Low-temperature fast curing coil steel household appliance primer as well as preparation method and application thereof

Abstract

The invention relates to a low-temperature fast-curing coil steel household appliance primer which comprises the following components in percentage by weight: 20-60% of straight-chain saturated polyester resin, 1-20% of amino resin, 1-20% of blocked isocyanate, 1-20% of anti-rust pigment, 4-30% of filler, 10-30% of solvent, 1-5% of phosphate adhesion promoter and 0.1-2% of sulfonic acid catalyst. The sum of the weight percentages of the components is 100%. According to the low-temperature fast-curing primer for the coil steel household appliances, through the synergistic effect of the phosphate adhesion promoter and the sulfonic acid type catalyst, fast curing is achieved when the plate surface temperature is lower than 200 DEG C or the baking time is shorter than 18 seconds, and energy conservation and emission reduction are achieved for a client side production line. Meanwhile, after being matched with universal finish paint, the primer for the household appliances has excellent processability, boiling resistance, chemical resistance, salt spray resistance and the like, and can provide long-term effective attractiveness and protection effects for coil steel color-coated sheets. The invention further discloses a preparation method and application of the low-temperature fast-curing primer for the coil steel household appliances.

Description

Technical Field

[0001] The present invention relates to the field of coatings, and specifically, to a low-temperature and rapid-curing coil steel household appliance primer, a preparation method thereof, and an application of the coil steel household appliance primer in household appliance color-coated plates. Background Art

[0002] Household appliances refer to various electrical appliances used in family life and similar places, which can be divided into two categories: black and white. Among them, white household appliances refer to household appliances that can reduce people's labor intensity, improve living environment, and enhance material and living standards, such as washing machines, air conditioners, refrigerators, and some kitchen appliances. By the mid-1990s, China had entered the forefront of the world in the production of major white household appliances, such as the production of refrigerators and washing machines. Entering the 21st century, with the rapid economic growth and the improvement of manufacturing levels, China has become the world's largest household appliance manufacturing base. The production of major products such as refrigerators, washing machines, air conditioners, and microwave ovens has ranked first in the world for many consecutive years and the proportion is increasing continuously.

[0003] CN110760249A discloses a low-temperature curing polyester topcoat for pre-coated metal coils and a preparation method thereof. The polyester topcoat for the coil steel uses a composite polyester resin composed of a micro-branched polyester resin and a high hydroxyl value polyester resin as the main raw material, and an amino resin as the curing agent, and can achieve film formation by curing under the conditions of a plate surface temperature of 202°C and a baking time of 30 seconds, and the MEK wiping resistance performance reaches more than 100 times; CN105419575A discloses a low-temperature curing back paint for coil coatings with a combined bottom and top layer and a preparation method thereof. The back paint uses a highly reactive long-chain low-hydroxyl polyester resin in combination with an epoxy resin and an amino resin to react, and can achieve film formation by curing under the conditions of a plate surface temperature of 204°C and a baking time of 30 seconds, and the MEK wiping resistance performance reaches more than 90 times.

[0004] However, due to the long service time and short oven length of the production lines of some color-coated plate manufacturers, the plate surface temperature of the coil steel cannot reach 200°C; in addition, in order to improve production efficiency, the production line usually needs to increase the line speed for production, resulting in a short baking time for the coil steel, and most of them do not exceed 30 seconds. Therefore, most of the coatings currently on the market cannot meet the requirements of such low-temperature and rapid curing.

[0005] In view of this, it is necessary to develop a primer for household appliance color-coated plates that can be widely applied to all categories, which has excellent processing performance, boiling water resistance performance, chemical resistance performance, salt spray resistance performance, etc. while achieving low-temperature and rapid-curing performance, so as to solve the problems faced in the prior art field. Summary of the Invention

[0006] Based on the above facts, the object of the present invention is to provide a low-temperature and rapid-curing coil steel household appliance primer. Through the synergistic effect between the phosphate adhesion promoter and the sulfonic acid type catalyst, it realizes rapid curing at a panel temperature lower than 200 °C or a baking time lower than 18 seconds, saving energy and reducing emissions for the client's production line. At the same time, after being matched with a general-purpose topcoat, this household appliance primer has excellent processing performance, boiling water resistance, chemical resistance, salt spray resistance, etc., and can provide long-term effective beauty and protection for coil steel color coated plates.

