Biodegradable plastic having excellent processability and mechanical properties, plastic product obtained by molding same, and manufacturing method therefor

Abstract

The present invention relates to a biodegradable plastic having excellent processability and mechanical properties, a plastic product obtained by molding same, and a manufacturing method therefor, and, more specifically, to a biodegradable plastic having excellent processability and mechanical properties, a plastic product obtained by molding same, and a manufacturing method therefor, the biodegradable plastic comprising thermoplastic starch, and thus has excellent molding processability and mechanical properties and exhibits excellent biodegradability, and having an eco-friendly manufacturing process.

Description

Biodegradable plastic with excellent processability and mechanical properties, plastic products molded and processed from the same, and manufacturing method thereof

[0001] The present invention relates to a biodegradable plastic having excellent processability and mechanical properties, a plastic product obtained by molding and processing the same, and a method for manufacturing the same. Specifically, the present invention relates to a biodegradable plastic having excellent processability and mechanical properties, including thermoplastic starch, which has excellent biodegradability, and also has excellent molding and processing properties and an environmentally friendly manufacturing process, a plastic product obtained by molding and processing the same, and a method for manufacturing the same.

[0002] Plastics containing polymers are widely used in various fields due to their ease of manufacturing, wide controllability of physical properties, and ease of molding and processing. However, these plastics are virtually non-biodegradable in the natural environment, making plastic waste a major cause of environmental destruction.

[0003] Recent economic policies in major countries are prioritizing reducing carbon emissions to prevent global warming and increasing the use of renewable energy to achieve sustainable growth. International treaties are increasingly reflecting this approach. Preventing environmental destruction by recycling plastics or allowing them to decompose naturally also aligns with this trend.

[0004] Conventional biodegradable plastics have been developed primarily from polyesters, which are biodegradable under composting or soil conditions. However, the production of biodegradable polymers such as polylactic acid and polybutylene adipate terephthalate requires extracting monomers from natural polymers or using petrochemical methods, followed by biochemical conversion or polymerization. This process emits carbon, which continues to pose a burden on the environment. Therefore, research and development to reduce carbon emissions during the manufacturing process is also necessary. As a result, interest is growing in methods for manufacturing biodegradable plastics that utilize natural polymers to reduce carbon emissions during the manufacturing process.

[0005] However, natural polymers tend to have inferior mechanical properties compared to synthetic plastics and have poor processability, so there is a need to develop a method for manufacturing biodegradable plastics that can minimize the deterioration of mechanical properties while also reducing carbon emissions during the manufacturing process.

[0006] The present invention has been designed to solve the above-described technical problems, and the problem to be solved by the present invention is to provide an environmentally friendly biodegradable plastic that can be manufactured in an environmentally friendly manner by including starch, a natural polymer, and has excellent processability, and the physical properties of the manufactured plastic are also at the same level as those of existing biodegradable plastics.

[0007] Other objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments in conjunction with the accompanying drawings.

[0008] In order to solve the above-described technical problem, the present invention comprises a thermoplastic starch composition and a biodegradable polymer resin,

[0009] A biodegradable plastic satisfying the following relational expression 1 is provided.

[0010] [Relationship 1]

[0011] 0.01 ≤ FC / V ≤ 0.06

[0012] In the above relational expression 1, FC / V is obtained from the FC and V values ​​obtained according to the following measurement method.

[0013] [measurement method]

[0014] The above biodegradable plastic sample is heated to 105°C in a nitrogen atmosphere and maintained isothermally for 10 minutes (step 1) using a thermogravimetric analysis (TGA) method according to the standard of ASTM D 7582-15, and then heated a second time to 800°C while maintaining the nitrogen atmosphere and maintained isothermally at 800°C for 10 minutes (step 2), and the nitrogen atmosphere is changed to an air atmosphere and the remaining biodegradable plastic sample is burned (step 3). When the mass loss at each step is measured, the mass loss at step 2 is referred to as V, and the mass loss at step 3 is referred to as FC.

[0015] In a preferred embodiment of the present invention, the biodegradable plastic may contain a thermoplastic starch composition in an amount of 10% to 75% by weight.

[0016] In a preferred embodiment of the present invention, the thermoplastic starch composition may include starch, a plasticizer, and an additive.

[0017] In a preferred embodiment of the present invention, the additive may include a filler, an antioxidant, and a polymer derived from a natural product other than starch.

[0018] In a preferred embodiment of the present invention, the biodegradable polymer resin may include at least one selected from the group consisting of polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), and polyhydroxy alkanoates (PHAs).

[0019] In a preferred embodiment of the present invention, the biodegradable polymer resin may further include, as a compatibilizer, one or more biodegradable polymer resins selected from PLA, PBAT, PBS, and PHAs grafted with a cyclic unsaturated anhydride or an unsaturated multifunctional carboxylic acid.

