Method for preparing polypropylene

Abstract

To provide polypropylene having a high melt flow index and a preparation method thereof, and a melt blown textile fabric.SOLUTION: A preparation method of a polypropylene comprises: a step for providing a reaction mixture including a propylene monomer, a Ziegler Natta catalyst, an organic aluminum compound, and an electron donor; and a step for executing a polymerization process to the reaction mixture in a different phase reaction system so as to prepare polypropylene. The polymerization process includes, a step for performing preliminary polymerization reaction, and a step for performing polymerization reaction. The acquired polypropylene has a high melt flow index, an adjustable melting point and molecular weight distribution, and is applied for production of a melt blown textile fabric.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for preparing polypropylene. Regarding It belongs to.

Background Art

[0002] Polypropylene is a well-known polymer material and has good thermoplasticity and good mechanical properties, so it is often used in the manufacture of various products. Polypropylene can also be produced as a meltblown fiber cloth by the meltblown process and can be used as a filter medium. However, conventional polypropylene has a low melt flow index and is difficult to meet the application requirements.

Summary of the Invention

Problems to be Solved by the Invention

[0003] In order to effectively increase the melt flow index of polypropylene, it is common to add hydrogen gas during the reaction. However, the added hydrogen gas easily inactivates the catalyst, making it impossible to prepare polypropylene by the reaction. As another method, in order to increase the melt flow index, the product of the polymerization reaction may be decomposed by a peroxide. However, the smell of the peroxide remaining in the polypropylene is strong, which affects its application field. In addition, the molecular weight distribution of the decomposed polypropylene is narrow and it is difficult to meet the application requirements.

[0004] In view of this, in order to overcome the disadvantages of the conventional polypropylene of preparation method, there is an urgent need to provide a polypropylene of preparation method having a high melt flow index.

Means for Solving the Problems

[0005] Therefore, one aspect of the present invention improves the defect that the catalyst is deactivated by using a specific electron donor. Moreover, by performing a polymerization process in a heterogeneous reaction system, a method for preparing polypropylene is provided in which the obtained polypropylene has good properties and meets the application requirements.

[0008] According to one aspect of the present invention, a method for preparing polypropylene is proposed. In this method, first, a propylene monomer and, magnesium chloride-supported titanium compound, and a phthalic acid ester compound, a glycol ester compound, a diether compound substance or is a succinic acid ester compound at least one of including obtained by reacting a compound a Ziegler-Natta catalyst, an organoaluminum compound, and having no alkoxy group an electron donor containing an aminosilane compound are included wherein the molar ratio (Al / Ti) of the aluminum atom of the organoaluminum compound to the titanium atom of the magnesium chloride-supported titanium compound is 30 to 500, and the molar ratio (Si / Ti) of the silicon atom of the aminosilane compound to the titanium atom of the magnesium chloride-supported titanium compound is 0.1 to 20. to provide a reaction mixture.

[0009] Next, a polymerization process is performed on the reaction mixture in a heterogeneous reaction system so as to form polypropylene having a melt flow index of 500 g / 10 min or more. In the polymerization process, a prepolymerization reaction is first performed, and then a copolymerization monomer is added, followed by a polymerization reaction. The copolymerization monomer includes an α-olefin compound having 2 to 8 carbon atoms. When the usage amount of the propylene monomer is 100% by weight, the usage amount of the copolymerization monomer is 5% by weight or less. The polymerization reaction excludes the additional addition of an electron donor.

[0010] Before The polymerization process is performed in a hydrogen gas-containing atmosphere.

[0011] According to some embodiments of the present invention, the polymerization reaction is performed at 50°C to 80°C.

[0014] Reference embodiment According to, polypropylene having a melt flow index prepared by the method and having a melt flow index of 500 g / 10 min or more is proposed.

[0015] Reference embodimentAccording to some embodiments, the melting point of the polypropylene is higher than 150°C.

[0016] Reference embodiment According to some embodiments, the molecular weight distribution of the polypropylene is 3 or more.

[0017] Another reference embodiment According to [the present invention], a melt-blown fiber cloth having a plurality of polypropylene fibers each having a yarn diameter of 4 μm or less and manufactured by performing a melt-blown process on the polypropylene is proposed.

Advantages of the Invention

[0018] According to the polypropylene having a high melt flow index of the present invention, its preparation method, and the melt-blown fiber cloth, by using a specific electron donor, the defect that the conventional Ziegler-Natta catalyst is inactivated by hydrogen gas is improved, the melt flow index of the obtained polypropylene is increased, and furthermore, the applicability of the polypropylene can be enhanced. Also, the obtained polypropylene can have a high isotactic index and a high melting point. Furthermore, since the polypropylene of the present invention has a wide molecular weight distribution, it can have a wide processing window during application.

