A recycled polypropylene composite material with high surface finish and high paint adhesion and a method for preparing the same

Abstract

The application discloses a recycled polypropylene composite material with high surface smoothness and high paint adhesion and a preparation method thereof, which comprises the following raw materials in percentage by weight: recycled polypropylene resin 46-75, high-performance composite master batch 15-30, elastomer 10-20, antioxidant 0.2-1, and other additives 0.2-3. The application adopts a high-performance composite master batch to replace the traditional method of directly using talcum powder and additives, fully utilizes the die swell effect of polymers, and in the double-screw extrusion or injection molding process, the polypropylene with super high melt flow rate flows to the outside of the melt, drives the modified chlorinated polypropylene and epoxy resin to uniformly disperse and enrich in the material surface layer, so that the surface polarity of the recycled polypropylene composite system is greatly improved. Meanwhile, by using the interlayer gap characteristics of the regular layered structure of the high-aspect-ratio talcum powder in the high-performance composite master batch, the paint components with small volume molecules are further adsorbed, so that the adhesion between the recycled polypropylene base material and the paint is further improved.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials and their processing technology, and relates to a recycled polypropylene composite material with high surface smoothness and high paint adhesion, and its preparation method. Background Technology

[0002] In automotive plastics, polypropylene (PP) has become one of the most widely used plastic materials in automotive parts due to its lightweight, low cost, ease of processing, corrosion resistance, impact strength, flexural strength, and good electrical insulation, accounting for approximately 40% of automotive plastics. Therefore, major automakers are actively seeking recycled polypropylene composites to replace traditional polypropylene composites, thereby reducing overall vehicle carbon emissions. Currently, the main sources of recycled polypropylene are post-consumer recycled materials, namely PCR materials, primarily from recycled polypropylene materials from household appliances, daily consumer goods, and automobile dismantling. Considering the ease of recycling, scale of production, and the purity and performance of recycled materials, recycled polypropylene from household appliances, especially washing machine drums, has already seen some industrial application in automotive exterior system components due to its relatively high purity and excellent overall performance, such as underbody protection panels, wheel covers, and bumper brackets—non-exterior components. For exterior paint-painted parts such as bumper bodies, tailgate panels, and fenders, which are used in large quantities, recycled polypropylene cannot be completely cleaned during dismantling and recycling. The presence of pits, impurities, and small molecules on the surface results in poor adhesion and weak bonding with paint, limiting its further development and application in painted parts. Therefore, how to achieve good paint adhesion for recycled polypropylene while maintaining its original mechanical properties has become an urgent problem to be solved in the development of this type of material.

[0003] Currently, there has been some research in the industry regarding the paint adhesion of recycled polypropylene materials. Chinese patent CN117106260 discloses a polypropylene material and its preparation method and application. It improves the paint adhesion of recycled polypropylene by adding polyurethane as a toughening agent, kaolin and graphene oxide as reinforcing agents, and supplementing them with compatibilizers and coupling agents. However, adding too much polyurethane affects the shrinkage rate and linear expansion coefficient of the composite system, which is not mentioned in this patent. Chinese patent CN113999575 discloses a recycled polypropylene spraying material and its preparation method. It improves the adhesion between recycled polypropylene material and paint by adding a high-melting-point toughening agent and silica-grafted butyl acrylate adhesive. On the one hand, the preparation process of silica-grafted butyl acrylate adhesive is complex and the industrialization cost is high. On the other hand, the resulting composite material has poor rigidity-toughness balance performance and cannot be used for parts such as exterior painted bumpers that require high rigidity-toughness balance. Summary of the Invention

[0004] The purpose of this invention is to provide a recycled polypropylene composite material with high surface smoothness and high paint adhesion, and a method for preparing the same, in order to solve the above-mentioned problems in the prior art.

[0005] To improve the surface adhesion of recycled polypropylene composites to paint and enhance the surface finish of composite products, this invention employs a high-performance composite masterbatch instead of the traditional method of directly using talc powder and additives. This fully utilizes the out-of-mold expansion effect of the polymer. During twin-screw extrusion or injection molding, the polypropylene, with its ultra-high melt flow rate, flows outwards, driving the modified chlorinated polypropylene and epoxy resin to disperse and accumulate uniformly on the material surface, thereby significantly improving the surface polarity of the recycled polypropylene composite system. Simultaneously, leveraging the interlayer voids in the regular layered structure of the high aspect ratio talc powder in the high-performance composite masterbatch, smaller paint molecules can be further adsorbed, further enhancing the adhesion between the recycled polypropylene substrate and the paint. The resulting recycled polypropylene composite material exhibits paint adhesion comparable to that of virgin composite systems. Furthermore, it was found that the introduction of the high-performance composite masterbatch significantly improves the surface finish of the recycled polypropylene composite system, eliminating surface defects such as pitting and shrinkage. This makes it suitable for applications requiring high aesthetic quality, such as automotive exterior bumpers and tailgate panels, where high-quality painting is essential.

