High-strength yellowing-resistant plastic based on modified polypropylene and method for producing same

Abstract

The application relates to the field of plastics, and more particularly to a high-strength yellowing-resistant plastic based on modified polypropylene and a preparation method thereof. The high-strength yellowing-resistant plastic based on modified polypropylene is prepared from the following raw materials: a modified polypropylene matrix, functional fillers, antioxidants, auxiliary agents, light stabilizers and ultraviolet absorbers. The finally-prepared polypropylene plastic system can not only effectively improve the yellowing resistance of the system, but also ensure the enhancement of the mechanical properties of the system, greatly reduce the negative influence of the filler particles on the yellowing of the polypropylene matrix, and further improve the waterproofing, moisture resistance, aging resistance and other properties of the polypropylene plastic, improve the performance contradiction problems existing in the polypropylene plastic, promote the further development of the polypropylene plastic, expand the application environment and field of the polypropylene plastic, and have very excellent application prospect and practical significance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of plastics, and more particularly to a high-strength yellowing-resistant plastic based on modified polypropylene and a preparation method thereof. BACKGROUND

[0002] Polypropylene (PP) is a thermoplastic plastic, which has been widely used in fields such as daily plastic products (such as plastic bottles, storage boxes, plastic pots, plastic cups, etc.), automotive plastic products (automobile parts, interior and exterior trim, etc.), and household appliances (plastic parts or outer protective shells) due to its low density, large surface hardness of finished products, high elasticity, good heat resistance, chemical stability, and insulation.

[0003] However, as the fields, environments, and time of application continue to increase, the performance problems of polypropylene plastics have gradually become apparent. For example, conventional polypropylene plastics have significant shortcomings in mechanical properties (such as impact resistance and flexural modulus) and long-term weather resistance (especially anti-yellowing ability), especially in outdoor application scenarios (such as automotive interior and exterior trim, solar device housings, and daily plastic products) or products with high-gloss surface requirements (such as high-end home appliance panels). Ordinary polypropylene is prone to molecular chain rupture due to ultraviolet radiation, humid heat, or high-temperature oxidation, resulting in degradation of material mechanical properties and surface yellowing, which severely reduces product aesthetics and service life.

[0004] In recent years, in order to break through this bottleneck, existing technologies have improved polypropylene plastics from aspects such as mechanical reinforcement, yellowing-resistant additives (such as light stabilizers and antioxidants, etc.). However, the improved polypropylene plastics still have some systematic problems. For example, there is a contradiction between mechanical properties and yellowing resistance. Typically, to enhance mechanical properties, the addition of inorganic fillers greatly exacerbates the light scattering phenomenon on the surface of the plastic, which in turn accelerates the apparent yellowing of the plastic. Moreover, due to the addition of fillers, the increase in the pore size and fine cracks on the surface further reduces the waterproof and moisture resistance of the plastic. Therefore, in a high-humidity and high-temperature environment, conventional light stabilizers are prone to migration and failure. In addition, the interface defects between the fillers and the matrix are prone to become stress concentration points and aging initiation points, which inevitably leads to significant performance degradation in long-term outdoor use environments. SUMMARY

[0005] Therefore, in order to effectively solve the above-mentioned existing problems, the application provides a high-strength yellowing-resistant plastic based on modified polypropylene and a preparation method thereof. The finally prepared polypropylene plastic system can not only effectively improve the yellowing resistance of the system itself, but also ensure the enhancement of the mechanical properties of the system itself, greatly reduce the negative influence of the filler particles on the yellowing of the polypropylene matrix, and further improve the waterproofing, moisture resistance, aging resistance and other properties of the polypropylene plastic, improve the performance contradiction problem existing in the polypropylene plastic, promote the further development of the polypropylene plastic, expand the application environment and field of the polypropylene plastic, and has very excellent application prospect and practical significance.

