KR20090098350A - Pla/mwnt-g-pla including mwnt-g-pla and method for preparing the same - Google Patents

Abstract

A method for manufacturing the multi-walled carbon nanotube-g-poly(lactic acid), and the multi-walled carbon nanotube-g-poly(lactic acid) prepared by the method are provided to improve tensile modulus and tensile strength without using a solvent. A method for manufacturing the multi-walled carbon nanotube-g-poly(lactic acid) comprises the step of melt condensation polymerizing 0.1-50 wt% of multi-walled carbon nanotube-COOH and 50-99.9 wt% of lactic acid by using a catalyst. The multi-walled carbon nanotube-COOH has 1~5x10^22 carboxyl groups (-COOH) per 1 g of a multi-walled carbon nanotube. The multi-walled carbon nanotube-COOH is prepared by mixing a multi-walled carbon nanotube and a nitric acid/sulfuric acid (3M/1M) mixture solution.

Description

Polymer PLA / MWN-g-PLA containing MWNT-g-PLA and its manufacturing method {PLA / MWNT-g-PLA including MWNT-g-PLA and method for preparing the same}

The present invention relates to a polymer MWNT-g-PLA and a polymer PLA / MWNT-g-PLA including the same and a method of manufacturing the same. The invention also relates to articles made from the polymer PLA / MWNT-g-PLA.

At present, with high oil prices and environmental problems all over the world, interest in renewable and environmentally friendly polymer materials is rapidly increasing. Among the polymer materials having such useful properties as biodegradability, biocompatibility, reproducibility, environmental friendliness, PLA has received the greatest attention, but has a disadvantage in that the mechanical strength is weak. In order to make up for these drawbacks, efforts are being made to use carbon nanotubes (CNTs) with excellent mechanical strength, heat resistance, and electrical conductivity as reinforcing materials. Carbon nanotubes are a new material shaped like a tube formed by six carbons connected to each other and joined in a hexagonal honeycomb pattern to form a tube. The diameter of the tube is very small, with nanometers (nm = 1 billionth of a meter). Carbon nanotubes are available in two symmetrical structures known as zigzag and armchair. In practice, most carbon nanotubes have a symmetrical structure, but instead have a chiral structure in which honeycomb-shaped hexagons are arranged spirally along the tube axis. Carbon nanotubes are in a state where a graphite sheet is rounded to a nano size diameter and exhibits characteristics of a metal or a semiconductor depending on the angle and structure of the graphite sheet being dried. In addition, single-walled carbon nanotubes (SWNTs), double-walled carbon nanotubes (DWNTs), and multi-walled carbon nanotubes (MWNTs) Nanotube) and bundle carbon nanotubes (RNT).

The prior art using the carbon nanotubes are registered Patent No. 10-0773729 "Polyethylene terephthalate (PET) using the surface-treated carbon nanotubes (CNT) and its manufacturing method" and Patent Publication No. 10-2007-0071960 No. "Polymer nanocomposite containing carbon nanotubes and a method for producing the same". In Polymer 48 (2007) 3658-3663, released in 2007, Polymer-g-CNT was prepared by condensation of LA using a solvent (xylene) on the surface of CNT-COOH obtained by acid treatment of CNT. However, no research has been made on a method of preparing a melt condensation reaction without using a solvent.

An object of the present invention is to provide a method for producing a polymer MWNT-g-PLA without using a solvent, thereby producing a polymer MWNT-g-PLA by a melt condensation reaction than conventional methods for producing a solvent using a solvent. .

The present invention aims to improve the mechanical properties such as tensile modulus and tensile strength of the polymer PLA / MWNT-g-PLA prepared by mixing PLA homopolymer with the polymer MWNT-g-PLA.

In addition, it is an object of the film, fiber, plastic using the polymer PLA / MWNT-g-PLA to improve the mechanical properties such as tensile modulus and tensile strength than the film, fiber, plastic using the PLA alone polymer.

