Low-molecular-weight propylene copolymer and preparation method thereof

Abstract

The invention relates to a method for preparing a low-molecular-weight propylene copolymer and the low-molecular-weight propylene copolymer prepared by the method. The preparation method has the advantages of high polymerization activity, mild polymerization conditions, easiness in operation, high volatile component removal efficiency and extremely low metal content in the obtained polymer. The low-molecular-weight propylene copolymer provided by the invention is narrow in molecular mass distribution, low in density, wide in melting point and melt viscosity regulation range, suitable for processing technologies at various different temperatures, high in comonomer insertion rate, and more excellent in resin compatibility compared with a homopolymer; and the dispersing agent can be used as a dispersing agent, a modifying agent or a processing aid, and is beneficial to improving dispersion uniformity, precipitation uniformity and processing flowability.

Description

Technical Field

[0001] The present invention relates to a method for preparing a low molecular weight propylene copolymer and a low molecular weight propylene copolymer prepared by the method. Prior art

[0002] Low molecular weight polypropylene, also known as polypropylene wax, is a waxy-looking polypropylene with a relative molecular mass usually ranging from several hundred to tens of thousands. It can be divided into homopolymer polypropylene wax and copolymer polypropylene wax. The melting point of homopolymer polypropylene wax is usually between 135 and 160°C, with relatively high crystallinity, melting point and density, and high hardness. It is usually used as a dispersant, wear-resistant agent, lubricant, etc. The melting point of copolymer polypropylene wax is usually low (less than 140°C), and can even be lower than 90°C. The melting point can be adjusted in a wide range, the melting point and density are relatively low, the hardness is relatively soft, and it has better compatibility with resins such as polyethylene and polypropylene. It is usually used as a modifier, pigment dispersant, masterbatch carrier, etc. Polypropylene wax has similar physical and chemical properties to polyethylene wax, such as excellent chemical stability, colorless, odorless, non-toxic, completely insoluble in water and all aqueous solutions, good lubricity and dispersibility, and can be used to improve the gloss of plastic products and improve processing efficiency. But at the same time, the melting point and softening point of polypropylene wax are significantly higher than those of polyethylene wax, and it has better compatibility with plastic products such as polypropylene. At the same time, it has excellent properties such as high hardness, high lubricity, moisture resistance, better thermal stability, and a wide range of melt viscosity selection, which gives polypropylene wax more special properties and uses. For example, it can replace polyethylene wax in the manufacture of high-temperature resistant hot spinning masterbatch and high-temperature resistant hot melt adhesive products, which can effectively solve the shortcomings of polyethylene wax such as easy sublimation and odor at high temperatures, thereby broadening the application range of polyolefin wax. Polypropylene wax has higher hardness and wear resistance than polyethylene wax, and is more suitable for the wear resistance of copier toner or printing ink. Moreover, the compatibility of polypropylene wax with polypropylene resin is better than that of polyethylene wax both at the microscopic level and in the macroscopic level, and has little effect on the mechanical properties of the substrate. Due to the large difference in melting point between polyethylene wax and polypropylene resin, its unevenness and unsuitable rheology during use may cause the spinning process to break, affecting the textile properties of the fiber. The use of polypropylene wax can effectively avoid such situations.

[0003] In addition to the apparent factors such as whiteness, density, viscosity, etc., the factors affecting the quality of polypropylene wax include the molecular weight and molecular weight distribution of polypropylene wax. The molecular weight of polypropylene wax determines its product use, and the molecular weight distribution affects its application performance. Taking the application in masterbatch as an example, the molecular weight distribution has a certain influence on the performance of polypropylene wax. When waxes with basically similar molecular weights but different molecular weight distributions are used as dispersants for carbon black masterbatches, when the same coloring power is achieved, the dosage of 400P wax (MWD = 2.74) is 3%, while F4 wax (MWD = 15.97) requires more than 10%. This shows that polyolefin waxes with narrow molecular weight distribution have better dispersion effects than those with wide molecular weight distribution.

[0004] In the prior art, polypropylene wax is usually obtained by thermal cracking or peroxide-catalyzed degradation of high molecular weight polypropylene. However, the molecular weight distribution of the polypropylene wax obtained by this method is relatively wide, and the addition of peroxide will also cause the product to have an odor problem. The double bond content in the degradation product is relatively high, which easily causes the product to turn yellow, and the product quality is poor and the added value is also low. Moreover, this method has high energy consumption and does not meet the requirements of energy conservation and environmental protection under the current "dual carbon" background. A more advanced production process is to obtain low molecular weight polypropylene wax by direct polymerization of propylene monomer. This method has high polymerization activity, narrow molecular weight distribution and composition of the polymerization product, low ash content, and the polymerization product can be precisely controlled. The polymerization conditions can be controlled to obtain a series of polypropylene wax products ranging from low melting point and low viscosity to high melting point and high viscosity, and the product added value is high. Patents CN98115939.7, US4962248A, CN 105622807A, CN109422830A, etc. disclose methods for preparing polypropylene wax by catalyzing propylene polymerization using metallocene catalysts. However, these methods all adopt a propylene bulk polymerization process, and the polypropylene wax product obtained by polymerization needs to be discharged in the form of a melt. Since the melting point of the polypropylene wax is much higher than the polymerization reaction temperature and the melt viscosity of the polymer is relatively high, the pipeline is easily blocked during the discharge process, making it difficult to achieve continuous and stable production.

[0005] Therefore, the current situation is that there is still a need to develop a method for preparing polypropylene wax that is more energy-saving and environmentally friendly and has better product quality, with mild polymerization conditions, easy operation, and suitable for continuous and stable industrial production. Summary of the invention

[0006] The object of the present invention is to provide a process for preparing a low molecular weight propylene copolymer and a low molecular weight propylene copolymer prepared by said process.

[0007] In order to achieve the above object, on the one hand, the present invention provides a method for preparing a low molecular weight propylene copolymer, which comprises: reacting propylene, a comonomer and hydrogen in a polymerization solvent in the presence of a catalytic system comprising a main catalyst and a cocatalyst to obtain a low molecular weight propylene copolymer,

[0008] The main catalyst is at least one selected from metallocene catalysts and non-metallocene catalysts, and the co-catalyst is at least one selected from alkyl aluminum, aluminoxane, and boride;

[0009] The polymerization solvent is selected from an alkane solvent having a boiling point of 5-55°C or a mixed alkane solvent having a saturated vapor pressure of 20-150 KPa, preferably 40-110 KPa at 20°C, and

[0010] The molar ratio of propylene to hydrogen is (500-10):1, preferably (300-20):1, and more preferably (100-50):1.

[0011] On the other hand, the present invention provides a low molecular weight propylene copolymer prepared by the above method, whose weight average molecular weight M w The dispersion index PDI is 1.0-4.0, and the density is 0.85-0.89 g / cm 3 , crystallinity is 4-40%, melting point T m The temperature is 80 to 140° C., the Brookfield viscosity (at a temperature of 170° C.) is 30 to 15,000 mPa·s, the melting enthalpy ΔH is 8 to 85 J / g, and the comonomer content is 5 to 35 mol%.

