Poly (lactic acid-3-hydroxypropionic acid) copolymer and preparation method thereof

Abstract

The present disclosure relates to a poly (lactic acid-3-hydroxypropionic acid) copolymer comprising a novel network structure and a method for preparing the same.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2023-0055420 filed on April 27, 2023, in the Korean Intellectual Property Office, and Korean Patent Application No. 10-2024-0055649 filed on April 25, 2024, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference in their entirety.

[0003] The present disclosure relates to a poly(lactic acid-3-hydroxypropionic acid) copolymer comprising a novel network structure and a preparation method thereof. Background Art

[0004] Poly(3-hydroxypropionic acid) has biodegradable properties, and due to this eco-friendly property, research on its use has recently been actively conducted.

[0005] Methods for preparing poly(3-hydroxypropionic acid) can be broadly divided into two types, one of which is a method using petrochemical-based β-propiolactone (PL) for polymerization, and the other is a method using bio-based 3-hydroxypropionic acid (3HP).

[0006] In the case of using PL, several synthesis steps must be performed using ethylene oxide, which is disadvantageous in terms of economic efficiency compared to the case of using 3HP.

[0007] In the case of polymerization using 3HP biosynthesis, several steps such as freeze drying, ultrasonic treatment and solvent extraction must be performed to obtain poly (3-hydroxypropionic acid), and in this case, a large amount of solvent must be used. In the case of biosynthesis of polymerization in this manner, the biocontent of poly (3-hydroxypropionic acid) is 100%, but due to the residue remaining after fermentation, it contains a large amount of organic nitrogen and has a high YI.

[0008] To address the above problems, attempts have been made to polycondense 3HP, but due to the formation of by-products in the form of cyclic oligomers, there are limitations in obtaining high molecular weight poly (3-hydroxypropionic acid). Attempts have been made to increase the molecular weight by subjecting low molecular weight cyclic oligomers to ROP (ring-opening polymerization), but separation and purification are difficult.

[0009] Furthermore, there is a need for a technology for synthesizing such poly(3-hydroxypropionic acid) polymers to have novel structures that achieve excellent physical properties for application in a wider range of product groups.

[0010] Therefore, there is a need to develop a method for preparing poly(3-hydroxypropionic acid) by polycondensation of 3HP, but preparing a polymer having a novel structure that achieves excellent physical properties and is easily applicable to various product groups. Summary of the Invention

[0011] Technical issues

[0012] An object of the present disclosure is to provide a poly(lactic acid-3-hydroxypropionic acid) copolymer having a novel network structure.

[0013] Another object of the present disclosure is to provide a method for preparing poly(lactic acid-3-hydroxypropionic acid) copolymer.

[0014] Technical Solution

[0015] Poly(lactic acid-3-hydroxypropionic acid) copolymer

[0016] To achieve the above-mentioned object, according to one embodiment of the present disclosure, a poly(lactic acid-3-hydroxypropionic acid) copolymer is provided, comprising: a first repeating unit derived from a poly(3-hydroxypropionic acid) polymer having a network structure; and a second repeating unit derived from lactide represented by the following Chemical Formula 2, wherein a plurality of 1-1 repeating units derived from 3-hydroxypropionic acid represented by the following Chemical Formula 1 are contained in the first repeating unit, wherein the network structure is formed by bonding any one end group of the 1-1 repeating unit to the end group of another 1-1 repeating unit by a reactive monomer, and wherein the α value measured by a multi-angle light scattering (MALS) detector is 0.4 to 0.8.

[0017] [Chemical Formula 1]

[0018]

[0019] [Chemical Formula 2]

[0020]

[0021] The term "poly(lactic acid-3-hydroxypropionic acid) copolymer" used herein comprises a first repeating unit derived from 3-hydroxypropionic acid and a second repeating unit derived from lactide, wherein a novel network structure comprising 1-1 repeating units represented by Chemical Formula 1 is contained within the first repeating unit.

[0022] Due to the molecular structure of the repeating units, the poly(lactic acid-3-hydroxypropionic acid) copolymers according to the present disclosure have biodegradable properties. The poly(lactic acid-3-hydroxypropionic acid) copolymers according to the present disclosure are characterized in that 3-hydroxypropionic acid is polymerized with reactive monomers under specific conditions, as described below, to prepare a polymer having a novel network structure, which is then polymerized with lactide to introduce the network structure into the final copolymer, which exhibits excellent physical properties.

