JP2006182926A - Stereocomplex polylactic acid, its production process, composition, and molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high melting point stereocomplex polylactic acid of a high molecular weight and high crystallinity, excellent in molding processability, and to provide its production process, its composition and its molded article. <P>SOLUTION: This stereocomplex polylactic acid comprises (1) a polylactic acid unit A with >99 to 100 mol% L-lactic acid unit and a polylactic acid unit B with 90-99 mol% D-lactic acid unit; or (2) a polylactic acid unit C with >99 to 100 mol% D-lactic acid unit and a polylactic acid unit D with 90-99 mol% L-lactic acid unit, where A and B, or C and D, are each in a specific weight ratio, has a weight-averaged molecular weight of 100,000-500,000, and the ratio of the melting peak ≥205°C is ≥80% among melting peaks in the course of the temperature-raising process in the differential scanning calorimetry (DSC) measurement. Its production process, its composition and its molded article are provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to stereocomplex polylactic acid and a method for producing the same. The present invention also relates to a composition containing the stereocomplex polylactic acid. Furthermore, the present invention relates to a molded article comprising the stereocomplex polylactic acid.

  Plastic products such as polyethylene and polyvinyl chloride are used for food packaging, building materials, home appliances, and other essential products for our daily lives. However, while these plastic products are durable, they remain undecomposed in the natural environment, are discarded as waste, and are a cause of environmental destruction. In recent years, for the purpose of protecting the global environment, biodegradable polymers that are decomposed in a natural environment have attracted attention and are being studied all over the world. As the biodegradable polymer, polyhydroxybutyrate, polycaprolactone, aliphatic polyester and polylactic acid are known, and these can be melt-molded and are expected to be versatile polymers.

  Among these, especially polylactic acid, lactic acid or lactide, which is a raw material of polylactic acid, can be produced from natural products, and is not just a biodegradable polymer, but also a petroleum substitute polymer that is environmentally friendly. And is expected as a versatile polymer.

Biodegradable polymers such as polylactic acid are highly transparent and tough, but they are easily hydrolyzed in the presence of water and, after disposal, decompose without polluting the environment, resulting in low environmental impact. It is a general-purpose resin.
The melting point of polylactic acid is about 170 ° C., but it is not sufficient for use as a general-purpose resin, and further improvement in heat resistance is called out.

  On the other hand, by mixing poly-L-lactic acid (PLLA) consisting only of L-lactic acid units and poly-D-lactic acid (PDLA) consisting only of D-lactic acid units in a solution or in a molten state, a polylactic acid stereocomplex is obtained. It is known that it is formed (see Patent Document 1 and Non-Patent Document 1). This stereocomplex polylactic acid has a higher melting point and higher crystallinity than PLLA and PDLA, and an interesting phenomenon has been discovered.

  However, when producing stereocomplex polylactic acid, if the molecular weights of PLLA and PDLA are 100,000 or more, stereocomplex polylactic acid is difficult to obtain. On the other hand, in order to have practical strength as a molded product, it is necessary that the molecular weight is 100,000 or more. Further, in solution blending, attempts have been made to form a stereocomplex from high molecular weight PLLA and PDLA having a molecular weight of 100,000 or more. However, there is a problem in productivity because it needs to be maintained in a solution state for a long period of time.

  Further, a stereocomplex obtained by melt-blending an amorphous polymer having a molecular weight of about 200,000 having 70 to 95 mol% of L-lactic acid units and an amorphous polymer having a molecular weight of about 200,000 having 70 to 95 mol% of D-lactic acid units. Also disclosed is a method of manufacturing (see Patent Document 2). However, its melting point is about 194 ° C., and there is room for improvement in heat resistance.

As described above, the method for producing high molecular weight stereocomplex polylactic acid using poly-L-lactic acid and poly-D-lactic acid having an optical purity close to 100% has a problem in productivity. On the other hand, when amorphous poly-L-lactic acid and amorphous poly-D-lactic acid having an optical purity of about 70 to 95 mol% are used, although there is no problem in productivity, stereocomplex polylactic acid having a high melting point is obtained. There is a problem that it cannot be obtained.
JP 63-24014 A JP 2000-17163 A Macromolecules, 24, 5651 (1991)

  An object of the present invention is to provide a stereocomplex polylactic acid having a high molecular weight, a high crystallinity and a high melting point, and a method for producing the same, by solving the above-mentioned problems of the prior art and having excellent molding processability. It is in. Another object of the present invention is to provide a composition and a molded product of stereocomplex polylactic acid.

  The inventor of the present invention coexists a specific crystalline polymer mainly composed of L (D) -lactic acid units and a specific crystalline polymer mainly composed of D (L) -lactic acid units at a specific weight ratio. The present inventors have found that a stereocomplex polylactic acid having a high molecular weight, a high crystallinity, and a high melting point can be obtained by heat treatment at a high temperature, and the present invention has been completed.

