Polyethylene having excellent heat resistance

Abstract

The polyethylene of the present invention is characterized in that it has an oxidation induction time of 10 minutes or more at a temperature of 210 to 230°C as measured by a rotational rheometer, and there is a peak corresponding to polypropylene when measured by NMR.

Description

Technical Field

[0001] This invention relates to polyethylene with excellent heat resistance. More specifically, this invention relates to polyethylene with excellent heat resistance and adhesive properties. Background Technology

[0002] Due to the process characteristics, polyethylene resins used for spinning need to have a high melt index of 15 g / 10 min or higher (15 MI or higher). To improve the melt index of polyethylene, a method of relatively increasing the proportion of low molecular weight components has been considered. Polyethylene with a high proportion of low molecular weight components has advantages in extrusion processability (extrusion loading) and post-processing (web formation step).

[0003] However, the melt spinning process is carried out at high temperatures of 200°C or higher. At this temperature, in the case of low molecular weight polyethylene, the heat resistance is low, so the resin may be oxidized to produce carbides or gels, which can lead to monofilament breakage (fiber breakage).

[0004] Therefore, there is a need to develop a polyethylene resin with excellent melt spinning processability and heat resistance.

[0005] As a related prior art, there is Korean Patent No. KR10-2022-0076357. Summary of the Invention

[0006] [Technical Issues] The purpose of this invention is to provide polyethylene with excellent melt spinning processability and heat resistance, and a method for preparing the same.

[0007] Another object of the present invention is to provide polyethylene with excellent adhesion and tensile strength, and a method for preparing the same.

[0008] Another object of the present invention is to provide a polyethylene wherein gel formation during melt spinning is significantly reduced, and a method thereof for preparation thereof.

[0009] Another object of the present invention is to provide a fiber and nonwoven fabric formed by melt spinning polyethylene.

[0010] Another object of the present invention is to provide a method for preventing yarn breakage during melt spinning of polyethylene.

[0011] The above and other objectives of the present invention can be achieved by the invention described below.

[0012] [Technical Solution] 1. One aspect of the present invention relates to polyethylene, wherein the polyethylene is characterized in that the oxidation induction time of the polyethylene at a temperature of about 210 to about 230°C, as measured by rotational rheometer, is about 10 minutes or longer, for example about 10 to 20 minutes, specifically about 10 to 15 minutes, and a peak corresponding to polypropylene is present in NMR measurements.

[0013] 2. In embodiment 1, the polyethylene may have a weight-average molecular weight of about 40,000 g / mol to about 60,000 g / mol, for example about 41,000 to about 45,000 g / mol, about 45,000 to about 49,000 g / mol, about 49,000 to about 53,000 g / mol or about 53,000 to about 59,000 g / mol, and may have a polydispersity index (PDI) of about 7 or higher.

[0014] 3. In embodiments 1 and 2, the polyethylene may contain more than about 0 and less than or equal to about 5 wt%, for example about 1 to about 3 wt%, preferably about 1.1 to about 2 wt% of polypropylene.

[0015] 4. In embodiments 1 to 3, polyethylene per 1m 2 It can have fewer than about 150 gels, each with a maximum diameter of about 400 μm or larger, for example, about 1 to about 40, about 40 to about 80, or about 80 to about 140.

[0016] 5. In embodiments 1 to 4, the melt index (ASTM D1238, 190°C, 2.16 kg) of polyethylene can be about 15 to about 40 g / 10 min, for example about 15.5 to about 20 g / 10 min, about 20 to about 25 g / 10 min, about 25 to about 30 g / 10 min, or about 30 to about 38.5 g / 10 min.

[0017] 6. In embodiments 1 to 5, the melt flow ratio (MFR, 190°C, MI) of polyethylene is... 21.6 / MI 2.16 The value can be approximately 20 to approximately 30, for example, approximately 20.5 to approximately 23.5, approximately 23.5 to approximately 26.5, or approximately 26.5 to approximately 29.5.

[0018] 7. In embodiments 1 to 6, the density of polyethylene can be from about 0.948 to about 0.965 g / cm³. 3 For example, approximately 0.950 to approximately 0.953 g / cm³ 3 Approximately 0.953 to approximately 0.956 g / cm³ 3 Approximately 0.956 to approximately 0.960 g / cm³ 3 Or approximately 0.960 to approximately 0.963 g / cm³ 3 .

[0019] 8. In embodiments 1 to 7, the melt spinning index (MSI) of polyethylene according to the following formula 1 can be from about 30 to about 200, for example from about 32 to about 74, from about 74 to about 116, from about 116 to about 158, or from about 158 ​​to about 198: [Formula 1]

[0020] (In Formula 1, MI is the melt index of polyethylene (ASTM D1238, 190℃, 2.16kg) (unit: g / 10min), OIT is the oxidation induction time at 210 to 230℃ measured by rotational rheometer (unit: min), P is the polypropylene content (wt%), and G is the molecular weight per 1000 ml / kg.) 2 The number of gels with a diameter of 400 μm or larger. 9. In embodiments 1 to 8, polyethylene per 1m 2 It can have fewer than about 150 gels of about 400 μm or larger, for example, about 1 to about 40, about 40 to about 80, or about 80 to about 140.

