An EB-cured antibacterial inner-layer iron-printing coating and a preparation method thereof

Abstract

The present invention belongs to the field of tinplate coatings, and specifically relates to an EB-cured antibacterial inner tinplate coating and a preparation method thereof, wherein the tinplate coating is composed of the following components: 40-60% of a photosensitive resin base material, 20-35% of an active diluent, 1-3% of an auxiliary agent, 0.1-1% of an antioxidant, and 0.5-3% of an inorganic metal antibacterial agent. The preparation method of the tinplate coating is composed of the following steps: S1, weighing each component material and cleaning the tinplate surface; S2, fully mixing the component materials and uniformly applying them to the tinplate surface; S3, using EB for radiation curing to obtain an antibacterial inner tinplate coating. The tinplate coating of the present invention has a simple formula, is environmentally friendly, has a fast curing speed, has a high production efficiency, has a good comprehensive coating quality, and has a good long-term antibacterial effect.

Description

Technical Field

[0001] The invention belongs to the field of tinplate coatings, and in particular relates to an EB-cured antibacterial inner-layer tinplate coating and a preparation method thereof. Background Art

[0002] Tinplate is the common name for electroplated tin steel sheet, which refers to cold-rolled low-carbon steel sheet or strip coated with commercial pure tin on both sides. It combines the strength and formability of steel with the corrosion resistance, solderability and beautiful appearance of tin in one material. It has the characteristics of corrosion resistance, non-toxicity, high strength and good ductility. It is widely used in the field of packaging containers. For example, tinplate is widely used in milk powder cans, biscuit cans, tea cans, beverage cans and other products. In the food and beverage industry, many products are highly acidic, such as ketchup and pickles. Some foods contain a lot of protein, such as milk powder and canned meat products. S will be produced during high-temperature sterilization. 2+ Ions and H + Ions are highly corrosive to the inner wall of the can, which not only affects the shelf life of the can, but also affects the flavor of the product, and in serious cases, it is easy to cause the product to spoil. With the rapid development of my country's packaging industry, the various demands of the tinplate canning industry are constantly updated and upgraded, and the requirements for product packaging are also correspondingly improved. The continuous application of tinplate packaging has driven the development of the related industry - tinplate coatings.

[0003] The main characteristics of tinplate coatings are strong adhesion to metal sheets, corrosion resistance, boiling resistance, baking resistance, solvent resistance, light resistance and good processability (molding, punching, seams, etc.). From the coating formula, most of the current tinplate internal coating formulas are based on epoxy resin, and the main component is phenolic compounds of bisphenol A, which have certain harm to human organs, especially to children's intellectual development and women's reproduction. In terms of drying form, the main types are baking type and UV curing type. In the traditional tinplate process, the thermosetting tinplate coating that needs to be baked is used. Although it has advantages such as good adhesion and excellent alkali resistance, the slow curing speed is the biggest problem of thermosetting tinplate coating. It often needs to be baked and cured at 180-220℃ for 30-35 minutes. Due to the long drying time, continuous production cannot be achieved, resulting in most of the current tinplate yellow and white tinplate printing units still using a single sheet of tinplate working mode, which has a long working time and cycle and high energy consumption. Ultraviolet curing (UV) is to utilize ultraviolet light to irradiate, so that photosensitive material molecules are decomposed to form highly activated atoms or highly activated atomic groups, wherein the organic compound containing unsaturated bonds induces a series of light-triggered chain reactions, and finally reaches the purpose of molecular cross-linking polymerization curing and drying, which is a development direction of tinplate coating, but the adhesion of UV tinplate coating is poor, and the performance in terms of alkali resistance, post-processing resistance, flexibility, wear resistance, etc. is not as good as that of thermal curing tinplate coating. In addition, after milk powder, canned food and other products are opened, they will soon become corrupt due to contact with various pathogens in the air, and the current tinplate coating can rarely give tinplate good antibacterial properties. Patent CN110882880A discloses a coating process for tinplate, wherein the antibacterial properties of the coating are brought by adding a carrier-nanosilver, but the inorganic nanosilver particles, whose particle size is too small, may be inhaled by the human body during use, and the nanosilver particles have super strong permeability, causing certain damage to the human liver. Therefore, developing an iron printing coating with simple formula, environmental protection, fast curing speed, high production efficiency and good antibacterial function has obvious market prospects and economic value. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a tinplate coating with simple formula, environmental protection, fast curing speed, high production efficiency and good antibacterial function. The present invention adopts accelerated high-energy electron beam (EB) curing technology, uses electron beam as radiation source, and induces a specially formulated 100% reactive antibacterial coating liquid to quickly transform into a cured coating. The curing rate is high, the process is simple, no photoinitiator is required, no VOC is contained, and has significant antibacterial performance.

