KR20140112200A - A Reforming Method of Poly Lactic Acid, A Bio Degradable Compounds for Foam Using therof and A Foam for Shoes Using therof - Google Patents

Abstract

The present invention relates to a modification method of poly lactic acid and a biodegradable foam compound using the same. The modification method comprises a step of polymerizing poly lactic acid into a molecule with double bonds and modifying the same. The biodegradable foam compound mixes the modified poly lactic acid with mixing materials and polymerizes the same.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for modifying polylactic acid, a biodegradable foam composition using the modified polylactic acid, and a foam for footwear using a biodegradable foam composition }

The present invention relates to a method for modifying polylactic acid, more particularly, to a method for modifying polylactic acid by modifying polylactic acid to prepare it as a biodegradable foam, a biodegradable foam composition using the modified polylactic acid, To a footwear foam using the same.

Polylactic acid (PLA), poly (lactic acid), and polylactic acid are the most biodegradable thermoplastic polyesters that have the potential to replace traditional petrochemical polymers. Possible polymer material.

Polylactic acid has the ability to rapidly decompose under certain composting conditions to reproduce carbon dioxide, providing a more disposable option for these resins than most other organic polymers. In addition, polylactic acid exhibits excellent thermal processing characteristics as compared with biopolymers such as polyethylene glycol, polycaprolactone, etc. in addition to the environmental compatibility, biocompatibility, and resource saving that are commonly found in biopolymers. Therefore, the use of polylactic acid as a general consumable material such as a suture material and a reinforcing material utilizing biocompatibility and bioabsorbability of polylactic acid as well as a packaging material utilizing biodegradability, processability, and transparency is expanding. These packaging areas include various rigid or semi-rigid articles such as 'clamshell' containers, prepared foods and other food serving trays and bottles or other containers.

However, the above-described conventional techniques have the following problems.

The polylactic acid material has problems such as a break point, a decomposition rate, and a hydrophobic point. In particular, polylactic acid has a high tensile strength and elastic modulus and low elongation so that it has poor impact resistance, which is an obstacle to various packaging materials and elastic materials. Also, the slow biodegradation characteristics have problems in application to various general consumer goods as well as medical materials. Therefore, various attempts have been made to improve the impact resistance as well as the decomposition speed.

It is an object of the present invention to solve the above-mentioned problems, and it is an object of the present invention to provide a method for modifying polylactic acid which has improved flexibility and biodegradability and can be used under various conditions, a biodegradable foam composition using a modified polylactic acid and a biodegradable foam composition To provide a foam for shoes.

In order to achieve the above object, the present invention is a method for modifying poly (Lactic Acid) according to the present invention, characterized in that poly (Lactic Acid) is modified by polymerization with a molecule having a double bond.

Then, the molecules having the double bond, an acrylate _{(Acrylate, CH 2 = CH-} CO-), methacrylate _{(Methacrylate, CH 2 = C (} CH 3) -CO-), vinyl (Vinyl, CH ₂ = CH-, or -CH = CH-), maleate (maleate, -CO-CH = CH -CO-), styrene _{(styrene, CH 2 = CH (} C 6 H 5)), allyl (allyl, CH ₂ = CH -O-) is contained in the molecule.

The polymerization reaction is characterized in that the reaction is carried out in a dry manner without using any other solvent during the reaction.

Further, an initiator is added to the polymerization reaction during the reaction to effect the reaction.

The initiator may be at least one selected from the group consisting of 2,2 azobis (2,4-dimethylvaleronitrile), 2,2-azobisisobutyronitrile, 2,2-azodi (2-methylbutyronitrile) Azobis (cyanocyclohexane), dimethyl-2,2-azobis (2-methylpropionate), 1 - ((cyano-1- methylethyl) azo) formamide, 2,5-bis 2,5-dimethyl-3-hexene, ditertbutyl peroxide, 2,5-bis (tertbutylperoxy) Bis (tertbutylperoxy) benzene, butyl 4,4-bis (tertbutylperoxy) valerate, 1,1-bis (tertbutylperoxy) 3,3,5-trimethylchlorohexane, , Lauryl peroxide, and dicumyl peroxide.

In another embodiment of the present invention, the biodegradable foam composition is characterized in that it comprises a modified polylactic acid and a mixed base material and is constituted by foam polymerization thereof.

