Impact-resistant polypropylene resin and its preparation method, polypropylene materials and their preparation method and their application in large thin-walled injection molding

Abstract

This invention discloses impact-resistant polypropylene resin and its preparation method, polypropylene materials and their preparation method, and their application in large thin-walled injection molding, belonging to the field of polypropylene materials. The impact-resistant polypropylene resin comprises a matrix material and a rubber phase dispersed in the matrix material. The matrix material is homopolymer polypropylene, and the rubber phase is a copolymer of ethylene and propylene. The intrinsic viscosity of the rubber phase is 4–8 dL / g; the intrinsic viscosity ratio of the rubber phase to the homopolymer polypropylene is 5–10. This invention solves the problem of tiger-skin pattern on the surface of injection-molded products by controlling the structure of the impact-resistant polypropylene. It makes the polypropylene into a wide molecular weight distribution structure, i.e., a large difference in molecular weight between the rubber phase and the homopolymer phase, manifested in a large intrinsic viscosity ratio between the rubber phase and the homopolymer phase. This structural control improves the stability of melt flow during the injection molding process, thus enabling large injection-molded parts made from this impact-resistant polypropylene material to possess excellent rigidity, high gloss, fewer "flow marks," and good surface effects such as no tiger-skin pattern.

Description

Technical Field

[0001] This invention relates to the field of polypropylene materials, specifically to an impact-resistant polypropylene resin based on Spherizone polymerization process, a method for preparing the same, polypropylene materials, a method for preparing the same, and their application in large-scale thin-wall injection molding. Background Technology

[0002] Polypropylene is a high-performance general-purpose thermoplastic synthetic resin. Its raw materials are abundant and inexpensive. It has advantages such as good processability, non-toxicity, and good electrical insulation. Therefore, it is widely used in many fields such as automotive industry, home appliances, electronics, agriculture, packaging, building materials, furniture, and textiles.

[0003] To address the insufficient toughness of polypropylene materials, industrial processes often employ chemical reaction methods to prepare impact-resistant polypropylene copolymers, which consist of a homopolymer polypropylene matrix phase and a rubber phase dispersed within the matrix. In recent years, due to the demand for lightweight and weight-reduction products, impact-resistant polypropylene has seen increasingly widespread applications in large, thin-walled injection molding. However, during the injection molding of large, thin-walled parts, the large mold size and long melt flow path can easily lead to problems such as corner defects, placing higher demands on the melt flowability of polypropylene materials. Furthermore, due to the large size and thin wall thickness of the products, the material also needs to possess good rigidity to meet application requirements.

[0004] Impact-resistant polypropylene (PP) has a two-phase structure. During injection molding, especially for thin-walled, large-sized, or long products, PP is prone to localized thinning under shear forces, leading to unstable melt flow. This results in variations in surface gloss and the formation of tiger-stripe defects, or "flow marks," on the molded product surface. These defects severely affect the product's appearance and mechanical properties, hindering PP's application in high-end applications and representing a long-standing technical challenge in PP injection molding. Currently, industrial methods often employ blending modification to improve surface properties, but this increases costs and makes material recycling more difficult. Downstream solutions often use filler modification or surface painting to conceal the tiger-stripe defects, which is detrimental to plastic recycling and contradicts green environmental protection principles.

[0005] Therefore, there is an urgent need in the field of large-scale thin-wall injection molding for an impact-resistant polypropylene material prepared by a suitable polymerization process, which can reduce flow marks while meeting the requirements of high flow and high rigidity, and provide a good surface for the product. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem that existing polypropylene cannot simultaneously achieve high flowability, high rigidity, and good surface finish. This invention provides an impact-resistant copolymer polypropylene material, its preparation method, and its applications. By controlling the structure of the impact-resistant polypropylene, this invention solves the problem of tiger-skin patterns on the surface of injection-molded products. The key concept lies in making the polypropylene into a structure with a wide molecular weight distribution, i.e., a large difference in molecular weight between the rubber phase and the homopolymer phase, manifested in a high intrinsic viscosity ratio between the rubber phase and the homopolymer phase. This structural control can improve the stability of melt flow during the injection molding process, thereby enabling large injection-molded parts made from this impact-resistant polypropylene material to possess excellent rigidity, high gloss, fewer "flow marks," and a good surface finish without tiger-skin patterns.

[0007] The present invention provides an impact-resistant polypropylene resin comprising a matrix material and a rubber phase dispersed in the matrix material, wherein the matrix material is homopolymer polypropylene and the rubber phase is a copolymer of ethylene and propylene; the intrinsic viscosity of the rubber phase is 4 to 8 dL / g; and the intrinsic viscosity ratio of the rubber phase to the homopolymer polypropylene is 5 to 10.

[0008] As a preferred technical solution, the molecular weight distribution index (Mw / Mn) of the impact-resistant polypropylene resin is 15-22 (the ratio of weight-average molecular weight to number-average molecular weight); the content of ethylene structural units in the impact-resistant polypropylene resin is 3wt%-10wt%; the content of the rubber phase in the impact-resistant polypropylene resin is 5wt%-15wt%, and the ethylene content in the rubber phase is 25wt%-40wt%, preferably 15wt%-30wt%.

