Biodegradable composition and biodegradable film

Abstract

The present invention provides a biodegradable composition containing polybutylene adipate terephthalate (PBAT), thermoplastic starch, and polybutylene adipate terephthalate (PBAT) grafted with starch maleate, and a biodegradable film.

Description

Technical Field

[0001] [Cross - Reference to Related Applications] This application claims the benefit of priority based on Korean Patent Application No. 10 - 2022 - 0070913 filed on June 10, 2022 and Korean Patent Application No. 10 - 2023 - 0073707 filed on June 8, 2023, and all the contents disclosed in the documents of the Korean patent applications are included as part of this specification.

[0002] The present invention relates to a biodegradable composition and a biodegradable film.

Background Art

[0003] Recently, the interest in environmental protection and eco - awareness has increased rapidly, and the need for methods of cultivating eco - friendly agricultural products has been growing. As one such eco - friendly farming method, mulching farming is known. When cultivating crops, the surface of the soil is covered with a mulching film or the like to prevent the growth of weeds, prevent pests and diseases, retain soil moisture or regulate soil temperature, prevent soil erosion by rainwater during rainy days, and reduce the use of pesticides.

[0004] The mulching film used in such mulching farming greatly contributes to the productivity of agricultural products, but there are difficulties in collection and recycling after use. Usually, although biodegradable components are added as additives using synthetic resins such as polypropylene and polyethylene to impart biodegradability, the biodegradation of the synthetic resin itself is impossible in reality. In addition, the synthetic resin left without being biodegraded has a problem of polluting the soil.

[0005] Therefore, there have been attempts to manufacture a mulching film using polybutylene adipate terephthalate (PBAT), which is a biodegradable plastic. However, although PBAT has a high elongation rate, there is a problem in that its mechanical properties such as Young's modulus are lower than those of existing films such as polyethylene. In addition, since PBAT is a 100% petroleum-based material, its bio-based raw material content is low.

[0006] Therefore, attempts have been made to compound various biodegradable materials with PBAT to improve its physical properties and increase the content of bio-based raw materials. However, there is a problem in that the compatibility between PBAT and other biodegradable materials is low and the tensile properties are inferior.

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention provides a biodegradable composition and a biodegradable film that are excellent in tensile properties such as tensile strength, elongation at break, and Young's modulus, and have an increased content of bio-based raw materials.

Means for Solving the Problems

[0008] According to an embodiment of the present invention, there is provided a biodegradable composition including polybutylene adipate terephthalate (PBAT), thermoplastic starch, and polybutylene adipate terephthalate (PBAT) grafted with starch maleate.

[0009] According to another embodiment of the present invention, there is provided a biodegradable film including polybutylene adipate terephthalate (PBAT), thermoplastic starch, and polybutylene adipate terephthalate (PBAT) grafted with starch maleate.

[0010] Hereinafter, the biodegradable composition and the biodegradable film according to specific embodiments of the invention will be described in more detail.

[0011] Throughout this specification, unless otherwise specifically mentioned, the terms "comprising" or "containing" refer to including a certain component (or constituent) without any special limitation, and shall not be construed as excluding the addition of other components (or constituents).

[0012] Throughout this specification, "polylactic acid prepolymer" means polylactic acid with a weight average molecular weight of 1,000 to 50,000 g / mol obtained by oligomerizing lactic acid.

[0013] Throughout this specification, "poly(3-hydroxypropionate) prepolymer" means poly(3-hydroxypropionate) with a weight average molecular weight of 1,000 to 50,000 g / mol obtained by oligomerizing 3-hydroxypropionate.

[0014] Also, unless otherwise mentioned in this specification, the weight average molecular weights of the polylactic acid prepolymer, poly(3-hydroxypropionate) prepolymer, and copolymer can be measured using gel permeation chromatography (GPC). Specifically, after dissolving the prepolymer or copolymer in chloroform to a concentration of 2 mg / ml, 20 μl is injected into the GPC, and GPC analysis is performed at 40°C. At this time, chloroform is used as the mobile phase of the GPC, which flows in at a flow rate of 1.0 mL / min. Two Agilent Mixed-B columns are connected in series and used, and an RI Detector is used as the detector. The Mw value is derived using a calibration curve formed with polystyrene standard specimens. Nine polystyrene standard specimens with weight average 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 are used.

[0015] Conventionally, for the composition for producing a biodegradable film, only polybutylene adipate terephthalate was included, or polybutylene adipate terephthalate was compounded with other biodegradable materials to produce a film. However, when only the polybutylene adipate terephthalate was used, there were problems such as low mechanical properties such as Young's modulus and low content of bio-based raw materials. When polybutylene adipate terephthalate was compounded with other biodegradable materials, there was a problem that the compatibility between the materials was low and the tensile properties of the film were low.

