Polypropylene wear-resistant additive as well as preparation method and application thereof

Abstract

The invention relates to the technical field of polymer materials, in particular to a polypropylene wear-resistant additive as well as a preparation method and application thereof. The polypropylene wear-resistant additive is a graft modifier of high-molecular-weight polysiloxane, the high-molecular-weight polysiloxane is high-molecular-weight polysiloxane nanoparticles with reserved grafting points, and a monomer used for graft modification is a monomer with good compatibility with polypropylene. The polypropylene wear-resistant additive is convenient to use, the compatibility and dispersity in polypropylene are remarkably improved, nanoscale dispersion is easily formed in the polypropylene, and the wear resistance of the polypropylene can be remarkably improved under the condition that the addition amount is small.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, in particular to a polypropylene wear-resistant additive and a preparation method and application thereof. Background Art

[0002] Polypropylene is a key component of general-purpose plastics, with annual consumption second only to polyethylene. In 2023, domestic consumption in China was approximately 34 million tons. Polypropylene, which includes homopolymers and copolymers, is characterized by its excellent heat and chemical resistance and is commonly used in automotive parts, home appliances, and fiber products.

[0003] However, compared to wear-resistant polymers such as nylon, polypropylene has weaker inter-chain forces, resulting in lower strength and stiffness. This makes its wear resistance significantly insufficient in many applications. Therefore, it is often necessary to add wear-resistant additives to polypropylene to improve its wear resistance.

[0004] Adding polytetrafluoroethylene (PTFE) powder to polypropylene can improve wear resistance. However, since polytetrafluoroethylene is a perfluoro / polyfluoroalkyl substance (PFAS), the CF bond of PFAS is extremely difficult to degrade and can accumulate in the environment and organisms for a long time, polluting water sources and soil. This has led to rising calls for a global ban on fluorine, and the trend of restricting the use of fluorine-based substances is becoming increasingly obvious.

[0005] Polysiloxanes, as wear-resistant additives for polypropylene, are not subject to the above restrictions. Lower molecular weight polysiloxanes have low viscosity, good fluidity, and are easy to use. They also have low equipment and process requirements, making them relatively easy to add to polypropylene. However, they do not improve the wear resistance of polypropylene as well as higher molecular weight polysiloxanes. Furthermore, due to differences in polarity and their high fluidity, they tend to precipitate from the polypropylene, causing the surface of the product to become sticky and the wear resistance to decrease over time. High molecular weight polysiloxanes can improve the wear resistance of polypropylene with minimal or no precipitation. However, due to their high viscosity and lack of fluidity, their addition to polypropylene is difficult, placing high demands on equipment and process, and can easily lead to significant fluctuations in wear resistance between product batches. Furthermore, due to the polarity difference between polysiloxane and polypropylene, their improvement in wear resistance is limited and cannot be compared to PTFE.

[0006] Therefore, there is an urgent need to develop a fluorine-free polypropylene nano-wear-resistant additive that has good dispersibility in polypropylene and long-lasting wear resistance. Summary of the Invention

[0007] In view of the shortcomings of the prior art described above, the present invention aims to provide a polypropylene wear-resistant additive, its preparation method, and its use. The polypropylene wear-resistant additive described in this application solves the problems of the prior art, such as the difficulty in reducing the C-F bonds in polytetrafluoroethylene, which is environmentally unfriendly, and the inability of conventional polysiloxanes to achieve a balance between wear resistance, dispersibility, and usability.

[0008] To achieve the above objectives and other related objectives, the present invention is achieved through the following technical solutions.

[0009] The first aspect of the present invention discloses a polypropylene wear-resistant additive, which is a grafted modified product of high molecular weight polysiloxane. The high molecular weight polysiloxane is a high molecular weight polysiloxane nanoparticle with reserved grafting points. The monomer used for the grafting modification is a monomer with good compatibility with polypropylene.

[0010] Preferably, the raw material components of the polypropylene wear-resistant additive include: high molecular weight polysiloxane nanoparticles and monomers with good compatibility with polypropylene.

[0011] Preferably, the particle size of the high molecular weight polysiloxane nanoparticles is 5 to 500 nm, and the viscosity at 25° C. is greater than 2 million mPa·s.

[0012] More preferably, the particle size of the high molecular weight polysiloxane nanoparticles is 50 to 500 nm. For example, the particle size of the high molecular weight polysiloxane nanoparticles can be 50 to 100 nm, 100 to 150 nm, 150 to 200 nm, 200 to 250 nm, 250 to 300 nm, 300 to 350 nm, 350 to 400 nm, 400 to 450 nm, or 450 to 500 nm. In a specific embodiment, the particle size of the high molecular weight polysiloxane nanoparticles is 150 to 300 nm.

[0013] More preferably, the viscosity of the high molecular weight polysiloxane nanoparticles at 25°C is 5 million to 15 million mPa.s. Furthermore, the viscosity of the high molecular weight polysiloxane nanoparticles at 25°C is 5 million to 10 million mPa.s. For example, the viscosity of the high molecular weight polysiloxane nanoparticles at 25°C is 5 million to 6 million mPa.s, 6 million to 7 million mPa.s, 7 million to 8 million mPa.s, 8 million to 9 million mPa.s, or 9 million to 10 million mPa.s. In a specific embodiment, the viscosity of the high molecular weight polysiloxane nanoparticles at 25°C is 7 million to 10 million mPa.s.

[0014] Preferably, the monomer having good compatibility with polypropylene is acrylate, especially methacrylate.

[0015] More preferably, the monomer having good compatibility with polypropylene is selected from one or more of n-hexyl methacrylate, isobornyl methacrylate, 3,3,5-trimethylcyclohexanol methacrylate, benzyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, n-decyl methacrylate, isodecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, hexadecyl methacrylate, heptadecyl methacrylate, octadecyl methacrylate, eicosyl methacrylate, behenyl methacrylate, neopentyl glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol dimethacrylate, and 1,6-hexanediol dimethacrylate.

[0016] Furthermore, the monomer having good compatibility with polypropylene is selected from one or more of octadecyl methacrylate, eicosyl methacrylate, behenyl methacrylate, 1,4-butanediol dimethacrylate, and 1,6-hexanediol dimethacrylate. The monomer having good compatibility with polypropylene is low in cost, readily available, and has a suitable long-chain alkyl length.

[0017] Preferably, the amount of the monomer having good compatibility with polypropylene is 0.1 to 95 wt % based on the mass of the high molecular weight polysiloxane. More preferably, the amount of the monomer having good compatibility with polypropylene is 1 to 60 wt %. For example, the amount of the monomer having good compatibility with polypropylene can be 1 to 3 wt %, 3 to 15 wt %, 15 to 25 wt %, 25 to 35 wt %, 35 to 45 wt %, or 45 to 60 wt %. In a specific embodiment, the amount of the monomer having good compatibility with polypropylene is 3 to 45 wt %.

[0018] Preferably, the high molecular weight polysiloxane nanoparticles are obtained by emulsion polymerization of low molecular weight polysiloxane and silane containing unsaturated groups.

[0019] More preferably, the unsaturated group in the unsaturated group-containing silane is selected from one or more of vinyl and methacryloxy groups.

[0020] Furthermore, the silane containing an unsaturated group is selected from vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri-(2-methoxyethoxy)-silane, vinyltriisopropoxysilane, vinylmethylbis(trimethylsiloxy)silane, 3-(methacryloyloxy)propylmethyldimethoxysilane, 3-(methacryloyloxy)propylmethyldiethoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane, 3-(methacryloyloxy)propyltriethoxysilane, 3-(methacryloyloxy)propyl One or more of 3-(acryloyloxy)propyltriisopropoxysilane, 3-(acryloyloxy)propyltrimethoxysilane, 3-(acryloyloxy)propyltriethoxysilane, 3-(acryloyloxy)propylmethyldimethoxysilane, 3-(acryloyloxy)propylmethyldiethoxysilane, 3-(acryloyloxy)propylmethyldiisopropoxysilane, (4-vinylphenyl)trimethoxysilane, (4-vinylphenyl)triethoxysilane, (4-vinylphenyl)methyldimethoxysilane, (4-vinylphenyl)methyldiethoxysilane, styreneethyltrimethoxysilane, and styreneethyltriethoxysilane.

