CN118103450A - Biodegradable composition and biodegradable film - Google Patents

Abstract

The present invention provides biodegradable compositions and biodegradable films, each comprising polybutylene adipate terephthalate (PBAT); and polybutylene adipate terephthalate (PBAT) in which a terminal hydroxyl (-OH) ester is bonded with maleic acid.

Description

Biodegradable composition and biodegradable film

Technical Field

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No. 10-2022-0070912 filed in the Korean Intellectual Property Office on June 10, 2022, and Korean Patent Application No. 10-2023-0073708 filed in the Korean Intellectual Property Office on June 8, 2023, the disclosures of which are incorporated herein by reference in their entirety.

The present invention relates to biodegradable compositions and biodegradable films.

Background technique

Recently, as the concern for environmental protection and eco-friendliness has rapidly increased, the demand for methods of growing environmentally friendly crops is increasing. A known mulching method is one of these environmentally friendly farming methods. When growing crops, this is a method in which the soil surface is covered with a mulch film or the like, thereby preventing weed growth, preventing pests, maintaining soil moisture or regulating soil temperature, preventing soil erosion by rainwater on rainy days, and reducing the use of pesticides.

The mulching films used in such mulching tillage methods greatly contribute to the production volume of agricultural crops, but there are difficulties in collecting and recycling them after use. Generally, synthetic resins such as polypropylene and polyethylene are used, and biodegradable components are added as additives to impart biodegradability, but in reality, biodegradation of the synthetic resin itself is impossible. In addition, there is a problem that the synthetic resin that is not biodegraded and remains contaminates the soil.

Therefore, attempts have been made to produce cover films using polybutylene adipate terephthalate (PBAT), which is a biodegradable plastic. However, polybutylene adipate terephthalate (PBAT) has a high elongation, and has a problem that mechanical properties such as Young's modulus are lower than those of existing films such as polyethylene. In addition, since polybutylene adipate terephthalate (PBAT) is a 100% petroleum-based material, it has a low biomaterial content.

Therefore, attempts have been made to improve physical properties and increase the content of bio-based materials by compounding various biodegradable materials with polybutylene adipate terephthalate (PBAT). However, there is a problem that the compatibility between polybutylene adipate terephthalate and other biodegradable materials is low, resulting in poor tensile properties.

Summary of the invention

technical problem

An object of the present invention is to provide a biodegradable composition and a biodegradable film which are excellent in tensile properties such as tear strength, maximum tensile strength, elongation at break, and Young's modulus, and are increased in the content of biological raw materials.

Technical solutions

According to one embodiment of the present invention, there is provided a biodegradable composition comprising: polybutylene adipate terephthalate (PBAT); and polybutylene adipate terephthalate (PBAT) in which terminal hydroxyl (—OH) is ester-bonded with maleic acid.

According to another embodiment of the present invention, there is provided a biodegradable film comprising: polybutylene adipate terephthalate (PBAT); and polybutylene adipate terephthalate (PBAT) in which terminal hydroxyl (—OH) is ester-bonded with maleic acid.

Now, a biodegradable composition and a biodegradable film according to specific embodiments of the present invention will be described in more detail.

Unless particularly mentioned herein, the term “include” or “comprising” means that some elements (or components) are included without any limitation, and should not be interpreted as excluding the addition of other elements (or components).

Throughout the specification, the term "polylactic acid prepolymer" refers to polylactic acid having a weight average molecular weight of 1,000 to 50,000 g/mol obtained by oligomerizing lactic acid.

Throughout the specification, the term "poly(3-hydroxypropionate) prepolymer" refers to poly(3-hydroxypropionate) having a weight average molecular weight of 1,000 to 50,000 g/mol obtained by oligomerizing 3-hydroxypropionate.

In addition, unless otherwise specified herein, the weight average molecular weight of polylactic acid prepolymer, poly (3-hydroxypropionate) prepolymer and copolymer can be measured using gel permeation chromatography (GPC). Specifically, the prepolymer or copolymer is dissolved in chloroform to a concentration of 2 mg/ml, and then 20 μl of the dissolved polymer is injected into GPC, and GPC analysis is performed at 40 ° C. At this time, chloroform is used as the mobile phase of GPC, and the flow rate is 1.0 mL/min, and the column used is two Agilent Mixed-B units connected in series. RI detector is used as a detector. The value of Mw can be obtained using a calibration curve formed using a polystyrene standard sample. Nine polystyrene standard samples having molecular weights of 2,000 g/mol, 10,000 g/mol, 30,000 g/mol, 70,000 g/mol, 200,000 g/mol, 700,000 g/mol, 2,000,000 g/mol, 4,000,000 g/mol, and 10,000,000 g/mol were used.

As used herein, the term "substituted or unsubstituted" means unsubstituted or substituted with one or more substituents selected from the group consisting of deuterium, halogen group, nitrile group, nitro group, hydroxyl group, carbonyl group, ester group, imido group, amino group, phosphine oxide group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkylsulfonyl group, arylsulfonyl group, silyl group, boron group, alkyl group, cycloalkyl group, alkenyl group, aryl group, aralkyl group, aralkenyl group, alkylaryl group, alkylamino group, aralkylamino group, heteroarylamino group, arylamino group, arylphosphino group, and heterocyclic group containing at least one of N, O and S atoms, or unsubstituted or substituted with substituents in which two or more substituents are connected among the substituents exemplified above. For example, "substituents in which two or more substituents are connected" may be biphenyl. That is, the biphenyl may be an aryl group, or it may be interpreted as a substituent in which two phenyl groups are connected.