[0016] Regarding this, the present inventors found that in the case of a biodegradable composition produced by compounding polybutylene adipate terephthalate (PBAT), thermoplastic starch, and polybutylene adipate terephthalate (PBAT) grafted with starch maleate, the compatibility between the materials is excellent, and the tensile properties such as tear strength, tensile strength, elongation at break, and Young's modulus of the film produced therefrom are also excellent. Based on this finding, the present invention was completed.

[0017] In addition, the biodegradable composition may contain a hydroxyalkanoate-lactide copolymer. Since the hydroxyalkanoate-lactide copolymer exhibits eco-friendliness and biodegradability while containing a large amount of bio-based raw materials, the biodegradable film produced from the composition containing this copolymer can also contain a large amount of bio-based raw materials while maintaining eco-friendliness and biodegradability.

[0018] According to an embodiment of the invention, there is provided a biodegradable composition containing polybutylene adipate terephthalate (PBAT), thermoplastic starch, and polybutylene adipate terephthalate (PBAT) grafted with starch maleate.

[0019] The above-mentioned polybutylene adipate terephthalate (PBAT) may be contained in an amount of 30 to 90% by weight, more specifically, 30% by weight or more, 35% by weight or more, 40% by weight or more, or 90% by weight or less, 80% by weight or less, 75% by weight or less, 70% by weight or less, based on the total 100% by weight of the biodegradable composition.

[0020] When the above-mentioned polybutylene adipate terephthalate (PBAT) is contained in an excessively small amount in the biodegradable composition, the elongation rate may decrease. When the above-mentioned polybutylene adipate terephthalate (PBAT) is contained in an excessively large amount in the biodegradable composition, the tensile properties such as Young's modulus and yield tensile strength may decrease.

[0021] The above-mentioned biodegradable composition may contain thermoplastic starch in order to improve the processability of polybutylene adipate terephthalate and accelerate the biodegradation rate.

[0022] The above-mentioned thermoplastic starch may be starch, which is a natural polymer, to which a plasticizer is added to impart thermoplasticity such that it does not carbonize even at a temperature above a certain level and its form can be freely changed, like existing general-purpose resins such as polyethylene, polystyrene, and polypropylene.

[0023] The above-mentioned thermoplastic starch may contain one or more selected from the group consisting of corn starch, wheat starch, corn starch, sweet potato starch, potato starch, tapioca starch, cassava starch, and modified starches thereof.

[0024] Also, the above-mentioned plasticizer contained in starch, which is a natural polymer, may be one or more selected from the group consisting of isosorbide, glycerol, sorbitol, fructose, formamide, xylitol, corn oil, and salad oil.

[0025] The plasticizer may be contained in an amount of 5% by weight or more and 50% by weight or less, 10% by weight or more and 45% by weight or less, or 15% by weight or more and 35% by weight or less based on 100% by weight of the total amount of the thermoplastic starch.

[0026] The thermoplastic starch may be contained in an amount of 10 to 70% by weight based on 100% by weight of the total amount of the biodegradable composition. More specifically, it may be contained in an amount of 10% by weight or more, 15% by weight or more, 20% by weight or more, or 70% by weight or less, 60% by weight or less, 50% by weight or less.

[0027] When the thermoplastic starch is contained in an excessively small amount in the biodegradable composition, the biodegradation rate may become slow and the tensile properties such as Young's modulus and yield tensile strength may decrease. When the thermoplastic starch is contained in an excessively large amount in the biodegradable composition, the elongation rate may become low.

[0028] The weight ratio of the thermoplastic starch and poly(butylene adipate terephthalate) (PBAT) contained 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.

[0029] When the poly(butylene adipate terephthalate) (PBAT) is contained in an excessively small amount compared to the thermoplastic starch, the elongation rate may become low. When the poly(butylene adipate terephthalate) (PBAT) is contained in an excessively large amount compared to the thermoplastic starch, the biodegradation rate may become slow and the tensile properties such as Young's modulus and yield tensile strength may decrease.

[0030] The biodegradable composition according to one embodiment may contain poly(butylene adipate terephthalate) (PBAT) grafted with starch maleate.

[0031] The polybutylene adipate terephthalate (PBAT) grafted with the starch maleate may be included as a compatibilizer that improves the binding force of the polybutylene adipate terephthalate (PBAT), the hydroxyalkanoate-lactide copolymer, and / or the thermoplastic starch and improves the mechanical properties. The polybutylene adipate terephthalate (PBAT) grafted with the starch maleate can act as a chain extender to increase the molecular weight, increase the melt viscosity, and also improve the moldability such as stretchability.

