KR20220154418A - Method for preparation of biodegradable copolymer - Google Patents

Abstract

A manufacturing method of a biodegradable copolymer according to the present invention, by adding 3-hydroxypropionic acid at a specific point in a lactic acid polymerization reaction, can efficiently manufacture a poly(lactic acid-3-hydroxypropionic acid) copolymer in one reactor.

Description

Method for preparing biodegradable copolymer {Method for preparation of biodegradable copolymer}

The present invention relates to a method for preparing a biodegradable copolymer capable of preparing a poly(lactic acid-3-hydroxypropionic acid) copolymer by a simple process.

Polylactic acid (PLA) is a plant-derived resin obtained from plants such as corn, and has attracted attention as an eco-friendly material having excellent tensile strength and elastic modulus while having biodegradable properties.

Unlike petroleum-based resins such as polystyrene resin, polyvinyl chloride resin, and polyethylene, which are used in the past, it has effects such as preventing petroleum resource depletion and suppressing carbon dioxide emission, so it can reduce environmental pollution, which is a disadvantage of petroleum-based plastic products. have. Therefore, as the environmental pollution problem due to waste plastics has emerged as a social problem, efforts are being made to expand the scope of application to product fields where general plastics (petroleum-based resins) were used, such as food packaging materials and containers, and electronic product cases.

However, compared to conventional petroleum-based resins, polylactic acid has poor impact resistance and heat resistance, and its application range is limited. In addition, it has poor elongation to break characteristics and is easily broken (brittleness), so there is a limit as a general-purpose resin.

In order to improve the above disadvantages, research on copolymers containing other repeating units in polylactic acid is being conducted, and in particular, 3-hydroxypropionic acid (3HP) is used as a comonomer to improve elongation. is getting attention In particular, a lactic acid-3HP block copolymer is attracting attention, and the copolymer has an effect of improving elongation characteristics while maintaining the inherent characteristics of polylactic acid.

However, conventional lactic acid-3HP block copolymers have several disadvantages. First, P3HP is synthesized, and lactide is added thereto to perform ring-opening polymerization, or PLA and P3HP are separately polymerized and then annealed, thereby reducing process efficiency.

The present invention is to provide a method for effectively producing a poly(lactic acid-3-hydroxypropionic acid) copolymer in one reactor by introducing 3-hydroxypropionic acid at a specific point in the lactic acid polymerization reaction.

In order to solve the above problems, the present invention provides a method for preparing a biodegradable copolymer comprising the following steps.

First, a first step of preparing a lactic acid oligomer by polymerizing lactic acid; and

A second step of preparing a poly(lactic acid-3-hydroxypropionic acid) copolymer by adding 3-hydroxypropionic acid when the number average molecular weight of the lactic acid oligomer reaches 5,000 to 100,000.

In order to prepare a conventional poly(lactic acid-3-hydroxypropionic acid) copolymer, poly(3-hydroxypropionic acid) (P3HP) is biosynthesized, and lactide is added thereto to perform ring-opening polymerization, or PLA It was carried out in a multi-step reaction in which lactic acid and P3HP were separately polymerized and then annealed. This multi-step reaction not only reduces process efficiency, but also generates by-products during the reaction process, making it difficult to prepare a high molecular weight copolymer. There was a problem. Specifically, cyclic oligomers, which are low molecular weight by-products, are easily produced during the multi-step reaction process. Since these cyclic oligomers do not undergo further polycondensation, the reaction yield is reduced, and additional purification by separation of the by-products There was a problem that the reaction efficiency was also lowered because the process was required.

Therefore, the present inventors can effectively prepare a poly(lactic acid-3-hydroxypropionic acid) copolymer in one reactor by adding 3-hydroxypropionic acid (3HP) at a specific point in the polymerization reaction of lactic acid (LA), Accordingly, the present invention was completed by discovering that a poly(lactic acid-3-hydroxypropionic acid) copolymer with improved physical properties such as elongation and tensile strength could be prepared while maintaining the inherent physical properties of polylactic acid.

Hereinafter, the present invention will be described in detail for each step.

(First step)

According to one embodiment of the present invention, a first step of preparing a lactic acid oligomer by polymerizing lactic acid is included. The first step is a condensation polymerization step of lactic acid, which means a step before 3-hydroxypropionic acid is added, and the resulting lactic acid oligomer corresponds to a lactic acid homopolymer.

