JPH08301993A - Method for producing lactic acid-based polyester containing low lactide - Google Patents

Abstract

(57) [Summary] [Structure] A deactivator for the polymerization catalyst is added after the polymerization reaction of the lactic acid-based polyester, or a deactivator for the polymerization catalyst is added to the granular material after the polymerization reaction of the lactic acid-based polyester. A method for producing a lactic acid-based polyester having a low residual lactide, which comprises molding and processing. [Effects] The present invention is characterized by deactivating the catalyst added during the production of lactic acid-based polyester with a catalyst deactivator.
It is possible to provide a method for producing a lactic acid-based polyester having excellent moldability, biodegradability, heat resistance, and transparency by suppressing decomposition of the lactic acid-based polyester in the devolatilization step and the molding / processing step.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a lactic acid-based polyester having less residual lactide. More specifically, the present invention relates to a method for producing a lactic acid-based polyester having less residual lactide of a produced lactic acid-based polyester, which is less likely to be attached to an apparatus by sublimation of residual lactide and decomposed in the produced lactic acid-based polyester in a devolatilization step and a molding processing step It is a thing.

[Prior art]

[0002] In recent years, due to environmental problems and the like, researches have been actively conducted to widely utilize lactic acid-based polymers having excellent biodegradability as general-purpose polymers, and many studies and patent applications have been made regarding the production method. .

However, it is difficult to say that conventional polylactic acid, which is a polymer of lactic acid or lactide, or a copolymer of lactide and another monomer has sufficient performance in moldability and heat resistance. Except for special applications, polylactic acid has problems that it is too fast to decompose and difficult to use as a general-purpose resin, and suppression of decomposition, especially improvement of storage stability is an important development issue. .

Similarly, the deterioration of the resin during molding is severe,
The manufactured resin undergoes severe strength degradation before use. This is because the lactide component remaining at the time of polymerization and / or the lactide component generated at the time of molding is decomposed by moisture in the air to become an organic acid, which acts to break the polymer chain. On the other hand, lactic acid-based polyester with less residual lactide, the decomposition is significantly suppressed,
A lactic acid-based polyester having excellent storage stability can be produced.

Regarding the method of removing lactide from lactic acid-based polyester, a method of extracting with a solvent and a method of dissolving a polymer in a good solvent and precipitating it in a poor solvent are known in laboratory-level experiments. For manufacturing on an industrial scale, a method using a twin-screw extruder is disclosed in European Patent No. 532154, and a method of removing strands as volatile components in a depressurized pot is known in Japanese Patent Application Laid-Open No. 5-93050.

However, in these methods, even if the lactide is removed under reduced pressure and heating, lactide is regenerated, and the amount of lactide in the resin cannot be easily reduced. This is because the catalyst used for the polymerization contributes to the catalysis of the reaction that produces lactide from the polymer chain.

JP-A-6-116381 discloses a method for removing a catalyst from polylactic acid produced from lactic acid in the presence of a solvent. In this method, a hydrophilic organic solvent and a weak acid are added to polylactic acid dissolved in a solvent to remove the catalyst component.

However, this method is a method for removing a catalyst from polylactic acid in the presence of a large amount of a solvent. When the amount of the solvent is small, the catalyst cannot be removed by this method. Although it is in the form of granules, flakes, or blocks, the bulk density is set to 0.6 g / ml, and polylactic acid needs to be dissolved in a solvent after production to obtain a precipitate. Further, the treatment time is relatively long, and the treatment of the waste solvent which becomes a complicated mixture is complicated.

On the other hand, the addition of phosphorous acid, phosphoric acid, pyrophosphoric acid, and polyphosphoric acid in order to suppress the coloring of polylactic acid during production is disclosed in JP-A-62-25121. Phosphorous acid is H ₃ PO ₃ , phosphoric acid is H
₃ PO ₄ , pyrophosphoric acid is represented by H ₄ P ₂ O ₇ and polyphosphoric acid is represented by (HO) ₂ POO (PO) _n PO (OH) ₂ . The structures of other compounds disclosed in the patent are shown below.

General formula 1

Embedded image (In the formula, R and R′R ″ represent an alkyl group or a phenyl group)

General formula 2

Embedded image (In the formula, R and R′R ″ represent an alkyl group or a phenyl group)

General formula 3

Embedded image (In the formula, R represents an alkyl group or a phenyl group)

General formula 4

[Chemical 4] (In the formula, R represents an alkyl group and R ′ represents an alkyl group or a hydrogen atom)

However, this method does not deactivate the catalyst, does not suppress the generation of lactide during devolatilization and molding, and can be added at the time of initiation of polymerization.

[0015]

The problem to be solved by the present invention is that in the devolatilization step and the molding processing step, the residual lactide is attached to the device by sublimation and the produced lactic acid-based polyester is decomposed little, and it is produced. Another object of the present invention is to provide a method for producing a lactic acid-based polyester in which the lactic acid-based polyester has a sufficient high molecular weight and heat resistance and has a small residual lactide.

[0016]

[Means for Solving the Problems] In order to solve the above problems, the present inventors have earnestly studied, and as a result, after the polymerization of lactic acid-based polyester, a deactivator for a polymerization catalyst was added and devolatilization was performed under reduced pressure. It has been found that when a lactic acid-based polyester is produced by carrying out the production, a lactic acid-based polyester excellent in storage stability can be produced by minimizing the breakage of the polymer chain, and the present invention has been completed.

[0017]

[Structure] That is, the present invention is a method for producing a lactic acid-based polyester having a small residual lactide (lactic acid-based polyester containing low lactide), which comprises adding a deactivator to the polymerization catalyst after the polymerization reaction of the lactic acid-based polyester. .
Further, the deactivator is an alkyl phosphate and / or an alkyl phosphonate, which is a method for producing a lactic acid-based polyester having a small residual lactide.

More specifically, the present invention is characterized in that the deactivator is added before obtaining granules after polymerization of the lactic acid-based polyester, and a method for producing a lactic acid-based polyester having less residual lactide, and the deactivator is lactic acid. A method for producing a lactic acid-based polyester having a small residual lactide, which is characterized in that it is added after the polymerization of a polyester-based polyester and the volatile components are removed under reduced pressure to obtain a granular material.

