KR102159494B1 - Method for prepareing copolymer of 4-hydroxyalkanoate-2-hydroxyalkanoate - Google Patents

Abstract

The method of preparing the 4HA-2HA copolymer of the present invention overcomes the disadvantages of preparing a copolymer by a biosynthetic method using a conventional microorganism, and enables the synthesis and mass synthesis of a high molecular weight copolymer, thereby improving the synthesis efficiency of the copolymer. It is excellent in that it can expand the industrial use range of bioplastics using conventional biopolymers in that it can be increased.

Description

Preparation method of 4-hydroxyalkanoate-2-hydroxyalkanoate copolymer {METHOD FOR PREPAREING COPOLYMER OF 4-HYDROXYALKANOATE-2-HYDROXYALKANOATE}

The present invention relates to a method for preparing a copolymer comprising 4-hydroxyalkanoate and 2-hydroxyalkanoate as monomers, and 4-hydroxyalkanoate-2-hydroxyal prepared by the above preparation method. It relates to a canoate copolymer.

With the development of petrochemical and polymer chemistry, synthetic plastics have been developed as substitutes for natural materials such as wood and steel, and are being used in various ways due to low cost, low specific gravity and excellent formability. However, it takes several hundred years to decompose in the natural state of such plastics, and generally hardly decomposes, and is recognized as a major cause of environmental pollution due to the release of harmful environmental hormones, etc. Therefore, biodegradable biopolymers that are easily decomposed even in natural conditions and do not cause environmental pollution problems are in the spotlight as materials that can replace them.

Biopolymer is a polymer plastic manufactured using biomass as a raw material, and is an environmentally friendly material that can be easily decomposed and transformed into a form that can be absorbed by living things.

Polyhydroxyalkanoate (PHA), one of the representative biopolymers, is a polyhydroxyalkanoate (PHA) that microbes accumulate as energy or carbon source storage materials when there is an excessive carbon source and lacks other nutrients such as phosphorus, nitrogen, magnesium, and oxygen. It is a polyester material. PHA is recognized as a material to replace existing synthetic plastics because it exhibits complete biodegradability while having properties similar to synthetic polymers derived from petroleum.

However, the mechanical properties such as tensile strength of a typical PHA are poor, so there is still a limit to being used as a general purpose polymer.

PHA biopolymer is a known method of biopolymer biosynthesis using microorganisms that have been genetically engineered to have an enzyme that converts microbial metabolites into PHA monomers and a PHA synthase that synthesizes PHA polymers using PHA monomers. have. However, in the case of such a biosynthetic method, it is difficult to synthesize a biopolymer by controlling the physical properties and molecular weight according to the use of the biopolymer, and the biopolymer produced according to the biosynthesis method has a disadvantage in that the molecular weight of the polymer is small and the physical properties are large. As a specific example, polyhydroxyalkanoate (PHA)-based biopolymers can be produced only by biosynthesis using microorganisms having a PHA synthase or a variant thereof.In particular, microorganisms using 2HA monomers as substrates are extremely limited. In addition, it is difficult to mass-produce biopolymers at the level of industrial use. In addition, since biopolymers produced by microorganisms have a weight average molecular weight of less than 50,000 and only low molecular weight polymers can be produced, it is impossible to control molecular weight or to produce high molecular weight copolymers.

Therefore, the existing biosynthetic method has many limitations in mass production of biopolymers having desired physical properties, and mass production is possible, molecular weight control is possible, and a new method for producing biopolymers having excellent mechanical properties. Development is in demand.

In order to overcome the limitations of conventional biosynthetic methods, mass production is possible, and in order to produce a biopolymer having excellent mechanical properties while being able to easily control the molecular weight of the biopolymer during the synthesis process, the PHA monomer is chemically A method of synthesis, particularly specific conditions, was developed, and the biopolymer synthesized by the method of the present invention has high molecular weight and excellent mechanical properties, and the moldability and physical properties (strength, durability, etc.) of plastics using biopolymers It was confirmed that it can be improved to complete the present invention.

