KR102350740B1 - Acetylated lactide oligomer-based plasticizer and the method of manufacturing the same, pla resin composition comprising acetylated lactide oligomer-based plasticizer - Google Patents

Abstract

It is an object of the present invention to provide an acetylated lactide oligomer-based plasticizer having improved thermal stability, excellent plasticization performance, and excellent compatibility with a resin, and a method for preparing the same.
The present invention provides the steps of: (a) synthesizing a lactide oligomer by ring-opening polymerization (ROP) of an initiator and lactide; (b) performing an acetylation reaction by adding acetic anhydride to the lactide oligomer; and (c) removing acetic acid and unreacted acetic anhydride produced in step (b).

Description

An acetylated lactide oligomer-based plasticizer, a manufacturing method thereof, and a PLA resin composition comprising an acetylated lactide oligomer-based plasticizer PLASTICIZER}

The present invention relates to an acetylated lactide oligomer-based plasticizer, a method for preparing the same, and a PLA resin composition comprising the acetylated lactide oligomer-based plasticizer, and more particularly, to an acetylated lactide oligomer that is stable to heat and has excellent plasticizing performance. It relates to a PLA resin composition comprising a plasticizer, a method for manufacturing the same, and an acetylated lactide oligomer-based plasticizer.

In the field of polymers, biodegradable resins that decompose under natural environments are attracting attention along with the requirements for compatibility and biodegradability in terms of environmental protection. Accordingly, studies on polylactic acid, copolymers of lactic acid and other aliphatic hydroxycarboxylic acids, and polyesters derived from aliphatic polyhydric alcohols and aliphatic polyhydric carboxylic acids are being actively conducted.

In particular, polylactic acid (PLA) is an eco-friendly resin made from agricultural products that do not have a problem of resource depletion, and is mass-produced at low cost using the fermentation method of D,L-lactide. PLA has a glass transition temperature of 60 °C and is a material that exhibits properties similar to conventional plastics. PLA has been approved by the Food and Drug Administration (FDA) because of its biodegradability and biocompatibility, and is used in various fields such as packaging, medicine, agriculture, and pharmaceuticals.

However, such PLA has high crystallinity and rigid molecular structure, so it is hard and brittle, has poor flexibility, and has disadvantages in poor processability. Therefore, by itself, it is not suitable for the use which requires flexibility, such as a film and a packaging material.

As a method for softening PLA, methods such as addition of a plasticizer, blending of a soft polymer, copolymerization, and the like may be considered. However, the method of blending the soft polymer has a limitation in that it is limited to the blend of a biodegradable resin such as polybutylene succinate from the viewpoint of biodegradability. In addition, in order to give sufficient flexibility to PLA, a large amount of addition is required, and as a result, there is a problem that the properties of PLA are not sufficiently expressed and may be damaged. In the case of copolymerization, there is a problem in that physical properties such as melting point and heat resistance are changed according to a decrease in crystallinity and glass transition point.

When a plasticizer is added, as the plasticizer reduces intermolecular contact inside the resin, the processability, flexibility, and durability of the resin are improved, and in some cases, the cost of the product is reduced. An ideal eco-friendly plasticizer should be produced from renewable raw materials and be biodegradable. In addition, like the existing plasticizer, compatibility with the resin must be high, and it must be chemically stable during processing, and excellent dissolution resistance must be secured.

So far, as eco-friendly plasticizers, vegetable oil-based eco-friendly plasticizers, succinic acid-based eco-friendly plasticizers, and isosorbide plasticizers have been studied. However, these eco-friendly plasticizers have a limitation in that their physical properties are limited when compared to the existing phthalate plasticizers.

As described above, although plasticizers added to supplement and improve the physical properties of biodegradable resins with excellent environmental compatibility have been developed, there are various drawbacks such as poor processability and limitations in mechanical properties. It is necessary to develop a plasticizer with excellent mechanical properties and compatibility. In addition, there is a need for improvement so that eco-friendly biodegradable resins can be applied to a variety of industrial fields by application of these plasticizers.

Republic of Korea Patent Publication No. 10-1875130 (2018.08.02. Announcement)

An object of the present invention is to provide an acetylated lactide oligomer-based plasticizer that is stable to heat and has improved plasticizing performance.

Another object of the present invention is to provide an acetylated lactide oligomer-based plasticizer that has excellent compatibility with PLA resin and is environmentally friendly.

In order to achieve the above object, the present invention provides a method comprising: (a) synthesizing a lactide oligomer by ring-opening polymerization (ROP) of an initiator and lactide; (b) performing an acetylation reaction by adding acetic anhydride to the lactide oligomer; and (c) removing acetic acid and unreacted acetic anhydride produced in step (b).

The initiator of step (a) may be any one selected from the group consisting of 1,1,1-tris(hydroxymethyl)propane, diethylene glycol, and ethyl alcohol.

Step (a) may be performed at 100 to 120 °C for 2 to 6 hours.

Tin 2-ethyl hexanoate (tin(II) 2-ethylhexanoate) may be used as a catalyst for the ring-opening polymerization in step (a).

