Poly(lactic acid-b-3-hydroxypropionic acid) block copolymer with excellent transparency and articles containing the same

Abstract

The poly(lactic acid-b-3-hydroxypropionic acid) block copolymer of the present invention is characterized in that by introducing a monomer derived from 3-hydroxypropionic acid into polylactic acid, the transparency of polylactic acid can be improved, thereby expanding its application fields.

Description

[Technical field]

[0001] Cross-reference to related application(s) This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0024929 filed on February 24, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a poly(lactic acid-b-3-hydroxypropionic acid) block copolymer having excellent transparency properties and an article containing the same. [Background technology]

[0003] Polylactic acid (PLA) is a plant-derived resin obtained from plants such as corn, and has biodegradable properties, and is attracting attention as an excellent environmentally friendly material. Unlike currently used petroleum-based resins such as polystyrene resin, polyvinyl chloride resin, and polyethylene, polylactic acid has the effect of preventing the depletion of petroleum resources and suppressing carbon dioxide emissions, and therefore can reduce environmental pollution, which is a disadvantage of petroleum-based plastic products. Therefore, as the problem of environmental pollution caused by waste plastics and other substances has emerged as a social issue, efforts are being made to expand the scope of application of polylactic acid to product areas where general plastics (petroleum-based resins) have been used, such as food packaging materials and containers, and electronic product cases.

[0004] However, polylactic acid has low impact resistance and heat resistance compared to existing petroleum-based resins, limiting its range of application. In addition, it has low tensile strength and transparency is required in some application fields, but since it is difficult to adjust the physical properties of polylactic acid, it has limitations as a general-purpose resin.

[0005] To overcome these shortcomings, research is being conducted on copolymers containing other repeating units in polylactic acid, with 3-hydroxypropionic acid in particular drawing attention as a comonomer. However, since the properties expressed vary depending on the degree of 3-hydroxypropionic acid introduction, there is a risk that the inherent properties of polylactic acid will be impaired if the degree of introduction is not controlled.

[0006] Therefore, the present invention aims to provide a block copolymer having excellent physical properties such as transparency while maintaining the inherent physical properties of polylactic acid by controlling the degree of introduction of the monomer derived from 3-hydroxypropionic acid. Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a copolymer having excellent physical properties such as transparency while maintaining the inherent properties of polylactic acid, and an article containing the same. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides a poly(lactic acid-b-3-hydroxypropionic acid) block copolymer represented by the following chemical formula 1, wherein the poly(lactic acid-b-3-hydroxypropionic acid) block copolymer has a UV transmittance of 80% or more.

[0009] [ka] In the above Chemical Formula 1, m is an integer from 100 to 1000; n is an integer from 500 to 4000.

[0010] The term "poly(lactic acid-b-3-hydroxypropionic acid) block copolymer" used in the present invention refers to a block copolymer in which a lactide-derived monomer and a 3-hydroxypropionic acid-derived monomer are polymerized as represented by Chemical Formula 1 above, and in particular, refers to a block copolymer in which various physical properties of polylactic acid are controlled by introducing a 3-hydroxypropionic acid-derived monomer.

[0011] When a monomer derived from 3-hydroxypropionic acid is introduced as a comonomer of polylactic acid, various physical properties of polylactic acid can be improved, but the properties expressed vary depending on the degree of introduction. Therefore, in the present invention, the degree of introduction of the monomer derived from 3-hydroxypropionic acid is controlled to maintain the inherent physical properties of polylactic acid while controlling physical properties such as transparency.

[0012] Preferably, m is 120 to 350. The m means the repeat number of a monomer derived from 3-hydroxypropionic acid, and by introducing it within the above range, it is possible to adjust physical properties such as transparency while maintaining the inherent physical properties of polylactic acid. More preferably, m is 130 or more, 140 or more, 150 or more, 160 or more, 170 or more, 180 or more, 190 or more, or 200 or more, and 340 or less, 330 or less, 320 or less, 310 or less, or 300 or less.

