Bisphenol A-free coating for metal packaging material

Abstract

The invention provides a bisphenol A-free coating for a metal packaging material, which is prepared from the following components in parts by weight: 50 to 120 parts of dihydric alcohol diglycidyl ether, 5 to 20 parts of trihydric alcohol triglycidyl ether, 20 to 50 parts of chain extender, 50 to 100 parts of diluting solvent, 5 to 20 parts of curing agent, 1 to 10 parts of auxiliary curing agent, 20 to 40 parts of mixed solvent, 0.1 to 1 part of catalyst, 0.1 to 1 part of flatting agent and 0.1 to 1 part of defoaming agent. The bisphenol A-free coating for the metal packaging material provided by the invention does not adopt a formula of bisphenol A (bisphenol F and bisphenol S), derivatives thereof and the like, the coating with relatively good molecular weight, flexibility and chemical resistance is obtained through polymerization reaction, and the coating can be applied to metal packaging and coating of food, medicines, cosmetics and the like, and has a wide market prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of metal packaging coatings, and in particular relates to a coating that does not contain bisphenol A and is used for metal packaging materials. Background Art

[0002] Bisphenol A (BPA) is a chemical added to many commodities. It is often used as a monomer in the synthesis of polycarbonate, a plasticizer in the production of epoxy resins, and an additive to eliminate excess hydrochloric acid in the production of polyvinyl chloride (PVC). When mixed with other compounds, BPA can produce strong and elastic plastics. BPA is also used to make epoxy resins, which are coated on the lining of canned food containers to prevent metal corrosion and breakage, and improve the durability and protection of packaging. In the past, BPA was ubiquitous in daily life products, often used in plastic water cups, baby bottles, and coatings in metal cans. However, studies have found that BPA can enter the human body through a variety of routes, such as oral, inhalation, or through the skin. Among them, the most important route is ingestion. When food or liquid is added to a container containing BPA, some BPA will be emitted and mixed with the contents of the container. Heating or microwave cooking is more conducive to the mixing of BPA with food.

[0003] Therefore, out of consideration for human health, the use of bisphenol A in metal packaging is subject to increasingly strict restrictions. Some countries have begun to take measures to restrict or prohibit its use in food packaging. For example, China has explicitly banned the production of polycarbonate baby bottles and other baby bottles containing bisphenol A; and promoted the development of new coating products that do not contain bisphenol A to meet market demand and regulatory requirements. Currently, coatings that do not contain bisphenol A often use special epoxy resins that do not contain bisphenol A (bisphenol F, bisphenol S) in their structure. Generally, they can also be compounded with phenolic resins to form coatings. However, such coatings generally have a small molecular weight, poor flexibility, and poor adhesion to metals, making it difficult to meet the requirements of metal packaging processing. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a bisphenol A-free coating for metal packaging materials.

[0005] The present invention provides a bisphenol A-free coating for metal packaging materials, which comprises, by weight: 50-120 parts of diol diglycidyl ether, 5-20 parts of triol triglycidyl ether, 20-50 parts of chain extender, 50-100 parts of diluent solvent, 5-20 parts of curing agent, 1-10 parts of auxiliary curing agent, 20-40 parts of mixed solvent, 0.1-1 parts of catalyst, 0.1-1 parts of leveling agent and 0.1-1 parts of defoaming agent;

[0006] The preparation method of the coating comprises the following steps:

[0007] Step S1: Preparation of semi-finished epoxy resin:

[0008] Add diol diglycidyl ether, triol triglycidyl ether and catalyst into the reactor, keep stirring, heat the reactor and keep it at 80°C, stir evenly, add chain extender, and heat to 160°C after adding chain extender;

[0009] During the reaction, the reaction temperature was gradually increased to 210°C within 3 hours;

[0010] After the reaction is completed, the reactor temperature is maintained at 200-220°C for 2-3 hours;

[0011] Cool naturally to 150-160°C, add diluent solvent, and stir evenly to obtain a semi-finished epoxy resin with a solid content of 35-65%;

[0012] Step S2: Preparation of coating:

[0013] Add the semi-finished epoxy resin into a closed dispersion kettle and keep stirring;

[0014] Add leveling agent, defoamer and catalyst in sequence, and disperse at high speed for 15 minutes after adding;

[0015] After the dispersion is completed, add the curing agent, auxiliary curing agent and mixed solvent, and disperse at a medium speed for 30 minutes after the addition is completed;

[0016] Sampling, testing, filtering, and preparation are completed.

