WO2022173073A1 - Thermoplastic starch composition, method for preparing same, and uses thereof - Google Patents

Abstract

An example of the present invention provides a thermoplastic starch composition comprising starch, a plasticizer, a compatibilizer, a biodegradable polymer, and a reaction initiator. The thermoplastic starch composition according to the present invention exists in a state in which starch and a biodegradable polymer are chemically bonded by a graft reaction mediated by a compatibilizer. A biodegradable film can be produced when the biodegradable composition in which the thermoplastic starch composition and the biodegradable polymer are uniformly mixed is extruded, and the produced biodegradable film has excellent mechanical strength and low hygroscopicity. Accordingly, the biodegradable film produced by using the thermoplastic starch composition according to the present invention as a basic raw material may be used in various fields such as disposable bags, disposable packaging materials, mulching films, etc.

Description

Thermoplastic starch composition, preparation method thereof and use thereof

The present invention relates to a thermoplastic starch composition and the like, and more particularly, to a thermoplastic starch composition that can be added as a component of a biodegradable composition for producing a biodegradable film to provide excellent mechanical strength and improved hygroscopicity to a biodegradable film, and the It relates to a manufacturing method and uses thereof.

Plastics are light, easy to process, mass-produced, and have excellent durability, chemical resistance, and mechanical properties, so they have been used as an essential material in real life. However, as the severity of environmental pollution is increasing worldwide and plastic waste, particularly disposable waste, has emerged as a major cause of environmental pollution, the application and development of biodegradable resins to disposable products is being actively performed. In particular, biodegradable resin is spotlighted as an eco-friendly resin because carbon dioxide emissions are relatively low when biodegradable film is produced using biodegradable resin compared to when plastic film is produced using petroleum. Moreover, as biodegradable resin is an infinite resource that can be produced continuously, there is no concern about resource depletion compared to petroleum-based resin, so the use of products using it is greatly expanded every year.

In general, the biodegradable film is a biodegradable composition in which starch is mixed with a vinyl polymer or polylactic acid (PLA), butylene adipate-terephthalate copolymer [Poly (butylene adipate-co-terephtalate), PBAT], etc. It is manufactured by extruding a biodegradable composition in which a biopolyester-based biodegradable polymer and starch are mixed. However, in the case of a biodegradable film to which starch is applied, the amount of starch added is limited due to the deterioration of hydrophilicity and processability peculiar to starch. For example, a biodegradable film prepared from a biodegradable composition in which starch is mixed with a vinyl polymer has a problem of poor biodegradability. In addition, the biodegradable film prepared from the biodegradable composition mixed with the bio-polyester-based biodegradable polymer and starch is expensive, as well as the mechanical strength is weak compared to conventional plastic products, so it is easily torn and has high hygroscopicity. In this case, it is subject to various restrictions such as stickiness.

In order to provide thermoplasticity to starch while improving the above problems, a method using glycerin, sorbitol, and glucose together with water as a plasticizer of starch (USP 3,949,145, EP 32802A1) has been proposed. In addition, a method of manufacturing starch into thermoplastic starch by a separate apparatus and process and compounding it with a biodegradable resin (Korea Patent Registration No. 10-0339789) or an aliphatic polyester resin with excellent biodegradability and starch as main components and a method of manufacturing by adding a starch plasticizer, etc. (Korea Patent Registration No. 10-0465980) has been proposed.

The present invention has been derived under the prior technical background, and an object of the present invention is a thermoplastic starch that can be added as a component of a biodegradable composition for producing a biodegradable film to provide excellent mechanical strength and improved hygroscopicity to the biodegradable film To provide a composition and a method for preparing the same.

Another object of the present invention is to provide a biodegradable composition for use in film molding as the use of the thermoplastic starch composition.

Another object of the present invention is to provide a biodegradable film as a use of the thermoplastic starch composition.

In order to solve the above object, an embodiment of the present invention provides a thermoplastic starch composition comprising a starch, a plasticizer, a compatibilizer, a biodegradable polymer, and a reaction initiator. In the thermoplastic starch composition according to an embodiment of the present invention, the starch and the biodegradable polymer exist in a chemically bonded state by a graft reaction mediated by a compatibilizer.

The type of starch, which is one component of the thermoplastic starch composition, is not particularly limited, and for example, corn starch, waxy corn starch, potato starch, sweet potato starch, wheat starch, rice starch, tapioca starch, and sago starch. ), sorghum starch or high amylose starch, and preferably corn starch in consideration of film formability, film properties, or economic feasibility, which will be described later.

The plasticizer, which is one component of the thermoplastic starch composition, is a component for improving the processability of starch or biodegradable polymer, and may be selected from various known biodegradable or eco-friendly components. For example, the plasticizer is polyhydric alcohol, triethyl citrate, acetyl triethyl citrate, tributyl citrate, acetyl tributyl citrate, It may be selected from glycerin diacetate, etc., and in consideration of the mechanical strength or hygroscopicity of the film to be described later, it is preferably composed of one or more polyhydric alcohols selected from sorbitol, ethylene glycol, glycerin, or pentaerythritol, More preferably, it is glycerin.