In order to prepare a composition for producing a biodegradable film, polybutylene adipate terephthalate can be compounded with other biodegradable materials such as thermoplastic starch, but polybutylene adipate terephthalate is hydrophobic, while thermoplastic starch is hydrophilic. Therefore, there is a problem that polybutylene adipate terephthalate and thermoplastic starch cannot be mixed well, resulting in deterioration of compatibility.

Thus, the present inventors have found that when "polybutylene adipate terephthalate in which maleic acid is ester-bonded to a terminal hydroxy group" is used as a compatibilizer in a biodegradable composition comprising polybutylene adipate terephthalate, compatibility is improved and mechanical properties such as tensile strength of a biodegradable film produced from such a composition are improved, and have completed the present invention.

Furthermore, as the content of thermoplastic starch in a biodegradable composition comprising polybutylene adipate terephthalate increases, it has the advantages of being cheap and economical, improving biodegradability, and increasing the content of bio-based carbon, but by using "polybutylene adipate terephthalate in which maleic acid is ester-bonded to terminal hydroxyl groups" as a compatibilizer in a biodegradable composition, a large amount of thermoplastic starch can be contained and thus the above-mentioned effects are exhibited, and the present invention has been completed.

According to one embodiment of the present invention, there is provided a biodegradable composition comprising: polybutylene adipate terephthalate (PBAT); and polybutylene adipate terephthalate (PBAT) in which terminal hydroxyl (—OH) is ester-bonded with maleic acid.

"Polybutylene adipate terephthalate in which terminal hydroxyl groups are ester-bonded with maleic acid" can be used as a compatibilizer to improve the compatibility of the biodegradable composition. In addition, "polybutylene adipate terephthalate in which terminal hydroxyl groups are ester-bonded with maleic acid" can be used as a chain extender to increase molecular weight, increase melt viscosity, and improve formability such as stretchability.

"Polybutylene adipate terephthalate in which the terminal hydroxyl group is ester-bonded with maleic acid" can be prepared by performing an esterification reaction of maleic acid and/or maleic anhydride with the terminal hydroxyl group of polybutylene adipate terephthalate. At this time, maleic anhydride can have higher reactivity in the esterification reaction with polybutylene adipate terephthalate than maleic acid.

For example, polybutylene adipate terephthalate in which maleic acid is ester-bonded to a terminal hydroxyl group may be represented by Chemical Formula 1 or 2 below.

[Chemical formula 1]

[Chemical formula 2]

Wherein, in Chemical Formulas 1 and 2,

a to d may each independently be an integer of 1 to 500, 5 to 450, 10 to 400, or 20 to 300.

The "polybutylene adipate terephthalate in which the terminal hydroxyl group is ester-bonded with maleic acid" represented by Chemical Formula 1 can be ester-bonded by performing an esterification reaction of one carboxyl group contained in maleic acid with the terminal hydroxyl group of polybutylene adipate terephthalate. In addition, the "polybutylene adipate terephthalate in which the terminal hydroxyl group is ester-bonded with maleic acid" represented by Chemical Formula 2 can be ester-bonded by performing an esterification reaction of two carboxyl groups contained in maleic acid with the terminal hydroxyl group of another polybutylene adipate terephthalate.

As described above, polybutylene adipate terephthalate in which terminal hydroxyl ester is bonded with maleic acid can be prepared by conducting an esterification reaction of maleic acid and/or maleic anhydride with polybutylene adipate terephthalate, wherein polybutylene adipate terephthalate in which terminal hydroxyl ester is bonded with maleic acid can be prepared by adjusting the content of maleic acid and/or maleic anhydride, the content of polybutylene adipate terephthalate, the reaction temperature, the reaction time, the type and content of additives, etc., and the weight average molecular weight, structure, viscosity, etc. of polybutylene adipate terephthalate in which terminal hydroxyl ester is bonded with maleic acid can be controlled.

Meanwhile, in the past, sometimes a compatibilizer grafted with maleic anhydride on polybutylene adipate terephthalate was used. It is unlikely to form free radicals in the middle of the polybutylene adipate terephthalate chain, or the grafting reaction efficiency is low due to steric hindrance, and polybutylene adipate terephthalate wherein ester-bonded with maleic acid has the advantage of significantly higher reaction efficiency. Thereby, compared with the situation of using a conventional compatibilizer grafted with maleic anhydride, when polybutylene adipate terephthalate wherein terminal hydroxy ester bonded with maleic acid is included as a compatibilizer in biodegradable compositions and biodegradable films, it is excellent in tensile properties (such as tear strength, maximum tensile strength, elongation at break and Young's modulus).

