High-temperature-resistant and low-shrinkage PET film and preparation method thereof

Abstract

The application relates to the technical field of PET film preparation, in particular to a high-temperature-resistant and low-shrinkage PET film and a preparation method thereof, wherein the PET film comprises the following components by weight: 80-90 parts of polyethylene terephthalate, 10-15 parts of polyolefin, 6-8 parts of thermoplastic elastomer, 6-20 parts of filler and 1-5 parts of coupling agent. The prepared PET film has excellent high-temperature resistance through the synergistic effect of the raw materials, can not be deformed at 130-150 DEG C, has low shrinkage, and can meet the application requirements of the PET film in the electronic field.

Description

Technical Field

[0001] This invention relates to the field of PET film preparation technology, and in particular to a high-temperature resistant, low-shrinkage PET film and its preparation method. Background Technology

[0002] PET (polyethylene terephthalate) is an important engineering plastic due to its high hardness, high rigidity, good dimensional stability, and excellent mechanical and chemical resistance properties. It is often made into films and widely used in environmental protection, building materials, medical, printing, and packaging fields. However, PET also has drawbacks, such as slow crystallization speed, insufficient strength, and poor high-temperature resistance. After molding, it has a large thermal shrinkage rate at high temperatures, which cannot meet the requirements of high-temperature resistance and low shrinkage in the electronics industry. Films are also prone to deformation or curling at high temperatures, which limits its practical use. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a high-temperature resistant, low-shrinkage PET film and its preparation method. Through the synergistic effect of various raw materials, combined with specific process steps and conditions, the prepared PET film exhibits excellent high-temperature resistance, remaining undeformed at 130-150℃ while possessing a low shrinkage rate, thus meeting the application requirements of PET film in the electronics field.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention provides a high-temperature resistant, low-shrinkage PET film, which, by weight, comprises the following raw materials: 80-90 parts of polyethylene terephthalate, 10-15 parts of polyolefin, 6-8 parts of thermoplastic elastomer, 6-20 parts of filler, and 1-5 parts of coupling agent.

[0005] In some embodiments, the intrinsic viscosity of the polyethylene terephthalate is 0.7-0.9 dl / g.

[0006] Preferably, the intrinsic viscosity of the polyethylene terephthalate is 0.81-0.85 dl / g.

[0007] The present invention does not impose any special restrictions on the source of the polyethylene terephthalate, which can be obtained through commercial purchase, including but not limited to the polyethylene terephthalate purchased from Ningbo Dihong Plastics Co., Ltd., with the grade CZ-318.

[0008] In some embodiments, the thermoplastic elastomer is a hydrogenated styrene-butadiene block copolymer.

[0009] Preferably, the melt flow index of the hydrogenated styrene-butadiene block copolymer at 230°C / 5kg is 4-6 g / 10 min.

[0010] More preferably, the melt flow index of the hydrogenated styrene-butadiene block copolymer at 230°C / 5kg is 5.5g / 10min.

[0011] The present invention does not impose any special restrictions on the source of the hydrogenated styrene-butadiene block copolymer, which can be obtained through commercial purchase, including but not limited to the grade of the hydrogenated styrene-butadiene block copolymer, TSRC 6150.

[0012] In some embodiments, the polyolefin includes random copolymer polypropylene and / or linear low-density polyethylene.

[0013] Preferably, the polyolefin comprises random copolymer polypropylene and linear low-density polyethylene in a weight ratio of 1:1.

[0014] In some embodiments, the melt flow rate of the random copolymer polypropylene is 22-26 g / 10 min, and the test standard is ASTM 1238.

[0015] Preferably, the melt flow rate of the random copolymer polypropylene is 24.2 g / 10 min.

[0016] The present invention does not impose any special restrictions on the source of the random copolymer polypropylene, which can be obtained through commercial purchase, including but not limited to the brand of the random copolymer polypropylene selected from Maoming Petrochemical, with the grade name HT9025NX.

[0017] In some embodiments, the softening point of the linear low-density polyethylene is ≥95°C, preferably 100°C.

[0018] The present invention does not impose any special restrictions on the source of the linear low-density polyethylene, which can be obtained through commercial purchase, including but not limited to the linear low-density polyethylene selected from Dushanzi Petrochemical, with the grade LL0209.