Step (b) may be performed at 80 to 120 °C for 40 to 60 hours.

The present invention also provides an acetylated lactide represented by any one of the following Chemical Formulas 1 to 3, which is prepared by acetylation reaction of a lactide oligomer synthesized by ring-opening polymerization (ROP) of an initiator and lactide. An oligomeric plasticizer is provided.

[Formula 1]

[Formula 2]

[Formula 3]

The initiator may be any one selected from the group consisting of 1,1,1-tris(hydroxymethyl)propane, diethylene glycol, and ethyl alcohol.

As a catalyst for the ring-opening polymerization, tin 2-ethyl hexanoate (tin(II) 2-ethylhexanoate) may be used.

The ring-opening polymerization may be carried out at 100 to 120° C. for 2 to 6 hours.

The acetylation reaction may be performed at 80 to 120 °C for 40 to 60 hours.

The present invention also provides a PLA resin composition comprising a polylactic acid (PLA) resin and any one plasticizer selected from acetylated lactide oligomer-based plasticizers represented by the following Chemical Formulas 1 to 3.

[Formula 1]

[Formula 2]

[Formula 3]

The plasticizer may be included in the range of 25 to 70 phr with respect to the PLA resin composition.

According to the method for producing an acetylated lactide oligomer-based plasticizer according to the present invention, since the terminal of the hydroxy group of the plasticizer is replaced with an acetyl group by the acetylation reaction, there is an advantageous effect of improving the thermal stability of the plasticizer.

In addition, the acetylated lactide oligomer-based plasticizer prepared according to the present invention has superior plasticizing performance compared to commercial plasticizers and has excellent compatibility with PLA resin.

1 is a process flow diagram of a method for manufacturing an acetylated lactide oligomer-based plasticizer according to an embodiment of the present invention.
2 is a graph comparing ¹ H-NMR before and after acetylation of the hydroxyl group terminal of the lactide oligomer according to Example 1 of the present invention.
3 is a graph comparing ¹ H-NMR before and after acetylation of the hydroxyl group terminal of the lactide oligomer according to Example 2 of the present invention.
4 is a graph comparing ¹ H-NMR before and after acetylation of the hydroxyl group terminal of the lactide oligomer according to Example 3 of the present invention.
5 is a graph comparing MALDI-TOF-MS before and after acetylation of the hydroxyl terminal of the lactide oligomer according to Example 1 of the present invention.
6 is a graph comparing MALDI-TOF-MS before and after acetylation of the hydroxyl terminal of the lactide oligomer according to Example 2 of the present invention.
7 is a graph comparing MALDI-TOF-MS before and after acetylation of the hydroxyl terminal of the lactide oligomer according to Example 3 of the present invention.
8 is a graph comparing the analysis results of the plasticizers of Examples 1 to 3 and the DOA and ATBC plasticizers measured through thermogravimetric analysis (TGA).
9 is a graph comparing the evaluation results of thermal properties of the plasticizers of Examples 1 to 3 and the DOA and ATBC plasticizers measured through differential scanning calorimetry (DSC).
10 is a graph comparing the stress-strain curves of the PLA specimens of Examples 4 to 6 and Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when 10 phr of a plasticizer is added.
11 is a graph comparing the stress-strain curves of the PLA specimens of Examples 4 to 6 and Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when the plasticizer was added at 25 phr.
12 is a graph comparing the stress-strain curves of the PLA specimens of Examples 4 to 6, Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when the plasticizer was added at 65 phr.
13 is a graph comparing the storage modulus (G′) of the PLA specimens of Examples 4 to 6 and Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when 10 phr of a plasticizer is added.
14 is a graph comparing the storage modulus (G′) of the PLA specimens of Examples 4 to 6, Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when 25 phr of a plasticizer is added.
15 is a graph comparing the storage modulus (G′) of the PLA specimens of Examples 4 to 6, Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when the plasticizer is added at 65 phr.
16 is a graph comparing the tan δ of the PLA specimens of Examples 4 to 6 and Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when the plasticizer was added at 10 phr.
17 is a graph comparing the tan δ of the PLA specimens of Examples 4 to 6, Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when the plasticizer was added at 25 phr.
18 is a graph comparing the tan δ of the PLA specimens of Examples 4 to 6, Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when the plasticizer was added at 65 phr.
19 is a graph comparing the results of differential scanning calorimetry (DSC) analysis of the PLA specimens of Examples 4 to 6, Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when 10 phr of a plasticizer was added.
20 is a graph comparing the results of differential scanning calorimetry (DSC) analysis of the PLA specimens of Examples 4 to 6, Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when the plasticizer was added at 25 phr.
21 is a graph comparing the results of differential scanning calorimetry (DSC) analysis of the PLA specimens of Examples 4 to 6, Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when the plasticizer was added at 65 phr.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

Advantages and features of the present invention, and a method of achieving the same, will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings.

However, the present invention is not limited by the embodiments disclosed below, but can be implemented in various different forms, and only the present embodiments allow the disclosure of the present invention to be complete, and are common in the art to which the present invention pertains. It is provided to fully inform those with the knowledge of the scope of the invention. Moreover, the invention is only defined by the scope of the claims.

