Preparation method of polyolefin material with low dissolved matter and low ash content

Abstract

The invention belongs to the field of polyolefin preparation, and relates to a preparation method of a polyolefin material with low dissolved matter and low ash content. The method comprises the following steps: (1) adding a polyolefin resin raw material and a fatty ester solvent into an extraction kettle of a supercritical extraction device, introducing a gas medium into the extraction kettle, adjusting the temperature and pressure of the extraction kettle to enable the gas medium to be in a supercritical state, and treating the polyolefin resin raw material in supercritical fluid; the fatty ester solvent is at least one of fatty ester solvents of C2-C10; and (2) cooling and decompressing to separate the polyolefin resin raw material from the solvent, and drying to obtain the polyolefin material with low dissolved matter and low ash content. The method provided by the invention avoids the problems of complex solvent recovery and high difficulty in removal of the high-boiling-point chelating agent in the traditional deliming process, and the used fatty ester solvent can be easily removed without causing pollution to the polyolefin resin.

Description

Technical Field

[0001] This invention belongs to the field of polyolefin preparation, specifically, it relates to a method for preparing polyolefin materials with low leachate and low ash content. Background Technology

[0002] Polyolefin materials such as polyethylene (PE), polypropylene (PP), ethylene-α-olefin copolymers, and ethylene-cycloolefin copolymers (COC) possess excellent mechanical properties, good machinability, and outstanding chemical stability, and are widely used in agriculture, electronics, pharmaceuticals, and construction, playing an irreplaceable role in daily life. However, residual metal impurities in polyolefins can adversely affect the color, electrical properties, and optical properties of the products. Furthermore, metal ions and leached low-molecular-weight polymers may leach out during use, contaminating contact items and affecting usability. Therefore, industries with high purity requirements, such as packaging, medical devices, optical equipment, and electronics, have extremely stringent requirements for the metal and leached content of polyolefin products. Polyolefin materials with low leaching and low metal impurities are currently one of the key directions in polyolefin development and preparation.

[0003] Currently, in industry, complexation adsorption is generally used to treat polyolefin solutions to reduce their ash content. In practice, the adsorption column containing the deashing adsorbent is typically heated to above 100°C before the polyolefin solution is injected into it for metal complexation adsorption to remove metal ions. While this method effectively reduces metal impurities in polyolefins, it is only applicable to polyolefin solutions. Except for solution polymerization, which directly yields the polymer solution, polymers obtained through other polymerization methods require dissolution in a large amount of solvent before adsorption and deashing can be performed, making the process relatively complex. For example, CN202210909910.6 describes first impregnating or dissolving polyolefin resin in a hydrocarbon solvent, then adding an acidic reagent for further impregnation or dissolution to obtain a pretreated polyolefin mixture. A complexing agent is then added to this mixture to initiate a metal complexation reaction, followed by elution with an eluent, thereby reducing residual metal impurities in the polyolefin. This process not only fails to effectively remove low molecular weight polymers, but it is also cumbersome, consuming large amounts of solvent and time. Furthermore, it introduces multiple solvents, including hydrocarbon solvents, acidic reagents, metal complexing agents, and eluents, making the removal process complex and solvent recovery difficult. CN202210413155.2 uses the chelating agent triazine to chelate and adsorb metal ions in a polyolefin solution to form a complex. The solution containing the complex is then purified by adsorption using an adsorption column to remove metal impurities from the polyolefin. However, triazine has a high boiling point of 350℃; if elution is incomplete, it may remain in the polyolefin, making removal difficult and posing a risk of contaminating the polyolefin.

[0004] Therefore, developing new methods for preparing polyolefin materials with low solubility and low ash content suitable for industrial production remains one of the urgent problems to be solved in this field.

