Preparation method of polyolefin elastomer

Abstract

The invention provides a preparation method of a polyolefin elastomer, and belongs to the technical field of polyolefin production processes. The preparation method comprises the following steps: stirring an olefin monomer, a main catalyst and a co-catalyst in an organic solvent to carry out polymerization reaction under anhydrous and anaerobic conditions, so as to obtain a glue solution containing a polyolefin elastomer; and carrying out deliming and devolatilization on the glue solution through an n-stage screw rod, and then carrying out extrusion granulation to prepare the polyolefin elastomer, wherein n is greater than or equal to 2, and n is an integer.

Description

Technical Field

[0001] The invention relates to the technical field of polyolefin production technology, and in particular to a method for preparing a polyolefin elastomer. Background Art

[0002] In recent years, with the development of the photovoltaic industry, the demand for photovoltaic-grade thermoplastic polyolefin elastomers has increased. Photovoltaic-grade thermoplastic polyolefin elastomers have high requirements for volume resistivity and transmittance, so the removal of ash and volatile matter needs to be emphasized during its production process.

[0003] In the related art, the commonly used post-treatment process of polyolefin solution polymerization mainly uses adsorbents to adsorb ash, then flash evaporation is performed at high temperature, and finally extrusion granulation is performed. However, the process is complicated and energy-intensive, and the adsorption effect of the adsorbent is limited, which makes the removal of ash and volatile matter relatively limited. Summary of the invention

[0004] In view of this, in order to at least partially solve at least one of the above-mentioned technical problems, the present invention provides a method for preparing a polyolefin elastomer.

[0005] According to an embodiment of one aspect of the present invention, a method for preparing a polyolefin elastomer is provided, the method comprising: under water-free and oxygen-free conditions, stirring an olefin monomer, a main catalyst, and a co-catalyst in an organic solvent for polymerization reaction to obtain a rubber solution containing a polyolefin elastomer; passing the rubber solution through an n-stage screw for deashing and devolatilization, and then extruding and granulating to obtain a polyolefin elastomer; wherein n≥2, and n is an integer.

[0006] According to an embodiment of the present invention, n≤4; the temperature of the n-stage screw is 20-220° C., and the rotation speed is 20-200 rpm.

[0007] According to an embodiment of the present invention, each stage of the n-stage screw adopts a twin screw and is provided with an inert gas delivery unit for injecting inert gas into the screw and a degassing unit for removing gas from the glue solution.

[0008] According to an embodiment of the present invention, a reagent is added to each stage of the n-stage screw respectively; the reagent includes at least one of water, an acid aqueous solution, and an alkali aqueous solution.

[0009] According to an embodiment of the present invention, when the added reagent is an acid aqueous solution or an alkali aqueous solution, each of them further includes a step of adding an opposite reagent (ie, an alkali aqueous solution or an acid aqueous solution).

[0010] According to an embodiment of the present invention, the mass fraction of the acid aqueous solution is 0.1~10%; the mass fraction of the alkali aqueous solution is 0.1~10%; the volume of the acid aqueous solution is 0.01~1% of the volume of the organic solvent in the glue; the volume of the alkali aqueous solution is 0.01~1% of the volume of the organic solvent in the glue; the volume of water is 10~100% of the volume of the organic solvent in the glue.

[0011] According to an embodiment of the present invention, the rotation speed of the first stage screw is 20-30 rpm, and the temperature is 20-40°C; the rotation speed of the nth stage screw is 110-130 rpm, and the temperature is 180-200°C.

[0012] According to an embodiment of the present invention, the rotation speed of the second stage screw to the n-1 stage screw is 40-60 rpm, and the temperature is 20-40°C.

[0013] According to an embodiment of the present invention, the organic solvent includes at least one of isobutane, n-pentane, isopentane, n-hexane, methylcyclopentane, n-heptane, methylcyclohexane, isooctane and toluene; the olefin monomer includes ethylene, C3~C 20 The main catalyst includes at least one of a metallocene catalyst and an α-diimine nickel catalyst; the co-catalyst includes at least one of triethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, diethylaluminum chloride, ethylaluminum dichloride, methylaluminoxane, modified methylaluminoxane, perfluorophenyl boron, triphenylcarbon tetrakis (pentafluorophenyl) borate, N,N-dimethylaniline tetrakis (pentafluorophenyl) borate and N,N-di(hexadecyl)anilinium tetrakis (pentafluorophenyl) borate.

