Wear-resistant anticorrosive automobile steering wheel polyester decorative material and preparation method thereof

Abstract

The application relates to the technical field of polyester degradable materials, in particular to a wear-resistant and corrosion-resistant polyester decorative material for automobile steering wheels and a preparation method thereof. The preparation method overcomes the problem of poor wear resistance and corrosion resistance of the polyester material for the steering wheel. Modified boron nitride is prepared, PCL, PBS, 1,4-butylene glycol and ring-opening amide are melt copolymerized, polycondensation is carried out, HDI is added for chain extension and modified boron nitride sheet structure grafting, and aluminum oxide and magnesium stearate are added for reinforcement, finally, extrusion granulation, injection molding and post-treatment are carried out, multiple structures are synergized, the comprehensive performance of the material is improved, the material is good in degradability, and is suitable for automobile steering wheel decoration.

Description

Technical Field

[0001] This invention relates to the field of polyester biodegradable materials technology, specifically to a wear-resistant and corrosion-resistant polyester decorative material for automotive steering wheels and its preparation method. Background Technology

[0002] As a core component for driver control, the performance of the steering wheel's trim materials directly affects the driving experience and lifespan. Currently, mainstream steering wheel trim materials include genuine leather, artificial leather, plastic, and metal, but all have significant limitations: genuine leather offers excellent texture but is expensive, has poor wear resistance and corrosion resistance, and is prone to aging and deformation in humid environments; artificial leather is cheaper but lacks corrosion resistance and is easily discolored and cracked by car interior cleaners and sweat; plastic, while inexpensive and easy to mold, suffers from poor wear resistance and corrosion resistance, with noticeable surface scratches after frequent use and a tendency to react with corrosive substances; metal, while wear-resistant and corrosion-resistant, is hard, has a poor feel, and is detrimental to vehicle lightweighting.

[0003] To address these issues, existing technologies have been improved through methods such as surface coating with wear-resistant coatings or chemical treatments. However, wear-resistant coatings are prone to peeling off after long-term use, and chemical treatments not only affect the physical properties of the materials but may also cause environmental pollution. More importantly, most existing materials are non-degradable. With the surge in the number of scrapped vehicles, these materials are difficult to degrade naturally, exacerbating the environmental burden.

[0004] Against this backdrop, polycaprolactone (PCL) and its derived biodegradable polyester materials have gradually attracted attention. PCL possesses excellent biodegradability and flexibility. Polyester materials formed by copolymerization with other biomass monomers can retain their biodegradability while potentially improving mechanical properties through molecular structure design. However, existing PCL-based polyester materials still face problems such as insufficient wear resistance and limited corrosion resistance in automotive steering wheel trim applications, making it difficult to directly meet practical usage requirements. Therefore, developing a PCL-based automotive steering wheel polyester trim material that combines excellent wear resistance, corrosion resistance, and environmentally friendly biodegradability has become a key issue that the industry urgently needs to address. Therefore, this paper proposes a wear-resistant and corrosion-resistant automotive steering wheel polyester trim material and its preparation method. Summary of the Invention

[0005] The purpose of this invention is to provide a wear-resistant and corrosion-resistant polyester decorative material for automotive steering wheels and its preparation method. This material synergistically enhances wear resistance, corrosion resistance, and a wide temperature range. For wear resistance, ultrasonically dispersed nano-Al2O3 forms physical reinforcement points, modified boron nitride grafted with trifluoromethyl methacrylate double bonds constructs a network structure, and PCL / PLA / PBS blending provides toughness, reducing frictional loss. For corrosion resistance, magnesium stearate acts as a hydrophobic barrier to hinder media penetration, enzyme-catalyzed polymerization of amide bonds and fluorine atoms synergistically stabilizes the structure, and modified boron nitride reduces porosity, inhibiting corrosion. For heat resistance, the 1,4-cyclohexane monomer six-membered ring enhances rigidity, the PCL / PBS flexible chain provides low-temperature toughness, HDI chain extension enhances intermolecular forces, modified boron nitride provides thermal insulation, and amide bonds enhance hydrogen bonding, enabling the material to maintain stable mechanical properties over a wide temperature range and preserve its long-term appearance and function.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing a wear-resistant and corrosion-resistant polyester decorative material for automotive steering wheels. The preparation method is as follows: Biodegradable polymer, polymer monomers and polymer intermediates are added to a reactor for melt mixing, a catalyst is added for polycondensation reaction, hexamethylene diisocyanate (HDI) and modified boron nitride are added for chain extension and grafting reaction, nano alumina dispersion and magnesium stearate are added for reinforcement modification, and then wear-resistant and corrosion-resistant polyester decorative material for automotive steering wheels is prepared by extrusion granulation, injection molding and post-treatment. The biodegradable polymer is composed of polycaprolactone (PCL), polylactic acid (PLA), and polybutylene succinate (PBS); the polymer monomers are composed of succinic acid, 1,4-butanediol, 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexanediethanol and trifluoromethacrylic acid; the polymer intermediate is an oligomeric amide intermediate. The viscosity of PCL is 1.7 dL / g; the number-average molecular weight of PLA is 60,000; the CAS of PBS is 25777-14-4; the CAS of succinic acid is 110-15-6; the CAS of 1,4-cyclohexanedicarboxylic acid is 1076-97-7; and the CAS of trifluoromethylacrylic acid is 381-98-6.