[0006] To achieve the above objectives, the present invention specifically adopts the following technical solution:

[0007] A recycled polypropylene composite material with high surface finish and high paint adhesion, comprising the following raw materials by weight percentage:

[0008]

[0009]

[0010] In the polypropylene composite material system to which this invention applies,

[0011] The recycled polypropylene resin is obtained by recycling polypropylene from household appliance casings, consumer goods, etc., and has a melt flow rate of 10-50 g / 10 min under conditions of 230°C and 2.16 kg load. As one embodiment, the recycled polypropylene resin is obtained by granulation of recycled washing machine drums, and has a melt flow rate of 25-35 g / 10 min under conditions of 230°C and 2.16 kg load.

[0012] The high-performance composite masterbatch is prepared from the following components in parts by weight: 10 parts of ultra-high flowability polypropylene, 15 parts of modified chlorinated polypropylene, 70 parts of talc, 2 parts of epoxy resin, 2 parts of compatibilizer, and 1 part of lubricant.

[0013] In the high-performance composite masterbatch, the ultra-high flowability polypropylene is metallocene-catalyzed polypropylene, and the melt flow rate is 100-200 g / 10 min under the conditions of 230℃ and 2.16 kg load.

[0014] In the high-performance composite masterbatch, the ultra-high flowability polypropylene has a melt flow rate of 150 g / 10 min under conditions of 230°C and 2.16 kg load.

[0015] In the high-performance composite masterbatch, the modified chlorinated polypropylene is an organosiloxane-modified chlorinated polypropylene with an organosiloxane functional group grafting rate of 1.5-2.5% and a degree of chlorination of 10-20%. As an example, the organosiloxane-modified chlorinated polypropylene has an organosiloxane functional group grafting rate of 2.5% and a degree of chlorination of 15%.

[0016] In the high-performance composite masterbatch, the talc powder is a talc powder with a high aspect ratio of 10 to 30 and a mesh size of 5,000 to 10,000 mesh, and has the characteristics of a regular layered structure; as an example, the talc powder has a mesh size of 10,000 mesh and an aspect ratio of 25.

[0017] In the high-performance composite masterbatch, the compatibilizer is maleic anhydride-grafted polypropylene with a density of 0.89–0.91 g / cm³. 3 The grafting rate is 0.5%–2.0%, and it is obtained by melt extrusion modification of any block copolymer polypropylene with maleic anhydride. As an example, the maleic anhydride-grafted polypropylene has a density of 0.90 g / cm³. 3 The grafting rate was 1.5%.

[0018] In the high-performance composite masterbatch, the lubricant is a compound of ethylene bis-stearamide and stearate in a 1:1 ratio, wherein the ethylene bis-stearamide is N,N-ethylene bis-stearamide and the stearate is magnesium stearate.

[0019] In the polypropylene composite system, the elastomer is an ethylene-octene linear copolymer or an ethylene-butene linear copolymer, or a combination of both, with a density of 0.88–0.90 g / cm³. 3 The melt flow rate is 0.5–10 g / 10 min. As one example, the elastomer is an ethylene-octene linear copolymer with a density of 0.88 g / cm³. 3 The melt flow rate is 2 g / 10 min.

[0020] In the polypropylene composite material system, the antioxidant is one that is considered desirable by those skilled in the art, and is mainly composed of one or more of the following: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant 1010), tris[2,4-di-tert-butylphenyl] phosphite (antioxidant 168), octadecyl thiodipropionate (antioxidant DSTP), and octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (antioxidant 1076). As an example, the antioxidant is a mixture of antioxidant 1010, antioxidant DSTP, and antioxidant 168 in a ratio of 1:1:2.

[0021] In the polypropylene composite material system, the other additives are mainly one or more of the various color components, light stabilizers, processing aids, etc. that are deemed necessary by those skilled in the art.

