A stone chip resistant coating, its preparation and use

Abstract

The present application belongs to the technical field of paint, and particularly relates to a stone impact resistant paint, a preparation method and application thereof. The stone impact resistant paint comprises PVC copolymer resin A, PVC copolymer resin B and an adhesion promoter. The PVC copolymer resin A contains vinyl acetate structure and carboxyl groups, and the molar content of the vinyl acetate structure is greater than or equal to 14%. The PVC copolymer resin B contains hydroxyl groups. The present application realizes low-temperature baking at 120-140 DEG C through the PVC copolymer resin A containing high vinyl acetate. The PVC copolymer resin A containing carboxyl groups, the PVC copolymer resin B containing hydroxyl groups and the adhesion promoter can all directly react with the hydroxyl groups on the surface of the base material, thereby improving the adhesion to the base material, enhancing the heat resistance of the paint, realizing high-temperature baking at 180-200 DEG C, and making the paint have excellent low-temperature curing performance, high-temperature stability, stone impact resistance and mechanical properties, and good adhesion on different base materials.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coatings, and particularly relates to an anti-stone impact coating as well as a preparation method and application thereof. BACKGROUND

[0002] The anti-stone impact coating for automobiles is mainly applied to the vehicle coating link and is sprayed on the bottom of the vehicle body, such as the chassis, wheel hub and mudguard, by means of airless spraying, and can play the roles of blocking sandstone impact, isolating sewage, sealing and corrosion prevention, noise reduction and shock absorption after baking and curing, and belongs to an indispensable link in the automobile coating process. With the rapid development of the new energy automobile industry, new requirements and challenges are put forward for the anti-stone impact coating.

[0003] The existing anti-stone impact coatings on the market generally have the problem of poor base material adhesion matching. The traditional automobile chassis is first subjected to electrophoresis and then sprayed with the anti-stone impact coating, so that good adhesion can be achieved after adding a conventional polyamide or polyurethane adhesion promoter. However, the new energy vehicle body or battery shell is usually made of 6061 or 6063 series aluminum material, and the surface treatment process of the aluminum material is different, resulting in obvious differences in adhesion of the same coating to aluminum profiles from different manufacturers. The adhesion may be 4 levels, and the adhesion may be 1 level. The coating is difficult to adhere to the aluminum profile. In addition, in the coating process in the workshop, the structure, energy consumption, degree of newness and set temperature of the baking equipment such as ovens and baking lines are different. The set temperature can be between 140-190℃, and the temperature difference is large. The actual temperature difference of each baking point in the baking line is larger. The best baking temperature of the ordinary PVC anti-stone impact coating is 140-180℃. If the temperature is lower than the lower limit, it is difficult to dry. If the temperature exceeds the upper limit, yellowing, cracking, holes and poor adhesion may occur. The ordinary anti-stone impact coating often does not match the on-site baking process. The coating is difficult to dry at low temperature or is not resistant to high temperature, and the baking line is generally difficult to adjust accordingly. Therefore, the anti-stone impact coating needs to have better adaptability to the baking process.

[0004] Therefore, it is of great significance to provide a coating with good adhesion, baking process adaptability and good anti-stone impact performance. SUMMARY

[0005] The present application aims to solve one or more technical problems in the prior art and at least provide a beneficial choice or create conditions. The present application provides an anti-stone impact coating with wide and good adhesion, excellent baking process adaptability and anti-stone impact performance.

[0006] The inventive concept of the present application: the present application adds carboxyl-containing PVC copolymer resin A, hydroxyl-containing PVC copolymer resin B and adhesion promoter, the carboxyl, hydroxyl and adhesion promoter not only can directly react with the hydroxyl groups on the surface of the substrate to improve the adhesion between the coating and the substrate surface, but also can form an effective network bonding structure through the synergistic effect and cross-linking curing of the three copolymer resins A, B and adhesion promoter, thereby improving the adhesion and the heat resistance of the coating, and achieving high-temperature baking at 180-200℃. In addition, by combining PVC copolymer resin A containing high-molar-content vinyl acetate, low-temperature baking at 120-140℃ can be achieved, and the interaction of the components makes the coating have excellent low-temperature curing performance, high-temperature stability, stone chip resistance and mechanical properties, and good adhesion on different substrates.

