Crack-resistant thermoplastic resin coating and method of making and use thereof

Abstract

The present application belongs to the technical field of coating compositions, and particularly relates to a thermal plastic resin coating capable of preventing cracking, and a preparation method and application thereof. The thermal plastic resin coating capable of preventing cracking is prepared from the following raw materials in parts by weight: 88-95 parts of thermal plastic resin, 0.1-2 parts of antioxidant, 0.1-2 parts of light stabilizer, 2-8 parts of modified short fiber aluminum silicate, 2-5 parts of ethylene-vinyl acetate copolymer, and 0-2 parts of color powder. The modified short fiber aluminum silicate is used as a cracking preventing agent, and a double interface optimization mechanism of "surface activation + interface coupling" is utilized to improve the interface bonding force and structural stability of the thermal plastic resin. Meanwhile, the toughening effect of the ethylene-vinyl acetate copolymer is synergized, a silver crack-shear band mechanism is utilized, a synergistic system of "rigid anti-cracking + flexible toughening" is formed, and the anti-cracking performance of the thermal plastic resin coating is improved.

Description

Technical Field

[0001] This invention belongs to the field of coating composition technology, specifically relating to a crack-resistant thermoplastic resin coating, its preparation method, and its application. Background Technology

[0002] Thermoplastic resin coatings are a type of coating that uses thermoplastic resin as the main film-forming substance. Their characteristics include film formation through solvent evaporation or melt leveling, softening upon heating after drying and hardening upon cooling, and the ability to be repeatedly processed and recycled. Traditional thermoplastic resin coatings are prone to cracking due to thermal stress differences in environments below -40°C, leading to problems such as coating peeling and substrate corrosion in components like metal frames of refrigerators and freezers. To address these issues, existing technologies in the industry often employ rubber elastomer toughening, which involves adding elastomer particles such as nitrile rubber or EPDM rubber to the thermoplastic resin matrix. The elastomer's flexibility at low temperatures absorbs stress, improving the coating's crack resistance. However, this approach has two major technical drawbacks that directly affect the coating's processing performance and final quality: firstly, deterioration of powder leveling properties, resulting in pitting on the coating surface; and secondly, excessively high particle size distribution dispersion, affecting subsequent fluidized bed processes.

[0003] Chinese patent CN118909495A discloses a thermoplastic resin coating, its preparation method, and its application. The thermoplastic resin coating, by weight, comprises: 20-40 parts of thermoplastic acrylic resin, 10-20 parts of fatty alcohol, 10-15 parts of modified epoxy resin, 40-60 parts of glass frit, 4-8 parts of pigments and fillers, 10-20 parts of modified fillers, 0.2-0.8 parts of mildew inhibitor, 1.5-3 parts of defoamer, and 100-200 parts of solvent. However, the low-temperature resistance of this thermoplastic resin coating is poor. Summary of the Invention

[0004] The purpose of this invention is to provide a crack-resistant thermoplastic resin coating that solves the problem of environmental stress cracking of the coating under low-temperature conditions, which leads to its peeling off on the metal substrate or metal corrosion. This invention also provides a method for preparing and applying the crack-resistant thermoplastic resin coating.

[0005] The crack-resistant thermoplastic resin coating of the present invention is made from the following raw materials in parts by weight:

[0006] 88-95 parts of thermoplastic resin

[0007] Antioxidant 0.1-2 parts

[0008] Light stabilizer 0.1-2 parts

[0009] 2-8 parts of modified short fiber aluminum silicate

[0010] 2-5 parts of ethylene-vinyl acetate copolymer

[0011] 0-2 parts of coloring powder.

[0012] The thermoplastic resin is at least one of polyethylene, polypropylene, nylon 12 or thermoplastic phenolic resin, and the light stabilizer is one or two of 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, 3,5-di-tert-butyl-4-hydroxybenzoic acid-2,4-di-tert-butylphenyl ester or 2-hydroxy-4-n-octyloxybenzophenone.

[0013] The antioxidant is at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (antioxidant 1076) or 2,4,6-tri-tert-butylphenol.

[0014] The preparation method of modified short-fiber aluminum silicate includes the following steps:

[0015] (a) Citric acid, short-fiber aluminum silicate and deionized water are reacted, washed and dried to obtain short-fiber aluminum silicate complex;

[0016] (b) The short fiber aluminum silicate complex was added to a solution of triisostearate acyl titanate isopropyl ester, stirred and reacted, filtered and dried to obtain modified short fiber aluminum silicate.

