JP3458911B2 - Continuous production method of lactide copolymer - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for continuously producing a copolymer of lactide and a polymer having a hydroxyl group.
Examples of the use of this lactide copolymer include bags for foods, industrial products, fibers, sundries, packaging materials such as films and binding tapes, and agricultural mulch films. Examples of sheets and injection-molded products include sundries, food containers, curing sheets, seedling pots, industrial materials, and industrial products.

[0002]

2. Description of the Related Art Polylactic acid obtained by ring-opening polymerization of lactide is widely known as a biodegradable polymer that is hydrolyzed and further decomposed by microorganisms. Conventionally, there are two types of known manufacturing methods. That is, there are a method of directly obtaining a polymer by dehydration polycondensation from lactic acid, and a production method of once converting lactic acid into a dehydrated cyclic ester called lactide and further subjecting this to ring-opening polymerization.

According to the former direct polycondensation method, the molecular weight of 4,
It is difficult to obtain more than 000 polymers, and (C.H.H.
Alten, "Lactic Acid", page 226,
(Verlag Chemie, 1971) Even if a high molecular weight is attempted by studying reaction operating conditions, Japanese Patent Publication No. 2-52
The molecular weight of about 20,000 is the limit as seen in Japanese Patent No. 930, and when the production of a further high molecular weight polymer is required, the latter ring-opening polymerization method of a cyclic ester compound has been used. (For example, Japanese Patent Publication No. 56-14688)

These conventional production methods are specifically batch-type polymerization methods using a reaction vessel in which a solid lactide is charged into a stirring tank, heated and melted, and then ring-opening polymerization is carried out in the presence of a catalyst. However, polylactic acid obtained by ring-opening polymerization of lactide is accompanied by an increase in the average molecular weight,
Since the polymer viscosity rises to a very high viscosity region of 10,000 to several hundreds of thousands of poise and the melting point is 160 ° C. or higher, it is preferable to keep the reaction system at a high temperature to reduce the viscosity and proceed the reaction. However, polylactic acid and polylactic acid-based copolymers easily cause a decrease in molecular weight even by heat.

Even in a sealed reaction vessel, 18
Decomposition gradually starts from around 0 ° C, and accelerated decrease in molecular weight occurs at a high temperature of 250 ° C or higher. Therefore, continuous production of polylactic acid or a lactide-based copolymer from a high-viscosity polymer in a narrow temperature distribution range while preventing runaway of the reaction due to heat of reaction has not been easy in an ordinary reaction kettle.

Japanese Patent Laid-Open No. 5-93050 discloses an example in which a continuous polymerization method of monomers using a stirring reactor connected in series is applied to the production of a lactide copolymer. Examples of the monomer capable of reacting with lactide disclosed in this publication include epoxy compounds represented by propylene oxide, intermolecular cyclic esters represented by glycolide, lactones represented by ε-caprolactone, and trimethylene carbonate. A typical example is a cyclic carbonate monomer.

In the case of reaction with these monomers, the resulting copolymer usually has lower melting points and glass transition points than lactic acid homopolymers. In addition, the transparency becomes low, and further,
The reaction rate becomes slower than the polymerization reaction rate of the lactide homopolymer, and the productivity decreases even in continuous production.
Further, in the publication, a two-tank continuous type manufacturing apparatus is illustrated, but in the two-tank continuous manufacturing method, even if the residence time is actually lengthened, mixing of raw materials continuously supplied into the product by bypass occurs, The resulting polymer becomes opaque, and only those with insufficient physical properties are obtained.

Further, in Japanese Unexamined Patent Publication (Kokai) No. 5-93050, the reaction is limited to homopolymerization of lactide or reaction with a monomer capable of copolymerizing lactide, and three or more lactide and polymer are connected in series. A continuous production example using the agitated reactor was not known in the past.

[0009]

The problem to be solved by the present invention is to solve the problems such as high viscosity, thermal decomposability and coloring of the reaction solution, which are problems in the production of the lactide copolymer, and A degradable lactide-type copolymer that has a wider range of physical properties than lactide-type copolymers and is useful in a wide range of fields such as film sheets for packaging materials, injection molded products, lamination, and industrial products. It is to provide a continuous manufacturing method for efficiently producing.

[0010]

Means for Solving the Problems In order to solve the above-mentioned problems, the inventors of the present invention have made extensive studies on a method for continuously producing a lactide-based copolymer, and as a result, a polymer having lactide and a hydroxyl group at a specific ratio. By reacting with 3 or more reactors, it is possible to react with a wide variety of polymers, and various lactide copolymers obtained can be obtained from soft to hard ones. Further, a high molecular weight copolymer having a weight average molecular weight of 20,000 to 400,000 is obtained, and the transparency is not inferior as in the copolymer obtained by the copolymerization reaction of lactide and a monomer, and the reaction rate is also low. It has been found that high productivity can be obtained at a level equal to or higher than the reaction of lactide homopolymer, and the present invention has been completed.

That is, according to the present invention, a first reactor of a continuous reaction apparatus in which three or more stirred reactors are connected in series is provided.
50 to 98 parts by weight of lactide and 2 to 50 parts by weight of a polymer having a hydroxyl group are melted or dissolved in a solvent,
It is continuously fed, and further sequentially transferred from the first reactor to each reactor connected in series, and the reaction pressure is 1 to 5 atm in the first reactor and each connected reactor. A method for continuously producing a linear lactide copolymer having a molecular weight of 20,000 to 400,000, which is characterized by carrying out ring-opening copolymerization at a temperature of 140 to 210 ° C.

More specifically, the present invention has a lactide polymerization rate of 30% to 80% in the first reactor of a continuous reactor in which three or more stirred reactors are connected in series, and a reaction solution is used. Has a viscosity of 2000 poise or less. A continuous production method for a linear lactide copolymer having a molecular weight of 20,000 to 400,000.

According to the present invention, the polymer having a hydroxyl group has a hydroxyl group at the terminal and has a melting point or a softening point of 180.
The continuous production method described above, which is a polyester of ℃ or less, and a solvent having a boiling point of 70 to 180 ° C. as a reaction solvent, and a total of 1 of a polymer having lactide and a hydroxyl group.
It is a continuous manufacturing method characterized by adding 3 to 30 parts by weight to 00 parts by weight.

In the present invention, after the polymerization reaction, the residual lactide and / or the residual solvent in the produced copolymer is removed to 1% by weight or less, and the reaction solvent has a boiling point of 70%. A solvent at ˜180 ° C. is added in an amount of 3 to 30 parts by weight to 100 parts by weight of the total of the polymers having lactide and a hydroxyl group to carry out a ring-opening copolymerization reaction,
After the reaction, the above-mentioned continuous production method is characterized in that the residual lactide and / or the residual solvent in the produced copolymer is removed to 1% by weight or less.

Further, in the present invention, after the reaction is carried out in a stirring type reactor, the ring-opening copolymerization is further carried out by using a continuous reactor equipped with a static mixer, and as a reaction solvent. , A solvent having a boiling point of 70 to 180 ° C., a total of 1 of lactide and a polymer having a hydroxyl group.
After adding 3 to 30 parts by weight to 00 parts by weight, a ring-opening copolymerization reaction is carried out, and further ring-opening copolymerization is carried out using a continuous reactor equipped with a static mixer. It also includes a continuous production method characterized by removing residual lactide and / or residual solvent to 1% by weight or less.

