Polyolefin composition and preparation method thereof

Abstract

The present invention relates to the field of polyolefin, and discloses a polyolefin composition and a preparation method thereof, the polyolefin composition has a long-period thickness of 12 nm or more, a lamellar crystal region thickness of 6.5 nm or more, and a mass crystallinity of 56% or more. The polyolefin composition disclosed by the invention has the advantages of relatively high lamellar thickness, excellent bending modulus, good impact property and good heat resistance.

Description

Technical Field

[0001] The present invention relates to the field of polyolefins, and in particular to a polyolefin composition and a preparation method thereof. Background Art

[0002] Highly crystalline polypropylene has good heat deformation temperature, high bending modulus and certain impact resistance. It is widely used in food packaging boxes, heat-resistant parts of household appliances and blending modification. At present, the mainstream high-crystalline polypropylene at home and abroad is usually prepared by adding nucleating agents to polypropylene base resins. As a common additive for polymer modification, nucleating agents can improve the crystallinity of products, thereby improving the rigidity of products, shortening the molding cycle, and maintaining the dimensional stability of the final product. Its mechanism of action is: in the molten state, it provides crystal nuclei, so that the crystallization mechanism of the polymer is transformed from the original homogeneous nucleation to heterogeneous nucleation, improving the crystallization ability and refining the grains.

[0003] At present, the industry mainly adds nucleating agents during the polymer pelletizing process. Regardless of whether it is an inorganic nucleating agent, an organic nucleating agent or a polymer nucleating agent, adding it during the pelletizing stage will more or less lead to problems such as poor compatibility and poor dispersibility between the nucleating agent and the polymer, which will prevent many properties of polyolefin products from being brought into play, and sometimes will also lead to a deterioration in the appearance of the polymer product, such as the appearance of white spots in the product.

[0004] Another method of adding a nucleating agent is to produce or add the nucleating agent before or during the polymerization process, which is intermittent addition of the nucleating agent. In the continuous polymerization process, the catalyst is introduced uniformly, which can better ensure the stability of the performance of different batches of products. Compared with the introduction of the polymer of the vinyl compound into the polymerization reaction process, its stability may be affected by the polymerization reaction process, so that the nucleation effect cannot be guaranteed, and the obtained polymer lamellae are of low thickness, poor impact performance, and poor heat resistance. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems existing in the prior art and to provide a polyolefin composition and a preparation method thereof.

[0006] In order to achieve the above objectives, the first aspect of the present invention provides a polyolefin composition, wherein the long period thickness of the polyolefin composition is 12 nm or more; the thickness of the lamellar crystal region is 6.5 nm or more, and the mass crystallinity is 56% or more.

[0007] A second aspect of the present invention provides a method for preparing a polyolefin composition, the method comprising:

[0008] (1) in a first prepolymerization reactor, mixing a polymerizable monomer a with a first prepolymerization catalyst component to conduct a first prepolymerization reaction;

[0009] (2) continuously conveying the product obtained in step (1) to a second prepolymerization reactor, contacting it with a second prepolymerization catalyst component and a polymerizable monomer b to carry out a second prepolymerization reaction; the relationship between the prepolymerization ratio REP1 of the first prepolymerization reaction and the prepolymerization ratio REP2 of the second prepolymerization reaction satisfies: REP1 / REP2≤0.4, and the polymerizable monomer a is not propylene;

[0010] (3) The product obtained in step (2) is mixed with polymerizable monomer c to carry out polymerization reaction.

[0011] The third aspect of the present invention provides a polyolefin composition prepared by the above method.

[0012] Through the above technical scheme, the polyolefin composition of the present invention has high long-period thickness and lamellar crystal region thickness, excellent bending modulus, good impact performance (impact strength), and good heat resistance. The method of the present invention can significantly improve the melting temperature, crystallization temperature, crystal region thickness and long-period thickness of the polymer and the bending modulus of the polymer, and no nucleating agent needs to be added in the subsequent processing process. At the same time, compared with the method of intermittent pretreatment of catalysts and polymerization monomers, the polymer performance parameters obtained by the method of the present invention are more stable and the quality is more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the polymerization reaction of Example 1.

[0014] Description of Reference Numerals

[0015] 01, first prepolymerization reactor; 02, second prepolymerization reactor; 03, main reactor; 101, catalyst composition; 102, first material flow containing polymerization monomer a; 103, first prepolymerization reactor refrigerant inlet; 104, first prepolymerization reactor refrigerant outlet; 201, first prepolymerization catalyst slurry; 202, second material flow containing polymerization monomer b; 203, second prepolymerization reactor refrigerant inlet; 204, second prepolymerization reactor refrigerant outlet; 301, second prepolymerization catalyst slurry; 302, main reactor outlet. DETAILED DESCRIPTION

[0016] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0017] The first aspect of the present invention provides a polyolefin composition, wherein the long period thickness of the polyolefin composition is 12 nm or more, the lamellar crystal region thickness is 6.5 nm or more, and the mass crystallinity is 56% or more.

[0018] In the present invention, the long period thickness is 12-24nm, which can be 12nm, 12.5nm, 13nm, 13.5nm, 14nm, 14.5nm, 15nm, 15.5nm, 16nm, 16.5nm, 17nm, 17.5nm, 18nm, 18.5nm, 19nm, 19.5nm, 20nm, 21nm, 22nm, 23nm, 24nm or a range formed by any two of the above values ​​and a value within the range, preferably 14-22nm.

[0019] In the present invention, the thickness of the lamellar crystal region is 6.5-15nm, which can be 6.5nm, 7nm, 7.5nm, 8nm, 8.5nm, 9nm, 9.5nm, 10nm, 10.5nm, 11nm, 11.5nm, 12nm, 12.5nm, 13nm, 14nm, 15nm or a range formed by any two of the above values ​​and a value within the range, preferably 7.5-15nm.

[0020] According to the present invention, the polyolefin composition further contains xylene solubles, the content of which is 1-4wt%, which may be 1wt%, 2wt%, 3wt%, 4wt% or a range formed by any two of the above values ​​and a value within the range.

[0021] According to the present invention, the melt index of the polyolefin composition at 230°C and 2.16 kg load is 4-30 g / 10min, and can be 4 g / 10min, 6 g / 10min, 10 g / 10min, 15 g / 10min, 20 g / 10min, 25 g / 10min, 30 g / 10min or a range formed by any two of the above values ​​and a value within the range, preferably 6-25 g / 10min.

[0022] According to the present invention, the weight average molecular weight of the polyolefin is 200,000-40,000, preferably 230,000-350,000;

[0023] According to the present invention, the flexural modulus of the polyolefin composition is not less than 1800 MPa, and can be 1800 MPa, 1810 MPa, 1820 MPa, 1830 MPa, 1840 MPa, 1850 MPa, 1860 MPa, 1870 MPa, 1880 MPa, 1890 MPa, 1990 MPa, 1920 MPa, 1940 MPa, 1980 MPa, 2000 MPa, 2050 MPa, 2100 MPa, 2150 MPa, 2200 MPa, 2500 MPa or a range formed by any two of the above values, and a value within the range, preferably 1830-2000 MPa.

[0024] According to the present invention, the heat deformation temperature of the polyolefin composition is not less than 110°C, and can be 110°C, 112°C, 114°C, 116°C, 118°C, 119°C, 120°C, 122°C, 125°C, 130°C or a range formed by any two of the above values ​​and a value within the range, preferably 112-120°C.

