CN114058113A - High-impact transparent polypropylene resin and preparation method thereof - Google Patents

High-impact transparent polypropylene resin and preparation method thereof Download PDF

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CN114058113A
CN114058113A CN202010798707.7A CN202010798707A CN114058113A CN 114058113 A CN114058113 A CN 114058113A CN 202010798707 A CN202010798707 A CN 202010798707A CN 114058113 A CN114058113 A CN 114058113A
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polypropylene resin
stage
ethylene
propylene
high impact
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CN114058113B (en
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刘小燕
陈旭
李丽
李广全
张红星
王玲玲
王霞
赵东波
王福善
邓守军
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Petrochina Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
    • C08L23/10—Homopolymers or copolymers of propene
    • C08L23/12—Polypropene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F110/00—Homopolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
    • C08F110/04—Monomers containing three or four carbon atoms
    • C08F110/06—Propene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
    • C08F210/04—Monomers containing three or four carbon atoms
    • C08F210/06—Propene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2201/00—Properties
    • C08L2201/10—Transparent films; Clear coatings; Transparent materials
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2205/00—Polymer mixtures characterised by other features
    • C08L2205/03—Polymer mixtures characterised by other features containing three or more polymers in a blend

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  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
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  • Organic Chemistry (AREA)
  • Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)

Abstract

The invention provides a high impact transparent polypropylene resin and a preparation method thereof, wherein the preparation method of the polypropylene resin comprises the following steps: firstly, carrying out liquid-phase bulk polymerization on propylene in a first loop reactor in the presence of hydrogen and a Ziegler-Natta catalyst system containing an external electron donor; the polymerization product enters a second loop reactor, and propylene liquid phase bulk random polymerization is carried out in the presence of hydrogen and ethylene; removing unreacted propylene monomer, ethylene monomer and hydrogen from the polymer product, then feeding the polymer product into a third gas-phase reactor, and performing ethylene-propylene gas-phase copolymerization reaction to prepare polymer powder; polymer powderAdding a compound auxiliary agent into the materials, extruding and granulating to obtain the material with the melt flow rate of 10-30g/10min, the haze (1mm) of less than or equal to 13 percent and the normal temperature impact property (23 ℃) of 15-30kJ/m2And the low-temperature impact property (-20 ℃) is more than or equal to 3.5kJ/m2The polypropylene resin of (1). The polypropylene resin has the characteristics of excellent transparency and high impact resistance at normal and low temperatures, and the polypropylene resin has the advantages of small addition amount of the transparent nucleating agent, low cost and easy molding.

Description

High-impact transparent polypropylene resin and preparation method thereof
Technical Field
The invention belongs to the field of high polymer materials, and particularly relates to a transparent polypropylene resin with high impact resistance under normal temperature and low temperature conditions and a preparation method thereof.
Background
The polypropylene resin has the characteristics of good heat resistance, processability and mechanical strength, low density, easiness in recycling, recyclability and the like, and is widely applied to the fields of automobiles, electric appliances, daily necessities, houses, packaging and the like. The transparent polypropylene is widely applied to food packaging, medical products, media product packaging, sorting boxes, beverage bottles, milk bottles and the like because the product is transparent, beautiful, good in sanitation, heat-resistant and the like. Due to the advantages of transparent polypropylene, the development of polypropylene has been rapidly progressed in the world since the early eighties of the last century. In recent years, the consumption of the transparent polypropylene in China is also rapidly increased, and the annual demand of the transparent polypropylene in China in 2016 is about 100 ten thousand tons.
The traditional transparent polypropylene is usually obtained by adding a transparent agent into homo-polypropylene or random co-polypropylene, and the outstanding problem exists in the use at present that the impact property of the product is poor in low-temperature environment, and the damage of refrigerator drawers when being impacted can not be met. The impact-resistant copolymerized polypropylene has greatly improved normal-low temperature impact resistance due to the introduction of a rubber phase in a polypropylene matrix, but cannot meet the requirements of various fields on transparency due to large size of the rubber phase, poor transparency of products and haze of about 60 percent generally.