[0009] Another aspect of the present invention provides a method for preparing impact-resistant polypropylene resin, comprising the steps of:

[0010] S1 contains propylene as a raw material. It comes into contact with the main catalyst, co-catalyst and external electron donor to undergo prepolymerization and obtain a prepolymer. In order to achieve a wide molecular weight distribution of the final polypropylene product, this step requires the selection of a catalyst with a wide molecular weight distribution and a molecular weight distribution index Mw / Mn of 15 to 22.

[0011] S2 contains a mixture I of propylene, hydrogen and the prepolymer, which undergoes a homopolymerization reaction to obtain a homopolymer product. The homopolymerization reaction occurs in a multi-zone reactor, which is divided into an ascending section and a descending section. A barrier liquid can be introduced into the descending section to advance the hydrogen in the system and reduce gas entrainment in the powder.

[0012] S3 contains a mixture II of propylene, ethylene, hydrogen and the homopolymer product, which undergoes a copolymerization reaction to obtain a copolymer product. The rubber phase and the homopolymer phase have a high intrinsic viscosity ratio of 5 to 10.

[0013] As a preferred technical solution, the prepolymerization conditions include: a prepolymerization temperature of 20–30°C; a prepolymerization pressure of 2.5–3.5 MPa; a prepolymerization residence time of 12–18 min; a propylene flow rate of 25–35 t / h; a main catalyst flow rate of 1.3–1.4 kg / h; a cocatalyst flow rate of 4–6 kg / h; and an external electron donor flow rate of 0.3–0.7 kg / h.

[0014] As a preferred technical solution, the main catalyst is a Ziegler-Natta catalyst, preferably at least one of ZN101-1, ZN118, and ZN168 catalysts.

[0015] As a preferred technical solution, the co-catalyst is triethylaluminum.

[0016] As a preferred technical solution, the general formula of the external electron donor is R1R2Si(OR3)2, where R1 and R2 may be the same or different, and are independently C. 1-6 Straight-chain or branched aliphatic groups, and R1 and R2 are not simultaneously cyclic aliphatic groups; R3 is C 1-2 A straight-chain alkane group; preferably, the external electron donor is selected from at least one of diisopropyldimethoxysilane, diisobutyldiethoxysilane, cyclopentyl-methyl-dimethoxysilane, cyclopentyl-ethyl-dimethoxysilane, di(2-methylbutyl)-dimethoxysilane, di(2-methylpropyl)-dimethoxysilane, cyclohexyl-methyl-dimethoxysilane, cyclohexyl-ethyl-dimethoxysilane, and cyclohexyl-methyl-diethoxysilane, and is more preferably cyclopentyl-ethyl-dimethoxysilane.

[0017] As a preferred technical solution, in the mixture I, the H2 concentration of the gaseous components (propylene and hydrogen) is controlled at 3% to 12% mol, and the propylene concentration is controlled at 80% to 85% mol.

[0018] As a preferred technical solution, the homopolymerization reaction includes a sequentially connected ascending reaction zone and a descending reaction zone: the reaction conditions in the ascending reaction zone include: pressure 2.5–3.0 MPaG, temperature 62–75°C, and the density of the prepolymer is 100–250 kgPP / m³. 3 The concentration of H2 is 3%–12% / mol; the concentration of propylene is 80%–85% / mol; the reaction conditions in the descending reaction zone include: pressure 2.5–3.0 MPaG, temperature 62–75℃, and the density of the prepolymer is 300–500 kgPP / m³. 3 The concentration of H2 is 0.3%–0.8% / mol; the concentration of propylene is 40%–70% / mol.

[0019] The raw material propylene contains trace amounts of propane. Since propane does not participate in the reaction, it will accumulate as the reaction proceeds. In mixture I, the propane concentration is controlled at 8%–12% / mol. In the rising reaction zone, the propane concentration is 8%–12% / mol when the reaction reaches equilibrium; in the falling reaction zone, the propane concentration is 4%–8% / mol when the reaction reaches equilibrium.

[0020] As a preferred technical solution, a barrier liquid is introduced into the descending reaction zone, and the barrier liquid is liquid propylene.

[0021] As a preferred technical solution, the conditions for the copolymerization reaction include: pressure of 0.5 to 2.0 MPaG; temperature of 70 to 95°C; molar ratio of ethylene to (ethylene + propylene) of 0.1 to 0.4; and molar ratio of hydrogen to ethylene of 0.003 to 0.02.

[0022] In another aspect, the present invention provides a polypropylene material comprising, by weight percentage: an antioxidant, 0.15 wt% to 1.25 wt%; a halogen absorber, 0.05 wt% to 0.2 wt%; a nucleating agent, 0.03 wt% to 0.05 wt%; and an impact-resistant polypropylene resin of any one of the above, 98.7 wt% to 99.8 wt%.

[0023] As a preferred technical solution, the polypropylene material has a flexural modulus greater than 1600 MPa and a surface gloss greater than 80%.