Further, the present invention includes a method for producing a lactic acid-based polyester having a small residual lactide, which is characterized by adding a deactivator to a polymerization catalyst to the granular material after the polymerization reaction of the lactic acid-based polyester and molding the same. More specifically, it is a method for producing a lactic acid-based polyester, wherein the deactivator is an alkyl phosphate and / or an alkyl phosphonate.

Further, the present invention is characterized in that a deactivator is added to the granular material after the polymerization of the lactic acid type polyester, and the volatile components are removed by devolatilization under reduced pressure, and the molding process is carried out. The manufacturing method is included.

According to the present invention, the lactic acid-based polyester is particularly polylactic acid or comprises 50 to 98 parts of a lactic acid component and 2 to 50 parts of a polyester composed of a dicarboxylic acid component and a diol component. A method for producing a lactic acid-based polyester having less residual lactide.

Further, in the present invention, the lactic acid-based polyester after the polymerization is removed by a thin film distiller at a temperature of 150 to 180 ° C. and a reduced pressure of 0.01 to 30 to remove the residual lactide in the lactic acid-based polyester. The subsequent lactic acid-based polyester was heated at a temperature of 1 using a twin-screw extruder type devolatilizer.
It includes a method for producing a lactic acid-based polyester having a low residual lactide, which is characterized by removing residual lactide in the lactic acid-based polyester at 50 to 180 ° C. and a reduced pressure of 0.01 to 30 torr.

The present invention will be described in more detail below. The catalyst deactivator used in the present invention is an acidic compound,
Preferred because it binds to the catalyst used and loses activity.
Depending on the polymerization catalyst used in the polymerization reaction, it is generally a compound having one or more phosphoric acids or phosphoric acid esters, or a compound having one or more carboxylic acids, 1
Compounds having one or more sulfuric acid or sulfuric acid esters, 1
Included are compounds having one or more nitric acid or nitrate esters, and mixtures thereof.

Of these, a compound having phosphoric acid or a phosphoric acid ester is preferable in order to suppress the breakage of the polymer chain and efficiently bond with the catalyst. Generally, a compound called an alkyl phosphate and a compound group called an alkyl phosphonate are included. The alkyl chain represented by the general formula 5 is particularly preferably a monoalkyl compound and a dialkyl compound or a mixture thereof.

General formula 5

Embedded image (In the formula, R ₁ represents an alkyl group or an alkoxyl group, and R ₂ represents an alkyl group, an alkoxyl group or a hydroxyl group.)

As a more specific structure, phosphoric acid esters having one or two alkyl chains having 1 to 20 carbon atoms and mixtures thereof are preferable. More specific names include monomethyl phosphate, dimethyl phosphate, monoethyl phosphate, diethyl phosphate, monopropyl phosphate, dipropyl phosphate, monoisopropyl phosphate, diisopropyl phosphate,

Monobutyl phosphate, dibutyl phosphate, monopentyl phosphate, dipentyl phosphate, monohexyl phosphate, dihexyl phosphate, monooctyl phosphate, dioctyl phosphate, monoethylhexyl phosphate, diethylhexyl phosphate, monodecyl phosphate, didecyl phosphate, monoisodecyl Phosphate, diisodecyl phosphate,

Monoundecyl phosphate, diundecyl phosphate, monododecyl phosphate, didodecyl phosphate, monotetradecyl phosphate, ditetradecyl phosphate, monohexadecyl phosphate, dihexadecyl phosphate, monooctadecyl phosphate, dioctadecyl phosphate, monophenyl Phosphate, diphenyl phosphate, monobenzyl phosphate,

Dibenzyl phosphate, monomethylmethylphosphonate, monoethylethylphosphonate, monopropylpropylphosphonate, monoisopropylisopropylphosphonate, monobutylbutylphosphonate, monopentylpentylphosphonate, monohexylhexylphosphonate, monooctyloctylphosphonate, monoethylhexylethylhexylphosphonate. ,

Monodecyldecylphosphonate, monoisodecylisodecylphosphonate, monoundecylundecylphosphonate, monododecyldodecylphosphonate, monotetradecyltetradecylphosphonate, monohexadecylhexadecylphosphonate, monooctadecyloctadecylphosphonate, monophenylphenylphosphonate , Monobenzyl benzyl phosphonate, dimethyl phosphonate,

Diethylphosphonate, dipropylphosphonate, diisopropylphosphonate, dibutylphosphonate, dipentylphosphonate, dihexylphosphonate, dioctylphosphonate, diethylhexylphosphonate, didecylphosphonate, diisodecylphosphonate, diundecylphosphonate, didodecylphosphonate, ditetradecylphosphonate, di Hexadecylphosphonate,

Dioctadecyl phosphonate, diphenyl phosphonate, dibenzyl phosphonate, and mixtures thereof can be used. Some of the mixtures are generally called alkyl acid phosphates. Regarding the dialkyl chain in the compound, the two alkyl chains may be different, and a mixture of these may be used.

Examples of the polymerization catalyst of the present invention include metals such as tin, zinc, lead, titanium, bismuth, zirconium, germanium and cobalt, which are generally known as ring-opening polymerization catalysts for cyclic esters, and transesterification catalysts, and derivatives thereof. Among these derivatives, metal organic compounds, carbonates, oxides and halides are known.
More specifically, tin octoate, tin chloride, zinc chloride, zinc acetate, lead oxide, lead carbonate, titanium chloride, alkoxytitanium, germanium oxide, zirconium oxide can be mentioned.

The amount of the polymerization catalyst is preferably 0.005 to 0.5% by weight based on the weight of the lactic acid-based polyester produced. The reaction rate is sufficiently high, and in order to reduce the coloring of the obtained lactic acid-based polyester, 0.02 to 0.02 is particularly preferable.
0.1% by weight is preferred.

The lactic acid-based polyester used in the present invention is
Ring-opening polymerization of polylactic acid obtained by condensing lactic acid by decompression and dehydration in the presence or absence of a solvent, and a copolymer of other hydroxycarboxylic acid and lactic acid, and lactide, which is a compound of cyclic dimerization of lactic acid. Examples thereof include copolymers with the above-mentioned polylactic acid and other cyclic ester, and copolymers with a polymer having a copolymerizable hydroxyl group.

