JP5989946B2 - Method and apparatus for producing stereocomplex polylactic acid molded product - Google Patents

Description

The present invention relates to a method for producing a stereocomplex polylactic acid extrusion to produce a stereocomplex polylactic acid molded article using the optical isomers of polylactic acid.

Polylactic acid (PLA), which is an environmentally friendly plastic, includes L-form poly-L-lactic acid (hereinafter sometimes referred to as “PLLA”) and D-form poly-D-lactic acid (hereinafter referred to as “PDLA”). There are two types of optical isomers), and the natural product L-type PLLA is being put to practical use mainly as a general-purpose plastic. Development to engineering plastics is required to meet a wider range of applications. For this purpose, improvement of the heat resistance and elasticity of PLA is a problem. As a solution, stereocomplex polylactic acid, which is a racemic crystal of PLLA and PDLA, has attracted attention. If stereocomplex polylactic acid can be produced efficiently, the quality of polylactic acid reaches the engineering plastic grade, and it can be used as a structural substrate in a wide range.

At the laboratory level, stereocomplex polylactic acid has been obtained by the casting method and the melting method, but the expression of highly efficient stereocomplex polylactic acid in continuous extrusion as an industrial production method has not been established yet. Only a molding process with low versatility has been proposed in which a post-orientation process is added according to the product form such as highly oriented fibers and highly oriented films. In addition, problems such as molecular weight reduction and coloration due to thermal decomposition during molding, increase in racemic sequence and crystallinity due to transesterification, and production process with low reproducibility are unsolved. The prior art for producing stereocomplex polylactic acid from PLLA and PDLA will be described below.

In order to ensure the quality of the molded product, the stereocomplex polylactic acid needs to have a molecular weight of 100,000 or more. Although it is known that stereocomplex polylactic acid is formed by mixing PLLA and PDLA in a solution state, there is a problem in productivity because it needs to be precipitated from the solution state. In addition, this method is limited to a film-like molded article, and is not a continuous process. Therefore, a heat kneading method has been studied as an industrial production method.

Patent Document 1 describes that stereocomplex polylactic acid can be produced by mixing PLLA and PDLA and performing heat treatment at 270 to 300 ° C. for 0.2 to 60 minutes. However, transesterification and thermal decomposition occur during such high-temperature heat treatment, and the resulting stereocomplex polylactic acid molded product has problems in strength and heat-and-moisture stability, and cannot suppress deterioration in hue.

Patent Document 2 discloses a method for producing a polylactic acid composition by melt-kneading PLLA and PDLA at 230 to 300 ° C. in order to improve transparency, hue, and moist heat resistance. A production method in which a quencher and a carbodiimide compound are added in this order is disclosed. However, there is still a problem that the hue deteriorates and a bad odor occurs.

Patent Document 3 discloses a method of adding an aliphatic amide of a fatty acid and a phosphoric acid ester metal salt at the time of melt-kneading in order to improve hue and hydrolysis resistance. However, problems remain in molecular weight reduction, coloration, and production stability due to thermal decomposition during high temperature molding.

Patent Document 4 discloses a method for producing a film made of stereocomplex polylactic acid. However, this method is specified for film forming and further requires orientation crystallization by stretching.

In Patent Documents 5 and 6, in producing an injection molded product of a stereocomplex body, in order to disperse the nucleating agent in advance from the viewpoint of increasing the dispersibility of the crystal nucleating agent and the crystallization speed, the process (1) poly- It describes that L-lactic acid, poly-D-lactic acid and a nucleating agent are kneaded in the presence of a supercritical fluid to disperse the nucleating agent, and then injected into a mold with an injection molding machine (2). Yes.

However, in the examples, a nucleating agent, poly-L-lactic acid and poly-D-lactic acid are melt-kneaded at 230 ° C. at a high temperature to obtain pellets, and the obtained pellets are super (sub) critical in an injection molding machine. It is only described that they are brought into contact in the presence of carbon dioxide in a state and injected into a mold.
In addition, according to the description of the specification, since gas remains in the injection molded product, as a method of suppressing the expansion ratio of the polylactic acid resin injection molded product, the shape of the resulting injection molded product can be designed to be thin. In order to increase the injection speed or to maintain the supercritical state of the supercritical fluid in the injection mold, it is necessary to pressurize with a gas such as nitrogen gas above the critical pressure of the supercritical fluid in advance. In order to obtain a non-foamed injection-molded product, there is a problem that the shape of the product is limited or a special and complicated device is required to keep the inside of the mold at a high pressure.

As described above, the prior art has a problem that the thermal decomposition and coloring at the time of high-temperature molding, the molding method is limited, and post-oriented crystallization is required, and the product shape is also limited in the injection molding. There is a problem that an apparatus for maintaining the pressure in the injection mold at a high pressure is required.
Thus, there has been a demand for a simple method and apparatus for producing a stereocomplex polylactic acid molded product that has a small hue change due to thermal decomposition.

JP 2006-36808 A JP 2009-249517 A JP 2010-168507 A JP 2010-260900 A JP 2010-006040 A JP 2010-006041 A

The present invention has been made in view of the above problems, and the object of the present invention is to provide a method for manufacturing a simple molded product of stereocomplex polylactic acid with a small hue change and excellent productivity. It is to be.

The invention according to claim 1 supplies poly-L-lactic acid and poly-D-lactic acid to an extruder and press-fits a resin plasticizing gas into the polylactic acid in the extruder in a subcritical or supercritical state. Then, poly-L-lactic acid and poly-D-lactic acid are kneaded in the presence of the resin plasticizing gas, and the resin plasticizing gas is removed from the generated stereocomplex polylactic acid through a vent port provided in the extruder. Stereocomplex polylactic acid produced by producing a temperature of the mold attached to the extruder in the manufacturing method of a stereocomplex polylactic acid extrusion-molded product produced by extrusion molding with a mold attached to the extruder A method for producing a stereocomplex polylactic acid extrusion- molded product characterized by having a melting point of lactic acid or lower .

Hereinafter, the manufacturing method of the stereocomplex polylactic acid of this invention is demonstrated in detail.
In the present invention, poly-L-lactic acid (PLLA) or poly-D-lactic acid (PDLA) refers to a polymer represented by the following formula.

The poly-L-lactic acid of the present invention is preferably a polymer composed of 90 to 100 mol% of L-lactic acid units and 0 to 10 mol% of D-lactic acid units and / or copolymerization component units other than lactic acid. .
The poly-L-lactic acid of the present invention is preferably a polymer composed of 94 to 100 mol% of L-lactic acid units and 0 to 6 mol% of D-lactic acid units and / or copolymer component units other than lactic acid. .
The poly-L-lactic acid of the present invention is more preferably composed of 99.5 to 100 mol% of L-lactic acid units and 0 to 0.5 mol% of D-lactic acid units and / or copolymer component units other than lactic acid. Polymer.
The poly-L-lactic acid of the present invention is more preferably composed of 99.9 to 100 mol% of L-lactic acid units and 0 to 0.1 mol% of D-lactic acid units and / or copolymer component units other than lactic acid. Polymer.
The poly-L-lactic acid of the present invention is most preferably composed of 99.95 to 100 mol% of L-lactic acid units and 0 to 0.05 mol% of D-lactic acid units and / or copolymer component units other than lactic acid. Polymer.

The poly-D-lactic acid of the present invention is preferably a polymer composed of 90 to 100 mol% of D-lactic acid units and 0 to 10 mol% of L-lactic acid units and / or copolymerization component units other than lactic acid. .
The poly-D-lactic acid of the present invention is preferably a polymer composed of 94 to 100 mol% of D-lactic acid units and 0 to 6 mol% of L-lactic acid units and / or copolymer component units other than lactic acid. .
The poly-D-lactic acid of the present invention is more preferably composed of 99.5 to 100 mol% of D-lactic acid units and 0 to 0.5 mol% of L-lactic acid units and / or copolymerization component units other than lactic acid. Polymer.
The poly-D-lactic acid of the present invention is more preferably composed of 99.9 to 100 mol% of D-lactic acid units and 0 to 0.1 mol% of L-lactic acid units and / or copolymer component units other than lactic acid. Polymer.
The poly-D-lactic acid of the present invention is most preferably composed of 99.95 to 100 mol% of D-lactic acid units and 0 to 0.05 mol% of L-lactic acid units and / or copolymer component units other than lactic acid. Polymer.

Optical purity refers to the ratio of lactic acid units of the main optical isomerism in all lactic acid units. The optical purity of the poly-L-lactic acid and poly-D-lactic acid of the present invention is preferably 90% or higher, more preferably 94% or higher, still more preferably 99.5% or higher, still more preferably 99. It is 5% or more, more preferably 99.95% or more.

