Polyethylene with excellent heat resistance and method for preparing the same

Abstract

The polyethylene of the present invention is characterized by having an oxidative induction time of 10 minutes or more at a temperature of 210 to 230 ℃ using a rotational rheometer, and having a peak corresponding to polypropylene when measured by NMR.

Description

Technology Field

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

[0003] Due to process characteristics, spinning polyethylene resin requires a high melt index (15 MI or higher) of 15 g / 10 min or higher. To increase the melt index of polyethylene, measures are being taken to increase the proportion of relatively low molecular weight. Polyethylene with such a high proportion of low molecular weight has advantages in extrusion processability (extrusion load) and post-processing (web formation stage).

[0004] However, the melt spinning process is carried out at high temperatures of 200 degrees or higher, but in the case of low molecular weight polyethylene, the heat resistance is low, so the resin oxidizes, causing carbonization or gel formation, which leads to the problem of fiber breakage.

[0005] Therefore, there is a need to develop a polyethylene resin with excellent melt-spun processability and heat resistance.

[0006] Related prior art includes Korean patent KR10-2022-0076357. The problem to be solved

[0008] The objective of the present invention is to provide polyethylene having excellent melt-spun processability and heat resistance, and a method for manufacturing the same.

[0009] Another objective of the present invention is to provide polyethylene having excellent adhesiveness and tensile strength, and a method for manufacturing the same.

[0010] Another objective of the present invention is to provide polyethylene that significantly reduces gel formation in the melt spinning process and a method for manufacturing the same.

[0011] Another objective of the present invention is to provide fibers and nonwoven fabrics formed by melt spinning the polyethylene.

[0012] Another objective of the present invention is to provide a method for preventing monofilament during the melt spinning of polyethylene.

[0013] The above and other objectives of the present invention can all be achieved by the present invention described below. means of solving the problem

[0015] 1. One aspect of the present invention relates to polyethylene. The polyethylene is characterized by having an oxidative induction time of 10 minutes or more at a temperature of 210 to 230 ℃ using a rotational rheometer, and having a peak corresponding to polypropylene when measured by NMR.

[0016] 2. In the above 1 embodiment, the polyethylene may have a weight-average molecular weight of 40,000 g / mol to 60,000 g / mol and a polydispersity index (PDI) of 7 or higher.

[0017] 3. In the above 1-2 embodiments, the polyethylene may contain polypropylene of greater than 0 and less than or equal to 5 weight percent.

[0018] 4. In the above 1-3 embodiments, the polyethylene is 1 m 2 The number of gels with a maximum diameter of 400 μm or more may be less than 150.

[0019] 5. In the above 1-4 embodiments, the polyethylene may have a melt index (ASTM D 1238, 190 ℃, 2.16 kg) of 15 to 40 g / 10 min.

[0020] 6. In the above embodiments 1-5, the polyethylene has a melt flow index (MFR, 190 °C, MI 21.6 / MI 2.16 ) can be 20 to 30.

[0021] 7. In the above embodiments 1-6, the polyethylene has a density of 0.948 to 0.965 g / cm³3 It could be.

[0022] 8. In the above embodiments 1-7, the polyethylene may have a melt spinn index (MSI) of 30 to 200 according to Formula 1 below:

[0023] [Equation 1]

[0024]

[0025] (In Equation 1, MI is the melt index of polyethylene (ASTM D 1238, 190 °C, 2.16 kg) (unit: g / 10 min), OIT is the oxidative induction time at a temperature of 210 to 230 °C by a rotational rheometer (unit: min), P is the polypropylene content (weight%), and G is 1 m 2 (at which is the number of gels larger than 400 µm)

[0027] 9. In the above embodiments 1-8, the polyethylene is 1 m 2 The number of gels larger than 400 μm may be less than 150.

[0028] 10. In the above 1-9 embodiments, the polyethylene may have a tensile strength of 270 kg / cm2 or more as measured by ASTM D638.

[0029] 11. In the above 1-10 embodiments, the polyethylene is characterized by being used for melt spinning.

[0030] 12. Another aspect of the present invention relates to polyethylene fibers. The polyethylene fibers are formed by melt-spinning the polyethylene of any one of embodiments 1-11.

[0031] 13. In the above 12 embodiments, the polyethylene fiber may have a diameter greater than 0 and less than 100 μm.

[0032] 14. Another aspect of the present invention relates to a nonwoven fabric. The nonwoven fabric may be formed from the polyethylene fibers of the 12 embodiments.