Furthermore, in the description of the present invention, when it is determined that related known techniques may obscure the gist of the present invention, a detailed description thereof will be omitted.

Hereinafter, a method for producing an acetylated lactide oligomer-based plasticizer according to an embodiment of the present invention will be described in detail.

1 is a process flow diagram of a method for manufacturing an acetylated lactide oligomer-based plasticizer according to an embodiment of the present invention.

Referring to FIG. 1 , an acetylated lactide oligomer-based plasticizer according to an embodiment of the present invention comprises (a) synthesizing a lactide oligomer by ring-opening polymerization (ROP) of an initiator and lactide. step; (b) performing an acetylation reaction by adding acetic anhydride to the lactide oligomer; and (c) removing the acetic acid and unreacted acetic anhydride produced in step (b).

First, the initiator and lactide are subjected to a ring-opening polymerization reaction (S10).

In the above step, a catalyst is added to lactide and a lactide oligomer is synthesized through a ring-ring-opening polymerization reaction.

In the ring-opening polymerization reaction, ethanol, diethylene glycol, and 1,1,1-tris(hydroxymethyl)propane may be used as initiators, but the present invention is not limited thereto.

The ring-opening polymerization may be performed by adding the lactide and the initiator into a reactor, adding a catalyst, and then heating and stirring.

The catalyst may be tin 2-ethyl hexanoate (tin(II) 2-ethylhexanoate, Sn(Oct) ₂ ), dioctyltin dilaurate, preferably tin 2-ethyl hexanoate ( Sn(Oct) ₂ )).

The catalyst may be introduced in the form of a solution dissolved in a solvent, and when the catalyst is added in the form of a solution dissolved in a solvent, a process of preferentially removing the solvent before the reaction with the lactide and the initiator may be performed.

The solvent may be an aromatic solvent such as toluene, benzene, or xylene, a halogenated alkyl solvent such as methylene chloride or chloroform, an aliphatic solvent such as hexane, an organic solvent such as tetrahydrofuran, acetone, or dioxane, preferably toluene, benzene, acetone or tetrahydrofuran.

This step may be performed at 100 ~ 120 ℃ for 2 hours to 6 hours. Under such conditions, a relatively small amount of catalyst can be used. Under the above conditions, the amount of the catalyst added may be 0.002 to 0.003 moles, preferably 0.0025 moles, based on 1 mole of the initiator.

Next, an acetylation reaction is performed by adding acetic anhydride to the resulting lactide oligomer (S20).

In the above step, the hydroxyl group (-OH) at the end of the lactide oligomer is substituted _{with an acetyl group (-COCH 3 ) through an acetylation reaction.}

The acetylation step may be performed by solution polycondensation polymerization or bulk polycondensation polymerization.

A metal catalyst may be used to promote the reaction during the polycondensation reaction. Examples of such metal catalysts may include alkali metals such as lithium, sodium, potassium, or the like, or oxides, hydroxides, chlorides, and the like of these alkali metals. For example, the metal catalyst may include at least one selected from the group consisting of magnesium acetate, potassium acetate, calcium acetate, zinc acetate, manganese acetate, lead acetate, antimony acetate, and cobalt acetate.

The acid anhydride used in the above step may include at least one compound selected from the group consisting of acetic anhydride, diphenyl carbonate, and benzyl acetate, of which acetic anhydride is preferably used.

The amount of the acid anhydride used may be 1 to 4 moles based on 1 mole of the total amount of hydroxyl groups included in the lactide oligomer. When the amount of the acid anhydride used in the acetylation reaction is within the above range, the lactide oligomer used is sufficiently acetylated, and the unreacted amount of the acid anhydride used is small, so that its removal is facilitated.

The acetylation reaction may be carried out at 80 ~ 120 ℃, preferably carried out at 100 ℃. When the reaction temperature is 80 °C or higher, the hydroxyl group at the end of the lactide oligomer can be sufficiently converted to an acetyl group.

In addition, the reaction may be carried out for 40 to 60 hours, and is preferably carried out for 42 hours. Here, when the reaction time is less than 40 hours, there is a problem that the reaction is not easily induced, and when it exceeds 60 hours, there is a problem in that the amount of by-products is increased.

Finally, acetic acid and unreacted acetic anhydride generated in the acetylation reaction are removed to obtain an acetylated lactide oligomer-based plasticizer (S30).

The acetylated lactide oligomer-based plasticizer prepared according to an embodiment of the present invention may be represented by Chemical Formulas 1 to 3 below.

[Formula 1]

[Formula 2]

[Formula 3]

According to another aspect of the present invention, according to another aspect of the present invention, one of the following Chemical Formulas 1 to 3 is prepared by acetylation reaction of a lactide oligomer synthesized by ring-opening polymerization (ROP) of an initiator and lactide. The indicated acetylated lactide oligomer-based plasticizer is provided.