That is, in the present invention, (A) the L-lactic acid unit is more than 99 mol% and 100 mol% or less, and the D-lactic acid unit and / or the copolymer component unit other than lactic acid is 0 mol% or more and less than 1 mol%. Polylactic acid units A and (B) D-lactic acid units are 90 mol% or more and 99 mol% or less, and L-lactic acid units and / or copolymer component units other than lactic acid are 1 mol% or more and 10 mol% or less. Whether the weight ratio of (A) and (B) is in the range of 10:90 to 90:10,
(C) a polylactic acid unit C in which the D-lactic acid unit is more than 99 mol% and not more than 100 mol%, and the L-lactic acid unit and / or the copolymer component unit other than lactic acid is 0 mol% or more and less than 1 mol% (D) It comprises a polylactic acid unit D in which L-lactic acid units are 90 mol% or more and 99 mol% or less, and D-lactic acid units and / or copolymerization component units other than lactic acid are 1 mol% or more and 10 mol% or less. , (C) and (D) have a weight ratio in the range of 10:90 to 90:10,
A stereocomplex polylactic acid having a weight average molecular weight of 100,000 to 500,000 and having a melting peak at 205 ° C. or higher of 80% or more of melting peaks in a temperature rising process in a differential scanning calorimeter (DSC) measurement. is there.

Further, in the present invention, (A) the L-lactic acid unit is more than 99 mol% and 100 mol% or less, and the D-lactic acid unit and / or the copolymer component unit other than lactic acid is 0 mol% or more and less than 1 mol%. A crystalline polymer A having a melting point of 160 to 180 ° C. and a weight average molecular weight of 100,000 to 500,000,
(B) The D-lactic acid unit is 90 mol% or more and 99 mol% or less, the L-lactic acid unit and / or the copolymer component unit other than lactic acid is 1 mol% or more and 10 mol% or less, and the melting point is 140 to 170. Or a crystalline polymer B having a weight average molecular weight of 100,000 to 500,000 and a weight ratio of (A) to (B) in the range of 10:90 to 90:10,
(C) The D-lactic acid unit exceeds 99 mol% and is 100 mol% or less, the L-lactic acid unit and / or the copolymer component unit other than lactic acid is 0 mol% or more and less than 1 mol%, and the melting point is 160 to 180 ° C., a crystalline polymer C having a weight average molecular weight of 100,000 to 500,000,
(D) The L-lactic acid unit is 90 mol% or more and 99 mol% or less, the D-lactic acid unit and / or the copolymer component unit other than lactic acid is 1 mol% or more and 10 mol% or less, and the melting point is 140 to 170. A crystalline polymer D having a weight average molecular weight of 100,000 to 500,000 and a weight ratio of (C) to (D) in the range of 10:90 to 90:10,
It is a manufacturing method of stereocomplex polylactic acid characterized by heat-processing at 245-300 degreeC.

  Furthermore, this invention includes the composition containing 0.01-10 weight part plasticizer with respect to 100 weight part of said stereocomplex polylactic acid. The present invention also includes a molded article made of the stereocomplex polylactic acid.

  The stereocomplex polylactic acid of the present invention has a high molecular weight, excellent moldability, and excellent heat resistance. According to the production method of the present invention, the stereocomplex polylactic acid can be produced easily and at low cost.

  Hereinafter, the present invention will be described in detail.

<Stereo Complex Polylactic Acid>
The stereocomplex polylactic acid of the present invention comprises a polylactic acid unit A and a polylactic acid unit B, or comprises a polylactic acid unit C and a polylactic acid unit D. The polylactic acid unit A, the polylactic acid unit B, the polylactic acid unit C, and the polylactic acid unit D are mainly composed of an L-lactic acid unit or a D-lactic acid unit represented by the following formula.

(Polylactic acid unit A)
The polylactic acid unit A is mainly composed of L-lactic acid units. A D-lactic acid unit and / or a copolymer component unit other than lactic acid may be included. The L-lactic acid unit is more than 99 mol% and 100 mol% or less. Preferably they are 99.2 mol% or more and 100 mol% or less, More preferably, they are 99.5 mol% or more and 100 mol% or less, More preferably, they are 99.8 mol% or more and 100 mol% or less. The D-lactic acid unit and / or the copolymer component unit other than D-lactic acid is 0 mol% or more and less than 1 mol%. Preferably they are 0 mol% or more and 0.8 mol% or less, More preferably, they are 0 mol% or more and 0.5 mol% or less, More preferably, they are 0 mol% or more and 0.2 mol% or less.

(Polylactic acid unit B)
The polylactic acid unit B is composed of a D-lactic acid unit and an L-lactic acid unit and / or a copolymer component unit other than L-lactic acid. The D-lactic acid unit is 90 mol% or more and 99 mol% or less. Preferably they are 92 mol% or more and 99 mol% or less, More preferably, they are 95 mol% or more and 99 mol% or less. Moreover, L-lactic acid units and / or copolymerization component units other than L-lactic acid are 1 mol% or more and 10 mol% or less. Preferably they are 1 mol% or more and 8 mol% or less, More preferably, they are 1 mol% or more and 5 mol% or less.

