Method for producing a polylactide blow film

Abstract

The present invention relates to a manufacturing method capable of manufacturing a polylactide blow film. According to the present invention, it is possible to provide a polylactide blow film having high transparency and excellent surface characteristics without additives such as plasticizers, and it is possible to improve process stability.

Description

Technical Field

[0001] [Cross - Reference to Related Applications] This application claims the benefit of priority based on Korean Patent Application No. 10 - 2023 - 0028617 filed on March 3, 2023 and Korean Patent Application No. 10 - 2024 - 0029918 filed on February 29, 2024, and all contents disclosed in the documents of the Korean patent applications are incorporated herein by reference in their entirety.

[0002] The present invention relates to a manufacturing method capable of providing a polylactic acid blow film having excellent transparency and surface properties without a plasticizer.

Background Art

[0003] A polylactic acid polymer (hereinafter referred to as "PLA") is an eco - friendly material having biodegradability, and many recent studies have been conducted on it. PLA is generally a linear molecule and shows the characteristics of a thermoplastic polymer unless deformed, and is usefully utilized as a material for various films, fibers, and other molded products.

[0004] Films containing PLA, especially blow films, are known to be difficult to manufacture, and additives such as plasticizers must be added for production. However, plasticizers are often not preferred for films used in food - related applications and may leach out because they have poor compatibility with PLA. To avoid such problems, the solution casting method is used. However, when manufacturing a PLA film by the solution casting method, only films for limited applications can be produced, and there is a disadvantage that the process cost is very high.

[0005] Therefore, there is a need for a new manufacturing method capable of manufacturing a PLA blow film with excellent physical properties without a plasticizer.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention aims to provide a polylactide blow film having high transparency and excellent surface properties, and to provide a method for producing a polylactide blow film that can enhance process safety.

Means for Solving the Problems

[0007] Therefore, according to one embodiment of the present invention, a step of preparing a mixture containing a polylactide polymer and an epoxy group-containing acrylate terpolymer (step 1), a step of producing a branched polylactide polymer in pellet form by reacting and extruding the mixture (step 2), and a step of producing a blow film by blow-extruding the pellets (step 3), a method for producing a polylactide blow film, wherein the epoxy group-containing acrylate terpolymer contains 30% by weight to 50% by weight of repeating units derived from a first alkyl (meth)acrylate monomer, 30% by weight to 60% by weight of repeating units derived from a glycidyl (meth)acrylate monomer, and 10% by weight to 20% by weight of repeating units derived from a second alkyl (meth)acrylate monomer, the first alkyl (meth)acrylate monomer and the second alkyl (meth)acrylate monomer are different from each other, and the mixture in step 1 contains 0.1 part by weight or more and less than 1.0 part by weight of an epoxy acrylate terpolymer with respect to 100 parts by weight of the polylactide polymer, a method for producing a polylactide blow film is provided.

[0008] The epoxy group-containing acrylate terpolymer may contain 30% by weight to 45% by weight of repeating units derived from a first alkyl (meth)acrylate monomer, 30% by weight to 45% by weight of repeating units derived from a glycidyl (meth)acrylate monomer, and 10% by weight to 20% by weight of repeating units derived from a second alkyl (meth)acrylate monomer.

[0009] The epoxy group-containing acrylate terpolymer may have 30 to 80 epoxy groups per molecule.

[0010] The first alkyl (meth)acrylate and the second alkyl (meth)acrylate may each independently be at least one selected from the group consisting of methyl (meth)acrylate, butyl acrylate, and 2-(ethylhexyl)acrylate.

[0011] The polylactide film may have a weight average molecular weight measured by gel permeation chromatography using a polystyrene standard of 200,000 g / mol to 500,000 g / mol.

[0012] The mixture in Step 1 may contain 0.5 to 0.75 parts by weight of an epoxy acrylate terpolymer with respect to 100 parts by weight of the polylactide polymer.

[0013] The mixture in Step 1 may further contain one or more selected from the group consisting of a slip agent and an anti-blocking agent.

[0014] The reactive extrusion in Step 2 may be carried out at a temperature of 150°C to 220°C.

[0015] During the reactive extrusion in Step 2, the screw rotation speed of the extruder may be 100 rpm to 300 rpm.

[0016] The blow extrusion in Step 3 may be carried out at a temperature of 200°C to 230°C and a pressure of 10 bar to 50 bar.