[0022] The specific steps of the preparation method of the above-mentioned recycled polypropylene composite material with high surface smoothness and high paint adhesion are as follows:

[0023] A. Preparation of high-performance composite masterbatch:

[0024] Ultra-high flow polypropylene, modified chlorinated polypropylene, talc, epoxy resin, compatibilizer, and lubricant are added to a high-speed mixer according to their weight components and mixed evenly. Then, the mixture is transferred to the mixing chamber of an internal mixer for high-speed internal mixing. The mixed lumps are then transferred to a double-wrist feed inlet for feeding, and extruded, air-cooled, and granulated by a single-screw extruder to produce high-performance composite masterbatch. The temperature of the mixing chamber in the internal mixer is set at 170-190℃. The single screw diameter is 70mm, and the length-to-diameter ratio is 12. The single-screw extruder has three temperature control sections: 180℃, 190℃, and 200℃ from the feed inlet to the die head.

[0025] B. Preparation of recycled polypropylene composite materials with high surface finish and high paint adhesion:

[0026] (1) Weigh and prepare the above components according to the mass ratio;

[0027] (2) Place the recycled polypropylene resin, high-performance composite masterbatch, elastomer, antioxidant, and other additives in a high-speed mixer and mix at high speed for 5-10 minutes.

[0028] (3) The mixed raw materials are placed in a twin-screw extruder and melt-extruded and granulated. The process is as follows: Zone 1 180-190℃, Zone 2 190-200℃, Zone 3 200-210℃, Zone 4 200-210℃; the residence time of the entire extrusion process is 1-2 minutes, the pressure is 12-18 MPa, and the exhaust vacuum reaches 5-20 kPa. The extruder die head is equipped with an 80 / 100 mesh double-layer filter screen, and the screen is changed every 2-4 hours.

[0029] The advantages of this invention are:

[0030] (1) In the formulation design of recycled polypropylene composite materials, the present invention adopts a high-performance composite masterbatch to replace the traditional method of directly using talc powder + additives. The high-performance composite masterbatch uses ultra-high flow polypropylene as a carrier and makes full use of the polymer's demolding expansion effect. During twin-screw extrusion or injection molding, the ultra-high flow polypropylene flows to the outside of the melt, driving the modified chlorinated polypropylene and epoxy resin to be uniformly dispersed and enriched on the surface of the material, thereby greatly improving the surface polarity of the recycled polypropylene composite system.

[0031] (2) The present invention enables the recycled composite system to achieve high paint adhesion by adding a small amount of modified chlorinated polypropylene and epoxy resin.

[0032] (3) This invention utilizes the interlayer void characteristics of the regular layered structure of high aspect ratio talc powder in high-performance composite masterbatch, which can further adsorb paint components with smaller volume molecules during the painting process, thereby further improving the adhesion between recycled polypropylene substrate and paint. The resulting recycled polypropylene composite material can achieve the level of paint adhesion of the new material composite system.

[0033] (4) The addition of maleic anhydride-grafted polypropylene in the high-performance composite masterbatch of the present invention can increase the interfacial bonding force and compatibility between talc and polypropylene, thereby further improving the comprehensive mechanical properties of the recycled polypropylene composite material system.

[0034] (5) The present invention also found that after introducing high-performance composite masterbatch, the surface smoothness of the product obtained by the recycled polypropylene composite system is significantly improved, and there are no appearance defects such as pitting or shrinkage on the surface. After painting, the surface of the product is smooth and there are no appearance defects.

[0035] (6) The preparation process of the recycled polypropylene composite material with high surface smoothness and high paint adhesion proposed in this invention is simple and the production cost is low. Detailed implementation method:

[0036] The present invention will be further described in detail below by way of embodiments and comparative examples, but the invention is not limited to the scope of the embodiments described herein.

[0037] Example 1

[0038] The main components of the polypropylene composite material of this invention include 70.5% recycled polypropylene, 15% high-performance composite masterbatch A, 12% elastomer, 0.5% antioxidant, and 2% other additives. The main components of high-performance composite masterbatch A are 10% ultra-high flowability polypropylene, 15% modified chlorinated polypropylene, 70% talc, 2% epoxy resin, 2% compatibilizer, and 1% lubricant.

