High-transparency co-polypropylene resin and preparation method thereof

Abstract

The invention provides high-transparency co-polypropylene and a preparation method thereof. According to the high-transparency co-polypropylene provided by the invention, the melt mass flow rate is 5-10g / 10min, the 1-butene content is 4.8-13.7 wt%, and the n-hexane extract content is 0.38-1.10 wt%. By optimizing a Ziegler-Natta catalyst system, the content of 1-butene in co-polypropylene is increased, and the co-polypropylene material with high transparency and low precipitation can be obtained by selecting the di (3, 4-dimethylbenzylidene) sorbitol nucleating agent and adding a small amount of the di (3, 4-dimethylbenzylidene) sorbitol nucleating agent.

Description

Technical Field

[0001] The invention belongs to the technical field of polypropylene materials, and particularly relates to a highly transparent copolymerized polypropylene resin and a preparation method thereof. Background Art

[0002] Polypropylene possesses excellent physical and chemical properties, with the best mechanical and heat resistance among known thermoplastic resins. However, because polypropylene is a semi-crystalline polymer, it tends to form large spherulites during the molding process, resulting in poor transparency and significantly limiting its application in transparent products.

[0003] Currently, the vast majority of highly transparent and glossy polypropylene products sold on the market are modified by adding transparent nucleating agents. However, transparent nucleating agents are expensive, and high addition levels significantly increase the cost of polypropylene materials. Furthermore, with the improvement of people's quality of life, the concept of green and healthy products is being promoted in areas such as maternal and infant products, food packaging, and medical devices. Improving their hygiene, safety, and non-toxicity has become an inevitable trend and a key priority. By copolymerizing a second monomer onto the polypropylene molecular chain, the regularity of the polypropylene molecular segments is disrupted, which can reduce its crystallinity and improve transparency. If the embedding effect is sufficiently effective, the use of transparent nucleating agents can be greatly reduced, and even highly transparent polypropylene materials can be produced without relying on nucleating agents.

[0004] Compared to ethylene, copolymers using 1-butene as the second monomer in copolymers with propylene exhibit higher transparency and lower levels of n-hexane extracts, making them safer for contact with food and pharmaceuticals. Increasing the 1-butene content in copolymers not only reduces crystallinity and crystal size, but also increases transparency and gloss. It also lowers processing temperatures and reduces energy consumption.

[0005] Therefore, the preparation of propylene / 1-butene random copolymers with high 1-butene content and good distribution uniformity is a promising method for developing highly transparent copolymerized polypropylene. Summary of the Invention

[0006] In order to solve the above problems in the prior art, the present invention provides a highly transparent copolymerized polypropylene resin and a preparation method thereof.

[0007] In the first aspect, the present invention provides a highly transparent copolymerized polypropylene resin, which comprises a propylene-butene copolymerized polypropylene and a compounding auxiliary agent; based on the mass of the highly transparent copolymerized polypropylene resin, the content of 1-butene units is 4.8 to 13.7 wt%, and the content of n-hexane extract is 0.38 to 1.10 wt%; the melt mass flow rate of the resin is 5 to 10 g / 10 min (190° C., 2.16 kg).

[0008] As a specific embodiment of the present invention, the compounding auxiliary agent includes a primary antioxidant, an auxiliary antioxidant, a halogen absorber and a nucleating agent; the primary antioxidant is a hindered phenol antioxidant, preferably pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate; the auxiliary antioxidant is a phosphite antioxidant, preferably tris(2,4-di-tert-butylphenyl) phosphite; the halogen absorber is a calcium stearate halogen absorber; the nucleating agent is a sorbitol-type nucleating agent;

[0009] As a specific embodiment of the present invention, the resin is calculated based on the mass of the high-transparent copolymer polypropylene resin, wherein the propylene-butane copolymer polypropylene is 98.5-99.5%, and the compounding auxiliary agent is 0.5-1.5%; wherein, the main antioxidant is 0.1-0.5%, the auxiliary antioxidant is 0.1-0.5%, the halogen absorber is 0.01-0.5%, and the nucleating agent is 0.01-0.3%.

[0010] In a second aspect, the present invention provides a method for preparing a highly transparent copolymerized polypropylene resin, comprising the following steps:

[0011] S1: copolymerizing propylene and 1-butene in the liquid phase in the presence of hydrogen, an external electron donor, and a Ziegler-Natta catalyst system to obtain propylene-butene copolymerized polypropylene;

[0012] S2: Add compounding auxiliary agents to the propylene copolymerized polypropylene obtained in step S1, extrude and granulate, and prepare a highly transparent copolymerized polypropylene resin.