[0033] 15. Another aspect of the present invention relates to a method for producing polyethylene. The method comprises the step of polymerizing ethylene in the presence of a Ziegler-Natta catalyst.

[0034] 16. In the above 15 embodiments, the method is characterized by polymerizing by controlling the particle size of the Ziegler-Natta catalyst to less than 60 μm.

[0035] 17. In the above 15-16 embodiments, the method may involve polymerizing by adding propylene monomer in an amount greater than 0% and less than or equal to 5% by weight of the total monomer content.

[0036] 18. Another aspect of the present invention relates to a method for preventing monofilament during melt spinning of polyethylene. The method is characterized by using polyethylene polymerized by controlling the particle size of a Ziegler-Natta catalyst.

[0037] 19. In the above 18 embodiments, the polyethylene may have an oxidative induction time of 10 minutes or more at a temperature of 210 to 230 ℃ by a rotational rheometer.

[0038] 20. In the above 18-19 embodiments, 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. Effects of the invention

[0040] The present invention provides polyethylene with excellent melt-spinning processability, heat resistance, adhesion, and tensile strength, and a method for manufacturing the same, which significantly reduces gel formation during the melt-spinning process, as well as fibers and nonwoven fabrics formed by melt-spinning the said polyethylene, and has the effect of providing a method to prevent single filaments during the melt-spinning of polyethylene. Brief explanation of the drawing

[0042] Figure 1 is a surface photograph of the polyethylene nonwoven fabric prepared in Examples 1-3 and Comparative Examples 1-2. Figure 2 shows the gel permeation chromatography (GPC) measurement results of polyethylene prepared in Examples 1-3 and Comparative Examples 1-2. Figure 3 shows the results of measuring the oxidative induction time of polyethylene prepared in Examples 1-3 and Comparative Examples 1-2. Figure 4 shows the NMR measurement results of Example 1. Figure 5 shows the NMR measurement results of Comparative Example 1. Specific details for implementing the invention

[0043] The present invention will be described in more detail below. Where terms such as 'comprising,' 'having,' and 'consisting of' are used in this specification, other parts may be added unless 'only' is used. Where a component is expressed in the singular, it includes cases where it includes the plural unless specifically stated otherwise.

[0044] In interpreting the components, they are interpreted to include a margin of error even in the absence of a separate explicit statement.

[0046] polyethylene

[0047] One aspect of the present invention relates to polyethylene. The polyethylene may have an oxidative induction time of 10 minutes or more, for example, 10 to 20 minutes, or 10 to 15 minutes in specific examples, at a temperature of 210 to 230 °C using a rotational rheometer. Within this range, it possesses excellent heat resistance and processability, and no single filaments are generated during melt spinning.

[0048] The above polyethylene may have a peak corresponding to polypropylene when measured by NMR. In a specific example, the above polyethylene may contain polypropylene in an amount greater than 0 and less than or equal to 5 weight%, for example, 1 to 3 weight%, preferably 1.1 to 2 weight%. Within this range, it may have excellent heat resistance and processability.

[0049] In a specific example, the polyethylene may have a weight-average molecular weight of 40,000 g / mol to 60,000 g / mol, and in a specific example, 42,000 to 56,000 g / mol. Within this range, a balance of heat resistance and melt-spinning properties may be achieved.

[0050] In a specific example, the polyethylene is 1 m 2 The number of gels having a maximum diameter of 400 μm or more may be less than 150, 1 to 140 in specific examples, and preferably 1 to 100. In addition, the polyethylene is 1 m 2 The total number of gels may be less than 1,600, for example, 1 to 1,000. Within the above range, no single filament is generated during melt spinning.

[0051] The above polyethylene may have a melt index (ASTM D 1238, 190 °C, 2.16 kg) of 15 to 40 g / 10 min, preferably 20 to 38 g / 10 min. In this range, extrusion processability is excellent and web formation is advantageous.

[0052] In a specific example, the polyethylene has a melt flow index (MFR, 190 °C, MI 21.6 / MI 2.16 ) can be 20 to 30, for example, 22 to 25. It has excellent processability within the above range.

[0053] In a specific example, the polyethylene has a density of 0.948 to 0.965 g / cm³ 3 , preferably 0.950 to 0.960 g / cm³ 3 It could be.

