CN102174134B - Catalyst composition for preparing polypropylene with high melt index, preparation method and application thereof - Google Patents

Abstract

The present invention discloses a catalyst composition for the preparation of high melt index polypropylene, characterized in that the catalyst composition comprises the following components: (a) MgCl ₂ supported TiCl comprising a diester internal electron donor Type ₄ Ziegler-Natta catalyst; (b) trialkylaluminum compound; (c) one or both of isobutylisopropyldimethoxysilane and isobutylcyclohexyldimethoxysilane; and (d) normal One or both of propyltrimethoxysilane and n-propyltriethoxysilane. The catalyst composition can catalyze the polymerization of propylene in the presence of hydrogen to produce polypropylene with a high melt index. In addition, the invention also discloses a method for preparing high melt index polypropylene by using the catalyst composition and the application of the catalyst composition.

Description

Catalyst composition for preparing high melt index polypropylene, preparation method and use

technical field

The invention belongs to the technical field of material preparation and catalytic application, in particular, the invention relates to a catalyst composition for preparing high melt index polypropylene, a method for preparing high melt index polypropylene by using the catalyst composition and the Use of the catalyst composition.

Background technique

Polypropylene (PP) is cost-effective and widely used. When polypropylene is used in production processes such as injection molding, extrusion, blow molding, etc., in order to improve processing efficiency and be able to prepare large injection molded parts, it is usually necessary to increase the melt index of polypropylene to meet processing requirements. Generally, MgCl ₂ loaded Ziegler-Natta catalyst is used to polymerize propylene to prepare polypropylene, and hydrogen is added as a molecular weight regulator during propylene polymerization. Hydrogen can reduce the molecular weight of polypropylene and increase the melt index of polypropylene. However, when the amount of hydrogen increases to a certain extent, the degree of increase in the melt index decreases, and the catalytic activity decreases, which affects the catalytic efficiency. Therefore, the amount of hydrogen added is limited by the polymerization process. In addition, in order to obtain high melt index polypropylene in industry, a certain amount of peroxide is usually added after the production of polypropylene to promote the degradation of polypropylene to increase the melt index of polypropylene. The color of the high melt index polypropylene prepared by the method is easy to turn yellow, and has a certain smell, which affects the appearance of the polypropylene product.

At present, the catalysts used in the industrial production of polypropylene are mainly MgCl ₂ -supported Ziegler-Natta catalysts containing diester internal electron donors, which require external electron donors during polymerization. The main function of the external electron donor is to adjust the isotacticity of polypropylene and the sensitivity of the catalyst to hydrogen, and it also has a certain degree of influence on the catalyst activity, the apparent density of polypropylene, and the copolymerization performance of propylene and ethylene. The external electron donors currently used are mainly silane electron donors, containing 1 to 4 alkoxy groups, the most commonly used is dialkyldimethoxysilane. Different structures of external electron donors have different effects on the isotacticity of polypropylene, hydrogen sensitivity and activity of catalysts. According to different needs, different external electron donors can be selected to produce different grades of polypropylene products.

US5652303 and US5844046 report that the molecular weight distribution and melt index of polypropylene can be adjusted by combining dialkoxysilane and trialkoxysilane. The combination of diether and siloxane can also achieve the purpose of regulating the isotacticity, molecular weight distribution and melt index (MFR) of polypropylene (US5869418), but its effect is not as obvious as the combination of two silanes. US6087459 combines dicyclopentyldimethoxysilane and propyltriethoxysilane to regulate the melt index (MFR) of polypropylene within a wide range, especially to obtain high MFR polypropylene. The polypropylene isotacticity that tetraethoxysilane produces is low, but has high melt index, and the PP prepared by dicyclopentyldimethoxysilane has high isotacticity and low melt index, Exxson company (US6111039) in In the two-stage polymerization, the first stage uses tetraethoxysilane as the electron donor, and the second stage uses the tetraethoxysilane/dicyclopentyldimethoxysilane mixed electron donor to obtain high rigidity and medium molecular weight distribution. and medium melt index PP. US7183234 reports that the combination of didecahydroisoquinoline dimethoxysilane/propyltriethoxysilane can regulate the MFR and molecular weight distribution of polypropylene within a wide range. Chinese patent application CN99805994.3 reports the preparation of impact polypropylene using a combination of dicyclopentyldimethoxysilane and propyltriethoxysilane.