[0014] According to an embodiment of the present invention, the polymerization reaction temperature is 60-200°C, the pressure is 1-10 MPa, and the time is 5-60 min; C3-C 20 The α-olefin includes at least one of propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-hexadecene, 1-octadecene and 1-eicosene.

[0015] According to an embodiment of the present invention, the ash content of the polyolefin elastomer is ≤50 ppm, and the volatile matter is ≤50 ppm.

[0016] According to the embodiment of the present invention, the present invention performs deashing and devolatilization (i.e., removing ash and volatilization) through an n-stage screw, which can effectively remove unreacted monomers, used catalyst residues, and volatile impurities, thereby improving the quality of the polyolefin elastomer. The deashed and devolatile polyolefin elastomer is made colorless and transparent, and the light transmittance of the polyolefin elastomer is effectively improved. In addition, due to the use of an n-stage screw, more sufficient mixing and shearing can be provided for the polyolefin elastomer, which is conducive to forming a more uniform polyolefin elastomer structure, and the extrusion granulation process can directly convert the treated glue into a granular polyolefin elastomer, simplifying the production process, improving production efficiency, and facilitating subsequent storage and transportation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A flow chart showing a method for preparing a polyolefin elastomer according to an embodiment of the present invention;

[0018] Figure 2 The schematic diagram of the structure of each stage of the n-stage screw in the embodiment of the present invention is shown. DETAILED DESCRIPTION

[0019] Below, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0020] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The term "comprising" used herein indicates the existence of features, steps, operations, but does not exclude the existence or addition of one or more other features.

[0021] In the field of photovoltaic applications, the demand for polyolefin elastomers continues to increase. In the photovoltaic field, polyolefin elastomers are required to have high volume resistivity and good light transmittance, which requires attention to the removal of ash and volatile matter during the post-processing process of preparing polyolefin elastomers. The commonly used adsorbent adsorption method mentioned in the background technology has high energy consumption, limited adsorption capacity of the adsorbent, and needs to be replaced. The process flow is relatively complicated.

[0022] In view of this, the present invention provides a method for preparing a polyolefin elastomer. Figure 1 A flow chart showing a method for preparing a polyolefin elastomer according to an embodiment of the present invention is shown. Figure 1As shown, the preparation method includes operations S101~S102.

[0023] In operation S101, under anhydrous and oxygen-free conditions, olefin monomers, a main catalyst, and a co-catalyst are stirred in an organic solvent for polymerization reaction to obtain a rubber solution containing a polyolefin elastomer.

[0024] According to the embodiments of the present invention, the anhydrous and oxygen-free conditions can avoid the interference of moisture and oxygen on the polymerization reaction, and improve the purity and quality of the polyolefin elastomer in the glue. The olefin monomer can be understood as one olefin monomer or a mixture of multiple olefin monomers.

[0025] In operation S102, the rubber solution is deashed and devolatilized through an n-stage screw and then extruded and granulated to prepare a polyolefin elastomer, wherein n≥2, n is an integer, such as 2, 3, 4, 5, etc.

[0026] According to the embodiment of the present invention, deashing and devolatilization are performed by an n-stage screw, so that unreacted monomers, main catalyst, co-catalyst residues and other volatile impurities can be effectively removed, which helps to improve the quality of polyolefin elastomers.

[0027] According to an embodiment of the present invention, each stage of the n-stage screw adopts a twin screw and is provided with an inert gas delivery unit for injecting inert gas into the screw and a degassing unit for removing gas from the glue solution.

