A kind of powder coating specially used for wheel hub and preparation method thereof

Abstract

The invention provides a special powder coating for wheel hub and a preparation method thereof. The raw materials of the powder coating include, by weight: 50-90 parts of modified polyurethane resin; 20-40 parts of acrylic resin; 5-15 parts of filler; 5-15 parts of pigment; 0-5 parts of leveling agent; 0.5-3 parts of ultraviolet absorber; 1-5 parts of modified hollow glass microspheres; wherein the modified polyurethane resin is obtained by co-modification of fluorine-containing compounds and silane coupling agents; by modifying the polyurethane resin and the hollow glass microspheres, grafting silane compounds and fluorine compounds on the resin, reducing the surface tension of the coating, adjusting the molecular structure, enhancing the fluidity and wettability, etc., improving the smoothness and antistatic performance of the coating, reducing the adhesion of moisture, oil stains and dust, greatly reducing the possibility of adsorption and accumulation of dust, and maintaining the mechanical properties and long-lasting reflective effect of the coating.

Description

Technical Field

[0001] The invention relates to the technical field of coatings, and in particular to a special powder coating for wheel hubs and a preparation method thereof. Background Art

[0002] With the rapid development of industry, wheel hubs and rims, as an important part of vehicles, not only need to meet the requirements of load-bearing and driving in terms of mechanical properties, but also undertake the tasks of appearance decoration and functional protection. However, there are still many problems with existing wheel rim coatings in practical applications. First of all, most of the wheel rim coatings on the market are mainly high-gloss or metallic effects, but lack functional design. For example, ordinary coatings are easily contaminated with dust and brake dust during long-term use, resulting in a dull surface of the wheel rims and difficulty in cleaning. In addition, the coating has insufficient weather resistance and corrosion resistance, and is prone to cracking, fading or peeling in high temperature, high humidity and salt spray environments, and cannot fully meet the stringent external environment requirements during car driving. Especially for users who travel at night, traditional wheel rim coatings lack reflective function, and their auxiliary role in driving safety is relatively limited, posing safety hazards.

[0003] In order to solve the safety problem of night travel, it is particularly important to develop a wheel coating with a reflective effect. The reflective function can improve the visibility of the wheel rim by reflecting the light of car lights or street lights, thereby reminding surrounding vehicles and pedestrians to pay attention to moving vehicles, especially bicycles without lights, which can greatly improve night driving safety.

[0004] In addition, powder coating is a solvent-free coating that is completely different from traditional liquid coatings. It is made by mixing various oligomers or monomers, additives and photoinitiators and then crushing them. It has the characteristics of simplifying the process, saving energy and resources, no environmental pollution, and high production efficiency. At present, powder coating, as an environmentally friendly coating, has attracted widespread attention because it does not contain solvents, has low VOC (volatile organic compound) emissions, and has excellent coating performance. Combining the reflective function with powder coating technology can not only give the wheel rim coating outstanding functionality, but also meet increasingly stringent requirements in terms of environmental protection.

[0005] In summary, there is still a lack of a powder coating on the market that can achieve both long-term reflectivity and dust-proof effects. Summary of the invention

[0006] Purpose of the invention: The purpose of the present invention is to provide a special powder coating for wheel hub and a preparation method thereof, which can meet the harsh use environment and aesthetic requirements of vehicle driving, have long-lasting reflective and dust-proof properties, and improve the safety of vehicles driving at night.

[0007] The technical solution of the present invention:

[0008] In one aspect, the present invention provides a powder coating for a wheel hub, wherein the raw materials of the powder coating include, by weight:

[0009] 50-90 parts of modified polyurethane resin;

[0010] 20-40 parts of acrylic resin;

[0011] 5 to 15 parts of filler;

[0012] Pigment 5-15 parts;

[0013] Leveling agent 0-5 parts;

[0014] 0.5 to 3 parts of ultraviolet absorber;

[0015] 1 to 5 parts of modified hollow glass microspheres;

[0016] The modified polyurethane resin is obtained by modifying a fluorine-containing compound and a silane coupling agent.