[0012] The inventors of the present invention have conducted in-depth research and found that by using an alkane solvent with a boiling point of 5-55°C or a mixed alkane with a saturated vapor pressure of 20-150KPa at 20°C as a polymerization solvent, under the polymerization system and polymerization conditions of the present invention, the obtained propylene copolymer is beneficial to improving the subsequent devolatilization efficiency of the polymer for processing technology, and the VOCs content of the obtained polymer is lower than 100ppm, which is very beneficial to reducing the post-processing cost of the polymer and reducing the odor of the polymer.

[0013] In addition, the preparation method of the present invention has high polymerization activity (up to 10 5 gPP / gcat), the polymerization conditions are mild and easy to operate, and the metal content in the obtained polymer is extremely low (the catalyst residue is less than 5 mg / kg), which is more suitable for high-end application fields such as food packaging, medical packaging, and cosmetics that have extremely high requirements for metal content.

[0014] Compared with the prior art, the low molecular weight propylene copolymer provided by the method of the present invention has a narrow molecular weight distribution, low density, a wide melting point and melt viscosity control range, is suitable for processing at various temperatures, has a high comonomer insertion rate, and has a high grafting rate when subjected to polar group grafting modification. Compared with homopolymers, it has better resin compatibility, can be used as a dispersant, modifier or processing aid, and is beneficial to improving dispersion uniformity, precipitation uniformity and processing fluidity. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the GPC spectrum of the polymer obtained in Example 19.

[0016] Figure 2 This is the NMR spectrum of the polymer obtained in Example 18.

[0017] Figure 3 is the NMR spectrum of the polymer obtained in Example 8. DETAILED DESCRIPTION

[0018] The specific embodiments of the present invention are described in detail below, but it should be pointed out that the protection scope of the present invention is not limited by these specific embodiments, but is determined by the claims in the appendix.

[0019] Any specific numerical value disclosed herein (including the endpoint of the numerical range) is not limited to the exact value of the numerical value, but should be understood to also cover values ​​close to the exact value, such as all possible values ​​within the range of ±10% of the exact value. In addition, for the disclosed numerical range, the endpoint values ​​of the range, the endpoint values ​​and the specific point values ​​in the range, and the specific point values ​​can be arbitrarily combined to obtain one or more new numerical ranges, and these new numerical ranges should also be regarded as specifically disclosed herein.

[0020] Unless otherwise specified, the terms used herein have the same meaning as commonly understood by those skilled in the art. If a term is defined herein and its definition is different from the commonly understood meaning in the art, the definition herein shall prevail.

[0021] In the context of the present invention, unless otherwise expressly defined or the meaning is beyond the comprehension of a person skilled in the art, hydrocarbon or hydrocarbon derivative groups having more than 3 carbon atoms (such as propyl, propoxy, butyl, butane, butene, butenyl, hexane, etc.) have the same meaning when not preceded by the prefix "n". For example, propyl is generally understood to be n-propyl, and butyl is generally understood to be n-butyl, unless otherwise expressly defined.

[0022] In the present invention, except for the contents explicitly described, any matters or items not mentioned are directly applicable to the aspects known in the art without any changes. Moreover, any embodiment described herein can be freely combined with one or more other embodiments described herein, and the technical solutions or technical ideas formed thereby are regarded as part of the original disclosure or original record of the present invention, and should not be regarded as new contents not disclosed or anticipated herein, unless a person skilled in the art considers that the combination is obviously unreasonable.

[0023] All patent and non-patent literature, including but not limited to textbooks and journal articles, mentioned herein are incorporated herein by reference in their entirety.

[0024] In the context of the present invention, unless otherwise specified, the physical properties of a substance (such as boiling point) are measured at normal temperature (25° C.) and normal pressure (101325 Pa).

[0025] As described above, in a first aspect, the present invention provides a method for preparing a low molecular weight propylene copolymer, comprising: reacting propylene, a comonomer and hydrogen in a polymerization solvent in the presence of a catalyst system comprising a main catalyst and a cocatalyst to obtain a low molecular weight propylene copolymer,

[0026] The main catalyst is at least one selected from metallocene catalysts and non-metallocene catalysts, and the co-catalyst is at least one selected from alkyl aluminum, aluminoxane, and boride;

[0027] The polymerization solvent is selected from an alkane solvent having a boiling point of 5-55°C or a mixed alkane solvent having a saturated vapor pressure of 20-150 KPa, preferably 40-110 KPa at 20°C, and

[0028] The molar ratio of propylene to hydrogen is (500-10):1, preferably (300-20):1, and more preferably (100-50):1.

[0029] In one embodiment of the present invention, the polymerization solvent is one selected from n-pentane, isopentane, neopentane, and cyclopentane, or is a mixed alkane solvent of at least two selected from n-pentane, isopentane, neopentane and cyclopentane, preferably a combination of n-pentane and isopentane, a combination of isopentane and neopentane, a combination of n-pentane and cyclopentane, a combination of n-pentane and neopentane, a combination of isopentane and cyclopentane, a combination of neopentane and cyclopentane, a combination of n-hexane and n-pentane, and a combination of n-pentane-isopentane-cyclopentane.

[0030] In the present invention, there is no particular limitation on the polymerization temperature and the polymerization pressure, and the conventional polymerization temperature and the polymerization pressure for preparing low molecular weight propylene copolymers in the art can be adopted.

[0031] In one embodiment of the present invention, the polymerization temperature is 90-160°C, preferably 100-150°C.

[0032] In one embodiment of the present invention, the polymerization pressure is 1.5-6.0 MPa, preferably 2.0-5.0 MPa.

[0033] In the present invention, there is no particular limitation on the amount of the main catalyst used, and the conventional amount of catalyst used in the art can be used. In one embodiment of the present invention, the concentration of the main catalyst in the polymerization solvent is 0.1×10 -5 mol / L~50×10 -5 mol / L, preferably 0.5×10 -5 mol / L~20×10 -5 mol / L, more preferably 1×10 -5 mol / L~10×10 -5 mol / L.

[0034] In a preferred embodiment of the present invention, the molar ratio of propylene to comonomer is (30-2):1, preferably (25-5):1, more preferably (20-8):1.

[0035] In a preferred embodiment of the present invention, the comonomer is selected from one or more of ethylene, 1-butene, 1-hexene, and 1-octene, preferably selected from one or more of ethylene, 1-butene, and 1-hexene.

[0036] In the present invention, the main catalyst is selected from at least one of a metallocene catalyst and a non-metallocene catalyst. More specifically, the main catalyst can be selected from a metallocene catalyst, can be selected from a non-metallocene catalyst, or can be a mixture of a metallocene catalyst and a non-metallocene catalyst.

[0037] In the present invention, when the main catalyst is selected from a metallocene catalyst, there is no particular limitation on the type of the metallocene catalyst, and the catalyst conventionally used for propylene polymerization in the art can be used. There is no particular limitation on the form of the catalyst, and it can be a supported metallocene catalyst or a non-supported metallocene catalyst, preferably a non-supported metallocene catalyst.