[0054] In addition, the melt-spray index (MSI) according to the following Formula 1 may be 30 to 200, preferably 35 to 150:

[0055] [Equation 1]

[0056]

[0057] (In Equation 1, MI is the melt index of polyethylene (ASTM D 1238, 190 °C, 2.16 kg) (unit: g / 10 min), OIT is the oxidative induction time at a temperature of 210 to 230 °C by a rotational rheometer (unit: min), P is the polypropylene content (weight%), and G is 1 m 2 (at which is the number of gels larger than 400 µm)

[0059] In addition, the polyethylene may have a tensile strength of 270 kg / cm2 or more, for example, 270 to 300 kg / cm2, as measured by ASTM D638 standards.

[0060] The polyethylene according to the above specific example can be manufactured by the following manufacturing method.

[0061] Polyethylene manufacturing method

[0062] The above polyethylene includes the step of polymerizing ethylene in the presence of a Ziegler-Natta catalyst.

[0063] In one embodiment, the Ziegler-Natta catalyst comprises (i) a Ziegler-Natta pro-catalyst for olefin polymerization comprising a titanium compound represented by Formula 1 below, a magnesium compound represented by Formula 2 below, and an internal electron donor; (ii) an organoaluminum compound represented by Formula 7 below; and (iii) an external electron donor represented by Formula 3 below, wherein the internal electron donor comprises a mixture of a first internal electron donor represented by Formula 4 below; a second internal electron donor represented by Formula 5 below; and a third internal electron donor represented by Formula 6 below, and the molar ratio of the external electron donor to the mixture is 115 to 130:

[0064] [Chemical Formula 1]

[0065] TiX n (OR 1 ) 4-n

[0066] (In the above chemical formula 1,

[0067] R 1 C1-C of substituted or non-substituted 20 Alkyl groups, substituted or unsubstituted C3-C 20 Cycloalkyl groups, and substituted or unsubstituted C3-C 20 It is one species selected from the group composed of aryls, and

[0068] X is a halogen atom, and

[0069] n is an integer from 0 to 4, and

[0070] In the above substitution or non-substitution, the substituent is independently one or more selected from the group consisting of halogen groups, cyano groups, nitro groups, and C1-C8 alkyl groups.

[0071] [Chemical Formula 2]

[0072] Mg(OR 2 ) k X 2-k

[0073] (In the above chemical formula 2,

[0074] R 2 C1-C of substituted or non-substituted 20 Alkyl groups, substituted or unsubstituted C3-C 20 Cycloalkyl groups, and substituted or unsubstituted C3-C 20 It is one species selected from the group composed of aryls, and

[0075] X is a halogen atom, and

[0076] k is an integer from 0 to 2, and

[0077] In the above substitution or non-substitution, the substituent is independently one or more selected from the group consisting of halogen groups, cyano groups, nitro groups, and C1-C8 alkyl groups.

[0078] [Chemical Formula 3]

[0079]

[0080] (In the above chemical formula 3,

[0081] L1 and L2 are each independently substituted or non-substituted C1-C 20 It is an alkyl group, and in the above substitution or non-substitution, the substituent is independently one or more selected from the group consisting of halogen groups, cyano groups, nitro groups, and C1-C8 alkyl groups, and

[0082] L3 and L4 are each independently substituted or non-substituted C1-C 20 Alkyl groups and substituted or unsubstituted C3-C 20 It is one selected from the group consisting of cycloalkyl groups, and

[0083] In the above substitution or non-substitution, the substituent is independently one or more selected from the group consisting of halogen groups, cyano groups, nitro groups, and C1-C8 alkyl groups).

[0084] [Chemical Formula 4]

[0085]

[0086] (In the above chemical formula 4,

[0087] R 3 C1-C of substituted or non-substituted 20 Alkyl groups, substituted or unsubstituted C3-C 20 Cycloalkyl groups, and substituted or unsubstituted C3-C 20 It is one selected from the group consisting of aryl groups, and in the above substitution or non-substitution, the substituent is independently one or more selected from the group consisting of halogen groups, cyano groups, nitro groups, and C1-C8 alkyl groups, and

[0088] R 4 and R 5 Each independently, branched chain type C1-C 20 alkyl group,

[0089] m is an integer from 0 to 4)

[0090] [Chemical Formula 5]

[0091]

[0092] (In the above chemical formula 5,

[0093] R 6 is independently, substitutable or non-substitutable C1-C 20 Alkyl groups, substituted or unsubstituted C3-C 20 Cycloalkyl groups, and substituted or unsubstituted C3-C 20 It is one selected from the group consisting of aryl groups, and in the above substitution or non-substitution, the substituent is independently one or more selected from the group consisting of halogen groups, cyano groups, nitro groups, and C1-C8 alkyl groups, and

