Method for removing entrained light components in polymer powder and application of method

文档序号：695191 发布日期：2021-05-04 浏览：17次中文

阅读说明：本技术 脱除聚合物粉料中的夹带轻组分的方法及该方法的应用 (Method for removing entrained light components in polymer powder and application of method ) 是由宋文波胡慧杰李德展邹发生邹杰王路生于 2019-10-29 设计创作，主要内容包括：本发明涉及丙烯聚合物制备领域,公开了一种脱除聚合物粉料中的夹带轻组分的方法及该方法的应用。脱除聚合物粉料中的夹带轻组分的方法包括：将含有夹带轻组分的聚合物粉料与液相丙烯引入设置有气相出口的气固分离器中,所述液相丙烯在气固分离器中发生汽化从而携带夹带轻组分从所述气固分离器的气相出口排出。本发明的方法能够有效减少上游聚合物粉料夹带轻组分进入下游反应器,减少夹带轻组分对下游反应器组成控制的影响,进而有利于提高聚合物产品的性能。(The invention relates to the field of preparation of propylene polymers, and discloses a method for removing light components carried in polymer powder and application of the method. The method for removing the entrained light components in the polymer powder comprises the following steps: introducing polymer powder containing the entrained light components and liquid-phase propylene into a gas-solid separator provided with a gas-phase outlet, wherein the liquid-phase propylene is vaporized in the gas-solid separator so as to carry the entrained light components to be discharged from the gas-phase outlet of the gas-solid separator. The method can effectively reduce the light components carried by the upstream polymer powder to enter the downstream reactor, reduce the influence of the light components carried on the composition control of the downstream reactor, and further be beneficial to improving the performance of the polymer product.)

1. A method for removing entrained lights from polymer powder, the method comprising: introducing polymer powder containing the entrained light components and liquid-phase propylene into a gas-solid separator provided with a gas-phase outlet, wherein the liquid-phase propylene is vaporized in the gas-solid separator so as to carry the entrained light components to be discharged from the gas-phase outlet of the gas-solid separator.

2. The process according to claim 1, wherein the residence time of the polymer powder in the gas-solid separator is between 0.5 and 20min, preferably between 2 and 10 min.

3. The process according to claim 1 or 2, wherein the gas-solid separator is provided with an expanded section in the upper part and a stripping section in the lower part, the ratio of the maximum cross-sectional diameter of the expanded section to the stripping section being 1.5-3.

4. The process according to claim 1 or 2, wherein the weight ratio of liquid phase propylene to polymer powder is from 0.05 to 1, preferably from 0.1 to 0.5.

5. The process according to claim 1 or 2, wherein the temperature in the gas-solid separator is 50-100 ℃ and the pressure is 0.1-3 MPa.

6. A process for preparing an impact polypropylene, comprising:

(1) in the presence of hydrogen and a catalyst system, carrying out polymerization reaction on a monomer containing propylene to obtain polymer powder, wherein the catalyst system contains a catalyst, a cocatalyst and an optional external electron donor;

(2) introducing polymer powder and liquid-phase propylene into a gas-solid separator provided with a gas-phase outlet, wherein the liquid-phase propylene is vaporized in the gas-solid separator so as to carry and discharge light components from the gas-phase outlet of the gas-solid separator;

(3) and (3) carrying out copolymerization reaction of propylene and alpha-olefin on the basis of removing the polymer powder carrying light components in the step (2) to obtain the impact-resistant polypropylene powder, wherein the alpha-olefin is ethylene and/or alpha-olefin with 4-10 carbon atoms.

7. The process according to claim 6, wherein the residence time of the polymer powder in the gas-solid separator is between 0.5 and 20min, preferably between 2 and 10 min; the temperature in the gas-solid separator is 50-100 ℃, and the pressure is 0.1-3 MPa.

8. The process according to claim 6 or 7, wherein the gas-solid separator is provided with an expanded section in the upper part and a stripping section in the lower part, the ratio of the maximum cross-sectional diameter of the expanded section to the stripping section being 1.5-3;

preferably, the weight ratio of liquid phase propylene to polymer powder is from 0.05 to 1, preferably from 0.1 to 0.5.

9. The process of claim 6, wherein step (1) is carried out in a loop reactor.

10. An impact polypropylene produced by the process of any one of claims 6 to 9.

11. Use of a process according to any one of claims 1 to 5 for the preparation of impact polypropylene.

Technical Field

The invention relates to the field of preparation of propylene polymers, in particular to a method for removing light components carried in polymer powder when polypropylene powder is transferred between reactors, so that different reaction medium compositions between the reactors can be accurately controlled, and a high-performance polypropylene resin product is prepared.