[0005] Supercritical fluid extraction technology boasts advantages such as strong dissolving power, high efficiency, environmental friendliness, and mild operating conditions, demonstrating excellent application results in polymer purification. CN116217910A utilizes supercritical carbon dioxide fluid to extract most oligomers and tetrahydrofuran from polyesters containing 1,4-butanediol dicarboxylic acid structural units, yielding polyesters with low migration. CN1993385A describes the extraction of olefin polymers using static / flowing supercritical carbon dioxide, finding a significant reduction in impurities (mainly low molecular weight oligomers) in polypropylene after first undergoing flowing supercritical carbon dioxide extraction followed by static supercritical carbon dioxide treatment, making it suitable for manufacturing ultra-high purity products. However, this method uses pressures as high as 65 MPa and does not mention changes in the metal content of the polymer. Patent CN113500053A uses 75% ethanol to purify polypropylene granules under supercritical carbon dioxide conditions, reducing the ash content in polypropylene; however, the moisture introduced during purification is difficult to remove, resulting in low drying efficiency. There is still room for further improvement in the ash removal rate and soluble matter removal efficiency of the methods described in the aforementioned patents. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for preparing polyolefin materials with low solubility and low ash content. This method is based on supercritical fluid extraction technology, which simultaneously reduces the ash content of polyolefins and efficiently removes soluble low molecular weight polymers by selecting a suitable solvent. The aliphatic ester solvent used has the characteristics of low boiling point, strong solubility, and good diffusion volatility, leaving no more than 0.5 ppm residue in the polyolefin. This avoids the problems of complex solvent recovery and difficulty in removing high-boiling-point chelating agents in existing deashing processes. It has advantages such as simple process, easy operation, high removal efficiency, and low cost, and is applicable to polyolefin products of different forms prepared by various processes.

[0007] This invention provides a method for preparing a polyolefin material with low leachate and low ash content, comprising the following steps:

[0008] (1) The polyolefin resin raw material and a fatty ester solvent are added to the extraction vessel of a supercritical extraction device. A gaseous medium is introduced into the extraction vessel, and the temperature and pressure of the extraction vessel are adjusted to bring the gaseous medium into a supercritical state. The polyolefin resin raw material is then treated in a supercritical fluid. The fatty ester solvent is C2-C. 10 At least one of the fatty ester solvents;

[0009] (2) Cool down and depressurize to separate the polyolefin resin raw material from the solvent phase and dry it to obtain the polyolefin material with low solubility and low ash content.

[0010] This invention provides a method for preparing polyolefin materials with low leachate and low ash content. Compared with the prior art, the advantages of this invention are as follows:

[0011] (1) The method provided by the present invention has a wide range of applications and can be used for polyolefin products of different forms and different basic impurity contents prepared by various production processes.

[0012] (2) The method provided by the present invention has high efficiency in removing metal impurities from polyolefins and simultaneously achieves the removal and control of the content of soluble polymers, which significantly improves the purity and precipitation resistance of polyolefin resins.

[0013] (3) The method provided by the present invention avoids the problems of complex solvent recovery and difficulty in removing high-boiling-point chelating agents in traditional deashing processes. The fatty ester solvents used can be easily removed and will not cause pollution to polyolefin resin.

[0014] (4) The method provided by the present invention is simple to operate, has a short process flow, and uses solvents in a recyclable manner, which will not cause pollution to the environment and is conducive to industrialization and widespread application.

[0015] Other features and advantages of the present invention will be described in detail in the following detailed description section. Detailed Implementation

[0016] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0017] This invention provides a method for preparing a polyolefin material with low leachate and low ash content, comprising the following steps:

[0018] (1) The polyolefin resin raw material and a fatty ester solvent are added to the extraction vessel of a supercritical extraction device. A gaseous medium is introduced into the extraction vessel, and the temperature and pressure of the extraction vessel are adjusted to bring the gaseous medium into a supercritical state. The polyolefin resin raw material is then treated in a supercritical fluid. The fatty ester solvent is C2-C. 10 At least one of the fatty ester solvents;

[0019] (2) Cool down and depressurize to separate the polyolefin resin raw material from the solvent phase and dry it to obtain the polyolefin material with low solubility and low ash content.

[0020] According to the preparation method proposed in this invention, the prepared polyolefin resin has low metal impurities, controllable soluble content, and no risk of introducing new impurities.

[0021] The fatty ester solvents described in this invention are selected from at least one of ethyl formate, propyl formate, n-butyl formate, isobutyl formate, methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate, dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate. Preferably, they are ester solvents with a boiling point of 20-100°C at room temperature and pressure. Ester solvents meeting the above boiling point conditions are selected from at least one of ethyl formate, propyl formate, isobutyl formate, methyl acetate, ethyl acetate, and dimethyl carbonate.

