CN115558195B

CN115558195B - High-impact-resistance copolymerized polypropylene with high fluidity and rigidity and preparation method thereof

Info

Publication number: CN115558195B
Application number: CN202110746794.6A
Authority: CN
Inventors: 刘小燕; 赵东波; 樊洁; 陈旭; 李广全; 王福善; 李丽; 张红星; 邓守军; 段宏义
Original assignee: Petrochina Co Ltd
Current assignee: Petrochina Co Ltd
Priority date: 2021-07-01
Filing date: 2021-07-01
Publication date: 2024-04-30
Anticipated expiration: 2041-07-01
Also published as: CN115558195A

Abstract

The invention relates to a high-impact-resistance copolymerized polypropylene resin with high fluidity and rigidity, wherein the impact-resistance polypropylene comprises a base material part and a rubber phase dispersed in the base material, the base material part is homopolymerized polypropylene, the rubber phase is a copolymer of ethylene and propylene, and a long-sequence polyethylene chain segment is embedded in the polypropylene base material; the mass content of ethylene structural units of the impact copolymer polypropylene is 16-25%, the mass content of rubber phase is 30-40%, the isotacticity of polypropylene in the matrix material is more than 98%, and the ratio of the ethylene structural units to the propylene structural units in the rubber phase is 0.3-0.7:1; the molecular weight distribution of the rubber phase is 22-50, the melt flow rate of the composition is more than 40g/10min, and the notched impact strength of the simple beam at room temperature is more than 50kJ/m ². The invention also provides a method for preparing the high-impact polypropylene resin.

Description

High-impact-resistance copolymerized polypropylene with high fluidity and rigidity and preparation method thereof

Technical Field

The invention relates to high-impact-resistance copolymerized polypropylene with good fluidity and rigidity and a preparation method thereof, which directly prepare the high-impact-resistance copolymerized polypropylene with high ethylene content and rubber phase content in a reactor, and belongs to the field of polymer production.

Background

The high-impact copolymerized polypropylene is one of important marks for improving the performance of polypropylene, can obviously reduce the addition amount of an elastomer in an automobile modified material, has obvious price advantage and can also consider the trend of single and recyclable polypropylene materials. The high-impact copolymer polypropylene prepared in situ from the reactor is the best choice, and compared with the high-impact copolymer polypropylene product obtained by post-processing modification, the high-impact copolymer polypropylene has excellent comprehensive performance and high cost performance.

Patent CN102532380a discloses a high flow impact copolymer polypropylene with a melt flow rate of 25-100g/10min, but the series of products cannot well give consideration to fluidity and impact resistance, and the improvement of product fluidity causes significant decrease of impact performance. The impact copolymer polypropylene product developed in the same patent CN102532381a also causes a significant drop in impact properties with an impact strength of only 11.3kJ/m ² at the highest when the flowability is increased. The impact copolymer polypropylene product developed by the publication of patent CN103788256A has improved flexural modulus compared with the product developed by patent CN102532380A, CN102532381A, but the impact strength is only up to 16kJ/m ². Patent CN105566533B discloses an impact-resistant polypropylene with low odor and low VOC content, and the product has the characteristics of narrow molecular weight distribution, low molecular weight content and good rigidity and toughness balance, and the highest impact strength of the product is 14.8kJ/m ². The patent CN111892778A develops an impact-resistant copolymerized polypropylene product with better impact performance at normal temperature and low temperature by introducing functional auxiliary agents, but the melt flow rate of the product is only 0.1-10g/10min. Patent CN110746703A develops an impact-resistant copolymerized polypropylene product with a melt flow rate of more than 35g/10min, an ethylene content of more than 7wt%, a rubber phase mass content of more than 15%, a notched impact strength of a simply supported beam of more than 7kJ/m ² and a flexural modulus of more than 1500Mpa at room temperature, but the notched impact strength of the simply supported beam of the product is only 7-9 kJ/m ². Patent CN109111643A discloses an impact-resistant copolymerized polypropylene product with a melt flow rate of more than 25g/10min, an ethylene content of 7-13wt%, a rubber phase content of 18-25%, a notched impact strength of a simply supported beam of more than 8kJ/m ² and a flexural modulus of more than 1050Mpa, wherein the actual notched impact strength of the product is 10-11kJ/m ².

Currently, the processes for producing impact copolymer polypropylene in a reactor mainly include a liquid-gas phase process and a bulk phase process. The gas phase process for producing the impact copolymer polypropylene requires two gas phase reactors, propylene bulk homopolymerization is carried out in the first gas phase reactor, propylene and alpha-olefin copolymerization is carried out in the second gas phase reactor, and the gas phase process has advantages in developing the impact copolymer polypropylene product with excellent flowability, rigidity and impact property, but has higher product odor. A liquid phase bulk method, such as Spheripol-II propylene polymerization process, adopts liquid phase and gas phase reactors in series, performs propylene bulk homopolymerization in a kettle-type or loop reactor, and performs propylene and alpha-olefin (mainly ethylene) copolymerization in the gas phase reactor.