Lactic acid is a monomer having stereoisomers. That is, L-lactic acid and D-lactic acid exist in lactic acid. A polymer containing only L-lactic acid or D-lactic acid is crystallized and a high melting point is obtained. The lactic acid-based polyester of the present invention can achieve preferable resin properties by combining these two types of lactic acid.

In the present invention, since lactic acid exhibits high thermophysical properties, L-lactic acid preferably contains 75% or more of total lactic acid, and in order to exhibit even higher thermophysical properties, lactic acid is L
-It is preferable that 90% or more of lactic acid is contained in the total lactic acid.

It is known that polylactic acid type polyester is generally transparent but lacks flexibility. The lactic acid-based polyester used in the present invention can be produced as a flexible and highly heat-resistant lactic acid-based polyester by copolymerizing with a polyester composed of a dicarboxylic acid component and a diol component.

A polyester suitable in the present invention means a polyester composed of a dicarboxylic acid component and a diol.
Further, the molecular weight of the polyester is preferably high,
Specifically, the weight average molecular weight is 10,000 to 250,000.
00 is preferable, and the molar ratio of the dicarboxylic acid component and the diol component is preferably about 1.

The dicarboxylic acid component in the polyester is specifically an aromatic dicarboxylic acid component, specifically phthalic acid, isophthalic acid and / or terephthalic acid,
2,6-naphthalenedicarboxylic acid may be mentioned. Also,
It is preferably an aliphatic dicarboxylic acid component having 4 to 20 carbon atoms. Specific examples include succinic acid, adipic acid, azelaic acid, sebacic acid, brassic acid, and cyclohexanedicarboxylic acid. In addition to these, dimer acid and the like can also be mentioned.

The diol component is not particularly limited, but may be ethylene glycol, propylene glycol,
Butylene glycol, pentanediol, hexamethylene glycol, octanediol, neopentyl glycol, cyclohexanedimethanol, hydrogenated bisphenol A, xylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, dibutanediol, 3-hydroxypivalyl pivalate Etc.

With respect to the diol component, polyoxyalkylene is preferable for improving heat resistance, and examples thereof include polyethylene glycol, polypropylene glycol, polybutylene glycol, polypentanediol and polytetramethylene glycol.

Due to the nature of the polylactic acid moiety having many ester bonds, a higher melting point and a higher glass transition temperature can be realized, and the lactic acid-based polyester obtained by the present invention can realize a glass transition point of room temperature or higher and a melting point of 160 ° C. or higher. it can. For this purpose, the composition ratio of the polylactic acid component (L) and the polyester component (P) is L / P of 50/50 to 98/2, and in order to obtain high transparency and high altitude, L /
It is preferable that P is 70/30 to 98/2. Furthermore, in order to obtain high transparency and flexible properties, L / P is 5
It is preferably 0/50 to 70/30.

The lactic acid-based polyester is preferable because it has a higher molecular weight because it can be molded and processed in a wider temperature range. Specifically, the weight-average molecular weight is 20,000 to 40.
It is 10,000. When a lactic acid-based polyester having a molecular weight in this range is formed into a sheet, a sheet having a high strength to a flexible sheet can be obtained.
A sheet of ˜50,000 kg / cm ² is obtained.

Next, a method for producing a polyester composed of a dicarboxylic acid component and a diol component and a polylactic acid-based polyester composed of a lactic acid component will be described in order. The mixture of lactide and polyester is heated and melted or mixed with a solvent, and then a polymerization catalyst is added. When the reaction temperature is not lower than the melting point of lactide, the reaction system can be homogenized and a high polymerization rate can be obtained, which is preferable.

The reaction temperature in the solvent-free system is preferably a temperature above the melting point of lactide and below 180 ° C. in view of the equilibrium of the reaction, and it is possible to prevent coloring of the lactic acid type polyester due to the decomposition reaction. The melting point of lactide is around 100 ° C., and a temperature of 100 ° C. or higher and 185 ° C. or lower, more preferably 145 to 180 ° C. is desirable in terms of reaction equilibrium, and to prevent a decrease in the molecular weight and coloration of the lactic acid-based polyester accompanying the decomposition reaction. You can

In order to prevent the decomposition and coloration of lactide, the atmosphere suitable for the reaction is preferably a dry inert gas. In particular, the reaction is performed under a nitrogen or argon gas atmosphere or in a bubbling state. At the same time, it is necessary to remove water from the raw material components and dry them.

Since lactide can be dissolved in a solvent, it can be reacted using a solvent or the like. Examples of solvents that can be used include benzene, toluene, ethylbenzene, xylene, cyclohexanone, methyl ethyl ketone, isopropyl ether.

The lactic acid-based polyester of the present invention can be produced by using an ordinary reaction kettle, but generally, in a high viscosity region where the resin viscosity exceeds 10,000 poise, the heat of polymerization as well as the stirring is generally used. Stirring heat generated by shear stress is intensely generated, and in dynamic stirring, local heat generation in the stirring section becomes remarkable. Therefore, it is preferable to use a static mixer which has a small shear stress and acts uniformly.

The static mixer is usually tubular, and a plurality of static mixers are linearly connected to each other, and the raw material is continuously supplied from a raw material charging port under an inert gas atmosphere. By continuously moving the inside, it is possible to carry out the reaction continuously, and from the raw material charging to the reaction, the delumining, and the pelletizing of the polymer without any contact with the outside atmosphere.

In addition to this, continuous stirring type reaction tank, continuous polymerization by so-called CSTR, continuous reaction by a twin-screw extruder or the like is also effective. It is also possible to simultaneously perform manufacturing and molding by so-called reactive processing.
These reactions can be carried out continuously, from the charging of the raw materials to the reaction, delustration, and pelletization of the polymer, without any contact with the outside air.