[0032] The polybutylene adipate terephthalate (PBAT) grafted with the starch maleate may be different from the polybutylene adipate terephthalate (PBAT) in that the starch maleate is grafted.

[0033] The starch maleate may be a monomer or oligomer formed by the esterification reaction of the hydroxyl group of starch and the carboxyl group of maleic acid. The starch maleate may have a weight average molecular weight of 1,000 or more and 50 million or less, 10,000 or more and 30 million or less, 50,000 or more and 10 million or less, or 100,000 or more and 10 million or less. If the weight average molecular weight of the starch maleate is excessively small, it may be difficult to use as a compatibilizer with other compositions, and if the weight average molecular weight of the starch maleate is excessively large, the tensile properties such as tear strength may decrease.

[0034] The grafting ratio of maleic acid starch grafted onto polybutylene adipate terephthalate (PBAT) may be 0.1 to 10.0% by weight, 0.2 to 9.0% by weight, 0.3 to 5.0% by weight, 0.4 to 3.0% by weight, or 0.5 to 1.0% by weight. By adjusting the grafting ratio of maleic acid starch grafted onto polybutylene adipate terephthalate (PBAT) within the above-mentioned range, the tensile properties such as the tear strength of the biodegradable film produced from the biodegradable composition and the moldability can be improved.

[0035] The polybutylene adipate terephthalate (PBAT) grafted with the maleic acid starch may be contained in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the biodegradable composition. More specifically, it may be contained in an amount of 0.1 part by weight or more, 0.2 part by weight or more, 0.3 part by weight or more, or 10 parts by weight or less, 5 parts by weight or less, 3 parts by weight or less.

[0036] When the polybutylene adipate terephthalate (PBAT) grafted with the maleic acid starch is contained in an excessively small amount in the biodegradable composition, the mechanical properties are not improved. When the polybutylene adipate terephthalate (PBAT) grafted with the maleic acid starch is contained in an excessively large amount in the biodegradable composition, the melt viscosity may become excessively high and the moldability may decrease.

[0037] The biodegradable composition according to the one embodiment may further contain a hydroxyalkanoate-lactide copolymer.

[0038] The hydroxyalkanoate-lactide copolymer may be a block copolymer containing one or more polyhydroxyalkanoate (PHA) blocks and one or more polylactic acid blocks. By the hydroxyalkanoate-lactide copolymer containing the above-mentioned blocks, the eco-friendliness and biodegradability of polyhydroxyalkanoate and polylactic acid can be exhibited.

[0039] The hydroxyalkanoate may be 3-hydroxybutyrate, 4-hydroxybutyrate, 2-hydroxypropionate, 3-hydroxypropionate, a (D)-3-hydroxycarboxylate having an intermediate chain length of 6 to 14 carbon atoms, 3-hydroxyvalerate, 4-hydroxyvalerate, or 5-hydroxyvalerate. Accordingly, the hydroxyalkanoate-lactide copolymer may be a 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, the hydroxyalkanoate-lactide copolymer may be a 3-hydroxypropionate-lactide copolymer in order to improve flexibility and mechanical properties, etc.

[0040] The 3-hydroxypropionate-lactide copolymer may be a block copolymer obtained by polymerizing a polylactic acid prepolymer and a poly(3-hydroxypropionate) prepolymer.

[0041] While showing excellent characteristics in terms of the tensile strength and elastic modulus of the polylactic acid prepolymer, the 3-hydroxypropionate-lactide copolymer can prevent the poor elongation rate and brittleness characteristics of polylactic acid by reducing the glass transition temperature (Tg) and increasing flexibility of the poly(3-hydroxypropionate) prepolymer, thereby improving mechanical properties such as impact strength.

[0042] The polylactic acid prepolymer may be produced by fermenting or polycondensing lactic acid.

[0043] The polylactic acid prepolymer may have a weight average molecular weight of 1,000 g / mol or more, or 5,000 g / mol or more, or 6,000 g / mol or more, or 8,000 g / mol or more, and 50,000 g / mol or less, or 30,000 g / mol or less. When attempting to enhance the crystallinity of the block containing repeating units derived from the polylactic acid prepolymer in the finally produced block copolymer, it is preferable that the polylactic acid prepolymer has a high weight average molecular weight of more than 20,000 g / mol, or 22,000 g / mol or more, or 23,000 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, or 26,000 g / mol or less.

[0044] When the weight average molecular weight of the polylactic acid prepolymer is 20,000 g / mol or less, the crystals of the polymer are small, making it difficult to maintain the crystallinity of the polymer in the finally produced block copolymer. When the weight average molecular weight of the polylactic acid prepolymer exceeds 50,000 g / mol, the rate of side reactions occurring within the prepolymer chains becomes faster than the reaction rate between the polylactic acid prepolymers during polymerization.