For the polymerization process of Spheripol-II polypropylene, because the rubber phase is easy to flow, the reactor sticks to the kettle, so that it is difficult to develop an impact-resistant copolymerized polypropylene product with the rubber phase content of more than 30wt%, that is, it is difficult to develop a high impact-resistant copolymerized polypropylene product with good fluidity and rigidity. Because for impact copolymer polypropylene, the ethylene content, rubber phase content and composition in the product determine the final impact properties of the product. The final ethylene content, rubber phase content and composition of the impact copolymer polypropylene product is determined by the ethylene set point and the ethylene/ethylene+propylene gas ratio (C2/C2+c3) in the gas phase copolymerization stage, irrespective of the main catalyst. Under the condition of low C2/C2+C3, the ethylene propylene random content in the rubber generated by ethylene propylene copolymerization reaction is high, and the excessively low C2/C2+C3 ratio is extremely easy to cause the phenomenon of reactor sticking of a gas phase reactor, thereby influencing the long-period stable operation of the device. For the Spheripol-II process, higher C2/C2+ C3 is generally required, otherwise, the phenomenon of kettle sticking easily occurs. However, for high melt index, high impact copolymer polypropylene, to achieve high impact strength of the product, it is necessary to reduce the C2/c2+c3 in the gas phase reactor, which in turn increases the risk of sticking to the kettle, resulting in production that is not smooth.

Disclosure of Invention

In view of the shortcomings in the prior art, the first object of the present invention is to provide a high impact copolymer polypropylene with good fluidity and rigidity, and the second object of the present invention is to provide a preparation method of the above product on a spheropol-II process device, aiming at the technical prejudice that the spheropol-II polypropylene polymerization process is difficult to produce a copolymer polypropylene product with a melt flow rate of more than 40g/10min and an impact strength of more than 50KJ/m ².

The first object of the invention is to provide a high impact copolymer polypropylene with good fluidity and rigidity, wherein the impact copolymer polypropylene comprises a matrix and a rubber phase dispersed in the matrix, the matrix is homo-polypropylene, the rubber phase is a copolymer of ethylene and propylene, and the polypropylene matrix is embedded with more than 5wt% of long-sequence polyethylene segments; the mass content of the ethylene structural unit in the rubber phase is 16-25%, the mass content of the rubber phase in the high impact copolymer polypropylene is 30-40%, the isotacticity of the polypropylene in the matrix is more than 98%, and the ratio of the ethylene structural unit content to the propylene structural unit content in the rubber phase is 0.3-0.7:1; the molecular weight distribution of the rubber phase is 22-50, the melt flow rate of the composition is more than 40g/10min, the notch impact strength of the simple beam is more than 50kJ/m ² at room temperature, the notch impact strength of the simple beam at-20 ℃ is more than 8kJ/m ², and the flexural modulus is more than 850MPa.

The impact-resistant copolymerized polypropylene can be used for direct injection molding of soft materials, is more applied to polypropylene modified materials for automobiles, and has good processability due to higher melt flow rate, and meanwhile, has higher impact strength, so that the addition of elastomer such as POE in a modified formula can be obviously reduced in the automobile modified materials, and the cost of the modified materials can be obviously reduced.

Because the long-sequence polyethylene chain segments with the weight percentage of more than 5% are embedded in the impact-resistant copolymerized polypropylene matrix part, the compatibility of the homopolymerized polypropylene matrix and a rubber phase is increased, the stability and uniformity of the impact performance of the product are ensured by combining the characteristics of high rubber phase content and wide molecular weight distribution of the rubber phase in the product, the impact strength of the simply supported beams after the product is molded into a sample strip is only reduced by 1-2kJ/m ² after the product is placed for 4 hours, 8 hours, 24 hours and 48 hours, and the standard deviation s of the average value of test results of the notch impact strength of the simply supported beams (23 ℃ and the sample strip is placed for 48 hours) is less than 0.3.

The second object of the present invention is to provide a process for preparing the high impact copolymer polypropylene as described above.

The method specifically comprises the following steps:

1) The first stage: in the presence of hydrogen and a Ziegler-Natta catalyst system containing a first external electron donor, carrying out liquid phase bulk polymerization of propylene in a first loop reactor to obtain a polymerization product;

2) And a second stage: the polymerization product of the first stage enters a second loop reactor and further undergoes a propylene liquid phase bulk polymerization reaction in the presence of hydrogen to obtain a polymerization product;

3) And a third stage: the second stage polymer product is subjected to a high pressure flash tank to remove unreacted propylene monomer and hydrogen, then enters a gas phase reactor, and is subjected to gas phase copolymerization of propylene and ethylene in the presence of a Ziegler-Natta catalyst system containing a second external electron donor, so as to prepare the polymer.

