Tinplate snap lid outer coating suitable for strong alkali sterilization process

Abstract

The invention discloses a tinplate snap lid outer coating suitable for a strong alkali sterilization process, which comprises the following raw materials in percentage by weight: 40 to 60 percent of organic silicon modified polyester resin, 5 to 15 percent of amino resin, 5 to 15 percent of blocked isocyanate, 20 to 40 percent of solvent, 0.2 to 5.0 percent of wax powder, 0.01 to 0.5 percent of acid catalyst and 0.05 to 1.0 percent of defoaming agent. 0.5%-2.0% of an adhesion promoter, 0.01%-0.5% of a leveling agent; according to the organic silicon modified polyester resin, 2, 2, 4, 4-tetramethyl-1, 3-cyclobutanediol is introduced into polyester resin, and gamma-glycidyl ether oxypropyl trimethoxy silane is grafted into the polyester resin. The coating forms a protective coating on the surface of tinplate, has excellent mechanical properties, flexibility, machinability and water resistance, and can obviously improve the defects of the coating in high-temperature sterilization under a strong alkali condition.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of paint, and particularly relates to an outer paint for tinplate pop can suitable for strong alkali sterilization process. BACKGROUND

[0002] Tinplate pop cans are widely used in food, beverage, medicine and other industries, and the outer surface thereof needs to be coated with a protective coating to resist mechanical damage during processing and corrosion in the use environment. Traditional tinplate paint mainly uses epoxy-phenolic resin, which has excellent chemical resistance, but contains bisphenol A (BPA) and perfluoro and polyfluoro alkyl substances (PFAS), and does not meet the requirements of food safety regulations. Alternative solutions such as acrylic resin or ordinary polyester resin paint do not contain BPA, but are prone to hydrolysis under strong alkali conditions (such as high-temperature alkaline washing in food processing), and the coating is prone to problems such as loss of gloss, bubbling and reduced adhesion after high-temperature sterilization (121-135 DEG C cooking), which cannot meet the stringent use requirements. Therefore, it is an urgent need in the industry to develop an environmentally friendly tinplate outer coating that has strong alkali resistance, high-temperature sterilization resistance and mechanical properties. SUMMARY

[0003] To solve the above problems, the present application provides an outer paint for tinplate pop can suitable for strong alkali sterilization process, which realizes the stability of the coating after high-temperature sterilization in a strong alkali environment.

[0004] To achieve the above purpose, the present application provides an outer paint for tinplate pop can suitable for strong alkali sterilization process, which comprises the following raw materials in percentage by weight: 40-60% of silicone-modified polyester resin, 5-15% of amino resin, 5-15% of blocked isocyanate, 20-40% of solvent, 0.2-5.0% of wax powder, 0.01-0.5% of acid catalyst, 0.05-1.0% of defoaming agent, 0.5-2.0% of adhesion promoter and 0.01-0.5% of leveling agent.

[0005] The silicone-modified polyester resin introduces 2,2,4,4-tetramethyl-1,3-cyclobutanediol into the polyester resin, and grafts gamma-glycidyl ether oxypropyl trimethoxysilane in the polyester resin.

[0006] The outer coating of the tinplate pop can lid suitable for the strong alkali sterilization process according to the embodiment of the present application is prepared from the silicone modified polyester resin, the amino resin and the isocyanate as the main structure, the silicone modified polyester resin is introduced with 2,2,4,4-tetramethyl-1,3-cyclobutanediol, which can change the symmetry of the polyester structure, prolong the half-life period of the resin crystallization, effectively improve the glass transition temperature, the impact strength, the dimensional stability, the chemical resistance, the hydrolysis stability, the ductility and the like of the polyester resin, improve the overall TG point, the crosslinking density and the hydrolysis resistance of the polyester resin ester bond, and the introduction of 2,2,4,4-tetramethyl-1,3-cyclobutanediol also makes the polyester resin have some excellent physical properties of the bisphenol A resin, the chemical resistance of which is about 3 times of that of the traditional polyester resin; in addition, the gamma-glycidyl ether oxypropyl trimethoxysilane is grafted with the polyester resin, after the hydrolysis and condensation of the trimethoxysilane part in the molecule, the Si-O-Si crosslinking structure is formed between the polyester molecular chains, which replaces part of the easily hydrolyzed ester bond, thereby reducing the water permeation rate and the molecular weight reduction caused by the hydrolysis, and maintaining the mechanical properties and the appearance stability in the humid heat environment; the thermal stability of the Si-O-Si bond is better than that of the C-O-C bond and the ester bond, the dense SiO protective layer is formed under high temperature by the siloxane structure, the initial thermal decomposition temperature is improved, the leveling property after the coating film is dried and the hydrolysis resistance after the coating is dried are further improved, and the resistance of the paint film to strong alkali is further improved.

