JP2864218B2 - Method for producing polylactic acid copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a polylactic acid copolymer, and more particularly to a method for producing a polylactic acid copolymer having excellent physical properties and recyclability.

[0002]

2. Description of the Related Art Biodegradable plastics are decomposed in the natural environment after fulfilling the purpose of use, and finally reduced to the natural world in the form of low molecular compounds.
It is a material that is rapidly gaining attention these days. Above all, aliphatic polyesters are completely decomposed into monomers by microorganisms and water, and eventually incorporated into the natural material cycle as carbon dioxide and water. At the beginning, recently, application development to general-purpose materials that are expected to be disposed of in the environment after use has been started.

Polylactic acid, which is a kind of such an aliphatic polyester-based biodegradable plastic, has excellent decomposing properties and transparency, and has good compatibility with other polymers and is easily modified. In addition, since it is easily decomposed into monomers by a heating operation or addition of a specific solvent, application development of the material as a monomer recyclable material is highly expected.

However, polylactic acid has the following disadvantages in the case of a homopolymer. (1) High rigidity and brittleness (lack of flexibility and elasticity as a product) (2) Low heat resistance (prone to thermal decomposition and oxidative deterioration during molding) (3) High hydrolyticity (during storage) Tends to decrease in molecular weight)

[0005] Therefore, it has been considered difficult to mold and produce a homopolymer polylactic acid as it is to produce a product.

On the other hand, epoxy resins are thermosetting plastics which are widely used as adhesives for structures, anticorrosion coatings, etc. because of their excellent adhesiveness, mechanical properties and electrical properties. In addition, due to its high chemical resistance such as water resistance and chemical resistance, the reliability as a finished part is extremely high, and it is possible to maintain the characteristics as a product for a long period of time. Are showing an increasing trend in the future.

However, on the other hand, having such excellent durability means that the product is not easily decomposed even when the product is discarded after use and remains in nature for a long time. In recent years, as recycling of waste plastic has been strongly urged, urgent measures have been required for the same material.

[0008] Further, since the epoxy resin is a thermosetting material, it cannot be reused by heat melting it or reducing it to a monomer. Therefore, instead of recycling, a process of recovering and gasifying by thermal decomposition, that is, a process of reducing the volume is being studied (Japanese Patent Laid-Open Publication No.
No. 126744). However, this process is only applicable if the epoxy resin is used as a single material. The reason is that the same material is generally used in the form of a composite with another thermoplastic resin, and since the thermal decomposition temperatures of both are very close to 300 to 400 ° C., it is difficult to separate them. It is. There is also a method of separating and recovering only the epoxy resin portion, but it is not an industrially advantageous process because a large amount of solvent is required. For this reason, these epoxy resins also remain as impurities in the recycled thermoplastic resin, and as a result, also contributed to lowering the physical properties of the recycled material.

[0009]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for industrially advantageously producing a plastic which can be recycled after use and has excellent physical and chemical properties. .

[0010]

Means for Solving the Problems In view of such circumstances, the present inventors have conducted intensive studies, and found that a plastic obtained by carboxylating a lactic acid oligomer and using this as an esterifying agent to extend the chain with an epoxy resin, It is excellent in physical and chemical properties such as mechanical strength, and after use, if heated to 200 to 250 ° C, only the polylactic acid component is thermally decomposed, and lactide that can be reused as a polymerization raw material can be produced and recovered. Also, if the remaining thermosetting epoxy resin is heated to 250 to 300 ° C. by an existing method, it can be easily decomposed and reduced in volume, and is excellent in recyclability. completed.

That is, the present invention provides a number average molecular weight of 1,000
An object of the present invention is to provide a method for producing a polylactic acid copolymer, wherein a reaction product of 0 to 5,000 lactic acid oligomers and an acid anhydride is copolymerized with an epoxy resin.

The number average molecular weight used in the present invention is 1,000 to 1,000.
The 5,000 lactic acid oligomer can be obtained by a conventional method, that is, by subjecting lactic acid to a polycondensation reaction under heating and reduced pressure in an inert atmosphere.

