A modified polypropylene material, its preparation method and use

Abstract

The application discloses a modified polypropylene material and a preparation method and application thereof. The modified polypropylene material contains the following raw materials in percentage by mass: 25-32% of homopolymerization polypropylene, 34-42% of modified copolymerization polypropylene, 13-25% of inorganic filler, 5-13% of toughening agent, 5.4-7.5% of coupling agent and 0.4-0.6% of stabilizer; wherein, the coupling agent contains at least two primary amine groups, and the modified copolymerization polypropylene contains aldehyde groups. The modified polypropylene material has a reversible cross-linking macromolecular network structure formed by mutual cooperation between the raw materials, and has excellent comprehensive performance in the aspects of improving the strength, low-temperature resistance, toughness and processing performance of the modified polypropylene material.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a modified polypropylene material, its preparation method, and its applications. Background Technology

[0002] Polypropylene (PP) is inexpensive and possesses properties such as low density, excellent mechanical properties, superior electrical insulation, and resistance to chemical corrosion. Its products are used in textiles, packaging, the food industry, and automotive interior and exterior components. However, with the continuous development of the automotive industry, some automotive interior components with high safety requirements, such as door panels, dashboards, and pillars, are required not only to have sufficient strength to support other components mounted on the dashboard or door panel and resist deformation caused by external stress, but also sufficient toughness to withstand external impacts. This is to prevent significant cracking or sharp fragments in the event of a collision, thus avoiding endangering the safety of the driver and passengers.

[0003] To meet the aforementioned performance requirements, most existing technologies improve the toughness of polypropylene materials, especially their room-temperature impact resistance, by adding elastomers and / or employing crosslinking techniques. For example, Chinese patent document CN109553851A discloses a modified polypropylene for automotive bumpers, comprising the following components by weight: 63.5-79.3 parts polypropylene, 12-15 parts polyolefin elastomer, 5-8 parts silicon carbide, 0.5-1 part carbon black, 0.2-0.5 parts silane coupling agent, 11-21 parts nucleating agent, 0.12 parts chain extender, and 3-4 parts crosslinked polyolefin. This technical solution, by limiting the types and amounts of modified polypropylene raw materials, increases the crosslinking density between polypropylene molecules and between polypropylene and other macromolecules, thereby significantly improving the strength, rigidity, and other mechanical properties of the polypropylene material. However, since this crosslinking is irreversible, while improving the mechanical properties of the product, its processing performance is significantly reduced, and the injection-molded parts are not recyclable. Chinese patent document CN104592628A discloses a modified polypropylene material with high toughness and high rigidity and its preparation method. The main formulation consists of: 47.0-99.8% polypropylene, 0-20% talc, 0.2-1% antioxidant, 0-30% elastomer, 0.1-1.5% crosslinking agent, and 0.1-0.5% co-crosslinking agent. Unlike the usual principle of adding elastomers to toughen polypropylene, the technical solution in this document, based on a polypropylene-based formulation, adds an elastomer and uses a crosslinking agent and co-crosslinking agent to achieve dynamic vulcanization of the elastomer during melt blending with polypropylene. This results in a modified polypropylene material exhibiting the physical properties of thermoplastics at room temperature, possessing both the rigidity and high toughness of thermoplastics, thus yielding a modified polypropylene material with high toughness and high rigidity. However, the crosslinking in this technical solution is irreversible and only slightly crosslinked. Therefore, the improvement in the product's mechanical properties is limited. Due to the slight crosslinking, the product's processing performance is slightly reduced, and it cannot be recycled after injection molding. Chinese patent document CN104861295A discloses a method for preparing modified polypropylene material with improved impact resistance. The preparation method in this document is obtained by one-step blending and modification of raw materials including the following components: 100 parts of polypropylene, 20-40 parts of main modifier, 2.5-10 parts of secondary modifier, 0.5-5 parts of crosslinking modifier, and 0.5-5 parts of crosslinking aid. The main modifier is a polyolefin elastomer, the secondary modifier is high-density polyethylene, the crosslinking modifier is an organic peroxide, and the crosslinking aid is 50%-60% divinylbenzene. The difference between the decomposition temperature of the crosslinking modifier with a half-life of 1 minute and the melting temperature of polypropylene is 1-5℃.The technical solution in this document can significantly improve the impact strength of modified polypropylene materials, giving them excellent impact resistance, rigidity, aging resistance, cold resistance, and gasoline resistance. However, this crosslinking is irreversible, which reduces the processing performance while improving the mechanical properties of the product, and the parts cannot be recycled after injection molding.

[0004] In short, while existing technologies can significantly improve the impact performance of polypropylene materials, especially at room temperature, by adding elastomers and / or using cross-linking techniques, this also leads to a substantial decrease in the processability of the modified polypropylene materials. This contradicts the current technological demands for thinner and lighter automotive parts. Therefore, balancing the processability and stiffness / toughness of polypropylene materials has become a crucial breakthrough that urgently needs to be achieved.