A compatibilizer, which is one component of the thermoplastic starch composition, is a component for improving miscibility between the starch and the biodegradable polymer. In the present invention, the compatibilizer is a reactive compatibilizer capable of forming an ester bond by reacting with a hydroxyl group (-OH) present in starch and a hydroxyl group (-OH) present in a biodegradable resin. , unsaturated dicarboxylic acid, unsaturated dicarboxylic acid anhydride, styrene-unsaturated dicarboxylic acid copolymer, or styrene-unsaturated dicarboxylic acid anhydride copolymer may be composed of at least one selected from the group consisting of. In the present invention, the compatibilizer is preferably a first compatibilizer selected from unsaturated dicarboxylic acid or anhydrous unsaturated dicarboxylic acid in consideration of mechanical strength or hygroscopicity of the film, which will be described later, and a styrene-unsaturated dicarboxylic acid copolymer. copolymers or combinations of second compatibilizing agents selected from styrene-anhydride unsaturated dicarboxylic acid copolymers. In the present invention, when the compatibilizer is composed of a combination of the first compatibilizer and the second compatibilizer, the starch and biodegradable polymer constituting the thermoplastic starch composition are chemically synthesized by a graft reaction mediated by the first compatibilizing agent or the second compatibilizing agent. exists in a bound state. The first compatibilizing agent is, for example, maleic acid, fumaric acid, acetylenedicarboxylic acid, glutaconic acid, 2-decenedioic acid acid), Traumatic acid, Muconic acid, Glutinic acid, Citraconic acid, Mesaconic acid, Itaconic acid, maleic anhydride (Maleic anhydride), Fumaric anhydride, Acetylenedicarboxylic anhydride, Glutaconic anhydride, 2-Decenedioic anhydride, Traumatic anhydride ( Traumatic anhydride), muconic anhydride, Glutinic anhydride, Citraconic anhydride, Mesaconic anhydride, or Itaconic anhydride Maleic anhydride is preferable in consideration of compatibility with other components constituting the thermoplastic starch composition and mechanical strength or hygroscopicity of the film to be described later. In addition, the second compatibilizing agent is, for example, a styrene-maleic acid copolymer [Poly (Styrene-co-Maleic acid)], a styrene-fumaric acid copolymer [Poly (Styrene-co-Fumaric acid)], styrene-acetylenedi Carboxylic acid copolymer [Poly(Styrene-co-Acetylenedicarboxylic acid)], styrene-glutaconic acid copolymer [Poly(Styrene-co-Glutaconic acid)], styrene-2-decenedioic acid copolymer [Poly(Styrene) -co-2-Decenedioic acid)], styrene-traumatic acid copolymer [Poly(Styrene-co-Traumatic acid)], styrene-muconic acid copolymer [Poly(Styrene-co-Muconic acid)], styrene-glutine Acid copolymer [Poly (Styrene-co-Glutinic acid)], styrene-citraconic acid copolymer [Poly (Styrene-co-Citraconic acid)], styrene-mesaconic acid copolymer [Poly (Styrene-co-Mesaconic acid) ], styrene-itaconic acid copolymer [Poly(Styrene-co-Itaconic acid)], styrene-maleic anhydride copolymer [Poly(Styrene-co-Maleic anhydride)], styrene-fumaric anhydride copolymer [Poly(Styrene-Itaconic acid)] co-Fumaric anhydride], styrene-acetylenedicarboxylic acid copolymer [Poly(Styrene-co-Acetylenedicarboxylic anhydride)], styrene-glutaconic anhydride copolymer [Poly(Styrene-co-Glutaconic anhydride)], styrene -Anhydrous 2-decenedioic acid copolymer [Poly(Styrene-co-2-Decenedioic anhydride)], styrene-traumatic anhydride copolymer [Poly(Styrene-co-Traumatic anhydride)], styrene-muconic anhydride copolymer [Poly(Styrene-co-Muconic anhydride), styrene-glutinic anhydride copolymer [Poly( Styrene-co-Glutinic anhydride], styrene-citraconic anhydride copolymer [Poly(Styrene-co-Citraconic anhydride)], styrene-mesaconic anhydride copolymer [Poly(Styrene-co-Mesaconic anhydride)] or styrene- It may be composed of one or more selected from itaconic anhydride copolymer [Poly (Styrene-co-Itaconic anhydride)], and miscibility with other components constituting the thermoplastic starch composition, mechanical strength or hygroscopicity of the film to be described later In consideration of the like, it is preferably a styrene-maleic anhydride copolymer [Poly (Styrene-co-Maleic anhydride)]. In addition, the weight average molecular weight of the second compatibilizer is not particularly limited, but is preferably 3,000 to 300,000 g/mol, and is preferably 3,000 to 300,000 g/mol in consideration of miscibility with other components, and harmony of mechanical strength and hygroscopicity of the film to be described later. More preferably -200,000 g/mol.

The reaction initiator, which is a component of the thermoplastic starch composition, is a radical reaction initiator that easily generates radicals by heat, and may be selected from a variety of known materials, and a graft reaction mediated by a first compatibilizer or a second compatibilizer Considering the efficiency, it is preferable that it is a peroxide-based reaction initiator. The peroxide-based reaction initiator is, for example, benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-tert-butyl peroxide (di-tert-) butyl peroxide, cumyl hydroperoxide, di-tert-butyl hydroperoxide, dibenzoyl peroxide, succinic peroxide, dilauryl peroxide Dilauryl peroxide, didecanoyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane [2,5-dimethyl -2,5-di-(tert-butylperoxy)hexane], α-cumyl peroxy-neodecanoate, 1,1-dimethyl-3-hydroxybutyl peroxy-2-ethyl Hexanoate (1-1-dimethyl-3-hydroxybutyl peroxy-2-ethyl hexanoate), tert-amyl peroxy-benzoate, tert-butyl peroxypivalate (tert-butyl) peroxy-pivalate), 2,5-dihydroxyperoxy-2,5-dimethylhexane (2,5-dihydroperoxy-2,5-dimethylhexane), cumene hydroperoxide or 1,3-bis ( It may be composed of one or more selected from tert-butylperoxyisopropyl)benzene [1,3-Bis(tert-butylperoxyisopropyl)benzene], and 2,5-dimethyl-2,5- Di(tert-butylperoxy)hexane [2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane] or 1,3-bis(tert-butylperoxy) It is preferably selected from isopropyl)benzene [1,3-Bis(tert-butylperoxyisopropyl)benzene].