Method for producing a polymer MWNT-g-PLA according to the present invention for achieving the above object is melt condensation using 0.1 to 50 wt% MWNT-COOH and 50 to 99.9 wt% LA (catalyst) using a catalyst It is characterized by producing by polymerization.

Preferably, the MWNT-COOH is characterized in that it has 1 to 5 × 10 ²² carboxyl groups (-COOH) per 1 g of MWNT.

Preferably, the MWNT-COOH is produced by reacting MWNT with a nitric acid / sulfuric acid (3M / 1M) mixed solution.

Preferably, the LA is characterized by using L-lactic acid or D-lactic acid.

Preferably, the catalyst is tin (II) chloride, titanium (IV) butoxide, titanium (IV) isopropxide, titanium-2-ethyl (hexoxide), indium acetate, indium hyeroxide, antimony acetate, antimony trioxide, dibutyl tin oxide , stannous-2-ethyl-1-hexanoate is characterized by using a catalyst selected from.

Preferably, the melt condensation reaction is characterized in that the reaction temperature of 120 to 240 ℃.

Preferably, the melt condensation reaction is characterized in that the reaction pressure is 0.1 to 760 mmHg.

In addition, the method for producing a polymer PLA / MWNT-g-PLA according to the present invention is characterized in that the polymer MWNT-g-PLA prepared by the above method is prepared by melting or solution mixing the PLA-only polymer.

Preferably, the PLA homopolymer is characterized by using at least one monomer selected from the group consisting of L-lactic acid, D-lactic acid and combinations thereof.

Preferably, the melt mixing is characterized in that the temperature is 160 to 240 ℃.

Preferably, the solution mixture is characterized in that the temperature is 20 to 70 ℃.

More preferably, the solution mixture is characterized by using chloroform, toluene, tetrahydrofuran, methylene chloride or xylene as a solvent.

Preferably, the solution mixture is characterized in that water, methanol, ethanol, dimethyl ether or diethyl ether is used as the non-solvent.

In addition, the polymer MWNT-g-PLA according to the present invention is characterized in that it is prepared by the above method.

In addition, the polymer PLA / MWNT-g-PLA according to the present invention is characterized in that it is prepared by the above method.

In addition, the article according to the invention is characterized in that it is prepared from the polymer PLA / MWNT-g-PLA.

Preferably, the article is characterized in that the film, fiber, plastic.

As described above, the present invention provides a method of preparing the polymer MWNT-g-PLA without using a solvent, thereby making it easier to prepare the polymer MWNT-g-PLA than a conventional method using a solvent. It has an effect.

In another aspect, the present invention provides a method for producing a polymer PLA / MWNT-g-PLA, the prepared polymer PLA / MWNT-g-PLA has the effect of improving the mechanical properties such as tensile modulus and tensile strength than the PLA polymer alone .

In addition, the present invention has the effect of improving the mechanical properties such as tensile modulus and tensile strength than the film, fiber, plastic using the above-described polymer PLA / MWNT-g-PLA film, fiber, plastic using the PLA alone polymer.

Justice

The term MWNT, as used herein, refers to Multiwalled Carbon Nanotube. MWNT used herein is a CM-95 product of Iljin Nanotech.

As used herein, the term MWNT-COOH refers to a carboxyl group (-COOH) on the surface of the MWNT. The MWNT-COOH herein has 1 to 5 × 10 ²² carboxyl groups (—COOH) per gram of MWNT.

The term LA, as used herein, refers to a lactic acid monomer. In addition, PLA represents polylactide and refers to a polymer containing 50% or more of the above LA.

As used herein, the term MWNT-g-PLA is prepared by melt condensation polymerization of the MWNT-COOH and LA. G is an abbreviation of graft (meaning "union"), and means that PLA chain branch is formed on the surface of MWNT.

As used herein, the term PLA / MWNT-g-PLA refers to one prepared by melt mixing or solution mixing the MWNT-g-PLA and PLA homopolymer.