[0007] In addition, the outer coating of the tinplate pop can lid suitable for the strong alkali sterilization process according to the above-mentioned embodiment of the present application can also have the following additional technical features.

[0008] Optionally, the acid value of the silicone modified polyester resin is 1-5 mg KOH / g, the number average molecular weight is 11000-18000, and the TG point is 85-93℃.

[0009] Optionally, the silicone modified polyester resin is prepared by esterification reaction of the following raw materials in percentage by weight: 2,2,4,4-tetramethyl-1,3-cyclobutanediol 5%-15%, trimethylolpropane 5%-10%, neopentyl glycol 5%-15%, terephthalic acid 5%-15%, isophthalic acid 5%-10%, adipic acid 5%-10%, monobutyl tin oxide 0.5%-2%, dimethylbenzene 20-30%, 150# solvent oil 20%-30%, gamma-glycidyl ether oxypropyl trimethoxysilane 1%-5%, ethyl triphenyl phosphonic acid 0.5%-2%, and hydroquinone 0.1%-0.2%.

[0010] Further, the esterification reaction is as follows:

[0011] 2,2,4,4-tetramethyl-1,3-cyclobutanediol, neopentyl glycol, trimethylolpropane, terephthalic acid, isophthalic acid, adipic acid, monobutyl tin oxide were added into a reaction vessel, nitrogen was introduced, and the temperature was slowly increased to 140-160°C for 1 h, and then dehydration was started;

[0012] The temperature was gradually increased to 200-230°C at a rate of 10-15°C / h, and the temperature was maintained for 3-4 h until the esterification rate was more than 95%. Then, the reaction system was vacuumized, and the pressure was reduced to -0.01 MPa. The polycondensation was performed until the acid value was less than 5 mgKOH / g. Then, the vacuum was broken by introducing nitrogen, and the temperature was cooled to 160°C. Then, 150# solvent oil and xylene were sequentially added. The temperature was maintained at 110-120°C.

[0013] Ethyl triphenyl phosphonic acid was added, and γ-glycidyl ether oxypropyl trimethoxysilane was added at a rate of 1-2 g / min using a peristaltic pump. After the addition was completed, the initial epoxy value was determined by sampling. The temperature was slowly increased to 130-140°C, and the temperature was maintained for 2-3 h. During the process, the epoxy value was determined by sampling. When the epoxy value was less than 5% of the initial value, the reaction was terminated. When the temperature of the material was lower than 80°C, a polymerization inhibitor, hydroquinone, was added. After cooling, the material was filtered and poured out.

[0014] Optionally, the amino resin is one or more of methyl etherified benzoguanamine formaldehyde resin, butyl etherified benzoguanamine formaldehyde resin, methyl-ethyl etherified benzoguanamine formaldehyde resin, butyl etherified melamine formaldehyde resin, and butyl etherified urea formaldehyde resin.

[0015] Optionally, the blocked isocyanate is one or more of blocked hexamethylene diisocyanate, blocked isophorone diisocyanate, diphenylmethane diisocyanate, and 4,4-dicyclohexylmethane diisocyanate.

[0016] Optionally, the solvent is one or more of xylene, 100# solvent oil, 150# solvent oil, 200# solvent oil, divalent acid ester DBE, n-butanol, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, propylene glycol methyl ether, cyclohexanone, and methyl ethyl ketone.

[0017] Optionally, the wax powder is one or more of polyethylene wax, oxidized polyethylene wax, carnauba wax, Fischer-Tropsch wax, polymethyl methacrylate wax powder, polypropylene wax, and lanolin.

[0018] Optionally, the defoaming agent is one or more of silicone defoaming agent, polyether defoaming agent, polyester defoaming agent, and mineral oil defoaming agent.

