Branched polylactide polymer and method for producing same

Abstract

The present invention relates to a branched polylactide polymer that has been branched to improve its rheological properties, and a method for producing the same. The present invention provides a branched polylactide polymer that contains units derived from a polylactide polymer, has an average number of 3 to 10 long chain branches per molecule, and has a melt mass flow rate of 1 g / 10 min or more and 20 g / 10 min or less, measured at 190°C under a load of 2.16 kg in accordance with ASTM D1238 conditions, and a method for producing the same.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0001715, dated January 5, 2023, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to branched polylactide polymers that have been branched to improve rheological properties and methods for making the same. [Background technology]

[0003] Polylactic acid polymer (PLA) is a biodegradable, environmentally friendly material, and much research has been conducted in recent years to develop its applications. Unless modified, PLA is generally a linear molecule with thermoplastic polymer-like properties, making it useful as a material for a variety of films, fibers, and other molded products.

[0004] However, PLA is brittle and has poor rheological properties, including melt strength. Its low crystallinity makes it unsuitable for applications requiring high thermal and mechanical properties. Its poor rheological properties also place significant limitations on its use in blow molding and injection molding processes.

[0005] To solve these problems, attempts have been made to blend or copolymerize polybutylene succinate and polybutylene adipate terephthalate, which are biodegradable resins similar to PLA, with resins such as PP and PE, which have high heat resistance. However, there are problems with compatibility between the resins, and the effects of blending or copolymerization are minimal.

[0006] For example, a thermoplastic polymer should have low shear viscosity, form an easily processable melt, and have sufficient strength and / or dimensional stability to maintain the desired shape once formed. Generally, melt strength can be increased by increasing the molecular weight of the polymer, but increasing molecular weight also increases shear viscosity, making the processing more difficult. To improve both the melt strength and processability of PLA, techniques have been attempted to modify the linear structure of PLA by introducing long-chain branches (LCBs) into PLA using chain extenders or branching agents. Examples of such chain extenders and branching agents include isocyanate-based agents such as methylene diphenyl diisocyanate and hexamethylene diisocyanate, epoxy-based agents such as multifunctional epoxy- and styrene-acrylic oligomers, and anhydride-based agents such as pyromellitic dianhydride.

[0007] Furthermore, KR10-2007-0049140A (May 10, 2007) discloses a polylactide resin containing long chain branches obtained by reacting a polylactide resin with an acrylate polymer or copolymer containing an epoxide group, and a method for producing the same. However, there is a problem in that the viscosity of the polylactide resin produced by reacting the acrylate polymer or copolymer increases significantly, making it difficult to control in the molding process, and the industrial application field of the polylactide resin is very narrow and limited.

[0008] Therefore, there is a need to develop PLA that maintains the high reactivity of the epoxide group while improving melt strength and rheological properties through an appropriate increase in viscosity, as well as a method for producing the same. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] KR10-2017-0049140A(2007.05.10.) Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a branched polylactide polymer having excellent melt strength and rheological properties.

[0011] Another object of the present invention is to provide a method for producing the branched polylactide polymer. [Means for solving the problem]

[0012] To solve the above problems, the present invention provides a branched polylactide polymer and a method for producing the branched polylactide polymer.

[0013] (1) The present invention provides a branched polylactide polymer that contains units derived from a polylactide polymer, has an average number of 3 to 10 long-chain branches per molecule, and has a melt mass-flow rate of 1 g / 10 min or more and 20 g / 10 min or less, measured at 190°C under a load of 2.16 kg in accordance with ASTM D1238 conditions.

[0014] (2) The present invention provides a branched polylactide polymer according to (1), further comprising units derived from an epoxy group-containing acrylate copolymer, wherein the epoxy group-containing acrylate copolymer comprises 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, and the first alkyl (meth)acrylate monomer and the second alkyl (meth)acrylate monomer are different from each other.

[0015] (3) The present invention provides a branched polylactide polymer according to (2), which contains 0.5 to 1.0 parts by weight of units derived from an epoxy group-containing acrylate copolymer per 100 parts by weight of units derived from the polylactide polymer.

[0016] (4) The present invention provides the branched polylactide polymer according to (2) or (3), wherein the epoxy group-containing acrylate copolymer has 30 to 80 epoxy groups per molecule.

[0017] (5) The present invention provides a branched polylactide polymer according to any one of (2) to (4), wherein 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, and the first alkyl (meth)acrylate monomer and the second alkyl (meth)acrylate monomer are different from each other.

[0018] (6) The present invention provides the branched polylactide polymer according to any one of (1) to (5), which has a weight-average molecular weight of 30,000 g / mol to 250,000 g / mol as measured by gel permeation chromatography using a polystyrene standard.

[0019] (7) The present invention provides the branched polylactide polymer according to any one of (1) to (6), which has an absolute weight-average molecular weight of 100,000 g / mol to 1,500,000 g / mol and a polydispersity index of 2.0 to 3.5, as measured by multi-angle light scattering-gel permeation chromatography.