[0020] In a preferred embodiment of the present invention, the biodegradable plastic may further satisfy the following relationships 2 and 3.

[0021] [Relationship 2]

[0022] 1.00(%) ≤ X c ≤ 30.00(%)

[0023] [Relationship 3]

[0024] 150 ≤ X c / (FC / V) ≤ 750

[0025] In the above relations 2 and 3, FC / V is the same as the definition in the above relation 1, and X c represents the crystallinity of the biodegradable plastic.

[0026] The present invention also provides a biodegradable plastic product manufactured by molding the biodegradable plastic.

[0027] In a preferred embodiment of the present invention, the biodegradable plastic article may be a biodegradable film or a plastic injection molded body.

[0028] The biodegradable plastic according to the present invention can be manufactured using an environmentally friendly method, exhibits excellent processability, and possesses properties suitable for practical use. Therefore, the biodegradable plastic according to the present invention can significantly reduce the environmental burden during its manufacturing and disposal processes, and can be usefully utilized in a variety of fields, including films, containers, and injection-molded articles.

[0029] Figure 1 is a graph showing the change in weight of a biodegradable plastic sample according to temperature when thermogravimetric analysis was performed on the biodegradable plastic according to a preferred embodiment of the present invention.

[0030] Figure 2 shows the XRD spectrum of a biodegradable plastic according to a preferred embodiment of the present invention (orange) and the spectrum with background noise removed through a data program (blue).

[0031] Before going into a detailed description of the composition and effects of the present invention, the meanings of terms used in this specification will be defined.

[0032] As used herein, "thermoplastic starch (TPS)" refers to starch extracted from grains such as rice, barley, soybeans, corn, sweet potatoes, and mung beans, mixed with excess water and a plasticizer at a temperature higher than the gelatinization temperature of the starch. "Thermoplastic starch composition" refers to a composition comprising starch and a plasticizer.

[0033] Hereinafter, each component of the present invention and its effects will be described in more detail.

[0034] 1. Biodegradable plastic

[0035] One embodiment of the present invention provides an environmentally friendly biodegradable plastic with improved processability by appropriately selecting a thermoplastic starch composition and a biodegradable polymer resin and combining them in a specific content.

[0036] The above biodegradable plastic satisfies the following relational expression 1, and accordingly, can have sufficient processability during production and mechanical properties suitable for use in biodegradable vinyl or various plastic products.

[0037] [Relationship 1]

[0038] 0.01 ≤ FC / V ≤ 0.06

[0039] In the above relational expression 1, FC / V is obtained from the FC and V values ​​obtained according to the following measurement method 1.

[0040] [Measurement Method 1]

[0041] The above biodegradable plastic sample is heated to 105°C in a nitrogen atmosphere using a thermogravimetric analysis (TGA) method according to the standard of ASTM D 7582-15, and isothermally maintained for 10 minutes (step 1), heated a second time to 800°C while maintaining the nitrogen atmosphere, and isothermally maintained at 800°C for 10 minutes (step 2), and the nitrogen atmosphere is changed to an air atmosphere and the remaining biodegradable plastic sample is burned (step 3). When the mass loss at each step is measured, the mass loss at step 2 is referred to as V, and the mass loss at step 3 is referred to as FC.

[0042] The above relational equation 1 is an analysis of biodegradable plastics using the proximate analysis method used to evaluate and understand the composition of biodegradable plastics, and is numerically expressed to enable understanding of the chemical properties of biodegradable plastics.

[0043] Figure 1 shows a curve obtained by analyzing a biodegradable plastic with a thermogravimetric analyzer according to the above measurement method 1. Referring to Figure 1, the rapid weight loss around 105℃ corresponds to the first step of the above measurement method, and the reduced weight corresponds to the weight of residual water. This is because the water evaporates as the temperature of the sample rises above 100℃, the boiling point of water, and the weight decreases by that amount. In addition, the weight of the sample continuously decreases as the temperature rises to approximately 800℃, which corresponds to the second step of the above measurement method, and the weight decreased up to 800℃ corresponds to the weight V of volatile matter contained in the entire plastic sample. If the weight does not decrease further even after maintaining the isotherm at 800℃ for 10 minutes, most of the volatile matter has been removed, and therefore, in the third step, the sample is switched to an air atmosphere and the remaining residue is burned to cause the weight loss at 800℃. The weight reduction according to the 3rd step is the weight (FC) corresponding to fixed carbon, and the FC / V in the above relational expression 1 is related to the FC / V value obtained by thermogravimetric analysis of a biodegradable plastic sample through this process.