[0006] As a preferred embodiment, the high-strength yellowing-resistant plastic based on modified polypropylene is prepared from the following raw materials in parts by mass: 65-85 parts of a modified polypropylene matrix, 15-25 parts of a functional filler, 0.5-1.5 parts of an antioxidant, 0.3-0.5 parts of an auxiliary agent, 0.5-1.2 parts of a light stabilizer, 0.4-1 part of an ultraviolet absorber, 0.8-1.5 parts of a nucleating agent, 2-3 parts of a lubricant, and 4-8 parts of a toughening agent.

[0007] As a preferred embodiment, the modified polypropylene matrix is a functional graft modified polypropylene resin.

[0008] As a preferred embodiment, the preparation method of the functional graft modified polypropylene resin specifically comprises the following steps: S1: uniformly mixing homopolymerized polypropylene, glycidyl methacrylate, 2-hydroxyethyl acrylate and dicumyl peroxide at a temperature of 80-85°C and a rotation speed of 1000-1200 rpm for 15-20 min to obtain a premix; S2: extruding the premix after heating and stirring in a twin-screw extruder, with a temperature of 160-170°C in the first zone, 175-180°C in the second zone, and 190-195°C in the third zone, a screw rotation speed of 200-250 rpm, and vacuum devolatilization at -0.06 to -0.04 MPa, and then water-cooling and granulating to obtain the product.

[0009] As a preferred embodiment, the homopolymerized polypropylene has a melt index of 20-22 g / 10 min under the condition of 230°C and 2.16 kg.

[0010] As a preferred embodiment, the mass ratio of the homopolymerized polypropylene, glycidyl methacrylate and 2-hydroxyethyl acrylate is (48-54):(3.5-5):(2-3).

[0011] As a preferred embodiment, the mass ratio of the homopolymerized polypropylene, glycidyl methacrylate and 2-hydroxyethyl acrylate is (49-51):(4-4.5):(2.4-2.8).

[0012] By the modification of the homopolypropylene, more active surface groups can be introduced into the polypropylene, the presence of these active groups can not only form stronger hydrogen bonding with the hydroxyl surface of kaolin and titanium dioxide, greatly improve the interfacial bonding force between the resin system and the filler particles, enhance the system strength, but also enhance the overall hydrolysis resistance through the mutual reaction of the grafted molecular chain segments with the surface hydroxyl groups, and avoid the excessive attraction of the particles to water molecules in actual operation, and effectively reduce the active oxygen production of the composite particles; on the other hand, the modification of the homopolypropylene can promote the formation of multi-branched molecular chains and long molecular chains, thereby strengthening the construction of the three-dimensional molecular chain network between the internal resin systems, thereby enhancing the internal connection viscosity, improving the intermolecular interaction, thereby optimizing the interfacial performance, and synergistically reducing the interfacial stress concentration, thereby effectively improving the overall mechanical, yellowing resistance aging and waterproof moisture resistance.

[0013] As a preferred embodiment, the functional filler is a composite modified particle of kaolin and titanium dioxide.

[0014] As a preferred embodiment, the preparation method of the composite modified particle of kaolin and titanium dioxide specifically comprises the following steps: S1: dry mixing kaolin and titanium dioxide, then adding PP wax to obtain blended particles; S2: adding the blended particles into toluene solvent, then adding zinc nitrate and dimethyl imidazole, heating to 65-70°C, and reacting for 4-5h, after the reaction is completed, removing the excess solvent, washing and drying to obtain pretreated particles; S3: adding the pretreated particles into a mixing mill, the temperature is 150-160°C, the rotation speed is 60-80rpm, the mixing time is 20-30min, after mixing is completed, cooling and crushing, and passing through a 500-600 mesh sieve, and the composite modified particle of kaolin and titanium dioxide is obtained.

[0015] As a preferred embodiment, the average particle size of the kaolin is 600-800nm.

[0016] As a preferred embodiment, the titanium dioxide is rutile titanium dioxide, and the average particle size is 40-50nm.

[0017] As a preferred embodiment, the mass ratio of the kaolin, titanium dioxide and PP wax is (6-7):(3-4):(1.8-2.2).

[0018] As a preferred embodiment, the mass ratio of the blended particles, zinc nitrate and dimethyl imidazole is (12-14):(0.5-0.6):(0.8-1).

