KR20230057724A - Thermoplastic starch composition, manufacturing method thereof, and use thereof - Google Patents

Abstract

According to an embodiment of the present invention, a thermoplastic starch composition including starch, a plasticizer, a first compatibilizer, a second compatibilizer, a biodegradable polymer, and a reaction initiator is provided. At least a portion of the starch and biodegradable polymer, which are components of the thermoplastic starch composition according to the present invention, exist in a chemically bonded state through a graft reaction mediated by the first compatibilizer. In addition, at least a portion of the starch, which is a component of the thermoplastic starch composition according to the present invention, exists in a form chemically bonded to the second compatibilizer and having a hydrophobic functional group introduced. Accordingly, a biodegradable film can be produced by extruding a biodegradable composition in which the thermoplastic starch composition and a biodegradable polymer are uniformly mixed, and the produced biodegradable film has excellent mechanical properties.

Description

Thermoplastic starch composition, manufacturing method thereof, and use thereof {Thermoplastic starch composition, manufacturing method thereof, and use thereof}

The present invention relates to a thermoplastic starch composition, etc., and more particularly, to a thermoplastic starch composition capable of imparting excellent mechanical properties to a biodegradable film by being added as a component of a biodegradable composition for preparing a biodegradable film, a method for preparing the same, and a method for preparing the same It's about uses, etc.

Plastics have been used as important materials indispensable in real life because they are lightweight, easy to process, mass-produced, and have excellent durability, chemical resistance, and mechanical properties. However, as the seriousness of environmental pollution increases worldwide and plastic waste, especially disposable waste, emerges as a major cause of environmental pollution, the application and development of biodegradable resins for disposable products are being actively conducted. In particular, compared to the case of manufacturing a plastic film using petroleum, when a biodegradable film is manufactured using a biodegradable resin, carbon dioxide emission is relatively small, and the biodegradable resin is in the spotlight as an eco-friendly resin. Moreover, biodegradable resins are infinite resources that can be produced sustainably, and there is no concern about resource depletion compared to petroleum-based resins, so the use of products using them is expanding significantly every year.

In general, a biodegradable film is a biodegradable composition in which starch is mixed with a vinyl polymer, polylactic acid (PLA), butylene adipate-terephthalate copolymer [Poly (butylene adipate-co-terephtalate), PBAT], etc. It is prepared by extruding a biodegradable composition in which a biopolyester-based biodegradable polymer and starch are mixed. However, in the case of a biodegradable film using starch, the addition amount of starch is limited due to degradation 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 poor biodegradability. In addition, the biodegradable film prepared from a biodegradable composition that is a mixture of biopolyester-based biodegradable polymer and starch is not only expensive, but also suffers from various limitations such as easy tearing due to its low mechanical properties compared to existing plastic products. are receiving

In order to impart thermoplasticity to starch while improving the above problems, a method of using glycerin, sorbitol, and glucose together with water as a starch plasticizer (USP 3,949,145, EP 32802A1) has been proposed. In addition, a method in which starch is made into thermoplastic starch by a separate device and process and then compounded with a biodegradable resin (Korean Patent Registration No. 10-0339789) or an aliphatic polyester resin with excellent biodegradability and starch as main components A method of manufacturing by adding a starch plasticizer and the like (Korean Patent Registration No. 10-0465980) has been proposed. In addition, Korean Patent Publication No. 10-2017-0075052 discloses (i) a biodegradable resin; (ii) starch in which at least one of the hydroxyl groups (-OH groups) of glucose units is hydrophobized with silane; and (iii) one or two or more compatibilizers selected from the group consisting of a graft copolymer obtained by grafting maleic anhydride (MA) on a biodegradable polymer, an epoxidized oil, and a multifunctional compound having an epoxy group. A resin composition for a mulching film is disclosed.

The present invention was derived under the conventional technical background, and an object of the present invention is a thermoplastic starch composition capable of imparting excellent mechanical properties to a biodegradable film by being added as a component of a biodegradable composition for preparing a biodegradable film, and preparation thereof It's about providing a way.

In addition, an object of the present invention is to provide a biodegradable composition used for forming a film as a use of the thermoplastic starch composition.

