Polylactide resin composition with excellent crystallinity and method for producing same

Abstract

The present invention relates to a polylactide resin composition using a combination of specific nucleating agents, which has the characteristics of excellent crystallinity, excellent dispersibility between the components, and excellent transparency, and therefore has excellent processability while maintaining the properties inherent to the polylactide resin according to the present invention.

Description

[Technical Field]

[0001] Cross-citation with related applications (etc.) This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0035552 dated March 22, 2022, and all contents disclosed in the Korean patent application and other documents are incorporated herein by reference.

[0002] The present invention relates to a polylactide resin composition having an excellent degree of crystallinity and a method for producing the same. [Background technology]

[0003] Polylactide (or polylactic acid; PLA) resin is an environmentally friendly material that is manufactured from bio-based materials, emits little carbon dioxide, a greenhouse gas, during the manufacturing process, and decomposes at a specific temperature in a composting facility. Recently, it has been attracting attention as a possible alternative to existing crude oil-based resins as a response to regulations on the use of waste plastics and carbon emissions.

[0004] Furthermore, polylactide resin has the advantage of being cheaper than other biodegradable polymers and having high tensile strength and modulus properties.

[0005] However, polylactide resins have the problem of having a rigid polymer backbone repeated in short units and a slow crystallization rate due to slow chain transfer, resulting in a long molding cycle and poor productivity. Therefore, to address these issues, much research is being conducted into improving productivity and heat resistance by introducing substances such as nucleating agents.

[0006] Typically, the nucleating agent is primarily inorganic, such as talc, mica, or nanoclay. It has been reported that adding a portion of these nucleating agents during molding of PLA can improve heat resistance and strength. However, adding an excessive amount of these nucleating agents increases the resin's specific gravity and reduces transparency. Meanwhile, organic nucleating agents such as LAK 301 (aromatic sulfonate drivate), sodium benzoate, N-aminophthalimide, phthalhydrazide, and cadmium phenylmalonate have been used to improve crystallinity and transparency. However, these materials are not bio-based and therefore have poor dispersion characteristics with PLA resin.

[0007] Therefore, it is necessary to introduce a bio-based organic nucleating agent that can be used to produce environmentally friendly products without impairing transparency. It is also necessary to introduce a nucleating agent that has fewer dispersion problems with polylactide resin to further improve the crystallinity of polylactide resin. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention aims to provide a polylactide resin composition having excellent crystallinity by using a specific combination of nucleating agents.

[0009] The present invention also relates to a method for producing the polylactide resin composition. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides the following polylactide resin composition.

[0011] Polylactide resin, a first nucleating agent, and a second nucleating agent Agent and , including the first nucleating agent is uracil or orotic acid; The second nucleating agent is a compound containing a lactide oligomer structure. Polylactide resin composition.

[0012] The term "polylactide resin" used in the present invention is defined as a comprehensive term for homopolymers or copolymers containing the following repeating units: [ka]

[0013] The polylactide resin may be produced by forming the repeating unit through ring-opening polymerization of a lactide monomer, and the polymer obtained after the ring-opening polymerization and the repeating unit formation processes are completed may be referred to as a "polylactide resin."

[0014] In this application, "lactide monomer" can be defined as follows. Lactide can generally be classified into L-lactide consisting of L-lactic acid, D-lactide consisting of D-lactic acid, and meso-lactide consisting of one L-form and one D-form. A 50:50 mixture of L-lactide and D-lactide is called D,L-lactide or rac-lactide. It is known that polymerization using only L-lactide or D-lactide with high optical purity among these lactides results in L- or D-polylactide (PLLA or PDLA) with very high stereoregularity. Such polylactides are known to have a faster crystallization rate and higher crystallinity than polylactides with lower optical purity. However, in this specification, "lactide monomer" is defined to include all forms of lactide, regardless of differences in the properties of each form of lactide and the properties of polylactide resins formed therefrom.

[0015] On the other hand, the polylactide resin according to the present invention has a weight average molecular weight of, for example, 70,000 to 400,000.

[0016] The present invention is characterized in that the crystallinity of the polylactide resin is improved by using such a polylactide together with the first and second nucleating agents.