[0019] The addition of the modified composite particles of kaolin and titanium dioxide can not only serve as rigid support sites and UV reflection sites of the polypropylene plastic system to improve the mechanical properties and yellowing resistance of the plastic system, but also can greatly reduce the refractive index difference between the composite particles and the polypropylene resin system in the system through the joint action of the framework particles and PP coating, avoid more severe surface light scattering phenomenon caused by the large refractive index difference, avoid the extension of the light path and the formation of surface defects of the plastic due to the photosensitization effect, thereby reducing the local reflection effect caused by the above effects, accelerating the rapid degradation and yellowing of the PP molecular chain, and further improving the stability and aging resistance of the polypropylene plastic.

[0020] On the other hand, the modified composite particles can also greatly strengthen the interaction force between the polypropylene resin system through the action of the surface active groups, improve the interfacial adhesion, reduce the interfacial stress concentration phenomenon, and reduce the surface pore size and microcrack pore size and length, reduce the specific surface area, reduce the adsorption of oxygen and more moisture, and the addition of the framework particles can form a more three-dimensional ladder structure, reduce the penetration speed of water, improve the penetration resistance, and also can weaken the photosensitization effect, thereby comprehensively improving the mechanical properties, yellowing resistance and waterproof and moisture resistance of the polypropylene plastic.

[0021] As a preferred embodiment, the mass ratio of the modified polypropylene matrix, functional filler and toughening agent is (70-78):(16-22):(4-6).

[0022] As a preferred embodiment, the mass ratio of the modified polypropylene matrix, functional filler and toughening agent is (72-76):(17-20):(4.5-5.5).

[0023] As a preferred embodiment, the antioxidant is a combination of antioxidant 1076 and antioxidant DSTDP.

[0024] As a preferred embodiment, the mass ratio of the antioxidant 1076 and the antioxidant DSTDP is (3-4):(1-1.5).

[0025] As a preferred embodiment, the mass ratio of the antioxidant 1076 and the antioxidant DSTDP is (3.2-3.5):(1.2-1.4).

[0026] As a preferred embodiment, the auxiliary agent is at least one of ethoxylated fatty acid amine, sodium dodecyl sulfonate, dioctadecyl dimethyl ammonium chloride and polyethylene glycol ester.

[0027] As a preferred embodiment, the auxiliary agent is a combination of ethoxylated fatty acid amine and polyethylene glycol ester.

[0028] As a preferred embodiment, the mass ratio of the ethoxylated fatty acid amine and the polyethylene glycol ester is (3-5):(1.2-2).

[0029] As a preferred embodiment, the mass ratio of the ethoxylated fatty acid amine and the polyethylene glycol ester is (4-4.2):(1.6-1.8).

[0030] As a preferred embodiment, the light stabilizer is a combination of light stabilizer 770 and light stabilizer 622.

[0031] As a preferred embodiment, the mass ratio of the light stabilizer 770 and the light stabilizer 622 is (2-2.5):(0.8-1.2).

[0032] As a preferred embodiment, the mass ratio of the light stabilizer 770 and the light stabilizer 622 is (2-2.2):(0.9-1).

[0033] As a preferred embodiment, the ultraviolet absorber is at least one of benzotriazole-based, benzophenone-based, triazine-based, and cyanoacrylate-based.

[0034] As a preferred embodiment, the ultraviolet absorber is benzotriazole-based or benzophenone-based.

[0035] As a preferred embodiment, the nucleating agent is at least one of sorbitol-based, organic phosphate-based, carboxylate-based, and arylamide-based.

[0036] As a preferred embodiment, the nucleating agent is sorbitol-based.

[0037] As a preferred embodiment, the lubricant is a combination of zinc stearate and ethylene bis-stearamide.

[0038] As a preferred embodiment, the mass ratio of the zinc stearate and the ethylene bis-stearamide is (5.5-6.5):(2-2.4).

[0039] As a preferred embodiment, the toughening agent is at least one of polyolefin elastomer, ethylene-propylene-diene rubber, hydrogenated styrene-based elastomer, and ethylene-vinyl acetate copolymer.

[0040] As a preferred embodiment, the toughening agent is polyolefin elastomer.