[0005] Inspired by thermoplastic elastomers, dynamic covalent bonds have been introduced into traditional rubber to prepare elastomer materials that combine reproducible processability and excellent crosslinking properties. Dynamic covalent bonds are covalent bonds that can reversibly break / bond upon exposure to specific stimuli (such as heat, light, and pH). The resulting polymer crosslinked network can undergo topological rearrangement under external influences, thus exhibiting characteristics such as plasticity, self-healing, and stimulus responsiveness. Among these, associative dynamic covalent bonds were first applied to vitrimer-like polymers by Leibler et al. in 2011 and have seen rapid development in recent years. Vitrimers are crosslinked networks constructed from associative dynamic covalent bonds, exhibiting processing properties similar to glass. Imino bonds (C=N) are a type of associative dynamic covalent bond, a class of dynamic reversible covalent bonds formed by the reaction of carbonyl-containing compounds (aldehydes or ketones) with amino-containing compounds (primary amines, hydrazines, and hydroxylamines), characterized by mild reaction conditions and fast reaction rates.

[0006] J Polym Sci (Part A: Polym Chem, 2017, 55(12): 2011-2018) discloses a method for preparing dynamically imine-crosslinked polybutadiene elastomers by crosslinking amine-functionalized polybutadiene with aldehydes. This literature utilizes an imine exchange reaction between aldehyde and amine groups to prepare Vitrimer-reversibly crosslinked cis-butadiene rubber. The drawback of this technique, or its relative deficiency compared to the present invention, is that both cis-butadiene rubber and styrene-butadiene rubber side groups have a large number of double bonds available for reaction, making system implementation easy, but this method is not applicable to polypropylene systems (polypropylene molecules do not contain double bonds).

[0007] Chinese patent document CN111662561A discloses a method for preparing a flame-retardant, reprocessable wood-plastic composite material. In this document, organic aldehydes are first dispersed in ethyl acetate, then a certain amount of ammonium polyphosphate is added, followed by ethyl acetate containing amines, to obtain a yellow suspension. This suspension is then dried to obtain a solid powder of ammonium polyphosphate containing imine dynamic covalent bonds. The ammonium polyphosphate powder containing imine dynamic covalent bonds is then initially mixed with plant fibers and plastics, dried, plasticized, molded, and cooled to produce a flame-retardant, reprocessable wood-plastic composite material. The method in this document simultaneously imparts flame retardancy, toughness, and processability to the wood-plastic composite material by introducing imine dynamic covalent bonds; however, the imine dynamic bonds are between small molecules and do not form a large molecular cross-linked network structure.

[0008] Therefore, improving the overall performance of polypropylene materials, including strength, rigidity, processing properties, and recyclability of parts, is a pressing technical problem that needs to be solved. Summary of the Invention

[0009] The purpose of this invention is to address the problems in the prior art where polypropylene materials prepared by adding elastomers and / or using crosslinking technology, although improving strength and rigidity, suffer from poor processing performance and non-recyclability after injection molding. This invention provides a modified polypropylene material, its preparation method, and its applications to improve the overall performance of polypropylene materials.

[0010] To achieve the above objectives, the present invention provides a modified polypropylene material, wherein the modified polypropylene material comprises the following raw materials by weight percentage:

[0011] Homopolymer polypropylene 25%-32%, modified copolymer polypropylene 34%-42%, inorganic filler 13%-25%, toughening agent 5%-13%, coupling agent 5.4%-7.5%, and stabilizer 0.4%-0.6%;

[0012] The coupling agent contains at least two primary amine groups, and the modified copolymer polypropylene contains aldehyde groups.

[0013] Optionally, the modified copolymer polypropylene contains aldehyde groups in its side chains.

[0014] Optionally, the modified copolymer polypropylene is a product obtained by free radical polymerization of copolymer polypropylene and a modifier; the modifier is selected from at least one of the compounds shown in Formula III;

[0015] CH2=CH-R 3 -CHO

[0016] III

[0017] Among them, R 3Selected from C1-C12 straight-chain or branched alkylene groups, C3-C8 cycloalkylene groups, and unsubstituted or substituted C6-C12 arylene or heteroarylene groups; preferably, R 3 Selected from C1-C6 straight-chain or branched alkylene groups, and unsubstituted or substituted C6-C12 arylene groups; more preferably, R 3 Selected from methylene, -CH2CH2-, -CH2CH2CH2- or phenylene;

[0018] R 3 In the definition of a group, "substituted" means that at least one H on the group is substituted by a straight-chain or branched alkyl or alkoxy group selected from C1-C4.

[0019] Optionally, the modified copolymer polypropylene comprises the following raw materials by weight percentage:

[0020] The copolymer contains 80%-90% polypropylene, 0.5%-2.0% initiator, and 4.5%-18.0% modifier.

[0021] The melt flow rate (230℃, 2.16Kg) of the copolymer polypropylene is 2-60g / 10min.

[0022] Optionally, the coupling agent is at least one of the structures shown in Formula I and / or Formula II.