[0020] (8) The present invention provides a branched polylactide polymer according to any one of (1) to (7), which has two peak tops in a differential molecular weight distribution graph obtained by measurement by gel permeation chromatography using a polystyrene standard, where the horizontal axis is the logarithmic molecular weight [log(M)] and the vertical axis is dw / dlog(M) obtained by differentiating the concentration fraction w with respect to the logarithmic molecular weight, and the first peak top (Pt1) is 0.8 to 1.2 and the second peak top (Pt2) is 0.1 to 0.6.

[0021] (9) The present invention provides a branched polylactide polymer according to any one of (1) to (8), which has two peak tops in a differential molecular weight distribution graph obtained by measurement by gel permeation chromatography using a polystyrene standard, where the horizontal axis is the logarithmic molecular weight [log(M)] and the vertical axis is dw / dlog(M) obtained by differentiating the concentration fraction w with respect to the logarithmic molecular weight, the first peak top (Pt1) exists at 4.5 ≦ log(M) ≦ 5.8, and the second peak top (Pt2) exists at 5.8 < log(M) ≦ 6.5.

[0022] (10) The present invention provides a branched polylactide polymer according to any one of (1) to (9), which has a slope of -0.1 to -0.6 in a complex viscosity (Pa·s) graph according to the angular frequency (rad / s) at 180°C.

[0023] (11) The present invention provides a method for producing a branched polylactide polymer according to any one of (1) to (10), which includes a step of mixing a polylactide polymer and an epoxy group-containing acrylate copolymer while heat-treating in a temperature range of 180°C to 200°C. The epoxy group-containing acrylate copolymer 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 in a solvent in the presence of an emulsifier, and the first alkyl (meth)acrylate monomer and the second alkyl (meth)acrylate monomer are different from each other.

[0024] (12) The present invention provides a method for producing a branched polylactide polymer according to (11), wherein the epoxy group-containing acrylate copolymer is used in an amount of 0.5 to 1.0 part by weight per 100 parts by weight of the polylactide polymer.

[0025] (13) The present invention provides a method for producing a branched polylactide polymer according to (11) or (12), wherein the epoxy group-containing acrylate copolymer has 30 to 80 epoxy groups per molecule. [Effects of the Invention]

[0026] The branched polylactide polymer according to the present invention has a modified linear structure and is therefore excellent in melt strength and elasticity. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a graph showing the differential molecular weight distribution of branched and unbranched polylactide polymers according to examples of the present invention and comparative examples. [Figure 2a] 1 is a multi-angle light scattering-gel permeation chromatography analysis graph of the branched polylactide polymer of Example 1 of the present invention, showing the curve of refractive index versus retention volume. [Figure 2b] 1 is a graph showing a multi-angle light scattering-gel permeation chromatography analysis of the branched polylactide polymer of Example 1 of the present invention, which is a curve of MALS signal (MALS intensity, 90° scattering angle) versus retention volume. [Figure 2c] 1 is a multi-angle light scattering-gel permeation chromatography analysis graph of the branched polylactide polymer of Example 1 of the present invention, showing the curve of long chain branches (branching index) versus retention volume. [Figure 2d]1 is a multi-angle light scattering-gel permeation chromatography analysis graph of the branched polylactide polymer of Example 1 of the present invention, showing the curve of weight average molecular weight against retention volume. [Figure 3a] 1 is a multi-angle light scattering-gel permeation chromatography analysis graph of the branched polylactide polymer of Example 2 of the present invention, showing the curve of refractive index versus retention volume. [Figure 3b] 1 is a graph showing a multi-angle light scattering-gel permeation chromatography analysis of the branched polylactide polymer of Example 2 of the present invention, which is a curve of MALS signal (MALS intensity, 90° scattering angle) versus retention volume. [Figure 3c] 1 is a multi-angle light scattering-gel permeation chromatography analysis graph of the branched polylactide polymer of Example 2 of the present invention, showing the curve of long chain branches (branching index) versus retention volume. [Figure 3d] 1 is a multi-angle light scattering-gel permeation chromatography analysis graph of the branched polylactide polymer of Example 2 of the present invention, showing the curve of weight average molecular weight against retention volume. [Figure 4a] 1 is a multi-angle light scattering-gel permeation chromatography analysis graph of the non-branched polylactide polymer of Comparative Example 1 of the present invention, showing the curve of refractive index versus retention volume. [Figure 4b] 1 is a graph showing a multi-angle light scattering-gel permeation chromatography analysis of the non-branched polylactide polymer of Comparative Example 1 of the present invention, which is a curve of MALS signal (MALS intensity, 90° scattering angle) versus retention volume. [Figure 4c]1 is a multi-angle light scattering-gel permeation chromatography analysis graph of the non-branched polylactide polymer of Comparative Example 1 of the present invention, showing the curve of long chain branches (branching index) versus retention volume. [Figure 4d] 1 is a multi-angle light scattering-gel permeation chromatography analysis graph of the non-branched polylactide polymer of Comparative Example 1 of the present invention, showing the curve of weight average molecular weight against retention volume. [Figure 5a] 1 is a multi-angle light scattering-gel permeation chromatography analysis graph of the branched polylactide polymer of Comparative Example 2 of the present invention, showing the curve of refractive index versus retention volume. [Figure 5b] 1 is a graph showing a multi-angle light scattering-gel permeation chromatography analysis of the branched polylactide polymer of Comparative Example 2 of the present invention, which is a curve of MALS signal (MALS intensity, 90° scattering angle) versus retention volume. [Figure 5c] 1 is a multi-angle light scattering-gel permeation chromatography analysis graph of the branched polylactide polymer of Comparative Example 2 of the present invention, showing the curve of long chain branches (branching index) versus retention volume. [Figure 5d] 1 is a multi-angle light scattering-gel permeation chromatography analysis graph of the branched polylactide polymer of Comparative Example 2 of the present invention, showing the curve of weight average molecular weight against retention volume. [Figure 6] 1 is a graph of complex viscosity (Pa.s) at 180° C. versus angular frequency (rad / s) for branched and unbranched polylactide polymers according to examples of the present invention and comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0028] For better understanding of the present invention, the present invention will be described in more detail below.