[0022] The amount of the fatty ester solvent should be as small as possible while ensuring the impurity removal effect. According to a preferred embodiment of the present invention, the mass ratio of the fatty ester solvent to the polyolefin resin raw material is (0.5-40):1, and more preferably (2-20):1.

[0023] The method of the present invention is carried out in the presence of a supercritical fluid, and various gaseous media that provide supercritical conditions conventional in the art can be used. Preferably, the gaseous medium is at least one of carbon dioxide, ethane, propane and nitrogen dioxide, and correspondingly, the supercritical fluid is at least one of supercritical carbon dioxide, supercritical ethane, supercritical propane and supercritical nitrogen dioxide.

[0024] Once the gas medium is determined, the corresponding temperature and pressure conditions can also be determined. Specifically, the temperature of the extraction vessel is adjusted to 60-140℃ and the pressure to 5-25MPa; the treatment time of the polyolefin resin raw material in the supercritical fluid is 2-10 hours, preferably 4-8 hours.

[0025] To further enhance the diffusion and solubility of the fatty ester solvent in the polymer network, step (1) preferably includes adding a co-solvent to the extraction vessel, i.e., using a mixed solvent, wherein the co-solvent is one of an alkane solvent and a haloalkane solvent with a boiling point of 20-90℃; preferably at least one of n-pentane, n-hexane, cyclohexane, petroleum ether, dichloromethane, trichloromethane and dichloroethane.

[0026] According to a preferred embodiment of the present invention, the mass ratio of the fatty ester solvent to the co-solvent is (0.2-4):1, more preferably (0.5-2):1.

[0027] The method proposed in this invention is applicable to processing polyolefin resins in different states obtained by various polymerization methods, and has good universality and significant impurity removal effect.

[0028] Specifically, the resin in the polyolefin resin raw material includes, but is not limited to, at least one of polyethylene, polypropylene, ethylene-α-olefin copolymer, ethylene-cyclic olefin copolymer, propylene-α-olefin copolymer, and propylene-cyclic olefin copolymer. The α-olefin typically refers to C3-C4. 12 olefins.

[0029] In particular, the method of the present invention is applicable to the purification of solid polyolefin resins, wherein the polyolefin resin raw material can be in any solid form, including but not limited to powder, granules, flakes or other shapes.

[0030] According to the method of the present invention, after the solvent phase is separated from the polyolefin resin raw material, it can be recovered by distillation and recycled. The term "solvent phase" in this invention refers to all solvents in the system. When only aliphatic ester solvents are used, the "solvent phase" refers to the aliphatic ester solvents; when a mixed solvent of aliphatic ester solvents and co-solvents is used, the "solvent phase" refers to the mixed solvent.

[0031] The present invention does not particularly limit the drying conditions in step (2), as long as the residual solvent phase is evaporated as cleanly as possible. Preferably, the drying conditions include vacuum drying at 70-110°C for 2-10 hours.

[0032] The method of the present invention has no significant effect on the weight of the polyolefin resin raw material. After supercritical treatment and drying, the weight of the obtained polyolefin resin is reduced by 0-2 wt% compared with that before treatment.

[0033] Compared with the untreated polyolefin resin raw material, the polyolefin resin prepared by the method provided by the present invention has an ash removal efficiency of 60%-90% and a soluble content reduction efficiency of 60%-95%.

[0034] According to the method of the present invention, the polyolefin material with low solubility and low ash content obtained after treatment has an ash content of no more than 30 ppm, a residual amount of fatty ester solvents of no more than 0.5 ppm, and a soluble content of less than 0.2 wt%, wherein the soluble content is tested according to the standard GB / T 5009.58-2003.

[0035] Normally, the method of the present invention can reduce the impurities in polyolefin resin raw materials to the expected standard by performing it once. If necessary, the above process can be repeated 1-2 times to further reduce the ash content and solubles of polyolefin materials.