The present invention will be described in more detail below. First, a continuous reaction apparatus equipped with a stirring reactor according to the present invention will be described. For ease of understanding, the description will be given along with FIG. 1 and FIG. 2 which illustrate the continuous reactor diagram. The agitated reactor referred to in the present invention is a dynamic mixer having an ordinary agitator.

Specifically, it refers to a reaction kettle equipped with a stirring device having stirring blades connected to a normal power machine, and causes the reactant of the fluid in the reactor to swirl or change the swirling speed by the power machine. It refers to an apparatus having a stirring type reactor that mixes solutions by disturbing or changing or reversing the flow direction and repeating division, conversion and inversion. (R ₁ ~ in FIG. 1
R _4, and indicated by R ₁ to R ₃ in Figure 2. )

In the case of a polymer having thermal decomposability, in dynamic stirring, if the stirring force is increased in order to homogenize the inside of the reaction system, the heat of stirring also increases, resulting in the progress of decomposition of the polymer. However, stirring is an important factor that determines the performance of the polymer produced. Although the stirring effect is largely controlled by the stirring speed, the stirring time, the shape and size of the stirring blade,
It largely depends on the size of the reactor, the clearance between the stirring blade and the reactor wall, and the like.

Further, the stirring effect depends on the viscosity of the polymer to be stirred and cannot be determined only by the stirring speed. However, in the low viscosity region at the initial stage of the reaction, the stirring should be set so that the Reynolds number is 100 or more according to the following formula. In the high viscosity region in the latter half of the reaction,
It is considered impossible to set the Reynolds number to 100 or more for stirring, and it is necessary to make the stirring efficient by the shape of the stirring blade.

Re = n × Di ² × ρ / η (Equation 1) (In the equation, Re is the Reynolds number, and n is the rotational speed (rotation /
Sec), Di is the stirring blade diameter (m), ρ is the solution density (kg / m
³ ) and η represent solution viscosity (kg / cm · sec). )

In the case of a continuous reaction using a multi-tank reactor, the reaction product in the reactor used in the initial stage of the reaction has a low viscosity, and the stirring is good regardless of the shape of the stirring blade. However, turbine blades, furdler blades, helical ribbon blades or multistage blades thereof are preferable for the purpose of efficiently generating the upstream and downstream in the reactor. Alternatively, a blade capable of uniformly stirring the entire reaction system such as an anchor blade is also preferable.

The reaction product of the reactor used in the latter stage of the reaction has a high viscosity, and the shape of the stirring blade greatly affects the stirring. In particular, it is difficult to stir well around the wall in the reactor, so in order to efficiently scrape the reaction product from the wall, the entire reaction system such as turbine blade, helical ribbon blade, anchor blade, etc. It is preferable to use a stirring blade that can stir the mixture uniformly.

In the case of the anchor blade, it may be difficult to stir the central portion of the reactor, and in order to confirm that the stirring is performed well, the reactor wall and the stirring blade, or the stirring blade is used. It is effective to install a temperature sensor that monitors the temperature of the shaft. This temperature sensor is also effective for efficiently controlling the temperature inside the reactor.

The power of the stirrer largely depends on the viscosity of the reactant and the shape of the reactor, but can be estimated by the equation (2). P = k × n ² × Di × Dt ^1.1 Wi ^0.3 × H ^0.6 (Equation 2) (In the equation, P is the stirring power (kg · m / sec), k is the coefficient depending on the stirring blade, and n is the rotation speed ( (Rotation / second), Di is the stirring blade diameter (m), Dt is the reactor width (m), Wi is the stirring blade vertical length (m), and H is the liquid depth (m).)

Depending on the type of the stirred reactor, many reactors are equipped with a jacket for heat exchange on the outer peripheral portion thereof. There is also a reactor equipped with a tube for heat exchange for passing a heat medium. Regarding the temperature control of the stirred reactor, it is common to circulate steam and / or an oil heating medium on the side surface and / or the bottom surface of the reactor.

The medium to be circulated is preferably steam when a reaction of 170 ° C. or lower is used as a control, and a cooling medium such as water can be injected when the reaction system is abnormally heated, which is preferable. When the reaction temperature exceeds 150 ° C., the pressure becomes too high with the steam heating medium, and an oil circulation type heating medium is preferable.

In the multi-tank reaction apparatus of the present invention, the reactor that performs the reaction in the initial stage of the reaction generates heat, and it is not preferable to carry out the reaction at a too high temperature for the purpose of preventing runaway of the reaction. Therefore, heating with steam is sufficient. A reactor that performs a reaction in the latter half of the reaction has high viscosity and generates little heat. Further, since it is preferable to carry out the reaction at a high temperature for the purpose of completing the reaction, heating with an oil heating medium is preferable. The oil heat medium can be used even at a low temperature, and the whole reactor can be heated with the oil heat medium.

In the case of the continuous reactor of the present invention, the more the number of stirring reactors is, the more homogeneous polymer is produced. In some cases, the polymer can be continuously produced even by using two stirred reactors connected in series. However, in the production of the lactide-based copolymer comprising the lactide and the polymer having a hydroxyl group according to the present invention, Two stirred reactors connected in series are unsuitable.

This is because, as a result of the raw material and the product being continuously supplied being mixed in the stirring type reactor, the raw material or the intermediate product does not have a sufficiently high molecular weight, and the reaction is not completed and the reactor is still incomplete. It will be leaked. In order to prevent this, it is necessary to increase the reactor size and lengthen the residence time.However, when the reactor size is increased, the reaction liquid of the lactide-based copolymer that accompanies the higher molecular weight of the product is With the increase in viscosity, stirring and removal of heat generation become extremely difficult, and the reaction temperature cannot be controlled. Therefore, it is necessary to further increase the number of reactors, specifically, 3 or more reactors are required.

In the production method of the present invention in which the same amount of product is withdrawn while continuously supplying the raw material, the larger the total number of reactors, the better the separation of the raw material and the product.
The amount of unreacted raw material mixed in the product is reduced. Further, the capacity of the reactor becomes small, the stirring power for each reactor is small, and the temperature control by the heat medium becomes easy.

However, as the number of reactors increases,
There is a problem that the number of motive power of the apparatus increases and the number of pumps connecting the reactors also increases, which complicates the control. Therefore, the number of stirring reactors used should be set as small as possible within the range where a sufficient polymerization rate can be obtained, and the number of reactors used in the present invention is preferably 3 or more, usually 3 to 5.

The latent heat cooling type stirred reactor as an example of the present invention has a condenser for trapping a monomer and / or a solvent installed at the upper part of the reactor (C _{1 in} FIG. 1). The reaction temperature can be controlled by using the heat of vaporization of the raw material monomer or solvent. That is, when the raw materials are put into the reactor, a space is formed in the upper part of the reactor, and cooling is possible by radiating heat from the liquid surface in the upper part of the solution to dissipate heat.

For this reason, the temperature control is easy, the reaction temperature can be set high, and high productivity can be realized. The inside of the reactor can be depressurized or pressurized for the purpose of promoting or suppressing the evaporation of the monomer and solvent, and it is important to control the temperature of the reaction system by installing a pressure sensor for this purpose. The reaction system in the present invention is preferably in an atmosphere of an inert gas, and in order to prevent decomposition by heat or oxygen during the reaction, pressurization is preferably performed with an inert gas such as nitrogen or argon.