[0039] Example 2

[0040] The main components of the polypropylene composite material of this invention include 61.5% recycled polypropylene, 22% high-performance composite masterbatch A, 14% elastomer, 0.5% antioxidant, and 2% other additives. The main components of high-performance composite masterbatch A are the same as in Example 1.

[0041] Example 3

[0042] The main components of the polypropylene composite material of this invention include 63.5% recycled polypropylene, 22% high-performance composite masterbatch A, 12% elastomer, 0.5% antioxidant, and 2% other additives. The main components of high-performance composite masterbatch A are the same as in Example 1.

[0043] Example 4

[0044] The main components of the polypropylene composite material of this invention include 54.5% recycled polypropylene, 29% high-performance composite masterbatch A, 14% elastomer, 0.5% antioxidant, and 2% other additives. The main components of high-performance composite masterbatch A are the same as in Example 1.

[0045] Example 5

[0046] The main components of the polypropylene composite material of this invention include 52.5% recycled polypropylene, 29% high-performance composite masterbatch A, 16% elastomer, 0.5% antioxidant, and 2% other additives. The main components of high-performance composite masterbatch A are the same as in Example 1.

[0047] Example 6

[0048] The main components of the polypropylene composite material of this invention include 50.5% recycled polypropylene, 29% high-performance composite masterbatch A, 18% elastomer, 0.5% antioxidant, and 2% other additives. The main components of high-performance composite masterbatch A are the same as in Example 1.

[0049] Comparative Example 1

[0050] The main components of the polypropylene composite material of this invention include 52.5% recycled polypropylene, 29% high-performance composite masterbatch B, 16% elastomer, 0.5% antioxidant, and 2% other additives. The main components of high-performance composite masterbatch B are 25% ultra-high flowability polypropylene, 70% talc, 2% epoxy resin, 2% compatibilizer, and 1% lubricant.

[0051] Comparative Example 2

[0052] The main components of the polypropylene composite material of this invention include 52.5% recycled polypropylene, 29% high-performance composite masterbatch C, 16% elastomer, 0.5% antioxidant, and 2% other additives. The high-performance composite masterbatch C mainly consists of 12% ultra-high flowability polypropylene, 15% modified chlorinated polypropylene, 70% talc, 2% compatibilizer, and 1% lubricant.

[0053] Comparative Example 3

[0054] The main components of the polypropylene composite material of this invention include 52.5% recycled polypropylene, 29% high-performance composite masterbatch D, 16% elastomer, 0.5% antioxidant, and 2% other additives. The main components of high-performance composite masterbatch D are 12% ultra-high flowability polypropylene, 15% modified chlorinated polypropylene, 70% talc, 2% epoxy resin, and 1% lubricant.

[0055] Comparative Example 4

[0056] The main components of the polypropylene composite material of this invention include 52.5% recycled polypropylene, 29% high-performance composite masterbatch E, 16% elastomer, 0.5% antioxidant, and 2% other additives. The high-performance composite masterbatch E mainly consists of 10% virgin polypropylene resin, 15% modified chlorinated polypropylene, 70% talc, 2% epoxy resin, 2% compatibilizer, and 1% lubricant.

[0057] Comparative Example 5

[0058] The main components of the polypropylene composite material of the present invention include 67.44% virgin polypropylene resin, 15.4% talc, 14% elastomer, 0.44% compatibilizer, 0.22% lubricant, 0.5% antioxidant and 2% other additives.

[0059] Comparative Example 6

[0060] The main components of the polypropylene composite material of the present invention include 60.33% virgin polypropylene resin, 20.3% talc, 16% elastomer, 0.58% compatibilizer, 0.29% lubricant, 0.5% antioxidant and 2% other additives.

[0061] Comparative Example 7

[0062] The main components of the polypropylene composite material of this invention include 52.5% recycled polypropylene resin, 2.9% ultra-high flow polypropylene, 4.35% modified chlorinated polypropylene, 20.3% talc, 16% elastomer, 0.58% epoxy resin, 0.58% compatibilizer, 0.29% lubricant, 0.5% antioxidant, and 2% other additives.

[0063] The content of each component in the embodiments and comparative examples of the present invention is shown in Table 1.

[0064] Table 1. Content (mass percentage) of each major component in the examples and comparative examples.

[0065]

[0066]

[0067] The raw materials described in the embodiments and comparative examples in Table 1 above are as follows:

[0068] The recycled polypropylene resin was produced by GEM Co., Ltd., with the grade A310 and a melt flow rate of 35 g / 10 min.

