Multicomponent copolymer polypropylene and preparation method thereof

Abstract

The present invention provides a method for preparing a multi-component copolymer polypropylene and the polypropylene obtained. The method uses propylene as a main polymerization monomer, ethylene as a first comonomer, 1-butene as a second comonomer, and 4-methyl-1-pentene as a third comonomer, and is bulk polymerized by a Zielger-Natta spherical catalyst system, wherein the polymerization temperature is 55 to 70° C., the polymerization pressure is 2.5 to 3.0 MPa, and the polymerization reaction time is 1 to 3 hours. The method has the advantages of simple process, stable reaction, low melting point, wide melting range, and good thermal adhesion of the obtained polypropylene.

Description

Technical Field

[0001] The present invention relates to the field of polypropylene preparation, in particular to a multi-component copolymer polypropylene and a preparation method thereof. Background Art

[0002] Random copolymerization of comonomers with propylene can reduce the degree of crystallinity of polypropylene, refine the crystals, and lower its melting temperature. The comonomer content generally has a significant impact on the melting point of the polymer. However, excessive addition of a single comonomer and its uneven distribution within the polymer can affect the crystallinity of the polymer, leading to deficiencies in rigidity and other properties. Introducing a second or even third comonomer into the polymerization further disrupts the regularity of the polymer, significantly altering this situation. The industry typically uses 1-butene, pentene-1, hexene-1, or higher alpha-olefins as the second and third comonomers. Currently, the production of polypropylene (PP) through multi-component copolymerization is primarily focused on terpolymerization. U.S. Patent No. 6,365,682 describes a CPP production method using one or two liquid-phase reactors and a gas-phase reactor in series for the terpolymerization of propylene, ethylene, and 1-butene (or 4-methyl-1-pentene, 1-hexene, 1-heptene, or 1-octene). The liquid-phase reactor can be one or two loop reactors, and the gas-phase reactor is a fluidized bed reactor. The resulting terpolymerized polypropylene has a high melting point, a narrow melting range, and poor thermal adhesion, making it difficult to develop subsequent products.

[0003] In order to solve the above problems, we have been looking for an ideal technical solution. Summary of the Invention

[0004] The purpose of the present invention is to address the deficiencies of the prior art and provide a method for preparing multi-component copolymerized polypropylene by multi-component polymerization of olefins and the copolymerized polypropylene. The polypropylene has the characteristics of controllable melting point, wide melting range, good thermal adhesion, etc., and is suitable for use in the fields of films, fibers, etc.

[0005] The invention relates to a method for preparing multi-component copolymer polypropylene, comprising using propylene as a main polymerization monomer, ethylene as a first comonomer, 1-butene as a second comonomer, and 4-methyl-1-pentene as a third comonomer, and carrying out bulk polymerization using a Zielger-Natta spherical catalyst system, wherein the polymerization temperature is 55 to 70° C., the polymerization pressure is 2.5 to 3.0 MPa, and the polymerization reaction time is 1 to 3 hours;

[0006] The Ziegler-Natta spherical catalyst system consists of a Ziegler-Natta main catalyst, a co-catalyst, and an external electron donor. The main catalyst is formed by transesterification between a magnesium chloride-supported titanium catalyst and diethyl phthalate; the co-catalyst is triethylaluminum; and the external electron donor is a dimethoxysilane-based structure. The molar ratio of Al to Ti in the catalyst system is 60 to 250, and the molar ratio of Al to Si is 5 to 30. Within this range of Al, Ti, and Si, the catalyst system exhibits excellent activity release characteristics, particularly for a four-component polymerization system.

[0007] As a further improvement of the technical solution, the external electron donor is dicyclopentyldimethoxysilane, which has the advantages of regulating the stereoregularity of polypropylene and controlling the atactic form of polypropylene.

[0008] As a further improvement of the technical solution, the polymerization temperature is 60-70°C, and the polymerization reaction is more stable within this temperature range.

[0009] As a further improvement of the technical solution, the molar ratio of Al to Ti in the catalyst system is 80 to 180.

[0010] As a further improvement of the technical solution, the molar ratio of Al to Si in the catalyst system is 7 to 15.

[0011] As a further improvement of the technical solution, the polymerization reaction time is 1.5 hours.