In addition, as described later, 3-hydroxypropionic acid is added when the number average molecular weight of the lactic acid oligomer reaches 5,000 to 100,000, and poly(lactic acid-3-hydroxypropionic acid) copolymer is obtained by a simple process without generation of by-products. can be manufactured.

Meanwhile, 'lactic acid' used in the present invention refers to L-lactic acid, D-lactic acid, or a mixture thereof.

In the first step, the reaction is performed at 80 ° C to 120 ° C and 8 mbar to 12 mbar for 110 minutes to 130 minutes, and then the temperature is raised to 120 ° C to 180 ° C for 17 hours to 19 hours under vacuum conditions of 10 ^-2 torr. The reaction is carried out during, and when polymerized under the above conditions, it is suitable for adjusting the number average molecular weight of the oligomer to a desired range, and it is preferable because it can effectively suppress the generation of products of side reactions.

More preferably, in the first step, the reaction is performed at 90 ° C to 110 ° C and 9 mbar to 10 mbar for 115 minutes to 125 minutes, and then the temperature is raised to 140 ° C to 160 ° C under a vacuum condition of 10 ^-2 torr 18 The reaction can be carried out for a time ± 10 minutes.

The first step may be performed in the presence of a sulfonic acid-based catalyst and a tin-based catalyst. The catalyst has an effect of promoting lactic acid polymerization and at the same time suppressing the production of cyclic oligomers during polymerization.

Preferably, the sulfonic acid-based catalyst is p-toluenesulfonic acid, m-xylene-4-sulfonic acid, 2-mesitylenesulfonic acid, or p-xylene-2-sulfonic acid. Also preferably, the tin-based catalyst is SnCl ₂ .

Preferably, the sulfonic acid-based catalyst is included in an amount of 0.1 mol% to 1.0 mol% based on lactic acid. Within the above range, polymerization of lactic acid may be promoted and generation of cyclic oligomers may be suppressed. More preferably, the sulfonic acid-based catalyst is included in an amount of 0.2 mol% to 0.5 mol% relative to lactic acid.

Preferably, the tin-based catalyst is included in an amount of 0.025 mol% to 0.5 mol% relative to lactic acid. Within the above range, polymerization of lactic acid may be promoted and generation of cyclic oligomers may be suppressed. More preferably, the sulfonic acid-based catalyst is included in an amount of 0.05 mol% to 0.3 mol% relative to lactic acid.

Meanwhile, if necessary, a step of pre-treating lactic acid at 50° C. to 70° C. and 30 mbar to 80 mbar may be performed prior to the first-stage polymerization. Through the pretreatment step, moisture inside the lactic acid may be removed.

(Step 2)

According to one embodiment of the present invention, 3-hydroxypropionic acid is added at the time when the number average molecular weight of the lactic acid oligomer produced during the first step of preparing lactic acid oligomer by polymerization of lactic acid reaches 5,000 to 100,000, (lactic acid-3-hydroxypropionic acid) a second step of preparing the copolymer. In the second step, the unreacted lactic acid monomer in the first step, the produced lactic acid oligomer and 3-hydroxypropionic acid are subjected to condensation polymerization to prepare a poly(lactic acid-3-hydroxypropionic acid) copolymer. It is a step.

Here, the first step and the second step are performed in the same reactor, the reaction efficiency is excellent, and the input time of 3-hydroxypropionic acid is adjusted within the above-mentioned range, effectively poly(lactic acid-3-hydride) without side reaction products. hydroxypropionic acid) copolymer can be prepared, which is preferable.

In the second step, when lactic acid is added at the time when the number average molecular weight of the lactic acid oligomer is 5,000 to 100,000, the desired poly(lactic acid-3-hydroxypropionic acid) copolymer can be produced in excellent yield in a single reactor. Yes, the process efficiency is excellent. On the other hand, when 3-hydroxypropionic acid is added at the time when the number average molecular weight of the lactic acid oligomer is less than 5,000, the LA block of the final copolymer becomes too short, making it difficult to form the LA block copolymer, and at the time when the number average molecular weight exceeds 100,000 When 3-hydroxypropionic acid is added in, the PLA block becomes relatively large, making it difficult to effectively implement the physical properties of the 3HP block. Preferably, 3-hydroxypropionic acid may be additionally added when the number average molecular weight of the lactic acid oligomer is 10,000 to 90,000.