[0013] As a specific embodiment of the present invention, in step S1, the mass ratio of 1-butene / propylene is (1-40):(60-99), preferably (5-30):(70-95);

[0014] As a specific embodiment of the present invention, the polymerization reaction temperature is 60°C to 80°C, preferably 65°C to 75°C.

[0015] As a specific embodiment of the present invention, in step S1, the Ziegler-Natta catalyst system includes a main catalyst and a co-catalyst; the main catalyst comprises a titanium tetrachloride / magnesium dichloride spherical catalyst having an ester or ether internal electron donor, such as diisobutyl phthalate, preferably an ester internal electron donor; more preferably, the main catalyst is MgCl2 / TiCl4 / Diester, wherein Mg = 17.2%, Ti = 2.5%, and internal electron donor = 9.8%;

[0016] As a specific embodiment of the present invention, the co-catalyst is an organoaluminum compound; preferably, the organoaluminum compound is one of trimethylaluminum, triethylaluminum, and triisobutylaluminum, preferably triethylaluminum.

[0017] As a specific embodiment of the present invention, the amount of the Ziegler-Natta catalyst system added is based on an activity of 40,000 g PP / g cat.

[0018] As a specific embodiment of the present invention, in step S1, the external electron donor is a siloxane compound; the external electron donor is selected from at least one of isobutyltriethoxysilane, diisopropyldimethoxysilane, diisopropyldimethoxysilane, and cyclohexylmethyldimethoxysilane, preferably diisopropyldimethoxysilane.

[0019] As a specific embodiment of the present invention, the mass ratio of the co-catalyst to the main catalyst is (10-1000):1, preferably (20-200):1, calculated on the basis of the mass of aluminum / titanium.

[0020] As a specific embodiment of the present invention, the molar ratio of the co-catalyst to the external electron donor is (1-50):1, preferably (5-25):1, calculated on the basis of aluminum / silicon moles.

[0021] As a specific embodiment of the present invention, in step S2, the compounded auxiliary agent includes a primary antioxidant, a secondary antioxidant, a halogen absorber and a nucleating agent; the primary antioxidant is a hindered phenol antioxidant, including but not limited to pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; the secondary antioxidant is a phosphite antioxidant, including but not limited to tris(2,4-di-tert-butylphenyl)phosphite; the halogen absorber is a calcium stearate halogen absorber; and the nucleating agent is a sorbitol-type nucleating agent.

[0022] As a specific embodiment of the present invention, in the step S2, the prepared high-transparency copolymer polypropylene resin has a propylene-butane copolymer polypropylene content of 98.5% to 99.5% and a compounding auxiliary agent content of 0.5% to 1.5%, based on the mass of the high-transparency copolymer polypropylene resin; wherein the primary antioxidant accounts for 0.1% to 0.5%, the auxiliary antioxidant accounts for 0.1% to 0.5%, the halogen absorber accounts for 0.01% to 0.5%, and the nucleating agent accounts for 0.01% to 0.3%.

[0023] As a specific embodiment of the present invention, in step S2, the extrusion granulation temperature is 180-250°C.

[0024] The above raw materials in the present invention can be prepared in-house or purchased commercially, and the present invention is not particularly limited thereto.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The method for preparing high-transparency copolymer polypropylene of the present invention prepares high-transparency copolymer polypropylene with low n-hexane extract by optimizing the Ziegler-Natta catalyst system, the amount of external electron donor and the 1-butene / propylene feed ratio, and selects di(3,4-dimethylbenzylidene)sorbitol as a nucleating agent, which significantly improves the transparency of the polypropylene.

[0027] 2. Transparent polypropylene produced by existing technology, either by adding a large amount of nucleating agent to homopolymer polypropylene or using ethylene-propylene copolymer polypropylene as the matrix, may have the problem of additive precipitation or high n-hexane extractives, which affects the application of transparent polypropylene materials in the fields of medical and food packaging.

[0028] 3. The highly transparent copolymer polypropylene prepared by the present invention uses 1-butene as a comonomer, has lower hexane extracts than ethylene-propylene copolymer polypropylene, and the amount of nucleating agent used is much lower than that of homopolymer polypropylene. It also has higher transparency and gloss, showing greater performance and cost advantages. DETAILED DESCRIPTION

[0029] The present invention will be further described below with reference to specific examples, but they do not constitute any limitation to the present invention.