[0029] The terms and words used in the description of the present invention and the claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best describe their invention.

[0030] Definition of Terms As used herein, the term "long chain branching (LCB)" refers to a long chain in which the number of carbon atoms in the branch is similar to that of the backbone, to the extent that it is indistinguishable from the backbone.

[0031] As used herein, the terms "unit derived from" and "repeating unit derived from" may mean to include components, units, structures originating from a certain substance, or the substance itself.

[0032] As used herein, the term "peak top" refers to the maximum dw / dlog(M) value in a differential molecular weight distribution graph obtained by measurement by gel permeation chromatography using a polystyrene standard, where the horizontal axis is logarithmic molecular weight [log(M)] and the vertical axis is dw / dlog(M), which is the derivative of concentration fraction w with logarithmic molecular weight. In addition, in the differential molecular weight distribution graph, if the graph is unimodal, there is one peak top, and if the graph is multimodal, there are multiple peak tops.

[0033] As used herein, the term "polydispersity index (PDI)" refers to the weight average molecular weight (Mw) / number average molecular weight (Mn), and the weight average molecular weight and number average molecular weight can be measured by gel permeation chromatography (GPC) equipped with a refractive index detector (RI).

[0034] Measurement method Herein, long chain branching was measured by multi-angle light scattering-gel permeation chromatography (MALS-GPC) using a Viscotek VE2001 GPC / SEC system equipped with a Viscotek TDA305 triple detector array module (light scattering, viscometer, and refractive index detector) under the following conditions: All results were calculated using OmniSEC version 4.7 software. Column: Two Plgel mixed-B (Agilent) columns Solvent: tetrahydrofuran (THF) Flow rate: 1.0ml / min Column temperature: 40℃ Sample: 3.0 mg / 1.0 ml THF Standard material: polystyrene

[0035] In the present specification, the relative weight average molecular weight and differential molecular weight distribution graphs are measured by gel permeation chromatography (GPC) equipped with a differential refractive index detector (RI), and the gel permeation chromatography was measured under the following conditions. Columns: Two PLgel Olexis (Polymer Laboratories) columns Solvent: tetrahydrofuran (THF) Flow rate: 0.3ml / min Column temperature: 40℃ Sample: 1.5 mg / 1.0 ml THF Standard material: polystyrene

[0036] In this specification, complex viscosity versus angular frequency graphs were measured using an ARES (Advanced Rheometric Expansion System) (TA Instruments). The sample was measured at 180°C using parallel plates with a diameter of 25.0 mm, with a gap of 1.0 mm, in angular frequency sweep mode at a strain of 5% and frequencies ranging from 0.1 rad / s to 500 rad / s. The vGP (van Gurp-Plamen plot) was plotted using the values ​​confirmed by frequency sweep mode measurement. The slope of the graph was calculated by replacing each complex viscosity with a logarithm for the entire frequency range and averaging all X and Y values.

[0037] Branched polylactide polymers The present invention provides branched polylactide polymers with modified linear structure and improved melt strength and rheological properties.

[0038] The branched polylactide polymer according to one embodiment of the present invention is characterized in that it contains units derived from a polylactide polymer, has an average number of 3 to 10 long chain branches per molecule, and has a melt mass flow rate of 1 g / 10 min or more and 20 g / 10 min or less, measured at 190°C under a load of 2.16 kg in accordance with ASTM D1238 conditions.

[0039] Here, "per molecule" means each of the polymer chains constituting the branched polylactide polymer (i.e., per chain).