[0023] As used herein, the term "network structure" may refer to a structure including at least two branch structures formed by combining at least three or more repeating units to form a mesh structure, which is different from a branched structure or a multi-branched hyperbranched structure.

[0024] The poly(lactic acid-3-hydroxypropionic acid) copolymer with a novel network structure has suitable molecular weight characteristics and can also simultaneously exhibit a high degree of crosslinking and suitable elasticity. Copolymers generally have the brittle characteristics of highly crosslinked polymers, but the copolymer with a novel network structure disclosed herein supplements elasticity through voids in the network structure, thereby reducing brittleness (fragility), making it easy to apply to a variety of product groups.

[0025] Specifically, the poly(lactic acid-3-hydroxypropionic acid) copolymer according to one embodiment of the present disclosure has a structure including a plurality of 1-1 repeating units derived from 3-hydroxypropionic acid represented by Chemical Formula 1 within a first repeating unit. Any one end group of the 1-1 repeating unit is bonded to the end group of another 1-1 repeating unit through a reactive monomer to form a novel network structure, and the second repeating unit derived from lactide is copolymerized in the network structure to form the final copolymer.

[0026] The α value of the poly(lactic acid-3-hydroxypropionic acid) copolymer measured by a multi-angle light scattering (MALS) detector is 0.4 to 0.8, preferably 0.4 to 0.7. A desired network structure can be achieved by satisfying the above range.

[0027] Therefore, the present disclosure can be manufactured into various molded products, and in particular, even when manufactured in a foam shape, the network structure supports the foam so that the shape is maintained without collapsing even after final processing.

[0028] The α value measured by a multi-angle light scattering (MALS) detector is an indicator that can grasp the structure of the polymer, and the α value refers to the constant value of the Mark-Houwink equation obtained according to the multi-angle light scattering (MALS) detector. If the α value is close to 1 outside the above range, it means that the structure of the polymer is close to linear, which is not suitable. In addition, if the α value in the cross-linked structure is too low outside the above range, gelation occurs, which reduces the processing performance and mechanical properties, making it difficult to maintain the shape of the final polymer in a foam shape, which makes it difficult to apply to various product groups. Its specific measurement method will be described in more detail in the experimental examples provided below.

[0029] The poly(lactic acid-3-hydroxypropionic acid) copolymer according to one embodiment of the present disclosure includes a first repeating unit derived from a poly(3-hydroxypropionic acid) polymer.

[0030] A plurality of 1-1 repeating units derived from 3-hydroxypropionic acid represented by the following Chemical Formula 1 are included in the first repeating unit, and any one end group of the 1-1 repeating unit is bonded to an end group of another 1-1 repeating unit through a reactive monomer, thereby forming a network structure.

[0031] [Chemical Formula 1]

[0032]

[0033] Herein, the "terminal group of the 1-1 repeating unit" refers to a terminal group obtained by a reaction between 3-hydroxypropionic acid and a reactive monomer, which are unit monomers forming the repeating unit.

[0034] The reactive monomer may contain at least one terminal reactive substituent selected from the group consisting of a hydroxyl group (-OH), a carboxyl group (-COOH), an amino group (-NH2), a cyano group (-CN), a thiol group (-SH), and an isocyanate group (-N=C=O). Preferably, the reactive monomer may be a multifunctional monomer containing multiple terminal reactive substituents, thereby facilitating the formation of a novel network structure.

[0035] The reactive monomer may be selected from poly (C 1-60 Alkylene polyol or C 1-60 At least one of the alkyl dicarboxylic acids, and poly C 1-60 Alkylene polyol or C 1-60 Alkyl dicarboxylic acids.

[0036] In this paper, poly C 1-60 The alkylene polyol may include glycerol, three-arm poly (ethylene glycol) n＝2～15 , four-arm poly (ethylene glycol) n＝2～10 , erythritol, pentaerythritol, di(trierythritolpropane), xylitol, sorbitol, tripentaerythritol, inositol and β-cyclodextrin, and preferably, glycerol may be included, but is not limited thereto.

[0037] In addition, C 1-60 The alkyl dicarboxylic acid may include at least one selected from malonic acid, succinic acid, adipic acid, 1,3,5-benzenetricarboxylic acid, 1,3,5-triazine-2,4,6-tricarboxylic acid, citric acid, and 2,2-bis(hydroxymethyl)butanoic acid, and preferably may include succinic acid, but is not limited thereto.