[0041] As a preferred embodiment, the preparation method of the high-strength yellowing-resistant plastic based on modified polypropylene specifically comprises the following steps: S1: mixing the modified polypropylene matrix, functional filler and toughening agent in a high-speed mixer, the mixing temperature is 85-90℃, the mixing speed is 1000-1200rpm, the mixing time is 20-25min, and after mixing is completed, the remaining raw materials are added and high-speed mixing is continued for 10-15min, and the blend is obtained after completion.

[0042] As a preferred embodiment, the temperature of the melt extrusion in S2 is 175-180℃ in the first zone, 190-195℃ in the second zone, and 200-205℃ in the third zone, the screw speed is 200-300rpm, and the vacuum degree is -0.10 to -0.08MPa.

[0043] The application also limits the application of the high-strength yellowing-resistant plastic based on modified polypropylene in daily plastic products, automotive plastic products and plastic housings / parts of household appliances.

[0044] The application has the following beneficial effects:

[0045] 1. The high-strength yellowing-resistant plastic based on modified polypropylene provided in the application not only effectively improves the yellowing resistance of itself, but also ensures the enhancement of the mechanical properties of itself, greatly reduces the negative influence of filler particles on the yellowing of the polypropylene matrix, and further improves the waterproofing, aging resistance and other properties of the polypropylene plastic, improves the performance contradiction problem of the existing polypropylene plastic, and promotes the further development of the polypropylene plastic.

[0046] 2. The high-strength yellowing-resistant plastic based on modified polypropylene provided in the application can form stronger hydrogen bond with the hydroxyl surface of kaolin and titanium dioxide through modification of the homopolypropylene, greatly improve the interfacial bonding force between the resin system and the filler particles, enhance the system strength, and through the mutual reaction of the grafted molecular chain segment and the surface hydroxyl group, enhance the overall hydrolysis resistance, and through the occupation of the particle surface hydroxyl group, avoid the excessive attraction of the particles to water molecules in actual operation, and effectively reduce the production of active oxygen of the composite particles, thereby effectively enhancing the aging resistance, mechanical and waterproofing comprehensive performance of the system.

[0047] 3、The high-strength yellowing-resistant plastic based on modified polypropylene provided in the application can improve the mechanical properties and yellowing resistance of the plastic system by adding the composite modified particles of kaolin and titanium dioxide as rigid support sites and ultraviolet reflection sites of the polypropylene plastic system. The modified composite particles can greatly reduce the refractive index difference between the composite particles and the polypropylene resin system in the system through the combined action of the framework particles and the PP coating. The more severe surface light scattering phenomenon caused by the large refractive index difference is avoided, the light path is not prolonged, and the photosensitization effect is avoided to form surface defects of the plastic, thereby reducing the local reflection effect caused by the above effects, accelerating the rapid degradation and yellowing phenomenon of the PP molecular chain, and further improving the stability and aging resistance of the polypropylene plastic. DETAILED DESCRIPTION

[0048] In the detailed description, the content in the summary of the application will be more intuitively displayed and explained through specific implementation cases. The following examples are only actual examples for illustrating and explaining the content of the technical solutions in the specification, and should not limit the scope of the claims of the application.

[0049] Example 1

[0050] The high-strength yellowing-resistant plastic based on modified polypropylene has the following raw materials in mass parts: modified polypropylene matrix 74.6 parts, functional filler 18.2 parts, antioxidant 1.2 parts, auxiliary agent 0.4 parts, light stabilizer 0.6 parts, ultraviolet absorber 0.5 parts, nucleating agent 0.9 parts, lubricant 2.4 parts, and toughening agent 4.9 parts.

[0051] The modified polypropylene matrix is a functional graft modified polypropylene resin, and its preparation method includes the following steps in mass parts: S1: 50 parts of homopolymer polypropylene is pre-dried and mixed with 4.2 parts of glycidyl methacrylate, 2.5 parts of 2-hydroxyethyl acrylate, and 0.1 parts of dicumyl peroxide at 85°C and 1000 rpm for 20 min to obtain a premix; S2: The premix is extruded after heating and stirring in a twin-screw extruder, the temperature is 165°C in the first zone, 180°C in the second zone, and 195°C in the third zone, the screw speed is 240 rpm, and the vacuum devolatilization is carried out at -0.06 MPa, and then water cooling and granulation are carried out to obtain the product.