[0017] The preparation method of short-fiber aluminum silicate in step (a) is as follows: the raw materials are crushed, mixed evenly, melted, fiberized, solidified, and cut to obtain short-fiber aluminum silicate. The raw materials are quartz sand and Al2O3. The molar ratio of Al2O3 to SiO2 in quartz sand is 1:2.2-2.5. The melting temperature is 1750-1760℃ and the melting time is 2-4 hours. The length of the short-fiber aluminum silicate is 20-22 mm. The mass ratio between short-fiber aluminum silicate, citric acid and deionized water is 1:0.05-0.08:2-2.5. The reaction temperature is 50-80℃ and the reaction time is 2-3 hours.

[0018] In step (b), the concentration of the triisostearyl titanate isopropyl ester solution is 1-2 wt.%, the mass ratio of the triisostearyl titanate isopropyl ester solution to the short fiber aluminum silicate complex is 1:30-50, the stirring reaction temperature is 40-60℃, and the stirring reaction time is 40-90 minutes.

[0019] The method for preparing the crack-resistant thermoplastic resin coating of the present invention includes the following steps:

[0020] (1) Modified short fiber aluminum silicate is blended and granulated with thermoplastic resin in one step, and then dried to obtain blended particles;

[0021] (2) The blended particles are mixed with antioxidants, light stabilizers, ethylene-vinyl acetate copolymers and color powders for secondary blending and granulation, and then dried to obtain plastic particles;

[0022] (3) The plastic particles are ground, sieved, and packaged to obtain a crack-resistant thermoplastic resin coating.

[0023] The moisture content of the blended particles in step (1) is <0.1 wt.%, and the moisture content of the plastic particles in step (2) is <0.1 wt.%.

[0024] In steps (1) and (2), a twin-screw extruder is used for blending and granulation. The conditions for blending and granulation are as follows:

[0025] The twin-screw extruder has a main unit speed of 200-800 r / min. The temperature settings for the twin-screw extruder are as follows: Zone 1: 80-100℃, Zone 2: 160-200℃, Zone 3: 160-200℃, Zone 4: 160-200℃, Zone 5: 160-200℃, Zone 6: 160-200℃, Zone 7: 160-200℃, Zone 8: 160-200℃, Zone 9: 160-200℃, Zone 10: 160-200℃, and Die head temperature: 180-220℃.

[0026] In step (3), the crack-resistant thermoplastic resin coating D 50 It is 100-200μm.

[0027] The application of the anti-cracking thermoplastic resin coating described in this invention is its application in anti-cracking coatings.

[0028] The preparation mechanism of modified short-fiber aluminum silicate is as follows: First, citric acid is used to modify short-fiber aluminum silicate (aspect ratio > 50:1), forming coordination bonds between the two to generate a short-fiber aluminum silicate complex. This achieves surface activation of the short-fiber aluminum silicate, breaking through the original surface inertness and hydrophobicity barriers, and initially improving the interfacial bonding force between the short-fiber aluminum silicate complex and the thermoplastic resin. Then, triisostearate isopropyl titanate is used for the second modification. As a bifunctional coupling agent, the alkoxy group of triisostearate isopropyl titanate can undergo a de-alcoholization reaction with the hydroxyl groups remaining on the surface of the short-fiber aluminum silicate complex, realizing the chemical combination of triisostearate isopropyl titanate and the short-fiber aluminum silicate complex, generating a more structurally stable modified short-fiber aluminum silicate. At the same time, the long-chain alkyl group in the triisostearate isopropyl titanate molecule can undergo physical entanglement or chemical interaction with the molecular chain of the thermoplastic resin, constructing a stable multi-scale interfacial system at the molecular level. The entire modification process significantly enhances the chemical bond and physical interaction between short-fiber aluminum silicate and thermoplastic resin through a dual interface optimization mechanism of "surface activation + interface coupling". The mechanical properties and crack resistance of the thermoplastic resin are improved by the molecular chain entanglement effect.

