Multi-component co-polypropylene and preparation method thereof

Abstract

The present invention relates to a multi-component co-polypropylene and a method for preparing the multi-component co-polypropylene through olefin multi-component gas phase copolymerization, the method is suitable for a kettle type gas phase method polypropylene production process, and the method comprises the following steps: propylene, ethylene, 1-butene, and a C5-C8 alpha-monoolefin are contacted in the presence of a Zielger-Natta catalyst system in a gas phase reactor for bulk polymerization, the polymerization temperature is 65 to 85 DEG C, the polymerization pressure is 2.0 to 3.0 MPa, and the average residence time of polymerization is 1.0 to 1.5 hours. The preparation method is simple in process and stable in polymerization reaction, and the prepared multi-component copolymerized polypropylene is low in melting point, good in product appearance and good in thermal cohesiveness.

Description

Technical Field

[0001] The present invention relates to the field of polypropylene preparation, in particular to a multi-component copolymer polypropylene and a preparation method thereof. Background Art

[0002] In recent years, polypropylene for thermal bonding fibers has been increasingly pursuing lower melting temperatures. Similarly, cast film heat sealing layers tend to have lower initial heat sealing temperatures, high heat sealing strength, wide heat sealing windows, excellent optical properties, and higher low-temperature impact properties. Ordinary homopolymer and copolymer polypropylene are difficult to meet the above requirements. The use of comonomers and propylene for random copolymerization can reduce the degree of crystallization of polypropylene, refine the crystals, and achieve the purpose of lowering its melting temperature. The composition and content of the comonomers generally have a significant effect on the melting point of the polymer. In terms of technology, although a large amount of a single comonomer can reduce the melting temperature, it will also affect the rigidity and other properties of the polymer. By introducing more types of monomers for copolymerization, the regularity of the polymer can be further destroyed, further reducing the degree of crystallization of polypropylene, thereby reducing its melting temperature, which can significantly change this situation.

[0003] At present, the production methods of multi-component copolymerized polypropylene in the art are mainly concentrated in terpolymerization. U.S. Patent No. 6365682 describes a method for producing CPP by terpolymerizing propylene-ethylene-1-butene (or 4-methyl-1-pentene, or 1-hexene, or 1-heptene or 1-octene) in series with one or two liquid phase reactors and a gas phase reactor. US6583253 describes a terpolymer obtained in a slurry by using a Zigler-Natta catalytic system or a metallocene-based catalytic system. Compared with a propylene binary copolymer containing the same comonomer content, the terpolymer described in the patent has a lower melting point. WO03 / 099884 relates to a terpolymer, the copolymer at least contains propylene as the first monomer component, 1-pentene as the second monomer component, and is combined with other third components, and is polymerized using a Zigler-Natta catalytic system or a metallocene catalytic system to obtain a terpolymer. Its technical feature is that 1-pentene must be contained in the polymer. No multi-component gas phase copolymerized polypropylene product technology of more than three components has been found.

[0004] According to the prior art, random copolymer materials with a melting temperature below 132°C and ethylene as a comonomer are difficult or impossible to prepare by a slurry method using a Zigler-Natta catalyst. The reason is that both bulk and slurry polymerizations are carried out in the liquid phase, and the viscous low-molecular random polymers in the reaction product are easily dissolved and dispersed in the liquid phase, which increases the viscosity of the liquid. Continuous polymerization will cause more and more of these random oligomers to adhere to the kettle wall and internal components such as stirring blades and baffles. Moreover, as the polymerization continues, the oligomers will accumulate more and more, agglomerate and fall off, block the discharge pipeline, and cause the device to stop production. Gas phase polymerization only has two phases, gas and solid, and the low-molecular random polymers generated are few. Even if there are any, they are attached to the surface of the polymer particles or are taken away by the wall scraping and stirring, and are not easy to constitute agglomeration factors. Therefore, the use of a gas phase reaction polymerization process, rather than the aforementioned patented kettle liquid phase bulk polymerization process, slurry polymerization method, or liquid phase bulk + gas phase polymerization process, can ensure the continuous, stable and long-term operation of the device. Summary of the invention

[0005] Therefore, the object of the present invention is to provide a multi-component copolymer polypropylene having more than three components and a gas phase continuous polymerization method for preparing the polypropylene, the method comprising using a Ziegler-Natta supported porous catalyst in a gas phase polymerization reactor, with gas phase propylene as the polymerization body, ethylene as the first comonomer, 1-butene as the second comonomer, and C5-C8 α-monoolefin as the third comonomer for multi-component copolymerization.