[0038] More specifically, as metallocene catalysts, such as invention patents CN201110247347.2, CN201110080343.X, CN201010518904.5, CN201010519660.2, CN201210289014.0, CN200910078596.6, CN201310090758.4, CN201310090736.8, CN201310521768.9, CN201410589467.4, CN201410590067.5, CN201610835700.1, CN201610944191.6, CN201710 959423.X, CN201110247349.1, CN201110080294.X, CN201110080395.7, CN 201210289017.4, CN201210289031.4, CN201310091192.7, CN20131054097 3.X, CN201510724626.1, CN200410086283.2, CN200610137777.8, CN20161 0944182.7, CN201710312720.5, CN201110080422.0, CN201110080394.2, CN 201010519406.2, CN201010519715.X, CN201010519174.0, CN20101051942 9.3, CN201210289004.7, CN201310090847.9, CN201310091209.9, CN20131 0540975.9, CN201410554709.6, CN201410513506.2, CN00130388.0, CN200 710176589.0, CN201610944083.9, CN201110246705.8, CN201110247085.X, CN2011102914899, CN201010521674.8, CN201310090752.7, CN2013100908 48.3, CN2013100908483, CN201510624502.6, CN201710166709.2, CN201710 31225.2, CN201110246710.9, CN201110080374.5, CN201010519797.8, CN2 01210289012.1, CN201210418645.8, CN201310090998.4, CN201410252254.2. Metallocene catalysts described in CN201610393399.3, CN201610956141.X, CN201710958837.0, etc.

[0039] In one embodiment of the present invention, when the main catalyst comprises a metallocene catalyst, one metallocene catalyst may be used, or a combination of multiple metallocene catalysts may be used.

[0040] In the present invention, when the main catalyst is selected from a non-metallocene catalyst, there is no particular limitation on the type of the non-metallocene catalyst, and the catalyst conventionally used for propylene polymerization in the art can be used. There is no particular limitation on the form of the catalyst, and it can be a supported non-metallocene catalyst or an unsupported non-metallocene catalyst, preferably an unsupported non-metallocene catalyst.

[0041] Specifically, as non-metallocene catalysts, such as invention patents CN200310106156.X, CN200310106157.4, CN200410066068.6, CN200510119401.X, CN200610107651.6, CN200710162677.5, CN200710162667.1, CN200710162672.2, CN200710162675.6, CN200710162676.0, CN200710162666.7, CN20091010180607.1, CN200 910180601.4, CN200910180606.7, CN200910180602.9, CN200910180605. 2. CN200910180603.3, CN200910180604.8, CN200910210988.3, ​​CN2009102 10984.5, CN200910210989.8, CN200910210986.4, CN200910210985.X, CN2 00910210990.0, CN200910210987.9, CN200910210991.5, CN201010286008 .0, CN201010286012.7, CN201010284870.8, CN201010285982.5, CN20101 0284856.8, CN201010285970.2, CN201010285956.2, CN201010285969.X, C N201010285958.1, CN201010285967.0, CN201010285994.8, CN2011102593 36.6, CN201110259219.X, CN201110259330.9, CN201110259327.7, CN2011 10259367.1, CN201110259289.5, CN201110259359.7, CN201110259282.3 , CN201110259318.8, CN201110259258.X, CN201110259300.8, CN20111025 9254.1, CN201110259245.2, CN201110259296.5, CN201110259338.5, CN20 1110259370.3, CN201110259339.X, CN201110259293.1, CN201110259356.3. CN201210063756.1, CN201210063777.3, CN201210063788.1, CN20121006 3818.9, CN201210063824.4, CN201210063843.7, CN201210063854.5, CN2012 10063876.1, CN201210063878.0, CN201210063891.6, CN201210063894.X, C N201210063907.3, CN201210063909.2, CN201210063935.5, CN201210063941 .0, CN201210063945.9, CN201310189677.X, CN201310227368.7, CN201310227370.4, CN201310227830.3, CN201310227393.5, CN201310452714.1, CN201710814678.7, CN201710814595.8, CN201710814594.3, CN201710814593.9, CN201710814592.4, CN201710814591.X, CN201310091208.4, etc. .

[0042] In one embodiment of the present invention, when the main catalyst comprises a non-metallocene catalyst, one non-metallocene catalyst may be used, or a combination of multiple non-metallocene catalysts may be used.

[0043] In one embodiment of the present invention, the non-metallocene catalyst is selected from any one of the metal complexes represented by general formula (I) or a mixture thereof in any proportion:

[0044]

[0045] In formula (I), the groups R1, R2, R3, R4, R6, R7, R8, and R9 are each independently selected from hydrogen, optionally substituted C1-C6 straight chain or branched alkyl, optionally substituted C2-C6 straight chain or branched alkenyl, optionally substituted C2-C6 straight chain or branched alkynyl, halogen, optionally substituted C1-C6 straight chain or branched alkoxy, or optionally substituted C6-C 10 Aryl, or, wherein two adjacent groups are bonded to each other, together with the carbon atoms to which they are attached, to form an optionally substituted C4-C8 ring, preferably each independently selected from hydrogen and optionally substituted C1-C6 straight or branched alkyl, more preferably each independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl;

[0046] R5 is selected from hydrogen, C1-C 12 Straight or branched hydrocarbon, or C3-C 12 Cyclic hydrocarbon group, preferably hydrogen, C1-C6 straight chain or branched alkyl, C6-C 10 Aryl, more preferably hydrogen, C1-C3 straight or branched alkyl or phenyl, more preferably hydrogen, methyl, ethyl, propyl, isopropyl or phenyl;

[0047] R 10 Each is independently selected from hydrogen or C1-C6 straight or branched hydrocarbon group, preferably hydrogen or C1-C6 straight or branched alkyl group, more preferably hydrogen, methyl or ethyl; p is selected from 1 or 2;

[0048] The group Y is selected from O or S, preferably O; the group Z is selected from S or O, preferably S;

[0049] M is selected from metal elements of Group IVB, preferably titanium, zirconium or hafnium;

[0050] The group X is selected from fluorine, chlorine, bromine and iodine, preferably chlorine or bromine;

[0051] represents a single bond or a double bond, where When it is a single bond, p is 2, and the hydrogen on N exists. When it is a double bond, p is 1, and the hydrogen on N does not exist;

[0052] represents coordination bond, covalent bond or ionic bond;

[0053] n depends on the valence state of the atom M, more precisely n represents the valence state of the atom M -1, and can be 1, 2, 3, 4 or 5.

[0054] In one embodiment of the present invention, the radicals R1, R2, R3, R4, R7, and R9 are each independently selected from hydrogen, optionally substituted C1-C6 straight chain or branched alkyl, optionally substituted C2-C6 straight chain or branched alkenyl, optionally substituted C2-C6 straight chain or branched alkynyl, halogen, optionally substituted C1-C6 straight chain or branched alkoxy, or optionally substituted C6-C 10 Aryl, or wherein two adjacent groups are bonded to each other to form an optionally substituted C4-C8 ring together with the carbon atoms to which they are connected; preferably, each is independently selected from hydrogen, optionally substituted C1-C6 straight or branched alkyl; more preferably, each is independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl; further preferably, each is independently selected from hydrogen, methyl, ethyl.

