Highly transparent copolymerized polypropylene resin and method for preparing the same

Abstract

The application provides a kind of high transparency copolymerized polypropylene and its preparation method.The high transparency copolymerized polypropylene of the application has melt mass-flow rate of 5-10 g / 10 min, 1-butene content of 4.8-13.7 wt%, and n-hexane extract of 0.38-1.10 wt%.The application improves 1-butene content in copolymerized polypropylene by optimizing Ziegler-Natta catalyst system, and selects di(3,4-dimethyl benzyl) sorbitol nucleating agent, to obtain copolymerized polypropylene material with high transparency and low segregation under a small amount of addition.

Description

Technical Field

[0001] This invention belongs to the field of polypropylene material technology, specifically relating to a high-transparency copolymer polypropylene resin and its preparation method. Background Technology

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

[0003] Currently, most high-transparency and high-gloss transparent polypropylene products on the market are obtained by modifying them with transparent nucleating agents. However, transparent nucleating agents are expensive, and high addition amounts significantly increase the cost of polypropylene materials. Furthermore, with the improvement of people's living standards, the concept of green and healthy products is being promoted in fields such as baby products, food packaging, and medical devices, making improved hygiene, safety, and non-toxicity an inevitable trend and key. By copolymerizing a second monomer onto the polypropylene molecular chain, the regularity of the polypropylene molecular chain segments can be disrupted, thereby destroying its crystallinity and improving transparency. If the embedding effect is good enough, the use of transparent nucleating agents can be greatly reduced, and even high-transparency polypropylene materials can be prepared without relying on nucleating agents.

[0004] Compared to ethylene, 1-butene, as the second monomer in the copolymerization with propylene, results in copolymers with higher transparency and lower hexane extract, making them safer for contact with food and pharmaceuticals. Increasing the 1-butene content in the copolymer not only reduces crystallinity and crystal size, increasing transparency and gloss, but also lowers processing temperature and reduces energy consumption for enterprises.

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

[0006] To address the aforementioned problems in the prior art, this invention proposes a highly transparent copolymer polypropylene resin and its preparation method.

[0007] In a first aspect, the present invention provides a high-transparency copolymer polypropylene resin, which comprises propylene-butadiene copolymer polypropylene and compounding additives; based on the mass of the high-transparency copolymer 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 flow rate of the resin is 5 to 10 g / 10 min (190 °C, 2.16 kg).

[0008] In a specific embodiment of the present invention, the compound adjuvant includes a primary antioxidant, a secondary antioxidant, a halogen absorber, and a nucleating agent; the primary antioxidant is a hindered phenolic antioxidant, preferably pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; the secondary 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-type nucleating agent.

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

[0010] Secondly, the present invention provides a method for preparing a highly transparent copolymer polypropylene resin, comprising the following steps:

[0011] S1: Propylene and 1-butene in liquid phase bulk form are copolymerized in the presence of hydrogen, external electron donor and Ziegler-Natta catalyst system to obtain propylene-butene copolymer polypropylene.

[0012] S2: Add compounding agents to the propylene-butadiene copolymer polypropylene obtained in step S1, and extrude and granulate to prepare a highly transparent copolymer 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℃~80℃, preferably 65℃~75℃.

[0015] In 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 contains an ester or ether internal electron donor, such as diisobutyl phthalate, preferably a titanium tetrachloride / magnesium dichloride spherical catalyst with 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] In 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, with triethylaluminum being the most preferred.

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

[0018] In 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, based on the mass of aluminum / titanium, is (10-1000):1, preferably (20-200):1.

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

[0021] In a specific embodiment of the present invention, in step S2, the compounding adjuvant includes a primary antioxidant, a secondary antioxidant, a halogen absorber, and a nucleating agent; the primary antioxidant is a hindered phenolic 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] In a specific embodiment of the present invention, in step S2, the high-transparency copolymer polypropylene resin obtained has a propylene-butadiene copolymer polypropylene content of 98.5% to 99.5% and a compounding agent content of 0.5% to 1.5% by mass; wherein, the main 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] In a specific embodiment of the present invention, in step S2, the extrusion granulation temperature is 180-250°C.

[0024] All of the above-mentioned raw materials used in this invention can be prepared in-house or purchased commercially; this invention does not impose any particular limitations on them.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

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

[0027] 2. Existing technologies for producing transparent polypropylene, whether by adding a large amount of nucleating agent to homopolymer polypropylene or by using ethylene-propylene copolymer polypropylene as the matrix, all suffer from issues such as additive precipitation or high levels of n-hexane extract, which affect the application of transparent polypropylene materials in the fields of medical and food packaging.

