Polypropylene resin, polypropylene resin composition, and respective production methods thereof

Abstract

The present application relates to the field of polyolefins, in particular, to a polypropylene resin, a polypropylene resin composition and respective preparation methods thereof. The polypropylene resin comprises: (a) component A: 60-80 wt%, a high crystalline homopolymer polypropylene, the isotactic pentad fraction of which is greater than or equal to 96%; (b) component B: 20-40 wt%, an ethylene-propylene elastomeric copolymer, the ethylene-propylene elastomeric copolymer containing 50-70 wt% ethylene structural units and 30-50 wt% propylene structural units, based on the total weight of the ethylene-propylene elastomeric copolymer; the molar fraction of ethylene / ethylene / ethylene sequences EEE in the polypropylene resin is not less than 15%; the ratio of the melt mass flow rate of the component A and the polypropylene resin under the action of a 2.16 kg load at 230℃ is 1.5-3.5:1. The final polypropylene resin composition has the characteristics of low shrinkage, high modulus, high heat distortion temperature and low linear expansion coefficient.

Description

Technical Field

[0001] This invention relates to the field of polyolefins, and more specifically, to a polypropylene resin, a polypropylene resin composition, and methods for preparing the respective. Background Technology

[0002] In recent years, with the continuous efforts in energy conservation and emission reduction, automotive lightweighting, as an effective means to reduce fuel consumption in passenger vehicles, has received significant attention from automakers. Polypropylene possesses excellent properties such as light weight, low price, ease of processing, and excellent electrical insulation, and its application in automotive interior and exterior parts such as dashboards and bumpers is becoming increasingly widespread, making it an important resin material in the field of automotive polymers. However, companies generally report that polypropylene suffers from problems such as high molding shrinkage, leading to warping and deformation of products, which affects product performance and aesthetics. Low-shrinkage polypropylene is a key development direction for functionalized polypropylene. Patent CN104204069B discloses a high-flowability polyolefin composition with low shrinkage and low linear thermal expansion coefficient. Although this composition has a low shrinkage rate, its intrinsic viscosity of xylene-soluble matter is less than 1.5 dL / g, indicating that its low-temperature impact performance will be poor, and the powder flowability will also deteriorate significantly during polymerization, making material feeding difficult. CN101309961B discloses a polypropylene resin with low shrinkage, high impact strength, stiffness, and scratch resistance. This polypropylene resin is prepared by blending polypropylene, ethylene-propylene copolymer, and ethylene polymer. However, the blending preparation process is relatively complex and not suitable for industrial application. CN110628131B discloses a polypropylene composite material with low shrinkage and low linear expansion coefficient, prepared by blending polypropylene base resin, toughening agent, and talc, wherein the amount of talc added is 20-40 parts by weight. Although the high amount of talc and toughening agent significantly reduces the shrinkage of the composition, it brings problems in terms of lightweighting and recyclability. Summary of the Invention

[0003] The purpose of this invention is to overcome the aforementioned problems in the prior art and to provide a polypropylene resin, a polypropylene resin composition, and a method for preparing the respective. The polypropylene resin of this invention contains homopolymer polypropylene and ethylene-propylene elastic copolymer with specific components, and the molar fraction of ethylene / ethylene / ethylene sequence EEE in the polypropylene resin is controlled to be not less than 15%. The ratio of the melt mass flow rate of the homopolymer polypropylene to that of the polypropylene resin is controlled. In particular, the addition of polypropylene resin and inorganic sheet filler can change the crystallization of the matrix, which is beneficial to the final polypropylene resin composition having the characteristics of low shrinkage, high modulus, high heat distortion temperature, and low linear expansion coefficient.

[0004] To achieve the above objectives, a first aspect of the present invention provides a polypropylene resin, the polypropylene resin comprising: (a) Component A: Highly crystalline homopolymer polypropylene, with an isotactic five-unit component fraction greater than or equal to 96%; (b) Component B: Ethylene-propylene elastic copolymer, based on the total weight of the ethylene-propylene elastic copolymer, which contains 50-70% by weight of ethylene structural units and 30-50% by weight of propylene structural units; Wherein, based on the total weight of the polypropylene resin, the content of component A is 60-80% by weight, and the content of component B is 20-40% by weight; The molar fraction of the ethylene / ethylene / ethylene sequence EEE in the polypropylene resin is not less than 15%. The ratio of the melt flow rate of component A and the polypropylene resin under a load of 2.16 kg at 230 °C is 1.5-3.5:1.

[0005] A second aspect of the present invention provides a method for preparing the polypropylene resin described in the first aspect, the method comprising: (1) Under the first olefin polymerization conditions, propylene monomer was contacted with a Ziegler-Natta catalyst with high stereoselectivity, and unreacted monomer was removed from the mixture obtained after the contact reaction to obtain component A; (2) Under olefin gas-phase polymerization conditions, ethylene monomer, propylene monomer and component A obtained in step (1) are contacted and reacted, and unreacted monomers are removed from the mixture obtained after the contact reaction to obtain the polypropylene resin; In step (2), the molar ratio of ethylene to (ethylene + propylene) is 0.3-0.6:1; the molar ratio of hydrogen to ethylene is 0.35-0.6:1.

[0006] Preferably, the method does not include cooling and / or drying operations between steps (1) and (2).

[0007] A third aspect of the present invention provides a polypropylene resin obtained by the preparation method described in the second aspect above.

[0008] A fourth aspect of the present invention provides a polypropylene resin composition comprising: the polypropylene resin described in the first or third aspect above, inorganic fillers, and additives.

[0009] The fifth aspect of the present invention provides a method for preparing the polypropylene resin composition described in the fourth aspect above, the method comprising: mixing, melting and extruding the polypropylene resin, inorganic filler, antioxidant and halogen absorbent described in the first or third aspect above, granulating.

[0010] A sixth aspect of the present invention provides a polypropylene resin composition prepared by the method described in the fifth aspect above.

