A kind of impact-resistant copolymer polypropylene resin and preparation method thereof

Abstract

The invention discloses an impact-resistant copolymerized polypropylene resin and a preparation method thereof. The impact-resistant copolymerized polypropylene resin comprises a propylene copolymer and a coupling agent. The propylene copolymer is a copolymer obtained by comprising propylene and an aldehyde-containing compound, and the coupling agent is an amine-containing compound; wherein the aldehyde-containing compound comprises an olefin group, and the amine-containing compound comprises at least two amine groups. The invention applies an associative exchange reaction of imine heat excitation between aldehyde-amine groups to the preparation of impact-resistant copolymerized polypropylene, improves the rigidity and processing performance of the resin without reducing the impact resistance of the impact-resistant copolymerized polypropylene resin, and will greatly expand the application field of the impact-resistant copolymerized polypropylene resin.

Description

Technical Field

[0001] The invention belongs to the field of chemical materials, and in particular relates to an impact-resistant copolymer polypropylene resin and a preparation method thereof. Background Art

[0002] Impact copolymer polypropylene (IPC) is formed in multiple reactors and is a microscopic mixture of propylene homopolymer (ipp), ethylene-propylene random copolymer (EPR) and ethylene-propylene block copolymer (EbP). Compared with homopolymer polypropylene, IPC has greatly improved its impact resistance due to its special molecular structure and phase morphology, but at the same time it also sacrifices the rigidity of homopolymer polypropylene to varying degrees. When used in downstream automotive modification and other fields, it is often necessary to add reinforcing agents such as calcium carbonate, talcum powder, and glass fiber to improve the rigidity of the product.

[0003] The Chinese patent with publication number CN 102311583A discloses a preparation method and formula of a rigid-toughness balanced polypropylene, the formula of which is: 45% to 90% polypropylene, 5% to 20% coupling agent modified low-mesh calcium carbonate, 5% to 30% high-mesh calcium carbonate, 0% to 15% toughening agent, 0% to 2% antioxidant and 0% to 2% other additives; the mesh of the low-mesh calcium carbonate is 400 to 1500 mesh; the mesh of the high-mesh calcium carbonate is 2000 to 10000 mesh. The rigidity and toughness of the polypropylene material are relatively balanced, and can be widely used in natural color and other color mid-to-high-end automotive interior and exterior trims. The Chinese patent with publication number CN106317637A discloses a preparation method of a polypropylene reinforced toughened composite material, which includes drying polypropylene, glass fiber and nano calcium carbonate; then adding a toughening agent to stir and mix; then melt-extruding and granulating the mixture on a twin-screw extruder; and obtaining a reinforced toughened composite material. The invention modifies polypropylene by polypropylene, glass fiber and nano calcium carbonate, wherein glass fiber and toughening agent can strengthen and toughen the prepared material, and nano calcium carbonate can further improve the strength of the prepared composite material. The strength of the composite material is greatly improved. The Chinese patent with publication number CN102532706A discloses a method for preparing a high-strength and high-toughness polypropylene composite material, wherein homopolymer polypropylene 10-45, copolymer polypropylene K8303 10-25, copolymer polypropylene 7726 15-40, POE 8-16, polypropylene strengthening and toughening modifier 5-35, nucleating agent 0.15-0.4, antioxidant 0.25-0.55, lubricant 0.2-0.5 are put into a high-speed mixer, fully mixed at a speed of 1000r / min, and the material is released after two minutes. The mixed material is put into the hopper of a twin-screw extruder, and the material is extruded into composite material particles according to the process parameters. The polypropylene composite material of the invention changes the crystal state of polypropylene by using components such as polypropylene reinforcement and toughening modifier, ethylene-octene copolymer, nucleating agent, etc., thereby changing the mechanical properties such as strength and toughness of the composite material.

[0004] At present, the methods for producing impact copolymer polypropylene in reactors mainly include gas phase method and liquid phase bulk method. The gas phase process for producing impact copolymer polypropylene requires two gas phase reactors, in which propylene bulk homopolymerization is carried out in the first gas phase reactor, and propylene and α-olefin (mainly ethylene) copolymerization is carried out in the second gas phase reactor. The liquid phase bulk method, such as the Spheripol-II propylene polymerization process, uses liquid phase and gas phase reactors in series, propylene bulk homopolymerization is carried out in the loop reactor, and propylene and α-olefin (mainly ethylene) copolymerization is carried out in the gas phase reactor.

[0005] Polypropylene (PP) cross-linking technology is another important means to improve the performance of PP materials. The performance of PP modified by cross-linking is greatly improved. At present, the commonly used polypropylene cross-linking methods mainly include radiation cross-linking and chemical cross-linking. The Chinese patent with publication number CN1962750A discloses a method for irradiation cross-linking polypropylene / montmorillonite composite materials. It includes extruding and granulating maleic anhydride grafted polypropylene and organic montmorillonite in an extruder to obtain maleic anhydride grafted polypropylene / organic montmorillonite masterbatch; then the masterbatch is evenly mixed with a cross-linking agent and polypropylene and extruded and granulated again to obtain a polypropylene / organic montmorillonite material to be irradiated; the above-mentioned material to be irradiated is irradiated with high-energy rays in an air atmosphere to obtain a cross-linked polypropylene composite material with high gel content and excellent mechanical properties. Chemical cross-linking uses a chemical cross-linking agent to cross-link the polymer, transforming the linear structure into a network structure. Among them, the peroxide crosslinking method uses an organic peroxide as a crosslinking agent, such as the Chinese patent publication number CN103497414A, which discloses a crosslinked polypropylene, wherein the crosslinked polypropylene is α-silane crosslinked polypropylene, comprising the following components: polypropylene, peroxide, and α-silane. The prepared material is not only lighter and more environmentally friendly than nylon materials, but also has a low cost. However, the crosslinking bond formed by the currently used polypropylene crosslinking technology is irreversible, which makes the crosslinked polypropylene unable to be processed again, thus bringing about the problem that the crosslinked polypropylene is difficult to recycle.

[0006] Dynamic covalent bonds refer to covalent bonds that can be reversibly broken / bonded after being exposed to specific stimuli (such as heat, light, and pH). The polymer cross-linked network formed by this can achieve topological rearrangement under external influences, so it has the characteristics of plasticity, self-repair, and stimulus response. According to different reaction mechanisms, dynamic covalent bonds can be divided into two categories: dissociative and associative. (1) Dissociative dynamic covalent bonds are represented by Diels-Alder (DA, [4+2] cycloaddition) reactions. At high temperatures, new cross-linking points are formed by first breaking and then re-bonding. That is, the breaking of old bonds and the re-formation of new bonds are independent of each other. In this process, the cross-linking density of the material will change. (2) Associative dynamic covalent bonds: The topological rearrangement of the cross-linked network is achieved through exchange reactions. That is, the breaking of old bonds and the formation of new bonds are carried out simultaneously, so the cross-linking density remains unchanged. Imine bonds are a classic associative dynamic covalent bonds that can be formed by dehydration condensation between amine groups and aldehyde groups. The advantages of this dynamic covalent bond are good solvent resistance, self-repair and recycling without a catalyst, and it is an effective way to obtain a thermally reversible structure. If this reaction is used to achieve chemical cross-linking between polypropylene molecular chains, and the chemical bond is used to undergo a reversible reaction at high temperature to de-crosslink polypropylene, a new thermoplastic cross-linked polypropylene material can be obtained, and the cross-linked polypropylene can be recycled. Although the dissociated dynamic covalent cross-linking network based on the DA reaction can be processed again, there is a problem of a narrow processing window caused by a sudden drop in viscosity, which increases the difficulty and cost of production.