Advantages of the Invention

[0017] According to the present invention, it is possible to provide a polylactide blow film having high transparency and excellent surface characteristics without additives such as plasticizers, and to improve process stability without increasing costs.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0019] The terms used in this specification are used only for explaining exemplary embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates a different meaning. In this specification, terms such as "including", "comprising", or "having" are intended to specify the presence of implemented features, steps, components, or combinations thereof, and it should be understood that they do not preclude the presence or addition of one or more other features, steps, components, or combinations thereof in advance.

[0020] Since the present invention can be modified in various ways and can have various forms, specific examples are illustrated and described in detail below. However, this is not intended to limit the present invention to a specific disclosed form, and it should be understood that it includes all modifications, equivalents, or alternatives included in the spirit and technical scope of the present invention.

[0021] In this specification, the term "long chain branching (LCB)" means a long chain in which the number of carbon atoms in the branch is similar to that of the backbone chain to the extent that it is indistinguishable from the backbone chain.

[0022] In this specification, the terms "derived unit and derived repeating unit" may each mean a component, unit, structure, or the substance itself resulting from a certain substance.

[0023] The present invention will be described in detail below.

[0024] The present invention relates to a method for producing a polylactide blow film having high transparency and excellent surface properties without a plasticizer.

[0025] Specifically, according to one embodiment of the present invention, a step of preparing a mixture containing a polylactide polymer and an epoxy group-containing acrylate terpolymer (step 1); a step of producing a branched polylactide polymer in pellet form by reactive extrusion of the mixture (step 2); a step of producing a blow film by blow extrusion of the pellets (step 3), which is a method for producing a polylactide blow film, wherein the epoxy group-containing acrylate terpolymer contains 30% to 50% by weight of repeating units derived from a first alkyl (meth)acrylate monomer, 30% to 60% by weight of repeating units derived from a glycidyl (meth)acrylate monomer, and 10% to 20% by weight of repeating units derived from a second alkyl (meth)acrylate monomer, and the first alkyl (meth)acrylate monomer and the second alkyl (meth)acrylate monomer are different from each other; a method for producing a polylactide blow film is provided, wherein the mixture in step 1 contains 0.1 part by weight or more and less than 1.0 part by weight of an epoxy acrylate terpolymer based on 100 parts by weight of the polylactide polymer.

[0026] Conventionally, a plasticizer has been required to produce a polylactide blow film. However, plasticizers are often not suitable for films used in food-related applications due to human toxicity and the like, and there are problems such as leaching because they have poor compatibility with PLA. In addition, when producing a PLA film by the solution casting method, only films for limited applications can be produced, and there is a demerit that the process cost is very high.

[0027] Therefore, the inventors of the present invention have studied a method for producing a PLA blow film with excellent physical properties without additives such as plasticizers. As a result, they have found that a PLA blow film with excellent physical properties can be produced by subjecting a mixture containing a PLA and an epoxy group-containing acrylate terpolymer to reactive extrusion and blow extrusion, thereby completing the present invention.

[0028] Specifically, the epoxy group-containing acrylate terpolymer serves as a branching agent for the PLA. Therefore, during the reactive extrusion of the mixture, long-chain branching (LCB) is introduced into the PLA, the linear structure of the PLA polymer is modified, and a sufficient branched structure is formed. The PLA polymer with such a branched structure has increased elasticity and can stably form bubbles during blow extrusion. Therefore, a blow film with a smooth surface and uniform thickness can be produced. In addition, when the epoxy group-containing acrylate terpolymer is used as a branching agent, the produced blow film has high transparency and can exhibit excellent appearance characteristics.

[0029] Hereinafter, the manufacturing method of the polylactide blow film will be described in more detail step by step.

[0030] (Step 1) In the manufacturing method according to an embodiment of the present invention, first, a mixture containing a polylactide polymer and an epoxy group-containing acrylate-based terpolymer is prepared.

[0031] The polylactide polymer is a thermoplastic polyester obtained by polymerizing lactide or lactic acid, and includes a polymer having a repeating unit of -[OC(O)CH(CH3)]-.

[0032] Also, the polylactide polymer may be one or more selected from the group consisting of poly-L-lactide, poly-D-lactide, and poly-L,D-lactide.

[0033] Further, the polylactide polymer may have a repeating unit derived from an alkylene oxide or a repeating unit derived from another monomer copolymerizable with lactide. In this case, the repeating unit derived from the alkylene oxide or the repeating unit derived from another monomer copolymerizable with lactide may be present in a block and / or random arrangement. Further, when the polylactide polymer contains the repeating unit derived from the alkylene oxide or the repeating unit derived from another monomer copolymerizable with lactide, it may be contained in an amount of 10% by weight or less, specifically 5% by weight or less.