When the agitated reactor is a latent heat cooling type, there is a space above the reactor, and liquid feeding from the reactor to the reactor requires power for each reactor. Pump the raw material liquid by the first
It is supplied to the stirring reactor of No. 1 and is then pumped from the first reactor to the subsequent second reactor, and liquid is also pumped from the third reactor onward.

A plunger pump is suitable as a pump (indicated by P ₀ in FIG. 1) because the raw material becomes a low-viscosity solution for liquid feeding to the first reactor. The liquid can be sent to the second reactor by a plunger pump when the reaction liquid has a low viscosity, but when the reaction proceeds in the first reactor and the viscosity increases,
A gear pump may be suitable. (Indicated by P _{1 to} P ₄ in FIG. 1)

From the third reactor to the final reactor, the first reactor
The type of pump is selected according to the viscosity of the medium to be fed, as well as the selection of the liquid feeding method between the reactor and the second reactor. In order to make the amount of solution in each tank the same, it is important that the amount of liquid sent between the reactors is always the same.The flow meter that measures the amount of liquid sent or the liquid level that measures the amount of liquid in each tank It is preferable to provide a meter and control the whole as a whole.

The liquid-filled stirred reactor (shown in FIG. 2), which is one example of the present invention, is a multi-reactor in which multiple reactors are connected in series and a single pump is used. It is a device that can send liquid to a container. When putting the raw materials in the reactor, one pump may be used, and the reaction can be performed in a closed system, from the raw material charging to the reaction, the devolatilization, and the pelletization of the polymer without contact with the outside air. Can be done.

In the continuous polymer continuous production method of the present invention, in which multiple tanks are filled and filled with a stirring reaction, the reaction, the devolatilization, and the polymer are carried out from the raw material charging without any contact with the outside air. Can be pelletized. This is an advantage that cannot be obtained by the conventional production method using a batch reactor, and is a very suitable continuous polymerization method particularly for producing a decomposable polymer that is decomposed by heat, oxygen and water used in the present invention.

Since the lactide is solid at room temperature and the polymer having a hydroxyl group used for copolymerization is generally in a solid or semi-solid state, the raw materials are supplied by a dissolving tank or a solvent for heating and melting them. A dissolution tank is required. Since a polymer having a hydroxyl group is often a solid and has a high viscosity even when melted, it is preferable in view of the operation of the apparatus that the polymer is dissolved in a solvent and then fed to be mixed with a lactide solution.

As these solvents, benzene, toluene, ethylbenzene, xylene, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, THF,
Isopropyl ether is preferably used.

The method of supplying the raw material lactide and the polymer having a hydroxyl group is extremely important in the continuous production method of the present invention. That is, most of the polymers having a hydroxyl group used in the present invention contain a catalyst for the production thereof, and for example, a hydroxyl group-containing polyester contains an esterification catalyst.

Since these catalysts have a function as a polymerization reaction catalyst with the raw material lactide and the polymer having a hydroxyl group, when these raw materials are mixed before being transferred to the reactor, they have a lactide and a hydroxyl group. Polymer,
When melted by heating or dissolved by heating with a solvent, a polymerization reaction is initiated, which may unnecessarily increase the viscosity of the transfer liquid and cause a trouble in the transfer of the raw material liquid to the reactor. It is preferable to prepare the solution in a separate dissolution tank and transfer the solution to the reactor through a separate transfer line.

Specifically, as an example, a tank (indicated by T ₁ in FIG. 2) for preparing a reaction raw material solution by mixing and heating lactide, a polymer having a hydroxyl group, and / or a solvent, and this solution. This is a raw material supply method including a tank (indicated by T ₂ in FIG. 2) for stocking the raw material so that a uniform raw material is always fed into the reactor before the liquid is fed to the reactor.

As another raw material supply method, lactide,
And a polymer having a hydroxyl group are separately melted or dissolved in a solvent, fed in two lines, and mixed at an arbitrary ratio before being supplied to a stirring reactor, so that a uniform raw material is always present in the reactor. It is a raw material supply method that is sent (shown in FIG. 1).

In any of the feeding methods, it is important to control the temperature of melting and melting of the raw materials, and melting of lactide,
It is preferable to keep the dissolution tank at 95 to 145 ° C. in order to prevent decomposition and coloring of lactide, and it is preferable to keep the melting and dissolution tank of the polymer having a hydroxyl group at 95 to 165 ° C. in order to prevent decomposition and coloring. . Further, the atmosphere of the raw material melting tank is preferably replaced with an inert gas, and nitrogen, argon or the like is preferably used in order to prevent mixing of oxygen and water.

The catalyst is preferably supplied from the first reactor or the raw material dissolving tank in the line of the first reactor, or an appropriate amount is gradually added to each reactor. It is preferable that the solution catalyst is supplied as it is or after being dissolved and diluted in a solvent, and the solid catalyst is dissolved in the solvent and quantitatively sent by a plunger pump (indicated by A ₁ in the figure). ).

It is important to uniformly mix the lactide, the polymer having a hydroxyl group, and the solvent in order to carry out the reaction rapidly and homogeneously. When mixing the catalyst solution and the raw material solution, a static mixer and Alternatively, it is preferable to thoroughly mix with an in-line mixer.

When the reaction solvent or residual lactide remains in the produced polymer after completion of the reaction, the heat resistance of the polymer is lowered, the lactide is decomposed to generate lactic acid, the hydrolysis is promoted, or the resin is molded and processed. It is preferable to remove the solvent and residual lactide from the produced polymer also from the viewpoint of odor and safety and health afterward.

In the present invention, in order to modify the physical properties of the polymer, the reaction is carried out in a stirring reactor, and then in a devolatilizer (indicated by V ₁ and V ₂ in the figure) connected, the produced polymer is contained. It is preferred to remove residual lactide, residual solvent or low molecular weight impurities.

The method of taking out the produced polymer from the stirring type reactor after the completion of the polymerization reaction is, for example, by using a preheater (indicated by H in the figure) equipped with a static mixer connected to the stirring type reactor. The composition is heated and melted for the purpose of giving sufficient fluidity to the material and providing heat equivalent to the latent heat of vaporization of the devolatilized material.

The product withdrawn from the reactor also contains some unreacted raw materials and products in the process of reaction, and for the purpose of completing this reaction, a vertical multitubular heat exchanger and a heat exchanger were used. It is preferable to heat using a static mixer equipped with a vessel. In particular, in the production of the high molecular weight polymer of the present invention, in the high viscosity region where the resin viscosity exceeds 10,000 poise, not only the heat of polymerization but also the heat of stirring caused by the shear stress of stirring is violently generated, and dynamic stirring is performed. However, since local heat generation in the stirring section becomes remarkable, it is particularly preferable to use a static mixer which has a small shearing stress and acts uniformly.

The devolatilizing apparatus is usually a vertical type, and a one-step devolatilizing apparatus can be used to carry out devolatilization at a temperature at which the residual lactide or the residual solvent is volatilized. It is also possible to perform devolatilization by combining the devices. That is, in the first stage devolatilizer, the degree of vacuum is 20 to 150 mm.
It is a method in which devolatilization is performed with Hg, and devolatilization is performed in a second stage devolatilization device at a higher vacuum degree, that is, a vacuum degree of 1 to 20 mmHg.

As the vacuum devolatilizer, a normal devolatilizer can be used, and a flash devolatilizer for extruding the molten polymer into a tank in the form of one or a plurality of strands can be used, or an extruder with a vent can be used. Alternatively, a high-viscosity thin film type devolatilizer can be used.