[0044] If the FC / V value is less than 0.01, the content of the thermoplastic starch composition becomes excessively low, and the melt flow index (MFI) increases, which improves injection moldability and processability, but there is a problem that the elongation of the manufactured biodegradable plastic decreases. On the other hand, if the FC / V value exceeds 0.06, the content of the thermoplastic starch composition becomes excessive, and the melt flow index decreases, which may cause a problem that the product molding processability is poor.

[0045] In addition, a biodegradable plastic according to a preferred embodiment of the present invention may further satisfy the following relationships 2 and 3.

[0046] [Relationship 2]

[0047] 1.00(%) ≤ X c ≤ 30.00(%)

[0048] [Relationship 3]

[0049] 150 ≤ X c / (FC / V) ≤ 750

[0050] In the above relations 2 and 3, FC / V is the same as the definition in the above relation 1, and X c represents the crystallinity of the biodegradable plastic.

[0051] The crystallinity of the biodegradable plastic according to the above equations 2 and 3 can be measured by the following measurement method 2.

[0052] [Measurement Method 2]

[0053] The XRD spectrum of the above biodegradable plastic sample is obtained in the range of 10˚ to 40˚ 2θ, and background noise is removed from it. The ratio of the peak area corresponding to the crystal region among the total area of ​​the XRD spectrum from which the background noise has been removed (X c ) to obtain the degree of crystallinity.

[0054] If the crystallinity according to Equation 2 is less than 1.00%, the melt flow index of the biodegradable plastic may become excessively high and the elongation may become low. Conversely, if it exceeds 30.00%, the tensile strength and elastic modulus may become excessively low.

[0055] In a preferred embodiment of the present invention, the biodegradable plastic may contain a thermoplastic starch composition in an amount of 10 to 75 wt%. If the amount of the thermoplastic starch composition is less than 10 wt%, there is no significant effect in reducing carbon emissions during the manufacturing process, and there is a problem that the elongation of the biodegradable plastic decreases. On the other hand, if the amount of the thermoplastic starch composition exceeds 75 wt%, the melt flow index of the biodegradable plastic may decrease, resulting in poor molding processability, and the mechanical properties of the biodegradable plastic, such as tensile strength and elastic modulus, may deteriorate.

[0056] Preferably, when the biodegradable plastic is to be manufactured into a plastic product such as a packaging material, wrap, or coating film by manufacturing the biodegradable plastic into a biodegradable film having excellent elongation, the thermoplastic starch composition may be included in an amount of 30 wt% to 75 wt% based on the total weight of the biodegradable plastic.

[0057] In addition, when the biodegradable plastic is preferably manufactured into an injection molded article having high tensile strength or elastic modulus and used as a structure utilizing strength, the thermoplastic starch composition may be included in an amount of 10 wt% to 40 wt% based on the total weight of the biodegradable plastic.

[0058] The biodegradable plastic according to the present invention can be manufactured by compounding and extruding the above-described raw materials, the thermoplastic starch composition, and the biodegradable polymer resin, and cutting them into pellets or chips. The biodegradable plastic can be manufactured into a desired shaped article through post-processing, and has the advantage of excellent processability during post-processing.

[0059] A two-step extrusion process or a one-step extrusion process can be used to manufacture biodegradable plastics using the above raw materials. The two-step extrusion process is a method performed by two extrusions. Specifically, by physically mixing starch and a plasticizer with optional additives using a mixer, a thermoplastic starch composition is formed, which is first extruded and pelletized through a twin-screw extruder to manufacture thermoplastic starch pellets. Secondarily, the thermoplastic starch pellets are mixed with the biodegradable polymer resin (including a compatibilizer), compounded and extruded again through a twin-screw extruder, and pelletized to manufacture a biodegradable plastic.

[0060] The 1-step extrusion process is a method of manufacturing a biodegradable plastic by simultaneously feeding a thermoplastic starch composition and a biodegradable polymer resin into a twin-screw extruder, compounding, and extruding the mixture, without extruding the thermoplastic starch composition to manufacture thermoplastic starch pellets. The 1-step extrusion process can manufacture a biodegradable plastic with just one extrusion.

[0061] 2. Thermoplastic starch composition

[0062] The biodegradable plastic according to the present invention comprises a thermoplastic starch composition, enabling the raw material for the biodegradable plastic to be obtained from natural materials such as grains, thereby reducing carbon emissions during the manufacturing process. Furthermore, the inclusion of a thermoplastic starch composition in the biodegradable plastic enhances its elongation, thereby increasing its usability as a material requiring flexibility.

[0063] In a preferred embodiment of the present invention, the thermoplastic starch composition may include starch, a plasticizer, and an additive.