[0011] Through the above technical solutions, the polypropylene resin, polypropylene resin composition, and their respective preparation methods provided by the present invention achieve the following beneficial effects: The polypropylene resin of this invention contains homopolymer polypropylene with a high fraction of isotactic five-unit components and ethylene-propylene elastic copolymer with a high content of ethylene structural units. The molar fraction of ethylene / ethylene / ethylene sequence EEE in the polypropylene resin is controlled to be not less than 15%, and the ratio of melt mass flow rate of homopolymer polypropylene to that of the polypropylene resin is controlled. In particular, the addition of polypropylene resin and inorganic sheet filler changes the crystallinity of the matrix, which is beneficial to the final polypropylene resin composition having the characteristics of low shrinkage, high modulus, high heat distortion temperature and low linear expansion coefficient. Detailed Implementation

[0012] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0013] A first aspect of the present invention provides a polypropylene resin, the polypropylene resin comprising: (a) Component A: Highly crystalline homopolymer polypropylene, with an isotactic five-unit component fraction greater than or equal to 96%; (b) Component B: Ethylene-propylene elastic copolymer, based on the total weight of the ethylene-propylene elastic copolymer, which contains 50-70% by weight of ethylene structural units and 30-50% by weight of propylene structural units; Wherein, based on the total weight of the polypropylene resin, the content of component A is 60-80% by weight, and the content of component B is 20-40% by weight; The molar fraction of the ethylene / ethylene / ethylene sequence EEE in the polypropylene resin is not less than 15%. The ratio of the melt flow rate of component A and the polypropylene resin under a load of 2.16 kg at 230 °C is 1.5-3.5:1.

[0014] In this invention, a polypropylene resin is prepared from homopolymer polypropylene containing the above-mentioned specific component content with a high fraction of isotactic five-unit components and an ethylene-propylene elastic copolymer with a high ethylene structural unit content. The ratio of the melt mass flow rate of the homopolymer polypropylene and the polypropylene resin under a load of 2.16 kg at 230 °C is controlled within a specific range, and the molar fraction of the ethylene / ethylene / ethylene sequence EEE in the polypropylene resin is controlled to be not less than 15%. Due to the addition of the ethylene-propylene elastic copolymer, the arrangement of some lamellar crystals in the matrix homopolymer polypropylene is changed, thereby reducing the shrinkage rate of the polypropylene resin composition prepared from the polypropylene resin in both the horizontal and vertical directions. This results in a final product with low shrinkage, high modulus, high heat distortion temperature, and low linear expansion coefficient.

[0015] In this invention, the ethylene / ethylene / ethylene EEE sequence in the polypropylene resin is determined by nuclear magnetic resonance spectroscopy, indicating that three ethylene structural units are arranged continuously in the molecular chain. In copolymer polypropylene, when ethylene monomer is used as the copolymer unit, the sequence structure on the molecular chain is divided into three-unit groups: PPE sequence, EPE sequence, EEP sequence, PEP sequence, and EEE sequence, representing the arrangement of structural units on the molecular chain as propylene / propylene / ethylene, ethylene / propylene / ethylene, ethylene / ethylene / propylene, propylene / ethylene / propylene, and ethylene / ethylene / ethylene, respectively. The sequence structure can be calculated by assigning peaks (carbon atoms at different positions) at different chemical shifts in the nuclear magnetic resonance spectrum.

[0016] In this invention, when the contents of the homopolymer polypropylene and the ethylene-propylene elastic copolymer, the molar fraction of the ethylene / ethylene / ethylene sequence EEE in the polypropylene resin, and the ratio of the melt mass flow rate of the homopolymer polypropylene and the polypropylene resin under a load of 2.16 kg at 230 °C meet the above ranges, the final polypropylene resin composition can have high modulus, high heat distortion temperature, low shrinkage, and low linear expansion coefficient.

[0017] More preferably, the isotactic five-unit component fraction of the homopolymer polypropylene is greater than or equal to 97%; In this invention, the fraction of isotactic five-unit components is equivalent to isotacticity, the meaning of which is well known to those skilled in the art. The fraction of isotactic five-unit components is determined according to the method specified in GB / T2412-2008, which will not be repeated below.

[0018] More preferably, based on the total weight of the ethylene-propylene elastic copolymer, the ethylene-propylene elastic copolymer contains 50-65% by weight of ethylene structural units and 35-50% by weight of propylene structural units.

[0019] More preferably, based on the total weight of the polypropylene resin, the content of the homopolymer polypropylene is 65-80% by weight, and the content of the ethylene-propylene elastic copolymer is 20-35% by weight.

[0020] In this invention, the content of homopolymer polypropylene and ethylene-propylene elastic copolymer is determined by Fourier transform infrared spectroscopy.

[0021] More preferably, the molar fraction of the ethylene / ethylene / ethylene sequence EEE in the polypropylene resin is 15-25%.

[0022] In this invention, the ethylene / ethylene / ethylene sequence EEE in the polypropylene resin was determined by statistical tri-unit analysis based on 13C-NMR data, and the specific analytical method refers to SH / T 1800-2016.

[0023] More preferably, the ratio of the melt mass flow rate of component A and the polypropylene resin under a load of 2.16 kg at 230 °C is 2.2-3.2:1.

[0024] Preferably, the melt flow rate of the polypropylene resin under a load of 2.16 kg at 230 °C is 10-50 g / 10 min, more preferably 15-45 g / 10 min, and even more preferably 15-35 g / 10 min.

[0025] In this invention, the melt mass flow rate of the homopolymer polypropylene and polypropylene resin under a load of 2.16 kg at 230 °C was determined according to GB / T 3682.1-2018, and will not be repeated below.

[0026] According to the present invention, preferably, the melt mass flow rate of the homopolymer polypropylene under a load of 2.16 kg at 230 °C is 20-200 g / 10 min.

[0027] In this invention, when the melt flow rate of the homopolymer polypropylene at 230°C and under a load of 2.16 kg meets the above-mentioned range, the final polypropylene resin composition can have high modulus, high heat distortion temperature, low shrinkage and low linear expansion coefficient.

[0028] More preferably, the melt flow rate of the homopolymer polypropylene under a load of 2.16 kg at 230 °C is 30-100 g / 10 min.

