Polypropylene resin as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of high polymer materials, and discloses a polypropylene resin and a preparation method and application thereof, the polypropylene resin contains a propylene / ethylene copolymer and an auxiliary agent at least containing a nucleating agent; the polypropylene resin has the following characteristics: the melt index at 230 DEG C under the load of 2.16 kg is not greater than 2g / 10min; the ethylene content is 1 wt% to 5 wt%; the content of room-temperature xylene soluble substances is not less than 9wt%; the content of n-hexane extract is lower than 3%; the rheological polydispersity index is less than 2.8; a segmented isothermal separation technique is utilized to determine the lamellar thickness of the copolymer containing at least 28 wt% of crystalline fractions having a lamellar thickness of more than 9.96 nm. The polypropylene resin provided by the invention has the advantages of low n-hexane precipitate, good impact property and excellent optical property, and is especially suitable for extrusion blowing products.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a polypropylene resin and a preparation method and application thereof. Background Art

[0002] Random copolymer polypropylene (PPR) is a very important type of polypropylene material. It is widely used in fields requiring high transparency, low melting point, high temperature and pressure resistance due to its balanced mechanical properties and good comprehensive performance. Compared with homopolymers, random copolymers have higher flexibility and impact strength; compared with impact copolymers, random copolymers have lower melting points, rigidity and higher transparency, so they are widely used in clothing, transparent containers for household and food, medical equipment, heat-sealed oriented films, pipes, etc.

[0003] Although random copolymer polypropylene has advantages in many aspects, it also has certain shortcomings. For example, the thermal expansion coefficient is large at high temperature (95°C), and the impact strength is not enough, especially it is easy to become brittle at low temperature, and the toughness is poor, which limits the application of PPR materials in fields with high toughness requirements. In response to this problem, if PPR materials can be developed to meet the impact performance requirements in various fields while maintaining good bending performance and transparency, it will greatly promote the application field and scope of use of PPR.

[0004] There is huge potential for domestic market demand for special transparent products such as random copolymer polypropylene, but most products still rely on imports. Among them, extrusion blow molding (EBM) transparent PP is mainly a type of transparent material suitable for blow molding and compression molding with a melt flow rate MFR between 1-2g / 10min. Extrusion blow molding is mainly used in laundry detergent, disinfectant bottles / beverage bottles / cosmetic bottles, hoses, etc. It is well known in the art that in order to obtain better processing performance and make it easier to extrude and blow bottles and other products, catalysts with a wide molecular weight distribution are generally used to obtain copolymers. However, extruded products produced using copolymers synthesized using wide molecular weight distribution catalysts are not suitable for use in food, cosmetics, medical and health fields with high safety requirements because they contain more n-hexane extracts.

[0005] Patent document CN110016097B discloses an ethylene-propylene random copolymer with low extractables, low melting point, narrow molecular weight distribution and thermal oxygen stability. The copolymer has an ethylene content of 0.1-8wt%, a room temperature xylene soluble content of less than 10wt%, a melting point of less than 160°C, and a rheological polydispersity index PI of less than 3.5. The copolymer is characterized by excellent thermal oxygen stability and a low MFR change rate after multiple granulation. However, the patent document does not focus on the improvement of the mechanical properties of the polymer, nor does it focus on whether the polymer is used in extrusion blow products.

[0006] Patent document CN104768989B discloses a propylene copolymer for making bottles. The copolymer has a relatively high total monomer content and moderate xylene solubles, and the bottles made by extrusion blow molding of the copolymer have excellent optical properties. However, the document does not focus on the mechanical properties of the copolymer.

[0007] Therefore, a method is needed to prepare a polypropylene resin with low n-hexane precipitate, good transparency and excellent impact performance, which is more suitable for application in extrusion blow molding products. Summary of the invention

[0008] Based on the above situation, the purpose of the present invention is to provide a polypropylene resin and a preparation method and application thereof. The polypropylene resin has low n-hexane precipitate, good impact resistance and excellent optical properties, and is particularly suitable for extrusion blow molding products.