[0024] As a preferred technical solution, the antioxidant is selected from at least one of phenolic antioxidants, hindered amine antioxidants, phosphite antioxidants, thiolated antioxidants, and benzofuranone antioxidants.

[0025] As a preferred technical solution, the phenolic antioxidant is selected from at least one of 2-(4-tert-butyl)-5-methylphenol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], catechol, resorcinol, 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane and triethylene glycol bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl)acrylonitrile.

[0026] As a preferred technical solution, the hindered amine antioxidant is selected from at least one of N,N'-di-sec-butyl-p-phenylenediamine, N-phenylaniline, N,N'-di(2-naphthyl)-p-phenylenediamine, 4,4'-bis(α-methylbenzyl)diphenylamine and 4,4'-bis(α,α'-dimethylbenzylamine)diphenylamine.

[0027] As a preferred technical solution, the phosphite antioxidant is selected from at least one of tris(2,4-di-tert-butylphenyl) phosphite, distearate pentaerythritol phosphite, 2,2'-ethylene bis(4,6-di-tert-butylphenyl) fluorophosphite, tris(nonylphenyl) phosphite, bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite, 2,2'-methylene bis(4,6-di-tert-butylphenyl) isooctyloxy phosphite, bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphate, tetrakis(2,4-di-tert-butylphenyl-4,4'-biphenyl) bisphosphonate, and 2,2',2”-hypoazine triethyl-tris[3,3',5,5'-tetratert-butyl-1,1'-methylenediphenyl-2,2'-diyl]phosphite.

[0028] As a preferred technical solution, the thiolated antioxidant is selected from at least one of 4,4'-thiobis(6-tert-butyl-3-methylphenol) and 2,2'-thiobis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0029] As a preferred technical solution, the benzofuranone antioxidant is selected from at least one of 5,7-di-tert-butyl-3-(4-methyl)3-hydro-benzofuran-2-one, 5,7-di-tert-butyl-3-(3,4-dimethyl)3-hydro-benzofuran-2-one, and 5,7-di-tert-butyl-3-(2,4-dimethyl)3-hydro-benzofuran-2-one.

[0030] As a preferred technical solution, the antioxidant is a composite antioxidant, including antioxidant A and antioxidant B; antioxidant A is selected from at least one of phenolic antioxidants and hindered amine antioxidants; antioxidant B is a phosphite antioxidant; the mass ratio of antioxidant A to antioxidant B is 1:1 to 1:6.

[0031] As a preferred technical solution, the halogen absorbent is selected from calcium stearate and / or hydrotalcite.

[0032] As a preferred technical solution, the nucleating agent is selected from at least one of talc, carboxylic acid metal salt nucleating agents, and organophosphate nucleating agents.

[0033] As a preferred technical solution, the carboxylic acid metal salt nucleating agent is selected from at least one of sodium benzoate, bis(p-tert-butylbenzoic acid)hydroxyaluminum, (1R,2R,3S,4S)-rel-bicyclo[2.2.1]hept-2,3-dicarboxylic acid disodium salt and bicyclo[2.2.1]heptane-2,3-dicarboxylic acid disodium salt.

[0034] As a preferred technical solution, the organophosphate nucleating agent is selected from the nucleating agents sodium 2,2'-methyl-bis-(4,6-di-tert-butylphenyl)phosphate and / or bis[2,2'-methyl-bis-(4,6-di-tert-butylphenyl)phosphate]hydroxyaluminum.

[0035] Another aspect of the present invention provides a method for preparing polypropylene material, comprising a mixture III of an antioxidant, a nucleating agent, a halogen absorber and the impact-resistant polypropylene resin, which is co-extruded and pelletized to obtain the polypropylene material.

[0036] As a preferred technical solution, the mixture III is a melt with a mass flow rate of 50-100 g / 10 min; in the mixture III, by mass percentage, the impact-resistant polypropylene resin is 98.5%-99.77%; the antioxidant is 0.15%-1.25%; the halogen absorbent is 0.05%-0.2%; and the nucleating agent is 0.03%-0.05%.

[0037] As a preferred technical solution, the co-extrusion conditions include: an extruder barrel temperature of 210–260°C; and pelleting conditions include: a pelleting water temperature of 50–65°C.

[0038] Another aspect of the present invention provides its application in thin-walled injection molded products, namely, providing a class of thin-walled injection molded products containing any of the polypropylene materials described above. Preferably, the thin-walled injection molded product is a large injection molded part with a projected area of ​​50 cm². 2 The injection molding wall thickness is 0.5mm to 4.0mm; preferably, the ratio of the flow length (L) to the thickness (T) of the thin-walled injection molded product is greater than 100.

[0039] According to the present invention, the impact-resistant polypropylene material has good melt flowability, wide application scenarios, and excellent mechanical properties such as material rigidity. It is mainly used in large injection molded parts such as car bumpers, dashboards, door panels and other long interior and exterior trim parts. The products have good surface gloss and fewer surface "flow marks".