A biodegradable polymer, which is one component of the thermoplastic starch composition, may be decomposed by bacteria or living organisms and may be selected from a variety of known polymers having a hydroxyl group (-OH) inside or at the terminal. The biodegradable polymer is, for example, polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL), polyvinyl alcohol, polybutylene succinate (Polybutylene succinate, PBS) ), polyhydroxyalkanoate (PHA), butylene succinate-adipate copolymer [Poly (butylene succinate-co-adipate), PBSA], butylene adipate-butylene terephthalate copolymer [Poly (butylene adipate-co-bytylene terephtalate), PBABT] or butylene adipate-terephthalate copolymer [Poly (butylene adipate-co-terephtalate), PBAT] may be composed of at least one selected from, and other components It is preferable that the butylene adipate-terephthalate copolymer [Poly (butylene adipate-co-terephtalate), PBAT] is used in consideration of miscibility with and mechanical strength or hygroscopicity of the film to be described later.

The content of the components in the thermoplastic starch composition according to an embodiment of the present invention may be selected within a generally acceptable range in consideration of various parameters such as miscibility, extrudability, reaction efficiency, and the like. Specifically, the thermoplastic starch composition according to an embodiment of the present invention comprises 60 to 90 wt% of starch, 3 to 30 wt% of a plasticizer, 0.1 to 5 wt% of a compatibilizer, 2 to 25 wt% of a biodegradable polymer, and It may contain 0.01 to 0.8% by weight of the reaction initiator. In addition, in the thermoplastic starch composition according to an embodiment of the present invention, in consideration of the miscibility of the components, the mechanical strength or hygroscopicity of the film, which will be described later, preferably 70 to 85% by weight of starch and 5 plasticizers based on the total weight. ~20% by weight, compatibilizer 0.2 ~ 4% by weight, biodegradable polymer 5 ~ 20% by weight and may contain 0.05 ~ 0.4% by weight of the reaction initiator. In addition, the thermoplastic starch composition according to a preferred embodiment of the present invention may include starch, a plasticizer, a first compatibilizer, a second compatibilizer, a biodegradable polymer, and a reaction initiator. The thermoplastic starch composition according to a preferred embodiment of the present invention contains 60 to 90% by weight of starch, 3 to 30% by weight of a plasticizer, 0.05 to 2% by weight of the first compatibilizer, and 0.05 to 3% by weight of the second compatibilizing agent, based on the total weight. , 2 to 25% by weight of the biodegradable polymer and 0.01 to 0.8% by weight of the reaction initiator. In addition, the thermoplastic starch composition according to a preferred embodiment of the present invention contains 70 to 85% by weight of starch, 5 to 20% by weight of a plasticizer based on the total weight, in consideration of the miscibility of the components and the mechanical strength or hygroscopicity of the film to be described later. Weight%, the first compatibilizer 0.15 to 1.5% by weight, the second compatibilizer 0.05 to 2.5% by weight, biodegradable polymer 5 to 20% by weight and 0.05 to 0.4% by weight of the reaction initiator may be included.

In order to solve the above object, an example of the present invention comprises the steps of obtaining a first mixture by mixing starch and a plasticizer; adding a compatibilizer and a reaction initiator to the first mixture and mixing while heating to obtain a second mixture; adding and mixing a biodegradable polymer to the second mixture to obtain a third mixture; and inducing a chemical bond between the starch and the biodegradable polymer mediated by the graft reaction of the compatibilizer while extruding the third mixture at a temperature of 160°C to 220°C. In addition, a preferred embodiment of the present invention comprises the steps of obtaining a first mixture by mixing starch and a plasticizer; adding a first compatibilizer, a second compatibilizer and a reaction initiator to the first mixture and mixing with heating to obtain a second mixture; adding and mixing a biodegradable polymer to the second mixture to obtain a third mixture; and inducing a chemical bond between the starch and the biodegradable polymer mediated by the graft reaction of the first compatibilizer or the second compatibilizer while extruding the third mixture at a temperature of 160 to 220° C. It provides a manufacturing method of The specific types and amounts of starch, plasticizers, compatibilizers (including first and second compatibilizers), reaction initiators, and biodegradable resins used as components in the method for preparing the thermoplastic starch composition according to the present invention are as described above. see

In the step of inducing a chemical bond between the starch and the biodegradable polymer in the method for preparing the thermoplastic starch composition according to the present invention, the grafting reaction temperature may be preferably selected in the range of 170 to 205°C in consideration of the reaction efficiency.

In order to solve the above object, an embodiment of the present invention provides a biodegradable composition for film molding comprising the above-described thermoplastic starch composition and a biodegradable polymer in a weight ratio of 1:9 to 5:5. In the biodegradable composition for film molding according to an embodiment of the present invention, the weight ratio of the thermoplastic starch composition and the biodegradable polymer is preferably 2:8 to 4:6 in consideration of the film formability, mechanical strength or hygroscopicity of the film, which will be described later. do. The biodegradable composition for film molding according to an embodiment of the present invention comprises the steps of mixing a thermoplastic starch composition and a biodegradable polymer in a weight ratio of 1:9 to 5:5 to obtain a fourth mixture, and 150 to 200 of the fourth mixture It can be prepared by the step of extruding at a temperature condition of °C.

In order to solve the above object, an example of the present invention provides a biodegradable film prepared by extruding a biodegradable composition for film molding into a film form. The biodegradable film according to an embodiment of the present invention exhibits high tensile strength, elongation and tear strength, and at the same time exhibits low water absorption. Therefore, the disposable bag, the disposable packaging material, the mulching film, etc. made of the biodegradable film according to an embodiment of the present invention are excellent in mechanical strength and durability.

The thermoplastic starch composition according to the present invention exists in a state in which starch and a biodegradable polymer are chemically bonded by a graft reaction mediated by a compatibilizer. When the biodegradable composition in which the thermoplastic starch composition and the biodegradable polymer are uniformly mixed is extruded, a biodegradable film can be prepared, and the prepared biodegradable film has excellent mechanical strength and low hygroscopicity. Therefore, the biodegradable film prepared using the thermoplastic starch composition according to the present invention as a basic raw material can be used in various fields such as disposable bags, disposable packaging materials, and mulching films.