[0007] Dalian University of Technology's 2020 master's thesis "Preparation of Thermally Reversible Cross-linked Polypropylene" designs and synthesizes a series of functional -olefin monomers containing furan groups. Through copolymerization with propylene, polypropylene containing furan side groups is obtained. During the extrusion granulation process, a thermally reversible Diels-Alder reaction occurs with bismaleimide to obtain polypropylene with a thermally reversible cross-linked structure. Petrochemicals, 2020, 49(8), 753-758, Technical description: Reversible cross-linked polypropylene is prepared by Diels-Alder reaction. This technology has the problems of rapid dissociation of the cross-linked network after heating, sudden drop in material viscosity, and narrow material processing temperature window. In actual application, the material performance quickly collapses and the safety performance is poor.

[0008] The Chinese patent with publication number CN106189040A discloses a method for synthesizing a thermally reversible cross-linked modified elastomeric material based on a Schiff base reaction. The patent first dissolves an elastomer containing isolated double bonds and a thiolamino compound in an organic solvent, stirs them evenly, adds a photoinitiator, and reacts with a thiolene click reaction under ultraviolet light to obtain an amino-grafted modified elastomer; then the amino-grafted modified elastomer and a polyaldehyde compound are dissolved in an organic solvent, film-formed and cross-linked at a temperature of 60-120°C to obtain a thermally reversible cross-linked modified elastomeric material. Among them, the elastomer containing isolated double bonds is a styrene-based thermoplastic elastomer SBS, SIS or SIBS and butadiene rubber, nitrile rubber, natural rubber or EPDM; the thiolamino compound is mercaptoethylamine, mercaptopropylamine, 4-mercaptoaniline or 2-mercaptoaniline, and their hydrochlorides. The defects of this technology are: the styrene-based thermoplastic elastomer contains isolated double bonds, which can be reacted with mercaptoamino compounds and are easy to implement in the system, but this method is not suitable for polypropylene systems (polypropylene molecules do not contain double bonds), and amino compounds are toxic to the polypropylene Zigler-Natta catalyst system, and it is not easy to graft amino compounds first in the polymerization kettle.

[0009] J Polym Sci, Part A: Polym Chem, 2017, 55(12): 2011-2018, discloses a polybutadiene elastomer with dynamic imine crosslinking prepared by crosslinking reaction of amine-functionalized polybutadiene with aldehyde. The document uses the imine exchange reaction between aldehyde groups and amine groups to prepare Vitrimer reversibly crosslinked cis-butadiene rubber. Compos Sci Technol, 2018, 168: 214-223, technical description: Preparation of styrene-butadiene rubber SBR / graphene composite material based on interfacial imine bond crosslinking. The defect of this technology is that there are a large number of double bonds available for reaction in both the cis-butadiene rubber side groups and the styrene-butadiene rubber side groups, which is easy to implement in the system, but the method is not suitable for polypropylene systems (polypropylene molecules do not contain double bonds).

[0010] Therefore, further research on the polypropylene polymerization system is needed in this field. Summary of the invention

[0011] The main purpose of the present invention is to provide an impact-resistant copolymer polypropylene resin and a preparation method thereof, so as to overcome the problems in the prior art that polypropylene resin is difficult to balance better rigidity and toughness, and that cross-linked polypropylene cannot be reprocessed or recycled.

[0012] In order to achieve the above object, the present invention provides an impact-resistant copolymer polypropylene resin, comprising a propylene copolymer and a coupling agent, wherein the propylene copolymer is a copolymer obtained from propylene and an aldehyde-containing compound, and the coupling agent is an amine-containing compound;

[0013] Wherein, the aldehyde-containing compound includes an olefin group, and the amine-containing compound includes at least two amine groups.

[0014] The impact-resistant copolymer polypropylene resin of the present invention, wherein the propylene copolymer is a copolymer obtained from propylene, ethylene and an aldehyde-containing compound; wherein the molar content of propylene in the propylene copolymer is 50-85%, the molar content of ethylene in the propylene copolymer is 5-40%, and the molar content of the aldehyde-containing compound in the propylene copolymer is 5-15%.

[0015] The impact-resistant copolymer polypropylene resin of the present invention, wherein the coupling agent is at least one of the following structures of formula I:

[0016]

[0017] Among them, R 1 is a straight or branched chain alkylene group having 1 to 12 carbon atoms, R 2 It is a straight chain or branched chain alkylene group having 1 to 6 carbon atoms.

[0018] The impact-resistant copolymer polypropylene resin of the present invention comprises: based on the mass of the impact-resistant copolymer polypropylene resin as 100%, the content of the propylene copolymer is 75-97%, the content of the coupling agent is 3-25%; the aldehyde-containing compound is olefin benzaldehyde, and the benzene ring contains or does not contain an alkyl substituent.

[0019] The impact-resistant copolymer polypropylene resin of the present invention, wherein the aldehyde-containing compound is at least one of o-vinylbenzaldehyde, m-vinylbenzaldehyde, p-vinylbenzaldehyde and o-vinylbenzaldehyde, m-vinylbenzaldehyde and p-vinylbenzaldehyde containing at least one methyl substituent on the benzene ring.

[0020] In order to achieve the above object, the present invention also provides a method for preparing the above impact-resistant copolymer polypropylene resin, comprising mixing a propylene copolymer and a coupling agent to obtain an impact-resistant copolymer polypropylene resin;

[0021] Wherein, the preparation method of the propylene copolymer comprises:

[0022] Copolymerizing propylene and an aldehyde-containing compound under the action of a catalyst to obtain the propylene copolymer;

[0023] The aldehyde-containing compound includes an olefin group, and the coupling agent is an amine-containing compound, and the amine-containing compound includes at least two amine groups.

[0024] The method for preparing the impact-resistant copolymer polypropylene resin of the present invention, wherein the method for preparing the propylene copolymer comprises:

[0025] Step 1, subjecting propylene and an aldehyde-containing compound to liquid phase bulk polymerization under the action of a catalyst;

[0026] Step 2, copolymerizing the polymerization product obtained in step 1, propylene and ethylene in gas phase to obtain the propylene copolymer.

[0027] The method for preparing the impact-resistant copolymer polypropylene resin of the present invention, wherein the catalyst in step 1 comprises a main catalyst, a co-catalyst and an external electron donor, wherein the main catalyst is a Zigler-Natta catalyst, and the co-catalyst is an organic aluminum compound; the general formula of the external electron donor is R1R2Si(OR3)2, wherein R1 and R2 are the same or different and are selected from C1-C6 straight-chain or branched aliphatic groups, C5-C10 branched or unbranched cyclic alkane groups or aromatic groups.