The mixed base material is characterized by comprising at least one of an ethylene vinyl acetate copolymer, a styrene isoprene styrene copolymer, and an ethylene methacrylate copolymer.

And a crosslinking initiator and a foaming agent in the polymerization.

The crosslinking initiator may be at least one selected from the group consisting of 2,5-bis (tertbutylperoxy) -2,5-dimethyl-3-hexene, ditertbutylperoxide, 2,5- bis (tert- butylperoxy) Bis (tertbutylperoxy) benzene, butyl 4,4-bis (tertbutylperoxy) valerate, 1,1-bis (tertbutylperoxy) 3,3,5 -Trimethyl chlorohexane, tert-butyl peroxybenzoate, lauryl peroxide, and dicumyl peroxide.

The foaming agent is characterized by being composed of at least one of an azodicarbonamide blowing agent or a dinitrosopentamethylenetetraamine blowing agent.

A foam for footwear according to still another embodiment of the present invention is characterized by comprising a biodegradable foam composition.

The foamed product using the modified polylactic acid according to the present invention, the biodegradable foam composition using the modified polylactic acid and the biodegradable foam composition has the following effects.

It has lower tensile strength and elastic modulus than polylactic acid, shows higher softness, durability and flexibility, and has excellent biodegradability, so it can be used as a foam material for biodegradable shoe soles.

1 is a view showing a modification process of polylactic acid according to the present invention
2 is a graph showing the results of measurement of a nuclear magnetic resonance spectrometer of a composition obtained by blending polyethylene glycol acrylate with polylactic acid according to the present invention ((a) pure polylactic acid of Comparative Example 1, (b) modified polylactic acid of Example 2 )
3 is a graph showing the results of infrared spectroscopy (FT-IR) measurement of a composition obtained by blending polyethylene glycol acrylate with polylactic acid according to the present invention ((a) pure polylactic acid of Comparative Example 1, (b) Simple blend, (c) modified polylactic acid of Example 2)
4 is a graph showing the result of solvent extraction of a composition obtained by blending poly (ethylene glycol) acrylate with polylactic acid according to the present invention ((a) pure polylactic acid of Comparative Example 1, (b) modified polylactic acid of Example 1 (D) modified polylactic acid of Example 2, (e) simple blend of Comparative Example 2)
Fig. 5 is a graph showing the result of DSC thermogram measurement of a composition obtained by blending polyethylene glycol acrylate with polylactic acid according to the present invention ((a) pure polylactic acid of Comparative Example 1, (b) (C) the modified polylactic acid of Example 2, (d) the modified polylactic acid of Example 3, and (e) the modified polylactic acid of Example 4)
6 is a graph showing the results of biodegradability measurement of a composition blended with polylactic acid and polyethylene glycol acrylate according to the present invention ((a) pure polylactic acid of Comparative Example 1, (b) modified polylactic acid of Example 1 c) the modified polylactic acid of Example 2, (d) the modified polylactic acid of Example 3, and (e) the modified polylactic acid of Example 4)
7 is a view showing molecules of another embodiment for modification of polylactic acid according to the present invention

Hereinafter, preferred embodiments of the method for modifying polylactic acid and the biodegradable foam composition using the modified polylactic acid according to the present invention will be described in detail with reference to the accompanying drawings.

The constitution of the method for modifying polylactic acid according to the present invention is such that the polylactic acid is modified by polymerization with a molecule having a double bond.

First, Poly Lactic Acid is a polyester synthesized by polycondensation of lactic acid or by ring-opening polymerization of lactide, and is a polyester intermediate between polyamide and polyethylene terephthalate (PET) And has a high biodegradability due to a natural vegetable sugar component derived from potato and corn as a raw material, but generally has high hardness, low elasticity, and low durability.

Depending on the steric structure of the monomers used in the synthesis, the polymers can be synthesized in the form of poly-L-lactic acid, poly-D-lactic acid and poly-DL-lactic acid. Among them, poly-L-lactic acid (PLLA) synthesized by using pure L-lactic acid or L-lactide has crystallinity and is called crystalline polylactic acid, and D-lactic acid or D- The produced poly-DL-lactic acid is produced as amorphous polylactic acid (PDLA).

When the polylactic acid is heated in the state that the monomer containing a double bond and a thermal initiator are contained, as shown in FIG. 1, the initiator is thermally decomposed to form a radical, and the radical is bonded to the methyl group of the polylactic acid Hydrogen is taken away to form radicals on the polylactic acid chain.