In order to improve the compatibility of the thermoplastic starch composition, the inventor of the present invention induces a graft reaction mediated by an anhydrous unsaturated dicarboxylic acid, which is a reactive compatibilizer, to obtain a thermoplastic starch composition in which starch and a biodegradable polymer are chemically bonded. It was prepared and used to prepare a biodegradable film. Recognizing the problem that the biodegradable film has good elongation among mechanical properties, but relatively low tensile strength and tear strength, a compatibilizer that exhibits a synergistic effect in combination with anhydrous unsaturated dicarboxylic acid was searched for, and a specific compatibilizer The present invention was completed after confirming that elongation, tensile strength, and tear strength of the biodegradable film are all improved when combining anhydrous unsaturated dicarboxylic acid and the like.

In order to solve the above object, one embodiment of the present invention provides a thermoplastic starch composition comprising starch, a plasticizer, a first compatibilizer, a second compatibilizer, a biodegradable polymer, and a reaction initiator.

The type of starch, which is one component of the thermoplastic starch composition, is not significantly limited. For example, corn starch, waxy corn starch, potato starch, sweet potato starch, wheat starch, rice starch, tapioca starch, sago starch ), sogeom starch (sorghum starch) or high amylose starch, etc., and it is preferable that it is 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 processability of starch or biodegradable polymers, and may be selected from various known components having biodegradability or eco-friendliness. For example, the plasticizer may be polyhydric alcohol, triethyl citrate, acetyl triethyl citrate, tributyl citrate, acetyl tributyl citrate, It may be selected from glycerin diacetate, etc., and considering the mechanical strength or hygroscopicity of the film to be described later, it may be selected from sorbitol, ethylene glycol, propylene glycol, diethylene glycol, glycerin or pentaerythritol It is preferably composed of one or more polyhydric alcohols, and more preferably glycerin.

The thermoplastic starch composition according to one embodiment of the present invention includes a compatibilizer, and specifically includes a first compatibilizer and a second compatibilizer. It is a component for improving the miscibility between the starch, which is the compatibilizer, and the biodegradable polymer.

The first compatibilizer, which is one component of the thermoplastic starch composition, reacts with the hydroxyl group (-OH) present in starch to form an ester bond and at the same time chemically bonds with the biodegradable polymer to graft the starch and the biodegradable polymer It is a reactive compatibilizer capable of grafting. The first compatibilizing agent is selected from unsaturated dicarboxylic acids or anhydrous unsaturated dicarboxylic acids. The carboxyl group present in unsaturated dicarboxylic acid or anhydrous unsaturated dicarboxylic acid can react with the hydroxyl group (-OH) present in starch or biodegradable polymer to form an ester bond, and unsaturated dicarboxylic acid or anhydrous Unsaturated bonds (eg, double bonds) present in unsaturated dicarboxylic acids can react with biodegradable polymer radicals to form covalent chemical bonds. In the thermoplastic starch composition according to one embodiment of the present invention, the starch and the biodegradable polymer, which are one of the components, preferably exist in a state in which at least a portion is chemically bonded by a graft reaction mediated by the first compatibilizer. The first compatibilizer 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. It may consist of the above, and it is preferably maleic anhydride in consideration of miscibility with other components constituting the thermoplastic starch composition, mechanical strength or hygroscopicity of the film to be described later.

The second compatibilizer, which is one component of the thermoplastic starch composition, improves the compatibility between starch and the hydrophobic biodegradable polymer and exhibits a synergistic effect when used together with the first compatibilizer to improve the mechanical properties of the biodegradable film described later play a role The second compatibilizer is benzaldehyde. It has been confirmed that the benzaldehyde reacts with starch during the reactive extrusion process to introduce a hydrophobic functional group into the starch, thereby increasing the compatibility between the starch and the hydrophobic biodegradable polymer. In the thermoplastic starch composition according to one embodiment of the present invention, at least a portion of the starch, which is one component, is present in a hydrophobized state by chemically bonding with the second compatibilizer.