Background

Polypropylene is one of the most important artificially synthesized materials, and the preparation method comprises a slurry method, a liquid phase bulk method, a gas phase method and the like, wherein a loop polypropylene process is the most important liquid phase bulk method for preparing the polypropylene. When the process is adopted, homopolymerization of propylene or random copolymerization with other monomers such as ethylene and the like is carried out in the loop reactor, most of propylene monomers are separated from polymer slurry from the loop reactor through flash evaporation, polymer powder, entrained propylene and other reaction media enter a subsequent gas phase reactor, copolymerization of propylene and other monomers such as ethylene and the like is carried out on the same particle to obtain a rubber phase, and then the impact polypropylene with high rigidity and toughness balance performance is obtained.

When the method is adopted to produce the impact-resistant polypropylene, a large amount of light components such as hydrogen and the like carried in the rubber phase enter a subsequent gas-phase reactor, so that the composition in a gas-phase copolymerization stage can not meet the production requirement of a high-performance polypropylene product, and the obtained rubber phase has small molecular weight and the low-temperature impact strength and other properties of the polymer are poor.

In order to solve the problem, in the Innovene process polypropylene device, a scheme of an air lock device is adopted, namely, the gas phase propylene is used for replacing polypropylene powder prepared in one kettle so as to remove hydrogen carried in the powder from the first gas phase kettle. In order to achieve the replacement effect, the air lock device needs to perform the pressure increasing and reducing operation of the replacement equipment, the process is complex, and the device construction and operation investment are high.

Similar to the case of hydrogen, when the first-stage polymerized monomer contains ethylene, the removal of ethylene is more difficult, and the entrained ethylene sometimes participates in the subsequent polymerization process, thereby affecting the control of the target structure of the product.

Disclosure of Invention

The invention aims to overcome the problems in the prior art and provides a method for removing entrained light components in polymer powder and application of the method.

In order to achieve the above object, the present invention provides, in a first aspect, a method for removing entrained light components from a polymer powder, comprising: introducing polymer powder containing the entrained light components and liquid-phase propylene into a gas-solid separator provided with a gas-phase outlet, wherein the liquid-phase propylene is vaporized in the gas-solid separator so as to carry the entrained light components to be discharged from the gas-phase outlet of the gas-solid separator.

A second aspect provides a process for preparing an impact polypropylene, characterized in that the process comprises:

A third aspect provides an impact polypropylene made by the process as described above.

In a fourth aspect the present invention provides the use of a process as described above for the preparation of impact polypropylene.

Through the technical scheme, the method can effectively reduce the light components (including hydrogen and ethylene) carried by the upstream polymer powder to enter the downstream reaction, reduce the influence of the carried light components on the composition control of the downstream reaction, and further be beneficial to improving the performance of the polymer product. The invention has low requirement on equipment, particularly relates to simple modification of the existing equipment (flash tank) in a loop polypropylene production process of liquid-phase bulk polymerization and gas-phase polymerization, and can realize removal of entrained light components without increasing the process flow.

Drawings

For the purpose of illustrating the invention more clearly, the drawings are illustrative of particular embodiments of the invention and are not to be construed as limiting the invention.

FIG. 1 is a schematic flow diagram according to one embodiment of the present invention.

Description of the reference numerals

1 first stage polymerization reactor

2 gas-solid separator

3 second stage polymerization reactor

100 feed inlet of first stage polymerization reactor

101 discharge port of first-stage polymerization reactor

102 liquid phase propylene inlet

Gas phase outlet of 103 gas-solid separator

104 gas-solid separator

105 discharge port of second stage polymerization reactor

106 gas phase outlet of the second stage polymerization reactor

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

In the present invention, the term "removal" is used, without going to the contrary, to mean a reduction of the content of entrained light components by at least 80%; the unit "ppmV" refers to parts per million by volume.

The invention provides a method for removing light components carried in polymer powder, which is characterized by comprising the following steps: introducing polymer powder containing the entrained light components and liquid-phase propylene into a gas-solid separator provided with a gas-phase outlet, wherein the liquid-phase propylene is vaporized in the gas-solid separator so as to carry the entrained light components to be discharged from the gas-phase outlet of the gas-solid separator. Wherein the liquid-phase propylene is additionally introduced (added) with the liquid-phase propylene, and is not the liquid-phase propylene entrained in the polymer powder or the liquid-phase propylene from an upstream process.

In the present invention, the entrained light components are generally materials having a boiling point lower than that of propylene, and may be hydrogen, or may be nitrogen, methane, ethane, ethylene, or the like. The inventor of the invention also finds that the propylene has certain removal effect on heavy components such as 1-butene and the like carried in polymer powder along with the increase of the amount of the propylene in the external liquid phase.