In the biodegradable composition according to one embodiment, polybutylene adipate terephthalate to which maleic acid is bonded to a terminal hydroxyl ester may be contained in an amount of 0.5 wt % or more and 10.0 wt % or less, based on 100 wt % of the total solid content of the biodegradable composition. For example, polybutylene adipate terephthalate to which maleic acid is bonded to a terminal hydroxyl ester may be contained in an amount of 0.7 wt % or more, 0.9 wt % or more, 1.0 wt % or more, 2.0 wt % or more, and 9.0 wt % or less, 7.0 wt % or less, 6.0 wt % or less, 5.0 wt % or less, based on 100 wt % of the total solid content of the biodegradable composition. If polybutylene adipate terephthalate in which maleic acid is ester-bonded to a terminal hydroxyl group is contained in too small an amount, the effect of improving compatibility may not be exhibited, and thus, mechanical properties such as tensile strength of a film produced from the composition may be reduced, and if polybutylene adipate terephthalate in which maleic acid is ester-bonded to a terminal hydroxyl group is contained in too large an amount, melt viscosity may become too high and formability may be reduced.

In addition, the biodegradable composition according to one embodiment may further include polyhydroxyalkanoate. The polyhydroxyalkanoate is not limited thereto, but may be poly(3-hydroxybutyrate), poly(4-hydroxybutyrate), poly(2-hydroxypropionate), poly(3-hydroxypropionate), poly(3-hydroxyvalerate), poly(4-hydroxyvalerate), or poly(5-hydroxyvalerate), but in order to improve the tensile properties of the film using the biodegradable composition, the polyhydroxyalkanoate is preferably poly(3-hydroxypropionate).

In addition, the polyhydroxyalkanoate has a weight average molecular weight (Mw) measured using gel permeation chromatography (GPC) of 50,000 g/mol to 300,000 g/mol, more specifically, 50,000 g/mol or more, 70,000 g/mol or more, or 100,000 g/mol or more, and 300,000 g/mol or less, or 200,000 g/mol or less, or 150,000 g/mol or less. If the weight average molecular weight of the polyhydroxyalkanoate is too small, the overall mechanical properties may be significantly reduced, and if the weight average molecular weight is too large, the processing may be difficult, and the processability and elongation may be low.

In addition, the biodegradable composition may contain the polyhydroxyalkanoate in an amount of 3 wt % to 40 wt %, more specifically, 3 wt % or more, 5 wt % or more, or 7 wt % or more, and 40 wt % or less, 35 wt % or less, or 30 wt % or less, based on 100 wt % of the total solid content of the biodegradable composition. If the polyhydroxyalkanoate is contained in the biodegradable composition in too small an amount, the tensile properties such as Young's modulus and yield tensile strength of the film produced therefrom may be reduced, and if the polyhydroxyalkanoate is contained in the biodegradable composition in too large an amount, the elongation of the film produced therefrom may be reduced.

Furthermore, the biodegradable composition according to one embodiment may further include a hydroxyalkanoate-lactide copolymer.

The hydroxyalkanoate-lactide copolymer may be a block copolymer comprising one or more polyhydroxyalkanoate (PHA) blocks and one or more polylactic acid blocks. Since the hydroxyalkanoate-lactide copolymer comprises the above blocks, it can exhibit the environmental friendliness and biodegradability of polyhydroxyalkanoate and polylactic acid.

Hydroxyalkanoate can be 3-hydroxybutyrate, 4-hydroxybutyrate, 2-hydroxypropionate, 3-hydroxypropionate, (D)-3-hydroxycarboxylate containing 6 to 14 carbon atoms, 3-hydroxyvalerate, 4-hydroxyvalerate, or 5-hydroxyvalerate. Therefore, hydroxyalkanoate-lactide copolymer can be 3-hydroxybutyrate-lactide copolymer, 4-hydroxybutyrate-lactide copolymer, 2-hydroxypropionate-lactide copolymer, 3-hydroxypropionate-lactide copolymer, 4-hydroxyvalerate-lactide copolymer, or 5-hydroxyvalerate-lactide copolymer. For example, hydroxyalkanoate-lactide copolymer can be 3-hydroxypropionate-lactide copolymer to improve flexibility and mechanical properties, etc.

The 3-hydroxypropionate-lactide copolymer may be a block copolymer obtained by polymerizing a polylactic acid prepolymer and a poly(3-hydroxypropionate) prepolymer.

3-Hydroxypropionate-lactide copolymer exhibits excellent tensile strength and elastic modulus properties possessed by polylactic acid prepolymer, and poly(3-hydroxypropionate) prepolymer also lowers the glass transition temperature (Tg), increases flexibility and improves mechanical properties such as impact strength, which can prevent polylactic acid from having poor elongation and brittle properties of easy cracking.

The polylactic acid prepolymer can be prepared by fermentation or polycondensation of lactic acid.

The weight average molecular weight of polylactic acid prepolymer can be 1,000g/mol or more, or 5,000g/mol or more, or 6,000g/mol or more, or 8,000g/mol or more, and 50,000g/mol or less, or 30,000g/mol or less. If it is desired to increase the crystallinity of the block comprising the repeating unit derived from polylactic acid prepolymer in the block copolymer finally prepared, the polylactic acid prepolymer preferably has a high weight average molecular weight greater than 20,000g/mol, or 22,000g/mol or more, or 23,000g/mol or more, or 25,000g/mol or more, and 50,000g/mol or less, or 30,000g/mol or less, or 28,000g/mol or less, or 26,000g/mol or less.