[0030] In each embodiment of the present invention, the specific information of the reagents used is as follows:

[0031] Propylene: polymer grade, Maoming Petrochemical Co., Ltd.;

[0032] 1-Butene: polymerization grade, Maoming Petrochemical Co., Ltd.;

[0033] Triethylaluminum: 1.0 mol / L (toluene solvent), Anaiji Chemical;

[0034] Diisopropyldimethoxysilane: purity ≥95%, Anaiji Chemical;

[0035] Main catalyst C1: MgCl2 / TiCl4 / Diester, Mg = 16.1%, Ti = 2.8%, internal electron donor diisobutyl phthalate = 10.7%; the amount of main catalyst added is based on an activity of 40,000 g PP / g cat.

[0036] The n-hexane extract was tested and analyzed in accordance with the provisions of GB / T5009.71-2003 "Analytical Methods for Hygienic Standards of Polypropylene Resins for Food Packaging".

[0037] Example 1

[0038] This embodiment provides a highly transparent copolymerized polypropylene resin and a preparation method thereof, the specific details of which are as follows:

[0039] S1: Propylene, 1-butene, triethylaluminum, and diisopropyldimethoxysilane were added sequentially to a kettle reactor and stirred at room temperature for 30 minutes to remove impurities. The mass ratio of propylene to 1-butene was 94.8:5.2, the molar ratio of triethylaluminum to diisopropyldimethoxysilane was 10:1, and the propylene to triethylaluminum ratio (wt%) was 1000:0.16.

[0040] S2: hydrogen and main catalyst C1 were added to the mixture in step S1 to carry out propylene / 1-butene copolymerization reaction, with a hydrogen concentration of 500 ppm, a triethylaluminum / main catalyst C1 mass ratio of 20:1, and a reaction temperature of 70°C to obtain polypropylene powder.

[0041] S3: The polypropylene powder obtained in step S2 is mixed with a compounding auxiliary agent. The mixture comprises the following components by mass: 99.57% copolymerized polypropylene powder, 0.1% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 0.05% tris(2,4-di-tert-butylphenyl) phosphite, 0.08% calcium stearate, and 0.2% di(3,4-dimethylbenzylidene) sorbitol.

[0042] S4: The mixture in step S3 is extruded through an extruder with a barrel temperature of 200°C and a cooling water temperature of 50°C to obtain a high-transparency copolymerized polypropylene having a melt mass flow rate of 5.5 g / 10 min (190°C, 2.16 kg), a 1-butene unit content of 4.8%, and an n-hexane extract content of 0.38%.

[0043] Example 2

[0044] This embodiment provides a highly transparent copolymerized polypropylene resin and a preparation method thereof, the specific details of which are as follows:

[0045] S1: Propylene, 1-butene, triethylaluminum, and diisopropyldimethoxysilane were added sequentially to a kettle reactor and stirred at room temperature for 30 minutes to remove impurities. The mass ratio of propylene to 1-butene was 90.1 / 9.9, the molar ratio of triethylaluminum to diisopropyldimethoxysilane was 10:1, and the propylene to triethylaluminum ratio (wt%) was 1000:0.16.

[0046] S2: hydrogen and main catalyst C1 were added to the mixture in step S1 to carry out propylene / 1-butene copolymerization reaction, with a hydrogen concentration of 500 ppm, a triethylaluminum / main catalyst C1 mass ratio of 20:1, and a reaction temperature of 70°C to obtain polypropylene powder.

[0047] S3: The polypropylene powder obtained in step S2 is mixed with a compounding auxiliary agent. The mixture comprises the following components by mass: 99.57% copolymerized polypropylene powder, 0.1% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 0.05% tris(2,4-di-tert-butylphenyl) phosphite, 0.08% calcium stearate, and 0.2% di(3,4-dimethylbenzylidene) sorbitol.

[0048] S4: The mixture in step S3 is extruded through an extruder with a barrel temperature of 200° C. and a cooling water temperature of 50° C. to prepare a high-transparency copolymer polypropylene with a melt mass flow rate of 5.9 g / 10 min, a 1-butene content of 9.2%, and an n-hexane extract content of 0.70%.