[0017] Furthermore, the composition comprises, by weight: 60-100 parts of diol diglycidyl ether, 5-15 parts of triol triglycidyl ether, 25-40 parts of chain extender, 60-80 parts of diluent solvent, 5-10 parts of curing agent, 3-8 parts of auxiliary curing agent, 20-30 parts of mixed solvent, 0.1-1 parts of catalyst, 0.1-1 parts of leveling agent and 0.1-1 parts of defoaming agent.

[0018] Furthermore, the composition comprises, by weight: 75-95 parts of diol diglycidyl ether, 5-10 parts of triol triglycidyl ether, 20-40 parts of chain extender, 60-80 parts of diluent solvent, 5-10 parts of curing agent, 3-8 parts of auxiliary curing agent, 20-30 parts of mixed solvent, 0.1-1 parts of catalyst, 0.1-1 parts of leveling agent and 0.1-1 parts of defoaming agent.

[0019] Furthermore, in parts by weight, it includes: 80-85 parts of diol diglycidyl ether, 5-10 parts of triol triglycidyl ether, 30-40 parts of chain extender, 60-80 parts of diluent solvent, 5-10 parts of curing agent, 3-8 parts of auxiliary curing agent, 20-30 parts of mixed solvent, 0.1-1 part of catalyst, 0.1-1 part of leveling agent, and 0.1-1 part of defoaming agent.

[0020] Furthermore, the diol diglycidyl ether is one or more of diethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, and polypropylene glycol diglycidyl ether.

[0021] Furthermore, the triol triglycidyl ether is one or more of glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, and glycerol triglycidyl ether.

[0022] Furthermore, the chain extender is one of hydroquinone, tert-butyl hydroquinone, biphenol, tetramethyl biphenol, hydroquinone dihydroxyethyl ether, and resorcinol dihydroxyethyl ether.

[0023] Furthermore, the catalyst is one of tri-n-butylamine, tetramethylammonium chloride, triphenylphosphine, and ethyltriphenylphosphine bromide, and the diluent solvent is one of propylene glycol butyl ether, cyclohexanone, dimethyl nylonate, trimethylbenzene, and propylene glycol methyl ether acetate.

[0024] Furthermore, the curing agent is butanol etherified phenolic resin, and the auxiliary curing agent is butanol etherified amino resin.

[0025] The bisphenol A-free coating for metal packaging materials provided by the present invention does not adopt the formula of bisphenol A (bisphenol F, bisphenol S) and its derivatives, and obtains a coating with good molecular weight, flexibility and chemical resistance through polymerization reaction. It can be applied to the needs of metal packaging coating for food, medicine, cosmetics, etc., and has broad market prospects. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0027] The present invention provides a bisphenol A-free coating for metal packaging materials, which comprises, by weight: 50-120 parts of diol diglycidyl ether, 5-20 parts of triol triglycidyl ether, 20-50 parts of chain extender, 50-100 parts of diluent solvent, 5-20 parts of curing agent, 1-10 parts of auxiliary curing agent, 20-40 parts of mixed solvent, 0.1-1 parts of catalyst, 0.1-1 parts of leveling agent and 0.1-1 parts of defoaming agent;

[0028] The preparation method of the coating comprises the following steps:

[0029] Step S1: Preparation of semi-finished epoxy resin:

[0030] Add diol diglycidyl ether, triol triglycidyl ether and catalyst into the reactor, keep stirring, heat the reactor and keep it at 80°C, stir evenly, add chain extender, and heat to 160°C after adding chain extender;

[0031] During the reaction, the reaction temperature was gradually increased to 210°C within 3 hours;

[0032] After the reaction is completed, the reactor temperature is maintained at 200-220°C for 2-3 hours;

[0033] Cool naturally to 150-160°C, add diluent solvent, and stir evenly to obtain a semi-finished epoxy resin with a solid content of 35-65%;

[0034] Step S2: Preparation of coating:

[0035] Add the semi-finished epoxy resin into a closed dispersion kettle and keep stirring;

[0036] Add leveling agent, defoamer and catalyst in sequence, and disperse at high speed for 15 minutes after adding;

[0037] After the dispersion is completed, add the curing agent, auxiliary curing agent and mixed solvent, and disperse at a medium speed for 30 minutes after the addition is completed;

[0038] Sampling, testing, filtering, and preparation are completed.