Preparation Example 1 (MWNT-g-PLA)

Pure MWNTs are added to a mixed solution of nitric acid / sulfuric acid (3M / 1M) and sonicated for 1 hour to form a suspension solution. The suspension solution is refluxed for 2 hours while maintaining 120 ℃ in the reflux apparatus. After reflux, the suspension solution is cooled to room temperature, precipitated in excess distilled water, and washed with water until pH reaches 7. Subsequently, vacuum drying at 80 ° C. through a filter process yields MWNT-COOH. In the MWNT-COOH, the carboxyl group (-COOH) may have 1 to 5 × 10 ²² per g of MWNT.

The MWNT-COOH was adjusted to 0.1 to 50 weight ratio (wt%), mixed with LA, dried in an oven at 150 ° C. for 12 hours to remove moisture, and added with catalyst tin (II) chloride (SnCl ₂ ) 120 To 240 ° C. for 1 hour in a vacuum (0.1 to 760 mmHG) to reduce the pressure and proceed with polymerization for 15 hours. MWNT-g-PLA may be obtained by dissolving the polymerized sample in chloroform, followed by precipitation and filtration (FIG. 1).

In addition, the catalyst tin (II) chloride) Instead of titanium (IV) butoxide, titanium (IV) isopropoxide, titanium-2-ethyl (hexoxide), indium acetate, indium hydroxide, antimony acetate, antimony trioxide, dibutyl tin oxide, stannous-2-ethyl-1-hexanoate Can be used.

Preparation Example 2 (PLA / MWNT-g-PLA)

(1) Manufacture by melt mixing

MWNT-g-PLA and PLA homopolymer prepared in Preparation Example 1 may be melt mixed at 160 to 240 ° C. using a kneader (mixer or extruder) to obtain PLA / MWNT-g-PLA.

PLA / MWNT and PLA / MWNT-COOH were prepared in the same manner as above for physical property comparison with PLA / MWNT-g-PLA. That is, PLA / MWNT was prepared by melt mixing MWNT and PLA homopolymer, and PLA / MWNT-COOH was prepared by melt mixing MWNT-COOH and PLA homopolymer.

(2) Preparation by Solution Mixing

MWNT-g-PLA prepared in Preparation Example 1 was adjusted to 0.1 to 50 weight ratio (wt%), dissolved in a solvent at 20 to 70 ° C., and subjected to ultrasonic treatment for 1 hour. Chloroform, toluene, tetrahydrofuran, methylene chloride and xylene can be used as the solvent. PLA alone polymer (high viscosity 1.01 dL / g, L-lactic acid 99 mol%) was added to the solution of MWNT-g-PLA dissolved for 6 hours, stirred in excess methanol, precipitated and filtered. PLA / MWNT-g-PLA can be obtained. Methanol described above was used as a non-solvent to obtain precipitation, but water, ethanol, dimethyl ether, diethyl ether and the like can be used instead of methanol.

PLA / MWNT and PLA / MWNT-COOH were prepared in the same manner as above for physical property comparison with PLA / MWNT-g-PLA. That is, PLA / MWNT was prepared by solution mixing MWNT and PLA homopolymer, and PLA / MWNT-COOH was prepared by melt mixing MWNT-COOH and PLA homopolymer.

Preparation Example 3 (Film)

PLA alone polymer, MWNT-COOH and MWNT-g-PLA prepared in Preparation Example 1, PLA / MWNT-g-PLA prepared in Preparation Example 2, PLA / MWNT, PLA / MWNT-COOH sufficiently vacuum-dried at 80 ℃ After compression to 0.2mm thickness using a heating press at 180 ℃ can be obtained in the form of a film.

Experimental Example 1 (Confirmation of Structure through Infrared Spectroscopy)

Infrared spectroscopy was carried out to confirm the structures of MWNT-COOH and MWNT-g-PLA prepared in Preparation Example 1 (FIG. 2).

-COOH (carboxyl group) shows inherent peaks around 1720 cm ^-1 . And, since the MWNT-COOH (b) of Figure 2 shows a 1720 cm ^-1 peak it can be confirmed that it has a carboxyl group.