The reaction initiator, which is one component of the thermoplastic starch composition, is a radical reaction initiator that easily generates radicals by heat, and may be selected from various known materials, and may be a graft reaction mediated by a first compatibilizer or a second compatibilizer. Considering the reaction efficiency between starch and starch, it is preferable to use a peroxide-based reaction initiator. The peroxide-based reaction initiator is, for example, benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-tert-butyl peroxide, 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, cumene hydroperoxide or 1,3-bis( tert-butylperoxyisopropyl) benzene [1,3-Bis (tert-butylperoxyisopropyl) benzene], and may be composed of one or more selected from 2,5-dimethyl-2,5- when considering the efficiency of the graft reaction Di(tert-butylperoxy)hexane[2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane] or 1,3-bis(tert-butylperoxyisopropyl)benzene[1,3- It is preferably selected from Bis (tert-butylperoxyisopropyl) benzene].

The biodegradable polymer, which is one component of the thermoplastic starch composition, can be degraded by bacteria or living organisms and can be selected from various 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 (PBS) ), polyhydroxyalkanoate (PHA), butylene succinate-adipate copolymer [Poly (butylene succinate-co-adipate), PBSA], butylene adipate-butylene terephthalate copolymer [Poly (butylene adipate-co-butylene terephtalate), PBABT] or butylene adipate-terephthalate copolymer [Poly (butylene adipate-co-terephtalate), PBAT], and may be composed of one or more selected from other components Polylactic acid (PLA) or butylene adipate-terephthalate copolymer [Poly (butylene adipate-co-terephtalate), PBAT] in consideration of compatibility with it is desirable

In the thermoplastic starch composition according to an embodiment of the present invention, the content of the components may be selected within a generally acceptable range in consideration of various parameters such as miscibility, ease of extrusion, and reaction efficiency. Specifically, the thermoplastic starch composition according to one embodiment of the present invention contains 60 to 90% by weight of starch, 3 to 30% by weight of plasticizer, 0.1 to 3% by weight of a first compatibilizer, and 0.01 to 2% by weight of a second compatibilizer based on the total weight. % by weight, 2 to 25% by weight of a biodegradable polymer, and 0.01 to 1% by weight of a 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 and 5 to 20% plasticizer based on the total weight when considering the miscibility of the components and the mechanical strength or hygroscopicity of the film to be described later. % by weight, 0.2 to 2% by weight of the first compatibilizer, 0.02 to 1% by weight of the second compatibilizer, 5 to 20% by weight of the biodegradable polymer, and 0.05 to 0.5% by weight of the reaction initiator.

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; obtaining a second mixture by adding a first compatibilizer, a second compatibilizer, and a reaction initiator to the first mixture and mixing while heating; obtaining a third mixture by adding and mixing a biodegradable polymer to the second mixture; and performing reactive extrusion on the third mixture at a temperature of 160 to 220° C. to obtain an extrudate. Specific types and amounts of the starch, plasticizer, first compatibilizer, second compatibilizer, reaction initiator, and biodegradable resin used as constituents in the preparation method of the thermoplastic starch composition according to the present invention refer to the above description.

In the method for preparing a thermoplastic starch composition according to an embodiment of the present invention, the first compatibilizer is selected from unsaturated dicarboxylic acid or anhydrous unsaturated dicarboxylic acid, and the second compatibilizer is benzaldehyde.

In the method for producing a thermoplastic starch composition according to an embodiment of the present invention, during the reactive extrusion process, the hydroxyl group (-OH) present in the starch or biodegradable polymer reacts with the carboxyl group present in the first compatibilizer, An ester bond may be formed, and the biodegradable polymer may form a chemical covalent bond at an unsaturated bond (for example, a double bond) present in the first compatibilizer after being converted into a radical form by a reaction initiator. In addition, during the reactive extrusion process, the starch may form a chemical bond with the second compatibilizer to exist in the form of introducing a hydrophobic functional group.

In the method for preparing a thermoplastic starch composition according to the present invention, the reactive extrusion temperature is preferably 170 to 205° C. considering various chemical reaction efficiencies between starch, biodegradable polymer, first compatibilizer, and second compatibilizer. can be selected from the range of

In order to solve the above object, one embodiment of the present invention provides a biodegradable composition for forming a film comprising the thermoplastic starch composition and the biodegradable polymer in a weight ratio of 1:9 to 5:5. In the biodegradable composition for forming a film 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 considering film formability, mechanical strength or hygroscopicity of the film, which will be described later. do. The biodegradable composition for forming a film according to an embodiment of the present invention comprises the steps of obtaining a fourth mixture by mixing a thermoplastic starch composition and a biodegradable polymer in a weight ratio of 1:9 to 5:5, and mixing the fourth mixture with a weight ratio of 150 to 200 It can be prepared by extruding at a temperature condition of ℃. The biodegradable composition for forming a film according to one embodiment of the present invention may exist in a pelletized form to facilitate film forming.

