Polyolefin in-situ blend, its preparation method and application

Abstract

This invention discloses an in-situ polyolefin blend, its preparation method, and its applications. The in-situ polyolefin blend comprises polyolefin A and polyolefin B. Polyolefin A is an ethylene homopolymer or a copolymer of ethylene and α-olefin, with a weight-average molecular weight ≥800 kg / mol, and accounts for 50-99 wt% of the total mass of the blend. Polyolefin B is a synthetic mineral wax with a weight-average molecular weight of 300-30000 g / mol. Specifically, the polyolefin A particles on the surface of the in-situ blend exhibit a nanosheet structure with a thickness of 10-300 nm and a spacing between adjacent lamellar crystals of 200-4000 nm. The thickness and spacing of the nanosheets can be adjusted by the type and content of polyolefin B. The melt index of the in-situ polyolefin blend is 0.1-12 g / 10 min. When this in-situ polyolefin blend is added to general-purpose polyolefin materials at an addition rate of 1-50 wt%, it can increase the tensile breaking strength of general-purpose polyolefin materials by 40-250% and the single-notch impact strength of cantilever beams by 200-700%.

Description

Technical Field

[0001] This invention relates to a polyolefin material, and more specifically, to a polyolefin in-situ blend, its preparation method, and its application. Background Technology

[0002] Polyolefin resins (such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE) are widely used in packaging, construction, and automotive industries due to their excellent chemical stability, ease of processing, and low cost. Compared to other engineering plastics, polyolefin materials suffer from low strength, poor heat resistance, static electricity, and poor thermal conductivity, which significantly limit their application in many engineering fields. Adding a suitable proportion of polyolefin functional additives can improve many of these shortcomings while endowing them with one or more functional properties. Developing functional materials with intelligent properties can significantly increase the added value of polyolefin materials, broaden their application areas, and is of great significance for the practical application of polyolefin materials.

[0003] Improving the strength, rigidity, and toughness of polyolefin resins has long been a crucial issue for polyolefin materials. The conventional method for polyolefin reinforcement modification is additive, which involves adding inorganic salts or oxides such as calcium carbonate and titanium dioxide in the molten state at a ratio of 0.5% to 5% to polyolefin materials such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE) to improve their strength, rigidity, and toughness. However, inorganic salts or oxides such as calcium carbonate and titanium dioxide have compatibility issues with polyolefin materials, making it difficult to achieve good blending and limiting the modification effect. Adding excessive amounts of inorganic salts or oxides can easily lead to phase separation, which in turn reduces the strength, rigidity, and toughness of the polyolefin material. The initial intention of this invention is to develop novel polyolefin-based reinforcing materials, aiming to design and prepare such materials to solve the problems of poor blend compatibility, low addition ratios, and limited modification, reinforcement, and toughening effects during material modification. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention aims to provide a polyolefin in-situ blend, its preparation method and application. This polyolefin in-situ blend can be used as a reinforcing agent to enhance and toughen general-purpose polyolefin materials. Furthermore, when this polyolefin in-situ blend is blended with general-purpose polyolefin materials, it exhibits excellent processing performance and is easy to process.

[0005] According to one objective of the present invention, a polyolefin in-situ blend is provided, comprising polyolefin A and polyolefin B, wherein polyolefin A is an ethylene homopolymer or a copolymer of ethylene and α-olefin, having a weight-average molecular weight ≥800 kg / mol, and the mass percentage of polyolefin A in the polyolefin in-situ blend is 50-99 wt%; polyolefin B is a synthetic mineral wax, having a weight-average molecular weight of 300-30000 g / mol, and the mass percentage of polyolefin B in the polyolefin in-situ blend is 1-50 wt%; the polyolefin A on the surface of the polyolefin in-situ blend particles exhibits a nanosheet structure, the nanosheet thickness is 10-300 nm, and the spacing between adjacent lamellar crystals is 200-4000 nm; the melt index of the polyolefin in-situ blend is 0.1-12 g / 10 min.