[0021] Furthermore, the unsaturated group-containing silane is selected from diethoxysilanes, including one or more of vinylmethyldiethoxysilane and 3-(methacryloyloxy)propylmethyldiethoxysilane. Diethoxysilanes themselves do not crosslink, which facilitates molecular weight growth, and hydrolysis does not produce harmful substances, which is beneficial to the environment and the health of manufacturers. Vinylmethyldiethoxysilane and 3-(methacryloyloxy)propylmethyldiethoxysilane are relatively low-cost and readily available.

[0022] More preferably, the amount of the silane containing an unsaturated group is 0.01 wt% to 30 wt% based on the mass of the low molecular weight polysiloxane. For example, the amount of the silane containing an unsaturated group can be 0.1 to 0.5 wt%, 0.5 to 1 wt%, 1 to 5 wt%, 5 to 10 wt%, 10 to 20 wt%, or 20 to 30 wt%. In a specific embodiment, the amount of the silane containing an unsaturated group is 0.5 to 10 wt%.

[0023] More preferably, the low molecular weight polysiloxane is selected from one or more of dihydroxyl-terminated polysiloxane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and dodecamethylcyclohexasiloxane. In one specific embodiment, the viscosity of the dihydroxyl-terminated polysiloxane at 25°C is less than 5000 mPa·s. More preferably, the viscosity of the dihydroxyl-terminated polysiloxane at 25°C is between 20 and 130 mPa·s. In one specific embodiment, the low molecular weight polysiloxane is one or more of dihydroxyl-terminated polysiloxane and / or octamethylcyclotetrasiloxane. Dihydroxyl-terminated polysiloxane and octamethylcyclotetrasiloxane are readily available, highly reactive, and economical. Their low viscosity makes it easy to obtain small-sized, high-molecular-weight polysiloxane nanoparticles.

[0024] The second aspect of the present invention discloses a method for preparing the polypropylene wear-resistant additive as described above, comprising the following steps: grafting reaction between high molecular weight polysiloxane nanoparticles with reserved grafting points and a monomer having good compatibility with polypropylene.

[0025] Preferably, the high molecular weight polysiloxane nanoparticles are prepared by polymerization of low molecular weight polysiloxane and silane containing unsaturated groups.

[0026] More preferably, the polymerization method of the polymerization reaction is selected from one or more of anionic emulsion polymerization and cationic emulsion polymerization.

[0027] The emulsifier for anionic emulsion polymerization is a negatively charged hydrophilic group, such as sulfonic acid group - SO3 - , carboxylic acid group—COO - , sulfate group—OSO3 - . Furthermore, the emulsifier for the anionic emulsion polymerization is selected from one or more of sodium dodecyl sulfate, sodium dodecyl sulfonate, dodecyl sulfonic acid, sodium dodecylbenzenesulfonate, dodecylbenzenesulfonic acid, dodecyl-p-toluenesulfonic acid, sodium dodecyl-p-toluenesulfonate or sodium stearate. Most preferably, the emulsifier for the anionic emulsion polymerization is selected from one or more of sodium dodecyl sulfate and dodecylbenzenesulfonic acid. The catalyst can be selected from sulfuric acid, hydrochloric acid, nitric acid, p-toluenesulfonic acid, and trifluoromethanesulfonic acid. Dodecylbenzenesulfonic acid, which itself has an emulsifying function, is preferred.

[0028] Cationic emulsion polymerization emulsifiers are selected with positively charged hydrophilic groups, such as quaternary ammonium salts - NR4 + , amine salt—NH3 +. Further, the emulsifier for the cationic emulsion polymerization is selected from hexadecyltrimethylammonium bromide, dodecyldimethylbenzylammonium chloride, and tri(dodecyl)methylammonium hydroxide. More preferably, the tri(dodecyl)methylammonium hydroxide is obtained by exchanging tri(dodecyl)methylammonium chloride with a quaternary amine type I ion exchange resin. Most preferably, the emulsifier for the cationic emulsion polymerization is tri(dodecyl)methylammonium hydroxide.

[0029] More preferably, the polymerization reaction includes a first-stage polymerization and a second-stage polymerization; the first-stage polymerization involves particle size control through shearing and emulsification, and the second-stage polymerization involves chain growth at low temperature. The first-stage shearing and emulsification particle size control involves dispersing the unsaturated group-containing silane, low molecular weight polysiloxane, and anionic or cationic emulsifier in water, and then shearing and emulsifying to obtain an organosilicon emulsion; the second-stage polymerization involves further polycondensation of the first-stage emulsion to obtain high molecular weight polysiloxane nanoparticles.

[0030] Furthermore, the temperature of the first stage shearing and emulsification is 1-100°C.

[0031] Furthermore, the first stage of shearing and emulsification is carried out at room temperature.

[0032] Furthermore, the temperature of the second stage polymerization is 1-25°C.

[0033] Furthermore, the temperature of the second stage polymerization is 1-15°C. For example, the temperature of the second stage polymerization can be 1-3°C, 3-5°C, 5-7°C, 7-9°C, 9-10°C, 12-14°C, or 14-15°C. In a specific embodiment, the temperature of the second stage polymerization is 5-10°C. The temperature of the second stage polymerization is both energy-saving and sufficient for molecular weight growth.

[0034] Furthermore, the time of the second stage polymerization is 2 to 300 hours. Further, the time of the second stage polymerization is 2 to 300 hours. For example, the time of the second stage polymerization can be 2 to 12 hours, 12 to 24 hours, 24 to 48 hours, 48 ​​to 96 hours, 96 to 120 hours, 120 to 150 hours, 150 to 200 hours, 200 to 250 hours, or 250 to 300 hours. In a specific embodiment, the time of the second stage polymerization is 24 to 96 hours. The time of the second stage polymerization meets the actual needs of production efficiency, energy conservation, and degree of polymerization.

[0035] Furthermore, the shearing and emulsification treatment is performed until the particle size of the silicone emulsion is 5 to 500 nm.

[0036] Furthermore, the shear treatment equipment includes one or more of a high-pressure homogenizer, a colloid mill, a high-shear emulsifier, and an ultrasonic emulsifier;

[0037] Preferably, the grafting reaction is a free radical reaction, and the initiation method is selected from one or more of high-energy ray source irradiation, persulfate initiator, oxidation-reduction initiation system, azo initiator, and thermal initiation.

[0038] More preferably, the initiation method is an oxidation-reduction initiation system, which has better economy, effectiveness, safety and degree of reaction completion.

[0039] More preferably, the amount of the initiator is 0.001-30 wt% of the mass of the monomer having good compatibility with polypropylene. For example, the amount of the initiator can be 0.001-0.01 wt%, 0.01-0.1 wt%, 0.1-5 wt%, 5-10 wt%, 10-15 wt%, 15-20 wt%, 20-25 wt%, or 25-30 wt%. In a specific embodiment, the amount of the initiator is 0.1-10 wt%.

[0040] More preferably, the high-energy ray source irradiation is selected from one or more of a cobalt source, X-rays, ultraviolet rays, and a high-energy electron accelerator. In a specific embodiment, the high-energy ray source irradiation is a cobalt source irradiation.

[0041] Furthermore, the irradiation dose range of the high-energy ray source is 0.1 to 30 Mrad. For example, the irradiation dose range of the high-energy ray source is 0.1 to 1 Mrad, 1 to 5 Mrad, 5 to 10 Mrad, 10 to 15 Mrad, 15 to 20 Mrad, 20 to 25 Mrad, or 25 to 30 Mrad. In a specific embodiment, the irradiation dose range of the high-energy ray source is 1 to 10 Mrad.

[0042] More preferably, the persulfate initiator is selected from one or more of potassium persulfate, sodium persulfate, and ammonium persulfate.

[0043] More preferably, the amount of the persulfate initiator added is 0.001-30wt% based on the weight of the monomer having good compatibility with polypropylene. For example, the amount of the persulfate initiator added can be 0.001-0.01wt%, 0.01-0.1wt%, 0.1-5wt%, 5-10wt%, 10-15wt%, 15-20wt%, 20-25wt%, or 25-30wt%. In a specific embodiment, the amount of the persulfate initiator added is 0.1-10wt%.

[0044] More preferably, the azo initiator is selected from one or more of azobisisobutylnitrile, azobisisoheptonitrile, azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobiscyanovaleric acid, and azobisisopropylimidazoline.