1 shows a thermoplastic starch composition obtained in Preparation Example 1 (referred to as 'Starch-g-PBAT'), a thermoplastic starch composition obtained in Comparative Preparation Example 2 (referred to as 'Ref. TPS'), and a comparison of Examples of the present invention; It is the result of FT-IR analysis using the biodegradable composition for film molding (referred to as 'Ref. Compound') obtained in Preparation Example 2 as a sample.

2 is a thermogravimetric analysis (TGA) analysis result of the thermoplastic starch composition (referred to as 'Ref. TPS') obtained in Comparative Preparation Example 2 of Examples of the present invention, and FIG. 3 is Preparation Example of Examples of the present invention. These are the results of thermogravimetric analysis (TGA) analysis of the thermoplastic starch composition (referred to as 'Starch-g-PBAT') obtained in step 1.

4 is a thermogravimetric analysis (TGA) analysis result of the biodegradable composition for film molding (referred to as 'Ref. Compound') obtained in Comparative Preparation Example 2 among Examples of the present invention, and FIG. 5 is an Example of the present invention. These are the results of thermogravimetric analysis (TGA) analysis of the biodegradable composition for film molding (referred to as 'Starch-g-PBAT Compound') obtained in Preparation Example 1.

Hereinafter, the present invention will be described in detail through examples. However, the following examples are only for clearly illustrating the technical features of the present invention, and do not limit the protection scope of the present invention.

1. Preparation of thermoplastic starch composition, biodegradable composition for film molding, and biodegradable film

Preparation Example 1.

85 parts by weight of corn starch and 15 parts by weight of glycerin were added to a mixer and mixed to obtain a first mixture. Then, 0.5 parts by weight of maleic anhydride, styrene-maleic anhydride copolymer [Poly (Styrene-co-Maleic Anhydride); weight average molecular weight of 5,500 g/mol] 0.5 parts by weight and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane [2,5-dimethyl-2,5-di(tert-butylperoxy) as a reaction initiator ) hexane] 0.1 parts by weight was added and mixed while heating to obtain a second mixture. Then, 11.11 parts by weight of a biodegradable polymer PBAT [Poly (butylene adipate-co-terephthalate)] was added to 100 parts by weight of the second mixture and uniformly mixed to obtain a third mixture. Thereafter, the third mixture was put into a twin-screw extruder and extruded under the conditions of a barrel temperature of 185 to 190° C., a screw rotation speed of 300 rpm, and a feed rate of 20 rpm. Corn using maleic anhydride and a styrene-maleic anhydride copolymer A chemical bond was induced between the starch and the biodegradable polymer. Thereafter, the extrudate of the third mixture was pelletized to obtain a thermoplastic starch composition in pellet form.

Then, 33.3 parts by weight of the thermoplastic starch composition and 66.7 parts by weight of PBAT [Poly(butylene adipate-co-terephthalate)] were uniformly mixed to obtain a fourth mixture. After that, the fourth mixture is put into the twin-screw extruder and extruded under the conditions of a barrel temperature of 175 to 180 ℃, a screw rotation speed of 400 to 410 rpm, and a raw material supply speed of 110 to 120 rpm, and then the extrudate is cooled with water, pelletized, and about 60 ℃ was dried to obtain a biodegradable composition for film molding in the form of pellets. Thereafter, the biodegradable composition for film molding was put into a film extrusion molding machine and molded under the conditions of a molding temperature of 150 to 160° C. and a raw material supply rate of 700 to 800 rpm to prepare a biodegradable film.

Preparation Example 2.

The same conditions and methods as in Preparation Example 1 were used except that a styrene-maleic anhydride copolymer having a weight average molecular weight of 9,000 g/mol was used instead of a styrene-maleic anhydride copolymer having a weight average molecular weight of 5,500 g/mol. A thermoplastic starch composition, a biodegradable composition for film molding, and a biodegradable film were prepared.

Preparation Example 3.

The same conditions and methods as in Preparation Example 1 were used except that a styrene-maleic anhydride copolymer having a weight average molecular weight of 27,000 g/mol was used instead of a styrene-maleic anhydride copolymer having a weight average molecular weight of 5,500 g/mol. A thermoplastic starch composition, a biodegradable composition for film molding, and a biodegradable film were prepared.

Preparation Example 4.

The same conditions as in Preparation Example 1 except that a styrene-maleic anhydride copolymer having a weight average molecular weight of about 1.1 × 10 ⁵ g/mol was used instead of the styrene-maleic anhydride copolymer having a weight average molecular weight of 5,500 g/mol And a thermoplastic starch composition, a biodegradable composition for film molding, and a biodegradable film were prepared in the same manner.

Preparation 5.

The same conditions as in Preparation Example 1 except that a styrene-maleic anhydride copolymer having a weight average molecular weight of about 1.5 × 10 ⁵ g/mol was used instead of the styrene-maleic anhydride copolymer having a weight average molecular weight of 5,500 g/mol And a thermoplastic starch composition, a biodegradable composition for film molding, and a biodegradable film were prepared in the same manner.

Preparation 6.

Thermoplastic starch under the same conditions and in the same manner as in Preparation Example 1, except that the amount of styrene-maleic anhydride copolymer (weight average molecular weight: 5,500 g/mol) was changed to 0.1 parts by weight instead of 0.5 parts by weight in the second mixture preparation step. A composition, a biodegradable composition for forming a film, and a biodegradable film were prepared.

Preparation 7.

Thermoplastic starch in the same manner and under the same conditions as in Preparation Example 1, except that in the second mixture preparation step, the input amount of the styrene-maleic anhydride copolymer (weight average molecular weight 5,500 g/mol) was changed to 0.3 parts by weight instead of 0.5 parts by weight. A composition, a biodegradable composition for forming a film, and a biodegradable film were prepared.

Preparation 8.

