CN107629155B

CN107629155B - Polypropylene, preparation method and application thereof

Info

Publication number: CN107629155B
Application number: CN201610565238.8A
Authority: CN
Inventors: 赵瑾; 夏先知; 刘月祥; 谭扬; 任春红; 高富堂; 凌永泰; 李威莅; 彭人琪; 张天一; 陈龙
Original assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Priority date: 2016-07-18
Filing date: 2016-07-18
Publication date: 2020-06-09
Anticipated expiration: 2036-07-18
Also published as: CN107629155A

Abstract

The invention relates to the field of olefin polymerization, and particularly provides polypropylene and a preparation method and application thereof. The melt flow index MFR of the polypropylene is more than 30g/10min, the isotactic index is 96-99.5 wt%, and the molecular weight distribution index MW/Mn is 3-5.5. The preparation method of the polypropylene comprises the step of polymerizing propylene to obtain a polypropylene product in the presence of a catalyst under the condition of olefin polymerization, wherein the catalyst contains a catalyst component, an alkyl aluminum compound and an optional external electron donor, the catalyst component contains a product obtained by the reaction of a magnesium source, a titanium source and an internal electron donor, the internal electron donor contains a phosphate compound and a diether compound, and the phosphorus content in the catalyst component is not more than 0.06 wt% based on phosphorus. The polypropylene provided by the invention has the characteristics of high isotactic index, high melt flow index and narrow molecular weight distribution.

Description

Polypropylene, preparation method and application thereof

Technical Field

The invention relates to the field of olefin polymerization, and in particular relates to polypropylene, a preparation method of the polypropylene, the polypropylene prepared by the method and application of the polypropylene in preparing fibers and non-woven fabrics.

Background

Polypropylene has many advantages, such as low density, high flexural modulus and melting point, good processability, excellent chemical stability, electrical insulation, cheap and readily available propylene raw materials for making polypropylene, etc. However, although polypropylene materials have these advantages, in some fields, due to their intrinsic properties, they have a low isotactic index when they have a high melt flow index; when the isotactic index is higher, the melt flow index is lower, that is, polypropylene having a higher melt flow index and a higher isotactic index cannot be obtained. In the prior art, when the propylene polymer has an isotactic index of 96 to 99.5 wt%, the melt flow index, as determined according to ASTM D1238-99, tends to be only 0.5 to 35 g/10 min; whereas the isotactic index of a propylene polymer, measured according to ASTM D1238-99, is only 91-95% by weight, at a melt flow index of 40-50 g/10 min. Because the properties of polypropylene are mutually constrained, an increase in one property index may often result in a decrease in another property index, and thus, it is not easy to change the properties of polypropylene.

Melt flow index is an important indicator of the processability of polypropylene materials, such as: extrusion or molding, in which the polypropylene material must be softened or melted. The low melt flow index polypropylene material obtained for the initial polymerization must be further modified to improve its processability. This is generally done by controlled rheology techniques, for example, by adding peroxides to reduce the molecular weight of the polypropylene material, thereby improving its flowability. However, this method of processing has several disadvantages, such as: the processing steps are added, so that the manufacturing cost is increased; organic peroxides are unstable and difficult to handle; the degradation reaction produces toxic by-products, such as t-butanol. Thus, their use in certain fields, such as the field of food packaging, is limited.

In addition, the performance of polypropylene can be improved by using a high-performance polypropylene catalyst, and at present, a phthalate ester compound (plasticizer) is a relatively commonly used internal electron donor of the polypropylene catalyst, but researches show that when a high-melt-index product is prepared by using the catalyst containing the phthalate ester compound, the isotactic index of a polymer is relatively low due to insufficient orientation capability of the catalyst, the product requirement cannot be met, the growth and development of animals and reproductive systems can be seriously damaged, and meanwhile, similar influences can be caused to human beings.

At present, the fiber and non-woven fabrics have a large market prospect, and the need to be able to obtain polymers with narrow molecular weight distribution, large melt flow index and high isotactic index by using a low-cost catalyst is needed, so that finding a catalyst without phthalate (plasticizer) to obtain polymers with narrow molecular weight distribution, large melt flow index and high isotactic index is a problem to be solved urgently.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide polypropylene which is obtained by adopting a plasticizer-free catalyst and has high isotactic index, high melt flow index and narrow molecular weight distribution, and a preparation method and application thereof.

The present invention provides a polypropylene having a melt flow index MFR>30g/10min, isotactic index of 96-99.5 wt%, and molecular weight distribution index M_Wthe/Mn is 3-5.5.

The invention also provides a preparation method of polypropylene, which comprises the step of polymerizing propylene in the presence of a catalyst under the condition of olefin polymerization to obtain a polypropylene product, wherein the catalyst contains a catalyst component, an alkyl aluminum compound and an optional external electron donor, the catalyst component contains a product obtained by the reaction of a magnesium source, a titanium source and an internal electron donor, the internal electron donor contains a phosphate compound and a diether compound, and the phosphorus content in the catalyst component is not more than 0.06 wt% based on the total weight of the catalyst component.

The invention also provides polypropylene prepared by the method.