[0007] Modified boron nitride is obtained by esterification of ethacrylic acid with hydroxylated boron nitride and pinacol diboronate; boron nitride has the CAS number 10043-11-5 and is a white powder.

[0008] Boron nitride (h-BN) is hydroxylated with concentrated nitric acid to form BN-OH, introducing hydroxyl groups (-OH) to the surface; pinacol diboronic acid modified with ethacrylic acid (EA-B) combines with the hydroxyl groups on the surface of BN-OH through an esterification reaction to form chemically bonded modified boron nitride; EA-B retains unsaturated double bonds, which are used to enhance interfacial bonding through subsequent free radical reactions; Boron nitride has a diamond-like layered structure and a Mohs hardness close to 9, which can effectively resist mechanical scratches and wear from grinding wheels. The layered structure is similar to graphite and has self-lubricating properties. Boron atoms form a weakly bonded layered structure through van der Waals forces, which allows for interlayer sliding during friction, reducing the coefficient of friction and minimizing surface wear. Boron nitride is not easily decomposed under high-temperature friction, maintaining surface stability and enhancing wear resistance. In EA-B, pinacol diboronate is bonded to ethacrylic acid via boron-oxygen bonds, with the boron atom acting as a bridging atom to enhance intermolecular bonding. After grafting, the unsaturated double bonds of EA-B react with the polymer matrix to form a covalent network. The boron atoms in pinacol diboronate have empty p orbitals, which can coordinate with polar groups such as ester amide bonds in the polyester matrix or form hydrogen bonds with hydroxyl groups in the matrix. These polar interactions further enhance the interfacial compatibility between BN and the matrix, reduce interfacial defects, improve the overall strength and surface hardness of the material, and prevent material damage caused by the concentration of frictional stress at the interface.

[0009] Preferably, the oligoamide intermediate is obtained by reacting caprolactam and lipase under nitrogen protection; the CAS of caprolactam is 105-60-2; the lipase is Candida lipase B (CLAB), with a molecular weight of 33000 Da, a pale yellow powder, and the activity conditions are pH 6-8 and temperature 30-60℃.

[0010] It should be noted that all parts involved in this invention are "parts by weight". The amount of PCL used is 45-65 parts; PLA is 13-20 parts; PBS is 10-17 parts; succinic acid is 10-18 parts; 1,4-butanediol is 6-10 parts; 1,4-cyclohexanedicarboxylic acid is 7-15 parts; 1,4-cyclohexanediethanol is 4-8 parts; the amount of nano-alumina in the nano-alumina dispersion is 4-10 parts; trifluoromethylacrylic acid is 3.5-8.0 parts; the reaction temperature for the preparation of the oligomeric amide intermediate is 38-55℃, and the reaction time is 5-12 hours; the average particle size of the nano-alumina is 80 nm, and the density is 3.97 g / cm³. 3 ; The unsaturated double bonds of trifluoromethyl methacrylate are grafted onto modified boron nitride EA-B via free radical reaction to form a cross-linked network, which improves the overall strength and surface hardness of the material; at the same time, the hydrophobic properties of trifluoromethyl reduce surface hygroscopicity and reduce wear caused by wet friction. The cyclohexane structure in 1,4-cyclohexanedicarboxylic acid / diethanol increases the rigidity of the polymer chain, improves the material's hardness and resistance to deformation, and reduces wear marks; succinic acid and 1,4-butanediol form a high molecular weight polyester through polycondensation reaction, which enhances the overall strength of the material and indirectly supports surface wear resistance.

[0011] The preferred method for preparing ethacrylic acid modified with pinacol diboron ester is as follows: ethacrylic acid is dissolved in a mixed solvent to obtain an ethacrylic acid solution; the ethacrylic acid solution, pinacol diboron ester, potassium acetate, and catalyst are added to a reaction vessel, and the reaction is carried out under nitrogen protection at a high temperature. After adding deionized water, the mixture is filtered, extracted, washed again with water, and dried to obtain ethacrylic acid modified with pinacol diboron ester; the CAS number of ethacrylic acid is 58-54-8; the CAS number of pinacol diboron ester is 73183-34-3; the equations for the above reaction process are as follows: ; Subsequently, it undergoes an esterification reaction with hydroxylated boron nitride, and the reaction equation is as follows: .

[0012] After obtaining modified boron nitride, the following processes were carried out sequentially: enzymatic ring-opening polymerization (amide copolymerization), melt mixing, polycondensation reaction, chain extension and grafting reaction, reinforcement modification, extrusion granulation, injection molding and post-treatment.

[0013] In the enzymatic ring-opening polymerization step, the preferred mass ratio of caprolactam to initiator is 100:(1-2), and the amount of lipase added is 0.5%-1.5% of the mass of caprolactam. This step constructs a highly regular amide structure fragment under relatively mild conditions through enzymatic reaction, laying the foundation for subsequent copolymerization with the polyester matrix.

[0014] In the melt mixing and polycondensation reaction, the vacuum degree can be controlled at -0.09MPa for 5 hours; the pressure in the vacuum polycondensation stage can be adjusted to be between -0.08MPa and -0.098MPa, and the temperature can be increased stepwise, first reacting at 170-190℃ for 1-2 hours, and then increasing the temperature to 210-235℃ for another 3-5 hours.