The copolymer component unit includes units derived from dicarboxylic acid, polyhydric alcohol, hydroxycarboxylic acid, lactone, etc. having functional groups capable of forming two or more ester bonds, and various polyesters and various polyethers composed of these various components. In addition, units derived from various polycarbonates and the like are 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 poly-L-lactic acid and poly-D-lactic acid used in the present invention may be those having various terminal cappings on the terminal groups. Examples of such terminal blocking groups include acetyl groups, ester groups, ether groups, amide groups, urethane groups, and the like.

The weight ratio of mixing poly-L-lactic acid and poly-D-lactic acid in the present invention is 80:20 to 20:80. 75:25 to 25:75 is preferable, 60:40 to 40:60 is more preferable, and it is particularly preferable because the L-lactic acid unit and the D-lactic acid are preferably mixed so as to have an equal amount. Is 50:50.

In the present invention, poly-L-lactic acid is composed of (a) 90 to 100 mol% of L-lactic acid units and 0 to 10 mol% of D-lactic acid units and / or copolymer component units other than lactic acid, and has a melting point of 140. Crystalline polymer A having a weight average molecular weight of 100,000 to 500,000 may be used.
On the other hand, poly-D-lactic acid is composed of (b) 90 to 100 mol% of D-lactic acid units and 0 to 10 mol% of L-lactic acid units and / or copolymer component units. Crystalline polymer B having an average molecular weight of 100,000 to 500,000 may be used.
Polymer A and polymer B are mixed in a weight ratio of 60:40 to 40:60, and particularly preferably 50:50. It is preferable that the L-lactic acid unit and the D-lactic acid are mixed so as to have an equal amount.

The melting points of the crystalline polymers A and B are not limited, but for normal applications, both are 140 to 200 ° C., preferably 150 to 185 ° C., and more preferably 175 to 185 ° C., from the balance of performance and price. Within this range, polymers A and B themselves have high crystallinity, and a stereocomplex polylactic acid having a high melting point and high crystallinity can be obtained.
The weight average molecular weights of the crystalline polymers A and B are preferably 100,000 to 500,000. More preferably, it is 100,000-300,000. The weight average molecular weights of the crystalline polymers A and B are the weight in terms of standard polymethyl methacrylate by gel permeation chromatography (GPC) measurement using hexafluoroisopropanol (containing 1 mol% trifluoroacetic acid sodium salt) as an eluent. Average molecular weight value.

The crystalline polymer A and the polymer B 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.

Poly-L-lactic acid and poly-D-lactic acid, and crystalline polymer A and polymer B can be produced by any known polylactic acid polymerization method, such as ring-opening polymerization of lactide, dehydration condensation of lactic acid, Further, it can be produced by a method combining these and solid phase polymerization.

The method for producing stereocomplex polylactic acid according to claim 1, wherein poly-L-lactic acid and poly-D-lactic acid are supplied to an extruder, and a resin plasticizing gas is fed into the extruder in a subcritical or supercritical state. The poly-L-lactic acid and the poly-D-lactic acid are kneaded into the polylactic acid and kneaded with poly-D-lactic acid in the presence of the resin plasticizing gas, and from the generated stereocomplex polylactic acid through the vent port provided in the extruder The resin plasticizing gas is degassed, and extrusion molding is performed with a mold attached to the extruder to produce an extrusion molded product.
By kneading in the presence of a resin plasticizing gas, poly-L-lactic acid and poly-D-lactic acid are efficiently plasticized in nano order, and the L-lactic acid block in poly-L-lactic acid and in poly-D-lactic acid The D-lactic acid block can be associated at the molecular level to produce stereocomplex polylactic acid.

Examples of the material for the resin plasticizing gas include carbon dioxide, water, nitrogen, methane, ethane, propane, butane, ethylene, propylene, methanol, and ethanol. Carbon dioxide is preferably used from the viewpoint of safety and solubility.

In general, when a liquid is warmed at a pressure lower than the critical pressure (subcritical pressure), a part of the liquid becomes vapor (gas) and the liquid and the gas coexist, that is, a subcritical state. On the other hand, at a pressure higher than the critical pressure (supercritical pressure), this “state where the liquid and the gas coexist” is not observed, and when the liquid is heated, the whole becomes a vapor (gas) at the critical temperature.

For example, carbon dioxide liquefies under temperature and pressure conditions above the triple point (−56.6 ° C., 0.52 MPa). Further, when the temperature and pressure exceed the critical point (31.1 ° C., 7.4 MPa), a supercritical state is obtained, and the characteristics of gas and liquid are combined.

Thus, these gases become a critical fluid having a density and solubility like a liquid and a diffusibility like a gas by making a subcritical state at a certain temperature or higher under a certain pressure. When such a fluid is brought into contact with the resin, particularly when it is injected into the molten resin, the fluid dissolves well in the molten resin and the plasticizing effect is greatly increased, and the fluidity of the molten resin is greatly improved.

In the present invention, the state of the resin plasticizing gas may be either a subcritical state or a supercritical state, but it is preferably used in the subcritical state from the viewpoint of ease of operation in terms of equipment design.
The present invention allows poly-L-lactic acid and poly-D-lactic acid to be nano-ordered by allowing a resin plasticizing gas to act on poly-L-lactic acid and poly-D-lactic acid under supercritical conditions or subcritical conditions. And is made to associate at the molecular level to produce stereocomplex polylactic acid.

In the present invention, when carbon dioxide is used as the resin plasticizing gas, the subcritical state is a state where the temperature is 31.1 ° C. or higher, the pressure is 1.0 MPa or more to less than 7.4 MPa, and the supercritical state is In a state where the temperature is 31.1 ° C. or higher, the pressure is 7.4 MPa or higher.

The amount of the resin plasticizing gas used is not limited, but the resin plasticizing gas is preferably 3 to 20% by weight, more preferably 5 to 5%, based on the total amount of poly-L-lactic acid and poly-D-lactic acid. 10% by weight.

The temperature at which the poly-L-lactic acid and the poly-D-lactic acid are kneaded in the presence of the resin plasticizing gas is not limited as long as kneading is possible, but industrially preferably 150 to 250 ° C. 180-220 ° C is more preferable, and 190-210 ° C is more preferable. This is because if the temperature is too low, the efficiency of plasticization and kneading is poor, and if it is too high, coloring and molecular weight decrease occur.

The order of injection of resin plasticizing gas, mixing of poly-L-lactic acid and poly-D-lactic acid, and kneading is such that poly-L-lactic acid and poly-D-lactic acid are finally in a subcritical or supercritical state. May be kneaded with poly-L-lactic acid and poly-D-lactic acid, kneaded, and a resin plasticizing gas may be injected into the kneaded resin and kneaded. You may knead | mix after inject | pouring gas.
In terms of the structure of the apparatus, the injection system can be made simpler if injection is performed at one place, and when an extruder is used for the apparatus, leakage of the resin plasticizing gas from the rear part of the screw can be prevented. It is preferable to press-fit and knead in a state in which poly-D-lactic acid is mixed and melted.

As an apparatus for kneading poly-L-lactic acid and poly-D-lactic acid in the supercritical state or subcritical state in the presence of a resin plasticizing gas, high pressure can be maintained and warm kneading can be performed, and stereocomplex polylactic acid can be used. Although it is not particularly limited as long as it is a warming kneader with a degassing device that can degas the resin plasticizing gas in the apparatus after formation, the degassing of the resin plasticizing gas is provided in the apparatus while stirring at a predetermined temperature, for example. This can be done by releasing gas from the opening into the atmosphere or forcibly degassing under reduced pressure. As such an apparatus, an extruder with a vent port is preferable from the viewpoint of handling and productivity. In the case of an extruder, a mold is usually attached and the resin is extruded into a certain shape, so that the stereocomplex polylactic acid is produced as an extruded product of the stereocomplex polylactic acid.

As a production apparatus for producing an extruded product of stereocomplex polylactic acid by mixing, melting, and kneading poly-L-lactic acid and poly-D-lactic acid, the cylinder is sequentially moved from the upstream side toward the downstream side, A raw material input port, an injection port for injecting a subcritical or supercritical resin plasticizing gas, and a vent port for separating and removing the resin plasticizing gas from the melted and kneaded stereocomplex polylactic acid are provided. An extruder, a mold for extruding a resin from the extruder attached to the extruder, and a gas supply device for supplying a resin plasticizing gas to the extruder in a subcritical or supercritical state An apparatus for producing an extrusion-molded product of stereocomplex polylactic acid characterized by having: Of course, since it is an extruder, each section is preferably capable of temperature measurement and temperature adjustment. The stereocomplex polylactic acid extrusion molded product here refers to a film / sheet, a strand, a profile extrusion material, and the like.

