Method for predicting stretchable temperature window of polyolfin resin, and preparation method for stretched film

Abstract

The present invention relates to a method for predicting the stretchable temperature of a polyolefin resin, which can reliably predict the stretchable temperature range during the manufacture of a stretchable film even without actually manufacturing a stretchable film from a polyolefin resin, and a method for manufacturing a stretchable film using the same.

Description

Technology Field

[0001] The present invention relates to a method for predicting the stretchable temperature of a polyolefin resin, which can reliably predict the stretchable temperature range during the manufacture of a stretchable film even without actually manufacturing a stretchable film from a polyolefin resin, and a method for manufacturing a stretchable film using the same. Background Technology

[0002] Stretched films made from polyolefin resins, such as polyethylene resin, are used for various purposes. In particular, compared to other types of films such as blown films or cast films, these polyolefin-based stretched films have excellent resistance to external impact at the same thickness and excellent barrier properties against oxygen or moisture. In addition, they also possess excellent transparency and stiffness, so they are widely used as packaging materials for various products, such as food or beverages.

[0003] These polyolefin-based stretched films are manufactured by heat-treating and stretching a polyolefin resin at a certain stretching temperature, and setting an appropriate stretching temperature according to the type or physical properties of each polyolefin resin is a very important factor in the physical properties of the stretched film. For example, if the stretching temperature is set too low, the polyolefin resin may not be stretched properly and may tear or deviate from the stretching zig, and if the stretching temperature is set too high, the polyolefin resin may completely melt and become impossible to stretch.

[0004] For this reason, setting an appropriate stretching temperature for each type or physical property of polyolefin resin can be a very important factor in manufacturing stretched films and achieving excellent physical properties. The appropriate stretching temperature of such polyolefin resin is determined by considering the melting point of the resin and the stretchable temperature range (so-called "stretch window"), and the stretchable temperature range can be defined as the range of stretchable temperatures (i.e., the difference between the upper and lower limits of the stretchable temperature) at which the stretched film can have a thickness variation of within 10% over the entire area when the polyolefin resin is stretched to manufacture a film.

[0005] Therefore, for a certain polyolefin resin, the wider the stretchable temperature range, the better the resin can be stretchable processability, and conversely, if the stretchable temperature range is narrow, it becomes very difficult to control the stretching process, and the stretchable processability and process stability may be significantly reduced.

[0006] Therefore, in developing a polyolefin resin suitable for use in the manufacture of stretched films, it is very important to identify a polyolefin resin with a relatively wide stretchable temperature range.

[0007] However, these stretchable temperature ranges vary significantly for each resin, and previously, no studies or proposals have been made regarding which physical properties or factors of each resin influence this range. Consequently, it was impossible to predict the stretchable temperature range of a given polyolefin resin without conducting numerous stretching processes while manufacturing actual stretched films; this led to significant trial and error in the research and development of polyolefin resins for stretched films.

[0008] Accordingly, to reduce such trial and error, there has been a continuous demand for the development of a method that can reliably predict the stretchable temperature range when applying the stretching process to polyolefin resins, even without actually performing the stretching process. The problem to be solved

[0009] Accordingly, the present invention provides a method for predicting the stretchable temperature of a polyolefin resin that can reliably predict the stretchable temperature range during the manufacture of a stretchable film, even without actually manufacturing a stretchable film from the polyolefin resin.

[0010] In addition, the present invention provides a method for manufacturing a polyolefin-based stretched film capable of producing a polyolefin-based stretched film with high processability and process stability by applying the above-described prediction method. means of solving the problem

[0011] The present invention comprises the step of measuring, for a plurality of polyolefin resins, the NDR X1 (%), which is defined as the elongation (%) at the point where strain hardening occurs in each resin, while conducting a stretching test according to ASTM D638;

[0012] A step of measuring and calculating, for each of the above plurality of polyolefin resins, the Tm-width X2 (°C), which is defined as the value obtained by dividing the endothermic curve area (melting enthalpy) of the second temperature rise section on the DSC curve by the heat flow at the endothermic peak point while measuring the melting point by DSC;

[0013] A step of measuring, for each, a stretchable temperature range Y (°C) in which a film is formed with a thickness variation of 10% or less over the entire area while stretching the plurality of polyolefin resins to manufacture a film; and

[0014] A method for predicting the stretchable temperature of a polyolefin resin is provided, comprising the step of deriving a stretchable temperature range prediction equation by linearly regressing the measured values ​​of NDR X1 (%), Tm-width X2 (°C), and Y (°C).