[0007] The first aspect of the present invention provides a low-temperature and rapid-curing coil steel household appliance primer, which, calculated by weight percentage, comprises:

[0008]

[0009] The total weight percentage of the above components is 100%.

[0010] Furthermore, in addition to the above components, the low-temperature and rapid-curing coil steel household appliance primer may further include rheological aids, matting agents, defoamers, leveling agents, other pigments, etc. In some preferred embodiments of the present invention, calculated by weight percentage, the low-temperature and rapid-curing coil steel household appliance primer comprises:

[0011]

[0012]

[0013] The total weight percentage of the above components is 100%.

[0014] Linear saturated polyester resin

[0015] In the present invention, the linear saturated polyester resin has a relatively large molecular weight and a relatively low glass transition temperature. After the condensation reaction of the hydroxyl group with the amino resin, the formed paint film has excellent processing performance, adhesion and chemical resistance. Preferably, the hydroxyl value of the linear saturated polyester resin is 10 - 40 mgKOH / g, the number average molecular weight is 5000 - 20000, the glass transition temperature is 25 - 80 °C, the acid value is 0 - 5 mgKOH / g, and the solid content is 40 - 70%.

[0016] Specifically, the linear saturated polyester resin is selected from one or more of the resins with the model numbers DYNAPOL LH826 - 29 resin, DYNAPOL L411 - 03 resin, DYNAPOL LS 436 - 12 resin provided by Evonik Industries AG, and the resin with the model number C1141 resin provided by Anhui Hannhai New Materials Co., Ltd.

[0017] Amino resin

[0018] In the present invention, the amino resin is selected from one or more of fully methylated melamine formaldehyde resin, highly imino methylated melamine formaldehyde resin, partially methylated melamine formaldehyde resin, butylated melamine resin, methylated urea-formaldehyde resin, butylated urea-formaldehyde resin and benzoguanamine formaldehyde resin.

[0019] Specifically, the amino resin is selected from one or more of the following: high-imino methylated melamine formaldehyde resin YP5627B, partially methylated melamine formaldehyde resin YP5629, fully methylated melamine formaldehyde resin YP5603 provided by Yuanbang Company, fully methylated melamine formaldehyde resin CYMEL 303, and high-imino methylated melamine formaldehyde resin CYMEL 325 provided by Zhanxin Company. Preferably, the amino resin is fully methylated melamine formaldehyde resin YP5603 provided by Yuanbang Company.

[0020] Blocked isocyanate

[0021] In the present invention, the blocked isocyanate in the low-temperature fast-curing coil steel appliance primer is an aromatic or aliphatic polyisocyanate blocker. The aromatic or aliphatic polyisocyanate blocker is selected from one or more of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and dicyclohexylmethane-4,4'-diisocyanate blockers.

[0022] Specifically, the blocked isocyanate is selected from one or more of butanone oxime blocked HDI trimer DESMODUR BL3175 and ε-caprolactam blocked HDI trimer BL3272 provided by Covestro, and ε-caprolactam blocked HDI trimer 3275 and butanone oxime blocked HDI trimer 3075 provided by Runchang Chemical Company.

[0023] Antirust pigment

[0024] In the present invention, the anti-rust pigment is selected from one or more of calcium ion exchange silica gel, enhanced surface active silica, modified phosphate compounds, and modified magnesium hydroxide.

[0025] In some preferred embodiments of the present invention, the modified magnesium hydroxide meets the following condition: after adding 1 g of the modified magnesium hydroxide to 100 g of pure water, the conductivity of the aqueous solution formed is below 250 μS / cm.

[0026] Specifically, the calcium ion-exchanged silica gel is preferably one or more selected from the calcium ion-exchanged silica gels of model SHIELDEX C303, SHIELDEX C 311, SHIELDEX AC 3, SHIELDEX C 500 provided by Grace Company, and the calcium ion-exchanged silica gels of model LM-30 and LM-50 provided by Lingwei Technology Company; the modified phosphate compounds are selected from one or more of aluminum tripolyphosphate CLF-102 provided by Guangxi Xinjing Technology Company, LF BOWSEI MZP-500 imported from Japan, and zinc phosphate.

[0027] Filler

[0028] In the present invention, the filler includes extender pigment. The extender pigment is a white or colorless filler with a moderate specific gravity, which can appropriately increase the volume of the paint itself and play a role in filling the paint film, thereby reducing the raw material cost of the paint.