[0029] According to the present invention, preferably, based on the total weight of the polypropylene resin, the content of ethylene structural units is 15-30% by weight, for example, it can be any two of the following values: 15% by weight, 16% by weight, 17% by weight, 18% by weight, 19% by weight, 20% by weight, 21% by weight, 22% by weight, 23% by weight, 24% by weight, 25% by weight, 26% by weight, 27% by weight, 28% by weight, 29% by weight, 30% by weight, or values ​​within the range of such values, and more preferably 15-25% by weight.

[0030] In this invention, the content of ethylene structural units in the ethylene-propylene elastic copolymer and polypropylene resin was determined using a Fourier transform infrared spectrometer, which will not be elaborated further below.

[0031] According to the present invention, preferably, the polypropylene resin further contains xylene solubles, the content of which is 10-30% by weight, for example, it can be any two of the following values: 10% by weight, 11% by weight, 12% by weight, 13% by weight, 14% by weight, 15% by weight, 16% by weight, 17% by weight, 18% by weight, 19% by weight, 20% by weight, 21% by weight, 22% by weight, 23% by weight, 24% by weight, 25% by weight, 26% by weight, 27% by weight, 28% by weight, 29% by weight, 30% by weight, or values ​​within the range of these values.

[0032] In this invention, when the content of xylene-soluble substances in the polypropylene resin meets the above-mentioned range, the final polypropylene resin composition has good impact resistance, and is more preferably 15-25% by weight.

[0033] In this invention, the content of xylene-soluble substances in the polypropylene resin is determined according to GB / T 24282-2009.

[0034] According to the present invention, preferably, the content of ethylene structural units in the xylene soluble content is 40-55% by weight, based on the total weight of the xylene soluble content in the polypropylene resin.

[0035] In this invention, when the content of ethylene structural units in the xylene soluble content meets the above-mentioned range, the final polypropylene resin composition has good impact resistance, and is more preferably 45-55% by weight.

[0036] In this invention, the content of ethylene structural units in the xylene soluble content is determined using a PolymerCharts Cryst-EX instrument.

[0037] A second aspect of the present invention provides a method for preparing the polypropylene resin described in the first aspect, the method comprising: (1) Under the first olefin polymerization conditions, propylene monomer was contacted with a Ziegler-Natta catalyst with high stereoselectivity, and unreacted monomer was removed from the mixture obtained after the contact reaction to obtain component A; (2) Under olefin gas-phase polymerization conditions, ethylene monomer, propylene monomer and component A obtained in step (1) are contacted and reacted, and unreacted monomers are removed from the mixture obtained after the contact reaction to obtain the polypropylene resin; In step (2), the molar ratio of ethylene to (ethylene + propylene) is 0.3-0.6:1; the molar ratio of hydrogen to ethylene is 0.35-0.6:1.

[0038] In this invention, by controlling the molar ratio of ethylene / (ethylene + propylene) and hydrogen to ethylene in step (2) to meet the above range, the molar fraction of ethylene / ethylene / ethylene sequence EEE in the obtained polypropylene resin can meet the requirements of this invention, so that the final obtained polypropylene resin composition has high modulus, high heat distortion temperature, low shrinkage and low linear expansion coefficient.

[0039] In this invention, in step (1), hydrogen is used as a chain transfer agent in the homopolymerization reaction, which has the function of adjusting the molecular weight and controlling the melt index of the product. By controlling the ratio of the first hydrogen and the first propylene, the product containing homopolymer polypropylene prepared in step (1) can have a specific melt index, and affect the intrinsic viscosity of the final polypropylene resin and the intrinsic viscosity of xylene solubles. Preferably, the molar ratio of hydrogen to propylene is 0.001-0.01:1, preferably 0.002-0.008:1.

[0040] In this invention, the intrinsic viscosity of the polypropylene resin and the intrinsic viscosity of the xylene-soluble substance were measured using a PolymerChar Cryst-EX instrument.

[0041] In this invention, in step (2), the content of ethylene structural units in the ethylene-propylene rubber phase and the content of ethylene structural units in the ethylene-propylene rubber phase can be adjusted by adjusting the molar ratio of ethylene / (ethylene+propylene), thereby controlling the content of the ethylene / ethylene / ethylene sequence in the final polypropylene resin. When the molar ratio of ethylene / (ethylene+propylene) is too low, it will lead to a decrease in the content of the rubber phase in the polypropylene resin system and the content of ethylene structural units in the rubber phase, affecting the light transmittance, flexural modulus and impact resistance of the final polypropylene resin. The molar ratio of ethylene / (ethylene+propylene) must be controlled within a specific range. Preferably, the molar ratio of ethylene / (ethylene+propylene) is 0.30-0.6:1.

[0042] In this invention, in step (2), hydrogen is used as a chain transfer agent in the copolymerization reaction, which has the function of adjusting molecular weight and controlling the melt index of the product. By controlling the ratio of hydrogen to ethylene, the molecular weight of the rubber phase and the intrinsic viscosity of the rubber phase can be further controlled. Preferably, the molar ratio of hydrogen to ethylene is 0.1-0.5:1.

[0043] According to the present invention, preferably, the highly stereoselective Ziegler-Natta catalyst comprises: (i) a main catalyst comprising a product obtained by reacting a magnesium source, a titanium source and an internal electron donor; (ii) a co-catalyst; and (iii) an optional external electron donor.

[0044] In this invention, the main catalyst has active sites and can be any existing main catalyst in the art for preparing polypropylene resin. The contents of magnesium, titanium, and the internal electron donor are not particularly limited and can be any values ​​found in conventional catalyst components. Specific examples of such main catalysts that can be used are found in patent documents CN85100997, CN98126383.6, CN98111780.5, CN98126385.2, CN93102795.0, CN00109216.2, CN99125566.6, CN99125567.4, and CN02100900.7. The entire contents of these patent documents are incorporated herein by reference. In this invention, the range of types of co-catalysts is relatively wide, preferably organoaluminum compounds, and more preferably alkylaluminum compounds, including but not limited to: at least one of triethylaluminum, tri-n-butylaluminum, triisobutylaluminum, tri-n-hexylaluminum, diethylaluminum chloride, di-n-butylaluminum chloride, diisobutylaluminum chloride, di-n-hexylaluminum chloride, diethylaluminum chloride, di-n-butylaluminum chloride, diisobutylaluminum chloride, and di-n-hexylaluminum chloride, more preferably trialkylaluminum, such as at least one of triethylaluminum, tri-n-butylaluminum, and triisobutylaluminum.