[0012] A multi-component copolymer polypropylene prepared by the above-mentioned preparation method. Currently, polypropylene with a melting point below 133°C is more suitable for the production of CPP films and heat-sealing films, while polypropylene with a melting point range of around 140°C can form short-fiber polypropylene with good bonding properties. The polypropylene prepared by this method changes the crystallization state of propylene due to the addition of multiple olefin comonomers, and the melting point meets the requirements for the production of CPP films, heat-sealing films, and heat-bonding fibers.

[0013] Beneficial Effects: The preparation method provided by this patented invention is suitable for propylene polymerization in a liquid-phase bulk autoclave process. Without changing the main polypropylene process conditions and equipment, it can be used to prepare and produce multi-component copolymerized polypropylene. Advantages of this preparation method include: no prepolymerization is required, the polymerization process is smooth, process control is simple, and the polymer has a low melting point, a wide melting range, and good thermal bonding properties. DETAILED DESCRIPTION

[0014] The technical solution of the present invention is further described in detail below through specific implementation methods.

[0015] In each embodiment:

[0016] The main catalyst A is a titanium-based Ziegler-Natta polypropylene catalyst, which is a mature product available in the domestic market. The Ti content in the catalyst is 2.2 wt%.

[0017] Cocatalyst B: triethylaluminum, diluted with hexane to a concentration of 0.88 mol / L before use;

[0018] External electron donor C: dicyclopentyldimethoxysilane, diluted with hexane to a concentration of 0.2 mol / L before use.

[0019] The preparation process is carried out in a 10L high-pressure polymerization reactor. After the reactor is purged with nitrogen, catalyst components A, B, and C are added to the catalyst feeder under nitrogen protection. Hydrogen is metered by the reactor pressure difference and enters the reactor first. Liquid propylene is pressurized by a diaphragm pump and added to the reactor, measured using an online electronic scale. Ethylene is injected through a Brooks flowmeter pipeline. Other comonomers are precisely added using a micro-chromatographic pump. During the reaction, the reaction temperature and agitator speed are controlled by a DCS system, and the gas composition within the reactor is monitored by an online gas chromatograph.

[0020] Example 1

[0021] Accurately weigh 32.5 mg of Catalyst A, 2.5 ml of Solution B, and 1.0 ml of Solution C (where the molar ratio of Al, Si, and Ti is 245:22:1) and add them to the catalyst feeder under nitrogen. First, introduce H₂ into the polymerization reactor to raise the reactor pressure by 0.01 MPa. Then, add 1010 g of propylene, 60 g of 1-butene monomer, and 40 g of 4-methyl-1-pentene monomer. Rapidly increase the temperature to 60 ± 2°C and conduct bulk polymerization at a pressure of 2.5 MPa and a stirring speed of 140 rpm. After 30 minutes of polymerization, add 12 g of ethylene, raise the polymerization pressure to 2.8 MPa, and after 90 minutes of polymerization, discharge the material through the discharge valve, dry it, and weigh it. The total weight is 776 g.

[0022] Example 2

[0023] Accurately weigh 30.7 mg of Catalyst A, 1.5 ml of Solution B, and 0.5 ml of Solution C (where the molar ratio of Al, Si, and Ti is 157:11.7:1) and add them to the catalyst feeder under nitrogen. First, introduce H₂ into the polymerization reactor to raise the reactor pressure by 0.01 MPa. Then, add 1130 g of propylene, 60 g of 1-butene monomer, and 40 g of 4-methyl-1-pentene monomer. Rapidly increase the temperature to 60 ± 2°C and conduct bulk polymerization at a pressure of 2.5 MPa and a stirring speed of 140 rpm. After 30 minutes of polymerization, add 12 g of ethylene, raise the polymerization pressure to 2.8 MPa, and polymerize for 120 minutes through the feed valve. After drying and weighing, the total weight is 923 g.

[0024] Example 3

[0025] Accurately weigh 31.9 mg of Catalyst A, 0.8 ml of Solution B, and 0.5 ml of Solution C (where the molar ratio of Al, Si, and Ti is 83:6.2:1) and add them to the catalyst feeder under nitrogen. First, introduce H2 into the polymerization reactor to raise the reactor pressure by 0.01 MPa. Then, add 1090 g of propylene, 60 g of 1-butene monomer, and 40 g of 4-methyl-1-pentene monomer. Rapidly increase the temperature to 65 ± 2°C and conduct bulk polymerization at a pressure of 2.5 MPa and a stirring speed of 140 rpm. After 30 minutes of polymerization, add 12 g of ethylene, raise the polymerization pressure to 2.8 MPa, and polymerize for an additional 90 minutes. The material is then discharged, dried, and weighed for a total of 951 g.