A radical polymerization reaction is caused by a monomer having a double bond in the radical of the polylactic acid phase to produce a modified polylactic acid in which a branched chain of a monomer is formed on the polylactic acid chain.

In this case, when the amount of the introduced double bond molecules is changed, the physical properties of the modified polylactic acid can be controlled and the reaction temperature and reaction rate can be controlled according to the type and amount of the initiator. In the polymerization reaction, other solvents are not used during the reaction, so that the reaction is carried out in a dry state.

Due to the branches of the double bond molecules, the polylactic acids have lower tensile strength, lower elasticity and elongation as shown in Fig.

The molecules having the double bond may be any material capable of causing grafting coplolymerization to the polylactic acid. For example, acrylate (CH ₂ = CH-CO- ), methacrylate _{(methacrylate, CH 2 = C (} CH 3) -CO-), vinyl (vinyl, CH ₂ = CH- or -CH = CH-), maleate (maleate, -CO-CH = CH- CO-), styrene (CH ₂ ═CH (C ₆ H ₅ )), allyl (Allyl, CH ₂ ═CH-O-), and the like.

Further, the polymerization initiator may be further added to the reaction system. Wherein the initiator is an azo group (-N = N-), azo-based compound, peroxide groups (-OO-) an organic peroxide, hydroperoxide (-COOH) comprising a persulfate-based (S ₂ O ₈ ^-2, including ), And an organometallic compound, and specifically, azo compounds such as 2,2 azobis (2,4-dimethylvaleronitrile), 2,2-azobisisobutyronitrile, 2,2-azodi (2-methylbutyronitrile 1-azobis (cyanocyclohexane), dimethyl-2,2-azobis (2-methylpropionate), 1 - ((cyano-1-methylethyl) azo) formamide, 2,5-bis (tert-butylperoxy) -2,5-dimethyl-3-hexene, ditertbutyl peroxide, 2,5-bis Bis (tert-butylperoxy) benzene, butyl 4,4-bis (tertbutylperoxy) valerate, 1,1-bis (tert- butylperoxy) 3,3,5-trimethylchlorohexane, Tert-butyl peroxybenzoate, lauryl peroxide, dicumyl peroxide, DE peroxide, potassium persulfate, are ethyl, propyl, the butyl may be characterized in that the use of one or more of the.

More specifically, in the present invention, experiments using polyethylene glycol acrylate (PEGA) containing an acrylate as shown in Table 1 will be described in detail.

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Example 3 Example 4 Example 5 PLLA ¹⁾ 100 80 90 90 80 70 60 PDLA ²⁾ 80 PEGA ³⁾ 20 10 10 20 30 40 20 DCP ⁴⁾ 0.8 0.8 0.8 0.8 0.8

1) poly (L-lactic acid) 2) poly (D, L-lactic acid) 3) polyethyleneglycol acrylate 4) dicumyl peroxide

[Comparative Example 1]

In order to confirm the change in physical properties of the polylactic acid, Comparative Example 1 was prepared by thermocompression bonding 100 parts by weight of pure crystalline polylactic acid (PLLA, Natureworks, 4032D) at 180 占 폚 using a hot press to obtain a sheet of 0.1 to 2 mm.

[Comparative Example 2]

In Comparative Example 2, 80 parts by weight of crystalline polylactic acid (PLLA) was heated to 180 DEG C in a kneader as a compound kneader, 20 parts by weight of polyethylene glycol acrylate (PEGA) was added and kneaded for 5 minutes to obtain a simple blending compound . The compound thus prepared was hot-pressed at 180 DEG C using a hot press to prepare a sheet having a thickness of 0.1 to 2 mm.

[Comparative Example 3]

In Comparative Example 3, 90 parts by weight of crystalline polylactic acid (PLLA) was heated to 180 ° in a kneader as a compound kneader, 10 parts by weight of polyethylene glycol acrylate (PEGA) was added and kneaded for 5 minutes to prepare a simple blending compound Respectively. The compound thus prepared was hot-pressed at 180 ° C. using a hot press to obtain a sheet having a thickness of 0.1 to 2 mm.