[0045] In this invention, the external electron donor is an organosilicon compound. Its general formula is R0. n Si(OR') 4-nIn the formula, 0 < n ≤ 3, R is preferably selected from hydrogen atoms, halogens, alkyl, cycloalkyl, aryl, haloalkyl, and R' is preferably selected from alkyl, cycloalkyl, aryl, haloalkyl. The external electron donor is preferably selected from at least one of tetramethoxysilane, tetraethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, trimethylphenoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methyl tert-butyldimethoxysilane, methyl isopropyldimethoxysilane, diphenoxydimethoxysilane, diphenyldiethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, and vinyltrimethoxysilane, as well as at least one of cyclohexylmethyldimethoxysilane, dicyclopentyldimethoxysilane, diisopropyldimethoxysilane, diisobutyldimethoxysilane, 2-ethylpiperidinyl-2-tert-butyldimethoxysilane, (1,1,1-trifluoro-2-propyl)-2-ethylpiperidinyldimethoxysilane, and (1,1,1-trifluoro-2-propyl)-methyldimethoxysilane.

[0046] The inventors of this invention have discovered that using tetraethoxysilane and dicyclopentyldimethoxysilane as external electron donors in a compound formulation can effectively improve the hydrogen sensitivity and stereoregulation of the catalyst, resulting in a polypropylene resin with high modulus. Most preferably, when tetraethoxysilane and dicyclopentyldimethoxysilane are used as external electron donors in a compound formulation, controlling the weight ratio of tetraethoxysilane to dicyclopentyldimethoxysilane to be 2-8:1 can further effectively improve the hydrogen sensitivity and stereoregulation of the catalyst, resulting in a polypropylene resin with high modulus.

[0047] In this invention, the product characteristics of the product containing homopolymer polypropylene in step (1) can be controlled by controlling the molar ratio of the main catalyst to the co-catalyst and the weight ratio of the co-catalyst to the external electron donor. Under preferred conditions, the molar ratio of the main catalyst to the co-catalyst is 1:10-200, preferably 1:25-100, the main catalyst is calculated as titanium, and the co-catalyst is calculated as aluminum; the weight ratio of the co-catalyst to the external electron donor is 2-150:1, preferably 3-50:1.

[0048] In this invention, there are no particular limitations on the mixing method of the components in the highly stereoselective Ziegler-Natta catalyst. During the preparation of the catalyst, the co-catalyst, the external electron donor, and the main catalyst can be mixed together and then added to the reaction, or the co-catalyst and the external electron donor can be pre-mixed and then mixed with the main catalyst before being added to the reaction.

[0049] In this invention, there are no particular limitations on the method of adding the highly stereoselective Ziegler-Natta catalyst. It can be added directly to the first olefin polymerization reactor, or it can be added to the first olefin polymerization reactor after pre-complexation and / or pre-polymerization. The terms "pre-complexation" and "pre-polymerization" as used refer to polymerization reactions carried out to achieve lower reaction rates and monomer conversion rates compared to those under normal polymerization conditions.

[0050] In this invention, the pre-complexation process can be carried out in a pre-complexation or pre-polymerization reactor with or without polymerizable monomers. When performing the pre-complexation reaction, the reactor can be a continuous stirred tank reactor, or other forms that achieve sufficient mixing, such as a loop reactor, a section of pipeline containing a static mixer, or even a section of pipeline where the material is in a turbulent state. There are no particular limitations on the pre-complexation conditions; preferably, the pre-complexation temperature is -10 to 60°C, more preferably 0 to 30°C; the pre-complexation time is 0.1 to 180 min, more preferably 5 to 30 min.

[0051] In this invention, step (1) further includes prepolymerizing the highly stereoselective Ziegler-Natta catalyst.

[0052] In this invention, the highly stereoselective Ziegler-Natta catalyst can be used directly or after pre-complexation for prepolymerization. There are no particular limitations on the reactor used for the prepolymerization reaction; it can be any reactor commonly used in the art, such as a continuous stirred tank reactor or a loop reactor. The prepolymerization reaction can be carried out continuously in bulk liquid conditions or intermittently in an inert solvent.

[0053] In this invention, there are no particular limitations on the prepolymerization conditions. Preferably, the prepolymerization temperature is -10 to 60°C, more preferably 0 to 40°C; the time is 0.01 to 2 hours, more preferably 0.1 to 0.5 hours; and the prepolymerization ratio is 0.5 to 1000 times, more preferably 1 to 500 times. "Prepolymerization ratio" refers to the ratio of the mass of polymer produced in the prepolymerization reactor to the mass of the catalyst.

[0054] In this invention, the first olefin polymerization reaction can be carried out continuously or intermittently. Continuous polymerization can use two or more reactors in series. There are no particular limitations on the reactor for the first olefin polymerization reaction; it can be a liquid-phase reactor or a gas-phase reactor. The liquid-phase reactor can be a loop reactor or a stirred tank reactor, and the gas-phase reactor can be at least one of a horizontal stirred bed reactor, a vertical stirred bed reactor, a fluidized bed reactor, or a multi-zone circulating reactor.

