Method for predicting neck-in property of polylactide resin

Abstract

The present invention relates to a method for predicting or evaluating the neck-in property of a film produced from a polylactide resin. This method is simple and highly predictive, and thus can replace actual measurement methods. Therefore, the method makes it possible determine the film properties of a new structure in advance.

Description

Neck-in prediction method for polylactide resins

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0175672, filed December 6, 2023, the entire disclosure of which is incorporated herein by reference.

[0003]

[0004] The present invention relates to a method for predicting the neck-in of a polylactide resin.

[0005] Polylactic acid (PLA) is a plant-derived resin derived from plants such as corn. Its biodegradability has garnered attention as an excellent, eco-friendly material. Unlike conventional petroleum-based resins like polystyrene, polyvinyl chloride, and polyethylene, PLA prevents the depletion of petroleum resources and reduces carbon dioxide emissions, potentially reducing the environmental pollution associated with petroleum-based plastic products. Consequently, as environmental pollution caused by waste plastics becomes a growing social issue, efforts are being made to expand the application of PLA to products previously dominated by conventional plastics (petroleum-based resins), such as food packaging and containers and electronic device cases.

[0006]

[0007] However, polylactide resin inherently has low melt strength and melt elasticity due to its structural characteristics, which reduces its molding process stability during film manufacturing. Specifically, increasing production speeds to enhance productivity increases neck-in, limiting the ability to reduce film thickness for processability. Furthermore, edge weave during the molding process increases, leading to significant deviations in the width and thickness of the resulting film.

[0008]

[0009] To improve the above shortcomings, many attempts have been made to develop new polylactide resins with branched structures to enhance polymer chain entanglements. One approach is to add an epoxy-based compatibilizer to the polylactide resin to improve melt strength. This is because the branched structure is primarily formed by the reaction between the carboxyl groups and epoxy groups at the end groups of the polylactide resin, and thus, its reactivity can vary significantly depending on the acid value (terminal group influence from additives, initiators, etc.) and purity (D content) of the polylactide resin. Therefore, branching tendencies vary, and it is difficult to determine the degree to which processing stability and neck-in can be improved until actual product evaluation is performed.

[0010]

[0011] Accordingly, the present invention provides a method for predicting or evaluating the neck-in characteristics of a film manufactured from a polylactide resin with a simple yet high degree of accuracy, thereby replacing the actual measurement method and enabling the film properties of a new structure to be determined in advance.

[0012] The present invention provides a method for predicting the neck-in of a polylactide resin.

[0013] To solve the above problem, the present invention provides a method for predicting the neck-in of a polylactide resin, comprising the following steps:

[0014] 1) A step of measuring the following physical properties A and B for each of a plurality of polylactide resins (step 1);

[0015] - Property A: Tan δ(@0.4rad / s)

[0016] - Property B: η" (@0.3rad / s)

[0017] 2) A step of measuring the Neck-in value (N) for the plurality of polylactide resins (step 2); and

[0018] 3) A step for deriving a Neck-in prediction formula of polylactide resin by regression analysis of the Neck-in value (N) according to the measured values ​​of the above properties A and B (step 3).

[0019]

[0020] The term "polylactide resin" used in the present invention is defined to encompass a single polymer or copolymer containing the following repeating units.

[0021]

[0022]

[0023] The above polylactide resin can be manufactured by including a step of forming the above repeating unit by ring-opening polymerization of a lactide monomer, and the polymer obtained after the ring-opening polymerization and the above repeating unit formation process are completed can be referred to as the above “polylactide resin.”

[0024]

[0025] Here, the "lactide monomer" can be defined as follows. Typically, lactide can be classified into L-lactide composed of L-lactic acid, D-lactide composed of D-lactic acid, and mesolactide composed of one L-form and one D-form. In addition, a 50:50 mixture of L-lactide and D-lactide is called D,L-lactide or rac-lactide. It is known that when polymerization is performed using only L-lactide or D-lactide with high optical purity among these lactides, L- or D-polylactide (PLLA or PDLA) with very high stereoregularity is obtained, and such polylactide is known to have a fast crystallization rate and high crystallization degree compared to polylactide with low optical purity. However, in this specification, “lactide monomer” is defined to include all forms of lactide regardless of differences in the properties of lactide according to each form and differences in the properties of polylactide resins formed therefrom.

[0026]

[0027] Meanwhile, the plurality of polylactide resins each have a weight average molecular weight of 70,000 to 400,000. Preferably, the polylactide resin according to the present invention has a weight average molecular weight of 80,000 or more, 90,000 or more, or 100,000 or more; or 300,000 or less, 250,000 or less, or 200,000 or less.

[0028]

[0029] In addition, the number average molecular weight of the plurality of polylactide resins is 50,000 to 100,000. Preferably, the polylactide resin according to the present invention has a number average molecular weight of 55,000 or more, or 60,000 or more; or 90,000 or less, 85,000 or less, or 80,000 or less.