If the weight average molecular weight of the polylactic acid prepolymer is 20,000 g/mol or less, the crystals of the polymer are small, which makes it difficult to maintain the crystallinity of the polymer in the finally prepared block copolymer. If the weight average molecular weight of the polylactic acid prepolymer is greater than 50,000 g/mol, the rate of the side reaction occurring within the prepolymer chain becomes faster than the reaction rate between the polylactic acid prepolymers during polymerization.

On the other hand, the term "lactic acid" as used herein refers to L-lactic acid, D-lactic acid, or a mixture thereof.

The poly(3-hydroxypropionate) prepolymer can be prepared by performing fermentation or condensation polymerization of 3-hydroxypropionate.

The weight average molecular weight of the poly(3-hydroxypropionate) prepolymer may be 1,000 g/mol or more, or 5,000 g/mol or more, or 8,000 g/mol or more, or 8,500 g/mol or more, and 50,000 g/mol or less, or 30,000 g/mol or less. If the purpose is to increase the crystallinity of the repeating unit derived from the poly(3-hydroxypropionate) prepolymer in the finally prepared block copolymer, the poly(3-hydroxypropionate) prepolymer preferably has a high weight average molecular weight of more than 20,000 g/mol, or 22,000 g/mol or more, or 25,000 g/mol or more, and 50,000 g/mol or less, or 30,000 g/mol or less, or 28,000 g/mol or less.

As explained for the polylactic acid prepolymer, if the weight average molecular weight of the poly(3-hydroxypropionate) prepolymer is 20,000 g/mol or less, the polymer crystals are small, which makes it difficult to maintain the crystallinity of the polymer in the finally prepared block copolymer, and if the weight average molecular weight of the poly(3-hydroxypropionate) prepolymer is greater than 50,000 g/mol, the rate of side reactions occurring within the prepolymer chain is higher than the rate of reactions between the poly(3-hydroxypropionate) prepolymers during polymerization.

That is, at least one of the polylactic acid prepolymer and the poly(3-hydroxypropionate) prepolymer may have a weight average molecular weight of more than 20,000 g/mol and 50,000 g/mol or less.

On the other hand, lactic acid and 3-hydroxypropionate can be plastics and biodegradable compounds prepared from renewable sources by microbial fermentation, and the block copolymers comprising polylactic acid prepolymers and poly(3-hydroxypropionate) prepolymers formed by polymerizing them can also show environmental friendliness and biodegradability. For this reason, biodegradable compositions and biodegradable films comprising the block copolymers can include a large amount of biological raw materials while showing environmental friendliness and biodegradability.

3-hydroxypropionate-lactide copolymer is a block copolymer obtained by polymerizing polylactic acid prepolymer and poly (3-hydroxypropionate) prepolymer. In the block copolymer, the weight ratio of polylactic acid prepolymer to poly (3-hydroxypropionate) prepolymer is 95:5 to 50:50, 90:10 to 55:45, 90:10 to 60:40, 90:10 to 70:30 or 90:10 to 80:20. If poly (3-hydroxypropionate) prepolymer is included in too small an amount relative to polylactic acid prepolymer, brittleness may increase, if poly (3-hydroxypropionate) prepolymer is included in too large an amount relative to polylactic acid prepolymer, molecular weight is reduced, and processability and thermal stability may be reduced.

As described above, the 3-hydroxypropionate-lactide copolymer includes one or more poly(3-hydroxypropionate) blocks and one or more polylactic acid blocks, and may exhibit high crystallinity.

For example, the 3-hydroxypropionate-lactide copolymer can have a crystallinity of the polylactic acid block in the copolymer ( _{Xc_PLA} ) greater than 0 and 50 or less, or a crystallinity of the poly(3-hydroxypropionate) block ( _{Xc_P(3HP)} ) of 0 to 50, or greater than 0 and 50 or less, calculated according to the following Equations 1 and 2 using the crystallization temperature and the melting temperature measured by differential scanning calorimetry.

In addition, the sum of the crystallinity of the polylactic acid block and the crystallinity of the poly(3-hydroxypropionate) block in the copolymer may be 20 to 100, more specifically, 20 or more, or 30 or more, or 32 or more, and 100 or less, or 70 or less, or 50 or less, or 48 or less.

Since the copolymer satisfies the above-mentioned crystallinity, it can improve flexibility and mechanical properties in a well-balanced manner, and can simultaneously exhibit excellent strength properties of polylactic acid and excellent elongation properties of poly(3-hydroxypropionate).

On the other hand, if the sum of the crystallinity is too high, biodegradability and processability may be reduced, and if the sum of the crystallinity is too low, strength may be reduced.

[Equation 1]

Crystallinity of polylactic acid block ( _{Xc_PLA} ) = [(PLATm area) - (PLATcc area)] / 93.7

In Equation 1, the PLATm area is an integrated value of a peak at a melting temperature (Tm) of a polylactic acid (PLA) block in a block copolymer measured by differential scanning calorimetry, and the PLATcc area is an integrated value of a peak at a crystallization temperature (Tcc) of a polylactic acid block in a block copolymer measured by differential scanning calorimetry.