In the above aspect, the present invention provides a method for synthesizing a biopolymer having high molecular weight, excellent mechanical properties, and excellent physical properties of plastics using biopolymers for general use of biopolymers that have been poorly utilized industrially. It aims to provide.

Specifically, the present invention provides a method for preparing a copolymer comprising 4-hydroxyalkanoate (4HA) and 2-hydroxyalkanoate (2HA) as monomers.

Further, the present invention provides a 4HA-2HA copolymer having a weight average molecular weight (Mw) of 100,000 or more.

The method for preparing a copolymer containing 4-hydroxyalkanoate (4HA) and 2-hydroxyalkanoate (2HA) as monomers according to the present invention uses a chemical method, so it is compared with the biosynthesis method by microorganisms. Thus, the copolymer can be mass-produced more efficiently. In particular, industrially, since it is possible to adjust the ratio of monomers in the copolymer according to the mechanical properties required according to the type of bioplastic, or to manufacture a high molecular weight copolymer, it is possible to further expand the industrial application of the biopolymer.

1 shows the results of GC analysis of the p(4HB-2HB) copolymer prepared according to the polymerization method according to an embodiment of the present invention.
2 shows the results of confirming the molecular weight distribution of the p(4HB-2HB) copolymer prepared according to the polymerization method according to an embodiment of the present invention.
3 shows the results of H-NMR analysis of a 2HB monomer prepared according to an embodiment of the present invention.
4 shows the results of H-NMR analysis of the p(4HB-2HB) copolymer prepared according to the polymerization method according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail.

In order to achieve the object of the present invention, the present invention is to polymerize a 4-hydroxyalkanoate (4HA) monomer and a 2-hydroxyalkanoate (2HA) monomer in the presence of a polymerization catalyst; It provides a method for preparing a hydroxyalkanoate-2-hydroxyalkanoate (4HA-2HA) copolymer.

In the present invention, the 4-hydroxyalkanoate-2-hydroxyalkanoate (4HA-2HA) copolymer comprises a 4-hydroxyalkanoate (4HA) monomer and a 2-hydroxyalkanoate (2HA) monomer. It means including all the copolymers included as repeating units. The content of the 4-hydroxyalkanoate monomer and the 2-hydroxyalkanoate monomer in the copolymer may be differently controlled by the method or conditions of polymerization, and the 4-hydroxyalkanoate monomer in the copolymer and It is not limited to the number of repeating units of the 2-hydroxyalkanoate monomer. In addition, in the present specification, 4-hydroxyalkanoate-2-hydroxyalkanoate (4HA-2HA) copolymer or 2-hydroxyalkanoate-4-hydroxyalkanoate (2HA-4HA) copolymer It can be expressed as

In the present invention, 4-hydroxyalkanoate refers to hydroxyalkanoate in which the carbon at position 4 is hydroxylated, and in 4-hydroxyalkanoate, some hydrogens are alkyl groups having 1 to 5 carbon atoms. Includes substituted ones. For example, 4-hydroxybutyric acid (4HB), 4-hydroxyvaleric acid (4HV), 4-hydroxyhexanoic acid, 4-hydroxy Heptanoic acid (4-hydroxyheptanoic acid), 4-hydroxyoctanoic acid (4-hydroxyoctanoic acid) and may be selected from the group consisting of 4-hydroxydecanoic acid (4-hydroxydecanoic acid), but is not limited thereto, preferably For example, it may be 4-hydroxybutyric acid (4HB).