[0052] The melt index of the homopolymer polypropylene is 22 g / 10 min under the condition of 230°C and 2.16 kg, and the product is purchased from Z30S model product sold by Dalian Xitai Petrochemical Co., Ltd.

[0053] The functional filler is a composite modified particle of kaolin and titanium dioxide, and a preparation method thereof, specifically comprising the following steps: S1: 7 parts of kaolin and 3 parts of titanium dioxide are dry mixed, and then 2 parts of PP wax is added to obtain blended particles; S2: 13.6 parts of the blended particles are added to 140 parts of a toluene solvent, and then 0.55 parts of zinc nitrate and 0.92 parts of dimethyl imidazole are added, and the mixture is heated to 65°C for reaction for 4.5 hours, after the reaction is completed, the excess solvent is removed, and then the pretreated particles are washed and dried to obtain the pretreated particles; S3: the pretreated particles are added to a banbury mixer for blending, the temperature is 155°C, the rotation speed is 80 rpm, and the mixing time is 22 minutes, after the mixing is completed, the mixture is cooled and crushed, and then the mixture is passed through a 550-mesh screen to obtain the functional filler.

[0054] The average particle size of the kaolin is 620 nm, and the titanium dioxide is rutile titanium dioxide with an average particle size of 50 nm.

[0055] The PP wax is a product of CS-52NC type purchased from Shanghai Hongzhuang Chemical Technology Co., Ltd.

[0056] The antioxidant is a combination of antioxidant 1076 and antioxidant DSTDP, and the mass ratio of the two is 3.3:1.2.

[0057] The auxiliary agent is a combination of ethoxylated fatty acid amine and polyethylene glycol ester, and the mass ratio of the two is 4:1.8.

[0058] The light stabilizer is a combination of light stabilizer 770 and light stabilizer 622, and the mass ratio of the two is 2.1:0.9.

[0059] The lubricant is a combination of zinc stearate and ethylene bis-stearamide, and the mass ratio of the two is 5.8:2.2.

[0060] The ultraviolet absorber is UV-P of benzotriazole type, the nucleating agent is Millad NX8000 of sorbitol type, and the toughening agent is polyolefin elastomer POE, which is a product of Engage 8180 type purchased from Dow Chemical.

[0061] A preparation method of a high-strength yellowing-resistant plastic based on modified polypropylene, specifically comprising the following steps: S1: a modified polypropylene matrix, a functional filler, and a toughening agent are mixed in a high-speed mixer, the mixing temperature is 90°C, the mixing rotation speed is 1000 rpm, the mixing time is 21 minutes, after the mixing is completed, the remaining raw materials are added and high-speed mixing is continued for 12 minutes, and then a blend is obtained; S2: the blend is melt-extruded through a twin-screw extruder, the temperature of the melt-extrusion is 175°C in the first zone, 195°C in the second zone, and 205°C in the third zone, the screw rotation speed is 300 rpm, and the vacuum degree is -0.08 MPa; S3: after the melt-extrusion, an injection mold is added, the barrel temperature is 210°C, the mold temperature is 50°C, and the holding pressure is 75 MPa, and then the preparation is completed.

[0062] Example 2

[0063] The only difference between this example and Example 1 is that the high-strength yellowing-resistant plastic based on modified polypropylene has the following raw materials in parts by mass: modified polypropylene base 78 parts, functional filler 16 parts, antioxidant 1.1 parts, auxiliary agent 0.3 parts, light stabilizer 0.7 parts, ultraviolet absorber 0.5 parts, nucleating agent 1 part, lubricant 2.2 parts, and toughening agent 4.2 parts.

[0064] The antioxidant is a combination of antioxidant 1076 and antioxidant DSTDP in a mass ratio of 4:1.