In the case of a flash type devolatilizer for extruding the molten polymer into a tank in the form of one or a large number of strands, if the molten polymer is heated by a heat exchanger etc. before being sent to the devolatilizer, the devolatilization will occur It is preferable because the polymer can be prevented from being hardened by latent heat of vaporization of the substance. In addition, it is preferable to quantitatively send the polymer by using a gear pump or the like. After devolatilization, the devolatilized polymer is extracted from the bottom of the flash tank by a gear pump or screw pump and sent to a pelletizer.

In the case of an extruder type devolatilizer with a vent,
A twin-screw extruder is preferred from the viewpoint of polymer driving force, but a single-screw extruder is also possible. In this type of devolatilization, the screw shape is an important factor in the degree of vacuum of the vent, the devolatilization time, and the devolatilization efficiency. With this type, it is easy to control the devolatilization time, but it is preferable to devolatilize in a short time because shear stress is easily applied to the molten polymer. Further, it is preferable that the number of vents is plural and the degree of vacuum is adjusted as necessary.

A high-viscosity thin-film type devolatilizer can also be used. In this type of devolatilization, the screw shape is an important factor in devolatilization time and devolatilization efficiency. In this type,
Although shear stress is likely to be applied to the molten polymer, it can be devolatilized in a short time by efficiently taking the surface area.

After devolatilization, the devolatilized polymer can be taken out from the devolatilizer and pelletized by a pelletizer (indicated by D in the figure), or the vented extruder can be used to pelletize the polymer to a diameter of 0. It can also be extruded and pelletized as a plurality of linear polymers having a diameter of 3 to 3 mm.

The polymer whose devolatilization was completed was taken out by a gear pump, and the lactide was a condenser (C in the figure).
Shown in ₂ . ) Is used to condense, recover, and recycle (E in the figure
Indicate. ), And can be subjected to the reaction with the raw material lactide again.

The lactide is regenerated by distillation and / or recrystallization, and the solvent is regenerated by distillation. By using these devolatilizers, the residual monomer content in the lactide-based copolymer produced can be reduced to 1% or less, more preferably 0.2% or less.

Additives are added to improve the physical properties of the polymer for the purpose of further plasticizing the produced lactide copolymer, improving thermal stability during molding, preventing oxidation, and improving flame retardancy. be able to. Immediately after the final tank of the stirred reactor,
And / or an additive addition line (indicated by A ₂ in the drawing) can be provided immediately after the devolatilization device. After the additives are added, the pellets can be pelletized as they are, or can be pelletized after being mixed with an extruder, a static mixer or the like, if necessary.

In the continuous production method of the present invention, the lactide solidifies at room temperature, and usually, the decomposition of the produced lactide copolymer gradually starts from around 180 ° C. Therefore, the temperature control during the transfer of the raw material and the product is controlled. Is especially important. Regarding the transfer of raw materials and products, the melting point of lactide is about 100 ° C., and the polymer having a hydroxyl group used for copolymerization is also in a solid or semi-solid state, and the resulting copolymer is also solid. For at least 10
It is preferable to transfer at 0 ° C or higher.

More preferably, the transfer line is preferably maintained at 125 to 165 ° C., which is a temperature at which a rapid reaction does not occur in the transfer line and sufficient fluidity is exhibited. Further, regarding the transfer of the raw material lactide, the polymer and the solvent solution thereof, when the catalyst is present, the polymerization reaction proceeds and a rapid increase in viscosity occurs.
It is preferable to add in a reactor or in a transfer line from the raw material preparation tank to the first reactor, or to add an appropriate amount gradually for each reactor.

Regarding the transfer of the produced copolymer and these solvent solutions, it is preferable that the viscosity is high and the transfer temperature is high. Since the decomposition start temperature of the produced copolymer varies depending on the components used, it cannot be unconditionally specified. However, the decomposition start temperature of the produced copolymer is about 1 if it is low.
The temperature is around 85 ° C., and it is originally not preferable to raise the temperature more than this.

However, even if the produced copolymer contains a solvent, the produced copolymer solidifies or separates from the solvent at a low temperature. Therefore, the produced copolymer should be transferred in a state of maintaining fluidity. Is usually 150 ℃
The above is necessary, and the temperature at which decomposition is minimized and sufficient fluidity is maintained is usually 160 to 210 ° C, and more preferably 160 to 180 ° C.

Next, the polymerization components of the lactide copolymer of the present invention will be described. The lactide referred to in the present invention is
Two molecules of lactic acid are intermolecularly dehydrated and cyclic esterified. Since lactic acid has stereoisomers, lactide is also a monomer having stereoisomers. That is, lactide includes L-lactide composed of two L-lactic acids, D-lactide composed of D-lactic acid, and M composed of L-lactic acid and D-lactic acid.
There is ESO-lactide.

These have slightly different physical properties, and their mixtures also show different physical properties. Therefore, the lactide-based copolymer of the present invention can realize preferable resin properties by arbitrarily combining these three types of lactide. In the present invention, it is preferable that the lactide contains 75% or more of L-lactide in the total lactide in order to express high thermophysical properties, and in order to express higher thermophysical properties, the lactide should contain L-lactide in 90% of total lactide.
% Or more is preferable.

There are many kinds of hydroxyl group-containing polymers referred to in the present invention, and various lactide copolymers can be obtained from hard to soft ones depending on the characteristics of the polymers. . The polymer having a hydroxyl group is not particularly limited, but polyester having a hydroxyl group at the terminal and polyoxyalkylene ether are particularly preferably used. The lactide-based copolymer using these is easy to obtain a block-like or random copolymer.

In addition, polyvinyl alcohol, starch, cellulose and cellulose ether can be used.
When these are used, a polymer close to graft polymerization is easily obtained. Similarly, a polymer having an ester bond can be used for copolymerization, and examples thereof include polyvinyl acetate, vinyl acetate / ethylene copolymer, polycarbonate, and cellulose ester.

When reacted with a polymer having a hydroxyl group,
Not only lactide-based copolymers having various properties can be obtained, but also high-molecular-weight copolymers are obtained, and the reaction rate is equivalent to that of the reaction of lactide homopolymers. This is because the hydroxyl group of the polymer acts to control the chain transfer in the growth reaction of the polymer chain.

The polymer chain growth reaction is considered to be a reaction in which a catalytic metal is coordinated to a carboxy anion and a lactide monomer is inserted (Macro Chem. 1).
87, 1611-1625 (1986) and E
ur. Polym. J. 25, 585-591 (19
1989)). The growing end of the polymer activated by the catalyst undergoes chain transfer due to the hydroxyl group. At this time, unlike a functional group having a strong acidity such as a carboxyl group, it has an advantage of not deactivating the catalyst.

Therefore, the polymer having a hydroxyl group has both the functions of adjusting the molecular weight of the polymer and accelerating the reaction. By reacting a polymer having a hydroxyl group with lactide, it is possible to produce lactide-based copolymers having various properties from flexible copolymers to high-strength copolymers. For example, polyvinyl alcohol, polyvinyl acetate, vinyl acetate / ethylene copolymer, cellulose ether, or a lactide-based copolymer with a flexible polyester has flexible properties.