[0026] Example 4

[0027] Accurately weigh 31.9 mg of Catalyst A, 1.0 ml of Solution B, and 0.3 ml of Solution C (where the molar ratio of Al:Si:Ti is 60:4.1:1) and add them to the catalyst feeder under nitrogen. First, introduce H₂ into the polymerization reactor to raise the reactor pressure by 0.01 MPa. Then, add 1170 g of propylene, 60 g of 1-butene monomer, and 45 g of 4-methyl-1-pentene monomer. Rapidly increase the temperature to 65±2°C and conduct bulk polymerization at a pressure of 2.5 MPa and a stirring speed of 140 rpm. After 30 minutes of polymerization, add 12 g of ethylene, raise the polymerization pressure to 2.8 MPa, and polymerize for an additional 90 minutes. The material is then discharged, dried, and weighed for a total of 984 g.

[0028] Example 5

[0029] Accurately weigh 31.9 mg of catalyst A, 1.0 ml of solution B, and 1.1 ml of solution C, where the molar ratio of Al, Si, and Ti is 60:15:1, and add them to a catalyst feeder under nitrogen. First, H₂ is introduced into the polymerization kettle to increase the kettle pressure by 0.01 MPa. Then, 1110 g of propylene, 70 g of 1-butene monomer, and 45 g of 4-methyl-1-pentene monomer are added. The temperature is rapidly raised to 65 ± 2°C and bulk polymerization is carried out at a polymerization pressure of 2.5 MPa and a stirring speed of 140 rpm. After 30 minutes of polymerization, 12 g of ethylene is added, and the polymerization pressure is raised to 2.8 MPa. The gas composition in the polymerization kettle is detected by online gas chromatography. The polymerization is continued for an additional 120 minutes, and the material is then discharged and weighed after drying to a total of 982 g.

[0030] Example 6

[0031] Accurately weigh 38.3 mg of Catalyst A, 5.0 ml of Solution B, and 0.8 ml of Solution C (where the molar ratio of Al, Si, and Ti is 250:9.1:1) and add them to the catalyst feeder under nitrogen. First, introduce H₂ into the polymerization reactor to raise the reactor pressure by 0.01 MPa. Then, add 1250 g of propylene, 70 g of 1-butene monomer, and 45 g of 4-methyl-1-pentene monomer. Rapidly increase the temperature to 65 ± 2°C and conduct bulk polymerization at a pressure of 2.5 MPa and a stirring speed of 140 rpm. After 30 minutes of polymerization, add 12 g of ethylene, raise the polymerization pressure to 2.8 MPa, and polymerize for an additional 180 minutes. The material is then discharged, dried, and weighed for a total of 1132 g.

[0032] Example 7

[0033] Accurately weigh 30 mg of Catalyst A, 1.5 ml of Solution B, and 0.5 ml of Solution C, and add them to a catalyst feeder under nitrogen. The molar ratio of Al, Si, and Ti is 95.7:7.1:1. First, introduce H2 into the polymerization reactor to raise the reactor pressure by 0.01 MPa. Then, add 1020 g of propylene, 60 g of 1-butene monomer, and 40 g of 4-methyl-1-pentene monomer. Heat rapidly to 55 ± 1°C and perform bulk polymerization at a pressure of 2.5 MPa and a stirring speed of 140 rpm. After 30 minutes of polymerization, add 12 g of ethylene, raise the polymerization pressure to 2.8 MPa, and polymerize for an additional 90 minutes. The material is then discharged, dried, and weighed for a total of 633 g.

[0034] Example 8

[0035] Accurately weigh 30 mg of Catalyst A, 1.5 ml of Solution B, and 0.5 ml of Solution C, and add them to a catalyst feeder under nitrogen. The molar ratio of Al:Si:Ti is 95.7:7.1:1. H₂ is first introduced into the polymerization reactor to raise the reactor pressure by 0.01 MPa. Then, 1210 g of propylene, 60 g of 1-butene monomer, and 40 g of 4-methyl-1-pentene monomer are added. The temperature is rapidly raised to 70 ± 2°C and bulk polymerization is carried out at a pressure of 2.5 MPa and a stirring speed of 140 rpm. After 30 minutes of polymerization, 12 g of ethylene is added, raising the polymerization pressure to 2.8 MPa. The polymerization continues for an additional 90 minutes, the material is discharged, dried, and weighed for a total of 895 g.