[0040] The above technical solution has achieved the following beneficial effects:

[0041] (1) Based on the multi-zone circulating gas phase reactor process, this invention selects appropriate main catalyst, catalyst promoter, external electron donor and promoter system, and precisely controls parameters such as polymer melt flowability, rubber phase content and ethylene content in rubber phase by adjusting polymerization conditions such as H2 concentration in the feed monomer and ethylene / (ethylene+propylene) content, and obtains a series of high flowability impact-resistant polypropylene materials. The impact-resistant polypropylene materials have the characteristics of high flowability and high rigidity, and the flexural modulus is greater than 1600MPa;

[0042] (2) In the preparation method, propylene barrier liquid is selectively added to the top of the descending section of the multi-zone circulating gas phase reactor to control the concentration of raw materials such as ethylene and H2 in the ascending and descending sections, thereby widening the molecular weight distribution of the homopolymer phase. In addition, the molecular weight of the rubber phase is controlled to be relatively large, which makes the overall molecular weight distribution of the impact-resistant polypropylene resin wider, and improves the intrinsic viscosity of xylene soluble matter and the intrinsic viscosity of xylene soluble matter / insoluble matter. This helps to improve the melt flow stability when the impact-resistant polypropylene material is used in large injection molded parts or long strip injection molded parts.

[0043] (3) The polypropylene material of the present invention has the structural characteristics of high viscosity ratio of rubber phase and homopolymer phase and wide molecular weight distribution. Due to this specific structure, when large thin-walled injection molded parts are prepared using the polypropylene resin material of the present invention, the phase separation degree and melt elasticity in the melt are high, so that the surface of the product has high gloss and uniform gloss, with few surface "flow marks", that is, no tiger skin defects. Attached Figure Description

[0044] Figure 1 Spherizone Process Flow Overview Detailed Implementation

[0045] 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.

[0046] like Figure 1 As shown, the core of the Spherizone process is a multi-zone circulating reactor (the reactor for the gas-phase Spherizone technology developed by LyondellBasell), comprising two independent reaction zones—an ascending zone and a descending zone. In the ascending zone, the generated polypropylene solid undergoes rapid fluidization and gas-phase transport along with the gaseous monomers from bottom to top. After the gas-solid two-phase flow enters the top of the ascending zone, gas-solid separation occurs, and the solid enters the descending zone. The solid in the downcomer moves downward under gravity, re-entering the ascending zone via the bottom "L" section, thus continuously circulating. The content of hydrogen and comonomers can be controlled independently in the ascending and descending zones, thereby adjusting the polymer structure at the macromolecular scale (in terms of melt flow rate and comonomer concentration and type). Introducing liquid propylene (barrier liquid) at the top of the descending zone allows for control of the composition in the descending zone to be completely different from that in the ascending zone, thus enabling the generation of components with different molecular weights in the ascending and descending zones.

[0047] Because the polypropylene particles generated in the multi-zone circulating reactor are continuously circulated with the propylene gas flow, a layer of polymer is generated in both the rising and falling sections to coat the outer layer. The resulting polypropylene particles have an "onion"-like morphology, which allows for a more uniform mixing of molecules with different structures.

[0048] The present invention will be described in detail below through embodiments.

[0049] In the embodiments and comparative examples of this invention, the raw materials used to prepare the polypropylene materials were sourced from:

[0050] The main catalyst, ZN101, was purchased from LyondellBasell Industries.

[0051] The main catalyst, ZN168, was purchased from LyondellBasell Industries.

[0052] The main catalyst, DQC602, was purchased from Sinopec Aoda Catalyst Company.

[0053] The main catalyst, HR, was purchased from Sinopec Aoda Catalyst Company.

[0054] Injection Molding Test Samples: The injection molding samples of thermoplastic materials were prepared according to the method described in GB / T 17037.1-2019;

[0055] Melt flow index (MFR): determined according to the method described in GB / T3682-2000 at 230℃ and 2.16kg load;

[0056] Tensile strength: Measured according to GB / T 1040.2-2022 for injection molded samples;

[0057] Flexural modulus: determined according to the method described in GB / T 9341-2008;

[0058] Impact strength of simply supported beams: determined according to the method described in GB / T 1043.1-2008;

[0059] Heat distortion temperature (HDT): determined according to the method described in GB / T 1634.2-2004;

[0060] All test items were parallel samples, and the average value was calculated for 5 groups.

[0061] Using flammable propylene as raw material, a Spherizone polymerization process is employed, utilizing a catalyst with a wide molecular weight distribution and hydrogen as a molecular weight regulator. Propylene barrier liquid can be introduced into the descending section of a multi-zone reactor to further broaden the molecular weight distribution of the polymer by stripping off a portion of the hydrogen in the descending section. This yields a homopolymer polypropylene matrix phase with a wide molecular weight distribution. The homopolymer polypropylene retains residual polymerization activity, allowing it to continue copolymerizing in a gas-phase copolymerization reactor containing a mixture of ethylene and propylene gases, resulting in a rubber phase dispersed within the matrix. The mixture of the matrix phase and rubber phase (impact-resistant polypropylene resin base material), antioxidant, halogen absorber, and nucleating agent is then uniformly mixed and melt-extruded into granules using an extruder.