(Polylactic acid unit C)
The polylactic acid unit C is mainly composed of D-lactic acid units. L-lactic acid units and / or copolymerization component units other than lactic acid may be included. The D-lactic acid unit is more than 99 mol% and 100 mol% or less. Preferably they are 99.2 mol% or more and 100 mol% or less, More preferably, they are 99.5 mol% or more and 100 mol% or less, More preferably, they are 99.8 mol% or more and 100 mol% or less. Moreover, L-lactic acid units and / or copolymerization component units other than L-lactic acid are 0 mol% or more and less than 1 mol%. Preferably they are 0 mol% or more and 0.8 mol% or less, More preferably, they are 0 mol% or more and 0.5 mol% or less, More preferably, they are 0 mol% or more and 0.2 mol% or less.

(Polylactic acid unit D)
The polylactic acid unit D is composed of an L-lactic acid unit and a D-lactic acid unit and / or a copolymer component unit other than D-lactic acid. The L-lactic acid unit is 90 mol% or more and 99 mol% or less. Preferably they are 92 mol% or more and 99 mol% or less, More preferably, they are 95 mol% or more and 99 mol% or less. The D-lactic acid unit and / or the copolymer component unit other than D-lactic acid is 1 mol% or more and 10 mol% or less. Preferably they are 1 mol% or more and 8 mol% or less, More preferably, they are 1 mol% or more and 5 mol% or less.

  The copolymer component unit is a unit derived from dicarboxylic acid, polyhydric alcohol, hydroxycarboxylic acid, lactone, etc. having a functional group capable of forming two or more ester bonds, and various polyesters, various polyethers composed of these various components, Units derived from various polycarbonates and the like can be used alone or in combination.

  Examples of the dicarboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, terephthalic acid, and isophthalic acid. Examples of polyhydric alcohols include aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, octanediol, glycerin, sorbitan, neopentyl glycol, diethylene glycol, triethylene glycol, polyethylene glycol, and polypropylene glycol. Or aromatic polyhydric alcohol etc., such as what added ethylene oxide to bisphenol, etc. are mentioned. Examples of the hydroxycarboxylic acid include glycolic acid and hydroxybutylcarboxylic acid. Examples of the lactone include glycolide, ε-caprolactone glycolide, ε-caprolactone, β-propiolactone, δ-butyrolactone, β- or γ-butyrolactone, pivalolactone, δ-valerolactone, and the like.

  The weight ratio of the polylactic acid unit A to the polylactic acid unit B is 10:90 to 90:10. It is preferable that it is 25: 75-75: 25, More preferably, it is 40: 60-60: 40. Similarly, the weight ratio of the polylactic acid unit C to the polylactic acid unit D is 10:90 to 90:10. It is preferable that it is 25: 75-75: 25, More preferably, it is 40: 60-60: 40.

  The molar ratio of the L-lactic acid unit and the D-lactic acid unit in the stereocomplex polylactic acid of the present invention can be arbitrarily set in the range of 20:80 to 80:20, preferably from 25:75. 75:25, more preferably 40:60 to 60:40. If the ratio is within this range, a high-melting-point stereocomplex polylactic acid can be produced, but the crystallinity of the stereocomplex polylactic acid is impaired as the ratio deviates from 50:50.

  The weight average molecular weight of the stereocomplex polylactic acid of the present invention is 100,000 to 500,000. More preferably, it is 100,000 to 300,000. The weight average molecular weight is a weight average molecular weight value in terms of standard polystyrene as measured by gel permeation chromatography (GPC) using chloroform as an eluent.

  In the stereocomplex polylactic acid of the present invention, in the differential scanning calorimeter (DSC) measurement of the resin in the glass state, the ratio of the melting peak at 205 ° C. or higher is 80% or higher, preferably 90%, among the melting peaks in the temperature rising process. Above, more preferably 95% or more, and most preferably 100%.

  Melting | fusing point is the range of 205-250 degreeC, More preferably, it is the range of 205-220 degreeC. The melting enthalpy is 20 J / g or more, preferably 30 J / g or more.

  Specifically, in the differential scanning calorimeter (DSC) measurement, the ratio of the melting peak at 205 ° C. or higher of the melting peak in the temperature rising process is 90% or higher, and the melting point is in the range of 205 to 250 ° C., It is preferable that the melting enthalpy is 20 J / g or more.

<Method for producing stereocomplex polylactic acid>
Stereocomplex polylactic acid can be produced by coexisting crystalline polymers A and B in a predetermined weight ratio or coexisting crystalline polymers C and D in a predetermined weight ratio and heat-treating at 245 to 300 ° C. it can.