[0021] 10. In embodiments 1 to 9, the tensile strength of polyethylene, measured according to ASTM D638, can be approximately 270 kg / cm². 2 Or higher, for example, about 272 to about 278 kg / cm³ 2 Approximately 278 to approximately 284 kg / cm³ 2 Approximately 284 to approximately 290 kg / cm³ 2 Or approximately 290 to approximately 298 kg / cm³ 2 .

[0022] 11. In embodiments 1 to 10, polyethylene is characterized in that it is used for melt spinning.

[0023] 12. Another aspect of the invention relates to polyethylene fibers. The polyethylene fibers are formed by melt spinning the polyethylene of any one of embodiments 1 to 11.

[0024] 13. In embodiment 12, the diameter of the polyethylene fiber can be greater than about 0 and less than about 100 μm, for example about 1 to about 25 μm, about 25 to about 50 μm, about 50 to about 75 μm or about 75 to about 99 μm.

[0025] 14. Another aspect of the invention relates to a nonwoven fabric. The nonwoven fabric may be formed from the polyethylene fibers of Example 12.

[0026] 15. Another aspect of the invention relates to a method for preparing polyethylene, the method comprising polymerizing ethylene in the presence of a Ziegler-Natta catalyst.

[0027] 16. In embodiment 15, the method is characterized in that polymerization is carried out while controlling the particle size of the Ziegler-Natta catalyst to be less than about 60 μm, for example, about 1 to about 15 μm, about 15 to about 30 μm, or about 30 to about 45 μm or about 45 to about 59 μm.

[0028] 17. In embodiments 15 and 16, the method may include polymerization by adding an amount of propylene monomer based on a total monomer content greater than about 0 and less than or equal to about 5 wt%, for example about 1 to about 3 wt%, preferably about 1.1 to about 2 wt%.

[0029] 18. Another aspect of the invention relates to a method for preventing yarn breakage during melt spinning of polyethylene, characterized by using polyethylene polymerized by controlling the particle size of a Ziegler-Natta catalyst.

[0030] 19. In embodiment 18, the oxidation induction time of polyethylene at a temperature of about 210 to about 230°C, as measured by a rotational rheometer, can be 10 minutes or longer, for example, about 10 to 20 minutes, specifically about 10 to about 15 minutes.

[0031] 20. In embodiments 18 to 19, the polyethylene may have a weight-average molecular weight of about 40,000 g / mol to about 60,000 g / mol, for example about 41,000 to about 45,000 g / mol, about 45,000 to about 49,000 g / mol, about 49,000 to about 53,000 g / mol or about 53,000 to about 59,000 g / mol, and may have a polydispersity index (PDI) of 7 or higher.

[0032] [Beneficial Effects] The present invention has the following effects: providing polyethylene with excellent melt spinning processability, heat resistance, adhesion and tensile strength, and significantly reduced gel formation during melt spinning, a method for preparing the polyethylene, fibers and nonwoven fabrics formed by melt spinning polyethylene, and a method for preventing yarn breakage during melt spinning of polyethylene. Attached Figure Description

[0033] Figure 1 These are surface photographs of the polyethylene nonwoven fabrics prepared in Examples 1 to 3 and Comparative Examples 1 to 2.

[0034] Figure 2The gel permeation chromatography (GPC) measurements of the polyethylene prepared in Examples 1 to 3 and Comparative Examples 1 to 2 are shown.

[0035] Figure 3 The results of oxidation induction time measurements for polyethylene prepared in Examples 1 to 3 and Comparative Examples 1 to 2 are shown.

[0036] Figure 4 The NMR measurement results of Example 1 are shown.

[0037] Figure 5 The NMR measurement results for Comparative Example 1 are shown. Detailed Implementation

[0038] The invention will be described in more detail below. As used in this specification, when words such as "comprising," "having," or "compose of" are used, other parts may be added unless "only" is used. When a component is expressed in a singular form, it includes the plural unless otherwise specified.

[0039] When interpreting components, they are interpreted as including a range of error, even if not explicitly stated separately.

[0040] polyethylene One aspect of the invention relates to polyethylene. The oxidation induction time of polyethylene at a temperature of about 210 to about 230°C, as measured by a rotational rheometer, can be about 10 minutes or longer, for example, about 10 to 20 minutes, specifically about 10 to 15 minutes. Within the above range, polyethylene exhibits excellent heat resistance and processability, and yarn breakage does not occur during melt spinning.

[0041] During NMR measurements, polyethylene can exhibit peaks corresponding to those of polypropylene. In a specific embodiment, the polyethylene may contain greater than about 0 and less than or equal to about 5 wt%, for example, about 1 to about 3 wt%, preferably about 1.1 to about 2 wt% of polypropylene. Within these ranges, excellent heat resistance and processability can be achieved.