[0055] According to the present invention, preferably, the first olefin polymerization reaction can be liquid-phase or gas-phase polymerization, and there are no particular limitations on the conditions of the first olefin polymerization reaction. When the first olefin polymerization is a liquid-phase polymerization, preferably, the polymerization temperature is 0-150℃, which can be any two of the following ranges: 0℃, 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 120℃, 140℃, 150℃, or a value within that range, preferably 40-100℃. There is no particular limitation on the polymerization pressure of the first olefin, as long as the polymerization pressure is higher than the saturated vapor pressure of propylene at the corresponding polymerization temperature, preferably 2-10 MPaG. The residence time is 0.5-5 h, preferably 1.4-1.6 h. When the first olefin polymerization is a gas-phase polymerization, preferably, the polymerization temperature is 0-150℃, preferably 40-100℃. The polymerization pressure of the first olefin is greater than or equal to atmospheric pressure, preferably 0.5-2.5 MPaG. The residence time is 0.5-5 h, preferably 1.4-1.6 h.

[0056] In this invention, preferably, the conditions for the gas-phase polymerization of olefins include: a temperature of 40-100℃, which can be any two values ​​of 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃ or higher, preferably 60-80℃; a pressure of 0.6-1.4 MPaG, which can be any two values ​​of 0.6MPaG, 0.7MPaG, 0.75MPaG, 0.8MPaG, 0.9MPaG, 1MPaG, 1.1MPaG, 1.15MPaG, 1.2MPaG, 1.25MPaG, 1.3MPaG, 1.4MPaG or higher, preferably 1-1.3MPaG; and a residence time of 0.1-2 h, preferably 0.4-0.6 h.

[0057] In this invention, after the first olefin polymerization reaction is completed, the olefin gas phase polymerization reaction is carried out directly. Preferably, the cooling and / or drying operation is not included between step (1) and step (2) in the method.

[0058] In this invention, step (2) further includes deactivating the product after reaction. Under preferred conditions, the deactivation treatment includes: degassing the product after reaction, introducing wet nitrogen gas formed by mixing nitrogen and steam to remove residual hydrocarbons in the product after reaction, and deactivating the residual catalyst to finally obtain polypropylene resin.

[0059] A third aspect of the present invention provides a polypropylene resin obtained by the preparation method described in the second aspect above.

[0060] A fourth aspect of the present invention provides a polypropylene resin composition comprising: the polypropylene resin described in the first or fourth aspect above, inorganic fillers, and additives.

[0061] According to the present invention, preferably, based on 100 parts by weight of polypropylene resin, the content of the inorganic filler is 0.5-2% by weight, preferably 0.5-1.5% by weight; and the content of the additive is 0.05-0.5% by weight, preferably 0.1-0.4% by weight.

[0062] According to the present invention, preferably, the inorganic filler is at least one selected from talc, nano-calcium carbonate, nano-montmorillonite, and glass fiber, more preferably talc. Using the aforementioned preferred inorganic filler is more beneficial in reducing the shrinkage rate of the final polypropylene resin composition. Preferably, the talc has a particle size D50 of 1-15 μm and an aspect ratio of 5-40:1. The inventors of the present invention have discovered that during injection molding, talc with a lamellar structure aligns in an oriented manner along the flow direction under shear stress. Furthermore, polypropylene resin segments undergo oriented epigenetic crystallization on the surface of the talc. Since the growth direction of the polypropylene resin crystals is perpendicular to the talc surface, the number of crystals oriented in the flow direction is reduced, thus significantly reducing the shrinkage rate of the product along the flow direction.

[0063] According to the present invention, preferably, the adjuvant is an antioxidant and / or a halogen absorbent.

[0064] In this invention, the antioxidant can be a conventional choice in the art. Preferably, the antioxidant can be a hindered phenolic antioxidant or a phosphite antioxidant, or an antioxidant composed of a hindered phenolic antioxidant and a phosphite antioxidant in any proportion. The phosphite antioxidant can be, for example, tris[2,4-di-tert-butylphenyl] phosphite, and the hindered phenolic antioxidant can be, for example, pentaerythritol tetrakis[b-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0065] In this invention, there is no particular limitation on the type of halogen absorbent. Any halogen absorbent that can be used to eliminate halogens and residual catalysts in resin can be applied to this invention. Preferably, the halogen absorbent can be calcium stearate and / or hydrated talc.

[0066] In this invention, the polypropylene resin composition may also contain other conventional additives, such as α-crystal nucleating agents, antistatic agents, weather-resistant agents, colorants, etc., which can be added according to actual conditions.

[0067] The fifth aspect of the present invention provides a method for preparing a polypropylene resin composition, the method comprising: mixing, melting and extruding the polypropylene resin, inorganic filler and additives described in the first or third aspect above, and granulating them.

[0068] In this invention, the polypropylene resin, inorganic filler, and additives are defined as described above and will not be repeated here.

[0069] In this invention, there are no particular limitations on the specific method and conditions of mixing, as long as the components, including polypropylene resin, inorganic fillers, and additives, are thoroughly and uniformly mixed. For example, the mixing can be carried out in a high-speed mixer. The mixing process can be continuous or intermittent.

[0070] In this invention, the melt extrusion granulation can be carried out on conventional equipment in the art. Preferably, the preparation method includes: mixing polypropylene resin, inorganic filler, and additives, then performing melt extrusion on a twin-screw extruder, and then granulating the mixture through a pelletizer to obtain the polypropylene resin composition.

[0071] In this invention, the mixed material is placed in a twin-screw extruder for melt extrusion, which can be carried out under conventional operating conditions in the art. Preferably, the processing temperature is 190-230°C.

[0072] A sixth aspect of the present invention provides a polypropylene resin composition prepared by the method described in the fifth aspect above.

[0073] In this invention, there is no particular limitation on the form of the polypropylene resin composition during use, and it can be adapted to the actual application scenario. Preferably, before application, the polypropylene resin composition is further subjected to molding or blow molding, and the molding method includes, but is not limited to, extrusion molding and injection molding.

[0074] According to the present invention, preferably, the horizontal shrinkage rate of the polypropylene resin composition is less than or equal to 0.8%, more preferably less than or equal to 0.7%; and the vertical shrinkage rate is less than or equal to 0.85%, more preferably less than or equal to 0.8%.

[0075] In this invention, polymer resin product samples are obtained by screw granulation and injection molding, and the shrinkage rate of the injection molded samples is determined according to GB / T17037.4-2003.