[0015] The present invention also includes the step of predicting a stretchable temperature range of a target polyolefin resin different from the plurality of polyolefin resins by the prediction method; and

[0016] A method for manufacturing a stretched film is provided, comprising the step of stretching the target polyolefin resin to form a film within the predicted temperature range.

[0018] Hereinafter, a method for predicting the stretchable temperature of a polyolefin resin and a method for manufacturing a stretched film according to an embodiment of the invention will be described in detail.

[0019] According to one embodiment of the invention, for a plurality of polyolefin resins, a stretching test is performed in accordance with ASTM D638, and the NDR X1 (%), defined as the elongation (%) at the point where each resin undergoes strain hardening, is measured for each;

[0020] A step of measuring and calculating, for each of the above plurality of polyolefin resins, the Tm-width X2 (°C), which is defined as the value obtained by dividing the endothermic curve area (melting enthalpy) of the second temperature rise section on the DSC curve by the heat flow at the endothermic peak point while measuring the melting point by DSC;

[0021] A step of measuring, for each, a stretchable temperature range Y (°C) in which a film is formed with a thickness variation of 10% or less over the entire area while stretching the plurality of polyolefin resins to manufacture a film; and

[0022] A method for predicting the stretchable temperature of a polyolefin resin is provided, comprising the step of deriving a stretchable temperature range prediction equation by linearly regressing the measured values ​​of NDR X1(%), Tm-width X2(°C), and Y(°C).

[0023] First, the inventors have continued to conduct research on the physical properties of the polyolefin resin in order to predict in advance the stretchable temperature range during the stretching process based on the physical properties of the polyolefin resin itself.

[0024] In the course of such continuous research, it was discovered that the stretchable temperature range can be reliably predicted from two resin properties: NDR X1 (%), which is measured as the elongation (%) at the point where the resin undergoes strain hardening during a tensile (stretch) test on a polyolefin resin specimen according to ASTM D638, and Tm-width X2 (°C), which is defined as the value obtained by dividing the endothermic curve width (melting enthalpy) of the second temperature rise section by the heat flow at the endothermic peak point during a DSC analysis of the resin to determine the melting point. This invention was completed.

[0025] More specifically, the tensile test process for measuring the NDR can simulate the stretching process for manufacturing a stretched film from the polyolefin resin. For example, the point of deformation hardening of the resin, which is the point of measurement for the NDR, can simulate the point in time when the resin is not properly stretched and tears, etc., because it exceeds the stretchable temperature range during the stretching process. Therefore, as the larger the NDR, the greater the possibility of stretching over a wider temperature range, the NDR can be proportional to the stretchable temperature range.

[0026] In addition, the above Tm-width is a physical property regarding whether the rheological properties of the resin are uniformly expressed at a specific temperature, and it can be predicted that the narrower (smaller) this Tm-width, the smoother the stretching of the resin can be achieved. Therefore, the above Tm-width may be inversely proportional to the above-mentioned stretchable temperature range.

[0027] In this way, by clarifying the relationship between the physical properties of the polyolefin resin itself, namely NDR X1 (%) and Tm-width X2 (°C), and the stretching processing temperature range Y (°C) during stretching processing, the prediction method of one embodiment can derive a prediction equation for the stretchable temperature range of the polyolefin resin by linearly regressing Y as a multiple linear function of X1 and X2 based on the measured values ​​of X1, X2 and Y.

[0028] Based on this prediction formula, the stretchable temperature range of the polyolefin resin under evaluation, which is different from the plurality of resins mentioned above, was predicted by measuring only its NDR and Tm-width. As a result, it was confirmed that the stretchable temperature range of the resin under evaluation can be predicted with great reliability.

[0029] As such, according to the method of one embodiment, the stretchable temperature range of the resin to be evaluated can be predicted with great reliability in advance, even without actually measuring the stretchable temperature by performing an actual stretching process on the resin. Therefore, during the process of researching and developing polyolefin resins for manufacturing stretched films, many trial-and-error steps can be reduced, and a polyolefin resin with excellent stretchability and process stability due to a wide stretchable temperature range can be easily developed.

[0030] Furthermore, by utilizing the above prediction method to manufacture a stretched film, the stretching process of the polyolefin resin can be made very smooth and the process stability can be greatly increased.