Polycarbonate, cellulose ester,
Alternatively, a lactide-based copolymer with a hard polyester has high strength properties. In the present invention, one or more polymers having these hydroxyl groups, or a mixture thereof can be used without particular limitation, but it is preferable that the polymers used have a relatively large molecular weight, specifically, a weight average molecular weight of 10,000. To 300,000, more preferably those having a weight average molecular weight of 20,000 to 200,000 and having a melting point or softening point of 180 ° C. or lower.

The reaction mechanism of copolymerization between lactide and a polymer having a hydroxyl group and / or an ester bond is complicated, but the reaction mechanism with a polyester having a hydroxyl group is as follows when the polymerization reaction is traced by GPC. , Ring-opening polymerization of lactide takes precedence, and after polylactic acid oligomer is produced to some extent, graft copolymerization and transesterification with a polyester having a hydroxyl group proceed to produce a copolymer. The lactide-based copolymer produced through these ring-opening polymerization and transesterification reaction has a substantially linear structure.

The polyester having a hydroxyl group used in the present invention has a lower melting point or softening point of 180 ° C.
The following are preferable, and those of 50 to 150 ° C. are particularly preferable. This is to obtain a homogeneous lactide-based copolymer, and the lactide and the polymer having a hydroxyl group are dissolved during the polymerization, and the reaction is performed in a well mixed state.

The polymerization temperature is 140 ° C. or higher. At this temperature, the polymer having a hydroxyl group is easily dissolved in lactide, and the lower one of the melting point and the softening point is 18
It is preferably 0 ° C. or less. In addition, crystalline or amorphous may be used, but amorphous transparent polyester is preferable. The melting point referred to here is based on the differential scanning calorimetry (DSC), and the softening point is based on JIS-K-2531.

The polyester having a hydroxyl group preferably has a high molecular weight, specifically, a weight average molecular weight of 10,000 to 300,000 is preferable.
The molar ratio of the dicarboxylic acid component and the diol component is preferably about 1. The dicarboxylic acid component and the diol component constituting the polyester having a hydroxyl group may be of any kind, but the aliphatic dicarboxylic acid component has 4 to 2 carbon atoms.
It is preferable that the aliphatic dicarboxylic acid component is 0.

Specific examples thereof 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 aromatic dicarboxylic acid component is preferably phthalic acid, isophthalic acid and / or terephthalic acid, and other examples include 2,6-naphthalenedicarboxylic acid.

The diol component is not particularly limited as long as it is a diol, but ethylene glycol, propylene glycol, butylene glycol, pentane diol, hexamethylene glycol, octane diol, neopentyl glycol, cyclohexane dimethanol,
Hydrogenated bisphenol A, xylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, dibutanediol, 3-hydroxypivalyl pivalate and the like can be mentioned.

Among them, as the dicarboxylic acid component, it is preferable that the aliphatic dicarboxylic acid component is contained in the total dicarboxylic acid component in a molar ratio of 10 to 50%. When the polymer having a hydroxyl group is subjected to the reaction, it is preferable to remove water and dry it. Examples of the drying method include a method using reduced pressure, a method of storing in a dry atmosphere, and a method of dissolving in a solvent and blowing a dry gas to dry. The smaller the amount of water, the more preferable it is, but 1,000 ppm or less, more preferably 100 ppm or less.

Due to the nature of the polylactic acid moiety having many ester bonds, a higher melting point and glass transition temperature can be realized, and the lactide-based copolymer obtained in the present invention has a glass transition temperature of room temperature or higher or 160 ° C. or higher. A melting point can also be realized. For this purpose, the constituents of the polyester having lactide and hydroxyl group are 50/50 to 98/2 of the polyester having lactide / hydroxyl group, and further, high transparency and thermal characteristics such as glass transition point of 45 ° C. or higher. For the purpose of obtaining, the ratio of lactide to be used and the ratio of lactide to polyester having a hydroxyl group are preferably 85/15 to 95/5 of lactide / polyester having a hydroxyl group.

In the production method of the present invention, it is desirable to use a ring-opening polymerization catalyst. As the ring-opening polymerization catalyst that can be used, tin, which is generally known as a ring-opening polymerization catalyst for cyclic esters and a transesterification catalyst, Examples thereof include metals such as zinc, lead, titanium, bismuth, zirconium, and germanium, and derivatives thereof, and among the derivatives, metal organic compounds, carbonates, oxides, and halides are particularly preferable.

Specifically, tin octoate, tin chloride, zinc chloride, zinc acetate, lead oxide, lead carbonate, titanium chloride, alkoxy titanium, germanium oxide and zirconium oxide are suitable. The amount of the ring-opening polymerization catalyst is 10 to 2,000 based on the total weight of the lactide and the polymer having a hydroxyl group.
ppm is preferred. The reaction rate is sufficiently fast, and in order to reduce the coloring of the obtained lactide-based copolymer,
Particularly, 20 to 1,000 ppm is preferable.

In producing the lactide-based copolymer of the present invention, a lactide-based copolymer is prepared by adding a cyclic ester other than lactide in addition to lactide, a polymer having a hydroxyl group, and a ring-opening polymerization catalyst. You can also Other cyclic esters include glycolides and lactones, and particularly ε-caprolactone and δ-valerolactone. When the amount of glycolide or lactone added is increased, the glass transition temperature is lowered and the flexibility is increased.

Further, when the amount of glycolide or lactone added is 30 parts by weight or more based on the total weight of the lactide and the polymer having a hydroxyl group, the transparency becomes low.
The amount of glycolide or lactone added is preferably 30 parts by weight or less. In the present invention, water, lactic acid, glycolic acid,
And other alcohols and molecular weight regulators such as carboxylic acids can be used up to 0.1%.

The molecular weight of the lactide copolymer produced by the production method of the present invention is 20,0 in terms of weight average molecular weight.
The lactide-based copolymer having a molecular weight range of 0 to 400,000 is formed into a sheet, whereby a sheet having high strength to a flexible sheet can be obtained. Specifically, when a sheet having a thickness of 100 to 500 μm is used, the tensile viscoelasticity is 500 to 50,000 kg / cm ² (measurement conditions: 23 ° C., 50% relative humidity, Seiko Denshi Dynamic Viscoelasticity Measuring Device DMS200). ) Is obtained.

The lactide-type copolymer obtained in the present invention has good biodegradability and is discarded after being used as a general-purpose resin, packaging material, or the like, or even if discarded from the manufacturing process. Helps to lose weight. Even if it is dumped in the sea, it is hydrolyzed and decomposed by microorganisms. It can be decomposed in seawater before the outer shape is maintained because the strength of the resin deteriorates within several months.

Next, the continuous manufacturing method of the present invention will be described more specifically. In the continuous production method of the lactide-based copolymer of the present invention, the residence time in all reactors, that is, the residence time from the first reactor to the final reactor, depends on the type of polymer having a hydroxyl group used for production and the lactide. It depends on the mixing ratio and cannot be determined unconditionally, but it is usually 2 to 8 hours, preferably 3 to 6 hours in the case of a full-fill reactor, and 1 in the case of a latent heat reactor. ~
5 hours, preferably 1.5 to 3 hours.

The residence time and the corresponding polymerization rate differ depending on the type of the polymer having a hydroxyl group used and the mixing ratio with the lactide and cannot be unconditionally determined,
Usually, the polymerization rate in the initial stage of the whole reaction (referred to as the first section), particularly in the first reactor is 30 to 80%, preferably 4%.
It is 0 to 70%.