-COO- (ester group) shows inherent peaks around 1755 cm ^-1 . In addition, since MWNT-g-PLA (c) of FIG. 2 shows a peak of 1750 cm ⁻¹ and PLA (d) shows a peak of 1755 cm ⁻¹ , MWNT-g-PLA (c) and PLA (d) show a peak of 1750 cm ⁻¹ . It can be confirmed that it has an ester group. When two or more LAs are bonded to the ester group, polymerization occurs as H ₂ O is released to form an ester bond.

Experimental Example 2 (Content Analysis of PLA Chain Branch through Thermogravimetric Analysis)

In the MWNT-g-PLA prepared in Preparation Example 1, a thermogravimetric experiment was conducted to determine what percentage of the total weight of PLA. The experiment was carried out using a TA Instruments SDT Q600 TGA at a temperature of 20 to 800 ℃ under nitrogen atmosphere conditions, the temperature increase rate was set to 20 ℃ / min.

Referring to the thermogravimetric decomposition curve of Figure 3, MWNT (a) and MWNT-COOH (b) is almost no weight loss even if the temperature is increased to 600 ℃. However, PLA (d) hardly remains at 600 ° C. Therefore, 68.54% of the residual amount of MWNT-g-PLA (c) at 600 ° C means that 31.46% of PLA was included.

Comparative Example 1 (Tensile Modulus and Tensile Strength of PLA / MWNT-g-PLA Film)

Figure 4 shows the tensile test results of the PLA alone polymer film (A) and PLA / MWNT-g-PLA film (b) prepared in various weight ratio (wt%).

In the tensile modulus, the PLA homopolymer film (A) was 1928 ± 156 MPa. In the case of PLA / MWNT-g-PLA film (B) to PLA / MWNT-g-PLA film (B) made of MWNT 1 wt% from PLA / MWNT-g-PLA film (B) made of 0.1 wt% Tensile elastic modulus increased with (E), but the tensile elastic modulus was kept constant in PLA / MWNT-g-PLA film (bar) made of 5 wt% MWNT. Compared with the PLA homopolymer film (a), it can be seen that the tensile modulus of the PLA / MWNT-g-PLA film (e) manufactured with 1 wt% of MWNT was increased by about 32%. 32% of the above is calculated from the formula (2541-1928) /1928×100=31.79%.

Looking at the tensile strength, PLA homopolymer film (A) was 49.3 MPa. In the case of PLA / MWNT-g-PLA film (B) to PLA / MWNT-g-PLA film (B) made of MWNT 1 wt% from PLA / MWNT-g-PLA film (B) made of 0.1 wt% Tensile strength was increased to (e), but the tensile strength was decreased in the PLA / MWNT-g-PLA film (bar) made of 5 wt% MWNT. Compared with the PLA homopolymer film (a), it can be seen that the tensile strength of the PLA / MWNT-g-PLA film (e) prepared with MWNT 1 wt% increased about 47%. 47% of the above is calculated from the formula (72.3-49.3) /49.3×100=46.65%.

Comparative Example 2 (Tensile Modulus and Tensile Strength of Various Types of Film)

Through Comparative Example 1, it was confirmed that the tensile modulus and tensile strength of PLA / MWNA-g-PLA film having MWNT of 1 wt% is the best. Therefore, when 1 wt% of MWNT was included, various kinds of films prepared through Preparation Example 3 were tested to determine whether the tensile strength was good.

Figure 5 shows the elongation-stress curve and tensile modulus of elasticity and tension of PLA homopolymer film (A), PLA / MWNT film (B), PLA / MWNT-COOH film (C), PLA / MWNA-g-PLA film (D) Strength is shown. Looking at the results shown in Figure 5, it can be seen that the PLA / MWNA-g-PLA film (D) is the best tensile strength. This is because MWNA-g-PLA has better dispersibility than MWNT or MWNT-COOH in PLA homopolymer, and the PLA chain on the surface of MWNA-g-PLA increases the interfacial bonding force with PLA homopolymer.