It is necessary to sufficiently degas the resin plasticizing gas from the stereocomplex polylactic acid produced in the apparatus. This is because if the gas is not degassed, the resin plasticizing gas remains trapped in the stereocomplex polylactic acid molded product from the mold and bubbles remain in the molded product.
Further, when injection molding is performed using the stereocomplex polylactic acid pelletized by cutting the strand-shaped molded product into pellets or the like, bubbles remain in the injection molded product. This is because if bubbles remain in the molded product, quality such as mechanical properties is impaired.

As the extruder with a vent, either a multi-axis or a single-axis can be used. A twin screw extruder is preferred from the viewpoint of kneading efficiency. In addition, it is preferable to provide a plurality of vent ports in order to surely degas after the stereocomplex polylactic acid is produced, and it is also preferable that the venting method be more surely degassed.

The obtained molded product of stereocomplex polylactic acid such as a strand may be used as it is, or may be formed into pellets by a pelletizer or the like and injection molded by a normal injection molding machine without using a plasticizing gas.

This will be described in detail with reference to the drawings. FIG. 1 is a schematic explanatory view showing an example of an extruder 1 used in the present invention. The extruder 1 includes an extruder body 2 (the motor portion of the extruder is not shown), a hopper 3, a cylinder 4, a screw 5, a resin plasticizing gas injection port 6, a resin plasticizing gas injection device 11, and an open vent. It consists of a port 7, a forced exhaust vent port 8, an adapter 9 and a die 10. In the upper part of the extruder 1 in FIG. 1, C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, and C13 indicate the cylinder 4 of the extruder 1 in the length direction. Each of the sections divided into 13 is shown, A is an adapter, and Die is a die (die). The compartments C1 to C13 of the cylinder 4 and adapters, dies, and the like can be independently adjusted in temperature by a heater or the like. Further, apart from the temperature detection sensors for adjusting the temperature provided in the cylinder, adapter 9 and die 10, respectively, holes are formed so as to be close to the inner wall, and the temperature detection sensor is provided near the inner wall in the hole. Therefore, it is possible to detect the resin temperature indirectly (the resin temperature means the indirectly measured temperature unless otherwise specified). The resin plasticizing gas is injected through the resin plasticizing gas injection port 6 by the resin plasticizing gas injection device 11.

The die is not limited, and a strand die, a film die, or the like can be used. When a strand die is used, pelletization can be performed in the line by connecting a pelletizer that cools the strand and then cuts and pelletizes the strand.
It is also possible to insert the temperature measuring unit tip directly into the resin extruded from the die and measure the resin temperature.
The rotation by the motor is decelerated through a speed reducer as necessary, and torque is increased and transmitted to the screw for use.

Using the extruder 1, stereocomplex polylactic acid is produced as follows. Poly-L-lactic acid and poly-D-lactic acid are put into the cylinder 4 from the hopper 3. It is preferable that poly-L-lactic acid and poly-D-lactic acid are previously dried, weighed and mixed. In the sections C1 to C3 of the cylinder 4, the temperature on the downstream side is higher than the upstream side. The poly-L-lactic acid and poly-D-lactic acid that have entered the cylinder 4 are heated by the heat of the heated cylinder 4 and are moved downstream while being mixed and stirred by the screw 5.

In the sections C4 to C6 of the cylinder 4, the temperature is higher than in the sections C1 to C3, and the poly-L-lactic acid and the poly-D-lactic acid are further heated and mixed and stirred and kneaded at a temperature equal to or higher than their melting points. The By making this kneaded and integrated state, even if the resin plasticizing gas is injected after that, gas will no longer leak from the gap between the pellets to the upstream side (hopper side). It is.

Next, a resin plasticizing gas in a supercritical or subcritical state is injected from the resin plasticizing gas injection port 6 provided in the section C7 by the resin plasticizing gas injection device 11. Examples of the resin plasticizing gas injection device 11 include a resin plasticizing gas injection device including a gas cylinder, a pump, and the like provided with an injection valve and a pressure adjustment valve. In the compartments C7 to C10, poly-L-lactic acid and poly-D-lactic acid are further plasticized with a resin plasticizing gas and kneaded to produce stereocomplex polylactic acid. This is presumed to be due to mixing at or near the molecular level or molecular block level. The resin temperature of the part where poly-L-lactic acid and poly-D-lactic acid are kneaded in the presence of a resin plasticizing gas is preferably 180 ° C. or higher and lower than 220 ° C. As will be described later, the generated stereocomplex polylactic acid does not undergo thermal decomposition and does not cause crystallization of a single polymer.

The superplastic or subcritical resin plasticizing gas is gasified and separated and removed from the open vent port 7 provided in the section C11. Furthermore, it is also possible to forcibly exhaust the resin plasticizing gas from the forced exhaust vent port 8 provided in the section C12 by venting at a reduced pressure (eg, gauge pressure 760 mmHg). It should be noted that it is possible to simply open without reducing the pressure forcibly, and it is possible to operate in an open state so that the powdery resin is not clogged.

The stereocomplex polylactic acid from which the resin plasticizing gas has been removed passes through the adapter 9 and is formed into a strand, a film, or the like by the die 10. The die temperature at this time is preferably lower than the melting point of the generated stereocomplex. The moment of exit from the die is presumed to be due to supercooling, low crystal ratio, or small crystals, but extrusion can be performed even below the melting point of the stereo complex. A high torque is required to perform such extrusion stably. The torque value is also related to the melting point of the stereocomplex polylactic acid to be produced and the temperature of the mold. Naturally, if the amount of extrusion increases, a higher torque is required depending on the amount of extrusion. If the margin of the torque value of the extruder is large, stable production with a high extrusion amount is possible. In order to stably extrude stereocomplex polylactic acid at an extrusion rate of 2 to 4 kg / hr, the torque value per screw is preferably 50 N · m or more, more preferably 100 N · m or more. Although there is no particular upper limit, 500 N · m or less is preferable in terms of the structure of the apparatus, the apparatus production cost, and the production cost of the stereocomplex polylactic acid.
The inventors discovered that the melting point of the stereocomplex polylactic acid that generates the die temperature is lower than the melting point of the stereocomplex polylactic acid, but the generated stereocomplex polylactic acid does not give a thermal history at a temperature higher than the melting point. However, the stereocomplex is preferable because it prevents the single polymer from crystallizing. For this reason, it is preferable to extrude at a low temperature with a high torque. Thereafter, the strand may be air-cooled or water-cooled, pelletized by a pelletizer, and used as a raw material for secondary processing.

According to the invention described in claim 1, in the presence of a resin plasticizing gas in which poly-L-lactic acid and poly-D-lactic acid are injected in a subcritical or supercritical state of the resin plasticizing gas, an extruder is used. Since it is kneaded in, poly-L-lactic acid and poly-D-lactic acid can be mixed and associated at the molecular level, and stereocomplex polylactic acid can be produced efficiently. Moreover, since the resin plasticizing gas is degassed from the vent port of the extruder, no bubbles are left in the produced stereocomplex polylactic acid. The hue change is small, the manufacturing is easy, and the manufacturing apparatus is simple.
Since the temperature of the mold attached to the extruder is equal to or lower than the melting point of the generated stereocomplex polylactic acid, crystallization of a single polymer from the stereocomplex occurring at a high temperature can be easily and efficiently suppressed.

It is typical explanatory drawing which shows an example of the extruder used for this invention. 2 is a WAXD chart of pellets obtained in Example 1. FIG. 7 is a WAXD chart of resin recovered from a section C11 in Example 2. FIG. 6 is a WAXD chart of resin recovered from an adapter in Example 2. FIG. 4 is a WAXD chart of pellets obtained in Comparative Example 1. FIG. 6 is a WAXD chart of pellets obtained in Example 3. FIG. 6 is a WAXD chart of pellets obtained in Comparative Example 2. FIG. 6 is a DSC chart of pellets obtained in Example 4. FIG. It is a chart of WAXD of the pellet obtained in Example 4. It is a XRD chart figure of the film which hot-pressed the pellet obtained in Example 4. FIG. It is a chart of WAXD after annealing the film which heat-pressed the pellet obtained in Example 4. FIG. It is the DSC chart figure of the pellet and raw material which were obtained in Example 6. FIG. 7 is a WAXD chart of pellets and raw materials obtained in Example 6.

Hereinafter, the present invention will be further described with reference to examples of the present invention.