[0055] In one embodiment of the present invention, the groups R6 and R8 are each independently selected from hydrogen, optionally substituted C1-C6 straight chain or branched alkyl, optionally substituted C2-C6 straight chain or branched alkenyl, optionally substituted C2-C6 straight chain or branched alkynyl, halogen, optionally substituted C1-C6 straight chain or branched alkoxy or optionally substituted C6-C 10 Aryl; preferably, each independently selected from optionally substituted C1-C6 straight or branched alkyl; more preferably, each independently selected from optionally substituted C3-C6 straight or branched alkyl, further preferably, each independently selected from propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl.

[0056] In one embodiment of the present invention, R5 is selected from hydrogen, C1-C6 straight or branched alkyl, C6-C 10 Aryl is preferably selected from hydrogen, C1-C3 straight or branched alkyl, and phenyl, and more preferably selected from hydrogen, methyl, ethyl, propyl, isopropyl, and phenyl.

[0057] In one embodiment of the present invention, R 10 It is selected from hydrogen, C1-C6 straight chain or branched alkyl, preferably hydrogen or C1-C6 straight chain or branched alkyl, more preferably hydrogen, methyl, ethyl.

[0058] In one embodiment of the present invention, the group Y is selected from O.

[0059] In one embodiment of the present invention, the group Z is selected from S.

[0060] In a further preferred embodiment, the non-metallocene catalyst is preferably selected from any one of the metal complexes having the following chemical formulas or a mixture thereof in any proportion:

[0061]

[0062] In a more preferred embodiment, the non-metallocene catalyst is more preferably selected from one or more metal complexes having the following chemical formula:

[0063]

[0064] In one embodiment of the present invention, the metallocene complex is selected from any one of the metal complexes represented by general formula (II) or a mixture thereof in any proportion:

[0065]

[0066] In formula (II), R' is a C1-C8 straight or branched chain alkylene, a C6-C 10 Aryl alkylene, di-C1-C8 dialkyl silylene or di-C6-C10 Arylsilylene, preferably C1-C4 straight or branched alkylene, diphenylalkylene, di-C1-C4 dialkylsilylene or diphenylsilylene, more preferably methylene, ethylene, isopropylidene, diphenylmethylene, dimethylsilylene or diphenylsilylene;

[0067] and Each independently represents unsubstituted or substituted by 1-5 independently selected from halogen, C1-C4 alkyl, C1-C4 haloalkyl or C6-C 10 Aryl, preferably cyclopentadienyl, fluorenyl, indenyl, benzoindenyl, tetrahydroindenyl or benzodihydroindenyl substituted with methyl or phenyl;

[0068] M is a Group IVB metal, preferably titanium or zirconium;

[0069] Each X is independently selected from halogen, C1-C6 alkyl or C2-C6 alkenyl; preferably independently selected from halogen; more preferably chlorine or bromine.

[0070] In a further preferred embodiment, the metallocene catalyst is preferably selected from ethylene bis-1-indenyl zirconium dichloride, ethylene bis-1-(2-methyltetrahydroindenyl) zirconium dichloride, ethylene bis-1-(4,7-dimethylindenyl) zirconium dichloride, ethylene bis-1-(2-methyl-4-phenylindenyl) zirconium dichloride, ethylene bis-1-(2-methyl-4,5-benzoindenyl) zirconium dichloride, ethylene bis-1-(2-methyl-4,5-benzoindenyl) zirconium dichloride, ethylene bis-1-(2-methyl-4,5-benzo-6,7-dihydro any one of the following: ethylenebis-1-(2-methylindenyl)zirconium dichloride, ethylenebis-1-tetrahydroindenyl zirconium dichloride, dimethylsilylenebis-1-indenyl zirconium dichloride, dimethylsilylenebis-1-(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride, dimethylsilylenebis-1-(2-methylindenyl)zirconium dichloride, and dimethylsilylenebis-1-(2-methyl-4-phenylindenyl)zirconium dichloride, or a mixture thereof in any proportion.

[0071] It should be noted that the above-mentioned non-metallocene catalysts and metallocene catalysts can be used alone or in any proportion. When used in a mixed manner, the ratio of the non-metallocene catalyst to the metallocene catalyst is not particularly limited, and the molar ratio can be 1:100 to 100:1, or 1:50 to 50:1, or 1:10 to 10:1, for example, 1:1, based on the central active metal atoms of each catalyst.

[0072] In the present invention, the cocatalyst is selected from at least one of alkyl aluminum, aluminoxane, and boride. For various types of cocatalysts of alkyl aluminum, aluminoxane, and boride, each can be selected from one or more, such as one or more alkyl aluminum, one or more aluminoxane, and one or more boride.

[0073] In one embodiment of the present invention, the structural formula of the alkyl aluminum as a co-catalyst is as shown in formula (IIIa),

[0074] Al(R)3(IIIa)

[0075] Wherein, each group R is independently selected from C1-C8 alkyl, preferably selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl, n-hexyl, more preferably selected from ethyl, isobutyl or n-hexyl. The alkyl aluminum can be used alone or in any combination of any proportion.

[0076] Specifically, examples of the alkyl aluminum include trimethyl aluminum (Al(CH3)3), triethyl aluminum (Al(CH3CH2)3), tri-n-propyl aluminum (Al(n-C3H7)3), tri-isopropyl aluminum (Al(i-C3H7)3), tri-isobutyl aluminum (Al(i-C4H9)3), tri-n-pentyl aluminum (Al(n-C5H 11 )3) Tri-n-hexyl aluminum (Al(n-C6H 13 )3), diethylmethylaluminum (Al(CH3)(CH3CH2)2), and dimethylethylaluminum (Al(CH3)2(CH3CH2)), etc., preferably selected from trimethylaluminum, triethylaluminum, triisobutylaluminum or tri-n-hexylaluminum.

[0077] In one embodiment of the present invention, the general structural formula of the aluminoxane used as a co-catalyst is as shown in formula (IIIb) or (IIIc),

[0078]

[0079] Wherein, each group R is independently selected from C1-C8 alkyl, preferably selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl or n-hexyl, more preferably selected from methyl, ethyl or isobutyl, and n is any integer in the range of 1-50, preferably any integer in the range of 10-30. The alkylaluminoxane can be used alone or in combination in any proportion.

[0080] Specifically, the aluminoxane is preferably selected from methylaluminoxane, ethylaluminoxane, isobutylaluminoxane, n-butylaluminoxane, n-hexylaluminoxane, triisobutylaluminum-modified methylaluminoxane and tri-n-hexylaluminum-modified methylaluminoxane, and more preferably selected from methylaluminoxane, triisobutylaluminum-modified methylaluminoxane or tri-n-hexylaluminum-modified methylaluminoxane.