(Crystalline polymer A)
Crystalline polymer A is mainly composed of L-lactic acid units. It may contain a copolymer component unit other than D-lactic acid units and / or D-lactic acid. The L-lactic acid unit is more than 99 mol% and 100 mol% or less. Preferably they are 99.2 mol% or more and 100 mol% or less, More preferably, they are 99.5 mol% or more and 100 mol% or less, More preferably, they are 99.8 mol% or more and 100 mol% or less. The D-lactic acid unit and / or the copolymer component unit other than D-lactic acid is 0 mol% or more and less than 1 mol%. Preferably they are 0 mol% or more and 0.8 mol% or less, More preferably, they are 0 mol% or more and 0.5 mol% or less, More preferably, they are 0 mol% or more and 0.2 mol% or less.

  Copolymerization component units other than D-lactic acid are composed of units derived from dicarboxylic acids, polyhydric alcohols, hydroxycarboxylic acids, lactones and the like having a functional group capable of forming two or more ester bonds as described above, and various components thereof. Units derived from various polyesters, various polyethers, various polycarbonates and the like can be used alone or in combination.

  The melting point of the crystalline polymer A is 160 to 180 ° C, preferably 165 to 176 ° C. The weight average molecular weight of the crystalline polymer A is 100,000 to 500,000. Preferably it is 100,000-300,000, More preferably, it is 150,000-250,000.

(Crystalline polymer B)
Crystalline polymer B is composed of D-lactic acid units, L-lactic acid units and / or copolymer component units other than lactic acid. The D-lactic acid unit is 90 mol% or more and 99 mol% or less. Preferably they are 92 mol% or more and 99 mol% or less, More preferably, they are 95 mol% or more and 99 mol% or less. Moreover, L-lactic acid unit and / or copolymerization component units other than L-lactic acid are 1 mol% or more and 10 mol% or less. Preferably they are 1 mol% or more and 8 mol% or less, More preferably, they are 1 mol% or more and 5 mol% or less.

  Copolymerization component units other than L-lactic acid are composed of units derived from dicarboxylic acids, polyhydric alcohols, hydroxycarboxylic acids, lactones and the like having a functional group capable of forming two or more ester bonds as described above, and these various components. Units derived from various polyesters, various polyethers, various polycarbonates and the like can be used alone or in combination.

  The melting point of the crystalline polymer B is 140 to 170 ° C, preferably 150 to 160 ° C. Within this range, polymer B itself has high crystallinity, and even when it becomes stereocomplex polylactic acid, a high melting point crystal is formed and the degree of crystallinity is further increased, which is preferable. The weight average molecular weight of the crystalline polymer B is 100,000 to 500,000. Preferably it is 100,000-300,000, More preferably, it is 150,000-250,000.

(Crystalline polymer C)
Crystalline polymer C is mainly composed of D-lactic acid units. The copolymer component unit other than L-lactic acid unit and / or L-lactic acid may be included. The D-lactic acid unit is more than 99 mol% and 100 mol% or less. Preferably they are 99.2 mol% or more and 100 mol% or less, More preferably, they are 99.5 mol% or more and 100 mol% or less, More preferably, they are 99.8 mol% or more and 100 mol% or less. Moreover, L-lactic acid unit and / or copolymerization component units other than L-lactic acid are 0 mol% or more and less than 1 mol%. Preferably they are 0 mol% or more and 0.8 mol% or less, More preferably, they are 0 mol% or more and 0.5 mol% or less, More preferably, they are 0 mol% or more and 0.2 mol% or less.

  Copolymerization component units other than L-lactic acid are composed of units derived from dicarboxylic acids, polyhydric alcohols, hydroxycarboxylic acids, lactones and the like having a functional group capable of forming two or more ester bonds as described above, and these various components. Units derived from various polyesters, various polyethers, various polycarbonates and the like can be used alone or in combination.

  The melting point of the crystalline polymer C is 160 to 180 ° C, preferably 165 to 176 ° C. The weight average molecular weight of the crystalline polymer C is 100,000 to 500,000. Preferably it is 100,000-300,000, More preferably, it is 150,000-250,000.

(Crystalline polymer D)
The crystalline polymer D is composed of L-lactic acid units and D-lactic acid units and / or copolymer component units other than lactic acid. The L-lactic acid unit is 90 mol% or more and 99 mol% or less. Preferably they are 92 mol% or more and 99 mol% or less, More preferably, they are 95 mol% or more and 99 mol% or less. The D-lactic acid unit and / or the copolymer component unit other than D-lactic acid is 1 mol% or more and 10 mol% or less. Preferably they are 1 mol% or more and 8 mol% or less, More preferably, they are 1 mol% or more and 5 mol% or less.

  Copolymerization component units other than D-lactic acid are composed of units derived from dicarboxylic acids, polyhydric alcohols, hydroxycarboxylic acids, lactones and the like having a functional group capable of forming two or more ester bonds as described above, and various components thereof. Units derived from various polyesters, various polyethers, various polycarbonates and the like can be used alone or in combination.

  The melting point of the crystalline polymer D is 140 to 170 ° C., preferably 150 to 160 ° C. Within this range, the polymer D itself has high crystallinity, and even when it becomes stereocomplex polylactic acid, a high melting point crystal is formed and the degree of crystallinity is further increased, which is preferable. The weight average molecular weight of the crystalline polymer D is 100,000 to 500,000. Preferably it is 100,000-300,000, More preferably, it is 150,000-250,000.