Thermoplastic starch under the same conditions and in the same manner as in Preparation Example 1, except that the amount of styrene-maleic anhydride copolymer (weight average molecular weight: 5,500 g/mol) was changed to 0.7 parts by weight instead of 0.5 parts by weight in the second mixture preparation step. A composition, a biodegradable composition for forming a film, and a biodegradable film were prepared.

Comparative Preparation Example 1.

85 parts by weight of corn starch and 15 parts by weight of glycerin were added to a mixer and mixed while heating to obtain a first mixture. Thereafter, the first mixture was put into a twin-screw extruder and extruded under the conditions of a barrel temperature of 185 to 190° C., a screw rotation speed of 300 rpm, and a raw material supply rate of 20 rpm. Thereafter, the extrudate of the first mixture was pelletized to pelletize the extrudate to obtain a thermoplastic starch composition in pellet form.

Then, 30 parts by weight of the thermoplastic starch composition and 70 parts by weight of PBAT [Poly(butylene adipate-co-terephthalate)] were uniformly mixed to obtain a second mixture. After that, the second mixture is put into the twin-screw extruder and extruded under the conditions of a barrel temperature of 175-180 ℃, a screw rotation speed of 400-410 rpm, and a raw material supply speed of 110-120 rpm, and then the extrudate is cooled with water, pelletized, and about 60 ℃ was dried to obtain a biodegradable composition for film molding in the form of pellets. Thereafter, the biodegradable composition for film molding was put into a film extrusion molding machine and molded under the conditions of a molding temperature of 150 to 160° C. and a raw material supply rate of 700 to 800 rpm to prepare a biodegradable film.

Comparative Preparation Example 2.

85 parts by weight of corn starch and 15 parts by weight of glycerin were added to a mixer and mixed to obtain a first mixture. Thereafter, 0.5 parts by weight of maleic anhydride and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane [2,5-dimethyl-2,5-di as a reaction initiator, in 100 parts by weight of the first mixture (tert-butylperoxy)hexane] 0.1 parts by weight was added and mixed while heating to obtain a second mixture. Thereafter, the second mixture was introduced into a twin-screw extruder and extruded under conditions of a barrel temperature of 185 to 190° C., a screw rotation speed of 300 rpm, and a raw material feed rate of 20 rpm to induce chemical bonding between corn starch and maleic anhydride. Thereafter, the extrudate of the second mixture was pelletized to obtain a thermoplastic starch composition in pellet form.

Then, 30 parts by weight of the thermoplastic starch composition and 70 parts by weight of PBAT [Poly(butylene adipate-co-terephthalate)] were uniformly mixed to obtain a third mixture. After that, the third mixture is put into the twin-screw extruder and extruded under the conditions of a barrel temperature of 175 to 180 ° C, a screw rotation speed of 400 to 410 rpm, and a raw material supply rate of 110 to 120 rpm, and then the extrudate is cooled with water, pelletized, and about 60 ° C. was dried to obtain a biodegradable composition for film molding in the form of pellets. Thereafter, the biodegradable composition for film molding was put into a film extrusion molding machine and molded under the conditions of a molding temperature of 150 to 160° C. and a raw material supply rate of 700 to 800 rpm to prepare a biodegradable film.

Comparative Preparation Example 3.

85 parts by weight of corn starch and 15 parts by weight of glycerin were added to a mixer and mixed to obtain a first mixture. Then, 0.5 parts by weight of maleic anhydride in 100 parts by weight of the first mixture, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane [2,5-dimethyl-2,5- di(tert-butylperoxy)hexane] 0.1 parts by weight was added and mixed while heating to obtain a second mixture. Then, 11.11 parts by weight of a biodegradable polymer PBAT [Poly (butylene adipate-co-terephthalate)] was added to 100 parts by weight of the second mixture and uniformly mixed to obtain a third mixture. Thereafter, the third mixture is put into a twin-screw extruder and extruded under the conditions of a barrel temperature of 185 to 190°C, a screw rotation speed of 300 rpm, and a raw material supply speed of 20 rpm. was induced. Thereafter, the extrudate of the third mixture was pelletized to obtain a thermoplastic starch composition in pellet form.

Then, 33.3 parts by weight of the thermoplastic starch composition and 66.7 parts by weight of PBAT [Poly(butylene adipate-co-terephthalate)] were uniformly mixed to obtain a fourth mixture. After that, the fourth mixture is put into the twin-screw extruder and extruded under the conditions of a barrel temperature of 175 to 180 ℃, a screw rotation speed of 400 to 410 rpm, and a raw material supply speed of 110 to 120 rpm, and then the extrudate is cooled with water, pelletized, and about 60 ℃ was dried to obtain a biodegradable composition for film molding in the form of pellets. Thereafter, the biodegradable composition for film molding was put into a film extrusion molding machine and molded under the conditions of a molding temperature of 150 to 160° C. and a raw material supply rate of 700 to 800 rpm to prepare a biodegradable film.

Comparative Preparation Example 4.

85 parts by weight of corn starch and 15 parts by weight of tributyl citrate were added to a mixer and mixed to obtain a first mixture. Then, 0.5 parts by weight of maleic anhydride, 0.5 parts by weight of a styrene-maleic anhydride copolymer (weight average molecular weight 27,000 g/mol), and 2,5-dimethyl-2,5-di, which is a reaction initiator, in 100 parts by weight of the first mixture 0.1 parts by weight of (tert-butylperoxy)hexane [2,5-dimethyl-2,5-di(tert-butylperoxy)hexane] was added and mixed while heating to obtain a second mixture. Then, 11.11 parts by weight of a biodegradable polymer PBAT [Poly (butylene adipate-co-terephthalate)] was added to 100 parts by weight of the second mixture and uniformly mixed to obtain a third mixture. Thereafter, the third mixture was put into a twin-screw extruder and extruded under the conditions of a barrel temperature of 185 to 190° C., a screw rotation speed of 300 rpm, and a feed rate of 20 rpm. Corn using maleic anhydride and a styrene-maleic anhydride copolymer A chemical bond was induced between the starch and the biodegradable polymer. Thereafter, the extrudate of the third mixture was pelletized to obtain a thermoplastic starch composition in pellet form.