[0019] To improve the high-temperature resistance of the prepared PET film, this application incorporates a hydrogenated styrene-butadiene block copolymer with a specific melt flow rate, achieving positive results. The applicant believes the likely reason lies in the difference in flexibility between the hard polystyrene segments and the soft ethylene-butene segments in the hydrogenated styrene-butadiene block copolymer, which allows it to form a thermoplastic interpenetrating polymer structure with polyethylene terephthalate in the system during melting, further enhancing the high-temperature resistance of the PET film. However, the applicant found that the addition of the hydrogenated styrene-butadiene block copolymer leads to a decrease in the fluidity of the melt system, thus affecting the quality of the prepared PET film. After extensive research, the applicant discovered that adding specific polyolefins to the system, especially random copolymer polypropylene and linear low-density polyethylene in a 1:1 weight ratio, can impart good melt fluidity, which is beneficial to improving the molding quality of the PET film. Moreover, the addition of random copolymer polypropylene can also synergistically enhance heat resistance. In addition, the applicant unexpectedly discovered that the added linear low-density polyethylene can also increase the crystallization rate of the melt, which is beneficial to obtaining a low-shrinkage PET film.

[0020] In some embodiments, the filler is a combination of silica, montmorillonite and wollastonite fibers in a weight ratio of (0.5-1):1:(0.75-1.1).

[0021] Preferably, the filler is a combination of silica, montmorillonite and wollastonite fibers in a weight ratio of 0.75:1:0.9.

[0022] In some embodiments, the silica is spherical silica with an average particle size of 2-50 μm.

[0023] The present invention does not impose any special restrictions on the source of the silicon dioxide, which can be obtained through commercial purchase, including but not limited to the silicon dioxide purchased from Lianyungang Ruichuang New Materials Technology Co., Ltd.

[0024] In some embodiments, the montmorillonite has a particle size of 1250 mesh.

[0025] The present invention does not impose any special restrictions on the source of the montmorillonite, which can be obtained through commercial purchase, including but not limited to the montmorillonite purchased from Lingshou County Runhao Mineral Products Processing Plant.

[0026] In some embodiments, the wollastonite fibers have a fiber diameter ≤20μm and an aspect ratio of (8-15):1.

[0027] Preferably, the wollastonite fiber has a fiber diameter ≤18μm and an aspect ratio of (10-12):1.

[0028] The present invention does not impose any special restrictions on the source of the wollastonite fiber, which can be obtained through commercial purchase, including but not limited to the wollastonite fiber purchased from Jiangxi Huajietai Mineral Fiber Technology Co., Ltd., model BA800.

[0029] In some embodiments, the raw material also includes 5-10 parts by weight of a toughening agent.

[0030] In some embodiments, the toughening agent is at least one of maleic anhydride-grafted polyethylene, maleic anhydride-grafted polypropylene, and maleic anhydride-grafted polyolefin elastomer.

[0031] Preferably, the toughening agent is maleic anhydride-grafted polypropylene.

[0032] Those skilled in the art typically add fillers during the preparation of PET films to impart excellent mechanical properties. However, the addition of fillers increases the film's orientation, which in turn leads to a higher shrinkage rate, especially at high temperatures. Through extensive research, the applicant discovered that by specifically controlling the type and proportion of fillers—specifically, a combination of silica, montmorillonite, and wollastonite fibers in a weight ratio of (0.5-1):1:(0.75-1.1)—and combining this with a special toughening agent, not only can the PET film be endowed with excellent mechanical properties, but it also exhibits low shrinkage at high temperatures. This is likely because, with the synergistic effect of the toughening agent, the fillers can be uniformly dispersed in the system, exhibiting good compatibility with PET and imparting excellent impact toughness. Simultaneously, silica, montmorillonite, and wollastonite fibers act as active sites for physical nucleation within the system, inducing and promoting crystallization, accelerating the crystallization rate of PET, thereby reducing the shrinkage rate of the prepared PET film and resulting in excellent dimensional stability. In addition, the spherical silica used in this application can increase the micro-roughness of the film surface, allowing a small amount of air to enter the PET film during the winding process, thus preventing the films from sticking together.