[0013] Preferably, n is 1000 to 2500. The n means the repeating number of a monomer derived from lactide. More preferably, n is 1100 or more, 1200 or more, 1300 or more, 1400 or more, or 1500 or more, and 2400 or less, 2300 or less, 2200 or less, 2100 or less, or 2000 or less.

[0014] In addition, in the present invention, the relative ratio of the monomers is important, and preferably the m / n is 0.05 to 0.20. Within this range of m / n, it is possible to adjust physical properties such as transparency while maintaining the inherent physical properties of polylactic acid. More preferably, the m / n is 0.06 or more, 0.07 or more, or 0.08 or more, and 0.19 or less, 0.18 or less, 0.17 or less, 0.16 or less, or 0.15 or less.

[0015] Preferably, the UV transmittance of the poly(lactic acid-b-3-hydroxypropionic acid) block copolymer according to the present invention is 81% or more, 82% or more, 83% or more, 84% or more, 85% or more, 86% or more, 87% or more, 88% or more, 89% or more, or 90%. The upper limit of the UV transmittance is theoretically 100%, but for example, it is 99.5% or less, 99.0% or less, 98.5% or less, or 98.0% or less. The method for measuring the UV transmittance will be specifically described in the examples below.

[0016] Preferably, the elongation of the poly(lactic acid-b-3-hydroxypropionic acid) block copolymer according to the present invention is 1% to 250%. Preferably, the elongation of the poly(lactic acid-b-3-hydroxypropionic acid) block copolymer according to the present invention is 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 100% or more. Also, preferably, the elongation of the poly(lactic acid-b-3-hydroxypropionic acid) block copolymer according to the present invention is 240% or less, 230% or less, 220% or less, 210% or less, 200% or less, 150% or less, or 120% or less. The method for measuring the elongation will be specifically described in the examples described later.

[0017] The tensile strength of the poly(lactic acid-b-3-hydroxypropionic acid) block copolymer according to the present invention is 30 MPa to 60 MPa. The method for measuring the tensile strength will be embodied in the examples described below. Preferably, the tensile strength of the poly(lactic acid-b-3-hydroxypropionic acid) block copolymer according to the present invention is 31 MPa or more, 32 MPa or more, 33 MPa or more, 34 MPa or more, or 35 MPa or more. On the other hand, the higher the tensile strength, the better, but if the value is excessively high, the application field of the copolymer may be limited. From this viewpoint, preferably, the tensile strength of the poly(lactic acid-b-3-hydroxypropionic acid) block copolymer according to the present invention is 60 MPa or less. More preferably, the tensile strength of the poly(lactic acid-b-3-hydroxypropionic acid) block copolymer according to the present invention is 55 MPa or less, 50 MPa or less, 45 MPa or less, or 40 MPa or less.

[0018] Preferably, the poly(lactic acid-b-3-hydroxypropionic acid) block copolymer according to the present invention has a tensile modulus of 1.5 to 2.5 GPa. A method for measuring the tensile modulus will be specifically described in the Examples below.

[0019] Also, preferably, the weight average molecular weight of the poly(lactic acid-b-3-hydroxypropionic acid) block copolymer is 50,000 to 350,000. More preferably, the weight average molecular weight of the poly(lactic acid-b-3-hydroxypropionic acid) block copolymer is 60,000 or more, 70,000 or more, 80,000 or more, 90,000 or more, or 100,000 or more, and 300,000 or less, 250,000 or less, 200,000 or less, or 150,000 or less.

[0020] The present invention also provides a method for producing the aforementioned poly(lactic acid-b-3-hydroxypropionic acid) block copolymer, comprising the steps of: polymerizing a 3-hydroxypropionic acid polymer, lactide, and a catalyst.

[0021] The 3-hydroxypropionic acid polymer means a homopolymer of 3-hydroxypropionic acid, and is prepared by controlling the degree of polymerization in consideration of the above-mentioned ranges of m and n.