[0042] In specific embodiments, polyethylene can have a weight-average molecular weight of about 40,000 g / mol to about 60,000 g / mol, specifically about 42,000 to about 56,000 g / mol, for example about 41,000 to about 45,000 g / mol, about 45,000 to about 49,000 g / mol, about 49,000 to about 53,000 g / mol, or about 53,000 to about 59,000 g / mol. Within the above ranges, a balance can be achieved between heat resistance and melt spinnability.

[0043] In a specific implementation, polyethylene per 1m 2It can have fewer than about 150 gels, each with a maximum diameter of about 400 μm or greater, specifically about 1 to about 140, preferably about 1 to about 100, for example about 1 to 40, about 40 to about 80, or about 80 to about 140. Furthermore, polyethylene can have per 1m 2 Fewer than approximately 1600, for example, approximately 1 to approximately 1000, specifically approximately 1 to 400, approximately 400 to approximately 800, approximately 800 to approximately 1200, or approximately 1200 to approximately 1600 total gels. Within the above range, yarn breakage will not occur during melt spinning.

[0044] Polyethylene can have a melt index (ASTM D1238, 190°C, 2.16 kg) of about 15 to about 40 g / 10 min, preferably about 20 to about 38 g / 10 min, for example, about 15.5 to about 20 g / 10 min, about 20 to about 25 g / 10 min, about 25 to about 30 g / 10 min, or about 30 to about 38.5 g / 10 min. Within the above range, extrusion processability is excellent, and network formation is advantageous.

[0045] In a specific embodiment, polyethylene may have a melt flow ratio (MFR, 190°C, MI) of about 20 to about 30, for example about 22 to about 25. 21.6 / MI 2.16 In a specific embodiment, the melt flow ratio (MFR, 190°C, MI) is... 21.6 / MI 2.16 The value can be from about 20.5 to about 29.5, for example, from about 20.5 to about 23.5, from about 23.5 to about 26.5, or from about 26.5 to about 29.5. Within the above range, excellent processability is obtained.

[0046] In a specific embodiment, polyethylene may have a content of about 0.948 to about 0.965 g / cm³. 3 Preferably, it is about 0.950 to about 0.960 g / cm³. 3 The density. In a specific embodiment, the density can be from about 0.950 to about 0.963 g / cm³. 3 For example, approximately 0.950 to approximately 0.953 g / cm³ 3 Approximately 0.953 to approximately 0.956 g / cm³ 3 Approximately 0.956 to approximately 0.960 g / cm³ 3 Or approximately 0.960 to approximately 0.963 g / cm³ 3 .

[0047] Furthermore, the melt spinning index (MSI) according to Formula 1 below can be from about 30 to about 200, preferably from about 35 to about 150. In a specific embodiment, the melt spinning index (MSI) can be from about 32 to about 198, for example, from about 32 to about 74, from about 74 to about 116, from about 116 to about 158, or from about 158 ​​to about 198. [Formula 1]

[0048] (In Formula 1, MI is the melt index of polyethylene (ASTM D1238, 190°C, 2.16 kg) (unit: g / 10 min), OIT is the oxidation induction time at a temperature of 210 to 230°C as measured by rotational rheometer (unit: min), P is the polypropylene content (wt%), and G is 1 m 2 The number of gels with a diameter of 400 μm or larger. In addition, polyethylene can have a strength of approximately 270 kg / cm³. 2 Or higher, for example, about 270 to about 300 kg / cm³ 2 The tensile strength is measured according to ASTM D638. In a specific embodiment, the tensile strength can be from about 272 to about 298 kg / cm². 2 For example, approximately 272 to approximately 278 kg / cm³ 2 Approximately 278 to approximately 284 kg / cm² 2 Approximately 284 to approximately 290 kg / cm³ 2 Or approximately 290 to approximately 298 kg / cm² 2 .

[0049] The polyethylene according to the above embodiments can be prepared by the following preparation method.

[0050] Methods for preparing polyethylene Polyethylene can be prepared by polymerizing ethylene in the presence of a Ziegler-Natta catalyst.

[0051] In one embodiment, the Ziegler-Natta catalyst comprises: (i) a Ziegler-Natta pre-catalyst for olefin polymerization, comprising a titanium compound represented by Chemical Formula 1, a magnesium compound represented by Chemical Formula 2, and an internal electron donor; (ii) an organoaluminum compound represented by Chemical Formula 7; and (iii) an external electron donor represented by Chemical Formula 3, wherein the internal electron donor comprises a first internal electron donor represented by Chemical Formula 4; a second internal electron donor represented by Chemical Formula 5; and a third internal electron donor represented by Chemical Formula 6, and the molar ratio of the external electron donor to the mixture is about 115 to about 130. In a specific embodiment, the molar ratio may be about 117 to about 128, for example, about 117 to about 121, about 121 to about 125, or about 125 to about 128. [Chemical Formula 1] TiX n (OR 1 ) 4-n (In chemical formula 1, R 1 Choose either freely substituted or unsubstituted C1-C. 20 Alkyl, substituted or unsubstituted C3-C 20 Cycloalkyl and substituted or unsubstituted C3-C 20 One of the groups composed of aryl groups. X is a halogen atom. n is an integer between 0 and 4, and In the substituted or unsubstituted group, the substituent is independently at least one selected from the group consisting of halogen, cyano, nitro, and C1-C8 alkyl. [Chemical Formula 2] Mg(OR 2 ) k X 2-k (In chemical formula 2, R 2 Choose either freely substituted or unsubstituted C1-C. 20 Alkyl, substituted or unsubstituted C3-C 20 Cycloalkyl and substituted or unsubstituted C3-C 20 One of the groups composed of aryl groups. X is a halogen atom. k is an integer between 0 and 2, and In the substituted or unsubstituted group, the substituent is independently at least one selected from the group consisting of halogen, cyano, nitro, and C1-C8 alkyl. [Chemical Formula 3]