[0033] In some embodiments, the coupling agent is one or more of vinyltriethoxysilane, vinyltriperoxide tert-butylsilane, isobutyltriethoxysilane, chromium chloride methacrylate, butadienetriethoxysilane, and tetrabutyl titanate.

[0034] Preferably, the coupling agent is vinyltriethoxysilane.

[0035] Another aspect of the present invention provides a method for preparing a high-temperature resistant, low-shrinkage PET film, comprising the following steps: S1. Weigh each raw material according to the proportion, mix the filler and coupling agent, and then mix them with other raw materials and add them to the granulator for granulation to obtain substance A; S2. Substance A is subjected to pre-crystallization and drying to obtain substance B; S3. The substance B is melted and plasticized using a twin-screw extruder to obtain a mixture; S4. The mixture obtained in S3 is subjected to a casting process to obtain pretreated sheets; S5. The pretreated sheet is stretched longitudinally and transversely in sequence to obtain the PET film.

[0036] In some embodiments, step S1 involves mixing the filler and coupling agent at a stirring speed of 2000-3000 r / min for a stirring time of 10-30 min.

[0037] Preferably, in step S1, the stirring speed for mixing the filler and coupling agent is 2500 r / min, and the stirring time is 20 min.

[0038] In some embodiments, the granulation temperature in step S1 is 90-100°C, the pre-crystallization temperature in step S2 is 153-168°C, and the melting temperature of the twin-screw extruder in step S3 is 280-300°C.

[0039] In some embodiments, the longitudinal stretching temperature is 105-115°C and the longitudinal stretching ratio is 3.0-4.0, while the transverse stretching temperature is 110-125°C and the transverse stretching ratio is 4.0-5.0.

[0040] In some embodiments, the temperature of the casting process is 25-35°C, preferably 30°C.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention achieves excellent high temperature resistance of the PET film prepared by the synergistic effect between the raw materials and the specific process steps and conditions. It can remain undeformed at 130-150℃ and has a low shrinkage rate, which can meet the application requirements of PET film in the electronic field. (2) By adding hydrogenated styrene-butadiene block copolymer with a specific melt flow rate, the present invention can form a thermoplastic interpenetrating polymer structure with polyethylene terephthalate in the system during the melting process, which further improves the high temperature resistance of PET film. At the same time, the addition of random copolymer polypropylene and linear low-density polyethylene in a weight ratio of 1:1 can give the melt good fluidity, which is beneficial to improving the molding quality of PET film. It can also synergistically enhance heat resistance and is beneficial to obtaining low shrinkage PET film. (3) The present invention makes specific adjustments to the type and proportion of fillers, making the filler a combination of silica, montmorillonite and wollastonite fibers with a weight ratio of (0.5-1):1:(0.75-1.1), and combining it with a special toughening agent, which not only gives the PET film excellent mechanical properties, but also has low shrinkage characteristics at high temperature. Detailed Implementation

[0042] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0043] Example 1 A high-temperature resistant, low-shrinkage PET film, comprising the following raw materials by weight: 85 parts polyethylene terephthalate, 12 parts polyolefin, 7 parts hydrogenated styrene-butadiene block copolymer, 13 parts filler, 3 parts coupling agent, and 8 parts toughening agent.

[0044] The intrinsic viscosity of polyethylene terephthalate is 0.81-0.85 dl / g. It was purchased from Ningbo Dihong Plastics Co., Ltd., and its grade is CZ-318.

[0045] The hydrogenated styrene-butadiene block copolymer is designated as TSRC 6150, and its melt flow index is 5.5 g / 10 min at 230℃ / 5 kg.

[0046] Polyolefins include random copolymer polypropylene and linear low-density polyethylene in a weight ratio of 1:1.

[0047] The random copolymer polypropylene is from Maoming Petrochemical, grade HT9025NX, and the melt flow rate obtained according to the test standard ASTM1238 is 24.2 g / 10 min; the linear low-density polyethylene is from Dushanzi Petrochemical, grade LL0209, and the softening point is 100℃.

[0048] The filler is a combination of silica, montmorillonite and wollastonite fibers in a weight ratio of 0.75:1:0.9.