[0023]

[0024] Among them, R 1 Selected from C1-C12 straight-chain or branched alkylene groups, C3-C8 cycloalkylene groups, and unsubstituted or substituted C6-C12 arylene or heteroarylene groups; preferably, R 1 Selected from C2-C6 straight-chain alkylene groups; more preferably, R 1 Selected from -CH2CH2- or -CH2CH2CH2-;

[0025] R 2 Selected from C1-C6 straight-chain or branched alkylene groups, C3-C6 cycloalkylene groups, unsubstituted or substituted C6-C12 arylene or heteroarylene groups; preferably, R 2 Selected from C2-C6 straight-chain alkylene groups; more preferably, R 2 Selected from -CH2CH2- or -CH2CH2CH2-;

[0026] R 1 and R 2 In the definition of a group, "substituted" means that at least one H on the group is substituted by a straight-chain or branched alkyl or alkoxy group selected from C1-C4.

[0027] Optionally, the inorganic filler is selected from at least one of talc, montmorillonite, mica, carbon black and wollastonite, and the average particle size of the inorganic filler is 1-20 μm; preferably, the inorganic filler is talc with an average particle size of 1-10 μm.

[0028] The melt flow rate (230℃, 2.16Kg) of the homopolymer polypropylene is 10-100g / 10min;

[0029] The toughening agent is ethylene-octene copolymer (POE), and the melt flow rate (190℃, 2.16Kg) of the ethylene-octene copolymer is 0.5-30g / 10min;

[0030] The stabilizer is at least one of hindered phenolic antioxidants and phosphorous antioxidants; preferably, the stabilizer is a mixture of hindered phenolic antioxidants and phosphorous antioxidants; more preferably, the mass ratio of the hindered phenolic antioxidant to the phosphorous antioxidant in the stabilizer is (1-5):1; even more preferably, the mass ratio of the hindered phenolic antioxidant to the phosphorous antioxidant in the stabilizer is (1-3):1; even more preferably, the mass ratio of the hindered phenolic antioxidant to the phosphorous antioxidant in the stabilizer is 2:1.

[0031] Specifically, the hindered phenolic antioxidants include, but are not limited to, mono-hindered phenols and poly-hindered phenols, such as butylated hydroxytoluene (BHT), antioxidant 1024, antioxidant 3114, antioxidant 1010, and antioxidant 1330; the phosphite antioxidants, i.e., phosphite ester antioxidants, include, but are not limited to, phenol-free phosphite ester antioxidants, low-phenolic phosphite ester antioxidants, and phenolic phosphite ester antioxidants, such as antioxidant 168.

[0032] Optionally, the modified polypropylene material further contains at least one of a colorant, a light stabilizer, and a lubricant, wherein the total content of the colorant, light stabilizer, and lubricant in the modified polypropylene material does not exceed 2% by mass percentage.

[0033] Optionally, the colorant, light stabilizer, and lubricant may be selected from any commonly used in the art, such as the lubricant being selected from at least one of stearate, polyolefin wax, ethylene bis-stearamide, and pentaerythritol stearate; the light stabilizer being at least one of hindered amine light stabilizers, triazine light stabilizers, and benzotriazole light stabilizers; and the colorant being selected from inorganic pigments and / or organic pigments.

[0034] The invention also provides a method for preparing the above-mentioned modified polypropylene material, comprising the following steps:

[0035] The modified polypropylene material is obtained by mixing homopolymer polypropylene, modified copolymer polypropylene, inorganic filler, toughening agent, coupling agent and stabilizer and then extruding at 190-230℃.

[0036] Optionally, the length-to-diameter ratio of the extruder in the extrusion step is (40-60):1.

[0037] Optionally, the homopolymer polypropylene, modified copolymer polypropylene, inorganic filler, toughening agent, coupling agent and stabilizer are mixed by dry mixing, with a mixing time of 5-15 minutes.

[0038] Optionally, the preparation method of the modified copolymer polypropylene includes the following steps:

[0039] The modified copolymer polypropylene is obtained by mixing the copolymer polypropylene, initiator and modifier and extruding at 180-210°C; the modifier is selected from at least one of the compounds shown in Formula III above.

[0040] Optionally, the mixing time of the copolymer polypropylene, initiator and modifier is 5-15 min.

[0041] The modifier's role is to introduce (graft) the aldehyde group from the modifier onto the side chain of the copolymer polypropylene.

[0042] Optionally, the initiator is at least one of conventional initiators such as azobisisobutyronitrile and dicumyl peroxide.

[0043] Optionally, the method for preparing the modified polypropylene material further includes the step of mixing at least one of a colorant, a light stabilizer, and a lubricant with the homopolymer polypropylene, the modified copolymer polypropylene, the inorganic filler, the toughening agent, the coupling agent, and the stabilizer.

[0044] Optionally, in the preparation method of the modified polypropylene material and the preparation process of the modified copolymer polypropylene, the mixing step can use any existing conventional mixing device, such as an open mill or a mixer; the extrusion step can use any existing conventional basic device, such as a single-screw extruder or a twin-screw extruder.

[0045] The present invention also provides the application of the modified polypropylene material described above or the modified polypropylene material prepared by the above-described method in automotive interiors.