[0006] According to a preferred embodiment of the present invention, the molecular weight distribution index of the polyolefin in situ blend is 30-500, the degree of branching of polyolefin A is 0.1-50C / 10000C, the melting point is 130-145℃, and the degree of branching of polyolefin B is 0.1-50C / 10000C, the melting point is 50-110℃.

[0007] According to a preferred embodiment of the present invention, the polyolefin B uniformly occupies the space between the polyolefin A nanosheets, and the crystallinity of the polyolefin in situ blend is 60-99%.

[0008] According to a preferred embodiment of the present invention, the thickness and spacing of the nanosheets can be adjusted by the type and content of polyolefin B.

[0009] According to another objective of the present invention, the present invention provides a method for preparing the above-mentioned polyolefin in-situ blend: the reactor is pre-treated for dehydration and deoxygenation, polyolefin B is pre-dissolved completely in solvent C, solvent C containing polyolefin B is added to the reactor, and then solvent C, co-catalyst, catalyst and ethylene or ethylene and α-olefin are added in sequence, the mass concentration of polyolefin B in the liquid phase in the reactor is maintained at 0.5-15 wt%, the polymerization reaction is carried out at a set temperature and pressure for a period of time, the material is cooled, discharged and dried to obtain the polyolefin in-situ blend.

[0010] According to a preferred embodiment of the present invention, the polyolefin B is selected from polyolefin materials with a molecular weight not exceeding 10000 g / mol, and is preferably one or more of polyethylene wax, polypropylene wax, polyamide wax, Fischer-Tropsch wax, paraffin wax, oxidized polyethylene wax, and oxidized polypropylene wax.

[0011] According to a preferred embodiment of the present invention, the solvent C is selected from one or more of n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, 2-methylpentane, 3-methylpentane, n-heptane, 2-methylhexane, 3-methylhexane, n-octane, 2-methylheptane, 3-methylheptane, n-nonane, and n-decane.

[0012] According to a preferred embodiment of the present invention, the co-catalyst is selected from one or more of methylaluminoxane, modified methylaluminoxane, ethylaluminoxane, butylaluminoxane, trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, diethylaluminum chloride, diethylaluminum chloride, triphenylborane, tri(4-fluorophenyl)borane, tri(pentafluorophenyl)borane, tri(3,5-difluorophenyl)borane, and tri(2,4,6-trifluorophenyl)borane; the catalyst is selected from one or more of metallocene catalysts, post-transition metal catalysts, Ziegler-Natta catalysts, non-metallocene catalysts, and FI catalysts.

[0013] According to a preferred embodiment of the present invention, the α-olefin selected in the polymerization is one or more of 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, or 1-decene.

[0014] According to a preferred embodiment of the present invention, the polymerization reaction is characterized by a temperature of 50-110°C, a pressure of 1-50 bar, and a polymerization time of 0.1-10 h.

[0015] According to a third objective of the present invention, the present invention provides an application of the above-mentioned in-situ polyolefin blend as a blending modifier for general-purpose polyolefin materials. The general-purpose polyolefin material can be HDPE, LDPE, LLDPE, POE, EVA, etc.

[0016] Preferably, the in-situ blend of the polyolefin is added to HDPE, LDPE, LLDPE, POE, or EVA at an addition amount of 1-50 wt%, thereby increasing the tensile breaking strength of HDPE, LDPE, LLDPE, POE, or EVA by 40-250% and the cantilever beam single-notch impact strength by 200-700%.