[0094] R 7 It is a straight-chain C1-C 20 alkyl group,

[0095] R 8 It is a branched chain type C1-C 20 alkyl group,

[0096] n is an integer from 0 to 4)

[0097] [Chemical Formula 6]

[0098]

[0099] (In the above chemical formula 6,

[0100] R 9 Each is independently a substituted or non-substituted C1-C 20 Alkyl groups, substituted or unsubstituted C3-C 20 Cycloalkyl groups, and substituted or unsubstituted C3-C 20 It is one selected from the group consisting of aryl groups, and in the above substitution or non-substitution, the substituent is independently one or more selected from the group consisting of halogen groups, cyano groups, nitro groups, and C1-C8 alkyl groups, and

[0101] R 10 and R 11 Each is independently a linear C1-C 20 alkyl group,

[0102] p is an integer from 0 to 4),

[0103] [Chemical Formula 7]

[0104] Al(R 13 ) p X 3-p

[0105] (In the above chemical formula 7,

[0106] R 13 hydrogen atoms, substituted or non-substituted C1-C 20 Alkyl groups, substituted or unsubstituted C3-C 20 Cycloalkyl groups, and substituted or unsubstituted C3-C 20 It is one species selected from the group composed of aryls, and

[0107] X is a halogen atom, and

[0108] p is an integer from 0 to 3, and

[0109] In the above substitution or non-substitution, the substituent is independently one or more selected from the group consisting of halogen groups, cyano groups, nitro groups, and C1-C8 alkyl groups).

[0110] According to one embodiment, the catalyst may include one type of external electron donor represented by the chemical formula 3, namely, a first external electron donor alone or a second external electron donor alone.

[0111] According to one embodiment, the catalyst may be a mixture comprising two types of external electron donors represented by Chemical Formula 3. In one embodiment, the catalyst may be a mixture of the first external electron donor and the second external electron donor. For example, in 10 moles of the mixture, the first external electron donor : the second external electron donor may be included in a molar ratio of 3:7 to 7:3, a molar ratio of 4:6 to 6:4, or a molar ratio of 5:5.

[0112] In one embodiment, L1 and L2 are each independently substituted or non-substituted C1-C 10 It may be an alkyl group, for example, a substituted or unsubstituted C1-C5 alkyl group.

[0113] In one embodiment, the first external electron donor is represented by the following chemical formula 3-1, and the second external electron donor can be represented by the following chemical formula 3-2:

[0114] [Chemical Formula 3-1]

[0115]

[0116] [Chemical Formula 3-2]

[0117]

[0118] According to one embodiment, an external electron donor may be included in an amount of 30% to 50% by weight based on 100% by weight of the total Ziegler-Natta catalyst for olefin polymerization. Within this content range, the stability of the catalyst active sites is high, and there may be no problem of reduced activity due to poisoning of the catalyst active sites.

[0119] According to one embodiment, the external electron donor represented by Formula 3 may be included in an amount of 95% or more by weight, preferably 99% to 100% by weight, and more preferably 100% by weight, based on 100% by weight of the total external electron donor contained in the Ziegler-Natta catalyst. Within this range, the effect of the present invention may be easily realized. Here, "total external electron donor" may refer to a compound included independently of the main catalyst in the olefin Ziegler-Natta catalyst, and may mean a compound known to those skilled in the art to perform the role of stabilizing the catalytic active site of a titanium compound.

[0120] The internal electron donor was selected to satisfy the aforementioned polyolefin with excellent processability, namely a specific range of density, melt index, and melt index ratio, when the external electron donor is included in the olefin-Ziegler-Natta catalyst. The internal electron donor enables the production of a polyolefin resin with excellent processability by providing various active sites when the external electron donor is applied.

[0121] In the present invention, the external electron donor comprises a mixture of a first internal electron donor represented by Formula 4; a second internal electron donor represented by Formula 5; and a third internal electron donor represented by Formula 6, wherein the molar ratio of the external electron donor to the mixture is 115 to 130.