[Equation 2]

Crystallinity of poly(3-hydroxypropionate) block ( _{Xc_P(3HP)} ) = [(P(3HP)Tm area) - (P(3HP)Tcc area)]/64

In Equation 2, P(3HP)Tm area is the integrated value of the peak at the melting temperature (Tm) of the poly(3-hydroxypropionate) (P(3HP)) block in the block copolymer measured by differential scanning calorimetry, and P(3HP)Tcc area is the integrated value of the peak at the crystallization temperature (Tcc) of the poly(3-hydroxypropionate) block in the block copolymer measured by differential scanning calorimetry.

Furthermore, the integrated values of the peaks at Tm and Tcc mean values obtained by integrating the areas under the peaks indicating Tm and Tcc, respectively.

At this time, differential scanning calorimetry for measuring Tm and Tcc of each block can be performed using a PerkinElmer DSC 800 instrument. In addition, the sample to be analyzed is heated from 25°C to 250°C at a rate of 10°C per minute under a nitrogen atmosphere, cooled from 250°C to -50°C at a rate of -10°C per minute, and then heated from -50°C to 250°C at a rate of 10°C per minute, so that an endothermic curve can be obtained and Tm and Tcc can be determined.

The hydroxyalkanoate-lactide copolymer has a weight average molecular weight (Mw) measured using gel permeation chromatography (GPC) of 50,000 g/mol to 300,000 g/mol, more specifically, 50,000 g/mol or more, 70,000 g/mol or more, or 100,000 g/mol or more, and 300,000 g/mol or less, or 200,000 g/mol or less, or 150,000 g/mol or less. If the weight average molecular weight of the hydroxyalkanoate-lactide copolymer is too small, the overall mechanical properties may be significantly reduced, and if the weight average molecular weight is too large, the processing may be difficult, and the processability and elongation may be low.

The biodegradable composition according to one embodiment includes a hydroxyalkanoate-lactide copolymer, wherein the copolymer may be included in an amount of, for example, 3 to 40 wt %, more specifically, 3 wt % or more, 5 wt % or more, or 7 wt % or more, and 40 wt % or less, 35 wt % or less, or 30 wt % or less, based on 100 wt % of the total solid content of the biodegradable composition.

If the hydroxyalkanoate-lactide copolymer is included in an excessively small amount in the biodegradable composition, the tensile properties of a film produced therefrom, such as Young's modulus and tensile strength at yield, may decrease, and if the hydroxyalkanoate-lactide copolymer is included in an excessively large amount in the biodegradable composition, the elongation of a film produced therefrom may decrease.

The biodegradable composition according to one embodiment includes polybutylene adipate terephthalate (PBAT).

Polybutylene adipate terephthalate (PBAT) is a biodegradable resin and may be included in an amount of 30 to 80 wt %, more specifically, 30 wt % or more, 35 wt % or more, 40 wt % or more and 80 wt % or less, 75 wt % or less, or 70 wt % or less, based on 100 wt % of the total solid content of the biodegradable composition.

If polybutylene adipate terephthalate (PBAT) is included in an excessively small amount in a biodegradable composition, the elongation of a film produced using the same may be reduced, and if polybutylene adipate terephthalate (PBAT) is included in an excessively large amount in a biodegradable composition, the tensile properties of a film produced using the same, such as Young's modulus and tensile strength at yield, may be reduced.

The weight ratio of the hydroxyalkanoate-lactide copolymer to polybutylene adipate terephthalate (PBAT) included in the biodegradable composition according to one embodiment may be 5:95 to 50:50, 5:95 to 40:60, or 10:90 to 30:70.

If polybutylene adipate terephthalate (PBAT) is included in too small an amount compared to the hydroxyalkanoate-lactide copolymer, elongation may decrease, and if polybutylene adipate terephthalate (PBAT) is included in too large an amount compared to the hydroxyalkanoate-lactide copolymer, tensile properties such as Young's modulus and yield tensile strength may deteriorate.

The biodegradable composition according to one embodiment may include thermoplastic starch.

The biodegradable composition may further comprise thermoplastic starch to enhance the processability of the polybutylene adipate terephthalate and to accelerate the rate of biodegradation.

Thermoplastic starch may be starch to which thermoplasticity is imparted by adding a plasticizer to starch which is a natural polymer, and thus is not carbonized at a prescribed temperature or higher and can freely change its shape like existing general-purpose resins such as polyethylene, polystyrene, and polypropylene.

The thermoplastic starch may include at least one selected from the group consisting of rice starch, wheat starch, corn starch, sweet potato starch, potato starch, tapioca starch, cassava starch, and modified starches thereof.

Furthermore, the plasticizer contained in the starch which is a natural polymer may be at least one selected from the group consisting of isosorbide, glycerin, sorbitol, fructose, formamide, xylitol, corn oil, and edible oil.

The plasticizer may be included in an amount of 5 wt % or more and 50 wt % or less, 10 wt % or more and 45 wt % or less, or 15 wt % or more and 35 wt % or less, based on 100 wt % in total of the thermoplastic starch.

The thermoplastic starch may be included in an amount of 10 to 70 wt %, more specifically, 10 wt % or more, 15 wt % or more, or 20 wt % or more, and 70 wt % or less, 60 wt % or less, or 50 wt % or less, based on 100 wt % of the total solid content of the biodegradable composition.