[0034] Further, the polylactide polymer may have a relative weight average molecular weight measured by gel permeation chromatography using a polystyrene standard of 50,000 g / mol or more, or 100,000 g / mol or more, and 300,000 g / mol or less, or 250,000 g / mol or less, and the molecular weight distribution may be 1.2 or more, or 1.5 or more, and 4 or less, or 3 or less.

[0035] The polylactide polymer can be purchased and used as those commonly known in the art, or can be manufactured and used. When it is manufactured and used, it may be manufactured by a conventional polymerization method in the art using lactide or lactic acid as a monomer.

[0036] The epoxy group-containing acrylate terpolymer plays a role of reacting with the polylactide polymer in Step 2 described below to introduce long-chain branching (LCB). Thereby, a branched structure is formed in the polylactide polymer, the elasticity can be improved, bubbles can be stably formed during blow extrusion, and a polylactide blow film with excellent quality can be provided.

[0037] The epoxy group-containing acrylate terpolymer contains 30% to 50% by weight of repeating units derived from a first alkyl (meth)acrylate monomer, 30% to 60% by weight of repeating units derived from a glycidyl (meth)acrylate monomer, and 10% to 20% by weight of repeating units derived from a second alkyl (meth)acrylate monomer, and the first alkyl (meth)acrylate monomer and the second alkyl (meth)acrylate monomer are different from each other.

[0038] In one embodiment, the epoxy group-containing acrylate terpolymer may contain 30% to 45% by weight of repeating units derived from a first alkyl (meth)acrylate monomer, 30% to 45% by weight of repeating units derived from a glycidyl (meth)acrylate monomer, and 10% to 20% by weight of repeating units derived from a second alkyl (meth)acrylate monomer.

[0039] Alternatively, the epoxy group-containing acrylate terpolymer may contain 40% to 45% by weight of repeating units derived from a first alkyl (meth)acrylate monomer, 40% to 45% by weight of repeating units derived from a glycidyl (meth)acrylate monomer, and 10% to 20% by weight of repeating units derived from a second alkyl (meth)acrylate monomer.

[0040] The first alkyl (meth)acrylate monomer and the second alkyl (meth)acrylate monomer are each independently at least one selected from the group consisting of methyl methacrylate, methyl acrylate, butyl methacrylate, butyl acrylate, and 2-ethylhexyl acrylate, and they may be different from each other. Specifically, the first alkyl (meth)acrylate monomer and the second alkyl (meth)acrylate monomer are each independently methyl methacrylate, methyl acrylate, butyl methacrylate, or butyl acrylate, and they may be different from each other. Even more specifically, the first alkyl (meth)acrylate monomer may be methyl methacrylate, and the second alkyl (meth)acrylate monomer may be butyl methacrylate.

[0041] Also, the glycidyl (meth)acrylate monomer may be a glycidyl methacrylate monomer or a glycidyl acrylate monomer.

[0042] The epoxy group-containing acrylate terpolymer can be produced by polymerizing a first alkyl (meth)acrylate monomer, a glycidyl (meth)acrylate monomer, and a second alkyl (meth)acrylate monomer different from the first alkyl (meth)acrylate monomer in a solvent in the presence of an emulsifier.

[0043] Specifically, the epoxy group-containing acrylate terpolymer is produced by polymerizing 30% to 50% by weight of a first alkyl (meth)acrylate monomer, 30% to 60% by weight of a glycidyl (meth)acrylate monomer, and 10% to 20% by weight of a second alkyl (meth)acrylate monomer different from the first alkyl (meth)acrylate monomer in a solvent and in the presence of an emulsifier. At this time, the polymerization may be carried out at 70°C to 80°C over 3 to 10 hours.

[0044] Also, the polymerization may be carried out in an aqueous solvent. In this case, the solvent is distilled water.

[0045] The emulsifier may be one or more selected from the group consisting of an anionic emulsifier, a cationic emulsifier, and a nonionic emulsifier. Examples include one or more selected from the group consisting of alkylaryl sulfonate, alkaline methylalkyl sulfate, soap of fatty acid, alkaline salt of oleic acid, alkaline salt of rosin acid, alkaline salt of lauric acid, sodium diethylhexyl phosphate, phosphonated polyoxyethylene alcohol, and phosphonated polyoxyethylene phenol. Further, the emulsifier may be used in an amount of 5 parts by weight or less, specifically 3.0 parts by weight or less, or 0.5 part by weight to 2.5 parts by weight based on 100 parts by weight of the total monomer content.