The inventor of the present invention has unexpectedly found in the research process that, in the process of synthesizing polypropylene, when the internal electron donor in the used catalyst component contains both diether compound and phosphate compound, and when the phosphorus content in the catalyst component is not more than 0.06 wt% based on the total weight of the catalyst component, the prepared polypropylene has the characteristics of high isotactic index, high melt flow index and narrow molecular weight distribution. Further, the inventors of the present invention have also found that, according to a preferred embodiment of the present invention, when a trace amount of phosphate ester is added during the preparation of a catalyst component for olefin polymerization using a diether based compound as an internal electron donor, that is, when the molar ratio of the amount of the phosphate ester to the diether based compound is 0.02 to 0.25: 1. preferably 0.04 to 0.15: 1, the two internal electron donors can be perfectly matched, so that the hydrogen response and the stereospecificity of the catalyst are more effectively improved, the isotactic index and the melt flow index of polypropylene are further improved, and the molecular weight distribution index of the polypropylene is reduced. In addition, when the molar ratio of the amounts of the phosphate compound and the diether compound used in the internal electron donor is controlled within the above-described preferred range, the content of the phosphate compound in the finally obtained catalyst is extremely small, and thus the problem caused by the presence of a large amount of the phosphate compound can be effectively avoided.

In addition, the invention also provides application of the polypropylene in preparing fibers and non-woven fabrics.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The melt flow index MFR, isotactic index and molecular weight distribution index M of the polypropylene according to the invention_Wthe/Mn can be selected by the product requirements, for example the melt flow index MFR of the polypropylene>50g/10min, isotactic index of 96.5-98.5 wt%, and molecular weight distribution index M_Wthe/Mn is 3.5-5.

According to one embodiment of the invention, the polypropylene has a melt flow index MFR of 70 to 90g/10min, an isotactic index of 97.5 to 98.5 wt%, a molecular weight distribution index M_Wthe/Mn is 4-5.

The polypropylene provided by the present invention may have a melt flow index MFR of more than 30g/min, preferably more than 50g/min, more preferably 70-90g/10min, e.g. any value between 70-75g/10min, 75-80g/10min, 80-85g/10min or 85-90g/10 min.

The isotactic index of the polypropylene provided by the invention can be 96-99.5 wt%, preferably 96.5-98.5 wt%, more preferably 97.5-98.5 wt%, and for example can be any value between 97.5-98 wt% or 98-98.5 wt%.

The molecular weight distribution index of the polypropylene provided by the invention can be properly selected according to the specific application of the polypropylene, and can be any value between 3 and 5.5, preferably between 3.5 and 5, and more preferably between 4 and 5, on the basis of meeting the use requirement.

The melt flow index MFR is determined according to the method of ASTM D1238-99; the isotactic index is measured by adopting a heptane extraction method (boiling extraction of heptane for 6 hours), namely 2g of dried polymer sample is taken and placed in an extractor to be extracted by boiling heptane for 6 hours, then the remainder is dried to constant weight, and the ratio of the weight (g) of the obtained polymer to 2 is the isotactic index; the molecular weight distribution index M_Wthe/Mn was determined by Shimadzu LC-10AT Gel Permeation Chromatograph (GPC), in which trichlorobenzene was used as the mobile phase and the temperature was 150 ℃.

The invention overcomes the defects that in the prior art, when the melt flow index of the prepared polypropylene is higher, the isotactic index is lower, and when the isotactic index is higher, the melt flow index is lower.

According to a preferred embodiment of the present invention, the phosphorus content in the catalyst component, calculated as phosphorus element, is from 0.002 to 0.05% by weight, preferably from 0.005 to 0.04% by weight, based on the total weight of the catalyst component. By adopting the preferred embodiment, the post-treatment problem caused by the existence of a large amount of phosphate compounds is avoided, the synergistic effect of the diether compounds and the phosphate compounds can be ensured, the hydrogen regulation sensitivity and the stereospecificity of the catalyst can be further improved, and the catalyst component is applied to olefin polymerization to obtain the polymer with the characteristics of high isotactic index, high melt flow index and narrow molecular weight distribution.

In the invention, the content of the phosphorus element in the catalyst component can be measured by adopting an X-ray fluorescence spectrum analysis method.

According to the present invention, when the internal electron donor comprises a diether compound and a phosphate compound, a certain synergistic effect can be generated, and the total amount of the phosphate compound and the diether compound is preferably 70 to 100 wt%, more preferably 80 to 100 wt%, even more preferably 90 to 100 wt%, and most preferably 100 wt%, based on the amount of the internal electron donor.

The inventor of the invention researches and discovers that when the dosage of the phosphate ester compound is 0.02-0.25 mol, preferably 0.04-0.15 mol, relative to each mol of the diether compound, the phosphate ester compound and the diether compound can be better blended synergistically, so that a catalyst with better hydrogen response and stereospecificity is obtained, and the prepared polypropylene has the characteristics of higher isotactic index, melt flow index and narrower molecular weight distribution.