As poly-L-lactic acid (PLLA), an optical purity of 99.5%, TM = 180 ° C., Mn = 130,000, Mw = 338,000, Mw / Mn = 2.6, manufactured by Musashino Chemical Laboratory, Inc. I used something. Here, optical purity refers to the ratio of lactic acid units of the main optical isomerism in all lactic acid units. That is, if it is poly-L-lactic acid, the ratio of the L-lactic acid unit in all the lactic acid units is shown. Poly-D-lactic acid (PDLA) manufactured by Toyobo Co., Ltd. with an optical purity of 99.5%, TM = 180 ° C., Mn = 106,000, Mw = 238,000, Mw / Mn = 2.5 used.

PLLA and PDLA were mixed at a weight ratio of 1: 1, charged into the hopper 3 of the twin-screw extruder 1 shown in FIG. 1, and extruded. The temperature of the section C1 of the cylinder 4 was set to 130 ° C, the temperature of the section C2 was set to 170 ° C, the temperature of the section C3 was set to 190 ° C, and the temperatures of the sections C4 to C6 were set to 240 ° C. The temperatures of the sections C7 to C13 were adjusted so that the actually measured resin temperature was 205 ° C. The temperature of the adapter and the die was set to 210 ° C, but at 210 ° C, the crystallization of the stereocomplex polylactic acid might suddenly progress in the adapter and the die. In this case, the load on the motor that rotates the screw of the extruder rapidly increases. In this case, the temperature of the adapter and the die was increased to 220 ° C., and the formation of the stereocomplex polylactic acid in the adapter and the die was moderated.

Although the rotation by the vector inverter motor was via a reduction gear, the reduction ratio was set to 1: 1, so that it was not substantially reduced and used for the rotation of the screw of the extruder. As described above, the rated output of the motor is 75 KW, the rated rotational speed is 2000 rpm, the rated torque is 358 N · m, and the maximum torque per screw is 179 N · m because of the twin-screw extruder. When the motor was overloaded during extrusion, the motor current could reach as high as 330 A, and stable operation was performed at 236 A. At that time, the rotational speed was 100 rpm, and the torque was 256 N · m per two screws.
Incidentally, the torque T (kgf · m) = 975 P (kW) / N (rpm) is obtained by further converting to N · m. Dividing this value by the number of screws in the extruder gives the torque value per screw.

High-pressure carbon dioxide was injected from the resin plasticizing gas injection port 6 provided in the section C7 by the resin plasticizing gas injection device 11. The amount of carbon dioxide was 10 parts by weight with respect to 100 parts by weight of the resin. In compartments C7 to C10, carbon dioxide was injected into the kneaded mixture of PLLA and PDLA and melt kneaded. Carbon dioxide was gasified and separated and removed from the open vent port 7 provided in the section C11. Further, carbon dioxide was forcibly exhausted from the forced exhaust vent port 8 provided in the section C12. The strand from which the carbon dioxide had been removed was extruded from the die 10 (single hole having a hole diameter of 4 mm) through the adapter 9. The strand had a diameter of about 3 mm, and was cut with a pelletizer to obtain pellets. The pellets were not yellowed.

In addition, the diameter of the screw of the twin screw extruder 1 was 30 mm, and the total length from the sections C1 to C13 was 1800 mm. The screw rotation speed of the twin screw extruder 1 was 100 rpm. The amount of extrusion was 4 kg / hr, and the pressure measured in section C9 was 5.0 MPa. Therefore, the resin was melted and kneaded in the subcritical state of carbon dioxide.

In order to investigate the crystal structure and crystallinity of the obtained pellets, WAXD (wide angle X-ray diffraction) was performed.
As a measuring apparatus for WAXD, Rigaku 2500VHF manufactured by Rigaku Corporation was used. Measurement was performed at 2θ = 10 ° to 30 ° and a speed of 4 ° / min with a CuKα X-ray light source (wavelength 0.154 nm, voltage 40 kV, 40 A). The obtained chart is shown in FIG. In FIG. 2, the horizontal axis is 2θ (°), and the vertical axis is intensity (diffraction intensity). From this, it was found that the pellets obtained by extrusion molding produced only stereocomplex polylactic acid and no single polymer crystals existed.
The reason for the determination as described above is as follows.
The diffraction peaks seen in the vicinity of 2θ = 12, 21, and 24 ° are peaks specific to polylactic acid stereocomplex polylactic acid. Stereocomplex polylactic acid is formed in the obtained pellet. When a single polymer crystal is formed, a strong diffraction peak is observed at around 16 °, but it is not observed in the obtained pellet. Therefore, it can be seen that a stereocomplex was selectively formed in the obtained pellet.
Moreover, as a result of comparing the area of the diffraction peak derived from the crystal and the area of the halo peak derived from the amorphous to determine the crystallinity, the area ratio was 1: 1, so the crystallinity was 50%. there were.
Moreover, when the hue of the pellet was observed, no significant change in hue was observed as compared with PLLA and PDLA which were raw materials, and the pellet was milky white.
As a result of measuring the melting point by DSC, the melting point determined from the peak temperature was 220 ° C. Since the melting point of the single polymer crystal of each raw material was 180 ° C., 220 ° C. is due to the formation of stereocomplex polylactic acid. Details of the melting point measurement method by DSC will be described later.

The same poly-L-lactic acid (PLLA) and poly-D-lactic acid (PDLA) as in Example 1 were used. PLLA and PDLA were mixed at a weight ratio of 1: 1, charged into the hopper 3 of the same twin-screw extruder 1 used in Example 1, and extruded. The temperature of the section C1 of the cylinder 4 was set to 130 ° C, the temperature of the section C2 was set to 170 ° C, the temperature of the section C3 was set to 190 ° C, and the temperatures of the sections C4 to C6 were set to 240 ° C. The temperatures of the sections C7 to C13 were adjusted so that the actually measured resin temperature was 205 ° C. Adapter and die temperatures were set between 210 ° C and 220 ° C.

Carbon dioxide in a critical fluid state was injected from the resin plasticizing gas injection port 6 provided in the section C7 by the resin plasticizing gas injection device 11. The amount of carbon dioxide was 10 parts by weight with respect to 100 parts by weight of the resin. In sections C7 to C10, poly-L-lactic acid (PLLA) and poly-D-lactic acid (PDLA) were mixed and melt-kneaded, and carbon dioxide was injected and kneaded. Carbon dioxide was exhausted and removed from the open vent port 7 provided in the section C11. Further, carbon dioxide was forcibly exhausted from the forced exhaust vent port 8 provided in the section C12. The resin from which carbon dioxide was removed was passed through the adapter 9 and formed into a strand with the die 10. The strand diameter was about 3 mm.

The screw rotation speed of the twin screw extruder 1 was 100 rpm, and the extrusion rate was 4 kg / hr. The pressure measured in the section C7 was 4.9 MPa, the pressure measured in the section C9 was 4.7 MPa, and the pressure measured between the section C13 and the adapter was 2.4 MPa. Therefore, the resin was melted and kneaded in the subcritical state of carbon dioxide.

When the above extrusion molding is performed stably in a steady state, in order to observe the state of stereocomplex polylactic acid formation in the extruder, the extruder is stopped, the screw wrapped with resin is taken out, and the screw is removed from the screw. The resin wound around the cylinders corresponding to the sections C1 to C13 was quickly peeled off and collected. Similarly, the resin in the adapter was also collected.

In order to investigate the crystal structure and crystallinity of the collected resin, WAXD (wide angle X-ray diffraction) was performed. The apparatus and conditions used for WAXD are the same as those in the first embodiment.
FIG. 3 is a chart of the resin recovered from the section C11.
From this figure, it was found that in the section C11, the ratio of stereocomplex polylactic acid and homopolymer crystals was stereocomplex polylactic acid: monopolymer crystals = 2: 1. In the course of the extrusion process, formation of a sufficiently selective stereocomplex polylactic acid has not been achieved.
The reason for the determination as described above is as follows.
The diffraction peaks seen in the vicinity of 2θ = 12, 21, 24 ° are peaks characteristic of stereocomplex polylactic acid. On the other hand, a strong diffraction peak is observed in the vicinity of 2θ = 16 °, which is a diffraction peak of a crystal of a single polymer of PLLA and PDLA. From the area ratio of these peaks, it can be seen that the ratio of the crystals of the stereocomplex polylactic acid and the homopolymer is 2: 1.