[Example 1]

In Example 1, 90 parts by weight of crystalline polylactic acid (PLLA) was heated and melted at 180 DEG C in a kneader as a compound kneader, and 10 parts by weight of polyethylene glycol acrylate (PEGA) was added and kneaded for 5 minutes. Thereafter, 0.8 part by weight of dicumylperoxide (DCP) as an initiator was further added thereto, followed by reactive blending at 180 DEG C for 10 minutes to prepare a modified polylactic acid. The compound thus prepared was hot-pressed at 180 DEG C using a hot press to prepare a sheet having a thickness of 0.1 to 2 mm.

[Example 2]

In Example 2, 80 parts by weight of crystalline polylactic acid (PLLA) is heated and melted at 180 DEG C in a kneeder as a compound kneader, 20 parts by weight of polyethylene glycol acrylate (PEGA) is added, and the mixture is kneaded for 5 minutes. Thereafter, 0.8 part by weight of dicumylperoxide (DCP) as an initiator was further added thereto, followed by reactive blending at 180 DEG C for 10 minutes to prepare a modified polylactic acid. The compound thus prepared was hot-pressed at 180 DEG C using a hot press to prepare a sheet having a thickness of 0.1 to 2 mm.

[Example 3]

In Example 3, 70 parts by weight of crystalline polylactic acid (PLLA) was heated and melted at 180 DEG C in a kneader as a compound kneader, and 30 parts by weight of polyethylene glycol acrylate (PEGA) was added and kneaded for 5 minutes. Thereafter, 0.8 part by weight of dicumylperoxide (DCP) as an initiator was further added thereto, followed by reactive blending at 180 DEG C for 10 minutes to prepare a modified polylactic acid. The compound thus prepared was hot-pressed at 180 DEG C using a hot press to prepare a sheet having a thickness of 0.1 to 2 mm.

[Example 4]

In Example 4, 60 parts by weight of crystalline polylactic acid (PLLA) is heated and melted at 180 DEG C in a kneader as a compound kneader, and then 40 parts by weight of polyethylene glycol acrylate (PEGA) is added and kneaded for 5 minutes. Thereafter, 0.8 part by weight of dicumylperoxide (DCP) as an initiator was further added thereto, followed by reactive blending at 180 DEG C for 10 minutes to prepare a modified polylactic acid. The compound thus prepared was hot-pressed at 180 DEG C using a hot press to prepare a sheet having a thickness of 0.1 to 2 mm.

[Example 5]

In Example 5, 80 parts by weight of amorphous polylactic acid (PDLA) was heated and melted at 180 in a compound kneader kneader, and then 40 parts by weight of polyethylene glycol acrylate (PEGA) was added thereto, followed by kneading for 5 minutes. Then, 0.8 part by weight of dicumylperoxide (DCP) as an initiator was further added thereto, followed by reactive blending at 180 for 10 minutes to prepare a modified polylactic acid. The compound thus prepared was hot-pressed at 180 ° C. using a hot press to obtain a sheet having a thickness of 0.1 to 2 mm.

Comparative Example 1 to Comparative Example 3 and Examples 1 to 5 as described above were subjected to structural analysis, solvent extraction, thermodynamic analysis, tensile characterization and biodegradation characteristics analysis, respectively.

1. Structural Analysis

Structural analysis was carried out to determine whether polylactic acid (PLA) was modified with polyethylene glycol acrylate (PEGA) using nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FTIR) for structure analysis of modified polylactic acid And the results as shown in FIG. 2 and FIG. 3 were obtained.

As shown in Fig. 2, a peak due to the methylene structure of polyethylene glycol acrylate (PEGA) was newly generated at about 3.6 ppm in the case of the polylactic acid (B) modified by the reactive blend of polylactic acid (a) (PLA) reactive blend was modified with acrylate after the blend.

Further, as shown in FIG. 3, the peak appeared newly at 2900 cm ^-1 in the case of (a) polylactic acid (PLA), (b) polylactic acid (PLA) / polyethylene glycol acrylate (PEGA) simple blend, And the C = C double bond peak found at around 1640 cm ^-1 of the simple blend (b) disappears in the reactive blend (c), so that the double bond of the acrylate monomer is polymerized by the reaction of the polymer .