[0031] Meanwhile, in the prediction method of the above embodiment, the plurality of polyolefin resins used to derive the prediction formula for the stretchable temperature range may be any polyethylene resin known to be usable for manufacturing stretchable films. In a specific example, the polyolefin resin may be a polyethylene resin selected from the group consisting of copolymers of ethylene and alpha-olefins having three or more carbon atoms.

[0032] In addition, in a more specific example, the polyethylene resin is 0.91 to 0.94 g / cm³ 3 It may have a density of 0.2 to 4.0 g / 10 min (2.16 kg), a number average molecular weight of 20,000 to 50,000, a weight average molecular weight of 80,000 to 130,000, and a molecular weight distribution of 5 or less, or 2 to 4.

[0033] Additionally, the polyethylene resin may have an average number of short chain branches (SCB) per 1,000 carbon atoms of 10 to 30, or 15 to 25.

[0034] By using a plurality of polyethylene resins having the aforementioned properties to derive a prediction formula for the stretchable temperature range, the reliability of the prediction method according to one embodiment can be further improved.

[0035] Meanwhile, in the method of one embodiment, a tensile test is performed on the plurality of polyolefin resins according to ASTM D638, and the NDR X1 (%), defined as the elongation (%) at the point where each resin undergoes strain hardening, is measured for each. At this time, the polyolefin resin may be used in the form of a sheet-shaped tensile specimen, and a tensile test may be performed on such specimens using a universal tensile testing machine. During this tensile test process, the elongation (%) of the specimen at the point where each resin specimen undergoes strain hardening is measured, and this can be calculated as the NDR X1 (%).

[0036] These properties simulate and reflect the degree to which each polyolefin resin can be smoothly stretched. Since a larger NDR indicates that smoother stretching is performed and stretching is possible over a wide temperature range, it can be predicted that the NDR is approximately proportional to the stretchable temperature range.

[0037] Apart from the above NDR, for the plurality of polyolefin resins, a melting point analysis can be performed using DSC, and a DSC curve can be derived. This DSC analysis can be performed under the same conditions as the general melting point analysis process of polyolefin resins, for example, by heating the resin to a temperature of 190°C, then cooling it to -50°C while changing the temperature at a heating and cooling rate of 10°C / min, and then raising the temperature again.

[0038] From the DSC curve derived from this DSC analysis, Tm-width X2 (°C) can be calculated, which is defined as the value obtained by dividing the endothermic curve width (melting enthalpy) of the second temperature rise section by the heat flow at the endothermic peak point.

[0039] At this time, the Tm-width X2(°C) can be corrected to the heating rate during DSC analysis (e.g., a heating rate of 10°C / min) to derive the final calculated value, and through this process, the reliability of the prediction method of one embodiment can be further improved.

[0040] These properties reflect how intensively each resin exhibits rheological properties at a specific temperature; a narrower (smaller) Tm width may reflect that elongation occurs smoothly in the pre-melting stage and may be approximately inversely proportional to the elongation-possible temperature range.

[0041] In addition to measuring the NDR and Tm widths respectively, for the plurality of polyolefin resins, the stretchable temperature range Y (°C) for deriving the prediction formula can be measured. At this time, the stretchable temperature range can be defined as the range of stretchable temperatures (i.e., the difference between the upper and lower limits of the stretchable temperature) at which, when the polyolefin resin is stretched to manufacture a film, the stretched film can have a thickness variation of within 10% over the entire area. Therefore, the larger the stretchable temperature range, the wider the stretchable temperature range, and the polyolefin resin can be evaluated as having excellent stretchability and being suitable for manufacturing a stretched film.

[0042] This stretchable temperature range can be measured during the process of manufacturing a stretched film by setting various stretch temperatures, preheating each resin at the corresponding stretch temperature, biaxially stretching each resin while maintaining the stretch temperature, and performing additional heat treatment. When a stretched film is manufactured in this way and the thickness deviation in the entire area of ​​the stretched film is within 10%, the corresponding stretch temperature can be defined as the stretchable temperature. After determining the range of the stretchable temperature by repeating this experiment, the difference between the upper and lower limits can be calculated to obtain the actual value of the stretchable temperature range Y (°C).

[0043] However, if the stretchable temperature range for the aforementioned multiple polyolefin resins is already known, it goes without saying that such known measured values ​​may also be utilized.

[0044] As described above, for a plurality of polyolefin resins, after calculating and collecting data regarding the stretchable temperature range Y, NDR X1, and width of Tm-width X2 respectively, these data can be linearly regressed in the form of a multiple linear function such as, for example, Equation 1 below to derive a prediction equation for the stretchable temperature range of the polyolefin resin:

[0045] [Equation 1]

[0046] Y(℃) = A*

[0047] (Where A, B, and C are constants determined by linear regression.)