[0007] Therefore, the first aspect of the present application provides a stone chip resistant coating.

[0008] Specifically, a stone chip resistant coating comprises PVC copolymer resin A, PVC copolymer resin B and adhesion promoter.

[0009] The PVC copolymer resin A contains vinyl acetate structure and carboxyl, and the molar content of the vinyl acetate structure is ≥14%.

[0010] The PVC copolymer resin B contains hydroxyl.

[0011] Preferably, the PVC copolymer resin A is a copolymer resin of chloroethylene, vinyl acetate and dicarboxylic acid compound.

[0012] Preferably, the PVC copolymer resin B comprises at least one of chloroethylene and hydroxy acrylate copolymer resin, and chloroethylene and ethylene alcohol copolymer resin.

[0013] Preferably, the molar content of the carboxyl in the PVC copolymer resin A is ≥0.9%, and the molar content of the hydroxyl in the PVC copolymer resin B is ≥0.9%.

[0014] Further preferably, the molar content of the carboxyl in the PVC copolymer resin A is ≥1%, and the molar content of the hydroxyl in the PVC copolymer resin B is ≥1%.

[0015] Specifically, by using PVC copolymer resin A with high vinyl acetate content, the solubility of the resin in the solvent can be increased, and by controlling the molar content of the carboxyl in the PVC copolymer resin A and the molar content of the hydroxyl in the PVC copolymer resin B, the flexibility of the stone chip resistant coating can be increased and the softening temperature thereof can be reduced, thereby achieving the purpose of reducing the lower limit of the heat curing temperature of the coating, which is beneficial to cope with low-temperature (below 140℃) baking conditions and reduces the minimum baking temperature to about 120℃.

[0016] Specifically, the PVC copolymer resin B containing hydroxyl functional groups and the PVC copolymer resin A containing carboxyl functional groups, in cooperation with the adhesion promoter containing active groups, can cross-link the system to resist resin decomposition in high-temperature environment, thereby significantly improving the heat resistance of the product, and the formed coating has good surface hardness and wear resistance. The coating prepared from general homopolymer resin or copolymer resin will appear yellowing, cracking, bubbling and other phenomena after baking and curing at 180℃ / 40min, while the coating of the present application still has good surface state after baking and curing at 200℃ / 70min, without yellowing, cracking, bubbling and other phenomena.

[0017] Preferably, the adhesion promoter comprises at least one of polyamide, isocyanate, polyurethane resin, and epoxy resin.

[0018] Specifically, the polar groups such as amino, isocyanate group, and epoxy group in the adhesion promoter can directly bond or react with the groups on the surface of the substrate, thereby improving the adhesion, and can also co-react with the carboxyl and hydroxyl groups in the copolymer resin to promote cross-linking and curing and improve the adhesion.

[0019] Specifically, the traditional PVC paste resin is generally a homopolymer of vinyl chloride or a copolymer of vinyl chloride and vinyl acetate, which has poor adhesion to the surface of metal substrates such as aluminum due to its own polar groups. Therefore, in actual use, the surface often needs to be polished and cleaned before spraying and baking, and if the baking effect in the baking tunnel is poor, the phenomenon of poor adhesion such as plate peeling often occurs. The carboxyl group in the PVC copolymer resin A and the hydroxyl group in the PVC copolymer resin B of the present application can not only directly react with the hydroxyl groups on the surface of the treated substrate to improve the adhesion to the substrate surface, but also form an effective network bonding structure through the synergistic effect and cross-linking and curing of the copolymer resin A, the copolymer resin B, and the adhesion promoter, thereby improving the adhesion. The coating has excellent adhesion to different substrates, and the adhesion to electrophoretic paint plates and various aluminum materials is grade 4.