[0017] The first nucleating agent is uracil or orotic acid. The first nucleating agent is a bio-based organic material that acts as a nucleation site when added to polylactide resin, and can induce the formation of crystal nuclei at high temperatures, thereby improving the crystallization rate.

[0018] Preferably, the first nucleating agent is included in an amount of 0.1 to 5 wt % based on the total weight of the polylactide resin composition. If the amount is less than 0.1 wt %, the effect of using the first nucleating agent is negligible, while if the amount is more than 5 wt %, the inherent physical properties of the polylactide resin may be impaired. More preferably, the first nucleating agent is included in an amount of 0.2 wt % or more, 0.3 wt % or more, 0.4 wt % or more, or 0.5 wt % or more, and 4.5 wt % or less, 4.0 wt % or less, or 3.5 wt % or less based on the total weight of the polylactide resin composition.

[0019] The second nucleating agent is a nucleating agent containing a lactide monomer oligomer structure, and due to this lactide monomer oligomer structure, it has high compatibility with polylactide resin and is added to the polylactide resin to function similarly to a plasticizer, thereby forming free volume within the polylactide resin, improving chain transfer and increasing the degree of crystallinity of the polylactide resin.

[0020] Preferably, the second nucleating agent is a compound represented by the following Chemical Formula 1: [ka]

[0021] In the above Chemical Formula 1, L is any one selected from the group consisting of: [ka] In the above, n1 is an integer from 1 to 4, n2 is an integer from 1 to 4, n3 is an integer from 1 to 30, R is a substituent represented by the following chemical formula 2: [Chemical formula 2] [ka] n represents the number of repeating units, R' is hydrogen or acetyl.

[0022] The weight-average molecular weight of the second nucleating agent can be adjusted by adjusting the number of each lactide repeating unit. Preferably, the weight-average molecular weight of the second nucleating agent is 1,000 to 50,000. More preferably, the weight-average molecular weight of the second nucleating agent is 1,100 or more, 1,200 or more, 1,300 or more, 1,400 or more, or 1,500 or more, and 40,000 or less, 30,000 or less, 20,000 or less, 10,000 or less, 9,000 or less, or 8,000 or less.

[0023] Preferably, the second nucleating agent is included in an amount of 3 to 25 wt % based on the total weight of the polylactide resin composition. If the amount is less than 3 wt %, the effect of using the second nucleating agent is negligible, while if the amount is more than 25 wt %, the inherent physical properties of the polylactide resin may be impaired. More preferably, the second nucleating agent is included in an amount of 3.5 wt % or more, 4.0 wt % or more, or 4.5 wt % or more, based on the total weight of the polylactide resin composition, and 24 wt % or less, 23 wt % or less, 22 wt % or less, or 21 wt % or less.

[0024] Meanwhile, the method for producing the polylactide resin composition according to the present invention is not particularly limited as long as it is a method of mixing the polylactide resin, the first nucleating agent, and the second nucleating agent. For example, since each of the components is easily soluble in CHCl3 solvent, the polylactide resin composition can be produced by dissolving each component in CHCl3 solvent, mixing the components, and then removing the solvent. [Effects of the Invention]

[0025] The polylactide resin composition according to the present invention has excellent crystallinity, excellent dispersibility between components, and excellent transparency, and therefore has excellent processability while maintaining the properties inherent to the polylactide resin according to the present invention. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 shows the NMR results of the second nucleating agent prepared in Preparation Example 1. [Figure 2] FIG. 2 shows the results of DSC measurements of the polylactide resin compositions produced in the examples and comparative examples. [Figure 3] FIG. 3 shows the results of DSC measurements of the polylactide resin compositions prepared in the examples and comparative examples. [Figure 4] FIG. 4 shows the results of DSC measurements of the polylactide resin compositions prepared in the examples and comparative examples. [Figure 5] FIG. 5 shows the results of DSC measurements of the polylactide resin compositions prepared in the examples and comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, the present invention will be described in more detail with reference to the following examples, but the following examples are merely illustrative of the present invention and are not intended to limit the scope of the present invention.