The contents of magnesium, titanium and an internal electron donor in the catalyst component are not particularly limited, and may be any value in the catalyst component conventional in the art, preferably, the magnesium element is 2 to 15 parts by weight, preferably 3 to 12 parts by weight, and more preferably 4 to 10 parts by weight, per part by weight of the titanium element; the internal electron donor is 2 to 10 parts by weight, preferably 3 to 8 parts by weight, and more preferably 4 to 7 parts by weight.

In the invention, the contents of titanium element and magnesium element in the catalyst component can be measured by adopting an X-ray fluorescence spectrum analysis method; the content of internal electron donor (phosphate compound and diether compound) in the catalyst component is obtained by chromatographic analysis and mass spectrometric analysis.

The kind of the phosphate ester compound is not particularly limited in the present invention, and may be various phosphate ester compounds that can be used as an internal electron donor of a catalyst for olefin polymerization, and preferably, the phosphate ester compound has a structure represented by formula (1),

wherein R is₁₃、R₁₄And R₁₅Each independently selected from C₁-C₄Straight or branched alkyl of (2), C₃-C₂₀Cycloalkyl of, C₆-C₂₀Aryl of (C)₇-C₂₀Alkylaryl and C of₇-C₂₀The aryl group, the alkylaryl group and the arylalkyl group wherein the hydrogen atom on the benzene ring is optionally substituted with a halogen atom; further preferred is R₁₃、R₁₄And R₁₅Each independently selected from C₁-C₄Straight or branched alkyl of (2), C₃-C₁₂Cycloalkyl of, C₆-C₁₂Aryl of (C)₇-C₁₂Alkylaryl and C of₇-C₁₂The aryl group, the alkylaryl group and the arylalkyl group wherein the hydrogen atom on the benzene ring is optionally substituted with a halogen atom; further preferred is R₁₃、R₁₄And R₁₅Each independently selected from C₁-C₄Straight or branched alkyl of (2), C₃-C₆Cycloalkyl of, C₆-C₈Aryl of (C)₇-C₈Alkylaryl and C of₇-C₈The aryl group, the alkylaryl group and the arylalkyl group wherein the hydrogen atom on the benzene ring is optionally substituted with a halogen atom; for example R₁₃、R₁₄And R₁₅Each independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, phenyl, tolyl, dimethylphenyl, ethylphenyl, benzyl, methylbenzyl or phenethyl.

Preferably, the phosphate ester compound is at least one selected from the group consisting of trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, tricresyl phosphate, triisopropylphenyl phosphate, trimethoxyphenyl phosphate, phenyl dimethyl phosphate, tolyl dibutyl phosphate, isopropylphenyl dimethyl phosphate, isopropylphenyl diethyl phosphate, isopropylphenyl dibutyl phosphate, phenyl dimethyl phosphate, phenyl diisopropylphenyl phosphate, p-tolyl dibutyl phosphate, m-tolyl dibutyl phosphate, p-isopropylphenyl dimethyl phosphate, p-isopropylphenyl diethyl phosphate, p-tert-butylphenyl dimethyl phosphate, and o-tolyl-p-di-tert-butylphenyl phosphate.

Most preferably, the phosphate ester compound is tributyl phosphate.

According to the present invention, the diether compound may be various diether compounds capable of serving as an internal electron donor of a catalyst for olefin polymerization, and preferably the diether compound is at least one selected from diether compounds represented by formula (2),

R¹R²C(CH₂OR³)(CH₂OR⁴) Formula (2)

Wherein R is¹And R²Each independently selected from hydrogen and C₁-C₂₀Straight or branched alkyl of (2), C₃-C₂₀Cycloalkyl of, C₆-C₂₀Aryl of (C)₇-C₂₀Aralkyl and C₇-C₂₀Optionally bonded to form a ring; r³And R⁴Each independently selected from C₁-C₁₀Alkyl group of (1).

Preferably, the diether is selected from the group consisting of 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-dicyclohexyl-1, 3-dimethoxypropane, 2-dicyclopentyl-1, 3-dimethoxypropane, 2-diethyl-1, 3-dimethoxypropane, 2-dipropyl-1, 3-dimethoxypropane, 2-diisopropyl-1, 3-dimethoxypropane, 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-dimethyl-2-propyl-1, 3, 2-methyl-2-isopropyl-1, 3-dimethoxypropane, 2-methyl-2-phenyl-1, 3-dimethoxypropane, 2-methyl-2-cyclohexyl-1, 3-dimethoxypropane, 2-bis (2-cyclohexylethyl) -1, 3-dimethoxypropane, 2-methyl-2-isobutyl-1, 3-dimethoxypropane, 2-methyl-2- (2-ethylhexyl) -1, 3-dimethoxypropane, 2-diisobutyl-1, 3-dimethoxypropane, 2-diphenyl-1, 3-dimethoxypropane, 2-dibenzyl-1, 3-dimethoxypropane, 2-bis (cyclohexylmethyl) -1, 3-dimethoxypropane, 2-isobutyl-2-isopropyl-1, 3-dimethoxypropane, 2- (1-methylbutyl) -2-isopropyl-1, 3-dimethoxypropane, 2-isopropyl-2-isoamyl-1, 3-dimethoxypropane, 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.