[0045] More preferably, the amount of the water-soluble azo initiator added is 0.001 wt% to 30 wt% based on the mass of the monomer having good compatibility with polypropylene. For example, the amount of the water-soluble azo initiator added can be 0.001 to 0.01 wt%, 0.01 to 0.1 wt%, 0.1 to 5 wt%, 5 to 10 wt%, 10 to 15 wt%, 15 to 20 wt%, 20 to 25 wt%, or 25 to 30 wt%. In a specific embodiment, the amount of the water-soluble azo initiator added is 0.1 to 10 wt%.

[0046] More preferably, the initiator of the redox initiation system is selected from one or more of ammonium persulfate-sodium bisulfite, potassium persulfate-sodium bisulfite, ammonium persulfate-ferrous sulfate, hydrogen peroxide-ferrous sulfate, ammonium persulfate-ferrous chloride, hydrogen peroxide-ferrous chloride, potassium persulfate-silver nitrate, persulfate-thiol, tert-butyl hydroperoxide-rongalite, isopropyl benzene hydroperoxide-rongalite, diisopropyl benzene hydroperoxide-rongalite, and isopropyl benzene hydroperoxide-FF6M.

[0047] Furthermore, the initiator of the redox initiation system is selected from cumene hydroperoxide-rongalite, ammonium persulfate-sodium bisulfite, tert-butyl hydroperoxide-rongalite, and cumene hydroperoxide-FF6M. FF6M is a sodium salt of an organic sulfinic acid derivative produced by Bruggemann, Germany.

[0048] More preferably, the amount of the initiator added to the redox initiation system is 0.001 wt% to 30 wt% based on the weight of the monomer having good compatibility with polypropylene. For example, the amount of the initiator added to the redox initiation system can be 0.001 to 0.01 wt%, 0.01 to 0.1 wt%, 0.1 to 0.5 wt%, 0.5 to 2 wt%, 2 to 5 wt%, 5 to 15 wt%, 15 to 25 wt%, or 25 to 30 wt%. In a specific embodiment, the amount of the initiator added to the redox initiation system is 0.5 to 5 wt%.

[0049] More preferably, the thermal initiation temperature is 30°C to 100°C.

[0050] Furthermore, the thermal initiation temperature is 50° C. to 95° C. For example, the thermal initiation temperature can be 50° C. to 55° C., 55° C. to 60° C., 60° C. to 65° C., 65° C. to 70° C., 70° C. to 75° C., 75° C. to 80° C., 80° C. to 85° C., 85° C. to 90° C., or 90° C. to 95° C. In a specific embodiment, the thermal initiation temperature is 60° C. to 90° C.

[0051] More preferably, before the grafting reaction, the step of dispersing the high molecular weight polysiloxane nanoparticles in a medium and deoxygenating the medium is further included. The deoxygenation eliminates oxygen inhibition and improves polymerization efficiency. In a specific embodiment, the medium is water.

[0052] More preferably, when the monomer having good compatibility with polypropylene includes a polymerization inhibitor, the step of removing the polymerization inhibitor from the monomer having good compatibility with polypropylene is further included before the grafting reaction.

[0053] More preferably, the grafting reaction further comprises the step of adding a chain transfer agent. Further, the chain transfer agent is selected from one or more of n-dodecyl mercaptan, tert-dodecyl mercaptan, thioglycolate, thioglycerol, thiophenol, thiosalicylic acid, etc.

[0054] More preferably, the grafting reaction further includes the steps of solid-liquid separation and drying.

[0055] Furthermore, the drying method is selected from one or more of freeze drying, spray drying, flash drying, fluidized bed drying, microwave drying, and vacuum drying.

[0056] More preferably, after the grafting reaction and before the solid-liquid separation, a flocculation step is further included, wherein the flocculant used in the flocculation is one or more selected from calcium chloride, calcium acetate, magnesium sulfate, and aluminum sulfate. The flocculation reduces the loss of the product during the filtration process.

[0057] The third aspect of the present invention further discloses the use of the polypropylene wear-resistant additive described above in improving the wear resistance of polypropylene.

[0058] The fourth aspect of the present invention further discloses a wear-resistant polypropylene composition, wherein the raw materials of the wear-resistant polypropylene composition include the polypropylene wear-resistant additive according to any one of claims 1 to 3 and polypropylene.

[0059] Preferably, the raw materials further include an antioxidant, which can prevent polypropylene from being oxidatively degraded and yellowing during processing.

[0060] More preferably, the antioxidant comprises one or both of a primary antioxidant and a secondary antioxidant. In a specific embodiment, the primary antioxidant is selected from one or more of antioxidant 1010 and antioxidant 1076. In a specific embodiment, the secondary antioxidant is selected from one or more of antioxidant 168 and antioxidant 398.

[0061] More preferably, the antioxidant is added in an amount of 0.1 to 1 wt % based on the mass of the polypropylene.

[0062] Preferably, based on the total weight of the polypropylene wear-resistant additive and the polypropylene, the content of the polypropylene wear-resistant additive is 0.1-10 wt%, such as 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, or 10 wt%.

[0063] More preferably, the content of the polypropylene wear-resistant additive is 0.3-5.0 wt%. For example, the content of the polypropylene wear-resistant additive can be 0.3-0.5 wt%, 0.5-1.0 wt%, 1.0-2.0 wt%, 2.0-3.0 wt%, 3.0-4.0 wt%, or 4.0-5.0 wt%. In a specific embodiment, the content of the polypropylene wear-resistant additive is 0.5-3.0 wt%.

[0064] Preferably, the polypropylene is selected from one or more of homopolypropylene and copolymer polypropylene.

[0065] The fifth aspect of the present application further discloses a method for preparing the wear-resistant polypropylene composition as described above, the preparation method comprising the following steps: adding the polypropylene wear-resistant additive as described above into molten polypropylene and dispersing the mixture.

[0066] Preferably, the polypropylene wear-resistant additive is added into the molten polypropylene through a twin-screw extruder and / or an internal mixer and dispersed.

[0067] Compared with the prior art, the present invention has the following beneficial effects:

[0068] The polypropylene wear-resistant additive disclosed in the present application is more convenient to use than ungrafted high-viscosity, high-molecular-weight polysiloxanes, and has significantly improved compatibility and dispersibility in polypropylene; it effectively solves the problems of poor wear resistance and weak durability of low-molecular-weight polysiloxanes; and the difficulty in adding ungrafted high-molecular-weight polysiloxanes, limited improvement in wear resistance, and large fluctuations in wear resistance between product batches. In addition, due to the grafting of monomers with good compatibility with polypropylene, the polypropylene wear-resistant additive has good compatibility with polypropylene, is easy to form nano-scale dispersion in polypropylene, and can significantly improve the wear resistance of polypropylene with a relatively small addition amount. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 Shown is a photograph of the appearance of three wear-resistant discs before grinding, which is the average value in Application Example 1 of this application.

[0070] Figure 2 Shown is a photograph of the appearance of three wear-resistant discs after grinding, which is the average value of the wear-resistant discs in Application Example 1 of this application.

[0071] Figure 3 The figure shows a scanning electron microscope image of a cross-section of a high-viscosity polysiloxane (HV PDMS) and an antioxidant in Application Example 5 of the present application, extruded into a PP S1003 strip through a twin-screw extruder, and then frozen in liquid nitrogen and broken.

[0072] Figure 4 Shown is a scanning electron microscope photograph of a cross-section formed by adding the anti-wear agent #3 and antioxidant in Application Example 3 of this application to PPS1003 extruded strips through a twin-screw extruder, freezing them with liquid nitrogen, and then breaking them. DETAILED DESCRIPTION

[0073] The following describes the implementation of the present invention through specific embodiments. People skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0074] Before further describing the specific embodiments of the present invention, it should be understood that the scope of the present invention is not limited to the specific embodiments described below. It should also be understood that the terminology used in the examples is intended to describe specific embodiments and is not intended to limit the scope of the present invention. The experimental procedures in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0075] When the embodiments provide numerical ranges, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range and any numerical value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those generally understood by those skilled in the art. In addition to the specific methods, equipment, and materials used in the embodiments, according to the understanding of the prior art by those skilled in the art and the description of the present invention, any methods, equipment, and materials of the prior art similar or equivalent to the methods, equipment, and materials described in the embodiments of the present invention may also be used to implement the present invention.