[0028] Preparation Example 1: Second nucleating agent (preparation of P4-oligomer) 1) Preparation of the second nucleating agent (P4-O-oligomer) Oligomers were prepared using PEG-400 (P4) as an initiator. Specifically, 4.5 g of lactide:P4 were poured into 20 mL vials at molar ratios of 4:1, 8:1, 12:1, and 16:1, respectively, and Sn(°C)2 catalyst was added at 0.1 to 0.2 wt%. The mixture was then reacted at 130°C for 4 hours. After vacuum drying, the mixture was cooled to room temperature to prepare secondary nucleating agents. These were named P4-O-001, P4-O-002, P4-O-003, and P4-O-004, respectively, and their weight-average molecular weights are listed in Tables 1 and 2.

[0029] 2) Preparation of the second nucleating agent (P4-A-oligomer) Oligomers were prepared using PEG-400 (P4) as an initiator. Specifically, lactide:P4 molar ratios of 4:1, 8:1, 12:1, and 16:1 were poured into 20 mL vials, totaling 4.5 g. Sn(°C)2 catalyst was added at 0.1 to 0.2 wt% and the reaction was carried out at 130°C for 4 hours. The temperature was then adjusted to 120°C, and acetic anhydride (4 equivalents per terminal OH group) was added, and the reaction was continued for an additional 12 hours. After the reaction was completed, the by-product acetic acid and residual acetic anhydride were removed by vacuum drying. Secondary nucleating agents with acetyl-substituted terminal groups were prepared. These were named P4-A-001, P4-A-002, P4-A-003, and P4-A-004, respectively. Their weight-average molecular weights are listed in Tables 1 and 2.

[0030] The prepared secondary nucleating agent was subjected to NMR analysis together with the starting material PEG-400, and the results are shown in FIG.

[0031] As shown in Figure 1, OH groups (2.5 ppm) or acetyl groups (2.1-2.2 ppm) were observed at both ends of the oligomer.

[0032] Preparation Example 2: Second Nucleating Agent (Preparation of P10-Oligomer) 1) Preparation of the second nucleating agent (P10-O-oligomer) Oligomers were prepared using PEG-1000 (P10) as an initiator. Specifically, lactide:P10 molar ratios of 4:1, 8:1, 12:1, and 16:1 were poured into 20 mL vials, totaling 4.5 g, and Sn(Oct)2 catalyst was added at 0.1 to 0.2 wt%. The mixture was then reacted at 130°C for 4 hours. After vacuum drying, the mixture was cooled to room temperature to prepare secondary nucleating agents. These were named P10-O-001, P10-O-002, P10-O-003, and P10-O-004, respectively, and their weight-average molecular weights are listed in Tables 1 and 2.

[0033] 2) Preparation of the second nucleating agent (P10-A-oligomer) Oligomers were prepared using PEG-1000 (P10) as an initiator. Specifically, lactide:P10 molar ratios of 4:1, 8:1, 12:1, and 16:1 were poured into 20 mL vials, totaling 4.5 g. Sn(°C)2 catalyst was added at 0.1 to 0.2 wt% and the reaction was carried out at 130°C for 4 hours. The temperature was then adjusted to 120°C, and acetic anhydride (4 equivalents per terminal OH group) was added, and the reaction was continued for an additional 12 hours. After the reaction was completed, the by-product acetic acid and residual acetic anhydride were removed by vacuum drying to prepare secondary nucleating agents with terminal acetyl groups. These were named P10-A-001, P10-A-002, P10-A-003, and P10-A-004, respectively, and their weight-average molecular weights are listed in Tables 1 and 2.

[0034] Preparation Example 2: Second nucleating agent (preparation of CD-oligomer) Oligomers were prepared using cyclohexanedimethanol (CD) as an initiator. Specifically, lactide:CD molar ratios of 4:1, 8:1, 12:1, and 16:1 were poured into 20 mL vials, totaling 4.5 g, and Sn(°C)2 catalyst was added at 0.1 to 0.2 wt%. The mixture was then reacted at 130°C for 4 hours. After vacuum drying, the mixture was cooled to room temperature to prepare secondary nucleating agents. These were named CD-O-001, CD-O-002, CD-O-003, and CD-O-004, respectively, and their weight-average molecular weights are listed in Tables 1 and 2.