If the thermoplastic starch is included in an excessively small amount in the biodegradable composition, the biodegradation rate may be slowed down, and the tensile properties of a film using the same, such as Young's modulus and yield tensile strength, may be reduced, and if the thermoplastic starch is included in an excessively large amount in the biodegradable composition, the elongation of the film using the same may be reduced.

The weight ratio of the thermoplastic starch to polybutylene adipate terephthalate (PBAT) included in the biodegradable composition according to one embodiment may be 5:95 to 50:50, 5:95 to 40:60, or 10:90 to 30:70.

If polybutylene adipate terephthalate (PBAT) is included in too small an amount compared to thermoplastic starch, elongation may decrease, and if polybutylene adipate terephthalate (PBAT) is included in too large an amount compared to thermoplastic starch, biodegradation rate may be slowed down, and tensile properties such as Young's modulus and yield tensile strength may decrease.

Biodegradable composition according to an embodiment may include hydrophobic polybutylene adipate terephthalate, hydrophilic thermoplastic starch etc. About whether their compatibility is improved, it can be seen that when the dispersed phase of thermoplastic starch is dispersed on the polybutylene adipate terephthalate matrix, as the dispersed phase of thermoplastic starch is distributed more densely and evenly, compatibility is improved. In addition, about whether compatibility is improved, it can be seen that as the bonding force at the interface between polybutylene adipate terephthalate and thermoplastic starch becomes stronger, their compatibility is improved. In other words, it can be considered that the dispersed phase of thermoplastic starch is distributed more densely and evenly on the polybutylene adipate terephthalate matrix, and compatibility is better, and the bonding force at the interface between polybutylene adipate terephthalate and thermoplastic starch is stronger, and compatibility is better.

In addition, whether the compatibility is improved can be numerically determined by analysis using a polymer viscoelasticity analyzer (DMA; dynamic mechanical analyzer) device. For example, the glass transition temperature (Tg) of thermoplastic starch and polybutylene adipate terephthalate can be measured using a polymer viscoelasticity analyzer (DMA: dynamic mechanical analyzer) device to check whether the compatibility is improved.

Specifically, the dispersed phase of thermoplastic starch is distributed more densely and evenly on the polybutylene adipate terephthalate matrix, and the glass transition temperature (Tg) of thermoplastic starch is lower.Polymer viscoelasticity analyzer can be used to analyze the glass transition temperature of such thermoplastic starch to determine whether compatibility is improved.In addition, the adhesion at the interface between polybutylene adipate terephthalate and thermoplastic starch is stronger, and the dispersed phase of thermoplastic starch is more effectively transferred to polybutylene adipate terephthalate by stress, so that the glass transition temperature (Tg) of polybutylene adipate terephthalate, especially the glass transition temperature (Tg) of the butylene adipate repeating unit of soft segment increases.Polymer viscoelasticity analyzer can be used to analyze the glass transition temperature of polybutylene adipate terephthalate to determine whether compatibility is improved.

Therefore, the better the compatibility between polybutylene adipate terephthalate and thermoplastic starch, the lower the glass transition temperature (Tg) of thermoplastic starch. For example, the glass transition temperature (Tg) of thermoplastic starch is 10°C or higher and 140°C or lower, 15°C or higher and 120°C or lower, 20°C or higher and 100°C or lower, 25°C or higher and 80°C or lower, 25°C or higher and 50°C or lower, or 25°C or higher and 40°C or lower.

In addition, the better the compatibility between polybutylene adipate terephthalate and thermoplastic starch, the higher the glass transition temperature (Tg) of polybutylene adipate terephthalate. For example, the glass transition temperature (Tg) of polybutylene adipate terephthalate may be -23.0°C or higher and -10.0°C or lower, or -22.5°C or higher and -15.0°C or lower.

In addition, the absolute value of the difference between the glass transition temperature (Tg) of the thermoplastic starch and polybutylene adipate terephthalate is 20°C or more and 70°C or less, 25°C or more and 65°C or less, 30°C or more and 60°C or less, or 35°C or more and 59°C or less.

According to one embodiment of the present invention, there is provided a biodegradable film comprising: polybutylene adipate terephthalate (PBAT); and polybutylene adipate terephthalate (PBAT) in which terminal hydroxyl (—OH) is ester-bonded with maleic acid.

The method for producing a biodegradable film is not particularly limited, but it can be obtained by an existing film production method such as a known expansion method, a tubular method, and a T-die casting method using a biodegradable composition according to an embodiment. For example, the composition is granulated, and the pellets are dried at 60°C to 100°C for 6 hours or more so that the moisture content can be controlled to 1,200ppm or less, 500ppm or less, or 200ppm or less. Subsequently, the granulated composite material can be applied to a release film and then placed in a hot press, and pressure can be applied thereto to produce a film. At this time, the temperature can be 130°C to 250°C, 150°C to 220°C, or 160°C to 200°C, and the pressure can be 5MPa to 20MPa, 8MPa to 17MPa, or 10MPa to 15MPa.