[0019] Optionally, the adhesion promoter is one or more of polyester phosphate, epoxy phosphate, acrylic phosphate, titanate, and organosiloxane.

[0020] Optionally, the leveling agent is one or more of silicone leveling agent, acrylic leveling agent, and fluorocarbon compound leveling agent, urea-formaldehyde resin.

[0021] Additional aspects and advantages of the application will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following and the accompanying drawings or can be learned by practice of the application. DETAILED DESCRIPTION

[0022] The technical solutions of the present application are described below by specific examples. It should be understood that the one or more method steps mentioned in the present application do not exclude other method steps before and after the described combination steps or other method steps inserted between the explicitly mentioned steps; it should also be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool to identify each method step, and is not a limitation on the arrangement order of each method step or a limitation on the scope of the present application that can be implemented, and the change or adjustment of the relative relationship without substantial change of the technical content is also regarded as the scope of the present application that can be implemented.

[0023] In order to better understand the above technical solutions, the exemplary embodiments of the present application are described in more detail below. Although exemplary embodiments of the present application are shown, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough and complete understanding of the present application and to convey the full scope of the present application to those skilled in the art.

[0024] The test materials used in the present application are all ordinary commercially available products and can be purchased in the market.

[0025] Among them, the silicone-modified polyester resin is a self-made product with an acid value of 1-5 mg KOH / g, a number average molecular weight of 11000-18000, and a TG point of 85-93℃.

[0026] In the following comparative example, Haohan MARCOA TM CH470 is a conventional linear saturated polyester resin with an acid value of 1 mg KOH / g, a molecular weight of 17000, and a TG point of 70℃; Haohan MARCOA in the comparative example TM CL372 is a branched saturated polyester resin with an acid value of 5 mg KOH / g, a molecular weight of 12000, and a TG point of 78℃.

[0027] The amino resin is used as a crosslinking agent, which can be selected from one or more of methyl etherified benzoguanamine formaldehyde resin, butyl etherified benzoguanamine formaldehyde resin, methyl-ethyl etherified benzoguanamine formaldehyde resin, butyl etherified melamine formaldehyde resin, butyl etherified urea formaldehyde resin, and preferably methyl etherified benzoguanamine formaldehyde resin, which can be selected from commercially available Zannan resin CYMEL 659.

[0028] The blocked isocyanate is used as a crosslinking agent, which can be selected from one or more of blocked hexamethylene diisocyanate, blocked isophorone diisocyanate, diphenylmethane diisocyanate, and 4,4-dicyclohexylmethane diisocyanate. Preferably, the blocked isophorone diisocyanate can be selected from Wannate ITBL-460S.

[0029] The solvent includes one or more of xylene, 100# solvent oil, 150# solvent oil, 200# solvent oil, divalent acid ester DBE, n-butanol, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, propylene glycol methyl ether, cyclohexanone, and methyl ethyl ketone. Preferably, the solvent includes xylene, 150# solvent oil, 100# solvent oil, divalent acid ester DBE, and propylene glycol methyl ether acetate.

[0030] The wax powder includes one or more of polyethylene wax, oxidized polyethylene wax, carnauba wax, Fischer-Tropsch wax, polymethyl methacrylate wax powder, polypropylene wax, and lanolin. Preferably, the wax powder includes polyethylene wax and lanolin, which can be selected from commercially available Clearlan 650 lanolin and PEW-0273 polyethylene wax.

[0031] The acid catalyst includes one or more of phosphoric acid, p-toluenesulfonic acid, dinonyl naphthalene sulfonic acid, dinonyl naphthalene disulfonic acid, and dodecyl benzene sulfonic acid. Preferably, the acid catalyst includes p-toluenesulfonic acid, which can be selected from K-Cure 1040W.

[0032] The defoaming agent includes one or more of silicone defoaming agent, polyether defoaming agent, polyester defoaming agent, and mineral oil defoaming agent. Preferably, the defoaming agent includes silicone defoaming agent, which can be selected from FoamStar SI 2210.

[0033] The adhesion promoter includes one or more of polyester phosphate, epoxy phosphate, acrylic phosphate, titanate, and organosiloxane. Preferably, the adhesion promoter includes acrylic phosphate, which can be selected from SIPOMER PAM-100.