[0046] Compared with existing technologies, the present invention has the following advantages:

[0047] 1. The modified polypropylene material provided by the present invention uses a coupling agent containing at least two primary amine groups and a modified copolymer polypropylene containing aldehyde groups, combined with homopolymer polypropylene, to form a reversible cross-linked macromolecular network structure. Inorganic fillers, stabilizers and toughening agents fill the gaps in the macromolecular network structure, which significantly improves the toughness and processing performance of the modified polypropylene material while improving its strength and rigidity, and has excellent comprehensive performance.

[0048] 2. The method for preparing modified polypropylene material provided by this invention involves mixing and extrusion, which causes the aldehyde groups in the side chains of the modified copolymer polypropylene to react with the amino groups in the coupling agent, generating uniformly distributed dynamic reversible covalent bonds (C=N) on the side chains of the copolymer polypropylene. Combined with other components, the resulting modified polypropylene material crosslinks at low temperatures, thus giving the material good rigidity, toughness, and low-temperature resistance, reducing the amount of toughening agents and elastomers used. At high temperatures, the crosslinking bonds rearrange their network structure through thermally activated associative exchange reactions. The formation of new bonds and the breaking of old bonds occur simultaneously, thus endowing the material with thermoplasticity. This allows the material to crosslink during use and de-crosslink during processing, and the components have good interfacial compatibility. This solves the problem of reduced processing performance when polypropylene is modified by adding elastomers and / or crosslinking technology to improve the physical and mechanical properties of the product in the prior art.

[0049] 3. The modified polypropylene material provided by this invention uses free radical polymerization to randomly insert aldehyde groups from the modifier into the copolymer polypropylene segments, increasing the material's disorder and improving its toughness. Furthermore, the crosslinking of macromolecules in this modified polypropylene material is reversible, allowing for repeated processing and recycling of waste parts. The modified polypropylene material retains essentially the same performance after three repeated processing cycles. During repeated processing, only an appropriate amount of stabilizer needs to be added to the existing modified polypropylene material, followed by dry mixing and extrusion. The stabilizer can be any one or a mixture of several commonly used stabilizers in the industry. The amount of stabilizer added, the dry mixing time, and the extrusion temperature can be adjusted according to actual conditions. For example, the mass of the stabilizer added can be 0.5wt%-1.5wt% of the modified polypropylene material mass, the dry mixing time can be 5-10 min, and the extrusion temperature can be 180-210℃. Detailed Implementation

[0050] The present invention will now be described in detail through embodiments. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0051] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0052] Any commercially available toughening agent and stabilizer can meet the requirements of the present invention. For ease of comparison, the toughening agent used in the following examples and comparative examples is Dow's POE8150, and the stabilizer is a mixture of hindered phenolic antioxidant 1010 and phosphite antioxidant 168 (wherein the mass ratio of hindered phenolic antioxidant 1010 to phosphite antioxidant 168 is 2:1). The melt flow rates of the homopolymer and copolymer polypropylene involved in the examples and comparative examples were measured at 230°C and 2.16 kg.

[0053] The equipment used in the following embodiments and comparative examples is as follows:

[0054] Type 35 twin-screw extruder: Benelux Nanjing Machinery Co., Ltd., with a length-to-diameter ratio of 45:1 (the choice of length-to-diameter ratio does not affect the effect of the technical solution of this invention; this value is adopted for ease of comparison).

[0055] Injection molding machine: Liuzhou Injection Molding Machinery Factory UN-100, which injects standard samples into the sample.

[0056] Example 1

[0057] This embodiment provides a modified polypropylene material granule, the preparation method of which is as follows:

[0058] 1) Preparation of modified copolymer polypropylene:

[0059] The modified copolymer polypropylene (grade EP533N, melt flow rate 30g / 10min, produced by Lanzhou Petrochemical Company of China National Petroleum Corporation), initiator (azobisisobutyronitrile) and modifier (methacrylaldehyde) were mixed for 10min and then extruded at 180℃ to obtain the modified copolymer polypropylene; the grafting rate of the modifier methacrolein in the modified copolymer polypropylene was 5wt%.

[0060] The contents of each raw material in the above modified copolymer polypropylene, by mass percentage, are as follows:

[0061] The copolymer contains 90% polypropylene, 1% initiator, and 9% modifier.

[0062] 2) Weigh the modified copolymer polypropylene and other raw materials obtained in step 1) according to the following mass percentages:

[0063] Homopolymer polypropylene (grade H9018, melt flow rate 65g / 10min, produced by Lanzhou Petrochemical Company of China National Petroleum Corporation) 32%, modified copolymer polypropylene 37%, inorganic filler (talc powder with an average particle size of 1-10μm) 17%, toughening agent 8%, coupling agent (ethylenediamine) 5.6% and stabilizer 0.4%.

[0064] 3) After dry mixing the raw materials weighed in step 2) in a high-speed mixer for 6 minutes, add them to a twin-screw extruder and melt extrude and granulate at 200°C to obtain granules of modified polypropylene material.