[0005] Specifically, the present invention provides an EB-cured antibacterial inner layer iron printing coating, characterized in that it is composed of the following components, calculated by weight percentage: 40-60% photosensitive resin base material, 20-35% active diluent, 1-3% auxiliary agent, 0.1-1% antioxidant, and 0.5-3% inorganic metal antibacterial agent.

[0006] Preferably, the photosensitive resin base material includes vinyl ether ester, silicone acrylate, multifunctional acrylate, urethane acrylate;

[0007] Preferably, the mass ratio of each component in the photosensitive resin base material is vinyl ether ester: silicone acrylate: multifunctional acrylate: urethane acrylate = 1-1.5:1.2-1.5:0.6-1:0.8-1.2;

[0008] Compared with acrylates, vinyl ether esters have higher reactivity, faster curing speed, lower shrinkage and good flexibility; silicone acrylates have excellent high temperature resistance, weather resistance and chemical corrosion resistance, and the addition of silicone can improve the scratch resistance and surface smoothness of the coating; the multifunctional acrylate is an acrylate with multiple reactive groups, that is, an acrylate with more than two functional groups, and the multifunctional acrylate can significantly improve the curing speed and crosslinking density, and enhance the hardness and chemical resistance of the coating; urethane acrylate has excellent wear resistance, elasticity and yellowing resistance, and can improve the wear resistance and toughness of the coating; mixing the four substances in a reasonable proportion can effectively bring into play the characteristics of each component, which is the key to improving the comprehensive performance of the coating.

[0009] Preferably, the reactive diluent is triethylene glycol diacrylate and pentaerythritol triacrylate;

[0010] Preferably, the mass ratio of the components of the reactive diluent is triethylene glycol diacrylate: pentaerythritol triacrylate = 1-2:1;

[0011] Reactive diluents help to reduce the viscosity of the coating, improve the fluidity of the coating, facilitate construction and coating, and cross-link with the base resin to form a film during the curing process, thereby increasing the curing rate and hardness. A single reactive diluent can provide relatively simple viscosity control, but due to the different physical and chemical properties of each diluent, it is difficult to simultaneously balance low viscosity and final coating performance, and certain limitations are exhibited during the construction process, such as unsatisfactory fluidity and coating properties during construction. Using two reactive diluents, triethylene glycol diacrylate and pentaerythritol triacrylate, and mixing them in appropriate proportions can optimize the viscosity adjustment of the coating, more flexibly adjust the rheological properties and construction properties of the coating, and make it smoother and more uniform during printing or coating. At the same time, the curing rate and cross-linking density can be adjusted. Faster-reacting diluents can increase the overall curing speed, while slower-reacting diluents can help extend the curing time to avoid excessive brittleness or uneven curing of the coating. The final coating strength and flexibility can be more flexibly adjusted according to demand.