Specifically, for example, lactic acid as a raw material is charged into a batch-type reaction tank, the inside of the tank is replaced with nitrogen gas or argon gas, and then a polycondensation reaction is carried out under heating and reduced pressure to obtain lactic acid. Obtain the oligomer.

The lactic acid may be any of optically active forms such as D-form and L-form, or D and L-forms having no optical activity, and mixtures thereof, preferably those having a purity of 85% or more.

The heating temperature is preferably from 90 to 180 ° C.
10-170 ° C is more preferred. If the heating temperature is too low, the reaction does not proceed, while if it is too high, depolymerization occurs and the lactide formation reaction is accelerated, which is not preferable. The reduced pressure level is 0.1 to 100 mmHg, more preferably 1 to 10 mmHg.
Hg range. This is because, when the inside of the reaction tank is in this depressurized range, the azeotropic temperature of lactic acid and water exists in the temperature range described above, and the reaction by-product water is easily distilled off efficiently. . It is difficult to lower the decompression level further (≦ 0.1 mmHg), considering the structure of the reaction tank and the pumping capacity of the pump. It is not appropriate because it could be. Conversely, increase the pressure reduction level (≥100 mmHg)
This is not preferred because the reaction by-product water is less likely to be distilled out of the reaction system.

In the dehydration polycondensation of lactic acid, in order to increase the reaction rate, a reflux pipe is installed in the reaction tank to recover vaporized lactide and low-molecular-weight compounds of lactic acid, and to return to the reaction system again. Perform the operation. At this time, if the temperature in the reflux tube is set to be equal to or lower than the reduced pressure boiling point of lactide and lactic acid as a reaction solution, only water is selectively distilled off.

This reflux tube is made of SUS316 and has an outer diameter of 43
It has a double cylindrical structure with a height of 400 mm and a height of 400 mm. A spiral resistor having a reverse screw direction is provided in the tube, and the temperature in the tube is controlled at 90 to 120 ° C, preferably 95 to 110 ° C by circulating a heating medium or using an electric heater. At this time, the degree of decompression in the reflux tube was set at 0.1 as described above.
Adjust to 1-100 mmHg.

When refluxing lactide, if the temperature in the reflux tube becomes lower than the melting point of lactide, it immediately crystallizes and blocks the tube, so that an appropriate solvent may be used for the purpose of preventing this. Above all, judging from the fact that the reflux operation is easy, the reduced-pressure boiling point (10 mm
Hg; 146 ° C.) (10 mmHg;
114 ° C.), dimethylbenzyl ether (10 mmHg; 1
44 ° C.), benzyl phenyl ether (10 mmHg; 14)
4 ° C.). At this time, the amount of the solvent added is 5 to 30% by weight, preferably 10 to 30% by weight based on the charged amount of the raw materials.
A range of 20% by weight is suitable.

With these solvents, lactide refluxes again into the reaction solution. In order to completely reflux the solvent, a dedicated cooling pipe made of glass (outer diameter: 40 mm, height: 300 mm) is placed above the reflux pipe. , A Dimroth type), and cooling and recovering using cooling water, dry ice, or liquid nitrogen according to the boiling point of the solvent, and then performing a reflux operation.

In the reaction, a catalyst can be used. Examples of the catalyst include stannous chloride, tin octylate, antimony oxide and the like. These catalysts include tetrahydrofuran, ethyl lactate, butyl lactate, chloroform, acetone, xylene, ethanol,
After completely dissolving in a solvent such as benzene, it is desirable to add the reaction solution. If this catalyst addition operation is performed at a stage where the temperature of the reaction solution is high, it acts as a depolymerization catalyst for the lactic acid oligomer which is the reaction solution and causes a decrease in molecular weight. It is necessary to go gradually.