[Formula 1]

[Formula 2]

[Formula 3]

The initiator may be any one selected from the group consisting of 1,1,1-tris(hydroxymethyl)propane, diethylene glycol, and ethyl alcohol.

As a catalyst for the ring-opening polymerization, tin 2-ethyl hexanoate (tin(II) 2-ethylhexanoate) may be used.

The ring-opening polymerization may be carried out at 100 to 120° C. for 2 to 6 hours. Under such conditions, a relatively small amount of catalyst can be used. Under the above conditions, the amount of the catalyst added may be 0.002 to 0.003 moles, preferably 0.0025 moles, based on 1 mole of the initiator.

The acetylation reaction may be carried out at 80 ~ 120 ℃, preferably carried out at 100 ℃. When the reaction temperature is 80 °C or higher, the hydroxyl group at the end of the lactide oligomer can be sufficiently converted to an acetyl group.

In addition, the reaction may be carried out for 40 to 60 hours, and is preferably carried out for 42 hours. Here, when the reaction time is less than 40 hours, there is a problem that the reaction is not easily induced, and when it exceeds 60 hours, there is a problem in that the amount of by-products is increased.

The plasticizer according to an embodiment of the present invention has excellent compatibility with PLA resin, and excellent thermal stability through an acetylation reaction in which a hydroxy group at the end of the plasticizer is substituted with an acetyl group. In addition, mechanical properties are improved by making the elongation and tensile strength superior to those of commercial plasticizers through the acetylation reaction.

In addition, the acetylated lactide oligomer-based plasticizer has an advantage in that the elastic storage rate does not decrease compared to commercial plasticizers, so that the plasticizing performance is excellent.

According to another aspect of the present invention, the present invention provides a PLA resin composition comprising a polylactic acid (PLA) resin and any one plasticizer selected from acetylated lactide oligomer-based plasticizers represented by the following Chemical Formulas 1 to 3 do.

[Formula 1]

[Formula 2]

[Formula 3]

The PLA resin has excellent biodegradability and is a circulating resource material that has intermediate properties between a polyethylene terephthalate (PET) resin and a polyamide (PA) resin, and is a direct polycondensation of lactic acid. Or, it can be prepared by ring-opening polymerization (ROP) of lactide (lactide).

The lactic acid and lactide have L-, D-, and meso-type isomers, and the crystallinity, melting point, mechanical properties, etc. vary depending on the composition. In particular, the L-lactide polymer is crystalline compared to the amorphous D-form polymer and has excellent mechanical properties due to its crystallinity.

The PLA resin is applied in various fields as an environmentally friendly resin material, but it has the disadvantage of being easy to decompose when heated at high temperature for a long time. . Therefore, it is required to improve processability, flexibility, and durability by reducing intermolecular contact inside the resin through a plasticizer.

An ideal green plasticizer should be produced from renewable raw materials and should be biodegradable. In addition, like the existing plasticizer, compatibility with the resin must be high, and chemical stability and excellent dissolution resistance must be secured during processing.

Eco-friendly plasticizers such as vegetable oil-based eco-friendly plasticizers, succinic acid-based eco-friendly plasticizers, and isosorbide plasticizers have been studied so far, but compared to existing phthalate-based plasticizers, their physical properties are limited.

Accordingly, by producing a plasticizer through the ring-opening polymerization of D,L-lactide, compatibility between the plasticizer and PLA resin is excellent, and the thermal decomposition temperature is lowered through an acetylation reaction in which the hydroxyl group at the end of the plasticizer is replaced with an acetyl group. improved In addition, the mechanical properties were improved by making the elongation and tensile strength superior to those of commercial plasticizers through the acetylation reaction.

PLA resin composition comprising a plasticizer according to an embodiment of the present invention can be prepared by a method well known in the art, for example, added to a resin having a sufficiently high molecular weight through crosslinking or curing, or added to an oligomeric precursor After curing, the curing process may be performed.

The PLA resin composition according to an embodiment of the present invention may contain any one plasticizer selected from among the acetylated lactide oligomer-based plasticizers represented by Chemical Formulas 1 to 3 in the range of 25 to 70 phr with respect to the PLA resin composition. have. The acetylated lactide oligomer-based plasticizer according to the present invention can be appropriately increased or decreased depending on the use of the resin composition, but when added at less than 25 phr as described above, the flexibility or processability expressed by the plasticizer cannot be achieved. When added in excess of 70 phr, it is difficult to secure the necessary mechanical properties and there is a possibility of eluting, so the above range is preferable.

The PLA resin composition according to the present invention has excellent thermal stability and excellent physical properties of tensile strength, elongation, elastic modulus, and glass transition temperature compared to the conventional resin composition to which a commercial plasticizer is added.

Accordingly, in the case of manufacturing plastic using the PLA resin composition containing the plasticizer according to the present invention, it has excellent tensile strength and low glass transition temperature, so it is easy to form into a film and maintains flexibility even at low temperature to make a film or artificial leather. It can be processed into flexible products such as sheets. In addition, when the plasticizer according to the present invention is included, bleeding does not occur due to excellent compatibility with PLA resin, and since it has excellent thermal stability, the life of the film, sheet, etc. manufactured using the PLA resin can be extended. have.