In addition, the sum of diffraction peak areas of stereocomplex polylactic acid and single polymer crystals (area of diffraction peaks derived from crystals) was compared with the area of halo peaks derived from amorphous to determine the crystallinity, Since the area ratio was 25.8: 74.2, the crystallinity was 25.8%.
As a result of measuring the melting point by DSC, the melting points were 180 ° C. and 220 ° C. 180 ° C. is due to crystals of a single polymer, and 220 ° C. is due to stereocomplex polylactic acid.

FIG. 4 is a chart of the resin recovered from the adapter.
From this figure, it was found that the resin recovered from the adapter produced only stereocomplex polylactic acid and no single polymer crystal was present.
The reason for the determination as described above is as follows.
The diffraction peaks seen in the vicinity of 2θ = 12, 21, and 24 ° are peaks specific to stereocomplex polylactic acid, and the resulting resin is formed of stereocomplex polylactic acid. When a single polymer crystal is formed, a strong diffraction peak is observed at around 16 °, but not in the obtained resin. Therefore, it can be seen that the obtained resin selectively formed stereocomplex polylactic acid.

Moreover, as a result of comparing the area of the diffraction peak derived from stereocomplex polylactic acid with the area of the halo peak derived from amorphous, the crystallinity was found to be 58%.
As a result of measuring the melting point by DSC, the melting point was 220 ° C. 220 ° C. is due to stereocomplex polylactic acid.

(Comparative Example 1)
As poly-L-lactic acid (PLLA) and poly-D-lactic acid (PDLA), the same ones used in Example 1 were used, and PLLA and PDLA were mixed at a weight ratio of 1: 1, and the same as in Example 1 Then, it was put into the hopper 3 of the twin-screw extruder 1 shown in FIG. The temperature of the section C1 of the cylinder 4 was set to 130 ° C, the temperature of the section C2 was set to 170 ° C, the temperature of the section C3 was set to 190 ° C, and the temperatures of the sections C4 to C13 were set to 240 ° C. The adapter and die temperatures were set at 210 ° C.

The carbon dioxide inlet 6 provided in the section C7 was sealed and carbon dioxide was not injected. Both the open vent port 7 provided in the section C11 and the forced exhaust vent port provided in the section C12 were sealed. The resin mixed, melted and kneaded in the sections C1 to C13 was passed through the adapter 9 to extrude the strand from the die 10 and cut with a pelletizer to obtain pellets. The strand diameter was about 3 mm. The pellet was yellowed.

The screw rotation speed of the twin screw extruder 1 was 100 rpm. The extrusion rate was 4 kg / hr.

In order to investigate the crystal structure and crystallinity of the obtained pellets, WAXD (wide angle X-ray diffraction) was performed in the same manner as in Example 1. The apparatus and conditions used for WAXD are the same as those in the first embodiment.
FIG. 5 is a chart of the obtained pellet.

From FIG. 5, it was found that the ratio of stereocomplex polylactic acid to homopolymer crystals in this pellet was stereocomplex polylactic acid: monopolymer crystals = 1: 4.
The reason for the determination as described above is as follows.
The diffraction peaks seen in the vicinity of 2θ = 12, 21, and 24 ° are peaks specific to polylactic acid stereocomplex polylactic acid. On the other hand, a strong diffraction peak is observed around 2θ = 16 °, which is a diffraction peak of a single polymer crystal. From the area ratio of these peaks, it can be seen that the ratio of stereocomplex polylactic acid to homopolymer crystals is 1: 4.

In addition, the sum of diffraction peak areas of stereocomplex polylactic acid and single polymer crystals (area of diffraction peaks derived from crystals) was compared with the area of halo peaks derived from amorphous to determine the crystallinity, Since the area ratio was 21.8: 78.2, the crystallinity was 21.8%.
As a result of measuring the melting point by DSC, the melting points were 180 ° C. and 220 ° C. 180 ° C. is due to homopolylactic acid, and 220 ° C. is due to stereocomplex polylactic acid.

Poly-L-lactic acid (PLLA) manufactured by Shimadzu Corporation with an optical purity of 95.0%, TM = 162 ° C., Mn = 92,000, Mw = 184,000, Mw / Mn = 2.0 is used. did. Poly-D-lactic acid (PDLA) manufactured by Toyobo Co., Ltd. with an optical purity of 99.5%, TM = 180 ° C., Mn = 106,000, Mw = 238,000, Mw / Mn = 2.5 used.
PLLA and PDLA were mixed at a weight ratio of 1: 1, and the mixture was put into the hopper 3 of the twin-screw extruder 1 shown in FIG. The temperature of the section C1 of the cylinder 4 was set to 120 ° C, the temperature of the section C2 was set to 160 ° C, the temperature of the section C3 was set to 180 ° C, and the temperatures of the sections C4 to C6 were set to 205 ° C. The temperatures of the sections C7 to C13 were adjusted so that the actually measured resin temperature was 185 ° C. The adapter and die temperatures were set at 200 ° C.

Carbon dioxide in a critical fluid state was injected from the resin plasticizing gas injection port 6 provided in the section C7 by the resin plasticizing gas injection device 11. The amount of carbon dioxide was 10 parts by weight with respect to 100 parts by weight of the resin. In compartments C7 to C10, resin components such as PLLA, PDLA, and generated stereocomplex polylactic acid and carbon dioxide in a critical state were melted and kneaded. Carbon dioxide was gasified and separated and removed from the open vent port 7 provided in the section C11. Further, carbon dioxide was forcibly exhausted from the forced exhaust vent port 8 provided in the section C12. The resin from which carbon dioxide had been removed was extruded from the die 10 through the adapter 9 and cut with a pelletizer to obtain pellets. The strand diameter was about 3 mm. The pellets were not yellowed.

In addition, the diameter of the screw of the twin screw extruder 1 was 30 mm, and the total length from the sections C1 to C13 was 1800 mm. The screw rotation speed of the twin screw extruder 1 was 100 rpm. The extrusion rate was 4 kg / hr, and the pressure measured in section C9 was 5.2 MPa. Therefore, the resin was melted and kneaded in the subcritical state of carbon dioxide.

In order to investigate the crystal structure and crystallinity of the obtained pellets, WAXD (wide angle X-ray diffraction) was performed. The apparatus and conditions used for WAXD are the same as those in the first embodiment.
FIG. 6 is a chart of the obtained pellet.
From this figure, it was found that the pellets obtained in Example 3 produced only stereocomplex polylactic acid and no single polymer crystals existed.
The reason for the determination as described above is as follows.
The diffraction peaks seen in the vicinity of 2θ = 12, 21, and 24 ° are peaks peculiar to stereocomplex polylactic acid, and the obtained pellets are formed of stereocomplex polylactic acid. When a single polymer crystal is formed, a strong diffraction peak is observed at around 16 °, but it is not observed in the obtained pellet. Therefore, it can be seen that the obtained pellet selectively formed a stereocomplex.
Moreover, as a result of comparing the area of the diffraction peak derived from the crystal and the area of the halo peak derived from the amorphous to determine the crystallinity, the area ratio was 24:76, so the crystallinity was 24%. there were.
As a result of measuring the melting point by DSC, the melting point was 206 ° C. 206 ° C. is due to stereocomplex polylactic acid.

(Comparative Example 2)
As poly-L-lactic acid (PLLA) and poly-D-lactic acid (PDLA), the same one as used in Example 3 was used, and PLLA and PDLA were mixed at a weight ratio of 1: 1. The same thing as what was used was thrown into the hopper 3 of the twin-screw extruder 1 shown in FIG. 1, and extrusion-molded.
The temperature of the section C1 of the cylinder 4 was set to 120 ° C, the temperature of the section C2 was set to 160 ° C, the temperature of the section C3 was set to 240 ° C, and the temperatures of the sections C4 to C6 were set to 240 ° C. The temperatures of the sections C7 to C13 were adjusted so that the actually measured resin temperature was 240 ° C. The adapter and die temperatures were set at 200 ° C.

The carbon dioxide inlet 6 provided in the section C7 was sealed and carbon dioxide was not injected. Both the open vent port 7 provided in the section C11 and the forced exhaust vent port provided in the section C12 were sealed. The resin mixed, melted and kneaded in the sections C1 to C13 was passed through the adapter 9 to extrude the strand from the die 10 and cut with a pelletizer to obtain pellets. The strand diameter was about 3 mm. The pellet was yellowed

The screw rotation speed of the twin screw extruder 1 was 100 rpm, and the extrusion rate was 4 kg / hr.

In order to investigate the crystal structure and crystallinity of the obtained pellets, WAXD (wide angle X-ray diffraction) was performed in the same manner as in Example 1. The apparatus and conditions used for WAXD are the same as those in the first embodiment.
FIG. 7 is a chart of the obtained pellet.