Under the condition of needing both transparency and high impact resistance, the random polypropylene is mainly blended with elastomers such as POP, POE, SEBS and the like at present, the method can improve the impact resistance of the product to a certain extent, and on the other hand, secondary processing is needed, so that the cost of the product is increased, and meanwhile, the haze of the product is increased due to the addition of the elastomer. Patent publication No. CN106554448A (application No. 201510640822.0), discloses "high impact transparent polypropylene": the patent prepares an ethylene-propylene copolymer with the ethylene content of 4.0-8.0 wt% by controlling gas-phase reaction process parameters, wherein 1-3 wt% participates in the random copolymerization of ethylene and propylene to form random copolymerization polypropylene, 3-5 wt% participates in the block copolymerization of ethylene and propylene to form impact copolymerization polypropylene, and the prepared product has good transparent impact-resistant comprehensive performance by adding additives such as a transparent agent and the like, but the formed random copolymerization polypropylene and the impact copolymerization polypropylene are both generated in a gas-phase reactor, and in order to give consideration to the transparency of the product at the same time, the normal temperature impact performance is good, but the low temperature impact performance (-20 ℃) is only 1.2-1.5kJ/m2。
Invention patent publication No. CN107880402A (application No. 201711183177.X), discloses "high transparent high impact polypropylene resin suitable for blow molding process": the patent mixes and extrudes a random copolymer of propylene and ethylene, the ethylene content of which is 3-5 wt% and the melt flow rate of which is 0.1-2.0g/10min, with an auxiliary agent, namely a transparent nucleating agent, a halogen absorbent and an antioxidant, to obtain a plate and a sheet which have good transparency and high normal and low temperature impact properties and are suitable for preparing a central control blow molding product and a plastic molding product, but the prepared transparent impact resistant product has low melt flow rate and cannot meet the requirement of daily necessities on higher molding efficiency.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide the high-impact transparent polypropylene resin and the preparation method thereof.
The high impact transparent polypropylene resin is prepared by carrying out bulk polymerization on propylene in a first loop reactor to form a homo-polypropylene matrix, carrying out bulk polymerization on propylene and a small amount of ethylene in a second loop reactor, and carrying out gas-phase copolymerization on propylene and alpha-olefin (such as ethylene) in a third gas-phase reactor aiming at the technology of Spheripol-II double loop tubes and a single gas-phase reactor.
The preparation method specifically comprises the following steps:
1) the first stage is as follows: carrying out propylene liquid-phase bulk polymerization reaction in a first loop reactor in the presence of hydrogen and a Ziegler-Natta catalyst system containing an external electron donor to obtain a polymerization product;
2) and a second stage: feeding the first-stage polymerization product into a second loop reactor, and carrying out propylene liquid-phase bulk random polymerization reaction in the presence of hydrogen and ethylene to obtain a polymerization product;
3) and a third stage: removing unreacted propylene monomer, ethylene monomer and hydrogen from the polymer product in the second stage, then feeding the polymer product into a third gas-phase reactor, and performing propylene gas-phase copolymerization reaction to prepare polymer powder;
4) a fourth stage: adding the polymer powder obtained in the third stage into a compound auxiliary agent, extruding and granulating to obtain a melt with the flow rate of 10-30g/10min, the haze of 1mm of less than or equal to 13 percent and the normal-temperature impact property of 15-30kJ/m at 23 DEG C2Low temperature impact performance at-20 ℃ of more than or equal to 3.5kJ/m2A polypropylene resin.
In the first stage, the external electron donor has the general formula R1xR2ySi(OR3)2Wherein R1 is a C4-C10 branched or cyclic alkyl group, wherein R2 is a C1-C10 branched or cyclic alkyl group, and R3 is a C1-C2 straight chain alkyl group, wherein 1. ltoreq. x.ltoreq.2, 0. ltoreq. y < 2, such as at least one of Dicyclopentyldimethoxysilane (DCPMS), cyclohexylmethyldimethoxysilane, diisobutyldimethoxysilane and di-tert-butyldimethoxysilane, preferably dicyclopentyldimethoxysilane.
The first-stage propylene polymerization pressure is 4000-4500KPa, and the homopolymerized polypropylene matrix with high porosity is obtained at the polymerization temperature of 70-75 ℃.