The lactic acid introduced in the first step and the 3-hydroxypropionic acid introduced in the second step may be included in a molar ratio of 1:0.1 to 1:1.2, and when included within the above range, the finally produced poly(lactic acid-3) -Hydroxypropionic acid) copolymer is preferred because it can improve physical properties such as elongation and tensile strength while maintaining the inherent physical properties of polylactic acid. Preferably, it may be included in a molar ratio of 1:0.25 to 1:1.

In the second step, the reaction is performed at 80 ° C to 120 ° C and 8 mbar to 30 mbar for 110 minutes to 130 minutes, and then the temperature is raised to 120 ° C to 180 ° C for 22 hours to 26 hours under vacuum conditions of 10 ^-2 torr. The reaction is carried out during, and when polymerized under the above conditions, it is suitable for adjusting the number average molecular weight of the oligomer to a desired range, and it is preferable because it can effectively suppress the generation of products of side reactions.

More preferably, in the second step, the reaction is performed at 90 ° C to 110 ° C and 9 mbar to 10 mbar for 115 minutes to 125 minutes, and then the temperature is raised to 140 ° C to 160 ° C under vacuum conditions of 10 ^-2 torr. The reaction can be carried out for a time ± 10 minutes.

Meanwhile, since the second step is performed in the same reactor after the first step, the catalyst added in step 1 also participates in the reaction in the second step. Additionally, the second step may be performed by further introducing a sulfonic acid-based catalyst and a tin-based catalyst.

The catalyst promotes the additional polymerization of 3-hydroxypropionic acid together with the unreacted lactic acid monomer and the produced lactic acid oligomer in the first step, and at the same time has an effect of suppressing the generation of by-products during the polymerization process.

Preferably, the sulfonic acid-based catalyst is p-toluenesulfonic acid, m-xylene-4-sulfonic acid, 2-mesitylenesulfonic acid, or p-xylene-2-sulfonic acid. Also preferably, the tin-based catalyst is SnCl ₂ .

Preferably, the sulfonic acid-based catalyst is added in an amount of 0.1 mol% to 1.0 mol% relative to 3-hydroxypropionic acid added in the second step, suppressing the production of by-products within the above range, and improving the yield of the final copolymer can make it More preferably, the sulfonic acid-based catalyst is added in an amount of 0.2 mol% to 0.5 mol% relative to 3-hydroxypropionic acid.

Preferably, the tin-based catalyst is added in an amount of 0.025 mol% to 0.5 mol% relative to 3-hydroxypropionic acid, suppressing the production of by-products within the above range, and improving the yield of the final copolymer. More preferably, the tin-based catalyst is added in an amount of 0.05 mol% to 0.3 mol% relative to 3-hydroxypropionic acid.

On the other hand, if necessary, a step of pre-treating 3-hydroxypropionic acid at 50 °C to 70 °C and 30 mbar to 80 mbar may be performed prior to the second-stage polymerization. Through the pretreatment step, moisture inside 3-hydroxypropionic acid may be removed.

The poly(lactic acid-3-hydroxypropionic acid) copolymer prepared according to one embodiment of the present invention has a weight average molecular weight of 50,000 to 200,000, more preferably 50,000 to 100,000. The method for measuring the weight average molecular weight will be described in detail in the experimental examples to be described later.

In addition, according to another embodiment of the present invention, an article including the poly(lactic acid-3-hydroxypropionic acid) copolymer is provided.

The article may include a packaging material, a film, a nonwoven fabric, and the like, and when applied to the article, elongation characteristics may be excellent and brittleness may be supplemented at the same time.

As described above, the production method of the biodegradable copolymer according to the present invention is a poly(lactic acid-3-hydroxy acid in one reactor by introducing 3-hydroxypropionic acid at a specific point in the lactic acid polymerization reaction. propionic acid) copolymer can be effectively prepared.

Hereinafter, embodiments of the present invention will be described in more detail in the following examples. However, the following examples are merely illustrative of embodiments of the present invention, and the content of the present invention is not limited by the following examples.