[0062] The preparation method of impact-resistant polypropylene material includes the following steps:

[0063] (1) Propylene undergoes prepolymerization under the combined action of the main catalyst, the co-catalyst and the first external electron donor;

[0064] (2) The prepolymer product, propylene and hydrogen obtained in step (1) are fed into a multi-zone circulating reactor for polymerization reaction to obtain polypropylene homopolymer powder (containing residual catalytic activity) and unreacted monomers are removed by a medium-pressure degassing system.

[0065] (3) The polypropylene homopolymer powder obtained in step (2), propylene, ethylene and hydrogen are further copolymerized in a gas phase copolymerization reactor to obtain impact-resistant polypropylene powder, which is then sent to the post-processing system.

[0066] (4) After the impact-resistant polypropylene powder obtained in step (3) is degassed under low pressure, it is mixed evenly with antioxidant, nucleating agent and halogen absorbent to obtain a mixture.

[0067] (5) The mixture obtained in step (4) is extruded through an extruder to prepare an impact-resistant polypropylene material with a melt mass flow rate of 50-100 g / 10 min, a molecular weight distribution index of 15-22, a xylene soluble content (rubber phase content in impact-resistant polypropylene) of 5-15 wt%, an ethylene content in xylene solubles (ethylene content in rubber phase) of 15-30 wt%, a xylene soluble intrinsic viscosity (rubber phase intrinsic viscosity) of 4-8 dL / g, and a xylene soluble intrinsic viscosity / xylene insoluble intrinsic viscosity ratio (the intrinsic viscosity ratio of rubber phase to homopolymer polypropylene) of 5-10.

[0068] The main catalyst is a catalyst with a wide molecular weight distribution, preferably ZN168 or ZN101-1.

[0069] According to the present invention, in step (2):

[0070] The multi-zone circulating reactor (a reactor using the gas-phase Spherizone technology developed by LyondellBasell) has its rising section pressure controlled at 2.5–3.0 MPaG, rising section temperature controlled at 62–75°C, and rising section density controlled at 100–250 kgPP / m³. 3 In the rising section, the H2 concentration is controlled at 3% mol to 12% mol; the propylene concentration is controlled at 80% to 85% mol; and the propane concentration is controlled at 8% to 12% mol.

[0071] The pressure in the downflow section of the multi-zone circulating reactor is controlled at 2.5–3.0 MPaG, the temperature in the downflow section is controlled at 62–75℃, and the density in the downflow section is controlled at 300–500 kgPP / m³. 3 Optional propylene barrier liquid can be added to the top of the descending section. The barrier liquid is liquid propylene, which will rapidly vaporize after addition and flow in the opposite direction to the solid polypropylene powder in the descending section. This reduces the entrainment of gas in the polypropylene powder and can strip hydrogen from the gas in the ascending section, reducing the hydrogen concentration in the descending section. This widens the molecular weight difference between the homopolymer in the ascending and descending sections, thereby broadening the polymer molecular weight distribution. Furthermore, adding the barrier liquid can reduce downstream hydrogen carryover and reduce the hydrogen content in the gas phase reactor. By adding an appropriate amount of barrier liquid to the descending section, the H2 concentration in the gas components of the descending section is controlled at 0.3% mol to 0.8% mol; the propylene concentration is controlled at 40% mol to 70% mol; and the propane concentration is controlled at 4% mol to 8% mol.

[0072] According to the present invention, in step (3), the pressure of the gas phase copolymerization reactor is controlled at 0.5 to 2.0 MPaG, the temperature is controlled at 70 to 95°C, the ethylene / (ethylene + propylene) ratio is controlled at 0.1 to 0.5, and the hydrogen / ethylene ratio is controlled at 0.01 to 0.5.

[0073] According to the present invention, in step (5), the temperature of the extruder barrel is controlled at 250°C and the temperature of the pelletizing water is 60°C.

[0074] The specific production process and polymerization conditions of this invention can precisely control the material's fluidity, molecular weight distribution, rubber phase content, and ethylene content in the rubber phase, thereby producing large injection molded parts that have both excellent rigidity and good surface effects such as high gloss and fewer "flow marks".

[0075] Example 1

[0076] Step (1): The main catalyst ZN101 (flow rate 1.35 kg / h), triethylaluminum (flow rate 5 kg / h), cyclohexyl-methyl-dimethoxysilane (Donor C, flow rate 0.5 kg / h) and gaseous propylene (flow rate 30 t / h) were prepolymerized in a single loop reactor. The flow rate ratio of triethylaluminum to cyclohexyl-methyl-dimethoxysilane was 10, the reaction temperature was 25℃, the reaction pressure was 3.0 MPa, and the residence time was 12 min to obtain the prepolymer.

[0077] Step (2): The prepolymer and unreacted propylene flow from the prepolymerization reactor into the multi-zone circulating reactor, which consists of an ascending section and a descending section. The ascending section of the multi-zone circulating reactor has a pressure of 3.0 MPa, a temperature of 75°C, and an H2 concentration of 6% in the feed monomer; the descending section has a pressure of 3.0 MPa, a temperature of 90°C, and an average residence time of 90 min, yielding a homopolymer polypropylene matrix. It should be noted that a liquid propylene barrier liquid is introduced at the top of the descending section. This barrier liquid is stripped from the mixed gas in the ascending section, thus differentiating the H2 concentration between the ascending and descending sections.