The catalyst deactivator is preferably added after the polymerization step is completed. If it is added during the polymerization step, the catalyst is deactivated, the reaction ends midway and a large amount of residual monomer component is generated. Regarding the specific addition timing, the conversion rate of monomers such as lactide to the polymer is preferably 85% to 99%, and 93% to 99% in consideration of a more efficient devolatilization process.
It is preferred that

The amount of addition varies greatly depending on the type of deactivator, the type of catalyst, and the deactivation reaction conditions, but it is preferable to add 50% to 400% of the catalyst weight before taking out the polymer after the reaction. The quenching agent can minimize polymer chain scission. Although the deactivation reaction largely depends on the stirring condition, it is relatively fast, about 3 minutes is sufficient, and preferably 5 to 20 minutes. The deactivation reaction temperature is 140 ° C to 200
C is preferred.

Regarding the timing of addition of the quenching agent, in batch polymerization, it is preferable to add and stir after completion of the polymerization reaction, and take out. Alternatively, it is also possible to form an addition line in the take-out line, mix and take it out. In the case of continuous reaction using a static mixer, CSTR, and a twin-screw extruder, it is preferable to form an addition line of the quenching agent after the reaction end point, mix, and take out.

When a solvent is used for the polymerization and is removed after the polymerization regardless of whether the polymerization is batch polymerization or continuous polymerization, and when a devolatilization tank for removing residual monomer components and odorous components is provided after the polymerization, the solvent is lost. The activator is preferably added after the polymerization reaction and before the devolatilization tank in order to suppress the decomposition of the polymer chains and prevent the generation of volatile components, thereby increasing the devolatilization efficiency. When the devolatilizing tank for removing the solvent and the devolatilizing tank for removing the monomer component are separately provided, it does not matter which of the devolatilizing tanks is provided.

In addition to this, there is also a method in which a deactivator is added to the granulated material after the polymerization, and immediately sprinkled, coated or mixed. Granules,
Generally speaking, it is possible to mix a deactivator with pellets, react them at the time of molding, and devolatilize as needed to mold. It is also possible to add additives such as fillers and pigments at the same time when they are repellerted. Further, an addition line may be provided in an extruder or an injection molding machine at the time of molding and used.

When a polylactic acid type polyester is produced by a method of decompressing and condensing in the coexistence of an organic solvent, it may be added in the coexistence of an organic solvent after completion of the polymerization, or only the resin component except the solvent may be added. It can be added to the catalyst after it has been isolated, or it can be used for deactivating the catalyst component remaining in a very small amount after removing the catalyst by the method described in JP-A-6-116381, or added at the time of re-pelleting. You can also

It is desirable to carry out devolatilization under reduced pressure for the purpose of removing lactide, solvent and odorous substances remaining in the latter stage of polymerization. By this devolatilization step, the amount of residual lactide can be reduced, and the storage stability of the obtained lactic acid-based polyester can be significantly increased. Further, the residual lactide is not preferable because it causes hydrolysis due to adhesion of water or fusion due to heat when the lactic acid-based polyester is formed into a sheet.

Further, since it is scattered by sublimation from the commercialized film or sheet, the packaged product is contaminated, which is not preferable. Therefore, the amount of residual lactide in the lactic acid-based polyester of the present invention is preferably 1% by weight or less, more preferably 0.1% by weight or less.

As a concrete devolatilization method, a method of taking out the mixture under reduced pressure and heating after the polymerization is preferable. In order not to reduce the molecular weight of the lactic acid-based polyester, the devolatilization conditions are as follows: devolatilization time: 2 to 30 minutes, temperature: 145 to 230
It is preferable that the temperature and the degree of reduced pressure are 0.1 to 50 Torr. As another devolatilization method, after the polymerization is completed, the lactic acid-based polyester is pelletized or crushed, and under reduced pressure,
There is a method of taking out while heating. Also in this case, it is preferable that the devolatilization time is 15 to 400 minutes, the temperature is 60 to 200 ° C., and the degree of vacuum is 0.1 to 50 Torr for the purpose of not reducing the molecular weight of the lactic acid-based polyester.

The device used to remove and reduce the lactide is not particularly limited, but 760 torr of lactic acid type polyester in a molten state, a solid state or a powder state is used.
There is a method of removing lactide, a solvent, and an odor component under the following reduced pressure conditions. Specifically, a method in which lactic acid-based polyester in the form of a strand is introduced into a depressurized pot and volatile components are removed and discharged, a thin-film distiller-type devolatilizer, 2
A shaft extruder type devolatilizer is preferred for continuous processes,
Recommended.

Particularly, as a method for positively renewing the polymer surface, a thin film distillation type devolatilizer and a twin-screw extruder type devolatilizer can be preferably used. As the thin film distillation apparatus, it is preferable to have a cylindrical outer wall and a stirring blade for pressing the liquid material against the wall surface on the inner side thereof, and a mechanism for taking out the treated liquid material to the outside of the apparatus at the lower part. .

The inside of the thin film distillation machine is highly decompressed,
Volatile components in the liquid material can be removed. There are both an apparatus in which the cylindrical main body is placed horizontally and one in which it is placed vertically, but when treating a high-viscosity molten resin such as devolatilization from the lactic acid-based polyester of the present invention, the apparatus is placed vertically. It is preferable that the discharge is performed by gravity.

As for the aspect ratio of the cylindrical barrel portion when the thin film distillation apparatus is placed vertically, the vertically long one is preferable because the torque applied to the stirring blade is smaller and a large devolatilization area can be obtained for the volume. . The stirring blade for pressing the liquid material against the wall has an important role in obtaining an effective devolatilization surface area, and it is necessary to have two or more threads, and a split blade such as a paddle blade or a helical blade. Any of the integrated wings such as can be used.

The clearance between the blade and the wall surface determines the residence time of the liquid material, and the smaller the clearance, the better the surface efficiency of the liquid film can be formed. However, the shearing force is large and it is necessary to strike a balance. Regarding the mechanism for taking out the treated liquid material to the outside of the device, it is possible to let it take out by its own weight by gravity, but it can be taken out by a method such as a screw blade or a gear pump. The more stable extraction can be performed by using.