[0049] Example 3

[0050] This embodiment provides a highly transparent copolymerized polypropylene resin and a preparation method thereof, the specific details of which are as follows:

[0051] S1: Propylene, 1-butene, triethylaluminum, and diisopropyldimethoxysilane were added sequentially to a kettle reactor and stirred at room temperature for 30 minutes to remove impurities. The mass ratio of propylene to 1-butene was 87.3 / 12.7, the molar ratio of triethylaluminum to diisopropyldimethoxysilane was 10:1, and the propylene to triethylaluminum (wt%) ratio was 1000:0.16.

[0052] S2: Add hydrogen and main catalyst C1 system to the mixture in step S1 to carry out propylene / 1-butene copolymerization reaction, with a hydrogen concentration of 1000 ppm, a triethylaluminum / main catalyst C1 mass ratio of 20:1, and a reaction temperature of 70°C to obtain polypropylene powder.

[0053] S3: The polypropylene powder obtained in step S2 is mixed with a compounding auxiliary agent. The mixture comprises the following components by mass: 99.57% copolymerized polypropylene powder, 0.1% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 0.05% tris(2,4-di-tert-butylphenyl) phosphite, 0.08% calcium stearate, and 0.2% di(3,4-dimethylbenzylidene) sorbitol.

[0054] S4: The mixture in step S3 is extruded through an extruder with a barrel temperature of 200° C. and a cooling water temperature of 50° C. to prepare a high-transparency copolymerized polypropylene with a melt mass flow rate of 8.9 g / 10 min, a 1-butene content of 11.5%, and an n-hexane extract content of 0.93%.

[0055] Example 4

[0056] This embodiment provides a highly transparent copolymerized polypropylene resin and a preparation method thereof, the specific details of which are as follows:

[0057] S1: Propylene, 1-butene, triethylaluminum, and diisopropyldimethoxysilane were added sequentially to a kettle reactor and stirred at room temperature for 30 minutes to remove impurities. The mass ratio of propylene / 1-butene was 84.8 / 15.2, the molar ratio of triethylaluminum / diisopropyldimethoxysilane was 10:1, and the propylene / triethylaluminum (wt%) ratio was 1000:0.16.

[0058] S2: hydrogen and main catalyst C1 were added to the mixture in step S1 to carry out propylene / 1-butene copolymerization reaction, with a hydrogen concentration of 500 ppm, a triethylaluminum / main catalyst C1 mass ratio of 20:1, and a reaction temperature of 70°C to obtain polypropylene powder.

[0059] S3: The polypropylene powder obtained in step S2 is mixed with a compounding auxiliary agent. The mixture comprises the following components by mass: 99.57% copolymerized polypropylene powder, 0.1% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 0.05% tris(2,4-di-tert-butylphenyl) phosphite, 0.08% calcium stearate, and 0.2% di(3,4-dimethylbenzylidene) sorbitol.

[0060] S4: The mixture in step S3 is extruded through an extruder with a barrel temperature of 200° C. and a cooling water temperature of 50° C. to obtain a high-transparency copolymerized polypropylene having a melt mass flow rate of 5.6 g / 10 min, a 1-butene content of 13.4%, and an n-hexane extract content of 1.06%.

[0061] Example 5

[0062] This embodiment provides a highly transparent copolymerized polypropylene resin and a preparation method thereof, the specific details of which are as follows:

[0063] S1: Propylene, 1-butene, triethylaluminum, and diisopropyldimethoxysilane were added sequentially to a kettle reactor and stirred at room temperature for 30 minutes to remove impurities. The mass ratio of propylene / 1-butene was 85.0 / 15.0, the molar ratio of triethylaluminum / diisopropyldimethoxysilane was 8:1, and the propylene / triethylaluminum (wt%) ratio was 1000:0.16.

[0064] S2: hydrogen and main catalyst C1 were added to the mixture in step S1 to carry out propylene / 1-butene copolymerization reaction, with a hydrogen concentration of 600 ppm, a triethylaluminum / main catalyst C1 mass ratio of 20:1, and a reaction temperature of 70°C to obtain polypropylene powder.

[0065] S3: The polypropylene powder obtained in step S2 is mixed with a compounding auxiliary agent. The mixture comprises the following components by mass: 99.57% copolymerized polypropylene powder, 0.1% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 0.05% tris(2,4-di-tert-butylphenyl) phosphite, 0.08% calcium stearate, and 0.2% di(3,4-dimethylbenzylidene) sorbitol.

[0066] S4: The mixture in step S3 is extruded through an extruder with a barrel temperature of 200° C. and a cooling water temperature of 50° C. to obtain a high-transparency copolymerized polypropylene having a melt mass flow rate of 6.1 g / 10 min, a 1-butene content of 13.7%, and an n-hexane extract content of 1.10%.