Example

Hereinafter, examples will be given to describe the present invention in detail. However, the embodiment according to the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the embodiment described in detail below. The embodiments of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art.

<Example 1> Preparation of acetylated lactide oligomer-based plasticizer (LO-1Ac)

100 g (0.69 mol) of D,L-Lactide and 20.2 mL (0.35 mol) of ethanol as an initiator were added to the pressure vessel. As a catalyst, 0.09 mmol of Sn(Oct) ₂ was added, and ring-opening polymerization of lactide was performed at 110° C. for 4 hours without the use of a separate solvent to synthesize lactide oligomer (LO-1).

Acetic anhydride was added to the synthesized lactide oligomer (LO-1) and acetylated at 100° C. for 42 hours. The disappearance of the hydroxyl group was observed by NMR and the reaction was terminated. Upon completion of the reaction, the temperature was lowered to room temperature, and acetic acid and unreacted acetic anhydride were removed in a vacuum to obtain an acetylated lactide oligomer-based plasticizer (LO-1Ac).

<Example 2> Preparation of acetylated lactide oligomer-based plasticizer (LO-2Ac)

Lactide oligomer (LO-2) was synthesized by ring-opening polymerization of lactide in the same manner as in Example 1 using 32.9 mL (0.35 mol) of diethylene glycol (DEG) as an initiator.

The synthesized lactide oligomer (LO-2) was acetylated in the same manner as in Example 1 to obtain an acetylated lactide oligomer-based plasticizer (LO-2Ac).

<Example 3> Preparation of acetylated lactide oligomer-based plasticizer (LO-3Ac)

A lactide oligomer ( LO-3) was synthesized.

The synthesized lactide oligomer (LO-3) was acetylated in the same manner as in Example 1 to obtain an acetylated lactide oligomer-based plasticizer (LO-3Ac).

<Experimental Example 1> Structural analysis of acetylated lactide oligomer-based plasticizer

Acetylated lactide oligomer plasticizers (LO-1Ac, LO-2Ac, LO-3Ac) prepared in Examples 1 to 3 and lactide oligomer plasticizers before acetylation (LO-1, LO-2, LO-3) ) was compared and analyzed.

^{2 is a graph comparing 1} H-NMR before and after acetylation of the hydroxyl group terminal of the lactide oligomer according to Example 1 of the present invention, and FIG. 3 is a graph comparing the lactide oligomer according to Example 2 of the present invention. ^{It is a graph comparing 1} H-NMR before and after acetylation of the hydroxy group terminal ^{, and FIG. 4 is 1} H-NMR before and after acetylation of the hydroxy group terminal of the lactide oligomer according to Example 3 of the present invention. This is a comparison graph.

2 to 4 , as a ^{result of 1} H-NMR analysis, it was confirmed that two lactide monomers per initiator were ring-opening polymerization in the form of an oligomer (LO) through molecular weight calculation. Thereafter, it was confirmed that, during the acetylation reaction, the hydrogen peaks of the oligomer terminal and the hydroxyl group disappeared, and the methyl hydrogen peak of the terminal acetyl group was generated. All plasticizers exhibited molecular weights similar to the actual molecular weights and were synthesized with high conversion rates.

5 is a graph comparing MALDI-TOF-MS before and after acetylation of the hydroxyl group terminal of the lactide oligomer according to Example 1 of the present invention, and FIG. 6 is a lactide oligomer according to Example 2 of the present invention. A graph comparing MALDI-TOF-MS before and after acetylation of the hydroxyl terminal of - This is a graph comparing MS.

5 to 7 , in the measurement result of MALDI-TOF-MS, a 144 Da interval was confirmed from the main peak of the peak for the molar mass corresponding to the lactide unit, which is consistent with the molecular weight of the lactide monomer. could In addition, since lactide appeared as two 72 Da repeating units during ring-opening polymerization, an interval of 72 Da appeared on the graph. Through this, it was confirmed that the molecular weight increased as much as the change in the terminal through the acetylation reaction.

In addition, in order to calculate the molecular weight of the plasticizer, an equation such as (molecular weight of initiator) + (molecular weight of monomer) × (number of polymerized monomers) + (molecular weight of ions in the matrix used in the analysis) was used. Through this, the distribution of oligomers in which about 3 to 7 monomers were polymerized was confirmed.

<Experimental Example 2> Thermal properties of an acetylated lactide oligomer-based plasticizer

In general, since processing of the resin is performed at a high temperature, thermal stability of the plasticizer is important. Acetylated lactide oligomer-based plasticizers (LO-1Ac, LO-2Ac, LO-3Ac) prepared in Examples 1 to 3 and commercially available bis-2 (ethylhexyl) adipate (Bis (2-ethylhexyl) adipate; DOA) and acetyl tributyl citrate (ATBC) plasticizers were evaluated for thermal stability.