Most preferably, the diether compound is 2-isopropyl-2-isoamyl-1, 3-dimethoxypropane.

In the invention, when the tributyl phosphate and the 2-isopropyl-2-isoamyl-1, 3-dimethoxypropane are preferably used as the internal electron donor, the hydrogen regulation sensitivity and the stereospecificity of the catalyst can be particularly and effectively improved, and the obtained polypropylene has the characteristics of high isotactic index, high melt flow index and narrow molecular weight distribution.

According to a preferred embodiment of the present invention, the magnesium source, the titanium source and the internal electron donor react in the following manner: the method comprises the following steps of carrying out contact reaction on a magnesium source and a titanium source, and adding an internal electron donor in one or more time periods before, during and after the contact reaction of the magnesium source and the titanium source.

The contact reaction of the magnesium source and the titanium source may be carried out in the same manner as in the prior art, for example, the titanium source may be cooled to 0 ℃ or lower (preferably-5 to-25 ℃), then the magnesium source may be added and mixed with stirring at that temperature for 10 to 60 minutes, after which the temperature is raised to the reaction temperature (i.e., about 60 to 130 ℃) and maintained at that reaction temperature for 0.5 to 10 hours. The internal electron donor compound containing the phosphate compound and the diether compound is added in one or more time periods before, during and after the contact reaction of the magnesium source and the titanium source. The time period before the contact reaction of the magnesium source and the titanium source means a time period after the magnesium source is added to the reactor and before the temperature is raised to the reaction temperature. The internal electron donor at least containing the phosphate compound and the diether compound can be added together or can be added separately in different time periods. Preferably, an internal electron donor containing at least a phosphate compound and a diether compound is added in a period of time before the reaction.

According to the present invention, it is preferred that the molar ratio of the magnesium source in terms of magnesium element, the titanium source in terms of titanium element and the internal electron donor is 1: 20-150: 0.1 to 0.9, more preferably 1: 30-120: 0.15-0.6.

In the present invention, the magnesium source may be a magnesium-containing compound of existing various catalysts capable of being used for olefin polymerization, for example, the magnesium source may be magnesium halide, alcoholate of magnesium or haloalcoholate and magnesium halide adduct support, etc.; the magnesium halide may be, for example, magnesium chloride and/or magnesium bromide; the alcoholate of magnesium may be, for example, diethoxymagnesium; the haloalcoholate of magnesium may be, for example, magnesium ethoxychloride; the kind of the magnesium halide adduct carrier is 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, etc., and the relevant contents of these patent publications are all incorporated into the present application by reference. A specific method of preparing the magnesium halide adduct carrier may include the steps of: mixing the components for forming the magnesium halide adduct, heating to react to generate magnesium halide adduct melt, wherein the reaction temperature is 90-140 ℃, putting the magnesium halide adduct melt into a cooling medium after high shear action in a dispersion medium to form spherical magnesium halide adduct particles, washing and drying to obtain a spherical carrier, and optionally adding an internal electron donor during or after the process. The high shear may be achieved by conventional means such as high speed stirring (eg CN1330086), spraying (eg US6020279) and high gravity rotating beds (eg CN1580136A) and emulsifying machine (CN 1463990A). The dispersion medium may be, for example, a hydrocarbon-based inert solvent such as one or more of kerosene, white oil, silicone oil, paraffin oil, vaseline oil, and the like. The cooling medium may be selected from one or more of pentane, hexane, heptane, petroleum ether, raffinate oil, etc., for example.

In the preparation of the catalyst component for the polymerization of olefins according to the present invention, the source of titanium may be chosen conventionally in the art, and may be, for example, of the general formula Ti (OR')_3-aZ_aand/OR Ti (OR')_4-bZ_bWherein R' is C₁-C₂₀Z 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 one or more of titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, tributoxy titanium chloride, dibutoxy titanium dichloride, butoxytitanium trichloride, triethoxy titanium chloride, diethoxy titanium dichloride, ethoxy titanium trichloride, and titanium trichloride.

In the catalyst of the present invention, the alkylaluminum compound may be various alkylaluminum compounds conventionally used in the art, for example, the alkylaluminum compound may have a general formula of AlR₁₆R₁₆′R₁₆", wherein R₁₆、R₁₆' and R₁₆Each independently is C₁-C₈And wherein one or both of the groups may be halogen, and the hydrogen on the alkyl group may also be substituted by halogen; said C is₁-C₈Specific examples of the alkyl group of (a) may include, but are not limited to: methyl, ethyl, propyl, n-butyl, isobutyl, pentyl, hexyl, n-heptyl, n-octyl and the halogen may be fluorine, chlorine, bromine, iodine. Specifically, the alkyl aluminum compound may be selected from, for example, triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, diethylaluminum monochloride, diisobutylaluminum monochloride, aluminum chlorohydrate, aluminum chlorohydr,One or more of di-n-butylaluminum monochloride, di-n-hexylaluminum monochloride, monoethylaluminum dichloride, monoisobutylaluminum dichloride, mono-n-butylaluminum dichloride and mono-n-hexylaluminum dichloride.