[0049] The silica was spherical with an average particle size of 2-50 μm, purchased from Lianyungang Ruichuang New Material Technology Co., Ltd.; the montmorillonite had a particle size of 1250 mesh, purchased from Lingshou County Runhao Mineral Products Processing Plant; the wollastonite fiber was purchased from Jiangxi Huajietai Mineral Fiber Technology Co., Ltd., model BA800, with a fiber diameter ≤18 μm and an aspect ratio of (10-12):1.

[0050] The toughening agent is maleic anhydride-grafted polypropylene, brand name Exxon PO 11020, with a melt flow rate of 110 g / 10 min at 190℃ / 1.2 kg.

[0051] The coupling agent is vinyltriethoxysilane.

[0052] The method for preparing the high-temperature resistant, low-shrinkage PET film in this embodiment includes the following steps: S1. Weigh each raw material according to the proportion, stir the filler and coupling agent at 2500 r / min for 20 min, then mix with other raw materials and add to the granulator for granulation at 95℃ to obtain substance A. S2. Substance A is pre-crystallized and dried at 162°C to obtain substance B; S3. The substance B is melted and plasticized at 290°C for 3 hours using a twin-screw extruder to obtain a mixture; S4. The mixture obtained in S3 is subjected to a casting process at 30°C to obtain a pretreated sheet. S5. The pretreated sheet is stretched longitudinally and transversely in sequence to obtain the PET film.

[0053] The longitudinal stretching temperature is 110℃, and the longitudinal stretching ratio is 3.6. The transverse stretching temperature is 120℃, and the transverse stretching ratio is 4.5.

[0054] Example 2 A high-temperature resistant, low-shrinkage PET film, comprising the following raw materials by weight: 80 parts polyethylene terephthalate, 10 parts polyolefin, 6 parts hydrogenated styrene-butadiene block copolymer, 6 parts filler, 1 part coupling agent, and 5 parts toughening agent.

[0055] The intrinsic viscosity of polyethylene terephthalate is 0.81-0.85 dl / g. It was purchased from Ningbo Dihong Plastics Co., Ltd., and its grade is CZ-318.

[0056] The hydrogenated styrene-butadiene block copolymer is designated as TSRC 6150, and its melt flow index is 5.5 g / 10 min at 230℃ / 5 kg.

[0057] Polyolefins include random copolymer polypropylene and linear low-density polyethylene in a weight ratio of 1:1.

[0058] The random copolymer polypropylene is from Maoming Petrochemical, grade HT9025NX, and the melt flow rate obtained according to the test standard ASTM1238 is 24.2 g / 10 min; the linear low-density polyethylene is from Dushanzi Petrochemical, grade LL0209, and the softening point is 100℃.

[0059] The filler is a combination of silica, montmorillonite and wollastonite fibers in a weight ratio of 0.5:1:0.75.

[0060] The silica was spherical with an average particle size of 2-50 μm, purchased from Lianyungang Ruichuang New Material Technology Co., Ltd.; the montmorillonite had a particle size of 1250 mesh, purchased from Lingshou County Runhao Mineral Products Processing Plant; the wollastonite fiber was purchased from Jiangxi Huajietai Mineral Fiber Technology Co., Ltd., model BA800, with a fiber diameter ≤18 μm and an aspect ratio of (10-12):1.

[0061] The toughening agent is maleic anhydride-grafted polypropylene, brand name Exxon PO 11020, with a melt flow rate of 110 g / 10 min at 190℃ / 1.2 kg.

[0062] The coupling agent is vinyltriethoxysilane.

[0063] The method for preparing the high-temperature resistant, low-shrinkage PET film in this embodiment includes the following steps: S1. Weigh each raw material according to the proportion, stir the filler and coupling agent at 2000 r / min for 30 min, then mix with other raw materials and add to the granulator for granulation at 90℃ to obtain substance A. S2. Substance A is pre-crystallized and dried at 153°C to obtain substance B; S3. The substance B is melted and plasticized at 280°C for 4 hours using a twin-screw extruder to obtain a mixture; S4. The mixture obtained in S3 is subjected to a casting process at 25°C to obtain a pretreated sheet. S5. The pretreated sheet is stretched longitudinally and transversely in sequence to obtain the PET film.