[0015] In the chain extension and grafting reactions, HDI acts as a chain extender, reacting with the terminal hydroxyl or amino groups of the polymer to form urethane or urea bonds. Meanwhile, the EA-B double bonds on the modified boron nitride surface, under the action of a free radical initiator, covalently graft with residual unsaturated sites in the system. The grafting rate is controlled between 15% and 35% to ensure that the interfacial shear strength between the filler and the matrix reaches its maximum value.

[0016] The temperatures and parameters of each zone of the twin-screw extruder are as follows: Zone 1 (feeding zone) is set at 160-180℃ to prevent premature melting and bridging of the material; Zones 2-4 (melting and conveying zones) are set at 200-215℃, during which the material is fully melted and mixed; Zones 5-7 (high-shear mixing zone) are set at 220-230℃, which is the highest temperature zone for extrusion, using high shear force to achieve secondary uniform dispersion of nano-alumina and modified boron nitride in the matrix; Zones 8-9 (venting and devolatilization zone) are set at 210-220℃, controlling the vacuum degree to -0.05 to -0.08 MPa to remove residual ethylene glycol dimethyl ether solvent and reaction byproducts; Zone 10 (die zone) is set at 200-210℃, with appropriate cooling to increase melt strength and facilitate stranding and pelletizing; the screw speed is set at 150 rpm, and the length-to-diameter ratio (L / D) is set at 40:1 to ensure sufficient reaction time and mixing effect.

[0017] Preferably, the extrusion granulation temperature is 200-235℃; the injection molding temperature is 210-240℃, and the injection pressure is 90-110MPa.

[0018] This invention also provides a wear-resistant and corrosion-resistant polyester decorative material for automotive steering wheels, which is prepared by any of the above preparation methods; the raw materials for preparing the decorative material include: PCL, PLA, PBS, succinic acid, 1,4-butanediol, 1,4-cyclohexanedicarboxylic acid, nano-alumina, trifluoromethylacrylic acid and modified boron nitride.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. By hydroxylating boron nitride and grafting pinacol ester onto ethacrylic acid, and simultaneously adding nano-Al2O3 after ultrasonic pre-dispersion with magnesium stearate, the interfacial bonding problem between inorganic fillers and the polymer matrix is ​​effectively solved. Polar groups are introduced on the surface of modified boron nitride to achieve chemical bonding, nano-alumina uniformly fills the matrix, and magnesium stearate optimizes dispersibility. The three work synergistically to improve the surface hardness and structural uniformity of the material, reduce filler spalling during friction, significantly enhance the wear resistance of the material, and extend the service life of the steering wheel trim material.

[0020] 2. By employing enzymatic ring-opening polymerization to prepare oligoamide intermediates, and combining melt mixing and stepwise polycondensation processes, a high molecular weight polyester-amide copolymer system was constructed. Enzymatic polymerization endows the oligoamides with a regular structure, forming a dense molecular chain network with the bio-based polyester. The hydrogen bonding of the amide bonds enhances intermolecular forces. The optimized melt mixing and polycondensation processes ensure uniform dispersion of raw materials and sufficient reaction, improving the toughness and strength of the polymer matrix and laying a solid structural foundation for the stable performance of various material properties.

[0021] 3. A hydrophobic film is formed by the directional arrangement of hydrophobic alkyl chains. The layered structure of modified boron nitride extends the penetration path of corrosive media. The hydrophobicity of trifluoromethylacrylic acid and the chemical inertness of boron nitride work synergistically to construct a multi-layered anti-corrosion barrier. The hydrophobic film hinders the penetration of polar corrosive media, the layered filler physically blocks the penetration channels, and the fluorine groups reduce the water absorption rate of the material. The combination of these three factors significantly improves the material's resistance to salt spray, sweat, and chemical corrosion, ensuring the appearance and performance stability of the steering wheel in complex usage environments.

[0022] 4. By leveraging the high thermal stability of boron nitride and alumina, the regular structure of oligoamides, and the high bond energy of trifluoromethylacrylic acid, the heat resistance of the material is synergistically improved. Boron nitride does not decompose at high temperatures and enhances interfacial bonding, alumina's high melting point and high thermal conductivity reduce thermal deformation, the amide bonds of oligoamides impart excellent thermal stability, and the fluorine groups resist thermal decomposition. Optimized processes ensure uniform dispersion of fillers and a dense matrix structure, reducing thermal degradation, deformation, and cracking at high temperatures, and improving the material's heat distortion temperature and resistance to thermal aging.