[0036] Compared to polyolefin resins that have only been treated once: resins treated twice will have their ash content further reduced by 0-2 ppm and their soluble content reduction efficiency further increased by 0-3%; resins treated three times will have their ash content further reduced by 0-3 ppm and their soluble content reduction efficiency further increased by 0-5%.

[0037] The present invention will be further described below with reference to the embodiments, but the scope of the present invention is not limited to these embodiments.

[0038] The following test methods were used in the following examples and comparative examples:

[0039] The ash content in polyolefins was determined by direct calcination method according to the national standard GB / T 9345.1-2008.

[0040] The content of residual solvent components in polyolefins is determined according to the VDA277 test standard of the German Association of the Automotive Industry.

[0041] Content of soluble low molecular weight polymers in polyolefins: According to the standard test of GB / T 5009.58-2003, weigh about 2.00g of sample into a flask with a 250mL reflux condenser, add 100mL of n-hexane, connect the condenser tube, heat and reflux in an 80℃ water bath for 2h, immediately filter with rapid qualitative filter paper, wash the filter and sample with a small amount of n-hexane, combine the washings and filtrate, then put the n-hexane into a small bottle of a pre-concentrated concentrator, concentrate and recover the n-hexane, dry the residue at 100-105℃ for 2h, cool in a desiccator for 30min, and weigh.

[0042] Example 1

[0043] 50g of polyethylene granules and 500g of ethyl formate were added to the extraction vessel of a supercritical extraction device. Carbon dioxide was injected into the vessel, and the pressure was maintained at 12MPa. After treatment at 100℃ for 6 hours, the temperature was lowered and the pressure was released to separate the polyethylene from the ethyl formate. The resulting polyethylene was then vacuum dried at 90℃ for 5 hours.

[0044] Example 2

[0045] Add 50g of polyethylene granules and 500g of ethyl acetate to the extraction vessel of the supercritical extraction device. After injecting carbon dioxide, maintain the pressure at 12MPa and treat at 100℃ for 6 hours. Then cool down and depressurize to separate the polyethylene from the ethyl acetate. The obtained polyethylene is then vacuum dried at 90℃ for 5 hours.

[0046] Example 3

[0047] Add 50g of polyethylene granules and 100g of ethyl acetate to the extraction vessel of a supercritical extraction device. After injecting carbon dioxide, maintain the pressure at 12MPa and treat at 100℃ for 6 hours. Then cool down and depressurize to separate the polyethylene from the ethyl acetate. Dry the obtained polyethylene under vacuum at 90℃ for 5 hours.

[0048] Example 4

[0049] 50g of polypropylene granules and 500g of dimethyl carbonate were added to the extraction vessel of a supercritical extraction device. Carbon dioxide was injected into the vessel, and the pressure was maintained at 12MPa. After treatment at 100℃ for 6 hours, the temperature was lowered and the pressure was released to separate the polypropylene from the dimethyl carbonate. The resulting polypropylene was then vacuum dried at 90℃ for 5 hours.

[0050] Example 5

[0051] The polypropylene granules treated in Example 4 were subjected to a second treatment. 50g of the treated polypropylene granules and 200g of dimethyl carbonate were added to the extraction vessel of the supercritical extraction device. Carbon dioxide was injected into the vessel, and the pressure was maintained at 12MPa. After treatment at 100°C for 6 hours, the temperature was lowered and the pressure was released to separate the polypropylene from the dimethyl carbonate. The resulting polypropylene was then vacuum dried at 90°C for 5 hours.

[0052] Example 6

[0053] 50g of polyethylene granules and 500g of n-butyl acetate were added to the extraction vessel of a supercritical extraction device. Carbon dioxide was injected into the vessel, and the pressure was maintained at 12MPa. After treatment at 100℃ for 6 hours, the temperature was lowered and the pressure was released to separate the polyethylene from the n-butyl acetate. The resulting polyethylene was then vacuum dried at 90℃ for 5 hours.

[0054] Example 7

[0055] Add 50g of polyethylene granules, 200g of dichloromethane and 200g of ethyl acetate to the extraction vessel of a supercritical extraction device. After injecting carbon dioxide into the vessel, maintain the pressure at 14MPa and treat at 100℃ for 4 hours. Then cool down and depressurize to separate the polyethylene from the dichloromethane and ethyl acetate. Dry the polyethylene under vacuum at 90℃ for 5 hours.