[0035] Preparation Example 3: Second nucleating agent (preparation of PD-oligomer) Oligomers were prepared using 1,5-pentanediol (PD) as an initiator. Specifically, lactide:PD molar ratios of 4:1, 8:1, 12:1, and 16:1 were poured into 20 mL vials, totaling 4.5 g, and Sn(Oct)2 catalyst was added at 0.1 to 0.2 wt%. The mixture was then reacted at 130°C for 4 hours. After vacuum drying and cooling to room temperature, secondary nucleating agents were prepared. These were named PD-O-001, PD-O-002, PD-O-003, and PD-O-004, respectively, and their weight-average molecular weights are listed in Tables 1 and 2.

[0036] Preparation Example 4: Second nucleating agent (preparation of DG-oligomer) Oligomers were prepared using diethylene glycol (DG) as an initiator. Specifically, lactide:DG molar ratios of 4:1, 8:1, 12:1, and 16:1 were poured into 20 mL vials, totaling 4.5 g, and Sn(Oct)2 catalyst was added at 0.1 to 0.2 wt%. The mixture was then reacted at 130°C for 4 hours. After vacuum drying, the mixture was cooled to room temperature to prepare secondary nucleating agents. These were named DG-O-001, DG-O-002, DG-O-003, and DG-O-004, respectively, and their weight-average molecular weights are listed in Tables 1 and 2.

[0037] Preparation Example 5: Second nucleating agent (preparation of GL-oligomer) Oligomers were prepared using glycerol (GL) as an initiator. Specifically, lactide:GL molar ratios of 6:1, 12:1, and 18:1 were poured into 20 mL vials, totaling 4.5 g, and Sn(Oct)2 catalyst was added at 0.1 to 0.2 wt%. The mixture was then reacted at 130°C for 4 hours. After vacuum drying, the mixture was cooled to room temperature to prepare secondary nucleating agents, which were named GL-O-001, GL-O-002, and GL-O-003, respectively. Their weight-average molecular weights are listed in Tables 1 and 2.

[0038] Preparation Example 6: Secondary Nucleating Agent (Preparation of PT-Oligomer) Oligomers were prepared using pentaerythritol (PT) as an initiator. Specifically, 4.5 g of lactide:PT molar ratios of 8:1, 16:1, 24:1, and 32:1 were poured into 20 mL vials, and Sn(Oct)2 catalyst was added at 0.1 to 0.2 wt%. The mixture was then reacted at 130°C for 4 hours. The resulting mixture was vacuum dried and cooled to room temperature to prepare secondary nucleating agents, designated PT-O-001, PT-O-002, PT-O-003, and PT-O-004, respectively. Their weight-average molecular weights are listed in Tables 1 and 2.

[0039] Preparation Example 7: Second nucleating agent (preparation of SB-oligomer) Oligomers were prepared using sorbitol (SB) as an initiator. Specifically, 4.5 g of lactide:SB molar ratios of 12:1, 24:1, and 36:1 were poured into 20 mL vials, and Sn(Oct)2 catalyst was added at 0.1 to 0.2 wt%. The mixture was then reacted at 130°C for 4 hours. The resulting mixture was vacuum dried and cooled to room temperature to prepare secondary nucleating agents. These were named SB-O-001, SB-O-002, and SB-O-003, respectively, and their weight-average molecular weights are listed in Tables 1 and 2.

[0040] Examples and Comparative Examples 300 g of PLA pellets (NatureWorks 4032D; weight-average molecular weight approximately 200,000) were placed in a 500 mL vial and completely dissolved in 12 mL of CHCl3. The primary and secondary nucleating agents listed in Table 1 below were dissolved or evenly dispersed in 4 mL of CHCl3 according to their respective contents to prepare solutions, which were then mixed with the previously prepared PLA solution. The resulting solution was sonicated for 1 hour and then air-dried in an Al dish (diameter: 80 mm) to remove the solvent. The solution was then dried in a vacuum at 60°C for 5 hours to produce PLA films (thickness: approximately 0.5 mm to 1.0 mm).