[0028] Figure 2 The schematic diagram of the structure of each screw in the n-stage screw of the embodiment of the present invention is shown. The structure of each screw is as follows Figure 2 As shown, the n-stage screw can be understood as each stage of the screw being connected in series. Each stage of the screw includes a transmission unit 1, a twin screw 2, an inert gas conveying unit 3, and a degassing unit 4 distributed at different positions. The degassing unit 4 can be set to multiple as needed, such as 6 as shown in the figure. The transmission unit 1 is connected to one end of the twin screw 2. The transmission unit 1 is suitable for providing power to the twin screw 2, transmitting the power to the twin screw 2 to rotate it, and adjusting the mixing degree and conveying speed of the glue by adjusting the rotation speed of the twin screw 2. The twin screw 2 applies shear force to the material through the relative movement between the screws, promotes the mixing of the material, and reduces the residual impurities. The inert gas conveying unit 3 is connected to the other end (upstream end) of the twin screw 2, and is suitable for injecting inert gas into the screw, which helps to maintain the oxygen-free environment of the screw, prevents the oxidation degradation of the polyolefin elastomer, and also helps to carry volatile substances out of the screw. The degassing units 4 are respectively arranged at different positions downstream of the inert gas conveying unit 3, which helps to remove gases in the glue solution, such as unreacted monomers, solvents and other volatile components, thereby reducing the volatile matter and improving the purity of the polyolefin elastomer.

[0029] According to the embodiments of the present invention, the present invention realizes direct extrusion granulation after deashing and devolatilization by first conducting a polymerization reaction and then directly entering an n-stage screw, so that the production process is relatively simple and the energy consumption is low, and the removal effect of ash and volatile matter is better, and the preparation of polyolefin elastomers suitable for photovoltaics can be realized.

[0030] According to the embodiment of the present invention, the ash content of the polyolefin elastomer is ≤50ppm, and the volatile matter is ≤50ppm. By setting an n-stage screw for deashing and devolatilization, not only the production process is simplified, but also the removal effect of ash and volatile matter in the polyolefin elastomer can be optimized, the qualified rate of the polyolefin elastomer is improved, and it is more suitable for fields with high requirements on light transmittance such as photovoltaics.

[0031] It should be noted that, by setting n-stage screws, the temperature and rotation speed of each stage of the screw can be set separately as needed, which is conducive to achieving better effects of removing ash and volatile matter.

[0032] According to an embodiment of the present invention, n≤4, for example, it can be 2, 3, 4, preferably 3 or 4. The temperature of the n-stage screw is 20~220°C, for example, it can be 20°C, 50°C, 80°C, 100°C, 130°C, 150°C, 180°C, 200°C or 220°C, and the rotation speed is 20~200rpm, for example, it can be 20rpm, 50rpm, 100rpm, 150rpm or 200rpm. By adjusting the number of n-stage screws, the temperature and rotation speed of each stage screw in a suitable range, the ash and volatile matter can be fully removed before extrusion granulation, and the temperature and rotation speed of each stage screw can be adjusted separately, and can be adaptively adjusted according to the different needs of the prepared products, with a wider range of adaptability.

[0033] According to an embodiment of the present invention, reagents are added to each screw of the n-stage screw respectively; the reagents include at least one of water, an aqueous solution of an acid, and an aqueous solution of an alkali, and the water can be, for example, deionized water. The addition of water helps to dissolve soluble impurities therein, such as catalyst residues that have not reacted completely or water-soluble by-products, helps to clean the glue, and can also take away some volatile substances when the water evaporates, assisting the devolatilization process. The aqueous solution of the acid can neutralize the residual alkaline substances, for example, when the catalyst used is alkaline. At the same time, the acid can also react with metal ions to form compounds that are easier to remove, helping to reduce the ash content. The aqueous solution of the alkali has a similar mechanism of action to the aqueous solution of the acid, and also has the function of neutralizing residual acidic substances. In addition, for metal salt catalysts, alkaline conditions help to deactivate the metal salt catalyst and avoid unnecessary side reactions. By adding reagents, it helps to make the polyolefin elastomer easier to carry out subsequent processing steps such as molding, extrusion, and granulation.