[0028] 3. The high-transparency copolymer polypropylene prepared by this invention uses 1-butene as the comonomer, which has a lower hexane extract content than ethylene-propylene copolymer polypropylene, and the amount of nucleating agent is much lower than that of homopolymer polypropylene. It also has higher transparency and gloss, showing greater performance and cost advantages. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation on the present invention.

[0030] The specific information of the reagents used in the various embodiments of the present invention is as follows:

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

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

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

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

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

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

[0037] Example 1

[0038] This embodiment provides a highly transparent copolymer polypropylene resin and its preparation method, with specific details as follows:

[0039] S1: Propylene, 1-butene, triethylaluminum, and diisopropyldimethoxysilane were added sequentially to a batch reactor and stirred at room temperature for 30 min 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 / triethylaluminum (wt%) ratio was 1000:0.16.

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

[0041] S3: Mix the polypropylene powder obtained in step S2 with compounding additives. The mixture, by mass fraction, comprises the following components: 99.57% copolymer 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-dimethylbenzylmethyl)sorbitol.

[0042] S4: The mixture from step S3 is extruded through an extruder. The temperature of each section of the extruder barrel is 200℃, and the cooling water temperature is 50℃. A high-transparency copolymer polypropylene with a melt mass flow rate of 5.5g / 10min (190℃, 2.16Kg), a 1-butene unit content of 4.8%, and a hexane extract of 0.38% is obtained.

[0043] Example 2

[0044] This embodiment provides a highly transparent copolymer polypropylene resin and its preparation method, with specific details as follows:

[0045] S1: Propylene, 1-butene, triethylaluminum, and diisopropyldimethoxysilane were added sequentially to a batch reactor and stirred at room temperature for 30 min 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 / triethylaluminum (wt%) ratio was 1000:0.16.

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

[0047] S3: Mix the polypropylene powder obtained in step S2 with compounding additives. The mixture, by mass fraction, comprises the following components: 99.57% copolymer 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-dimethylbenzylmethyl)sorbitol.

[0048] S4: The mixture from step S3 is extruded through an extruder. The temperature of each section of the extruder barrel is 200℃ and the cooling water temperature is 50℃. A highly transparent copolymer polypropylene with a melt mass flow rate of 5.9 g / 10 min, a 1-butene content of 9.2%, and a hexane extract of 0.70% is obtained.

[0049] Example 3

[0050] This embodiment provides a highly transparent copolymer polypropylene resin and its preparation method, with specific details as follows:

[0051] S1: Propylene, 1-butene, triethylaluminum, and diisopropyldimethoxysilane were added sequentially to a batch reactor and stirred at room temperature for 30 min 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 / triethylaluminum (wt%) ratio was 1000:0.16.

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

[0053] S3: Mix the polypropylene powder obtained in step S2 with compounding additives. The mixture, by mass fraction, comprises the following components: 99.57% copolymer 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-dimethylbenzylmethyl)sorbitol.

[0054] S4: The mixture from step S3 is extruded through an extruder. The temperature of each section of the extruder barrel is 200℃ and the cooling water temperature is 50℃. A highly transparent copolymer polypropylene with a melt mass flow rate of 8.9 g / 10 min, a 1-butene content of 11.5%, and a hexane extract of 0.93% is obtained.

[0055] Example 4

[0056] This embodiment provides a highly transparent copolymer polypropylene resin and its preparation method, with specific details as follows:

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

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

[0059] S3: Mix the polypropylene powder obtained in step S2 with compounding additives. The mixture, by mass fraction, comprises the following components: 99.57% copolymer 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-dimethylbenzylmethyl)sorbitol.

[0060] S4: The mixture from step S3 is extruded through an extruder. The temperature of each section of the extruder barrel is 200℃, and the cooling water temperature is 50℃. A highly transparent copolymer polypropylene with a melt mass flow rate of 5.6 g / 10 min, a 1-butene content of 13.4%, and a hexane extract of 1.06% is obtained.

[0061] Example 5

[0062] This embodiment provides a highly transparent copolymer polypropylene resin and its preparation method, with specific details as follows:

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

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

[0065] S3: Mix the polypropylene powder obtained in step S2 with compounding additives. The mixture, by mass fraction, comprises the following components: 99.57% copolymer 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-dimethylbenzylmethyl)sorbitol.