[0081] In one embodiment of the present invention, the boride as a co-catalyst is selected from triphenylboron, tri(pentafluorophenyl)boron, triphenylcarbon tetra(pentafluorophenyl)borate, N,N-dimethylanilinium tetra(pentafluorophenyl)borate, triethylammonium tetra(pentafluorophenyl)borate, 1-butyl-3-methylimidazole tetrafluoroborate, ferrocene tetrafluoroborate, trimethylammonium tetraphenylborate, triethylammonium tetraphenylborate, triisopropylammonium tetraphenylborate, tri-n-butylammonium tetraphenylborate, trimethylammonium tetra(4-methylphenyl)borate, triisopropylammonium tetra(4-methylphenyl)borate The invention further comprises one or more of tris(pentafluorophenyl)borate, triphenylcarbon tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, trimethylammonium tetrakis(2,4-dimethylphenyl)borate, triethylammonium tetrakis(2,4-dimethylphenyl)borate, trimethylammonium tetrakis(4-trifluoromethylphenyl)borate, tri-n-butylammonium tetrakis(4-trifluoromethylphenyl)borate, tri-n-butylammonium tetrakis(pentafluorophenyl)borate and N,N-diethylanilinium tetrakis(pentafluorophenyl)borate, and more preferably one or more of tris(pentafluorophenyl)boron, triphenylcarbon tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate and triethylammonium tetrakis(pentafluorophenyl)borate.

[0082] It should be noted that in the present invention, "C6-C 10 The term "aryl" refers to an aromatic hydrocarbon group having 6 to 10 carbon atoms, and specifically, it may be phenyl or naphthyl.

[0083] In the present invention, "C4-C8 ring" means a cyclic group having 4-8 ring carbon atoms, which may be an unsaturated ring or a saturated ring, and may or may not be aromatic. When it is an unsaturated ring, it may have 1, 2 or 3 double bonds, for example, it may be a cyclopentene ring or a cyclopentadiene ring. When it is an aromatic ring, it may be a benzene ring.

[0084] In the present invention, "C3-C 12 The term "cyclic hydrocarbon group" refers to a cyclic group having 3 to 12 ring carbon atoms, which may be an unsaturated ring or a saturated ring, and may or may not be aromatic. Examples of saturated cyclic hydrocarbon groups include cyclopropyl, cyclobutyl, and cyclopentyl. When the ring is unsaturated, it may have 1, 2, or 3 double bonds, and may be, for example, cyclopentenyl or cyclopentadienyl. When the ring is aromatic, it may be phenyl or naphthyl.

[0085] In the present invention, the substituent in "optionally substituted" or "optionally substituted" is selected from halogen, C1-C6 alkyl, C3-C6 cycloalkyl, C1-C6 haloalkyl, phenyl, and halogenated phenyl. More specifically, it can be selected from fluorine, chlorine, bromine, iodine, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl and its isomers, hexyl and its isomers, cyclobutyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, halomethyl (e.g., trifluoromethyl), haloethyl (e.g., trifluoroethyl, pentafluoroethyl), halopropyl, haloisopropyl, halobutyl, haloisobutyl, halogenated sec-butyl, halotert-butyl, halopentyl, halohexyl, phenyl, and halophenyl (e.g., chlorophenyl, dichlorophenyl, pentafluorophenyl). Unless otherwise specified, the upper limit of the number of the substituents is the upper limit of the positions that can be substituted on the substituted group. More specifically, the number of the substituents can be 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. For example, it can be 1-8, 1-6, 1-5, 1-4, 1-3, 1-2. When there are multiple substituents, each substituent can be the same or different.

[0086] In the present invention, the "halogen atom" or "halogen" means fluorine, chlorine, bromine or iodine, preferably fluorine, chlorine or bromine.

[0087] In the present invention, unless otherwise specified, the upper limit of the number of substituents in "optionally substituted by..." is the upper limit of the positions that can be substituted on the substituted group, and the number of the substituents can be 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. For example, it can be 1-8, 1-6, 1-5, 1-4, 1-3, 1-2. When there are multiple substituents, each substituent can be the same or different.

[0088] In one embodiment of the present invention, the molar ratio of the total amount of the co-catalyst alkylaluminum and / or aluminoxane (calculated as aluminum atom) added to the reaction system to the total amount of the main catalyst (non-metallocene complex and / or metallocene complex) (calculated as central metal atom) is (10-5000):1, preferably (100-2000):1, and more preferably (250-1200):1.

[0089] In one embodiment of the present invention, the molar ratio of the total amount of the co-catalyst boride added in the reaction system (calculated in terms of boron atoms) to the total amount of the main catalyst (non-metallocene complex and / or metallocene complex) (calculated in terms of central metal atoms) is (1-10):1, preferably (2-5):1.

[0090] In the preparation of the low molecular weight propylene copolymer of the present invention, a chain transfer agent may be used or not, preferably not used. As the chain transfer agent, other metal alkyl compounds other than the above-mentioned co-catalysts of the present invention may be listed, for example, one or more of n-butyl lithium, diethyl zinc, dipropyl zinc, dibutyl zinc, diisobutyl zinc, diethyl magnesium, dibutyl magnesium or n-butyl ethyl magnesium may be listed. In one embodiment of the present invention, when a chain transfer agent is used, the molar ratio of the amount of the chain transfer agent calculated by the metal content of the chain transfer agent to the total amount of the main catalyst (non-metallocene complex and / or metallocene complex) calculated by the central metal atom is 1-300=1, preferably 10-200:1.

[0091] In addition, the cocatalyst alkylaluminum, aluminoxane, and boride are generally used in the form of a solution. When preparing the solution of the cocatalyst, there is no particular limitation on the solvent used, as long as it can dissolve / disperse the cocatalyst. The solvent is generally selected as an alkane solvent, such as n-pentane, isopentane, cyclopentane, neopentane, etc., or an aromatic solvent, such as toluene, ethylbenzene, xylene, etc. According to the present invention, in order to facilitate subsequent separation, it is preferred to use a solvent that is the same as the polymerization solvent; or a solvent that is the same as one of the solvents in the mixed solvent for polymerization.

[0092] In the polymerization preparation method of the low molecular weight propylene copolymer of the present invention, the propylene solution polymerization reactor is not limited in form, as long as propylene, comonomer, hydrogen can be brought into contact with a catalyst comprising a main catalyst and a co-catalyst in a solvent, and polymerization can be carried out within the polymerization pressure and temperature range of the present invention, and it can effectively avoid material adhesion and aggregation. In one embodiment of the present invention, the reactor is a kettle stirrer, and its stirring rate is not particularly limited, as long as it can ensure that the solution in the reactor can be normally dispersed. The stirring speed is related to the reactor volume. Generally speaking, the smaller the reactor volume, the greater the stirring speed required, and the stirring speed is 10-1000 rpm, preferably 20-500 rpm.