[0029] Citric acid introduces active sites to the surface of short-fiber aluminum silicate through esterification, reserving anchor points for triisostearate titanate isopropyl ester, thus solving the problem of difficult anchoring of triisostearate titanate isopropyl ester. Triisostearate titanate isopropyl ester achieves interfacial compatibility between inorganic filler and organic matrix through its amphiphilic structure, and can anchor citric acid to the surface of short-fiber aluminum silicate through chemical bonding, preventing citric acid from falling off during subsequent processing and ensuring long-lasting surface activation effect. The synergistic modification of the two achieves a relay process of "polar activation-nonpolar coupling", ultimately significantly improving the dispersibility, mechanical properties and processing flowability of modified short-fiber aluminum silicate.

[0030] This invention uses modified short-fiber aluminum silicate with dual modification of "surface activation + interface coupling" as an anti-cracking agent. It is first blended and granulated with thermoplastic resin to ensure uniform dispersion of modified short-fiber aluminum silicate in thermoplastic resin and avoid agglomeration. Then, by utilizing the chain entanglement effect between modified short-fiber aluminum silicate and thermoplastic resin, as well as the continuous physical support network formed by modified short-fiber aluminum silicate, the interfacial bonding force and structural stability of thermoplastic resin are significantly improved. At the same time, ethylene-vinyl acetate copolymer is introduced as a toughening agent. Utilizing the crazing-shear band mechanism, it forms a synergistic system of "rigid crack resistance + flexible toughening" with modified short-fiber aluminum silicate. Modified short-fiber aluminum silicate provides a physical support skeleton for thermoplastic resin to enhance strength, while the flexible segments of ethylene-vinyl acetate copolymer fill gaps and relieve stress concentration to improve the toughness of thermoplastic resin. Especially in low-temperature environments, ethylene-vinyl acetate copolymer can still maintain excellent toughness, which can effectively compensate for the defect of thermoplastic resin being brittle at low temperatures, thereby improving its performance in low-temperature environments.

[0031] The beneficial effects of this invention are as follows:

[0032] (1) This invention uses modified short fiber aluminum silicate as an anti-cracking agent, and utilizes its dual interface optimization mechanism of "surface activation + interface coupling" to improve the interfacial bonding force and structural stability of thermoplastic resin. At the same time, it works synergistically with the toughening effect of ethylene-vinyl acetate copolymer, and utilizes the silver ripple-shear band mechanism to form a synergistic system of "rigid crack resistance + flexible toughening" to improve the anti-cracking performance of thermoplastic resin.

[0033] (2) The anti-cracking thermoplastic resin coating in this invention can be applied to the surface of metal brackets and other components in refrigerators and freezers. The surface of the components after coating with the anti-cracking thermoplastic resin coating is smooth and flat, and the coating has high peel strength, which can improve the service life of refrigerators and freezers and achieve the purpose of cost reduction and efficiency improvement. It solves the problem that the coating is prone to environmental stress cracking under low temperature conditions and is prone to falling off the metal substrate or causing metal corrosion, which is conducive to reducing costs and promoting the development of high-performance coatings in China. Attached Figure Description

[0034] Figure 1 The image shows the DSC curve of the anti-cracking thermoplastic resin coating in Example 1.

[0035] Figure 2 This is the DSC curve of the anti-cracking thermoplastic resin coating in Example 2.

[0036] Figure 3 This is the DSC curve of the anti-cracking thermoplastic resin coating in Example 3.

[0037] Figure 4 This is the DSC curve of the anti-cracking thermoplastic resin coating in Example 4.

[0038] Figure 5 The image shows the infrared spectrum of the anti-cracking thermoplastic resin coating in Example 1.

[0039] Figure 6 The figures show the surface morphology of metal dip-coated parts with anti-cracking coatings in Examples 1-4 and Comparative Examples 1-5 after high and low temperature anti-cracking tests. In the figures, a is the surface morphology of Example 1, b is the surface morphology of Example 2, c is the surface morphology of Example 3, d is the surface morphology of Example 4, e is the surface morphology of Comparative Example 1, f is the surface morphology of Comparative Example 2, g is the surface morphology of Comparative Example 3, h is the surface morphology of Comparative Example 4, and i is the surface morphology of Comparative Example 5. Detailed Implementation

[0040] The present invention will be further described below with reference to embodiments.

[0041] Example 1

[0042] Preparation of short-fiber aluminum silicate:

[0043] Quartz sand and Al2O3 were crushed to below 200 mesh and then mixed evenly according to the molar ratio of Al2O3 to SiO2 in quartz sand of 1:2.2. The mixture was then sent to a furnace at 1750℃ to melt for 4 hours to obtain a melt. The melt flowed out through a 0.5mm nozzle and was blown into fibers by a high-pressure airflow of 0.8MPa. After air cooling and solidification, the fibers were cut and graded into 20mm short fibers to obtain short fiber aluminum silicate.