In the present invention, the content of the entrained volatilizable component in the polymer powder entering the gas-solid separator is usually 500-50000ppm by weight, and the content of the light component (i.e., entrained light component, mainly hydrogen) in the volatilizable component is 1000-50000ppmV, preferably 2000-10000 ppmV. The method of the invention is suitable for removing light components carried in polymer powder with various shapes, including particle shape, spherical shape or sphere-like shape.

According to a preferred embodiment of the present invention, in order to more effectively achieve the removal of the entrained light components in the polymer powder, the residence time of the polymer powder in the gas-solid separator is 0.5 to 20min, more preferably 2 to 10min, still more preferably 5 to 10min, such as 5min, 8min, 9min, 10min or any value therebetween.

In order to more effectively achieve separation of entrained volatile components and propylene from solids after vaporization, the gas-solid separator is preferably a device (e.g., a fluidized bed device) provided with an expansion section at the upper part, which can be designed by calculation methods known in the art, wherein the expansion section is a region free of solid materials, and the ratio of the maximum cross-sectional diameter of the expansion section to the holding section (i.e., the stripping section mentioned below) is generally 1.5-3 (e.g., 1.5, 1.8, 1.9, 2, 2.1, 2.2, 2.5, 3 or any value therebetween), and the height is also set to meet the requirements of solid settlement and avoiding stacking along the wall. Furthermore, the gas-solid separator may be a cyclone separator. The lower part of the gas-solid separator is a stripping section, namely a region where solid materials exist. Maintaining a certain material level of the polypropylene powder in the stripping section, adding the added liquid-phase propylene into a polypropylene powder bed layer below the bubble point temperature, vaporizing under the action of polymerization reaction heat, and stripping out light components carried in the polymer powder. The residence time of the polymer powder in the stripping section is from 0.5 to 20min, preferably from 2 to 10 min.

According to the invention, the liquid phase propylene is preferably added in a proportion to the polymer powder, the weight ratio of liquid phase propylene to polymer powder being 0.05-1, more preferably 0.1-0.5, even more preferably 0.2-0.5, such as 0.2, 0.3, 0.4, 0.5 or any value between the above values.

According to the invention, in order to realize the uniform distribution of the liquid-phase propylene in the solid-phase polymer powder, the structures of a spray head, a dispersion pipe, a distribution disc and the like which are common in the field can be adopted. When the scheme of the gas-solid separator with the expansion section arranged at the upper part is adopted, the upper part can be also configured into a power separator, a filter and the like which are increased by realizing good gas-solid separation effect.

According to a preferred embodiment of the invention, the temperature in the gas-solid separator is between 50 ℃ and 100 ℃, more preferably between 60 ℃ and 80 ℃ (such as 60 ℃, 62 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃ or any value in between). The temperature is the temperature in the zone in which the polymer powder is located, for example the stripping section.

According to a preferred embodiment of the invention, the pressure in the gas-solid separator may be controlled between the pressure in the reactor upstream of the gas-solid separator and the pressure in the equipment downstream of the gas-solid separator, so that the material may be transported and transferred by means of a pressure difference, which may be in the range of 0.1-3MPa, preferably the pressure in the gas-solid separator is in the range of 1-2.5MPa, more preferably 1.5-2MPa (such as 1.5MPa, 1.6MPa, 1.7MPa, 1.8MPa, 1.9MPa, 2MPa or any value in between the above mentioned values).

The method is suitable for the process for preparing the propylene polymer by the multistage reactor, and comprises various combinations of a liquid phase body and a gas phase, a liquid phase body and a liquid phase body, a gas phase and a gas phase, a multi-zone reactor and a gas phase. The method is particularly suitable for liquid-phase bulk polymerization and gas-phase polymerization processes such as a loop polypropylene process, and the like, in the process, polymer powder generally needs to be subjected to gas-solid separation by a gas-solid separator and then subjected to gas-phase polymer reaction, so that the process of removing light components carried in the polymer powder can be carried out in the gas-solid separator (such as a flash tank) originally existing in the process.

The invention also provides a method for preparing the impact-resistant polypropylene, which is characterized by comprising the following steps:

(1) in the presence of hydrogen and a catalyst system, carrying out polymerization reaction on a monomer containing propylene to obtain polymer powder, wherein the catalyst system contains a (main) catalyst, a cocatalyst and an optional external electron donor;

According to the present invention, in the step (1), there is no particular requirement on the content of hydrogen and propylene, and for example, the weight ratio of hydrogen to propylene may be 1: 700-105000.