[0039] Furthermore, the composition comprises, by weight: 60-100 parts of diol diglycidyl ether, 5-15 parts of triol triglycidyl ether, 25-40 parts of chain extender, 60-80 parts of diluent solvent, 5-10 parts of curing agent, 3-8 parts of auxiliary curing agent, 20-30 parts of mixed solvent, 0.1-1 parts of catalyst, 0.1-1 parts of leveling agent and 0.1-1 parts of defoaming agent.

[0040] Furthermore, the composition comprises, by weight: 75-95 parts of diol diglycidyl ether, 5-10 parts of triol triglycidyl ether, 20-40 parts of chain extender, 60-80 parts of diluent solvent, 5-10 parts of curing agent, 3-8 parts of auxiliary curing agent, 20-30 parts of mixed solvent, 0.1-1 parts of catalyst, 0.1-1 parts of leveling agent and 0.1-1 parts of defoaming agent.

[0041] Furthermore, in parts by weight, it includes: 80-85 parts of diol diglycidyl ether, 5-10 parts of triol triglycidyl ether, 30-40 parts of chain extender, 60-80 parts of diluent solvent, 5-10 parts of curing agent, 3-8 parts of auxiliary curing agent, 20-30 parts of mixed solvent, 0.1-1 part of catalyst, 0.1-1 part of leveling agent, and 0.1-1 part of defoaming agent.

[0042] Furthermore, the diol diglycidyl ether is one or more of diethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, and polypropylene glycol diglycidyl ether.

[0043] Furthermore, the triol triglycidyl ether is one or more of glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, and glycerol triglycidyl ether.

[0044] Furthermore, the chain extender is one of hydroquinone, tert-butyl hydroquinone, biphenol, tetramethyl biphenol, hydroquinone dihydroxyethyl ether, and resorcinol dihydroxyethyl ether.

[0045] Furthermore, the catalyst is one of tri-n-butylamine, tetramethylammonium chloride, triphenylphosphine, and ethyltriphenylphosphine bromide, and the diluent solvent is one of propylene glycol butyl ether, cyclohexanone, dimethyl nylonate, trimethylbenzene, and propylene glycol methyl ether acetate.

[0046] Furthermore, the curing agent is butanol etherified phenolic resin, and the auxiliary curing agent is butanol etherified amino resin.

[0047] Specifically, the mixed solvent may be a mixture of anhydrous ethanol and ethyl acetate.

[0048] To better illustrate the solutions of the present invention, the following are specific embodiments.

[0049] Embodiment 1

[0050] A bisphenol A-free coating for metal packaging materials, having a formula as follows: in parts by weight, 85 parts of 1,4-butanediol diglycidyl ether, 8 parts of glycerol triglycidyl ether, 30 parts of hydroquinone, 70 parts of propylene glycol butyl ether, 8 parts of butanol etherified phenolic resin, 6 parts of butanol etherified amino resin, 25 parts of a mixed solvent, 0.5 parts of a catalyst, 0.2 parts of a leveling agent, and 0.3 parts of a defoaming agent.

[0051] Preparation method:

[0052] Step S1: Preparation of semi-finished epoxy resin:

[0053] Add 1,4-butanediol diglycidyl ether, glycerol triglycidyl ether and a catalyst into a reactor, keep stirring, heat the reactor and keep it at 80°C, stir evenly, add hydroquinone, and heat to 160°C after adding hydroquinone;

[0054] During the reaction, the reaction temperature was gradually increased to 210°C within 3 hours;

[0055] After the reaction is completed, the reactor temperature is maintained at 200-220°C for 2-3 hours;

[0056] Cool naturally to 150-160°C, add diluent solvent, and stir evenly to obtain a semi-finished epoxy resin with a solid content of 35-65%;

[0057] Step S2: Preparation of coating:

[0058] Add the semi-finished epoxy resin into a closed dispersion kettle and keep stirring;

[0059] Add leveling agent, defoamer and catalyst in sequence, and disperse at high speed for 15 minutes after adding;

[0060] After the dispersion is completed, add butanol etherified phenolic resin, butanol etherified amino resin and mixed solvent, and disperse at a medium speed for 30 minutes after the addition is completed;

[0061] Sampling, testing, filtering, and preparation are completed.