[0056] Example 8

[0057] Add 50g of polyethylene granules, 200g of n-hexane, and 200g of ethyl acetate to the extraction vessel of a supercritical extraction apparatus. After injecting carbon dioxide, maintain the pressure at 14MPa and treat at 100℃ for 4 hours. Then cool down and depressurize to separate the polyethylene from the ethyl acetate and n-hexane. Dry the polyethylene under vacuum at 90℃ for 5 hours.

[0058] Example 9

[0059] 50g of polypropylene granules, 200g of methyl acetate and 200g of dimethyl carbonate were added to the extraction vessel of a supercritical extraction device. Carbon dioxide was injected into the vessel, and the pressure was maintained at 14MPa. After treatment at 100℃ for 4 hours, the temperature was lowered and the pressure was released to separate the polypropylene from the ethyl acetate and dimethyl carbonate. The polyethylene was then vacuum dried at 90℃ for 5 hours.

[0060] Example 10

[0061] 50g of cyclic olefin copolymer granules and 200g of ethyl acetate were added to the extraction vessel of a supercritical extraction device. Carbon dioxide was injected into the vessel, and the pressure was maintained at 14MPa. After treatment at 60℃ for 4 hours, the temperature was lowered and the pressure was released to separate the cyclic olefin copolymer from the ethyl acetate. The cyclic olefin copolymer was then vacuum dried at 90℃ for 5 hours.

[0062] Example 11

[0063] 50g of polyethylene granules, 300g of cyclohexane and 200g of n-butyl acetate were added to the extraction vessel of a supercritical extraction device. Carbon dioxide was injected into the vessel, and the pressure was maintained at 12MPa. After treatment at 100℃ for 6 hours, the temperature was lowered and the pressure was released to separate the polyethylene from the cyclohexane and n-butyl acetate. The obtained polyethylene was then vacuum dried at 90℃ for 5 hours.

[0064] Example 12

[0065] Add 50g of polyethylene granules and 500g of ethyl acetate to the extraction vessel of a supercritical extraction apparatus. After injecting propane into the vessel, maintain the pressure at 6MPa and treat at 100℃ for 6 hours. Then cool down and depressurize to separate the polyethylene from the ethyl acetate. The resulting polyethylene is then vacuum dried at 90℃ for 5 hours.

[0066] Comparative Example 1

[0067] Add 50g of polyethylene granules and 500g of ethyl acetate to a flask with a 1L reflux condenser, and heat under reflux in an oil bath at 100°C for 6 hours. Filter the mixture containing the resin raw materials, and then vacuum dry the resulting polyethylene at 90°C for 5 hours.

[0068] Comparative Example 2

[0069] Without introducing fatty ester solvents, 50g of polyethylene granules were directly added to the extraction vessel of the supercritical extraction device. After injecting carbon dioxide, the pressure was maintained at 12MPa. After treatment at 100℃ for 6 hours, the temperature was lowered and the pressure was released. The resulting polyethylene was then vacuum dried at 90℃ for 5 hours.

[0070] Comparative Example 3

[0071] The process was carried out according to the method of Example 1, except that ethyl formate was replaced with ethanol.

[0072] Comparative Example 4

[0073] The process was carried out according to the method of Example 1, except that ethyl formate was replaced with cyclohexane.

[0074] Test case

[0075] The ash content, soluble content, and solvent residue in the polyolefin resins obtained in each example and comparative example were tested, and the data are shown in Table 1 below.

[0076] Table 1

[0077]

[0078]

[0079] In Examples 1-12, the ash content and soluble content of different types and states of polyolefin resins treated by the method provided by this invention were significantly reduced, and the precipitation resistance was improved. Furthermore, the aliphatic ester solvents used had low boiling points and suitable polarity, exhibiting good solubility and volatility, leaving almost no residue in the resin and ensuring the high purity of the polyolefins. Compared to Example 2, Comparative Example 1 did not use supercritical fluid assistance, and the removal effect of aliphatic ester solvents on ash and soluble matter was significantly reduced. In Comparative Example 2, the ash and soluble matter content of the polyolefin resin treated only with supercritical fluid was relatively high, indicating that aliphatic ester solvents can promote the dissolution and extraction of metal ions and soluble matter. Comparative Example 3 used ethanol solvent, a solvent used in the prior art, and the ash removal efficiency and soluble matter removal efficiency were worse than those of the aliphatic ester solvent of this invention. Comparative Example 4 used only a co-solvent, and the removal rate of metal impurities was significantly lower than that of Example 1.