[0064] The longitudinal stretching temperature is 105℃, and the longitudinal stretching ratio is 3.0. The transverse stretching temperature is 110℃, and the transverse stretching ratio is 5.0.

[0065] Example 3 A high-temperature resistant, low-shrinkage PET film, comprising the following raw materials by weight: 90 parts polyethylene terephthalate, 15 parts polyolefin, 8 parts hydrogenated styrene-butadiene block copolymer, 20 parts filler, 6 parts coupling agent, and 10 parts toughening agent.

[0066] The intrinsic viscosity of polyethylene terephthalate is 0.81-0.85 dl / g. It was purchased from Ningbo Dihong Plastics Co., Ltd., and its grade is CZ-318.

[0067] The hydrogenated styrene-butadiene block copolymer is designated as TSRC 6150, and its melt flow index is 5.5 g / 10 min at 230℃ / 5 kg.

[0068] Polyolefins include random copolymer polypropylene and linear low-density polyethylene in a weight ratio of 1:1.

[0069] The random copolymer polypropylene is from Maoming Petrochemical, grade HT9025NX, and the melt flow rate obtained according to the test standard ASTM1238 is 24.2 g / 10 min; the linear low-density polyethylene is from Dushanzi Petrochemical, grade LL0209, and the softening point is 100℃.

[0070] The filler is a combination of silica, montmorillonite and wollastonite fibers in a weight ratio of 1:1:1.1.

[0071] The silica was spherical with an average particle size of 2-50 μm, purchased from Lianyungang Ruichuang New Material Technology Co., Ltd.; the montmorillonite had a particle size of 1250 mesh, purchased from Lingshou County Runhao Mineral Products Processing Plant; the wollastonite fiber was purchased from Jiangxi Huajietai Mineral Fiber Technology Co., Ltd., model BA800, with a fiber diameter ≤18 μm and an aspect ratio of (10-12):1.

[0072] The toughening agent is maleic anhydride-grafted polypropylene, brand name Exxon PO 11020, with a melt flow rate of 110 g / 10 min at 190℃ / 1.2 kg.

[0073] The coupling agent is vinyltriethoxysilane.

[0074] The method for preparing the high-temperature resistant, low-shrinkage PET film in this embodiment includes the following steps: S1. Weigh each raw material according to the proportion, stir the filler and coupling agent at 3000 r / min for 10 min, then mix with other raw materials and add to the granulator for granulation at 100℃ to obtain substance A. S2. Substance A is pre-crystallized and dried at 168°C to obtain substance B; S3. The substance B is melted and plasticized at 300°C for 2 hours using a twin-screw extruder to obtain a mixture; S4. The mixture obtained in S3 is subjected to a casting process at 35°C to obtain a pretreated sheet. S5. The pretreated sheet is stretched longitudinally and transversely in sequence to obtain the PET film.

[0075] The longitudinal stretching temperature is 115℃, and the longitudinal stretching ratio is 3.0. The transverse stretching temperature is 125℃, and the transverse stretching ratio is 4.0.

[0076] Example 4 This embodiment provides a high-temperature resistant, low-shrinkage PET film and its preparation method. The specific implementation method is the same as that in Embodiment 1, except that hydrogenated styrene-butadiene block copolymer is not added.

[0077] Example 5 This embodiment provides a high-temperature resistant, low-shrinkage PET film and its preparation method. The specific implementation method is the same as that in Embodiment 1, except that the polyolefin does not include random copolymer polypropylene.

[0078] Example 6 This embodiment provides a high-temperature resistant, low-shrinkage PET film and its preparation method. The specific implementation method is the same as that in Embodiment 1, except that no toughening agent is added.

[0079] Example 7 This embodiment provides a high-temperature resistant, low-shrinkage PET film and its preparation method. The specific implementation method is the same as that in Embodiment 1, except that the filler does not include montmorillonite.

[0080] Example 8 This embodiment provides a high-temperature resistant, low-shrinkage PET film and its preparation method. The specific implementation method is the same as that in Embodiment 1, except that the filler does not include wollastonite fibers.