The inside of the thin film distillation machine is evacuated to a vacuum,
Although the volatile component in the liquid material is removed, it is necessary to keep the temperature so that the volatile component does not deposit on the stirring blade or in the decompression pipe. Further, as a method for reducing the pressure inside the thin film distillation machine, the pressure is reduced from near the inlet of the liquid material to be volatilized,
That is, there are a method of reducing the pressure in the direction opposite to the flow direction and a method of reducing the pressure from the vicinity of the outlet of the liquid material to be devolatilized, that is, the method of reducing the pressure in the forward direction with respect to the flow direction. The depressurizing direction is not particularly limited, but in the case of devolatilizing a highly viscous material, depressurizing in the opposite direction is preferable because it does not contaminate the piping of the depressurizing system.

As a concrete devolatilization method by thin-film distillation, a method of heating under reduced pressure after polymerization is preferable. In order to prevent re-generation of lactide from the polymerized lactic acid-based polyester and perform effective devolatilization without lowering the molecular weight, the devolatilization time is 0.5 to 30 minutes, preferably 0.5 to 30 minutes.
~ 15 minutes, more preferably 0.5-5 minutes, temperature 145
To 230 ° C, preferably 155 to 190 ° C, more preferably 155 to 180 ° C, and the degree of reduced pressure is 0.01 to 50 Torr.
r, preferably 0.01 to 30 Torr, more preferably 0.01 to 10 Torr.

The devolatilization surface area is a major factor that determines the devolatilization ability, but is approximately 1 for 100 kg of resin.
It is preferable to devolatilize with a surface area of about m ³ as a guide.
The faster the rotation speed of the stirring blade, the faster the surface renewal is, which is preferable. However, since shear stress is applied, it is necessary to study an appropriate value for each resin.

The twin-screw extruder has originally been used for mixing resins with additives in resin production or for molding. However, in recent years, a device in which a vent port is installed and the odor and foreign matter of a resin can be removed has been widely put into practical use. It can also be used to remove volatile components from the resin.

The cylinder plays an important role in obtaining an effective devolatilization surface area, and when the inside of the vent port is depressurized to remove the volatile matter, the resin itself also flows into the depressurization system at the same time as the volatile matter (so-called vent up). It is necessary to consider the shape of the cylinder so as not to do so, and also to consider the combination with the screw. It is necessary to provide one or more vent ports if necessary.

It is preferable that the opening area is large, but it is necessary to prevent the above-mentioned vent up. Further, it is possible to install a line for adding an additive, particularly a catalyst deactivator as disclosed in the present invention, on the way in the twin-screw extruder.

The screw also plays an important role in the purpose of obtaining an effective devolatilization surface area, and it is necessary to have two or more threads, and in order to maintain the degree of sealing of the devolatilization port, a dullage is provided between the devolatilization ports. Alternatively, it is desirable to have a ring-shaped sealing mechanism. When installing a line for adding an additive, especially a catalyst deactivator as disclosed in the present invention in a twin-screw extruder, partially provide a kneading screw having a high kneading effect. Is preferred.

In the twin-screw extruder, the screw rotates in the same direction or in different directions. In the case of two-axis rotation in the same direction, a complete meshing type can be obtained, and the shaft self-cleaning property is excellent. In the case of biaxial rotation in different directions, it can be rotated in the opening direction and the closing direction with respect to the opening of the vent port, a large devolatilization effective area can be taken, and different direction rotation is often used in the production of many resins. ing. However, in the case of different rotation, since the shear applied to the resin is strong and there is a high possibility that it contributes to the breakage of the polymer chain, the biaxial rotation in the same direction is more preferable in the present invention.

When the resin viscosity in the twin-screw extruder is high and the discharge is not successful, a method of installing a gear pump in the discharge part and discharging can be used for more stable discharge. The inside of the vent port of the twin-screw extruder is depressurized, and the volatile components in the liquid material are removed, but the vent port and the vacuum are prevented so that these volatile components do not deposit in the vent port or in the decompression pipe. It is necessary to keep the piping warm. Specifically, the residual lactide in the lactic acid-based polyester after polymerization is removed at a temperature of 150 to 180 ° C. and a reduced pressure of 0.01 to 30 torr.

As another method for reducing the residual lactide, there is a reprecipitation method in which after the completion of the polymerization reaction, the lactic acid-based polyester is dissolved in a solvent and added to a poor solvent to obtain a polymer. Solvents for dissolving lactic acid-based polyester include benzene, toluene, ethylbenzene, xylene,
Cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dioxane,

Methyl isobutyl ketone, methyl ethyl ketone, isopropyl ether, dichloromethane, chloroform, carbon tetrachloride, chlorobenzene, dichlorobenzene, trichlorobenzene, chloronaphthalene and the like and mixed solvents thereof are preferable because of good solubility, and the poor solvent is water, Examples of the solvent include methanol, ethanol, propanol, butanol, pentane, hexane, heptane, octane, nonane, decane, and diethyl ether, and mixed solvents thereof.

The reprecipitation is carried out by dissolving the lactic acid-based polyester in a solvent at a concentration of 2 to 20% by weight at room temperature or while heating.
While stirring, gradually add 2 to 15 times the amount of poor solvent to 1
A method is preferred in which it is allowed to stand for 0 to 180 minutes to form a precipitate and is taken out. The precipitated precipitate is removed under reduced pressure or under heating to remove the residual solvent. By these devolatilization methods, the amount of lactide remaining, usually about 2.5%, can be reduced to 1.0% or less, and if necessary, to 0.1% or less.

Another method for reducing the residual volatile components is to add the lactic acid-based polyester after the completion of the polymerization reaction to a solvent that is a poor solvent for the polymer and is capable of dissolving the volatile components to remove the volatile components from the polymer. There is a cleaning method with the solvent except. Examples of the solvent for washing the lactic acid-based polyester include propyl acetate, butyl acetate, methyl butyrate, ethyl butyrate, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, methyl ethyl ketone, isopropyl ether, methanol, ethanol, propanol, butanol, and diethyl ether. A mixed solvent may be used.

For washing, at room temperature or while cooling or heating, a lactic acid-based polyester in an amount of 2 to 80% by weight of the solvent is added, washed for 2 to 15 minutes with stirring, the precipitated resin is taken out, and / or under reduced pressure. A method of drying under heating is preferable.