[0025] According to the present invention, at 23°C, the simply supported beam notch of the polyolefin composition is not less than 3 kJ / m 2 , can be 3kJ / m 2 、3.1kJ / m 2 、3.2kJ / m 2 3.3kJ / m 2 、3.4kJ / m 2 、3.5kJ / m 2 、3.6kJ / m 2 3.7kJ / m 2 、3.8kJ / m 2 、3.9kJ / m 2 , 4kJ / m 2 Or the range formed by any two of the above values ​​and the value within the range, preferably 3-3.5 kJ / m 2 .

[0026] According to the present invention, the tensile yield stress of the polyolefin composition is not less than 40 MPa, and can be 40 MPa, 40.1 MPa, 40.2 MPa, 40.3 MPa, 40.4 MPa, 40.5 MPa, 40.6 MPa, 40.7 MPa, 40.8 MPa, 40.9 MPa, 41 MPa, 41.1 MPa, 41 MPa, 41.1 MPa, 41.2 MPa, 41.3 MPa, 41.5 MPa, 42 MPa, 42.5 MPa, 43 MPa, 44 MPa, 45 MPa, 46 MPa, 47 MPa, 48 MPa, 49 MPa, 50 MPa or a range formed by any two of the above values, or a value within the range, and is preferably 40-42 MPa.

[0027] According to the present invention, the mass crystallinity of the polyolefin composition can be 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68% or a range formed by any two of the above values ​​and a value within the range, preferably 59-63%.

[0028] According to the present invention, the crystallization temperature of the polyolefin composition is not less than 125°C, and can be 125°C, 126°C, 127°C, 128°C, 129°C, 130°C, 131°C, 132°C, 135°C, 137°C, 138°C, 140°C or a range formed by any two of the above values ​​and a value within the range, preferably 126-131°C.

[0029] According to the present invention, the melting temperature of the polyolefin composition is not less than 164°C, and can be 164°C, 165°C, 166°C, 167°C, 168°C, 169°C, 170°C, 175°C, 180°C or a range formed by any two of the above values ​​and a value within the range, preferably 165-167°C.

[0030] According to the present invention, the polyolefin in the polyolefin composition is at least one of a homopolymer, a random copolymer, a block copolymer and an impact copolymer; preferably, the structural units of the polyolefin in the polyolefin composition are provided by olefins having 4 to 16 carbon atoms; more preferably, the polyolefin contains structural units provided by propylene.

[0031] A second aspect of the present invention provides a method for preparing a polyolefin composition, the method comprising:

[0032] (1) in a first prepolymerization reactor, mixing a polymerizable monomer a with a first prepolymerization catalyst component to conduct a first prepolymerization reaction;

[0033] (2) continuously conveying the product obtained in step (1) to a second prepolymerization reactor, contacting it with a second prepolymerization catalyst component and a polymerizable monomer b to carry out a second prepolymerization reaction; the relationship between the prepolymerization ratio REP1 of the first prepolymerization reaction and the prepolymerization ratio REP2 of the second prepolymerization reaction is REP1 / REP2≤0.4, preferably ≤0.2, and the polymerizable monomer a is not propylene;

[0034] (3) The product obtained in step (2) is mixed with polymerizable monomer c to carry out polymerization reaction.

[0035] In the present invention, the terms "prepolymerization" and "prepolymerization" used refer to a polymerization reaction carried out to achieve a lower reaction rate and monomer conversion rate than the reaction rate and monomer conversion rate under normal polymerization conditions. "Prepolymerization ratio" refers to the ratio of the mass of the polymer produced in the prepolymerization reactor to the mass of the catalyst. The prepolymerization ratio in the first prepolymerization reaction is expressed by the formula: the mass of the polymer produced in the first prepolymerization / the mass of the main catalyst; the prepolymerization ratio in the second prepolymerization reaction is expressed by the formula: the mass of the polymer produced in the second prepolymerization / the polymer produced / the mass of the main catalyst. "Time" refers to the average residence time of the polyolefin catalyst in the prepolymerization reactor, which is expressed by the formula: the reactor volume / the volume flow rate of the medium entering the reactor.

[0036] In the present invention, in order to make the obtained polyolefin composition have thicker lamella thickness and long period thickness, better impact performance and good heat resistance, the prepolymerization ratio REP1 of the first prepolymerization reaction is ≤50 times, and can be 0 times, 1 times, 2 times, 3 times, 4 times, 5 times, 7 times, 9 times, 10 times, 12 times, 15 times, 18 times, 20 times, 25 times, 30 times, 35 times, 40 times, 45 times, 50 times or the range formed by any two of the above values ​​and the value within the range, more preferably ≤30 times, and further preferably 2-15 times.

[0037] In the present invention, in order to make the obtained polyolefin composition have thicker lamella thickness and long period thickness, better impact performance and good heat resistance, the prepolymerization ratio REP2 of the second prepolymerization reaction is 1-1000 times, and can be 1 times, 10 times, 50 times, 100 times, 150 times, 200 times, 250 times, 300 times, 350 times, 400 times, 450 times, 500 times, 600 times, 700 times, 800 times, 900 times, 1000 times or the range formed by any two of the above values ​​and the value within the range, more preferably 10-500 times, and further preferably 30-300 times.

[0038] In the present invention, the second prepolymerization reaction is directly carried out after the first prepolymerization reaction is completed. Preferably, the method does not include cooling and / or drying operations between step (1) and step (2).

[0039] In the present invention, in order to make the obtained polyolefin composition have thicker lamella thickness and long period thickness, better impact performance and good heat resistance, the conditions of the first prepolymerization reaction include: the temperature is 0-90°C, which can be 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C or the range formed by any two of the above values ​​and the value within the range, preferably 10-70°C; the pressure is 0.1-10MPaG, which can be 0.1MPaG, 0.5MPaG, 1MPaG, 2MPaG, 3MPaG, 4MPaG, 5MPaG, 6MPaG, 7MPaG, 8MPaG, 9MPaG, 10MPaG or the range formed by any two of the above values, and the value within the range, preferably 1-5MPaG; the time is 1-36h, and can be 1h, 5h, 10h, 15h, 20h, 25h, 30h, 36h or the range formed by any two of the above values, and the value within the range, preferably 5-20h.

[0040] In the present invention, in order to make the obtained polyolefin composition have thicker lamella thickness and long period thickness, better impact performance and good heat resistance, the conditions of the second prepolymerization reaction include: the temperature is -30°C to 100°C, which can be -30°C, -20°C, -10°C, 0°C, 10°C, 20°C, 30°C, 50°C, 70°C, 100°C or the range formed by any two of the above values ​​and the value within the range, preferably -10°C to 70°C; the pressure is 0.1-10MPaG, which can be 0.1MPaG, 0.5MPaG, 1MPaG, 2MPaG, 3MPaG PaG, 4MPaG, 5MPaG, 6MPaG, 7MPaG, 8MPaG, 9MPaG, 10MPaG or the range formed by any two of the above values, and the value within the range, preferably 1-5MPaG; the time is ≤2h, and can be 0min, 1min, 5min, 10min, 20min, 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 120min or the range formed by any two of the above values, and the value within the range, preferably 1-90min.

[0041] In the present invention, in order to make the obtained polyolefin composition have thicker lamella thickness and long period thickness, better impact performance and good heat resistance, the polymerization reaction conditions include: temperature of 20-100°C, which can be 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C or the range formed by any two of the above values ​​and the value within the range, preferably 40-91°C; pressure of 0.1-10MPaG, which can be 0.1MPaG, 0.5 MPaG, 1MPaG, 2MPaG, 3MPaG, 4MPaG, 5MPaG, 6MPaG, 7MPaG, 8MPaG, 9MPaG, 10MPaG or the range formed by any two of the above values ​​and the value within the range, preferably 1-5MPaG; the time is ≤4h, and can be 0h, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h or the range formed by any two of the above values ​​and the value within the range, preferably 1-3h.