[0076] In this application, the applicant addresses the technical issues of existing fluorine-free polypropylene wear-resistant additives, such as low-molecular-weight polysiloxanes with poor wear resistance and weak durability, and high-molecular-weight polysiloxanes that are difficult to add, resulting in limited wear resistance improvements and large fluctuations in wear resistance between product batches. The applicant provides a polypropylene wear-resistant additive, its preparation method, and its use. The polypropylene wear-resistant additive described in this application is easy to use, significantly improves compatibility and dispersibility in polypropylene, easily forms nanoscale dispersions in polypropylene, and can significantly improve the wear resistance of polypropylene with a relatively small addition amount.

[0077] Specifically, embodiments of the present invention provide a specific polypropylene wear-resistant additive and a method for preparing the same. The polypropylene wear-resistant additive comprises a grafted modified product of a high molecular weight polysiloxane, wherein the high molecular weight polysiloxane is a high molecular weight polysiloxane nanoparticle with reserved grafting points, and the grafted modified product is a monomer that exhibits good compatibility with polypropylene. In other words, the raw material components of the polypropylene wear-resistant additive include high molecular weight polysiloxane nanoparticles and a monomer that exhibits good compatibility with polypropylene.

[0078] In the present application, during grafting, the reaction is a free radical reaction type.

[0079] In a more specific embodiment, when the amount of the grafted monomer is greater than 30 wt % based on the mass of the high molecular weight polysiloxane nanoparticles, a chain transfer agent may be used. The chain transfer agent is selected from one or more of n-dodecyl mercaptan, tert-dodecyl mercaptan, thioglycolate, thioglycerol, thiophenol, thiosalicylic acid, and the like. The amount used can be selected based on the specific circumstances of the free radical polymerization reaction. For example, based on the mass of the high molecular weight polysiloxane, the amount of the grafted monomer used can be 0.1 to 5 wt %, such as 0.1 to 1 wt %, 1 to 2 wt %, 2 to 3 wt %, 3 to 4 wt %, or 4 to 5 wt %.

[0080] In the present application, the high molecular weight polysiloxane is a nanoscale high molecular weight polysiloxane.

[0081] In one specific embodiment, the present application obtains high molecular weight polysiloxane nanoparticles through emulsion polymerization. In a more specific embodiment, the raw materials for the emulsion polymerization include: a low molecular weight polysiloxane, a silane containing an unsaturated group, and an emulsifier. In a more specific embodiment, the specific method for preparing the high molecular weight polysiloxane nanoparticles includes: 1) dispersing the raw materials for the emulsion polymerization in deionized water, completing a first stage of shearing and emulsification, and shearing the silicone emulsion to a predetermined particle size of 5 to 500 nm; 2) conducting a second stage of polymerization, further polycondensing at low temperature, and then neutralizing to terminate the polymerization reaction to obtain the high molecular weight polysiloxane nanoparticles.

[0082] In a more specific embodiment, the particle size of the final product in step 2) is determined by step 1); since the second stage polymerization is a condensation dehydration reaction of the terminal hydroxyl groups, to a certain extent, the particle size of the final product in step 2) is slightly smaller than that in step 1), but the change is not large.

[0083] In a more specific embodiment, the dispersion time in step 1) is 10 to 120 minutes. Preferably, the dispersion time is 20 to 60 minutes. For example, the dispersion time can be 20 to 30 minutes, 30 to 40 minutes, 40 to 50 minutes, or 50 to 60 minutes. Taking into account the dispersion effect and energy saving, the dispersion time in a specific embodiment is 30 minutes. It should be noted that the dispersion time can be adjusted according to the actual dispersion equipment and its power, as long as the effect of uniformly dispersing the raw materials for emulsion polymerization can be achieved, such as when the rotation speed is faster, the dispersion time is shorter; when the rotation speed is slower, the dispersion time is longer.

[0084] In a more specific embodiment, the low molecular weight polysiloxane in step 1) is selected from one or more of bihydroxyl-terminated polysiloxane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and dodecamethylcyclohexasiloxane. Preferably, the viscosity of the bihydroxyl-terminated polysiloxane at 25° C. is less than 5000 mPa.s. More preferably, the viscosity of the bihydroxyl-terminated polysiloxane at 25° C. is 20-130 mPa.s, such as 20-30 mPa.s, 30-40 mPa.s, 40-50 mPa.s, 50-60 mPa.s, 60-70 mPa.s, 70-80 mPa.s, 80-90 mPa.s, 90-100 mPa.s, 100-110 mPa.s, 110-120 mPa.s, or 120-130 mPa.s. Considering the availability, reactivity, and economy, as well as the low viscosity and easy acquisition of small particle size, in a specific embodiment, the low molecular weight polysiloxane is one or more of dihydroxyl-terminated polysiloxane and octamethylcyclotetrasiloxane. It should be noted that the dihydroxyl-terminated polysiloxane can be obtained by hydrolysis and ring-opening polymerization of hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and dodecamethylcyclohexasiloxane, and thus used as the raw material for dihydroxyl-terminated polysiloxane.

[0085] In a more specific embodiment, the silane unsaturated group containing an unsaturated group in step 1) is selected from one or more of vinyl and acryloxy groups.

[0086] Furthermore, the silane containing an unsaturated group is selected from vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri-(2-methoxyethoxy)-silane, vinyltriisopropoxysilane, vinylmethylbis(trimethylsiloxy)silane, 3-(methacryloyloxy)propylmethyldimethoxysilane, 3-(methacryloyloxy)propylmethyldiethoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane, 3-(methacryloyloxy)propyltriethoxysilane, 3-(methacryloyloxy)propyl The present invention can be used in combination with one or more of triisopropoxysilane, 3-(acryloyloxy)propyltrimethoxysilane, 3-(acryloyloxy)propyltriethoxysilane, 3-(acryloyloxy)propylmethyldimethoxysilane, 3-(acryloyloxy)propylmethyldiethoxysilane, 3-(acryloyloxy)propylmethyldiisopropoxysilane, (4-vinylphenyl)trimethoxysilane, (4-vinylphenyl)triethoxysilane, (4-vinylphenyl)methyldimethoxysilane, (4-vinylphenyl)methyldiethoxysilane, styreneethyltrimethoxysilane, and styreneethyltriethoxysilane. Considering that trialkoxysilanes can produce crosslinking, which is not conducive to the growth of molecular weight; and that methoxysilanes can produce methanol upon hydrolysis, which is not conducive to the environment and the health of producers, ethoxysilanes are preferred; and considering cost and availability, one or a mixture of two of vinylmethyldiethoxysilane and 3-(methacryloyloxy)propylmethyldiethoxysilane is preferred.

[0087] In a more specific embodiment, in step 1), the amount of the silane containing an unsaturated group is 0.01 wt% to 30 wt% based on the mass of the low molecular weight polysiloxane. For example, the amount of the silane containing an unsaturated group can be 0.1 to 0.5 wt%, 0.5 to 1 wt%, 1 to 5 wt%, 5 to 10 wt%, 10 to 20 wt%, or 20 to 30 wt%. In a specific embodiment, the amount of the silane containing an unsaturated group is 0.5 to 10 wt%.

[0088] In a more specific embodiment, the solid content of the silicone emulsion in step 1) is 10-65 wt%. Preferably, the solid content of the silicone emulsion is 20-50%, such as 20-25 wt%, 25-30 wt%, 30-35 wt%, 35-40 wt%, 40-42 wt%, 42-44 wt%, 44-46 wt%, 46-48 wt%, and 48-50 wt%.

[0089] In a more specific embodiment, the temperature of the second stage polymerization in step 1) is 1-25°C. Furthermore, the temperature of the second stage polymerization is 1-15°C. For example, the temperature of the second stage polymerization can be 1-3°C, 3-5°C, 5-7°C, 7-9°C, 9-10°C, 12-14°C, or 14-15°C. Taking into account energy saving and the degree of molecular weight growth, in a specific embodiment, the temperature of the second stage polymerization is 5-10°C.

[0090] In a more specific embodiment, the time of the second stage polymerization in step 1) is 2 to 300 hours. Further, the time of the second stage polymerization is 2 to 300 hours. For example, the time of the second stage polymerization can be 2 to 12 hours, 12 to 24 hours, 24 to 48 hours, 48 ​​to 96 hours, 96 to 120 hours, 120 to 150 hours, 150 to 200 hours, 200 to 250 hours, or 250 to 300 hours. Taking into account the actual needs of production efficiency, energy conservation, and degree of polymerization, in a specific embodiment, the time of the second stage polymerization is 24 to 96 hours.