[0009] The first aspect of the present invention provides a polypropylene resin, which contains a propylene / ethylene copolymer and an auxiliary agent containing at least a nucleating agent; the polypropylene resin has the following characteristics:

[0010] The melt index at 230°C and 2.16kg load is not more than 2g / 10min;

[0011] Ethylene content is 1 wt% to 5 wt%;

[0012] The room temperature xylene soluble content is not less than 9wt%;

[0013] Hexane extract is less than 3%;

[0014] The rheological polydispersity index is less than 2.8;

[0015] The copolymer lamellae thickness was determined using a segmented isothermal separation technique and contained at least 28 wt% of a crystalline portion having a lamellae thickness exceeding 9.96 nm.

[0016] The second aspect of the present invention provides a method for preparing the above-mentioned polypropylene resin, wherein the materials contained in the polypropylene resin are mixed, and extruded and granulated to obtain the polypropylene resin.

[0017] The third aspect of the present invention provides the use of the above-mentioned polypropylene resin in an extrusion blown product.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The polypropylene resin of the invention has low n-hexane precipitate, good impact property and excellent optical property, and is particularly suitable for extrusion blow products.

[0020] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the thickness range of SIST lamellae in various embodiments and comparative examples. DETAILED DESCRIPTION

[0022] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0023] According to a first aspect of the present invention, the present invention provides a polypropylene resin, which contains a propylene / ethylene copolymer and an auxiliary agent containing at least a nucleating agent; the polypropylene resin has the following characteristics:

[0024] The melt index at 230°C and 2.16kg load is not more than 2g / 10min;

[0025] Ethylene content is 1 wt% to 5 wt%;

[0026] The room temperature xylene soluble content is not less than 9wt%;

[0027] Hexane extract is less than 3%;

[0028] The rheological polydispersity index is less than 2.8;

[0029] The copolymer lamellae thickness was determined using a segmented isothermal separation technique and contained at least 28 wt% of a crystalline portion having a lamellae thickness exceeding 9.96 nm.

[0030] Preferably, the copolymer lamellae thickness, as determined using a segmented isothermal fractionation technique, contains at least 29 wt% of a crystalline portion having a lamellae thickness exceeding 9.96 nm.

[0031] Preferably, the n-hexane extractables are less than 2.2%.

[0032] Preferably, the rheological polydispersity index is less than 2.7.

[0033] In the present invention, the haze of the polypropylene resin is not greater than 12%, and the 23°C simply supported beam notched impact strength is not less than 23kg / m 2 .

[0034] Preferably, the 23°C simply supported beam notched impact strength of the polypropylene resin is not less than 25 kg / m 2 , more preferably not less than 28kg / m 2 .

[0035] According to the present invention, the preparation method of the propylene / ethylene copolymer comprises: polymerizing propylene and ethylene in the presence of a catalyst, the polymerization temperature is 0°C to 150°C, the polymerization pressure is higher than the saturated steam pressure of propylene at the corresponding polymerization temperature, and hydrogen is used as a molecular weight regulator.

[0036] Preferably, the polymerization temperature is 40°C to 90°C, and the polymerization pressure is 3-4 MPa.

[0037] In the present invention, the catalyst used may include the following components:

[0038] (i) a solid catalyst component, the solid catalyst component comprising a product obtained by reacting a magnesium source, a titanium source and an internal electron donor, the internal electron donor comprising a phosphate compound and a diether compound, and the phosphorus content in the solid catalyst component as phosphorus element is not more than 0.06% by weight, preferably 0.002-0.05% by weight, and more preferably 0.005-0.04% by weight, based on the total weight of the solid catalyst component;

[0039] (ii) an organoaluminum compound; and

[0040] (iii) an external electron donor, wherein the external electron donor is isobutyltriethoxysilane.

