Iron easy-to-open cover scribed line repairing coating as well as preparation method and application thereof

Abstract

The invention relates to the field of metal packaging coatings, in particular to an iron easy-open cover scribed line repairing coating and a preparation method and application thereof. The iron easy-to-open cover scribed line repair coating provided by the invention is composed of a component A and a component B, wherein the component A is composed of 30-43% of polyester resin, 0.8% of an auxiliary agent and 56.2-69.2% of a mixed solvent; the component B is prepared from a curing agent polyhexamethylene diisocyanate and a mixed solvent, wherein the mixed solvent is prepared from 100 # solvent oil, butanone and propylene glycol methyl ether acetate according to the mass percent ratio of 30%: 30%: 40%; the mass part ratio of the component A to the component B is 17: 1. The invention further provides a preparation method of the iron easy-to-open cover scribed line repairing coating, and the obtained iron easy-to-open cover scribed line repairing coating is high in solid content, high in electrocorrosion resistance and strong in adhesive force and can be applied to the field of iron easy-to-open cover scribed line repairing.

Description

Technical Field

[0001] The invention relates to the field of metal packaging coatings, and in particular to an iron easy-open lid score line repair coating, and a preparation method and application thereof. Background Art

[0002] Easy-open lids, also known as easy-pull lids, are lids with pull rings used to seal cans. They are metal packaging products, mostly made of iron, and come in a variety of sizes. They are suitable for iron cans, aluminum cans, composite cans, PET plastic cans, and paper cans. Existing easy-open lids usually have a 0.1mm cut mark processed on the iron lid substrate with a thickness of about 0.2mm, so that consumers can open the lid along the pull ring. However, the cut will damage the original lid coating, and in actual use, most of the products in the easy-open lids need to be cooked at high temperatures. If there is no protective coating at the cut, corrosion will occur at the cut, thereby destroying the seal of the food lid. Rust may even penetrate the iron lid, causing damage to the food quality and loss of use and edible value. Therefore, the cut part must be sprayed for protection.

[0003] Chinese patent CN107163821A provides a two-component iron easy-open cover score repair coating using hydroxy acrylic resin and isocyanate as curing agent. The coating has a low solid content under the actual spraying viscosity, and the spraying amount is too thin when repairing the score, resulting in insufficient electrical corrosion resistance.

[0004] In addition, after the development of iron easy-open lids in recent years, the topcoat coatings of easy-open lids have become diversified, including acrylic resin topcoats, epoxy resin topcoats, and polyester resin topcoats. Different colors and surface additives are used on different topcoats, which increases the scratch resistance and slipperiness of the topcoats. Spraying hydroxyl acrylic resin-based line repair coatings on the surface of such substrates has the defect of poor adhesion. In addition, the spraying efficiency of line repair coatings has been improved, which has been shortened from the original 80-90℃ / 5min to the current 80-120℃ / 3min, and the number of lids sprayed with repair coatings per minute has increased from 200 / min to 400-500 / min. The existing iron easy-open lid repair coatings of hydroxyl acrylate and isocyanate resin systems cannot adapt to the high-speed machine equipment process, and bubbles often appear during use. The market urgently needs to develop an iron easy-open lid line repair coating with strong adhesion, high electrical corrosion resistance, and can be used on high-speed line repair spraying machines. Summary of the invention

[0005] The purpose of the present invention is to provide a paint for repairing the score lines of an iron easy-open lid which has high electrical corrosion resistance, strong adhesion, is adaptable to high-speed machine equipment technology, and avoids frequent bubbles during use, and at the same time provides a preparation method and application of the paint for repairing the score lines of an iron easy-open lid.

[0006] 2. To achieve the above object, the present invention provides a paint for repairing the score line of an easy-open lid, wherein the paint for repairing the score line of an easy-open lid is composed of component A and component B:

[0007] The component A is composed of 30-43% polyester resin, 0.8% auxiliary agent and 56.2%-69.2% mixed solvent.

[0008] The B component is composed of a curing agent, polyhexamethylene diisocyanate, and a mixed solvent of 100# solvent oil, butanone, and propylene glycol methyl ether acetate in a mass percentage of 30%: 30%: 40%.

[0009] Furthermore, in the iron easy-open lid score line repair coating, the weight average molecular weight of the polyester resin in the A component is 1,000 to 200,000.

[0010] Furthermore, in the iron easy-open lid score line repair paint, the resin glass transition temperature of the polyester resin is -45°C to 141°C.

[0011] Furthermore, in the iron easy-open lid score line repair coating, the hydroxyl value of the polyester resin is 20 mgKOH / g to 500 mgKOH / g.

[0012] Furthermore, in the iron easy-open lid score line repair coating, the auxiliary agent in component A comprises one of polyether-modified polydimethylsiloxane, polyether-modified siloxane or fluorocarbon-modified polyacrylate.

[0013] Furthermore, in the iron easy-open lid score line repair coating, the curing agent in the B component is a yellowing-resistant aliphatic diisocyanate.