Therefore, biodegradable film can similarly include the above-mentioned components in biodegradable composition.For example, biodegradable film can include polybutylene adipate terephthalate, polybutylene adipate terephthalate, thermoplastic starch, polyhydroxyalkanoate and hydroxyalkanoate-lactide copolymer etc., wherein terminal hydroxy ester is bonded with maleic acid.In addition, the molecular weight, content, structure etc. of polybutylene adipate terephthalate, polybutylene adipate terephthalate, thermoplastic starch, polyhydroxyalkanoate and hydroxyalkanoate-lactide copolymer included in biodegradable film are as described above.For example, based on the biodegradable film of 100 wt %, biodegradable film can include polybutylene adipate terephthalate, wherein terminal hydroxy ester is bonded with maleic acid, with the amount of 0.5 wt % to 10.0 wt %. For example, polybutylene adipate terephthalate in which terminal hydroxyl esters are bonded with maleic acid is contained in an amount of 0.7 wt % or more, 0.9 wt % or more, 1.0 wt % or more, or 2.0 wt % or more, and 9.0 wt % or less, 7.0 wt % or less, 6.0 wt % or less, or 5.0 wt % or less, based on 100 wt % in total of the biodegradable film.

Based on 100 wt % of the biodegradable film, the thermoplastic starch may be included in an amount of 10 wt % or more and 50 wt % or less. For example, based on a total of 100 wt % of the biodegradable film, the thermoplastic starch may be included in an amount of 10 wt % or more, 15 wt % or more, 20 wt % or more, or 25 wt % or more, and 45 wt % or less, 40 wt % or less, 35 wt % or less.

The thickness of the biodegradable film according to an embodiment can be 10 μm to 300 μm, more specifically, 10 μm or more, 13 μm or more, 15 μm or more, 20 μm or more, 20 μm or more, or 25 μm or more, and 300 μm or less, 200 μm or less, 150 μm or less, 100 μm or less, 80 μm or less, 50 μm or less. Since the thickness of the film is within the above range, the film can have strong elasticity, excellent handling characteristics, satisfactory winding state and unfolding characteristics of the roll. If the film thickness is too thin, tensile strength, tear strength and elongation may deteriorate, and holes or tears may be formed in the film during use. If the film thickness is too thick, the unit price competitiveness may be reduced. The biodegradable film can be used as an agricultural covering film, disposable gloves, personal medical packaging, food wrapping paper, garbage bags, or bags for various industrial products.

The biodegradable film according to one embodiment may have a maximum tensile strength measured according to ASTM D882-07 of 5 MPa or more, 7 MPa or more, 8 MPa or more, or 5 MPa to 30 MPa.

The biodegradable film according to one embodiment may have an elongation at break measured according to ASTM D882-07 of 300% or more, 350% or more, 400% or more, 420% or more, 430% or more, or 300 to 700%.

In addition, the biodegradable film may have a Young's modulus measured according to ASTM D882-07 of 50 MPa or more, 70 MPa or more, 74 MPa or more, 80 MPa or more, or 50 MPa to 800 MPa.

The maximum tensile strength, elongation at break, and Young's modulus of the biodegradable film measured in MD (machine direction) and TD (transverse direction) directions may each satisfy the above numerical ranges.

Beneficial Effects

According to the present invention, a biodegradable composition and a biodegradable film comprising a biological raw material having excellent tensile properties such as tear strength, maximum tensile strength, elongation at break, and Young's modulus while maintaining environmental friendliness and biodegradability can be provided.

Detailed ways

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, these examples are presented for illustrative purposes only, and the scope of the present invention is not limited thereto in any way.

Preparation Example 1: Preparation of thermoplastic starch

Based on dry weight, 225 g corn starch and 75 g glycerol were mixed in a mixer, then loaded into an extruder and compounded. The temperature range of the extruder was set to 80° C. to 150° C., the screw speed was set to 150 rpm, and the extruded strands were cut with a granulator to prepare thermoplastic starch granules.

Preparation Example 2: Preparation of polybutylene adipate terephthalate in which the terminal hydroxyl (-OH) ester is bonded with maleic acid

100 g of polybutylene adipate terephthalate (PBAT, Solpol 1000N, SOLTECH) and 10 g of maleic acid were put into an internal mixer and reacted at 160° C. and 50 rpm for 30 minutes to prepare “polybutylene adipate terephthalate in which terminal hydroxyl group (—OH) is ester-bonded with maleic acid”.

<Examples and Comparative Examples>

Example 1: Preparation of biodegradable film

Based on dry weight, 750g of polybutylene adipate terephthalate (PBAT, Solpol1000N, SOLTECH), 250g of thermoplastic starch prepared in Preparation Example 1 and 50g of polybutylene adipate terephthalate in which the terminal hydroxyl (-OH) ester is bonded with maleic acid prepared in Preparation Example 2 were mixed by hand, then loaded into an extruder and compounded. The temperature range of the extruder was set to 120°C to 150°C, and the screw speed was set to 150rpm. The extruded strands were cut with a granulator to prepare composite pellets. The composite pellets prepared were heated to 180°C to produce a film with a thickness of 15 μm using a film blowing device (BL50T) from Collin.

Comparative Example 1: Production of biodegradable film

A film was produced in the same manner as in Example 1, except that 50 g of polybutylene adipate terephthalate in which a terminal hydroxyl group (—OH) was ester-bonded with maleic acid prepared in Preparation Example 2 was not used.