According to the invention, in step (1), the catalyst system is used in an amount such that the weight ratio of (main) catalyst to propylene is from 1 to 10: 200000. The (main) catalyst may be any of the various catalysts known to be suitable for the preparation of propylene polymers, including single site catalysts such as Ziegler-Natta catalysts or metallocenes.

According to the present invention, in step (1), the cocatalyst is generally an organoaluminum, which is not limited to any organoaluminum commonly used in the polyolefin industry at present, and is preferably at least one member selected from the group consisting of trialkylaluminums (e.g., trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, trihexylaluminum, trioctylaluminum, etc.), diethylaluminum monochloride, diisobutylaluminum monochloride, ethylaluminum dichloride and ethylaluminum dichloride. The external electron donor is a substance to be selectively used, and generally, when a Ziegler-Natta catalyst is used, the external electron donor is required to be used, and when a single-site catalyst such as metallocene is used, the external electron donor may not be used. The external electron donor is preferably an organosilicon compound with a general formula of R_nSi(OR')_4-nWherein n is more than 0 and less than or equal to 3, R is selected from hydrogen atom, halogen, alkyl, cycloalkyl, aryl and halogenated alkyl, and R' is selected from alkyl, cycloalkyl, aryl and halogenated alkyl. Specifically, the method may include but is not limited to: diisopropyldimethoxysilane, cyclohexylmethyldimethoxysilane, tetramethoxysilane, tetraethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, trimethylphenoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methyl-tert-butyldimethoxysilane, methylisopropyldimethoxysilane, diphenoxydimethoxysilane, diphenyldiethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, vinyltrimethoxysilane, (1,1, 1-trifluoro-2-propyl) -2-ethylpiperidinyldimethoxysilane, and (1,1, 1-trifluoro-2-propyl) -methyldimethoxysilane, and the like. The catalyst, cocatalyst and external supplyThe amount of the electron donor can be determined according to the requirement, and the weight ratio of the cocatalyst to the catalyst is preferably 1:4-50:1, more preferably 2:1-20: 1. The weight ratio of the cocatalyst to the external electron donor can be 0.1:1-150:1, preferably 2:1-150: 1.

According to the present invention, in the step (1), the propylene-containing monomer may further contain an α -olefin other than propylene, such as ethylene and/or an α -olefin having 4 to 10 carbon atoms (at least one of 1-butene, 1-pentene, 1-hexene, 4-methylisoalene, 1-octene and 1-decene). When the propylene-containing monomer contains alpha-olefin except propylene, the polymer powder generally carries the alpha-olefin except propylene, and the method can effectively remove the alpha-olefin except propylene (especially ethylene) in the carried light components, thereby being more beneficial to the control of the subsequent reaction. The weight ratio of alpha-olefins other than propylene to propylene may be from 0.5 to 35: 100.

According to the present invention, in the step (1), the conditions of the polymerization reaction are not particularly required, and may include, for example: the temperature is 30-150 ℃, preferably 50-100 ℃; the pressure is 1-8MPa, preferably 1.2-5.5 MPa; the time is 10-180min, preferably 20-120 min.

According to the present invention, in the step (2), the residence time of the polymer powder in the gas-solid separator, the amount of the liquid-phase propylene, the temperature in the gas-solid separator, the pressure and the like are as described above and will not be described herein.

According to the present invention, in the step (3), the amount of the α -olefin to be used has the following relationship with respect to propylene in the reaction system: α -olefin/(α -olefin + propylene) ═ 0.05 to 0.7 (v/v).

According to the present invention, the α -olefin may be any conventional olefin capable of undergoing a polymerization reaction with propylene, for example, the α -olefin is ethylene and/or an α -olefin having 4 to 10 carbon atoms, preferably at least one of ethylene, 1-butene, 1-pentene, 1-hexene, 4-methylisoalene, 1-octene and 1-decene.

According to the present invention, in the step (3), the conditions of the copolymerization reaction are not particularly required, and may include, for example: the temperature is 50-150 ℃, preferably 60-95 ℃; the pressure is 0.5-4MPa, preferably 0.8-2.5 MPa; the time is 10-180min, preferably 20-90 min.

As mentioned above, the process for removing entrained light components from polymer powder according to the invention is particularly suitable for liquid-phase bulk + gas-phase polymerization processes such as the loop polypropylene process, whereby, according to a preferred embodiment of the invention, propylene is polymerized in liquid form in step (1) and alpha-olefins are copolymerized in gaseous form in step (3). Thus, according to a preferred embodiment of the present invention, step (1) is carried out in a loop reactor.