[0044] Preparation of modified short-fiber aluminum silicate:

[0045] (a) 0.5 kg of citric acid, 10 kg of short-fiber aluminum silicate and 20 kg of deionized water were mixed and reacted at 80 °C for 3 hours. After washing and drying, the short-fiber aluminum silicate complex was obtained.

[0046] (b) 30 kg of short fiber aluminum silicate complex was added to 1 kg of 1.5 wt.% triisostearyl titanate isopropyl ester solution, stirred at 60 °C for 60 minutes, filtered, and dried to obtain modified short fiber aluminum silicate.

[0047] Preparation of crack-resistant thermoplastic resin coatings:

[0048] (1) 3 kg of modified short fiber aluminum silicate and 89 kg of polyethylene were blended and granulated once in a twin-screw extruder. The granulated particles were dried in a vacuum oven until the moisture content was <0.1 wt.% to obtain blended particles.

[0049] (2) The blended particles in step (1) are mixed at high speed with 1.5 kg of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1.5 kg of 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, 3 kg of ethylene-vinyl acetate copolymer, and 2 kg of color powder in a twin-screw extruder for secondary blending and granulation. The granulated particles are then placed in a vacuum oven and dried until the moisture content is <0.1 wt.% to obtain plastic particles.

[0050] (3) The plastic granules were ground into powder using a disc mill, then sieved and graded, and packaged in moisture-proof bags to obtain D. 50 The coating is a 200μm crack-resistant thermoplastic resin coating. Differential scanning calorimetry (DSC) was used to test the crack-resistant thermoplastic resin coating; its DSC curve is shown below. Figure 1 The temperature corresponding to the melting peak in the figure is approximately 112.5℃, indicating that the crack-resistant thermoplastic resin coating has excellent solubility and thermal stability.

[0051] The conditions for co-granulation in steps (1) and (2) are as follows:

[0052] The twin-screw extruder has a main unit speed of 500 r / min and the temperature settings are as follows: Zone 1: 80-100℃, Zone 2: 160-200℃, Zone 3: 160-200℃, Zone 4: 160-200℃, Zone 5: 160-200℃, Zone 6: 160-200℃, Zone 7: 160-200℃, Zone 8: 160-200℃, Zone 9: 160-200℃, Zone 10: 160-200℃, and Die head temperature: 180-220℃.

[0053] Applications of crack-resistant thermoplastic resin coatings:

[0054] A crack-resistant thermoplastic resin coating is applied to the surface of a metal dip-molded part and then allowed to flow and level, resulting in a metal dip-molded part with a crack-resistant coating on the surface.

[0055] Example 2

[0056] Preparation of short-fiber aluminum silicate:

[0057] Quartz sand and Al2O3 were pulverized to below 200 mesh and then mixed evenly according to the molar ratio of Al2O3 to SiO2 in quartz sand of 1:2.5. The mixture was then sent to a furnace at 1760℃ to melt for 3 hours to obtain a melt. The melt flowed out through a 0.5mm nozzle and was blown into fibers by a high-pressure airflow of 0.8MPa. After air cooling and solidification, the fibers were cut and graded into 22mm short fibers to obtain short fiber aluminum silicate.

[0058] Preparation of modified short-fiber aluminum silicate:

[0059] (a) 0.8 kg of citric acid, 10 kg of short-fiber aluminum silicate and 25 kg of deionized water were mixed and reacted at 70 °C for 2.5 hours. After washing and drying, the short-fiber aluminum silicate complex was obtained.

[0060] (b) 30 kg of short fiber aluminum silicate complex was added to 1 kg of 2 wt.% triisostearyl titanate isopropyl ester solution, stirred at 40 °C for 90 minutes, filtered, and dried to obtain modified short fiber aluminum silicate.

[0061] Preparation of crack-resistant thermoplastic resin coatings:

[0062] (1) 2 kg of modified short fiber aluminum silicate and 88 kg of thermoplastic phenolic resin were blended and granulated once in a twin-screw extruder. The granulated particles were placed in a vacuum oven and dried until the moisture content was <0.1 wt.% to obtain blended particles.