[0048] According to a more specific example, for polyethylene resins well known for manufacturing stretched films, the above prediction formula was derived in the following examples, and a prediction formula for the stretchable temperature range was derived in which A is -0.0513, B is 0.0143, and C is -3.2681 in Equation 1.

[0049] When such a prediction formula is derived, for a polyolefin resin subject to evaluation having different physical properties from the plurality of polyolefin resins mentioned above, only NDR X1 (%) and Tm-width X2 (°C) are measured respectively, and then substituted into the prediction formula such as Equation 1 to predict the stretchable temperature range of the resin subject to evaluation.

[0050] Through this process, for a newly developed resin under evaluation, the stretchable temperature range can be reliably predicted based solely on the resin properties, even without actually measuring the stretchable temperature range by conducting a stretching process. Consequently, the development process for the resin used to manufacture stretched films can be significantly shortened, and trial and error during this development process can be greatly reduced.

[0051] In addition, by manufacturing a stretched film using a polyolefin resin predicted to have a wide stretchable temperature range through the above prediction method, a stretched film with excellent properties at a wide stretching temperature can be manufactured without additional trial and error, thereby significantly improving the process stability of the stretching process.

[0052] According to another embodiment of the invention, a method for manufacturing a stretched film is provided, comprising the steps of: predicting a stretchable temperature range of a target polyolefin resin different from the plurality of polyolefin resins according to the method of the above-described embodiment; and stretching the target polyolefin resin to form a film within the predicted temperature range.

[0053] In this manufacturing method, based on the above prediction results, a stretching step can be performed using a polyolefin resin with a wide stretching temperature range. In addition, in performing this stretching step, the stretching temperature can be determined by considering the predicted stretching temperature range and the melting point of the target polyolefin resin, and in a specific example, the temperature for performing the stretching step can be determined by considering the stretching temperature range together within the range of 105 to 135°C.

[0054] Meanwhile, the method for manufacturing the above-mentioned stretched film may follow the manufacturing process and conditions of a conventional polyolefin-based stretched film, except for predicting the stretchable temperature and range using the method of one embodiment and determining the stretching temperature thereby; therefore, further explanation regarding this is omitted. Effects of the invention

[0055] As described above, according to the present invention, the stretchable temperature range of a polyolefin resin can be predicted with great reliability in advance, even without actually measuring the stretchable temperature by performing an actual stretching process on the polyolefin resin. Therefore, during the research and development of polyolefin resins for the manufacture of stretched films, many trial-and-error steps can be reduced, and a polyolefin resin with excellent stretchability and process stability due to a wide stretchable temperature range can be easily developed.

[0056] Furthermore, by utilizing the above prediction method to manufacture a stretched film, the stretching process of the polyolefin resin can be made very smooth and the process stability can be greatly increased. Brief explanation of the drawing

[0057] Figure 1 is a graph showing the results of DSC analysis of the first to fifth polyethylene resins in the example. Specific details for implementing the invention

[0058] Preferred embodiments are presented below to aid in understanding the invention. However, the following embodiments are intended only to illustrate the invention and do not limit the invention to these embodiments.

[0060] Resin Examples 1 to 5: Evaluation of the 1st to 5th polyethylene resins and physical properties

[0061] Four types of commercially available stretched film grade polyethylene resins were obtained and these were used as the first to fourth polyethylene resins.

[0062] Polyethylene Resin No. 1: SP311 manufactured by LG Chemical (Density: 0.920 g / cm³) 3 );

[0063] No. 2 Polyethylene Resin: ExxonMobil Exceed 1018MF (Density: 0.925 g / cm³) 3 );

[0064] Third-class polyethylene resin: HP1018 manufactured by LG Chemical (Density: 0.920 g / cm³) 3 );

[0065] Class 4 Polyethylene Resin: Dow Chemical Elite TF80 (Density: 0.930 g / cm³) 3 );

[0066] No. 5 Polyethylene Resin: Sabic BX202 (Density: 0.920 g / cm³) 3 )

[0068] The physical properties of the above 1st to 5th polyethylene resins were evaluated by the following method and are shown in Table 1:

[0069] 1. Melt Index (2.16 kg) and MFR: First, the molten resin was evaluated at a temperature of 190°C and under a load of 2.16 kg according to the standard method of ASTM D1238. The evaluation result was derived as the weight (g) of the resin that melted over 10 minutes. The molten resin was evaluated under a load of 21.6 kg using the same method, and the MFR of each resin was evaluated by dividing this by the melt index under a load of 2.16 kg.