[0038] According to one embodiment of the present disclosure, the poly(lactic acid-3-hydroxypropionic acid) copolymer includes a second repeating unit derived from lactide, which is represented by the following Chemical Formula 2.

[0039] [Chemical Formula 2]

[0040]

[0041] “Lactide” refers to L-lactide, D-lactide, meso-lactide composed of L-lactide and D-lactide, or D,L-lactide or racemic lactide in which L-lactide and D-lactide are mixed in a weight ratio of 50:50.

[0042] According to one embodiment of the present disclosure, the poly(lactic acid-3-hydroxypropionic acid) copolymer having a novel network structure may have the following structure, but is not limited thereto.

[0043]

[0044] Here, R1 and R2 may refer to structures derived from reactive monomers.

[0045] n can be 1 to 100.

[0046] Preferably, the poly(lactic acid-3-hydroxypropionic acid) copolymer has a weight average molecular weight (Mw) of 100,000 to 500,000. More preferably, the weight average molecular weight is 120,000 or more, 150,000 or more, 170,000 or more, or 200,000 or more, and 450,000 or less, 400,000 or less, 380,000 or less, 350,000 or less, or 300,000 or less.

[0047] Preferably, the poly(lactic acid-3-hydroxypropionic acid) copolymer has a number average molecular weight (Mn) of 10,000 to 250,000. More preferably, the number average molecular weight is 15,000 or more, 18,000 or more, 20,000 or more, 25,000 or more, or 30,000 or more, and 200,000 or less, 150,000 or less, 100,000 or less, 90,000 or less, 70,000 or less, 50,000 or less, or 45,000 or less.

[0048] Preferably, the poly(lactic acid-3-hydroxypropionic acid) copolymer has a polydispersity index (PDI) of 2.0 to 7.0. More preferably, the polydispersity index is 2.1 or more, 2.3 or more, 2.5 or more, 2.8 or more, or 3.2 or more, and 6.8 or less, 6.3 or less, 6.0 or less, 5.5 or less, or 5.0 or less.

[0049] Preferably, the crystallization temperature (Tc) of poly (lactic acid -3-hydroxypropionic acid) copolymer is 90 ℃ to 120 ℃, preferably 95 ℃ to 118 ℃. By satisfying the above-mentioned thermal characteristics, it is conducive to achieving the desired effect. In addition, the crystallization temperature (Tc) of poly (lactic acid -3-hydroxypropionic acid) copolymer is 90 ℃ to 120 ℃, and the total enthalpy (ΔH) in this region is 20 J / g to 40 J / g, more preferably 29 J / g to 39 J / g. The crystallization temperature and its enthalpy can be measured by DSC (differential scanning calorimetry), and its specific measurement method will be described in more detail in the experimental examples provided below.

[0050] Preferably, the melting temperature (Tm) of the poly(lactic acid-3-hydroxypropionic acid) copolymer is 160°C to 170°C, more preferably 165°C to 168°C. Meeting these thermal properties facilitates achieving the desired effect. The specific measurement method is described in more detail in the experimental examples provided below.

[0051] Method for preparing poly (lactic acid-3-hydroxypropionic acid) polymer

[0052] On the other hand, according to one embodiment of the present disclosure, a method for preparing the poly(lactic acid-3-hydroxypropionic acid) polymer is provided, which can be prepared from 3-hydroxypropionic acid and lactide, wherein 3-hydroxypropionic acid can be prepared by biosynthesis.

[0053] Therefore, preferably, the poly (lactic acid-3-hydroxypropionic acid) prepared according to the present disclosure can have a biocontent of more than 90%. The biocontent can be determined by graphitizing the sample to be measured and then analyzing the content of radioisotope 14C (biosourced) by ASTM D6866-22.

[0054] More specifically, the method for preparing a poly(lactic acid-3-hydroxypropionic acid) polymer includes a first step of polymerizing 3-hydroxypropionic acid and a reactive monomer to form an oligomer; a second step of polymerizing the oligomer to prepare a poly(3-hydroxypropionic acid) polymer having a network structure; and a third step of subjecting the poly(3-hydroxypropionic acid) polymer and lactide to ring-opening polymerization to prepare a poly(lactic acid-3-hydroxypropionic acid) copolymer.

[0055] At this time, by adjusting the preparation conditions of steps 1 and 2, a poly(3-hydroxypropionate) polymer having a network structure can be prepared, wherein the final copolymer is prepared by ring-opening polymerization of lactide. The details of 3-hydroxypropionic acid, reactive monomers, and lactide used herein can be similarly applied to the above content.