[0034] The leveling agent includes one or more of silicone leveling agent, acrylic leveling agent, and fluorocarbon compound leveling agent. Preferably, the leveling agent includes silicone leveling agent, which can be selected from commercially available MONENG 1310.

[0035] The application will be described below with reference to specific embodiments, which are illustrative only and not limiting of the application in any way.

[0036] An outer coating for tinplate pop can lid, comprising the following raw material components by weight percentage:

[0037] Table 1

[0038]

[0039]

[0040] Specifically, the preparation of polyester resin a comprises:

[0041] (1) 180g of 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 150g of neopentyl glycol, 110g of trimethylolpropane, 250g of terephthalic acid, 150g of isophthalic acid, and 160g of adipic acid are dried to a moisture content of <0.1%, and the terephthalic acid and isophthalic acid are further pulverized to improve reactivity, and are put into a 3L four-necked flask, and 1g of monobutyl tin oxide is added.

[0042] (2) Nitrogen is introduced, and the temperature is slowly raised to 140-160°C, and kept for 1h to start dehydration. The temperature is gradually raised to 200-230°C at a rate of 10-15°C / h, and the temperature at the top of the distillation column is kept ≤100°C during the process. The temperature is kept for 3-4h until the esterification rate is >95%.

[0043] (3) The reaction system is vacuumed, and the pressure is reduced to -0.01MPa to perform polycondensation until the acid value is <5mgKOH / g, and then the vacuum is broken by introducing nitrogen, and the temperature is cooled to 160°C, and then 500g of 150# solvent oil and 500g of dimethylbenzene are sequentially added, and the temperature is kept at 110-120°C.

[0044] (4) 1g of ethyl triphenyl acetic phosphine is added, and 50g of γ-glycidyl ether oxypropyl trimethoxysilane is added dropwise at a rate of 1-2g / min using a peristaltic pump, and after the dropwise addition is completed, the initial epoxy value is determined by sampling.

[0045] (5) The temperature is slowly raised to 130-140°C, and kept constant for 2-3h, and during the process, the epoxy value is detected by sampling, and when the epoxy value is reduced to <5% of the initial value, the reaction is terminated, and when the temperature of the material is reduced to <80°C, 20g (0.1-0.2%) of the polymerization inhibitor hydroquinone is added, and then filtered and poured out, and the self-prepared polyester resin a is obtained.

[0046] The preparation of polyester resin b comprises:

[0047] (1) 285 g of neopentyl glycol, 155 g of trimethylolpropane, 250 g of terephthalic acid, 150 g of isophthalic acid, and 160 g of adipic acid were dried to a moisture content of <0.1%, and the terephthalic acid and isophthalic acid were further pulverized to increase the reactivity, and were put into a 3L four-necked flask, and 1 g of monobutyl tin oxide was added.

[0048] (2) Nitrogen was introduced, and the temperature was slowly increased to 140-160°C, and was kept for 1 h, and dehydration was started. The temperature was gradually increased to 200-230°C at a rate of 10-15°C / h, and the temperature at the top of the distillation column was kept ≤100°C. The temperature was kept for 3-4 h until the esterification rate was >95%.

[0049] (3) The reaction system was vacuumed, and the pressure was reduced to -0.01 MPa, and the polycondensation was carried out under reduced pressure until the acid value was <5 mgKOH / g, and the vacuum was broken by introducing nitrogen, and the temperature was cooled to 160°C, and 500 g of 150# solvent oil and 500 g of xylene were sequentially added, and the temperature was kept at 110-120°C.

[0050] (4) 1 g of ethyl triphenyl phosphonium acetate was added, and 50 g of γ-glycidyl ether oxypropyl trimethoxysilane was added dropwise at a rate of 1-2 g / min using a peristaltic pump, and after the dropwise addition was completed, the initial epoxy value was determined by sampling.

[0051] (5) The temperature was slowly increased to 130-140°C, and was kept for 2-3 h, and during this time, the epoxy value was detected by sampling, and when the epoxy value was reduced to <5% of the initial value, the reaction was terminated, and when the temperature of the material was reduced to <80°C, 20 g (0.1-0.2%) of the polymerization inhibitor hydroquinone was added, and was filtered and poured out, and thus the self-made polyester resin b was obtained.