[0070] 2. Mn, Mw, and Molecular Weight Distribution:

[0071] For each resin, GPC analysis was performed using a Waters PL-GPC220 GPC instrument with a Polymer Laboratories PLgel MIX-B 300 mm long column. The temperature during analysis was approximately 160°C, and 1,2,4-trichlorobenzene was used as the solvent. The flow rate was measured at 1 mL / min, and the resin samples were prepared at a concentration of 10 mg / 10 mL and supplied in a volume of 200 μL. Additionally, polystyrene resin was used as the standard material for GPC analysis, and the molecular weights of these standard materials were 2,000, 10,000, 30,000, 70,000, 200,000, 700,000, 2,000,000, 4,000,000, or 10,000,000.

[0072] In this way, each resin was analyzed by GPC, and a molecular weight distribution curve for each resin was derived from the GPC analysis results. From this, the number average molecular weight and weight average molecular weight of each resin were calculated, and the molecular weight distribution was calculated from their ratios.

[0073] 3. Average number of single chain branches (SCB) per 1,000 carbon atoms:

[0074] From the GPC analysis results of "2" above, a distribution curve of the molecular weight of the polymer chains contained in each resin was derived with log Mw as the x-axis and the differential value of the content of the polymer chains by molecular weight (dwt / dlog M) as the y-axis.

[0075] Separately, each resin was analyzed using FT-IR to derive the distribution curve of SCBs per 1,000 carbon atoms according to the molecular weight of the polymer chain. From this, the average number of short chain branches (SCBs) per 1,000 carbon atoms was calculated for each of the above resins.

[0077] 1st PE resin 2nd PE resin 3rd PE resin 4th PE resin 5th PE resin Melt index (2.16kg)(g / 10min) 1.0 1.0 1.1 1.8 1.9 MFR 24 18 25 31 29 Mn (g / mol) 45000 52000 44000 30000 25000 Mw (g / mol) 120000 114000 116000 95000 94000 molecular weight distribution 2.67 2.19 2.64 3.16 3.72 Average number of SCBs (pieces) 16.4 14.4 16.6 14.9 19.7

[0078] Examples 1 to 5: Derivation of a formula for predicting the stretchable temperature range

[0079] First, the above-mentioned first and second polyethylene resins were prepared in the form of tensile specimens (thickness 1T) conforming to the standard method of ASTM D638. These tensile specimens were introduced into a universal tensile testing machine to conduct a tensile test, and the elongation (%) was measured at the point where strain hardening of the specimen occurred, and this was derived as the measurement value of NDR X1.

[0080] Next, specimens of the first to fifth polyethylene resins were analyzed using DSC 2920 equipment (manufactured by TA instrument). First, each resin was heated to a temperature of 190°C and maintained for 5 minutes, then cooled to -50°C, and then heated again while proceeding with the analysis. At this time, the heating and cooling rates were set to 10°C / min, and DSC curves for the first to fifth polyethylene resins (Examples 1 to 5) were derived from the results of this DSC analysis and are shown in Fig. 1.

[0081] In this DSC curve, Tm-width X2 (°C) was calculated, which is defined as the value obtained by dividing the endothermic curve width (melting enthalpy) of the second temperature rise section by the heat flow at the endothermic peak point, and the final calculated value was obtained by correcting this calculated value with the heating rate during DSC analysis (e.g., a heating rate of 10°C / min).

[0082] Meanwhile, the first to fifth polyethylene resins were preheated at a constant stretching temperature for 5 minutes, each resin was biaxially stretched while maintaining the stretching temperature, and an additional heat treatment was performed for 3 minutes at the same temperature to produce a stretched film.

[0083] As a result of manufacturing stretched films using this method, if the thickness deviation in the entire area of ​​each stretched film is within 10%, the corresponding stretching temperature was defined as the stretchable temperature. By repeating the above experimental process with various stretching temperatures set within the range of 105 to 135°C, the range of the stretchable temperature for each resin was determined. After determining this range, the difference between the upper and lower limits was calculated to determine the measured value of the stretchable temperature range Y(°C).