From FIG. 7, it was found that in this pellet, the ratio of stereocomplex polylactic acid to homopolymer crystals was stereocomplex polylactic acid: monopolymer crystals = 3: 1.
The reason for the determination as described above is as follows.
The diffraction peaks seen in the vicinity of 2θ = 12, 21, and 24 ° are peaks specific to polylactic acid stereocomplex polylactic acid. On the other hand, a strong diffraction peak is observed around 2θ = 16 °, which is a diffraction peak of a single polymer crystal. From the area ratio of these peaks, it can be seen that the ratio of the crystals of the stereocomplex polylactic acid and the homopolymer is 3: 1.

In addition, as a result of calculating the degree of crystallinity by comparing the sum of the diffraction peak areas of the stereocomplex crystal and the single polymer crystal (the area of the diffraction peak derived from the crystal) with the area of the halo peak derived from the amorphous, the area The crystallinity was 22.0% because the ratio was 22.0: 78.0.
As a result of measuring the melting point by DSC, the melting points were 170 ° C. and 206 ° C. 170 ° C. is due to single polymer crystals, and 206 ° C. is due to stereocomplex polylactic acid.
It is presumed that the melting point of the single polymer crystal decreased due to the mixture of the low melting point PLLA and the high melting point PDLA.

As poly-L-lactic acid (PLLA), Synbra Technology B.I. V. PLLA 1010 (Mn = 58,000, Mw = 129,000, Mw / Mn 2.2) manufactured by the company was used. The melting point determined from the peak by DSC measurement described later was 182.5 ° C., and the crystallinity was It was 53.3% (crystals of a single polymer) and ΔH was 49.9 (J / g).
As poly-D-lactic acid (PDLA), Synbra Technology B.I. V. PDLA 1010 (Mn = 81,500, Mw = 162,000, Mw / Mn 2.0) manufactured by the company was used. The melting point determined from the peak by DSC measurement described later was 190.2 ° C., and the crystallinity was 63.7% (crystals of a single polymer) and ΔH was 59.7 (J / g).

A mixture of PLLA and PDLA dried in a hot air dryer was mixed at a weight ratio of 1: 1, and charged into the hopper 3 of the twin-screw extruder 1 shown in FIG. The temperature of the section C1 of the cylinder 4 was set to 130 ° C, the temperature of the section C2 was set to 170 ° C, the temperature of the section C3 was set to 190 ° C, and the temperatures of the sections C4 to C6 were set to 240, 240, and 230 ° C. The difference between the set temperature in the section and the actually measured resin temperature is the section C3 in which the measured value is 185 ° C. and the difference is 5 ° C., and the section in which the actually measured resin temperature is 234.6 ° C. with respect to the set temperature of 240 ° C. All except C4 were within 1 ° C.

The temperature of the cylinder part of the sections C7 to C13 was adjusted so that the actually measured resin temperature was 197 to 199 ° C., but in the section C7, the measured value 194.2 ° C. with respect to the set value 198 ° C. In the section C11, there was a difference of 194.5 with respect to the set value 198 ° C., but in the other sections, the difference between the set temperature and the actually measured resin temperature was within 1 ° C.

Carbon dioxide in a critical fluid state was injected from the resin plasticizing gas injection port 6 provided in the section C7 by the resin plasticizing gas injection device 11. The amount of carbon dioxide was 10 parts by weight with respect to 100 parts by weight of the resin. The cylinder pressure of carbon dioxide was 8 MPa, the injection pressure was 13.3 MPa, the internal pressure (valve pressure) was 14 MPa, and the carbon dioxide supply amount was 0.2 kg / hour.

In sections C7 to C10, poly-L-lactic acid (PLLA) and poly-D-lactic acid (PDLA) were mixed and melt-kneaded, and carbon dioxide was injected and kneaded. Carbon dioxide was gasified and separated and removed from the open vent port 7 provided in the section C11. Further, carbon dioxide was forcibly exhausted at a gauge pressure of 760 mmHg from the forced exhaust vent port 8 provided in the section C12, and carbon dioxide was degassed from the generated stereocomplex polylactic acid.
The stereocomplex polylactic acid from which carbon dioxide was removed was extruded from the die 10 through the adapter 9 and cut with a pelletizer to obtain pellets. The strand diameter was about 3 mm.

In Examples 1, 2, and 3, since the current value of the screw rotation motor of the extruder was full of the upper limit of the allowable amperage value, the reduction ratio in Example 4 was increased so that the torque value for rotating the screw could be increased. The torque was halved and improved so that twice the torque was obtained, enabling high torque extrusion. For the rotation by the vector inverter motor, the reduction ratio was set to 1/2 through the reduction gear. Since the rated output of the motor is 75 kW, the rated rotational speed is 2000 rpm, and the rated torque is 358 N · m, the maximum torque per screw is 358 N · m for the twin-screw extruder.
The temperature of the adapter 9 and the die 10 was set to 215 ° C., and the strand was extruded at the resin temperature. The temperature of the resin provided in the adapter and the die was 215 ° C., but the temperature measured by directly sticking the tip of the temperature terminal to the resin extruded from the die was 219 ° C. The rotational speed of the screw was 65 rpm, the current value of the motor was 187 to 193 A, and the rotational torque value per two screws was 206 N · m. A strand having a diameter of about 3 mm was then pelletized with a pelletizer to obtain a pellet. The pellets were not yellowed.
The extrusion rate was 2 kg / hr, and the pressure measured in section C9 was 6.3 MPa. Therefore, it seems that the resin was melted and kneaded in the subcritical state of carbon dioxide.

Using the obtained pellets, injection molding was performed with a normal injection molding machine (Si-80IV manufactured by Toyo Machine Metal Co., Ltd.). Molding and molding are synonymous. However, in the case of injection, the term “molding” is often used for customary purposes. Therefore, molding is used for convenience when explaining the injection in the following examples. Molding conditions are from the screw tip side near the die, HEN (nozzle die side) is 230 ° C, HIN (nozzle cylinder side) is 230 ° C, the cylinder is divided into four, and from H1 H3 is 230 ° C, H4 in the section where the hopper is attached is 40 ° C, mold temperature is 110 ° C, injection position is 42 mm, cooling timer is 180 seconds, filling pressure is 100 MPa, injection speed is 40 mm / sec, The pressure was 50 MPa, the holding time was 10 seconds, the SC rotation speed was 30 rpm, the back pressure was 2 MPa, and the VP switching was 10 mm.
The shape of the injection-molded product was molded into a JISK7113 No. 1 dumbbell shape for a tensile test. The thickness was 3 mm and the width was 10 mm. For the bending test, it was molded into a strip shape for bending test according to JISK7203. The thickness was 5 mm and the width was 12.7 mm.

A tensile test was performed using a tensile test apparatus at a distance between grips of 100 mm and a tensile speed of 5 mm / min.
The tensile strength of the injection molded product was 24.7 MPa.

A bending test was performed with a bending test apparatus at a distance between lower fulcrums of 80 mm.
The bending strength of the injection molded product was 31.0 MPa.

On the other hand, DSC measurement was performed on the pellets obtained by extrusion in the same manner as in Example 1. FIG. 8 shows a chart. The horizontal axis of FIG. 8 is temperature (° C.). The peak was 245.75 ° C. For comparison, the DSC chart of Comparative Example 3 in which carbon dioxide was not injected is also shown in the figure for reference.
WAXD (wide angle X-ray diffraction) was performed by the method described above. The results are shown in FIG. The horizontal axis is 2θ (°). The degree of crystallinity was 52%, and the Sc ratio (ratio of stereocomplex crystals) was 100% (single polymer crystals were 0%).

Moreover, 10 g of the obtained pellets were melted at 250 ° C. using a hot press machine (5 minutes), pressed at 12 to 13 MPa, quenched with water cooling for 5 minutes, and formed into a film.
The crystal structure of this film was analyzed by XRD (X-ray diffraction). The results are shown in FIG. The horizontal axis in FIG. 10 is 2θ (°). It was 100% amorphous.
The film was then annealed at 100 ° C. for 30 minutes. The annealed film was subjected to WAXD (wide angle X-ray diffraction). The results are shown in FIG. The horizontal axis is 2θ (°). The degree of crystallinity was 56%, and the Sc ratio (stereo complex crystal ratio) was 5% (single polymer crystal ratio was 95%).

That is, once the stereocomplex polylactic acid is formed, the single polymer is crystallized by placing it at a high temperature thereafter. Therefore, there is no problem when a stereocomplex polylactic acid molded product is directly extruded by this method, but it is suggested that the conditions must be appropriately selected when performing heat molding such as hot pressing and annealing after extrusion molding. Seems to have been.