In the catalyst of the present invention, the external electron donor may be various external electron donors commonly used in the art, for example, the external electron donor may be at least one selected from the group consisting of carboxylic acids, carboxylic anhydrides, carboxylic esters, ketones, ethers, alcohols, lactones, organic phosphorus compounds, and organic silicon compounds. Preferably, the external electron donor is a compound containing at least one Si-OR bond and having the general formula (R)₁₇)_x(R₁₈)_ySi(OR₁₉)_zWherein R is₁₇、R₁₈And R₁₉Is C₁-C₁₈X and y are each independently an integer from 0 to 2, z is an integer from 1 to 3, and the sum of x, y and z is 4. Preferably, R₁₇、R₁₈Is C₃-C₁₀Alkyl, cycloalkyl, optionally containing heteroatoms; r₁₉Is C₁-C₁₀Optionally containing heteroatoms. Specifically, the external electron donor may be at least one selected from the group consisting of cyclohexylmethyldimethoxysilane, diisopropyldimethoxysilane, di-n-butyldimethoxysilane, diisobutyldimethoxysilane, diphenyldimethoxysilane, methyl-t-butyldimethoxysilane, dicyclopentyldimethoxysilane, 2-ethylpiperidinyl-2-t-butyldimethoxysilane, (1,1, 1-trifluoro-2-propyl) -2-ethylpiperidinyldimethoxysilane and (1,1,1-, trifluoro-2-propyl) -methyldimethoxysilane, for example.

In addition, in general, in the catalyst of the invention, the molar ratio between the amounts of the catalyst component, expressed as titanium element, and the alkylaluminum compound, expressed as aluminum element, can be 1: 1-2000, preferably 1: 20-500; the molar ratio of the external electron donor to the amount of aluminum alkyl compound used, calculated as aluminum element, may be 1: 2-200, preferably 1: 2.5-100.

According to the invention, when the catalyst is used for olefin polymerization, the catalyst component, the alkyl aluminum compound and the external electron donor can be respectively added into a polymerization reactor, or can be added into the polymerization reactor after being mixed, or can be added into the polymerization reactor after olefin prepolymerization by adopting a prepolymerization method known in the industry.

According to a preferred embodiment of the present invention, the catalyst component, the alkyl aluminum compound and the external electron donor compound are subjected to a pre-contact reaction before the polymerization reaction, wherein the pre-contact reaction temperature can be-15 ℃ to 40 ℃, preferably 0 to 20 ℃, and the pre-contact reaction time can be 0.5 to 60min, preferably 1 to 20 min. The pre-contact reaction can obviously improve the polymerization activity of the catalyst and the apparent density of the polypropylene, and simultaneously enhance the impurity interference resistance of the active center of the catalyst, thereby reducing the ash content in the polypropylene and the crushing of polypropylene particles.

According to a preferred embodiment of the present invention, the catalyst is preferably prepolymerized with propylene after the precontacting and before the polymerization. The prepolymerization can be carried out at 10-70 deg.C, preferably 15-30 deg.C, with or without hydrogen, and the prepolymerization time can be 0-60min, preferably 4-30 min.

According to the present invention, the polymerization reaction can be carried out according to various methods, and specifically, the polymerization reaction can be carried out in a liquid phase monomer or an inert solvent containing a polymeric monomer, or in a gas phase, or by a combined polymerization process in a gas-liquid phase under the protection of an inert gas. The polymerization temperature may be generally 0 to 150 ℃ and preferably 60 to 90 ℃. The pressure of the polymerization reaction may be normal pressure or higher; for example, it may be in the range of 0.01 to 10MPa, preferably 0.01 to 6MPa, more preferably 0.1 to 4 MPa. The pressure in the present invention is a gauge pressure. Hydrogen may be added to the reaction system as a polymer molecular weight modifier to adjust the molecular weight and melt flow index of the polymer during the polymerization, and the concentration of hydrogen may be 1500ppm or more, preferably 2500ppm or more, and most preferably 2500-. The polymerization time of propylene and catalyst is preferably from 0.5 to 6h, more preferably from 1 to 2 h. In addition, the types and amounts of the inert gas and the solvent are well known to those skilled in the art during the polymerization of olefins, and will not be described herein.

According to the present invention, preferably, the preparation method of polypropylene further comprises: the polymerization product is pelletized after the polymerization reaction is completed. Specifically, additives such as an antioxidant and a stabilizer are preferably added during granulation. The kinds and amounts of the antioxidant, stabilizer and other additives are well known to those skilled in the art and will not be described herein.

The invention also provides the polypropylene prepared by the preparation method of the polypropylene.

The present invention will be further illustrated by the following examples.

In the following examples and comparative examples:

Example 1

This example serves to illustrate the polypropylene according to the invention and its preparation.

(1) Preparation of the catalyst component

Into a 300ml glass reaction flask, 90ml (820mmol) of titanium tetrachloride was charged and cooled to-20 ℃ and 37mmol, in terms of magnesium element, of a magnesium halide support (prepared as disclosed in example 1 of CN 1330086A) was added thereto, followed by warming to 110 ℃ and adding 0.3mmol of tributyl phosphate and 7.3mmol of 2-isopropyl-2-isopentyl-1, 3-dimethoxypropane during the warming, the liquid was filtered after maintaining at 110 ℃ for 30min, washed 2 times with titanium tetrachloride, washed 5 times with hexane, and dried under vacuum to give a catalyst component Cat-1 for olefin polymerization.