In the present invention, 2-hydroxyalkanoate refers to a hydroxyalkanoate in which the carbon at the position 2 is hydroxylated, and in 2-hydroxyalkanoate, some hydrogens are alkyl groups having 1 to 5 carbon atoms. Includes substituted ones. For example, 2-hydroxybutyric acid (2HB), 2-hydroxyvaleric acid, 2-hydroxyhexanoic acid, 2-hydroxyheptanoic acid (2-hydroxyheptanoic acid), 2-hydroxyoctanoic acid (2-hydroxyoctanoic acid), and may be selected from the group consisting of 2-hydroxydecanoic acid (2-hydroxydecanoic acid), but is not limited thereto, preferably May be 2-hydroxybutyric acid (2HB). Specific examples of 4-hydroxyalkanoate-2-hydroxyalkanoate copolymer 4-hydroxybutylic acid-2-hydroxybutyric acid copolymer; 4-hydroxybutyric acid-2-hydroxyvaleric acid copolymer; 4-hydroxybutyl acid-2-hydroxyhexanoic acid copolymer; 4-hydroxybutyl acid-2-hydroxyheptanoic acid copolymer; 4-hydroxybutyl acid-2-hydroxyoctanoic acid copolymer; 4-hydroxybutyl acid-2-hydroxydecanoic acid copolymer; 4-hydroxyvaleric acid-2-hydroxybutyric acid copolymer; 4-hydroxyhexanoic acid-2-hydroxybutyric acid copolymer; 4-hydroxyheptanoic acid-2-hydroxybutylic acid copolymer; 4-hydroxyoctanoic acid-2-hydroxybutyric acid copolymer; Or it may be a 4-hydroxydecanoic acid-2-hydroxybutyric acid copolymer, but is not limited thereto.

In this aspect, the copolymer prepared by the production method of the present invention may have various molecular weights (Mw), but preferably a copolymer having a weight average molecular weight (Mw) exceeding 50,000 (Da), more preferably Can prepare a copolymer having a weight average molecular weight of 100,000 (Da) or more. In the conventional method of synthesis using microorganisms, only low molecular weight copolymers with a weight average molecular weight of 50,000 or less could be produced, but in the case of the manufacturing method of the present invention, compared to a copolymer produced by a method of biosynthesis using microorganisms. There is an advantage of being able to prepare a high molecular weight copolymer. In particular, the 4HA-2HA copolymer having a high molecular weight of 100,000 (Da) or more is more suitable for use as a raw material for plastics because it has excellent mechanical properties when processed into bioplastics.

In one embodiment of the present invention, it was experimentally confirmed that a copolymer containing 4-hydroxybutyric acid and 2-hydroxybutyric acid as monomers can be synthesized by a chemical method using a tin catalyst. The copolymer prepared according to the synthesis method of the present invention exhibited a weight average molecular weight of 200,000 (Da) or more, and it was confirmed that the copolymer having physical properties suitable for use as a plastic could be prepared.

Accordingly, the present invention may be a method of preparing a 4-hydroxybutyrate (4HB)-2-hydroxybutyrate (2HB) copolymer having a weight average molecular weight of more than 50,000 Da or 100,000 Da or more.

In the production method of the present invention, an organic tin (Sn) compound (Tin catalyst) may be used as a polymerization catalyst. The organotin compound means a tin compound having a hydrocarbon substituent. In particular, the catalyst used to prepare the copolymer of the present invention may be an organotin compound represented by the following formula (1).

[Formula 1]

(C _x H _(2x-1) O ₂ ) _2- Sn

In Formula 1, x is an integer of 4 to 16.

The organic tin compound may preferably be a tin (II) compound catalyst, and preferably tin (II) 2-ethylhexanoate (Tin (II) 2-ethylhexanoate). The catalyst may be prepared by a method known to a person skilled in the art, and may be used by purchasing a commercially available material.