[0093] In the preparation method of the present invention, the form of propylene entering the reactor is not limited. Propylene can be directly pumped into the reactor in the form of liquid propylene through a propylene pump, or it can be first evaporated into gaseous propylene through a propylene preheater and then pumped into the reactor. The comonomer ethylene is directly introduced into the reactor in the form of gaseous state, and the comonomers butene, hexene, octene, etc. can be directly pumped into the reactor in the form of liquid through a metering pump, or they can be vaporized through an evaporator and then pumped into the reactor.

[0094] In the preparation method of the present invention, the catalytic system comprises a homogeneous single-site catalyst as a main catalyst and a mixture of one or more selected from aluminoxane, alkyl aluminum or boride as a co-catalyst, and the addition method to the polymerization reaction system can be to first add the main catalyst and then add the co-catalyst, or to first add the co-catalyst and then add the main catalyst, or to first contact and mix the two and then add them together, or to add them separately at the same time. When the main catalyst and the co-catalyst are added separately, they can be added sequentially in the same feeding pipeline or in multiple feeding pipelines, and when the two are added separately at the same time, a multiple feeding pipeline should be selected.

[0095] The method of the present invention can carry out propylene copolymerization in a continuous manner or in a batch manner.

[0096] After the method of the present invention, the propylene copolymer can be recovered from the polymerization solvent by conventional techniques in the art. For example, after the polymerization reaction is completed, the polymerization solvent is removed by flash evaporation, and the propylene copolymer is further processed as needed.

[0097] In a second aspect, the present invention provides a low molecular weight propylene copolymer having a weight average molecular weight Mw of 600 to 30,000 g / mol, a dispersion index PDI of 1.0 to 4.0, and a density of 0.85 to 0.89 g / cm 3 , crystallinity is 4-40%, melting point T m The temperature is 80-140° C., the Brookfield viscosity (at a temperature of 170° C.) is 30-15000 mPa·s, the melting enthalpy ΔH is 8-85 J / g, and the comonomer content is 5-35 mol%.

[0098] In one embodiment of the present invention, the low molecular weight polypropylene is prepared by the method for preparing a low molecular weight propylene copolymer of the present invention.

[0099] Example

[0100] The embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0101] The test method for the molecular weight and distribution of the polymer obtained in the following examples is as follows: with reference to GB / T 21864-2005 standard, using Polymer Laboratories PL-220 gel permeation chromatograph, using 1,2,4-trichlorobenzene as mobile phase, polystyrene as standard sample, using differential detector, flow rate of 1.0 mL / min, measuring temperature of 150° C., sample concentration of 2.0 mg / mL. The polymer dispersity index (PDI) is calculated based on the measured weight average molecular weight and number average molecular weight.

[0102] The melt viscosity of the polymers obtained in the following examples is measured by using a DV2T viscometer from Brookfield Company, in accordance with DIN 53019 standard, at a test temperature of 170°C.

[0103] The melting point, melting enthalpy and crystallinity of the obtained polymers in the following examples were tested by using a differential scanning calorimeter (Perkin-Elmer DSC 7) in accordance with GB / T28724-2012. The sample size tested was 3-5 mg, and the atmosphere was nitrogen. The sample was first heated from 30°C to 200°C at a rate of 20°C / min, stayed for 3 min, then decreased to 20°C at a rate of 20°C / min, stayed for 3 min, and then increased to 200°C at a rate of 20°C / min. The second heating curve was used for analysis.

[0104] The density of the polymers obtained in the following examples is measured by using an Anton Paar DMA 4500M densitometer at 23° C. in accordance with ISO 1183 standard.

[0105] The comonomer content of the polymer obtained in the following examples was calculated by carbon nuclear magnetic resonance spectroscopy. The specific test method was as follows: the microstructure of the polyethylene sample was determined using a Bruker Avance 600M nuclear magnetic resonance spectrometer. The sample was dissolved in deuterated o-dichlorobenzene to prepare a solution. The test temperature was 120°C. The nuclear magnetic resonance hydrogen spectrum was obtained by scanning 2000 times and 6000 times respectively. 1 H-NMR) and carbon nuclear magnetic resonance spectroscopy ( 13 C-NMR).

[0106] Propylene solution copolymerization method: In a glove box, the main catalyst and the co-catalyst are dissolved in a polymerization solvent respectively and then added to the catalyst feed tank in sequence for standby. After the 300L high-pressure reactor is purged with high-purity nitrogen at 100°C for 6 hours, 120L of polymerization solvent is added to the reactor, vented, and stirring is started. After the reactor is heated to the set temperature, propylene, comonomer and hydrogen are added to the reactor in a certain proportion by flow meter control. After the reactor pressure reaches the set pressure, the catalyst solution in the catalyst feed tank is added to the reactor for propylene solution polymerization. The ratio of gas phase propylene, comonomer and hydrogen in the reactor is monitored and controlled by online chromatography at the set value. After the propylene absorption reaches the set value, stop feeding propylene, comonomer and hydrogen. After the polymer solution in the reactor is flashed to remove the solvent through a flash tank, the final polymer is obtained, the polymer is weighed, and the polymerization activity is calculated.

[0107] Application test of grafting modification of polymer: Weigh a certain amount of polymer and transfer it to a multi-mouth reaction bottle with a stirrer, add a certain amount of toluene solvent, heat and stir to dissolve the polymer. Weigh a certain amount of methacrylic acid, styrene and benzoyl peroxide, add toluene and prepare a mixed solution for standby use. At a certain temperature, slowly drip the above mixed solution into the multi-mouth reaction bottle, keep constant temperature and continue stirring the reaction for 5 hours after the dripping is completed, and terminate the reaction. After cooling to room temperature, pour the product into the acetone solvent prepared in advance, let it stand for a period of time, pour the supernatant into the waste liquid bucket, add a certain amount of toluene to dissolve, pour it into acetone again for precipitation, repeat several times, filter and dry the solid product obtained by precipitation, and finally extract it with distilled water in a Soxhlet extractor for two days and then put it into a vacuum oven to dry to constant weight to obtain the grafted polymer.

[0108] Determination of grafting rate: weigh about 0.2g of grafted product and dissolve it in 30ml toluene, heat the solution under reflux for half an hour and then cool it, add excess potassium hydroxide-ethanol solution and continue to reflux for 1 hour to make it fully react, continue to add excess hydrochloric acid-isopropanol solution after cooling, react for a period of time and cool to the set temperature. Use phenolphthalein as an indicator and use potassium hydroxide-ethanol solution to back titrate at a constant temperature. The grafting rate is calculated according to the following formula:

[0109]

[0110] Where, Gd represents the grafting rate, in %; C KOH Indicates the concentration of potassium hydroxide-ethanol solution in mol / L; V KOH Indicates the volume of potassium hydroxide-ethanol solution added and consumed in titration, in mL; C HCl Indicates the concentration of hydrochloric acid-isopropanol solution in mol / L; V HClrepresents the volume of the hydrochloric acid-isopropanol solution added, in mL; W represents the mass of the grafted polymer, in g.