[0030]

[0031] Additionally, each of the plurality of polylactide resins may further include additives. Examples of such additives include polylactide oligomers, compatibilizers, and the like. For example, some polylactide resins may not contain any components other than polylactide resin, while others may include additives. Furthermore, by using the same polylactide resin and varying only the type or content of the additives, it is possible to predict the effect of the additives on the neck-in properties.

[0032]

[0033] The present invention relates to a method for predicting or evaluating the neck-in characteristics of a film manufactured from polylactide resin with a simple yet highly accurate method. To this end, the present invention measures the rheological properties of the polylactide resin, namely, property A and property B.

[0034]

[0035] The above property A is Tan delta, and the tan delta value can be confirmed by frequency range through rheological property measurement, and the specific measurement method for this is specified in the examples below. In the low frequency (0.3 to 0.4 rad / s) range, there is a correlation in which the Neck-in decreases as Tan delta decreases when compared to the actual Neck-in value within the processing conditions.

[0036]

[0037] The above property B is η", and the results of η' and η" for each frequency range can be confirmed through the measurement of rheological properties, and can be obtained by plotting a Cole-Cole Plot, and the specific measurement method for this is specified in the examples below. In the range of low frequency (0.3 to 0.4 rad / s), there was a correlation in which the Neck-in decreased as η" increased when compared with the actual Neck-in value within the processing conditions.

[0038]

[0039] Therefore, for a plurality of polylactide resins, the above physical properties A and B are measured (step 1), and the Neck-in values ​​(N) for the plurality of polylactide resins are actually measured (step 2); and by performing a regression analysis on the Neck-in values ​​(N) according to the measured values ​​of the physical properties A and B, a Neck-in prediction formula for the polylactide resin can be derived. Meanwhile, the method for measuring the actual value of the Neck-in is specified in the following examples.

[0040]

[0041] The above-mentioned plurality of polylactide resins means at least two types of polylactide resins, and considering the correlation coefficient of the prediction equation, it is preferable that there are many types. Preferably, the above-mentioned plurality of polylactide resins are 5 or more types, 6 or more types, 7 or more types, 8 or more types, 9 or more types, or 10 or more types, and 50 or less types, 40 or less types, 30 or less types, or 20 or less types of polylactide resins.

[0042]

[0043] Preferably, the neck-in prediction formula of the polylactide resin is as follows:

[0044] [Mathematical Formula 1]

[0045] N = (0.077 * A) - (0.085 * B) + 27.69

[0046] In the above mathematical formula 1,

[0047] A stands for Tan δ(@0.4rad / s), and B stands for η"(@0.3rad / s).

[0048]

[0049] As illustrated in the examples below, the prediction formulas obtained according to the present invention have a high correlation with actual measurements, and the differences between the values ​​calculated using the prediction formulas and the actual measurements are very small. Therefore, the present invention enables the simple and highly predictive prediction of film properties without the need for actual film manufacturing.

[0050] As described above, the present invention provides a method for predicting or evaluating the neck-in characteristics of a film manufactured from a polylactide resin, which is simple and has a high predictability, and thus can replace an actual measurement method, thereby enabling the film properties to be determined in advance for a new structure.

[0051] Figure 1 shows the results of mapping the two factors measured in Experimental Example 1.

[0052] Figure 2 shows a method for obtaining a neck-in prediction formula in Experimental Example 1.

[0053] Hereinafter, embodiments of the present invention will be described in more detail in the following examples. However, the following examples are merely illustrative of embodiments of the present invention, and the content of the present invention is not limited by the following examples.

[0054]

[0055] Manufacturing example: PT-SA manufacturing

[0056] PLA oligomers were prepared using pentaerythritol (PT) as an initiator. Specifically, 75 g of lactide and PT were added to a 500 mL reactor at a molar ratio of 100:1, and a Sn(Oct)2 catalyst (0.075 g) was added, followed by a reaction at 180°C for 5 hours to prepare oligomers. In order to substitute the hydroxyl end groups of the prepared oligomers with carboxyl groups (COOH), the mole number was calculated using the amount of lactide added (g) and the number-average molecular weight (g / mol) of the prepared oligomers, and the total hydroxyl end groups of the prepared oligomers were calculated considering the number of end groups (4) of the initiator (PT). Subsequently, 2 equivalents of succinic anhydride (SA) relative to the total hydroxyl end groups of the oligomers were added in one pot, and the reaction was performed for an additional 3 hours. After the reaction was completed, the PLA oligomer prepared in the CHCl3 / MeOH solvent system was precipitated / isolated to remove unreacted SA and remaining impurities. The final product was obtained by vacuum drying at 45°C for 12 hours, which was designated 'PT-SA'.