[0012] Preferably, the auxiliary agent is a leveling agent and a defoaming agent, and the mass ratio of the leveling agent to the defoaming agent is 1 to 1.2:2;

[0013] Preferably, the leveling agent is an acrylic leveling agent, more preferably, an acrylic ester copolymer;

[0014] Preferably, the defoamer is a polyether defoamer, more preferably, a polyether alcohol;

[0015] The main function of the leveling agent is to improve the fluidity of the coating, avoid unevenness such as orange peel and shrinkage holes on the coating surface, and ensure the uniformity and smoothness of the coating. The acrylic copolymer leveling agent can significantly improve the wettability and fluidity of the coating and is suitable for silicone-free systems.

[0016] The main function of the defoamer is to inhibit and eliminate bubbles generated during the preparation and construction of the coating, to prevent bubbles from remaining in the coating film and affecting the appearance and performance of the coating; polyether alcohol defoamers can effectively prevent the generation of bubbles and promote the rupture of bubbles, and are suitable for systems with low surface tension and for silicone-free systems.

[0017] When leveling agents and defoamers are used in iron printing coatings, their dosage must be strictly controlled to avoid coating defects or other negative effects caused by excessive use.

[0018] Preferably, the antioxidant is 2,6-di-tert-butyl-p-cresol;

[0019] The main function of antioxidants is to prevent oxidative degradation of coatings during storage and processing, especially in high temperature and irradiation environments. Oxidation reactions may cause degradation of coating performance. Antioxidants are usually used to inhibit free radical reactions, extend the service life of coatings, and ensure the stability and durability of the final coating.

[0020] Preferably, the inorganic metal antibacterial agent is electrolytic silver ion water or electrolytic copper ion water;

[0021] Preferably, the concentration of the electrolytic silver ion water or electrolytic copper ion water is 80-100 ppm.

[0022] Silver ions (Ag+) and copper ions (Cu 2 +) is a positively charged particle at the single atomic level with high chemical activity. It can quickly combine with the cell membranes and proteins of bacteria, viruses, fungi and other microorganisms, destroy their structure, and then kill the microorganisms. It has a fast sterilization speed and strong antibacterial effect.

[0023] Electrolytic silver ions and electrolytic copper ions have certain advantages over nanosilver ions or copper ions in terms of antibacterial speed, activity, permeability and environmental friendliness; electrolytic silver ions or copper ions are soluble, their concentration can be precisely controlled, they have good solubility and biocompatibility, and are relatively safe to human tissues at appropriate concentrations. However, nanosilver ions or nanocopper, their nanoparticles may accumulate in the body during application, posing certain risks to human health or the environment. In addition, the metabolic pathways and long-term effects of nanoparticles in the body are still under study.

[0024] A method for preparing an EB-cured antibacterial inner-layer iron-printing coating, characterized in that the preparation method comprises the following steps:

[0025] S1, accurately weighing the components according to their weight percentage, and cleaning and degreasing the surface of the tinplate to be coated;

[0026] S2, mixing the components weighed in step S1 and stirring them thoroughly to make the components evenly mixed, and applying the mixed materials evenly to the surface of the tinplate using a scraper;

[0027] S3, using EB to irradiate and cure the tinplate surface treated in step S2, the irradiation height is 60-80 mm, the EB energy is 120-150 KeV, the EB curing dose is 60-70 kGy, and the irradiation time is 3-5 s, so as to obtain an antibacterial inner tinplate coating.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. Compared with the traditional solvent-based thermosetting coatings that need to be cured at a high temperature of 180-220°C for 5-10 minutes or longer, the present invention only takes 3-5 seconds to cure under EB irradiation, with extremely high curing efficiency, suitable for efficient continuous production, and the energy consumption is only about one-tenth of that of thermosetting coatings, saving energy consumption;

[0030] 2. Compared with UV light-curing coatings, it does not need to introduce expensive photoinitiators. While reducing costs, it will not produce unpleasant toxic gases such as VOC due to residual photoinitiators and photodecomposition products, making it more suitable for packaging materials in the fields of food and medicine;

[0031] 3. The coating prepared by the present invention has no defects such as orange peel, wrinkles, pores, etc., is transparent and colorless, has uniform coating thickness, high gloss, good flexibility, solvent resistance, strong adhesion, high hardness, and has long-term bactericidal and antibacterial properties.