In order to solve the above object, one embodiment of the present invention provides a biodegradable film prepared by extruding a biodegradable composition for forming a film into a film form. The biodegradable film according to an example of the present invention exhibits high tensile strength, elongation and tear strength. Therefore, a disposable bag, a disposable packaging material, a mulching film, etc. made of a biodegradable film according to an example of the present invention have excellent mechanical strength and durability.

Starch and biodegradable polymers, which are components of the thermoplastic starch composition according to the present invention, exist in a state in which at least a portion is chemically bonded by a graft reaction mediated by the first compatibilizer. Starch, which is a component of the thermoplastic starch composition according to the present invention, exists in the form of introducing a hydrophobic functional group by chemically bonding at least a part of the second compatibilizing agent. By extruding a biodegradable composition in which the thermoplastic starch composition and the biodegradable polymer are uniformly mixed, a biodegradable film can be prepared, and the prepared biodegradable film has excellent mechanical properties. 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 is a result of FT-IR analysis of each of the third mixture and the thermoplastic starch composition obtained in Preparation Example 2 among the examples of the present invention as samples. In FIG. 1, 'before extrusion' is the analysis result for the third mixture, and 'after extrusion' is the analysis result for the thermoplastic starch composition.

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, but do not limit the protection scope of the present invention.

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

Preparation Example 1.

85 parts by weight of corn starch and 15 parts by weight of glycerin were put into a mixer and mixed to obtain a first mixture. Then, 0.5 parts by weight of maleic anhydride, 0.05 parts by weight of benzaldehyde and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane [2,5 -dimethyl-2,5-di (tert-butylperoxy) hexane] was added, the temperature of the mixer was raised to 50-60 ° C, and mixed for about 4 hr to obtain a second mixture. Thereafter, 10 parts by weight of polylactic acid (PLA), a biodegradable polymer, was added to 100 parts by weight of the second mixture, and mixed uniformly 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 180 to 185 ° C, a screw rotation speed of 300 rpm, and a raw material supply speed of 20 rpm, resulting in a chemical bond between corn starch and biodegradable polymers through maleic anhydride. and chemical bonding between corn starch and benzaldehyde. Thereafter, the extrudate of the third mixture was pelletized to obtain a thermoplastic starch composition in the form of pellets.

Thereafter, 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. Thereafter, the fourth mixture was put into a twin screw extruder and extruded under the conditions of a barrel temperature of 175 to 180 ° C, a screw rotation speed of 415 to 420 rpm, and a raw material supply speed of 110 to 120 rpm, and then the extrudate was water-cooled, pelletized, and heated to about 60 ° C. was dried for 24 hr or more to obtain a biodegradable composition for forming a film in pellet form. Thereafter, the biodegradable composition for film molding was put into a film extruder and molded under conditions of a molding temperature of 150 to 160 ° C and a raw material supply speed of about 1000 rpm to prepare a biodegradable film.

Preparation Example 2.

Thermoplastic starch composition and biodegradable composition for film molding under the same conditions and methods as in Preparation Example 1, except that 0.1 part by weight of benzaldehyde was added instead of 0.05 part by weight of benzaldehyde based on 100 parts by weight of the first mixture. and biodegradable films were prepared.

Preparation Example 3.

A thermoplastic starch composition and a biodegradable composition for film molding under the same conditions and methods as in Preparation Example 1, except that 0.15 parts by weight of benzaldehyde was added instead of 0.05 parts by weight of benzaldehyde based on 100 parts by weight of the first mixture. and biodegradable films were prepared.

Preparation Example 4.

Thermoplastic starch composition and biodegradable composition for film forming under the same conditions and methods as in Preparation Example 1, except that 0.2 parts by weight of benzaldehyde was added instead of 0.05 parts by weight of benzaldehyde based on 100 parts by weight of the first mixture. and biodegradable films were prepared.

Comparative Preparation Example 1.