[0014] On the other hand, the present invention provides a method for preparing the iron easy-open cover score line repair coating, the preparation method comprising the following steps:

[0015] Step 1: Weigh the polyester resin, the additive and the mixed solvent according to the mass percentage, disperse, mix, grind and filter to obtain component A.

[0016] Step 2: Weigh the curing agent and the mixed solvent according to the mass percentage, disperse, mix and filter to obtain component B.

[0017] Step 3: Mix component A and component B to prepare iron easy-open cover score line repair paint.

[0018] Furthermore, in the preparation method of the iron easy-open cover score line repair coating, in the step three, the mass ratio of component A to component B is 17:1.

[0019] Furthermore, the iron easy-open lid score line repairing paint can be applied to the field of iron easy-open lid score line repairing.

[0020] Compared with the prior art, the present invention has at least the following advantages or beneficial effects:

[0021] (1) The iron easy-open lid score line repair coating provided by the present invention has excellent high temperature resistance and high pressure cooking performance. The coating can be cooked at a high temperature of 121°C, a pressure of 0.2MPa, and 60 minutes without falling off, turning white or decomposing. It is suitable for high temperature cooking and sterilization processes, and can be widely used in canned food and medical supplies packaging to ensure the safety and durability of products under extreme temperatures.

[0022] (2) The iron easy-open lid score line repair coating provided by the present invention can effectively resist the erosion of various chemical substances and protect the metal surface from corrosion, so that it can be applied to iron products that are often exposed to harsh environments.

[0023] (3) The iron easy-open lid score line repair coating provided by the present invention has a high solid content, so that the coating can form a thicker coating after drying, which not only enhances the anti-electrical corrosion protection effect, but also improves the wear resistance and durability of the coating.

[0024] (4) The iron easy-open lid score line repair coating provided by the present invention has good matching performance: the iron easy-open lid score line repair coating can be used in conjunction with various types of topcoats and can match the process conditions of rapid spray score line repair equipment, which not only enhances the overall performance of the coating, but also improves construction efficiency. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is described below in conjunction with embodiments; however, the present invention is not limited to the following embodiments.

[0026] The experimental methods and detection methods in the following embodiments are all conventional methods unless otherwise specified; the raw materials and materials are all commercially available unless otherwise specified; the index data are all conventional measurement methods unless otherwise specified.

[0027] Example 1.

[0028] This embodiment is for preparing 8 kinds of iron easy-open lid score line repair coatings.

[0029] Raw materials:

[0030] Polyester resin: CH470 (saturated polyester resin) was purchased from Suzhou Hanhai New Materials Co., Ltd.; SETAL1703XX-75 (polyester resin), SETAL 16-1084 (polyester resin), DUROFTAL VPI 2803 (polyester resin), DUROFTALPI 2801 (polyester resin) were purchased from Allnex Resins (China) Co., Ltd., SETAL 189XX-65 (polyester resin), Desmophen 1200 (polyester resin) were purchased from Covestro Polymers (China) Co., Ltd.

[0031] Curing agent: Desmodur N 31000 (polyhexamethylene diisocyanate) was purchased from Covestro Polymers (China) Co., Ltd.

[0032] Additives: BYK088 (polyacrylic acid defoamer) was purchased from BYK Additives (Shanghai) Co., Ltd.

[0033] Solvent: 100# solvent oil, butanone, and propylene glycol methyl ether acetate are mixed in a mass percentage of 30%:30%:40% and used.

[0034] Preparation of 8 kinds of iron easy-open cover scoring repair coatings:

[0035] According to the components and mass percentages of component A in Table 1, the polyester resin, additives and mixed solvent were weighed and put into a stirring reactor in sequence (the reactor was a sandwich structure with a cooling coil inside the sandwich to control the temperature below 40° C.), and stirred and mixed for 30 minutes to obtain component A.

[0036] Weigh 70 parts of polyhexamethylene diisocyanate curing agent Desmodur N 31000 and dilute it with 30 parts of mixed solvent to a solid content of 70%, and obtain component B after filtering.

[0037] The 8 kinds of A components prepared as above were respectively mixed with B component at a mass ratio of 17:1 to prepare 8 kinds of iron easy-open cover score line repair coatings.

[0038] Table 1 Components and their mass percentage ratios of component A of iron easy-open cover score repair coating

[0039]

[0040] Example 2

[0041] This embodiment is a test of iron easy-open cover scoring repair coating and contrast agent spraying.

[0042] In this embodiment, 1 contrast agent group and 7 experimental groups are set up. The contrast agents are 3N3675-851A (component A) and 3N3675-851B (component B) coatings of Suzhou Sanxin Material Technology Co., Ltd., which are mixed at the recommended ratio of 6:1 and tested; the 7 experimental groups respectively use 7 groups of iron easy-open cover score line repair coatings prepared in Example 1.