[0017] In some embodiments, the fluorine-containing compound is selected from one or more combinations of 3-(perfluoro-n-hexyl)propylene oxide, 3-(perfluoro-n-octyl)-1,2-propylene oxide, 3-(perfluoro-n-butane)-1,2-propylene oxide, 2-(2,2,3,3,4,4,4-heptafluorobutyl)ethylene oxide, 3-(perfluoro-5-methylhexyl)-1,2-propylene oxide, and [2,3,3,3-tetrafluoro-2-(trifluoromethyl)propyl]ethylene oxide.

[0018] In some embodiments, the silane coupling agent has an amine group, and the amine group is one or more combinations of a primary amine group or a secondary amine group; the number of the amine groups is any number between 1 and 3.

[0019] Further, the silane coupling agent is selected from one or more combinations of γ-aminopropyltriethoxysilane, N-β (aminoethyl)-γ-aminopropyltrimethoxysilane, N-β (aminoethyl)-γ-aminopropylmethyldimethoxysilane, anilinomethyltriethoxysilane, and anilinomethyltrimethoxysilane.

[0020] In some embodiments, the method for preparing the modified polyurethane resin comprises the following steps:

[0021] S1: Add the fluorine-containing compound and the silane coupling agent into a reaction container, mix and stir at room temperature for 0.5 to 1 hour, and then stir at 20 to 30° C. for 12 to 24 hours to obtain an intermediate;

[0022] S2: dissolving diisocyanate and polyol in a solvent, adding a catalyst and reacting under heating conditions to obtain a modified polyurethane precursor;

[0023] S3: slowly drop the intermediate solution into the modified polyurethane precursor at room temperature, stir and react for 2 to 5 hours after the dropwise addition is completed, and obtain the modified polyurethane resin after the reaction is completed.

[0024] In some embodiments, the molar ratio of the fluorine-containing compound to the silane coupling agent is 1 to 1.2:1.

[0025] In some embodiments, the diisocyanate is selected from one or more combinations of toluene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate or 1,4-cyclohexane diisocyanate.

[0026] In some embodiments, the polyol is selected from one or more combinations of polyethylene adipate, poly-1,6-hexanediol adipate, poly-1,6-hexanediol sebacate, polyethylene terephthalate, poly-1,4-butylene terephthalate or poly-1,4-butylene glycol.

[0027] In some embodiments, the molar ratio of the diisocyanate, the polyol and the intermediate is 1:0.5-0.8:0.5-1.

[0028] In some embodiments, the acrylic resin is selected from one or more combinations of Dianal LR-2080, Dianal HR-2215, Kuraraylac MX-311, Kuraraylac SX-325, Encor 450, Dianal MB-2854, Neocryl B-725, and Neocryl B-728. Acrylic resin is used as an auxiliary resin, and a product with good adhesion and hardness can be obtained by matching reaction with modified polyurethane resin.

[0029] In some embodiments, the filler is selected from one or more of silicon powder, aluminum oxide powder, zirconium oxide powder, cerium oxide powder, and boron nitride powder. In order to improve the compatibility of the filler with other organic substrates, the particle size of the inorganic wear-resistant filler is preferably less than 200 nm.

[0030] In some embodiments, the pigment is an inorganic pigment or an organic pigment, the inorganic pigment is selected from titanium white, titanium yellow, cobalt blue, cobalt green, cobalt black or iron red, and the organic pigment is selected from organic red, organic yellow, organic blue or carbon black; the selection can be made according to actual needs.

[0031] In some embodiments, the leveling agent can be selected from one or more combinations of acrylates, silicones, and fluorides, for example, one or more combinations of BYK-361 N, TEGO Glide 100, Siliko 7108, Fluorad™ FC-4430, or Novec™ 230. The present invention greatly improves the fluidity of the resin and the flatness and smoothness of the film-forming surface by modifying the polyurethane resin, and can correspondingly reduce or omit the use content of the leveling agent, thereby achieving certain technical progress.

[0032] In some embodiments, the ultraviolet absorber is selected from one or more combinations of Tinuvin 144, Tinuvin 783, and UV531 of BASF.

[0033] In some embodiments, the method for preparing the modified hollow glass microspheres comprises the following steps:

[0034] S1: placing hollow glass microspheres in a reaction container, adding sodium hydroxide solution, heating under reflux reaction, washing with clean water, removing moisture and drying to obtain pretreated hollow glass microspheres;

[0035] S2: placing the pretreated hollow glass microspheres in a reaction container, adding a solvent, and then adding a silane coupling agent, reacting under heating conditions, washing, filtering, and drying to obtain modified hollow glass microspheres.