[0034] According to an embodiment of the present invention, when the added reagent is an acid aqueous solution or an alkali aqueous solution, each of the steps further includes a step of adding an opposite reagent (alkali aqueous solution or acid aqueous solution).

[0035] The opposite reagent can be understood as the case where the actual added acid aqueous solution is an aqueous solution of an alkali, which is subsequently added to neutralize the acid aqueous solution introduced in the previous process. Or it can be understood as the case where the actual added alkali aqueous solution is an aqueous solution of an acid, which is subsequently added to neutralize the alkali aqueous solution introduced in the previous process. The prepared polyolefin elastomer is placed in a pH environment close to neutral, which helps to maintain the stability of the polyolefin elastomer. By alternating between acidic and alkaline conditions, inorganic ash and other volatile components can be more effectively removed, which helps to better separate different types of impurities.

[0036] For example, when the n-stage screw used is a 2-stage screw, water can be used as a reagent in the 1st stage screw, and extrusion granulation can be performed in the 2nd stage screw.

[0037] When the n-stage screw used is a 3-stage screw, water can be used as a reagent in the 1st stage screw, water can be used as a reagent in the 2nd stage screw, and extrusion granulation can be performed in the 3rd stage screw; acid can be used as a reagent in the 1st stage screw, alkali can be used as a reagent in the 2nd stage screw, and extrusion granulation can be performed in the 3rd stage screw; alkali can be used as a reagent in the 1st stage screw, acid can be used as a reagent in the 2nd stage screw, and extrusion granulation can be performed in the 3rd stage screw.

[0038] When the n-stage screw used is a 4-stage screw, acid can be used as a reagent in the 1st stage screw, water can be used as a reagent in the 2nd stage screw, alkali can be used as a reagent in the 3rd stage screw, and extrusion granulation can be performed in the 4th stage screw; alkali can be used as a reagent in the 1st stage screw, water can be used as a reagent in the 2nd stage screw, acid can be used as a reagent in the 3rd stage screw, and extrusion granulation can be performed in the 4th stage screw; water can also be used as a reagent in all the 1st to 3rd stage screws, and extrusion granulation can be performed in the 4th stage.

[0039] According to an embodiment of the present invention, the mass fraction of the aqueous solution of acid and / or the aqueous solution of alkali is 0.1-10%, for example, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, preferably 1wt%. The volume of the aqueous solution of acid and / or the aqueous solution of alkali is 0.01-1% of the organic solvent in the glue, for example, 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%; the volume of water is 10-100% of the organic solvent in the glue, for example, 10%, 50% or 100%. The aqueous solution of acid can be any commercially available strong acid or weak acid, such as hydrochloric acid solution, sulfuric acid solution, etc. The aqueous solution of alkali can be any commercially available strong base or weak base, such as sodium hydroxide solution or potassium hydroxide solution, etc. By adjusting the type and mass fraction of the acid aqueous solution or the alkali aqueous solution within the above ranges, the ash and volatile matter can be effectively removed while the properties of the polyolefin elastomer will not be affected due to the addition of too concentrated solution.

[0040] According to an embodiment of the present invention, the speed of the first stage screw is 20-30 rpm, for example, 20 rpm, 25 rpm or 30 rpm, preferably 20 rpm, and the temperature is 20-40° C., for example, 20° C., 30° C. or 40° C., preferably 30° C. The speed of the nth stage screw is 110-130 rpm, for example, 110 rpm, 120 rpm, or 130 rpm, preferably 120 rpm, and the temperature is 180-200° C., for example, 180° C., 190° C. or 200° C., preferably 190° C.

[0041] The first stage screw uses a lower temperature and a lower speed, that is, a slower material conveying speed and a longer residence time, which is conducive to fully mixing the glue and the reagent, and improving the removal effect of ash. In addition, the lower speed corresponds to a lower shearing effect, which can reduce the damage to the polymer segments in the polyolefin elastomer. The lower temperature avoids pyrolysis or unnecessary side reactions. The nth stage screw uses a higher speed and a higher temperature to extrude and granulate the polyolefin elastomer, and at the same time accelerates the removal of ash and volatiles, thereby achieving the refining of the polyolefin elastomer.