[0017] Compared with the prior art, the present invention has the following outstanding advantages: (1) In the polyolefin in-situ blend of the present invention, the high molecular weight polyolefin A component and the low molecular weight polyolefin B component have a microphase separation structure (see Figure 1 and Figure 2The microphase separation structure exhibits an interpenetrating phenomenon. This microphase separation structure allows the low molecular weight polyolefin B to lubricate the molecular chains of the high molecular weight polyolefin A and the general polyolefin more quickly and significantly when the polyolefin in situ blend is blended with general polyolefin materials. The molecular chains of high molecular weight polyolefin A can open up more quickly, and there is less entanglement between and within the molecular chains. As a result, the molecular chains of polyolefin A have a higher degree of orientation during the orientation process, making it easier to form a tandem crystal reinforcement structure. This significantly improves the strength, rigidity, and toughness of general polyolefin materials (HDPE, LDPE, LLDPE, POE, EVA, etc.).

[0018] (2) When polyolefin in-situ blends are used to reinforce general-purpose polyolefin materials, the wax molecular chains of low molecular weight polyolefin B have higher lubrication efficiency, resulting in a shorter screw processing cycle and lower material torque on the screw, making the processing more efficient. Attached Figure Description

[0019] Figure 1 These are scanning electron microscope images of the in-situ polyolefin blends in Examples 1-4.

[0020] Figure 2 The images are scanning electron microscope (SEM) images of the surface of polyolefin A particles after eluting polyolefin component B with n-heptane in the polyolefin in situ blends of Examples 1-4. Detailed Implementation

[0021] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0022] The following methods are used to test the structure or properties of the polyolefins produced in the embodiments described:

[0023] Scanning electron microscopy (SEM) is used to test the lamellar thickness and interlamellar spacing of polyolefin materials (see...). Figure 2 ).

[0024] Differential scanning calorimetry (DSC) is used to determine the melting point and crystallinity of polyolefin materials.

[0025] High-temperature gel permeation chromatography (GPC) is used to determine the molecular weight and distribution of polyolefin materials.

[0026] The universal testing machine is used to test the tensile breaking strength of polyolefin materials.

[0027] Impact testing machines are used to test the single-notch impact strength of cantilever beams in polyolefin materials.

[0028] Nuclear magnetic resonance spectrometer (NMR spectrometer) 13 C-NMR is used to test the degree of branching of polyolefin materials.

[0029] A melt indexer is used to test the melt index of polyolefin materials.

[0030] Polyolefin B component in the in-situ polyolefin blend was separated by heating and rinsing with n-heptane, thereby determining the mass ratio of polyolefin A and polyolefin B.

[0031] Example 1

[0032] The polymerization apparatus was purged with high-purity nitrogen to remove moisture and oxygen. Polyethylene wax (weight average molecular weight 800 g / mol, melting point 86℃, branching degree 2.3C / 10000C) was pre-dissolved in hexane. The hexane solution of polyethylene wax was added to the reactor, followed by hexane, methylaluminoxane, and a supported metallocene catalyst. The polyethylene wax accounted for 5 wt% of the total liquid phase in the reactor. Ethylene was introduced to start polymerization. The polymerization temperature was 80℃, the polymerization pressure was 12 bar, and the polymerization time was 2 hours. After cooling, discharge, and drying, polyolefin in-situ blend 1 was obtained.

[0033] The characterization results of polyolefin in situ blend 1 are shown in Table 1. The reinforcement and toughening results of polyolefin in situ blend 1 on high-density polyethylene (HDPE) are shown in Table 2 (polyolefin in situ blend 1 accounts for 10 wt% of the total mass of the reinforced and toughened product).

[0034] Example 2

[0035] The polymerization apparatus was purged with high-purity nitrogen to remove moisture and oxygen. Polyethylene wax (weight-average molecular weight 1300 g / mol, melting point 96℃, branching degree 2.1C / 10000C) was pre-dissolved in n-heptane. The n-heptane solution of polyethylene wax was added to the reactor, followed by n-heptane, methylaluminoxane, a supported metallocene catalyst, and the comonomer 1-hexene. The polyethylene wax accounted for 3 wt% of the total liquid phase in the reactor. Ethylene was then introduced to initiate polymerization at 76℃, 8 bar, and 3 h. After cooling, discharging, and drying, polyolefin in-situ blend 2 was obtained.