The invention also provides impact polypropylene prepared by the method. By reducing the amount of light components (including hydrogen and ethylene) entrained with the upstream polymer powder entering the downstream reaction, an impact polypropylene product having improved properties can be obtained.

The invention also provides the application of the method for removing the entrained light components in the polymer powder in the preparation of the impact polypropylene.

The present invention will be described in detail below by way of examples. In the following examples:

the catalysts used were: DQC-602 catalyst from Odada, Beijing, China petrochemical catalyst division;

the method for detecting hydrogen is online chromatography, and TGC-2000 type online chromatograph of ABB company is adopted;

the method for detecting ethylene is online chromatography, and TGC-2000 type online chromatograph of ABB company is adopted;

melt mass flow rate (melt index, MFR): measured according to the method described in GB/T3682-2000, using a melt index apparatus model 7026 from CEAST, at 230 ℃ under a load of 2.16 kg;

izod impact strength: the determination is carried out according to the method described in GB/T1843-2008;

ethylene content in impact polypropylene product: measuring the ethylene content by using a ThermoNicolet200 type infrared analyzer;

the following examples were carried out on a 25kg/h loop polypropylene pilot plant, as shown in FIG. 1, comprising:

a first-stage polymerization reactor 1 provided with a feed port 100 of the first-stage polymerization reactor and a discharge port 101 of the first-stage polymerization reactor;

the gas-solid separator 2 comprises an expansion section arranged at the upper part and a stripping section arranged at the lower part, the ratio of the maximum cross section diameter of the expansion section to the maximum cross section diameter of the stripping section is 2, the expansion section is provided with a feed inlet of the gas-solid separator and a gas phase outlet 103 of the gas-solid separator, and the stripping section is provided with a liquid phase propylene inlet 102 and a material outlet 104 of the gas-solid separator;

a second-stage polymerization reactor 3 provided with a feed port of the second-stage polymerization reactor, a discharge port 105 of the second-stage polymerization reactor, and a gas-phase outlet 106 of the second-stage polymerization reactor;

wherein the discharge port 101 of the first-stage polymerization reactor is connected to the feed port of a gas-solid separator, the material outlet 104 of the gas-solid separator is connected to the feed port of the second-stage polymerization reactor, and the second-stage polymerization reactor 3 is further provided with a circulation line for circulating the gas discharged from the gas-phase outlet 106 of the second-stage polymerization reactor in the second-stage polymerization reactor.

Example 1

(1) In a first-stage polymerization reactor 1, in the presence of hydrogen and a catalyst, carrying out polymerization reaction on a monomer containing propylene to obtain polymer powder, introducing reaction raw materials into the first-stage polymerization reactor 1 from a feed inlet 100 of the first-stage polymerization reactor, wherein the feed amounts of the hydrogen, the catalyst, a cocatalyst (triethylaluminum), an external electron donor (cyclohexylmethyldimethoxysilane) and the propylene are respectively 2.8g/H, 0.6g/H, 6.3g/H, 0.7g/H and 40kg/H, the polymerization reaction temperature is 70 ℃, the pressure is 4MPa, the time is 60min, the obtained polymer powder is discharged from a discharge outlet 101 of the first-stage polymerization reactor, and detecting the concentration of the hydrogen in the discharged material (recorded as H)₂(101))；

(2) Respectively introducing polymer powder and liquid-phase propylene into a stripping section in a gas-solid separator 2 from a feed inlet of the gas-solid separator and a liquid-phase propylene inlet 102 for removing entrained light components (hydrogen), wherein the feeding amounts of the polymer powder and the liquid-phase propylene are respectively15kg/h and 7.5kg/h, the feeding temperature of the polymer powder is 70 ℃; the liquid phase propylene is vaporized in a gas-solid separator so as to carry light components to be discharged from a gas phase outlet 103 of the gas-solid separator for recycling, the operating temperature and the pressure of the gas-solid separator are respectively 70 ℃ and 1.8MPa, the retention time of polymer powder in the gas-solid separator is 10min, the polymer powder without the light components is discharged from a material outlet 104 of the gas-solid separator, and the concentration (marked as H) of hydrogen in the discharged material is detected₂(104))；

(3) The polymer powder without the entrained light components enters the second-stage polymerization reactor 3 from the feed port of the second-stage polymerization reactor, the copolymerization reaction of propylene and ethylene (ethylene/(ethylene + propylene) ═ 0.4(v/v)) is carried out on the basis of the polymer powder without the entrained light components, the temperature of the copolymerization reaction is 70 ℃, the pressure is 1.4MPa, and the time is 30min, and the product is continuously discharged from the discharge port 105 of the second-stage polymerization reactor, granulated and tested correspondingly.