Considering the high toxicity of the catalyst group, manganese acetate, acetoacetylaluminum,
Aluminum acetate, diethyl zinc or the like can be used as a catalyst. The above catalyst is, for example, a catalyst for using manganese acetate to promote the polycondensation reaction, suppressing side reactions during the reaction, and shifting the equilibrium state between the lactic acid polymer / monomer in the reaction solution to the polymer side. It can also be used in an appropriate combination such as using antimony oxide. The amount of the catalyst used is preferably in the range of 0.01 to 1.0% by weight, more preferably 0.1 to 0.5% by weight, based on the raw material lactic acid monomer.

In the batch type reaction vessel, the number average molecular weight is 1,0.
100-5,000 lactate oligomers are obtained. This is because it is difficult to obtain an oligomer having a number average molecular weight exceeding 5,000 in a batch reaction tank in a short time, and for an oligomer having a number average molecular weight of less than 1,000, an acid necessary for carboxylating both terminals in the next step is required. Not only is the amount of the anhydride too large, but the reaction time required to reach the target acid value is prolonged, so that it is not practical as a process.

The reaction between the lactic acid oligomer and the acid anhydride thus obtained is preferably a melting reaction in a nitrogen gas atmosphere. By this reaction, a lactic acid prepolymer in which both terminal groups of the lactic acid oligomer are carboxylated is obtained. As the acid anhydride used at this time, succinic anhydride, phthalic anhydride, maleic anhydride, tetrabromophthalic anhydride,
Tetrahydrophthalic anhydride, trimellitic anhydride, dodecyl succinic anhydride and the like can be mentioned, but taking into account that the toxicity is low and that the boiling point is high and hardly lost during the reaction, succinic anhydride (boiling point: 261 C) or phthalic anhydride (boiling point: 285 C). These addition amounts are adjusted so as to be equimolar to the charged amount of the lactic acid oligomer.

The reaction is carried out at 140-170 ° C. and further at 150-1
More preferably, it is performed at 60 ° C. The reaction time is 1 to 5 hours, and the progress of the reaction is judged by measuring the acid value of the obtained carboxylated lactic acid oligomer. The reaction is completed when the acid value of the reaction solution reaches the theoretical value.
The method of measuring and calculating the acid value at that time and the method of obtaining the theoretical value are as follows.

<Measurement method of acid value> About 1 g of the produced polymer was weighed, dissolved in 20 ml of a toluene / methanol solution at room temperature, a mixed indicator of thymol blue / phenol red was added dropwise thereto, and 0.01N KOH was added. Titrate with isopropyl alcohol solution.

[0026]

(Equation 1)

[0027]

(Equation 2)

In this reaction, the acid anhydride added for carboxylation loses sublimation by heating during the reaction, so that a solvent such as toluene or xylene is added to the reaction solution in an amount of 0.5 to 10% by weight, more preferably. By adding 1 to 5% by weight, it is preferable to perform an operation of sequentially dissolving and liquefying the components and returning them to the reaction system.

The number average molecular weight of the lactic acid prepolymer thus obtained is in the range of 2,000 to 7,000. At this time, if the number average molecular weight is less than 2,000, in the next step of the copolymerization reaction with the epoxy resin,
It is not suitable because the molecular chain of each lactic acid oligomer having both ends carboxylated is too short to obtain a sufficient high molecular weight product. Furthermore, when the number of reactive groups is large, the amount of heat generated by the reaction is large, and an excessive amount of heat supply causes a cross-linking reaction. Further, when trying to obtain a lactic acid prepolymer having a molecular weight exceeding 7,000, a long time is required in the molecular weight range of the lactic acid oligomer (number average molecular weight: 1,000 to 5,000), so that it is not practical. Absent.

The copolymerization reaction between the lactic acid prepolymer having both terminal groups carboxylated and the epoxy resin is preferably carried out under heating in a screw type extruder.

The screw type extruder used in the present invention may be a screw or a screw extruder which is usually used for molding plastics.
A single-screw or twin-screw extruder including a cylinder, a heating unit, and a driving device can be used. Among them, a twin-screw extruder is preferable, and as this device, any of those in which the rotation direction of the screw is the same or different, and those in which the flights of the screw are meshed with each other or not meshed can be used. . In the present invention, a plurality of temperature control units are provided so as to be individually divided so as to be capable of temperature control and provided around the cylinder, and a ratio (L / L) of the screw length (L) to the screw diameter (D) is provided.
It is preferable to use a meshing twin screw type extruder having a D ratio of 30 to 70. By using such a twin-screw extruder with a large number of temperature control units,
This is preferable because temperature control according to the reaction stage can be performed for each of the different zones of the extruder cylinder.