Sodium metaphosphate trade name of Taihei Chemical Sangyo Co., Ltd. as a polymerization catalyst inactivator for 100 parts by weight of the total of 1: 1 poly-L-lactic acid and poly-D-lactic acid resin used in Example 4 “Sodium hexametaphosphate” is 0.2%, Nisshinbo Chemical's trade name “Carbodilite LA-1 (registered trademark)” is 0.2% as a hydrolysis inhibitor, and Polylactic acid crystal nucleating agent is manufactured by Nissan Chemical Industries, Ltd. The trade name “Eco Promote (registered trademark)” was added at a rate of 3%, dry blended (hand-mixed), and supplied to the hopper. A stereocomplex polylactic acid was obtained in the same manner as in Example 5 except for the items specifically mentioned below.
In the section C4, there was a difference from the measured value 234.9 ° C. with respect to the set value 240 ° C., but in the other sections, the difference between the set temperature and the measured resin temperature was within 1 ° C.
The cylinder pressure of carbon dioxide was 8.5 MPa, the injection pressure was 11.5 MPa, the internal pressure (valve pressure) was 12 MPa, and the amount of carbon dioxide supplied was 0.2 kg / hour.

The measured temperature of the resin extruded from the die was 218.4 ° C. The number of rotations of the screw was the same 65 rpm, but the current value of the motor was 197 to 203A. The strand was then pelletized with a pelletizer to obtain pellets. The pellets were not yellowed.
The extrusion rate was 2 kg / hr. The pressure measured in the section C9 was 7.2 MPa. Therefore, it seems that the resin was melted and kneaded in the subcritical state of carbon dioxide.
(Comparative Example 3)

The L- and D-polylactic acid resins used in Example 4 were heated and kneaded at a high temperature without injecting carbon dioxide to obtain stereocomplex polylactic acid.
The same procedures as in Example 4 were performed except for the items specifically described below.
The temperature of the section C1 of the cylinder 4 is set to 130 ° C, the temperature of the section C2 is set to 170 ° C, the temperature of the section C3 is set to 190 ° C, the temperature of the section C4 is set to 240 ° C, the sections C5 to C13, the adapter, and the mold are set to 230 ° C. . In section C3, measured value 234.9 ° C. for set value 240 ° C., in section C4, measured value 232.8 ° C. for set value 240 ° C., in section C8, measured value 226.8 ° C. for set value 230 ° C. However, in the other sections, the difference between the set temperature and the actually measured resin temperature was within 1 to 2 ° C.
Carbon dioxide was not injected, and both vent ports were open.
A strand was extruded from the die 10 and then pelletized to obtain pellets.
Screw speed is 65rpm, motor current is 56A, extrusion rate is 2kg / hr
Met. The strand was then pelletized with a pelletizer to obtain pellets.

<Measurement of amount of remaining bubbles in molded product>
Using a density measurement kit manufactured by METTLER TOLEDO, Switzerland, the density of the pellet was determined as an average value of two measurements by the buoyancy method.
The expansion ratio was obtained by dividing the density of the pellet obtained in Comparative Example 3 by the density of the pellet obtained in Example 4. The expansion ratio was 1.00. That is, the pellet obtained in Example 4 was a solid body containing no bubbles, and was completely degassed by the vent.

As poly-L-lactic acid (PLLA), Synbra Technology B.I. V. PLLA 1510 (extrusion grade Mn = 104,000, Mw = 238,000, Mw / Mn = 2.3 as a result of molecular weight measurement described later) was used.
As poly-D-lactic acid (PDLA), Synbra Technology B.I. V. PDLA 1510 (extrusion grade Mn = 72,900, Mw = 157,000, Mw / Mn = 2.2 as a result of molecular weight measurement described below), which is an extrusion grade manufactured by the company, was used.

The same procedure as in Example 4 was performed except for the items specified below using the above raw materials.
The temperature of the section C1 of the cylinder 4 is 130 ° C, the temperature of the section C2 is 170 ° C, the temperature of the section C3 is 190 ° C, the temperature of the section C4 is 240 ° C, the sections C5 and C6 are 230 ° C, and the sections C7 to C13 are 198 ° C. The adapter and mold were set at 215 ° C. In section C3, the measured value 191.2 ° C. for the set value 190 ° C., in section C 7 the measured value 191.8 ° C. for the set value 198 ° C., in section C 8 the measured value for the set value 198 ° C. in section C 9 Although the difference was 201.2 ° C., the difference between the set temperature and the actually measured resin temperature was within 1 to 2 ° C. in the other sections.
The cylinder pressure of carbon dioxide was 7.5 MPa, the injection pressure was 10.8 MPa, the internal pressure (valve pressure) was 11 MPa, and the carbon dioxide supply amount was 0.2 kg / hour.

The number of rotations of the screw was 65 rpm, but the current value of the motor was 149 to 153A. The torque value was 163 N · m per two screws. The strand was then pelletized with a pelletizer to obtain pellets. The pellets were not yellowed.
The extrusion rate was 2 kg / hr. Therefore, it seems that the resin was melted and kneaded in the supercritical state of carbon dioxide.
When DSC was measured by the method described later for the obtained stereocomplex polylactic acid pellets, there was no peak due to single polymer crystals, only a stereocomplex peak was observed, and the melting point determined from the peak value was 239.6 ° C., ΔH Was 85.7 J / g (stereo complex crystals only). The crystals were all stereocomplex crystals, and the crystallinity was 69.1%. FIG. 12 shows a DSC chart. The horizontal axis is temperature (° C.). In the figure, sc1510 represents the obtained stereocomplex polylactic acid.

Incidentally, the melting point of the starting material PLLA1510 was 177.5 ° C., the crystallinity was 44.0%, the melting point of PDLA1510 was 182.0 ° C., and the crystallinity was 53.8%.
WAXD (wide angle X-ray diffraction) was performed by the method described above. The results are shown in FIG. The horizontal axis is 2θ (°). In the figure, sc1510 represents the obtained stereocomplex polylactic acid. The degree of crystallinity obtained from the peak area of this chart was 38%.

The obtained pellets were injection-molded in the same manner as in Example 4 except for the items specified below.
Injection conditions are HEN 230 ° C, HIN, H1-H3 230 ° C, H4 40 ° C, mold temperature 110 ° C, injection position 45mm, cooling timer 230 seconds, filling time 0.75 seconds, filling The pressure was 100 MPa, the injection speed was 50 mm / sec, the holding pressure was 30 MPa, the holding pressure time was 100 seconds, the SC rotation speed was 60 rpm, the back pressure was 3.5 MPa, and the VP switching was 10 mm. The above are the injection conditions set so that the injection molded product crystallizes.

For reference, the injection molded product was also injected under the following conditions.
From the screw tip side where the cylinder temperature is close to the mold, HEN is 230 ° C, HIN, H1 to H3 are 230 ° C, hopper part H4 is 40 ° C, mold temperature is 30 ° C, injection position is 45mm, cooling timer is 40 Seconds, filling time 0.75 seconds, filling pressure 100 MPa, injection speed 50 mm / sec, holding pressure 30 MPa, holding pressure 20 seconds, SC rotation speed 60 rpm, back pressure 3.5 MPa, VP switching Was 10 mm.

The shape of the injection-molded product was molded into a JISK7113 No. 1 dumbbell shape for a tensile test. The thickness was 3 mm and the width was 10 mm. For the bending test, it was molded into a strip shape for bending test of JISK7203. The thickness was 5 mm and the width was 12.7 mm.

A tensile test was performed using a tensile test apparatus at a distance between grips of 100 mm and a tensile speed of 5 mm / min.
The tensile strength of the crystalline injection molded product was 23.2 MPa, and the tensile strength of the amorphous injection molded product was 57.5 MPa.

The elastic modulus was determined by the tensile test. The elastic modulus of the crystalline injection molded product was 3510 MPa, and the elastic modulus of the amorphous injection molded product was 3290 MPa.

A bending test was performed with a bending test apparatus at a distance between lower fulcrums of 80 mm.
The bending strength of the crystalline injection molded product was 35.3 MPa, and the bending strength of the amorphous injection molded product was 61.3 MPa.

For comparison, the raw materials PLLA 1510 alone and PDLA 1510 alone were respectively extruded under the following conditions by the extruder used in Example 4, and pelletized. No injection of carbon dioxide, C1 130 ° C, C2 170 ° C, C3 190 ° C, C4 240 ° C, C5 and C6 230 ° C, C7-C13 198 ° C, adapter and mold 215 ° C Set. The number of revolutions was 65 rpm, the current values were 96 A for PLLA 1510 and 68 A for PDLA 1510, and the extrusion rates were both 2 kg / hr.