[0023] 5. Using bio-based polyesters such as PCL, PLA, and PBS as the main raw materials, and through reasonable copolymerization and processing techniques, the material possesses excellent biodegradability. In a composting environment, the material is gradually decomposed by microorganisms, avoiding the environmental pollution caused by the disposal of traditional non-degradable decorative materials. At the same time, the material's performance characteristics are comparable to commercially available products, achieving a balance between environmental friendliness and practicality, aligning with the current trend of green and environmentally friendly material development. Attached Figure Description

[0024] Figure 1 The figures show the wear resistance test results of the wear-resistant and corrosion-resistant polyester decorative materials for automotive steering wheels in Examples 1-7, Comparative Examples 1-4, and Comparative Examples 9-11 of this invention. Figure 2 The relationship between the mass of the materials prepared in Example 2 and Example 2 before modification of boron nitride and temperature is shown. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Please see Figures 1 to 2 This invention provides a wear-resistant and corrosion-resistant polyester decorative material for automotive steering wheels and its preparation method. The technical solution is as follows:

[0027] Preparation Example 1 The preparation method of modified boron nitride is as follows: Eight portions of h-BN powder with a particle size of 80 nm were added to 100 mL of concentrated nitric acid (65% by mass). The mixture was placed in an oil bath and heated to 90 °C. Reflux condensation was started, and the mixture was stirred at 400 rpm for 18 h. After the reaction was completed, the mixture was cooled to room temperature, and the solid was separated by filtration through a 0.22 μm filter membrane. The solid was washed six times with deionized water until the filtrate was neutral. The solid was then dried in a vacuum drying oven at 70 °C for 12 h to obtain hydroxylated boron nitride (BN-OH), which was then set aside for later use. 16.2 parts of ethacrylic acid were dissolved in 600 parts of a mixed solvent to obtain an ethacrylic acid solution. The ethacrylic acid solution, 13.5 parts of pinacol diboronate, 16.0 parts of potassium acetate, and 0.08 parts of palladium chloride were added to a reaction vessel and heated to 80°C under nitrogen protection. The mixture was stirred at 200 rpm for 8 hours and then cooled to room temperature to obtain a pinacol diboronate-modified ethacrylic acid solution. 300 parts of deionized water were added to the solution, and the mixture was filtered. The solution was extracted three times with 200 parts of ethyl acetate, washed twice with water, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain pinacol diboronate-modified ethacrylic acid (EA-B). The volume ratio of N,N-dimethylformamide to dimethyl sulfoxide in the mixed solvent was 2:3. 0.1 parts of BN-OH and 2 parts of EA-B were added to 20 mL of ethylene glycol dimethyl ether, and 0.05 parts of tetrabutyl titanate were added. The mixture was stirred at 300 rpm for 4 h at 80 °C under nitrogen protection to esterify the carboxyl groups of EA-B with the hydroxyl groups on the surface of BN-OH. At the same time, the unsaturated double bonds of EA-B were retained for subsequent grafting.

[0028] Preparation Examples 2-4 Unlike Preparation Example 1, the preparation method was changed as shown in Table 1. It should be noted that the total amount of BN-OH and EA-B was 10 parts.

[0029] Table 1. Preparation methods of modified boron nitride

[0030] Example 1 Eight parts of 80nm Al2O3 nanoparticles were added to 20 parts of ethylene glycol dimethyl ether, and the mixture was treated with an ultrasonic disperser at 400W and 40kHz for 20 minutes to form a uniform dispersion. After vacuum drying all other raw materials to remove moisture, the following experimental procedures were performed: 10 parts caprolactam and 0.15 parts deionized water were added as initiators to the enzyme reactor, along with 0.1 parts CALB lipase. The pH was maintained at 6, and the reaction was carried out at 50°C under nitrogen protection for 6 hours with a stirring speed of 100 rpm. The reaction was terminated by heating to 80°C to inactivate the enzyme and form an oligoamide intermediate. The reaction system was kept anhydrous to avoid enzyme inactivation. Add 50 parts PCL, 15 parts PLA, 15 parts PBS, 15 parts succinic acid, 8 parts 1,4-butanediol, 10 parts 1,4-cyclohexanedicarboxylic acid, 6 parts 1,4-cyclohexanediethanol, 5 parts trifluoromethacrylic acid, and 8 parts oligomeric amide intermediate to the reactor. Then, purge with nitrogen for protection and heat to 170°C. Melt and mix for 30 minutes at a stirring speed of 200 rpm to ensure uniform mixing of the raw materials. Add 0.2 parts of tetrabutyl titanate to the mixture, slowly heat to 230℃, start the vacuum pump, control the vacuum degree to -0.09MPa, and react for 5 hours; monitor the reaction progress by the change of the stirring paddle torque or online infrared, and measure the final acid value after the reaction is completed. Stop the reaction when the acid value is ≤5mgKOH / g. The reactor temperature was lowered to 180℃, 2 parts of HDI were added, and the mixture was stirred at 300 rpm for 1 h to increase the molecular weight of the polyester-amide copolymer to Mn = 80,000-120,000. 5 parts of the modified boron nitride obtained in Preparation Example 1 and 0.1 parts of dicumyl peroxide were added, and the mixture was stirred at 500 rpm for another 1 h to allow the unsaturated double bonds of EA-B to be grafted onto the remaining unsaturated bonds in the system via a free radical-initiated reaction, with a grafting rate of 28%. Add the pre-dispersed nano-Al2O3 dispersion and 3 parts of magnesium stearate to the reactor, and stir at high speed of 2000 rpm for 30 min to ensure uniform dispersion of the filler. The reaction product was extruded through a twin-screw extruder at a screw speed of 150 rpm and an extrusion temperature of 200-230℃. The product was then drawn into strands and granulated to obtain polyester-amide masterbatch. The masterbatch was placed in the injection molding machine, and the injection temperature was set to 210℃, the mold temperature to 70℃, the injection pressure to 90MPa, the holding time to 10 seconds, and the cooling time to 20 seconds to prepare a steering wheel decorative material sample. The molded sample was placed in a vacuum drying oven at 60°C and dried for 6 hours to remove residual solvent and moisture, thus obtaining the final product.