In an embodiment of the present invention, it was confirmed that in order to synthesize a 4HB-2HB copolymer by a chemical method, it is a very important condition to use a tin-based compound of Formula 1 as a catalyst. In particular, it was confirmed that the 4HB-2HB copolymer could be prepared using tin (II) 2-ethylhexanoate. However, in the case of using a catalytic enzyme other than the organotin compound, the polymerization reaction does not occur even though the polycondensation reaction was performed using the same monomer, and the organotin compound was used as a polymerization catalyst in the preparation of the copolymer of the present invention. It can be seen that it is a very important condition to use. When the total amount of the total monomer included in the polymerization reaction is 100 parts by weight, the catalyst may be included in an amount of 0.05 to 20 parts by weight, 0.1 to 10 parts by weight, and preferably 0.5 to 5 parts by weight.

The polymerization step may be carried out at more than 120 ℃ to 200 ℃, preferably at 150 ℃ to 190 ℃. When the polymerization reaction proceeds at a temperature of less than 120 ℃, it was experimentally confirmed that the efficiency of the monomer participating in the reaction was significantly lowered and the 2HA-4HA copolymer was not produced, and the polymerization was performed at a temperature exceeding 200 ℃ Problems can arise that the 2HA monomer is removed or decomposed.

The polymerization reaction may proceed for 3 to 6 hours.

The method for preparing the copolymer may further include reacting the polymerization reaction product through the polymerization step for 1 to 48 hours under a pressure condition of 0.01 Torr (Torr, mmHg) to 760 Torr (Torr, mmHg). Preferably, in a pressure condition of 0.01 Torr (Torr, mmHg) to 200 Torr (Torr, mmHg), the reaction can be maintained for 1 hour to 6 hours, more preferably 0.01 Torr (Torr, mmHg) to 50 Torr ( Torr, mmHg) under pressure conditions, it is possible to maintain the reaction for 1 to 6 hours. When water is removed by treating the reactant under low pressure conditions after the reaction as described above, polymerization efficiency can be increased by preventing decomposition of the monomer, and a polymer having a higher molecular weight can be prepared.

The method for preparing the copolymer may further include dissolving the product by adding a hydrophobic solvent after completion of the polymerization reaction. The hydrophobic solvent may be added after maintaining the polymerization reaction under reduced pressure conditions.

The hydrophobic solvent may be used regardless of its type as long as it is a solvent capable of dissolving polyester, and specifically, may be selected from the group consisting of chloroform, dichloromethane, dichloroethane, and hexane, but is not limited thereto.

The method for preparing the copolymer may further include adding a precipitant to a solution in which the product is dissolved to precipitate the target copolymer. The precipitating agent refers to a reagent used in the precipitation generation reaction, and any precipitating agent exhibiting hydrophilicity can be used regardless of its type. Specifically, it may be alcohols having 1 to 12 carbon atoms, and specifically, may be selected from the group consisting of ethanol, methanol, ethyl acetate, and acetone, but is not limited thereto.

Preferably, in the production method of the present invention, after the polymerization reaction, chloroform is added to the polymerization reaction product, and then a precipitant of alcohol is added to solve the problem of decomposition of the prepared copolymer.

In addition, it is possible to further reduce the catalytic activity by adding a phosphoric acid-based additive after the polymerization reaction, and by performing such a step, the synthesis yield of the copolymer of the present invention can be adjusted.

The method for preparing the copolymer may further include preparing a monomer prior to the polymerization step. It may further include a step of preparing 4-hydroxybutyrate (4HB). In the step of preparing 4HB, butyrolactone as a starting material, more preferably γ-butyrolactone as a starting material, reacted by adding a strong base to the mixture of the starting material and water, and then again strong acid It can be carried out by a method of addition reaction. However, since the monomer may be used commercially, the composition of the method for preparing the copolymer of the present invention is not limited.

The strong base is also called strong alkali, and includes all those having an ionization degree close to 1, generating hydroxide ions quantitatively, and having a large base ionization constant, for example, sodium hydroxide, potassium hydroxide, or barium hydroxide, but limited thereto. It does not become.