[0111] Test of low molecular weight propylene copolymer modified PP / PE blending system: The materials of each blending system were blended and extruded in a specific ratio using a twin-screw extruder (ZSK-25, WP, Germany), the processing temperature was 190°C, and the granules were dried to constant weight. The performance of the low molecular weight propylene copolymer modified PP / PE blending system was tested using the torque rheometer R600 of HAAKE Company of Germany, the test temperature was 170°C, the speed was 50rpm, and the time was 20min. The equilibrium torque is used to characterize the processing fluidity of the material. The smaller the equilibrium torque, the lower the apparent viscosity of the material, and the better the fluidity of the melt, indicating that the processing fluidity performance of the low molecular weight propylene copolymer improved blending system is better.

[0112] Method for determining the metal content as an impurity: The metal content is detected by inductively coupled plasma emission spectrometry. After the polymer sample solution is carried into the atomization system by the carrier gas for atomization, it enters the axial channel of the plasma in the form of an aerosol, and is fully evaporated, atomized, ionized and excited in the high temperature and inert gas. The characteristic spectral lines of the emitted elements enter the spectrum detector through the spectroscopic system, and the spectrum detector performs qualitative and quantitative analysis based on the characteristic spectrum of the elements.

[0113] VOCs determination method: gas chromatography is used to detect the VOCs content in polymers. Quantitative toluene is used as an extractant to extract the residual solvent in the polymer. Based on the parameters of the set gas chromatograph, a 10μL microinjection needle is used to repeatedly extract the solution to be tested to remove the bubbles in the needle, and then 1μL of the solution is drawn into the gas chromatograph. After the components of the sample are fully presented in the chromatogram, the characteristic chromatographic peak area of ​​the component to be tested is recorded, and the content of the component to be tested in the tested solution is calculated by comparing the characteristic peak area with the standard curve.

[0114] Examples 1-21 and Comparative Examples 1-2

[0115] According to the above propylene solution copolymerization method, according to the conditions in the following Table 1, Examples 1-21 and Comparative Examples 1-2 were implemented.

[0116] According to the above determination method, various properties of the polymers obtained in Examples 1-21 and Comparative Examples 1-2 were determined, and the determination results are shown in the following Table 2. The blank sample result refers to the equilibrium torque measured without adding any polymer.

[0117]

[0118]

[0119]

[0120]

[0121] By comparing the examples and comparative examples, it can be seen that the technology described in the present invention has higher activity and higher devolatilization efficiency, which can greatly reduce the cost of polymer post-processing. The obtained polymer has extremely low VOCs content and metal residues, has lower odor, and is more suitable for application in high-end application fields such as food packaging, medical packaging and cosmetics. The obtained polymer has a higher grafting rate when subjected to polar monomer grafting modification, giving the material better compatibility. Under the condition of adding the same amount, the polymer obtained by the present invention has a better processing improvement effect on the PP / PE system.

[0122] It can be seen from the above table that the mixed solvent used in the method of the present invention not only has higher polymerization activity, lower volatile matter and metal residue, but also the obtained polymer has a higher grafting rate when used for polar group grafting modification, and has a lower equilibrium torque when blended with the PP / PE system, indicating that it has more advantages as a processing improver.

[0123] From the table above, we can see that the propylene / hydrogen molar ratio in the polymerization system has a great influence on the molecular weight of the polymer. The precise control of the propylene / hydrogen ratio can achieve customized synthesis of polymers with different molecular weights. The molecular weight has a great influence on the application performance of the polymer, so in the actual production process, the propylene / hydrogen ratio must be strictly controlled.

[0124] Although the specific implementations of the present invention have been described in detail above in conjunction with the embodiments, it should be pointed out that the protection scope of the present invention is not limited by these specific implementations, but is determined by the appended claims. Those skilled in the art may make appropriate changes to these implementations without departing from the technical ideas and purposes of the present invention, and these changed implementations are obviously also included in the protection scope of the present invention.

Claims

1. A method for preparing a low molecular weight propylene copolymer, wherein include: Propylene, comonomer and hydrogen are reacted in a polymerization solvent in the presence of a catalyst system comprising a main catalyst and a cocatalyst to obtain a low molecular weight propylene copolymer, The main catalyst is at least one selected from metallocene catalysts and non-metallocene catalysts, and the co-catalyst is at least one selected from alkyl aluminum, aluminoxane, and boride; The polymerization solvent is selected from an alkane solvent having a boiling point of 5-55°C or a mixed alkane solvent having a saturated vapor pressure of 20-150 KPa, preferably 40-110 KPa at 20°C, and The molar ratio of propylene to hydrogen is (500-10):1, preferably (300-20):1, and more preferably (100-50):

1.

2. The method according to claim 1, It is characterized in that The polymerization solvent is one selected from n-pentane, isopentane, neopentane, and cyclopentane, or a mixed alkane solvent of at least two selected from n-pentane, isopentane, neopentane, and cyclopentane, preferably one selected from a combination of n-pentane and isopentane, a combination of isopentane and neopentane, a combination of n-pentane and cyclopentane, a combination of n-pentane and neopentane, a combination of isopentane and cyclopentane, a combination of neopentane and cyclopentane, a combination of n-hexane and n-pentane, and a combination of n-pentane-isopentane-cyclopentane.

3. The method according to any one of claims 1 to 2, It is characterized in that The molar ratio of propylene to comonomer is (30-2):1, preferably (25-5):1, more preferably (20-8):1, and / or The concentration of the main catalyst in the polymerization solvent is 0.1×10 -5 mol / L~50×10 -5 mol / L, preferably 0.5×10 -5 mol / L~20×10 -5 mol / L, more preferably 1×10 -5 mol / L~10×10 -5 mol / L, and / or The polymerization temperature is 90-160°C, preferably 100-150°C, and / or The polymerization pressure is 1.5-6.0 MPa, preferably 2.0-5.0 MPa.

4. The method according to any one of claims 1 to 3, It is characterized in that The comonomer is selected from one or more of ethylene, 1-butene, 1-hexene, and 1-octene, and is preferably selected from one or more of ethylene, 1-butene, and 1-hexene.

5. The method according to any one of claims 1 to 4, in, The non-metallocene catalyst is one or a mixture thereof selected from the metal complexes represented by general formula (I): In formula (I), the group R 1 , R 2 , R 3 , R 4 , R 6 , R 7 , R 8 , R 9 are each independently selected from hydrogen, optionally substituted C 1 -C 6 Straight or branched alkyl, optionally substituted C 2 -C 6 Straight-chain or branched alkenyl, optionally substituted C 2 -C 6 Straight-chain or branched alkynyl, halogen, optionally substituted C 1 -C 6 Straight chain or branched alkoxy or optionally substituted C 6 -C 10 Aryl, or, wherein two adjacent groups are bonded to each other, together with the carbon atoms to which they are attached, to form an optionally substituted C 4 -C 8 rings, preferably each independently selected from hydrogen and optionally substituted C 1 -C 6 Straight or branched alkyl, more preferably each independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl; R 5 Selected from hydrogen, C 1 -C 12 Straight or branched hydrocarbon group, or C 3 -C 12 Cyclic hydrocarbon group, preferably hydrogen, C 1 -C 6 Straight or branched alkyl, C 6 -C 10 Aryl, more preferably hydrogen, C 1 -C 3 Straight or branched alkyl or phenyl, more preferably hydrogen, methyl, ethyl, propyl, isopropyl or phenyl; R 10 are each independently selected from hydrogen or C 1 -C 6 Straight or branched hydrocarbon group, preferably hydrogen or C 1 -C 6 Straight or branched alkyl, more preferably hydrogen, methyl or ethyl; p is selected from 1 or 2; The group Y is selected from O or S, preferably O; the group Z is selected from S or O, preferably S; M is selected from metal elements of Group IVB, preferably titanium, zirconium or hafnium; the group X is selected from fluorine, chlorine, bromine and iodine, preferably chlorine or bromine; represents a single bond or a double bond, where When it is a single bond, p is 2, and the hydrogen on N exists. When it is a double bond, p is 1, and the hydrogen on N does not exist; ------ represents coordination bond, covalent bond or ionic bond; n depends on the valence state of atom M and can be 1, 2, 3, 4 or 5.