[0052] (In chemical formula 3, L1 and L2 are independently substituted or unsubstituted C1-C. 20 Alkyl group, and in substituted or unsubstituted groups, the substituent is independently at least one selected from the group consisting of halogen, cyano, nitro and C1-C8 alkyl. L3 and L4 are each independently selected from either substituted or unsubstituted C1-C. 20 Alkyl and substituted or unsubstituted C3-C 20 One of the groups consisting of cycloalkyl groups, and In the substituted or unsubstituted group, the substituent is independently at least one selected from the group consisting of halogen, cyano, nitro, and C1-C8 alkyl. [Chemical Formula 4]

[0053] (In chemical formula 4, R 3 Choose either freely substituted or unsubstituted C1-C. 20 Alkyl, substituted or unsubstituted C3-C 20 Cycloalkyl and substituted or unsubstituted C3-C 20 It is one of the groups consisting of aryl groups, and in the substituted or unsubstituted groups, the substituent is independently selected from at least one of the groups consisting of halogen, cyano, nitro, and C1-C8 alkyl. R 4 and R 5 Each is an independent branch C1-C 20 Alkyl, and m is an integer between 0 and 4. [Chemical Formula 5]

[0054] (In chemical formula 5, R 6 Independently, C1-C is either freely substituted or unsubstituted. 20 Alkyl, substituted or unsubstituted C3-C 20 Cycloalkyl and substituted or unsubstituted C3-C 20 It is one of the groups consisting of aryl groups, and in the substituted or unsubstituted groups, the substituent is independently selected from at least one of the groups consisting of halogen, cyano, nitro, and C1-C8 alkyl. R 7 It is a straight-chain C1-C 20 alkyl, R 8 It is a branch C1-C 20 Alkyl, and n is an integer between 0 and 4. [Chemical Formula 6]

[0055] (In chemical formula 6, R 9 Each can be independently selected as either substituted or unsubstituted C1-C. 20 Alkyl, substituted or unsubstituted C3-C 20 Cycloalkyl and substituted or unsubstituted C3-C 20 It is one of the groups consisting of aryl groups, and in the substituted or unsubstituted groups, the substituent is independently selected from at least one of the groups consisting of halogen, cyano, nitro, and C1-C8 alkyl. R 10 and R 11 Each is an independent linear C1-C chain. 20 alkyl (p is 0, indicating an integer of 4.) [Chemical Formula 7] Al(R 13 ) p X 3-p (In chemical formula 7, R 13 It is selected from hydrogen atoms, substituted or unsubstituted C1-C. 20 Alkyl, substituted or unsubstituted C3-C 20 Cycloalkyl and substituted or unsubstituted C3-C 20 One of the groups composed of aryl groups. X is a halogen atom. p is an integer between 0 and 3, and In the substituted or unsubstituted group, the substituent is independently at least one selected from the group consisting of halogen, cyano, nitro, and C1-C8 alkyl. According to one embodiment, the catalyst may contain an external electron donor represented by chemical formula 3, namely a single first external electron donor or a single second external electron donor.

[0056] According to one embodiment, the catalyst may be a mixture comprising two external electron donors represented by chemical formula 3. In one embodiment, the catalyst may be a mixture of a first external electron donor and a second external electron donor. For example, based on 10 moles of the mixture, the first external electron donor: second external electron donor may be contained in a molar ratio of about 3:7 to about 7:3, about 4:6 to about 6:4, or about 5:5.

[0057] In one implementation, L1 and L2 can each be independently substituted or unsubstituted C1-C. 10Alkyl, such as substituted or unsubstituted C1-C5 alkyl.

[0058] In one embodiment, the first external electron donor can be represented by the following formula 3-1, and the second external electron donor can be represented by the following formula 3-2: [Equation 3-1]

[0059] [Equation 3-2]

[0060] According to one embodiment, based on 100 wt% of the total Ziegler-Natta catalyst for olefin polymerization, an external electron donor may be included in an amount of about 30 wt% to about 50 wt%. In a specific embodiment, this amount may be about 32 wt% to about 48 wt%, for example, about 32 wt% to about 36 wt%, about 36 wt% to about 40 wt%, about 40 wt% to about 44 wt%, or about 44 wt% to about 48 wt%. Within the above ranges, the stability of the catalyst active sites is high, and there is no problem of reduced activity due to poisoning of catalyst active sites.