[0067] Example 6

[0068] This embodiment provides a highly transparent copolymerized polypropylene resin and a preparation method thereof, the specific details of which are as follows:

[0069] S1: Propylene, 1-butene, triethylaluminum, and diisopropyldimethoxysilane were added sequentially to a kettle reactor and stirred at room temperature for 30 minutes to remove impurities. The mass ratio of propylene to 1-butene was 85.3 / 14.7, the molar ratio of triethylaluminum to diisopropyldimethoxysilane was 10:1, and the propylene / triethylaluminum (wt%) ratio was 1000:0.16.

[0070] S2: hydrogen and main catalyst C1 were added to the mixture in step S1 to carry out propylene / 1-butene copolymerization reaction, with a hydrogen concentration of 600 ppm, a triethylaluminum / main catalyst C1 mass ratio of 20:1, and a reaction temperature of 70°C to obtain polypropylene powder.

[0071] S3: The polypropylene powder obtained in step S2 is mixed with a compounding auxiliary agent. The mixture comprises the following components by mass: 99.52% copolymerized polypropylene powder, 0.1% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 0.05% tris(2,4-di-tert-butylphenyl) phosphite, 0.08% calcium stearate, and 0.25% di(3,4-dimethylbenzylidene) sorbitol.

[0072] S4: The mixture in step S3 is extruded through an extruder with a barrel temperature of 200° C. and a cooling water temperature of 50° C. to prepare a high-transparency copolymerized polypropylene with a melt mass flow rate of 6.4 g / 10 min, a 1-butene content of 13.1%, and an n-hexane extract content of 1.02%.

[0073] Example 7

[0074] This embodiment provides a highly transparent copolymerized polypropylene resin and a preparation method thereof, the specific details of which are as follows:

[0075] S1: Propylene, 1-butene, triethylaluminum, and diisopropyldimethoxysilane were added sequentially to a kettle reactor and stirred at room temperature for 30 minutes to remove impurities. The mass ratio of propylene / 1-butene was 85.0 / 15.0, the molar ratio of triethylaluminum / diisopropyldimethoxysilane was 15:1, and the propylene / triethylaluminum (wt%) ratio was 1000:0.16.

[0076] S2: hydrogen and main catalyst C1 were added to the mixture in step S1 to carry out propylene / 1-butene copolymerization reaction, with a hydrogen concentration of 600 ppm, a triethylaluminum / main catalyst C1 mass ratio of 40:1, and a reaction temperature of 70°C to obtain polypropylene powder.

[0077] S3: The polypropylene powder obtained in step S2 is mixed with a compounding auxiliary agent. The mixture comprises the following components by mass: 99.57% copolymerized polypropylene powder, 0.1% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 0.05% tris(2,4-di-tert-butylphenyl) phosphite, 0.08% calcium stearate, and 0.2% di(3,4-dimethylbenzylidene) sorbitol.

[0078] S4: The mixture in step S3 is extruded through an extruder with a barrel temperature of 200° C. and a cooling water temperature of 50° C. to obtain a high-transparency copolymerized polypropylene having a melt mass flow rate of 8.7 g / 10 min, a 1-butene content of 12.1%, and an n-hexane extract content of 1.16%.

[0079] Example 8

[0080] This embodiment provides a highly transparent copolymerized polypropylene resin and a preparation method thereof, the specific details of which are as follows:

[0081] S1: Propylene, 1-butene, triethylaluminum, and diisopropyldimethoxysilane were added sequentially to a kettle reactor and stirred at room temperature for 30 minutes to remove impurities. The mass ratio of propylene / 1-butene was 85.0 / 15.0, the molar ratio of triethylaluminum / diisopropyldimethoxysilane was 20:1, and the propylene / triethylaluminum (wt%) ratio was 1000:0.16.

[0082] S2: hydrogen and main catalyst C1 were added to the mixture in step S1 to carry out propylene / 1-butene copolymerization reaction, with a hydrogen concentration of 600 ppm, a triethylaluminum / main catalyst C1 mass ratio of 70:1, and a reaction temperature of 70°C to obtain polypropylene powder.

[0083] S3: The polypropylene powder obtained in step S2 is mixed with a compounding auxiliary agent. The mixture comprises the following components by mass: 99.57% copolymerized polypropylene powder, 0.1% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 0.05% tris(2,4-di-tert-butylphenyl) phosphite, 0.08% calcium stearate, and 0.2% di(3,4-dimethylbenzylidene) sorbitol.