Then, 33.3 parts by weight of the thermoplastic starch composition and 66.7 parts by weight of PBAT [Poly(butylene adipate-co-terephthalate)] were uniformly mixed to obtain a fourth mixture. After that, the fourth mixture is put into the twin-screw extruder and extruded under the conditions of a barrel temperature of 175 to 180 ℃, a screw rotation speed of 400 to 410 rpm, and a raw material supply speed of 110 to 120 rpm, and then the extrudate is cooled with water, pelletized, and about 60 ℃ was dried to obtain a biodegradable composition for film molding in the form of pellets. Thereafter, the biodegradable composition for film molding was put into a film extrusion molding machine and molded under the conditions of a molding temperature of 150 to 160° C. and a raw material supply rate of 700 to 800 rpm to prepare a biodegradable film.

Comparative Preparation Example 5.

85 parts by weight of corn starch and 15 parts by weight of glycerin were added to a mixer and mixed to obtain a first mixture. Then, 0.5 parts by weight of maleic anhydride and 0.5 parts by weight of a styrene-maleic anhydride copolymer (weight average molecular weight 27,000 g/mol) were added to 100 parts by weight of the first mixture and mixed with heating to obtain a second mixture. Then, 11.11 parts by weight of a biodegradable polymer PBAT [Poly (butylene adipate-co-terephthalate)] was added to 100 parts by weight of the second mixture and uniformly mixed to obtain a third mixture. Then, the third mixture was put into a twin-screw extruder and extruded under the conditions of a barrel temperature of 185 to 190° C., a screw rotation speed of 300 rpm, and a raw material supply speed of 20 rpm. Thereafter, the extrudate of the third mixture was pelletized to obtain a thermoplastic starch composition in pellet form.

Then, 33.3 parts by weight of the thermoplastic starch composition and 66.7 parts by weight of PBAT [Poly(butylene adipate-co-terephthalate)] were uniformly mixed to obtain a fourth mixture. After that, the fourth mixture is put into the twin-screw extruder and extruded under the conditions of a barrel temperature of 175 to 180 ℃, a screw rotation speed of 400 to 410 rpm, and a raw material supply speed of 110 to 120 rpm, and then the extrudate is cooled with water, pelletized, and about 60 ℃ was dried to obtain a biodegradable composition for film molding in the form of pellets. Thereafter, the biodegradable composition for film molding was put into a film extrusion molding machine and molded under the conditions of a molding temperature of 150 to 160° C. and a raw material supply rate of 700 to 800 rpm to prepare a biodegradable film.

2. Analysis of physical properties of thermoplastic starch composition, biodegradable composition for film molding, and biodegradable film

(1) FT-IR (Fourier-transform infrared spectroscopy) analysis

The thermoplastic starch composition obtained in Preparation Example 1 (referred to as 'Starch-g-PBAT'), the thermoplastic starch composition obtained in Comparative Preparation Example 2 (referred to as 'Ref. TPS') and the film molding obtained in Comparative Preparation Example 2 FT-IR analysis was performed using the biodegradable composition (referred to as 'Ref. Compound') as a sample, and the results are shown in FIG. 1 . As shown in FIG. 1 , the FT-IR analysis results of the thermoplastic starch composition (referred to as 'Starch-g-PBAT') obtained in Preparation Example 1 were compared with the thermoplastic starch composition obtained in Comparative Preparation Example 2 (referred to as 'Ref. TPS'). In the FT-IR analysis result of As a result, PBAT, a biodegradable polymer, was chemically combined with starch, and the peak (3,200-3,300 cm ^-1 ) of the OH group present in the starch was greatly reduced, and a C=O peak representing the ester group and carboxylic acid was generated. On the other hand, looking at the FT-IR analysis results of the biodegradable composition for film molding (referred to as 'Ref. Compound') obtained in Comparative Preparation Example 2, the biodegradable composition for film molding obtained in Comparative Preparation Example 2 contained a thermoplastic starch composition. Since PBAT, which is a biodegradable polymer, was well blended and an excess of PBAT was present, a peak corresponding to the unsaturated ester group was shown.

(2) Thermogravimetric Analysis (TGA)

The thermoplastic starch composition obtained in Preparation Example 1 (referred to as 'Starch-g-PBAT'), the biodegradable composition for film molding obtained in Preparation Example 1 (referred to as 'Starch-g-PBAT Compound'), Comparative Preparation Example 2 Thermogravimetric analysis (TGA) was performed using the thermoplastic starch composition (referred to as 'Ref. TPS') obtained in and the results are shown in FIGS. 2 to 5 . 2 is a thermogravimetric analysis (TGA) analysis result of the thermoplastic starch composition (referred to as 'Ref. TPS') obtained in Comparative Preparation Example 2 of Examples of the present invention, and FIG. 3 is Preparation Example of Examples of the present invention. These are the results of thermogravimetric analysis (TGA) analysis of the thermoplastic starch composition (referred to as 'Starch-g-PBAT') obtained in step 1. 4 is a thermogravimetric analysis (TGA) analysis result of the biodegradable composition for film molding (referred to as 'Ref. Compound') obtained in Comparative Preparation Example 2 of the Examples of the present invention, and FIG. 5 is the result of the present invention. These are the results of thermogravimetric analysis (TGA) analysis of the biodegradable composition for film molding (referred to as 'Starch-g-PBAT Compound') obtained in Preparation Example 1 among Examples. As shown in FIGS. 2 and 3, in the case of the thermoplastic starch composition (referred to as 'Starch-g-PBAT') obtained in Preparation Example 1, a graft reaction mediated by maleic anhydride and a styrene-maleic anhydride copolymer was performed. A peak indicating the chemical bonding between starch and PBAT, a biodegradable polymer, was observed, and the peak of the starch decomposition temperature was shifted to higher than 300° C. due to the chemical bond between starch and PBAT, a biodegradable polymer. In addition, as shown in FIGS. 4 and 5, in the case of the biodegradable composition for film molding (referred to as 'Starch-g-PBAT Compound') obtained in Preparation Example 1, the thermoplastic starch composition obtained in Preparation Example 1 ('Starch- g-PBAT'), the decomposition temperature of PBAT, a biodegradable polymer, was shifted to a lower side than 410 °C.