[0046] In addition, the polymerization can be carried out by further using a polymerization initiator as needed. At this time, an inorganic peroxide or an organic peroxide can be used as the initiator. For example, water-soluble polymerization initiators such as potassium persulfate, sodium persulfate, and ammonium persulfate, and oil-soluble polymerization initiators such as cumene hydroperoxide and benzoyl peroxide can be used.

[0047] In addition, an activator can be further used to promote the reaction initiation of the peroxide together with the polymerization initiator. As such an activator, one or more selected from the group consisting of sodium formaldehyde sulfoxylate, sodium ethylenediaminetetraacetate, ferrous sulfate, and dextrose can be used.

[0048] Further, the polymerization initiator may be used in an amount of 0.1 part by weight to 10 parts by weight, specifically 0.1 part by weight to 5 parts by weight based on 100 parts by weight of the total monomer content.

[0049] As another example, from the perspective of increasing the efficiency of the polymerization reaction, a chain transfer agent (or a chain transfer agent) may be further used. As the chain transfer agent, a linear or branched alkyl thiol compound having 5 to 20 carbon atoms may be used. By way of example, any one or more selected from hexane thiol, cyclohexane thiol, adamantane thiol, heptane thiol, octane thiol, nonane thiol, decane thiol, undecane thiol, dodecane thiol, hexadecane thiol and octadecane thiol may be used.

[0050] In addition, the epoxy group-containing acrylate terpolymer may be further produced by performing one or more steps selected from washing, dehydration and drying after the polymerization. At this time, washing, dehydration and drying may be performed by methods commonly known in the art. On the other hand, the mixture contains an epoxy-based acrylate terpolymer in an amount of 0.1 part by weight or more and less than 1.0 part by weight based on 100 parts by weight of the polylactide polymer. Specifically, the mixture may contain an epoxy-based acrylate terpolymer in an amount of 0.1 part by weight or more, 0.2 part by weight or more, 0.3 part by weight or more, or 0.4 part by weight or more, or 0.5 part by weight or more, and 0.9 part by weight or less, 0.8 part by weight or less, 0.75 part by weight or less, or 0.7 part by weight or less based on 100 parts by weight of the polylactide polymer.

[0051] When the mixture contains less than 0.1 part by weight of the epoxy-based acrylate terpolymer with respect to 100 parts by weight of the polylactide polymer, sufficient branching may not occur during the reactive extrusion process, and thus it may be difficult to form bubbles during subsequent blow extrusion. Conversely, when the content of the epoxy-based acrylate terpolymer is 1.0 part by weight or more with respect to 100 parts by weight of the polylactide polymer, gels may be formed during blow film extrusion due to excessive branching, and thus the bubbles may not be well maintained, resulting in smooth blow extrusion not being performed.

[0052] The mixture may further contain, as additives, one or more selected from the group consisting of a slip agent and an antiblocking agent, together with the aforementioned polylactide polymer and the epoxy group-containing acrylate terpolymer.

[0053] The slip agent can be used to reduce the coefficient of friction between films. As the slip agent, for example, one or more selected from the group consisting of oleamide, erucamide, stearamide, behenamide, oleyl palmitamide, stearyl erucamide, ethylene bis-oleamide, and N,N'-ethylene bis(stearamide) (EBS) can be used. When using the slip agent, its content may be 5% by weight or less, 3% by weight or less, or 1% by weight or less, and 0.1% by weight or more, 0.3% by weight or more, or 0.5% by weight or more with respect to the total weight of the mixture.

[0054] The antiblocking agent can be used to prevent the produced films from adhering to each other and to improve processability. For example, one or more selected from the group consisting of natural silica, synthetic silica, talc, and calcium carbonate can be used. The antiblocking agent may be contained, for example, at 10% by weight or less, 8% by weight or less, 5% by weight or less, or 3% by weight or less, and 0.1% by weight or more, 0.5% by weight or more, 1% by weight or more, or 1.5% by weight or more with respect to the total weight of the mixture.

[0055] In one embodiment, the mixture may contain oleamide as a slip agent and talc as an antiblocking agent. At this time, oleamide may be contained at 0.1% by weight to 5% by weight, or 0.5% by weight to 1.0% by weight, and talc may be contained at 0.1% by weight to 10% by weight, or 1.5% by weight to 3% by weight with respect to the total weight of the mixture.

[0056] The method for producing the mixture is not particularly limited, and the mixture can be produced by dry-blending the aforementioned raw materials without a solvent. Equipment such as a plowshare mixer or an extruder can be used for mixing, but it is not limited thereto.

[0057] (Step 2) Next, the mixture is reaction-extruded to produce a pelletized branched polylactide polymer.