[0041] Experimental example The physical properties of the first nucleating agent, the second nucleating agent, and the PLA film prepared above were measured by the following methods.

[0042] 1) Weight average molecular weight Using a GPC (Gel Permeation Chromatography) device, the number average molecular weight (Mn) and weight average molecular weight (Mw) were calculated, and the oligomer molecular weight distribution (Mw / Mn) was measured. The specific measurement conditions are as follows: -Column: PLgel Mixed E x 2 Solvent: THF -Flow rate: 0.7mL / min -Sample concentration: 3.0 mg / mL -Injection volume: 100μl -Column temperature: 40℃ -Detector: Waters 2414 RID -Standard: PS (Polystyrene)

[0043] 2)DSC(differential scanning calorimetry) To completely transform the PLA film into an amorphous state and erase its thermal history, the film was heated to 250°C, which is above the melting point of PLA, at a heating rate of 10°C / min, and then stabilized for 5 minutes to transform it into an amorphous molten state. To analyze ΔHc and crystallization behavior, the film was then cooled to -20°C at a cooling rate of 10°C / min, and the crystallization peak was observed. After stabilization, the film was reheated to 250°C at a rate of 10°C / min (2 nd The ΔHm at the melting peak was confirmed by the run. The crystallinity Xc was calculated using the following formula (100% crystalline PLA ΔHm=93 J / g). -Crystallization during cooling: (area of ​​exothermic peak during cooling, ΔHc) / 100% crystalline PLA ΔHm) -2 nd Run crystallinity: (2 nd The area of ​​the endothermic peak in the thermogram, ΔHm (area of ​​the exothermic peak in cold crystallization, ΔHcc) / 100% crystalline PLA ΔHm) × 100 The results are shown in Tables 1 and 2 below, and some of the DSC measurement results are shown in Figures 2 to 5. Meanwhile, in Tables 1 and 2 below, the meanings of the abbreviations are as follows: D-SB (D-Sorbitol), PT (pentaerythritol), OA (Orotic acid), L-PA (L-phenylalanine), PH (phthalhydrazide)

[0044] [Table 1] [Table 2]

[0045] As shown in Tables 1 and 2, in the examples where the first and second nucleating agents were used together according to the present invention, it was confirmed that the crystallization temperature and degree of crystallinity were improved even at a small content.

[0046] In contrast, when no nucleating agent was used (Comparative Example 1), when only the first nucleating agent was used (Comparative Examples 2 to 9), or when only the second nucleating agent was used (Comparative Examples 10 to 27), the degree of crystallinity was low, and when the second nucleating agent was used but talc was used as the first nucleating agent (Comparative Examples 28 to 36), the crystallization temperature was low.

Claims

1. a polylactide resin, a first nucleating agent, and a second nucleating agent; the first nucleating agent is uracil or orotic acid, and is included in an amount of 0.3 to 5 wt % based on the total weight of the polylactide resin composition; the second nucleating agent is a compound containing a lactide oligomer structure and is contained in an amount of 4 to 25 wt % based on the total weight of the polylactide resin composition; Polylactide resin composition.

2. The weight average molecular weight of the polylactide resin is 70,000 to 400,000. The polylactide resin composition according to claim 1.

3. The first nucleating agent is contained in an amount of 0.5 to 3.5 wt % based on the total weight of the polylactide resin composition. The polylactide resin composition according to claim 1.

4. The second nucleating agent is a compound represented by the following Chemical Formula 1: The polylactide resin composition according to claim 1. 【Chemistry 1】 In the above Chemical Formula 1, L is any one selected from the group consisting of: 【Chemistry 2】 In the above, n1 is an integer from 1 to 4; n2 is an integer from 1 to 4; n3 is an integer from 1 to 30; R is a substituent represented by the following chemical formula 2: 【Transformation 3】 n represents the number of repeating units, R' is hydrogen or acetyl.

5. The weight average molecular weight of the second nucleating agent is 1,000 to 50,000. The polylactide resin composition according to claim 1.

6. The second nucleating agent is contained in an amount of 4.5 to 21 wt % based on the total weight of the polylactide resin composition. The polylactide resin composition according to claim 1.

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