  In the method of the present invention, the crystalline polymers A and B are allowed to coexist in a predetermined weight ratio, or the crystalline polymers C and D are allowed to coexist in a predetermined weight ratio, and heat treatment is performed at a predetermined temperature. The case where the crystalline polymers A and B are used will be described below. However, when the crystalline polymers C and D are used, the crystalline polymer A is read as the crystalline polymer C, and the crystalline polymer B is replaced with the crystalline polymer. It shall be read as D.

The crystalline polymers A and B used in the method of the present invention may be those having various end cappings at the end groups. Examples of such terminal blocking groups include acetyl groups, ester groups, ether groups, amide groups, urethane groups, and the like.
The crystalline polymers A and B used in the method of the present invention may contain a catalyst involved in polymerization as long as the thermal stability of the resin is not impaired. As such a catalyst, various tin compounds, titanium compounds, calcium compounds, organic acids, inorganic acids, and the like can be raised, and at the same time, a stabilizer that inactivates them may coexist.
Crystalline polymers A and B can be produced by any known polylactic acid polymerization method, such as lactide ring-opening polymerization, lactic acid dehydration condensation, and a combination of these with solid phase polymerization. can do.

  The coexistence ratio of the crystalline polymers A and B in the method of the present invention is 10:90 to 90:10 by weight, preferably 25:75 to 75:25, more preferably 40:60 to 60:40. If the weight ratio of one is less than 10 or more than 90, homocrystallization is prioritized and it is difficult to form a stereo complex, which is not preferable.

  In the method of the present invention, the method of allowing the crystalline polymer A and the crystalline polymer B to coexist can be any method as long as they are uniformly mixed when heat-treated. Examples of such a method include a method in which the crystalline polymers A and B are mixed in the presence of a solvent and then reprecipitated to obtain a mixture, and a method in which the solvent is removed by heating to obtain a mixture. In this case, it is preferable to prepare a solution in which the polymers A and B are separately dissolved in a solvent and mix them, or to dissolve the polymers A and B together in a solvent and mix them.

  The solvent is not particularly limited as long as the crystalline polymers A and B can be dissolved. For example, chloroform, methylene chloride, dichloroethane, tetrachloroethane, phenol, tetrahydrofuran, N-methylpyrrolidone, N, N -It is preferable to use dimethylformamide, butyrolactone, trioxane, hexafluoroisopropanol or the like alone or in combination.

  The method of removing the solvent by heating is preferable because the solvent can be heated in a solvent-free state after evaporation of the solvent, so that the heat treatment described later can be performed simultaneously. The rate of temperature increase after evaporation of the solvent (heat treatment) is preferably, but not limited to, a short time since there is a possibility of decomposition when heat treatment is performed for a long time.

  As another mixing method, the crystalline polymers A and B can be mixed in the absence of a solvent. That is, a method of melting a predetermined amount of the crystalline polymers A and B and mixing them by kneading can be mentioned. Further, there is a method in which one of the crystalline polymers A and B is melted and the remaining one is added, kneaded, and mixed.

  Further, there is a method in which powders or chips of crystalline polymers A and B having a predetermined size are uniformly mixed and then melted. The size of the powder or chip is not particularly limited as long as the powders or chips of the crystalline polymers A and B are uniformly mixed, but is preferably 3 mm or less, and more preferably 1 to 0.25 mm. It is preferable that

  In the case of melt mixing, a stereocomplex crystal is formed regardless of the size of the powder or chip. However, if the powder or chip is simply melted after being uniformly mixed, the diameter of the powder or chip is 3 mm or more. In this case, homocrystals are also crystallized, which is not preferable.

  In the method of the present invention, as a mixing apparatus used for mixing the crystalline polymers A and B, in the case of mixing by melting, in addition to a reactor with a batch type stirring blade, a continuous reactor, Alternatively, in the case of mixing with a uniaxial extruder or powder, a tumbler type powder mixer, a continuous powder mixer, various milling devices, or the like can be suitably used.

  The method of the present invention is characterized in that the crystalline polymers A and B are mixed in the above weight ratio and heat-treated at 245 to 300 ° C.

  The heat treatment in the production method of the present invention means that the crystalline polymers A and B coexist in the above weight ratio and are maintained in a temperature range of 245 ° C to 300 ° C. The temperature of the heat treatment is preferably 250 to 280 ° C. If it exceeds 300 ° C., it is difficult to suppress the decomposition reaction, which is not preferable. The heat treatment time is not particularly limited as long as the crystalline polymers A and B are uniformly mixed, but is 0.2 to 60 minutes, preferably 1 to 20 minutes. As an atmosphere during the heat treatment, either an inert atmosphere at normal pressure or a reduced pressure can be applied.

  In the method of the present invention, the apparatus and method used for the heat treatment can be any apparatus and method that can be heated while adjusting the atmosphere. For example, a batch reactor, a continuous reactor, biaxial or A single-screw extruder or the like, or using a press machine or a flow tube type extruder, can be processed while being molded.