[0036] The characterization results of polyolefin in situ blend 2 are shown in Table 1. The reinforcement and toughening results of polyolefin in situ blend 2 on high-density polyethylene (HDPE) are shown in Table 2 (polyolefin in situ blend 2 accounts for 20 wt% of the total mass of the reinforced and toughened product).

[0037] Example 3

[0038] The polymerization apparatus was purged with high-purity nitrogen to remove moisture and oxygen. Oxidized polyethylene wax (weight-average molecular weight 3700 g / mol, melting point 104℃, branching degree 2.7C / 10000C) was pre-dissolved in n-heptane. The n-heptane solution of oxidized polyethylene wax was added to the reactor, followed by n-heptane, triethylaluminum, supported Ziegler-Natta catalyst, and the comonomer 1-octene. The oxidized polyethylene wax accounted for 6 wt% of the total liquid phase in the reactor. Ethylene was then introduced to initiate polymerization at 86℃, 17 bar, and 4 h. After cooling, discharge, and drying, polyolefin in-situ blend 3 was obtained.

[0039] The characterization results of polyolefin in situ blend 3 are shown in Table 1. The reinforcement and toughening results of polyolefin in situ blend 3 on high-density polyethylene (HDPE) are shown in Table 2 (polyolefin in situ blend 3 accounts for 8 wt% of the total mass of the reinforced and toughened product).

[0040] Example 4

[0041] The polymerization apparatus was purged with high-purity nitrogen to remove moisture and oxygen. Fischer-Tropsch wax (weight-average molecular weight 700 g / mol, melting point 76℃, branching degree 1.0C / 10000C) was pre-dissolved in n-pentane. The n-pentane solution of Fischer-Tropsch wax was added to the reactor, followed by n-pentane, triethylaluminum, and a supported Ziegler-Natta catalyst. The Fischer-Tropsch wax accounted for 8 wt% of the total liquid phase mass in the reactor. Ethylene was then introduced to initiate polymerization at 76℃, a polymerization pressure of 6 bar, and a polymerization time of 7 h. After cooling, discharge, and drying, polyolefin in-situ blend 4 was obtained.

[0042] The characterization results of polyolefin in situ blend 4 are shown in Table 1. The reinforcement and toughening results of polyolefin in situ blend 4 on high-density polyethylene (HDPE) are shown in Table 2 (polyolefin in situ blend 4 accounts for 25 wt% of the total mass of the reinforced and toughened product).

[0043] Comparative Example 1

[0044] Commercially available ultra-high molecular weight polyethylene powder and polyethylene wax were physically blended (the weight-average molecular weight of ultra-high molecular weight polyethylene was 2260 kg / mol, the degree of branching was 0.12 C / 10000 C, and the mass ratio was 86 wt%; the weight-average molecular weight of polyethylene wax was 0.8 kg / mol, the degree of branching was 2.1 C / 10000 C, and the mass ratio was 14 wt%), and then melt-blended with high-density polyethylene (HDPE) and injection molded. The mechanical properties were characterized as shown in Table 2 (HDPE accounted for 90 wt% of the total mass of the product after blending and injection molding).

[0045] Comparative Example 2

[0046] High-density polyethylene (HDPE) products, composed of high-molecular-weight polyethylene (HMWPE) and low-molecular-weight polyethylene (LMWPE) components, were prepared using the Hostalen tandem process. This HDPE product is a PE100 grade pipe material. The mass ratio of HMWPE to LMWPE in the HDPE product is 48:52. The weight-average molecular weight of the HDPE product is 246 kg / mol, and the molecular weight distribution is 28.9. The weight-average molecular weight of the HMWPE component is 402 kg / mol, and that of the LMWPE component is 102 kg / mol. The mechanical properties of the HDPE injection-molded specimens are shown in Table 2.