[0020] Preferably, the coating comprises 4.5-22 parts by weight of the PVC copolymer resin A, 4.5-22 parts by weight of the PVC copolymer resin B, and 0.9-5.5 parts by weight of the adhesion promoter.

[0021] Further preferably, the coating comprises 5-20 parts by weight of the PVC copolymer resin A, 5-20 parts by weight of the PVC copolymer resin B, and 1-5 parts by weight of the adhesion promoter.

[0022] Preferably, the coating further comprises at least one of a PVC blended resin, a filler, a plasticizer, a heat stabilizer, and a moisture absorbent.

[0023] Preferably, the coating includes PVC blend resin, filler, plasticizer, heat stabilizer, moisture absorbent; and the coating includes, by weight parts, PVC copolymer resin A 4.5-22 parts, PVC copolymer resin B 4.5-22 parts, adhesion promoter 0.9-5.5 parts, PVC blend resin 4.5-11 parts, filler 18-55 parts, plasticizer 9-33 parts, heat stabilizer 0.9-5.5 parts, moisture absorbent 2.7-5.5 parts.

[0024] Further preferably, the coating includes, by weight parts, PVC copolymer resin A 5-20 parts, PVC copolymer resin B 5-20 parts, adhesion promoter 1-5 parts, PVC blend resin 5-10 parts, filler 20-50 parts, plasticizer 10-30 parts, heat stabilizer 1-5 parts, moisture absorbent 3-5 parts.

[0025] Preferably, the PVC blend resin includes at least one of chloroethylene-vinyl acetate copolymer, chloroethylene-vinylidene chloride copolymer, chloroethylene-maleate copolymer, chloroethylene-acrylate copolymer plasticized paste blend resin.

[0026] Preferably, the viscosity of the PVC blend resin at 20℃ is 6.0-11.0 Pa·s; further preferably, the viscosity of the PVC blend resin at 20℃ is 6.5-10.0 Pa·s.

[0027] Preferably, the mass ratio of the total mass of the PVC copolymer resin A and the PVC copolymer resin B to the mass of the PVC blend resin is (18-36):(4.5-11); further preferably, the mass ratio of the total mass of the PVC copolymer resin A and the PVC copolymer resin B to the mass of the PVC blend resin is (18-36):(4.5-10); more further preferably, the mass ratio of the total mass of the PVC copolymer resin A and the PVC copolymer resin B to the mass of the PVC blend resin is (21-33):(5-7).

[0028] Specifically, the present application further strengthens the mechanical properties by adjusting the ratio of PVC copolymer resin to PVC blend resin. Specifically, although the PVC blend resin has poor paste forming property and cannot be used alone, the plasticizer absorption amount is low, the PVC paste can be replaced by part of the PVC paste resin in the preparation of the PVC paste, the product cost is reduced, the paste viscosity is greatly reduced, the paste processing performance is improved, but the mechanical properties are not as good as those of the PVC paste resin, and the addition amount is large, which will lead to the decrease of tensile strength, tensile shear strength and elongation at break. When the mass ratio of the total mass of the PVC copolymer resin A and the PVC copolymer resin B to the mass of the PVC blend resin is (18-36):(4.5-11), the best mechanical properties, good construction spraying performance and storage stability can be obtained while appropriately increasing the proportion of cheap raw materials and reducing the amount of plasticizer.

[0029] Preferably, the filler comprises at least one of heavy calcium carbonate, light nano calcium carbonate; further preferably, the filler comprises heavy calcium carbonate and light nano calcium carbonate.

[0030] Preferably, the plasticizer comprises at least one of benzoate, trioctyl trimellitate, dioctyl cyclohexane dicarboxylate, dioctyl terephthalate.