[0041] Preferably, based on the amount of the internal electron donor, the total amount of the phosphate compound and the diether compound is 70-100% by weight, more preferably 80-100% by weight, further preferably 90-100% by weight, and most preferably 100% by weight.

[0042] The content of phosphorus in the solid catalyst component can be measured by X-ray fluorescence spectrometry.

[0043] The present invention does not particularly limit the type of the phosphate compound, and can be any existing phosphate compound that can be used as an electron donor in an olefin polymerization catalyst. Preferably, the phosphate compound is selected from at least one of the phosphate compounds represented by formula (1):

[0044]

[0045] Among them, R 13 , R 14 and R 15 Each independently selected from a C1-C4 straight chain or branched alkyl group, a C3-C 20 Cycloalkyl, C6-C 20 Aryl, C7-C 20 Alkyl and C7-C 20One of the aralkyl groups; further preferably R 13 , R 14 and R 15 Each independently selected from a C1-C4 straight chain or branched alkyl group, a C3-C 12 Cycloalkyl, C6-C 12 Aryl, C7-C 12 Alkyl and C7-C 12 The hydrogen atoms on the benzene ring in the aryl, alkaryl and aralkyl groups are optionally substituted by halogen atoms; further preferably R 13 , R 14 and R 15 Each is independently selected from one of a C1-C4 straight or branched alkyl group, a C3-C6 cycloalkyl group, a C6-C8 aryl group, a C7-C8 alkaryl group and a C7-C8 aralkyl group, wherein the hydrogen atoms on the benzene ring in the aryl group, alkaryl group and aralkyl group are optionally substituted by halogen atoms.

[0046] Preferably, the phosphate compound is selected from at least one of trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, tricresyl phosphate, triisopropylphenyl phosphate, trimethoxyphenyl phosphate, phenyl dimethyl phosphate, cresyl dibutyl phosphate, isopropylphenyl dimethyl phosphate, isopropylphenyl diethyl phosphate, isopropylphenyl dibutyl phosphate, phenyl ditolyl phosphate, phenyl diisopropylphenyl phosphate, p-cresyl dibutyl phosphate, m-cresyl dibutyl phosphate, p-cumyl dimethyl phosphate, p-cumyl diethyl phosphate, p-tert-butylphenyl dimethyl phosphate and o-cresyl p-di-tert-butylphenyl phosphate.

[0047] The diether compound may be any diether compound that can be used as an electron donor in an olefin polymerization catalyst. Preferably, the diether compound is selected from at least one of the diether compounds represented by formula (2).

[0048] R1R2C(CH2OR3)(CH2OR4) Formula (2)

[0049] wherein R1 and R2 are each independently selected from hydrogen, C1-C 20 Straight or branched alkyl, C3-C 20 Cycloalkyl, C6-C 20 Aryl, C7-C 20 Arylalkyl and C7-C 20 R3 and R4 are each independently selected from C1-C 10 of alkyl.