[0032] Yes, the antibacterial rate against Escherichia coli and Staphylococcus aureus reaches more than 98%, effectively extending the shelf life of stored items after opening the lid. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0035] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. Without departing from the spirit and substance of the present invention, modifications or substitutions made to the method, steps or conditions of the present invention are within the scope of the present invention. Unless otherwise specified, the chemical reagents used in the examples are conventional commercial reagents, and the technical means used in the examples are conventional means well known to those skilled in the art.

[0036] Example 1

[0037] (1) Calculate by weight percentage and accurately weigh the following components:

[0038] 40% of the photosensitive resin base material, wherein the mass ratio of the four base material components of vinyl ether ester, silicone acrylate, multifunctional acrylate and urethane acrylate is 1:1.2:0.6:0.8, and the multifunctional acrylate is trimethylolpropane triacrylate;

[0039] Active diluent 20%, wherein the mass ratio of triethylene glycol diacrylate to pentaerythritol triacrylate is 1:1;

[0040] The additive is 1%, wherein the mass ratio of the acrylic acid ester copolymer to the polyether alcohol is 1:2;

[0041] 2,6-di-tert-butyl-p-cresol 0.1%;

[0042] Electrolyzed copper ion water 0.5%, concentration 100ppm.

[0043] (2) The tinplate surface to be coated is thoroughly cleaned with alcohol to remove the surface oil film; the components weighed in the above step are mixed and stirred thoroughly to make the components mixed evenly, and the mixed material is evenly applied to the tinplate surface with a scraper;

[0044] (3) The tinplate surface coated with the coating was irradiated and cured by EB, with an irradiation height of 60 mm, an EB energy of 120 KeV, an EB curing dose of 60 kGy, and an irradiation time of 3 s to obtain an antibacterial inner tinplate coating.

[0045] Example 2

[0046] (1) Calculate by weight percentage and accurately weigh the following components:

[0047] 50% of the photosensitive resin base material, wherein the mass ratio of the four base material components of vinyl ether ester, silicone acrylate, multifunctional acrylate and urethane acrylate is 1.2:1.3:0.8:1, and the multifunctional acrylate is trimethylolpropane triacrylate;

[0048] Active diluent 28%, wherein the mass ratio of triethylene glycol diacrylate to pentaerythritol triacrylate is 1.5:1;

[0049] The additive is 2%, wherein the mass ratio of the acrylic acid ester copolymer to the polyether alcohol is 1.1:2;

[0050] 2,6-di-tert-butyl-p-cresol 0.5%;

[0051] Electrolyzed silver ion water 1.7%, concentration 90ppm.

[0052] (2) The tinplate surface to be coated is thoroughly cleaned with alcohol to remove the surface oil film; the components weighed in the above step are mixed and stirred thoroughly to make the components mixed evenly, and the mixed material is evenly applied to the tinplate surface with a scraper;

[0053] (3) The tinplate surface coated with the coating was irradiated and cured by EB, with an irradiation height of 70 mm, an EB energy of 135 KeV, an EB curing dose of 65 kGy, and an irradiation time of 4 s to obtain an antibacterial inner tinplate coating.

[0054] Example 3

[0055] (1) Calculate by weight percentage and accurately weigh the following components:

[0056] 60% of the photosensitive resin base material, wherein the mass ratio of the four base material components of vinyl ether ester, silicone acrylate, multifunctional acrylate and urethane acrylate is 1.5:1.5:1:1.2; the multifunctional acrylate is propoxylated trimethylolpropane triacrylate;

[0057] Active diluent 35%, wherein the mass ratio of triethylene glycol diacrylate to pentaerythritol triacrylate is 2:1;

[0058] 3% additive, wherein the mass ratio of acrylate copolymer to polyether alcohol is 1.2:2;

[0059] 2,6-di-tert-butyl-p-cresol 1%;

[0060] Electrolyzed silver ion water 3%, concentration is 80ppm.