[0065] Example 2

[0066] This embodiment provides a modified polypropylene material granule, the preparation method of which is as follows:

[0067] 1) Preparation of modified copolymer polypropylene:

[0068] The modified copolymer polypropylene (grade SP179, melt flow rate 9 g / 10 min, produced by Lanzhou Petrochemical Company of China National Petroleum Corporation), initiator (azobisisobutyronitrile) and modifier (methacrylaldehyde) were mixed for 13 min and then extruded at 210 °C to obtain the modified copolymer polypropylene; the grafting rate of the modifier vinylbenzaldehyde in the modified copolymer polypropylene was 7.2 wt%.

[0069] The contents of each raw material in the above modified copolymer polypropylene, by mass percentage, are as follows:

[0070] The copolymer consists of 85.5% polypropylene, 1.5% initiator, and 13% modifier.

[0071] 2) Weigh the modified copolymer polypropylene and other raw materials obtained in step 1) according to the following mass percentages:

[0072] The composition includes: homopolymer polypropylene (grade H9068, melt flow rate 100g / 10min, produced by Lanzhou Petrochemical Company of China National Petroleum Corporation) 30%, modified copolymer polypropylene 34%, inorganic filler (montmorillonite with an average particle size of 1-10μm) 24%, toughening agent 6%, coupling agent (N,N-bis(aminomethyl)methyldiamine) 5.4%, and stabilizer 0.6%.

[0073] After dry mixing the raw materials weighed in step 2) in a high-speed mixer for 8 minutes, add them to a twin-screw extruder and melt-extrude and granulate at 190°C to obtain modified polypropylene material granules.

[0074] Example 3

[0075] This embodiment provides a modified polypropylene material granule, the preparation method of which is as follows:

[0076] 1) Preparation of modified copolymer polypropylene:

[0077] The modified copolymer polypropylene (grade EP508N, melt flow rate 60g / 10min, produced by Lanzhou Petrochemical Company of China National Petroleum Corporation), initiator (azobisisobutyronitrile) and modifier (4-vinylbenzaldehyde) were mixed for 10min and then extruded at 190℃ to obtain the modified copolymer polypropylene; the grafting rate of the modifier vinylbenzaldehyde in the modified copolymer polypropylene was 6.5wt%.

[0078] The contents of each raw material in the above modified copolymer polypropylene, by mass percentage, are as follows:

[0079] The copolymer contains 87.2% polypropylene, 0.6% initiator, and 12.2% modifier.

[0080] 2) Weigh the modified copolymer polypropylene and other raw materials obtained in step 1) according to the following mass percentages:

[0081] Homopolymer polypropylene (grade H8020, melt flow rate 12g / 10min, produced by Lanzhou Petrochemical Company of China National Petroleum Corporation) 25%, modified copolymer polypropylene 42%, inorganic filler (talc powder with an average particle size of 1-10μm) 13%, toughening agent 13%, coupling agent (ethylenediamine) 6.4% and stabilizer 0.6%.

[0082] After dry mixing the raw materials weighed in step 2) in a high-speed mixer for 10 minutes, they are added to a twin-screw extruder and melt-extruded into granules at 230°C to obtain modified polypropylene granules.

[0083] Example 4

[0084] This embodiment provides a modified polypropylene material granule, the preparation method of which is as follows:

[0085] 1) Preparation of modified copolymer polypropylene:

[0086] The modified copolymer polypropylene (grade EP100N, melt flow rate 100g / 10min, produced by Lanzhou Petrochemical Company of China National Petroleum Corporation), initiator (azobisisobutyronitrile) and modifier (methacrylaldehyde) were mixed for 8min and then extruded at 200℃ to obtain the modified copolymer polypropylene; the grafting rate of the modifier vinylbenzaldehyde in the modified copolymer polypropylene was 8.2wt%.

[0087] The contents of each raw material in the above modified copolymer polypropylene, by mass percentage, are as follows:

[0088] The copolymer contains 82.5% polypropylene, 1.7% initiator, and 15.8% modifier.

[0089] 2) Weigh the modified copolymer polypropylene and other raw materials obtained in step 1) according to the following mass percentages:

[0090] Homopolymer polypropylene (grade H9018, melt flow rate 60g / 10min, produced by Lanzhou Petrochemical Company of China National Petroleum Corporation) 25%, modified copolymer polypropylene 37%, inorganic filler (talc powder with an average particle size of 1-10μm) 25%, toughening agent 5%, coupling agent (ethylenediamine) 7.5% and stabilizer 0.5%.

[0091] After dry mixing the raw materials weighed in step 2) in a high-speed mixer for 9 minutes, they are added to a twin-screw extruder and melt-extruded into granules at 210°C to obtain modified polypropylene granules.

[0092] Example 5

[0093] This embodiment provides a method for the repeated processing of modified polypropylene granules, the specific steps of which are as follows:

[0094] Weigh a certain amount of the modified polypropylene material granules obtained in Example 4 (denoted as composite material A), and add a stabilizer (the stabilizer is a mixture of hindered phenolic antioxidant 1010 and phosphite antioxidant 168, with a mass ratio of hindered phenolic antioxidant 1010 to phosphite antioxidant 168 of 2:1). Then, dry mix in a high-speed mixer for 1 minute, and then add it to a twin-screw extruder for melt extrusion granulation at 190°C to obtain the modified polypropylene material granules.