[0052] The preparation of the polyester resin c includes:

[0053] (1) 180 g of 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 150 g of neopentyl glycol, 110 g of trimethylolpropane, 250 g of terephthalic acid, 150 g of isophthalic acid, and 160 g of adipic acid were dried to a moisture content of <0.1%, and the terephthalic acid and isophthalic acid were further pulverized to increase the reactivity, and were put into a 3L four-necked flask, and 1 g of monobutyl tin oxide was added.

[0054] (2) Nitrogen was introduced, and the temperature was slowly increased to 140-160°C, and was kept for 1 h, and dehydration was started. The temperature was gradually increased to 200-230°C at a rate of 10-15°C / h, and the temperature at the top of the distillation column was kept ≤100°C. The temperature was kept for 3-4 h until the esterification rate was >95%.

[0055] (3) The reaction system is vacuumed, and the pressure is reduced to -0.01 MPa. The polycondensation is carried out under the condition until the acid value is less than 5 mgKOH / g, and then the reaction is stopped. Nitrogen is introduced to break the vacuum, and the temperature is cooled to 160°C. Then 500 g of 150# solvent oil and 500 g of dimethylbenzene are sequentially added. After cooling and filtering, the product is obtained, which is the self-made polyester resin c.

[0056] The preparation of the polyester resin d includes:

[0057] (1) 285 g of neopentyl glycol, 155 g of trimethylolpropane, 250 g of terephthalic acid, 150 g of isophthalic acid, and 160 g of adipic acid are dried to have a moisture content of less than 0.1%. The terephthalic acid and isophthalic acid are further pulverized to improve the reactivity. The mixture is put into a 3L four-necked flask, and 1 g of monobutyl tin oxide is added.

[0058] (2) Nitrogen is introduced, and the temperature is slowly increased to 140-160°C and kept for 1 h to start dehydration. The temperature is gradually increased to 200-230°C at a rate of 10-15°C / h, and the temperature at the top of the distillation column is kept at less than or equal to 100°C. The temperature is kept for 3-4 h until the esterification rate is more than 95%.

[0059] (3) The reaction system is vacuumed, and the pressure is reduced to -0.01 MPa. The polycondensation is carried out under the condition until the acid value is less than 5 mgKOH / g, and then the reaction is stopped. Nitrogen is introduced to break the vacuum, and the temperature is cooled to 160°C. Then 500 g of 150# solvent oil and 500 g of dimethylbenzene are sequentially added. After cooling and filtering, the product is obtained, which is the self-made polyester resin d.

[0060] The preparation of the polyester resin e and the polyester resin f includes:

[0061] The MARCOA TM CH470, the MARCOA TM CL372, dimethylbenzene 25%, and divalent acid ester DBE 25% are added into a dispersion cylinder, and dispersed at 800-1000 rpm for 2 h until the material is clear and transparent. After cooling, the polyester resin e (MARCOA TM CH470 solution) and the polyester resin f (MARCOA TM CL372 solution) are obtained.

[0062] Specifically, the preparation of the tinplate easy-open lid topcoat includes the following steps:

[0063] (1) The polyester resin, 100# solvent oil, propylene glycol methyl ether acetate, and dimethyl acid value DBE are added into a dispersion cylinder according to the formula in Table 1, and dispersed at 600 rpm for 15 min until uniform dispersion.

[0064] (2) Add amino resin, blocked isocyanate in sequence, disperse evenly at 600 rpm for 15 min.

[0065] (3) Add acid catalyst, wax powder, defoaming agent, adhesion promoter, leveling agent in sequence under stirring, disperse at 600 rpm for 30 min until evenly stirred, filter, and the tin lid outer coating is obtained.

[0066] Test Example

[0067] The coating of the above examples and comparative examples is coated on tin substrate for testing: film thickness: 8 g / m 2 ; film coating method: using a wire bar for scraping; baking condition: 180-205℃ constant temperature for 10-12 min. Test items: gloss, hardness, adhesion, solvent resistance, scratch resistance, cooking resistance, impact resistance, and machinability.

[0068] 1. Film gloss test: according to GB / T 9754, the 60° angle gloss of the coating is measured by a gloss meter.

[0069] 2. Pencil hardness test: according to GB / T 6739, the maximum pencil hardness of the coating without plowing is measured by a Chinese pencil.