[0058] Reaction extrusion is a chemical reaction step that uses an extruder as a reactor to induce modification of a polymer. In the present invention, it is carried out for the branching of a polylactide polymer. Reaction extrusion does not require a solvent, has the advantages that the transfer, kneading, and mixing of reactants having high viscosity are easy, and various reaction conditions can be set.

[0059] The reaction extrusion can be carried out through a single-screw extruder or a twin-screw extruder, and preferably, a twin-screw extruder can be used. A twin-screw extruder has the advantages that the residence time distribution in the extruder can be adjusted, it is excellent in kneading performance, heat conductivity, and polymer transfer ability, and the combination of the screw and the barrel is easy.

[0060] The reaction extrusion is preferably carried out at a temperature of 150°C to 220°C. If the extrusion temperature is low, the modification of the polylactide polymer may not occur smoothly, and if the temperature is excessively high, the polylactide polymer and the epoxy group-containing acrylate terpolymer may be modified.

[0061] From such a viewpoint, the extrusion temperature is preferably 150°C or higher, 170°C or higher, or 180°C or higher, or 190°C or higher, and 220°C or lower, or 210°C or lower, or 200°C or lower.

[0062] The aforementioned reaction extrusion temperature means the temperature in the reaction zone (barrel) of the extruder, and the temperatures of the raw material input part and the die part may be about 20°C to 40°C lower than the reaction zone.

[0063] Also, during the reactive extrusion, the screw rotation speed of the extruder is preferably 100 rpm or more, or 150 rpm or more, or 170 rpm or more, and 300 rpm or less, or 250 rpm or less, or 200 rpm or less. This can prevent excessive mixing and modification of the reactants and prevent excessive branching, which is preferable.

[0064] The preferable residence time in the reactive extrusion step is 1 minute or more, or 2 minutes or more, and may be 10 minutes or less, or 5 minutes or less under the conditions described above.

[0065] The pelletized branched polylactide polymer produced through the reactive extrusion may have an average number of long-chain branches per molecule of 7 to 10, and can exhibit excellent melt strength and elastic properties due to such branching characteristics.

[0066] (Step 3) Next, the pellets are blow-extruded to produce a blow film.

[0067] The blow extrusion can generally be performed using a blow film extruder used for producing polymer films. In the examples described later, a small single-screw extruder was used, but the present invention is not limited thereto.

[0068] The temperature of the barrel during the blow extrusion is preferably 200°C to 230°C, and the pressure is preferably 10 bar to 50 bar. When the temperature and pressure of the barrel satisfy the above range, sufficient branching occurs, which is preferable from the viewpoint of melt elasticity. More preferably, the temperature of the barrel is 200°C or more, or 210°C or more, and 230°C or less, or 220°C or less, and the pressure is 10 bar or more, or 15 bar or more, and 50 bar or less, or 30 bar or less.

[0069] The pressure of the barrel is the pressure across the entire barrel, and the temperature of the barrel is the temperature of the remaining barrel excluding the first barrel connected to the raw material input section. The first barrel is directly connected to the raw material hopper, and in order to prevent the raw material from fusing, it is preferable to maintain a temperature of 30°C to 100°C.

[0070] Also, for sufficient branching, the screw rotation speed is preferably 10 rpm or more, or 15 rpm or more, and 50 rpm or less, or 30 rpm or less.

[0071] The branched polylactide film produced by the above method has a weight average molecular weight of 200,000 g / mol to 500,000 g / mol as measured by gel permeation chromatography using a polystyrene standard, and the polydispersity index may be 2.0 to 4.0, or 2.0 to 3.5. The method for measuring the weight average molecular weight and polydispersity index by gel permeation chromatography will be specifically described in the examples below.

[0072] According to the above-described production method, it is possible to provide a polylactide blow film that has high transparency, a smooth surface, and excellent appearance characteristics without additives such as plasticizers. In particular, the production method has a significantly lower production cost compared to the casting method, is excellent in process efficiency and process stability, and is suitable for mass production. The polylactide blow film produced by the production method can be used as a substitute for conventional non-degradable films, and since it is biodegradable, it has the advantage of being environmentally friendly. The polylactide blow film can be suitably used as a transparent film for packaging foods such as meat, fish, and vegetables, and for packaging toys, etc.

[0073] Hereinafter, preferred examples are presented for the understanding of the present invention. However, it is obvious to those skilled in the art that the following examples are only illustrative of the present invention, and various changes and modifications are possible within the scope and technical concept of the present invention. It is natural that such changes and modifications belong to the scope of the appended claims.