[0047] Comparative Example 3

[0048] In-situ polyethylene blends were prepared using a dual-reactor tandem process. In the first reactor, ethylene monomer oligomerization was performed, yielding oligomeric components with molecular weights ranging from 58 to 1000 g / mol. Olefins with fewer than 20 carbon atoms constituted the liquid phase (major component), while olefins with more than 20 carbon atoms constituted the solid phase (minor component), with a mass concentration of less than 0.2 wt% in the reaction system. The second reactor underwent copolymerization of ethylene with the product from the first reactor, using a supported metallocene catalyst as the main catalyst and alkylaluminum as the co-catalyst. The polymerization temperature was 60 °C, yielding an in-situ polyethylene blend with a weight-average molecular weight of 320 kg / mol and a molecular weight distribution of 2.8. The major component of this in-situ blend was the polyethylene obtained from the second reactor polymerization, with a very small amount of minor olefins from the first reactor that did not participate in the copolymerization reaction. The mechanical properties of injection-molded samples from this in-situ polyethylene blend are shown in Table 2.

[0049] Table 1. Characterization results of polyolefin in-situ blends from Examples 1-4

[0050] Example 1 Example 2 Example 3 Example 4 Weight-average molecular weight of polyolefin A (kg / mol) 2300 1670 1290 3120 Polyolefin A as a percentage of the blend (wt%) 86 92 76 88 Melting point of polyolefin A (°C) 143.2 142.8 141.6 143.6 Branching degree of polyolefin A (C / 10000C) 0.8 11.3 5.6 0.6 Average thickness of polyolefin A nanosheets (nm) 23.6 20.7 26.1 31.5 Average spacing of polyolefin A (nm) 530 660 290 1200 Weight-average molecular weight of polyolefin B (kg / mol) 0.8 1.3 3.7 0.7 Polyolefin B as a percentage of the blend (wt%) 14 8 4 12 Melting point of polyolefin B (°C) 86 96 104 76 Branching degree of polyolefin B (C / 10000C) 2.3 2.1 2.7 1.0 <![CDATA[Melt index (g / 10 min) of polyolefin in-situ blend a > 3.6 5.7 4.3 1.2 Molecular weight distribution of polyolefin in situ blends 128 182 105 312 Crystallinity (%) of in-situ polyolefin blends 68.3 62.4 65.9 67.3

[0051] a Melt index: melting temperature 190℃, load 10kg.

[0052] Table 2 Results of In-situ Polyolefin Blends on Reinforcing and Toughening General-Purpose Polyolefins

[0053]

[0054]

[0055] As shown in Tables 1 and 2, the results of the in-situ polyolefin blends of Examples 1-4 on the reinforcement and toughening of general-purpose polyolefin high-density polyethylene (HDPE) demonstrate that their reinforcement and toughening effects on HDPE are significant, considerably better than those of the physical blends of ultra-high molecular weight polyethylene (UHMWPE) and polyethylene wax in Comparative Example 1. This is mainly because the polyethylene wax in the in-situ polyolefin blends has a significant lubricating effect on the high-molecular-weight polyethylene component, enabling it to better open the UHMWPE molecular chains. During injection molding, the UHMWPE molecular chains can form more oriented and crystalline structures, resulting in better reinforcement of strength, rigidity, and toughness. In contrast, the physically blended UHMWPE and polyethylene wax powder, during melt blending with HDPE, do not open the UHMWPE molecular chains sufficiently, resulting in excessive physical entanglement within and between molecular chains. This leads to insufficient formation of oriented structures during injection molding, thus limiting the reinforcement and toughening effect on HDPE. The polyethylene samples in Comparative Examples 2 and 3, however, do not contain [specific ingredients]. Figure 2 The nanosheet-like structure shown, and the low molecular weight of the high molecular weight component, result in slow opening of the molecular chains during thermal processing and low content of oriented structure formation, leading to poor mechanical properties of the injection-molded sample.