[0040] Polylactide polymers (PLA) are biodegradable and environmentally friendly materials that are used in a variety of films, fibers, and other molded products. However, their linear structure makes them brittle and their rheological properties, including melt strength, are poor, limiting their use in blow molding and injection molding processes. Furthermore, their low crystallinity makes them unsuitable for applications requiring high thermal and mechanical properties. To address these issues, attempts have been made to blend or copolymerize PLA-like biodegradable resins, such as polybutylene succinate and polybutylene adipate terephthalate, with high-temperature-resistant resins like PP and PE. Other attempts have involved modifying the linear structure of PLA by introducing long-chain branching (LCB) into PLA using chain extenders or branching agents, thereby altering its properties. However, these efforts have been hampered by compatibility issues between resins and limited benefits.

[0041] Additionally, polylactide resins have been proposed in which long-chain branching has been introduced by reacting a polylactide polymer with an acrylate polymer or copolymer containing an epoxide group. However, the viscosity of the polylactide resin produced by reacting the acrylate polymer or copolymer increases significantly, making it difficult to control during molding and processing, thereby narrowly limiting the industrial application of the polylactide resin. However, the branched polylactide polymer of the present invention is produced by introducing long-chain branching into a polylactide polymer using an epoxy group-containing acrylate copolymer as a branching agent, which is 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. The high reactivity of the epoxide groups in the branching agent and excellent compatibility with the polylactide resin result in improved linearity without a rapid increase in viscosity, as well as improved melt strength and rheological properties. Therefore, it can be applied to a very wide range of applications.

[0042] The branched polylactide polymer according to the present invention will be described in more detail below, dividing it into its constituent components.

[0043] Polylactide polymer-derived units In the present invention, the units derived from a polylactide polymer are those originating from a polylactide polymer that is a starting material constituting the backbone of a branched polylactide polymer, and can, for example, mean units originating from a polylactide polymer in a branched polylactide polymer formed by reacting a polylactide polymer with an epoxy group-containing acrylate copolymer by a production method described below.

[0044] Polylactide polymers are thermoplastic polyesters obtained by polymerizing lactide or lactic acid, and include polymers having repeating units of the -[OC(O)CH(CH3)]- structure.

[0045] The polylactide polymer may also have repeating units derived from alkylene oxides or other monomers copolymerizable with lactide, in which case the repeating units derived from alkylene oxides or other monomers copolymerizable with lactide may be present in block and / or random arrangement. When the polylactide polymer contains repeating units derived from alkylene oxides or other monomers copolymerizable with lactide, the amount may be 10% by weight or less, specifically 5% by weight or less.

[0046] The polylactide polymer may have a relative weight average molecular weight of 30,000 g / mol to 250,000 g / mol, and a molecular weight distribution of 1.5 to 2.0, as measured by gel permeation chromatography using a polystyrene standard.

[0047] As yet another example, a polylactide polymer having an appropriate relative weight-average molecular weight within the above range may be selected and used depending on the desired effects, applications, and other requirements. For example, a low-molecular-weight polylactide polymer having a relative weight-average molecular weight of 30,000 g / mol to 120,000 g / mol, or a high-molecular-weight polylactide polymer having a relative weight-average molecular weight of 120,000 g / mol to 250,000 g / mol may be selected and used.

[0048] Units derived from epoxy group-containing acrylate copolymers The branched polylactide polymer according to the present invention further contains units derived from an epoxy group-containing acrylate copolymer, and the epoxy group-containing acrylate copolymer 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.

[0049] The units derived from the epoxy group-containing acrylate copolymer according to one embodiment of the present invention are derived from the epoxy group-containing acrylate copolymer, and may, for example, refer to units derived from the epoxy group-containing acrylate copolymer in a branched polylactide polymer formed by reacting the epoxy group-containing acrylate copolymer with a polylactide polymer by a production method described below.

[0050] The epoxy group-containing acrylate copolymer contains repeating units derived from a first alkyl (meth)acrylate monomer, repeating units derived from a glycidyl (meth)acrylate monomer, and repeating units derived from a second alkyl (meth)acrylate monomer, and the first alkyl (meth)acrylate monomer and the second alkyl (meth)acrylate monomer may be different from each other.

[0051] Specifically, the epoxy group-containing acrylate copolymer 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 may be different from each other.

[0052] The first alkyl (meth)acrylate monomer and the second alkyl (meth)acrylate monomer may be, independently of each other, at least one selected from the group consisting of methyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl acrylate. Specifically, the first alkyl (meth)acrylate monomer may be methyl methacrylate, and the second alkyl (meth)acrylate monomer may be butyl methacrylate.

[0053] The glycidyl (meth)acrylate monomer may be a glycidyl methacrylate monomer or a glycidyl acrylate monomer.

[0054] Branched polylactide polymers A branched polylactide polymer according to one embodiment of the present invention may contain 0.5 to 1.0 parts by weight of units derived from an epoxy group-containing acrylate copolymer per 100 parts by weight of units derived from the polylactide polymer, whereby the branched polylactide polymer containing the units may have uniformly branched properties without the problem of gel formation due to branching.