(3) Measurement of mechanical strength and water absorption rate

The mechanical strength and water absorption rate of the biodegradable films prepared in Preparation Examples 1 to 8 and Comparative Preparation Examples 1 to 5 were measured.

*Mechanical strength measurement method

A specimen was prepared by cutting the biodegradable film to a width of 10 mm according to the KSS M1008 standard, and the film thickness was recorded using a thickness gauge. Tensile strength, elongation, and tear strength of the prepared specimens were measured using an Instron Tensile testing machine. Tensile test conditions were a distance between grips of 60 mm and a test speed of 500 mm/min.

* How to measure moisture absorption

A specimen was prepared by cutting the biodegradable film into a size of 10 cm × 5 cm. Thereafter, the specimen was placed in an oven and dried at 50° C. for about 16 hr, and the weight of the dried specimen was measured. Thereafter, the dried specimen was placed in a desiccator containing distilled water and stored for 5 days in a thermo-hygrostat at a temperature of 35° C. and a humidity of 80% to absorb moisture into the specimen. Thereafter, the moisture-absorbed specimen was taken out, weight was measured, and the moisture absorption rate was calculated by the following formula.

Table 1 below summarizes the mechanical strength and moisture absorption measurement results of the biodegradable films prepared in Preparation Examples 1 to 8 and Comparative Preparation Examples 1 to 5.

Classification of biodegradable films	Tensile strength (N/㎟)		Elongation (%)		Tear strength (N/mm)		Moisture absorption rate (%)
	MD	CD	MD	CD	MD	CD
Preparation Example 1	33	30	749	694	154	142	2.0
Preparation 2	40	32	441	719	162	460	2.3
Preparation 3	35	28	319	640	152	166	2.9
Preparation 4	37	27	628	704	148	158	3.2
Preparation 5	37	25	575	815	136	151	4.1
Preparation 6	37	32	547	737	161	158	3.5
Preparation 7	37	28	381	643	160	161	1.7
Preparation 8	38	31	423	619	176	160	2.6
Comparative Preparation Example 1	4	2	85	38	40	20	20
Comparative Preparation Example 2	23	18	285	676	96	95	10.0
Comparative Preparation Example 3	30	28	667	746	102	85	7.8
Comparative Preparation Example 4	20	15	187	714	75	84	3.4
Comparative Preparation Example 5	25	19	236	692	105	104	7.4

* MD (machine direction): extrusion direction (longitudinal direction)

* CD (cross direction) : Extrusion vertical direction (cross direction)

As shown in Table 1, the biodegradable films prepared in Preparation Examples 1 to 8 exhibited high tensile strength, elongation and tear strength, and at the same time exhibited low water absorption. These results show that starch and biodegradable polymers were subjected to a graft reaction mediated by maleic anhydride and a styrene-maleic anhydride copolymer in the thermoplastic starch composition used as a component of the biodegradable film prepared in Preparation Examples 1 to 8. It is thought to be due to the chemical bond formed between the phosphorus PBATs. In addition, as in Comparative Preparation Example 3, when the styrene-maleic anhydride copolymer was excluded as a component of the thermoplastic starch composition, the water absorption rate of the biodegradable film was significantly increased. In addition, as shown in Comparative Preparation Example 4, when tributyl citrate was used instead of glycerin as a plasticizer, which is a component of the thermoplastic starch composition, the moisture absorption rate was good, but the mechanical properties were overall poor.

As described above, the present invention has been described through the above embodiments, but the present invention is not necessarily limited thereto, and various modifications are possible without departing from the scope and spirit of the present invention. Accordingly, the protection scope of the present invention should be construed to include all embodiments falling within the scope of the claims appended hereto.

Claims (10)

1. Contains starch, a plasticizer, a compatibilizer, a biodegradable polymer, and a reaction initiator,

   The compatibilizer is composed of at least one selected from unsaturated dicarboxylic acid, unsaturated dicarboxylic acid anhydride, styrene-unsaturated dicarboxylic acid copolymer or styrene-unsaturated dicarboxylic acid anhydride copolymer,

   The thermoplastic starch composition, characterized in that the starch and the biodegradable polymer exist in a chemically bonded state by a graft reaction mediated by a compatibilizer.
2. The thermoplastic starch composition according to claim 1, wherein the plasticizer comprises at least one polyhydric alcohol selected from sorbitol, ethylene glycol, glycerin, and pentaerythritol.
3. According to claim 1, wherein the compatibilizer is composed of a first compatibilizer and a second compatibilizer,

   The first compatibilizing agent is selected from an unsaturated dicarboxylic acid or an anhydrous unsaturated dicarboxylic acid,

   The second compatibilizer is selected from a styrene-unsaturated dicarboxylic acid copolymer or a styrene-anhydride unsaturated dicarboxylic acid copolymer,

   A thermoplastic starch composition, characterized in that the starch and the biodegradable polymer exist in a chemically bonded state by a graft reaction mediated by the first compatibilizing agent or the second compatibilizing agent.
4. 4. The method of claim 3,

   The first compatibilizing agent is maleic acid, fumaric acid, acetylenedicarboxylic acid, glutaconic acid, 2-decenedioic acid, Traumatic acid, Muconic acid, Glutinic acid, Citraconic acid, Mesaconic acid, Itaconic acid, Maleic anhydride ), Fumaric anhydride, Acetylenedicarboxylic anhydride, Glutaconic anhydride, 2-Decenedioic anhydride, Traumatic anhydride , composed of at least one selected from muconic anhydride, glutinic anhydride, citraconic anhydride, mesaconic anhydride, or itaconic anhydride become,