[0064] starch

[0065] In a preferred embodiment of the present invention, the thermoplastic starch composition may contain starch in an amount of 50 to 70 wt%. Sources of starch include, but are not limited to, corn (Zea mays L.), cassava (Manihot esculenta), potato (Solanum tuberosum), sweet potato (Ipomoea batatas), mung bean (Vigna radiata), rice (Oryza sativa), barley (Hordeum vulgare), and wheat (Hordeum vulgare). Alternatively, the starch source may be a by-product from the food industry.

[0066] Depending on the type of starch source, the ratio of amylose to amylopectin can vary. When the amylose ratio is high, biodegradable plastics tend to have lower elongation and higher tensile strength and elastic modulus. Conversely, when the amylopectin ratio is high, biodegradable plastics can be produced with higher elongation at the expense of lower tensile strength and elastic modulus. Furthermore, when storing manufactured biodegradable plastics with a high amylopectin ratio, the degree of deterioration in physical properties is greater due to the absorption of moisture from the air.

[0067] Typically, starch contains amylose and amylopectin in a weight ratio of 20:80 to 30:70. Preferably, starch containing 25 to 30 wt% of amylose can be used.

[0068] If the starch content is less than 50 wt% of the thermoplastic starch composition, there may be a problem of deterioration in the mechanical properties of the manufactured biodegradable plastic, and if it exceeds 70 wt%, there may be a problem of deterioration in the molding processability of the biodegradable plastic.

[0069] plasticizer

[0070] Plasticizers are added to improve the processability of starch. Insufficient plasticizer content can make it difficult to shape the biodegradable plastic into the desired shape. Conversely, excessive plasticizer content can deteriorate the mechanical properties of the resulting biodegradable plastic.

[0071] In a preferred embodiment of the present invention, the plasticizer may be included in an amount of 20% to 35% by weight relative to the total weight of the thermoplastic starch composition.

[0072] The plasticizer may be one or more selected from among short-chain lipid polyhydric alcohols such as glycerol, polyalcohols such as polyethylene glycol (weight average molecular weight 400 g / mol to 4,000 g / mol), citric acid or its ester compounds, urea, and hexose compounds. An example of a hexose compound is sorbitol. However, it is not necessary to select from these, and it may be selected from among biodegradable polyhydric alcohols or water-soluble compounds. Preferably, glycerol can be used as the plasticizer, and specifically, a plasticizer with high compatibility can be selected and used depending on the type of starch. Depending on the type of plasticizer, the thermoplastic starch-containing biodegradable plastic manufactured can flexibly control its physical properties such as tensile strength and elongation, and can be provided with functionality such as hydrophobicity, so that it can be selected according to the purpose.

[0073] additives

[0074] Additives may be added to enhance the physical properties of biodegradable plastics or prevent long-term deterioration of their properties. Specifically, the additives may be included in an amount of 15 wt% or less based on the total weight of the thermoplastic starch composition. If the amount of the additive exceeds 15 wt% of the total weight of the thermoplastic starch composition, the processability, biodegradability, and mechanical properties of the biodegradable plastic may deteriorate.

[0075] In a preferred embodiment of the present invention, the additive may include a filler, an antioxidant, and a polymer derived from a natural product other than starch.

[0076] The filler may preferably be talc, calcium carbonate (CaCO3), or titanium dioxide (TiO2). The filler prevents the deterioration of the physical properties of the biodegradable plastic and reduces the cost. In addition, by including such a filler, the color of the biodegradable plastic can be made white, thereby improving dyeability. The filler may be included in an amount of preferably 15 wt% or less relative to the total weight of the thermoplastic starch composition. If the filler content exceeds 15 wt%, the mechanical properties of the manufactured biodegradable plastic may deteriorate.

[0077] Additionally, the additive may preferably further include an antioxidant. The antioxidant may be added to prevent the starch in the biodegradable plastic from carbonizing and discoloring during high-temperature processing, or from decomposing the polymer of the starch and reducing its molecular weight. Specifically, the antioxidant inhibits starch oxidation and prevents discoloration by reacting with free radicals within the biodegradable plastic generated by heat, shear, etc. The antioxidant may preferably include a primary antioxidant and a secondary antioxidant.

[0078] The above primary antioxidant is a heat stabilizer that reacts with free radicals generated by heat, shear, etc. instead of the starch polymer to prevent oxidation of the starch. A radical initiator can be used as the above primary antioxidant. Preferably, a phenol-based or amine-based radical initiator can be used.

[0079] In addition, the secondary antioxidant functions to prevent further oxidation of starch by decomposing radicals, specifically peroxides, generated by heat or shear. Preferably, at least one selected from sulfur-based and phosphorus-based antioxidants may be used as the secondary antioxidant.