[0078] Step (3): The polypropylene homopolymer powder obtained by polymerization in the multi-zone circulating reactor enters the gas phase copolymerization reactor and continues to copolymerize with propylene, ethylene and hydrogen. The molar ratio of ethylene / (propylene + ethylene) introduced is 0.3 and the molar ratio of H2 / ethylene is 0.05. The pressure of the copolymerization reactor is 1.5MPa, the temperature is 85℃, and the average residence time is 0.3-0.5h, to obtain impact-resistant copolymer polypropylene powder.

[0079] Step (4): After degassing the impact-resistant polypropylene powder obtained from the gas-phase copolymerization reactor under low pressure (pressure 0.05-0.08MPa), it is mixed evenly with the main antioxidant, auxiliary antioxidant, halogen absorbent and nucleating agent, with the following mass ratios: polypropylene powder 99.56%, antioxidant 0.3%, halogen absorbent 0.1% and nucleating agent 0.04%, to obtain a mixture.

[0080] Step (5): The mixture is extruded through an extruder to obtain a melt with a mass flow rate of 50-100 g / 10 min. The extruder barrel temperature is 250℃. After extrusion, the material is pelletized at a pelletizing water temperature of 60℃ to obtain a polypropylene material. Testing shows that the material has a molecular weight distribution index of 22, a rubber phase content of 15 wt%, an ethylene content of 40 wt% in the rubber phase, a xylene-soluble intrinsic viscosity of 7.5 dL / g, and a xylene-soluble intrinsic viscosity / insoluble intrinsic viscosity ratio of 8. The impact-resistant polypropylene material has a flexural modulus of 1650 MPa and a surface gloss of 83%.

[0081] Example 2

[0082] This embodiment is basically the same as that of embodiment 1, except that in step (1), the main catalyst is ZN168 and the flow rate is 1.35 kg / h.

[0083] Example 3

[0084] This embodiment is basically the same as embodiment 1, except that in step (2), the H2 concentration in the feed monomer is 9%.

[0085] Example 4

[0086] This embodiment is basically the same as that of embodiment 1, except that in step (2), the H2 concentration in the feed monomer is 12%.

[0087] Example 5

[0088] This embodiment is basically the same as embodiment 1, except that: in step (2), liquid propylene barrier liquid is not added at the top of the descending section.

[0089] Comparative Example 1

[0090] This comparative example is basically the same as Example 5, except that the main catalyst in step (1) is DQC602 with a flow rate of 1.35 kg / h.

[0091] Comparative Example 2

[0092] This comparative example is basically the same as Example 5, except that the main catalyst in step (1) is HR and the flow rate is 1.35 kg / h.

[0093] Comparative Example 3

[0094] This comparative example is basically the same as Example 5, except that the molar ratio of ethylene / (propylene + ethylene) introduced in step (3) is 0.7.

[0095] Comparative Example 4

[0096] This comparative example is basically the same as Example 1, except that the molar ratio of H2 to ethylene introduced in step (3) is 0.2.

[0097] The performance of the polypropylene materials prepared in the examples and comparative examples was tested, and the results are shown in Table 1.

[0098] Table 1

[0099]

[0100] Examples 1 to 5 show that, using the technical means of the present invention, a series of impact-resistant copolymer polypropylene materials with a melt flow rate of 50-100 g / 10 min, a flexural modulus >1600 MPa, and a gloss of greater than 80% can be prepared by the Spherizone propylene polymerization process. Furthermore, the large thin-walled injection molded samples prepared from this material have slight flow marks on the surface and no tiger-skin defects.

[0101] In Comparative Examples 1 and 2, the difference between the product preparation process and Example 5 was the use of different catalysts. Comparing the product performance of Example 5 and Comparative Example 1, it was found that the molecular weight distribution of the impact-resistant polypropylene products prepared by the processes of Comparative Examples 1 and 2 was significantly narrower, the ratio of xylene-soluble intrinsic viscosity to xylene-insoluble intrinsic viscosity was small, and surface flow marks were severe. In addition, the catalyst led to an increase in the rubber phase content, which resulted in a decrease in flexural modulus and gloss.

[0102] In Comparative Example 3, the difference between the product preparation process and Example 5 is that the ethylene / (propylene + ethylene) ratio introduced into the copolymerization reactor is increased. Comparing the product performance of Example 5 and Comparative Example 3, it is shown that the impact-resistant polypropylene product prepared by the process of Comparative Example 3 has a narrower molecular weight distribution, a very small xylene-soluble intrinsic viscosity / insoluble intrinsic viscosity ratio, severe surface flow marks, and due to the increased ethylene / (propylene + ethylene) ratio, the rubber phase content and the ethylene content in the rubber phase are significantly increased, which leads to a decrease in flexural modulus and gloss.