[0069] The new polypropylene resin is a blend of EP5075X and BX3500 in a 2:1 ratio. EP5075X is produced by Sinopec and has a melt flow rate of 60g / 10min. BX3500 is produced by SK Corporation of South Korea and has a melt flow rate of 8g / 10min.

[0070] The ultra-high flow polypropylene is MH7900 manufactured by LG Corporation, with a melt flow rate of 150 g / 10 min.

[0071] The modified chlorinated polypropylene is an organosiloxane-modified chlorinated polypropylene with a functional group grafting rate of 2.5% and a chlorination degree of 15%. It is self-made.

[0072] The talc powder is approximately 10,000 mesh with a diameter-to-thickness ratio of 25, and comes from Shanghai Yuanjiang Chemical Co., Ltd.

[0073] The elastomer is a thermoplastic POE elastomer manufactured by LG Corporation, with the grade 168.

[0074] The epoxy resin is KD-213 produced by Guodu Chemical.

[0075] The compatibilizer is maleic anhydride-grafted polypropylene with a grafting rate of 1.5%, manufactured by Prilang.

[0076] The lubricant is a compound of ethylene bis-stearamide and stearate in a 1:1 ratio. The ethylene bis-stearamide is N,N-ethylene bis-stearamide, which is supplied by Sigma-Aldrich (Shanghai) Trading Co., Ltd., and the stearate is magnesium stearate, which is supplied by Shanghai Yuanye Biotechnology Co., Ltd.

[0077] The antioxidants are a compound antioxidant consisting of 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] / DSTP (octadecyl thiodipropionate) / antioxidant 168 (tris[2,4-di-tert-butylphenyl]phosphite) in a mass ratio of 1:1:2, all of which are commercially available.

[0078] Other additives mainly refer to color components, light stabilizers, etc.

[0079] The specific implementation methods of the above embodiments and comparative examples 1-4 are as follows:

[0080] A. Preparation of high-performance composite masterbatch:

[0081] According to the mass ratio, all components of the high-performance composite masterbatch from Examples 1-4 were added to a high-speed mixer and mixed evenly. Then, the mixture was transferred to the mixing chamber of an internal mixer for high-speed internal mixing. The mixed lumps were then transferred to a dual-wrist feed inlet for feeding, and extruded, air-cooled, and granulated by a single-screw extruder to produce the high-performance composite masterbatch. The temperature of the mixing chamber in the internal mixer was set at 170-190℃, the single screw diameter was 70mm, and the length-to-diameter ratio was 12. The single-screw extruder had three temperature control sections: 180℃, 190℃, and 200℃ from the feed inlet to the die head.

[0082] B. Preparation of recycled polypropylene composite materials with high surface finish and high paint adhesion:

[0083] (1) Weigh out the components in Examples 1-4 and Comparative Examples 1-4 according to the mass ratio;

[0084] (2) Place the weighed components in a high-speed mixer and mix at high speed for 5-10 minutes;

[0085] (3) The mixed raw materials are placed in a twin-screw extruder and melt-extruded and granulated. The process is as follows: Zone 1 180-190℃, Zone 2 190-200℃, Zone 3 200-210℃, Zone 4 200-210℃; the residence time of the entire extrusion process is 1-2 minutes, the pressure is 12-18 MPa, and the exhaust vacuum reaches 5-20 kPa. The extruder die head is equipped with an 80 / 100 mesh double-layer filter screen, and the screen is changed every 2-4 hours.

[0086] The specific implementation methods of the above comparative examples 5-7 are as follows:

[0087] (1) Weigh and prepare each component in Comparative Example 5-7 according to the mass ratio;

[0088] (2) Place the weighed components in a high-speed mixer and mix at high speed for 5-10 minutes;

[0089] (3) The mixed raw materials are placed in a twin-screw extruder and melt-extruded and granulated. The process is as follows: Zone 1 180-190℃, Zone 2 190-200℃, Zone 3 200-210℃, Zone 4 200-210℃; the residence time of the entire extrusion process is 1-2 minutes, the pressure is 12-18 MPa, and the exhaust vacuum reaches 5-20 kPa. The extruder die head is equipped with an 80 / 100 mesh double-layer filter screen, and the screen is changed every 2-4 hours.

[0090] The composite material particles prepared according to the above examples and comparative examples were dried in a forced-air oven at 80-100°C for 2 hours. The dried particles were then injection molded on an injection molding machine, and then the performance was tested.