[0091] In a more specific embodiment, the shear treatment in step 1) is performed until the average particle size of the silicone emulsion is 5 to 500 nm, such as 50 to 100 nm, 100 to 150 nm, 150 to 200 nm, 200 to 250 nm, 250 to 300 nm, 300 to 350 nm, 350 to 400 nm, 400 to 450 nm, or 450 to 500 nm. Furthermore, the shear treatment equipment includes one or more of a high-pressure homogenizer, a colloid mill, a high-shear emulsifier, and an ultrasonic emulsifier. Most preferably, the average particle size is 200 to 300 nm.

[0092] The high molecular weight polysiloxane with nano-scale particle size in the present application has a smaller particle size than that of micron-scale particles, and has a higher degree of spatial dispersion after being evenly dispersed in polypropylene, thereby achieving better wear resistance.

[0093] In a more specific embodiment, the emulsifier in step 1) is an anionic emulsifier or a cationic emulsifier.

[0094] The emulsifier for anionic emulsion polymerization is a negatively charged hydrophilic group, such as sulfonic acid group - SO3 - , carboxylic acid group—COO - , sulfate group—OSO3 -. Furthermore, the emulsifier for the anionic emulsion polymerization is selected from one or more of sodium dodecyl sulfate, sodium dodecyl sulfonate, dodecyl sulfonic acid, sodium dodecylbenzenesulfonate, dodecylbenzenesulfonic acid, dodecyl-p-toluenesulfonic acid, sodium dodecyl-p-toluenesulfonate or sodium stearate. Most preferably, the emulsifier for the anionic emulsion polymerization is selected from one or more of sodium dodecyl sulfate and dodecylbenzenesulfonic acid. The catalyst can be selected from sulfuric acid, hydrochloric acid, nitric acid, p-toluenesulfonic acid, and trifluoromethanesulfonic acid. Dodecylbenzenesulfonic acid, which itself has an emulsifying function, is preferred.

[0095] Cationic emulsion polymerization emulsifiers are selected with positively charged hydrophilic groups, such as quaternary ammonium salts - NR4 + , amine salt—NH3 + . Further, the emulsifier for the cationic emulsion polymerization is selected from hexadecyltrimethylammonium bromide, dodecyldimethylbenzylammonium chloride, and tri(dodecyl)methylammonium hydroxide. More preferably, the tri(dodecyl)methylammonium hydroxide is obtained by exchanging tri(dodecyl)methylammonium chloride with a quaternary amine type I ion exchange resin. Most preferably, the emulsifier for the cationic emulsion polymerization is tri(dodecyl)methylammonium hydroxide.

[0096] In step 1), the first stage is to obtain the particle size of polysiloxane nanoparticles by shearing and emulsification. The size can be adjusted by the amount of emulsifier, shear strength and frequency, such as the amount of emulsifier is large, the particle size is small; the pressure of the high-pressure homogenizer is high, the particle size is small.

[0097] In step 2), the pH of the neutralization system is in the range of 3 to 7, more preferably 4 to 7, such as 4 to 4.2, 4.2 to 4.4, 4.4 to 4.6, 4.6 to 4.8, 4.8 to 5.0, 5.0 to 5.2, 5.2 to 5.4, 5.4 to 5.6, 5.6 to 5.8, 5.8 to 6, 6 to 6.2, 6.2 to 6.4, 6.4 to 6.6, 6.6 to 6.8, and 6.8 to 7. The most preferred pH is 4 to 6. Furthermore, during neutralization, one or more of sodium carbonate, sodium bicarbonate, and acetic acid may be used depending on the pH.

[0098] Specifically, the preparation method comprises the following steps: high molecular weight polysiloxane nanoparticles with reserved grafting points undergo grafting reaction with a monomer having good compatibility with polypropylene.

[0099] In a specific embodiment, the grafting reaction is initiated by a method selected from the group consisting of high-energy ray source irradiation, persulfate initiator, oxidation-reduction initiation system, azo initiator, and thermal initiation.

[0100] Preferably, the high-energy ray source is selected from one of a cobalt source, X-rays, ultraviolet rays, and a high-energy electron accelerator, more preferably selected from a cobalt source; the irradiation dose range is 0.1 Mrad to 30 Mrad, more preferably 1 Mrad to 10 Mrad.

[0101] Preferably, the persulfate initiator is selected from a combination of one or more of potassium persulfate, sodium persulfate, and ammonium persulfate, and the added amount of the persulfate initiator is 0.001 wt% to 30 wt% of the weight of the group having good compatibility with polypropylene, and in a specific embodiment, it is 0.1 wt% to 10 wt%.

[0102] Preferably, the azo initiator is selected from azobisisobutylnitrile, azobisisoheptonitrile, azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobiscyanovaleric acid, azobisisopropylimidazoline, and a combination of one or more thereof. The water-soluble azo initiator is 0.001wt% to 30wt% of the weight of the group having good compatibility with polypropylene, and more preferably, the added amount of the azo initiator is 0.1wt% to 10wt%.

[0103] Preferably, the water-soluble redox initiator is selected from a combination of ammonium persulfate-sodium bisulfite, potassium persulfate-sodium bisulfite, ammonium persulfate-ferrous sulfate, hydrogen peroxide-ferrous sulfate, ammonium persulfate-ferrous chloride, hydrogen peroxide-ferrous chloride, potassium persulfate-silver nitrate, persulfate-thiol, tert-butyl hydroperoxide-rongalite, isopropylbenzene hydroperoxide-rongalite, and diisopropylbenzene hydroperoxide-rongalite, more preferably, isopropylbenzene hydroperoxide-rongalite, ammonium persulfate-sodium bisulfite, tert-butyl hydroperoxide-rongalite, and isopropylbenzene hydroperoxide-FF6M; the redox initiator is 0.001wt% to 30wt% of the weight of the group having good compatibility with polypropylene. For example, the amount of the initiator added to the oxidation-reduction initiation system can be 0.001-0.01 wt%, 0.01-0.1 wt%, 0.1-0.5 wt%, 0.5-2 wt%, 2-5 wt%, 5-15 wt%, 15-25 wt%, or 25-30 wt%. In a specific embodiment, the amount of the initiator added to the oxidation-reduction initiation system is 0.5 wt% to 5.0 wt%.

[0104] Preferably, the thermal initiation temperature is 30° C. to 100° C., preferably 50° C. to 95° C. For example, the thermal initiation temperature may be 50° C. to 55° C., 55° C. to 60° C., 60° C. to 65° C., 65° C. to 70° C., 70° C. to 75° C., 75° C. to 80° C., 80° C. to 85° C., 85° C. to 90° C., or 90° C. to 95° C. In a specific embodiment, the thermal initiation temperature is 60° C. to 90° C.

[0105] The technical solutions and technical effects of the present invention are further described and explained through the following specific embodiments and implementation effects.

[0106] In the following embodiments of the present application:

[0107] The average particle size was obtained using a BeNano 90 nanoparticle size analyzer from Dandong Better Instrument Co., Ltd.

[0108] The viscosity was measured at 25°C using a rotational viscometer.

[0109] In the embodiment of the present application, the wear and wear reduction are calculated by the following formula:

[0110] The wear calculation formula is: (initial weight of the disc - weight of the disc after wear) / initial weight of the disc;

[0111] The calculation formula for wear reduction is: (blank sample wear – non-blank sample wear) / blank sample wear;

[0112] Abrasion testing equipment: TABER 5135;

[0113] Abrasion test conditions: 750 g weight, CALLBRADE H-18 grinding wheel, total 10 minutes;

[0114] Measuring balance: METTLER TOLEDO MS304TS, accurate to 0.0001 g.

[0115] Example 1

[0116] In this embodiment, a specific polypropylene wear-resistant additive and a preparation method thereof are provided, and the preparation method comprises the following steps:

[0117] 1) Preparation of high molecular weight polysiloxane nanoparticles with reserved grafting points: A mixture of 490 g of bihydroxyl-terminated polysiloxane with a viscosity of 30 mPa.s (25° C.) and 10 g of vinylmethyldiethoxysilane was added to a mixture of 7 g of sodium lauryl sulfate, 7 g of dodecylbenzenesulfonic acid and 700 g of deionized water, stirred at high speed for 30 minutes, and then heated to 80° C.