[0080] The thermoplastic starch composition of the present invention can more effectively prevent oxidation of starch due to heat or shear by simultaneously using a primary antioxidant and a secondary antioxidant.

[0081] The above antioxidant may be included in an amount of 2,000 ppm or less relative to the total weight of the thermoplastic starch composition. Specifically, the primary antioxidant may be included in an amount of 1,000 ppm or less, and the secondary antioxidant may be included in an amount of 1,000 ppm or less. Since the secondary antioxidant functions to prevent further oxidation, it is useless to exceed the amount of the primary antioxidant. If the amount of the primary antioxidant exceeds 1,000 ppm, the mechanical properties of the biodegradable plastic may deteriorate and the appearance may deteriorate.

[0082] Additionally, the additive may preferably further include a naturally derived polymer other than starch. These are added to increase compatibility with biodegradable polymer resins or improve the mechanical properties of biodegradable plastics. Since they are naturally derived, they can alter the properties of biodegradable plastics containing thermoplastic starch compositions while minimizing environmental impact.

[0083] The above natural polymer may preferably include one or more polymers selected from the group consisting of natural polymers excluding starch, such as alginic acid, carrageenan, maltodextrin, cyclodextrin, carboxymethyl cellulose, pectin, chitin, xanthan gum, casein, and whey, but is not limited thereto, and may be selected from natural polysaccharides.

[0084] According to a preferred embodiment of the present invention, the term "thermoplastic starch composition" refers to a composition in which starch, a plasticizer, and optionally, additives are mixed in a mixer and physically mixed together. In addition, the term "thermoplastic starch pellet" refers to a thermoplastic starch composition extruded through a twin screw extruder and cut into pellets.

[0085] 2. Biodegradable polymer resin

[0086] biodegradable polymer resin

[0087] In a preferred embodiment of the present invention, the biodegradable polymer resin may include at least one selected from the group consisting of polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), and polyhydroxy alkanoates (PHAs).

[0088] Here, the polyhydroxyalkanoate may be derived from an alkanoate ester such as a hydroxyalkanoate having 3 to 8 carbon atoms, i.e., hydroxy propionate, hydroxy butanoate, hydroxy pentanoate, hydroxy hexanoate, hydroxy heptanoate, and hydroxy octanoate.

[0089] Among these, polylactic acid is preferably added to biodegradable plastics for manufacturing molded products requiring strength, such as vessels and injection-molded products. Furthermore, polylactic acid is advantageous over other resins in terms of manufacturing cost and exhibits excellent compatibility with thermoplastic starch compositions, making it a desirable raw material.

[0090] Biodegradable plastics using polybutylene adipate terephthalate (PAT) exhibit excellent elongation, making it a suitable choice as a biodegradable polymer resin, the primary raw material for biodegradable film production. To enhance the elastic modulus of biodegradable films, polylactic acid or polybutylene succinate can be added in addition to PAT.

[0091] commercialization agent

[0092] In a preferred embodiment of the present invention, the biodegradable polymer resin may further include one or more biodegradable polymer resins selected from polylactic acid, polybutylene adipate terephthalate, polybutylene succinate, and polyhydroxyalkanoate grafted with a cyclic unsaturated anhydride or an unsaturated multifunctional carboxylic acid as a compatibilizer.

[0093] The compatibilizer serves to improve compatibility between the biodegradable polymer resin and the thermoplastic starch composition, and the cyclic unsaturated anhydride may preferably be succinic anhydride, and the unsaturated polyfunctional carboxylic acid may be succinic acid.

[0094] The biodegradable polymer resin may preferably contain the compatibilizer in an amount of 1 to 5 wt%. If the content of the compatibilizer is less than 1 wt%, compatibility between the thermoplastic starch composition and the biodegradable polymer resin may be poor, resulting in poor quality of the manufactured biodegradable polymer. In addition, if the content of the compatibilizer exceeds 5 wt%, the physical properties of the manufactured biodegradable polymer may be affected, resulting in problems such as deterioration in mechanical properties.

[0095] 3. Biodegradable plastic products

[0096] The present invention also provides a biodegradable plastic product manufactured by molding the biodegradable plastic.

[0097] Molding can preferably be accomplished by extrusion or injection molding. Extrusion is a molding method that continuously extrudes a certain shape from an extruder, while injection molding refers to molding a single product of a certain shape by injecting extruded molten plastic into a mold (or die). Specifically, the biodegradable plastic product can be manufactured by molding the biodegradable plastic manufactured in the form of pellets or chips through a post-processing process.

[0098] In a preferred embodiment of the present invention, the biodegradable plastic article may be a biodegradable film or a plastic injection molded body.