[0084] S4: The mixture in step S3 is extruded through an extruder with a barrel temperature of 200° C. and a cooling water temperature of 50° C. to obtain a high-transparency copolymerized polypropylene having a melt mass flow rate of 9.8 g / 10 min, a 1-butene content of 11.7%, and an n-hexane extract content of 1.13%.

[0085] Example 9

[0086] This embodiment provides a highly transparent copolymerized polypropylene resin and a preparation method thereof, the specific details of which are as follows:

[0087] S1: Propylene, 1-butene, triethylaluminum, and diisopropyldimethoxysilane were added sequentially to a kettle reactor and stirred at room temperature for 30 minutes to remove impurities. The mass ratio of propylene / 1-butene was 85.0 / 15.0, the molar ratio of triethylaluminum / diisopropyldimethoxysilane was 5:1, and the propylene / triethylaluminum (wt%) ratio was 1000:0.16.

[0088] S2: hydrogen and main catalyst C1 were added to the mixture in step S1 to carry out propylene / 1-butene copolymerization reaction, with a hydrogen concentration of 600 ppm, a triethylaluminum / main catalyst C1 mass ratio of 150:1, and a reaction temperature of 70°C to obtain polypropylene powder.

[0089] S3: The polypropylene powder obtained in step S2 is mixed with a compounding auxiliary agent. The mixture comprises the following components by mass: 99.57% copolymerized polypropylene powder, 0.1% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 0.05% tris(2,4-di-tert-butylphenyl) phosphite, 0.08% calcium stearate, and 0.2% di(3,4-dimethylbenzylidene) sorbitol.

[0090] S4: The mixture in step S3 is extruded through an extruder with a barrel temperature of 200° C. and a cooling water temperature of 50° C. to obtain a high-transparency copolymerized polypropylene having a melt mass flow rate of 9.5 g / 10 min, a 1-butene content of 11.9%, and an n-hexane extract content of 1.15%.

[0091] Comparative Example 1

[0092] This comparative example provides a copolymerized polypropylene and a preparation method thereof, the specific details of which are as follows:

[0093] S1: Propylene, triethylaluminum, and diisopropyldimethoxysilane were added sequentially to a kettle reactor and stirred at room temperature for 30 minutes to remove impurities. The molar ratio of triethylaluminum to diisopropyldimethoxysilane was 10:1.

[0094] S2: hydrogen and main catalyst C1 were added to the mixture in step S1 to carry out propylene polymerization reaction, with a hydrogen concentration of 500 ppm, a triethylaluminum / main catalyst C1 mass ratio of 20:1, and a reaction temperature of 70°C to obtain polypropylene powder.

[0095] S3: The polypropylene powder obtained in step S2 is mixed with a compounding auxiliary agent. The mixture comprises the following components by mass: 99.57% copolymerized polypropylene powder, 0.1% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 0.05% tris(2,4-di-tert-butylphenyl) phosphite, 0.08% calcium stearate, and 0.2% di(3,4-dimethylbenzylidene) sorbitol.

[0096] S4: The mixture in step S3 is extruded through an extruder with a barrel temperature of 200° C. and a cooling water temperature of 50° C. to prepare a homopolypropylene with a melt mass flow rate of 6.8 g / 10 min.

[0097] Comparative Example 2

[0098] This comparative example provides a copolymerized polypropylene and a preparation method thereof, the specific details of which are as follows:

[0099] S1: Ethylene, propylene, triethylaluminum, and diisopropyldimethoxysilane were added sequentially to a kettle reactor and stirred at room temperature for 30 minutes to remove impurities. The mass ratio of ethylene to propylene was 95.3 / 4.7, and the molar ratio of triethylaluminum to diisopropyldimethoxysilane was 10:1.

[0100] S2: hydrogen and main catalyst C1 were added to the mixture in step S1 to carry out ethylene / propylene copolymerization reaction, with a hydrogen concentration of 500 ppm, a triethylaluminum / main catalyst C1 mass ratio of 20:1, and a reaction temperature of 70°C to obtain polypropylene powder.

[0101] S3: The polypropylene powder obtained in step S2 is mixed with a compounding auxiliary agent. The mixture comprises the following components by mass: 99.52% copolymerized polypropylene powder, 0.1% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 0.05% tris(2,4-di-tert-butylphenyl) phosphite, 0.08% calcium stearate, and 0.2% di(3,4-dimethylbenzylidene) sorbitol.