[0042] In the present invention, in order to make the obtained polyolefin composition have thicker lamella thickness and long period thickness, better impact performance and good heat resistance, the first prepolymerization catalyst component includes a main catalyst, a first co-catalyst and a first external electron donor; more preferably, the weight ratio of the polymerization monomer a and the main catalyst is 1:0.01-0.5, which can be 1:0.01, 1:0.05, 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5 or the range formed by any two of the above values ​​and the value within the range.

[0043] In the present invention, in order to make the obtained polyolefin composition have thicker lamella thickness and long period thickness, better impact performance and good heat resistance, the weight ratio of the polymerization monomer a and the first co-catalyst is 1:0.01-1, and can be 1:0.01, 1:0.05, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1 or the range formed by any two of the above values ​​and the value within the range.

[0044] In the present invention, in order to make the obtained polyolefin composition have thicker lamella thickness and long period thickness, better impact performance and good heat resistance, the weight ratio of the polymerized monomer a and the first external electron body is 1:0.001-0.1, and can be 1:0.001, 1:0.005, 1:0.01, 1:0.05, 1:0.1 or the range formed by any two of the above values ​​and the value within the range.

[0045] In the present invention, in order to make the obtained polyolefin composition have thicker sheet thickness and long period thickness, better impact resistance and good heat resistance, the weight ratio of the polymerized monomer a to the polymerized monomer b is 1:10. 2 -10 4 , can be 1:(1×10 2 )、1:(2×10 2 )、1:(4×10 2 )、1:(6×10 2 )、1:(8×10 2 )、1:(1×10 3 )、1:(2×10 3 )、1:(4×10 3 )、1:(6×10 3 )、1:(8×10 3 )、1:(1×10 4 ) or the range formed by any two of the above values ​​and the values ​​within the range.

[0046] Preferably, relative to the first prepolymerization reactor with a volume of 3L, the flow rate of the polymerization monomer a is 0.2-5g / hr; preferably, relative to the second prepolymerization reactor with a volume of 5L, the flow rate of the polymerization monomer b is 5-30kg / hr.

[0047] In the present invention, in actual operation, the polymerizable monomer a, the main catalyst, the first cocatalyst and the first external electron donor are input in the form of a solution, wherein the concentration of the main catalyst in the main catalyst solution is 0.01-0.5 g / mL, the concentration of the first cocatalyst in the first cocatalyst solution is 5-15 wt%, and the concentration of the external electron donor in the first external electron donor solution is 5-15 g / mL. The solvent is an inert solvent. Preferably, the first cocatalyst and the first external electron donor are delivered in the form of pure components.

[0048] In the present invention, in order to make the obtained polyolefin composition have thicker lamella thickness and long period thickness, better impact performance and good heat resistance, the main catalyst is selected from at least one of Ziegler-Natta hydrocarbon catalyst, chromium-based catalyst and vanadium-based catalyst, more preferably a Ziegler-Natta polymerization catalyst.

[0049] In the present invention, in order to make the obtained polyolefin composition have thicker lamella thickness and long period thickness, better impact performance and good heat resistance, the second prepolymerization catalyst component includes a second cocatalyst and an optional second external electron donor. Preferably, based on the total weight of the first co-catalyst and the second co-catalyst, the amount of the first co-catalyst is 1-99 weight%, which can be 1 weight%, 5 weight%, 10 weight%, 20 weight%, 30 weight%, 40 weight%, 50 weight%, 60 weight%, 70 weight%, 80 weight%, 90 weight%, 99 weight% or the range formed by any two of the above values ​​and the value within the range, more preferably 5-90 weight%; further preferably, based on the total weight of the first external electron donor and the second external electron donor, the amount of the first external electron donor is 1-100 weight%, which can be 1 weight%, 5 weight%, 10 weight%, 20 weight%, 30 weight%, 40 weight%, 50 weight%, 60 weight%, 70 weight%, 80 weight%, 90 weight%, 100 weight% or the range formed by any two of the above values ​​and the value within the range, more preferably 5-90 weight%.

[0050] In the present invention, the main catalyst contains active sites and is a common catalyst for preparing polyolefins in the art. The main catalyst is at least one of a Ziegler-Natta catalyst, a chromium-based catalyst and a vanadium-based catalyst, preferably a Ziegler-Natta catalyst.

[0051] In the present invention, the main catalyst is a product prepared from a magnesium source, a titanium source and an internal electron donor. The contents of magnesium, titanium and the internal electron donor are not particularly limited and can be any value of the content in conventional catalyst components in the art. Preferably, the molar ratio of the magnesium source calculated as magnesium element, the titanium source calculated as titanium element and the internal electron donor is 1:20-150:0.1-0.9, preferably 1:30-120:0.15-0.6.

[0052] In the present invention, the magnesium source is at least one of a magnesium halide, a magnesium alcoholate, a magnesium halogenated alcoholate and a magnesium halide adduct carrier. The magnesium halide may be magnesium chloride and / or magnesium bromide; the magnesium alcoholate may be diethoxymagnesium; the magnesium halogenated alcoholate may be ethoxymagnesium chloride; the types of the magnesium halide adduct carrier are well known to those skilled in the art, for example, the magnesium halide adduct carriers disclosed in CN1091748A, CN101050245A, CN101486722A, 201110142357.X, 201110142156.X and 201110142024.7, and all the relevant contents disclosed in these patents are introduced into the present invention as reference. The specific preparation method of the magnesium halide adduct carrier may include the following steps: mixing the components forming the magnesium halide adduct, heating the reaction to generate a magnesium halide adduct melt, the reaction temperature is 90-140°C, placing the components in a cooling medium after high shearing in a dispersion medium to form spherical magnesium halide adduct particles, washing and drying to obtain a spherical carrier, and selectively adding an internal electron donor during or after the high shearing process. The high shearing process can be obtained by conventional methods, such as high-speed stirring method (such as CN1330086A), spray method (such as US6020279), high-gravity rotating bed (such as CN1580136A) and emulsifier method (CN1463990A). The dispersion medium may be, for example, a hydrocarbon inert solvent, such as at least one of kerosene, white oil, silicone oil, paraffin oil and vaseline oil. The cooling medium may be, for example, selected from at least one of pentane, hexane, heptane and petroleum ether.

[0053] In the present invention, the titanium source may be a general formula of Ti(OR') 3-a Z a and / or Ti(OR') 4-b Z b A substance wherein R' is C1-C 20 alkyl, Z is F, Cl, Br or I, a is an integer of 1 to 3, and b is an integer of 1 to 4. Preferably, the titanium source is at least one of titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, tributoxytitanium chloride, dibutoxytitanium dichloride, butoxytitanium trichloride, triethoxytitanium chloride, diethoxytitanium dichloride, ethoxytitanium trichloride and titanium trichloride.

[0054] In the present invention, the internal electron donor is at least one of phthalate, phosphate and diether compounds.