[0045] On the other hand, the "lactic acid" used in the present invention refers to L-lactic acid, D-lactic acid, or a mixture thereof.

[0046] The poly(3-hydroxypropionate) prepolymer may be produced by fermenting or polycondensing 3-hydroxypropionate.

[0047] The weight-average molecular weight of the poly(3-hydroxypropionate) prepolymer is 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 may be 50,000 g / mol or less, or 30,000 g / mol or less. When attempting to enhance the crystallinity of the repeating units derived from the poly(3-hydroxypropionate) prepolymer in the finally produced block copolymer, it is preferable that the poly(3-hydroxypropionate) prepolymer has a high weight-average molecular weight exceeding 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.

[0048] As described for the polylactic acid prepolymer, when the weight-average molecular weight of the poly(3-hydroxypropionate) prepolymer is 20,000 g / mol or less, the crystals of the polymer are small, making it difficult to maintain the crystallinity of the polymer in the finally produced block copolymer. When the weight-average molecular weight of the poly(3-hydroxypropionate) prepolymer exceeds 50,000 g / mol, the rate of side reactions occurring within the prepolymer chains becomes faster than the reaction rate between the poly(3-hydroxypropionate) prepolymers during polymerization.

[0049] That is, at least one of the polylactic acid prepolymer and the poly(3-hydroxypropionate) prepolymer may have a weight-average molecular weight exceeding 20,000 g / mol and 50,000 g / mol or less.

[0050] On the one hand, the lactic acid and 3-hydroxypropionate may be plastic and biodegradable compounds produced from renewable sources by microbial fermentation, and the block copolymer containing the polylactic acid prepolymer and poly(3-hydroxypropionate) prepolymer formed by polymerizing them can also exhibit eco-friendliness and biodegradability. Accordingly, the biodegradable composition containing the block copolymer can contain a large amount of bio-based raw materials while exhibiting eco-friendliness and biodegradability.

[0051] The 3-hydroxypropionate-lactide copolymer is a block copolymer in which a polylactic acid prepolymer and a poly(3-hydroxypropionate) prepolymer are polymerized. In the block copolymer, the weight ratio of the polylactic acid prepolymer to the poly(3-hydroxypropionate) prepolymer may be 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 the poly(3-hydroxypropionate) prepolymer is contained in an excessively small amount relative to the polylactic acid prepolymer, the brittleness may increase. If the poly(3-hydroxypropionate) prepolymer is contained in an excessively large amount relative to the polylactic acid prepolymer, the molecular weight may decrease, resulting in a decrease in processability and heat resistance stability.

[0052] As described above, the 3-hydroxypropionate-lactide copolymer contains one or more poly(3-hydroxypropionate) blocks and one or more polylactic acid blocks, and can exhibit high crystallinity.

[0053] For example, the 3-hydroxypropionate-lactide copolymer uses the crystallization temperature and melting temperature measured through differential scanning calorimetry, and the crystallinity (Xc_ of the polylactic acid block in the copolymer calculated by the following formulas 1 and 2. PLA) is more than 0 and 50 or less, or the crystallinity (Xc_ P(3HP) ) of the poly(3-hydroxypropionate) block may be 0 to 50, or more than 0 and 50 or less.

[0054] Also, the total 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.

[0055] By satisfying the above-described crystallinity, the copolymer improves flexibility and mechanical properties in a well-balanced manner, and can simultaneously exhibit the excellent strength characteristics of polylactic acid and the excellent elongation rate characteristics of poly(3-hydroxypropionate).

[0056] On the other hand, if the total of the crystallinity is excessively high, biodegradability and processability may decrease, and if the total of the crystallinity is excessively low, strength may decrease.

[0057] [Formula 1] Crystallinity (Xc_) of the polylactic acid block PLA ) = [(PLA Tm area) - (PLA Tcc area)] / 93.7

[0058] In the above Formula 1, the PLA Tm area is the integrated value for the peak at the melting temperature (Tm) of the polylactic acid (PLA) block in the block copolymer measured through differential scanning calorimetry analysis, and the PLA Tcc area may be the integrated value for the peak at the crystallization temperature (Tcc) of the polylactic acid block in the block copolymer measured through differential scanning calorimetry analysis.

[0059] [Formula 2] Crystallinity (Xc_) of the poly(3-hydroxypropionate) block P(3HP) ) = [(P(3HP) Tm area) - (P(3HP) Tcc area)] / 64

[0060] In the formula 2, the P(3HP) Tm area is the integrated value for the peak at the melting temperature (Tm) of the poly(3-hydroxypropionate) (P(3HP)) block in the block copolymer measured through differential scanning calorimetry analysis, and the P(3HP) Tcc area may be the integrated value for the peak at the crystallization temperature (Tcc) of the poly(3-hydroxypropionate) block in the block copolymer measured through differential scanning calorimetry analysis.