[0103] In Comparative Example 4, the difference between the product preparation process and Example 5 is that the ratio of H2 to ethylene introduced into the copolymerization reactor is increased. Comparing the product performance of Example 5 and Comparative Example 4 shows that, due to the increase of H2, it is not conducive to the growth of rubber phase molecular chains, resulting in a narrower molecular weight distribution of the impact-resistant polypropylene product prepared by the process of Comparative Example 4, a very small ratio of xylene-soluble intrinsic viscosity to insoluble intrinsic viscosity, and severe surface flow marks.

[0104] Any numerical value mentioned in this invention, if there is only a two-unit interval between any minimum and any maximum value, includes all values ​​that increase by one unit each time from the minimum to the maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, or time, is stated as 50–90, in this specification it means specifically listing values ​​such as 51–89, 52–88, ..., 69–71, and 70–71. For non-integer values, it may be appropriately considered that a unit is 0.1, 0.01, 0.001, or 0.0001. These are merely some specifically specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0105] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. An impact-resistant polypropylene resin, characterized in that, The invention comprises a matrix material and a rubber phase dispersed in the matrix material, wherein the matrix material is homopolymer polypropylene and the rubber phase is a copolymer of ethylene and propylene; The intrinsic viscosity of the rubber phase is 4–8 dL / g; The intrinsic viscosity ratio of the rubber phase to the homopolymer polypropylene is 5 to 10.

2. The impact-resistant polypropylene resin according to claim 1, characterized in that, The molecular weight distribution index (Mw / Mn) of the impact-resistant polypropylene resin is 15–22. The ethylene structural unit content in the impact-resistant polypropylene resin is 3wt% to 10wt%. The rubber phase content in the impact-resistant polypropylene resin is 5wt% to 15wt%. The ethylene content in the rubber phase is 25wt% to 40wt%.

3. The method for preparing the impact-resistant polypropylene resin according to claim 1 or 2, characterized in that, Including the following steps: S1, a raw material containing propylene, comes into contact with the main catalyst, co-catalyst, and external electron donor to undergo prepolymerization, yielding a prepolymer. S2 contains a mixture I of propylene, hydrogen, and the prepolymer, which undergoes a homopolymerization reaction to obtain a homopolymer product. S3 contains a mixture II of propylene, ethylene, hydrogen, and the homopolymer product, which undergoes a copolymerization reaction to obtain the impact-resistant polypropylene resin.

4. The method for preparing impact-resistant polypropylene resin according to claim 3, characterized in that, The prepolymerization conditions include: a prepolymerization temperature of 20–30°C; and a prepolymerization pressure of 2.5–3.5 MPa. The residence time for prepolymerization is 12–18 min; the propylene flow rate is 25–35 t / h; the main catalyst flow rate is 1.3–1.4 kg / h; the co-catalyst flow rate is 4–6 kg / h; and the external electron donor flow rate is 0.3–0.7 kg / h. And / or, the main catalyst is a Ziegler-Natta catalyst, preferably at least one of ZN101-1, ZN118, and ZN168 catalysts; And / or, the co-catalyst is triethylaluminum; And / or, the general formula of the external electron donor is R1R2Si(OR3)2, where R1 and R2 may be the same or different, and are independently C. 1-6 Straight-chain or branched aliphatic groups, and R1 and R2 are not simultaneously cyclic aliphatic groups; R3 is C 1-2 Straight-chain alkane group; Preferably, the external electron donor is selected from at least one of diisopropyldimethoxysilane, diisobutyldiethoxysilane, cyclopentyl-methyl-dimethoxysilane, cyclopentyl-ethyl-dimethoxysilane, di(2-methylbutyl)-dimethoxysilane, di(2-methylpropyl)-dimethoxysilane, cyclohexyl-methyl-dimethoxysilane, cyclohexyl-ethyl-dimethoxysilane, and cyclohexyl-methyl-diethoxysilane, and is more preferably cyclopentyl-ethyl-dimethoxysilane.

5. The preparation method according to claim 3 or 4, characterized in that, In the mixture I, the H2 concentration in the gaseous component is controlled at 3% to 12%, and the propylene concentration is controlled at 80% to 85%.

6. The preparation method according to claim 3, 4, or 5, characterized in that, The homopolymerization reaction includes a sequentially connected ascending reaction zone and a descending reaction zone: The reaction conditions in the rising reaction zone include: pressure 2.5–3.0 MPaG, temperature 62–75°C, and the density of the prepolymer 100–250 kgPP / m³. 3 The concentration of H2 is 3%–12%; the concentration of propylene is 80%–85%. The reaction conditions in the descending reaction zone include: pressure 2.5–3.0 MPaG, temperature 62–75°C, and the density of the prepolymer 300–500 kgPP / m³. 3 The concentration of H2 is 0.3%–0.8%; the concentration of propylene is 40%–70%.

7. The preparation method according to claim 6, characterized in that, A barrier liquid, which is liquid propylene, is introduced into the descending reaction zone.

8. The preparation method according to any one of claims 3-7, characterized in that, The conditions for the copolymerization reaction include: pressure of 0.5–2.0 MPaG; temperature of 70–95°C; The molar ratio of ethylene to (ethylene + propylene) is 0.1 to 0.4, and the molar ratio of hydrogen to ethylene is 0.003 to 0.

02.