[0057]

[0058] The weight average molecular weight of the above-mentioned manufactured PLA oligomer, 'PT-SA', was measured. Specifically, the weight average molecular weight (Mw) was measured using GPC (Gel Permeation Chromatography) equipment, and the specific measurement conditions were as follows, and the measured weight average molecular weight was approximately 40,000.

[0059] - Column: PLgel Mixed E x 2

[0060] - Solvent: THF

[0061] - Flow rate: 0.7 mL / min

[0062] - Sample concentration: 3.0 mg / mL

[0063] - Injection volume: 100 μl

[0064] - Column temperature: 40℃

[0065] - Detector: Waters 2414 RID

[0066] - Standard: PS (polystyrene)

[0067]

[0068] Example: Preparation of polylactide resin

[0069] Reactive extrusion was performed using 19Ψ extruder equipment (BA-19, Bautek) for the components listed in Table 1 below.

[0070]

[0071] Specifically, for 1 kg of polylactide resin (Anhui BBCA Biochemical & Futerro PLA Corp., FY201; FY202; FY212; FY601; FY801), the components (epoxy-based compatibilizer (Joncryl ADR 4468), or PT-SA) listed in Table 1 below were mixed, extruded at a screw speed of 200 rpm while controlling the maximum temperature value (190 to 230°C) to obtain PLA pellets. The number average molecular weight and weight average molecular weight of the obtained PLA pellets were measured as follows, and the results are shown in Table 1.

[0072] - Column: PL mixed B x 2

[0073] - Solvent: THF

[0074] - Flow rate: 1.0 ml / min

[0075] - Sample concentration: 1.5 mg / ml

[0076] - Injection volume: 100 μl

[0077] - Column temperature: 40℃

[0078] - Detector: Waters 2414 RID

[0079] - Standard: PS (polystyrene)

[0080]

[0081] Sample#1#2#3#4#5#6#7#8PLAFY201FY201FY201FY202FY202FY202FY212FY212AdditiveJoncryl 1.0Joncryl 1.0Joncryl 1.0Joncryl 1.0Joncryl 1.0PT-SA 5.0Joncryl 1.0Joncryl 1.0F / R55555555RPM200200200200200200200Zone 7(℃)130130130130130130110130Zone 6 (℃)170190200190200200170200Zone 5(℃)190210230210230230190230Zone 4(℃)190210230210230230190230Zone 3(℃)190210230210230230190230Zone 2(℃)190210230210230230190230Zone 1(℃)190210230210230230190230Header(℃)190210230210210210210210Mn66,18461,37363,96363,95063,01760,2517 6,58874,391Mw121,979117,746128,905128,895132,086139,512162,102190,793PDI21.922.022.022.12.322.122.57

[0082]

[0083] Additionally, the following four types of polylactide resins were additionally used in the following experiments.

[0084] #9: NW 4032D (NatureWorks)

[0085] #10: FY601 (Anhui BBCA Biochemical & Futerro PLA Corp)

[0086] #11: FY604 (Anhui BBCA Biochemical & Futerro PLA Corp)

[0087] #12: FY801 (Anhui BBCA Biochemical & Futerro PLA Corp)

[0088]

[0089] Experimental Example 1

[0090] 1) Neck-in measurement of polylactide resin

[0091] The above-obtained pellets were vacuum-dried at 85°C for more than 4 hours, and a PLA film was manufactured through T-die extrusion molding (Eurotech benchtop monolayer cast film equipment, Screw Ψ17.5 mm, T-die width 120 mm).

[0092]

[0093] The neck-in value was measured by the film width (X) manufactured under the same conditions of a calendar speed of 3.0 M / m and a haul-off speed of 4.5 M / m, and the results are shown in Table 2 below.

[0094] Neck-in evaluation: ((T-die width) - (Film width)) / 2 = (120 - X) / 2

[0095]

[0096] SampleT-die ConditionCalenderHaul-offFilm EvaluationScrewCyl 1Cyl 1HeadLipM / mM / mFilm ThicknessFilm WidthNeck-in Evaluation (rpm) (℃) (℃) (℃) (μm) (mm) (mm) #150 150 200 200 190 34.535-6924-6548 #250 150 200 200 190 34.537-6824-4848 #350 150 200 200 190 34.535-4745-6237.5 #450 150 200 200 190 34.547-6848-5836 #550 150 200 200 190 34.522-7335-5042.5 #650 150 200 200 190 34.538-4764-7328#75015020020019034.522-3494-9513#85011020020019034.525-3194-9513#95011020020019034.518-2356-5932#105015020020019034.517-3644-5438#115011020020019034.522-2650-5835#125011020020019034.515-2350-7035

[0097]

[0098] 2) Deriving a neck-in prediction formula for polylactide resin

[0099] The rheological properties were evaluated using an ARES-G2 Rheometer (Strain-Controlled Type) from TA Instruments based on a geometry of 25 mm diameter parallel plates and 1 mm gap. PLA samples were filled with the above geometry size and measured, and an appropriate strain was set for each sample through an amplitude sweep at the initial measurement temperature of 210℃. Based on the set strain (5-10%), an angular frequency sweep of 0.1 rad / s to 500 rad / s was performed at the same measurement temperature of 210℃. From this, the following two factors were derived.