[0061] Also, the integrated values for the peaks at Tm and Tcc mean the values obtained by integrating the lower areas of the peaks indicating Tm and Tcc, respectively.

[0062] At this time, the differential scanning calorimetry analysis for measuring Tm and Tcc of each block may be performed using a PerkinElmer DSC800 instrument. Also, 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 again from 250°C to -50°C at a rate of -10°C per minute, and then heated again from -50°C to 250°C at a rate of 10°C per minute to obtain an endothermic curve, and Tm and Tcc can be confirmed.

[0063] The hydroxyalkanoate-lactide copolymer has a weight average molecular weight (Mw) of 50,000 to 300,000 g / mol as measured using gel permeation chromatography (GPC), and more specifically, has a weight average molecular weight of 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 excessively small, the general mechanical properties may be significantly reduced, and if the weight average molecular weight is excessively large, the process may be difficult and the processability and elongation rate may be low.

[0064] The biodegradable composition according to the embodiment includes the hydroxyalkanoate-lactide copolymer, and may be included, for example, in an amount of 3 to 40% by weight based on 100% by weight of the total biodegradable composition. More specifically, it may be included in an amount of 3% by weight or more, 5% by weight or more, 7% by weight or more, or 40% by weight or less, 35% by weight or less, 30% by weight or less.

[0065] When the hydroxyalkanoate-lactide copolymer is contained in the biodegradable composition in an excessively small amount, tensile properties such as Young's modulus and yield tensile strength may decrease. When the hydroxyalkanoate-lactide copolymer is contained in the biodegradable composition in an excessively large amount, the elongation rate may decrease.

[0066] The weight ratio of the hydroxyalkanoate-lactide copolymer and polybutylene adipate terephthalate (PBAT) may be 5:95 to 50:50, 5:95 to 40:60, or 10:90 to 30:70.

[0067] When the polybutylene adipate terephthalate (PBAT) is contained in an excessively small amount compared to the hydroxyalkanoate-lactide copolymer, the elongation rate may decrease. When the polybutylene adipate terephthalate (PBAT) is contained in an excessively large amount compared to the hydroxyalkanoate-lactide copolymer, tensile properties such as Young's modulus and yield tensile strength may decrease.

[0068] According to another embodiment of the present invention, there is provided a biodegradable film including polybutylene adipate terephthalate (PBAT), thermoplastic starch, and polybutylene adipate terephthalate (PBAT) grafted with starch maleate.

[0069] The polybutylene adipate terephthalate, thermoplastic starch, and polybutylene adipate terephthalate grafted with maleated starch, and the weight ratio between them, etc., are the same as those described above for the biodegradable composition. Further, the biodegradable film may contain a hydroxyalkanoate-lactide copolymer, and such a hydroxyalkanoate-lactide copolymer and its molecular weight, etc., are the same as those described above for the biodegradable composition.

[0070] Also, the thermoplastic starch may be contained in an amount of 10 to 70% by weight, more specifically, 10% by weight or more, 15% by weight or more, 20% by weight or more, or 70% by weight or less, 60% by weight or less, 50% by weight or less, based on 100% by weight of the total biodegradable film. When the thermoplastic starch is contained in an excessively small amount in the biodegradable film, the biodegradation rate may become slow, and the tensile properties such as Young's modulus and yield tensile strength may decrease. When the thermoplastic starch is contained in an excessively large amount in the biodegradable film, the elongation rate may become low.

[0071] Also, the polybutylene adipate terephthalate (PBAT) grafted with maleated starch may be contained in an amount of 0.1 to 10 parts by weight, more specifically, 0.1 part by weight or more, 0.2 part by weight or more, 0.3 part by weight or more, or 10 parts by weight or less, 5 parts by weight or less, 3 parts by weight or less, based on 100 parts by weight of the biodegradable film. When the polybutylene adipate terephthalate (PBAT) grafted with maleated starch is contained in an excessively small amount in the biodegradable film, the mechanical properties are not improved. When the polybutylene adipate terephthalate (PBAT) grafted with maleated starch is contained in an excessively large amount in the biodegradable film, the melt viscosity may become excessively high and the moldability may decrease.