[0055] In the present invention, when the internal electron donor is a phthalate compound, its general formula is as shown in Formula 1 below:

[0056]

[0057] Wherein, R1 is C2-C8 straight chain alkyl, C3-C 10 Branched alkyl, C5-C 10 Cycloalkyl, C6-C 15 Aryl, or C7-C 15 Preferably, R1 is a C3-C8 straight chain alkyl, a C3-C 10 Branched alkyl, C6-C 10 Aryl, or C7-C 10 Alkaryl or aralkyl.

[0058] Wherein, R2-R5 may be the same or different and are hydrogen, halogen, C1-C6 straight chain alkyl, C3-C 10 Branched alkyl, C5-C 10 Cycloalkyl, C6-C 20 Aryl, or C7-C 20 Preferably, R2-R5 may be the same or different and are hydrogen, halogen, C1-C6 straight chain alkyl, C3-C6 branched chain alkyl, and the hydrogen on the alkyl carbon may be optionally replaced by an alkane or a halogen atom.

[0059] In the present invention, the specific implementation examples of the phthalate compounds include but are not limited to: dimethyl phthalate, diethyl phthalate, di-n-propyl phthalate, diisopropyl phthalate, di-n-butyl phthalate, diisobutyl phthalate, di-n-pentyl phthalate, diisopentyl phthalate, di-n-hexyl phthalate, diisohexyl phthalate, di-n-octyl phthalate, diisooctyl phthalate, dibenzyl phthalate, tetramethyl Dimethyl phthalate, diethyl tetramethylphthalate, di-n-propyl tetramethylphthalate, diisopropyl tetramethylphthalate, di-n-butyl tetramethylphthalate, diisobutyl tetramethylphthalate, di-n-pentyl tetramethylphthalate, diisopentyl tetramethylphthalate, di-n-hexyl tetramethylphthalate, diisohexyl tetramethylphthalate, di-n-octyl tetramethylphthalate, diisooctyl tetramethylphthalate, dibenzyl tetramethylphthalate, etc. Preferably, dibutyl phthalate is used.

[0060] In the present invention, the type of the phosphate compound is not particularly limited, and can be any existing phosphate compound that can be used as an electron donor in an olefin polymerization catalyst. Preferably, the phosphate compound is selected from at least one of the phosphate compounds shown in Formula 2.

[0061]

[0062] wherein R6, R7 and R8 are each independently selected from a C1-C4 straight chain or branched chain alkyl, a C3-C 20 Cycloalkyl, C6-C 20 Aryl, C7-C 20 Alkyl and C7-C 20 Further preferably, R6, R7 and R8 are each independently selected from a C1-C4 straight chain or branched chain alkyl, a C3-C 12 Cycloalkyl, C6-C 12 Aryl, C7-C 12 Alkyl and C7-C 12 Preferably, R6, R7 and R8 are each independently selected from one of a C1-C4 straight or branched alkyl group, a C3-C6 cycloalkyl group, a C6-C8 aryl group, a C7-C8 alkylaryl group and a C7-C8 arylalkyl group, and the hydrogen atoms on the benzene ring in the aryl group, the alkylaryl group and the arylalkyl group are optionally substituted by halogen atoms; for example, R6, R7 and R8 are each independently selected from a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a phenyl group, a tolyl group, a dimethylphenyl group, an ethylphenyl group, a benzyl group, a methylbenzyl group or a phenethyl group.

[0063] In the present invention, the phosphate compound is selected from at least one of trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, tricresyl phosphate, triisopropylphenyl phosphate, trimethoxyphenyl phosphate, phenyl dimethyl phosphate, cresyl dibutyl phosphate, isopropylphenyl dimethyl phosphate, isopropylphenyl diethyl phosphate, isopropylphenyl dibutyl phosphate, phenyl ditolyl phosphate, phenyl diisopropylphenyl phosphate, p-cresyl dibutyl phosphate, m-cresyl dibutyl phosphate, p-cumyl dimethyl phosphate, p-cumyl diethyl phosphate, p-tert-butylphenyl dimethyl phosphate and o-cresyl p-di-tert-butylphenyl phosphate.

[0064] In the present invention, the diether compound can be any diether compound that can be used as an electron donor in an olefin polymerization catalyst. Preferably, the diether compound has the general formula: R9R 10 C(CH2OR 11 )(CH2OR 12 ), where R9 and R 10 Each independently selected from hydrogen, C1-C 20 Straight or branched alkyl, C3-C 20 Cycloalkyl, C6-C 20 Aryl, C7-C 20 Arylalkyl and C7-C 20 One of the alkylaryl groups, R11 and R 12 Each independently selected from C1-C 10 Preferably, the diether compound is selected from 2-(2-ethylhexyl)-1,3-dimethoxypropane, 2-isopropyl-1,3-dimethoxypropane, 2-butyl-1,3-dimethoxypropane, 2-sec-butyl-1,3-dimethoxypropane, 2-cyclohexyl-1,3-dimethoxypropane, 2-phenyl-1,3-dimethoxypropane, 2-(2-phenylethyl)-1,3-dimethoxypropane, 2-(2-cyclohexylethyl)-1,3-dimethoxypropane, 2-(p-chlorophenyl)-1,3-dimethoxypropane, 2-(diphenylmethyl)-1,3-dimethoxypropane, 2,2-dicyclohexyl-1,3-dimethoxypropane, 2 ,2-dicyclopentyl-1,3-dimethoxypropane, 2,2-diethyl-1,3-dimethoxypropane, 2,2-dipropyl-1,3-dimethoxypropane, 2,2-diisopropyl-1,3-dimethoxypropane, 2,2-dibutyl-1,3-dimethoxypropane, 2-methyl-2-propyl-1,3-dimethoxypropane, 2-methyl-2-benzyl-1,3-dimethoxypropane, 2-methyl-2-ethyl-1,3-dimethoxypropane, 2-methyl-2-isopropyl-1,3-dimethoxypropane, 2-methyl-2-phenyl-1,3-dimethoxypropane, 2-methyl-2-cyclohexyl-1,3-dimethoxypropane, 2,2- Bis(2-cyclohexylethyl)-1,3-dimethoxypropane, 2-methyl-2-isobutyl-1,3-dimethoxypropane, 2-methyl-2-(2-ethylhexyl)-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxypropane, 2,2-diphenyl-1,3-dimethoxypropane, 2,2-dibenzyl-1,3-dimethoxypropane, 2,2-bis(cyclohexylmethyl)-1,3-dimethoxypropane, 2-isobutyl-2-isopropyl-1,3-dimethoxypropane, 2-(1-methylbutyl)-2-isopropyl-1,3-dimethoxypropane, 2-isopropyl-2-isopentyl-1,3-dimethoxypropane, At least one of 2-phenyl-2-isopropyl-1,3-dimethoxypropane, 2-phenyl-2-sec-butyl-1,3-dimethoxypropane, 2-benzyl-2-isopropyl-1,3-dimethoxypropane, 2-cyclopentyl-2-isopropyl-1,3-dimethoxypropane, 2-cyclopentyl-2-sec-butyl-1,3-dimethoxypropane, 2-cyclohexyl-2-isopropyl-1,3-dimethoxypropane, 2-cyclohexyl-2-sec-butyl-1,3-dimethoxypropane, 2-isopropyl-2-sec-butyl-1,3-dimethoxypropane, 2-cyclohexyl-2-cyclohexylmethyl-1,3-dimethoxypropane and 9,9-dimethoxymethylfluorene.