When producing the copolymer of the present invention, a lactic acid-based polyester may be produced by further adding other components than the lactic acid component. Particularly, for the purpose of softening, 1 to 20% by weight of a lactone and a hydroxycarboxylic acid component can be added. These components are not particularly limited, but specifically, cyclic dimers of hydroxy acids such as glycolide and intramolecular lactides, particularly ε-caprolactone, γ
-Valerolactone, γ-undecalactone and the like and hydroxycarboxylic acids corresponding to these. When the amount of lactone or the like is increased, the glass transition point and melting point are lowered and the flexibility is increased.

The production method according to the present invention can provide lactic acid-based polyester having high rigidity to lactic acid-based polyester having high flexibility. That is, it has a degradability and tensile viscoelasticity of 500 to 50,000 kg / cm ^2, and can be widely used as a general-purpose resin, such as resin for packaging materials such as sheets and films, resin for foaming, resin for extrusion molding, injection molding. It is possible to provide a polymer useful as a general-purpose resin such as a resin for use in ink, a resin for ink, a resin for lamination, etc., and it is particularly useful as a method for producing a polymer for packaging materials.

When forming these sheets and films, a general filler such as an inorganic filler such as talc, calcium carbonate, silica, clay, diatomaceous earth and perlite, or an organic filler such as wood powder is mixed. You may add. In addition, 2,6-di-t-butyl-4-methylphenol (BHT), butyl hydroxyanisole (BH
Uses antioxidants such as A), salicylic acid derivatives, UV absorbers such as benzophenone and benzotriazole, and stabilizers such as phosphoric acid ester, isocyanate, carbodiimide, etc. to improve thermal stability during molding. be able to.

The addition amount of these stabilizers is not particularly limited, but it is usually preferable to add them in an amount of 0.1 to 10% based on the weight of the lactic acid-based polyester. Further, the lactic acid-based polyester of the present invention alone has a sufficient plasticizing effect and has moldability, but when particularly high plasticization is intended, dioctyl adipate, dioctyl sebacate, trioctyl trimellitate, phthalate Diethyl acid,

A plasticizer such as dioctyl phthalate, polypropylene glycol adipic acid and butanediol adipate may be added. Among them, the adipic acid-based polyester plasticizer is particularly preferable from the viewpoint of compatibility and plasticizing effect by addition, and those having a weight-average molecular weight of 20,000 or less and having polyester terminals sealed with alcohol or the like are molded, It is particularly preferable because it has good stability during processing.

The addition amount of these plasticizers is not particularly limited, but for the purpose of avoiding the phenomenon that excess plasticizer is eluted from the resin and bleeding, it is 1 to 30% relative to the weight of the lactic acid-based polyester. Is preferably added in an amount of. Also, metal soaps such as zinc stearate, magnesium stearate and calcium stearate, lubricants such as mineral oil, liquid paraffin and ethylene bisstearyl amide, nonionics such as glycerin fatty acid ester and sucrose fatty acid ester, and ions such as alkyl sulfonate. It is also possible to add a surface active agent, a coloring agent such as titanium oxide or carbon black.

The lactic acid-based polyester obtained by the present invention is
It has good biodegradability and is useful for reducing the amount of waste even if it is discarded after being used for general-purpose resins, packaging materials, etc., or if it is discarded from the manufacturing process. Even when it is dumped into the sea, it is hydrolyzed and decomposed by microorganisms. Decomposition in seawater also deteriorates the strength of the resin within a few months, and it can be decomposed before the outer shape is maintained.

Further, the lactic acid-based polyester of the present invention is excellent in devolatilization, so that it can be stored with good storage stability, can suppress the decomposition of the resin during molding and is excellent in processability.
Molding can be performed by various methods such as extrusion molding, injection molding, inflation molding, lamination molding, press molding, etc., it is possible to mold using existing equipment used for general-purpose resins, especially packaging It is useful as a material.

For example, as the use of the film, garbage bags, plastic shopping bags, general-standard bags, bags such as heavy bags, packaging materials for agriculture, food, industry, textiles, miscellaneous goods, and binding tapes. , Agricultural mulch film, etc. Also useful as sheets and injection molded products such as agricultural, food, industrial sheets, trays, sundries, food containers, curing sheets, seedling pots, industrial materials, industrial products, etc. Is.

[0089]

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples. All parts in the examples are on a weight basis unless otherwise specified.

[Example 1] Aromatic polyester (terephthalic acid component 25 mol%, isophthalic acid component 25 mol%, ethylene glycol component 20 mol%, neopentyl glycol component 30 mol%, number average molecular weight 39,400
(Polystyrene equivalent), softening point 163 ° C) L to 5 parts by weight
-93 parts by weight of lactide and 2 parts by weight of D-lactide were added, the atmosphere was replaced with an inert gas, both were melted and mixed at 165 ° C for 1 hour, and 400 ppm of tin octoate was added as an esterification catalyst.

Thereafter, the reaction was carried out for 6 hours, and after the reaction was completed, 8000 ppm of a 10% toluene solution of a mixture of monostearyl phosphate and distearyl phosphate was added and stirred for 20 minutes to prepare a lactic acid-based polyester composition. Gel permeation chromatography (hereinafter G
Abbreviated as PC. From the results of (1), a lactic acid-based polyester having a weight average molecular weight of 158,000, which was larger than the molecular weight of the starting aromatic polyester, was confirmed.

The peak of GPC was single, and a single copolymer was formed. 3.9% of the lactide monomer remained. Residual lactide was removed from this lactic acid-based polyester composition at a vacuum degree of 4 torr and 200 ° C. At 60 minutes lactide became undetectable. No decrease in molecular weight was observed.

[Example 2] Aromatic polyester (terephthalic acid component 30 mol%, isophthalic acid component 20 mol%, ethylene glycol component 20 mol%, bisphenol A diethylene glycol ether 30 mol%, number average molecular weight 54,200 (polystyrene Conversion), softening point 18
0 ° C.) 82 parts by weight of L-lactide and 3 parts by weight of D-lactide are added to 15 parts by weight of the mixture, and the mixture is added to 1 part under an inert gas atmosphere.
Both were melted and mixed at 70 ° C. for 1 hour, 500 ppm of tin octoate was added as an esterification catalyst, and the reaction was carried out for 6 hours.

