the acid value was 95 (eq / t).

  A mixture of 30 parts by weight of the obtained polylactic acid plasticizer and 70 parts by weight of a polylactic acid resin (manufactured by Cargill Dow: number average molecular weight 130,000) was dried under reduced pressure at 100 ° C. for 6 hours, and then twin-screw extrusion with a vent at a cylinder temperature of 200 ° C. When kneading was carried out with a machine, there was little adhesion of sublimated lactide to the vent, and kneading was possible without problems. This was formed into a sheet by a hot press, and then stored for 1 week at a relative humidity of 65% and a temperature of 25 ° C. When the presence or absence of precipitates was confirmed on the sheet surface after storage with a microscope (450 times), no precipitates were observed. The polylactic acid plasticizer was stored in a refrigerator at 65% relative humidity and 5 ° C. for 1 month. When the molecular weight and acid value before and after storage were evaluated, the decrease in molecular weight and increase in acid value after storage were less than 10%, and the quality stability during long-term storage was good.

Example 2
A polylactic acid plasticizer is produced in the same manner as in Example 1 except that the high purity phosphoric acid is changed to high purity phosphorous acid and the polymerization reaction pressure is 120 kPa, and then kneaded with polylactic acid to obtain a sheet. It was. The raw material composition and moisture content are shown in Table 1, and the production conditions are shown in Table 2. The evaluation results of the obtained polylactic acid plasticizer are shown in Table 3. The yield, lactide content, moisture content and acid value of the polylactic acid plasticizer were good, and the compatibility with polylactic acid and the quality stability during long-term storage were also excellent.

Example 3
A polylactic acid plasticizer was produced in the same manner as in Example 1 except that polyethylene glycol (number average molecular weight: 8300) was used without being dehydrated. Thereafter, the obtained polylactic acid plasticizer and polylactic acid were kneaded to form a sheet. The evaluation results of the polylactic acid plasticizer are shown in Table 3. Compared with Example 1, although molecular weight became low, the acid value, the compatibility with polylactic acid, and the quality stability at the time of long-term storage were also favorable.

Example 4
A polylactic acid plasticizer was produced in the same manner as in Example 1 except that the optical purity of lactide was 85% L-lactide and polypropylene glycol (number average molecular weight 15000) was used as the polyether glycol. A plasticizer and polylactic acid were kneaded to form a sheet. The evaluation results of the polylactic acid plasticizer are shown in Table 3. The lactide content, moisture content, acid value, quality stability during long-term storage, and compatibility with polylactic acid were good.

Example 5
Addition ratio of lactide and polyethylene glycol, 0.3% by weight of high-concentration phosphoric acid was added, the polymerization reaction pressure was changed to 182.3 kPa, and the polylactic acid plasticizer obtained from the polymerization reaction can was made 60% relative humidity A polylactic acid-based plasticizer was produced in the same manner as in Example 1 except that it was taken out in the atmosphere of, cooled and crystallized. Thereafter, a polylactic acid plasticizer and polylactic acid were kneaded to form a sheet. The evaluation results of the polylactic acid plasticizer are shown in Table 3. The evaluation results of the polylactic acid plasticizer were all good.

Example 6
Using lactide having a moisture content of 2100 ppm and polyethylene glycol, 0.2% by weight of dimethyl phosphate was added as a catalyst deactivator, and the polylactic acid plasticizer obtained from the polymerization reaction can was taken out in an atmosphere with a relative humidity of 70%. A polylactic acid plasticizer was obtained in the same manner as in Example 1 except that it was cooled and crystallized. Thereafter, a polylactic acid plasticizer and polylactic acid were kneaded to form a sheet. The evaluation results of the polylactic acid plasticizer are shown in Table 3. Compared to Example 1, the plasticizer had a lower molecular weight and a higher moisture content, but the evaluation results of the polylactic acid-based plasticizer were all good.

Example 7
A polylactic acid plasticizer was obtained in the same manner as in Example 1 except that 0.2 parts by weight of an aqueous phosphoric acid solution (85% aqueous solution) was added as a catalyst deactivator instead of high-purity phosphoric acid. Thereafter, a polylactic acid plasticizer and polylactic acid were kneaded to form a sheet. The evaluation results of the polylactic acid plasticizer are shown in Table 3. Compared to Example 1, the molecular weight of the polylactic acid plasticizer was low and the lactide content was high, but both the compatibility with polylactic acid and the quality stability during long-term storage were good.

Example 8
A polylactic acid plasticizer was obtained in the same manner as in Example 1, except that 0.05 part by weight of zirconium butanoate was added as a polymerization catalyst. Thereafter, a polylactic acid plasticizer and polylactic acid were kneaded to form a sheet. The evaluation results of the polylactic acid plasticizer are shown in Table 3. Compared with Example 1, the molecular weight of the polylactic acid-based plasticizer was low, but the evaluation results of the polylactic acid-based plasticizer were all good.