The reaction temperature for obtaining these polymerization rates also differs depending on the type of the polymer having a hydroxyl group to be used, the mixing ratio with the lactide, and the reaction time, and cannot be unconditionally determined. However, since the reaction proceeds rapidly and the calorific value is large, it is preferable to control the temperature of the first section, particularly the temperature of the first reactor, to be low, specifically 120 to 165 ° C. Is also preferably 0.5 to 2 hours.

At this time, it is essential to control the viscosity of the reaction solution in the first reactor so as to improve the mixing property with the polyester to be copolymerized. Sufficient mixing of the polymer component and the monomer to be copolymerized is important for obtaining a homogenous copolymer, and the mixing with the catalyst is also good and the reaction rate and homogeneity are improved.

Specifically, it is desirable to maintain the viscosity of the reaction solution in the first reactor at 2000 poise or less,
Preferably 0.1 to 1000 poise, more preferably 1
It is preferred to maintain ~ 500 poise. In order to achieve such a polymerization rate in the first reactor, a reaction time, and a reaction liquid viscosity, the reaction temperature, the feed rate of the raw material lactide and the raw polyester, the amount of the solvent, and the amount of the catalyst are appropriately selected. There is a need to.

To describe the first section of these conditions, especially the general combination in the first reactor, the reaction temperature is 145
~ 160 ° C, reaction time 0.5 ~ 1 hour, catalyst amount 15
It is preferable to maintain 0 to 250 ppm, the amount of solvent to 10 to 20%, the polymerization rate to 40 to 70%, and the viscosity to 10 to 500 poises.

In the second half of the next intermediate reaction period, that is, in the second intermediate reaction period from the second reactor of the reactor to the reactor immediately before the final reactor, the polymerization rate of lactide is 55 to 95%, preferably 60%. It is preferably set to 90%. In the second section, the reaction is rather slow, so the reaction temperature is preferably 150 to 180 ° C. from the viewpoint of increasing the reaction rate.

The reaction solution viscosity in this second section varies depending on the properties of the lactide copolymer produced and the presence or absence of a solvent. In the case of a hard lactide copolymer, it is specifically 100 to 3000. It is preferable to maintain the poise, more preferably 200 to 2000 poise.

In particular, in the reactor immediately before the final reactor, the viscosity of the reaction solution is 4000 poise or less, more preferably 500 to 3000 poise. When obtaining a soft lactide-based copolymer,
Although the viscosity does not increase extremely during the reaction, it is preferable to maintain the viscosity of the reaction solution at 20 to 1500 poise.

Even in the reactor immediately before the final reactor,
Usually, the viscosity of the reaction solution is 1500 poise or less, and preferably maintained at 100 to 1500 poise. For the intermediate properties between hard and soft, the viscosity is in this range. To give an example of a general combination of these conditions in the second section, the reaction temperature is 160-170.
C, reaction time 0.5 to 3 hours, polymerization rate 80 to 95
%, It is preferable to maintain the viscosity at 100 to 3000 poise.

In the latter stage of the reaction, particularly in the final reactor, the polymerization rate of lactide is set to 80 to 99%, preferably 85 to 98%. Since the amount of the reactive monomer is small, the reaction rate is slow and the calorific value is small, but the viscosity of the reaction liquid is high due to the large amount of the polymer. Therefore, for the purpose of completing the reaction and reducing the viscosity of the reaction solution, it is preferable to control the reaction temperature at a high temperature, specifically 160 to 200 ° C.

The viscosity of the reaction solution varies depending on the properties of the lactide copolymer produced, but in the case of a hard lactide copolymer, the viscosity of the reaction solution in the final reactor is 1
It is 000 poises or more, and usually about 4000 poises. In the case of a soft lactide-based copolymer, the viscosity does not extremely increase even in the final reactor, and particularly when a solvent is used in combination, the viscosity of the reaction solution is about 100 poise, and most is about 500 poise. . For the intermediate properties between hard and soft, the viscosity is in this range.

In the third section, examples of general combinations of these conditions, particularly in the final reactor, include a reaction temperature of 160 to 170 ° C., a reaction time of 0.5 to 2 hours, and a polymerization rate of 90 to 98. %, The viscosity of the reaction solution is 3000 to 5000 poise in the case of a hard one, and 30 in the case of a soft one.
It is preferable to maintain at 0 to 1000 poise.

In the production of the lactide-based copolymer comprising the lactide and the polymer having a hydroxyl group according to the present invention, a polyfunctional isocyanate and / or a polyfunctional acid anhydride such as pyromellitic dianhydride is further added. By cross-linking the polymer chain, a lactide-based copolymer having a higher molecular weight can also be obtained.

Specific examples of the polyfunctional isocyanate include hexamethylene diisocyanate, toluene diisocyanate, diisocyanylphenylmethane, and
Preferred are those obtained by reacting a polyol such as pentaerythritol with diisocyanate, those obtained by reacting polyether with diisocyanate, and those obtained by reacting polyester with diisocyanate.

The addition amount of these is preferably determined depending on the molecular weight of the lactide copolymer and the molecular weight of the diisocyanate to be used, but generally 0.5 to 1.5 times the equivalent of the lactide copolymer is preferable. For example, molecular weight 17
When hexamethylene diisocyanate is added to 50,000 lactide-based copolymers, 50 to 150 p
pm is preferred.

Various known and customary additives for resins may be further added to the lactide copolymer composed of lactide and a polymer having a hydroxyl group by the continuous production method of the present invention. These additives can be added before the reaction, during the reaction, or after the completion of the reaction.

Typical examples of the additive are 2,6-di-tert-butyl-4-methylphenol (BHT) and pentaerythrityl-tetrakis (3- (3,3). 5-di-t-butyl-4-hydroxyphenyl) propionate), octadecyl-3-
(3,5-di-t-butyl-4-hydroxyphenyl)
Antioxidants such as propionate, triphenyl phosphite, trinonyl phenyl phosphite, butyl hydroxyanisole (BHA),

A UV absorber such as a salicylic acid derivative, a benzophenone type or a benzotriazole type, or a phosphoric acid ester, an isocyanate, a carbodiimide or the like can be used as a stabilizer to improve the thermal stability during molding. The amount of these stabilizers added is not particularly limited, but 100 to 10,000 ppm relative to the weight of the lactide-based copolymer.
Is preferably added in an amount of. Preferably, 500-
It is preferably added in an amount of 5000 ppm.

The lactide copolymer of the present invention is
Although it has a sufficient plasticizing effect and has moldability by itself, when particularly high plasticization is to be achieved, dioctyl adipate, dioctyl sebacate, trioctyl trimellitate, diethyl phthalate, dioctyl phthalate, polypropylene glycol adipate Alternatively, a plasticizer such as butanediol adipate may be added.

Among them, the adipic acid type polyester plasticizer is particularly preferable because of its compatibility and the plasticizing effect by addition.
It is preferable that the molecular weight is 20,000 or less and the end of the polyester is sealed with alcohol or the like because the stability during molding and processing is good. The addition amount of these plasticizers is not particularly limited, but it is preferably added in an amount of 1 to 30% with respect to the weight of the lactide copolymer for the purpose of avoiding bleeding.

Further, metal soaps such as zinc stearate, magnesium stearate and calcium stearate, mineral oil, liquid paraffin, lubricants such as ethylenebisstearyl amide, nonionics such as glycerin fatty acid ester and sucrose fatty acid ester, and alkyl sulfone. The addition of ionic surfactants such as acid salts, titanium oxide, and coloring agents such as carbon black may also be used within a range that does not impair the physical properties of the lactide copolymer obtained by the production of the present invention. Is also good.