[0062] Embodiment 2

[0063] A bisphenol A-free coating for metal packaging materials has the following formula: in parts by weight, 85 parts of diethylene glycol diglycidyl ether, 8 parts of propylene glycol triglycidyl ether, 35 parts of hydroquinone dihydroxyethyl ether, 76 parts of propylene glycol butyl ether, 8 parts of butanol etherified phenolic resin, 6 parts of butanol etherified amino resin, 25 parts of a mixed solvent, 0.5 parts of a catalyst, 0.2 parts of a leveling agent, and 0.3 parts of a defoaming agent.

[0064] Preparation method:

[0065] Step S1: Preparation of semi-finished epoxy resin:

[0066] Add diethylene glycol diglycidyl ether, propylene glycol triglycidyl ether and a catalyst into a reaction kettle, keep stirring, heat the reaction kettle and keep it at 80°C, stir evenly, add hydroquinone dihydroxyethyl ether, and heat to 160°C after adding hydroquinone dihydroxyethyl ether;

[0067] During the reaction, the reaction temperature was gradually increased to 210°C within 3 hours;

[0068] After the reaction is completed, the reactor temperature is maintained at 200-220°C for 2-3 hours;

[0069] Cool naturally to 150-160°C, add diluent solvent, and stir evenly to obtain a semi-finished epoxy resin with a solid content of 35-65%;

[0070] Step S2: Preparation of coating:

[0071] Add the semi-finished epoxy resin into a closed dispersion kettle and keep stirring;

[0072] Add leveling agent, defoamer and catalyst in sequence, and disperse at high speed for 15 minutes after adding;

[0073] After the dispersion is completed, add butanol etherified phenolic resin, butanol etherified amino resin and mixed solvent, and disperse at a medium speed for 30 minutes after the addition is completed;

[0074] Sampling, testing, filtering, and preparation are completed.

[0075] Embodiment 3

[0076] A bisphenol A-free coating for metal packaging materials has the following formula: in parts by weight, 75 parts of diethylene glycol diglycidyl ether, 8 parts of propylene glycol triglycidyl ether, 35 parts of hydroquinone dihydroxyethyl ether, 76 parts of propylene glycol butyl ether, 8 parts of butanol etherified phenolic resin, 6 parts of butanol etherified amino resin, 25 parts of a mixed solvent, 0.5 parts of a catalyst, 0.2 parts of a leveling agent, and 0.3 parts of a defoaming agent.

[0077] Preparation method:

[0078] Step S1: Preparation of semi-finished epoxy resin:

[0079] Add diethylene glycol diglycidyl ether, propylene glycol triglycidyl ether and a catalyst into a reaction kettle, keep stirring, heat the reaction kettle and keep it at 80°C, stir evenly, add hydroquinone dihydroxyethyl ether, and heat to 160°C after adding hydroquinone dihydroxyethyl ether;

[0080] During the reaction, the reaction temperature was gradually increased to 210°C within 3 hours;

[0081] After the reaction is completed, the reactor temperature is maintained at 200-220°C for 2-3 hours;

[0082] Cool naturally to 150-160°C, add diluent solvent, and stir evenly to obtain a semi-finished epoxy resin with a solid content of 35-65%;

[0083] Step S2: Preparation of coating:

[0084] Add the semi-finished epoxy resin into a closed dispersion kettle and keep stirring;

[0085] Add leveling agent, defoamer and catalyst in sequence, and disperse at high speed for 15 minutes after adding;

[0086] After the dispersion is completed, add butanol etherified phenolic resin, butanol etherified amino resin and mixed solvent, and disperse at a medium speed for 30 minutes after the addition is completed;

[0087] Sampling, testing, filtering, and preparation are completed.

[0088] Embodiment 4

[0089] A bisphenol A-free coating for metal packaging materials, the formula of which is different from that of Example 3 in that the amount of diethylene glycol diglycidyl ether is 65 parts.

[0090] Embodiment 5

[0091] A bisphenol A-free coating for metal packaging materials, the formula of which is different from that of Example 3 in that the amount of diethylene glycol diglycidyl ether is 55 parts.