[0056] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing an in-situ polyolefin blend, characterized in that, The polyolefin in-situ blend comprises polyolefin A and polyolefin B, wherein polyolefin A is an ethylene homopolymer or a copolymer of ethylene and α-olefin, with a weight-average molecular weight ≥800 kg / mol, and the mass percentage of polyolefin A in the polyolefin in-situ blend is 50-99 wt%; polyolefin B is a synthetic mineral wax, with a weight-average molecular weight of 300-30000 g / mol, and the mass percentage of polyolefin B in the polyolefin in-situ blend is 1-50 wt%; the polyolefin A on the surface of the polyolefin in-situ blend particles exhibits a nanosheet structure, with a nanosheet thickness of 10-300 nm and a spacing between adjacent lamellar crystals of 200-4000 nm; the melt index of the polyolefin in-situ blend is 0.1-12 g / 10 min, the melting temperature of the melt index is 190℃, and the load is 10 kg. The polyolefin B uniformly occupies the space between the polyolefin A nanosheets, and the crystallinity of the in-situ polyolefin blend is 60-99%; the thickness and spacing of the nanosheets can be adjusted by the type and content of polyolefin B. The preparation method is as follows: the reactor is pre-treated for dehydration and deoxygenation, polyolefin B is pre-dissolved completely in solvent C, solvent C containing polyolefin B is added to the reactor, and then solvent C, co-catalyst, catalyst and ethylene or ethylene and α-olefin are added in sequence. The mass concentration of polyolefin B in the liquid phase in the reactor is maintained at 3-8 wt%. The polymerization reaction is carried out for a period of time under the set temperature and pressure. After cooling, discharging and drying, the in-situ polyolefin blend is obtained. The polyolefin B is selected from polyolefin materials with a molecular weight not exceeding 10,000 g / mol.

2. The method according to claim 1, characterized in that, The molecular weight distribution index of the polyolefin in situ blend is 30-500, the branching degree of polyolefin A is 0.1-50 C / 10000 C, the melting point is 130-145 ℃, and the branching degree of polyolefin B is 0.1-50 C / 10000 C, the melting point is 50-110 ℃.

3. The method according to claim 1, characterized in that, The polyolefin B is one or more of polyethylene wax, polypropylene wax, polyamide wax, Fischer-Tropsch wax, paraffin wax, oxidized polyethylene wax, and oxidized polypropylene wax.

4. The method according to claim 1, characterized in that, The solvent C is selected from one or more of the following: n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, 2-methylpentane, 3-methylpentane, n-heptane, 2-methylhexane, 3-methylhexane, n-octane, 2-methylheptane, 3-methylheptane, n-nonane, and n-decane.

5. The method according to claim 1, characterized in that, The co-catalyst is selected from one or more of methylaluminoxane, modified methylaluminoxane, ethylaluminoxane, butylaluminoxane, trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, diethylaluminum chloride, diethylaluminum chloride, triphenylborane, tri(4-fluorophenyl)borane, tri(pentafluorophenyl)borane, tri(3,5-difluorophenyl)borane, and tri(2,4,6-trifluorophenyl)borane; the catalyst is selected from one or more of metallocene catalysts, post-transition metal catalysts, Ziegler-Natta catalysts, non-metallocene catalysts, and FI catalysts.

6. The method according to claim 1, characterized in that, The α-olefin selected in the polymerization is one or more of 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, or 1-decene.

7. The method according to claim 1, characterized in that, The polymerization reaction is carried out at a temperature of 50-110 °C, a pressure of 1-50 bar, and a polymerization time of 0.1-10 h.

8. An application of the polyolefin in-situ blend prepared by the method according to any one of claims 1-2, characterized in that, The in-situ blend of the polyolefin is added to HDPE, LDPE, LLDPE, POE, or EVA at an addition amount of 1-50 wt%, thereby increasing the tensile breaking strength of HDPE, LDPE, LLDPE, POE, or EVA by 40-250% and the cantilever beam single-notch impact strength by 200-700%.

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