[0099] Since biodegradable films have important mechanical properties such as flexibility and elongation, polybutylene adipate terephthalate is preferably selected as the biodegradable polymer resin. The plastic injection molded article requires high strength, such as containers and structures. For the biodegradable plastic used in the plastic injection molded article, polylactic acid is preferably selected as the biodegradable polymer resin. In each case, a small amount of other biodegradable polymers may be added for functionality.

[0100] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, this is merely an example, and the scope of the present invention is not limited by the following contents.

[0101] <Example>

[0102] Example 1: Biodegradable plastic - thermoplastic starch composition and polylactic acid

[0103] 67 wt% of corn starch was mixed with 33 wt% of glycerin as a plasticizer, and 10 wt% of calcium carbonate and 2,000 ppm of antioxidant were further mixed based on the weight of the mixture. This mixture was fed into a twin-screw extruder, and first extruded and molded, and then cut into an appropriate size to produce thermoplastic starch pellets.

[0104] In addition, a biodegradable polymer resin was obtained by mixing 5 wt% of maleic acid grafted polylactic acid as a compatibilizer into a polylactic acid (weight average molecular weight: 150,000 g / mol) resin. The biodegradable polymer resin containing the polylactic acid and the thermoplastic starch pellets were simultaneously fed into a twin-screw extruder, and the twin-screw extruder was operated to perform compounding, secondary extrusion, and molding at a temperature of about 170°C to obtain a biodegradable plastic.

[0105] The mixing weight ratio of the thermoplastic starch pellets and the biodegradable polymer resin was adjusted as shown in Examples 1a to 1f of Table 1 below.

[0106] In Table 1, the TPS content refers to the weight ratio of the thermoplastic starch composition added to the biodegradable plastic in the form of the thermoplastic starch pellets.

[0107] Example 2: Biodegradable plastic - thermoplastic starch composition and polybutylene adipate terephthalate

[0108] The same procedure as in Example 1 was followed, but the biodegradable polymer resin was changed from polylactic acid to polybutylene adipate terephthalate, the compatibilizer was also maleic acid grafted polybutylene adipate terephthalate, and the biodegradable polymer resin contained the compatibilizer at 5 wt%, the same as in Example 1.

[0109] In addition, the weight ratio between TPS and biodegradable polymer resin was as shown in Examples 2a to 2f in Table 1 below.

[0110] Example 3: Biodegradable plastics - thermoplastic starch composition, polybutylene adipate terephthalate and polylactic acid

[0111] The same procedure as in Example 1 was followed, but the biodegradable polymer resin was changed to a mixture of polylactic acid and polybutylene adipate terephthalate, and the compatibilizer was also a mixture of maleic acid grafted polybutylene adipate terephthalate and maleic acid grafted polylactic acid. The amount of the maleic acid compatibilizer included in the biodegradable polymer resin was 5 wt%, the same as in Examples 1 and 2.

[0112] The weight ratios of TPS, PLA, and PBAT contained in the biodegradable plastic were as shown in Examples 3a to 3f in Table 1 below.

[0113] Comparative Example 1: Biodegradable Plastic - Thermoplastic Starch Composition

[0114] The same procedure as Example 1 was followed, but a biodegradable plastic was manufactured by extruding and molding only a thermoplastic starch composition without using the above biodegradable polymer resin.

[0115] Comparative Example 2: Biodegradable Plastic - Polylactic Acid

[0116] The same procedure as in Example 1 was followed, but only polylactic acid was extruded and molded, excluding the TPS and the maleic acid grafted polylactic acid as a commercializing agent, to produce a biodegradable plastic according to the prior art.