Modes for Carrying Out the Invention

[0019] Hereinafter, the production and use of the embodiments of the present invention will be examined in detail. However, it should be understood that the embodiments provide numerous applicable inventive concepts that can be implemented in various specific contexts. The specific embodiments discussed are not intended to limit the scope of the present invention but are for illustrative purposes.

[0020] The polypropylene of the present invention is prepared by a Ziegler-Natta catalyst system. To solve the defect that the conventional Ziegler-Natta catalyst is inactivated by hydrogen gas, a specific electron donor is selected to carry out the polymerization process of propylene monomers. Therefore, the polypropylene obtained by the present invention has a high melt flow index, a high isotactic index, and adjustable melting point and molecular weight distribution. Since the obtained polypropylene has a high melt flow index, polypropylene fibers with a small fiber diameter can be produced by the melt blowing process, and further, a melt blown fiber cloth can be produced.

[0021] The polypropylene of the present invention is prepared by performing a polymerization process on a mixed reactant. The mixed reactant includes a propylene monomer, a Ziegler-Natta catalyst, an organoaluminum compound, and an electron donor.

[0022] The Ziegler-Natta catalyst is obtained by reacting a magnesium chloride-supported titanium compound with a phthalic acid ester compound, a glycol ester compound, a diether compound, and / or a succinic acid ester compound. Since the preparation method and process of the Ziegler-Natta catalyst are well-known to those skilled in the art, they will not be repeatedly described here.

[0023] The titanium compound may have a structure represented by the following formula (I). Ti(R1) n (X1) 4-n (I)

[0024] In formula (I), R1 may independently represent alkyl or oxyalkyl having 1 to 4 carbon atoms, X1 represents a halogen atom or a hydrogen atom, and n represents an integer of 0 to 4. In some specific examples, the titanium compound used may include, but is not limited to, titanium tetrahalide, tetraalkoxytitanium, alkyltitanium trihalide, dialkyltitanium dihalide, trialkyltitanium monohalide, titanium trihalide, trialkoxytitanium, alkyltitanium dihalide, dialkyltitanium monohalide, or any mixture of the above titanium compounds.

[0025] As an example, the phthalate ester compound may include, but is not limited to, diisobutyl phthalate, di-n-butyl phthalate, di-n-propyl phthalate, diisooctyl phthalate, other suitable phthalate ester compounds, or any mixture of the above compounds.

[0026] After reacting the magnesium chloride-supported titanium compound with the phthalate ester compound, the Ziegler-Natta catalyst used in the present invention can be obtained.

[0027] The organoaluminum compound of the reaction mixture may have a structure represented by the following formula (II). Al(R2) m (X2) 3-m (II)

[0028] In formula (II), R2 may independently represent alkyl or alkenyl having 1 to 8 carbon atoms, X2 may represent a halogen atom or a hydrogen atom, and m represents an integer of 0 to 3. In some specific examples, R2 may independently represent, for example, methyl, ethyl, triisobutyl, n-hexyl, n-octyl, ethoxy, isopentenyl, or other suitable functional groups. As an example, the organoaluminum compound may include, but is not limited to, triethylaluminum, tripropylaluminum, tributylaluminum, triisobutylaluminum, trioctylaluminum, diethylaluminum monohydride, diisobutylaluminum monohydride, diethylaluminum monochloride, diisobutylaluminum chloride, ethylaluminum dichloride, or any mixture of the above compounds.

[0029] The molar ratio (Al / Ti) of the aluminum atom of the organoaluminum compound to the titanium atom of the magnesium chloride-supported titanium compound is greater than 0 and not more than 1000, preferably 30 to 500.

[0030] The electron donor of the reaction mixture may include an aminosilane compound. In some embodiments, this aminosilane compound does not have an alkoxy group. When the aminosilane compound does not have an alkoxy group, the resulting Ziegler-Natta catalyst can have high reactivity in the polymerization process and contribute to the preparation of polypropylene having a high melt flow index.

[0031] The molar ratio (Si / Ti) of the silicon atom of the aminosilane compound to the titanium atom of the magnesium chloride-supported titanium compound is greater than 0 and not more than 50, preferably 0.1 to 20. When the molar ratio of the silicon atom of the aminosilane compound to the titanium atom of the titanium compound is within the above range, the Ziegler-Natta catalyst is less likely to be deactivated by the hydrogen gas introduced in the polymerization process.