[0006] Compared with ordinary EPDM binary random polypropylene and ternary copolymers, the multipolymer produced by this technical method has the characteristics of low melting point, good product appearance, good thermal adhesion, etc. The product is suitable for fields such as heat-sealing film and heat-bonding fiber.

[0007] Other features and advantages of the present application will be described in detail in the subsequent detailed description. DETAILED DESCRIPTION

[0008] The specific implementation methods of the present application are described in detail below, but it should be noted that the protection scope of the present application is not limited by these specific implementation methods, but is determined by the claims in the appendix.

[0009] Any specific numerical value disclosed herein (including the endpoint of the numerical range) is not limited to the exact value of the numerical value, but should be understood to also cover values ​​close to the exact value, such as all possible numerical values ​​within the range of ±5% of the exact value. In addition, for the disclosed numerical range, the endpoint values ​​of the range, the endpoint values ​​and the specific point values ​​in the range, and the specific point values ​​can be arbitrarily combined to obtain one or more new numerical ranges, and these new numerical ranges should also be regarded as specifically disclosed herein.

[0010] Unless otherwise specified, the terms used herein have the same meaning as commonly understood by those skilled in the art. If a term is defined herein and its definition is different from the commonly understood meaning in the art, the definition herein shall prevail.

[0011] In this application, except for the contents clearly stated, any matters or items not mentioned are directly applicable to the aspects known in the art without any changes. Moreover, any embodiment described herein can be freely combined with one or more other embodiments described herein, and the technical solutions or technical ideas formed thereby are deemed to be part of the original disclosure or original record of this application, and should not be regarded as new contents not disclosed or anticipated herein, unless a person skilled in the art considers that the combination is obviously unreasonable.

[0012] All patent and non-patent literature, including but not limited to textbooks and journal articles, mentioned herein are incorporated herein by reference in their entirety.

[0013] In one embodiment, the present invention provides a multi-copolymer polypropylene, which may contain polymerization units based on propylene, ethylene, 1-butene and a C5-C8 α-monoolefin, wherein the propylene polymerization unit content in the multi-copolymer polypropylene may be 85-98 weight % relative to the weight of the multi-copolymer polypropylene, the ethylene polymerization unit content may be 1.0-5.0 weight % relative to the weight of the multi-copolymer polypropylene, the 1-butene polymerization unit content may be 0.5-5.0 weight % relative to the weight of the multi-copolymer polypropylene, and the C5-C8 α-monoolefin polymerization unit content may be 0.5-5.0 weight % relative to the weight of the multi-copolymer polypropylene.

[0014] In a preferred embodiment, the content of propylene units in the multi-copolymer polypropylene may be 92-97 weight % relative to the weight of the multi-copolymer polypropylene, the content of ethylene units may be 1.0-2.5 weight % relative to the weight of the multi-copolymer polypropylene, the content of 1-butene units may be 0.8-3.0 weight % relative to the weight of the multi-copolymer polypropylene, and the content of C5-C8 α-monoolefin units may be 1.2-2.5 weight % relative to the weight of the multi-copolymer polypropylene.

[0015] In a preferred embodiment, the content of ethylene units in the multi-copolymer polypropylene may be 1.0-1.5 wt % relative to the weight of the multi-copolymer polypropylene, the content of 1-butene units may be 1.0-2.0 wt % relative to the weight of the multi-copolymer polypropylene, and the content of C5-C8 α-monoolefin units may be 1.5-2.5 wt % relative to the weight of the multi-copolymer polypropylene.