The preparation method of the high-fluidity high-impact-resistance copolymerized polypropylene further comprises the steps of adding a compounding auxiliary agent into the polymer obtained in the third stage, extruding and granulating, wherein the compounding auxiliary agent is an antioxidant and an acid absorber which are commonly added in the field, the antioxidant content is 1000-3000ppm, the acid absorber content is 300-600ppm, and the polymer is obtained after extrusion granulation by polyolefin common equipment.

In the first stage, the polymerization temperature is 65-75 ℃ and the polymerization pressure is 4000-4500KPa.

In the first stage, zigler-Natta catalyst system mainly comprises: a solid catalyst component mainly comprising magnesium, titanium, halogen and an internal electron donor; an organoaluminum compound component; a first external electron donor component; wherein the ratio of the solid catalyst component to the organic aluminum compound is 1:10 to 1:500 by mass of titanium/aluminum; preferably 1:25 to 1:100. The mass ratio of the organic aluminum compound to the external electron donor is 1-10, preferably 3-7.

The specific surface area of the Ziegler-Natta catalyst is more than 350m ²/g, and the pore diameter is more than 5nm.

The organoaluminum compound is an alkylaluminum compound, preferably triethylaluminum.

The general formula of the first external electron donor is R ₁R₂Si(OR₃)₂, wherein R ₁ and R ₂ are respectively identical or different C1-C6 linear or branched aliphatic groups, and if the first external electron donor is a cyclic aliphatic group, only one cyclic aliphatic group can exist in R ₁ and R ₂; r ₃ is C1-C2 straight-chain alkane. Such as diisopropyldimethoxysilane, diisobutyldiethoxysilane, cyclopentyl-methyl-dimethoxysilane, cyclopentyl-ethyl-dimethoxysilane, di-2-methylbutyl-dimethoxysilane, di-2-methylpropyl-dimethoxysilane, cyclohexyl-methyl-dimethoxysilane, cyclohexyl-ethyl-dimethoxysilane, cyclohexyl-methyl-diethoxysilane, preferably cyclopentyl-ethyl-dimethoxysilane.

In the second stage, the polymerization temperature is 70-75 ℃ and the polymerization pressure is 4000-4500KPa. And simultaneously controlling the hydrogen concentration in the water to obtain a target product.

In the third stage, the polymerization temperature is 75-85 ℃ and the polymerization pressure is 1200-1400KPa.

The second external electron donor is selected from compounds of the general formula R ₄R₅Si(OR₆)₂, wherein R ₄、R₅ is the same or different C5-C10 branched or unbranched cyclic alkyl or aromatic hydrocarbon group, R ₆ is a C1-C2 linear alkyl group, such as dicyclopentyl dimethoxy silane (DCPMS), dicyclopentyl-dimethoxy silane, dicyclohexyldimethoxy silane, bis 3, 4-methylcyclohexyl-dimethoxy silane, diphenyl diethoxy silane, bis 2 methylphenyl-dimethoxy silane, bis 3 isopropylphenyl-dimethoxy silane, pentyl, phenyl-dimethoxy silane, preferably diphenyl dimethoxy silane.

The mass ratio of the organoaluminum component added in the first stage to the second external electron donor component is 1 to 7, preferably 2 to 5.

In the third stage, the ratio of each monomer in the gas phase polymerization is adjusted according to the product property, and ethylene/(ethylene+propylene) is usually controlled to 0.20 to 0.40 (molar ratio), preferably 0.22 to 0.30 (molar ratio).

In the compound auxiliary agent, the main antioxidant of the antioxidant is pentaerythritol tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ] (1010), the auxiliary antioxidant is tri (2, 4-di-tert-butylphenyl) phosphite (168), and the acid absorbing agent is calcium stearate.

According to the invention, a high specific surface area and high pore diameter catalyst is adopted on a Spheripol-II process device, different types of external electron donors are added in a loop reactor and a gas phase reactor, the composition and sequence structure of propylene and ethylene copolymers generated in the gas phase reactor are regulated and controlled, the rubber phase content is higher than 30wt% under the condition that the key process parameter gas phase ratio (C2/C2+C3) for determining whether the gas phase reactor can run for a long period is not reduced, the molecular weight of the rubber phase is distributed to 22-50, the high-flow high-impact copolymerized polypropylene product with a long sequence polyethylene chain segment of more than 5wt% is embedded in a polypropylene matrix part, the melt flow rate is higher than 40g/10min, and the impact strength of a simple beam is higher than 50kJ/m ². Overcomes the technical prejudice that the development of the high-fluidity and high-impact-resistance copolymerized polypropylene product is difficult to carry out on a Spheripol-II process device.