[0091] Basic mechanical property tests: density was tested according to ISO 1183-1 standard; melt flow index was tested according to ISO 1133-1 standard, with a test temperature of 230℃ and a load of 2.16kg; flexural modulus was tested according to ISO 178 standard, with a specimen size of 80*10*4mm, a span of 64mm, and a bending speed of 2mm / min; notched impact strength was tested according to ISO 179-1 standard, with a specimen size of 80*10*4mm and a notch depth of one-fifth of the specimen width.

[0092] Surface tension test: The surface dyne value was used for characterization. A 150*100*3.2mm injection molded sample was tested for surface dyne value before and after flame treatment using a dyne pen. The larger the dyne value, the greater the surface tension of the sample.

[0093] High-pressure water jet performance test: A 150*100*3.2mm injection-molded sample was flame-treated and spray-painted using mass-produced paint and processes. After 7 days of aging at room temperature, a high-pressure water jet test was conducted. The specific experimental method was as follows: X-lines were drawn on the painted sample down to the bottom layer of the coating using a scriber. Each line was 100mm long. The high-pressure nozzle was aimed at each edge of the X-line and sprayed, with the nozzle distance from the line being 13cm, the spray angle being 90°, the water temperature being 60℃, the flow rate being 11.5L / min, and the spraying time being 60s. The degree of coating peeling after spraying was graded as follows: Grade 1 (no coating peeling), Grade 2 (slight coating peeling at the X-line), Grade 3 (significant coating peeling at the X-line), and Grade 4 (large-area coating peeling). The lower the grade, the better the adhesion between the substrate and the paint.

[0094] Surface finish assessment: For injection-molded 150*100*3.2mm samples, under standard light source, count the appearance defects such as pits, pinholes, and impurities on the sample surface. No appearance defects are grade 0. The average number of appearance defects per sample is 1 to 2, grade 1. The average number of appearance defects per sample is 3 to 5, grade 2. The average number of appearance defects per sample is >5, grade 3.

[0095] The performance test results of the recycled polypropylene composite materials of Examples 1-6 and Comparative Examples 1-7 of the present invention are shown in Table 2.

[0096] Table 2. Material performance test data for the examples and comparative examples.

[0097]

[0098]

[0099] From the data results of the examples and comparative examples 5-6 in the table above, it can be found that after introducing high-performance composite masterbatch with ultra-high flowability polypropylene as carrier, the surface tension and high-pressure water flushing performance of the recycled polypropylene composite system before and after flame treatment reached or even exceeded the level of the new material system. The surface dyne value of the samples after flame treatment can reach 50+, and there is no coating peeling on the surface of the paint samples after high-pressure water flushing. The data results from Example 5 and Comparative Examples 1-2 show that neither the addition of modified chlorinated polypropylene nor epoxy resin alone in the high-performance composite masterbatch can achieve a high level of surface paint adhesion. The data results from Example 5 and Comparative Example 3 show that the addition of maleic anhydride-grafted polypropylene compatibilizer in the high-performance composite masterbatch can increase the interfacial bonding force and compatibility between talc and polypropylene, thereby improving the comprehensive mechanical properties of the recycled polypropylene composite system. The data results from Example 5 and Comparative Examples 4 and 7 show that the ultra-high flowability polypropylene carrier in the high-performance composite masterbatch plays a crucial role in the system. In particular, pre-processing it into a high-performance composite masterbatch can maximize the release expansion effect of the polymer. With the addition of a relatively small amount of modified chlorinated polypropylene and epoxy resin, the recycled composite system can achieve a high level of paint adhesion. Meanwhile, an unexpected finding was made from the comparison of Examples 1-6 and Comparative Examples 1-2 and 5-6 that after introducing high-performance composite masterbatch, the surface finish of the recycled composite material system was all grade 0, and the sample surfaces were free of appearance defects such as shrinkage pits, pinholes, and impurities, which can reach the same level as new polypropylene composite materials and are suitable for molding and processing painted parts with high appearance requirements.