[0100]

[0101] (i) Tan delta

[0102] Through rheological measurements, tan delta values ​​were confirmed for each frequency range, and when compared with the Neck-in test results within processing conditions in the low frequency (0.3 to 0.4 rad / s) range reflecting structural (LCB) effects, there was a correlation in which Neck-in decreased as Tan delta decreased.

[0103]

[0104] (ii) η"

[0105] Through the same measurement method, the results of η' and η" by frequency range could be confirmed, and the Cole-Cole Plot could be drawn. η" in the Cole-Cole Plot showed a tendency to increase according to the structural change (LCB) of PLA, and when compared with the results of the Neck-in test within the processing conditions in the low frequency (0.3 to 0.4 rad / s) range reflecting the structural (LCB) influence, there was a correlation in which the Neck-in decreased as η" increased.

[0106]

[0107] The two significant factors above are highly correlated with Neck-in, and mapping between the significant factors can be performed, which is illustrated in Figure 1.

[0108]

[0109] The correlation between the two significant factors mentioned above and Neck-in is high, and based on this, Neck-in prediction using the rheological factors is possible. The above data is summarized in Table 3 below, and a prediction equation between the factors was constructed using a linear regression model, as shown in Figure 2. The correlation coefficient between the prediction equation and Neck-in was 0.82.

[0110] SampleLow(0.4rad / s)Tan deltaLow(0.3rad / s)η*Neck-in Actual valueNeck-in predicted value@210℃@210℃@3M / m@3M / m#1261.8840.106964847.8#2143.8730.106964838.8#3149.3312.0948437.539#4131.0032.873263637.5#5114.1182.8401442.536.2#610.4315 35.01992825.5#75.83055219.489139.5#86.98884154.0571315.1#990.37469.458543233.8#10182.2542.60883841.5#11147.5322.99283538.8#12129.6844.260713537.3

[0111]

[0112] Neck-in (predicted equation) = 0.077 * A - 0.085 * B + 27.69

[0113] In the above formula,

[0114] A is Tan delta (@0.4 rad / s)

[0115] B is η”(@0.3 rad / s)

[0116]

[0117] Experimental Example 2

[0118] In order to evaluate the prediction formula obtained in the above Experimental Example 1, a polylactide resin composition was prepared using the same method as the sample #7 above, but using 0.5 phr of Joncryl ADR 4468. The weight average molecular weight and number average molecular weight were 162,102 and 76,588, respectively.

[0119]

[0120] For the polylactide resin composition, Tan delta and η" were measured in the same manner as in Example 1, and were measured as 21.5255 and 16.431, respectively. By substituting these values ​​into the prediction formula obtained in Experimental Example 1, the Neck-in value was predicted as follows.

[0121]

[0122] Neck-in = 0.077 * (21.5255) - 0.085 * (16.431) + 27.69

[0123] = 27.95

[0124]

[0125] For the polylactide resin composition, the Neck-in actual value was obtained in the same manner as in Example 1, and was 27.5, which was confirmed to be almost the same as the value obtained using the above predicted formula.

Claims

1. 1) A step of measuring the following physical properties A and B for each of a plurality of polylactide resins (step 1); - Property A: Tan δ(@0.4rad / s) - Property B: η" (@0.3rad / s) 2) A step of measuring the Neck-in value (N) for the above plurality of polylactide resins (step 2); and 3) A step (step 3) of deriving a prediction formula for the Neck-in of the polylactide resin by performing regression analysis on the Neck-in value (N) according to the measured values ​​of the above properties A and B. Neck-in prediction method of polylactide resin.

2. In paragraph 1, The neck-in prediction formula for the above polylactide resin is the following mathematical formula 1: How to predict: [Mathematical Formula 1] N = (0.077 * A) - (0.085 * B) + 27.69 In the above mathematical expression 1, A stands for Tan δ(@0.4rad / s), B stands for η"(@0.3rad / s).

3. In paragraph 1, The above-mentioned plurality of polylactide resins each have a weight average molecular weight of 70,000 to 400,000. How to predict.

4. In paragraph 1, The number average molecular weight of the above plurality of polylactide resins is 50,000 to 100,000. How to predict.

5. In paragraph 1, Some of the above polylactide resins further comprise an additive. How to predict.

6. In paragraph 1, The above-mentioned plurality of polylactide resins are 10 to 20 types, How to predict.

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