[0036] In some embodiments, the heating reflux reaction in S1 is heated at 80-100° C. and the reaction time is 1-2 h.

[0037] In some embodiments, the silane coupling agent in S2 is selected from one or more combinations of KH550, KH560, KH570, KH591, KH792, KH602, KH580, KH553, and KH593.

[0038] The hydrogen atoms of the hollow glass microspheres can form hydrogen bonds with nitrogen atoms on other resin bonds, and can also form hydrogen bonds with fluorine atoms on the resin. The formation of hydrogen bonds in the coating enhances the binding ability of different functional groups in the coating, making the entire coating form a denser whole. Therefore, the powder coating of the present invention has excellent hydrophobic and oleophobic properties, can effectively prevent dust, and also has good weather resistance and strong adhesion and impact resistance.

[0039] In a second aspect, the present invention also provides a method for preparing the powder coating as described above, comprising the following preparation steps:

[0040] Weigh each raw material according to its weight, mix them and put them into a mixer for mixing, put the mixed material into a twin-screw extruder for extrusion, cool the extruded flake material, put it into a pulverizer for crushing and grinding into a powder of 200-220 mesh, and sieve it to obtain a powder coating.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. By modifying the polyurethane resin and grafting silane compounds and fluorine compounds, the surface tension of the coating can be effectively reduced, the molecular structure can be adjusted, the fluidity and wettability can be enhanced, the smoothness and antistatic properties of the coating can be improved, the adhesion of water, oil and dust can be reduced, the possibility of adsorption and accumulation of dust can be greatly reduced, and the beauty and reflective effect of the coating can be maintained.

[0043] 2. By modifying the surface of hollow glass microspheres and grafting silane coupling agents, hydrogen bonds can be formed with nitrogen atoms on other resin bonds, and hydrogen bonds can also be formed with fluorine atoms on the resin. The formation of hydrogen bonds in the coating enhances the binding ability of different functional groups in the coating, improves the coating's good weather resistance, adhesion, and strong impact resistance, while maintaining a lasting reflective effect. DETAILED DESCRIPTION

[0044] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. In addition, it is specifically stated that the hollow glass microspheres used in the embodiments are purchased from 3M Company, model IM16K; the molecular weight of polyethylene adipate used in the embodiments is 10000 Mw; the particle size of the filler zirconium oxide is 50μm; the titanium dioxide is the product No. R-566 of Alatau Company; other raw materials and equipment of the present invention are commonly available on the market, well known to those skilled in the art, and will not be repeated.

[0045] Preparation of modified polyurethane resin 1

[0046] S1: Add 0.1 mol of 3-(perfluoro-n-hexyl)propylene oxide and 0.1 mol of γ-aminopropyltriethoxysilane into a flask, mix at room temperature for 30 min, and then heat to 20°C and stir for 24 h to obtain an intermediate;

[0047] S2: 0.15 mol of isophorone diisocyanate and 0.075 mol of polyethylene adipate were dissolved in 100 ml of toluene solvent, 0.05 mol of dibutyltin dilaurate was added, and the mixture was heated at 75° C. for 4 h to obtain a modified polyurethane precursor solution;

[0048] S3: Take 0.075 mol of the intermediate prepared in S1 and mix it in 20 ml of toluene to obtain an intermediate solution; slowly add the intermediate solution to the modified polyurethane precursor solution prepared in S2 at room temperature, stir and react for 2 to 5 hours after the addition is completed, then add 0.02 mol of γ-aminopropyltriethoxysilane and stir and react for 2 hours, and after the reaction is completed, obtain the modified polyurethane resin 1.

[0049] The infrared spectrum of the synthesized modified polyurethane resin 1 powder was analyzed by Fourier transform infrared spectrometer and potassium bromide tablet. The infrared spectrum of the reaction product shows that:

[0050] At 1355 cm -1 There is a strong absorption peak of -CF3 at 1250 cm -1 There is a characteristic peak of Si-OC at 1725cm -1 There is a C=O absorption characteristic peak at 3345 cm -1 The presence of NH stretching vibration is a characteristic of polyurethane, indicating that the modified polyurethane resin 1 was successfully prepared in the above steps.