[0050] Preferably, the diether compound is selected from 2-(2-ethylhexyl)-1,3-dimethoxypropane, 2-isopropyl-1,3-dimethoxypropane, 2-butyl-1,3-dimethoxypropane, 2-sec-butyl-1,3-dimethoxypropane, 2-cyclohexyl-1,3-dimethoxypropane, 2-phenyl-1,3-dimethoxypropane, 2-(2-phenylethyl)-1,3-dimethoxypropane, 2-(2-cyclohexylethyl)-1,3-dimethoxypropane, 2-(p-chlorophenyl)-1,3-dimethoxypropane, 2-(diphenylmethyl)-1,3-dimethoxypropane, 2,2-dicyclohexyl-1,3-dimethoxypropane, 2 , 2-dicyclopentyl-1,3-dimethoxypropane, 2,2-diethyl-1,3-dimethoxypropane, 2,2-dipropyl-1,3-dimethoxypropane, 2,2-diisopropyl-1,3-dimethoxypropane, 2,2-dibutyl-1,3-dimethoxypropane, 2-methyl-2-propyl-1,3-dimethoxypropane, 2-methyl-2-benzyl-1,3-dimethoxypropane, 2-methyl-2-ethyl-1,3-dimethoxypropane, 2-methyl-2-isopropyl-1,3-dimethoxypropane, 2-methyl-2-phenyl-1,3-dimethoxypropane, 2-methyl-2-cyclohexyl-1,3-dimethoxypropane, 2,2- Bis(2-cyclohexylethyl)-1,3-dimethoxypropane, 2-methyl-2-isobutyl-1,3-dimethoxypropane, 2-methyl-2-(2-ethylhexyl)-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxypropane, 2,2-diphenyl-1,3-dimethoxypropane, 2,2-dibenzyl-1,3-dimethoxypropane, 2,2-bis(cyclohexylmethyl)-1,3-dimethoxypropane, 2-isobutyl-2-isopropyl-1,3-dimethoxypropane, 2-(1-methylbutyl)-2-isopropyl-1,3-dimethoxypropane, 2-isopropyl-2-isopentyl-1,3-dimethoxypropane, At least one of 2-phenyl-2-isopropyl-1,3-dimethoxypropane, 2-phenyl-2-sec-butyl-1,3-dimethoxypropane, 2-benzyl-2-isopropyl-1,3-dimethoxypropane, 2-cyclopentyl-2-isopropyl-1,3-dimethoxypropane, 2-cyclopentyl-2-sec-butyl-1,3-dimethoxypropane, 2-cyclohexyl-2-isopropyl-1,3-dimethoxypropane, 2-cyclohexyl-2-sec-butyl-1,3-dimethoxypropane, 2-isopropyl-2-sec-butyl-1,3-dimethoxypropane, 2-cyclohexyl-2-cyclohexylmethyl-1,3-dimethoxypropane and 9,9-dimethoxymethylfluorene.

[0051] Preferably, tributyl phosphate and 2-isopropyl-2-isopentyl-1,3-dimethoxypropane are used in combination as internal electron donors. In this case, the hydrogen modulation sensitivity and stereospecificity of the catalyst can be particularly effectively improved, and the obtained polymer has the characteristics of a narrow molecular weight distribution. Most preferably, when tributyl phosphate and 2-isopropyl-2-isopentyl-1,3-dimethoxypropane are used in combination as internal electron donors, the molar ratio of tributyl phosphate to 2-isopropyl-2-isopentyl-1,3-dimethoxypropane is controlled at 0.04-0.15:1, which can further effectively improve the hydrogen modulation sensitivity and stereospecificity of the catalyst, and the obtained polymer has a narrower molecular weight distribution.

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

[0053] The titanium source may be a conventional choice in the art, for example, the titanium source may be a titanium-containing compound of the general formula Ti(OR')3-aZa and / or Ti(OR')4-bZb, wherein R' is C1-C 20alkyl, Z is F, Cl, Br or I, a is an integer of 1 to 3, and b is an integer of 1 to 4. Preferably, the titanium source is one or more of titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, tributoxytitanium chloride, dibutoxytitanium dichloride, butoxytitanium trichloride, triethoxytitanium chloride, diethoxytitanium dichloride, ethoxytitanium trichloride and titanium trichloride.

[0054] There is no particular restriction on the contents of magnesium, titanium and internal electron donor in the solid catalyst component, which may be any value in conventional catalyst components in the art. Preferably, the molar ratio of the magnesium source calculated as magnesium element, the titanium source calculated as titanium element and the internal electron donor is 1:20-150:0.1-0.9, preferably 1:30-120:0.15-0.6.

[0055] The content of titanium and magnesium in the catalyst component can be measured by X-ray fluorescence spectrometry; the content of internal electron donors (phosphate compounds and diether compounds) in the catalyst component can be obtained by chromatography and mass spectrometry.