[0036] Comparative Example 1

[0037] Accurately weigh 31.9 mg of Catalyst A, 2.0 ml of Solution B, and 1.0 ml of Solution C, and add them to the catalyst feeder under nitrogen. The molar ratio of Al, Si, and Ti is 120:13.6:1. First, introduce H2 into the polymerization kettle to raise the pressure by 0.01 MPa. Then, add 1180 g of propylene. After rapidly increasing the temperature, add 12 g of ethylene. Bulk polymerization is carried out at 65 ± 2°C, a pressure of 2.5 MPa, and a stirring speed of 140 rpm. After 30 minutes of polymerization, increase the temperature to 2.8 MPa. Polymerize for an additional 90 minutes before discharging the material through the discharge valve. After drying and weighing, the total weight is 911 g.

[0038] Comparative Example 2

[0039] Accurately weigh 31.9 mg of Catalyst A, 2.0 ml of Solution B, and 1.0 ml of Solution C into a catalyst feeder under nitrogen. The molar ratio of Al:Si:Ti was 120:13.6:1. H₂ was first introduced into the polymerization reactor to raise the reactor pressure by 0.01 MPa. Then, 1230 g of propylene and 60 g of 1-butene monomer were added. The temperature was rapidly raised to 65±2°C for bulk polymerization at a pressure of 2.5 MPa and a stirring speed of 140 rpm. After 30 minutes of polymerization, 12 g of ethylene was added, raising the polymerization pressure to 2.8 MPa. The polymerization continued for an additional 90 minutes, the material was discharged, dried, and weighed for a total of 863 g.

[0040] The test results of the polymers obtained in each embodiment and comparative example are shown in Table 1, where:

[0041] The melting point and melting range were determined using a TA differential scanning calorimeter DSC Q2000;

[0042] The ethylene segment content in the copolymer was determined using a Bruke infrared tester;

[0043] The contents of 1-butene and 4-methyl-1-pentene segments in the copolymer were measured using an FX-90Q nuclear magnetic resonance spectrometer. 13 C-NMR determination;

[0044] The appearance of the copolymer particles was observed with the naked eye.

[0045] Table 1 Basic test data of test examples and comparative test examples

[0046]

[0047]

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solutions of the present invention. They should all be included in the scope of the technical solutions claimed for protection by the present invention.

Claims

1. A method for preparing multi-component copolymer polypropylene, characterized in that: The method comprises the following steps: using propylene as the main monomer, ethylene as the first comonomer, 1-butene as the second comonomer, and 4-methyl-1-pentene as the third comonomer, and carrying out bulk polymerization using a Zielger-Natta spherical catalyst system, wherein the polymerization temperature is 55-70° C., the polymerization pressure is 2.5-3.0 MPa, and the polymerization reaction time is 1-3 hours; The Zielger-Natta spherical catalyst system consists of a Zielger-Natta main catalyst, a co-catalyst, and an external electron donor. The main catalyst is formed by transesterification between a magnesium chloride-supported titanium catalyst and diethyl phthalate; the co-catalyst is triethylaluminum; the external electron donor is a dimethoxysilane structure; the molar ratio of Al to Ti in the catalyst system is 60-250, and the molar ratio of Al to Si is 5-30; The mass ratio of propylene to ethylene, 1-butene and 4-methyl-1-pentene is 1130:12:60:40 or 1110:12:70:45 or 1250:12:70:45 or 1210:12:60:

40.

2. The method for preparing multi-component copolymer polypropylene according to claim 1, wherein: The external electron donor is dicyclopentyldimethoxysilane.

3. The method for preparing multi-component copolymer polypropylene according to claim 1, characterized in that: The polymerization temperature is 60-70°C.

4. The method for preparing multi-component copolymer polypropylene according to claim 1, wherein: The molar ratio of Al to Ti in the catalyst system is 80 to 180.

5. The method for preparing multi-component copolymer polypropylene according to claim 1, characterized in that: The molar ratio of Al to Si in the catalyst system is 7 to 15.

6. The method for preparing multi-component copolymer polypropylene according to claim 1, characterized in that: The polymerization reaction time was 1.5 hours.

7. A multi-component copolymer polypropylene prepared by the preparation method according to any one of claims 1 to 6.

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