[0042] According to an embodiment of the present invention, the rotation speed of the second stage screw to the n-1 stage screw is 40-60 rpm, for example, 40 rpm, 50 rpm or 60 rpm, preferably 50 rpm. The temperature is 20-40°C, for example, 20°C, 30°C or 40°C, preferably 30°C.

[0043] The second screw to the n-1 screw plays a transitional role, ensuring the transition of the glue from the initial treatment to the final extrusion granulation process. Compared with the first screw, the second screw to the n-1 screw speeds up the delivery of the glue, but the temperature remains within a mild range to avoid the influence of excessive shear on the structure of the polyolefin elastomer, which helps to further homogenize the material and promote the dispersion of ash and polyolefin elastomer, so that the polyolefin elastomer can achieve better ash and volatile matter removal after passing through the n-stage screw.

[0044] According to an embodiment of the present invention, the organic solvent includes at least one of isobutane, n-pentane, isopentane, n-hexane, methylcyclopentane, n-heptane, methylcyclohexane, isooctane and toluene, preferably at least one of n-hexane, methylcyclopentane and n-heptane, more preferably n-hexane or n-heptane. The olefin monomers include ethylene, C3~C 20 α-olefins, for example, copolymerization of ethylene, or homopolymerization of ethylene and α-olefins, preferably ethylene. The main catalyst includes at least one of a metallocene catalyst and an α-diimine nickel catalyst, and the concentration of the main catalyst in the reaction vessel (for example, a reactor) is 1 to 100 μmol / L, preferably 20 μmol / L. The cocatalyst includes at least one of triethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, diethylaluminum chloride, dichloroethylaluminum, methylaluminoxane, modified methylaluminoxane, perfluorophenyl boron, triphenylcarbon tetrakis (pentafluorophenyl) borate, N,N-dimethylaniline tetrakis (pentafluorophenyl) borate, and N,N-di(hexadecyl)anilinium tetrakis (pentafluorophenyl) borate, and the concentration of the cocatalyst in the reaction vessel (for example, a reactor) is 50 to 2000 μmol / L, preferably 2000 μmol / L.

[0045] According to an embodiment of the present invention, the polymerization temperature is 60-200°C, for example, 60°C, 80°C, 100°C, 120°C, 140°C, 160°C, 180°C or 200°C, preferably 80°C. The pressure is 1-10MPa, for example, 1MPa, 3MPa, 5MPa, 7MPa, 9MPa or 10MPa, preferably 3MPa. The time is 5-60min, for example, 5min, 10min, 20min, 30min, 40min, 50min or 60min, preferably 30min. C3-C 20 The α-olefin includes at least one of propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-hexadecene, 1-octadecene and 1-eicosene.

[0046] The performance of the polyolefin elastomer prepared by the preparation method of the present invention can reach the following indicators: branching degree 60-80, using high temperature nuclear magnetic resonance testing, the reagent is deuterated tetrachloroethane, and the value represents the number of branches in 1000 carbons. Volatile matter ≤100ppm, volatile matter is tested in accordance with GB / T24131.2-2017. Ash content ≤100ppm, ash content is tested in accordance with GB / T 9345.1-2008. Hardness is 55-70Shore A, hardness is tested in accordance with GB / T 2411-2008. Tensile strength ≥4MPa, tensile strength is tested in accordance with GB / T1040.3-2006. Melt index 0.5-30, melt index is tested in accordance with GB / T3682.1-2018, temperature is 190°C, load is 2.16kg. Weight average molecular weight is M w 200,000-400,000, molecular weight distribution PDI is 1.5-2.5, weight average molecular weight M w The molecular weight distribution PDI is tested according to SN / T 4183-2015. Melting point T m 55-70℃, density 0.860-0.880g / cm 3 , density is tested according to GB / T1033.1-2008. Volume resistivity ≥1×10 17 Ω·cm, volume resistivity is tested in accordance with GB / T31838.2-2019. Light transmittance ≥92.0%, light transmittance is tested in accordance with GB / T2410-2008.