[0031] Specifically, there is a considerable content of plasticizer in the PVC coating formula, and the traditional coating generally selects phthalate plasticizer, such as DBP (dibutyl phthalate), DEHP (di-2-ethylhexyl phthalate), DINP (diisononyl phthalate) and the like, but the phthalate plasticizer has toxic effect and is harmful to human body and environment. The above-mentioned plasticizer can play the role of plasticizer in the coating, and is green and environmentally friendly, and friendly to human body and environment.

[0032] Preferably, the heat stabilizer comprises a liquid calcium-zinc composite stabilizer.

[0033] Preferably, the mass content of calcium and zinc in the liquid calcium-zinc composite stabilizer is ≥4.5%; further preferably, the mass content of calcium and zinc is ≥5%.

[0034] Specifically, by adding the liquid calcium-zinc composite stabilizer with mass content of calcium and zinc ≥4.5%, the heat stabilizing performance can be further improved.

[0035] Preferably, the hygroscopic agent comprises calcium oxide.

[0036] The second aspect of the present application provides a preparation method of the stone-resistant coating according to the first aspect of the present application.

[0037] Specifically, the preparation method of the stone-resistant coating comprises the following steps:

[0038] Mixing each raw material component to prepare the stone-resistant coating.

[0039] Preferably, the preparation method of the stone-resistant coating comprises the following steps:

[0040] (1) mixing the filler, the hygroscopic agent and part of the plasticizer, and stirring to obtain a first mixture;

[0041] (2) adding the remaining raw material components into the first mixture obtained in step (1), and stirring under vacuum to prepare the stone-resistant coating.

[0042] Preferably, in step (1), the part of the plasticizer accounts for 45-90% of the total mass of the plasticizer; further preferably, the part of the plasticizer accounts for 50-90% of the total mass of the plasticizer.

[0043] Preferably, in step (1), the stirring time is 25-35 min; further preferably, the stirring time is 27-33 min.

[0044] Preferably, in step (2), the vacuum stirring time is 1.3-1.7 h; further preferably, the vacuum stirring time is 1.4-1.6 h.

[0045] Preferably, in step (2), the vacuum stirring is followed by maturation; the maturation time is greater than or equal to 11 h; further preferably, the maturation time is greater than or equal to 12 h.

[0046] Preferably, after the maturation, vacuum stirring is continued; the vacuum stirring time is 1.3-1.7 h; further preferably, the vacuum stirring time is 1.4-1.6 h.

[0047] The third aspect of the present application provides a use of the stone chip resistant coating according to the first aspect of the present application in the field of vehicle coating.

[0048] Compared with the prior art, the technical solution provided by the present application has the following beneficial effects:

[0049] (1) The present application adds PVC copolymer resin A containing carboxyl, PVC copolymer resin B containing hydroxyl, and adhesion promoter. The carboxyl, hydroxyl, and adhesion promoter can not only directly react with the hydroxyl groups on the surface of the substrate to improve the adhesion to the substrate surface, but also form an effective network bonding structure through the synergistic effect and cross-linking solidification of copolymer resin A, copolymer resin B, and adhesion promoter, thereby improving the adhesion and the heat resistance of the coating, achieving high-temperature baking at 180-200℃. In addition, by combining PVC copolymer resin A containing high-molar-content vinyl acetate, low-temperature baking at 120-140℃ can be achieved. The interaction of the components makes the coating have excellent low-temperature curing performance, high-temperature stability, stone chip resistance, mechanical properties, good adhesion on different substrates, and can be normally used at a temperature and time interval of 120-200℃ baking for 20-70 minutes, and the stone chip resistance is 0.5 level, and the adhesion to electrophoretic paint plate or bare aluminum substrate is 4 level.

[0050] (2) The present application uses environmentally friendly raw materials, which are friendly to the environment and human body.