The strong acid is an acid having a hydrogen ion index (pH) of 3 or less. Also referred to as strong acid or strong acid, for example, it may be perchloric acid (HCIO4), hydrochloric acid (HCI), nitric acid (HNO3), sulfuric acid (H2SO4), or phosphoric acid (H3PO4), but is not limited thereto.

In the method for preparing the copolymer of the present invention, the 4-hydroxyalkanoate (4HA) monomer and the 2-hydroxyalkanoate (2HA) monomer may be polymerized by a melt polymerization method. When a copolymer is prepared by a polycondensation reaction by melt polymerization, it has excellent properties in that it can produce a high molecular weight 4HA-2HA copolymer.

In this aspect, the present invention provides a 4-hydroxyalkanoate-2-hydroxyalkanoate (4HA-2HA) copolymer having a weight average molecular weight (Mw) of 100,000 or more.

The copolymer of the present invention may be synthesized by the method for preparing the copolymer of the present invention described above. The copolymer synthesized by the method for producing a copolymer of the present invention has excellent properties in that it has a weight average molecular weight of 100,000 Da or more, preferably 200,000 Da or more. In particular, the copolymer comprising 4HA and 2HA produced by conventional biosynthetic methods as monomers had a weight average molecular weight of about 50,000 Da on average. In the case of a copolymer having an average molecular weight of 50,000 Da, when used as a raw material for plastics, it was difficult to use industrially because of poor mechanical properties, and improving its properties has been suggested as a continuous problem.

However, since the copolymer of the present invention has a weight average molecular weight of 100,000 Da or more, preferably 200,000 Da or more, it has technically excellent properties in that it can provide desirable physical properties for use as bioplastics. In particular, the high molecular weight copolymer prepared according to the present invention has excellent tensile properties such as tensile strength, tensile modulus and elongation, and impact strength, so it is very advantageous for use as a raw material for plastics.

In the case of the polyhydroxyalkanoate (PHA) of the present invention, when polymerization is carried out by chemical polymerization, the yield and the possibility of polymerization are completely different depending on the conditions. It is meaningful in that specific conditions for efficiently producing the 4HA-2HA copolymer were established by the polymerization method, and the copolymer having a high molecular weight could be produced. In particular, since the conventional polyhydroxyalkanoate-based 4HA-2HA copolymer was dependent on a biosynthesis method using microorganisms, a high molecular weight copolymer was prepared or the content of the monomer contained in the copolymer was adjusted to have desired physical properties. There was a great difficulty in preparing the copolymer. However, when the melt polymerization method of the present invention is used, it has excellent properties in that it can produce a high molecular weight copolymer compared to a copolymer produced by a bio-biosynthesis method. In addition, since the content of monomers in the copolymer can be easily controlled and mass-produced, it has great significance in that it can industrially expand the range of bioplastics using biodegradable polyhydroxyalkanoate. .

Hereinafter, the present application will be described in detail through examples. However, the following Examples and Test Examples are only illustrative of the present invention, and the scope of the present invention is not limited thereto.

[Preparation Example 1] Preparation and Preparation of Monomer

4-hydroxybutyrate (4-Hydroxybutyric acid, 4HB) as a monomer for the preparation of the 4-hydroxybutyrate-2-hydroxybutyrate copolymer is [Ciolino LA et, The chemical interconversion of GHB and GBL: forensic issues and implications. J Fprensic Sci 2001; 46(6):1315-1323] was referenced and synthesized. 2-Hydroxybutyric acid (2HB) was used by purchasing Na·2HB (Sodium 2-Hydroxybutyrate) from TCI (Japan). Ethyl glycolide was purchased and used from Alfa Aesar.

Specifically, γ-butyrolactone (JUNSEI) is mixed with water, sodium hydroxide (NaOH) is added to the mixture to adjust the pH to 12, reacted for 1 hour, and then hydrochloric acid (HCl) is used. Then, the pH was adjusted to 7 to prepare a 4HB stock solution having a concentration of 200 g/L.