Polypropylene with a high melt index can be prepared by combining an external electron donor with a Ziegler-Natta catalyst containing a diester. The technical problem to be solved in this patent is to provide a better combination of external electron donors to prepare high melt index polypropylene with higher catalytic activity and higher efficiency.

Contents of the invention

In view of the above technical problems, an object of the present invention is to provide a catalyst composition for preparing high melt index polypropylene.

Another object of the present invention is to provide a method for preparing high melt index polypropylene using said composition.

Another object of the present invention is to provide the use of the composition.

In order to achieve the above object, the technical scheme that the present invention takes is as follows:

In one aspect, the present invention provides a catalyst composition for the preparation of high melt index polypropylene, said catalyst composition comprising the following components:

(a) _MgCl supported TiCl ₄ type Ziegler-Natta catalyst comprising diester internal electron donor;

(b) trialkylaluminum compounds;

(c) one or both of isobutylisopropyldimethoxysilane and isobutylcyclohexyldimethoxysilane; and

(d) One or both of n-propyltrimethoxysilane and n-propyltriethoxysilane.

Wherein, in the TiCl ₄ type Ziegler-Natta catalyst of the TiCl 4 type Ziegler-Natta catalyst that the described component (a) comprises diester internal electron donor MgCl ₂ loads, the content of Ti is 1.5-3.5wt%;

And in the component (a), the electron donor in the diester is a phthalic acid diester compound; preferably, the electron donor in the diester is selected from diisobutyl phthalate, phthalate One or more of di-n-butyl formate and di-n-propyl phthalate.

In addition, the component (b) trialkylaluminum compound is selected from one or more of trimethylaluminum, triethylaluminum and triisobutylaluminum.

Preferably, in the catalyst composition, the molar ratio of Al in component (b) to Ti in component (a) is 10-1000, preferably 100-600, more preferably 100-400. The molar ratio of the sum of components (c) and (d) in terms of Si to Ti in component (a) is 1-100, preferably 10-60, more preferably 10-40. The molar ratio of Al in component (b) to the sum of components (c) and (d) in terms of Si is 5-100, preferably 10-50, more preferably 10-30.

And, the molar percentage between component (c) and component (d) is 2.5-15:85-97.5; preferably, said molar percentage is 2.5-10:90-97.5, more preferably 3.0-10:90 -97.

In another aspect, the present invention provides a method for preparing high melt index polypropylene, the method comprising: using the catalyst composition according to any one of claims 1-5 to catalyze the polymerization of propylene in the presence of hydrogen ;

Preferably, the propylene polymerization is carried out in propylene bulk or in gas phase propylene.

Preferably, the reaction temperature of the propylene polymerization is 50-90°C. Further preferably, the reaction temperature is 60-80°C. In the above method, the polypropylene produced by the method has a melt index of 5-60 g/10 minutes.

In yet another aspect, the present invention provides the use of the above catalyst composition in the preparation of polypropylene.

The present invention will be described in detail below.

The present invention provides a process for the preparation of high melt index polypropylene characterized by the use of (a) MgCl ₂ supported TiCl ₄ type Ziegler-Natta catalyst solid component containing diester internal electron donor, (b) trioxane (c) one or both of isobutylisopropyldimethoxysilane and isobutylcyclohexyldimethoxysilane and (d) n-propyltrimethoxysilane, n-propyltriethoxysilane One or two of the base silanes form a catalytic system to catalyze the polymerization of propylene in the presence of hydrogen to prepare polypropylene with a high melt index.