[0056] (Step 1)

[0057] Step 1 of the present disclosure is a step of subjecting 3-hydroxypropionic acid and a reactive polymer to melt polymerization to prepare an oligomer. Melt polymerization means that 3-hydroxypropionic acid and a reactive polymer as reactants and an oligomer as a product remain in a liquid state.

[0058] The reactive monomer functions to combine multiple repeating units formed from 3-hydroxypropionic acid, allowing the polymer to form a new network.

[0059] The reactive monomer may contain at least one terminal reactive substituent selected from a hydroxyl group (-OH), a carboxyl group (-COOH), an amino group (-NH2), a cyano group (-CN), a thiol group (-SH), and an isocyanate group (-N=C=O). Preferably, the reactive monomer may be a multifunctional monomer containing a plurality of terminal reactive substituents, which facilitates the formation of a novel network structure. The specific type of reactive monomer may be similarly applied to all of the above.

[0060] Preferably, the reactive monomer may include a monomer selected from poly C 1-60 Alkylene polyol or C 1-60 At least one of the alkyl dicarboxylic acids, and preferably, may include poly C 1-60 Alkylene polyols and C 1-60 Alkyl dicarboxylic acid. Poly C 1-60 Alkylene polyols and C 1-60 The specific type of alkyl dicarboxylic acid can be similarly applied to all of the above.

[0061] Relative to 100 mol of 3-hydroxypropionic acid, the poly C 1-60 The alkylene polyol may be contained in an amount of 0.1 mol% to 15 mol%, preferably 0.5 mol% to 10 mol%. 1-60 The alkyl dicarboxylic acid may be included in an amount of 0.01 mol% to 5 mol%, preferably 0.25 mol% to 5 mol%. By using each reactive monomer within the above content range, a novel network structure can be easily formed.

[0062] Step 1: The reaction temperature is adjusted to 80° C. to 100° C. Preferably, the reaction temperature in step 1 is 81° C. or higher, 82° C. or higher, 83° C. or higher, 84° C. or higher, or 85° C. or higher, and 99° C. or lower, 98° C. or lower, 97° C. or lower, 96° C. or lower, or 95° C. or lower.

[0063] In addition, step 1 is performed at a pressure of 5 to 20 Torr. Preferably, the pressure of step 1 is 6 Torr or more, 7 Torr or more, 8 Torr or more, or 9 Torr or more, and 19 Torr or less, 18 Torr or less, 17 Torr or less, 16 Torr or less, or 15 Torr or less.

[0064] Furthermore, the reaction time of step 1 can be appropriately determined in consideration of the molecular weight of the produced oligomer, the yield, and the like, and the reaction is preferably performed for 1 to 3 hours.

[0065] Preferably, step 1 is carried out in the presence of a sulfonic acid catalyst. Preferably, the sulfonic acid catalyst is p-toluenesulfonic acid, m-xylene-4-sulfonic acid, 2-mesitylenesulfonic acid, or p-xylene-2-sulfonic acid. The amount of the catalyst used is 0.1 mol% to 0.5 mol% relative to 3-hydroxypropionic acid.

[0066] (Step 2)

[0067] Step 2 of the present disclosure is a step of further polymerizing the oligomer of step 1 to prepare a poly(3-hydroxypropionate) polymer having a novel network structure.

[0068] Through the steps, a first repeating unit derived from a poly(3-hydroxypropionate) polymer is formed, wherein a plurality of 1-1 repeating units derived from 3-hydroxypropionate represented by the following Chemical Formula 1 are included in the first repeating unit.

[0069] [Chemical Formula 1]

[0070]

[0071] The reactive monomer functions to bind multiple 1-1 repeating units formed from 3-hydroxypropionic acid, allowing the polymer to form a new network.

[0072] Unlike step 1, step 2 can be carried out at a lower pressure because the reactants are oligomers.

[0073] Preferably, the reaction temperature of step 2 is 75° C. to 95° C. More preferably, the reaction temperature of step 2 is 80° C. or 85° C. and 94° C. or less, 93° C. or less, 92° C. or less, or 91° C. or less.

[0074] Preferably, the reaction pressure in step 2 is 5 Torr or less. More preferably, the pressure in step 2 is 4 Torr or less, 3 Torr or less, 2 Torr or less, 1 Torr or less, 0.5 Torr or less, 0.4 Torr or less, or 0.3 Torr or less, and 0.01 Torr or more, 0.02 Torr or more, 0.03 Torr or more, 0.04 Torr or more, 0.05 Torr or more, 0.06 Torr or more, 0.07 Torr or more, 0.08 Torr or more, 0.09 Torr or more, or 0.1 Torr or more.