[0022] Meanwhile, since the preparation method involves a lactide ring-opening polymerization reaction, the method is carried out in the presence of a lactide ring-opening catalyst. For example, the catalyst may be a catalyst represented by Chemical Formula 2.

[0023] [Chemical formula 2] MA 1 p A 2 2-p In the above Chemical Formula 2, M is Al, Mg, Zn, Ca, Sn, Fe, Y, Sm, Lu, Ti or Zr; p is an integer from 0 to 2; A 1 and A 2 are each independently an alkoxy or carboxyl group.

[0024] More specifically, the catalyst represented by Formula 2 may be tin(II) 2-ethylhexanoate (Sn(Oct)2).

[0025] Preferably, the amount of the catalyst used may be 0.001 to 10 mol %, 0.01 to 5 mol %, or 0.03 to 1 mol %, assuming that the total moles of lactide is 100 mol %.

[0026] Preferably, the production method is carried out at 150 to 200° C. Preferably, the production method is carried out for 5 minutes to 10 hours, more preferably 10 minutes to 1 hour. Preferably, the production method is carried out at 0.5 to 1.5 atm.

[0027] The present invention also provides an article comprising the poly(lactic acid-b-3-hydroxypropionic acid) block copolymer described above. Effect of the Invention

[0028] As described above, the poly(lactic acid-b-3-hydroxypropionic acid) block copolymer according to the present invention has the characteristic that by introducing a monomer derived from 3-hydroxypropionic acid into polylactic acid, the transparency of polylactic acid can be improved and the field of application can be expanded. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are merely illustrative of the present invention, and the present invention is not limited to the following examples. EXAMPLES

[0030] Production Example: Production of Poly(3-hydroxypropionate) Oligomer In the biosynthesis of high molecular weight poly(3-hydroxypropionate) according to the present invention, fermentation was carried out under the following conditions to produce a fermentation liquid containing 3-hydroxypropionate as a fermentation substrate. Specifically, E. coli W3110 having GDH and ALDH enzyme genes was used as the fermentation strain. M9 was used as the medium, and 70 g / L of glycerol was used as the substrate for fermentation to produce 3-hydroxypropionate.

[0031] Thereafter, the produced 3-hydroxypropionate was used as a substrate to produce poly(3-hydroxypropionic acid) (hereinafter, "P(3HP)") by fermentation. Specifically, a 5L fermenter (internal volume: 3L) was used for fermentation, and the microorganism used for fermentation was a recombinant E. coli produced by transforming XL1-Blue E. coli with a recombinant vector in which the RecC gene, which is a polyhydroxyalkanoate synthase (PHA synthase) derived from Ralstonia eutropha, and the mutant 540 (CPPCT_540) gene of propionyl-CoA transferase derived from Clostridium propionicum were cloned into the pBLuescript II KS+ vector.

[0032] The CPPCT_540 gene is an improved gene in which the base sequence has been substituted so that the 193rd amino acid, valine, is expressed as alanine (V194A), and in which three silent mutations (T669C, A1125G, T1158C) consisting of DNA substitutions without any amino acid changes have been made (WO09 / 022797).

[0033] The medium was a modified Riesenberg (MR) medium containing glucose (20 g / L) and the fermentation liquid (2.0 g / L) containing the 3-hydroxypropionate produced above as a substrate. This was fermented under aeration conditions of 300 rpm and 1 vvm, and finally high molecular weight poly(3-hydroxypropionate) was produced (Mn: 136,645; Mw: 354,615; PDI: 2.60; measured using an Agilent 1200 series and calibrated with PC standard).

[0034] The prepared poly(3-hydroxypropionate) was placed in distilled water and hydrolyzed at 100°C for 12, 18, 24, and 72 hours, respectively, to obtain poly(3-hydroxypropionate) oligomers with weight average molecular weights (measured using an Agilent 1200 series and calibrated with PC standard) of 15,000 g / mol, 30,000 g / mol, 60,000 g / mol, and 80,000 g / mol, respectively.