[0061] According to one embodiment, based on 100 wt% of the total external electron donor contained in the Ziegler-Natta catalyst, the external electron donor represented by Formula 3 may be included in an amount of about 95 wt% or more, preferably about 99 wt% to about 100 wt%, more preferably about 100 wt%. Within the above range, the effects of the present invention can be readily achieved. Here, "total external electron donor" may refer to compounds known to those skilled in the art as compounds contained independently of the pre-catalyst in the olefin Ziegler-Natta catalyst and used to stabilize the catalytic active sites of the titanium compound.

[0062] The selection of internal electron donors allows for the preparation of polyolefins with excellent processability, i.e., polyolefins meeting specific ranges of density, melt index, and melt flow ratio, when external electron donors are included in the olefin Ziegler-Natta catalyst. Internal electron donors provide various active sites when external electron donors are applied, enabling the preparation of polyolefin resins with excellent processability.

[0063] In this invention, relative to the external electron donor, the internal electron donor comprises a mixture of a first internal electron donor represented by Chemical Formula 4, a second internal electron donor represented by Chemical Formula 5, and a third internal electron donor represented by Chemical Formula 6, and the molar ratio of the external electron donor to the mixture is about 115 to about 130. In a specific embodiment, the molar ratio may be about 117 to about 128, for example, about 117 to about 121, about 121 to about 125, or about 125 to about 128.

[0064] In one specific embodiment, in chemical formula 4, R 4 and R 5 It can be a branched C3-C independently. 10 Alkyl or C3-C5 alkyl. For example, in formula 4, R 4 and R 5 C3-C can be independently terminally branched. 10 Alkyl or C3-C5 alkyl. The first internal electron donor represented by Formula 4 may include at least one compound selected from any of the following formulas 4-1 to 4-3: [Equation 4-1]

[0065] [Equation 4-2]

[0066] [Formula 4-3]

[0067] In one specific embodiment, in chemical formula 5, R 7 It can be a straight chain C1-C 10 Alkyl or straight-chain C1-C5 alkyl. In formula 5, R 8 It can be a branch C2-C 10 Alkyl or C2-C5 alkyl. For example, in formula 5, R 8 It can be terminally branched C2-C 10 Alkyl or C2-C5 alkyl. The second internal electron donor represented by formula 5 may include at least one compound selected from any of the following formulas 5-1 to 5-4: [Equation 5-1]

[0068] [Equation 5-2]

[0069] [Equation 5-3]

[0070] [Equation 5-4]

[0071] In one specific embodiment, in chemical formula 6, R 10 and R 11 Each can be a straight chain C1-C independently. 10Alkyl or straight-chain C1-C5 alkyl. For example, the third internal electron donor represented by Formula 6 may include at least one compound selected from any of the following formulas: 6-1 to 6-3 [Equation 6-1]

[0072] [Equation 6-2]

[0073] [Equation 6-3]

[0074] According to one embodiment, based on 100 wt% of the total internal electron donor contained in the Ziegler-Natta catalyst, a mixture of the first internal electron donor, the second internal electron donor, and the third internal electron donor may be included in an amount of about 95 wt% or more, preferably about 99 wt% to about 100 wt%, more preferably about 100 wt%.

[0075] The titanium compound and the external electron donor may be contained in a molar ratio of about 1:3 to about 1:9, preferably about 1:4 to about 1:8. In one specific embodiment, the molar ratio may be about 1:3.2 to about 1:8.8, for example, about 1:3.2 to about 1:4.6, about 1:4.6 to about 1:6, about 1:6 to about 1:7.4, or about 1:7.4 to about 1:8.8. Within the above ranges, the stability of the catalyst active sites is excellent, and there is no problem of reduced catalyst activity due to poisoning of catalyst active sites.

[0076] According to another specific embodiment, the Ziegler-Natta catalyst includes a Ziegler-Natta pre-catalyst for olefin polymerization, comprising a titanium compound represented by Formula 1, a magnesium compound represented by Formula 2, and an internal electron donor; an organoaluminum compound represented by Formula 7; and an external electron donor represented by Formula 3, wherein the internal electron donor is a mixture of a first internal electron donor and a second internal electron donor, the first internal electron donor being selected from Formulas 8, 5, and 9, and the second internal electron donor being selected from Formulas 8, 5, and 9 and different from the first internal electron donor, and comprising the first internal electron donor: second internal electron donor in a molar ratio of about 3:7 to about 7:3 based on 10 moles of the mixture. In a specific embodiment, the molar ratio may be about 3.5:6.5 to about 6.5:3.5, for example about 4:6 to about 6:4, about 4.5:5.5 to about 5.5:4.5, or about 5:5.