[0047] The present invention is further described below by examples, drawings and related test experiments and results thereof. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present invention. However, it is obvious that one or more embodiments may also be implemented without these specific details. And, in the absence of conflict, the details in the following embodiments may be combined arbitrarily into other feasible embodiments.

[0048] It should be noted that the following specific examples are only for illustration and the protection scope of the present invention is not limited thereto. The chemicals and raw materials used in the following examples are commercially available or homemade by recognized processing methods. Each of the n-stage screws used in the following examples is as follows Figure 2 The structure shown.

[0049] Embodiment 1:

[0050] The preparation process of polyolefin solution polymerization is as follows:

[0051] Polymerization reaction: Ethylene, nickel diimide catalyst and triethylaluminum are fully stirred in n-hexane for polymerization reaction for 30 minutes. The polymerization temperature is 80°C, the polymerization pressure is 3MPa, the concentration of nickel diimide catalyst is 20μmol / L, the concentration of triethylaluminum is 2000μmol / L, and the volume of n-hexane is 7L to obtain polyolefin glue.

[0052] Post-treatment of the adhesive solution: a 4-stage screw was selected, wherein the first-stage screw had a speed of 20 rpm, a temperature of 30°C, and 100 ml of a hydrochloric acid aqueous solution (1 wt% concentration) was added; the second-stage screw had a speed of 50 rpm, a temperature of 30°C, and 5 L of deionized water was added; the third-stage screw had a speed of 50 rpm, a temperature of 30°C, and 100 ml of a NaOH aqueous solution (1 wt% concentration) was added; the fourth-stage screw had a speed of 120 rpm, a temperature of 190°C, and extrusion granulation was performed to obtain polyolefin elastomer particles 1.

[0053] Embodiment 2:

[0054] The preparation process of polyolefin solution polymerization is as follows:

[0055] Polymerization reaction: Ethylene, nickel diimide catalyst and triethylaluminum are fully stirred in n-hexane for polymerization reaction for 30 minutes. The polymerization temperature is 80°C, the polymerization pressure is 3MPa, the concentration of nickel diimide catalyst is 20μmol / L, the concentration of triethylaluminum is 2000μmol / L, and the volume of n-hexane is 7L to obtain polyolefin glue.

[0056] Post-treatment of the adhesive solution: a 4-stage screw was selected, wherein the first-stage screw had a speed of 20 rpm, a temperature of 30°C, and 100 ml of a NaOH aqueous solution (1 wt% concentration) was added; the second-stage screw had a speed of 50 rpm, a temperature of 30°C, and 5 L of deionized water was added; the third-stage screw had a speed of 50 rpm, a temperature of 30°C, and 100 ml of a HCL aqueous solution (1 wt% concentration) was added; the fourth-stage screw had a speed of 120 rpm, a temperature of 190°C, and extrusion granulation was performed to obtain polyolefin elastomer particles 2.

[0057] Embodiment 3:

[0058] The preparation process of polyolefin solution polymerization is as follows:

[0059] Polymerization reaction: Ethylene, nickel diimide catalyst and triethylaluminum are fully stirred in n-hexane for polymerization reaction for 30 minutes. The polymerization temperature is 80°C, the polymerization pressure is 3MPa, the concentration of nickel diimide catalyst is 20μmol / L, the concentration of triethylaluminum is 2000μmol / L, and the volume of n-hexane is 7L to obtain polyolefin glue.

[0060] Post-treatment of the adhesive solution: a three-stage screw was selected, wherein the first-stage screw had a speed of 20 rpm, a temperature of 30°C, and 100 ml of a hydrochloric acid aqueous solution (1 wt% concentration) was added; the second-stage screw had a speed of 50 rpm, a temperature of 30°C, and 100 ml of a NaOH aqueous solution (1 wt% concentration) was added; the third-stage screw had a speed of 120 rpm, a temperature of 190°C, and extrusion granulation was performed to obtain polyolefin elastomer particles 3.