[0051] (3) The preparation process of the present application is simple and convenient for large-scale production and application. DETAILED DESCRIPTION

[0052] In order to make those skilled in the art more clearly understand the technical solutions of the present application, the following examples are given for illustration. It should be pointed out that the following examples do not constitute a limitation on the scope of protection required by the present application.

[0053] The raw materials, reagents or devices used in the following examples can be obtained from conventional commercial channels, or can be obtained by existing known methods, unless otherwise specified.

[0054] The model and manufacturer of each raw material component of the stone-resistant coating of embodiments 1-9 of the present application are as follows:

[0055] PVC copolymer resin A-1: H15 / 45M, Shanghai Wacker;

[0056] PVC copolymer resin A-2: TP-400M, South Korea Hancheng;

[0057] PVC copolymer resin B-1: SOLBIN A, industrial grade, Shanghai Derui;

[0058] PVC copolymer resin B-2: TP-500A, industrial grade, South Korea Hancheng;

[0059] PVC blending resin 1: ZCP-110, industrial grade, Hunan Yuhang;

[0060] PVC blending resin 2: SB-100C, industrial grade, Shanghai Chlor-alkali;

[0061] Adhesion promoter 1: 308, industrial grade, Wincell DKS;

[0062] Adhesion promoter 2: XA-350, industrial grade, Jiadida;

[0063] Thermal stabilizer: SAK-LCZ5033, industrial grade, Singapore Sanyi;

[0064] Plasticizer 1: DEHCH, industrial grade, Foshan Jinjia;

[0065] Plasticizer 2: DOTP, industrial grade, Qilu Lanfan.

[0066] The raw material components and amounts (parts) of the stone-resistant coating of embodiments 1-9 of the present application are shown in Table 1.

[0067] Table 1: Raw material components and amounts of the stone-resistant coating of embodiments 1-9

[0068]

[0069] Example 1

[0070] A stone-resistant coating, the raw material components and amounts of which are shown in Table 1.

[0071] The preparation method of the stone-resistant coating comprises the following steps:

[0072] (1) The filler, moisture absorbent and 50% of the plasticizer are added into the planetary stirring kettle and stirred for 30 min;

[0073] (2) The PVC copolymer resin, PVC blending resin, adhesion promoter, heat stabilizer and the remaining plasticizer are added into the planetary stirring kettle and stirred for 30 min, then vacuum stirring is carried out for 1.5 h; after standing for 12.5 h for curing, vacuum stirring is carried out for 1.5 h again, then the product is discharged and packaged to obtain the stone-resistant coating.

[0074] Example 2

[0075] A stone-resistant coating, the raw material components and amounts of which are shown in Table 1.

[0076] The preparation method of the stone-resistant coating comprises the following steps:

[0077] (1) The filler, moisture absorbent and 60% of the plasticizer are added into the planetary stirring kettle and stirred for 30 min;

[0078] (2) The PVC copolymer resin, PVC blending resin, adhesion promoter, heat stabilizer and the remaining plasticizer are added into the planetary stirring kettle and stirred for 30 min, then vacuum stirring is carried out for 1.5 h; after standing for 12 h or more for curing, vacuum stirring is carried out for 1.5 h again, then the product is discharged and packaged to obtain the stone-resistant coating.

[0079] Example 3

[0080] A stone-resistant coating, the raw material components and amounts of which are shown in Table 1.

[0081] The preparation method of the stone-resistant coating comprises the following steps:

[0082] (1) The filler, moisture absorbent and 60% of the plasticizer are added into the planetary stirring kettle and stirred for 30 min;

[0083] (2) The PVC copolymer resin, PVC blending resin, adhesion promoter, heat stabilizer and the remaining plasticizer are added into the planetary stirring kettle and stirred for 35 min, then vacuum stirring is carried out for 1.5 h; after standing for 14 h for curing, vacuum stirring is carried out for 1.5 h again, then the product is discharged and packaged to obtain the stone-resistant coating.