85 parts by weight of corn starch and 15 parts by weight of glycerin were put into a mixer, the temperature of the mixer was raised to 50 to 60 ° C, and the mixture was mixed for about 4 hr 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 180 to 185 ° C, a screw rotation speed of 300 rpm, and a raw material supply speed of 20 rpm. Thereafter, the extrudate of the first mixture was pelletized to obtain a thermoplastic starch composition in the form of pellets.

Thereafter, 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. Thereafter, the second mixture was put into a 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 speed of 110 to 120 rpm, and then the extrudate was water-cooled, pelletized, and then heated to about 60 ° C. was dried for 24 hr or more to obtain a biodegradable composition for forming a film in pellet form. Thereafter, the biodegradable composition for film molding was put into a film extruder and molded under conditions of a molding temperature of 150 to 160 ° C and a raw material supply speed of about 1000 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 put into a mixer and mixed to obtain a first mixture. Then, 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 were added to 100 parts by weight of the first mixture. 0.1 part by weight of (tert-butylperoxy)hexane] was added, the temperature of the mixer was raised to 50 to 60 ° C, and the mixture was mixed for about 4 hr to obtain a second mixture. Thereafter, the second mixture was put into a twin-screw extruder and extruded under the conditions of a barrel temperature of 180 to 185 ° C, a screw rotation speed of 300 rpm, and a raw material supply speed of 20 rpm. Thereafter, the extrudate of the second mixture was pelletized to obtain a thermoplastic starch composition in the form of pellets.

Thereafter, 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. Thereafter, the third mixture was put into a 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 speed of 110 to 120 rpm, and then the extrudate was water-cooled, pelletized, and heated to about 60 ° C. was dried for 24 hr or more to obtain a biodegradable composition for forming a film in pellet form. Thereafter, the biodegradable composition for film molding was put into a film extruder and molded under conditions of a molding temperature of 150 to 160 ° C and a raw material supply speed of about 1000 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 put into a mixer and mixed to obtain a first mixture. Then, 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 were added to 100 parts by weight of the first mixture. 0.1 part by weight of (tert-butylperoxy)hexane] was added, the temperature of the mixer was raised to 50 to 60 ° C, and the mixture was mixed for about 4 hr to obtain a second mixture. Thereafter, 10 parts by weight of polylactic acid (PLA), a biodegradable polymer, was added to 100 parts by weight of the second mixture, and mixed uniformly 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 180 to 185 ° 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 the form of pellets.

Thereafter, 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. Thereafter, the fourth mixture was put into a 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 speed of 110 to 120 rpm, and then the extrudate was water-cooled, pelletized, and heated to about 60 ° C. was dried for 24 hr or more to obtain a biodegradable composition for forming a film in pellet form. Thereafter, the biodegradable composition for film molding was put into a film extruder and molded under conditions of a molding temperature of 150 to 160 ° C and a raw material supply speed of about 1000 rpm to prepare a biodegradable film.

Comparative Preparation Example 4.

85 parts by weight of corn starch and 15 parts by weight of glycerin were put into a mixer and mixed to obtain a first mixture. Then, 0.5 parts by weight of maleic anhydride, 0.5 parts by weight of citric acid and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane [2, 0.1 part by weight of 5-dimethyl-2,5-di(tert-butylperoxy)hexane] was added, the temperature of the mixer was raised to 50-60 °C, and the mixture was mixed for about 4 hr to obtain a second mixture. Thereafter, 10 parts by weight of polylactic acid (PLA), a biodegradable polymer, was added to 100 parts by weight of the second mixture, and mixed uniformly 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 180 to 185 ° 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 the form of pellets.

Thereafter, 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. Thereafter, the fourth mixture was put into a 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 speed of 110 to 120 rpm, and then the extrudate was water-cooled, pelletized, and heated to about 60 ° C. was dried for 24 hr or more to obtain a biodegradable composition for forming a film in pellet form. Thereafter, the biodegradable composition for film molding was put into a film extruder and molded under conditions of a molding temperature of 150 to 160 ° C and a raw material supply speed of about 1000 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 put into a mixer and mixed to obtain a first mixture. Then, 0.5 parts by weight of maleic anhydride, 0.1 part by weight of vanillin, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane [2,5 -dimethyl-2,5-di (tert-butylperoxy) hexane] was added, the temperature of the mixer was raised to 50-60 ° C, and mixed for about 4 hr to obtain a second mixture. Thereafter, 10 parts by weight of polylactic acid (PLA), a biodegradable polymer, was added to 100 parts by weight of the second mixture, and mixed uniformly 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 180 to 185 ° 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 the form of pellets.