The melt index of the high melt index polypropylene is between 5-60g/10min. The diester internal electron donor in the catalyst solid component (a) is a phthalic acid diester compound, derived from diisobutyl phthalate, di-n-butyl phthalate, di-n-phthalate One or more of propyl esters. The component (b) trialkylaluminum of the catalytic system is selected from one or more of trimethylaluminum, triethylaluminum and triisobutylaluminum. The mole percentage of (c) component and (d) component is 2.5-15:97.5-85. Propylene polymerization is carried out in propylene bulk or in gas phase propylene.

Component (a) of the above catalytic system comprises _MgCl2 , _TiCl4 and a diester internal electron donor.该固体组分可以采取多种方法制备，如中国专利申请CN 00109216.2，CN02122750.0，CN 02136543.1，CN 200310101833.9，CN 200380106197.X，CN 200410017269.7，CN 87101423，CN 90104123.8，CN 93102795.0，CN94102813.5，CN 94103454, the method described in CN 97112005.6. The electron donor in the diester is a diester compound of phthalate, which is obtained from one or more of diisobutyl phthalate, di-n-butyl phthalate, and di-n-propyl phthalate .

When the catalyst component (c) is an external electron donor alone, it has high isotropic orientation and low hydrogen tuning sensitivity, and when the catalyst component (d) is an external electron donor alone, it generally has low isotropic orientation and high hydrogen sensitivity. Part of the function of the external electron donor is to complex with the alkylaluminum to reduce the reduction ability of the alkylaluminum, and the other part is to complex with the active center of the Ziegler-Natta catalyst to suppress the active center with poor isotropic property and further improve the isotropic property High isotropic orientation of the active center. Different electron donors have different interaction strengths with the active centers of Ziegler-Natta catalysts. Component (c) can replace the complexation of component (d) at the active site. When component (c) and component (d) are used in combination, when the content of component (c) is less than 2.5 mol%, the isotropic orientation of the catalyst is poor; when the content of component (c) is greater than 15 mol% , the hydrogen adjustment performance of the catalyst is the same as when component (c) is used alone, and high melt index polypropylene cannot be obtained. When component (c) and component (d) are used in combination, in an appropriate ratio, the hydrogen adjustment performance of the catalyst can be effectively enhanced, and high isotactic and high melt index polypropylene can be prepared.

Compared with the prior art, the present invention provides a novel catalyst composition for preparing high-melt-index polypropylene. When the catalyst composition is used in the polymerization of propylene in the presence of hydrogen, it can obtain high-melt-index polypropylene. Melt index polypropylene, which can even be as high as nearly 60 g/min, helps to meet the current demand for high melt index polypropylene in industrial applications.

Detailed ways

The present invention will be further described in detail below in conjunction with specific examples and with reference to data. It should be understood that these examples are only to illustrate the present invention and not to limit the scope of the invention in any way.

In the following examples, various procedures and methods not described in detail are conventional methods well known in the art.

The propylene used in the examples is polymer grade propylene, the catalyst component (a) is the CS-I catalyst produced by Yingkou Xiangyang Catalyst Factory, and the internal electron donor contained therein is diisobutyl phthalate.

The polypropylene that makes in following embodiment has been carried out the test of isotacticity and melt index, described method is as follows:

The isotacticity of polypropylene is determined by the heptane extraction method. About 2 g of polypropylene is placed in a Soxhlet extractor, extracted with boiling heptane for 6 hours, and the remaining polymer is dried to constant weight. The weight ratio of the polymer added for the first time is isotactic.

The melt index of polypropylene is measured according to the elastomer melt index test standard ASTM D1238, and the experimental conditions are 2.16Kg and 230°C.