[0051] Preparation Example of Modified Polyurethane Resin 2

[0052] Modified polyurethane resin 2 is prepared by the same method as modified polyurethane resin 1 except that the molar amounts of isophorone diisocyanate, polyethylene adipate and the intermediate are 0.15 mol: 0.12 mol: 0.15 mol.

[0053] Preparation Example of Modified Polyurethane Resin 3

[0054] The modified polyurethane resin 3 is prepared by the same method as the modified polyurethane resin 1 except that the fluorine-containing compound used is 3-(perfluoro-n-butane)-1,2-propylene oxide.

[0055] Preparation Example of Modified Polyurethane Resin 4

[0056] The modified polyurethane resin 4 is basically the same as the modified polyurethane resin 1, except that propylene oxide is used to replace 3-(perfluoro-n-hexyl)propylene oxide, to prepare the modified polyurethane resin 4.

[0057] Preparation Example of Modified Polyurethane Resin 5

[0058] The modified polyurethane resin 5 is prepared by the same method as the modified polyurethane resin 1 except that n-hexylamine is used to replace γ-aminopropyltriethoxysilane.

[0059] Polyurethane resin 6

[0060] 0.15 mol of isophorone diisocyanate and 0.15 mol of polyethylene adipate were dissolved in 100 ml of toluene, 0.05 mol of dibutyltin dilaurate was added, and the mixture was heated at 75° C. for 4 h to obtain polyurethane 6.

[0061] Preparation of modified hollow glass microspheres

[0062] S1: 10 g of hollow glass microspheres were placed in a beaker, 200 ml of 0.5 mol / L sodium hydroxide solution was added, and the mixture was heated to reflux at 80°C for 2 h, and then washed with clean water until neutral, and dried after removing the water to obtain pretreated hollow glass microspheres;

[0063] S2: 10 g of pretreated hollow glass microspheres were placed in a flask, and a mixed solvent of ethanol and water (volume ratio 1:1) was added, followed by 2 g of silane coupling agent KH550, and the mixture was heated at 80°C for 2 h. After washing, the mixture was filtered and dried to obtain modified hollow glass microspheres.

[0064] Examples and Comparative Examples

[0065] The modified polyurethane resin, acrylic resin, filler, pigment, leveling agent, ultraviolet absorber and modified hollow glass microspheres are weighed according to the formula shown in Table 1 or Table 2; then put into a mixer for mixing, put the mixed mixture into a twin-screw extruder for extrusion, and after the extruded sheet material is cooled, put into a pulverizer for crushing and grinding into a 200-mesh powder, and then sieve to obtain a powder coating.

[0066] Table 1 Example formula (unit: weight parts)

[0067]

[0068] Table 2 Comparative Example Formula (Unit: Parts by Weight)

[0069]

[0070] Performance Tests of Experimental Examples and Comparative Examples

[0071] The powder coatings obtained in the above examples and comparative examples were applied on the same substrate and subjected to the following tests. The performance evaluation method and test standards are as follows:

[0072] 1. Abrasion resistance test: refer to GBT 1768-2006 "Determination of abrasion resistance of paints and varnishes - Rotating rubber grinding wheel method". The lower the value, the lower the wear, indicating that the better the wear resistance of the coating;

[0073] 2. Leveling test: refer to GB / T 1750-1979 "Coating Leveling" for testing (0-10 points, 10 points means the best leveling, 0 points means no leveling performance at all);

[0074] 3. 60° gloss test: refer to ISO 2813, place the coating outdoors and test it 0 days and 30 days after coating (0-100 GU, where 0 GU means completely matte, 0-10 GU means low gloss, 10-70 GU means medium gloss, 70-100 GU means high gloss, and 100 GU means completely mirror gloss);

[0075] 4. Coating appearance test: visual observation;

[0076] The test results are shown in Tables 3 and 4.

[0077] Table 3 Test results of the embodiment

[0078]

[0079] Table 4 Test results of comparative examples

[0080]

[0081] It can be seen from the above tests that the present invention greatly improves the leveling and wear resistance of the obtained polyurethane resin by designing and modifying the structure of the polyurethane resin, grafting perfluorinated segments and silicone structures, reducing the surface tension of the coating, adjusting the molecular structure, and enhancing fluidity. Correspondingly, it can improve its dustproof ability and time, so that the coating has an efficient and long-lasting reflective effect, and is more suitable for use on vehicle rims.