The Ziegler-Natta catalyst system of the first stage comprises the following components: the catalyst comprises a first solid catalyst component, a second organic aluminum compound component and a third external electron donor component, wherein the first solid catalyst component takes magnesium, titanium, halogen and an internal electron donor as main components; wherein the ratio of the solid catalyst component I to the organic aluminum compound component II is 1: 10-1: 500 in terms of titanium/aluminum; preferably 1:25 to 1: 100. Wherein the mass ratio of the organic aluminum compound component II to the external electron donor component III is 1-50, preferably 2-40.
The solid catalyst component I in the Zigler-Natta catalyst system adopted by the invention is a polypropylene main catalyst commonly used in the prior art, and can be obtained by adopting the catalysts disclosed in CN85100997, CN98126385.2, CN00109216.2, CN99125567.4, CN201210077908.3 and CN201310552108.7 or the preparation methods disclosed by the patent documents. The invention provides a preparation method of a preferable solid catalyst component I, which comprises the following steps:
a) adding a spherical magnesium halide carrier into a liquid titanium compound at a temperature of between 15 ℃ below zero and 20 ℃ below zero, wherein the molar ratio of Ti to Mg is 20 to 40, preferably 25 to 30, and reacting at a low temperature for 1 to 2 hours;
b) the temperature is raised to 60-80 ℃, and an internal electron donor compound is added, wherein the internal electron donor compound is commonly used phthalic acid ester compounds, succinic acid ester compounds, diether compounds and the like, and the phthalic acid ester compounds are preferred. The molar ratio of the internal electron donor to the magnesium halide is 0.01-0.20, and the temperature is continuously increased to 110-120 ℃ for reaction for 2 hours;
c) filtering out liquid substances, adding fresh liquid titanium compound again, wherein the molar ratio of Ti to Mg is 20-40, preferably 25-30, and reacting for 2 hours at 110-120 ℃;
e) filtering out liquid substances, washing by normal hexane, and drying in vacuum to obtain the solid catalyst component I.
The second component of the organic aluminum compound is alkyl aluminum compound, preferably triethyl aluminum.
In the second stage, the comonomer is ethylene, and during copolymerization, the feeding amount of ethylene is adjusted according to the product performance requirement, the ethylene/(ethylene + propylene) is usually controlled to be 0.03-0.08 (molar ratio), preferably 0.04-0.07 (molar ratio), and the hydrogen concentration therein is controlled to obtain the target product.
The polymerization temperature of propylene in the second stage is 70-75 ℃, the polymerization pressure is 4000-4500KPa, and pure ethylene-propylene random copolymer is generated in the second stage.
The copolymerization reaction temperature in the third gas phase reactor of the third stage is 70-80 ℃, and the copolymerization reaction pressure is 1200-1400 KPa.
In the third stage, the comonomer is ethylene, and during copolymerization, the ratio of the monomers during gas phase polymerization is adjusted according to the product performance, and the ethylene/(ethylene + propylene) is usually controlled to be 0.15 to 0.35 (molar ratio), preferably 0.2 to 0.27 (molar ratio).
The compound auxiliary agent in the fourth stage comprises antioxidant, acid absorbent and transparent nucleating agent which are commonly added in the field, wherein the content of the antioxidant is 3000ppm, the content of the acid absorbent is 1000ppm, and the content of the transparent nucleating agent is 1000ppm, and the compound auxiliary agent is obtained after extrusion granulation by common polyolefin equipment.
The main antioxidant of the antioxidant is tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester (1010), and the auxiliary antioxidant is tris (2, 4-di-tert-butylphenyl) phosphite (168); the acid absorbent is calcium stearate; the transparent nucleating agent is sorbitol diacetal.