[0028] The method for preparing the impact-resistant copolymer polypropylene resin of the present invention comprises the following steps: in step 1, the temperature of the liquid phase bulk polymerization is 65-75° C., the pressure is 4000-4500 KPa, and the molar ratio of propylene to the aldehyde-containing compound is 60-800:1; in step 2, in the gas phase copolymerization, the molar ratio of ethylene to the total amount of ethylene and propylene is 20-40%, the reaction temperature of the gas phase copolymerization is 75-85° C., and the reaction pressure is 1200-1400 KPa.

[0029] The method for preparing the impact-resistant copolymer polypropylene resin of the present invention further comprises a prepolymerization step of prepolymerizing propylene under the action of a catalyst and then performing liquid phase bulk polymerization with an aldehyde-containing compound.

[0030] The method for preparing the impact-resistant copolymer polypropylene resin of the present invention further comprises a pre-complexation step and then the pre-polymerization step; the pre-complexation step comprises: mixing the main catalyst, the co-catalyst and the external electron donor, the mixing temperature is -10-60°C, and the mixing time is 30-100 minutes.

[0031] The preparation method of the impact-resistant copolymer polypropylene resin of the present invention comprises the following steps: an antioxidant and an acid absorber are added during the mixing process of the propylene copolymer and the coupling agent, the antioxidant comprising a primary antioxidant and a secondary antioxidant, the primary antioxidant being pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, the secondary antioxidant being tris(2,4-di-tert-butylphenyl)phosphite, and the acid absorber being hydrotalcite; and the mixing temperature being 190-230°C.

[0032] Beneficial effects of the present invention:

[0033] The impact-resistant copolymer polypropylene resin of the invention is a material with a reversible cross-linked network structure. The aldehyde group of the side group of the ethylene-propylene copolymer can react with the amine group of the coupling agent to cross-link the polymer. When heated, the cross-linked bond realizes the rearrangement of its network structure through a heat-excited associative exchange reaction, and the formation of new bonds and the breaking of old bonds are carried out simultaneously, thereby giving the material thermoplasticity, making the material cross-linked when used and de-cross-linked when processed, thereby solving the problem that the traditional cross-linked polypropylene cannot be processed and recycled.

[0034] The impact-resistant copolymer polypropylene resin of the present invention belongs to a heat-activated associative cross-linked polymer, and its viscosity gradually decreases with increasing temperature, providing a larger processing window for material molding, and solving the problems of the dissociative cross-linked network structure represented by DA reaction being not resistant to high temperature, having a sudden drop in viscosity, and having a narrow processing window.

[0035] The present invention applies the associative exchange reaction of imine heat excitation between aldehyde groups and amine groups to the preparation of impact-resistant copolymer polypropylene, improves the rigidity and processing performance of the resin without reducing the impact resistance of the impact-resistant copolymer polypropylene resin, and will greatly expand the application field of the impact-resistant copolymer polypropylene resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The infrared spectra of the copolymerized polypropylene resins prepared in Comparative Example 1, Comparative Example 2 and Example 1 of the present invention are shown in FIG.

[0037] Figure 2 The infrared spectra of the copolymerized polypropylene resins prepared in Comparative Example 4 and Example 1 of the present invention are shown. DETAILED DESCRIPTION

[0038] The following is a detailed description of the embodiments of the present invention. The embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and processes are given. However, the protection scope of the present invention is not limited to the following embodiments. The experimental methods in the following embodiments where specific conditions are not specified are usually based on conventional conditions.

[0039] The present invention provides an impact-resistant copolymer polypropylene resin, comprising a propylene copolymer and a coupling agent, wherein the propylene copolymer is a copolymer obtained from propylene and an aldehyde-containing compound, and the coupling agent is an amine-containing compound;

[0040] Wherein, the aldehyde-containing compound includes an olefin group, and the amine-containing compound includes at least two amine groups.

[0041] The present invention applies the associative exchange reaction of imine heat excitation between aldehyde group and amine group to the preparation of impact-resistant copolymer polypropylene, so that the aldehyde group of the side group of ethylene-propylene copolymer reacts with the amine group of the coupling agent, and then the polymer is cross-linked to form a reversible cross-linked network structure, which improves the rigidity and processing performance of the resin without reducing the impact resistance of the impact-resistant copolymer polypropylene resin. In addition, the prepared resin material is cross-linked during use and de-cross-linked during processing, which solves the problem that traditional cross-linked polypropylene cannot be processed and recycled.

[0042] In one embodiment, the propylene copolymer further comprises ethylene, i.e., the propylene copolymer is a copolymer obtained from propylene, ethylene and an aldehyde-containing compound. In another embodiment, the molar content of propylene in the propylene copolymer is 50-85%, the molar content of ethylene in the propylene copolymer is 5-40%, and the molar content of the aldehyde-containing compound in the propylene copolymer is 5-15%.

[0043] Wherein, the aldehyde-containing compound includes an olefin group and an aldehyde group. In one embodiment, the aldehyde-containing compound is an olefin group benzaldehyde, and the benzene ring contains or does not contain an alkyl substituent. Wherein, the olefin group and the aldehyde group are, for example, in the ortho position, meta position or para position. In another embodiment, the aldehyde-containing compound is at least one of o-vinylbenzaldehyde, m-vinylbenzaldehyde, p-vinylbenzaldehyde, and o-vinylbenzaldehyde containing at least one methyl substituent on the benzene ring, m-vinylbenzaldehyde containing at least one methyl substituent on the benzene ring, and p-vinylbenzaldehyde containing at least one methyl substituent on the benzene ring. Wherein, containing at least one methyl substituent refers to containing one methyl substituent, containing two methyl substituents, containing three methyl substituents, or containing four methyl substituents.

[0044] Wherein, the coupling agent is an amine-containing compound, and the amine-containing compound includes at least two amine groups. In one embodiment, the coupling agent is at least one of the following structures of formula I:

[0045]

[0046] Among them, R 1 is a straight or branched chain alkylene group having 1 to 12 carbon atoms, R 2 is a straight or branched alkylene group having 1 to 6 carbon atoms. 2 It is a straight or branched chain alkylene group having 2 to 3 carbon atoms.

[0047] In one embodiment, based on 100% of the mass of the impact-resistant copolymer polypropylene resin, the content of the propylene copolymer is 75-97%, and the content of the coupling agent is 3-25%.

[0048] The impact-resistant copolymer polypropylene resin of the present invention is prepared by mixing a propylene copolymer and a coupling agent to cause an imine exchange reaction between the aldehyde groups and the amine groups therein, thereby obtaining the Vitrimer reversibly cross-linked impact-resistant copolymer polypropylene.

[0049] The present invention also provides a method for preparing the above-mentioned propylene copolymer, comprising:

[0050] Propylene and aldehyde-containing compounds are copolymerized under the action of a catalyst to obtain a propylene copolymer.

[0051] In one embodiment, ethylene is also added during the polymerization reaction. The aldehyde-containing compound is copolymerized with propylene in the propylene homopolymerization section (first reactor) and continues to participate in the polymerization in the propylene and ethylene copolymerization section (second reactor), and the aldehyde group is introduced into the side group of the copolymer.