Example 1

_The 5L autoclave is heated and evacuated, air and water are removed, replaced with nitrogen, repeated three times, and then added with MgCl 20 mg of TiCl supported catalyst solid component, the _content of Ti in the solid component is 2.36wt%, triethyl The amount of aluminum added is Al/Ti (mol)=600, adding 30mmol hydrogen, isobutylisopropyldimethoxysilane (IBIPDMS), n-propyltrimethoxysilane (NPTMS), and the molar percentage of the two is 5:95 , the total addition of the two silanes is calculated as Al/Si (mol)=20 by silicon, then hydrogen and 1.2 kg of propylene are added, and the hydrogen to propylene molar ratio is 2.94mmol/mol. Close the reaction kettle, raise the temperature of the kettle to 70°C, and start polymerization. After 2 hours of reaction, unreacted propylene is discharged to obtain 830g of polypropylene particles. The calculated catalytic activity is 41.5KgPP/g catalyst, and the melt index of polypropylene is 10.7gPP /10min, the isotacticity of polypropylene is 98.2%.

Example 2

_The 5L autoclave is heated and evacuated, air and water are removed, replaced with nitrogen, repeated three times, and then added with MgCl 20 mg of TiCl supported catalyst solid component, the _content of Ti in the solid component is 2.36wt%, triethyl Aluminum addition is Al/Ti (mol)=600, adds 30mmol hydrogen, isobutylcyclohexyldimethoxysilane (IBCHDMS), n-propyltrimethoxysilane (NPTMS), the molar percentage of the two is 5: 95, The total amount of the two silanes added is calculated as Al/Si (mol)=20 based on silicon, then hydrogen and 1.2 kg of propylene are added, and the molar ratio of hydrogen to propylene is 2.94 mmol/mol. Close the reactor, raise the temperature of the kettle to 70°C, and start polymerization. After 2 hours of reaction, unreacted propylene is discharged to obtain 810g of polypropylene particles, the catalytic activity is 40.5KgPP/g catalyst, and the melt index of polypropylene is 15.7gPP/ After 10 minutes, the isotacticity of polypropylene is 98.1%.

Example 3

_The 5L autoclave is heated and evacuated, air and water are removed, replaced with nitrogen, repeated three times, and then added with MgCl 20 mg of TiCl supported catalyst solid component, the _content of Ti in the solid component is 2.36wt%, triethyl Aluminum addition is Al/Ti (mol)=600, adds 30mmol hydrogen, isobutyl isopropyl dimethoxysilane (IBIPDMS), n-propyltriethoxysilane (NPTES), the molar percentage of the two is 5: 95. The total amount of the two silanes added is calculated as Al/Si (mol)=20 based on silicon, then hydrogen and 1.2 kg of propylene are added, and the molar ratio of hydrogen to propylene is 2.94 mmol/mol. Close the reactor, raise the temperature of the kettle to 70°C, and start polymerization. After 2 hours of reaction, unreacted propylene is discharged to obtain 810g of polypropylene particles, the catalytic activity is 40.5KgPP/g catalyst, and the melt index of polypropylene is 16.2gPP/ After 10 minutes, the isotacticity of polypropylene is 98.1%.

Example 4

_The 5L autoclave is heated and evacuated, air and water are removed, replaced with nitrogen, repeated three times, and then added with MgCl 20 mg of TiCl supported catalyst solid component, the _content of Ti in the solid component is 2.36wt%, triethyl The amount of aluminum added is Al/Ti (mol)=600, add 30mmol hydrogen, isobutylcyclohexyldimethoxysilane (IBCHDMS), n-propyltriethoxysilane (NPTES), the molar percentage of the two is 5:95 , the total addition of the two silanes is calculated as Al/Si (mol)=20 by silicon, then hydrogen and 1.2 kg of propylene are added, and the hydrogen to propylene molar ratio is 2.94mmol/mol. Close the reaction kettle, raise the temperature of the kettle to 70° C., and start polymerization. After 2 hours of reaction, unreacted propylene is discharged to obtain 790 g of polypropylene particles, the catalytic activity is 39.5 KgPP/g catalyst, and the melt index of polypropylene is 22.3 gPP/ After 10 minutes, the isotacticity of polypropylene is 97.9%.