[0056] The solid catalyst component can be prepared by contacting a magnesium source with a titanium source, and adding an internal electron donor in one or more time periods before, during and after the contacting reaction of the magnesium source with the titanium source.

[0057] Specifically, the reaction of the magnesium source and the titanium source can be carried out in the same manner as in the prior art, for example, the titanium source can be cooled to below 0°C (preferably -5 to -25°C), then the magnesium source is added, and the mixture is stirred and mixed at this temperature for 10-60 minutes, and then the temperature is raised to the reaction temperature (about 60-130°C), and the reaction temperature is maintained for 0.5-10 hours. In the preparation method of the catalyst component for olefin polymerization, the internal electron donor is added in one or more time periods before, during and after the reaction of the magnesium source and the titanium source. The time period before the reaction of the magnesium source and the titanium source refers to the time period after the magnesium source is added to the reactor and before the temperature is raised to the reaction temperature.

[0058] The amounts of the solid catalyst, organoaluminum and external electron donor can be determined as needed. Preferably, the amount ratio of the solid catalyst component to the organoaluminum compound in terms of titanium / aluminum molar ratio is 1:25-100; the weight ratio of the organoaluminum compound to the external electron donor is 0-150:1, preferably 2-150:1.

[0059] The organoaluminum compound as a co-catalyst is preferably an alkylaluminum compound, including but not limited to: one or more of triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, diethylaluminum monochloride, diisobutylaluminum monochloride, di-n-butylaluminum monochloride, di-n-hexylaluminum monochloride, ethylaluminum dichloride, diisobutylaluminum dichloride, n-butylaluminum dichloride and n-hexylaluminum dichloride. The alkylaluminum compound is more preferably a trialkylaluminum, such as triethylaluminum, triisobutylaluminum and tri-n-butylaluminum.

[0060] According to the present invention, the amount of the nucleating agent is 0.02-0.3 wt % based on the weight of the propylene / ethylene copolymer.

[0061] In the present invention, the nucleating agent can be selected from at least one of organic carboxylic acid and salt nucleating agents, sorbitol nucleating agents, aromatic phosphate nucleating agents, dehydroabietic acid and salt nucleating agents, aromatic amide nucleating agents, aromatic amine nucleating agents, rare earth compound nucleating agents, condensed ring compound nucleating agents with a quasi-planar structure, and polymer nucleating agents, preferably a sorbitol nucleating agent.

[0062] According to the present invention, the auxiliary agent may also include other conventional polymer auxiliary agents, such as antioxidants, antistatic agents, and colorants. When other auxiliary agents are included, the total amount of the auxiliary agent is preferably 0.1-0.6 wt % based on the weight of the propylene / ethylene copolymer.

[0063] According to a second aspect of the present invention, the present invention provides a method for preparing the above-mentioned polypropylene resin, wherein the materials contained in the polypropylene resin are mixed, and extruded and granulated to obtain the polypropylene resin.

[0064] According to the present invention, the mixing and extrusion granulation methods may be various methods conventionally used in the art, and the present invention is not particularly limited thereto. For example, a twin-screw extruder may be used for granulation.

[0065] According to a third aspect of the present invention, the present invention provides use of the above-mentioned polypropylene resin in an extrusion blown product.

[0066] In the present invention, the extrusion blown product can be a product used in various fields such as food and beverage bottles, cosmetic bottles, disinfectant bottles, etc.

[0067] The materials and process parameters not limited in the present invention can be selected according to the existing technology and belong to the conventional technical means in this field.

[0068] The present invention will be further described below with reference to the following examples, but is not limited to these examples.

[0069] In the following examples and comparative examples, the relevant raw materials and data were obtained by the following method:

[0070] Catalyst HR and catalyst DQ401 were purchased from Beijing Aoda Branch of Sinopec Catalyst Co., Ltd.