[0065] The auxiliary agent is a combination of ethoxylated fatty acid amine and polyethylene glycol ester in a mass ratio of 5:2.

[0066] The light stabilizer is a combination of light stabilizer 770 and light stabilizer 622 in a mass ratio of 2.5:0.8.

[0067] The lubricant is a combination of zinc stearate and ethylene bis-stearamide in a mass ratio of 6.5:2.

[0068] Example 3

[0069] The only difference between this example and Example 1 is that the high-strength yellowing-resistant plastic based on modified polypropylene has the following raw materials in parts by mass: modified polypropylene base 70 parts, functional filler 22 parts, antioxidant 1 part, auxiliary agent 0.5 parts, light stabilizer 0.6 parts, ultraviolet absorber 0.6 parts, nucleating agent 1.2 parts, lubricant 2.8 parts, and toughening agent 5 parts.

[0070] The antioxidant is a combination of antioxidant 1076 and antioxidant DSTDP in a mass ratio of 3:1.4.

[0071] The auxiliary agent is a combination of ethoxylated fatty acid amine and polyethylene glycol ester in a mass ratio of 3:1.2.

[0072] The light stabilizer is a combination of light stabilizer 770 and light stabilizer 622 in a mass ratio of 2:1.2.

[0073] The lubricant is a combination of zinc stearate and ethylene bis-stearamide in a mass ratio of 5.5:2.4.

[0074] Comparative Example 1

[0075] The comparative example 1 and the example 1 only exist in the following differences: the raw materials of the high-strength yellowing-resistant plastic based on the modified polypropylene are as follows in mass parts: the modified polypropylene matrix 80.5 parts, functional filler 6.5 parts, antioxidant 1.2 parts, auxiliary agent 0.4 parts, light stabilizer 0.6 parts, ultraviolet absorber 0.5 parts, nucleating agent 0.9 parts, lubricant 1.2 parts, and toughening agent 4.9 parts.

[0076] Comparative example 2

[0077] The comparative example 1 and the example 1 only exist in the following differences: the raw materials of the high-strength yellowing-resistant plastic based on the modified polypropylene are as follows in mass parts: the modified polypropylene matrix 60.5 parts, functional filler 30 parts, antioxidant 1.2 parts, auxiliary agent 0.4 parts, light stabilizer 0.6 parts, ultraviolet absorber 0.5 parts, nucleating agent 0.9 parts, lubricant 2.4 parts, and toughening agent 4.9 parts.

[0078] Comparative example 3

[0079] The comparative example 1 and the example 1 only exist in the following differences: the modified polypropylene matrix is a functional grafting modified polypropylene resin, and the preparation method thereof specifically includes the following steps in mass parts: S1: 85 parts of homopolymerized polypropylene is pre-dried and mixed with 1.8 parts of glycidyl methacrylate, 1 part of 2-hydroxyethyl acrylate, and 0.05 parts of dicumyl peroxide at 85°C and a high-speed mixing speed of 1000 rpm for 20 min to obtain a premix; S2: the premix is extruded after being heated and stirred in a twin-screw extruder, with a temperature of 165°C in the first zone, 180°C in the second zone, and 195°C in the third zone, a screw speed of 240 rpm, and a vacuum devolatilization under -0.06 MPa, and then water-cooled and granulated to obtain the product.

[0080] Comparative example 4

[0081] The comparative example 1 and the example 1 only exist in the following differences: the functional filler is a composite modified particle of kaolin and titanium dioxide, and the preparation method thereof specifically includes the following steps in mass parts: S1: 10 parts of kaolin and 5 parts of titanium dioxide are dry-mixed, and then 1.5 parts of PP wax is added to obtain blended particles; S2: 13.6 parts of the blended particles are added to 140 parts of a toluene solvent, and then 0.55 parts of zinc nitrate and 0.92 parts of dimethyl imidazole are added, and the mixture is heated to 65°C for 4.5 h of reaction, after which the excess solvent is removed, and the product is washed and dried to obtain pretreated particles; S3: the pretreated particles are blended in an internal mixer, with a temperature of 155°C, a speed of 80 rpm, and a mixing time of 22 min, and then the product is cooled and broken into pieces after mixing is completed, and then the product is sieved through a 550-mesh sieve to obtain the product.