The invention only needs to connect a second external electron donor inlet after the gas-phase circulating gas heat exchanger of the gas-phase reactor, and the second external electron donor enters the gas-phase reactor for reaction along with the high-speed vaporization of the circulating gas, so that the device has small modification, low cost and easy implementation.

Before the first loop reactor reaction, it is generally necessary to carry out a prepolymerization of a small amount of propylene in the presence of Zigler-Natta catalyst system, and then to the first loop reactor of the first stage, the temperature of the prepolymerization being-10 to 60℃and preferably 10 to 30 ℃. The factor of the prepolymerization is 30 to 300 times, preferably 50 to 150 times. The prepolymerization can be carried out in a continuous stirrer or in a small loop reactor.

Propylene can be directly subjected to prepolymerization reaction in the presence of the Zigler-Natta catalyst system, or can be subjected to precomplexation reaction before entering a prepolymerization reactor for prepolymerization reaction, and then entering a first reactor. The purpose of the pre-complexation reaction is to allow for sufficient and efficient mixing of the catalyst components (main catalyst, alkyl aluminum compound and first external electron donor), which may be a continuous stirred tank reactor, loop reactor, etc. The pre-complexation reaction temperature is-10-60 ℃, preferably 10-30 ℃. The pre-complexation reaction time is 30-100min, preferably 5-30min.

Drawings

FIG. 1 is a graph showing the sequence of ethylene, propylene binary and ternary monomers for the rubber phase portion of example 1 and comparative example 2;

FIG. 2 shows the ethylene, propylene binary and ternary monomer sequence profiles for the polypropylene matrix portion of example 1 and comparative example 2;

FIG. 3 distribution plots of ethylene, propylene binary and ternary monomer sequences for the polypropylene matrix portion of example 3 and comparative example 4;

FIG. 4 shows the ethylene, propylene binary and ternary monomer sequence profiles for the rubber phase portion of example 3 and comparative example 4.

Detailed Description

The following describes embodiments of the present invention in detail: the present example is implemented on the premise of the technical scheme of the present invention, and detailed implementation modes and processes are given, but the protection scope of the present invention is not limited to the following examples, and experimental methods without specific conditions are not noted in the following examples, and generally according to conventional conditions.

The polymer-related data in the examples were obtained as follows:

(1) Melt Flow Rate (MFR): measured according to GB/T3682-2000 at 230℃under a load of 2.16 kg.

(2) Impact strength of simple beam: according to GB/T1043.1-2008

(3) Flexural modulus: measured according to GB/T9341-2008.

(4) Polymer ethylene content determination: infrared (IR) method.

(5) Polymer ortho-xylene solubles content (rubber phase): measured according to the method described in astm d 5492.

(6) Polymer monomer sequence distribution: the measurement is carried out by using a Bruce DMX400 nuclear magnetic instrument, the solvent is deuterated o-dichlorobenzene, and the scanning is carried out 6000 times.

Example 1

This example used a Zigler-Natta catalyst with a specific surface area of 377.2m ²/g, a pore size of 5.413nm and an ethylene binding rate of up to 98 wt%.

Pre-complexation: the solid catalyst, triethylaluminum (TEA), and the first external electron Donor cyclopentyl-ethyl-dimethoxy silane (Donor-1) were pre-complexed at 10deg.C for 20min. The flow rate of triethylaluminum entering the pre-complexation was 6.33g/hr, the flow rate of cyclopentyl-ethyl-dimethoxy silane was 1.58g/hr, and the flow rate of the main catalyst was 0.158g/hr. Wherein the TEA/Donor mass ratio is 4.

Prepolymerization: the pre-complexed catalyst system continuously enters a pre-polymerization reactor for pre-polymerization reaction, the pre-polymerization is carried out under the liquid phase body environment of propylene, the temperature is 15 ℃, the residence time is 4min, and the pre-polymerization multiple of the catalyst under the condition is 120-150 times.

The slurry after the prepolymerization was fed into a first loop reactor, the polymerization reaction temperature in the first loop reactor was 70℃and the reaction pressure was 4000KPa, and the hydrogen addition was 6000ppm (gas chromatography).

The polymer slurry prepared in the first loop reactor enters the second loop reactor, the polymerization temperature is 72 ℃, the reaction pressure is 4000KPa, and the hydrogen adding amount is 6000ppm.