[0029] Specifically, the filler is selected from one or more of titanium dioxide, precipitated barium sulfate, talc powder, calcium carbonate, kaolin, magnesium silicate, aluminum silicate, calcium sulfate, crystalline silica, and diatomaceous earth; more specifically, the filler can be selected from one or more of heavy calcium carbonate, magnesium silicate, aluminum silicate, kaolin, calcium sulfate, crystalline silica, diatomaceous earth, and ultrafine precipitated barium sulfate. In the specific implementation process, those skilled in the art can select appropriate fillers according to the specific gravity, color, and gloss of the required primer.

[0030] Solvent

[0031] In the present invention, the solvent is selected from one or more of propylene glycol methyl ether acetate, butyl acetate, S100 solvent oil, S150 solvent oil, and dibasic acid ester mixed solvent DBE.

[0032] Phosphate adhesion promoter

[0033] In the present invention, the phosphate adhesion promoter is one or more of epoxy phosphate, modified epoxy phosphate, polyester phosphate, and modified polyester phosphate with an acid value greater than 80 mgKOH / g and a solid content greater than or equal to 50%. During the curing process of the phosphate adhesion promoter, the active groups (such as hydroxyl groups, epoxy groups, carboxyl groups, etc.) at one end can react with the resin hydroxyl groups in the paint film, and the phosphate groups at the other end are easily complexed with the metal substrate, thereby firmly binding the coating to the substrate. At the same time, the phosphate adhesion promoter has a relatively strong acidity and can also assist in catalyzing the curing reaction of the polyester resin and the amino resin in the primer.

[0034] Specifically, the phosphate adhesion promoter is selected from one or more of the SD AP-1010 epoxy phosphate adhesion promoter provided by Sudy High Polymer Materials Co., Ltd., the SD AP-9063 modified polyester phosphate adhesion promoter, the polyester phosphate adhesion promoter Lubrizol 2063 provided by Lubrizol Corporation, and the epoxy phosphate adhesion promoter ETERKYD4901 provided by Changxing.

[0035] Sulfonic acid catalyst

[0036] In the present invention, the sulfonic acid catalyst is a blocked sulfonic acid catalyst with a deblocking temperature lower than 130°C or an unblocked sulfonic acid catalyst with good thermal storage stability. The sulfonic acid catalyst can be deblocked at high temperature, and by providing an organic protonic acid, it catalyzes the condensation reaction between the hydroxyl groups in the polyester resin and the amino resin to form a cured film.

[0037] Specifically, the sulfonic acid catalyst is selected from one or more of the blocked p-toluenesulfonic acid catalyst Nacure 2500 provided by King Catalysts Co., Ltd., the unblocked dinonylnaphthalenesulfonic acid catalyst Nacure 1051, and the unblocked dodecylbenzenesulfonic acid catalyst SD Coilcat-500 provided by Sudy High Polymer Materials Co., Ltd.

[0038] Defoamer and leveling agent

[0039] In the present invention, the leveling agent is a non-silicon system leveling agent, and the defoaming agent is a non-silicon system defoaming agent. The addition of the leveling agent and the defoaming agent can improve the surface leveling and defoaming of the wet paint sample, making the paint have good application performance and a smooth paint film surface.

[0040] In some preferred embodiments of the present invention, by weight percentage, the dosage of both the leveling agent and the defoaming agent in the low-temperature rapid-curing coil steel and household appliance primer is 0.1-2%, preferably 0.1-1%.

[0041] Specifically, the leveling agent is selected from one or more of the acrylate leveling agents BYK-392, BYK-355, BYK-358N provided by BYK-Chemie GmbH, and the acrylate leveling agent AFCONA-3773 provided by Efka Chemicals. The defoaming agent is selected from one or more of the acrylate defoaming agents BYK-352, BYK-354 provided by BYK-Chemie GmbH, and the acrylate defoaming agent AFCONA 2720 provided by Efka Chemicals.