[0122] In one embodiment, in the above chemical formula 4, R 4 and R 5 is independently, branched chain type C3-C 10 It may be an alkyl group, a C3-C5 alkyl group. For example, in the above chemical formula 4, R 4 and R 5 C3-C with independently branched ends 10It may be an alkyl group or a C3-C5 alkyl group. The first internal electron donor represented by the above chemical formula 4 may include at least one compound represented by any one of the following chemical formulas 4-1 to 4-3:

[0123] [Chemical Formula 4-1]

[0124]

[0125] [Chemical Formula 4-2]

[0126]

[0127] [Chemical Formula 4-3]

[0128]

[0129] In one embodiment, in the above chemical formula 5, R 7 It is a straight-chain C1-C 10 It may be an alkyl group, or a straight-chain C1-C5 alkyl group. In the above Chemical Formula 5, R 8 It is a branched chain type C2-C 10 It may be an alkyl group or a C2-C5 alkyl group. For example, in the above chemical formula 5, R 8 C2-C with branched ends 10 It may be an alkyl group or a C2-C5 alkyl group. For example, the second internal electron donor represented by the above formula 5 may include at least one compound represented by any one of the following formulas 5-1 to 5-4:

[0130] [Chemical Formula 5-1]

[0131]

[0132] [Chemical Formula 5-2]

[0133]

[0134] [Chemical Formula 5-3]

[0135]

[0136] [Chemical Formula 5-4]

[0137]

[0138] In one embodiment, in the above chemical formula 6, R 10 and R 11 Each is independently a linear C1-C 10 It may be an alkyl group, a straight-chain C1-C5 alkyl group. For example, the third internal electron donor represented by the above chemical formula 6 may include at least one compound represented by any one of the following chemical formulas 6-1 to 6-3:

[0139] [Chemical Formula 6-1]

[0140]

[0141] [Chemical Formula 6-2]

[0142]

[0143] [Chemical Formula 6-3]

[0144]

[0145] According to one embodiment, the 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 95% or more, preferably 99% to 100%, and more preferably 100%, based on 100% by weight of the total internal electron donor contained in the Ziegler-Natta catalyst.

[0146] The titanium compound and the external electron donor may be included in a molar ratio of 1:3 to 1:9, preferably 1:4 to 1:8. Within the above molar ratio range, the stability of the catalytic active sites is excellent, and there may be no problem of reduced catalytic activity due to poisoning of the catalytic active sites.

[0147] According to another embodiment, the Ziegler-Natta catalyst comprises: a titanium compound represented by Formula 1, a magnesium compound represented by Formula 2, and an internal electron donor; a Ziegler-Natta pro-catalyst for olefin polymerization comprising; 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 selected from Formulas 8, 5, and 9; and a second internal electron donor selected from Formulas 8, 5, and 9 and different from the first internal electron donor, wherein the first internal electron donor : the second internal electron donor are included in a molar ratio of 3:7 to 7:3 in 10 moles of the mixture:

[0148] [Chemical Formula 8]

[0149]

[0150] (In the above chemical formula 8,

[0151] R 31 , R 32 , R 33 and R 34 Each is independently hydrogen, substituted, or unsubstituted C1-C 20 Alkyl groups, substituted or unsubstituted C3-C 20 Cycloalkyl groups, and substituted or unsubstituted C3-C 20 It is one type selected from the group consisting of aryl groups, or R 31 and R 33 They are connected to each other, forming substitutive or non-substitutive C3-C 20 It can form a cycloalkyl group, and

[0152] R 4 and R 5 is independently, substitutable or non-substitutable C1-C 20 Alkyl groups, substituted or unsubstituted C3-C 20 Cycloalkyl groups, and substituted or unsubstituted C3-C20 It is one species selected from the group composed of aryls, and

[0153] In the above substitution or non-substitution, the substituent is independently one or more selected from the group consisting of halogen groups, cyano groups, nitro groups, and C1-C8 alkyl groups.

[0154] [Chemical Formula 5]

[0155]

[0156] (In the above chemical formula 5,

[0157] R 6 , R 7 and R 8 is independently, substitutable or non-substitutable C1-C 20 Alkyl groups, substituted or unsubstituted C3-C 20 Cycloalkyl groups, and substituted or unsubstituted C3-C 20 It is one species selected from the group composed of aryls, and

[0158] n is an integer from 0 to 4, and

[0159] In the above substitution or non-substitution, the substituent is independently one or more selected from the group consisting of halogen groups, cyano groups, nitro groups, and C1-C8 alkyl groups.