And (3) removing unreacted propylene monomers and hydrogen from the polymer slurry prepared in the second loop reactor through a high-pressure flash evaporator, and then, feeding the polymer slurry into a gas phase reactor to perform ethylene-propylene gas phase copolymerization. The second external electron Donor diphenyldimethoxysilane (Donor-2) was continuously added into the gas phase reactor from the gas phase circulating gas heat exchanger to participate in the reaction. The second external electron donor added here was calculated as TEA added to the whole system, and the mass ratio of TEA added to the second external electron donor added to the whole system was 3. The reaction temperature was 80 ℃, the reaction pressure was 1400KPa, the ratio of control gas to C2/C2+C3 was 0.24 (molar ratio), and the hydrogen addition amount was 1.5g/h.

500Ppm of pentaerythritol tetrakis [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate (1010), 1000ppm of tri (2, 4-di-tert-butylphenyl) phosphite (168) and 400ppm of calcium stearate serving as an acid absorber are added into polymer powder prepared by a gas phase reactor, and after uniform mixing, the mixture is extruded and granulated, and the obtained granules are subjected to performance test according to the current relevant GBT standard.

The specific process conditions and the performance test results are shown in Table 1.

Example 2

Example 2 the procedure is similar to example 1, except that the polymerization stage components are added in different amounts, specifically, in the pre-complexation stage, the mass ratio of triethylaluminum to the first external electron Donor cyclopentyl-ethyl-dimethoxy silane (Donor-1) is 6. The mass ratio of triethylaluminum to diphenyldimethoxysilane (Donor-2) as a second external electron Donor was 4.

In the first loop reactor, the reaction temperature was 72℃and the reaction pressure was 4200KPa, the hydrogen concentration was 7000ppm.

In the second loop reactor, the reaction temperature was 70 ℃, the reaction pressure was 4100KPa, and the hydrogen concentration was 7000ppm.

In the gas phase reactor, the reaction temperature was 84℃and the ethylene/(ethylene+propylene) molar ratio was 0.28, and the hydrogen addition was 2g/h.

600Ppm of main antioxidant 1010, 1200ppm of auxiliary antioxidant 168 and 500ppm of acid absorber calcium stearate are added into polymer powder.

Other process conditions were consistent with example 1, and specific process conditions and performance test results are shown in table 1.

Example 3

Example 3 the procedure is similar to example 1 except that the external electron donor is changed, the first external electron donor is changed to cyclohexyl-methyl-dimethoxysilane and the second external electron donor is dicyclopentyl dimethoxysilane. Wherein the mass ratio of TEA to the first external electron donor is 3, and the mass ratio of TEA to the second external electron donor is 2.5.

In the first loop reactor, the hydrogen concentration was 9500ppm, otherwise identical to the reaction conditions of the first loop reactor of example 1.

In the second loop reactor, the reaction temperature was 71 ℃, the reaction pressure was 4200KPa, and the hydrogen concentration was 9500ppm.

In the gas phase reactor, the reaction temperature was 82℃and the reaction pressure was 1300KPa, the ethylene/(ethylene+propylene) molar ratio was 0.23, and the hydrogen addition was 3g/h. .

Other process conditions and additive amounts were consistent with example 1, and specific process conditions and performance test results are shown in table 1.

Example 4

Example 4 the procedure is similar to that of example 3, except that the polymerization stage components are added in different amounts, specifically, in the pre-complexation stage, the mass ratio of triethylaluminum to the first external electron donor cyclohexyl-methyl-dimethoxysilane is 7. The mass ratio of TEA to the second external electron donor dicyclopentyl dimethoxy silane is 5.

In the first loop reactor, the reaction temperature was 69℃and the hydrogen concentration was 2000ppm, otherwise identical to the reaction conditions in the first loop reactor of example 3.

In the second loop reactor, the reaction temperature was 72℃and the hydrogen concentration 9000ppm, otherwise identical to the reaction conditions of the second loop reactor of example 3.

In the gas phase reactor, the ethylene/(ethylene+propylene) molar ratio was 0.28, and the hydrogen addition amount was 2.5g/h, otherwise identical to the reaction conditions in the gas phase reactor of example 3.

Other process conditions were consistent with example 3, and specific process conditions and performance test results are shown in table 1.

Example 5

Example 5 the procedure is similar to example 1 except that without the pre-complexation step, the three components of the catalyst system are fed directly into the pre-polymerization reactor for pre-polymerization in the presence of a small amount of propylene, and the specific process conditions and performance test results are shown in Table 1.

Example 6

Example 6 the procedure was similar to example 5, except that the external donor was changed, the first external donor was changed to diisobutyldiethoxysilane, and the second external donor was dicyclopentyldimethoxysilane. Wherein the mass ratio of TEA to the first external electron donor is 3.5, and the mass ratio of TEA to the second external electron donor is 3.

In the first loop reactor, the reaction temperature was 68 ℃, the reaction pressure was 4200KPa, and the hydrogen concentration was 3000ppm.

In the second loop reactor, the reaction temperature was 73 ℃, the reaction pressure was 4200KPa, and the hydrogen concentration was 8500ppm.