[0074] [Example] Production Example 1 200 parts by weight of distilled water and 0.5 part by weight of sodium dodecylbenzenesulfonate (SDBS) were charged into a reactor, and the temperature was raised to 70°C while stirring. 0.2 part by weight of potassium persulfate (KPS) was added, and after stirring for 20 minutes, a mixture of 45 parts by weight of methyl methacrylate, 40 parts by weight of glycidyl methacrylate, 15 parts by weight of butyl methacrylate, and 0.7 part by weight of 1-octanethiol was continuously added to the reactor over 4 hours. After the addition was completed, the mixture was cooled to 25°C while stirring for 30 minutes to produce an emulsion polymerization latex. The produced emulsion polymerization latex was coagulated with an aqueous calcium acetate solution, heat-treated by raising the temperature to 90°C, dehydrated, and dried at 60°C for 16 hours to produce an epoxy group-containing acrylate terpolymer.

[0075] Production Example 2 200 parts by weight of distilled water and 0.5 part by weight of sodium dodecylbenzenesulfonate (SDBS) were charged into a reactor, and the temperature was raised to 70°C while stirring. 0.2 part by weight of potassium persulfate (KPS) was added, and after stirring for 20 minutes, a mixture of 45 parts by weight of methyl methacrylate, 45 parts by weight of glycidyl methacrylate, 10 parts by weight of 2-ethylhexyl acrylate, and 0.7 part by weight of 1-octanethiol was continuously added to the reactor over 4 hours. After the addition was completed, the mixture was cooled to 25°C while stirring for 30 minutes to produce an emulsion polymerization latex. The produced emulsion polymerization latex was coagulated with an aqueous calcium acetate solution, heat-treated by raising the temperature to 90°C, dehydrated, and dried at 60°C for 16 hours to produce an epoxy group-containing acrylate terpolymer.

[0076] Production Example 3 200 parts by weight of distilled water and 0.5 part by weight of sodium dodecylbenzenesulfonate (SDBS) were charged into a reactor and heated to 70 °C with stirring. 0.2 part by weight of potassium persulfate (KPS) was added and stirred for 20 minutes. Then, a mixture of 65 parts by weight of methyl methacrylate, 20 parts by weight of glycidyl methacrylate, 15 parts by weight of butyl methacrylate, and 0.7 part by weight of 1-octanethiol was continuously added to the reactor over 4 hours. After the addition was completed, it was cooled to 25 °C with stirring for 30 minutes to produce an emulsion polymerization latex. The produced emulsion polymerization latex was coagulated with an aqueous calcium acetate solution, heat-treated by raising the temperature to 90 °C, dehydrated, and dried at 60 °C for 16 hours to produce an epoxy group-containing acrylate terpolymer.

[0077] Example 1 The polylactide polymer (4032D, manufactured by Natureworks) was prepared by drying at 80 °C for 24 hours. In the following examples and comparative examples, "polylactide polymer" means the polylactide polymer prepared in this way.

[0078] 0.5 part by weight of the epoxy group-containing acrylate terpolymer produced in Production Example 1, 0.5 part by weight of oleamide, and 1.5 parts by weight of talc were mixed with 97.5 parts by weight of the prepared polylactide polymer to produce a mixture.

[0079] The mixture was extruded using a twin-screw extruder (manufactured by Bautek, BA-19) under the conditions shown in Table 1 below to produce pellets.

Table 1

[0080] Thereafter, the produced pellets were extruded using a blown film extruder (Collin Lab & Pilot Solutions, Blown Film Line E Entrance) under the conditions shown in Table 2 below to produce a polylactide blown film.

Table 2

[0081] Example 2 Using a mixture containing 97.25 parts by weight of a polylactide polymer, 0.75 parts by weight of the epoxy group-containing acrylate terpolymer produced in Production Example 1, 0.5 parts by weight of oleamide, and 1.5 parts by weight of talc, pellets were produced in the same manner as in Example 1.

[0082] Thereafter, the produced pellets were extruded using a blown film extruder under the conditions shown in Table 3 below to produce a polylactide blown film. [Table 3]

[0083] Example 3 Using a mixture containing 97.9 parts by weight of a polylactide polymer, 0.1 parts by weight of the epoxy group-containing acrylate terpolymer produced in Production Example 2, 0.5 parts by weight of oleamide, and 1.5 parts by weight of talc, pellets were produced in the same manner as in Example 1.