[0070] 3. Adhesion test: according to GB / T 1720, a cross-shaped grid with 6-8 intervals of 1 mm is drawn on the coating by a cross-cut knife, then a 3M tape is used to tear the grid, and the peeling of the coating is observed, which is divided into 0-5 grades, and the smaller the grade, the better the adhesion.

[0071] 4. Solvent resistance: according to GB / T 23989, the coating surface is wiped once back and forth with a kerosene-soaked cotton under a pressure of 1 kg, and the more times of complete back and forth wiping, the better the solvent resistance.

[0072] 5. Scratch resistance: according to GB / T 9279, the minimum negative weight value of the coating that is scratched through is measured by a scratch tester, which is the scratch resistance value of the coating. The larger the value, the better.

[0073] 6. Cooking resistance test: according to GB / T 1733, the coating sample is prepared, and then subjected to high-temperature cooking in water phase and steam phase at 127℃ for 65 min by a high-pressure vertical sterilizer, and the abnormality such as water vapor penetration, whitening, blistering, and peeling of the coating is observed.

[0074] 7. Impact resistance test: according to GB / T 1732, a 1Kg weight hammer is dropped from a height of 50 cm to hit the coating sample, and then the sample is immersed in copper sulfate solution for 2-5 min, and the corrosion at the impact site is observed.

[0075] 8. Machinability test: the sample sheet after coating is punched into a sample by an unequal angle can-RC box die, and high temperature cooking sterilization is carried out, and the film rupture of the four different arc angle positions of the RC box is observed, and the total is divided into 0-4 levels, 0 level indicating the best machinability and flexibility, and 4 level being the worst.

[0076] The performance test results of the coating of the examples and the comparative examples are shown in Table 2.

[0077] Table 2 Performance test results of the coating of the examples and the comparative examples

[0078]

[0079]

[0080] As can be seen from Table 2, from Example 4, Comparative Example 1 and Comparative Example 2, it can be seen that when the polyester resin is not introduced with 2,2,4,4-tetramethyl-1,3-cyclobutanediol, whether it is a conventional linear saturated polyester resin or a branched saturated polyester resin, the coating cannot resist the erosion of strong alkali in a high temperature environment; from Example 2, Example 3 and Example 4, it can be seen that the grafting of silicone oligomers alone or the introduction of 2,2,4,4-tetramethyl-1,3-cyclobutanediol alone has a greater contribution to the solvent resistance of the coating, but there is still room for improvement in the resistance to strong alkali; as can be seen from Example 1, when the polyester resin with 2,2,4,4-tetramethyl-1,3-cyclobutanediol and γ-glycidyl ether oxypropyl trimethoxysilane works together, the coating prepared therefrom has no whitening and bubbling after 127℃ / 60min strong alkali (0.1% NaOH) cooking, and the adhesion remains 0 level, that is, it exhibits excellent resistance to the erosion of sodium hydroxide solution under high temperature conditions, and the pencil hardness of the coating is ≥1H, the impact resistance has no rust spots, and the machinability is 0 level, meeting the requirements of easy-to-pull can stamping forming; the coating does not contain BPA and PFAS, and meets the food contact material regulations.

[0081] In summary, the tinplate easy-to-pull can outer coating suitable for strong alkali sterilization process according to the embodiments of the present application can ensure that it has excellent mechanical properties, machinability and chemical resistance, and meets the requirements of tinplate easy-to-pull can resistance to strong alkali high temperature cooking sterilization process.

[0082] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative description of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate different embodiments or examples described in the specification.

[0083] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary, and should not be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A coating for the exterior of tinplate easy-open lids suitable for strong alkali sterilization processes, characterized in that, It includes the following raw materials by weight percentage: 40%-60% silicone-modified polyester resin, 5%-15% amino resin, 5-15% blocked isocyanate, 20%-40% solvent, 0.2%-5.0% wax powder, 0.01%-0.5% acid catalyst, 0.05%-1.0% defoamer, 0.5%-2.0% adhesion promoter, and 0.01%-0.5% leveling agent; The organosilicon-modified polyester resin incorporates 2,2,4,4-tetramethyl-1,3-cyclobutanediol and grafts γ-glycidoxypropyltrimethoxysilane onto the polyester resin.