[Production Example] Preparation of copolymer by melt polymerization method

In order to prepare a copolymer (p(2HB-co-4HB)) containing 4-hydroxybutyrate and 2-hydroxybutyrate as monomers using a chemical synthesis method, polymerization was performed using 2HB and 4HB as monomers. I did.

Example 1. Preparation of P(2HB-4HB) by melt polymerization method

To prepare a P(2HB-4HB) copolymer using melt polymerization, 30 mmol (Na·2HB- 3.78 g; 4HB) of Na·2HB (Sodium 2-Hydroxybutyrate, TCI) and 4HB prepared in Preparation Example 1, respectively, were prepared by melt polymerization. -3.12 g) each was put in a 100 mL flask, and the pH was dropped to 3.6, the pKa value, using hydrochloric acid (HCl) so that Na·2HB could be dissociated. After heating to 90 ℃ to remove the water contained in the reaction product as much as possible. Then, the reaction temperature of the mixture was adjusted to 165° C., and 69 mg of Tin(II) 2-ethylhexanoate (Sigma Aldrich) as a catalyst was added, which is 1 wt% of the total amount of monomers (2HB and 4HB), and reacted for 5 hours. Thereafter, the reaction was continued for 1.5 hours under reduced pressure with a vacuum degree of 30 Torr. After the reaction was completed, chloroform was added to dissolve the product, and then it was poured into methanol (MeOH) to allow the resulting polymer to precipitate. The precipitated polymer was recovered (yield 37.5), dried, and analyzed using GC and GPC. The results are shown in FIGS. 1 and 2 by confirming the number average molecular weight (M _n ), weight average molecular weight (M _w ), maximum pit (peak) molecular weight (M _p ), and polydispersity index (PDI), respectively, and Table 1 Shown in.

Example 1 Mn(x 10 ⁵ Da) Mw(x 10 ⁵ Da) Mp(x 10 ⁵ Da) PDI (2HB-4HB) 0.56 2.39 1.99 4.30

As shown in FIG. 1, it was confirmed that the 2HB-4HB copolymer was well prepared, and the molecular weight distribution of the prepared copolymer was as shown in FIG. 2. In particular, as shown in Table 1, since the weight average molecular weight of the copolymer prepared by the method of Example 1 is 200,000 Da or more, a high molecular weight copolymer can be prepared compared to the copolymer produced by the conventional biosynthetic method. Confirmed that it can.

Example 2. Preparation of P(2HB-4HB) by melt polymerization method

For 2-hydroxybutyric acid (2-Hydroxybutyric acid, 2HB), Na·2HB (Sodium 2-Hydroxybutyrate) was dropped to pH 3 with 2N HCl, and water was removed at 90° C. after stirring for 1 hour. At this time, since sodium chloride (NaCl) as a by-product exists in the same weight ratio as 2HB, in order to remove sodium chloride, a by-product, it was removed using H ₂ O/MEK (methyl ethyl ketone) over-extraction method. After the extraction method, 2HB was confirmed through ¹ H-NMR, and it was confirmed that about 5% of MEK was present (FIG. 3).

After removing sodium chloride (NaCl), 2HB (3g) and 4HB (obtained by the preparation example 1 method, 3g) were adjusted to 165°C, and Tin(II) 2-ethylhexanoate (Sigma Aldrich) was used as a catalyst to 1 of the total amount of monomers. After adding 60 mg of wt%, it was reacted for 5 hours. Thereafter, the reaction was continued for 5 hours under reduced pressure with a vacuum degree of 30 Torr. After the reaction was completed, chloroform was added to dissolve the product, and then it was poured into methanol (MeOH) to allow the resulting polymer to precipitate. The precipitated polymer was recovered, dried, and analyzed using ¹ H-NMR (FIG. 4).

As shown in FIG. 4, it was confirmed that the 2HB-4HB copolymer was well prepared even under the conditions of Example 2.