[0095] The amount of stabilizer added is 0.5 wt% of the mass of particle A in the composite material.

[0096] Example 6

[0097] This embodiment provides a method for the repeated processing of modified polypropylene granules, the specific steps of which are as follows:

[0098] Weigh a certain amount of the modified polypropylene material granules prepared in Example 5 (denoted as composite material B), and add a stabilizer (the stabilizer is a mixture of hindered phenolic antioxidant 1010 and phosphite antioxidant 168, with a mass ratio of hindered phenolic antioxidant 1010 to phosphite antioxidant 168 of 2:1). Then, dry mix in a high-speed mixer for 1 min, and then add it to a twin-screw extruder for melt extrusion at 190°C, followed by cold cutting and granulation to obtain the modified polypropylene material granules. The performance data of the granules are shown in Table 1.

[0099] The amount of stabilizer added is 0.5 wt% of the mass of particle B in the composite material.

[0100] Comparative Example 1

[0101] This comparative example provides a modified polypropylene material granule, the preparation method of which is as follows:

[0102] 1) Weigh each raw material according to the following mass percentages:

[0103] Homopolymer polypropylene (grade H9018, melt flow rate 65g / 10min, produced by Lanzhou Petrochemical Company of China National Petroleum Corporation) 34.6%, copolymer polypropylene (grade EP533N, melt flow rate 30g / 10min, produced by Lanzhou Petrochemical Company of China National Petroleum Corporation, ungrafted modified) 40%, inorganic filler (talc powder with an average particle size of 1-10μm) 17%, toughening agent 8% and stabilizer 0.4%;

[0104] 2) After dry mixing the raw materials weighed in step 1) in a high-speed mixer for 6 minutes, add them to a twin-screw extruder and melt extrude and granulate at 200°C to obtain granules of modified polypropylene material.

[0105] Comparative Example 2

[0106] This comparative example provides a modified polypropylene material granule, the preparation method of which is as follows:

[0107] 1) Preparation of modified copolymer polypropylene:

[0108] The modified copolymer polypropylene (grade EP533N, melt flow rate 30g / 10min, produced by Lanzhou Petrochemical Company of China National Petroleum Corporation), initiator (azobisisobutyronitrile) and modifier (methacrylaldehyde) were mixed for 10min and then extruded at 180℃ to obtain the modified copolymer polypropylene; the grafting rate of the modifier methacrolein in the modified copolymer polypropylene was 5wt%.

[0109] The contents of each raw material in the above modified copolymer polypropylene, by mass percentage, are as follows:

[0110] The copolymer contains 90% polypropylene, 1% initiator, and 9% modifier.

[0111] 2) Weigh the modified copolymer polypropylene and other raw materials obtained in step 1) according to the following mass percentages:

[0112] Homopolymer polypropylene (grade H9018, melt flow rate 65g / 10min, produced by Lanzhou Petrochemical Company of China National Petroleum Corporation) 34.6%, modified copolymer polypropylene 40.0%, inorganic filler (talc powder with an average particle size of 1-10μm) 17%, toughening agent 8% and stabilizer 0.4%.

[0113] 3) After dry mixing the raw materials weighed in step 2) in a high-speed mixer for 6 minutes, add them to a twin-screw extruder and melt extrude and granulate at 200°C to obtain granules of modified polypropylene material.

[0114] Comparative Example 3

[0115] This comparative example provides a modified polypropylene material granule, the preparation method of which is as follows:

[0116] 1) Weigh each raw material according to the following mass percentages:

[0117] The composition of the product is as follows: homopolymer polypropylene (grade H9018, melt flow rate 65 g / 10 min, produced by Lanzhou Petrochemical Company of China National Petroleum Corporation) 31%, copolymer polypropylene (grade EP533N, melt flow rate 30 g / 10 min, produced by Lanzhou Petrochemical Company of China National Petroleum Corporation, ungrafted) 34.5%, inorganic filler (talc powder with an average particle size of 1-10 μm) 20%, toughening agent 10.6%, coupling agent (ethylenediamine) 3.5%, and stabilizer 0.4%.

[0118] 2) After dry mixing the raw materials weighed in step 1) in a high-speed mixer for 5 minutes, add them to a twin-screw extruder and melt extrude and granulate at 200°C to obtain granules of modified polypropylene material.

[0119] Comparative Example 4

[0120] This comparative example provides a modified polypropylene material granule, the preparation method of which is as follows:

[0121] 1) Preparation of modified copolymer polypropylene:

[0122] The modified copolymer polypropylene (grade EP533N, melt flow rate 30g / 10min, produced by Lanzhou Petrochemical Company of China National Petroleum Corporation), initiator (azobisisobutyronitrile) and modifier (methacrylaldehyde) were mixed for 10min and then extruded at 180℃ to obtain the modified copolymer polypropylene; the grafting rate of the modifier methacrolein in the modified copolymer polypropylene was 5wt%.