[0032] Since the polymerization process of the present invention is carried out in a heterogeneous (slurry) reaction system, the obtained polypropylene powder can be extracted by removing low-molecular by-products with the liquid medium in the reaction system. Therefore, the quality of the polypropylene powder (for example, the defect of abnormal odor caused by low-molecular by-products) can be improved, and when applied later, the formation of fluff can be reduced. When carrying out the polymerization process, propylene gas first dissolves in the reaction solvent, and then the Ziegler-Natta catalyst, the organoaluminum compound and the electron donor are added. And 5 mol% to 60 mol% of hydrogen gas (when the propylene gas is 100 mol%) is introduced, the prepolymerization reaction is carried out at 5°C to 30°C, and the polymerization reaction is carried out at 50°C to 80°C. The organic solvent used in the present invention is not particularly limited as long as it can dissolve the reaction mixture and does not affect the polymerization process. Preferably, the selected organic solvent may have low biotoxicity and / or light abnormal odor, and can enhance the application value of the obtained polypropylene fiber. In some specific examples, the organic solvent used may be heptane and / or hexane.

[0033] When carrying out the polymerization process, in order to prepare the polypropylene of the present invention, the reaction mixture may first carry out a prepolymerization reaction and then a polymerization reaction. In some embodiments, the polymerization time of the polymerization process may be 0.5 hour to 4 hours, and the reaction pressure may be, for example, 0.5 kg / cm 3 ~10 kg / cm 3 For example. The polymerization process of the present invention may be carried out in a plurality of reaction units (for example, reaction tanks). During the prepolymerization reaction, the temperature of the reaction unit is 5°C to 30°C, but in the polymerization reaction stage, the temperature of each reaction unit is controlled to be 50°C to 80°C, which can effectively adjust the molecular weight distribution of the obtained polypropylene and improve the influence of hydrogen gas on the Ziegler-Natta catalyst activity.

[0034] In some embodiments, after the prepolymerization reaction, in this polymerization process, a comonomer may be selectively added to the reaction system. The comonomer may include, but is not limited to, α-olefin compounds having 2 to 8 carbon atoms. In some embodiments, the comonomer may preferably be, for example, an α-olefin compound having 2 or 4 carbon atoms, and more preferably an α-olefin compound having 2 carbon atoms. When the comonomer is added to the reaction system, the comonomer reacts with the prepolymerized polypropylene, thereby reducing the crystallinity of the subsequently obtained polypropylene and enabling the obtained polypropylene fibers to have flexible mechanical properties. This improves the defect that conventional polypropylene fibers have hard mechanical performance due to the use of Ziegler-Natta catalysts. It should be noted that the comonomer can reduce the crystallinity and melting point of polypropylene, but does not reduce the isotactic index of the obtained polypropylene.

[0035] From the above description, it can be seen that the comonomer is added in the polymerization reaction stage. When the polymerization reaction is carried out in a plurality of reaction units, preferably, the comonomer may be added to the first reaction unit or the second reaction unit so as to react with the prepolymerized polypropylene. More preferably, the comonomer is added to the first reaction unit. It should be noted that the comonomer of the present invention is not limited to being added to the first reaction unit or the second reaction unit in the polymerization reaction stage, and may be added to other reaction units in the polymerization reaction stage, or may be added to at least two reaction units simultaneously.

[0036] In some embodiments, when the amount of propylene monomer dissolved in the aforementioned organic solvent is 100% by weight, the amount of comonomer used may be 5% by weight or less. When the amount of comonomer used is greater than 5% by weight, the resulting polypropylene becomes sticky due to the excess comonomer, and its operability decreases. In some specific examples, when the resulting polypropylene has a comonomer, when the resulting polypropylene is 100% by weight, the content of the comonomer is 2% by weight or less.

[0037] After performing the polymerization process, when the liquid medium in the heterogeneous reaction system is filtered and a baking operation is performed, the polypropylene powder of the present invention can be obtained. The obtained polypropylene has a melt flow index of 500 g / 10 min or more, and its polymer chain has a high isotactic index. In some specific examples, the melt flow index of the obtained polypropylene is 500 g / 10 min, 1500 g / 10 min, 2000 g / 10 min, 3200 g / 10 min, 3500 g / 10 min, 4000 g / 10 min, greater than 4000 g / 10 min, or a value between any two of the above numerical values. Further, the polypropylene of the present invention has an adjustable melting point and molecular weight distribution. In some specific examples, the polypropylene of the present invention has a melting point greater than 150°C (for example, 150°C to 165°C), and since the resulting polypropylene has a molecular weight distribution of 3 or more, it has a wide processing window and good applicability.

[0038] In some application examples, in the preparation method and the polypropylene obtained in the present invention, selectively, by adjusting the content and / or type of the comonomer, the melting point of the polypropylene can be adjusted. And the molecular weight distribution of the polypropylene can be adjusted by a plurality of reaction units and / or the reaction conditions (for example, reaction time) of each reaction unit.