[0052] In a first embodiment, the method for preparing a propylene copolymer comprises:

[0053] Step 1, subjecting propylene and an aldehyde-containing compound to liquid phase bulk polymerization under the action of a catalyst;

[0054] Step 2, copolymerizing the polymerization product obtained in step 1, propylene and ethylene in gas phase to obtain a propylene copolymer.

[0055] The specific structure of the aldehyde-containing compound has been described in detail above and will not be repeated here.

[0056] Wherein, the catalyst in step 1 includes a main catalyst, a co-catalyst and an external electron donor, the main catalyst is a Zigler-Natta catalyst, and the co-catalyst is an organic aluminum compound; the general formula of the external electron donor is R1R2Si(OR3)2, wherein R1 and R2 are the same or different and are respectively selected from C1-C6 straight-chain or branched aliphatic groups, C5-C10 branched or unbranched cyclic alkane groups or aromatic groups.

[0057] In one embodiment, the main catalyst is a solid catalyst component with magnesium, titanium, halogen and internal electron donor as main components; the co-catalyst is an alkyl aluminum compound, preferably triethyl aluminum; the external electron donor is diisopropyldimethoxysilane, diisobutyldiethoxysilane, cyclopentyl-methyl-dimethoxysilane, cyclopentyl-ethyl-dimethoxysilane, di(2-methylbutyl)-dimethoxysilane, di(2-methylpropyl)-dimethoxysilane, cyclohexyl-methyl-dimethoxysilane, cyclohexyl-ethyl-dimethoxysilane Alkane, cyclohexyl-methyl-diethoxysilane, dicyclopentyldimethoxysilane (DCPMS), di(3-methylcyclopentyl)-dimethoxysilane, dicyclohexyldimethoxysilane, di(3,4-methylcyclohexyl)-dimethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, di(2-methylphenyl)-dimethoxysilane, di(3-isopropylphenyl)-dimethoxysilane, pentyl, phenyl-dimethoxysilane, preferably cyclopentyl-ethyl-dimethoxysilane and diphenyldimethoxysilane.

[0058] In one embodiment, the mass ratio of the solid catalyst component to the organoaluminum compound is 1:10 to 1:500, preferably 1:25 to 1:100, based on the mass of titanium / aluminum. The mass ratio of the organoaluminum compound to the external electron donor is 1 to 10, preferably 3 to 7.

[0059] The temperature of the liquid phase bulk polymerization in step 1 is 65-75°C and the pressure is 4000-4500 KPa. The liquid phase bulk polymerization is carried out in the presence of a certain amount of hydrogen, and the reaction device is, for example, a loop reactor. The molar ratio of propylene to the aldehyde-containing compound is, for example, 60 to 800:1.

[0060] Step 2 is to perform gas phase copolymerization of the polymerization product obtained in step 1, propylene and ethylene to obtain a propylene copolymer. The polymerization product obtained in step 1 may contain aldehyde-containing compounds that are not completely reacted in step 1. According to the product performance requirements, the ratio of each monomer during gas phase polymerization is adjusted, usually ethylene / (ethylene+propylene) (hereinafter abbreviated as C2 / C2+C3) is controlled to be 0.20-0.40 (molar ratio), preferably 0.25-0.35 (molar ratio), the polymerization reaction temperature is 75-85°C, and the polymerization reaction pressure is 1200-1400KPa.

[0061] In a second embodiment, the method for preparing a propylene copolymer comprises:

[0062] A prepolymerization step, prepolymerizing propylene under the action of a catalyst;

[0063] Step 1, subjecting the prepolymerized mixture, propylene and an aldehyde-containing compound to liquid phase bulk polymerization under the action of a catalyst;

[0064] Step 2, copolymerizing the polymerization product obtained in step 1, propylene and ethylene in gas phase to obtain a propylene copolymer.

[0065] The prepolymerization step is to conduct a prepolymerization reaction of a small amount of propylene under the action of a catalyst, and the temperature of the prepolymerization reaction is -10-60°C, preferably 10-30°C. The multiple of the prepolymerization reaction is 30-300 times, preferably 50-150 times. The prepolymerization reaction can be carried out in a continuous mixer or a small loop reactor, and the feed amount of prepolymerized propylene is 15-25 kg / h.

[0066] Step 1 and step 2 are similar to those in the first embodiment and are not described again.

[0067] In a third embodiment, the method for preparing a propylene copolymer comprises:

[0068] In the pre-complexation step, the main catalyst, the co-catalyst and the external electron donor are mixed at a mixing temperature of -10-60° C. and a mixing time of 30-100 min.

[0069] A prepolymerization step, in which a small amount of propylene is prepolymerized under the action of the catalyst obtained in the precomplexation step;

[0070] Step 1, subjecting the prepolymerized mixture, propylene and an aldehyde-containing compound to liquid phase bulk polymerization under the action of a catalyst;

[0071] Step 2, copolymerizing the polymerization product obtained in step 1, propylene and ethylene in gas phase to obtain a propylene copolymer.

[0072] The pre-complexation step can make the catalyst components (main catalyst, co-catalyst and external electron donor) fully and effectively mixed, and can be carried out in a continuous stirred tank reactor or a loop reactor. The pre-complexation reaction temperature is -10-60°C, preferably 10-30°C. The pre-complexation reaction time is 30-100min, preferably 5-30min.

[0073] In addition to the propylene copolymer and the coupling agent, other additives such as antioxidants, acid absorbers, etc. may be added to the impact-resistant copolymer polypropylene resin of the present invention. In one embodiment, the method for preparing the impact-resistant copolymer polypropylene resin of the present invention comprises the following steps:

[0074] 1) mixing a propylene copolymer, a coupling agent, an antioxidant, and an acid scavenger to obtain a premixed raw material;

[0075] The antioxidant includes, for example, a primary antioxidant and a secondary antioxidant. The primary antioxidant is, for example, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, the secondary antioxidant is, for example, tris(2,4-di-tert-butylphenyl) phosphite, and the acid absorbent is, for example, hydrotalcite.

[0076] 2) Add the premixed raw materials into the reactive processing equipment and react at 190-230°C.

[0077] The reactive processing equipment is, for example, any one of a single-screw extruder, a twin-screw extruder, an open mixer, and an internal mixer.

[0078] Therefore, the present invention provides a method for preparing impact-resistant copolymer polypropylene, and synthesizes impact-resistant copolymer polypropylene containing aldehyde groups on the side groups, so that Vitrimer reversibly cross-linked impact-resistant copolymer polypropylene can be prepared through an imine exchange reaction between aldehyde groups and amine groups, thereby solving the problems of poor rigidity of impact-resistant copolymer polypropylene resin and reduced processing performance of the resin due to the introduction of ethylene-propylene rubber phase.

[0079] The technical solution of the present invention will be further described below through specific embodiments.

[0080] The equipment used in the following examples is as follows:

[0081] Extruder: 35-type twin-screw extruder (Belong Keya Nanjing Machinery Co., Ltd.)