[0082] Modifying the hollow glass microspheres so that they can form hydrogen bonds with the resin helps to improve the overall bonding ability of the coating, improve wear resistance, reduce the possibility of reduced reflectivity due to coating loss during use, and correspondingly increase the service life of the coating.

[0083] From the comparison between the examples and comparative examples 2-5 in the table, it can be seen that by adjusting the composite use of modified polyurethane, acrylic resin and modified hollow glass microspheres, the composite properties of the coating can be improved by mutual assistance, and from comparative example 4, it can be seen that the raw materials of the powder coating provided by the present invention do not need to use a leveling agent, but can achieve the same effect.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the best embodiments, the present invention is not limited to the embodiments disclosed above, but should cover various modifications and equivalent combinations based on the essence of the present invention.

Claims

1. A powder coating for wheel hub, characterized in that: The raw materials of the powder coating include, by weight: 50-90 parts of modified polyurethane resin; Acrylic resin 20-40 parts; Filler 5-15 parts; Pigment 5-15 parts; Leveling agent 0-5 parts; 0.5 to 3 parts of ultraviolet absorber; Modified hollow glass microspheres 1-5 parts; The preparation method of the modified polyurethane resin comprises the following steps: S1: Add a fluorine-containing compound and a silane coupling agent into a reaction container, mix and stir at room temperature for 0.5 to 1 hour, and then stir at 20 to 30° C. for 12 to 24 hours to obtain an intermediate; the fluorine-containing compound is selected from one or more combinations of 3-(perfluoro-n-hexyl)propylene oxide, 3-(perfluoro-n-octyl)-1,2-propylene oxide, 3-(perfluoro-n-butane)-1,2-propylene oxide, 2-(2,2,3,3,4,4,4-heptafluorobutyl)ethylene oxide, 3-(perfluoro-5-methylhexyl)-1,2-propylene oxide, and [2,3,3,3-tetrafluoro-2-(trifluoromethyl)propyl]ethylene oxide; the silane coupling agent has an amine group, and the amine group is one or more combinations of a primary amine group or a secondary amine group; S2: dissolving diisocyanate and polyol in a solvent, adding a catalyst and reacting under heating conditions to obtain a modified polyurethane precursor; S3: slowly adding the intermediate solution to the modified polyurethane precursor at room temperature, stirring and reacting for 2 to 5 hours after the addition is completed, and obtaining a modified polyurethane resin after the reaction is completed; The preparation method of the modified hollow glass microspheres comprises the following steps: S1: placing hollow glass microspheres in a reaction container, adding sodium hydroxide solution, heating under reflux reaction, washing with clean water, removing moisture and drying to obtain pretreated hollow glass microspheres; S2: placing the pretreated hollow glass microspheres in a reaction container, adding a solvent, and then adding a silane coupling agent, reacting under heating conditions, washing, filtering, and drying to obtain modified hollow glass microspheres.

2. The powder coating according to claim 1, characterized in that: In step S1 of preparing the modified polyurethane resin, the silane coupling agent is selected from one or more combinations of γ-aminopropyltriethoxysilane, N-β (aminoethyl)-γ-aminopropyltrimethoxysilane, N-β (aminoethyl)-γ-aminopropylmethyldimethoxysilane, anilinomethyltriethoxysilane, and anilinomethyltrimethoxysilane.

3. The powder coating according to claim 1, characterized in that: In step S1 of preparing the modified polyurethane resin, the molar ratio of the fluorine-containing compound to the silane coupling agent is 1 to 1.2:

1.

4. The powder coating according to claim 1, characterized in that: The molar ratio of the diisocyanate, the polyol and the intermediate is 1:0.5-0.8:0.5-1.

5. The powder coating according to claim 1, characterized in that: In step S2 of preparing the modified hollow glass microspheres, the silane coupling agent is selected from one or more combinations of KH550, KH560, KH570, KH591, KH792, KH602, KH580, KH553, and KH593.

6. The method for preparing the special powder coating for wheel hub according to any one of claims 1 to 5, characterized in that: The method comprises the following preparation steps: Weigh each raw material according to its weight, then mix and put it into a mixer for mixing, put the mixed material into a twin-screw extruder for extrusion, cool the extruded flake material, put it into a pulverizer for crushing and grinding into a powder of 200-220 mesh, and sieve it to obtain a powder coating for wheel hubs.

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