[0072] Also, the hydroxyalkanoate-lactide copolymer may be contained in an amount of 3 to 40% by weight, more specifically, 3% by weight or more, 5% by weight or more, 7% by weight or more, or 40% by weight or less, 35% by weight or less, 30% by weight or less, based on 100% by weight of the total of the biodegradable film. When the hydroxyalkanoate-lactide copolymer is contained in an excessively small amount in the biodegradable film, tensile properties such as Young's modulus and yield tensile strength may decrease. When the hydroxyalkanoate-lactide copolymer is contained in an excessively large amount in the biodegradable film, the elongation rate may become low.

[0073] Also, the biodegradable film according to the one embodiment may have a tensile strength measured by ASTM D882-07 of 6 MPa or more, 7 MPa or more, 8 MPa or more, 10 MPa or more, 12 MPa or more, or 6 MPa to 30 MPa.

[0074] The biodegradable film according to the one embodiment may have an elongation at break measured by ASTM D882-07 of 300% or more, 350% or more, 400% or more, 420% or more, 430% or more, 440% or more, 450% or more, or 300% to 700%.

[0075] Also, the biodegradable film may have a Young's Modulus measured by ASTM D882-07 of 50 MPa or more, 55 MPa or more, 60 MPa or more, 65 MPa or more, 70 MPa or more, 80 MPa or more, or 50 MPa to 800 MPa.

[0076] The tensile strength, elongation at break, and Young's modulus of the biodegradable film can satisfy the above-described numerical ranges for the values measured in the MD (Machine Direction) and TD (Transverse Direction).

[0077] The thickness of the biodegradable film according to the embodiment may be 10 to 300 μm, more specifically, it may be 10 μm or more, 20 μm or more, 30 μm or more, or 300 μm or less, 200 μm or less, 150 μm or less. When the thickness of the film is within the above-mentioned range, the elasticity becomes strong, the handleability is excellent, and the winding state and unwinding property of the roll can be improved.

[0078] When the film thickness is excessively thin, the tensile strength, tear strength and elongation rate deteriorate, and holes may be formed in the film or it may be torn during use. When the film thickness is excessively thick, the unit price competitiveness may be low.

[0079] The biodegradable film can be used as an agricultural mulching film, disposable gloves, medical individual wrapping paper, food wrapping paper, garbage bag or bags for various industrial products.

[0080] The manufacturing method of the biodegradable film is not particularly limited, but a melt-kneading method of melt-kneading polybutylene adipate terephthalate (PBAT), polybutylene adipate terephthalate (PBAT) grafted with maleic acid starch, thermoplastic starch and / or hydroxyalkanoate-lactide copolymer can be used, or a composition can be manufactured by uniformly mixing a solution in which each component is dissolved in a solvent and then removing the solvent.

[0081] In the case of the melt-kneading method, there is no particular limitation on the method, but ordinary mixers such as kneaders, roll mills, Banbury mixers, single-screw or twin-screw extruders can be used. During melt-kneading, the temperature of the extruder may be 150°C to 240°C, 160°C to 220°C or 170°C to 200°C.

[0082] The biodegradable film is obtained by using a composition produced by a melt-kneading method or the like and by an existing film production method such as a known inflation method, a tubular method, or a T-die casting method. For example, the composition can be pelletized, and the pellets can be dried at 60 to 100°C for 6 hours or more to control the moisture content to 1,200 ppm or less, 500 ppm or less, or 200 ppm or less. Then, the pelletized composite is applied to a release film and then put into a thermocompression bonding machine to apply pressure 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 5 MPa to 20 MPa, 8 MPa to 17 MPa, or 10 MPa to 15 MPa.

Advantages of the Invention

[0083] According to the present invention, while maintaining eco-friendliness and biodegradability, it is possible to provide a biodegradable composition and a biodegradable film containing a bio-based raw material, which are excellent in tensile properties such as tensile strength, elongation at break, and Young's modulus.

Modes for Carrying Out the Invention

[0084] The invention will be described in more detail with the following examples. However, the following examples are only illustrative of the present invention, and the content of the present invention is not limited by the following examples.

[0085] Production Example 1: Production of 3-hydroxypropionate-lactide block copolymer (1) Production of polylactic acid prepolymer 25 g of an 85% aqueous L-lactic acid solution was placed into a 100 ml Schlenk flask in an oil bath, and the pressure was reduced to 50 mbar at 70 °C for 2 hours to remove the moisture in the L-lactic acid. Then, based on 100 parts by weight of the lactate, 0.4 part by weight of p-toluenesulfonic acid (p-TSA) and 0.1 part by weight of SnCl2 catalyst were respectively added, and a melt polycondensation reaction was carried out at a temperature of 150 °C for 12 hours. After the reaction was completed, the reaction product was dissolved in chloroform and then extracted with methanol to obtain a polylactic acid prepolymer (weight average molecular weight: 8,000 g / mol).