[0066] S4: The mixture from step S3 is extruded through an extruder. The temperature of each section of the extruder barrel is 200℃ and the cooling water temperature is 50℃. A highly transparent copolymer polypropylene with a melt mass flow rate of 6.1 g / 10 min, a 1-butene content of 13.7%, and a hexane extract of 1.10% is obtained.

[0067] Example 6

[0068] This embodiment provides a highly transparent copolymer polypropylene resin and its preparation method, with specific details as follows:

[0069] S1: Propylene, 1-butene, triethylaluminum, and diisopropyldimethoxysilane were added sequentially to a batch reactor and stirred at room temperature for 30 min 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: Add hydrogen and main catalyst C1 to the mixture in step S1 to carry out a propylene / 1-butene copolymerization reaction. The hydrogen concentration is 600 ppm, the mass ratio of triethylaluminum to main catalyst C1 is 20:1, and the reaction temperature is 70℃ to obtain polypropylene powder.

[0071] S3: Mix the polypropylene powder obtained in step S2 with the compounding additives. The mixture, by mass fraction, comprises the following components: 99.52% copolymer 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-dimethylbenzylmethyl)sorbitol.

[0072] S4: The mixture from step S3 is extruded through an extruder. The temperature of each section of the extruder barrel is 200℃ and the cooling water temperature is 50℃. A highly transparent copolymer polypropylene with a melt mass flow rate of 6.4 g / 10 min, a 1-butene content of 13.1%, and a hexane extract of 1.02% is obtained.

[0073] Example 7

[0074] This embodiment provides a highly transparent copolymer polypropylene resin and its preparation method, with specific details as follows:

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

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

[0077] S3: Mix the polypropylene powder obtained in step S2 with compounding additives. The mixture, by mass fraction, comprises the following components: 99.57% copolymer 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-dimethylbenzylmethyl)sorbitol.

[0078] S4: The mixture from step S3 is extruded through an extruder. The temperature of each section of the extruder barrel is 200℃ and the cooling water temperature is 50℃. A highly transparent copolymer polypropylene with a melt mass flow rate of 8.7g / 10min, a 1-butene content of 12.1%, and a hexane extract of 1.16% is obtained.

[0079] Example 8

[0080] This embodiment provides a highly transparent copolymer polypropylene resin and its preparation method, with specific details as follows:

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

[0082] S2: Add hydrogen and main catalyst C1 to the mixture in step S1 to carry out propylene / 1-butene copolymerization reaction. The hydrogen concentration is 600 ppm, the mass ratio of triethylaluminum to main catalyst C1 is 70:1, and the reaction temperature is 70℃ to obtain polypropylene powder.

[0083] S3: Mix the polypropylene powder obtained in step S2 with compounding additives. The mixture, by mass fraction, comprises the following components: 99.57% copolymer 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-dimethylbenzylmethyl)sorbitol.

[0084] S4: The mixture from step S3 is extruded through an extruder. The temperature of each section of the extruder barrel is 200℃, and the cooling water temperature is 50℃. A highly transparent copolymer polypropylene with a melt mass flow rate of 9.8 g / 10 min, a 1-butene content of 11.7%, and a hexane extract of 1.13% is obtained.

[0085] Example 9

[0086] This embodiment provides a highly transparent copolymer polypropylene resin and its preparation method, with specific details as follows:

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

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

[0089] S3: Mix the polypropylene powder obtained in step S2 with compounding additives. The mixture, by mass fraction, comprises the following components: 99.57% copolymer 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-dimethylbenzylmethyl)sorbitol.

[0090] S4: The mixture from step S3 is extruded through an extruder. The temperature of each section of the extruder barrel is 200℃, and the cooling water temperature is 50℃. A highly transparent copolymer polypropylene with a melt mass flow rate of 9.5g / 10min, a 1-butene content of 11.9%, and a hexane extract of 1.15% is obtained.

[0091] Comparative Example 1

[0092] This comparative example provides a copolymerized polypropylene and its preparation method, with specific details as follows:

[0093] S1: Propylene, triethylaluminum, and diisopropyldimethoxysilane are added sequentially to a batch reactor, and the mixture is stirred at room temperature for 30 minutes to remove impurities. The molar ratio of triethylaluminum to diisopropyldimethoxysilane is 10:1.