The invention utilizes a Spheripol-II polymerization process to realize the balance among high transparency, high normal temperature and low temperature impact resistance of propylene copolymer resin, and the specific method can be summarized as follows: the method is carried out in three reactors connected in series, specifically, propylene bulk polymerization is carried out in a first loop reactor to form a homopolymerized polypropylene body, liquid-phase propylene and ethylene bulk polymerization is carried out in a second loop reactor to generate a pure ethylene propylene random copolymer, propylene and ethylene gas-phase copolymerization reaction is carried out in a third gas-phase reactor to continuously generate a part of ethylene propylene random copolymer and a part of ethylene propylene block copolymer. The random copolymerization polypropylene part has positive effects of improving the transparency of the product, increasing the compatibility of the homopolymerization part and the impact-resistant part and increasing the normal-temperature impact-resistant performance of the product, and the ethylene-propylene block copolymer part has obvious effects of improving the normal-temperature and low-temperature impact performance of the product. Compared with the common impact-resistant copolymerized polypropylene, the resin has high content of the random copolymerized polypropylene, the ethylene-propylene block copolymer has low content and good dispersibility, can effectively absorb impact energy to block initiated cracks, and does not generate adverse effect on the transparency of the product because the content of the random copolymerized polypropylene is improved while greatly improving the impact performance of the product at normal temperature and low temperature. The special composition structure of the product is caused by the characteristics of the preparation process, so that the polypropylene resin has the characteristics of high normal-temperature and low-temperature impact performance and high transparency.
Wherein the yield ratio of the first loop reactor, the second loop reactor and the third gas phase reactor is controlled to be 52:43:5-40: 20, preferably 49:45:6-41:46: 13.
In the first stage, a first solid catalyst component, a second organic aluminum compound component and a third external electron donor component of a Ziegler-Natta catalyst system are subjected to prepolymerization reaction, and then enter a first loop reactor of the first stage, wherein the prepolymerization reaction temperature is-10-60 ℃, and preferably 10-30 ℃. The ratio of the prepolymerization reaction is 30 to 300 times, preferably 50 to 150 times. The prepolymerization can be carried out in a continuous stirrer or in a loop reactor.
The invention mainly aims at the Spheripol double-ring pipe and single gas phase reactor technology, three polymerization reactions are respectively carried out in three reactors, in the first stage polymerization reaction, the solid catalyst component I, the organic aluminum compound component II and the external electron donor component III of the Ziegler-Natta catalyst system can be directly added into a prepolymerization reactor, or can be firstly subjected to pre-complexation reaction, then are added into the prepolymerization reactor for prepolymerization reaction, and then are added into the first reactor. The pre-complexing reaction aims to fully and effectively mix the components of the catalyst and can be used as a continuous stirred tank reactor, a loop reactor and the like. The temperature of the pre-complexation reaction is-10 to 60 ℃, preferably 10 to 30 ℃. The pre-complexing reaction time is 10-60 min, preferably 20-40 min.
The first-stage bulk polymerization of propylene is carried out in a first loop reactor of a Spheripol process, and simultaneously the hydrogen concentration in the reactor is controlled, the polymerization temperature is 70-75 ℃, and the polymerization pressure is 4000-4500 KPa.
The second-stage bulk polymerization of propylene with a small amount of added ethylene is carried out in a second loop reactor of a Spheripol process, the polymerization temperature is 70-75 ℃, and the polymerization pressure is 4000-4500 KPa. The ethylene feed is adjusted according to product performance requirements, typically to control the ethylene/(ethylene + propylene) to 0.03-0.08 (molar ratio), preferably 0.04-0.07 (molar ratio), while controlling the hydrogen concentration in the reactor.
The third stage of copolymerization of propylene and comonomer alpha-olefin is carried out in the third gas phase reactor of Spheripol process, the reaction temperature is 70-80 ℃, and the reaction pressure is 1200-1400 KPa. The comonomer alpha-olefin is ethylene or butene, preferably ethylene. When the comonomer is ethylene, ethylene/(ethylene + propylene) is usually controlled to be 0.15 to 0.35 (molar ratio), preferably 0.2 to 0.25 (molar ratio).
The polymerization process of the present invention is particularly suitable for use in the Spheripol-II process, but is not limited to this process. The polypropylene resin with transparency and good comprehensive performance of normal and low temperature impact resistance is prepared, and the product has the advantages of small transparent nucleating agent adding amount, low cost and easy molding. According to the invention, partial random ethylene propylene copolymers are generated in the second reactor and the third reactor, so that the haze of the product is further reduced, the compatibility of a homopolymerization part and a block part is increased, and the normal-temperature impact resistance of the product is improved. The ethylene-propylene block copolymer with moderate content and good dispersibility is generated in the third gas phase reactor, so that the normal and low temperature impact resistance, especially the low temperature impact resistance, of the product can be effectively improved. The invention does not need special high-cost catalyst active components, does not need to modify the existing device, and is easy to operate and implement for the existing large device.