[0082] Injection molding machine: Standard specimens are molded by injection molding machine (UN-100 of Liuzhou Injection Molding Machinery Factory). The data related to the polymers in the following embodiments are obtained according to the following test methods:

[0083] Melt flow rate (MFR): measured in accordance with GB / T 3682-2000, 230°C, under a load of 2.16 kg.

[0084] Simply supported beam impact strength: measured according to GB / T1043.1-2008

[0085] Flexural modulus: measured according to GB / T 9341-2008.

[0086] Qualitative analysis of polymer groups: infrared (IR) determination.

[0087] Example 1

[0088] This example uses a specific surface area of ​​242m 2 / g, and a Zigler-Natta catalyst with a pore size of 3.413 nm. The specific preparation method refers to document CN103319638B (the Zigler-Natta catalyst not specifically described in the following examples and comparative examples is prepared according to this reference).

[0089] Pre-complexation: Zigler-Natta catalyst, triethylaluminum (TEA), external electron donor cyclopentyl-ethyl-dimethoxysilane (Donor) at 10°C, pre-complexation for 20 minutes. The flow rate of triethylaluminum entering the pre-complexation is 6.33g / hr, the flow rate of cyclopentyl-ethyl-dimethoxysilane is 1.58g / hr, and the flow rate of the main catalyst (Zigler-Natta catalyst) is 0.158g / hr. Among them, the mass ratio of TEA / Donor is 4.

[0090] Prepolymerization: The pre-complexed catalyst system continuously enters the prepolymerization reactor for prepolymerization reaction. The prepolymerization is carried out in a bulk propylene liquid phase environment. The prepolymerization propylene feed rate is 18kg / h. The temperature is 15°C and the residence time is 4min. Under this condition, the prepolymerization multiple of the catalyst is 120-150 times.

[0091] The slurry after prepolymerization enters the loop reactor. The polymerization reaction temperature in the loop reactor is 70°C, the propylene monomer feed rate is 60kg / h, the 3-vinylbenzaldehyde feed rate is 6.2kg / h, the hydrogen addition rate is 1000ppm, and the reaction pressure is 4000KPa.

[0092] The polymer slurry prepared in the loop reactor is passed through a high-pressure flash evaporator to remove unreacted propylene monomer and hydrogen, and the unreacted vinylbenzaldehyde enters the gas phase fluidized bed reactor along with the polymer to carry out gas phase copolymerization of ethylene, propylene and vinylbenzaldehyde. The reaction temperature is 80°C, the reaction pressure is 1400KPa, and the gas phase ratio C2 / C2+C3 is controlled to be 0.26 (molar ratio) to prepare impact copolymer polypropylene powder.

[0093] 80000ppm coupling agent N1-(2-aminoethyl)-N1-(aminomethyl)ethane-1,2-diamine, 500ppm tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] pentaerythritol ester (1010), 1000ppm tris(2,4-di-tert-butylphenyl)phosphite (168), 400ppm acid absorbent calcium stearate were added to the impact-resistant copolymer polypropylene powder, and after being uniformly mixed, extrusion granulation was carried out through a 35-type twin-screw extruder (Belong Keya Nanjing Machinery Co., Ltd.), the melting section temperature of the extruder was 220°C, the outlet temperature was 180°C, the extruded product was cooled in a circulating water bath and pelletized to obtain the target product. The obtained pellets were subjected to performance tests according to the current relevant GBT standards.

[0094] The specific process conditions and resin performance test results are shown in Table 1.

[0095] Comparative Example 1

[0096] Comparative Example 1 is the same as Example 1, except that 3-vinylbenzaldehyde is not added to the loop reactor, and coupling agent is not added during the extrusion granulation process, and the rest is the same as Example 1. Specific process conditions and resin performance test results are shown in Table 1.

[0097] Comparative Example 2

[0098] Comparative Example 2 is the same as Example 1, except that no coupling agent is added during the extrusion granulation process, and the rest is the same as Example 1. The specific process conditions and resin performance test results are shown in Table 1.

[0099] Comparative Example 3

[0100] This example uses a specific surface area of ​​242m 2 / g, Zigler-Natta catalyst with a pore size of 3.413nm.

[0101] Pre-complexation: Zigler-Natta catalyst, triethylaluminum (TEA), external electron donor cyclopentyl-ethyl-dimethoxysilane at 10°C, pre-complexation for 20 minutes. The flow rate of triethylaluminum entering the pre-complexation is 6.33g / hr, the flow rate of cyclopentyl-ethyl-dimethoxysilane is 1.58g / hr, and the flow rate of the main catalyst is 0.158g / hr. Among them, the mass ratio of TEA / Donor is 4.

[0102] Prepolymerization: The pre-complexed catalyst system continuously enters the prepolymerization reactor for prepolymerization reaction. The prepolymerization is carried out in a propylene liquid phase bulk environment at a temperature of 15°C and a residence time of 4 minutes. Under this condition, the prepolymerization multiple of the catalyst is 120-150 times.

[0103] The slurry after prepolymerization enters the loop reactor. The polymerization reaction temperature in the loop reactor is 70°C, the propylene monomer feed rate is 60kg / h, the hydrogen addition rate is 1000ppm, and the reaction pressure is 4000KPa.

[0104] The polymer slurry prepared by the loop reactor is passed through a high-pressure flash evaporator to remove unreacted propylene monomer and hydrogen, thereby preparing homopolymerized polypropylene powder.

[0105] 500ppm of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester (1010), 1000ppm of tris(2,4-di-tert-butylphenyl) phosphite (168), and 400ppm of acid absorbent calcium stearate were added to homopolymerized polypropylene powder, and after being uniformly mixed, extrusion granulation was performed by a 35-type twin-screw extruder (Belong Keya Nanjing Machinery Co., Ltd.), the melting section temperature of the extruder was 220°C, the outlet temperature was 180°C, the extruded product was cooled in a circulating water bath and pelletized to obtain the target product. The obtained pellets were subjected to performance tests according to the current relevant GBT standards.

[0106] The specific process conditions and resin performance test results are shown in Table 1.

[0107] Comparative Example 4

[0108] This example uses a specific surface area of ​​242m 2 / g, Zigler-Natta catalyst with a pore size of 3.413nm.

[0109] Pre-complexation: Zigler-Natta catalyst, triethylaluminum (TEA), external electron donor cyclopentyl-ethyl-dimethoxysilane at 10°C, pre-complexation for 20 minutes. The flow rate of triethylaluminum entering the pre-complexation is 6.33g / hr, the flow rate of cyclopentyl-ethyl-dimethoxysilane is 1.58g / hr, and the flow rate of the main catalyst is 0.158g / hr. Among them, the mass ratio of TEA / Donor is 4.

[0110] Prepolymerization: The pre-complexed catalyst system continuously enters the prepolymerization reactor for prepolymerization reaction. The prepolymerization is carried out in a bulk propylene liquid phase environment. The prepolymerization propylene feed rate is 19 kg / h. The temperature is 15°C and the residence time is 4 minutes. Under this condition, the prepolymerization multiple of the catalyst is 120-150 times.

[0111] The slurry after prepolymerization enters the loop reactor. The polymerization reaction temperature in the loop reactor is 70°C, the propylene monomer feed rate is 60kg / h, the 8-furan-1-hexene feed rate is 6.2kg / h, the hydrogen addition rate is 1000ppm, and the reaction pressure is 4000KPa.