2. The coating for the tinplate easy-open lid as described in claim 1, characterized in that, The organosilicon-modified polyester resin has an acid value of 1-5 mg KOH / g, a number-average molecular weight of 11,000-18,000, and a TG point of 85-93℃.

3. The coating for the tinplate easy-open lid as described in claim 1, characterized in that, The organosilicon-modified polyester resin is prepared by esterification reaction of the following raw materials in weight percentages: 2,2,4,4-tetramethyl-1,3-cyclobutanediol 5%-15%, trimethylolpropane 5%-10%, neopentyl glycol 5%-15%, terephthalic acid 5%-15%, isophthalic acid 5%-10%, adipic acid 5%-10%, monobutyltin oxide 0.5%-2%, xylene 20-30%, 150# solvent oil 20%-30%, γ-glycidyl etheroxypropyltrimethoxysilane 1%-5%, ethyltriphenylphosphine acetate 0.5%-2%, and hydroquinone 0.1%-0.2%.

4. The tinplate easy-open cover coating as described in claim 3, characterized in that, The esterification reaction is as follows: Add 2,2,4,4-tetramethyl-1,3-cyclobutanediol, neopentyl glycol, trimethylolpropane, terephthalic acid, isophthalic acid, adipic acid, and monobutyltin oxide to a reaction vessel, purge with nitrogen, slowly raise the temperature to 140-160℃, keep at this temperature for 1 hour, and begin dehydration. The temperature is gradually increased to 200-230℃ at a rate of 10-15℃ / h, and held for 3-4 hours until the esterification rate is above 95%. The reaction system is then evacuated and polycondensation is carried out under reduced pressure to -0.01MPa until the acid value is <5mgKOH / g. The reaction is then stopped, nitrogen is introduced to break the vacuum, and the system is cooled to 160℃. 150# solvent oil and xylene are added in sequence, and the system is held at 110-120℃. Add ethyltriphenylphosphine acetate, and use a peristaltic pump to add γ-glycidoxypropyltrimethoxysilane dropwise at a rate of 1-2 g / min. After the addition is complete, take a sample to determine the initial epoxy value. Slowly raise the temperature to 130-140℃ and keep it at that temperature for 2-3 hours. During this period, take a sample to determine the epoxy value. When the epoxy value drops to less than 5% of the initial value, terminate the reaction. After the material temperature drops to below 80℃, add the polymerization inhibitor hydroquinone, cool, filter, and pour out.

5. The coating for tinplate easy-open lids as described in claim 1, characterized in that, The amino resin is one or more of the following: methyl etherified benzo-formaldehyde resin, butyl etherified benzo-formaldehyde resin, methyl ethyl etherified benzo-formaldehyde resin, butyl etherified melamine-formaldehyde resin, and butyl etherified urea-formaldehyde resin.

6. The coating for tinplate easy-open lids as described in claim 1, characterized in that, The blocked isocyanate is one or more of blocked hexamethylene diisocyanate, blocked isophorone diisocyanate, diphenylmethane diisocyanate, and 4,4-dicyclohexylmethane diisocyanate.

7. The coating for tinplate easy-open lids as described in claim 1, characterized in that, The solvent is one or more of xylene, 100# solvent oil, 150# solvent oil, 200# solvent oil, divalent ester DBE, n-butanol, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, propylene glycol methyl ether, cyclohexanone, and methyl ethyl ketone.

8. The coating for tinplate easy-open lids as described in claim 1, characterized in that, The wax powder is one or more of the following: polyethylene wax, oxidized polyethylene wax, carnauba wax, Fischer-Tropsch wax, polymethyl methacrylate wax powder, polypropylene wax, and lanolin. Optionally, the defoamer is one or more of the following: silicone defoamer, polyether defoamer, polyester defoamer, and mineral oil defoamer.

9. The coating for tinplate easy-open lids as described in claim 1, characterized in that, The adhesion promoter is one or more of polyester phosphate, epoxy phosphate, acrylate phosphate, titanate, and organosiloxane.

10. The tinplate easy-open cover coating as described in claim 1, characterized in that, The leveling agent is one or more of the following: silicone leveling agent, acrylic leveling agent, fluorocarbon leveling agent, and urea-formaldehyde resin.

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