[0086] (2) Production of poly(3-hydroxypropionate) prepolymer 25 ml of a 60% aqueous 3-hydroxypropionate solution was placed into a 100 ml Schlenk flask in an oil bath, and the pressure was reduced to 50 mbar at 50 °C for 3 hours to remove the moisture in the 3-hydroxypropionate. Then, oligomerization was carried out at 70 °C and 20 mbar for 2 hours. After that, based on 100 parts by weight of the 3-hydroxypropionate, 0.4 part by weight of p-toluenesulfonic acid (p-TSA) catalyst was added to the reaction flask, and a melt polycondensation reaction was carried out at a temperature of 110 °C for 24 hours. After the reaction was completed, the reaction product was dissolved in chloroform and then extracted with methanol to obtain a poly(3-hydroxypropionate) prepolymer (weight average molecular weight: 26,000 g / mol).

[0087] (3) Production of block copolymer The above-mentioned polylactic acid prepolymer and the above-mentioned poly(3-hydroxypropionate) prepolymer were mixed in a weight ratio of 9:1 in a 100 ml Schlenk flask in an oil bath and added so that the total content was 30 g. Then, 90 mg of p-toluenesulfonic acid (p-TSA) was added, and annealing was carried out at 60 °C for 3 hours. Then, using an evaporator, mixing was carried out at 150 °C and 0.5 mbar for 24 hours for a solid-phase polymerization reaction to produce a 3-hydroxypropionate-lactide block copolymer (weight average molecular weight: 130,000 g / mol).

[0088] On the one hand, the weight-average molecular weights of the polylactic acid prepolymer, poly(3-hydroxypropionate) prepolymer, and block copolymer were measured using gel permeation chromatography (GPC).

[0089] Production Example 2: Production of Thermoplastic Starch Based on the dry weight, 225 g of corn starch and 75 g of glycerol were mixed in a mixer and then fed into an extruder for compounding. The temperature range of the extruder was 80 to 150 °C, the screw speed was set at 150 rpm, and the extruded strand was cut by a pelletizer to produce thermoplastic starch pellets.

[0090] Production Example 3: Production of Polybutylene Adipate Terephthalate Grafted with Starch Maleate 20 g of starch and 50 mL of water were placed in a 500 mL round bottom flask (RBF) and stirred at room temperature, and then 50 mL of a 2.0 M sodium hydroxide (NaOH) solution was added. As the starch, potato starch was used. Stirring was continued for 2 hours for mixing, about 100 g of maleic anhydride was added, and the reaction was carried out at 65 °C for about 5 hours. After the reaction was completed, the temperature was lowered to room temperature, and acetone was added to form a precipitate. The precipitate was collected and dried in a vacuum drying oven at 40 °C for one day to obtain solid starch maleate.

[0091] 130 g of polybutylene adipate terephthalate, 33.5 g of starch maleate, and 0.86 g of dicumyl peroxide were sequentially placed in an internal mixer and reacted at 160 °C and 60 rpm for 30 minutes. After drying the obtained reaction product, it was pulverized and recovered using a cutting mill.

[0092] <Examples and Comparative Examples> Example 1: Production of Biodegradable Film Based on the dry weight, 75 g of polybutylene adipate terephthalate (PBAT, Solpol 1000N, SOLTECH), 25.0 g of the thermoplastic starch produced in Production Example 2, and 5.0 g of polybutylene adipate terephthalate grafted with maleic acid starch produced in Production Example 3 were hand-mixed and then put into an extruder for compounding. The temperature range of the extruder was 170 to 190 °C, the screw speed was set at 150 rpm, and the extruded strand was cut by a pelletizer to produce composite pellets. The produced composite pellets were used to produce a film with a thickness of 15 to 25 μm at 180 °C using a Film blown unit (BL50T) from Collin.

[0093] Example 2: Production of Biodegradable Film A biodegradable film was produced in the same manner as in Example 1, except that 75 g of polybutylene adipate terephthalate was replaced with 67.5 g of polybutylene adipate terephthalate and 7.5 g of the 3-hydroxypropionate-lactide block copolymer produced in Production Example 1.

[0094] Example 3: Production of Biodegradable Film A biodegradable film was produced in the same manner as in Example 1, except that 5.0 g of polybutylene adipate terephthalate grafted with maleic acid starch produced in Production Example 3 was replaced with 4.0 g of polybutylene adipate terephthalate grafted with maleic acid starch produced in Production Example 3.

[0095] Comparative Example 1: Production of Biodegradable Film A biodegradable film was produced in the same manner as in Example 1, except that polybutylene adipate terephthalate grafted with maleic acid starch was not used.