[0118] MPa high-pressure homogenizer twice to obtain a vinyl-containing silicone emulsion with a particle size of 250 nm. The silicone content was 40 wt% based on the total mass of the emulsion. The mixture was then placed in a low-temperature environment at 10°C for 60 hours to complete anionic emulsion polymerization. The polymerization reaction was terminated by neutralization with sodium carbonate to a pH of 6.5, resulting in an emulsion of high-molecular-weight polysiloxane nanoparticles. The viscosity of the high-molecular-weight polysiloxane nanoparticles was tested to be 7.95 million mPa.s.

[0119] (25℃).

[0120] 2) Grafting reaction of monomers having good compatibility with polypropylene: 1160 g of the above-mentioned emulsion having a pH of 6.5 and a high molecular weight polysiloxane nanoparticle content of 40 wt % was taken, diluted with 750 g of deionized water, and then 0.02 g of ferrous sulfate and 0.08 g of ethylenediaminetetraacetic acid were added. The mixture was stirred and heated to 68° C., and then a mixture of 140 g of 1,4-butylene glycol dimethacrylate, 55 g of octadecyl methacrylate, and 5 g of cumene hydroperoxide, and a mixture of 4.0 g of Rongalite and 196 g of deionized water were added dropwise. The addition was completed over 5 hours to complete the grafting. The amount of the monomers having good compatibility with polypropylene was 42 wt %, based on the mass of the high molecular weight polysiloxane nanoparticles.

[0121] 3) Solid-liquid separation: Calcium chloride was added to the above product to form flocculation, and water was removed by filter pressing. Deionized water was then added, and the dilution, flocculation, and filter pressing were repeated three times.

[0122] 4) Dilute to 40% solid content and prepare polypropylene wear-resistant additive through spray drying. The polypropylene wear-resistant additive prepared in this example is wear-resistant agent #1.

[0123] Example 2

[0124] In this embodiment, a specific polypropylene wear-resistant additive and a preparation method thereof are provided, and the preparation method comprises the following steps:

[0125] 1) Preparation of high molecular weight polysiloxane nanoparticles with reserved grafting points: A mixture of 290 g of a bihydroxy-terminated polysiloxane having a viscosity of 60 mPa.s (25° C.), 195 g of octamethylcyclotetrasiloxane, and 15 g of 3-(methacryloyloxy)propylmethyldiethoxysilane was added to a mixture of 15 g of sodium lauryl sulfate and 700 g of deionized water. The mixture was stirred at high speed for 30 minutes and passed through a high-pressure homogenizer at 75 MPa three times to obtain a methacryloyloxy-containing organosilicon emulsion with a particle size of 210 nm. The organosilicon content was 40 wt % based on the total mass of the emulsion. The pH was adjusted to 1.0 with sulfuric acid, and the mixture was heated and stirred at 80° C. for 10 hours. The mixture was then placed in a low-temperature environment at 10° C. for 96 hours to complete anionic emulsion polymerization. The polymerization reaction was terminated by neutralization with sodium bicarbonate to pH 6.5 to obtain an emulsion of high molecular weight polysiloxane nanoparticles. The viscosity of the high molecular weight polysiloxane nanoparticles was tested to be 7.87 million mPa·s (25° C.).

[0126] 2) Grafting reaction of monomers with good compatibility with polypropylene: 1100 g of the above-mentioned emulsion having a pH of 6.5 and containing 40 wt% of high molecular weight polysiloxane nanoparticles was diluted with 750 g of deionized water, and then 0.02 g of ferrous sulfate and 0.07 g of ethylenediaminetetraacetic acid were added. The mixture was stirred and heated to 75° C. Then, a mixture of 128.5 g of 1,6-hexanediol dimethacrylate, 30 g of behenyl methacrylate, and 4.5 g of tert-butyl hydroperoxide, and a mixture of 3.5 g of Rongalite and 165 g of deionized water were added dropwise simultaneously. The additions were completed over 4.5 hours, thereby completing the grafting. The amount of the monomers with good compatibility with polypropylene was 36 wt% based on the mass of the high molecular weight polysiloxane nanoparticles.

[0127] 3) Solid-liquid separation: Calcium acetate was added to the above product to form flocculation, and water was removed by filter pressing. Deionized water was then added, and the dilution, flocculation, and filter pressing were repeated three times.

[0128] 4) The filter cake formed by the filter press is prepared into a solid powdered polypropylene wear-resistant additive by a flash dryer. The polypropylene wear-resistant additive prepared in this example is wear-resistant agent #2.

[0129] Example 3

[0130] In this embodiment, a specific polypropylene wear-resistant additive and a preparation method thereof are provided, and the preparation method comprises the following steps:

[0131] 1) Preparation of high molecular weight polysiloxane nanoparticles with reserved grafting points: A mixture of 465 g of octamethylcyclotetrasiloxane and 25 g of vinylmethyldiethoxysilane was added to a mixture of 25 g of an 80% by weight tridodecylmethylammonium chloride isopropanol solution and 710 g of deionized water, stirred at high speed for 40 minutes, and passed through a high-pressure homogenizer at 60 MPa three times to obtain a vinyl-containing organosilicon emulsion with a particle size of 260 nm. The organosilicon content was 40 wt % based on the total mass of the emulsion. The emulsion was treated with 50 g of macroporous quaternary amine type I ion exchange resin IRA-900 (DuPont product) to convert the tridodecylmethylammonium chloride into tridodecylmethylammonium chloride.

[0132] Methylammonium hydroxide was reacted at 72°C for 15 hours, then reduced to 30°C for 20 hours, and then placed in a low-temperature environment of 10°C for 36 hours to complete the cationic emulsion polymerization. Acetic acid was used to neutralize the mixture to pH 5.9 to terminate the polymerization reaction, obtaining an emulsion of high molecular weight polysiloxane nanoparticles. The viscosity of the high molecular weight polysiloxane nanoparticles was tested to be 8.13 million mPa.s (25°C).

[0133] 2) Grafting reaction of monomers having good compatibility with polypropylene: 1050 grams of the above-mentioned emulsion with a pH of 5.9 and a high molecular weight polysiloxane nanoparticle content of 40 wt% were taken, 700 grams of deionized water were added for dilution, 0.02 grams of ferrous sulfate and 0.06 grams of ethylenediaminetetraacetic acid were added, and the mixture was stirred and heated to 79°C. Then, 100 grams of 1,4-butylene glycol dimethacrylate, 26 grams of eicosyl methacrylate and 5 grams of cumene hydroperoxide, and a mixture of 4.0 grams of FF6M and 130 grams of deionized water, which were preheated to 60°C, were added dropwise simultaneously. The addition was completed dropwise over 4.0 hours to complete the grafting. The amount of the monomers having good compatibility with polypropylene was 30 wt% based on the mass of the high molecular weight polysiloxane nanoparticles.

[0134] 3) Solid-liquid separation: magnesium sulfate was added to the above product to form flocculation, and water was removed by filter pressing. Deionized water was then added, and the dilution, flocculation, and filter pressing were repeated three times.

[0135] 4) Dilute to 40% solid content and prepare into solid powder polypropylene wear-resistant additive by spray drying. The polypropylene wear-resistant additive prepared in this example is wear-resistant agent #3.

[0136] Example 4

[0137] In this embodiment, a specific polypropylene wear-resistant additive and a preparation method thereof are provided, and the preparation method comprises the following steps:

[0138] 1) Preparation of high molecular weight polysiloxane nanoparticles with reserved grafting points: A mixture of 480 g of a bihydroxylated polysiloxane having a viscosity of 110 mPa.s (25° C.) and 20 g of 3-(methacryloyloxy)propylmethyldiethoxysilane was added to a mixture of 25 g of an 80% by weight solution of tridodecylmethylammonium chloride in isopropyl alcohol and 710 g of deionized water. The mixture was stirred at high speed for 40 minutes and passed through a high-pressure homogenizer at 70 MPa three times to obtain a methacryloyloxy-containing organosilicon emulsion having a particle size of 270 nm and a silicone content of 40 wt % based on the total mass of the emulsion. The emulsion was treated with 50 g of macroporous quaternary amine type I ion exchange resin IRA-900 (DuPont product) to convert the tridodecylmethylammonium chloride into tridodecylmethylammonium hydroxide, and then placed in a low-temperature environment at 10° C. for 80 hours to complete cationic emulsion polymerization. The polymerization reaction was terminated by neutralization with acetic acid to pH 6.8 to obtain an emulsion of high molecular weight polysiloxane nanoparticles. The viscosity of the high molecular weight polysiloxane nanoparticles was tested to be 8.09 million mPa·s (25° C.).