[0055] As yet another example, the branched polylactide polymer may have an average number of 3 to 10 long chain branches per molecule, and may have a melt mass flow rate of 1 g / 10 min or more and 20 g / 10 min or less, measured at 190°C under a load of 2.16 kg in accordance with ASTM D1238 conditions.

[0056] As yet another example, the branched polylactide polymer may have an average number of long chain branches per molecule of 5 to 10 or 7 to 10, and may have a melt mass flow rate measured at 190°C under a load of 2.16 kg in accordance with ASTM D1238 conditions of 1 g / 10 min to 20 g / 10 min, 1 g / 10 min to 7 g / 10 min, or 7 g / 10 min to 20 g / 10 min.

[0057] As yet another example, a branched polylactide polymer can exhibit different melt mass-flow rate characteristics, with the average number of long chain branches and melt mass-flow rate satisfying ranges depending on the molecular weight characteristics of the polylactide polymer constituting the polylactide polymer-derived units. For example, when the branched polylactide polymer contains units derived from a low molecular weight polylactide polymer, the melt mass-flow rate may be 7 g / 10 min or more and 20 g / 10 min or less, and when the branched polylactide polymer contains units derived from a high molecular weight polylactide polymer, the melt mass-flow rate may be 1 g / 10 min or more and 7 g / 10 min or less.

[0058] The branched polylactide polymer may have an absolute weight average molecular weight of 100,000 g / mol to 1,500,000 g / mol and a polydispersity index of 2.0 to 3.5, as measured by multi-angle light scattering-gel permeation chromatography.

[0059] As yet another example, the branched polylactide polymer has different absolute weight-average molecular weight characteristics measured by multi-angle light scattering-gel permeation chromatography depending on the molecular weight characteristics of the polylactide polymer units constituting the polylactide polymer. Exemplarily, when it contains polylactide polymer units derived from a low molecular weight polylactide polymer, the absolute weight-average molecular weight may be 100,000 g / mol to 500,000 g / mol and the polydispersity index may be 2.0 to 3.5. When it contains polylactide polymer units derived from a high molecular weight polylactide polymer, the absolute weight-average molecular weight may be 500,000 g / mol to 1,500,000 g / mol and the polydispersity index may be 2.0 to 3.5.

[0060] As yet another example, the branched polylactide polymer has two peak tops in a differential molecular weight distribution graph obtained by measurement by gel permeation chromatography using a polystyrene standard, where the horizontal axis is the logarithmic molecular weight [log(M)] and the vertical axis is dw / dlog(M) obtained by differentiating the concentration fraction w with respect to the logarithmic molecular weight. The first peak top (Pt1) may be 0.8 to 1.2 and the second peak top (Pt2) may be 0.1 to 0.6.

[0061] As yet another example, the first peak top (Pt1) of the branched polylactide polymer may be 1.0 to 1.2 and the second peak top (Pt2) may be 0.2 to 0.6.

[0062] Further, the branched polylactide polymer has two peak tops in a differential molecular weight distribution graph obtained by measurement by gel permeation chromatography using a polystyrene standard, where the horizontal axis is the logarithmic molecular weight [log(M)] and the vertical axis is dw / dlog(M) obtained by differentiating the concentration fraction w with respect to the logarithmic molecular weight. The first peak top (Pt1) may be present at 4.5 ≦ log(M) ≦ 5.8 and the second peak top (Pt2) may be present at 5.8 < log(M) ≦ 6.5.

[0063] As yet another example, a branched polylactide polymer may have a slope of -0.1 to -0.6 or -0.3 to -0.6 in a graph of complex viscosity (Pa.s) versus angular frequency (rad / s) at 180°C, calculated by replacing each complex viscosity with logarithm over all frequencies and averaging all X and Y values.

[0064] Method for producing branched polylactide polymers The present invention provides a method for producing branched polylactide polymers.

[0065] A method for producing a branched polylactide polymer according to one embodiment of the present invention includes a step of mixing a polylactide polymer and an epoxy group-containing acrylate copolymer while heat-treating them in a temperature range of 180°C to 200°C, and the epoxy group-containing acrylate copolymer is produced by polymerizing 30% by weight to 50% by weight of a first alkyl (meth)acrylate monomer, 30% by weight to 60% by weight of a glycidyl (meth)acrylate monomer, and 10% by weight to 20% by weight of a second alkyl (meth)acrylate monomer in a solvent in the presence of an emulsifier, wherein the first alkyl (meth)acrylate monomer and the second alkyl (meth)acrylate monomer are different from each other.

[0066] The specific description of the polylactide polymer as the starting material is as described above.

[0067] In addition, the polylactide polymer may be a commercially available product commonly known in the art or may be prepared and used. When prepared and used, it may be prepared by a polymerization method commonly used in the art using lactide or lactic acid as a monomer.