[0031] The difference between Examples 2-7 and Example 1 is that the following preparation conditions are changed, as shown in Tables 2-1 and 2-2.

[0032] Table 2-1 Methods for amide copolymerization and melt mixing

[0033] Table 2-2 Melt Mixing, Polycondensation Reaction, Reinforcement Modification and Extrusion Granulation Methods

[0034] The comparative example is identical to Example 6 except for the following parameters.

[0035] Comparative Example 1: Modified boron nitride was replaced with an equal amount of boron nitride.

[0036] Comparative Example 2: Modified boron nitride was replaced with an equal amount of EA-B.

[0037] Comparative Example 3: No modified boron nitride added.

[0038] Comparative Example 4: No magnesium stearate or nano-Al2O3 dispersion added.

[0039] Comparative Example 5 did not involve enzymatic ring-opening polymerization (amide copolymerization). Instead, caprolactam was added to the reactor along with other raw materials, such as PCL, PLA, and PBS.

[0040] Comparative Example 6: No oligoamide intermediates, 4-cyclohexanedicarboxylic acid, 1,4-cyclohexanediethanol and trifluoromethacrylic acid were added. The amount of succinic acid was increased to 20 parts and the amount of 1,4-butanediol was increased to 12 parts.

[0041] Comparative Example 7: No oligoamide intermediates and trifluoromethacrylic acid were added, and the amount of succinic acid was increased to 18 parts.

[0042] Comparative Example 8: 1,4-cyclohexanedicarboxylic acid was replaced with an equal mass of terephthalic acid.

[0043] Comparative Example 9: The polycondensation reaction temperature was 260℃.

[0044] Comparative Example 10: Injection temperature was 240℃, and injection pressure was 110MPa.

[0045] Comparative Example 11 uses a commercially available artificial leather steering wheel trim product, sourced from Nan Ya Plastics Industry (Nantong) Co., Ltd., model 1VVEM1.

[0046] Test Example 1 The wear resistance of the wear-resistant and corrosion-resistant automotive steering wheel polyester decorative materials obtained in Examples 1-7, Comparative Examples 1-4, and Comparative Examples 9-11 was tested.

[0047] The specific test method is as follows: Referring to ISO 9352:2012, the specimen is fixed on the turntable of the Taber abrasion tester, ensuring full contact between the specimen surface and the H-18 grinding wheel. The specimens are standard-sized specimens (100mm diameter, 5mm thickness) cut from the examples and comparative samples. The equipment is started, the grinding wheel rotates at 60 rpm, a 500g load is applied, and continuous abrasion is performed for 1500 revolutions. The specimen surface is checked every 250 revolutions, and wear marks are recorded. After 1000 revolutions of abrasion testing, the specimen mass loss (mg) is measured, and the surface is observed for obvious peeling, cracks, or color changes. A mass loss ≤50mg is excellent, 50-100mg is good, and >100mg is unacceptable. The final test results are shown in Table 3 and... Figure 1 As shown.

[0048] Table 3 Abrasion resistance test results

[0049] The wear-resistant and corrosion-resistant polyester decorative material for automotive steering wheels prepared according to the method of this invention has good wear resistance. (See Table 3 and...) Figure 1 As shown in Examples 1-7, the quality loss is small and the quality evaluation is high. Modified boron nitride forms chemical bonds with the polymer matrix through hydroxylation (BN-OH) and grafting EA-B, which enhances the interfacial bonding force with the polymer matrix, reduces filler spalling, and improves surface hardness and wear resistance. High-hardness nano-alumina particles are uniformly dispersed in the matrix, increasing the surface hardness of the material and resisting scratches and wear from the grinding wheel. Magnesium stearate acts as a lubricant and dispersant, improving the dispersibility of fillers in the matrix, reducing agglomeration, and improving the overall uniformity and wear resistance of the material. Enzymatic ring-opening polymerization and oligomeric intermediates form oligomeric amides through enzymatic polymerization, which enhances the regularity and strength of the polymer molecular chain. Combined with bio-based polyesters such as PCL, PLA, and PBS, high molecular weight polyester-amide copolymers are formed, which increase the toughness and wear resistance of the material. Furthermore, through optimized processes such as melt mixing, polycondensation reaction, grafting reaction, and extrusion granulation, adjustments are made to various aspects such as temperature, vacuum degree, and stirring speed to ensure uniform material structure, good filler dispersion, and excellent surface properties.

[0050] Unmodified boron nitride (BN) has an inert surface with a significant surface energy difference from the polar polyester matrix, making it prone to aggregation and poor dispersibility. After grafting with EA-B, polar groups such as carboxylic acid and ester groups are introduced into the BN surface, resulting in a better match with the matrix surface energy. This promotes uniform dispersion of BN within the matrix, ensuring even distribution of rigid fillers on the friction surface and preventing localized aggravation of wear. Therefore, Comparative Example 1, using unmodified boron nitride, lacks chemical bonding with the matrix, resulting in weak interfacial adhesion, easy filler peeling, and decreased wear resistance. Comparative Example 2, using only EA-B, lacks the hardness support of boron nitride. The surface hardness of the material was insufficient, resulting in poor wear resistance. Comparative Example 3 lacked modified boron nitride and high-hardness filler, making the surface easily worn. Comparative Example 4 lacked nano-Al2O3 and magnesium stearate, resulting in poor filler dispersion, reduced surface hardness and uniformity, and further decreased wear resistance. Comparative Example 9's excessively high polycondensation temperature led to polymer degradation, reduced molecular weight, and affected wear resistance. Comparative Example 10's excessively high injection molding temperature and pressure damaged the material structure, causing microscopic defects and reducing wear resistance. Comparative Example 11's commercially available artificial leather material had wear resistance comparable to the examples.