The polymer MWNT-g-PLA and the polymer PLA / MWNT-g-PLA prepared according to the method of the present invention have improved tensile modulus and tensile strength than the conventional PLA homopolymer as demonstrated by the results of the above experimental example. Therefore, it can be usefully applied in various fields such as film, fiber, plastic, etc. The present invention is not limited to these specific examples.

FIG. 1 is a view illustrating a manufacturing process of MWNT-g-PLA having PLA chain branch on MWNT surface by melt condensation polymerization of MWNT-COOH and LA (Lactic acid).

2 is a diagram showing an infrared spectroscopy spectrum of MWNT, MWNT-COOH, MWNT-g-PLA, PLA.

3 is a diagram showing a thermal decomposition curve of PLA, MWNT, MWNT-COOH, MWNT-g-PLA.

Figure 4 shows the tensile test results of the PLA alone polymer film (A) and PLA / MWNT-g-PLA film (b) prepared in various weight ratio (wt%).

Figure 5 shows the elongation-stress curve and tensile modulus of elasticity and tension of PLA homopolymer film (A), PLA / MWNT film (B), PLA / MWNT-COOH film (C), PLA / MWNA-g-PLA film (D) Strength is shown.

Claims (17)

A method of preparing a polymer MWNT-g-PLA by melt condensation polymerization of 0.1 to 50 wt% MWNT-COOH and 50 to 99.9 wt% LA (Lactic acid) using a catalyst. The method of claim 1, wherein the MWNT-COOH has 1 to 5 × 10 ²² carboxyl groups (—COOH) per gram of MWNT. The method of claim 1, wherein the MWNT-COOH is prepared by reacting MWNT with a nitric acid / sulfuric acid (3M / 1M) mixed solution. The method of claim 1, wherein the LA is a method for producing a polymer MWNT-g-PLA using L-lactic acid or D-lactic acid. The method of claim 1, wherein the catalyst is tin (II) chloride, titanium (IV) butoxide, titanium (IV) isopropxide, titanium-2-ethyl (hexoxide), indium acetate, indium hyeroxide, antimony acetate, antimony trioxide, dibutyl Method for preparing a polymer MWNT-g-PLA using a catalyst selected from tin oxide, stannous-2-ethyl-1-hexanoate. The method of claim 1, wherein the melt condensation reaction is a method for producing a polymer MWNT-g-PLA at a reaction temperature of 120 to 240 ℃. The method of claim 1, wherein the melt condensation reaction produces a polymer MWNT-g-PLA using a reaction pressure of 0.1 to 760 mmHg. A method for preparing a polymer PLA / MWNT-g-PLA by melt-mixing or solution-mixing PLA homopolymer to the polymer MWNT-g-PLA prepared by the method of claim 1. The method of claim 8, wherein the PLA homopolymer is a polymer PLA / MWNT-g-PLA using at least one monomer selected from the group consisting of L-lactic acid, D-lactic acid, and combinations thereof. The method of claim 8, wherein the melt mixing is a method for producing a polymer PLA / MWNT-g-PLA at a temperature of 160 to 240 ℃. The method of claim 8, wherein the solution mixture is a method for producing a polymer PLA / MWNT-g-PLA at a temperature of 20 to 70 ℃. The method of claim 11, wherein the solution mixture is a method for preparing the polymer PLA / MWNT-g-PLA using chloroform, toluene, tetrahydrofuran, methylene chloride or xylene as a solvent. 12. The method of claim 11, wherein the solution mixture is a non-solvent, wherein the polymer PLA / MWNT-g-PLA is prepared using water, methanol, ethanol, dimethyl ether or diethyl ether. Polymer MWNT-g-PLA prepared by the method of claim 1. Polymer PLA / MWNT-g-PLA prepared by the method of claim 8. An article made from the polymer PLA / MWNT-g-PLA of claim 15. 17. The article of claim 16, which is a film, fiber, plastic.

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