[0016] In a preferred embodiment, the weight ratio of ethylene polymerization unit: 1-butene polymerization unit: C5-C8 α-monoolefin polymerization unit in the multi-polymer polypropylene can be 1: 0.5-3.0: 0.5-2.5, preferably 1: 0.8-2.5: 0.8-2.0.

[0017] In a preferred embodiment, the multi-copolymer polypropylene may have a melting point lower than 132°C, preferably 124°C-130°C.

[0018] In a preferred embodiment, the multi-copolymer polypropylene may have a melt flow rate measured according to the national standard GB / T 3682-2018 (230° C., 2.16 kg load) of 0.8-10.0 g / 10 min, preferably 1.0-5.0 g / 10 min.

[0019] In a preferred embodiment, the C5-C8 α-monoolefin may be selected from 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene or 1-octene.

[0020] In another embodiment, the present invention also provides a gas phase continuous polymerization method for preparing a multi-copolymer polypropylene according to the present invention, which comprises contacting propylene, ethylene, 1-butene, and a C5-C8 α-monoolefin in the presence of a Zielger-Natta catalyst system in a gas phase reactor, wherein the polymerization temperature can be 65-85°C, the polymerization pressure can be 2.0-3.0 MPa, and the average polymerization residence time can be 1.0-1.5 hours.

[0021] In a preferred embodiment, the gas phase reactor is a vertical or horizontal kettle stirred gas phase polymerization reactor.

[0022] In a preferred embodiment, the polymerization temperature may be 70-80° C., the polymerization pressure may be 2.2-2.7 MPa, and the average polymerization residence time may be 1.2 hours.

[0023] In a preferred embodiment, the Zielger-Natta catalyst system may include a main catalyst, a co-catalyst and an external electron donor.

[0024] In a preferred embodiment, the main catalyst may be a magnesium chloride-supported titanium catalyst; the co-catalyst may be triethylaluminum (TEA), triisobutylaluminum (TIBA) or a mixture thereof; the external electron donor may be a dimethoxysilane, preferably dicyclopentyldimethoxysilane. In a preferred embodiment, the molar ratio of Al to Ti in the catalyst system may be 60-200, preferably 80-160, more preferably 80-100, and the molar ratio of Al to Si may be 5-25, preferably 7-15, more preferably 10-12.

[0025] The polymerization method provided by the present invention is suitable for propylene polymerization in a gas phase kettle process, and is suitable for various gas phase reaction facilities such as a vertical gas phase fluidized bed reactor and a horizontal gas phase stirred bed reactor. Under the premise that the main process conditions and equipment are not changed, the preparation and production of multi-component copolymer polypropylene of more than three components can be carried out. The advantages are: a stable polymerization process; simple process control; good product appearance and no adhesion; the polymer has a low melting point and good thermal bonding performance, and is suitable for special materials for cast film heat sealing layers and low melting point thermal bonding fibers, which is superior to the current ternary copolymer products.

[0026] In multipolymerization, the increase in the concentration of the second comonomer (1-butene) and the third comonomer (C5-C8 α-monoolefin) in the reactor will lead to: the content of the monomer in the copolymer will also increase; the crystallinity of the copolymer will decrease, which is due to the increase in the α-olefin content in the copolymer, the increase in the side groups on the polymer chain, and the destruction of the regularity of the chain. The melting point of the polymer is not only related to the crystallinity, but also to the molecular weight of the product. Therefore, the decrease in crystallinity and molecular weight may lead to a decrease in the melting point.

[0027] Polymerization reaction:

[0028] Use 1.1m 3 Continuous polymerization in a gas phase fluidized bed reactor (see Figure 1 ), the polymerization system includes a gas phase fluidized bed reactor, a heat exchanger, a circulating fan and a drying and separation device. The catalyst system including the main catalyst, the co-catalyst and the external electron donor is contacted with propylene, ethylene, 1-butene and C5-C8 α-monoolefin monomers in a gas phase reactor, and a gas phase reaction is carried out under the conditions of a polymerization temperature of 65-85°C and a polymerization pressure of 2.0-3.0MPa. A certain amount of hydrogen is continuously added 2 hours before the start of the reaction to adjust the molecular weight. The reaction time is based on 3-6 average residence times of stable operation (generally each average residence time is 1.2 hours). In the meantime, the online sampling system can be used to take real-time samples to observe the polymer state and monitor the polymerization situation.