Claims

1. A recycled polypropylene composite material with high surface finish, high paint adhesion, characterized in that: The raw materials are prepared according to the following weight percentage: Recycled polypropylene resin 46~75%, High-performance composite master batch 15~30%, Elastomer 10~20%, Antioxidant 0.2~1%, Other additives 0.2~3%; The recycled polypropylene resin has a melt flow rate of 10~50g / 10min under the condition of 230℃ and 2.16kg load. The high-performance composite master batch is prepared from the following components according to weight percentage: Ultra-high flow polypropylene 10%; Modified chlorinated polypropylene 15%; Talc 70%; Epoxy resin 2%; Compatibilizer 2%; Lubricant 1%; The ultra-high flow polypropylene is metallocene-catalyzed polypropylene, which has a melt flow rate of 100~200g / 10min under the condition of 230℃ and 2.16kg load.

2. A recycled polypropylene composite material with high surface finish, high paint adhesion according to claim 1, characterized by: The recycled polypropylene resin is prepared from household appliance shell recycled polypropylene and consumer product recycled polypropylene.

3. A recycled polypropylene composite material with high surface finish, high paint adhesion according to claim 1, characterized in that: The modified chlorinated polypropylene is organosiloxane-modified chlorinated polypropylene, with a functional group grafting rate of 1.5~2.5% and a chlorination degree of 10~20%.

4. A recycled polypropylene composite material with high surface finish, high paint adhesion according to claim 1, characterized by: The talc is talc with a high aspect ratio, with an aspect ratio of 10~30 and a mesh size of 5000~10000 mesh, and has a regular layered structure.

5. A recycled polypropylene composite material with high surface finish, high paint adhesion according to claim 1, characterized by: The compatibilizer is maleic anhydride grafted polypropylene with a density of 0.89-0.91 g / cm 3 and a grafting rate of 0.5-2.0%, which is obtained by melt extrusion modification of any block copolymerized polypropylene with maleic anhydride.

6. A recycled polypropylene composite material with high surface finish, high paint adhesion according to claim 1, characterized by: The lubricant is a compound of ethylene bis-stearyl amide and stearate in a 1:1 ratio, where ethylene bis-stearyl amide is N,N-ethylene bis-stearamide and stearate is magnesium stearate.

7. A recycled polypropylene composite material with high surface finish, high paint adhesion according to claim 1, characterized by: The elastomer is an ethylene-octene linear copolymer or an ethylene-butene linear copolymer or a combination of both, having a density of 0.88 to 0.90 g / cm 3 and a melt flow rate of 0.5 to 10 g / 10 min.

8. A recycled polypropylene composite material with high surface finish, high paint adhesion according to claim 1, characterized by: The antioxidant is one or a mixture of two or more of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol ester, tris[2,4-di-tert-butylphenyl]phosphite, octadecyl thiodipropionate, and β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecanol ester.

9. A recycled polypropylene composite material with high surface finish, high paint adhesion according to claim 1, characterized by: The other additives are one or a combination of several color components, light stabilizers, and processing aids.

10. The high surface finish, high paint adhesion, recycled polypropylene composite of any of claims 1-9, characterized by: The specific steps are as follows: A. Preparation of high-performance composite master batch: Mix the ultra-high flow polypropylene, modified chlorinated polypropylene, talc, epoxy resin, compatibilizer, and lubricant together in a high-speed mixer, then transfer them to the mixing chamber of an internal mixer for high-speed mixing, and then transfer the mixed block material to a double-wrist feeding port for feeding. The material is extruded, air-cooled, and granulated by a single-screw extruder to prepare a high-performance composite master batch. The temperature of the mixing chamber in the internal mixer is set to 170-190℃, the diameter of the single screw is 70mm, the length-diameter ratio is 12, and the single-screw extruder is divided into three sections with temperature control. The temperature of each section from the feeding port to the die head is 180℃, 190℃, and 200℃, respectively; B. Preparation of recycled polypropylene composite material with high surface finish and high paint adhesion: (1) Weigh and prepare the above components according to the mass ratio; (2) Mix the recycled polypropylene resin, high-performance composite master batch, elastomer, antioxidant, and other additives in a high-speed mixer for 5~10min. (3) the mixed raw materials are placed in a twin-screw extruder, melted and extruded, and granulated, and the process is as follows: 180-190 DEG C in the first zone, 190-200 DEG C in the second zone, 200-210 DEG C in the third zone, and 200-210 DEG C in the fourth zone; The residence time of the whole extrusion process is 1-2 minutes, the pressure is 12-18 MPa, the exhaust vacuum degree reaches 5-20 kPa; the extruder head is provided with 80 / 100 mesh double-layer filter screen, and the screen changing frequency is 2-4 h / time.

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