[0063] (2) The blended particles in step (1) are mixed at high speed with 0.1 kg of 2,4,6-tri-tert-butylphenol, 2 kg of 3,5-di-tert-butyl-4-hydroxybenzoic acid-2,4-di-tert-butylphenyl ester, 5 parts of ethylene-vinyl acetate copolymer and 1 kg of color powder in a twin-screw extruder for secondary blending and granulation. The granulated particles are then placed in a vacuum oven and dried until the moisture content is <0.1 wt.% to obtain plastic particles.

[0064] (3) The plastic granules were ground into powder using a disc mill, then sieved and graded, and packaged in moisture-proof bags to obtain D. 50 This is a 100μm crack-resistant thermoplastic resin coating. The DSC curve of the crack-resistant thermoplastic resin coating is shown below. Figure 2 The temperature corresponding to the melting peak in the figure is approximately 115.4℃, indicating that the crack-resistant thermoplastic resin coating has excellent solubility and thermal stability.

[0065] The conditions for co-granulation in steps (1) and (2) are as follows:

[0066] The twin-screw extruder has a main unit speed of 500 r / min and the temperature settings are as follows: Zone 1: 80-100℃, Zone 2: 160-200℃, Zone 3: 160-200℃, Zone 4: 160-200℃, Zone 5: 160-200℃, Zone 6: 160-200℃, Zone 7: 160-200℃, Zone 8: 160-200℃, Zone 9: 160-200℃, Zone 10: 160-200℃, and Die head temperature: 180-220℃.

[0067] Applications of crack-resistant thermoplastic resin coatings:

[0068] A crack-resistant thermoplastic resin coating is applied to the surface of a metal dip-molded part and then allowed to flow and level, resulting in a metal dip-molded part with a crack-resistant coating on the surface.

[0069] Example 3

[0070] Preparation of short-fiber aluminum silicate:

[0071] Quartz sand and Al2O3 were pulverized to below 200 mesh and then mixed evenly according to the molar ratio of Al2O3 to SiO2 in quartz sand of 1:2.3. The mixture was then sent to a furnace at 1755℃ to melt for 2 hours to obtain a melt. The melt flowed out through a 0.5mm nozzle and was blown into fibers by a high-pressure airflow of 0.8MPa. After air cooling and solidification, the fibers were cut and graded into 21mm short fibers to obtain short fiber aluminum silicate.

[0072] Preparation of modified short-fiber aluminum silicate:

[0073] (a) 0.6 kg of citric acid, 10 kg of short-fiber aluminum silicate and 22 kg of deionized water were mixed and reacted at 50 °C for 2 hours. After washing and drying, the short-fiber aluminum silicate complex was obtained.

[0074] (b) 40 kg of short fiber aluminum silicate complex was added to 1 kg of 1 wt.% triisostearyl titanate isopropyl ester solution, stirred at 50 °C for 40 minutes, filtered, and dried to obtain modified short fiber aluminum silicate.

[0075] Preparation of crack-resistant thermoplastic resin coatings:

[0076] (1) 8 kg of modified short fiber aluminum silicate and 95 kg of polypropylene were blended and granulated once in a twin-screw extruder. The granulated particles were dried in a vacuum oven until the moisture content was <0.1 wt.% to obtain blended particles.

[0077] (2) The blended particles in step (1) are mixed at high speed with 2 kg of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester, 0.1 kg of 2-hydroxy-4-n-octyloxybenzophenone, and 2 kg of ethylene-vinyl acetate copolymer in a twin-screw extruder for secondary blending and granulation. The granulated particles are then placed in a vacuum oven and dried until the moisture content is <0.1 wt.%, to obtain plastic particles.

[0078] (3) The plastic granules were ground into powder using a disc mill, then sieved and graded, and packaged in moisture-proof bags to obtain D. 50 This is a 150μm crack-resistant thermoplastic resin coating. The DSC curve of the crack-resistant thermoplastic resin coating is shown below. Figure 3 The temperature corresponding to the melting peak in the figure is approximately 115.7℃, indicating that the crack-resistant thermoplastic resin coating has excellent solubility and thermal stability.

[0079] The conditions for co-granulation in steps (1) and (2) are as follows:

[0080] The twin-screw extruder has a main unit speed of 500 r / min and the temperature settings are as follows: Zone 1: 80-100℃, Zone 2: 160-200℃, Zone 3: 160-200℃, Zone 4: 160-200℃, Zone 5: 160-200℃, Zone 6: 160-200℃, Zone 7: 160-200℃, Zone 8: 160-200℃, Zone 9: 160-200℃, Zone 10: 160-200℃, and Die head temperature: 180-220℃.