[0123] The contents of each raw material in the above modified copolymer polypropylene, by mass percentage, are as follows:

[0124] The copolymer contains 90% polypropylene, 1% initiator, and 9% modifier.

[0125] 2) Weigh the modified copolymer polypropylene and other raw materials obtained in step 1) according to the following mass percentages:

[0126] The composition of the product is as follows: homopolymer polypropylene (grade H9018, melt flow rate 65 g / 10 min, produced by Lanzhou Petrochemical Company of China National Petroleum Corporation) 32%, modified copolymer polypropylene 37%, inorganic filler (talc powder with an average particle size of 1-10 μm) 17%, toughening agent 8%, coupling agent (ethylamine) 5.6%, and stabilizer 0.4%.

[0127] 3) After dry mixing the raw materials weighed in step 2) in a high-speed mixer for 6 minutes, add them to a twin-screw extruder and melt extrude and granulate at 200°C to obtain granules of modified polypropylene material.

[0128] Comparative Example 5

[0129] This comparative example provides a modified polypropylene material granule, the preparation method of which is as follows:

[0130] 1) Weigh each raw material according to the following mass percentages:

[0131] The composition of the product is as follows: homopolymer polypropylene (grade H9018, melt flow rate 65 g / 10 min, produced by Lanzhou Petrochemical Company of China National Petroleum Corporation) 32%, copolymer polypropylene (grade EP533N, melt flow rate 30 g / 10 min, produced by Lanzhou Petrochemical Company of China National Petroleum Corporation) 35.1%, modifier (methacrylaldehyde) 1.9%, inorganic filler (talc powder with an average particle size of 1-10 μm) 17%, toughening agent 8%, coupling agent (ethylenediamine) 5.6%, and stabilizer 0.4%.

[0132] 2) After dry mixing the raw materials weighed in step 1) in a high-speed mixer for 6 minutes, add them to a twin-screw extruder and melt extrude and granulate at 200°C to obtain granules of modified polypropylene material.

[0133] Experimental Example

[0134] The modified polypropylene granules prepared in the above embodiments and comparative examples were tested according to the following test methods, and the specific test results are shown in Table 1 below.

[0135] Melt flow rate (MFR): determined according to GB / T 3682-2000, 230℃, 2.16Kg load.

[0136] Impact strength of simply supported beams: determined according to GB / T1043.1-2008

[0137] Flexural modulus: determined according to GB / T 9341-2008.

[0138] Table 1 Test Results

[0139]

[0140] Data Analysis:

[0141] Comparative Example 1: The copolymer polypropylene was not grafted with a modifier (aldehyde compound), and no coupling agent was added to the formulation. Comparative Example 2: The copolymer polypropylene was grafted with a modifier (aldehyde compound), but no coupling agent was added to the formulation. Comparative Example 3: The copolymer polypropylene was not grafted with a modifier (aldehyde compound), but a coupling agent was added to the formulation. In Comparative Example 4, ethylamine was used instead of ethylenediamine as the coupling agent. Comparative Example 5: The copolymer polypropylene was not grafted with a modifier (aldehyde compound), but the modifier methacrolein was added to the formulation; otherwise, it was the same as in Example 1.

[0142] In all embodiments, modified copolymer polypropylene was used. The aldehyde groups grafted onto the side chains of the copolymer polypropylene react with the amino groups on the coupling agent to form a polypropylene material with reversible crosslinking function based on imine bonds (Vitrimer reaction). Comparing Example 1 with Comparative Examples 1, 2, and 3, it can be seen that the processing performance of the modified polypropylene material provided by this invention is significantly improved, and it exhibits excellent rigidity, toughness, and low-temperature resistance. In Examples 2-4, by adjusting the composition and content of each raw material in the formulation, the processing performance, rigidity, and toughness of the obtained modified polypropylene material can be adjusted within a wide range to meet the performance requirements of modified polypropylene materials in different fields. Compared with Example 1, Comparative Example 4 shows that replacing the coupling agent with a single primary amine group does not significantly improve the mechanical properties of the composite material. This may be because the single primary amine group in Comparative Example 4 failed to form an effective macromolecular network crosslinking structure. Comparing Comparative Example 5 with Comparative Example 1, it can be seen that the performance of the modified polypropylene material prepared in Comparative Example 5 is comparable to that of the modified polypropylene material prepared in Comparative Example 1 without the addition of modifiers and coupling agents. The possible reason is that only some small molecules are cross-linked in the system, which has almost no effect on the overall performance of the material.

[0143] The modified polypropylene material provided by this invention has high rigidity and high toughness, and its performance can still be well maintained after repeated processing. Specifically, as can be seen from the comparison between Examples 4-6, Example 5 is obtained by adding a small amount of stabilizer to Example 4 and then processing it again, and Example 6 is obtained by adding a small amount of stabilizer to Example 5 and then processing it further. After repeated processing, the performance of the material is basically maintained without reduction. The maintenance of this excellent effect is due to the fact that the crosslinking in the modified polypropylene material is thermally reversible crosslinking. The crosslinking structure can still be stably restored after repeated processing, which is completely different from the permanent crosslinking network formed by traditional crosslinking technology, thus giving the crosslinked polymer excellent thermoplastic properties.