[0092] Embodiment 6

[0093] A bisphenol A-free coating for metal packaging materials, the formula of which is different from that of Example 3 in that the amount of diethylene glycol diglycidyl ether is 95 parts.

[0094] Embodiment 7

[0095] A bisphenol A-free coating for metal packaging materials, the formula of which is different from that of Example 2 in that 1,4-butanediol diglycidyl ether is used to replace diethylene glycol diglycidyl ether.

[0096] Embodiment 8

[0097] A bisphenol A-free coating for metal packaging materials, the formula of which is different from that of Example 2 in that glycerol triglycidyl ether is used to replace propylene glycol triglycidyl ether.

[0098] The coatings of the above embodiments were tested for performance:

[0099] (1) Solvent-resistant wiping: Use absorbent cotton soaked in butanone, press with a force of one kilogram, and wipe back and forth on the coating surface in a straight line. One back and forth is counted as one time. Count the number of times the substrate is exposed after wiping. If it is more than 50 times, it will be counted as more than 50.

[0100] (2) Citric acid resistance test: After the coating is cured, the board is cut into long strips, bent several times, and then placed in a 2% citric acid solution and boiled at 121°C / 30 min. The gloss and smoothness of the surface after boiling are then observed and scored according to the gloss and smoothness. If the surface is smooth and has no gloss loss, the score is 10; if the surface loses gloss and the coating falls off, the score is 0. A score below 7 is considered unqualified.

[0101] (3) Acetic acid resistance test: After the coating is cured, the board is cut into long strips, bent several times, and then placed in a 2% acetic acid solution and boiled at 121°C / 30 min. The gloss and smoothness of the surface after boiling are then observed and scored according to the gloss and smoothness. If the surface is smooth and has no gloss loss, the score is 10; if the surface loses gloss and the coating falls off, the score is 0. A score below 7 is considered unqualified.

[0102] (4) Boiling resistance test: After the coating is cured, the board is cut into long strips, bent several times, and placed in distilled water at 85°C / 30 min. The gloss and smoothness of the surface after boiling are observed and scored according to the gloss and smoothness. If the surface is smooth and has no gloss loss, it is scored as 10; if the surface loses gloss and the coating falls off, it is scored as 0. A score below 7 is considered unqualified.

[0103] (5) Deep drawing resistance test: The coated plate is punched into a 206 basic cover using a punch press, and the coating in the punching and stretching area is observed to see if there is any cracking. No cracking is excellent, one crack is good, and more than one crack is poor.

[0104] (6) Adhesion test: Adhesion is measured by the cross-cut method, which is graded according to the national standard GB9286-88 Cross-cut Test for Paint and Varnish Films, and is combined with the tape method. If the paint film in the first part is intact, the adhesion is the best and is rated as Grade 1. If the second part is intact, it is rated as Grade 2, which is weaker than the previous grade. And so on. The larger the number, the worse the adhesion.

[0105] (7) 10% sodium hydroxide resistance test: After the coating is cured, the plate is cut into long strips, bent several times, and placed in a 10% sodium hydroxide solution at 25°C / 60 min. After cleaning, the surface gloss and smoothness of the coating are observed, and the gloss and integrity of the coating (bubbling, shedding, wrinkling, pinholes) are scored. If the surface is smooth and has no gloss loss and the coating is normal, the score is 10; if the surface is gloss loss and the coating is completely detached, the score is 0. A score below 7 is considered unqualified.

[0106] (8) 25% ammonia water resistance test: After the coating is cured, the board is cut into long strips, bent several times, and placed in 25% ammonia water at 50°C / 120 min. After cleaning, the surface gloss and smoothness of the coating are observed. The gloss and the integrity of the coating (bubbling, shedding, wrinkling, pinholes) are scored. If the surface is smooth and has no gloss loss and the coating is normal, the score is 10; if the surface is gloss loss and the coating is completely detached, the score is 0. A score below 7 is considered unqualified.

[0107] The results are as follows:

[0108] Table 1 Performance test results

[0109]

[0110] It can be seen from the above test data that the bisphenol A-free coating for metal packaging materials provided by the present invention has good adhesion to metal, flexibility, resistance and processability, as well as acid resistance and alkali resistance.