[0042] The second aspect of the present invention provides a method for preparing the low-temperature rapid-curing coil steel and household appliance primer described in the first aspect of the present invention, comprising the following steps:

[0043] S1: Add part of the linear saturated polyester resin and part of the solvent into a container in sequence, stir at a speed of 800 - 1300 rpm for 15 - 20 min to make them evenly mixed;

[0044] S2: Add the anti-rust pigment and filler in sequence under stirring, stir at a speed of 800 - 1300 rpm for 15 - 20 min to make the initial dispersion uniform, and obtain slurry A;

[0045] S3: Grind the above slurry A with a grinder for 4 - 6 hours until the fineness is less than or equal to 10 μm;

[0046] S4: Add the ground slurry into a container, stir at a speed of 800 - 1300 rpm, and add the remaining linear saturated polyester resin, amino resin, blocked isocyanate, sulfonic acid type catalyst, phosphate adhesion promoter and part of the solvent under stirring, and continue to stir for 15 - 20 min to make them evenly mixed, and obtain slurry B;

[0047] S5: Use the remaining solvent to adjust the viscosity of the above slurry B to 110 - 130 seconds (measured with a No. 4 cup), filter and package to obtain the low-temperature rapid-curing coil steel household appliance primer.

[0048] The third aspect of the present invention provides an application of the low-temperature rapid-curing coil steel household appliance primer described in the first aspect of the present invention, including the following steps:

[0049] S1: Primer coating and plate making: Roll coat the low-temperature rapid-curing coil steel household appliance primer on a galvanized or aluminized zinc substrate that has undergone chromium-free pretreatment with a wire bar, bake it in an oven at 300 °C for 18 s, and the metal plate temperature PMT is 199 °C to obtain a primer layer with a film thickness of 5 μm;

[0050] S2: Topcoat coating and plate making: Roll coat the topcoat on the primer layer, bake it in an oven at 300 °C for 26 s, and the metal plate temperature PMT is 216 °C to obtain a topcoat layer with a film thickness of 15 μm.

[0051] The beneficial effects of the present invention are as follows:

[0052] The present invention provides a low-temperature rapid-curing coil steel household appliance primer, which does not contain heavy metal substances, meets the EU REACH and ROHS detection standards, is green and environmentally friendly, and can be widely applied to all categories of household appliance color coated plates. Through the synergistic effect between the phosphate adhesion promoter and the sulfonic acid type catalyst, it realizes rapid curing when the plate surface temperature is lower than 200 °C or the baking time is less than 18 s, saving energy and reducing emissions for the client's production line. At the same time, after the household appliance primer is matched with a general-purpose topcoat, it has excellent processing performance, boiling water resistance, chemical resistance and salt spray resistance, etc., and can provide long-term effective beauty and protection for the coil steel color coated plate. Detailed implementation mode

[0053] To more clearly illustrate the present invention, the present invention will be further described below in conjunction with specific embodiments and comparative examples. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the protection scope of the present invention. Unless otherwise specified, the experimental methods used in the following examples and comparative examples are all conventional methods, and the raw materials and reagents used are all products that can be purchased from conventional commercial channels unless otherwise specified.

[0054] The technical solutions provided by the present invention will be further explained below in conjunction with specific implementation examples. It should be noted that the performance test requirements in all implementation examples of the present invention are carried out in accordance with the standards of GB / T 13448-2019, and the results meet the requirements of GB / T 13448-2019.

[0055] Examples 1-6: Low-temperature rapid-curing coil steel home appliance primer 1-6

[0056] Prepare the low-temperature rapid-curing coil steel home appliance primer 1-6 described in the present invention according to the formula in Table 1 below. The preparation steps are as follows:

[0057] S1: Add part of the linear saturated polyester resin and part of the solvent to the container in sequence, and stir at a speed of 800-1300 rpm for 15-20 min to make them evenly mixed;

[0058] S2: Add the anti-rust pigment, other pigments, filler and rheology aid in sequence under stirring, and stir at a speed of 800-1300 rpm for 15-20 min to make it evenly dispersed initially, and obtain slurry A;

[0059] S3: Grind the above slurry A with a grinder for 4-6 hours until the fineness is less than or equal to 10 μm;

[0060] S4: Add the ground slurry to the container, stir at a speed of 800-1300 rpm, and add the remaining linear saturated polyester resin, amino resin, blocked isocyanate, sulfonic acid catalyst, phosphate adhesion promoter, defoamer, leveling agent and part of the solvent under stirring, and continue to stir for 15-20 min to make them evenly mixed, and obtain slurry B;

[0061] S5: Adjust the viscosity of the above slurry B to 110-130 seconds (measured with a No. 4 cup) with the remaining solvent, filter and package to obtain the low-temperature rapid-curing coil steel home appliance primer 1-6.