Example 5

_The 5L autoclave is heated and evacuated, air and water are removed, replaced with nitrogen, repeated three times, and then added with MgCl 20 mg of TiCl supported catalyst solid component, the _content of Ti in the solid component is 2.36wt%, triethyl The amount of aluminum added is Al/Ti (mol)=600, adding 30mmol hydrogen, isobutylisopropyldimethoxysilane (IBIPDMS), n-propyltrimethoxysilane (NPTMS), and the molar percentage of the two is 5:95 , the total addition of the two silanes is calculated as Al/Si (mol)=20 by silicon, then hydrogen and 1.2 kg of propylene are added, and the hydrogen to propylene molar ratio is 6.83mmol/mol. Close the reaction kettle, raise the temperature of the kettle to 70°C, and start polymerization. After 2 hours of reaction, unreacted propylene is discharged to obtain 790g of polypropylene particles, the catalytic activity is 39.0KgPP/g catalyst, and the melt index of polypropylene is 50.4gPP/ After 10 minutes, the isotacticity of polypropylene was 97.6%.

Example 6

_The 5L autoclave is heated and evacuated, air and water are removed, replaced with nitrogen, repeated three times, and then added with MgCl 20 mg of TiCl supported catalyst solid component, the _content of Ti in the solid component is 2.36wt%, triethyl Aluminum addition is Al/Ti (mol)=600, adds 30mmol hydrogen, isobutylcyclohexyldimethoxysilane (IBCHDMS), n-propyltrimethoxysilane (NPTMS), the molar percentage of the two is 5: 95, The total amount of the two silanes added is calculated as Al/Si (mol)=20 based on silicon, then hydrogen and 1.2 kg of propylene are added, and the molar ratio of hydrogen to propylene is 6.83 mmol/mol. Close the reaction kettle, raise the temperature of the kettle to 70°C, and start polymerization. After 2 hours of reaction, unreacted propylene is discharged to obtain 760g of polypropylene particles, the catalytic activity is 38.0KgPP/g catalyst, and the melt index of polypropylene is 56.4gPP/ After 10 minutes, the isotacticity of polypropylene was 97.6%.

Example 7

_The 5L autoclave is heated and evacuated, air and water are removed, replaced with nitrogen, repeated three times, and then added with MgCl 20 mg of TiCl supported catalyst solid component, the _content of Ti in the solid component is 2.36wt%, triethyl The amount of aluminum added is Al/Ti (mol)=600, add 30mmol hydrogen, isobutylcyclohexyldimethoxysilane (IBCHDMS), n-propyltriethoxysilane (NPTES), the molar percentage of the two is 3:97 , the total addition of the two silanes is calculated as Al/Si (mol)=20 by silicon, then hydrogen and 1.2 kg of propylene are added, and the hydrogen to propylene molar ratio is 2.94mmol/mol. Close the reaction kettle, raise the temperature of the kettle to 70°C, and start polymerization. After 2 hours of reaction, unreacted propylene is discharged to obtain 750g of polypropylene particles, the catalytic activity is 37.5KgPP/g catalyst, and the melt index of polypropylene is 32.3gPP/ After 10 minutes, the isotacticity of polypropylene was 97.3%.

In order to more fully illustrate the effect of the catalyst composition of the present invention, comparative examples are provided below.