[0035] Example 1: Preparation of poly(lactic acid-b-3-hydroxypropionic acid) block copolymer Lactide (25g), poly(3-hydroxypropionate) oligomer (3g) having a weight average molecular weight of 15,000g / mol produced in the above production example, tin(II) ethylhexanoate (0.014g) as a catalyst, and toluene (100uL) were added to the reactor and dried for about 30 minutes to 1 hour. Then, the reactor was placed in an oil bath preheated to 180°C and polymerization was carried out for 1.5 hours. After removing the product from the reactor, the product was devolitilized at 140°C and 1 to 5 torr reduced pressure for about 3 hours to remove the monomer, and finally poly(lactic acid-b-3-hydroxypropionic acid) block copolymer was produced.

[0036] Examples 2 to 5 and Comparative Example: Production of poly(lactic acid-b-3-hydroxypropionic acid) block copolymer The same procedure as in Example 1 was followed, but the starting materials were changed as shown in Table 1 below to prepare poly(lactic acid-b-3-hydroxypropionic acid) block copolymers. [Table 1]

[0037] Experimental Example The copolymers prepared in the above examples were evaluated for their properties as follows. Weight average molecular weight: Measured by GPC using Agilent 1200 series and PC Standard. - Elongation, tensile strength and tensile modulus: According to ASTM D638, ASTM D536 V Type specimens were made using a hot-press machine (Limotem QM900S) and then measured using a UTM machine (Universal Testing Machine) at 10mm / s and 60kg / f load. -3-hydroxypropionic acid content (wt%) in block copolymer: Measured through NMR analysis of the block copolymer. -UV transmittance: The copolymer was made into a sheet of 80um thickness using a hot press (Limotem QM900S), and the transmittance was measured by installing it in a UV-visible spectrophotometer (Agilent 8453). At this time, the transmittance value in the 480nm region was confirmed.

[0038] The measured results are shown in the table below. [Table 2]

Claims

1. In the poly(lactic acid-b-3-hydroxypropionic acid) block copolymer represented by the following chemical formula 1, The poly(lactic acid-b-3-hydroxypropionic acid) block copolymer has a UV transmittance of 80% or more; The poly(lactic acid-b-3-hydroxypropionic acid) block copolymer has an elongation of 1% to 120%. Poly(lactic acid-b-3-hydroxypropionic acid) block copolymer. 【Chemistry 1】 (In the above Chemical Formula 1, m is an integer from 100 to 1000; n is an integer from 500 to 4000; m / n is 0.05 to 0.

20.

2. The poly(lactic acid-b-3-hydroxypropionic acid) block copolymer according to claim 1, wherein m is 120 to 350.

3. The poly(lactic acid-b-3-hydroxypropionic acid) block copolymer according to claim 1 or 2, wherein n is 1,000 to 2,500.

4. The poly(lactic acid-b-3-hydroxypropionic acid) block copolymer according to any one of claims 1 to 3, wherein the elongation of the poly(lactic acid-b-3-hydroxypropionic acid) block copolymer is 5% to 35%.

5. The poly(lactic acid-b-3-hydroxypropionic acid) block copolymer according to any one of claims 1 to 4, wherein the poly(lactic acid-b-3-hydroxypropionic acid) block copolymer has a tensile strength of 30 MPa to 60 MPa.

6. The poly(lactic acid-b-3-hydroxypropionic acid) block copolymer according to any one of claims 1 to 5, wherein the poly(lactic acid-b-3-hydroxypropionic acid) block copolymer has a tensile modulus of 1.5 to 2.5 GPa.

7. The poly(lactic acid-b-3-hydroxypropionic acid) block copolymer according to any one of claims 1 to 6, wherein the weight average molecular weight of the poly(lactic acid-b-3-hydroxypropionic acid) block copolymer is 50,000 to 350,000.

8. An article comprising the poly(lactic acid-b-3-hydroxypropionic acid) block copolymer of any one of claims 1 to 7.

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