[0061] (2) The tinplate surface to be coated is thoroughly cleaned with alcohol to remove the surface oil film; the components weighed in the above step are mixed and stirred thoroughly to make the components mixed evenly, and the mixed material is evenly applied to the tinplate surface with a scraper;

[0062] (3) The tinplate surface coated with the coating was irradiated and cured by EB, with an irradiation height of 80 mm, an EB energy of 150 KeV, an EB curing dose of 70 kGy, and an irradiation time of 5 s to obtain an antibacterial inner tinplate coating.

[0063] Table 1 shows the test performance of the EB-cured antibacterial inner iron-printing coating prepared in Examples 1 to 3

[0064]

[0065] It can be seen from the above table that the tinplate coating prepared by the present invention has no defects such as orange peel, wrinkles, pores, etc. in appearance, is transparent and colorless, has uniform coating thickness, high gloss, good flexibility, solvent wiping resistance, strong adhesion, high hardness, high antibacterial rate against Escherichia coli and Staphylococcus aureus, and has excellent comprehensive performance.

[0066] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. An EB-cured antibacterial inner-layer iron-printing coating, characterized in that: Calculated by weight percentage, it is composed of the following components: 40-60% of photosensitive resin base material, 20-35% of active diluent, 1-3% of auxiliary agent, 0.1-1% of antioxidant, and 0.5-3% of inorganic metal antibacterial agent.

2. The EB-cured antibacterial inner-layer iron-printing coating according to claim 1, characterized in that: The photosensitive resin base material includes vinyl ether ester, silicone acrylate, multifunctional acrylate and urethane acrylate.

3. The EB-cured antibacterial inner-layer iron-printing coating according to claim 2, characterized in that: The mass ratio of each component in the photosensitive resin base material is vinyl ether ester: silicone acrylate: multifunctional acrylate: urethane acrylate=1-1.5:1.2-1.5:0.6-1:0.8-1.

2.

4. The EB-cured antibacterial inner-layer tinplate coating according to claim 1, characterized in that: The active diluents are triethylene glycol diacrylate and pentaerythritol triacrylate.

5. The EB-cured antibacterial inner-layer tinplate coating according to claim 4, characterized in that: The mass ratio of each component of the active diluent is triethylene glycol diacrylate: pentaerythritol triacrylate=1-2:

1.

6. The EB-cured antibacterial inner-layer iron-printing coating according to claim 1, characterized in that: The auxiliary agents are a leveling agent and a defoaming agent, and the mass ratio of the leveling agent to the defoaming agent is 1 to 1.2:

2. The leveling agent is an acrylic leveling agent, and the defoaming agent is a polyether defoaming agent.

7. The EB-cured antibacterial inner-layer iron-printing coating according to claim 1, characterized in that: The antioxidant is 2,6-di-tert-butyl-p-cresol.

8. The EB-cured antibacterial inner-layer tinplate coating according to claim 1, characterized in that: The inorganic metal antibacterial agent is electrolytic silver ion water or electrolytic copper ion water, and the concentration of the electrolytic silver ion water or electrolytic copper ion water is 80-100 ppm.

9. A method for preparing an EB-cured antibacterial inner-layer iron-printing coating, characterized in that: The preparation method consists of the following steps: S1, accurately weighing the components according to their weight percentage, and cleaning and degreasing the surface of the tinplate to be coated; S2, mixing the components weighed in step S1 and stirring them thoroughly to make the components evenly mixed, and applying the mixed materials evenly to the surface of the tinplate using a scraper; S3, using EB to irradiate and cure the tinplate surface treated in step S2, so as to obtain an antibacterial inner tinplate coating.

10. A method for preparing an EB-cured antibacterial inner-layer iron-printing coating, characterized in that: The parameters of the EB irradiation curing are: irradiation height of 60-80 mm, EB energy of 120-150 KeV, EB curing dose of 60-70 kGy, and irradiation time of 3-5 s.

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