The lactide-type copolymer comprising a lactide and a polymer having a hydroxyl group, which is produced by the continuous production method of the present invention, has less restrictions on the copolymerization component such as copolymerization with a monomer, and is a vinyl-type polymer or a condensation-type polymer. It can be copolymerized with polyester and the like. In the case of a reaction with a monomer capable of reacting with lactide, the reactive monomer used is limited to epoxide, cyclic ester, lactone and cyclic carbonate, so that the obtained copolymer is limited to one having a highly flexible property. It was

However, the lactide copolymer obtained by the reaction of the lactide and the polymer of the present invention can be copolymerized with a polymer having high heat resistance such as polyethylene terephthalate and bisphenol A type polycarbonate. Further, it is possible to copolymerize with a crystalline polyester such as polyethylene succinate in a block form and / or a random form.

[0111]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these. All percentages are by weight unless otherwise specified.

(Example 1) A condenser is provided on the upper part,
A reactor in which four latent heat cooling type stirring reactors with an internal capacity of 7 liters that can be stirred by an anchor type stirring blade were connected in series, and a 1/2 inch static mixer (Noritake) was added to this final reactor. It was connected to the devolatilization tank via a Kenix static mixer.

The raw materials were supplied in two raw material supply tanks under a nitrogen gas atmosphere. Lactide was melted in a 110 ° C dissolution tank, and another dissolution tank was used to make a polymer with hydroxyl groups into a 25% toluene solution at 140 ° C, and a plunger pump was used so that the average residence time would be 6 hours. To the first reactor. The catalyst uses tin octoate,
It was added in the transfer line from the raw material supply tank to the first reactor.
The supply amount of each component is shown below.

Lactide supply flow rate: 4.63 (l / hour) Polymer / toluene solution supply flow rate: 0.97 (l / hour) Catalyst supply flow rate: 2.2 (ml / hour)

The constituent components of the raw material lactide, the polymer having a hydroxyl group, and the solvent are shown below. L-lactide: 78% D-lactide: 4% Polyester: 5% Toluene: 13%

Polyester was used as the polymer having a hydroxyl group. The constituent components of the polyester are terephthalic acid 14 mol%, isophthalic acid 16 mol%, adipic acid 20 mol%, ethylene glycol 28 mol%, neopentyl glycol 22 mol%, and the number average molecular weight is 4
It is 5,000 (in terms of polystyrene).

Further, tin octoate was supplied as a catalyst so as to be 500 ppm with respect to the reaction contents. Regarding the transfer of the reaction liquid between the reactors, while confirming the liquid level from the liquid level confirmation window on the side surface of the reactor, it was continuously transferred from the discharge part at the bottom of the reactor using a gear pump.

The control temperatures of the four reactors used and the viscosity of the reaction solution are shown below. First reactor reaction temperature: 145 ° C, 20 poise Second reactor reaction temperature: 165 ° C, 700 poise Third reactor reaction temperature: 175 ° C, 2600 poise Fourth reactor reaction temperature: 175 ° C, 3200 poise

The pressure in the reactor during the polymerization reaction was 1.3.
~ 1.5 atm. The devolatilization condition after the reaction is
The temperature of the heat exchanger in front of the devolatilizer was 220 ° C., and the degree of vacuum in the devolatilization tank was 6 Torr.

The evaporate from the devolatilization tank was recovered by a condenser and subjected to a distillation operation to try to reuse lactide and toluene. About 6% of the supplied amount of lactide was recovered, and the reaction rate of lactide was calculated to be 94%. After pelletizing the obtained polymer, various properties and physical properties were measured. The obtained pellet was a slightly yellowish transparent resin.

As a result of gel permeation chromatography (hereinafter abbreviated as GPC) analysis, the molecular weight was 140.
It was 900. 0.4% of the lactide monomer remained, and toluene was not confirmed. The melting point measured by differential calorimetric analysis (hereinafter abbreviated as DSC) was 174.1 ° C.

(Example 2) A reactor in which three liquid-filled stirring reactors each having a capacity of 4 liter and equipped with a helical stirring blade were connected in series, and a 1/2 inch static reactor was connected to the final reactor. -Connected to two devolatilization tanks via a mixer (Kenix static mixer manufactured by Noritake).

The raw materials were supplied under a nitrogen gas atmosphere using a polymer having lactide and a hydroxyl group at 110 ° C. with toluene 1
A 5% solution was prepared, and a plunger pump was used to supply the solution to the first reactor so that the average residence time was 8 hours. Tin octoate was used as the catalyst, and was added to the transfer line to the first reactor in the same manner as in Example 1. 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)

The constituents of the raw material lactide, the polymer having a hydroxyl group and the solvent are shown below. L-lactide: 73% D-lactide: 4% Polyester: 10% Toluene: 13%

Polyester was used as the polymer having a hydroxyl group. The constituent component of polyester is succinic acid 5
It is 0 mol%, ethylene glycol 50 mol%, and a number average molecular weight of 77,000 (in terms of polystyrene). The catalyst is
Tin octoate was fed to the reactants at 400 ppm. Further, the produced polymer was continuously withdrawn from the discharge section at the upper part of the tank of the final reactor using a gear pump.

The control temperatures of the three reactors used and the viscosity of the reaction solution are shown below. First reactor reaction temperature: 155 ° C, 100 poise Second reactor reaction temperature: 165 ° C, 2100 poise Third reactor reaction temperature: 165 ° C, 3900 poise

The conditions of the devolatilization treatment are as follows: the temperature of the heat exchanger before the first devolatilizer is 220 ° C., and the degree of vacuum of the devolatilization tank is 110To.
It was rr. The temperature of the heat exchanger in front of the second devolatilizer is 2
At 20 ° C., the degree of vacuum in the devolatilization tank was 8 Torr. Evaporate from the devolatilization tank was collected by a condenser. The recovered product from the first devolatilization tank was almost 100% in toluene and could be reused after drying. A large amount of lactide was found in the recovered product from the second devolatilization tank, and lactic acid and a lactic acid dimer were confirmed. Distillation was performed to collect lactide.

After the obtained polymer was pelletized, various properties and physical properties were measured. The obtained pellet was a slightly yellowish transparent resin. As a result of GPC analysis, the molecular weight was 128,800. 0.5% of the lactide monomer remained, and toluene was not confirmed. From the DSC analysis result, the melting point was 158.2 ° C.

(Comparative Example 1) Two of the liquid-filled stirring reactors having the helical stirring blade used in Example 2 and having an internal capacity of 4 liters were used, and one reactor was used as the second reactor. It was connected to two devolatilization tanks via a 1/2 inch static mixer. Raw materials are supplied under a nitrogen gas atmosphere under lactide and ε-
Melt caprolactone at 110 ° C. and use a plunger pump to achieve a first residence time of 8 hours.
Feed to the reactor. Tin octoate was used as the catalyst, and was added in the same manner as in Example 2. The supply amount of each component is shown below.

Raw material supply flow rate: 1.0 (l / hour) Catalyst supply flow rate: 0.3 (ml / hour)

The constituents of the raw material lactide and the polymer having a hydroxyl group are shown below. L-lactide: 95% ε-caprolactone: 5%

400 pp of tin octoate as a catalyst
It was supplied so that m. The extraction of the generated polymer is
It was continuously withdrawn from the discharge part above the tank of the final reactor using a gear pump.