The catalyst component Cat-1 for olefin polymerization had a phosphorus content of 0.011 wt.% in terms of phosphorus element and a titanium content of 2.6 wt.% in terms of titanium element, as measured by X-ray fluorescence spectroscopy.

(2) Preparation of Polypropylene

Pre-contacting a catalyst component Cat-1, triethylaluminum and cyclohexyl methyldimethoxysilane (the molar ratio of the catalyst component Cat-1 in terms of titanium element to triethylaluminum in terms of aluminum element is 1: 200; the molar ratio of the cyclohexyl methyldimethoxysilane to the triethylaluminum in terms of aluminum element is 1:10) at 10 ℃ for 15min, adding the catalyst component Cat-1, the triethylaluminum and the triethylaluminum in terms of aluminum element into a prepolymerization reactor for prepolymerization, performing prepolymerization reaction in a propylene liquid phase body environment at the prepolymerization temperature of 17 ℃ for 15min, continuously introducing the obtained mixture into a loop reactor for propylene polymerization reaction at the polymerization reaction temperature of 70 ℃ and the reaction pressure of 3.5MPa, introducing hydrogen into the feed of the loop reactor, wherein the hydrogen concentration (detected by on-line chromatography) is 3800ppm, the reaction time is 1h, then cooling and relieving the pressure, the discharge was carried out, and the propylene homopolymer obtained was dried, weighed and analyzed, the results being shown in Table 1.

Example 2

A catalyst component and polypropylene were prepared by the method of example 1, except that the amounts of tributyl phosphate and 2-isopropyl-2-isopentyl-1, 3-dimethoxypropane added during the temperature increase were 1mmol and 10mmol, respectively, to give a catalyst component Cat-2 for olefin polymerization.

The catalyst component Cat-2 for olefin polymerization had a phosphorus content of 0.025 wt% in terms of phosphorus element and a titanium content of 2.5 wt% in terms of titanium element, as measured by X-ray fluorescence spectroscopy.

The resulting propylene homopolymer was dried, weighed and analyzed, and the results are shown in Table 1.

Example 3

A catalyst component and polypropylene were prepared in the same manner as in example 1, except that tributyl phosphate and 2-isopropyl-2-isopentyl-1, 3-dimethoxypropane were added in amounts of 1.1mmol and 7.3mmol, respectively, during the temperature increase, to give a catalyst component Cat-3 for olefin polymerization.

The catalyst component Cat-3 for olefin polymerization had a phosphorus content of 0.04% by weight in terms of phosphorus element and a titanium content of 2.6% by weight in terms of titanium element, as measured by X-ray fluorescence spectroscopy.

Example 4

A catalyst component and polypropylene were prepared in the same manner as in example 1 except that tributyl phosphate and 2-isopropyl-2-isopentyl-1, 3-dimethoxypropane were added in amounts of 0.15mmol and 7.3mmol, respectively, during the temperature increase to obtain a catalyst component Cat-4 for olefin polymerization.

The catalyst component Cat-4 for olefin polymerization had a phosphorus content of 0.005% by weight in terms of phosphorus element and a titanium content of 2.7% by weight in terms of titanium element, as measured by X-ray fluorescence spectroscopy.

Example 5

A catalyst component and polypropylene were prepared as in example 1, except that 0.3mmol of triisopropylphenyl phosphate and 7.3mmol of 9, 9-dimethoxymethylfluorene were added during the temperature rise, and 0.3mmol of tributyl phosphate and 7.3mmol of 2-isopropyl-2-isopentyl-1, 3-dimethoxypropane were not added, to give a catalyst component Cat-5 for olefin polymerization having a phosphorus content of 0.009 wt% in terms of phosphorus element and a titanium content of 2.6 wt% in terms of titanium element; the resulting propylene homopolymer was dried, weighed and analyzed, and the results are shown in Table 1.

Example 6

A catalyst component and polypropylene were produced in the same manner as in example 1 except that the hydrogen concentration was 3300ppm, and the analysis results of the propylene homopolymer obtained were as shown in Table 1.

Example 7

A catalyst component and polypropylene were produced in the same manner as in example 1 except that the concentration of hydrogen was 2800ppm, and the analysis results of the propylene homopolymer obtained were as shown in Table 1.

Example 8

A catalyst component and polypropylene were produced in the same manner as in example 1 except that the hydrogen concentration was 2500ppm, and the analysis results of the propylene homopolymer obtained were as shown in Table 1.

Example 9

A catalyst component and polypropylene were produced in the same manner as in example 1 except that the hydrogen concentration was 2300ppm, and the analysis results of the propylene homopolymer obtained were as shown in Table 1.

Comparative example 1

This comparative example serves to illustrate a reference polypropylene and a process for its preparation.