[0077] [Chemical Formula 8]

[0078] (In chemical formula 8, R 31 R 32 R 33 and R 34 Each is independently selected from hydrogen, substituted or unsubstituted C1-C. 20 Alkyl, substituted or unsubstituted C3-C 20 Cycloalkyl and substituted or unsubstituted C3-C 20 One of the groups consisting of aryl groups, or R 31 and R 33 They can connect with each other to form substituted or unsubstituted C3-C 20 cycloalkyl, R 4 and R 5 Independently, C1-C is either freely substituted or unsubstituted. 20 Alkyl, substituted or unsubstituted C3-C 20 Cycloalkyl and substituted or unsubstituted C3-C 20 One of the groups composed of aryl groups, and In the substituted or unsubstituted group, the substituent is independently at least one selected from the group consisting of halogen, cyano, nitro, and C1-C8 alkyl. [Chemical Formula 5]

[0079] (In chemical formula 5, R 6 R 7 and R 8 Independently, C1-C is either freely substituted or unsubstituted. 20 Alkyl, substituted or unsubstituted C3-C 20 Cycloalkyl and substituted or unsubstituted C3-C 20 One of the groups composed of aryl groups. n is 0, which refers to an integer of 4, and In the substituted or unsubstituted group, the substituent is independently at least one selected from the group consisting of halogen, cyano, nitro, and C1-C8 alkyl. [Chemical Formula 9]

[0080] (In chemical formula 9, R 9 and R 10 Each is independently selected from hydrogen, substituted or unsubstituted C1-C. 20 Alkyl, substituted or unsubstituted C3-C 20 Cycloalkyl and substituted or unsubstituted C3-C 20One of the groups consisting of aryl groups, or R 9 and R 10 They can connect with each other to form substituted or unsubstituted C3-C 20 cycloalkyl R 11 and R 120 Each can be independently selected as either substituted or unsubstituted C1-C. 20 Alkyl, substituted or unsubstituted C3-C 20 Cycloalkyl and substituted or unsubstituted C3-C 20 One of the groups composed of aryl groups, and In the substituted or unsubstituted group, the substituent is independently at least one selected from the group consisting of halogen, cyano, nitro, and C1-C8 alkyl. In a specific implementation, the first internal electron donor: the second internal electron donor may be contained in a molar ratio of about 3:7, about 3.5:6.5, about 4:6, about 4.5:5.5, about 5:5, about 5.5:4.5, about 6:4, about 6.5:3.5 or about 7:3.

[0081] In a specific embodiment, the compound of formula 8 is a diethyl diester compound, and may include at least one compound selected from compounds represented by any of formulas 8-1 to 8-7: [Chemical Formula 8-1]

[0082] [Chemical Formula 8-2]

[0083] [Chemical Formula 8-3]

[0084] [Chemical Formula 8-4]

[0085] [Chemical Formula 8-5]

[0086] [Chemical Formula 8-6]

[0087] [Chemical Formula 8-7]

[0088] The compound of formula 9 is a diethyl diester compound, and may include at least one compound selected from compounds represented by any of formulas 9-1 to 9-4 below: [Chemical Formula 9-1]

[0089] [Chemical Formula 9-2]

[0090] [Chemical Formula 9-3]

[0091] [Chemical Formula 9-4]

[0092] According to one embodiment, the internal electron donor, i.e., the mixture, may be included in an amount of about 0.002 to about 0.008 mol, preferably about 0.003 to about 0.004 mol or about 0.007 to about 0.008 mol, relative to 1 mol of external electron donor. Within the above range, polyethylene that satisfies the above-mentioned density, melt index, and melt flow ratio can be readily prepared.

[0093] In specific embodiments, polymerization can be carried out while controlling the particle size of the catalyst to less than 60 μm. Particle size refers to the particle size measured using SEM (scanning electron microscopy). In specific embodiments, the particle size can be greater than about 0 and less than about 60 μm, preferably from about 0.01 to about 50 μm, for example, from about 0.01 to about 2 μm, from about 2 to about 14 μm, from about 14 to about 26 μm, from about 26 to about 38 μm, or from about 38 to about 50 μm. By controlling the particle size within the above range during polymerization, heat resistance, melt processability, and adhesion properties can be ensured.

[0094] Specifically, based on the total monomer content, the copolypropylene monomer can be included in an amount greater than about 0 and less than or equal to about 5 wt%, for example, about 1 to about 3 wt%, preferably about 1.1 to about 2 wt%. Within the above range, excellent heat resistance and processability can be ensured simultaneously.

[0095] Furthermore, if necessary, conventional additives may be added before and / or after polymerization without prejudice to the purpose of the invention.

[0096] The prepared polyethylene can be melt-spun to produce fibers. Because the polyethylene of this invention exhibits excellent melt spinnability and does not break yarns, as measured by rotational rheology, at a temperature of about 210 to about 230°C with an oxidation induction time of about 10 minutes or longer, for example, about 10 to about 20 minutes, specifically about 10 to about 15 minutes, and has a peak corresponding to polypropylene in NMR measurements. Due to this excellent melt spinnability, fibers with diameters greater than about 0 and less than about 100 μm can also be prepared, for example, about 1 to about 25 μm, about 25 to about 50 μm, about 50 to about 75 μm, or about 75 to about 99 μm.