[0084] Example 4

[0085] A stone-resistant coating, the raw material components and amounts of which are shown in Table 1.

[0086] The preparation method of the stone-resistant coating comprises the following steps:

[0087] (1) The filler, moisture absorbent and 70% of the plasticizer are added into the planetary stirring kettle and stirred for 35 min;

[0088] (2) Add PVC copolymer resin, PVC blend resin, adhesion promoter, heat stabilizer and the rest of plasticizer into the planetary stirring kettle, continue to stir for 35 min, then vacuum stirring for 1.6 h; after standing for 14 h, vacuum stirring for 1.6 h again, then discharge and package to obtain the stone-resistant coating.

[0089] Example 5

[0090] A stone-resistant coating, the raw material components and the amount are shown in Table 1.

[0091] The preparation method of the stone-resistant coating comprises the following steps:

[0092] (1) Add filler, hygroscopic agent and 70% of plasticizer into the planetary stirring kettle, stir for 35 min;

[0093] (2) Add PVC copolymer resin, PVC blend resin, adhesion promoter, heat stabilizer and the rest of plasticizer into the planetary stirring kettle, continue to stir for 35 min, then vacuum stirring for 1.5 h; after standing for 13 h, vacuum stirring for 1.5 h again, then discharge and package to obtain the stone-resistant coating.

[0094] Example 6

[0095] A stone-resistant coating, the raw material components and the amount are shown in Table 1.

[0096] The preparation method of the stone-resistant coating comprises the following steps:

[0097] (1) Add filler, hygroscopic agent and 90% of plasticizer into the planetary stirring kettle, stir for 35 min;

[0098] (2) Add PVC copolymer resin, PVC blend resin, adhesion promoter, heat stabilizer and the rest of plasticizer into the planetary stirring kettle, continue to stir for 35 min, then vacuum stirring for 1.5 h; after standing for 13 h, vacuum stirring for 1.5 h again, then discharge and package to obtain the stone-resistant coating.

[0099] Example 7

[0100] A stone-resistant coating, the raw material components and the amount are shown in Table 1.

[0101] The preparation method of the stone-resistant coating of Example 7 is the same as that of Example 1.

[0102] Example 8

[0103] A stone-resistant coating, the raw material components and the amount are shown in Table 1.

[0104] The preparation method of the stone-resistant coating of Example 8 is the same as that of Example 1.

[0105] Example 9

[0106] A stone-impact-resistant coating, the raw material components and amounts of which are shown in Table 1.

[0107] The preparation method of the stone-impact-resistant coating of Example 9 is the same as that of Example 1.

[0108] Comparative Example 1

[0109] The difference between Comparative Example 1 and Example 1 is only that Comparative Example 1 uses an equal amount of a vinyl chloride homopolymer resin (PB-1702, industrial grade, Anhui Tianchen) to replace the PVC copolymer resin A-1 of Example 1, and the others are the same as Example 1.

[0110] Comparative Example 2

[0111] The difference between Comparative Example 2 and Example 1 is only that Comparative Example 2 uses an equal amount of a vinyl chloride-acetic acid vinyl binary copolymer resin (KCH-15, industrial grade, Korea Hanhua) to replace the PVC copolymer resin B-1 of Example 1, and the others are the same as Example 1.

[0112] Comparative Example 3

[0113] The difference between Comparative Example 3 and Example 1 is only that Comparative Example 3 uses an equal amount of a vinyl chloride homopolymer resin to replace the PVC copolymer resin B-1 of Example 1, and the others are the same as Example 1.

[0114] Comparative Example 4

[0115] The difference between Comparative Example 4 and Example 1 is only that Comparative Example 4 does not add an adhesion promoter, and the others are the same as Example 1.