A catalyst component and polypropylene were prepared in the same manner as in example 1, except that in the preparation of the catalyst component, the tributyl phosphate was replaced with the same parts by weight of 2-isopropyl-2-isopentyl-1, 3-dimethoxypropane to give a catalyst component DCat-1 for olefin polymerization; the resulting propylene homopolymer was dried, weighed and analyzed, and the results are shown in Table 1.

Comparative example 2

The catalyst component and polypropylene were prepared in the same manner as in comparative example 1 except that the hydrogen concentration was 3300ppm, and the analysis results of the propylene homopolymer obtained were as shown in Table 1.

Comparative example 3

The catalyst component and polypropylene were prepared in the same manner as in comparative example 1 except that the hydrogen concentration was 2300ppm, and the analysis results of the propylene homopolymer obtained were as shown in Table 1.

Comparative example 4

A catalyst component and polypropylene were prepared in the same manner as in example 2, except that, in the preparation of the catalyst component, the tributyl phosphate was replaced with the same weight part of 2-isopropyl-2-isopentyl-1, 3-dimethoxypropane to obtain a catalyst component DCat-4 for olefin polymerization; the resulting propylene homopolymer was dried, weighed and analyzed, and the results are shown in Table 1.

Comparative example 5

A catalyst component and polypropylene were prepared in the same manner as in example 1 except that in the preparation of the catalyst component, tributyl phosphate and 2-isopropyl-2-isopentyl-1, 3-dimethoxypropane were added in amounts of 2.2mmol and 7.3mmol, respectively, to give a catalyst component for olefin polymerization, DCat-5, in which the phosphorus content in terms of phosphorus element was 0.07% by weight; the resulting propylene homopolymer was dried, weighed and analyzed, and the results are shown in Table 1.

Comparative example 6

A catalyst component and polypropylene were prepared in the same manner as in example 1, except that, in the preparation of the catalyst component, the 2-isopropyl-2-isopentyl-1, 3-dimethoxypropane was replaced with the same weight part of 2, 4-pentanediol dibenzoate to give a catalyst component DCat-6 for olefin polymerization; the resulting propylene homopolymer was dried, weighed and analyzed, and the results are shown in Table 1.

Comparative example 7

A catalyst component and polypropylene were prepared in the same manner as in example 1, except that the catalyst component Cat-1 was replaced with the same parts by weight of a DQ catalyst component (hereinafter referred to as DCat-7, and the internal electron donor is diisobutylphthalate) available from Oda catalyst division, petrochemical, China, and the resulting propylene homopolymer was dried, weighed, and analyzed, and the results are shown in Table 1.

Comparative example 8

A catalyst component and polypropylene were prepared in the same manner as in example 9, except that the catalyst component Cat-1 was replaced with the same parts by weight of a DQ catalyst component (hereinafter referred to as DCat-8, and the internal electron donor is diisobutylphthalate) available from Oda catalyst division, petrochemical, China, and the resulting propylene homopolymer was dried, weighed, and analyzed, and the results are shown in Table 1.

TABLE 1

As can be seen from the results of examples 1-9 and comparative examples 1-8, the polypropylene produced according to the present invention at different hydrogen concentrations can increase the melt index without decreasing the isotactic index and without increasing the molecular weight distribution, i.e., can combine a high isotactic index and a high melt flow index with a narrow molecular weight distribution, preferably, the isotactic index is as high as 98.4 wt%, the melt index is as high as 90g/10min, and the molecular weight distribution index M is_WThe Mn is 4.2, the invention realizes the joint improvement of the isotactic index and the melt index of the polypropylene, and the catalyst used by the invention does not contain phthalate (plasticizer), thereby being more beneficial to the application of the polypropylene in various fields, in particular to the application in fibers and non-woven fabric products.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. The invention is not described in detail in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims

1. A polypropylene, characterized in that the polypropylene has a melt flow index MFR>30g/10min, isotactic index of 96-99.5 wt%, and molecular weight distribution index M_Wthe/Mn is 3 to 5.5;

the preparation method of the polypropylene comprises the following steps: under the condition of olefin polymerization, propylene is polymerized in the presence of a catalyst to obtain a polypropylene product, wherein the catalyst contains a catalyst component, an alkyl aluminum compound and an optional external electron donor, the catalyst component contains a product obtained by the reaction of a magnesium source, a titanium source and an internal electron donor, and the catalyst is characterized in that the internal electron donor contains a phosphate compound and a diether compound, and the phosphorus content in the catalyst component is not more than 0.06 wt% based on the total weight of the catalyst component;

the amount of the phosphate compound is 0.02-0.25 mol per mol of the diether compound.

2. The polypropylene according to claim 1, wherein the polypropylene has a melt flow index MFR>50g/10min, isotactic index of 96.5-98.5 wt%, and molecular weight distribution index M_Wthe/Mn is 3.5-5.

3. The polypropylene according to claim 1 or 2, wherein the polypropylene has a melt flow index MFR of 70-90g/10min, an isotactic index of 97.5-98.5 wt%, a molecular weight fractionCloth index M_Wthe/Mn is 4-5.