[0112] After the polymer slurry prepared in the loop reactor is passed through a high-pressure flash evaporator to remove unreacted propylene monomer and hydrogen, the unreacted 8-furan-1-hexene enters the gas phase fluidized bed reactor along with the polymer to carry out gas phase copolymerization of ethylene, propylene and 8-furan-1-hexene. The reaction temperature is 80°C, the reaction pressure is 1400KPa, and the gas phase ratio C2 / C2+C3 is controlled to be 0.26 (molar ratio) to prepare impact copolymer polypropylene powder.

[0113] 80000ppm coupling agent 1,6-bismaleimide, 500ppm tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester (1010), 1000ppm tris(2,4-di-tert-butylphenyl) phosphite (168), 400ppm acid absorber calcium stearate were added to impact-resistant copolymer polypropylene powder, mixed evenly, and extruded and granulated by a 35-type twin-screw extruder (Belong Keya Nanjing Machinery Co., Ltd.), the melting section temperature of the extruder was 220°C, the outlet temperature was 180°C, the extruded product was cooled in a circulating water bath and pelletized to obtain the target product. The obtained pellets were tested for performance according to the current relevant GBT standards.

[0114] The specific process conditions and resin performance test results are shown in Table 1.

[0115] Example 2

[0116] This embodiment uses a Zigler-Natta catalyst with a specific surface area of ​​300 m2 / g and a pore size of 4.125 nm.

[0117] Pre-complexation: Zigler-Natta catalyst, triethylaluminum (TEA), and external electron donor cyclohexyl-methyl-dimethoxysilane were pre-complexed for 20 minutes at 10°C. The flow rate of triethylaluminum entering the pre-complexation was 6.33 g / hr, the flow rate of cyclohexyl-methyl-dimethoxysilane was 1.81 g / hr, and the flow rate of the main catalyst was 0.158 g / hr. Among them, the mass ratio of TEA / Donor was 3.5.

[0118] Prepolymerization: The pre-complexed catalyst system continuously enters the prepolymerization reactor for prepolymerization reaction. The prepolymerization is carried out in a propylene liquid phase bulk environment, with a prepolymerization propylene feed rate of 20 kg / h. The temperature is 15°C, the residence time is 4 minutes, and the prepolymerization multiple of the catalyst under this condition is 120-150 times.

[0119] The slurry after prepolymerization enters the loop reactor. The polymerization reaction temperature in the loop reactor is 72°C, the propylene monomer feed rate is 60kg / h, the 2-vinylbenzaldehyde feed rate is 3.8kg / h, the hydrogen addition rate is 2000ppm, and the reaction pressure is 4200KPa.

[0120] The polymer slurry prepared in the loop reactor is passed through a high-pressure flash evaporator to remove unreacted propylene monomer and hydrogen, and the unreacted vinylbenzaldehyde enters the gas phase fluidized bed reactor along with the polymer to carry out gas phase copolymerization of ethylene, propylene and vinylbenzaldehyde. The reaction temperature is 84°C, the reaction pressure is 1400KPa, and the gas phase ratio C2 / (C2+C3) is controlled to be 0.30 (molar ratio) to prepare impact copolymer polypropylene powder.

[0121] 50000ppm coupling agent N, N-bis(aminoethyl)methanediamine, 500ppm tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol ester (1010), 1000ppm tris(2,4-di-tert-butylphenyl)phosphite (168), 400ppm acid absorber calcium stearate were added to impact-resistant copolymer polypropylene powder, and after uniform mixing, extrusion granulation was carried out through a 35-type twin-screw extruder (Belong Keya Nanjing Machinery Co., Ltd.), the melting section temperature of the extruder was 210°C, the outlet temperature was 175°C, the extruded product was cooled in a circulating water bath and pelletized to obtain the target product. The obtained pellets were subjected to performance tests according to the current relevant GBT standards.

[0122] The specific process conditions and resin performance test results are shown in Table 1.

[0123] Example 3

[0124] This example uses a specific surface area of ​​242m 2 / g, Zigler-Natta catalyst with a pore size of 3.413nm.

[0125] Pre-complexation: Zigler-Natta catalyst, triethylaluminum (TEA), external electron donor cyclopentyl-ethyl-dimethoxysilane at 10°C, pre-complexation for 20 minutes. The flow rate of triethylaluminum entering the pre-complexation is 6.33g / hr, the flow rate of cyclopentyl-ethyl-dimethoxysilane is 1.41g / hr, and the flow rate of the main catalyst is 0.158g / hr. Among them, the mass ratio of TEA / Donor is 4.5.

[0126] Prepolymerization: The pre-complexed catalyst system continuously enters the prepolymerization reactor for prepolymerization reaction. The prepolymerization is carried out in a bulk propylene liquid phase environment. The prepolymerization propylene feed rate is 19 kg / h. The temperature is 15°C and the residence time is 4 minutes. Under this condition, the prepolymerization multiple of the catalyst is 120-150 times.

[0127] The slurry after prepolymerization enters the loop reactor. The polymerization reaction temperature in the loop reactor is 73°C, the propylene monomer feed rate is 60kg / h, the 4-vinylbenzaldehyde feed rate is 1.9kg / h, the hydrogen addition rate is 4000ppm, and the reaction pressure is 4000KPa.

[0128] The polymer slurry prepared in the loop reactor is passed through a high-pressure flash evaporator to remove unreacted propylene monomer and hydrogen, and the unreacted vinylbenzaldehyde enters the gas phase fluidized bed reactor along with the polymer to carry out gas phase copolymerization of ethylene, propylene and vinylbenzaldehyde. The reaction temperature is 82°C, the reaction pressure is 1400KPa, and the gas phase ratio C2 / (C2+C3) is controlled to be 0.32 (molar ratio) to prepare impact copolymer polypropylene powder.

[0129] 80000ppm of coupling agent propane-1,3-diamine, 500ppm of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester (1010), 1000ppm of tris(2,4-di-tert-butylphenyl) phosphite (168), 400ppm of acid absorbent calcium stearate were added to the impact copolymer polypropylene powder, and after uniform mixing, extrusion granulation was carried out through a 35-type twin-screw extruder (Belong Keya Nanjing Machinery Co., Ltd.), the melting section temperature of the extruder was 210°C, the outlet temperature was 175°C, and the extruded product was cooled and pelletized in a circulating water bath to obtain the target product. The obtained pellets were tested for performance according to the current relevant GBT standards. The specific process conditions and resin performance test results are shown in Table 1.

[0130] Example 4

[0131] This example uses a specific surface area of ​​300m 2 / g, Zigler-Natta catalyst with a pore size of 4.125nm.

[0132] Pre-complexation: Zigler-Natta catalyst, triethylaluminum (TEA), and external electron donor diisopropyldimethoxysilane were pre-complexed for 20 minutes at 10°C. The flow rate of triethylaluminum entering the pre-complexation was 6.33 g / hr, the flow rate of diisopropyldimethoxysilane was 1.58 g / hr, and the flow rate of the main catalyst was 0.158 g / hr. Among them, the mass ratio of TEA / Donor was 4.