<Composition>
The composition of the present invention contains 0.01 to 10 parts by weight, preferably 0.1 to 10 parts by weight of a plasticizer with respect to 100 parts by weight of the stereocomplex polylactic acid. Although it does not specifically limit as a plasticizer, A lactide, aliphatic ester, etc. are mentioned.

  The composition of the present invention is a conventional additive, for example, an antioxidant, a light stabilizer, an ultraviolet absorber, a heat stabilizer, a lubricant, a release agent, various fillers, within the range not impairing the object of the present invention. It may contain one or more of antistatic agents, flame retardants, foaming agents, fillers, antibacterial / antifungal agents, nucleating agents, dyes, and colorants including pigments.

<Molded product>
Using the stereocomplex polylactic acid of the present invention, injection molded products, extrusion molded products, vacuum / pressure molded products, blow molded products, films, sheet nonwoven fabrics, fibers, fabrics, composites with other materials, agricultural materials, fishery Materials, civil engineering / building materials, stationery, medical supplies, or other molded articles can be obtained. Molding can be performed by a conventional method.

  For example, after casting a solution containing crystalline polymer A and crystalline polymer B in a solvent at a weight ratio A: B = 10: 90 to 90:10, the solvent is evaporated to form a film. A film can be produced by heat treatment at ˜300 ° C.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Moreover, each value in an Example was calculated | required with the following method.
(1) Reduced viscosity:
0.12 g of the polymer was dissolved in 10 mL of tetrachloroethane / phenol (volume ratio 1/1), and the reduced viscosity (mL / g) at 35 ° C. was measured.
(2) Weight average molecular weight (Mw):
The weight average molecular weight of the polymer was determined by GPC (column temperature 40 ° C., chloroform) in comparison with a polystyrene standard sample.
(3) Crystallization point, melting point, melting enthalpy and proportion of melting peak at 205 ° C. or higher:
Using DSC, measurement was performed under a nitrogen atmosphere at a heating rate of 20 ° C./min, and a crystallization point (Tc), a melting point (Tm), and a melting enthalpy (ΔHm) were determined.

  The ratio (%) of the melting peak at 205 ° C. or higher was calculated from the melting peak area at 205 ° C. or higher (high temperature) and the melting peak area at 140 to 180 ° C. (low temperature) by the following formula.

R _{205 or more} (%) = A _{205 or more} / (A _{205 or more} + A _{140 to 180} ) × 100
R _{205 or higher} : Ratio of melting peak at 205 ° C. or higher
A _{205 or higher} : melting peak area of 205 ° C. or higher
A _140-180 : melting peak area of 140-180 ° C.

(Production Example 1: Production of polymer B ¹ )
1.25 g of L-lactide (Musashino Chemical Laboratory Co., Ltd.) and 48.75 g of D-lactide (Musashino Chemical Laboratory Co., Ltd.) were added to the flask, the inside of the system was replaced with nitrogen, and then 25 mg of tin octylate was added as a catalyst. , 190 ° C., 2 hours, subjected to polymerization to produce a polymer ^{B 1.} The reduced viscosity of the polymer ^{B 1} represents 2.26 (mL / g), a weight average molecular weight 190,000. The melting point (Tm) was 156 ° C. The crystallization point (Tc) was 117 ° C.

(Production Example 2: Production of polymer B ² )
1.25 g of L-lactide (Musashino Chemical Laboratory Co., Ltd.) and 48.75 g of D-lactide (Musashino Chemical Laboratory Co., Ltd.) were added to the flask, and the system was purged with nitrogen. Then, 0.05 g of stearyl alcohol was used as a catalyst. 25 mg of tin octylate was added, and polymerization was performed at 190 ° C. for 2 hours to obtain a polymer. The polymer was washed with acetone solution of 7% 5N hydrochloric acid to remove the catalyst and to obtain a polymer B ^2. The obtained polymer B ^{2 had} a reduced viscosity of 2.71 (mL / g) and a weight average molecular weight of 200,000. The melting point (Tm) was 159 ° C. The crystallization point (Tc) was 132 ° C.

(Production Example 3: Production of Polymer A ¹ )
After adding 50 g of L-lactide (Musashino Chemical Laboratory Co., Ltd.) to the flask and replacing the system with nitrogen, 0.1 g of stearyl alcohol and 25 mg of tin octylate as a catalyst were added, and polymerization was performed at 190 ° C. for 2 hours. to produce a polymer ^{a 1.} Obtained had a reduced viscosity of the polymer ^{A 1} is 2.92 (mL / g), a weight average molecular weight 190,000. The melting point (Tm) was 168 ° C. The crystallization point (Tc) was 122 ° C.