[0051] In summary, the wear-resistant and corrosion-resistant polyester decorative material for automotive steering wheels prepared according to the process of the present invention has good wear resistance. Under the conditions of the examples, the wear resistance of the products is better than that of the comparative examples, and the overall wear resistance of the products of the examples and the comparative examples is better than that of the commercially available product of comparative example 11.

[0052] Test Example 2 The wear-resistant and corrosion-resistant polyester decorative materials for automotive steering wheels prepared by the methods of Examples 1-7, Comparative Examples 4-7, and Comparative Examples 9-11 were subjected to corrosion resistance tests. The specific test methods are as follows: salt spray test, acid sweat immersion test, and sunscreen resistance test were conducted to examine the corrosion resistance of the decorative materials. The samples were cut into 50mm×50mm×2mm flat plates, cleaned with anhydrous ethanol, and dried for 24 hours before subsequent experiments. The salt spray test followed the national standard GB / T10125-2012 "Artificial Atmosphere Corrosion Test - Salt Spray Test". The samples were placed in a salt spray chamber at 35℃, with a 5% NaCl solution at pH 7.2, and continuously sprayed for 240 hours. The samples were positioned at a 30° angle to the vertical. The acidic sweat immersion test was conducted using a solution composed of 0.5% NaCl, 0.1% lactic acid, and 0.1% urea, pH 4.5, at 40℃, for 168 hours of complete immersion. The sunscreen tolerance test involved applying a commercially available sunscreen (containing diethylaminobenzoyl benzoate and glycerin) evenly to the sample surface, placing it in a 40℃ oven for 72 hours, sealing it with plastic wrap after application, and wiping the surface with cotton balls after the test to observe for any residue penetration or material softening. In the salt spray test, the performance of the products gradually decreased, ranging from no rust, slight rust, local blistering, local rust, moderate rust, obvious rust, surface cracks with rust, to severe rust. The sunscreen tolerance test results showed no penetration softening, slight softening, penetration marks, severe softening, and complete softening, with performance gradually decreasing. The final test results are shown in Table 4.

[0053] Table 4 Corrosion Resistance Test Results

[0054] Under the conditions described in the examples, the preparation method was adjusted to achieve excellent corrosion resistance in the material. Magnesium stearate is a long-chain fatty acid magnesium salt containing hydrophobic alkyl chains and hydrophilic carboxylate groups. On the material surface, the carboxylate groups are bonded to the polar groups of the polyester / amide through ionic or hydrogen bonds, while the alkyl chains are oriented outwards to form a hydrophobic film approximately 10-20 nm thick, hindering the penetration of polar corrosive media such as water, salt ions, and organic acids. Modified boron nitride is grafted onto trifluoromethylacrylic acid via the unsaturated double bond of EA-B and is uniformly dispersed in the matrix. Its layered structure physically fills the micropores inside the material, extending the penetration path of corrosive media. The hydrophobicity of trifluoromethylacrylic acid and the chemical inertness of boron nitride work synergistically to reduce the material's water absorption and improve its chemical corrosion resistance. The material exhibits strong corrosion resistance and provides dual protection against salt spray corrosion. Enzymatic ring-opening polymerization introduces oligoamide intermediates that enhance intermolecular forces with PCL / PLA / PBS through hydrogen bonds, forming a dense network structure that reduces water absorption and minimizes diffusion channels for corrosive media. Nano-alumina is uniformly embedded into the matrix surface through ultrasonic dispersion, where its surface hydroxyl groups react with the carboxyl groups of magnesium stearate, further solidifying the hydrophobic film. Simultaneously, the high chemical inertness of alumina resists corrosion from weak acids such as lactic acid in sweat. Furthermore, the synergistic effect of the above preparation methods and raw materials, including melt mixing, polycondensation, grafting, and extrusion granulation, improves the final corrosion resistance of the material.

[0055] Under comparative conditions, Comparative Example 4, lacking nano-alumina and magnesium stearate, exhibited poor filler dispersibility, increased matrix micropores, and easy salt spray penetration, resulting in reduced corrosion resistance. Comparative Example 5, lacking enzymatic ring-opening polymerization and with direct addition of caprolactam, failed to form a regular oligomeric amide, leading to reduced matrix chemical stability and poor corrosion resistance. Comparative Example 6, with increased amounts of succinic acid and 1,4-butanediol, showed a higher proportion of flexible methylene groups in the polyester segments, but lacked oligomeric amide intermediates, 4-cyclohexanedicarboxylic acid, 1,4-cyclohexanediethanol, and trifluoromethylacrylic acid, resulting in significant corrosion during salt spray testing. The rate of quality change due to sweat immersion increased, and sunscreen softened significantly; Comparative Example 7 lacked hydrogen bonding of amide bonds and double bond grafting sites, as well as trifluoromethylacrylic acid, resulting in decreased corrosion resistance; Comparative Example 9: High temperature caused thermal degradation of polyester chains, and molecular chain breakage produced polar groups such as carboxyl groups; the material's hydrophilicity increased, making it easy to adsorb corrosive media, thus reducing corrosion resistance; Comparative Example 10: High temperature and high pressure caused excessive molecular chain orientation, resulting in microcracks on the surface, and corrosive media penetrated along the cracks, reducing corrosion resistance; Comparative Example 11: Traditional PVC has good corrosion resistance, but it is not degradable.