In the gas phase reactor, the reaction temperature was 85℃and the reaction pressure was 1400KPa, the ethylene/(ethylene+propylene) molar ratio was 0.25, and the hydrogen addition was 3.5g/h.

600Ppm of main antioxidant 1010, 1200ppm of auxiliary antioxidant 168 and 500ppm of acid absorber calcium stearate are added into the polymer powder.

Example 7

Example 7 the procedure was similar to example 6, except that the pre-complexation step was omitted and the amounts of the components added in the polymerization stages were different, specifically, in the pre-polymerization stage, the mass ratio of TEA to diisobutyldiethoxysilane as the first external donor was 6 and the mass ratio of TEA to dicyclopentyldimethoxysilane as the second external donor was 4.

In the first loop reactor, the reaction temperature was 70℃and the hydrogen concentration was 9500ppm, the other conditions being identical to those of example 6.

In the second loop reactor, the reaction temperature was 72 ℃, the reaction pressure was 4000Kpa, and the hydrogen concentration was 4000ppm.

In the gas phase reactor, the reaction temperature was 82℃and the reaction pressure was 1300Kpa, the ethylene/(ethylene+propylene) molar ratio was 0.22, and the hydrogen addition amount was 5g/h.

400Ppm of main antioxidant 1010, 800ppm of auxiliary antioxidant 168 and 400ppm of acid absorber calcium stearate are added into the polymer powder.

Other process conditions and additive amounts were consistent with example 6, and specific process conditions and performance test results are shown in table 1.

Example 8

Example 8 the procedure is similar to example 1 except that the external electron donor is changed, the first external electron donor is changed to cyclopentyl-methyl-dimethoxysilane and the second external electron donor is diphenyldimethoxysilane. Specifically, in the pre-complexation stage, the mass ratio of TEA to the first external electron donor cyclopentyl-methyl-dimethoxy silane is 4. In the gas phase reactor, the mass ratio of TEA to diphenyldimethoxysilane as the first external electron donor was 2.5.

In the first loop reactor, the reaction temperature was 74℃and the hydrogen concentration was 9500ppm, otherwise identical to the reaction conditions in the first loop reactor of example 1.

In the second loop reactor, the hydrogen concentration was 9500ppm, otherwise identical to the reaction conditions in the second loop reactor of example 1.

In the gas phase reactor, the reaction temperature was 84℃and the ethylene/(ethylene+propylene) molar ratio was 0.23, and the hydrogen addition amount was 1.9g/h, otherwise identical to the reaction conditions in the second loop reactor of example 1.

Comparative example 1

The gas phase reactor of comparative example 1 was not charged with the second external electron donor, and the other conditions were the same as in example 1. The specific process conditions and the performance test results are shown in Table 1.

Comparative example 2

In comparative example 2, the second external electron donor was not added to the gas phase reactor, and ethylene/(ethylene+propylene) was controlled to 0.20 (molar ratio), and the other conditions were the same as in example 1.

Other conditions were the same as in example 1. The specific process conditions and the performance test results are shown in Table 1.

Comparative example 3

Comparative example 3 the procedure was similar to example 2 except that the first external donor was changed to tetraethoxysilane. Specifically, in the pre-complexation stage, the mass ratio of TEA to the tetraethoxysilane as the first external electron donor is 3. In the gas phase reactor, the mass ratio of TEA to diphenyldimethoxysilane as the first external electron donor was 2.5.

In the first loop reactor, the reaction temperature was 70℃and the hydrogen concentration was 5000ppm, otherwise the reaction conditions in the first loop reactor of example 2 were identical.

In the second loop reactor, the hydrogen concentration was 5000ppm, otherwise identical to the reaction conditions in the second loop reactor of example 2.

In the gas phase reactor, the hydrogen addition was 1g/h, otherwise identical to the reaction conditions in the second loop reactor of example 1.

Other process conditions and additive amounts were consistent with example 2, and specific process conditions and performance test results are shown in table 1.

Comparative example 4

In comparative example 4, the second external electron donor was not added to the gas phase reactor, and ethylene/(ethylene+propylene) was controlled to 0.18 (molar ratio) in the gas phase reactor, and the other conditions were the same as in example 3. The specific process conditions and the performance test results are shown in Table 1.