[0139] 2) Grafting reaction of monomers having good compatibility with polypropylene: 1000 g of the above-mentioned emulsion having a pH of 6.8 and containing 40 wt% of high molecular weight polysiloxane nanoparticles was diluted with 750 g of deionized water, and then 0.02 g of ferrous sulfate and 0.06 g of ethylenediaminetetraacetic acid were added. The mixture was stirred and heated to 78° C., and then a mixture of 120 g of 1,6-hexanediol dimethacrylate and 30 g of behenyl methacrylate, preheated to 70° C., 6.0 g of ammonium persulfate and 60 g of deionized water, and a mixture of 4.8 g of sodium bisulfite and 160 g of deionized water, which were added dropwise simultaneously over 3.5 hours to complete the addition, thereby completing the grafting. The amount of the monomers having good compatibility with polypropylene was 40 wt% based on the mass of the high molecular weight polysiloxane nanoparticles.

[0140] 3) Solid-liquid separation: Aluminum sulfate was added to the above product to form flocculation, and water was removed by filter pressing. Deionized water was then added, and the dilution, flocculation, and filter pressing were repeated three times.

[0141] 4) Dilute to 40% solid content and prepare into solid powder polypropylene wear-resistant additive by spray drying. The polypropylene wear-resistant additive prepared in this example is wear-resistant additive #4.

[0142] Application Examples 1 to 4

[0143] The anti-wear agent #1, anti-wear agent #2, anti-wear agent #3 and anti-wear agent #4 prepared in Examples 1 to 4 were respectively added to polypropylene and mixed with an antioxidant. The mixture was melt-granulated by a twin-screw extruder and then injection-molded into wear-resistant samples for wear resistance testing. As Application Examples 1 to 4, the amounts of the anti-wear agents #1 to 4 and the antioxidants are shown in Table 1.

[0144] The twin-screw extruder has an aspect ratio of 48, a rotation speed of 600 rpm, and temperatures in each zone of ℃: feed port = 81, 180, 190, 190, 195, 195, 195, 195, 190, 180 = die port.

[0145] The polypropylene is homopolymer polypropylene, brand S1003, produced by Shanghai Secco Petrochemical Co., Ltd.

[0146] The antioxidants include: a primary antioxidant Irganox 1010: tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentyl erythritol ester, produced by BASF; and a secondary antioxidant Irgafos 168: tris(2,4-di-tert-butyl)phenyl phosphite, produced by BASF. The amounts of the primary and secondary antioxidants are shown in Table 1.

[0147] The temperatures of the injection molding sections of the wear-resistant test disc are as follows: 198, 228, 222, 219, 192 = die opening.

[0148] The wear resistance test was carried out using a rotary abrader, the rotary abrader equipment brand: TABER5135, the test conditions: #18 grinding wheel, 750g weight, 10 minutes, each group of 12 discs were weighed before and after grinding, the wear was calculated, the maximum and minimum values ​​were removed, and the average value of the remaining 10 discs was taken.

[0149] Application Examples 5-6

[0150] The difference between Application Examples 5 to 6 and Application Examples 1 to 4 is that the anti-wear agent is replaced with equal amounts of high-viscosity polysiloxane of 8.5 million mPa.s (25° C.) and low-viscosity polysiloxane of 80,000 mPa.s (25° C.).

[0151] Application Example 7

[0152] The difference between Application Example 7 and Application Examples 1 to 4 is that no anti-wear agent is added, and only polypropylene is contained, and the amount of antioxidant is the same as that of Application Examples 1 to 4. The disc obtained in Application Example 7 is a blank sample.

[0153] The test results of Application Examples 1 to 7 are shown in Tables 1 and 2 below, where PP S1003 represents brand S1003 homopolypropylene produced by Shanghai Secco Petrochemical Co., Ltd.; HV PDMS and LV PDMS represent high-viscosity polysiloxane (8.5 million mPa.s at 25°C) and low-viscosity polysiloxane (80,000 mPa.s at 25°C), respectively. The abrasion and wear reduction values ​​in Table 1 were calculated using the above formulas. Table 2 shows the tensile strength and elongation at break test results for Application Examples 1 to 7, where the tensile strength and elongation at break were measured in accordance with GB / T 1040-2006.

[0154] Table 1

[0155]

[0156] Table 2

[0157] Tensile strength (MPa) Elongation at break (%) Application Example 1 30.61 139.88 Application Example 2 31.46 151.11 Application Example 3 31.05 171.09 Application Example 4 31.15 167.09 Application Example 5 30.06 154.92 Application Example 6 29.86 195.00 Application Example 7 33.61 122.94

[0158] Test effect data description:

[0159] a) The wear of polypropylene in Application Examples 1 to 4 using wear-resistant agents #1 to 4 was significantly reduced. Compared with the blank sample in Application Example 7 without the addition of the wear-resistant agent, under the same test conditions, the wear was reduced by 66.55% to 72.11%, which was much higher than the 43.2% in Application Example 5 using high molecular weight polysiloxane and the 35.9% in Application Example 6 using low molecular weight polysiloxane. This shows that the polypropylene wear-resistant additive described in this application can significantly improve the wear resistance of polypropylene at a relatively low addition amount.

[0160] b) In Application Examples 1-4, using anti-wear agents #1-4, wear retention was good, demonstrating the excellent compatibility of the polypropylene wear-resistant additives described herein with polypropylene. However, in Application Examples 5-6, using both high-molecular-weight polysiloxane and low-molecular-weight polysiloxane, the wear resistance of polypropylene decreased to varying degrees, with the wear resistance retention of polypropylene in Application Example 6, using low-molecular-weight polysiloxane, decreasing significantly.

[0161] c) Figure 1 This is a photo of the appearance of three wear-resistant discs before grinding, which were averaged in Application Example 1. Figure 2 The following is a photo of the appearance of three wear-resistant discs after grinding, which are the average values ​​in Application Example 1. Figures 1-2 By comparison, it can be seen that after the wear-resistant disc using the polypropylene wear-resistant additive described in this application is ground under the above-mentioned rotary abraser parameter conditions, only shallow wear marks appear on the surface.

[0162] d) Figure 3 The high-viscosity polysiloxane (HV PDMS) and antioxidant described in Application Example 5 were extruded from PP S1003 strips through a twin-screw extruder. After freezing with liquid nitrogen, the strips were broken to form a scanning electron microscope image of a cross-section. The high-viscosity polysiloxane, while still hot-melt, sheared by the twin-screw extruder, formed particles approximately 300 nanometers in size and dispersed within the polypropylene, forming an island-in-the-sea structure. However, due to the low polarity of the polysiloxane, its interfacial bonding with polypropylene is weak, causing some HV PDMS particles to break off during the breaking process, forming voids. Without grafting groups with good compatibility with polypropylene, HV PDMS exhibits poor bonding with polypropylene, contributing to its poor wear-resistant properties as a polypropylene wear-resistant additive.

[0163] e) Figure 4 The anti-wear agent #3 and antioxidant in Application Example 3 were added to PP S1003 and extruded through a twin-screw extruder. After being frozen with liquid nitrogen, the extruded strips were broken and a scanning electron microscope photograph of the cross-section was taken. It can be seen that the anti-wear agent #3 is well dispersed in the polypropylene, with a particle size of approximately 300 nanometers. However, due to the excellent bonding between the grafted material and the polypropylene, there are basically no holes formed by particle detachment in the entire cross-section. The bond between the particle and the polypropylene is fuzzy, and the interface is not obvious, indicating good bonding and corresponding excellent wear resistance.

[0164] f) According to the test of GB / T 1040-2006, compared with the blank sample, the tensile strength of the wear-resistant discs of Application Examples 1 to 6 with the addition of wear-resistant agent decreased slightly, and the elongation at break increased slightly, but both were within the range allowed by material application.