[Comparative Example]

In order to confirm whether the copolymer of the present invention can be prepared even when using other conditions or polymerization methods, polymerization of the 4HB-2HB copolymer was attempted under conditions different from the preparation method of the above example.

Comparative Example 1.

Na·2HB and 4HB of Preparation Example 1 were each 30 mmol (Na·2HB- 3.78 g; 4HB- 3.12 g) in a 100 mL flask, and then 30 ml of diphenyl ether was added. Then, CalB enzyme (Lipase acrylic resin from Candida antarctica , Sigma) was added to 0.69 g, which is 10 wt% of the total monomer content, and stirred at 80-90°C and normal pressure for 5 hours. The reaction was reacted for 72 hours after reducing the pressure to 0.04 bar while maintaining the temperature of the reactant at 80 to 90°C. After the reaction was completed, chloroform was added to dissolve the product, and then it was poured into methanol (MeOH) to precipitate the resulting polymer. The precipitated polymer was recovered, dried, and analyzed using GC and GPC.

However, as a result of recovering and analyzing the precipitate of Comparative Example 1, it was confirmed that the 4-hydroxybutyl acid-2-hydroxybutyric acid copolymer was not formed.

Comparative Example 2.

As in Example 1, Na·2HB (Sodium 2-Hydroxybutyrate, TCI) and 4HB of Preparation Example 1 were each 30 mmol (3.78 g, 3.12 g, respectively) in a 100 mL flask, and then pH using hydrochloric acid (HCl). Was dropped to the pKa value of 3.6 to allow Na·2HB to dissociate and reacted.

Then, in the same conditions and method as in Comparative Example 1, the polymerization reaction was carried out by adding CalB enzyme, and the polymer was precipitated. The precipitated polymer was recovered and dried, and then analyzed using GC and GPC.

However, as a result of recovering and analyzing the precipitate of Comparative Example 2, it was confirmed that the 4-hydroxybutyl acid-2-hydroxybutyric acid copolymer was not formed.

Comparative Example 3.

As in Example 1, Na 2HB (Sodium 2-Hydroxybutyric acid, TCI) and 4HB of Preparation Example 1 were each 30 mmol (3.78 g, 3.12 g, respectively) in a 100 mL flask, and then hydrochloric acid (HCl) was used. By dropping the pH to 3.6, the pKa value, Na·2HB was allowed to dissociate and reacted.

Then, the polymerization reaction and vacuum decompression were carried out under the same conditions as in Example 1, except that the reaction temperature was set to 120°C, and the polymer was precipitated. The precipitated polymer was recovered, dried, and analyzed using GC and GPC.

As a result of recovering and analyzing the precipitate of Comparative Example 3, it was confirmed that a 4-hydroxybutyric acid-2-hydroxybutyric acid copolymer was not formed. Therefore, through these results, it can be seen that in the preparation of the 4HA-2HA copolymer of the present invention, not only the catalyst conditions but also the polymerization temperature conditions must be satisfied.

Claims (11)

In the presence of the polymerization catalyst tin (II) 2-ethylhexanoate (Tin (II) 2-ethylhexanoate, Sn (Oct) ₂ ), 4-hydroxybutyric acid (4HB) and 2-hydroxy Polymerizing hydroxybutyric acid (2HB) by melt polymerization at a reaction temperature of 150° C. to 190° C. for 3 to 6 hours; And
4-hydroxybutyric acid having a weight average molecular weight (Mw) of 100,000 or more, including sustaining the polymerization reaction product under reduced pressure conditions of 0.01 Torr to 760 Torr for 1 to 48 hours, and Method for producing a 2-hydroxybutyric acid (4HB-2HB) copolymer. The method of claim 1,
The polymerization catalyst is contained in an amount of 0.05 to 20 parts by weight based on 100 parts by weight of the total monomer, the method for producing a 4HB-2HB copolymer.
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