[0043] Test substrate: tinplate, Suzhou Sanxin Material Technology Co., Ltd. produced epoxy transparent paint 3N2044-803, polyester transparent topcoat 3N3144-801,

[0044] Epoxy golden paint 3N2044-630

[0045] Test the film thickness, the varnish 8-10 micron experimental curing method is ordinary electric oven baking curing, the curing temperature is 120℃, 3min.

[0046] Example 3

[0047] This embodiment is a test for the performance of iron easy-open lid score line repair coating.

[0048] The comparative agent spraying product prepared in Example 2 and 8 groups of iron easy-open cover scoring line repair coating spraying products were subjected to performance tests according to the requirements of water boiling resistance test, adhesion test, impact resistance test and electrical corrosion anti-missile test, and the test results were statistically analyzed. The test results are as follows:

[0049] Boiling resistance test: Place the above samples in a pressure cooker at 121°C and 0.2MPa pressure. After boiling for 60 minutes, observe if the samples have no whitening, bubbles, degumming or corrosion, and are qualified.

[0050] Adhesion test: The control group spray products and 88 groups of iron easy-open cover score line repair paint spray products were tested according to the method in the test standard GB / T9286-2021 "Scratch test for paints and varnishes".

[0051] Impact resistance test: The control group spray products and 88 groups of iron easy-open cover score line repair paint spray products were tested in accordance with the test standard GB / T 1732-2020 "Determination of impact resistance of paint film" at a 50Kg impact level, and then immersed in 20% copper sulfate. The results were qualified if there was no corrosion spot.

[0052] Electric corrosion anti-conductivity test: The control group spray products and 88 groups of iron easy-open cover score line repair paint spray products were all passed 6.3V DC for 60s, with 1% NaCl electrolyte. The number of bubbles ≤1mm was observed, and less than 10 were judged as level 1.

[0053] The results of the water boiling resistance test, adhesion test, impact resistance test and electrical corrosion and anti-conductivity test are shown in Table 2:

[0054] Table 2 Performance test of iron easy-open cover scoring line repair coating

[0055]

[0056]

[0057] The test results show that the iron easy-open cover score line repair paint spraying has good high temperature resistance and high-pressure boiling water resistance. Due to the high solid content of the spraying, no corrosion points appeared in the reverse conductive test. The impact resistance and adhesion tests were both level 1, and the performance was better than the control group. The iron easy-open cover score line repair paint of the present invention has level 1 adhesion on different topcoat substrates, good spray flowability, no shrinkage holes, and good permeability at the score. There is no corrosion in the reverse conductive test and it has a good repair and repainting effect.

[0058] As described above, the present invention can be well implemented. The above embodiments only describe the preferred implementation methods of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various changes and improvements made to the technical scheme of the present invention by ordinary technicians in this field should fall within the protection scope determined by the present invention.

Claims

1. A paint for repairing the score line of an iron easy-open lid, characterized in that: The iron easy-open lid score line repair paint is composed of component A and component B: The component A is composed of 30-43% polyester resin, 0.8% auxiliary agent and 56.2%-69.2% mixed solvent. The B component is composed of a curing agent, polyhexamethylene diisocyanate, and a mixed solvent of 100# solvent oil, butanone, and propylene glycol methyl ether acetate in a mass percentage of 30%: 30%: 40%.

2. The iron easy-open lid score line repair paint according to claim 1, characterized in that: The weight average molecular weight of the polyester resin in the A component is 1,000 to 200,000.

3. The iron easy-open lid score line repair paint according to claim 2, characterized in that: The polyester resin has a glass transition temperature of -45°C to 141°C.

4. The iron easy-open lid score line repair paint according to claim 3, characterized in that: The polyester resin has a hydroxyl value of 20 mgKOH / g to 500 mgKOH / g.

5. The iron easy-open lid score line repair paint according to claim 1, characterized in that: The auxiliary agent in the component A comprises one of polyether-modified polydimethylsiloxane, polyether-modified siloxane or fluorocarbon-modified polyacrylate.

6. The iron easy-open lid score line repair paint according to claim 1, characterized in that: The mixed solvent in the component A is prepared by mixing 100# solvent oil, butanone and propylene glycol methyl ether acetate in a mass percentage of 30%:30%:40%.

7. The iron easy-open lid score line repair paint according to claim 1, characterized in that: The curing agent in the B component is a yellowing-resistant aliphatic diisocyanate.

8. A method for preparing the iron easy-open lid score line repair coating according to claim 1, characterized in that: The preparation method comprises the following steps: Step 1: Weigh the polyester resin, the additive and the mixed solvent according to the mass percentage, disperse, mix, grind and filter to obtain component A. Step 2: Weigh the curing agent and the mixed solvent according to the mass percentage, disperse, mix and filter to obtain component B. Step 3: Mix component A and component B to prepare iron easy-open cover score line repair paint.

9. The preparation method according to claim 8, characterized in that: In the step 4, the mass ratio of component A to component B is 17:

1.

10. The iron easy-open lid score line repairing paint according to claim 1 is used for repairing score lines of iron easy-open lids.

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