[0056] Test Example 3 The wear-resistant and corrosion-resistant polyester decorative materials for automotive steering wheels prepared in Examples 1-7 and Comparative Examples 1-11 were subjected to heat resistance tests. The specific test methods are as follows: referring to the national standard GB / T7141-2008 "Plastics - Test Method for Thermal Aging" and ISO75-2:2013 "Plastics - Determination of Deformation Temperature under Load", and adjusted according to the actual application scenarios of automotive interior materials.

[0057] Standard-sized specimens (80mm × 10mm × 4mm) were cut from the samples prepared in Examples 1-7 and Comparative Examples 1-11, conforming to ISO 75-2. The specimens had smooth surfaces without obvious defects. After cleaning with anhydrous ethanol and drying for 24 hours, they were transferred to a thermal aging test chamber for thermal aging experiments. The temperature was 90℃, simulating the high-temperature environment of automotive interiors in summer, and the exposure time was 240 hours, simulating long-term high-temperature aging. The relative humidity was 28%. After thermal aging, mass loss was tested. Mass loss ≤0.5% was considered excellent, 0.5%-1.0% was good, and >1.0% was unacceptable. The final test results are shown in Table 5. The heat resistance of boron nitride before modification, the modified boron nitride of Preparation Example 2, and the decorative material of Example 2 were also tested, as detailed below. Figure 2 As shown.

[0058] Table 5 Results of heat resistance test

[0059] Figure 2The results show that the boron nitride before modification has a high mass retention rate, while the mass loss increases under the same test conditions after modification. The mass loss of the wear-resistant and corrosion-resistant automotive steering wheel polyester decorative material in Example 2 is also significantly increased, but there is no significant mass loss at 200℃. Under the conditions of this invention, modified boron nitride (BN-OH) grafted with EA-B, oligoamide intermediates, and nano-Al2O3, and optimized through processes such as enzymatic ring-opening polymerization, polycondensation, and grafting, exhibits excellent heat resistance. Boron nitride has extremely high thermal stability and does not decompose at high temperatures, enhancing the material's thermal stability and resistance to thermal degradation. EA-B combines with BN-OH through chemical bonding and esterification, enhancing the interfacial bonding force between the filler and the matrix, reducing filler peeling or interfacial cracking at high temperatures. The oligoamide formed by enzymatic ring-opening polymerization has a regular structure, and the high bond energy of the amide bonds endows it with excellent thermal stability. Copolymerization with PCL, PLA, and PBS forms a high molecular weight polyester-amide copolymer, increasing the heat distortion temperature. Alumina has high thermal conductivity and a high melting point, improving the material's heat resistance. The material exhibits excellent thermal stability, reducing thermal degradation and deformation at high temperatures. It uniformly disperses and fills the micropores of the matrix, enhancing structural rigidity and delaying thermal deformation. The fluorinated groups of trifluoromethyl methacrylate possess high bond energy and are resistant to thermal decomposition. Through grafting reactions, they form a cross-linked network, improving the thermal stability of the matrix. Magnesium stearate improves filler dispersibility, reduces agglomeration, ensures structural uniformity of the material at high temperatures, and reduces cracks caused by thermal stress concentration. PCL provides flexibility, while PLA and PBS provide rigidity, synergistically forming a high molecular weight copolymer that balances toughness and thermal stability. The cyclohexane structure increases the rigidity of the polymer chain, enhancing resistance to heat deformation while preventing yellowing. These conditions, combined with processes such as melt mixing, polycondensation, grafting reactions, and extrusion granulation, ensure a dense matrix structure, uniform filler dispersion, and reduced microscopic defects at high temperatures.

[0060] Table 5 shows that Comparative Example 1, without modified boron nitride, lacked chemical bonding, resulting in weak interfacial adhesion, filler spalling at high temperatures, and decreased heat resistance; Comparative Example 2, using only EA-B without the thermal stability support of boron nitride, had insufficient matrix rigidity and poor heat resistance; Comparative Example 3, without modified boron nitride, lacked high thermal stability fillers, making the matrix prone to thermal degradation; Comparative Example 4, lacking nano-Al2O3 and magnesium stearate, had poor filler dispersibility, increased matrix micropores, and severe cracking at high temperatures; Comparative Example 5, without enzymatic ring-opening polymerization, directly added caprolactam, failing to form a regular oligoamide, resulting in reduced thermal stability; Comparative Example 6, without oligoamide, trifluoromethylacrylic acid, and 1,4-cyclohexanedicarboxylic acid / dimethylethanol, had a matrix... Insufficient rigidity and thermal stability; Comparative Example 7 lacks oligoamide and trifluoromethacrylic acid, resulting in the absence of amide bonds and crosslinking networks, leading to decreased thermal stability, but its heat resistance is better than Comparative Example 6; Comparative Example 8 uses terephthalic acid to replace 1,4-cyclohexanedicarboxylic acid, increasing rigidity but reducing flexibility, making it prone to cracking at high temperatures, with reduced mass loss compared to other comparative examples, but causing yellowing; Comparative Examples 9 and 10 suffer from excessively high polycondensation temperatures, excessively high injection molding temperatures and pressures, leading to polymer thermal degradation, reduced molecular weight, and poor heat resistance; Comparative Example 11 shows that the thermal stability of commercially available artificial leather is slightly lower than that of the examples, and although commercially available decorative products are similar to the products of this invention in performance, they are non-degradable and cannot meet environmental protection requirements.