[0084] As described above, for the first to fifth polyethylene resins, after calculating and collecting the actual values ​​of X1, X2, and Y respectively, a prediction equation was derived by linearly regression of these data in the form of a multiple linear function as shown in Equation 1 below:

[0085] [Equation 1]

[0086] Y(℃) = A*

[0087] (However, A, B, and C were determined to be -0.0513, 0.0143, and -3.2681.)

[0088] The actual values ​​of X1, X2, and Y above, and the predicted values ​​of the stretchable temperature range derived from the prediction formula of Equation 1 above, are summarized and shown together in Table 2 below.

[0090] Example 1 (First PE resin) Example 2 (Second PE Resin) Example 3 (Third PE resin) Example 4 (4th PE resin) Example 5 (5th PE resin) NDF X1(%) 410 420 440 870 750 Tm-width X2(℃) 17.6 24.6 23.3 13.3 12.7 Y(Measured value; ℃) 1.7 1.5 1.8 8.5 6.8 Y(Predicted value; ℃) 1.69202 1.47592 1.82861 8.49061 6.80539

[0091] As confirmed from Table 2 above, it was confirmed that the stretchable temperature range of polyethylene resin can be reliably predicted from the prediction equation of Equation 1.

Claims

Claim 1 A method for predicting the stretchable temperature of a polyolefin resin, comprising: a step of measuring, for each of the plurality of polyolefin resins, the NDR X1 (%), defined as the elongation (%) at the point where strain hardening occurs in each resin, while conducting a tensile test according to ASTM D638; a step of measuring and calculating, for each of the plurality of polyolefin resins, the Tm-width X2 (°C), defined as the value obtained by dividing the endothermic curve area (melting enthalpy) of the second temperature rise section on the DSC curve by the heat flow at the endothermic peak point, while measuring the melting point by DSC for each of the plurality of polyolefin resins; a step of measuring, for each of the plurality of polyolefin resins, the stretchable temperature range Y (°C), in which a film with a thickness deviation of within 10% over the entire area is formed, while manufacturing a film by stretching the plurality of polyolefin resins; and a step of deriving a stretchable temperature range prediction formula by linear regression of the measured values ​​of NDR X1 (%), Tm-width X2 (°C), and Y (°C). Claim 2 A method for predicting the stretchable temperature of a polyolefin resin according to claim 1, wherein the polyolefin resin is a polyethylene resin selected from the group consisting of copolymers of ethylene and alpha-olefins having 3 or more carbon atoms. Claim 3 In claim 2, the polyethylene resin is 0.91 to 0.94 g / cm³ 3 A method for predicting the stretchable temperature of a polyolefin resin having a density of 0.2 to 4.0 g / 10 min and a melt index (2.16 kg). Claim 4 In claim 2, the polyethylene resin is a method for predicting the stretchable temperature of a polyolefin resin having a number average molecular weight of 20,000 to 50,000, a weight average molecular weight of 80,000 to 130,000, and a molecular weight distribution of 5 or less. Claim 5 In claim 2, the polyethylene resin is a method for predicting the stretchable temperature of a polyolefin resin having an average number of short chain branches (SCB) per 1,000 carbon atoms of 10 to 30. Claim 6 A method for predicting the stretchable temperature of a polyolefin resin according to claim 1, wherein the Tm-width X2(°C) is corrected by the heating rate during DSC analysis to produce the final result. Claim 7 A method for predicting the stretchable temperature of a polyolefin resin according to claim 1, wherein the stretchable temperature prediction formula is in the form of Y(°C) = A* X2(°C)+B* X1(%)+C (where A, B, and C are constants determined by linear regression). Claim 8 A method for predicting the stretchable temperature of a polyolefin resin according to claim 1, further comprising the step of predicting the stretchable temperature range of the polyolefin resin to be evaluated by measuring the NDR X1 (%) and Tm-width X2 (°C) of a polyethylene resin different from the plurality of polyolefin resins based on the stretchable temperature prediction formula. Claim 9 A method for manufacturing a stretched film, comprising: a step of predicting a stretchable temperature range of a target polyolefin resin different from the plurality of polyolefin resins by the method of claim 1; and a step of stretching the target polyolefin resin to form a film within the predicted temperature range. Claim 10 A method for manufacturing a stretched film according to claim 9, wherein the stretching temperature of the step of forming the film is determined by considering the predicted stretchable temperature range and the melting point of the target polyolefin resin. Claim 11 A method for manufacturing a stretched film according to claim 10, wherein the stretching temperature of the step of forming the film is determined within the range of 105 to 135℃.

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