<2-1> Thermogravimetric analysis (TGA) measurement result

In order to measure the thermal decomposition temperature of the plasticizer, thermogravimetric analysis (TGA) was performed using TA's Q-5000. A sample of 10 to 30 mg was measured by raising the temperature to 25 to 600 °C in a nitrogen atmosphere at a rate of 10 °C/min.

8 is a graph comparing the analysis results of the plasticizers of Examples 1 to 3 and the DOA and ATBC plasticizers measured through thermogravimetric analysis (TGA).

Referring to FIG. 8 , it was confirmed that thermal decomposition of all plasticizers occurred by a single mechanism through the thermal decomposition curve of TGA. Both DOA and ATBC were decomposed at around 200 °C, and in the case of LO-Ac plasticizer, decomposition occurred even at 200 °C or higher. Also, in the case of the LO-Ac plasticizer, it was confirmed that the temperature at which thermal decomposition occurs increased as the number of branches increased in the course of LO-1Ac, LO-2Ac, and LO-3Ac.

<2-2> Glass transition temperature (Tg) measurement

The plasticizers of Examples 1 to 3, DOA, and ATBC plasticizers were measured by increasing the temperature to -80 to 200 °C in a nitrogen atmosphere at a rate of 10 °C/min using TA's Q-20.

9 is a graph comparing the evaluation results of thermal properties of the plasticizers of Examples 1 to 3 and the DOA and ATBC plasticizers measured through differential scanning calorimetry (DSC).

Referring to FIG. 9 , although the change in the glass transition temperature of the oligomer according to the acetylation reaction was not related to the structure of the initiator, it was confirmed that the plasticizer was in a liquid state of low viscosity through the low glass transition temperature.

<2-3> Measurement of 5 % Decomposition Temperature (T _{d,5 % )}

Examples 1 to 3, Comparative Examples 1 and 2 were measured by increasing the temperature of a sample of 10 to 30 mg using Q-20 of TA Corporation at a rate of 10 °C/min to 25 to 600 °C in a nitrogen atmosphere. .

Table 1 shows acetylated lactide oligomer plasticizers (LO-1Ac, LO-2Ac, LO-3Ac) and lactide oligomer plasticizers before acetylation (LO-1, LO-2, LO-3), DOA and ATBC This table summarizes the 5% weight loss temperature and glass transition temperature.

Referring to Table 1, the 5% weight loss temperature (T _{d,5 %} ) increased in the order of LO-1Ac < DOA <ATBC < LO-2AC < LO-3AC. Specifically, it was found that the 5% weight loss temperature of LO-2Ac and LO-3Ac was similar or higher than that of DOA at 205 °C and ATBC at 217 °C.

As a result, it can be seen that the LO-Ac plasticizer can be processed at a higher temperature than the conventional plasticizer. The reason for this result is that the hydroxy group at the end of the LO-Ac plasticizer was protected by an acetyl group, so that transesterification did not occur due to the back-bitting reaction of the lactide oligomer.

<Example 4> Preparation of PLA specimen containing acetylated lactide oligomer-based plasticizer (LO-1Ac)

First, the LO-1Ac plasticizer of Example 1 was added to PLA resin so that the content thereof was 10, 25, and 65 phr (part per hundred resin), respectively, and a 10% (w/v) solution was prepared with chloroform. The solution was stirred for at least one day until completely dissolved, then poured into a PFA (PerFluoroAlkoxy) watch glass and dried at room temperature for 72 h using a solvent-casting method at 70 °C in a vacuum oven for 24 h. After that, it was cut into small pieces, mixed using a micro compounder at 200 °C for 3 minutes, and then injected to prepare a PLA specimen.

<Example 5> Preparation of PLA specimen containing acetylated lactide oligomer-based plasticizer (LO-2Ac)

A PLA specimen was prepared in the same manner as in Example 4, except that the LO-2Ac plasticizer of Example 2 was added to the PLA resin so that the content thereof was 10, 25, and 65 phr, respectively.

<Example 6> Preparation of PLA specimen containing acetylated lactide oligomer-based plasticizer (LO-3Ac)

A PLA specimen was prepared in the same manner as in Example 4, except that the LO-3Ac plasticizer of Example 3 was added to the PLA resin so that the content thereof was 10, 25, and 65 phr, respectively.

<Comparative Example 1> Preparation of PLA specimen containing adipate-based plasticizer (DOA)

Except for adding a petroleum-based adipate-based plasticizer, Bis(2-ethylhexyl) adipate (DOA) plasticizer to PLA resin so that the content is 10, 25, and 65 phr, respectively A PLA specimen was prepared in the same manner as in Example 4.

<Comparative Example 2> Preparation of PLA specimen containing citric acid-based plasticizer (ATBC)

A PLA specimen was prepared in the same manner as in Example 4, except that acetyl tributyl citrate (ATBC) plasticizer, a citric acid-based plasticizer, was added to the PLA resin so that the content thereof was 10, 25, and 65 phr, respectively. prepared.