[0068] The epoxy group-containing acrylate copolymer can be prepared 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. Specific examples of the first alkyl (meth)acrylate monomer, the glycidyl (meth)acrylate monomer, and the second alkyl (meth)acrylate monomer are as described above.

[0069] Specifically, the epoxy group-containing acrylate copolymer is prepared by polymerizing 30% by weight to 50% by weight of a first alkyl (meth)acrylate monomer, 30% by weight to 60% by weight of a glycidyl (meth)acrylate monomer, and 10% by weight to 20% by weight of a second alkyl (meth)acrylate monomer different from the first alkyl (meth)acrylate monomer in a solvent in the presence of an emulsifier, and the polymerization may be carried out at 70°C to 80°C for 3 to 10 hours.

[0070] The polymerization may also be carried out in an aqueous solvent, in which case the solvent is distilled water.

[0071] The emulsifier may be one or more selected from the group consisting of anionic emulsifiers, cationic emulsifiers, and nonionic emulsifiers, e.g., one or more selected from the group consisting of alkylaryl sulfonates, alkali methyl alkyl sulfates, fatty acid soaps, alkali oleates, alkali rosinates, alkali laurates, sodium diethylhexyl phosphate, phosphonated polyoxyethylene alcohols, and phosphonated polyoxyethylene phenols. Furthermore, 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 to 2.5 parts by weight, based on 100 parts by weight of the total content of the monomers.

[0072] The polymerization may be carried out using a polymerization initiator, if necessary. In this case, the polymerization initiator may be an inorganic peroxide or an organic peroxide, such as a water-soluble polymerization initiator such as potassium persulfate, sodium persulfate, or ammonium persulfate, or an oil-soluble polymerization initiator such as cumene hydroperoxide or benzoyl peroxide.

[0073] In addition, an activator may be further used together with the polymerization initiator to promote the initiation of the peroxide reaction. 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.

[0074] The polymerization initiator may be used in an amount of 0.1 to 10 parts by weight, specifically 0.1 to 5 parts by weight, based on 100 parts by weight of the total content of the monomers.

[0075] As yet another example, a chain transfer agent may be further used to increase the efficiency of the polymerization reaction. As the chain transfer agent, a linear or branched alkylthiol compound having 5 to 20 carbon atoms may be used, and for example, it may be any one or more selected from hexanethiol, cyclohexanethiol, adamantanethiol, heptanethiol, octanethiol, nonanethiol, decanethiol, undecanethiol, dodecanethiol, hexadecanethiol, and octadecanethiol.

[0076] The chain transfer agent may be used in an amount of 0.1 to 10 parts by weight, or 0.1 to 5 parts by weight, based on 100 parts by weight of the monomer.

[0077] In addition, the epoxy group-containing acrylate copolymer may be prepared by further performing one or more steps selected from washing, dehydration, and drying after polymerization, and in this case, washing, dehydration, and drying can be performed by methods commonly known in the art.

[0078] Example The present invention will be described in more detail below with reference to examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0079] Manufacturing example A reactor was charged with 200 parts by weight of distilled water and 0.5 parts by weight of sodium dodecylbenzenesulfonate (SDBS) and heated to 70°C with stirring. After adding 0.2 parts by weight of potassium persulfate (KPS) and 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 parts 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 with stirring for 30 minutes to produce an emulsion polymerized latex. The produced emulsion polymerized latex was coagulated with an aqueous calcium acetate solution, heat-treated at 90°C, dehydrated, and dried at 60°C for 16 hours to produce an epoxy group-containing acrylate copolymer.

[0080] Comparative manufacturing example A reactor was charged with 200 parts by weight of distilled water and 0.5 parts by weight of sodium dodecylbenzenesulfonate (SDBS) and heated to 70°C with stirring. After adding 0.2 parts by weight of potassium persulfate (KPS) and stirring for 20 minutes, 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 parts 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 with stirring for 30 minutes to produce an emulsion polymerized latex. The produced emulsion polymerized latex was coagulated with an aqueous calcium acetate solution, heat-treated at 90°C, dehydrated, and dried at 60°C for 16 hours to produce an epoxy group-containing acrylate copolymer.

[0081] Example 1 Polylactide polymer (4032D, Mw = 214,900 g / mol, Natureworks) was prepared by drying at 80°C for 24 hours.

[0082] 100 parts by weight of the prepared polylactide polymer was mixed with 0.5 parts by weight of the copolymer prepared in the above Preparation Example to prepare a mixture, and the mixture was blended at 180°C for 10 minutes at 60 rpm using a lab batch mixer to prepare a branched polylactide polymer.

[0083] Example 2 A branched polylactide polymer was prepared in the same manner as in Example 1, except that 1.0 part by weight of the copolymer prepared in Preparation Example was used.

[0084] Example 3 A branched polylactide polymer was prepared in the same manner as in Example 1, except that 0.75 parts by weight of the copolymer prepared in Preparation Example was used.

[0085] Comparative Example 1 Polylactide polymer (4032D, Natureworks) was dried at 80°C for 24 hours, and unbranched polylactide polymer was used as a control.