[0116] Comparative Example 5

[0117] The difference between Comparative Example 5 and Example 1 is only that Comparative Example 5 uses an equal amount of PVC copolymer resin B-2 to replace the PVC copolymer resin A-1 of Example 1, i.e., does not contain PVC copolymer resin A-1, i.e., does not contain PVC copolymer resin A, and the others are the same as Example 1.

[0118] Comparative Example 6

[0119] The difference between Comparative Example 6 and Example 1 is only that Comparative Example 6 uses an equal amount of PVC copolymer resin A-2 to replace the PVC copolymer resin B-1 of Example 1, i.e., does not contain PVC copolymer resin B-1, i.e., does not contain PVC copolymer resin B, and the others are the same as Example 1.

[0120] Performance test

[0121] The stone-impact-resistant coatings prepared in Examples 1-9 and Comparative Examples 1-6 were tested for relevant performance, and the test items and methods are as follows:

[0122] 120°C dry time: The stone chip resistant coatings prepared in Examples 1-9, Comparative Examples 1-6 were sprayed on the surface of an electrophoresis painted steel panel substrate at a thickness of 1 mm, and the resulting sample was placed in an oven at 120°C to bake, and the dry time was determined; a dry time > 40 min was unqualified.

[0123] 200°C aging resistance: The stone chip resistant coatings prepared in Examples 1-9, Comparative Examples 1-6 were sprayed on the surface of an electrophoresis painted steel panel substrate at a thickness of 1 mm, and the resulting sample was placed in an oven at 200°C to bake, and the surface was checked every 5 min for yellowing, cracking, charring, hardening, and other phenomena; if the above phenomena appeared, it was determined that the aging end point was reached; an aging end point time < 50 min was unqualified.

[0124] Tensile strength and elongation at break: tested according to GB / T 528-2009, with a tensile machine clamp moving speed of 200 ± 2 mm / min, and a sample gauge length of 25 mm.

[0125] The stone chip resistant coatings prepared in Examples 1-9, Comparative Examples 1-6 were coated on the relevant substrates, with a wet film thickness of 2 mm, and the samples were placed in an oven at 140°C to bake for 30 min, and then the following performance tests were performed:

[0126] Shear strength: the substrate was 6061T5 aluminum material, the adhesive layer size was 25 mm*25 mm*2 mm, and the test was performed according to GB / T 7124-2008, with a tensile rate of 50 ± 1 mm / min.

[0127] Electrophoresis paint plate adhesion: the substrate was electrophoresis paint treated steel material, two parallel lines were cut on the sample with an art knife blade, the distance between the two lines was 5 mm, the cutting force was uniform and moderate, the blade edge penetrated the coating and reached the substrate, and then the coating was peeled off uniformly from the bottom, and the adhesion level was determined by the following standard: the adhesion by hand tearing could be divided into 4 levels, with level 4 being the best, with a peeling area of 100% cohesive failure; level 3 was ≥ 90% cohesive failure; level 2 was ≥ 30% cohesive failure; level 1 was the worst, with a cohesive failure of 0-29%.

[0128] 6061-T5 aluminum material adhesion: the substrate was 6061-T5 aluminum material, and the adhesion was tested by hand tearing (the test method was the same as the electrophoresis paint plate adhesion test).

[0129] 6063-T6 aluminum material adhesion: the substrate was 6063-T6 aluminum material, and the adhesion was tested by hand tearing (the test method was the same as the electrophoresis paint plate adhesion test).

[0130] Stone chip resistance: tested according to DIN EN ISO 20567-1, test method A was selected; according to the standard, the impact trace area was divided into 10 grades, 0.5-5 grades, 0.5 grade was the best, 5 grade was the worst.

[0131] The test results of each test item are shown in Table 2.