[0165] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A polypropylene wear-resistant additive, characterized in that: The polypropylene wear-resistant additive is a grafted modified product of high molecular weight polysiloxane, the high molecular weight polysiloxane is a high molecular weight polysiloxane nanoparticle with reserved grafting points, and the monomer used for the grafting modification is a monomer with good compatibility with polypropylene.

2. The polypropylene wear-resistant additive according to claim 1, characterized in that: The raw material components of the polypropylene wear-resistant additive include: high molecular weight polysiloxane nanoparticles and monomers with good compatibility with polypropylene; And / or, the high molecular weight polysiloxane nanoparticles are prepared by polymerization of low molecular weight polysiloxane and silane containing unsaturated groups; and / or, the high molecular weight polysiloxane nanoparticles have an average particle size of 5 to 500 nm and a viscosity of greater than 2 million mPa.s at 25° C.; And / or, the monomer having good compatibility with polypropylene is an acrylate; and / or, the high molecular weight polysiloxane nanoparticles are obtained by emulsion polymerization of low molecular weight polysiloxane and silane containing unsaturated groups; And / or, based on the mass of the high molecular weight polysiloxane, the amount of the monomer having good compatibility with polypropylene is 0.1 to 95 wt%.

3. The polypropylene wear-resistant additive according to claim 2, characterized in that: The unsaturated group in the silane containing an unsaturated group is selected from one or more of vinyl and acryloyloxy groups; and / or, based on the mass of the low molecular weight polysiloxane, the amount of the silane containing an unsaturated group is 0.01 wt% to 30 wt%; And / or, the low molecular weight polysiloxane is selected from one or more of dihydroxy-terminated polysiloxane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and dodecamethylcyclohexasiloxane; And / or, the monomer having good compatibility with polypropylene is selected from one or more of n-hexyl methacrylate, isobornyl methacrylate, 3,3,5-trimethylcyclohexanol methacrylate, benzyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, n-decyl methacrylate, isodecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, hexadecyl methacrylate, heptadecyl methacrylate, octadecyl methacrylate, eicosyl methacrylate, behenyl methacrylate, neopentyl glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol dimethacrylate, and 1,6-hexanediol dimethacrylate; and / or, based on the mass of the high molecular weight polysiloxane, the amount of the monomer having good compatibility with polypropylene is 3.0 to 45.0 wt%; And / or, the polymerization reaction includes a first stage and a second stage polymerization; the particle size is controlled by emulsification and shearing in the first stage, The second stage of polymerization is chain growth at low temperature; And / or, the polymerization reaction is one selected from anionic emulsion polymerization and cationic emulsion polymerization.

4. The polypropylene wear-resistant additive according to claim 3, characterized in that: The unsaturated group in the silane containing an unsaturated group is selected from one or more of vinyl and methacryloxy groups; and / or, the silane containing an unsaturated group is selected from vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri-(2-methoxyethoxy)-silane, vinyltriisopropoxysilane, vinylmethylbis(trimethylsiloxy)silane, 3-(methacryloyloxy)propylmethyldimethoxysilane, 3-(methacryloyloxy)propylmethyldiethoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane, 3-(methacryloyloxy)propyltriethoxysilane, 3-(methacryloyloxy)propyl one or more of 3-(acryloyloxy)propyltriisopropoxysilane, 3-(acryloyloxy)propyltrimethoxysilane, 3-(acryloyloxy)propyltriethoxysilane, 3-(acryloyloxy)propylmethyldimethoxysilane, 3-(acryloyloxy)propylmethyldiethoxysilane, 3-(acryloyloxy)propylmethyldiisopropoxysilane, (4-vinylphenyl)trimethoxysilane, (4-vinylphenyl)triethoxysilane, (4-vinylphenyl)methyldimethoxysilane, (4-vinylphenyl)methyldiethoxysilane, styreneethyltrimethoxysilane, and styreneethyltriethoxysilane; and / or, the temperature of the shearing and emulsification in the first stage is 1 to 100° C.; and / or, the temperature of the second stage polymerization is 1 to 25°C; And / or, the second stage polymerization time is 2 to 300 hours.

5. A method for preparing the polypropylene wear-resistant additive according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: carrying out grafting reaction between high molecular weight polysiloxane nanoparticles with reserved grafting points and a monomer having good compatibility with polypropylene.

6. The preparation method according to claim 5, characterized in that The grafting reaction is a free radical reaction, and its initiation mode is selected from one or more of high-energy ray source irradiation, persulfate initiator, oxidation-reduction initiation system, azo initiator, and thermal initiation.

7. The preparation method according to claim 6, characterized in that The high-energy ray source is selected from one or more of a cobalt source, X-rays, ultraviolet rays, and a high-energy electron accelerator; And / or, the irradiation dose of the high-energy ray source is selected in the range of 0.1 to 30 Mrad; And / or, the persulfate initiator is selected from one or more of potassium persulfate, sodium persulfate, and ammonium persulfate; and / or, based on the mass of the monomer having good compatibility with polypropylene, the amount of the persulfate initiator added is 0.001 to 30 wt%; And / or, the azo initiator is selected from one or more of azobisisobutylnitrile, azobisisoheptonitrile, azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobiscyanovaleric acid, and azobisisopropylimidazoline; and / or, based on the mass of the monomer having good compatibility with polypropylene, the amount of the water-soluble azo initiator added is 0.001 to 30 wt%; and / or, the initiator of the oxidation-reduction initiation system is selected from one or more of ammonium persulfate-sodium bisulfite, potassium persulfate-sodium bisulfite, ammonium persulfate-ferrous sulfate, hydrogen peroxide-ferrous sulfate, ammonium persulfate-ferrous chloride, hydrogen peroxide-ferrous chloride, potassium persulfate-silver nitrate, persulfate-thiol, tert-butyl hydroperoxide-rongalite, cumene hydroperoxide-rongalite, diisopropylbenzene hydroperoxide-rongalite, and cumene hydroperoxide-sodium 2-methyl-4-nitrobenzenesulfinate; and / or, the amount of the initiator of the oxidation-reduction initiation system added is 0.001 to 30 wt % based on the mass of the monomer having good compatibility with polypropylene; and / or, the temperature of the thermal initiation is 30° C. to 100° C.; and / or, the amount of the initiator is 0.001 to 30 wt% of the mass of the monomer having good compatibility with polypropylene; And / or, before the grafting reaction, the method further comprises the steps of dispersing high molecular weight polysiloxane nanoparticles in a medium and deoxygenating the medium; And / or, when the monomer having good compatibility with polypropylene includes a polymerization inhibitor, the step of removing the polymerization inhibitor from the monomer having good compatibility with polypropylene is further included before the grafting reaction; And / or, the grafting reaction further comprises the step of adding a chain transfer agent; And / or, the grafting reaction further includes the steps of solid-liquid separation and drying; And / or, after the grafting reaction, a flocculation step is further included before solid-liquid separation.

8. The preparation method according to claim 7, characterized in that The drying method is selected from one or more of freeze drying, spray drying, flash drying, fluidized bed drying, microwave drying, and vacuum drying; and / or, the chain transfer agent is selected from one or more of n-dodecyl mercaptan, tert-dodecyl mercaptan, thioglycolate, thioglycerol, thiophenol, thiosalicylic acid, etc.; And / or, the flocculant used in the flocculation is one or more selected from calcium chloride, calcium acetate, magnesium sulfate, and aluminum sulfate.

9. Use of the polypropylene wear-resistant additive according to any one of claims 1 to 4 in improving the wear resistance of polypropylene.

10. A wear-resistant polypropylene composition, characterized in that: The raw materials of the wear-resistant polypropylene composition include the polypropylene wear-resistant additive according to any one of claims 1 to 4 and polypropylene; preferably, the content of the polypropylene wear-resistant additive is 0.1 to 10 wt% based on the total mass of the polypropylene wear-resistant additive and the polypropylene; preferably, The raw materials further include an antioxidant; preferably, the antioxidant includes a primary antioxidant and a secondary antioxidant, the primary antioxidant being selected from one or more of antioxidant 1010 and antioxidant 1076, and the secondary antioxidant being selected from one or more of antioxidant 168 and antioxidant 398; Preferably, the antioxidant is added in an amount of 0.1 to 1 wt % based on the mass of the polypropylene.

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