[0075] Furthermore, the reaction time of step 2 may be appropriately determined in consideration of the molecular weight, yield, etc. of the produced poly(3-hydroxypropionate) polymer, and the reaction is preferably performed for 5 to 30 hours.

[0076] Preferably, step 1 and step 2 are performed for a total of 7 hours to 30 hours, more preferably 7 hours to 24 hours.

[0077] Meanwhile, since step 2 is performed after step 1, the catalyst added in step 1 also participates in the reaction in step 2. Therefore, the catalyst described in the previous step 1 can be applied even in step 2.

[0078] In addition, according to one embodiment of the present disclosure, the second step can be carried out by further adding a tin-based catalyst. Preferably, the tin-based catalyst is SnCl2 or Sn(oct)2. The amount of the catalyst is 0.001 mol% to 0.5 mol% relative to 3-hydroxypropionic acid.

[0079] (Step 3)

[0080] Next, the method includes a third step of subjecting the poly(3-hydroxypropionic acid) polymer and lactide to ring-opening polymerization to prepare a poly(lactic acid-3-hydroxypropionic acid) copolymer.

[0081] Through the steps, a second repeating unit derived from lactide is formed, which is represented by the following Chemical Formula 2:

[0082] [Chemical Formula 2]

[0083]

[0084] Lactide can be mixed in an amount of 100 to 1,000 parts by weight relative to 100 parts by weight of the poly(lactic acid-3-hydroxypropionic acid) copolymer, and preferably, 300 to 1,000 parts by weight or 500 to 900 parts by weight. When the ring-opening reaction is carried out by mixing within the above range, a novel copolymer having a network structure and excellent physical properties within the desired molecular weight range can be prepared, which is preferred.

[0085] Step 3: Adjust the reaction temperature to 100° C. to 250° C. Preferably, the reaction temperature in step 3 is 150° C. or higher, 160° C. or higher, 170° C. or higher, or 180° C. or higher, and 240° C. or lower, 230° C. or lower, 220° C. or lower, 210° C. or lower, or 200° C. or lower.

[0086] In addition, step 3 is performed under normal pressure (about 760 Torr).

[0087] Furthermore, the reaction time of step 3 can be appropriately determined in consideration of the molecular weight, yield, etc. of the resulting final copolymer, and the reaction is preferably performed for 1 to 3 hours.

[0088] Preferably, step 3 can be carried out by further adding a tin-based catalyst. Preferably, the tin-based catalyst is SnCl2 or Sn(oct)2. The amount of the catalyst used is 0.001 mol% to 0.5 mol% relative to lactide.

[0089] Meanwhile, before steps 1, 2, and 3, if necessary, 3-hydroxypropionic acid, reactive monomers, and lactide may be pretreated independently at 30° C. to 100° C. and 30 mbar to 150 mbar. The pretreatment step can remove moisture present in 3-hydroxypropionic acid, reactive monomers, and lactide.

[0090] The poly(lactic acid-3-hydroxypropionic acid) polymer with a novel network structure prepared by the above method has suitable molecular weight characteristics and can simultaneously exhibit a high degree of crosslinking and suitable elasticity. Copolymers generally have the brittle characteristics of polymers with a high degree of crosslinking. However, the copolymer with a novel network structure disclosed herein supplements elasticity through the voids in the network structure, thereby reducing brittle characteristics (fragility), which makes it easy to apply to various product groups.

[0091] Beneficial effects

[0092] As described above, the present disclosure can effectively prepare poly(lactic acid-3-hydroxypropionic acid) copolymers having a novel network structure and excellent physical properties. DETAILED DESCRIPTION

[0093] Hereinafter, the present disclosure will be described in more detail through examples. However, the following examples are only for illustrative purposes, and the content of the present disclosure is not limited thereto.

[0094] [Examples and Comparative Examples]

[0095] Example 1

[0096] (Step 1)

[0097] 70 g of 3-hydroxypropionic acid (from which water had been removed), 7.156 g of the reactive monomer glycerol (10 mol% relative to 3-HP), and 4.59 g of succinic acid (5 mol% relative to 3-HP) were placed in a reactor, and 295.6 mg of p-toluenesulfonic acid (0.2 mol% relative to 3-HP) was added as a catalyst. The temperature and pressure in the reactor were maintained at 90° C. and 10 mbar (7.5 Torr), respectively, and the reaction was carried out for 2 hours to produce an oligomer.