2. Solvent Extraction

Solvent extraction can be carried out by simply blending polylactic acid (PLA), modified polylactic acid (PLEA), and polylactic acid (PLA) / polyethylene glycol acrylate (PEGA) with a methanol solvent using a soxhlet method PLA). ≪ / RTI >

In the case of the polylactic acid modified with reactive blends of polylactic acid (PLA) and polyethylene glycol acrylate (PEGA) (Example 1, Example 2) as shown in Figure 4, its simple blend (Comparative Example 3, It can be seen that, compared to Example 2, the amount of dissolved and extracted by the solvent is considerably small, and therefore, the modification is effectively carried out.

3. Thermal Characterization

Thermal properties of the modified polylactic acid (PLEA) were analyzed by DSC (Differential Scanning Calorimetry) at 0 ℃ to 200 ℃ and the glass transition temperature was measured.

As shown in FIG. 5, in the case of glass transition temperature, as the amount of added polyethylene glycol acrylate (PEGA) increases, the glass transition temperature is lowered. In the case of polylactic acid (PLEA) modified with respect to pure polylactic acid But it is not a distinction. This result shows that the acrylate grafted to the polylactic acid (PLA) weakens the rigidity of the polylactic acid (PLA) chain so that the modified polylactic acid has a soft physical property at room temperature.

4. Tensile Characteristic Analysis

The tensile strength, elastic modulus and elongation of the modified polylactic acid were measured using a universal testing machine (UTM).

Evaluation items unit Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Example 5 The tensile strength MPa 51 49 37 28 14 35 Modulus of elasticity MPa 1290 1070 880 690 440 760 Elongation % 4.6 6.1 9.5 10.8 17.8 11.3

As shown in Table 2, the modified polylactic acid showed a smaller tensile strength and elastic modulus than the pure polylactic acid, and the elongation was increased. As the amount of added polyethylene glycol acrylate increased, . From these results, it can be seen that the modified polylactic acid has soft and flexible properties as compared with pure polylactic acid.

5. Analysis of biodegradation characteristics

Biodegradation characteristics were measured by immersing modified polylactic acid (PLEA) having a thickness of 0.1 mm and a size of 2 * 2 cm in a NaHCO ₃ / NaOH buffer solution having a pH of 10.7.

As shown in FIG. 5, the biodegradability of the polylactic acid (PLEA) modified in the aqueous solution of pH 10.7 was found to be superior to that of the pure polylactic acid (PLA), and the addition of the added polyethylene glycol acrylate PEGA), the more biodegradation occurs.

A method for producing a biodegradable foam composition using the modified polylactic acid according to the present invention will now be described.

As shown in Table 3, the biodegradable foam composition may be composed of polylactic acid (PLA), modified polylactic acid (PLEA), mixed base, crosslinking initiator, and blowing agent.

The modified polylactic acid may be a modified crystalline polylactic acid (PLLEA) or a modified amorphous polylactic acid (PDLEA).

The mixed base material may be an ethylene-vinyl acetate copolymer (EVA), a styrene-isoprene styrene copolymer (SIS), or an ethylene-methacrylate copolymer (EMA) Can be used, and is a resin widely used as a foam because of its excellent compression strain, shock absorption rate, mechanical strength and the like.

As the crosslinking initiator, an organic peroxide crosslinking initiator may be used. 2,5-bis (tertbutylperoxy) -2,5-dimethyl-3-hexene, ditertbutyl peroxide, 2,5-bis (tert- butylperoxy) Hexane, dibenzoyl peroxide, bis (tertbutylperoxyisopropyl) benzene, butyl 4,4-bis (tertbutylperoxy) valerate, 1,1-bis (tert- butylperoxy) Trimethyl chlorohexane, tert-butyl peroxybenzoate, lauryl peroxide, and dicumyl peroxide.

The blowing agent may be used alone or in combination with an azodicarbonamide blowing agent or a dinitrosopentamethylenetetraamine blowing agent. For example, the JTR series of Kumyang Chemical may be used.