4. A preparation method of polypropylene comprises the steps of polymerizing propylene in the presence of a catalyst under the condition of olefin polymerization to obtain a polypropylene product, wherein the catalyst contains a catalyst component, an alkyl aluminum compound and an optional external electron donor, the catalyst component contains a product obtained by the reaction of a magnesium source, a titanium source and an internal electron donor, and the preparation method is characterized in that the internal electron donor contains a phosphate compound and a diether compound, and the phosphorus content in the catalyst component calculated by phosphorus element is not more than 0.06 wt% based on the total weight of the catalyst component;

5. The production method according to claim 4, wherein the catalyst component has a phosphorus content of 0.002 to 0.05% by weight in terms of phosphorus element, based on the total weight of the catalyst component.

6. The production method according to claim 4, wherein the content of phosphorus in the catalyst component in terms of phosphorus element is 0.005 to 0.04% by weight based on the total weight of the catalyst component.

7. The preparation method of claim 4, wherein the magnesium source, the titanium source and the internal electron donor are reacted in a manner that: and carrying out contact reaction on the magnesium source and the titanium source, and adding an internal electron donor in one or more time periods before, during and after the contact reaction of the magnesium source and the titanium source.

8. The preparation method of claim 4, wherein the total amount of the phosphate compound and the diether compound is 70-100 wt% based on the amount of the internal electron donor.

9. The production method according to claim 4, wherein the phosphate ester compound is used in an amount of 0.04 to 0.15 mol per mol of the diether compound.

10. The preparation method according to claim 4, wherein 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.

11. The preparation method according to claim 4, wherein 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: 30-120: 0.15-0.6.

12. The production method according to any one of claims 4 to 11, wherein the phosphate ester compound has a structure represented by formula (1),

wherein R is₁₃、R₁₄And R₁₅Each independently selected from C₁-C₄Straight or branched alkyl of (2), C₃-C₂₀Cycloalkyl of, C₆-C₂₀Aryl of (C)₇-C₂₀Alkylaryl and C of₇-C₂₀One of the aralkyl groups of (1).

13. The production method according to any one of claims 4 to 11, wherein the phosphate-based 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 dimethyl phenyl phosphate, phenyl diisopropyl phenyl phosphate, p-tolyl dibutyl phosphate, m-tolyl dibutyl phosphate, p-isopropylphenyl dimethyl phosphate, p-isopropylphenyl diethyl phosphate, p-tert-butylphenyl dimethyl phosphate, and o-tolylp-di-tert-butylphenyl phosphate.

14. The production method according to any one of claims 4 to 11, wherein the diether-based compound is at least one compound selected from diether-based compounds represented by formula (2),

R¹R²C(CH₂OR³)(CH₂OR⁴) Formula (2)

Wherein R is¹And R²Each independently selected from hydrogen and C₁-C₂₀Straight or branched alkyl of (2), C₃-C₂₀Cycloalkyl of, C₆-C₂₀Aryl of (C)₇-C₂₀Aralkyl and C₇-C₂₀One of the alkylaryl groups of (1), R³And R⁴Each independently selected from C₁-C₁₀Alkyl group of (1).

15. The production method according to any one of claims 4 to 11, wherein the diether compound is selected from the group consisting of 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-dicyclohexyl-1, 3-dimethoxypropane, 2-dicyclopentyl-1, 3-dimethoxypropane, 2-diethyl-1, 3-dimethoxypropane, 2-dipropyl-1, 3-dimethoxypropane, 2-diisopropyl-1, 3-dimethoxypropane, 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-bis (2-cyclohexylethyl) -1, 3-dimethoxypropane, 2-methyl-2-isobutyl-1, 3-dimethoxypropane, 2-methyl-2- (2-ethylhexyl) -1, 3-dimethoxypropane, 2-diisobutyl-1, 3-dimethoxypropane, 2-diphenyl-1, 3-dimethoxypropane, 2-methyl-2- (2-ethylhexyl) -1, 3-dimethoxypropane, 2-diisobutyl-1, 3-dimethoxypropane, 2-diphenyl-1, 3-dimethoxypropane, 2-methyl-2-, 2, 2-dibenzyl-1, 3-dimethoxypropane, 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, 2-phenyl-2-isopropyl-1, 3-dimethoxypropane, 2-phenyl-2-sec-butyl-1, 3-dimethoxypropane, 2-benzyl-2-isopropyl-1, 3-dimethoxypropane, 2-methyl-2-isopropyl-1, 3, 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.

16. The process according to claim 4, wherein the molar ratio between the catalyst component in terms of titanium and the alkyl aluminum compound in terms of aluminum is 1: 1-2000; the molar ratio of the external electron donor to the alkyl aluminum compound dosage calculated by aluminum element is 1: 2-200.

17. The process according to claim 4, wherein the molar ratio between the catalyst component in terms of titanium and the alkyl aluminum compound in terms of aluminum is 1: 20-500; the molar ratio of the external electron donor to the alkyl aluminum compound dosage calculated by aluminum element is 1: 2.5-100.

18. Polypropylene produced by the process of any one of claims 4 to 17.

19. Use of the polypropylene according to any one of claims 1 to 3 and 18 for the preparation of fibers and nonwovens.