[0097] Polyethylene fibers can be used to prepare nonwoven fabrics, and according to certain embodiments, the generation of fluff can be minimized and excellent adhesion can be exhibited.

[0098] Another aspect of the invention relates to a method for preventing yarn breakage during melt spinning of polyethylene. Conventionally, a method of increasing the proportion of low molecular weight components has been used for melt spinning, but in this case, yarn breakage occurs. In the present invention, yarn breakage during melt spinning can be prevented by using polyethylene polymerized by controlling the particle size of a Ziegler-Natta catalyst. In a specific embodiment, the polyethylene is characterized by an oxidation induction time of about 10 minutes or longer at a temperature of about 210 to about 230°C, as measured by rotational rheology, for example, about 10 to about 20 minutes, specifically about 10 to about 15 minutes, at which a peak corresponding to polypropylene is present in NMR measurements.

[0099] The invention will be described in more detail below by way of examples; however, these examples are for illustrative purposes only and should not be construed as limiting the invention.

[0100] Example Preparation example: Synthesis of Ziegler-Natta catalysts 4 g of magnesium compound Mg(OC2H5)2 support and 8 ml of TiCl4 (a titanium compound) were placed in 12 ml of toluene. A mixture of formula 4-1 (4.5 mmol), formula 5-1 (0.45 mmol), formula 6-1 (0.45 mmol), formula 6-2 (0.45 mmol), and formula 6-3 (0.45 mmol) was added as an internal electron donor to prepare the pre-catalyst. Subsequently, 0.18 ml of formula 3-2 was added as an external electron donor, and 2 mmol of triethylaluminum (an organoaluminum compound) (co-catalyst) (in 2 ml of 1 M hexane solution) was added. The Ziegler-Natta catalyst was prepared by stirring at 300 rpm.

[0101] Examples 1 to 3 Ethylene was polymerized by selecting Ziegler-Natta catalyst particles with a particle size of less than 60 μm prepared in the above preparation example, while propylene monomer was added in the amounts shown in Table 1. The prepared polyethylene was melt-spun under extrusion conditions of 230 to 250 °C to prepare polyethylene fibers. The physical properties of the prepared polyethylene fibers were measured according to the methods used to evaluate their physical properties, and the results are shown in Table 1 below.

[0102] Comparative Examples 1 to 2 Except for the absence of propylene, the same procedures as in Example 1 are performed.

[0103] Comparative Example 3 Except that the catalyst prepared in the preparation example was used without controlling the particle size, the same procedures as in Example 1 were performed. The particle size distribution of the catalyst was D10 = 10 μm, D50 = 62 μm, and D90 = 100 μm.

[0104] Table 1

[0105] Physical property evaluation methods (1) Melt flow index (MI, g / 10min): The melt flow index (MI) was measured at 190°C under a load of 2.16 kg according to ASTM D1238. 2.16 ).

[0106] (2) Melt Flow Ratio (MFR): The melt flow index (MFR) was measured at 190°C under a load of 2.16 kg according to ASTM D1238. 21.6 After that, by MI 21.6 / MI 2.16 Obtain the melt flow ratio.

[0107] (3) Density: The density of polyethylene (g / cm³) was measured according to ASTM D1505. 3 ).

[0108] (4) NMR: The NMR of polyethylene was measured to confirm the presence or absence of peaks corresponding to polypropylene and the content of those peaks. The NMR results of Example 1 and Comparative Example 1 are shown in the figures below. Figure 4 and Figure 5 middle.

[0109] (5) Tm and Tc: The melting point and crystallization temperature were obtained using differential scanning calorimetry (DSC).

[0110] (6) Weight-average molecular weight and PDI: 5 mg of sample was dissolved in 2 ml of chloroform as solvent, and the weight-average molecular weight and number-average molecular weight were measured using gel permeation chromatography (GPC). The molecular weight distribution (PDI, Mw / Mn) was calculated by dividing the weight-average molecular weight by the number-average molecular weight. The GPC measurement results are shown below. Figure 2 As shown.

[0111] (7) Tensile strength (Kg / cm) 2 ): Measured according to ASTM D638.

[0112] (8) OIT (Oxidative Induction Time): Oxidation induction time was measured using a rotational rheometer at temperatures ranging from 210 to 230 °C. The time-scan results are shown below. Figure 3 As shown.

[0113] (9) Gel: After extrusion of the resin using a T-die for evaluation, a gel foreign matter detector was used to obtain the gel per 1m. 2 The number and total number of gels with a maximum inner diameter of 400 μm or larger.

[0114] (10) Thermal adhesion: When thermal adhesion is performed after spinning, whether interface separation occurs is determined by SEM; when interface separation occurs, it is rated as X, and when interface separation does not occur, it is rated as O.