[0098] (Step 2)

[0099] Then, the temperature and pressure in the reactor were adjusted to 80° C. and 0.1 Torr, respectively, and 157.4 mg of SnOct2 (0.05 mol % relative to 3-HP) was added thereto as an additional catalyst, and the reaction was further performed for 5 hours to prepare a poly(3-hydroxypropionic acid) polymer.

[0100] (Step 3)

[0101] Next, 4g of poly (3-hydroxypropionic acid) polymer was mixed with 40g of lactide in a new reactor and dried at room temperature for 12 hours. 180 μl of 0.01M Sn (Oct) 2 solution (relative to lactide, 0.03mol%) was injected into the reactor, and the toluene was vacuum dried for 30 minutes. Next, the reactor was filled with nitrogen and reacted in an oil bath preheated to 180°C for 90 minutes. Thus, a product comprising poly (lactic acid-3-hydroxypropionic acid) copolymer with a novel network structure was obtained. In order to remove the residual lactide in the product, devolatilization was carried out at 140°C for 4 hours to prepare the final copolymer.

[0102] Example 2 to Example 4

[0103] A poly(lactic acid-3-hydroxypropionic acid) copolymer was prepared in the same manner as in Example 1, except that the reaction conditions were changed as shown in Table 1 below.

[0104] Comparative Example 1

[0105] (Step 1)

[0106] 3-Hydroxypropionic acid (60 g) from which water had been removed was placed in a reactor, to which 253.4 mg of p-TSA (p-toluenesulfonic acid) (0.2 mol % relative to 3-HP) was added as a catalyst. The temperature and pressure in the reactor were maintained at 90° C. and 10 mbar (7.5 Torr), respectively, and the reaction was carried out for 2 hours to produce 3-hydroxypropionic acid oligomers.

[0107] (Step 2)

[0108] Then, the temperature and pressure in the reactor were adjusted to 80° C. and 0.1 Torr, respectively, and the reaction was performed for 5 hours to prepare a linear poly(3-hydroxypropionate) polymer.

[0109] (Step 3)

[0110] Next, 4g of poly (3-hydroxypropionic acid) polymer was mixed with 40g of lactide in a new reactor and dried at room temperature for 12 hours. 180 μl of 0.01M Sn (Oct) 2 solution (relative to lactide, 0.03mol%) was injected into the reactor, and the toluene was vacuum dried for 30 minutes. Next, the reactor was filled with nitrogen and reacted in an oil bath preheated to 180°C for 90 minutes. Thus, the product comprising poly (lactic acid-3-hydroxypropionic acid) copolymer was obtained. In order to remove the residual lactide in the product, devolatilization was carried out at 140°C for 4 hours to prepare the final copolymer.

[0111] Comparative Example 2

[0112] (Step 1)

[0113] 70 g of dried 3-hydroxypropionic acid (3HP) and 3.578 g of glycerol (5 mol % relative to 3HP) were placed in a reactor and oligomerized using 295.6 mg of p-TSA (0.2 mol % relative to 3HP) as a catalyst while maintaining at 90° C. and 10 mbar (7.5 Torr) for 2 hours.

[0114] (Step 2)

[0115] Then, the temperature and pressure in the reactor were adjusted to 80° C. and 0.1 Torr, respectively, 157.4 mg of Sn(Oct) 2 (relative to 3HP, 0.05 mol%) was added thereto as a co-catalyst, and the reaction was further carried out for 5 hours to prepare a branched polymer.

[0116] (Step 3)

[0117] Next, 4g of this branched type was mixed with 40g of lactide in a new reactor and dried at room temperature for 12 hours. 180μl of a 0.01M Sn(oct)2 solution in toluene (0.03mol% relative to lactide) was injected into the reactor, and the toluene was vacuum dried for 30 minutes. Next, the reactor was filled with nitrogen and reacted in an oil bath preheated to 180°C for 90 minutes. Thus, a product comprising a poly(lactic acid-3-hydroxypropionic acid) copolymer having a novel network structure was obtained. In order to remove the residual lactide in the product, devolatilization was carried out at 140°C for 4 hours to prepare the final copolymer.