Detailed Description
The present invention will now be described in detail by way of specific examples, which are set forth herein for the purpose of illustration and explanation only and are not intended to be limiting of the present invention.
The polymer related data in the examples were obtained according to the following test methods:
melt Flow Rate (MFR): measured according to GB/T3682-2000, 230 ℃, under a load of 2.16 kg.
Bending modulus: measured according to GB/T9341-2008.
③ Izod impact strength: measured according to GB/T1043.1-2008.
Content of random ethylene-propylene copolymer: the product has a percent soluble in n-heptane at 50 ℃.
Ethylene-propylene block copolymer content: the product is insoluble in n-heptane at 50 ℃ and soluble in n-heptane at 98 ℃.
Measurement of haze: measured according to GBT 2410-.
Example 1
The main catalyst (i.e. titanium-containing solid catalyst component one) is obtained by adopting the method described in example 1 of Chinese patent CN201310552108.7, and the titanium content is as follows: 2.76%, magnesium content: 18.0%, diisobutyl phthalate content: 7.54 percent. The polymerized monomers are propylene and ethylene.
The polymerization was carried out in a Spheripol double loop plus single gas phase reactor apparatus.
Pre-polymerization: adding a Ziegler-Natta catalyst system containing a solid catalyst component I (which is selected from the main catalyst), an organic aluminum compound component II (namely, a cocatalyst, in this embodiment, triethylaluminum) and an external electron donor component III (in this embodiment, cyclohexylmethyldimethoxysilane) into a prepolymerization reactor for prepolymerization, wherein the mass ratio of the triethylaluminum to the cyclohexylmethyldimethoxysilane is 3. The prepolymerization is carried out in a propylene liquid phase bulk environment, the temperature is 15 ℃, and the prepolymerization times of the catalyst under the condition is about 120-150 times.
And continuously feeding the slurry after prepolymerization into a first loop reactor, finishing the preparation of a homopolypropylene matrix in the first loop reactor, wherein the polymerization temperature is 70 ℃, the reaction pressure is 4.0MPa, and 3000ppm of hydrogen is added into the first loop reactor (gas chromatography detection).
The slurry passing through the first loop reactor continuously enters a second loop reactor, the polymerization temperature is 72 ℃, the reaction pressure is 4.0MPa, the ethylene/(ethylene + propylene) is controlled to be 0.05 (molar ratio), and simultaneously, the hydrogen concentration added into the second loop reactor is controlled to be 1000ppm (gas chromatography detection).
And continuously feeding the slurry passing through the second loop reactor into a third gas phase reactor of a fluidized bed with an expansion section to perform gas phase copolymerization reaction of ethylene and propylene, wherein the reaction temperature is 80 ℃, the reaction pressure is 1.4MPa, the ethylene/(ethylene + propylene) molar ratio is controlled to be 0.211, and a final product obtained after passing through the third gas phase reactor is subjected to deactivation and drying treatment to obtain polymer powder.
The polymer powder was added with 500ppm of pentaerythrityl tetrakis [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ] (1010), 1000ppm of tris (2, 4-di-tert-butylphenyl) phosphite (168), 400ppm of calcium stearate, 1200ppm of sorbitol diacetal, mixed well, extruded and pelletized, and the pellets were tested for performance according to the current GBT standard.
Specific process conditions and performance test results are shown in table 1.
Examples 2 to 4
Examples 2 to 4 were similar to the procedure of example 1, except that the amounts of the components added in the respective polymerization stages were different, and the specific process conditions and the results of the performance test were as shown in Table 1.