[0133] Prepolymerization: The pre-complexed catalyst system continuously enters the prepolymerization reactor for prepolymerization reaction. The prepolymerization is carried out in a bulk propylene liquid phase environment, with a prepolymerization propylene feed rate of 22 kg / h. The temperature is 15°C, the residence time is 4 minutes, and the prepolymerization multiple of the catalyst under this condition is 120-150 times.

[0134] The slurry after prepolymerization enters the loop reactor. The polymerization reaction temperature in the loop reactor is 75°C, the propylene monomer feed rate is 60kg / h, the 3-vinylbenzaldehyde feed rate is 6.2kg / h, the hydrogen addition rate is 5000ppm, and the reaction pressure is 4000KPa.

[0135] The polymer slurry prepared in the loop reactor is passed through a high-pressure flash evaporator to remove unreacted propylene monomer and hydrogen, and the unreacted vinylbenzaldehyde enters the gas phase fluidized bed reactor along with the polymer to carry out gas phase copolymerization of ethylene, propylene and vinylbenzaldehyde. The reaction temperature is 82°C, the reaction pressure is 1400KPa, and the gas phase ratio C2 / (C2+C3) is controlled to be 0.35 (molar ratio) to prepare impact copolymer polypropylene powder.

[0136] 40000ppm coupling agent butane-1,4-diamine, 500ppm tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester (1010), 1000ppm tris(2,4-di-tert-butylphenyl) phosphite (168), 400ppm acid absorber calcium stearate were added to impact-resistant copolymer polypropylene powder, and after uniform mixing, extrusion granulation was carried out through a 35-type twin-screw extruder (Belong Keya Nanjing Machinery Co., Ltd.), the melting section temperature of the extruder was 200°C, the outlet temperature was 170°C, the extruded product was cooled in a circulating water bath and pelletized to obtain the target product. The obtained pellets were subjected to performance tests according to the current relevant GBT standards.

[0137] The specific process conditions and resin performance test results are shown in Table 1.

[0138] Example 5

[0139] This example uses a specific surface area of ​​300m 2 / g, Zigler-Natta catalyst with a pore size of 4.125nm.

[0140] Pre-complexation: solid catalyst, triethylaluminum (TEA), and external electron donor diphenyldimethoxysilane were pre-complexed for 20 minutes at 10°C. The flow rate of triethylaluminum entering the pre-complexation was 6.33 g / hr, the flow rate of diphenyldimethoxysilane was 1.06 g / hr, and the flow rate of the main catalyst was 0.158 g / hr. Among them, the mass ratio of TEA / Donor was 6.

[0141] Prepolymerization: The pre-complexed catalyst system continuously enters the prepolymerization reactor for prepolymerization reaction. The prepolymerization is carried out in a propylene liquid phase bulk environment, with a prepolymerization propylene feed rate of 24kg / h. The temperature is 15°C, the residence time is 4min, and the prepolymerization multiple of the catalyst under this condition is 120-150 times.

[0142] The slurry after prepolymerization enters the loop reactor. The polymerization reaction temperature in the loop reactor is 75°C, the propylene monomer feed rate is 60kg / h, the 4-vinylbenzaldehyde feed rate is 4.2kg / h, the hydrogen addition rate is 8000ppm, and the reaction pressure is 4200KPa.

[0143] The polymer slurry prepared in the loop reactor is passed through a high-pressure flash evaporator to remove unreacted propylene monomer and hydrogen, and the unreacted vinylbenzaldehyde enters the gas phase fluidized bed reactor along with the polymer to carry out gas phase copolymerization of ethylene, propylene and vinylbenzaldehyde. The reaction temperature is 84°C, the reaction pressure is 1400KPa, and the gas phase ratio C2 / (C2+C3) is controlled to be 0.40 (molar ratio) to prepare impact copolymer polypropylene powder.

[0144] 80000ppm coupling agent isobutane-1,3-diamine, 800ppm tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester (1010), 1600ppm tris(2,4-di-tert-butylphenyl) phosphite (168), 500ppm acid absorbent calcium stearate were added to impact-resistant copolymer polypropylene powder, mixed evenly, and extruded and granulated by a 35-type twin-screw extruder (Belong Keya Nanjing Machinery Co., Ltd.), the melting section temperature of the extruder was 200°C, the outlet temperature was 170°C, the extruded product was cooled in a circulating water bath and pelletized to obtain the target product. The obtained pellets were tested for performance according to the current relevant GBT standards.

[0145] The specific process conditions and resin performance test results are shown in Table 1.

[0146] Example 6

[0147] The product obtained in Example 5 was added to a 35-type twin-screw extruder again for melting. The melting section temperature of the extruder was 200°C, the outlet temperature was 175°C, and the extruded product was cooled in a circulating water bath and pelletized to obtain the final product. The specific process conditions and resin performance test results are shown in Table 1.

[0148] Example 7

[0149] The product obtained in Example 6 was added to a 35-type twin-screw extruder again for melting. The melting section temperature of the extruder was 200°C, the outlet temperature was 175°C, and the extruded product was cooled in a circulating water bath and pelletized to obtain the final product. The specific process conditions and the resin performance test results are shown in Table 1.

[0150] Table 1 Specific process conditions and performance test results of embodiments and comparative examples

[0151]

[0152]

[0153] First, compared with Comparative Example 1, Comparative Example 2 added 3-vinylbenzaldehyde during polymerization. -1 The absorption peak of aldehyde group (HC=O) appears. Example 1 is based on Comparative Example 2. A coupling agent is added during extrusion granulation. The aldehyde group on 3-vinylbenzaldehyde and the amine group on the added coupling agent can undergo a dehydration condensation reaction to form an imine bond (Vitrimer reaction). For details, please refer to Figure 1 Infrared spectrum.

[0154] The cross-linked network structure is formed in the polymer prepared by the present invention, which can be confirmed by the performance changes of the polymer in the examples: compared with Comparative Examples 1 and 2, due to the introduction of the cross-linked structure in Example 1, the flexural modulus (rigidity) of the product is increased from 879MPa of ordinary impact copolymer polypropylene to 1548MPa without reducing the impact resistance of the resin, which is almost equivalent to the performance of homopolymer polypropylene (Comparative Example 3). By adjusting the polymerization process parameters and increasing the content of 3-vinylbenzaldehyde and the content of coupling agent to increase the cross-linking density, the flexural modulus of the product reaches a maximum of 1567MPa, while maintaining 45.9kJ / m 2 The high impact resistance and high melt flow rate of more than 75g / 10min can further optimize the comprehensive mechanical properties of the resin through process adjustment.