[0062] Primer Coating and Panel Preparation: The obtained low-temperature and fast-curing coil steel appliance primer 1-6 was roll-coated on a 0.4mm Haier galvanized steel sheet that had undergone chromium-free pretreatment using a No. 10 wire bar of RDS, and baked in an oven at 300°C for 18s. The metal plate temperature PMT was 199°C, and finally, the primer layers 1-6 with a film thickness of 5μm were obtained.

[0063] Topcoat Coating and Panel Preparation: The selected topcoat was the self-produced Nippon appliance topcoat FLC188 Brown Grey polyester topcoat. This topcoat was roll-coated on the primer layers obtained in Examples 1-6 using a No. 24 wire bar of RDS, and baked in an oven at 300°C for 26s. The metal plate temperature PMT was 216°C, and the topcoat layers 1-6 with a film thickness of 15μm were obtained.

[0064] Comparative Examples 1-5: Primers 1-5 as comparative examples

[0065] Primers 1-5 as comparative examples were prepared according to the formula in Table 1 below. Among them, the preparation steps of Comparative Examples 1-4 were the same as those of Examples 1-6, and the preparation steps of Comparative Example 5 were as follows:

[0066] S1: Add part of the linear saturated polyester resin and part of the solvent into a container in sequence, and stir at a speed of 800 - 1300 pm for 15 - 20 min to make them evenly mixed;

[0067] S2: Add the anti-rust pigment, other pigments, fillers, and rheological additives in sequence under stirring, and stir at a speed of 800 - 1300 rpm for 15 - 20 min to make them evenly dispersed initially, and obtain slurry A;

[0068] S3: Grind the above slurry A with a grinder for 4 - 6 hours until the fineness is less than or equal to 10μm;

[0069] S4: Add the ground slurry into a container, stir at a speed of 800 - 1300 rpm, and add the remaining linear saturated polyester resin, amino resin, blocked isocyanate, sulfonic acid catalyst, defoamer, leveling agent, and part of the solvent under stirring, and continue to stir for 15 - 20 min to make them evenly mixed, and obtain slurry B;

[0070] S5: Adjust the viscosity of the above slurry B to 110 - 130 seconds (measured with a coating cup No. 4) using the remaining solvent, filter and package, and thus obtain the primer 5 as the comparative example.

[0071] It should be noted that the sulfonic acid catalysts selected in Comparative Example 1 and Comparative Example 2 are the blocked dinonyl dinaphthalene sulfonic acid Nacure 1419 and the mixed blocked sulfonic acid Nacure XC-300 provided by King Catalyst Co., respectively. Their deblocking temperatures are relatively high, exceeding 130°C, and they do not belong to the blocked sulfonic acid catalysts described in the present invention or the sulfonic acid catalysts that are not blocked but have good thermal storage stability. Therefore, they are used as comparative examples. Selecting such sulfonic acid catalysts with relatively high deblocking temperatures will cause the primer to fail to cure when the temperature of the metal plate surface is relatively low, resulting in poor performance such as MEK wipe resistance and boiling water resistance after being coated with the topcoat.

[0072] The phosphate adhesion promoters selected in Comparative Example 3 and Comparative Example 4 are the SD AP-8063 polyester phosphate adhesion promoter and the high molecular weight ADP polyester adhesion promoter, respectively. Their acid values are less than 80 mgKOH / g or the solid content is less than 50%, which is not within the scope described in the present invention. Therefore, they are used as comparative examples. Selecting such phosphate adhesion promoters will reduce the biting ability to the metal substrate and do not have sufficient co-catalytic ability for the primer, resulting in poor curing performance of the primer when the temperature of the metal plate surface is relatively low, and poor performance such as MEK wipe resistance and boiling water resistance after being coated with the topcoat.

[0073] No phosphate adhesion promoter was added to the formulation of Comparative Example 5, which is not within the protection scope of the present invention. Without the phosphate adhesion promoter, relying solely on the sulfonic acid catalyst with a relatively low deblocking temperature to catalyze the crosslinking and curing reaction cannot form good biting and adhesion to the metal substrate, resulting in poor curing performance of the primer when the temperature of the metal plate surface is relatively low, and poor performance such as T-bend, MEK wipe resistance, and boiling water resistance after being coated with the topcoat.

[0074] Primer coating and panel preparation: The primers 1-5 used as comparative examples were roll-coated on a 0.4 mm Haier galvanized steel sheet that had undergone chromium-free pretreatment using a No. 10 wire bar of RDS, and baked in an oven at 300°C for 18 s. The metal plate temperature PMT was 199°C, and finally, the comparative primer layers 1-5 with a film thickness of 5 μm were obtained.