[0065] In the present invention, tributyl phosphate is preferably used in combination with 2-isopropyl-2-isopentyl-1,3-dimethoxypropane as an internal electron donor, which can effectively improve the hydrogen modulation sensitivity and stereospecificity of the catalyst. Most preferably, when tributyl phosphate and 2-isopropyl-2-isopentyl-1,3-dimethoxypropane are used in combination as internal electron donors, the molar ratio of tributyl phosphate to 2-isopropyl-2-isopentyl-1,3-dimethoxypropane is controlled at 0.03-0.15:1, which can further effectively improve the hydrogen modulation sensitivity and stereospecificity of the catalyst.

[0066] In the present invention, the first cocatalyst and the second cocatalyst are organic aluminum compounds. Preferably, they are alkyl aluminum compounds, including but not limited to: at least one of triethyl aluminum, triisobutyl aluminum, tri-n-butyl aluminum, tri-n-hexyl aluminum, diethyl aluminum monochloride, diisobutyl aluminum monochloride, di-n-butyl aluminum monochloride, di-n-hexyl aluminum monochloride, ethyl aluminum dichloride, diisobutyl aluminum dichloride, n-butyl aluminum dichloride and n-hexyl aluminum dichloride. The alkyl aluminum compound is more preferably trialkyl aluminum, such as triethyl aluminum, triisobutyl aluminum, tri-n-butyl aluminum. The first cocatalyst and the second cocatalyst may be the same or different.

[0067] In the present invention, the first external electron donor and the second external electron donor are organic silicon compounds. The general formula is R 13 R 14 Si(OR 15 )2; wherein R 13 With R 14 Each independently selected from C1-C6 straight or branched alkyl, C3-C8 cycloalkyl and C5-C 12 The heteroaryl group, R 15is a C1-C3 straight-chain aliphatic group. Specific examples include, but are not limited to, methyl-cyclopentyl-dimethoxysilane, ethyl-cyclopentyl-dimethoxysilane, n-propyl-cyclopentyl-dimethoxysilane, bis(2-methylbutyl)-dimethoxysilane, bis(3-methylbutyl)-dimethoxysilane, 2-methylbutyl-3-methylbutyl-dimethoxysilane, bis(2,2-dimethyl-propyl)-dimethoxysilane, 2-methylbutyl-2,2-dimethyl-propyl-dimethoxysilane, 3-methylbutyl-2,2-dimethyl-propyl- Dimethoxysilane dimethyldimethoxysilane, dimethyldiethoxysilane, diisobutyldimethoxysilane, methylcyclohexyldimethoxysilane, methylisobutyldimethoxysilane, dicyclohexyldimethoxysilane, methyl-isopropyldimethoxysilane, isopropyl-cyclopentyldimethoxysilane, dicyclohexyldimethoxysilane, methyl-isopropyldimethoxysilane, isopropyl-cyclopentyldimethoxysilane, dicyclopentyldimethoxysilane, isopropyl-isobutyldimethoxysilane, diisopropyldimethoxysilane, etc. Preferably dicyclopentyldimethoxysilane, dicyclohexyldimethoxysilane, methylcyclohexyldimethoxysilane, diisopropyldimethoxysilane, diisobutyldimethoxysilane, tetramethoxysilane. The first external electron donor and the second external electron donor can be the same or different. When they are different, the second external electron donor is preferably an external electron donor that can further increase the isotactic index of the polymer. The degree of influence of different external electron donors on the isotactic index of the polymer is well known to those skilled in the art.

[0068] In the present invention, in order to make the obtained polyolefin composition have thicker sheet thickness and long period thickness, better impact performance and good heat resistance, the structural formula of the polymerized monomer a is CH2=CR 16 R 17 , where R 16 and R 17 Each is independently hydrogen, a substituted or unsubstituted chain carbon-containing group, a substituted or unsubstituted aromatic ring group or a substituted or unsubstituted condensed ring group; more preferably, the chain carbon-containing group contains 4-20 carbon atoms; further preferably, the aromatic ring group or condensed ring group contains 4-20 carbon atoms, preferably 5-16 carbon atoms.

[0069] In the present invention, in order to make the obtained polyolefin composition have thicker lamella thickness and long period thickness, better impact performance and good heat resistance, the polymerized monomer a is at least one of vinyl compounds containing cyclic alkyl, aromatic or branched alkyl groups; preferably, the polymerized monomer a is selected from at least one of vinyl cyclohexane, styrene, vinyl cyclopentane, vinyl-2-methylcyclohexane, 3-methyl-1-butene, 3-ethyl-1-hexene, 3-methyl-1-pentene and 4-methyl-1-pentene.

[0070] In the present invention, the first prepolymerization reaction system further includes an inert solvent, which does not participate in the polymerization reaction, and is selected from at least one of oils and fats and hydrocarbon compounds; preferably, the carbon number of the oils and fats is 8-40; more preferably, the carbon number of the hydrocarbon compounds is 2-16, more preferably 3-10; further preferably, the hydrocarbon compounds are selected from at least one of propane, n-butane, isobutane, n-pentane, isopentane, n-hexane and cyclohexane. The inert solvent accounts for 50wt% and below of the total slurry content, preferably <10wt%.

[0071] In the present invention, the first prepolymerization reactor can be in various forms, such as a kettle reactor, a tubular reactor, or even a pipeline reactor. Any container that meets the above operating conditions can be defined as the first prepolymerization reactor, preferably a tubular reactor or a pipeline reactor.

[0072] In the present invention, the first prepolymerization reaction can even be carried out in a continuous pre-complexing reactor. Pre-complexing reactors are well known to those skilled in the art.

[0073] In the present invention, the second prepolymerization reaction system further comprises an inert solvent, which has been described above and will not be described in detail here.

[0074] In the present invention, in order to adjust the molecular weight, the first prepolymerization reactor and the second prepolymerization reactor may further contain hydrogen.

[0075] In the present invention, the second prepolymerization reactor can be in various forms, such as a kettle reactor, a tubular reactor, or even a pipeline reactor. Any container that meets the above operating conditions can be defined as the first prepolymerization reactor, preferably a tubular reactor or a pipeline reactor.

[0076] In the present invention, in order to make the obtained polyolefin composition have thicker lamella thickness and long period thickness, better impact performance and good heat resistance, the polymerized monomer b is selected from olefin compounds and / or aromatic hydrocarbon compounds; preferably, the polymerized monomer b contains a carbon-carbon double bond and / or a carbon-carbon triple bond; more preferably, the number of carbon atoms in the polymerized monomer b is 2-16; further preferably, the polymerized monomer b is selected from ethylene, propylene, butene-1, hexene-1, octene-1, propadiene, C3-C 12 One of cycloolefin, 1,3-butadiene, 1,4-butadiene, 1,2-pentadiene, 1,3-pentadiene, 1,4-pentadiene, vinylcyclopentane and vinylcyclohexane.

[0077] Preferably, the polymerized monomer b and the polymerized monomer a may be the same or different, preferably different.

[0078] According to the present invention, the method comprises:

[0079] (1) in a first prepolymerization reactor, mixing a polymerizable monomer a with a main catalyst, a first cocatalyst and a first external electron donor to carry out a first prepolymerization reaction;

[0080] (2) continuously conveying the product obtained in step (1) to a second prepolymerization reactor, contacting it with a polymerizable monomer b, a second cocatalyst, and a second external electron donor to carry out a second prepolymerization reaction; the relationship between the prepolymerization ratio REP1 of the first prepolymerization reaction and the prepolymerization ratio REP2 of the second prepolymerization reaction is REP1 / REP2≤0.4, and the polymerizable monomer a is not propylene;

[0081] (3) The product obtained in step (2) is mixed with polymerizable monomer c to carry out polymerization reaction.