[0160] [Chemical Formula 9]

[0161]

[0162] (In the above chemical formula 9,

[0163] R 9 and R 10 Each is independently hydrogen, substituted, or unsubstituted C1-C 20 Alkyl groups, substituted or unsubstituted C3-C 20 Cycloalkyl groups, and substituted or unsubstituted C3-C 20 It is one type selected from the group consisting of aryl groups, or R 9 and R 10 They are connected to each other, resulting in substitutive or non-substitutive C3-C 20 It can form a cycloalkyl group, and

[0164] R 11 and R 12 Each is independently a substituted or non-substituted C1-C 20 Alkyl groups, substituted or unsubstituted C3-C 20 Cycloalkyl groups, and substituted or unsubstituted C3-C 20 It is one species selected from the group composed of aryls, and

[0165] In the above substitution or non-substitution, the substituent is independently one or more selected from the group consisting of halogen groups, cyano groups, nitro groups, and C1-C8 alkyl groups),

[0166] In a specific example, the first internal electron donor: second internal electron donor may be included in a molar ratio of 3:7, 3.5:6.5, 4:6, 4.5:5.5, 5:5, 5.5:4.5, 6:4, 6.5:3.5, 7:3.

[0167] In a specific example, the compound of Formula 8 is a diethyl diester-based compound and may include one or more compounds represented by any one of Formulas 8-1 to 8-7 below:

[0168] [Chemical Formula 8-1]

[0169]

[0170] [Chemical Formula 8-2]

[0171]

[0172] [Chemical Formula 8-3]

[0173]

[0174] [Chemical Formula 8-4]

[0175]

[0176] [Chemical Formula 8-5]

[0177]

[0178] [Chemical Formula 8-6]

[0179]

[0180] [Chemical Formula 8-7]

[0181]

[0183] The compound of Chemical Formula 9 above is a diethyl diester-based compound and may include one or more compounds represented by any one of Chemical Formulas 9-1 to 9-4 below:

[0184] [Chemical Formula 9-1]

[0185]

[0186] [Chemical Formula 9-2]

[0187]

[0188] [Chemical Formula 9-3]

[0189]

[0190] [Chemical Formula 9-4]

[0191]

[0193] According to one embodiment, for every 1 mole of the external electron donor, the internal electron donor, i.e., the mixture, may be included in an amount of 0.002 to 0.008 moles, preferably 0.003 to 0.004 moles or 0.007 to 0.008 moles. Within this range, it may be easy to manufacture polyethylene satisfying the density, melt index, and melt index ratio described above.

[0194] In a specific example, the polymerization can be carried out by controlling the particle size of the catalyst to less than 60 μm. The particle size refers to the particle diameter measured using a scanning electron microscope (SEM). In a specific example, the particle diameter is greater than 0 and less than 60 μm, preferably 0.01 to 50 μm. By controlling the particle size within the above range and carrying out the polymerization, heat resistance, melt processability, and adhesive performance can be secured.

[0195] Specifically, propylene monomer can be polymerized together by including more than 0 and less than or equal to 5 weight percent of the total monomer, for example, 1 to 3 weight percent, preferably 1.1 to 2 weight percent. In the above range, excellent heat resistance and processability can be secured simultaneously.

[0196] In addition, conventional additives may be added before and after polymerization as needed, provided that such addition does not impede the purpose of the invention.

[0197] The polyethylene produced above can be manufactured into a fiber form by melt spinning. The polyethylene of the present invention has an oxidative induction time of 10 minutes or more at a temperature of 210 to 230 ℃ using a rotational rheometer, and a peak corresponding to polypropylene exists when measured by NMR, so it has excellent melt spinnability and does not produce monofilaments. Since it has excellent melt spinnability, fibers with a diameter greater than 0 and less than 100 μm can also be manufactured.

[0198] The above-mentioned polyethylene fibers can be used to manufacture a nonwoven fabric, and according to a specific embodiment, lint generation can be minimized and excellent adhesion can be achieved.

[0199] Another aspect of the present invention relates to a method for preventing monofilament formation during melt spinning of polyethylene. Conventionally, a method of increasing the low molecular weight ratio was used for melt spinning, but this resulted in the problem of monofilament formation. In the present invention, monofilament formation during melt spinning can be prevented by using polyethylene polymerized by controlling the particle size of the Ziegler-Natta catalyst. In a specific example, the polyethylene has the characteristic of having an oxidative induction time of 10 minutes or more at a temperature of 210 to 230 ℃ using a rotational rheometer, and the presence of a peak corresponding to polypropylene when measured by NMR.

[0201] The present invention is to be explained more specifically through the following examples, but these examples are for illustrative purposes only and should not be interpreted as limiting the invention.