[0084] Thereafter, the produced pellets were extruded using a blown film extruder under the conditions shown in Table 4 below to produce a polylactide blown film. [Table 4]

[0085] Example 4 Using a mixture containing 97.1 parts by weight of a polylactide polymer, 0.9 parts by weight of the epoxy group-containing acrylate terpolymer produced in Production Example 2, 0.5 parts by weight of oleamide, and 1.5 parts by weight of talc, pellets were produced in the same manner as in Example 1.

[0086] Thereafter, the produced pellets were extruded using a blown film extruder under the conditions shown in Table 5 below to produce a polylactide blown film. [Table 5]

[0087] Comparative Example 1 Using a mixture containing 98.0 parts by weight of a polylactide polymer, 0.5 part by weight of oleamide, and 1.5 parts by weight of talc, pellets were produced in the same manner as in Example 1.

[0088] Thereafter, the produced pellets were extruded using a blown film extruder under the conditions shown in Table 6 below to produce a polylactide blown film. [Table 6]

[0089] Comparative Example 2 Using a mixture containing 97.0 parts by weight of a polylactide polymer, 1.0 part by weight of the epoxy group-containing acrylate terpolymer produced in Production Example 1, 0.5 part by weight of oleamide, and 1.5 parts by weight of talc, pellets were produced in the same manner as in Example 1.

[0090] Thereafter, the produced pellets were extruded using a blown film extruder under the conditions shown in Table 7 below to produce a polylactide blown film. [Table 7]

[0091] Comparative Example 3 Using a mixture containing 97.5 parts by weight of a polylactide polymer, 0.5 part by weight of BASF's chain extender Joncryl-ADR 4468 (registered trademark), 0.5 part by weight of oleamide, and 1.5 parts by weight of talc, pellets and a polylactide blown film were produced in the same manner as in Example 1.

[0092] Thereafter, the produced pellets were extruded using a blown film extruder under the conditions shown in Table 8 below to produce a polylactide blown film. [Table 8]

[0093] Comparative Example 4 Using a mixture containing 97.5 parts by weight of a polylactide polymer, 0.5 part by weight of the epoxy group-containing acrylate terpolymer produced in Production Example 3, 0.5 part by weight of oleamide, and 1.5 parts by weight of talc, pellets were produced in the same manner as in Example 1.

[0094] Thereafter, the produced pellets were extruded under the conditions shown in Table 9 below using a blow film extruder to produce a polylactide blow film. [Table 9]

[0095] Experimental Example (1) Analysis of GPC (gel permeation chromatography) of pellets Using gel permeation chromatography (GPC: Tosoh ECO SEC Elite) equipped with a differential refractive index detector (RI), the number average molecular weight (Mn), weight average molecular weight (Mw), peak top molecular weight (Mp), Z average molecular weight (Mz), and polydispersity index (PDI) of the pellets produced in each of the above Examples and Comparative Examples were measured, and the results are shown in Table 10 below and Figure 1. The peak top characteristics were confirmed by obtaining a fine powder molecular weight distribution curve in which the horizontal axis is the logarithmic molecular weight [log(M)] and the vertical axis is dw / dlog(M), which is the concentration fraction w differentiated with respect to the logarithmic molecular weight.

[0096] The GPC measurement conditions are as follows. Columns: 2 PLgel Olexis columns (manufactured by Polymer Laboratories) Solvent: Tetrahydrofuran (THF) Flow rate: 1.0 ml / min Column temperature: 40°C Sample: 1.5 mg / 1.0 ml THF Standard substance: Polystyrene (corrected by cubic function, 10 kinds with molecular weights of 580 / 3,320 / 9,310 / 29,460 / 75,050 / 128,900 / 298,600 / 739,500 / 2,327,000 / 6,545,000 were used)

Table 10

[0097] Referring to Table 7 above, unlike the pellets of Comparative Example 1 without using a branching agent, it can be confirmed that branching occurred in the pellets of Examples 1 and 2 and Comparative Example 2 using a branching agent.

[0098] (2) GPC (gel permeation chromatography) analysis of blown films In the same manner as in (1) above, GPC analysis of the blown films produced in the respective Examples and Comparative Examples was performed, and the results are shown in Table 11 and Figure 2 below.

Table 11

[0099] (3) Measurement of thickness and haze of blown films Using a Mitutoyo thickness gauge, the thickness was measured at three different points on the blown film, and the average value was derived as the thickness of the blown film.

[0100] The haze of the blown film was measured according to the ASTM D1003 standard using a colorimeter, and C / 2 was used as the light source. At this time, the thickness of the specimens was all in the range of 70 - 80 μm (see Table 9 below), and each specimen was measured 10 times, and the average value was taken.

[0101] The thickness and haze measurement results are shown in Table 12 below.