[0061] Embodiment 4:

[0062] The preparation process of polyolefin solution polymerization is as follows:

[0063] Polymerization reaction: Ethylene, nickel diimide catalyst and triethylaluminum are fully stirred in n-hexane for polymerization reaction for 30 minutes. The polymerization temperature is 80°C, the polymerization pressure is 3MPa, the concentration of nickel diimide catalyst is 20μmol / L, the concentration of triethylaluminum is 2000μmol / L, and the volume of n-hexane is 7L to obtain polyolefin glue.

[0064] Post-treatment of the adhesive solution: a three-stage screw was selected, wherein the first-stage screw had a speed of 50 rpm, a temperature of 30°C, and 5 L of deionized water was added; the second-stage screw had a speed of 50 rpm, a temperature of 30°C, and 5 L of deionized water was added; the third-stage screw had a speed of 120 rpm, a temperature of 190°C, and extrusion granulation was performed to obtain polyolefin elastomer particles 4.

[0065] Example 5

[0066] The preparation process of polyolefin solution polymerization is as follows:

[0067] Polymerization reaction: Ethylene, metallocene constrained configuration catalyst (CGC), and methylaluminoxane are fully stirred in n-heptane for polymerization reaction for 15 minutes. The polymerization temperature is 130°C, the polymerization pressure is 4 MPa, the concentration of the metallocene CGC catalyst is 10 μmol / L, the concentration of methylaluminoxane is 2000 μmol / L, and the volume of n-heptane is 7 L to obtain a polyolefin glue.

[0068] The post-treatment process of the glue solution in this embodiment 5 is the same as that in embodiment 1 and will not be repeated here, and polyolefin elastomer particles 5 are prepared.

[0069] Comparative Example 1

[0070] The preparation process of traditional polyolefin solution polymerization is as follows:

[0071] Polymerization reaction: Ethylene, nickel diimide catalyst and triethylaluminum are fully stirred in n-hexane for polymerization reaction for 30 minutes. The polymerization temperature is 80°C, the polymerization pressure is 3MPa, the concentration of nickel diimide catalyst is 20μmol / L, the concentration of triethylaluminum is 2000μmol / L, and the volume of n-hexane is 7L to obtain polyolefin glue.

[0072] Post-treatment of the glue liquid: The glue liquid coming out of the polymerization kettle is deashed by adsorption deashing, the adsorbent is 3A molecular sieve, the pressure is 3MPa, and the temperature is 170℃. The deashed glue liquid enters the devolatilization unit and passes through two flash evaporators connected in series. The flash evaporation temperature of the two flash evaporators is 170℃, the pressure in the flash tank is 0.1MPa, and the stirring form in the flash tank is single-screw stirring. The residence time of the glue liquid in the first and second flash evaporations is 10min and 20min respectively. The material after two flash evaporations is pumped to a single-screw extruder for extrusion granulation. The screw speed is 110rpm / min and the screw temperature is controlled at 190℃ to obtain polyolefin elastomer particles 1'.

[0073] The polyolefin elastomer particles prepared in Examples 1 to 5 and Comparative Example 1 were tested according to national standards, and the test results are shown in Table 1 below.

[0074] Table 1 Vinyl polyolefin elastomer performance test

[0075]

[0076] By comparing Comparative Example 1 with Example 1, it can be found that compared with the traditional post-processing method, the polyolefin elastomer particles prepared by the n-stage screw have high purity, extremely low ash and volatile residues, and high volume resistivity and transmittance. By comparing Example 1 with Example 2, it can be found that the order of adding the acid solution and the alkaline solution can be interchanged, and the overall performance of the polyolefin elastomer particles is basically unaffected, and there is basically no difference between volatilization and volatiles. By comparing Example 1 with Example 3, it can be found that when the 1-stage screw is reduced, the performance of the polyolefin elastomer particles remains unchanged, but the volatile matter increases slightly and the ash content remains unchanged. By comparing Example 3 with Example 4, it can be found that only deionized water is used in the screw, which does not substantially affect the performance of the polyolefin elastomer particles, the volatile matter remains basically unchanged, and the ash content increases slightly. By comparing Example 1 with Example 5, it can be found that under the metallocene catalyst system, the performance of the polyolefin elastomer particles changes, but the ash and volatile matter remain basically unchanged, so the preparation method of the present invention is not only applicable to diimine nickel catalyst systems, but also to metallocene catalyst systems.