In addition to the exothermic reaction, the amount of heat supplied from the inside of the cylinder and the shearing heat generated as the reaction progresses are added to this reaction, so that the generated polymer is thermally decomposed. May be lost.
Therefore, in order to avoid such a phenomenon, it is necessary to strictly control the cylinder temperature so as to be within the above-mentioned temperature range. Regarding temperature control in the cylinder, a temperature sensor insertion port is installed in the cylinder section, and the temperature of the material inside the cylinder is measured with time using an infrared sensor in a non-contact manner.

The material temperature inside the cylinder is 100 to 160
C is preferable, and 110 to 150 C is more preferable. When the material temperature is lower than 100 ° C., the reaction rate becomes too slow. It is not preferable because a crosslinking reaction which preferentially reacts with a group and eventually generates a gel proceeds.

At this time, a reaction time of about 5 to 15 minutes is sufficient. If the reaction time is long, a cross-linking reaction is likely to occur between the remaining hydroxyl group and epoxy group in the after-mentioned copolymerization reaction, so care must be taken.

The epoxy resin to be used is not particularly limited. For example, Epicoat (made by Yuka Shell), Araldite (made by Ciba Geigy), Epolite (made by Kyoei Chemical), D.I. E. FIG. R. (Manufactured by Dow Chemical Japan), Epomic (manufactured by Mitsui Petrochemical), Sumiepoxy (manufactured by Sumitomo Chemical), Epicron (manufactured by Dainippon Ink and Chemicals), etc. The type and grade can be arbitrarily selected according to the purpose of use. I do. These vary from liquids to pastes and solid powders, and are supplied from a hopper by a feeder or supplied from a solvent injection port provided in a cylinder by a rotary pump or the like according to each shape. I do.

The weight ratio (mixing ratio) of the epoxy resin and the lactic acid prepolymer at that time is adjusted so that the epoxy resin in the epoxy resin has the same chemical equivalent. The method of obtaining the charged amount at that time is as follows.

[0037]

## EQU3 ## Epoxy resin charge (g) = molar number of COOH groups of carboxylated lactic acid oligomer × epoxy equivalent (g)
/ Equiv. ³⁾ Note 3) Average molecular weight of epoxy resin divided by number of epoxy groups per molecule

The epoxy resin can be diluted with a solvent, if necessary, or heated to reduce the viscosity, thereby improving the accuracy of quantitative supply. As the solvent, a solvent having an oxygen atom in the molecule, for example, an appropriate one selected from ketones, esters, ethers, alcohols and the like can be used. The alcohol may be used in the form of a mixed solution with toluene or xylene. In the addition operation at this time, if the epoxy resin is not supplied quantitatively and is mixed unevenly with the lactic acid oligomer, the crosslinking reaction partially proceeds,
Care must be taken because the polymer gels and the value of the product is impaired.

In the reaction, a catalyst can be used for the purpose of bonding the epoxy group and the active hydrogen of the terminal carboxyl group of the lactic acid prepolymer. Examples of the catalyst include benzyldimethylamine (BDMA), triethylbenzylammonium chloride (TEBAC), tetramethylammonium chloride (TMAC), and triphenylphosphine (TPP). The addition amount is 0.005 to 0.2% by weight, and further 0.01 to 0.2% by weight.
A range of 0.1% by weight is preferred.

In the present invention, the screw rotation speed of the screw extruder is also very important in terms of accelerating the epoxidation reaction and suppressing the three-dimensional crosslinking reaction caused by the non-uniform progress of the reaction. Therefore, its rotation speed is 10
It is preferably set in the range of 0 to 300 rpm, particularly 150 to 250 rpm.

Thus, the number average molecular weight is 30,000 to 10
A copolymer of 000 polylactic acid and an epoxy resin is obtained.