[0080] The above examples and comparative examples verify that the preparation method of low-leaching and low-ash polyolefin materials provided by the present invention has significant effects. Based on supercritical fluid-assisted extraction technology and combined with fatty ester solvents, it can effectively remove ash and soluble substances from various polyolefins in different states, with almost no solvent residue. This makes up for the shortcomings of existing deashing processes, such as narrow applicability, long process flow, complex solvent recovery, and difficulty in removing high-boiling-point chelating agents.

[0081] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0082] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A method for preparing a polyolefin material with low leachate and low ash content, comprising the following steps: (1) The polyolefin resin raw material and a fatty ester solvent are added to the extraction vessel of a supercritical extraction device. A gaseous medium is introduced into the extraction vessel, and the temperature and pressure of the extraction vessel are adjusted to bring the gaseous medium into a supercritical state. The polyolefin resin raw material is then treated in a supercritical fluid. The fatty ester solvent is C2-C. 10 At least one of the fatty ester solvents; (2) Cool down and depressurize to separate the polyolefin resin raw material from the solvent phase and dry it to obtain the polyolefin material with low solubility and low ash content.

2. The preparation method according to claim 1, wherein, The fatty ester solvent is selected from at least one of ethyl formate, propyl formate, n-butyl formate, isobutyl formate, methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate, preferably at least one of ethyl formate, propyl formate, isobutyl formate, methyl acetate, ethyl acetate, and dimethyl carbonate.

3. The preparation method according to claim 1, wherein, The mass ratio of the fatty ester solvent to the polyolefin resin raw material is (0.5-40):1, preferably (2-20):

1.

4. The preparation method according to claim 1, wherein, The gaseous medium is at least one of carbon dioxide, ethane, propane, and nitrogen dioxide, and correspondingly, the supercritical fluid is at least one of supercritical carbon dioxide, supercritical ethane, supercritical propane, and supercritical nitrogen dioxide.

5. The preparation method according to claim 4, wherein, Adjust the temperature of the extraction vessel to 60-140℃ and the pressure to 5-25MPa; treat the polyolefin resin raw material in supercritical fluid for 2-10 hours, preferably 4-8 hours.

6. The preparation method according to claim 1, wherein, Step (1) further includes adding a co-solvent to the extraction vessel, wherein the co-solvent is one of an alkane solvent and a haloalkane solvent with a boiling point of 20-90℃; preferably at least one of n-pentane, n-hexane, cyclohexane, petroleum ether, dichloromethane, trichloromethane and dichloroethane.

7. The preparation method according to claim 6, wherein, The mass ratio of the co-solvent to the fatty ester solvent is (0.2-4):1, preferably (0.5-2):

1.

8. The preparation method according to claim 1, wherein, The resin in the polyolefin resin raw material includes at least one of polyethylene, polypropylene, ethylene-α-olefin copolymer, ethylene-cyclic olefin copolymer, propylene-α-olefin copolymer, and propylene-cyclic olefin copolymer.

9. The preparation method according to claim 1, wherein, The polyolefin resin raw material is solid, preferably in powder, granule, flake, or other form.

10. The preparation method according to claim 1, wherein, After the solvent phase is separated from the polyolefin resin raw material, it is recovered by distillation and reused.

11. The preparation method according to claim 1, wherein, The drying conditions include vacuum drying at 70-110°C for 2-10 hours.

12. The preparation method according to claim 1, wherein, The polyolefin material with low solubility and low ash content has an ash content of no more than 30 ppm, a residual amount of fatty ester solvents of no more than 0.5 ppm, and a soluble content of less than 0.2 wt%. The soluble content is tested according to the standard GB / T5009.58-2003.

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