Examples 1-4 and examples 7-8 show that the impact-resistant copolymerized polypropylene resin with the melt flow rate of more than 40g/10min and the impact strength of more than 50kJ/m ² can be prepared by adopting the technical means of the invention in the Spherepol-II propylene polymerization process. In comparative example 1, the process for preparing the product was such that the second external electron donor was not added to the gas phase reactor, and the properties of the products prepared in comparative example 1 and comparative example 1 showed that the impact copolymer polypropylene product prepared by the process of comparative example 1 was slightly higher in melt flow rate than example 1, but lower in flexural modulus and impact strength than example 1, while maintaining higher ethylene content and rubber phase content. In comparative example 2, the process for preparing the product was to add no second external electron donor into the gas phase reactor, and simultaneously reduce the ratio of C2/C2+C3 in the gas phase reactor, and the properties of the products prepared in comparative example 2 and example 1 show that the impact copolymer polypropylene product prepared by the process of comparative example 2 maintains higher impact property on the basis of maintaining higher content of rubber phase, but the melt flow rate and flexural modulus of the product are far lower than those of example 1. In comparative example 3, the first external electron donor in the production process of the product was changed to tetraethoxysilane having good hydrogen tone sensitivity, and the melt flow rate of the product was greatly increased as compared with the examples, but the flexural modulus and impact strength of the product were greatly reduced as compared with the examples. The properties of the products prepared in comparative example 3 and comparative example 4 show that the impact copolymer polypropylene product prepared by the process of comparative example 4, due to the lower C2/C2+C3, still has a higher rubber phase content with the ethylene content kept low, but the rubber phase molecular weight distribution of the product is smaller than that of example 3, and the melt flow rate, impact strength and flexural modulus of the product are lower than those of example 3. Examples 5-6, wherein the polymerization process did not have a pre-complexation step, and wherein the process parameters were fine-tuned, produced products with properties that were not significantly different from examples 1-4.

The impact copolymer polypropylene prepared in example 1, example 3, comparative example 2, comparative example 4 was fractionated with o-xylene to obtain xylene solubles (rubber phase) and xylene insoluble matters (polypropylene matrix), and the obtained two-part fractionated products were subjected to microscopic sequence distribution analysis of monomers. Comparative example 1 and comparative example 2, the ratio of C2/c2+c3 in the preparation process of example 1 was higher than that of comparative example 2, while the ethylene content in the product was slightly higher than that of comparative example 2, but the EP and EE contents in the binary parts of ethylene and propylene in the rubber phase of example 1 were smaller than that of comparative example 2, as shown in fig. 1 and table 3, and the ternary composition EEP and EEE contents in the product of example 1 were also lower than that of comparative example 2, that is, the second external electron donor of the present invention added in the gas phase reactor was equivalent to the effect of reducing the gas phase ratio, and a high impact copolymer product could be developed without significantly reducing the gas phase ratio under the process conditions. The EEE content in the ethylene and propylene ternary composition of the polypropylene matrix of example 1 was higher than that of the comparative example 2 sample, as shown in FIG. 2, table 3. The existence of the long-sequence polyethylene chain segments embedded in the polypropylene matrix of the anti-impact copolymerized polypropylene product increases the compatibility of the ethylene propylene random copolymer and the polypropylene phase, so that the anti-impact copolymerized polypropylene product with the structure has more excellent impact performance stability. Example 3 and comparative example 4 the distribution of ethylene and propylene monomers in the rubber phase and polypropylene matrix is similar to that of example 1 and comparative example 1, as shown in fig. 4, 3 and table 4.

TABLE 3 binary and ternary monomer sequence distribution of the rubber phase fraction, the polypropylene matrix fraction of example 1 and comparative example 2

TABLE 4 binary and ternary monomer sequence distribution of the rubber phase fraction, the polypropylene matrix fraction of example 3 and comparative example 4

Of course, the present invention is capable of other various embodiments and its several details are capable of modification and variation in light of the present invention by one skilled in the art without departing from the spirit and scope of the invention.

Claims

1. The high impact copolymer polypropylene resin with good fluidity and rigidity is characterized by comprising a matrix and a rubber phase dispersed in the matrix, wherein the matrix is homo-polypropylene, has isotacticity of more than 98 percent and is embedded with a long-sequence polyethylene chain segment of more than 5 weight percent; the rubber phase is a copolymer of ethylene and propylene, the molecular weight distribution is 22-50, wherein the ratio of the content of ethylene structural units to the content of propylene structural units is 0.3-0.7:1;

the mass content of ethylene structural units of the impact copolymer polypropylene is 16-25%, and the mass content of rubber phases is 30-40%;

The melt flow rate of the polypropylene copolymer resin is greater than 40g/10min, the notch impact strength of the simply supported beam is greater than 50kJ/m ² at room temperature, the notch impact strength of the simply supported beam at-20 ℃ is greater than 8kJ/m ², and the flexural modulus is greater than 850MPa.