   The second compatibilizing agent is a styrene-maleic acid copolymer [Poly(Styrene-co-Maleic acid)], a styrene-fumaric acid copolymer [Poly(Styrene-co-Fumaric acid)], a styrene-acetylenedicarboxylic acid copolymer [Poly(Styrene-co-Acetylenedicarboxylic acid)], styrene-glutaconic acid copolymer [Poly(Styrene-co-Glutaconic acid)], styrene-2-decenedioic acid copolymer [Poly(Styrene-co-2- Decenedioic acid)], styrene-traumatic acid copolymer [Poly(Styrene-co-Traumatic acid)], styrene-muconic acid copolymer [Poly(Styrene-co-Muconic acid)], styrene-glutinic acid copolymer [Poly(Styrene-co-Traumatic acid)] (Styrene-co-Glutinic acid)], styrene-citraconic acid copolymer [Poly(Styrene-co-Citraconic acid)], styrene-mesaconic acid copolymer [Poly(Styrene-co-Mesaconic acid)], styrene-ita Conic acid copolymer [Poly(Styrene-co-Itaconic acid)], Styrene-maleic anhydride copolymer [Poly(Styrene-co-Maleic anhydride)], Styrene-Fumaric anhydride copolymer [Poly(Styrene-co-Fumaric anhydride) ], styrene-acetylenedicarboxylic acid anhydride copolymer [Poly(Styrene-co-Acetylenedicarboxylic anhydride)], styrene-glutaconic anhydride copolymer [Poly(Styrene-co-Glutaconic anhydride)], styrene-anhydride 2-de Senedioic acid copolymer [Poly (Styrene-co-2-Decenedioic anhydride)], styrene-traumatic anhydride copolymer [Poly (Styrene-co-Traumatic anhydride)], styrene-muconic anhydride copolymer [Poly (Styrene- co-Muconic anhydride), styrene-glutinic anhydride copolymer [Poly (Styrene-co -Glutinic anhydride)], styrene-citraconic anhydride copolymer [Poly(Styrene-co-Citraconic anhydride)], styrene-mesaconic anhydride copolymer [Poly(Styrene-co-Mesaconic anhydride)] or styrene-itaconic anhydride A thermoplastic starch composition comprising at least one selected from copolymer [Poly (Styrene-co-Itaconic anhydride)].
5. The thermoplastic starch composition according to claim 3, wherein the weight average molecular weight of the second compatibilizer is 3,000 to 300,000 g/mol.
6. According to claim 1, wherein the biodegradable polymer is polylactic acid (Polylactic acid, PLA), polyglycolic acid (Polyglycolic acid, PGA), polycaprolactone (Polycaprolactone, PCL), polyvinyl alcohol, polybutylene succinate ( Polybutylene succinate (PBS), polyhydroxyalkanoate (PHA), butylene succinate-adipate copolymer [Poly (butylene succinate-co-adipate), PBSA], butylene adipate-butylene terephthalate Characterized in that it is composed of at least one selected from copolymer [Poly (butylene adipate-co-bytylene terephtalate), PBABT] or butylene adipate-terephthalate copolymer [Poly (butylene adipate-co-terephtalate), PBAT] A thermoplastic starch composition comprising
7. According to claim 1, wherein the reaction initiator is benzoyl peroxide (benzoyl peroxide), acetyl peroxide (acetyl peroxide), dilauryl peroxide (dilauryl peroxide), di-tert-butyl peroxide (di-tert-butyl peroxide) , cumyl peroxide, di-tert-butyl hydroperoxide, dibenzoyl peroxide, succinic peroxide, dilauryl peroxide peroxide), didecanoyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane [2,5-dimethyl-2, 5-di-(tert-butylperoxy)hexane], α-cumyl peroxy-neodecanoate, 1,1-dimethyl-3-hydroxybutyl peroxy-2-ethylhexanoe ytite (1-1-dimethyl-3-hydroxybutyl peroxy-2-ethyl hexanoate), tert-amyl peroxy-benzoate, tert-butyl peroxy-pivalate ), 2,5-dihydroxyperoxy-2,5-dimethylhexane (2,5-dihydroperoxy-2,5-dimethylhexane), cumene hydroperoxide or 1,3-bis (tert-butyl) A thermoplastic starch composition comprising at least one peroxide-based reaction initiator selected from peroxyisopropyl)benzene [1,3-Bis(tert-butylperoxyisopropyl)benzene].
8. According to claim 1, based on the total weight, 60 to 90% by weight of starch, 3 to 30% by weight of a plasticizer, 0.1 to 5% by weight of a compatibilizer, 2 to 25% by weight of a biodegradable polymer, and 0.01 to 0.8% by weight of a reaction initiator A thermoplastic starch composition comprising:
9. mixing starch and a plasticizer to obtain a first mixture;

   adding a compatibilizer and a reaction initiator to the first mixture and mixing while heating to obtain a second mixture;

   adding and mixing a biodegradable polymer to the second mixture to obtain a third mixture; and

   A method comprising inducing a chemical bond between starch and biodegradable polymer mediated by a graft reaction of a compatibilizer while extruding the third mixture at a temperature of 160 to 220 ° C.

   The compatibilizer is characterized in that it is composed of at least one selected from unsaturated dicarboxylic acid, unsaturated dicarboxylic acid anhydride, styrene-unsaturated dicarboxylic acid copolymer, or styrene-unsaturated dicarboxylic acid anhydride copolymer. A method for preparing a thermoplastic starch composition.
10. A biodegradable composition for film molding comprising the thermoplastic starch composition of any one of claims 1 to 8 and the biodegradable polymer in a weight ratio of 1:9 to 5:5.

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