Hereinafter, an example of a method for producing a polylactic acid copolymer according to the present invention will be introduced with reference to FIG. 1 attached to the application.

Lactic acid is supplied to a batch-type polymerization reaction tank 1, the temperature of the reaction solution is set to a predetermined temperature, and an inert gas is supplied to a cylinder 2.
The dehydration polycondensation reaction is performed while supplying more. At this time, the inside of the reaction vessel is evacuated using a vacuum pump 4 to produce lactic acid oligomers while collecting / refluxing the produced lactide and low molecular weight lactic acid into the reaction vessel through a reflux pipe 5. At this time, the by-product water not recovered in the reflux pipe is cooled / recovered by the trap 6.

Next, an acid anhydride is added to the lactic acid oligomer 7 in the heat-melted state to carry out a carboxyl grouping reaction. The acid anhydride sublimated in an unreacted state is dissolved in the reflux tube 5 by adding a solvent such as toluene,
Return this to the system again.

When the acid value of the reaction solution reaches the theoretical value, the reaction is terminated, and the obtained lactic acid prepolymer 8 is transferred by the plunger pump 9 to the hopper 11 of the twin screw type extruder 10 which is the next step. Supply a fixed amount.

At the same time, the rotary pump 12
The epoxy resin is supplied from the supply port 13 in a fixed amount. At this time, a catalyst can be added as needed.

The lactic acid prepolymer supplied to the inside of the extruder is copolymerized with the epoxy resin heated at different temperatures for each zone by a plurality of temperature control units in the course of traveling inside the cylinder while being kneaded by the screw. .

As described above, the copolymerization reaction between the epoxy resin and the lactic acid prepolymer in the extruder is performed so as to be completed within the residence time of the apparatus. The copolymer 14 in a molten state generated after the reaction is extruded by a screw, passes through a screen 15, and is further extruded through a die 16. These are stored in the storage tank 17 and formed into final products such as films and containers.

The copolymer of epoxy resin and lactic acid prepolymer obtained as described above is used after 200 to 250
When heated to ℃, only the polylactic acid component is thermally decomposed and can be recovered as lactide which can be reused as a polymerization raw material. Furthermore, if the remaining epoxy resin is heated to 250 to 300 ° C., it is thermally decomposed and the volume can be easily reduced.

[0050]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 10 kg of L-lactic acid was charged into a 14-liter batch polymerization reactor equipped with a stirrer, a thermocouple, a nitrogen gas inlet tube, and a reflux tube, and stannous chloride was used as a catalyst. It was added at a rate of 0.3% by weight. Next, 5-7mm
The reaction temperature was set to 120 to 170 ° C. under a reduced pressure of Hg, and the polycondensation reaction was carried out for about 8 hours, and the number average molecular weight was 4,650.
Of lactic acid oligomer was obtained. 0.15 kg of succinic anhydride was added to 7 kg of this oligomer so as to be equimolar, and a carboxylation reaction was carried out at 150 ° C. under normal pressure so as to approximate a theoretical acid value of 24. When the acid value of the carboxylated lactic acid oligomer obtained after the reaction for about 1.5 hours was measured, the acid value was 23 and the number average molecular weight was 5,220.
At this time, the succinic anhydride sublimated during the reaction is continuously added to the reaction solution while dissolving it in the reflux tube by adding toluene at a ratio of 5% by weight based on the charged amount of the lactic acid oligomer. I put it back inside. Next, this is supplied to a twin-screw extruder as a lactic acid prepolymer,
A copolymerization reaction with the epoxy resin was performed. The extruder used at that time was a meshing type co-rotating twin-screw extruder of L / D 42 and a screw diameter of 32 mm. As shown in FIG. It has. The term “zone” used herein means that different positions of the cylinder can be set to different temperatures, and is not limited to the meaning that each zone is separated. The operating conditions at that time are as follows.