With reference to Table 3 below, Comparative Example 4 and Examples 6 to 11 will be described in detail by comparing their characteristics in different compositions.

division Comparative Example 4 Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 PLLA ¹⁾ 30 PLLEA20 ²⁾ 10 20 30 50 70 PDLEA20 ³⁾ 30 EVA ⁴⁾ 70 90 80 70 50 30 70 Crosslinking initiator ⁵⁾ 0.7 0.7 0.7 0.7 0.7 0.7 0.7 Blowing agent ⁶⁾ 4.5 4.5 4.5 4.5 4.5 4.5 4.5

1) poly (L-lactic acid), 2) modified crystalline polylactic acid prepared from Example 2, 3) modified amorphous polylactic acid prepared from Example 5, 4) ethylene-vinyl acetate (EVA1328) , 5) DCP, dicumylperoxide, 6) DOP, dioctylphthalate, 7) JTR,

[Comparative Example 4]

In Comparative Example 4, 30 parts by weight of crystalline polylactic acid (PLLA) and 70 parts by weight of ethylene vinyl acetate (EVA) were kneaded at 180 DEG C for 5 minutes using a compound kneader kneader to prepare a compound. Then, 0.7 part by weight of a crosslinking initiator and 4.5 parts by weight of a foaming agent were added to 100 parts by weight of the compound on a roll mill, and uniformly mixed to prepare a 4 mm sheet-like compound. Then, the sheet compound was put into a mold and molded under press conditions of 170 DEG C and 150 kg / cm < ² > for about 20 minutes to prepare a foam.

[Example 6]

In Example 6, 10 parts by weight of modified crystalline polylactic acid (PLLEA20) and 90 parts by weight of ethylene vinyl acetate (EVA) were kneaded at 180 degrees for 5 minutes using a kneader as a compound kneader to prepare a compound. Then, 0.7 part by weight of a crosslinking initiator and 4.5 parts by weight of a foaming agent were added to 100 parts by weight of the compound on a roll mill, and uniformly mixed to prepare a 4 mm sheet-like compound. Then, the sheet compound was put into a mold and molded under press conditions of 170 DEG C and 150 kg / cm < ² > for about 20 minutes to prepare a foam.

[Example 7]

In Example 7, 20 parts by weight of modified crystalline polylactic acid (PLLEA20) and 80 parts by weight of ethylene vinyl acetate (EVA) were kneaded at 180 DEG C for 5 minutes using a kneader as a compound kneader to prepare a compound. Then, 0.7 part by weight of a crosslinking initiator and 4.5 parts by weight of a foaming agent were added to 100 parts by weight of the compound on a roll mill, and uniformly mixed to prepare a 4 mm sheet-like compound. Then, the sheet compound was put into a mold and molded under press conditions of 170 DEG C and 150 kg / cm < ² > for about 20 minutes to prepare a foam.

[Example 8]

In Example 8, 30 parts by weight of modified crystalline polylactic acid (PLLEA20) and 70 parts by weight of ethylene vinyl acetate (EVA) were kneaded at 180 degrees for 5 minutes using a kneader as a compound kneader to prepare a compound. Then, 0.7 part by weight of a crosslinking initiator and 4.5 parts by weight of a foaming agent were added to 100 parts by weight of the compound on a roll mill, and uniformly mixed to prepare a 4 mm sheet-like compound. Then, the sheet compound was put into a mold and molded under press conditions of 170 DEG C and 150 kg / cm < ² > for about 20 minutes to prepare a foam.

[Example 9]

In Example 9, 50 parts by weight of modified crystalline polylactic acid (PLLEA20) and 50 parts by weight of ethylene vinyl acetate (EVA) were kneaded at 180 degrees for 5 minutes using a compound kneader kneader to prepare a compound. Then, 0.7 part by weight of a crosslinking initiator and 4.5 parts by weight of a foaming agent were added to 100 parts by weight of the compound on a roll mill, and uniformly mixed to prepare a 4 mm sheet-like compound. Then, the sheet compound was put into a mold and molded under press conditions of 170 DEG C and 150 kg / cm < ² > for about 20 minutes to prepare a foam.

[Example 10]

In Example 10, 70 parts by weight of modified crystalline polylactic acid (PLLEA20) and 30 parts by weight of ethylene vinyl acetate (EVA) were kneaded at 180 DEG C for 5 minutes using a kneader as a compound kneader to prepare a compound. Then, 0.7 part by weight of a crosslinking initiator and 4.5 parts by weight of a foaming agent were added to 100 parts by weight of the compound on a roll mill, and uniformly mixed to prepare a 4 mm sheet-like compound. Then, the sheet compound was put into a mold and molded under press conditions of 170 DEG C and 150 kg / cm < ² > for about 20 minutes to prepare a foam.