[0102] S4: The mixture in step S3 is extruded through an extruder with a barrel temperature of 200° C. and a cooling water temperature of 50° C. to prepare ethylene-propylene copolymer polypropylene with a melt mass flow rate of 6.3 g / 10 min, an ethylene content of 4.5%, and an n-hexane extract content of 2.50%.

[0103] Comparative Example 3

[0104] This comparative example provides a copolymerized polypropylene and a preparation method thereof, the specific details of which are as follows:

[0105] S1: Propylene, 1-butene, triethylaluminum, and diisopropyldimethoxysilane were added sequentially to a kettle reactor and stirred at room temperature for 30 minutes to remove impurities. The mass ratio of propylene to 1-butene was 87.5 / 12.5, and the molar ratio of triethylaluminum to diisopropyldimethoxysilane was 15:1.

[0106] S2: Hydrogen and main catalyst C2 (MgCl2 / TiCl4 / Diester, Mg=6.6%, Ti=1.0%, internal electron donor di-n-butyl phthalate=6.6%) were added to the mixture in step S1 to carry out propylene polymerization reaction, with a hydrogen concentration of 500 ppm, a triethylaluminum / main catalyst mass ratio of 20:1, and a reaction temperature of 70°C to obtain polypropylene powder.

[0107] S3: The polypropylene powder obtained in step S2 is mixed with a compounding auxiliary agent. The mixture comprises the following components by mass: 99.57% copolymerized polypropylene powder, 0.1% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 0.05% tris(2,4-di-tert-butylphenyl) phosphite, 0.08% calcium stearate, and 0.2% di(3,4-dimethylbenzylidene) sorbitol.

[0108] S4: The mixture in step S3 is extruded through an extruder with a barrel temperature of 200° C. and a cooling water temperature of 50° C. to prepare a copolymerized polypropylene having a melt mass flow rate of 9.1 g / 10 min, a 1-butene content of 7.4%, and an n-hexane extract content of 1.08%.

[0109] The parameters and properties of the highly transparent copolymerized polypropylene resins prepared in Examples 1-6 and Comparative Examples 1-3 are shown in Table 1:

[0110] Table 1 Parameters and performance test results of Examples 1-6 and Comparative Examples 1-2

[0111]

[0112] As can be seen from Examples 1-6, the present invention prepares propylene / 1-butene copolymerized polypropylene through a kettle polymerization process. By adjusting the polymerization process parameters, optimizing the catalyst system and external electron donor, a polypropylene material with high transparency and low precipitation can be obtained by adding a small amount of nucleating agent.

[0113] From the results of Example 1 and Comparative Examples 1 and 2, it can be seen that compared with homopolypropylene and ethylene-propylene copolymer, the propylene-butyl copolymer polypropylene of the present invention has higher transparency and lower n-hexane extracts, thereby improving the comprehensive performance of the polypropylene resin.

[0114] From the results of Example 3 and Comparative Example 3, it can be seen that compared with Ziegler-Natta catalyst C2, under the same propylene / 1-butene feed conditions, the propylene-butene copolymer polypropylene prepared by the preferred Ziegler-Natta catalyst C1 has higher transparency and lower n-hexane extracts.

[0115] In summary, the method for preparing high-transparency copolymer polypropylene of the present invention prepares copolymer polypropylene with high transparency and low n-hexane extract by optimizing the Ziegler-Natta catalyst system, the amount of external electron donor and the 1-butene / propylene feed ratio, and selects di(3,4-dimethylbenzylidene)sorbitol as a nucleating agent, which significantly improves the transparency of polypropylene.

[0116] Any numerical value mentioned in the present invention includes all values ​​that increase by one unit each time from the lowest value to the highest value if there is only a gap of two units between any minimum value and any maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, time, etc. is stated to be 50-90, it is meant in this specification to specifically list values ​​such as 51-89, 52-88... and 69-71 and 70-71. For non-integer values, it is appropriate to consider units of 0.1, 0.01, 0.001 or 0.0001. These are just some special examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed lowest value and the listed highest value are considered to have been disclosed.

[0117] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of 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 words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A highly transparent copolymer polypropylene resin, characterized in that: The resin comprises propylene-butylene copolymerized polypropylene and a compounding auxiliary agent; based on the mass of the highly transparent copolymerized polypropylene resin, the content of 1-butene units is 4.8-13.7wt%, and the content of n-hexane extract is 0.38-1.10wt%; the melt mass flow rate of the resin is 5-10g / 10min (190°C, 2.16Kg).