Example 9
A polylactic acid-based plastic was produced in the same manner as in Example 1 except that the number average molecular weight of polyethylene glycol was 16000, the addition amount of tin octylate as a polymerization catalyst was 0.4 weight, and the polymerization reaction pressure was changed to 182.3 kPa. An agent was obtained. Thereafter, a polylactic acid plasticizer and polylactic acid were kneaded to form a sheet. The evaluation results of the polylactic acid plasticizer are shown in Table 3. Compared with Example 1, the lactide content and the acid value were higher, but the compatibility with polylactic acid and the quality stability during long-term storage were both good.

Example 10
A polylactic acid plasticizer was obtained in the same manner as in Example 1 except that the addition amount ratio of lactide and polyethylene glycol, the polymerization reaction pressure was changed to 300.0 kPa, and the polymerization reaction temperature was changed to 180 ° C. Thereafter, a polylactic acid plasticizer and polylactic acid were kneaded to form a sheet. The evaluation results of the polylactic acid plasticizer are shown in Table 3. The lactide content, moisture content, quality stability during long-term storage, and compatibility with polylactic acid were good.

Example 11
Polylactic acid was prepared in the same manner as in Example 1, except that 0.8% by weight of tin octylate was added as a polymerization catalyst, and the atmosphere for taking out the polylactic acid plasticizer obtained from the polymerization reaction vessel was set to 50% relative humidity. A plasticizer was obtained. Thereafter, a polylactic acid plasticizer and polylactic acid were kneaded to form a sheet. The evaluation results of the polylactic acid plasticizer are shown in Table 3. Compared with Example 1, the molecular weight of the polylactic acid-based plasticizer was lowered, but the lactide content, moisture content, quality stability during long-term storage, and compatibility with polylactic acid were good.

Comparative Example 1
A polylactic acid plasticizer was obtained in the same manner as in Example 1 except that the pressure during the polymerization reaction was changed to normal pressure (101.3 kPa). The evaluation results of the polylactic acid plasticizer are shown in Table 3. The yield of polylactic acid plasticizer was 73.0%. As a result of confirmation after the polymerization reaction, a large number of lactide sublimates were adhered in the polymerization reaction apparatus. The lactide content of the polylactic acid plasticizer was 4.0%. Quality stability during long-term storage was also poor. When 30 parts by weight of the obtained polylactic acid plasticizer and 70 parts by weight of polylactic acid were kneaded by a twin screw extruder with a vent, kneading was possible, but a sublimate that appeared to be lactide was deposited on the top of the vent. . This was formed into a sheet by a hot press, and then stored for 1 week at a relative humidity of 65% and a temperature of 25 ° C. When the presence or absence of precipitates was confirmed with a microscope (450 times) on the sheet surface after storage, a large number of precipitates were confirmed. The polylactic acid plasticizer was stored in a refrigerator at 65% relative humidity and 5 ° C. for 1 month. When the molecular weight and acid value before and after storage were evaluated, the decrease in molecular weight after storage was 20% or more, and the increase in acid value was 50% or more.

Comparative Example 2
A polylactic acid plasticizer was obtained in the same manner as in Example 1 except that no catalyst deactivator was added. The yield of polylactic acid plasticizer was 75.0%. After completion of the reaction, the inside of the polymerization reaction apparatus was confirmed, and a large amount of lactide sublimate was adhered. Table 1 shows the evaluation results of the obtained polylactic acid plasticizer. The obtained polylactic acid plasticizer had a large amount of residual lactide and was colored yellow. Quality stability during long-term storage was also poor. When 30 parts by weight of the obtained polylactic acid-based plasticizer and 70 parts by weight of polylactic acid were kneaded using a twin screw extruder with a vent, a sublimate that appeared to be lactide was deposited on the top of the vent. The compatibility with polylactic acid was also insufficient.

Claims (7)

In producing a polylactic acid plasticizer having a number average molecular weight of 8000 to 20000 from lactide and polyether glycol, in the presence of a catalyst, a polymerization reaction is performed at a pressure in the range of more than 101.3 kPa and not more than 304.0 kPa. A catalyst deactivator is added, and after completion of the catalyst deactivation reaction, the remaining lactide and low molecular weight substances are removed under reduced pressure conditions of a temperature of 140 ° C. to 200 ° C., a pressure of 1.33 kPa to 1.33 Pa, and a time of 30 to 300 minutes. A process for producing a polylactic acid-based plasticizer characterized by the above. The method for producing a polylactic acid plasticizer according to claim 1, wherein the water content of either lactide or polyether glycol is 3000 ppm or less. The method for producing a polylactic acid plasticizer according to claim 1 or 2, wherein the catalyst deactivator is a phosphorus compound. The method for producing a polylactic acid plasticizer according to claim 3, wherein the phosphorus compound is phosphoric acid and / or phosphorous acid. The polylactic acid-based plasticizer according to any one of claims 1 to 4, wherein after the addition of the catalyst deactivator, the pressure is reduced until the lactide content is 3.0% by weight or less. Production method. The method for producing a polylactic acid plasticizer according to any one of claims 1 to 5, wherein the polyether glycol is polyethylene glycol. The method for producing a polylactic acid plasticizer according to any one of claims 1 to 6, wherein the polylactic acid plasticizer is cooled and crystallized in an atmosphere having a relative humidity of 65% or less.