[0144] In summary, the modified polypropylene material provided by this invention is a novel modified polypropylene material with reversible crosslinking function. During melt processing, it has the significant characteristics of decrosslinking at high temperature (during processing) and easy processing, while forming crosslinks at low temperature (after molding) and high performance, which can meet the application requirements of modified polypropylene materials in automotive interiors.

[0145] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A modified polypropylene material, characterized in that, By weight percentage, the modified polypropylene material comprises the following raw materials: 25%-32% homopolymer polypropylene, 34%-42% modified copolymer polypropylene, 13%-25% inorganic filler, 5%-13% toughening agent, 5.4%-7.5% coupling agent, and 0.4%-0.6% stabilizer; The coupling agent contains at least two primary amine groups, and the modified copolymer polypropylene contains aldehyde groups. The modified copolymer polypropylene is the product obtained by free radical polymerization of copolymer polypropylene and a modifier; the modifier is selected from at least one of the compounds shown in Formula III; Ⅲ Among them, R 3 Selected from C1-C12 straight-chain or branched alkylene groups, C3-C8 cycloalkylene groups, and unsubstituted or substituted C6-C12 arylene or heteroarylene groups; The coupling agent is at least one of the structures shown in Formula I and / or Formula II. Among them, R 1 Selected from C1-C12 straight-chain or branched alkylene groups, C3-C8 cycloalkylene groups, unsubstituted or substituted C6-C12 arylene or heteroarylene groups; R 2 Selected from C1-C6 straight-chain or branched alkylene groups, C3-C6 cycloalkylene groups, and unsubstituted or substituted C6-C12 arylene or heteroarylene groups.

2. The modified polypropylene material as described in claim 1, characterized in that, R 3 Selected from C1-C6 straight-chain or branched alkylene groups, and unsubstituted or substituted C6-C12 arylene groups.

3. The modified polypropylene material as described in claim 2, characterized in that, The modified copolymer polypropylene comprises the following raw materials by weight percentage: Copolymer polypropylene 80%-90%, initiator 0.5%-2.0% and modifier 9.0%-18.0%; and / or The melt flow rate of the copolymer polypropylene is 2-60 g / 10 min.

4. The modified polypropylene material as described in claim 1, characterized in that, R 1 Selected from C2-C6 straight-chain alkylene groups; R 2 Selected from C2-C6 straight-chain alkylene groups.

5. The modified polypropylene material as described in claim 1, characterized in that, The inorganic filler is selected from at least one of talc, montmorillonite, mica, carbon black and wollastonite, and the average particle size of the inorganic filler is 1-20 μm; The melt flow rate of the homopolymer polypropylene is 10-100 g / 10 min; The toughening agent is an ethylene-octene copolymer, and the melt flow rate of the ethylene-octene copolymer is 0.5-30 g / 10 min; The stabilizer is at least one of hindered phenolic antioxidants and phosphorous antioxidants.

6. The modified polypropylene material according to any one of claims 1-5, characterized in that, The modified polypropylene material also contains at least one of a colorant, a light stabilizer, and a lubricant, and the total content of the colorant, light stabilizer, and lubricant in the modified polypropylene material does not exceed 2% by mass percentage.

7. The modified polypropylene material as described in claim 2, characterized in that, R 3 Selected from methylene, -CH2CH2-, -CH2CH2CH2- or phenylene.

8. The modified polypropylene material as described in claim 4, characterized in that, R 1 Selected from -CH2CH2- or -CH2CH2CH2-.

9. The modified polypropylene material as described in claim 4, characterized in that, R 2 Selected from -CH2CH2- or -CH2CH2CH2-.

10. The modified polypropylene material as described in claim 5, characterized in that, The inorganic filler is talc powder with an average particle size of 1-10 μm.

11. The modified polypropylene material as described in claim 5, characterized in that, The stabilizer is a mixture of hindered phenolic antioxidants and phosphorous antioxidants.

12. The method for preparing the modified polypropylene material according to any one of claims 1-11, characterized in that, Includes the following steps: The modified polypropylene material is obtained by mixing homopolymer polypropylene, modified copolymer polypropylene, inorganic filler, toughening agent, coupling agent and stabilizer, and then extruding at 190-230℃.

13. The method for preparing the modified polypropylene material as described in claim 12, characterized in that, The preparation method of the modified copolymer polypropylene includes the following steps: The modified copolymer polypropylene is obtained by mixing the copolymer polypropylene, initiator and modifier and extruding at 180-210°C.

14. The method for preparing the modified polypropylene material as described in claim 12 or 13, characterized in that, It also includes the step of mixing at least one of the colorant, light stabilizer and lubricant with the homopolymer polypropylene, modified copolymer polypropylene, toughening agent, coupling agent and stabilizer.

15. The application of the modified polypropylene material according to any one of claims 1-11 or the modified polypropylene material prepared by the preparation method according to any one of claims 12-14 in automotive interiors.

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