[0118] [Table 1]

[0119]

[0120]

[0121] [Experimental example]

[0122] (1) Evaluation of molecular weight characteristics

[0123] The weight average molecular weight, number average molecular weight and polydispersity index of the copolymers prepared in each step of Examples and Comparative Examples were measured by gel permeation chromatography (GPC, Waters Alliance e2695), and the results are shown in Table 2 below.

[0124] -Solvent: Chloroform (eluent)

[0125] -Flow rate: 1.0ml / min

[0126] - Column temperature: 40°C

[0127] -Standard: Polystyrene

[0128] [Table 2]

[0129]

[0130] (2) Evaluation of α value by multi-angle light scattering (MALS) detector

[0131] The α values ​​of the copolymers prepared in Examples and Comparative Examples were measured using a multi-angle light scattering (MALS) detector, and the results are shown in Table 1 below.

[0132] First, the copolymer was dissolved in chloroform (stabilized with ETOH) at a concentration of 5 mg / mL to prepare a sample, and the mobile phase was prepared by filtering 1000 mL of chloroform (stabilized with ETOH) through a solvent clarification system. The radius of gyration (Rg) of the solvated chain of the polymer was measured using a multi-angle light scattering (MALS) detector, thereby obtaining a curve of intrinsic viscosity (η) and absolute molecular weight (M; absolute MW). The constant alpha (α) value was calculated using the Mark-Houwink equation of mathematical equation 1 below, and the results are shown in Table 3 below.

[0133] -RI (refractive index) measurement: DAWN8 (manufacturer: Wyatt)

[0134] -Viscometer (viscosity) measurement: Viscostar III (manufacturer: Wyatt)

[0135] -Light scattering measurement: Optilab T-rEX (manufacturer: Wyatt)

[0136] -Stationary phase: 2xAgilent PLgel MIXED-B and C, 7.5x300mm, 5μm

[0137] -Mobile phase: chloroform (stabilized with ETOH) = 100 (v / v, %)

[0138] -Flow rate: 1.0mL / min

[0139] -Stationary phase temperature: 40℃

[0140] -Injection volume: 100 μl (0.45 μm filtered)

[0141] -Analysis time: 35 minutes

[0142] -System calibration: Polystyrene (Mp: 135700)

[0143] -Chloroform refractive index: 1.45

[0144] [Mathematical equation 1]

[0145] log[η]=αlogM+logK

[0146] In mathematical equation 1,

[0147] [η] is the intrinsic viscosity of the copolymer (dl / g),

[0148] M is the absolute molecular weight (absolute MW) of the copolymer,

[0149] K is a constant.

[0150] [Table 3]

[0151] category α Example 1 0.4 Example 2 0.4 Example 3 0.7 Example 4 0.5 Comparative Example 1 1.1

[0152] (3) Evaluation of thermal properties by DSC (Differential Scanning Calorimetry)

[0153] The thermal properties (Tg, Tm, cold crystallization (second heating result), Tc (first cooling result), total enthalpy (ΔH)) of the copolymers prepared in the Examples and Comparative Examples were measured using a TA DSC250 model device under nitrogen flow conditions. The results are shown in Table 2 below.

[0154] Heat from 40°C to 190°C at 5°C / min (first heating) / maintain at 190°C for 10 minutes

[0155] Cool from 190°C to -60°C at 5°C / min (first cooling) / hold at -60°C for 10 minutes

[0156] Heating from -60°C to 190°C at 5°C / min (second heating)

[0157] [Table 4]

[0158]

[0159] In general, if the crystallization rate is fast, the enthalpy of Tc is large, and cold crystallization is few or does not exist, and further, as crystallinity is higher, the enthalpy of Tm may be larger. In addition, it can be confirmed that when crystallinity is high, the strength of the material increases, but it is brittle and has no elasticity. However, in the case of novel network structures as disclosed herein, crystallinity can be reduced, thereby reducing brittle properties. In the case of comparative example 2, it can be confirmed that the enthalpy of Tc is significantly lower than that of embodiment, and cold crystallization occurs. Thus, it is confirmed that the speed of crystal formation is slower than in the embodiment. In addition, it is confirmed that crystallinity is lower than embodiment by the enthalpy value of Tm.