[0111] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A bisphenol A-free coating for metal packaging materials, characterized in that: In parts by weight, it comprises: 50-120 parts of diol diglycidyl ether, 5-20 parts of triol triglycidyl ether, 20-50 parts of chain extender, 50-100 parts of diluent solvent, 5-20 parts of curing agent, 1-10 parts of auxiliary curing agent, 20-40 parts of mixed solvent, 0.1-1 parts of catalyst, 0.1-1 parts of leveling agent and 0.1-1 parts of defoaming agent; The preparation method of the coating comprises the following steps: Step S1: Preparation of semi-finished epoxy resin: Add diol diglycidyl ether, triol triglycidyl ether and catalyst into the reactor, keep stirring, heat the reactor and keep it at 80°C, stir evenly, add chain extender, and heat to 160°C after adding chain extender; During the reaction, the reaction temperature was gradually increased to 210°C within 3 hours; After the reaction is completed, the reactor temperature is maintained at 200-220°C for 2-3 hours; Cool naturally to 150-160°C, add diluent solvent, and stir evenly to obtain a semi-finished epoxy resin with a solid content of 35-65%; Step S2: Preparation of coating: Add the semi-finished epoxy resin into a closed dispersion kettle and keep stirring; Add leveling agent, defoamer and catalyst in sequence, and disperse at high speed for 15 minutes after adding; After the dispersion is completed, add the curing agent, auxiliary curing agent and mixed solvent, and disperse at a medium speed for 30 minutes after the addition is completed; Sampling, testing, filtering, and preparation are completed.

2. The bisphenol A-free coating for metal materials according to claim 1, characterized in that: Calculated in parts by weight, it includes: 60-100 parts of diol diglycidyl ether, 5-15 parts of triol triglycidyl ether, 25-40 parts of chain extender, 60-80 parts of diluent solvent, 5-10 parts of curing agent, 3-8 parts of auxiliary curing agent, 20-30 parts of mixed solvent, 0.1-1 part of catalyst, 0.1-1 part of leveling agent and 0.1-1 part of defoaming agent.

3. The bisphenol A-free coating for metal materials according to claim 2, characterized in that: Calculated in parts by weight, it includes: 75-95 parts of diol diglycidyl ether, 5-10 parts of triol triglycidyl ether, 20-40 parts of chain extender, 60-80 parts of diluent solvent, 5-10 parts of curing agent, 3-8 parts of auxiliary curing agent, 20-30 parts of mixed solvent, 0.1-1 part of catalyst, 0.1-1 part of leveling agent and 0.1-1 part of defoaming agent.

4. The bisphenol A-free coating for metal materials according to claim 3, characterized in that: Calculated in parts by weight, it includes: 80-85 parts of diol diglycidyl ether, 5-10 parts of triol triglycidyl ether, 30-40 parts of chain extender, 60-80 parts of diluent solvent, 5-10 parts of curing agent, 3-8 parts of auxiliary curing agent, 20-30 parts of mixed solvent, 0.1-1 part of catalyst, 0.1-1 part of leveling agent and 0.1-1 part of defoaming agent.

5. The bisphenol A-free coating for metal materials according to any one of claims 1 to 4, characterized in that: The diol diglycidyl ether is one or more of diethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, and polypropylene glycol diglycidyl ether.

6. The bisphenol A-free coating for metal materials according to any one of claims 1 to 4, characterized in that: The triol triglycidyl ether is one or more of glycerol triglycidyl ether, trimethylolpropane triglycidyl ether and glycerol triglycidyl ether.

7. The bisphenol A-free coating for metal materials according to any one of claims 1 to 4, characterized in that: The chain extender is one of hydroquinone, tert-butyl hydroquinone, biphenol, tetramethyl biphenol, hydroquinone dihydroxyethyl ether, and resorcinol dihydroxyethyl ether.

8. The bisphenol A-free coating for metal materials according to any one of claims 1 to 4, characterized in that: The catalyst is one of tri-n-butylamine, tetramethylammonium chloride, triphenylphosphine and ethyltriphenylphosphine bromide, and the diluent is one of propylene glycol butyl ether, cyclohexanone, dimethyl nylonate, trimethylbenzene and propylene glycol methyl ether acetate.

9. The bisphenol A-free coating for metal materials according to any one of claims 1 to 4, characterized in that: The curing agent is butanol etherified phenolic resin, and the auxiliary curing agent is butanol etherified amino resin.

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