[0094] S2: Add hydrogen and main catalyst C1 to the mixture in step S1 to carry out propylene polymerization reaction. The hydrogen concentration is 500 ppm, the mass ratio of triethylaluminum to main catalyst C1 is 20:1, and the reaction temperature is 70℃ to obtain polypropylene powder.

[0095] S3: Mix the polypropylene powder obtained in step S2 with compounding additives. The mixture, by mass fraction, comprises the following components: 99.57% copolymer 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-dimethylbenzylmethyl)sorbitol.

[0096] S4: The mixture from step S3 is extruded through an extruder. The temperature of each section of the extruder barrel is 200℃ and the temperature of the cooling water is 50℃, to prepare homopolymer polypropylene with a melt mass flow rate of 6.8g / 10min.

[0097] Comparative Example 2

[0098] This comparative example provides a copolymerized polypropylene and its preparation method, with specific details as follows:

[0099] S1: Ethylene, propylene, triethylaluminum, and diisopropyldimethoxysilane were added sequentially to a batch reactor and stirred at room temperature for 30 min 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: Add hydrogen and main catalyst C1 to the mixture in step S1 to carry out ethylene / propylene copolymerization reaction. The hydrogen concentration is 500 ppm, the mass ratio of triethylaluminum to main catalyst C1 is 20:1, and the reaction temperature is 70℃ to obtain polypropylene powder.

[0101] S3: Mix the polypropylene powder obtained in step S2 with compounding additives. The mixture, by mass fraction, comprises the following components: 99.52% copolymer 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-dimethylbenzylmethyl)sorbitol.

[0102] S4: The mixture from step S3 is extruded through an extruder. The temperature of each section of the extruder barrel is 200℃, and the cooling water temperature is 50℃. This produces an ethylene-propylene copolymer polypropylene with a melt mass flow rate of 6.3 g / 10 min, an ethylene content of 4.5%, and a hexane extract of 2.50%.

[0103] Comparative Example 3

[0104] This comparative example provides a copolymerized polypropylene and its preparation method, with specific details as follows:

[0105] S1: Propylene, 1-butene, triethylaluminum, and diisopropyldimethoxysilane were added sequentially to a batch reactor and stirred at room temperature for 30 min 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%) are added to the mixture in step S1 to carry out propylene polymerization reaction. The hydrogen concentration is 500 ppm, the mass ratio of triethylaluminum to main catalyst is 20:1, and the reaction temperature is 70℃ to obtain polypropylene powder.

[0107] S3: Mix the polypropylene powder obtained in step S2 with compounding additives. The mixture, by mass fraction, comprises the following components: 99.57% copolymer 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-dimethylbenzylmethyl)sorbitol.

[0108] S4: The mixture from step S3 is extruded through an extruder. The temperature of each section of the extruder barrel is 200℃ and the cooling water temperature is 50℃. Copolymer polypropylene with a melt mass flow rate of 9.1 g / 10 min, a 1-butene content of 7.4%, and a hexane extract of 1.08% is obtained.

[0109] The parameters and properties of the high-transparency copolymer 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 copolymer polypropylene through batch polymerization process. By adjusting the polymerization process parameters and optimizing the catalyst system and external electron donor, a polypropylene material with high transparency and low precipitation can be obtained with a small amount of nucleating agent added.

[0113] As can be seen from the results of Example 1, Comparative Examples 1 and 2, compared with homopolymer polypropylene and ethylene-propylene copolymer, the propylene-butadiene copolymer polypropylene of the present invention has higher transparency and lower n-hexane extract, thus improving the overall performance of polypropylene resin.

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

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

[0116] 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… and 69-71 and 70-71, etc. 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.

[0117] 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. A highly transparent copolymer polypropylene resin, characterized in that, The resin comprises propylene-butadiene copolymer polypropylene and compounding additives; based on the mass of the high-transparency copolymer polypropylene resin, the content of 1-butene units is 4.8~13.7 wt%, and the content of n-hexane extract is 0.38~1.10 wt%; the melt flow rate of the resin under test conditions of 190℃ and 2.16Kg is 5~10 g / 10min. The preparation method of the high-transparency copolymer polypropylene resin includes the following steps: S1: A copolymerization reaction is carried out in 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 copolymer polypropylene. S2: Add compounding agents to the propylene-butadiene copolymer polypropylene obtained in step S1, and extrude and granulate to prepare a highly transparent copolymer polypropylene resin. In step S1, the mass ratio of 1-butene to propylene is (15-15.2):(84.8-85). 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 with an ester or ether internal electron donor, and the co-catalyst is an organoaluminum compound; In step S1, the external electron donor is a siloxane compound; The mass ratio of the co-catalyst to the main catalyst, based on the mass of aluminum / titanium, is (20~40):1; The molar ratio of the co-catalyst to the external electron donor is (8~15):1, based on the aluminum / silicon molar ratio.