[0039] The polypropylene powder obtained by conventional processes and apparatuses in the art is used to produce polypropylene products suitable for various applications.

[0040] As an example, by the conventional meltblown process, the polypropylene of the present invention can be made into polypropylene fibers, and further, a meltblown fiber cloth composed only of polypropylene fibers or containing polypropylene fibers can be formed. By the meltblown process, the yarn diameter of the polypropylene fibers can be made 4 μm or less (for example, 1.5 μm to 4 μm).

[0041] Hereinafter, the applications of the present invention will be described using examples, which do not limit the present invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention.

[0042] <Preparation of Polypropylene>

[0043] First, the air in the reactor is replaced with nitrogen gas, and heptane is added in a nitrogen gas atmosphere. Next, the gas in the reactor is replaced with propylene, and propylene is dissolved in heptane while stirring. Subsequently, after depressurizing to slightly higher than atmospheric pressure, a Ziegler-Natta catalyst, an organoaluminum compound, and an electron donor are added under a positive propylene pressure, and 10 mol% to 60 mol% of hydrogen gas is introduced. Also, the pressure of the reactor can be 0.5 kg / cm 3 ~10 kg / cm 3 Yes.

[0044] A prepolymerization reaction is carried out at 5 °C to 30 °C. After the reaction is completed, the temperature is raised to 50 °C to 80 °C to carry out the polymerization reaction. After 0.5 hours to 4 hours, filtration is carried out to bake the powder, and the polypropylene powder of the present invention can be obtained.

[0045] The melting point and molecular weight distribution of the obtained polypropylene are measured by methods well-known to those skilled in the art, and thus will not be repeatedly described here. Also, as a method for detecting the melt flow index of polypropylene, polypropylene is heated at 230 °C, and after 240 seconds, the weight of polypropylene passing through the die hole every 10 minutes is measured under a load of 2.16 kg. The die has a diameter of 9.5504 ± 0.0076 mm, a height of 8.000 ± 0.025 mm, and a hole of 2.095 ± 0.005 mm.

[0046] Also, when performing the polymerization process, different Ziegler-Natta catalysts and electron donors are selected, the activity of the catalytic active center and the melt flow index of the obtained polypropylene are measured, and the results are as shown in Table 1. The selected Ziegler-Natta catalysts (phthalic acid ester-based catalysts, diether-based catalysts, glycol ester-based catalysts, and succinic acid ester-based catalysts) are commonly used catalysts, and thus will not be repeatedly described here.

[0047]

Table 1

[0048] The present invention can effectively improve the defect that the conventional Ziegler-Natta catalyst is inactivated by the hydrogen gas introduced during the reaction by using a specific aminosilane compound as an electron donor, and can further effectively increase the melt flow index of the obtained polypropylene. Also, the obtained polypropylene has a high isotactic index, a highly adjustable melting point, and a highly adjustable molecular weight distribution, and can have a wide processing window. Thereby, the obtained polypropylene powder can be made into polypropylene fibers by the melt blowing process, and the high melting point contributes to improving the physical properties and applicability of the obtained polypropylene fibers.

[0049] Although the present invention has been disclosed as described above according to the embodiments, it is not limited thereto, and those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention is based on the content specified in the claims.

Claims

1. A Ziegler-Natta catalyst obtained by reacting a propylene monomer with a magnesium chloride-supported titanium compound and at least one compound selected from the group consisting of a phthalic acid ester compound, a glycol ester compound, a diether compound, and a succinic acid ester compound, an organoaluminum compound, and an electron donor containing an aminosilane compound having no alkoxy group, A step of providing a reaction mixture in which the molar ratio (Al / Ti) of the aluminum atom of the organoaluminum compound to the titanium atom of the magnesium chloride-supported titanium compound is 30 to 500, and the molar ratio (Si / Ti) of the silicon atom of the aminosilane compound to the titanium atom of the magnesium chloride-supported titanium compound is 0.1 to 20; A step of performing a polymerization process on the reaction mixture in a heterogeneous reaction system so as to form polypropylene having a melt flow index of 500 g / 10 min or more; comprising; The polymerization process includes: A step of performing a prepolymerization reaction; A step of adding a copolymerization monomer after the prepolymerization reaction; A step of performing a polymerization reaction after adding the copolymerization monomer; including; The copolymerization monomer includes an α-olefin compound having 2 to 8 carbon atoms. When the amount of the propylene monomer used is 100% by weight, the amount of the copolymerization monomer used is 5% by weight or less. The polymerization reaction excludes additional addition of an electron donor. The polymerization process is carried out in a hydrogen gas-containing atmosphere, a method for preparing polypropylene.

2. The method for preparing polypropylene according to claim 1, wherein the polymerization reaction is carried out at 50°C to 80°C.

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