[Example 11]

In Example 11, 30 parts by weight of modified amorphous polylactic acid (PDLEA20) and 70 parts by weight of ethylene vinyl acetate (EVA) were kneaded at 180 degrees for 5 minutes using a kneader as a compound kneader to prepare a compound. Then, 0.7 part by weight of a crosslinking initiator and 4.5 parts by weight of a foaming agent were added to 100 parts by weight of the compound on a roll mill, and uniformly mixed to prepare a 4 mm sheet-like compound. Then, the sheet compound was put into a mold and molded under press conditions of 170 DEG C and 150 kg / cm < ² > for about 20 minutes to prepare a foam.

Evaluation items unit Comparative Example 4 Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 importance g / cm ³ 0.21 0.20 0.20 0.21 0.21 0.22 0.20 The tensile strength kg / cm ² 18 19 24 24 23 20 24 Elongation % 380 470 450 440 420 380 460 Phosphorus strength kg / cm 9.3 8.7 11.7 14.2 12.6 9.4 13.8 Elasticity % 36 38 38 38 37 37 38

As shown in Table 4, in Examples 6 to 11, as compared with Comparative Example 4, the tensile strength was increased, the elongation was increased, and the elasticity was also large. That is, since the modified polylactic acid exhibits soft physical properties, it is excellent in durability and flexibility and is modified to be used as a foam material.

In another embodiment of the present invention, a method for producing a biodegradable foam composition using polylactic acid (PLVA, PLEM, PLAU) modified with other double bond components will be described.

division Example 12 Example 13 Example 14 PLVA20 ¹⁾ 30 PLEM20 ²⁾ 30 PLVU2 ⁰³⁾ 30 EVA ⁴⁾ 70 70 70 Crosslinking initiator ⁵⁾ 0.7 0.7 0.7 Blowing agent ⁶⁾ 4.5 4.5 4.5

1) crystalline polylactic acid modified with vinyl acetate, 2) crystalline polylactic acid modified with polyethylene glycol maleate, 3) polylactic acid modified with allyl polyurethane, 4) ethylene-vinyl acetate (Hanwha Chemical, EVA1328) ) DCP, dicumylperoxide, 6) DOP, dioctylphthalate, JTR,

(PLVA, PLEM, PLAU), a mixed substrate, a crosslinking initiator and a foaming agent, as shown in Table 5.

The constitution of the method for modifying polylactic acid according to the present invention is such that the polylactic acid is polymerized with vinyl acetate, polyethylene glycol maleate or allyl polyurethane, .

Was prepared in the same manner as in Example 2, except that vinyl acetate, polyethylene glycol maleate or allyl polyurethane was used instead of the polyethylene glycol acrylate used in Example 2 for the polylactic acid modification.

[Example 12]

In Example 12, 30 parts by weight of crystalline polylactic acid (PLVA20) modified with vinyl acetate and 70 parts by weight of ethylene vinyl acetate (EVA) were kneaded at 180 DEG C for 5 minutes using a kneader as a compound kneader to prepare a compound . Then, 0.7 part by weight of a crosslinking initiator and 4.5 parts by weight of a foaming agent were added to 100 parts by weight of the compound on a roll mill, and uniformly mixed to prepare a 4 mm sheet-like compound. Then, the sheet compound was put into a mold and molded under press conditions of 170 DEG C and 150 kg / cm < ² > for about 20 minutes to prepare a foam.

[Example 13]

In Example 13, 30 parts by weight of crystalline polylactic acid (PLEM20) modified with polyethylene glycol maleate and 70 parts by weight of ethylene vinyl acetate (EVA) were kneaded at 180 DEG C for 5 minutes using a compound kneader, . Then, 0.7 part by weight of a crosslinking initiator and 4.5 parts by weight of a foaming agent were added to 100 parts by weight of the compound on a roll mill, and uniformly mixed to prepare a 4 mm sheet-like compound. Then, the sheet compound was put into a mold and molded under press conditions of 170 DEG C and 150 kg / cm < ² > for about 20 minutes to prepare a foam.

[Example 14]

In Example 14, 30 parts by weight of crystalline polylactic acid (PLAU20) modified with allyl polyurethane and 70 parts by weight of ethylene vinyl acetate (EVA) were kneaded at 180 DEG C for 5 minutes using a kneader as a compound kneader to prepare a compound Respectively. Then, 0.7 part by weight of a crosslinking initiator and 4.5 parts by weight of a foaming agent were added to 100 parts by weight of the compound on a roll mill, and uniformly mixed to prepare a 4 mm sheet-like compound. Then, the sheet compound was put into a mold and molded under press conditions of 170 DEG C and 150 kg / cm < ² > for about 20 minutes to prepare a foam.