[0117] Composition (wt%) FC / V ― X c - X c / (FC / V)Tensile strength(MPa)Elongation(%)Elastic modulus(MPa)MFI(g / min)Biodegradability(%)Example 1aTPS 5PLA 950.008 ― 1.16 ― 145.068.781.692838.019.8365Example 1bTPS 10PLA 900.014 ― 2.48 ― 172.461.483.742825.274.6272Example 1cTPS 20PLA 800.017 ― 3.39 ― 195.746.774.372333.934.2579Example 1dTPS 30PLA 700.026 ― 6.15 ― 232.837.454.741787.553.8684Example 1eTPS 50PLA 500.056 ― 8.64 ― 155.523.026.94970.252.7792Example 1fTPS 70PLA 300.061 ― 11.17 ― 183.115.857.18656.890.8796Example 1gTPS 80PLA 200.068 ― 13.63 ― 200.411.227.41570.380.3398Example 2aTPS 5PBAT 950.012 ― 3.34 ― 278.333.61886.34115.2423.8476Example 2bTPS 10PBAT 900.034 ― 15.01 ― 444.131.05832.88110.7015.283Example 2cTPS 20PBAT 800.033 ― 18.37 ― 559.532.15937.45102.7314.386Example 2dTPS 30PBAT 700.030 ― 22.76 ― 748.726.81810.0689.327.6194Example 2eTPS 50PBAT 500.042 ― 24.30 ― 585.118.56624.2578.614.4397Example 2fTPS 70PBAT 300.038 ― 29.61 ― 779.213.28596.3667.983.9498Example 2gTPS 80PBAT 200.047 ― 33.04 ― 703.012.06534.4862.712.3598Example 3aTPS 5PLA 90PBAT 50.001 ― 0.93 ― 931.957.62159.322571.415.5873Example 3bTPS 20PLA 60PBAT 200.011 ― 8.21 ― 718.133.91156.641607.17.9282Example 3cTPS 20PLA 40PBAT 400.026 ― 15.45 ― 590.527.89186.151050.064.4988Example 3dTPS 20PLA 20PBAT 600.030 ― 16.91 ― 559.615.79362.07636.584.9789Example 3eTPS 30PLA 10PBAT 600.029 ― 17.54 ― 612.017.38490.07162.514.5692Example 3fTPS 30PLA 20PBAT 500.030 ― 17.15 ― 562.4221.39217.27112.314.0993Example 3gTPS 70PLA 15PBAT 150.053 ― 17.36 ― 327.613.03338.16151.363.6396Example 3hTPS 80PLA 10PBAT 100.062 ― 19.02 ― 306.810.37259.0678.902.6398Comparative Example 1TPS 1000.068 ― 13.87 ― 204.255.8787.7354.0056.8699Comparative Example 2PLA 1000.001 ― 0.89 ― 883.772.401.44119.7826.9660.

[0118] <Experimental Example>

[0119] Experimental Example 1: Thermogravimetric Analysis

[0120] Samples of biodegradable plastics manufactured according to each of the examples and comparative examples shown in Table 1 above were taken in an amount of approximately 10 mg and analyzed using a thermogravimetric analyzer as follows. The test method was based on ASTM D7582-15.

[0121] Step 1: Set to a nitrogen environment, load about 10 mg of each sample into a thermogravimetric analyzer, heat up to about 105°C at a rate of 5°C / min, and when it reached 105°C, maintain it under isothermal conditions for about 10 minutes to evaporate and remove moisture.

[0122] Step 2: When moisture has been sufficiently removed and the weight no longer changes, the temperature is increased at a rate of approximately 10°C / min while maintaining a nitrogen atmosphere until the sample temperature reaches 800°C. Once the temperature reaches 800°C, the temperature is maintained isothermally for approximately 10 minutes while maintaining a nitrogen atmosphere to remove volatile components.

[0123] Step 3: After leaving it for about 10 minutes to ensure that the volatile components were sufficiently removed, the temperature was maintained and the atmosphere was changed from nitrogen to air to ensure that all remaining carbon components were burned.

[0124] The mass lost in step 2 is the mass of the volatile component, V (Volatile Matter), and the mass lost in step 3 is FC (Fix Carbon), and the calculated FC / V values ​​are shown in Table 1 above.

[0125] Experimental Example 2: XRD Spectrum Analysis - Crystallinity Measurement

[0126] Additionally, X-ray diffraction experiments were performed on each sample to obtain its spectrum. Since the obtained XRD spectrum contained a lot of noise signals, background signals were removed using a data processing program from Rigaku.

[0127] Using the above data program, the crystallinity (X) is calculated by calculating the area ratio (%) of the crystal peak signal to the total graph area in the corrected XRD spectrum. c ) value was obtained. Obtained X c The values ​​are shown in Table 1 above.

[0128] Experimental Example 3: Measurement of tensile strength, elongation, and elastic modulus

[0129] Biodegradable plastics according to the examples and comparative examples in Table 1 were each molded into dumbbell-shaped specimens according to the ASTM D638 standard. Each specimen was stretched until it broke using a tensile strength and elongation measuring tester, and the elastic modulus during elastic behavior and the tensile strength and elongation at the time of specimen breakage were measured, respectively, and are shown in Table 1 above.

[0130] Experimental Example 4: Melt Flow Index Measurement

[0131] The melt flow index of biodegradable plastics according to the examples and comparative examples in Table 1 was measured according to the standards of ISO 1133 or ASTM D1238. Specifically, each plastic was molded into pellets or granules and placed in the cylinder of a melt flow index measuring device (Hanatek MFI tester), heated to a temperature of approximately 180°C, a load of 2.16 g was applied to the cylinder, and the weight of the resin discharged through the die (diameter of approximately 2.09 mm) was measured to calculate the melt flow index (MFI). The values ​​are respectively shown in Table 1 above.