[0081] Applications of crack-resistant thermoplastic resin coatings:

[0082] A crack-resistant thermoplastic resin coating is applied to the surface of a metal dip-molded part and then allowed to flow and level, resulting in a metal dip-molded part with a crack-resistant coating on the surface.

[0083] Example 4

[0084] Preparation of short-fiber aluminum silicate:

[0085] Quartz sand and Al2O3 were crushed to below 200 mesh and then mixed evenly according to the molar ratio of Al2O3 to SiO2 in quartz sand of 1:2.2. The mixture was then sent to a furnace at 1750℃ to melt for 4 hours to obtain a melt. The melt flowed out through a 0.5mm nozzle and was blown into fibers by a high-pressure airflow of 0.8MPa. After air cooling and solidification, the fibers were cut and graded into 20mm short fibers to obtain short fiber aluminum silicate.

[0086] Preparation of modified short-fiber aluminum silicate:

[0087] (a) 0.5 kg of citric acid, 10 kg of short-fiber aluminum silicate and 20 kg of deionized water were mixed and reacted at 80 °C for 3 hours. After washing and drying, the short-fiber aluminum silicate complex was obtained.

[0088] (b) 50 kg of short fiber aluminum silicate complex was added to 1 kg of 1.5 wt.% triisostearyl titanate isopropyl ester solution, stirred at 60 °C for 60 minutes, filtered, and dried to obtain modified short fiber aluminum silicate.

[0089] Preparation of crack-resistant thermoplastic resin coatings:

[0090] (1) 6 kg of modified short fiber aluminum silicate and 88 kg of polyethylene were blended and granulated once in a twin-screw extruder. The granulated particles were dried in a vacuum oven until the moisture content was <0.1 wt.% to obtain blended particles.

[0091] (2) The blended particles in step (1) are mixed at high speed with 1.5 kg of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1.5 kg of 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, 3 kg of ethylene-vinyl acetate copolymer, and 2 kg of color powder in a twin-screw extruder for secondary blending and granulation. The granulated particles are then placed in a vacuum oven and dried until the moisture content is <0.1 wt.% to obtain plastic particles.

[0092] (3) The plastic granules were ground into powder using a disc mill, then sieved and graded, and packaged in moisture-proof bags to obtain D. 50 This is a 100μm crack-resistant thermoplastic resin coating. The DSC curve of the crack-resistant thermoplastic resin coating is shown below. Figure 4 The temperature corresponding to the melting peak in the figure is approximately 116.4℃, indicating that the crack-resistant thermoplastic resin coating has excellent solubility and thermal stability.

[0093] The conditions for co-granulation in steps (1) and (2) are as follows:

[0094] The twin-screw extruder has a main unit speed of 500 r / min and the temperature settings are as follows: Zone 1: 80-100℃, Zone 2: 160-200℃, Zone 3: 160-200℃, Zone 4: 160-200℃, Zone 5: 160-200℃, Zone 6: 160-200℃, Zone 7: 160-200℃, Zone 8: 160-200℃, Zone 9: 160-200℃, Zone 10: 160-200℃, and Die head temperature: 180-220℃.

[0095] Applications of crack-resistant thermoplastic resin coatings:

[0096] A crack-resistant thermoplastic resin coating is applied to the surface of a metal dip-molded part and then allowed to flow and level, resulting in a metal dip-molded part with a crack-resistant coating on the surface.

[0097] Comparative Example 1

[0098] Without adding modified short-fiber aluminum silicate, the other operations are the same as in Example 1, resulting in a crack-resistant thermoplastic resin coating and a metal dip-molded part with a crack-resistant coating on the surface.

[0099] Comparative Example 2

[0100] Without adding ethylene-vinyl acetate copolymer, other operations are the same as in Example 1, resulting in a crack-resistant thermoplastic resin coating and a metal dip-molded part with a crack-resistant coating on the surface.