[0082] In the present invention, in order to make the obtained polyolefin composition have thicker lamella thickness and long period thickness, better impact performance and good heat resistance, the polymerized monomer c is selected from olefin compounds and / or aromatic hydrocarbon compounds; more preferably, the polymerized monomer c contains a carbon-carbon double bond and / or a carbon-carbon triple bond; more preferably, the number of carbon atoms in the polymerized monomer c is 2-16; further preferably, the polymerized monomer c is selected from ethylene, propylene, butene-1, hexene-1, octene-1, propadiene, C3-C 12 One of cycloolefins, 1,3-butadiene, 1,4-butadiene, 1,2-pentadiene, 1,3-pentadiene, 1,4-pentadiene, vinylcyclopentane and vinylcyclohexane, preferably at least one of ethylene, propylene, butene-1, hexene-1 and octene-1.

[0083] In the present invention, the polymerizable monomer c and the polymerizable monomer b may be the same or different, and are preferably the same.

[0084] In the present invention, the weight ratio of the total weight of the polymerized monomer b and the polymerized monomer c to the weight of the polymerized monomer a is 10 3 -10 5 :1, which can be (1×10 3 ):1,(2×10 3 ):1,(4×10 3 ):1,(6×10 3 ):1,(8×10 3 ):1,(1×10 4 ):1,(2×10 4 ):1,(4×10 4 ):1,(6×10 4 ):1,1:(8×10 4 ):1,(1×10 5 ):1 or the range formed by any two of the above values ​​and the values ​​within the range.

[0085] In the present invention, the polyolefin catalyst composition flows out from the second prepolymerization reactor and is continuously transported to the main reactor.

[0086] In the present invention, the main reactor is in the form of one or more reactors in various forms such as fluidized bed reactor, tubular reactor, kettle reactor, multiphase multi-zone reactor, etc., and the reaction phase in the reactor is various phases such as gas-solid phase, solid-liquid phase, solid-liquid-gas phase, solution phase, etc.

[0087] In the present invention, the main reactor also includes hydrogen, and the concentration of the hydrogen is 1000-4000 ppmv.

[0088] The third aspect of the present invention provides a polyolefin composition prepared by the above method.

[0089] According to the present invention, the polyolefin has been described above and will not be described in detail here.

[0090] The present invention will be described in detail below through examples. In the following examples, the first prepolymerization ratio (REP1) = the mass of the polymer produced by the first prepolymerization / the mass of the main catalyst, wherein the mass of the main catalyst in the sampling tank is calculated by weighing the sample using an online fixed volume sampling tank and calculating the mass of the main catalyst in the sampling tank, and the calculation and analysis method is used to obtain the result.

[0091] The second prepolymerization ratio (REP2) = mass of polymer produced by the second prepolymerization / mass of the main catalyst, wherein the mass of the main catalyst in the sampling tank is calculated by sampling and weighing using an online fixed volume sampling tank, and the mass of the main catalyst in the sampling tank is calculated and obtained by calculation and analysis.

[0092] Tensile yield stress: The prepared polymer was granulated by screw and injection molded to obtain a specimen, which was measured in accordance with GB / T1040.2-2006;

[0093] Flexural modulus: The prepared polymer was granulated by screw and injection molded to obtain a specimen, which was measured in accordance with GB / T 9341-2008;

[0094] Charpy notched impact strength: The prepared polymer was granulated by screw and injection molded to obtain a specimen, which was measured at 23°C in accordance with GB / T 1043.1-2008;

[0095] Heat deformation temperature: The prepared polymer is granulated by screw and injection molded to obtain specimens, which is measured according to GB / T 1634.2-2004.

[0096] Calculation of long-period thickness and lamellar crystal thickness: The injection molded splines were tested using a Nanostar small-angle X-ray scattering instrument from Bruker, Germany. The instrument tube voltage was 45 kV, the tube current was 0.65 mA, and the Cu Kα ray (wavelength 0.1542 nm) was used. The resolution of the two-dimensional surface detector was 2048×2048, and the pixel size was 68 μm×68 μm. The distance from the injection molded spline to the detector was 104.65 cm. The test time for a single spline was 30 minutes. The obtained two-dimensional scattering pattern was normalized and back-ground corrected. Subsequently, the one-dimensional Iq (I is the scattering intensity, q is the scattering vector) scattering curve was obtained by integration, and the fan integration angle was 0-180°. Long-period thickness d ac According to the Bragg formula based on one-dimensional scattering curve Calculate, where q max is the q value at the maximum scattering intensity I of the one-dimensional scattering curve. The thickness of the lamellar crystal region d c =d ac *Quality crystallinity.

[0097] Melting temperature, crystallization temperature and mass crystallinity: measured by using a Diamond differential scanning calorimeter from Perkin-Elmer. Take about 5-6 mg of sample and place it in a crucible. In a nitrogen atmosphere, heat the sample to 200°C at 10°C / min, which is recorded as the first heating melting curve. Keep at 200°C for 5 minutes. Cool down to 25°C at 10°C / min, which is recorded as the first cooling crystallization curve. Keep at 25°C for 5 minutes. Heat up to 200°C at 10°C / min again, which is recorded as the second heating melting curve. The melting temperature is the peak point of the second melting curve, and the crystallization temperature is the peak point of the first crystallization curve. The mass crystallinity is calculated by comparing the area of ​​the melting peak in the second melting curve with the corresponding enthalpy value when polypropylene is 100% crystallized, and calculating the ratio. The corresponding enthalpy value when polypropylene is 100% crystallized is 208J / g.

[0098] The xylene soluble content (XS) was tested using the Cryst-EX instrument from Polymer Char. Trichlorobenzene was used as solvent, the temperature was raised to 150°C for dissolution, the sample was tested at a constant temperature for 90 minutes, then the temperature was lowered to 40°C, the temperature was kept constant for 70 minutes, and the sample was tested. The obtained 40°C trichlorobenzene soluble content was converted to the room temperature xylene soluble content of GB / T 24282-2009 through the standard curve.

[0099] Melt flow index (MFR): The pellets obtained from each granulation were measured according to GB / T3682-2000 using a 7026 melt flow indexer from CEAST at 230°C and a load of 2.16 kg.

[0100] Polymer weight average molecular weight: measured by GPC method.

[0101] Example 1

[0102] Propylene polymerization Figure 1 Process:

[0103] The propylene polymerization reaction is carried out in a bulk propylene polymerization device, which mainly includes a first prepolymerization reactor (3L), a second prepolymerization reactor (5L) and a loop reactor (75L).

[0104] (1) First Prepolymerization Reaction

[0105] The main catalyst (DQC-401, produced by Beijing Aoda Branch of Sinopec Catalyst Co., Ltd., catalyst grease slurry 0.2g / mL) has a flow rate of 4mL / hr, the flow rate of triethylaluminum hexane solution (10wt%) is 6g / hr, and the flow rate of external electron donor (cyclohexylmethyldimethoxysilane, C-donor) hexane solution (10wt%) is 1g / hr to form a catalyst composition 101, which is continuously injected into the first prepolymerization reactor 01.

[0106] The liquid phase feed stream 102 composed of 4-methyl-1-pentene hexane solution (1wt%) has a flow rate of 0.2kg / hr and is continuously injected into the first prepolymerization reactor 01; the prepolymerization temperature of the first prepolymerization reactor 01 is 55°C, the operating pressure is 4MPaG, the residence time is about 9.5h, and the prepolymerization ratio measured by sampling is about 5 times.