With reference to Table 6 below, the characteristics of Example 12, Example 13, and Example 14 will be described in detail with different compositions.

Evaluation items unit Comparative Example 12 Example 13 Example 14 importance g / cm ³ 0.22 0.20 0.20 The tensile strength kg / cm ² 26 22 23 Elongation % 420 460 450 Phosphorus strength kg / cm 15.3 13.2 13.6 Elasticity % 39 35 38

As shown in Table 6, the tensile strength, elongation, and elasticity of Examples 12 to 14 are larger than those of Comparative Example 4. That is, it was found that the modified polylactic acid (PLVA20, PLEM20, PLAU20) exhibited soft physical properties and was thus modified to be used as a foam material because of its excellent durability and flexibility.

Further, a plasticizer may be further added during the reaction for producing the biodegradable foam composition. The plasticizer is a hydroxycarboxylic acid ester plasticizer which is used as a plasticizer in tributyl o-acetylcitrate, triethyl oacetylcitrate, tributyl citrate, Or may be used in combination.

It is to be understood that the invention is not limited to the disclosed embodiment, but is capable of many modifications and variations within the scope of the appended claims. It is self-evident.

Claims (11)

A method for modifying a polylactic acid characterized by polymerizing polylactic acid with a molecule having a double bond to modify the polylactic acid. The method according to claim 1,
Molecules having the double bond, an acrylate _{(Acrylate, CH 2 = CH-} CO-), methacrylate _{(Methacrylate, CH 2 = C (} CH 3) -CO-), vinyl (Vinyl, CH ₂ = CH- or -CH = CH-), maleate (maleate, -CO-CH = CH -CO-), styrene _{(styrene, CH 2 = CH (} C 6 H 5)), allyl _{(allyl, CH 2 = CH-} O -). ≪ / RTI > The method according to claim 1,
In the polymerization reaction,
Wherein the reaction is carried out in a dry state. The method according to claim 1,
Wherein the polylactic acid is reacted by further adding an initiator in the polymerization. 5. The method of claim 4,
The initiator,
Azobis (2,4-dimethylvaleronitrile), 2,2-azobisisobutyronitrile, 2,2-azodi (2-methylbutyronitrile), 1,1-azobis (Cyclohexane), dimethyl-2,2-azobis (2-methylpropionate), 1 - ((cyano-1- methylethyl) azo) formamide, 2,5- ) -2,5-dimethyl-3-hexene, ditertbutylperoxide, 2,5-bis (tertbutylperoxy) -2,5-dimethylhexene, dibenzoylperoxide, bis Propyl) benzene, butyl 4,4-bis (tertbutylperoxy) valerate, 1,1-bis (tertbutylperoxy) 3,3,5-trimethylchlorohexane, Wherein the polylactic acid is used as at least one of an oxide, an oxide, and a dicumyl peroxide. A biodegradable foam composition comprising the modified polylactic acid of claim 1 and a mixed substrate, wherein the biodegradable foam composition comprises the foam polymerization. The method according to claim 6,
In the mixed substrate,
Ethylene vinyl acetate copolymer, styrene isoprene styrene copolymer, or ethylene methacrylate copolymer. The biodegradable foam composition according to claim 1, The method according to claim 6,
Wherein the crosslinking initiator and the foaming agent are added to the biodegradable foam composition. 9. The method of claim 8,
The cross-
2,5-bis (tert-butylperoxy) -2,5-dimethyl-3-hexene, ditertbutyl peroxide, 2,5-bis Bis (tert-butylperoxy) benzene, butyl 4,4-bis (tertbutylperoxy) valerate, 1,1-bis (tert- butylperoxy) 3,3,5-trimethylchlorohexane, Butyl peroxybenzoate, lauryl peroxide, and dicumyl peroxide. ≪ RTI ID = 0.0 > 21. < / RTI > 9. The method of claim 8,
The blowing agent may contain,
An azodicarbonamide blowing agent or a dinitrosopentamethylenetetraamine blowing agent. The biodegradable foam composition according to claim 1, A foam for footwear comprising the biodegradable foam composition of claim 6.

Images