Claims

1. A poly(lactic acid-3-hydroxypropionic acid) copolymer comprising: a first repeating unit derived from a poly(3-hydroxypropionic acid) polymer having a network structure; and a second repeating unit derived from lactide represented by the following Chemical Formula 2, wherein the first repeating unit comprises a plurality of 1-1 repeating units derived from 3-hydroxypropionic acid represented by the following Chemical Formula 1, wherein the network structure is formed by bonding any one end group of the 1-1 repeating unit to the end group of another 1-1 repeating unit through a reactive monomer, and The α value measured by the multi-angle light scattering (MALS) detector is 0.4 to 0.8 [Chemical Formula 1] [Chemical Formula 2] 2. The poly(lactic acid-3-hydroxypropionic acid) copolymer according to claim 1, wherein: The network structure includes at least two branch structures formed by combining at least three or more 1-1 repeating units.

3. The poly(lactic acid-3-hydroxypropionic acid) copolymer according to claim 1, wherein: The reactive monomer comprises at least one terminal reactive substituent selected from the group consisting of a hydroxyl group (-OH), a carboxyl group (-COOH), an amino group (-NH2), a cyano group (-CN), a thiol group (-SH) and an isocyanate group (-N=C=O).

4. The poly(lactic acid-3-hydroxypropionic acid) copolymer according to claim 1, wherein: The reactive monomer is selected from poly C 1-60 Alkylene polyol or C 1-60 At least one of alkyl dicarboxylic acids.

5. The poly(lactic acid-3-hydroxypropionic acid) copolymer according to claim 4, wherein: The poly C 1-60 Alkylene polyol is selected from glycerol, three-arm poly (ethylene glycol) n＝2～15 , four-arm poly (ethylene glycol) n＝2～10 , erythritol, pentaerythritol, di(trierythritol propane), xylitol, sorbitol, tripentaerythritol, inositol and at least one of β-cyclodextrin.

6. The poly(lactic acid-3-hydroxypropionic acid) copolymer according to claim 4, wherein: The C 1-60 The alkyl dicarboxylic acid is at least one selected from malonic acid, succinic acid, adipic acid, 1,3,5-benzenetricarboxylic acid, 1,3,5-triazine-2,4,6-tricarboxylic acid, citric acid, and 2,2-bis(hydroxymethyl)butanoic acid.

7. The poly(lactic acid-3-hydroxypropionic acid) copolymer according to claim 1, wherein: The copolymer has a weight average molecular weight (Mw) of 100,000 to 500,000.

8. The poly(lactic acid-3-hydroxypropionic acid) copolymer according to claim 1, wherein: The copolymer has a number average molecular weight (Mn) of 10,000 to 250,000.

9. The poly(lactic acid-3-hydroxypropionic acid) copolymer according to claim 1, wherein: The copolymer has a polydispersity index (PDI) of 2.0 to 7.

0.

10. The poly(lactic acid-3-hydroxypropionic acid) copolymer according to claim 1, wherein: The copolymer has a crystallization temperature (Tc) of 90 to 120° C., and a total enthalpy (ΔH) in this region of 20 to 40 J / g.

11. The poly(lactic acid-3-hydroxypropionic acid) copolymer according to claim 1, wherein: The melting temperature (Tm) of the copolymer is 160°C to 170°C.

12. A method for preparing the poly (lactic acid-3-hydroxypropionic acid) copolymer according to claim 1, the method comprising: a first step of polymerizing 3-hydroxypropionic acid with a reactive monomer to form an oligomer; a second step of polymerizing the oligomer to prepare a poly(3-hydroxypropionic acid) polymer having a network structure; and The third step is to subject the poly(3-hydroxypropionic acid) polymer and lactide to ring-opening polymerization to prepare a poly(lactic acid-3-hydroxypropionic acid) copolymer.

13. The method for preparing poly(lactic acid-3-hydroxypropionic acid) copolymer according to claim 12, wherein: The reactive monomer comprises at least one terminal reactive substituent selected from the group consisting of a hydroxyl group (-OH), a carboxyl group (-COOH), an amino group (-NH2), a cyano group (-CN), a thiol group (-SH) and an isocyanate group (-N=C=O).

14. The method for preparing poly(lactic acid-3-hydroxypropionic acid) copolymer according to claim 12, wherein: The reactive monomer is selected from poly C 1-60 Alkylene polyol or C 1-60 At least one of alkyl dicarboxylic acids.

15. The method for preparing poly(lactic acid-3-hydroxypropionic acid) copolymer according to claim 14, wherein: Relative to 100 mol of 3-hydroxypropionic acid, the poly C 1-60 The alkylene polyol is contained in an amount of 0.1 mol% to 15 mol%, and Relative to 100 mol of 3-hydroxypropionic acid, the C 1-60 The alkyl dicarboxylic acid is contained in an amount of 0.01 mol% to 5 mol%.

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