The control temperatures of the two reactors used and the viscosity of the reaction solution are shown below. First reactor reaction temperature: 165 ° C, 6800 poise Second reactor reaction temperature: 165 ° C, 24000 poise

The conditions for the devolatilization treatment are as follows: the temperature of the heat exchanger in front of the first devolatilizer is 220 ° C., and the degree of vacuum in the devolatilization tank is 110 To.
It was rr. The temperature of the heat exchanger in front of the second devolatilizer is 2
The degree of vacuum of the devolatilization tank was 8 Torr at 20 ° C. Evaporate from the devolatilization tank was collected by a condenser. Almost no recovered product was obtained from the first devolatilization tank, and many recovered products from the second devolatilization tank were lactide, and lactic acid and lactic acid dimer were confirmed.

About 27% of the supplied amount of lactide was recovered, and the reaction rate of lactide was calculated to be 73%. After the obtained resin was pelletized, various properties and physical properties were measured. The obtained pellet was a slightly yellowish transparent resin. From the GPC analysis result, the molecular weight was 182.
It was 300. 1.7% of the lactide monomer remained. As a result of DSC, the melting point was 156.7 ° C.

(Comparative Example 2) Two of the latent heat cooling type stirring reactors having an internal capacity of 7 liters equipped with the same anchor type stirring blades as in Example 1 were used to carry out the second reaction. 2 via a 1/2 inch static mixer
It was connected to the devolatilization tank of the machine. For the raw material supply, in a nitrogen gas atmosphere, 1 polymer containing lactide and a hydroxyl group is used.
A 15% solution of toluene at 10 ° C. was supplied to the first reactor using a plunger pump so that the average residence time was 6 hours.

The raw material solution of the polymer having lactide and hydroxyl group was polymerized by the function of the catalyst contained in the polymer having hydroxyl group, and the viscosity was increased, which hindered the supply to the reactor.

Tin octoate was used as the catalyst, and was added before the first reactor in the same manner as in Example 1. The supply amount of each component is shown below. Raw material supply flow rate: 2.3 (l / hour) Catalyst supply flow rate: 1.1 (ml / hour)

The components of the raw material lactide, the polymer having a hydroxyl group and the solvent are shown below. L-lactide: 73% D-lactide: 4% Polyester: 10% Toluene: 13%

Polyester was used as the polymer having hydroxyl groups. The constituent components of the polyester are
It was 50 mol% succinic acid and 50 mol% ethylene glycol, and had a number average molecular weight of 77,000. As a catalyst, tin octoate was supplied so as to have a concentration of 500 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 temperatures of the two reactors used and the viscosity of the reaction solution are shown in the table below. First reactor reaction temperature: 165 ° C, 2200 poise Second reactor reaction temperature: 165 ° C, 2700 poise

The conditions of the devolatilization treatment are as follows: the temperature of the heat exchanger in front of the first devolatilizer is 220 ° C., and the degree of vacuum of the devolatilization tank is 110 To.
It was rr. The temperature of the heat exchanger in front of the second devolatilizer is 2
The degree of vacuum of the devolatilization tank was 8 Torr at 20 ° C. About 19% of the supplied amount of lactide was recovered, and the reaction rate of lactide was 81%. After pelletizing the obtained polymer, various properties and physical properties were measured.

The pellet was a yellowish translucent resin of brittle nature. From the GPC analysis result, the molecular weight is 10
It was 1,200. Further, a fraction having a molecular weight of about 82,000, which is considered to be a polymer having a hydroxyl group, was recognized. 2.2% of lactide monomer remained, and toluene was not confirmed. As a result of DSC analysis, the melting point is 1
It was 56.2 ° C.

[0145]

INDUSTRIAL APPLICABILITY The present invention solves problems such as high viscosity, thermal decomposability, and coloring of a reaction solution, which are problems in producing a lactide copolymer, and has a wider range than conventional lactide copolymers. We provide a continuous production method that efficiently produces degradable lactide copolymers that have excellent physical properties and are useful in a wide range of fields such as film sheets for packaging materials, injection molded products, lamination, and industrial products. it can.

[0146]

[Brief description of drawings]

FIG. 1 is a view showing an example of a latent heat cooling type continuous stirring type reactor that can be used in the present invention.

FIG. 2 is a view showing an example of a liquid-filled continuous stirring reactor that can be used in the present invention.

[Explanation of symbols]

T _1: raw material dissolution and melting tank T _2: raw material supply tank A _1: catalyst feed vessel P _0: plunger pump _{R 1, R 2, R 3} , R 4: stirred reactor M: motor P _1, P ₂ , P _3, P _4: gear pump H: static mixer type heat exchanger V _1, V _2: devolatilization vessel A _2: additive addition system D: pelletizer C _1: condenser C _2: devolatilizer volatiles recovery condenser E: Recovered product refining device ---: Indicates a recovered product circulation line.

Claims (8)

(57) [Claims] 1. A lactide 50 is attached to a first reactor of a continuous reactor in which three or more stirred reactors are connected in series.
~ 98 parts by weight and 2 to 50 parts by weight of a polymer having a hydroxyl group are melted or dissolved in a solvent, continuously supplied, and further reacted from the first reactor to each reactor connected in series. A molecular weight of 20,000, characterized in that the contents are sequentially transferred and subjected to ring-opening copolymerization in the first reactor and each connected reactor at a reaction pressure of 1 to 5 atm and a reaction temperature of 140 to 210 ° C. ~ 400,000 continuous production method of linear lactide copolymer. 2. The polymerization rate of lactide in the first reactor of the continuous reactor is 30% to 80%, and the viscosity of the reaction solution is 2000 poise or less. Continuous manufacturing method. 3. The continuous production method according to claim 1, wherein the polymer having a hydroxyl group is a polyester having a hydroxyl group at a terminal and having a melting point or a softening point of 180 ° C. or lower. 4. A solvent having a boiling point of 70 to 180 ° C. is added as a reaction solvent in an amount of 3 to 30 parts by weight based on 100 parts by weight of a total of lactide and a polymer having a hydroxyl group. The continuous manufacturing method as described in 1 above. 5. The continuous production according to claim 1, wherein after the polymerization reaction, residual lactide and / or residual solvent in the produced copolymer is removed to 1% by weight or less. Method. 6. As a reaction solvent, a solvent having a boiling point of 70 to 180 ° C. is added in an amount of 3 to 30 parts by weight based on 100 parts by weight of the total of the polymers having a lactide and a hydroxyl group, and a ring-opening copolymerization reaction is carried out. The residual lactide and / or the residual solvent in the produced copolymer is removed to 1% by weight or less, and the continuous production method according to any one of claims 1 to 3. 7. The method according to claim 1, wherein the ring-opening copolymerization is further carried out by using a continuous reactor equipped with a static mixer after the reaction in the stirred reactor. The continuous manufacturing method described. 8. A ring-opening copolymerization reaction is carried out by adding 3 to 30 parts by weight of a solvent having a boiling point of 70 to 180 ° C. as a reaction solvent to a total of 100 parts by weight of a polymer having lactide and a hydroxyl group, and further statically 1% by weight of residual lactide and / or residual solvent in the resulting copolymer after ring-opening copolymerization using a continuous reactor equipped with a mixer
The continuous manufacturing method according to any one of claims 1 to 3, characterized in that it is removed as follows.