After completion of the reaction, a mixture of monoisopropyl phosphate and diisopropyl phosphate was added at 300 pp.
m and stirred for 5 minutes to prepare a lactic acid-based polyester composition. A lactic acid-based polyester having a weight average molecular weight of 102,000 was confirmed. 4.2% of the lactide monomer remained. Residual lactide was removed from this lactic acid-based polyester composition at a vacuum degree of 7 torr and 220 ° C. The lactide reached 0.9% in 45 minutes, and no decrease in the molecular weight was observed.

Example 3 To 3 parts by weight of an aliphatic polyester (sebacic acid component 48.5 mol%, propylene glycol component 48.5 mol%, pyromellitic acid component 3 mol%, weight average molecular weight 62,000) L-lactide 95
1 part by weight and 2 parts by weight of D-lactide were added, the atmosphere was replaced with an inert gas, both were melted and mixed at 165 ° C. for 1 hour, and tin octoate was added at 500 p as an esterification catalyst.
pm was added and the reaction was carried out for 6 hours to prepare a lactic acid-based polyester composition.

After the reaction was completed, 800 ppm of a mixture of monooctyl phosphate and dioctyl phosphate was added,
The mixture was stirred for 5 minutes to prepare a lactic acid-based polyester composition. It was confirmed to be a lactic acid-based polyester having a weight average molecular weight of 210,000. 3.8% of the lactide monomer remained.
This lactic acid-based polyester composition was vacuumed at 4 torr,
The residual lactide was removed at 170 ° C. At 60 minutes lactide became undetectable and no reduction in molecular weight was observed.

[Example 4] 50 parts by weight of an aliphatic polyester (48.5 mol% sebacic acid component, 48.5 mol% polypropylene glycol, 3 mol% pyromellitic acid component 120,000 weight average molecular weight) L- Lactide 4
9 parts by weight and 1 part by weight of D-lactide were added, the atmosphere was replaced with an inert gas, and both were melted at 165 ° C. for 1 hour.
When mixed, tin octoate 400 is used as an esterification catalyst.
ppm was added and reacted for 4 hours.

After completion of the reaction, a mixture of monoethylhexyl phosphate and diethylhexyl phosphate was added to 800
ppm was added and stirred for 10 minutes to prepare a lactic acid-based polyester composition. From the result of GPC, the weight average molecular weight is 123,
It was confirmed to be 500 lactic acid type polyester. 2.0% of the lactide monomer remained. Residual lactide was removed from this lactic acid-based polyester composition at a vacuum degree of 2 torr and 165 ° C. At 15 minutes lactide became undetectable. No decrease in molecular weight was observed.

[Embodiment 5] In this embodiment, a reaction apparatus in which three liquid-filled stirring type reactors each having a 4-liter internal volume and equipped with helical stirring blades are arranged in series, A 1/2 inch static mixer (Kenix type static mixer manufactured by Noritake) was connected to two devolatilization tanks as a heat exchanger in the reaction tank. The raw material is supplied to the first reactor in a nitrogen gas atmosphere by using a plunger pump as a 15% toluene solution of a polymer having lactide and a hydroxyl group at 110 ° C so that the average residence time of the raw material is 8 hours. Supplied.

The catalyst used was tin octoate, which was added before the first reactor. Ethylhexyl acid phosphate was used as the catalyst deactivator, and the addition line was connected immediately after the first devolatilization tank. The supply amount of each component is shown below.

Raw material supply flow rate: 1.5 l / hour Catalyst supply flow rate: 0.5 ml / hour Catalyst deactivator supply flow rate: 0.5 ml / hour

The composition of the raw material lactide and aliphatic polyester is summarized below. L-lactide: 62% D-lactide: 2% Aliphatic polyester: 23% Toluene: 13%

The constituent components of the polyester are 49 mol% succinic acid, 49 mol% polypropylene glycol, 2 mol% pyromellitic acid component, and a number average molecular weight of 115,000 (in terms of polystyrene). Tin octoate as a catalyst was supplied at 400 ppm. The produced polymer was continuously withdrawn from the discharge part at the upper part of the final reaction tank using a gear pump.

The control temperature of the three-tank reactor used is shown below. First reaction tank reaction temperature: 145 ° C Second reaction tank reaction temperature: 155 ° C Third reaction tank reaction temperature: 165 ° C The conditions for the devolatilization treatment are: the temperature of the heat exchanger before the first devolatilization device: 200 ° C The degree of vacuum in the devolatilization tank was 400 Torr. The temperature of the heat exchanger before the second devolatilization device was 180 ° C., and the degree of vacuum in the devolatilization tank was 1 Torr. Evaporate from the devolatilization tank was collected by a condenser.

The product recovered from the first devolatilization tank was dried at about 100% toluene and then could be reused. A large amount of lactide was collected from the second devolatilization tank, and toluene was also confirmed. A crystallization operation was performed from toluene to collect lactide. After the obtained resin was pelletized, various properties and physical properties were measured.

After the obtained polymer was pelletized, various properties and physical properties were measured. The obtained pellet was a slightly yellowish transparent resin. From the result of GPC, a lactic acid-based polyester having a weight average molecular weight of 140,000 was confirmed. 0.1% of the lactide monomer remained, and toluene was not confirmed. As a result of DSC,
The melting point was 159 ° C.

[Sixth Embodiment] A second method is performed in the same manner as in the fifth embodiment.
Pellets obtained without devolatilization in a devolatilization tank were thoroughly dried, and extruded with a vented single-screw extruder with an extrusion screw diameter of 50 mm and L / D = 30 under conditions of an extrusion temperature of 170 ° C., A sheet having a thickness of 1.0 mm and excellent transparency was obtained. The vent conditions were a vacuum degree of 1 torr, a screw rotation speed of 20 rpm, and a discharge rate of 5 kg / hr.
The molecular weight of the obtained sheet and the amount of residual lactide were measured, and the results are shown in Table 1.