[0107] (2) Second Prepolymerization

[0108] The first prepolymerization catalyst slurry 201, about 0.21kg / hr, is mixed with the liquid propylene stream 202 with a flow rate of 12kg / hr and then injected into the second prepolymerization reactor 02; the flow rate of triethylaluminum hexane solution (10wt%) is 90g / hr, and the flow rate of external electron donor (cyclohexylmethyldimethoxysilane, C-donor) hexane solution (10wt%) is 8g / hr; the prepolymerization temperature of the second prepolymerization reactor 02 is 18°C, the operating pressure is 4MPaG, the residence time is about 12min, and the prepolymerization ratio measured by sampling is about 100 times.

[0109] (3) Polymerization reaction in the main reactor

[0110] The second prepolymerization catalyst slurry 301, about 12.3 kg / hr, is continuously injected into the main reactor 03. The polymerization reaction temperature is 70°C, the reaction pressure is 4.0 MPaG, the total propylene feed in the reactor (including liquid propylene feed stream 202) is 30 kg / h, and hydrogen enters with the main reactor propylene feed. The hydrogen concentration in the reactor is about 2400 ppmv.

[0111] (4) Granulation

[0112] 100 parts by weight of polymer powder, 0.25 parts by weight of antioxidant B225 (168:1010=1:1 (g / g)), and 0.05 parts by weight of halogen absorber (calcium stearate) were blended, and then extruded and granulated by a twin-screw extruder to obtain polymer pellets. The speed of the screw extruder was 350 rpm, and the temperatures of the first to sixth sections were 200° C., 210° C., 215° C., 215° C., 215° C., and 210° C., respectively. The properties of the obtained polyolefin composition are shown in Tables 1 and 2.

[0113] Example 2

[0114] The method of Example 1 was followed, except that 4-methyl-1-pentene was replaced with vinylcyclohexane. The obtained polyolefin compositions are shown in Tables 1 and 2.

[0115] Example 3

[0116] The method of Example 1 was followed, except that cyclohexylmethyldimethoxysilane was replaced with dicyclopentyldimethoxysilane (Donor-D) in step (2), and the hydrogen concentration in the reactor was about 3400 ppmv in step (3). The properties of the obtained polyolefin composition are shown in Tables 1 and 2.

[0117] Example 4

[0118] According to the method of Example 1, the difference is that in step (1), the main catalyst is replaced, and the main catalyst is prepared as follows: in a 300mL glass reaction bottle, 90mL (820mmol) of titanium tetrachloride is added and cooled to -20°C, 37mmol of magnesium halide carrier is added thereto in terms of magnesium element, and then the temperature is raised to 110°C, and 0.3mmol of tributyl phosphate and 7.3mmol of 2-isopropyl-2-isopentyl-1,3-dimethoxypropane are added during the heating process, and the liquid is filtered off after maintaining at 110°C for 30min, and the catalyst component Cat-1 is obtained after washing with titanium tetrachloride twice and with hexane five times. The catalyst component Cat-1 is obtained after vacuum drying. The phosphorus content in terms of phosphorus element in the catalyst component Cat-1 is 0.011% by weight as measured by X-ray fluorescence spectrometry. The preparation process of the magnesium halide carrier is to mix the components that form the magnesium halide adduct, heat the reaction to generate a magnesium halide adduct melt, the reaction temperature is 125°C, and after high shearing in a methyl silicone oil medium, put it into a hexane medium to form spherical magnesium halide adduct particles, and obtain a spherical carrier after washing and drying.

[0119] In step (3), the hydrogen concentration in the reactor is controlled to be about 1300 ppmv. The properties of the obtained polyolefin composition are shown in Tables 1 and 2.

[0120] Example 5

[0121] The method of Example 1 was followed, except that the flow rate of the liquid phase stream 102 composed of 4-methyl-1-pentene hexane solution (1 wt%) was 0.5 kg / hr. The residence time was about 3.6 h. The properties of the obtained polyolefin composition are shown in Tables 1 and 2.

[0122] Example 6

[0123] The method of Example 1 is different in that the first prepolymerization reaction in step (1) is as follows:

[0124] The main catalyst (Ziegler-Natta catalyst, HR, produced by Sinopec Oda Catalyst Branch, catalyst oil slurry 0.1g / mL) flow rate is 4mL / hr, the triethylaluminum hexane solution (10wt%) flow rate is 10g / hr, and the external electron donor (cyclohexylmethyldimethoxysilane, C-donor) hexane solution (10wt%) flow rate is 1g / hr to form a catalyst composition, which is continuously injected into the first prepolymerization reactor 01.

[0125] The liquid phase stream 102 composed of 4-methyl-1-pentene hexane solution (1 wt%) was continuously injected into the first prepolymerization reactor 01 at a flow rate of 0.2 kg / hr; the prepolymerization temperature of the first prepolymerization reactor 01 was 55° C., the operating pressure was 4 MPaG, and the residence time was about 9.5 h. The properties of the obtained polyolefin composition are shown in Tables 1 and 2.

[0126] Example 7

[0127] The method of Example 1 is followed, except that 4-methyl-1-pentene is adjusted to be a pure solvent feed with a flow rate of 0.1 kg / hr, the first prepolymerization residence time is about 19 hours, and the first prepolymerization ratio is about 35 times. The properties of the obtained polyolefin composition are shown in Tables 1 and 2.

[0128] Comparative Example 1

[0129] The method of Example 1 is different in that the first prepolymerization reactor is eliminated, and the materials entering the first prepolymerization are mixed with the liquid propylene stream 202 and then injected into the second prepolymerization reactor 02. The properties of the obtained polyolefin composition are shown in Tables 1 and 2.

[0130] Comparative Example 2

[0131] The method of Example 1 was followed, except that 4-methyl-1-pentene was replaced with liquid propylene, and the flow rate of liquid propylene was 6 g / hr. The properties of the obtained polyolefin composition are shown in Tables 1 and 2.

[0132] Comparative Example 3

[0133] (1) Catalyst modification treatment

[0134] The main catalyst (Ziegler-Natta catalyst, DQC-401, produced by Sinopec Aoda Catalyst Branch) has a mass of 100 g, triethylaluminum hexane solution (10 wt%) is 2500 g, external electron donor (C-donor) hexane solution (10 wt%) is 25 g, and vinyl cyclohexane (VCH) is 500 g. They are stirred and blended in a 10 L stainless steel container at 55 ° C for 12 h. Then the solid catalyst particles are obtained by cooling and drying.

[0135] (2) Prepolymerization

[0136] Same as Comparative Example 1, except that 4-methyl-1-pentene hexane solution (1 wt %) was not added.

[0137] (3) Polymerization reaction in the main reactor

[0138] Same as Example 1.

[0139] (4) Granulation

[0140] Same as Example 1. The properties of the obtained polyolefin composition are shown in Table 1 and Table 2 (Comparative Example 3-1).

[0141] (5) Repeat steps (1) to (4) once. The properties of the obtained polyolefin composition are shown in Table 1 and Table 2 (Comparative Example 3-2).

[0142] Table 1

[0143]

[0144]

[0145] Table 2

[0146]

[0147] From the results in Table 1, it can be seen that the polyolefin composition obtained by the method of the present invention has a thicker long period thickness and lamellar crystal region thickness, a lower content of xylene solubles and a higher crystallinity, and the melting temperature and crystallization temperature are also improved. From the results in Table 2, it can be seen that the mechanical properties of the polyolefin composition obtained are also highly improved.