[0132] Table 2: Performance test results of stone chip resistant coatings prepared in Examples 1-9 and Comparative Examples 1-6

[0133]

[0134]

[0135] As can be seen from Table 2, the stone chip resistant coatings prepared in the examples of the present application have a 120℃ real drying time of less than 35 min, a 200℃ aging resistance of more than 60 min, even up to 70 min, a tensile strength of more than 1.42 MPa, an elongation at break of more than 140%, a shear strength of more than 1.45 MPa, an adhesion between the coating and the electrophoretic paint plate, 6061-T5 and 6063-T6 aluminum material of 4 grade, and an anti-stone chip performance of 0.5 grade. It shows that the stone chip resistant coatings prepared in the examples of the present application have excellent low-temperature curing performance, high-temperature stability, anti-stone chip performance, good adhesion matching performance on different substrates, and mechanical properties.

[0136] As can be seen from Examples 1 and Comparative Examples 1, 2, 3, 4, 5 and 6, when any one of the PVC copolymer resin A containing vinyl acetate and carboxyl groups, the PVC copolymer resin B containing hydroxyl groups, and the adhesion promoter is not added, the comprehensive performance of the product is significantly reduced, among which the 120℃ real drying time is increased to 40 min or more, the 200℃ aging resistance is less than 50 min and unqualified, the anti-stone chip performance is 2.0 grade or 2.5 grade, the electrophoretic paint adhesion is reduced to 3 grade, the 6061-T5 and 6063-T6 aluminum material adhesion is reduced to 3 grade or 2 grade, even 1 grade, and the mechanical properties also show a significant decrease. It shows that the PVC copolymer resin A containing carboxyl groups, the PVC copolymer resin B containing hydroxyl groups, and the adhesion promoter are added at the same time, and there is an obvious synergistic effect among the three, and the three work together to achieve excellent low-temperature curing performance, high-temperature stability, anti-stone chip performance, adhesion, and mechanical properties.

[0137] In addition, as can be seen from Example 1 and Example 9, the mass ratio of the PVC copolymer resin to the PVC blended resin also affects the performance of the product. When the mass ratio of the PVC copolymer resin to the PVC blended resin is (21-33):(5-7), the comprehensive performance of the product is better, wherein the stone impact resistance performance is rated as 0.5, the tensile strength is 1.55 MPa, the elongation at break is 148%, and the shear strength is 1.61 MPa.

[0138] The above examples are only used to illustrate the technical solutions of the present application and not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A coating, characterized in that, By weight, the coating comprises 4.5-22 parts of PVC copolymer resin A, 4.5-22 parts of PVC copolymer resin B, 0.9-5.5 parts of adhesion promoter, 4.5-11 parts of PVC blended resin, 18-55 parts of filler, 9-33 parts of plasticizer, 0.9-5.5 parts of heat stabilizer, and 2.7-5.5 parts of moisture absorber; The PVC copolymer resin A contains vinyl acetate structure and carboxyl groups; the molar content of the vinyl acetate structure is ≥14%. The PVC copolymer resin B contains hydroxyl groups; The PVC copolymer resin A is a copolymer resin of vinyl chloride, vinyl acetate, and dicarboxylic acid compound; The PVC copolymer resin B is selected from at least one of vinyl chloride and hydroxy acrylate copolymer resin and vinyl chloride and vinyl alcohol copolymer resin; The adhesion promoter contains active groups that react with the carboxyl groups in PVC copolymer resin A and the hydroxyl groups in PVC copolymer resin B.

2. The coating according to claim 1, characterized in that, The molar content of carboxyl groups in the PVC copolymer resin A is ≥0.9%; the molar content of hydroxyl groups in the PVC copolymer resin B is ≥0.9%.

3. The coating according to claim 1, characterized in that, The adhesion promoter includes at least one of polyamide, isocyanate, polyurethane resin, and epoxy resin.

4. The method for preparing the coating according to any one of claims 1-3, characterized in that, Includes the following steps: The coating is prepared by mixing the various raw material components.

5. The application of the coating according to any one of claims 1-3 in the field of vehicle painting.

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