Example 5
Example 5 adds a pre-complexation step. Pre-complexing reaction: the catalyst containing the solid catalyst component I (selected from the main catalyst in example 1), the organic aluminum compound component II (i.e., the cocatalyst, in this example, triethylaluminum) and the external electron donor component III (selected from the cyclohexylmethyldimethoxysilane) were pre-complexed at 10 ℃ for 30 min. The flow rate of triethyl aluminum entering the pre-complexing reactor is 6.33g/hr, the flow rate of cyclohexyl methyl dimethoxy silane is 2.11g/hr, and the flow rate of the main catalyst is 0.01 g/hr. Wherein the mass ratio of the triethyl aluminum to the cyclohexyl methyl dimethoxy silane is 3. The catalyst system after pre-complexing was continuously added to a prepolymerization reactor for prepolymerization, the other process was similar to example 1, and the specific process conditions and performance test results are shown in table 1.
Example 6
Example 6 is similar to the process of example 5, except that the addition amount of the components in each polymerization stage is different, and the specific process conditions and performance test results are shown in Table 1.
Example 7
Example 7 is similar to the process of example 5, except that only the polymerization stage components are added, and the specific process conditions and performance test results are shown in Table 1.
Example 8
Example 8 is similar to the process of example 5, with differences in the amounts of polymerization stage components added, and the specific process conditions and performance test results are shown in Table 1.
Comparative example 1
Comparative example 1 ethylene was not added to the second loop reactor and ethylene propylene copolymerization was carried out only in the third gas phase reactor, under the same conditions as in example 1. Specific process conditions and performance test results are shown in table 1.
Comparative example 2
The hydrogen concentration in the first loop reactor in comparative example 2 was increased from 3000ppm to 5000ppm, ethylene was not added in the second loop reactor, the gas phase ratio C2/C2+ C3 (molar ratio) in the third gas phase reactor was increased from 0.211 to 0.378, and the content of the clearing agent was increased from 1200ppm to 1500ppm during extrusion granulation, under the same conditions as in example 1. Specific process conditions and performance test results are shown in table 1.
Comparative example 3
Comparative example 3 the mass ratio of triethylaluminum to cyclohexylmethyldimethoxysilane was 2.5, the hydrogen concentration in the first loop reactor was increased from 3000ppm to 3500ppm, the C2/C2+ C3 (molar ratio) in the second loop reactor was increased from 0.050 to 0.055, the C2/C2+ C3 (molar ratio) in the third gas phase reactor was increased from 0.211 to 0.380, and the hydrogen concentration in the third gas phase reactor was increased from 800ppm to 900ppm, under otherwise the same conditions as in example 1. The specific process conditions are shown in Table 1, and the performance test results are shown in Table 1.
Comparative example 4
In comparative example 4, the temperature in the first loop reactor was increased from 70 ℃ to 75 ℃, the reaction pressure was increased from 4.0MPa to 4.2MPa, the hydrogen concentration in the first loop reactor was increased from 3000ppm to 4500ppm, and the C2/C2+ C3 (molar ratio) in the second loop reactor was increased from 0.050 to 0.110, without continuing the gas phase reaction, the other conditions were the same as in example 1. Specific process conditions and performance test results are shown in table 1.
Figure BDA0002625603710000101
Figure BDA0002625603710000111

Claims (14)

1. A preparation method of high impact transparent polypropylene resin is characterized by comprising the following steps:
1) the first stage is as follows: carrying out a propylene liquid-phase bulk polymerization reaction in a first loop reactor in the presence of hydrogen and a Ziegler-Natta catalyst system containing an external electron donor to obtain a polymerization product;
2) and a second stage: the polymerization product of the first stage enters a second loop reactor, and propylene liquid-phase bulk random polymerization reaction is carried out in the presence of hydrogen and ethylene to obtain a polymerization product;
3) and a third stage: removing unreacted propylene monomer, ethylene monomer and hydrogen from the polymer product in the second stage, then feeding the polymer product into a third gas-phase reactor, and performing propylene gas-phase copolymerization reaction to prepare polymer powder;
4) a fourth stage: adding the polymer powder obtained in the third stage into a compound auxiliary agent, extruding and granulating to obtain the melt with the flow rate of 10-30g/10min, the haze of 1mm of less than or equal to 13 percent and the normal-temperature impact property of 15-30kJ/m at 23 DEG C2Low temperature impact performance at-20 ℃ of more than or equal to 3.5kJ/m2The polypropylene resin of (1).
