COPOLYMER AND PREPARATION METHOD THEREOF

Abstract

Provided is a copolymer comprising an irregularly arranged structure of a repeating unit of the following Chemical Formula 1 and a repeating unit of the following Chemical Formula 2, and a repeating unit of the following Chemical Formula 3 present at least at one end of the structure:

##STR00001##

and is characterized by having an improved elongation and also having a high weight average molecular weight while maintaining intrinsic properties of a polylactic acid. Also provided are methods of preparing the copolymer.

Claims

1. A copolymer, comprising an irregularly arranged structure of a repeating unit of the following Chemical Formula 1 and a repeating unit of the following Chemical Formula 2, and a repeating unit of the following Chemical Formula 3 present at least at one end of the structure: ##STR00003##

2. The copolymer of claim 1, wherein a weight ratio of the repeating unit of Chemical Formula 1 and the repeating unit of Chemical Formula 2 is 20:80 to 80:20.

3. The copolymer of claim 1, wherein a total weight of the repeating unit of Chemical Formula 1 and the repeating unit of Chemical Formula 2 is 1 wt % to 40 wt % with respect to the total weight of the copolymer.

4. The copolymer of claim 1, wherein a total weight of the repeating unit of Chemical Formula 1 and the repeating unit of Chemical Formula 2 is 5 wt % to 15 wt % with respect to the total weight of the copolymer.

5. The copolymer of claim 1, wherein the copolymer has a weight average molecular weight of 50,000 g/mol to 300,000 g/mol.

6. The copolymer of claim 1, wherein the copolymer has a tensile strength of 20 MPa to 50 MPa.

7. The copolymer of claim 1, wherein the copolymer has an elongation of 4% to 200%.

8. A method of preparing the copolymer of claim 1, wherein the method comprises the following steps of: 1) preparing an oligomer by polycondensation of 3-hydroxypropionic acid and lactic acid; and 2) polymerizing the oligomer of the step 1 and a lactide.

9. The method of claim 8, wherein a catalyst of the step 2 is a catalyst of the following Chemical Formula 4:
MA.sup.1.sub.pA.sup.2.sub.2−p   [Chemical Formula 4] wherein in Chemical Formula 4: M is Al, Mg, Zn, Ca, Sn, Fe, Y, Sm, Lu, Ti, or Zr; p is an integer of 0 to 2; and A.sup.1 and A.sup.2 are each independently an alkoxy group or a carboxyl group.

10. The method of claim 8, wherein a catalyst of the step 2 is tin(II) 2-ethylhexanoate.

Description

DETAILED DESCRIPTION

[0046] Hereinafter, exemplary embodiments of the present invention will be described in more detail in the following Examples. However, the following Examples are only for illustrating the exemplary embodiments of the present invention, and the content of the present invention is not limited to the following Examples.

[0047] Hereinafter, a weight average molecular weight, a tensile strength, and an elongation were measured by the following methods. [0048] Weight average molecular weight: Measurement was performed by GPC using PC Standards and Agilent 1200 series HPLC system. [0049] Elongation, Tensile strength, and Tensile modulus: Measurement was performed in accordance with ASTM D638. Each copolymer was prepared in the form of pellet, and then processed into a dog-bone specimen, followed by measuring using a universal testing machine (UTM). At this time, the measurement speed was 10 mm/min. [0050] Content of 3HP (wt %) in copolymer: Measurement was performed by NMR analysis of each copolymer.

PREPARATION EXAMPLES 1 TO 4

[0051] In a reactor, 3-Hydroxypropionic acid (3HP), lactic acid (LA), and a catalyst (p-TSA; 0.3 wt % with respect to the total weight of 3HP and LA) were mixed in the amounts as described in Table 1 below, and dried under conditions of 70° C. and 50 mbar for 3 hours. Subsequently, the temperature and the pressure in the reactor were controlled to 130° C. and 20 mbar, and then a polycondensation reaction was allowed to proceed for 24 hours.

[0052] With respect to each of the prepared random copolymers, the content of 3HP in each copolymer and its weight average molecular weight were measured and shown in Table 1 below.

TABLE-US-00001 TABLE 1 3HP 3HP Weight average 3HP LA input content molecular weight input input ratio (wt %) in (Mw, g/mol) of (g) (g) (wt %) copolymer random copolymer Preparation 7 3 70 68 16,700 Example 1 Preparation 5 5 50 44 15,850 Example 2 Preparation 3 7 30 31 27,600 Example 3 Preparation 10 0 100 100 2,430 Example 4

EXAMPLES AND COMPARATIVE EXAMPLES

[0053] As in Table 2 below, each of the random copolymers prepared in Preparation Examples, lactide, and a catalyst (Tin Octoate, 0.05 mol % with respect to lactide) were put in a reactor, which was controlled to 170° C. and 20 mbar, and a lactide ring-opening polymerization was allowed to proceed for 30 minutes.

[0054] Meanwhile, in Table 2 below, Comparative Example 1 indicates a copolymer prepared by ring-opening polymerization using lactide alone without using the random copolymer prepared in Preparation Example.

TABLE-US-00002 TABLE 2 Random copolymer Lactide Example 1-1 Random copolymer of Preparation lactide Example 1 (10 wt %) (90 wt %) Example 1-2 Random copolymer of Preparation lactide Example 1 (30 wt %) (70 wt %) Example 1-3 Random copolymer of Preparation lactide Example 1 (5 wt %) (95 wt %) Example 2-1 Random copolymer of Preparation lactide Example 2 (10 wt %) (90 wt %) Example 3-1 Random copolymer of Preparation lactide Example 3 (10 wt %) (90 wt %) Example 3-2 Random copolymer of Preparation lactide Example 3 (20 wt %) (80 wt %) Example 4-1 Random copolymer of Preparation lactide Example 3 (30 wt %) (70 wt %) Comparative None lactide Example 1 (100 wt %) Comparative Random copolymer of Preparation lactide Example 2 Example 4 (10 wt %) (90 wt %)

EXPERIMENTAL EXAMPLE

[0055] A weight average molecular weight, a tensile strength, and an elongation were measured for the copolymers prepared in Examples and Comparative Examples, and the results are shown in Table 3 below.

TABLE-US-00003 TABLE 3 3HP content Weight average Tensile (wt %) in molecular weight strength Elongation copolymer (Mw, g/mol) (MPa) (%) Example 1-1 7.2 164,650 36.80 14.90 Example 1-2 21.0 80,900 27.7 107 Example 1-3 3.8 214,500 44.5 3.4 Example 2-1 5.0 190,370 32.40 5.0 Example 3-1 2.5 255,000 41.45 4.3 Example 3-2 7.6 179,200 32.8 66.2 Example 4-1 9.8 108,360 28.73 152.5 Comparative 0 239,000 50.13 2.2 Example 1 Comparative 10 31,700 Evaluation of Example 2 physical properties was impossible due to low molecular weight

[0056] As shown in Table 2, it was confirmed that the copolymer according to the present invention had the increased elongation, as compared with the copolymer prepared by polymerizing lactide alone (Comparative Example 1). When Example 4 was compared with Comparative Example 2, in which lactic acid was not used in the polymerization, the effect of increasing the molecular weight was observed when lactic acid was copolymerized, indicating improvement of physical properties.