[0115] (11) Melt spinning index (MSI): The value is obtained according to the following formula 1.

[0116] [Formula 1]

[0117] (In Formula 1, MI is the melt index of polyethylene (ASTM D1238, 190°C, 2.16 kg) (unit: g / 10 min), OIT is the oxidation induction time at a temperature of 210 to 230°C as measured by rotational rheometer (unit: min), P is the polypropylene content (wt%), and G is 1 m 2 The number of gels with a diameter of 400 μm or larger. As can be seen from the results in Table 1, compared with Comparative Examples 1 to 3, the polyethylene of the present invention has a good balance of heat resistance, excellent melt spinnability, adhesion and tensile strength.

[0118] Nonwoven fabrics were prepared from polyethylene fibers of Examples 1 to 3 and Comparative Examples 1 to 2, and surface photographs are shown below. Figure 1 As shown. Figure 1 As shown, it can be confirmed that a large amount of fuzz was generated on the surface of Comparative Examples 1 to 2 compared with Examples 1 to 3.

[0119] Those skilled in the art can readily make simple modifications and alterations to this invention, and all such modifications and alterations are considered to fall within the scope of this invention.

[0120] [Industrial Availability] The present invention has the following effects: providing polyethylene with excellent melt spinning processability, heat resistance, adhesion and tensile strength, and significantly reduced gel formation during melt spinning, a method for preparing the polyethylene, fibers and nonwoven fabrics formed by melt spinning polyethylene, and a method for preventing yarn breakage during melt spinning of polyethylene.

Claims

1. Polyethylene with an oxidation induction time of 10 minutes or longer at a temperature of 210 to 230°C, as measured by a rotational rheometer. in, A peak corresponding to polypropylene was observed during NMR measurements.

2. The polyethylene according to claim 1, wherein, The polyethylene has a weight-average molecular weight of 40,000 g / mol to 60,000 g / mol and a polydispersity index (PDI) of 7 or higher.

3. The polyethylene according to claim 1, wherein, The polyethylene contains more than 0 wt% and no more than 5 wt% of polypropylene.

4. The polyethylene according to claim 1, wherein, The polyethylene per 1m 2 It has fewer than 150 gels with a maximum diameter of 400 μm or larger.

5. The polyethylene according to claim 1, wherein, The melt index (ASTM D1238, 190°C, 2.16 kg) of the polyethylene is 15 to 40 g / 10 min.

6. The polyethylene according to claim 1, wherein, The melt flow ratio (MFR, 190°C, MI) of the polyethylene 21.6 / MI 2.16 The value is 20 to 30.

7. The polyethylene according to claim 1, wherein, The polyethylene has a density of 0.948 to 0.965 g / cm³. 3 .

8. The polyethylene according to claim 1, wherein, The polyethylene has a melt spinning index (MSI) of 30 to 200 according to Formula 1 below: [Formula 1] (In Formula 1, MI is the melt index of polyethylene (ASTM D1238, 190°C, 2.16 kg) (unit: g / 10 min), OIT is the oxidation induction time at a temperature of 210 to 230°C measured by a rotational rheometer (unit: min), P is the polypropylene content (wt%), and G is 1 m 2 The number of gels with an inner diameter of 400 μm or larger.

9. The polyethylene according to claim 1, wherein, The polyethylene per 1m 2 It has fewer than 150 gels of 400 μm or larger.

10. The polyethylene according to claim 1, wherein, The tensile strength of the polyethylene, measured according to ASTM D638, is 270 kg / cm². 2 Or higher.

11. The polyethylene according to claim 1, wherein, The polyethylene is used for melt spinning.

12. Polyethylene fibers formed by melt spinning polyethylene according to any one of claims 1 to 11.

13. The polyethylene fiber according to claim 12, wherein, The diameter of the polyethylene fiber is greater than 0 and less than 100 μm.

14. A nonwoven fabric formed from polyethylene fibers according to claim 12.

15. A method for preparing polyethylene according to any one of claims 1 to 11, the method comprising polymerizing ethylene in the presence of a Ziegler-Natta catalyst.

16. The method for preparing polyethylene according to claim 15, wherein, The method includes polymerization while controlling the particle size of the Ziegler-Natta catalyst to less than 60 μm.

17. The method for preparing polyethylene according to claim 15, wherein, The method involves polymerization by adding propylene monomer in an amount greater than 0 wt% and not greater than 5 wt% of the total monomer content.

18. A method for preventing yarn breakage during melt spinning of polyethylene, the method comprising using polyethylene polymerized by controlling the particle size of a Ziegler-Natta catalyst.

19. The method according to claim 18, wherein, The oxidation induction time of the polyethylene at a temperature of 210 to 230°C, as measured by a rotational rheometer, is 10 minutes or longer. Furthermore, a peak corresponding to polypropylene was observed during NMR measurement.

20. The method according to claim 18, wherein, The polyethylene has a weight-average molecular weight of 40,000 g / mol to 60,000 g / mol and a polydispersity index (PDI) of 7 or higher.

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