[0076] According to the present invention, preferably, the linear expansion coefficient of the polypropylene resin composition is less than or equal to 7.5 × 10⁻⁶. -5 ℃ -1 Preferably less than or equal to 6.5 × 10 -5 ℃ -1 .

[0077] In this invention, polymer resin product samples are obtained by screw granulation and injection molding, and the linear expansion coefficient of the injection molded samples is determined according to GB / T1036-2008.

[0078] According to the present invention, preferably, the flexural modulus of the polypropylene resin composition is greater than or equal to 1100 MPa, and more preferably greater than or equal to 1200 MPa.

[0079] In this invention, polymer resin product samples are obtained by screw granulation and injection molding, and the flexural modulus of the injection molded samples is determined according to GB / T9341-2008.

[0080] According to the present invention, preferably, the tensile strength of the polypropylene resin composition is 20-40 MPa, more preferably 25-35 MPa.

[0081] In this invention, polymer resin product samples are obtained by screw granulation and injection molding, and the tensile strength of the injection molded samples is determined according to GB / T9341-2008.

[0082] According to the present invention, preferably, the heat distortion temperature of the polypropylene resin composition is greater than or equal to 80°C, and more preferably, the heat distortion temperature is greater than or equal to 85°C.

[0083] In this invention, polymer resin product samples are obtained by screw granulation and injection molding, and the heat distortion temperature of the injection molded samples is determined in accordance with GB / T1634.2-2019.

[0084] The present invention will be described in detail below through embodiments.

[0085] The test methods for each parameter involved in the following embodiments and comparative examples are as follows: (1) Melt mass flow rate (MFR, g / 10 min): Tested according to GB / T 3682.1-2018, with test conditions including 230℃ and 2.16kg load.

[0086] (2) Shrinkage (%): The prepared composite resin was granulated by screw and injection molded to obtain a sample. The injection molded sample was measured in accordance with GB / T17037.4-2003.

[0087] (3) Linear expansion coefficient: The prepared composite resin was granulated by screw and injection molded to obtain a sample. The injection molded sample was measured according to GB / T1036-2008.

[0088] (4) Flexural modulus (MPa): The prepared composite resin was granulated by screw and injection molded to obtain a sample. The injection molded sample was measured in accordance with GB / T9341-2008.

[0089] (5) Heat distortion temperature (°C): The prepared composite resin is granulated by screw and injection molded to obtain a sample. The injection molded sample is measured in accordance with GB / T1634.2-2019.

[0090] (6) Tensile strength (MPa): The prepared composite resin was granulated by screw and injection molded to obtain a sample. The injection molded sample was measured in accordance with GB / T1040.1-2018.

[0091] (7) Notched impact strength of simply supported beam (kJ / m) 2 The prepared composite resin was granulated by screw extruder and injection molded to obtain sample strips, which were then tested at 23℃ according to GB / T 1043.1-2008.

[0092] (8) The xylene-soluble content (XS) was tested using a PolymerCharts Cryst-EX instrument. Trichlorobenzene solvent was used, and the mixture was heated to 150°C for dissolution. After holding the temperature for 90 minutes, a sample of the prepared polypropylene composition was taken for testing. The temperature was then lowered to 40°C and held for 70 minutes before testing. The obtained trichlorobenzene-soluble content at 40°C was converted to the room temperature xylene-soluble content according to GB / T 24282-2009 using a standard curve.

[0093] (9) The hydrogen concentration in the reactor was determined by online chromatography, in mol%.

[0094] (10) The intrinsic viscosity of xylene-soluble substances in polypropylene resin was determined by the Cryst-EX instrument of PolymerChar.

[0095] (11) The intrinsic viscosity of polypropylene resin was determined by a Cryst-EX instrument from PolymerChar.

[0096] In the following examples and comparative examples, The propylene polymerization reaction was carried out in a polypropylene pilot plant.

[0097] The main catalyst is DQ-401 catalyst, purchased from Sinopec Catalyst Company Beijing Aoda Branch.

[0098] Unless otherwise specified, the reagents used in the examples and comparative examples of this invention are all commercially available.

[0099] Example 1 The first polymerization catalyst prepolymerization consisted of main catalyst DQ401, cocatalyst (triethylaluminum), and external electron donor (a mixture of tetraethoxysilane (TEOS) and dicyclopentyldimethoxysilane (DCPMS), wherein TEOS and DCPMS were present in 85 parts by weight and 15 parts by weight, respectively). After a pre-contact reaction at 10°C for 20 min, the mixture was continuously added to the prepolymerization reactor. The flow rate of triethylaluminum (TEAL) was 6 g / hr, the flow rate of the external electron donor was 1.2 g / hr, and the flow rate of the main catalyst was 0.36 g / hr. Prepolymerization was carried out in a propylene liquid phase environment at 15°C for approximately 25 min. The prepolymerization factor was measured to be 100 times.

[0100] The prepolymerized catalyst is continuously fed into a loop reactor, where the homopolymerization of propylene is completed. After the reaction, unreacted propylene is removed by flash evaporation. The loop polymerization reaction temperature is 70°C, the reaction pressure is 4 MPaG, and the molar ratio of hydrogen to propylene in the reactor is 0.0034.

[0101] After the reaction in the loop reactor, the homopolymerized material is injected into a fluidized bed gas-phase reactor for copolymerization of ethylene and propylene. The gas-phase reaction temperature is 70℃, the reaction pressure is 1.1 MPaG, the molar ratio of ethylene to (propylene + ethylene) is 0.45, and the molar ratio of hydrogen to ethylene in the circulating gas of the gas-phase reactor, as detected by online chromatography, is 0.35. The product obtained from the reaction is degassed and deactivated by wet nitrogen to obtain polypropylene resin. Specific parameters are shown in Table 1.

[0102] Example 2 The method of Example 1 is the same, except that the molar ratio of hydrogen to propylene in the loop reactor is 0.0045; the molar ratio of ethylene to (propylene + ethylene) in the gas phase reactor is 0.55, and the molar ratio of hydrogen to ethylene is 0.38. The specific parameters are shown in Table 1.