<Examples and Comparative Examples>

Example 1

(Step 1) Add 40 g (0.44 mol) of lactic acid (LA), 100 mg of SnCl ₂ (0.1 mol% compared to LA), and 333 mg (0.4 mol) of p-TSA (0.4 mol compared to LA) to the reactor, and heat at 110°C and 10 mbar for 2 hours. reacted. The temperature was raised to 160 °C and the reaction was carried out for 18 hours in a vacuum of 10 ^-2 torr. The number average molecular weight of the lactic acid oligomer obtained through the above reaction was 88,200.

(Step 2) In the reactor containing the oligomer, 10 g (0.11 mol) of 3-hydroxypropionic acid (3HP), 25 mg of SnCl ₂ (0.1 mol% compared to 3HP), and 83 mg of p-TSA (0.4 mol% 0.4 mol% compared to 3HP) ) was added and reacted for 2 h at 110 ° C and 10 mbar. A copolymer was obtained by raising the temperature to 140° C. and performing the reaction in a vacuum of 10 ⁻² torr for 24 hours.

Example 2

(Step 1) Add 30 g (0.33 mol) of lactic acid (LA), 75 mg of SnCl ₂ (0.1 mol% compared to LA), and 250 mg (0.4 mol) of p-TSA (0.4 mol compared to LA) to the reactor, and heat at 110°C and 10 mbar for 2 hours. reacted. The temperature was raised to 160 °C and the reaction was carried out for 18 hours in a vacuum of 10 ^-2 torr. The number average molecular weight of the lactic acid oligomer obtained through the above reaction was 78,900.

(Step 2) In the reactor containing the oligomer, 30 g (0.33 mol) of 3-hydroxypropionic acid (3HP), 75 mg of SnCl ₂ (0.1 mol% compared to 3HP), and 250 mg of p-TSA (0.4 mol% 0.4 mol% compared to 3HP) ) was added and reacted for 2 h at 110 ° C and 10 mbar. A copolymer was obtained by raising the temperature to 140° C. and performing the reaction in a vacuum of 10 ⁻² torr for 24 hours.

Comparative Example 1

(Step 1) 40 g of lactic acid (LA), 100 mg of SnCl ₂ , and 333 mg of p-TSA were added to the reactor and reacted at 110° C. and 10 mbar for 2 hours. The temperature was raised to 160 °C and the reaction was carried out for 6 hours under a vacuum of 10 ^-2 torr. The number average molecular weight of the lactic acid oligomer obtained through the above reaction was 2,700.

(Step 2) 10 g of 3-hydroxypropionic acid (3HP), 25 mg of SnCl ₂ , and 83 mg of p-TSA were added to the reactor and reacted at 110° C. and 10 mbar for 2 h. A copolymer was obtained by raising the temperature to 140° C. and performing the reaction in a vacuum of 10 ⁻² torr for 24 hours.

<Experimental example>

The properties of the copolymers prepared in Examples and Comparative Examples were evaluated as follows.

1) Evaluation of molecular weight characteristics

For each step of the copolymer prepared in the above Examples and Comparative Examples, the weight average molecular weight, number average molecular weight, and polydispersity index were measured by gel permeation chromatography (GPC: Tosoh ECO SEC Elite), and the results are shown in Table 1.

Solvent: chloroform (eluent)

Flow rate: 1.0 ml/min

Column temperature: 40 ℃

Standard: Polystyrene (corrected with a cubic function)

2) Evaluation of Elongation (%) characteristics

For the copolymers prepared in Examples and Comparative Examples, elongation was measured and the results are shown in Table 1.

Specifically, with respect to the copolymers prepared in the above Examples and Comparative Examples, V Type specimens were prepared according to ASTM D536 using a hot-press machine (Limotem QM900S). The elongation of the prepared specimen was measured using an Instron 5982 under a load of 10 mm/s and 60 kg/f.

3) Evaluation of melting temperature (Tm (℃))

For the copolymers prepared in Examples and Comparative Examples, melting points were measured and the results are shown in Table 1.