2. A method for preparing the high impact copolymer polypropylene resin as claimed in claim 1, wherein the polymerization process of spheropol-II propylene is adopted, comprising the following steps:

(1) Under the action of hydrogen and a Ziegler-Natta catalyst containing a first external electron donor, carrying out liquid phase bulk polymerization of propylene in a first loop reactor to obtain a polypropylene product;

(2) The polypropylene product enters a second loop reactor to carry out propylene liquid phase bulk polymerization in the presence of hydrogen to obtain a polymerization product;

(3) Removing unreacted propylene monomers and hydrogen from the polymerization product in the step (2) through a high-pressure flash tank, then entering a gas phase reactor, and carrying out gas phase copolymerization reaction of propylene and ethylene under the action of a Ziegler-Natta catalyst containing a second external electron donor to prepare a copolymerization product;

Wherein the general formulas of the first external electron donor are R ₁R₂Si(OR₃)₂,R₁ and R ₂ which are the same or different and are respectively and independently C1-C6 straight-chain or branched aliphatic groups, and only one cyclic aliphatic group can exist in R ₁ and R ₂; r ₃ is C1-C2 straight-chain alkane;

The general formula of the second external electron donor is R ₄R₅Si(OR₆)₂,R₄、R₅ which are the same or different and are respectively and independently aromatic hydrocarbon groups or C5-C10 branched or unbranched cyclic alkane groups, and R ₆ is C1-C2 linear alkane groups;

The specific surface area of the Ziegler-Natta catalyst is more than 350m ²/g, and the pore diameter is more than 5 nm.

3. The method according to claim 2, wherein the first external electron donor is at least one selected from the group consisting of diisopropyldimethoxysilane, diisobutyldiethoxysilane, cyclopentyl-methyl-dimethoxysilane, cyclopentyl-ethyl-dimethoxysilane, bis (2-methylbutyl) -dimethoxysilane, bis (2-methylpropyl) -dimethoxysilane, cyclohexyl-methyl-dimethoxysilane, cyclohexyl-ethyl-dimethoxysilane, and cyclohexyl-methyl-diethoxysilane.

4. The method of claim 3, wherein the first external electron donor is cyclopentyl-ethyl-dimethoxy silane.

5. The method according to claim 2, wherein the second external electron donor is at least one selected from dicyclopentyldimethoxy silane (DCPMS), bis (3 methylcyclopentyl) -dimethoxy silane, dicyclohexyldimethoxy silane, bis (3, 4-methylcyclohexyl) -dimethoxy silane, diphenyldimethoxy silane, diphenyldiethoxy silane, bis (2 methylphenyl) -dimethoxy silane, bis (3 isopropylphenyl) -dimethoxy silane, and cyclopentylphenyl-dimethoxy silane.

6. The method of claim 5, wherein the second external electron donor is diphenyldimethoxysilane.

7. The process according to claim 2, wherein the temperature in the first loop reactor is 65-75 ℃ and the pressure is 4000-4500KPa; the temperature in the second loop reactor is 70-75 ℃ and the pressure is 4000-4500KPa; the temperature in the gas phase reactor is 75-85 ℃ and the pressure is 1200-1400KPa.

8. The process according to claim 2, wherein the molar ratio of ethylene/(ethylene+propylene) in the gas phase reactor is 0.20 to 0.40.

9. The process according to claim 8, wherein the molar ratio of ethylene/(ethylene+propylene) in the gas phase reactor is 0.22 to 0.30.

10. The method of claim 2, wherein the gas phase reactor comprises a gas phase recycle gas heat exchanger followed by a second external electron donor feed.

11. The preparation method according to claim 2, further comprising adding a compounding aid to the copolymerization product obtained in the step (3), and then extruding and granulating, wherein the compounding aid is an antioxidant and an acid absorber, and the antioxidant content is 1000-3000ppm and the acid absorber content is 300-600ppm.

12. The method of claim 11, wherein the primary antioxidant is pentaerythritol tetrakis [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate (1010), the secondary antioxidant is tris (2, 4-di-tert-butylphenyl) phosphite (168), and the acid acceptor is calcium stearate.

13. The process according to claim 2, wherein propylene is prepolymerized prior to step (1), comprising the steps of: propylene is subjected to a prepolymerization reaction in the presence of the Zigler-Natta catalyst containing the first external electron donor, wherein the temperature of the prepolymerization reaction is between-10 and 60 ℃, and the multiple of the prepolymerization reaction is between 30 and 300 times.

14. The method according to claim 13, wherein the temperature of the prepolymerization is-10 to 30℃and the multiple of the prepolymerization is 50 to 150 times.

15. The process of claim 13, wherein propylene is pre-complexed prior to the pre-polymerization reaction, the pre-complexation reaction being at a temperature of-10 to 60 ℃.

16. The method of claim 15, wherein the temperature of the pre-complexation reaction is 10-30 ℃.

17. The method of claim 15, wherein the pre-complexation reaction is performed for a period of 30-100 minutes.

18. The method of claim 15, wherein the pre-complexation reaction is performed for a period of 5 to 30 minutes.