Comparative Example 1

_The 5L autoclave is heated and evacuated, air and water are removed, replaced with nitrogen, repeated three times, and then added with MgCl 20 mg of TiCl supported catalyst solid component, the _content of Ti in the solid component is 2.36wt%, triethyl Aluminum addition is Al/Ti (mol)=600, adds 300mmol hydrogen, isobutyl isopropyl dimethoxysilane, and addition is calculated as Al/Si (mol)=20 by silicon, then adds hydrogen and 1.2 kilograms of propylene, The molar ratio of hydrogen to propylene was 2.94 mmol/mol. Close the reaction kettle, raise the temperature of the kettle to 70° C., and start polymerization. After 2 hours of reaction, unreacted propylene is discharged to obtain 860 g of polypropylene particles, the catalytic activity is 43.0 KgPP/g catalyst, and the melt index of polypropylene is 2.7 gPP/ After 10 minutes, the isotacticity of polypropylene is 98.5%.

Claims (15)

1. A catalyst composition for preparing high melt index polypropylene, characterized in that, the catalyst composition comprises the following components: (a) _MgCl2- supported _TiCl4- type Ziegler-Natta catalysts containing diester internal electron donors; (b) trialkylaluminum compounds; (c) One or both of isobutylisopropyldimethoxysilane and isobutylcyclohexyldimethoxysilane; and (d) One or both of n-propyltrimethoxysilane and n-propyltriethoxysilane; The molar percentage between the component (c) and the component (d) is 2.5-15:85-97.5; The molar ratio of Al in component (b) to Ti in component (a) is 10 to 1000; the molar ratio of the sum of components (c) and (d) to Ti in component (a) in terms of silicon is 10 to 1000 60; the molar ratio of Al in component (b) and the sum of components (c) and (d) in terms of Si is 10 to 50; The high melt index means that the melt index is 5-60 g/10 minutes, and the melt index is measured according to the elastomer melt index test standard ASTM D1238, and the experimental conditions are 2.16Kg and 230°C. 2. Catalyst composition as claimed in claim 1, it is characterized in that, in the Ziegler-Natta catalyst of TiCl ₄ type that _described component (a) comprises the MgCl of diester internal electron donor, the content of Ti is 1.5 ~3.5wt%; in the component (a), the electron donor in the diester is a phthalic acid diester compound. 3. The catalyst composition according to claim 2, wherein the electron donor in the diester is selected from diisobutyl phthalate, di-n-butyl phthalate, di-phthalate One or more of n-propyl esters. 4. The catalyst composition according to any one of claims 1 to 3, wherein the component (b) trialkylaluminum compound is selected from trimethylaluminum, triethylaluminum, triisobutyl One or more of the base aluminum. 5. The catalyst composition according to any one of claims 1-3, characterized in that the molar ratio of Al in component (b) to Ti in component (a) is 100-600. 6. The catalyst composition according to any one of claims 1-3, characterized in that the molar ratio of Al in component (b) to Ti in component (a) is 100-400. 7. The catalyst composition according to any one of claims 1 to 3, wherein the molar ratio of the sum of components (c) and (d) in terms of silicon to Ti in component (a) is 10- 40. 8. The catalyst composition according to any one of claims 1 to 3, wherein the molar ratio of Al in component (b) and the sum of components (c) and (d) in terms of Si is 10- 30. 9. The catalyst composition according to any one of claims 1-3, characterized in that, in the catalyst composition, the molar percentage between component (c) and component (d) is 2.5-10 : 90～97.5. 10. The catalyst composition according to claim 9, characterized in that, in the catalyst composition, the molar percentage between component (c) and component (d) is 3.0-10:90-97. 11. A method for preparing high melt index polypropylene, characterized in that the method comprises: using the catalyst composition according to any one of claims 1-10 to catalyze the polymerization of propylene in the presence of hydrogen. 12. The method of claim 11, wherein the propylene polymerization is carried out in bulk propylene or in gas phase propylene. 13. The method according to claim 11, characterized in that, the reaction temperature of the propylene polymerization is 50-90°C. 14. The method according to claim 13, characterized in that the reaction temperature is 60-80°C. 15. Use of the catalyst composition according to any one of claims 1 to 10 for the preparation of polypropylene.