(Production Example 4: Production of the polymer ^{A 2)}
After adding 50 g of L-lactide (Musashino Chemical Laboratory Co., Ltd.) to the flask and replacing the system with nitrogen, 0.1 g of stearyl alcohol and 25 mg of tin octylate as a catalyst were added, and polymerization was performed at 190 ° C. for 2 hours. A polymer was produced. The polymer was washed with acetone solution of 7% 5N hydrochloric acid to remove the catalyst and to obtain a polymer A ^2. The obtained polymer A ^{2 had} a reduced viscosity of 2.65 (mL / g) and a weight average molecular weight of 200,000. The melting point (Tm) was 176 ° C. The crystallization point (Tc) was 139 ° C.

(Production Example 5: Production of polymer D ¹ )
48.75 g of L-lactide (made by Musashino Chemical Laboratory Co., Ltd.) and 1.25 g of D-lactide (made by Musashino Chemical Laboratory Co., Ltd.) were added to the flask, and the inside of the system was purged with nitrogen, then 0.1 g of stearyl alcohol, tin octylate 25mg was added as a catalyst, 190 ° C., 2 hours to produce a polymer ^{D 1} polymerization was conducted. The reduced viscosity of the obtained polymer ^{D 1} is 2.48 (mL / g), a weight average molecular weight 170,000. The melting point (Tm) was 158 ° C. The crystallization point (Tc) was 117 ° C.

(Production Example 6: Production of polymer ^{C 1)}
After adding 50 g of D-lactide (Musashino Chemical Laboratory Co., Ltd.) to the flask and replacing the system with nitrogen, 0.1 g of stearyl alcohol and 25 mg of tin octylate as a catalyst were added, followed by polymerization at 190 ° C. for 2 hours. A polymer was produced. The polymer was washed with acetone solution of 7% 5N hydrochloric acid to remove the catalyst and to obtain a polymer C ^1. The reduced viscosity of the obtained polymer ^{C 1} in 2.80 mL / g, and a weight average molecular weight 220,000. The melting point (Tm) was 168 ° C. The crystallization point (Tc) was 122 ° C.

<Example 1>
An equal amount of a 5% chloroform solution of polymer B ^{1 and} a 5% chloroform solution of polymer A ¹ were mixed and cast into a film, then heated in a nitrogen atmosphere to evaporate the chloroform, and then 280 at 20 ° C./min. The temperature was raised to 0 ° C. and maintained at 280 ° C. for 3 minutes, and then quenched with liquid nitrogen to obtain a film.

The weight average molecular weight of the obtained film was 190,000. DSC measurement was performed on this film. As a result, a melting peak with a melting point of 211 ° C. was observed on the DSC chart, and the melting enthalpy was 51 J / g. The melting peak at 140 to 180 ° C. was not observed, and the ratio of the melting peak at 205 ° C. or higher (R _{205 or higher} ) was 100%. The crystallization point was 99 ° C. This DSC chart is shown in FIG.

<Example 2>
Added polymer ^{B 2} and polymer ^{A 2} eq, to the flask, after nitrogen substitution, the temperature was raised to 260 ° C., 3 minutes at 260 ° C., were melt blended.
The weight average molecular weight of the obtained resin was 160,000, and the reduced viscosity was 2.65 mL / g.
DSC was measured for this resin. As a result, a melting peak with a melting point of 209 ° C. was observed on the DSC chart, and the melting enthalpy was 32 J / g. Although a slight melting peak at 140 to 180 ° C. was observed, the ratio of the melting peak at 205 ° C. or higher (R _{205 or higher} ) was 93%. The crystallization point was 116 ° C.

<Example 3>
The same operation as in Example 2 was performed except that heat treatment was performed at 280 ° C.
The weight average molecular weight of the obtained resin was 160,000, and the reduced viscosity was 2.42 mL / g.
DSC was measured for this resin. As a result, a melting peak with a melting point of 209 ° C. was observed on the DSC chart, and the melting enthalpy was 38 J / g. The melting peak at 140 to 180 ° C. was not observed, and the ratio of the melting peak at 205 ° C. or higher (R _{205 or higher} ) was 100%. The crystallization point was 107 ° C.

<Example 4>
Added polymer ^{C 1} and Polymer ^{D 1} eq, to the flask, after nitrogen substitution, the temperature was raised to 260 ° C., 3 minutes at 260 ° C., were melt blended.
The weight average molecular weight of the obtained resin was 150,000, and the reduced viscosity was 2.35 mL / g.
DSC was measured for this resin. As a result, a melting peak with a melting point of 211 ° C. was observed on the DSC chart, and the melting enthalpy was 31 J / g. Few melting peaks at 140 to 180 ° C. were hardly observed, and the proportion of melting peaks at 205 ° C. or higher (R _{205 or higher} ) was 97%. The crystallization point was 114 ° C.

<Comparative Example 1>
After cast film formation, the same operation as Example 1 was performed except heat-processing at 240 degreeC.
The weight average molecular weight of the obtained film was 190,000. In the DSC chart, a peak derived from the homocrystal and a peak derived from the stereocomplex crystal were observed. _{R205 or more} was 39%.