[0029] Catalyst system addition steps:

[0030] Main catalyst: First, vaseline and white oil are fully mixed in a 1:1 weight ratio while heated in a fluid state, and nitrogen is bubbled for 2 hours. Then, the main catalyst is added and stirred evenly, cooled to 0-2°C to form a paste, and nitrogen-sealed in a catalyst preparation tank for use. When used, it is squeezed into the reactor through a special metering pump. The concentration of the prepared catalyst in the present invention is prepared at a specification of 100 mg / L.

[0031] Co-catalyst: Considering the safety in the test production, a 0.88 mol / L triethylaluminum n-hexane solution was prepared.

[0032] External electron donor: Dimethoxysilane is in liquid state and cannot be mixed with other substances.

[0033] The cocatalyst, external electron donor and main catalyst are added to the gas phase reactor in sequence and continuously to contact with the reactants, and polymerization occurs at a certain temperature, and other components are metered into the reactor in a continuous addition manner. In addition, the method optionally adopts a catalyst prepolymerization method.

[0034] The above catalyst components are added in a molar ratio of Al / Ti of 60-200, preferably 80-160, more preferably 80-100. The molar ratio of Al / Si is 5-25, preferably 7-15, more preferably 10-12. The catalyst system within the above range has a good activity release law, especially corresponding to the four-component polymerization system. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Gas Phase Reactor Polymerization System

[0036] Example

[0037] The present invention is further described in detail below using examples, but the present invention is not limited to these examples.

[0038] Using a gas phase reactor polymerization system ( Figure 1 ) was used to prepare a propylene tetrapolymer. The following measurement methods were used in characterizing the prepared polymers:

[0039] The Avance III HD NMR spectrometer (120°C, 600 MHz, 13 C NMR) calibrated Bruker Alpha-T Fourier transform infrared spectrometer (370-7500 em- 1 , FTIR) was used to determine the content of each comonomer in the polymer.

[0040] The polymer melting crystallization temperature was tested using a TA Q2000 differential scanning calorimeter (DSC) in the range of 20-200°C at a cooling rate of 10°C / min to obtain the melting point Tm data.

[0041] The melt flow rate (MFR) of polypropylene was measured according to the national standard GB / T 3682-2018 (230°C, 2.16 kg load) and expressed in g / 10 min.

[0042] Table 1 Analysis and test items

[0043]

[0044] The main catalyst is a titanium-based Ziegler-Natta polypropylene catalyst, provided by Beijing Aoda Branch of Sinopec Catalyst Co., Ltd., with a trade name of BCM catalyst, and the Ti content of the catalyst is 2.2%. The co-catalyst is triethylaluminum, provided by Liaoyang Xiangyang Science and Technology Chemical Group, and its concentration is diluted to 0.88 mol / L with hexane before use; the external electron donor is dicyclopentyldimethoxysilane, provided by Wuhan Huabang Chemical Co., Ltd. The above components are continuously added by a feed pump, and the catalyst system here must be added to the middle position of the reactor bed to facilitate better dispersion and heat transfer and reduce the risk of agglomeration.

[0045] The gas composition in the gas phase reactor can be observed by online gas chromatography. During the polymerization, the reactor material level rises to a certain measured material level and then automatically discharges in small batches. The catalyst activity is calculated based on the discharge weight per unit time. After drying, the additives are added for granulation, and then the performance test is performed. The process adjustment of each batch of experiments is based on online monitoring and short-term test data. The reactor polymerization transition time between different batches must reach 3-6 catalyst average residence times, so that the material is fully transitioned and the difference and stability of the sample collection of each embodiment are guaranteed.