<Experimental Example 3> Evaluation of the plasticizing performance of an acetylated lactide oligomer-based plasticizer

<3-1> Measurement of tensile strength (MPa) and elongation (%)

Examples 4 to 6, by manufacturing a PLA specimen in the form of micro-tensile bars (ASTM D1708) and using a universal testing machine (UTM, Instron 5567) at room temperature using a 1000 N load cell at a speed of 10 mm/min. Tensile strength (σ _, Stress at break), and elongation ( ε , Strain at break) of the PLA film specimens of Comparative Examples 1 and 2 were measured.

10 is a graph comparing the stress-strain curves of the PLA specimens of Examples 4 to 6, Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when a plasticizer is added at 10 phr; 11 is a graph comparing the stress-strain curves of the PLA specimens of Examples 4 to 6, Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when the plasticizer was added at 25 phr; 12 is a graph comparing the stress-strain curves of the PLA specimens of Examples 4 to 6, Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when the plasticizer was added at 65 phr.

In general, the mechanical strength of a material due to the interaction between polymer chains can be determined through the tensile strength of the material. The yield point is the stress at the point where a large elongation occurs without an increase in stress in the stress-strain diagram, or the value obtained by dividing the maximum load at that time by the original cross-sectional area.

In addition, when the deformation force applied to an elastic object is called tensile strength ( σ ) and strain in the longitudinal direction is called ε , Young's modulus E is E=σ/ε . It means that it is a material and has great resilience.

Referring to FIGS. 10 to 12 , the PLA specimen containing no plasticizer exhibited high tensile strength (71.6 MPa) and no yield point was observed. This is because the polymer is easily broken by the cohesive force of the polymer chain. However, in the case of PLA specimens with added plasticizer, the yield point appeared as the ductility increased. This is because the interaction between the polymer chains in PLA is weakened through blending with the plasticizer and the PLA specimen, which reduces the tensile strength, increases the tensile elongation, and improves the flexibility and mobility of the polymer chains.

In Examples 4 to 6, Comparative Examples 1 and 2, when the plasticizer was added at a concentration of 10 phr, the amount was not sufficient and the fluidity between the polymer chains did not increase. When the DOA plasticizer of Comparative Example 1 was added, the compatibility with PLA was low, and cavitation and crazing occurred.

However, when the plasticizer was added at a concentration of 25 phr, the tensile elongation of the specimens mixed with the LO-Ac plasticizer of Examples 4 to 6 increased the most and the Young's modulus decreased the most, and the plasticizer of Comparative Example 1 showed superior performance. it was

<3-2> Storage modulus (G′), Tan delta (Tan δ) measurement

TA's Q-800 dynamic mechanical analyzer was used to measure the dynamic and mechanical properties of the softened PLA specimen. A rectangular-shaped specimen (20 mm × 5.3 mm × 1 mm) was heated from -100°C to 100°C at a rate of 3°C/min, and the storage moduli (G′) and tan delta (Tan δ) were measured obtained as a function of

Tanδ (tangent delta) refers to the ratio of the lost elastic modulus to the stored elastic modulus, and is used to measure the viscoelastic properties of polymers. In general, it is known that as the content of the plasticizer increases, the storage modulus decreases and the peak temperature of Tanδ decreases.

Through DMA analysis, the dynamic and mechanical properties and glass transition temperature values of the specimens were measured.

13 is a graph comparing the storage modulus (G ') of the PLA specimens of Examples 4 to 6, Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when 10 phr of a plasticizer is added, and FIG. 14 is a plasticizer is a graph comparing the storage modulus (G ') of the PLA specimens of Examples 4 to 6, Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when 25 phr is added, Figure 15 is a plasticizer at 65 phr It is a graph comparing the storage modulus (G') of the PLA specimens of Examples 4 to 6 and Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when added.

16 is a graph comparing the tan δ of the PLA specimens of Examples 4 to 6, Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when 10 phr of a plasticizer is added, and FIG. 17 is a plasticizer at 25 phr. When added, it is a graph comparing the tan δ of the PLA specimens of Examples 4 to 6, Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer, Figure 18 is Examples 4 to 6 when the plasticizer is added at 65 phr , It is a graph comparing the tan δ of the PLA specimens of Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer.

In addition, Figure 19 is a graph comparing the results of differential scanning calorimetry (DSC) analysis of the PLA specimens of Examples 4 to 6, Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when 10 phr of a plasticizer is added. , Figure 20 is a graph comparing the results of differential scanning calorimetry (DSC) analysis of the PLA specimens of Examples 4 to 6, Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when the plasticizer was added at 25 phr, 21 is a graph comparing the results of differential scanning calorimetry (DSC) analysis of the PLA specimens of Examples 4 to 6, Comparative Examples 1 and 2 and the PLA specimen without the addition of a plasticizer when the plasticizer was added at 65 phr.