2. The highly transparent copolymerized polypropylene resin according to claim 1, characterized in that: The compounding auxiliary agent comprises a primary antioxidant, an auxiliary antioxidant, a halogen absorber and a nucleating agent; the primary antioxidant is a hindered phenol antioxidant, preferably pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate; the auxiliary antioxidant is a phosphite antioxidant, preferably tris(2,4-di-tert-butylphenyl) phosphite; the halogen absorber is a calcium stearate halogen absorber; the nucleating agent is a sorbitol nucleating agent; The resin, based on the mass of the highly transparent copolymerized polypropylene resin, has a content of 98.5-99.5% of propylene-butyl copolymerized polypropylene and a content of 0.5-1.5% of compounding auxiliary agents; wherein the main antioxidant accounts for 0.1-0.5%, the auxiliary antioxidant accounts for 0.1-0.5%, the halogen absorber accounts for 0.01-0.5%, and the nucleating agent accounts for 0.01-0.3%.

3. A method for preparing the highly transparent copolymerized polypropylene resin according to claim 1 or 2, characterized in that: The following steps are involved: S1: copolymerizing a liquid phase containing propylene and 1-butene in the presence of hydrogen, an external electron donor and a Ziegler-Natta catalyst system to obtain propylene-butene copolymerized polypropylene; S2: Add compounding auxiliary agents to the propylene-butane copolymer polypropylene obtained in step S1, extrude and granulate, and prepare a highly transparent copolymer polypropylene resin.

4. The preparation method according to claim 3, characterized in that: In the step S1, the mass ratio of 1-butene to propylene is (1-40):(60-99), preferably (5-30):(70-95); And / or the polymerization reaction temperature is 60°C to 80°C, preferably 65°C to 75°C.

5. The preparation method according to claim 3 or 4, characterized in that: In step S1, the Ziegler-Natta catalyst system includes a main catalyst and a co-catalyst; the main catalyst comprises a titanium tetrachloride / magnesium dichloride spherical catalyst having an ester or ether internal electron donor, such as diisobutyl phthalate, preferably an ester internal electron donor; more preferably, the main catalyst is MgCl2 / TiCl4 / Diester, wherein Mg=17.2%, Ti=2.5%, and internal electron donor=9.8%; The co-catalyst is an organic aluminum compound; preferably, the organic aluminum compound is one of trimethyl aluminum, triethyl aluminum, and triisobutyl aluminum, preferably triethyl aluminum.

6. The preparation method according to any one of claims 3 to 5, characterized in that: In the step S1, the external electron donor is a siloxane compound; the external electron donor is selected from at least one of isobutyltriethoxysilane, diisopropyldimethoxysilane, diisopropyldimethoxysilane, and cyclohexylmethyldimethoxysilane, preferably diisopropyldimethoxysilane.

7. The preparation method according to any one of claims 3 to 6, characterized in that: Calculated by the mass of aluminum / titanium, the mass ratio of the co-catalyst to the main catalyst is (10-1000):1, preferably (20-200):

1.

8. The preparation method according to any one of claims 3 to 7, characterized in that: The molar ratio of the co-catalyst to the external electron donor is (1-50):1, preferably (5-25):1, calculated on the basis of aluminum / silicon moles.

9. The preparation method according to any one of claims 3 to 8, characterized in that: In step S2, the compounded auxiliary agent includes a primary antioxidant, an auxiliary antioxidant, a halogen absorber and a nucleating agent; the primary antioxidant is a hindered phenol antioxidant, preferably pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate; the auxiliary antioxidant is a phosphite antioxidant, preferably tris(2,4-di-tert-butylphenyl) phosphite; the halogen absorber is a calcium stearate halogen absorber; and the nucleating agent is a sorbitol nucleating agent; And / or the prepared high-transparency copolymer polypropylene resin, based on the mass of the high-transparency copolymer polypropylene resin, has a content of propylene-butyl copolymer polypropylene of 98.5-99.5% and a content of compounding auxiliary agents of 0.5-1.5%; wherein the primary antioxidant accounts for 0.1-0.5%, the auxiliary antioxidant accounts for 0.1-0.5%, the halogen absorber accounts for 0.01-0.5%, and the nucleating agent accounts for 0.01-0.3%.

10. The preparation method according to any one of claims 3 to 9, characterized in that: In the step S2, the extrusion granulation temperature is 180-250°C.

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