[0203] Examples

[0204] Preparation Example: Synthesis of Ziegler-Natta Catalyst

[0205] 4 g of magnesium compound Mg(OC2H5)2 carrier and 48 ml of titanium compound TiCl were added to 12 ml of toluene, and a mixture of chemical formulas 4-1 (4.5 mmol), 5-1 (0.45 mmol), 6-1 (0.45 mmol), 6-2 (0.45 mmol), and 6-3 (0.45 mmol) was added as an internal electron donor to prepare the main catalyst. Then, 0.18 ml of chemical formula 3-2 and 2 mmol of triethylaluminum (2 ml of 1 M hexane solution), an organoaluminum compound (co-catalyst), were additionally added as external electron donors, and a Ziegler-Natta catalyst was prepared while stirring at 300 rpm.

[0207] Examples 1-3

[0208] The Ziegler-Natta catalyst prepared in the above preparation example was selected to have a particle size of less than 60 µm, and ethylene was polymerized using this catalyst, while polyethylene was polymerized by adding propylene monomer in the amounts shown in Table 1. The prepared polyethylene was melt-spun under extrusion conditions of 230–250°C to produce polyethylene fibers. The physical properties of the prepared polyethylene fibers were measured using the following physical property evaluation methods, and the results are shown in Table 1:

[0210] Comparative Examples 1~2

[0211] The procedure was performed in the same manner as Example 1 above, except that propylene was not added.

[0213] Comparative Example 3

[0214] The procedure was carried out in the same manner as Example 1, except that the particle size of the catalyst prepared in the preparation example was used without control. The particle size distribution of the catalyst was 10 μm for D10, 62 μm for D50, and 100 μm for D90.

[0216] Sample name Units Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Example 3 MI(190 ℃) g / 10min 19 20 1.1 20 24 35 MFR(190 ℃) - 26 21 25 24 24 23 Density g / cm 3 0.956 0.957 0.954 0.954 0.955 0.956 NMR PP content (wt%) - - 1.5 1.5 1.2 1.4 Tm ℃ 132 131 134 129 130 130 Tc ℃ 117 113 118 118 118 118 Mw g / mol 65,671 54,873 124,500 55,914 52,844 45,065 PDI - 6.7 4.5 8.5 7.4 7.3 9.4 UTM tensile strength kg / cm 2 266 273 - 282 295 270 OIT (Oxidation Stability) min 7.75 0.75 9.5 11.0 11.8 10.3 Gel >400㎛, 1m 2 ea 179 795 128 102 36 136 Total, 1m 2 ea 1,122 9,646 3,420 1,515 899 1,457 heat seal X X X O O O Melting Radiation Index (MSI) - 0 0 1.16 35.6 111.4 38.2

[0218] Physical property evaluation method

[0219] (1) Melt index (MI, g / 10 min): Melt index (MI) at 190 ℃ with a load of 2.16 kg according to ASTM D 1238 2.16 ) was measured.

[0220] (2) Melt Flow Index (MFR): Melt index (MI) at 190°C with a load of 21.6 kg according to ASTM D 1238 21.6 After measuring ), MI 21.6 / MI 2.16 It was obtained by.

[0221] (3) Density: The density of polyethylene (g / cm3) was measured according to ASTM D 1505 standards.

[0222] (4) NMR: The NMR of polyethylene was measured to determine the presence and content of the peak corresponding to polypropylene. Figures 4 and 5 show the NMR results of Example 1 and Comparative Example 1, respectively.

[0223] (5) Tm and Tc: The melting point and crystallization temperature were determined using differential scanning calorimetry (DSC), respectively.

[0224] (6) Weight-average molecular weight and PDI: 5 mg of sample was dissolved in 2 ml of chloroform as a solvent, and the weight-average molecular weight and number-average molecular weight were measured using gel permeation chromatography (GPC). Then, 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 in Figure 2.

[0225] (7) Tensile strength (kg / cm²) 2) : Measured according to ASTM D638 standards.

[0226] (8) OIT (Oxidative Stability): The oxidative induction time was measured at a temperature of 210 to 230 °C using a rotational rheometer. The time sweep results are shown in Figure 3.

[0227] (9) Gel: After extruding the evaluation resin into a T-die, use a gel foreign object detector to check 1 m 2 The number of gels with a maximum diameter of 400 μm or more and the total number of gels were calculated.