Table 12

[0102] (4) Evaluation of Bubble Stability during Blow Film Production and Appearance of Blow Film The stability of bubbles during the production of the blow films of the respective examples and comparative examples, and the appearance (smoothness level) of the produced blow films were visually evaluated. Fig. 3 shows the state of bubbles during blow film production and a photograph of the surface of the produced film.

[0103] It was found that the bubble stability during blow film production, that is, the degree to which the bubbles maintained their form without bursting, and the smoothness of the film surface were at an equivalent level and most excellent in Examples 1 and 2 and Comparative Example 3. On the other hand, in the case of Comparative Example 2 in which the branching agent of Production Example 1 was used in an amount of 1 part by weight or more based on 100 parts by weight of polylactide, the bubbles continuously burst and could not maintain their form, and the bubble stability was the worst, and the surface of the produced film was also rough.

[0104] Combining such results with the measurement results of the molecular weight of the blow film, it was determined that sufficient branched structures were formed in Examples 1 and 2 using the branching agent and Comparative Example 3, and the elasticity increased, so they exhibited excellent bubble stability. Therefore, it was determined that the produced films had excellent appearance characteristics. On the other hand, in the case of Comparative Example 2, it was determined that gels were formed during blow film extrusion due to excessive branching, and the bubbles were not well maintained.

[0105] On the other hand, comparing the blow films of Examples 1 and 2 with Comparative Example 3, it can be confirmed that the haze values of Examples 1 and 2 are significantly lower than those of Comparative Example 3, and the transparency is very excellent.

[0106] From the above experimental results, it can be confirmed that the polylactide blow film produced according to the present invention exhibits significantly excellent haze characteristics while showing a similar level of processability compared to the polylactide blow film using an existing branching agent.

Claims

1. Step 1: preparing a mixture including a polylactide polymer and an epoxy-containing acrylate terpolymer; (Step 2) reactively extruding the mixture to produce a branched polylactide polymer in pellet form; and (3) blow-extruding the pellets to produce a blown film, The epoxy group-containing acrylate terpolymer comprises 30% to 50% by weight of a repeating unit derived from a first alkyl (meth)acrylate monomer, 30% to 60% by weight of a repeating unit derived from a glycidyl (meth)acrylate monomer, and 10% to 20% by weight of a repeating unit derived from a second alkyl (meth)acrylate monomer, the first alkyl (meth)acrylate monomer and the second alkyl (meth)acrylate monomer being different from each other; The mixture of step 1 includes 0.1 parts by weight or more and less than 1.0 parts by weight of an epoxy group-containing acrylate terpolymer based on 100 parts by weight of a polylactide polymer; Method for producing polylactide blown film.

2. The epoxy group-containing acrylate terpolymer comprises 30% to 45% by weight of a repeating unit derived from a first alkyl (meth)acrylate monomer, 30% to 45% by weight of a repeating unit derived from a glycidyl (meth)acrylate monomer, and 10% to 20% by weight of a repeating unit derived from a second alkyl (meth)acrylate monomer; The method for producing the polylactide blown film according to claim 1 .

3. The epoxy group-containing acrylate terpolymer has 30 to 80 epoxy groups per molecule. The method for producing the polylactide blown film according to claim 2 .

4. The first alkyl(meth)acrylate and the second alkyl(meth)acrylate are each independently at least one selected from the group consisting of methyl(meth)acrylate, butyl acrylate, and 2-(ethylhexyl)acrylate; The method for producing the polylactide blown film according to claim 2 .

5. The polylactide blown film has a weight average molecular weight of 200,000 g / mol to 500,000 g / mol as measured by gel permeation chromatography using polystyrene standards. The method for producing the polylactide blown film according to claim 1 .

6. The mixture of step 1 includes 0.5 to 0.75 parts by weight of an epoxy-based acrylate terpolymer based on 100 parts by weight of a polylactide polymer; The method for producing the polylactide blown film according to claim 1 .

7. The mixture of step 1 further comprises one or more selected from the group consisting of slip agents and anti-blocking agents. The method for producing the polylactide blown film according to claim 1 .

8. The reactive extrusion of step 2 is carried out at a temperature of 150° C. to 220° C. The method for producing the polylactide blown film according to claim 1 .

9. During the reactive extrusion in step 2, the screw rotation speed of the extruder is 100 rpm to 300 rpm; A method for producing the polylactide blown film according to claim 1 or claim 8.

10. The blow extrusion in step 3 is carried out at a temperature of 200° C. to 230° C. and a pressure of 10 bar to 50 bar. The method for producing the polylactide blown film according to claim 1 .

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