2. The method of claim 1, wherein the external electron donor in the first stage has a general formula of R1xR2ySi(OR3)2Wherein R1 is C4-C10 branched or cyclic alkyl, R2 is C1-C10 branched or cyclic alkyl, R3 is C1-C2 straight chain alkyl, wherein x is not less than 1 and not more than 2, and y is not less than 0 and not more than 2<2。
3. The method for preparing high impact transparent polypropylene resin according to claim 1, wherein the external electron donor in the first stage is at least one of dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane, diisobutyldimethoxysilane and di-t-butyldimethoxysilane, preferably dicyclopentyldimethoxysilane.
4. The method for preparing high impact transparent polypropylene resin as claimed in claim 1, wherein the polymerization pressure in the first stage and the second stage is 4000-4500KPa, the polymerization temperature is 70-75 ℃, the copolymerization pressure in the third gas phase reactor is 1200-1400KPa, and the copolymerization temperature is 70-80 ℃.
5. The process for preparing a high impact transparent polypropylene resin according to claim 1, wherein the Ziegler-Natta catalyst system in the first stage comprises the following components: the catalyst comprises a first solid catalyst component, a second organic aluminum compound component and a third external electron donor component, wherein the first solid catalyst component takes magnesium, titanium, halogen and an internal electron donor as main components; wherein the ratio of the solid catalyst component I to the organic aluminum compound component II is 1: 10-1: 500 in terms of titanium/aluminum; preferably 1:25 to 1:100, and the mass ratio of the organic aluminum compound component II to the external electron donor component III is 1 to 50, preferably 2 to 40.
6. The method for preparing a high impact transparent polypropylene resin according to claim 5, wherein the organoaluminum compound component two is an alkylaluminum compound, preferably triethylaluminum.
7. The process for preparing a high impact transparent polypropylene resin according to claim 1, wherein the ethylene/(ethylene + propylene) molar ratio in the second stage is 0.03 to 0.08, preferably 0.04 to 0.07.
8. The process for preparing a high impact transparent polypropylene resin according to claim 1, wherein the comonomer for the gas phase copolymerization of propylene in the third stage is ethylene, and the molar ratio of ethylene/(ethylene + propylene) is 0.15-0.35, preferably 0.2-0.27.
9. The method for preparing a high impact transparent polypropylene resin according to claim 1, wherein the productivity ratio of the first loop reactor, the second loop reactor and the third gas phase reactor is 52:43:5 to 40:40:20, preferably 49:45:6 to 41:46: 13.
10. The preparation method of the high impact transparent polypropylene resin according to claim 5, wherein the first solid catalyst component, the second organoaluminum compound component and the third external electron donor component of the Ziegler-Natta catalyst system in the first stage are subjected to a prepolymerization reaction, and then enter the first loop reactor in the first stage, wherein the temperature of the prepolymerization reaction is-10 to 60 ℃, preferably 10 to 30 ℃, and the multiple of the prepolymerization reaction is 30 to 300 times, preferably 50 to 150 times.
11. The preparation method of the high impact transparent polypropylene resin according to claim 10, wherein in the first stage, the first solid catalyst component, the second organoaluminum compound component and the third external electron donor component of the Ziegler-Natta catalyst system are subjected to a pre-complexation reaction, and then the pre-complexation reaction is performed in a prepolymerization reactor, wherein the pre-complexation reaction temperature is-10 to 60 ℃, preferably 10 to 30 ℃, and the pre-complexation reaction time is 10 to 60min, preferably 20 to 40 min.
12. The method for preparing high impact transparent polypropylene resin according to claim 1, wherein the compounding aid in the fourth stage comprises antioxidant, acid acceptor and transparent nucleating agent, the antioxidant content is 3000ppm, the acid acceptor content is 300 ppm, and the transparent nucleating agent content is 1000ppm, 2000 ppm.
13. The method for preparing high impact transparent polypropylene resin according to claim 12, wherein the antioxidant comprises a primary antioxidant of tetra [ β - (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ] pentaerythritol ester and a secondary antioxidant of tris (2, 4-di-tert-butylphenyl) phosphite; the acid absorbent is calcium stearate; the transparent nucleating agent is sorbitol diacetal.
14. A high impact transparent polypropylene resin, which is prepared by the method for preparing the high impact transparent polypropylene resin according to any one of claims 1 to 13.
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