[0103] Example 3 The method is the same as in Example 1, except that the molar ratio of hydrogen to propylene in the loop reactor is 0.0042; the molar ratio of ethylene to (propylene + ethylene) in the gas phase reactor is 0.52, and the molar ratio of hydrogen to ethylene is 0.36. The specific parameters are shown in Table 1.

[0104] Example 4 The method is the same as in Example 1, except that the molar ratio of hydrogen to propylene in the loop reactor is 0.0028; the molar ratio of ethylene to (propylene + ethylene) in the gas phase reactor is 0.45, and the molar ratio of hydrogen to ethylene is 0.48. The specific parameters are shown in Table 1.

[0105] Example 5 The method of Example 1 is the same, except that the external electron donor is only dicyclopentyldimethoxysilane (DCPMS), and the specific parameters are shown in Table 1.

[0106] Comparative Example 1 The method is the same as in Example 1, except that the molar ratio of hydrogen to propylene in the loop reactor is 0.0041; the molar ratio of ethylene to (propylene + ethylene) in the gas phase reactor is 0.46, and the molar ratio of hydrogen to ethylene is 0.22. The specific parameters are shown in Table 1.

[0107] Comparative Example 2 The method is the same as in Example 1, except that the molar ratio of hydrogen to propylene in the loop reactor is 0.0067; the molar ratio of ethylene to (propylene + ethylene) in the gas phase reactor is 0.46, and the molar ratio of hydrogen to ethylene is 0.12. The specific parameters are shown in Table 1.

[0108] Comparative Example 3 The method is the same as in Example 1, except that the molar ratio of hydrogen to propylene in the loop reactor is 0.0058; the molar ratio of ethylene to (propylene + ethylene) in the gas phase reactor is 0.25, and the molar ratio of hydrogen to ethylene is 0.42. The specific parameters are shown in Table 1.

[0109] Table 1

[0110] The polypropylene resins obtained in the above examples and comparative examples are mixed with inorganic fillers, antioxidants, and halogen absorbers, melted, and extruded and granulated to obtain polypropylene resin compositions.

[0111] Application Example 1 100 parts by weight of the polypropylene resin prepared in Example 1, 0.2 parts by weight of antioxidant B225 (168:1010=1:1 (g / g)), 0.05% by weight of calcium stearate, and 0.8 parts by weight of talc (D50 of 10 μm, aspect ratio of 30, brand name HAR T84, purchased from Yirui Stone (Shanghai) Investment Management Co., Ltd.) were blended and then granulated using a twin-screw extruder to obtain the polypropylene resin composition. The processing temperature of the screw extruder was 220℃. The performance test results of the obtained polypropylene resin composition Z1 are shown in Table 2.

[0112] Application Example 2-5 Following the method of Application Example 1, except that the polypropylene resins selected from Examples 2-5 were used, the performance test results of the resulting polypropylene resin compositions Z2-Z5 are shown in Table 2.

[0113] Application Example 6 Following the method of Application Example 1, except that the amount of talc in the polypropylene resin composition was 0.5 parts by weight, the performance test results of the resulting polypropylene resin composition Z7 are shown in Table 2.

[0114] Application Example 7 Following the method of Application Example 1, except that the type of talc in the polypropylene resin composition was changed to D50=6.5μm, aspect ratio of 15, and grade TYT-777A, purchased from Liaoning Haicheng Tianyuan Chemical Co., Ltd. The performance test results of the obtained polypropylene resin composition Z8 are shown in Table 2.

[0115] Application Example 8 The method used in Application Example 1 was the same, except that the inorganic filler was glass fiber, model SE4805-2400, with a diameter of 17 μm, purchased from Owens Corning, USA. The performance test results of the obtained polypropylene resin composition Z8 are shown in Table 2.

[0116] Comparative Application Examples 1-3 Following the method of Application Example 1, except that the polypropylene resins selected from Comparative Examples 1-3 were used, the performance test results of the resulting polypropylene resin compositions DZ1-DZ3 are shown in Table 2.

[0117] Table 2

[0118] As can be seen from the results in Table 2, the polypropylene resin composition prepared from the specific polypropylene resin of this invention has the characteristics of low shrinkage, high modulus, high heat distortion temperature and low linear expansion coefficient.

[0119] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A polypropylene resin, characterized in that, The polypropylene resin comprises: (a) Component A: Highly crystalline homopolymer polypropylene, with an isotactic five-unit component fraction greater than or equal to 96%; (b) Component B: Ethylene-propylene elastic copolymer, based on the total weight of the ethylene-propylene elastic copolymer, which contains 50-70% by weight of ethylene structural units and 30-50% by weight of propylene structural units; Wherein, based on the total weight of the polypropylene resin, the content of component A is 60-80% by weight, and the content of component B is 20-40% by weight; The molar fraction of the ethylene / ethylene / ethylene sequence EEE in the polypropylene resin is not less than 15%. The ratio of the melt flow rate of component A and the polypropylene resin under a load of 2.16 kg at 230 °C is 1.5-3.5:

1.

2. The polypropylene resin according to claim 1, wherein, The polypropylene resin comprises: (a) Component A: Highly crystalline homopolymer polypropylene, with an isotactic five-unit component fraction greater than or equal to 97%; (b) Component B: Ethylene-propylene elastic copolymer, based on the total weight of the ethylene-propylene elastic copolymer, which contains 50-65% by weight of ethylene structural units and 35-50% by weight of propylene structural units; Preferably, based on the total weight of the polypropylene resin, the content of component A is 65-80% by weight, and the content of component B is 20-35% by weight. Preferably, the molar fraction of the ethylene / ethylene / ethylene sequence (EEE) in the polypropylene resin is 15-25%; Preferably, the ratio of the melt mass flow rate of component A and the polypropylene resin under a load of 2.16 kg at 230 °C is 2.2-3.2:1; Preferably, the melt flow rate of the polypropylene resin under a load of 2.16 kg at 230 °C is 10-50 g / 10 min, more preferably 15-45 g / 10 min, and even more preferably 15-35 g / 10 min.