13 to 21 , when the plasticizer was added at a concentration of 10 phr, the glass transition temperature, which is the temperature at which the physical properties transition from the glass phase to the rubber phase, did not decrease because the amount of the plasticizer was not sufficient. When added at a concentration of 25 phr, when the ATBC plasticizer of Comparative Example 2 was added, the storage modulus near room temperature began to decrease, and flow started at a temperature of 60° C. or higher. When the DOA plasticizer of Comparative Example 1 was used, the transition to the glass phase occurred near 40 ° C., and when the LO-Ac plasticizer of Examples 4 to 6 was used, the transition to the glass phase occurred near 30 ° C., and near 70 to 80 ° C. started to flow from

However, in the case of the specimen added at a concentration of 65 phr, the characteristics of the plasticizer were clearly shown. When the LO-Ac plasticizer of Examples 4 to 6 was used, while maintaining the storage modulus of PLA, the glass phase transition started near room temperature and flow started around 60 °C. On the other hand, when the DOA plasticizer of Comparative Example 1 was added and when the ATBC plasticizer of Comparative Example 2 was added, the storage modulus was not maintained and decreased. In particular, the shape of the Tanδ peak of the ATBC plasticizer of Comparative Example 2 was not wide. Another peak appeared in this wide and low temperature range.

In general, it is known that a single glass transition temperature appears when the compatibility of a polymer composite is excellent. Therefore, in the case of ATBC, since miscibility is limited, it is judged that the low glass transition temperature (Tg) in the area with a lot of plasticizer and the glass transition temperature (Tg) of the area with a lot of PLA resin are separated.

Through this, it was confirmed that the PLA resin composition according to the present invention has excellent thermal stability and excellent physical properties of tensile strength, elongation, modulus, and glass transition temperature compared to the conventional resin composition to which a commercial plasticizer is added.

When plastic is manufactured using the PLA resin composition containing the plasticizer according to the present invention, it has excellent tensile strength and low glass transition temperature, so it is easy to form into a film and maintains flexibility even at low temperatures to make a film or artificial leather sheet. There is an advantageous effect that it can be processed into flexible products such as In addition, when the plasticizer according to the present invention is included, bleeding does not occur due to excellent compatibility with PLA resin, and since it has excellent thermal stability, the life of the film, sheet, etc. manufactured using the PLA resin can be extended. have.

Up to now, specific examples of the acetylated lactide oligomer-based plasticizer, the method for preparing the same, and the PLA resin composition including the acetylated lactide oligomer-based plasticizer according to an embodiment of the present invention have been described, but the scope of the present invention It is obvious that various implementation modifications are possible within the limit not departing from the .

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the following claims as well as the claims and equivalents.

That is, it should be understood that the above-described embodiments are illustrative in all respects and not restrictive, and the scope of the present invention is indicated by the claims to be described later rather than the detailed description, and the meaning and scope of the claims; All changes or modifications derived from the concept of equivalents should be construed as being included in the scope of the present invention.

Claims (12)

(a) synthesizing a lactide oligomer by ring-opening polymerization (ROP) of an initiator and lactide;
(b) performing an acetylation reaction by adding acetic anhydride to the lactide oligomer; and
(c) removing acetic acid and unreacted acetic anhydride produced in step (b); including,
The initiator is characterized in that 1,1,1-tris (hydroxymethyl) propane or diethylene glycol,
A method for producing an acetylated lactide oligomer-based plasticizer.
delete According to claim 1,
Step (a) is a method for producing an acetylated lactide oligomer-based plasticizer, characterized in that it is carried out at 100 ~ 120 ℃ for 2 hours to 6 hours.
According to claim 1,
of step (a)
A method for producing an acetylated lactide oligomer-based plasticizer, characterized in that tin 2-ethylhexanoate (tin(II) 2-ethylhexanoate) is used as a catalyst for the ring-opening polymerization.
According to claim 1,
Step (b) is a method for producing an acetylated lactide oligomer-based plasticizer, characterized in that it is carried out at 80 to 120 ℃ for 40 to 60 hours.
An acetylated lactide oligomer-based plasticizer represented by any one of the following Chemical Formulas 2 to 3, which is prepared by acetylation reaction of a lactide oligomer synthesized by ring-opening polymerization (ROP) of an initiator and lactide:
[Formula 2]

[Formula 3]

7. The method of claim 6,
The initiator is an acetylated lactide oligomer-based plasticizer, characterized in that 1,1,1-tris(hydroxymethyl)propane or diethylene glycol.
7. The method of claim 6,
Acetylated lactide oligomer-based plasticizer, characterized in that tin 2-ethyl hexanoate (tin(II) 2-ethylhexanoate) is used as a catalyst for the ring-opening polymerization.
7. The method of claim 6,
The ring-opening polymerization reaction is an acetylated lactide oligomer-based plasticizer, characterized in that it is carried out at 100 ~ 120 ℃ for 2 hours to 6 hours.
7. The method of claim 6,
The acetylation reaction is an acetylated lactide oligomer-based plasticizer, characterized in that it is carried out at 80 ~ 120 ℃ for 40 to 60 hours.
PLA resin composition comprising a polylactic acid (PLA) resin and any one plasticizer selected from acetylated lactide oligomer-based plasticizers represented by the following Chemical Formulas 2 to 3:
[Formula 2]

[Formula 3]

12. The method of claim 11,
The plasticizer PLA resin composition, characterized in that included in the range of 25 to 70 phr with respect to the PLA resin composition.

Images