[0046] The basic implementation process, taking Example 1 as an example, in the aforementioned gas phase polymerization reaction system, propylene monomer is added, the reaction gas is made to form an external circulation through a circulating fan, and the temperature and pressure in the reactor are increased by a heat exchanger. After the reactor reaches 65°C and 2.3MPa conditions, the co-catalyst, external electron donor and main catalyst are added in sequence according to the molar ratio of Al / Si / Ti=120 / 10 / 1 (i.e., co-catalyst 68ml / h, external electron donor 0.02ml / min, main catalyst 0.18ml / min). The three substances are initially added in sequence with an interval of 2 hours, and then a continuous polymerization reaction begins in the reactor. When the polymer in the reactor reaches a certain material level (bed weight), the reactor is set to start unloading, and the average residence time is about 1.2 hours. After stabilizing the unloading for 2 hours, ethylene, 1-butene and 4-methyl-1-pentene are added to the reactor. The amount of each polymerization monomer is dynamically adjusted according to the infrared test value. Since the polymerization system controls the pressure rise by discharging the flare system, the non-equiproportional linear relationship between the monomer additions is based on whether the target value is reached in the polymer after online sampling or discharging. In addition, the polymer and the monomer are first separated by pressure relief in the unloading pipe to remove a part of the unreacted monomers, and then the continuous nitrogen pressure rise and fall mode is adopted after entering the drying separator to achieve the purpose of thoroughly removing the unreacted monomers. The polymerization reaction of the embodiment is all continuous polymerization, and each monomer and catalyst are all added continuously, and the product morphology is a solid particle with a diameter of 0.5mm-2.0mm.

[0047] The differences between the embodiments are:

[0048] Examples 1-5, evaluating the effect of polymerization temperature variation on polymer melting point and particle appearance;

[0049] Examples 6-8, evaluating the effect of changes in ethylene polymer unit content on polymer melting point and particle appearance;

[0050] Examples 9-11 evaluate the effect of adding different amounts of 1-butene on the melting point of the polymer and the apparent properties of the particles after increasing the content of 4-methyl-1-pentene polymerization units.

[0051] Comparative Example 1-2 is the effect of changing the ethylene and 1-butene polymerization unit contents on the polymer melting point and particle appearance without adding the third comonomer (4-methyl-1-pentene).

[0052] The specific parameters adjusted in each embodiment and the data of the test results are shown in Table 2, wherein the apparent properties of the particles are graded according to the following standards: Grade 5: the particles do not stick together and have good fluidity; Grade 1: the particles stick together and are easy to agglomerate; grades from 5 to 1 indicate that the fluidity of the particles gradually deteriorates, and at Grade 2, adhesion begins to occur.

[0053] Table 2 Test parameters and test results of Examples 1-11 and Comparative Examples 1-2

[0054]

[0055] It can be seen from the test results of Examples 1-11 and Comparative Examples 1-2 that a balance between the low melting point and the apparent properties of polypropylene particles can be achieved by adjusting the polymerization reaction conditions and the composition and content of the comonomer. As the reaction temperature increases, the softening degree of the rubber phase of the obtained polymer particles increases, resulting in an increase in the apparent viscosity of the particles. By comparing Examples 6-8, it can be seen that when the content of other polymer monomers remains unchanged, as the content of ethylene polymerization units increases, the melting point of copolymerized polypropylene decreases and the degree of particle adhesion increases. When the content of ethylene polymerization units increases to 3.4% by weight, the polymer particles adhere and agglomerate, blocking the pipeline and making it difficult to continue the reaction. Examples 9-11 achieve a good balance between low melting point and apparent properties.

[0056] Although the specific implementations of the present invention have been described in detail above in conjunction with the embodiments, it should be pointed out that the protection scope of the present invention is not limited by these specific implementations, but is determined by the claims. Those skilled in the art may make appropriate changes to these implementations without departing from the technical ideas and purport of the present invention, and these changed implementations are obviously also included in the protection scope of the present invention.