[0082] Comparative example 5

[0083] The comparative example and example 1 only exist in the following differences: the functional filler is a composite modified particle of kaolin and titanium dioxide, and the preparation method thereof, specifically comprising the following steps: S1: 7 parts of kaolin and 3 parts of titanium dioxide are dry mixed, then 2 parts of PP wax is added to obtain blended particles; S2: 20 parts of blended particles are added to 180 parts of toluene solvent, then 0.25 parts of zinc nitrate and 0.55 parts of dimethyl imidazole are added, and the mixture is heated to 65°C for 4.5h. After the reaction is completed, the excess solvent is removed, and then washed and dried to obtain pretreated particles; S3: the pretreated particles are added to a mixing machine and blended, the temperature is 155°C, the rotation speed is 80 rpm, and the mixing time is 22 min. After mixing is completed, it is cooled and broken, and then passed through a 550 mesh sieve to obtain the product.

[0084] Comparative example 6

[0085] The comparative example and example 1 only exist in the following differences: the average particle size of kaolin is 1200 nm; and the titanium dioxide is rutile titanium dioxide, and the average particle size thereof is 110 nm.

[0086] Performance evaluation

[0087] 1. The tensile strength and bending strength of the polypropylene plastic prepared in the examples and comparative examples were tested, and the test results were taken as the average of 10 tests to enter Table 1, according to the standard ASTM D638 / D790.

[0088] 2. The accelerated yellowing resistance aging test of the polypropylene plastic prepared in the examples and comparative examples was carried out, and the test results were taken as the average of 10 tests to enter Table 1, according to the standards ASTM G154 and ASTM E313, the cycle period was 8h light (UVA-340 lamp, 60°C) + 4h cooling (45°C), the total test time was 500h, and the ΔYI value before and after the test was calculated after 500h, and the test results were taken as the average of 10 tests to enter Table 1.

[0089] 3. The waterproof and moisture resistance test of the polypropylene plastic prepared in the examples and comparative examples was carried out, and the test results were taken as the average of 10 tests to enter Table 1, according to the standard ASTM D570.

[0090] Table 1 Performance evaluation results

[0091]

[0092] From the final performance test results of the examples and comparative examples, comparative examples 1-6 achieved worse performance results relative to the examples, while the examples prepared more excellent plastic internal systems because the correct technical solutions were adopted, the interface bonding force was greatly improved through better functional grafting modification of the polypropylene resin and the mutual connectivity and interface force of the composite modified particles, the system strength was enhanced, the overall hydrolysis resistance was enhanced through the mutual reaction of the grafted molecular chain segments and the surface hydroxyl groups, the occupation of the surface hydroxyl groups of the particles avoided excessive attraction of the particles to water molecules in actual operation, and the active oxygen production of the composite particles was effectively reduced, thereby comprehensively improving the overall performance, avoiding the performance contradiction between the yellowing resistance and the mechanical properties, and on the other hand, the examples could obtain better internal molecular chain three-dimensional networks and smaller surface micropore diameters, the specific surface area was reduced, the adsorption of oxygen and more water was reduced, and the overall performance was further improved.