Thereafter, 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. Thereafter, the fourth mixture was put into a 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 speed of 110 to 120 rpm, and then the extrudate was water-cooled, pelletized, and heated to about 60 ° C. was dried for 24 hr or more to obtain a biodegradable composition for forming a film in pellet form. Thereafter, the biodegradable composition for film molding was put into a film extruder and molded under conditions of a molding temperature of 150 to 160 ° C and a raw material supply speed of about 1000 rpm to prepare a biodegradable film.

2. Physical property analysis of thermoplastic starch composition and biodegradable film

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

FT-IR analysis was performed on each of the third mixture and the thermoplastic starch composition obtained in Preparation Example 2 as samples, and the results are shown in FIG. 1 . The third mixture obtained in Preparation Example 2 is obtained by adding 10 parts by weight of biodegradable polymer, polylactic acid (PLA) to 100 parts by weight of the second mixture and mixing them uniformly, which is put into a reactive extrusion process. used as a raw material. The second mixture is a mixture in which corn starch, glycerin, maleic anhydride, benzaldehyde, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane are uniformly mixed in predetermined contents. In addition, the third mixture is a uniform mixture of corn starch, glycerin, maleic anhydride, benzaldehyde, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane and polylactic acid in a predetermined content relationship is a mixture In addition, the thermoplastic starch composition obtained in Preparation Example 2 was commercialized by introducing the third mixture into an extruder, melting it under a predetermined temperature condition, and performing reaction extrusion. The reactive extrusion process converts the polysaccharide and biopolymer into a uniform phase by dissolving the polysaccharide and biopolymer in the presence of a compatibilizer and inducing a chemical bonding reaction, and is one of the reactive compatibilization methods.

[Schematic diagram of reactive extrusion process]

As shown in Figure 1, after reactive extrusion, the OH group peak (3200 ~ 3300 cm ^-1 ) of starch was reduced, and the aldehyde group present in benzaldehyde (C = O stretch 1650 cm ^-1 peak and CH stretch 2750 ~ 3000 cm ^{-1 1} peak) was reduced by chemical bonding between starch and benzaldehyde after reactive extrusion. Benzaldehyde forms an acetal-acetal linkage with the hydroxyl group present in starch to introduce a hydrophobic functional group into starch, thereby increasing the compatibility of starch with a hydrophobic polymer (eg polyester). judged

[Binding mechanism of starch and benzaldehyde in reactive extrusion process]

In addition, C=O peaks corresponding to ester groups and carboxyl groups were generated by esterification between starch and maleic anhydride after reactive extrusion. In addition, in the process of reactive extrusion, polylactic acid has a radical form by a reaction initiator and forms a chemical covalent bond at the position of the double bond (C=C) present in maleic anhydride. In addition, the carboxyl group present in maleic anhydride and the hydroxyl group present in starch form a covalent chemical bond through an ester reaction, and as a result, starch and polylactic acid are chemically bonded by a graft reaction mediated by maleic anhydride. It exists in a state of being [J.J. Koh et al. / International Journal of Biological Macromolecules 109 (2018) 99-113].

(2) Analysis of mechanical properties

Various mechanical properties of the biodegradable films prepared in Preparation Examples 1 to 4 and Comparative Preparation Examples 1 to 5 were measured as follows. A specimen was prepared by cutting the biodegradable film into a width of 10 mm according to KSS M1008 standard, and the film thickness was recorded using a thickness meter. 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. Table 1 summarizes the mechanical property measurement results of the biodegradable films prepared in Preparation Examples 1 to 4 and Comparative Preparation Examples 1 to 5.