[0075] Topcoat coating and panel preparation: The selected topcoat was the self-produced household appliance topcoat FLC188 Brown Gray polyester topcoat of Nippon Paint. This topcoat was roll-coated on the primer layers obtained in Comparative Examples 1-5 using a No. 24 wire bar of RDS, and baked in an oven at 300°C for 26 s. The metal plate temperature PMT was 216°C, and the comparative topcoat layers 1-5 with a film thickness of 15 μm were obtained.

[0076] Table 1 Raw material components of the low-temperature rapid-curing coil steel household appliance primers 1-6 and the primers 1-5 used as comparative examples

[0077]

[0078]

[0079] The primer layer and the topcoat layer prepared in Examples 1-6 and Comparative Examples 1-5 were tested respectively, and the test results are shown in Table 2.

[0080] Table 2 Performance test results of primer layer and topcoat layer prepared in Examples 1-6 and Comparative Examples 1-5

[0081]

[0082] As can be seen from Tables 1 and 2 above, the present invention makes the home appliance primers of Examples 1-6 have low-temperature curing properties by preferably selecting formula structures such as straight-chain saturated polyester resins, amino resins, blocked isocyanates, rust-proof pigments, other fillers, solvents, phosphate adhesion promoters and sulfonic acid catalysts. When the plate temperature is 199°C and the baking time is 18 seconds, the MEK wiping resistance of the primer reaches 5-8 times. At the same time, the comprehensive performance of the primer after matching the topcoat is also relatively excellent, and it can be widely used in all categories of home appliance color-coated plates, providing long-term and effective beauty and protection. Among them, the amino resin selected in Example 5 is pure high-imino methyl etherified melamine formaldehyde resin YP5627B, which can undergo cross-linking and curing reaction with polyester at a lower temperature, and self-cross-linking reaction will also occur. Therefore, the primer can meet the low-temperature rapid curing performance, but the hardness is high and the T-bend performance is relatively reduced. On the contrary, the amino resin selected in Example 6 is pure high-iminomethyl etherified melamine formaldehyde resin YP5629, which has a different chemical structure from YP5627B, has a lower reaction activity, and cannot undergo rapid cross-linking and curing reaction with polyester at a lower temperature, so the low-temperature MEK wiping resistance of the primer is relatively reduced.

[0083] The selected sulfonic acid catalysts in Comparative Example 1 and Comparative Example 2 were the blocked dinonyl dinaphthalene sulfonic acid Nacure 1419 with a relatively high deblocking temperature and the mixed blocked sulfonic acid Nacure XC-300 provided by King Catalysts Co., Ltd. Therefore, when the temperature of the metal plate surface was relatively low, the primer could not cure, and there was almost no MEK rubbing resistance. The properties such as MEK rubbing resistance and boiling water resistance after matching with the topcoat were poor. The selected phosphate adhesion promoters in Comparative Example 3 and Comparative Example 4 were the polyester phosphate adhesion promoter SD AP-8063 and the high molecular weight type ADP polyester adhesion promoter respectively. These two types of phosphate adhesion promoters lacked the biting ability for the metal substrate and sufficient co-catalytic ability for the primer. Therefore, when the temperature of the metal plate surface was relatively low, the curing performance of the primer was poor, and the properties such as MEK rubbing resistance and boiling water resistance after matching with the topcoat were poor. In the formulation of Comparative Example 5, no phosphate adhesion promoter was added, and only the sulfonic acid catalyst with a relatively low deblocking temperature was relied on to catalyze the crosslinking curing reaction, which could not form good biting and adhesion to the metal substrate. Therefore, when the temperature of the metal plate surface was relatively low, the curing performance of the primer was poor, and the properties such as T-bend, MEK rubbing resistance and boiling water resistance after matching with the topcoat were poor.

[0084] In summary, the low-temperature rapid-curing coil steel appliance primer of the present invention realizes rapid curing at a plate surface temperature lower than 200 °C or a baking time shorter than 18 seconds through the synergistic effect between the phosphate adhesion promoter and the sulfonic acid catalyst, so as to save energy and reduce emissions in the client's production line. At the same time, after the appliance primer is matched with a general-purpose topcoat, it has excellent processing performance, boiling water resistance, chemical resistance, salt spray resistance, etc., and can provide long-term effective beauty and protection for the coil steel color coated plate.