[0081] Performance testing 1. Thermal shrinkage rate The PET films obtained in Examples 1-8 were subjected to heat shrinkage rate determination at 150°C for 1 hour according to GB / T 34848-2017 standard, and the test results are recorded in Table 1.

[0082] 2. Tensile strength The PET films obtained in Examples 1-9 were tested for tensile strength according to GB / T13022-1991 standard, and the test results are recorded in Table 1.

[0083] Table 1 As shown in Table 1, the PET films prepared in Examples 1-3 exhibited low thermal shrinkage rates at 150°C for 1 hour, indicating excellent high-temperature resistance and dimensional stability, which meet the application requirements in the electronics field. In Example 4, the absence of hydrogenated styrene-butadiene block copolymer led to increased shrinkage and a significant decrease in tensile strength. In Example 5, the polyolefin did not include random copolymer polypropylene, resulting in a significant increase in shrinkage and a slight decrease in tensile strength. In Example 6, the lack of toughening agent resulted in increased thermal shrinkage and a significant decrease in tensile strength. Examples 7 and 8, by changing the type of filler, showed a certain degree of increase in shrinkage and a decrease in tensile strength.

[0084] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high-temperature resistant, low-shrinkage PET film, characterized in that, The raw materials, by weight, include the following components: 80-90 parts of polyethylene terephthalate, 10-15 parts of polyolefin, 6-8 parts of thermoplastic elastomer, 6-20 parts of filler, 1-5 parts of coupling agent, and 5-10 parts of toughening agent; wherein the thermoplastic elastomer is a hydrogenated styrene-butadiene block copolymer. The intrinsic viscosity of the polyethylene terephthalate is 0.7-0.9 dl / g; The melt flow index of the hydrogenated styrene-butadiene block copolymer at 230℃ / 5kg is 4-6g / 10min; The filler is a combination of silica, montmorillonite, and wollastonite fibers in a weight ratio of (0.5-1):1:(0.75-1.1). The silica is spherical silica with an average particle size of 2-50 μm; the montmorillonite has a particle size of 1250 mesh; the wollastonite fiber has a fiber diameter of ≤18 μm and an aspect ratio of (10-12):

1. The polyolefin comprises random copolymer polypropylene and linear polyethylene in a weight ratio of 1:1; The melt flow rate of the random copolymer polypropylene is 22-26 g / 10 min; The softening point of the linear polyethylene is ≥95℃; The toughening agent is maleic anhydride-grafted polypropylene. The filler is first mixed with a coupling agent, then mixed with other raw materials and added to a granulator for granulation to obtain substance A. Substance B is then pre-crystallized and dried.

2. The high-temperature resistant, low-shrinkage PET film according to claim 1, characterized in that, The coupling agent is one or more of vinyltriethoxysilane, vinyltriperoxide tert-butylsilane, isobutyltriethoxysilane, chromium chloride methacrylate, butadienetriethoxysilane, and tetrabutyl titanate.

3. A method for preparing a high-temperature resistant, low-shrinkage PET film according to any one of claims 1-2, characterized in that, Includes the following steps: S1. Weigh each raw material according to the proportion, mix the filler and coupling agent, and then mix them with other raw materials and add them to the granulator for granulation to obtain substance A; S2. Substance A is subjected to pre-crystallization and drying to obtain substance B; S3. The substance B is melted and plasticized using a twin-screw extruder to obtain a mixture; S4. The mixture obtained in S3 is subjected to a casting process to obtain pretreated sheets; S5. The pretreated sheet is stretched longitudinally and transversely in sequence to obtain the PET film.

4. The method for preparing high-temperature resistant, low-shrinkage PET film according to claim 3, characterized in that, The granulation temperature in step S1 is 90-100℃, the pre-crystallization temperature in step S2 is 153-168℃, and the melting temperature of the twin-screw extruder in step S3 is 280-300℃.

5. The method for preparing high-temperature resistant, low-shrinkage PET film according to claim 3, characterized in that, The longitudinal stretching temperature is 105-115℃, and the longitudinal stretching ratio is 3.0-4.

0. The transverse stretching temperature is 110-125℃, and the transverse stretching ratio is 4.0-5.0.

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