Table 1

[0096] Evaluation 1. Evaluation of Tensile Properties The tensile properties of the films of the examples and comparative examples were evaluated according to ASTM D882-07. The tensile properties include the Young's modulus, tensile strength, and elongation at break in the MD (Machine Direction) and TD (Transverse Direction), and the results are shown in Table 2 below.

[0097] [Table 2]

[0098] According to Table 2 above, Examples 1 and 2 showed excellent Young's modulus and tensile strength, etc., and it was confirmed that the Young's modulus and tensile strength, etc. were superior compared to Comparative Example 1 that did not contain polybutylene adipate terephthalate grafted with maleic acid starch. In addition, it was confirmed that Example 2 further containing a 3-hydroxypropionate-lactide block copolymer was significantly superior in terms of Young's modulus, tensile strength, etc. compared to Comparative Example 1.

Claims

1. A biodegradable composition comprising polybutylene adipate terephthalate (PBAT), thermoplastic starch, and polybutylene adipate terephthalate (PBAT) grafted with starch maleate.

2. The biodegradable composition according to claim 1, further comprising a hydroxyalkanoate-lactide copolymer.

3. The biodegradable composition according to claim 2, wherein the hydroxyalkanoate-lactide copolymer is a 3-hydroxypropionate-lactide copolymer.

4. The biodegradable composition according to claim 3, wherein the 3-hydroxypropionate-lactide copolymer is a block copolymer obtained by polymerizing a polylactic acid prepolymer and a poly(3-hydroxypropionate) prepolymer.

5. The biodegradable composition according to claim 4, wherein at least one of the polylactic acid prepolymer and the poly(3-hydroxypropionate) prepolymer has a weight average molecular weight exceeding 20,000 g / mol and not exceeding 50,000 g / mol.

6. The biodegradable composition according to claim 4, wherein the weight ratio of the polylactic acid prepolymer to the poly(3-hydroxypropionate) prepolymer is 95:5 to 50:

50.

7. The biodegradable composition according to claim 4, wherein the 3-hydroxypropionate-lactide copolymer has a total of 20 to 100 of the crystallinity of the polylactic acid block and the crystallinity of the poly(3-hydroxypropionate) block calculated by the following formulas 1 and 2. [Formula 1] Crystallinity of polylactic acid block (Xc_ ＰＬＡ ) = [(PLA Tm area) - (PLA Tcc area)] / 93.7 (In the above formula (1), the PLA Tm area is the integrated value for the peak at the melting temperature (Tm) of the polylactic acid (PLA) block in the block copolymer measured through differential scanning calorimetry analysis, and the PLA Tcc area is the integrated value for the peak at the crystallization temperature (Tcc) of the polylactic acid block in the block copolymer measured through differential scanning calorimetry analysis.) [Formula 2] Crystallinity (Xc_ of the poly(3-hydroxypropionate) block Ｐ（３ＨＰ） ) = [(P(3HP) Tm area) - (P(3HP) Tcc area)] / 64 (In the above formula (2), the P(3HP) Tm area is the integrated value for the peak at the melting temperature (Tm) of the poly(3-hydroxypropionate) (P(3HP)) block in the block copolymer measured through differential scanning calorimetry analysis, and the P(3HP) Tcc area is the integrated value for the peak at the crystallization temperature (Tcc) of the poly(3-hydroxypropionate) block in the block copolymer measured through differential scanning calorimetry analysis.)

8. The biodegradable composition according to claim 2, wherein the hydroxyalkanoate-lactide copolymer has a weight average molecular weight of 50,000 to 300,000.

9. The biodegradable composition according to claim 1, wherein the thermoplastic starch comprises one or more 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.

10. The biodegradable composition according to claim 1, wherein the weight ratio of the thermoplastic starch and polybutylene adipate terephthalate (PBAT) is 5:95 to 50:

50.

11. The biodegradable composition according to claim 2, wherein the weight ratio of the hydroxyalkanoate-lactide copolymer and polybutylene adipate terephthalate (PBAT) is 5:95 to 50:

50.

12. The biodegradable composition according to claim 1, comprising 0.1 to 10 parts by weight of polybutylene adipate terephthalate (PBAT) grafted with the starch maleate based on 100 parts by weight of the biodegradable composition.

13. A biodegradable film comprising polybutylene adipate terephthalate (PBAT), thermoplastic starch, and polybutylene adipate terephthalate (PBAT) grafted with starch maleate.

14. The biodegradable film according to claim 13, having a tensile strength of 6 MPa or more as measured by ASTM D882-07.

15. The biodegradable film according to claim 13, having an elongation at break of 300% or more as measured by ASTM D882-07.

16. The biodegradable film according to claim 13, having a Young's modulus of 50 MPa or more as measured by ASTM D882-07.

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