[0086] Comparative Example 2 A branched polylactide polymer was prepared in the same manner as in Example 1, except that JONCRYL® 4368 acrylic copolymer (Mn = 2,000 g / mol, average number of epoxy groups per molecule: 7) was used instead of the copolymer prepared in Preparation Example 1.

[0087] Comparative Example 3 A branched polylactide polymer was produced in the same manner as in Example 1, except that the copolymer produced in Comparative Preparation Example was used instead of the copolymer produced in Preparation Example in Example 1.

[0088] Experimental Example 1 The molecular weight characteristics and rheological properties of each of the branched and non-branched polylactide polymers prepared in the Examples and Comparative Examples were compared and analyzed, and the results are shown in Table 1 below and Figures 1 to 6.

[0089] (1) Molecular weight characteristics The molecular weight characteristics were compared between the relative molecular weight characteristics analyzed by gel permeation chromatography (GPC) using polystyrene as a standard substance and the absolute molecular weight characteristics analyzed by multi-angle light scattering-gel permeation chromatography (MALS-GPC).

[0090] 1) Relative molecular weight characteristics The relative molecular weight characteristics were measured using gel permeation chromatography (GPC) equipped with a refractive index detector (RI) under the following conditions, and the weight average molecular weight, number average molecular weight, and molecular weight distribution were confirmed from the molecular weight distribution graph obtained.

[0091] In addition, a differential molecular weight distribution graph (see Figure 1) was obtained, 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 by the logarithmic molecular weight, and the peak top characteristics were confirmed. Columns: Two PLgel Olexis (Polymer Laboratories) columns Solvent: tetrahydrofuran (THF) Flow rate: 0.3ml / min Column temperature: 40℃ Sample: 1.5 mg / 1.0 ml THF Standard material: polystyrene

[0092] 2) Multi-angle light scattering-gel permeation chromatography The analysis was performed using a Viscotek VE2001 GPC / SEC system equipped with a Viscotek TDA305 triple detector array module (light scattering, viscometer, and refractive index detector) under the following conditions, and all results were calculated using OmniSEC version 4.7 software. Column: Two Plgel mixed-B (Agilent) columns Solvent: tetrahydrofuran (THF) Flow rate: 1.0ml / min Column temperature: 40℃ Sample: 3.0 mg / 1.0 ml THF Standard material: polystyrene

[0093] (2) Rheological properties The rheological properties were measured using a viscometer, and the complex viscosity, storage modulus, and vGP plot (van Gurp-Palmen) were compared.

[0094] Specifically, measurements were performed using an ARES (Advanced Rheometric Expansion System) (TA Instruments). The sample was measured at 180°C using parallel plates with a diameter of 25.0 mm and a gap of 1.0 mm, in angular frequency sweep mode at a strain of 5% and frequencies ranging from 0.1 rad / s to 500 rad / s. The vGP (van Gurp-Plamen plot) was plotted using the values ​​confirmed by frequency sweep mode measurement (see Figure 6). The slope of the complex viscosity graph was calculated by replacing each complex viscosity for the entire set frequency with a logarithm and averaging all X and Y values.

[0095] (3) Melt mass flow rate (MFR) Measurement was carried out using MI-4 (Gottfert) at 190°C and a load of 2.16 kg in accordance with the conditions of ASTM D1238.

[0096] [Table 1]

[0097] In Table 1, Bn represents the average number of long chain branches per molecule, and the slope is the Mark-Houwink slope, with a lower slope indicating a higher degree of branching.

[0098] From Table 1, it was confirmed that the branched polylactide polymers of Examples 1 to 3 satisfy the properties proposed by the present invention, that is, the average number of long chain branches per molecule is 3 to 10 and the MFR is 1 g / 10 min or more and 20 g / 10 min or less. Furthermore, it was confirmed that Examples 1 to 3 were produced using high molecular weight polylactide polymers and have the properties of the average number of long chain branches per molecule is 3 to 10 and the MFR is 1 g / 10 min or more and 7 g / 10 min or less.

[0099] In contrast, the unbranched or branched polylactide polymers of Comparative Examples 1 to 3 did not satisfy the average number of long chain branches per molecule of 3 to 10 or the MFR of 1 g / 10 min or more and 20 g / 10 min or less.

[0100] Experimental Example 2 Blown films were prepared using each of the branched and unbranched polylactide polymers prepared in the above examples and comparative examples, and the processability of the blown films was confirmed. The results are shown in Table 2 below.

[0101] Blown films were produced by extruding each of the polymers using a single-screw extruder (Collin Lab&Pilot Solutions, Blown Film Line E Entranc, Blown Film M / C, 19mm diameter, L / D=25) at an extrusion temperature of 210-220°C to a thickness of 0.08mm. The blow-up ratio was set to approximately 1.8.