Evaluate

1. Evaluation of tensile properties

The tensile properties of the films of Examples and Comparative Examples were evaluated according to ASTM D882-07. The tensile properties included tear strength, maximum tensile strength and elongation at break in MD (machine direction) and TD (transverse direction), and the results are shown in Table 1 below.

[Table 1]

According to Table 1, it is confirmed that Example 1 is significantly superior to Comparative Example 1 in all aspects of tear strength, maximum tensile strength and elongation at break.

Claims (20)

1. A biodegradable composition comprising: Polybutylene adipate terephthalate (PBAT); and Polybutylene adipate terephthalate (PBAT) in which maleic acid is ester-bonded to the terminal hydroxyl group (-OH). 2. The biodegradable composition according to claim 1, wherein: The polybutylene adipate terephthalate (PBAT) in which the terminal hydroxyl group (-OH) is ester-bonded with maleic acid is represented by the following chemical formula 1 or 2: [Chemical formula 1] [Chemical formula 2] Wherein, in Chemical Formulas 1 and 2, a to d are each independently an integer of 1 to 500. 3. The biodegradable composition according to claim 1, Also included are polyhydroxyalkanoates. 4. The biodegradable composition according to claim 3, wherein: The polyhydroxyalkanoate is poly(3-hydroxypropionate). 5. The biodegradable composition according to claim 1, Also included are hydroxyalkanoate-lactide copolymers. 6. The biodegradable composition according to claim 5, wherein: The hydroxyalkanoate-lactide copolymer is a 3-hydroxypropionate-lactide copolymer. 7. The biodegradable composition according to claim 6, wherein: The 3-hydroxypropionate-lactide copolymer is a block copolymer obtained by polymerizing a polylactic acid prepolymer and a poly(3-hydroxypropionate) prepolymer. 8. The biodegradable composition according to claim 7, wherein: At least one of the polylactic acid prepolymer and the poly(3-hydroxypropionate) prepolymer has a weight average molecular weight of more than 20,000 g/mol and 50,000 g/mol or less. 9. The biodegradable composition according to claim 7, wherein: The weight ratio between the polylactic acid prepolymer and the poly(3-hydroxypropionate) prepolymer is 95:5 to 50:50. 10. The biodegradable composition according to claim 7, wherein: The 3-hydroxypropionate-lactide copolymer has a sum of the crystallinity of the polylactic acid block and the crystallinity of the poly(3-hydroxypropionate) block calculated according to the following equations 1 and 2, ranging from 20 to 100: [Equation 1] Crystallinity of polylactic acid block (X _{c_PLA} ) = [(PLATm area) - (PLATcc area)] / 93.7 (In Equation 1, PLATm area is the integrated value of the peak at the melting temperature (Tm) of the polylactic acid (PLA) block in the block copolymer measured by differential scanning calorimetry, and PLATcc area is the integrated value of the peak at the crystallization temperature (Tcc) of the polylactic acid block in the block copolymer measured by differential scanning calorimetry) [Equation 2] Crystallinity of poly(3-hydroxypropionate) block ( _{Xc_P(3HP)} ) = [(P(3HP)Tm area) - (P(3HP)Tcc area)]/64 (In Equation 2, P(3HP)Tm area is the integrated value of the peak at the melting temperature (Tm) of the poly(3-hydroxypropionate) (P(3HP)) block in the block copolymer measured by differential scanning calorimetry, and P(3HP)Tcc area is the integrated value of the peak at the crystallization temperature (Tcc) of the poly(3-hydroxypropionate) block in the block copolymer measured by differential scanning calorimetry). 11. The biodegradable composition according to claim 5, wherein: The hydroxyalkanoate-lactide copolymer has a weight average molecular weight of 50,000 to 300,000. 12. The biodegradable composition according to claim 1, Also contains thermoplastic starch. 13. The biodegradable composition according to claim 12, wherein: The thermoplastic starch includes at least one selected from the group consisting of rice starch, wheat starch, corn starch, sweet potato starch, potato starch, cassava starch, tapioca starch, and modified starches thereof. 14. The biodegradable composition according to claim 5, wherein: A weight ratio between the hydroxyalkanoate-lactide copolymer and the polybutylene adipate terephthalate (PBAT) is 5:95 to 50:50. 15. The biodegradable composition according to claim 12, wherein: A weight ratio between the thermoplastic starch and the polybutylene adipate terephthalate (PBAT) is 5:95 to 50:50. 16. A biodegradable film comprising: Polybutylene adipate terephthalate (PBAT); and Polybutylene adipate terephthalate (PBAT) in which maleic acid is ester-bonded to the terminal hydroxyl group (-OH). 17. The biodegradable film according to claim 16, wherein: The polybutylene adipate terephthalate (PBAT) in which terminal hydroxyl (—OH) is ester-bonded with maleic acid is included in an amount of 0.1 to 10 parts by weight, based on 100 parts by weight of the biodegradable film. 18. The biodegradable film according to claim 16, wherein: The biodegradable film has a maximum tensile strength measured according to ASTM D882-07 of 5 MPa or more. 19. The biodegradable film according to claim 16, wherein: The biodegradable film has an elongation at break measured according to ASTM D882-07 of 300% or more. 20. The biodegradable film according to claim 16, wherein: The biodegradable film has a Young's modulus measured according to ASTM D882-07 of 50 MPa or more.