<Comparative Example 2>
A film was obtained in the same manner as in Example 1 except that poly-L-lactic acid (PLLA) and poly-D-lactic acid (PDLA) shown below were used. The obtained film was subjected to DSC measurement. As a result, a melting peak with a melting point of 173 ° C. and a melting peak with a melting point of 220 ° C. were observed. R _{205 or more} was 40%.

    PLLA: L-lactic acid unit 99.5 mol%, D-lactic acid unit 0.5 mol%, reduced viscosity 2.70 mL / g, weight average molecular weight 250,000, melting point (Tm) 166 ° C., crystallization point (Tc) 125 ° C.

PDLA: D-lactic acid unit 99.3 mol%, L-lactic acid unit 0.7 mol%, viscosity 2.80 mL / g, weight average molecular weight 260,000, melting point (Tm) 168 ° C, crystallization point (Tc) 122 ° C .

  The stereocomplex polylactic acid of the present invention is expected to be used in fields where heat resistance is required.

1 is a DSC chart of a stereocomplex polylactic acid obtained in Example 1. FIG.

Claims (8)

(A) a polylactic acid unit A in which the L-lactic acid unit is more than 99 mol% and not more than 100 mol%, and the D-lactic acid unit and / or the copolymer component unit other than lactic acid is 0 mol% or more and less than 1 mol% (B) A polylactic acid unit B in which D-lactic acid units are 90 mol% or more and 99 mol% or less, and L-lactic acid units and / or copolymerization component units other than lactic acid are 1 mol% or more and 10 mol% or less. The weight ratio of (A) to (B) is in the range of 10:90 to 90:10,
(C) a polylactic acid unit C in which the D-lactic acid unit is more than 99 mol% and not more than 100 mol%, and the L-lactic acid unit and / or the copolymer component unit other than lactic acid is 0 mol% or more and less than 1 mol% (D) It comprises a polylactic acid unit D in which L-lactic acid units are 90 mol% or more and 99 mol% or less, and D-lactic acid units and / or copolymerization component units other than lactic acid are 1 mol% or more and 10 mol% or less. , (C) and (D) have a weight ratio in the range of 10:90 to 90:10,
Stereocomplex polylactic acid having a weight average molecular weight of 100,000 to 500,000 and having a melting peak ratio of 205 ° C. or higher of the melting peak in the temperature rising process of 80% or higher in differential scanning calorimetry (DSC) measurement. In the differential scanning calorimeter (DSC) measurement, the ratio of the melting peak at 205 ° C. or higher in the melting peak in the temperature rising process is 90% or higher, the melting point is in the range of 205 to 250 ° C., and the melting enthalpy is 20 J. The stereocomplex polylactic acid according to claim 1, which is at least / g. (A) The L-lactic acid unit exceeds 99 mol% and is 100 mol% or less, the D-lactic acid unit and / or the copolymer component unit other than lactic acid is 0 mol% or more and less than 1 mol%, and the melting point is 160 to 180 ° C., a crystalline polymer A having a weight average molecular weight of 100,000 to 500,000,
(B) The D-lactic acid unit is 90 mol% or more and 99 mol% or less, the L-lactic acid unit and / or the copolymer component unit other than lactic acid is 1 mol% or more and 10 mol% or less, and the melting point is 140 to 170. Or a crystalline polymer B having a weight average molecular weight of 100,000 to 500,000 and a weight ratio of (A) to (B) in the range of 10:90 to 90:10,
(C) The D-lactic acid unit exceeds 99 mol% and is 100 mol% or less, the L-lactic acid unit and / or the copolymer component unit other than lactic acid is 0 mol% or more and less than 1 mol%, and the melting point is 160 to 180 ° C., a crystalline polymer C having a weight average molecular weight of 100,000 to 500,000,
(D) The L-lactic acid unit is 90 mol% or more and 99 mol% or less, the D-lactic acid unit and / or the copolymer component unit other than lactic acid is 1 mol% or more and 10 mol% or less, and the melting point is 140 to 170. A crystalline polymer D having a weight average molecular weight of 100,000 to 500,000 and a weight ratio of (C) to (D) in the range of 10:90 to 90:10,
A method for producing stereocomplex polylactic acid, wherein the heat treatment is performed at 245 to 300 ° C. In the case of stereocomplex polylactic acid, in the differential scanning calorimeter (DSC) measurement, of melting peaks in the temperature rising process, the proportion of melting peaks at 205 ° C. or higher is 90% or higher, and the melting point is in the range of 205 to 250 ° C. The production method according to claim 3, wherein the melting enthalpy is 20 J / g or more. (I) crystalline polymer A and crystalline polymer B, or (ii) crystalline polymer C and crystalline polymer D are mixed in the presence of a solvent or melt-mixed in the absence of a solvent and heat-treated. The manufacturing method according to claim 3. The composition containing 0.01-10 weight part plasticizer with respect to 100 weight part of stereocomplex polylactic acid of Claim 1. The composition of claim 6 wherein the plasticizer is lactide. A molded article comprising the stereocomplex polylactic acid according to claim 1.

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