[0228] (10) Heat bondability: When heat bonding is performed after spinning, the separation of the interface was determined by SEM. If separation of the interface occurs, it is evaluated as X, and if separation of the interface does not occur, it is evaluated as O.

[0229] (11) Melt-Speed ​​Radiation Index (MSI): The calculated value was obtained using the following Equation 1.

[0230] [Equation 1]

[0231]

[0232] (In Equation 1, MI is the melt index of polyethylene (ASTM D 1238, 190 °C, 2.16 kg) (unit: g / 10 min), OIT is the oxidative induction time at a temperature of 210 to 230 °C by a rotational rheometer (unit: min), P is the polypropylene content (weight%), and G is 1 m 2 (at which is the number of gels larger than 400 µm)

[0234] From the results of Table 1 above, it can be seen that the polyethylene of the present invention has a balance of heat resistance, excellent melt-spinning properties, adhesion, and tensile strength compared to Comparative Examples 1-3.

[0236] Nonwoven fabrics were prepared using polyethylene fibers from Examples 1-3 and Comparative Examples 1-2, and a surface photograph is shown in Fig. 1. As shown in Fig. 1, it can be seen that a large amount of lint was generated on the surface of Comparative Example 1-2 compared to Example 1-3.

[0238] Simple variations or modifications of the present invention can be easily implemented by those skilled in the art, and all such variations or modifications are considered to be included within the scope of the present invention.

Claims

Claim 1 Melt-spinning polyethylene having an oxidative induction time of 10 minutes or more at a temperature of 210 to 230 °C using a rotational rheometer, and a peak corresponding to polypropylene present during NMR measurement. Claim 2 In claim 1, 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. Claim 3 In claim 1, the polyethylene comprises polypropylene in an amount greater than 0 and less than or equal to 5 weight percent. Claim 4 In claim 1, the polyethylene is 1 m 2 Polyethylene having fewer than 150 gels with a maximum diameter of 400 μm or more. Claim 5 In claim 1, the polyethylene is polyethylene having a melt index (ASTM D 1238, 190 ℃, 2.16 kg) of 15 to 40 g / 10 min. Claim 6 In claim 1, the polyethylene is a melt flow index (MFR, 190 ℃, MI 21.6 / MI 2.16 Polyethylene with 20 to 30 ) Claim 7 In claim 1, the polyethylene has a density of 0.948 to 0.965 g / cm³ 3 Phosphoric polyethylene. Claim 8 In claim 1, the polyethylene is polyethylene having a melt spinn index (MSI) of 30 to 200 according to the following Formula 1: [Formula 1] (In Equation 1, MI is the melt index of polyethylene (ASTM D 1238, 190 °C, 2.16 kg) (unit: g / 10 min), OIT is the oxidative induction time at a temperature of 210 to 230 °C by a rotational rheometer (unit: min), P is the polypropylene content (weight%), and G is 1 m 2 (at which is the number of gels larger than 400 µm) Claim 9 In claim 1, the polyethylene is 1 m 2 Polyethylene with fewer than 150 gels of 400 µm or more. Claim 10 In claim 1, the polyethylene is polyethylene having a tensile strength of 270 kg / cm2 or more as measured by ASTM D638 standards. Claim 11 delete Claim 12 Polyethylene fiber formed by melt spinning the polyethylene of any one of claims 1 to 10. Claim 13 In paragraph 12, the polyethylene fiber is a polyethylene fiber with a diameter greater than 0 and less than 100 μm. Claim 14 A nonwoven fabric formed from polyethylene fibers of Clause 12. Claim 15 A method for manufacturing polyethylene according to any one of claims 1 to 10, wherein the method comprises the step of polymerizing ethylene in the presence of a Ziegler-Natta catalyst. Claim 16 In claim 15, the above method is a method for manufacturing polyethylene by polymerizing by controlling the particle size of the Ziegler-Natta catalyst to less than 60 μm. Claim 17 In claim 15, the above method is a method for producing polyethylene by polymerizing propylene monomer in an amount greater than 0% and less than or equal to 5% by weight of the total monomer content. Claim 18 A method for preventing monofilament during melt spinning of polyethylene, wherein the method is characterized by using polymerized polyethylene by controlling the particle size of a Ziegler-Natta catalyst. Claim 19 In claim 18, the polyethylene has an oxidative induction time of 10 minutes or more at a temperature of 210 to 230 ℃ using a rotational rheometer, and a peak corresponding to polypropylene is present when measured by NMR. Claim 20 In claim 18, the method 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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