[0071] NX8000 nucleating agent is a nucleating agent produced by Milliken.

[0072] 1. Melt index (MFR): measured according to GB / T 3682.1-2018 at 230°C and 2.16 kg load.

[0073] 2. Melting point (T m ): The crystallization behavior and melting behavior of the sample were studied using a TA Instruments Waters DSC25 differential scanning calorimeter. In a nitrogen atmosphere, the sample was heated to 200°C at 10°C / min and held for 5 minutes to eliminate the thermal history, then cooled to 40°C at 10°C / min and heated to 160°C at 10°C / min again for measurement.

[0074] 3. Room temperature xylene solubles: Tested using the Cryst-EX instrument from Polymer Char. Trichlorobenzene solvent was used, heated to 150°C for dissolution, constant temperature for 90 minutes for sampling and testing, then cooled to 40°C, constant temperature for 70 minutes, and sampling and testing. The obtained 40°C trichlorobenzene solubles content was converted to the room temperature xylene solubles content of GB / T 24282-2009 through the standard curve.

[0075] 4. Tensile strength: Measure injection molded samples according to GB / T 1040.1-2006.

[0076] 5. Flexural modulus: Measure injection molded samples according to GB / T 9341-2008.

[0077] 6. Charpy notched impact strength: According to GB / T 1043.1-2008, the injection molded samples were measured at 23°C.

[0078] 7. Rheological polydispersity index (PI): Dynamic frequency scanning was performed using an American HAAKE MARS 60 rotational rheometer. The angular frequency scanning range was 300 rad / s to 0.1 rad / s at 190°C and the strain was 1%. The reciprocal of η', η", G', G", and their intersection modulus (the modulus at the intersection of the storage modulus and the dissipation modulus) was measured and multiplied by the coefficient corresponding to the unit.

[0079] 8. Hexane extract: Test samples according to GB / T 5009.60-2003.

[0080] 9. Haze: measured according to ASTM1003.

[0081] 10. Lamellar thickness: An appropriate amount of sample was taken from DSC and the isothermal crystallization process for SIST analysis was carried out:

[0082] (1) The sample was heated to 200°C at a rate of 10°C / min and maintained at 200°C for 5 min;

[0083] (2) Cool to 160°C at a rate of 80°C / min and maintain at 160°C for 2 h;

[0084] (3) Cool to 150°C at a rate of 80°C / min and maintain at 150°C for 2 h;

[0085] (4) Cooling to 140°C at a rate of 80°C / min and maintaining at 140°C for 2 h;

[0086] (5) Cool to 130°C at a rate of 80°C / min and maintain at 130°C for 2 h;

[0087] (6) Cool to 120°C at a rate of 80°C / min and maintain at 120°C for 2 h;

[0088] (7) Cool to 110°C at a rate of 80°C / min and maintain at 110°C for 2 h;

[0089] (8) Cool to 100 °C at a rate of 80 °C / min and maintain at 100 °C for 2 h;

[0090] (9) Cool to room temperature at a rate of 80 °C / min and hold for 10 min;

[0091] (10) The melting curve was obtained by heating to 200 °C at a rate of 10 °C / min.

[0092] All tests were performed under nitrogen atmosphere and the melting enthalpy was recorded as a function of temperature and estimated by measuring the melting enthalpy of each part that melts within the temperature interval.

[0093] The melting curve of a material crystallized in the above manner can be used to calculate the lamella thickness distribution according to the Thomson-Gibbs equation (e.g. Figure 1 ).

[0094]

[0095] Among them, T0=, ΔH0=, σ=, and L is the thickness of the layer.

[0096] Example 1

[0097] Propylene and ethylene were polymerized in the presence of a HR catalyst. The polymerization temperature was 70°C and the polymerization pressure was 4 MPa. The concentrations of ethylene, propylene and hydrogen in the feed were as shown in Table 1.