[0155] Secondly, the impact-resistant copolymer polypropylene resin of the present invention is a new type of polypropylene resin with reversible crosslinking function. The reaction of generating imine bonds has dynamic reversibility and belongs to a heat-sensitive reversible reaction, that is, the crosslinked network can be decrosslinked (through the reverse dissociation reaction mechanism of imine bonds) in the melt processing state, so that the material has thermoplasticity. The crosslinked polymer samples of all embodiments can be subjected to melt index measurement, indicating that the material has thermoplasticity. For example, by comparing the resin properties obtained in Comparative Example 1, Comparative Example 2 and Example 1, it can be seen that due to the crosslinked structure, the comprehensive performance of Example 1 is significantly better than that of Comparative Example 1 and Comparative Example 2, but the melt indexes of the three polymers are similar (i.e., the processing properties are similar), which indicates that the polypropylene resin of the present invention has the unique properties of forming a network by cooling and releasing the network at high temperature, which is completely different from the permanent crosslinked network formed by traditional crosslinked polypropylene, thereby giving the crosslinked polymer the excellent characteristics of thermoplasticity. This realizes the repeated processing of the crosslinked polymer. In addition, the molecular weight and processing properties of polypropylene can be regulated by adjusting the amount of hydrogen added to the polymerization reaction. For example, Examples 2 to 5 increase the hydrogen concentration to obtain a polymerization product with a higher melt index. After the polymerization product is cross-linked, the cross-linked polypropylene obtained has a good network structure, so that the bending modulus and tensile yield strength of the material are higher than those of Comparative Examples 1 and 2.

[0156] Third, the cross-linked polypropylene prepared by the present invention can maintain good performance after repeated processing: Example 6 is obtained by secondary processing of Example 5, and Example 7 is obtained by further processing of Example 6. After continuous multiple processing, the material performance is basically maintained without degradation. This is due to the thermally reversible cross-linking function of the polypropylene resin of the present invention. The cross-linked structure can still be stably restored after repeated processing.

[0157] Fourth, all samples in the embodiments of the present invention have a heat deformation temperature above 100°C, which is not only higher than that of the uncrosslinked polypropylene samples (Comparative Examples 1-2), but also higher than that of the reversibly crosslinked impact copolymer polypropylene resin prepared by the dissociative DA reaction (Comparative Example 4); in addition, thanks to the characteristics of the associative dynamic covalent bond, even above the heat deformation temperature, the crosslinked polypropylene resin of the present invention still has a crosslinked structure, which makes the melt viscosity of the material decrease slowly, greatly broadening the processing temperature window and processing stability. Please refer to Figure 2 , Comparative Example 4 at 1197cm -1 The characteristic peak at belongs to the in-plane bending vibration of the cyclic molecule formed by the DA reaction, and there is no obvious peak here in Example 1. Of course, due to different coupling agent structures and different cross-linked network structures, the product performance will also be affected. Coupling agents with different structures and addition amounts can be used according to product performance requirements.

[0158] In summary, the impact-resistant copolymer polypropylene resin of the present invention is a new type of polypropylene resin with reversible crosslinking function. During melt processing, it has the remarkable characteristics of high temperature (during processing) decrosslinking and easy processing, and low temperature (after molding) crosslinking and high performance.

[0159] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims of the present invention.

Claims

1. An impact-resistant copolymer polypropylene resin, characterized in that: The invention comprises a propylene copolymer and a coupling agent, wherein the propylene copolymer is a copolymer obtained by comprising propylene, ethylene and an aldehyde-containing compound, wherein the molar content of propylene in the propylene copolymer is 50-85%, the molar content of ethylene in the propylene copolymer is 5-40%, and the molar content of the aldehyde-containing compound in the propylene copolymer is 5-15%; Wherein, the aldehyde-containing compound is olefin benzaldehyde, and the benzene ring may or may not contain an alkyl substituent; The coupling agent is at least one of the following structures of formula I: Among them, R 1 is a straight or branched chain alkylene group having 1 to 12 carbon atoms, R 2 It is a straight chain or branched chain alkylene group having 1 to 6 carbon atoms.

2. The impact-resistant copolymer polypropylene resin according to claim 1, characterized in that: Taking the mass of the impact-resistant copolymer polypropylene resin as 100%, the content of the propylene copolymer is 75-97%, and the content of the coupling agent is 3-25%.

3. The impact-resistant copolymer polypropylene resin according to claim 2, characterized in that: The aldehyde-containing compound is at least one of o-vinylbenzaldehyde, m-vinylbenzaldehyde, p-vinylbenzaldehyde and o-vinylbenzaldehyde, m-vinylbenzaldehyde and p-vinylbenzaldehyde containing at least one methyl substituent on the benzene ring.

4. The method for preparing the impact-resistant copolymer polypropylene resin according to any one of claims 1 to 3, characterized in that: The method comprises mixing a propylene copolymer and a coupling agent at a mixing temperature of 190 to 230° C. to obtain an impact-resistant copolymerized polypropylene resin; Wherein, the preparation method of the propylene copolymer comprises: Propylene and an aldehyde-containing compound are copolymerized under the action of a catalyst to obtain the propylene copolymer.

5. The method for preparing the impact-resistant copolymer polypropylene resin according to claim 4, characterized in that: The preparation method of the propylene copolymer comprises: Step 1, subjecting propylene and an aldehyde-containing compound to liquid phase bulk polymerization under the action of a catalyst; Step 2, copolymerizing the polymerization product obtained in step 1, propylene and ethylene in gas phase to obtain the propylene copolymer.

6. The method for preparing the impact-resistant copolymer polypropylene resin according to claim 5, characterized in that: The catalyst in step 1 comprises a main catalyst, a co-catalyst and an external electron donor, wherein the main catalyst is a Zigler-Natta catalyst, and the co-catalyst is an organic aluminum compound; the general formula of the external electron donor is R1R2Si(OR3)2, wherein R1 and R2 are the same or different and are selected from C1-C6 straight-chain or branched aliphatic groups, C5-C10 branched or unbranched cyclic alkane groups or aromatic groups.

7. The method for preparing the impact-resistant copolymer polypropylene resin according to claim 5, characterized in that: In step 1, the temperature of liquid phase bulk polymerization is 65-75°C, the pressure is 4000-4500KPa, and the molar ratio of propylene to the aldehyde-containing compound is 60-800:1; in step 2, in gas phase copolymerization, the molar ratio of ethylene to the total amount of ethylene and propylene is 20-40%, the reaction temperature of gas phase copolymerization is 75-85°C, and the reaction pressure is 1200-1400KPa.

8. The method for preparing the impact-resistant copolymer polypropylene resin according to claim 6, characterized in that: The preparation method of the propylene copolymer also includes a prepolymerization step, in which propylene is prepolymerized under the action of a catalyst, and then liquid-phase bulk polymerization is carried out with the aldehyde-containing compound.

9. The method for preparing the impact-resistant copolymer polypropylene resin according to claim 8, characterized in that: The preparation method of the propylene copolymer also includes a pre-complexation step and then the pre-polymerization step; the pre-complexation step is: mixing the main catalyst, the co-catalyst and the external electron donor, the mixing temperature is -10-60°C, and the mixing time is 30-100 minutes.

10. The method for preparing the impact-resistant copolymer polypropylene resin according to claim 8, characterized in that: Antioxidants and acid absorbers are added during the mixing process of the propylene copolymer and the coupling agent. The antioxidants include a main antioxidant and a secondary antioxidant. The main antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, the secondary antioxidant is tris(2,4-di-tert-butylphenyl) phosphite, and the acid absorber is hydrotalcite.

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