9. A polypropylene material, characterized in that, By weight percentage, it contains: Antioxidant, 0.15wt%~1.25wt%; Halogen absorbent, 0.05wt%~0.2wt%; Nucleating agent, 0.03wt%~0.05wt%; And the impact-resistant polypropylene resin according to claim 1 or 2, 98.5 wt% to 99.77 wt%.

10. The polypropylene material according to claim 9, characterized in that, The polypropylene material has a flexural modulus greater than 1600 MPa and a surface gloss greater than 80%.

11. The polypropylene material according to claim 9 or 10, characterized in that, The antioxidant is selected from at least one of phenolic antioxidants, hindered amine antioxidants, phosphite antioxidants, thiolated antioxidants, and benzofuranone antioxidants; Preferably, the phenolic antioxidant is selected from at least one of 2-(4-tert-butyl)-5-methylphenol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], catechol, resorcinol, 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane and triethylene glycol bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl)acrylonitrile; Preferably, the hindered amine antioxidant is selected from at least one of N,N'-di-sec-butyl-p-phenylenediamine, N-phenylaniline, N,N'-di(2-naphthyl)-p-phenylenediamine, 4,4'-bis(α-methylbenzyl)diphenylamine and 4,4'-bis(α,α'-dimethylbenzylamine)diphenylamine; Preferably, the phosphite antioxidant is selected from at least one of tris(2,4-di-tert-butylphenyl) phosphite, distearate pentaerythritol phosphite, 2,2'-ethylene bis(4,6-di-tert-butylphenyl) fluorophosphite, tris(nonylphenyl) phosphite, bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite, 2,2'-methylene bis(4,6-di-tert-butylphenyl) isooctyloxy phosphite, bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphate, tetrakis(2,4-di-tert-butylphenyl-4,4'-biphenyl) bisphosphonate, and 2,2',2'-hypoazine triethyl-tris[3,3',5,5'-tetratert-tert-butyl-1,1'-methylenediphenyl-2,2'-diyl]phosphite; Preferably, the thiolated antioxidant is selected from at least one of 4,4'-thiobis(6-tert-butyl-3-methylphenol) and 2,2'-thiobis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. Preferably, the benzofuranone antioxidant is selected from at least one of 5,7-di-tert-butyl-3-(4-methyl)3-hydro-benzofuran-2-one, 5,7-di-tert-butyl-3-(3,4-dimethyl)3-hydro-benzofuran-2-one, and 5,7-di-tert-butyl-3-(2,4-dimethyl)3-hydro-benzofuran-2-one; Preferably, the antioxidant is a composite antioxidant, comprising antioxidant A and antioxidant B; Antioxidant A is selected from at least one of phenolic antioxidants and hindered amine antioxidants; Antioxidant B is a phosphite antioxidant; The mass ratio of antioxidant A to antioxidant B is 1:1 to 1:

6.

12. The polypropylene material according to any one of claims 9-11, characterized in that, The halogen absorbent is selected from calcium stearate and / or hydrotalcite.

13. The polypropylene material according to any one of claims 9-12, characterized in that, The nucleating agent is selected from at least one of talc, metal carboxylic acid salt nucleating agents, and organophosphate nucleating agents; Preferably, the carboxylic acid metal salt nucleating agent is selected from at least one of sodium benzoate, bis(p-tert-butylbenzoic acid)hydroxyaluminum, (1R,2R,3S,4S)-rel-bicyclo[2.2.1]hept-2,3-dicarboxylic acid disodium salt and bicyclo[2.2.1]heptane-2,3-dicarboxylic acid disodium salt; Preferably, the organophosphate nucleating agent is selected from the nucleating agents sodium 2,2'-methyl-bis-(4,6-di-tert-butylphenyl)phosphate and / or bis[2,2'-methyl-bis-(4,6-di-tert-butylphenyl)phosphate]hydroxyaluminum.

14. A method for preparing the polypropylene material according to any one of claims 9-13, characterized in that, A mixture III containing antioxidants, nucleating agents, halogen absorbers, and the impact-resistant polypropylene resin is co-extruded and pelletized to obtain the polypropylene material.

15. The preparation method according to claim 14, characterized in that, The mixture III is a melt with a mass flow rate of 50–100 g / 10 min; In the mixture III, by mass percentage, The impact-resistant polypropylene resin is 98.5% to 99.77%; Antioxidant, 0.15%–1.25%; Halogen absorbent, 0.05%–0.2%; Nucleating agent: 0.03%–0.05%.

16. The preparation method according to claim 14 or 15, characterized in that, The conditions for co-extrusion include: an extruder barrel temperature of 210–260°C; The conditions for pelleting include: pelleting water temperature of 50-65℃.

17. A thin-walled injection molded product, characterized in that, The thin-walled injection molded product contains the polypropylene material according to any one of claims 9-13, and the injection wall thickness is 0.5 mm to 4.0 mm.

18. The thin-walled injection molded product according to claim 17, characterized in that, The projected area of ​​the thin-walled injection molded product is 50cm². 2 above; And / or, the ratio of flow length to thickness of thin-walled injection molded products is greater than 100.

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