[0098] The obtained propylene / ethylene copolymer was mixed with the nucleating agent NX8000 and extruded into pellets to obtain a polypropylene resin. The amount of the nucleating agent used and the properties of the polypropylene resin are shown in Table 1.

[0099] Comparative Examples 1-4

[0100] Propylene and ethylene were polymerized in the presence of HR catalyst or DQ401 catalyst. The polymerization temperature was 70°C and the polymerization pressure was 4 MPa. The concentrations of ethylene, propylene and hydrogen in the feed were as shown in Table 1.

[0101] The obtained propylene / ethylene copolymer was mixed with the nucleating agent NX8000 and extruded into pellets to obtain a polypropylene resin. The amount of the nucleating agent used and the properties of the polypropylene resin are shown in Table 1.

[0102] Table 1

[0103]

[0104] The SIST results of various embodiments and comparative examples are shown in Table 2.

[0105] Table 2

[0106]

[0107] It can be seen from Table 1 and Table 2 that the polypropylene resin of the present invention has low n-hexane precipitate, good impact resistance and excellent optical properties, and is particularly suitable for extrusion blow molding products.

[0108] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A polypropylene resin, characterized in that The polypropylene resin contains a propylene / ethylene copolymer and an auxiliary agent containing at least a nucleating agent; the polypropylene resin has the following characteristics: exist The melt index at 230℃ and 2.16kg load is not more than 2g / 10min; Ethylene content is 1 wt% to 5 wt%; The room temperature xylene soluble content is not less than 9wt%; Hexane extract is less than 3%; The rheological polydispersity index is less than 2.8; The copolymer lamellae thickness was determined using a segmented isothermal separation technique and contained at least 28 wt% of a crystalline portion having a lamellae thickness exceeding 9.96 nm.

2. The polypropylene resin according to claim 1, wherein The copolymer lamellae thickness was determined using a segmented isothermal separation technique and contained at least 29 wt% of a crystalline portion having a lamellae thickness exceeding 9.96 nm.

3. The polypropylene resin according to claim 1 or 2, wherein The haze of the polypropylene resin is not greater than 12%, and the 23°C simply supported beam notched impact strength is not less than 23kg / m 2 .

4. The polypropylene resin according to claim 3, wherein The 23°C simply supported beam notched impact strength of the polypropylene resin is not less than 25 kg / m 2 .

5. The polypropylene resin according to claim 1, wherein The preparation method of the propylene / ethylene copolymer comprises: polymerizing propylene and ethylene in the presence of a catalyst, wherein the polymerization temperature is 0° C. to 150° C., the polymerization pressure is higher than the saturated steam pressure of propylene at the corresponding polymerization temperature, and hydrogen is used as a molecular weight regulator.

6. The polypropylene resin according to claim 5, wherein The polymerization temperature is 40°C to 90°C, and the polymerization pressure is 3-4MPa.

7. The polypropylene resin according to claim 1, wherein The amount of the nucleating agent used is 0.02-0.3 wt % based on the weight of the propylene / ethylene copolymer.

8. The polypropylene resin according to claim 1 or 7, wherein The nucleating agent is selected from at least one of organic carboxylic acid and salt nucleating agents, sorbitol nucleating agents, aromatic phosphate nucleating agents, dehydroabietic acid and salt nucleating agents, aromatic amide nucleating agents, aromatic amine nucleating agents, rare earth compound nucleating agents, condensed ring compound nucleating agents with a quasi-planar structure, and polymer nucleating agents, and is preferably a sorbitol nucleating agent.

9. The method for preparing a polypropylene resin according to any one of claims 1 to 8, characterized in that: The preparation method comprises mixing materials contained in the polypropylene resin, and extruding and granulating the materials to obtain the polypropylene resin.

10. Use of the polypropylene resin according to any one of claims 1 to 8 in extrusion blow products.

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