Claims

1. A high-strength, yellowing-resistant plastic based on modified polypropylene, characterized in that: The raw materials are: 65~85 parts of modified polypropylene matrix, 15~25 parts of functional filler, 0.5~1.5 parts of antioxidant, 0.3~0.5 parts of auxiliary agent, 0.5~1.2 parts of light stabilizer, 0.4~1 part of ultraviolet absorber, 0.8~1.5 parts of nucleating agent, 2~3 parts of lubricant, and 4~8 parts of toughening agent, all by mass fraction. The modified polypropylene matrix is a functionally grafted modified polypropylene resin, and the preparation method specifically comprises the following steps: S1: uniformly polypropylene is pre-dried and mixed with glycidyl methacrylate, 2-hydroxyethyl acrylate and dicumyl peroxide at a speed of 80~85℃ and 1000~1200rpm for 15~20min to obtain a premix; S2: the premix is extruded after heating and stirring in a twin-screw extruder, the temperature is 160~170℃ in the first zone, 175~180℃ in the second zone, and 190~195℃ in the third zone, the screw speed is 200~250rpm, and the vacuum devolatilization is carried out under-0.06~-0.04MPa, and then water cooling and granulation are carried out to obtain the product. The functional filler is a composite modified particle of kaolin and titanium dioxide. The preparation method of the composite modified particle of kaolin and titanium dioxide specifically comprises the following steps: S1: kaolin and titanium dioxide are dry mixed, and then PP wax is added to obtain a blended particle; S2: the blended particle is added to toluene solvent, and then zinc nitrate and dimethyl imidazole are added, and the mixture is heated to 65~70℃ for 4~5h, after the reaction is completed, the excess solvent is removed, and then washed and dried to obtain a pretreated particle; S3: the pretreated particle is added to a banbury mixer for blending, the temperature is 150~160℃, the speed is 60~80rpm, and the mixing time is 20~30min, after mixing is completed, cooling and crushing are carried out, and then the product is obtained by passing through a 500~600 mesh screen. The mass ratio of kaolin, titanium dioxide and PP wax is (6~7):(3~4):(1.8~2.2). The mass ratio of the blended particle, zinc nitrate and dimethyl imidazole is (12~14):(0.5~0.6):(0.8~1).

2. The high-strength, yellowing-resistant plastic based on modified polypropylene according to claim 1, characterized in that: The mass ratio of the modified polypropylene matrix, the functional filler and the toughening agent is (70~78):(16~22):(4~6).

3. The high-strength, yellowing-resistant plastic based on modified polypropylene according to claim 2, characterized in that: The melt index of the homopolymer polypropylene is 20~22g / 10min, and the conditions are 230℃ and 2.16kg; the mass ratio of the homopolymer polypropylene, glycidyl methacrylate and 2-hydroxyethyl acrylate is (48~54):(3.5~5):(2~3).

4. The high-strength, yellowing-resistant plastic based on modified polypropylene according to claim 3, characterized in that: The antioxidant is a combination of antioxidant 1076 and antioxidant DSTDP, and the mass ratio of the two is (3~4):(1~1.5); the light stabilizer is a combination of light stabilizer 770 and light stabilizer 622, and the mass ratio of the two is (2~2.5):(0.8~1.2).

5. The high-strength, yellowing-resistant plastic based on modified polypropylene according to claim 4, characterized in that: The average particle size of the kaolin is 600~800nm, and / or the titanium dioxide is rutile titanium dioxide, and the average particle size is 40~50nm.

6. The high-strength, yellowing-resistant plastic based on modified polypropylene according to claim 5, characterized in that: The ultraviolet absorber is at least one of benzotriazole, benzophenone, triazine and cyanoacrylate, and / or the nucleating agent is at least one of sorbitol, organic phosphate, carboxylate and arylamide.

7. The high-strength, yellowing-resistant plastic based on modified polypropylene according to claim 6, characterized in that: The lubricant is a combination of zinc stearate and ethylene bis-stearamide, and the mass ratio of the two is (5.5-6.5):(2-2.4).

8. A process for the preparation of a high-strength, yellowing-resistant plastic based on modified polypropylene according to any one of claims 1 to 7, characterized in that: Specifically comprising the following steps: S1: mixing the modified polypropylene matrix, functional filler and toughening agent in a high-speed mixer, the mixing temperature is 85-90℃, the mixing speed is 1000-1200rpm, the mixing time is 20-25min, after mixing, the remaining raw materials are added and high-speed mixing is continued for 10-15min, and then the blending is completed; S2: melting and extruding the blending through a double-screw extruder; S3: after melting and extruding, the blending is added into an injection mold, the barrel temperature is 200-215℃, the mold temperature is 45-50℃, the holding pressure is 70-75MPa, and then the process is completed.

9. Application of the high-strength yellowing-resistant plastic based on modified polypropylene according to any one of claims 1-7 in daily plastic products, automotive plastic products and plastic housings / parts of household appliances.

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