[0108]

[Table 1]

Example 7 To 3 parts by weight of an aliphatic polyester (sebacic acid component 48.5 mol%, propylene glycol component 48.5 mol%, pyromellitic acid component 3 mol%, weight average molecular weight 62,000) L-lactide 95
1 part by weight and 2 parts by weight of D-lactide are added, the atmosphere is replaced with an inert gas, both are melted and mixed at 165 ° C. for 1 hour, and tin octanoate is added at 400 p as an esterification catalyst.
pm was added and the reaction was carried out for 6 hours to prepare a lactic acid-based polyester composition.

After completion of the reaction, 400 ppm of a mixture of monoisodecyl phosphate and diisodecyl phosphate was added, and the mixture was stirred for 5 minutes, after which it was taken out from the die at the bottom of the reactor in a strand form using a gear pump to prepare pellets of lactic acid type polyester. The weight average molecular weight is 164,
000, 4.6% of lactide monomer remained.

Using a thin film distillation apparatus, the lactic acid-based polyester was vacuumed at a pressure of 1 torr and the temperature of the drawn resin was set to 180.
Residual lactide was removed at ° C. The weight average molecular weight after the treatment was 146,000, and the residual lactide was 0.7%.

[Example 8] 50 parts by weight of an aliphatic polyester (48.5 mol% sebacic acid component, 48.5 mol% polypropylene glycol, 3 mol% pyromellitic acid component 120,000 weight average molecular weight) L- Lactide 4
9 parts by weight and 1 part by weight of D-lactide were added, the atmosphere was replaced with an inert gas, and both were melted at 165 ° C. for 1 hour.
Mix and add 300 parts of tin octoate as an esterification catalyst.
ppm was added and the reaction was carried out for 4 hours.

After completion of the reaction, 600 ml of a mixture of monoethylhexyl phosphate and diethylhexyl phosphate was added.
ppm was added and the mixture was stirred for 10 minutes to prepare a lactic acid-based polyester in the same manner as in Example 1. From the GPC measurement results, the weight average molecular weight was 145,000, and the residual lactide monomer was 4.2.
%Met. This lactic acid-based polyester composition was continuously introduced into a twin-screw extruder type devolatilization tank by a gear pump, a vacuum degree of 1 torr and a screw rotation speed of 200 rp.
The residual lactide was removed at m, the resin flow rate was 10 kg / hr, and the resin temperature was 185 ° C. Weight average molecular weight is 127,000
0, the residual lactide was 0.3%.

[Comparative Example 1] A second method was carried out in the same manner as in Example 5.
The obtained pellets were prepared in the devolatilization tank without adding the catalyst deactivator. The devolatilization conditions were the same as in Example 5. The molecular weight and residual lactide amount of the obtained pellet were measured, and
The results are shown in Table 2 in comparison with.

[0115]

[Table 2]

[Comparative Example 2] In the same manner as in Example 5, the catalyst deactivator was not added, and the pellets obtained without devolatilization in the second devolatilization tank were sufficiently dried. Extrusion temperature 17
Extrusion screw diameter 5 with L / D = 30 at 0 ° C
It was extruded by a 0 mm vented single-screw extruder to obtain a 1.0 mm-thick sheet having excellent transparency.

The vent conditions were a vacuum degree of 1 torr, a screw rotation speed of 20 rpm, and a discharge rate of 5 kg / hr. The molecular weight of the obtained sheet and the amount of residual lactide were measured, and the results are shown in Table 3.

[0118]

[Table 3]

[0119]

INDUSTRIAL APPLICABILITY The present invention is excellent in that the catalyst added during the production of lactic acid-based polyester is deactivated by a catalyst deactivator, thereby suppressing the decomposition of lactic acid-based polyester in the devolatilization step and the molding processing step. It is possible to provide a method for producing a biodegradable lactic acid-based polyester having a sufficient high molecular weight and heat resistance, which is useful as a versatile packaging material such as a sheet and a film having moldability, biodegradability and transparency.

Claims (11)

[Claims] 1. A method for producing a low-lactide-containing lactic acid-based polyester, which comprises adding a deactivator to a polymerization catalyst after the polymerization reaction of the lactic acid-based polyester. 2. The method for producing a low lactide-containing lactic acid-based polyester according to claim 1, wherein the deactivator is an alkyl phosphate and / or an alkyl phosphonate. 3. The method for producing a low-lactide-containing lactic acid-based polyester according to claim 1, wherein the deactivator is added before obtaining the granular material after the polymerization of the lactic acid-based polyester. 4. A granular material is obtained by adding a deactivator after polymerization of a lactic acid-based polyester and devolatilizing and removing volatile components under reduced pressure. A method for producing a lactic acid-based polyester containing low lactide. 5. A method for producing a low-lactide-containing lactic acid-based polyester, which comprises adding a deactivator for a polymerization catalyst to a granular material after a polymerization reaction of a lactic acid-based polyester and molding the same. 6. The method for producing a low-lactide-containing lactic acid-based polyester according to claim 5, wherein the deactivator is an alkyl phosphate and / or an alkyl phosphonate. 7. The low lactide according to claim 5, wherein a deactivator is added to the granular material after the polymerization of the lactic acid-based polyester, the volatile components are removed by devolatilization under reduced pressure, and the molding is performed. Method for producing lactic acid-containing polyester. 8. A lactic acid-based polyester having a lactic acid component of 50 to 9
The method for producing a low-lactide-containing lactic acid-based polyester according to any one of claims 1 to 7, which comprises 8 parts and 2 to 50 parts of a polyester composed of a dicarboxylic acid component and a diol component. 9. The method for producing a low-lactide-containing lactic acid-based polyester according to claim 1, wherein the lactic acid-based polyester is polylactic acid. 10. The lactic acid-based polyester after polymerization is heated at a temperature of 150 to 180 ° C. and a vacuum degree of 0.01 using a thin film distiller.
The method for producing a lactic acid-based polyester according to any one of claims 1 to 9, wherein residual lactide in the lactic acid-based polyester is removed at -30 torr. 11. The lactic acid-based polyester after polymerization is heated at a temperature of 150 to 180 ° C. using a twin-screw extruder type devolatilizer.
The residual lactide in the lactic acid-based polyester is removed at a reduced pressure of 0.01 to 30 torr.
9. The method for producing a lactic acid-based polyester according to any one of 9.