The injection conditions for obtaining a crystalline injection-molded product are: HEN 200 ° C, HIN, H1-H3 200 ° C, hopper part H4 40 ° C, mold temperature 110 ° C., injection position 45 mm, cooling timer 150 seconds, filling time 0.75 seconds, filling pressure 100 MPa, injection speed 50 mm / sec, holding pressure 30 MPa, holding pressure 100 seconds, SC rotation The number was 60 rpm, the back pressure was 3.5 MPa, and the VP switching was 10 mm.

On the other hand, the conditions for obtaining an amorphous injection-molded product are as follows: HEN is 200 ° C., HIN, H1 to H3 are 200 ° C., and hopper portion H4 is 40 ° C. Mold temperature is 31 ° C., injection position is 45 mm, cooling timer is 40 seconds, filling time is 0.75 seconds, filling pressure is 100 MPa, injection speed is 50 mm / sec, holding pressure is 30 MPa, holding pressure time is 20 seconds, The SC rotation speed was 60 rpm, the back pressure was 3.5 MPa, and the VP switching was 10 mm.

The extruded products of these raw material resins alone were also subjected to a tensile test and a bending test in the same manner as the stereocomplex polylactic acid.
Furthermore, a comparative test was conducted with respect to Izod and the deflection temperature under load. However, in the injection molded product, no particular advantage was found in the stereo complex with respect to mechanical properties. It is presumed that the product once pelletized through extrusion was injection-molded at a cylinder temperature of 230 ° C.

On the other hand, a tensile test was performed on the strand (diameter: about 3 mm) of the stereocomplex polylactic acid obtained by extrusion in Example 6 without being pelletized. The tensile strength was 34 MPa.

<Change in molecular weight due to stereocomplex polylactic acid production>
1) The molecular weight was measured by the following method.
Polymer weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw / Mn): polymer weight average molecular weight and number average molecular weight are measured by gel permeation chromatography (GPC), standard polymethacryl Converted to methyl acid.
GPC measurement was performed with the following apparatus and conditions.
Pump: LC10AD manufactured by Shimadzu Corporation
Detector: RID-10A manufactured by Shimadzu Corporation
Analysis device: GPC for Windows (registered trademark)
(Detection data A / D converter (data output device): pico ADC-216)
Column: SHODEX HFIP-806 column Hexafluoroisopropanol (containing 5 mM sodium trifluoroacetate) as eluent, temperature 40 ° C, flow rate 0.6 ml / min, concentration 10 mg / ml
10 μl of the sample was injected and measured.

2) Measurement result 1
Molecular weight poly-L-lactic acid (PLLA) before extrusion molding of Examples 1 and 2: Mn = 130,000. Mw = 338,000.
Mw / Mn = 2.6
Poly-D-lactic acid (PDLA): Mn = 106,000. Mw = 238,000.
Mw / Mn = 2.5
Molecular weight Mn = 108,000 after extrusion molding (pellet) in Example 1. Mw = 310,000.
Mw / Mn = 2.8
Molecular weight Mn of the resin recovered from the adapter of Example 2 = 102,000. Mw = 256,000.
Mw / Mn = 2.6
As a result, it can be determined that there is no decrease in molecular weight during the production of stereocomplex polylactic acid.

3) Measurement result 2
Molecular weight poly-L-lactic acid (PLLA) before extrusion molding of Example 3: Mn = 92,000. Mw = 184,000.
Mw / Mn = 2.0
Poly-D-lactic acid (PDLA): Mn = 106,000. Mw = 238,000.
Mw / Mn = 2.5
Molecular weight Mn after extrusion molding (pellet) of Example 3 = 110,000. Mw = 264,000.
Mw / Mn = 2.4
As a result, it can be determined that there is no decrease in molecular weight during the production of stereocomplex polylactic acid.

Molecular weight poly-L-lactic acid (PLLA) before extrusion molding of Example 4: Mn = 58,000. Mw = 129,000.
Mw / Mn = 2.2
Poly-D-lactic acid (PDLA): Mn = 81,500. Mw = 162,000.
Mw / Mn = 2.0
Molecular weight Mn after extrusion (pellet) in Example 4 = 52,200. Mw = 94,000.
Mw / Mn = 1.8

Molecular weight poly-L-lactic acid (PLLA) before extrusion molding of Comparative Example 3: Mn = 58,000. Mw = 129,000.
Mw / Mn = 2.2
Poly-D-lactic acid (PDLA): Mn = 81,500. Mw = 162,000.
Mw / Mn = 2.0
Molecular weight Mn after extrusion molding (pellet) of Comparative Example 3 = 55,000. Mw = 101,000.
Mw / Mn = 1.8

Molecular weight poly-L-lactic acid (PLLA) before extrusion molding of Example 6: Mn = 104,000. Mw = 238,000. Mw / Mn = 2.3
Poly-D-lactic acid (PDLA): Mn = 72,900. Mw = 157,000.
Mw / Mn = 2.2
Molecular weight Mn after extrusion molding (pellet) of Example 6 = 67,400. Mw = 134,000.
Mw / Mn = 2.0

<Melting point of stereocomplex polylactic acid obtained>
The melting point of the obtained stereocomplex polylactic acid was determined from the peak top of the DSC, but again, it was 220 ° C. for Example 1 and Example 2, 206 ° C. for Example 3, and 245 for Example 4. It was .75 ° C. and 239.6 ° C. in Example 6.
The DSC measurement was performed as follows.
DSC: manufactured by Shimadzu Corporation, DSC-50
Sample adjustment: Weigh out 5.0 mg of sample and adjust using an aluminum pan.
Measurement conditions: Measurement was carried out at a heating rate of 10 ° C./min in a nitrogen gas flow of 20 ml / min.
The cause of the difference in melting point of the stereocomplex polylactic acid among the examples is not clear, but it seems to be related to the difference in the optical purity of the raw material and the crystallinity and crystal size of the stereocomplex polylactic acid produced. It is considered that stereocomplex polylactic acid having a high melting point was obtained by using polylactic acid having high optical purity.

<Coloring by molding>
The hue of the pellet was measured with a visible spectrophotometer for colorimetry, and coloring was examined.
A high-speed colorimeter C-2000S manufactured by Hitachi, Ltd. was used for the measurement.
A 5 mm thick pellet was placed in a glass 5 mm cylinder, a reflector was placed on the back, and the reflected light was measured using an integrating sphere. The light source was D65 and the viewing angle was 10 °.
L * a * b * was measured, but b * was used for evaluation of the degree of yellowing.
b * is 5.91 for PLLA used in Example 4, 5.07 for PDLA, 5.80 for the stereo complex obtained in Example 4, using the same raw materials as in Example 4, and without injecting carbon dioxide. The stereocomplex obtained in Comparative Example 3 molded at high temperature was 7.70. That is, it was also shown as a measured value that yellowing is smaller when the production method according to the present invention in which carbon dioxide is injected and molded at a low temperature is used.

According to the method for producing stereocomplex polylactic acid of the present invention, the resulting stereocomplex polylactic acid has a high melting point, a small hue change, and excellent productivity. The method for producing a stereocomplex polylactic acid molded product of the present invention is suitable as a method for producing a stereocomplex polylactic acid molded product because a stereocomplex polylactic acid molded product is obtained with many stereocomplex components and excellent performance and low cost. Since the production apparatus for stereocomplex polylactic acid of the present invention is simple and excellent in productivity, it is preferably used in a method for producing stereocomplex polylactic acid.

DESCRIPTION OF SYMBOLS 1 Extruder 2 Extruder main body 3 Hopper 4 Cylinder 5 Screw 6 Resin plasticization gas injection port 7 Open vent port 8 Forced exhaust vent port 9 Adapter 10 Die 11 Resin plasticization gas injection device

Claims (1)

Presence of the resin plasticizing gas by supplying poly-L-lactic acid and poly-D-lactic acid to an extruder and press-fitting a resin plasticizing gas into the polylactic acid in the extruder in a subcritical or supercritical state Lower poly-L-lactic acid and poly-D-lactic acid were kneaded, the resin plasticizing gas was degassed from the generated stereocomplex polylactic acid through a vent port provided in the extruder, and attached to the extruder In a method for producing an extruded product of a stereocomplex polylactic acid produced by extrusion molding with a mold, the temperature of the mold attached to the extruder is lower than the melting point of the generated stereocomplex polylactic acid. A method for producing a stereocomplex polylactic acid extruded product.