[0101] Comparative Example 3

[0102] Replace steps (1) and (2) in Example 1 with mixing 3 kg of modified short-fiber aluminum silicate, 89 kg of polyethylene, 1.5 kg of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 3 kg of 2-(2H-benzotriazole-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, 3 kg of ethylene-vinyl acetate copolymer, and 2 kg of color powder at high speed in a twin-screw extruder, and then granulate them. The granulated particles are placed in a vacuum oven and dried until the moisture content is <0.1 wt.%, to obtain plastic particles. Other operations are the same as in Example 1, to obtain crack-resistant thermoplastic resin coating and metal dip-molded parts with crack-resistant coating on the surface.

[0103] Comparative Example 4

[0104] Preparation of modified short-fiber aluminum silicate:

[0105] Without adding citric acid, the other operations are the same as in Example 1, to obtain modified short-fiber aluminum silicate.

[0106] The preparation and application of the crack-resistant thermoplastic resin coating are the same as in Example 1, resulting in a crack-resistant thermoplastic resin coating and a metal dip-molded part with a crack-resistant coating on the surface.

[0107] Comparative Example 5

[0108] Preparation of modified short-fiber aluminum silicate:

[0109] Without adding triisostearyl titanate isopropyl ester, the other operations were the same as in Example 1, to obtain modified short fiber aluminum silicate.

[0110] The preparation and application of the crack-resistant thermoplastic resin coating are the same as in Example 1, resulting in a crack-resistant thermoplastic resin coating and a metal dip-molded part with a crack-resistant coating on the surface.

[0111] Infrared spectroscopy test

[0112] Infrared spectroscopy was performed on the anti-cracking thermoplastic resin coating in Example 1. The infrared spectrum is shown below. Figure 5 The figure shows 2915cm. -1 The absorption peak near the -CH2- asymmetric stretching vibration is at 2848 cm⁻¹. -1 The nearby peak is the absorption peak of the -CH2- symmetric stretching vibration, at 1463 cm⁻¹. -1 The nearby peaks are due to the bending vibration absorption of -CH2-. All three peaks are characteristic of polyethylene. Additionally, at 1050 cm⁻¹... -1 The absorption peak appearing nearby corresponds to the stretching vibration of the Si-O bond, 965 cm⁻¹. -1 The nearby peaks are absorption peaks of the CH bond plane outward bending vibration, indicating that modified short-fiber aluminum silicate was successfully introduced into the anti-cracking thermoplastic resin coating of Example 1.

[0113] High and low temperature crack prevention test

[0114] The metal dip-coated parts with anti-cracking coatings from Examples 1-4 and Comparative Examples 1-5 were sequentially placed in an environment with a temperature of 58-62℃ and a relative humidity of 90-96% for 1 hour, in an environment with a temperature of 23-27℃ and a relative humidity of 30-60% for 1 hour, in an environment with a temperature of -42 to -40℃ and a relative humidity of 30-80% for 3 hours, and in an environment with a temperature of 23-27℃ and a relative humidity of 30-60% for 1 hour. This constituted one cycle, and a total of 20 cycles were performed. The surface morphology of the metal dip-coated parts before and after the experiment was examined. Table 1 shows the surface morphology of the metal dip-coated parts with anti-cracking coatings from Examples 1-4 and Comparative Examples 1-5 before and after the high and low temperature anti-cracking experiment. The image shows the surface morphology of the metal dip-coated parts with anti-cracking coatings from Examples 1-4 and Comparative Examples 1-5 after the high and low temperature anti-cracking experiment. Figure 6 .

[0115] Table 1. Surface morphology of metal dip-coated parts with anti-cracking coatings in Examples 1-4 and Comparative Examples 1-5 before and after high and low temperature anti-cracking tests.

[0116]

[0117] According to the results in Table 1, the coatings formed by the anti-cracking thermoplastic resin coatings prepared in Examples 1-4 have stronger anti-cracking ability.

[0118] After undergoing multiple high and low temperature cycles, the crack-resistant thermoplastic resin coating prepared by this invention improves the crack resistance of the thermoplastic resin coating through the interaction between the short-fiber aluminum silicate and thermoplastic resin through the dual modification of "surface activation + interface coupling" and the toughening effect of ethylene-vinyl acetate copolymer. This is achieved by utilizing the crazing-shear band mechanism. As a result, the coating formed by the crack-resistant thermoplastic resin coating can withstand greater external forces without cracking after multiple high and low temperature cycles.

[0119] Tensile strength test

[0120] The tensile strength of the anti-cracking coatings in Examples 1-4 and Comparative Examples 1-5 was tested according to the national standard GB / T 1040. The tensile strength of the anti-cracking coatings in Examples 1-4 and Comparative Examples 1-5 is shown in Table 2.