[0148] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A polyolefin composition, characterized in that The long period thickness of the polyolefin composition is 12 nm or more; the thickness of the lamellar crystal region is 6.5 nm or more, and the mass crystallinity is 56% or more.

2. The polyolefin composition according to claim 1, wherein The long period thickness is 12-24 nm, preferably 14-22 nm; And / or, the lamellar crystal region has a thickness of 6.5-15 nm, preferably 7.5-15 nm; And / or, the polyolefin composition further contains xylene solubles, and the content of the xylene solubles is 1-4wt%; and / or, the polyolefin composition has a melt index of 4-30 g / 10 min, preferably 6-25 g / 10 min, at 230° C. and 2.16 kg load; and / or, the weight average molecular weight of the polyolefin is 200,000-40,000, preferably 230,000-350,000; and / or, the flexural modulus of the polyolefin composition is not less than 1800 MPa, preferably 1830-2000 MPa; and / or, the heat deformation temperature of the polyolefin composition is not less than 110°C, preferably 112-120°C; and / or, at 23°C, the polyolefin composition has a simple supported beam notch of not less than 3 kJ / m 2 , preferably 3-3.5 kJ / m 2 ; and / or, the tensile yield stress of the polyolefin composition is not less than 40 MPa, preferably 40-42 MPa; And / or, the mass crystallinity of the polyolefin composition is 59-63%; and / or, the crystallization temperature of the polyolefin composition is not less than 125°C, preferably 126-131°C; And / or, the melting temperature of the polyolefin composition is not less than 164°C, preferably 165-167°C.

3. The polyolefin composition according to claim 1 or 2, wherein The polyolefin in the polyolefin composition is at least one of a homopolymer, a random copolymer, a block copolymer and an impact copolymer; Preferably, the structural units of the polyolefin in the polyolefin composition are provided by olefins having 4 to 16 carbon atoms; Preferably, the polyolefin contains structural units provided by propylene.

4. A method for preparing a polyolefin composition, characterized in that: The method comprises: (1) in a first prepolymerization reactor, mixing a polymerizable monomer a with a first prepolymerization catalyst component to conduct a first prepolymerization reaction; (2) continuously conveying the product obtained in step (1) to a second prepolymerization reactor, contacting it with a second prepolymerization catalyst component and a polymerizable monomer b to carry out a second prepolymerization reaction; the relationship between the prepolymerization ratio REP1 of the first prepolymerization reaction and the prepolymerization ratio REP2 of the second prepolymerization reaction satisfies: REP1 / REP2≤0.4, and the polymerizable monomer a is not propylene; (3) The product obtained in step (2) is mixed with polymerizable monomer c to carry out polymerization reaction.

5. The method according to claim 4, wherein: REP1 / REP2≤0.2; And / or, the prepolymerization ratio REP1 of the first prepolymerization reaction is ≤50 times, preferably ≤30 times, more preferably 2-15 times; And / or, the prepolymerization ratio REP2 of the second prepolymerization reaction is 1-1000 times, preferably 10-500 times, more preferably 30-300 times; And / or, the method does not include cooling and / or drying operations between step (1) and step (2); And / or, the conditions of the first prepolymerization reaction include: temperature of 0-90°C, preferably 10-70°C; pressure of 0.1-10MPaG, preferably 1-5MPaG; time of 1-36h, preferably 5-20h; And / or, the conditions of the second prepolymerization reaction include: temperature of -30°C to 100°C, preferably -10°C to 70°C; pressure of 0.1-10 MPaG, preferably 1-5 MPaG; time of ≤2h, preferably 1-90min; And / or, the polymerization reaction conditions include: temperature of 20-100° C., preferably 40-91° C.; pressure of 0.1-10 MPaG, preferably 1-5 MPaG; time of ≤4 h, preferably 1-3 h.

6. The method according to claim 4 or 5, wherein: The first prepolymerized catalyst component comprises a main catalyst, a first co-catalyst and a first external electron donor; Preferably, the weight ratio of the polymerizable monomer a, the main catalyst and the first co-catalyst is 1:0.01-0.5:0.01-1; Preferably, the weight ratio of the polymerizable monomer a to the first external electron donor is 1:0.001-0.1; More preferably, the weight ratio of the polymerizable monomer a to the polymerizable monomer b is 1:

10. 2 -10 4 ; Preferably, relative to the first prepolymerization reactor with a volume of 3L, the flow rate of the polymerization monomer a is 0.2-5g / hr; Further preferably, relative to the second prepolymerization reactor with a volume of 5L, the flow rate of the polymerization monomer b is 5-30kg / hr; Preferably, the main catalyst is selected from at least one of a Ziegler-Natta catalyst, a chromium-based catalyst and a vanadium-based catalyst, more preferably a Ziegler-Natta catalyst; More preferably, the second prepolymerized catalyst component comprises a second cocatalyst and optionally a second external electron donor; Preferably, based on the total weight of the first co-catalyst and the second co-catalyst, the amount of the first co-catalyst is 1-99% by weight, more preferably 5-90% by weight; Further preferably, based on the total weight of the first external electron donor and the second external electron donor, the amount of the first external electron donor is 1-100 wt %, more preferably 5-90 wt %.

7. The method according to claim 4 or 5, wherein: The structural formula of the polymerizable monomer a is CH2=CR 16 R 17 , where R 16 and R 17 Each is independently hydrogen, a substituted or unsubstituted chain carbon-containing group, a substituted or unsubstituted aromatic ring group or a substituted or unsubstituted condensed ring group; Preferably, the chain carbon-containing group contains 4-20 carbon atoms; Preferably, the aromatic ring group or condensed ring group contains 4-20 carbon atoms, preferably 5-16 carbon atoms; Preferably, the polymerizable monomer a is at least one of vinyl compounds containing a cyclic alkyl group, an aryl group or a branched alkyl group; Preferably, the polymerizable monomer a is at least one selected from vinylcyclohexane, styrene, vinylcyclopentane, vinyl-2-methylcyclohexane, 3-methyl-1-butene, 3-ethyl-1-hexene, 3-methyl-1-pentene and 4-methyl-1-pentene.

8. The method according to claim 4 or 5, wherein: The polymerizable monomer b contains a carbon-carbon double bond and / or a carbon-carbon triple bond; More preferably, the number of carbon atoms in the polymerizable monomer b is 2-16; More preferably, the polymerizable monomer b is selected from ethylene, propylene, butene-1, hexene-1, octene-1, propadiene, C3-C 12 at least one of cycloolefins, 1,3-butadiene, 1,4-butadiene, 1,2-pentadiene, 1,3-pentadiene, 1,4-pentadiene, vinylcyclopentane and vinylcyclohexane; Preferably, the polymerized monomer b is different from the polymerized monomer a.

9. The method according to claim 4 or 5, wherein: The polymerizable monomer c contains a carbon-carbon double bond and / or a carbon-carbon triple bond; More preferably, the number of carbon atoms in the polymerizable monomer c is 2-16; More preferably, the polymerizable monomer c is selected from ethylene, propylene, butene-1, hexene-1, octene-1, propadiene, C3-C 12 One of cycloolefins, 1,3-butadiene, 1,4-butadiene, 1,2-pentadiene, 1,3-pentadiene, 1,4-pentadiene, vinylcyclopentane and vinylcyclohexane, preferably at least one of ethylene, propylene, butene-1, hexene-1 and octene-1; More preferably, the polymerized monomer b and the polymerized monomer c are the same or different.

10. The polyolefin composition prepared by the method according to any one of claims 4 to 9.

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