[0132] Experimental Example 5: Biodegradability Evaluation

[0133] The biodegradability of biodegradable plastics according to the examples and comparative examples in Table 1 was evaluated using the evaluation method below.

[0134] The biodegradability of each biodegradable plastic sample was measured according to the KS M ISO 14855-1 standard. Specifically, each sample was placed under industrial composting conditions and allowed to biodegrade for 45 days, and the amount of carbon dioxide generated from each sample was measured. The measured carbon dioxide emission was expressed as a percentage of the theoretical carbon dioxide emission, and is presented as aerobic biodegradability (%) in Table 1.

[0135] Referring to Table 1 above, it can be seen that the biodegradable plastic of Comparative Example 1, which was manufactured using only a thermoplastic starch composition, has very low tensile strength and elastic modulus, while its melt flow index is excessively high. Therefore, it can be seen that Comparative Example 1 is not suitable for use as a structure that utilizes mechanical properties. Comparative Example 2, which used only PLA and excluded a thermoplastic starch composition, had a very low FC / V value, indicating that it lacked volatile components and thus had an excessive melt flow index. In addition, the biodegradable plastic of Comparative Example 2 was found to have properties that are not suitable for use as a film due to its low elongation.

[0136] Comparing Examples 1a to 1f, 2a to 2f, and 3a to 3g, it was found that the Examples using PLA had higher tensile strength and elastic modulus but lower elongation than the Examples using PBAT, making them suitable for use in applications requiring strength rather than biodegradable films. Conversely, it was found that the Examples using PBAT had higher elongation and relatively lower tensile strength and elastic modulus, making them suitable for use in biodegradable films requiring flexibility.

[0137] Referring to Examples 1a, 1f, 2a, 2f, 3a and 3g, it was found that in Examples 1a, 2a and 3a, where the weight ratio of the thermoplastic starch composition was low, the crystallinity of the plastic was significantly low or the melt flow index was excessively high, resulting in poor processability or inferior mechanical properties. On the contrary, in Examples 1f, 2f and 3g, where the weight ratio of the thermoplastic starch composition was excessive, it was found that the crystallinity of the plastic was excessively high, and the mechanical properties and elastic modulus were poor. In addition, it was found that the biodegradability of the biodegradable plastic increased proportionally as the weight ratio of the thermoplastic starch composition increased.

Claims

1. Containing a thermoplastic starch composition and a biodegradable polymer resin, Biodegradable plastic satisfying the following relation 1: [Relationship 1] 0.01 ≤ FC / V ≤ 0.06 In the above relational expression 1, FC / V is obtained from the FC and V values ​​obtained according to the following measurement method 1: [Measurement Method 1] The above biodegradable plastic sample is heated to 105°C in a nitrogen atmosphere and maintained isothermally for 10 minutes (step 1) using a thermogravimetric analysis (TGA) method according to the standard of ASTM D 7582-15, and then heated a second time to 800°C while maintaining the nitrogen atmosphere and maintained isothermally at 800°C for 10 minutes (step 2), and the nitrogen atmosphere is changed to an air atmosphere and the remaining biodegradable plastic sample is burned (step 3). When the mass loss at each step is measured, the mass loss at step 2 is referred to as V, and the mass loss at step 3 is referred to as FC.

2. In paragraph 1, A biodegradable plastic comprising a thermoplastic starch composition in an amount of 10% to 75% by weight.

3. In paragraph 2, A biodegradable plastic, wherein the thermoplastic starch composition comprises starch, a plasticizer and an additive.

4. In paragraph 3, A biodegradable plastic, wherein the additives include fillers, antioxidants, and polymers derived from natural materials other than starch.

5. In paragraph 1, A biodegradable plastic, wherein the biodegradable polymer resin comprises at least one selected from the group consisting of polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), and polyhydroxy alkanoates (PHAs).

6. In paragraph 1, The above biodegradable polymer resin is a commercializing agent, A biodegradable plastic further comprising one or more biodegradable polymer resins selected from PLA, PBAT, PBS and PHAs grafted with a cyclic unsaturated anhydride or an unsaturated multifunctional carboxylic acid.

7. In paragraph 1, The above biodegradable plastic further satisfies the following relationships 2 and 3: [Relationship 2] 1.00(%) ≤ X c ≤ 30.00(%) [Relationship 3] 150 ≤ X c / (FC / V) ≤ 750 In the above relations 2 and 3, FC / V is the same as the definition in the above relation 1, and X c represents the crystallinity of the biodegradable plastic.

8. A biodegradable plastic product manufactured by molding a biodegradable plastic according to any one of paragraphs 1 to 7.

9. In paragraph 8, The above biodegradable plastic article is a biodegradable film.

10. In paragraph 8, The above biodegradable plastic article is a plastic injection molded article.

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