[0077] The glue solution was taken from the sampling port of the reactor (before entering the n-stage screw), and the performance was tested after rotary evaporation and drying. The test results are shown in Table 2 below.

[0078] Table 2 Performance test of samples from the sampling port of the reactor in Examples 1 to 5

[0079]

[0080] As shown in Table 2, the test results show that the ash and volatile matter of the polyolefin elastomer that has not passed through the n-stage screw are more than 5 times higher than those that have passed through the n-stage screw, the volume resistivity is about 2 orders of magnitude lower, and the transmittance is reduced by more than 4%. This shows that the n-stage screw has a good effect on removing ash and volatile matter from polyolefin elastomers and can be promoted in industry.

[0081] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a polyolefin elastomer, characterized in that: The preparation method comprises: Under anhydrous and oxygen-free conditions, olefin monomers, a main catalyst and a co-catalyst are stirred in an organic solvent for polymerization reaction to obtain a rubber solution containing a polyolefin elastomer; The rubber solution is deashed and devolatilized by an n-stage screw and then extruded and granulated to prepare a polyolefin elastomer; Wherein, n≥2, n is an integer.

2. The preparation method according to claim 1, characterized in that: n≤4； The temperature of the n-stage screw is 20-220° C., and the rotation speed is 20-200 rpm.

3. The preparation method according to claim 1, characterized in that: Each of the n-stage screws adopts a twin screw and is provided with an inert gas delivery unit for injecting an inert gas into the screw and a degassing unit for removing gas from the glue solution.

4. The preparation method according to claim 1, characterized in that: Add reagents to each of the n-stage screws separately; The reagent includes at least one of water, an acidic aqueous solution, and an alkaline aqueous solution; In the case where the added reagent is an aqueous acid solution or an aqueous alkali solution, each of the steps further includes a step of adding the opposite reagent.

5. The preparation method according to claim 4, characterized in that: The mass fraction of the aqueous solution of the acid is 0.1-10%; The mass fraction of the aqueous solution of the alkali is 0.1-10%; The volume of the acid aqueous solution is 0.01-1% of the volume of the organic solvent in the glue solution; The volume of the aqueous solution of the alkali is 0.01-1% of the volume of the organic solvent in the glue solution; The volume of water is 10-100% of the volume of the organic solvent in the glue.

6. The preparation method according to claim 2, characterized in that: The speed of the first-stage screw is 20~30rpm, and the temperature is 20~40℃; the speed of the n-stage screw is 110~130rpm, and the temperature is 180~200℃.

7. The preparation method according to claim 6, characterized in that: The speed of the second-stage screw to the n-1-stage screw is 40~60rpm, and the temperature is 20~40℃.

8. The preparation method according to claim 1, characterized in that: The organic solvent comprises at least one of isobutane, n-pentane, isopentane, n-hexane, methylcyclopentane, n-heptane, methylcyclohexane, isooctane and toluene; The olefin monomers include ethylene, C3~C 20 At least one of the α-olefins; The main catalyst comprises at least one of a metallocene catalyst and an α-diimine nickel catalyst; The co-catalyst includes at least one of triethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, diethylaluminum chloride, ethylaluminum dichloride, methylaluminoxane, modified methylaluminoxane, perfluorophenylboron, triphenylcarbon tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, and N,N-di(hexadecyl)anilinium tetrakis(pentafluorophenyl)borate.

9. The preparation method according to claim 8, characterized in that: The polymerization reaction temperature is 60-200°C, the pressure is 1-10MPa, and the time is 5-60min; C3~C 20 The α-olefin includes at least one of propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-hexadecene, 1-octadecene and 1-eicosene.

10. The preparation method according to claim 1, characterized in that: The polyolefin elastomer has an ash content of ≤50 ppm and a volatile content of ≤50 ppm.

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