[0052]

[Table 1] (Operating conditions) Raw material supply amount: 2.83 kg / h Screw rotation speed: 150 rpm Cylinder temperature: Zone 1 and 2 = 110 ° C Zone 3 to 11 = 120 to 140 ° C Zone 12, die = 120 ° C

Also, it is attached to zone 2 of the cylinder.
Araldite at a rate of 0.19 kg / h from the supply port
(Epoxy equivalent; 168). At the same time,
TEBAC is used as a catalyst in an amount of 0.01 to epoxy resin.
The copolymerization reaction was performed while adding at a ratio of weight%. So
Reaction time in the extruder at the time of
Calculated by the time) was about 15 minutes. After the reaction,
The basic characteristics of the copolymer discharged from the extruder were examined.
On the other hand, the number average molecular weight was 52,640. This polymer
Heat-pressed to form a film, and its mechanical strength
When the degree was measured, the tensile strength was 1.82 kgf / mm.
^TwoAnd the elongation was 185%. In addition, the film after use
Is heated to 220 ° C and pyrolyzed.
It is theoretically decomposed into lactide at a rate of almost 100%,
The epoxy resin component is also thermally decomposed at 260-280 ° C.
It is clear that the volume can be significantly reduced
Was.

Example 2 L-lactic acid was placed in a 14-liter batch polymerization reactor equipped with a stirrer, thermocouple, nitrogen gas inlet tube and reflux tube.
0 kg was charged, and tin octylate was added as a catalyst at a rate of 0.25% by weight based on the raw material. Next, 2-8
The reaction temperature was set to 120 to 170 ° C. under reduced pressure of mmHg,
The polycondensation reaction was carried out for about 8 hours, and the number average molecular weight was 1,300.
Of lactic acid oligomer was obtained. 0.56 kg of succinic anhydride was added to 7.3 kg of this oligomer so as to be equimolar,
The carboxylation reaction was performed at 150 ° C. under normal pressure to approximate the theoretical acid value of 80. The acid value of the carboxylated lactic acid oligomer obtained after the reaction for about 3 hours was 81, and the number average molecular weight was 2,220.
At this time, the succinic anhydride sublimated in the course of the reaction contains toluene in the reaction solution in an amount of 2.5 to the charged amount of the lactic acid oligomer.
By adding it in a ratio of weight%, it was continuously returned to the reaction system while being dissolved in the reflux tube. Next, this was supplied as a lactic acid prepolymer to the same twin-screw extruder as in Example 1 to perform a copolymerization reaction with an epoxy resin. The operating conditions at that time are as follows.

[0055]

[Table 2] (Operating conditions) Raw material supply amount: 2.65 kg / h Screw rotation speed: 200 rpm Cylinder temperature: Zone 1, 2 = 110 ° C Zone 3 to 11 = 130 to 150 ° C Zone 12, die = 120 ° C

Further, it is attached to zone 2 of the cylinder.
Epolite (e.g.) at a rate of 0.52 kg / h
135). At the same time, the catalyst
0.02% by weight of TMAC based on epoxy resin
The copolymerization reaction was carried out while adding at a ratio of. then
Reaction time in the extruder (depending on the average residence time in the extruder)
Calculation) was about 14 minutes. After completion of the reaction, the extruder
Investigating the basic characteristics of the discharged polymer,
The average molecular weight was 34,530. This polymer is
Press to form a film and measure its mechanical strength.
As a result, the tensile strength was 1.12 kgf / mm ^Two, Extension
And 192%. Keep the used film at 225 ° C
When heated and thermally decomposed, the polylactic acid component is theoretically almost
100% of epoxide that is decomposed into lactide and remains
If the resin component is also thermally decomposed at 260-280 ° C, the volume will be reduced.
It was clarified that the chemical treatment could be performed.