2. The high-transparency copolymer polypropylene resin according to claim 1, characterized in that, The compound adjuvants include a primary antioxidant, a secondary antioxidant, a halogen absorber, and a nucleating agent; the primary antioxidant is a hindered phenolic antioxidant; the secondary antioxidant is a phosphite antioxidant; the halogen absorber is a calcium stearate halogen absorber; and the nucleating agent is a sorbitol-type nucleating agent. Based on the mass of high-transparency copolymer polypropylene resin, the resin contains 98.5% to 99.5% propylene-butadiene copolymer polypropylene and 0.5% to 1.5% compounding additives; among which, the main 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%.

3. The high-transparency copolymer polypropylene resin according to claim 2, characterized in that, The primary antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; and / or, the secondary antioxidant is tris(2,4-di-tert-butylphenyl) phosphite.

4. A method for preparing a high-transparency copolymer polypropylene resin according to any one of claims 1-3, characterized in that, Includes the following steps: S1: A copolymerization reaction is carried out in 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 copolymer polypropylene. S2: Add compounding agents to the propylene-butadiene copolymer polypropylene obtained in step S1, and extrude and granulate to prepare a high-transparency copolymer polypropylene resin. In step S1, the mass ratio of 1-butene to propylene is (15-15.2):(84.8-85). 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 with an ester or ether internal electron donor, and the co-catalyst is an organoaluminum compound; In step S1, the external electron donor is a siloxane compound; The mass ratio of the co-catalyst to the main catalyst, based on the mass of aluminum / titanium, is (20~40):1; The molar ratio of the co-catalyst to the external electron donor is (8~15):1, based on the aluminum / silicon molar ratio.

5. The preparation method according to claim 4, characterized in that, The copolymerization reaction is carried out at a temperature of 60℃ to 80℃.

6. The preparation method according to claim 5, characterized in that, The copolymerization reaction is carried out at a temperature of 65℃~75℃.

7. The preparation method according to claim 4, characterized in that, In step S1, the main catalyst comprises a titanium tetrachloride / magnesium dichloride spherical catalyst with an ester internal electron donor. The organoaluminum compound is one of trimethylaluminum, triethylaluminum, and triisobutylaluminum.

8. The preparation method according to claim 7, characterized in that, In step S1, the main catalyst comprises a titanium tetrachloride / magnesium dichloride spherical catalyst containing diisobutyl phthalate. The organoaluminum compound is triethylaluminum.

9. The preparation method according to claim 7, characterized in that, In step S1, the main catalyst is MgCl2 / TiCl4 / Diester, wherein Mg = 17.2%, Ti = 2.5%, and internal electron donor = 9.8%.

10. The preparation method according to claim 4, characterized in that, In step S1, the external electron donor is selected from at least one of isobutyltriethoxysilane, diisopropyldimethoxysilane, diisopropyldimethoxysilane, and cyclohexylmethyldimethoxysilane.

11. The preparation method according to claim 10, characterized in that, In step S1, the external electron donor is selected from diisopropyldimethoxysilane.

12. The preparation method according to any one of claims 4-11, characterized in that, In step S2, the compound adjuvant includes a primary antioxidant, a secondary antioxidant, a halogen absorber, and a nucleating agent; the primary antioxidant is a hindered phenolic antioxidant; the secondary antioxidant is a phosphite antioxidant; the halogen absorber is a calcium stearate halogen absorber; and the nucleating agent is a sorbitol-type nucleating agent. And / or the high-transparency copolymer polypropylene resin prepared therefrom, based on the mass of the high-transparency copolymer polypropylene resin, has a propylene-butadiene copolymer polypropylene content of 98.5-99.5% and a compounding agent content of 0.5-1.5%; 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%.

13. The preparation method according to claim 12, characterized in that, The primary antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; and / or, the secondary antioxidant is tris(2,4-di-tert-butylphenyl) phosphite.

14. The preparation method according to any one of claims 4-11, characterized in that, In step S2, the extrusion granulation temperature is 180~250℃.

Images