Claims

1. A multi-component copolymer polypropylene, characterized in that: The multi-copolymer polypropylene comprises polymerization units based on propylene, ethylene, 1-butene and a C5-C8 α-monoolefin, wherein the propylene polymerization unit content in the multi-copolymer polypropylene is 85-98 weight % relative to the weight of the multi-copolymer polypropylene, the ethylene polymerization unit content is 1.0-5.0 weight % relative to the weight of the multi-copolymer polypropylene, the 1-butene polymerization unit content is 0.5-5.0 weight % relative to the weight of the multi-copolymer polypropylene, and the C5-C8 α-monoolefin polymerization unit content is 0.5-5.0 weight % relative to the weight of the multi-copolymer polypropylene.

2. The multi-component copolymer polypropylene according to claim 1, characterized in that: The content of propylene polymerization units in the multi-polymerized polypropylene is 92-97% by weight relative to the weight of the multi-polymerized polypropylene, the content of ethylene polymerization units is 1.0-2.5% by weight relative to the weight of the multi-polymerized polypropylene, the content of 1-butene polymerization units is 0.8-3.0% by weight relative to the weight of the multi-polymerized polypropylene, and the content of C5-C8 α-monoolefin polymerization units is 1.2-2.5% by weight relative to the weight of the multi-polymerized polypropylene.

3. The multi-component copolymer polypropylene according to claim 1, characterized in that: The ethylene polymerization unit content in the multi-polymerized polypropylene is 1.0-1.5 wt % relative to the weight of the multi-polymerized polypropylene, the 1-butene polymerization unit content is 1.0-2.0 wt % relative to the weight of the multi-polymerized polypropylene, and the C5-C8 α-monoolefin polymerization unit content is 1.5-2.5 wt % relative to the weight of the multi-polymerized polypropylene.

4. The multi-component copolymer polypropylene according to claim 1, characterized in that: The weight ratio of ethylene polymerization unit: 1-butene polymerization unit: C5-C8 α-monoolefin polymerization unit in the multi-polymerized polypropylene is 1: 0.5-3.0: 0.5-2.5, preferably 1: 0.8-2.5: 0.8-2.

0.

5. The multi-component copolymer polypropylene according to claim 1, characterized in that: It has a melting point below 132°C, preferably 124°C-130°C.

6. The multi-component copolymer polypropylene according to claim 1, characterized in that: It has a melt flow rate measured according to the national standard GB / T 3682-2018 (230° C., 2.16 kg load) of 0.8-10.0 g / 10 min, preferably 1.0-5.0 g / 10 min.

7. The multi-component copolymer polypropylene according to claim 1, characterized in that: The C5-C8 α-monoolefin is selected from 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene or 1-octene.

8. A gas phase continuous polymerization method for preparing the multi-component copolymer polypropylene according to any one of claims 1 to 7, characterized in that: Propylene, ethylene, 1-butene and a C5-C8 α-monoolefin are contacted in the presence of a Zielger-Natta catalyst system in a gas phase reactor, wherein the polymerization temperature is 65-85°C, the polymerization pressure is 2.0-3.0 MPa, and the average polymerization residence time is 1.0-1.5 hours.

9. The method according to claim 8, characterized in that The gas phase reactor is a vertical or horizontal kettle type stirred gas phase polymerization reactor.

10. The method according to claim 8, characterized in that The polymerization temperature is 70-80°C, the polymerization pressure is 2.2-2.7 MPa, and the average polymerization residence time is 1.2 hours.

11. The method according to claim 8, characterized in that The Zielger-Natta catalyst system comprises a main catalyst, a co-catalyst and an external electron donor.

12. The method according to claim 11, characterized in that The main catalyst is a magnesium chloride-supported titanium catalyst; the co-catalyst is triethylaluminum, triisobutylaluminum or a mixture thereof; and the external electron donor is a dimethoxysilane, preferably dicyclopentyldimethoxysilane.

13. The method according to claim 12, characterized in that The molar ratio of Al to Ti in the catalyst system is 60-200, preferably 80-160, more preferably 80-100, and the molar ratio of Al to Si is 5-25, preferably 7-15, more preferably 10-12.

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