Example 3 L-lactic acid was placed in a 14-liter batch polymerization reactor equipped with a stirrer, a thermocouple, a nitrogen gas inlet tube and a reflux tube.
0 kg was charged, and tin octylate was added as a catalyst at a ratio of 0.3% by weight to the raw material. Next, 1-10
The reaction temperature was set to 120 to 170 ° C. under reduced pressure of mmHg,
The polycondensation reaction was carried out for about 8 hours, and the number average molecular weight was 3,400.
Of lactic acid oligomer was obtained. 0.31 kg of phthalic anhydride was added to 7.2 kg of this oligomer so as to be equimolar,
The carboxylation reaction was carried out at 160 ° C. under normal pressure for about 2 hours to approximate the theoretical acid value of 32. When the acid value of the carboxylated lactic acid oligomer obtained after the reaction was examined, it was 32 and the number average molecular weight was 3,840. At this time, the phthalic anhydride sublimated during the reaction contained 3% by weight of xylene in the reaction solution based on the charged amount of the lactic acid oligomer.
To the reaction system while dissolving it in the reflux tube. Next, this was supplied as a lactic acid prepolymer to the same twin-screw extruder as in Example 1 to perform a copolymerization reaction with an epoxy resin. The operating conditions at that time are as follows.

[0058]

(Table 3) (Operating conditions) Raw material supply amount: 3.00 kg / h Screw rotation speed: 200 rpm Cylinder temperature: Zones 1 and 2 = 110 ° C Zones 3 to 11 = 130 to 150 ° C Zone 12, die = 120 ° C

Further, it is attached to zone 2 of the cylinder.
Epolite at a rate of 0.32 kg / h
188). At the same time, the catalyst
0.01% by weight of TPP based on the epoxy resin
The copolymerization reaction was performed while adding at a ratio. At that time
Reaction time in the extruder (depending on the average residence time in the extruder
Calculation) was about 13 minutes. After the reaction is complete,
When the basic characteristics of the discharged polymer were examined,
The average molecular weight was 40,350. This polymer is heated
Press to form a film and measure its mechanical strength
As a result, the tensile strength was 1.64 kgf / mm ^Two, Elongation
Was 186%. After use, heat the film to 225 ° C.
When heated and pyrolyzed, the polylactic acid component theoretically becomes almost 1
Decomposed into lactide at a rate of 00% and the remaining epoxy
Resin components can also be thermally decomposed at 260-280 ° C to reduce volume
It became clear that it could be processed.

[0060]

According to the method of the present invention, a copolymer can be produced industrially advantageously using inexpensive lactic acid as a raw material.
Further, the copolymer obtained by the method of the present invention is excellent in recyclability because it is excellent in physical properties such as mechanical strength and weather resistance and can be easily decomposed after use.

[Brief description of the drawings]

FIG. 1 is a schematic view of an example of an apparatus used for a manufacturing method of the present invention.

FIG. 2 is a view showing an example of a screw type extruder.

[Explanation of symbols]

 1. 1. Polymerization reaction tank 2. Inert gas cylinder Stirrer 4. Vacuum pump 5. Reflux tube 6. 6. Trap (water) 7. Lactic acid oligomer 8. Lactic acid prepolymer Plunger pump 10. Twin screw extruder 11. Hopper 12. Rotary pump 13. Supply port 14. 14. Polylactic acid copolymer Screen 16. Die 17. Storage tank

Continued on the front page (72) Inventor Kayoko Yokota 1-6-1, Funakoshi-Minami, Aki-ku, Hiroshima-shi, Hiroshima Japan Steel Works Co., Ltd. (72) Inventor Yukihiro Sumihiro 1-6-1, Funakoshi-minami, Aki-ku, Hiroshima-shi, Hiroshima (56) References JP-A-1-43522 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08G 59/14 C08G 63/06-63/08 C08G 63/78-63/87

Claims (3)

(57) [Claims] 1. A method for producing a polylactic acid copolymer, which comprises copolymerizing a reaction product of a lactic acid oligomer having a number average molecular weight of 1,000 to 5,000 with an acid anhydride with an epoxy resin. 2. The method for producing a polylactic acid copolymer according to claim 1, wherein the copolymerization reaction is carried out in a screw type extruder. 3. The method for producing a polylactic acid copolymer according to claim 1, wherein the reaction between the lactic acid oligomer having a number average molecular weight of 1,000 to 5,000 and the acid anhydride is carried out in a batch type reaction vessel.