6. The method according to any one of claims 1 to 5, in, The non-metallocene catalyst is selected from any one of the metal complexes having the following chemical formulas or a mixture thereof in any proportion: The non-metallocene catalyst is more preferably selected from one or more metal complexes having the following chemical formula:

7. The method according to any one of claims 1 to 6, in, The metallocene catalyst is selected from one or more metal complexes represented by general formula (II): In formula (II), R' is C 1 -C 8 Straight or branched chain alkylene, di-C 6 -C 10 Aryl alkylene, di-C 1 -C 8 Alkylsilylene or di-C 6 -C 10 Arylsilylene, preferably C 1 -C 4 Straight chain or branched chain alkylene, diphenyl alkylene, di-C 1 -C 4 Alkylsilylene or diphenylsilylene, more preferably methylene, ethylene, isopropylidene, diphenylmethylene, dimethylsilylene or diphenylsilylene; and Each independently represents unsubstituted or substituted by 1-5 independently selected from halogen, C 1 -C 4 Alkyl, C 1 -C 4 Haloalkyl or C 6 -C 10 Aryl, preferably cyclopentadienyl, fluorenyl, indenyl, benzoindenyl, tetrahydroindenyl or benzodihydroindenyl substituted with methyl or phenyl; M is a Group IVB metal, preferably titanium or zirconium; Each X is independently selected from halogen, C 1 -C 6 Alkyl or C 2 -C 6 alkenyl; preferably each independently selected from halogen; more preferably chlorine or bromine.

8. The method according to any one of claims 1 to 7, in, The metallocene catalyst is preferably selected from ethylenebis-1-indenyl zirconium dichloride, ethylenebis-1-(2-methyltetrahydroindenyl) zirconium dichloride, ethylenebis-1-(4,7-dimethylindenyl) zirconium dichloride, ethylenebis-1-(2-methyl-4-phenylindenyl) zirconium dichloride, ethylenebis-1-(2-methyl-4,5-benzoindenyl) zirconium dichloride, ethylenebis-1-(2-methyl-4,5-benzoindenyl) zirconium dichloride, ethylenebis-1-(2-methyl-4,5-benzo-6,7-dihydroindenyl) zirconium dichloride , ethylenebis-1-(2-methylindenyl)zirconium dichloride, ethylenebis-1-tetrahydroindenyl zirconium dichloride, dimethylsilylenebis-1-indenyl zirconium dichloride, dimethylsilylenebis-1-(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride, dimethylsilylenebis-1-(2-methylindenyl)zirconium dichloride, dimethylsilylenebis-1-(2-methyl-4-phenylindenyl)zirconium dichloride, or any mixture thereof in any proportion.

9. The method according to any one of claims 1 to 8, It is characterized in that The aluminoxane is selected from methylaluminoxane, ethylaluminoxane, isobutylaluminoxane, n-hexylaluminoxane, triisobutylaluminum-modified methylaluminoxane, tri-n-hexylaluminum-modified methylaluminoxane or a mixture thereof, preferably selected from methylaluminoxane, triisobutylaluminum-modified methylaluminoxane or tri-n-hexylaluminum-modified methylaluminoxane or a mixture thereof; The alkylaluminum is selected from trimethylaluminum, triethylaluminum, tripropylaluminum, triisobutylaluminum, tri-n-butylaluminum, triisopentylaluminum, tri-n-pentylaluminum, tri-n-hexylaluminum, triisohexylaluminum, diethylmethylaluminum and dimethylethylaluminum or a mixture thereof, preferably selected from trimethylaluminum, triethylaluminum, triisobutylaluminum or tri-n-hexylaluminum or a mixture thereof, most preferably selected from triethylaluminum or triisobutylaluminum or a mixture thereof; The boron compound is selected from triphenylboron, tris(pentafluorophenyl)boron, triphenylcarbon tetra(pentafluorophenyl)borate, N,N-dimethylanilinium tetra(pentafluorophenyl)borate, triethylammonium tetra(pentafluorophenyl)borate, 1-butyl-3-methylimidazole tetrafluoroborate, ferrocene tetrafluoroborate, trimethylammonium tetraphenylborate, triethylammonium tetraphenylborate, triisopropylammonium tetraphenylborate, tri-n-butylammonium tetraphenylborate, trimethylammonium tetra(4-methylphenyl)borate, triisopropylammonium tetra(4-methylphenyl)borate, trimethylammonium tetra(4-methylphenyl)borate, ammonium tetrakis(pentafluorophenyl)borate, triethylammonium tetrakis(2,4-dimethylphenyl)borate, trimethylammonium tetrakis(4-trifluoromethylphenyl)borate, tri-n-butylammonium tetrakis(4-trifluoromethylphenyl)borate, tri-n-butylammonium tetrakis(pentafluorophenyl)borate and N,N-diethylanilinium tetrakis(pentafluorophenyl)borate or a mixture thereof, preferably selected from tris(pentafluorophenyl)boron, triphenylcarbon tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate or triethylammonium tetrakis(pentafluorophenyl)borate or a mixture thereof.

10. The method according to any one of claims 1 to 9, in, The molar ratio of the total amount of alkylaluminum and / or aluminoxane in the co-catalyst (calculated as aluminum atoms) to the total amount of the main catalyst (calculated as central metal atoms) is (10-5000):1, preferably (100-2000):1, more preferably (250-1200):1; and / or The molar ratio of the total amount of boride in the co-catalyst (calculated as boron atoms) to the total amount of the main catalyst (calculated as central metal atoms) is (1-10):1, preferably (2-5):

1.

11. A low molecular weight propylene copolymer prepared according to the process of any one of claims 1 to 10, It is characterized in that Its weight average molecular mass M w The dispersion index PDI is 1.0-4.0, and the density is 0.85-0.89 g / cm 3 , crystallinity is 4-40%, melting point T m The temperature is 80-140° C., the Brookfield viscosity (at a temperature of 170° C.) is 30-15000 mPa·s, the melting enthalpy ΔH is 8-85 J / g, and the comonomer content is 5-35 mol%.

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