[0061] Test Example 4 The wear-resistant and corrosion-resistant polyester decorative materials for automotive steering wheels prepared in Examples 1-7 were subjected to degradation performance tests. The specific test methods are as follows: The sample size was set to 50mm×50mm×2mm. The specimens were placed in a standard composting environment, referring to GB / T 19277.1-2011 "Determination of final aerobic biodegradation and disintegration of materials under controlled composting conditions - Part 1: Analysis by measuring released carbon dioxide". The composting conditions were a temperature of 58℃, a relative humidity of 60%, and the compost substrate was mature compost (organic matter content ≥50%). The specimens were buried in the compost to a depth of about 5cm. The test lasted for 180 days. The specimens were periodically removed every 30 days, the surface compost residue was cleaned, dried, and weighed. The mass loss rate, i.e., the degradation rate, was calculated. The test results are summarized in Table 6.

[0062] It can be observed that the wear-resistant and corrosion-resistant polyester decorative material for automotive steering wheels prepared according to the method of the embodiments of the present invention can be naturally degraded by microorganisms, exhibiting good degradation performance and better environmental performance compared with commercially available products.

[0063] Table 6 Degradability Test Results

[0064] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a wear-resistant and corrosion-resistant polyester decorative material for automotive steering wheels, characterized in that, The preparation method is as follows: Biodegradable polymer, polymer monomers and polymer intermediates are added to a reactor for melt mixing, a catalyst is added for polycondensation reaction, hexamethylene diisocyanate and modified boron nitride are added for chain extension and grafting reaction, nano alumina dispersion and magnesium stearate are added for reinforcement modification, and then the wear-resistant and corrosion-resistant automotive steering wheel polyester decorative material is prepared by extrusion granulation, injection molding and post-treatment. The modified boron nitride is obtained by esterification of hydroxylated boron nitride with pinacol diboron ester modified ethacrylic acid.

2. The method for preparing a wear-resistant and corrosion-resistant polyester decorative material for automotive steering wheels according to claim 1, characterized in that, The biodegradable polymer is composed of polycaprolactone, polylactic acid, and polybutylene succinate; the polymer monomer is composed of succinic acid, 1,4-butanediol, 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexanediethanol, and trifluoromethacrylic acid; the polymer intermediate is an oligomeric amide intermediate.

3. The method for preparing a wear-resistant and corrosion-resistant polyester decorative material for automotive steering wheels according to claim 2, characterized in that, The oligoamide intermediate was obtained by reacting caprolactam and lipase under nitrogen protection.

4. The method for preparing a wear-resistant and corrosion-resistant polyester decorative material for automotive steering wheels according to claim 1, characterized in that, The hydroxylated boron nitride is obtained by reflux reaction of boron nitride and concentrated nitric acid, followed by filtration, washing and drying.

5. The method for preparing a wear-resistant and corrosion-resistant polyester decorative material for automotive steering wheels according to claim 1, characterized in that, The preparation method of the ethacrylic acid modified by pinacol diboron ester is as follows: ethacrylic acid is dissolved in a mixed solvent to obtain an ethacrylic acid solution; the ethacrylic acid solution, pinacol diboron ester, potassium acetate and catalyst are added to a reaction vessel, and the reaction is carried out under nitrogen protection. After adding deionized water for filtration, extraction and washing with water again and drying, the ethacrylic acid modified by pinacol diboron ester is obtained.

6. The method for preparing a wear-resistant and corrosion-resistant polyester decorative material for automotive steering wheels according to claim 1, characterized in that, The modified boron nitride is obtained by esterification of the hydroxylated boron nitride and the pinacol diboron ester modified ethacrylic acid in the presence of tetrabutyl titanate.

7. The method for preparing a wear-resistant and corrosion-resistant polyester decorative material for automotive steering wheels according to claim 1, characterized in that, The nano-alumina dispersion is obtained by ultrasonic dispersion of nano-alumina and ethylene glycol dimethyl ether.

8. A wear-resistant and corrosion-resistant polyester decorative material for automotive steering wheels, characterized in that: The wear-resistant and corrosion-resistant polyester decorative material for automotive steering wheels is prepared by the preparation method described in any one of claims 1-7; the raw materials for preparing the decorative material include: polycaprolactone, polylactic acid, polybutylene succinate, succinic acid, 1,4-butanediol, 1,4-cyclohexanedicarboxylic acid, nano-alumina, trifluoromethacrylic acid, and modified boron nitride.

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