[0085] Obviously, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limitations on the implementation modes of the present invention. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is impossible to list all the implementation modes here. Any obvious changes or variations derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. A low-temperature and rapid-curing coil steel primer for household appliances, by weight percentage, it includes: The total weight percentage of the above components is 100%.

2. The low-temperature rapid-curing coil steel home appliance primer according to claim 1, wherein, The low-temperature and rapid-curing coil steel primer for household appliances further includes one or more of a rheology aid, a matting agent, an antifoaming agent, a leveling agent, and other pigments. By weight percentage, the low-temperature and rapid-curing coil steel primer for household appliances includes: The total weight percentage of the above components is 100%.

3. The low-temperature and rapid-curing coil steel appliance primer according to claim 1 or 2, characterized in that, The hydroxyl value of the linear saturated polyester resin is 10 - 40mgKOH / g, the number-average molecular weight is 5000 - 20000, the glass transition temperature is 25 - 80°C, the acid value is 0 - 5mgKOH / g, and the solid content is 40 - 70%; preferably, the linear saturated polyester resin is selected from one or more of the resins with model numbers DYNAPOL LH826-29 resin, DYNAPOL L411-03 resin, DYNAPOL LS 436-12 resin provided by Evonik, and C1141 resin provided by Bohai New Materials.

4. The low-temperature rapid-curing coil steel home appliance primer according to claim 1 or 2, characterized in that The amino resin is selected from one or more of fully methylated melamine formaldehyde resin, high-imino methylated melamine formaldehyde resin, partially methylated melamine formaldehyde resin, butylated melamine resin, methylated urea formaldehyde resin, butylated urea formaldehyde resin, and phenylated melamine formaldehyde resin; preferably, the amino resin is one or more of high-imino methylated melamine formaldehyde resin YP5627B, partially methylated melamine formaldehyde resin YP5629, fully methylated melamine formaldehyde resin YP5603 provided by Yuanbang Company, fully methylated melamine formaldehyde resin CYMEL 303, high-imino methylated melamine formaldehyde resin CYMEL 325 provided by Axalta; more preferably, the amino resin is fully methylated melamine formaldehyde resin YP5603 provided by Yuanbang Company.

5. The low-temperature and rapid-curing coil steel household appliance primer according to claim 1 or 2, characterized in that, The blocked isocyanate is an aromatic or aliphatic polyisocyanate blocking agent; preferably, the blocked isocyanate is selected from one or more of the blocking agents of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane - 4,4'-diisocyanate; more preferably, the blocked isocyanate is selected from one or more of the butanone oxime-blocked HDI trimer DESMODUR BL3175, ε-caprolactam-blocked HDI trimer BL3272 provided by Covestro, ε-caprolactam-blocked HDI trimer 3275, butanone oxime-blocked HDI trimer 3075 provided by Run Chang Chemical.

6. The low-temperature and rapid-curing coil steel home appliance primer according to claim 1 or 2, characterized in that, The rust-inhibiting pigment is selected from one or more of calcium ion-exchanged silica gel, enhanced surface activity silica, modified phosphate compounds, and modified magnesium hydroxide; preferably, the modified magnesium hydroxide satisfies the following condition: after adding 1 g of the modified magnesium hydroxide to 100 g of pure water, the conductivity of the formed aqueous solution is below 250 μS / cm; the calcium ion-exchanged silica gel is preferably selected from one or more of the calcium ion-exchanged silica gels with the models of SHIELDEX C 303, SHIELDEX C 311, SHIELDEX AC 3, SHIELDEX C 500 provided by Grace Company, and the calcium ion-exchanged silica gels with the models of LM-30 and LM-50 provided by Lingwei Technology Company, the modified phosphate compounds are preferably selected from one or more of aluminum tripolyphosphate CLF-102 provided by Guangxi Xinjing Technology Company, LFBOWSEIMZP-500 imported from Japan, and zinc phosphate; the filler includes extender pigments, and the extender pigments are white or colorless pigments with moderate specific gravity, preferably selected from one or more of titanium dioxide, precipitated barium sulfate, talc powder, calcium carbonate, kaolin, magnesium silicate, aluminum silicate, calcium sulfate, crystalline silica, and diatomaceous earth, more preferably, the filler is selected from one or more of heavy calcium carbonate, magnesium silicate, aluminum silicate, kaolin, calcium sulfate, crystalline silica, diatomaceous earth, and ultrafine precipitated barium sulfate; the solvent is selected from one or more of propylene glycol methyl ether acetate, butyl acetate, S100 solvent oil, S150 solvent oil, and dibasic acid ester mixed solvent DBE.