[0102] The blown film processability was compared based on the pressure (bar) measured when the extruded pellets were extruded from the die. The higher the viscosity of the processed extruded pellets or the lower the degree of branching, the higher the pressure value. The lower the pressure value, the better the processability.

[0103] [Table 2]

[0104] From Table 2, it was confirmed that the branched polylactide polymers of Examples 1 to 3, which have an average number of long chain branches per molecule of 3 to 10 and an MFR of 1 g / 10 min to 20 g / 10 min, are superior in processability for blown film compared to Comparative Examples 1 to 3.

[0105] Specifically, it was confirmed that Comparative Example 1, which did not satisfy either the average number of long-chain branches per molecule or the MFR, showed a significant decrease in blown film processability to a level of approximately 81% to 90% compared to Examples 1 to 3. Comparative Example 2, which satisfied the above conditions for the average number of long-chain branches per molecule but had a low MFR, showed a significant decrease in blown film processability to approximately 63% to 70% compared to Examples 1 to 3. Furthermore, Comparative Example 3, which satisfied the MFR but did not satisfy the above conditions for the average number of long-chain branches per molecule, showed a decrease in blown film processability to approximately 85% to 95% compared to Examples 1 to 3.

Claims

1. containing units derived from polylactide polymers, The average number of long chain branches per molecule is 3 to 10, A branched polylactide polymer having a melt mass flow rate of 1 g / 10 min or more and 20 g / 10 min or less, measured at 190°C under a load of 2.16 kg in accordance with ASTM D1238 conditions.

2. Further containing units derived from an epoxy group-containing acrylate copolymer, 2. The branched polylactide polymer of claim 1, wherein the epoxy group-containing acrylate copolymer comprises 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.

3. 3. The branched polylactide polymer according to claim 2, comprising 0.5 to 1.0 parts by weight of units derived from the epoxy group-containing acrylate copolymer per 100 parts by weight of units derived from the polylactide polymer.

4. 3. The branched polylactide polymer according to claim 2, wherein the epoxy group-containing acrylate copolymer has 30 to 80 epoxy groups per molecule.

5. 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(meth)acrylate, butyl acrylate, and 2-(ethylhexyl)acrylate; 3. The branched polylactide polymer of claim 2, wherein the first alkyl (meth)acrylate monomer and the second alkyl (meth)acrylate monomer are different from each other.

6. 2. The branched polylactide polymer of claim 1, having a weight average molecular weight of 30,000 g / mol to 250,000 g / mol as measured by gel permeation chromatography using polystyrene standards.

7. 2. The branched polylactide polymer of claim 1, having an absolute weight average molecular weight of 100,000 g / mol to 1,500,000 g / mol and a polydispersity index of 2.0 to 3.5, as measured by multi-angle light scattering-gel permeation chromatography.

8. In a differential molecular weight distribution graph obtained by measurement by gel permeation chromatography using a polystyrene standard, the horizontal axis is logarithmic molecular weight [log(M)] and the vertical axis is dw / dlog(M) obtained by differentiating the concentration fraction w with the logarithmic molecular weight, the polymer has two peak tops; First peak top (Pt １ ) is 0.8 to 1.2, Second peak top (Pt ２ 2. The branched polylactide polymer of claim 1, wherein β is from 0.1 to 0.

6.

9. In a differential molecular weight distribution graph obtained by measurement by gel permeation chromatography using a polystyrene standard, the horizontal axis is logarithmic molecular weight [log(M)] and the vertical axis is dw / dlog(M) obtained by differentiating the concentration fraction w with the logarithmic molecular weight, the polymer has two peak tops; First peak top (Pt １ ) exists in the range of 4.5≦log(M)≦5.8, Second peak top (Pt ２ 2. The branched polylactide polymer of claim 1, wherein log(M) is in the range 5.8<log(M)≦6.

5.

10. 2. The branched polylactide polymer of claim 1, wherein a graph of complex viscosity (Pa.s) versus angular frequency (rad / s) at 180°C has a slope of -0.1 to -0.

6.

11. The method includes a step of mixing a polylactide polymer and an epoxy group-containing acrylate copolymer while heat treating the mixture at a temperature in the range of 180°C to 200°C, The epoxy group-containing acrylate copolymer is prepared by polymerizing 30% by weight to 50% by weight of a first alkyl (meth)acrylate monomer, 30% by weight to 60% by weight of a glycidyl (meth)acrylate monomer, and 10% by weight to 20% by weight of a second alkyl (meth)acrylate monomer in a solvent in the presence of an emulsifier; The first alkyl (meth)acrylate monomer and the second alkyl (meth)acrylate monomer are different from each other.

12. The method for producing a branched polylactide polymer according to claim 11, wherein the epoxy group-containing acrylate copolymer is used in an amount of 0.5 to 1.0 part by weight per 100 parts by weight of the polylactide polymer.

13. The method for producing a branched polylactide polymer according to claim 11, wherein the epoxy group-containing acrylate copolymer has 30 to 80 epoxy groups per molecule.

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