3. The polypropylene resin according to claim 1 or 2, wherein, The melt mass flow rate of component A under a load of 2.16 kg at 230 °C is 20-200 g / 10 min, preferably 30-100 g / 10 min; Preferably, based on the total weight of the polypropylene resin, the content of ethylene structural units is 15-30% by weight, preferably 15-25% by weight.

4. The polypropylene resin according to any one of claims 1-3, wherein, The polypropylene resin further contains xylene-soluble substances, the content of which is 10-30% by weight, preferably 15-25% by weight; Preferably, based on the total weight of xylene-soluble matter in the polypropylene resin, the content of ethylene structural units in the xylene-soluble matter is 40-55% by weight.

5. A method for preparing the polypropylene resin according to any one of claims 1-4, characterized in that, The method includes: (1) Under the first olefin polymerization conditions, propylene monomer was contacted with a Ziegler-Natta catalyst with high stereoselectivity, and unreacted monomer was removed from the mixture obtained after the contact reaction to obtain component A; (2) Under olefin gas-phase polymerization conditions, ethylene monomer, propylene monomer and component A obtained in step (1) are contacted and reacted, and unreacted monomers are removed from the mixture obtained after the contact reaction to obtain the polypropylene resin; In step (2), the molar ratio of ethylene to (ethylene + propylene) is 0.3-0.6:1; the molar ratio of hydrogen to ethylene is 0.35-0.6:

1.

6. The method according to claim 5, wherein, The highly stereoselective Ziegler-Natta catalyst comprises: (i) a main catalyst, which is a product obtained by reacting a magnesium source, a titanium source and an internal electron donor; and (ii) a co-catalyst. and (iii) optional external electron donor; Preferably, the co-catalyst is an organoaluminum compound, more preferably an alkylaluminum compound, and more preferably selected from at least one of triethylaluminum, tri-n-butylaluminum, triisobutylaluminum, tri-n-hexylaluminum, diethylaluminum chloride, di-n-butylaluminum chloride, diisobutylaluminum chloride, di-n-hexylaluminum chloride, diethylaluminum chloride, di-n-butylaluminum chloride, diisobutylaluminum chloride, and di-n-hexylaluminum chloride, more preferably trialkylaluminum, and more preferably at least one of triethylaluminum, tri-n-butylaluminum, and triisobutylaluminum. Preferably, the external electron donor is an organosilicon compound, preferably selected from at least one of tetramethoxysilane, tetraethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, trimethylphenoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methyl tert-butyldimethoxysilane, methyl isopropyldimethoxysilane, diphenoxydimethoxysilane, diphenyldiethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, and vinyltrimethoxysilane, as well as at least one of cyclohexylmethyldimethoxysilane, dicyclopentyldimethoxysilane, diisopropyldimethoxysilane, diisobutyldimethoxysilane, 2-ethylpiperidinyl-2-tert-butyldimethoxysilane, (1,1,1-trifluoro-2-propyl)-2-ethylpiperidinyldimethoxysilane, and (1,1,1-trifluoro-2-propyl)-methyldimethoxysilane; Preferably, the molar ratio of the main catalyst to the co-catalyst is 1:25-100, the main catalyst is calculated as titanium, and the co-catalyst is calculated as aluminum; Preferably, the weight ratio of the co-catalyst to the external electron donor is 2-150:1, more preferably 3-50:

1.

7. The method according to claim 5 or 6, wherein, The polymerization conditions in step (1) include: a temperature of 0-150℃, preferably 40-100℃; and a residence time of 0.5-5h, preferably 1-2h. Preferably, the polymerization reaction conditions in step (2) include: a temperature of 40-100℃, preferably 60-80℃; a pressure of 0.6-1.4 MPaG, preferably 1-1.3 MPaG; and a residence time of 0.1-2 h, preferably 0.3-0.8 h. Preferably, the method does not include cooling and / or drying operations between steps (1) and (2).

8. The polypropylene resin obtained by the preparation method according to any one of claims 5-7.

9. A polypropylene resin composition, characterized in that, The resin composition comprises: the polypropylene resin according to any one of claims 1-4 or 8, inorganic fillers, and additives; Preferably, based on 100 parts by weight of polypropylene resin, the content of the inorganic filler is 0.5-2% by weight, and the content of the additives is 0.05-0.5% by weight.

10. The polypropylene resin composition according to claim 9, wherein, The inorganic filler is at least one of talc, nano-calcium carbonate, nano-montmorillonite and glass fiber, preferably talc. Preferably, the talc powder has a particle size D50 of 1-15 μm and a diameter-to-thickness ratio of 5-40:1; Preferably, based on 100 parts by weight of polypropylene resin, the content of the inorganic filler is 0.5-1.5% by weight, and the content of the additives is 0.1-0.4% by weight. Preferably, the adjuvant is an antioxidant and / or a halogen absorbent; Preferably, the antioxidant is a hindered phenolic antioxidant and / or a phosphite antioxidant; Preferably, the halogen absorbent is calcium stearate and / or hydrated talc.

11. A method for preparing a polypropylene resin composition, characterized in that, The method comprises: mixing, melting, and extruding granulation of the polypropylene resin, inorganic filler, and additives as described in any one of claims 1-4 and 8; Preferably, the melt extrusion is carried out on a twin-screw extruder at a processing temperature of 190-230°C.

12. The polypropylene resin composition prepared by the method of claim 11.

13. The polypropylene resin composition according to claim 12, characterized in that, The horizontal shrinkage rate of the polypropylene resin composition is less than or equal to 0.8%, and the vertical shrinkage rate is less than or equal to 0.85%. Preferably, the linear expansion coefficient of the polypropylene resin composition is less than or equal to 7.5 × 10⁻⁶. -5 ℃ -1 ; Preferably, the flexural modulus of the polypropylene resin composition is greater than or equal to 1100 MPa; Preferably, the tensile strength of the polypropylene resin composition is 20-40 MPa; Preferably, the heat distortion temperature of the polypropylene resin composition is greater than or equal to 80°C.

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