[0121] Table 2 Tensile strength of the anti-cracking coatings in Examples 1-4 and Comparative Examples 1-5

[0122]

[0123] According to the results in Table 2, the coatings formed by the anti-cracking thermoplastic resin coatings prepared in Examples 1-4 of this invention have higher tensile strength. This is due to the synergistic reinforcement mechanism of modified short-fiber aluminum silicate and ethylene-vinyl acetate copolymer in the anti-cracking thermoplastic resin coatings of this invention, which improves the performance of the coatings formed by the thermoplastic resin coatings.

Claims

1. A hotmelt resinous coating which is resistant to cracking, characterized in that By weight parts, made of the following raw materials: Thermoplastic resin 88-95 parts Antioxidant 0.1-2 parts Light stabilizer 0.1-2 parts Modified short fiber aluminum silicate 2-8 parts Ethylene-vinyl acetate copolymer 2-5 parts Color powder 0-2 parts; The preparation method of modified short fiber aluminum silicate comprises the following steps: (a) citric acid, short fiber aluminum silicate and deionized water are reacted, washed, dried to obtain short fiber aluminum silicate complex; (b) short fiber aluminum silicate complex is added to triisostearoyl isopropyl titanate solution, stirred and reacted, filtered, dried to obtain modified short fiber aluminum silicate; The preparation method of the anti-cracking thermoplastic resin coating comprises the following steps: (1) the modified short fiber aluminum silicate is blended and granulated with the thermoplastic resin for the first time, dried to obtain blended particles; (2) the blended particles are blended and granulated with the antioxidant, light stabilizer, ethylene-vinyl acetate copolymer and color powder for the second time, dried to obtain plastic particles; (3) the plastic particles are ground, sieved, packaged to obtain the anti-cracking thermoplastic resin coating.

2. The anti-cracking thermoplastic resin coating material according to claim 1, characterized by The thermoplastic resin is at least one of polyethylene, polypropylene, nylon 12 or thermoplastic phenolic resin, and the light stabilizer is one or two of 2-(2H-benzotriazole-2-yl)-4-(1,1,3,3-tetramethylbutyl) phenol, 3,5-di-tert-butyl-4-hydroxybenzoic acid-2,4-di-tert-butyl phenyl ester or 2-hydroxy-4-n-octyloxybenzophenone.

3. The anti-cracking thermoplastic resin coating material according to claim 1, characterized by The antioxidant is at least one of tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid] pentaerythritol ester, β-(3,5-di-tert-butyl-4-hydroxyphenyl) propyl n-octadecyl ester or 2,4,6-tri-tert-butyl phenol.

4. The anti-cracking thermoplastic resin coating material according to claim 1, characterized by In step (a), the preparation method of short fiber aluminum silicate is to crush and uniformly mix the raw materials, melt, fiberize, solidify, cut to obtain short fiber aluminum silicate, wherein the raw materials are quartz sand and Al2O3, the molar ratio of Al2O3 to SiO2 in quartz sand is 1:2.2-2.5, the melting temperature is 1750-1760℃, the melting time is 2-4 hours, and the length of short fiber aluminum silicate is 20-22mm; the mass ratio among short fiber aluminum silicate, citric acid and deionized water is 1:0.05-0.08:2-2.5, the reaction temperature is 50-80℃, and the reaction time is 2-3 hours.

5. The anti-cracking thermoplastic resin coating material according to claim 1, characterized by In step (b), the concentration of triisostearoyl isopropyl titanate solution is 1-2wt.%, the mass ratio of triisostearoyl isopropyl titanate solution to short fiber aluminum silicate complex is 1:30-50, the stirring reaction temperature is 40-60℃, and the stirring reaction time is 40-90 minutes.

6. The anti-cracking thermoplastic resin coating material according to claim 1, characterized by In step (1), the moisture content of blended particles is <0.1wt.%, and in step (2), the moisture content of plastic particles is <0.1wt.%.

7. The anti-cracking thermoplastic resin coating material according to claim 1, characterized by D of the anti-cracking thermoplastic resin coating in step (3) 50 was 100-200 μm.

8. Use of the anti-cracking thermoplastic resin coating according to any one of claims 1 to 7, characterized in that Application in anti-cracking coating.

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