Specifically, for the copolymers prepared in the above Examples and Comparative Examples, using Mettler Toledo DSC (N ₂ 50 mL / min), target temperature range (-70 ℃ to 220 ℃), 1st heating (+10 ℃ /min), 1st cooling (-10 ℃ / min), 2nd heating (+10 ℃ / min) based on the measurement data was measured melting point.

division Step 1 Molecular Weight final molecular weight thermal properties mechanical properties Mn Mw PDI Mn Mw PDI Tm(℃) Elongation (%) Example 1 88,200 146,900 1.67 110,200 195,054 1.77 170 110 Example 2 78,900 158,589 2.01 100,700 214,500 2.13 170 106 Comparative Example 1 2,700 4,600 1.72 21,300 38,800 1.82 N.A. N.A.

As can be seen in Table 1 above, the poly(lactic acid-3-hydroxypropionic acid) copolymer prepared by adding 3-hydroxypropionic acid at a specific point in the lactic acid polymerization reaction in one reactor has excellent process efficiency In addition, it was confirmed that excellent thermal properties and mechanical properties were realized.

In the case of Comparative Example 1, a copolymer is formed in a single reactor, but the timing of adding 3-hydroxypropionic acid is out of the scope of the present invention. Accordingly, rather than forming a block copolymer of PLA and P3HP, a random airborne copolymer is formed. to form a composite. In the case of such a random copolymer, it was confirmed that it was difficult to measure the melting point and the elongation was also difficult to measure because it was difficult to manufacture a specimen in the form of a gum at room temperature.

Claims (11)

A first step of polymerizing lactic acid to prepare a lactic acid oligomer; and
A second step of preparing a poly(lactic acid-3-hydroxypropionic acid) copolymer by adding 3-hydroxypropionic acid when the number average molecular weight of the lactic acid oligomer reaches 5,000 to 100,000;
A method for producing a biodegradable copolymer.
According to claim 1,
When the number average molecular weight of the lactic acid oligomer is 10,000 to 90,000, 3-hydroxypropionic acid is added,
A method for producing a biodegradable copolymer.
According to claim 1,
The first step and the second step are carried out in the same reactor,
A method for producing a biodegradable copolymer.
According to claim 1,
The lactic acid and 3-hydroxypropionic acid are used in a molar ratio of 1:0.1 to 1:1.2,
A method for producing a biodegradable copolymer.
According to claim 1,
In the first step, after performing the reaction at 80 ° C. to 120 ° C. and 8 mbar to 12 mbar for 110 minutes to 130 minutes,
The temperature is raised to 120 ° C to 180 ° C and the reaction is carried out for 17 hours to 19 hours under a vacuum condition of 10 ^-2 torr,
A method for producing a biodegradable copolymer.
According to claim 1,
In the second step, after performing the reaction at 80 ° C. to 120 ° C. and 8 mbar to 30 mbar for 110 minutes to 130 minutes,
Carrying out the reaction for 22 hours to 26 hours under a vacuum condition of 10 ^-2 torr at 120 ℃ to 180 ℃,
A method for producing a biodegradable copolymer.
According to claim 1,
The first step and the second step are performed in the presence of a sulfonic acid-based catalyst and a tin-based catalyst,
A method for producing a biodegradable copolymer.
According to claim 1,
The first step is performed in the presence of a sulfonic acid-based catalyst and a tin-based catalyst,
The sulfonic acid-based catalyst is included in an amount of 0.1 to 1.0 mol% based on lactic acid,
The tin-based catalyst is contained in 0.025 to 0.5 mol% with respect to lactic acid,
A method for producing a biodegradable copolymer.
According to claim 1,
The second step is performed in the presence of a sulfonic acid-based catalyst and a tin-based catalyst,
The sulfonic acid-based catalyst is added in an amount of 0.1 to 1.0 mol% based on 3-hydroxypropionic acid,
The tin-based catalyst is 0.025 to 0.5 with respect to 3-hydroxypropionic acid added as mol%,
A method for producing a biodegradable copolymer.
According to claim 1,
The lactic acid and 3-hydroxypropionic acid are each independently pretreated at 50 ° C to 70 ° C and 30 mbar to 80 mbar before polymerization.
A method for producing a biodegradable copolymer.
According to claim 1,
The poly(lactic acid-3-hydroxypropionic acid) copolymer prepared above has a weight average molecular weight of 50,000 to 200,000,
A method for producing a biodegradable copolymer.