7. The low-temperature rapid-curing coil steel appliance primer according to claim 1 or 2, characterized in that, The phosphate ester adhesion promoter is one or more of epoxy phosphate esters, modified epoxy phosphate esters, polyester phosphate esters, and modified polyester phosphate esters with an acid value greater than 80 mgKOH / g and a solid content greater than or equal to 50%; preferably, the phosphate ester adhesion promoter is selected from one or more of the SD AP-1010 epoxy phosphate adhesion promoter provided by Sudi High Polymer Materials Company, the SD AP-9063 modified polyester phosphate adhesion promoter, the polyester phosphate adhesion promoter Lubrizol2063 provided by Lubrizol Company, and the epoxy phosphate adhesion promoter ETERKYD4901 provided by Changxing; the sulfonic acid type catalyst is a blocked sulfonic acid type catalyst with a deblocking temperature below 130°C or an unblocked sulfonic acid type catalyst with good thermal storage stability; preferably, the sulfonic acid type catalyst is selected from one or more of the blocked p-toluenesulfonic acid catalyst Nacure2500 provided by King Catalyst Company, the unblocked dinonylnaphthalene sulfonic acid catalyst Nacure 1051, and the unblocked dodecylbenzene sulfonic acid catalyst SD Coilcat-500 provided by Sudi High Polymer Materials Company.

8. The low-temperature rapid-curing coil steel appliance primer according to claim 2, wherein The leveling agent is a non-silicon system leveling agent, and the defoaming agent is a non-silicon system defoaming agent; calculated by weight percentage, the preferred dosages of the leveling agent and the defoaming agent in the low-temperature rapid-curing coil steel home appliance primer are both 0.1-2%, and more preferably both 0.1-1%; preferably, the leveling agent is selected from one or more of acrylate leveling agents BYK-392, BYK-355, BYK-358N provided by BYK Chemie GmbH, and acrylate leveling agent AFCONA-3773 provided by EFKA Chemie B.V., and the defoaming agent is selected from one or more of acrylate defoaming agents BYK-352, BYK-354 provided by BYK Chemie GmbH, and acrylate defoaming agent AFCONA 2720 provided by EFKA Chemie B.V.

9. A preparation method of a low-temperature and rapid-curing coil steel home appliance primer as described in any one of claims 1-8, characterized in that, It includes the following steps: S1: Add part of the linear saturated polyester resin and part of the solvent into a container in sequence, and stir at a speed of 800-1300 rpm for 15-20 min to make them evenly mixed; S2: Add the anti-rust pigment and the filler in sequence under stirring, and stir at a speed of 800-1300 rpm for 15-20 min to make them evenly dispersed initially, and obtain slurry A; S3: Grind the above slurry A with a grinder for 4-6 hours until the fineness is less than or equal to 10 μm; S4: Add the ground slurry into a container, stir at a speed of 800-1300 rpm, and add the remaining linear saturated polyester resin, amino resin, blocked isocyanate, sulfonic acid catalyst, phosphate adhesion promoter and part of the solvent under stirring, and continue to stir for 15-20 min to make them evenly mixed, and obtain slurry B; S5: Use the remaining solvent to adjust the viscosity of the above slurry B to 110-130 seconds (measured with a No. 4 cup), filter and package to obtain the low-temperature rapid-curing coil steel home appliance primer.

10. An application of the low-temperature rapid-curing coil steel home appliance primer according to any one of claims 1-8, which includes the following steps: S1: Primer coating and plate making: Roller coat the low-temperature rapid-curing coil steel home appliance primer on a galvanized or aluminized zinc substrate that has undergone chromium-free pretreatment with a wire bar, bake it in an oven at 300 °C for 18 s, and the metal plate temperature PMT is 199 °C to obtain a primer layer with a film thickness of 5 μm; S2: Topcoat coating and plate making: Roller coat the topcoat on the primer layer, bake it in an oven at 300 °C for 26 s, and the metal plate temperature PMT is 216 °C to obtain a topcoat layer with a film thickness of 15 μm.

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