Classification of biodegradable film Tensile strength (N/㎟) Elongation (%) Tear strength (N/mm) MD CD MD CD MD CD Preparation Example 1 37 34 638 667 160 170 Preparation Example 2 44 45 589 756 185 200 Preparation Example 3 45 41 604 741 178 189 Production Example 4 52 49 527 666 165 186 Comparative Preparation Example 1 4 2 85 38 40 20 Comparative Preparation Example 2 23 19 285 676 96 95 Comparative Preparation Example 3 28 29 633 667 129 134 Comparative Preparation Example 4 36 30 627 653 134 131 Comparative Preparation Example 5 13 12 180 527 66 73

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

* CD (cross direction): vertical direction of extrusion (transverse direction)

As shown in Table 1, the biodegradable films prepared in Preparation Examples 1 to 4 had good mechanical properties. On the other hand, compared to the biodegradable film prepared in Preparation Example 2, the biodegradable film prepared in Comparative Preparation Example 5 was prepared under the same conditions and the same method except that vanillin was used instead of benzaldehyde as one of the compatibilizers. made by applying Both benzaldehyde and vanillin have a common feature of aromatic aldehyde, but their effects on the mechanical properties of biodegradable films are very different.

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)

A composition comprising starch, a plasticizer, a first compatibilizer, a second compatibilizer, a biodegradable polymer and a reaction initiator,
The first compatibilizing agent is selected from unsaturated dicarboxylic acids or anhydrous unsaturated dicarboxylic acids,
The second compatibilizer is a thermoplastic starch composition, characterized in that benzaldehyde (benzaldehyde).
The thermoplastic starch composition according to claim 1, wherein at least a portion of the starch and the biodegradable polymer exist in a chemically bonded state by a graft reaction mediated by the first compatibilizer.
The thermoplastic starch composition according to claim 1, wherein at least a portion of the starch is hydrophobized by chemically bonding with the second compatibilizer.
The thermoplastic starch composition according to claim 1, wherein the plasticizer is composed of at least one polyhydric alcohol selected from sorbitol, ethylene glycol, propylene glycol, diethylene glycol, glycerin, and pentaerythritol.
The method of claim 1, wherein the first compatibilizer is maleic acid, fumaric acid, acetylenedicarboxylic acid, glutaconic acid, 2-decenedioic 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, Anhydride Choose from Traumatic anhydride, Muconic anhydride, Glutinic anhydride, Citraconic anhydride, Mesaconic anhydride or Itaconic anhydride A thermoplastic starch composition, characterized in that consisting of one or more species.
The method of claim 1, wherein the biodegradable polymer is 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 Characterized in that it consists of at least one selected from copolymer [Poly (butylene adipate-co-butylene terephtalate), PBABT] or butylene adipate-terephthalate copolymer [Poly (butylene adipate-co-terephtalate), PBAT] A thermoplastic starch composition.
The method of 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 hydroperoxide, 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 1-1-dimethyl-3-hydroxybutyl peroxy-2- ethyl hexanoate, tert-amyl peroxy-benzoate, tert-butyl peroxy-pivalate ), 2,5-dihydroxyperoxy-2,5-dimethylhexane, cumene hydroperoxide or 1,3-bis(tert-butyl) A thermoplastic starch composition characterized in that it consists of at least one peroxide-based reaction initiator selected from peroxyisopropyl) benzene [1,3-Bis (tert-butylperoxyisopropyl) benzene].
The method of claim 1, based on the total weight, starch 60 ~ 90% by weight, plasticizer 3 ~ 30% by weight, first compatibilizer 0.1 ~ 3% by weight, second compatibilizer 0.01 ~ 2% by weight, biodegradable polymer 2 ~ A thermoplastic starch composition comprising 25% by weight and 0.01 to 1% by weight of a reaction initiator.
mixing starch and a plasticizer to obtain a first mixture;
obtaining a second mixture by adding a first compatibilizer, a second compatibilizer, and a reaction initiator to the first mixture and mixing while heating;
obtaining a third mixture by adding and mixing a biodegradable polymer to the second mixture; and
A method comprising the step of obtaining an extrudate by performing reactive extrusion on the third mixture at a temperature condition of 160 to 220 ° C.,
The first compatibilizer is selected from unsaturated dicarboxylic acids or anhydrous unsaturated dicarboxylic acids,
The second compatibilizer is a method for producing a thermoplastic starch composition, characterized in that benzaldehyde (benzaldehyde).
A biodegradable composition for forming a film comprising the thermoplastic starch composition according to any one of claims 1 to 8 and a biodegradable polymer in a weight ratio of 1:9 to 5:5.

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